Talk:Book - Buchanan's Manual of Anatomy including Embryology 12: Difference between revisions

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ribs. (The movement round the  
ribs. (The movement round the  
axis A, B resembles the raising of  
axis A, B resembles the raising of  
the handle of a bucket.)  
the handle of a bucket.)
 
 
 
==CHAPTER XIII DEVELOPMENT OF VASCULAR SYSTEMS==
 
 
Principal Arteries and Veins.
 
It was shown at the beginning of this book (pp. 51, 91) that the vase
system, in its earliest stages, came into existence as the result of the establishn
of connections between networks of channels formed on the yolk-sac, in
body-stalk, and in the embryonic body; an extension from the body-stall
 
 
 
Fig. 670. —Scheme of Earliest Circulatory System. (Founded on Eternc
 
The lower figure is a diagrammatic section to show position of aortae and umbil
veins (UV). Am, amnion; N, neural groove; coe, intra-embryonic coelom
 
the chorion (where similar channels are possibly formed also) puts tl
anastomosing systems into relation with the growing villi.
 
The primitive circulation would seem to be possible through channels est
lished in this way at an early stage in embryonic formation; such might
represented schematically as in Fig. 670. In this figure it can be seen t
 
1116
 
 
 
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1117
 
 
ns (vitelline) pass up the wall of the yolk-sac to reach the posterior part of
! embryonic rim, where they join a vein coming from the body-stalk and
ming forward to enter the primitive heart-tube. This (C) is a very short
)e, doubled in origin, which runs back towards the bucco-pharyngeal area (bp),
ing off here two primitive aortcs, which pass back on each side of the area
the future membrane, and continue their course caudally to reach the bodylk. As they pass back in the embryo they give off vitelline branches downrds on to the wall of the yolk-sac; later, as the somites form, they will be found
give intersegmental branches running dorsally between the somites. When
:y reach the chorion they are distributed throughout it and to its villi.
 
The veins which return the blood in this early circulation must come into
stence, of course, with the * arteries,’ and can be said in general terms to
 
 
 
 
r. 671. — Schemes founded on Conditions in an Embryo of About
Twelve Somites, in which the Intra- and Extra-embryonic Ccelomic
Cavities are Continuous.
 
se from the common vascular network as enlargements of its ‘ peripheral ’
t, the ‘ central ’ vessels becoming arterial. Thus veins are found extending
the heart along the embryonic rim, which receive the blood returning through
body-stalk; these veins (uv), are the umbilical veins, which, passing forward
ng the margins of the embryonic plate, reach the anterior end of the heart,e in this margin. The vein is shown in black in the figure, where only the
sels of the left side are seen; actually there are two primitive aortae and two
bilical veins.
 
The conditions illustrated in the last figure are those present in the embryo,
which there are as yet no somites and no body cavity continuous with the
ernal coelom. The result of somite formation, with the reversal of the
erior end of the embryonic plate, is shown in the next figure (Fig. 671),
 
 
 
 
 
 
 
 
 
nt8
 
 
A MANUAL OF ANATOMY
 
 
where the heart is now reversed, and the arterial end points forward, while
paired aortae run upwards beside the bucco-pharyngeal membrane and then ti
back; intersegmental branches are appearing now. It can be seen now, moreo\
that well-defined vitelline veins are reaching the venous end of the heart (n
posterior) by passing up the front of the yolk-sac; the earlier posterior ve
have disappeared. The splitting of the embryonic rim by the ccelomic extens
leaves the vitelline arteries on the splanchnic wall, but puts the umbilical ve
in the somatic wall, close to the continuity of this wall with the amnion; thi:
shown in the section in Fig. 671.
 
The paired aortae lie oh the roof of the primitive pharynx, and receive in t
situation ‘ aortic arches ’ from the ventrally placed arterial trunk and vessi
but behind the pharynx they fuse into a single vessel, which divides again ii
two as it approaches the hinder end; these two umbilical arteries pass into •
body-stalk.
 
Development of Principal Arteries.
 
The arterial end of the heart opens into a dilated arterial sinus, from wh
right and left arteries run into the pharyngeal arches, passing through th
to join the right and left dorsal aortee which are lying on the roof of the primit
pharynx. All told, there are six of these aortic arches (or pharyngeal artei
arches) on each side, but they are never present at any one moment in th
totality. They appear from before backward, like the mesodermal arches
which they lie. The first is possibly the direct descendant of the primitive ao:
of its side, passing dorsally round the bucco-pharyngeal membrane; in any c;
it is found very early, before reversal is nearly completed. The second aor
arch comes a little later. The third, when it appears, seems to take on the din
supply of blood to the dorsal aorta at its anterior end, where this vessel is givi
branches to the growing neural (brain) tube, and the first and second arcl
break up rapidly and disappear, except for their upper and lower ends for soi
little time. The fourth arch appears at about the same time as the third, i
fifth is very small and short-lived, like the rudimentary mesodermal arch in whi
it lies, and the sixth appears behind this. All these arterial arches, then, appt
as vessels running ventro-dorsally within their corresponding pharyngeal arch
and conveying blood from the ventrally-placed arterial sinus to the dor
aortae for distribution.
 
The presence of the arterial sinus makes the details of further developmt
slightly different in the human embryo from those in lower forms, but t
differences are only slight, and the main evolution of the adult pattern frc
that of the aortic arches is in line with the generalized vertebrate evolutic
Such a generalized conception of the system of aortic arches is that (Fig. 6;
given by Rathke many years ago, on which the special variations found amo
vertebrates can be worked out. The plan shows the arterial arrangemei
flattened out, so that, from the arterial stem, right and left ventral aortce r
forward (below the pharynx) and give off at intervals the six aortic arches
reach the d or sal aortas (above the pharynx). Small branches pass from i
sixth arches into the lungs, evidently the future pulmonary arteries, while f
anterior end of each dorsal aorta is carried (beyond the scheme) into the cran
cavity as a cerebral artery. It may be added here that eight intersegmen:
branches arise from each dorsal aorta, the lowest coming off about oppos
or just below the fourth arch on each side; seven of these arteries are cervic
but the first is cranial, accompanying the hypoglossal.
 
Disregarding the gill-bearing vertebrates, we may come at once to 1
Amniota, where the differences in the various phyla are classifiable easily on t
scheme. In the first place it is a general rule that the third aortic arch is devot
to supplying the brain, while the fourth becomes the main stem for the sup],
of the body. Thus the third arch plus the dorsal aorta in front of it becon;
the internal carotid, and the fourth arch becomes the ‘ arch 5 of the syster
aorta, from which facts it can be assumed that the dorsal aorta between 1
third and fourth arches loses its function, is stretched out, and disappea
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1119
 
 
e matter of the two fourth arches, these persist in the reptiles ; the right one
5 the systemic arch in birds, and the left one in mammals.
he human conditions are thus shown (Fig. 672) on the scheme as mammalian,
first two arches disappear, leaving the ventral aorta opposite them as
nal carotid; the third, with the dorsal aorta in front of it, forms the
nal carotid; the dorsal aorta behind it, between it and the fourth arch,
•pears; the ventral aorta between third and fourth becomes the common
id. The original symmetry is disturbed behind this. The fourth left arch
s part of the systemic arch, but not the whole of it; the dorsal part of this
is formed by dorsal aorta, and the ventral end is the beginning of the ventral
; this is represented on the right side by the innominate artery. The right
i arch becomes part of the right subclavian; the whole of the left subclavian
he terminal piece of the right subclavian are of intersegmental value. Behind
 
 
External Carotid
 
 
 
'ig. 672.—Scheme of the Aortic Arches and their Destination.
 
 
e the fifth arches disappear; the left sixth remains as the ductus arteriosus;
right sixth disappears except for its ventral end, from which the right
lonary artery arises. The common arterial trunk is divided by a septum
a dorsal part continuous with the sixth arches, and a ventral part for the
ral aortae, and this septum extends towards the heart in a spiral manner,
nee the changing relations of pulmonary artery and ascending aorta; this
vessel represents the common trunk and its systemic subdivision, binally,
right dorsal aorta disappears behind the right fourth arch, so that the rest
ie thoracic aorta comes from the fused vessels.
 
n the human embryo there is no ventral aorta giving origin, as in the scheme,
11 the arterial arches, but if we look at the arterial sinus as having the value
hortened ventral aortae conjoined, this difficulty disappears. In any case
difference is not of much importance, big. 673 gives, in the uppei row,
is showing the changes in the human embryo as seen from the left. The
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1120
 
 
A MANUAL OF ANATOMY
 
 
external carotid showing here may be a new formation, but might be some dr<
out persisting remnant of the ventral supply to the early anterior arches,
the common carotid is either part of the third arch or a drawn-out portion o
sinus; it is a very difficult question to decide. The lower figure shows
 
 
 
biG. 673. —Plans to show Changes in Human Embryo: Upper Row f
 
Left, Lower from Right.
 
Aortic arches and their remnants numbered in Roman figures.
 
conditions on the right side; the carotid developments are as on the left, but
fourth arch is part of the subclavian, and the dorsal aorta disappears behind
 
In estimating and following the changes which occur in the art<
arches in the neck it must be remembered that the head grows forw
leaving structures behind it which were originally ventral to it; th
what is really meant when the heart, for example, is said to ‘ desce
 
 
 
 
Fig. 674.— Plans to show how the Embryonic Relations between Ner
and Arteries are exhibited in the Adult Condition.
 
The growth of the head and elongation of the neck straighten out
carotids, while the connection of the fourth arch with the trunk keeps it 1
the heart.
 
The relationship between the arterial stems (in the pharyngeal arc]
and the nerves of the arches is of interest from the point of view of the nor
relations in the adult, and also in cases where the adult conditions are unusu
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1121
 
 
The nerves of the first four arches lie near the grooves in front of them, and
thus in front of the arteries which lie more or less in the middle of the mesomal masses. In the sixth arch, however, possibly because its artery runs
k to it and is formed relatively late, the artery lies in front of the nerve. In
:ases the nerve, having crossed the dorsal aorta on its lateral side, then turns
ards to gain the visceral surface; thus they all cross obliquely the lines of
ir corresponding arteries, but whereas the first four cross in front of their
sels, the last crosses behind it. It follows that, when the neck is elongated
the vessels drawn out, they are drawn over the nerves of the arches behind
m. Thus the internal carotid (third arch) has the superior laryngeal (fourth arch
ve) deep to it, while its own nerve, the glosso-pharyngeal, is superficial to it
rsal aorta). The fourth aortic arch (arch of aorta and right subclavian) has the
irrent laryngeal deep to it, but this nerve on the left turns first round the
mentum arteriosum because it crosses behind that artery in the sixth arch.
 
The fifth arch, with its artery and nerve, is a tiny and transient formation,
only brought into description to complete the various systems. Its artery
may be as in Fig. 673, or may arise from the arterial sinus and end in one
of the neighbouring arches, or even in the dorsal vessel, or may even arise
from the proximal part of the sixth artery.
 
It disappears early and completely.
 
The right subclavian artery, as shown in the scheme, has its first part formed
n the fourth right aortic arch, and its terminal piece from the seventh cervical
srsegmental artery. Between these two there is a portion of the right dorsal
ta; there is considerable doubt about the limits of these various parts.
 
There are two well-known varieties of the right subclavian artery of developntal interest. In one the artery arises from the descending thoracic aorta,
the other it arises from the left end of the arch of the aorta; in both cases it
ses behind the oesophagus to gain the right side. The first of these varieties
ms to be an example of persistence of the right dorsal aorta ; the same explanation
iometimes given for the second variety, but with much less probability, and
would seem to be more probably an example of anastomosis between the two
sal aortw. In both cases the fourth aortic arch has evidently disappeared
the right side, and as a result the right recurrent nerve turns round the next
h in front— i.e., it runs directly downwards to the lower border of the larynx ,
sing deep to the internal carotid.
 
Intersegmental Branches : Vertebral Artery. —The first intersegmental artery
en by each dorsal aorta accompanies the hypoglossal nerve. After this come
en cervical intersegmental vessels. These pass back between the somites,
ich they supply, and give branches also to the neural formations lying
ernal to these. Since the cranial end of the dorsal aorta is about to be stretched
: in the internal carotid, and the next part of it is about to disappear, it is
dent that, if these intersegmental arteries are to continue to supply the
uctures mentioned, they must be provided with another artery of origin,
e provision is made very early in their history in the form of a longitudinal
istomosis connecting them together some little distance from their origins.
 
An anastomosis of such a sort is a normal occurrence among the intersegmental vessels in the trunk. Usually it remains very small or disappears,
but is seen occasionally in the adult, especially in the thoracic region.
In the ordinary way, however, it is only in the cervical region that it enlarges
and becomes functionally important.
 
This longitudinal anastomosis ends caudally in the seventh cervical intermental artery. Thus, when the origins from the dorsal aorta fail, the series
vessels obtains its blood from this seventh artery. The longitudinally running
'tebral artery is thus made up of these bits of interarterial anastomosis, the
ginal intersegmental vessels persisting as its branches. The portion above the
as, however, which has a different relation to the issuing nerve, is of another
[ue, being the enlarged intersegmental spinal or neural branch.
 
 
 
1122
 
 
A MANUAL OF ANATOMY
 
 
The origin of a vertebral artery precedes that of the corresponding subcla 1
artery, so that the subclavian artery is originally a lateral branch of the verte
artery. As the development proceeds, however, the subclavian artery incre
in size, and greatly exceeds the vertebral artery, the latter vessel being :
regarded as a branch of the subclavian.
 
Origin of Left Vertebral Artery from Aortic Arch. —This, the commo
additional branch arising from the arch, is probably an example of the
sistence (see Fig. 675) of the sixth intersegmental origin from the dorsal ac
with the portion of this aorta remaining as far as the level of the fourth ac
arch.
 
The thoracic and abdominal intersegmental arteries have been refe
to already in connection with the aorta.
 
 
 
Fig. 675. —Development of Cervical, Intersegmental, and Vertebra
 
Arteries, according to Scheme.
 
The intracranial prolongation of the dorsal aorta on each side is an exan
of the enlargement of a neural branch arising from the beginning of this ari
and running dorsally into the paraxial tissue round the brain; the dorsal a<
itself lies on the upper in-turned ends of the visceral mesoderm of the arc
below the layer of paraxial mesoderm. This terminal neural branch en
the paraxial layer beside Rathke’s pouch, and, in the adult, pierces the d
mater here. Before reaching this, the internal carotid lies on the roof of
tubo-tympanic recess, covered by the otic capsule; much later, this cap:
extends its ossification partly round it, enclosing it in the carotid canal, bi
portion of the artery, still unenclosed, lies in front of this and crosses (as it
in the foramen lacerum) the anterior margin of the recess, the auditory tube,
 
The ramifications of the cerebral arteries are formed in accorda
with the growth of the parts of the brain, which is surrounded by a vasci
network from a relatively early stage. These vessels are dealt witl
part in the section on the central nervous system.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1123
 
 
•teries of Limbs. —The arteries of the upper limb have been already considered,
the lower limb, the accepted views on their development are in large part
lptions based on comparative anatomical observations, direct observation
» human embryo being an undertaking of great difficulty.
 
) W er Limb. —At the beginning of the second month the main artery accoms the sciatic nerve, passes deep to the rudiment of the popliteus, and runs
:en the primordia of the leg bones to the foot. This ‘ axial ’ vessel is
:cted with a small plexus on the extensor aspect of the limb, from which at
ir stage the femoral artery will form. As the femoral channel enlarges,
axis ’ vessel sends a secondary branch down superficial to the popliteus,
hen degenerates above the level of its connection with the femoral; this
dary branch divides to form the tibial arteries, anastomosing with the
lal interosseous trunk, which has already given off the anterior tibial, and
becomes a small branch of this. The inferior gluteal artery, the popliteal,
•art of its middle genicular branch, are remains of the original ‘ axis ' supply,
 
 
Fig. 676.— The Venous Trunks of the Septum Transversum of
 
the Human Embryo (His).
 
X.X. Upper separated portions of Umbilical Veins
R.U.V. Right Umbilical Vein
L.U.V. Left Umbilical Vein
 
V.P. Venous Loops round Gut
V.V. Vitelline Veins
 
the peroneal and perhaps part of the arterial structures in the sole are
ed from its interosseous prolongation; the two femoral arteries and the
snous branch of the descending genicular artery, when present, are remains
e femoral extensor plexus.
 
Development of the Principal Veins (p. 5 1 )
he primitive veins form two groups. One group returns the blood from the
sac and the placenta; and the other group returns the blood from the head
neck, anterior limbs, body-wall, mesonephric bodies, and posterior limbs,
first group comprises: (1) the vitelline veins, in connection with which the
il vein is developed; and (2) the umbilical veins. The second group consists
) the anterior cardinal or primitive jugular veins; (2) the posterior cardinal
;; and (3) the subcardinal veins; they drain into the veins (or ducts) of
2r on each side. The veins of each group are arranged in pairs, right and
 
 
J.V. Primitive Jugular Vein
:.V. Cardinal Vein
V.C. Right Duct of Cuvier
/.C. Left Duct of Cuvier
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1124
 
Sinus Venosus. —This is the venous space made by the confluence of
veins of the body; it discharges directly into the common atrium the bloo
receives from the veins. It is placed in the septum transversum (pp. 46 and
and consists of two ‘ horns,' each of which is made by the junction of the umbili
vitelline, and Cuvierian veins of its own side. As described in the developrr
of the heart, the right horn is taken up into the right atrium, the left horn becon
the coronary sinus. The vitelline veins reach the sinus venosus by rum
in the visceral wall to the septum transversum, the others get to the septuir
 
the body-wall. 1
 
1. Vitelline Veins and Portal Veins— These veins are developed early,
they return the blood from the yolk-sac. They enter the body of the emt
along the vitelline duct, and finally open into the sinus venosus after traver
the septum transversum. Within the body they ascend parallel with each ot
at first in front of, and subsequently on either side of, the duodenal portio
the primitive intestinal tube. In the latter region on the caudal side of
 
 
 
Fig. 677. _Schemes to show Formation of Portal Vein from Doi
 
Connecting Loop between the Right and Left Vitelline Veins.
 
hepatic bud they become connected by three transverse anastomotic ves
two of which lie across the ventral aspect of the gut, and one being placed 0
dorsal aspect. The first or lowest anastomotic vessel lies on the ventral as
of the gut; the second or middle vessel is dorsal to the gut; and the tnir
highest, like the first or lowest, is ventral to the gut. This is shown m tne
 
scheme in Fig. 677. , . ,
 
By means of these three anastomotic vessels two venous rings—lowe
caudal, and upper or cephalic—are formed around the duodenal portion oi
primitive intestinal tube, these rings constituting the sinus annularis. t
their formation the two divisions of the liver-bud are breaking up into ne
cylinders, and these are giving off secondary cylinders. Owing to these ne]
developments the vitelline veins cease to communicate directly with tne .
venosus. The portions of the vitelline veins above the upper duodenal ve
ring (shown in Fig. 676 to proceed from its sides) become surrounded
hepatic cylinders, and invaded by the secondary cylinders. In this ma
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1125
 
 
portions of the vitelline veins are freely subdivided into blood-channels,
 
1 are known as sinusoids (Minot). These sinusoids form a network which
>ies the meshes of the network formed by the branches of the hepatic cylinders,
veins which convey blood from the upper duodenal ring to the hepatic
oids are now known as the vence advehentes, and they become the right and
\ivisions of the portal vein. The veins which carry the blood from the
tic sinusoids to the sinus venosus are known as the vence revehentes, and they
ne the hepatic veins.
 
runk of the Portal Vein. —The portions of the two vitelline veins which
id in front of the primitive duodenum lie close together and parallel with
other. These portions fuse for a short distance, and form a single venous
, which opens into the first, or lowest, ventral anastomotic vessel, or, in
■ words, into the lower part of the lower duodenal venous ring. This short
receives the veins of the primitive intestinal tube, and it forms the root
e portal vein. The primitive portal vein, therefore, receives its blood from
tie yolk-sac, and (2) the primitive intestinal tube within the abdomen. The
r ventral anastomosis and the right vein immediately above it quickly
 
ipear (Fig. 677). . .
 
is the yolk-sac atrophies the portions of the vitelline veins between it and
commencement of the portal vein also atrophy, and the tributaries of the
il vein gradually assume their condition in adult life. The vitelline vein,
ever, does not disappear for a considerable time, but remains as a free cord
,4) passing out of the umbilicus up to the entrance of the umbilical loop into
belly. #
 
"he following parts of the sinus annularis, or double duodenal ring, undergo
phy (see Fig. 677):
 
1. Right half of lower ventral anastomotic vessel.
 
2. Right half of lower duodenal ring.
 
3. Left half of upper duodenal ring.
 
rhe following parts of the sinus annularis persist:
 
1. Left half of lower ventral anastomotic vessel.
 
2. Left half of lower duodenal ring.
 
3. Middle or dorsal anastomotic vessel.
 
4. Right upper half of duodenal ring.
 
5. Upper ventral anastomotic vessel.
 
These persistent portions, with the exception of the upper ventral anastomotic
el, form the greater part of the trunk of the portal vein, the upper ventral
stomotic vessel represents a part of the left division of the portal vein.
 
The portal vein has originally a spiral relation to the duodenal portion of
primitive intestinal tube—that is to say, it winds round the left side and
sal aspect of the duodenum, and then appears on its right side.
 
Divisions of the Portal Vein.— These are connected with the upper duodenal
ous ring. As previously stated, the veins which convey the blood from this
\ to the hepatic sinusoids are known as the vence advehentes, right and lefL.
; right division of the portal vein is formed by the right vena advehens, which
ings from the right half of the upper duodenal venous ring, dhe left division
firmed by (1) the upper ventral anastomotic vessel, and (2) the left vena
ehens
 
Umbilical Veins.— The two umbilical veins return the blood from the placenta
the sinus venosus. They are of small size during the period of the vitelline
mlation, but become enlarged as the placenta gradually forms, the two
ns unite and form a single trunk within the umbilical cord At the umbi icus
5 trunk enters the body of the embryo, and immediately divides into wo
bilical veins, right and left, which traverse the septum transversum and open
n the sinus venosus. As they traverse the septum transversum ey are
se to the developing liver.
 
 
 
1126
 
 
A MANUAL OF ANATOMY
 
 
The left umbilical vein enlarges fairly rapidly, that on the right s
atrophying more slowly. Just before the 5 mm. stage the left vein effect
capillary junction with the left vitelline vein on the caudal aspect of the sept
transversum— i.e., on the caudal or visceral surface of the small liver. 1
connection between the umbilical and vitelline veins of the left side enlar
very rapidly, thus making the vessel on the visceral aspect of the liver wt
is usually referred to as the ‘ left umbilical vein ’; actually, of course, it is a vite
umbilical anastomosis, and the real umbilical vein passes up still beside the lb
but dwindles rapidly, and cannot be certainly traced after a fairly short inter
When the anastomotic vessel collapses, after birth, it makes the ligament
teres of the liver.
 
In this region part of this fibrous cord lies in the abdominal wall ;
part below the liver; the first of these parts is the true umbilical vein, w
the second is the vitello-umbilical anastomosis.
 
 
 
Fig. 678. —Scheme to show Early Circulation in Liver, and Direct
 
of Ductus Venosus.
 
The right umbilical vein also seems to develop some similar anastom
with the vitelline system, but owing to the atrophy of the vein the anastom
does not become evident.
 
The anastomosis of the left umbilical vein with the left vitelline vein oc
at the level (in this last vessel) of the upper junctional loop with its fellow, as sh
in Fig. 677. As already stated, this upper loop becomes embedded in the lb
and forms a part of the left portal vein, whence the fact that the ligamen;
teres, buried between two lobes of the liver, runs to join the left division of
portal vein.
 
There is possibly some connection between the entrance of the umbi
blood at this level and the disappearance of the original vitelline
(A in Fig. 677) between this and the next anastomotic loop, the vol
of blood from the larger vein prohibiting entrance of vitelline blood it
below.
 
Ductus Venosus. —Blood from the left umbilical vein enters the live; j
increasing amount as the placenta grows, and before long there becomes evil
a dilatation into a large vessel of the vascular spaces in the liver lying bet\i
the point of entrance of the blood and that of its discharge into the infc
 
 
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1127
 
 
, cava. This vessel is termed the ductus venosus (or ductus Arantii). It
nds from the left portal vein, which has been formed from the uppermost
line loop and receives (Fig. 678) the vitello-umbilical anastomotic vessel;
,sses upwards and to the right, reaching the terminal part of the right hepatic
nage into the inferior vena cava, which becomes dilated to form its terminal
*
 
✓ •
 
After birth, when the placental circulation has ceased, the ductus venosus
becomes a fibrous cord, the ligamentum venosum.
 
 
minute portion of the lumen
he left umbilical vein remains
ious within the ligamentum
> of the liver. This pervious
ion communicates at the liver
. the left division of the portal
, and at the umbilicus it is
lected with the epigastric veins
:he abdominal wall. It thus
is a channel of communication
yeen the left division of the
al vein and the systemic veins
tie anterior abdominal wall. In
pervious portion the blood can
towards the umbilicus. This
stomosis between the portal and
emic circulations accounts for
enlargement of the veins of the
irior abdominal wall in cases of
:al obstruction within the liver.
 
2. The cardinal system of veins
iprises several vessels on each
;, which ultimately drain their
d into the sinus venosus through
right and left veins {or ducts) of
ier. A general idea of their
ribution can be gained from
. 679A. A large vessel, the primijugular or anterior cardinal (or
cardinal), drains the cranial part
the body, beginning in associa1 with the venous drainage of
brain, and passing back through
cervical region, where it re/es intersegmental veins, includthe subclavian (S). The posterior
dinal runs caudo-cranially, being
med in association primarily with
mesonephros (W) and receiving
srsegmental veins. The posterior
1 anterior cardinal veins join to
m the ‘duct of Cuvier,’ situated
the septum transversum, cranial
the liver ('LL and thus
 
 
 
Fig. 679.—Scheme of Main Venous
Drainages of Embryo.
 
SV, sinus venosus; DC, duct of Cuvier;
PJ, anterior cardinal or primitive jugular; C, posterior cardinal; UV and VV,
umbilical and vitelline veins.
 
 
(L), and thus running
ctly into the sinus venosus. # . .
 
rhe anterior cardinal or primitive jugular veins are two m number—right
left—and return the blood from the head, neck, and fore-limbs. Each vein
>ists of two parts—intracranial and extracranial. The intracranial part gives
, directly and indirectly, to the intracranial sinuses, whilst the extracranial
‘ becomes the internal jugular vein. The intracranial part is known as the
 
 
 
 
1128
 
 
A MANUAL OF ANATOMY
 
 
principal or primary head vein. This vein at its anterior end is on the inner
of the trigeminal ganglion; passing backwards from this point, it lies just al
the outer part of the tubo-tympanic recess lateral to the facial ganglion and f
nerve, and reaches behind this the outer side of the glosso-pharyngeal and va
 
Its different relations with the several cranial nerve-roots indicate
it has been produced from two venous trunks, connected between the rc
these trunks are represented in lower vertebrates by the vena capitis late
and vena capitis medialis.
 
At its anterior end the principal head vein receives on each side the anti
cerebral veins, a plexiform set of vessels draining the mid-brain, the back ol
fore-brain, and the optic outgrowth. The anterior cerebral veins anastoi
 
 
 
Fig. 679A.— To show Main Trunk Veins in Young Embryo.
 
with their opposite fellows dorsally between the two small cerebral vesic
thus forming the rudiment of the superior sagittal sinus, which is elongated
the vesicles grow backwards (Fig. 680).
 
Between the trigeminal and facial ganglia the principal vein receive
middle cerebral vein or plexus, draining the front limb of the pontine flex
and anastomosing with the anterior veins.
 
A plexiform posterior cerebral vein opens into the principal head vein betw
the facial and glosso-pharyngeal ganglia; it drains the back of the poni
flexure and the myelencephalon. These details are shown in Fig. 680, f
scheme.
 
As the cerebral vesicles grow backwards, the anterior plexus becomes n
closely connected with the middle set, and its blood is returned by this set
 
 
 
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS 1129
 
asing amount. Ultimately the superficial middle cerebral vein, the sphenotal sinus, and the ophthalmic veins, are the only vessels left of the original
isive anterior venous plexus. The cavernous sinus is the persisting anterior
 
>f the principal head vein (second figure).
 
he middle cerebral vein, however, has in the meantime formed a secondary
’ding channel with the posterior cerebral vein, this channel lying above the
capsule and beside the pontine flexure within the developing cranium,
the blood which has already been seen to be derived from the anterior
1 into the middle set is carried back through this new channel, and the
lal principal vein in its intermediate part gets smaller and disappears, the
1 from its anterior end (cavernous sinus) now passing up the lower portion
e original trunk of the middle cerebral vein to reach the new channel, through
h it passes to the hinder part of the posterior vein, along which it runs down
-enter the hinder part of its old vessel, and thus leaves the cranium with
r agus.
 
 
 
680.— Semi-schematic Figures to show Changes in Venous Drainage
of Brain (founded on Streeter’s Figures).
 
 
Continuing their growth backwards (third figure), the cerebral vesicles carry
elongating longitudinal sinus with them, so that it ultimately comes to open
*th figure) into the posterior set of veins, from the lower part of which the
al sinus is made. The middle cerebral plexus is covered over by the growing
des, but is represented in the great cerebral veins and their tributaries, the
ar veins being also remnants of their connections with the anterior venous
The straight sinus is a new connection (arising on the dorsal side of the
-brain flexure when this closes) between the middle and posterior sets of
s. The inferior petrosal sinus represents the secondary re-establishment
direct connection between the original and persisting anterior and posterior
1 of the primary head vein, but the new channel is within the cranium, and is
 
a reappearance of the old vein. .
 
die extracranial part of the anterior cardinal vein, after the obliteration of
vena capitis lateralis, commences at the jugular foramen, whence it extends
lad, receiving in its course the cervical inter segmental veins. In the vicinity
te sinus venosus it meets the posterior cardinal vein of its own side, with which
lites. The venous trunk thus formed is called the duct of Cuvier, of which
e are two—right and left. These two ducts pass transversely, one on either
 
 
 
ii3o
 
 
A MANUAL OF ANATOMY
 
 
side, to the sinus venosus, into which they open. At this stage the sinus venc
also receives the vitelline and umbilical veins of each side. The ducts of Cu
are in the septum transversum (see pp. 46 and 52).
 
As the heart descends from the region of the fore-gut, the ducts of Cu
become vertical, and are in line with the anterior cardinal veins. When
sinus venosus becomes merged into the right atrium, and the heart undergo^
slight rotation from right to left, the left duct of Cuvier is placed dorsal to
left atrium before opening into the right atrium.
 
Each anterior cardinal vein is joined, near its caudal extremity, by
corresponding subclavian vein.
 
Close to the junction the subclavian vein receives the external jugular V
This vein is a secondary formation, and is probably derived from a poste
auricular vein, being subsequently reinforced by a pre-auricular vein.
 
 
 
F IG . 681.— The Venous Plexus lying between the Two Primitive.Jugui
 
JUST BEGINNING TO FORM THE LEFT INNOMINATE CONNECTION (19 MM.)
 
A transverse anastomotic vessel is now formed, called the transverse jug
vein. It is developed (Fig. 681) in the ventral plexus connecting the
primitive jugulars. It extends from the junction of the left anterior cardinal
left subclavian veins to the right anterior cardinal vein at a point a little b<
the place where it receives the right subclavian vein. This transverse jug
vein, which extends obliquely from left to right, with a downward inclmal
gives rise to the left innominate vein. The venous blood from (i) the left
of the head and neck and (2) the left fore-limb now passes through the
innominate vein into the permanent superior vena cava. The right innomi
vein is formed by the short portion of the right anterior cardinal vein w
intervenes between the place where it receives the right subclavian vein and
place where the transverse jugular vein joins it. The portion of the right ante
cardinal vein, which lies immediately below the place where the transverse jug
vein joins it, forms the upper or extra-pericardial part of the permanent sup(
vena cava —that is to say, the part above the point where the vena azygos o]
into it. The lower or intrapericardial part of the superior vena cava is develc
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
n 3 J
 
 
. the right duct of Cuvier. The permanent superior vena cava therefore
isents (i) the lower part of the right anterior cardinal vein, and (2) the
; duct of Cuvier.
 
'he portion of the left anterior cardinal vein immediately below the left
unity of the transverse jugular vein forms the upper part of the left superior
costal vein, thus accounting for the ending of that vein in the left innominate
which, as stated, is formed by the transverse jugular vein.
 
'he left duct of Cuvier undergoes partial obliteration. Its terminal part,
l with the left lateral cornu of the sinus venosus, gives rise to the coronary
5. The portion next the terminal part also persists in the form of a very
ite vein, called the oblique vein of left atrium, which lies over the posterior
ct of the left auricle. The obliterated portion is represented by the vestigial
 
 
 
bo. 682. — Sectional Plans to illustrate Venous Modifications in
Cardinal Systems in the Middle Region of the Abdomen.
 
 
of left atrium, which is a small triangular fold of the serous pericardium in
t of the root of the left lung.
 
‘osterior Cardinal Veins. —These are two in number—right and left—and
return the blood from the mesonephroi, body-wall, and hind-limbs. They
>n either side of the aorta dorsal to the mesonephroi. The caudal end of
vein receives the inferior gluteal vein, which is the primitive vein of the
-limb. A little above this point it is joined at a later period by the external
vein, which has now been developed.
 
die cephalic end of each posterior cardinal vein joins the corresponding
nor cardinal vein, and the trunk so formed is the duct of Cuvier.
 
Amongst other tributaries, the posterior cardinal veins receive intersegmental
s, such as the lumbar and intercostal veins, and veins from the intermediate
mass.
 
 
 
 
 
 
 
 
 
 
 
 
 
1132
 
 
A MANUAL OF ANATOMY
 
 
The posterior cardinal veins lie on the dorsal side of the mesonephroi,
cardinal veins run longitudinally on the inner and ventral sides of the mesonep
within which the cardinals and subcardinals are connected by anastomt
veins; they run into the cardinals at the two ends of the bodies. A third sy:
of veins develops on the dorsal side of the cardinal on each side, forming a pi
round the groups of sympathetic ganglion cells as these grow down from
posterior root ganglia. As this ‘ periganglionic ’ system enlarges with the gn
and extension of the nervous masses, it forms an extensive plexus, joi
laterally with the inter segmental veins , ventrally with the cardinal, and wit)
subcardinal internal to this. In many animal forms this venous system constil
a definite supracardinal vein on each side, with retro-aortic anastomoses, but
a development is not found in the human subject, and retro-aortic conned
are few and far between; hence it seems convenient to use the term
ganglionic as representing the human condition or modification of the supracarc
formations.
 
Progressing with the ganglionic and nervous growth, the perigangli
plexus extends forwards and inwards on each side as a juxta-aortic plexi
veins, and from this a pre-aortic plexus is quickly formed. The pre-ai
extension is seen in the thorax, and is very marked in the abdomen belov
level of the superior mesenteric artery; between these two parts the growt
the suprarenal and its association with the sympathetic and the formatio
the diaphragmatic crura seem to interfere with the formation of the pre-ai
plexus. The part of the left renal vein that lies in front of the aorta is made 1
this plexus below the superior mesenteric artery, putting the two subcard]
in connection owing to the extensive anastomoses between these and the gny
supracardinal vessels. Caudally, the aorta divides into two umbilical arte
and the supracardinal plexus is carried down on each side dorsal to these arte
extensions from this plexus here on the sacrum appear to be the origin of
left common iliac vein in this part.
 
The sectional plans shown in Fig. 682 will be of use probably in enabling
reader to follow the complicated changes going on in these different sets of ves
In I are shown the two mesonephric formations in section, beside the mei
mesentery. On the left an intersegmental vein (in) is seen opening into
posterior cardinal (C), which is situated on the dorsal and lateral side of
mesonephros, and is joined by a plexus within that body with the subcarc
(SC) in the medial part of the body near the base of the mesentery. On the r
side is shown a stage a very little later, in which a plexus of minute veins is
surrounding the sympathetic neuroblasts which have descended from the ne
crest; this ‘ periganglionic ' plexus is connected with the intersegmental \
and also (although this is not shown) actually with the posterior cardinal,
plexus, following the extension of the neuroblasts, shows a rapid ventral extern
as seen in II, towards the ventral aspect of the aorta, over which (III) it pa
and joins with the plexus of the other side. It is to be noted that this exten
is correlated with a marked anastomosis with the subcardinal, as seen in III,
in the same figure is shown the evident tendency of the intersegmental vei:
transfer its drainage to the plexus—that is, in general terminology, to trar
it to the supracardinal vessels. The connection with the subcardinals ii
marked that the transaortic plexus appears very soon to be intersubcardi
as is suggested in III, and becomes intersubcardinal in actuality before
(IV), as the original anastomosis with the plexus begins to atrophy or break
This break is favoured by the establishment of longitudinal anastomoses betv
the successive ‘ plexus ' units, so that their blood is now carried cranially
longitudinally running and definite supracardinal vessel, which only communic
with the subcardinals here and there. In the meantime the intersegme
veins have come to drain altogether via the ‘ plexus ’ into this longitud
vessel, and the posterior cardinal (in this abdominal region) disappears (c) f
the scene. These changes are shown in IV. The last figure (V) is a schem
illustrate the age-changes described above. The intersegmental veins in f
younger stages (below) are joined by a plexus with the subcardinal (SC), bu
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
1133
 
 
become older (higher) they establish a longitudinal drainage of their own
lose their connections with the subcardinal, except, for example, where the
renal vein is made.
 
'he changes just described are of the nature of general changes; their modificai and extensions, as shown in the development of the inferior vena cava
azygos systems, remain for description.
 
humming up these matters from the viewpoint of the respective cardinal
it may be said that the posterior cardinal is formed on each side in association
the mesonephros, which it drains, and also receives intersegmental veins,
he mesonephros degenerates the cardinal vein gets smaller, and disappears
pletely in the abdomen. Its intersegmental tributaries have previously
. transferred to the supracardinal (periganglionic) system. Changes in the
ax will be dealt with later.
 
die subcardinal is an accessory channel in the inner part of the mesonephros,
extent corresponds with this body, and it joins the main cardinal at its
smities. It is connected with this vein by a venous plexus throughout its
se, and also secondarily with the supracardinal system and its derivatives;
of these last is the left renal vein in front of the aorta, which in this way
mes practically an intersubcardinal connection.
 
rhe supracardinal system is not developed so completely in man as in most
le other mammals; its early state constitutes a ‘ periganglionic ’ system, but
term, it must be understood, is only a descriptive word applicable to the human
yo, and indicates its supracardinal arrangements. The veins of this system
lorsal to those described above, with which they are connected by free
.tomosis. They take over secondarily the intersegmental drainage, allowing
posterior cardinals to disappear, and they develop a longitudinal drainageel of their own, so that their contained blood is not (or is only in part) carried
the subcardinal; at the upper end, however, this longitudinal vessel opens
the subcardinal, as will be seen when treating of the thoracic vessels,
rhe compound systems of cardinal veins, as shortly described above, are
metrically placed on the right and left sides, in the abdominal and (future)
acic parts of the embryo. The development of the suprarenal glands, of
liver, and of the diaphragmatic structures altogether breaks the continuity
le systems, which can now be said to have thoracic and abdominal developts only indirectly connected. The abdominal development is concerned
he formation of the inferior vena cava and its associated vessels, while the
*os and left superior intercostal systems are produced from the thoracic
dopments; these vessels, therefore, can be considered at once.
 
 
Development of the Inferior Vena Cava.
 
The inferior vena cava, as regards its development, consists of two divisions
>wer or postrenal, and upper or prerenal.
 
These descriptive names are given to the two parts because it is at the
level of the left renal vein, which has been seen to be practically intersubcardinal, that the developmental values of the parts of the vein .change ;
the ‘ renal' term, therefore, applies to the venous level, and not necessarily
to the kidney itself.
 
Below the level of the left renal vein, the inferior vena cava is formed from the
it longitudinal vessel of the supracardinal system, which receives the intermental (lower lumbar) veins of the right side; a similar formation is found
■he left side. The posterior cardinals disappear when the intersegmental veins
their terminations, and the subcardinals also atrophy, as the mesonephros
ins to move down, only retaining the drainage of the gonad at this level;
s the supracardinal alone is left to carry on the drainage of the body-wall,
Further changes usually occur on the left side, where the longitudinal vessel
supplanted by a deeper longitudinal channel connecting the intersegmental
 
 
 
H34
 
 
A MANUAL OF ANATOMY
 
 
veins on the transverse processes, deep to the psoas. Thus the more superb
vessel disappears; but it occasionally persists as a left inferior vena cava, extend
up to the left renal vein (see Fig. 684).
 
Sometimes the retro-aortic anastomosis, which is a feature of the suf
cardinal system in other forms, may make a partial appearance in the hun
individual, when one or more lower left lumbar veins will pass behind
aorta to empty into the inferior vena cava.
 
Above the level of the left renal vein the subcardinals on each side lie in fr
of the suprarenal glands, round the outer sides of which the posterior cardii
course cranially. Before long the right subcardinal establishes a commumcat
 
 
 
Fig. 683.— Cardinal and Subcardinal Veins, etc.
 
(Frederick T. Lewis, in the American Journal of Anatomy.)
 
with the veins (hepatic) emerging from the dorsal aspect of the liver; this C(
munication is situated in the right-hand part of the common dorsal mesentf
This junction, enlarging steadily, provides a new and direct channel by which
blood in the right subcardinal can reach the heart, and the left renal, ahead)
position, affords a means by which that from the left subcardinal can '
advantage also of the new channel. Thus the prerenal portion of the inte.
vena cava is of subcardinal origin from the entrance of the left renal vein to
relation with the suprarenal gland, where it receives the suprarenal vein.. Ab
this it is formed by the hepatic anastomosis and the common hepatic vein, wi
 
The supracardinal system-which empties itself fundamentally (w.
possible) into the subcardinal—forms the lower part of the main vein, but as s
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
ii35
 
 
ssible— i.e., where the subcardinal persists—opens into it. Thus the cony of the great vein is effected.
 
le kidneys, growing cranially, lie among the veins of the supracardinal
n, and drain into them. Thus the right renal vein is altogether supra ml in value, and joins the longitudinal supracardinal vessel as this reaches
bcardinal ending, thus a very little below the level of the left vein. The
snal vein, at its renal end, is of the same value as the whole of the right vein,
:s transaortic portion is not represented on the right side; it passes through
 
 
 
Fig. 684. —Schemes to show 1 Formation of Inferior Vena Cava.
 
 
ardinals (Sub) are plain; supracardinals (Sup) black; posterior cardinals
are not shown, as they are not concerned in the formation.
 
In A the supracardinal system is establishing its longitudinal vessel on
?ach side, and so communicates with subcardinal. Subcardinals pass
aeyond suprarenals (dotted ovals) and there is no connection with the
aepatic veins (H). They are joined by a transaortic (dotted) junction, and
receive veins (G, G) from the gonads.
 
In B the supracardinal no longer communicates with subcardinal, except
it R; here the renal vein is placed on each side. Subcardinals accordingly
iegenerate below entrance of gonad veins. Right subcardinal has now
diected a junction with hepatic veins behind liver.
 
In C any upper continuation of subcardinal above suprarenal is cut off
3 y diaphragm. Final values of parts of I.V.C. are apparent. The ascending
supracardinal (X) on left is replaced by the deeper (Y). The junctional part
)f left common iliac is an intersupracardinal (periganglionic) formation.
 
 
tion of the subcardinal, where this remnant exists to receive the left supraand left spermatic or ovarian veins.
 
he right and left veins of the gonad drain from the beginning into the
'rdinals, and thus, in the adult, reach the renal level because there is no
ordinal remaining below this.
 
he left suprarenal vein is probably a remnant of the left subcardinal, correcting with the part of the vena cava formed by the subcardinal above the
level; the current of blood in it, however, is reversed.
 
he posterior cardinal vein, having lost its intersegmental branches, disappears
the abdomen by the middle of the second month, having taken no part in
'rrnation of the inferior vena cava.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1136
 
 
A MANUAL OF ANATOMY
 
 
Thoracic Cardinal Formations.
 
The prolongation of the three cardinal systems into the thorax from
abdomen is interrupted first by the rapid enlargement of the suprarenal gla
This particularly affects the subcardinals, but these glands still, for a little i
discharge some of their blood by small veins into the thoracic parts of the
cardinals; soon, however, the extension of the diaphragm, over and be
them, cuts them off finally from this way of discharge and leaves them onl)
abdominal subcardinals for drainage.
 
The terminal piece of the posterior cardinal remains on both sides,
persisting portion is the part above the entrance of the subcardinal, exten
 
 
 
 
Fig. 685.— Schemes of Cardinal Systems in the Thorax.
 
On each side upper part of posterior cardinal (PC) persists. Longituc
supracardinal (Sup), connected at first with subcardinal (Sub), only ret
ultimately its terminal opening into this; thus this extreme terminal f
of subcardinal persists, the rest of subcardinal and of postcardinal
appearing below this point. On left side the original symmetry is fur
broken up, and retro-aortic junctions cross to right supracardinal.
 
A is early condition, B the final state. VC, duct of Cuvier; PJ, primi
jugular or anterior cardinal.
 
from this to the duct of Cuvier. The extreme terminal bit of the subcard
also persists, joining the posterior cardinal; immediately below this tern
section the longitudinal supracardinal vessel joins the subcardinal, and the
of the subcardinal disappears. This junction of the two veins corresponds r
or less with the entrance of the sixth thoracic intersegmental vein into the
of the supracardinal longitudinal vein. These details will be followed r
easily, perhaps, with the aid of the diagrams in Fig. 685.
 
On the right the azygos vein is formed, below the sixth intercostal level, 1
supracardinal elements; at this level a very short ring of subcardinal come
and above this it is persistent posterior cardinal.
 
On the left the conditions are at first symmetrical and similar, but as the
innominate vein forms and the intersupracardinal junctions appear behind
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
ii37
 
 
, the system is broken in variable ways. The termination of the posterior
tal is in the left superior intercostal vein, but the terminal piece of this is
true jugular (anterior cardinal). The lower hemiazygos is always supralal.
 
Development of the Lymphatic System.
 
ie lymphatic system consists of lymphatic vessels and lymphatic glands
des. There is also lymphoid or adenoid tissue, as in the thymus body,
tioid follicles and villi of the intestinal mucous membrane, lymphatic
es of the spleen, palatine tonsils, and pharyngeal tonsil. There are two
5 in the development of the lymphatic system—primary and secondary.
irimary stage is concerned in the formation of lymph-sacs, and the secondary
consists in the formation of lymphatic vessels and lymph-glands.
fmph-Sacs. —There are two pair of lymph-sacs and two single sacs, as
vs:
 
1. Jugular (2).
 
2. Retro-peritoneal (1).
 
3. Cisterna chyli (1).
 
4. Posterior (2).
 
pinions differ as to the development of these lymph-sacs. The view of
nee R. Sabin will be stated first. According to this lady the sacs are
oped as sproutings from the endothelial lining of veins, and this constitutes
rimary stage in the development of the lymphatic system,
lgular Sacs. —The jugular lymph-sacs, right and left, are the first to appear,
is situated on the outer side of the lower part of the primitive anterior
nal vein, which becomes the internal jugular vein. It is formed from part
capillary venous plexus, connected in early life with the anterior cardinal
A large part of this plexus disappears, whilst the connection of the
inder with the anterior cardinal vein is severed. There thus results a
died collection of capillaries, lined with endothelium and in close proximity
e outer side of the lower part of the anterior cardinal vein. These capillaries
ne dilated, and subsequently join to form the jugular lymph-sac of each side,
h is lined with endothelium, and which establishes a fresh connection with
ower part of the anterior cardinal vein, where it is joined by the subclavian
a valve being formed at the venous junction by a protrusion of part
ie lymph-sac at the place of junction. The jugular sac of each side is
ected externally with peripheral lymphatic vessels which extend to the
, neck, and fore-limb bud of the same side. The caudal end of the left sac
mes connected with the thoracic duct, whilst the caudal end of the right
becomes connected with the right lymphatic duct. The dorsal part of
sac becomes converted into a plexus of lymphatic vessels, from which
is of lymph-glands are developed.
 
tetro-peritoneal Sac. —The retro-peritoneal or pre-aortic lymph-sac is single,
is formed from a capillary venous plexus in the root of the mesentery, which
ns is connected with the great pre-aortic transverse anastomotic vessel which
nds between the two subcardinal veins. The capillary plexus in the root
tie mesentery becomes converted into a lymph-sac, without any venous
tection, and this constitutes the retro-peritoneal sac, which establishes a
munication with the cisterna chyli, and through it with the thoracic duct,
ultimately replaced by a plexus of lymphatic vessels, and from this plexus
ns of lymphatic glands are developed which lie along the ventral aspect of
abdominal aorta. From the retro-peritoneal sac lymphatic vessels pass
in the mesentery along the branches of the superior mesenteric artery, and
e form another lymphatic plexus, from which the mesenteric lymphatic
leal) glands are developed. Subsequently lymphatic (lacteal) vessels enter
wall of the small intestine.
 
’osterior Sacs. —The sciatic lymph-sacs, right and left, are developed from
llary venous plexuses in connection with the two primitive iliac veins. On
 
72
 
 
A MANUAL OF ANATOMY
 
 
1138
 
either side the sac extends from near the caudal end of the cisterna chyli alo
the outer side of the primitive iliac vein. It ultimately becomes convert
into lymphatic glands.
 
Cisterna Chyli .—The cisterna or receptaculum chyli is a single sac, situat
at the caudal end of the thoracic duct. It is developed from, and replaces
venous plexus. The thoracic duct connects the cisterna chyli with the 1
jugular lymph-sac, and the cisterna chyli communicates with each poster
sac. From each jugular sac a vessel grows caudalwards. On the right si
this vessel constitutes the right lymphatic trunk, and on the left side it forms 1
thoracic duct. As the thoracic duct approaches the developing aortic arch
divides and gives rise to two thoracic ducts, which embrace that arch and th
pass to join separately the cisterna chyli opposite the mesonephroi. Subsequen
these two ducts fuse, and one duct is formed.
 
The thoracic duct is developed from a series of venous capillaries, origina
having a connection with veins.
 
Lymphatic Vessels. —The formation of these vessels, along with that
ymph-glands, constitutes the second stage in the development of the lympha
 
 
Afferent Lymphatics
 
 
 
Fig. 686.—Diagrammatic Section of Lymphatic Gland (Sharpey, fr
 
Quain).
 
system. According to Sabin, the lymphatic vessels are formed from the en
thelial lining of the lymph-sacs, whilst the lymph-glands are. developed ft
plexuses of lymphatic capillaries. The development of the thoracic duct, as stat
takes place from several groups of venous capillaries. It is the largest lympha
vessel, and it connects the cisterna chyli with the left jugular sac.
 
The lymphatics derived from the jugular lymph-sacs pass to the head, ne
and fore-limb buds; those from the posterior lymph sacs extend to the hi]
limb buds; and those from the retro-peritoneal (mesenteric) lymph-sac en
the mesentery, within which lymph-glands (mesenteric) are developed
connection with them. From these mesenteric glands, in succession, m
lymphatic vessels pass to the intestinal tube.
 
The other view of the development of the lymphatic system, held by Hu
ington amongst others, is that the connection of the lymphatic vessels with
venous system is secondary\ and not primary, as Sabin holds. According
this other view the lymphatic vessels spring from lymph-spaces, which are forn
in the mesoderm (mesenchyme), and are lined with mesothelium. The endothe
cells of the lymphatic vessels are derived from this mesothelium, and not fr
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEVELOPMENT OF VASCULAR SYSTEMS
 
 
ii39
 
 
lous endothelium, according to Sabin, and the vessels establish a connection
le venous system at a later period.
 
nph-Glands. —Some of these are formed in connection with the lymphdiilst others are formed in connection with peripheral lymphatic vessels,
are three stages in the development of a lymph-gland. The first stage
s in the formation of a plexus of lymphatic capillaries pervaded by con;-tissue septa. The second stage consists in the invasion of these septa
od-capillaries, surrounded by lymphocytes. The third stage consists in
mation of a lymph-sinus from the original plexus of lymphatic capillaries.
 
3 essential elements of a lymph-gland are thus threefold—namely: (1) a
of lymph-capillaries; (2) blood-capillaries, surrounded by lymphocytes,
connective-tissue septa; and (3) a lymph-sinus.
 
:h lymph-gland is connected with several lymphatic vessels. 1 hose which
;he gland are known as afferent vessels, and they open into the peripheral
deal part of the lymph-sinus. Those which emerge from the gland are
L efferent vessels, and they arise in the central or medullary part of the
-sinus. In no case does a lymphatic vessel pass uninterruptedly through
>h-gland. The gland is a station in the path of a lymphatic vessel, which
3nts the terminus of that vessel, but not the terminus of the lymph. That
after leaving the afferent vessel, flows in succession through the cortical
edullary parts of the lymph-sinus, and from the medullary part it flows
re efferent vessels. It is, therefore, so far as the lymph is concerned, a
f, so to speak, changing carriages at a glandular station. During this
s any injurious matter is taken up by the branched cells (phagocytes) of
nph-sinus, and the lymph is furnished with a contingent of lymphocytes.
 
Structure of Lymphatic Vessels.
 
lymphatic vessel, of large size, consists of three coats-—inner, middle,
iter. The internal coat {tunica intima) consists of a longitudinal network
stic fibres lined with endothelial cells. The middle coat {tunica media)
ts of plain muscular and elastic tissues disposed for the most part transy. The external coat {tunica externa) consists of (1) longitudinal bundles of
:tive tissue, and (2) plain muscular and elastic fibres, disposed for the
part longitudinally, lined with endothelium.
 
mphatic vessels are furnished with bloodvessels and nerves. Most ol
are also provided with valves, similar to those of the veins. Each valve
ts of two semilunar segments, facing one another, which are foldings of the
coat, containing connective and elastic tissues. They project slightly
ds each other, and their free edges are directed in the course of the lymfih1. The valves are situated at short intervals, and they serve to prevent
of lymph. When a lymphatic vessel becomes distended it presents a
d appearance, with constrictions between the projections, these constrictions
ponding to the attached margins of the valvular segments,
svelopment. —According to Sabin, the lymphatic vessels are developed from
Ldothelial lining of the primitive lymph-sacs (see Development of Lymphatic
m).
 
Structure of Lymphatic Glands.
 
lymphatic gland consists of a capsule, which encloses the glandular sube. The capsule is composed of connective tissue, containing elastic fibres.
:ie glandular substance presents two parts—superficial or cortical, and
al or medullary. Each of these parts is permeated by a supporting frarneof trabeculae derived from the capsule. Ihese trabeculae are composed o
active tissue, with a few plain muscular fibres. They subdivide the cortex
follicles, between which they form incomplete septa. In the medulla the
 
culae are arranged in a reticular manner. .. ,
 
be glandular substance is formed by lymphoid or adenoid tissue, wnic
sts of retiform tissue, with lymphocytes in its meshes. In the cortex o
 
 
1140
 
 
A MANUAL OF ANATOMY
 
 
the gland this lymphoid tissue is disposed as lymph-follicles, and in the m
it forms lymph-cords. In both parts of the gland there are spaces betwe<
glandular substance and the supporting trabecular framework. These s
which are for the passage of lymph, constitute the lymph-sinus. This si
broken up at all parts of the gland by retiform tissue, the meshes of whi
partially lined with branched cells of the nature of phagocytes. The glai
substance, except the lymph-sinus, is permeated by blood-capillaries.
 
Lymphatic glands are furnished with bloodvessels, nerves, and lym
vessels. The arterioles pass to the glandular substance, being at first enshe
by the supporting trabeculae of connective tissue, and subsequently by the re
tissue of the glandular substance. The nerves are destined for the plain mu
tissue of the trabeculae and bloodvessels.
 
The lymphatic vessels are of two kinds—afferent and efferent. The a
vessels enter the gland over its surface, whilst the efferent vessels emerge
definite part of the gland, where there is a slight depression, called the t
The afferent vessels convey lymph to the cortical part of the lymph-sinus,
the efferent vessels convey lymph from the medullary part of that sinus,
much as the medullary part of the gland extends quite to the surface at the
where the depression, known as the hilum, exists, the efferent vessels e
from the gland through this hilum, which also gives passage to the arterie
veins.
 
Development. —Lymphatic glands are developed partly from the prii
lymph-sacs and partly from peripheral lymphatic vessels (see Developm*
Lymphatic System).
 
 
CHAPTER XIV
 
THE HEAD AND NECK
 
 
BACK OF THE SCALP AND NECK.
 
andmarks. —The external occipital protuberance can, as a rule, be
: out readily enough in the male, and the superior nuchal line,
ill developed, may be felt extending outwards from it. The
oid process of the temporal bone can be distinguished without
ulty behind the auricle. The occipital artery, with the greater
iital nerve on its inner side, lies about inches to the outer side
e external occipital protuberance. The occipital lymphatic gland,
[ands, may be felt, when enlarged, over the upper part of the
izius or semispinalis capitis muscle. The spine of the seventh
cal vertebra, or vertebra prominens, can easily be felt, and that
le sixth may also be made out. Extending from the external
)ital protuberance to the seventh cervical spine there is an elonI depression, called the nuchal furrow, which indicates the position
tie ligamentum nuchse. It is possible to feel the strong bifid
3 of the axis by sinking the finger deeply into the upper part of
luchal furrow near the occipital bone, but the spines of the third,
Hi, and fifth cervical vertebrae lie too deeply for detection. Lymic glands may be felt, when enlarged, along the posterior border
le sterno-mastoid muscle.
 
Jack and Side of the Neck—Fasciae. —The superhcial fascia presents
ing worthy of note. The deep fascia closely invests the cervical
ion of the trapezius, and is then prolonged over the posterior
lgle of the neck to the posterior border of the sterno-mastoid,
re it divides to ensheathe that muscle. It will be described in
lection with the deep cervical fascia.
 
Jutaneous Nerves. —The nerves of this region are as follows: the
)Ccipital; the greater occipital; the third occipital; the medial
iches of the posterior primary rami of the third, fourth, and fifth
ical spinal nerves; the lesser occipital; the great auricular; the
rior cutaneous nerve of neck; and the descending superficial
iches of the cervical plexus—namely, the supraclavicular nerves
Fig. 687).
 
Die suboccipital nerve is the posterior primary ramus of the first
ical nerve; it only occasionally supplies the skin on the outer
of the greater occipital area.
 
Fhe greater occipital nerve is the medial branch of the posterior
lary ramus of the second cervical nerve. It pierces the upper
 
1141
 
 
 
1142
 
 
A MANUAL OF ANATOMY
 
 
part of the semispinalis capitis muscle, and sometimes the trape2
about -J inch from the middle line. It then runs upwards, with
inclination outwards, and accompanies the occipital artery to the era
integument, lying on the inner side of that vessel. Its branches
long, and have an extensive distribution, reaching as far as the vei
of the skull. Laterally it communicates with the small occif
nerve, and medially with the third occipital.
 
The third occipital nerve is a small offset from the me
branch of the posterior primary ramus of the third cervical ne
Having pierced the trapezius, it ascends medial to the gre;
occipital nerve, with which it communicates, and has a lim
distribution to the occipital integument inside that nerve.
 
The medial bran<
of the posterior prin
rami of the third, fou
and fifth cervical ne;
appear through
trapezius close to
middle line, and t
outwards to supply
skin of the back of
neck, that of the tl
furnishing, as j
stated, the third c
pital nerve.
 
The lesser occij
nerve is one of the
cending superfw
branches of the cerv
plexus, and arises fi
the anterior prim
ramus of the sec
cervical nerve, so
times receiving a bra
from that of the third. It appears at the posterior border of the stei
mastoid muscle, and ascends along that border to the occipital reg
Here it divides into mastoid and occipital branches, which supply
skin of the mastoid, outer part of the occipital, and adjacent porl
of the parietal regions. It furnishes an auricular branch to the 5
of the upper part of the inner surface of the auricle, and it commi
cates with the greater occipital, the posterior branch of the gi
auricular, and the posterior auricular branch of the facial,
lesser occipital nerve is sometimes double, and in these cases one port
of it usually pierces the anterior border of the trapezius.
 
The great auricular nerve, like the lesser occipital, is one of
ascending superficial branches of the cervical plexus, and arises
two roots from the anterior primary rami of the second and tl
cervical nerves. It turns round the posterior border of the stei
 
 
 
Occ. Front.
 
G. Occ. N.
Third Occ. N.
Less. Occ. N.
 
 
Fig. 687.—To show the Nerves and Vessels
on the Back of Scalp and Neck.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND-NECK
 
 
ii 43
 
 
istoid immediately below the lesser occipital nerve, and passes
wards and forwards upon that muscle towards the lobule of the
ricle, on approaching which it divides into anterior and posterior
anches. The posterior branch is distributed to the skin over the
istoid region, the skin of the inner surface of the auricle, and sends
e or two twigs through the cartilage of the auricle to the skin covery the lower part of the outer surface; and the anterior branch is dis
 
Auricularis Anterior
 
 
Auricularis Superior
 
 
Auricularis Posterior
 
 
Occipital Belly of
Occipito-frontalis
 
Greater Occipital Nerve
Semispinalis Capitis
Lesser Occipital Nerve
 
Splenius Capitis
 
 
Levator Scapulae
 
Great Auricular Nerve
 
Accessory Nerv e
anches from Third and Fourth
Cervical Nerves to Trapezius
Scalenus Medius
 
 
Lateral Supraclavicular
Nerve
 
 
Trapezius
 
 
 
' Frontal Belly of Occipitofrontalis
 
 
Orbicularis Oculi
 
Levator Labii
Superioris Alaeque Nasi
 
Levator Labii Superioris
- Zygomaticus Minor
Zygomaticus Major
 
Masseter
Orbicularis Oris
Depressor Labii Inferioris
_ Depressor Anguli Oris
Mentalis
 
Anterior Belly of Digastric
Stemo-hyoid
 
Superior Belly of Omo-hyoid
Sterno-mastoid
 
Anterior Cutaneous Nerve of the
Neck
 
— Medial Supraclavicular Nerve
 
— Intermediate Supraclavicular Nerve
 
 
Scalenus Anterior
 
»
 
Inferior Belly of Omo-hyoid Subclavian Artery (third part)
 
Fig. 688.—The Right Side of the Head and Neck.
The platysma has been removed, and the nerves are shown.
 
 
ibuted to the skin over the parotid gland and angle of the jaw. The
)sterior branch communicates with the lesser occipital and posterior
lricular nerves, and the anterior branch communicates in the parotid
and with the facial nerve.
 
The anterior cutaneous nerve of the neck (transverse cervical
irve), like the lesser occipital and great auricular, is a superficial
'anch of the cervical plexus, and arises by two roots from the anterioi
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
ii 4 4
 
 
A MANUAL OF ANATOMY
 
 
primary rami of the second and third or third and fourth cervic
nerves. It appears at the posterior border of the sterno-mastc
close below the great auricular, and turns over that muscle deep
the external jugular vein to reach the front of the neck, where it w
be afterwards described.
 
The supraclavicular nerves from the cervical plexus appear at t
posterior border of the sterno-mastoid below the accessory, usua]
as a single trunk which arises by two roots from the anterior prima
rami of the third and fourth cervical nerves or from the fourth alor
This trunk, as it descends, divides into three branches—name]
medial, intermediate, and lateral —which pass downwards over t
clavicle, and will be afterwards referred to.
 
Deeper Structures.
 
Ligamentum Nuchse. —This is a strong fibrous band which occupi
the median line of the neck. Its superficial fibres are attached superior
to the external occipital protuberance, and interiorly to the spi
of the seventh cervical vertebra. Its deep fibres are attached
the external occipital crest, and to the spines of cervical vertebr
from the second to the sixth inclusive. They also extend into t
interspinous intervals between the interspinales muscles, where th
represent interspinous ligaments.
 
Muscles—Cervical Portion of the Trapezius — Origin. —fi) T
inner third of the superior nuchal line of the occipital bone, and t]
external occipital protuberance; and (2) the ligamentum nuchse.
 
Insertion. —(1) The posterior border of the outer third of ti
clavicle; and (2) the inner border of the acromion process of t]
scapula.
 
Nerve-supply. — (1) The accessory nerve (spinal root); ai
(2) branches from the cervical plexus, which are derived from t]
anterior primary rami of the third and fourth cervical nerves. T]
nerves enter the deep surface of the muscle after passing benea
its anterior border a little above the clavicle, and they here for
a plexiform communication with each other.
 
Blood-supply .—The superficial branch (superficial cervical arter
of the transverse cervical artery ramifies on and gives branches
the deep surface of the muscle.
 
The fibres are directed downwards, forwards, and outwards.
 
This part of the muscle lies on the semispinalis capitis just belo
the occiput, and below this on the splenius and levator scapuke; tl
superficial branch of the transverse cervical artery and superfici
branch of the ramus descendens (arteria princeps cervicis) of tl
occipital artery anastomose deep to it, and its nerves enter it. As
approaches its insertion its fibres lie over the supraspinatus, a fati
pad being interposed.
 
Action .—The cervical fibres, acting from their origin, elevate tl
outer end of the clavicle and the point of the shoulder. Acting froi
 
 
 
Fig. 689. —Dissection to show Muscles on Back of Neck.
 
Insertion and Posterior Border of the Sterno-mastoid.—This muscle
nserted into (1) the outer surface of the mastoid process of the
poral bone, and (2) the superior nuchal line of the occipital bone
r about its outer half, or more. The posterior border of the
$cle forms the anterior boundary of the posterior triangle of the
k, and has the following nerves related to it: (1) the lesser occipital
snds along it to the head; (2) the great auricular passes upwards
 
 
THE HEAD AND NECK
 
 
1145
 
 
r insertion they extend the head, and incline the neck towards
same side, the face being directed towards the opposite side.
 
The anterior border of the muscle forms the posterior boundary
he posterior triangle of the neck.
 
)ccasionally a small muscle, called the transversus nuchse, is met with,
nding from the external occipital protuberance to the tendon of insertion
le sterno-mastoid. It may be fleshy or tendinous.
 
 
Cut. Muscles
Longiss. Cap.
Semispin. Cap.
 
 
Splenius Cerv.
Levator Scap.
 
 
Semisp. Cap.
Sterno-mastoid
Splenius Cap.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1146
 
 
A MANUAL OF ANATOMY
 
 
and forwards superficial to it towards the lobule of the auricle; (3)
anterior cutaneous nerve of the neck crosses it in a forward directi
(4) the accessory appears from behind it, along with the branc
of the third and fourth cervical nerves to the trapezius; and (5)
supraclavicular branches of the cervical plexus emerge from unt
neath it.
 
Some deep cervical lymph glands are situated along the poste
border of the sterno-mastoid muscle. They will be described h
(see p. 1199).
 
The levator scapulae, rhomboids, serratus posticus super
splenius, semispinalis capitis, longissimus cervicis, longissimus cap:
semispinalis cervicis, intertransversales, and interspinales muscles
be found described in connection with the muscles of the back 1
p. 400 et seq.).
 
Second and Third Parts of the Occipital Artery. —At the mast
process this vessel lies very deeply. Having crossed the rectus cap
lateralis muscle, it enters the occipital groove on the inner aspeci
the mastoid process, where it is covered by the following structu
in order from the surface inwards: (1) sterno-mastoid; (2) spier
capitis; (3) longissimus capitis; (4) mastoid process; and (5)
posterior belly of the digastric. In its backward course the ve
rests in succession upon the insertions of the obliquus capitis supe
and semispinalis capitis, and it escapes from beneath the musi
covering it in the following order: posterior belly of the digast
longissimus capitis, splenius capitis, and sterno-mastoid. A
emerging from beneath the last-named muscle, it lies for a little
the posterior angle close to the apex, and then, frequently pierc
the occipital origin of the trapezius, it enters upon the third pari
its course. This part ascends along with the greater occipital ne
to the occipital region, where it divides into several long tortu
branches (Figs. 690 and 691).
 
Branches. —The branches of the second and third parts are
follows: mastoid, meningeal, descending, communicating, muscu
and occipital. The mastoid branch passes through the mast
foramen when there is one on the outer surface of the mastoid proc
and supplies the diploe and mastoid air-cells, as well as the adjac
dura mater. The meningeal branches enter the cranial cavity throi
the jugular foramen, and take part in the supply of the dura me
of the posterior fossa. The descending branch (arteria princeps cervi<
arises under cover of the splenius capitis, and at the outer bor
of the semispinalis capitis it divides into a superficial and deep brar
The superficial branch is distributed to the splenius capitis and trapez
and anastomoses in the latter muscle with the superficial brand
the transverse cervical artery. The deep branch passes deep to
semispinalis capitis, and anastomoses upon the semispinalis cerv.
with (1) the deep cervical artery, a branch of the costo-cervical tm
and (2) branches of the vertebral artery. The communicating branc
enter the suboccipital triangle, where they anastomose with branc
 
 
 
THE HEAD AND NECK
 
 
1147
 
 
the vertebral artery. The muscular branches supply the contiguous
iscles. The occipital branches, which are the terminal branches,
; at first two in number, but these soon divide into several long
tuous branches, which supply the occipital belly of the occipitontalis and the integument as high as the vertex. They anastomose
 
 
 
g. 690. — To show Course of Occipital Artery (OA) as a Dotted Line on
 
the Under Side of Skull.
 
passes deep to mastoid process and muscles attached to this (digastric, longissimus capitis, sterno-mastoid, and splenius). It is lateral to rectus lateralis
(RL), rectus major (R.Mj), superior oblique (SO), and semispinalis capitis
(SSC). It emerges between splenius and trapezius (T).
 
th one another, with the posterior auricular, the posterior branch
the superficial temporal, and their fellows of the opposite side.
 
The occipital venous plexus communicates with the posterior
iricular and the posterior branch of the superficial temporal veins,
receives the parietal emissary vein, which emerges through the
 
 
 
 
 
 
 
 
1148
 
 
A MANUAL OF ANATOMY
 
 
parietal foramen, and so a communication is established with t]
superior sagittal sinus; a communication is also formed with tl
sigmoid sinus by means of the mastoid emissary vein through tl
mastoid foramen. Sometimes it receives a small occipital emissa\
vein which emerges through an opening at the external occipit
protuberance, and then a communication would be established wii
the confluence of the sinuses.
 
Two or three occipital veins leave the occipital plexus. Tl
external vessel is known as the posterior external jugular vein. Havii
 
been reinforced by tributaries from the superficial structures at tl
upper part of the back of the neck, the posterior external jugular ve
passes on to the sterno-mastoid, where it opens into the extern
jugular. The middle occipital vein (inconstant) accompanies tl
occipital artery, and usually opens into the internal jugular. Tl
internal occipital vein, having in some cases pierced the trapeziu
passes beneath the semispinalis capitis, and enters the suboccipit
triangle. In this situation it joins the suboccipital plexus, from whi(
the deep cervical and vertebral veins emerge.
 
Occipital Lymph Glands. —These glands are usually two in numbe
and he superficial to the occipital portion of the trapezius, or the upp
part of the semispinalis capitis. They receive their afferent lymphati
from the back part of the scalp, and their efferent lymphatics pass
the deep cervical glands.
 
Deep Cervical Artery. —This vessel is in most cases a branch of tl
costo-cervical trunk of the second part of the subclavian. Havii
passed backwards between the transverse process of the seveni
cervical vertebra and the neck of the first rib, it ascends upon tl
semispinalis cervicis, under cover of the semispinalis capitis, towar<
the level of the spine of the axis, where it anastomoses with the de(
branch of the ramus descendens of the occipital. In its course
furnishes a spinal branch, which enters the vertebral canal throu^
the intervertebral foramen for the eighth cervical nerve, and mu
cular branches, which anastomose with branches of the vertebr
artery.
 
The deep cervical vein begins within the suboccipital triangle
the suboccipital plexus, which receives the internal occipital vei
It descends in company with the deep cervical artery to the low'
part of the neck, where it passes forwards between the transver:
process of the seventh cervical vertebra and the neck of the first ri
and ends by joining the vertebral vein just before that vessel terminate
in the innominate vein.
 
In addition to the muscular branches of the occipital and dee
cervical arteries, the deep muscles of the back of the neck receh
twigs from the second part of the vertebral artery, which travers*
the foramina transversaria of the upper six cervical vertebrae. The:
twigs pass backwards through the intertransverse spaces, and anas!
mose with branches of the ramus descendens of the occipital artei
and the deep cervical artery.
 
 
 
 
THE HEAD AND NECK
 
 
1149
 
 
Suboccipital Region—Muscles—Rectus Capitis Posterior Major
 
Origin .—The ridge leading to one of the tubercles in which the
ne of the axis ends.
 
Insertion .—The outer part of the inferior nuchal line of the occipital
ne, and the subjacent area.
 
 
 
Nerve-supply .—The posterior primary ramus of the suboccipital
rve.
 
The direction of the fibres is upwards and outwards, in spite of its
ime.
 
Action. —(1) To rotate the face towards the same side; and (2) to
tend the head.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1150
 
The muscle is pyramidal, and its insertion is largely covered
the obliquus capitis superior.
 
Rectus Capitis Posterior Minor— Origin.— The posterior arch
the atlas close to the tubercle.
 
Insertion. —The inner third of the inferior nuchal line of the occipi
bone, and the subjacent area as low as the foramen magnum.
 
Nerve-supply .—The posterior primary ramus of the suboccipi
nerve.
 
The direction of the fibres is upwards in an expanded manner.
 
Action. —To extend the head.
 
The muscle is fan-shaped, and lies deeper than, and medial
the rectus capitis posterior major.
 
Obliquus Capitis Inferior — Origin.- —The outer and upper aspect
the spine of the axis.
 
Insertion. —The lower surface of the transveise process of the at
at its back part.
 
Nerve-supply. —The posterior primary ramus of the suboccipi
nerve.
 
The direction of the fibres is outwards and slightfy upwards.
 
Action .—To rotate the atlas along with the head, so that the fa
looks towards the same side.
 
The muscle is thick and fleshy. At its origin it is interpos
between the rectus capitis posterior major superiorly and the high
bundle of the semispinalis cervicis interiorly. The greater occipi
nerve winds round its lower border.
 
Obliquus Capitis Superior — Origin. —The upper surface of the trai
verse process of the atlas at its back part.
 
Insertion .—The occipital bone between the outer parts of i
superior and inferior nuchal lines.
 
Nerve-supply. —The posterior primary ramus of the suboccipi
nerve.
 
The direction of the fibres is upwards and very slightly inwards.
 
Action .—(1) To extend the head, and (2) to act as a slight late
flexor of the head.
 
The muscle is triangular.
 
Suboccipital Triangle. —This triangle is situated under cover of 1
upper part of the semispinalis capitis close below the occipital bone.
 
Boundaries — Supero-medial. —The rectus capitis posterior maj
External. —The obliquus capitis superior. Inferior. —The obliqi
capitis inferior. The roof is formed by the semispinalis capitis a
longissimus capitis, and the floor by half of the posterior arch
the atlas and half of the posterior atlanto-occipital membrane. *
contents are (1) the third part of the vertebral artery, (2) the si
occipital plexus of veins, and (3) the posterior primary ramus of
first cervical nerve. The greater occipital nerve turns upwards rou
the inferior oblique and crosses the inner part of the triangle deep
the semispinalis capitis, and the deep division of the ramus descend*
of tde occipital artery runs down near this.
 
 
 
THE HEAD AND NECK
 
 
1151
 
 
lird Part of the Vertebral Artery. —The vertebral artery, having
i through the foramen transversarium of the atlas, enters upon
bird part of its course, and takes a winding course backwards
 
 
Recti Capitis Posteriores Minores
 
 
Rectus Capitis Posterior
Major
 
 
Tubercle on Posterior
Arch of Atlas
 
 
Spine of Axis-
 
Interspinales
 
 
 
,Suboccipital Triangle
 
 
Obliquus Capitis
Superior
 
 
’-.Mastoid Process
 
 
Vertebral Artery
(Third Part)
 
Posterior Primary Ramus
of Suboccipital Nerve
' Transverse Process of
-- Atlas
 
'''* Obliquus Capitis Inferior
Greater Occipital Nerve
 
 
Semispinalis Cervicis (upper
two bundles)
 
 
Fig. 692.—The Suboccipital Triangle.
 
 
inwards. It lies in the vertebrarterial groove of the atlas, the
;rior primary ramus of the first cervical nerve being beneath it,
it passes under an arched band of the posterior atlanto-occipital
 
 
 
693.—Atlas seen from Above, to show Position of Vertebral Artery
 
and Suboccipital Nerve.
 
hrane, which is sometimes ossified. It thus leaves the suboccipital
igle, pierces the dura mater, and enters the cranial cavity through
oramen magnum. The third part of the vessel furnishes muscular
 
 
 
 
 
 
 
 
 
 
1152
 
 
A MANUAL OF ANATOMY
 
 
branches to the adjacent muscles, which anastomose with the rai
descendens of the occipital and the deep cervical of the costo-cerv
trunk.
 
Suboccipital Plexus of Veins. —This plexus is formed by bram
which proceed from (i) the vertebral venous plexuses, (2) the adjat
muscles, and (3) the occipital periosteum. It receives the inte:
occipital vein, and the blood is conveyed away from it by the d
cervical vein, already described, and the vertebral vein, which wil
afterwards considered.
 
Posterior Primary Division of the First Cervical or Suboccii
Nerve. —This division passes backwards as a single nerve in the ve
brarterial groove of the atlas, lying between the bone and the tl
part of the vertebral artery. On entering the suboccipital triangl
divides into branches which supply the obliqui, recti posteriores,
semispinalis capitis muscles. A filament joins the greater occip
nerve.
 
Posterior Primary Rami of the Cervical Spinal Nerves.—
 
cervical nerves are eight in number, the first being known as the s
occipital nerve. Each breaks up into an anterior and a poste
primary ramus. The posterior primary ramus of the first or s
occipital is single, and has just been described. The posterior prim
rami of the lower six arise in the intervertebral foramina, and e
soon divides into a lateral and medial branch. The upper two cerv
nerves make their exit behind the articular masses, and their poste
primary rami cross the vertebral arches behind these; the second div:
into medial and lateral branches. The lateral branches of all are
tributed to the deep muscles, and do not become cutaneous.
medial branch of the posterior primary ramus of the second, whic
of large size, constitutes the greater occipital nerve. It winds nr
the lower border of the obliquus capitis inferior, and pierces
semispinalis capitis, to which it gives branches. Later it r
pierce the trapezius to reach its cutaneous distribution, which
been already described. The medial branches of the third, fou:
and fifth are directed inwards superficially to the semispin
cervicis, to which, as well as to the semispinalis capitis, they {
branches. Close to the cervical spines they pass backwards me^
to the spinalis capitis (biventer cervicis), and, having pierced
splenius and trapezius, they reach the integument, which they sup]
The medial branch of the posterior primary ramus of the third, be]
piercing the trapezius, gives off a small ascending branch, knowr
the third occipital. It passes upwards, lying at first under cove:
the trapezius, and then passing through it to reach the occipital inte
ment. The medial branches of the posterior primary rami of
sixth, seventh, and eighth are directed inwards towards the cerv
spines beneath the semispinalis cervicis, and are distributed to
adjacent muscles. They do not furnish any branches to the inte
ment.
 
 
 
 
THE HEAD AND NECK
 
 
ii53
 
 
The Scalp and Temporal Region.
 
ascise. —The place of the deep fascia beneath the skin may be
to be taken by the epicranial aponeurosis of the occipito-frontalis
:le. The aponeurosis becomes thin and fascial over the temporal
ns. Where it is thick and aponeurotic it is firmly attached to
overlying skin by fibrous processes, between which are small
r lobules, so that the subcutaneous laver is firm and somewhat
ular in appearance. The vessels and nerves are distributed in this
*, which loses its fibrous nature in the temporal regions and becomes
lerficial soft fatty layer.
 
uperficial Nerves and Vessels. —The superficial nerves of the
ero-lateral aspect; the greater, small, and third occipital nerves;
the mastoid branch of the great auricular , have been described
idy. In the fronto-parietal region two sensory nerves are met
—namely, the supra-orbital and supratrochlear —both of which
lerived from the frontal nerve, which is one of the branches of the
:halmic division of the fifth cranial nerve. In the temporal region
the temporal branches of the facial nerve , the auriculo-temporal
 
 
 
1 n
 
u 6
Uf.
*Y «r
 
 
Skull
 
 
Fig. 694.—Diagram of Section through Scalp.
 
 
e, and the zygomatico-temporal nerve. Of the arteries of the
p, the third part of the occipital artery, in the posterior region, has
1 described. Those of the fronto-parietal region are three in
ber—namely, the supra-orbital , supratrochlear , and anterior branch
he superficial temporal. The superficial temporal artery ramifies
he side of the head in the temporal region.
 
Qie supra-orbital nerve, which is of large size, leaves the orbit
•ugh the supra-orbital foramen. It then ascends, lying at first
) to the upper part of the orbicularis oculi and the frontal belly
he occipito-frontalis muscle, but subsequently piercing the latter
cle in two branches, medial and lateral. The lateral branch is the
er of the two, and its offsets extend as far back as the lambdoid
ire. As the supra-orbital nerve passes through the supra-orbital
'h it furnishes one or two twigs to the mucous membrane of the
tal sinus and to the diploe of the frontal bone, and after leaving
notch it sends downwards branches to the integument of the upper
id. After this the nerve supplies the integument of the frontoetal region.
 
rhe medial and lateral branches of the supra-orbital nerves sometimes leave
orbit separately, and each may form a notch or foramen of its own.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1154
 
The supratrochlear nerve, which is of small size, is medial to
supra-orbital nerve. It leaves the orbit close to the medial angi
process of the frontal bone, where it lies above the pulley of the s-upe
oblique muscle of the eyeball. It then ascends deep to the upper j
of the orbicularis oculi and the frontal belly of the occipito-front
muscle, and, piercing the former muscle, it has a limited distribui
to the frontal integument close to the median line. As the nt
leaves the orbit it furnishes twigs to the inner part of the integurr
of the upper eyelid.
 
The supra-orbital artery is a branch of the ophthalmic, and emei
from the orbit with the supra-orbital nerve. It is distributed to
structures covering the frontal bone, and anastomoses with the su]
trochlear branch of the ophthalmic artery and the anterior brand
the superficial temporal artery. In the supra-orbital notch it fumis
one or two branches to the mucous membrane of the frontal sinus
to the diploe of the bone, and after leaving the notch it sends do
wards branches to the integument of the upper eyelid (Fig. 698).
 
The supra-orbital vein passes downwards and inwards to a p(
just above the medial angle of the orbit, where it joins the suj
trochlear vein. In this manner the angular vein is formed, whic
the commencement of the anterior facial vein. The supra-orbital ^
receives tributaries from the frontal region and the upper eyelid, ;
in the region of the medial angle of the orbit it communicates with
superior ophthalmic vein. It also communicates with the supe
ophthalmic vein through the supra-orbital notch, and this commun
tion receives the frontal diploic vein, which returns the blood from
diploe of the frontal bone and mucous membrane of the frontal sir
 
The supratrochlear artery (frontal artery), like the supra-orbita
a branch of the ophthalmic, and leaves the orbit with the supratroch.
nerve. It is distributed to the structures over the frontal bone me*
to the supra-orbital artery, with which it anastomoses, as well as v
its fellow of the opposite side.
 
The supratrochlear vein (frontal vein), of large size, passes do
wards near the median line, and at a point just above the medial ar
of the orbit is joined by the supra-orbital vein, the resultant ve
being the angular vein. At the root of the nose it communicates v
its fellow of the opposite side by a transverse vessel, called the m
arch.
 
The supra-orbital and supratrochlear veins communicate with e
other, and with the tributaries of the anterior branch of the superfi
temporal vein.
 
Occipito-frontalis. —This muscle consists of the following pa
(1) two occipital bellies, (2) two frontal bellies, and (3) the epicra
aponeurosis.
 
Each occipital belly arises from (1) the highest nuchal line of
occipital bone; and (2) the outer surface of the mastoid process of 1
temporal bone immediately above the insertion of the sterno-mas
muscle.
 
 
 
 
 
THE HEAD AND NECK
 
 
ii55
 
 
Insertion .—The epicranial aponeurosis.
 
Each belly forms a thin, broad sheet, the length of the fasciculi
Lg about ij inches. The two bellies, right and left, are separated
ards the median line by a portion of the epicranial aponeurosis,
ch here dips down between them.
 
Each frontal belly, right and left, is separated superiorly by a
row angular portion, of the epicranial aponeurosis, but interiorly
/ are in contact. Origin .—(1) The subcutaneous tissue of the
 
 
Fig. 695.—To show Occipital Belly of Occipito-frontalis.
 
)row and root of the nose, where the fibres blend with the upper
- of the orbicularis oculi and the corrugator supercilii; and (2) slightly
1 the zygomatic process of the frontal bone, and from the nasal
 
e.
 
Insertion ,—The epicranial aponeurosis a little below the level of
fronto-parietal suture.
 
Hie fasciculi are about 3^ inches long, and the innermost fibres
riorly are regarded by some as being prolonged downwards upon
nasal bone as the procerus muscle.
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1156
 
Epicranial Aponeurosis. —This is the intermediate tendon of
occipito-frontalis muscle. It forms an aponeurotic stratum ben<
the superficial fascia, and is connected firmly to the skin by fib
processes, which separate the subcutaneous tissue into lobules,
deep surface is loosely connected by areolar tissue to the subja*
periosteum. Posteriorly it gives insertion to the two occipital be
and in the interval between these it dips down to be attached to
inner part of the superior nuchal line of the occipital bone and
external occipital protuberance. Anteriorly it gives insertion to
two frontal bellies. Laterally, below the superior temporal :
it is prolonged downwards over the temporal fascia as a deh
 
 
 
Fig. 696. —Shows Frontal Portion of Occipito-frontalis.
 
expansion, which gives origin to the auricularis superior and auricul
anterior muscles. It is connected to the superior temporal line I
thickening of the loose areolar tissue between it and the bone.
 
Nerve-supply .—Each occipital belly is supplied by the poste
auricular branch of the facial nerve, and each frontal belly is supp
by the temporal branches of the facial nerve.
 
Action .—The two occipital bellies draw backwards the epicra
aponeurosis, and along with it the scalp. The two frontal bellies
from above, elevating the eyebrows, and throwing the skin of
frontal region into transverse wrinkles. When the occipital and fro'
bellies act simultaneously the scalp is drawn backwards, and
eyebrows are forcibly raised. In certain cases the frontal bellies 1
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
ii57
 
 
n the reverse direction, their lower attachment being fixed by other
muscles, such as the orbicularis oculi, corrugator supercilii, and
crus. When this is done the scalp may be alternately twitched
r ard and backward, a simian habit which may be acquired by
:tice.
 
Pericranium. —This is the periosteum of the cranium, and it is
sly connected by areolar tissue to the superjacent epicranial
leurosis.
 
 
Parotid Duct.
Buccinator Muscle_
 
Facial Artery
Submental Artery
 
Lingual Artery
Sup. Lar. Art. and Nerve
Thyro-hyoid Muscle
Superior Thyroid Artery
 
 
Inf. Belly of Omo-hyoid
 
Subclavian Artery
(third part)
 
 
 
Transverse Facial Artery
 
 
Superficial Temporal Artery
 
- Maxillary Artery
 
 
Posterior Auricular
Artery
---- Occipital Artery
 
 
-Stylo-hyoid Muscle
 
 
-Post. Belly of Digastric
 
-Hypoglossal Nerve
 
-Nervus Descendens
 
Cervicalis
External Carotid
Artery
 
 
Stemo-mastoid
— Trapezius
 
 
_Transverse Cervical Artery
 
-.Suprascapular
Artery
 
 
Fig. 697. —The Left Side of the Head and Neck.
The platysma has been removed.
 
 
The temporal branches of the facial nerve pass upwards a little in
tt of the auricle, and supply the following muscles: the frontal
Y of occipito-frontalis, upper part of the orbicularis oculi, corrusupercilii, auricularis superior and auricularis anterior. They
municate with the auriculo-temporal, zygomatico-temporal, and
'a-orbital nerves.
 
Hie auriculo-temporal nerve is a branch of the mandibular nerve,
'h is the third division of the fifth cranial nerve. It emerges just
nd the capsule of the mandibular joint, turns upwards round the
of the zygoma, and ascends immediately in front of the auricle in
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1158
 
company with the superficial temporal artery, lying between that, ves
and the auricle
 
Branches.—In this part of its course the nerve furnishes
following branches! (1) two branches to the external auditory meat
which enter the canal between its osseous and cartilaginous walls, a
supply the integument of the meatus, the upper of the two branc.
giving an offset to the tympanic membrane; (2) two auricular brand
which supply the skin of the tragus and outer aspect of the auri
over less than its upper half; and (3) superficial temporal brand
which supply the integument above and in front of the auricle, and
the temporal region generally.
 
The zygomatico-temporal nerve (temporal branch of temporo-ma
nerve) from the maxillary is of small size, and pierces the tempc
fascia about 1 inch above the anterior part of the zygoma, and cl
behind the frontal process of the zygomatic bone. Having cc
municated with one of the temporal branches of the facial nerve
has a limited distribution to the integument of the anterior part
the temporal region.
 
The superficial temporal artery is one of the terminal branches
the external carotid artery, from which it arises within the pare
gland on a level with the neck of the mandible. Leaving the gla
it ascends in front of the auricle in company with the auriculo-tempc
nerve, which lies between the vessel and the auricle, and after a cou
of about 2 inches it divides into its two terminal branches.
 
Branches.—These are as follows: (1) transverse facial; (2) articul
(3) auricular; (4) middle temporal; (5) zygomatic; and (6) termina
namely, anterior and posterior.
 
The transverse facial artery will be described in connection w
the face. It arises within the parotid gland, and in its course furnis
glandular branches. The articular branches supply the mandiby
joint. The auricular branches supply the outer aspect of the auri'
and in part the external auditory meatus. The middle tempc
artery pierces the temporal fascia immediately above the zygoma, c
then ascends in a groove on the outer surface of the squamous p
of the temporal bone deep to the temporalis. It gives branches to
temporalis, and anastomoses with the deep temporal branches of
maxillary artery. The zygomatic artery passes forwards close above
zygoma, where it lies between the two layers of the temporal fas<
It is distributed to the outer part of the orbicularis oculi muscle,
anterior branch passes forwards and upwards in a tortuous man:
and is distributed to the structures covering the frontal bone, wher
anastomoses with the supra-orbital and supratrochlear branches 0T
ophthalmic artery, and with its fellow of the opposite side,
posterior branch takes an arched course upwards and backwa
above the auricle, supplying the adjacent structures, and anas
mosing with the posterior auricular and occipital arteries, and v
its fellow of the opposite side (see Fig. 698).
 
The arteries of the scalp are peculiar in many ways. In the f
 
 
 
THE HEAD AND NECK
 
 
ii59
 
 
; they are very superficial, lying in the fatty layer of the scalp
deep to the skin; they are thus very liable to injury, and in old
le, where their walls are hardening and the superficial fat diminishthey may easily be seen in the temporal region,
n the second place they are very tortuous, a condition which is
lly associated with arteries supplying movable parts, and in
ige this tortuosity increases.
 
'hirdly, they not only anastomose with one another, as most
'ies do, but they anastomose freely across the middle line, thus
lg wonderful vitality to a piece of scalp which has been torn away
>st completely.
 
 
 
L. Testut’s ‘ Anatomie Humaine ’).
 
fourthly, when cut they bleed most profusely, because their walls
prevented from collapsing by the dense connective tissue between
skin and the epicranium in which they lie. For this reason, too,
difficult to pick them up when they have to be tied,
fhe superficial temporal vein is formed in front of the auricle by
union of an anterior and a posterior branch, the former communing freely with the supra-orbital and supratrochlear veins, and the
T with the posterior auricular vein and the occipital venous plexus,
ve the zygoma it is joined by the middle temporal vein, which
inates in a plexus in the temporal fossa, and pierces the temporalis
temporal fascia, receiving in its course the zygomatic vein. The
Official temporal vein then descends over the zygoma and enters
 
 
 
 
 
 
 
 
n6o
 
 
A MANUAL OF ANATOMY
 
 
the parotid gland, within which it receives the auricular, articu
and transverse facial veins. Finally, it joins the maxillary vein ah
the level of the neck of the mandible to form the posterior facial's
(temporo-maxillary vein).
 
Extrinsic Muscles of the Auricle.—These are three in number,
follows: (i) auricularis superior; (2) auricularis anterior; and (3) aur:
laris posterior.
 
Auricularis Superior (Attollens Aurem)— Origin. —The lateral par
the epicranial aponeurosis and temporal fascia.
 
Insertion. —The inner or cranial surface of the auricle over
convexity corresponding to the fossa of the antihelix on its 01
surface.
 
Nerve-supply. —The temporal branches of the facial nerve,
posterior part of the muscle may be supplied by the posterior aurici
branch of the facial nerve.
 
The muscle is very thin, pale, and fan-shaped, and. its fibres c
verge in a downward direction.
 
Action. —To raise the auricle, though all the auricular muscles
vestigial in man and practically functionless.
 
Auricularis Anterior (Attrahens Aurem)— Origin .—The lateral p
of the epicranial aponeurosis in front of the auricularis superior, v
which muscle it is continuous. Also from the temporal fascia.
 
Insertion. —The anterior part of the helix of the auricle.
 
Nerve-supply. —The temporal branches of the facial nerve.
 
The muscle is directed backwards.
 
Action. —To draw forwards the auricle.
 
Auricularis Posterior (Retrahens Aurem)— Origin. —The upper p
of the outer surface of the mastoid process of the temporal bone.
 
Insertion. —The inner or cranial surface of the auricle over
convexity of the concha.
 
Nerve-supply. —The posterior auricular branch of the facial nerv
 
The muscle is directed forwards.
 
Action. —To draw back the auricle.
 
The auricularis posterior is more distinct than the other two muse
and is usually arranged in two bundles.
 
Behind the ear, in the mastoid region, which is not a part of
scalp proper, there are certain structures which have some conned
with the scalp. These comprise posterior auricular nerves (branc
of the facial and vagus), posterior auricular vessels, and poste
auricular lymph glands.
 
Posterior Auricular Nerve.—This is a branch of the facial ne;
immediately after it emerges from the facial canal through the st;
mastoid foramen. It passes upwards between the mastoid pro<
and the auricle, where it lies deeply in company with the postej
auricular artery, and it divides into two branches—auricular ;
occipital. The auricular branch supplies the auricularis poste;
muscle on its deep aspect, and those intrinsic muscles of the aur
which lie on its inner or cranial aspect. It may also send a bra
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1161
 
 
yards beneath the auricularis posterior to supply the posterior
t of the auricularis superior. The occipital branch passes back■ds, lying deep to the lesser occipital nerve and posterior branch
the great auricular, and supplies the corresponding half of the
ipital belly of the occipito-frontalis muscle. The posterior auricular
ve communicates with the lesser occipital and great auricular
ves, and also with the auricular branch of the vagus.
 
The Auricular Branch of the Vagus Nerve (Nerve of Arnold). —This
t branch of superior ganglion of the nerve. Having traversed the
stoid canaliculus in the petrous part of the temporal bone, it
srges through the tympano-mastoid fissure between the mastoid
cess and tympanic plate, and then divides into two branches. One
nch takes part in the supply of the inner or cranial surface of the
icle, and also supplies the lower and back part of the external
litory meatus; and the other branch joins the posterior auricular
ve.
 
Posterior Auricular Artery. —This vessel is one of the two posterior
nches of the external carotid artery, the other branch being the
ipital artery. Having passed backwards and upwards on the
loid process under cover of the parotid gland, it lies deeply between
i mastoid process and the auricle in close relation to the posterior
icular nerve, and divides into two branches—auricular and occipital,
e auricular branch supplies the inner or cranial surface of the auricle
i adjacent structures, and it anastomoses with the posterior branch
the superficial temporal artery. The occipital branch passes backrds to the occipital belly of the occipito-frontalis muscle, and
istomoses with the occipital artery.
 
The posterior auricular vein is of fairly large size, and returns the
od from the lateral portion of the scalp posteriorly and the inner
face of the auricle. Its radicles communicate with the occipital
xus and with the posterior branch of the superficial temporal vein,
e vessel passes downwards and forwards over the upper part of the
rno-mastoid muscle, and terminates on this muscle about the level
the angle of the mandible by joining the posterior division of the
sterior facial vein to form the external jugular vein.
 
Mastoid Lymph Glands (Posterior Auricular Lymph Glands). These
all glands lie close to the insertion of the sterno-mastoid muscle,
ey receive their afferent lymphatics from the lateral part of the back
the scalp and the back of the auricle, and their efferent lymphatics
$s to the upper deep cervical lymph glands.
 
Temporal Fascia. —This is a strong aponeurosis which covers the
nporalis. Superiorly it is attached from before backwards to the
nporal border of the zygomatic bone, the superior temporal line of
i frontal and parietal bones, and the supramastoid crest. of the
nporal bone. Interiorly it divides into two laminae, which aie
ached to the outer and inner margins of the upper border of the
somatic arch. Between these two laminae there are a small amount
adipose tissue, and the zygomatic branch of the superficial temporal
 
 
1162
 
 
A MANUAL OF ANATOMY
 
 
artery, and the zygomatico-temporal nerve. Superficial to the fasc
there are the delicate prolongation of the lateral portion of the e]
cranial aponeurosis and the auriculares superior et anterior muscl<
with the superficial temporal vessels and auriculo-temporal nen
Superiorly the fascia gives origin by its deep surface to superfic:
fibres of the temporalis, but it is separated from that muscle towar
the zygoma by fat.
 
The temporalis muscle is described on p. 1302.
 
Lymphatic Vessels of the Scalp—Frontal Region. —These pass
the parotid lymph glands. The anterior lymphatics pass directly
the parotid lymph glands, and the posterior lymphatics terminate in t
mastoid lymph glands.
 
The Scalp as a Whole. —Before leaving the scalp it may be w<
to review its general structure and to notice that it is made up of fi
layers.
 
(1) The skin is very thick, and nee^6 a firm incision to penetrate:
 
(2) The subcutaneous tissue binds the skin closely to the epicrani
aponeurosis, with which it moves; it contains lobular, granulated f
in which are the bloodvessels and nerves as well as the roots of t.
hair follicles. On account of the presence of the nerves as well as of t.
density of the connective tissue any suppuration in this layer will
strictly localized and very painful.
 
(3) The epicranial aponeurosis is formed by the very thin, flatten
tendon of the occipito-frontalis muscle.
 
(4) The subaponeurotic layer, sometimes known to surgeons as t.
‘ dangerous layer * of the scalp, is composed of very loose connectf
tissue, and is little more than a lymph space. The looseness of tj
cellular tissue allows the first three layers to move freely over t]
skull, and if septic matter reaches it and suppuration follows, t]
pus readily spreads all over the space and tends to bag at the mo
dependent points in front and behind. The absence of nerves and tl
looseness of the tissue account for the little pain which accompani
suppuration in this layer.
 
(5) The periosteum or pericranium covers the skull bones, and
continuous with the dura mater at the sutures as long as these a
unclosed. For this reason a subpericranial collection of blood
pus will be limited to the area of one skull bone, while a subepicrani
collection, as has been seen, has no such definition.
 
Basal Part of the Cranial Cavity.
 
Dura Mater on the Base of the Skull. —A full and general accoui
of the membranes of the brain will be found on p. 1598 ^ se ^->
short description of the dura mater, as it is seen on the base of tl
skull after removal of the brain, will be given here.
 
The dura mater is seen to be continuous with the falx cerebri in t
middle line in front. Just outside this it covers the cribriform pla
of the ethmoid at the bottom of a well-marked hollow which contai
 
 
 
 
THE HEAD AND NECK
 
 
1163
 
olfactory bulb. External to this it covers the irregularities of the
tal plate of the frontal and the lesser wing of the sphenoid behind
. In the middle fossa it lines the so-called ‘ optic groove/ and at
 
I end of this is carried into the optic foramina. Behind the groove
>rms the diaphragma sella, covering the hypophyseal fossa, while
; pierced by the internal carotid artery just behind the foramen.
 
diaphragma sellae shows a central hole for the infundibulum of
hypophysis cerebri. The membrane is attached to the clinoid
:esses and the interclinoid ligaments, and stretches outwards from
;e to line the hollow of the greater wing and upper surfaces of the
•ous bone. It is carried upwards and forwards here to cover the
erior orbital fissure and gain the lower aspect of the lesser wing,
mall fold of dura mater projects from the edge of the lesser wing
he sphenoid, the sphenoidal fold , and a small ‘ lunula ’ overhangs
optic foramen. At the upper border of the petrous bone the
nbrane projects upwards and inwards as the tentorium cerebelli,
ch is a two-layered reflection of the dura mater. Below the
torium it lines the posterior fossa, and presents apertures through
ch all the nerves which come from the pons and medulla pass to
:h their bony foramina. A small fold, the falx cerebelli, projects
he middle line behind. The dura mater becomes continuous with
spinal dura at the foramen magnum, but the exact position of this
mien is not easily distinguished when the membrane is in position,
ng to the smooth, continuous slope formed by it as it passes from
basi-occiput over the odontoid process and its ligaments into the
tebral canal.
 
Certain structures lie deep to the dura mater, between it and the
y skull— i.e., between the inner layer, which we have been consider, and the outer layer, which covers the bones. These are venous
ises, nerves, and arteries. The venous sinuses on the base of the
 
II are (see p. 1603 et seq. for further details):
 
The sigmoid, running downwards and then forwards in the posterior
>a to reach the jugular foramen.
 
The inferior petrosal, passing forwards and upwards from the
ular foramen to the apex of the petrous bone along its lower edge.
The superior petrosal, running forward along the upper edge of the
rous bone at the base of the tentorium cerebelli.
 
The cavernous, placed on the side of the body of the sphenoid
ere this joins the greater wing, and formed by the junction of the
) petrosal sinuses; in front it is continuous with the superior ophImic vein and with the spheno-parietal sinus, which lies in the fold
lura mater along the lesser wing of the sphenoid.
 
The circular sinus is a spongy venous network which surrounds
: pituitary body and connects the two cavernous sinuses.
 
The transverse sinus lies under the central basal dura mater, and
n the form of a network joining the inferior petrosal sinuses.
 
The cranial nerves must necessarily pierce the dura mater to
ch and pass through the base of the skull, and the situations of the
 
 
1164
 
 
A MANUAL OF ANATOMY
 
 
points of passage through the membranous and bony parts do n
always correspond. Those nerves which leave the skull in relati(
with the greater wing of the sphenoid pass through the dura mat
at points some distance behind their bony foramina, and in the inte
vening parts of their courses lie deep to the inner layer of dura mate
lying near or in relation with the cavernous sinus. These nerv
 
 
Frontal Sinus
 
 
Anterior Fossa
 
 
Optic Nerve
Ophthalmic Artery
 
 
Oculo-motor Nerve / •
 
 
Trochlear Nerve
 
 
Region of Cavum
Trigeminale
 
Trigeminal Nerve
 
 
Facial Nerve
 
Auditory Nerve
 
G losso-pharyngeal
Nerve
 
Vagus Nerve
 
 
 
Posterior Border c
Small WingofSphi
 
 
Ant. Intercav., S:
Hypophysis C«
 
 
.-Cavernous S
-- Abducent N
 
 
;— Middle Foss
 
 
4 - - Basilar Plex
 
 
Sup. PetrosE
Sinus
 
Inf. Petrosa]
Sinus
 
 
" Sigmoid Sin
 
 
'•Cerebellar Fossa
 
 
Accessory Nerve
 
 
Transverse Sinus
 
 
Hypoglossal Nerve]
 
 
Cerebral Fossa
 
 
Spinal]Cord j Confluence of Sinuses
Occipital Sinus
 
 
Fig. 699. —The Internal Base of the Skull, showing the Cranial Nervi
 
and Venous Sinuses.
 
are the oculo-motor, trochlear, trigeminal, and abducent; the oth<
cranial nerves pierce the dura mater opposite their bony foramina.
 
It is not quite correct to say that the cranial nerves ‘ pierce ’ the dura mat
at the places where their apertures of exit are seen; they carry out with the
a covering from the membrane, so that they could be described rightly 1
evaginating it. The covering layer, however, is so thin in most cases, and
so soon lost in the ordinary fibrous sheath of the nerve, that little exceptk
is taken to the descriptive expression ‘ piercing.' In the case of the trigemin
nerve, however, the evaginated covering of dura mater is better marked, and '
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1165
 
:he whole, looser; it envelops the roots of the nerve and the trigeminal
jlion, and is known as the cavum trigeminale (.Meckel's cave). The cavum
jminale, therefore, lies between the dura and the skull. The optic nerve,
eover, should not be described as ‘ piercing ’ the membrane, for the eye and
lervous stalk are developmentally parts of the brain itself, and the dura
er is carried along the nerve to become directly continuous with the sclerotic
: of the eye, which represents the same layer.
 
Some other nerves, such as the superficial petrosals and the nasoiry in a part of its course, lie deep to the dura mater, and will be
bribed later.
 
All the meningeal vessels lie between skull and dura mater, and do
pierce the inner membranous layer. The only things which pass
Dugh this layer are the cranial nerves and the cerebral vessels;
$e last are represented by (a) the internal carotid, which, lying
irst between dura and bone with the cavernous sinus, pierces the
nbrane medial to the anterior clinoid process to reach the brain;
 
. ( b ) the vertebral arteries, which pierce the membrane below the
11 and run up through the foramen magnum to reach the brain,
tain cerebral veins pierce the dura mater at various points (see p.
8 ) to open into extradural sinuses.
 
Hie aqueduct of cochlea is described as passing through the dura to reach
subarachnoid space, and the endolymphatic duct lies between the membrane
the bone.
 
Cranial Nerves at the Base of the Skull. —The cranial nerves are
inged in twelve pairs, and as they leave the cranial cavity they
five sheaths from the meninges of the brain.
 
The olfactory bulb rests upon one half of the cribriform plate of
ethmoid bone, with dura mater interposed. Through the fora1a of that plate it receives about twenty olfactory filaments, which
;e as the axons of the olfactory cells of the olfactory mucous
[nbrane of the nasal fossa.
 
The optic nerve passes forwards and outwards from the optic
asma to the optic foramen, through which it enters the orbit. It
.ccompanied by the ophthalmic artery, which lies below and lateral
t. Before reaching the foramen it is crossed by the anterior cerebral
ery, and the internal carotid comes through the dura mater just
dnd and lateral to it.
 
The third or oculo-motor nerve pierces the dura mater, which
ns the upper and outer wall of the cavernous sinus, a little in front
the posterior clinoid process of the sphenoid bone.
 
The fourth or trochlear nerve, of small size, pierces the dura mater
a point a little behind the posterior clinoid process of the sphenoid
ie, lateral to the third nerve, and in or just beneath the free margin
the tentorium cerebelli. Afterwards it traverses the outer wall of
: cavernous sinus.
 
The fifth or trigeminal nerve consists of two roots—sensory and
tor. These two roots pierce the dura mater near the apex of the
rous part of the temporal bone below the tentorium, and enter
 
 
 
n66
 
 
A MANUAL OF ANATOMY
 
 
a'recess of the dura mater, called the cavurn ingeminate (Meckel's cav
where they will be presently described.
 
The sixth or abducent nerve pierces the dura mater £ inch behi
the level of the posterior clinoid process, and near the apex of t
petrous bone, where it enters the inferior petrosal sinus. It lies
little to the inner side of the fifth nerve.
 
The seventh or facial nerve, the eighth or auditory nerve, accoi
panied by the internal auditory artery, enter the internal meatus.
 
The ninth or glosso-pharyngeal nerve, the tenth or vagus ner
and the eleventh or accessory nerve pass through the middle compa:
 
 
 
Fig. 700.—Showing the Venous Sinuses on the Petrous Bone, and
 
Relation with the Trigeminal Nerve.
 
Also shows great superficial petrosal nerve.
 
ment of the jugular foramen. This foramen is divided into thi
compartments—namely, antero-medial, middle, and postero-later
The antero-medial compartment gives passage to the inferior petro.j
sinus. The middle compartment transmits the glosso-pharyngeal, vagi
and accessory nerves, in this order from before backwards. T
glosso-pharyngeal nerve pierces the dura mater separately, a
receives special sheaths from the dura mater and arachnoid membrai
The vagus and accessory nerves pass together through a sin^
aperture in the dura mater, and receive common sheaths from t
dura and arachnoid membrane. The postero-lateral compartment trai
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1167
 
 
5 the sigmoid sinus, which terminates in the internal jugular vein,
the vein is deep to the dura, this part of the foramen cannot be
1 directly when the dura mater is in position.
 
The twelfth or hypoglossal nerve pierces the dura mater in two
dies, which pass through separate apertures. As these bundles
5 through the anterior condylar canal they unite to form one nerve,
ween the points of exit of the hypoglossal and the last three nerves
jugular tubercle is seen, forming a very useful landmark.
 
Structures passing through the Foramen Magnum. —(1) The medulla
mgata, with its membranes, passes out and becomes the spinal
i. (2) The spinal root of the accessory nerve of either side, having
mded from the interval between the posterior roots of the cervical
lal nerves and the ligamentum denticulatum, enters the cranial
ity. It then turns outwards behind the jugular tubercle to the
Idle compartment of the jugular foramen, where it meets the
rial root of the nerve, with which it becomes closely connected
it passes through the foramen. (3) The vertebral artery of each
j enters the cranial cavity after having pierced the dura mater.
The two anterior spinal branches of the vertebral arteries descend
the front of the medulla oblongata, and, inclining inwards towards
h other, they unite in passing through the foramen magnum to
n the anterior spinal artery, the membrana tectoria, and the apical
ment of the odontoid process.
 
Trigeminal Ganglion (Gasserian Ganglion) (Fig. 700).—The trilinal ganglion occupies the trigeminal impression (Gasserian imssion) on the superior surface of the petrous part of the temporal
Le near the apex, where its posterior part lies in a recess of the
a mater, called the cavum trigeminale ( Meckel’s cave). It is someit semilunar, being convex in front and concave behind, and measures
y \ inch from before backwards. It is associated with the sensory
t of the fifth nerve, which, before entering the posterior concave
ect of the ganglion, becomes expanded, its fasciculi at the same
e becoming separated and assuming a plexiform arrangement,
lially the ganglion is intimately related to the back part of the
ernous sinus, and by its inner and lower aspect to the internal
otid artery in the foramen lacerum, and on this aspect it receives
icate filaments from the internal carotid sympathetic plexus. The
tor root of the fifth nerve, small in size, lies below the deep surface
:he ganglion; but there is no blending of the two sets of fibres, the
tor root passing independently in an outward direction to the
imen ovale. The greater superficial petrosal nerve, on its way to
foramen lacerum, passes beneath the ganglion, though not in the
r um trigeminale.
 
The ganglion contains cells similar to those of a spinal ganglion,
1 it receives its blood from the middle and accessory meningeal
eries. It is important in connection with modern surgery to notice
■t the front part of the ganglion does not lie in the cavum trininale, but has a close investment of dura mater. Hence the front
 
 
 
1168
 
 
A MANUAL OF ANATOMY
 
 
part may be removed without opening the subarachnoid space
allowing cerebro-spinal fluid to escape.
 
Branches. —The branches of the ganglion arise from its anteri
convex aspect, and are known as divisions. They are as follow
the first or ophthalmic division; the second or maxillary divisio
and the third or mandibular division. The ophthalmic and maxilla
nerves are entirely sensory, but the mandibular nerve, being join
by the motor root, is both sensory and motor.
 
The first division of the trigeminal nerve, or the ophthalmic ner\
is the smallest of the three branches of the ganglion. It passes fc
wards in the outer wall of the cavernous sinus, where it lies below t]
fourth nerve. On approaching the superior orbital fissure it divid
into branches in the following order from behind forwards: (i) nas
ciliary (nasal), (2) lacrimal, and (3) frontal. All these three branch
enter the orbit through the superior orbital fissure. As the ophthaln
nerve passes forwards it receives a communicating branch from t'
internal carotid sympathetic plexus, and it furnishes the nervus tento>
to the tentorium cerebelli. It also communicates with each of t
oculo-motor, trochlear, and abducent nerves.
 
The naso-ciliary nerve, having passed through the orbit, re-ente
the skull by running between the orbital plate of the frontal and t'
upper surface of the ethmoid. It then lies deep to the dura mater <
the cribriform plate near its anterior extremity, and soon disappea
by passing down between this bone and the nasal area of the frontal
 
The second division of the trigeminal nerve, or the maxillary ner
(superior maxillary nerve), passes horizontally forwards for a she
distance in the lower part of the outer wall of the cavernous sinus, ai
it leaves the cranial cavity through the foramen rotundum, whi
leads to the pterygo-palatine fossa. Before leaving the cranial cavi
it furnishes the delicate meningeal nerve to the dura mater of tl
middle fossa.
 
The third division of the trigeminal nerve, or the mandibular ner
(inferior maxillary nerve), is the largest of the three branches of t.
ganglion. It passes downwards to the foramen ovale, through whi
it leaves the cranial cavity, and so enters the infratemporal foss
It is accompanied by the motor root of the fifth nerve, which joi
it as it passes through the foramen ovale. The nervus spinosus fre
the mandibular nerve is not given off until after the parent trui
has issued through the foramen ovale, and it enters the cranial cavi
through the foramen spinosum in company with the middle meninge
artery. It then divides into two branches, anterior and posterior. T
anterior branch supplies the dura mater over the greater wing of t
sphenoid bone, and the posterior branch passes through the fissr
between petrous and squamous parts of the temporal bone to supp
the mucous membrane of the mastoid air-cells.
 
Greater Superficial Petrosal Nerve. —This nerve is a branch of the gangli
of the facial nerve in the facial canal. It enters the middle fossa of the be
of the skull through its hiatus, and passes forwards and inwards in a groove
 
 
THE HEAD AND NECK
 
 
1169
 
 
anterior surface of the petrous part of the temporal bone. Having passed
sath the trigeminal ganglion embedded in the dura mater, it enters the upper
of the foramen lacerum, where it is placed on the outer side of the internal
tid artery, and it joins the deep petrosal nerve from the internal carotid
pathetic plexus. In this manner the nerve of the pterygoid canal is formed,
:h enters the latter canal by its opening on the anterior aspect of the foramen
rum, and so reaches the spheno-palatine ganglion in the pterygo-palatine
i. The greater superficial petrosal nerve is accompanied by the superficial
osal branch of the middle meningeal artery.
 
jesser Superficial Petrosal Nerve. —This nerve represents the continuation
ugh the tympanic plexus of the tympanic branch (Jacobson's nerve) of the
30-pharyngeal nerve. It is reinforced by a small branch from the ganglion
he facial nerve, Avhich joins it as it traverses a small canal in the petrous
of the temporal bone beneath the canal for the tensor tympani muscle,
nerve enters the middle fossa through a small opening on the lateral side
he hiatus for the greater superficial petrosal nerve. It then passes for a
3 forwards and inwards, and leaves the cranial cavity through the canaliculus
iminatus (when present), or through the fissure between the petrous temporal
the greater wing of the sphenoid, or, it may be, through the foramen ovale,
r which it terminates in the otic ganglion.
 
External Petrosal Nerve. —This nerve, which is inconstant, passes from the
pathetic plexus on the middle meningeal artery backwards and outwards
:he anterior surface of the petrous part of the temporal bone, and it leaves
cranial cavity through a minute aperture situated within the thin margin
tie hiatus for the greater superficial petrosal nerve. It ends in the ganglion
re facial nerve.
 
 
Interior of the Cavernous Sinus.—The interior of this sinus ia
ken up by a network of delicate trabeculae. The outer wall of
sinus contains the following
rial nerves, in order from above
mwards: the oculo-motor, the
ihlear, the ophthalmic division
:he trigeminal, and the maxilr division of the fifth. These
ves, as they pass forwards,
separated from the bloodrent by the endothelial lining
the outer wall of the sinus.
 
J cavity of the sinus is travel by (1) the cavernous portion
the internal carotid artery,
rounded by a plexus of symhetic filaments; and (2) the
Lucent nerve, which lies in
>e contact with the outer side of the artery. These structures are
) separated from the blood-current by the endothelial lining of the
is.
 
For the processes and other sinuses of the dura mater see p. 1601.
Cavernous Portion of the Internal Carotid Artery.—This part of the
irnal carotid artery lies within the cavernous sinus, which occupies
carotid groove on the lateral aspect of the body of the sphenoid
ie. It is separated from the blood-current by the endothelial
 
74
 
 
Internal Carotid Artery
Abducent.Nerve
Oculo-motor Nerve
Trochlear Nerve
Ophthalmic Nerve
 
 
Sella Turcica
 
 
 
Maxillary Nerve
 
Left Sphenoidal Sinus
 
Fig. 701.—Diagram of the Left Cavernous Venous Sinus and its Outer
Wall, showing the Relative Positions of the Contained Structures
(Posterior View).
 
 
 
 
 
1170
 
 
A MANUAL OF ANATOMY
 
 
lining of the sinus. The course of the vessel is at first upwan
between the lingula of sphenoid and the posterior petrosal process
the sphenoid; then forwards as far as the anterior clinoid process
the sphenoid; and finally upwards medial to the anterior clinc
process. In the latter situation it pierces the dura mater, whi
forms the roof of the cavernous sinus, and enters upon the cerebi
part of its course.
 
The vessel is accompanied by the internal carotid sympathe
plexus, and the abducent nerve lies in close contact with its out
side, all being invested by the endothelial lining of the sinus.
 
 
 
Fig. 702.—Right Internal Carotid put in Position on Base of Skui
 
and Crossed by Sixth Nerve.
 
Great superficial petrosal nerve is also seen.
 
Branches.—These are as follows: hypophysial, to the hypophys
cerebri; ganglionic, to the trigeminal ganglion; cavernous, to the w£
of the cavernous sinus, and to the oculo-motor, trochlear, trigemim
and abducent nerves; meningeal, to the dura mater of the midd
cranial fossa; and the ophthalmic artery. The latter vessel arises fro:
the cavernous portion of the internal carotid on the inner side of tl
anterior clinoid process, and it enters the orbit, with the optic nerv
through the optic foramen, lying at first beneath the nerve, and the
on its outer side.
 
The Medial Part of the Internal Carotid Sympathetic Plexus (Caveri
ous Plexus).—This plexus is situated principally on the inner and low<
aspects of the bend which the cavernous portion of the internal caroti
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1171
 
 
•y describes medial to the anterior clinoid process. Its branches
as follows; (1) vascular, to the internal carotid artery and its
ches; (2) hypophysial, to the hypophysis cerebri; (3) communing, to the oculo-motor, trochlear, ophthalmic division of the tri[nal, and abducent cranial nerves; and (4) the sympathetic root of
;iliary ganglion. The last-named branch enters the orbit through
superior orbital fissure.
 
"he hypophysis cerebri (pituitary body) is a small oval mass which
tuated in the hypophysial fossa, or sella turcica, of the sphenoid
It lies under cover of a circular fold of the dura mater, called the
hragma sellce, in the centre of which is an opening for the passage
le infundibulum. Its long measurement extends transversely, and
msists of two lobes—anterior and posterior. The anterior lobe is
larger of the two, and the posterior lobe is connected with the
rior part of the tuber cinereum by means of the infundibulum,
rhe infundibulum projects downwards from the anterior part of
tuber cinereum to the posterior lobe of the pituitary body. Its
sr part is hollow, and contains
mnel-shaped diverticulum of the
ty of the third ventricle.
 
tructure. —The anterior lobe consists of
ral tubules lined with epithelium, and
sted by capillary bloodvessels. The
jrior lobe, though developed from the
1, is destitute of nervous elements. It
imposed of a reticulum of connective
e, which contains branched cells. Bern the two lobes is the middle part.
 
)evelopment. —The anterior lobe is deped from a diverticulum of the buccal
tomatodaeal ectoderm, which is known
ie pouch of Rathke. The diverticulum
rs upwards, and, when the cranio•yngeal canal of early life becomes closed,
connection of the diverticulum with the
:al ectoderm is severed. The diverurn later on becomes converted into
lies, which form the anterior lobe, dhe
Brior lobe of the pituitary body and the
ndibulum, which is connected with it, are
sloped as a diverticulum which grows
nwards from that part of the diencephalon
:h forms the floor of the third ventricle. #
 
cavity of the diverticulum remains permanent in the upper part of its
ndibular portion, but elsewhere it becomes obliterated. The lower part of
diverticulum thereafter becomes converted into a reticulum of connective
ie with branched cells, which forms the posterior lobe.
 
 
 
Fig. 703. —Diagram of Anteroposterior Section through
the Hypophysis.
 
A, anterior lobe: PT, its pars
tuberalis. Pars Interm., pars
intermedia. N, neural or posterior lobe. INF, infundibulum. OPT. CH, optic chiasma.
 
 
Side of the Neck.
 
The side of the neck has a quadrilateral outline, the boundaries
which are as follows: superior, the lower border of the mandible
. a line prolonged from the angle of that bone over the mastoid
 
 
1172
 
 
A MANUAL OF ANATOMY
 
 
process to the inner third of the superior rruchal line of the occipi
bone; inferior , the clavicle and one half of the upper border of 1
manubrium sterni; anterior , the middle line of the neck; and posteri
the outer border of the trapezius in the neck.
 
Landmarks.—The body and angle of the mandible can easily
felt, and the clavicle, together with the upper border of the manubrii
sterni, is conspicuous. A deep depression, called the supraster:
fossa, is perceptible above the upper border of the manubrium ster
lying between the sternal h'eads of origin of the sterno-mastoid muscl
The outline of the sterno-mastoid muscle is readily discernible when 1
head is turned so as to direct the face towards the opposite should
The muscle extends in a diagonal direction from the sterno-clavicu
joint to the mastoid process and outer half or two-thirds of the super
nuchal line of the occipital bone, and it divides the side of the ne
into two triangles—anterior and posterior. A small triangular inter
may be felt between the sternal and clavicular heads of origin of t
sterno-mastoid just above the inner end of the clavicle, in which t
common carotid artery and internal jugular vein lie deeply. T
external jugular vein crosses the sterno-mastoid muscle in the directi
of a line extending from a point just behind the angle of the mandil
to a point above the centre of the clavicle, and it is accompanied
the superficial cervical glands. The common carotid artery lies unc
cover of the anterior border of the sterno-mastoid muscle in the directi
of a line drawn from the sterno-clavicular joint to a point midw
between the angle of the mandible and the tip of the mastoid proc(
of the temporal bone. The vessel extends along this line as high
the level of the upper border of the thyroid cartilage, above which
is replaced by the external carotid artery. The internal jugular vt
is close to the outer side of the common carotid artery, and the vag
nerve lies deeply between the two vessels. If deep pressure is ma
over the common carotid artery on a level with the cricoid cartila
of the larynx, the anterior tubercle of the transverse process of t
sixth cervical vertebra may be felt. It is known as the carotid tuber
(of Chassaignac.)
 
The bifurcation of the innominate artery lies behind the upp
border of the right sterno-clavicular joint, and the left common carol
artery lies behind the left sterno-clavicular joint, while the lower pa
of the internal jugular vein on each side is behind the inner end
the clavicle. Near the middle line of the neck the anterior jugul
vein descends vertically. The spinal root of the accessory ner
passes downwards and outwards beneath the anterior border of t
sterno-mastoid to pierce the deep part of that muscle at about t
junction of the upper fourth and lower three-fourths. The nerve
met with fully 1 inch below the tip of the mastoid process, and in t
direction of a line let fall vertically from the mastoid tip. It is ve
nearly on a level with the body of the hyoid bone. Along the posteri
border of the sterno-mastoid some superficial cervical lymph glan
may be felt.
 
 
 
THE HEAD AND NECK
 
 
ii 73
 
 
Important structures occupy the middle line of the neck, and can
usually distinguished without difficulty. These are as follows, in
sr from above downwards: (1) the body of the hyoid bone, lying
; below the mandible, and having the greater horn projecting
kwards and upwards on either side; (2) the thyro-hyoid membrane;
the thyroid cartilage, with its laryngeal prominence (pomum
imi) in the middle line, leading up to the V-shaped thyroid notch
the upper border, and its expanded ala on either side, each of which
s behind in a superior and an inferior horn; (4) the crico-thyroid
ment; (5) the narrow anterior part of the cricoid cartilage, which
icides with the level at which the superior belly of the omo-hyoid
 
 
 
scle crosses the carotid sheath; and (6) the rings of the trachea,
ich, however, are covered superiorly by the isthmus of the thyroid
nd, and inferiorly by the sterno-hyoid and sterno-thyroid muscles
1 adipose tissue.
 
The lateral lobes of the thyroid gland may be felt on either side of
larynx and trachea as low as about the fifth ring; and in young
Idren the thymus extends upwards upon the trachea for some
tance above the manubrium sterni.
 
The greater horn of the hyoid bone is the guide to the lingual artery
, hypoglossal nerve for operative purposes, the structures lying just
ve the greater horn.
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1174
 
The upper border of the thyroid cartilage is on a level with the di
between the bodies of the third and fourth cervical vertebra.
 
The narrow anterior part of the cricoid cartilage is on a level wi
the disc between the bodies of the fifth and sixth cervical vertebrae,
which level the pharynx becomes the oesophagus. In this situatior
foreign body, when swallowed, is liable to become impacted.
 
Below the cricoid, in the middle line, one or two rings of the trach
may be felt above the thyroid isthmus, and it is here that a hi
tracheotomy is performed, an easy operation since the windpipe is
 
 
 
Fig. 705. —Superficial Dissection.
 
 
close to the skin. Below the isthmus the trachea rapidly recedes,
that a low tracheotomy is often a difficult and sometimes a ve
dangerous operation; dangerous because, often in children and son
times in the adult, the left innominate vein lies in the suprasterr
region above the level of the manubrium sterni, and so in the way
the knife. Ignorance of this fact has meant, and may mean aga
the loss of a life.
 
Above the middle third of the clavicle, between the sterno-mash
and trapezius muscles, there is a depression known as the greai
 
 
 
 
THE HEAD AND NECK
 
 
ii 75
 
 
aclavicular fossa, which indicates the position of the subclavian
lgle, with the third part of the subclavian artery and the trunks
ie brachial plexus of nerves.
 
Platysma (Platysma Myoides)— Origin .—The superficial fascia which
>rs the clavicular parts of the pectoralis major and deltoid muscles.
Insertion. —(1) The outer part of the body of the mandible from
symphysis menti to the anterior border of the masseter muscle;
(2) the angle of the mouth, where the fibres blend with those of
depressor anguli oris and orbicularis oris.
 
Nerve-supply .—The cervical branch of the facial nerve, which comlicates with branches of the anterior cutaneous nerve of the neck.
The fibres are directed upwards and forwards or inwards over the
dele and side of the neck.
 
Action. —(1) To draw the angle of the mouth downwards and outds; (2) to act as a feeble depressor of the mandible; (3) to raise the
1 of the neck and upper pectoral region as far out as the acromion
cess, throwing it into obliquely-disposed folds.
 
The muscle forms an extensive, thin, pale sheet, which is embedded
hin the superficial fascia. In the region of the symphysis menti
innermost fibres decussate across the middle line with those of the
>osite side, the fibres of the right muscle being superficial. The
scle covers the external and anterior jugular veins, the superficial
nches of the cervical plexus of nerves, the subclavian triangle, and
sterno-mastoid, sterno-hyoid, omo-hyoid, and digastric muscles.
 
The platysma in man is a remnant of a subcutaneous muscular sheet, called
panniculus carnosus, which exists in many animals, and by which the twitchof the skin is produced.
 
Jugular Veins.—The jugular veins are four in number on either
e—anterior, external, posterior external, and internal.
 
The anterior jugular vein begins in the roof of the digastric triangle,
Lere it is formed by the union of radicles which communicate with
3 submental vein, and are joined by radicles which have descended
>m the structures over the body of the mandible. It descends
rtically near the median line, lying at first superficial to the deep
rvical fascia, but subsequently entering the suprasternal space. II
en describes a bend, and, passing outwards behind the sternoistoid muscle, and in front of the scalenus anterior, it opens
to the lower part of the external jugular vein. It may, however,
>en into the subclavian vein. It communicates with the external
gular vein by one or more tributaries, and usually receives a branch
3 m the facial vein which descends along the anterior border of the
erno-mastoid and joins it towards the lower part of the neck,
urther, it communicates with its fellow, of the opposite side by a
ansverse branch, the jugular arch, which crosses in front of the
achea, and lies in the suprasternal space.
 
The anterior jugular veins are usually asymmetrical, one or other
sing of small size. Occasionally there is only one vein, which divides
 
 
A MANUAL OF ANATOMY
 
 
1176
 
into two vessels interiorly. The anterior jugular vein is destitute ^
valves.
 
The external jugular vein commences close behind the angle of tl
mandible in the substance of the parotid gland, where it is formed t
the union between the posterior division of the posterior facial ve:
and the posterior auricular vein. On leaving the parotid gland
descends almost vertically to a point above the centre of the clavicl
In its course the vessel crosses the sterno-mastoid muscle, lying supe
ficial to its sheath, and deep to the superficial fascia containing tl
fibres of the platysma. At this level the main part of the anteri<
 
 
 
Fig. 706. —Superficial Veins of Neck.
 
SF, CF, superficial and common facial. TM, posterior facial or temporo-maxillar
PA, posterior auricular. PJ, EJ, AJ, posterior, external, and anterior juguls
 
cutaneous nerve of -the neck runs forward deep to the vein, and offse
of the nerve pass superficial to it. Having crossed the sterno-masto
muscle, the vein descends not far from its posterior border, where
lies in the roof of the subclavian triangle over the third part of tl
subclavian artery. Up to this point the vessel is superficial to tl
deep cervical fascia, but it now pierces that fascia and opens into tl
subclavian vein.
 
The course of the external jugular vein is indicated by a line draw
from a point close behind the angle of the mandible to a point abo^
the centre of the clavicle. Its tributaries are as follows: (1) poster!
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1177
 
 
3rnal jugular, which joins it about the middle of the neck; (2) trans;e cervical; (3) suprascapular; and (4) anterior jugular, the latter
;e joining it not far from its termination. It also communicates
1 the anterior jugular vein by one or more branches. The vessel
rovided with valves, both at its termination and about i\ inches
ve this point, and the transverse cervical and suprascapular veins
 
 
isterior Auricular
Lymph Glands
 
Occipital Vein
 
;al Lymph Gland
 
>r Auricular Vein
 
terior Division of
;erior Facial Vein
 
iperficial Cervical
Lymph Glands
 
 
osterior External
Jugular Vein
 
mal J ugular Vein
 
 
:rse Cervical Vein_
 
 
 
 
P, ,
 
whi 1 \n\
 
 
_Supratrochlear Vein
 
-Supra-orbital Vein
 
- Angular Vein
 
 
Superficial Temporal Vein
Maxillary Vein
 
 
Posterior Facial Vein
Anterior Facial Vein
 
Ant. Div. of Posterior
Facial Vein
 
Submandibular Lymph
Glands
 
Common Facial Vein
Internal J ugular Vein
Lingual Vein
 
Superior Thyroid Vein
 
 
Middle Thyroid Vein
 
 
Anterior Jugular Vein
 
. Suprasternal Lymph
Gland
 
 
. 1 ■"
 
 
Suprascapular Vein and.Supraclavicular;
Lymphatic Glands
 
 
r. 707. —The Superficial Veins and Superficial Lymph Glands of the
 
Right Side of the Head and Neck.
 
The platysma muscle has been removed.
 
 
i also furnished with valves where they open into the external
;ular vein, or near their orifices.
 
The external jugular vein is sometimes very small, or even absent,
I it may communicate with the cephalic vein by a vessel which
sses over the clavicle.
 
r
 
Development. —The external jugular vein was formerly regarded as being
sloped from the anterior cardinal vein; but according to most authorities
anterior cardinal vein gives rise to the internal jugular vein, the external
ular being of later development.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1178
 
The posterior external jugular vein represents the most exter:
occipital vein, and is formed by tributaries which issue from the ou
part of the occipital plexus, reinforced by veins from the superfic
structures at the back of the neck. It usually receives the mast'
emissary vein and passes downwards and forwards, joining the exter:
jugular vein about the middle of the neck.
 
The internal jugular vein will be found described on p. 1211.
 
Superficial Cervical Lymph Glands.— These are about six in numb
and they lie upon the sterno-mastoid muscle, along the course of 1
external jugular vein, and deep to the superficial fascia and platysi
muscle. They receive their afferent lymphatics from the adjac<
superficial structures, the occipital and mastoid lymph glands, a
some of those of the parotid and submandibular lymph glands. Tb
efferent lymphatics pass to the deep cervical lymph glands.
 
Deep Cervical Fascia. —The deep cervical fascia is divided ii
(1) a superficial investing layer, which completely invests the neck
the form of a collar; and (2) deep processes or laminae, which inv
the muscles, viscera, and chief bloodvessels and nerves.
 
Investing Layer. —This layer is attached posteriorly to the li\
mentum nuchae; superiorly to (1) the superior nuchal line of the oc
pital bone, (2) the mastoid process of the temporal bone, (3) the zyj
matic arch, and (4) the body of the mandible, under cover of 1
platysma, as far forwards as the symphysis menti; and interiorly
the clavicle and upper border of the manubrium sterni, being pierc
above the centre of the clavicle by the external jugular vein. Ale
the middle line of the neck anteriorly it is continuous with the invest]
layer of the opposite side.
 
The investing layer invests the cervical portion of the trapezi
and from the anterior border of that muscle it passes forwards 0 1
the posterior triangle of the neck to the posterior border of the sten
mastoid. In doing so it furnishes a deep process, which ensheat]
the inferior belly of the omo-hyoid muscle. This process also embra^
the intermediate tendon of that muscle, after which it passes dov
wards and inwards to be attached to the back of the inner end of 1
clavicle and the first rib. In this manner the horizontal position
the inferior belly of the omo-hyoid is accounted for. When the
vesting layer of the deep cervical fascia reaches the posterior bore
of the sterno-mastoid it splits into two laminae, which ensheathe tl
muscle, the superficial lamina being underneath the external jugu
vein and platysma. At the anterior border of the sterno-mastoid 1
two laminae reunite, and the fascia passes forwards over the anter
triangle of the neck to the median line, where it is continuous with 1
corresponding layer of the opposite side.
 
Between the upper part of the anterior border of the sterno-masb
and the angle of the mandible the investing layer is of considera
strength, and draws that border of the muscle forwards and upwar
so as to render it convex and keep it over the line of the leading vess<
Between the mastoid process and the angle of the mandible the
 
 
 
 
THE HEAD AND NECK
 
 
1179
 
 
ting layer is prolonged upwards over the parotid gland as the parotid
:ia, which is very dense, and is attached superiorly to the lower
der of the zygomatic arch.
 
Below the level of the thyroid gland the investing layer divides
0 two laminae, anterior and posterior, both of which are superficial
the infrahyoid muscles. At the middle line these laminae are conuous with those of the opposite side, and inferiorly they are attached
the anterior and posterior margins of the upper border of the
nubrium sterni. Between them there is an interfascial interval,
led the suprasternal space (space of Burns). This interval contains
:olar tissue, one or more lymphatic glands, the lower portions of the
terior jugular veins, with the jugular arch which here connects
im, and the sternal heads of the sterno-mastoid muscles.
 
Deep Processes or Laminae.— The deep laminae, as stated, invest the
iscles, viscera, and chief bloodvessels and nerves. The most imrtant are derived from that lamina of the investing layer which
ms the posterior wall of the sheath of the sterno-mastoid muscle,
d they are three in number—namely, carotid sheath, pretracheal
icia, and prevertebral fascia—all of which have an intimate initial
nnection.
 
The carotid sheath contains in separate compartments (1) the
mmon carotid artery and the constituents of the ansa hypoglossi,
the internal jugular vein, and (3) the vagus nerve, the latter being
ntained within the back part of the septum, which separates the
tery from the vein.
 
The pretracheal fascia, which is at first intimately connected with
e anterior wall of the carotid sheath, passes forwards behind the
frahyoid muscles, in which situation it splits to ensheathe the
yroid gland, trachea, and oesophagus, and then it passes to the
sdian line, where it is continuous with the pretracheal fascia of the
•posite side. The pretracheal fascia is attached superiorly to the
>dy of the hyoid bone, and inferiorly it descends over the trachea
Ld bloodvessels into the superior mediastinum of the thorax, where it
ends with the fibrous pericardium.
 
The prevertebral fascia, which is at first intimately connected with
e posterior wall of the carotid sheath, passes forwards behind the
larynx and oesophagus, and in front of the prevertebral muscles,
t the middle line it is continuous with the corresponding fascia of
e opposite side; superiorly it is attached to the base of the skull;
id inferiorly it descends over the longus cervicis muscle into the
isterior mediastinum of the thorax. Along a line corresponding to
le inner wall of the carotid sheath the pretracheal fascia furnishes a
condary lamina, called the bucco-pharyngeal fascia, which covers
ie constrictor muscles of the pharynx and the buccinator muscle,
etween the bucco-pharyngeal and prevertebral fasciae there is an
terval, called the retro-pharyngeal space, which contains the loosely
'ranged connective tissue uniting the two fasciae. This space extends
high as the base of the skull, and inferiorly is continuous with the
 
 
ii8o
 
 
A MANUAL OF ANATOMY
 
 
posterior mediastinum of the thorax. Another process of the pi
vertebral fascia passes downwards and outwards in front of t
scalenus anterior muscle. After this it invests the third part of t
subclavian artery and subclavian vein, together with the nerve-trun
of the brachial plexus, and, passing behind the clavicle, it becom
continuous with the axillary sheath, which latter blends with t
posterior aspect of the clavi-pectoral fascia. In the region of the su
clavian triangle there is an interfascial space between this proce
of the pretracheal fascia and the investing layer of the deep cervic
fascia. This space extends downwards behind the clavicle to the poi
where the axillary sheath and clavi-pectoral fascia join. It contai
 
 
Stemo- thyroid
Sterno-hyoid
 
Investing Layer of Deep Cervical Fascia
Superior Belly of Omo-hyoid
Pretracheal Fascia
Prevertebral Fascia
 
 
Suprasternal Space
Trachea
 
Muscular Compartment
 
Lateral Lobe of Thyroid Gland
 
 
Carotid Sheath
 
 
Scalenus Anterior
 
 
Scalenus Medius
 
 
Levator Scapulae
 
Semispinalis Capitis
 
 
 
(Esophagus
 
Descendens hypoglossi
^ Common Carotid Artery
Internal Jugular Vein
- Vagus Nerve
Platysma
 
 
Splenius
 
 
Sympathetic Trunk
 
Longus Cervicis
- Stemo-mastoid
 
 
External Jugular V<
 
 
' Vertebral Vessels
 
 
Trapezius
 
 
Semispinalis Cervicis
 
 
Tig. 708. Diagram of a Transverse Section of the Neck at the Lev
of the Sixth Cervical Vertebra, showing the Arrangement of ti
Deep Cervical Fascia and the Positions of Other Structures.
 
 
the inferior belly of the omo-hyoid muscle, the suprascapular ar
transverse cervical vessels, the lower part of the external jugular vei
and the terminal portion of the anterior jugular vein.
 
Interfascial Compartments. —It has been stated that the det
cervical fascia reaches the median line of the neck anteriorly in thr
layers—namely, investing (in two divisions), pretracheal, and pr
vertebral. It is therefore evident that there are four interfasci
compartments as follows: (1) the suprasternal space (space of Burn!
which is situated between the two divisions of the investing layer, ai
contains the structures already enumerated; (2) the muscular cor
partment, which is situated between the investing layer and the pr
tracheal layer, and contains the infrahyoid muscles; (3) the viscer
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1181
 
 
partment, which lies between the pretracheal and prevertebra
rs, and contains the larynx, trachea, thyroid gland, pharynx,
phagus, and carotid sheath, the retro-pharyngeal space being in
subdivision of this compartment behind the bucco-pharyngeal
ia; and (4) the vertebral compartment, which lies between the
vertebral layer and the attachment of the fascia to the ligamentum
iae posteriorly, and contains the vertebral column, spinal cord, and
vertebral and postvertebral muscles.
 
rhe suprasternal and muscular compartments are shut off from
thoracic cavity. The visceral compartment in front of the trachea
mtinuous with the superior mediastinum of the thorax, and behind
oesophagus it, along with the retro-pharyngeal space, is continuous
1 the posterior mediastinum.
 
Parotid Process of the Deep Cervical Fascia. —This process is given
a little below the angle of the mandible, and it passes upwards on
deep surface of the parotid gland to the skull. Along with the
Dtid fascia superficial to the gland it forms a dense sheath which
ely invests the glandular substance. The parotid process furnishes
aths to the posterior belly of the digastric, styloid, and pterygoid
scles, and it also gives an investment to the superficial part of the
mandibular gland. Connected with the parotid process there are
sral bands, usually called ligaments, which are as follows: (1) sphenoadibular; (2) stylo-mandibular; (3) pterygo-mandibular; and
 
pterygo-spinous.
 
The spheno-mandibular ligament will be described in connection
h the mandibular joint, of which it is sometimes regarded as an
essory medial ligament (see p. 1316).
 
The stylo-mandibular ligament extends from the styloid process of
temporal bone near its tip to the angle and adjacent part of the
terior border of the ramus of the mandible, where it is placed
ween the masseter and internal pterygoid muscles.
 
The pterygo-mandibular ligament is a narrow band which extends
hi the hamulus of the medial pterygoid plate of the sphenoid bone
the posterior extremity of the mylo-hyoid line of the mandible
$e to the last molar socket. Anteriorly it gives origin to fibres of
buccinator muscle, and posteriorly to fibres of the superior condor muscle of the pharynx.
 
The pterygo-spinous ligament is a narrow band which extends from
harp spine on the posterior border of the lateral pterygoid plate of
sphenoid bone, towards its upper part, to the spine process of the
lenoid. This ligament is liable to become ossified.
 
The foregoing description is orthodox and traditional, and every fact stated
be demonstrated by a good dissector; but there are some observers who
3rd the whole of these fascial planes as artifacts, and believe that all the
irstices between the structures in the neck are filled with loose connective
ue which, when it is cleaned from the surrounding parts, collapses into
Y definite sheets. If this is the case, it should be possible, by varying the
action of the incisions, to produce sheets in any plane. As a matter of fact,
> can be done.
 
 
Il82
 
 
A MANUAL OF ANATOMY
 
 
Sterno-mastoid — Origin .—The sternal head, which is narrow ar
round, arises from the upper and outer part of the anterior surfa*
of the manubrium sterni. It is tendinous in front, and fleshy behin
The clavicular head, which is broad and flat, arises from a rough rid|
about ij inches long on the upper surface of the clavicle at its inn
end.
 
Insertion .—The outer surface of the mastoid process of the ter
poral bone, and the superior nuchal line of the occipital bone ov
about its outer half or two-thirds.
 
 
 
Fig. 709. —Showing Sterno-mastoid and the Muscular Floor of
 
Posterior Triangle.
 
 
 
 
Nerve-supply .—The accessory nerve, and a branch from the cervic
plexus, more particularly from the anterior primary ramus of the secor
cervical nerve.
 
The spinal root of the accessory nerve passes deep to the anteri
border of the muscle fully 1 inch below the tip of the mastoid proces
and in passing downwards and backwards it pierces the deep part
the muscle, giving off as it does so its branches to it.
 
The muscle is directed upwards, outwards, and backwards.
 
Action .—To flex the head towards the side on which the muse
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1183
 
aced, the face being turned towards the opposite side. This is
position of the head in torticollis or wry-neck, a condition which
be due to an organic contraction to the muscle, affecting both
s, or, it may be, the sternal head alone. When both muscles act
ther from their origin they flex the head towards the thorax,
when the head has been already thrown back the sterno-mastoid
ls capable of extending it still farther instead of flexing it. It
t be remembered, however, that a certain amount of flexion of
lead may take place between any of the cervical vertebrae. When
muscles act together from their insertion they elevate the upper
of the anterior thoracic wall in forced inspiration.
 
"he sternal and clavicular heads are separated by a triangular
Jar interval for a short distance above the sterno-clavicular joint,
before their junction the fibres of the clavicular head to a large
nt pass behind those of the sternal head, so that overlapping
s place. The muscle is surrounded by a strong sheath, which is
led by the deep cervical fascia. The platysma covers a large part
:, and the external jugular vein, the anterior cutaneous nerve of
: and great auricular nerves, and the superficial cervical lymph
ds are related to its superficial surface under cover of the platysma.
principal deep relations are as follows: in the lower part of the
: it covers the first and second parts of the subclavian artery, the
10-hyoid, sterno-thyroid, omo-hyoid, and scalenus anterior muscles,
l the phrenic nerve lying upon the last-named muscle. In this
rtion it also covers the anterior jugular vein, and the transverse
ical and suprascapular arteries. Higher up it covers the cervical
;us of nerves, the levator, scapulae, scalenus medius, and scalenus
erior muscles, and the accessory and the hypoglossal nerves. At
insertion it covers the splenius capitis, longissimus capitis, and
:erior belly of the digastric muscles, and a portion of the occipital
ry, in this order from the surface downwards. The anterior border
he muscle forms the posterior boundary of the anterior triangle of
neck, and covers the carotid sheath, with its contents, as high as
level of the upper border of the thyroid cartilage ; and above that
1 it covers the external and internal carotid arteries. This border
overlaps slightly the lateral lobe of the thyroid gland.. The
;erior border forms the anterior boundary of the posterior triangle
he neck, and along it there lie the following structures: the superI cervical lymph glands, the lesser occipital nerve, great auricular,
nrior cutaneous nerve of neck, the accessory, and the descending
srficial branches of the cervical plexus of nerves, and a portion of
external jugular vein.
 
The sterno-mastoid muscle, from its diagonal position upon the
; of the neck, divides the quadrilateral space into two triangles terior and anterior.
 
Posterior Triangle. —This is the region which lies behind the sterno>toid muscle.
 
Boundaries — Anterior. —The posterior border of the sterno-mastoid.
 
 
A MANUAL OF ANATOMY
 
 
1184
 
Posterior .—The anterior border of the trapezius. Inferior (base).—
middle third of the clavicle. The apex is at the superior nuchal
of the occipital bone, where the sterno-mastoid and trapezius may n
but the apex is usually truncated. The roof is formed by the ;
superficial and deep fasciae, and for a short distance interiorly by
platysma. The lesser occipital nerve lies in the upper part of
roof, and the descending superficial branches of the cervical pi
and the external jugular vein lie in the lower part of the roof,
floor is formed by the following muscles, in order from above dc
wards: (1) small angle of the semispinalis capitis, provided the trapt
 
 
 
is not well developed at the occiput; (2) the splenius capitis; (3)
levator scapulae; (4) the scalenus medius and scalenus poster
(5) the scalenus anterior; and (6) the first digitation of the sern
anterior if the clavicle is depressed.
 
The posterior triangle is subdivided by the inferior belly of
omo-hyoid into a large upper portion, called the occipital trian
and a small lower portion, called the subclavian triangle.
 
Occipital Triangle—Boundaries — Anterior .—The posterior boi
of the sterno-mastoid. Posterior .—The anterior border of
trapezius. Inferior (base). —The inferior belly of the omo-hy
The muscles in its floor are (1) a small angle of the semispinalis caj
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1185
 
instant), (2) splenius capitis, (3) levator scapulae, and (4) scalenus
.ius and posterior. The contents are the superficial branches of the
ical plexus, the accessory nerve, the branches of the cervical
:us to the levator scapulae and trapezius, a small part of the occipital
ry close to the apex, and some superficial cervical lymph glands.
 
t should be realized that the foregoing gives a picture of the triangle as seen
le dissected body. In life and in the undissected part it is little more than
tter, the anterior edge of the trapezius being only about \ inch from the
srior border of the sterno-mastoid.
 
 
Parotid Duct
Buccinator Muscle
 
Facial Artery
Submental Artery
 
 
Lingual Artery
Sup. Lar. Art. and Nerve
Thyro-hyoid Muscle
Superior Thyroid Artery
 
 
 
.Transverse Facial Artery
 
 
, Superficial Temporal Artery
 
- Maxillary Artery
 
/_Posterior Auriculat
 
wma ^ . Artery
 
Occipital Artery
 
 
-Stylo-hyoid Muscle
 
-Post. Belly of Digastric
 
-Hypoglossal Nerve
 
_Descendens Hypogloss'
 
_External Carotid
 
Artery
 
 
-Sterno-mastoid
 
.— w Trapezius
 
 
_Transverse Cervical Artery
 
-. Suprascapular
Artery
 
 
Inf. Belly of Omo-hyoid
 
Subclavian Artery
(third part)
 
 
, y 1, An
 
Fig. 711.—The Left Side of the Head and Neck.
The platysma has been removed.
 
 
 
Cervical Plexus. —The cervical plexus lies deep to the upper part
:he sterno-mastoid muscle, and immediately in front of the slips
•rigin of the scalenus medius. It is formed by the anterior primary
ii of the first three cervical nerves and the greater part of that of
fourth, a small branch of the latter descending to join the anterior
nary ramus of the fifth, and so taking part in the brachial plexus,
h of the anterior primary rami of the first four cervical nerves is
nected with the superior cervical ganglion of the sympathetic by
'ey ramus communicans.
 
 
75
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1186 A MANUAL OF ANATOMY
 
The anterior primary ramus of the first cervical nerve lies at f
in the vertebrarterial groove of the atlas below the vertebral arte
It then passes forwards in a groove on the outer surface of the supei
articular process of the atlas, having the vertebral artery on its or
side. It next emerges between the rectus capitis lateralis mu;
(to which it gives a branch) and the rectus capitis anterior, ;
descends in front of the root of the lateral mass of the atlas to join
ascending branch of the second nerve. From the loop so forr
 
 
Vagus
 
 
Lesser Occip. N.
 
 
N.toTh
 
Int. La
 
Ne
 
 
Accessory Nerve ..
 
 
Ext. Li
Nerv
 
 
Descent
Hvpog
Desc. C
 
 
Ansa
 
 
Ant. Jv
 
 
Fig. 712.—Deep Relations of Sterno-mastoid, showing Cervical
 
Plexus, etc.
 
 
branches are given to the rectus capitis anterior and the longus cap
muscles, and one or more branches pass to the hypoglossal nerve,
destination of their fibres being the ramus descendens cervicalis 2
the nerves to thyro-hyoid and genio-hyoid.
 
The anterior primary rami of the second, third, and fourth cervi
nerves, having emerged between the corresponding intertransversa
muscles, form a superficial and a deep part of the plexus, of wh
the superficial is altogether cutaneous, while the deep is divided h
 
 
Phrenic
 
 
Upper Cord of
Brachial Plexus
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1187
 
 
tor and communicating branches. It will also be found that the
p plexus consists of an external and an internal set of branches.
Superficial Group. —The branches of this group are ascending,
nsverse, and descending.
 
The ascending and transverse branches arise from the second and
:d cervical nerves.
 
The ascending nerves are the lesser occipital and great auricular
; p. 1141). The transverse branch is the anterior cutaneous nerve
:he neck.
 
The anterior cutaneous nerve of the neck (superficial cervical nerve)
 
;es by two roots from the anterior primary rami of the second and
 
 
 
Fig. 713. —Scheme of Cervical Plexus.
superficial plexus red ; deep plexus black. I., E., medial and^lateral sides.
 
 
'rd cervical nerves, and, turning round the posterior border of the
Tno-mastoid muscle, it passes forwards superficial to that muscle,
ng deep to the platysma and the external jugular vein. Having
iched the anterior triangle of the neck, it divides into two branches,
:ending and descending, which are distributed to the integument
er the anterior triangle. The offsets of the ascending branch commicate freely with the cervical branch of the facial nerve deep to the
itysma.
 
The descending branches are the medial, intermediate, and lateral
3 raclavicular nerves, and they arise in common from the third and
irth cervical nerves. As they descend they form distinct nerves,
 
 
 
 
 
 
 
 
 
 
 
n88
 
 
A MANUAL OF ANATOMY
 
 
which lie on the roof of the subclavian triangle under cover of t
platysma. For their distribution see p. 412.
 
Deep Group. —The nerves of this group are arranged in two sets
external and internal.
 
External Set .—These nerves are muscular. The second ner
furnishes a branch to the sterno-mastoid, which communicates in tb
muscle with the branch of the accessory nerve. The third and four
 
 
 
Fig. 714. —Superficial Branches of Cervical Plexus.
 
SO, lesser occipital; GA, greater auricular; TC, anterior cutaneous;
DC, descending supraclavicular; XI, accessory nerve.
 
 
nerves furnish (a) two branches to the trapezius, which communicc
with the accessory nerve deep to the upper part of the muscle formi
the subtrapezial plexus; ( b) two branches to the levator scapulae; a
(c) branches to the scalenus medius.
 
Internal Set .—The nerves of this set are communicating a
muscular.
 
The communicating branches are as follows: (1) connecting brand
(grey rami communicantes) pass from the superior cervical gangli
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1189
 
 
the sympathetic; (2) communicating branches pass to the vagus
d hypoglossal nerves from the highest loop of the plexus; and
two rami communicantes cervicales pass from the second and third
rves forwards and downwards, usually superficial, but sometimes
ep to the internal jugular vein, and join the descendens hypoglossi,
aether or separately, to form the ansa hypoglossi.
 
The muscular branches are distributed to the rectus capitis lateralis,
:tus capitis anterior and longus capitis, upper part of the scalenus
terior, longus cervicis, and the diaphragm. The nerve to the
iphragm is the phrenic, which, from its importance, requires a special
scription.
 
The phrenic nerve arises, as a rule, by two roots, the larger of
lich is derived from the anterior primary ramus of the fourth cervical
rve, and the other from that of the third. In some cases the fifth
rvical nerve, which enters into the brachial plexus, furnishes an
ditional small root. In the neck the nerve descends in front of the
ilenus anterior muscle, which it crosses obliquely downwards and
wards, passing deep to the intermediate tendon of the omo-hyoid
uscle, the transverse cervical and suprascapular arteries, the anterior
gular vein, and, on the left side, the thoracic duct. At the root of
e neck the nerve, having left the scalenus anterior, passes behind
e terminal part of the subclavian vein, and crosses in front of the
ternal mammary artery from without inwards. Having come into
ntact with the inner surface of the cupola of the pleura, it disappears
kind the inner end of the clavicle, and enters upon the thoracic part
its course (see p. 1015).
 
The right nerve at the root of the neck is superficial to the second
irt of the right subclavian artery, with the intervention of the
alenus anterior muscle. The left nerve at the root of the neck is
iterior and parallel to the first part of the left subclavian artery.
 
The phrenic nerve is sometimes reinforced towards the root of the
ick by a branch from the nerve to the subclavius muscle, and when
is takes place the root from the fifth cervical nerve is usually absent,
efore leaving the neck the phrenic nerve receives a twig from the
iddle or inferior cervical ganglion of the sympathetic.
 
No branches arise from the phrenic nerve in the neck.
 
Lower Group of Deep Cervical Lymph Glands (Supraclavicular
pmph Glands). —These glands lie in the anterior part of the subclavian
iangle, and are related superficially to the intermediate supraclavicular
'rve and deeply to the upper and middle trunks of the brachial plexus.
'iperiorly they are continuous with the upper deep cervical lymph
ands. They receive their afferent vessels from the following sources:
 
1. The back of the neck.
 
2. The axillary lymph glands.
 
3. The upper part of the pectoral region.
 
4. Occasionally the lymphatics along the cephalic vein, which
ay ascend over the clavicle.
 
5- The internal mammary lymph glands.
 
 
 
 
1190
 
 
A MANUAL OF ANATOMY
 
 
Their efferent vessels form the subclavian trunk, which, with t
jugular trunk, opens into the thoracic, or into the right lymphai
duct.
 
Subclavian or Supraclavicular Triangle. —The subclavian triangle
the lower division of the posterior triangle of the neck, and is separate
from the upper division or occipital triangle by the inferior belly
 
 
 
Fig. 715. —Common Carotid and Subclavian Arteries exposed by Remow
of Sterno-mastoid, Omo-hyoid, and Internal Jugular Vein.
 
the omo-hyoid muscle. Situated above the middle third of the clavicl*
it is of small size until the deep cervical fascia, which ensheathes tt
inferior belly of the omo-hyoid, has been divided.
 
Boundaries — Superior .—The inferior belly of the omo-hyoid muscf
Inferior .—The middle third of the clavicle. Anterior .—The clavicuk
part of the sterno-mastoid muscle. Roof .—The skin; superficial fasci
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1191
 
 
platysma muscle; medial, intermediate, and lateral supraclavicular
es; a part of the external jugular vein; and the deep cervical fascia,
if.—The scalenus medius and posterior muscles, and the serratus
:rior.
 
rhe extent of the triangle is affected by (T) the height to which
inferior belly of the omo-hyoid ascends above the clavicle, and
the extent of the clavicular attachments of the sterno-mastoid
trapezius muscles. The depth of the triangle is influenced by the
tion of the shoulder, being greater when the shoulder is raised
carried forwards, and less when it is depressed and carried
kwards.
 
Contents. —The contents are: (1) the greater portion of the third
t of the subclavian artery; (2) small portions of the transverse
 
 
 
Brachial Plexus
Cephalic Vein
Musculo-cutaneous Nerve
Deltoid
 
 
Trapezius
 
1 Suprascapular Vessels
 
\ Transverse Cervical Artery
 
Inferior Belly of Omo-hyoid
 
Scalenus Anterior
/ Sterno-mastoid
 
 
-Clavicle in section
 
 
Subclavius
 
 
Axillary Artery
- Axillary Vein
 
Pectoralis Major (cut)
 
 
Pec!oralis Minor
Lateral Root of Median Nerve
 
 
Medial Cutaneous
Nerve of Arm
 
Axillary Vein
 
Ulnar Nerve
 
 
Medial Root of Median Nerve
Medial Cutaneous Nerve of Forearm
 
 
Fig. 716. —Subclavian and Axillary Regions.
 
 
vical artery and vein; (3) the lower portion of the external jugular
in; (4) the nerve-trunks of the brachial plexus; and (5) the nerve
the subclavius muscle, the suprascapular nerve, and the nerve
serratus anterior
 
Third Part of the Subclavian Artery. —1 his part of the vessel extends
>m the outer border of the scalenus anterior muscle to the outer
rder of the first rib, where it becomes the axillaiy artery. Its course
downwards and outwards, and for the greater part of its extent it
s in the subclavian triangle. Its last inch or so, howevei, passes
 
hind the clavicle and subclavius muscle.
 
Relations- — Anterior .—The skin; superficial fascia and platysma;
edial, intermediate, and lateral supraclavicular nerves; deep cervical
>cia; clavicle and subclavius muscle; transverse cervical vessels;
prascapular vessels; nerve to the subclavius muscle; and the termina
 
 
 
 
 
 
 
 
 
1192
 
 
A MANUAL OF ANATOMY
 
 
portion of the external jugular vein. The last-named vessel cro:
in front of the artery close to the sterno-mastoid muscle, and in ■
situation is joined by the transverse cervical and suprascapular ve
A plexiform arrangement of veins is sometimes met with in from
the artery, which may be rendered more complex by a branch ascenc
superficial to the clavicle from the cephalic vein. Posterior .—'
scalenus medius, the lower nerve-trunk of the brachial plexus in
vening. Superior .—The upper and middle nerve-trunks of the brad
plexus, the latter being nearest the vessel. Inferior .—The upper s
face of the first rib and the subclavian vein, the vein being on a m
anterior plane than the artery, and lying behind the clavicle.
 
It is most important to understand that, though the first rib is spoken o
an inferior relation, its surface is so oblique that it is just as much behinc
below.
 
The third part of the subclavian artery does not always give
any branch. In very many cases, however, the deep branch of
transverse cervical artery arises from it, instead of from the latter arte
 
which is a branch of the first, p
of the subclavian. In these ca
the posterior scapular art
passes outwards between
nerve - trunks of the brad
plexus.
 
The direction of the third p
of the artery is indicated b^
line drawn from a point on i
posterior border of the ster
mastoid muscle, about J ir
above the clavicle, to the cen
of that bone. The artery may
compressed as it passes over 1
first rib, the guide to it at t
point being the centre of i
clavicle. In order to tie the si
clavian artery in the dead bo<
after fully depressing the clavi(
feel for the outer edge of the scalenus anterior muscle, and follow
to its insertion on the first rib. The structure which lies immediat
behind the muscle here is the artery; and great care must be taken i
to mistake it for the lower trunk of the brachial plexus.
 
For the manner in which the collateral circulation is carried
after ligation of the third part of the subclavian artery, see p. 441.
 
The subclavian vein, in the region of the subclavian triangle,
situated behind the clavicle, where it lies below and anterior to 1
artery. On the upper surface of the first rib it is anterior to the scaler
anterior, and it receives the external jugular vein, and in some ca
the anterior jugular vein,
 
 
 
Fig. 717.— Plan of Branches of
Subclavian Artery.
 
 
 
 
 
THE HEAD AND NECK
 
 
ii 93
 
 
L'he transverse cervical artery lies in the subclavian triangle for
Lort distance only, close to where the inferior belly of the omoid passes deep to the sterno-mastoid. It passes outwards behind
former muscle into the lower part of the occipital triangle, where
ivides into its superficial and deep branches, the former entering
trapezius, and the latter passing in front of the levator scapulae,
r which it descends along the base of the scapula in front of the
nboid muscles.
 
rhe transverse cervical vein opens into the external jugular vein,
•e being a valve at or near its ending.
 
rhe suprascapular artery is not in the subclavian triangle, but lies
ind the clavicle, close to its upper aspect. It will be described in
nection with the first part of the subclavian artery (see p. 1243).
 
The suprascapular vein also lies behind the clavicle, and it opens
> the external jugular vein, there being a valve at or near its ending.
The external jugular vein will be found described on p. 1176.
 
Brachial Plexus. —The brachial plexus is situated in the lower part
he posterior triangle of the neck, behind the clavicle, and in the
>er part of the axilla. Its complex formation is rendered simple
arranging it into four stages—namely (1) nerve-roots, (2) nervenks, (3) divisions of nerve-trunks, and (4) nerve-cords.
 
First Stage .—The nerves which form the plexus are the anterior
nary rami of the fifth, sixth, seventh, and eighth cervical, and the
ater part of that of the first thoracic. Superiorly the plexus is
lforced by a small descending branch from the fourth cervical,
ich joins the fifth, and interiorly it is occasionally reinforced by a
,nch from the second thoracic, which joins the first. As regards the
t thoracic nerve, the part of it which does not join the plexus, and
ich is of small size, enters the first intercostal space to become the
t intercostal nerve. The nerves, as thej^ emerge at the side of the
k, are placed between the scalenus anterior and scalenus medius,
which they give branches.
 
Second Stage .—The fifth and sixth cervical nerves join at the
;er border of the scalenus anterior to form the upper trunk ; the
r enth cervical remains meanwhile single, and forms the middle
nk ; and the eighth cervical and greater part of the first thoracic
ite between the scalene muscles to form the lower trunk. There
! thus three trunks—upper, middle, and lower.
 
Third Stage.—A little above the clavicle each of the three trunks
^aks up into anterior and posterior divisions.
 
Fourth Stage.— The anterior divisions of the upper and middle
inks unite to form the lateral cord of the plexus; the anterior
dsion of the lower trunk, which is of large size, forms the medial
rd; and all three posterior divisions (that of the lower trunk being
small size) unite to form the posterior cord. There are thus three
rds—lateral, medial, and posterior. As a variety, the anterior
/ision of the middle trunk may subdivide into two branches, one
tering the lateral cord and the other the medial.
 
 
H 94
 
 
A MANUAL OF ANATOMY
 
 
Branches of the Plexus above the Clavicle. —The branches are c<
veniently divided into two groups—supraclavicular, arising above 1
clavicle, and coming from nerve-roots and nerve-trunks; and inf
clavicular, arising below the clavicle, and coming from nerve-cords.
 
Supraclavicular Branches .—These are muscular branches fr<
the four cervical nerves to the scalene muscles and longus cervicis.
 
One root of the phrenic nerve (inconstant) from the front of 1
fifth cervical.
 
The Nerve to the Rhomboids. —This branch arises from the ba
of the fifth cervical, close to or along with the highest root of 1
 
 
 
Iug. 718. —The Brachial Plexus.
 
\ ellow=spinal nerves and their branches; blue=trunks; red=lateral cord
 
purple=medial cord; grey=posterior cord.
 
neive to serratus anterior, and it takes a backward course throu
the scalenus medius.
 
The Nerve to the Serratus Anterior (Nerve of Bell or Posteri
Thoracic Nerve). —This branch arises by three roots from the ba
of the fifth, sixth, and seventh cervical nerves. The upper two ro(
pierce the scalenus medius muscle below the nerve to the rhomboi(
either conjointly or separately, whilst the lowest root passes in fro
of the scalenus medius, and joins the trunk formed by the oth(
neai the first rib. The nerve then courses behind the brachial plex
and the first part of the axillary artery to the axillary surface of t
serratus anterior, which it supplies.
 
 
 
 
 
THE HEAD AND NECK
 
 
ii95
 
 
*
 
he Nerve to the Subclavius. —This small branch arises from the
of the upper trunk, its fibres being derived from the fifth cer. It descends in front of the third part of the subclavian artery,
passing behind the clavicle, enters the subclavius muscle on
leep aspect. This nerve sometimes communicates with the
nic nerve.
 
he Suprascapular Nerve. —This is a large nerve which arises from
Dack of the upper trunk, its fibres being derived from the fifth
 
 
 
Fig. 719. —Plan of Triangles of Neck.
 
sixth cervical. It is directed downwards, outwards, and backds beneath the trapezius and inferior belly of the omo-hyoid to
upper border of the scapula, on approaching which it meets the
rascapular artery. It is distributed to the supraspinatus and
ispinatus muscles and shoulder-joint.
 
[t will be seen that all the branches of the brachial plexus belong
er to the anterior or posterior divisions, even if they come off before
>e divisions become separate, and that their distribution gives a clue
 
 
 
 
 
 
 
 
 
 
1196
 
 
A MANUAL OF ANATOMY
 
 
to the division to which they belong. The nerves to the scale]
medius and posterior, as well as that to the rhomboids, the sup
scapular, and to serratus anterior, are, from their distribution, clea
dorsal or posterior in their origin; while the nerves to the scale]
anterior, longus cervicis, and subclavius are equally clearly anteric
 
Below the clavicle the lateral and medial cords give off all the antei
branches, while the posterior come entirely from the posterior cord.
 
For the infraclavicular branches of the brachial plexus, see p. 4
 
Anterior Triangle. —This triangle is situated in front of the ster:
mastoid muscle, and its base is directed upwards.
 
Boundaries — Anterior. —The middle line of the neck—that is
say, a line extending from the chin to the upper border of the mai
brium sterni. Posterior. —The anterior border of the sterno-mast
muscle. Superior. —The lower border of the mandible and a 1
drawn from the angle of that bone to the mastoid process. 1
triangle is covered by the skin, superficial cervical fascia, platysr
and deep cervical fascia. Superficial to the deep fascia there
the following structures: the anterior jugular vein, the ramificati<
of the anterior cutaneous nerve of neck, and the cervical branch of 1
facial nerve.
 
The anterior triangle is subdivided into three triangles by i
superior belly of the omo-hyoid muscle inferiorly, and posterior be
of the digastric muscle superiorly. The subdivisions from bel
upwards are called muscular, carotid, and submandibular.
 
The muscular triangle is bounded anteriorly by the middle line
the neck; posteriorly by the anterior border of the sterno-mastoid; a
superiorly by the superior belly of the omo-hyoid.
 
The carotid triangle is bounded inferiorly by the superior be
of the omo-hyoid; superiorly by the posterior belly of the digast
and stylo-hyoid; and posteriorly by the anterior border of the sten
mastoid.
 
The submandibular triangle (submaxillary triangle) is bound
 
postero-inferiorly by the lower part of the posterior belly of the digasti
the stylo-hyoid, and by the body of the hyoid bone: antero-inferio
by the mid-line of the neck; and superiorly by one half of the be
of the mandible, and a line drawn from the angle of that bone to t
sterno-mastoid muscle.
 
Contents of the Triangles—Muscular Triangle (Fig. 719).—The ai
of this triangle is occupied by the sterno-hyoid and sterno-thyn
muscles; hence the name muscular triangle. Under cover of th<
muscles there are the carotid sheath with its contents, the late
lobe of the thyroid gland, the trachea, and the larynx. The oesophag
lies behind the trachea, with a slight inclination towards the 1
side at the root of the neck, and the recurrent laryngeal nerve 1
in the groove between the trachea and the oesophagus. The infer
thyroid artery has a tortuous course inwards behind the lower p;
of the carotid sheath, and the trunk of the sympathetic descer
behind both.
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1197
 
 
arotid Triangle. —This triangle contains the upper part of the
non carotid, and the beginnings of the external and internal
:id arteries, all of which are overlapped by the anterior border
le sterno-mastoid, when the connective tissue which ensheathes
muscle is undisturbed. The common carotid and internal carotid
ies, together with the vagus nerve, are contained within the
tid sheath, and the descendens hypoglossi lies in front of the
th, or within it, being situated in either case in front of the common
tid artery. The sterno-mastoid artery and the superior thyroid
cross the sheath near the bifurcation of the common carotid
 
 
.Transverse Facial Artery
 
 
Parotid Duct -Buccinator Muscle
Facial Artery -Submental Artery
 
 
Lingual Artery —
Sup. Lar. Art. and Nerve
Thyro-hyoid Muscle _.
Superior Thyroid Artery
 
 
 
Inf. Belly of Omo-hyoid-,
 
Subclavian Artery
(third part)
 
 
, Superficial Temporal Artery
 
HPI"' Maxillary Artery
 
Posterior Auriculav
 
r Artery
 
/r _ Occipital Artery
 
>itW
 
,,,, . .-. - JIlifL. _Stylo-hyoid Muscle
 
WyMSm---- Post - Bel, y of Di s astric
 
!£- _Hypoglossal Nerve
 
-Descendens Hypoglossi
 
Jj_External Carotid Artery
 
 
-Sterno-mastoid
 
Trapezius
 
_Transverse Cervical Artery
 
_. Suprascapular
f\ Artery
 
 
^iwii iin^wiu !ii wu M1 1 \w ' An '
 
Fig. 720.—The Left Side of the Head and Neck.
The platysma myoides has been removed.
 
 
*ry, and the carotid body lies behind the vessel about the same
d. The deep cervical lymph glands lie just lateral to the course
he internal jugular vein. The origins of the superior thyroid, lingual,
ial, and occipital arteries are contained in this triangle, and the
ending pharyngeal branch of the external carotid lies deeply between
t vessel and the internal carotid. The internal jugular vein in this
ingle receives the common facial, lingual, and superior thyroid veins,
e hypoglossal nerve lies along the lower border of the posterioi
ly of the digastric muscle, and it here gives off, fiom behind
wards, the descendens hypoglossi and the nerves to thyio-hyoid
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1198
 
 
and genio-hyoid, the former passing downwards in front of, or witl
the carotid sheath, and the latter passing forwards and downwards
an acute angle with the parent trunk. The internal branch of
superior laryngeal nerve lies deeply behind the bloodvessels, and
external laryngeal branch of that nerve descends parallel and deep
the superior thyroid artery, and passes deep to the upper end of
posterior border of the sterno-thyroid muscle. The vagus nerve
within the carotid sheath, and the sympathetic trunk is behind
The accessory nerve lies deeply, its course being downwards and ba
wards beneath the sterno-mastoid, the deep portion of which usual!
pierces about an inch below the angle of the mandible.
 
Digastric Triangle.—This triangle is divided into two parts, antei
and posterior, by the stylo-mandibular ligament. The anterior p
contains the superficial part of the submandibular gland, the antei
facial vein being superficial to it, and the facial artery being embed(
in its upper and back part. In this triangle the facial artery gives
its ascending palatine, tonsillar, glandular, and submental brand
The muscles in the floor of the anterior part of the triangle are
mylo-hyoid and a part of the hyo-glossus. The superficial part of
submandibular gland is superficial to the mylo-hyoid muscle, a
conceals the mylo-hyoid nerve and submental artery, which are
direct contact with the muscle. The hypoglossal nerve lies upon t]
part of the hyo-glossus muscle which appears in the anterior part
the triangle, but it soon disappears beneath the posterior free bon
of the mylo-hyoid muscle. It is important to notice that it lies para
to and just above the greater horn of the hyoid bone, which forms
important structure in the floor of the triangle, and shows a little
the insertion of the thyro-hyoid muscle below it.
 
The anterior jugular vein and the anterior cutaneous nerve of 1
neck have been already described (see pp. /1173 and 1187). 1
cervical branch of the facial nerve will be found described on p. 12
 
Submandibular Lymph Glands (Submaxillary Lymphatic Glands)
These glands lie upon the superficial surface of the submandibu
salivary gland, under cover of the deep cervical fascia. They forn
chain beneath the corresponding half of the base of the mandit
which extends from near the angle of the bone to near the origin of 1
anterior belly of the digastric muscle. The central gland of the chi
is closely related to the facial artery as that vessel is about to asce
 
 
over the base of the mandible,
from the following sources:
 
1. The front of the scalp.
 
2. The side of the nose.
 
3. A few from the lower eyelid.
 
4. The lower part of the cheek.
 
5. Half of the upper lip.
 
6. The lateral part of the lower lip
 
7. The anterior third of the lat
eral border of the tongue.
 
 
They receive their afferent vess
 
 
8.
 
 
9
10.
 
 
11.
 
12.
 
 
The subjacent portion of
floor of the mouth.
 
Half of the upper gum.
 
The lateral part of the lo^
gum.
 
The facial lymph glands.
 
The submandibular and si
lingual salivary glands.
 
 
 
THE HEAD AND NECK
 
 
1199
 
 
Their efferent vessels pass to the upper deep cervical lymph glands,
ch are on a level with the upper border of the thyroid cartilage of
larynx.
 
The submental lymph glands lie beneath the chin, and are two or
;e in number. They receive their afferent lymphatics from the tip
he tongue, the front of the floor of the mouth, and the inner part
the lower lip; and their efferent lymphatics pass to the subidibular lymphatic glands. It must be borne in mind that these
Lphatic vessels, like those elsewhere in the body, frequently comnicate across the middle line.
 
The prelaryngeal lymph glands, when present, are situated in front
the crico-thyroid ligament, and are one or two in number. They
give their afferent lymphatics from the interior of the larynx,
dw the rima glottidis, and from the adjacent part of the thyroid
nd. Their efferent lymphatics pass to the inferior deep cervical
lph glands. The upper part of the larynx drains into the superior
p cervical lymph glands along a course accompanying that of the
>erior laryngeal vessels.
 
The para- and pretracheal lymph glands lie in front and at the sides
the trachea, from which, as well as from the adjacent part of the
a*oid gland, they receive their afferent lymphatics. Their efferent
iphatics pass to the inferior deep cervical lymph glands.
Occasionally a few lymph glands are met with along the course
the anterior jugular vein.
 
Deep Cervical Lymph Glands. —These glands lie deep to the sternostoid muscle, and are very numerous. They are arranged in two
tups, superior and inferior.
 
The superior deep cervical lymph glands lie along the internal
;ular vein above the level of the upper border of the thyroid cartilage,
ey receive their afferent lymphatics from the cranial cavity, the
ernal maxillary glands, some of the parotid and submandibular
nph glands, the root of the tongue, the upper part of the thyroid
nd, the upper part of the larynx, and the lower part of the pharynx,
eir efferent lymphatics pass to the inferior deep cervical lymph
nds. One large gland of this group is very constant, and lies close
the angle of the mandible. It drains the dorsum and sides of the
igue, but not the tip as a rule.
 
The inferior deep cervical lymph glands lie along the lower part of
j internal jugular vein, and extend outwards and backwards deep to
 
1 sterno-mastoid as far as its posterior border. These lymph glands
J continuous inferiorly with the deep cervical lymph glands lying
the subclavian triangle, and, through these, with the axillary glands,
ey receive their afferent lymphatics from the superior deep cervical
nph glands, the upper superficial cervical lymph glands, the lower
rt of the thyroid gland and larynx, and the cervical portions of the
ichea and oesophagus. Their efferent lymphatics unite to form a
^gle vessel, called the jugular trunk, which opens on the left side into
 
2 thoracic duct, and on the right side into the right lymphatic duct.
 
 
1200
 
 
A MANUAL OF ANATOMY
 
 
Infrahyoid Muscles. —These are the omo-hyoid, sterno-hyoi
sterno-thyroid, and thyro-hyoid.
 
Omo-hyoid. —This muscle consists of two bellies, superior (anteric
and inferior (posterior), and an intermediate tendon. Origin .—I
means of the inferior belly from (i) the upper border of the scapu
close to the inner side of the suprascapular notch, and (2) the supr
scapular ligament, which bridges over the suprascapular notch.
 
Insertion .—By means of the superior belly into the outer third
the lower border of the body of the hyoid bone immediately later
to the insertion of the sterno-hyoid muscle.
 
Nerve-supply .—The superior belly is supplied by the ramus desce
dens hypoglossi, and the posterior belly derives its branches from t]
ansa hypoglossi.
 
 
 
Greater Horn
 
 
Lesser Horn
 
 
Omo-hyoid (Sup. Belly)
 
 
1
 
 
Fig. 721.—The Hyoid Bone, showing its Muscular Attachments.
 
The inferior belly is contained in the posterior triangle of the nec
and separates the occipital from the subclavian triangle. Its course
forwards and slightly upwards, and it passes deep to the stern
mastoid muscle, where its fibres terminate in the intermediate tendo
It is ensheathed by a deep process of the deep cervical fascia as th
fascia crosses the posterior triangle, and this process is attached to t
back of the inner end of the clavicle and the first rib, which explai
the almost horizontal position occupied by the inferior belly.
 
The superior belly proceeds from the intermediate tendon, ai
passes upwards and slightly inwards to the body of the hyoid bor
As it emerges from beneath the anterior border of the sterno-mastc
muscle the superior belly crosses the carotid sheath on a level wi
the narrow anterior part of the cricoid cartilage, and in the anteri
triangle of the neck it forms the separation between the muscular ai
carotid triangles.
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1201
 
 
rno-hyoid — Origin. —(i) The posterior surface of the manubrium
at its upper and outer part; (2) the posterior sterno-clavicular
jnt; and, sometimes, (3) the posterior surface of the clavicle at
Ler end.
 
sertion. —The inner two-thirds of the lower border of the body of
roid bone, extending from the middle line to the insertion of the
or belly of the omo-hyoid.
irve-supply. —The ansa hypoglossi.
 
ie muscle is flat and ribbon-like, and rests upon the sternod and thyro-hyoid.
 
irno-thyroid — Origin. —(r) The posterior surface of the manusterni at its upper and outer part below the origin of the sterno; and (2) the posterior surface of the first costal cartilage.
sertion. —The oblique line on the -outer surface of the lamina of
Lyroid cartilage.
 
irve-supply. —The ansa hypoglossi. The nerves enter this and
st muscle quite at the lower part of the neck,
ie muscle is broader, but shorter, than the sterno-hyoid underwhich it lies. Within the thorax the right muscle lies in front
3 innominate artery, and the left in front of the left common
d artery and left innominate vein. In the neck each muscle
upon the carotid sheath and the corresponding right or left lobe
5 thyroid gland.
 
ie sterno-hyoid muscles as they leave the thorax are separated
1 interval, in which situation the sterno-thyroid muscles lie in
contact. As the muscles ascend the sterno-hyoids converge, but
erno-thyroids diverge.
 
tyro-hyoid — Origin. —The oblique line on the outer surface of
tmina of the thyroid cartilage.
 
\sertion. —(1) The outer half of the lower border of the body of
yoid bone; and (2) the basal half of the greater horn of that
 
erve-supply. —A special branch of the hypoglossal, though originlerived from the first and second cervical nerves. The nerve
3 the surface of the muscle close to its posterior border,
ie muscle is quadrilateral. Its superficial surface supports the
ior belly of the omo-hyoid and the sterno-hyoid muscles, and its
surface is related to the lamina of the thyroid cartilage, the
-hyoid membrane, the internal branch of the superior laryngeal
;, and the superior laryngeal artery.
 
e nerves which supply the infrahyoid group of muscles are derived from
'st, second, and third cervicals through the hypoglossal and ansa hypo
ction of the Infrahyoid Muscles — Omo-hyoid. —(1) lo depress
yoid bone; and (2) to render tense the deep cervical fascia in the
part of the neck.
 
erno-hyoid. —To depress the hyoid bone,
erno-thyroid. —To depress the thyroid cartilage.
 
 
76
 
 
 
 
 
1202
 
 
A MANUAL OF ANATOMY
 
 
Thyro-hyoid.— (i) To depress the hyoid bone; and (2) to ele
the thyroid cartilage, as in the production of high notes, or in
glutition.
 
Structures in the Median Line of the Neck. —The median line of
neck is divisible into two regions, suprahyoid and infrahyoid.
 
Suprahyoid Region. —The innermost fibres of the two platy
muscles decussate at the median line for a short distance below
chin. On either side of the median line, under cover of the platy<
is the anterior belly of the digastric muscle. The anterior bellic
 
 
Posterior Belly of Digastric—
and Stylo-hyoid
Hyo-glossus Muscle and
Hypoglossal Nerve
 
 
Ster. Head of St.-mas. -Crico-thyroid Muscle -
 
Cricoid Cartilage
Lat. Lobe of Thyroid Gland
 
Trapezius
 
Clavicular Head of
Stemo-mastoid
Brachial Plexus
 
 
Subclavian Artery
(third part)
 
Clavicle
 
 
 
Anterior 'Belly of Diga:
jf Mylo-hyoid
 
 
Body of Hyoid Bone
_ Superior Belly of Omo
' - Stemo-hyoid
 
 
Thyro-hyoid
 
 
Thyroid Cartilage
Sterno-thyroid
Superior Belly of Omo
Crico-thyroid Ligamen
 
 
Stemo-hyoid
 
 
Isthmus of Thyr
Gland
 
 
■s Inferior Thyroid
y of Veins
 
Cla. Head of St.-i
 
 
,T\T
 
-\r Sterno-thyroid
 
 
Sternal Head of Sternomastoid
 
 
Sterno-thyroid
 
 
Sterno-hyoid
 
 
Fig. 722.—Dissection of the Front of the Neck.
 
The area bounded on either side by the anterior belly of the digastric a
below by the body of the hyoid bone is the submental triangle.
 
 
opposite sides are near each other at the chin, but as they des<
with an inclination outwards they diverge from each other, and 1
between them a triangular interval sometimes called the subm<
triangle. The base of this triangle is formed by the body of the h
bone, and each lateral boundary is constructed by the anterior 1
of the digastric, the apex being placed at the chin. The area oi
triangle is occupied by the anterior portions of the mylo-hyoid mus
which meet at the median line in a tendinous raphe, and super!
to these muscles there are the submental lymph glands.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1203
 
 
Epiglottis
 
 
Greater Horn of Hyoid Bone~
 
Lesser Horn of Hyoid Bone Body of Hyoid Bone-"
 
Thyro-hyoid Membrane -Levator (Mandril® )
Thyroid® Muscle /
Thyroid Cartilage -
Crico-thyroid Ligament.
Pyramidal LobeCricoid Cartilage'
 
Right Lobe of Thyroid Gland
Isthmus
 
 
Trachea
 
 
lubmental Lymph Glands. —These glands, usually two in number,
 
1 the submental triangle beneath the chin and above the body of
hyoid bone, one being on either side of the median line. Each
d receives its afferent vessels from (1) the medial portions of the
;r lip and lower gum; (2) the tip of the tongue and adjacent portion
le floor of the mouth; (3) the skin of the chin; and (4) sometimes
upper lip. Their efferent vessels pass to (1) the submandibular
ph glands, and (2) the
ilo-omo-hyoid lymph gland,
of the superior deep cer
1 lymph glands,
infrahyoid Region. —The re
from the hyoid bone downis to the suprasternal notch
the upper border of the
Lubrium sterni is of conrable importance in conion with bronchocele or
re, laryngotomy, and traDtomy.
 
The body of the hyoid bone
 
r well-marked structure,
lg with the greater horn on
er side of it. Below the
id bone there is the thyroid membrane, which passes
/ards within the lower borof the hyoid bone. The
t structure is the thyroid
kilage, the upper border of
ch has a well - marked
iian notch, whilst its two
form by their union the
minent laryngeal prominence
mum Adami).
 
Succeeding the thyroid carti
2 there is a narrow interval, which is occupied by the crico-thyroid
iment, and immediately below this is the narrow anterior part of
 
cricoid cartilage. The crico-thyroid ligament is only exposed close
the median line, being elsewhere covered by the two crico-thyroid
scles. The exposed part of the ligament is crossed by the cricovoid arterial arch, which is situated midway between the thyroid
1 cricoid cartilages, and lying upon the ligament there may be
i or two prelaryngeal lymphatic glands. Laryngotomy may be
formed in the crico-thyroid region, and the crico-thyroid arterial
h has to be borne in mind.
 
Succeeding the cricoid cartilage is the trachea, which, as it
cends, inclines backwards, and therefore becomes somewhat
 
 
Right Bronchus^
Eparterial Bronchus,
Hyparterial Bronchus.^'
 
 
Si'- ; .
 
err::.?*,
 
iCZZZv
 
.
 
^ ".."..-A
 
 
 
Left Bronchus
 
Fig. 723. —The Hyoid Bone, Larynx
Trachea, Bronchi, and Thyroid Gland
(Anterior View).
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1204
 
 
A MANUAL OF ANATOMY
 
 
inaccessible; at the suprasternal notch it may be i£ inches fr
the surface. The thyroid gland is intimately related to it superioi
Each lobe closely embraces it laterally as low as about the fifth ri
and the isthmus lies in front of the second and third rings as a n
but its position is liable to variation. Crossing the upper border of
isthmus there is one of the branches of the superior thyroid arte
known as the artery of the isthmus.
 
There is nothing of any importance in front of the trachea ab<
the isthmus of the thyroid gland. Below the isthmus there is a m
or less copious plexus of veins, called the inferior thyroid plexus, fr
which the right and left inferior thyroid veins descend. OccasI
ally a small artery, called the arteria thyroidea ima, ascends direc
in front of this part of the trachea in the median line to reach i
 
 
\c
 
 
 
 
% \
 
 
\ \ \ » / / / / /
—V-A-A-/ / /
 
 
phrenic ru-^
scalenus anterior'--.,
thyro-cervical trunk—-.
 
sub'elcw^ ay—
scalenus medius—
 
vertebral vn.-vertebral ay.-
 
 
-vagus n.
'omo-hyoid
 
—brachial plexus
 
-I 5 - 1 rib
 
sympathetic
trunk
 
Z n _d r jb
 
 
zura—"
 
oesophagus
 
long, cap. and long cer.
disc, between 1st and 2nd thoracic vtb.
 
 
\2 n - d thoracic tr pr
'"'I s - thoracic spinous pr
 
 
Fig. 724.—Section through Lower Part of Neck.
 
 
isthmus of the thyroid gland. The innominate, and even the rig
common carotid, artery and the left innominate vein sometirr
encroach upon the front of the trachea towards the root of the nec
The latter is a particularly important arrangement to remember, a:
occurs more frequently in women and children. In early life t
upper part of the thymus covers the front of the trachea. The foi
going structures are covered by the sterno-thyroid and sterno-hyc
muscles in the following manner: the two sterno-thyroid muscles a
in contact with each other for a short distance above the manubriri
sterni, so as to cover the trachea, but the two sterno-hyoid muse!
are here separated by an interval; superiorly the two sterno-thyre
muscles diverge, and the two sterno-hyoid muscles come very near
together.
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1205
 
 
he operation performed upon the trachea is tracheotomy,
rding as it is performed above or below the isthmus of the thyroid
1 , it is spoken of as the high or the low operation. In the high
ition there is no anatomical obstacle, unless it be a close attach: of the isthmus of the thyroid gland to the tracheal rings which
vers. In the low operation the following obstacles are present:
he trachea is here less accessible, because it recedes from the
,ce; (2) the inferior thyroid plexus of veins might prove trouble
 
 
 
.Ansa
 
 
- Ant. Jug. V.
Vagus
 
 
N. toThyro-hyoid
 
Int. Laryngeal
Nerve
 
 
Ext. Laryngeal
Nerve
 
Descendens
Hypoglossi
Desc. Cerv.
 
 
sser Occip. N. •
 
 
Upper Cord of
rachial Plexus
 
 
cessory Nerve..
 
 
Phrenic
 
725.— Deep Nerves in the Neck in Relation with Carotid Sheath.
 
 
e; (3) an arteria thyroidea ima may be present; (4) the innominate
right common carotid arteries and the left innominate vein may
endangered; and (5) in young children the thymus would be in the
 
Fhe Ramus Descendens Hypoglossi (Descendens Cervicis Nerve).
 
ramus descendens arises from the hypoglossal nerve as the latter
ks round the occipital artery, its fibres being derived from the
municating branches which the hypoglossal receives from the loop
 
 
 
 
 
 
 
 
1206
 
 
A MANUAL OF ANATOMY
 
 
between the first and second cervical nerves. The nerve, whicl
long, passes downwards and slightly forwards, lying upon, or witl
the carotid sheath, and in either case directly over the line of
common carotid artery. Before reaching the centre of the necl
furnishes a branch to the superior belly of the omo-hyoid mus
Lower down it is joined by a branch which is formed by the unior
the two rami communicantes cervicales from the anterior primary r;
of the second and third cervical nerves. These two rami, howe^
sometimes join it separately. In this manner a loop is formed usu;
about the level of the cricoid cartilage, which is called the ansa hy
 
 
H.G.
 
 
 
Fig. 726.— Scheme of the Hypoglossal Nerve, showing its
Connections with Cervical Spinal Nerves.
 
Sy., twig from sympathetic; Pn., communicating with vagus; ic, 2c, 3c, fi
second, and third cervical; C.H., communicans hypoglossi; C.C., c<
municantes cervicalis; D.C., descendens hypoglossi; A.B.O.H., to ante
belly of omo-hyoid; A.C., ansa hypoglossi; S.H., to sterno-hyoid; S.T.
sterno-thyroid; P.B.O.H., to inferior belly of omo-hyoid; T.H., to th]
hyoid; G.H., to genio-hyoid; G.H.G., to genio-glossus; H.G., to hyo-gloss
S.G., to stylo-glossus.
 
glossi. The convexity of the loop is directed downwards, and fr
it branches are given off to (1) the sterno-hyoid, (2) the sterno-thyrc
and (3) the inferior belly of the omo-hyoid muscles.
 
The fibres of the ramus descendens hyo-glossi are of spinal, not hypoglos;
origin.
 
For the rami communicantes cervicales, see Cervical Plexus (p. ii£
 
The Nerve to Thyro-hyoid. —This nerve, which is composed of spf
fibres derived from the loop between the first and second cervi
nerves, arises from the hypoglossal at the lower border of the poster
belly of the digastric. It passes forwards and downwards, formi
 
 
 
THE HEAD AND NECK
 
 
1207
 
 
:ute angle with the parent trunk, and enters the thyro-hyoid
le on its superficial surface.
 
irotid Sheath. —The carotid sheath, already described on p. 1179,
ived from the posterior lamina of the sheath of the sterno-mastoid
le, and is intimately connected anteriorly with the pretracheal
, and posteriorly with the prevertebral layer, of the deep cervical
i The interior of the sheath is divided into three compartments—
•, inner, and posterior. The outer and inner compartments are
•ated from each other by a septum, the inner compartment containhe common carotid artery and, it may be, the ramus descendens
glossi, and the outer compartment the internal jugular vein. The
rior compartment is situated within the back part of the septum,
contains the vagus nerve. The ramus descendens hypoglossi may
pon the sheath, or within it, and the trunk of the sympathetic
mds behind, and in intimate relation with it.
 
tie foregoing is the usual account of this sheath, but there are some anaits who believe that not only it, but many other fascial planes are hardly
 
 
 
Fig. 727.—Scheme of Section through Carotid Sheath showing
 
Contents and Certain Relations.
 
 
mizable in the living or in the undisturbed dead body In any case, there
> reason to believe that the carotid has more or less of a sheath than any
r artery of its own size elsewhere.
 
[Jommon Carotid Arteries— The right common carotid artery arises
1 the innominate artery behind the upper border of the right sternoicular joint, and the left common carotid aitery arises from the
er surface of the arch of the aorta, in close proximity to the origin
he innominate artery. The vessel of the right side is therefore
rely cervical, whilst that of the left side is partly thoracic and part y
 
The thoracic part of the left common carotid artery has alieady
n described in connection with the thorax (see p. 1039)In the neck the common carotid artery of each side extends from
back of the corresponding sterno-clavicular joint to the level o
upper border of the thyroid cartilage of the larynx, which corrends to the disc between the bodies of the third and fourth cervica
tebrse. At this level the vessel divides into the external and interna
 
 
 
 
1208
 
 
A MANUAL OF ANATOMY
 
 
 
Fig. 728. —The Aorta in
 
 
1. Arch of the Aorta
 
2. Aortic Isthmus
 
3. Aortic Spindle
 
4. Descending Aorta
 
5. Coronary Arteries (from
 
Ascending Aorta)
 
6. Innominate Artery
 
7. Left Common Carotid
 
8. Left Subclavian
 
9. Right Common Carotid
 
 
the Thorax, and the
Head and Neck.
 
10. Right Subclavian
 
11. External Carotid
 
12. Internal Carotid
 
13. Maxillary
 
14. Superficial Temporal
 
15. Vertebral
 
16. Internal Mammary
 
17. Thyro-cervical Trunk
 
18. Inferior Thyroid
 
19. Transverse Cervical
 
 
Principal Arteries of i
 
 
20. Suprascapular
 
21. Superior Thyroid
 
22. Lingual
 
23. Facial
 
24. Occipital
 
25. Posterior Auricular
 
26. Ascending Pharyngea
 
27. Transverse Facial
 
28. Posterior Intercostals
 
29. Ligamentum Arteriosum
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1209
 
 
rotid arteries. The place of bifurcation is sometimes opposite the
dy of the hyoid bone, and, more rarely, on a level with the cricoid
rtilage of the larynx. The vessel is about 3J inches long, and its
urse is upwards and outwards in the direction of a line drawn from
3 sterno-clavicular joint to a point midway between the angle of
3 mandible and the mastoid process of the temporal bone. This
e, as high as the level of the upper border of the thyroid cartilage,
Dresents the course of the common carotid artery. At the root of
e neck the two common carotid arteries are not very far apart, and
e trachea lies in the intervening space. As the two vessels ascend
ey become more divergent, on account of the projection of the right
d left lobes of the thyroid gland and the thyroid cartilage.
 
The artery, along with the internal jugular vein and vagus nerve,
d, perhaps, the ramus descendens hypoglossi, is contained within
e carotid sheath, already described. Opposite the cricoid cartilage
is crossed by the superior belly of the omo-hyoid muscle. Below
is level it lies deeply in the region of the muscular triangle, being
Lder cover of the sterno-hyoid and sterno-thyroid muscles, in addition
the platysma and the anterior border of the sterno-mastoid. Above
is level it is situated in the carotid triangle, where it is more super:ially placed, its only muscular coverings being the platysma and the
iterior border of the sterno-mastoid.
 
Relations — Anterior .—The skin; superficial fascia and platysma;
vesting layer of the deep cervical fascia; anterior border of the
erno-mastoid; sterno-hyoid; sterno-thyroid; superior belly of the
no-hyoid; and the anterior wall of the carotid sheath. Three veins
oss the artery from without inwards: (1) the anterior jugular vein
osses it immediately above the clavicle, superficial to the sternoA>id and sterno-thyroid muscles; (2) the middle thyroid vein just
jlow the level of the cricoid cartilage; and (3) the superior thyroid
jin near its bifurcation. The sterno-mastoid branch of the superior
lyroid artery, which is of small size, passes obliquely downwards
id outwards in front of the carotid sheath in the carotid triangle,
tie ramus descendens hypoglossi descends in front of the carotid
Leath to form the ansa hypoglossi.
 
Posterior .—The posterior wall of the carotid sheath; the cervical
ansverse processes as high as the level of the fourth; the longus
irvicis, scalenus anterior, and part of the longus capitis muscles;
ie sympathetic trunk, which is intimately related to the posterior
all of the carotid sheath; the recurrent laryngeal nerve; and the
iferior thyroid artery, both of which latter structures pass inwards
id upwards behind the lower part of the sheath.
 
Lateral .—The internal jugular vein and the vagus nerve, the latter
ing between the artery and the vein, on a plane posterior to both,
t the lower part of the neck, on the right side, the internal jugular
ein leaves the common carotid artery, making a slight interval in
hich the right vagus nerve appears as it is about to pass in front
F the first part of the right subclavian artery. On the left side,
 
 
 
12 IO
 
 
A MANUAL OF ANATOMY
 
 
however, the internal jugular vein is very closely related to the commo
carotid artery, and even overlaps it.
 
Medial .—From below upwards (i) the trachea and oesophagu:
with the recurrent laryngeal nerve and the inferior thyroid arter
lying in the intervening groove; (2) the corresponding lobe of th
thyroid gland, upon which the vessel impresses a groove, and by whic
it is usually overlapped; and (3) the larynx and pharynx.
 
 
Accessory Part of Parotid Gland
 
Parotid Gland ! _ ., ,
 
Parotid Gland
 
 
Transverse Facial Artery i
 
 
Superficial Temporal Artery
Maxillary Artery
 
 
Mental Branch
of Inferior Dental |
Artery
 
 
Facial Artery
Lingual Artery
 
 
Inferior Thyroid Artery_
 
 
 
__ Posterior Auricula
Artery
 
 
\Occipital Artery
 
 
Greater Occipital
Nerve
 
Internal Carotid
Artery
 
 
External Carotid Artery.I
Superior Laryngeal Artery ,
Superior Thyroid Artery
 
Vagus Nerve (
Internal Jugular Vein l
C ommon Carotid Artery V
 
Superior Belly of Omo-hyoid __
Ascending Cervical Artery _.J
 
 
Deep Cervical
" Lymph Glands
 
 
Phrenic Nerve
 
 
! \
 
Subclavian Artery (first part) \
 
 
 
Scalenus Anterior
Muscle
 
Transverse Cervict
Artery
 
 
\ Suprascapular Artery
Thyro-cervical Trunk
 
 
Fig. 729.—Deep Dissection of the Left Side of the Neck
 
(after Spalteholz).
 
 
The common carotid artery, as a rule, gives off no branch. Th
superior thyroid artery, however, may arise from it superiorly, and i
some cases the ascending pharyngeal artery.
 
Surgery—Compression. —The part of the vessel most favourabl
situated for compression lies in front of the tubercle of the transvers
process of the sixth cervical vertebra, this tubercle, known as th
carotid tubercle, being on a level with the cricoid cartilage of the larynx
Ligation. —The part of the vessel most favourably placed fo
ligation is situated on a level with the cricoid cartilage just abov
the point where it is crossed by the anterior belly of the omo-hyoi'
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1211
 
 
,cle. The structures to be avoided in the operation are: (i) the
us descendens hypoglossi upon, or it may be within, the sheath;
the internal jugular vein and vagus nerve, both of which are
lin the sheath, and upon the outer side of the artery; and (3) the
ipathetic trunk, which lies behind and in close contact with the
ith. The small sterno-mastoid branch of the superior thyroid
;ry will probably be cut, as it passes obliquely downwards and
wards over the sheath in the carotid triangle. Ligation of the
;ry below the level of the cricoid cartilage is attended with diffi:y, the vessel being here covered by the sterno-hyoid and sternoroid muscles, in addition to the platysma and sterno-mastoid.
the left side the internal jugular vein is an additional difficulty.
Collateral Circulation after Ligation. —(1) Cross anastomoses take
:e freely between the external and internal carotid arteries of
losite sides. (2) The inferior thyroid artery of the side operated
►n anastomoses freely with the superior thyroid of the same side,
ch is a branch of the external carotid. (3) The deep cervical
nch of the superior intercostal, which latter is a branch of the
Dnd part of the subclavian artery on the right side, and of the
t part on the left side, anastomoses with the descending branch
the occipital, which is a branch of the external carotid. (4) The
tebral artery undergoes much enlargement.
 
Carotid Body.— This small body is situated behind the common
otid artery close to its bifurcation. It is composed of a few lobules
ted by connective tissue, and it receives minute twigs from the
acent part of the common carotid artery. The lobules consist
groups of polyhedral cells permeated by blood-capillaries and
apathetic nerve-filaments. Some of the cellular constituents are
omaffin cells, similar to those which are met with in the medulla
the suprarenal gland and in the sympathetic ganglia. These cells
derived from the contiguous ganglia of the sympathetic system,
e carotid body of each side is similar to the glomus coccygeum
1 organs of Zuckerkandl.
 
The carotid body is developed in part from the sympathetic system, and in
 
t from the lymphatic system. # _ , ,, , ,
 
Development.— The common carotid arteries are developed from the parts of
ventral aortae which are situated between the third and fourth aortic arches.
 
Internal Jugular Vein. —The internal jugular vein is the continuon of the intracranial sigmoid sinus. It begins in the posteroeral compartment of the jugular foramen, and ends behind the
ler end of the clavicle by joining the subclavian to form the j nn o~
nate vein. At its beginning it has a slight dilatation, called the
berior bulb. The vein descends vertically, lying at first on the outer
e of the internal carotid, and then on the outer side of the common
~otid artery, the vagus nerve being interposed in each case, and
being enclosed within the carotid sheath. The relations of the
ssel for the most part correspond to those of the artenes which 1
 
companies.
 
 
1212
 
 
A MANUAL OF ANATOMY
 
 
Tributaries.—These are as follows:
 
 
Pharyngeal.
Superior thyroid.
Middle thyroid.
 
 
Inferior petrosal sinus.
 
Common facial.
 
Lingual.
 
A small vein accompanying the occipital artery may occasional
open into it.
 
Hypoglossal Nerve
 
Second Cervical Nerve / Occipital Artery
 
 
Accessory
 
Nerve
 
 
Lesser Occipital
Nerve
 
 
Great Auricular
Nerve
 
 
R am i Communicantes (
Cervicales \
 
 
Fourth Cervical Nerve
 
 
Descending Branch of Fourth
Cervical Nerve
 
 
Supraclavicular Nerves
 
 
External Jugular
 
vd " (ci '° /if
 
Nerve to Subclavius jdjP®®
 
 
Subclavian Vein
 
 
 
Vagus Nerve
 
Nerve to Thyro-hyoid Muscl
 
 
Terminal Branches
M Hypoglossal Ner
 
 
Internal Laryngea
Nerve
 
 
External Larynge;
Nerve
 
— Ramus Descenden
Hypoglossi
 
-Nerve to Superior I
 
of Omo-hyoid
Ansa Hypoglossi
 
 
------- Anterior J ugular V
 
- -. Internal Jugular V
 
 
v //i/lfJM
 
 
Fig. 730. —Deep Dissection of the Right Side of the Neck (after
 
Hirschfeld and Leveill£).
 
1, upper part of sterno-mastoid; 2, trapezius; 3, tendon of omo-hyoid.
 
 
The inferior petrosal sinus leaves the cranial cavity through th
antero-medial compartment of the jugular foramen, and opens int
the internal jugular vein close to the base of the skull.
 
Development. —The internal jugular vein is developed from the anteric
cardinal vein.
 
The vagus nerve in the neck will be found described on p. 1327.
 
External Carotid Artery.—The external carotid artery is one c
the terminal branches of the common carotid, the other being th
internal carotid artery. In spite of its name, it is, at its origin, th
medial of the two vessels, and it lies anterior to, and nearer the media
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1213
 
 
than, the internal carotid. It extends from a point on a level
1 the upper border of the thyroid cartilage to one immediately
ind the neck of the mandible, where it divides in the substance of
parotid gland into the superficial temporal and maxillary arteries,
s about 2J inches in length, and its direction is at first upwards
forwards as far as the angle of the mandible, and then upwards
backwards. At first the artery lies in the carotid triangle, and is
iparatively superficial. As it leaves this triangle it is more deeply
:ed, being crossed by the posterior belly of the digastric and styloid muscles, and the hypoglossal nerve. Then the vessel is eroded in the substance of the parotid gland, where it is crossed from
ind forwards by the facial nerve.
 
Relations.— Antero--lateral. —The skin; superficial fasciaplatysma;
p fascia; anterior border of the sterno-mastoid; the lingual and
imon facial veins; the hypoglossal nerve (all the foregoing being
grior relations, whilst the artery lies in the carotid triangle); the
terior belly of the digastric and stylo-hyoid muscles; the greater
t of the parotid gland; the posterior facial vein; and the facial
ve. Deep or Postero-medial. —(1) The stylo-pharyngeus muscle,
;so-pharyngeal nerve, and styloid process of the temporal bone,
of which lie between the vessel and the internal carotid (the latter
g lying on a plane behind the external carotid); and (2) a small
tion of the parotid gland. The pharynx and hyoid bone; the
erior laryngeal nerve; a portion of the parotid gland; and the
terior border of the ramus of the mandible.
 
The external carotid artery has no vein in the sense of a companion
sel, but the posterior facial vein descends superficially to it in the
otid gland to near the angle of the mandible, beyond which point
artery has no vein.
 
The course of the vessel may be indicated by a line drawn from
side of the cricoid cartilage of the larynx to the tragus of the
icle.
 
Development. —The external carotid artery is, for a short portion of its
rse, the persistent part of the ventral aorta above the level of the third aortic
1. In the rest of its extent it is formed from enlarged side-branches of the
inal stem.
 
Branches.—These are arranged in four sets
ending, and terminal—and are as follows:
 
Anterior. Posterior. Ascending.
 
'erior thyroid. Occipital. Ascending
 
glial. Posterior auricular. pharyngeal.
 
ial.
 
Superior Thyroid Artery.—This vessel arises in the carotid tiiangle
m the front part of the external carotid close to its oiigin. It
:es an arched course forwards and downwards, passing undei covei
the infrahyoid muscles. On reaching the apex of the corresponding
>e of the thyroid gland it breaks up into its terminal branches,
 
 
—anterior, posterior,
 
Terminal.
 
Superficial temporal.
Maxillary.
 
 
 
1214
 
 
A MANUAL OF ANATOMY
 
 
 
which enter the lobe on its superficial aspect, and anastomose free
within it with branches of the inferior thyroid artery, and in the isthm
with its fellow of the opposite side.
 
Branches:
 
Infrahyoid. Crico-thyroid
 
Sterno-mastoid. Glandular.
 
Superior laryngeal. Muscular.
 
The infrahyoid artery passes inwards on the thyro-hyoid membrar
deep to the thyro-hyoid muscle, and close to the lower border of i
 
 
Fig. 731. —Dissection of Carotid Triangle.
 
hyoid bone. It anastomoses at the middle line with its fellow of t
opposite side, and with the suprahyoid branch of the lingual arte:
of the same side. The sterno-mastoid branch passes obliquely downwar.
and outwards, lying superficial to the carotid sheath, to enter the de<
surface of the muscle from which it takes its name. It is liable to
cut in tying the common carotid artery. The superior laryngeal arte
accompanies the internal laryngeal nerve, and, passing deep to tj
outer border of the thyro-hyoid muscle, pierces the thyro-hycl
membrane, to be distributed to the interior of the larynx. The cril
thyroid branch passes transversely inwards upon the crico-thyrC
ligament, and anastomoses with its fellow of the opposite side to foil
 
 
Hypoglossal
 
 
Digastric Post. Belly
; Comm. Facial V.
 
 
N. Desc. Hypog.
Sup. Laryng. N.
Inf. Constrict.
 
 
. Laryng. N.
>uter div.)
 
Sup. Thyr. V.
 
Omo-hyoid
 
Sterno-hyoid
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1
 
 
1215
 
 
crico-thyroid arch. The glandular branches are distributed to the
responding lobe of the thyroid gland. They anastomose freely
h branches of the inferior thyroid of the same side, and with branches
the fellow of the opposite side to a less extent. One very constant
.nch, known as the artery of the isthmus, courses along the upper
-der of the isthmus, and anastomoses with its fellow of the opposite
e. The muscular branches are distributed to the infrahyoid muscles.
The superior thyroid vein issues from the upper part of the corremding lobe of the thyroid gland, and crosses in front of the common
otid artery near its bifurcation to open into the internal jugular
n. Its tributaries for the most part correspond to the branches
the artery.
 
Lingual Artery. —The lingual artery arises from the front part of
i external carotid a little above the origin of the superior thyroid
d opposite the greater horn of the hyoid bone. From its comcated course it is convenient to divide the artery into three parts.
 
 
Dorsum of Tongue
 
Sublingual Gland (turned >
 
UP) !
 
 
Stylo-glossus Muscle
N Lingual Nerve
 
x
 
 
 
Submandibular Ganglion
 
Submandibular Gland
(deep part)
 
^Facial Artery
 
 
Mandible .
(in section)
 
 
Genio-glossus Muscle , (
 
Genio-hyoid Muscle !
Sublingual Artery
Arteria Profunda Linguae
 
 
_Lingual Artery
 
_Sup. Thy. Artery
 
. Ext. Car. Artery
 
\ \ Vena Comitans Hypoglossi
 
t Hypoglossal Nerve
 
Submandibular Duct
 
 
Fig. 732.—Deep Dissection of the Left Submandibular Region.
 
 
First Part. —The first part of the vessel ascends for a little, and
en, bending sharply, descends to the greater horn of the hyoid bone,
issing deep to the posterior belly of the digastric and stylo-hyoid
uscles. So far the vessel lies in the carotid triangle, and the bend
tiich it describes is crossed by the hypoglossal nerve. It is for the
ost part comparatively superficial.
 
Second Part. —The second part passes horizontally forwards along
ie upper border of the hyoid bone deep to the hyo-glossus, the hypoossal nerve and its vena comitans being superficial to that muscle,
eep to it is the middle constrictor. At the anterior border of the
^o-glossus it enters upon the third part of its course.
 
Third Part.— Near the anterior border of the hyo-glossus muscle
ie lingual artery describes another sharp bend in an upward direction,
id ascends almost vertically to the under surface of the tongue,
:sting upon the genio-glossus, and being under cover of the anterior
irder of the hyo-glossus. Having reached the tongue, the artery
 
 
 
 
 
 
 
1216
 
 
A MANUAL OF ANATOMY
 
 
passes forwards on its under surface in a tortuous manner under th
name of arteria profunda linguae.
 
Branches:
 
1. Suprahyoid. 3. Sublingual.
 
2. Rami dorsales linguae. 4. Arteria profunda linguae.
 
The suprahyoid artery arises from the lingual at the posterior horde
of the hyo-glossus, and passes along the upper border of the hyof
bone.
 
The rami dorsalis linguce arise under cover of the hyo-glossn
muscle, which they pierce, and so reach the posterior third of th
 
 
Superficial
Temporal \
 
Occipital
 
Maxillary
 
Posterior Auricular
 
 
Transverse Facial
 
 
Supraorbital
 
Supratrochlear
 
 
 
Angular
 
Lateral Nasal
 
Superior Labial
Inferior Labial
 
 
Submental
Submandibular Gland
 
 
Internal Carotid '
 
 
External Carotid
 
 
Lingual
 
Suoerior Thyroid
 
 
Fig. 733. —The Arteries of the Right Side of the Head (after
 
L. Testut’s ‘ Anatomie Humaine ’)•
 
dorsum of the tongue. They are distributed to the mucous membran
and substance of the tongue, the tonsil, and the soft palate.
 
The sublingual artery arises close to the anterior border of th
hyo-glossus muscle. It supplies the sublingual gland, the adjacen
muscles, and the mucous membrane of the floor of the mouth. On
of the lateral branches anastomoses at the median line with a com
sponding branch of the opposite artery, and another of them is know
as the artery of the frenulum linguce.
 
The arteria profunda linguce [ranine artery) is the terminal pai
of the lingual. It passes forwards on the under surface of the tongu<
lying immediately lateral to the insertion of the genio-glossus, betwee
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1217
 
id the longitudinalis linguae inferior. It is more or less embedded
le substance of the tongue, and its course is tortuous in adaptation
tie mobility of the organ to which it is so intimately related. ToIs the tip of the tongue the vessel is very superficially placed,
close by the side of the frenulum linguae, and it anastomoses
l its fellow of the opposite side near the tip. Elsewhere the cross
domoses are remarkable for their absence, and if one lingual artery
led with fine injection hardly any crosses the mid-line of the tongue
pt at the tip. The arteria profunda linguae furnishes branches
y to the substance of the tongue. Its close relation to the frenulum
rae is to be carefully noted in connection with the operation for
f of tongue-tied children.
 
rhe lingual veins are as follows: (1) the vena comitans hypoglossi
ine vein), which is of large size, commences under the tip of the
pe, and passes backwards, in company with the hypoglossal nerve,
;rficial to the hyo-glossus muscle, receiving tributaries from the
ounding structures; (2) two vence comitantes accompanying the
ral artery; and (3) the dorsal lingual veins, which originate in a
us beneath the mucous membrane over the posterior third of the
.n. These three sets of veins may join into a common trunk, called
lingual vein, which opens into the internal jugular vein, or they
r terminate independently in that vein.
 
jingual Lymph Glands.—These glands, which are of small size,
pon the outer surfaces of the genio-glossus and hyo-glossus muscles,
g the vena comitans hypoglossi. They are really small glandions lying in the course of the lymphatic vessels of the tongue
hese pass to join the deep cervical lymph glands.
 
Facial Artery.—The facial artery arises from the front part of
external carotid in the carotid triangle immediately above the
nal artery, or sometimes in common with that vessel. It passes
ards and forwards deep to the hypoglossal nerve, the posterior
7 of the digastric and the stylo-hyoid muscles, into the submanilar triangle. It then becomes embedded in a groove on the upper
back part of the submandibular gland, its general course being
^ards with many curves. From this groove it describes a sharp
i upwards over the base of the mandible in front of the masseter
cle. The vessel then enters upon the facial part of its course, for
scription of which see p. 1278.
 
Branches. —Four branches arise from the cervical part of the facial
ry:
 
1. Ascending palatine. 3. Glandular.
 
2. Tonsillar. 4. Submental.
 
rhe ascending palatine artery passes upwards between the stylosus and stylo-pharyngeus muscles, and then over the upper
ler of the superior constrictor of the pharynx along with the levator
ti muscle. It is distributed to the soft palate, tonsil, and auditory
The tonsillar artery passes upwards between the stylo-glossus
 
77
 
 
 
1218
 
 
A MANUAL OF ANATOMY
 
 
and medial pterygoid muscles, and, after piercing the superior c<
strictor muscle, it is distributed to the tonsil and the posterior p
of the side of the tongue. The glandular branches axe distributed
the submandibular gland. The submental artery arises from i
facial just below the mandible, and passes forwards superficial
the mylo-hyoid muscle. It gives branches to the submandibular gla
and mylo-hyoid muscle, some of the branches piercing that mus
to reach the sublingual gland and anastomose with the subling
artery.
 
The cervical part of the anterior facial vein passes downwai
and backwards superficial to the submandibular gland. Hav:
received tributaries corresponding to the branches of the cervical p
of the artery, it unites with the anterior division of the posterior fac
vein to form the common facial vein, which opens into the inter:
jugular opposite the body of the hyoid bone.
 
Occipital Artery. —The occipital artery arises from the poster
aspect of the external carotid opposite the facial artery. It pas
 
at first upwards and sligh
 
 
UATERfll
 
J>IC,
 
 
 
r rvi T.
CAROT.
 
 
MX 1.
 
 
NJ.X 11
 
 
occ i P.
 
ARTERV.
 
 
Fig. 734.—Plan of Course of
Occipital Artery in Neck.
 
 
backwards beneath the poster
belly of the digastric and sty
hyoid muscles, and the hy]
glossal nerve, having hool
round it, passes forwards sup
ficial to it. Having reached
level of the interval between 1
transverse process of the at
and the mastoid process, '
artery changes its course, a
passes backwards to occupy
occipital groove on the in:
aspect of the mastoid proc(
where it is in touch with
rectus capitis lateralis. In t
backward course it crosses
 
 
internal carotid artery, internal jugular vein, and vagus, accessc
and hypoglossal nerves. As it lies in the occipital groove the ve<
is very deeply placed, being covered by the following structui
(1) the origin of the posterior belly of the digastric; (2) the lon$
simus capitis; (3) the splenius capitis; and (4) the sterno-mastc
After escaping from beneath the splenius capitis, the vessel takes
upward course superficial to the semispinalis capitis to the occip:
region, where it ramifies in a tortuous manner along with the branc
of the greater occipital nerve.
 
Branches. — Muscular; meningeal; mastoid; descending; s
Occipital.
 
The muscular branches are distributed to the adjacent muse
one of them, the sterno-mastoid branch, crosses the hypoglossal ne:
and enters the deep surface of the sterno-mastoid muscle in comps
 
 
 
 
THE HEAD AND NECK
 
 
1219
 
 
the accessory nerve. The meningeal branch accompanies the internal
lar vein, and enters the cranial cavity through the jugular foramen
apply the dura mater of the posterior fossa. The mastoid branch
es through the mastoid foramen when present, and supplies the
cent dura mater. The descending and the occipital [terminal)
Lches have been already described (see p. 1146).
 
Tie description of the occipital veins will be found on p. 1147.
tosterior Auricular Artery. —This vessel arises from the posterior
ct of the external carotid a little above the origin of the occipital
ry, and above the posterior belly of the digastric. It passes
ards and slightly backwards under cover of the lower part of the
tid gland, and behind the styloid process of the temporal bone,
g crossed by the facial nerve. Having reached the groove between
back of the auricle and the mastoid process, where it meets the
erior auricular nerve, it divides into two branches, auricular and
aital.
 
branches. —These are as follows: muscular; glandular; stylotoid; auricular; and occipital.
 
rhe muscular branches supply the adjacent muscles. The glandular
ches are distributed to the lower part of the parotid gland. The
-mastoid artery enters the facial canal through the stylo-mastoid
men. It is distributed to the tympanic cavity and the mastoid
:ells, and anastomoses with the tympanic branch of the first part
ae maxillary artery. With this latter branch it forms a ring at the
lmference of the tympanic membrane on its inner aspect. Within
facial canal the stylo-mastoid artery anastomoses with the super1 petrosal branch of the middle meningeal artery, which branch
rs the canal through the hiatus for greater superficial petrosal
r e. The auricular branch passes upwards deep to the auricularis
erior muscle, and furnishes branches to the inner aspect of the
:le, some of which reach the outer surface by piercing the cartilage
by turning round its margin. The auricular branch anastomoses
l the posterior branch of the superficial temporal artery. The
'ntal branch passes backwards over the mastoid process to the
pital region, and anastomoses with the occipital artery,
rhe posterior auricular vein, of fairly large size, often unites with
posterior division of the posterior facial vein near the angle of
inferior maxilla, and by this union the external jugular vein is
led. The arrangement, however, is very variable.
 
Ascending Pharyngeal Artery. —This long, slender vessel arises from
beginning of the deep surface of the external carotid. It runs
ically upwards towards the base of the skull, lying very deeply
1 the longus capitis muscle, and between the internal carotid
ry, in front of which it has passed, and the pharynx,
branches :
 
1. Pharyngeal. 3. Prevertebral.
 
2. Palatine. 4. Inferior tympanic.
 
5. Meningeal.
 
 
1220
 
 
A MANUAL OF ANATOMY
 
 
The pharyngeal branches are distributed to the pharynx. TJ
palatine branch passes over the superior constrictor muscle of t]
pharynx, and is distributed to the soft palate, auditory tube, and tons
The prevertebral branches supply the prevertebral muscles. T]
inferior tympanic artery passes with the tympanic branch of the gloss
pharyngeal nerve through the tympanic canaliculus in the petro
part of the temporal bone, and so reaches the tympanic cavity, to t]
inner wall of which it is distributed. The meningeal branches are t'
terminal branches of the ascending pharyngeal, and are three in numbe
One passes through the foramen lacerum, a second through the jugul
foramen, and a third through the anterior condylar canal, to be d:
tributed to the dura mater in the vicinity of these foramina.
 
The descending pharyngeal vein accompanies the ascending phary
 
geal artery.
 
For the superficial temporal and maxillary branches of the extern
carotid artery, see pp. 1158 and 1304.
 
The internal carotid artery will be found described on p. 1323.
 
Thyroid Gland. —The thyroid gland is situated on either side
the upper part of the trachea and larynx, and a small portion of it li
in front of the upper part of the trachea. Its size is subject to mu
variation; its weight is rather more than 1 ounce; and it is larger
the female than in the male. It consists of right and left lobes and;
isthmus.
 
Each lobe is conical and about 2 inches long, the rounded ba
being directed downwards. It extends from the middle of the lami:
of the thyroid cartilage to about the level of the fifth ring of the trache
Its superficial surface , which looks forwards and outwards, is somewb
convex, and is covered by the sterno-thyroid, sterno-hyoid, and superi
belly of the omo-hyoid muscles. It is also overlapped by the anted
border of the sterno-mastoid. Its deep surface is concave in adaptati
to the trachea and larynx. The anterior border is thin, and towar
its lower part is connected with that of the opposite lateral lobe
means of the isthmus. The posterior border is thick, and is in conta
with the pharynx and oesophagus, and has the parathyroid glan
embedded in it. Each lobe overlaps the corresponding common carol
artery, enclosed in the carotid sheath, and is frequently grooved by tb
vessel. Interiorly it overlaps the recurrent laryngeal nerve and infer]
thyroid artery. The apex of each lobe rests upon the inferior constrict
muscle of the pharynx, and the superior thyroid artery enters it sup<
ficially and deeply4
 
The isthmus is inconstant as regards size and position. Its dep
ranges from J to 1 inch, and its breadth is about \ inch. It conne^
the lower parts of the anterior borders of the lateral lobes, but dc
not reach quite so low as their bases. .It lies in front of the trach<
usually upon the second and third rings, and fits closely to the rir
upon which it rests. Along its upper border there is a branch of t
superior thyroid artery, known as the artery of the isthmus, which an.
tomoses with its fellow of the opposite side. From its lower bore
 
 
THE HEAD AND NECK
 
 
1221
 
 
?ral veins issue, which take part in the inferior thyroid plexus of
is in front of the trachea.
 
In some cases an additional lobe is present, called the pyramidal
!. It forms a long pyramid, which is attached by its base to the
ier border of the isthmus, usually at its junction with the left lobe,
apex is attached to the body of the hyoid bone by a fibrous band,
ch sometimes contains muscular fibres, known as the levator glandulcz
oidce muscle. It is seldom quite median in position.
 
 
erior Belly of Digastricand Stylo-hyoid
lyo-glossus Muscle and’
Hypoglossal Nerve
 
 
Head of Sterno-mastoid
Crico-thyroid Muscle
Cricoid Cartilage
t Lobe of Thyroid Body
 
 
Trapezius
vicular Head of
 
7 / 7 ,
 
 
sterno-mastoid
Brachial Plexus
 
 
Subclavian Artery
(third part)
 
Clavicle
 
 
 
Anterior Belly of Digastric
L Mylo-hyoid
 
 
Body of Hyoid Bone
 
Superior Belly of Omo-hyoid
Sterno-hyoid
 
K ljnimr- Thyro-hyoid
 
USSr - Laryngeal Prominence
"m sterno-thyroid
 
 
Superior Belly of Omo-hyoid
Crico-thyroid Membrane
 
Sterno-hyoid
 
 
Isthmus of Thyroid
Gland
 
 
Inferior Thyroid
Plexus of Veins
— - Cla. Head'd St.-mas.
Sterno-thyroid
 
Sternal Head of Sternomastoid
 
 
Fig. 735
 
he area bounded
below by the
 
 
Sterno-thyroid
 
 
Sterno-hyoid
 
—Dissection of the Front of the Neck.
 
on either side by the anterior belly of the digastric and
body of the hyoid bone is the submental triangle.
 
 
The thyroid gland is invested by a fibrous sheath which is derived
u the pretracheal layer of the deep cervical fascia.
 
When a portion or portions of the pyramidal lobe, or of the right or
lobes, become detached, the isolated masses are known as accessory
roids.
 
Blood-supply—Arteries. —The thyroid gland is very vascular. The •
sries on either side are (i) the superior thyroid, which is a branch of
external carotid; and (2) the inferior thyroid, which is a branch of
thyro-cervical trunk of the first part of the subclavian. Occasion7 there is a third thyroid artery, called the arteria thyroidea ima,
ich is derived from the innominate artery, or from the arch of the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1222
 
 
A MANUAL OF ANATOMY
 
 
aorta, and is distributed to the isthmus, its position being in fro
of the trachea at the median line, or close to it.
 
The veins are superior, middle, and inferior. The superior ai
middle thyroid veins open into the internal jugular. The inferi
thyroid veins, right and left, issue from a plexus of veins in front
the trachea below the isthmus. The left vein opens into the 1 <
innominate vein, whilst the right may open into the left innomina
vein, into the angle of junction of the right and left innominate veil
or into the lower part of the right innominate vein.
 
Nerves. —These are derived from the sympathetic plexuses whi
accompany the superior and inferior thyroid arteries.
 
Lymphatics. —The lymphatic vessels
the thyroid body are disposed in t
groups —ascending and descending. T
ascending lymphatics form three sets
median and two lateral, right and le
The median ascending lymphatics retn
lymph from the upper part of the isthmi
and pass to the prelaryngeal lym
glands. The lateral ascending lymphat
on either side accompany the super
thyroid artery, and pass to the infer
deep cervical lymph glands on a level wi
the cricoid cartilage of the larynx. T
descending lymphatics also form three st
The median descending lymphatics retr
lymph from the lower part of the isthm
and pass to the pretracheal lymph glam
The lateral descending lymphatics on eitl
side accompany the inferior thyroid artery, and pass to the pa:
tracheal lymph glands, which lie in the groove between the tract
and oesophagus, the efferents of which terminate in the inferior de
cervical lymph glands.
 
Structure. —The thyroid gland has an external capsule of dense connect
tissue which sends trabeculae into the interior, thereby dividing it into irregu
lobules. These lobules are composed of groups of closed vesicles, which ;
connected together by areolar tissue. The vesicles are oval or spherical, a
each is lined with a single layer of columnar or cubical epithelium. They cont;
a yellowish viscid, albuminous fluid called colloid and are surrounded by n
works of capillary bloodvessels.
 
Development. —The thyroid body is developed from the entoderm of 1
ventral wall of the pharyngeal portion of the primitive gut.
 
The first indication of the median thyroid is an evagination of the vent
pharyngeal entoderm immediately behind the tuberculnm impar. This evagu
tion is called the median thyroid diverticulum. It forms a thick-walled epithe.
vesicle embedded in mesoderm, which soon becomes solid. As the vesicle grc
its distal end becomes bilobed. Superiorly it retains for a little time its co
munication with the ventral wall of the pharynx behind the tuberculum im]
by a hollow pedicle, which constitutes the thyro-glossal duct (canal of H
This duct usually disappears, its superior orifice being represented on the dorsi
of the adult, tongue by the blind recess, called the foramen ccecum. In very r;
 
 
 
Fig. 736. — Section of the
Thyroid Gland, showing
the Vesicles and their
Epithelial Lining.
 
The colloid is indicated.
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1223
 
 
the lingual portion of the duct may persist for a short distance, in which
the foramen caecum leads to the lumen of a short tube, known as the ductus
%lis.
 
tie median thyroid, as stated, gives rise to the isthmus and lobes of the
thyroid gland.
 
tie median bud almost from its beginning is in contact with the pericardial
and the two ventral aortae arising from the truncus arteriosus; it extends
these vessels. It lies in loose mesoderm ventral to the condensations
e second and third visceral arches. As the head grows forward and the
irdium assumes in consequence a more caudal position, the thyroid bud
h has separated from its lingual attachment) remains in contact with the
irdium and the vessels; thus it moves caudally with reference to the pharynloor above it, and as a result of its lateral extension at the same time along
vessels, comes into relation with the ventral angle of the fourth lateral
1 (P- 77 )■ Becoming attached to this, its farther caudal dislocation is
 
>ed, save perhaps in the middle line, where some of its cells may still follow
Dericardium in its retrogression. The main part of the bud, however,
ins in its fixed position, and forms the lobes and isthmus,
he ventral bud from the fourth pouch is sometimes termed the lateral
id bud, being supposed to contribute to the formation of each lobe. It is
•ally believed, however, that it does not do so, but remains as a small
elial mass in the lobe; under some circumstances it appears to show a
;ncy to thyroid vacuolization.
 
□nnective tissue derived from this mesodermic investment now invades the
mass, and it is broken up into numerous solid epithelial cords, which
;omose freely, and so give rise to an intricate reticulum, the meshes of which
ccupied by connective tissue and bloodvessels of mesodermic origin. The
epithelial cords of the reticulum become hollow, and the lumina so produced
)roken up at intervals by constrictions into closed vesicles , which contain
olloid material.
 
he pyramidal lobe of the thyroid gland sometimes met with in connection
the isthmus of the adult thyroid is developed from the median bud.
he epithelial cells of the vesicles of the adult thyroid are derived from the
lerm of the pharyngeal part of the fore-gut.
 
Parathyroid Glands. —The parathyroids are four in number, and are
tiged in pairs. The upper pair are related to the dorsal borders
ie lobes of the thyroid gland, and the lower pair are placed behind
ower ends of the lobes. They are difficult to distinguish with the
id eye, but the best way to find them is to follow the anastomosis
reen the superior and inferior thyroid arteries. They are developed
^aginations of the entoderm of the third and fourth visceral pouches
ther side. The parathyroids present no traces of closed vesicles
he colloid material.
 
ccessory Thyroid Glands. —These glands are sometimes met in the neighhood of the hyoid bone, and are known as the suprahyoid and prehyoid
!S. They are developed as buds or evaginations of the thyroglossal duct,
they consist of thyroid tissue.
 
 
The Trachea and (Esophagus.
 
trachea. —The trachea extends from the cricoid cartilage of the
nx to about the level of the disc between the bodies of the fourth
fifth thoracic vertebrae, where it divides into the two bronchi,
t and left. Its average length is about inches, and its width
 
 
1224
 
 
A MANUAL OF ANATOMY
 
 
about i inch. Anteriorly and laterally it is cylindrical and fi
but posteriorly it is flattened and membranous, so that it does
press upon the oesophagus, in front of which it lies. It occupie
medial position, and its direction is downwards with an inclinat
backwards. It is divisible into two parts, cervical and thoracic.
 
For the trachea in the thorax, see p. 1085.
 
The cervical part of the trachea extends from the cricoid cartil
to the level of the upper border of the manubrium sterni, and it measr
about 2 \ inches in length. It is freely movable, and is surroun<
 
by areolar tissue, which c
 
 
Epiglottis
 
 
Greater Horn of Hyoid Bone
Lesser Horn of Hyoid Bone_
 
Body of Hyoid Bone —
 
 
Thyro-hyoid Membrane —
 
Levator Glandulae \
Thyroidm Muscle/
 
Thyroid Cartilage -
Crico-thyroid Ligament
Pyramidal Lobe f
Cricoid Cartilage Right Lobe of Thyroid Gland _
 
Isthmus
 
Right Bronchus
Eparterial Bronchus
 
 
Hyparterial Bronchus.._ f
 
 
 
Trachea
 
 
tains many elastic fibres, ;
is somewhat loosely arrange
Relations — A nterior. —'
isthmus of the thyroid gli
lies directly upon the sect
and third rings as a rule,
first ring usually lying expo
between its upper border 1
the cricoid cartilage. Su]
ficial to the first ring, on
left of the median line, th
may be the lower part of
pyramidal lobe of the thyi
gland. Below the isthmus
the inferior thyroid plexus
veins, from which the ri
and left inferior thyroid v(
pass downwards one on eit
side of the median line. '
arteria thyroidea ima may
cend to the isthmus of
thyroid gland, lying in fr
of the trachea at the med
line, or slightly to the right
it. The anterior jugular ve:
 
 
Fig.
 
 
Left Bronchus
 
737 .-The Hyoid Bone, Larynx, r ig ht and J eft - are a " teri “
Trachea, Bronchi, and Thyroid Gland it, and just above the ma
(Anterior View). brium sterni it is crossed by
 
communicating branch wh
passes between these two veins. In children under two years
age the cervical portion of the thymus forms an important ante]
relation. Close to the upper border of the manubrium sterni
innominate artery may encroach slightly upon it. The pretract
layer of the deep cervical fascia forms an anterior relation, as \
as the superficial layer of that fascia, which is here usually descril
as dividing to form the suprasternal space above the supraster
notch. Another, and perhaps more common-sense, description is
say that in front of the trachea is a layer of cellular tissue c
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1225
 
 
Lateral Thyrohyoid
Ligament
 
Upper Border of
Thyroid Cartilage
 
 
Epiglottis
 
 
— Cartilago Triticea
 
_Corniculate Cartilage
 
-Arytenoid Cartilage
 
f_i.__Cricoid Cartilage
 
ft 3
 
Vfj--Right Lobe of
Thyroid Body
 
 
)us with that in which the thyroid gland is embedded, and that
tissue increases in thickness from before backward as the
lea recedes from the surface on approaching the thorax. Other
rior relations are the anterior jugular veins, along with one or two
)h glands, and in some cases the left innominate vein. The sternod and sterno-thyroid muscles cover it in the following manner:
derno-hyoid muscles are separated by an interval below, but they
3 nearly into contact above; and the sterno-thyroid muscles are
intact below, but diverge above. Between the muscles of opposite
1 there is a very narinterval, along which
trachea is free from
cular covering.
lateral .—The trachea
fiosely embraced on
sr side by the lobes
he thyroid gland as
as about the level of
fifth ring, and lateral
this is the carotid
.th with its contents,
common carotid artery
g nearest the lobe.
 
Posterior .—The trachea
n front of the cesogus, which projects a
e to its left side tods the root of the neck,
ween the two there is
groove, in which the
irrent laryngeal nerve
inferior laryngeal
:ry ascend. For a reflce to the high and
operations of tracheny, see p. 1174.
 
Blood-supply. —The ar- , ,,
 
es of the cervical part of the trachea are derived from the m
or thyroid of each side, which is a branch of the thyro-cervica
nk
 
The veins terminate in the inferior thyroid plexus and inferioi
 
roid veins. . , , ,
 
The lymphatics pass to the inferior deep cervical lymph glands
 
Pretracheal Lymph Glands. —These glands lie upon the front of e
deal part of the trachea, below the isthmus of the thyroid gland,
fir afferent vessels are derived from the front of the trachea, an
lower part of the isthmus of the thyroid gland. Their efferent
sels pass to the inferior deep cervical lymph glands. The lymphatic
 
 
 
Fig. 7^8.—The Epiglottis, Larynx, Trachea,
Bronchi, and Thyroid Gland (Posterior
View).
 
 
 
 
 
 
 
 
 
1226
 
 
A MANUAL OF ANATOMY
 
 
vessels of the cervical part of the trachea pass to the pretrache;
inferior thyroid, and inferior deep cervical lymph glands.
 
Nerve-supply.— The nerves are derived from the vagus, recurre:
laryngeal, and sympathetic.
 
 
Structure. —The trachea is composed of about twenty so-called rings
hyaline cartilage, which are incomplete posteriorly. They serve to keep t
tube permanently open for the transmission of air, and are embedded in fibro
tissue, which also connects together their contiguous borders. They are hon
shoe shaped, and each forms rather more than two-thirds of a circle, being fl
externally and convex internally. The deficient portions of the rings are plac
posteriorly, and here each ring ends in two round extremities. The inters
between these extremities are bridged over by fibrous tissue continuous wi
that which connects the borders of the rings and in which they are embedde
 
In some cases a ring m;
 
 
 
Ciliated Epithelium
Basement Membrane
 
 
Mucosa
 
 
_ Elastic Fibres
 
 
Submucosa, with
Mucous Glands
 
 
Hyaline Cartilage
of Ring
 
 
Fibrous Investment
 
 
Fig. 739. —Longitudinal Section of the
 
Trachea.
 
 
end in a bifurcated e
tremity, or it may jc
one of the adjacent rin^
The lowest ring is dee
and its lower border pr
jects backwards so as
form a ridge betwe
the openings of the t\
bronchi.
 
In the posterior w<
of the trachea within t
fibrous layer there is
continuous layer of u:
striped muscular tissu
the fibres of which e
tend transversely betwe*
the ends of the rings
which they are attache
In the intervals betwe<
the extremities of ti
rings they are attach*
to the fibrous coat. The
fibres serve to approj
mate the ends of t]
rings, and so diminish t]
calibre of the tube.
 
 
The submucous coat consists of loosely-arranged areolar tissue, and contai]
the larger bloodvessels and nerves, together with the mucous glands.
 
The mucous coat consists of areolar and elastic tissues, and a large amoui
of lymphoid or adenoid tissue. It contains the ramifications of the arteri
and nerves, as well as the lymphatics. Superficial to the mucosa there is
well-marked basement membrane which supports the epithelium. The dee
portion of the mucosa consists principally of elastic fibres. On the poster!
wall these elastic fibres are very numerous, and are arranged in longitudin
bundles which give rise to elevations of the mucosa.
 
The epithelium is of the stratified columnar ciliated variety.
 
The wall of the trachea contains many mucous glands. Some of these a
situated in the submucous coat. Others, which are of large size, lie on t
posterior wall, where they are very superficial, many of them appearing li
small grains superficial to the fibrous layer. Others are contained within t.
fibrous layer. The ducts of these glands have to pass through the muscula
elastic, and mucous walls of the tube.
 
Development. —The trachea is developed from the lower part of the laryng
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1227
 
 
ial tube from the ventral aspect of the fore-gut superiorly, the upper part
is diverticulum giving rise to the larynx.
 
Esophagus.—The oesophagus is that part of the alimentary canal
h extends from the pharynx to the stomach. In the neck it
ns on a level with the lower border of the cricoid cartilage, and
on a level with the upper border of the manubrium sterni. It
>mpressed from before backwards and
between the trachea and the vertebral
mn covered by the longus cervicis
cles. At first it occupies the median
but as it descends it inclines slightly
ie left side, so as to be partly visible on
left side of the trachea,
delations— Anterior. —The trachea; the
;erior parts of the lobes of the thyroid
y ; the recurrent laryngeal nerves; and
inferior thyroid arteries. Posterior. —The
ebral column and the longus cervicis
icles covered by the prevertebral cellular
ie. Lateral. —On either side there is the
)tid sheath with its contents. The right
left recurrent laryngeal nerves are inately related to the oesophagus, and
md on each side in the groove between
nd the trachea.
 
The cervical part of the oesophagus reres its blood-supply from the inferior
roid arteries, which accompany the corDonding recurrent laryngeal nerves.
 
Paratracheal Lymph Glands (Inferior
rroid Lymph Glands).—These glands lie
the groove between the cervical parts of
trachea and oesophagus, along the course
the inferior thyroid artery and recurrent
^ngeal nerve. Their afferent vessels are
ived from (1) the lower part of the lobe p IG —schematic View
 
the thyroid body, and (2) the adja- of CEsophagus.
 
it parts of the trachea and oesophagus.
 
eir efferent vessels pass to the inferior deep cervical lymph glands.
For a description of the oesophagus in the thoiax, including its
 
ucture and development, see p. 1087. .
 
Suprahyoid Region—Muscles—Digastric. The digastric muscle
isists of two bellies, posterior and anterior. Origin. The posterior
ly arises from the mastoid notch on the inner aspect of the mastoid
ft of the temporal bone; and the anterior belly arises from the distric fossa on the inner surface of the base of the mandible close to
 
"symphysis.
 
Insertion. —The two bellies end upon an intermediate tendon,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1228
 
 
A MANUAL OF ANATOMY
 
 
about 2 inches long, which is inserted by means of a broad fibr
band into the anterior surface of the body of the hyoid bone at
outer part, and the adjacent portion of the greater horn.
 
Nerve-supply .—The posterior belly is supplied by the facial nei
and the anterior belly by the mylo-hyoid branch of the inferior den
a branch of the mandibular nerve.
 
The posterior belly is directed downwards and forwards, and
anterior belly downwards and slightly outwards.
 
Action .—To elevate the hyoid bone, as in the act of deglutiti
and to depress the mandible.
 
Relations. —The posterior belly is at first deeply placed, be
overhung by the mastoid process, and lying under cover of the Ion
simus capitis, splenius capitis, and sterno-mastoid muscles. It is ;
overlapped by the lower part of the parotid gland. It crosses
external and internal carotid arteries, internal jugular vein, ;
 
hypoglossal nerve,
stylo-hyoid muscle
above it, and the hy
glossal nerve below it
a short distance. i
intermediate tendon
embraced by the fibres
the stylo-hyoid mus
This tendon crosses
hypoglossal nerve, ;
forms two sides of a
angle, known as the
angle of Lesser, the b
of which is directed
wards, and is formed
the hypoglossal nerve. In the area of this triangle is a portion
the hyo-glossus muscle, and deep to this is the lingual artery. 1
anterior belly, which is shorter than the posterior, is covered
the integument, platysma, and deep cervical fascia. It rests u{
the mylo-hyoid muscle, and forms part of the floor of the digasl
triangle. Its inner border is connected with that of its fellow b]
fascial expansion.
 
The posterior belly of the digastric, along with the stylo-hyoid muscle,
the stapedius muscle, is associated with the posterior end of the second vise
or hyoid arch. The nerve of this arch is the facial nerve, and this explains
nerve-supply of the posterior belly.
 
The anterior belly is associated with the anterior or medial end of the )
visceral or mandibular arch. The nerve of this arch is the mandibular from
trigeminal nerve, thus accounting for the nerve-supply of the anterior belly
Stylo-hyoid — Origin .—The posterior and outer aspect of the sty!
process of the temporal bone near its base.
 
Insertion .—The anterior surface of the hyoid bone at the junct
of the body and greater horn.
 
 
5TVIOHVOIP
 
 
 
Fig. 741. —Plan of Main Deep Relations of
Digastric in Anterior Triangle.
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1229
 
 
erv e-supply. —The facial nerve.
 
he muscle is directed downwards and forwards.
 
ction. _To draw the hyoid bone upwards and backwards.
 
he muscle lies close above the posterior belly of the digastric,
before taking insertion, it usually splits into two bundles, which
■ace the intermediate tendon of the digastric. It is morphological delamination of the same sheet as the posterior belly of the di•ic, which explains its nerve-supply.
 
[ylo-hyoid — Origin. — The mylo-hyoid line of the mandible.
nsertion— The posterior fibres are inserted into the anterior surface
.e body of the hyoid bone; and the principal part of the muscle is
ted into a central fibrous raphe, which extends from the symphysis
ti on its deep and lower aspect to the body of the hyoid bone.
 
 
Mandible
 
 
 
Raph
 
 
)-hyoid Muscle -
Lingual Nerve
 
Deep Part of nandibular Gland
Post. Belly of Digastric
Hypoglossal Nerve
Stylo-hyoid
 
 
Body of Hyoid Bone
 
 
e
 
 
Infrahyoid Muscles
 
 
Fig. 74 2.—The Mylo-hyoid Region.
Anterior belly of digastric removed.
 
 
Nerve-supply. —The mylo-hyoid branch of the inferior dental nerve,
ch is a branch of the mandibular nerve.
 
The muscle is directed downwards and f01 wards.
 
Action.— To raise the floor of the mouth, and, in doing so, to
ss the tongue against the hard palate, as in the first stage of the
of deglutition; to elevate the hyoid bone, and diaw it forwards,
 
L to depress the mandible. .
 
The two mylo-hyoid muscles form a muscular floor for the buccal
 
ity, which is known as the diaphragma oris. >
 
Relations —Superficial or Inferior .—The anterior belly of the ditric; the superficial part of the submandibular gland, lodging a
'tion of the facial artery; and the mylo-hyoid nerve and submenta
mch of the facial artery.
 
 
 
 
1230
 
 
A MANUAL OF ANATOMY
 
 
Posterior Border .—Passing deep to the posterior free border of
muscle there are the following structures, in order from above do
wards: (i) the lingual nerve; (2) a portion of the submandibular gla
and (3) the hypoglossal nerve and its vena comitans.
 
Deep or Superior. —The hyo-glossus muscle, external to which
the lingual nerve, the submandibular ganglion, the deep part of the s
mandibular gland and the submandibular duct, the hypoglossal ne
and its vena comitans. In front of the hyo-glossus is the genio-h}
muscle, and between it and the hyo-glossus is a portion of the gei
glossus, with the sublingual gland resting upon it.
 
Genio-hyoid— Origin. —The inferior genial tubercle of the mand
close to the symphysis on its deep aspect.
 
insertion .—The inner two-thirds of the anterior surface of
body of the hyoid bone over its upper part. At its insertion the mu
is divided externally into two laminae, anterior and posterior,
former of which extends farthest out upon the hyoid bone. The ini
most fibres of origin of the hyo-glossus pass inwards between tl
two laminae.
 
N erv e-supply. —The hypoglossal nerve, the branch of which is
garded as being composed of spinal fibres.
 
The muscle is directed downwards and slightly backwards.
 
Action. —To elevate the hyoid bone and draw it forwards, and
depress the mandible.
 
The muscle is in intimate contact with its fellow of the oppo
side at the median line. Its inferior or superficial surface is cove
by the mylo-hyoid, and its superior or deep surface is related to
lower or posterior border of the genio-glossus.
 
Genio-glossus— Origin. —The upper genial tubercle of the mand
close to the symphysis on its deep aspect.
 
Insertion. —The under surface of the tongue close to the med
line, and extending from near the tip to the root; very slightly i
the inner part of the anterior surface of the body of the hyoid b
close to its upper margin; and slightly into the side of the phary
where the fibres blend with those of the middle constrictor muscle.
 
N erv e-supply. —The hypoglossal nerve, the branches of which er
the outer surface of the muscle.
 
The upper or anterior fibres arch upwards and forwards, and
lower downwards and backwards, whilst the intervening fibres spr
out in a fan-like manner.
 
Action. —The entire glossal fibres depress the tongue at the med
line, and, along with those of the opposite side, they give rise to
antero-posterior groove on the dorsum of the organ; the postei
glossal fibres draw forwards the tongue, causing its tip to be protru<
from the mouth; the anterior glossal fibres retract the tip of the ton]
when it has been protruded from the mouth; and the lower or postei
(hyal) fibres elevate the hyoid bone, and draw it forwards.
 
The muscle is fan-shaped. The medial surface is closely app]
to that of its fellow of the opposite side. The lateral surface is rela
 
 
 
THE HEAD AND NECK
 
 
1231
 
 
ie longitudinalis inferior muscle, the arteria profundae linguae, the
glossus and stylo-glossus muscles, and the sublingual gland. The
rior border is covered by the buccal mucous membrane, and the
r or posterior border by the genio-hyoid muscle,
lyo-glossus— Origin. —The greater horn of the hyoid bone over its
•e length; the anterior surface of the body of the bone over about
uter half; and the lesser horn (inconstant). The innermost fibres
rigin from the hyoid bone lie between the two laminae of the geniod muscle.
 
 
Tip of Styloid Process of
Temporal Done
 
 
 
Fig. 743. —The Extrinsic Muscles of the Tongue.
The longitudinalis inferior is an intrinsic muscle.
 
 
Insertion —The posterior half of the under surface of the tongue
se to its lateral border, the fibres being situated medial to those of
! stylo-glossus, and both sets of fibres being intimately intermixed
;h each other and with the intrinsic lingual muscles.
 
Nerve-supply .—The hypoglossal nerve, the branches of which enter
 
i superficial surface. , .. , .
 
The muscle is for the most part directed upwards, but its anterior
 
res have a slight inclination forwards.
 
Action .—To depress the side of the tongue, and, along with its
low, to render the dorsum of the organ convex; and to assist m
 
xacting the protruded tongue.
 
The hyo-glossus is a flat, four-sided muscle.
 
 
 
1232
 
 
A MANUAL OF ANATOMY
 
 
Relations — Superficial. —The mylo-hyoid muscle; the intermedi
tendon of the digastric, and stylo-hyoid muscle; the lingual nerve, w
the submandibular ganglion lying a little below it; the deep part of
submandibular gland, and the submandibular duct; the hypoglos
nerve; and the vena comitans hypoglossi. Posterior Border .—The :
lowing structures pass deep to this border in order from above do\
wards: the glosso-pharyngeal nerve; the stylo-hyoid ligament; and
lingual artery. Deep .—The posterior part of the genio-glossus; a port
of the middle constrictor muscle of the pharynx; the lingual arte
the lower end of the stylo-hyoid ligament; and the glosso-pharyng
nerve.
 
The fibres of the hyo-glossus which arise from the lesser horn
the hyoid bone are separated from the rest of the muscle by th<
fibres of the genio-glossus which take insertion into the side of i
 
 
Hyo-glossus
Glosso-pharyngeal N.
 
Lingual N.-\ _
 
Hyo-glossus-_
 
Submandibular Duct-A - __
 
Vena Comitans Hypoglossi—\_ Al
 
Hypoglossal N.---X — ^
 
 
 
- -Longitudinalislnfi
Stylo-glossus
 
 
Sublingual Gland
Ant. Facial V. and Fat
- Deep Submandibular G 1
• Sup. Submandibular Giant
' Mylo-hyoid
 
-/- Stylo-hyoid
 
~ —/Digastric
 
Hyoid Bone
 
\ ' Stylo-hyoid Lig.
 
 
Lingual ArteryA 'Middle Constrictor
 
Fig. 744.—Coronal Section through Submandibular Region.
 
 
pharynx, and they are vestigial remains of the chondro-glossus
monkeys. These fibres, however, are inconstant.
 
Stylo-glossus — Origin .—The front of the styloid process of t
temporal bone near its tip; and the upper extremity of the sty.
mandibular ligament.
 
Insertion .—The under surface of the tongue close to its latei
border. The fibres extend as far forwards as the tip, and are situat
lateral to the fibres of the hyo-glossus, both sets of fibres being in
mately intermixed with each other, and with longitudinalis inferi
muscle.
 
Nerve-supply .—The hypoglossal nerve.
 
The muscle is directed downwards, forwards, and inwards.
 
Action. —(1) To draw the tongue backwards; and (2) to elevate t
root of the tongue.
 
Stylo-hyoid Ligament. —This is a narrow fibrous cord which
attached superiorly to the tip of the styloid process, and interiorly
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1233
 
 
lesser horn of the hyoid bone. Its direction is downwards and
ards, superficial to the glosso-pharyngeal nerve and deep to the
rnal carotid artery, and its lower extremity is covered by the
glossus muscle. It is liable to become ossified more or less
pletely.
 
rhe ligament represents the usually unossified skeletal part of the
nd visceral arch, and ossification in it, when it occurs, corresponds
le epihyal bone of lower mammals, so well seen in the ruminants,
lubmandibular Gland (Submaxillary Gland).—This gland is situated
he anterior part of the digastric triangle. It consists of a large
jrficial part and a small deep part. The superficial part superiorly
ipies the submandibular fossa on the inner surface of the body of
mandible, and inferiorly it is covered by
skin, superficial fascia, platysma, and
) fascia. The anterior facial vein deds superficial to it. Its deep surface
3 anteriorly upon the mylo-hyoid muscle,
 
1 the intervention of the mylo-hyoid
^e and submental branch of the facial
ry; and posteriorly upon the hyo-glossus,
slightly upon the posterior belly of the
istric and stylo-hyoid muscles. The
jrficial part is grooved at its upper and
£ part by the facial artery, which lies
>edded in the gland. Posteriorly the
jrficial part is related to the cervical
ion of the parotid gland, from which
s separated by the stylo-mandibular
ment. The deep part of the gland is of
.11 size, and is continuous with the superficial part at the posterior
ier of the mylo-hyoid muscle. It lies under cover of that muscle
n the hyo-glossus, and is related to the sublingual gland.
 
Ihe submandibular duct (Wharton’s duct) emerges from the deep
set of the superficial part of the gland close to the posterior border
he mylo-hyoid muscle. It is about 2 inches in length, and passes
ards upon the hyo-glossus muscle, lying beneath the deep part of
gland. In this situation it has the submandibular ganglion and
ual nerve above it, and the hypoglossal nerve below it. After
dng the hyo-glossus muscle, the duct lies superficial to the geniossus, and, passing slightly upwards, it is crossed from above down'ds by the lingual nerve. Having passed just below the mucous
nbrane of the floor of the mouth on the inner side of the sublingual
id, the duct opens upon the floor of the mouth by a minute orifice,
ch is situated on the summit of a papilla lying close to the side of
frenulum linguae.
 
The submandibular gland corresponds to the posterior half of the
ly of the mandible, and sometimes reaches down below the level of
hyoid bone.
 
 
Lumen of Alveolus
 
 
 
Crescents of Gianuzzi
 
 
Fig. 745.—Section of the
Submandibular Gland
of a Dog.
 
 
78
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1234
 
Blood-supply.—The gland derives its blood chiefly from the cerv
part of the facial artery.
 
Nerve-supply.—The nerves are derived from the submandibi
ganglion, and through this from the chorda tympani, the lingual, <
the sympathetic plexus on the facial artery.
 
Lymphatics.—These pass to the submandibular lymph glands, <
thence to the superficial and deep cervical lymph glands.
 
Structure. —The submandibular gland is a muco-serous gland, and its gen
structure is similar to that of the parotid gland. The essential difference
tween the two has reference to the alveoli or acini, and the nature of t
secretion. The cells of the parotid alveoli are serous or albuminous. The 1
mandibular alveoli contain around the lumen mucous cells filled with gran
mucigen, which is discharged as mucus. They, however, also contain s<
albuminous cells, known as the marginal cells, which are situated externa
 
 
Parotid Duct
 
 
 
the mucous cells, but within the membrana propria of the alveolus. Th
cells usually form groups which, from their crescentic arrangement, are knc
as the crescents of Gianuzzi.
 
Development. —The submandibular gland is developed as a solid outgro
of the buccal epithelium. This outgrowth undergoes ramifications, and fl
subsequently become hollow. The outgrowth takes place from the floor of
sulcus between the tongue and the mandibular arch, far back in its lateral p
at the beginning of the second month. The lingual nerve passes to the ton
below the floor of the sulcus in front of the outgrowth. The submandibular d
is gradually produced from before backwards by the closing off of the lov
part of the sulcus, so that it really corresponds with the original floor of
groove. Thus it possesses a lumen from its earliest stages, while the glan<
still solid, and the lingual nerve has to pass below it.
 
Sublingual Gland.—This is the smallest of the salivary glands, '<
resembles an almond in shape. It measures about i\ inches in len£
and is situated beneath the mucous membrane of the floor of
mouth, where it gives rise to a mucous fold, called the plica sublingua
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1235
 
 
iriorly it rests upon the mylo-hyoid muscle, and is here related to
deep part of the submandibular gland, the submandibular duct,
L the lingual nerve. Laterally it occupies the sublingual fossa on
inner surface of the body of the mandible above the mylo-hyoid
and medially it is in contact with the genio-glossus muscle. Its
dial extremity comes into contact with its fellow of the opposite
3 over the anterior border of the genio-glossus muscle.
 
The sublingual ducts (ducts of Rivini) vary in number from ten to
:nty. A few of them open into the submandibular duct, but the
jority open in a linear manner upon the summit of the plica sub;ualis.
 
Blood-supply.—The gland receives its blood from the sublingual
rich of the lingual artery.
 
Nerve-supply.—The nerves are derived from the chorda tympani
1 lingual nerves, and the sympathetic plexus on the facial artery,
means of a branch of the submandibular ganglion, which is con:ted to the sublingual gland by the lingual nerve.
 
Structure. —-The sublingual gland is a mucous gland, and its general structure
imilar to that of the parotid and submandibular glands, but the lobules are
re loosely arranged. The cells of the sublingual alveoli are for the most part
cous cells, but there are also serous or albuminous cells.
 
Development.— The sublingual gland is developed as a number of outgrowths
21 the buccal epithelium. These undergo ramifications, and subsequently
:ome hollow.
 
 
Scalene Muscles and Subclavian Artery.
 
Scalene Muscles.—The scalene muscles
5 three.
 
Scalenus Anterior (Scalenus Anticus)—
 
igin .—By four short tapering tendons
)m the anterior tubercles of the transrse processes of the third, fourth, fifth,
d sixth cervical vertebrae.
 
Insertion .—The scalene tubercle of the
st rib.
 
Nerve-supply .—The anterior primary
mi of the fifth and sixth cervical nerves.
 
The muscle is directed downwards,
itwards, and forwards.
 
Action .—To fix the first rib in ordinary
spiration, and to elevate it in forced
spiration; and to bend the neck to one
le.
 
Chief Relations — Anterior. —The
irenic nerve, which crosses the muscle
diquely downwards and inwards; the
ternal jugular vein, which lies in front of its origin; the subclavian
iin close to its insertion; the thoracic or the right lymphatic duct;
 
 
 
Anterior.
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1236
 
the transverse cervical and suprascapular arteries; and the omo-hy
muscle. Posterior. —The scalenus medius, with the intervention of
second part of the subclavian artery, the nerve-roots of the bract
plexus, and the cupola of the pleura. Medial. —The ascending cervi
artery and the origin of the longus capitis.
 
Scalenus Medius — Origin. —By six short tapering tendons from
posterior tubercles of the transverse processes of the lower six cervi
vertebrae.
 
Insertion. —The upper surface of the first rib from the groove
the subclavian artery backwards to the tubercle. Sometimes a i
fibres are inserted into the suprapleural membrane (Sibson’s fasc
over the cupola of the pleura. When distinct they are called 1
scalenus pleuralis.
 
Nerve-supply. —The anterior primary rami of cervical nerves fr
the third to the eighth inclusive.
 
The muscle is directed downwards and outwards.
 
Action. —(1) To fix the first rib in ordinary inspiration, and (2)
bend the neck to one side.
 
Relations — Anterior.— The cervical plexus, the nerve-roots of 1
brachial plexus, except the first thoracic, and the second and th
parts of the subclavian artery. Posterior. —The levator scapulae a
scalenus posterior muscles.
 
The scalenus medius is pierced by the following nerves: the nei
to the rhomboids, which passes in a backward direction; and the up]
and middle roots of the nerve to serratus anterior. These two roi
usually emerge from the muscle as a single cord, and the lower or th
root of the nerve descends in front of the scalenus medius, and jo
the foregoing cord about the level of the first rib.
 
Scalenus Posterior (Scalenus Posticus) — Origin. —By two or th
short tendons from the posterior tubercles of the transverse proces
of the lower two or three cervical vertebrae.
 
Insertion. —The upper part of the outer surface of the second
in front of the insertion of the highest slip of the serratus poster
superior, and behind the origin of a portion of the first and the seco
digitations of the serratus anterior.
 
Nerve-supply. —The anterior primary rami of the sixth, seven
and eighth cervical nerves, the branches of which pass through 1
scalenus medius.
 
The muscle is directed downwards and outwards.
 
Action. —To elevate the second rib, and to extend the neck.
 
The scalenus posterior is the vestige of an important extensor muscle of
neck in pronograde mammals, in which it is attached to several ribs. In
orthograde position, however, with its balanced head, the need for it has (
appeared.
 
Relations — Anterior. —The scalenus medius. Posterior. —The lov
two tendons of origin of the levator scapulae. The scalenus poster
is intimately connected with the scalenus medius, of which it is pn
tically a part.
 
 
 
 
THE HEAD AND NECK
 
 
1237
 
 
Subclavian Artery.—The right subclavian vessel arises from the
)minate artery behind the right sterno-clavicular joint on a level
1 its upper part, and the left subclavian vessel arises from the
>er aspect of the arch of the aorta towards its back part. On each
the artery ends at the outer border of the first rib by becoming
axillary artery. In its course the vessel is crossed superficially
the scalenus anterior muscle, which divides it into three parts.
 
 
Rectus Capitis Anterior
 
 
Rectus Capitis Lateralis -
 
Basilar Part of Occipital Bone
 
 
Longus Capitis
 
 
Scalenus Posterior
 
 
 
Vertebral Artery
(third part)
 
 
Scalenus Anterior.
Scalenus Medius .
 
 
Longus Cervicis(upper oblique part)
_Vertebral Artery (second part)
 
 
_Longus Cervicis (vertical part)
 
 
Vertebral Artery (first part)
 
HP. Longus Cervicis (lower
oblique part)
 
 
Scalene Tubercle
 
Fig. 748. — The Right Prevertebral Muscles.
The vertebral artery is also shown.
 
 
The first part extends from the origin of the vessel to the inner
:der of the scalenus anterior; the second part lies behind that muscle;
I the third part extends from the outer border of the muscle to the
ter border of the first rib. The. total length of the vessel on the
ht side is about 3 inches, and on the left about 4 i inches. The
ery describes an arch in front of the apex of the corresponding
lg and pleura, and the height to which it rises above the clavicle
 
ibout inch.
 
First Part of the Right Subclavian Artery.—This part extends from
i bifurcation of the innominate artery behind the light sterno
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 749.—Right Subclavian Artery in situ: Jugular and Subclavia
 
Veins Removed.
 
ficially. The internal jugular and vertebral veins cross it from abc
downwards close to the scalenus anterior, the latter vessel being belli
the former, and the anterior jugular vein crosses it from within 0
wards, but superficial to the sterno-hyoid and sterno-thyroid muse]
The vagus and its cervical cardiac branches, the cervical card
branches of the sympathetic, and the nerve-loop known as the ai
 
 
1238
 
 
A MANUAL OF ANATOMY
 
 
clavicular joint, on a level with its upper part, to the inner border
the scalenus anterior muscle. Its direction is upwards and out war
and it lies very deeply.
 
Relations— Anterior .—The skin, superficial fascia and platysr
deep cervical fascia, clavicular origin of the sterno-mastoid, and ster
hyoid and sterno-thyroid muscles. Three veins are related to it sup
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1239
 
 
 
. 750.—The Aorta in the Thorax, and the Principal Arteries of the
 
Head and Neck.
 
 
t. Arch of the Aorta
Aortic Isthmus
l- Aortic Spindle
p Descending Aorta
5. Coronary Arteries (from
Ascending Aorta)
 
5 . Innominate Artery
7 • Left Common Carotid
3 . Left Subclavian
?• Right Common Carotid
 
 
10. Right Subclavian
 
11. External Carotid
 
12. Internal Carotid
 
13. Maxillary
 
14. Superficial Temporal
 
15. Vertebral
 
16. Internal Mammary
 
17. Thyro-cervical Trunk
 
18. Inferior Thyroid
 
19. Transverse Cervical
 
 
20. Suprascapular
 
21. Superior Thyroid
 
22. Lingual
 
23. Facial
 
24. Occipital
 
25. Posterior Auricular
 
26. Ascending Pharyngeal
 
27. Transverse Facial
 
28. Posterior Iutercostals
 
29. Ligamentum Arteriosum
 
 
 
 
 
 
 
 
 
 
 
 
 
1240
 
 
A MANUAL OF ANATOMY
 
 
subclavia also cross it superficially. Posterior .—The recurrent lan
geal nerve, sympathetic trunk, fat, longus cervicis muscle, first thora
vertebra, cupola of the pleura, and apex of the lung. Inferior .—1
recurrent laryngeal nerve, part of the ansa subclavia, and the pleura
 
The right subclavian and right internal jugular veins unite in fr<
of this part of the vessel to form the right innominate vein.
 
First Part of the Left Subclavian Artery.—This part extends fr<
the upper aspect of the arch of the aorta, towards its back part,
the inner border of the scalenus anterior muscle. It is therefore plac
at first in the thoracic cavity. Its course is almost vertical until
reaches the root of the neck, where it curves sharply outwards upon 1
cupola of the pleura, and so reaches the scalenus anterior. The re
tions of the intrathoracic portion have been described in connect]
with the thorax (see p. 1040).
 
Cervical Relations— Anterior .—The skin, superficial fascia a
platysma, deep cervical fascia, clavicular origin of the sterno-masto
sterno-hyoid, and sterno-thyroid muscles, and the thoracic duct whi
arches over it. The left internal jugular and subclavian veins un
 
in front of it to form the left innomim
vein, and the left vertebral vein descer
in front of it under cover of the left interi
jugular vein. Posterior .—The sympathe
trunk with the inferior cervical ganglk
fat, and the left longus cervicis muse
Right. —The trachea, oesophagus, left :
current laryngeal nerve, and thoracic du
The varieties in origin of the subclavi
artery have been described in connecti
with the arch of the aorta (see p. 1040
seq.).
 
Second Part of the Subclavian Artery.
 
This portion of the vessel is situated behi
the scalenus anterior muscle. It lies abo
\ inch above the clavicle, and forms t
highest part of the arch described by t
vessel.
 
Relations— Anterior. — Its only din
anterior relation is the scalenus anteri<
Posterior .—The pleura. Superior. —T
nerve-roots of the brachial plexus. 1
ferior .—The pleura.
 
In some cases the second part of the vessel passes through the scalenus ariter
and in rare cases it passes in front of the muscle.
 
 
 
Fig. 751. —Left Subclavian
Vessels and Terminal
Piece of Thoracic Duct.
 
 
For the third part of the subclavian artery see p. 1191.
 
 
Development. —The right subclavian artery as far as the origin of the inter]
mammary artery is developed from the fourth right aortic arch.
 
The left subclavian artery is developed from the seventh left, segmen
arterv.
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1241
 
 
Branches of the subclavian artery are the vertebral, internal
nmary, thyro-cervical trunk, and superior intercostal. The first
;e arise from the first part of the artery towards its termination, and
last arises from the second part on the right side, and from the
; part on the left side.
 
Vertebral Artery. —This, the first branch on the right side, arises
n the upper and back part of the artery about an inch from its
^n, and on the left side from the vessel just after it enters the root
he neck. It passes for a short distance upwards, backwards, and
htly outwards, and disappears from view by entering the foramen
isversarium in the sixth cervical vertebra as a rule. It then ascends
tically through the successive foramina transversaria above that of
sixth vertebra, passing outwards between the axis and atlas,
ving traversed the foramen transversarium of the atlas, it passes
kwards and inwards, lying in
vertebrarterial groove on the
)er surface of the posterior arch
the atlas behind the superior
icular process, pierces the dura
ter and arachnoid, and having
ched the side of the spinal
d, it turns upwards and forrds in the subarachnoid space,
 
I enters the cranial cavity
ough the foramen magnum,
gradually inclines from the
eral to the ventral aspect of
; medulla, and at the lower
rder of the pons it joins its
low to form the basilar artery.
 
On account of its complicated
arse, the vertebral artery is
dded into four parts—namely, first or cervical, second or costoms verse, third or suboccipital, and fourth or intercranial.
 
The first part extends from the origin of the vessel to the foramen
insversarium in the transverse process of the sixth cervical vertebra,
lies between the scalenus anterior and longus cervicis muscles,
ving the internal jugular and vertebral veins in front of it, being
assed by the inferior thyroid artery, and having the sympathetic
ank and the transverse process of the seventh cervical vertebra
hind it. The vessel of the left side has the thoracic duct as an
.ditional anterior relation.
 
The first part gives off no branches. . . .
 
The second part traverses the foramina transversaria ol the cervical
:rtebrae from, as a rule, the sixth upwards. It is surrounded by t e
;rtebral venous plexus, and by the vertebral plexus of the s}/mpaetic, and it lies in front of the cervical spinal neives as these emerge
3m the intervertebral foramina.
 
 
 
 
 
 
 
 
1242
 
 
A MANUAL OF ANATOMY
 
 
Branches.—These are as follows: spinal and muscular. T
spinal branches enter the vertebral canal through the interverteb:
foramina. The muscular branches supply the deep muscles of t
neck, and anastomose with the deep cervical, ascending cervical, a
occipital arteries.
 
For the third or suboccipital, and the fourth or intracranial, pai
of the vertebral artery, see p. 1151.
 
Varieties. —(1) The left vertebral artery not uncommonly arises from the ai
of the aorta between the origins of the left common carotid and left subclavi
arteries. (2) The vessel may pass the foramen transversarium of the sh
cervical vertebra, and may enter that of the fifth, or even that of the four
(3) The vessel has been found in rare cases to enter the foramen transversarii
of the seventh cervical vertebra.
 
Development. —The vertebral artery is developed from (1) the seventh cervi<
somatic artery, and (2) the longitudinal anastomotic chain which connects f
seven cervical somatic arteries.
 
Internal Mammary Artery.—This vessel, so named in contr
 
distinction to the external mammary, or lateral thoracic, a branch of t
second part of the axillary artery, arises from the lower aspect of t'
first part of the subclavian very nearly opposite the thyro-cervic
trunk. Its course is downwards, forwards, and slightly inwards, ai
it disappears behind the sternal end of the clavicle and first cost
cartilage. For its subsequent course and relations, see p. 999.
 
Relations of Cervical Part— Anterior .—The clavicular part of tl
sterno-mastoid, and the internal jugular and subclavian veins. Tl
phrenic nerve crosses the vessel superficially from without inward
Posterior .—The pleura.
 
No branches arise from this part of the vessel.
 
Thyro-cervical Trunk (Thyroid Axis).—This is a short trunk whi<;
springs from the front of the first part of the subclavian artery clo
to the inner border of the scalenus anterior muscle. It almost imm
diately divides into three diverging branches—inferior thyroi
transverse cervical, and suprascapular.
 
The inferior thyroid artery passes upwards and inwards in a tc
tuous manner in front of the vertebral artery, and behind the carot
sheath and sympathetic trunk, the middle cervical ganglion of whit
often rests upon it. Having reached the lower part of the lobe of tl
thyroid body, the artery breaks up into its terminal branches, whi<
enter the lobe on its deep aspect, and ramify in it, anastomosing wi
the superior thyroid and with its fellow of the opposite side of tl
isthmus. As the vessel ascends it is intimately related to the recurre:
laryngeal nerve, which usually lies behind it.
 
Branches.—These are as follows: muscular, ascending cervic;
inferior laryngeal, tracheal, and oesophageal.
 
The muscular branches supply the scalenus anterior, longus cervic::
the infrahyoid muscles, and inferior constrictor of the pharynx. Tl
ascending cervical artery arises from the inferior thyroid as it pass
inwards behind the carotid sheath. It ascends in front of the trait
verse processes of the cervical vertebrae, lying between the scalenj
 
 
 
 
 
THE HEAD AND NECK
 
 
1243
 
 
rior and longus capitis, and having the phrenic nerve on its outer
and the sympathetic trunk just medial to it. It anastomoses
branches of the vertebral, occipital, and ascending pharyngeal
ries. It may furnish some spinal branches which enter the vertebral
il through the intervertebral foramina to be distributed in a manner
lar to the other spinal arteries. The inferior laryngeal artery
impanies the recurrent laryngeal nerve to the larynx. The tracheal
oesophageal branches are distributed as their names suggest,
rhe transverse cervical artery passes transversely outwards in
t of the scalenus anterior and phrenic nerve, and behind the
icular part of the sterno-mastoid, lying a little above the clavicle,
also above the suprascapular artery. It then enters the subdan triangle, which it soon leaves by passing deep to the inferior
y of the omo-hyoid. It then passes in front of, or between, the
^e-trunks of the brachial plexus to the deep surface of the trapezius
$cle. Having reached the anterior border of the levator scapulae,
ivides into its two terminal branches—superficial and deep.
 
The superficial branch [superficial cervical artery) passes superficial
the levator scapulae, and is distributed to the trapezius, levator
pulae, splenius, and the adjacent lymph glands. The deep branch
sterior scapular artery) passes backwards in front of the levator
pulae to the superior angle of the scapula. It then descends along
base of the bone, under cover of the rhomboid muscles, as far as
inferior angle, where it anastomoses with the circumflex scapular
1 subscapular arteries. The artery gives branches to the adjacent
iscles, and anterior and posterior branches to the scapula, which
:e part in the scapular anastomoses proper (see p. 438).
 
The deep branch of the transverse cervical is frequently a branch
the third part of the subclavian, in which cases there is no transverse
vical artery, the superficial branch of the latter artery taking its
ice and arising from the thyro-cervical trunk (see p. 1192).
 
The suprascapular artery passes downwards and outwards in front
the scalenus anterior and phrenic nerve, and behind the clavicular
rt of the sterno-mastoid. Having reached the back of the clavicle,
courses outwards behind that bone, passing in front of the third
rt of the subclavian artery and the trunks of the brachial plexus,
then passes to the upper border of the scapula in company with the
prascapular nerve. For the further course of the vessel and for the
 
ipular anastomoses of arteries see p. 441.
 
Branches in the neck are muscular, suprasternal, and nutrient,
le muscular branches supply the sterno-mastoid and subclavius.
le suprasternal branch descends over the inner end of the clavicle to
pply the integument over the manubrium sterni. The nutrient
tery of the clavicle is directed outwards, and enters the nutrient
 
ramen of that bone. It is often double.
 
Superior Intercostal Artery. —This vessel arises from the second
irt of the subclavian on the right side, and from the first part on
le left side, in each case from the posterior aspect of the paient
 
 
 
i 2 4 4
 
 
A MANUAL OF ANATOMY
 
 
trunk. On the right side it is therefore behind the scalenus anter
and on the left side close to the inner border of that muscle. '
vessel at first passes backwards and upwards for a short distance, ;
then descends in front of the neck of the first rib. At the postei
extremity of the first intercostal space it furnishes the first postei
intercostal artery to that space, and then descends in front of
neck of the second rib to become the second posterior intercom
artery. The superior intercostal artery therefore furnishes the fi
and second posterior intercostal arteries for the first and second inf
costal spaces, their distribution being similar to that of the succeed
posterior (aortic) intercostal arteries. Besides these two brand:
the vessel gives off the deep cervical artery. This branch, which
homologous with the posterior branch of a posterior intercostal arte
arises from the superior intercostal before it descends in front of 1
neck of the first rib.
 
The superior intercostal artery and the deep cervical art<
are often described as terminal branches of a common trunk
origin. This trunk is called the costo-cervical trunk; in 1
description adopted here this trunk is looked on as part of f
superior intercostal itself.
 
It passes backwards between the transverse process of the sever
cervical vertebra and the neck of the first rib, and then ascends betwe
the semispinalis capitis and semispinalis cervicis muscles to about f
level of the axis. In this situation it anastomoses with the de
division of the descending branch of the occipital artery. The de
cervical in its course gives off muscular branches which anastomc
with branches of the vertebral and ascending cervical arteries,
also furnishes a spinal branch which enters the vertebral canal throu
the intervertebral foramen between the seventh cervical and fii
thoracic vertebrae.
 
The superior intercostal artery on each side is developed from the anast<
motic loop between the upper two or three thoracic somatic arteries.
 
Subclavian Vein. —This vessel, which is the direct continuation
the axillary vein, extends from the outer border of the first rib to t
back of the inner end of the clavicle, where it unites with the intern
jugular to form the innominate vein. It lies in front of, and on
lower plane than, the subclavian artery, and it passes in front of t
scalenus anterior muscle and phrenic nerve. In rare cases the ve
has been met with passing behind the scalenus anterior. Its princip
tributary is the external jugular vein (sometimes also the anteri
jugular). The external jugular vein joins it close to the outer bord
of the sterno-mastoid.
 
The thoracic duct opens at the angle of junction of the left su
clavian and left internal jugular veins, and the right lymphatic du
opens into the angle of junction of the corresponding veins on t]
right side. The duct often opens in two or more parts.
 
Vertebral Vein. —This vein begins in the suboccipital veno
 
 
 
THE HEAD AND NECK
 
 
1245
 
 
ms within the suboccipital triangle. It passes through the foramen
lsversarium in the atlas, and accompanies the vertebral artery
nigh the succeeding foramina transversaria as low as the sixth,
ning a plexus around the vessel. This plexus is ultimately replaced
a single vein, which emerges through the foramen transversarium
he sixth cervical vertebra (sometimes the seventh). It then descends
ront of the first part of the subclavian artery under cover of the
irnal jugular vein, and opens into the back part of the innominate
1, the opening being provided with a single or double valve.
 
The chief tributaries of the vertebral vein are as follows: muscular,
lal, anterior vertebral, and deep cervical. It also, as a rule,
dves the first intercostal vein.
 
No vein accompanies the ceral part of the internal mamry artery. The inferior thyroid
a, which does not accompany
corresponding artery, is found
cribed in connection with the
Toid gland on p. 1222.
 
The transverse cervical and
irascapular veins return the
od from the parts supplied by
i corresponding arteries, and
tributaries of the lower part
the external jugular vein.
 
The deep cervical vein starts
the suboccipital venous plexus
 
Tin the suboccipital triangle. ^ 0
 
descends in company with the Fk, 753-^*^^™ V*™
'P cervical artery, and passes . , ,, ,•
 
* J xr Anterior jugular frequently opens di
rectly into subclavian vein. Vertebral
vein," which receives superior intercostal, opens into beginning of innominate.
 
 
 
INNOM,
 
 
wards between the transverse
•cess of the seventh cervical
tebra and the neck of the first
to terminate in the vertebral
 
 
rhe anterior vertebral vein begins in a plexus in front of the uppei
ical transverse processes. It descends in company with the
nding cervical branch of the inferior thyroid artery receiving
cular tributaries in its descent, and it opens into the lower part
 
Jollateral^irculation after Ligature of the Third Part of the Subian Artery.— (i) The suprascapular and the deep branch of the
sverse cervical, both branches of the thyro-cervical trunk fiom
part of the subclavian, take part in the scapular anastomoses and
stomose freely with branches of the first and t rr par s 0 e
lary artery. (2) The internal mammary from the first part of
subclavian anastomoses with the lateral thoracic from the second
 
: of the axillary.
 
 
 
 
 
1246
 
 
A MANUAL OF ANATOMY
 
 
Collateral Circulation after Occlusion of the First Part of
Subclavian Artery. —(1) The vertebral artery of one side anastomc
with that of the opposite side. (2) The internal mammary anas
moses with the inferior epigastric from the external iliac, and w
the posterior intercostal arteries. (3) The inferior thyroid anas
moses with the superior thyroid from the external carotid. (4) 1
superior intercostal anastomoses with the third posterior intercosi
(5) The deep cervical of the superior intercostal anastomoses with
deep division of the descending branch of the occipital from the exter
carotid. (6) The scapular branches of the thyro-cervical trr
anastomose with branches of the axillary artery. (7) The thora
branches of the axillary artery anastomose with the posterior ini
costals.
 
Cervical Part of the Thoracic Duct (Fig. 751). — This part of 1
thoracic duct occupies the root of the neck on the left side, and ]
upon the side of the oesophagus, between it and the left subclav:
arteries. In this position it ascends to about the level of the sevei
cervical vertebra, and then it describes a curve and passes outwar
forwards, and downwards in contact with the cupola of the left pleu
It then inclines inwards, and, after receiving the left jugular and si
clavian trunks, ends in the angle of junction of the internal jugu
and subclavian veins of the left side. The terminal orifice of the di
is guarded by a valve composed of two segments, which are so direcl
as to effectually prevent the reflux of chyle and the flow of blood ii
it. The duct crosses the left vertebral artery, passing either in frc
of or behind the vertebral vein. In half the cases the duct is dou'
for some distance before it enters the internal jugular, and one brar
may open into the subclavian vein. Occasionally three or m<
openings have been found, and this multiple opening is of surgi
importance, for if one branch is cut in an operation on the root of i
neck, it is an even chance that there may be another to carry t
chyle to the blood-stream. It is important to notice that the di
passes behind the vagus and in front of the phrenic nerves.
 
Right Lymphatic Duct. —The position of this duct corresponds
that of the thoracic duct on the left side. It is about inch in lengi
and is formed by the union of the right subclavian trunk and rig
jugular trunk. Besides returning lymph from the right side of t
head and neck and the right upper limb, it receives the lympha
vessels from the right side of the heart, the right lung, the upp
part of the right half of the thoracic wall, and some of those from t
antero-superior surface of the liver. It ends in the angle of juncti
of the internal jugular and subclavian veins of the corresponding sic
its orifice being guarded by a double valve.
 
Cervical Portion of the Lung. —The apex of the lung projects in
the root of the neck as high as the neck of the first rib. It is cover
by the cupola of the pleura, on the inner and anterior aspects of whi
the subclavian artery arches outwards. The cupola of the pleura
covered by the suprapleural membrane (Sibson’s fascia), which exten
 
 
THE HEAD AND NECK
 
 
1247
 
 
im the medial border of the first rib to the front of the transverse
Dcess of the seventh cervical vertebra. This membrane is probably
rived from the adjacent scalene muscles, and it may contain some
iscular fibres.
 
 
The Contents of the Orbit.
 
The following structures are found in the orbit:
 
Orbital Fascia. —The periosteum of the orbit is continuous posteriorly
th the dura mater through the superior orbital fissure, and constitutes
0 orbital fascia. Anteriorly it becomes continuous with the periinium of the frontal bone, and the periosteum of the maxilla and
gomatic bones. Along the supra-orbital and infra-orbital margins
0 superior and inferior palpebral fascia0 blend with it. The orbital
>cia is loosely attached to the bony walls of the orbit, and forms a
0ath for the contents of the cavity, which is incomplete in front.
Lacrimal Gland. —This gland lies at the anterior and outer part
the orbit superiorly, where it occupies the lacrimal fossa on the
ler side of the zygomatic process of the frontal bone. It is discaped. Its upper surface is convex, and its under surface is conve in adaptation to the eyeball. The anterior part of the gland is
rtly cut off by the outer edge of the levator palpebrae superioris,
d is known as the palpebral portion , the chief part being known
the orbital portion . The ducts, which issue from both portions,
0 about twelve in number, and they open in a row into the outer part
the superior conjunctival fornix.
 
Blood-supply. —The lacrimal artery.
 
Nerve-supply. —The lacrimal nerve and sympathetic filaments.
 
The structure of the gland is something like to that of the parotid.
Development. —The lacrimal gland, like the tarsal and ciliary glands, is
/eloped as solid epithelial cords from the conjunctiva. These epithelial
'ds spring from the upper and outer part of the conjunctiva, where it is rented from the inner surface of the upper eyelid on to the front of the eyeball,
e solid cords grow into the neighbouring mesoderm, and give off lateral proses. Cords and processes, at first solid, soon become hollow, and so give
3 to the alveoli, or acini, and ducts of the lacrimal gland.
 
In reptiles the ducts open all round the fornix of the conjunctiva, but in
unmals only the upper and outer ones persist.
 
Muscles.— These are the levator palpebrae superioris, rectus superior,
:tus inferior, rectus medialis, rectus lateralis, obliquus superior, and
liquus inferior.
 
Levator Palpebrae Superioris — Origin. —The under surface of the
of of the orbit above, in front of, and medial to the optic foramen.
Insertion. —By a broad membranous expansion, which divides into
ree tendinous laminae. The middle lamina, which is the chief
serf ion, and consists largely of involuntary muscular fibres, is attached
the upper margin of the superior tarsus. The upper or superficial
yer, which is fibrous, passes in front of the superior tarsus, lying
tween it and the palpebral fibres of the orbicularis oculi. Its fibres
 
 
1248
 
 
A MANUAL OF ANATOMY
 
 
pierce the superior palpebral fascia, and, having passed between
bundles of the palpebral portion of the orbicularis oculi, they
attached to the skin of the upper eyelid. The lower or deep layer , wl
is also fibrous, is attached to the conjunctiva along the superior for
 
 
Supra-orbital Nerve
(in two divisions)
 
 
Supratrochlear Nerve
Infratrochlear Nerve S™
 
 
Olfactory Bulb
 
 
Naso-ciliary Nerve
 
 
Optic Nerve-
 
 
Frontal Nerve on Levator
Palpebrae Superioris
 
Lacrimal Nerve passing
along Rectus Lateralis
 
 
Ophthalmic Artery’-'
 
Oculo-motor Nerve"*
 
Trochlear Nerve'
 
Abducent Nerve-'
 
Motor Root of Trigeminal Nerve
 
Fig. 754. —Dissection of the Orbit from above (Hirschfeld and Leveil
 
 
Maxillary Nerve
Ophthalmic Nerve
7 Mandibular Nerve
'-Trigeminal Ganglion
 
'•Sensory Root of Trigeminal Nerve
 
 
The outer and inner margins of the broad membranous expans
are attached to the outer and inner margins of the orbit close to
lateral and medial palpebral ligaments, and at the inner angle a <
is attached to the pulley of the obliquus superior.
 
Nerve-supply .—The 1
per division of the th
cranial nerve, the brai
from which enters the d<
or ocular surface of
muscle near its ori£
having pierced the rec
superior.
 
Action .—To raise
upper eyelid. The mus
is the antagonist of
superior palpebral fibres
the orbicularis oculi.
 
The levator palpebrse is a delamination of the rectus superior, to whicl
is so closely attached that, even when it is paralyzed, the upper lid may
raised a little by looking upwards.
 
Relations. — Superiorly , the frontal nerve and the supra-orbi
artery. Inferiorly , the rectus superior and the conjunctiva.
 
 
 
WHICH MOVE THE EYEBALL.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1249
 
Recti Muscles Rectus Superior— Origin. —The upper part of the
rnmon tendinous ring in relation to the optic foramen.
 
Insertion. By a thin expanded tendon into the upper surface of
e sclera about three or four lines from the margin of the cornea.
Nerve-supply.-' The upper division of the oculo-motor nerve, the
anch from which enters the deep or ocular surface of the muscle
ar its origin.
 
The muscle is flattened from above downwards, and its direction
forwards and slightly outwards.
 
The actions of the muscles of the eyeball are considered together
tp- 1251
Relations.' Superiorly , the levator palpebrae superioris, which is
e narrower of the two muscles. Inferiorly , the tendon of the obliquus
penor, the eyeball, and the soft fat of the orbit.
 
Rectus Medialis (Internal Rectus)— Origin. —The inner part of the
mmon tendinous ring in relation to the optic foramen, the origin
:ing wide.
 
Insertion. By a thin expanded tendon into the inner surface of
e sclera about three or four lines from the margin of the cornea.
Nerve-supply. —The lower division of the oculo-motor nerve, the
anch from which enters the deep or ocular surface of the muscle.
 
The muscle is flattened from within outwards, and its borders are
perior and inferior. Its direction is almost straight forwards.
 
Relations.—Above the upper border of the muscle is the obliquus
perior, and between the two the naso-ciliary nerve and the anterior
id posterior ethmoidal vessels pass.
 
Rectus Inferior— Origin. —The lower part of the common tendinous
ig in relation to the optic foramen.
 
Insertion. —By a thin expanded tendon into the lower surface
the sclera about three or four lines from the margin of the
rnea.
 
Nerve-supply. —The lower division of the oculo-motor nerve, the
anch from which enters the deep or ocular surface of the muscle.
 
The muscle is flattened from above downwards, and its direction
forwards and slightly outwards.
 
Relations— Inferior. —A part of the obliquus inferior.
 
Rectus Lateralis (External Rectus)— Origin. —This muscle arises bv
[0 heads. y
 
Inferior Head.—(1) The lower part of the common tendinous ring
relation to the optic foramen, where it is near the rectus inferior;
d (2) the prominent spine on the lower margin of the superior orbital
sure near its inner end.
 
Superior Head.—The outer portion of the upper part of the common
idinous ring in relation to the optic foramen, where it is above
2 superior orbital fissure, external to the optic foramen, and near
- rectus superior. The two heads are connected by a tendinous
nd which arches over the superior orbital fissure, and gives origin
some of the fibres of the inferior head of the muscle.
 
 
79
 
 
 
 
1250
 
 
A MANUAL OF ANATOMY
 
 
Insertion. —The outer surface of the sclera from three to four li
from the margin of the cornea.
 
Nerve-supply. —The abducent nerve, the branches of which en
the deep or ocular surface of the muscle.
 
The muscle is flattened from without inwards, and its directioi
forwards and outwards.
 
Action. —To abduct the eyeball, so as to direct the cornea outwai
 
Relations.—The following structures pass between the two he
of the muscle in order from above downwards: (i) the upper divis
of the oculo-motor nerve; (2) the naso-ciliary nerve; (3) the hr
division of the oculo-motor nerve; (4) the abducent nerve; and (5)
superior ophthalmic vein or veins.
 
Common Tendinous Ring of the Recti Muscles.—This tendon ta
the form of a fibrous ring, which is attached to the upper, inner, ;
lower margins of the optic foramen. It then crosses transvers
the inner portion of the superior orbital fissure to a prominent sp
on the lower margin of that fissure near its inner end. From 1
spine it recrosses the superior orbital fissure in a vertical direct
near its centre, and finally reaches the upper part of the optic foram
This latter portion gives origin to some fibres of the inferior head
the rectus lateralis. The upper part of the ring is sometimes knc
as the tendon of Lockwood , and gives origin from within outwa
to part of the rectus medialis, the rectus superior, and the supei
head of the rectus laterals. The lower part is also sometimes ca]
 
the ligament of Zinn y which gives ori
from within outwards to part of the rec
medialis, the rectus inferior, and the infei
head of the rectus lateralis.
 
Obliqui Muscles — Obliquus Superio:
Origin. —The wall of the orbit directly
front of the upper and inner part of
optic foramen, close to the recti superio]
medialis.
 
Insertion. —By an expanded tendon i
the upper and outer aspect of the sc]
just beyond the outer border of the supe:
rectus, and midway between the margir
the cornea and the entrance of the oj
nerve.
 
The muscle is situated at the upper 1
inner part of the orbit, internal to
levator palpebrae superioris. It is directed forwards towards
inner angle of the orbit, on approaching which it ends in a sr
round tendon. This tendon passes through a fibro-cartilagin
pulley close to the medial angular process of the frontal bone,
then changes its direction, and passes downwards, outwards, ;
backwards beneath the tendon of the rectus superior to reach
insertion just lateral to that tendon.
 
 
 
Fig. 756.—The Superior
Oblique Muscle.
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1251
 
The fibro-cartilaginous pulley or trochlea is attached by fibrous
;sue to the trochlear fossa on the orbital plate of the frontal bone
)se to the medial angular process. It is lined with synovial membrane
lubricate the tendon and facilitate its movement at this abrupt
ange in its course. The tendon receives a fibrous investment from
e outer margin of the pulley.
 
Nerve-supply.—The trochlear nerve, which enters the muscle on
; superficial or orbital surface near its origin.
 
Relations— Superior. —The roof of the orbit and the rectus superior.
ferior. —The upper border of the rectus medialis, having the nasoiary nerve and the anterior and posterior ethmoidal vessels between
em. Lateraf^—-The levator palpebrae superioris.
 
Obliquus Snpemr — Origin. —A small depression at the anterior and
tier part of the floor of the orbit immediately lateral to the upper
>ening of the lacrimal canal.
 
Insertion. —The outer surface of the sclera under cover of the rectus
teralis, and slightly posterior to the level of the insertion of the
iliquus superior.
 
Nerve-supply— The lower division of the oculo-motor nerve, the
anch of which is long and enters the posterior border of the muscle.
The muscle at first passes outwards and backwards upon the floor
the orbit beneath the rectus inferior, and then it turns upwards
itween the sclera and the rectus lateralis, where its tendon expands
lore its insertion.
 
Relations. —Towards the eyeball the muscle is related to the
ctus inferior and the sclera, and towards the orbit to the floor of
e cavity and the rectus lateralis. The borders of the muscle are
Lterior and posterior, the latter, as stated, receiving the nerve
ppiy
Movements of the Eyeball. —The movements of the eyeball con>t of rotation round a point situated just behind the centre of its
hero-posterior axis. When the eyeball rotates round its vertical
:is, horizontal or lateral movements take place, and the cornea
directed outwards or inwards according to the muscle which acts.
ie rectus lateralis abducts the eyeball, so as to direct the cornea
itwards, and the rectus medialis adducts the eyeball, so as to
rect the cornea inwards. When the eyeball rotates round its trans;rse axis vertical or upward and downward movements take place,
id the cornea is directed upwards or downwards according to the
uscle which acts. The rectus superior elevates the eyeball, and
e rectus inferior depresses it. It is to be borne in mind, however,
at these two muscles in passing forwards have each a slight innation outwards. Whilst, then, they respectively elevate and depress
e cornea on the transverse axis of the eyeball, each of them also
^es it a certain amount of inward movement on the vertical axis,
companied by slight rotation on the antero-posterior axis. In
e case of the rectus superior this inward and rotatory movement
corrected by the obliquus inferior acting in association with it, and
 
 
 
 
1252
 
 
A MANUAL OF ANATOMY
 
 
in the case of the inferior rectus by the obliquus superior acting
association with it.
 
Direct elevation of the eyeball is therefore effected by the re<
superior, aided by the obliquus inferior, and direct depression of
eyeball is effected by the rectus inferior, aided by the obliquus supei
The superior oblique, acting alone, would depress the cornea
abduct it, making the eye look downwards and outwards, and
obliquus inferior, acting alone, would elevate and abduct it, tl
movements in each case being accompanied by slight rotation on
antero-posterior axis.
 
Fascia of the Orbit.—This fascia forms (i) the fascial sheath
 
 
the eyeball, fascia bulbi; and (2) sheaths for the ocular muscles.
 
The fascia bulbi is practically the thickened wall of a lyn
space round the sclerotic coat of the eyeball, and extends from
 
point of entrance of the o]
 
 
 
nerve to near the margin of
cornea. Posteriorly it is perfora
by the ciliary vessels and ner
and blends with the dura ma
sheath of the optic nerve, ;
anteriorly it fades away when
meets the ocular conjunctiva,
outer surface of the capsule h
contact with the orbital fat, ;
anteriorly with the ocular c
junctiva. The fascial sheath (c
sule of Tenon) forms a cavity
socket, within which the eyel
glides with perfect freedom fr
friction.
 
The lower part of the fas<
sheath of the eyeball is said to
thickened by the suspensory li
ment of the eye (Lockwood). This is attached laterally to Whitna
tubercle on the zygomatic bone, and medially to the lacrimal bo
It is expanded beneath the eyeball, to the fore part of which it a
as a sling or support.
 
The muscular sheaths are derived from the fascial sheath of
eyeball. The tendons of the six ocular muscles pierce the fas(
sheath on their way to their insertions, which latter are under cover
the fascial sheath, each muscle receiving a prolongation from the mar ;
of the cleft in the sheath through which its tendon passes. Th
prolongations extend backwards around the muscles, and ultimat
blend with their perimysial sheaths. As regards the obliquus super
muscle, the prolongation around its tendon extends upwards, inwar
and forwards as far as the margin of the pulley, to which it is attach
The prolongation around the tendon of the obliquus inferior mus
extends downwards as far as the outer part of the floor of the orbit
 
 
It has an endothelial lining (dotted line)
which is reflected along the tendons
to their insertions; the fibrous basis
is reflected back towards the muscle.
 
 
 
 
 
THE HEAD AND NECK
 
 
1253
 
 
The sheaths of the four recti muscles give off important expanms. The expansion from the sheath of the rectus lateralis is strong,
id is attached to the frontal process of the zygomatic bone, and
at from the sheath of the rectus medialis, also strong, is attached
the lacrimal crest of the lacrimal bone. These two expansions
their bony attachments are connected with the lateral extremities
the suspensory ligament of the eye. The expansion from the
eath of the rectus superior blends with the deep layer of the tendon
the levator palpebrae superioris, and that from the sheath of the
:tus inferior is connected with the inferior tarsus. These expansions
>m the sheaths of the recti, especially from those of the recti lateralis
medialis, moderate the action of the muscles, and the latter two
e hence known as the check ligaments.
 
Nerves in the Orbit—Optic Nerve.—The optic nerve extends forirds and outwards from the optic chiasma, and enters the orbit
rough the optic foramen, having the ophthalmic artery below it
first, and then on its outer side. It receives sheaths from the
ira mater and arachnoid, the former being strong, and at its entrance
to the orbit it is surrounded by the origins of the four recti muscles.
 
? direction is forwards and outwards, with a slight inclination
wnwards, to the back part of the eyeball, where it pierces the sclera
out inch medial to, and a little below, the centre. It then pierces
e choroid coat, and ends in the nerve-fibre layer of the retina. The
iary ganglion is close to the outer side of the nerve towards the back
rt of the orbit, and in front of this the nerve is surrounded by the
iary nerves and vessels. It is crossed superiorly by the ophthalmic
tery, the superior ophthalmic vein, and the naso-ciliary nerve,
feriorly, about J inch behind the eyeball, the central artery of the
tina enters it and then runs forward within it to the retina.
 
Third or Oculo-motor Nerve.—This nerve, having left the outer
dl of the cavernous sinus, breaks up at the superior orbital fissure into
0 divisions, upper and lower. These enter the orbit between the
0 heads of the rectus lateralis muscle, the naso-ciliary nerve being
uated between the two.
 
The superior division enters the deep surface of the rectus superior
pplying it, after which it pierces the muscle and ends in the levator
lpebrae superioris.
 
The inferior division, larger than the upper, has three branches,
lich supply the rectus medialis, the rectus inferior, and the obliquus
hrior. The twigs to the recti medialis et inferior enter these muscles
their deep or ocular surfaces. The branch to the obliquus inferior
a long nerve which passes forwards between the recti inferior et
eralis, and its twigs enter the obliquus inferior muscle at its posterior
'der. Posteriorly it furnishes the ganglionic branch, which forms the
3 rt or parasympathetic root of the ciliary ganglion.
 
The fourth, trochlear, or pathetic nerve, of small size, having left
2 wall of the cavernous sinus, enters the orbit through the superior
sital fissure above the muscles, and medial to, but on a slightly
 
 
 
I2 54
 
 
A MANUAL OF ANATOMY
 
 
higher plane than, the frontal nerve. Having passed inwards o 1
the levator palpebrae superioris, it enters the posterior part of the ol
quus superior muscle on its superficial or orbital surface, this bei
the only muscle which it supplies.
 
The sixth or abducent nerve, having left the cavernous sinus, ent
the orbit through the superior orbital fissure, and passes between 1
 
two heads of the rectus lateralis muscle,
this situation it has the lower division of 1
oculo-motor nerve above it, and the super
ophthalmic veins below it. It supplies 1
rectus lateralis, its twigs entering the mus
on its deep or ocular surface.
 
Branches of the Ophthalmic Division of I
Trigeminal Nerve. — The ophthalmic ner
having left the outer wall of the cavernc
sinus, and before reaching the superior orbi
fissure, divides into frontal, lacrimal, a
naso-ciliary nerves.
 
The frontal nerve, of large size, enters 1
orbit through the superior orbital fissure abc
the muscles. In this situation it has the 1;
rimal nerve lateral to, and on the same pla
with it, and the trochlear nerve medial to
but on a slightly higher plane. It then pas:
forwards on the upper surface of the levai
palpebrae superioris, underneath the periostei
of the roof of the orbit, and before arrivi
at the supra-orbital margin it divides into t
branches, supra-orbital and supratrochlear.
 
The supra-orbital nerve, which in size a
direction is the continuation of the front
passes forwards to the supra-orbital notch
foramen, through which it leaves the orbit
company with the supra-orbital artery. (
the forehead it divides into two branches, late
and medial, which have been already descrit
(see p. 1153). Sometimes this division takes place within the ort
and in these cases the inner branch usually passes through the sup:
orbital notch.
 
The supratrochlear nerve, of small size, passes forwards and inwai
to the pulley to the obliquus superior muscle, above which it runs
the forehead, where it has been already described (see p. 1154)- Bef(
leaving the orbit it gives off a small twig, which passes downwar
close to the pulley of the obliquus superior, to form a loop with i
infratrochlear branch of the naso-ciliary nerve.
 
The lacrimal nerve enters the orbit through the superior orbi
fissure above the muscles, and external to the frontal nerve. It tt
passes forwards and outwards along the upper border of the rec
 
 
 
Fig. 758. —The Third
and Sixth Cranial
Nerves in the Orbit .
 
 
I.O., nerve to inferior oblique; other branches
running directly forward from lower division of the third nerve
are going to inferior
rectus.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1255
 
 
:eralis in company with the lacrimal artery. On reaching the lacrimal
md it gives numerous branches to its deep surface, and is then coniued through the orbital septum to the skin and conjunctiva of the
ter part of the upper eyelid, and the skin in the region of the zygoitic process of the frontal bone. Near the lacrimal gland it sends
wnwards a small twig, which joins the zygomatico-temporal nerve.
The naso-ciliary nerve (nasal nerve) is more deeply placed than the
rntal and lacrimal. It enters the orbit through the superior orbital
sure, and passes between the two heads of the rectus lateralis muscle,
[ng between the upper and lower divisions of the oculo-motor nerve,
then passes obliquely inwards and forwards to the inner wall of the
bit, lying beneath the rectus superior and above the optic nerve,
d, later on, between the obliquus superior and the rectus medialis.
iving reached the inner wall of the orbit at the anterior ethmoidal
 
 
 
g. 759- —Scheme of the Distribution of the Oculo-motor, Trochlear,
 
and Abducent Nerves (Flower).
 
f U - D - { L rJ: Sg2£sSKZ" SUPeri ° riS
 
! rR.Int. Rectus Medialis
 
Oculo-Motor Nerve ' L.D. Lower Division -j R.Inf. Rectus Inferior
 
( O.I. Obliquus Inferior
 
 
C.G. Ciliary Ganglion
^ M.R. Motor Root
 
S.R. Sensory Root (from Naso-ciliary Nerve)
Sy.R. Sympathetic Root
S.C. Short Ciliary Nerves
Trochlear Nerve—O.S. Obliquus Superior
Abducent Nerve—R.E. Rectus Lateralis.
 
 
ramen, it parts with its infratrochlear branch, and then passes through
e foramen in company with the anterior ethmoidal artery, and so
iters the anterior fossa of the base of the skull. It then passes forwards
id inwards in a groove on the upper surface of the cribriform plate
the ethmoid bone, lying under cover of the dura mater. Having
ached the nasal slit at the side of the fore part of the crista galli,
descends through this slit, or through a small foramen just in front
it, into the nasal cavity, and immediately gives off two internal nasal
anches. Then the nerve descends in a groove on the posterior surface
the nasal bone, giving offsets to the mucous membrane of the outer
all of the nasal cavity in front of the superior and middle nasal
•nchae. Finally, the nerve comes out, as the external nasal branch,
dween the lower border of the nasal bone and the upper nasal cartilage,
id supplies the skin of the tip and lower part of the side of the nose.
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1:256
 
In connection with this remarkable course of the nerve it is to t
noted that it is to be met with in four different regions—name!
(1) in the orbit; (2) on the cribriform plate of the ethmoid bone :
the anterior cranial fossa; (3) in the nasal cavity; and (4) on the fa<
in the region of the tip of the nose.
 
Branches. —The ramus communicans to the ciliary ganglion forms tl
long or sensory root of that ganglion. It is slender, about ^ inch Ion
and arises from the naso-ciliary as it passes between the two hea(
of the rectus lateralis. It enters the ciliary ganglion at its poster
superior angle.
 
The long ciliary nerves , usually two in number, arise from tl
naso-ciliary immediately after it has crossed the optic nerve, and the
 
 
Supra-orbital Nerve
(in two divisions)
 
 
Supratrochlear Nerve—:
In fra trochlear Naso-ciliary—'
 
 
Olfactory Bulb
Naso-ciliary Nerved
 
 
Optic Nerve—
 
?
 
Ophthalmic Artery —
Oculo-motor Nerve- - """
 
 
Trochlear Nerve
 
 
 
-•Frontal Nerve on Levator
Palpebrae Superioris
 
 
**• Lacrimal Nerve passing along
Rectus Lateralis
 
 
~ Maxillary Nerve
Ar Ophthalmic Nerve
 
*** Mandibular Nerve
'.Trigeminal Ganglion
 
Abducent Nerve"' j ,,v ‘ Sensory Root of Trigeminal Nerve
 
Motor Root of Trigeminal Nerve
 
Fig. 760. —Dissection of the Orbit from above (Hirschfeld and
 
Leveille) .
 
 
communicate with the short ciliary nerves from the ciliary ganglioi
which they accompany to the back part of the sclera. Here they pierc
the sclera, and are distributed along with the short ciliary nerves.
 
The infratrochlear nerve arises from the naso-ciliary close to th
anterior ethmoidal foramen, and passes forwards beneath the obliqur
superior muscle. Near the pulley of that muscle it receives a twi
from the supratrochlear nerve, and then, passing beneath the puller
it leaves the orbit at the medial angle to be distributed to the ski
and conjunctiva of the inner parts of the eyelids, the side of the roc
of the nose, the lacrimal sac, and the caruncula lacrimalis.
 
As the nerve traverses the anterior ethmoidal canal it gives twig
to the mucous membrane of the frontal sinus and of the anterior etl
moidal sinus.
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1257
 
 
A posterior ethmoidal nerve is described as passing through the
isterior ethmoidal canal to supply the mucous membrane of the
jsterior ethmoidal sinus and of the sphenoidal sinus.
 
For the branches of the naso-ciliarv nerve to the exterior of the nose
id to the nasal fossa, see p. 1276.
 
Ciliary Ganglion (Lenticular Ganglion).—This is a small quadriteral body, about the size of a moderately large pin-head, which is
:uated in the posterior part of the orbit, where it lies flattened upon
e outer side of the optic nerve. It is usually in close contact with
 
 
A
 
 
 
 
Fig. 761.—A, The Ciliary Ganglion; B, The Nerves of the Orbit
(Lateral Aspect) (Hirschfeld and Leveille).
 
 
lternal Carotid Plexus
phthalmic Nerve
aso-ciliary Nerve
ympathetic Root of Ciliary
Ganglion
 
 
rigeminal Ganglion
'culo-motor Nerve
bducent Nerve
lternal Carotid Artery
ptic Nerve
 
ommon Tendinous Ring for
Recti
 
 
A
 
5. Sensory Root of Ciliary Gang
lion
 
6. Long Ciliary Nerves
 
7. Branch of Oculo-motor Nerve
 
to Obliquus Inferior
 
B
 
7. Levator Palpebrae Superioris
 
8. Rectus Superior
 
9. Frontal Nerve
 
10. Rectus Lateralis
 
11. Obliquus Superior
 
12. Rectus Inferior
 
13. Short Ciliary Nerves
 
 
8. Motor Root of Ciliary Ganglion
 
9. Ciliary Ganglion
 
10. Infratrochlear Branch of Naso
ciliary Nerve
 
11. Short Ciliary Nerves
 
 
14. Branch of Oculo-motor Nerve to
 
Obliquus Inferior
 
15. Ciliary Ganglion
 
16. Ophthalmic Nerve
 
17. Maxillary Nerve
 
18. Mandibular Nerve
 
 
it nerve, and is recognized by its reddish-pink colour. Posteriorly
receives its three roots, and anteriorly the short ciliary nerves pass
wards from it. The roots are called sensory, motor, and sympathetic,
e sensory root is derived from the naso-ciliary nerve as it passes
:ween the two heads of the rectus lateralis. It is slender, about
nch long, and enters the postero-superior angle of the ganglion,
e motor root is derived from the long branch of the lower division
the oculo-motor nerve which supplies the obliquus inferior muscle,
1 it enters the postero-inferior angle of the ganglion. The sym
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1258
 
 
A MANUAL OF ANATOMY
 
 
pathetic root is a very minute nerve which is derived from the interi
carotid plexus of the sympathetic, and it usually reaches the gangli
in company with the sensory root. It may, however, join the gangli
separately, and then it does so in close proximity to the entrance
the long root.
 
The branches of the ciliary ganglion are called the short cilic,
nerves. They are from six to eight in number, and come off in b
groups from the antero-superior and antero-inferior angles. T
nerves of the lower group usually exceed those of the upper in numb
As they pass forward above and below the optic nerve they divide, a
give rise to from sixteen to twenty delicate filaments. Having reach
the back of the eyeball, they pierce the sclera around the entrar
of the optic nerve. They then pass forwards between the sclera a
 
 
Infratrochlear Artery Medial Palpebral Arteries
 
 
Dorsal Nasal Artery-—
Pulley of Obliquus Oblique-.
 
 
Anterior Ethmoidal Artery.
 
Posterior Ethmoidal Artery..
 
 
Central Artery of the Retina
(in outline)
 
Obliquus Superior
Rectus Superior (cut)
 
Levator Palpebra? Superioris
(cut)
 
 
Optic Nerve
Optic Chiasma (right half)
 
 
 
Lacrimal Gland
 
 
Supra-orbital Artery
 
 
Long Posterior Ciliary
Arteries
 
Lacrimal Artery
 
 
Rectus Lateralis (cut)
Ophthalmic Artery
 
 
Right Optic Tract
 
Fig. 762. —Dissection of the Right Orbit from above, showing the Op
Nerve, Ophthalmic Artery, and Superior Oblique Muscle.
 
 
the choroid, giving twigs to the latter, and they are finally distribul
to the ciliary muscle, the iris, and the cornea. The short cilic
nerves thus convey co the eyeball sensory fibres from the ophthalr
division of the trigeminal nerve, motor fibres from the oculo-mo
nerve, and sympathetic fibres from the internal carotid plexus of 1
sympathetic.
 
Summary of the Ophthalmic Nerve. —This nerve is entirely sensory,
supplies (1) the skin of (a) the frontal region and top of the skull; (&) the up
eyelid, and (c) the root, tip, and lower part of the side of the nose; (2) the cari
cula lacrimalis and lacrimal sac; (3) the mucous membrane of the nasal cavi
and the conjunctiva; (4) the eyeball; and (5) the lacrimal gland.
 
Summary of the Ciliary Ganglion. —The branches of this ganglion supply 1
cornea, iris, and ciliary muscle. The fibres which supply the sphincter pUpi
are derived from the oculo-motor nerve by means of the motor root of the gangli
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1259
 
 
le fibres which supply the dilator pupillse are derived from the sympathetic by
eans of the sympathetic root of the ganglion, which is derived from the internal
rotid sympathetic plexus.
 
 
Branch of the Maxillary Division of the Trigeminal Nerve.—The
rgomatic nerve (temporo-malar nerve), of small size, arises from the
axillary in the pterygo-palatine fossa. It enters the orbit through
Le inferior orbital fissure, and soon divides into two branches, zygoatico-temporal and zygomatico-facial. The zygomatico-temporal nerve
imp oral branch) ascends upon the outer wall of the orbit, and, having
ceived a communicating twig from the lacrimal nerve, it leaves the
ivity by passing through the zygomatico-temporal canal in the
rgomatic bone. Its destination is the skin of the anterior part of
Le temporal region.
 
 
Medial Palpebral Arteries
Supratrochlear Artery
 
 
Dorsal Nasal Artery
 
 
Anterior Ethmoidal Artery
 
 
Posterior Ethmoidal Artery
Ophthalmic Artery
 
Posterior Ciliary Arteries
Ophthalmic Artery (in Optic Foramen)
 
 
 
Lacrimal Gland
 
 
-\ Lateral Palpebral
. j Arteries
 
 
Supra-orbital Artery
 
 
Lacrimal Artery
 
- Muscular Arteries
Arteria Centralis Retinae
'■ Posterior Ciliary Arteries
 
— Internal Carotid Artery
 
 
Fig. 763. —Diagram of the Ophthalmic Artery and its Branches.
 
 
The zygomatico-facial nerve [malar branch ) passes forwards in the
lgle between the outer wall and floor of the orbit, and leaves the
vity by passing through the zygomatico-facial canal, from which
comes out through the corresponding foramen. It is distributed
1 the skin over the zygomatic bone.
 
Ophthalmic Artery.—This vessel arises from the internal carotid
tery on the inner aspect of the anterior clinoid process, and enters
e orbit through the optic foramen, lying beneath the optic nerve,
ithin the orbit it is situated for a short distance on the outer side
the optic nerve, and then it passes obliquely inwards and forwards
a tortuous manner over the nerve to the inner wall of the orbit,
len it passes forwards to the region of the medial angular process
the frontal bone, near which it divides into its three terminal branches
dorsal nasal, supratrochlear, and palpebral.
 
 
 
 
 
 
 
 
I26o
 
 
A MANUAL OF ANATOMY
 
 
Branches. —These are as follows:
 
 
1. Central artery of the retina.
 
2. Posterior ciliary.
 
3. Lacrimal.
 
4. Muscular.
 
5. Supra-orbital.
 
 
6. Posterior ethmoidal.
 
7. Anterior ethmoidal.
 
8. Palpebral (two),
g. Nasal.
 
10. Frontal.
 
 
The central artery of the retina (arteria centralis retinae) aris
from the ophthalmic at the back part of the orbit below the opt
nerve. Its direction is forwards beneath the nerve, and at a poii
about \ inch behind the eyeball it enters the nerve, and passes forwan
in its centre to the retina, upon which it ramifies. It must be unde
stood that this is the only blood-supply of the retina, and that i
obliteration means blindness of the eye to which it goes; it is therefor
in spite of its small size, one of the most important arteries in the bod;
 
The posterior ciliary arteries arise from the ophthalmic whilst
is below the optic nerve. They are arranged in two sets, lateral an
medial, which pass forwards on either side of the optic nerve to the bac
part of the eyeball. Here they pierce the sclera, and the majorit
of them enter the choroid coat under the name of the short postern
ciliary arteries. Two of them, however, are fairly large, and are know
as the long posterior ciliary arteries. They pass forwards betwee
the sclera and the choroid, one on each side, and are distributed 1
the ciliary muscle and iris.
 
The lacrimal artery arises from the ophthalmic on the outer sic
of the optic nerve, and passes forwards along the upper border of tl
rectus lateralis muscle to the lacrimal gland. In its course it furnish*
the following branches: (1) a recurrent meningeal branch, whic
passes through the outer part of the superior orbital fissure to tl
middle cranial fossa, where it anastomoses with the middle meninge;
artery; (2) muscular and anterior ciliary branches, the latter piercir
the sclera very near the corneal margin; (3) zygomatic offsets, whic
pass through the zygomatico-temporal and zygomatico-facial canals (
the zygomatic bone to the face and temporal region in company wit
the respective branches of the temporo-zygomatic nerve; (4) tw
lateral palpebral arteries, superior and inferior, which pass inwarc
in the upper and lower eyelids, and anastomose with the medi;
palpebral branches of the ophthalmic, thus forming arterial arches
and (5) glandular branches to the lacrimal gland.
 
The muscular branches arise from the ophthalmic in two set:
outer and inner, and also from some of its branches— e.g., the lacrime
and supra-orbital. They furnish a few of the anterior ciliary arteries
 
The supra-orbital artery arises from the ophthalmic as it crossc
inwards over the optic nerve. It courses forwards to the supra
orbital notch, through which it passes, with the corresponding nerv*
to the forehead. It supplies the upper eyelid and the frontal regior
and anastomoses with the superficial temporal and supratrochlea
arteries.
 
 
 
THE HEAD AND NECK
 
 
1261
 
 
Ihe posterior ethmoidal artery, a small vessel, passes through the
jsterior ethmoidal canal on the inner wall of the orbit, and is distributed
the mucous membrane of the posterior ethmoidal sinus and the
ucous membrane of the upper and back part of the outer wall of
e nasal cavity. The latter branches pass through foramina in the
ibriform plate.
 
The anterior ethmoidal artery is larger than the preceding. It
isses through the anterior ethmoidal canal with the naso-ciliary
:rve, and enters the anterior fossa of the base of the skull. Here
crosses the cribriform plate of the ethmoid bone to the nasal slit
T the side of the crista galli. It then descends through this slit,
rverses the nasal groove on the posterior surface of the nasal bone,
id finally passes between the lower border of the nasal bone and the
>per nasal cartilage to the tip of the nose. Its branches supply the
ira mater in the anterior cranial fossa, the mucous membrane of
e anterior ethmoidal sinus and corresponding frontal sinus, the mucous
smbrane of the upper and Lcsxl wing of Sphenoid
 
.tenor parts of the nasal T . , . T ;
 
isa, and the skin of the tip Frontal Nerve o P uc
 
the nose. Nerve
 
The medial palpebral ar- Upper Division of Oculo-motor Nerve_
 
ies are superior and in- Lower Division /
 
'ior, and are distributed Abdueent Nerve -.ym /
 
. .. A . Ophthalmic Vein V/
 
the eyelids, they arise, _ T _
 
^ • • A r Fig. 764.—Diagram of the Left Superior
 
a ^jy °, r c ? n J om t^y» ^ rom Orbital Fissure, showing the Trans
e ophthalmic close to the mitted Structures (Posterior View).
 
Hey of the obliquus su
rior muscle, and each takes an outward course in the corresponding
elid. They anastomose with the two lateral palpebral branches of
e lacrimal artery, thus forming arterial arches.
 
The dorsal nasal artery leaves the orbit above the medial palpebral
;ament, and is distributed to the upper part of the side of the nose
the region of the root, where it anastomoses with the angular and
teral nasal branches of the facial artery.
 
The supratrochlear artery (frontal artery) is the third terminal
anch of the ophthalmic. It leaves the orbit at the inner angle,
d then ascends to the frontal region, along with the supratrochlear
rve, to be distributed to the integument by the side of the median
ie. It anastomoses with the supra-orbital artery and its fellow
the opposite side. The above description is fairly typical, but the
3 de of origin of the orbital arteries is very variable and, as in most
rts of the body, the normal is seldom seen.
 
Ophthalmic Veins.—These are superior and inferior. The superior
hthalmic vein, of large size, begins at the inner angle of the orbit,
iere it communicates freely with the facial through the angular
in. It accompanies the ophthalmic artery, passing outwards and
ckwards over the optic nerve. Having reached the inner end of the
perior orbital fissure, the vessel passes between the two heads of the
 
 
 
 
 
 
1262
 
 
A MANUAL OF ANATOMY
 
 
rectus lateralis muscle, and through the fissure, after which it ope:
into the anterior part of the cavernous sinus. Its tributaries corr
spond for the most part to the branches of the ophthalmic arter
It does not, however, receive the supratrochlear nor the supra-orbit
vein. The inferior ophthalmic vein arises in connection with t]
lower posterior ciliary and lower muscular veins. It passes backwar
along the floor of the orbit, and may join the superior ophthalmic vei
open independently into the cavernous sinus, or pass through t]
inferior orbital fissure into the pterygoid plexus, with which in ai
case it freely communicates.
 
Structures passing through the Superior Orbital Fissure (Sphenoid
Fissure). —These structures are as follows:
 
 
1. The oculo-motor nerve.
 
2. The trochlear nerve.
 
3. The naso-ciliary, lacrimal,
 
and frontal nerves.
 
4. The abducent nerve.
 
5. The sympathetic root of the
 
ciliary ganglion.
 
 
6. The ophthalmic veins.
 
7. The orbital branch of t]
 
middle meningeal artery
 
8. The recurrent branch of t]
 
lacrimal artery.
 
9. The dura mater.
 
 
The lacrimal, frontal, and trochlear nerves enter the orbit abo 1
the rectus lateralis muscle, in the order named from without inwards
The oculo-motor nerve, the naso-ciliary nerve, and the abduce
nerve enter the orbit between the two heads of the rectus lateral
muscle, the oculo-motor nerve having already broken up into t\
divisions; and the ophthalmic veins leave the orbit between the t\
heads of the rectus lateralis. The order of parts between the two hea
of the rectus lateralis, from above downwards, is as follows:
 
 
1. The superior division of the oculo-motor nerve.
 
2. The naso-ciliary nerve.
 
3. The inferior division of the oculo-motor nerve.
 
4. The abducent nerve.
 
5. The ophthalmic veins (or vein).
 
 
The sympathetic root of the ciliary ganglion passes through t
superior orbital fissure independently, or along with the naso-cilia
nerve, or sometimes with the oculo-motor nerve.
 
Structures passing through the Inferior Orbital Fissure (Spher
maxillary Fissure):
 
1. Infra-orbital vessels.
 
2. Infra-orbital nerve.
 
3. Zygomatic nerve.
 
4. Inferior ophthalmic vein.
 
5. Orbital branches of the spheno-palatine ganglion.
 
6. Lymphatics.
 
 
The opening is bridged over by fascia in which involuntary mus:
fibres, representing Muller’s muscle of the lower animals, are found. i
 
 
 
 
THE HEAD AND NECK
 
 
1263
 
 
THE FACE.
 
Landmarks.—The glabella can be seen between the eyebrows, and
[tending outwards from it on either side is the superciliary arch,
ihind the inner part of which is the corresponding frontal sinus!
elow the superciliary arch the supra-orbital margin can readily be
It, and at the junction of its inner third and outer two-thirds is the
[pra-orbital notch, or foramen for the passage of the supra-orbital
irve and artery. A line drawn from the position of the suprabital notch to the base of the mandible in such a manner as to pass
itween the lower premolar teeth, or, which comes to the same thing,
1 the angle of the mouth, crosses in succession the infra-orbital and
ental foramina. The infra-orbital foramen lies in this line at a point
)out l inch below the infra-orbital margin, and it indicates the exit
the infra-orbital nerve and artery from the infra-orbital canal. The
ental foramen in the adult lies midway between the alveolar and
Lsilar borders of the mandible, and locates the exit of the mental
irve and artery from the mandibular canal.
 
In line with the tragus of the auricle the zygomatic arch can be
It, and leading backwards from it above the orifice of the external
iditory meatus is the posterior root of the zygoma. This root is
>ntinued into the supramastoid crest, which corresponds to the level
the tegmen tympani. Below the supramastoid crest, and just above
id behind the external auditory meatus, is the suprameatal triangle,
bis triangle lies superficial to the tympanic antrum, and is a most
lportant surgical landmark.
 
The superficial temporal artery and auriculo-temporal nerve lie
rectly in front of the tragus, the division of the artery into its anterior
id posterior branches taking place about the level of the upper part
the auricle. The anterior branch of the artery lies nearly an inch
diind the zygomatic process of the frontal bone, and the posterior
*anch about an inch above the upper part of the auricle.
 
The parotid gland is situated in front of the auricle. It is limited
)ove by the zygoma, behind by the auricle, and interiorly it extends
r a limited distance into the digastric triangle of the neck. Anteriorly
extends for a short distance superficial to the masseter muscle, and
ie parotid duct issues from its anterior border. The course of this
ict may be indicated by a line drawn from the intertragic notch to a
)int midway between the nostril and the red margin of the upper lip.
bout the middle third of this line corresponds to the duct. Above
is the transverse facial artery, and below it are the infra-orbital
ranches of the facial nerve.
 
The posterior border of the ramus of the mandible is easily felt,
leads superiorly to the condyloid process and mandibular joint,
id interiorly to the angle of the bone. Extending forwards from
e angle is the base of mandible, which, about an inch from the angle,
is a groove for the facial artery, pulsation being readily felt during
e in this part of the vessel in front of the masseter muscle, the
 
 
 
1264
 
 
A MANUAL OF ANATOMY
 
 
anterior vein intervening between the two. In this situation
lymphatic gland lies in contact with the artery. From this po
the facial artery extends in a tortuous manner to the medial an
of the eye, passing close to the angle of the mouth, the anterior fac
vein pursuing a comparatively straight course.
 
Near the mid-line of the face the structures to be noted are '
nasal bones, nasal cartilages, dorsum and apex of the nose, alae n;
columna, and the philtrum, which latter is the median groove lead
from the columna to the upper lip.
 
For the component parts of the auricle, see p. 1294.
 
The eyelids or palpebrae are to be noted, along with the palpeb
fissure between them, and the medial and lateral angles at eitl
extremity. The tarsus of the upper eyelid can be demonstrated
everting the eyelid, and connected with its inner extremity is 1
medial palpebral ligament. This latter may be made tense by draw:
the eyelids outwards. It crosses the lacrimal sac a little above 1
centre. The eyelids being everted, the outlines of the tarsal glai
may be seen as yellowish streaks perpendicular to the palpeb
margins. Behind the eyelashes, or cilia, on the margins of the eyel
are the minute orifices of the ducts of the tarsal glands, which ;
arranged in a row. Along the line of the eyelashes the skin of i
eyelid becomes continuous with the conjunctiva, and along the line
reflection of the conjunctiva on to the eyeball the recess, known
the fornix, is to be noted. At the medial angle, where the eyelids
not meet, there is a recess, known as the lacus lacrimalis, between 1
lids and the eyeball, which lodges a small red fleshy protuberan
called the caruncula lacrimalis, provided with a few delicate hai
Lateral to this is the fold called the plica semilunaris, which is a vest:
of the nictitating membrane or third eyelid of birds. Upon t
eyelids at their inner ends the lacrimal papillae are visible, and
each papilla is a minute orifice, called the punctum lacrimale. T
lower papilla is larger than the upper, and is placed a little farther 0
Each punctum leads into a lacrimal canaliculus, and by these can
the tears are conveyed into the lacrimal sac, and thence by the na:
lacrimal duct into the inferior meatus of the nose. The position
the lacrimal sac may be indicated by drawing the eyelids outwan
so as to render tense the medial palpebral ligament, which, as stafi
crosses the sac a little above its centre.
 
Muscles of the Face.
 
Orbicularis Oculi (Orbicularis Palpebrarum)—Orbital Portion
 
Origin .—The outer surface of the frontal process of the maxilla, a
the medial angular process of the frontal bone.
 
Insertion .—It is usually said that the orbicular fibres form compl<
circles, but it is almost certain that they are serially inserted into t
skin, and their place taken by fresh fibres rising from the skin. It
only necessary to watch the puckering of the skin on the outer si
 
 
 
THE HEAD AND NECK
 
 
1265
 
ie orbit, where the ' crow’s feet ’ are formed, or the wince of pain
w the lower eyelid, to be convinced that there are distinct insertions
bres into the skin in these parts.
 
Palpebral Portion— Origin. —The upper and lower surfaces of the
iial palpebral ligament.
 
Insertion. — 1 he upper and lower surfaces of the lateral palpebral
re.
 
\erve-supply. —Temporal and zygomatic branches of the facial
re, in which there may be fibres derived from the nucleus of the
o-motor nerve.
 
Action —Orbital Portion.—(1) The upper half depresses the eyev, and antagonizes the frontal belly of the occipito-frontalis muscle;
the lower half elevates the skin of the infra-orbital region. PalpePortion.—This closes the eyelids, as in winking, the upper lid
tg depressed and the lower raised, the former movement being
e free than the latter. By means of its connection with the medial
>ebral ligament the palpebral portion draws forwards the front
: of the lacrimal sac, and so contributes to the removal of the tears,
en the entire muscle contracts, the lids are forcibly closed and
vn slightly inwards.
 
rhe upper part of the muscle is related by its deep surface to the
dal belly of the occipito-frontalis, the supra-orbital vessels and
re, and the supratrochlear nerve, the chief deep relations of the
ix part of the levator labii superioris, and, beneath that, the infratal nerve.
 
Medial Palpebral Ligament (Internal Tarsal Ligament or Tendoli).—It is attached medially to the outer surface of the frontal
;ess of the maxilla immediately in front of the naso-lacrimal groove,
direction is outwards in front of the lacrimal sac, and it bifurcates
:he medial angle, the divisions diverging, and being attached to
inner extremities of the corresponding tarsus. As the ligament
>es just in front of the lacrimal sac it gives origin to the palpebral
don of the orbicularis oculi, which explains the action of that
don of the muscle upon the sac.
 
Lateral Palpebral Raph6 (External Tarsal Ligament).—This is
tched laterally to the frontal process of the zygomatic bone. Its
ction is inwards, and it bifurcates at the lateral angle of the eye
the outer extremities of the tarsi.
 
Lacrimal Portion of Orbicularis Oculi (Tensor Tarsi or Muscle of
ner)— Origin. —The crest of the lacrimal bone behind the lacrimal
 
Insertion .—By means of two slips into the inner extremities of the
i of the eyelids, where the fibres become continuous with the ciliary
ss of the orbicularis oculi.
 
Nerve-supply. —As for the rest of orbicularis oculi.
 
The direction of the muscle is outwards and forwards, and its two
s pass behind the lacrimal canaliculi.
 
Action. —To draw backwards the outer part of the medial palpebral
 
80
 
 
 
 
1266
 
 
A MANUAL OF ANATOMY
 
 
ligament, and in this manner compress the lacrimal sac, the effec
which is to force the tears into the naso-lacrimal duct.
 
Corrugator Supercilii— Origin .—The inner extremity of the su
ciliary arch of the frontal bone.
 
Insertion .—The deep surface of the skin of the eyebrow at
centre.
 
Nerve-supply .—Temporal branches of the facial nerve.
 
 
Auricularis Superior
 
 
Auricularis Anterior
 
 
Auricularis Posterior*
 
 
Occipital Belly of -y
Occipito-frontalis
 
 
Branches from Third and Fourth
Cervical Nerves to Trapezius
 
Scalenus Medius
 
 
Lateral Supraclavicular
Nerve
 
 
Trapezius
 
 
 
"‘Frontal Belly of Occipito
frontalis
 
 
Orbicularis Oculi
 
 
Greater Occipital Nerve
Semispinalis Capitis'"'
Lesser Occipital Nerve""
 
Splenius Capitis
 
 
Levator Labii
Superioris Alaeque N
 
Levator Labii Super
Zygomaticus Minor
"Zygomaticus Major
“•Masseter
 
 
‘“'Orbicularis Oris
Depressor Labii Infer!
Depressor Anguli Oris
Mentalis
 
 
Levator Scapulas —
Great Auricular Nerve —
Accessory Nerve
 
** Anterior Belly of Digast
Stemo-hyoid
 
Mfr SnpeTi ° r Omo-hyoid
 
 
- Sterno-mastoid
. Anterior Cutaneous Nerve of N
 
 
— Medial Supraclavicular Nerve
Intermediate Supraclavicular N
 
 
Scalenus Anterior
 
/
 
Inferior Belly of Omo-hyoid Subclavian Artery (third part)
 
Fig. 765. —The Right Side of the Head and Neck.
The platysma has been removed, and the nerves are shown.
 
 
The direction of the muscle is outwards and upwards, and to re
the skin the fibres pass through the upper part of the orbicularis 0
and the adjacent portion of the frontal belly of occipito-frontalis.
 
Action .—To draw the skin of the eyebrow inwards and do
wards, giving rise to vertical wrinkles between the eyebrows, a:
frowning.
 
The muscle is under cover of the inner portion of the upper ]
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK 1267
 
the orbicularis oculi, and it conceals the supratrochlear nerve as
merges from the orbit.
 
Muscles of the Nose—Procerus (Pyramidalis Nasi)— Origin .—The
neurosis of the compressor naris over the lower part of the nasal
ie.
 
Insertion. —The deep surface of the skin over the glabella of the
ital bone. Some of the fibres become continuous with the medial
tion of the frontal belly of occipito-frontalis.
 
Nerve-supply .—Upper buccal branches of the facial nerve.
 
Action .—To draw downwards the skin between the eyebrows,
ng rise to transverse wrinkles.
 
 
 
Fig. 766. —Dissection of Muscles of Face.
 
Compressor Naris— Origin .—The maxilla between the canine fossa
the nasal notch.
 
Insertion .—By means of an expanded aponeurosis which blends
h its fellow of the opposite side over the cartilaginous portion of
nose, and gives origin superiorly to the procerus.
 
A J erve-snpply .—Upper buccal branches of the facial nerve.
 
Action .—To depress the cartilaginous portion of the nose.
 
The muscle is triangular, and at its origin is under cover of the
dor labii superioris alaeque nasi.
 
Levator Labii Superioris Alaeque Nasi— Origin .—The outer surface
he frontal process of the maxilla by a pointed extremity.
insertion .—By means of two slips. The medial or nasal slip is
 
 
 
 
 
 
 
 
 
 
 
 
1268
 
 
A MANUAL OF ANATOMY
 
 
inserted into the skin of the ala of the nose, and is often absent. 1
lateral or labial slip is inserted into the skin of the upper lip, some
its fibres blending with the levator labii superioris, and others w
the upper part of the orbicularis oris.
 
Nerve-supply .—Buccal branches of the facial nerve.
 
Action. —(i) To raise the upper lip, and (2) to raise and dilate
nostril.
 
The muscle is triangular, and covers the origin of the compres
naris.
 
Depressor Alse Nasi or Depressor Septi— Origin .—The incisive fo:
of the maxilla.
 
Insertion .—The posterior part of the ala, and the adjacent part
the septum of the nose.
 
N erve-supply .—Upper buccal branches of the facial nerve.
 
Action .—To depress the ala of the nose.
 
Dilator Naris Anterior— Origin .—The cartilage of the aperture
the nose.
 
Insertion .—The deep surface of the skin over the ala of the nose
 
Nerve-supply .—Upper buccal branches of the facial nerve.
 
Action .—To dilate the nostril.
 
Dilator Naris Posterior— Origin. —(1) The margin of the na
notch of the maxilla; and (2) the accessory cartilages of the nose.
 
Insertion .—The skin over the back part of the ala of the nose.
 
Nerve-supply .■—Upper buccal branches of the facial nerve.
 
Action .—To dilate the nostril.
 
Levator Labii Superioris— Origin .—The maxilla between the inf
orbital foramen and the lower margin of the orbit.
 
Insertion .—The skin of the upper lip.
 
Nerve-supply .—Buccal branches of the facial nerve.
 
Action .—To raise the upper lip.
 
The muscle is quadrilateral. At its origin it is overlapped by 1
lower half of the orbicularis oculi, and it covers the infra-orbital nei
and artery as they leave the infra-orbital foramen. At its insert]
the fibres interlace with those of the upper half of the orbicularis ori
 
Levator Anguli Oris— Origin .—The upper part of the canine fo;
of the maxilla under cover of the levator labii superioris.
 
Insertion .—The angle of the mouth, where some of the fibres <
inserted into the skin, whilst others decussate with those of the <
pressor anguli oris, and enter the lower lip, mingling with those of 1
lower half of the orbicularis oris.
 
Nerve-supply .—Buccal branches of the facial nerve.
 
The direction of the muscle is downwards and slightly outwards
 
Action .—To raise the angle of the mouth, and at the same time
draw it slightly inwards.
 
The infra-orbital nerve and artery are superficial to the muscle.
 
Zygomaticus Minor— Origin .—The anterior and lower part of t
zygomatic bone close to the maxilla.
 
Insertion .—The skin of the upper lip immediately lateral to t
 
 
THE HEAD AND NECK I2 6 9
 
itor labii superioris, with the outer border of which muscle some
ts fibres blend.
 
Nerve-supply . Buccal branches of the facial nerve.
 
The muscle is directed downwards and inwards, and is often
irded as part of the orbicularis oculi.
 
Action.— -To raise feebly the upper lip, and at the same time to
w it slightly outwards.
 
Zygomaticus Major— Origin.— The outer surface of the zygomatic
e near the zygomatico-maxillary suture.
 
Insertion.—The skin at the angle of the mouth, where its fibres
id with those of the orbicularis oris.
 
Nerve-supply. —Buccal branches of the facial nerve.
 
The muscle is directed downwards and inwards.
 
Action.— To draw the angle of the mouth upwards and outwards.
 
 
Buccal Nerve (cut)
 
 
 
i
 
Upper Head of Lateral Pterygoid
 
i
 
 
Capsule of Mandibular '^
Joint
 
 
Lower Head of Lateral
Pterygoid
 
Pterygo-mandibular
 
Ligament
 
* Parotid Duct
 
 
X Buccinator
 
 
Medial Pterygoid
 
 
Fig. 767. —The Pterygoid and Buccinator Muscles.
 
 
Risorius— Origin. — The deep fascia which covers the masseter
scle and parotid gland.
 
Insertion. The skin at the angle of the mouth, where its fibres
id with the orbicularis oris.
 
Nerve-supply. —Buccal branches of the facial nerve.
 
The direction of the muscle is inwards, some of its fasciculi also
ending.
 
Action. —To draw the angle of the mouth outwards and slightly
mwards. It is often the first muscle affected in tetanus, and gives
to the ‘ risus sardonicus/
 
The muscle consists of a few scattered fasciculi, which are emded in the adipose tissue over the buccinator; it is a detached
tion of the platysma.
 
Buccinator— Origin. — (1) The outer surfaces of the alveolar pro
 
 
 
 
 
 
1270
 
 
A MANUAL OF ANATOMY
 
 
cesses of the maxilla and mandible, opposite the three molar socl
and (2) the anterior aspect of the pterygo-mandibular ligament.
 
Insertion. —The orbicularis oris at the angle of the mouth.
 
The central fibres decussate, those from above entering the lc
lip, and those from below entering the upper lip. The highest
lowest fibres take no part in this decussation, the highest pas
directly into the upper lip, and the lowest into the lower lip
Fig. 768).
 
N erve-supply. —Lower buccal branches of the facial nerve.
 
Action. —To draw the angle of the mouth outwards, and p
the lips and cheeks against the teeth, thus preventing the food f
accumulating between the lips and the teeth during masticat
and to contract the vestibular part of the mouth spasmodically, a
whistling.
 
The muscle is expanded over the cheek, but towards the angl
the mouth it becomes narrow and thick. It is pierced by the par
duct opposite the second upper molar tooth, and the buccal n(
also passes through it on its way to the mucous membrane of
cheek. Externally the muscle is overlapped by the anterior bo]
of the masseter, from which it is separated by the suctorial
of fat.
 
Suctorial Pad of Fat (Buccal Pad). —This is a well-defined colleci
of fat which is situated upon the buccinator muscle close to the ante
border of the masseter. Well developed in healthy young adults
may be absorbed or replaced very quickly, causing marked chang<
the facial expression.
 
Depressor Anguli Oris (Triangularis Menti)— Origin. —The obli
line of the mandible from about the level of the canine socket to t
of the first molar.
 
Insertion. —The angle of the mouth, where some of the fibres
attached to the skin, whilst others decussate with those of the leva
anguli oris and enter the upper lip, in which they mingle with
upper part of the orbicularis oris.
 
N erve-supply. —The mandibular branch of the facial nerve.
 
Action .—To depress the angle of the mouth.
 
Depressor Labii Inferioris (Quadratus Menti)— Origin. —The loi
part of the outer surface of the body of the mandible close to
symphysis, and extending outwards to below the mental foramen.
 
Insertion .—The skin of the lower lip.
 
Nerve-supply. —The mandibular branch of the facial nerve.
 
The muscle is directed upwards and inwards.
 
Action .—To draw the lower lip downwards and slightly outward
 
The muscle is overlapped laterally by a portion of the depres
anguli oris, and medially it is in contact superiorly with its fellow
the opposite side. The deep surface is related laterally to the men
foramen and the mental nerve and vessels, and medially to part
the mentalis. In the lower lip its fibres pass amongst those of 1
lower part of the orbicularis oris.
 
 
THE HEAD AND NECK
 
 
1271
 
 
Mentalis ^Levator Menti)— Origin. —The incisive fossa of the
 
mdible.
 
Insertion. — The skin of the chin.
 
Nerve-supply. —The mandibular branch of the facial nerve.
 
The muscle is directed downwards and forwards.
 
Action. — (1) To raise the integument of the chin, and (2) to elevate
 
d protrude the lower lip.
 
Orbicularis Oris. —This is a complex muscle composed of three
‘ata. The superficial stratum consists of fibres which are prolonged
>m the elevators and depressors of the angles of the mouth, and
tend as far as the centre of the lip, but are not continuous with
ose of the opposite half. They are inserted into the skin, and are
rtially reinforced by fibres from the elevators of the upper lip, thegomatic muscles, the risorius, the posterior fibres of the platysma,
d the depressor labii inferioris.
 
The intermediate stratum consists of fibres which are derived from
e buccinator muscles. These fibres are disposed transversely, ard
 
 
 
Fig. 768. —Plan of Composition of Orbicularis Oris.
 
 
ose of opposite sides are directly continuous. The fibres of this
ratum extend to the margins of the lips.
 
The foregoing fibres are destitute of bony and cartilaginous attaches.
 
The deepest stratum consists of fibres which arise from the incisive
sSct of the upper and lower jaws, as well as from each side of the
 
terior nasal spine.
 
Nerve-supply. —The low*er buccal and mandibular branches of the
 
dal nerve.
 
Action .— 1 To close the oral aperture; and [2) to press the lips
ainst the alveolar margins.
 
The muscle is separated from the buccal mucous membrane by the
Mai arteries and the labial mucous glands.
 
The labial mucous glands, which are racemose, or acino-tubular,
e numerous, and each is about the size of a small pea. They are
uated on the deep surface of the mucous membrane of the lips,
lere thev lie in the loose areolar tissue between the mucous memane and the orbicularis oris. Their ducts open into the vestibule
the mouth.
 
 
 
 
 
 
 
 
 
 
 
 
I2J2
 
 
A MANUAL OF ANATOMY
 
 
The buccal mucous glands, also racemose, or acino-tubular,
situated between the mucous membrane of the cheek and the d
surface of the buccinator.
 
The molar mucous glands, also racemose, or acino-tubular,
superficial to the buccinator in the vicinity of the terminal pari
the parotid duct. They are four or five in number, and their du
having pierced the buccinator, open into the vestibule of the mo
opposite the molar teeth.
 
 
Nerves of the Face.
 
The nerves of the face are thirteen in number on either si
Twelve of these are sensory nerves, and one is motor—namely,
facial nerve.
 
The facial or seventh cranial nerve will only be described b
after its emergence from the facial canal in the petrous part of
temporal bone. It comes out of that canal through the stylo-mast
foramen, after which it passes downwards and then forwards into
parotid gland. Near the posterior border of the ramus of the mandi
it breaks up into two terminal parts, called the temporo-facial c
cervico-facial divisions.
 
Branches. —The posterior auricular, digastric, stylo-hyoid, c
the terminal divisions.
 
The posterior auricular nerve arises from the facial close to
stylo-mastoid foramen. It ascends between the auricle and
mastoid process, where it lies deeply, and divides into two branch
auricular and occipital. The auricular branch passes upwards beh:
the auricle and deep to the auricularis posterior, to be distributed
that muscle, and it may be to the auricularis superior, as well as
the small intrinsic muscles on the inner aspect of the auricle. 1
occipital branch passes backwards to supply the occipital belly of i
occipito-frontalis muscle. The posterior auricular nerve communica
with the great auricular, the lesser occipital, and the auricular brar
of the vagus.
 
The digastric branch is directed downwards to the posterior be
of the digastric muscle. One of the digastric branches communica
with the glosso-pharyngeal nerve.
 
The stylo-hyoid branch usually arises in common with the p
ceding. It is of some length, and, passing forwards, it enters the sty
hyoid muscle about its centre.
 
The terminal branches continue to pass forwards in the paro
gland, crossing superficially the posterior facial vein and the exteri
carotid artery, the direction of these vessels being vertical. In t
part of their course these branches receive the following communi<
tions: two branches from the auriculo-temporal nerve, and brand
from the great auricular nerve. Each terminal branch breaks,
within the gland into smaller branches, and as these pass in varic
directions over the face and upper portion of the neck they ram
 
 
THE HEAD AND NECK
 
 
1273
 
 
3ely. The latter branches frequently communicate with each other
a plexiform manner, both in the parotid gland and on the face, the
exus thus formed being known as the parotid plexus (pes anserinus).
le ramifications also communicate with the branches of the three
visions of the trigeminal nerve which appear on the face, these being
nsory nerves.
 
The terminal branches of the facial nerve are; The temporal branches
cend over the zygomatic arch to the temporal region, and are dis
 
Upper Terminal Division of Facial Nerve
 
Temporal Branches of Facial Nerve
 
 
Zygomatic Branches of Facial Nerve
 
 
llo-temporal Nerve
 
5 rior Auricular Nerve
;ater Occipital Nerve
 
acial Nerve at Stylomastoid Foramen
 
Digastric Branch of
Facial Nerve
 
er Terminal Division
of Facial Nerve
 
 
 
Branch of Lacrimal Nerve
 
 
Supra-orbital Nerve
(in two divisions)
 
.. Infratrochlear Nerve
 
 
Zygomatico-facial
 
Nerve
 
Ext. Nasal N.
Infra-orbital N.
 
Upper Buccal
Branches of
Facial Nerve
 
-Buccal Nerve
 
 
.. Mental Nerve
 
 
Lesser Occipital Nerve
 
Great Auricular Nerve
Anterior Cutaneous Nerve of Neck
 
 
Parotid Gland
 
' Lower Buccal Branches of Facial N.
 
\
 
'Mandibular Branches of Facial Nerve
Cervical Branches of Facial Nerve
 
 
External Jugular Vein
 
 
ig. 769. —Superficial Dissection of the Right Side of the Head and
Upper Part of the Neck (Hirschfeld and Leveille).
 
1, sterno-mastoid; 2, trapezius.
 
 
ibuted to the auriculares anterior et superior, the intrinsic muscles
1 the outer surface of the auricle, the frontal belly of the occipito^ntalis, the upper part of the orbicularis oculi, and the corrugator
percilii. These branches communicate with the supra-orbital and
-rimal branches of the ophthalmic, the zygomatico-temporal nerve
=>m the maxillary, and the auriculo-temporal of the mandibular,
l of these being sensory nerves.
 
The zygomatic branches pass forwards over the zygomatic bone
wards the outer angle of the orbit, and supply the outer part of the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
I2 74
 
 
A MANUAL OF ANATOMY
 
 
orbicularis oculi. They form communications with the lacrimal bran
of the ophthalmic and with the zygomatico-facial nerve.
 
The upper buccal branches pass forwards to the region betwe
the lower margin of the orbit and the upper lip. They supply t
lower part of the orbicularis oculi, the muscles of the nose, the elevah
of the upper lip, and the upper part of the orbicularis oris. Th
communicate with the following sensory nerves: the infra-orbital
the maxillary, the infratrochlear of the naso-ciliary, and the exteri
nasal branch of the naso-ciliary from the ophthalmic. The commu:
 
 
 
C.A. Communicating Twigs with Auditory
G.G. Facial Ganglion
G.S.P. Greater Superficial Petrosal
S.S.P. Branch to Lesser Superficial Petrosal
E.S.P. External Petrosal
 
S. Branch to Stapedius Muscle
C.T. Chorda Tympani
A Auricular Branch
S.M.F. Stylo-mastoid Foramen
P.A. Posterior Auricular
S.H. Branch to Stylo-hyoid Muscle
 
D. Branch to Posterior Belly of Digastric
 
 
A.T. Communicating Branches from Auriculotemporal
 
T.F. Upper Terminal Division
T. Temporal Branches
M. Zygomatic Branches
I.O. Upper Buccal Branches
G.A. Communicating Branches from Great
Auricular
 
C.F. Lower Terminal Division
B. Lower Buccal Branches
S.M. Mandibular Branches
I.M. Cervical Branches
 
 
cations with the infra-orbital nerve take place under cover of t
levator labii superioris muscle, and form a somewhat intricate plexi
called the infra-orbital plexus.
 
The lower buccal branches pass forwards over part of the massei
and the buccinator muscles to the angle of the mouth. They supply t
buccinator and the outer part of the orbicularis oris, and are connect
with the infra-orbital branches of the temporo-facial division, and wi
the buccal nerve , which is a branch of the mandibular division of t
trigeminal nerve. The latter communications take the form of a plex
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1275
 
 
ituated on the superficial surface of the buccinator muscle, called the
uccal plexus.
 
The mandibular branches pass forwards over the mandible to the
sgion below the lower lip. They supply the lower part of the orbicuiris oris, depressor anguli oris, depressor, labii inferioris and mental
luscles. They communicate with the mental branch of the inferior
ental from the mandibular nerve under cover of the depressor anguli
ris.
 
The cervical branch descends beneath the upper part of the platysma
nd the deep cervical fascia to the suprahyoid region. Having pierced
tie deep fascia, it divides into branches which curve forwards and
upply the platysma on its deep surface. It communicates freely
 
 
 
Fig. 771.— Diagram of the Sensory Nerves of the Right Side of
 
the Head.
 
 
1. Supra-orbital
 
2. Supratrochlear
 
3. Infratrochlear
 
4. External Nasal
 
5. Lacrimal
 
 
6 . Zygomatico-temporal
 
7. Zygomatico-facial
 
8. Infra-orbital
 
9. Auriculo-temporal
 
10. Buccal
 
 
11. Mental
 
12. Great Auricular
 
13. Lesser Occipital
 
14. Greater Occipital
 
 
ith the upper branch of the anterior cutaneous nerve of the neck from
tie cervical plexus.
 
Summary of the Facial Nerve. —The facial nerve, after leaving the facial
anal through the stylo-mastoid foramen, supplies the following muscles: (1) the
xtrinsic and intrinsic muscle of the auricle; (2) the posterior belly of the digastric
nd the stylo-hyoid; (3) the occipito-frontalis; (4) the superficial muscles of the
ice, including the buccinator, but not the masseter, nor the levator palpebrae
aperioris; and (5) the platysma. All these muscles, except the posterior belly
f the digastric and the stylo-hyoid, are spoken of as muscles of expression. The
erve establishes free communications with all three divisions of the trigeminal
erve, which are sensory. It also communicates with the lesser occipital, great
uricular, and anterior cutaneous nerve of neck, which are branches of the
ervical plexus.
 
Sensory Nerves of the Face. —These, with one exception, are deived from the trigeminal nerve, the exception being the great auricular,
duch is a branch of the cervical plexus.
 
 
 
 
 
 
 
 
 
 
1276
 
 
A MANUAL OF ANATOMY
 
 
A. Branches of the Trigeminal Nerve.
 
 
Distal Sources.
 
 
Proximate Sources.
 
 
t. Ophthalmic nerve.
 
 
2. Maxillary nerve.
 
 
3. Mandibular nerve.
 
 
(a) Frontal
 
- ( b ) Lacrimal.
 
(c) Naso-ciliary.
 
[ (a) Maxillary.
 
| ( b ) Zygomatic.
 
f (a) Anterior division.
 
| ( b) Posterior division.
 
I ( c ) Inferior dental of
I posterior division.
 
 
Terminations.
 
f Supra-orbital.
 
I Supratrochlear.
 
Lacrimal,
j Infratrochlear.
 
( External nasal.
 
Infra-orbital.
 
/ Zygomatico-temporal.
I Zygomatico-facial.
Buccal.
 
Auriculo-temporal.
j Mental.
 
 
B. Facial Branches of the Great Auricular Nerve.
 
Branches of the Trigeminal Nerve. —The supra-orbital and supri
trochlear nerves have been already described (see p. 1153). T1
former is distributed to the skin of the frontal region and the upp<
part of the scalp; and the latter to the skin of the lower and centr;
portion of the frontal region. Both these nerves furnish twigs to tt
skin of the upper eyelid.
 
The lacrimal nerve pierces the orbital septum, and is distribute
to the skin and conjunctiva of the outer part of the upper eyelid, as we
as to the skin in the immediate vicinity of the zygomatic process (
the frontal bone.
 
The infratrochlear branch of the naso-ciliary nerve leaves the orb
below the pulley of the obliquus superior muscle, and furnishes twig
to the skin and conjunctiva of the inner parts of the eyelids, the sic
of the root of the nose, the lacrimal sac, and the caruncula lacrimalis.
 
The external nasal branch of the naso-ciliary nerve emerges betwee
the lower border of the nasal bone and the upper nasal cartilage, an
descends beneath the compressor naris muscle to the apex of the nos<
Its twigs supply the skin of the tip and lower part of the side of th
nose.
 
The infra-orbital nerve is the terminal part of the maxillary divisio
of the trigeminal. It leaves the infra-orbital canal through the infn
orbital foramen, where it is under cover of the levator labii superior!
In this situation it communicates with the upper buccal branches (
the facial, forming the infra-orbital plexus, and it divides into three sel
of branches—namely, palpebral, nasal, and labial. The palpebra
branches ascend to supply the skin and conjunctiva of the lower eyelic
The nasal branches pass inwards, and are distributed to the skin of th
side of the nose. The labial branches, long and large, descend to suppl
the skin and mucous membrane of one half of the upper lip. As the
descend they furnish twigs to the skin between the infra-orbital forame
and the upper lip.
 
The zygomatico-temporal nerve (temporo-malar nerve) is of sma
 
size. Having traversed the zygomatico-tempora] canal in the zygomati
 
 
 
THE HEAD AND NECK
 
 
1277
 
one, it pierces the temporal fascia about 1 inch above the front part
f the zygoma, and behind the marginal process on the postero-superior
r temporal border of the zygomatic bone, and is distributed to a
mited portion of the skin over the anterior part of the temporal
3gion.
 
The zygomatico-facial nerve (temporo-malar nerve) is of small size,
nd emerges from the zygomatico-facial canal in the zygomatic bone
tirough the zygomatico-facial foramen. It is distributed to the skin
ver the malar bone.
 
 
 
The buccal nerve is a branch of the anterior division of the mandiblar nerve. Coming from under cover of the middle of the anterior
order of the masseter on to the superficial surface of the buccinator,
divides into branches which communicate freely with the buccal
ranches of the facial nerve, forming the buccal plexus. Its final
(stribution is to the skin and mucous membrane of the cheek, the
ranches to the latter piercing the buccinator.
 
The auriculo-temporal nerve, which is a branch of the posterior
ivision of the mandibular nerve, has been already described as
! gards its cutaneous distribution (see p. 1157).
 
The mental nerve is one of the terminal branches of the inferior
5ntal, which in turn is a branch of the posterior division of the
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1278
 
mandibular nerve. Leaving the mental foramen under cover of t
depressor anguli oris, and in line with the interval between the t\
lower premolar sockets, its branches supply the skin and muco
membrane of one half of the lower lip, and the skin covering the bo<
of the mandible.
 
The supra-orbital, infra-orbital, and mental nerves being frequent
the seat of neuralgia, their positions for purposes of operative tre;
ment can readily be ascertained in the following manner: A line dra\
upwards from the position of the mental foramen, which is in line wi
the interval between the two lower premolar sockets, to the supr
orbital notch, which is situated at the junction of the outer two-thir
and the inner third of the supra-orbital arch, will cross the infra-orbil
foramen. This line, therefore, is over the points of emergence of the
three important sensory nerves.
 
From a clinical point of view it is sometimes more important
recognize the areas supplied by the three divisions of the trigemir
nerve than to identify the distribution of each particular branc
These areas are shown in Fig. 772. It must be clearly understoc
however, that here, as in all other parts of the surface of the bod
one nerve area overlaps another very greatly.
 
Branches of the Great Auricular Nerve.—The facial branches
the great auricular nerve, which is a branch of the cervical plexi
are distributed to the skin over the parotid gland. They send twi
into the gland which communicate with the branches of the fac:
nerve.
 
 
Arteries of the Face.
 
The arteries of the face are as follows:
 
 
Sources.
 
External
 
carotid.
 
Ophthalmic,
 
from
 
internal
 
carotid.
 
Lacrimal,
 
from
 
ophthalmic.
 
 
Arteries.
 
| Facial.
 
'Dorsal nasal.
 
Supra-trochlear.
 
Supra-orbital.
 
Medial palpebral
 
(superior and inferior).
f Lateral palpebral
 
(superior and inferior).
[ Zygomatic.
 
 
Sources.
 
Superficial
 
temporal.
 
Maxillary.
 
Inferior dental,
from
 
maxillary.
 
 
Arteries.
 
(Transverse facial.
 
■j Anterior temporal
’ Zygomatic.
Infra-orbital.«
Buccal. ~
 
l Mental.
 
)
 
 
The chief of these arteries are the facial and the transverse faci;
 
Facial Artery.—The facial artery (external maxillary ) is the highe
of the three anterior branches of the external carotid. It is situat
at first in the upper portion of the anterior triangle of the neck, whe
it has been previously described (see p. 1217). It leaves the neck ai
enters upon its facial course by mounting over the body of d
mandible in front of the anterior border of the masseter, where it
very superficial, being covered only by the platysma and the integ
ment. From this point it has a very tortuous course to the angle
 
 
 
 
THE HEAD AND NECK
 
 
1279
 
 
e mouth, the angle of the nose, and the inner angle of the eye, though
may end at either of the two former points. The facial part of the
:ssel is never very deepfy placed.
 
Relations— Siiperficial. —The skin and platysma, the risorius, the
gomatic muscles, and branches of the facial nerve. It may be deep
superficial to the levator labii superioris; where it crosses the body
the mandible the anterior facial vein is often superficial to it. Deep.
The body of the mandible (where pulsation can readily be felt in the
:ssel), the buccinator, the levator anguli oris, and the infra-orbital
:rve.
 
 
 
Fig. 773. —The Arteries of the Right Side of the Head (after
 
L. Testut’s ‘ Anatomie Humaine ’).
 
 
Facial Branches.—-(1) Muscular branches, of small size, arise from
e outer side of the vessel, and are distributed to the structures in the
asseteric, buccal, and infra-orbital regions, where they anastomose
ith the buccal, transverse facial, and infra-orbital arteries. (2) The
ental branch [inferior labial artery of the O.T.) passes forwards over
e body of the mandible, and deep to the depressor anguli oris, to
pply the structures between the lower lip and the base of the mandible,
anastomoses with the inferior labial, mental, and submental arteries.
) The inferior labial a,rtery (inferior coronary artery ) arises just below
e angle of the mouth, and passes inwards deep to the depressor
iguli oris. In the lower lip it lies near the margin, between the
bicularis oris and the mucous membrane, and anastomoses with its
How of the opposite side, and with the previous branch. (4) The
 
 
 
 
 
 
 
I28o
 
 
A MANUAL OF ANATOMY
 
 
superior labial artery (superior coronary artery ), of larger size than 1
inferior, arises just above the angle of the mouth under cover of 1
zygomaticus major. Its position in the upper lip is similar to that
the inferior labial in the lower lip, and it anastomoses with its fell
of the opposite side. Near the middle line it furnishes the sefi
branch , which ramifies on the columna as far as the tip of the no
The superior and inferior labial arteries of each side sometimes ar
together. The vessels of each side, superior and inferior, form in ea
lip a tortuous arterial arch, which is necessarily divided in operatic
upon one or other lip. (5) The lateral nasal branch arises oppos
the nose, and lies on the sulcus above' the ala. It anastomoses w:
the dorsal nasal branch of the ophthalmicy^the septal branch, t
terminal branch of the anterior ethmoidal artery, and its fellow of i
opposite side, the facial at the medialNartery of the eye.
 
lies either deep to, or; embedded in, the levator labii superioris alaeq
nasi, and supplies the. side of the root of the nose and the adjacc
part of the orbicularis oculi. It anastomoses with the dorsal na
branch of the ophthalmic artery. ; x x
 
The anterior facial vein starts above the medial angle of the e
by the union of the supratrochlear and ^upfa-orbital veins. T
course of the vessel is a straight one, downwards ancboutwards, late:
to the artery, and at a little distance from 1 it, except over the low
border of the mandible, where' it lies close to its outer side and
contact with the anterior border of the masseter. In its course
crosses the end of the parotid duct. The cervical part of the ve
which ends in the internal jugular, has been already described. T
 
muscular relations of the vein are the same as those of the arte]
 
’ ' ., - ? 1 *
 
except that it is always superficial to the levator labii superioris.
 
Its tributaries are: (1) the supratrochlear vein (frontal veil
(2) the supra-orbital vein, which communicates with the ophthaln
vein; (3) the lateral nasal veins, and laterally a few superior palpeb:
veins, whilst posteriorly it communicates with the superior ophthaln
vein, and may communicate with its fellow of the opposite side by mea
of the transverse nasal vein, which lies over the bridge of the no<
(4) a few inferior palpebral veins, which are in communication wi
the infra-orbital vein; (5) the superior labial vein, which issues fron
plexus in the upper lip (the blood from the similar plexus in the low
lip passing to the submental region, where it takes part in the formati
of the anterior jugular vein); (6) the deep facial vein, of variable si:
which, coming from the pterygoid plexus, appears deep to the anter:
border of the ramus of the mandible and of the masseter muscle; a:
(7) parotid, masseteric, and buccal branches.
 
Facial Lymph Glands. — These glands lie on the face along t
course of the anterior facial vein. Some are situated upon the mandil
deep to the platysma, one of them being placed upon the base of t
mandible close to the facial vessels; others ( buccal ) rest upon t
fascia, covering the buccinator muscle; and the remaining glar
of this group are met with between the angle of the mouth and t
 
 
THE HEAD AND NECK 1281
 
edial angle of the eye. I hey receive their afferent vessels from
ie neighbouring structures, and their efferent vessels pass to the
ibmandibular lymph glands. ‘
 
Transverse Facial Artery.— This vessel arises from the superficial
mporal in the parotid gland, and passes horizontally forwards,
fter leaving the anterior border of the gland it crosses the masseter,
iving the zygoma above it and the parotid duct below it, the upper
lccal branches of the facial nerve being in turn below the parotid
ict. The order of structures from above downwards is, accordingly,
tery, duct, and nerves. The artery is distributed to the parotid
and, the masseter muscle, and the structures on the side of the
 
ce, and it anastomoses with the infra-orbital, zygomatic, facial
id buccal arteries.
 
The transverse facial vein joins the superficial temporal vein,
ihe dorsal nasal artery is one of the terminal branches of the
ihthalmic, and leaves the orbit at the medial angle of the eye above
e medial palpebral ligament. It is distributed to the lacrimal sac
id the side of the root of the nose, and anastomoses with the terminal
anches of the facial artery. Sometimes it gives off a transverse
isal branch, which crosses the root of the nose and anastomoses
th its fellow of the opposite side.
 
The supra-orbital and supratrochlear arteries have been already
scribed (see p. 1153).
 
Ihe medial palpebral arteries, superior and inferior, arise from
e ophthalmic and leave the orbit at the medial angle, one passing
•ove and the other below the medial palpebral ligament. Their
urse is outwards between the palpebral fibres of the orbicularis
uli and the tarsi of the eyelids, and they anastomose and form arches
th the lateral palpebral branches of the lacrimal artery. They
e distributed to the palpebral structures, the lacrimal sac, and
e caruncula lacrimalis.
 
The corresponding veins from the upper and lower eyelids open
to the commencement of the anterior facial vein.
 
The terminal branch of the anterior ethmoidal artery emerges,
)ng with the terminal branch of the naso-ciliary nerve, between
e lower border of the nasal bone and the upper nasal cartilage,
is distributed to the skin of the apex and the lower part of the
ie of the nose.
 
The lateral palpebral arteries, superior and inferior, are branches
the lacrimal artery within the orbit. Their course is inwards
tween the palpebral fibres of the orbicularis oculi and the tarsi
the eyelids, and they anastomose and form arches with the palpebral
inches of the ophthalmic.
 
the lateral palpebral veins end in the zygomatic vein, which opens
 
0 the middle temporal, and this in turn joins the superficial temporal
 
m.
 
The zygomatic branches of the lacrimal artery accompany the
^omatico-facial and zygomatico-temporal nerves.
 
 
81
 
 
1282
 
 
A MANUAL OF ANATOMY
 
 
The zygomatic artery and anterior branch of the superficial tempo
artery have been already described (see p. 1158).
 
The infra-orbital artery arises from the third part of the maxilh
in the pterygo-palatine fossa. Having passed horizontally forwar
with the infra-orbital nerve, through the infra-orbital canal, it ri
with that nerve through the infra-orbital foramen, lying under co''
of the levator labii superioris muscle. It then gives branches upwai
to the lower eyelids, inwards to the side of the nose, and downwai
towards the upper lip. It anastomoses with the palpebral, faci
transverse facial, and buccal arteries.
 
 
 
Sometimes, when the facial artery ends at the angle of the mou
the infra-orbital is very large, and supplies all the upper part of
face, including the nose. This arrangement, common enough
pronograde mammals, shows that the infra-orbital, and not
superficial temporal, is morphologically the terminal twig m
external carotid arterial tree.
 
The infra-orbital vein, having traversed the infra-orbital car
 
opens into the pterygoid plexus.
 
The buccal artery is a branch of the second part of the maxilla
It accompanies the buccal nerve to the superficial surface of
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1283
 
 
ccinator muscle, and is distributed to that muscle and to the mucous
■mbrane of the cheek. It anastomoses with branches of the facial
;ery.
 
The mental branch of the inferior dental from the first part of the
ixillary is found with the mental nerve at the mental foramen, lying
der cover of the depressor anguli oris muscle. It supplies the
uctures here, and anastomoses with the inferior labial and submtal arteries.
 
The mental vein joins the inferior dental vein, which opens into
s pterygoid plexus.
 
Lymphatics.—The lymphatics of the face are arranged in two
:s, superficial and deep. The superficial lymphatics for the most
rt take a course similar to that of the anterior facial vein, and end
the submandibular lymph glands. They receive the lymphatics
(1) the inner part of the frontal region at the medial angle of the eye;
the inner parts of the eyelids; (3) the side of the nose; (4) the part
the face between the lower eyelid and upper lip; and (5) sometimes
e upper lip. The lymphatics from the temporal and outer part of
e frontal regions, from the front of the auricle, from the greater
rt of the eyelids, and from the outer part of the cheek end in the
perficial parotid lymphatic glands. The deep lymphatics , including
ose of the orbit, anterior part of the nasal cavity, roof of the mouth,
d temporal and infratemporal fossae, run to the deep facial lymph
mds.
 
Parotid Lymph Glands (Pre-auricular Lymph Glands).—These
mds are arranged in two groups —superficial and deep.
 
The superficial parotid lymph glands lie upon the superficial surface
the parotid salivary gland immediately beneath the parotid fascia,
d in front of the tragus of the auricle. They receive their afferent
ssels from the following sources.
 
1. The outer surface of the auricle.
 
2. The anterior wall of the external auditory meatus.
 
3. The eyebrow, and upper and lower eyelids.
 
4. The root of the nose.
 
5. The upper part of the cheek.
 
Their efferent vessels pass to (1) the upper superficial cervical lymph
mds, and (2) the superior deep cervical lymph glands.
 
The deep parotid lymph glands lie within the parotid salivary gland
)ng the terminal part of the external carotid artery. They receive
eir afferent vessels from the following sources :
 
1. The tympanic cavity in part.
 
2. The frontal region of the scalp.
 
3. The anterior temporo-parietal region of the scalp.
 
4. The parotid salivary gland.
 
5. The deep facial lymph glands.
 
Their efferent vessels pass to the superior cervical lymph glands.
 
 
1284
 
 
A MANUAL OF ANATOMY
 
 
Buccinator Lymph Glands.—These glands are situated on
buccinator muscle. They receive a few afferent lymphatics from
zygomatic region and the lateral aspect of the face, but most of t
drainage is from the inner side of the cheek, and their efferent lympha
pass to the parotid and submandibular lymph glands.
 
Parotid Gland.—This gland is an inverted pyramid, having 1
sides and a base, and fills the space which is left by the ramus of
mandible anteriorly, the sterno-mastoid muscle posteriorly, the sty
process medially, and the articular eminence and root of the zyg(
 
 
 
Fig. 775. —The Parotid Gland in Position.
 
superiorly. Where the anterior border of the sterno-mastoid touc
the angle of the mandible the apex is situated. The anterior, poster
and medial surfaces are grooved by the structures which bound
gland.
 
The lateral surface is flat, flush with the side of the face, £
overlaps the ramus of the mandible and masseter muscle for a c
siderable extent, forming the accessory part, from the anterior bor
of which the parotid duct, the transverse facial artery, and the
branches of the facial nerve leave the gland.
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1285
 
 
Embedded in the upper part of the lateral surface are the superficial
otid lymph glands already described (p. 1283), while from the surface
gs of the great auricular nerve come out to supply the skin covering
gland.
 
The anterior surface is very deeply grooved by the posterior border
the ramus of the mandible and of the masseter muscle, the outer
of the groove projecting forwards as the accessory part already
ken of, while the inner or deep lip pushes its way forwards into
triangular space left between the lateral and medial pterygoid
scles. It is at the anterior border of the latter part of the gland
t the maxillary artery leaves and the maxillary vein enters the
 
 
 
Fig. 776. —Horizontal Section through Parotid Gland and
 
Neighbouring Structures.
 
 
id. The deep Surface is grooved by the styloid process and the
scles rising from it, though not very deeply, and the lips of the
ove may be conveniently referred to as pre- and post-styloid ridges.
 
' pre-styloid ridge is in contact with the internal carotid artery,
le the post-styloid is, perhaps, the most important and interes ting
t of the whole gland, because it touches the internal jugular vein
i the accessory and glosso-pharyngeal nerves, which are so closely
iciated with that vein, and also because, near its upper end, the facial
ve, and near its lower end the external carotid artery enter the
id. In addition to these, the posterior auricular artery runs up
ier just deep to or embedded in the post-styloid ridge until it lies
t behind the point of entry of the facial nerve.
 
 
 
 
 
 
 
 
 
1286
 
 
A MANUAL OF ANATOMY
 
 
The projection of the post-styloid ridge is evidently due to
gland pushing its way in between the styloid process in front and
transverse process of the atlas behind, and that part of the deep surf;
of the gland which lies behind the post-styloid ridge is close to
transverse process and to the muscles rising from it; while, near
apex, the posterior facial vein leaves the gland on this aspect.
 
The posterior surface is usually grooved by the mastoid proc
above and the sterno-mastoid muscle lower down, and entering
 
 
Fig. 777.—To show Deep Relations of Parotid (Interrupted Line)
 
lower part of the superficial lip of this groove is the great auricu
nerve.
 
The base of the gland is very deeply notched anteriorly by the ne
of the condyloid process, behind which the superficial temporal arte
and vein are seen leaving and entering the gland, the vein being sup
ficial; in front of them the temporal branch of the facial nerve rr
from the gland across the root of the zygoma, while behind them
the superficial temporal branch of the auriculo-temporal nerve. T
nerve is, as a rule, not really embedded in the gland, but rests for t
most part on its base, between the parotid and the skull, as it ru
 
 
 
Orb. Oculi
 
 
— Orb. Oris
 
-Masseter
 
Buccinator
 
_—r Mandible
 
Ext. Carotid
 
Plat ysma
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1287
 
 
lcIc from the region of the foramen spinosum, where it embraces the
iddle meningeal artery. Having passed back on the deep aspect of
e superficial temporal vessels, the nerve gives off its auricular, parotid,
id articular branches, and then runs outwards and upwards just
Tind the articulation and just in front of a thin, tongue-like process
 
the gland which moulds itself into the non-articular part of the
ticular fossa, behind the squamo-tympanic fissure, and in contact
ith the tympanic plate.
 
Summing up the foregoing, it will be understood that the parotid
and forms an accurate cast of the cavities which the surrounding
ructures have left for it, pushing its processes and its pre- and postyloid ridges into every available cranny. Doubtless, too, it is able
> adapt its shape to these cavities as they change with every moveten t of the jaw.
 
Several important structures traverse the gland: (1) The external
irotid artery ascends deeply in it as high as the level of the neck
f the mandible, where it divides into the superficial temporal and
laxillary arteries, which are at first embedded in the gland. Whilst
1 the gland the superficial temporal artery gives off its transverse facial
nd auricular branches. (2) The superficial temporal and maxillary
eins unite in the gland, at the level of the neck of the mandible, to form
tie posterior facial vein, which descends from that level within the
land, lying superficial to the external carotid artery, and close to the
iwer border of the gland it breaks up into an anterior and a posterior
ivision. (3) The external jugular vein is formed near the lower part
f the gland by the union of the posterior auricular vein with the
osterior division of the posterior facial vein. (4) The facial nerve
raverses the gland from behind forwards, and in doing so breaks
Lp into its terminal divisions, the branches of which leave the gland
nteriorly and superiorly. The nerve is superficial to the external
arotid artery and posterior facial vein. (5) Entering the lower part
f the gland are branches of the great auricular nerve, which comaunicate within the gland with the facial nerve. (6) The auriculoemporal nerve is related to the upper part of the gland, where it
;ives branches to it which communicate with the facial nerve.
 
Parotid duct, or duct of Stensen, dense and tough, leaves the anterior
)order of the gland, and passes forwards on the masseter muscle,
ying fully \ inch below the zygomatic arch. In this part of its course
t is accompanied for a short distance by the accessory part of the
)arotid gland which, with the transverse facial artery, lies above it,
vhilst the upper buccal branches of the facial nerve are placed below
t. After leaving the surface of the masseter muscle the duct dips
leeply through the fat covering the buccinator, and pierces that muscle,
[t then passes forwards for a very short distance between the muscle
uid tEe buccal mucous membrane, which it finally pierces to end in
1 minute opening on a small papilla situated opposite the crown of
he second upper molar tooth. The duct is about the size of a crowpiill, its diameter being about J inch, except at its buccal orifice,
 
 
 
12 88
 
 
A MANUAL OF ANATOMY
 
 
where it becomes narrow. It is about 2 inches in length, and it
course may be indicated by a line drawn from the intertragus note!
or from the junction of the lobule and cartilage of the auricle, to
point midway between the nostril and the red margin of the uppe
lip. About the middle third of this line corresponds to the duct.
 
Blood-supply. —The arteries are derived from (1) the externa
carotid, (2) the superficial temporal, (3) the transverse facial, an*
(4) the posterior auricular.
 
Lymphatics.— These pass to the superficial and deep cervical lympj
glands, having previously traversed the parotid lymph glands, and
in the case of some, the submandibular glands.
 
Nerve-supply. —(1) The auriculo-temporal nerve, which conveys t
the gland secretory fibres of the glosso-pharyngeal nerve through it
 
 
Parotid Duct
 
 
 
tympanic branch, the lesser superficial petrosal nerve, and the oti<
ganglion; (2) the great auricular nerve; (3) the sympathetic plexu;
on the external carotid artery; and (4) the facial nerve.
 
Structure. —The parotid gland is a compound racemose or acino-tubular gland
and is composed of large lobules, which are united by connective tissue. Eacl
of these is made up of smaller lobules, likewise connected by connective tissue
Each small lobule is a gland on a minute scale, and is made up of a group of mor<
or less sacculated tubules, called alveoli or acini. A duct passes from each smal
lobule, which unites with adjacent ducts, and these in turn unite, larger and stil
larger ducts being formed, the resultant being the principal duct, called th<
parotid duct. Each alveolus is serous or albuminous as regards the nature of it
secretion, and is composed of a basement membrane continuous with the wal
of the duct, and surrounded by a plexus of capillaries. The alveolus is linec
with polyhedral cells, which contain albuminous granules, and almost com
pletely fill the tube, leaving only a small lumen. The first portion of the duct
called the intercalary duct, is lined with flattened epithelium. Beyond this the
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1289
 
 
; becomes constricted into a neck, which is lined with cubical cells, these being
aced in the intralobular duct by columnar cells. These cells are granular
irds the lumen of the tube, but striated in the outer part. Each of the larger
:s is composed of a basement membrane, strengthened externally by a layer
onnective tissue, superadded to which there
stratum of plain muscular fibres.
 
Development of the Salivary Glands. —The
>tid is of ectodermal origin, the submandiband sublingual are derived from entoderm,
y appear as solid outgrowths of the epiium of the buccal cavity, which grow into
adjacent mesodermic connective tissue. The
helial constituents of each gland are derived
1 the buccal lining, whilst the capsule and
lective-tissue elements are of mesodermic
in.
 
Each solid epithelial outgrowth ramifies
t freely, and these ramifications, as well as
primary outgrowth, become tubular. The
owing process commences in the primary
growth, and extends thence throughout its
lerous ramifications. The primary outgrowth represents the principal duct
ach gland, and the acini, or alveoli, appear as dilatations of the walls of the
final ramifications.
 
rhe sublingual gland, from its numerous ducts, is to be regarded as a cluster
 
mall alveolo-lingual glands.
 
Appendages of the Eye.
 
The appendages of the eye consist of the eyelids and the lacrimal
jaratus.
 
Eyelids. —The eyelids, or palpebrae, are two movable curtains placed
front of the eyeball, to which they form an important protection.
 
inner surface of each is covered by mucous membrane, which
stitutes the conjunctiva. The upper eyelid is larger than the lower,
l, when closed, covers the transparent part of the eye or cornea,
s also more movable than the lower, being provided with a special
/ator muscle, the levator palpebrae superioris. The elliptical
srval between the lids is called the palpebral fissure, and the lateral
remities of this fissure are called the angles of the eye. The lateral
lie (canthus) is formed by the junction between the two lids. At
medial angle (canthus) the lids are separated by a recess, called
lacus lacrimalis, in which there is a small body, called the caruncula
rimalis. In this region the eyelids are separated from the eyeball
a vertical, semilunar fold of the conjunctiva, called the plica semiaris. The margin of each eyelid shows, at the commencement of
lacus lacrimalis, a slight conical elevation, called the papilla lacrilis, the apex of which presents a small orifice, termed the punctum
rimale, its direction being towards the eyeball. Each punctum is
entrance to a passage, called the lacrimal canaliculus, by which the
rs are conveyed from the surface of the eyeball into the lacrimal
, and thence, through the naso-lacrimal duct, into the inferior
rtus of the nasal cavity.
 
 
 
Fig. 779. —Structure of the
Parotid Gland.
 
 
 
 
 
 
 
 
1290
 
 
A MANUAL OF ANATOMY
 
 
The free margins of the eyelids, lateral to the puncta lacrima
are provided with hairs, called the eyelashes. They are short, stc
and curved, and are arranged in two rows. Those of the upper
are more numerous and larger than those of the lower. The up
eyelashes are curved upwards and the lower downwards, and in 1
manner intermingling is avoided. Within the lines of attachment
the eyelashes there is a row of modified sweat-glands, known as
ciliary glands (glands of Moll), the openings of which are associa
with the follicles of the eyelashes, and with the condition known as s
Structure of the Eyelids. —Each eyelid is composed of the follow
structures, from before backwards:
 
 
1. Skin.
 
2. Subcutaneous tissue.
 
3. Palpebral fibres of the orbicularis
 
oculi.
 
 
4. Cellular tissue.
 
5. The tarsi.
 
6. Tarsal glands.
 
7. Conjunctiva.
 
 
 
 
Fig. 780.—A, to show the Reflection of Conjunctiva at Upper ani
Lower Fornices; B, Plan of the Palpebral Fissure.
 
In addition to the foregoing structures the upper eyelid contc
the tendinous insertion of the levator palpebrse superioris muscle.
 
The skin is very thin, and at the ciliary margins of the eye
it becomes continuous with the conjunctiva, which is a mucous m<
brane. The subcutaneous connective tissue is scanty and devoid
fat, and in consequence the slightest contraction of the muscle cai
a noticeable movement of the skin. The palpebral fibres of the orbi
laris oculi form a very delicate, pale sheet. The cellular layer, d
to the orbicularis oculi, is lax, and allows the muscle to move frc
over the tarsal plate. The tarsus in each eyelid is composed of c(
pact fibrous tissue. The upper tarsus is larger than the inferior, ;
is semilunar, its depth at the centre being about J inch. Its up
part gives insertion to the levator palpebrae superioris. The lo
tarsus is narrow, and is almost of the same depth throughout.
ciliary margins of the tarsi are free, straight, and comparatively th:
The orbital margins are attached to the circumference of the orbit
a membranous expansion, called the orbital septum. The upper
 
 
 
THE HEAD AND NECK
 
 
1291
 
 
the orbital septum (superior palpebral ligament) is attached above
the upper part of the circumference of the orbit, where it blends
h the periosteum, and below it blends with the tendon of insertion
the levator palpebrae superioris on the upper , tarsus. The lower
i of the orbital septum (inferior palpebral ligament) extends between
: lower part of the circumference of the orbit and the lower margin
the lower tarsus.
 
Laterally and medially the tarsi are attached to the palpebral
iments. The lateral palpebral ligament is formed by the junction
the upper and lower parts of the orbital septum, and is attached
the malar bone. The medial palpebral ligament is independent
the orbital septum. Medially it is attached to the lateral surp of the frontal process of the maxilla in front of the lacrimal
cus. From this point it passes horizontally outwards for about
Uch, and then divides into two laminae, which are attached to the
si of both eyelids. It passes in front of the lacrimal sac, giving an
set, which passes behind the sac to be attached to the crest of the
ripial bone. The ligament gives origin to a few fibres of the
)icularis oculi.
 
The tarsal glands (Meibomian glands) are situated on the deep
rface of each tarsus, and lie between the plate and the conjunctiva
right angles to the ciliary margin. There are about thirty in the
pef ej^elid and about twenty in the lower, and they are arranged in
rallel rows, which occupy grooves on the ocular surface of each
'sus. Each gland opens by an independent orifice, and these orifices
j arranged in a single row, lying a little behind the ciliary margin
the eyelid.
 
Structure. —The tarsal glands are modified sebaceous glands, and their
retiqn lubricates the margins of the eyelids, and prevents them from adhering,
ch consists of a tube, closed at one end, and having its sides beset with
r erticula. The wall of the tube is composed of a basement membrane, which
lined with cubical epithelium throughout the greater part of the gland, but
se tq the orifice this is replaced by stratified epithelium.
 
In fhe neighbourhood of the closed ends of the tarsal glands there
5 some convoluted tubules, which are known as the posterior tarsal
mds f the orifices of which are placed close to the conjunctival fornix.
 
Conjunctiva. —This is the mucous membrane which covers the
ular surfaces of the eyelids and the front of the eyeball. It consists
two parts—palpebral and ocular.
 
The palpebral portion lines the ocular or deep surfaces of the
elids, and at their ciliary margins it is continuous with the skin on
eir outer surfaces. It is also continuous through the puncta lacrialiq, with the lining membrane of the lacrimal canaliculi, lacrimal
c, naso-lacrimal duct, and inferior meatus of the nose. In the region
the medial angle of the eye it gives rise to the plica semilunaris, and at
e outer part of the upper eyelid it is continuous with the lining
embrane of the lacrimal ducts. The palpebral portion is fairly thick
id highly vascular, and it has numerous papillae.
 
 
1292
 
 
A MANUAL OF ANATOMY
 
 
The ocular portion consists of two portions—sclerotic and cornea
It is continuous with the palpebral portion, and the line of reflectic
from the eyelids is known as the conjunctival fornix, superior ar
inferior respectively. Here the orifices of the posterior tarsal glanc
are met with. The conjunctiva is loosely connected to the scler;
and is thin, non-papillary, transparent, and contains only a fe
bloodvessels, the whiteness of the sclera being unaffected by it.
 
The palpebral portion is covered by columnar epithelium, whic
at the ciliary margin passes into the stratified epithelium of the skir
the sclerotic portion is also covered by columnar epithelium, but tl
corneal part is represented by the stratified epithelium of the corpe;
 
The conjunctiva is supplied with blood by offsets from the palpebr;
branches of the ophthalmic artery and its lacrimal branch. Tt
vessels are disposed in a tortuous manner, and are movable upon tl
eyeball when the conjunctiva is pressed upon and displaced. TI
nerves are numerous, and form plexuses. The lymphatics begin clos
to the corneal margin in a network, from which vessels proceed to
network in each evelid behind the tarsus. The efferent vesse.
ultimately reach the parotid and submandibular lymph glands.
 
The caruncuia lacrimalis occupies the lacus lacrimalis in the regio
of the medial angle of the eye. It is a small, reddish, spong
body, consisting of a detached portion of skin containing modifie
.sweat and sebaceous glands. The latter open into the follicles of ver
delicate hairs with which the surface of the caruncle is provided, an
they furnish the white secretion which may accumulate at the medic
angle.
 
The plica semilunaris is a vertical, semilunar fold of the conjunctiv
which is situated on the outer side of the caruncle, its concave margi:
being directed outwards. It corresponds to the membrana nictitam
or third eyelid, of some animals.
 
Development of the Eyelids and Tarsal Glands.— The eyelids make thei
appearance as two folds of skin, above and below the developing eyeball. Eac
fold contains some mesodermic tissue which gives rise to the connective-tissu
element and tarsus of the lid, muscle cells extending into the lids later from th
platysma sheet. The ectoderm of the posterior surfaces of the lids acquires th
characters of mucous membrane, and forms the conjunctival epithelium. In th
course of the third month the eyelids grow together and unite along their margins
a space being thereby enclosed between the lids and the front of the developin
eyeball. The union affects the epithelium only, and persists until near the em
of intra-uterine life.
 
During the period of fusion of the eyelids the tarsal glands and the cilia o
eyelashes are formed. The tarsal glands are developed from the epitheliur
along the line of fusion of the lids. Solid rods of epithelial cells are formei
which grow into the mesodermic tissue of the two lids and give off lateral prc
cesses. These solid rods become hollow, and so form the tarsal glands. Som
of the epithelial rods give rise to the ciliary glands. A short time before birt
the eyelids become separated, and the palpebral fissure is thereby formed.
 
The plica semilunaris is developed as a vertical fold of conjunctiva near th
medial angle of the eye, external to the caruncle, but it attains little developmen
in man.
 
The caruncle is developed from that portion of the margin of the lowe
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1293
 
 
?lid which intervenes between the inferior punctum lacrimale and the medial
y\e. The tarsal glands in this region become modified, and the tissue conning these modified glands becomes raised, and forms the reddish, spongy
 
•uncle.
 
Lacrimal Apparatus.—The constituent parts of the lacrimal
paratus are as follows:
 
1. The lacrimal gland. 3. The lacrimal sac.
 
2. The lacrimal canaliculi. 4. The naso-lacrimal duct.
 
The lacrimal gland will be found described on p. 1247.
 
The lacrimal canaliculi are two in number, superior and inferior,
ley commence at the puncta lacrimalia on the summit of the papillae
:rimales, which latter are situated on the ciliary margins of the
elids close to the lacus lacrimalis. The superior canaliculus at first
cends vertically for about T V inch, after which it makes a sudden
 
 
Tarsal Glands
 
 
Lacrimal Gland
Lacrimal Ducts
 
 
Plica Semilunaris
 
 
 
Superior Punctum Lacrimale
! Caruncula Lacrimalis
 
Superior Lacrimal Canaliculus
 
 
•V. Lacrimal Sac
 
it
 
4
 
rjsL Inferior Lacrimal Canaliculus
Naso-lacrimal Duct
 
 
Inferior Punctum Lacrimale
 
Fig. 781. — The Lacrimal Apparatus of the Right Eye.
 
The tarsal glands of the upper eyelid are also shown.
 
tid, and passes inwards and downwards to the lacrimal sac. The
ierior canaliculus at first descends vertically for about T \ inch, after
lich it makes a sudden bend, and passes almost horizontally inwards
the lacrimal sac. The tw r o canaliculi open into the lacrimal sac,
her close together or by a common orifice, and their mucous memane is lined with stratified squamous epithelium. The two slips
the lacrimal portion of the orbicularis oculi are closely related to the
rizontal portions of the canaliculi.
 
The lacrimal sac is the dilated upper part of the passage by which
2 tears are conveyed from the lacrimal canaliculi to the inferior
iatus of the nose. It occupies the lacrimal groove of the lacrimal
ne and frontal process of the maxilla. Above it has a round, closed
tremity, and below it opens into the naso-lacrimal duct. Externally
receives the lacrimal canaliculi separately or conjointly, and in front
is crossed by the medial palpebral ligament. Behind it is related
the lacrimal part of the orbicularis oculi.
 
 
 
 
 
 
 
 
1294
 
 
A MANUAL OF ANATOMY
 
 
The naso-lacrimal duct (nasal duct) extends from the lower end
the lacrimal sac to the anterior part of the inferior meatus of the n<
under cover of the front part of the inferior nasal concha. Its len^
is about f inch, and its diameter about ^ inch. It is directed dov
wards, outwards, and backwards, and its opening into the anterior p;
of the inferior meatus of the nose is usually guarded by an imperfi
mucous fold, known as the lacrimal fold (valve of Hasner). The na
orifice of the duct is about ij inches from the anterior nasal apertur
 
Structure of the Lacrimal Sac and Naso-lacrimal Duct. —The wall is compo
of fibro-elastic tissue, which adheres closely to the periosteum of the boi
and is covered by mucous membrane. The epithelial lining is of the colum
variety, and at intervals the cells are furnished with cilia. The mucous m(
brane is continuous superiorly with the conjunctiva through the lacrimal car
iculi and puncta, and inferiorly it is continuous with the nasal mucous membra
In the naso-lacrimal duct it may present one or two folds.
 
Development of the Naso-lacrimal Duct and its Appendages. —The effer
lacrimal apparatus consists of (i) the lacrimal canaliculi, (2) the lacrimal s
and (3) the naso-lacrimal duct.
 
In the course of the development of the face, the maxillary process and
lateral nasal process of either side are separated by a groove which extei
from the inner angle of the eye to the olfactory pit. This groove is called
naso-optic, or oculo-nasal groove, and it indicates deeply the position of
lacrimal duct. In the bottom of this groove a solid epithelial cord makes
appearance, which, becoming hollow, forms the naso-lacrimal duct. The up
extremity of the duct bifurcates, its two divisions becoming connected w
the margins of the eyelids near their inner ends, and forming the lacrimal cai
iculi. The lower end of the naso-lacrimal duct at a much later period opens i
the lower part of the nasal cavity. The lacrimal sac is the upper expam
extremity of the naso-lacrimal duct.
 
 
Auricle.
 
The auricle, or pinna, is that part of the external ear which proje
from the side of the head. It has two surfaces, outer and inner.
 
The outer surface is irregularly concave, and about its centre th
is a large deep fossa, called the concha of the auricle, which leads
the external auditory meatus. Towards the upper and anterior p
of the concha there is an elevation, called the crus of helix, whicl
directed upwards and forwards to the anterior border of the auri<
The concha is thus divided into two parts, upper and lower. In fr<
of the concha there is a small, somewhat conical prominence, called
tragus, which projects slightly backwards over the orifice of
external auditory meatus, and is provided with hairs on its in:
aspect. A short distance behind the tragus, and on a lower le
than it, there is another prominence, called the antitragus, whicl
separated from the tragus by a deep notch, called the intertragic not
The skin over the antitragus is also provided with hairs. Below
antitragus and intertragic notch is the most dependent part of
auricle, called the lobule, which is comparatively soft in consister
The prominent rim of the auricle is called the helix. It is incurv
and begins at the upper and front part of the concha in the crus
 
 
THE HEAD AND NECK
 
 
1295
 
 
e helix, already referred to. It then surrounds the margin of the
hide, and ends below in the back part of the lobule. In some cases
e auricular tubercle (Darwin’s tubercle) is situated on the incurved
argin slightly above the level where the antihelix, to be presently
iscribed, bifurcates into its crura. This projection is well developed
the ears of quadrupeds, and forms the point or tip. A short distance
[thin the helix there is another curved elevation, called the anti>lix. This begins at the back part of the antitragus and ascends
:hind the concha, above which it divides into two diverging crura,
)per and lower. Between the helix and the antihelix is an elongated,
irrow fossa, called the scaphoid fossa, and between the diverging
ura of the antihelix there is a depression, called the triangular fossa.
 
 
Auricular Tubercle
 
 
Scaphoid Fossa -/--
 
Helix
 
 
Antihelix
 
 
Concha/
 
 
 
Superior Crus of Antihelix
Fossa Triangularis
 
Helix
 
 
'—;'r - Inferior Crus of Antihelix
 
 
- - Crus of Helix
-Tragus
 
'-Orifice of External Auditory
Meatus
 
 
‘'Intertgraic Notch
"'■Antitragus
 
 
Lobule
 
 
Fig. 782. —The Right Auricle (Lateral Surface).
 
 
The inner or cranial surface of the auricle presents convexities
irresponding to the fossae on the outer surface, the convexity opposite
le concha being especially prominent.
 
Structure Of the Auricle. —The auricle, with the exception of the lobule, is
mposed of a plate of yellow elastic fibro-cartilage covered by skin. This
ate imparts firmness and elasticity to it, and is provided with ligaments and
trinsic muscles. The skin is thin, and adheres closely to the fibro-cartilaginous
ate. It is provided with hairs, which are most plentiful in the regions of the
agus and antitragus. The cartilage of the auricle is rolled upon itself so as to
rm the outer or cartilaginous part of the external auditory meatus. This
>rtion of it is attached medially to the external auditory process of the temporal
>ne by fibrous tissue. The rolled or tubular portion has a deficiency at the
iterior and upper part, between the tragus and the helix, which is occupied by
fibrous membrane. It has also a variable number of transverse clefts, which
e filled with fibrous tissue. The lower extremity of the cartilage of the helix
separated from the cartilage of the antihelix by a deep cleft. The part of the
rtilage of the helix behind this cleft is known as the tail of the helix. At the
>per and anterior part of the auricle, where the helix begins to curve backwards,
e cartilage has a small sharp projection called the spine of the helix.
 
 
 
 
 
 
 
1296
 
 
A MANUAL OF ANATOMY
 
 
Ligaments of the Auricle.—These are anterior and posterior. '
anterior ligament extends from the spine of the helix to the zygonu
the temporal bone close to its root. The posterior ligament extei
from the cranial aspect of the concha, under cover of the auricul;
posterior, to the mastoid process.
 
Intrinsic Muscles.—These muscles, which are very thin and p;
are confined to the auricle, and are six in number, four being situa
on the outer surface and two on the inner surface.
 
Muscles on Outer Surface.—These are: (1) the helicis major; (2)
helicis minor; (3) the tragicus; and (4) the antitragicus.
 
 
Auricuiaris Anterior
Helicis Major
 
Helicis Minor
 
 
 
--Auricuiaris Superior
 
 
^Auricuiaris
Posterior
 
 
> Tail of Helix
 
1
 
Antitragicus
 
 
Fig. 783.—The Outer Surface of the Left Auricular Cartilage and
 
Muscles (Arnold).
 
 
The helicis major extends from the spine of the helix along i
anterior part of the helix as high as the level at which it curves bat
wards.
 
The helicis minor lies upon the crus helicis.
 
The tragicus lies upon the outer surface of the tragus, its fib:
being almost vertical.
 
The antitragicus extends from the outer surface of the antitrag
backwards and slightly upwards, to be attached to the tail of the hel
 
Muscles on Inner Surface.—These are: (1) the transversus auricn
and (2) the obliquus auriculae.
 
The transversus auriculae extends over the depression which cor
sponds to the antihelix on the outer surface, its attachments being
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1297
 
 
convexity of the concha on the one hand, and the convexity of the
a of the helix on the other.
 
The obliquus auriculae extends over the depression corresponding
he lower crus of the antihelix on the outer surface.
 
Action of the Intrinsic Muscles.—The tragicus and antitragicus
inish the orifice of the external auditory meatus, and the muscles of
helix, major and minor, have an opposite effect.
 
Blood-supply of the Auricle.—The arteries are derived from (1) the
terior auricular branch of the external carotid, (2) the anterior
icular branches of the superficial temporal, and (3) the deep auricular
nch of the first part of the maxillary, the last named giving offsets
he cartilaginous part of the external auditory meatus.
 
 
 
, 784. —The Inner Surface of the Left Auricular Cartilage and its
 
Muscles (Arnold).
 
The veins end in the posterior auricular, superficial temporal, and
xillary veins, and one or two of them may open into the mastoid
issary vein.
 
The lymphatic vessels of the inner surface of the auricle pass chiefly
the mastoid lymph glands; but a few end in the superior deep
viced lymph glands. The lymphatics of the lobule pass to (1) the
'erficial cervical lymph glands, and (2) the superior deep cervical
lph glands. The lymphatics of the outer surface of the auricle pass
:he superficial parotid lymph glands.
 
Nerve-supply.—The inner surface receives three cutaneous nerves.
5 great auricular supplies about the lower three-fourths, the lesser
ipital about the upper fourth, and the auricular branch of the vagus
 
82
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1298
 
 
A MANUAL 'OF ANATOMY
 
 
supplies the integument over the convexity of the concha. The oui
surface is supplied by two cutaneous nerves. The auriculo-tempoi
nerve supplies the upper two-thirds, and the great auricular suppli
the lower third. The motor nerve of the intrinsic muscles is the fac
nerve.
 
The Nose.
 
 
The nose has a root, situated below the glabella of the frontal bor
an apex (tip), situated interiorly; and the dorsum nasi, which occup]
an intermediate position. The upper part of the dorsum is kno\
as the bridge of the nose. At the lower part of the nose there are t
openings of the nostrils, or nares. The outer margin of each nost
is slightly prominent and curved, and is called the ala. The nostr
are separated from each other by a septum, called the columna na
which, as well as the ala, is composed of fibrous tissue and skin. With
the circumference of each nostril there are several stout hairs or vibriss
 
The superficial or facial aspect of the nose derives its arteries frc
(1) the lateral nasal branches of the facial, (2) the dorsal nasal bran
of the ophthalmic, and (3) the infra-orbital branch of the maxillary.
 
The nerves are derived from the naso-ciliary and infra-orbil
nerves, the branches from the naso-ciliary being the infratrochlear ai
the terminal cutaneous offsets.
 
The cutaneous lymphatics of the root of the nose pass to the supt
ficial parotid lymph glands. Those from the greater part of the na<
integument pass to the submandibular lymph glands, the lymph glan
forming gland-stations in their path.
 
The framework of the nose is both osseous and cartilaginous.
 
Cartilages of the Nose.—The na<
 
 
 
cartilages are five:
 
 
Nasal Bone
 
 
Frontal Process of
Maxilla
 
 
Upper nasal cartilage.
Lower nasal cartilage.
Septal cartilage.
 
 
Upper Nasal Cartilage
Septal Cartilage
 
 
Small Alar Cartilages
 
 
^ 'V '
 
Subcutaneous Fat
 
 
The upper nasal cartilages (upp
lateral cartilages) are situated imir
diately below the nasal bones. Th
are triangular, and their anten
borders are continuous with ea
other, and with the anterior marg
of the septal cartilage, in each ca
superiorly. Inferiorly, the anteri
borders are separated by a slig
interval, in which the anterior m£
gin of the septal cartilage is visible. The posterior border of ea
cartilage is attached to the lower sloping border of the nasal bone, a:
also to the upper part of the nasal notch on the medial border of t
maxilla. The lower border is connected by fibrous tissue to the upp
margin of the lower nasal cartilage.
 
 
Lower Nasal Cartilage
 
Fig. 785.—The Cartilages of the
Nose (Anterior View) (Arnold).
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1299
 
 
The lower nasal cartilages (lower lateral cartilages) are situated
)w the upper pair, and each is bent so as to lie in front and on each
j of the nostril, which it keeps open. Its outer portion is called
lateral process, and its inner portion the septal process.
 
 
Small Cartilages of Ala
 
 
'ig. 786.—The Cartilages of the Nose (Lateral Aspect) (Arnold).
 
The lateral process is attached by fibrous tissue to the upper nasal
tilage, and to the lower part of the nasal notch on the medial border
the maxilla. The septal process is folded backwards, and touches
fellow of the opposite side. It lies along the upper part of the
umna nasi, and along the antero-inferior border of the septal cartie. Anteriorly it is separated from its fellow by a notch.
 
In the fibrous tissue which con:ts the lateral process to the
.xilla two or more isolated porns of cartilage are met with,
led the small cartilages of the ala
inor cartilages).
 
Development. —The upper and lower
>al cartilages are developed in the
sral nasal process.
 
The septal cartilage is medially
teed, and is usually inclined slightly
one side, most frequently the left,
forms a large part of the nasal
)tum anteriorly, and has the form
an irregularly four-sided, latery compressed plate. Its anterior border is attached to the back of
e nasal bones, along the course of the internasal suture; below this
is connected to the anterior borders of the upper nasal cartilages,
 
 
Lower Nasal Cartilages
 
 
 
A _ Septal Process
 
' Lateral Process
 
Anterior Aperture
 
 
J Small Cartilages
of Ala
 
 
Subcutaneous Fat
 
 
Septal Cartilage
 
Fig. 787. — The Cartilages of
the Nose (Inferior Aspect)
(Arnold).
 
 
 
 
 
 
 
 
 
1300
 
 
A MANUAL OF ANATOMY
 
 
and below these it lies between the septal processes of the lower na
cartilages. Its posterior border is accurately applied to the irregu
anterior margin of the perpendicular plate of the ethmoid bone.
inferior border is received into the front part of the groove on the antei
border of the vomer. The antero-inferior border passes upwards a
forwards from the front part of the inferior border to the antei
border. In early life the septal cartilage is prolonged backwards
 
 
~T Frontal Sinus
 
 
Sphenoidal Sinus
 
 
-Nasal Bone
 
 
Perpendicular Plate
of Ethmoid
 
 
Horizontal Plate of Palatine
Bone (in section)
 
 
 
\ Septal Process of Lc
\ Nasal Cartilage
Septal Cartilage
Womero-nasal Cartilage
 
 
Vomer
 
 
Palatine Process of Maxilla
(in section)
 
 
Fig. 788. —The Osseous and Cartilaginous Nasal Septum (Right
 
Lateral Aspect).
 
 
the body of the sphenoid bone in the form of a narrow strip, whi
intervenes between the lower border of the perpendicular plate
the ethmoid and the vomerine groove. This portion is known
the sphenoidal process. Along the inferior border of the sepi
cartilage, between it and the anterior border of the vomer, there 2
two narrow, elongated strips of cartilage, right and left, which £
called the vomero-nasal cartilages (cartilages of Jacobson).
 
Development. —The septal cartilage is derived from the chondrocranium.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1301
 
 
The Temporal and Infratemporal Regions.
 
Muscles of Mastication. —These are four in number—namely, the
;seter, temporal, lateral pterygoid, and medial pterygoid.
 
Masseter — Origin —(1) Superficial Portion. —The anterior twods of the lower border of the zygomatic arch. (2) Deep Portion,
he posterior third of the lower border, and the whole of the medial
'ace of the zygomatic arch.
 
 
 
Orb. Oculi
 
 
Orb. Oris
 
Masseter
 
Buccinator
 
 
Mandible
 
 
Ext. Carotid
 
 
Platysma
 
 
Fig. 789.—The Masseter Muscle.
 
Insertion .—The superficial portion is inserted into the lower margin
d the deep portion into the upper half of the outer surface of the
nus of the mandible. The superficial fibres extend as far as the
E*le, and the deep fibres encroach on the coronoid process.
Nerve-supply .—The masseteric branch of the anterior portion of
p mandibular division of the trigeminal nerve. This branch leaves
; pterygoid region by passing over the mandibular notch of the
nus of the mandible below the zygoma, and it therefore enters the
iscle on its deep surface accompanied by the masseteric artery.
 
The superficial portion of the muscle is directed downwards and
 
 
 
 
 
 
 
 
 
 
 
 
1302
 
 
A MANUAL OF ANATOMY
 
 
slightly backwards, and the deep portion downwards and very sligl
forwards.
 
Action. —To elevate the mandible. The superficial portion ;
draws it slightly forwards.
 
Relations — Superficial. —The parotid gland and its duct, branc
of the facial nerve, the transverse facial artery, the risorius, and
platysma. Deep. —The ramus of the mandible, and the masset
nerve and artery. The anterior border overlaps the buccinator, fi
which it is separated by the suctorial pad of fat.
 
Temporalis — Origin. —(i) The temporal fossa, extending as higl
the inferior temporal line of the frontal and parietal bones, and as
as the infratemporal crest on the external surface of the greater w
of the sphenoid, but excluding the portion of the fossa formed by
zygomatic bone; and (2) the deep surface of the temporal fascia 0
its upper part.
 
Insertion. —(1) The medial surface, summit, and anterior bor
of the coronoid process of the mandible; and (2) the elongated triangi
surface on the medial surface of the ramus of the mandible, close wit
the anterior border, and extending as low as a point on the inner «
of the last molar socket. w
Nerve-supply. —The deep temporal nerves, usually three in numl
which are branches of the anterior portion of the maairitofcv divis
of the trigeminal nerve, and which enter the deep surface of the mus
 
The muscle is fan-shaped. The anterior fibres descend aim
vertically; the middle fibres pass obliquely downwards and forwai
and the posterior fibres pass forwards almost horizontally.
 
Action. —To raise the mandible, as in closing the mouth,
posterior fibres also retract the mandible, and act in opposition to
lateral pterygoid, which protracts it.
 
Relations — Superficial. —The temporal fascia, supporting the auri
lares anterior et superior; the superficial temporal artery, aurici
temporal nerve, and temporal branches of the facial nerve; the zygor
and fat, which is continuous with the suctorial pad. Deep — 1
temporal fossa, the deep temporal arteries and nerves, and the late
pterygoid muscle.
 
The buccal nerve passes downwards and forwards under cover
the muscle close to the anterior border of the ramus of the mandil
and the masseteric nerve and artery pass outwards close to the poster
border in the region of the mandibular notch.
 
For the temporal fascia, see p. 1161.
 
Lateral Pterygoid (External Pterygoid) — Origin — (1) Upper Head
 
The infratemporal surface and infratemporal crest of the greater w
of the sphenoid. (2) Lower Head. —The outer surface of the late
pterygoid plate of the sphenoid. The upper head is small, and the lo\
head is of large size.
 
Insertion. —(1) The depression on the front of the neck of 1
mandible; and (2) the front of the articular capsule and disc of 1
mandibular joint.
 
 
THE HEAD AND NECK
 
 
1303
 
 
Nerve-supply. —The nerve to the lateral pterygoid, from the anterior
ision of the mandibular nerve.
 
The direction of the muscle is backwards and slightly outwards.
Action. —(1) To draw forwards the neck and condyloid process of
: mandible, and also the articular disc. When the muscles of opposite
es act in concert the mandible is protruded, and the lower incisor
1 canine teeth project beyond the level of those of the maxilla. The
scles of opposite sides, however, usually act alternately and thus
>duce the oblique or grinding movement, the lower molars of one
e being carried forwards and inwards under the corresponding
per molars, and vice versa. At the same time the elevators of the
ndible are in action. (2) To take part in opening the mouth by
iwing the condyloid process of the mandible and articular disc forrds on to the articular eminence of the temporal bone. The lateral
 
 
Buccal Nerve (cut)
 
 
 
Lower Head of Lateral
Pterygoid
 
^Pterygomandibular
 
Ligament
 
•Parotid Duct
 
 
Buccinator
 
 
Medial Pterygoid
 
 
Fig. 790. —The Pterygoid and Buccinator Muscles.
 
 
srygoid is antagonistic to the posterior portion of the temporalis
iscle.
 
Relations — Superficial. —Part of the ramus of the mandible, the
ver part of the temporalis, part of the pterygoid plexus of veins, the
[ccal nerve, and perhaps the second part of the maxillary artery.
lep. —The upper portion of the medial pterygoid muscle, the sphenomdibular ligament, in some cases the second part of the maxillary
tery, the middle meningeal artery, a part of the pterygoid plexus of
ins, the mandibular nerve, the otic ganglion, and the chorda tympani
rve. Superior. —The masseteric and deep temporal nerves. Inferior.
The inferior dental and lingual nerves, and the spheno-mandibular
;ament. The buccal nerve, with the anterior deep temporal nerve,
akes its appearance between the upper and lower heads, and the
axillary artery may sink between them.
 
 
 
 
 
 
 
 
1304
 
 
A MANUAL OF ANATOMY
 
Medial Pterygoid (Internal Pterygoid) — Origin. —(1) The inner surfs
of the lateral pterygoid plate of the sphenoid, and the portion of t
tubercle of the palatine bone which forms the lower part of the pterygc
fossa; and (2) the outer surface of the tubercle of the palatine boi
and the adjacent portion of the tuberosity of the maxilla.
 
Insertion. —(1) The inner aspect of the angle of the mandib
and (2) the back part of the inner surface of the ramus, between t
angle and the mandibular foramen.
 
Nerve-supply .—The medial pterygoid branch of the anterior port!
of the mandibular nerve.
 
The direction of the muscle is downwards, backwards, and 01
wards.
 
Action.—{ 1) To elevate the mandible; and (2) to draw it forwarc
 
Relations- — Superficial .—The lateral pterygoid muscle to a slig
extent superiorly, the spheno-mandibular ligament, the maxillary ai
inferior dental vessels, and the inferior dental and lingual nervt
 
Deep .—The tensor palati muscle, and the superior constrictor muse
of the pharynx.
 
For a description of the spheno-mandibular ligament, see p. 1316.
 
The Maxillary Artery (Internal Maxillary Artery) .—This vessei
the larger of the two terminal branches of the external carotid,
arises from that artery opposite the neck of the mandible and within tl
parotid gland. Its course is at first forwards and inwards behind tl
neck of the mandible, and superficial to the spheno-mandibular lig
ment. It then inclines upwards and forwards through the infr;
tempoial fossa, usually passing superficial to the lateral ptervgoi
muscle, though in many cases it passes deep to it. Having reached tl
interval between the two heads of the lateral pterygoid, it sinks deep]
between them, and, passing through the pterygo-maxillary fissure,
enters thepterygo-palatine fossa, where it gives off its terminal branche
In those cases in which the artery passes deep to the lateral pterygoi
muscle it forms a piojecting curve between the two heads of the muscl
The course of the vessel is very tortuous in adaptation to the mobilit
of the surrounding structures.
 
Owing to its complexity it is convenient to divide the artery inf
thiee parts. The first or mandibular part is situated between tb
neck of the mandible and the spheno-mandibular ligament, and it
course is horizontally forwards and inwards. It is accompanied b
the maxillary vein, and lies along the back part of the lower border c
the lateral pterygoid muscle, crossing in front of the inferior dents
nerve and embedded in the parotid gland. The second or pterygoi
part usually lies superficial to the lower head of the lateral ptervgoic
and under cover of the insertion of the temporalis. Its course througi
the infratemporal fossa is upwards and forwards, and it sinks betweei
the two heads of the lateral pterygoid on its way to the pterygo
maxillary fissure. In many cases, however, the second part of th<
vessel passes deep to the lower head of the lateral pterygoid, crossing
m front of the medial pterygoid muscle and lingual nerve. Unde:
 
 
THE HEAD AND NECK 1305
 
;e circumstances it forms a projecting curve between the two
is of the lateral pterygoid beneath the long buccal nerve. The
i or pterygo-palatine part is situated in the pterygo-palatine fossa,
ch it enters by passing through the pterygo-maxillary fissure. In
fossa the vessel and its branches are intimately related to the
ciliary nerve and the spheno-palatine ganglion, with its branches.
 
 
 
F ig . 791.— The Maxillary Artery and its Branches.
 
ramus of the mandible and one half of the calvaria have been removed.
1, lateral pterygoid muscle; 2, medial pterygoid muscle.
 
Branches. —These are as follows:
 
First Part.
 
:p auricular.
 
:erior tympanic,
idle meningeal, giving
if accessory meningeal,
srior dental.
 
 
Branches of the First Part.— The deep auricular artery, of small
s, ascends within the parotid gland just behind the mandibulai
it, and pierces the anterior cartilaginous wall of the external auditory
atus. It supplies the cutaneous lining of that passage and .the
ter surface of the tympanic membrane.
 
 
Second Part.
 
Masseteric.
 
Pterygoid.
 
Posterior deep temporal.
Anterior deep temporal.
Buccal.
 
 
Third Part.
 
Posterior superior
dental.
 
Infra-orbital.
 
Greater palatine.
Artery of the pterygoid
canal.
 
Pharyngeal.
 
Spheno-palatine.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1306
 
 
A MANUAL OF ANATOMY
 
 
The anterior tympanic artery may be associated with the precedi
at its origin. It ascends beneath the lateral pterygoid, and enters 1
tympanic cavity by passing through the squamo-tympanic fissu
It is distributed to the structures within the tympanic cavity and
the inner surface of the tympanic membrane. Around the circu
ference of that membrane it forms an arterial ring with an offset
the stylo-mastoid artery, which is a branch of the posterior auricula
The middle meningeal artery, of large size, ascends beneath 1
lateral pterygoid muscle, and, passing between the two roots of ori$
of the auriculo-temporal nerve, it enters the cranial cavity throu
 
 
 
Deep Temporal Vessels
and Nerves
 
 
Middle Meningeal Artery
 
 
Sph. Max.
Fossa
 
Buccal A. and
N.
 
 
Lingual N.
 
Sph. Mand. Lig.
 
Inf. Dental N.
and A.
 
 
Sup. Constrictor
 
 
Fig. 792.—Dissection of Right Pterygoid Region.
 
 
the foramen spinosum in the sphenoid bone. It then passes upwar
and forwards to the inner aspect of the antero-inferior angle of t]
parietal bone, where it divides into two branches, anterior ai
posterior, which ramify in the branching grooves on the inner surfa
of the parietal bone. The artery is accompanied by a plexus
sympathetic nerves, but its vein passes through the foramen oval
For the distribution of the vessel within the cranium, see p. 159
Before disappearing through the foramen spinosum the midd
meningeal artery usually gives off the accessory meningeal artery, whi<
enters the cranial cavity through the foramen ovale.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1307
 
 
The inferior dental artery arises nearly opposite the middle meningeal
ery, and descends upon the spheno-mandibular ligament in company
;h the inferior dental nerve, lying on its posterior and outer side.
,ving reached the mandibular foramen, it gives off the small mylorid branch y and then it passes through the mandibular foramen and
:ers the mandibular canal, which it traverses as far as the level
the mental foramen, where it ends by dividing into its mental and
:isor branches. Within the mandibular canal the artery is accomnied by the inferior dental nerve and inferior dental vein.
 
Branches. —-The mylo-hyoid branch, of small size, arises at the
r el of the mandibular foramen. In company with the mylo-hyoid
rve it pierces the spheno-mandibular ligament, and descends in
3 mylo-hyoid groove to be distributed to the under surface of the
do-hyoid muscle. The molar, premolar, and canine branches arise
thin the mandibular canal, and supply the pulps of these teeth,
Lich they reach by passing through the foramina on the extremities
their fangs. Th e mental branch leaves the mandibular canal through
s mental foramen, and has been already described (see p. 1283).
ie incisor branch supplies the pulps of the incisor teeth of one side.
Branches of the Second Part. —The branches of this part are muscular
their distribution. The masseteric artery passes outwards, with the
□responding nerve, over the mandibular notch, and enters the deep
rface of the masseter. The pterygoid branches are distributed to
e corresponding muscles. The posterior and anterior deep temporal
teries pass upwards to the posterior and anterior parts of the temporal
ssa beneath the temporalis. They supply the muscle and the bones
rming the fossa, and anastomose with the middle temporal artery,
lich is a branch of the superficial temporal. The anterior deep
mporal artery also anastomoses with the lacrimal artery by twigs
tiich pass through minute foramina in the outer wall of the orbit,
le buccal artery passes downwards and forwards in company with
e buccal nerve, and is distributed to the buccinator muscle and the
lccal mucous membrane which lines it internally.
 
Branches of the Third Part.— The posterior superior dental artery
ises from the maxillary as it is about to pass through the pterygoaxillary fissure into the pterygo-palatine fossa, and is sometimes
isociated with the infra-orbital artery at its origin. It descends
ion the zygomatic surface of the maxilla posterior to the zygomatic
'ocess, and its principal branches traverse the posterior dental canals
> supply the pulps of the upper molar teeth of one side. It also
irnishes twigs to the mucous lining of the maxillary sinus and to the
1m.
 
The infra-orbital artery arises in the pterygo-palatine fossa, somemes in common with the posterior superior dental. It passes through
ie inferior orbital fissure in company with the maxillary nerve, and
averses the infra-orbital groove and canal on the floor of the orbit,
ie accompanying nerve being now called the infra-orbital nerve,
rom this canal it emerges through the infra-orbital foramen on to
 
 
- 1308
 
 
A MANUAL OF ANATOMY
 
 
the face, where it has been already described (see p. 1282). The arter
is accompanied by the infra-orbital vein. As the artery traverse
the infra-orbital canal it furnishes (1) orbital branches to the structure
on the floor of the orbit; and (2) the anterior superior dental branch
which descends in the anterior dental canals in the maxilla, in compan
with the corresponding nerves, to supply the pulps of the upper premok
ingisor and canine teeth, and the mucous lining of the maxillary sinu:
 
The greater palatine artery (descending palatine artery) pass(
downwards in the greater palatine canal, in company with the greatc
palatine nerve, to the hard palate, where it passes forwards and in ware
to the incisive fossa. In this situation it furnishes a branch whic
ascends through the incisive canal, to anastomose with a branc
of the spheno-palatine artery. As the artery traverses the greate
palatine canal it gives off the lesser palatine arteries, which accompan
corresponding nerves in the lesser palatine, canals, and supply the sol
palate and tonsil.
 
The artery of the pterygoid canal (Vidian artery) passes backward
through the pterygoid canal in company with the correspondin
nerve, and its branches are: (1) to the upper part of the pharynx
(2) to the pharyngo-tympanic tube; and (3) to the tympanum.
 
The pharyngeal branch (pterygo-palatine artery), of small siz<
passes backwards through the pharyngeal canal in company with th
pharyngeal branch of the spheno-palatine ganglion, and is distribute
to the upper part of the pharynx, the pharyngo-tympanic tube, and th
mucous lining of the corresponding sphenoidal sinus.
 
The spheno-palatine artery enters the superior meatus of the nasa
cavity through the spheno-palatine foramen. Its branches are dis
tributed extensively on the outer wall of the nasal cavity, and suppt
the mucous membrane of the maxillary, ethmoidal, and frontal sinuses
One branch, called the posterior septal (naso-palatine artery), descend
upon the septum to the incisive canal, where it anastomoses with th
terminal ascending branch of the greater palatine artery.
 
Pterygoid Plexus of Veins. —This is a large plexus which surround
the lateral pterygoid muscle. Its tributaries correspond for th
most part to the branches of the maxillary artery, and are chief!;
as follows: the deep auricular, anterior tympanic, two middle menin
geal, inferior dental, masseteric, pterygoid, deep temporal, bucca]
superior dental, infra orbital, greater palatine, and spheno-palatine
The blood is conveyed away from the plexus by two veins—namely
the maxillary and the deep facial.
 
The maxillary vein (internal maxillary vein) is a short vessel whic]
issues from the posterior part of the plexus, and accompanies th<
first part of the maxillary artery. Opposite the neck of the mandibl
it joins the superficial temporal vein within the parotid gland t(
form the posterior facial vein.
 
The deep facial vein issues from the anterior part of the ptery
goid plexus, and, passing downwards and forwards, it emerges deej
to the mandibular ramus and masseter muscle, and joins the anterio:
 
 
THE HEAD AND NECK
 
 
 
1309,
 
ial vein on the buccinator muscle. The pterygoid plexus comnicates with the intracranial cavernous sinus by means of emissary
ns, which pass through the foramen ovale, the emissary sphenoidal
amen, and foramen lacerum; it communicates with the inferior - .
ithalmic vein at the inferior orbital fissure and with the pterygoid TT _
yus behind and below. (a£jv*-$ <? )
 
Deep Facial Lymph Glands (Internal Maxillary Lymph Glands).—
 
ese glands lie upon the lateral pterygoid muscle. Their afferent
>sels are derived from (1) the infratemporal and temporal fossae; 7
the orbit; (3) the palatal mucous membrane; (4) the nasal cavity
part; (5) the cerebral dura mater; and (6) the tympanic cavity,
eir efferent vessels pass to (t) the deep parotid lymph glands, and
the superior deep cervical lymph glands.
 
Mandibular Nerve (Inferior Maxillary Nerve). —This is the third
ision of the trigeminal nerve. It is a mixed nerve, and consists
two roots—sensory and motor. The sensory root, which is of large
e, arises from the trigeminal ganglion, and the motor root represents
i entire motor root of the trigeminal nerve. Both roots leave the
inial cavity through the foramen ovale, and immediately after their
it they unite to form a mixed nerve—that is to say, a nerve composed
both sensory and motor fibres. This nerve is very short, and lies
eply in the infratemporal fossa, under cover of the lateral pterygoid
iscle, where it gives off two branches—namely, the nervus spinosus
d the nerve to the medial pterygoid muscle. Then it immediately
saks up into two parts, known as the anterior and posterior trunks.
ie nervus spinosus enters the cranial cavity through the foramen
inosum, along with the middle meningeal artery, and divides into
0 branches—anterior and posterior. The anterior branch is
stributed to the adjacent dura mater, and the posterior branch
sses through the fissure between the petrous and squamous parts
the temporal bone, to be distributed to the mucous lining of the
istoid air-cells. The nerve to the medial pterygoid muscle arises from
e deep surface of the undivided mandibular nerve, and passes downirds to enter the deep surface of the medial pterygoid muscle.
 
3se to its origin it. is intimately related to the otic ganglion.
 
Anterior Trunk of the Mandibular Nerve. —Ihis division is smaller
an the posterior, and is principally motor in function, the only
nsory branch furnished by it being the buccal nerve. Its branches
e: (1) masseteric, furnishing the posterior deep temporal; (2) middle
ep temporal; and (3) buccal, giving off the lateral pterygoid and
terior deep temporal, after which it is purely sensory.
 
The masseteric nerve passes upwards deep to the upper head of
e lateral pterygoid muscle, where it furnishes the posterioi deep
mporal nerve. It then passes outwards over the upper bordei of
e lateral pterygoid, and over the mandibulai notch behind the
mporalis, to enter the upper part of the masseter on its deep surface.
 
The deep temporal nerves are three in numbet anterior, middle,
id posterior. The anterior deep temporal nerve usually arises from
 
 
 
i3io
 
 
A MANUAL OF ANATOMY
 
 
the buccal after it has passed between the two heads of the latei
pterygoid. It runs upwards superficial to the upper head of th
muscle, and enters the anterior part of the temporalis muscle on i
deep surface. The middle deep temporal nerve is a direct bran*
of the anterior trunk of the mandibular, and it ascends beneath t]
lateral pterygoid to enter the middle part of the temporalis on i
deep surface. The posterior deep temporal nerve springs from t]
masseteric nerve beneath the upper head of the lateral pterygoi
 
 
 
Fig. 793- The Nerves of the Temporal and Mandibular Regions
 
(Hirschfeld and Leveille).
 
i, temporalis; 2, lateral pterygoid; 3, medial pterygoid; 4, masseter;
 
5, buccinator.
 
and, passing upwards, it enters the posterior part of the temporal
on its deep surface.
 
The buccal nerve {long buccal nerve ) passes outwards betwee
the two heads of the lateral pterygoid, and then downwards an'
forwards in contact with the inner surface of the temporalis at it
insertion. Having emerged from deep to the mandibular ramus an'
anterior border of the masseter, it is received upon the outer surfac
of the buccinator, where it communicates with the buccal branche
of the facial nerve to form the buccal plexus. After this its termini
branches are distributed to the skin over the buccinator muscle an
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
i 3 Tl
 
 
mucous membrane which lines it. The buccal nerve furnishes
' branches, the lateral pterygoid and the anterior deep temporal
ye. The nerve to the external pterygoid muscle leaves it near its
[in, and enters the lateral pterygoid muscle on its deep surface.
 
; anterior deep temporal nerve arises from it after it has passed
ween the two heads of the lateral pterygoid. These two branches
e all the motor fibres from the buccal nerve, which after this is
irelv sensory.
 
Posterior Trunk. —This division is larger than the anterior, and
dmost entirely sensory, the only motor fibres which it contains
ng destined for the mylo-hyoid branch of the inferior dental nerve,
branches are three in number—namely, (i) auriculo-temporal,
inferior dental, and (3) lingual.
 
Auriculo-temporal Nerve. —This nerve, which is sensory, arises
two roots, between which the middle meningeal artery ascends
the foramen spinosum. Then the two roots join, and the nerve
is backwards deep to the lateral pterygoid muscle. Having passed
se behind the mandibular joint to the interval between that joint
1 the auricle, it enters the upper part of the parotid gland. It
:n changes its course and passes upwards, after which it crosses
; zygoma and descends close behind the superficial temporal artery
end in its terminal temporal branches.
 
Branches of Communication. —(1) Each root of the auriculonporal nerve receives a small branch from the otic ganglion. These
inches contain fibres of the glosso-pharyngeal nerve through (a) its
npanic branch, ( b) the tympanic plexus, and (c) the lesser superficial
trosal nerve, which latter is reinforced by a branch from the ganglion
the facial nerve. These glosso-pharyngeal fibres are destined for
3 parotid gland. (2) Two communicating branches pass to the
nal nerve in the parotid gland.
 
Branches of Distribution. —(1) Articular branches enter the temporomdibular joint through the back part of the capsule. (2) Glandular
inches are distributed to the parotid gland, to which they conduct
res of the glosso-pharyngeal nerve. (3) The branches to the ■ external
ditory meatus , upper and lower, enter the meatus between its carti^inous and osseous parts, and supply the skin which lines it, the
•per branch also giving twigs to the outer layer of the tympanic
mibrane. (4) Auricular branches are distributed to tfife skin of
e tragus and the upper part of the outer surface of the auricle. The
stribution of the meatal and auricular branches explains why pain
le to affections of the lower teeth may be referred to the ear canal
id auricle. (5) The temporal branches are terminal. They accommy the branches of the superficial temporal artery, and supply the
in of the temporal region as high as the vertex of the skull. They
mmunicate with the temporal branches of the facial and the zygoatico-temporal nerve.
 
Inferior Dental Nerve. —This nerve, though chiefly sensory, conins motor fibres, which, however, leave it in its mylo-hyoid branch.
 
 
 
 
1312
 
 
A MANUAL OF ANATOMY
 
 
It passes downwards, being at first under cover of the lateral ptery^
muscle. After escaping from beneath that muscle, it descends u
the spheno-mandibular ligament and medial pterygoid muscle to
mandibular foramen, through which it passes into the mandibular ca
after having parted with its mylo-hyoid branch. The lingual ne
is anterior and medial to it, and the inferior dental artery is postei
and lateral to it. Within the mandibular canal the nerve is accc
panied by the inferior dental artery, and, having arrived at the le
of the mental foramen, it terminates by dividing into two brand
mental and incisive.
 
Branches. —(i) The mylo-hyoid nerve is given off from the par
trunk just before it passes through the mandibular foramen,
takes all the motor fibres from the parent trunk, and in comp£
 
 
Internal Carotid Artery with Sympathetic Plexuses
Facial Nerve in Facial Canal
 
 
Maxillary Neive
 
Abducent Nerve . Internal Carotid Artery
 
 
Oculo-motor Nerve
Optic Nerve
 
 
Chorda Tympani
Glosso-pharyngeal f
Inferior Dental
 
Accessory "~j~
Mylo-hyoid
 
 
 
Supra-orbital Nerve
 
 
_ Supratrochlear
-- Frontal
'* Infratrochlear
Naso-ciliary
Lacrimal (cut)
Ophthalmic
Infra-orbital
 
 
Spheno-palatine Ganj
Anterior Superior De
Middle Superior Deni
 
I Posterior Superior
/ Dental
 
 
Hypoglossal
 
Vagus
 
 
Otic Ganglion
frA ' Lingual
') Submandibular Ganglion
 
 
Nerve to Thyro-hyoid Muscle
 
Fig. 794 .—General View of the Trigeminal Nerve (Hirschfeld ani
 
Leveille.
 
 
1, sterno-mastoid; 2, mylo-hyoid; 3, medial pterygoid.
 
 
with the mylo-hyoid branch of the inferior dental artery pierces f
lower part of the spheno-mandibular ligament, and then passes dow
wards and forwards in the mylo-hyoid groove of the mandible. T
nerve and artery are maintained in position within this groove by
expansion from the lower part of the spheno-mandibular ligamei
which is attached to the lips of the groove. Then the nerve pass
forwards on the inferior surface of the mylo-hyoid muscle unc
cover of the superficial part of the submandibular gland. Havi
furnished twigs to the mylo-hyoid muscle, it terminates in the anteri
belly of the digastric.
 
(2) The dental branches arise from the parent trunk, whilst
traverses the mandibular canal. They communicate with each oth
to form a delicate plexus, from which branches are given off to t
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
* 3*3
 
 
'S of the lower molar and premolar teeth, as well as to the adjacent
of the gum. The pulp branches correspond in number to the
s of the teeth, and each enters through a minute opening on the
emity of the fang.
 
3) The mental nerve is one of the two terminal branches. It
rges from the mandibular canal through the mental foramen,
its distribution, see p. 1277.
 
4) the incisive branch is the termination of the inferior dental.
>egins at the level of the mental foramen, and passes almost
ar as the middle line. Its dental branches communicate in a
iform manner, and supply the pulps of the lower canine and
»or teeth, as well as the adjacent portion of the gum.
 
 
Naso-ciliary Nerve
 
 
 
Frontal Nerve
Lacrimal Nerve
Ciliary Ganglion \
Internal Carotid Artery
 
Ophthalmic Nerve
Trigeminal Ganglion
ter Superficial Petrosal Nerve
 
1 to Lesser Sup. Pet. N.
 
acial Nerve in Facial
Canal
 
ior Auricular Nerve
 
Facial Nerve * /
 
/ I ' /
 
Internal Carotid Artery ' ] / / /
 
Chorda Tympani Nerve’ / < ‘
 
Mandibular Nerve / / /
 
Inferior Dental Nerve / j
Otic Ganglion
Lingual Nerve
 
 
Lacrimal Gland
Ciliary Nerves
 
 
Branch of Oculo-motor Nerve
to Inferior Oblique
Maxillary Nerve
Spheno-palatine Ganglion
 
 
Long Spheno-palatine Nerve
 
 
''•Greater Palatine Nerve
 
 
Submandibular Ganglion Sublingual Ganglion
 
 
Fig. 795. —Scheme of the Trigeminal Nerve and its Ganglia
 
(Hirschfeld and Leveille.)
 
 
jingual Nerve. —This nerve is sensory. It descends deep to the
ral pterygoid muscle, lying anterior and medial to the inferior
:al nerve. Whilst under cover of that muscle it receives near its
in the chorda tympani nerve, which joins it from behind at an
:e angle, in a direction downwards and forwards, after leaving
tympanic cavity through the anterior canaliculus for the chorda
pani nerve. Below the lateral pterygoid muscle the lingual nerve
:es downwards and forwards between the medial pterygoid muscle
the mandibular ramus, and over the mandibular fibres of the
aior constrictor muscle. Below the level of the third lower molar
h it lies immediately beneath the mucous membrane of the mouth,
is here easily reached. It then crosses the stylo-glossus, and
es forwards superficial to the hyo-glossus close to the side of the
'ue. Upon the latter muscle it describes a slight curve with the
/■exity downwards. It then passes deep to the mylo-hyoid muscle,
 
83
 
 
 
 
 
 
 
 
 
 
1314
 
 
A MANUAL OF ANATOMY
 
 
where it lies above the deep part of the submandibular gland a
the submandibular duct, and has the submandibular ganglion s
pended from it. Finally, having looped under the submandibu
duct from without inwards, it continues its course as far as the tip
the tongue. As it passes along the side of the tongue the nerve
immediately beneath the mucous membrane.
 
Branches of Communication. —(1) Chorda tympani (sensory
facial); (2) two branches to the submandibular ganglion; and (3) (
or two filaments to the hypoglossal nerve at the anterior border
the hyo-glossus muscle.
 
Branches of Distribution. —(1) Buccal , to the mucous membrs
of the floor of the mouth and of the gums; (2) glandular , to the si
 
 
Tympanic Plexus
 
\ Facial Ganglion
 
 
 
Fig. 706.—Relations of the Petrous Part of the Internal Carotii
 
Artery.
 
 
lingual gland; and (3) lingual , to the mucous membrane of the si(
and dorsum of the tongue over its anterior two-thirds. These lingi
branches pierce the muscular tissue of the tongue, and are destir
chiefly for the filiform and fungiform papillae.
 
Otic Ganglion. —The otic ganglion is a small oval body, of a pink:
colour, which is situated close to the foramen ovale on the deep surfc
of the mandibular nerve at the place of origin of the nerve to t
internal pterygoid muscle, with which it is closely connected. It I
the middle meningeal artery behind it, and the cartilaginous part
the pharyngo-tympanic tube on its inner side. The ganglion I
three roots. One root (motor-sensory) is derived from the nerve
internal pterygoid (motor and probably sensory fibres). A seco
root (sensory-motor) is represented by the lesser superficial petro:
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1315
 
 
/e, which joins the back part of the ganglion. The sensory fibres
Le from the glosso-pharyngeal by means of (1) the tympanic nerve,
the t}/mpanic plexus, and (3) the lesser superficial petrosal. The
or fibres conveyed by this root come from the ganglion of the facial
/e through the branch which that ganglion gives to join the lesser
grficial petrosal nerve. The third root (sympathetic) comes from
sympathetic plexus around the middle meningeal artery.
 
Branches—(1) Of Communication.— (a) Two branches pass to the
iculo-temporal nerve, one to each root. These carry secretory
so-pharyngeal fibres which are destined for the parotid gland.
A branch joins the chorda tympani. (c) A branch joins the nerve
he pterygoid canal.
 
(2) Of Distribution. —Muscular branches are said to be given to
tensor tympani and tensor palati, though the modern view is that
ti these nerves are direct branches of the nerve to the internal
-ygoid muscle.
 
Submandibular Ganglion (Submaxillary Ganglion). —This ganglion
f small size, and is connected with the lingual nerve in the subidibular region. It is situated upon the upper part of the hyo;sus muscle, between the lingual nerve and the deep part of the
mandibular gland, and under cover of the posterior part of the
lo-hyoid muscle. It is suspended from the lingual nerve by two
necting branches, posterior and anterior, which stand apart from
h other. The posterior connecting branch, sometimes broken up
) two or three twigs, conveys sensory fibres from the chorda tympani
isory portion of the facial) and lingual nerves, the latter being a
nch of the mandibular nerve. The anterior connecting branch
resents fibres passing from the ganglion to the lingual nerve.
 
The posterior branch consists of fibres which are derived from the
rda tympani of the facial, and from the lingual nerve. 1 his
terior branch may exist as two twigs. The anterior branch is an
et from the ganglion to join the lingual. I he sympathetic root of
ganglion is derived from the plexus on the cervical portion of the
al artery.
 
Roots of the Submandibular Ganglion.
 
Secretory. Sensory. Sympathetic.
 
tn chorda tympani From lingual. From plexus on cervical portion
 
of facial. of facial artery.
 
The submandibular ganglion has three roots—secretory, sensory..
I sympathetic. The secretory root comes from the chorda tympani
ve; the sensory root from the lingual nerve; and the sympathetic
t from the plexus on the cervical portion of the facial artery. I he
retory and sensory roots are the posterior connecting branch of the
tglion.
 
Branches. —These proceed from the lower and anterior parts of
ganglion, and are as follows: (1) glandular, to the submandibular
ad; (2) branches to the submandibular duct; (3) buccal, to the
 
 
1316
 
 
A MANUAL OF ANATOMY
 
 
mucous membrane of the floor of the mouth; and (4) an anter
connecting branch, which passes to the lingual nerve. The anter
connecting branch probably consists of both chorda tympani a
lingual fibres, and it accompanies the lingual nerve to the tongue,
furnishes twigs to the sublingual gland, and a small ganglion associa
with these twigs has been described under the name of the subling
ganglion.
 
Summary of the Mandibular Nerve—1. Cutaneous Distribution. —It supp
 
(1) a portion of the dura mater, and the mucous membrane of the mast
air-cells; (2) the skin over the greater part of the temporal region; (3) the s
of the external auditory meatus, and the outer surface of the tympanic m(
brane; (4) the skin of the tragus, and of the upper part of the outer surface
the auricle; (5) the skin over the body of the mandible, including the skin
the chin and lower lip, as well as the mucous membrane of the lower lip; (6)
mucous membrane of the floor of the mouth, and the lower gum; and (7)
sides and dorsum of the tongue over its anterior two-thirds. 2. Articular I
tribution. —It supplies the mandibular joint. 3. Dental Distribution. —It s
plies the pulps of all the lower teeth of one side, and the mucous membr;
of the outer surface of the lower gum of one side. 4. Glandular Distribution.gives branches to the parotid, submandibular, and sublingual glands. 5. Mi
cular Distribution. —It supplies (1) the muscles of mastication—namely, ■
masseter, temporal, lateral pterygoid, and medial pterygoid; (2) the mylo-hy
and anterior belly of the digastric; and (3) the tensor palati and tensor tympc
 
The Mandibular Joint.
 
The mandibular joint belongs to the class of synovial joints, a
to the subdivision of hinge joints. The articular surfaces are (1) t
anterior part of the articular fossa in front of the squamo-tympai
fissure, and (2) the head of the mandible.
 
Ligaments.— The capsular ligament consists of scattered fibr
which form a thin loose investment to the joint on its anterior, medi
and posterior aspects, being completed on the outer aspect by t
temporo-mandibular ligament.
 
The temporo-mandibular ligament (external lateral ligament) is
 
short strong bundle of fibres, which is attached above to the tuber*
of root of the zygoma, and below to the condylar tubercle and the out
and back part of the neck of the mandible. Its fibres are direct
obliquely downwards and backwards. This ligament forms the latei
portion of the capsular ligament.
 
The spheno-mandibular ligament (long internal lateral ligament)
a long flat band, which stands off from the joint, and therefore has :
direct relation to it. It is somewhat triangular, being narrow abo
and broad below. Superiorly it is attached to the spine of the sphenc
bone, and interiorly to the lingula and the inner margin of the mandibul
foramen. Its fibres are directed downwards and slightly forwarc
The first part of the maxillary artery separates it from the neck
the mandible; and inferiorly the inferior dental vessels and ner
intervene between it and the ramus of the mandible. At its low
attachment it is spread over the upper end of the mylo-hyoid groo\
and is here pierced by the mylo-hyoid nerve and artery. The maxilla
 
 
THE HEAD AND NECK
 
 
1317
 
 
:ry and the auriculo-temporal nerve pass between the temporoldibular and spheno-mandibular ligaments.
 
rhe spheno-mandibular ligament is formed beside the skeletal bar of the
visceral arch.
 
 
Capsular Ligament
 
 
 
Fig. 797.—The Mandibular Joint (Medial Aspect).
 
 
The stylo-mandibular ligament is a stout process of the deep cervical
:ia, which extends from the styloid process of the temporal bone
tr its tip to the angle and adjacent portion of the posterior border
 
 
Articular Disc
 
 
 
Fig. 798.—The Mandibular Joint opened (Lateral Aspect).
 
 
the ramus of the mandible. Superiorly it gives origin to a few
res of the stylo-glossus and interiorly it is implanted between the
sseter and medial pterygoid muscles. It separates the subman>ular gland from the lower portion of the parotid gland.
 
 
 
 
 
 
 
 
 
1318
 
 
A MANUAL OF ANATOMY
 
 
The articular disc is an oval plate which is interposed between t]
two articular surfaces. It is thinnest at the centre, where it is occ
sionally perforated, and thickest posteriorly. Its superior surface
concavo-convex from before backwards, in adaptation to the co
vexity of the articular eminence and the concavity of the articul
fossa. Its inferior surface is concave, and fits upon the head of ti
mandible. Its circumference is connected with the capsular ligamer
and anteriorly it gives partial insertion to the lateral pterygoid muse]
It divides the joint into two compartments, upper and lower, whit
are usually distinct.
 
The synovial membranes are two in number, upper and lower, oi
being above and the other below the articular disc. The upper synovi
membrane is larger and looser than the lower, and when the articul;
disc is perforated at the centre, the two synovial cavities are continuoi
through the perforation.
 
Arterial Supply .—The superficial temporal artery chiefly.
 
Nerve-supply .—The auriculo-temporal nerve and offsets from tl
masseteric nerve.
 
Movements. —These are as follows: (1) depression, (2) elevation, (3) protra
tion, (4) retraction, and (5) lateral movements. There being two divisions
the joint, upper and lower, different movements occur in each. The movemei
in the upper compartment is of a gliding character, whilst in the lower compartme
it is of a hinge character. When the mandible is depressed, as in opening t]
mouth, the head and the articular disc move forwards on to the articular eminent
In cases of over-depression, as in violent yawning, or forcing too large a boc
into the mouth, the head is apt to slip over the articular eminence into tl
infratemporal fossa, and when this takes place dislocation of the mandible
the result. The movement of forward gliding on the part of the head at
articular disc during depression takes place in the upper compartment of tl
joint. Another movement, however, of a hinge character is taking place in tl
lower compartment of the joint between the head and the articular disc. This co
sists in the head rotating on the under surface of the plate round a transverse axi
 
When the mandible is elevated, as in shutting the mouth, the changes whi<
occur in both compartments of the joint are the reverse of those just describe
as taking place in depression. The head and articular disc glide backwan
into the articular fossa, and at the same time the head rotates back to its previoi
position. In protraction, as when the lower incisors are protruded beyond tl
upper, and in retraction, the movement mainly takes place in the upper cor
partment of the joint, and consists in the head and the articular disc glidii
forwards and backwards. When these movements are performed alternate
on each side the lateral oblique movements, as in grinding or chewing, take plac
and the head and the articular disc of one side move forwards and backward
whilst the other head and the articular disc move in the opposite directio
During these movements oblique rotation is taking place in the lower compar
ment of the joint.
 
Muscles concerned in the Movements.—Depression is effected by the platysm
mylo-hyoid, anterior belly of the digastric, and genio-hyoid muscles; and elev.
tion by the anterior fibres of the temporal, masseter, and medial pterygo
muscles. Protraction is produced by the lateral pterygoid, the superficial fibr
of the masseter, and slightly by the medial pterygoid; and retraction by tl
posterior fibres of the temporal and the deep fibres of the masseter. The grindil
movement is effected by the lateral pterygoid muscles acting alternately. Tl
axis of the movement in opening and closing the mouth passes through tl
mandibular foramina.
 
 
 
THE HEAD AND NECK
 
 
1319
 
 
The Maxillary Nerve.
 
 
The maxillary nerve is the second division of the trigeminal nerve,
1 in size is intermediate between the mandibular and the ophthalmic,
is entirely sensory, and arises from the trigeminal ganglion. Its
irse is forwards to the foramen rotundum, by which it leaves the
nial cavity. Then it enters the posterior part of the pterygoatine fossa, and crosses the upper part of that fossa to the inferior
)itai fissure, through which it passes on to the floor of the orbit. It
w takes the name of the infra-orbital nerve, and traverses the infra)ital groove, and then the infra-orbital canal, on the floor of the
)it. Finally, it leaves this canal through the infra-orbital foramen
der cover of the levator labii superioris, and ends in its terminal
inches. The course of the maxillary nerve and its continuation,
> infra-orbital nerve, is almost directly forwards, with a slight
•lination outwards just before the orbit is entered.
 
Branches.— These are as follows:
 
 
In Infra-orbital Canal.
 
Middle superior dental.
Anterior superior dental.
 
 
Intracranial.
 
Meningeal.
 
 
On the Face.
 
Palpebral.
 
Nasal.
 
Labial.
 
 
In the Pterygo-palatine Fossa.
 
Zygomatic.
 
Ganglionic.
 
Posterior superior dental.
 
 
The meningeal branch supplies the dura mater of the middle
anial fossa.
 
The zygomatic nerve (temporo-malar nerve) is the first branch of
e maxillary in the pterygo-palatine fossa. It arises from its uppei
rface, and enters the orbit through the inferior orbital fissure. F01
; further course, see p. 1259.
 
The ganglionic branches (spheno-palatine nerves) are two in number,
ley arise from the lower aspect of the parent trunk, and, aftei a
:ry short descending course, they end for the most part in the sphenoilatine ganglion, to which they convey sensory fibres, and of which
ey are the sensory roots. Man} 7 of their fibres, howevei, pass cleai
the grey matter of the ganglion, and are prolonged into the nasal
 
id palatine branches of the ganglion.
 
The posterior superior dental branches arise from the maxillaiy as
is about to pass through the inferior orbital fissure. They are
mally two in number, but sometimes they arise by a single trunk,
hey descend in grooves on the posterior surface of the maxilla in
impany with branches of the posterior superior dental artery, and
ve off branches to the gum and contiguous parts of the mucous
membrane of the cheek. Then they traverse the posterior denta
inals, and within the substance of the bone communicate with each
filer and with the middle superior dental nerve to form a delicate
exus, from which branches are given^off to the pulps ot the thiee
 
 
 
!32o A MANUAL OF ANATOMY
 
upper molar teeth. Slender filaments are also furnished to the mucc
membrane lining the maxillary sinus.
 
The middle superior dental branch arises from the main trunk
it lies in the infra-orbital groove near the inferior orbital fissure,
descends in the middle dental canal of the maxilla. Its brand
communicate with each other, and with the posterior superior a
anterior superior dental branches within the substance of the boi
to form a delicate plexus, from which branches are given to the pu]
of the upper two premolar teeth and to the gum. This nerve a'
furnishes delicate filaments to the mucous membrane lining t
maxillary sinus. Two enlargements are described in connection wi
the middle superior dental branch. One is situated at its communk
tion with the posterior superior dental branch, and is known as t
ganglion 0} T alentin ; and the other at its communication with t
anterior superior dental, this one being known as the ganglion
Bochdalek. 86
 
The anterior superior dental branch arises from the infra-orbil
 
nerve near the front part of the infra-orbital canal, and descends,
company with the anterior superior dental artery, in the anterior deni
canal. Its branches communicate with each other, and with the midc
superior dental branch, to form a delicate plexus, from which branch
are given to the pulps of the upper canine and incisor teeth. Tt
nerve also furnishes delicate filaments to the mucous membrane linii
the maxillary sinus, and a nasal branch, which enters the nasal cavi
and supplies the mucous membrane of the anterior part of the infer!
meatus and adjacent portion of the inferior nasal concha.
 
The facial branches of the infra-orbital nerve—palpebral, nas£
and labial—have been already described (see p. 1276).
 
It is to be noted that there are three superior dental branche
the posterior being a branch of the maxillary, and the middle and anteri
being branches of the infra-orbital; whilst there is onlv one infer!
dental nerve, which is a branch of the mandibular.
 
Spheno-palatine Ganglion (Meckel’s Ganglion). —It is a sms
triangular, somewhat reddish body, situated in the upper part of tl
pterygo-palatine fossa close to the spheno-palatine foramen, whic
leads through the inner wall of the fossa to the superior meatus of tl
nasal cavity. It is suspended from the maxillary nerve by some <
the fibres of the two ganglionic branches of that nerve, many fibr<
of these two branches passing clear of the grey matter of the ganglic
into its nasal and palatine branches. The fibres conveved to tl
grey matter of the ganglion by the two ganglionic branches represer
its sensory root or roots.
 
The ganglion has sensory and sympathetic roots, but no mote
root. The sensory roots are derived from two sources—maxillary an
facial. The maxillary sensory root-fibres form two bundles, an
represent portions of the two ganglionic branches, by which the ganglio
is suspended from the trunk of the maxillary nerve in the pterygc
palatine fossa. The facial sensory root-fibres are represented by tb
 
 
THE HEAD AND NECK
 
 
1321
 
 
iter superficial petrosal nerve , which is a branch of the ganglion
the facial nerve. The sympathetic root is formed by the deep
vsal nerve from the carotid plexus of the sympathetic.
 
The facial sensory root (greater superficial petrosal) and the svmhetic root (deep petrosal) join to form the nerve of the pterygoid
al in the foramen lacerum. After traversing the pterygoid canal
n behind forwards, the nerve enters the pterygo-palatine fossa
l joins the back part of the spheno-palatine ganglion. In the
rygoid canal the nerve gives off one or two nasal branches, which
lS through the floor of the canal, and are distributed to the mucous
mbrane of the posterior part of the roof of the nasal cavity and
acent part of the septum.
 
 
Short Spheno-palatine Nerves Ganglionic Branches from Maxillary
Olfactory Filaments j i Nerve of Pterygoid Canal
 
 
 
Nasal Branches
 
 
i. 799. —Nerves of the Nasal Cavity, and the Spheno-palatine Ganglion,
with its Branches (Medial Aspect) (Hirschfeld and Leveill£).
 
 
Branches of the Spheno-palatine Ganglion. —These are arranged in
ir sets:
 
 
iscending.
 
Orbital.
 
 
Posterior.
 
Pharyngeal.
Nerve of pterygoid canal.
 
 
Medial.
 
Short sphenopalatine.
Long sphenopalatine.
 
 
Descending.
 
Greater palatine.
Lesser palatine.
 
 
Ascending Branches.—Orbital branches are two or three in number,
d enter the orbit through the inferior orbital fissure to be distributed
the periosteum. Thev have been described by Luschka as sending
iments through the inner wall of the orbit to supply the mucous
mbrane of the posterior ethmoidal and sphenoidal sinuses.
 
Posterior branches are the pharyngeal nerve and the nerve of the
irygoid canal. The pharyngeal nerve passes backwards in the
 
 
 
 
 
 
I 3 22
 
 
A MANUAL OF ANATOMY
 
 
palatovaginal canal along with the pharyngeal branch of the maxillai
artery, and is distributed to the mucous membrane of the upp<
part of the pharynx in the region of the orifice of the pharyngi
tympanic tube.
 
Medial branches are the long and short spheno-palatine nerve
The short spheno-palatine nerves (superior nasal nerves) are of sma
 
size, and derive some of their fibres from the ganglionic branches <
the maxillary nerve. They are about six in number, and, springir
from the inner part of the ganglion, they enter the superior meatus <
the nose through the spheno-palatine foramen. They supply tl
mucous membrane of the superior and middle conchae, the superb
meatus, the posterior ethmoidal sinus, the middle meatus, and tl
upper and back part of the septum.
 
The long spheno-palatine nerve (naso-palatine nerve) enters tl
nasal cavity along with the short spheno-palatine nerves. It cross<
the roof of the cavity, and then passes downwards and forwards upc
the septum, lying in the groove on the lateral surface of the vome
Having arrived at the incisor crest, the left long spheno-palatir
nerve descends through the anterior incisive canal, and the rigl
descends through the posterior. Having reached the incisive fos<
in this manner, the two nerves communicate in a plexiform manne
and delicate filaments are furnished to the mucous membrane of tl
hard palate behind the incisor teeth. In this situation communic;
tions are established with the greater palatine nerve of each sid<
As the long spheno-palatine nerve traverses the groove on the later;
surface of the vomer, it furnishes twigs to the mucous membrane <
the nasal septum, and in this part of its course it is accompanied b
the posterior septal branch of the spheno-palatine artery; but th
artery does not accompany it through the median incisive canal.
 
Descending branches are the greater and lesser palatine nerve
They arise from the lower part of the ganglion, usually by a commo
trunk, and they derive some of their fibres from the ganglionic branch*
of the maxillary nerve.
 
The greater palatine nerve descends in the greater palatine cana
and escapes from it through the greater palatine foramen. Then
divides into branches which pass forwards and inwards, occupyin
grooves on the hard palate, to the mucous membrane and glands (
which, as well as to the mucous membrane of the upper gum on it
inner aspect, they are distributed. In the region of the incisive foss
this nerve communicates with the long spheno-palatine nerve. A
it descends in the greater palatine canal it furnishes nasal branche
which enter the nasal cavit}/, and are distributed to the mucoi
membrane over the inferior concha,, except anteriorly, and to that <
the adjacent portion of the inferior meatus. The lesser palatine nerv<
descend in the lesser palatine canal, after emerging from which the
are distributed to the mucous membrane of the soft palate and tonsi
They have been said to furnish branches to the levator palati an
musculus uvulae, the fibres of these branches being derived from tl
 
 
 
 
 
THE HEAD AND NECK
 
 
i 3 2 3
 
 
liculate ganglion of the facial through the great superficial petrosal,
ich contributes to the formation of the nerve of the pterysoid canal,
i conveys motor fibres to the ganglion. The two muscles in question,
wever, are supplied by the bulbar part of the accessory nerve through
; pharyngeal plexus.
 
Summary of the Maxillary Nerve and the Spheno-palatine Ganglion.—1. Cuteous Distribution. —(1) The skin of the anterior part of the temporal region,
I over the zygomatic bone; (2) the skin from the lower eyelid down to the
per lip, including the skin of the side of the nose; (3) the mucous membrane
the naso-pharynx in the vicinity of the orifice of the pharyngo-tympanic;
the mucous membrane of the nasal cavity; (5) the mucous membrane of the
xillary sinus; (6) the mucous membrane of the soft palate and tonsil; and
the mucous membrane of the hard palate, with its glands, and that of the
ler surface of the upper gum. 2. Dental Distribution. —The pulps of all the
per teeth of one side, as well as the mucous membrane of the outer surface of
j upper gum.
 
In addition to the foregoing, the maxillary nerve supplies the periosteum of
? orbit, and the dura mater of the middle cranial fossa.
 
 
Deep Dissection of the Neck.
 
Stylo-pharyngeus — Origin .—The base of the styloid process of the
mporal bone on its inner aspect.
 
Insertion. —(1) The posterior border of the lamina of the thyroid
rtilage, and (2) the lateral wall of the pharynx, its fibres blending
th those of the palato- g-fv. process
 
 
 
 
 
 
 
 
 
 
 
 
 
1324
 
 
A MANUAL OF ANATOMY
 
 
bone, and, after traversing this canal, it enters the cranial cavit
The vessel is divided into three parts—cervical, petrous, and cavernoi
 
The Cervical Part. —This part of the vessel extends from the level
the upper border of the thyroid cartilage to the carotid canal on t
inferior surface of the petrous part of the temporal bone. Its com
is upwards, and at first it lies in the carotid triangle, where it is plac
lateral to and behind the external carotid artery.
 
Relations — Superficial .—This part of the vessel is comparative
superficial, being covered by the integument,, platysma, and sterr
mastoid, the latter overlapping it. After leaving the carotid trian^
the artery becomes deeply placed, and passes deep to the posteri
belly of the digastric and stylo-hyoid muscles, parotid gland, style
process, and stylo-pharyngeus muscle. In this part of its com
the vessel is crossed by the hypoglossal, accessory, and glosso-phary
geal nerves, and the pharyngeal branch of the vagus, and by t
occipital and posterior auricular arteries. The relation of the arte
to the external carotid here undergoes a change. The level where t
change takes place is as the internal carotid passes deep to the stylo
process of the temporal bone, and the change consists in the extern
carotid taking up a position directly anterior to the internal caroti
I he two arteries are, however, separated from each other by the folio 1
ing structures: (i) the styloid process or stylo-hyoid ligament; (2) t'
stylo-pharyngeus muscle; (3) the glosso-pharyngeal nerve; (4) t'
pharyngeal branch of the vagus; and (5) the parotid gland.
 
Posterior .—The longus capitis, the superior cervical ganglion
the sympathetic, and the superior laryngeal branch of the vagus.
 
Lateral .—The internal jugular vein and vagus nerve, the ner
being on a plane posterior to both artery and vein. These thr
structures are still surrounded by a sheath which is an upward e
tension of the carotid sheath previously described. Close to t.
base of the skull the glosso-pharyngeal, accessory, and hrypogloss
nerves lie between the internal artery and the internal jugular vei
The glosso-pharyngeal nerve soon passes forwards superficial to t.
artery, the accessory nerve passes backwards superficial to the vei
and the hypoglossal nerve passes forwards superficial to the arte
at the lower border of the posterior belly of the digastric muscle.
 
Medial .—The ascending pharyngeal artery, the lateral wall
the pharynx, the tonsil, and the superior laryngeal nerve.
 
Development. —The internal carotid artery is developed from the thi
aortic arch and the part of the dorsal aorta in front of this arch.
 
The Glosso-pharyngeal Nerve.
 
The glosso-pharyngeal or ninth cranial nerve is a mixed nerv
consisting of both afferent or sensory and efferent or motor fibre
It leaves the cranial cavity through the middle compartment of t]
jugular foramen, along with the vagus and accessory nerves, bi
enclosed in a separate sheath of the dura mater, and lying anteri
 
 
THE HEAD AND NECK
 
 
1325
 
 
 
these two nerves. In passing through the jugular foramen the
ve has two ganglia, the upper one, which is small and situated
the upper part of the foramen, being called the superior ganglion
yular ganglion) ; and the lower one, which is rather larger, being
ied the inferior ganglion {petrous ganglion). The latter is about
ich in length, and lies in the lower part of the foramen, where it
upies a groove on the petrous portion of
temporal bone. After leaving the jugular
mien, the nerve at first descends between
internal carotid artery and internal jugular
n, being lateral to the vagus nerve. It
n passes downwards and forwards in front
the internal carotid artery, and under
r er of the styloid process, stylo-pharyngeus
scle, and external carotid artery. It next
ves round the hinder border of the styloiryngeus, and crosses it (Fig. 800) superally in a forward direction. Finally, it
;ses deep to the hyo-glossus muscle, and
reaches the posterior third of the tongue,
ere it divides into its terminal branches.
 
The superior ganglion (jugular ganglion), as
ted, is very small, and involves only a few
the fibres of the nerve, the other fibres
>sing clear of, but close to, the ganglion,
 
I being continued into the nerve beyond it.
is ganglion neither gives nor receives any branches, and is someles absent.
 
The inferior ganglion (petrous ganglion), unlike the jugular, Fives all the fibres of the nerve, and it furnishes connecting branches
I the tympanic nerve.
 
Branches of the Glosso-pharyngeal Nerve—1. From the Inferior
Qglion — (a) Branches of Communication .—One to the superior cervical
lglion of the sympathetic; one to the auricular branch of the superior
lglion of the vagus; and one to the superior of the vagus.
 
(b) Branch of Distribution. —This is called the tympanic nerve
rve of Jacobson). After leaving the inferior ganglion it ascends,
company with the tympanic branch of the ascending pharyngeal
ery, through the canaliculus for the tympanic nerve. In this
y it enters the tympanic cavity at the junction of the inner wall and
ir, and ascends upon the inner wall. Being joined by the caroticonpanic branch of the carotid plexus of the sympathetic, it breaks
into branches which occupy grooves upon the promontory and
m the tympanic plexus. From this plexus the tympanic nerve
erges under the name of the lesser superficial petrosal nerve, which
ves the tympanic cavity and traverses a minute canal in the petrous
tie, passing in its course beneath the upper portion of the canal
ich lodges the tensor tympani muscle. Whilst in this canal it is
 
 
Fig. 801.—Sketch showing the Relations between Ninth, Tenth,
Eleventh, and
Twelfth Nerves, in
Carotid Sheath just
below Skull.
 
 
 
 
1326
 
 
A MANUAL OF ANATOMY
 
 
Auriculo temporal Nerve
Facial Nerve j
Posterior Auricular Nerve •, .
 
 
Glosso-pharyngeal Nerve
Accessory Nerve .
 
 
Greater Occipital Nerve
Hypoglossal Nerve
 
 
Sup. Cervical Symp. Ganglion —
External Carotid Artery
Internal Carotid Artery
Sympathetic Trunk.
 
Com. Car. Art. and'Symp. Plexus — V|j
Phrenic Nerve -jM I
 
 
Right Ansa Subclavia
 
 
First Thoracic Ganglion
 
 
Right Posterior-;
 
Pulmonary Plexus
 
 
Vena Azygos
Vascular Branch
 
 
Intercostal Vessels (
and Nerve 1 r
 
 
Ramus Communicans
Sympathetic Trunk
 
 
Lesser Splanchnic Nerve—Greater Splanchnic Nerve
Lowest Splanchnic Nerve.'
 
 
 
SL _
 
W m Hypoglossal Nerve
 
vZffl _ Superior Laryngeal Nerve
 
yriff-T . Vagus Nerve
 
- Middle Cervical Sympathetic
 
Ganglion
 
••jS-imv _ Recurrent Laryngeal Nerve
 
_Cardiac Branches of Vagus
 
_ Phrenic Nerve
 
Timex -- ’
 
rfii
 
 
_ Root of Right Lung
 
 
.. Right Vagus Nerve
on CEsophagus
 
 
CEsophageal Plexus
 
 
Liver (cut)
 
Left Vagus Nerve
 
 
A.Descending Aorta
Thoracic Duct
 
 
\ Branches of Vagus
I on Stomach
 
 
Right Coeliac Ganglion
"Coeliac Plexus
 
 
'•'Superior Mesenteric Artery
and Plexus
 
 
Renal Artery and Plexus Abdominal Aorta
 
S.V.C. Superior Vena Cava
 
 
I’ig. 802.—Nerves of the Right Side of the Face, Neck, and Thorax
 
(HlRSCHFELD AND LeVEILLEI.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1327
 
 
Led by a communicating branch from the ganglion of the facial
ve. It leaves the canal through the hiatus for the lesser superil petrosal nerve on the surface of the petrous bone, and then
ses forwards and inwards beneath the dura mater. After this
asses through the canaliculus innominatus, when present, or through
fissure between the petrous temporal and greater wings of the
Lenoid, or sometimes through the foramen ovale, into the infraiporal fossa, where it joins the otic ganglion, to which it conducts
sso-pharyngeal and facial fibres.
 
2. From the Trunk of the Nerve. —(1) A communicating branch
netimes passes from the nerve a little below the inferior ganglion
join the digastric branch of the facial nerve. (2) A carotid branch
ises to the sympathetic plexus on the internal carotid artery.
Pharyngeal Branches. —These are about four in number. Three of
im unite, over the middle constrictor of the pharynx, with the subnsions of the pharyngeal branch of the vagus, and with branches
the superior cervical ganglion of the sympathetic, to form the
aryngeal plexus. The other pharyngeal branch pierces the superior
istrictor, and is distributed to the mucous membrane of the upper
rt of the pharynx. (4) A muscular branch to the stylo-pharyngeus
iscle, some of the fibres of which pierce the muscle to supply the
icous membrane of the pharynx. (5) Tonsillar branches form a
cular plexus round the tonsil, known as the circulus tonsillaris;
>m it branches supply the tonsil and region of the oro-pharyngeal
hmus. (6) Lingual Branches. —Under cover of the hyo-glossus
iscle, the terminal part of the nerve divides into two branches,
rsal and lateral. The dorsal branch passes to the vallate papillae
d the mucous membrane over the posterior third of the tongue,
tending as far back as the front of the epiglottis. The lateral branch
distributed to the mucous membrane of the side of the tongue
r er about its posterior half.
 
Summary of the Glosso-pharyngeal Nerve— i- Cutaneous Distribution.— It
 
pplies (a) the mucous membrane of the tympanic cavity, the posterior third
the tongue, the region of the oro-pharyngeal isthmus, and the pharynx, and
the tonsil. 2. Muscular Distribution.— The stylo-pharyngeus. 3. Glandular
stribution.— Through (1) its tympanic, subsequently lesser superficial petrosal,
anch, (2) the otic ganglion, and (3) the auriculo-temporal neive, it furnishes
:retory branches to the parotid gland.
 
The Vagus Nerve in the Neck.
 
The vagus, or tenth cranial, is a mixed nerve, consisting of both
ferent and efferent fibres. It leaves the cranial cavity through the
iddle compartment of the jugular foramen, being enclosed m the
.me sheath of dura mater as the accessory, and, with that nerve,
ing posterior to the glosso-pharyngeal. In the foramen it presents
small enlargement called the superior ganglion. ATter emerging from
le foramen it is joined by the cranial root of the accessory nerve,
id here there is another enlargement, called the inferior ganglion.
 
 
1328
 
 
A MANUAL OF ANATOMY
 
 
This ganglion is larger and longer than the superior ganglion, full
j inch in length, and presenting a somewhat plexiform appearana
In this part of its course the nerve lies between the internal caroti
artery and the internal jugular vein, the glosso-pharyngeal nerve bein
in front of it and the accessory behind it. The hypoglossal'nerv
lies at first deeply behind it, but subsequently turns round the oute
side of the inferior ganglion. The vagus then descends within th
carotid sheath, lying at first between the internal carotid artery an
the internal jugular vein, and then between the common carotid arter
and the internal jugular vein, being on a plane posterior to both vessels
Within the sheath the nerve occupies a special compartment, situate
in the back part of the septum which separates the artery from th
vein. Below the root of the neck the right and left nerves have impor
tant differences in their course and relations.
 
Branches —A. The Superior Ganglion (Ganglion of the Root)1. Branches of Communication. — (a) It receives two filaments from th
cranial root of the accessory nerve. ( b) It communicates by a smal
twig with the inferior ganglion of the glosso-pharyngeal nerve. ( c ) I
communicates with the facial, and with the posterior auricular brand
of the facial, through its auricular branch of distribution, (d) I
receives a twig from the superior cervical ganglion of the sym
pathetic.
 
2. Branches of Distribution. — (a) The meningeal branch takes c
recurrent course, and, after entering the cranial cavity, supplies th<
dura mater which lines the cerebellar fossa of the occipital bone
( b ) The auricular branch is of small size, and is soon reinforced by a twi£
from the inferior ganglion of the glosso-pharyngeal. It enters th(
mastoid canaliculus through an aperture on the outer wall of th(
jugular fossa. In this canaliculus it traverses the petrous portion 0:
the temporal bone, crossing in its course the inner aspect of the
descending portion of the facial canal a little above the stylo-mastoic
foramen, where it forms its first communication with the facial nerve
It then leaves the petrous temporal through the tympano-mastoic
fissure, between the mastoid process and the tympanic plate, and
then divides into two branches. One of these joins the posterioi
auricular branch of the facial nerve, and the other is distributed tc
(1 a ) the skin of the inner surface of the auricle, and (b) the skin of the
lower and back part of the external auditory meatus.
 
B. The Inferior Ganglion (Ganglion of the Trunk)— 1. Branches
of Communication. — (a) The most important branch of communication
is the cranial root of the accessory nerve , which passes over the surface
of the ganglion in intimate contact with it. Most of the cranial fibres
are continued into the pharyngeal and superior laryngeal nerves, but
some of them descend in the main trunk of the vagus, and pass into
its cardiac and inferior laryngeal branches. The cranial fibres are to
be regarded as of two kinds—namely, motor , for the muscles of the soft
palate, pharynx, and larynx; and cardiac inhibitory, (b) Branches
pass between the inferior ganglion and the hypoglossal nerve, (c) A
 
 
 
THE HEAD AND NECK
 
 
1329
 
 
municating branch is received from the superior cervical ganglion
le sympathetic.
 
Branches of Distribution.—These are pharyngeal and superior
ngeal.
 
fhe pharyngeal branch arises from the upper part of the inferior
jlion, its fibres being chiefly derived from the cranial root of the
ssory nerve. It passes forwards and downwards between the
rnal and external carotid arteries, and divides into branches opposite
middle constrictor muscle, which join the pharyngeal branches of
^losso-pharyngeal and superior cervical ganglion of the sympathetic
)rm the pharyngeal plexus.
 
rhe pharyngeal plexus is situated upon the middle constrictor
cle opposite the greater horn of the hyoid bone. It is formed by
;he pharyngeal branch of the inferior ganglion of the vagus, derived
inally from the accessory; (2) the pharyngeal branches of the glossoryngeal; and (3) the pharyngeal branches of the superior cervical
^lion of the sympathetic.
 
Branches are distributed to (1) the constrictor muscles of the phai ynx,
the mucous membrane of the pharynx; and (3) the palato-glossus,
ito-pharyngeus, levator palati, and musculus uvulae. In this way
the muscles of the soft palate except the tensor palati are supplied
the accessory nerve. Branches of communication pass between
plexus and the superior laryngeal and external laryngeal nerves,
another branch, known as the lingual bvanch of the vagus, passes
 
:he hypoglossal nerve. .
 
Superior Laryngeal Nerve.—This nerve, which is principally sensory,
;es from the inferior ganglion of the vagus near its centre, and contains
es of the cranial root of the accessory nerve. It passes downwaids
1 forwards behind the internal carotid artery, having received comnicating branches from the superior cervical ganglion of the symhetic and from the pharyngeal plexus. As it passes behind the mnal carotid artery it divides into two branches, internal and externa .
5 internal laryngeal nerve, which is sensory, passes forwards, m
npany with the superior laryngeal branch of the superioi thyroi
ery, to the thyro-hyoid membrane, which it pierces under cover of
: posterior border of the thyro-hyoid muscle. Having reached the
erior of the larynx, it divides into branches which supply the mucous
mbrane of the epiglottis with its folds, a little of the back of the
igue, the mucous membrane of the larynx as low as the vocal to ds,
I that covering the lateral and posterior portions of the cricoid cartie. One branch descends over the inner surface of the lamina °f the
/roid cartilage, and joins a branch of the lecunent aiyngea . e
;ernal laryngeal nerve, of small size, descends deep o e s emo
^roid muscle to the crico-thyroid muscle, which it supplies. It
'nishes some twigs to the inferior constrictor, and a amen w ic \
ns the superior cardiac branch of the sympathetic. rec ? 1 ., s
communicating branch from the supeiior ceivica gang ion o c
 
npathetic, and one or two branches from the pharyngea p exus.
 
84
 
 
1330
 
 
A MANUAL OF ANATOMY
 
 
Recurrent Laryngeal Nerve. —This nerve is mainly motor, and
the principal motor nerve of the intrinsic muscles of the larynx,
contains fibres of the cranial root of the accessory nerve. The ri{
nerve arises from the vagus at the root of the neck in front of t
hrst. part of the subclavian artery, round the lower border of which
bends, and then ascends behind it. Then it passes upwards ai
inwards behind the carotid sheath and inferior thyroid artery to t
groove between the trachea and the oesophagus. The left nerve aris
in the thorax from the vagus in front of the arch of the aorta on a le\
with its lower border. It passes backwards below the arch and to t
left of the ligamentum arteriosum, and then it turns upwards behii
the arch. Having reached the groove between the trachea and t'
oesophagus, it ascends therein to the neck. The right and left nerv
pass upwards in the groove between the trachea and the cesophag
on each side, lying usually behind the corresponding inferior thyro
artery and in close relation with the lobes of the thyroid gland, i
the level of the cricoid cartilage each nerve passes beneath the low
border of the inferior constrictor muscle, and enters the larynx behii
the crico-thyroid joint.
 
Extralaryngeal Branches. —(i) Communicating twigs pass betwe<
the recurrent laryngeal nerve and the inferior cervical ganglion of tl
sympathetic; (2) cardiac branches, which contain cranial fibres fro
the accessory, are furnished to the deep cardiac plexus; (3) trache
and oesophageal branches are supplied to these tubes; and (4) muscul
offsets pass to the lower part of the inferior constrictor.
 
Intralaryngeal Branches. —These are chiefly muscular, and supp
the intrinsic muscles of the larynx, except the crico-thyroid, whi(
is supplied by the external laryngeal nerve. Sensory branches, howeve
are given to the laryngeal mucous membrane below the vocal fold
except over the lateral and posterior portions of the cricoid cartilag
Within the larynx the nerve communicates with a branch of tl
internal laryngeal nerve under cover of the lower part of the lamir
of the thyroid cartilage.
 
For the explanation of the recurrent course of each recurrei
laryngeal nerve, see p. 1121.
 
Cardiac Branches. —These are subject to variation as regan
numbers. As a rule there are two, upper and lower, both of whic
contain cranial fibres from the accessory. Those of the right sic
pass behind the first part of the subclavian artery, and end in tl
deep cardiac plexus. On the left side the upper nerve passes to tl
deep cardiac plexus, but the lower nerve ends in the superficial cardie
plexus.
 
Summary of the Vagus Nerve in the Neck— 1. Motor Distribution. —(1) Tl
 
muscles of the soft palate by accessory fibres, except the tensor palati; (2) tl
constrictor muscles of the pharynx; (3) the intrinsic muscles of the larynx; ar
(4) the muscular tissue of the oesophagus and trachea. 2. Sensory Distribution.It supplies (1) the pharynx, oesophagus, and trachea; (2) a limited portion of.tl
dura mater; and (3) a small portion of the skin on the inner surface of the auricl
as well as of the lower and back part of the external auditory meatus. 3. Con
 
 
 
THE HEAD AND NECK
 
 
I 33 I
 
 
.cations. —Each vagus nerve forms connections with the facial, glossoyngeal, accessory, hypoglossal, and sympathetic nerves. It is also con:d with the loop between the first and second cervical spinal nerves. Its
important connection is that which is established with the cranial root of
icessory nerve. The bulbar fibres of the nerve are probably chiefly conid in the innervation of the muscles of the soft palate (except the tensor
;i), pharynx, and larynx, but also to a certain extent in the innervation of
leart.
 
 
Accessory Nerve.
 
fhe accessory or eleventh cranial nerve consists of two roots—
ial and spinal. In the jugular foramen these two parts either
e to form one trunk or freely intermingle, and a communication
stablished between the cranial root and the superior ganglion of
vagus by means of two twigs. The nerve passes through the
liar foramen, being enclosed
he same sheath of dura mater
he vagus, behind which it lies,
lediately beneath the jugular
men the two parts of the nerve
irate from each other,
rhe cranial root passes over,
in intimate contact with, the
rior ganglion of the vagus,
its fibres are continued partly
• the pharyngeal and superior
ngeal branches of the inferior
glion, and partly into the
lk of the vagus below the
glion. These latter fibres are
mately prolonged into the
iiac and recurrent laryngeal
riches of the nerve. The
lial fibres of the accessor}/
regarded as (i) the motor nerves of (a) the muscles of the soft
ite, except the tensor palati, (b) the constrictor muscles of the
,rynx, and (c) the intrinsic muscles of the larynx; and (2) the
ibitory fibres of the heart.
 
The spinal root of the accessory nerve passes backwards and downds either behind or in front of the internal jugular vein. It then
*ces the deep surface of the sterno-mastoid, which it supplies along
h a branch of the second cervical nerve. Then it crosses the
terior triangle of the neck obliquely downwards and backwards to
anterior border of the trapezius, beneath which it passes, supplying
muscle, in company with branches from the third and fourth
rical nerves.
 
Summary. —The spinal root of the accessory nerve supplies the trapezius and
sterno-mastoid. The cranial root, through its connection with the vagus
/e and its branches, supplies (1) the muscles of the soft palate, except the
 
 
 
Fig. 803. —Showing Relations between Accessory Nerve, Hypoglossal Nerve, and Occipital
Artery a little below Skull
Base.
 
 
 
1332
 
 
A MANUAL OF ANATOMY
 
 
tensor palati; (2) the constrictor muscles of the pharynx; and (3) the intrin
muscles of the larynx. It also furnishes the inhibitory fibres of the heart, wh:
reach that organ through the cardiac branches of the vagus.
 
 
Hypoglossal Nerve.
 
 
The hypoglossal or twelfth cranial nerve consists at first of b
bundles, which pierce the dura mater separately. In passing throu
the anterior condylar canal these two bundles unite to form one trur
After leaving that canal the nerve lies deeply under cover of the interr
carotid artery and internal jugular vein. It then turns round t
outer side of the inferior ganglion of the vagus, with which it is close
connected, and passes forwards between the internal carotid arte
and internal jugular vein. Then it descends to the lower border
the posterior belly of the digastric, at which level it hooks round t
occipital artery from without inwards, and crosses in front of t
external carotid artery and its lingual branch. In this part of i
course the nerve lies in the superior carotid triangle. It next ru
forwards above the hyoid bone, passing deep to the tendon of f
digastric and the lower part of the stylo-hyoid muscle, and superfici
to the hyo-glossus. After this it disappears deep to the mylo-hyoi
still resting upon the hyo-glossus, where it is accompanied by tl
vena comitans hypoglossi, and is covered by the deep part of t]
submandibular gland. At the anterior border of the hyo-glossus
is connected with the lingual nerve, and then enters the genio-glossr
 
Branches —1. Of Communication. —After leaving the anterior co
dylar canal, the hypoglossal nerve .communicates with the infer!
ganglion of the vagus. It then receives a branch from the super!
cervical ganglion of the sympathetic, and one from the first cervic
nerve, or the loop between the first and second. As it hooks rour
the occipital artery it receives the lingual branch of the vagus fro
the pharyngeal plexus; and at the anterior border of the hyo-glossi
it is connected with the lingual nerve.
 
2. Of Distribution. —One or two meningeal branches arise from tl
nerve in the anterior condylar canal, which take a recurrent cours
and enter the cranial cavity to supply the dura mater near the canal
 
The ramus descendens hypoglossi nerve has been already describe
(see p. 1205).
 
The nerve to thyro-hyoid will be found described on p. 1206.
 
The muscular branches are given off from the nerve as it lies upo
the hyo-glossus under cover of the mylo-hyoid. These supply tl
stylo-glossus, hyo-glossus, genio-glossus, and genio-hyoid. The nen
to the genio-hyoid is composed of spinal fibres derived from the fin
and second cervical nerves.
 
Ihe terminal branches pierce the under surface of the tongue, an
are distributed to its muscular tissue.
 
The hypoglossal nerve receives many spinal fibres. Those derive
from the first cervical nerve, or the loop between the first and seconc
soon become applied to it, and most of them pass off to form the ramr
 
 
 
THE HEAD AND NECK
 
 
1333
 
 
:endens hypoglossi. A few of these, however, still pass along the
n trunk. The spinal fibres derived from the second and third
deal nerves in part ascend in the ramus descendens hypoglossi,
 
. then pass off from it to be applied to the main trunk in its onward
rse.
 
Summary.—1. Distribution. —The hypoglossal fibres of the nerve supply
stvlo-glossus, hyo-glossus, genio-glossus, and intrinsic muscles of the tongue,
spinal fibres supply both bellies of the omo-hyoid, the sterno-hyoid, sternoroid, thyfo-hyoid, and genio-hyoid muscles. The hypoglossal nerve also
plies the dura mater near the anterior condylar canal. 2. Connections. —-It
blishes connections with (1) the inferior ganglion of the vagus; (2) the superior
deal ganglion of the sympathetic; (3) the first two cervical nerves; (4) the
ryngeal plexus, through the lingual branch of the vagus; and (5) the lingual
/e from the mandibular division of the trigeminal nerve.
 
The Sympathetic Trunk.
 
Cervical Portion.—-This portion of the sympathetic trunk extends
m the base of the skull, at the carotid canal on the under surface
the petrous part of the temporal bone, to the root of the neck,
ere it enters the thorax, passing on the right side behind the subvian artery. It lies directly behind the carotid sheath, and in
nt of the transverse processes of the cervical vertebrae, resting upon
: longus capitis and longus cervicis muscles. The cord presents
ee ganglia—superior, middle, and inferior.
 
Superior Cervical Ganglion.—This ganglion is fusiform and more
in an inch long. It represents four ganglia united into one, and
'responding to the first four cervical nerves. It is situated in front
the transverse processes of the second and third cervical vertebrae,
d lies upon the longus capitis, the vagus nerve being lateral to it.
either end it tapers, being continued superiorly into its ascending
inch, and inferiorly into the descending trunk.
 
Branches.—-These may be conveniently arranged into internal
rotid, lateral, medial.
 
The internal carotid nerve enters the carotid canal in the petrous
rt of the temporal bone in company with the internal carotid artery,
d divides into two parts. The lateral branch lies upon the outer
le of the artery, and its subdivisions form by their interlacement the
;ernal carotid plexus. From this plexus several communicating
anches are given off. (1) The carotico-tympanic nerve enters the
mpanic cavity, and joins the tympanic branch of the glosso-pharynal, to take part in the tympanic plexus. (2) I he deep petrosal
rve joins the greater superficial petrosal from the ganglion of the
cial nerve in the upper part of the foramen lacerum, to form the
rve of the pterygoid canal, which passes through the latter to join
e spheno-palatine ganglion. (3) A branch (or branches) passes to
in the abducent nerve. (4) One or more branches pass to join the
Lgeminal ganglion. The internal carotid plexus furnishes filaments
the coats of the internal carotid artery, and it receives a branch
3 m the tympanic plexus.
 
 
1334
 
 
A MANUAL OF ANATOMY
 
 
The medial branch of the internal carotid nerve lies upon the ini
side of the internal carotid artery, to which it furnishes twigs, and
subdivisions form by their interlacement the medial part of the inter]
carotid plexus (cavernous plexus). This plexus lies in contact with 1
internal carotid artery as it traverses the cavernous sinus. Its co
municating branches pass to join the oculo-motor, trochlear, a
ophthalmic nerves, and the ciliary ganglion. The last-named brar
forms the sympathetic root of the ciliary ganglion, and enters the or
through the superior orbital fissure. It is the source of the motor sup]
of the dilator pupillse muscle. The medial part of the internal caro
plexus furnishes filaments to the coats of the internal carotid artei
and offsets which accompany the branches of that artery, around whi
they are disposed as plexuses.
 
The lateral branches are communicating, and pass to (i) each
the upper four cervical nerves; (2) the inferior ganglion of the gloss
pharyngeal; (3) the superior ganglion of the vagus; and (4) the hyp
glossal nerve.
 
The medial branches are laryngo-pharyngeal and cardiac. T
laryngo-pharyngeal branches, two or three in number, unite with t
pharyngeal branches of the glosso-pharyngeal and vagus to formt
pharyngeal plexus (see p. 1329).
 
The cardiac branch arises by two roots from the lower part of t
superior cervical ganglion, and descends behind the carotid sheath, lyii
medial to the main sympathetic trunk. The nerve of the right si
passes in front of or behind the first part of the subclavian artery, ai
then along the innominate artery, to end in the deep cardiac plexr
In its course down the neck it receives twigs from the external larynge
nerve, and is joined by the superior cervical cardiac branch of t]
vagus nerve. As it enters the thorax it receives a filament from tl
recurrent laryngeal nerve. The nerve of the left side within the thon
accompanies the left common carotid artery, and passes in front
the arch of the aorta to end in the superficial cardiac plexus.
 
The anterior branches are vascular, and pass to the external carot
artery, upon which and its branches they form delicate plexuses.
 
Middle Cervical Ganglion. —This ganglion is situated opposite tl
sixth cervical vertebra, and usually lies in front of the inferior thyro:
artery. It is the smallest of the three, and is connected by gn
rami communicantes with the fifth and sixth cervical nerves, thi
representing two fused ganglia. Its branches of distribution a]
thyroid and cardiac. The thyroid branches accompany the intern
thyroid artery to the thyroid gland, and communicate with the extern;
and recurrent laryngeal nerves. The cardiac branch of each side enc
in the deep cardiac plexus. The nerve of the right side passes eith(
in front of or behind the first part of the right subclavian artery. J
then descends in front of the trachea, and joins the right half of tt
deep cardiac plexus. The nerve of the left side enters the thora
between the left common carotid and left subclavian arteries, and
joins the left half of the deep cardiac plexus.
 
 
THE HEAD AND NECK
 
 
1335
 
 
Inferior Cervical Ganglion. —This ganglion is situated between the
nsverse process of the seventh cervical vertebra and the neck of
j first rib, where it lies behind the subclavian near the root of the
rtebral artery. It is intermediate in size between the superior and
ddle ganglia, and, like the middle, it probably represents two ganglia
ited into one. It is frequently fused with the first thoracic ganglion,
e connection between the middle and inferior cervical ganglia passes
bind the subclavian artery, but sometimes a cord or cords in front
the vessel form a loop around it, called the ansa subclavia (ansa
mssenii). The inferior cervical ganglion is connected by grey
ni communicantes with the seventh and eighth cervical nerves, and
branches of distribution are vascular and cardiac. The vascular
inches accompany the vertebral artery in the form of the vertebral
•xus, which gives filaments to the vessel and offshoots along its
rious branches. The plexus is continued along the basilar artery
d its branches, and on to the posterior cerebral arteries. The
rdiac branch on each side joins the deep cardiac plexus. The nerve
the right side passes behind the first part of the right subclavian
tery, and then in front of the trachea. It is connected with the
rdiac branch of the middle cervical ganglion and recurrent laryngeal
rves. The nerve of the left side in many cases joins the cardiac
anch of the middle cervical ganglion, and so reaches the deep cardiac
 
iXUS.
 
Constitution of the Cervical Sympathetic Trunk.
 
The sympathetic trunk in the neck contains the following important groups of
res: (1) dilator pupillae, (2) vaso-constrictor and vaso-dilator, (3) secretory,
d (4) accelerator.
 
The dilator pupillae fibres are derived from the upper three thoracic nerves ,
d ascend in the sympathetic trunk to the superior cervical ganglion, in which
3y end. From this ganglion they are continued as sympathetic fibres to
2 medial part of the internal carotid plexus, through this plexus to the ciliary
nglion, and thence to the dilator pupillae muscle.
 
The vaso-constrictor fibres are derived from a variable number of thoracic
rves, beginning at the second and ending at the eighth, ihe origin of the
SO-dilator fibres is not definitely known. The vaso-constrictor fibres ascend
the superior cervical ganglion, in which they end. hrom this ganglion they
2 continued as sympathetic fibres into the plexus around the external carotid
tery, and thence along the branches of that vessel.
 
The secretory fibres are destined for the submandibular gland, and are derived
iefly from the second and third thoracic nerves. They also ascend to the
perior cervical ganglion, in which they end. They are thence continued as
mpathetic fibres into the external carotid plexus, from that into the facial
2xus, and thence into the submandibular ganglion, from which the} r pass into
e submandibular and sublingual glands. .
 
The accelerator fibres of the heart are chiefly derived from the second and
ird thoracic nerves, but some also spring from the first, fouith, and fifth nerves,
le spinal fibres pass to the middle and lower cervical ganglia, from each of which
ey are continued as sympathetic fibres.
 
The Mouth Cavity.
 
The cavity of the mouth extends from the oral fissure in front,
here it opens externally on the face, to the oropharyngeal isthmus
hind, where it opens into the pharynx. It is divided by the upper
 
 
 
A MANUAL OF ANATOMY
 
 
1336
 
and lower alveolar arches into two compartments, the anterior of wh:
is called the vestibule and the posterior the mouth cavity proper.
 
The vestibule of the mouth is bounded anteriorly and externa
by the lips and cheeks, and internally by the alveolar arches and gur
Superiorly and inferiorly it is bounded by the reflection of the mucc
membrane from the lips and cheeks on to the gums. In the medi
line, above and below, the mucous membrane forms a small vertical f(
called the frenulum. On the inner surface of each cheek the vestibu
mucous membrane presents a small papilla opposite the second upj
molar tooth, and on this is the minute opening of the parotid duct.
 
The mouth cavity proper lies within the alveolar arches. It co
municates with the vestibule by the interval between the upper a
lower teeth, and also by an opening at either side situated behind t
last molar tooth. Anteriorly and externally it is bounded by t
alveolar arches and gums, and posteriorly it opens into the phary
by means of the oropharyngeal isthmus. The roof, which is arched,
formed by the hard palate and the soft palate. The floor is form
by the tongue, and the reflection of mucous membrane from the inr
surface of the lower alveolar arch on to its under surface. In t
region of the tip of the tongue the lateral reflections of mucous me]
brane from the two sides of the lower alveolar arch are continuo
across the median line. In the median line the mucous membra
forms a prominent fold, called the frenulum linguce, which is co
nected above with the under surface of the tongue a little distan
from the tip. In some children it may extend quite to the tip, impa
ing the utility of the organ, and giving rise to the condition known
'tongue-tied/ Close to each side of the frenulum there is a sm;
papilla, on which is the opening of the submandibular duct. A litl
posterior to this is a fold of the mucous membrane at either sic
produced by the upper border of the subjacent sublingual glan
This fold is known as the plica sublingualis, and it extends from t
side of the tongue to the alveolar arch. It is upon this plica that tl
majority of the sublingual ducts open.
 
The lips are covered by skin externally, and mucous membra]
internally. Between these two layers are the muscular fibres of ti
orbicularis oris, blended with which are the fibres of the buccinatc
and in the case of the upper lip fibres of the depressor anguli or:
whilst in the case of the lower lip there are the fibres of the levat
anguli oris. Between the mucous membrane and the muscul
element there are a number of small racemose glands, called the labi
glands, the ducts of which open on the inner surface of each lip. Tl
tortuous labial arteries are embedded in each lip, and those of opposi
sides anastomose at the median line.
 
Between the upper lip and the columna nasi there is a groov
called the philtrum.
 
The lymphatic vessels of the upper lip pass on either side to tl
submandibular, to the submental, or to the superficial parotid lymp
glands. The lymphatic vessels of the lateral portion of the lower 1
 
 
THE HEAD AND NECK
 
 
1337
 
 
50 pass on either side to the submandibular lymph glands, and
ose of the medial portion pass to the submental lymph glands of the
»rresponding side.
 
The cheeks are covered externally by skin, and internally are lined
ith mucous membrane. The muscular element consists of the
lccinator, which is covered by the buccal fascia. Posteriorly this
scia is continuous with the pharyngeal fascia, which is derived from
Le deep cervical fascia, the two being known as the bucco-pharyngeal
scia. Superiorly and interiorly it is attached to the alveolar arches.
The lymphatic vessels of the cheek pass to the superficial parotid
lymph glands and the submandibular glands, the buccal lymph
ands being a gland-station in the path of the latter.
 
 
Greater Palatine Artery
 
 
Palato-pharyngeus.^ $
 
 
Palato-glossus.
 
 
Posterior Wall of Pharynx^
 
 
 
Palatal RapW
 
.Uvula
 
Palato-pharyngeal Arch
 
^ '
 
Palatoglossal Arch
...Tonsil
 
 
. Dorsum of Tongue
 
 
u/ih " '' }i < <<(//{” ^\\v
 
jpUlin111.11
 
 
Fig. 804. —The Cavity of the Mouth and Oropharyngeal Isthmus.
 
The jaws are widely separated.
 
 
The suctorial pad of fat is situated upon the buccal fascia, and is
ell developed in young children. It is continuous with the fat in
le pterygoid region.
 
The buccal fascia, buccinator, and lining mucous membrane are
ierced by the parotid duct. Between the buccinator and the mucous
lembrane there are several racemose buccal glands. In addition to
lese there are three or four molar glands, mucous in character, which
re situated superficial to the buccal fascia in the angle between the
lasseter and buccinator.
 
The masseteric fascia is an upward prolongation of the deep cervical
iscia. It is attached superiorly to the zygoma, and externally is
ontinuous with the parotid fascia.
 
The alveolar arches are formed by the alveolar borders of the
laxillae and mandible, the teeth, and the gums.
 
 
 
 
 
 
 
 
 
1338
 
 
A MANUAL OF ANATOMY
 
 
The gums (gingivae) consist of dense fibrous tissue, which is covere
by mucous membrane and is closely connected with the periosteum c
the alveolar borders of the mandible and maxillae. The mucor
membrane, which is very vascular, is continuous with the labial an
buccal mucous membrane on the one hand, and with that of the floe
of the mouth on the other. Close to the necks of the teeth it is bese
with vascular papillae.
 
The lymphatic vessels of the upper gum pass on either side t
the submandibular lymph glands. The lymphatic vessels of th
lateral portion of the lower gum also pass on either side to the sut
mandibular lymph glands; and those of the medial portion pass to th
submental lymph glands of the corresponding side.
 
The mucous membrane of the gums is separated from the subjacen
periosteum by dense connective tissue, which connects the two i:
such a close manner that the mucous membrane is immovable. Clos
to the necks of the teeth it is beset with papillae. The mucous mem
brane of the hard palate, like that of the gums, is separated from th
periosteum by a thick layer of dense connective tissue, which bind
the two so closely that the mucous membrane is immovable. Ther
is a median raphe, which is continued over the soft palate, and end
in front at the incisive fossa in a small papillary elevation, known a
the incisor papilla. On either side of the raphe anteriorly there ar
a few transverse rugae. Each lateral half of the hard palate is traverse(
by the ramifications of the greater palatine artery, the branches o
which extend forwards and inwards from either lateral angle posteriorly
The mucous membrane of the hard palate is provided with racemose
palatal glands of a serous character, which are arranged in tw(
symmetrical groups laterally disposed.
 
Occasionally a hard swelling, lying antero-posteriorly in the mid
line of the hard palate, is seen, and must not be mistaken for a bom
tumour or exostosis. It is known as the torus palatinus.
 
The lymphatic vessels of the mucous membrane of the hard palah
pass to (i) the deep facial lymph glands, and (2) the superior deej
cervical lymph glands.
 
Nerves. — The greater palatine nerve descends in the greatei
palatine canal, which it leaves through the greater palatine foramen
Then it divides into branches which pass forwards in groove!
on the hard palate, and supply the mucous membrane, glands
and inner aspect of the upper gum. The long spheno-palatine is
distributed to the mucous membrane behind the incisor teeth, when
it communicates with twigs of the greater palatine nerve. To react
the hard palate the nerve of the right side passes through the posterior
incisive foramen, whilst the left nerve passes through the anterio /
foramen. The mucous membrane of the cheek is supplied by the
buccal nerve, which is a branch of the mandibular division of the
trigeminal nerve. The mucous membrane of the floor of the mouth
derives its nerves from the submandibular ganglion.
 
Arteries.—These are the right and left greater palatine branches of
 
 
THE HEAD AND NECK
 
 
1339
 
 
e third part of the maxillary. Each greater palatine artery takes
ie same course as, and has a similar distribution to, the greater palatine
;rve. At the incisive fossa it terminates in a small branch which
cends through the lateral incisive canal, and anastomoses at the
}per end of that canal with the posterior septal branch of the sphenoilatine artery.
 
Development of the Mouth, Lips, and Gums (pp. 70 & 85).
 
In the early stages of formation of the embryo, a transversely directed
ink or furrow exists between the overhanging fore-brain and the prominent
ricardium. This is known as the oral fossa or stomodaeum, and is frequently
 
 
 
Fig. 805.— Embryos of 10 Mm., 12 Mm., and 13*5 Mm.
 
ne first gives the facial aspect, the mandible being in situ, dhe maxillary
process has not vet come against the fronto-nasal process. The 12 mm.
specimen, seen from below after the mandible has been removed, shows
the maxillary process meeting the fronto-nasal. The 13 ’5 mm. specimen,
seen from below and somewhat from behind, shows the beginning of the
extension of maxillary mesoderm over the fronto-nasal process. The
primitive posterior naris can be seen in this embryo, in which the bucconasal plug has been destroyed, as a small point behind the maxillary extension and to the outer side of the globular or fronto-nasal process. Ihe
corresponding point in the previous stage can be seen, but there is no apeiture. The early palate folds are recognizable. FN, fronto-nasal process;
M, maxillary process, cut at its base; R, opening of Rathke s pouch, 11 ,
anterior margin of passage into tubo-tympanic recess.
 
 
erred to as an early stage in the developing mouth; it is, however, nearly,
not altogether, replaced by forward growths from the wall of the pharynx,
dosing between them the cavity of the adult mouth. ie stomodS6Um
shut off from the pharynx by the bucco-pharyngeal membrane, formed by
3 meeting of the ectoderm lining the stomodaeum with the entoderm lining the
arynx. The membrane is attached to the mandibular and maxillary pro
;ses, is carried forward by these as they begin to grow, and is quickly broken
 
d lost.
 
 
 
 
 
 
x 34°
 
 
A MANUAL OF ANATOMY
 
 
The mandibular arch grows forward above the pericardium and male
a new floor for the mouth. The maxillary processes grow forward on each sid
 
 
 
Fig. 806.— Plans showing Distribution of Maxillary Mesenchyme.
 
I. The early simple process reaches and just overlaps the hinder ends of tl
nasal folds. Its outer and thicker part (Im, lateral mass, dotted) thii
away internally, covering the paraxial mesoderm, and its inner part (s
septal process, interrupted lines) comes against the inner fold; it do
not reach the middle line, and Rathke’s pouch (R) is widely open.
 
II. The palate fold is a definite but blunt inner edge to the lateral mass, whi(
has thickened greatly and is fusing in front with the inner nasal fol
The septal process has reached the middle line in front and has spree
over the neighbouring area of the fronto-nasal process. The opening
is smaller, being compressed by deeper paraxial growth.
 
III. The extremity of the lateral part (having broken down the epithelial septu
at their junction) has invaded the fronto-nasal region and is spreadii
over it in front of the area covered by sp; this extension is going to for
the alveolus and lip in this part. The septal process is coming into r
lation with R, and reaches the middle line in front of this.
 
IV. Shows modifications in the lateral mass, which presents a labial edge (la
and an alveolar eminence (alv) as well as a definite palate fold. Tl
primitive posterior naris is represented as having extended to some degre
showing that the septal process is forming the back part of the septu
between the nares, thus explaining its name. The opening R, now on
a point, has been caught between the process and its fellow, and has bee
displaced slightly forwards, as indicated by the dotted line.
 
forming a side wall and lateral roof, and come up against the outer nasal fola
cross these, and come into contact with the fronto-nasal process. Thus tl
mouth has the mandibular arch and growing tongue as its floor, while its ro<
 
 
 
 
 
THE HEAD AND NECK
 
 
I 34 1
 
limited laterally by the deep maxillary processes, and in front by the frontosal process, with which the maxillary processes are joined.
 
Associated with the mouth are (i) the pouch of Rathke, (2) the tongue,
the salivary glands, (4) the tonsils, and (5) the teeth.
 
The pouch of Rathke is a diverticulum of the roof of the ectodermic stomo:um, ventral to the bucco-pharyngeal membrane. Its development is given
p. 87. It gives rise to the anterior lobe of the hypophysis cerebri, the posterior
e of which is developed from a diverticulum of the floor of the third ventricle
the cerebrum.
 
The development of the tongue, salivary glands, tonsils, and teeth will be
md after the description of each of these organs.
 
Each early nasal cavity lies above and behind the fronto-nasal process, and
opening into the mouth, very small, and closed at first by the bucco-nasal
'mbrane, is placed just above the junction of the maxillary with that process,
te opening extends in an upward direction (see p. 85), and at the same time
late folds make their appearance on the inner side of the maxillary processes
>se to the outer edges of these openings. These folds are turned down and lie
side the tongue, which occupies the cavity and is in contact with its roof,
le folds run into the outer edges of the fronto-nasal process in front.
 
 
 
Globular Process
 
 
Maxillary Palatal Process
Maxillary Process .
 
 
Oral Cavity
 
 
Palatal Part ot fronto-nasal Process
t
 
i
 
Aperture of Olfactory Pit
 
Lens
. Lye
 
Palatal Shelf
 
Pouch of Rathke
 
 
Fig. 807. —Roof of Mouth (Marshall, after His).
 
About the end of the ninth week—by which time the nasal openings have
tended up to the highest level of the roof of the cavity—the palate folds
me on to the dorsal surface of the tongue, as a result of this being carried below
z fronto-nasal process by the growing mandible. They are now pressed against
e ‘ edge ’ of the septum between the two openings, to which they adhere,
us shutting off the lower parts of these openings from the mouth and making
e hard palate. The folds meet behind the fronto-nasal process, which forms
e incisive papilla. The incisive canals are in the angles between folds and
ocess.
 
Lips (Labia Oris) and Gums (Gingivae).— Shortly after the fusion of the maxary and globular processes to form the maxilla, a groove appears along each
 
these processes on either side. The margins of this groove, which form
irallel ridges, are external and internal relatively to the oral cavity. The
ternal or labial ridge gives rise to the upper lip, the globular portion of the
Ige representing the premaxillary part of the lip, and the maxillary portion
rming the remainder. The internal or gingival ridge is the rudiment of the
>per gum.
 
The philtrum is probably developed from the mesodermic investment of the
lited globular processes.
 
A similar groove and similar ridges ( labial and gingival) appear along each
andibular arch, and from the ridges the lower lip and lower gum are developed.
 
 
 
 
 
 
I 34 2 ‘
 
 
A MANUAL OF ANATOMY
 
 
The angles of the mouth correspond to the union between the two lips o:
either side, and each originally represents the angle between a mandibular arc
and maxillary process.
 
 
The Tongue.
 
The tongue is a muscular and very sensitive organ, covered tr
the buccal mucous membrane, and situated on the floor of the mouth
It is concerned in the sense of taste, mastication, deglutition, am
speech, and it consists of a root or base, a body, and a tip. The roo
is attached to the hyoid bone. The tip is the anterior free extremity
 
 
EpiglottisGlosso-epiglottis Fold
 
 
Foramen Caecum _javWw//| ijllbtes
Lymphoid Tissue
 
 
Median RaplA
 
 
 
Palatopharyngeal Arch
 
AvTi *
 
Palatoglossal Arch
 
i vi/jI
 
/ Tonsil
 
 
^ Vallate Papillas
 
 
-Fungiform Papillae
 
 
Fig. 808.—The Dorsum of the Tongue.
 
 
which, in the quiescent state, lies behind the upper incisor teeth.
The body has an upper surface or dorsum, an under surface, and two
lateral borders, right and left. The dorsum is convex from before
backwards, and on its anterior twoThirds is a median depression oi
rap>he, on either side of which the surface is convex from side to side.
This ends posteriorly in the foramen ccscum. In this region the dorsum
has a V-shaped groove, known as the sulcus terminalis. The joint ol
the V is at the foramen caecum, and the two limbs pass outwards and
forwards to the sides of the tongue, where the palato-glossal arches
are connected with it. The sulcus terminalis marks the union of the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1343
 
 
0 parts from which the tongue is developed. The part behind it,
presenting one-third, is the basal, lymphoid, or pharyngeal portion,
occupies the buccal part of the pharynx, and overhangs the epi)ttis. The portion in front of the sulcus terminalis, representing twoirds, is known as the buccal or papillary portion.
 
Mucous Membrane.—The mucous membrane covering the basal
pharyngeal portion of the tongue is destitute of proper papillae, but
freely provided with lymphoid follicles like those of the tonsils,
d with mucous glands. The follicles are ranged upon the walls
crypts, the mouths of which open upon the surface. The mucous
embrane in this region forms the glosso-epiglottic fold, which is
sdially placed. On either side of this fold, between it and each
 
 
Plica fimbriata
 
 
Frenulum
 
 
Plica sublingualis
 
 
Fig. 809. —Under Surface of Tongue, with Sublingual Region.
 
 
 
laryngo-epiglottic fold, there is a pouch or depression, called the
llecula. In front of the sulcus terminalis the mucous membrane
the dorsum, borders, and tip of the tongue is freely covered by
laracteristic papillae, which, being visible to the naked eye, impart
this part its distinctive appearance. These papillae bear secondary
ipillae, which, however, are concealed by the epithelial covering.
ie mucous membrane on the under surface of the tongue in the median
ie forms near the tip a vertical fold, called the frenulum linguce.
little lateral to the frenum on either side is an indistinct fringed
Id, called the plica fimbriata. The two plicae converge as they pass
rwards towards the tip, and inside each the outline of the vena
mitans hypoglossi may be visible. They represent the under tongue
sublingua of lemurs and marmoset monkeys. On either side of
 
 
 
 
 
 
 
j 344
 
 
A MANUAL OF ANATOMY
 
 
Epithelial
 
Covering
 
 
the tongue, in the region of the limbs of the sulcus terminalis, the mucous
membrane presents a few ridges which represent the papilla foliata
of such animals as the rabbit.
 
Papillae.—These are of four kinds—filiform, fungiform, circum
vallate,and foliate—and they are confined to the anterior two-thirds
of the organ. The filiform papillae are the most numerous, and are
arranged in more or less parallel, closely-set rows, directed forwards
 
and outwards from the median line
except towards the tip, where the
rows tend to become transverse. Or
the sides of the tongue they are
arranged in vertical parallel rows.
 
The fungiform papillae are scattered amongst the filiform, and are
most numerous at the sides and tip
being rather sparse over the dorsum.
Each is round and enlarged at the
surface, but tapers at its deep end
like a button mushroom, and it bears
secondary papillae, but there is no
thread-like processes on the epithelial
caps.
 
The vallate papillae are conspicuous, and vary in number from seven
to thirteen. They are arranged in
two diverging rows which lie anterior
to, and parallel with, the limbs ol
the sulcus terminalis. The two rows
converge backwards and inwards, and
so form a capital V. In the median
 
 
 
- Papilla
 
 
Fig. 8io.—The Filiform Papillae
of the Tongue.
 
 
line, at the point of the V, there is a single vallate papilla, behind
which is the foramen caecum. The free surface of each papilla is
broad and flat, and bears secondary papillae, whilst the deep end
is somewhat constricted, and is received into a circular pit of the
mucosa. In this manner each papilla is surrounded by a space
known as the trench. The outer wall of the trench projects slightly
beyond the level of the free surface of the papilla, thus forming
a circular elevation around it, called the vallum (rampart). It is
from this circumstance that the papillae have received the name
‘ vallate/ Their sides, as well as the wall of the vallum, contain
the taste-buds.
 
The tongue contains a number of acinous glands. Some of them
open into the trenches around the vallate papillae, where taste-buds
are present, and are serous in character (Ebners glands). Others open
into the foramen caecum, into the crypts on the posterior third of the
dorsum, and along the sides of the organ, these being mucous in
character (Weber’s glands). Beneath the apex of the tongue, on
either side of the median line, there is a small group of glands, partly
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1345
 
 
ous and partly mucous. These two groups are known as the
 
;erior lingual glands (glands of Blandin or of Nuhn).
 
 
 
Fig. 811.—Extrinsic Muscles of Tongue.
 
 
The muscular tissue of the tongue is of the striped variety. It
ms two sets of muscles—namely, extrinsic and intrinsic. The
 
 
Taste-bud
 
 
 
B
 
 
 
Fig. 812.—Vertical Section of a Vallate Papilla of the Tongue.
 
A, vallate papilla, beset with secondary papillae; B, taste-bud,
 
C, gustatory cell.
 
trinsic muscles are those which have their origins outside the tongue,
id their insertions into it. They are: (1) the genio-glossus, (2) the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1346
 
 
hyo-glossus (including the chondro-glossus), (3) the stylo-glossus, ai
(4) the palato-glossus, all of which have been already described. T
intrinsic muscles are those which are contained entirely within t
tongue, and are: (1) the longitudinalis superior, (2) the longitudina
inferior, (3) the transverse linguae, and (4) the verticalis linguae.
 
The longitudinalis linguae superior is an expanded sheet placed <
the dorsum immediately beneath the mucous membrane. Its fibi
are disposed longitudinally, and the muscle extends from the t
backwards to the body of the hyoid bone. Posteriorly it is ovf
 
lapped by fibres of the hyo-glossi
 
 
 
Fig. 813. —Longitudinal Section of
the Tongue of a Cat (injected).
 
 
1. Muscosa M
 
2. Longitudinal Superior
 
3. Transversus et Verticalis Linguae
 
4. Longitudinalis Inferior
 
 
Its fibres do not extend over t.
whole length of the tongue, b
take attachment at short intervc
to the mucous membrane.
 
The longitudinalis linguae inf eri
is disposed as a round bundle (
the inferior surface of the tongu
Posteriorly it lies between the i
sertions of the genio-glossus mec
ally and the hyo-glossus laterall
and anteriorly fuses with the styl
glossus laterally. The muscle e:
tends from the tip of the tongi
to the body of the hyoid bone, wil
which it is connected.
 
The transversus linguae const
tutes a layer of considerable thicl
ness which is placed between tl
longitudinales superior et inferio
It arises from the median septun
and extends outwards, the upp<
fibres curving upwards, to be ii
serted into the mucous membrar
of the side of the tongue an
adjacent portion of the dorsun
This muscular stratum is intei
spersed with fat, and is muc
 
 
broken up by fibres of the verticalis linguae and genio-hyo-glossus.
 
The verticalis linguae extends from the mucosa of the dorsum
that of the inferior surface. Its fibres describe curves, having tl
convexities directed inwards, and they decussate freely with tl
fibres of the transversus linguae.
 
Septum Linguae.—The septum of the tongue is a fibrous partitic
which extends in the median line from the tip of the organ to tl
body of the hyoid bone. It divides the tongue into two symmetric
halves, and the transversus linguae muscle arises from it on eitb
side.
 
Arteries.—( 1 ) The arteria profunda linguae (ranine artery), which :
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1347
 
 
*anch of the lingual, and is situated on the inferior surface immediy lateral to the line of insertion of the genio-glossus muscle. It
stomoses with its fellow beneath the tip, but elsewhere there is no
stomosis across the septum linguae. (2) The dorsalis linguae,
ally several branches. (3) The tonsillar branch of the cervical
ion of the facial artery. (4) Pharyngeal branches of the ascending
ryngeal artery.
 
The veins pass to the internal jugular vein.
 
Lymphatics.—The lymphatic vessels of the tongue are disposed in
' groups —apical, marginal, basal, and central.
 
The apical lymphatics pass to the submental lymph glands of the
Le side, and to one of the medial chain of deep cervical lymph glands
a. level with the cricoid cartilage of the larynx.
 
The marginal lymphatics carry lymph from the anterior twods of the lateral border and marginal part of the dorsum. The
trior lymphatics of this set turn round the mylo-hyoid muscle,
 
. end in the anterior submandibular lymph glands. The posterior
s to the superior deep cervical lymph glands, and more particularly
one lying deep to the angle of the mandible. The small lingual
ids, which lie upon the outer surface of the hyo-glossus muscle,
je as gland-stations in their path.
 
The basal lymphatics return lymph from the posterior third of the
gue, and end in the same way as the posterior marginal lymphatics
t stated.
 
The central lymphatics return lymph from the median part of the
gue, and pass to the deep cervical lymph glands, which extend from
posterior belly of the digastric muscle to the level of the cricoid
tilage of the larynx.
 
Nerves.—The sensory nerves are: (1) the lingual branch of the
vidibular nerve , which is distributed to the mucous membrane over
anterior two-thirds of the tongue, including the filiform and fungin papillce, upon which it confers common sensibility; (2) the
rda tympani nerve, which accompanies the lingual nerve to the
erior two-thirds of the tongue, of which it is usually regarded as
nerve of taste; (3) the lingual branch of the glosso-pharyngeal
ve, which is distributed to the mucous membrane of the posterior
d and to the vallate papillce , of which it is the nerve of taste; (4) the
irnal branch of the superior laryngeal nerve, which furnishes a few
gs to the mucous membrane of the root of the tongue in the region
the epiglottis; and (5) the hypoglossal nerve, which supplies the
pial muscles.
 
Sympathetic filaments are also conducted to the tongue by the
*ious arteries.
 
Taste-buds.—These gustatory organs are modified epithelial cells,
1 are present in the following situations: (1) The sides of the vallate
fillae and the opposed surface of each vallum; (2) the sides of the
:erior two-thirds of the tongue, partly in connection with the fungim papillae, and partly embedded in the stratified epithelium; (3) the
 
 
 
 
1348
 
 
A MANUAL OF ANATOMY
 
 
folds which form the papilla foliatce ; (4) the buccal surface of the s
palate; and (5) the posterior surface of the epiglottis.
 
Each taste-bud is a flask-shaped body. The base rests upon 1
corium of the mucosa, and gives passage to nerve-fibres. The a]
or narrow end lies between the surface-cells of the epithelium, a
it is perforated by a minute opening called the gustatory pore , thror
which the peripheral processes of the gustatory cells in the inter
of the bud project as gustatory hairs.
 
Structure.—The wall of a taste-bud is composed of flatten*
nucleated, epithelial walls, called the supporting cells. These cc
are elongated in the direction of the bud, they taper at either ei
and their margins are closely applied to each other. The interior
the bud consists of . a bundle of gustatory cells. Each gustatory c
is nucleated and spindle-shaped. The body of the cell is prolong
at either end into a process, peripheral and central respectively. T
peripheral process passes to the gustatory pore at the apex of the bi
 
 
 
Fig. 814.—The Visceral Arches of the Embryo (Posterior View) (Hi
 
I. Mandibular Arch III. Thyrohyoid Arch
 
II. Hyoid Arch IV. Fourth Arch
 
 
through which it projects as a gustatory hair. The central proce
passes towards the base of the bud, which rests upon the corium 1
the mucosa. It is usually branched, and ends in free extremitie
It does not therefore become continuous with nerve-fibres, and therei
it differs from the corresponding process of an olfactory cell.
 
It has been seen that the base of each taste-bud gives passage i
nerve-fibres. These, as they enter the bud, lose their medullar
sheaths, and their axons end within the bud in arborizations aroun
the constituent gustatory cells. Nerve-fibrils also enter the ep
thelial wall of the bud, and ramify between the supporting cells.
 
Development. —The tongue is developed in the floor of the pharynx in tw
parts—buccal and pharyngeal—which are separated from each other by th
foramen caecum and V-shaped sulcus terminalis (see p. 72)."
 
The buccal or papillary part, which represents the anterior two-thirds, :
developed from the tuberculum impar of the first or mandibular visceral arcl
This eminence may give rise to the portion of the buccal part directly in fror
of the foramen caecum.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
*349
 
 
I'his, which appears very early, is a small rounded and well-defined swelling
he middle line of the pharyngeal floor; it is in the line of the first pharyngeal
)ve, but appears to belong really to the mandibular arch. It enlarges slowly
 
 
 
g 8is) but clearly as a separate formation, into which extend, fiom below
1 behind, the paired anterior ends of the ventral down-growths from post? (occipital) myotomes; with these the hypoglossal nerves and lingual vessels
 
ch the tongue.
 
 
 
 
 
 
 
 
 
*350
 
 
A MANUAL OF ANATOMY
 
 
This account is in keeping with the observations made on embryo
material of all the stages involved. The usual description, that paf
swellings on the mandibular arch envelop and in this way obliter;
the tubercle as a separate structure, appears to have little support in f;
(Fig. 815).
 
The pharyngeal or basal part of the tongue, the portion lying behind 1
foramen caecum and sulcus terminalis, is made from forward extension of 1
anterior end of the hypobranchial eminence coming against the back of the grc
ing tuberculum impar and extending behind it and postero-laterally. 1
actual mass which comes forward in this way is probably a third arch derivati
the mesoderm of this arch extending into and covering the anterior end of 1
hypobranchial eminence; the second arch, which at one time seems to rea
the eminence also, is overpowered by the third arch growth, which covers it a
comes forward above it. This is a part of the general movement in the pharyngi
floor in which the second arch drops completely out of the floor, except in t
tympanum, the third arch passing forward over it and coming against the fi:
arch in front of it. In the middle, the third arch masses apply themselves
the back of the tuberculum impar, and in doing so enclose temporarily a sm
entoderm-lined space which opens by a relatively wide aperture, the futr
foramen ccecum. This space would have the thyroglossal duct inserted into
floor, if the duct had not separated (apparently) from it long before. The spa
gradually fills up, as a rule, and the ‘ opening ' becomes the definitive foram
caecum. Thus the foramen caecum is not the actual impression of the thyrc
outgrowth, but, owing to the way in which it comes into existence, it is behind t
tuberculum impar, and thus marks on the surface the spot from which—b
at a deeper level—the thyroid growth took place.
 
 
The Soft Palate.
 
The soft palate is a movable musculo-aponeurotic curtain situah
at the back part of the hard palate, where it projects downwards ar
backwards into the pharynx. Anteriorly it is attached to the posters
border of the hard palate, laterally it is connected with the side <
the tongue and the wall of the pharynx, and postero-inferiorly it h;
a free border. Its surfaces, which occupy an oblique plane, a;
antero-inferior or buccal, which is concave, and postero-superior (
pharyngeal, which is convex and looks towards the naso-pharyn:
The postero-inferior border at its centre has a conical proces
called the uvula. On either side of the base of the uvula the]
are two prominent folds of mucous membrane, which extend ou
wards and downwards in a diverging manner. These constitul
the palato-glossal and palato-pharyngeal arches (anterior and posteric
pillars of the fauces). Each palato-pharyngeal arch belongs to tt
postero-inferior border of the soft palate, and it sweeps outward
downwards, and backwards to the lateral wall of the pharynx. 1
is due to the palato-pharyngeus muscle. Each palato-glossal arc
belongs to the buccal surface of the soft palate, and it sweeps ou
wards, downwards, and forwards to the back part of the side of tt
tongue. It is produced by the palato-glossus muscle. Between th
diverging palato-glossal and palato-pharyngeal arches on either sid
there is a triangular interval, which is occupied by the tonsil. Tt
passage which leads from the buccal cavity into the pharynx is calle
the oropharyngeal isthmus (isthmus of the fauces). It is somewha
 
 
 
THE HEAD AND NECK
 
 
I35i
 
 
istricted, and is bounded above by the soft palate, below by the
;k part of the dorsum of the tongue, and on either side by the
[ato-glossal arch.
 
Structure. —The soft palate is composed of a double fold of mucous
imbrane, which contains between its two layers an aponeurosis,
iscles, and many racemose glands, with bloodvessels and nerves,
e mucous membrane on the buccal surface has a median raphe,
iich is continuous with that on the mucous membrane of the hard
late, and along which the originally separate halves of the soft
late unite. On the buccal surface and along the postero-inferior
rder it is covered by stratified squamous epithelium, but on the
aryngeal surface by ciliated columnar epithelium. The glands.
 
 
 
 
Greater Palatine Artery
 
 
Palate pharyngeus __
 
 
Pnlato-glossus
 
 
Posterior Wall of Pharynx
 
 
 
Palatal Raph6
 
 
- Uvula
 
Palato-pharnygeal Arch
—-Palato-glossal Arch
 
— Tonsil
 
 
Dorsum of Tongue
 
 
biG. 816 .—The Cavity of the Mouth and Oropharyngeal Isthmus.
 
The jaws are widely separated.
 
 
hich are racemose or acinous, are especially abundant on the buccal
irface beneath the mucous membrane, where they are closely packed
igether. The palatine aponeurosis is attached anteriorly to the
Dsterior border of the hard palate, and laterally it becomes continuis with the aponeurosis of the pharynx. It affords attachment to
artions of the palatal muscles.
 
Muscles.— These are arranged in pairs, and are palato-glossus,
alato-pharyngeus, musculus uvulae, levator palati, and tensor palati.
 
Palato-glossus— Origin .—The surface of the palatine aponeurosis,
is fibres being continuous across the middle line with those of the
pposite muscle.
 
[ Insertion —The back part of the side of the tongue, where its
bres blend with the fibres of the transversus linguas.
 
 
 
 
 
 
 
 
 
 
1352
 
 
A MANUAL OF ANATOMY
 
 
Nerve-supply. —The pharyngeal plexus.
 
The direction of the muscle is outwards, downwards, and forward
Action. —(i) To depress the side of the soft palate, and (2)
draw the tongue upwards and backwards. The two muscles al‘
approximate the palato-glossal arches. By means of these combine
actions, aided by the tongue, the oropharyngeal isthmus is close<
and the anterior part of the buccal cavity is shut off from the pharyn
at the beginning of the second stage of deglutition.
 
The muscle forms the lowest layer in tt
soft palate, and it gives rise to the mucoi
fold, called the palato-glossal arch.
 
Palato - pharyngeus — Origin. — By tw
layers, upper and lower. The posterior (uppei
small layer arises from the palatine aponei
rosis of the back of the soft palate abov
the musculus uvulae, its fibres decussatin
with those of the opposite side; and th
anterior (lower) large layer arises from th
posterior margin of the hard palate, as we
as from the palatine aponeurosis, decussatin
with its fellow of the opposite side.
 
Insertion. —(1) The superior and posterio
borders of the lamina of the thyroid cartilage
and (2) the lateral and posterior wall of th
pharynx, its fibres blending with those 0
the stylo-pharyngeus.
 
The muscle receives an accessory sli]
from the lower part of the cartilage of th
pharyngo-tympanic tube, which is known a:
the salpingo-pharyngeus muscle.
 
Nerve-supply .—The pharyngeal plexus.
The muscle is directed downwards anc
backwards.
 
Action. —(1) To approximate the palatopharyngeal arch to its fellow at the commencement of the second act of deglutition,
and (2) to elevate the pharynx.
 
The muscle gives rise to the mucous fold
called the palato-pharyngeal arch.
 
Musculus Uvulae (Azygos Uvulae)— Origin.
— The side of the posterior nasal spine and the adjacent palatine
aponeurosis.
 
Insertion. —The submucous tissue of the uvula, having previously
united with its fellow of the opposite side.
 
Nerve-supply. —The pharyngeal plexus. The direction of the
muscle is backwards and downwards.
 
Action. —To elevate and shorten the uvula.
 
The muscle is double at its origin, but single at its insertion. It
 
 
 
Fig. 817.—Scheme to show
Planes in Composition
of Pharyngeal Wall,
with Relation of Muscles to Mucous Membrane (Dotted Line).
 
SUP., MID., INF., upper,
middle, and lower constrictors. Sinus of Morgagni is the interval between upper constrictor
and skull base; the tube
is seen coming through
this.
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1353
 
 
s above the levator palati, and beneath the upper layer of the
lato-pharyngeus.
 
Levator Palati— Origin. —(1) The rough surface on the inferior
pect of the petrous part of the temporal bone between the apex
d the carotid canal, and (2) the lower and posterior part of the
rtilage of the pharyngo-tympanic tube.
 
Insertion. —The aponeurosis of the soft palate, its posterior fibres
coming continuous across the middle line with the corresponding
res of the opposite muscle.
 
 
Tubal Elevation
 
 
Posterior Border
of the Vomer
 
Right Posterior Nasal Aperture
Levator Palati
 
 
 
 
 
 
Salpingopharyngeus
 
Musculus Uvulae
 
Palato
pharyngeus
 
 
Tensor Palati
 
 
-Medial Pterygoid
Uvula
 
l- Root of Tongue
 
 
-- Epiglottis
Wall of Pharynx
 
- Piriform Fossa
 
Arytenoideus Obliquus
 
- Arytenoideus Transversus
 
 
— Crico-arytenoideus
Posterior
 
 
(Esophagus
 
 
Fig. 818. —The Pharynx opened from Behind.
 
 
Nerve-supply. —The pharyngeal plexus.
 
The muscle is directed downwards, forwards, and inwards.
 
Action. —To raise the soft palate, and probably to open the pharyngonpanic tube.
 
The muscle, which is round and fleshy, passes over the upper
rder of the superior constrictor and through the pharyngeal apon:osis. At its origin it is closely related to* the membranous portion
the pharyngo-tympanic tube.
 
Tensor Palati— Origin. —The scaphoid fossa at the root of the
dial pterygoid plate of the sphenoid; and the ridge running back
far as the spine; and the lateral lamina of the cartilage of the
iryngo-tympanic tube.
 
 
 
 
 
 
 
 
 
 
 
 
1354
 
 
A MANUAL OF ANATOMY
 
 
Insertion. —(i) The transverse ridge on the under surface of th
horizontal plate of the palatine bone near the posterior border; an
(2) the aponeurosis of the soft palate.
 
Nerve-supply .—A branch from the nerve to the medial pterygoi
muscle.
 
The muscle at first descends vertically as a flat fleshy band betwee
the medial pterygoid plate and the medial pterygoid muscle, bein
in close contact with the medial surface of the latter. As it approache
the pterygoid hamulus it ends in a tendon, which turns round th
process, a synovial bursa intervening, and then passes horizontal!
inwards, expanding as it does so. From the fact that the muscle i
bent around the pterygoid hamulus it has been called the circum
flexus palati.
 
Action. —(1) To make tense the soft palate, and (2) to draw dowr
wards and backwards the margins of the cartilage of the pharyngc
tympanic tube, and so open the tube during deglutition. (See actio:
of levator palati.)
 
Sensory Nerves. —These are the greater and lesser palatine nerve
from the spheno-palatine ganglion, and the tonsillitic branches of th
glosso-pharyngeal.
 
Arteries. —The soft palate is supplied by the following arteries
(1) the ascending palatine of the cervical portion of the facial; (2) th
palatine branch of the ascending pharyngeal; and (3) the lesse
palatine branches of the greater palatine artery from the maxillary
which descends in the greater and lesser palatine canals.
 
Relation of Structures in the Soft Palate. —Supposing the sof
palate to be transfixed from its buccal to its pharyngeal surface, th
following structures would be pierced: (1) the mucous membran
covering the buccal surface, (2) the layer of closely-set racemos
glands, (3) the palato-glossus, (4) tensor palati, (5) the lower laye
of palato-pharyngeus, (6) the levator palati, (7) the musculus uvula
(8) the upper layer of the palato-pharyngeus, and (9) the mucou
membrane covering the pharyngeal surface.
 
Development. —The soft palate is developed from a differentiated portioi
of the palatal shelf or plate of the maxillary process of either side. This different!
ated portion does not undergo ossification, but acquires muscular tissue. Lik
the hard palate, the soft palate and the uvula are developed in two symmetrica
halves. The muscular tissue is derived from an upward growth from the wal
of the pharynx invading the posterior part of the (maxillary) palate fold. Thi
upgrowth makes the ‘posterior pillar of the fauces.’
 
 
The Tonsils.
 
The tonsils are two in number, right and left. Each is situatec
in the triangular depression between the palato-glossal and palato
pharyngeal arches on either side, and above it is a small recess, knowi
as the intratonsillar cleft (supratonsillar fossa), which is the remain:
of the inner portion of the second visceral cleft. The tonsil stands ou
as an oval enlargement covered by mucous membrane, and it lie;
 
 
 
THE HEAD AND NECK
 
 
1355
 
 
posite the angle of the mandible, being under cover of it and the
jacent portion of the ramus. The organ varies much in size, but
an average it measures about 1 inch in length, about f inch from
fore backwards, and about \ inch from within outwards. The
3dial surface is pitted with a number of orifices which lead into crypts
the interior. The outer surface, which has a fibrous covering, is
ated to the superior constrictor of the pharynx, some loose tissue
tervening, and lateral to the superior constrictor is the medial
erygoid muscle. Two of the tonsillar arteries, the tonsillar and
sending palatine, lie between the superior constrictor and medial
erygoid. The cervical portion of the facial artery in its course lies
little below the outer aspect of the tonsil. The internal carotid
tery is situated about 1 inch from it on its outer and posterior aspect.
Arteries.—(1) The tonsillar and ascending palatine branches of
e facial; (2) the ascending pharyngeal branch from the external
rotid; (3) the dorsalis linguae branches from the lingual; (4) the
 
 
 
Fig. 819. —Section through a Crypt of the Tonsil.
 
iser palatine offsets of the greater palatine artery from the third
rt of the maxillary; (5) tonsillar twigs from the internal carotid.
 
The veins form a plexus on the outer surface of the tonsil, from
lich the blood passes into the pharyngeal plexus.
 
Lymphatics.—These pass to the superior deep cervical lymph
mds.
 
Nerves.—The nerves are derived from (1) the glossopharyngeal,
> the lesser palatine branches of the spheno-palatine ganglion, and
) the sympathetic.
 
Structure. —The tonsils are composed of lymphoid follicles. The follicles
i ranged upon the sides of the crypts, which penetrate into the organ, these
/pts being lined with mucous membrane covered by stratified squamous
ithelium. Lymph corpuscles migrate from the follicles into the crypts, and
:ome salivary corpuscles.
 
Development. —The tonsil of either side is developed from the epithelium
the ventral part of the corresponding second visceral cleft. About the fourth
1 nth a depression, known as the sinus tonsillaris, makes its appearance. Solid
 
 
 
 
 
 
 
1356 A MANUAL OF ANATOMY
 
epithelial outgrowths or buds then extend from this sinus into the surroundinj
mesoderm. These buds subsequently become hollow, the surface of the sinu
becomes pitted, and so the crypts on the tonsil are formed. The mesoderm ii
relation to the buds and crypts becomes pervaded with lymphoid cells, and ii
this manner is formed the lymphoid tissue which constitutes the bulk of the tonsil
The intratonsillar cleft indicates the position of the ventral angle of th<
second lateral pouch.
 
The Nasal Cavity.
 
The nasal cavity extends from the anterior to the posterior aperture
of the nose. Anteriorly it opens upon the face, and posteriorly int(
the nasal part of the pharynx. The cavity is narrow above, bu
 
 
 
Fig. 820.—Sagittal Section through the Nasal Cavity, Mouth,
Pharynx, (Esophagus, and Larynx.
 
The outer wall of the right nasal cavity is shown.
 
 
expanded below. It is divided into right and left halves by the
nasal septum, and each half has two walls (outer and inner), a roof,
and a floor. The lateral wall is rendered very irregular by three bony
scrolls, disposed antero-posteriorly, which bulge into the fossa. These
are the superior, middle, and inferior nasal conchae. They overhang
deep channels, which are known as the meatus—superior, middle,
and inferior respectively.
 
The superior meatus is confined to the back part of the outer wall,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1357
 
 
id lies between tlie supeiior and middle conchae. It is short and
clique, and opening into it there are the spheno-palatine foramen,
hich leads from the pterygo-palatine fossa, and the posterior ethoidal sinus, by one or more openings. Above and behind the
Lpenor concha is a depression, called the spheno-ethmoidal recess,
to which the sphenoidal sinus opens.
 
The middle meatus is situated between the middle and inferior
>nchae, is directed from behind forwards, and is overhung by the
iddle concha. Anteriorly it describes a bend, and passes upwards
ider coyer of the front part of the middle concha, to be continued
to the infundibulum , which leads from the frontal sinus of the corre>onding side. The openings into the middle meatus are (1) the
fundibulum, leading from the frontal sinus, with the opening of the
iterior ethmoidal sinus * (2) the opening of the maxillary sinus;
 
 
Frontal Sinus
 
 
 
Orifice of Naso-lacrimal
Duct
 
 
Vestibule
 
 
Fig. 821.—The Lateral Wall of the Right Nasal Cavity.
 
The superior and middle conchae and part of the inferior concha have
 
been removed.
 
id (3) one or two openings of the middle ethmoidal sinus. These
irious openings are concealed by the middle concha. When this is
moved a deep curved groove, called the hiatus semilunaris, is seen
rected downwards and backwards from the lower end of the inndibulum. Behind and above this hiatus there is a round promince, called the bulla ethmoidalis (see Fig. 821). The opening of
e anterior ethmoidal sinus is situated in the vertical portion of the
atus semilunaris, and the opening of the maxillary sinus, which is
small size, is placed in its horizontal portion, whilst the middle
hmoidal sinus opens above the bulla ethmoidalis. In front of the
iddle meatus is the region known as the atrium, which communicates
teriorly with the vestibule, situated just within the ala of the nostril.
The inferior meatus is situated below the inferior concha. Openl into its anterior part, under cover of the inferior concha, is the
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1358
 
 
lower orifice of the naso-lacrimal duct, which is provided with an im
perfect mucous fold, called the lacrimal fold. The orifice is abou
ij inches from the anterior nasal aperture. Quite often the superio
nasal concha bifurcates posteriorly, and thus encloses a fourth o
highest meatus.
 
The inner wall forms the nasal septum.
 
The roof, which is narrow, is horizontal in its central part, th
anterior portion being sloped downwards and forwards, and th
posterior portion downwards and backwards.
 
 
Sphenoidal Sinus
 
 
Perpendicular
Plate of
Ethmoid
 
 
Frontal Sinus
 
 
Nasal Bone
 
 
 
1 Septal Process of
Lower Nasal Cartilage
 
 
Horizontal Plate of
Palatine Bone
(in section)
 
 
Septal Cartilage
 
 
Vomero-nasal Cartilage
 
 
Vomer
 
 
Palatine Process of Maxilla
(in section)
 
 
Fig. 822.—The Osseous and Cartilaginous Nasal Septum (Right
 
Lateral View).
 
 
The floor is smooth, and at its anterior and inner part is the incisoi
foramen, into which a funnel-shaped portion of the mucous membrane
extends. This region represents the wide communication whicl
existed in early life between the nasal and buccal cavities.
 
Each nasal cavity is divided into three regions—vestibular, olfactory, and respiratory. The vestibular region, or vestibule, form:
the anterior and lower part near the nostril. It is covered by skin
which is provided with hairs or vibrissce. The olfactory region i:
situated superiorly, and corresponds to the superior concha and th<
 
 
/
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1359
 
 
er third of the nasal septum. The respiratory region comprises
middle and inferior conchae, the middle and inferior meatus, and
corresponding part of the septum.
 
The Nasal Mucous Membrane. —With the exception of the vestibule,
ch is lined with skin, the nasal cavity is provided with a highly
sular and sensitive mucous membrane. It is continuous through the
terior nasal apertures with the mucous membrane of the nasal part
the pharynx; with that of the naso-lacrimal duct, lacrimal sac,
 
. lacrimal canaliculi, and thence with the conjunctiva; and with
t of the various air-sinuses which communicate with the nasal
ity. It is thick and spongy over the conchae, especially along the
er borders of the middle and inferior conchae, and also on the nasal
turn, but over the floor, atrium, and meatus it is comparatively
 
 
 
Fig. 823. _ The Nerves of the Nasal Septum (Hirschfeld and
 
Leveille).
 
 
n. It is freely provided with acinous glands, and contains a certain
 
ount of lymphoid tissue. •
 
The epithelium varies in different regions. In the vestibular
ion, where the lining membrane is skin, it is of the stratified squamous
'iety; in the respiratory region, as well as in the air-sinuses, it is
itified, columnar, ciliated epithelium; and in the olfactory region
s non-ciliated columnar epithelium.
 
Olfactory Mucous Membrane. —In the olfactory region the mucous
mbrane is thick and pulpy, and has a yellowish-brown colour,
3 to pigment in the epithelial cells. It contains a copious plexus
olfactory nerve-fibres, and many serous glands, which are known
the nasal glands (Bowman s glands). The epithelium is thick, and, as
5 been shown, is of the non-ciliated columnar variety, its free surface
ng covered by a delicate limiting membrane. The cells of whic
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1360
 
 
A MANUAL OF ANATOMY
 
 
it is composed are of three kinds: (1) Long columnar nucleated cel
called the supporting cells, the deep end of each of which is prolong
into a branched process. (2) Between these supporting cells the
are the olfactory cells, which are elongated and spindle-shaped. Ea
contains an almost spherical nucleus, and has a superficial and a de
process or pole. The superficial pole extends through the limiti
 
membrance to the free surface, and pi
jects slightly in the form of a tuft
delicate hair - like filaments called t
olfactory hairs. The deep pole , which
a delicate varicose filament, exten
towards the mucosa, where it becom
continuous with one of the nerve-fibr
of the olfactory plexus. (3) In the de
part of the epithelium there are in sor
places conical cells, the broad ends
which rest upon the basement membra
(see Fig. 824).
 
Olfactory Nerves. —These are from f
teen to twenty in number on each sic
After leaving the inferior surface of t
olfactory bulb, they pass through t
foramina in the corresponding half of t
cribriform plate of the ethmoid bor
and so reach the upper part of the nas
cavity invested by prolongations of t
membranes of the brain. Within t
nasal cavity they are arranged in t\
groups, inner and outer. The nerves
the inner group are distributed to the mucous membrane of the nas
septum over about its upper third. The nerves of the outer group a
distributed to the mucous membrane in the region of the superi
concha and olfactory sulcus. The nerves form a copious plexus
the mucous membrane, and the filaments which issue from this plex
become continuous, as has been shown, with the deep poles of t
olfactory cells. The olfactory nerves have no medullary sheath.
 
Nerves of Ordinary Sensation:
 
1. Upper nasal branches of the
 
spheno-palatine ganglion.
 
2. Nasal branches of the nerve of
 
the pterygoid canal.
 
3. Lower nasal branches of the
 
greater palatine nerve.
 
The upper nasal branches of the spheno-palatine ganglion enter the superi
meatus through the spheno-palatine foramen, and are distributed to the muco
membrane (1) over the superior and middle conchae, (2) over the upper ai
back part of the nasal septum, and (3) within the posterior ethmoidal sinus.
 
Branches from the nerve of the pterygoid canal pierce the floor of that can;
and are distributed to the mucous membrane over the back part of the roof
the nasal cavity and the adjacent part of the septum.
 
 
4. Anterior ethmoidal nerve.
 
5. Branches of the anterior superi
 
dental nerve.
 
6. Long spheno-palatine nerve.
 
7. Infra-orbital nerve.
 
 
 
 
Olfactory _
Hairs ||
 
 
Peripheral
 
Process
 
 
Supporting
 
Cell
 
 
Olfactory li
Cell ha
 
 
Nerve Fibre V.
Process
 
 
 
Fig. 824.— Cells of Olfactory Mucous Membrane
 
(SCHULTZE, FROM QuAIN’S
 
‘ Anatomy ’)•
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1361
 
 
Lower nasal branches arise from the greater palatine branch of the sphenolatine ganglion as that nerve traverses the greater palatine canal. They
ter the nasal cavity through foramina in the perpendicular plate of the
latine bone, and are distributed to the mucous membrane over the greater
rt of the inferior concha, and the corresponding parts of the middle and
ferior meatus.
 
The branches from the anterior ethmoidal nerve are two, septal and lateral,
le septal branch is distributed to the mucous membrane over the anterior and
>per part of the septum, and the lateral branch to that over the anterior
irtions of the middle and inferior conchae, and over the outer wall in front
these.
 
Upper nasal branches of the anterior superior dental nerve are distributed to
e mucous membrane over the anterior part of the inferior meatus and the
!jacent part of the floor of the nasal cavity.
 
The infra-orbital branch of the trigeminal supplies the vestibule.
 
Anterior Ethmoidal Arterv
 
 
 
Fig. 825. —The Arteries of the Nasal Septum (Hirschfeld and
 
Leveille).
 
It will be noticed that, with the exception of the anterior ethmoidal branch of
te naso-ciliary, all the nerves of the nasal cavity are derived from the maxillary
vision of the trigeminal nerve.
 
The long spheno-palatine nerve arises from the spheno-palatine ganglion,
id enters the nasal cavity through the spheno-palatine foramen. It then
osses the roof, and so reaches the septum, upon which it descends with a
rward inclination, occupying the groove on the outer surface of the vomer.
 
then passes downwards to the anterior part of the hard palate, the left nerve
aversing the anterior incisive canal, and the right nerve the posterior incisive
nal. As the long spheno-palatine nerve lies upon the nasal septum it furnishes
anches to its mucous membrane.
 
Arteries of the Nasal Cavity. —These are derived from the following sources:
 
1. The spheno-palatine. 4. The anterior ethmoidal.
 
2. The greater palatine. 5 - The posterior ethmoidal.
 
3. The artery of the pterygoid canal. 6. The superior labial.
 
The spheno-palatine artery is the principal artery of the nasal cavity. Arising
am the third part of the maxillary, it enters the cavity through the sphenoilatine foramen. Most of its branches are distributed to the outer wall; but
 
86
 
 
 
 
 
 
 
 
 
 
 
1362
 
 
A MANUAL OF ANATOMY
 
 
one, called the posterior septal branch, accompanies the long spheno-palati
nerve. This branch gives offsets to the septum, and enters the incisive forame
where it anastomoses with a branch of the greater palatine artery, which ascen
from the palate in the incisive canal.
 
The greater palatine artery arises from the third part of the maxillary. .
it traverses the greater palatine canal it gives off two or three branches whi
accompany the lower nasal branches of the greater palatine nerve throu,
foramina in the perpendicular plate of the palate bone, to be distributed to t
back part of the inferior concha and the adjacent parts of the middle and i
ferior meatus.
 
The artery of the pterygoid canal, arising from the third part of the maxillai
traverses the pterygoid canal, and furnishes a few twigs which accompany t
branches of the corresponding nerve, and supply the back part of the roof
the nasal cavity and the adjacent part of the septum.
 
The anterior and posterior ethmoidal arteries are branches of the ophthalm
The anterior ethmoidal enters the nasal cavity along with the anterior ethmoid
 
 
 
Posterior Lateral
Nasal Branches
 
 
Anterior EthmoiiJal
 
 
Posterior Ethmoidal
 
Posterior Septal Branch (cut)
Spheno-palatine
 
 
Ascending Branch of
Greater Palatine
 
 
Soft Palate
 
 
Fig. 826. —-The Arteries of the Lateral Wall of the Right Nasal
Cavity, (after Hirschfeld and Leveille).
 
nerve, and furnishes branches to the anterior and upper part of the septur
the front part of the outer wall, and the anterior portions of the middle ar
inferior conchae. The posterior ethmoidal gives nasal branches which enter tl
nasal cavity through some of the foramina in the cribriform plate of the ethmoii
and are distributed to the roof and upper part of the septum.
 
The superior labial artery, a branch of the facial, gives off a septal branc,
which supplies the anterior part of the septum and the columna nasi.
 
The veins form a free plexus, especially over the inferior concha and tl
lower margin and back part of the middle concha. The vessels which can
away the blood from the plexus correspond to the various arteries, and the
principal destination is threefold—namely, (1) the pterygoid plexus, (2) th
superior ophthalmic vein, and (3) the anterior facial vein. The ethmoidal vein
which open into the superior ophthalmic vein, communicate with the intracrani;
anterior meningeal veins and with the commencement of the anterior faci<
vein by means of twigs which pass through minute apertures in the front*
process of the maxilla, and, it may be, through a small foramen in the nas;
bone. In those cases where the foramen caecum is pervious it transmits a
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK 1363
 
issary vein which passes between the intracranial superior sagittal sinus
3 the veins of the roof of the nasal cavity.
 
The lymphatics of the atrium and vestibule pass to the submandibular lymph
nds. The principal lymphatics pass to (1) the retropharyngeal glands; (2) the
ip facial lymph glands; and (3) the superior deep cervical lymph glands,
e lymphatics of the air-sinuses end in a similar manner.
 
The lymphatics of the nasal fossae communicate with lymphatic spaces
ich are related to the olfactory nerve-filaments; and these lymphatic spaces
turn communicate with the intracranial, subdural, and subarachnoid spaces.
 
 
Development of the Nose (pp. 83-88).
 
 
The cavity of the mouth in the embryo is separated from the lower surface
the fore-brain and its derivatives by a layer of mesoderm which thickens
titinuously. The nasal cavities are developed in this mesodermal layer, and
as are not parts of the common mouth cavity', they open into this cavity by
ertures which lengthen as the mesoderm thickens, and of which the greater
rtions are secondarily closed by the palate folds, the unclosed parts forming
e definite posterior nasal apertures.
 
The first indications of the olfactory organ are the two olfactory areas,
ley consist of thickened ectoderm, and are placed on the ventral aspect of
e anterior cerebral vesicle, on either side of the mesial nasal process of the
mto-nasal process, and on the cephalic side of the orifice of the stomodaeum
ig. 54).
 
Each olfactory area soon becomes depressed and forms the olfactory pit.
le depression is due to the growth of mesoderm; on the inner and outer sides
is forms inner and outer nasal folds respectively, continuous in front but open
hind. The outer fold is the longer, and the maxillary process, growing inards across this, comes into contact with the inner fold, with which it fuses,
bus the pit becomes a shallow fossa. Its posterior end is closed by the junction
maxillary and inner nasal processes, and the epithelial fusion between these
akes the hucco-nasal membrane, separating it from the mouth. The membrane
oses what is, potentially, a primitive posterior naris ; it is stretched as this
■ows, and finally breaks and disappears. .
 
The subsequent development of the proportionately full-sized cavity from
tis small beginning has been described on p. 85, etc., to which the reader is
 
 
ferred. . .
 
The lower conchal mass is present at an early stage, being made by the mmal projection of the lower edge of the outer nasal fold. It is added to by
idition of maxillary mesoderm as the fossa increases in length backwards,
le middle and upper nasal conchce become evident later as the cavity grows
ey are present by the end of the second month. The upper mass is described
derived from the upper part of the inner wall, migrating across the roof,
ie ontogenetic evidence of this is very doubtful. The cartilaginous bases of
ie masses are derived from the cartilaginous capsule. In foetal life there is
marked tendency for the two upper masses to show longitudinal subdivisions,
ving the appearance of the presence of half a dozen or more conchae, but the
Dpearance is deceptive, as these are only surface formations, and are usua y
 
st by the time of birth. . , „ ,
 
The maxillary sinus can be recognized in the third month as a depression
l the outer wall. It extends very slowly, so that at birth it only makes a
ivity a few millimetres wide in the inner part of the maxilla.
 
A cartilaginous nasal capsule is built Up round the two cavities as t ey
ctend up. It is deficient below, where the elongated aperture is placed, e
s lateral plate has its lower edge turned in to make the cartilaginous asis o
ie lower nasal concha. The other nasal conchae are based on ingrowths from
s inner aspect. It presents the septal cartilage centrally, forme m e 1C
lesoderm between the two cavities. The vomer develops as a paire ossi ca
on in the mesoderm along the lower or free edge of the septal cartilage.
 
 
1364
 
 
A MANUAL OF ANATOMY
 
 
palatine bone ossifies on the deep surface of the capsule, and the maxilla
structures superficially. The premaxilla and incisive part of the palate devel
in the region of the primitive palate. The capsule is in contact with the bo
of the sphenoid above and behind, and a wing-like process here, the orbi
sphenoidal process, is related with the lesser wing.
 
 
 
Fig. 827.
 
 
The two upper figures show the lower aspects of the projecting heads of embry
of 4 mm. and 7 mm. (From reconstruction models.) The change
position of the olfactory region is due to the growth of the telencephah
in the 7 mm. specimen. This not only advances the front of the he;
beyond the site of the olfactory fields, but also, as a result of increase
breadth, turns them more on to the lower aspect. A and B in the low
figures are sections through the olfactory fields of the two embryos, showii
formation of olfactory pits and fronto-nasal process. C and D are diagrar
rnatic sections to illustrate the further changes. The maxillary process
are indicated by interrupted lines to show where they will come into po:
tion, as in D. ONF, INF, lateral and medial nasal folds; FNP, fronto-nas
process.
 
The Paranasal Sinuses. —The frontal, ethmoidal, sphenoidal, and maxilla!
sinuses are developed as evaginations of the nasal mucous membrane, whi(
extend into spaces formed by absorption within the respective bones. The ma
toid air-cells are developed as evaginations of the tympanic mucous membran
which is continuous with the nasal mucous membrane through the pharyngt
tympanic tube and nasal part of the pharynx.
 
Olfactory Organ. —The true olfactory organ is situated in the upper par
or olfactory region, of each nasal cavity. The olfactory epithelium, which cove:
 
 
 
 
 
 
THE HEAD AND NECK 1365
 
ie mucous membrane of this region, is developed from the upper part of the
orresponding olfactory pit.
 
External Nose. —The dorsum and tip of the nose, and the columna nasi, are
eveloped from the portion of the mesial nasal process which lies between the
lobular processes. The upper and lower nasal cartilages are derived from the
irtilaginous core of the corresponding lateral nasal process. The anterior
asal aperture of each side represents, as stated, the external orifice of the
 
 
 
 
Fig. 828. —Antero-posterior Sections of Heads of Embryos of
 
16 and 28 Mm.
 
 
corresponding olfactory pit, but it is modified by secondary extensions of
maxillary mesoderm round its margins.
 
The Vomero-nasal Organ (Organ of Jacobson). —The vomero-nasal
organ is rudimentary in man, but is well developed in reptiles.* It
takes the form of a blind pouch, which is situated in the lower and
anterior part of the nasal septum on either side. The minute orifice
 
* There is some doubt as to whether the rudimentary structure of man is
really vestigial of that of the lower forms.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1366
 
 
A MANUAL OF ANATOMY
 
 
of the pouch lies above the recess or depression of mucous membrane
which projects slightly into the upper end of the incisive canal. Th
pouch extends upwards and backwards in the nasal septum for a ver
short distance, and ends in a blind extremity. The vomero-nas;
(subvomerine) cartilage lies underneath it. The vomero-nasal orga
does not seem to perform any function in man. In those animal:
however, in which it is well developed it receives two nerves, one c
which is olfactory, the other being derived from the spheno-palatiu
ganglion. Moreover, its epithelial lining is similar to that of the o
factory region of the nasal cavity, inasmuch as it contains olfactor
cells, the deep poles of which are continuous with olfactory filaments
In such animals it acts as a supplementary organ of smell.
 
 
 
Fig. 829.—View, from below and behind, of the Roof of the
Mouth of an Embryo of 16 Mm. (Sixth Week).
 
Showing the palate folds reaching the fronto-nasal process, the evident shaj
of this process, though covered by a layer of maxillary mesoderm, and tl
growth of the labial extension of the mesoderm, only just meeting its fello
in the middle line. This will become much thicker and vertically deepe
hiding the fronto-nasal form altogether. The interrupted lines indicathe extension upward of the upper level of the posterior nasal apertures.
 
Development of the Vomero-nasal Organ. —This organ is developed as
diverticulum of a portion of the ectoderm of the olfactory pit. The diverticulu:
projects upwards and backwards into a recess situated laterally within tl
lower and anterior part of the septal nasal cartilage just above the upper er
of the incisive canal; it marks the meeting of the paraxial and visceral mesodern
in the septum.
 
The Pharynx.
 
The pharynx is situated behind the posterior nasal apertures, tl
oropharyngeal isthmus, and larynx, and it extends from the basik
region of the base of the skull to the level of the lower border of tl
cricoid cartilage of the larynx, where it becomes continuous with tl
oesophagus. It is a musculo-aponeurotic tube about 5 inches lon|
and it attains its greatest width between the base of the skull an
 
 
 
 
THE HEAD AND NECK
 
 
1367
 
 
e hyoid bone. Below the latter level it narrows, and is flattened
)m before backwards, so as to assume the form of a transverse cleft,
cept during the act of deglutition.
 
Relations. —Posteriorly it rests upon the bodies and discs of the
rvical vertebrae as low as the sixth, and the prevertebral muscles
vered by the prevertebral fascia. Between it and the last-named
scia is the retropharyngeal space, which is occupied by connective
ssue, but this is so loosely arranged that no obstacle is offered to
Le movement of the tube, and a post-pharyngeal abscess can readily
ffuse itself. Anteriorly it communicates with (1) the nasal cavities
trough the posterior nasal apertures, (2) the pharyngo-tympanic
 
 
Sinus of Morgagni
 
 
Lateral Pterygoid Muscle
Styloid Process
 
 
Superior Constrictor - .4 _
Muscle
 
 
Middle Constrictor
Muscle
 
 
 
Inferior Constrictor Muscle
 
 
--Head of Mandible
 
-Spheno-mandibu
lar Ligament
 
.Ramus of Mandible
 
_,Stylo-phar. Muse.
 
.Stylo-hyoid Lig.
 
f_Medial Pterygoid
 
Muscle
 
__.Greater Horn of
 
Hyoid Bone
 
-’Angle of Mandible
 
Ah--- .-Median Pharyngeal
 
Ms Raphe
 
 
Fig. 830.
 
 
Oesophagus
 
 
-The Posterior Wall of the Pharynx and Adjacent
 
Structures.
 
 
ubes, (3) the buccal cavity through the oropharyngeal isthmus, and
4) the larynx. On this aspect its attachments are effected by means
)f the constrictor muscles in its walls. Laterally it is related to the
irincipal bloodvessels and nerves of the neck, and comes into contact
vith the styloid muscles and the process from which they arise.
Superiorly it is attached to the basilar region of the base of the skull.
 
r nferiorly it is continuous with the oesophagus. .
 
The wall of the pharynx consists of the following four strata,
:rom without inwards: (1) the pharyngeal portion of the buccopharyngeal fascia, (2) the muscular coat, (3) the pharyngo-basi ar
; ascia, and (4) the mucous coat.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1368
 
 
A MANUAL OF ANATOMY
 
 
Bucco-pharyngeal Fascia.—This is an offshoot of the prevertebrs
layer of the deep cervical fascia along the medial aspect of the carotii
sheath. In front it becomes continuous with the fascia covering th
buccinator muscle. In association with this fascial stratum there ar
many veins upon the posterior and lateral walls of the pharynx, whicl
constitute the pharyngeal venous plexus.
 
Muscular Coat.—This is composed on either side of the three cou
strictor muscles—inferior, middle, and superior—the stylo-pharyngeus
 
and the palato-pharyngeus (including th
salpingo-pharyngeus).
 
Inferior Constrictor— Origin .—(i) The sid
of the cricoid cartilage at its posterior part
(2) the inferior horn of the thyroid cartilage
and (3) the outer surface of the lamin
behind the oblique line.
 
Insertion .—The median raphe on the pos
terior wall of the pharynx, where it meet
its fellow of the opposite side.
 
The lower fibres of the muscle are hori
zontal, but the upper fibres pass upward
and backwards more and more obliquel}
and the highest fibres of the two muscle
meet in the raphe to form a peak, which i
about an inch below the basilar part of th
occipital bone. The lower border of th
muscle overlaps the upper end of the oesc
phagus. The recurrent laryngeal nerve an
inferior laryngeal artery pass upwards be
 
 
 
Fig. 831.—Scheme to show neath the lower border behind the cricc
 
 
Planes in Composition
of Pharyngeal Wall,
with Relation of Mus
 
SUP., MID., INF., upper,
middle, and lower constrictors. Sinus of Morgagni is the interval be
 
 
thyroid joint. The upper border, which i
very oblique, overlaps the lower portion c
cles to Mucous Mem- the middle constrictor, and the interne
brane (Dotted Line). laryngeal nerve and the superior laryngee
 
artery, on their way to pierce the thyro-hyoi
membrane, pass between the two muscle
anteriorly.
 
, . . . Middle Constrictor— Origin. —(1) The oute
 
and Skull base; the tube border of the greater horn of the hyoid bon
is seen coming through over its entire length, (2) the lesser horr
this. and (3) the hyoid extremity of the style
 
hyoid ligament.
 
Insertion .—The median raphe on the posterior wall of the pharym
where it meets its fellow of the opposite side.
 
The muscle is fan-shaped, and its fibres consequently diverg
very much as they pass round to reach the raphe. The inferior fibre
descend very obliquely, and are overlapped by the upper fibres c
the inferior constrictor, the internal pharyngeal nerve and superic
laryngeal artery passing to the thyro-hyoid membrane between th
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1369
 
 
0 muscles anteriorly. The middle fibres pass more or less transrsely. The superior fibres ascend obliquely, and reach the basilar
rt of the occipital bone. They overlap the lower portion of the
perior constrictor, and the stylo-pharyngeus muscle and glossoaryngeal nerve pass between the two. The lingual artery lies
perficial to the muscle at the greater horn of the hyoid bone.
 
Superior Constrictor— Origin. —(1) The lower third of the posterior
rder of the medial pterygoid plate, and the pterygoid hamulus
ocess of the sphenoid bone; (2) the posterior aspect of the pterygo
 
 
Fig. 832. _Dissection showing the Cheek, Pharynx, Submandibular
 
Region, and Larynx (Right View).
 
landibular ligament, along which it meets the buccinator muscle,
]) the posterior extremity of the mylo-hyoid line of t e mandibe,
I-) the mucous membrane of the mouth; and (5) the side o e ongue.
 
Insertion .—The median raphe on the posterior wall of the pharynx
diere it meets its fellow of the opposite side. A few °f t e ig es
bres are inserted into the pharyngeal tubercle on the under sur ace
 
f the basilar part of the occipital bone. .
 
The muscle is four-sided. The fibres for the most part pass horiontally, but the lower fibres radiate in a downward direction, whi st
he upper fibres curve backwards and upwards. The lower portion
 
 
 
 
 
 
 
 
 
1370
 
 
A MANUAL OF ANATOMY
 
 
of the muscle is overlapped by the upper part of the middle constricto
the stylo-pharyngeus muscle and glosso-pharyngeal nerve passir
between the two. Between the upper, concave border and the bas
of the skull there is an interval occupied by the pharyngo-basik
fascia, which is here stronger than elsewhere, and so compensates f(
the absence of muscular fibres. This interval is semilunar, and
known as the sinus of Morgagni.
 
Nerve-supply of the Constrictor Muscles.—The nerves are derive
from the pharyngeal plexus, which is formed by the pharyngeal branc
 
 
 
Fig. 833. —Sagittal Section through the Nasal Cavity, Mouth,
Pharynx, (Esophagus, and Larynx.
 
The outer wall of the right nasal cavity is shown.
 
 
of the vagus, the pharyngeal branches of the glosso-pharyngeal, an
sympathetic filaments. The motor fibres of the plexus are derive
from the pharyngeal branch of the vagus, but their ultimate source i
the cranial root of the accessory nerve. The inferior constrictor musd
also receives twigs from (1) the external laryngeal branch of tb
superior laryngeal nerve, and (2) the recurrent laryngeal nerve as i
passes beneath the lower border of the muscle.
 
Action.—The constrictor muscles are concerned in the act of d(
glutition. The superior constrictor and upper portion of the midd]
constrictor act upon the nasal part of the pharynx—that is, the con
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
I 37 i
 
 
irtment of the pharynx which lies above the soft palate—and is in
mmunication with the nasal cavities through the posterior nasal
jertures. They narrow the nasal part of the pharynx in the lateral
rection, and this movement, in conjunction with the action of the
ilato-pharyngeal arch, shuts off the cavities, thus preventing relrgitation into and through the nasal cavities. The lower portion of
ie middle constrictor and the inferior constrictor diminish the calibre
the oral part of the pharynx. Coming into action during the second
age of deglutition, they grasp the bolus of food and press it downwards
to the oesophagus. The constrictor muscles contract rapidly, and
order from above downwards.
 
For a description of the stylo-pharyngeus and palato-pharyngeus
uscles (including the salpingo-pharyngeus), see pp. 1323 and 1352.
 
Pharyngo-basilar Fascia (Pharyngeal Aponeurosis).—This is situated
Tween the muscular coat and the mucosa. Interiorly it is weak and
distinct, but superiorly it acquires greater firmness and density,
specially where it is attached to the basi-occipital, the apex of the
strous part of the temporal bone, the adjacent portion of the pharyngounpanic tube, and the medial pterygoid plate of the sphenoid bone.
: receives an accession of strength in the median line from a strong
imdle of fibres which descends from the pharyngeal tubercle on the
nder surface of the basilar process of the occipital bone, and which
irms the raphe of the pharynx.
 
Interior of the Pharynx.—The mucous membrane, which forms
ie deepest stratum in the pharyngeal wall, is of a papillary
laracter, and has the following important continuations: (1) with
ie mucous membrane of the pharyngo-tympanic tube, and thence
ith that of the tympanic cavity; (2) with that of the nasal cavities
irough the posterior nares; (3) with that of the cavity of the mouth
irough the oropharyngeal isthmus; (4) with that of the larynx through
ie superior laryngeal aperture; and (5) with that of the oesophagus,
d its upper and back part it is richly provided with lymphoid tissue,
i be noticed presently, and in the submucous tissue there are many
cinous glands of a mucous character.
 
The soft palate projects into the cavity of the pharynx in a downward and backward direction, and divides it into two regions, upper
nd lower. The upper region is known as the nasal part of the pharynx,
nd is in communication with the nasal cavities and pharyngo-tympanic
iibes. It also communicates with the lower region. by means of
tie pharyngeal isthmus. The lower region is subdivided into two
arts, oral and laryngeal. The buccal part is limited above by the
3 ft palate, and below by the inlet of the larynx, and it communicates
dth the cavity of the mouth through the oropharyngeal isthmus,
he laryngeal part is situated behind the larynx, with which it
ommunicates, as well as with the oesophagus interiorly.
 
The Nasal Part of the Pharynx.—This is entirely respiratory in
motion, and is therefore always patent. It measures a little more
fan an inch from above downward, and about 2 inches from side to
 
 
 
^372
 
 
A MANUAL OF ANATOMY
 
 
side, while from before backward it is about f inch. It is bounded
front by the posterior nasal apertures and the posterior border of t]
vomer; behind, by the vertebral column; above, by the basilar pa
of the occipital and part of the body of the sphenoid; and below 1
the soft palate, which can be elevated and depressed. Four openin
communicate with it. The anterior wall has the oval openings
the posterior nasal apertures leading from the nasal cavities, ai
separated from each other by the posterior border of the vomer. Ea<
opening in the recent state measures about i inch from above dow
wards, and about \ inch from side to side. Through it, on the out
wall of the corresponding nasal cavity, are seen the posterior par
 
 
Posterior Border
of the Vomer
 
 
Tubal Elevation
 
 
Right Posterior Nasal Aperture
/ Levator Palati
 
 
Salpingo
pharyngeus
 
 
Musculus Uvulas
Palatopharyngeus
 
 
 
1 WL— . Tensor Palati
 
 
- Medial Pterygoid
Uvula
 
- Root of Tongue
 
 
-pL -Epiglottis
 
_ Wall of Pharynx
 
_ Pyriform Fossa
.. Arytenoideus Obliquus
. Arytenoideus Transversus
 
A Crico-arytenoideus Posterior
 
 
CEsophagus
 
 
Fig. 834.—The Pharynx opened from Behind.
 
of the middle and inferior nasal conchae, covered by mucous membram
and above and below the inferior nasal concha are seen the posteri(
parts of the middle and inferior meatus. The orifice of the pharyng'
tympanic tube is situated on each lateral wall behind and external 1
the corresponding posterior nasal aperture, and on the same lev
as the posterior end of the inferior nasal concha. It is somewhc
triangular, and has, above and behind, a prominent round bordf
formed of cartilage covered by lymphoid tissue, called the tub .
elevation. Behind the tubal elevation there is a deep pouch on tl
lateral wall of the nasal part of the pharynx, called the pharynge
recess (fossa of Rosenmuller), which is a secondary widening of til
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1373
 
 
of of the primitive pharynx. The mucous membrane extending
:tween the pharyngeal recesses at the upper and back part has a
imber of folds containing a large amount of lymphoid tissue, which
institute the naso-pharyngeal tonsil. When enlarged, this mass is
ible to obstruct the orifices of the pharyngo-tympanic tubes, and
ten the posterior nasal apertures, and is known as adenoids. At
le lower part of the naso-pharyngeal tonsil there may be seen a small
edian recess, called the pharyngeal bursa, which leads upwards and
ickwards towards the pharnygeal tubercle on the basilar part of the
xipital bone.
 
The mucous membrane is covered by ciliated columnar epithelium.
 
The Oral Part of the Pharynx.—This part is situated between the
)ft palate and the inlet of the larynx. Anteriorly it communicates
ith the cavity of the mouth, through the oropharyngeal isthmus,
elow which the root of the tongue forms its anterior wall. Each
iteral wall shows the palato-pharyngeal arch, the interval between
le two arches corresponding to the pharyngeal isthmus. In front
E each arch is a triangular depression which lodges the tonsil.
 
Laryngeal Part of the Pharynx.—This part is situated behind the
trynx. Anterior to it there are the epiglottis, the inlet of the larynx,
n either side of which is a recess called the pyriform fossa, and the
osterior parts to the arytenoid and cricoid cartilages, with the muscles
dated to them. It communicates with the larynx anteriorly and
tie oesophagus interiorly.
 
The mucous membrane of the buccal and laryngeal portions is
Dvered by stratified squamous epithelium.
 
Blood-supply.—The arteries of the pharynx are derived from the
scending pharyngeal branch of the external carotid, the ascending
alatine and tonsillar branches of the cervical part of the facial artery,
nd the greater palatine and pharyngeal branches of the maxillary.
 
The veins form a copious pharyngeal plexus, which is disposed
pon the lateral and posterior walls of the pharynx. It communicates
uperiorly with the pterygoid venous plexus, and receives tributaries
'om the soft palate, tonsils, and pharyngo-tympanic tubes. Interiorly
tie blood is conveyed from it into the internal jugular vein.
 
Lymphatics.—The lymphatic vessels from the upper part of the
harynx pass to the deep facial lymph glands, which are associated
rith the lateral walls of the tube, and those from the remaining part
ass to the upper group of deep cervical lymph glands. Some of the
^mphatics from the upper part pass to the retropharyngeal lymph
lands of its own side, each of which lies upon the upper part of the
orresponding longus capitis muscle.
 
development of the Pharynx and of the Pharyngeal Pouches or Visceral Grooves
 
and Visceral Arches (see Chapter II.).
 
The pharynx is developed from the anterior or cephalic part of the fore-gut.
 
On the ventral wall or floor of this part certain grooves are found at an
arly stage running more or less transversely, and separated from one another
•y thick and transversely directed masses of mesoderm; these are the visceral
 
 
 
1374
 
 
A MANUAL OF ANATOMY
 
 
 
arches, and the grooves are known as visceral grooves (clefts). Each groo\
runs out to the lateral part of the cavity, where it terminates in a deepe
pharyngeal pouch, which can again be divided into dorsal and ventral part:
each of these being the seat of distinct developments. On the outer aspect <
the embryo the arches are visible, except in the case of the fifth and sixth, an
the external grooves between them, lined with ectoderm, are at first in conta(
with the entodermal linings of the corresponding lateral pharyngeal pouche:
This contact is soon lost, save in the case of the first (external meatus).
 
As growth proceeds, the arches (and grooves) are placed (see Fig. 835) moi
obliquely as they are followed back. They run medially into a central long
tudinal prominence, the hypobranchial eminence, especially in the case of tt
 
 
Fig. 835.—A, external pharyngeal arches, 4 mm. B, floor of early pharyn
exposed from above. C, shows on left the adult formations, their arc!
origins being indicated on right. D, indicates remnants of skeletal structure
of arches. Visceral arches are numbered in Roman figures. M, R, Meckel
and Reichert's bars. On left, in C, the forward growth of third arch :
shown not only in tubo-tympanic part, but in back of tongue, across tonsi
fossa, and in pharyngeal extension to palate.
 
third and fourth, and in front of this is the little tuberculum impar, centrall
placed in the first groove. The opening of the pulmonary outgrowth is sagittall
placed just behind the eminence.
 
The arches and grooves are numbered from before backwards, the numbe
of each groove being that of the arch just in front of it. The first is often terme
the mandibular arch, as the lower jaw forms in it; its upper and outer part lie
under the head region in front of the ear, and from here a maxillary proC6£
grows forwards from it below the eye to form the upper arcade of the mouth,
There are,six arches and five grooves. The first four arches are distinc
(see Fig. 49A). The fifth is rudimentary, and is buried with its groove at the bottoy
of the fourth pouch. The sixth forms the immediate boundary on each sid
of the pulmonary opening. The first four grooves are distinct, the fifth i
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK 1375
 
uded in the fourth, and no definite groove limits the caudal part of the
th arch.
 
The widest part of the cavity is opposite the second arch. Here is formed
! tubo-tympanic recess from which the tympanic cavity and tube are differentid as the result of forward growth of the third arch over the second. This
wth goes over the region of the large second lateral pouch, but leaves the
sal or outer part of this in the tympanic cavity, while its ventral part remains
the pharyngeal wall and becomes the fossa in which the tonsil will develop,
e growth forward of the third arch comes up against the first arch to some
:ent, and obliterates its groove so far, but the dorsal part of the first pouch
aains in the tympanic cavity (Fig. 835, C).
 
The hypobranchial eminence forms the main epiglottic mass; the third arch
ning from this becomes the pharyngo-epiglotiic fold, and the fourth forms
s ary-epiglottic fold. The third pouch marks the pyriform fossa, while the
irth is lost, occasionally indicated as a depression beside the lower margin
the cricoid. The sixth arches are joined with an upward growth of the fourth
form a paired mass standing up behind the epiglottis; this mass (arytenoid
inences) is separated from the epiglottis by a transversely disposed cleft, bounded
erally by the ary-epiglottic folds, and hides the sagittal opening from view
d makes the supraglottic part of the larynx. The tongue is developed in front
the hypobranchial eminence, the tuberculum impar being enlarged to form
5 front part of the organ, while paired growths from the front of the eminence
d (?) the central parts of the second arches make its back part behind the
bus terminalis.
 
The ventral part of the third pouch gives origin to the bud from which the
miUS is formed. A similar bud from the fourth pouch develops into an
ithelial mass embedded in the back of the lobe of the thyroid. The thyroid
md proper is formed from a central entodermal downgrowth which takes
ice early just behind the tuberculum impar; the situation of this is therefore
irked in the adult by the foramen caecum, which is formed by the two masses
at make the back of the tongue meeting each other at an angle, and being
us applied to the front portion of the organ.
 
The third pouch and the constituents of the fourth pouch complex give off
rtain outgrowths which separate from them through atrophy of the pharynal connection, and which may be divided into dorsal and ventral bodies. Ventral
dies from the third pouch make the thymus, shifting caudally; from the
irth, make a ‘ rudimentary thymus 5 which remains applied to. the back of
e thyroid lobe; from the fifth rudiment, constitute an ‘ ultimo-branchial
dy’ which remains in the same situation. Dorsal bodies: from the third,
e lower parathyroid, carried down with the thymus; from the fourth, upper
rathyroid, remaining more or less in situ ; no dorsal body from the fifth has
t been found in human embryos.
 
At a later stage each visceral arch presents the following four elements:
 
) an artery; (2) a visceral myotome or muscle-segment; (3) a nerve (or nerves);
d (4) a rod of cartilage. The artery is known as a visceral arch artery, and it
one of the primitive aortic arches, establishing communications between the
rresponding primitive ventral and dorsal aortas.
 
Myotomes of Visceral Arches. —The visceral myotome in each arch gives rise
certain muscles. The myotome of the first arch furnishes (1) the. anterior
lly of the digastric ; (2) the mylo-hyoid; and (3) the muscles of mastication—
tmely, (a) masseter, ( b ) temporalis, (c) lateral pterygoid, and (d) medial pterygoid.
 
The myotome of the second arch furnishes (1) the posterior belly of the digastric;
) the stylo-hyoid; and (3) the stapedius. From this myotome are also derived
.e muscles Of expression on the face and epicranial region, as well as the platysma.
iese muscles migrate during ontogeny over the neighbouring areas.
 
The myotome of the third arch furnishes the stylo-pharyngeus, and the middle
•nstrictor of the pharynx may be regarded as derived from it.
 
The myotome of the fourth arch (and perhaps that of the fifth arch) may be
garded as furnishing the inferior constrictor of the pharynx.
 
 
A MANUAL OF ANATOMY
 
 
1376
 
Nerves of Visceral Arches—First or Mandibular (Oral) Arch. —The comm
 
nerve of this arch is the trigeminal nerve. The mandibular division belongs
the mandibular process of the arch, and to its muscles, and the lower teeth
one side; the maxillary division belongs to the maxillary process of the arch, a
to the upper teeth of one side. The ophthalmic division is not concerned in i
supply of the arch; it is a distinct nerve phylogenetically, only supplying parax
formations.
 
Second or Hyoid Arch. —The nerve of this arch and of the first pharyng(
pouch is the facial nerve. The auditory nerve may be included.
 
Third or Thyro-hyoid Arch. — The nerve of this arch and of the secoi
pharyngeal pouch is the glosso-pharyngeal nerve.
 
Fourth Arch. —The nerve of this arch is the superior laryngeal nerve, whi
is a branch of the vagus.
 
Sixth Arch. —The nerve of this arch is the recurrent laryngeal nerve, which
a branch of the vagus.
 
The bar of cartilage in each arch is developed in the mesenchyme, whi
forms the core of the arch.
 
Metamorphoses of the Visceral Arches.
 
First Visceral or Mandibular Arch. —This arch is situated, as stated, betwe
the first pharyngeal pouch and the stomodaeum or primitive oral cavity. ]
artery is the first primitive aortic arch; its nerve is the mandibular divisi
of the trigeminal nerve; its cartilaginous bar is known as Meckel’s cartilage. T
ventral end of this cartilage meets its fellow of the opposite side, and is join
to it by connective tissue. The dorsal end is related to the periotic cartilagino
capsule, and furnishes an offshoot, called the manubrium.
 
1. The upper or dorsal end of Meckel’s cartilage, becoming ossified, grv
rise to the malleus, and probably the incus.
 
2. The lower or ventral end of Meckel’s cartilage is ossified in the incis
portion of the mandible.
 
3. The part of Meckel’s cartilage between the upper and lower ends disappea:
The membranous investment of the lower or mandibular portion of this part grv
rise to the chief part of one-half of the body of the mandible, and the lower h
of the ramus as high as the mandibular foramen. The membranous investme
of the upper portion, between the periotic cartilaginous capsule and the mandibul
foramen, forms the spheno-mandibular ligament.
 
4. The maxillary process, aided by part of the fronto-nasal process —namel
the globular and lateral nasal processes —gives rise to the maxilla (see Develo
ment of the Skull).
 
5- The upper end of the first arch on its superficial surface gives rise to t
tragus, and part of the helix of the pinna.
 
Second or Hyoid Arch. —This arch is situated, as stated, between the fii
and second pharyngeal pouches. Its artery is the second primitive aortic arcl
its nerve is the facial nerve, with the chorda tympani; and its cartilaginous b
is called the hyoid bar, or cartilage of Reichert. This bar ventrally is connect
with its fellow of the opposite side by a transverse copula, forming part of t
body of the hyoid bone.
 
The second bar becomes transformed into the following structures:
 
1. The upper or dorsal segment of the hyoid bar gives rise to the head, net
and limbs of the stapes, the foot-piece of that ossicle perhaps being develop*
from the cartilaginous capsule of the labyrinth within the fenestra vestibuli.
 
2. The succeeding segment of the hyoid bar gives rise to (a) the tympar
hyal, and (b) the stylo-hyal, which collectively constitute the styloid process
the temporal bone.
 
3. The next portion of the hyoid bar becomes converted into fibrous tissr
and forms the stylo-hyoid ligament, which sometimes exists as an epi-hyal born
 
4. The lower or ventral segment of the hyoid bar gives rise to the cerato-hyt
or lesser horn of the hyoid bone.
 
 
THE HEAD AND NECK
 
 
1377
 
 
The second, arch also gives rise superiorly to the antihelix, antitragus , and
ule of the pinna; and inferiorly, along with the third arch, possibly helps to
 
m one-half of the posterior third of the tongue.
 
Third or Thyro-hyoid Arch— This arch is situated between the second and
rd pharyngeal pouches. Its artery is the third primitive aortic arch; its nerve
;he glosso-pharyngeal nerve; and its cartilaginous bar is known as the thyro)id bar. This bar is connected ventrally with its fellow by a copula.
 
A large portion of the thyro-hyoid bar disappears, but its lower or ventral
ment gives rise to the thyro-hyal or greater horn of the hyoid bone. The
i-hyal or body of the hyoid bone is developed from the copula.
 
Fourth and Fifth Visceral Arches. —The artery of the fourth arch is the fourth
mitive aortic arch, and its nerve is the superior laryngeal nerve, which is a
,nch of the vagus. The artery of the fifth arch is the fifth primitive aortic
h, and its nerve a small and transient branch of the vagus. The greater
•tions of these two arches disappear; but the lower or ventral ends of their
tilaginous bars are by some regarded as giving rise to a small part of the
lina of the thyroid cartilage. The lower musculature of the pharynx comes
m the cells of the fourth arch, as does also the crico-thyroid .
 
Sixth Visceral Arch. —The artery of this arch is the sixth primitive aortic
h. Its nerve is the recurrent laryngeal. The sixth arch itself, being unferentiated, leaves no traces behind it, but the internal intrinsic muscles of
! larynx are formed from its cells.
 
The metamorphoses of the pharyngeal pouches have been already described
connection with these pouches.
 
The first external furrow, corresponding to the first internal pharyngeal
ich, gives rise, as stated, to the external auditory meatus, and the walls of
: upper part of this furrow become differentiated into the component parts
 
the pinna.
 
Sinus Cervicalis and Cervical Fistula. —The first or mandibular and second
hyoid arches increase more rapidly in all directions than the succeeding
hes. The third and fourth visceral arches therefore become overlapped
the second or hyoid arch, and now lie at the bottom of a depression. This
Dression is called the sinus cervicalis. The lining membrane of the sinus is
med by the ectodermic coverings of the overlapped visceral arches. The
us is, as a rule, transitory, the second arch atrophying rapidly, and the
rd external groove disappearing, while the third arch flattens. The fourth
:h is partly covered from behind, a ‘ placodal duct ' being enclosed for a short
le. Otherwise there is no ‘ closing of a cervical sinus ’ in man such as has
m described in lower forms.
 
Morphology of the Visceral Arches and Clefts.— In aquatic animals — e.g.,
ihes and Amphibia at an early stage, but only in Perennibranchiata pernentlv—these are called the branchial or gill-arches and clefts. The clefts
lge in number from five to eight, and they differ from those of Mammals
I Birds, inasmuch as they are complete clefts, the closing membrane being
sent. They therefore establish free communications between the exterior
1 the fore-part of the alimentary canal, or throat, for the entrance and exit
water.
 
The functional branchial arches are those which are post-oral, commencing
:h the second. The second branchial or gill-arch is not, however, a real
tnchial arch in the functional sense, but is opercular, giving rise on either
e to the operculum or gill-cover. The real branchial or gill-arches, properly
called functionally, are those which succeed to the second, of which the third
1 fourth are conspicuous. I he mucous membrane of the real branchial
-hes is folded into parallel lamellae, which are placed close together, and
s freely furnished with capillary bloodvessels, the blood being derived from
^ branchial-arch arteries. These lamellae constitute the branchiae or gills.
Aquatic respiration consists in the passage of currents of water containing
pgen through the complete gill-clefts into the pharyngeal part of the foret. As the water bathes the branchiae, or gills, its oxygen is taken up into the
 
87
 
 
 
A MANUAL OF ANATOMY
 
 
1378
 
blood within the branchial capillaries, and the carbon dioxide of the capillc
blood is yielded up to the water. Thereafter the water is expelled throu
the gill-clefts, and is immediately replaced by a fresh current of respiratc
water. The branchiae, or gills, of aquatic animals therefore correspond functi(
ally to the lungs of Mammals and Birds, whose respiration is aerial.
 
The Pharyngo-tympanic Tube.
 
The pharyngo-tympanic tube (Eustachian tube) leads from t
tympanic cavity to the nasal part of the pharynx, and is about i| inct
in length. It is directed forwards, inwards, and slightly downwan
and is composed of two parts, bony and cartilaginous. The bo
or postero-lateral part is about \ inch long, and is situated in the anj
between the petrous and squamous parts of the temporal bone. T
cartilaginous or antero-medial part is about 1 inch in length, and 1
on the groove between the greater wing of the sphenoid and the api<
portion of the petrous part of the temporal bone. It is at first narro
but gradually enlarges, so as to resemble a trumpet. The narrow(
part of the whole tube is at the junction of the bony and cartilaginc
parts; this is the isthmus, and the widest part is at the pharyng<
orifice. The roof, inner wall, and upper part of the outer wall of t
cartilaginous part consist of a triangular plate of cartilage, the margi
of which are slightly rolled towards each other. The floor and mt
of the outer wall are formed of a dense fibrous membrane. T
pharyngeal orifice of the tube is expanded, and is situated on the late:
wall of the nasal part of the pharynx behind, and external to, t
corresponding posterior nasal aperture, and on the same level as t
posterior end of the inferior nasal concha. It is somewhat triangul;
and above and behind is the tubal elevation, already described, form
by the thick margin of the cartilage, and posterior to this is the phar)
geal recess.
 
The tube is lined with mucous membrane, which is continue
with that of the tympanic cavity on the one hand, and of the na
part of the pharynx on the other. It is thin in the bony part of t
tube, but in the cartilaginous part it is thick, and contains mucc
glands and lymphoid tissue. It is covered by stratified columr
ciliated epithelium.
 
Muscles connected with the Pharyngo-tympanic Tube. —The leva
palati has an origin from the lower margin of the cartilage of the tul
the tensor palati from the outer side of the cartilage, and the salpinj
pharyngeus is attached to the lower and front part of the tube. Duri
deglutition the orifice of the tube is opened.
 
Arteries are derived from the artery of the pterygoid canal, fr(
the third part of the maxillary, and the ascending pharyngeal bran
of the external carotid.
 
Nerves. —The nerves come from the tympanic plexus on the ini
wall of the tympanic cavity, and the nerve of the pterygoid canal.
 
Development. —From the tubo-tympanic recess of the primitive phary
modified and narrowed by forward growth of the third arch (Fig. 835, C).
 
 
 
THE HEAD AND NECK
 
 
1379
 
 
The Larynx.
 
The larynx is the upper part of the respiratory passage, being
)dified in structure so as to enable it to act as the organ of voice,
is situated in the median line of the neck above the trachea, and it
s opposite the fourth, fifth, and sixth cervical vertebrae. Superiorly
opens into the laryngeal portion of the pharynx, and interiorly into
e trachea. It is covered in front by the integument and the deep
rvical fascia, and the laryngeal portion of the pharynx lies behind
On either side it is in relation with the upper part of the lobe
the thyroid gland, the sterno-hyoid, omo-hyoid, sterno-thyroid,
d thyro-hyoid muscles, and the common carotid artery.
 
 
Epiglottis
 
Superior Horn of Thyroid . —
 
Cartilage / .
 
Cuneiform Cartilage _i_
Comiculate Cartilage !j—
 
 
Axytenoideus Obliquus —
Arytenoideus Transversus--'
 
Crico-arytenoideus Posterior
Crico-thyroid Joint
 
 
Cricoid Cartilage—— "
Trachea
 
 
Wu>. •••
 
 
SEI!
 
ll '!)
 
f 1
»•
 
tail,
 
(1 Ml
 
‘lull
 
 
?ig. 836. —The Intrinsic Muscles of the Larynx (Posterior View).
 
 
Structure.—The larynx consists of a framework of cartilages, some
which are connected by joints and ligaments; it is provided with
ecial muscles, spoken of as intrinsic ; and it is lined with mucous
embrane.
 
Cartilages are nine in number, three being single and three arranged
pairs. The single cartilages are The epiglottis, the thyroid, and the
icoid; and the three arranged in pairs are the arytenoid, corniculate,
id the cuneiform.
 
The epiglottis is a leaf-like plate of yellow elastic fibro-cartilage,
tiich is placed between the base of the tongue and the inlet of the
rynx. Its lower part forms a stalk which is attached to the receding
igle of the thyroid cartilage, just below the thyroid notch on its
 
 
 
 
 
 
 
 
 
 
 
 
1380
 
 
A MANUAL OF ANATOMY
 
 
upper border, by means of a fibro-elastic band, called the thyr
epiglottic ligament. Above it has a broad, round, free margin. Ea<
lateral border is free above, but its lower part is contained within t]
ary-epiglottic fold of mucous membrane. The anterior or lingu
surface is free over its upper part, where it faces the base of the tongr
and is covered by mucous membrane. This membrane is prolong!
on to the base of the tongue as the glosso-epiglottic fold, which
medially placed. It is also prolonged from the sides of the epiglotl
on to the lateral walls of the pharynx as the pharyngo-epiglottic fold
On either side of the glosso-epiglottic fold, between it and each pharyng
epiglottic fold, there is a depression or fossa, which is known as t]
vallecula. Lower down than these folds the anterior surface is co
nected to the back of the upper border of the body of the hyoid boi
by an elastic, semilunar membrane, called the hyo-epiglottic ligamer
 
 
Thyroid Notch
 
 
 
- Superior Horn of Thyoid
Cartilage
 
Superior Thyroid Tubercle
 
• Oblique Line of Lamina
Laryngeal Prominence
' Inferior Thyroid Tubercle
 
' Inferior Horn
 
 
Cricoid Cartilage Crico-thyroid Ligament
 
 
Fig. 837.—The Thyroid and Cricoid Cartilages of the Larynx
 
(Anterior View).
 
 
Above the upper border of the thyroid cartilage the anterior surfa<
is attached to the back of the body of the hyoid bone and of the thyr
hyoid membrane by dense connective tissue. The posterior or lary
geal surface is free over its whole extent, and is covered by mucoi
membrane. It is concave from side to side, and concavo-convt
from above downwards. The lower convexity forms the tuberc
(cushion). When the mucous membrane is removed, the epiglott
presents a number of small glandular pits.
 
Development.— The epiglottis is developed from the hinder part of the hyp
branchial eminence.
 
Thyroid Cartilage. —This cartilage is composed of two flat quadi
lateral laminae false), which meet in front by their anterior border
but diverge widely behind. The angular projection formed by the
union is called the laryngeal prominence (pomum Adami). The unic
is confined to about the lower half of each anterior border, and the
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1381
 
left superiorly a deep triangular cleft called the thyroid notch. The
►sterior border, of greater length than the anterior, is round, and
yes attachment to fibres of the palato-pharyngeus and stylo-pharynus muscles. At either extremity it is prolonged into a projection,
e superior horn and inferior horn respectively. The superior horn
yes attachment to the lateral thyro-hyoid ligament, and the inferior
irn, which is slightly incurved, is faceted on its inner aspect to
ticulate with the cricoid cartilage. The superior border is for the
ost part convex, and near its back part is a slight eminence, called
e superior thyroid tubercle. The inferior border is almost horizontal,
id has an eminence about the junction of the posterior third with the
terior two-thirds, called the inferior thyroid tubercle. It gives
tachment to the median portion of the crico-thyroid ligament and
e crico-thyroid muscle. The outer surface of the lamina is marked
 
 
Laryngeal Prominence
 
 
 
Fig. 838.—The Thyroid and Cricoid Cartilages of the Larynx
 
(Lateral View).
 
 
an oblique line, which extends downwards and forwards from the
perior to the inferior tubercle. This line gives insertion to the
irno-thyroid, and origin to the thyro-hyoid muscles. It divides the
ter surface into two unequal parts—an anterior three-fourths and
posterior fourth, the latter giving origin to fibres of the inferior
nstrictor muscle. The inner surface of the lamina is smooth, slightly
ncave, and covered by mucous membrane. In the median line,
hind the laryngeal prominence, there is a vertical depression known
the receding angle. Beginning just below the thyroid notch on
e upper border and passing downwards, this region gives attach^nt to the following structures: the thyro-epiglottic. ligament, the
stibular ligaments, and the vocal ligaments, in association with which
5 the fibres of the thyro-arytenoid muscles.
 
Development of the Thyroid Cartilage. —The thyroid cartilage represents
' ventral portions of the skeletal cartilages of the fourth (and ? fifth) visceral
lies of either side, which become united by a median plate.
 
 
 
 
1382
 
 
A MANUAL OF ANATOMY
 
 
Cricoid Cartilage.—The cricoid cartilage is situated below tl
thyroid cartilage, and forms the lower part of the larynx. It bea
some resemblance to a signet-ring, and it consists of two parts—s
anterior arch and a posterior lamina.
 
The arch is narrow from above downwards as well as from sic
to side. The inferior border is horizontal, and is connected with tl
first ring of the trachea by a fibro-elastic membrane. The superi
border is connected with the inferior border of thyroid cartilage t
the crico-thyroid ligament.
 
The lamina is quadrilateral, broad, and deep. Its depth is owii
to the rapid elevation of the superior border of the arch as it pass
backwards. The inferior border is connected laterally with the fir
 
ring of the trachea by a fibro-elastic membran
and medially, where the tracheal rings are d
ficient, to the same membrane. The superi
border has a median notch, and on either side «
this an oval convex facet for articulation wil
the base of the arytenoid cartilage. The posteri
surface is divided into two depressed areas by
median vertical ridge, which gives attachment
the longitudinal muscular fibres of the oesophagi!
The depressed area on either side of this medic
vertical ridge gives origin to the crico-arytenoidei
posterior.
 
The outer surface of the cricoid cartilage pr
sents posteriorly a circular facet for articulatic
with the inferior horn of the lamina of the thyroid cartilage. Tl
upper sloping border of this part gives attachment along its inn
margin to the lateral portion of the crico-vocal membrane.
 
The internal surface of the cricoid cartilage is lined with the mucoi
membrane of the larynx.
 
Development. —The cricoid cartilage, like the rings of the trachea, is develop!
in the mesoderm of the respiratory tube, in the sixth arch.
 
Arytenoid Cartilages.—These cartilages are placed above the crico
cartilage posteriorly. Each has the form of a three-sided pyrami
and measures about -J inch in height, and about J inch in width
the base. The apex looks upwards, and is curved in a backward at
inward direction. It is surmounted by the corniculate cartilag
The base looks downwards, and is slightly concave and faceted
articulate with the superior border of the cricoid cartilage posteriori
Two of the three angles of the base project. The anterior ang]
somewhat pointed, is directed straight forwards to form the voc
process. It gives attachment to the vocal ligament. The extern
angle, thick and somewhat round, has an inclination backwards
well as outwards, and is known as the muscular process. Anterior
it gives insertion to the crico-arytenoideus lateralis, and posterior
to the crico-arytenoideus posterior. The surfaces are antero-laten
 
 
For Articulation with
Arytenoid Cartilage
 
 
 
Fig. 839.— The Cricoid Cartilage of
the Larynx (Posterior View).
 
 
 
 
THE HEAD AND NECK
 
 
1383
 
 
sterior, and medial. The antero-lateral surface, a little above the
cal process, attaches to the vestibular ligament, and above and
:eral to the vocal process the thyro-arytenoideus muscle. The
sterior surface is triangular and concave, and gives attachment to
portion of the arytenoideus transversus. The medial surface faces
; fellow of the opposite side, and is covered by mucous membrane,
forms the posterior part of the lateral boundary of the rima glottidis.
le borders are anterior, posterior, and lateral. The anterior border
parates the medial from the antero-lateral surface, and terminates
low in the vocal process. The posterior border separates the medial
)m the posterior surface. The lateral border separates the antero-lateral
)m the posterior surface, and ends below in the muscular process.
 
The thyroid and cricoid cartilages usually retain their cartilaginous con:ion up to about the twentieth year. In the case of the thyroid cartilage
fification proceeds from the inferior horn, there being a special osseous nucleus
the region of the laryngeal prominence.
 
 
 
Fig. 840. —The Right Arytenoid Cartilage and Corniculate
Cartilage (Lateral Aspect Enlarged).
 
The anterior part and lower margin of the cricoid cartilage remain cartipnous for some time, but the remainder undergoes ossification simultaneously
ith the thyroid cartilage.
 
Ossification of the arytenoid cartilages takes place at a later date than in
e case of the two preceding cartilages.
 
Corniculate cartilages (cartilages of Santorini) are two small, somehat conical nodules of yellow elastic cartilage which cap the apical
arts of the arytenoid cartilages, their direction being backwards and
iwards. Each lies within the ary-epiglottic fold of mucous membrane.
 
Cuneiform cartilages are two nodules of yellow elastic cartilage,
Inch are situated, one on either side, in the ary-epiglottic fold of
iucous membrane at its back part, not far from the corniculate
irtilages.
 
Development. —The arytenoid cartilages are formed in the sixth arches,
id the ary-epiglottic folds from the fourth. The corniculate cartilages are
I shoots of the arytenoid cartilages. The cuneiform cartilages are derived from
 
ie epiglottis.
 
 
1384
 
 
A MANUAL OF ANATOMY
 
 
Ligaments 0! the Larynx—Thyro-hyoid Membrane.—This is
 
broad membranous sheet, which passes between the superior borde
of the thyroid cartilage and the back of the upper border of the bod
of the hyoid bone, as well as the deep border of each greater horr
Its central and lateral portions are strong, and are composed large!
of elastic tissue. The central portion is known as the median thy re
hyoid ligament, its lower attachment being to the border of the thyroii
cartilage. The lateral portions, round and cord-like, are very elastic
and are known as the lateral thyro-hyoid ligaments. Each extend
from the superior horn of the thyroid cartilage to the tip of the greate
horn of the hyoid bone, and enclosed within it, towards its upper pail
there is a small nodule of cartilage called the cartilago triticea
Between the upper median portion of the thyro-hyoid membrane ari(
the concave posterior surface of the body of the hyoid bone there i
a synovial bursa. It is to be noted that the superior attachment 0
 
 
 
the thyro-hyoid membrane is such as to enable the upper part of the
thyroid cartilage, when raised, to be received within the outline 0:
the hyoid bone. The central portion of the membrane is subcutaneous
but on either side it is covered by the thyro-hyoid muscle. Beneatf
the posterior border of this muscle the internal laryngeal nerve anc
superior laryngeal artery pierce the membrane.
 
Crico-vocal Membrane.—This membrane is composed of an anterioi
and two lateral portions. The anterior portion or crico-thyroid ligameni
portion, elastic and triangular, is attached by its base to the lowei
border of the thyroid, and by its apex to the upper border of the
cricoid, close to the mid-line. It is subcutaneous in the median line
except that it is crossed by the crico-thyroid branch of the superioi
thyroid arteries. Through this portion laryngotomy may be performed. The lateral part of the crico-vocal membrane is connectec
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1385
 
elow with the upper border of the lateral part of the cricoid cartilage,
uperiorly it is not connected with the thyroid cartilage, but passes
eep to its lamina into the larynx, where it expands in an inward
irection, and extends from the back of the lamina of the thyroid
artilage in its lower part, close to the receding angle, to the under
spect of the vocal process of the arytenoid cartilage. Between these
oints it becomes continuous with the vocal ligament. The lateral
ortion of the crico-thyroid membrane (within the lamina of the thyroid
artilage) is covered by the crico-arytenoideus lateralis and thyrorytenoideus.
 
Vestibular Ligaments (Superior Thyro-arytenoid Ligaments).—These
Drm two small fibrous bands, one at either side, which lie within the
dds of mucous membrane, called the vestibular folds (false vocal cords).
Lach is attached in front to the receding angle of the thyroid cartilage
mmediately below the attachment of the thyro-epiglottic ligament,
nd behind to the antero-lateral surface of the arytenoid cartilage
little above the vocal process.
 
Vocal Ligaments (Inferior Thyro-arytenoid Ligaments).—These
nportant ligaments, covered by mucous membrane, constitute the
ocal folds (true vocal cords), and each is continuous with the upper
•art of the expanded lateral portion of the crico-vocal membrane.
Lach is composed of yellow elastic tissue, and with its fellow is attached
1 front to the receding angle of the thyroid cartilage at its centre
nd behind to the vocal process of the arytenoid cartilage. Its inner
order, which is covered by mucous membrane, is free and clearly
efined. In its front part there is a very small nodule of elastic
artilage.
 
Crico-thyroid Joint.—This belongs to the class of synovial joints.
 
'he articular surfaces are the facet on the inner surface of the inferior
orn of the thyroid cartilage, and that on the outer surface of the
ricoid cartilage posteriorly. The joint is surrounded by a capsular
gament, and this is lined with a synovial membrane. The moveaents allowed are as follows: (1) rotation of the thyroid cartilage round
n axis passing transversely through both joints; and (2) gliding, in
diich the cricoid moves upwards and backwards, or downwards and
Drwards, this movement partaking somewhat of a swinging character.
 
The recurrent laryngeal nerve ascends close behind the cricohyroid joint before entering the larynx.
 
Crico-arytenoid Joint.—This belongs to the class of synovial
oints. The articular surfaces are the convex facet on the superior
'order of the cricoid cartilage posteriorly, and the concave under
urface of the base of the arytenoid cartilage. The joint is surrounded
y a capsular ligament, and this is lined with a synovial membrane,
he movements allowed are as follows: (1) rotation, in which the
rytenoid cartilage rotates on a nearly vertical axis, the effect being
0 invert or evert the vocal process; and (2) gliding in a lateral direction,
 
1 which one cartilage moves inwards towards its fellow, or outwards
way from its fellow.
 
 
1386
 
 
A MANUAL OF ANATOMY
 
 
The corniculate cartilages are usually connected to the arytenoit
cartilages by fibrous tissue, but in some cases there is a synovia
articulation.
 
Prelaryngeal Lymph Glands.—One or two glands may lie upon tin
median portion of the crico-vocal membrane in the interval betweei
 
 
Root of Tongue
 
 
 
 
 
Epiglottis
 
 
Ary-epiglottic Fold
 
 
Vestibular Fold
Ventricle
Vocal Fold
Cuneiform Cartilage
 
 
Vocal Process of
Arytenoid Cartilage
 
 
the crico-thyroid muscles. Thei
afferent vessels are derived fron
 
(1) the infraglottic portion of th
larynx, the lymphatics from whicl
pierce the crico-vocal membrane
 
(2) the beginning of the trachea
and (3) the upper part of the isthmu
of the thyroid gland. Their efferen
vessels pass either to the inferio
deep cervical lymph glands, or t<
the pretracheal glands as an inter
mediate gland-station.
 
The Cavity of the Larynx.—Tb
inlet of the larynx is situated be
hind and below the epiglottis. I
is triangular, being wide in fron
and narrow behind, and its plan
is sloped obliquely downwards an(
backwards. Above and in front i
n ls bounded by the epiglottis, am
behind by the fold of mucous membrane
which stretches between the arytenoid
cartilages. On either side are the prominent ary-epiglottic folds, which extend
from the tips of the arytenoid cartilages
to the sides of the epiglottis and contain muscular fibres. Each of these
folds, close to the arytenoid cartilage,
contains the corniculate cartilage, which
gives rise to a slight elevation, and a
little in front of this another slight
elevation is produced by the cuneiform
cartilage. Between the arytenoid cartilage and the back part of the aryepiglottic fold medially and the back
 
 
Rima Glottidis Corniculate Cartilage
 
Fig. 842. — The Inlet of the
Larynx and Adjacent Parts.
 
 
Epiglottis
 
 
 
Vestibule
 
 
Lamina of Thyroid
Cartilage
Middle Part
 
 
Cricoid Cartilage
 
 
Lower Part
 
 
Trachea
 
 
part of the lamina of the thyroid Fig. 843. —Vertical Transvers
cartilage laterally there is a depression, Section of the Larynx, shov
opening upwards, called the pyriform ing the Posterior Surface c
 
fossa. This is important, because unless Organ^Marshaix) ALF ° F ™
an instrument intended for the interior (Marshall).
 
of the larynx is kept carefully to the mid-line it will enter the foss
and be pressed against its floor, just below the mucous membrane (
which the internal laryngeal nerve passes on its way to the larynx.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1387
 
 
The cavity of the larynx begins at the inlet, and ends on a level with
he lower border of the cricoid cartilage. It is divided into three
ompartments by means of two antero-posterior folds of mucous
nembrane, which project into it from each lateral wall. The upper
>air of folds are called the vestibular cords, and the lower pair the
r ocal folds. The upper compartment is known as the vestibule of
he larynx, and it extends as low as the vestibular folds. It is wider
bove than below, and its anterior depth exceeds the posterior. The
niddle part is situated between the vestibular folds above and the
meal folds below. On either side is a recess, called the sinus of the
arynx (ventricle). This is bounded above by a vestibular fold, and
>elow by a vocal fold. Its outer wall is covered by fibres of the
hyro-arytenoid muscle. At the anterior part of the sinus there is
 
 
 
Fig. 844. —Sagittal Section of the Larynx and Trachea, showing
the Vocal Folds and Sinus of the Right Side.
 
 
1 small valvular aperture, which leads to a diverticulum of the
ventricle, called the saccule of the larynx. This extends upwards
Detween the vestibular fold and the lamina of the thyroid cartilage,
reaching as high as the upper border of the latter. On its medial aspect
there are some muscular fibres, which are known as the compressor
sacculi laryngis.
 
The lower part of the larynx is compressed from side to side above,
but becomes circular inferiorly, where it opens into the trachea.
 
The vestibular folds (false vocal cords) are two folds of mucous
membrane, which extend at either side from the receding angle of
the thyroid cartilage immediately below the attachment of the thyroepiglottic ligament to the antero-lateral surface of the arytenoid
cartilage a little above the vocal process. Each contains some fibrous
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1388
 
 
A MANUAL OF ANATOMY
 
 
tissue, forming the vestibular ligament. The vestibular folds ar
widely separated from each other by an interval known as the rim
vestibuli [false glottis), so that the vocal folds are visible on lookin
into the larynx from above.
 
The vocal folds (true vocal cords) are concerned in the productioi
of the voice. They are prominent folds at either side, which ar
rather less than an inch in length, and extend from the receding angl
of the thyroid cartilage to the vocal process of each arytenoid cartilage
Each cord consists of the vocal ligament, which is continuous with th
upper part of the expanded lateral portion of the crico-vocal membrane
 
and is composed of yellow elastic
 
 
Thyroid Notch
 
 
Lamina of Thyroid Cartilage / JMljift fif
 
/J
 
 
Thyro-arytenoideus
 
 
Vocal Fold '
 
 
Crico-arytenoideus
 
Lateralis
 
 
Arytenoid Cartilage
 
Crico-arytenoideus Posterior
 
 
 
Arytenoideus
 
 
tissue. The mucous membran<
covering the fold is thin, anc
firmly adherent to the elastii
tissue of the ligament, and it has ;
characteristic pearly white colour
The vocal folds are much nearei
to each other than the false, s(
that the latter are not visible
when the larynx is viewed froir
below.
 
Rima Glottidis.—The rima glottidis, or true glottis, is the narrov
fissure by which the upper anc
lower parts of the larynx communicate with each other, and il
 
 
Tig. 845. Dissection of the Larynx, fUp narrowest nart of f-fie ravhv
showing the Muscles, Vocal Folds 1 + • narro ^ e ^ P art °* tne cavl y
and Rima Glottidis (Superior 1S elongated from before backView) . wards, and is narrow in front at
 
. the receding angle of the thyroid
 
cartilage, but wider behind, where it is closed by the interarytenoid
° d °1 mucous membrane. It is divisible into an intermembranous,
part and an inter cartilaginous part. The intermembranous part is
nari ow, and is bounded on either side by the vocal cord. Its length
is rather less than an inch, and it forms about two-thirds of the
entire aperture. The intercartilaginous part is wider than the intermembranous part, and is bounded on either side by the inner aspect
oi the base of the arytenoid cartilage. It is about J inch in length,
an ^orms about one-third of the length of the entire aperture.
 
The shape of the rima glottidis is subject to alteration, and has
to be considered under three conditions:
 
( I ) During quiet respiration it has the form of an elongated triangle,
the apex being in front at the thyroid cartilage, and the base behind
at the mterarytenoid fold of mucous membrane. (2) During a deep
inspiration the rima is widely dilated, and assumes a diamond shape,
the widest part being opposite the tips of the vocal processes of the
aiytenoid cartilages, where the lateral angles of the diamond are
placed, the posterior angle at the interarytenoid fold of mucous mem
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1389
 
 
irane being truncated. (3) While talking, and especially in singing
igh notes , the vocal folds become so closely approximated as to be
►ractically parallel, and the rima glottidis assumes the form of a narrow
 
hink.
 
Mucous Membrane of the Larynx.—This is continuous above with
he mucous membrane of the pharynx, and below with that of the
rachea. Above the level of the rima glottidis its subjacent attachment is loose on account of the presence of submucous areolar tissue,
articularly near the ary-epiglottic folds, a condition which favours
 
 
Epiglottis and its Tubercle
 
 
Sinus of Larynx,
 
 
Vestibular Fold
 
 
Vocal Fold
Cuneiform Cartilage
Corniculate Cartilage ■""* __
Tip of Arytenoid Cartilage
 
 
 
 
 
 
 
 
r iG. 846. —The Inlet of the Larynx and the Rima Glottidis, as seen by
the Aid of the Laryngoscope under Different Conditions.
 
(The Figures on the left side are copied from Czermak.)
 
A, Ordinary quiet inspiration C, Vocalization, especially in singing high notes
 
B, Very deep inspiration R.G. Rima glottidis
 
 
he occurrence of oedema, but over the laryngeal surface of the epiglottis it is firmly attached. Over the vocal folds it is very thin,
md is so firmly connected to the vocal ligaments that oedema cannot
>ass this point. The membrane is covered by ciliated columnar
pithelium, except (1) near the margin of the ary-epiglottic folds,
vhere it is of the stratified squamous variety, as in the laryngeal
)ortion of the pharynx and the cavity of the mouth; and (2) over the
X)cal folds, where it is also of the stratified squamous vaiiety. Bodies
esembling the taste-buds of the tongue are met with on the laryngeal
surface of the epiglottis, the inner surfaces of the arytenoid cartilages
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1390
 
 
A MANUAL OF ANATOMY
 
 
and of the ary-epiglottic folds, and over the margins of the vestibula
folds.
 
The mucous membrane contains a large number of acinous mucou
glands, the ducts of which open freely on the surface, except over th
vocal folds, where there are no glands. They are arranged in the follow
ing groups: (i) epiglottic glands, which are very numerous, and occup;
the pits on the laryngeal surface of the epiglottis; (2) arytenoid glands
in front of the arytenoid cartilages, and in the adjacent portions 0
the ary-epiglottic folds; (3) along the vestibular folds; and (4) in th
wall of the laryngeal saccule, where they are very numerous.
 
It is of practical importance to remember that an opening mad
in the crico-thyroid space enters the larynx below the vocal folds
 
 
Epiglottis
 
Superior Horn of Thyroid
Cartilage
 
Cuneiform Cartilage
Corniculate Cartilage
 
Arytenoideus Obliquus
Arytenoideus Transversus
 
Crico-arytenoideus Posterior
Crico-thyroid Joint
 
 
Cricoid
 
 
Fig. 847. —The Intrinsic Muscles of the Larynx (Posterior View).
 
consequently, in those cases in which suffocation is threatened b}
a foreign body impacted in the upper part of the larynx, the simpb
operation of laryngotomy or incising the crico-thyroid space wil
usually give relief.
 
Intrinsic Muscles. —-These are the muscles by which the cartilages
are moved and the condition of the vocal folds determined. They art
the crico-thyroideus, crico-arytenoideus posterior, crico-arytenoideus
lateralis, thyro-arytenoideus, arytenoideus, and aryepiglotticus. The
arytenoideus is a single muscle, but all the others are arranged ir
pairs.
 
Crico-thyroideus — Origin .—The antero-lateral part of the cricoic
cartilage.
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
I 39 i
 
 
Insertion .—The lower margin of the lamina of the thyroid cartilage,
id the front of the inferior horn.
 
Nerve-supply .—The external laryngeal branch of the superior
ryngeal nerve.
 
The fibres are directed upwards and backwards in a diverging
Lanner, the posterior being horizontal and the anterior oblique,
hese two sets of fibres are often distinct.
 
Action .—To approximate the front parts of the cricoid and thyroid
irtilages in the following manner: the posterior horizontal fibres
raw the cricoid cartilage backwards, and the anterior oblique fibres
 
 
 
Fig. 848.—The Intrinsic Muscles of the Larynx (Lateral View).
 
The greater part of the right lamina of the thyroid cartilage has
 
been removed.
 
 
levate the anterior part of the cricoid cartilage. As a result of this
aovement the posterior part of the cricoid cartilage, carrying the
.rytenoid cartilages on its upper border, is depressed and carried
>ackward. Thus the vocal folds are put upon the stretch, and the
uuscle is a tensor of the fold.
 
Between the two muscles anteriorly there is a triangular interval
ibout ^ inch wide, in which the central portion of the crico-vocal
nembrane is visible, this portion being crossed at its centre by the
:rico-thyroid arch of arteries. In this region, just above the cricoid
:artilage, laryngotomy may be performed.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1392
 
 
A MANUAL OF ANATOMY
 
 
Crico-arytenoideus Posterior (see Fig. 847)— Origin. —The posterior
 
surface of the cricoid cartilage on one side of the median vertical
ridge.
 
Insertion. —The posterior aspect of the muscular process of the
arytenoid cartilage.
 
Nerve-supply. —The recurrent laryngeal nerve.
 
The fibres of the muscle are directed upwards and outwards, the
highest being short and nearly horizontal, the middle being oblique,
and the lowest almost vertical.
 
Action. —To draw the muscular process of the arytenoid cartilage
backwards, thereby swinging the vocal process outwards, the result
of which is to open the rima glottidis. The muscle is, therefore, a
dilator of the rima glottidis.
 
The muscle is separated from its fellow by the median vertical
ridge on the back of the cricoid cartilage.
 
Crico-arytenoideus Lateralis (see Fig. 848)— Origin— The lateral
portion of the cricoid cartilage along its upper sloping border, extending as far back as the crico-arytenoid joint.
 
Insertion. —The anterior aspect of the muscular process of the
arytenoid cartilage, and the adjacent portion of the antero-lateral
surface.
 
Nerve-supply. —The recurrent laryngeal nerve.
 
The fibres of the muscle are directed backwards and upwards.
 
Action. —To draw the muscular process of the arytenoid cartilage
forwards, thereby swinging the vocal process inwards, the result of
which is to narrow the rima glottidis. The two muscles therefore
approximate the vocal folds, and come into action in speaking. When
the crico-arytenoidei posteriores et laterales act together they prevent
rotation, and thus indirectly assist the arytenoideus in approximating
the arytenoid cartilages, and so the rima glottidis is closed. The
crico-arytenoideus lateralis is covered laterally by the lamina of the
thyroid cartilage and the upper fibres of the crico-thyroideus, and
medially by the lateral expanded portion of the crico-vocal membrane.
 
Thyro-arytenoideus.— This muscle consists of two parts, lateral
and medial.
 
Lateral Part— Origin. —(1) The lower half of the inner surface of
the lamina of the thyroid cartilage, and (2) the outer surface of the
lateral portion of the crico-vocal membrane.
 
Insertion. —The front of the muscular process and the adjacent
part of the outer border of the arytenoid cartilage, a few of the fibres
passing round the cartilage to become continuous with the arytenoideus.
The uppermost fibres of this part pass upwards and backwards to the
ary-epiglottic fold, and thence to the epiglottis, under the name of
the thyro-epiglotticus.
 
Medial Portion — Origin. — (1) The receding angle of the thyroid
cartilage, and (2) the anterior part of the vocal fold. The most medial
fibres of this portion, known as the vocalis muscle, spring from the
anterior part of the vocal fold.
 
 
 
THE HEAD AND NECK
 
 
1393
 
 
Insertion .—The outer surface of the vocal process of the arytenoid
rtilage, and the neighbouring part of the antero-lateral surface.
 
The fibres pass from before backwards, some of them having a
*ht inclination outwards, and the highest backwards.
 
Nerve-supply .—The recurrent laryngeal nerve.
 
Action —(1) Medial Part.—To draw forwards the arytenoid cartilage,
d the posterior part of the cricoid cartilage, swinging the latter in
upward and forward direction,
e result of this action is to relax
3 vocal folds by approximating the
ctenoid cartilage to the thyroid carti(e. This part of the muscle is,
srefore, the antagonist of the cricoyroideus. It is to be borne in mind,
wever, that one factor in relaxation
the vocal folds must of necessity be
istic recoil. The fibres representing
3 vocalis muscle act by rendering
lse that part of the vocal, fold which
in front of them, and relaxing the
rt behind them.
 
A very important action of the
idial part of the thyro-arytenoideus,
len it is acting in conjunction with
3 crico-thyroid, is accurately to approximate and straighten the
cal fold. A loss of accurate fitting of the fold of one side against
 
fellow is one of the first signs of incipient paralysis of the recurrent
•yngeal nerve from pressure or stretching, and, when it happens on
e left side, suggests an intrathoracic aneurism or new growth. The
tion of the vocalis part of the thyro-arytenoideus is to tighten a
rtion of the vocal fold, and may be concerned in the production of
e falsetto voice.
 
(2) Lateral Part.—In virtue of its insertion into the muscular process
the arytenoid cartilage, this portion will draw forwards that process,
e effect of which is to swing inwards the vocal process. The fibres
own as the thyro-epiglotticus have been supposed to assist in
pressing the epiglottis.
 
The outer portion of the muscle lies within the lamina of the thyroid
rtilage. Its lower border touches the crico-arytenoideus lateralis,
d its upper fibres lie on the outer wall of the sinus and saccule. The
tier portion of the muscle is in close contact with the outer side of
e vocal fold.
 
Arytenoideus.—The arytenoideus muscle lies across the posterior
rfaces of the arytenoid cartilages. It consists of two parts—superial and deep. The superficial part is composed of two decussating
ndles, each of which is known as the arytenoideus obliquus; and
e deep part constitutes the arytenoideus transversus.
 
Arytenoideus Obliquus.—Each of these muscles, which has the
 
88
 
 
 
Fig. 849. — Scheme to show
Actions on the Arytenoid
Cartilage of Lateral and
Posterior Crico-arytenoids
(CAL, CAP) and Thyro-aryTENOID (TA).
 
 
 
 
 
 
 
 
 
1394
 
 
A MANUAL OF ANATOMY
 
 
form of a narrow oblique bundle, arises from the back of the muscu
process of the arytenoid cartilage. Its direction is upwards a
inwards, and at the median line it decussates with its fellow of 1
opposite side, thus X. Having reached the summit of the oppos
arytenoid cartilage, a few of the fibres end, but the majority en
 
the corresponding a:
 
 
 
Fig. 850. —Skeletal Structures of Larynx,
with Crico-thyroid Muscle in Position.
 
 
epiglottic fold. Being
inforced by a few fib
from the summit of 1
arytenoid cartilage, i
fibres now constitute i
ary - epiglotticus muse
which passes forwai
within the ary-epiglot
fold to be inserted ir
the side of the epiglotl
Associated with the ai
epiglotticus there are th<
fibres of the lateral porti
of the thyro-arytenoide
which are known as 1
thyro-epiglotticus.
 
Nerve-supply .—The
current laryngeal nerve.
 
Action .—The two mi
cles, having the arytem
 
 
cartilages within their embrace, draw these cartilages together,
which action they are aided by the arytenoideus transversus a
ary-epiglotticus muscles, and the inlet of the larynx is narrowed.
 
Arytenoideus Transversus.—The fibres of this muscle extend trai
versely from the posterior surface and outer border of one arytenc
cartilage to those of the other.
 
Nerve-supply .—The recurrent laryngeal nerve.
 
Action .—To draw the arytenoid cartilages together, and th
approximate the vocal folds, and even close the rima glottidis.
 
The arytenoideus transversus muscle, clothed with mucous me:
brane anteriorly, bounds the rima glottidis posteriorly; and its sup
ficial or posterior surface is in contact with the decussating arytenok
obliqui muscles.
 
Compressor Sacculi Laryngis is a thin layer of muscular fibres
the medial side and upper end of the saccule of the larynx. The fibi
are related superiorly to those of the ary-epiglotticus, which are cc
tained within the ary-epiglottic fold.
 
Summary of the Actions of the Laryngeal Muscles.—The intrin
muscles of the larynx, by regulating the condition of the rima glottid
contribute to vocalization, and modify the pitch of notes. In so doi
they lengthen, so as to render tense, or shorten, so as to relax, t
vocal folds; and they also bring the folds together, or draw th(
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1395
 
 
art. In other words, the intrinsic muscles bring about tension and
vallelism of the true vocal folds, or give rise to the opposite conions—namely, relaxation and divergence.
 
Tension is effected by the crico-thyroidei muscles (see p. 1390).
Convergence of the vocal folds is effected by the crico-arytenoidei
erales and the arytenoidei.
 
Relaxation of the vocal folds is brought about by the thyro-aryloidei muscles, which draw the arytenoid cartilages, along with the
sterior part of the cricoid cartilage, forwards. The vocal folds are
the same time shortened by their own elastic recoil. The fibres of
3 thyro-arytenoideus muscle, known as the vocalis, act by producing
:al variations in tension.
 
Divergence of the vocal folds and opening of the rima glottidis is
 
ected by the crico-arytenoidei posteriores, which draw the muscular
Dcesses of the arytenoid cartilages backwards and inwards, the result
which is to rotate the vocal processes outwards.
 
Function of the Epiglottis.—The epiglottis is never folded down like
id. The superior aperture of the larynx is closed during deglutition
the action of the arytenoideus transversus and the lateral portions
the thyro-arytenoidei. The arytenoideus transversus approximates
e arytenoid cartilages, and the lateral portions of the thyro^tenoidei draw the arytenoid cartilages forwards until their apical
rts come into contact with the tubercle of the epiglottis.
 
The sphincter-like action of the ary-epiglottici upon the inlet of the
•ynx must also be taken into account.
 
Nerves.—The nerves of the larynx are the superior and recurrent
■yngeal, both of which are branches of the vagus.
 
The superior laryngeal nerve divides into two branches, external
d internal. The external laryngeal nerve, which is comparatively
lall, supplies the crico-thyroideus, and also gives twigs to the inferior
nstrictor muscle of the pharynx. The internal laryngeal nerve is
isory, passes deep to the posterior border of the thyro-hyoid muscle,
d enters the larynx by piercing the thyro-hyoid membrane in comny with the superior laryngeal artery, above which it lies. Crossing
e floor of the pyriform fossa, where a ganglion is situated upon it,
breaks up into branches, some of which ascend to the ary-epiglottic
Id and epiglottis, a few of them passing as far as the posterior suiface
the tongue close to the mid-line. The other branches descend
supply the laryngeal mucous membrane, and one of them joins a
 
dg from the recurrent laryngeal nerve.
 
The recurrent laryngeal nerve is the principal motor nerve 01 the
rynx. On the right side it arises from the vagus at the root of the
ck, and hooks round the first part of the right subclavian artery.
1 the left side it arises from the vagus in the upper part of the thorax,
 
id hooks round the arch of the aorta.
 
Having ascended in the groove between the trachea and oesophagus,
at the side of the trachea, it passes beneath the lower border ot the
ferior constrictor muscle, and ascends upon the cricoid carti age,
 
 
1396
 
 
A MANUAL OF ANATOMY
 
 
lying close behind the crico-thyroid joint. Here it divides into t\
branches, anterior and posterior. The anterior branch ascends und
cover of the thyroid cartilage, and is distributed to the crico-ar
tenoideus lateralis, thyro-arytenoideus, thyro-epiglotticus, and ar
epiglotticus muscles. The posterior branch passes upwards on t'
back of the cricoid cartilage beneath the crico-arytenoideus posteri
muscle, which it supplies, and then it goes on to end in the arytenoide
muscle.
 
Perhaps the most practically important relation of the recurre
laryngeal is the thyroid gland, since it passes just behind the pla
where that structure is most firmly attached to the cricoid cartila ;
and first ring of the trachea. During removal of one half of tl
thyroid the nerve is in great danger of being cut in freeing the glan
particularly as it is so often farther forward than its reputed positi<
in the groove between the trachea and oesophagus. Its relation
the inferior thyroid artery is variable, and branches often pass bo
in front of and behind the nerve, though most commonly the arte:
is in front. It has been noticed already that, in its course, the ner
is in close relation with the paratracheal lymph glands.
 
The recurrent laryngeal nerve carries some sensory branches
the mucous membrane of the larynx below the rima glottidis, and
communicates with the internal branch of the superior larynge;
The motor fibres of the external branch of the superior laryngeal ai
of the inferior laryngeal are derived from the cranial root of the acce
sory nerve.
 
Summary of the Laryngeal Nerves. —The superior laryngeal nerve, throui
its internal branch, is sensory, and its external branch supplies the crico-thyroide
and in part the inferior constrictor muscle of the pharynx.
 
The inferior or recurrent laryngeal nerve is chiefly motor, and it suppli
 
the intrinsic muscles of the larynx, with the single exception of the crico-thyroidev
it also supplies a twig to the inferior constrictor.
 
Arteries. —The arteries of the larynx are the superior and tl
inferior laryngeal. The superior laryngeal artery is a branch of tl
superior thyroid. It accompanies the internal laryngeal nerve, belc
which it lies, and enters the larynx by piercing the thyro-hyoid mer
brane. The inferior laryngeal artery is a branch of the inferior thyroi
and it accompanies the recurrent laryngeal nerve.
 
Veins. —The superior laryngeal vein opens into the superior thyroi
and the inferior laryngeal vein into the inferior thyroid vein.
 
Lymphatics. —These are arranged in two sets—superior and inferic
ihe superior lymphatics come from the portion of the larynx abo 1
the rima glottidis. Having pierced the thyro-hyoid membrane, th<
pass to the upper group of deep cervical lymph glands. The inferi
lymphatics come from the portion of the larynx below the rin
glottidis. Having pierced the crico-vocal membrane, they pass
the lower group of deep cervical lymph glands, having previous
traversed the pre- and para-laryngeal lymph glands.
 
In early life the larynx occupies a higher position than it does
 
 
THE HEAD AND NECK
 
 
1397
 
 
adult, its descent, which is gradual, being completed by puberty,
to that period the projection known as the laryngeal prominence
lot present. After puberty important changes take place. The
tilages increase in size, the laryngeal prominence assumes marked
r elopment, especially in the male, and the vocal folds undergo
rease in length. These various changes account for the modifications
ich the voice undergoes at and after puberty.
 
Development of the Larynx. —The larynx is developed from the upper part
1 median diverticulum from the ventral aspect of the fore-gut, which diverilum by its lower part gives rise to the trachea. The general development is
sn on p. 73. The epiglottis is formed from the caudal part of the hypochial eminence, its pharyngo-epiglottic fold being a remnant of the third
h and its ary-epiglottic fold of the fourth arch. The cricoid is formed in
sixth arch, as are the internal intrinsic muscles. The thyroid cartilage
r elops in the ventral part of the fourth arch, the lower part of the inferior
strictor belonging to the dorsal part; the crico-thyroideus is a part of this
scle cut off by the downgrowth of the lower thyroid horn to meet the cricoid.
3 vocal folds are formed in the edges of the original sagittal opening in the
iryngeal floor; the part of the larynx above the folds is a modification of
3 floor, while the lower part comes from the upper end of the pulmonary
growth. The pyriform fossa marks the site of the third lateral pouch.
 
 
Prevertebral Muscles.
 
Longus Capitis (Rectus Capitis Anticus Major) — Origin .—By four
art tendons from the anterior tubercles of the transverse processes
the third, fourth, fifth, and sixth cervical vertebrae, the same
tachment as that of the scalenus anterior.
 
Insertion .—The inferior surface of the basilar process of the occipital
ne, from the pharyngeal tubercle obliquely outwards and forwards
r about \ inch.
 
Nerve-supply. —The cervical plexus.
 
The muscle is directed upwards and inwards.
 
Action. —To flex the head and neck.
 
Relations — Anterior. —The upper part of the common carotid and
e internal carotid arteries, the internal jugular vein, the vagus
:rve and sympathetic trunk, and the pharynx. Posterior . A part
the longus cervicis, a large portion of the rectus capitis anterior,
id the transverse processes of the cervical vertebrae.
 
Rectus Capitis Anterior (Rectus Capitis Anticus Minor)— Origin.—
le front of the lateral mass of the atlas.
 
Insertion.— The inferior surface of the basilar part of the occipital
>ne between the foramen magnum and the outer part of the insertion
 
the longus capitis. .
 
Nerve-supply. —The anterior primary ramus of the first cervical
 
irve.
 
The muscle is directed upwards and slightly inwards.
 
A ction. —To flex the head.
 
Rectus Capitis Lateralis— Origin.— The upper aspect of the exemity of the transverse process of the atlas at its front part.
 
 
1398 A MANUAL OF ANATOMY
 
Insertion. —The inferior surface of the jugular process of tl
occipital bone.
 
Nerve-supply. —The anterior primary ramus of the first cervic
nerve.
 
Relations. — Anteriorly is the internal jugular vein, with the vagi
accessory, and hypoglossal nerves close to it, while only a little distam
in front is the styloid process, parotid gland, and facial nerve. Po
teriorly is the obliquus capitis superior. Laterally are the occipit
 
 
Basilar Part of Occiptal Bone
 
 
Rectus Capitis Anterior,
 
 
Rectus Capitis Lateralis —
 
 
Longus Capitis
 
 
Scalenus Posterior
 
 
Vertebral Artery
(third part)
 
 
-Longus Cervicis (upper oblique part)
Vertebral Artery (second part)
 
 
Scalenus Anterior
 
 
Scalenus Medius
 
 
Longus Cervicis (vertical part)
 
 
---Vertebral Artery (first part)
 
-Longus Cervicis (lower oblique
 
'• part)
 
 
Scalene Tubercle
 
 
Fig. 851. —The Right Prevertebral Muscles.
The vertebral artery is also shown.
 
 
artery, and often the accessory nerve, forming an X, and still mo
superficially the origin of the digastric; while medially the vertebr
artery comes up through the foramen transversarium.
 
The muscle passes vertically upwards.
 
Action. —To incline the head to one side.
 
Longus Cervicis (Longus Colli). —This muscle consists of thr<
portions—superior oblique, vertical, and inferior oblique.
 
Superior Oblique Portion— Origin. —The anterior tubercles of tt
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1399
 
 
lsverse processes of the third, fourth, fifth, and sixth cervical
tebrse.
 
Insertion. —The lateral aspect of the tubercle on the anterior arch.
The fibres are directed upwards and inwards.
 
Vertical Portion— Origin. —The fronts of the bodies of the last two
/ical and first three thoracic vertebrae.
 
Insertion. —The fronts of the bodies of the second, third, and fourth
/ical vertebrae.
 
Inferior Oblique Portion — Origin. —The fronts of the bodies of the
t three thoracic vertebrae in common with the lower portion of the
tical part.
 
Insertion. —The anterior tubercles of the transverse processes of
fifth and sixth cervical vertebrae.
 
Nerve-supply .—The anterior primary rami of the adjacent spinal
ves.
 
Action. —To flex the cervical part of the vertebral column.
 
Relations — Anterior. —The pharynx, oesophagus, and retro-pharyn.1 cellular tissue; the common and internal carotid arteries, and
ernal jugular vein; the vagus nerve, and the sympathetic trunk;
 
: longus capitis superiorly; and the recurrent laryngeal nerve, inferior
rroid artery, and first part of the subclavian artery infenorly.
sterior.— The bodies and discs of the adjacent vertebrae, and their
ns verse processes.
 
Petrous Portion of the Internal Carotid Artery.— This part of the
ernal carotid artery is contained within the carotid canal of the
trous part of the temporal bone. It is at first directed upwards,
i then, describing a bend, it passes forwards and inwards to the
amen lacerum, where it enters upon the cavernous part of its course,
e vessel is surrounded by a plexus of veins, and is accompanied by
3 internal carotid branch of the superior cervical ganglion of the
[apathetic trunk. This branch breaks up into two divisions. One
these lies on the outer side of the artery and gives rise to the m'nal carotid sympathetic plexus, whilst the other lies on the inner
Le of the artery and goes on to form the medial part of the latter
 
iXUS
 
As the artery ascends in the carotid canal it is situated in front
, and below, the tympanic cavity and cochlea; as it bends it has the
Laryngo-tympanic tube on its anterior and outer side, and as it
,sses forwards and inwards it has the trigeminal ganglion above it,
e partition between the two being partly membranous.
 
Branches.— The petrous portion gives off a carotico-tympamc branch 1,
hich enters the tympanic cavity through the posterior wall of the
.rotid canal, and it may furnish a petrosal branch to accompany t e
 
iep petrosal nerve. .. ,
 
For the cavernous portion of the internal carotid artery, see p. 1109.
 
Petrous Part of the Facial Nerve.— This part of the nerve extend,
om the orifice of the internal auditory meatus, on the posterior
irface of the petrous part of the temporal bone, to the stylo-mastoid
 
 
1400
 
 
A MANUAL OF ANATOMY
 
 
foramen, and it traverses (1) the internal auditory meatus, and (2) t]
facial canal.
 
Meatal Portion. —The motor root of the nerve is directed outwarc
and is accompanied by the sensory root (pars intermedia of Wrisber^
the auditory nerve, and the internal auditory artery. It is plac<
upon the upper and anterior aspect of the auditory nerve, and t]
sensory root lies between the two, and here joins the facial nerv
At the deep end of the internal auditory meatus the facial ner
parts company with the auditory nerve, and enters the faci
canal.
 
Branches. — Two branches connect the facial nerve with the auditoi
nerve.
 
Tympanic Plexus
 
 
 
Iog. 852. Relations of the Petrous Portion of the Internal
 
Carotid Artery.
 
 
Portion in the Facial Canal (Aqueduct of Fallopius). —The directic
of this portion of the nerve corresponds to that of the canal. It
divided into three stages. In the first stage, which is very short, tl
nerve passes horizontally outwards, between the cochlea and vestibul
to the inner wall of the tympanic cavity, where there is an enlargemen
called the facial ganglion (geniculate ganglion). Here it bends sharph
and in the second stage passes backwards, lying above the fenesti
vestibuli and enclosed in a very thin-walled bony canal which ma
easily be damaged in scraping the inner wall of the tympanic cavit 1
Then it describes another less abrupt curve, and in the third sta{
descends behind the posterior wall of the tympanic cavity to the styl<
mastoid foramen, by which it escapes from the facial canal. Tl
hiatus for greater superficial petrosal nerve {hiatus Fallopii) leads froi
near the beginning of the facial canal to the superior surface of tl
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1401
 
 
etrous part of the temporal bone. As the facial canal descends it
ommunicates with the canal of the pyramidal eminence of the tympanic
avity, and below this is another opening, called the posterior canaliulus for the chorda tympani nerve.
 
 
 
Fig. 853.
 
heater superficial petrosal nerve is seen lying on bone, exposed by removal of
dura mater. It enters foramen lacerum, having passed deep to trigeminal
ganglion. In the foramen lies by lateral side of internal carotid and its
plexus; is joined by a branch from this, and enters interpterygoid foramen.
 
 
Branches :
 
Emm (Greater superficial petrosal (to spheno-palatine ganglion).
 
facial I Communicating branch to lesser superficial petrosal (to the otic
 
ganglion | Externa^petrosal (to sympathetic plexus on middle meningeal
artery).*
 
Nerve to the stapedius muscle.
 
Chorda tympani nerve.
 
Communicating branch to the auricular branch of the vagus.
 
The greater superficial petrosal nerve arises from the facial ganglion,
ind passes forwards through the corresponding hiatus, by which it
eaves the facial canal. It then courses inwards and forwards in a
(roove on the anterior surface of the petrous part of the temporal
 
* There is grave doubt whether this nerve really exists in the body.
 
 
 
 
 
 
 
 
 
1402
 
 
A MANUAL OF ANATOMY
 
 
bone, and passes beneath the trigeminal ganglion to the foramei
lacerum. In the upper part of this foramen it joins the deep petrosa
nerve from the internal carotid plexus to form the nerve of the pterygoi(
canal, which passes forwards through the pterygoid canal into th
pterygo-palatine fossa, and joins the back part of the spheno-palatim
ganglion. The greater superficial petrosal nerve contains some moto
fibres, but to a large extent it consists of sensory fibres. These repre
sent peripheral branches of the unipolar cells of the facial ganglion
the central branches of which give rise to the sensory root of the facia
nerve.
 
A communicating branch passes from the facial ganglion to th
lesser superficial petrosal nerve, which latter represents the tympani*
branch of the glosso-pharyngeal after it has left the tympanic plexu;
on the promontory of the inner wall of the tympanic cavity. IT
means of the lesser superficial petrosal nerve this communicating
branch reaches the otic ganglion.
 
The external petrosal nerve is said to pass through an opening
just within the orifice of the hiatus for greater superficial nerve, an(
to join the sympathetic plexus around the middle meningeal artery.
 
The nerve to the stapedius muscle arises from the facial nerve ii
the descending part of the facial canal opposite the pyramidal eminence
of the tympanic cavity. It enters a small canal in the pyramida
eminence, and so reaches the stapedius as that muscle lies within th
canal.
 
The chorda tympani nerve arises in the facial ganglion, but is bounc
up with the facial nerve in the descending part of the facial canal
A little above the stylo-mastoid foramen it leaves the nerve, anc
passes upwards and forwards in a recurrent course through a minut<
canal, called the posterior canaliculus for chorda tympani nerve, b]
which it enters the tympanic cavity. At first it is placed on th
posterior wall of the tympanic cavity close to the posterior margii
of the tympanic cavity, and to the outer side of the pyramidal eminence
The nerve then passes forwards medial to the tympanic membram
near its upper margin, lying between its mucous and fibrous layers, s<
as to be ensheathed by the mucous membrane. In this part of it:
course it passes between the inner aspect of the handle of the malleu
and the limb of the incus. Having arrived at the inner end of th
petro-tympanic fissure, it leaves the tympanic membrane by passing
through the anterior canaliculus for chorda tympani nerve (canal 0
Huguier). It grooves the spine of the sphenoid, and then enters th
pterygo-maxillary region, and passes downwards and forwards deep t<
the lateral pterygoid muscle, where it receives a communicating twi{
from the otic ganglion, and then joins the lingual nerve at an acut*
angle at the upper margin of the medial pterygoid muscle. It shoul(
be noted that the chorda tympani lies deep to all the vessels and nerve
with which it comes in contact in the pterygoid region. The distribu
tion of the nerve has been already described (see p. 1315)
The chorda tympani is composed of fibres, which are the peri
 
 
THE HEAD AND NECK
 
 
I 4°3
 
 
iheral processes of the unipolar cells of the ganglion of the facial
erve. These represent the fibres which are distributed to the sides
nd dorsum of the tongue over its anterior two-thirds. They are
herefore regarded as gustatory, and functionally are afferent. They
re connected with the fibres of the sensory root by means of the
mipolar cells of the ganglion of the facial nerve. The chorda tympani
terve, however, also contains secretory fibres of the submandibular
nd sublingual glands. The nerve is therefore a mixed nerve.
 
A communicating branch is given off from the facial nerve just
hove the stylo-mastoid foramen, which connects it with the auricular
•ranch of the vagus.
 
Sensory Root of Facial Nerve (Pars Intermedia of Wrisberg).—
 
"he fibres of this small nerve arise from the unipolar cells of the ganglion
if the facial, being the central processes of these cells, the peripheral
>rocesses representing the principal fibres of origin of the chorda
ympani. The sensory root is at first closely incorporated with motor
oot of the facial nerve, and passes from the facial canal into the
nternal auditory meatus. Here it separates from the facial nerve,
nd lies between it and the auditory nerve. After passing through the
irifice of the internal auditory meatus the sensory runs to the lower
)order of the pons, where it enters the medulla oblongata, and ends
n the nucleus of the tractus solitarius.
 
The Ganglion of the Facial Nerve (Geniculate Ganglion). —The
acial ganglion is situated on the facial nerve in the facial canal
it the point where the canal, having reached the inner wall of the
ympanic cavity, makes a sharp bend before passing backwards,
fike a spinal ganglion and the trigeminal ganglion, it consists of unipolar
:ells, each of which has a central and a peripheral process. The
ganglion is the nucleus of origin of the sensory fibres of the facial
lerve. The central processes of the unipolar cells form the sensory
'oot of the facial nerve, and the majority of the peripheral processes
orm the chorda tympani nerve. Some of the peripheral processes,
lowever, pass into the greater superficial petrosal nerve and the
:ommunicating branch to the lesser superficial petrosal nerve.
 
Summary of the Petrosal Nerves. —There are four petrosal nerves—namely,
greater superficial, lesser superficial, external, and deep; and there are two deep
)etrosal nerves—namely, great and small.
 
Superficial Petrosal Nerves. —The greater superficial petrosal nerve is described
 
>n p. 1401.
 
The lesser superficial petrosal nerve issues from the tympanic plexus on the
nner wall of the tympanic cavity, and represents the continuation of the tympanic
)ranch of the inferior ganglion of the glosso-pharyngeal nerve. As it traverses
1 canal in the petrous portion of the temporal bone it is joined by a small branch
rom the ganglion of the facial nerve. Emerging from this canal through the
liatus for the lesser superficial petrosal nerve, it passes through the canaliculus
nnominatus, when present, or through the fissure between the petrous portion
>f the temporal bone and greater wing of the sphenoid, or sometimes through
he foramen ovale, into the infratemporal fossa, where it joins the otic ganglion
;lose below the foramen ovale.
 
The external petrosal nerve (of doubtful existence) is a branch of the ganglion
>f the facial nerve. It leaves the petrous part of the temporal bone through
 
 
I 4°4
 
 
A MANUAL OF ANATOMY
 
 
a small opening (inconstant) close to the hiatus for greater superficial petrosa
nerve, and joins the sympathetic plexus on the middle meningeal artery.
 
Deep Petrosal Nerve. —The deep petrosal nerve is a branch of the interna
carotid plexus of the sympathetic. It joins the greater superficial petrosa
in the upper part of the foramen lacerum medium to form the nerve of th
pterygoid canal, which, as stated, passes through the latter canal into the pterygo
palatine fossa, and joins the back part of the spheno-palatine ganglion.
 
The carotico-tympanic nerves from the tympanic plexus are often referrec
to as the small deep petrosal nerves, which form a communication with the in
ternal carotid plexus by piercing the wall of the carotid canal. There may b<
more than one such connection between the two plexuses.
 
Auditory Nerve in the Internal Auditory Meatus. —This nerve passe
outwards in the internal auditory meatus in company with the senson
and motor roots of the facial nerve, and the internal auditory artery
The motor root of the facial nerve is placed upon its upper and anterior
aspect, and the sensory root lies between the two. Two branche:
connect the auditory nerve with the facial.
 
At the deep end of the meatus the auditory nerve breaks up intc
two divisions—an upper, called the vestibular, and a lower, called th(
cochlear nerve. The vestibular ^nerve has a ganglion, called th(
 
 
 
Fig. 854.—Scheme of the Auditory Nerve (Flower).
 
C.F. Communicating with Facial E.S.C. To Lateral Semicircular Duct
 
C. Cochlear Nerve U. To Utricle
 
V. Vestibular Nerve S. To Saccule
 
S.S.C. To Superior Semicircular Duct P.S.C. To Posterior Semicircular Duct
 
vestibular ganglion [Scarpa s ganglion ), situated at the deep end of the
meatus, its bipolar cells giving origin to the vestibular fibres. Latei
it breaks up into two branches, upper and lower. The superior brand
gives branches to the ampullary crests of the superior and latera.
semicircular ducts, and to the utricle. These pass through the foramina of the superior vestibular area of the upper fossa of the lamina
cribrosa at the deep end of the meatus (see Fig. 126, p. 190). The
inferior branch supplies branches to the ampullary crest of the posterioi
semicircular duct and to the saccule. The former pass through the
foramen smgulare in the lower fossa of the lamina cribrosa, and the
latter through the foramina of the inferior vestibular area of the lowei
fossa of the lamina cribrosa.
 
The branches of the cochlear nerve pass through the foramina oi
the cochlear area of the lower fossa of the lamina cribrosa.
 
The Joints of the Atlas, Axis, and Occipital Bone.
 
Atlanto-axial Joints. —These are three in number, and they belong
to the class of synovial joints. One is medially placed, the articular
surfaces being the atlantal facet on the anterior surface of the odontoid
 
 
 
 
 
 
THE HEAD AND NECK
 
 
1405
 
 
cess of the axis and the odontoid facet on the posterior surface
the anterior arch of the atlas. This joint belongs to the subision of pivot-joints. The other two are placed one on either
3, the articular surfaces of each being the inferior articular process
the atlas and the corresponding superior articular process of the
s. These two joints belong to the subdivision of plane-joints.
Ligaments. —These are the transverse ligament, the capsular
iments, and the accessory ligaments. Besides these there are the
Dermost part of the anterior longitudinal ligament and the posterior
mto-axial ligament, which are not directly related to any of the
ats.
 
The transverse ligament of the atlas is the transverse portion of the
ciate ligament, to be presently referred to, and is a strong band,
ich is attached on either side to the tubercle on the inner aspect
 
 
Tubercle on Ant erior_ Arch
of Atlas
 
 
 
Spine of Axis
 
Fig. 855._The Articulation between the Anterior Arch of the
 
Atlas and the Odontoid Process of the Axis.
 
the lateral mass of the atlas. It is arched backwards behind the
Lontoid process, and at the median line it is connected on the posterior
pect with the limbs of the vertical portion of the cruciate ligament,
etween the ligament and the odontoid process there is an extensive
novial membrane, which extends well over each lateral aspect of
Le process, so as to come very near another synovial membrane
Tween the front of the process and the anterior aich of the atlas.
 
The capsular ligaments are loose sacs which surround the aiticulaons between the inferior articular processes of the atlas and the
 
iperior articular processes of the axis.
 
The accessory ligament on each side extends from the posterior
irface of the body of the axis, close to the root of the odontoid projss, to the inner and posterior part of the lateral mass of the a as
ee Fig. 857). The direction of each ligament is upwards and out
 
 
A MANUAL OF ANATOMY
 
 
1406
 
 
wards, and it is closely related superiorly to the capsular ligamen
which it strengthens internally and posteriorly. The accessory lig
ments are auxiliary in function to the alar ligaments, and limit rotatic
of the atlas upon the axis.
 
The uppermost part of the anterior longitudinal ligament (anterii
atlanto-axial ligament), broad, thin, and membranous, is attache
superiorly along the lower margin of the anterior arch of the atla
and interiorly to the anterior aspect of the body of the axis. It
continuous below with the anterior longitudinal ligament of the bodi<
of the vertebrae, and its central portion is rendered thick by accessoi
fibres derived from that ligament.
 
The posterior atlanto-axial ligament, also broad, thin, and men
branous, extends from the under aspect of the posterior arch of tl
atlas to the upper borders and adjacent portions of the outer surfac<
 
 
External Occipital Crest
 
 
Posterior Atlanto-occipital Membrane
 
 
 
Fig. 856. —The Occipital, Atlantal, and Axial Ligaments
(Superficial Posterior View).
 
 
of the laminae of the axis. It is serially continuous with, and reprt
sents, the ligamenta subflava of succeeding vertebrae.
 
Atlanto-occipital Joints. —These belong to the class of synovis
joints of the condyloid type. The articular surfaces are the condyle
of the occipital bone and the superior articular processes of the atlas
Ligaments. —These are the capsular ligaments and the anteric
and posterior atlanto-occipital membranes, the latter two being ir
directly connected with the joints.
 
The capsular ligaments are loose sacs which directly surroun
the articulations. Their fibres are attached superiorly round tb
margins of the occipital condyles, and inferiorly to the lateral masse
of the atlas round the superior articular processes.
 
The anterior atlanto-occipital membrane, thin and membranous, i
attached inferiorly to the upper margin of the anterior arch of tb
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
I 4°7
 
 
tlas, and superiorly to the under surface of the basilar part of the
capital bone, close to the front part of the foramen magnum, between
he occipital condyles. In the median line it is thickened by fibres
diich are attached below to the tubercle on the anterior arch of the
tlas, but some of them are prolonged into the thickened part of the
nterior longitudinal ligament.
 
The posterior atlanto-occipital membrane, broad, thin, and memiranous, is attached inferiorly to the upper margin of the posterior
rch of the atlas, except in the region of the vertebrarterial grooves,
nd superiorly to the lower margin of the foramen magnum behind
he occipital condyles. Over each vertebrarterial groove of the atlas
his ligament forms an arch which is sometimes ossified (see p. 131),
nd beneath which the vertebral artery and suboccipital nerve pass.
 
 
MembranajTectoria
 
 
Basilar Groove of Occipital Bone v /
 
\ /
 
AlarLigameut\ ^'• ' A
 
 
Superior Longitudinal Band of
Cruciate Ligament
 
 
/iav- Sm ,
 
 
Transverse
Ligament
of Atlas
 
 
Accessory
 
Atlanto-axial
 
Ligament
 
 
 
Atlanto
-occipital
 
Capsule
 
 
''-Atlanto-axial
 
Joint
 
(opened)
 
 
Inferior Longitudinal
Band of Cruciate
Ligament
 
Spine of Axis
 
'ig. 857. —Occipital, Atlantal, and Axial Ligaments (Posterior View).
 
 
Occipito-axial Ligaments. —These are the membrana tectoria; the
lar ligaments; the apical ligament; and the vertical portion of the
ruciate ligament.
 
The membrana tectoria (posterior occipito - axial ligament) is a
 
>road membranous band which is attached inferiorly to the posterior
urface of the body of the axis, where it is continuous with the fibres
I the posterior longitudinal ligament of the bodies of the vertebrae,
nd superiorly to the posterior part of the basilar groove of the
ccipital bone. It covers the odontoid process of the axis and the
lar and cruciate ligaments.
 
The vertical portion of the cruciate ligament consists of superior
Ind inferior longitudinal bands. Ihe superior band extends from the
•osterior surface of the transverse ligament of the atlas at the mid
 
 
 
 
 
 
 
 
 
 
 
1408
 
 
A MANUAL OF ANATOMY
 
 
line to the posterior part of the basilar groove of the occipital bone
between the anterior margin of the foramen magnum and the uppei
attachment of the membrana tectoria, under cover of which it lies
This band, as it ascends, is in contact with the posterior surface oj
the head of the odontoid process. The inferior band extends from
the posterior surface of the transverse ligament of the atlas at the
mid-line to the posterior surface of the body of the axis above the
inferior attachment of the membrana tectoria.
 
The transverse portion of the cruciate ligament is the transverse
ligament of the atlas, already described.
 
The apical ligament of the odontoid process (middle odontoid ligament) is a narrow round cord which is attached below to the ridge oi
 
 
Membrana Tectoria
 
Superior Longitudinal Band of
 
Cruciate Ligament . N 1,11 A .in
 
 
Anterior Margin of Foramen Magnum \
Odontoid Process of Axis
 
 
Basilar Groove of Occipital Bone
/ Apical Ligament
 
 
Anterior Condylar Canal
Alar Ligament
 
 
 
Atlantooccipital J oin t
(capsule)
 
 
Atlanto-axial
Joint(opened)
 
 
Spine of Axis
 
 
Fig. 858. The Occipital, Atlantal, and Axial Ligaments (Deep
 
Posterior View).
 
 
the head of the odontoid process, and above to the anterior margin
of the foramen magnum in the mid-line.
 
This structure has little or no ligamentous function, but is a remnant of the
notochordal sheath.
 
 
The alar ligaments of the odontoid process (check ligaments)
 
form two very strong bands which are attached medially to the lateral
surfaces on the head of the odontoid process, and laterally to an impression on the inner surface of each condylar part of the occipital
bone. The direction of each ligament is outwards and slightly upwards.
 
Movements-—Atlanto-axial Joints. —The atlas, bearing the head, rotates
on the axis, the odontoid process of which serves as a pivot. The extent of
rotation is about 30 degrees, and is limited by the alar, aided slightly by the
accessory atlanto-axial ligaments. On p. 130 it has been seen that the superior
 
 
/
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE HEAD AND NECK
 
 
I 4°9
 
 
icular processes of the axis are each divided by a slight transverse impression
o two parts—anterior and posterior. When the face is directed straight
wards, the inferior articular processes of the atlas are not in accurate contact
th the superior articular processes of the axis. Between the contiguous pairs
nre is a distinct interval all round. When, however, the atlas is rotated, the
terior division of the axial articular process of one side is brought into accurate
itact with the corresponding atlantal articular process, and the posterior
nsion of the opposite axial articular process into accurate contact with the
antal articular process of that side.
 
Atlanto-occipital Joints. —The movements allowed at these joints are flexion,
tension, and oblique movement. Flexion and extension constitute the forward
d backward, or nodding, movements. In over-extension (dorsi-flexion) the
s terior margins of the superior articular processes of the atlas enter the condylar
see of the occipital bone, and locking takes place. In complete forward or
ntral flexion the anterior margins of the superior articular processes of the
as come into contact with the occipital bone in front of each condyle.
 
 
 
89
 
 
CHAPTER XV
 
THE NERVOUS SYSTEM
 
 
The nervous system is arranged in two main divisions, cerebro-spina
and autonomic; this last contains the sympathetic and the parasym
pathetic.
 
The sympathetic system consists of two gangliated cords situate*
on either side of the vertebral column, and three main prevertebra
plexuses: the cardiac situated in the thorax; the epigastric or solar
and the hypogastric plexus, the latter two being situated in th
abdomen; subsidiary plexuses are associated with these.
 
The parasympathetic system includes cranial and sacral outflows
leaving the cerebro-spinal axis through certain nerves without joininj
the sympathetic cords.
 
The cerebro-spinal nervous sytem or axis consists of the encephaloi
and the spinal cord, the former being situated within the crania
cavity, and the latter within the spinal canal. The continuity betwee;
these two divisions is established through the foramen magnum.
 
The cerebro-spinal axis is central in position, and is connecte*
with the various parts of the body by the cranial and spinal nerves
It is composed of two kinds of nervous matter, white and grey. Th
white matter consists chiefly of nerve-fibres, and the grey matter c
nerve-cells, with their axis-cylinder processes or axons and dendrites
the pervading supporting tissue in each case being called neuroglk
In the spinal cord the white matter is disposed externally, whilst th
grey matter is situated in the interior. In the brain there is the sam
arrangement of grey matter in the centre, surrounded by white mattei
but a third and more modern layer of cortical grey matter has bee
added to the surface of the white, a layer which is unrepresented i
the spinal cord.
 
The cerebro-spinal axis is surrounded by three membranes, c
meninges , which, from without inwards, are named the dura matei
arachnoid membrane, and pia mater.
 
 
THE SPINAL CORD.
 
Membranes of the Spinal Cord. —The membranes are three: th
dura mater, the arachnoid membrane, and the pia mater.
 
Dura Mater. —This is the most external covering of the cord. I
forms a dense fibrous tube, known as the theca, which extends fror
the margin of the foramen magnum of the occipital bone to the lowe
level of the second sacral vertebra. Inferiorly, where it has becom
 
1410 1
 
 
 
THE NERVOUS SYSTEM
 
 
1411
 
 
Frontal Lobe
 
 
Temporal Lobe
 
/. Basilar Artery
Vertebral Arteries
 
 
[■six
 
 
j -— Superior Cervical Sympathetic
/ Ganglion
 
 
1>. Cervical Plexus
 
■j -Vertebral Artery
 
i-Middle Cervical Ganglion
 
Brachial Plexus
ist Thoracic Ganglion
 
 
4th Intercostal Nerve
Anterior Spinal Artery
 
 
U_ Thoracic Sympathetic Cord
 
 
 
 
 
 
. Spinal Ganglion
 
 
Subcostal Nerve
 
 
L-. Lumbar Sympathetic Cord
 
 
Lumbar Plexus
 
 
Pelvic Sympathetic Cord
 
 
^— Sacral Plexus
 
 
Ganglion Impar
 
 
Eig. 859.—The Cerebrospinal and Sympathetic Systems (Anterior
 
View) (Hirschfeld and Leveille).
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1412
 
 
A MANUAL OF ANATOMY
 
 
tapering behind the second sacral vertebra, the theca is perforate
by the filum terminale, and from this level the spinal dura mater i
prolonged downwards around the filum terminale, with which it blend:
Finally, it is attached, along with the filum terminale, to the bac
of the first coccygeal vertebra, where it is incorporated with th
periosteum. In this situation the spinal dura mater is firmly fixed.
 
The theca surrounds the spinal cord very loosely, and it is separate
from the wall of the spinal canal by an interval, called the extra-dur;
space, which is occupied by venous plexuses and loose areolar tissue.
 
Opposite the intervertebral foramina of each side the theca has
series of openings, which are arranged in two parallel rows. Th
openings constituting each pair are placed side by side, but are distinc
from each other, and they transmit the ventral or anterior and dors;
or posterior roots of the spinal nerves. Each of these roots, as it make
its exit, receives a tubular sheath from the margin of the corresponds
thecal opening, and these sheaths remain distinct as far as the spin;
ganglion of the dorsal root. After this the neighbouring sheath
form one which blends with the sheath of the corresponding spin;
nerve.
 
The spinal dura mater is maintained in position by several cor
nections. (i) Superiorly it is fixed to the margin of the forame
magnum of the occipital bone. (2) Opposite the body of the ax:
it is firmly attached anteriorly ’ to the posterior occipito-axial ligamen
(3) Below the level of the axis it is loosely connected anteriorly wit
the posterior longitudinal ligament of the bodies of the vertebrae b
fibrous bands. (4) Laterally it is connected with the sheaths of th
spinal nerves by means of the tubular sheaths which it gives to th
ventral and dorsal nerve-roots. (5) Inferiorly it blends with th
periosteum over the back of the first coccygeal vertebra through th
filum terminale. Posteriorly it is quite free from connections.
 
The spinal dura mater differs from the cranial dura mater in th
following respects: (1) It is destitute of an outer or periosteal layei
(2) it does not send septa into the spinal cord; and (3) it does nc
contain venous sinuses.
 
Blood-supply of Spinal Dura Mater.—The arteries are derive
from (1) the spinal branches of the vertebral, intercostal, and lumba
arteries; and (2) the lateral sacral arteries, which are branches of th
internal iliac artery.
 
Nerve-supply.—The nerves are partly spinal and partly sympatheth
 
Lymphatic Vessels.—There are no lymphatic vessels, their plac
being taken by perivascular lymph-spaces in connection with th
arteries.
 
Structure. —The spinal dura mater consists of fibrous tissue and some elast:
tissue disposed in parallel longitudinal bundles. Its internal and extern;
surfaces are covered by endothelial cells.
 
Subdural Space.—Between the spinal dura mater and the arachnoi
there is a narrow cleft-like interval, which is known as the subduri
space. It contains a small amount of fluid, and communicates freel
 
 
 
THE NERVOUS SYSTEM
 
 
T 4 X 3
 
 
Dura Mater (Theca)
 
 
—-Arachnoid
 
 
h the lymph-spaces or clefts in the sheaths of the spinal nerves,
has, however, no communication with the subarachnoid space.
Spinal Arachnoid Membrane.—This is a delicate transparent
mbrane which loosely surrounds the spinal cord between the theca
ernally and the pia mater internally. It is separated from the
:ca by the subdural space, and from the pia mater by the sub.chnoid space. Superiorly it is continuous with the cranial arachd, and inferiorly it encloses the cauda equina. On either side it
ms sheaths for the processes of the ligamentum denticulatum as
as the inner surface of
» theca. The ventral and
:sal roots of the spinal
:ves also receive sheaths
m it, which accompany
un through the openings
the theca, but soon cease.
 
It is of practical importce to remember that the
ichnoid membrane usually
Is at the lower level of the
iond sacral vertebra, and
ver extends lower than the
ird.
 
Subarachnoid Space (Ca- ,
m Subarachnoidale).—This l
ice, which is wide, is
uated, as stated, between
s arachnoid and pia mater,
contains cerebro-spinal
 
id, and its dorsal part is
 
ntinuous superiorly with Fig - 86 °- Portion of the Spinal Cord,
 
- rerebello rnednllarv cis- showing the Membranes, Ligamenta
o LEiEDEiio-iiiEuuiiaiy Lis Denticulata, and Roots of the Spinal
 
"na of the cranial sub- Nerves.
 
ichnoid space, which com
micates with the fourth ventricle by the ‘ foramen of Magendie,’
e median aperture of the roof.
 
The subarachnoid space is partially divided into two compartmts, ventral and dorsal, by ligamenta denticulata, which form inmplete lateral septa. The ventral roots of the spinal nerves traverse
e ventral compartment, and the dorsal roots the dorsal compartsnt. The dorsal compartment is partially subdivided into two
•rtions, right and left, by means of a third incomplete septum, called
e posterior septum. This partition extends from the pia mater as
crosses the dorsal median fissure of the spinal cord to the dorsal
-rt of the arachnoid at the median line. All the compartments of
 
 
 
Ligamentum Denticulatum
 
-Anterior Nerve-Root
 
Posterior Nerve-Root
Pia Mater
 
 
_ Spinal Cord
 
 
Anterior Nerve-Root (cut)
 
 
e subarachnoid space communicate freely with each other.
 
The subarachnoid space has no communication with the subdura
ace.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1414
 
 
A MANUAL OF ANATOMY
 
 
Structure of the Arachnoid Membrane. —The arachnoid consists of fine fibrou
tissue arranged in interlacing bundles, the intervals between these bundle
being occupied by delicate cellular membranes. Several such layers, intimatel
blended together, form the membrane.
 
Beneath the arachnoid, and constituting a part of it, there is a reticulum c
subarachnoid trabeculce. These trabeculae consist, as in the case of the arachnoi
proper, of fine fibrous tissue, but the intertrabecular spaces, instead of bein
occupied by cellular membranes, contain cerebro-spinal fluid. The trabecula
reticulum connects the arachnoid with the subjacent pia mater, and varie
greatly in density in different parts.
 
 
Spinal Pia Mater.—This is the deepest membrane of the spins
cord. It is definitely fibrous and very vascular, and closely invest
 
the cord. Superiorly it is con
 
 
 
A] Dura Mater (Theca)
 
 
. Linea Splendens
 
 
Ligamentum Denticulatuir.
 
 
Pia Mater
 
 
J_L \nterior Nerve-Root
 
 
Fig. 86i.—A Portion of the Spinal Cord
(Anterior View).
 
The theca has been laid open, and the
arachnoid membrane removed.
 
 
tinuous with the cranial pi
mater, and inferiorly it is pro
longed from the conus medul
laris over the upper half of th
intrathecal part of the filur
terminate. On either side i
forms tubular sheaths for th
ventral and dorsal roots of th
spinal nerves, which blend wit]
the sheaths of the nerves.
 
Along the course of th
ventral median fissure of th
cord it sends a vascular fob
into that fissure. Along th
course of the dorsal medial
fissure, over which it passes
the neuroglial septum occupy
ing that fissure is attached t<
it. From the deep orifice o
the pia mater several septa ar
 
 
prolonged into the cord, which carry with them portions of the glia
sheath.
 
The pia mater is separated from the arachnoid by the subarach
noid space, and opposite the dorsal median fissure of the cord it i
connected with the dorsal part of the arachnoid by the posterio
subarachnoid septum.
 
Blood-supply.—The pia mater derives its arteries from the anterio
and posterior spinal arteries, and the neural branches of the latera
spinal arteries.
 
Nerve-supply.—The nerves are derived from the sympathetic system
 
 
Structure. —The spinal pia mater consists of two layers—outer and innei
The outer layer consists of fibrous tissue, which is disposed for the most part i]
parallel longitudinal bundles. The inner layer consists of areolar tissue containing
a great many bloodvessels, and its outer and inner surfaces are covered by endcj
thelial cells. Between the two layers there are narrow cleft-like lymphati
spaces, which communicate with the subarachnoid space, and with lymphati
clefts around the arteries of the pia mater.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1415
 
 
The spinal pia mater differs from the cranial pia mater in being
icker and more adherent to the nervous matter. The greater thick:ss is due to the presence of the outer layer, the cranial pia mater
presenting the inner layer of the spinal pia mater.
 
Linea Splendens.—The pia mater at times presents a glistening
>pearance immediately in front of the ventral median fissure. This
ea is known as the linea splendens, and it extends along the entire
ngth of the cord and along the conus medullaris on to the filum
rminale.
 
Ligamentum denticulatum is a band of pia mater which extends
ong the spinal cord on each side opposite the corresponding lateral
>lumn. It lies between the ventral and dorsal roots of the spinal
irves, and extends from the margin of the foramen magnum to the
wer end of the cord. It lies within the subarachnoid space, and
 
 
Dura Mater
 
 
 
Fig. 862._Diagram of a Transverse Section of the Spinal Cord
 
and its Membranes.
 
 
A.M.F. Anterior Median Fissure, with
Process of Pia Mater
P.M.F. Posterior Median Sulcus
A.C. Anterior Column
L.C. Lateral Column
P.C. Posterior Column
 
 
A.R. Anterior Nerve-Root
P.R. Posterior Nerve-Root
G. Spinal Ganglion
S.P. Spinal Nerve
A.P.D. Anterior Primary Ramus
P.P.D. Posterior Primary Ramus
 
 
irtially divides that space into two compartments—ventral and
orsal
 
Internally it forms an uninterrupted band which is attached to
le pia mater along the lateral column of the cord. Laterally it is
enticulated. The denticulations (about twenty-one m number) carry
ith them sheaths from the arachnoid, and their pointed outer ends
re attached to the inner surface of the theca in the intervals between
ich pair of openings for the exit of the ventral and dorsal nerve-roots,
he topmost denticulation is at the foramen magnum, lying between
le eleventh nerve and the vertebral artery; the lowest is e ween
tie last thoracic and first lumbar nerves, at the first lumbar vertebral
 
iygl
 
The two ligamenta denticulata act as lateral supports to the spinal
°rd. ,. ,
 
Structure— Each ligamentum denticulatum consists of fibrous tissue, which
; continuous with the outer layer of the pia mater.
 
 
 
 
 
 
 
 
1416 A MANUAL OF ANATOMY
 
External Characters of the Spinal Cord. — The spinal cord, o
medulla spinalis, which is somewhat cylindrical, is that division o
the cerebro-spinal axis which is situated within the spinal canal. I
extends from the lower margin of the foramen magnum in the occipita
bone to about the level of the disc between the bodies of the firs
and second lumbar vertebrae, and it is about 18 inches in length
Superiorly it is continuous with the medulla oblongata, and inferiorh
it terminates in a tapering portion, called the conus medullaris. Fron
the lower end of this cone a slender, glistening thread, called tb
 
filum terminale, about io inche
long, is continued downward
between the bundles of lumbar
sacral, and coccygeal nerve
of either side, which constitut
the cauda equina, to be attache<
to the back of the first coccy
geal segment.
 
The spinal cord is of smalle
dimensions than the spina
canal, and is therefore relieve*
from pressure during the ordi
nary movements of the verte
bral column. It is surrounde*
by the three membranes alread;
described—the dura mater, th
archnoid membrane, and th
pia mater. Within its theca o
dura mater the cord is sus
pended by means of the liga
menta denticulata, and th
nerve - roots as they emerg
through the openings in th
theca.
 
The spinal cord varies ii
shape in different regions. L
the cervical region, as seen ii
transverse section, it is trans
versely oval, and is slights
flattened from before backwards. In the thoracic region it is almos
circular, but the transverse diameter exceeds the antero-posterior
In the lumbar region it is still more circular than in the thoraci
region.
 
The cord has two swellings, which are known as the cervical an*
lumbar enlargements, and are associated with the numerous larg<
nerve-trunks destined for the upper and lower limbs. The cervica
enlargement extends from near the upper end of the cord to the secon*
thoracic vertebra, and its breadth is greatest opposite the sixth cervica
vertebra. The lumbar enlargement, which is less conspicuous thai
 
 
 
Fig. 863. —Lumbar and Sacral Portions
of Spinal Canal, showing Lateral
View of Conus Medullaris, Filum
Terminale, and Theca (Testut).
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1417
 
 
he cervical, extends from the level of the tenth thoracic vertebra
o the conus medullaris, and its breadth is greatest opposite the twelfth
horacic vertebra.
 
Filum Terminale.—This delicate glistening thread lies in the
nedian line between the lumbar, sacral, and coccygeal nerves of either
side, which constitute the cauda equina, and it extends from the apex
)f the conus medullaris to the back of the first coccygeal segment.
 
[t is about 10 inches in length. As low as the back of the body of
;he second or third sacral segment it is situated within the theca,
Dut at that level it pierces the theca,
from which it receives an investment,
md then passes to be attached to the
back of the first coccygeal segment, where
it blends with the periosteum. The intrathecal portion is known as the filum
terminale internum, and the extrathecal
portion as the filum terminale externum.
 
Structure. —The filum terminale internum in its upper half consists of pia
mater prolonged from the conus medullaris of the spinal cord. This encloses
grey matter, within which, over about
the upper third, there is a continuation
of the central canal of the cord. The
lower half consists chiefly of connective
tissue. The filum terminale externum is
a mere fibrous filament invested by a
prolongation of the theca which blends
with it. It is also composed of pia mater
prolonged downwards from the conus
medullaris, and reinforced by fibres derived from the lower portions of the ligamenta denticulata and linea splendens.
 
Its lower part is purely fibrous. Fig . 864 ._the terminal
 
Cauda EQuina.—This is situated witmn Part of the Spinal Cord,
 
the lower part of the theca. It consists and the Cauda Equina
of the roots of the lumbar, sacral, and ~
 
coccygeal nerves of each side, which are arranged m the form o a
leash, and the filum terminale lies in the median line between the
two nerve-leashes. On account of the high origins of the individual
nerves, relatively to the positions of the intervertebral foramina
through which they pass, the direction of the nerves is almost vertical
until they reach the level of their respective foramina o exi .
 
Fissures of the Spinal Cord.—The spinal cord, which is somewhat
flattened in front and behind, is incompletely divided into two symmetrical halves by two median formations, anterior and posterior.
The anterior median Assure extends into the cord for one-third of its
thickness from before backwards, and it contains a o c o le pia
 
 
 
 
_ Linea Splendens
 
 
Cauda Equina
Conus Medullaris
 
 
If
 
 
_Filum Terminale
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1418
 
 
A MANUAL OF ANATOMY
 
 
mater. At the bottom of the fissure the transverse band of nervefibres, called the anterior white commissure , crosses between the two
halves of the cord. The posterior median septum is not an actual
fissure like the anterior, and does not contain a fold of the pia mater,
but is a septum of neuroglia, which extends into the cord for about
half its thickness from before backwards. The posterior grey commissure lies at the bottom of the septum. The anterior median fissure
is a definite depression, but it is not so deep as the posterior septum.
 
The posterior septum is marked on the surface by a median sulcus.
 
Each half of the cord presents a groove along the line of entrance
of the fasciculi of the posterior nerve-roots, called the postero-lateral
sulcus, but there is no similar groove along the line of emergence of
the fasciculi of the anterior nerve-roots, these being spread over an
area of some breadth. By means of the postero-lateral sulcus on the
one hand, and the area corresponding to the emergence of the fasciculi
of the anterior nerve-roots on the other, each half of the spinal cord is
divided superficially into three white columns—anterior, lateral, and
posterior.
 
The anterior white column is situated between the anterior median
fissure and the most lateral fasciculi of the anterior nerve-roots; the
lateral white column is the area between the most lateral fasciculi of
the anterior nerve-roots and the postero-lateral sulcus; and the posterior
white column lies between the postero-lateral sulcus and the posterior
median sulcus. Practically the anterior column represents the region
in front of the anterior nerve-roots, the lateral column the region between the anterior and posterior nerve-roots, and the posterior column
the region behind the posterior nerve-roots. According to some
authorities there are only two columns—namely, antero-lateral and
posterior, the former extending from the anterior median fissure to the
postero-lateral sulcus, and representing the combined anterior and
lateral columns.
 
In the cervical region the surface of each posterior white column
presents a slight groove which is situated nearer the posterior median
sulcus than the postero-lateral sulcus. This groove is called the
posterior intermediate or paramedian furrow . It contains a septum of
pia mater, and in this manner the posterior column of the cord is
marked off into two tracts. The medial and smaller tract is called
the fasciculus gracilis (postero-median column of Goll), and the lateral
and larger is called the fasciculus cuneatus (Burdach’s column, posterolateral column). These two columns extend throughout the cord, but it
is only above the level of the mid-thoracic region that they are separated
from each other by a septum of pia mater, known as the posterior
intermediate septum.
 
Origin of the Spinal Nerves.—There are thirty-one pairs of spinal
nerves, which arise from the sides of the spinal cord. They are arranged in five groups on either side as follows: cervical, eight in number;
thoracic, twelve ; lumbar, five ; sacral, five ; and coccygeal, one. Each
spinal nerve is attached superficially to the cord by two roots, anterior
 
 
THE NERVOUS SYSTEM
 
 
1419
 
 
nd posterior, the posterior root being the larger of the two. The
ortion of the cord from which each pair of spinal nerves arise is spoken
f as a segment of the cord. Each root is ensheathed by tubular probations of the coverings of the cord—namely, the pia mater, arachnid, and dura mater, in this order from within outwards—and these
heaths ultimately blend with the perineurium. The roots are separated
rom each other by the lateral column of the cord and the ligamentum
enticulatum, and they pass through separate openings in the theca of
;ura mater.
 
The anterior roots are composed of efferent or motor fibres, and their
asciculi emerge from the cord in an irregular manner, being spread
ver an area corresponding in breadth to the caput of the anterior
 
A
 
2
 
 
 
?IG. 865.—Two Segments of the Spinal Cord, showing the Attachments
of the Anterior and Posterior Nerve-Roots, and the Spinal Ganglia.
 
A, superior view; B, anterior view.
 
1, 1. Anterior Median Fissure 5 > 5 - Spinal Ganglion
 
2, 2. Posterior Median Sulcus 6, 6. Spinal Nerve
 
a, a. Anterior or Motor Nerve-Root 7 , 7 - Anterior Primary Ramus
 
4, 4. Posterior or Sensory Nerve-Root 8, 8. Posterior Primary Ramus
 
9, 9. Medial and Lateral Branches of Posterior Primary Ramus
 
horn of the grey matter in the interior. The posterior roots are composed of afferent or sensory fibres, and their fasciculi enter the cord
in a straight line along the course of the postero-lateral sulcus. Each
posterior root presents an oval swelling, called the spinal ganglion.
These ganglia are for the most part situated in the intervertebral
foramina, and immediately beyond each ganglion the anterior and
posterior roots unite to form a spinal nerve, which is necessarily a
mixed nerve, inasmuch as it is composed of afferent and efferent fibres.
 
Each spinal nerve breaks up into an anterior and a posterior primary
yamus
 
The upper cervical nerve-roots are short, and pass almost horizontally outwards. The succeeding nerve-roots, however, gradually
increase in length, and incline downwards as they pass outwards,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1420
 
 
A MANUAL OF ANATOMY
 
 
This downward inclination goes on increasing until it becomes almost
vertical in the case of the lumbar, sacral, and coccygeal nerves, which
constitute the cauda equina. From this disposition it follows that
in the majority of cases the superficial origins of the spinal nerves are
on a higher level than the intervertebral foramina through which they
emerge from the spinal canal.
 
Relation of the Spines of Vertebrae to the Bodies and to the Origins of the
Nerves. —In the case of the cervical and the eleventh and twelfth thoracic vertebra
the extremities of the spinous processes correspond to the lower margins of
the bodies of the respective vertebrae. In the case of the thoracic vertebra,
from the first to the tenth inclusive, the extremity of each spinous process corresponds to some part of the body immediately below. In the case of the lumbar
vertebrae the extremity of each spinous process corresponds to the centre of the
body of its own vertebra.
 
Each cervical spinous process is nearly opposite the lower fasciculi of the
roots of the nerve below. The spinous process of the seventh cervical vertebra
(vertebra prominens) is opposite the roots of the first thoracic nerve. From
the third to the tenth thoracic vertebrae the spinous processes correspond to
the second root below. The eleventh thoracic spine corresponds to the first and
second lumbar nerves. The twelfth thoracic spine corresponds to the third,
fourth, and fifth lumbar nerves. The first lumbar spine corresponds to the
first, second, and third sacral nerves. (Gowers, from an original investigation.)
 
 
Mode of distinguishing the Anterior and Posterior Surfaces of the
Spinal Cord.—These surfaces may be recognized by attending to the
following points:
 
 
Anterior Surface.
 
1. Linea splendens in median line,
 
especially in lower part.
 
2. Anterior spinal artery in
 
median line.
 
3. Fasciculi of anterior nerve
roots spread over a wide
area.
 
4. Presence of an anterior median
 
sulcus which can be opened.
 
 
Posterior Surface.
 
1. Ganglion on each posterior nerve
root.
 
2. Arterial anastomotic chain behind and
 
in front of the posterior nerve-roots.
 
3. Fasciculi of posterior nerve-roots lie
 
in a straight line, and enter through
postero-lateral sulcus.
 
4. Presence of a posterior median sulcus
 
which cannot be opened.
 
5. Presence of gracile and cuneate fasci
culi in upper part.
 
 
Internal Structure of the Spinal Cord.—The spinal cord, as seen in
transverse section, consists of a central portion composed of grey matter,
and an external portion composed of white matter.
 
Grey Matter.—This is arranged in the form of two irregular crescents,
the concavities of which are directed outwards, and the convexities
inwards, the latter being connected across the middle line by the
grey commissure. The arrangement has been likened to the letter )-(.
The grey commissure lies at the bottom of the posterior median sulcus,
and presents about its centre the minute opening of the central canal
of the cord. The part of the commissure in front of this canal is
known as the anterior grey commissure, and the part behind as the
posterior grey commissure. In front of the anterior grey commissure
there is a transverse band of white matter, called the anterior white
 
 
THE NERVOUS SYSTEM
 
 
1421
 
 
immissure, which lies at the bottom of the anterior median fissure,
ach crescent of grey matter consists of two horns, anterior and
osterior, the former being in front of, and the latter behind, the grey
mnmissure. The anterior horn is broad and blunt, and it stops short
f the surface of the cord, being separated from the surface by white
latter which is traversed by the fasciculi of the anterior nerve-roots,
he blunt extremity of the anterior horn is called the caput cornu, and
le portion adjoining the grey commissure, which is slightly constricted,
; called the cervix cornu. The posterior horn is for the most part
mg, narrow, and tapering, and its pointed extremity almost reaches
tie surface of the cord at the bottom of the postero-lateral sulcus,
'his pointed extremity is called the apex cornu, and it contains a transient substance, known as the substantia gelatinosa (of Rolando),
diich forms the cap for the caput cornu posterioris. It contains a
 
 
Central Canal
 
 
 
?i G . 866._ Transverse Section of the Spinal Cord in the Upper Thoracic
 
Region, showing the Arrangement of the Grey Matter and Cells
(Semi-diagrammatic) (after Poirier).
 
small amount of neuroglia, and numerous nerve-cells. The portion
idjoining the grey commissure, which is slightly constricted, is called
the cervix cornu, and the portion contiguous to the cervix, w 11c is
slightly enlarged, is called the caput cornu. The part between the
 
two cornua is called the body. ' ,
 
About the centre of the concavity of the body crescent the grey
 
matter projects into the lateral column in the form of processes arranged
in a reticular manner and enclosing white matter. This network is
sailed the processus reticularis, and it is most conspicuous m the
cervical region. In the thoracic region, more particular y in 1 s uppei
part, the grey matter of each crescent forms a triangular projection
which extends laterally for a short distance immediately m front of
the processus reticularis, and adjacent to the junction o e an erior
:ornu with the grey commissure. This projection is known as the
 
 
 
 
 
 
 
 
 
 
 
 
 
1422
 
 
A MANUAL OF ANATOMY
 
 
lateral horn. When followed into the lower cervical and into the
lumbar regions it blends with the anterior horn, the thickness of which
it increases, but it is again present above the level of the fourth cervical
vertebra.
 
The grey matter has been described, so far, as it would be seen on
looking at transverse sections through the cord; under such conditions
the use of the term ' horn ’ or ' cornu * is quite appropriate. As it
exists in the complete cord, however, the grey matter is in the form
of a continuous column , and in considering it in such a way it should
be described as possessing anterior, posterior, and lateral ' columns,’
rather than ‘ horns.’
 
The grey matter varies in amount in different parts of the cord.
It is present in largest quantity in the lumbar enlargement, where
the large nerve-trunks for the lower limbs arise, and next to this in
the cervical enlargement, where the large nerve-trunks for the upper
limbs arise.
 
The horns of the crescents of grey matter vary in shape, as seen
on section, in different regions. In the cervical region the anterior
 
 
A
 
 
 
Fig. 867. —Transverse Sections of the Spinal Cord in Different
 
Regions.
 
A, cervical region; B, mid-thoracic region; C, lumbar region; D, conus
 
medullaris.
 
horns are short, broad, and blunt, and the posterior horns are long,
narrow, and pointed. In the thoracic region both horns are narrow,
though the posterior is more so than the anterior. In the lumbar
region both are broad, though the anterior is more so than the posterior.
These differences render sections of the spinal cord in the cervical,
thoracic, and lumbar regions easily recognizable. As stated, the lateral
horn is also a characteristic of the cord in the thoracic region, more
particularly in its upper part.
 
Central Canal.—This minute canal is situated about the centre of
the grey commissure, and extends throughout the entire length of the
spinal cord. Superiorly it is continued into the lower half of the
medulla oblongata, and it opens into the lower part of the fourth
ventricle at the calamus scriptorius. Interiorly, near the apex of the
conus medullaris it becomes enlarged, and assumes the shape of an
inverted ±. This enlargement is known as the ventriculus terminalis.
From this point it is prolonged for some distance into the filum terminale,
and it ends in a closed extremity. In the cervical and thoracic regions
the central canal is nearer the anterior surface of the cord than the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
i 4 2 3
 
 
sterior, but in the lumbar region it occupies the centre. In the
aus medullaris it is near the posterior surface.
 
The canal is lined with ciliated columnar epithelium, the columnar
Is being known as ependymal cells.
 
The central canal represents the lumen of the neural tube of ectoderm from
ich the spinal cord is developed.
 
White Matter of the Spinal Cord.—The white matter forms the
ter part of the cord, and is arranged in three columns—anterior,
teral, and posterior. The anterior column is situated between the
iterior median fissure and the anterior horn of grey matter, and
tends as far as the most lateral fasciculi of the anterior nerve-roots,
therefore includes the superficial coating of the anterior horn, where
is traversed, over an area of some breadth, by the scattered fasciculi
the anterior nerve-roots. The lateral column is situated between the
iterior and posterior horns of grey matter, in the concavity of the
escent. Its superficial limits are the most lateral fasciculi of the
iterior nerve-roots and the fasciculi of the posterior nerve-roots at
e postero-lateral sulcus. The posterior column is situated between
e posterior median sulcus and the posterior horn of grey matter, its
perficial limit being the fasciculi of the posterior nerve-roots at the
>stero-lateral sulcus.
 
The white matter increases in quantity from below upwards, and
pta of pia mater and neuroglia fibres pass into it at various points.
 
 
Jhief Distinguishing Characters of the Spinal Cord in Different Regions, as
 
seen in Transverse Sections.
 
 
Cervical Region.
 
Transversely oval.
 
Anterior Horn, short,
broad, and blunt.
 
Posterior Horn, long,
narrow, and tapering.
 
Formatio Reticularis, well marked.
 
Lateral Horn, merged
into anterior, except above fourth
cervical vertebra.
 
White Matter, large
in amount.
 
 
Central Canal,
nearer the ventral
than the dorsal
surface.
 
Postero - intermediate Sulcus and
Septum of pia
mater, well
marked.
 
 
Thoracic Region.
 
1. Circular.
 
2. Anterior and Posterior
 
Horns, both narrow,
posterior more so
than anterior.
 
3. Formatio Reticularis,
 
not very distinct.
 
4. Lateral Horn, con
spicuous, especially
in upper part
 
5. White Matter, less in
 
amount, but large
in proportion to
Grey Matter.
 
6. Central Canal, nearer
 
the ventral than the
dorsal surface.
 
7. Postero - intermediate
 
Sulcus, absent, but
Septum of pia mater
recognizable.
 
 
Lumbar Region.
 
1. Almost circular.
 
2. Anterior and Posterior
 
Horns, both broad,
anterior more so
than posterior.
 
3. Formatio Reticularis,
 
absent.
 
4. Lateral Horn, merged
 
into anterior.
 
 
5. White Matter, small
 
in amount, and Grey
Matter, large.
 
6. Central Canal, in the
 
centre.
 
 
7. Postero - intermediate
Sulcus and Septum
of pia mater, absent.
 
 
I 4 2 4
 
 
A MANUAL OF ANATOMY
 
 
Minute Structure of the Spinal Cord—Grey Matter.—The grey
matter consists of nerve-cells, nerve-fibres, and neuroglia, and is very
vascular.
 
The nerve-cells are present in great numbers, and are multipolar.
Each cell sends off at various points several protoplasmic processes,
one of which becomes the axis-cylinder of a nerve-fibre, and is called
the axis-cylinder process, or axon. The other processes are known as
the protoplasmic processes {of Deiters), or dendrites, and, after successive
branchings, they terminate in free extremities. There are no anastomoses between the dendrites of the same cell, nor between those of
contiguous cells. A multipolar nerve-cell, with its axon and dendrites,
constitutes a neuron. The multipolar cells form longitudinal columns
of various lengths, and, as seen in transverse sections of the cord,
they are arranged in groups which occupy particular regions. These
 
Central Canal
 
 
 
Fig. 868.— Transverse Section of the Spinal Cord in the Upper Thoracic
Region, showing the Arrangement of the Grey Matter and Cells
(Semi-diagrammatic) (after Poirier).
 
cell-columns or groups are three in number—namely, anterior or
ventral, in the anterior horn of grey matter; lateral, in the lateral
horn of grey matter; and posterior, constituting the thoracic nucleus
(or posterior vesicular column of Lockhart Clarke), and being very
conspicuous in the medial portion of the cervix of the posterior grey
horn in the thoracic region. Besides these main columns or groups,
other nerve-cells are present, which are scattered irregularly throughout
the other portions of the grey matter.
 
The anterior or ventral cell-column is situated, as stated, in the
anterior horn of grey matter, and extends throughout the whole length
of the spinal cord. Its cells are of large size and very conspicuous,
and their axons, which are at first non-medullated, become medullated,
and then constitute the fasciculi which emerge to form the anterior
nerve-roots. These cells are therefore the sources from which the
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
*4 25
 
 
Trent or motor nerve-fibres proceed, and the ventral column is
nsequently spoken of as the motor column. The ventral or motor
11 s of this column are arranged in two groups, medial and lateral,
re medial group occupies the medial part of the anterior grey horn,
id the lateral group is situated in its outer part. In the cervical and
mbar enlargements of the cord the cells of the lateral group are very
imerous, and are arranged in two sub-groups, ventro-lateral and
)rso-lateral.
 
The intermedio-lateral cell-column is situated, as stated, in the
teral horn of grey matter, and the cells constitute a column known
 
; the intermedio-lateral nucleus.
 
The thoracic cell-column is situated in the medial part of the
:rvix of the dorsal cornu of grey matter. This extends throughout
le entire thoracic region of the cord, and for a short distance into
le cervical and lumbar enlargements. The cells make an elongated
jcleus (often termed Clarke’s column), and are of large size. This
)lumn exists chiefly in the thoracic portion of the cord, whence the
ime thoracic nucleus.
 
The cells of the grey matter differ as regards their axons, some having short,
id others long, axons.
 
The cells with short axons have their axons confined to the grey matter,
which they ramify not far from the parent-cells. They serve to bring contiguis cells into relation with one another.
 
The cells with long axons are partly root-cells and partly association-cells^
id their axons travel for some distance from the parent-cells. The axons of
le root-cells leave the cord in the fibres of the ventral or motor nerve-roots,
he axons of the association-cells constitute association-fibres, which are disused in two ways: (1) Some enter the white matter of the same side of the
>rd, in which they divide into ascending and descending branches. Eventually
iey re-enter the grey matter, and terminate in arborizations at some distance
om the parent-cells. (2) Other association-fibres cross to the opposite side
1 the ventral or white commissure. Some of these end in arborizations around
le cells of the grey crescent, whilst others enter the white matter, in which
ley are disposed as on the side from which they have crossed.
 
Destination of Axons of Cells of Grey Matter.
 
Cells of Ventral Horn. —(1) Many axons become the axis-cylinder processes
f the efferent fibres of the ventral nerve-roots. (2) Other axons constitute
ssociation-fibres, which cross to the opposite side in the ventral 01 white comlissure. After crossing, some end in arborizations around the cells of the
entral horn * others enter the white matter; and a few are regarded by some
uthorities as entering the ventral nerve-roots of the side to which they have
rossed
 
Cells Of Lateral Horn.—The axons of the cells of the intermedio-lateral nucleus
ass to the efferent fibres of the ventral nerve-roots, and they are regarded as
irnishing the white rami communicantes of the sympathetic system.
 
Cells Of Dorsal Horn. —The axons of the cells of the dorsal horn have various
irections; (1) Some pass to the ventral horn and ventral 01 white commissure.
>) The axons of the cells of the thoracic nucleus pass to the lateral column, and
re usually regarded as entering the dorsal cerebellar and ventro-lateral cereellar tracts. (3) The axons of the cells of the substantia gelatmosa pass partly
3 the lateral column, adjacent to the dorsal horn, where they divide into ascenc ig and descending branches, and partly into the posterior marginal bun e o
 
90
 
 
1426
 
 
A MANUAL OF ANATOMY
 
 
Lissauer. (4) The axons of other cells in the lateral part of the cervix of tb
dorsal horn pass to the lateral and ventral horns, the ventral or white commissure
and the lateral column. (5) The axons of the cells of the caput cornu posteriori
pass to the lateral column of the same side, and a few are regarded as passinj
to the opposite side in the ventral or white commissure.
 
Dorsal or Grey Commissure. —This commissure lies at the bottoir
of the dorsal median septum. It consists of (1) grey matter, con
taining a few small nerve-cells, and (2) medullated nerve-fibres. Thes(
fibres pass across from one side to the other, and later on diverge ir
each grey crescent. They serve as association fibres which bring th(
cells of opposite sides into relation with one another. This commissun
contains the central canal of the cord, which for the most part is nearei
the ventral portion of the commissure than the dorsal. The part o:
the commissure surrounding the central canal is called the substantia
gelatinosa centralis. It consists of neuroglia, a few nerve-cells, anc
nerve-fibres; and it is invaded by processes derived from the deep end. c
of the ciliated columnar epithelial cells which line the central canal.
 
Summary of the Gelatinous Substances of the Grey Matter. — These are
 
(1) The substantia gelatinosa, which forms a cap for the caput cornu posterioris :
 
(2) the substantia gelatinosa centralis, which surrounds the central canal ©f the
cord; and (3) the substantia gelatinosa externa, which forms the glial sheath oj
the cord beneath the pia mater.
 
White Matter. —The white matter of the cord consists of longitudinal medullated nerve-fibres, traversed by septa of the pia mater,
and embedded in neuroglia. The fibres have no primitive sheath or
neurilemma.
 
Ventral or White Commissure. —This commissure lies at the bottom
of the ventral median fissure, and it is separated from the central canal
of the cord by a part of the dorsal or grey commissure. It consists ol
medullated nerve-fibres, destitute of a neurilemma, some of which
pass transversely, but most of them decussate, entering the commissure ventrally on one side, and leaving it dorsally on the opposite
side. The fibres, after crossing, enter the grey crescent and the ventral
column. They are derived from (1) the anterior cerebro-spinal tract,
(2) the processes of root-cells and of association cells, and (3) the fibres
of the spino-thalamic tract, to be presently described.
 
Fibres of Roots of Spinal Nerves—Ventral or Anterior NerveRoots. —The fibres of the ventral nerve-roots arise within the cord
from several sources. (1) Many of them are axons of the medial cells
of the ventral horn of grey matter of the same side. (2) Some are axons
of the lateral cells of the ventral horn. (3) Others are axons of the
cells of the thoracic nucleus of the same side. (4) A few are axons
of cells in the dorsal horn of grey matter of the same side. (5) A few
are regarded as being axons of the medial cells of the ventral and intermediate grey matter of the opposite side , which cross in the ventral
or white commissure. All the axons receive their medullary sheaths
near the parent cells, and they form funiculi, which leave the white
matter of the ventral column over an area corresponding to the caput
 
 
THE NERVOUS SYSTEM
 
 
1427
 
 
the ventral horn of grey matter, after which each fibre acquires its
imitive sheath or neurilemma.
 
Most of the axons of the fibres of the ventral nerve-roots belong to the
ntral (motor) cells of the ventral horn of grey matter of the same side.
 
Dorsal or Posterior Nerve-Roots.—The fibres of the dorsal nerveots arise from the unipolar (orginally bipolar) cells of the spinal
nglia. The single pole or process of each of these cells is T-shaped,
le half of the horizontal limb of the T is central, and enters the cord
 
 
 
 
' IG . 869.— Course of Nerve-Fibres in the Spinal Cord (from Halliburton’s
* Handbook of Physiology ’ (after Schafer).
 
 
P. Cerebro-spinal Tract
1, 2, 3, 4. Anterior Cornual Cells
K, A, A, A. Axons of Anterior Cornual Cells
M. Muscular Fibre
 
G. Unipolar Cell of a Spinal Ganglion, giving
Origin to a Fibre of a Posterior NerveRoot
 
B. Peripheral Branch of Fibre
S. Skin . .
 
(lowerC) Central Branch of Fibre, passing into the
Spinal Cord
 
. Descending Branch of Fibre in the Spinal Cord
 
 
D. Ascending Branch of Fibre in the Spinal Cord
Pi, P2. Posterior Cornual Cells
 
C (upper C). Cell of Clarke’s Column or Thoracic
 
Nucleus .
 
5. Collateral, passing directly to arborize around an
 
Anterior Cornual Cell (2). >
 
6. Collateral, with an Intermediate Cell-Station in a
 
Posterior Cornual Cell (P 2 ).
 
7. Collateral, arborizing around a Cell ot Clarke s
 
Column (upper C). ,
 
8. Continuation of Main Ascending Branch of Fibre.
 
 
the dorso-lateral sulcus between the dorsal and lateral coiumns of
ilte matter. The other half of the horizontal limb is peripheral, and
 
sses outwards in the course of the nerve. • ol K 11 n f
 
Within the cord a few lateral fibres enter the marginal bundle
3sauer, and the dorsal horn of grey matter, but most of them pass
-o th e poslero-lateral column (Burdach) close to the dorsal horn of
;y matter. Within this column the fibres divide into ^ branches
lending and descending. The descending branches, after a short
 
 
 
 
 
 
 
 
 
1428
 
 
A MANUAL OF ANATOMY
 
 
course, enter the dorsal horn. These descending fibres are usualh
regarded as forming the ‘ comma tract.’ The ascending branches
are longer than the descending, and, at various levels, they also enter
the dorsal horn. The ascending branches of the fibres of the dorsal
roots of the lower spinal nerves enter the postero-medial column.
 
The ascending and descending branches give off numerous collateral
fibrils, which enter the dorsal grey column. These collaterals have
the following destinations: (1) The dorsal horn of the same side, and
that of the opposite side through the dorsal or grey commissure; and
(2) the ventral and lateral horns of the same side. In each case they
 
come into close relation with the corresponding nerve-cells_ e.g., the
 
cells of the dorsal horn, including the thoracic nucleus, the ventral or
motor cells of the ventral horn, and the cells of the thoracic nucleus
in the lateral horn.
 
 
Sensory Fibres entering Fasciculus Cuneatus (Burdach)
Cells of Posterior Column and Thoracic Nucleus ' Posterior Ro<
 
 
 
Spinal Ganglia. — these are situated on the posterior roots of the
spinal nerves in the intervertebral foramina, and outside the theca,
though invested by a prolongation from it. Each ganglion is oval,
and consists of unipolar nerve-cells. The single pole of each cell
divides into two processes, one of which is centripetal and forms part
of the posterior nerve-root, whilst the other is centrifugal and passes
into the spinal nerve. The pole and its inward and outward processes
resemble the letter T. In early life the cells are bipolar.
 
The fibres of the posterior nerve-roots have their deep origins in
the unipolar cells of the spinal ganglia, and they grow into the spinal
cord. On the other hand, the fibres of the anterior nerve-roots have
their deep origins within the spinal cord, where they arise as the axons
of the multipolar nerve-cells of the anterior column of grey matter, and
they grow outwards.
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1429
 
 
Tracts of the Spinal Cord.
 
Posterior Column. —The tracts of this column are ascending and
xending, and they are as follows:
 
Ascending Tracts. Descending Tracts
 
Fasciculus gracilis (Fig. 871, 1). Semilunar (comma) tract (Fig. 871, 9).
Fasc. cuneatus (Fig. 871, 2). Septo-marginal bundle (Fig. 871, 10).
 
Postero-lateral tract (of Lissauer)
 
(Fig. 871, 3).
 
Lissauer’s tract also belongs to the lateral column.
 
 
 
19
 
Descending
 
 
Ascending.
 
 
; F IG . 871.— The Tracts of the Spinal Cord.
 
 
Ascending.
 
Fasciculus gracilis (Goll’s column).
 
:. Fasciculus cuneatus (Burdach’s column).
 
Fasciculus postero-lateralis (Lissauer’s tract). _
 
|.. Posterior spino-cerebellar fasciculus (Flechsig’s
tract).
 
5. Anterior spino-cerebellar fasciculus (Gower’s
tract).
 
5 . Lateral spino-thalamic tract.
 
7. Anterior spino-thalamic tract.
 
1 . Intersegmental tract (fasciculus proprius: ground
bundle).
 
 
Descending.
 
9. Semilunar (or comma) tract.
 
10. Septo-marginal bundle.
 
n. Lateral cerebro-spinal fasciculus (crossed pyramidal tract).
 
12. Anterior cerebro-spinal fasciculus (direct pyra
midal tract).
 
13. Lateral intersegmental tract.
 
14. Anterior intersegmental tract.
 
15. Sulco-marginal tract.
 
16. Rubro-spinal tract (Monakow’s bundle).
 
17. Tecto-spinal tract.
 
18. Olivo-spinal tract (Helweg’s tract).
 
19. Vestibulo-spinal tract.
 
 
Ascending Tracts. —The fasciculus gracilis (tract of Goll) is situated
ose to the posterior median septum. Its fibres are derived from the
orsal roots of the coccygeal, sacral, lumbar, and lowei thoracic nerves,
hey are at first contained in the cuneate tract, but as they ascend
ley are gradually displaced medially, and so foim a special tract,
he fibres terminate superiorly in connection with the cells of the
 
ucleus gracilis of the medulla oblongata.
 
The fasciculus cuneatus (tract of Burdach) is situated on the lateial
ide of the tract of Goll next to the dorsal horn of grey mattei.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1430
 
 
A MANUAL OF ANATOMY
 
 
Above the mid-thoracic region it is separated from Goll’s tract by
the dorsal intermediate or paramedian furrow and a septum of pia
mater. Its fibres are derived from the dorsal nerve-roots. Above
the mid-thoracic region they are derived from the dorsal roots of the
upper thoracic and cervical spinal nerves, and these fibres terminate
superiorly in connection with the cells of the nucleus cuneatus of the
medulla oblongata. Below the mid-thoracic region the fibres are
derived from the lower dorsal nerve-roots, and these, being displaced
inwards into the gracile tract, terminate in connection with the cells
of the nucleus gracilis.
 
The postero-lateral fasciculus (Lissauer’s tract) is close to the outer
surface of the cord. It embraces the contiguous parts of the posterior
and lateral columns, and occupies the region of the dorso-lateral sulcus
where the funiculi of the dorsal nerve-roots enter the cord. It lies
between the substantia gelatinosa and the surface of the cord. Its
fibres are derived from the dorsal nerve-roots, and they ascend close
to the substantia gelatinosa , in which they terminate at different
levels.
 
Descending Tract.—The semilunar tract (comma) is situated in the
cuneate fasciculus. Its fibres are usually regarded as being derived
from the descending branches of the fibres of the dorsal nerve-roots,
in which case they are exogenous. The other view, however, is that
the fibres are intrinsic or endogenous, and spring from the cells of the
dorsal cornu of grey matter.
 
Antero-lateral Column,—1 he tracts of this column are arranged into
descending and ascending, and are as follows:
 
 
Descending Tracts.
 
1. Lateral cerebro-spinal (crossed pyra
midal) tract (Fig. 871, 11).
 
2. Anterior cerebro-spinal (direct pyra
midal) tract (Fig. 871, 12).
 
3. Intersegmental tract (Fig. 871, 13 and
 
14).
 
4. Rubrospinal tract (Fig. 871, 16).
 
5. Vestibulo-spinal tract (Fig. 871, 19).
 
6. Olivo-spinal tract (Fig. 871, 18).
 
7. Tecto-spinal tract (Fig. 871, 17).
 
 
Ascending Tracts.
 
1. Dorsal spino-cerebellar tract
 
(Fig. 871, 4).
 
2. Ventral spino-cerebellar tract
 
(Fig. 871, 5).
 
3. Anterior spino-thalamic tract
 
(Fig. 871, 7).
 
4. Lateral spino-thalamic tract
 
(Fig. 871, 6).
 
5. Spino-tectal tract (Fig. 871, 6).
 
 
Descending Tracts.—The crossed pyramidal or lateral cerebro-spinal
tract (fasciculus spinalis lateralis, Fig. 871, 11) is a long descending
tract of large size, which is situated deeply in the dorsal part of the
lateral column directly in front of the dorsal cornu of grey matter. It
is separated from the outer surface of the cord by the dorsal spinocerebellar (or direct cerebellar) tract. It diminishes in size as it
descends, and in the lumbar region it becomes superficial. At about
the level of the third sacral nerve it ends. The fibres of this tract have
their origin in the pyramidal cells of the motor area of the cortex of the
cerebral hemisphere of the opposite side. From this origin they descend
through (1) the internal capsule of the corpus striatum, (2) the crus
 
 
THE NERVOUS SYSTEM
 
 
i43i
 
 
srebri, and (3) the pons. On leaving the pons they enter the pyramid
f the medulla oblongata on the side from which they have arisen,
t the lower part of the pyramid they cross to the opposite side and
ike up their position deeply in the dorsal part of the lateral column
f the spinal cord. The fibres of the crossed pyramidal tract of one
de therefore come from the cerebral hemisphere of the opposite side,
nd they form the inner and larger part of the pyramid of the medulla
blongata, also of the opposite side. As this tract descends, fibres
;ave it in each segment of the cord. These fibres enter the ventral
orn of grey matter, and end in close relation with the ventral or
lotor cells, the axons of many of which form the axis-cylinder prossses of the fibres of the ventral or motor nerve-roots.
 
The direct pyramidal or anterior cerebro-spinal tract is of small size,
nd is situated in the anterior column, where it lies close to the ventral
ledian fissure. It diminishes in size as it descends, and usually
srminates about the centre of the thoracic region, but fibres have been
raced as low as the fourth sacral nerve. The fibres of this tract, like
lose of the crossed pyramidal tract, have their origin in the pyramidal
ills of the motor area of the cortex of the cerebral hemisphere, but in
his case of the same side. The fibres of the direct pyramidal tract of
ne side therefore come from the cerebral hemisphere of the same side,
hey pursue a similar downward path as low as the pyramid of the
ledulla oblongata of the same side, of which they form the smaller
art. They take no part, however, in the decussation of the pyramids,
s do the fibres of the crossed pyramidal tract. Their course is directly
ownwards into the corresponding half of the spinal cord, where most
fthem take up their position in the anterior column close to the ventral
ledian fissure. The fibres of the direct pyramidal tract, though they
ike no part in the decussation of the pyramids, cross to the opposite
ide at regular intervals as they descend in the anterior column of
tie cord. The crossing takes place in the ventral or white commissure,
nd, having entered the ventral horn of grey matter of the opposite
ide, the fibres end, like those of the crossed pyramidal tract of that
ide, in close relation with the ventral or motor cells, the axons of
lany of which pass to the ventral or motor nerve-roots.
 
Most of the pyramidal fibres therefore cross from the side on which
hey arise to the opposite side. In the case of the crossed pyramidal
ract the crossing takes place in the lower part of the medulla obmgata. In the case of the direct pyramidal tract the crossing takes
lace in the ventral median fissure of the spinal cord along the course
f the tract.
 
The ground-bundle or intersegmental tracts (fasciculus proprius
nterior, Fig. 871, 14; lateralis, Fig. 871, 13; and posterior , Fig. 871, 8)
ontain association fibres linking together various parts of the cord,
he fasciculus proprius anterior is continued up into the medulla as
he posterior longitudinal bundle, but the ground-bundles, as a whole,
re regarded as descending tracts.
 
The vestibulo-spinal tract (fasciculus vestibulo-spinalis, Fig. 871,
 
 
1432
 
 
A MANUAL OF ANATOMY
 
 
ig) is situated in the anterior column, where it lies superficially. It
forms a communication between the vestibular structures, through
Defiers’ nucleus, with the motor cells of the cord.
 
The prepyramidal or rubro-spinal tract (Fig. 871, 16) is situated
in the lateral column on the ventral aspect of the crossed pyramidal
tract. Its fibres are chiefly derived from the red nucleus of the tegmentum or dorsal part of the crus cerebri of the opposite side, and they
are regarded as terminating in the dorsal part of the ventral grey
matter.
 
The tecto-spinal tract (fasciculus tecto-spinalis , Fig. 871, 17) runs
from the superior corpus quadrigeminum of the opposite side to the
motor cells, and lies in front of the rubro-spinal tract.
 
The bulbo-spinal or olivo-spinal tract, or bundle of Helweg (Fig. 871)
18), is confined to the cervical region of the cord, and is triangular.
Its fibres are regarded as arising in the medulla oblongata behind the
olive, but their mode of termination is not known. They lie near the
surface of the cord external to the anterior nerve-roots.
 
Ascending Tracts.—The dorsal spino-cerebellar tract, or direct
cerebellar tract (of Flechsig) (Fig. 871, 4), is situated in the lateral
column. It lies in front of the dorso-lateral sulcus, between the
crossed pyramidal tract and the outer surface of the cord.. It commences in the lower part of the thoracic region, and superiorly it
traverses the lower part of the medulla oblongata on its lateral aspect,
after which it'enters the restiform body, by which it is conducted to
the vermis of the cerebellum. Its fibres are usually regarded as being
derived from the thoracic nucleus or column of Clarke.
 
The ventral spino-cerebellar tract, or tract of Gowers (Fig. 871, 5),
is situated chiefly in the lateral column, in front of the dorsal cerebellar tract, close to the outer surface of the cord. It is comma-shaped
in section, its dorsal part being broad, but as it extends forwards
between the funiculi of the ventral nerve-roots it tapers and enters
the ventral column superficially. It begins near the lumbar region
of the cord. Superiorly it extends through the medulla oblongata
and pons, and afterwards passes along the superior cerebellar peduncle
into the cerebellum, terminating in the vermis. It therefore takes an
indirect course as compared with that of the dorsal spino-cerebellar
tract. Its fibres are crossed and are usually regarded as being derived
from the thoracic nucleus and posterior horn of the opposite side. The
ventral spino-cerebellar tract contains the spino-thalamic and spinotectal tracts.
 
The spino-thalamic tract (Fig. 871, 6) consists of fibres which arise
as the axons of cells of the dorsal grey matter, around which cells the
fibres of the dorsal nerve-roots have terminated. The spino-thalamic
fibres cross to the opposite side in the ventral or white commissure,
thus giving rise to a spinal inferior sensory decussation or spino-thalamic
decussation, as distinguished from the superior sensory decussation in
the bulb, called the decussation of the fillets, which is produced by the
deep arcuate fibres which arise from the cells of the nucleus gracilis and
 
 
THE NERVOUS SYSTEM
 
 
1433
 
 
ucleus cuneatus. The spinothalamic fibres, having crossed in the
entral white commissure, ascend in the tract of Gowers, and after
raversing the bulb and pons they terminate in the optic thalamus
f the side to which they have crossed as a cell-station. It is important
d note that there are two sensory decussations —lower or spinal, and
pper or bulbar. In unilateral lesions of the spinal cord there would
nly be partial anaesthesia on the opposite side; whereas in unilateral
:sions of the bulb, involving both the fillet-fibres and the spino-thalamic
bres, there would be complete anaesthesia on the opposite side.
 
The spino-tectal tract (Fig. 871, 6) is also an ascending tract. Its
bres are connected with the cells of the ventral cornu of grey matter,
hey ascend in conjunction with the ventral spino-cerebellar tract, and
ass through the formatio reticularis of the bulb and pons. After
lis they decussate with those of the opposite side, forming the fountain
ecussation (of Meynert), which lies between the two red nuclei, to
duch nuclei the spino-tectal fibres furnish collaterals. After the
ecussation the fibres of either side pass to the corresponding superior
illiculus of the corpora quadrigemina.
 
The tracts of the antero-lateral column may be otherwise arranged
s follows:
 
 
Ventral Column.
 
nterior cerebro-spinal tract (descending). (12).
 
nterior intersegmental (descending)
 
( 1 4 ) - . ;
 
ulco-marginal tract (descending)
 
( 15 )
estibulo-spinal tract (descending)
 
( T 9);
 
nterior spino-thalamic tract (ascending) ( 7 ).
 
 
Lateral Column.
 
Lateral cerebro-spinal tract (descending) (11).
 
Rubro-spinal tract (descending) (16).
Tecto-spinal tract (descending) (17).
Olivo-spinal tract (descending) (18).
Dorsal cerebellar tract (ascending)
 
( 4 )-.
 
Anterior spino - cerebellar tract
(Gowers, ascending) (5).
 
Posterior spino-thalamic and spinotectal tracts (ascending) (6).
Lateral intersegmental (descending)
( 13 )
 
The spino-thalamic and spino-tectal tracts (ascending) are contained
1 the ventral spino-cerebellar tract. A part of the postero-lateral
isciculus (Lissauer’s tract) lies superficially in the dorsal part of the
iteral column, and it has been described in connection with the dorsal
olumn.
 
 
Association Fibres of Antero-lateral Column—Intersegmental Fasciculi.— The
 
art of the antero-lateral column which is not occupied by the descending and
scending tracts is adjacent to the grey matter, and it constitutes the antero,teral ground-bundle. It is divided into two parts—anterior and lateral.
 
The anterior intersegmental group is situated in the ventral column in front
: the ventral cornu of grey matter, and has been already described.
 
The lateral group occupies the lateral column ventral and medial to the crossed
framidal tract.
 
The portion of the ventro-lateral ground-bundle adjacent to the grey matter,
id almost surrounding it, is known as the limiting zone.
 
The fibres of the entire antero-lateral ground-bundle are association or
ngitudinal commissural fibres, which serve to connect the grey matter of sue
 
 
 
I 434
 
 
A MANUAL OF ANATOMY
 
 
cessive segments of the spinal cord. They are derived from the cells of the gre
matter of the same side, and also of the opposite side, the latter crossing in th
ventral or white commissure.
 
Arteries of the Spinal Canal and Spinal Cord—Arteries of the Spina
Canal.—These vessels enter the spinal canal through the intervertebra
and sacral foramina. In the cervical region they are branches of th
vertebral, deep cervical, and superior intercostal arteries; in th
thoracic and lumbar regions they are derived from the dorsal branche
of the intercostal lumbar and ilio-lumbar arteries; and in the sacra
region they come from the lateral sacral arteries. Within the spina
canal each spinal artery divides into three branches—neural or central
and anterior and posterior parietal. The neural or central brand
pierces the theca of the spinal cord. It supplies the coverings of th
cord and the nerve-roots, and it anastomoses with the anterior anc
posterior spinal arteries on the cord. This branch is sometimes spokei
of as the lateral spinal artery. The parietal branches divide and joii
again with one another in such a way that they form five anastomoti(
chains in the spinal canal outside the dura mater; of these, one i:
antero-median, two antero-lateral, and two postero-lateral.
 
Arteries of the Spinal Cord.—These are: (i) the anterior spina
artery; (2) the posterior spinal arteries, right and left; and (3) th
lateral spinal arteries, right and left (neural or central branches jus described in connection with the spinal canal).
 
The anterior spinal artery is formed by the union of the anterior
spinal branches, right and left, of the vertebral arteries. It descend:
along the front of the cord in the median line, and is reinforced at
regular intervals by the lateral spinal arteries. In this manner ar
anterior longitudinal anastomotic chain is formed, which descend:
for some distance on the filum terminale.
 
The anterior spinal branches of the vertebral arteries are seldom of equa
size, and often only one is present.
 
The posterior spinal arteries are two in number, right and left, anc
each is a branch of the corresponding vertebral artery. Each vesse
descends on the side of the cord in two branches, one being in front
of and the other behind the posterior nerve-roots. These are reinforcec
by branches from the lateral spinal arteries, and the lateral longitudinal
anastomotic chains formed in this manner extend over the entire length
of the cord. It will thus be seen that there are five anastomotic
chains inside the dura mater in relation to the cord, though they have
not quite the same distribution as the extradural; one is antero-median
and two on each side postero-lateral. Of these two, one lies in front
of and the other behind the posterior nerve-roots.
 
It is only under very favourable conditions that all these arteries are
injected equally.
 
Veins of the Spinal Column and Spinal Cord—Veins of the Spina)
Column.—These veins form two plexuses, extra- and intra-spinal, which
for convenience are divided into five groups from behind forward:
 
 
THE NERVOUS SYSTEM
 
 
1435
 
 
) posterior extraspinal, (2) posterior intraspinal, (3) veins of the
irtebral bodies, (4) anterior intraspinal, (5) anterior extraspinal.
 
The dorsal spinous venous plexus is situated deeply upon the supernal surface of the neural arches of the vertebrae under cover of the
ultifidus spinae muscle. It receives its tributaries from the integuent and muscles of the back, and it communicates with the posterior
ngitudinal intraspinal plexus by branches which pierce the ligamenta
iva. In the neck the blood is conveyed away from the plexus by
uns which open into the vertebral venous plexus around the vertebral
tery of each side; in the thoracic region by veins which join the dorsal
■anches of the intercostal veins; and in the lumbar region by veins
hich join the dorsal branches of the lumbar veins.
 
The veins of the bodies of the vertebrae (venae basis vertebrae) are
mtained within the cancellated tissue of the vertebral bodies. They
)mmunicate in front with the anterior extraspinal veins, and posteriorly
iey terminate in two venous trunks which, emerging through the
 
 
 
 
Fig. 872. —Schematic Sections to show Positions of Longitudinal
 
Arterial and Venous Channels.
 
vo foramina on the posterior surface of each vertebral body, open
ito the transverse communicating branch between the two anterior
•ngitudinal intraspinal veins.
 
The anterior longitudinal intraspinal veins form two anastomotic
lains, which are situated on the posterior surfaces of the bodies of
le vertebrae, one on either side. They communicate with each other
pposite the centre of each body by transverse branches which receive
le terminal trunks of the venae basis vertebrae. These transverse
ranches pass between the posterior longitudinal ligament and the
odies of the vertebrae. Superiorly the anterior intraspinal veins
)mmunicate with the vertebral and the transverse or basilar plexuses
f veins, and laterally an offset passes outwards through each interertebral foramen, which, with that of the posterior intraspinal vein,
)rms a plexus around the adjacent spinal nerve.
 
The posterior longitudinal intraspinal veins are situated in front of
le laminae, one on either side, and they are connected at frequent
itervals by transverse branches. They communicate with the dorsal
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
!436
 
spinous venous plexus by branches which pierce the ligamenta flava.
Superiorly they communicate with the marginal sinuses on either side
of the foramen magnum and vermiform fossa, which by their union
form the occipital sinus. With the marginal sinuses and the anterior
intraspinal veins they form a venous ring at the foramen magnum.
Laterally each vein sends outwards through the corresponding intervertebral foramen an offset, which, with that of the anterior intraspinal
vein, forms a plexus around the adjacent spinal nerve.
 
The anterior and posterior intraspinal veins are situated between
the theca of dura mater and the wall of the spinal canal.
 
The anterior extraspinal veins form a plexus along the anterior
aspect of the bodies of the vertebrae, which is most copious in the neck.
On either side it communicates with the vertebral plexus around the
vertebral artery in the neck, the intercostal veins in the thoracic region,
and the lumbar veins in the lumbar region. It is also connected with
the venae basis vertebrae.
 
Veins of the Spinal Cord.—These vessels lie within the substance
of the pia mater, and are disposed as venous chains, one being in front,
one behind, and two on either side. The anterior vessel lies over the
anterior median fissure beneath the anterior spinal artery; the posterior
vessel is also medially placed; and the two lateral vessels are situated
one in front of and the other behind the posterior nerve-roots (Fig. 872).
Besides these principal chains the veins form a plexus on the surface
of the cord. Laterally branches emerge through the intervertebral
foramina, which, along with the offsets of the anterior and posterior
intraspinal veins, form plexuses around the spinal nerves. From these
plexuses the blood is conveyed on either side into the vertebral plexus
and deep cervical vein in the neck, and into the intercostal and lumbar
veins in the corresponding regions.
 
Lymphatics.—There are no lymphatic vessels in the spinal cord.
Their place is taken by spaces in the outer coat of the arteries, called
perivascular spaces, which are in communication with the subarachnoid
space.
 
Development of the Spinal Cord.
 
The formation of the neural tube from the neural plate and groove is described
on pp. 34 and 39. A short general account of the formation of the cord from
the tube, and of the spinal nerves, is given on p. 53. Further details are given
in the following paragraphs.
 
The proliferating cells of the early neural tube become confluent and form
a syncytium, which is evident in the growing cord to a comparatively late
stage. Exhibiting this syncytial character, the ectodermic cells of the wall
of the tube undergo proliferation, the wall becomes thickened, and it consists
of two kinds of cells—namely, (1) sustentacular or supporting cells, and (2) nervecells proper. The former make the ependyma and neuroglia of the spinal cord,
and the latter give rise to the grey and white matter. The loosely arranged
syncytial network is known as the myelospongium. This myelospongium becomes
condensed internally and externally, and these condensed layers form the internal
and external limiting membranes . The wall of the young neural tube is arranged
in three layers or zones—namely, (1) inner or ependymal, (2) intermediate or
mantle zone, and (3) outer or marginal zone.
 
The ependymal zone consists of a single layer of elongated cells, connected
 
 
THE NERVOUS SYSTEM
 
 
1437
 
 
th the internal limiting membrane. Their bases are directed towards the
nen of the neural tube, and from their apices delicate radial fibres pass outrds to the external limiting membrane. Amongst them there are some concuous cells, called germinal cells. These lie close to the wall of the neural
?e, and by their proliferation they give rise to ependymal cells and neuroblasts,
e latter migrate outwards into the mantle zone.
 
The mantle layer consists mainly of neuroblasts derived from the lining layer
ependymal cells, but smaller neuroglial cells are scattered among- these, and
‘ whole is supported by a network of spongioplasm, in which, in fact, the
 
 
 
j. 873.—Three Sections from Different Levels of Cord in Embryo
 
of 4-9 Mm.
 
ft lower figure, under higher power, shows nerve-fibres leaving ventro-lateral
 
wall.
 
dei may be said to be embedded. Neuroglial fibres develop from the neuroil cells, and extend throughout the thickness of the cord, ramifying and joining
Tin the spongy basis.
 
The marginal zone is the peripheral and outlying part of the spongy netrk, forming a definite layer superficial to the mantle zone. It is a region
ich will be occupied by the tracts of nerve-fibres as these form, acting as
scaffolding or support for them; it increases enormously in thickness as the
r asion by fibres progresses.
 
As just said, the white matter of the cord is made by nerve-fibres growing
 
 
1438
 
 
A MANUAL OF ANATOMY
 
 
in the marginal zone, the grey matter is formed from the mantle zone, and th
ependymal layer, when it has ceased to proliferate and give off the cells of th
mantle zone, becomes the lining cell layer of the central canal. The cana
itself is the remains of the ventral part of the original cavity of the neural tube
 
Neuroglial cells have many branches, and are spoken of as glia-cells or spidet
cells. The neuroglial fibres are fibrillations of the peripheral protoplasm of th
cells, from which they become differentiated.
 
The neuroblasts lie in groups within the mantle layer, and they give ris
to the nerve-cells of the spinal cord. Each cell is primarily unipolar and pear
shaped. It has a prominent nucleus, and the body is prolonged into a proces
or pole, which represents the axon or axis cylinder process of a nerve-fibre. Sub
sequently the pear shape is lost, due to the formation of secondary processes o
dendrites, the cell being now multipolar.
 
Formation of the Cord. —The number of neuroblasts within the mantli
zone increases rapidly, the multiplication being due to frequent division of th
germinal cells in the ependymal zone.
 
The division of germinal cells is apparently very extensive and rapid
There is doubt, however, as to further addition by division of the nucle
within the mantle zone; if there is such division, it is probably amitotic
as the occurrence of mitotic figures in this zone is very exceptional.
 
Whatever may be the origin of all the nuclei, they soon show a tendency t(
gather more particularly in dorsal and ventral thickenings on each side. Thu:
 
there occur longitudinal bulgings on eacl
side, showing not only on the oute:
surface, but also markedly on the in
ternal surface, making the prominence:
known as the dorsal (or alar) and ventra
(or basal) laminae (Fig. 874) which affeci
the form of the contained cavity. Ai
interlaminar sulcus runs down the sid(
wall of the cavity between these tw(
laminae.
 
A semidiagrammatic sectior
across the cord of an embryo ai
the end of the first month is given
in Fig. 874 to illustrate thes*
points. The main collections 0:
neuroblasts in the mantle zone
make the ventral (V) and dorsa'
(D) laminae, separated by the
sulcus (IL). A floor-plate, (F)
connects the two sides and is composed of a thinner ependymal layer with
a fairly thick marginal zone; a roof plate (R) is practically only ependymal.
The neural crest, described on p. 53, lies beside the tube on each side,
and is represented here by a mass of neuroblasts which will become the
posterior root ganglion (G); the interganglionic parts of the neural crest
(p. 54) have disappeared by this time, leaving the ganglionic masses
in position. Differential disposition of neuroblasts in the mantle zone
has begun already.
 
General Formation. —The neuroblasts of the basal lamina make the cells of
the anterior grey column, and the fibres of the afferent roots pass out directly
from them. Those of the dorsal lamina are utilized in forming the matter of
the posterior grey column. The spinal ganglia send nerve-fibres (posterior roots)
into the dorsal region of the cord, the ganglia, as seen, being outside the cord
from the beginning. The marginal zone carries fibres from the neuroblasts, and
thus increases in depth gradually and continuously; in this way the white matter
of the cord is laid down round the grey substance. The cavity, becoming
relatively smaller, remains only as the central canal', there is some reason to think
 
 
 
Fig. 874. —Section across Cord,
Semi-diagrammatic, about End
of First Month.
 
(Explanation in text.)
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
J 439
 
 
at the dorsal portion of the original cavity is actively obliterated by fusion
;tween its walls. The ependymal zone, after its germinal functions have ceased
the end of the second month, becomes the ependymal lining of the canal.
 
The ventral lamina differentiates
ore quickly than the dorsal part,
id can be described first. In Fig.
 
74 it can be seen that a tract of
ldei ( b ) is present, having a distinct
irso-ventral direction and passing
edial to the main ventral or ventroteral neuroblastic mass (a). This
tract comes early. Its appearance
ggests at first a dorso-ventral
igration, but such migration is
rtainly not present, and the arngement seems only due to the
rection of early fibrils in this tract
path, directed towards the floorate, where they cross to the other
ie.
 
This early indication of decussation is of interest. For
some fundamental but not very
evident reason, the passage of
impulses—afferent or efferent
—to the opposite side seems to
be of basic importance, and a
glimpse at the drawings given
already will make it clear that
the floor-plate is the decussating region; the roof-plate does
not seem to provide the necessary marginal zone, and is in
fact stretched into a transparent cellular layer higher up,
so that the commissural fibres
have only the floor-plate for
their passage. So far, then, as
the primary neural tube extends, all commissural fibres
pass ventrally, and the tract b
might even be spoken of as
a ‘ lateral commissure path ’;
such a name, however, would
not take account of certain
other characters, which might
be summed up perhaps in a
‘ path of least resistance,’ so
that, for instance, vessels tend
to enlarge and lie in this path.
 
Without labouring the matter
further, it will be enough to direct attention to this ' path,’ to which reference
will be made from time to time.
 
 
 
Grouping of Ventral Neuroblasts. — Fig. 875 gives tracings from different
A els of the cord at 15 mm., showing the modifications found at this period
the ventro-lateral group (a of Fig. 874). The groups are not so clearly marked,
course, as indicated in the tracings, but are nevertheless quite evident; uC
d mC are upper and middle cervical levels, uD and mD are upper and middle
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1440
 
 
A MANUAL OF ANATOMY
 
 
thoracic, and iL and mL are first and middle lumbar levels. The ‘ commissun
path ’ already mentioned is shown at b, and the grouping of neuroblasts seems i
correspond well with the condition in the adult cord; hence the arrangements i
the ventral grey column appear to be attained at an early stage. The group c, i
the cervical and upper thoracic sections, increases in size as it is traced upward;
It is composed of neuroblasts originating from the ependymal zone at the sam
level of origin as. the a group, but separated from this last collection by the pat
b ; this suggests that it might be looked on as of the same morphological value a
the a group, but of later development. Whether this way of regarding it i
justifiable or not, the group is responsible for supplying the hypoglossal nucleu
and (possibly) that of the sixth nerve, while the a group, at the hypoglossal leve
is apparently taken into the formation of the olive; this will be dealt with in th
proper place.
 
Dorsal Lamina and Associated Formations. —The neuroblasts of the dorsa
lamina increase and differentiate slowly, forming a massive but apparent!
undifferentiated collection in the second month, when the ventral formation
(Fig. 875) are evident. There is at first very little marginal zone over thi
dorsal collection, but about the end of the first month the fibrils growing ii
from the ganglionic mass, beside the cord, begin to collect as a small bundl
(C, Fig. 874) on the dorso-lateral aspect of the neuroblastic mass. This bund!
is the earliest sign of the posterior white column, and increases rapidly in size, a
the same time extending medially. The bundle is to be identified with thi
cuneate fasciculus. The medial extension no doubt helps to form the gracil
fasciculus, but this may have some separate formation as well. The postero
lateral tract (Lissauer’s zone) begins to form a little later, as the entering fibre;
of the posterior root increase in number.
 
The method of elongation of the posterior horn is not clear; doubtless th<
increasing depth of the surrounding white columns has something to do with it
but the other factors are not apparent.
 
The deposition of fibrils within the marginal zone to make the white column!
goes on, seemingly, throughout foetal life; they can be recognized in the firs'
part of the second month at least, and perhaps earlier than this. It may b(
assumed that the shorter fibres are formed first, and occupy the marginal zon<
close to the neuroblasts; thus we get the short intersegmental fibres clothing
the grey matter. The subsequently developed longer fibres are laid down or
these short ones, and the latest developed would be the most superficial; thu;
we find long fibres reaching the mid-brain and thalamus, and superficial to these
although mixed with them to some extent, fibres running to the cerebellum,
a later formation. This, in a general way, agrees with what is known about the
position of such tracts in the cord.
 
The downward-running tracts doubtless follow a comparable regulation ir
their disposal, but the matter of decussation is important here. The cerebrospinal fibres, for example, decussate for the most part immediately before entering the cord, and thus pass at once into the b path mentioned above; following
this, they reach the space ventral to the posterior horn and Lissauer’s tract, in
which they lie as the lateral cerebro-spinal or crossed pyramidal tract. The
uncrossed fibres ultimately cross and also enter the b path, from which they reach
the anterior horn.
 
Myelinization. —The tracts are at first made up of axis cylinders alone, and
these acquire myelin sheaths subsequently. The time when this occurs differs
in the various tracts. The process begins about the fourth or fifth month in
the root fibres, and after this appears in the tracts more or less in the order of
their formation as laid down above. The pyramidal fibres do not begin to
develop their sheaths till about the time of birth, and the process is said to
continue until after puberty.
 
Caudal End of Spinal Cord. —This undergoes certain modifications. It can
be seen in Fig. 877 that a tail process, bent dorsally, represents the atrophied
remnant, in the early part of the second month, of the large ‘ tail ’ of younger
stages. This tail process contains a prolongation from the neural tube; it
 
 
THE NERVOUS SYSTEM
 
 
1441
 
smains up to about the 18 mm. stage, when the atrophied filament vanishes,
arrying with it the included neural prolongation. Fig. 876 shows two median
mgitudinal sections of the end of the cord in embryos of 16 and 35 mm. repectively, the tail remnant being present in the younger specimen, although
rst about to disappear. The neural cell-layers in this remnant are continued
ito a canal (c), the walls of which are continuous with the ependymal layers
f the cord. A second canal (vc) is seen on its ventral side, the cavity of which
pens into the central cavity of the cord (the continuity is not very clear in
ledian section). The central cavity of the cord ends in a dilated ventricle,
diich seems to be a normal condition at this stage. That part of the neural
ibe which corresponds with the quondam tail is evidently disappearing, shows
regular growth, and is represented by remnants.
 
In the 35 mm. embryo the tail has gone, and the caudal neural remnant shows
coccygeal vestigial cyst {cyst) where the caudal portion has separated, the
 
 
toirqinal jone
/ (ye rtf. comm.)
 
 
 
16 mm
 
 
!f- -\coccyK
 
cyst/ v
 
 
 
Fig. 876. —Median Sagittal Sections of Ends of Cords in Sixth and
 
Ninth Weeks.
 
Ependymal tissue shown in black. Description in text.
 
 
yrst lying very near the surface. Some nerve-fibres have developed in connection
ith this {%/) and pass to the cord itself. Remnants of this canal are seen
irther forward, and the ventral canal is seen opening into the ventral part of
 
le terminal ventricle, as in the younger stage.
 
After this stage the cord does not grow in length at the same rate as the
ertebral column, so that its caudal end gets farther and farther away from the
Dccygeal region. Hence, the vestigial cyst remaining in situ with a superficial
ttachment, the intervening cell-strands are drawn out in a lengthening conection The main cell masses caudal to the ventricle are drawn up with it,
taking the nervous elements found in the upper end of the filum terminate;
le rest of the filum is composed of drawn-out pia mater, the included and
 
fetched nerve-tissue having disappeared.
 
The coccygeal vestigial cyst enlarges somewhat and develops nerve-tissue
)und it, but disappears during the later foetal months; it is a possible cause,
y persistence, of certain congenital cysts found near the coccyx.
 
 
9i
 
 
 
 
1442
 
 
A MANUAL OF ANATOMY
 
 
Membranes of Spinal Cord. —The membranes—namely, pia mater, arachnoid
and dura mater (theca)—are developed from the mesoderm which invests th
neural tube.
 
Growth of Spinal Cord. —The cord originally occupies the entire length o
the spinal canal of the vertebral column. The vertebral column, however
grows more rapidly than the cord, so that at the period of birth the cord does no
extend lower than the level of the third or fourth lumbar vertebra. Sub
sequently its lower limit is the intervertebral disc between the bodies of th
first and second lumbar vertebrae. This produces a change in the course o
the lumbar, sacral, and coccygeal nerves. In order to reach the level of th
intervertebral foramina through which they emerge from the spinal cana
they descend almost vertically, and constitute the bundles of nerves known a
the cauda equina.
 
A linear reconstruction of the coccygeal portion of the cord in a 15 mm
embryo is given in Fig. 877. It shows the atrophying tail-remnant, with it
included piece of neural tissue, but also shows, proximal to this, a portion o
nerve-tube truly coccygeal in nature and position, from which take origii
four (? or more) nerves behind the coccygeal nerve. These post-coccygea
nerves, which have double roots, join with each other and with the coccygea
 
 
 
Fig. 877. —Linear Reconstruction of Caudal End (15 Mm.), showing thi
Prolongation of Cord into the Tail Filament, and the Presenci
of Four Nerves beyond the Coccygeal.
 
The vertebral levels of the spinal nerves are indicated.
 
nerve in a series of ill-defined loops. They emerge between the rudimentar]
vertebrae caudal to the sacrum. The broken-up post-coccygeal portion of th(
cord is in part carried up with the persisting coccygeal portion, and in pari
left behind; the intermediate part is drawn out with the filum terminale. Som<
nervous matter still persists at the upper end of this structure. The post
coccygeal nerves atrophy and disappear, but Rauber has described remains
of ganglia and nerves beside the upper part of the filum, which may repre
sent remnants of the upper post-coccygeal nerves, drawn up with the cord.
 
 
THE ENCEPHALON.
 
 
The encephalon is the part of the cerebro-spinal axis which if
contained within the cranial cavity. It is composed of the medulh
oblongata, pons Varolii, cerebellum, and cerebrum. In the embryc
it consists of three hollow vesicles.
 
 
Encephalon =
 
Prosencephalon or Fore-brain.
Mesencephalon or Mid-brain.
Rhombencephalon or Hind-brain.
 
 
 
 
THE NERVOUS SYSTEM
 
 
1443
 
 
The subdivisions of the prosencephalon are the telencephalon and
he thalamencephalon or diencephalon; the mesencephalon remains
mdivided; and the subdivisions of the rhombencephalon are the metncephalon and the myelencephalon.
 
 
Fore-brain or Prosencephalon = { ^alamencephalon or Diencephalon.
Mid-brain or Mesencephalon = Mesencephalon.
 
Hind-brain or Rhombencephalon = { Mydenceplulon.
 
 
rhe various parts of the encephalon which are developed from these
ubdivisions will be made evident from the following table:
 
 
Telencephalon
 
 
Thalamencephalon
 
or
 
Diencephalon
 
Mesencephalon
 
Metencephalon
 
Myelencephalon
 
 
 
 
Cerebral Hemispheres.
 
Lateral Ventricles.
 
Anterior Part of Third Ventricle.
Interventricular Foramina.
 
Olfactory Lobes.
 
Posterior Part of Third Ventricle.
 
Optic Thalami and Corpora Geniculata.
Pineal Body.
 
Interpeduncular Structures.
 
Pituitary Body.
 
Optic Nerve and Retina.
 
Corpora Quadrigemina.
 
Crura Cerebri.
 
Aqueduct (of Sylvius).
 
Cerebellum.
 
Pons (Varolii).
 
Pontine Part of the Fourth Ventricle.
 
 
( Medulla Oblongata (or Bulb).
 
\ Bulbar Part of Fourth Ventricle.
 
 
General Description of the Base and Superior Surface of the
 
Encephalon.
 
The inferior aspect of the encephalon is known as the base. In the
allowing general description of the parts which it presents the order
pursued is, as nearly as possible, from behind forwards and upwards.
 
The medulla oblongata (or bulb) lies on the under aspect of the
:erebellum in the median line, occupying the vallecula which separates
the two cerebellar hemispheres. The surface exposed is the ventral
surface, which presents (1) the anterior median sulcus, crossed at its
tower part by the decussation of the pyramids; (2) the pyramid, on
sither side of this sulcus; and (3) the olivary body, external to each
pyramid.
 
The hemispheres of the cerebellum lie one on either side of the
medulla oblongata, and they conceal from view the posterior parts
of the cerebral hemispheres and the posterior part of the great longitudinal fissure. They are characterized by the laminated arrangement
of their nervous matter, the laminae being curved and separated from
 
 
 
 
1444
 
 
A MANUAL OF ANATOMY
 
 
each other by fissures. Posteriorly the hemispheres are separated fror
each other by the posterior notch. When the medulla oblongata i
raised, and the cerebellar hemispheres slightly separated from each othei
the vallecula is fully exposed, and the inferior vermis is seen lyini
deeply in it, with the sulcus vallecula on either side of it.
 
The pons' (pons Varolii) forms a prominent elevation above th
medulla oblongata, the surface exposed being the ventral surface. L
the median line this surface presents a longitudinal groove, which i
 
 
Olfactory Bulb
Olfactory Tract
 
 
Lateral Sulcus
 
 
Optic Nerve
 
 
Gyrus Rectus
 
 
 
Subst. Perfor
Ant.
 
 
Tuber Cinere
and Infundibi
Corpus Mami
 
 
Crus Cerebri
 
 
Area Perforal
Post.
 
 
Fifth Nerve
Sixth Nerve
 
Facial Nerve
Pars Intermedia
 
 
Auditory Nerve-'
Glossopharyngeal Nerve Vagus Nerve
 
Accessory Nerve
 
 
Oblongata
 
 
Hypoglossal Nerve
 
 
Fig. 878. —The Base of the Encephalon, and the Cranial Nerves.
1, frontal lobe (orbital surface); 2, temporal lobe; 3, cerebellum.
 
 
occupied by the basilar artery. On either side the pons becomes th<
 
middle peduncle of the cerebellum, passing outwards and backwards
into the cerebellar hemisphere.
 
The temporal lobes of the cerebrum are situated in front of the
cerebellar hemispheres, and are conspicuous by their prominence.
Each terminates anteriorly in a projecting extremity, called the
 
temporal pole.
 
The stem of the lateral sulcus lies immediately in front of the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1445
 
 
;mporal lobe, and is occupied by the middle cerebral artery. At the
iner end of the stem of the fissure is the depression often referred to
5 the vallecula Sylvii or vallecula cerebri.
 
The frontal lobes of the cerebrum lie in front of the stem of the
,teral fissure. The exposed parts are the orbital surfaces, each of
hich is separated from its fellow of the opposite side by the great
ingitudinal fissure. Each orbital surface presents a straight fissure,
died the olfactory sulcus, which is situated near the great longitudinal
ssure, and is parallel to it. This sulcus is occupied by the olfactory
•act and olfactory bulb.
 
The crura cerebri, or peduncles, right and left, appear at the upper
order of the pons, and soon diverge from each other as they pass
awards and upwards to sink into the cerebral hemispheres.
 
The optic tract of each side winds round the outer and ventral
spects of the corresponding crus cerebri. Its course is forwards and
lwards towards its fellow of the opposite side.
 
The optic commissure, or chiasma, connects the two optic tracts
fter their convergence.
 
The optic nerves, right and left, leave the front of the commissure,
nd pass forwards and outwards to the optic foramina.
 
The interpeduncular space is situated in front of and above the
ons. It is somewhat diamond-shaped, and its boundaries are as
dlows: posteriorly, the divergence of the crura at the upper border
f the pons; anteriorly, the optic commissure; and, laterally, the crus
erebri and optic tract from behind forwards. The following parts
e within this space, in the order named, from behind forwards: (1) the
rea perforata posterior; (2) the corpora albicantia or mamillaria;
nd (3) the tuber cinereum, with the infundibulum. The structures
ccupying the interpeduncular space form for the most part the floor
f the third ventricle.
 
The area perforata posterior or posterior perforated substance
 
Drresponds to the posterior median angle of the diamond-shaped intereduncular space, and it lies in a deep depression, called the intereduncular fossa (or fossa Tarini). The grey matter which forms it is
erforated by openings for the passage of the postero-medial branches
f the posterior cerebral arteries.
 
The corpora mamillaria are situated directly in front of the area
erforata posterior, and present the appearance of small, white, peake bodies lying close to the median line.
 
The tuber cinereum extends from the mammillary bodies to the
ptic commissure, and is composed of grey matter. The infundibulum
; connected with the tuber cinereum close behind the optic comlissure, and passes downwards to the posterior part of the pituitary
ody.
 
The area perforata anterior or anterior perforated substance of each
de coincides with the vallecula at the inner end of the stem of the
iteral fissure. It lies outside the interpeduncular space, close to the
uter aspect of the optic commissure. It consists of grey matter, which
 
 
I446
 
 
A MANUAL OF ANATOMY
 
 
is perforated by openings for the passage of a few antero-medial branches
of the anterior cerebral artery, and numerous antero-lateral branches
of the middle cerebral artery. These branches are destined for the
nucleus caudatus and nucleus lenticularis of the corpus striatum, the
grey matter of which nuclei comes to the surface of the brain at the
anterior perforated substance.
 
The medulla oblongata and pons occupy the basilar groove of the
interior of the base of the skull; the cerebellar hemispheres occupy the
cerebellar fossae of the occipital bone; the temporal lobes of the cerebrum
sink deeply into the lateral divisions of the middle fossa of the base
of the skull; the orbital surfaces of the frontal lobes occupy the lateral
divisions of the anterior fossa; the stem of the lateral fissure faces the
posterior border of the small wing of the sphenoid; the optic commissure lies above the olivary eminence and optic groove of the sphenoid;
and the olfactory bulb rests upon one half of the cribriform plate of the
ethmoid bone. The olfactory bulb and olfactory tract, essential parts
of the brain, occupy the olfactory sulcus on the orbital surface of the
frontal lobe near the great longitudinal fissure; and the olfactory filaments pass through the foramina of the cribriform plate of the ethmoid
bone on their way from the olfactory cells of the olfactory mucous
membrane to the olfactory bulb. Posteriorly the olfactory tract
divides into two roots, medial and lateral. The medial root curves
inwards behind the ‘ area of Broca ’ to the callosal gyrus. The lateral
root passes backwards and laterally across the outer part of the area
perforata anterior. The triangular area of grey matter, which is
situated between the diverging roots of the olfactory tract, is called
the trigonum olfactorium. It is sometimes spoken of as the middle
or grey root of the olfactory tract. The area of Broca is situated in
front of the medial (inner) root of the olfactory tract, and is continuous
with the callosal gyrus.
 
Superficial Origins of the Cranial Nerves.
 
The first or olfactory nerve is represented by the filaments which,
as has been seen already, have their superficial origin from the lower
surfaces of the olfactory bulbs and pass through the cribriform plate.
 
The second or optic nerve is connected with the lateral extremity
of the front part of the optic commissure.
 
The third or oculo-motor nerve emerges through the oculo-motor
sulcus on the inner aspect of the crus cerebri, just above or in front
of the pons, and close to the posterior perforated substance.
 
The fourth or trochlear nerve, having emerged from the upper part
of the superior medullary velum, makes its appearance in the interval
between the crus cerebri internally and the temporal lobe externally.
 
The fifth or trigeminal nerve consists of two roots, which emerge close
together from the lateral aspect of the ventral surface of the pons.
The sensory root is large, and the motor root, which is small, lies above
and slightly medial to the sensory root.
 
 
 
THE NERVOUS SYSTEM
 
 
1447
 
 
The sixth or abducent nerve appears at the lower border of the pons
ust lateral to the pyramid of the medulla oblongata.
 
The seventh or facial nerve emerges at the lower border of the pons
n front of the restiform body of the medulla oblongata.
 
The eighth or auditory nerve likewise appears at the lower border of
:he pons in front of the restiform body of the medulla oblongata,
[t lies on the outer side of the facial nerve.
 
The N. intermedins is a small nerve which appears between the facial
md auditory nerves. It is regarded as the sensory root of the facial
lerve.
 
The ninth or glosso-pharyngeal nerve emerges, in the form of about
fix fasciculi, from the postero-lateral sulcus of the medulla oblongata,
Detween the olivary body and the restiform body, immediately below
the facial nerve.
 
The tenth or vagus nerve lies directly below the glosso-pharyngeal
nerve, and emerges by several fasciculi from the postero-lateral sulcus
Df the medulla oblongata in front of the restiform body.
 
The eleventh or accessory nerve has several roots which lie below
the fasciculi of the vagus nerve. These rise (a) from the medulla
nblongata and ( b ) the upper part of the lateral column of the spinal
:ord as low as the level of the fifth cervical nerve. The first is the
zranial origin of the nerve, the second its spinal root. They lie below
the fasciculi of the vagus nerve, and external to, or in front of, the
posterior roots of the adjacent cervical spinal nerves.
 
The twelfth or hypoglossal nerve emerges by several fasciculi
through the antero-lateral sulcus of the medulla oblongata between
the pyramid and the olivary body. These fasciculi lie in line with
the sixth nerve superiorly.
 
Arteries at the Base of the Encephalon. —The arteries which supply
the brain are the two vertebral and the two internal carotid arteries.
 
The vertebral arteries incline medially as they ascend on the ventral
aspect of the medulla oblongata, and at the lower border of the pons
they unite to form the basilar artery. The branches of each vertebral
artery to be noted are as follows: (1) the posterior spinal branch , which
arises from the main vessel immediately after it has pierced the dura
mater, and descends upon the side of the medulla oblongata to the
spinal cord; (2) the anterior spinal branch , which arises higher up than
the preceding, and passes downwards and inwards on the ventral aspect
of the medulla oblongata to unite with its fellow and form the anterior
spinal artery ; and (3) the posterior inferior cerebellar branch, of large
size, which arises from the main vessel near the pons, and passes backwards round the medulla oblongata to enter the vallecula of the cerebellum.
 
The basilar artery extends from the lower border of the pons to the
upper border, occupying the basilar groove on its ventral surface.
It is formed by the union of the two vertebral arteries, and terminates
by dividing into the two posterior cerebral arteries. The branches of
the basilar artery to be noted on either side are as follows. (1) the
 
 
 
1448 A MANUAL OF ANATOMY
 
transverse arteries of the pons ; (2) the internal auditory artery , which
accompanies the auditory nerve through the meatus auditorius internus; (3) the anterior inferior cerebellar artery , which arises from the
basilar about its centre, and passes backwards to the inferior surface of
the cerebellar hemisphere; (4) the superior cerebellar artery , which arises
from the basilar near its termination, and passes laterally close to the
 
 
 
upper border of the pons, and then round the outer side of the crus
cerebri to the superior surface of the cerebellar hemisphere; and (5) the
posterior cerebral artery , which arises from the termination of the basilar,
and passes laterally parallel to the superior cerebellar artery, and then
round the crus cerebri to the inferior surface of the occipital lobe. The
posterior cerebral and superior cerebellar arteries are separated from
 
 
}
 
 
*
 
 
 
 
THE NERVOUS SYSTEM
 
 
1449
 
 
iach other by the third and fourth cranial nerves. The branches of
;he posterior cerebral artery are: (1) postero-medial, which pass to the
posterior perforated substance; (2) postero-lateral, which pass round
:he crus cerebri; and (3) posterior choroidal, which pass to the upper
Dart of the choroidal fissure.
 
The internal carotid artery of each side appears at the vallecula
:erebri, and there divides into the anterior and middle cerebral arteries.
Near its termination it gives off the posterior communicating artery,
which passes backwards to join the posterior cerebral artery. It also
pves off the anterior choroidal artery, which passes backwards and
Dutwards between the crus cerebri and the uncinate gyrus to the lower
and anterior part of the choroidal fissure.
 
The anterior cerebral artery passes forwards and inwards between
the optic nerve and the medial root of the olfactory tract, and enters
the great longitudinal fissure.
 
As it is about to enter that
fissure it is connected with
its fellow of the opposite side
by the anterior communicating artery, which is short,
but of fairly large size.
 
Amongst other branches the
following are to be noted
arising from the anterior
cerebral artery: (1) anteromedial, few and inconstant;
and (2) antero-lateral, both of
which pass to the anterior
perforated substance.
 
The middle cerebral artery,
of large size, sinks into the
lateral fissure, which it traverses in an outward ‘direction. Before
disappearing into the fissure antero-lateral ganglionic branches are to be
noted arising from it, which are arranged in two sets, medial and
lateral striate, for the corpus striatum and internal capsule.
 
Circulus Arteriosus.—This is an important communication between
the vertebral and internal carotid arterial systems at the base of the
brain, which is situated around the interpeduncular space. It is not
actually a circle, though so named, but is a heptagon—that is to say,
it has seven angles and seven sides.
 
Beginning at the median line posteriorly, and proceeding forwards
on either side to the median line in front, at the great longitudinal
fissure, the component arteries of the circle are: (1) the basilar, (2) the
posterior cerebral, (3) the posterior communicating, (4) the internal
:arotid, (5) the anterior cerebral, and (6) the anterior communicating.
These communications serve to insure a uniform supply of arterial
fiood to the brain in cases of obstruction to one or other of the principal
irterial trunks. The communications also serve to equalize the circu
 
1. Internal Carotid
 
2. Middle Cerebral
 
3. Anterior Cerebral
 
4. Anterior Communicating
 
5. Posterior Communicating
 
6 . Posterior Cerebral
 
7. Basilar
 
8 . Superior Cerebellar
 
9. Transverse Pontine
xo. Internal Auditory
xr. Anterior Inferior Cerebellar
 
12. Posterior Inferior Cerebellar
 
13. Vertebral
 
14. Anterior Spinal
 
15. Posterior Spinal
 
16. Anterior Choroid
 
17. Posterior Choroid
 
18. Cential or Ganglionic
 
19. Central or Ganglionic
 
20. Central or Ganglionic
(Postero-mesial)
 
‘21. Central or Ganglionic
(Postero-lateral)
 
Fig. 880. —The Arteries at the Base of
the Brain, and the Circulus Arteriosus.
 
 
 
13 15 14
 
 
 
 
1450
 
 
A MANUAL OF ANATOMY
 
 
lation of blood through the different parts of the brain, an arrangement
which, though doubtless advantageous, cannot be essential, since one
or both of the posterior communicating arteries are often very small
and sometimes absent.
 
Superior Surface of the Brain. —The brain is ovoid superiorly, its
greatest breadth corresponding to the positions of the parietal eminences
of the parietal bones. In the median line it presents a deep cleft,
called the longitudinal fissure, which extends from the front to the
 
 
Great Longitudinal
Fissjarc
 
 
 
Fig. 88i.—The Cerebral Hemispheres (Superior View).
Fissure of Rolando—central fissure.
 
 
back, and divides it into two hemispheres, right and left. This fissure
is occupied by a process of the dura mater, called the falx cerebri, and
the corpus callosum lies at its deep part. In front of the corpus
callosum the fissure extends down to, and is visible on, the base of the
brain, but behind the corpus callosum it only extends to the level of the
tentorium cerebelli, which separates the cerebellum from the posterior
parts of the cerebral hemispheres. The fissure, therefore, in this situation is not visible inferiorly until the cerebellum and the tentorium
cerebelli have been removed.
 
 
/
 
 
 
 
THE NERVOUS SYSTEM
 
 
1451
 
 
Each hemisphere is semi-ovoid, its medial surface being flat. The
anterior and posterior extremities are rounded, the former being the
thicker of the two. The anterior extremity is known as the frontal
pole, and the posterior extremity forms the occipital pole. The surface
of each hemisphere consists of grey matter, which is spoken of as the
cerebral cortex. Superiorly and externally it is convex in adaptation
to the concavity of the vault of the cranium. It is broken up into a
number of tortuous eminences, called gyri or convolutions, and these
are separated from each other by clefts, called sulci or fissures. The
surfaces of the gyri which bound the sulci are covered with grey
matter, like their exterior. The pia mater closely covers the gyri, and
also dips into the sulci, so as to cover the opposed surfaces of the gyri.
The arachnoid membrane, however, does not dip into the sulci, but
passes over them. The sulci are of various depths, but the average
depth is about J inch.
 
RHOMBENCEPHALON.
 
1. The Medulla Oblongata.
 
The medulla oblongata (or bulb) is continuous with the spinal cord,
and extends from the lower margin of the foramen magnum of the
occipital bone to the lower border of the pons. Its direction is upwards
and forwards, and it measures 1 inch in length, f inch in breadth at
the widest part, and fully \ inch in thickness. Interiorly its girth
corresponds with that of the spinal cord, but it widens superiorly, so
that it is somewhat pyramidal. Its ventral surface faces the basilar
groove of the occipital bone, and its dorsal surface is directed towards
the vallecula of the cerebellum.
 
The bulb is composed of two symmetrical halves, its bilateral
symmetry being indicated superficially by upward prolongations of
the ventral or anterior sulcus and dorsal or posterior median septum
of the spinal cord. The anterior median fissure extends as high as the
lower border of the pons, where it expands slightly and forms a blind
recess, called the foramen ccecum. In its lower part this fissure is interrupted and crossed by bundles of nerve-fibres, which are derived
from the inner three-fourths of each pyramid, the decussation thus
formed being known as the decussation of the pyramids, or motor
decussation. The posterior median septum only extends along the lower
half of the bulb, and it terminates superiorly at the point of divergence
of the margins of the fourth ventricle.
 
Each half of the bulb presents two grooves. The antero-lateral
sulcus is situated between the pyramid and the olivary body, and along
this sulcus the roots of the hypoglossal nerve emerge in line with the
ventral roots of the spinal nerves. Whilst, however, the latter are
spread over a certain area, the hypoglossal roots emerge along a straight
line corresponding to the ventro-lateral sulcus of the bulb. This sulcus
is not represented on the surface of the spinal cord. The posterolateral sulcus lies on the dorso-lateral aspect of the olivary body. Along
 
 
1452
 
 
A MANUAL OF ANATOMY
 
 
this sulcus, in order from above downwards, there are (i) the roots of
the glosso-pharyngeal nerve, (2) the funiculi of the vagus nerve, and
(3) the funiculi of the bulbar part of the accessory nerve.
 
The bulb in its lower half contains a prolongation of the central
canal of the spinal cord. This part of the bulb is spoken of as the
closed part , and it extends as high as the level of the lower point
of the ventricle. In the upper half of the bulb the central canal
opens out at this level into the ^fourth ventricle, and the dorsal
aspect of the bulb forms the lower,.or bulbar half of the floor of the
fourth ventricle. The upper half of. the bulb is therefore spoken of as
the open part.
 
 
 
Optic Commissure
 
; Optic Nerve
Infundibulum, - ~
 
Tuber Cinereum '■» * # „ . „
 
C Optic Tract
 
Mamillary Body . /
 
Third Nerve
 
Mesial Root of Optic Tract '
 
Lateral Root of Optic Tract
Lateral Geniculate Body
 
 
Post.Perforated Subst.
 
 
Fourth Nerve
 
 
Sixth Nerve
 
 
Root of Fifth Nerve
Root of Fifth Nerve
 
 
Facial Nerve
 
Pars Intermedia
Auditory Nerve -
Glosso-pharyngeal Nerve -Vagus Nerve
Superficial Arcuate Fibres—
 
Accessory Nerve-"
 
First and Second Cervical Nerves;^
 
 
Middle Peduncle of
Cerebellum
 
Inferior Peduncle
- — Hypoglossal Nerve
..Anterior Median Fissure
 
Decussation of the Pyramids
 
 
Fig. 882. —The Medulla Oblongata, Pons, and Interpeduncular Region.
C.C., crus cerebri; P., pyramid; O.B., olivary body.
 
 
The surface of each half of the bulb is divided into three areas by
the above-mentioned sulci, with the corresponding nerve funiculi.
These surface areas are ventral, lateral, and dorsal.
 
Ventral or Anterior Area.—This superficial area is situated between
the median and the antero-lateral sulcus, along which the funiculi
of the hypoglossal nerve emerge. It constitutes the pyramid of the
bulb. The two pyramids, right and left, represent the motor tracts
of the bulb. As regards position, the pyramid is like the anterior
column of the spinal cord, and it consists of bundles of nerve-fibres
disposed longitudinally. Inferiorly it is somewhat narrow, but it
widens superiorly. At the lower border of the pons it undergoes a
slight constriction, after which it sinks into the pons. As it traverses
the pons its funiculi become separated into several strata, and these
are gathered together at the upper border of the pons into the crus
cerebri of the corresponding side.
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1453
 
 
Inferiorly each pyramid is disposed in two parts—medial and lateral.
The medial portion represents as a rule the inner three-fourths, and
its fibres cross to the opposite side in the lower part of the ventral
median sulcus of the bulb. Thereafter they sink deeply into the dorsal
part of the lateral column of the spinal cord on the side to which they
have crossed, where they constitute the crossed pyramidal or lateral
cerebro-spinal tract. The intercrossing of fibres which takes place in
the lower part of the ventral median fissure of the bulb is called the
decussation of the pyramids, or the motor decussation, and, as stated, it
usually involves the fibres of the inner three-fourths of the pyramid.
 
The lateral portion of the pyramid represents as a rule the lateral
fourth, and its fibres take no part in the decussation. The path of
most of them is downwards into the anterior column of the spinal cord
of the same side, where they lie close to the anterior median fissure of the
cord and constitute the direct pyramidal or anterior cerebro-spinal
tract. A few of them, however, descend into the lateral column of
the same side, and constitute the uncrossed lateral pyramidal tract.
 
The pyramid of the bulb, therefore, only corresponds topographically
with the anterior column of the spinal cord. The direct cerebro-spinal
tract of the anterior column of the cord forms the greater part of the
lateral fourth of the corresponding pyramid of the bulb; and the crossed
cerebro-spinal tract of the lateral column of the cord forms the medial
three-fourths of the pyramid of the opposite side. The remainder of
the anterior column of the cord sinks deeply into the bulb and lies on
the dorsal aspect of the pyramid.
 
The ventral surface of each pyramid is crossed above the level of
the decussation of the pyramids by the anterior superficial arcuate
fibres , which emerge from the ventral median fissure and take an
arched course outwards and then backwards to the inferior cerebellar
peduncle.
 
The sixth cranial nerve emerges close to the lower border of the
pons, immediately lateral to the pyramid, and in line with the funiculi
of the hypoglossal nerve as these leave the ventro-lateral sulcus.
 
Lateral Area of the Medulla Oblongata.— This superficial area is
situated behind the funiculi of the hypoglossal nerve. Superiorly the
oval eminence, called the olive, is included in it. Inferiorly it has the
appearance of being a prolongation of the lateral column of the spinal
cord, but this is not the case. The crossed cerebro-spinal tract of the
lateral column of the cord sweeps obliquely across to the opposite side,
where it forms the greater part of the pyramid of that side. The
parts, therefore, of the lateral column of the cord which form the
lateral area of the bulb below the olive are (1) the dorsal or direct spinocerebellar tract, (2) the ventral spino-cerebellar tract, and (3) the lateral
intersegmental bundle. The dorsal spino-cerebellar tract, as it ascends,
soon inclines obliquely backwards to join the inferior peduncle. The
ventral spino-cerebellar tract and intersegmental bundle ascend until
they reach the lower end of the olive. They then in part sink deeply,
and ascend to the pons on the dorsal or deep aspect of the olive. Most
 
 
T 454
 
 
A MANUAL OF ANATOMY
 
 
of the cerebellar fibres, however, remain on the surface, and ascend in
the small interval which lies between the outer part of the olive and
the funiculi of the glosso-pharyngeal and vagus nerves.
 
 
 
Fig. 883.—A Sketch to show
the Disposition of Spinocerebellar Fibres in Lateral Region of Medulla.
 
 
The lateral area of the bulb below the
olive thus represents the dorsal or direct
spino-cerebellar tract, ventral spino-cerebellar tract, and, deeply, the lateral
ground-bundle of the lateral column of
the spinal cord of the same side (Fig. 883).
 
Superiorly, as stated, the lateral area
presents an oval eminence, called the
olive. It lies between the funiculi of the
hypoglossal nerve on the one hand, and
the funiculi of the glosso-pharyngeal and
vagus nerves on the other, with the
intervention of some ascending fibres
belonging to the ventral spino-cerebellar
tract. Its long axis is placed vertically,
and in this direction it measures about
J inch. Superiorly it is separated from
the pons by a deep transverse groove, and
interiorly the anterior superficial arcuate
fibres arch over its lower part.
 
At the lower border of the pons,
lateral to the upper end of the olive, the
facial and auditory nerves make their
appearance. The facial nerve is in line
 
 
The dorsal fibres (interrupted
lines) run to inferior peduncle, therefore have a
dorsal tendency as they
ascend, covering in the
spinal root of fifth nerve,
which is making a slight
prominence, the tuberculum
gelatinosum (T). The ventral fibres (Gowers’ tract)
are dotted. The arrows
indicate many fibres from
other parts (olives, etc.),
helping to complete the
peduncle. C, G, cuneate
and gracile tubercles ;
P.R.O., position of pallidorubro-olivarv tract.
 
 
closed and open part of the
lower and upper.
 
 
with the roots of the glosso-pharyngeal
nerve. The auditory nerve appears lateral
to the facial nerve, and between the two
is the small pars intermedia (of Wrisberg ).
 
Dorsal or Posterior Area of the Medulla
Oblongata.—This superficial area is limited
in front by the sulcus containing the
funiculi of the glosso-pharyngeal, vagus,
and bulbar part of the spinal accessory
nerves. Posteriorly its lower half extends
as far as the dorsal median fissure, and
its upper half extends only as far as the
lateral boundary of the lower or bulbar
half of the floor of the fourth ventricle.
Inasmuch as this area belongs to both the
bulb, it will be considered in two sections—
 
 
Lower Portion of Posterior Area. —This, it has been shown, is limited
behind by the dorsal median fissure, and it is in direct continuity with
the dorsal column of the spinal cord of the same side, which is composed
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
*455
 
 
>f the gracile and cuneate columns. It presents three longitudinal
minences—namely, the funiculus gracilis, funiculus cuneatus, and
uniculus gelatinosus.
 
The funiculus gracilis is a prolongation of the column of the spinal
ord, and lies close to the dorsal median fissure. The funiculus cuneatus
3 a prolongation of the column of the cord, and lies lateral to the
uniculus gracilis, from which it is separated by an upward continuation
>f the dorsal intermediate or paramedian furrow of the cord.
 
At the lower level of the ventricle each of these two funiculi
)ecomes enlarged and terminates in a prominence or bulb. The enargement formed by the funiculus
;racilis is called the clava, or gracile
ubercle, and that formed by the funi:ulus cuneatus is termed the cuneate
ubercle. The two clavae, right and left,
ie on either side of the lower angle of
he fourth ventricle, and as the bulb
>pens out dorsally at this level to form
he lower or bulbar half of the floor of
he fourth ventricle each clava is dis)laced laterally. An angular interval
low separates the two clavae, and the
irolongation of the central canal of the
pinal cord through the lower or closed
>art of the bulb opens into the fourth
ventricle in the angle between the two
:lavae.
 
The funiculus gracilis, with its tu>ercle, and the funiculus cuneatus, with
ts cuneate tubercle, are to a large exent produced by the collections of grey
natter which they contain—namely, the
mcleus gracilis and nucleus cuneatus.
 
The funiculus gelatinosus is situated
>n the outer side of the funiculus cuneatus, between it and the funi:uli of the bulbar part of the spinal accessory nerve. It is produced
>y the substantia gelatinosa (of the spinal cord), which is close to the
urface in the lower or closed part of the bulb. Interiorly the funiculus
s narrow, but it widens as it ascends, and superiorly it terminates
n an enlarged extremity, called the spinal tract of the trigeminal or
uberculum gelatinosum.
 
The funiculus and tubercle are covered by a thin layer of longiudinal nerve-fibres which represent the spinal or descending sensory
oot of the fifth cranial nerve.
 
Upper Portion of Posterior Area.— This belongs to the upper or open
>art of the bulb, and extends as far as the lateral boundary of the
ower or bulbar half of the floor of the fourth ventricle. It presents
l prominent round tract, called the restiforrn body , which is situated
 
 
 
Fig. 884.—Posterior View
of Medulla.
 
G, C, gracile and cuneate tubercles ; g, c, corresponding
tracts; F, gelatinous tubercle; O, obex.
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1456
 
between the lower half of the floor of the fourth ventricle and the
funiculi of the vagus and glosso-pharyngeal nerves. Its direction
is upwards, outwards, and backwards, and it enters the corresponding hemisphere of the cerebellum. It is otherwise known as the
 
inferior cerebellar peduncle.
 
The inferior peduncle succeeds to the funiculus gracilis and funiculus
cuneatus of the lower portion of the posterior area of the bulb, but
it is quite distinct from these funiculi, and receives no fibres from
them. The sources of its fibres will be given in connection with
the internal structure of the bulb (see p. 1463). Meanwhile, it is
 
 
 
Fig. 885.—Section through Medulla just above Decussation of Pyramids: Shows the Prominence of Spinal Tract of Fifth Nerve.
 
F is the dorsal spino-cerebellar tract immediately ventral to this, and G is the
 
ventral tract.
 
clear that it constitutes the great tract of connection between the
cerebellar hemisphere, the bulb, and the spinal cord.
 
The restiform body becomes conspicuous above the level of the
cuneate tubercle, and forms the lateral boundary of the lower or
bulbar half of the floor of the fourth ventricle.
 
Internal Structure of the Medulla Oblongata. —Each half of the
bulb is composed of grey nervous matter and tracts of white nervous
matter.
 
Grey Matter. —The grey matter lies largely in the interior. Over
the dorsal aspect of the upper or open part of the bulb, however,
it comes to the surface, and covers the lower or bulbar half of the
floor of the fourth ventricle.
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1457
 
 
As compared with the grey matter of the spinal cord, it presents
mportant modifications, and its component parts are as follows:
 
1. Substantia or formatio reticularis.
 
2. A thick layer of grey matter around the central canal in the
 
lower or closed part of the bulb.
 
 
 
Fig. 886.—The Decussation of the Pyramids: Scheme representing the
Passage of the Various Tracts from the Spinal Cord to the Medulla
(L. Testut’s ‘ Anatomie Humaine ’).
 
 
a. Pons
 
b. Medulla Oblongata (anterior aspect)
 
c. Decussation of the Pyramids
 
d. Section of the Cervical Spinal Cord
 
1. Anterior Cerebro-spinal Tract
 
2. Lateral Cerebro-spinal Tract
 
3. Sensory Tract
 
 
3'. Nucleus Gracilis et Nucleus Cuneatus
 
4. Antero-lateral Intersegmental Tract
 
5. Anterior Pyramid
 
6. Fillet or Lemniscus
 
7. Posterior Longitudinal Bundle
 
8. Ventral Cerebellar Tract
 
9. Dorsal Cerebellar Tract
 
 
3. A thick layer of grey matter over the floor of the fourth
 
ventricle in the upper or open part of the bulb.
 
4. Substantia gelatinosa (nucleus of spinal tract, N. V.).
 
5. Nuclei of grey matter.
 
The modifications undergone by the grey matter of the bulb in
ts lower or closed part are brought about by the decussation of the
 
92
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1458
 
pyramids. The nerve funiculi of the lateral cerebro-spinal tract
of the spinal cord, on one side as they are traced upwards, pass through
the base of the ventral grey column of that side, and then cross in the
lower part of the ventral median fissure of the bulb to the pyramid
of the opposite side, of which they form the inner and larger part.
The nerve funiculi of the tract of the other side are disposed in a
similar manner. The ventral grey column of either side is thus broken
up by the corresponding crossed pyramidal tract. Its basal part
remains on the ventral and lateral aspects of the central canal, but
its caput is detached and displaced laterally by the pyramid and olive
of the same side (see Fig. 887).
 
The dorsal horn of grey matter is gradually displaced laterally and
ventralwards, in the lower or closed part of the bulb, by the funiculus
gracilis and funiculus cuneatus. Its basal part remains on the dorsal
and lateral aspects of the central canal; its cervix is broken up into
a network by intersecting nerve-fibres; and its caput is thereby detached.
 
 
 
Fig. 887.— Schematic Sections showing Decussation of Pyramids with
the Destruction of Base of Ventral Grey Column (Testut).
 
The caput lies close to the detached caput of the ventral grey matter,
but does not blend with it.
 
Substantia or Formatio Reticularis. —The grey matter of the detached caput of the ventral grey cornu is broken up into a network
by intersecting nerve-fibres, which run longitudinally and transversely. This reticulum, augmented by the network formed in
the cervix of the dorsal grey cornu, constitutes the substantia or
formatio reticularis of the bulb. It lies deeply within the bulb, dorsal
to the olive and pyramid of the same side, and it consists of grey
matter, longitudinal and transverse nerve-fibres, and some nerve-cells.
 
The funiculi of the hypoglossal nerve, as they pass forwards to
the ventro-lateral sulcus of the bulb, divide the formatio reticularis
into two parts—lateral and medial (Fig. 891). The lateral portion is
situated behind the olive, and is called the formatio reticularis grisea,
from the large amount of grey matter, with nerve-cells, which it
contains. The medial portion is situated behind the pyramid, and is
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1459
 
 
illed the formatio reticularis alba. It contains little grey matter
nd few nerve-cells.
 
Central Grey Matter. —The grey matter which surrounds the
jntral canal in the lower or closed part of the bulb is derived from
le basal portions of the ventral and dorsal grey columns of the upper
art of the spinal cord. In the upper or open part of the bulb this
mtral grey matter spreads out and forms a thick layer over the
wer or bulbar part of the floor of the fourth ventricle. The medial
%rt of this layer represents the basal part of the ventral grey horn,
id it contains the hypoglossal nucleus. The lateral part represents
le basal part of the dorsal grey horn, and it contains vagus, glossoharyngeal, and vestibular nuclei.
 
The hypoglossal nucleus is frequently spoken of as ' morphologically continuous with ’ or ‘ representing ’ the ventral grey
column above the cervical nerves. This continuity, however,
is not an actual anatomical fact; it exists only in the site of
ependymal zone origin of the neuroblasts concerned in forming
the nuclei. The ordinary motor cells of the ventral grey column
in the cord have been derived from the lower part of the ependymal zone, from which they have migrated to form the ventral
portion of the marginal zone. Later, when the collections of
neuroblasts in the ventral horn have already settled into something approaching their final arrangements, a secondary output
of neuroblasts frees itself from the ependymal zone in the same
region, but does not migrate any further; this, then, might be
looked on as of the same ependymal or original value as the
ventral cells, although not anatomically continuous with them.
It is from this secondary formation, which is found in the
cervical and hind-brain regions, that the hypoglossal nucleus
is formed; possibly the sixth nucleus owns a like origin, but
this cannot be said with certainty. The other nuclei mentioned
in the preceding paragraph are not concerned in this development in any way.
 
Substantia Gelatinosa (Fig. 885).—This caps the detached and
splaced caput of the dorsal horn of grey matter. Having increased
 
amount owing to the presence of root-fibres of the fifth nerves
id lying close to the surface, it gives rise to the tuberculum gelatinosum,
metimes referred to simplv as the ‘ spinal tract of the fifth nerve.
 
Nuclei of Grey Matter.— The nuclei, which will be considered in
is place, are as follows:
 
1. Nucleus gracilis.
 
2. Nucleus cuneatus.
 
3. Olivary nuclei.
 
4. Arcuate nucleus.
 
5. Nucleus lateralis.
 
The nucleus gracilis is a collection of grey matter within the funiclis gracilis. For the most part it is connected with the grey matter
 
 
A MANUAL OF ANATOMY
 
 
1460
 
on the dorsal and lateral aspects of the central canal, and it ma]
be regarded as being in large part an extension from the basal par
of the dorsal grey cornu. It is elongated, and increases in size a:
it ascends. It gives rise to the prominence of the funiculus gracilis
and to the clava, and the fibres of the funiculus gracilis, as they ascend
terminate at intervals around the cells of the nucleus (see Fig. 885).
 
The nucleus cuneatus is a collection of grey matter within th<
funiculus cuneatus. It is a direct extension from the basal part 0
 
 
 
Fig. 888.—The Formatio Reticularis of the Medulla Oblongata, showi
by a Horizontal Section passing through the Middle of the Olivary
Body (Demi-schematic) (L. Testut’s ‘ Anatomie Humaine ').
 
 
1. Anterior Median Fissure
 
2. Fourth Ventricle
 
3. Formatio Reticularis
3'. Reticularis Alba
 
3". Reticularis Grisea
 
4. Raphe
 
5. Anterior Pyramid
 
6. Lemniscus
 
7. Inferior Olive with the two
 
Accessory Nuclei
 
 
7'. Peduncle of Olivary Body
 
8. Hypoglossal Nerve
8'. Hypoglossal Nucleus
 
9. Vagus Nerve
 
g'. Terminal Nucleus of Vagus
Nerve
 
10. External Dorsal Vestibular
Nucleus
 
xx. Nucleus Ambiguus
 
12. Nucleus Gracilis
 
 
13. Nucleus Cuneatus
 
14. Caput of Posterior Cornu
14'. Lower Sensory Root of Fift
 
Nerve
 
15. Fasciculus Solitarius
 
16. External Anterior Arcuat
 
Fibres
 
16'. Arcuate Nucleus
 
17. Lateral Nucleus
 
 
the dorsal grey cornu, which lies on the dorsal and lateral aspect:
of the central canal. Like the nucleus gracilis it is elongated, anc
increases in size as it ascends. It gives rise to the prominence 0:
the funiculus cuneatus and to the cuneate tubercle, and the fibre:
of the funiculus cuneatus, as they ascend, terminate at interval:
around the cells of the nucleus.
 
 
Lateral to the nucleus cuneatus there is a small collection of grey matter
which is known as the external or accessory cuneate nucleus. It is on a highe:
level than the decussation of the pyramids, and it may be regarded as a detachec
portion of the substantia gelatinosa.
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1461
 
 
The olivary nuclei are associated with the olive, and are three in
imber—inferior, and two accessory (medial and dorsal).
 
The superior olivary nucleus is situated in the dorsal or tegmental part of
5 pons, and is not developmentally associated with those now dealt with.
 
 
The inferior olivary nucleus, which is the chief nucleus, is situated
thin the olive. As seen in transverse sections through the olive,
appears (Fig. 889) as a wavy lamina of grey matter, curved in such a
inner as to form an incomplete capsule, which encloses white matter.
 
 
 
Nucl. Grac.
 
 
Nucl. Cun.
 
— Fasc. Solitar.
 
Sp. Nucleus of
Trigeminal
Sp. Root Fibres of
Trigeminal
Med. Longit. Fasc.
(Post. Longit. Bundle)
Nucl. Ambiguus
Lateral Nucleus
 
Ant. Sp. Cerebellar
Fasc. (Gowers)
 
Dorsal Acc. 01 .
 
 
ig. 889.—Section through the Lower Half of Inferior Olive (shows
also the Medial and Dorsal Accessory Olives).
 
 
racile and cuneate nuclei are seen in position, but spinal tract of fifth is separated
from surface by fibres passing to inferior peduncle; these are dorsal spinocerebellar and fibres from olive from opposite side; some fibres from olive
pass between the nucleus and the nerve tract. Arrows show the direction
of fibres on one side. The upper ones come from the dorsal nuclei and fi th
nucleus, and run ventrallv to decussate. The lower fibies are running
dorsally, and come mainly from opposite olive, and some from same side.
 
 
he open part of the capsule is called the hilum, and is diiected
)wards the median line, but it stops short of either end of the nucleus.
 
great many nerve-fibres pass through the hilum, some inwards
nd others outwards, and these form what is known as the olivary
eduncle. The wavy lamina is traversed by nerve-fibres..
 
The medial accessory and dorsal accessory olivary nuclei are situated
n the medial and dorsal aspects respectively of the inferior or chiet
fivary nucleus, from which, however, they are distinct. Each consts of a band of grey matter, and the upper part of the medial
xessory nucleus lies opposite the hilum of the chief nucleus.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1462
 
Structure of Inferior Olivary Nucleus. —The wavy lamina consists
of many small nerve-cells and nerve-fibres which traverse it. The
axons of the nerve-cells leave the nucleus as nerve-fibres, and pass
to the raphe of the bulb. Some of the nerve-fibres which traverse
the wavy grey lamina terminate in connection with its cells, and
other fibres pass through it (see Fig. 889).
 
There are at least two fibre tracts (in addition to those passing
into the inferior peduncle) which connect the inferior olive with
more distant parts of the nervous system, and are recognizable
in sections; little is actually known about them otherwise. The
smaller one (olivo-spinal or Helweg’s tract) lies on the surface
of the lower medulla and cord immediately in front of the
ventral spino-cerebellar fibres. The upper tract, much larger
and longer, is the tractus pallido-rubro-olivaris, a name describing
its apparent connections.
 
The structure of the two accessory olivary nuclei corresponds to
that of the chief or inferior olivary nucleus.
 
Arcuate Nucleus. —This nucleus (seen in Fig. 889) consists of a
lamina of grey matter which lies upon the ventral aspect of the pyramid
of the bulb above the level of the decussation of the pyramids, and
beneath the anterior superficial arcuate fibres as they arch outwards
over the pyramid after emerging from the ventral median fissure.
Superiorly it lies over the medial aspect of the pyramid close to the
ventral median fissure. It contains small nerve-cells, in connection
with which some of the anterior superficial arcuate fibres terminate,
whilst others arise as axons of the cells, and many of them pass over
the nucleus without entering it.
 
Fibres of various sorts, which may be termed in general
circumolivary, may be found turning over the lower part of the
olive. Some are superficial arcuate fibres, as just described,
but others may come apparently from the pyramid, and others
again, associated with the ponto-bulbar body, may be really of
the nature of aberrant pontine fibres.
 
Nucleus Lateralis. —This is a special collection of nerve-cells in
that portion of the formatio reticularis grisea which lies on the dorsolateral aspect of the olive. It is situated deeply between the olive
and the substantia gelatinosa (see Fig. 889).
 
White Matter of the Medulla Oblongata. —The white matter is
situated chiefly on the surface. Over the dorsal aspect of the upper
or open part of the bulb, however, the grey matter comes to the
surface, and covers the lower or bulbar half of the floor of the fourth
ventricle. The white matter is disposed in tracts or strands which
are chiefly longitudinal, but a few run transversely in an arched
manner. The tracts are as follows:
 
1. Pyramidal tract (cerebro-spinal tract).
 
2. Dorsal spino-cerebellar tract (direct cerebellar tract).
 
3. Ventral spino-cerebellar tract (tract of Gowers).
 
 
/
 
 
 
THE NERVOUS SYSTEM
 
 
1463
 
4. Restiform body (inferior cerebellar peduncle).
 
5. Funiculus cuneatus.
 
6. Funiculus gracilis.
 
7. Medial or posterior longitudinal bundle.
 
8. Tecto-spinal tract.
 
g. Rubro-spinal tract.
 
10. Spino-tectal tract.
 
11. Superficial arcuate tract.
 
12. Deep arcuate tract.
 
13. Fillet (lemniscus).
 
14. Vestibulo-spinal tract.
 
15. Olivo-cerebellar tract.
 
The pyramid of either side and the decussation of the pyramids
rave been already described. It may, however, be again stated
Fat the path of their motor nerve-fibres is downwards into the spinal
:ord.
 
The pyramidal tract has descended from the pons.
 
Posterior (or Direct) Spino-cerebellar Tract. —This tract extends
upwards from the lateral column of the spinal cord. It traverses
:he lower part of the lateral area of the bulb nearly as high as the
ower part of the olive, and immediately anterior to the tuberculum
^elatinosum, after which it passes backwards and upwards into the
inferior peduncle, of which it forms a part (Fig. 883).
 
Anterior Spino-cerebellar Tract. —This tract, like the dorsal or
lirect spino-cerebellar tract, extends upwards from the lateral column
if the spinal cord. It is situated chiefly on the dorsal aspect of the
ilive, but some of its fibres appear close to the outer side of that
body. Whilst the dorsal spino-cerebellar tract passes into the restiform body, and so reaches the cerebellar hemisphere directly, the ventral
spino-cerebellar tract is continued upwards into and beyond the pons
before reaching the cerebellar hemisphere.
 
Restiform Body.— The restiform body, or inferior peduncle of the
cerebellum, is situated on the dorsal aspect of the bulb in its upper
ir open part, the funiculus gracilis and funiculus cuneatus occupying
the dorsal aspect in its lower or closed part. It succeeds to the clava
ind cuneate tubercle, in which these two funiculi respectively end,
but it receives no nerve-fibres from the funiculi. It makes its first
appearance in relation to the nucleus cuneatus, and above the cuneate
tubercle it is a conspicuous massive bundle, which forms the lateral
boundary of the lower or bulbar half of the floor of the fourth ventricle.
Its course is upwards, outwards, and then suddenly backwards. It
sinks into the corresponding hemisphere of the cerebellum.
 
This peduncle is composed of fibres which are derived from the
 
following sources:
 
1. The olivo-cerebellar fibres of the inferior olivary nucleus of the opposite
 
side
 
2. The posterior cerebellar tract of the lateral column of the spinal cord of
 
the same side.
 
 
* 4^4
 
 
A MANUAL OF ANATOMY
 
 
3. The anterior superficial arcuate fibres from the nucleus gracilis and
 
nucleus cuneatus of the opposite side.
 
4. The posterior arcuate fibres from the nucleus gracilis and nucleus
 
cuneatus of the same side.
 
5. Vestibular fibres from the vestibular nuclei of the vestibular division of
 
the auditory nerve.
 
The restiform body, from its composition, serves as an important
means of connection between the cerebellar hemisphere superiorly
and the medulla oblongata and spinal cord inferiorly.
 
Funiculus Cuneatus and Funiculus Gracilis. —These tracts are
prolonged upwards from the posterior column of the spinal cord.
As stated, each contains a grey nucleus, around the cells of which
the corresponding sensory nerve-fibres terminate at intervals as
they ascend. Towards the clava and cuneate tubercle the fibres
become few and are spread over the clava and cuneate tubercle,
finally ending in connection with the cells of the grey nuclei which
give rise to these prominences (Fig. 885).
 
Posterior Longitudinal Bundle. —The fibres of this bundle ( fasciculus
longitudinalis medialis ), when followed downwards into the anterior
column of the spinal cord on the same side, represent the fibres of the
ventral intersegmental tract. As these fibres are followed into the
lower part of the bulb they form a bundle, which lies close to the
median raphe and directly dorsal to the corresponding pyramid. This
strand represents the longitudinal bundle in the lower part of the
bulb. The deep arcuate fibres, to be presently described, pass obliquely
through it to the median line, where they decussate with those of the
opposite side. This decussation takes place in the interval between
the right and left dorsal longitudinal bundles. Having now reached the
other side, the deep arcuate fibres take an upward course, close to the
median line, as the medial lemniscus. The dorsal longitudinal bundle
and fillet are therefore now closely related to one another in the lower
part of the bulb, both lying dorsal to the pyramid, the fillet lying close
to the raphe.
 
In the upper part of the bulb the two tracts become distinct. The
posterior longitudinal bundle is displaced dorsalwards during the
formation of the fillet, and it comes into contact with the grey matter
on the floor of the fourth ventricle, whilst the lemniscus lies on the
dorsal aspect of the pyramid.
 
The posterior longitudinal bundle is prolonged into the ventral
column of the spinal cord on the same side, where it is represented,
as has been said, by the ventral intersegmental fibres.
 
A ventral or anterior longitudinal bundle (tecto-spinal tract) is described as
lyi n g on the ventral aspect of the dorsal or posterior longitudinal bundle. This
bundle, however, is not well defined. It descends into the anterior column of
the spinal cord, and is accompanied by the ponto-spinal tract, the fibres of which
spring from the cells of the formatio reticularis of the pons.
 
Arcuate Tracts. —These tracts form two goups—superficial and
deep.
 
 
THE NERVOUS SYSTEM
 
 
1465
 
 
The superficial arcuate fibres are arranged in two sets—anterior
md posterior.
 
The anterior superficial arcuate fibres arise from the nucleus gracilis
and nucleus cuneatus of the opposite side, and a few arise from the
arcuate nucleus of the same side. At the median line they decussate
with those of the opposite side, and emerge at the ventral median
fissure, where many of them arch over the medial and ventral
aspects of the pyramid. Others pierce the pyramid, whilst some
emerge at the ventro-lateral. sulcus between the pyramid and olive.
The fibres now pass outwards and dorsalwards, some arching over
the lower part of the olive, and finally enter the restiform body.
 
The posterior superficial arcuate fibres arise from the nucleus gracilis
and nucleus cuneatus of the same side, and they enter the restiform
body also of the same side.
 
 
 
Trigem. N.
 
Oblique Fasc.
 
Facial N.
 
Aud. N.
Flocculus
 
Circumoliv. Fasc.
 
 
Basilar Groove
 
 
Pyramid
 
 
Fig. 890. —Front Aspect of Pons and Medulla, showing Oblique Fibres
 
of Pons and Arcuate Fibres on Medulla.
 
 
The deep arcuate fibres are disposed in two sets—lemniscal and
olivo-cerebellar. The lemniscal deep arcuate fibres arise from the
nucleus gracilis and nucleus cuneatus of the same side. They sweep
forwards and inwards (Fig. 889) towards the raphe, passing obliquely
through the dorsal longitudinal bundle. At the median line they
decussate with those of the opposite side above the level of the decussation of the pyramids. Having reached the opposite side, the
deep arcuate fibres change their course, and now pass upwards The
ascending tract thus formed constitutes the medial lemniscus (or
medial fillet).
 
The decussation which takes place between the deep arcuate
fibres in the median line, immediately above the. decussation of the
pyramids, is called the decussation of . the lemnisci (decussatio lemmscorum), or the superior sensory decussation, as distinguished from
 
 
 
 
 
 
 
 
 
 
1466
 
 
A MANUAL OF ANATOMY
 
 
the inferior sensory or spino-thalamic decussation, which takes place
in the spinal cord.
 
The olivo-cerebellar deep arcuate fibres arise from the inferior olivary
nucleus of one side. Emerging through the hilum, they pass across
the median line to the opposite side. They then pass over or through
the inferior olivary nucleus of that side, on the dorsal aspect of which
they are collected into a distinct tract. This tract, arching backwards,
applies itself to the restiform body on its deep aspect, and is thereby
conducted to the cerebellar hemisphere. Its fibres terminate in the
cortex of the vermis and cerebellar hemisphere. The olivo-cerebellar
arcuate fibres constitute the olivo-cerebellar tract, which connects the
inferior olivary nucleus of one side with the cerebellar hemisphere of
the opposite side.
 
Lemniscus. —The lemniscus (or fillet), as seen in the bulb, is a wellmarked tract of fibres which lies on the dorsal aspect of the pyramid
close to the raphe. As just stated, its fibres are derived from the
lemniscal deep arcuate fibres of the opposite side. In the lower part
of the bulb the fillet and posterior longitudinal bundle are closely
related. In the upper part of the bulb, however, as already said,
the posterior longitudinal bundle is displaced dorsalwards by the
developing fillet, and the fillet, now distinct from the longitudinal
bundle, lies on the ventral aspect of that bundle, and on the dorsal
aspect of the pyramid. The ventral region of the bulb is thus traversed
by four longitudinal tracts, all of which lie close to the median line.
These tracts are related to each other in the following order from
before backwards (ventro-dorsally):
 
Pyramid.
 
Fillet.
 
Tecto-spinal.
 
Posterior longitudinal bundle.
 
Olivo-cerebellar Tract.— This tract has already been described in
connection with the olivo-cerebellar deep arcuate fibres.
 
Raphe of the Medulla Oblongata. —The raphe of the bulb occupies
the median plane above the decussation of the pyramids, and is
composed of fibres which, for the most part, cross obliquely from
one side to the other. These fibres represent (1) the anterior superficial
arcuate fibres, (2) the lemniscal deep arcuate fibres, and (3) the olivocerebellar deep arcuate fibres. A few fibres pass ventro-dorsally, and
some are disposed longitudinally. The fibres are therefore arranged
in an intersecting manner.
 
Central Canal of the Medulla Oblongata. —The central canal of the
spinal cord is prolonged upwards through the lower or closed part
of the bulb. As it ascends it is gradually displaced backwards, first
by the decussation of the pyramids, and afterwards by the decussation of the lemnisci. It is surrounded by a thick layer of grey matter,
which is derived from the basal portions of the ventral and dorsal
grey horns of the spinal cord, Superiorly, at the level of the obex,
 
 
/
 
 
THE NERVOUS SYSTEM
 
 
1467
 
 
it opens into the lower part of the fourth ventricle in the angle between
the two diverging clavse. The grey matter which surrounds the canal
is now spread out, and forms a thick covering over the lower part
of the ventricular floor, as has been said already.
 
Areas of Flechsig. —These areas involve the whole substance of the bulb,
and are mapped out by the funiculi of the hypoglossal and vagus nerves. Seen
in transverse section, these funiculi lie near each other as they arise from their
nuclei in the grey matter of the lower part of the floor of the fourth ventricle.
As the funiculi of the hypoglossal nerve pass forwards and those of the vagus
nerve outwards they diverge from each other, and the substance of the bulb
is thereby divided into three segments, which constitute the areas of Flechsig —
ventral, lateral, and dorsal (see Fig. 891).
 
 
 
Fig. 891. —Plan to illustrate the Three Areas of Flechsig, showing the
 
Main Structures in Each of These.
 
 
The ventral area lies between the raphe of the bulb and the funiculi of the
hypoglossal nerve. Throughout its thickness this area contains the following
structures:
 
The pyramid and arcuate nucleus (Fig. 891, P).
 
The lemniscus, decussating (L).
 
The posterior longitudinal bundle (B).
 
The formatio reticularis alba.
 
The lateral area lies between the funiculi of the hypoglossal nerve and those
of the vagus nerve. Throughout its thickness this area contains the following
structures:
 
The olive and inferior olivary nucleus.
 
The nucleus lateralis (NL).
 
The nucleus ambiguus (to be afterwards described) (NA).
 
The formatio reticularis grisea.
 
The dorsal area is the region behind the funiculi of the vagus nerve. Throughout its thickness this area contains the following structures:
 
The inferior peduncle.
 
The upper part of the cuneate nucleus (C).
 
The descending root of the vestibular nerve ^ 'po be afterwards
 
The fasciculus solitarius (S) \ described.
 
The spinal root of the fifth cranial nerve (V) )
 
The substantia gelatinosa (G).
 
 
 
 
 
 
 
 
1468 A MANUAL OF ANATOMY
 
Course of Chief Nerve Funiculi of Spinal Cord through Medulla Oblongata.
Spinal Cord. Medulla Oblongata.
 
Posterior Column.
 
Column of Goll (fasciculus gracilis).
 
Column of Burdach (fasciculus
cuneatus).
 
Lateral Column.
 
(Crossed) lateral cerebro-spinal tract.
 
Anterior cerebro-spinal tract.
 
Dorsal (or direct) spino - cerebellar
tract.
 
Ventral (or indirect) spino-cerebellar
(tract of Gowers).
 
Prepyramidal or rubro-spinal tract.
 
Lateral intersegmental.
 
Anterior Column.
 
Anterior cerebro-spinal tract.
 
Tecto-spinal tract.
 
Ventral intersegmental.
 
Anterior marginal bundle (of Lowenthal).
 
Development of Medulla Oblongata.— The bulb is developed from
the myelencephalon, which is the caudal division of the rhombencephalon.
 
2. The Pons.
 
The pons (Varolii) is situated above the medulla oblongata, and
between the hemispheres of the cerebellum. With the exception
of the inferior peduncles, all parts of the medulla oblongata are
prolonged into it. The pons presents two surfaces (ventral and
dorsal) and two borders (upper and lower). The ventral surface
(Fig. 890) rests upon the upper part of the basilar groove of the occipital
bone and the dorsum sellae of the sphenoid. It is convex from side to
side, and from above downwards, and has a transversely striated
appearance, due to the disposition of its superficial fibres. Along
the median line it presents the basilar groove, which extends from
the lower to the upper border, and lodges the basilar artery. On
either side of this groove the ventral surface is rendered prominent
by the prolongation upwards of the pyramids of the medulla oblongata, and the basilar groove is chiefly due to this circumstance. The
sensory and motor roots of the fifth nerve, lying close together, appear
on the lateral aspect of the ventral surface, the small motor root
being the upper of the two. The portion external to these two nerveroots constitutes the middle peduncle of the cerebellum. It is composed of the transverse fibres of the pons, which pass backwards and
laterally into the corresponding cerebellar hemisphere.
 
 
Funiculus gracilis and nucleus
 
gracilis.
 
Funiculus cuneatus and nucleus
 
cuneatus.
 
 
Inner three - quarters of opposite
pyramid.
 
Outer one-quarter of pyramid of
same side.
 
Lateral area below olive, and inferior
peduncle.
 
Lateral area below olive, and formatio reticularis.
 
 
Outer one-quarter of pyramid of
same side.
 
Posterior longitudinal bundle.
 
 
 
THE NERVOUS SYSTEM
 
 
1469
 
 
The dorsal surface is directed towards the cerebellum. It presents a triangular area which is covered with grey matter. This
area is continuous with the dorsal surface of the upper or open part of
the medulla oblongata, and it forms the upper or pontine part of the
floor of the fourth ventricle. On either side it is bounded by the
superior peduncle of the cerebellum as it passes upwards and inwards.
 
The upper border is slightly depressed at the centre, and on either
side of the median depression it slopes outwards and downwards
towards the middle peduncle of the cerebellum. The crura cerebri,
right and left, sink into the pons at the upper border.
 
 
 
Internal Structure of the Pons. —dhe pons is composed of a large
ventral and a small dorsal part.
 
Ventral Part.— This portion consists of (1) bundles of transverse
fibres, (2) bundles of longitudinal fibres, and (3) a large amount ot
 
 
grey matter. , , ,, £ •
 
The bundles of transverse fibres intersect the bundles of longitudinal fibres, and on either side they are collected into e mi e
peduncle of the cerebellum, which enters the corresponding cerebellar hemisphere. Some of the transverse fibres arise in, e cot ex
of the cerebellum as the axons of the cells of Purkinje, an 1
terminate in the pons in arborizations round the cells of the nucleus
pontis, mostly on the opposite side to that on which they arise
Other transverse fibres arise in the pons as the axons of of the nucleus pontis on one side. They then cross to the other
 
 
 
 
 
 
 
 
 
 
 
 
 
I 47 °
 
 
A MANUAL OF ANATOMY
 
 
Corpora Mamillaria
 
 
side, and enter the cerebellar hemisphere of that side, where they
terminate in arborizations in the cortex. The fibres, therefore, of
which the middle peduncle of the cerebellum is composed may be
regarded as being of two kinds—namely, efferent and afferent. The
efferent fibres arise in the cerebellar cortex and terminate in the
pons, whilst the afferent fibres arise in the pons and terminate in the
cerebellar cortex.
 
The bundles of longitudinal fibres in each half of the ventral part
of the pons are derived from the breaking up of the crusta or basis
 
pedunculi of the corresponding crus cerebri, which enters
the pons at its upper border.
Most of these bundles are
collected together at the
lower border of the pons,
and form the pyramid of the
medulla oblongata on the
same side. Certain of the
fibres of the basis pedunculi,
however, terminate in the
pons as follows: (i) some end
in arborizations around the
cells of the motor nucleus of
the fifth cranial nerve, the
nucleus of the sixth cranial
nerve, and the nucleus of the
seventh cranial or facial
nerve ; and (2) others end
in arborizations around the
 
 
Basis Pedunculi Cerebri --* 31 ;
Locus Perforatus Posterior
 
 
Right Pyramidal
Tract
 
Transverse Fibres
of Pons
 
Middle Peduncle of
Cerebellum
 
 
 
minL
 
Decussation of the Pyramids Ard :
 
■ f
 
Fig. 893.—Dissection of the Pons, showing the Course of the Pyramidal
Tracts of the Medulla Oblongata
(Hirschfeld and Leveille).
 
P., right pyramid; O.B., right olivary body.
 
 
cells of the nucleus pontis, all of the same side.
 
 
The fibres to cranial motor nuclei may run a more aberrant
course, leaving the basis pedunculi in the mid-brain and running
in the tegmentum of the pons to decussate and reach their
objectives. Some also run a recurrent course, leaving the pyramid
below the pons and turning upwards deeply.
 
The grey matter of the pons, which is large in amount, occupies
the intervals between the intersecting transverse and longitudinal
bundles, and contains small multipolar nerve-cells. It is known as
the nucleus pontis, and is continuous with the arcuate nuclei of the
medulla oblongata.
 
Corpus Trapezoides or Trapezium. —The trapezium is a fairly thick
layer of transverse fibres on either side, which have no connection
with the corresponding middle peduncle of the cerebellum. The
fibres are situated in the lower part of the pons dorsal to the pyramidal bundles. Within the trapezium are large multipolar cells,
which constitute the nucleus of the trapezium. The fibres of the
trapezium arise chiefly as the axons of the cells of the ventral cochlear
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1471
 
 
mcleus, and also of the dorsal cochlear nucleus (or tuberculum
icusticum), in which nuclei the fibres of the cochlear division of the
mditory nerve terminate, Some of the fibres arise from the superior
)livary nucleus; others are the axons of the cells of the nucleus of
;he trapezium; whilst a third set (auditory strice) arise from the
:uberculum acusticum of the opposite side. Certain of the fibres
 
 
 
Fig 8q4—Vertical Transverse Section through the Upper Part of
the Pons and Fourth Ventricle (from L. Testut’s ‘ Anatomie
Humaine,’ after Stilling).
 
 
1. Fourth Ventricle
 
2. Superior Velum
 
3. Superior Root of Fifth Nerve
 
4. Nerve-cells which accompany this Root
 
5. Posterior Longitudinal Bundle
 
6. Formatio Reticularis
 
7. Lateral Fissure of Isthmus
 
 
8. Section of Superior Cerebellar Peduncle
9,9. Medial and Lateral Portions of the
Lemniscus
 
10, 10. Transverse Fibres of the Pons
 
11, 11. Longitudinal Fibres of the Pons
 
12. Raph6
 
V. Fifth Nerve
 
 
: the trapezium terminate in the superior olivary nucleus, but the
laioritv cross the median plane, where they decussate with those
E the opposite side. Having crossed to the opposite side, they
ecome longitudinal, and form a well-marked ascending tract in the
orsal part of the pons, called the lateral lemniscus, which lies on the
 
uter side of the main or medial fillet. . ,
 
Dorsal or Tegmental Part of the Pons.— This portion is divided
ito two symmetrical halves by a median raphe, which is continuous
ith that of the upper or open part of the medulla oblongata It
insists of formatio reticularis, which is continued upwards from
re formatio reticularis of the bulb. The formatio reticularis of the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1472
 
 
A MANUAL OF ANATOMY
 
 
dorsal part of the pons contains certain tracts of nerve-fibres and
nuclei, with which important nerves are connected. These are so
complicated that it is convenient to divide the dorsal part of the pons
into two regions—lower and upper.
 
Lower Region. —This region corresponds to the level of the trapezium in the ventral part of the pons, and succeeds the upper end of
the bulb. The inferior peduncle of the bulb lies for a short distance
on the lateral aspect of this region, but soon passes backwards and sinks
into the hemisphere of the cerebellum.
 
The tracts and nuclei of the formatio reticularis of the lower region,
which will be described in this place, are as follows:
 
1. Spinal sensory root of the fifth cranial nerve.
 
2. Motor nucleus of the facial nerve.
 
3. Superior olivary nucleus.
 
4. Nucleus of the sixth cranial nerve.
 
5. Posterior longitudinal bundle.
 
6. Rubro-spinal tract.
 
7. Tecto-spinal tract.
 
8. Lemniscus.
 
The funiculi of the spinal or descending sensory root of the fifth
cranial nerve appear ventro-medial to the mass of the inferior cere
 
Sixth Nucleus
 
 
Post. Long. Bundle
Facial Nucleus
 
Corp. Trapez.
 
 
Basis Pontis
 
 
Fig. 895.—Nuclear Positions in Pons (Schematic).
 
bellar peduncle. Close to the inner side of this root, and accompanying it
in its downward course, there is the inferior sensory nucleus of the fifth
nerve, around the cells of which the fibres of the spinal or descending
root of that nerve terminate at intervals. The inferior sensory nucleus
is an upward prolongation of the substantia gelatinosa, and interiorly it
extends to about the level of the second cervical spinal nerve (see Fig. 885).
 
The motor nucleus of the facial nerve is internal to the funiculi
of the spinal root of the fifth nerve. It lies deeply in the lower region
of the dorsal part of the pons on the dorsal aspect of the superior
 
 
 
Sensory Nucl. N.V.
Motor Nucl. V.
 
Superior Olive
Fifth Nerve
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1473
 
 
•livary nucleus. The motor fibres of the facial nerve arise as the
xons of the cells of this nucleus (see Fig. 896).
 
The superior olivary nucleus is situated on the ventral aspect of
he facial nucleus, and is close to the lateral part of the trapezium,
he fibres of which arch round its ventro-lateral aspect. Some of
hese fibres terminate in the superior olivary nucleus, whilst others
.rise from its cells.
 
In connection with the superior olivary nucleus three other nuclei are
lescribed: (1) an accessory superior olivary nucleus on the medial side of the
)rincipal nucleus; (2) a lateral pre-olivary nucleus on the ventral aspect of the
>rincipal nucleus; and (3) a medial pre-olivary nucleus on the ventral aspect of
he nucleus of the trapezium.
 
The nucleus of the sixth cranial nerve lies immediately beneath
he grey matter of the pontine part of the floor of the fourth ventricle,
ind on the lateral side of the dorsal longitudinal bundle which separates
he nucleus from the median raphe. It corresponds to that portion
 
 
supC- cerebellar
peduncle.
 
 
facial colliculus _ _
 
nucleus of--.,
sixth H.
 
post- longitudbundie.
 
stalk of olive"'
 
median lemniscus
 
 
 
inferior! cerebellar
middle j peduncle.
 
_\jai- vestibular
 
> x \ nucleus.
 
TV 7- 5 pinai root of V*- h n.
facial nucleus
 
 
-facial nerve
 
^vestibular part
""'of 8th nerve.
 
. "''Corpus trapezoides
 
""Supr- olivary nucleus
 
' oibducens nerve
 
pyramidal tract.
 
Fig. 896.—Diagrammatic Section through the Pons, to show Deep
Origins of Sixth (Red) and Seventh (Black) Cranial Nerves.
 
 
f the facial colliculus which lies on the pontine part of the floor of
he fourth ventricle directly above the auditory striae.
 
The medial or posterior longitudinal bundle lies close to the median
iphe, and on the medial side of the nucleus of the sixth nerve. Like
bat nucleus, it lies immediately beneath the grey matter of the pontine
 
art of the floor of the fourth ventricle. . , „
 
The lemniscus (medial, medial fillet) lies, as it <loes in the bulb,
entral to the dorsal longitudinal bundle, but m the dorsal part of tl e
ons the two strands are separated by a distinct interval occupied
 
93
 
 
 
 
 
 
 
 
 
*474
 
 
A MANUAL OF ANATOMY
 
 
by the rubro- and tecto-spinal tracts. It will have been noticed tha J
in the spinal cord the tecto-spinal tract lies ventral to the rubro-spinal
but later on it will be seen that the tectum or quadrigeminal region i:
dorsal to the red nucleus. It is therefore clear that somewhere ir
their course they must reverse their relative positions, and the rubro
spinal become ventral to the tecto-spinal. Where this happens i:
not at present clear; indeed, the exact relations of these and man}
other tracts, such as the vestibulo-spinal, spino-thalamic, and spino
tectal in the upper part of their course, are still under investigation
The lemniscus occupies a broad area in that portion of the lowei
region of the dorsal part of the pons which is contiguous to the ventra
part. The area extends outwards from the median raphe.
 
Upper Region of the Dorsal Part of the Pons. —This region lies abovt
the level of the trapezium in the ventral part of the pons. The tracts
and nuclei of this region, which will be described in this place, are as
follows:
 
1. Superior peduncle of the cerebellum.
 
2. Nuclei of the fifth cranial nerve.
 
3. Medial or posterior longitudinal bundle.
 
4. Medial fillet or lemniscus.
 
5. Lateral fillet or lemniscus.
 
The superior peduncle of the cerebellum, after emerging from the
corresponding cerebellar hemisphere, lies on the lateral aspect of this
region, where it forms the lateral boundary of the upper or pontine pari
of the floor of the fourth ventricle. Its dorsal aspect is connected with
that of its fellow of the opposite side by the superior medullary velum l
and ventrally it sinks into the upper region of the dorsal part of the pons.
 
The pontine nuclei of the fifth cranial nerve are motor and sensory.
The motor and main sensory roots are pontine, and the sensory root is
prolonged down as the spinal tract, and up as the mesencephalic root.
 
The motor nucleus is situated close to the superior peduncle of the
cerebellum at the lower part of the lateral margin of the upper or
pontine part of the fourth ventricle. It lies near the surface, and the
axons of its cells form many of the fibres of the motor root of the nerve.
 
The main sensory nucleus is situated deeply on the outer side of
the motor nucleus, and on the ventral aspect of the superior peduncle
of the cerebellum. Some of the fibres of the sensory root ascend and
terminate in arborizations around the cells of this nucleus.
 
The lower or spinal sensory nucleus succeeds to the main sensory
nucleus, and is a continuation upwards of the substantia gelatinosa.
It is elongated, and extends into the upper part of the spinal cord to
about the level of the second cervical nerve. It lies on the medial
side of the spinal or descending sensory root of the fifth nerve, and
the fibres of that root (. spinal tract) terminate at intervals in arborizations
around its cells.
 
The mesencephalic root arises from groups of small cells which
are placed in the grey matter of the mid-brain, beside the aqueduct,
 
 
THE NERVOUS SYSTEM
 
 
1475
 
extending up as far as the canal of the lower end of the superior
:olliculus. Fibres run down from this part, but their actual disposition
n the fifth nerve is not yet settled.
 
There is some ground for supposing that this part of the nuclear
arrangement of the fifth nerve is concerned with the reception
of proprioceptive impulses from orbital muscles.
 
The posterior or medial longitudinal bundle has the same position
in the upper region as it has in the lower region. It lies close to the
median raphe, and immediately below the grey matter of the corresponding part of the floor of the fourth ventricle.
 
The main or medial lemniscus, like the main fillet in the lower
region, lies in that portion of the upper region of the dorsal part of the
pons which is near the ventral part, and it forms a layer of some breadth,
extending outwards from the median raphe.
 
The lateral lemniscus is a strand of fibres which lies on the outer side
of the medial fillet, and connects the cochlear nucleus with the opposite
inferior corpus quadrigeminum. Associated with the lateral fillet,
and lying between it and the medial fillet, there is a collection of nervecelis, called the nucleus of the lateral lemniscus.
 
Development of the Pons. —The pons is developed from the ventral and lateral
walls of the metencephalon, which is one of the divisions of the rhombencephalon. The nuclear matter seems to be derived from the ponto-bulbar body,
spreading over the surface of the neural tube.
 
3. The Cerebellum.
 
The cerebellum, or small brain, occupies the inferior occipital or
cerebellar fossae of the occipital bone. It lies beneath the posterior
parts of the hemispheres of the cerebrum, from which it is separated
by a septum of the dura mater, called the tentorium cerebelli, and it is
behind and above the medulla oblongata and pons. It is composed
of white and grey matter, the white matter being situated in the
interior, where it constitutes the medullary substance, and the grey
matter being spread over the surface of the cortex. In appearance it
is laminated or foliated, the laminae being separated from each other
by parallel, slightly curved sulci. It is composed of two large lateral
portions, called hemispheres, and a connecting median portion, termed
the vermis, these parts being much more distinct below than above.
When looked at from above it presents in the median line two notches,
anterior and posterior. The anterior notch, which is wide, is known
as the incisura semilunaris , and it contains the inferior pair of quadrigeminal bodies and the superior cerebellar peduncles. The posterior
notch is narrow, and is occupied by the falx cerebelli. The most
conspicuous sulcus of the cerebellum is the great horizontal fissure,
which extends round the circumference, and passes for some distance
into the interior. By means of this fissure the cerebellum is divided
into two parts, upper and lower.
 
Relatively smaller in the new-born child, the cerebellum forms
in the adult about an eighth of the whole mass of the brain.
 
 
 
I 47^
 
 
A MANUAL OF ANATOMY
 
 
The cerebellar surface is marked, as stated above, by the presence
of numerous flattened or laminar gyri or folds, each fold being separatee
from its neighbours by sulci of appreciable depth. Among these
fissures are certain ones which are evident and deeper, and these car
be taken to divide the surfaces into lobules or parts, which have some
small descriptive value.
 
 
The presence of the foliated surface, and of certain striking
appearances in different parts of the cerebellum, have led in the
past to a wealth of terminology and description which, for the
greater part, does not seem to be of much value or utility.
Moreover, since these terms have in many instances come dowr
from long past periods, they are archaic and fanciful. Thus it
seems desirable to replace these with a short account of the
cerebellar surface, broadly described, after which the older terms
 
 
Anterior Notch
(Incisura Semilunaris)
 
Central Lobule
 
Anterior Crescentic Lobule
 
/
 
Primary Fissure
 
Posterior Crescentic
Lobule
 
 
Postero-superior
Fissure
 
 
f;A^SL Cor P° ,a Q ua drigemina
 
 
Postero-superior
 
Lobule
 
 
 
-Culmen Monticuli
 
 
.Preclival Fissure
 
 
Postclival Fissure
 
 
Postero-inferior Lobule
 
 
Clivus Monticuli
 
 
Posterior Notch Folium Cacuminis
 
 
Fig. 897.—The Cerebellum (Superior View).
 
 
and descriptions will be given in small print, for purposes of
reference if required. Subsequently a short morphological consideration of the part can be added.
 
Upper Surface of the Cerebellum. —This surface presents in the
median line the upper part of the vermis, known as the superior vermis
(see Fig. 897). It extends from the incisura semilunaris to the posterior
notch, and it forms a laminated elevation, which is higher in front than
behind, the most prominent part being known as the monticulus cerebelli. On either side of the superior vermis the upper surface of each
hemisphere inclines downwards to the circumference, and there is no
distinct demarcation between it and the superior vermis.
 
This upper aspect is divided (Fig. 898) by two main fissures, primary
and postclival, which are continued across the slight elevation of the
superior vermis.
 
 
 
/
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
x 4 77
 
The primary fissure (Fig. 898, PR) cuts across the vermis a little
behind its highest point, the culmen. From this the fissure is continued
with a slight forward curve on each side, to reach the horizontal fissure.
 
The fissure is termed ‘ primary ’ because it forms the posterior
limit, at a fairly early stage, of the morphological entity, the
anterior lobe.
 
The postlunate or postclival fissure (PC) is behind the primary fissure
and below it; this is due to the descent of the vermis from the culmen,
forming its ‘ declive * behind the primary fissure. The postclival
fissure turns forward on each side with a bolder curve towards the
horizontal fissure.
 
 
 
Fig. 898. —Upper Aspect of Cerebellum, with Main Subdivisions.
 
C, culmen; D, declive (or clivus); PR, primary fissure; PC, postlunate (or postclival) fissure; H, posterior end of horizontal fissure.
 
The anterior lobe lies above and in front of the primary fissure, including the parts of the vermis and lateral lobes as a continuous whole.
 
The posterior lunate lobe lies between the primary and postlunate
fissures, and includes also the central vermis.
 
The posterior end of the horizontal sulcus (H) appears usually on
this aspect of the cerebellum. It fails to reach the vermis, usually
running into the postlunate sulcus.
 
The lobule which is seen on each side below the postlunate and
above the horizontal fissure is frequently referred to as the superior
crescentic lobule; it is also termed the superior (division of the) ansiform
lobe.
 
The superior vermis is composed of five lobules, named, in order from
before backwards, the lingula, central lobule, culmen monticuli, clivus
monticuli, and folium cacuminis. The lingula is deeply placed, and consists of about four laminae or folia, which lie over the superior medullary
 
 
 
 
[478
 
 
A MANUAL OF ANATOMY
 
 
velum as it extends between the superior cerebellar peduncles. Its laminae
may be continued on either side over the superior cerebellar peduncle,
and, when this is so, the prolongation is known as the frenulum lingulae.
 
The central lobule is of small size, and lies at the bottom of the incisura
semilunaris. It is separated from the lingula by the precentral fissure,
and from the culmen monticuli by the postcentral fissure.
 
The culmen monticuli forms the summit of the superior vermis. It is
composed of several laminae, and posteriorly is separated from the clivus
by the preclival fissure.
 
The clivus monticuli represents the sloping part of the monticulus
cerebelii. It is situated behind the culmen monticuli, and is composed of
several laminae. Posteriorly it is separated from the folium cacuminis
by the postclival fissure.
 
The folium cacuminis forms the posterior extremity of the superior
vermis, and lies at the posterior notch, where it is placed above the great
horizontal fissure.
 
 
i locculus
 
 
Biventral Lobule
 
 
Lobulus Gracilis 1
Great Horizontal
 
Fissure , I
 
t
 
Inferior Semilunar Lobule
 
 
 
Amygdala (Tonsil)
 
 
Pyramid
Tuber Valvulae
 
 
-Pregracile
Fissure
— Mid-gracile
Fissure
—Post gracile
Fissure
-•-Small Horizontal
Fissure
 
 
Fig. 899.— The Cerebellum (Inferior View).
 
1 he inferior semilunar lobule and the lobulus gracilis constitute the postero
inferior lobule. Old terminology used.
 
 
The upper surface of each hemisphere is mapped out into lobules, which
are continuous with the subdivisions of the superior vermis, with the
exception of the lingula. These are called, in order from before backwards, the ala, anterior crescentic lobule, posterior crescentic lobule, and
postero-superior lobule.
 
The ala is continuous with the central lobule, from which it is prolonged
for a limited distance round the anterior part of the hemisphere in the
region of the incisura semilunaris.
 
The anterior crescentic lobule is continuous with the culmen monticuli,
and represents the anterior subdivision of the upper surface of the cerebellar
hemisphere. It is limited posteriorly by a curved sulcus, called the anterosuperior fissure, which is continuous with the preclival fissure (fissura prima),
and opens at the circumference into the great horizontal fissure. The
right and left anterior crescentic lobules, together with the culmen monticuli, form the lobus culminis (see Fig. 897).
 
The posterior crescentic lobule is continuous with the clivus monticuli.
It is limited in front by the antero-superior fissure, and behind by the
postero-superior fissure, the latter being continuous with the postclival
fissure, and opening at the circumference into the great horizontal fissure.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1479
 
 
The right and left posterior crescentic lobules, together with the clivus
monticuli, form the lobus clivi.
 
The postero-superior lobule (superior semilunar lobule) corresponds to,
but is much more extensive than, the folium cacuminis. It is limited
in front by the postero-superior fissure, and behind by the great horizontal
fissure. The right and left postero-superior lobules, together with the
folium cacuminis, form the lobus cacuminis.
 
Under Surface of the Cerebellum. —The under surface presents in
:he median line a deep groove, called the vallecula, which is continuous
Dehind with the posterior notch. Anteriorly it lodges the medulla
Dblongata, and lying in the bottom of it there is the lower part of the
/ermis, which is known as the inferior vermis. The vallecula separates
the two cerebellar hemispheres from each other, and the inferior vermis
s separated on either side from the corresponding hemisphere by a
furrow called the sulcus valleculce. The under surfaces of the hemi
 
 
Fig. 900.—Lower Aspect of Cerebellum, showing the (Inferior) Ansiform
Lobe and the Paramedian Lobule or Tonsil; also the Flocculus.
 
 
spheres are markedly convex, and are received into the inferior occipital
or cerebellar fossae of the occipital bone.
 
The inferior aspect of the cerebellum (Fig. 900) presents on the
lateral lobes, near the margins, the greater part of the horizontal
fissure (H). The two additional fissures shown in the figure are of quite
secondary importance; the upper one of the two was taken formerly
as the lower boundary of the ‘ inferior crescentic lobule (ISL.), but it
is not necessary now to subdivide the inferior surface in this way, but
rather to term all this curved surface the posterior or posteio-inferior
lobe, or the inferior (part of the) ansiform lobe. #
 
The paramedian lobule or tonsil, however, stands out as a striking
formation on each side of the ‘ posterior notch, and is not included in
the name given to the rest of the inferior surface. The base of the
tonsil is received in a cup-shaped concavity on the inferior and medial
surface of the ansiform lobe, from which it is separated by a
deep retrotonsillar fissure. The loosely foliated flocculus (FLOCC) is
 
 
 
 
 
 
 
 
1480
 
 
A MANUAL OF ANATOMY
 
 
visible on each side, outside and in front of the tonsil. The flocculus
has a white ' stalk/ which is continuous with the inferior medullary
vellum, making with this a large part of the bed of the hollow which
contains the tonsil. This velum is connected centrally with the
* nodule/ the terminal piece of the inferior vermis.
 
The inferior vermis is composed of four lobules, named, in order from
behind forwards, tuber valvulse, pyramid, uvula, and nodule.
 
The tuber valvulae (tuber posticum) forms the posterior part of the
inferior vermis, and is composed of several laminae. On either side it is
prolonged into the corresponding hemisphere, and becomes continuous
with the postero-inferior lobule. It is the only part of the inferior vermis
which is prolonged into the cerebellar hemispheres.
 
The pyramid is situated in front of the tuber valvulae. It presents about
four laminae, and is separated by deep sulci from the tuber valvulae behind
and the uvula in front, whilst on either side it is separated from the cerebellar hemispheres by the sulcus valleculae. Laterally it is connected
with the biventral lobule of the hemisphere by means of a faint ridge, but
this lies low in the sulcus valleculae as it crosses.
 
The uvula is situated in front of the pyramid, and between the amygdalae
or tonsils of the hemispheres. It is triangular, the base being directed
backwards, and it consists of several laminae. It is separated on either
side from the hemisphere by the sulcus valleculae. Laterally its narrow
part is connected with the amygdala by a ridge of grey matter, but this
lies low in the sulcus valleculae as it crosses. This ridge is notched at
intervals, and is called the furrowed band.
 
The nodule forms the anterior part of the inferior vermis, and is composed of several laminae, which are largely concealed by the uvula. It is
connected on either side with the flocculus by a thin semilunar band of
white matter, which is the lateral portion of the inferior medullary velum.
 
The fissures of the inferior vermis are three: postpyr amidal, between the
pyramid and the tuber valvulae; prepyramidal (fissura secunda), between
the pyramid and the uvula; and postnodular, between the nodule and the
uvula.
 
The under surface of each hemisphere is mapped out into four lobules,
which are called, from behind forwards, the postero-inferior lobule, the
biventral lobule, the amygdala, and the flocculus.
 
The postero-inferior lobule is situated at the back part of the under
surface of the hemisphere. It is divided into four curved parts by three
curved Assures. The anterior two parts are known as the lobulus gracilis,
and the posterior two as the inferior semilunar lobule. The right and left
postero-inferior lobules, together with the tuber valvulae, form the lobus
tuberis.
 
The biventral lobule is composed of curved laminae, and is somewhat
triangular. The pointed end is directed backwards and inwards, and it
is connected with the pyramid by a faint ridge, which lies low in the sulcus
valleculae. The base is directed forwards towards the flocculus. The
lobulus gracilis lies external to it, and the amygdala is on its inner side.
The biventral lobule is divided by a sulcus into two portions, outer and
inner; hence the name ‘ biventral.’ The right and left biventral lobules,
together with the pyramid, form the lobus pyramidis.
 
The amygdala (tonsil) forms a conspicuous prominence between the
uvula and the biventral lobule. It is situated in a depression of the
vallecula, which is known as the nidus avis (‘ bird’s nest ’), and its long axis
is almost sagittal. It is connected with the narrow part of the uvula by
the furrowed band in the sulcus valleculae. The right and left amygdalae,
together with the uvula, form the lobus uvulae.
 
The flocculus (subpeduncular lobule) is a small irregular lobule which
 
 
THE NERVOUS SYSTEM
 
 
1481
 
is situated between the front of the biventral lobule and the middle peduncle
of the cerebellum. Internally it is connected with the nodule by the lateral
portion of the inferior medullary velum. The right and left flocculi,
together with the nodule, form the lobus noduli.
 
In the foetus a structure, known as the paraflocculus, lies behind and to the
outer side of the flocculus, and occupies a depression in the petrous bone.
In the lower monkeys it persists throughout life, but in man it atrophies
after birth.
 
The fissures of the under surface of each hemisphere are: (1) a continuation of the postnodular sulcus, between the biventral lobule and the
flocculus; (2) a continuation of the prepyramidal sulcus, between the
am yfl ( lala an< d the biventral lobule; (3) the pregracile, or anterior arcuate
sulcus, between the biventral lobule and the lobulus gracilis; (4) the midgracile, or middle arcuate sulcus, within the lobulus gracilis; (5) the postgracile, or posterior arcuate sulcus, between the lobulus gracilis and the
inferior semilunar lobule; and (6) the small horizontal sulcus within the
inferior semilunar lobule.
 
Cerebellar Morphology.—Extensive examination of the types and
varieties of the cerebellum found in different classes of animals has
gradually established the fundamental parts of this organ. It has
)een shown to consist essentially of three lobes—anterior, middle, and
bosterior—of which the anterior is the most primitive, the middle and
posterior appearing in higher forms; in birds both these are present,
md in mammals reach a more extensive development, while in man
md the higher mammals the middle lobe reaches its most expanded
:orm, varying much in the different orders of mammals below these,
[t may be added that the vermis is to be looked on as a more primitive
md older part of the organ than the lateral lobes, in which the paired
donations exhibit much variety.
 
The anterior lobe is represented in man by that portion of the cerebellum lying above and in front of the primary fissure; this has received
ts name from this relationship, and various names have been given
:o the part thus marked off, known now as the anterior lobe. The
obe includes the vermis in this part, as far back as behind the culmen,
vhere the fissure cuts through it.
 
The middle lobe is a simple lens-shaped formation (Fig. 901 a), as
;een on the surface in lower vertebrates. In the mammals, however,
t is found to present a simple transverse bar immediately behind the
brimary fissure, but behind this it shows medial and lateral parts, of
vhich the lateral portions exhibit (Fig. 901 a) two main divisions—an
ipper or anterior one, curved on itself, and hence termed the ansiform
obule \ and a lower one (continuous with the ansiform lobule) placed
beside the median formations, and hence named the paramedian
obule.
 
The posterior lobe is also composed of a median part (posterior
nedian lobule) and two lateral portions; these consist on each side of
1 flocculus and paraflocculus, as illustrated in the figure.
 
The human cerebellum possesses a relatively simple anterior lobe,
is pointed out above. There is also a recognizable ‘ transverse bar,’
narking the upper portion of the middle lobe, in the so-called ‘ lobulus
Implex ' (posterior lunate lobe or posterior crescentic), which includes
 
 
1482
 
 
A MANUAL OF ANATOMY
 
 
the central declive. It is behind this that the middle lobe is particularly
concerned in forming the greater part of the human lateral lobe from
the ansiform lobule on each side, while the posterior lobe remains
centrally, but degenerates in part in its lateral portions.
 
 
 
Fig. 901A.—Illustrations of Cerebellar Structural Morphology, based
 
on Figures by Ingvar.
 
1, higher reptile; 2, bird; 3, mammal; A, M, P, anterior, middle, and posterior
lobes; ANS, PM, ansiform and paramedian lobules; F, PF, flocculus and
paraflocculus.
 
The schematic drawings in Fig. 901B may make this transformation
clearer. In the first scheme the recognition of the fundamental parts,
as already described, is evident and straightforward; the anterior lobe
(A) is separated by the primary fissure from the ‘ lobulus simplex,'
marked by the upper M; the lower M indicates the lower portion of the
 
 
 
Fig. 901 b.— To illustrate Hypothetical Stages in the Evolution of
 
Form of Human Cerebellum.
 
(References as in previous figure.)
 
 
middle lobe, with its two lateral pieces consisting of ansiform (ANS)
and paramedian (PM) lobules. The overgrowth of the ansiform lobule
accounts for the greater part of the lateral lobe (behind the lobulus
simplex), as shown in the second figure, while the paramedian lobule
remains as the ‘ tonsil.' The great ansiform enlargement is naturally
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1483
 
in a doisal and lateral direction mainly, so that the paramedian lobule
is overlapped, and finds itself on the anterior aspect of the lower and
median part of the enlargement.
 
The posterior lobe, stippled, is seen (as in the primitive forms,
Fig. 901A) to have a central and two lateral pieces; these show floccular
(F) and parafloccular (PF) enlargements. In the human foetus these
ire represented, but the paraflocculus is lost, and the flocculus remains
done in the adult condition, connected still with the median part of the
posterior lobe.
 
When estimating the comparative values of the parts of the cerebellum, as above, it must be remembered that the growing thickness of
the organ affects not only the lateral, but also the median parts; thus,
the vermis is very thick in the middle lobe and fades rapidly in the
bosterior lobe, so that this last is turned down and comes to look
iownwards and forwards. 1 his is associated with the overgrowth
bf the ansiform lobule, whence the paramedian lobule is visible from
below and in front, and not from behind, as in the scheme; it is covered
behind by the increasing growth of the ansiform lobule extending
medially behind it and the buried posterior derivatives.
 
To sum up shortly: the lateral lobes of the cerebellum are, for
their posterior, lateral, and greater part, overgrowths of the
ansiform portion of the middle lobe, the tonsil being paramedian.
Above this is another part (lobulus simplex, upper crescentic) of
the middle lobe, separated by the primary fissure from the simple
anterior lobe, the oldest lobe of the organ. The vermis is represented in both anterior and middle lobes as the central portion,
thickened very much in these parts, but getting rapidly smaller
(and hence reversed, as it were) in the posterior lobe. The
flocculus is the remnant of the lateral portion of the posterior
lobe.
 
The vermis in front of the primary fissure is the central part of the
interior lobe, behind this fissure, down to and including the declive;
t belongs to the upper portion (lobulus simplex) of the middle lobe,
:he lower part of which includes the ‘ tuber vermis ' and ends at the
prepyramidal fissure/ The central part of the posterior lobe includes
:he pyramid, uvula, and nodule, and it is of interest to note that these
barts are particularly connected (Holmes and Stewart) with the medial
iccessory olive, the oldest part of the inferior olivary structures; the
arge inferior olive of higher mammals has appeared with the lateral
growth of the cerebellum in them, and in less direct connection with
:he development of the cerebral cortex.
 
Peduncles of the Cerebellum.—The peduncles are three in number
Dn either side—superior, middle, and inferior—and they are composed
bf fibres which enter or leave the central white medullary substance.
 
The superior peduncles (brachia conjunctiva) are largely composed
bf efferent fibres, and are at first concealed from view by the upper
br anterior portions of the hemispheres. After they leave the hemi
 
i 4 8 4
 
 
A MANUAL OF ANATOMY
 
 
spheres they pass upwards on the lateral aspects of the dorsal surface
of the pons in a converging manner towards the quadrigeminal bodies
(or colliculi of mid-brain). They form the lateral boundaries of the
upper part of the floor of the fourth ventricle, and by their convergence
they project slightly over that part of the ventricle, so as to take part
in its roof. The superior medullary velum extends between the two
peduncles, and closes the interval between them. On reaching the
inferior pair of quadrigeminal bodies the two peduncles pass beneath
them and enter the mesencephalon, where their course will be subsequently described (see p. 1553). Most of the fibres of each superior
peduncle are derived from the corresponding nucleus dentatus, but a
few come from the grey matter of the cerebellar cortex. In addition
to these there are the fibres of the ventral (or indirect) cerebellar tract
(of Gowers).
 
The middle peduncles are of large size, and are formed by the transverse fibres of the pons, these being gathered together on either side
into a large bundle, which passes backwards and laterally into the
white central medullary substance of the corresponding hemisphere.
The fibres of each middle peduncle are both afferent and efferent. The
afferent fibres arise in the pons from the cells of the nucleus pontis of
the opposite side, and terminate in arborizations around the cells of the
cerebellar cortex. The efferent fibres arise from the cells of the cerebellar cortex of the same side, and terminate in arborizations around
the cells of the nucleus pontis, mostly on the opposite side.
 
The inferior peduncles are principally composed of afferent fibres,
which are derived chiefly from the dorsal (or direct) cerebellar tract
and the olivo-cerebellar tract of either side. The fibres of the dorsal
cerebellar tract terminate in the cortex of the superior vermis on both
sides of the median line. The fibres of the olivo-cerebellar tract , which
are derived from the inferior olivary nucleus of the medulla oblongata
on the opposite side, terminate in the cortex of the vermis and cerebellar
hemisphere. The superficial arcuate fibres, which form part of the
inferior peduncle, are connected with the cortex of the vermis and
cerebellar hemisphere. There are also fibres connecting the vermis
with the vestibular nerve, thus forming the direct sensory cerebellar
tract (see p. 1623).
 
It should be noted that the inferior peduncle comes up from below
to a position between the other two, the middle peduncle being external
and the superior internal. Having reached this position, the inferior
peduncle suddenly bends backwards and passes into the cerebellum.
 
White and Grey Matter of the Cerebellum.—In the hemispheres
and vermis the white matter is situated in the centre as the medulla,
and the grey matter is disposed superficially as the cortex. The
white matter in the interior of the vermis is occasionally termed the
corpus trapezoides. When sagittal sections of a hemisphere are made,
the mass of white matter in the centre is seen to send offshoots into
the lobules. From the sides of these offshoots secondary processes
are given off, and these in turn furnish tertiary processes, the white
 
 
THE NERVOUS SYSTEM
 
 
1485
 
latter in all cases being covered by grey matter. When the section
5 made across the direction of the laminae or folia the appearance
•resented is like the trunk and branches of a tree; hence the name
rbor vitce cerebelli is applied to it (see Fig. 902).
 
Nuclei.—The corpus dentatum (Fig. 902) is a collection of grey
latter which is situated within the white matter of each hemisphere,
nd is very like the inferior olivary nucleus in the olivary body of the
aedulla oblongata. It is composed
if a wavy grey lamina, disposed
n the form of a capsule, which
ncloses white matter. The capsule
>resents an opening or hilum at its
ipper and inner part, and through
his a large number of the fibres
>f the superior cerebellar peduncle
merge from the interior.
 
There are three other nuclei on
;ach side as follows: (1) the nucleus
imboliformis, close to the inner
;ide of the hilum of the corpus
lentatum; (2) the nucleus globosus,
nternal to the preceding ; and
3) the nucleus fastigii, or rooflucleus, situated in the vermis,
dose to the median line, and contiguous to its fellow of the opposite
dde.
 
Commissural and Association Fibres.—The commissural fibres pass
 
horn the white matter of one hemisphere to that of the opposite hemisphere. They traverse the vermis in two sets, superior and inferior.
Die association fibres are confined to each side, and they connect
idjacent laminae, passing across the bottom of the fissures which
separate them.
 
Medullary Vela.—These are thin laminae or curtains of white
matter, and are two in number, superior and inferior.
 
The superior medullary velum (or valve of Vieussens) is continuous
with the white matter of the vermis. It extends between the converging superior cerebellar peduncles, bridging over the interval between
them, and becoming continuous with their inner margins. Superiorly
it extends to the inferior pair of quadrigeminal bodies, and inferiorly
it passes into the corpus trapezoides or white matter of the vermis.
It forms a large portion of the roof of the upper part of the fourth
ventricle, and its dorsal surface supports the lingula of the superior
vermis. From the upper part of the superior medullary velum a
band of white fibres, called the frenulum veil, passes to the lower part
of the median longitudinal groove which separates the lateral pairs of
quadrigeminal bodies. Immediately below the inferior pair of quadrigeminal bodies the fourth pair of cranial nerves emerge from the
superior medullary velum on either side of the frenulum veli. The
 
 
 
Fig. 902.—Anteroposterior Section through Lateral Lobe,
showing Dentate Nucleus.
 
 
 
I486
 
 
A MANUAL OF ANATOMY
 
 
tract of Gowers (ventral spino-cerebellar tract), after having traversed
the formatio reticularis of the medulla oblongata and the dorsal part
of the pons, passes into the superior medullary velum, and then descends in the superior cerebellar peduncle to the cerebellum.
 
The inferior or posterior medullary velum is a thin lamina of white
matter which consists of three parts—median and two lateral, right
and left.
 
The median part supports dorsally the nodule of the inferior
vermis. It is a prolongation of the white matter of the vermis, and
lies on the upper or ventral aspect of the nodule, to which it is adherent.
As it leaves the white matter it is contiguous to the superior medullary
velum, but the two laminae take different directions. As they diverge
they make the cerebellar recess or apex of the roof of the fourth ventricle.
 
 
Layer of Purkinje's Cells
 
 
 
Fia Mater
 
 
_ Molecular Layer
 
 
Granular Layer
 
 
White Medullary
Substance
 
 
Fig. 903. —Structure of a Lamina
■the Cerebellum (magnified).
 
 
of
 
 
The superior medullary velum
passes upwards between the
dorsal parts of the superior
peduncles of the cerebellum.
The median part of the inferior medullary velum passes
ventralwards and then downwards. It is succeeded in a
downward direction by the
ependymal epithelium and
pia mater (tela chorioidea
inferior), which form a large
portion of the lower part of
the roof of the fourth ventricle. The middle part of
the inferior medullary velum
forms the upper portion of
 
 
the lower part of the roof of the fourth ventricle.
 
Each lateral part of the inferior medullary velum extends laterally
to the corresponding flocculus in the form of a semilunar band. The
ventral surface of this band is directed towards the fourth ventricle,
and the dorsal surface is related to the amygdala or tonsil. One
border of the band is free and concave, whilst the other is continuous
with the white matter of the corresponding cerebellar hemisphere.
 
The inferior medullary velum forms a part of the lobns noduli, the
other parts being the nodule and the two flocculi.
 
 
Minute Structure of the Cerebellar Laminae. —Each lamina or folium of the
cerebellum consists of (1) a central part or core of white matter, which is an
offshoot from the white medullary substance; and (2) an external part or cortex
of grey matter.
 
Grey Cortex. —The grey cortex is composed of two layers, an outer molecular
layer and an inner granular layer. Between these two layers there is a stratum
of characteristic large cells, called the cells or corpuscles of Purkinje.
 
The cells of Purkinje are pyriform or flask-shaped, and are situated, as just
stated, between the molecular and granular layers. The narrow or superficial
end of each cell projects into the molecular layer, and the broad or deep end rests
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1487
 
 
1 the granular layer. From the broad or deep end of each cell a single axon
isses off, which enters the granular layer, where it soon becomes medullated,
id then forms a nerve-fibre of the white medullary substance. The axon of
urkinje’s cell gives off a few collateral recurrent branches, some of which end
1 the granular layer, whilst others enter the molecular layer.
 
From the narrow or superficial end of each cell one or two dendrons are given
ff. These divide and subdivide at frequent intervals in the molecular layer
like the antlers of a deer.' The dendritic processes so formed are arranged
1 an arborescent manner, and are distinct from those of adjacent cells. They
ermeate the molecular layer as far as the surface.
 
The molecular layer consists of a few nerve-cells and many nerve-fibres.
 
The nerve-cells are situated partly in the inner or deep portion of the
lolecular layer, and partly in its outer portion.
 
The inner cells are known as the basket-cells, and they lie in the vicinity of
tie cells of Purkinje. Each basket-cell has several dendritic processes which
imify in all directions. In addition to these processes there is an axon, which
prings from the side of the cell and takes a transverse course. It gives off a
umber of collaterals which pass towards the bodies of the cells of Purkinje.
'hese collaterals terminate by ramifying very freely around the cells of Purkinje
s well as around the axons of these cells for a short distance. The minute
srminal ramifications form a close basket-work, which encloses the ceil of
hirkinje and its axon for a short distance.
 
The outer cells of the molecular layer are small, and each has several denritic processes and an axon. Each axon springs from the side of the cell,
nd, taking a transverse course, it ends in numerous ramifications.
 
The fibres of the molecular layer are derived from the following sources:
1) The dendritic processes, and the recurrent collaterals of the axons of the
ells of Purkinje; (2) the dendritic processes and axons of the outer cells; (3) the
.endritic processes of the inner or basket cells; (4) the axons of the granule-cells
>f the granular layer; (5) the fibres of Bergmann, which represent the processes
I glia-cells in the granular layer; (6) the dendrons of the cells of Golgi; and
7) some fibres from the white medullary substance of the lamina.
 
The granular layer consists of (1) nerve- and glia-cells, and (2) fibres.
 
The nerve-cells are of two kinds—namely, granule-cells and cells of Golgi.
 
The granule-cells are small and very numerous. They are closely packed
ogether, and impart to this layer a granular appearance. Each has several
[endrons and one axon. The dendrons soon ramify, and the dendritic processes
erminate in minute clusters within the granular layer, which are closely related
o the granule-cells. The axon of each granule-cell passes into the molecular
ayer, where it ramifies, its branches diverging and being closely related to the
[endritic processes of the cells of Purkinje.
 
The cells of Golgi lie near the cells of Purkinje, and are larger than the granuleells. They are stellate, and each has several dendrons and an axon. The
lendrons enter the molecular layer, in which they ramify. The axon ramifies
r ery freely in the granular layer. The cells of Golgi may be regarded as associaion cells.
 
The glia-cells are situated close to the cells of Purkinje, and lie between the
mter granule-cells. The superficial processes enter the molecular layer, and
onstitute the fibres of Bergmann, which pass as far as the pia-matral covering
if the lamina. Their deep processes pass between the granule-cells of the
;ranular layer, and some of them enter the white medullary substance.
 
The fibres of the granular layer are derived from the following sources:
1) The axons of the cells of Purkinje; (2) the moss-fibres of Cajal; (3) the denIritic processes of the granule-cells; (4) the ramifications of the axons of the
:ells of Golgi; (5) some of the deep processes of the glia-cells; and (6) some fibres
rom the white medullary substance.
 
White Matter.—The white matter of a cerebellai lamina is an
>ffshoot of the principal white medullary substance, and composed
 
 
A MANUAL OF ANATOMY
 
 
1488
 
of nerve-fibres. (1) Some of these are the axons of the cells of Purkinje,
and these enter the white matter. (2) Others pass through the granular
layer into the molecular layer, where they divide into branches which
are closely related to the more deeply placed dendritic processes of
the cells of Purkinje. (3) A third set terminate in the granular layer,
where they divide into branches which present moss-like swellings,
furnished with short delicate filaments. These fibres are known as
the moss-fibres of Cajal.
 
Development of the Cerebellum. —The cerebellum is developed from the
dorsal laminae of the metencephalon, where this forms the front limb of the
pontine flexure. In its growth it extends into the roof-plate.
 
 
4. The Fourth Ventricle.
 
 
The fourth ventricle (ventriculus quartus) is situated behind (1) the
upper or open half of the medulla oblongata or bulb, and (2) the
pons. It has two walls—ventral and dorsal.
 
Ventral or Anterior Wall.—This wall is usually referred to as the
floor. It is formed by (1) the dorsal surface of the upper or open
 
half of the bulb, and
 
 
 
Fig. 904.— Diagram to show the Composition
of Floor and Roof of Fourth Ventricle.
 
 
SMV, IMV, upper and lower medullary vela.
 
 
(2) the dorsal surface of
the pons between the converging superior peduncles
of the cerebellum. In
shape it is rhomboidal,
the bulbar and pontine
parts being triangular and
having their bases applied
to each other. The floor
is sometimes spoken of as
the fossa rhomboidea (see
Fig. 892).
 
The lower end is tapering, and lies between the
clavae of the funiculi graciles. In this situation
the cavity of the ventricle
is continuous with the
central canal of the spinal
cord after that canal has
 
 
traversed the lower or closed half of the bulb. The upper end is
somewhat tapering, and lies between the converging superior peduncles
of the cerebellum. In this situation the cavity of the ventricle is
continued into the aqueduct (of Sylvius), which traverses the mesencephalon and opens superiorly into the third ventricle.
 
The floor is widest across its centre, which is on a level with the
upper ends of the ' restiform bodies ’ of the bulb. The cavity of the
ventricle is here prolonged on either side round the outer aspect
 
 
 
 
 
 
 
THE NERVOUS SYSTEM 1489
 
[ the corresponding restiform body towards the olive. This probation is known as the lateral recess.
 
An opening in the lateral part of this recess, involving the
wering pia mater and opening into the subarachnoid space, is known
5 the lateral aperture of the fourth ventricle.
 
The floor is covered by a thick layer of grey matter, which is
mtinuous with the central grey matter of the lower or closed half
[ the bulb. This grey matter is covered by ependyma, the epithelial
ills being continuous with those which line the central canal of the
unal cord.
 
The floor is traversed in the median line by a slight longitudinal
roove, which divides it into two symmetrical longitudinal halves.
 
 
 
Fig. 905.—Dorsal View of Mid- and Hind-Brains with Thalamus
 
(Cerebellum Removed) .
 
iach half is crossed at its widest part by bundles of white fibres,
ailed auditory stricB. They wind round the upper part of the restiorm body, and pass transversely across the corresponding half of
he floor as far as the median longitudinal groove, into which they
ink. They belong to the cochlear division of the auditory nerve, in
onnection with which they will be described.
 
The floor is divided into two parts, lower and upper, by the striae
 
if either side.
 
Lower or Bulbar Part.— The bulbar part is formed by the dorsal
urface of the upper or open part of the bulb. It is bounded on either
ide by fi) the clava of the funiculus gracilis, (2) the cuneate tubercle
if the funiculus cuneatus, and (3) the restiform body, in this order
 
94
 
 
 
 
 
 
 
 
 
 
 
1490
 
 
A MANUAL OF ANATOMY
 
 
from below upwards. The lower end constitutes, as stated, a tapering
point which carries a small ridge of grey matter, the obex, at its extremity. The bulbar part is traversed in the median line by a longitudinal groove, already referred to, and this groove subdivides it into twc
symmetrical halves.
 
Immediately below the auditory striae on either side, and not
far from the median longitudinal groove, there is a small triangular
depression, known as the fovea inferior. Its apex extends to the
striae and the lateral angles of its base are prolonged downwards as
two grooves—inner and outer. The inner groove passes in a somewhat curved manner towards the point of the lower end, and the outer
groove passes downwards and outwards towards the lateral boundary.
 
 
 
Between these two diverging grooves there is a triangular area, called
the vagal triangle. Its apex is at the fovea inferior, and its base is
directed downwards and outwards. It has a dark colour, and from
this circumstance it is known as the ala cinerea. Deep to it there
is the dorsal nucleus of the vagus and glosso-pharyngeal nerves (Fig 905).
 
A second triangular area, called the hypoglossal triangle, is situated
between the median longitudinal groove and the medial of the two
grooves prolonged from the angles of the base of the fovea inferior.
Its base is directed upwards towards the striae, and its apex downwards
towards the lower point. The area is slightly elevated, and is associated
with the lower part of the eminentia medialis. Subjacent to this area
is the upper part of the nucleus of the hypoglossal nerve.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM 1491
 
A third triangular area, called the vestibular area or triangle, is
ituated between the lateral boundary of the floor and the outer of
he two grooves prolonged from the angles of the base of the fovea
iferior. Its base, like that of the hypoglossal triangle, is directed
pwards, and is continued into an eminence, over which the auditory
triae pass. This eminence is known as the vestibular area or tubercle,
ubjacent to the vestibular area and tubercle there is the dorsal or
hief terminal nucleus of the vestibular division of the eighth nerve.
 
Upper or Pontine Part.—The pontine part of the floor is formed
y the dorsal surface of the pons between the converging superior
•eduncles of the cerebellum, which constitute its lateral boundaries,
ts upper somewhat tapering end adjoins the lower end of the aqueduct,
ike the bulbar part, it is traversed in the median line by a longiudinal groove, already referred to, which subdivides it into two
ymmetrical halves.
 
Above the auditory striae, and in line with the fovea inferior,
here is a slight depression, called the fovea superior, the two foveae
>eing separated from each other by the vestibular tubercle. Between
he fovea superior and the median longitudinal groove there is a
^ell-marked prominence, called the eminentia medialis. Deep to
his eminence immediately above the striae acusticae, is the
ibducent nucleus, or nucleus of the sixth cranial nerve, and the
minentia medialis is really formed by fibres of the seventh nerve curvound the dorsal surface of the sixth nucleus just deep to the floor
)f the ventricle. For this reason an alternative name for the eminence
s the colliculus facialis. The eminence is continued downwards
nto the trigonum hypoglossi, and superiorly it extends towards the
ower end of the aqueduct of the mid-brain. Extending upwards
rom the fovea superior towards the region of the lower end of the
iqueduct there is a slight depression, known as the locus cseruleus,
vhich has a dark grey or somewhat blue colour. This colour is due
:o a subjacent group of deeply pigmented nerve-cells, known as the
substantia ferruginea. This group may belong to the chief motor
lucleus of the fifth cranial nerve, or it may be a terminal nucleus for
some of the sensory fibres of that nerve.
 
Dorsal or Posterior Wall of Fourth Ventricle.— this wall is usually
eferred to as the roof, and it is divisible into two parts—upper and
ower.
 
The upper part is formed chiefly by the superior or anterior medulary velum, which extends between the inner margins of the dorsal
ispects of the superior peduncles of the cerebellum. It is also formed
:o a certain extent by these peduncles as they converge and slightly
overhang the angular space between them. I he lower part of the roof
s formed, from above downwards, by (1) the inferior or posterior
nedullary velum, and (2) the ependymal epithelium of the ventiicle,
covered by pia mater. The inferior medullary velum is separated from
;he superior velum by the recess (Fig. 9 ° 4 )> within which the cerebellum
ictually forms a part of the roof; the inferior velum terminates in a free
 
 
1492
 
 
A MANUAL OF ANATOMY
 
 
margin. Beyond this free margin there is the ependymal epitheliun
of the ventricle, covered, as stated, by pia mater. This portion o
pia mater is called the tela chorioidea inferior.
 
The epithelial part of the roof presents superficially threi
laminae of white nervous matter—namely, the obex and thi
ligulae. The obex is a thin triangular lamina which is situatec
at the lower point of the ventricle, being attached laterally t(
the diverging clavae. The ligulce are right and left. Each is c
narrow band, which is continuous interiorly with the obex
It is attached inferiorly to the clava and the cuneate tubercle
It then passes transversely outwards over the dorsal aspect of the
restiform body. The transverse part of the ligula forms the lowei
boundary of the lateral recess of the ventricle.
 
 
 
Fig. 907. —The Fourth Ventricle and Right Hemisphere of the
Cerebellum (in Section) (Hirschfeld and Leveille).
 
 
In the lower part of the roof of the fourth ventricle, below the
lower limit of the inferior medullary velum, there is a perforation
through the pia mater and ependyma, known as the foramen of
Magendie. This, situated in the mid-line, forms an opening between
the fourth ventricle and the subarachnoid space, and with the lateral
recesses allows the cerebro-spinal fluid to pass from the interior to the
surface of the brain. Its modern name is median aperture of fourth
ventricle.
 
Choroid Plexuses of Fourth Ventricle.—These are two in number,
 
right and left. Each is a longitudinal inflexion of the pia mater
which forms the tela chorioidea inferior, and it invaginates the ependymal epithelium of the lower part of the roof of the ventricle, by
which it is covered on its ventricular surface. Each choroid plexus
consists of two parts—longitudinal and transverse—and the two
plexuses are disposed thus: ] |". The longitudinal parts lie on either
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1493
 
 
ide of the median line, and extend upwards from the region of the
oramen of Magendie. Each transverse part extends outwards into
he corresponding lateral recess of the ventricle
 
Development of Fourth Ventricle.—The lower or bulbar part is
developed from the myelencephalon, and the upper or pontine
part is developed from the metencephalon, these being the two
divisions of the rhombencephalon. The cavity is the cavity
of the neural tube, dilated and made diamond-shaped as a result
of the formation of the pontine flexure (p. 57).
 
 
TELENCEPHALON.
 
Cerebral Hemispheres.
 
The cerebral hemispheres are right and left. Each is semi-ovoid,
md presents two extremities and three surfaces.
 
The extremities are anterior and posterior. The anterior is thick
md round, and its most projecting part is called the frontal pole,
rhe posterior extremity is narrow and pointed, and its most projecting
Dart is called the occipital pole. The surfaces are lateral, medial, and
inferior. The medial surface is convex, in adaptation to the concavity
Df the cranial vault. The lateral surface is flat and vertical, and it
forms the lateral boundary of the great longitudinal fissure. For the
most part it is in contact with the falx cerebri. The inferior surface is
irregular, being adapted to the corresponding lateral divisions of the
anterior and middle fossae of the interior of the base of the skull and
the upper surface of the tentorium cerebelli. It is crossed transversely
by a deep cleft, representing the stem of the lateral fissure.. The
portion in front of this fissure is known as the orbital area, and is concave, in adaptation to the convexity of the orbital plate of the frontal
bone, upon which it rests. The extensive portion behind the stem of the
lateral fissure is known as the tentorial area, and is prominent and
arched. Its anterior portion is received into the lateral division of the
middle cranial fossa, and its posterior portion rests upon the tentorium
cerebelli.
 
The borders of each hemisphere are four—supero-medial, mferolateral, superciliary, and internal occipital. The supero-medial border
separates the lateral from the medial surface. The infero-lateral border
separates the lateral surface from the tentorial area of the inferior
surface. The superciliary border separates the front part of the lateral
surface from the orbital area of the inferior surface. The internal
occipital border separates the medial surface from the tentorial area
of the inferior surface, and it extends from the occipital pole to the
splenium of the corpus callosum.
 
The exterior of each hemisphere is broken up into tortuous eminences,
called gyri or convolutions, and these are separated from each other by
clefts, called sulci or fissures. The exterior is composed of grey matter,
 
 
1494
 
 
A MANUAL OF ANATOMY
 
 
which is spoken of as the cerebral cortex, and the interior is occupied
by white matter, which forms the medullary centre. The breaking up
of the hemispheres into gyri, with the intervening sulci, greatly increases
the amount of cerebral cortex, and to a proportionate extent of pia
mater.
 
It is sometimes the practice to distinguish between fissures and sulci of the
brain, though many regard it as a refinement. If it is necessary, the fissures
may be defined as clefts which either pass from one surface of the brain to
another or, if they do not do that, cause an elevation in the wall of the lateral
 
 
 
biG. 908.— Views of Brain, not showing Convolutions.
A, from above; B, from left; C, from below; D, from behind.
 
 
ventricle. The difficulty is that, with this definition, the same depression is
sometimes a fissure and sometimes a sulcus.
 
Subject to this explanation, the following clefts would rank as fissures and
them claims will be dealt with as they are described: (1) Lateral, (2) central,
.( 4 ) hippocampal, (5) calcarine, (6) collateral, (7) parieto-occipital.
^Mwessions which do not fulfil these requirements merely rank as sulci.
 
the fissures thus defined are deeper and more constant in arrangement than
the sulci. 0
 
Each hemisphere presents six principal clefts, called interlobar, and
by means of these it is divided into six lobes.
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1495
 
 
Interlobular Clefts.
 
1. Lateral fissure [Sylvian). 4. Cingulate sulcus.
 
2. Central fissure [Rolando). 5. Collateral fissure.
 
3. Parieto-occipital fissure. 6. Circular or limiting sulcus.
 
Interlobular Fissures.—The lateral fissure (O.T., fissure of Sylvius),
which is the first fissure to appear in the course of development,
begins on the inferior surface of the hemisphere at the anterior perforated
substance in a depression, called the vallecula cerebri (or Sylvii). From
this point it passes horizontally outwards to the external surface of the
hemisphere, where it divides into three diverging branches. It is a
deep cleft, which is overhung posteriorly by the front part of the
temporal lobe, and it separates the orbital surface of the frontal from
 
 
 
 
 
Fig. 909.—Lateral View of Left Hemisphere.
 
In this specimen the horizontal (AH) and ascending (AV) anterior rami arise
separately from lateral fissure. The pars triangularis lies between them.
 
the temporal lobe. The posterior border of the small wing of the
sphenoid bone faces the fissure, which lodges the middle cerebral artery.
The limbs into which the fissure divides are anterior horizontal, ascending, and posterior horizontal. The anterior horizontal limb passes forwards into the frontal lobe, its length being about f inch. The ascending limb passes upwards and slightly forwards into the frontal lobe for
about 1 inch, but its length is variable. The posterior horizontal limb
is the longest and most conspicuous. It passes backwards on the
external surface of the hemisphere for at least 2 inches, having poi tions
of the frontal and parietal lobes above it, and the temporal lobe below
it. Finally, it turns upwards into the parietal lobe for a very short
 
distance
 
The central fissure (see Fig. 909), also known as the central sulcus
and fissure of Rolando , begins at the supero-medial border of the hemi
 
1496
 
 
A MANUAL OF ANATOMY
 
 
 
sphere a little behind its mid-point, and ends above the centre of the
posterior horizontal limb of the lateral fissure. It does not usually
open into this limb, but may do so. Superiorly the fissure in most cases
intersects the supero-medial border to reach the medial surface of the
hemisphere, upon which it passes backwards for a very short distance.
The direction of the fissure is irregularly downwards and forwards over
the external surface of the hemisphere, and it separates the frontal from
the parietal lobe. It describes two bends. The upper genu has its
concavity directed forwards, and is situated about the junction of the
upper and middle thirds of the fissure. The lower genu has its concavity directed backwards, and is situated on a more anterior plane
than the upper genu. Below the lower genu the direction of the fissure
is almost vertical, with a slight inclination backwards. The fissure
is sometimes interrupted.
 
 
Central Sulcus
 
 
Medial Frontal
Gyrus
 
 
Cingulate
Gyrus
 
Callos. Sulcus •
 
 
--- Paracentral
Lobule
 
 
Cingulate
 
Sulcus
 
Suprasplenial
Fissure
Parieto-occ.
 
Fissure
Cuneus
 
 
Calcarine
 
Fissure
 
 
Uncus
 
 
Rhinal Sulcus
 
 
, Lingual Gyrus
 
Collateral Fissure
 
\\ Occipito-Temp. Gyrus
' Hippocampal Gyrus
Inf. Temp. Gyrus
 
 
Fig. 910.—Medial Aspect of Right Hemisphere.
Approximate position of lateral ventricle marked in blue.
 
 
The parieto-occipital fissure is situated about 2 inches behind the
upper end of the central fissure, and separates the parietal from
the occipital lobe. It is composed of two limbs, external and internal,
which are continuous with each other at the supero-medial border of
the hemisphere, where they form a right hngle. The external limb is
situated on the lateral surface of the hemisphere, upon which it passes
transversely outwards for about £ inch, when it is arrested by the
convolution which connects the parietal and occipital lobes. The
internal limb appears as a deep, almost vertical cleft on the medial
surface of the hemisphere, which opens into the calcarine fissure a short
distance behind the splenium of the corpus callosum (see Figs. 910
and 917).
 
The cingulate sulcus is situated on the medial surface of the hemisphere. It commences below the rostrum of the corpus callosum,
 
 
 
THE NERVOUS SYSTEM
 
 
1497
 
 
near the anterior perforated area, and, bending round the genu, it
passes backwards above the corpus callosum, from which it is separated
by the cingulate gyrus. At a point a little behind the centre of the
internal surface of the hemisphere it turns upwards, and terminates
at the supero-medial border a short distance behind the upper end of
the central fissure. The cingulate fissure lies between the frontal
and limbic lobes, the medial frontal gyrus being above it and the cingulate gyrus below it (see Fig. 910).
 
The collateral fissure is situated on the inferior or tentorial surface
of the hemisphere. It starts near the occipital pole, and extends
forwards towards the temporal pole. Posteriorly it has the calcarine
fissure above, and in line with it, and anteriorly the hippocampal gyrus
holds this position on its medial side. It separates the temporal lobe
from the hippocampal portion of the limbic lobe. The middle portion
of the collateral fissure gives rise to the eminentia collateralis in the
floor of the lateral ventricle.
 
The circular or limiting sulcus is situated deeply in the anterior part
of the posterior horizontal limb of the lateral fissure. It almost
surrounds the convolutions which constitute the insula, and is composed of three parts-—superior, inferior, and anterior. The superior
part separates the insula from the frontal and parietal lobes, the inferior
part separates it from the temporal lobe, and the anterior part separates
it from the frontal lobe. The circular fissure is deficient in the region
of the apex of the insula (see Fig. 920).
 
Lobes of the Cerebral Hemisphere—Frontal Lobe.—This is of large
size. On the external surface of the hemisphere it is bounded behind
by the central fissure and below by the posterior horizontal limb of
the lateral fissure. On the inferior surface it is bounded behind by
the stem of this fissure. On the internal surface it is bounded by the
cingulate fissure. The frontal lobe has three surfaces—lateral, inferior,
and medial.
 
Lateral Surface.—This surface presents three principal sulci—precentral, superior frontal, and inferior frontal.
 
The precentral sulcus is more or less parallel to the central fissure,
the ascending frontal or precentral gyrus intervening between the two.
It may be a single cleft, but it more frequently consists of two parts,
superior and inferior. The superior part is usually joined above by
the superior frontal sulcus. The inferior part passes superiorly into the
middle frontal gyrus for a short distance in a forward and upward
direction (see Fig. 909).
 
The superior and inferior frontal sulci extend forwards from the
precentral sulcus.
 
The gyri of the external surface are as follows: precentral or ascendingfrontal, superior frontal, middle frontal, and inferior frontal (see Fig. 909)
The ascending frontal or precentral gyrus (Fig. 909, A) is bounded
behind by the central sulcus, and in front by the superior and inferior
parts of the precentral sulcus. It extends from the supero-medial
border of the hemisphere to a little behind the Sylvian point, which
 
 
 
A MANUAL OF ANATOMY
 
 
1498
 
 
corresponds to the place where the stem of the lateral fissure appears on
the external surface of the hemisphere, and divides into its three
branches. Below the lower end of the central fissure it is, as a rule,
connected with the ascending parietal or postcentral gyrus by an
annectant gyrus.
 
The superior or first , middle or second, and inferior or third frontal gyri
 
(C, D, E) are arranged in tiers, which are disposed antero-posteriorly, but
the first and second often are subdivided, so as to make five tiers in
 
all. They are separated from the ascending
frontal or precentral gyrus by the superior
and inferior parts of the precentral sulcus.
 
The superior frontal gyrus is narrow, and
lies between the supero-medial border of the
hemisphere and the superior frontal sulcus.
It is continuous with the medial frontal
gyrus on the medial surface of the hemisphere, and is partially broken up into two
parts, upper and lower.
 
The middle frontal gyrus, which is broad,
is usually connected with the ascending
frontal or precentral gyrus by an annectant
gyrus. It is broken up anteriorly into two
parts, upper and lower, by an anteroposterior secondary sulcus; and it is cut
into behind by the upper portion of the
inferior part of the precentral sulcus.
 
The inferior frontal gyrus lies below the
inferior frontal sulcus, and in front of the
lower part of the precentral sulcus. The
anterior horizontal and the ascending limbs
of the lateral fissure enter it and subdivide
it into three parts—namely, pars orbitalis,
pars triangularis, and pars basilaris, or,
better still, orbital, frontal, and fronto-parietal
opercala. The orbital operculum lies below
the anterior horizontal limb of the lateral
fissure; the frontal operculum is situated
between the anterior horizontal and the ascending limbs of the fissure;
and the fronto-parietal operculum is placed between the ascending
limb of the fissure and lower part of the precentral sulcus. The
inferior frontal gyrus is connected posteriorly with the lower end of
the ascending frontal or precentral gyrus by an annectant gyrus.
 
Inferior or Orbital Surface of the Frontal Lobe.—This surface presents
two sulci, olfactory and orbital (see Fig. 914).
 
The olfactory sulcus is parallel to the medial border, from which it is
separated by the gyrus rectus. It lodges the olfactory tract and olfactory bulb. The orbital sulcus is of very variable form, but, as a rule,
bears some resemblance to the letter )-(. It has, therefore, three limbs
 
 
 
Fig. 911.—The Left Cerebral Hemisphere (Superior Surface).
 
Red=frontal lobe.
Orange=parietal lobe.
Blue=occipital lobe.
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1499
 
 
—medial, lateral, and transverse. The medial limb is separated from
the olfactory sulcus by the medial orbital gyrus. The lateral limb is
curved, and has external to it the orbital part of the inferior frontal
gyrus. The transverse limb passes in a more or less curved manner
between the other limbs.
 
The gyri of the orbital surface are: gyrus rectus, medial orbital
gyrus, anterior orbital gyrus, lateral orbital gyrus, and posterior
orbital gyrus.
 
The gyrus rectus lies between the olfactory sulcus and the medial
border. The medial orbital gyrus is placed between the olfactory sulcus
and the inner limb of the orbital sulcus. The lateral orbital gyrus is
external to the other limb of the orbital sulcus. The anterior orbital
gyrus is situated in front of the transverse limb of the orbital sulcus.
The posterior orbital gyrus lies behind the transverse limb of the orbital
sulcus.
 
 
 
Fig. 912.—The Right Cerebral and Cerebellar Hemispheres (Lateral
 
Surface).
 
Red=frontal lobe. Blue=occipital lobe.
 
Orange—parietal lobe. Green=temporal lobe.
 
Purple=cerebellar hemisphere.
 
Medial Surface of the Frontal Lobe.— The medial surface presents
only one convolution, the medial frontal or marginal gyrus, which is
situated between the supero-medial border of the hemisphere and the
cingulate sulcus. It is continuous with the superior frontal gyrus, and
anteriorly is broken up by one or two sulci. Its posterior part is
almost completely detached, and forms the paracentral lobule, so named
because it contains the upper end of the central fissure (Fig. 910).
 
Parietal Lobe.— This lobe lies between the large frontal and small
occipital lobes, and above the temporal lobe. It is bounded anteriorly
by the central fissure, which separates it from the frontal lobe. Posteriorly it is bounded by (1) the external parieto-occipital fissure, and
(2) a line drawn across the external surface of the hemisphere from the
extremity of this fissure towards the pre-occipital notch. on the inferolateral border of the hemisphere, from i-| to 2 inches in fiont of the
occipital pole.
 
 
 
1500
 
 
A MANUAL OF ANATOMY
 
 
The parietal lobe has two surfaces—lateral and medial.
 
Lateral Surface.—This surface presents the following sulci: the
intraparietal sulcus, composed of four parts; and the terminal portions
of [a) the posterior limb of the lateral fissure, ( b ) the first temporal or
parallel sulcus, and (c) the second temporal sulcus.
 
The inferior and superior postcentral sulci may be distinct, or continuous with each other. They lie behind the central fissure, with
which they are parallel, and from which they are separated by the
ascending parietal or postcentral gyrus (Fig. 909, B).
 
 
Cerebral Hemisphere
 
 
OccipitaL
 
Poie
 
 
 
_Frontal
 
Pole
 
 
Pons
 
—Medulla Oblongata
 
 
Fig. 913.— The Encephalon (Right Lateral View) (Hirschfeld
 
and Leveille).
 
 
1. Central Fissure
 
2. Posterior Horizontal Limb of Lateral Fissure
 
3. Ascending Limb of Fissure
 
4. Anterior Horizontal Limb of Fissure
5,5. Intraparietal Sulcus
 
6. Ramus Horizontalis
 
 
7. Ramus Occipitalis
 
8. Transverse Occipital Sulcus
 
9. Lateral Occipital Sulcus
 
10. External Occipito-parietal Fissure
 
11. Superior Temporal, or Parallel, Sulcus
 
12. Inferior Temporal Sulcus
 
 
The intraparietal sulcus is often in two parts, horizontal and occipital (see Fig. 913).
 
The ramus horizontalis passes backwards and slightly upwards
from the upper end of the inferior postcentral sulcus. It has the
superior parietal lobule above it, and the inferior parietal lobule
below it.
 
The ramus occipitalis is usually continuous with the last branch, and
passes back into the occipital lobe as the lower boundary of the arcus
parieto-occipitalis.
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1501
 
 
The terminal portions of (a) the posterior horizontal limb of the
lateral fissure, (b) the first temporal or parallel sulcus, and (c) the second
temporal sulcus, are confined to the lower part of the external surface
of the parietal lobe, where they lie in the order named from before
backwards.
 
The gyri of the lateral surface are as follows: ascending parietal;
superior parietal; and inferior parietal,
with its supramarginal, angular, and
postparietal gyri.
 
The ascending parietal or postcentral
gyrus is situated immediately behind
the central fissure, which separates it
from the ascending frontal or precentral
gyrus in front of that fissure. Posteriorly it is limited by the superior
and inferior postcentral sulci. It extends from the supero-medial border
of the hemisphere to the posterior
horizontal limb of the lateral fissure,
and it lies parallel to the ascending
frontal or precentral gyrus, with which
it is connected below the central
fissure.
 
These two gyri, from their relation
to the central fissure, are often spoken
of by neurologists as the ‘ central gyri,’
though the name, if not clearly understood, is apt to lead to confusion with
the gyri of the central lobe or insula.
 
The superior parietal lobule is situated between the ramus horizontalis
and the supero-medial border of the
hemisphere, where it is continuous with
the quadrate lobule, or precuneus, of
the internal surface. Anteriorly it is
limited by the superior postcentral
sulcus, round the upper end of which
it is continuous with the postcentral
gyrus. Posteriorly it is bounded by the
external part of the parieto-occipital fissure, round the extremity of
which it is connected with the occipital lobe by the arcus parieto
 
 
Fig. 914. —The Inferior Surface of the Left Cerebral
Hemisphere, showing the
Gyri and Sulci.
 
 
occipitalis.
 
The inferior parietal lobule is situated behind the inferior postcentral sulcus, and below the ramus horizontalis and ramus occipitalis.
It is broken up into several gyri, three of which the supramarginal,
angular, and postparietal—lie in this order from before backwaids.
The supramarginal gyyus arches over the ascending extremity of the
posterior limb of the lateral fissure. The angular gyrus arches over the
 
 
 
 
 
 
 
 
 
 
 
 
1502
 
 
A MANUAL OF ANATOMY
 
 
ascending extremity of the first temporal or parallel sulcus, and is
continuous with the second temporal gyrus. The postparietal gyrus
arches round the ascending extremity of the second temporal sulcus,
and is continuous with the third temporal gyrus. These three subdivisions of the inferior lobule are sometimes described simpfy as
anterior, middle, and posterior parts.
 
Medial Surface of the Parietal Lobe.—The medial surface is of quadrilateral outline, and constitutes the quadrate lobule or precuneus. It
is bounded in front by the upturned posterior extremity of the cingulate
sulcus, behind by the internal parieto-occipital fissure, and below by
the suprasplenial sulcus and a portion of the gyrus cinguli (Fig. 916).
 
 
Corpus Callosum
 
 
Pineal Body
Splenium
 
 
Anterior Pillar of Fornix
Septum Lucidum
 
 
Genu passing into
Rostrum
 
 
Corpora
Quadri- g
gemina
 
 
 
Anterior Commissure
Optic Thai, and Connexus
Thalamus Nerve
Pituitary Body
Tuber Cinereum
Corpus Mamillare
 
 
Cerebellum
 
 
Fourth Ventricl
 
 
Third Nerve
 
1 1 Pons
 
i Crus Cerebri
Aqueduct
 
Medulla Oblongata
 
 
fG. 915 .—The Medial Surface of the Left Cerebral Hemisphere
 
(Hirschfeld and Leveille).
 
 
Occipital Lobe.—This lobe lies behind the parietal and temporal
lobes, and forms the posterior part of the cerebral hemisphere.
 
Laterally the lobe is bounded in front by the external parietooccipital fissure, and a line connecting this fissure with the pre-occipital
notch on the infero-lateral border of the hemisphere. Medially it is
bounded in front by the internal parieto-occipital fissure, which
separates it from the quadrate lobule, or precuneus, of the parietal lobe.
Inferiorly it is continuous with the temporal and hippocampal regions,
but the separation may be indicated by a line connecting the preoccipital notch with the portion of the hippocampal formations which
lie below the splenium of the corpus callosum, this portion being known
as the ‘ isthmus.’
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1503
 
 
The occipital lobe is pyramidal, having an apex and three surfaces—
lateral, medial, and inferior.
 
The apex forms the occipital pole of the cerebral hemisphere.
 
Lateral Surface (see Fig. 913).—This surface presents two sulci,
transverse occipital and lateral occipital. The transverse occipital
sulcus is formed by the bifurcation of the posterior end of the ramus
occipitalis of the intraparietal sulcus, and it crosses the upper part of
the occipital lobe obliquely. Its upper limb lies a little behind the
external part of the parieto-occipital fissure, from which it is separated
by a portion of the arcus parieto-occipitalis, and its lower limb is
behind the postparietal gyrus. The lateral occipital sulcus is situated
on the external surface of the occipital lobe, and extends almost horizontally from behind forwards. It divides the external surface of the
lobe into two parts, upper and lower, which are connected with the
 
 
 
Gyrus Dentatus
 
Fig. 916.—The Medial Surface of the Right Cerebral Hemisphere
 
(Hirschfeld and Leveille).
 
parietal and temporal lobes by annectant gyri. These sulci and gyri
are very variable in appearance.
 
Medial Surface.—On the medial surface is the calcarine fissure.
 
This is a deep cleft which starts on the internal aspect of the occipital
pole in a bifurcated manner. It takes a curved course forwards,
passing at first upwards and then downwards, and ends by reaching
the hippocampal gyrus beneath the splenium of the corpus callosum.
It is joined at a point anterior to its centre by the internal parietooccipital fissure, and between the two fissures is the cuneus. The
calcarine fissure is composed of two parts: precalcarine, representing
the portion in front of the internal part of the parieto-occipital fissure;
and postcalcarine, representing the portion behind that fissure. The
precalcarine fissure gives rise to the calcar avis, on the inner wall of
the posterior cornu of the lateral ventricle (Fig. 917)
The gyri of the internal surface are two in number—namely, the
 
cuneus and the gyrus lingualis.
 
 
 
 
 
 
 
 
1504
 
 
A MANUAL OF ANATOMY
 
 
The cuneus is triangular, and is wedged in between the posterior
calcarine fissure and the internal parieto-occipital fissure. The gyrus
lingualis (infracalcarine gyrus) is situated between the calcarine fissure
above and the posterior part of the collateral fissure below. Anteriorly
it becomes narrow, and joins the hippocampal gyrus. The lower
portion of this gyrus is visible on the inferior surface of the lobe.
 
Inferior Surface.—The inferior or tentorial surface presents the
posterior part of the occipito-temporal gyrus, medial to which is the
posterior part of the collateral fissure, and internal to this again there
is the lower portion of the gyrus lingualis (see Fig. 918).
 
Temporal Lobe.—The temporal lobe (see Fig. 913) is prominent,
and of large size. It is situated below the posterior horizontal limb
of the lateral fissure, and behind the stem of that fissure. Superiorly
it is bounded by the horizontal portion of the posterior limb of the
 
 
 
Fig. 917.—Medial Aspect of Parieto-occipital Region of Left Hemisphere, to show Internal Parietal Occipital Fissure, Anterior and
Posterior Calcarine.
 
Visual area coloured.
 
fissure, and a line prolonging this limb backwards to meet the anterior
boundary of the occipital lobe. Anteriorly it is bounded by the stem
of the fissure, which separates it from the orbital area of the frontal
lobe. Posteriorly it is continuous with the occipital lobe, but the
separation may be indicated by the following lines: externally by a line
connecting the extremity of the external parieto-occipital fissure with
the pre-occipital notch, and below and medially by a line connecting
the pre-occipital notch with the splenium of the corpus callosum. Its
medial surface above is separated from the hippocampal gyrus by the
collateral fissure. The temporal lobe is somewhat pyramidal, the
rounded apex being directed forwards. The apical part forms the
temporal pole, and underlies the stem of the lateral fissure. The uncus
of the hippocampal gyrus lies on its inner side, but on a more posterior
level, and separated from it by the temporal sulcus.
 
 
THE NERVOUS SYSTEM
 
 
1505
 
 
The lobe presents three surfaces—superior, lateral, and inferior.
 
The superior or opercular surface is concealed within the lateral
fissure, and is directed towards the insula.
 
The lateral surface has two horizontal sulci and three convolutions,
the latter being disposed one above the other.
 
The sulci are called first and second temporal. The first temporal
sulcus is parallel to the posterior limb of the lateral fissure, from which
:ircumstance it is called the parallel
sulcus. Starting near the temporal
pole, it turns upwards posteriorly into
the parietal lobe, where the angular
?yrus arches over it. The second temporal sulcus is parallel to the first, below
which it lies, and it is usually broken
up into two or more parts by annectant
^yri. Posteriorly it turns upwards into
the parietal lobe, where the postparietal
^yrus curves round it.
 
The first temporal gyrus is situated
uetween the posterior limb of the lateral
ussure and the parallel sulcus. Posteriorly it is continuous with the infraparietal lobule. The second temporal
?yrus lies between the parallel and
second temporal sulci. The third temporal gyrus lies below the second temporal sulcus, and posteriorly is con:inuous with the lower part of the
ixternal surface of the occipital lobe.
 
On the inferior or tentorial surface
)f the temporal lobe is the occipito:emporal sulcus and the occipito:emporal gyrus. The occipito-temporal
iulcus extends from before backwards,
ying near the infero-lateral margin of
he hemisphere, and lateral to the colateral fissure (see Fig. 918). It is
lsually broken up into parts by anlectant convolutions. The occipitotemporal gyrus is situated between the
)ccipito-temporal sulcus and the collateral fissure, and extends from
he occipital pole to the temporal pole. Lateral to the occipitoemporal sulcus there is the narrow inferior or tentorial surface of the
hird temporal gyrus.
 
Insula (Island of Reil) (see Fig. 920).—This lobe is situated deeply
vithin the lateral fissure, and is concealed from view by the opercular
[yri, to be presently described. It is triangular, the apex being
lirected downwards towards the vallecula cerebri and anterior per
95
 
 
 
Fig. 918.—The Inferior Surface of the Left Cerebral
Hemisphere, showing the
Gyri and Sulci.
 
 
 
 
 
 
 
 
 
 
1506
 
 
A MANUAL OF ANATOMY
 
 
forated area. The circular or limiting sulcus being here absent, the
grey matter of the apex is continuous with that of the perforated area,
this point being called the limen insulce. Elsewhere the island is
surrounded by the circular or limiting sulcus, which has been already
described. The insula presents several sulci, which diverge as the}/
pass from the apical region to the base, and these map it out into gyri.
One of these sulci is known as the sulcus centralis insulae. It extends
from the apex to the base in an upward and backward direction almost
in line with the central fissure, and it divides the insula into two lobules,
precentral and postcentral.
 
The precentral lobule is composed of three or four short gyri, called
the gyri breves , which converge as they descend from the base, but
they do not reach the apex or pole of the precentral lobule. The post
 
 
Fig. 919.—The Insula exposed by Removal of Opercula.
 
C, sulcus centralis insulae.
 
 
central lobule is formed by the gyrus longus, which is usually broken up
into two gyri towards the base of the insula.
 
The direct internal or medial relation of the insula is the claustrum,
internal to which there are, in succession, the external capsule, the
nucleus lentiformis, the internal capsule, and the nucleus caudatus.
 
Opercula Insulae.—The parts of the cerebral hemisphere which bound
the three limbs of the lateral fissure and overhang the insula are called;
the opercula insulae. They are four in number—fronto-parietal,
temporal, frontal, and orbital—and have been mentioned already
(p. 1498).
 
Limbic Lobe.—This name was given in former times to a part
of the brain, on its medial aspect, which included what is now
known as the rhinencephalon, and also the cingulate gyrus.
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1507
 
 
The interrelations of the various parts will be considered more
appropriately under the heading of rhinencephalon, but the
preliminary description of these parts can be taken here, including
that of the cingulate gyrus.
 
The gyrus cinguli arches round the corpus callosum. It begins at
the anterior perforated substance below the rostrum of the corpus
callosum, and it ends below the splenium of that body. Between these
two points it pursues a semicircular course, passing forwards beneath
the rostrum, upwards in front of the genu, backwards above the body
of the corpus callosum, and finally, curving round the splenium, it is
continued into the hippocampal gyrus through the isthmus. It is
bounded superiorly by the cingulate sulcus, which separates it from
the medial frontal gyrus (Fig. 921) and paracentral lobule, and posterior
 
 
Central Fissure
 
 
 
Fig. 920.— The Left Insula (Poirier, from Eberstaller).
1, 2, 3, gyri breves; 4, 5, gyri longi; X, limen insulae.
 
 
to the latter it is partially separated from the precuneus by the suprasplenial sulcus. The gyrus is separated from the corpus callosum by
 
the callosal sulcus.
 
The hippocampal gyrus, below the splenium of the corpus callosum,
is joined above to the callosal gyrus by the isthmus , and behind and
below it is continuous with the lingual gyrus (Fig. 921). As it passes
forwards it has the hippocampal fissure above it, and the anterior part
of the collateral fissure below it. Anteriorly , near the apex of the
temporal pole and close behind the anterior perforated substance, it
forms an enlargement, known as the caput gyri hippocampi, which is
separated from the temporal pole by a slight fissure, called the incisura
temporalis. From the caput a hook-like process, the uncus, passes
backwards for a short distance above the anterior part of the hippocampal or dentate fissure. The caput represents the largely-developed
 
 
 
 
A MANUAL OF ANATOMY
 
 
1508
 
lobus pyriformis of many mammals, and it constitutes an olfactory
centre of the cerebral cortex. Along with the uncus it forms part of
the rhinencephalon or rhinopallium, a large part of the hippocampal
gyrus belonging to the neopallium.
 
The incisura temporalis, which separates the caput gyri hippocampi
from the temporal pole, represents the ecto-rhinal fissure , defining the
well-developed rhinencephalon in some animals.
 
The cingulum, a narrow, tape-like band of white matter, is
associated with the cingulate gyrus, and, according to Cajal, its
fibres arise as the axons of cells of the gyrus, to the under surface
of which the cingulum adheres. On entering the cingulum some
fibres pass forwards and others backwards, whilst a few are
 
 
Central Sulcus
 
 
 
Rhinal Sulcus (Inc. temp.)
 
 
'Lingual Gyrus
Collateral Fissure
' O’cipito-Temp. Gyrus
 
Hippocampal Gyrus
Inf. Temp. Gyrus
 
 
Medial Frontal
Gyrus
 
 
Cingulate
 
Gyrus
 
 
Callos. Sulcus
 
■= Paracentral
Lobule
 
 
- Cingulate
Sulcus
 
Suprasplenial
Fissure
Parieto-occ.
 
Fissure
Cuneus
 
Calcarine
Fissure
 
 
Fig. 921. Medial Aspect of Hemisphere, with Approximate Position of
Lateral Ventricle represented in Colour.
 
 
described as branching into forward and backward branches.
The anterior branches pass as far as the caput of the corpus
striatum, where they are described as blending with the fibres
which enter the internal capsule. Some may even pass to the
cortex of the prefrontal region. The posterior branches turn
round the splenium, and then lie upon the subiculum, or upper
part of the hippocampal gyrus, as far forwards as the caput
and uncus. The posterior fibres are described as ending in the
cortex of (1) the subiculum hippocampi, and (2) occipital lobe.
The cingulum belongs to the class of long association fibres.
 
Hippocampal or Dentate Fissure. —This fissure commences behind
the splenium of the corpus callosum, where it is continuous with the
callosal sulcus. It is directed forwards, lying between the gyrus denta
 
 
 
 
THE NERVOUS SYSTEM
 
 
1509
 
 
tus above and the hippocampal gyrus below, and it terminates within
the uncus of the hippocampal gyrus.
 
The hippocampal fissure is a complete fissure. It appears in the
course of the fifth week, and is parallel to the temporal portion of the
choroidal fissure, below which it lies. The portion of the vesicular
wall between these two fissures is the gyrus dentatus, and the portion
below the hippocampal fissure forms the hippocampal gyrus.
 
 
 
 
Fig. 922.—To show the Arrangement of Structures below the
Level of the Splenium.
 
F, fimbria and posterior pillar of fornix; D, dentate gyrus; CALC, beginning of calcarine fissure; COLL,
collateral fissure; HG, hippocampal
gyrus. The * band of Giacomini,
continuous with the dentate gyrus,
is shown at G crossing the base of
the uncus. C, choroidal fissure ;
Fiss, hippocampal fissure.
 
 
Fig. 923.—Outline of Section across
Hippocampal Region.
 
Shows how the upper part of the region
is bent on itself to make a prominence, the hippocampus, which projects in the ventricle (LV), while the
thick lower part makes the hippocampal gyrus (H). The concavity of
the upper bent part is provided by
the hippocampal fissure (HF); the
dentate gyrus (DG) is only a surface
prominence on the part. The fimbria
(F) is receiving fibres from the white
covering of the hippocampus, known
as the alveus (ALV). S, the tail of
caudate nucleus.
 
 
The hippocampal fissure is associated with an internal elevation—
namely, the hippocampus —on the wall of the descending cornu of the
 
lateral ventricle (Fig. 923). , ,
 
Gyrus Dentatus Fascia Dentata).— The gyrus dentatus is situated
 
above the hippocampal gyrus, and below the fimbria It is separated
 
from the hippocampal gyrus by the hippocampal fissure, and from
 
the fimbria by a slight groove, called the fimbno-dentate sulcus - The
 
dentate gyrus is narrow, and its free margin is indented or n ,
 
hence the name dentatus. It begins behind the splenium of the corpus
 
callosum, and is directed forwards above the hippocampal gyrus
 
 
 
 
 
 
 
i5io
 
 
A MANUAL OF ANATOMY
 
 
the curve of the uncus. Here it describes a bend, after which it
emerges from the curve of the uncus, and, crossing the recurved part,
is lost on its lateral aspect. This portion, the tail of the dentate gyrus ,
is often called the band of Giacomini.
 
Posteriorly it is continuous round the splenium with the rudimentary gyrus supracallosus, or indusium griseum, which contains the medial
and lateral longitudinal strice of one-half of the upper surface of the
corpus callosum.
 
Fimbria.—The fimbria is the prolongation of the posterior pillar of
the fornix. It is situated above the gyrus dentatus, from which it is
separated by the fimbrio-dentate sulcus. Posteriorly it turns upwards
round the posterior extremity of the thalamus, and so becomes
continuous with the posterior pillar of the fornix. Anteriorly it enters
the uncus. It receives fibres along its length from the dentate gyrus
and from the layer of white fibres ( alveus ) covering the ventricular
surface of the hippocampus.
 
Development of the Cerebral Hemispheres. —Each hemisphere is developed
from the wall of the cerebral vesicle, and is a hollow protrusion from the upper
and lateral part of the telencephalon, the anterior subdivision of the prosencephalon. The anterior wall of that portion of the telencephalon which lies
between the two cerebral vesicles is called the lamina terminalis.
 
The hemispheres grow out of proportion to the other parts of the encephalon
in a forward, upward, and backward direction. Their backward growth is
so great that they completely cover the other parts of the encephalon by the
seventh month of intra-uterine life.
 
The sulci and gyri of the hemispheres first appear about the fifth month of
intra-uterine life.
 
Development of the Insula and Lateral Fissure. —The insula, or island of
 
Reil, appears as the floor of a depression, called the lateral fossa, on the lateral
aspect of the cerebral vesicle. The wall of this fossa becomes developed into
the opercula insulce, and as these grow they cover the insula, and give rise to
the limbs of the fissure. The insula is the superficial surface of the mass of the
corpus striatum, which does not increase in surface area so quickly as the thin
walls of the pallium round it, whence it is overlapped by these walls, which
form the opercula.
 
Olfactory Lobe.
 
The olfactory formations, taken as a whole, are rudimentary in
man. Although they are developments of the cerebral vesicles (with
the exception of the olfactory nerves) they can be divided on each side
for descriptive purposes into [a) external, lying apparently on the
surface of the hemisphere-; and ( b ) internal, forming part of the hemisphere, on its medial aspect.
 
(a) The external formations comprise the olfactory bulb and tract,
with the dispositions of the ‘ roots ' or * olfactory striae 5 and of the
formations in their immediate neighbourhood.
 
The olfactory bulb is the enlarged anterior extremity of the olfactory
tract. It is oval, and its upper surface is in contact with the orbital
surface of the frontal lobe, whilst its lower surface rests upon one half
of the cribriform plate of the ethmoid bone. The lower surface receives
the olfactory nerves, which arise from the olfactory cells of the olfactory
 
 
THE NERVOUS SYSTEM
 
 
* 5*1
 
 
nucous membrane, and pass through the foramina of the cribriform
date.
 
The olfactory tract is a white band which extends backwards from
:he olfactory bulb, both of them occupying the olfactory sulcus on
the medial part of the orbital surface of the frontal lobe. Posteriorly it
divides into two roots, medial and lateral, which diverge and enclose
between them the trigonum olfactorium.
 
The medial root passes medially and upwards in a curved manner
to reach the subcallosal region. Some of its fibres pass into this area,
and others enter the anterior extremity
of the callosal gyrus.
 
The lateral root passes backwards
and laterally over the outer part of the
anterior perforated area, and enters
the anterior part of the hippocampal
gyrus.
 
The trigonum olfactorium is the area
of grey matter which lies between the
diverging medial and lateral roots of
the olfactory tract. It is sometimes
described as the middle or grey root of
the olfactory tract.
 
The anterior perforated substance
lies behind and between the diverging
roots of the olfactory tract, and is
limited behind and medially by the
diagonal band, frequently not very
well defined, which lies between it
and the optic tract. At its anterior
and medial end, where the olfactory
roots are beginning to diverge, there
may be a slight prominence, the olfactory tubercle. The perforations are
made by central branches of the anterior and middle cerebral arteries.
 
The olfactory tubercle is, when present at all, a very small elevation.
It represents the remnant of a large rounded mass which is found in
macrosmatic brains, receiving an intermediate tract from the olfactory
bulb.
 
The grey matter of the anterior perforated substance is continuous
superiorly with the grey matter of the lentiform and caudate nuclei.
 
Development. —The olfactory lobe is developed from the antero-inferior
part of the cerebral vesicle; an area is marked off by a groove, which deepens,
and the area, growing, thus becomes a protrusion. This protrusion becomes
solid, and gives rise to the olfactory tract and olfactory bulb.
 
Development of the Olfactory Apparatus.
 
This is developed in two parts—the olfactory lobe, and the olfactory epithelium. The olfactory lobe is intracranial, and is an outgrowth from the anterior
part of the ventral aspect or floor of the telencephalon, which is the anterior
 
 
 
Fig. 924. —Plan of Structures
Round Right Anterior Perforated Substance.
 
M, L, medial and lateral olfactory
roots; D, diagonal band; T, olfactory tubercle. Bulb and
tract are seen at B and TR.
 
 
 
1512
 
 
A MANUAL OF ANATOMY
 
 
subdivision of the prosencephalon or fore-brain. It constitutes the olfactorylobe (rhinencephalon) of the brain, and it becomes transformed into several
parts, which will presently be stated, its terminal portion being the olfactory
bulb, which rests upon one-half of the cribriform plate of the ethmoid bone.
 
The olfactory epithelium is intranasal, and occupies the upper part of the
nasal fossa of either side. It represents a neuro-epithelium, which is derived
from an invagination of the surface ectoderm. The axons of its sensory cells
constitute the olfactory nerve-filaments, which pass upwards through the foramina
of the cribriform plate, and enter the under surface of the olfactory bulb.
 
Olfactory Bulb. —The olfactory bulb appears as part of a hollow protrusion,
slowly lengthening, of the anterior cerebral vesicle on its ventral aspect, and near
its anterior part. The cavity of this protrusion, which is continuous with the
lateral ventricle, soon undergoes obliteration, and the protrusion becomes solid.
Its terminal extremity undergoes enlargement, and the entire protrusion becomes
differentiated into the following parts: (i) the olfactory bulb; (2) the olfactory
tract; (3) the inner or medial, and outer or lateral, olfactory roots; (4) the trigonum olfactorium. Of these parts, the olfactory bulb is the enlarged terminal
extremity of the original protrusion, and rests upon one-half of the cribriform
plate of the ethmoid bone, through the foramina of which half it receives the
olfactory filaments, which are the axons of the sensory cells of the olfactory
epithelium of the upper part of the nasal fossa.
 
Olfactory Epithelium. —The first indications of the olfactory organ are the
two olfactory or nasal areas. They consist of thickened ectoderm, and are
placed on the ventral aspect of the anterior cerebral vesicle on either side of the
medial nasal process of the fronto-nasal process, and on the cephalic side of the
orifice of the stomodaeum. Each olfactory area soon becomes depressed, and
lies in the olfactory or nasal pit. The formation of the olfactory pits has been
described on pp. 83 et seq.
 
The olfactory epithelium is deeply placed in the upper part of the nasal pit,
in the roof of which the cribriform plate of the ethmoid bone will develop.
The ectodermic cells of the upper part of the nasal pit constitute a neuroepithelium, and each cell is prolonged into a slender process, which is an axiscylinder process, or axon. These axons form the olfactory nerve-filaments,
which are non-medullated, and they are connected with the olfactory area of
the brain from an early stage. Within the olfactory bulb they break up into
arborizations, which intermingle with the arborizations of the mitral cells of
the bulb.
 
For the development of the organ of Jacobson and further details about
nasal fossae, see pp. 1360 et seq.
 
(b) Internal Formations—Rhinencephalon.—The rhinencephalon is
that part of the cerebral hemisphere which receives and relays olfactory
impulses which have been transmitted to it through the olfactory roots.
It is feebly developed in man. It includes (Fig. 925) the formations
which make a ring round the passage into the cerebral vesicle, a ring
which is closed in front by the olfactory roots. They are the uncus
and caput hippocampi, the dentate gyrus, fimbria and fornix, and probably a large part of the hippocampal gyrus; the hippocampus (in the
ventricle), and the continuity (fasciola cinerea or splenial gyrus) between the hippocampal and dentate formations and the indusium
griseum, is carried over the front of the corpus callosum to join the
subcallosal region. The medial olfactory root reaches the subcallosal
region, the lateral root reaches the uncus, and the diagonal band
stretches also between these two parts. All the.se structures are thus
included in the rhinencephalon, and to them can be added the septum
lucidum and the anterior commissure.
 
 
 
THE NERVOUS SYSTEM
 
 
1513
 
 
Many of these formations have been described (p. 1507) already;
others will be described in their proper place, and the developmental
aspect of the part will also be considered.
 
Morphologically considered, the cerebral hemisphere is composed of three
parts—namely, the stem, rhinopallium, and neopallium. The stem or stalk is
formed by the corpus striatum; the rhinopallium consists of the parts which
compose the rhinencephalon; and the neopallium represents the remainder of
the hemisphere.
 
Corpus Callosum.—The corpus callosum is the great neopallial commissure, and connects the two cerebral hemispheres. It is situated
at the bottom of the great longitudinal fissure, and extends nearer to
the front than back of the hemispheres. It is arched and thicker in
front and behind than at the centre, its greatest thickness being
posteriorly , where more fibres cross in it than elsewhere, on account of
there being more of the hemisphere behind it than in front of it.
 
 
 
F IG . 925.— Plan of the Structures constituting the Rhinencephalon.
 
 
The superior surface is related to the falx cerebri, but is in contact
nth it only posteriorly. It is covered by a thin layer th ’
 
nd presents a transversely striated appearance, ind:icatv
iirection of its fibres. In the median line there s a slight antero
losterior furrow or raphd, and on either side of this there 1 . s l % T
ongitudinal band, called the stria longitudinalis medialis. ,Tf „s the
nd left striae longitudinales mediales are sometimes spoken of as the
 
Lateral to each medial stmi and si uated under
over of the callosal gyrus, there is another band, composed g V
 
natter called the stria longitudinalis lateralis. . ,
 
The strifof each side are lying in the grey layer alreadymentioned,
 
.nd may be traced postenorly round ^ ' s dentatus.
 
mown as fasciola cmerea, into the .f^rrespona b gy , it
 
interiorly each medial stria, along with the grey matter ^
ies, passes round the genu and backwards on t
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1514
 
 
A MANUAL OF ANATOMY
 
 
rostrum under the name of the geniculate gyrus. This enters the subcallosal gyrus, and finally passes to the temporal pole.
 
The medial and lateral longitudinal striae of each side, together with the thin
layer of grey matter, represent a rudimentary convolution of the rhinencephalon
called the supracallosal gyrus. The grey matter in the human brain is termed
 
the indusium griseum.
 
The posterior extremity of the corpus callosum is called the splenium,
and is rolled upon itself, so that its lower part is directed forwards and
lies over the mesencephalon and pineal body.
 
 
Great Longitudinal Fissure
 
Forceps Minor • Ganu of Corpus Callosum
 
 
 
Median Raph£
 
Stria
 
_ Longitudinalis
 
ijffljjjjfo Mesialis
 
Stria
 
. Longitudinalis
Lateralis
 
 
Tapeturri
F orceps
 
 
Splenium of Corpus
Callosum
 
 
Great Longitudinal Fissure
 
Fig. 926. —The Corpus Callosum (Superior View) (Hirschfeld
 
and Leveill£).
 
 
Anteriorly the corpus callosum is bent upon itself, and passes at !
first downwards and then backwards. The bent portion is called the
genu, and the portion which passes backwards the rostrum. The
rostrum ends by joining the lamina terminalis in the mid-line, and on
either side it passes into the so-called peduncles of the corpus callosum ,
otherwise known as the subcallosal gyri. Each subcallosal gyrus, with
the contained stria longitudinalis medialis, passes downwards on the
internal surface of the cerebral hemisphere to become continuous with
the anterior perforated substance, lying in front of the lateral portion of
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
*515
 
:he lamina terminalis. The gyrus then passes backwards and outwards
ilong the posterior margin of the perforated area, forming now the
liagonal band, and so reaches the temporal pole.
 
The inferior surface of the corpus callosum is divisible into a medial
md two lateral portions. The medial portion is connected posteriorly
with the fornix, and over the remainder of its extent with the septum
Aicidum. Each lateral portion enters into the roof of the body and
interior horn of the corresponding lateral ventricle (see Fig. 930).
 
Destination of the Callosal Fibres.—The transverse fibres of the
corpus callosum, on entering the white medullary substance of each
cerebral hemisphere, traverse it in a radiating manner as they pass
 
 
Corpus Callosum
 
Pineal Botly _ -'v^'f
 
Splenium v
 
 
Anterior Pillar of Fornix
Septum Luciuum
 
 
Genu passing into
Rostrum
 
■UU -V l X
 
X A 4
 
 
Corpora
 
Quadri
gemina
 
 
 
Cerebellum
 
 
Fourth Ventricle
 
 
Crus Cerebri
/ j \ Aqueduct
 
Medulla Oblongata
 
 
Fig. 927. —The Medial Surface of the Left Cerebral Hemisphere
 
(Hirschfeld and Leveille;).
 
 
to the cerebral cortex. They constitute the radiatio corporis callcsi,
and intersect in their course the fibres which pass between the internal
capsule and the cerebral cortex, which form the corona radiata. The
fibres from the central portion or body and upper part of the splenium
of the corpus callosum constitute the tapetum. This forms the roof
of the body of the lateral ventricle, the chief part of the roof, and the
outer wall of the commencement of the middle or descending horn, and
the roof and outer wall of the posterior horn. Most of the fibres of the
tapetum ultimately pass into the temporal and occipital lobes. The
fibres from the region of the genu curve forwards into the front part
of the frontal lobe, and form the roof of the anterior horn of the lateral
ventricle. They constitute the forceps minor . The fibres from the
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1516
 
lower part of the splenium curve backwards into the occipital lobe,
and give rise to an eminence on the inner wall of the posterior horn
of the lateral ventricle. They constitute the forceps major.
 
Development. —The corpus callosum is developed fro m the lamina terminalis,
but extends beyond this. It is the commissure of the neopallium.
 
Fornix.—This is an arched lamina of white longitudinal fibres
which lies beneath the corpus callosum, with which it is connected
posteriorly, but from which it is separated anteriorly by the septum
lucidum. It is composed of two lateral halves, which are united
together in the median line to form the body of the fornix; but in
front and behind they are separated from each other, and form the
anterior and posterior pillars. The fornix is thus composed of a body,
two anterior pillars, and two posterior pillars (Fig. 928).
 
 
 
%
 
Gyrus Dentatus
 
Fig. 928.—The Medial Surface of the Right Cerebral Hemisphere
 
(Hirschfeld and Leveille).
 
The body is triangular, being narrow in front, where it is continuous with the anterior pillars, and broad behind, where it is prolonged
into the posterior pillars. The superior surface of the body is connected
posteriorly with the corpus callosum, and anteriorly with septum
lucidum. Each lateral border is well defined, and projects slightly
into the lateral ventricle. The inferior surface rests directly upon the
tela chorioidea, beneath which, in the median line, is the third ventricle,
and on either side the upper surface of the thalamus.
 
The anterior pillars are two round bundles, which are continuous
with the anterior part of the body, and are slightly separated from
each other. They pass downwards in front of the interventricular
foramina, traversing the grey matter on the sides of the third ventricle.
On reaching the base of the brain each pillar becomes twisted in the
form of a loop, and forms the white portion of the corresponding
corpus mamillare. The fibres of the anterior pillar terminate in the
grey nucleus of the corpus, and from this nucleus a bundle of fibres,
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1517
 
 
called the mamillo-thalamic tract, or bundle of Vicq d’Azyr, passes
upwards and backwards into the thalamus.
 
The anterior pillars lie behind the anterior commissure, but give
off a few precommissural fibres which, passing down in front of the
 
 
Fig.
 
 
 
>29> _Part of Corpus Callosum cut away to expose Fornix and
 
Right Ventricle.
 
Inferior and posterior horns also opened from above.
 
 
Choroid Plexus
Corp. Call.
Fornix
 
 
Tail of Caudate
Nucleus
Hippocampus
 
 
Collateral Trigone
Bulb
 
Calcar Avis
 
 
commissure, reach the anterior perforated substance and subcallosal
 
^ The posterior pillars are prolongations of the posterior part
the body on either side. They are flattened bands, which at firs
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1518
 
adhere to the under surface of the corpus callosum. Subsequently,
however, each curves laterally and downwards round the posterior
extremity of the thalamus, and enters the descending horn of the
lateral ventricle. Here the posterior pillar comes into contact with
the hippocampus, upon the surface of which some of its fibres become
spread out, forming the alveus. The rest of the fibres are prolonged
as a narrow band of white matter, called the fimbria, or tcmia hippocampi , along the concave border of the hippocampus, to which it is
attached, as far as the uncus (see Fig. 929)* As the two posterior
pillars diverge from each other they enclose between them a small
triangular space on the under surface of the corpus callosum posteriorly.
This space is crossed by transverse fibres, and is known as the lyra,
from its supposed resemblance to a lyre. The transverse fibres form
a commissure between the two hippocampi, and the lyra is therefore
known as the hippocampal commissure. Each lateral half of the
fornix establishes a communication between the hippocampus, in
which the majority of its fibres originate, and the thalamus of’the
same side by means of the anterior pillar, the corpus mamillare, and
the bundle of Vicq d’Azyr (mamillo-thalamic tract).
 
Development.— The fornix is developed from the lamina terminalis.
 
Anterior Commissure.—This is a round bundle of white fibres
which crosses the middle line immediately in front of the anterior
pillars of the fornix. Anteriorly its central portion is connected
with the lamina terminalis (Fig. 930), and posteriorly the central
portion appears between the anterior pillars of the fornix, where it
forms part of the anterior boundary of the third ventricle, and is
covered by the ventricular ependyma. On either side the commissure
enters the cerebral hemisphere, and divides into two parts, olfactory
and temporal. The olfactory portion is of small size, and enters the
coi responding olfactory tract. Some of its fibres serve to connect
the olfactory bulb of one side with that of the other side. The
other fibres connect the olfactory bulb of one side with the temporal lobe of the opposite side. The temporal portion is of large
 
size, and its fibres disappear in the white matter of the temporal
lobe.
 
The anterior commissure, therefore, serves to connect the olfactory
bulbs and the temporal lobes.
 
Septum Lucidum.— This is a thin vertical partition which is situated between the anterior horns of the lateral ventricles, as well as
between the front parts of the bodies of these ventricles. It is
triangular, being broad in front and narrow behind. Posteriorly
it is attached above to the under surface of the corpus callosum,
and below to the upper surface of the body of the fornix. Anteriorly
it occupies the concavity behind the genu of the corpus callosum,
being attached above to the corpus callosum and below to the rostrum
of that body. It is seen in section in the first figure in Fig. 930.
The septum lucidum is composed of two delicate laminae. The lateral
 
 
THE NERVOUS SYSTEM
 
 
1519
 
 
surface of each lamina looks into the corresponding lateral ventricle,
and is covered by the ventricular ependyma (epithelium). The medial
 
 
 
Corp. Call. r
 
 
Caud. N. and
Int. Capsule
 
 
Rostrum i*
 
 
 
Ext .Caps, and
Claustrum
 
Fornix *
 
 
Ant. Comm.
 
 
Fig. 930.
 
The upper section is through the anterior horn, cutting the body and rostrum of
corpus callosum. The lower section is through the lamina terminalis and
anterior commissure, and has cut tangential slips from the anterior pillars
of fornix.
 
 
surface faces that of its fellow, a narrow lymph space, formerly called
the fifth ventricle, but now the cavity of the septum lucidum, intervening between the two. Each lamina consists of white matter, which
 
 
 
 
 
 
 
 
 
1520
 
 
A MANUAL OF ANATOMY
 
 
is covered by grey matter on the surface looking towards the fifth
ventricle.
 
The two laminas are formed from portions of the medial wall of the two
cerebral hemispheres, which have become detached in the course of the development of the corpus callosum and fornix.
 
Cavity of the septum lucidum, formerly known as the fifth ventricle,
is the narrow cleft-like interval between the two laminae of the septum
lucidum. It is a closed space, and has therefore no communication
with the other ventricles. It is destitute of any ependymal lining,
and contains a very little fluid.
 
 
Caudate Nucleus-.—
 
 
Internal Cerebral Vein
 
 
Vein of Corpus Striatu
Choroid Vein ^
 
 
Choroid Plexus J
entering Descending Horn of
Lateral Ventricle
 
 
 
Septum Lucidum
 
Space in Septum
Fornix
 
 
Tela Chorioidea
 
 
Vena Magna Cerebri
 
 
' Lyra
 
Anterior Pillar of Fornix
 
Fig. 931. —The Tela Chorioidea and Internal Cerebral Veins.
 
 
As regards development, it differs from the true ventricles in being
originally a part of the great longitudinal fissure.
 
Tela Chorioidea.—This is also known as the tela chorioidea superior,
in contradistinction to the tela chorioidea inferior, which is the pia
mater forming the roof of the lower part of the fourth ventricle. It
lies immediately beneath the fornix, and rests upon the ependymal
roof of the third ventricle, and also upon the adjacent portions of
the thalami (Fig. 932). It consists of two layers of pia mater, and is
triangular, the apex being situated behind the anterior pillars of the
fornix at the interventricular foramina and the base lying beneath
the splenium of the corpus callosum. In the latter situation the two
layers of the tela become continuous with the pia mater, which has
entered through the transverse fissure, situated between the splenium
 
 
/
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1521
 
 
>f the corpus callosum and the corpora quadrigemina. On either
ide the tela chorioidea projects beyond the lateral border of the
ornix, and appears as a vascular fringe in the lateral ventricle, where
t is covered by the ventricular ependyma. This fringe is known as
he choroid plexus of the lateral ventricle. Posteriorly it is prolonged
nto the descending cornu. Anteriorly it approaches its fellow of the
>pposite side, and the two unite in the median line behind the interventricular foramina. From this junction two other choroid plexuses
extend backwards on the inferior surface of the velum interposi;um, one on either side of the median line. They form the choroid
plexuses of the third ventricle, and lie superficial to the ependymal
•oof of the cavity. The choroid
dexuses are composed of a
lighly vascular villous arrangenent of the pi a mater, and are
:he structures which secrete
the cerebro-spinal fluid.
 
The principal veins in connection with the velum interpositum are the two choroid
veins and the two internal
:erebral veins. The choroid
vein of each side is situated in
the choroid plexus of the lateral
ventricle. It passes forwards
md inwards to a point behind
the corresponding foramen,
where it joins the vein of the
corpus striatum, which lies between the thalamus and the corpus striatum. In this manner the
 
internal cerebral vein of one side is formed.
 
The internal cerebral veins (or veins of Galen) are right and left.
Each is formed by the union between the choroid vein, the vein of
the corpus striatum, and the vein of the septum lucidum, behind the
corresponding interventricular foramen. The two veins pass backwards within the tela chorioidea, one on either side of the median line.
At first they are near each other; then they diverge; but subsequently
they come together again and unite to form one vessel, called the
vena magna cerebri, which opens into the anterior extremity of the
straight sinus. Each vein receives numerous tiibutaries from the
corresponding choroid plexus of the third ventricle, the thalamus,
corpus callosum, corpora quadrigemina, and pineal body. Near its
termination it is joined by the large basilar vein, which is formed at
the anterior perforated area by the union of the anterior cerebral
vein with the deep middle cerebral vein. The vena magna receives
tributaries from the upper surface of the cerebellum and from the
occipital lobes of the cerebral hemispheres.
 
 
 
Fig. 932.—Schematic Section to show
Disposition of Tela Chorioidea,
(T.C.).
 
LV, lateral ventricle; F, F, fornix; CN,
caudate nucleus; IC, internal capsule.
 
 
96
 
 
 
 
 
 
 
I 5 22
 
 
A MANUAL OF ANATOMY
 
 
Lateral Ventricles.
 
The lateral ventricles are cavities in the right and left cerebral
hemispheres. They are of irregular shape, and each is about twothirds of the length of the corresponding hemisphere. They are
lined with ependyma (epithelium), and contain cerebro-spinal fluid,
Each ventricle communicates with the third ventricle by the interventricular foramen, which is situated between the anterior pillar
 
 
Genu of
 
Corpus Callosum
 
 
Caudate Nucleus
 
 
Interventricular
 
Foramen
 
 
Stria Semicircularis
 
 
Thalamus
 
 
Choroid Plexus of
Central Part of
Late al Ventricle
 
 
Choroid Plexus of
Inferior Horn
 
 
Calcar Avis
 
 
Bulb of Posterior Horn
(due to Fibres of the
Forceps Major)
 
 
 
Anterior Horn of Lateral
Ventricle
 
 
Cavity of Septum
Lucidum
 
 
Posterior Pillai
of Fornix
Hippocampus
 
 
Great Cerebral
Vein
 
 
Posterior Horn of
Lateral Ventricle
 
 
Cerebellum
 
Fig. 933.— The Lateral Ventricles of the Cerebrum (after
 
Rirschfeld and Leveille).
 
 
of the fornix and the front part of the thalamus. The lateral ventricle
of either side consists of a body or central part and three horns—
anterior, middle or descending, and posterior.
 
The central part extends from the foramen to the level of the
splenium of the corpus callosum. The anterior horn is situated in
front of the foramen, and curves forwards and laterally into the
frontal lobe. The inferior horn enters the temporal lobe, and describes
a remarkable curve as it sweeps round the posterior extremity
of the thalamus. Its direction is backwards, laterally downwards ,
 
 
/
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1523
 
 
mvards, and finally medially to a point about 1 inch from the temporal
ole. The posterior horn curves backwards and laterally, and then
ackwards and medially into the occipital lobe.
 
The central part of the lateral ventricle has a roof, a medial wall,
nd a floor. The roof is formed by the corpus callosum (tapetum).
'he medial wall is formed by the posterior part of the septum lucidum,
nd, behind this, by the attachment of the body of the fornix to
tie under surface of the corpus callosum. Laterally the cavity is
mited by the meeting of the roof and floor. The floor presents
he following structures, in order from within outwards: (1) the
harp lateral border of the fornix; (2) the choroid plexus of the
 
 
Third Ventricle
 
 
- Anterior Horn
 
 
 
Descending Horn
 
 
Suprapineal Recess
 
 
Fourth Ventricle
 
Lateral Recess of
Fourth Ventricle
 
Impression for Bulb
of Posterior Horn
 
Posterior Horn
 
 
Fig. 934. —Drawing of a Metal Cast of the Ventricles of the
Brain of an Adult (Superior View) (Retzius).
 
 
ateral ventricle; (3) a portion of the upper surface of the thalamus,
covered by ependyma of ventricle; (4) an oblique groove, extending
orwards and inwards between the thalamus and caudate nucleus,
n which there are (a) a white band, called the stria semicircularis,
ind (b) the vein of the corpus striatum; and (5) the narrow part of
:he nucleus caudatus of the corpus striatum.
 
The anterior horn is compressed from side to side; its roof is formed
iy the forceps minor of the corpus callosum; its lateral wall by the
lead of the caudate nucleus, round which the cavity is moulding
tself; its inner wall by the septum lucidum; and its floor by the
neeting of the outer and inner walls.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
^524
 
 
A MANUAL OF ANATOMY
 
 
The posterior horn has its roof and lateral wall formed by th
tapetum of the corpus callosum. The medial wall presents tw
elongated curved eminences, upper and lower. The upper eminenc
is made by the fibres of the forceps major as they sweep backward
from the lower part of the splenium of the corpus callosum to th
occipital lobe. It is called the bulb of the posterior horn. The lowe
eminence is called the calcar avis, and is invaginated by the precalcarin
fissure on the medial surface of the cerebral hemisphere.
 
The inferior or descending horn is situated in the temporal lobe
The roof is formed chiefly by the tapetum of the corpus callosum
 
 
 
Trigonum Ventriculi-^
 
 
Bulb of Posterior Horn
 
 
Posterior Horn
 
 
Inferior Horn
Hippocampus
 
 
Pes Hippocampi
Uncus
 
Gyrus Dentatus
Hippocampal Gyrus
 
- Fimbria
 
Posterior Pillar of Fornix
Splenium
 
 
Calcar Avis
 
 
Fig. 935. —The Inferior and Posterior Horns of the Left Lateral
Ventricle (after Hirschfeld and Leveili.e).
 
 
The inferior cornu has been laid open throughout its entire extent.
 
 
and at its anterior end presents the amygdaloid tubercle, which is produced by a collection of grey matter, called the amygdaloid nucleus. The
narrow part or tail of the nucleus caudatus and the taenia semicircularis
are prolonged into the roof, and extend in it as far as the amygdaloid
nucleus, The floor of the descending horn presents the following
structures: (1) the hippocampus; (2) the fimbria; (3) the trigonum
collaterals; and (4) the choroid plexus of the descending horn. The
hippocampus is a prominent curved elevation which traverses the
entire length of the descending cornu, accurately adapting itself to its
curves. It enlarges as it descends, and beneath the amygdaloid
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
i 5 2 5
 
 
ubercle it terminates in a swelling, which is notched on the surface,
'his swelling is called the pes hippocampi.
 
The hippocampus is invaginated by the dentate or hippocampal
ssure on the medial surface of the cerebral hemisphere (see Fig. 923).
 
The fimbria is the continuation of the posterior pillar of the fornix,
t lies along the inner concave border of the hippocampus, to which
t is attached, and it is composed of white fibres, some of which form
he layer on the surface of the hippocampus, called the alveus.
 
The trigonum collaterals is an elevation which is situated in the
,ngle between the descending and posterior horns, where there is a
mall triangular space, called the trigonum ventriculi. It extends backyards into the posterior horn, and for a variable distance into the
lescending cornu.
 
 
 
Fig. qs6._Plan of Relations to Choroidal Fissure and to Each Other
 
of Structures found in Lateral Ventricle.
 
 
H, hippocampus;
 
 
B, bulb of posterior horn; C.A., calcar avis; C.T., collateral
 
trigone.
 
 
The trigonum collaterals is produced by the central portion of the
'ollateral fissure on the tentorial surface of the cerebial hemisp eie.
 
The choroid plexus of the descending horn rests upon the surface
jf the hippocampus, and is continuous with that of the body of the
ateral ventricle It is covered by the ependyma of the medial wall
jf the descending cornu, which it mvagmates. When the choroid
Dlexus is removed its ependymal covering comes away along with it,
md the choroidal fissure then becomes apparent.
 
The choroidal fissure is situated between the fimbria and the roof
3 f the descending cornu, and, curving round the back part of the
:halamus, it is traceable as far forwards as the mterventncular foramen
if the same side. In the other direction it extends to the lower ex
tremity of the inferior cornu.
 
 
 
 
 
 
 
1526
 
 
A MANUAL OF ANATOMY
 
 
It is produced by an infolding or invagination of the epithelia
medial wall of the cerebral vesicle of one side over the choroid plexus
of the descending horn of the lateral ventricle. On either side it is
continuous with the lateral and lower part of the transverse fissure.
 
When the choroid plexus is withdrawn from the descending horr
of the lateral ventricle the epithelial or ependymal covering of the
plexus comes away with it, or is broken down. Under these circumstances the descending horn opens freely upon the exterior.
 
Development. —The lateral ventricles represent the cavities of the primitive
cerebral vesicles. The choroidal fissure is developed as an invagination of the
medial wall of the cerebral vesicle; and the choroid plexus is developed from
a growth of mesoblast into the choroidal fissure.
 
 
Basal Ganglia of the Cerebral Hemispheres.
 
The basal ganglia of each cerebral hemisphere are the nucleus
caudatus and nucleus lentiformis of the corpus striatum, the claustrum,
and the amygdaloid nucleus.
 
The corpus striatum is a large ovoid mass, which is situated in front,
and on the outer side of the thalamus. It is composed of two collections of grey matter, one of which is intraventricular and the other
extraventricular. The intraventricular portion is called the nucleus
caudatus. The extraventricular portion is embedded in the white matter
of the cerebral hemisphere, and is termed the nucleus lentiformis.
Between these two nuclei there is a part of the thick tract of white
fibres which constitutes the internal capsule ; and on the outer side of
the nucleus lentiformis there is the thin lamina of white matter, called
the external capsule. When a coronal section is made through the
corpus striatum on a level with the anterior part of the nucleus lentiformis (see Fig. 939), the white matter of the front part of the internal
capsule is seen to be intersected by striae of grey matter which pass
between the nucleus caudatus and nucleus lentiformis. From the
striped appearance thus produced the body has received the name of
corpus striatum.
 
The nucleus caudatus is pyriform. The large round end is directed
forwards, and projects into the anterior horn of the lateral ventricle.
The narrow portion is directed laterally and backwards in the floor of
the central part of the lateral ventricle, where it lies lateral to the
thalamus, from which it is separated by the stria semicircularis. Its
tapering tail is continued into the roof of the descending horn of the
lateral ventricle, and is prolonged in the roof as far as the amygdaloid
nucleus, in which it terminates. The nucleus caudatus is composed
of grey matter, and its cells are of the multipolar variety.
 
The nucleus lentiformis is embedded in the white matter of the
cerebral hemisphere, and lies on the outer side of the nucleus caudatus
and thalamus, from both of which it is separated by the internal
capsule. It is of more limited extent than the nucleus caudatus, and
receives its name from the fact that in certain sections it has the
 
 
THE NERVOUS SYSTEM
 
 
1527
 
 
Lppearance of a biconvex lens, the broadest part being on a level
vith the front of the thalamus. Anteriorly it is closely related to
he front part of the nucleus caudatus, being continuous with it ineriorly, and connected with it superiorly by striae of grey matter which
ntersect the white matter of the front part of the internal capsule.
 
 
Great Longitudinal Fissure
 
 
 
Genu of Corpus Callosum
 
 
Anterior Horn of Latera
Ventricle
 
Caudate Nucleus
 
Cavity of the Septum
 
Anterior Pillars of Fornix
Ant. Tub. of Thalamus
Stria Semicircularis
. Connexus Thalami
 
~ Tasnia Thalami
Third Ventricle
 
-Posterior Commissure
 
-Vn \
 
^ Y\“V~ Habenular Commissure
 
.xV'' A.
 
 
Thalamic Groove for
Margin of Fornix
 
 
Trigorium Habenulae
 
Lower Quadrigeminal Body
 
 
' Pulvinar of Thalamus
'y v ’Pineal Body
 
\ ''Superior Peduncle of Cerebellum
 
Upper Quadrigeminal Body
 
ig. 937 ._The Third Ventricle, Portions of the Lateral Ventricles,
Pineal Body, and Corpora Quadrigemina (Superior View) (Henle).
 
The‘corpus callosum, fornix, and tela chorioidea have been removed.
 
Vhen either a horizontal or a coronal section is made through the centre
he nucleus has a triangular outline, the base being directed towards the
nsular surface; it is, therefore, clear that the nucleus is rea y a PJ 1 ^ 1 j
ying on its side with the base outwards, m contact with the external
:apsule, while above, behind, and in front the wa Is are surrou
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1528
 
 
A MANUAL OF ANATOMY
 
 
by the internal capsule. Below lies the anterior commissure and the
temporal lobe. In such a section the nucleus is seen to be traversed
vertically by two white bands, called the medullary lamina, which
divide it into three zones. The outer zone, which has a dark reddish
colour, is the largest, and is called the putamen. The inner two zones,
which are somewhat yellowish, are together known as the globus
pallidus. The putamen and globus pallidus, which consist of grey
matter, are traversed by white fibres.
 
The grey matter of the nucleus caudatus and nucleus lentiformis
comes to the surface at the base of the brain in the region of the anterior
 
 
 
Entrance to Descending Horn Hippocampus
 
of Lateral Ventricle
 
Fig. 938. Horizontal Section of the Brain through the Genu
AND SPLENIUM OF THE CORPUS CALLOSUM (DALTON).
 
perforated substance, where it is continuous with the grey matter of the
cerebral cortex.
 
The internal capsule is the thick tract of white matter which lies
between the nucleus lentiformis externally, and the nucleus caudatus,
stria semicircularis, and thalamus internally. As seen in horizontal
section it describes the bend opposite the front part of the thalamus
(see Fig. 938). This bend is called the genu, and its convexity
is directed inwards. The part of the internal capsule in front
of the genu is called the anterior limb. It forms about one-third of
the entire capsule, and its direction is forwards and outwards. The
part behind the genu is called the posterior limb. It forms about
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1529
 
 
two-thirds of the entire capsule, and its direction is backwards and
outwards.
 
The anterior limb of the internal capsule is situated between the
front part of the nucleus lentiformis and the nucleus caudatus. Anteriorly it is intersected by the striae of grey matter which pass between
the two nuclei.
 
The fibres which compose the anterior limb are partly corticipetal
and partly corticifugal. The corticipetal fibres are as follows: (1)
thalamo-frontal fibres, which pass from the thalamus to the cortex
of the frontal lobe; (2) thalamo-striate fibres, which pass from the
thalamus to the corpus striatum (thalamo-caudate and thalamo
 
Great Longitudinal Fissure c ~
 
, Genu of Corpus Callosum
 
Cavity of Septum Lucidum \ -—■" - 1 ■— L
 
 
Anterior Horn of
Lateral Ventricle
 
 
Left Anterior
Pillar of Fornix
 
 
Connexus- _
Thalami
 
 
Third Ventricle
 
 
Caudate Nucleus
 
 
Thalamus
 
Internal Capsule
 
 
 
- External Capsule
 
 
Claustrum
 
 
—=3 Grey Matter of
Insula
 
 
White Matter of
Insula
 
 
Optic Tract (cut)
 
 
Infundibulum
 
 
Lentiform Nucleus
 
 
Fig. 939. —Coronal Section of the Frontal Portions of the Cerebral
Hemispheres passing through the Anterior Horns of the Lateral
Ventricles (Posterior View).
 
1, putamen of lentiform nucleus; 2, 3, globus pallidus of lentiform nucleus.
 
 
lenticular fibres); and (3) strio-frontal fibres, which pass from the corpus
striatum to the cortex of the frontal lobe.
 
The chief corticifugal fibres constitute the fronto-pontine tract.
The fibres of this tract arise in the cortex of the prefrontal region.
They traverse the anterior limb of the internal capsule, and then
descend in the inner part of the basis pedunculi of the crus cerebri to
the pons, within which they terminate in connection with the cells of
 
the nucleus pontis. .
 
Other corticifugal fibres constitute fronto-thalamic , fronto-striate,
 
and strio-thalamic tracts. .
 
The posterior limb of the internal capsule is situated between the
back part of the nucleus lentiformis and the thalamus, and is pro
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1530
 
 
A MANUAL OF ANATOMY
 
 
longed backwards for a little beyond the posterior limit of the
nucleus lentiformis. It is therefore conveniently divided into two
parts—lenticular, representing the anterior two-thirds; and postlenticular, representing the posterior third.
 
The lenticular part of the posterior limb, like the anterior limb, is
composed of centripetal and centrifugal fibres. The corticipetal fibres
arise in the thalamus, and their destination is the cerebral cortex.
The corticifugal fibres represent the pyramidal or motor fibres , and they
 
 
 
Corpus Callosum
 
 
- Ant. Horn and Head
 
of Caudate Nerve
•••• Internal Capsule
 
External Capsule
---• Claus trum
■ -* Putamen
 
-• Globus Pallidus
... Thalamus
 
 
... Internal Capsule
..... Caudate Nucleus’ Tail
 
 
-Posterior Horn
 
 
Optic Radiation
 
 
Fig. 940.—Horizontal Section through Right Hemisphere, showing
Disposition of Corpus Striatum, etc.
 
 
occupy the anterior portion of the lenticular part of the posterior limb
of the internal capsule. These fibres descend from the central region
of the cerebral cortex. Some of them pass to the nucleus of the facial
nerve; others pass to the nucleus of the hypoglossal nerve; but the
majority of them are destined for the motor cells in the anterior grey
column of the spinal cord. The fibres which pass to the facial nucleus
lie close to the genu, and those which pass to the hypoglossal nucleus
lie close behind the facial fibres. The fibres of the pyramidal tract
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1531
 
 
FP
 
 
CAUD.
HA. '
 
 
occupy the central portion of the crusta of the crus cerebri in their
downward course.
 
The postlenticular part of the posterior limb contains the following
sets of fibres: (1) the fibres of the optic radiation on their way
from and to the thalamus, lateral geniculate body, and superior
quadrigeminal body; (2) the fibres of the auditory radiation, passing
between the auditory region of
the temporal lobe and the medial
geniculate body; and (3) the fibres
of the temporo-pontine tract (cortico-protuberantial fibres), which
pass from the cortex of the temporal lobe through the outer part
of the basis pedunculi to the
pons, where they terminate in the
nucleus pontis. The internal capsule is continuous inferiorly with
the crusta or basis of the crus
cerebri. Superiorly its fibres diverge in a radiating manner on
their way to the cerebral cortex,
forming the corona radiata, the
fibres of which are intersected by
those of the radiatio corporis
callosi.
 
The external capsule is a thin
lamina of white matter which is
situated on the outer side of the
nucleus lentiformis, where it lies
between that nucleus and the
claustrum. In front of and behind the nucleus lentiformis it is continuous with the internal capsule. The external capsule is, as stated,
only loosely connected with the putamen of the nucleus lentiformis.
The fibres of which it is composed are probably derived from the
anterior white commissure and the thalamus.
 
 
 
A UD .
 
 
Fig. 941.— Plan of Internal Capsule in Horizontal Section, to
show Positions of Main Fibretracts.
 
FP, fronto-pontine; T, thalamo-cortical; CR, motor for head and neck;
A, for arm; L, for leg; S, sensory
from thalamus; OPT, AUD, optic
and auditory fibres.
 
 
Connections of the Corpus Striatum. —(1) The nucleus caudatus and nucleus
lentiformis are partly continuous with each other, and partly connected by
stria of grey matter. (2) The corpus striatum is connected with the thalamus
by strio-thalamic and thalamo-striate fibres. (3) The nucleus caudatus is
said to be connected with the substantia nigra by a tract of fibres known
as the stratum intermedium. (4) The nucleus lentiformis is connected with the
thalamus by the ansa lenticularis. (5) The corpus striatum is connected with
 
the cerebral cortex by cortico-striate fibres. .
Development. _The corpus striatum is developed as a thickening of the floor
 
and outer wall of the cerebral vesicle.
 
t
 
The claustrum is a thin lamina of grey matter which is situated on
the outer surface of the external capsule. It lies embedded in the
white matter which occupies the region between the lentiform nucleus
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1532
 
 
A MANUAL OF ANATOMY
 
 
and the insula. Superiorly it is narrow and tapering, but interiorly it
expands and reaches the surface at the base of the brain in the region
of the anterior perforated substance. Its outer surface presents elevations and intervening depressions, which correspond to the sulci and
gyri of the insula.
 
The claustrum is regarded as an isolated portion of the grey matter
of the insula.
 
The amygdaloid nucleus is an oval collection of grey matter which
is situated in the anterior part of the temporal lobe, where it lies in
the roof of the extremity of the inferior horn of the lateral ventricle.
The putamen of the nucleus lentiformis lies above it; anteriorly it is
continuous with the cerebral cortex; posteriorly it receives the narrow
 
 
 
Subthal. N. and.
Caudate Tail
 
 
Dentate Gyrus
 
 
Hippocampal
 
Gyrus
 
 
Fig. 942. —Transverse Section across Cerebrum.
 
part or tail of the nucleus caudatus; and the stria semicircularis arises
from it.
 
The stria semicircularis is a narrow white band of fibres arising from
the amygdaloid nucleus. It passes backwards in the roof of the
descending horn of the lateral ventricle, and then sweeps upwards and
forwards into the central part of the lateral ventricle, lying between
the nucleus caudatus and the thalamus. Anteriorly in the region
of the interventricular foramen it dips downwards towards the anterior
pillar of the fornix and the anterior white commissure. In this situation its fibres are variously disposed. Some pass into the anterior
pillar of the fornix; others pass in front of the anterior commissure,
and enter the grey matter between the head of the nucleus caudatus and
the septum lucidum; whilst a few are regarded as entering the nucleus
caudatus.
 
 
 
THE NERVOUS SYSTEM
 
 
1533
 
 
Relation of Structures in the Region of the Corpus Striatum.—
 
When a coronal section has been made the relation of structures, from
within outwards, is as follows (see Fig. 942):
 
 
1. Nucleus caudatus.
 
2. Internal capsule.
 
3. Nucleus lentiformis.
 
 
4. External capsule.
 
5. Claustrum.
 
6. Insular cortex.
 
 
THIRD VENTRICLE.
 
The third ventricle is the cleft-like interval which is situated in
the median line between the two thalami. It extends from the
pineal body posteriorly to the anterior pillars of the fornix in front,
is very narrow from side to side, and is deeper in front than behind.
The cavity presents a roof, a floor, two lateral walls, an anterior boundary, and a posterior boundary.
 
The roof is formed by a delicate layer of epithelium which extends
across between the upper margins of the lateral walls, and is continuous
with the ependymal lining of the ventricle. Lying on this epithelial
roof, and intimately connected with it, is the tela chorioidea, from the
under surface of which the two choroid plexuses of the ventricle project
downwards, one on either side of the middle line, each invaginating
the epithelium of the roof. The epithelium of the roof is so intimately
connected with the tela that, when the latter is removed, the epithelium
comes away with it, and the cavity of the ventricle is exposed. Above
the tela chorioidea is the ‘ body ’ of the fornix, and above this again
is the ‘ body ' of the corpus callosum.
 
Summary of the Roof.— To expose the ventricle from above, the following
structures must be removed, in the order named: (1) the body of the corpus
callosum; (2) the body of the fornix; and (3) the tela chorioidea, along with the
 
epithelium of the roof.
 
The floor, which is sloped downwards and forwards (see Fig. 944 ).
is formed by the structures which lie within the interpeduncular space
at the base of the brain, from behind forwards: the locus perforatus
posterior, the corpora mamillaria, and the tuber cmereum, with the
upper end of the infundibulum. The tegmenta of the crura cerebri
enter to a certain extent into the floor posteriorly, and the optic
commissure lies across it anteriorly. Above the optic commissure
the floor presents a depression, called the optic r«c«ss, and behind i
there is another depression or diverticulum, called th e infundibular
recess. The latter forms the upper part of the infundibulum, which
 
leads to the posterior lobe of the hypophysis
 
The lateral wall is slightly convex and is formed for the m
part by the inner surface of the thalamus, which has
covering of grey matter. Towards its centre it presents a furrow,
which leads from the interventricular foramen m a backward direction
 
towards the upper opening of the aqueduct T'^^ralwall Ihere ^s
hypothalamic sulcus. At the upper part of the lateral wall there
 
 
1534
 
 
A MANUAL OF ANATOMY
 
 
a delicate band of white fibres, called the stria thalami, which runs
back toward the root of the pineal body, and passes to the anterior
pillar of the fornix. Connecting the two lateral walls (the thalami),
in front of the centre of the ventricle, there is a fragile band of grey
matter, formerly called the middle or soft commissure, but now usually
known as the massa intermedia or connexus thalami , since it is not
really a commissure. At the anterior part of the lateral wall the
corresponding anterior pillar of the fornix passes downwards and
backwards.
 
The anterior boundary is formed inferiorly by the lamina terminalis,
which extends upwards from the optic commissure to the rostrum of
the corpus callosum, and superiorly by the anterior pillars of the
fornix and the central portion of the anterior commissure.
 
 
 
Fig. 943. —Drawing of a Metal Cast of the Ventricles of the Brain of
 
an Adult (Right Lateral View) (Retzius).
 
The posterior boundary is formed by the pineal body and the
posterior commissure, and under cover of the latter is the upper
opening of the aqueduct. The posterior boundary presents two
recesses, pineal and suprapineal. The pineal recess passes backwards
for a very short distance above the posterior commissure into the
stalk of the pineal body, separating the stalk into two portions, dorsal
and ventral. The suprapineal recess is connected with the back part
of the epithelial roof of the ventricle, and passes backwards over the
pineal body. The third ventricle has thus four diverticula—namely,
the optic recess, the infundibular recess (both of which recesses are
associated with the floor), the pineal recess, and the suprapineal
recess. The cavity communicates with the fourth ventricle by means
of the aqueduct of the mid-brain, and with the two lateral ventricles
by means of the interventricular foramina.
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1535
 
 
Interventricular Foramina (Foramina of Monro).—These two openings lead one on each side from the third ventricle into the lateral
ventricles. Each foramen is situated between the anterior pillar of
the fornix in front and the anterior tubercle of the thalamus behind. From this point the foramen of each side leads medially and
slightly downwards, and opens into the third ventricle at the anterior
and upper part of the corresponding lateral wall. By means of the
foramina the lateral ventricles communicate with the third ventricle,
and through that ventricle with each other. The choroid plexuses
of the lateral ventricles also become continuous with each other and
with those of the third ventricle just above the roofs of these foramina.
 
Development. —The posterior and greater part of the third ventricle is the
cavity of the thalamencephalon or diencephalon; and the anterior part in the
region of the foramina represents the cavity of the telencephalon.
 
 
 
Fig. 944. —Left Wall of Third Ventricle.
 
 
The foramen of each side represents the original wide communication between
the cavity of the cerebral vesicle and the cavity of the telencephalon.
 
Thalami.—The thalami (O.T. optic thalami) are two large ovoid
masses of grey matter which lie obliquely, with their long axes directed
backwards and outwards, for the most part on the sides of the third
ventricle. Their anterior extremities are near each other, but their
posterior extremities stand apart, the superior corpora quadrigemina
being situated between them. Over their anterior two-thirds they
are separated from each other by the third ventricle.
 
Each thalamus presents four surfaces—superior, inferior, lateral,
and medial; and two extremities—anterior and posterior.
 
The superior surface is limited laterally by an oblique groove,
which separates it from the nucleus caudatus, and contains the stria
semicircularis, and anteriorly the vein of the corpus striatum. Medially it is bounded, from before backwards, by (1) the stria thalami,
(2) the trigonum habenulae, and (3) the corpora quadrigemina. It
is divided into two areas, lateral and medial, by a groove which is
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1536
 
directed backwards and laterally from near the anterior extremity
to the lateral end of the posterior extremity. This groove corresponds
to the lateral margin of the body of the fornix. The lateral area
enters descriptively into the body of the lateral ventricle, but is covered
by the ependyma of that ventricle. The medial area is excluded from
 
 
Great Longitudinal Fissure
 
 
 
F ig . 945 .—The Third Ventricle, Portions of the Lateral Ventricles,
Pineal Body, and Corpora Quadrigemina (Superior View) (Henle).
 
The corpus callosum, fornix, and tela chorioidea have been removed.
 
the lateral ventricle, and is covered by portions of the tela chorioidea
and body of the fornix (see Fig. 933). The superior surface is covered
by a thin layer of white fibres called the stratum zonale, these fibres
being derived from the optic tract and optic radiation.
 
The inferior surface lies posteriorly upon the upward prolongation
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1537
 
 
of the tegmental fibres of the crus cerebri, which constitutes the
subthalamic tegmental region, but anteriorly it rests upon the corpus
mamillare and a portion of the tuber cinereum.
 
The lateral surface is directly related to the posterior limb of the
internal capsule, which separates it from the nucleus lentiformis (see
Fig. 940). Many fibres emerge from this surface, and enter the internal
capsule on their way to the cerebral cortex, whilst others from the
cerebral cortex enter the thalamus through this surface. These fibres
constitute the thalamic radiation. On its surface the fibres form
a well-marked reticular layer of white matter, which is called the
external medullary lamina.
 
 
 
A, surface covered by ependyma of lateral ventricle; B, groove caused by fornix.
 
 
The medial surface faces its fellow of the opposite side, with which
it is connected by means of the connexus thalami. It forms the lateral
wall of the third ventricle, and superiorly is limited by the stria thalami.
It is covered by a thick layer of grey matter, which is continuous with
that around the aqueduct of the mid-brain.
 
The anterior extremity is marked by a prominence, called the
anterior tubercle , which enters into the body of the lateral ventiicle,
and forms the posterior boundary of the corresponding interventricular
 
foramen. . - ,
 
The posterior extremity presents at its inner end a well-marked
 
prominence, called the 'posterior tubercle or pulvinar . It lies over the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1538 A MANUAL OF ANATOMY
 
brachia of the corpora quadrigemina, which it almost conceals. Below
and external to the pulvinar there is an oval swelling, called the corpus
geniculatum externum. Medial to this body is the brachium of the upper
corpus quadrigeminum, and inferior to this is the corpus geniculatum
internum (see Fig. 946).
 
Metathalamus or Corpora Geniculata.—The corpora geniculata are
external or lateral and internal or medial. They are associated with
the posterior extremity of the thalamus, and the medial also with
that portion of the mesencephalon which constitutes the corpora
quadrigemina (see Fig. 946).
 
The corpus geniculatum laterale is an oval eminence situated on the
posterior extremity of the thalamus below and lateral to the pulvinar.
Internally it is connected with the upper quadrigeminal body by the
superior brachium.
 
It consists of grey and white curved lamellae, which alternate with
each other. The fibres of the white lamellae belong to the outer or visual
root of the optic tract. The axons of the cells of the grey matter enter
the optic radiation as corticipetal fibres. The lateral or outer geniculate body is associated with sight.
 
The corpus geniculatum mediale is a small oval eminence which
is situated below the pulvinar, and on the lateral aspect of that portion
of the mesencephalon which constitutes the corpora quadrigemina.
The inferior brachium, which is beneath it, connects it with the lower
quadrigeminal body.
 
The medial geniculate body contains many nerve-cells, the axons
of which become corticipetal fibres, their destination being the cortex
of the temporal region of the brain. By means of the lower quadrigeminal body and the inferior brachium this geniculate body receives
fibres from the lateral or acoustic fillet , which terminate in arborizations
around its cells. The axons of these cells become corticipetal fibres,
the destination of which is the cortex of the temporal region of the
brain. The medial geniculate body is associated with hearing.
 
Development. —The corpora geniculata appear as elevations on the lateral
wall of the thalamencephalon or diencephalon.
 
Structure of the Thalamus. —The thalamus is composed chiefly of grey
matter. Its superior surface is covered with a layer of white matter, known
as the stratum zonale, and its lateral surface is covered with a reticular layer
of white matter, called the external medullary lamina. The medial surface
has a thick coating of grey matter, which is continuous with the grey matter
around the aqueduct.
 
The grey matter of the interior of the thalamus is traversed by a plate of
white matter, called the internal medullary lamina, which divides it into tw r o
nuclear areas—lateral and medial. The lateral nuclear area lies between the
internal and external medullary laminae, and extends backwards as far as the
pulvinar. The medial nuclear area lies between the internal medullary lamina
and the thick layer of grey matter wdiich coats the medial surface of the
thalamus. It extends backwards as far only as the habenular region, and
anteriorly it is separated from the anterior tubercle by a lamina of white matter.
The region of the anterior tubercle therefore constitutes a third or anterior nuclear
area of grey matter. The grey nuclear areas are consequently three in number
—lateral, medial, anddnterior.
 
 
THE NERVOUS SYSTEM
 
 
1539
 
Lateral Nuclear Area. —1 his area includes the pulvinar, the geniculate bodies,
md the radiate nucleus. The pulvinar and geniculate bodies have just been
described. Ihe radiate nucleus is associated with the fibres of the thalamic
radiation, referred to later.
 
Anterior Nuclear Area. —This area includes the anterior tubercle, and is the
chief sensory nucleus. It receives corticifugal fibres, and its cells furnish corticipetal fibres. It also receives many of the fibres of the lateral lemniscus as
well as those of the superior cerebellar peduncle, and the fibres of the bundle of
Vicq d’Azyr, the mamillo-thalamic tract.
 
Medial Nuclear Area. —This area contains the ganglion habenulae, to be
presently described.
 
Connections of the Thalamus. —(1) Viewing the thalamus as an aggregation of ‘ cell-stations ' in the course of the centripetal fibres of the tegmentum of the crus cerebri, the tegmental fibres probably all terminate in
the thalamic cells. (2) Through the lateral geniculate the thalamus is connected with the optic tract and optic radiation. (3) The cells of the anterior
nucleus receive the fibres of the mamillo-thalamic tract, which are connected
through the corpus mamillare with the fibres of the anterior pillar of the fornix.
(4) Thalamic Radiation. —This is composed of thalamo-cortical fibres which
arise within the thalamus as the axons of the thalamic cells. They issue from
its lateral and inferior surfaces, and pass to all parts of the cerebral cortex.
They are conveniently arranged in four groups or stalks —frontal, parietal,
occipital, and inferior or ventral, (a) The fibres of the frontal stalk, having
emerged from the front part of the external surface, traverse the lateral part
of the anterior limb of the internal capsule, and most of them pass to the cortex
of the frontal lobe. Some of these fibres are thalamo-caudate and thalamolenticular as regards their destination. ( b ) The parietal stalk, having issued
from the thalamus, passes for the most part through the internal capsule, but
also to a certain extent through the external capsule, to the cortex of the
parietal lobe, and the central region of the frontal lobe, (c) The occipital stalk
issues from the pulvinar, and, having traversed the postlenticular portion of
the posterior limb of the internal capsule, it passes backwards and outwards
lateral to the posterior horn of the lateral ventricle, and so reaches the cortex
of the occipital lobe, (d) The inferior or ventral stalk emerges from the front
part of the inferior surface of the thalamus, and its fibres arise as the axons
of the cells of the lateral and medial nuclei. The most superficial of these
fibres constitute a band, called the ansa lenticularis, which enters the nucleus
lentiformis, where it terminates. The remaining fibres pass outwards beneath
the nucleus to the cortex of the temporal lobe and insula.
 
Besides the thalamo-cortical fibres there are cortico-thalamic fibres, which
pass from the various parts of the cerebral cortex into the thalamus, where
they terminate in arborizations around the thalamic cells.
 
Development. —The thalamus is developed as a thickening of the dorsal lamina
of the thalamencephalon.
 
Subthalamic Tegmental Region.—This region represents the upward
prolongation of the tegmental fibres of the crus cerebri beneath the
posterior portion of the thalamus. The parts to be noted are the
upward prolongations of the red nucleus and substantia nigra of
the tegmentum of the crus; the medial lemniscus; the fibres of the
superior peduncle of the cerebellum; and the corpus subthalamicum
(or nucleus of Luys). The red nucleus and the substantia nigra gradually
disappear, and are no longer visible at the level of the corpus mamillare.
The medial lemniscus lies on the superficial and lateral aspects of the
red nucleus. The fibres of the superior peduncle of the cerebellum
partly terminate in connection with the cells of the red nucleus, but
many of them surround it in the form of a capsule. Beyond the red
 
 
154°
 
 
A MANUAL OF ANATOMY
 
 
nucleus the medial fillet, fibres of the superior cerebellar peduncle, and
fibres which issue from the red nucleus enter the inferior surface of the
thalamus, and terminate in connection with the thalamic cells. Some
of these fibres may pass through the thalamus into the internal capsule,
and thence to the cortex of the central (Rolandic) region of the cerebral
hemisphere. The corpus or nucleus subthalamicum (or nucleus of Luys)
is a small lenticular mass of grey matter, surrounded by white fibres,
which lies above the substantia nigra.
 
Epithalamus.—The epithalamus includes the following parts:
 
1. Pineal body. 3. Trigonum habenulae.
 
2. Stria thalami. 4. Posterior commissure.
 
 
 
Subthal. N.
and Red N.
 
 
bm. 947.— Section showing the Intermediate Subthalamic Area, where
the Red Nucleus is appearing and the Subthalamic Nucleus has
not yet Disappeared.
 
 
Pineal Body, or Epiphysis Cerebri.—The pineal body resembles a
small pine-cone. It is situated on the dorsal or superior surface of
the mesencephalon, and occupies the depression between the upper
quadrigeminal bodies. It is of small size, dark red in colour, and
somewhat conical in shape. Superiorly it is intimately related to the
pia mater as that membrane passes through the transverse cerebral
fissure to form the tela chorioidea, and the splenium of the corpus
callosum lies above it with the intervention of the pia mater. Inferiorly
it is in contact with the depression between the upper quadrigeminal
bodies. Its apex,, which is directed downwards and backwards, is
free. Its base is directed upwards and forwards, and contains the pineal
recess, which is continuous anteriorly with the cavity of the third
ventricle. The portion of the base which lies below this recess is
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
I 54 I
 
 
:onnected with the posterior commissure, which separates it from the
jpper opening of the cerebral aqueduct. The portion above the recess
:ontains the habenular commissure.
 
Structure of the Pineal Body. —The pineal body is free from nervous constituents. It consists of a number of follicles lined with epithelial cells, and
containing a variable amount of calcareous matter, called acervulus cerebri or
brain-sand, which is composed of calcium phosphate, calcium carbonate, magnesium phosphate, and ammonium phosphate.
 
Development. —The pineal body is developed as a diverticulum of the posterior
part of the dorsal aspect of the thalamencephalon or diencephalon. This
diverticulum for the most part becomes solid, but a portion of its cavity persists
as the pineal recess of the third ventricle.
 
The pineal body is usually regarded as the representative of one of the stalks
of the two median eyes of some of the higher arthropods, such as the king crab,
among the Jnvertebrata, and is important in suggesting the possible line of
evolution of the Vertebrata. In many of the reptiles the pineal eye as well as
the eye-stalk is present, though it is never functional.
 
Striae Thalami or Habenulae.—Each stria is a narrow strip of
white longitudinal fibres lying along the upper part of the medial
surface of the corresponding thalamus. It constitutes the habenula.
Anteriorly most of its fibres are derived from the olfactory lobe,
more particularly the olfactory bulb and anterior perforated substance. Some, however, may be derived from the anterior pillar of the
fornix, and through the fornix from the cells of the hippocampus.
Posteriorly the fibres are disposed in two ways: (i) The lateral fibres
enter the ganglion habenulae, and terminate in connection with its
cells. (2) The medial fibres curve inwards towards the base of the
pineal body, in which they cross to the opposite side, lying above the
pineal recess. As they cross the median line they decussate with the
medial fibres of the opposite stria medullaris, and they terminate in
the ganglion habenulae of the side to which they have crossed. Their
decussation is known as the habenular commissure.
 
Trigonum Habenulae.—This is a small triangular area (Fig. 948) which
is bounded posteriorly by the upper quadrigeminal body, internally
by the posterior part of the stria thalami, and laterally by the adjacent
part of the thalamus. It contains an important group of multipolar nerve-cells, known as the ganglion habenulae. This ganglion
belongs to the medial area of the thalamus. It receives some of
the fibres of the stria, which come from the olfactory lobe, and, it
may be, from the anterior pillar of the fornix. The axons of the
ganglionic cells issue from the ventral surface of the ganglion and form
a bundle, called the fasciculus retroflexus. This bundle passes downwards and forwards in the tegmentum of the crus cerebri, lying on the
medial side of the red nucleus. Its fibres terminate in connection with
the cells of the ganglion interpedunculare , which is situated in the
lower part of the posterior perforated substance directly above the
pons.
 
The ganglia habenularum are connected with each other by fibres
which constitute the habenular commissure or commissure of the habenular
 
 
A MANUAL OF ANATOMY
 
 
*542
 
 
ganglia. These fibres cross in the dorsal part of the base of the pineal
body, and are on a higher plane than the posterior commissure.
 
The striae thalami, or habenulae, and the ganglia habenularum are
associated with the rhinencephalon or olfactory brain.
 
 
 
C. Call.
 
Thalamus
Str. Haben.
 
 
Pineal
 
Splenium and
Great Vein
 
 
Cerebellum
 
 
Fig. 948. —Thalamus partly exposed by Removal of Portions of Corpus
Callosum and Fornix, with Tela Chorioidea.
 
Shows trigonum and stria habenulae.
 
Posterior Commissure.—This is a band of white fibres which is
situated at the back part of the third ventricle. It lies in the posterior
wall of the ventricle directly above the upper opening of the aqueduct
and underneath the base of the pineal body. Its fibres are regarded
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1543
 
 
as arising from a nucleus in the grey matter of the lateral wall of the
third ventricle near the upper opening of the aqueduct. Some of the
fibres of either side, after crossing, may descend in the tegmentum
of the crus cerebri as part of the medial longitudinal bundle of that
side, and so reach the medulla oblongata.
 
Hypothalamus.—The hypothalamus consists of two parts—mammillary and optic. The pars mamillaris hypothalami represents the
 
 
 
Fig. 949. —Diagram to show Position and Relations of Structures in
 
Tegmental Subthalamus.
 
Supposed to be viewed from the medial aspect. R, red nucleus. The subthalamic nucleus is shown antero-lateral to this. Dotted line shows course
of fasciculus retroflexus from habenula to interpeduncular ganglion. Course
of anterior pillar of fornix is indicated, also mamillo-thalamic tract (bundle of
Vicq d’Azyr) passing up medial to front part of subthalamic nucleus. Substantia nigra is seen near pontine level, but passes upwards and laterally
out of the section higher up.
 
 
two corpora mamillaria. The pars optica hypothalami includes the
following structures:
 
 
1. Tuber cinereum.
 
2. Infundibulum.
 
3. Posterior or cerebral lobe of the hypophysis.
 
4. Optic chiasma.
 
5. Lamina terminalis.
 
 
The corpora mamillaria are two small, white, pea-like bodies,
which lie side by side directly in front of the posterior perforated
area Each is composed of white matter externally, and of a grey
nucleus internally. The white matter is derived from the corresponding
anterior pillar of the fornix, the fibres of which terminate in connection
with the cells of the grey nucleus. This grey nucleus contains many
cells the axons of which give rise to two fasciculi—namely, the
mamillo-thalamic tract (or bundle of Vicq d’Azyr). and the peduncle
of the corpus mamillare. The mamillo-thalamic tract, which is
 
 
 
l 5 44
 
 
A MANUAL OF ANATOMY
 
 
apparently a continuation of the anterior pillar of the fornix, enters
the thalamus, and its fibres terminate in connection with the cells of
the anterior nucleus. The peduncle of the corpus mamillare passes
downwards and backwards in the grey matter of the floor of the third
ventricle to the tegmental region of the mesencephalon, but the mode
of termination of its fibres is not known.
 
Development. — The corpora mamillaria are developed from the ventral
aspect of the thalamencephalon or diencephalon. Up to the third month of
intra-uterine life they are represented by a single corpus mamillare, but after
that period this divides into two corpora.
 
The tuber cinereum is an elevated area of grey matter which lies
in front of the corpora mamillaria and behind the optic commissure,
the anterior portion of each optic tract being on either side. It is
continuous anteriorly with the lamina terminalis, and on either side
with the grey matter of the anterior perforated substance.
 
In the lateral part of the tuber cinereum, in the vicinity of the optic tract,
there is a collection of nerve-cells, which is variously spoken of as the basal
ganglion of Meynert or the supra-optic nucleus of Cajal, and which is connected
 
with the fibres of the commissure of Gudden.
 
Behind the tuber cinereum, and in front of the corpora mamillaria, there is
a small prominence, medially placed, called the eminentia saccularis of Retzius,
who regards it as the homologue of the saccus vasculosus of some lower vertebrates— e.g., fishes.
 
Ihe infundibulum is a funnel-shaped stalk which extends downwards from the anterior part of the inferior surface of the tuber cinereum
to the posterior lobe of the hypophysis, or pituitary body. Its upper
part is hollow, and contains the infundibular recess or diverticulum
of the cavity of the third ventricle. The infundibulum is the peduncle
of the posterior lobe of the hypophysis.
 
Hypophysis (Pituitary Body).—As this structure is seldom removed
in the course of dissection with the brain, it has already been described
on p. 1171 with the pituitary fossa, in which it lies. It may be well,
however, to repeat in this place the fact that the anterior lobe is a
derivative of the ectodermal lining of the primitive mouth; that the
posterior lobe, which is connected to the infundibulum, is a downgrowth from the brain (hypophysis cerebri); and that, between the
two, lies the pars intermedia, which is only the posterior wall of the
ectodermal pouch. The name (pituitary) was derived from the old
belief that the gland secreted the pituita or mucus of the nose.
 
Lamina Terminalis.— This is a thin plate of grey matter which
extends between the upper surface of the optic commissure and the
rostrum of the corpus callosum near the genu. On either side it is
connected with the grey matter of the anterior perforated substance.
It forms the lower part of the anterior wall of the third ventricle.
 
Development. The lamina terminalis represents the terminal part of the
ventral wall of the embryonic neural tube.
 
 
THE NERVOUS SYSTEM
 
 
1545
 
 
Optic Nerve, Optic Chiasma, Optic Tract, and Optic Radiation.
 
The optic nerves, or nerves of sight, in the cranial cavity are
onnected together at the optic commissure or chiasma , where some
>f the fibres decussate. From the back part of the commissure each
lerve, under the name of the optic tract, passes backwards round
he crus cerebri to its cerebral connections.
 
The optic chiasma rests upon the tuberculum sellae and above the
iptic groove of the sphenoid bone. It lies in front of the tuber cinereum
,nd infundibulum, and its superior surface is connected with the lamina
erminalis, and is intimately related to the anterior part of the floor
>f the third ventricle. On either side of the commissure is the anterior
>erforated substance. Most of the fibres of the commissure proceed
rom each retina in the corresponding optic nerve, being afferent or
:entripetal; but at the back part of the commissure there are the
ibres of the medial roots of the optic tracts, which have no connection
vith either retina. The decussation of fibres in the commissure is
>nly partial. The fibres which arise in the nasal or medial half of
he retina cross and enter the optic tract of the opposite side. The
ibres which arise in the temporal or lateral half of the retina take no
>art in the decussation, but pass directly backwards into the optic tract
)f the same side (see Fig. 950).
 
Occupying the back part of the commissure there are, as stated,
iome fibres which have no connection with either retina.. These
ibres constitute the commissure of Gudden. I hey lie behind the
lecussating fibres, and represent the fibres of the medial root of the
)ptic tract of each side. They form the innermost fibres of each
>ptic tract, and connect one medial geniculate body with its fellow
)f the opposite side.
 
Summary. —The fibres which arise in the nasal half of one retina cross in
fie optic commissure, and enter the optic tract of the opposite side. The fibres
\fiich arise in the temporal half of one retina pass directly backwards into the
)ptic tract of the same side. The fibres of the inner ropt of each optic tract
:ross in the back part of the commissure, and form the commissure of Gudden,
he fibres of which have no connection with the optic nerves, but connect the
•wo medial geniculate bodies, right and left. The optic commissure therefore
insists of the following groups of fibres: (1) The crossed fibres, which arise
n the nasal portion of each retina; (2) the uncrossed fibres, which arise m the
temporal portion of each retina, and occupy the outer part of the commissure;
ind (3) the fibres of the commissure of Gudden, which occupy the back part of
fie commissure.
 
The optic tract of each side is a flattened white band which passes
backwards from the optic chiasma. It curves round the crus cerebri,
ind in the region of the posterior extremity of the thalamus it
divides into two roots, lateral and medial. Ihe lateral or visual
foot is the larger of the two. It is chiefly composed of afferent fibres,
which pass from the retina to the brain; but it also contains efferent
ibres, which pass from the brain to the retina.. The efferent fibres
ire derived from (1) the temporal half of the retma of the same side,
 
 
A MANUAL OF ANATOMY
 
 
1546
 
and (2) the nasal half of the retina of the opposite side, the
latter having crossed in the optic chiasma. The fibres of the lateral
root terminate in the lateral geniculate body and the upper quadrigeminal body, reaching the last-named body through the superior
brachium. They form arborizations around the cells of these bodies
which constitute the terminal nuclei or lower visual centres of the
 
 
 
Yellow, uncrossed fibres; red, crossed fibres ; blue, Gudden’s commissure.
Interrupted lines, connections with occipital pole—that is, within the
hemisphere ; mainly afferent, but some efferent fibres here.
 
outer or visual root. These lower visual centres are connected with
the higher or cortical visual centre by the strand of fibres forming
the optic radiation, the higher visual centre being situated in the cortex
of the cuneate and lingual gyri of the medial surface of the occipital
lobe. The medial or commissural root of the optic tract passes beneath
the medial geniculate body, which represents the nucleus of most of
its fibres. As stated, these fibres have no connection with the optic
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1547
 
 
nerve. Having traversed the inner part of the optic tract, they
cross in the back part of the optic commissure behind the decussating
fibres, and are continuous with the corresponding fibres of the opposite
side. These are the fibres which constitute the commissure of Gudden.
 
Optic Radiation. —The strand of fibres which forms the optic
(or thalamo-occipital) radiation of either side establishes a connection between the lower visual centres (lateral geniculate body and
upper quadrigeminal body) and the higher or cortical visual centre,
which is situated (1) on the medial surface of the occipital lobe close
to the calcarine fissure in the region of the cuneus and lingual gyrus,
and (2) on the adjacent part of the postero-lateral surface of the
occipital lobe. The strand passes through the post-lenticular part of the
internal capsule, and then backwards in the medullary substance of
the occipital lobe, lying on the lateral side of the posterior horn of
the lateral ventricle. Thereafter the fibres pass in a radiating manner
to the higher or cortical visual centre.
 
This visual area in the neighbourhood of the calcarine fissure is
distinguishable to the naked eye in a section of a fresh brain by the
white band of Gennari which traverses it.
 
The optic radiation consists of afferent or corticipetal and efferent
or corticifugal fibres. The corticipetal fibres for the most part arise as
the axons of the nerve-cells within the lateral geniculate body, which
are terminal nuclei of the retinal nerve-fibres, and they end in the
higher or cortical visual centre. Some corticipetal fibres arise in the
higher or cortical visual centre of the opposite side and cioss in the
splenium of the corpus callosum. These fibres are of a commissural
character. The corticifugal fibres arise as the axons of the pyramidal cells of the cortex of the visual area of the occipital lobe, and
they terminate in the pulvinar, geniculate, and upper quadrigeminal
 
body.
 
 
The lower visual centres are connected with the nuclei of origin of the nerves
which supply the ocular muscles, probably through the medial longitudinal
 
bundle.
 
 
Mesencephalon.
 
The mesencephalon is composed of the corpora quadngemma,
which form its upper or dorsal portion; the crura cerebri, which form its
lower or ventral portion; and the aqueduct, which passes through it
from the fourth ventricle below to the third ventricle above.
 
Corpora Quadrigemina. —These are four rounded eminences, which,
as just stated, form the dorsal portion of the mesencephalon. They are
covered by the splenium of the corpus callosum, and are arranged m
pairs, upper and lower, the upper pair being larger than the lower pair
but not quite so prominent. The four eminences are separated from
each other by two grooves, longitudinal and transverse, which are
arranged in a cruciform manner. The longitudinal groove extends
upwards as far as the posterior commissure and it separates ^Udd e
and lower quadrigeminal bodies of one side from those of the other side.
 
 
1548
 
 
A MANUAL OF ANATOMY
 
 
Its upper part lodges the pineal body, and from its lower part a band of
white fibres, called the frenulum veli , passes downwards to the superior
medullary velum, which lies below the lower pair of eminences. The
transverse groove separates the upper pair of quadrigeminal bodies
from the lower pair. Laterally each eminence is connected with a white
band, called the brachium, the two brachia being separated by a
continuation of the transverse groove.
 
The superior brachium extends outwards and forwards from the
upper quadrigeminal body to the lateral geniculate body and the
lateral root of the optic tract. It passes between the pulyinar of the
thalamus and the medial geniculate body.
 
 
Connexus Thalami
 
Pineal Peduncle ; Tllird Vtntricle
 
 
 
Thalamus
 
 
..Upper Quadrigeminal Body
W m( i!i'i(.( //).' VjV - Lower Quadi igeminal Body
 
 
Superior Fovea
Auditory Striae
 
Inferior Fovea_
 
 
Cuneate Tubercle -
 
Basis Pedunculi
 
 
Frenulum Veli
Sup. Med. Velum
~-»»Supei ior Peduncle of
Cerebellum
 
Mid. ped. (cut)
 
 
"" Auditory Striae
''' Vestibular Trigone
 
I dim J'-' Trigonum Hypoglossi
 
''•^Trieonum Vagi
 
( Spinal Tract of Fifth Nerve
 
tf# \ciava
ppT-- Funiculus Gracilis
 
Funiculus Cuneatus
 
Fig. 951. —The Floor of the Fourth Ventricle and Adjacent Parts.
I he pineal body has been removed to show the upper quadrigeminal bodies.
 
 
The superior brachium is associated with the visual apparatus. The
inferior brachium, though connected with the medial geniculate body,
with which body the inner or commissural root of the optic tract (commissure of Gudden) is also connected, is associated with the acoustic
apparatus.
 
The superior brachium contains two sets of fibres—namely, retinal
fibres, derived from the lateral root of the optic tract; and occipital
fibres, from the cortex of the occipital lobe of the cerebrum.
 
The inferior brachium passes upwards from the lower quadrigeminal
body to the under aspect of the medial geniculate body, which is a small
oval mass on the lateral aspect of the mesencephalon, under cover of
the pulvinar of the thalamus. Though the inner root of the optic
tract is connected with this geniculate body, the inferior brachium
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1549
 
 
passes clear of it, and most of its fibres are traceable to the thalamus
through the tegmentum.
 
Structure of Corpora Quadrigemina. —The lower quadrigeminal body {colliculus
 
inferior ) is composed of the following parts:
 
1. A central nucleus of grey matter.
 
2. A dorsal layer of white matter.
 
3. A ventral layer of white matter.
 
The central grey nucleus consists of many multipolar cells and nerve-fibres.
The axons of the cells pass partly to the dorsal and partly to the ventral layers
 
 
Pulvinar
 
Superior Quad. Body
 
Inferior Quad. Body •
Fourth Nerve
Lateral Fillet - ~ —
Basis Pedunculi
Superior Cerebellar Peduncle—
 
Inferior Cerebellar Peduncle. _
 
Middle Cerebellar Peduncle
Restiform Body Eighth Nerve ^
 
Olive
 
 
Med. Geniculate Body
 
-1 Lat. Geniculate Body
 
.Optic Tract
__ . Corpus Mam.
 
 
 
Tuber Cinereum
 
- Third Nerve
 
 
Fifth Nerve
 
 
- - Seventh Nerve
 
" * Sixth Nerve
 
 
Fig. 952.— Side View of the Mesencephalon.
 
 
of white matter. The nerve-fibres are derived from the lateral or acoustic
lemniscus , and terminate in arborizations around the cells of the central nucleus.
 
The dorsal white layer derives its fibres from the lateral lemniscus and from
the axons of the cells of the central grey nucleus. The fibres pass into the inferior brachium, by which they are conducted to the medial geniculate body.
 
The ventral white layer also derives its fibres from the lateral lemniscus
and from the axons of the cells of the central grey nucleus. This layer separates
the central nucleus from the subjacent grey matter of the aqueduct. Some of
the fibres cross the median plane, and decussate with corresponding fibres of
the opposite side superficial to the roof of the aqueduct. Others enter the tegmentum of the crus of the same side and also of the opposite side, in which their
course is downwards in the lateral lemniscus.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
L55°
 
 
A MANUAL OF ANATOMY
 
 
The lower quadrigeminal body ( colliculus inferior), which receives its fibres
from the lateral or acoustic lemniscus, is associated with the acoustic apparatus
The upper quadrigeminal body ( colliculus superior) is composed of the follow,
ing layers :
 
1. Stratum zonale. 3. Stratum opticum.
 
2. Stratum cinereum. 4. Stratum lemnisci.
 
The stratum zonale is the most superficial layer, and probably consists of
retinal fibres which are derived from the outer root of the optic tract. Many
of these fibres pass into the stratum cinereum and terminate in connection with
its cells. Others cross the median plane and decussate with corresponding fibres
from the opposite side superficial to the roof of the aqueduct.
 
The stratum cinereum, or second layer, lies beneath the stratum zonale,
and consists of a crescentic layer of grey matter containing many nerve-cells.
It represents the grey nucleus of the upper quadrigeminal body, and the axons
of its cells pass to the more deeply seated strata.
 
 
Infundibulum
Tuber Cinereum _
 
Mamillary Body
Mesial Root of Optic Tract
Lateral Root of Optic Tract /\
 
Lateral Geniculate Body b.
 
Locus Perforatus Posterior
 
 
Sixth Nerve
Motor Root, Facial Nerve
Sensory Root
Auditory Nerve "
Glosso-pharyngeal Nerve —3
Vagus Nerve
 
Superficial Arcuate Fibres
Accessory Ner y e
 
First and Second Cervical Nerv
 
 
Optic Chiasma
 
3-)ptie Nerve
 
 
 
.Optic Tract
 
 
Third Nerve
 
 
_Fourth Nerve
 
-Motor Root of Fifth Nerve
 
-Sensory Root of Fifth Nerve
 
 
Middle Peduncle of
Cerebellum
 
 
Restiform Body
—.Hypoglossal Nerve
■ --Anterior Median Fissure
 
.Decussation of the Pyramids
 
 
Fig. 953.—The Medulla Oblongata, Pons, and Interpeduncular Region.
C.C., crus cerebri; P., pyramid; O.B., olivary body.
 
 
The stratum opticum is the third layer, and consists of grey matter which
contains numerous nerve-cells and nerve-fibres. The fibres are conducted to
this stratum by the superior brachium, and are of two kinds: (1) Many are
retinal fibres, and are derived from the outer root of the optic tract. (2) Others
are corticifugal fibres, which come from the higher visual centre in the cortex of
the occipital lobe, and form part of the optic radiation. The fibres pass into
the stratum cinereum, and terminate in arborizations around its cells. The
axons of the cells of the stratum opticum pass into the stratum lemnisci.
 
The stratum lemnisci is the deepest layer. Like the stratum opticum, it
consists of , grey matter, which contains numerous nerve-cells and nerve-fibres.
The fibres are derived from the following sources: (1) Many are derived from
the medial or main lemniscus; and (2) some are the axons of cells belonging to
the stratum opticum and stratum lemnisci. The lemniscal fibres terminate
in the stratum lemnisci. The fibres formed by the axons of the cells of the
stratum opticum and stratum lemnisci cross the median plane, below the aqueduct, and decussate with the corresponding fibres of the opposite side. This
 
 
/
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
I55i
 
 
decussation is known as the fountain decussation (of Meynert). The fibres, after
crossing, form the tectospinal tract of that side, and this bundle or tract descends
through the pons and medulla oblongata into the corresponding ventral or
anterior column of the spinal cord.
 
The upper quadrigeminal body, by means of the superior brachium, is one
of the lower visual centres, the other being the external geniculate body.
 
Development of Corpora Quadrigemina. —The corpora quadrigemina are
developed from the dorsal wall or roof of the mesencephalon. They are at first
in the form of elongated paired swellings, later divided transversely.
 
 
Dorsal Tegmental Decussation (or Commissure of Meynert). —This
commissure or decussation consists of fibres which issue from each
upper quadrigeminal body, and cross partly to the opposite posterior
longitudinal bundle, but mostly form tecto-spinal tracts, in which they
descend towards the pons.
 
Crura Cerebri. —The crura or pedunculi cerebri are two large strands
which are situated above the pons. They lie at first near each other,
being separated by the interpeduncular fossa, but afterwards diverge
as they pass upwards and laterally
to the cerebral hemisphere. The
medial surface of each crus bounds
the interpeduncular region, and has
a furrow, the oculo-motor sulcus,
through which the roots of the
third nerve emerge near the pons.
 
The lateral surface looks towards
the temporal lobe of the brain,
which to a large extent overlaps
the crus, and this surface also has
a furrow, the sulcus lateralis. The slender fourth cranial nerve lies
upon this surface. Close to the cerebral hemisphere the ventral and
lateral aspects of the crus are embraced by the optic tract of the
corresponding side.
 
Each crus is composed of two parts—ventral and dorsal. The
ventral part is the basis (or crusta), and the dorsal the tegmentum. The
separation between these is indicated superficially by the sulcus
lateralis and the oculo-motor sulcus. Within the crus the two parts
are separated by a mass of dark grey matter, called the substantia
 
 
Aqueduct
 
 
 
Corpora Quadrigemina
Tectum
 
Tegmentum
 
 
Lateral Sulcus
 
 
Subst. Nigra
 
-- Basis
Pedunculi
 
 
Oculo-Motor Sulcus
 
 
Fig. 954. —Topography of the Crus
Cerebri (after Poirier).
 
 
uigia* # • i • 1 i
 
The basis pedunculi (crusta) is continuous superiorly with the
internal capsule of the corpus striatum, and inferiorly its fibres enter
the ventral part of the pons.
 
Structure of the Basis.— The crusta, or basis, as seen m transverse
section, presents a crescentic outline, the concavity of the crescent
being occupied by the convexity of the substantia nigra. It consists of
longitudinal corticifugal fibres which arise in the cells of the cerebral
cortex. These fibres form two groups—pyramidal and cortico-pontine.
 
The pyramidal fibres form the motor tract from the precentral
motor region of the cortex of the frontal lobe, and they arise for the
 
 
 
 
 
1552
 
 
A MANUAL OF ANATOMY
 
 
most part from the cells of that region, which control the voluntary
muscles of the body.
 
The cortico-pontine fibres lie on each side of the pyramidal tract,
those coming from the frontal region of the cortex being on the medial
and those from the temporal region on the lateral side; the basis of
each peduncle, therefore, is formed, from within outward, by frontopontine, pyramidal, and temporo-pontine tracts (see Fig. 958).
 
Tegmentum.— The tegmentum is continuous interiorly with the
formatio reticularis of the dorsal portion of the pons, which in turn is
continuous interiorly with the formatio reticularis of the medulla
oblongata; the upward prolongation of the tegmentum makes the
tegmental subthalamic region. The two tegmenta, right and left, are
separated from each other by a median raphe, which is continuous with
 
 
Nucl. of Inf. Corpus
Quadrigeminum
 
 
Fibres of Lat. Lemn.
 
 
Fourth N. Nucl.
 
 
Pallido-rubro-olivary
 
Tract
 
Medial longit. Bundle
 
 
Rubro-spinal Tr.
 
Fibres of Basis
Pedunculi
 
 
Decuss. of Sup.
Cerebell. Peduncle
 
Medial Lemniscus
 
 
Substantia Nigra
 
 
Pons
 
 
Fig. 955
 
Section through Inferior Corpora Quadrigemina.
 
 
that of the pons. In the lower part of the mesencephalon this raphe
is indistinct on account of the decussation which takes place across the
median plane between the superior cerebellar peduncles, underneath
the lower pair of quadrigeminal bodies.
 
The dorsal surface of each tegmentum extends on either side of
the grey matter of the aqueduct, and becomes continuous with the
basal parts of the upper and lower quadrigeminal bodies of the corresponding side, which constitute the tectum. The ventral surface is
separated from the crusta by the substantia nigra.
 
Structure of the Tegmentum. —Each tegmentum, besides being
continuous interiorly with the formatio reticularis of the dorsal portion
of the pons, consists of bundles of longitudinal and transverse fibres,
the intervals between which are occupied by grey matter.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1553
 
 
Grey Matter. —The grey matter of the tegmentum contains the
red nucleus.
 
The red nucleus (nucleus ruber) is a round reddish mass, which is
situated in the centre of the upper part of the tegmentum, and lies
in the path of the superior cerebellar peduncle of the opposite side.
It is on the same level as the upper quadrigeminal body, and is prolonged upwards into the subthalamic tegmental region. Some of the
fibres of the superior cerebellar peduncle of the opposite side surround the red nucleus in the form of a capsule on their way to the
thalamus. Other fibres of that peduncle enter the red nucleus, and
terminate in arborizations around its cells.
 
The axons of the cells of the red nucleus form two sets of nervefibres—ascending and descending. The ascending fibres pass to the
thalamus in company with those fibres of the superior cerebellar
peduncle which encapsule the red nucleus. These ascending fibres
form relays which carry on those fibres of the superior cerebellar
peduncle which terminate within the red nucleus, that nucleus
being a cell-station in their path. The descending fibres constitute
the rubro-spinal tract (or bundle of Monakow). The fibres of this
tract cross the median plane in the raphe, and by their decussation
with those of the opposite side they constitute the ventral fountain decussation [of Foret), in contradistinction to the dorsal fountain decussation (of Meynert). The latter decussation is on a higher level, and
involves the fibres of the ventral longitudinal bundles, or tecto-spinal
tracts, which derive their fibres from the cells of the stratum opticum
and stratum lemnisci of the upper quadrigeminal bodies. The rubrospinal tract of either side descends through the pons and medulla
oblongata into the lateral column of the spinal cord, where each
constitutes the prepyramidal tract, which lies on the ventro-lateral
aspect of the lateral cortico-spinal tract. (The tecto-spinal tract, or
ventral longitudinal bundle, on either side descends into the anterior
column of the spinal cord.)
 
White Matter of the Tegmentum. —The principal tracts of the
white matter on either side are as follows:
 
1. Superior cerebellar peduncle.
 
2. Medial (posterior) longitudinal bundle.
 
3. Ventral longitudinal bundle, or tecto-spinal tract.
 
4. Pallido-rubro-olivary tract.
 
5. Rubro-spinal tract.
 
6. Medial lemniscus (chief sensory tract).
 
7. Lateral (acoustic) lemniscus.
 
Superior Cerebellar Peduncle.— The fibres of this peduncle emerge
for the most part through the hilum of the nucleus dentatus in the
cerebellar hemisphere. The two peduncles, right and left, having
emerged from the hemispheres, pass upwards on the lateral parts
of the dorsal surface of the pons in a converging manner towards the lower pair of the quadrigeminal bodies, being connected
 
98
 
 
1554
 
 
A MANUAL OF ANATOMY
 
 
 
 
by the superior medullary velum. On entering the mesencephalon,
the two peduncles decussate across the raphe beneath the lower quadrigeminal bodies. This decussation extends as high as the upper
quadrigeminal bodies, and it involves almost all the fibres of the
two peduncles. Each peduncle, having gained the opposite side,
ascends in the upper part of the tegmentum as a longitudinal tract,
 
and soon comes into contact with the red
nucleus. Many of its fibres enter this
nucleus and terminate in arborizations
around its cells. Other fibres of the
peduncle encapsule the nucleus, and
then ascend through the subthalamic tegmental region to the anterior part of the
thalamus, within which they terminate
in arborizations around the cells of the
anterior nuclear area (chief sensory
nucleus). From the cells of the red nucleus
relays of fibres proceed upwards, which
carry on those fibres of the peduncle which
terminate within the nucleus, and these
relays ascend with those fibres of the
peduncle which encapsule the red nucleus
to the thalamus.
 
The superior cerebellar peduncle of
one side connects the cerebellar hemisphere of that side with the postcentral
in the Mid-brain as it re gion of the cerebral cortex of the
 
. opposite side, the red nucleus and the
 
lbres su P enor peduncles thalamus being cell-stations in the path
are shown decussating and f gu & r
 
rprl thipIahc '-'■l tilt; IlDlCS.
 
 
 
Fig. 956.—Plan of Relations
of Certain Fibre-tracts
 
 
reaching red nucleus, from
which the rubro-spinal tracts
emerge, decussate, and pass
below the cerebellar fibres
to enter the pons laterally.
On the right the pallidorubro-olivary tract is shown
in white, indicating its relation to the peduncular
fibres; it sinks deeply in
the pons, turning somewhat
laterally. It is not shown in
front of the red nucleus.
 
 
A few of the fibres of each superior
cerebellar peduncle do not take part
in the decussation beneath the
lower pair of quadrigeminal bodies,
but ascend to the red nucleus of
their own side.
 
 
Before the fibres decussate, or after
the decussation has taken place, each of
them furnishes a descending branch.
 
These descending branches form the descending cerebellar bundle (of Cajal), which traverses the dorsal part
of the pons and the medulla oblongata, giving off collaterals to the
motor nuclei of these parts. According to Cajal, the fibres of this
bundle enter the anterior column of the spinal cord, and are connected
with the cells of the ventral column of grey matter.
 
The superior cerebellar peduncle also contains the indirect or
ventral spino-cerebellar tract (of Gowers).
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1555
 
 
Medial or Posterior Longitudinal Bundle. —This bundle occupies
he dorsal part of the tegmentum, and is intimately related to the
;rey matter which forms the ventral wall or floor of the aqueduct,
t lies close to the median raphe, as does its fellow of the opposite
ide, and across the raphe an interchange of fibres takes place between
he two bundles. In the spinal cord it is represented by the anterior
ntersegmental fibres and the anterior marginal bundle (of Lowenthal).
n the medulla oblongata it traverses the dorsal part of the pyramid,
>eing separated from the pyramidal (motor) fibres by the medial
emniscus or chief sensory tract. Thereafter it traverses the formatio
eticularis of the dorsal part of the pons, and is continued upwards
is one of the tracts of the tegmentum of the crus cerebri.
 
The fibres of the medial longitudinal bundle are regarded as being
:he axons of cells belonging to (1) the nucleus of Deiters, which is
me of the terminal nuclei of the vestibular root of the auditory nerve,
 
2) the formatio reticularis of the medulla oblongata and pons,
 
3) the formatio reticularis of the tegmentum, (4) the sensory nucleus
)f the fifth cranial nerve, and (5) the nucleus of the longitudinal
rundle. Inferiorly the fibres of the bundle ramify within the
interior column of the spinal cord in connection with the motor cells
)f the ventral horn of grey matter. Superiorly its fibres are intimately
•elated to the following important nuclei—namely, (1) the oculonotor nucleus, or nucleus of the third cranial nerve; (2) the trochlear
lucleus, or nucleus of the fourth cranial nerve; and (3) the abducent
mcleus, or nucleus of the sixth cranial nerve, these being the nuclei
which control the muscles of the eyeball and upper eyelid. The
Dundle furnishes numerous collaterals to each of these nuclei, which
:erminate in arborizations around their cells. The bundle also estabishes connections with the motor nuclei in the pons and medulla
iblongata.
 
The medial longitudinal bundle extends as high as a special nucleus,
called the nucleus of the posterior longitudinal bundle, which is situated
n the grey matter of the ventro-lateral portion of the third ventricle
rear the upper opening of the aqueduct, from the cells of which nucleus
 
some of its fibres arise. . .
 
The bundle consists of ascending and descending association fibres,
which form connections between the important nuclei just referred
to. Probably the chief use of the bundle is to maintain a functional
association between these nuclei, and insure harmonious action of
the muscles which are supplied by the nerves arising from them.
 
Tecto-spinal Tract (Ventral Longitudinal Bundle). This bundle
ties on the ventral aspect of the medial longitudinal bundle.. Its fibres
are derived from the stratum opticum and stratum lemnisci of the
upper quadrigeminal body of the opposite side. These fibres, as stated
in connection with the upper quadrigeminal bodies, descend beside t e
°Tey matter round the aqueduct, cross the median plane, and decussate
with the corresponding fibres of the opposite side, the decussation
being known as the dorsal fountain decussation (of Meynert). Ihe
 
 
j 556
 
 
A MANUAL OF ANATOMY
 
 
fibres descend through the tegmentum, lying close to the red nucleus, to
which they furnish collaterals. Thereafter they traverse the formatio
reticularis of the pons and medulla oblongata, still lying on the ventral
aspect of the medial longitudinal bundle. From the medulla oblongata
the fibres pass into the anterior ground-bundle of the lateral column of
the spinal cord, where they lie just in front of the rubro-spinal tract,
and they form arborizations around the motor cells of the ventral horn
of grey matter.
 
The pallido-rubro-olivary tract (Figs. 955 and 956) is a well-formed
and marked bundle of fibres which can be found in sections through
the mid-brain and pons. The fibres lie between the red nucleus and
the olive, above the medial part of the red nucleus and the cerebellar
peduncular fibres in the crura, within the concavity of these fibres as
they pass between their decussation and the superior peduncle, more
laterally in the middle and lower parts of the pontine tegmentum, and
gain the inferior olive just below the lower border of the pons; they
may be visible in part on the surface here (Fig. 883). The exact path
of the tract between the red nucleus and the globus pallidus is not
certainly known; the tract is probably in great part interrupted at the
red nucleus, from which the rubro-olivary fibres take origin, but direct
pallido-olivary fibres are known to be present also.
 
This tract is essentially a structure belonging to the brains of
the higher vertebrates, in which the inferior olive replaces or
reinforces the primitive olivary formation; this is represented in
the human brain by the medial and other accessory olives.
 
Rubro-spinal Tract (or Bundle of Monakow). —The fibres of this
tract are derived, as previously stated, from the axons of the cells
of the red nucleus. They cross the median plane, decussating with
the corresponding fibres of the opposite side, and constituting the
ventral fountain decussation [of Foret). The tract then descends through
the pons and medulla oblongata into the lateral column of the spinal
cord, in which it constitutes the prepyramidal tract on the ventrolateral aspect of the lateral cortico-spinal tract.
 
Medial Lemniscus. —The medial or main lemniscus of either side
begins in the lower part of the medulla oblongata. It is here the only
lemniscus on either side, and its fibres are derived from the deep
lemniscal arcuate fibres, which arise from the cells of the nucleus gracilis
and nucleus cuneatus of the opposite side. The main lemniscus therefore represents the upward continuation of the posterior column of
the spinal cord (gracile and cuneate fasciculi), and it is spoken of as
the chief sensory tract. The deep lemniscal arcuate fibres cross the
median plane directly above the decussation of the pyramids [motor
decussation) , thus constituting the decussation of the lemnisci (main
fillets or chief sensory tracts), or the sensory decussation. The fibres,
after crossing the median plane, form the tract of the side to which they
have crossed. In the medulla oblongata it lies close to the median
raphe, and at first is in front of the medial longitudinal bundle, and
 
 
 
 
THE NERVOUS SYSTEM
 
 
1557
 
 
iirectly behind the pyramid. The main lemniscus then ascends through
:he dorsal part of the pons, its relative position remaining unchanged,
[n this situation the lateral lemniscus, to be presently described, takes
jp its position on the outer or lateral aspect of the main or medial
Dand. The main tract, on leaving the pons, enters the ventral part
i)f the tegmentum, still having the lateral tract on its outer side. As
t encounters the red nucleus it is displaced laterally and backwards,
md then occupies the dorso-lateral part of the tegmentum, lying almost
beneath the medial geniculate body.
 
The fibres of the main or medial lemniscus (chief sensory tract)
terminate in two ways: (1) Some enter the upper quadrigeminal body,
md these probably terminate in the stratum lemnisci; (2) others traverse
the subthalamic tegmental region, and enter the anterior part of the
thalamus, within which they terminate in arborizations around the
cells of the ventro-lateral nuclear area (chief sensory nucleus). From
these cells relays of thalamo-corticipetal fibres proceed to the cerebral
cortex.
 
It is convenient to refer to the main or medial band as the sensory
lemniscus.
 
Lateral Lemniscus. —The main or medial band being the sensory lemniscus, it is convenient to refer to the lateral one as the auditory fillet or
lemniscus. The fibres of this fillet are derived from the following sources:
(1) The corpus trapezoides, the fibres of which come from the ventral
cochlear nucleus, the nucleus trapezoides, and the superior olive of the
opposite side, as well as from the superior olive of the same side; (2) the
auditory striae, which are derived from the lateral cochlear nucleus of
the opposite side; and (3) the nucleus of the lateral lemniscus.
 
The fibres of the right and left lateral lemnisci decussate across the
median plane. Having crossed to the opposite side, the fibres become
longitudinal and form a well-marked ascending tract in the dorsal part
of the pons, which takes up a position on the lateral or outer side of the
main or medial tract. In this part of its course the lateral lemniscus
encounters a collection of grey matter, called its nucleus. Some of its
fibres end in this nucleus. Others pursue their upward couise, and are
reinforced by relays of fibres which arise from the nerve-cells of the
nucleus On leaving the pons the lateral band enters the tegmentum,
and its fibres terminate in (1) the nuclei of the lower quadrigeminal
body, and (2) the cells of the medial geniculate body. The fibres
destined for the lower quadrigeminal body, having curved round
the lateral aspect of- the superior cerebellar peduncle, become superficial on the outer side of the tegmentum. The fibres destined for
the medial geniculate body reach it through the inferior brachium
partly directly and partly through the intervention of the lower quadrigeminal body. The axons of the cells of the geniculate body form
corticipetal fibres which pass to the cortex of the first or superior
 
temporal gyrus of the temporal lobe. .
 
The lateral lemniscus, therefore, is associated with the auditory
apparatus. It is chiefly composed of ascending fibres. There are,
 
 
 
A MANUAL OF ANATOMY
 
 
I55 8
 
however, some descending fibres which are probably derived from the
lower quadrigeminal bodies.
 
In addition to the foregoing, there are other tracts.
 
Fasciculus Retroflexus. —The fibres of this bundle, already described, arise
from the cells of the ganglion habenulce. They descend in the upper part of the
tegmentum internal to the red nucleus, and they terminate in arborizations
around the cells of the interpeduncular ganglion.
 
Bundle of Munzer. —The fibres of this tract descend from the lower quadrigeminal body to the formatio reticularis of the lateral part of the pons.
 
Spino-thalamic Tract. —The fibres of this tract, as stated in connection with
the tracts of the spinal cord, arise from the cells of the dorsal grey column of
the opposite side. Having crossed in the ventral or white commissure, they
enter the antero-lateral or indirect cerebellar tract (tract of Gowers), in which
they ascend through the medulla oblongata, pons, and tegmentum of the crus
cerebri to the thalamus of the side to which they have crossed.
 
 
 
Fig. 957.—Diagram to show Position and Relations of Structures in
 
Tegmental Subthalamus.
 
Supposed to be viewed from the medial aspect. R, red nucleus. The subthalamic nucleus is shown antero-lateral to this. Dotted line shows course
of fasciculus retroflexus from habenula to interpeduncular ganglion. Course
of anterior pillar of fornix is indicated, also mamillo-thalamic tract (bundle
of Vicq d’Azyr) passing up medial to front part of subthalamic nucleus.
Substantia nigra is seen near pontine level, but passes upwards and laterally
out of the section higher up.
 
Subthalamic Tegmental Region. —This region represents the upward prolongation of the tegmentum of the crus cerebri beneath the
posterior part of the inferior or ventral surface of the thalamus. The
prolongation contains (1) an upward extension of the red nucleus of
the tegmentum, (2) the fibres of the superior peduncle of the cerebellum, and (3) the main or medial lemniscus (chief sensory tract).
 
The upward extension of the red nucleus ceases about the level
of the corresponding corpus mamillare. Some of the fibres of the
superior peduncle of the cerebellum terminate, as stated, in the red
nucleus, and others encapsule it, as they do in the tegmentum. Many
fibres issue from the cells of the red nucleus, and these, along with the
investing fibres of the superior cerebellar peduncle, enter the inferior
or ventral surface of the thalamus.
 
 
 
THE NERVOUS SYSTEM
 
 
1559
 
 
The main lemniscus (chief sensory tract), which lies on the dorsolateral aspect of the red nucleus, also enters the inferior or ventral
surface of the thalamus.
 
Development of the Crura Cerebri. —The crura cerebri are developed
in the ventral wall of the mesencephalon.
 
Basis Pedunculi (Crusta or Pes). —The basis is the ventral portion
of the crus cerebri, and is separated from the tegmentum of the crus by
a mass of dark grey matter, called the substantia nigra, which is
situated in the interior. Externally the separation is indicated on the
outer aspect by the lateral sulcus, and on the inner aspect by the oculomotor sulcus, through which the fasciculi of the oculo-motor nerve
emerge. The basis is continuous with the internal capsule of the
corpus striatum, and it consists of longitudinal centrifugal fibres, which
arise in the cells of the cerebral cortex. These fibres are arranged in
two sets, pyramidal and cortico-pontine. The pyramidal fibres form
 
 
supr cerebellar
peduncle —
red nucleus^
fillet-_
posi c long 1 , bundlenucleus of 3 rd nerve
 
supr corpus_
 
quadrigeminum
 
 
 
corpus mammilare
3 r - d cranial nerve
-optic tract
-fronto pontine fibres
 
--pyramidal tract
_ temporo pontine fibres
_ -substantia nigra
 
-exT geniculate body
 
-inti- do. do.
--fimbria
-—dentate fissure
-optic radiations
 
aqueduct
 
 
F IG . 958.—The Crura Cerebri and their Relations.
 
 
the motor tract from the precentral region of the cerebral cortex, and
the cortico-pontine fibres are arranged in two strands—namely, frontopontine and temporo-pontine.
 
The pyramidal fibres form the motor tract from the precentral
region of the cerebral cortex. T hey traverse the lenticular portion
of the posterior limb of the internal capsule, and then occupy the
middle three-fifths of the crusta. Thereafter they descend through
the ventral portion of the pons and the pyramid of the medulla
oblongata. In the lower part of the pyramid they give rise to the
crossed and direct pyramidal tracts. The crossed pyramidal tract,
having taken part in the decussation of the pyramids, descends in the
spinal cord as the lateral corticospinal tract, occupying the posterior
part of the lateral column of the opposite side The direct pyramidal tract descends (anterior cortico-spmal tract) in the spinal cord,
occupying the medial part of the anterior column of the same side.
Its fibres however, cross at intervals to the opposite side.
 
 
 
 
 
 
 
1560
 
 
A MANUAL OF ANATOMY
 
 
As the pyramidal tract descends through the pons and medulla
oblongata, some of its fibres pass to the motor nuclei of the cranial
nerves in these regions.
 
The cortico-pontine fibres are arranged in two strands, frontopontine and temporo-pontine. The fibres of the fronto-pontine
strand arise from the cells of the cortex of the anterior part of the
frontal lobe, and, having traversed the anterior limb of the internal
capsule, they are regarded as occupying the medial fifth of the basis
pedunculi. The fibres of the temporo-pontine strand arise from the
cells of the cortex of the temporal lobe, and having traversed the postlenticular part of the internal capsule, they occupy the lateral fifth of
the crusta. In the ventral part of the pons both the fronto-pontine
and the temporo-pontine fibres terminate in arborizations around the
cells of the nucleus pontis, whereas the pyramidal fibres pass uninterruptedly through the ventral part of the pons.
 
Substantia Nigra. — t his is a mass of dark grey matter which is
situated between the tegmentum and the basis of the crus cerebri.
Like the basis, it is semilunar or crescentic, as seen in transverse
section. It contains many multipolar nerve-cells, which are deeply
pigmented, and it extends from the upper border of the pons into the
subthalamic tegmental region. Laterally it reaches the lateral sulcus
on the lateral aspect of the crus, where it is thin, and the oculo-motor
sulcus on the medial aspect, where it is thick, and is traversed by the
fasciculi of the third cranial or oculo-motor nerve. Its tegmental
surface is concave, and the surface directed towards the basis is
convex. From the latter surface prolongations extend into the basis.
 
1 he substantia nigra does not acquire its pigment before the
second or third year after birth.
 
Aqueduct of Mid-brain. —The aqueduct is the narrow passage which
leads through the mesencephalon from the third to the fourth ventricle (iter a tertio ad quartum ventriculum ). It lies nearer the dorsal
than the ventral aspect of the mesencephalon; its direction is from
above downwards, and its length is rather more than J inch. Its
upper opening is situated on the posterior boundary of the third
ventricle immediately underneath the posterior commissure, and its
lower opening occupies the superior median angle of the floor of the
fourth ventricle. In transverse section the aqueduct is T-shaped
in its upper part near the third ventricle, and triangular in its lower
part near the fourth ventricle. The passage is lined with ciliated
columnar epithelium, external to which there is a thick layer of grey
matter, which is spoken of as the central (Sylvian) grey matter. This
is continuous superiorly with the grey matter of the floor and lateral
walls of the third ventricle, and inferiorly with that which covers
the floor of the fourth ventricle. It contains numerous nerve-cells
disposed in a scattered manner, but, in addition to these, there are
certain definite cell-groups.. These groups constitute the nuclei of
origin of the following cranial nerves: the third or oculo-motor, the
 
 
THE NERVOUS SYSTEM
 
 
1561
 
 
fourth or trochlear, and the mesencephalic root of the fifth nerve.
The oculo-motor nucleus is situated in the ventral portion of the
grey matter underneath the upper quadrigeminal body, and it extends upwards into the layer of grey matter on the adjacent portion
of the lateral wall of the third ventricle. The trochlear nucleus is
also situated in the ventral portion of the grey matter, but at a
lower level than the oculo-motor nucleus, being placed underneath
the upper part of the lower quadrigeminal body. The nucleus of
the mesencephalic root of the fifth nerve is extensive, and is situated
in the lateral portion of the grey matter.
 
Development. —The aqueduct is the persistent remains of the cavity of the
mesencephalon.
 
Posterior Perforated Substance. —This area has been previously
described in a general way in connection with the base of the encephalon. It will here be considered more fulfy. It lies at the bottom
of a deep depression, called the interpeduncular fossa, which forms
the back part of the interpeduncular space. The fossa is bounded
posteriorly by the median portion of the upper border of the pons,
and laterally by the crura cerebri. Anteriorly it is limited by the
corpora mamillaria.
 
The locus perforatus is a perforated lamina of grey matter which
forms the floor of the interpeduncular fossa, the openings being for
the passage of the postero-medial ganglionic branches of the posterior
cerebral arteries. This grey lamina extends between the tegmenta of
the crura cerebri.
 
Ganglion Interpedunculare. —This is a collection of nerve-cells
situated medially in the lower part of the grey lamina which constitutes the posterior perforated substance. On either side it receives
the fibres of the fasciculus retroflexus , which are derived from the
ganglion habenulae.
 
 
Structure of the Cerebral Hemispheres.
 
 
The cerebral hemisphere is composed of grey and white matter.
The grey matter is disposed externally, and forms the cerebral cortex,
which, with the exception of the rhinencephalon, is known as the neopallium. The white matter occupies the interior, and constitutes the
 
medullary centre.
 
Cerebral Cortex.— The grey matter forms a continuous covering
to the entire hemisphere, dipping into the sulci, so as to cover the
opposed surfaces of the gyri, as well as the bottom of the sulci,
is thicker over the superficial surfaces of the gyri than at the bottom
of the sulci, and attains its greatest thickness over the upper portions
of the precentral and postcentral gyri, whilst it is thinnest over the
 
 
The cerebral cortex is indistinctly divided into strata by means
of layers of a whitish substance. When examined m section it therefore presents a stratified appearance, and is seen to consist of successive
 
 
1562
 
 
A MANUAL OF ANATOMY
 
 
grey and white layers alternating with each other. In most parts
of the cerebral cortex there are four superimposed strata; but in certain
situations— e.g., over the precentral gyrus—there are as many as six.
These strata are as follows, from without inwards:
 
 
1. Molecular layer, a superficial
 
white layer (pale and narrow).
 
2. Superficial grey layer, the outer
 
granular.
 
3. Outer white band of Baillarger.
 
4. Middle grey layer.
 
 
5. Inner white band of Baillarger.
 
6. Inner or deep grey layer, the
 
polymorphous layer, subjacent to which is the white
matter of the medullary
centre.
 
 
Layers 3, 4, and 5 are included in the pyramidal layer, in which the
cells tend to increase in size as they lie more deeply; the largest lie
over the inner band of Baillarger.
 
The medullated fibres of the medullary centre pass into the stratified grey cortex in a radiating manner, and within the cortex their
course for the most part is perpendicular to the superficial surface,
and between the component cells of the cortex.
 
Minute Structure of the Cerebral Cortex. —The cortex is composed
of nerve-cells and nerve-fibres.
 
Nerve-cells. —These are arranged in four layers, which are, from
without inwards: (1) the molecular layer; (2) the layer of small pyramidal cells; (3) the layer of large pyramidal cells; and (4) the layer
of polymorphous cells.
 
The molecular or plexiform layer, which is the most superficial,
is thin, and consists of cells and fibres. Many of the cells are neurogliacells, the others being nerve-cells. These nerve-cells are for the
most part fusiform, and are disposed horizontally. They are known
as the horizontal cells of Cajal. Their dendrons and axons are long,
the latter forming medullated fibres which are disposed horizontally
or parallel to the surface. These furnish minute branches which pass
vertically towards the surface. The horizontal cells, according to
Cajal, receive impulses from the corticipetal fibres which extend from
the thalamus to the cerebral cortex.
 
In addition to these fibres there are many others which enter the
molecular layer from deeper sources, and form a dense interlacement
by their ramifications. The sources from which these extraneous fibres
are derived are: (1) the terminal ramifications of the apical dendrons
of the pyramidal cells (small and large); (2) the axons of the cells of
Martinotti, which lie in the polymorphous layer; and (3) corticipetal
fibres derived from the medullary centre of the gyrus.
 
The pyramidal layers represent the second and third layers, and
are composed of characteristic pyramidal cells which are peculiar
to the cerebral cortex, those of the second layer being small, whilst
those of the third layer are large. The layer of small pyramidal
cells is narrow, but the layer of large pyramidal cells is of considerable
thickness. The giant pyramidal cells of the motor cortex are known
as cells of Betz. There is no well-marked line of demarcation between
 
 
THE NERVOUS SYSTEM 1563
 
these two layers, the one passing imperceptibly into the other. They
constitute the chief part of the cerebral cortex.
 
 
Molecular j
Plexiiorm
Layer
 
 
Layer of Small £
Pyramidal
Cells
 
 
Layer of Large
Pyramidal °
Cells
 
 
Layer of .
Polymorphous **
Cells
 
 
 
Plexus of Exne r
(.Superficial
Tangential
Fibres)
 
 
Band ot
Bechterew
 
 
Outer Band of
Bail larger
 
 
Radiating
 
Vertical
 
Fibres
 
Inner Band of
Baillarger
 
 
Deep Tangential
Fibres
 
 
•White Medullary
Centre
 
 
Fig , W -Diagram showing the Minute Structure of the Cerebral
J Cortex (Poirier).
 
The fibres are shown on the right, and the cells on the left.
 
 
The apex of each pyramidal cell is directed towards the surface
of the evrus and is prolonged into a long tapering dendrite which
(Fig. 960) passes into the molecular layer, giving off delicate collatera s
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
*564
 
 
A MANUAL OF ANATOMY
 
 
Terminal Ramifications
 
 
in its course. Near the surface of the molecular layer it divides into
terminal filaments, which are disposed horizontally and mingle with
the tangential fibres. The base of the pyramidal cell is directed
towards the medullary centre of the gyrus, and from its centre an
axon is given off, which enters the medullary centre, giving off
collaterals in its course. From each side of the body of the cell, as
well as from each lateral angle of its base, dendrites are given off.
 
The polymorphous layer is the deepest layer, and is composed of
cells which have different shapes. Each cell gives off several dendrites, which pass towards, but
do not enter, the molecular
layer. The axon of each cell
enters the medullary centre as
a nerve-fibre.
 
In addition to the foregoing
cells of the cerebral cortex, two
other kinds of cells are met
with amongst the pyramidal and
polymorphous cells—namely, the
cells of Golgi and the cells of
Martinotti. The cells of Golgi
are characterized by the fact
that the axon of each almost
immediately divides into several
branches, which pass towards
the surface, but soon terminate
without entering the molecular
layer. The cells of Martinotti
are chiefly met with in the polymorphous layer. The axon of
each cell passes towards the surface, and enters the molecular
 
 
 
Human Cerebral Cortex (Ramon
y Cajal).
 
 
layer, where it divides into terminal branches, which form part of the
tangential fibres of this layer.
 
 
Nerve-fibres of the Cortex. —1 hese are arranged in two groups—
vertical and tangential.
 
The vertical (radial) fibres are disposed in radiating bundles,
which issue from the medullary centre, and traverse the polymorphous and large pyramidaf layers, after which they become
indistinguishable. The polymorphous and large pyramidal cells
lie m the spaces between these bundles, and assume a columnar
arrangement. The fibres of the radiating bundles gradually
become less numerous, some of them becoming the axons of the
polymorphous cells, but most of them becoming the axons of the
large pyramidal cells. The radiating bundles contain centripetal
cortical fibres, which pass into the molecular layer and end in
terminal ramifications, forming part of its tangential fibres.
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1565
 
The tangential fibres are disposed horizontally at different
levels, and form the following strata: (1) the superficial tangential
fibres (plexus of Exner), which occupy the superficial part of the
molecular layer; (2) the band of Bechterew, which is situated in
the superficial part of the small pyramidal layer; (3) the outer
band of Baillarger (band of Vicq d’Azyr), which intersects the
large pyramidal layer; (4) the inner band of Baillarger, which is
situated between the large pyramidal and polymorphous layers;
and (3) the deep tangential fibres (intracortical association fibres),
which are situated in the deep part of the polymorphous layer.
 
The tangential fibres are formed by (1) the collaterals of the
polymorphous and pyramidal cells and of the cells of Martinotti;
(2) the ramifications of the axons of the cells of Golgi; and (3) association fibres.
 
Medullary Centre of Cerebral Hemisphere. —The white matter of
the medullary centre consists of medullated nerve-fibres, which
pursue different courses, and are arranged in three groups—namely,
projection fibres, commissural fibres, and association fibres.
 
The projection fibres connect the cerebral cortex with parts at
a lower level, and they are of two kinds—corticipetal or afferent,
and corticifugal or efferent. The commissural fibres pass from one
hemisphere to the other, and connect portions of the cerebral cortex
of opposite hemispheres. The association fibres are confined to
one side of the median plane, and they bring different parts of the
cerebral cortex of the same hemisphere into association with one
another.
 
Projection Fibres. —These fibres, as stated, are both corticipetal
and corticifugal, and the majority of them constitute the internalcapsule of the corpus striatum, and the diverging arrangement of
its fibres known as the corona radiata, which passes to all parts of the
cerebral cortex. Some projection fibres, however, do not traverse
the internal capsule and corona radiata—£.g., the fibres of the ansa
peduncularis.
 
Corticifugal Fibres.— The corticifugal or efferent fibres constitute
the following tracts:
 
1. Pyramidal or motor. 3 - Fronto-pontine.
 
2. Cortico-thalamic. 4- Temporo-pontine.
 
5. Optic radiation (portion).
 
The pyramidal or motor tract derives its fibres from the axons
of the pyramidal cells of the cortex of the precentral gyrus, which
is situated in front of the central fissure. Having traversed the
corona radiata, these fibres pass in succession through (1) the posterior
limb of the internal capsule, (2) the middle three-fifths of the basis of the
crus cerebri, (3) the ventral portion of the pons, and (4) the pyramid
of the medulla oblongata. The motor strand enters the spinal cord
in three ways—partly as the direct or ventral cortico-spinal tract,
partly as the uncrossed lateral tract, but chiefly as the crossed lateral
 
 
1566
 
 
A MANUAL OF ANATOMY
 
 
corticospinal tract. Ultimately the fibres terminate at different
levels in arborizations around the motor-cells of the ventral column of
grey matter of the opposite side, from which cells the fibres of the motor
nerve-roots proceed.
 
The efferent fibres which pass to the motor nuclei of the cranial
nerves do not, as a whole, run in the cortico-spinal pathway through the
basis pedunculi and basis pontis. They leave this path, usually in the
upper part of the mid-brain, and pass down (Fig. 961) in the tegmentum
of the mid-brain and pons. They reach the tegmentum also at lower
levels, passing usually either medial or lateral to the substantia nigra,
but they are not constant in this matter. These cortico-pontine or
 
cortico-bulbar fibres are thus aberrant
or extra-pyramidal fibres. The figure,
which is modified from Dejerine, shows
the nuclei supplied by this group, the
remnant of which rejoins the main tract
in the medullary pyramid. Each central supply to the nuclei decussates,
crossing the middle line nearly at the
level of the nucleus to which it is going.
 
The cortico-thalamic tract extends
only between the cerebral cortex and
the thalamus. Its fibres arise as the
axons of the pyramidal cells of various
parts of the cerebral cortex, and they
terminate in arborizations around the
cells of the thalamus.
 
The fronto-pontine tract does not
extend lower than the pons. It consists of fibres which arise as the axons
of the pyramidal cells of the cortex of
the prefrontal region—that is to say,
the region of the frontal lobe in front
of the precentral sulcus. These fibres
traverse the anterior limb of the internal capsule, and then descend through the inner or medial fifth of
the basis of the crus cerebri into the pons. Within the pons they
terminate in arborizations around the cells of the nucleus pontis.
 
The temporo-pontine tract, like the preceding, does not extend lower
than the pons. It consists of fibres which arise as the axons of the
pyramidal cells of the cortex of the first and second temporal gyri.
These fibres traverse the postlenticular part of the posterior limb of the
internal capsule, and then descend through the outer fifth of the basis
of the crus cerebri into the ventral part of the pons. Within this part
of the pons they terminate in arborizations around the cells of the
nucleus pontis.
 
The corticifugal fibres of the optic radiation consist of fibres which
arise as the axons of the pyramidal fibres of the cortex of the occipital
 
 
 
N. III.
 
 
' ~ ' N. IV.
 
 
N. V.
 
N. VI.
 
N. VII.
 
N. Amb.
N. XII.
 
 
Fig. 961. — Plan of Extrapyramidal Fibres running
in the Tegmentum to Nuclei
of Cranial Nerves (modified from Dejerine).
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1567
 
lobe. Ihey traverse the post lenticular part of the posterior limb of
the internal capsule, and thereafter pass to the lower visual centres—
namely, the lateral geniculate body and the upper quadrigeminal body.
Within these bodies they terminate in arborizations around their component cells.
 
Corticipetal Fibres. —The corticipetal or afferent fibres belong to the
following tracts:
 
1. Medial lemniscus. 3. Thalamic radiation.
 
2. Superior cerebellar peduncle. 4. Auditory radiation.
 
5. Optic radiation.
 
The medial lemniscus, or principal sensory tract , arises from the
nucleus gracilis and nucleus cuneatus of the medulla oblongata, and is
the upward prolongation of the posterior column of the spinal cord.
Having decussated with its fellow, it ascends through the dorsal part
of the pons through the tegmentum of the crus cerebri, and through
the subthalamic tegmental region to the thalamus. Within this
body its fibres terminate in arborizations around the thalamic cells.
As the medial lemniscus ascends towards the thalamus some of its
fibres enter the upper quadrigeminal body, in which they end. From
the thalamus the fillet-fibres are continued to the cerebral cortex by
relays of thalamo-cortical fibres.
 
The superior cerebellar peduncle, having decussated with its fellow,
soon comes into contact with the red nucleus. Many of the fibres of
the peduncle enter this nucleus and terminate in arborizations around
its cells. Numerous fibres encapsule the nucleus, and continue their
course upwards, traversing the subthalamic tegmental region, and
finally entering the ventral aspect of the thalamus, within which
they terminate in arborizations around the thalamic cells. As in the
case of the fillet-fibres, they are continued to the cerebral cortex by
relays of thalamo-cortical fibres.
 
The thalamic radiation is composed of thalamo-cortical fibres
which arise as the axons of the cells within the thalamus, that body
being regarded as an aggregation of cell-stations in the path of such
corticipetal fibres as those of the medial lemniscus and superior
cerebellar peduncle. These thalamo-cortical fibres, as stated in the
description of the thalamus, issue from that body in four groups or
stalks—frontal, parietal, occipital, and inferior or ventral. The fibres
of the frontal stalk traverse the anterior limb of the internal capsule,
and most of them pass to the cortex of the frontal lobe. The fibres
of the parietal stalk pass partly through the internal capsule and partly
through the external capsule to the cortex of the parietal lobe and of
the central region of the frontal lobe. The fibres of the occipital stalk
belong to the optic radiation, to be presently described. The fibres
of the inferior or ventral stalk form the ansa lenticularis and ansa
peduncularis. The ansa lenticularis enters the nucleus. lentiformis,
within which its fibres terminate. the ansa peduncularis passes beneath the nucleus lentiformis and traverses the external capsule, the
 
 
1568
 
 
A MANUAL OF ANATOMY
 
 
destination of its fibres being the cortex of the temporal lobe and
insula.
 
The auditory radiation consists of fibres which arise as the axons
of the cells of the medial geniculate body. Having issued from that
body, they traverse the postlenticular part of the posterior limb of the
internal capsule, and pass to the cortex of the middle part of the first
temporal gyrus of the temporal lobe.
 
The corticipetal fibres of the optic radiation are associated with the
corticifugal fibres, already described. The corticipetal fibres arise as
the axons of the cells of the corpus geniculatum laterale and upper
quadrigeminal body. They traverse the postlenticular part of the
posterior limb of the internal capsule, and then pass to the cortex of
the occipital lobe.
 
Commissural Fibres. —These fibres are disposed transversely, and
serve to connect the grey cortex of one hemisphere with that of the
other. They constitute the following commissures: (1) the corpus
callosum ; (2) the anterior commissure ; and (3) the lyra, which is known
as the hippocampal commissure. The fibres of the corpus callosum, as
they enter each hemisphere, are disposed so as to form an extensive
callosal radiation, and serve to connect the cortex of one hemisphere with
that of the other. The individual portions of cortex so connected
may be symmetrical, but to a large extent are not. The fibres arise
on one side as (1) the axons of pyramidal or of polymorphous cells, or
(2) collaterals of projection or of association fibres; and on the opposite
side they terminate in delicate arborizations.
 
The anterior commissure, which crosses from side to side in front
of the anterior pillars of the fornix, divides on either side into two parts,
olfactory and temporal. The olfactory portion enters the olfactory
tract. Some of its fibres serve to connect the olfactory bulb of one
side with that of the other side; and other fibres connect the olfactory
bulb of one side with the temporal lobe of the opposite. The temporal
portion enters the white matter of the temporal lobe on either side.
 
The hippocampal commissure lies below the splenial portion of the
corpus callosum, and is separated from the roof of the third ventricle
by the tela chorioidea. It is a thin layer of arched fibres connecting
the posterior pillars and sides of the fornix, and derived mainly from
the hippocampus of each side; it is shown in Fig. 933. The commissure,
which is not well developed in the human brain, was known as the
‘ lyra ’ in former days.
 
The corpus callosum is the great commissure of the neopallium; the hippocampal and anterior commissures, phylogenetically much older, are connections
of the rhinencephalon, and hence archipallial.
 
Association Fibres. —These fibres serve to connect different parts of
the cortex of the same hemisphere, and they are of two kinds, short
and long.
 
The short association fibres pass between neighbouring gyri, extending in their course across the bottom of the sulci. Some of them
 
 
/
 
 
 
THE NERVOUS SYSTEM 1569
 
lie beneath the grey cortex, whilst others are contained within its
deep part.
 
The long association fibres pass between portions of the grey cortex,
which are at some distance from each other. They are arranged in
bundles, the chief of which are as follows: (1) the superior longitudinal
fasciculus; (2) the interior longitudinal fasciculus; (3) the perpendicular
fasciculus; (4) the uncinate fasciculus; (5) the cingulum; (6) the occipitofrontal fasciculus; and (7) the fornix.
 
The superior longitudinal fasciculus consists of fibres which extend
from the frontal to the occipital lobe. Posteriorly many of its fibres
sweep downwards and forwards into the temporal lobe, and from this
circumstance it is sometimes spoken of as the arcuate fasciculus.
 
The inferior longitudinal fasciculus connects the occipital and
temporal lobes, its fibres being disposed upon the lateral walls of the
posterior and inferior horns of the lateral ventricle.
 
The perpendicular fasciculus connects the inferior parietal lobule
with the occipito-temporal gyrus.
 
The uncinate fasciculus crosses the stem of the lateral fissure, and
connects the frontal and temporal lobes.
 
The cingulum is connected with the rhinencephalon, and lies upon
the under surface of the callosal gyrus and the upper surface of the
hippocampal gyrus. Its fibres connect the gyri of the lobe with the
cerebral cortex.
 
The occipito-frontal fasciculus connects the frontal with the occipital and temporal lobes. It lies internal to the corona radiata, in
intimate relation to the nucleus caudatus, and as the fibres pass backwards they lie on the outer walls of the inferior and posterior horns
of the lateral ventricle.
 
The fornix connects the hippocampus major of one side with the
corresponding corpus mamillare, and through the latter with the
thalamus by means of the mamillo-thalainic tract (bundle of Vicq
d’Azyr), the fibres of which arise in the corpus mamillare.
 
Peculiarities of the Cerebral Cortex-— 1. Calcarine Area.— This area is situated
on the medial surface of the occipital lobe in close proximity to the calcarine
fissure, and it is known as the visual area. In this region the outer band of
Baillarger is very conspicuous, and is known as the white band of Gennari, whilst
the inner band of Baillarger is absent.
 
2. Central Area. —In this region, more especially in the cortex of the precentral gyrus, there are groups of very large pyramidal cells, which are known
as the giant-cells of Betz, and nerve-fibres are present in large numbers.
 
3. Hippocampal Area. —The hippocampus corresponds to the hippocampal
or dentate fissure, and is produced by an infolding of the cerebral cortex. It is
therefore composed chiefly of grey matter, and is covered superficially by a
thin layer of white matter, called the alveus, which is continuous with the fimbria.
The hippocampus is composed of the following layers, named in order from
the ventricular surface outwards: (1) the alveus, composed of white matter, and
covered by the ventricular ependyma; (2) neuroglial layer, consisting of neuroglia
fibres and cells; (3) pyramidal layer, composed of large pyramidal cells; (4) stratum
radiatum, which is the outer part of the pyramidal layer, and is composed of the
dendrites of the apical parts of the pyramidal cells, being thereby rendered
striated in appearance; (5) stratum laciniosum, composed of the ramifications
 
99
 
 
1570
 
 
A MANUAL OF ANATOMY
 
 
of the foregoing apical dendrites intimately intermixed; (6) stratum granulosum,
composed of many small cells; and (7) the involuted medullary lamina, consisting
of white fibres.
 
Olfactory Tract and Olfactory Bulb. —These are developed as a
hollow outgrowth from the anterior cerebral vesicle, more particularly
from the part of it which ultimately gives rise to the lateral ventricle,
and is known as the telencephalon. In many animals the central cavity
persists, and maintains its connection with the lateral ventricle; but
in man the cavity disappears, though traces of its ependymal lining
remain. External to the vestigial ependyma there is a layer of white
matter, and superficial to this there is a layer of grey matter. In the
olfactory tract the layer of grey matter is very thin over the ventral
or inferior aspect, but over the dorsal or superior aspect it is fairly
thick. In the bulb the reverse is the case, the grey matter being thick
over the ventral aspect, where it receives the olfactory filaments, but
thin over the dorsal aspect.
 
Structure of the Ventral Grey Matter of the Olfactory Bulb. —The
 
grey matter consists of three layers—namely, (1) the nerve-fibre layer,
(2) the glomerular layer, and (3) the granular layer.
 
The nerve-fibre layer is the most superficial layer, and is composed
of olfactory nerve-fibres. These fibres are non-medullated, and arise
as the axons of the olfactory cells of the olfactory mucous membrane
of the nasal fossa. Having passed through the foramina of one half
of the cribriform plate of the ethmoid bone, they enter the grey matter
on the ventral aspect of the bulb, where they break up and form
arborizations. These intermingle with the arborizations formed by
the dendrites of the mitral cells, to be presently described.
 
The glomerular layer is composed of round bodies or glomeruli,
which are formed by the interlacements between the arborizations
of the olfactory nerve-fibres and those of the dendrites of the mitral
cells.
 
The granular layer lies next to the layer of white matter, and is
chiefly characterized by the presence of large mitral cells. These are
pyramidal, and one dendrite from each cell passes into the glomerular
layer, where it gives rise to a glomerulus in the manner just described
in connection with the glomerular layer. Other dendrites intermingle
with those of adjacent mitral cells. The axon of each mitral cell enters
the white layer of the bulb, and passes along the olfactory tract to the
cerebrum.
 
Weight of the Brain. —The average weight of the brain of the adult
male is about 48 ounces (1,360 grammes), and that of the adult female
about 44 ounces.
 
Arteries of the Encephalon.
 
Cerebral Part of the Internal Carotid Artery. —The internal carotid
artery, having pierced the roof of the cavernous sinus internal to the
anterior clinoid process of the sphenoid bone, ascends between the
second and third cranial nerves to the inner end of the stem of the
 
 
THE NERVOUS SYSTEM 1571
 
lateral fissure. Here it divides into its terminal branches, anterior
and middle cerebral.
 
Branches are posterior communicating, anterior choroidal, anterior
cerebral, and middle cerebral.
 
The posterior communicating artery arises from the back part of
the internal carotid, and passes backwards to anastomose with the
 
 
 
Fig. 962.—Arteries on the Base of the Brain.
 
 
posterior cerebral artery. It is usually small, but is often larger on
one side than the other. Occasionally it is absent.
 
The anterior choroidal artery arises from the back part of the
internal carotid close to its termination. It passes backwards and
outwards between the crus cerebri and the "hippocampal gyrus, and
enters the lower and anterior extremity of the descending horn of the
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
U572
 
lateral ventricle by passing through the choroidal fissure. In its course
it passes just above the uncus, gives twigs to the hippocampal gyrus
and crus cerebri, and terminates in the choroid plexus of the lateral
ventricle.
 
Anterior Cerebral Artery. —This is the smaller of the two terminal
branches of the internal carotid artery, and it has a more limited distribution than the other terminal branch—namely, the middle cerebral
artery. It passes forwards and inwards above the optic nerve, and
just internal to the roots of the olfactory tract, to the commencement
of the great longitudinal fissure, where it is connected with its fellow
of the opposite side by a short transverse vessel, called the anterior
communicating artery. After this it enters the great longitudinal
fissure, turns round the genu of the corpus callosum, and passes back
 
 
Fig. 963.—Median Section of Brain with Distribution of Anterior
 
Cerebral Artery.
 
wards over the upper surface of that body to the splenium, where it
anastomoses with the posterior cerebral artery.
 
Branches .—These are arranged in two groups, antero-medial or
ganglionic and cortical.
 
The antero-medial or ganglionic branches, small in size, pass through
the lamina cinerea along with twigs from the anterior communicating
artery, and supply the front part of the caudate nucleus.
 
The cortical branches are as follows: (1) medial orbital, to the medial
orbital gyrus, olfactory lobe, and gyrus rectus; (2) anterior medial
frontal, to the superior frontal gyrus, the anterior two-thirds of the
middle frontal gyrus, and the anterior part of the marginal gyrus;
(3) middle frontal, to the collosal gyrus, the posterior part of the marginal gyrus, and the upper part of the precentral gyrus; and (4) posterior
 
 
 
 
THE NERVOUS SYSTEM
 
 
1573
 
 
frontal, to the precuneus and the corpus callosum, the branch of the
latter being known as the artery of the corpus callosum.
 
Anterior Communicating Artery. —This vessel connects the two
anterior cerebral arteries at the entrance to the great longitudinal
fissure, and lies over the lamina terminalis in front of the optic commissure. It gives off a few twigs, which accompany the antero-medial
branches of each anterior cerebral artery.
 
Middle Cerebral Artery. —This is the larger of the two terminal
branches of the internal carotid artery, and it has a wider distribution
than the anterior cerebral artery. It enters the stem of the lateral
fissure, in which it passes outwards.
 
Branches .—These are arranged in two groups, antero-lateral or
ganglionic and cortical. The antero-lateral or ganglionic branches
 
 
 
Pig. 964._Distribution of the Left Middle Cerebral Artery (Charcot).
 
 
F.i. Superior Frontal Gyrus
F.2. Middle Frontal Gyrus
F.3. Inferior Frontal Gyrus
F.A. Ascending Frontal Gyrus
P.A. Ascending Parietal Gyrus
L.P.S. Superior Parietal Gyrus
L.P.I. Inferior Parietal Gyrus
P.C. Angular Gyrus
L.O. Occipital Lobe
 
 
L.T. Temporal Lobe
 
S. Middle Cerebral Artery entering Lateral
Fissure
 
P. Lenticulo-striate Arteries
 
1. Artery to Inferior Frontal Gyrus
 
2. Ascending Frontal Artery
 
3. Ascending Parietal Artery
 
4. Parieto-Temporal Artery
 
5. Arteries to Temporal Lobe
 
 
pass through the anterior perforated substance, and foim two sets,
medial striate and lateral striate. The medial striate arteries repiesem
the ‘ lenticular arteries * of Duret, and they supply the globus pallidus
(inner part) of the lentiform nucleus, the internal capsule, and the
caudate nucleus. Ihe lateral striate arteries represent the. lenticulostriate ’ and ‘ lenticulo-optic ’ arteries of Duret. The lenticulo-striate
arteries supply the putamen (outer part) of the lentiform nucleus and the
external capsule. One of the lenticulo-striate aiteries is said to be
larger than the others, and is subject to rupture in cases of cerebral
haemorrhage. It is often termed the artery of cerebral hcemorrhage
(Charcot). Its course is laterally and upwards round the outer aspect
of the lentiform nucleus, between it and the external capsule, and then
through the internal capsule to the caudate nucleus. The lenticulo
 
 
 
 
1574
 
 
A MANUAL OF ANATOMY
 
 
thalamic arteries supply the posterior part of the lentiform nucleus and
the anterior part of the thalamus on its lateral aspect.
 
The most important point to notice about all the ganglionic arteries
of the brain is that they are ‘ end arteries/ and their branches, once
having divided, never anastomose again; hence, if one of them is
blocked by an embolus, which is often a piece of fibrin from a diseased
heart valve, the area of brain supplied will be cut off from all bloodsupply, and the clinical effects may be very grave.
 
The cortical branches arise in the vicinity of the insula, and are:
(i) inferior lateral orbital, to the orbital surface of the frontal lobe
lateral to the internal orbital sulcus, and to the inferior frontal gyrus;
 
 
 
Fig. 965.- —Coronal Section of the Cerebral Hemispheres made One
Centimetre behind the Optic Commissure (Charcot, from Duret).
 
 
The arteries of this region are shown.
 
 
I. Area of Cerebral Artery
 
II. Area of Middle Cerebral Artery
 
III. Area of Posterior Cerebral Artery
V.V. Sections of Anterior Cornua of Lateral
Ventricles
 
P.P. Anterior Pillars of Fornix
C.N. Caudate Nucleus
L.S.A. Lenticulo-Striate Arteries
CL. Claustrum
I.R. Insula
E.C. External Capsule
 
 
L. N. Lentiform Nucleus
I.C. Internal Capsule
O.T. Optic Tract (cut)
 
G.M. Grey Matter of Third Ventricle
O.C. Optic Chiasma
O.N. Optic Nerve
A.C. Anterior Cerebral Artery
C. Internal Carot'd Artery
 
M. C. Middle Cerebral Artery
L.A. Lenticular Arteries
 
A.C.H. Artery of Cerebral Hemorrhage
 
 
(2) ascending frontal, to the posterior third of the middle frontal gyrus,
and to the lower and greater part of the precentral gyrus; (3) ascending
parietal, to the postcentral gyrus and superior parietal gyrus; (4) parietotemporal, which traverses the posterior horizontal limb of the lateral
fissure, and supplies the inferior parietal lobule and the posterior parts
of the superior and middle temporal gyri; and (5) the temporal branches,
which emerge from the posterior horizontal limb of the fissure, and
supply the anterior and greater parts of the superior and middle
temporal gyri.
 
Fourth or Intracranial Part of the Vertebral Artery. —The vertebral artery, on leaving the suboccipital triangle, pierces the dura
mater and arachnoid, and enters the cranial cavity through the foramen
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1575
 
 
magnum. As it ascends, it lies at first on the side of the medulla
oblongata, between the hypoglossal nerve and the anterior root of the
suboccipital nerve. It then passes upwards on the ventral surface of
the medulla, and on reaching the lower border of the pons it unites
with its fellow of the opposite side to form the basilar artery. It will
generally be found that one vertebral artery is larger than the other.
 
Branches. —Posterior meningeal, posterior spinal, posterior inferior
cerebellar, anterior spinal, and bulbar.
 
The posterior meningeal artery arises from the vertebral artery
just before it pierces the dura mater, and it enters the cerebellar fossa
of the occipital bone where it supplies the dura mater.
 
The posterior spinal artery arises from the vertebral artery immediately after it has pierced the dura mater. It descends upon the
side of the spinal cord in front of the posterior roots of the spinal nerves,
and it gives off a branch which descends behind these roots. These
two arteries, in themselves small, are reinforced by the spinal branches
of the second part of the vertebral artery and of the dorsal branches of
the intercostal arteries. In this manner lateral anastomotic arterial
chains are formed upon each side of the spinal cord in front of and
behind the posterior nerve-roots.
 
The posterior inferior cerebellar artery, of large size, arises a little
above the preceding branch. It passes backwards between the vagus
and accessory nerves, and then over the restiform body to the vallecula
of the cerebellum, where it divides into branches. Some of these supply
the inferior vermis, and others ramify on the inferior surface of the
cerebellar hemisphere, at the periphery of which they anastomose
with branches of the superior cerebellar artery. The artery furnishes
branches to the corresponding choroid plexus of the fourth ventricle
and to the medulla oblongata.
 
The anterior spinal branch of the vertebral artery arises from that
vessel near its termination. It passes obliquely downwards and
inwards over the ventral aspect of the medulla oblongata, and at the
median line it unites with its fellow of the opposite side to form the
anterior spinal artery of the spinal cord. It furnishes twigs to the
medulla oblongata.
 
The bulbar branches are distributed to the medulla oblongata.
 
Basilar Artery. —This vessel is formed by the union of the two
vertebral arteries. It extends from the lower to the upper border of
the pons, occupying the median basilar groove on its ventral surface.
It lies deep to the arachnoid membrane within the cisterna pontis, and
at the upper border of the pons it divides into the two posterior cerebral
arteries.
 
Branches. —These are as follows, on either side: transverse, internal
auditory, anterior inferior cerebellar, superior cerebellar, and posterior
cerebral.
 
The transverse or pontine arteries are numerous, and pass outwards
on either side to supply the pons, the sensory and motor roots of the
fifth cranial nerve, and the middle peduncle of the cerebellum.
 
 
 
 
1576 A MANUAL OF ANATOMY
 
 
The internal auditory artery, long and slender, accompanies the
auditory nerve through the internal auditory meatus, and is distributed
to the internal ear.
 
The anterior inferior cerebellar artery arises from the centre of the
basilar, and passes backwards to be distributed to the anterior part of
the inferior surface of the cerebellar hemisphere. It anastomoses
 
with the posterior inferior
 
 
cerebellar artery, which is
a branch of the vertebral.
 
The superior cerebellar
artery arises from the
basilar close to its termination. It passes outwards parallel to the posterior cerebral artery, from
which it is separated by
the third cranial nerve.
It then winds round the
outer side of the crus
cerebri below the fourth
cranial nerve, and so
reaches the superior surface of the cerebellar hemisphere, where it divides
into branches. These supply the superior vermis,
the upper medullary velum, the tela chorioidea,
and the superior surface of
the cerebellar hemisphere,
at the periphery of which
they anastomose with
branches of the inferior
cerebellar arteries.
 
Posterior Cerebral Artery. —This is one of the
terminal branches of the basilar artery at the upper border of the pons.
It passes at first outwards beneath the crus cerebri, and parallel to the
superior cerebellar artery, from which it is separated by the third
cranial nerve. It then winds round the outer side of the crus cerebri,
lying between it and the hippocampal gyrus, and above the fourth cranial
nerve. In this manner it reaches the tentorial or inferior and medial
surfaces of the occipital lobe of the cerebral hemisphere. It receives,
not far from its commencement, the posterior communicating artery.
 
Branches .—These are arranged in three groups—ganglionic,
choroidal, and cortical.
 
The ganglionic group includes two sets of branches, postero-medial
and postero-lateral.
 
 
Fig. 966. —The Areas of Distribution on
the Surface of the Three Main Cerebral Arteries.
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM 1577
 
The postero-medial ganglionic arteries pass medial to the crus
cerebri, and pierce the posterior perforated substance. They supply
the inner part of the crus cerebri and the posterior part of the
thalamus.
 
The postero-lateral ganglionic arteries pass on the lateral side of
the crus cerebri, and supply the outer part of the crus, the posterior
part of the thalamus, the corpora quadrigemina, and the corpora
geniculata.
 
The posterior choroidal arteries are two or three in number, and
pass through the choroidal fissure to the tela chorioidea, which they
supply, together with the choroid plexus of the lateral ventricle, and
the corresponding choroid plexus of the third ventricle.
 
The cortical branches are: (i) anterior temporal, to the anterior
parts of the occipito-temporal and hippocampal gyri; (2) posterior
temporal, to the posterior
parts of the occipito-temporal
and hippocampal gyri, and
the inferior temporal gyrus;
and (3) occipital, to the occipital lobe. One of the occipital branches is called the
calcarine artery. It lies in
the calcarine fissure, and
supplies the lingual or infracalcarine gyrus and the
cuneus.
 
Circulus Arteriosus (Circle
of Willis).—This circle or (to
be more exact) heptagon is
formed in front by the anterior communicating artery,
 
which connects the two .
 
anterior cerebral arteries; behind by the basilar artery as it divides
into the two posterior cerebral arteries; and on either side by (1) the
anterior cerebral artery, (2) the trunk of the internal carotid aitery,
 
(3) the posterior communicating artery, and (4) the posterior cerebra
artery, in this order from before backwards. The cncle furnishes
twigs to the grey cortex of the interpeduncular region. It serves
to equalize the blood-pressure in the cerebral arteries, and it also
provides for the regular supply of blood to the brain m cases where
one of the main arterial trunks may be obstructed.
 
The following parts are contained within the circulus arteriosus,
in order from behind forwards: (1) the posterior perforated area; (2) the
corpora mamillaria; (3) the tuber cinereum and infundibulum; and
 
(4) the optic chiasma.
 
 
 
13 15 1*
 
 
x. Internal Carotid
 
2. Middle Cerebral
 
3. Anterior Cerebral _
 
4. Anterior Communicating
 
5. Posterior Communicating
 
6. Posterior Cerebral
 
7. Basilar
 
8 Superior Cerebellar
9. Transverse Pontine
 
10. Internal Auditory
 
11. Anterior Inferior Cerebellar
 
12. Posterior Inferior Cerebellar
 
13. Vertebral
 
14. Anterior Spinal
 
15. Posterior Spinal
 
16. Anterior Choroid
 
17. Posterior Choroid
 
18. Central or Ganglionic
 
19. Central or Ganglionic
 
20. Central or Ganglionic
 
(Postero-mesia!)
 
21. Central or Ganglionic
 
(Postero-lateral)
 
 
Fig. 967. —The Arteries at the Base of
the Brain, and the Arterial Circle.
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1578
 
Veins of the Encephalon.
 
The cerebral veins are arranged in two groups—superficial and deep.
 
The superficial cerebral veins are divided into two sets—superior
and inferior.
 
The superior cerebral veins return the blood from the upper parts
of the outer surfaces of the cerebral hemispheres. They lie in the pia
mater, and pierce the arachnoid membrane and inner layer of the
dura mater, after which they open into the superior longitudinal sinus,
having previously received the veins from the medial surface of either
hemisphere. Their direction for the most part is forwards and medially,
whilst the direction of the blood-current in the superior longitudinal
sinus is backwards.
 
The inferior cerebral veins return the blood from the lower parts
of the cerebral hemispheres, and they terminate in the cavernous,
superior petrosal, and lateral sinuses. One of these veins is known
as the superficial middle cerebral or superficial Sylvian vein. It passes
along the lateral fissure, and opens into the front part of the cavernous
sinus or else into the spheno-parietal sinus. This vein communicates
posteriorly with (1) the superior longitudinal sinus by means of the
great or superior anastomotic vein (of Trolard); and (2) the transverse
sinus by means of the inferior anastomotic vein (of Labbe).
 
the deep cerebral veins are as follows: (1) the choroidal veins;
(2) the veins of the corpora striata; (3) the internal cerebral veins
(veins of Galen); (4) the anterior cerebral veins; (5) the deep middle
cerebral veins; and (6) the basilar veins.
 
The choroidal vein of each side begins in the choroid plexus of the
inferior horn of the lateral ventricle. It ascends at first, and then
passes forwards in the lateral margin of the tela chorioidea to the interventricular foramen, where it unites with the vein of the corpus striatum
to form the corresponding internal cerebral vein (vein of Galen).
 
The vein of the corpus striatum is formed by branches which
issue from the corpus striatum and thalamus. It runs forwards in
the groove between these two bodies, lying superficial to the taenia
semicircularis, and at the interventricular foramen it joins the choroidal
vein to form the corresponding internal cerebral vein.
 
The internal cerebral vein (vein of Galen) of each side is formed close
to the interventricular foramen by the union of the choroidal vein, the
vein of the corpus striatum, and the vein of the septum lucidum. The
two veins, right and left, pass backwards between the two layers of the
tela chorioidea, and they unite beneath the splenium of the corpus
callosum to form one vessel, called the great cerebral vein, which opens
into the front part of the straight sinus. Each vein receives tributaries
from the thalamus, the corresponding choroid plexus of the third
ventricle, the corpus callosum, and the corpora quadrigemina; and,
before joining its fellow, it takes up the basilar vein of its own side.
The great cerebral vein receives tributaries from the upper surface of
the cerebellum.
 
 
THE NERVOUS SYSTEM
 
 
1579
 
 
The anterior cerebral vein of each side is situated in the great longitudinal fissure, along with the corresponding artery. Having curved
round the genu of the corpus callosum, it passes to the anterior perforated region, where it joins the deep middle cerebral vein to form
the basilar vein.
 
The deep middle cerebral vein returns the blood from the insula
and lies deeply within the stem of the lateral fissure.
 
The basilar vein of each side begins at the anterior perforated area,
where it is formed by the union of the anterior cerebral and deep
middle cerebral veins. It passes backwards round the crus cerebri,
and opens into the internal cerebral vein of its own side just before
that vessel joins its fellow to form the great cerebral vein. The basilar
vein receives, close to its commencement, one or more inferior striate
veins, which descend from the corpus striatum through the anterior
perforated substance. It also receives tributaries from the parts
within the interpeduncular space.
 
The cerebellar veins are arranged in two groups—superior and
 
inferior.
 
The superior cerebellar veins terminate in the great cerebral vein,
and in the straight, transverse, and superior petrosal sinuses. The
inferior cerebellar veins pass to the sigmoid, inferior petrosal, and
occipital sinuses.
 
 
Blood-supply of the Different Parts of the Encephalon.
 
The medulla oblongata is supplied by the vertebral, anterior spinal, and
 
posterior inferior cerebellar arteries. .,
 
The pons is supplied by the transverse or pontine branches of the basilar
 
The cerebellum is supplied inferiorly by the posterior inferior cerebellar
branches of the vertebral arteries, and the anterior inferior cerebellar branches
of the basilar artery. Superiorly it is supplied by the superior cerebellar branches
of the basilar artery, and to a limited extent by the posterior inferior cerebellar
 
arteries
 
The crus cerebri is supplied by the postero-medial and postero-lateral
branches of the posterior cerebral artery, and by the posterior communicating
 
Th’e posterior perforated substance is pierced by the postero-medial branches
 
of the posterior cerebral arteries. , , . v
 
The corpora quadrigemina are supplied by the postero-lateral ganglionic
 
branches of the posterior cerebral arteries. , +
 
The thalamus is supplied posteriorly by the postero-meclial and posterolateral ganglionic branches of the posterior cerebral artery. Anteriorly its outer
part is supplied by the lenticulo-thalamic branches of the middle cerebral artery,
 
and its inner part by the posterior communicating artery. .
 
The anterior perforated substance is pierced by the antero-lateral ganglionic
 
branches of the middle cerebral artery. , ., . . c ,,
 
Frontal Lobe— The superior frontal gyrus, the anterior two-thirds of the
middle frontal gyrus, and the upper portion of the precentral gyrus are supplied
bv cortical branches of the anterior cerebral artery. The posterior third of the
 
middle frontal gyrus, the inferior frontal gyrus and the .lower “h^ce-ebra*
of the precentral gyrus are supplied by cortical branches of the^middle <cerebral
„ rfpr * Q n t h e orbital surface the internal orbital gyrus, olfactory lobe, ana
gyrus rectus are supplied by the anterior cerebral artery, whilst the remainder
is supplied by the middle cerebral artery.
 
 
1580 A MANUAL OF ANATOMY
 
Parietal Lobe. —The whole of this lobe, practically, is supplied by the middle
cerebral artery.
 
Occipital Lobe. —This lobe is supplied by the posterior cerebral artery.
 
Temporal Lobe. —The superior and middle temporal gyri and the pole are
supplied by the middle cerebral artery, and the remainder is supplied by the
posterior cerebral artery.
 
Medial Surface of the Cerebral Hemisphere. —The anterior cerebral artery has
an extensive distribution to this surface, which it supplies as far back as the
internal part of the parieto-occipital fissure. The parts behind this fissure—
namely, the cuneus and the parts around the calcarine fissure—are supplied by
the posterior cerebral artery.
 
The corpus callosum is supplied by the anterior cerebral arteries.
 
Corpus Striatum. —The nucleus caudatus and nucleus lentiformis are supplied
for the most part by the antero-lateral or ganglionic branches of the middle
cerebral artery, which pass through the anterior perforated substance. According
to Duret they form three sets—lenticular, lenticulo-striate, and lenticulo-thalamic.
The lenticular (internal striate) arteries supply the globus pallidus (inner part)
 
 
 
Fig. 968. —Brain of an Embryo about Four Weeks Old (from
 
Quain’s ‘ Anatomy ’) (His).
 
1. Telencephalon 4. Metencephalon 7. Spinal Cord
 
2. Thalamencephalon 5. Myelencephalon 8. Pontine Flexure
 
3. Mesencephalon 6. Cervical Flexure 9. Olfactory Lobe
 
1, 2=prosencephalon; 3 = mesencephalon; 4, 5 = rhombencephalon
 
of the lentiform nucleus, the internal capsule, and the caudate nucleus. The
lenticulo-striate (external striate) arteries supply the putamen (outer part) of
the lenticular nucleus, and the external capsule. One of the lenticulo-striate
arteries is larger than the others, and is subject to rupture in cases of cerebral
haemorrhage. It is known as the artery of cerebral hcemorrhage (Charcot). Its
course is outwards and upwards round the lateral aspect of the lentiform nucleus,
between it and the external capsule, and then through the internal capsule to
the caudate nucleus. The lenticulo-thalamic arteries supply the posterior part
of the lentiform nucleus, and the anterior part of the thalamus on its lateral
aspect.
 
1 he front part of the caudate nucleus is supplied by the antero-medial ganglionic branches of the anterior cerebral and anterior communicating arteries.
 
The larger arteries occupy the subarachnoid space, where they divide into
branches which enter the pia mater. These in turn give off smaller branches,
which enter the cerebral substance, some of them being cortical and others
medullary in their distribution.
 
Blood-supply of the Choroid Plexuses. —The choroid plexus of the lateral
ventricle derives its blood from (i) the anterior choroidal artery, which is a
 
 
 
THE NERVOUS SYSTEM
 
 
1581
 
 
branch of the internal carotid or the middle cerebral; and (2) the posterior
choroidal arteries, which are branches of the posterior cerebral. The choroid
plexuses Of the third ventricle derive their blood from the posterior choroidal
arteries. The choroid plexuses of the fourth ventricle are supplied from the
posterior inferior cerebellar arteries.
 
The tela chorioidea derives its blood from the posterior choroidal arteries
and from the superior cerebellar arteries.
 
Lymphatics of the Brain. —There are no lymphatic vessels in the brain.
Their place is taken by spaces in the outer coat of the arteries, called perivascular spaces, which are in communication with the subarachnoid space.
 
 
Development of the Encephalon.
 
A brief outline of the formation of the brain has been given on pp. 55-59*
in which can be followed the development of the primary cerebral divisions into
fore-, mid- and hind-brain, the formation of the cerebral vesicles, the appearance
of the brain flexures, and in general the changes which lead to the existence
in their proper positions of the main structures in the brain. The student
is advised to read this general account before proceeding to the following descriptions, which deal with the conditions in the developing brain in a more detailed
manner.
 
 
Metamorphoses of the Hind-brain.
 
The pontine flexure begins to show about the beginning of the fourth week,
is well marked at the beginning of the second month, and has its two limbs
very close to one another by the end of this month. The posterior limb of the
flexure, down to the nuchal bend, is termed the myelencephalon, the anterior
limb the metencephalon, and the narrow junction with the mid-brain is the
 
isthmus.
 
Myelencephalon. —The walls, opened out in their upper parts, with a wide
roof-plate, give origin to the medulla oblongata, and the cavity forms the lowei
half of the fourth ventricle ; at the extreme lower end the cavity is not enlarged.
The development of this lower or hinder portion of the myelencephalon proceeds
in general on the lines of development already described for the spinal cord,
with certain modifications due to the opening out and change in direction in
certain tracts passing to the brain, the crossing of pyramidal fibres, and the
presence of certain tracts and nuclei (to be described later) associated with the
 
existence of visceral arches. , ,
 
A little higher up the myelencephalon broadens to make the lower part of
 
the fourth ventricle. The alar and basal laminae are now in the floor of the wide
cavity. The broad roof-plate, a single layer of epithelium, is attached at the
sides to an everted edge of the alar lamina, known as the rhombic lip, an over
hanging the outer parts of the laminae. Such a definite rhombic lip however, is
only found in the cranial part of the myelencephalon, where, as will be seen later,
the great enlargements appear which are due to growth of the vestibular nuclei.
 
The widened roof-plate is covered by vascular mesenchyme, representing
pia mater. At the level of the pontine flexure the ependymal or epithelial roof
is invaginated into the fourth ventricle in the form of a transverse fold —plica
chorioidea, containing pia mater—which extends between the lateral recesses of
the ventricle From this transverse fold two vertical folds —phcce chorioidea, e
wise containing pia mater—extend vertically downwards into the ventricle close
to the median line. These ependymal folds, containing pia mater, form the two
 
choroid nlexuses of the lateral ventricle. . , .
 
At a comparatively early stage the afferent fibres of the seventh, ninth and
 
tenth nerves pass into the marginal zone of the alar lamina, and form a bund
here i ZZausTolitarius; this bundle becomes deeply buried by subsequent
 
thl °Thehvno!gloss afnucleus deveiops, as has been mentioned already on p. 1440
praetor witWnth"ndymal P zone, in the upper part of the column of
 
 
1582
 
 
A MANUAL OF ANATOMY
 
 
loosened nuclei seen here in the cervical region formed from the ependymal zone
ventro-laterally. The sixth nucleus possibly arises from the extreme cranial
end of the same column, but this is not certainly known. In the young embryo
the efferent nuclei (except that of the hypoglossal) lie in the basal lamina, where
they cause internal depressions by their rapid growth in the thin wall (Fig. 970).
These depressions are known as neuromeres, and are a marked though temporary
feature of most embryonic brains. In the illustration they are seen from
within, and have a curious distribution, in that the sixth neuromere is placed
behind the seventh. The fifth has two neuromeres, of which the most cranial
is much the deeper; the line of flexure of the hind-brain, which has not yet
begun in this specimen, will pass through this deep neuromere of the fifth nerve.
 
 
 
Fig. 969.—Lateral View of Brain, End of Second Month.
 
Cbl, cerebellar rudiment; P, N, pontine and nuchal flexures; M, mid-brain
flexure; Pit, hypophysis; Cpb, corpus ponto-bulbare. Roof-plate of hindbrain is only shown in outline.
 
A little later a neuromere will mark, rather indefinitely, the ninth efferent
nucleus, but is not seen in the figure.
 
It must be understood that the neuromeres are present only in the basal
lamina; this, for practical purposes, is the one seen in the figure, the thin and
narrow strip (D) being the only representative of the alar lamina.
 
Behind the region of neuromeres the myelencephalon narrows down to its
continuity with the spinal cord, and it is here, extending cranially, that the
olive is laid down.
 
The inferior olive, with its medial and dorsal accessory formations, is developed as a modification of the upper part of the ventro-lateral column of neuroblasts in the mantle zone, from which the ventral column is formed at a lower
level. The early stages of this development are shown in Fig. 971, while Fig. 972
 
 
THE NERVOUS SYSTEM
 
 
1583
 
 
 
 
Fig. 970.
 
A, sagittal section of brain of 4-9 mm. embryo; B, section through two adjacent
 
neuromeres.
 
 
 
Fig. 971. —Hind-brain, 13-5 Mm. Embryo.
 
Outline of longitudinal median section on right below; m this cr. is the cranial
slope and sp. the spinal cord; TS, tractus solitanus; vl ventro-lateral nuclei.
Planes of sections a, b, and c correspond with those showm on the outline.
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1584
 
gives the appearances in subsequent stages. In these it can be seen that the
median accessory olive (m.o.) is first defined, the main olivary mass being constructed from the more lateral condensations.
 
It must be said here that the classical and accepted account of olivary
development refers it to the ventral migration of neuroblasts from the
‘ rhombic lip/ The account given above is put forward because it is in
accord with observed facts, whereas the older story is very unsatisfactory
in several particulars.
 
 
 
Fig. 972.
 
Transverse sections through olivary region in embryos of 15 and 16 mm.; horizontal sections, 18, 21, and 28 mm. in neighbourhood of nuchal flexure.
 
The cuneate and gracile nuclei are formed directly from the dorsal neuroblasts.
 
Each pyramid is a ventral bulging of that part of the basal lamina which is
on the mesial side of the olivary body, and it is produced by the motor tracts as
they descend in the marginal layer from the central area of the cerebral cortex
through the pons. This begins in the fourth month.
 
The ponto-bulbar body is represented in the embryo by a collection of small
and darkly-staining nuclei lying below the caudal part of the ‘ rhombic lip/
It appears in the latter part of the second month, and its nuclei spread fairly
rapidly over the surface of the myelencephalon, especially ventrally and cranially;
here they lay down the beginnings of the pontine nuclei. On the myelencephalon
further back they appear to be responsible for the various small superficial
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1585
 
 
arcuate nuclei which may be found on the surface of the pyramid, etc. There is
also a possibility that the lateral accessory cochlear nucleus may possess a
similar origin.
 
As the pyramids, right and left, bulge ventralwards, the floor-plate, which
connects the basal laminaj, sinks, and the anterior median fissure is formed, as
in the development of the spinal cord. The spongioblastic floor-plate is now
invaded by nerve-fibres, most of which cross from one side to the other, these
fibres being (1) the anterior superficial arcuate fibres, (2) the deep arcuate fibres,
and (3) the cerebello-olivary fibres. In this manner the raphe of the bulb is
formed, as in the development of the anterior or white commissure of the spinal
cord.
 
In the more cranial portion of the myelencephalon, where the efferent nuclei
have been laid down in the neuromeres, the subsequent growth of the alar lamina
affords opportunity for the development of the vestibular nuclei, which thus lie
just cranial to the great dorsal masses of the gracile and cuneate nuclei. The
 
 
 
Fig. 973._ Plans to show Areas in Floor of Fourth Ventricle, with
 
Position of Developing Structures.
 
changes which take place in the floor of the ventricle in this part are verv com
plicated and not by any means understood; the plans in Fig. 973 are attempts
to show the results of the changes. The first figure gives the positions of the
neuromeres on the left, with the sites of the afferent nuclei on the r t§tit. n . e
second and third the vestibular masses are associated with considerable widening
but there is apparently a marked forward upgrowth of the floor in the basal
area which carries the sixth and seventh nuclei forward and brings them against
the metencephalic surface. This is no doubt associated with the curious relations
between the two nuclei and nerves, but the way in which it comes about, as well
as the reason for its occurrence, is not known. The positions of the various
nuclei are given approximately in the plans, and a general idea of their origins
and changes can be obtained by a study of the figures.
 
Metencephalon.— -From this are developed the pons, cerebellum, its
upper and middle peduncles, and the superior and inferior medullary
vela Its cavity forms the upper part of the fourth ventricle .
 
 
100
 
 
 
 
 
 
 
 
 
 
 
 
1586
 
 
A MANUAL OF ANATOMY
 
 
1 he pons develops as a ventral thickening on the lower end of the
region, immediately cranial to the pontine flexure. Its nuclei appear to
owe their origin to the neuroblasts which have spread over the surface
from the ponto-bulbar body; presumably they increase subsequently
in situ, but no definite indications of mitotic activity have been
 
 
 
Fig. 974.— Semi-diagrammatic Figures showing Cerebellar Rudiments.
 
 
found among them. The down-growing cerebro-spinal fibres find
their way into and among these nuclei in the third month and
subsequently.
 
The cerebellum is developed from the alar laminae of the metencephalon, the thickening involving the roof-plate in its growth. The
 
two lateral cerebellar plates formed by
the laminae are at first inclined to each
other at an angle (Fig. 976), but as the
angle of the pontine flexure becomes more
closed and the metencephalon widens, the
paired cerebellar rudiments come nearly
into line with one another (Figs. 974,
977). The lateral plates, being thickenings in the floor of the cavity, project
at first into the cavity, covered by the
roof-plate, which is attached to the margins outside them ; subsequently the
attachment of the roof-plate is turned in
(Fig. 977) below the bulging lateral formations, so that it becomes attached,
descriptively, to the anterior and lower
aspect of the transversely disposed cerebellar rudiment. It is in the taenial fold
to which the roof-plate is attached here
that the floccular enlargement occurs a
little later.
 
In some lower vertebrates the cerebellum develops altogether within the
cavity of the hind-brain, as in the early human stage; the later change in the
human conditions enables the structure to expand freely outside the ventricle.
 
The upper part of the roof-plate of the rhombencephalon, at the
angle of junction of the lateral plates, is invaded by them, and forms
 
 
 
Fig. 975.— Brain of Third
Month Embryo seen
 
FROM BEHIND, TO SHOW *
 
the Transverse Cerebellar Rudiment.
 
This stage is between those
shown in the previous
figure.
 
 
/
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1587
 
 
the basis in which the vermis develops; growth here is slow, and the
lateral lobes in their enlargement come to overlap it and cover it in.
 
The lateral plates come into evidence during the second month;
the transversely disposed plate (Fig. 975) is well marked in the middle
of the third month, when the flocculus may be recognized, and after this
the development proceeds slowly. After the third month the vermis
shows transverse fissures, and in the fifth month these are found also
on the lateral lobes.
 
 
 
Fig 076_Ventricular Aspect of Cranial Slope of Hind-brain in Em
bryos OF 12, 16, AND 28 Mm., TO SHOW BEGINNINGS OF CEREBELLAR FOLD.
 
 
The fissure cutting off the flocculus extends across the region of the
vermis, marking off the nodule here. At the end of the third month
a fissura prima forms across the vermis, making the lowei edge of the
future culmen, and a little later a fissura secunda forms below the
future pyramid . Other secondary fissures follow, and some ol the
fissures of the vermis extend into the lateral lobes, but most of the
 
fissures here are separate local formations. , A
 
Cerebellar thickening, spreading into the roof-plate above and
below the main development, forms the upper and lower medullary
vela, the first extending (valve of Vieussens) to the closed isthmus, the
 
 
 
 
 
 
1588
 
 
A MANUAL OF ANATOMY
 
 
second being continuous below with the undeveloped ependymal or
epithelial roof-plate of the myelencephalon.
 
On either side of the valve of Vieussens the roof-plate is thickened by the
superior cerebellar peduncles.
 
 
 
Fig. 977.—Views from behind of the Hind-brain in Embryos of 35
 
and 48 Mm.
 
EV, IV, extra- and intra-ventricular surfaces.
 
The superior peduncles of the cerebellum, right and left, arise from the cells
 
of the nucleus dentatus of the corresponding lateral cerebellar hemisphere.
Emerging from the anterior parts of the dentate nuclei, the peduncles give rise
to two thickenings of the roof-plate of the metencephalon, one on either side of
the valve of Vieussens. Thereafter they enter the mesencephalon or mid-brain,
 
 
 
THE NERVOUS SYSTEM
 
 
1589
 
 
and, after decussating, each passes to the corresponding red nucleus of the
tegmentum of either crus cerebri, which constitutes its lower cell-station.
 
The middle peduncles of the cerebellum ( brachia pontis) are developed from
the cells of the pontine nuclei of the pons right and left. The fibres of each
peduncle issue from the lateral portion of the corresponding pontine nucleus,
and enter the adjacent cerebellar hemisphere.
 
Mesencephalon. —This portion makes a sharp curve (Fig. 969) as it develops.
It has a large cavity, which is slowdy lessened in size by the growing thickness
of the walls, finally remaining as the small aqueduct. The thickened walls
around this are composed of a floor lamina and roof lamina (tectum); in the
former are formed the crura cerebri, while the tectum gives rise to the corpora
quadrigemina.
 
The isthmus is a part of some interest; it is essentially a derivative of the
hind-brain, so that its name isthmus rhombencephali is correct. The isthmus
is produced at the spot where the two regions of growth, metencephalic and
mesencephalic, meet each other, but there is in addition a definite forward
extension of the basal lamina from the hind-brain into the opening, of which it
makes the immediate wall. This extension carries with it the trochlear nucleus,
which develops in the basal lamina of the hind-brain just above the opening;
the decussation of the nerves, originally in the floor-plate of the hind-brain, is
carried down also and lies therefore on the dorsum of the isthmus.
 
 
 
Fig. 978._Schemes to show the Parts of the Third Ventricle formed
 
FROM THE THALAMENCEPHALON (Bi.ACK LlNE) AND TELENCEPHALON (INTERRUPTED Line).
 
A little later there is an extension forwards from the alar lamina of the hindbrain, passing on the outer side of the basal extension, and carrying with it
(sensory) nuclei from the upper part of the trigeminal nucleus; this appears to
be the beginning of the mesencephalic root of the nerve, further short connections
 
developing subsequently. .
 
The mid-brain presents dorsally a median longitudinal groove, which
separates two rounded eminences, known as the corpora bigemina . At a latei
period a transverse groove appears, which divides each of the corpoia bigemina
into two, thus giving rise to the corpora quadrigemina.
 
The third nucleus forms in the ventral mantle zone, and the fourth nucleus
o-ains its position here secondarily. The red nucleus is probably, formed
in situ, from the mantle zone of the floor lamina. I he corpora quadrigemina,
formed from the alar laminae (and probably from the roof-plate secondarily
involved), are hollow at first. -They become solid in the fourth and fifth months.
The bases peduneulornm begin to appear in the fourth month in the central
 
parts of the marginal zone. . . . . . ,
 
Diencephalon or Thalamencephalon.— This is the anterior primary vesicle
(Fig 978) Its cavity forms the greater part of the third ventricle (the anterior
portion being derived from the secondary outgrowth, the telencephalon). Its
walls develop into the thalamus, corpora mamillaria, tuber cmereum, mfundibulum, and posterior lobe of pituitary, and from the roof-plate grow the pineal
 
 
 
1590
 
 
A MANUAL OF ANATOMY
 
 
body and the ependymal roof of the ventricle. Moreover, when it is first formed,
the thalamencephalon gives origin to the optic outgrowth on each side.
 
The pineal body, or epiphysis cerebri, is developed from the dorsal part of
the ependymal roof of the third ventricle. It appears as a diverticulum of
the ependymal roof close to the mesencephalon, and it is directed backwards,
so that it comes to lie over the corpora quadrigemina. The distal end is blind,
and in connection with it a number of closed follicles are formed which contain
calcareous particles forming the acervulus cerebri, or brain-sand. The proximal
part of the diverticulum forms the stalk of the pineal body, which contains the
pineal recess and opens into the third ventricle.
 
The basal laminae, smaller than the alar, give origin to the tuber cinereum
and the outgrowth which makes the infundibular process of the pituitary formation (see p. 1171). These structures are (Fig. 978) on the lower part of the
 
 
 
Fig. 979.— Diagram showing Parts of the Fore-brain and Structures
 
Derived from These.
 
D, diencephalon; Tel, telencephalon; T, E, M, are thalamus, epithalamus, and
metathalamus; H is hypothalamus; CV, cerebral vesicle; CS, corpus
striatum.
 
posterior aspect of the fore-brain immediately behind the site of the optic
outgrowth. Corpora mamillaria are formed from basal laminae just behind and
above the tuber. The position of these structures is due to the length and curve
of the mid-brain; when this gets relatively shorter, and the nasal fossae grow
upwards from below, the fore-brain is rotated upwards to some extent, and the
structures thus come to lie more below the third ventricle.
 
The optic outgrowths, although they are actually low down with reference
to the fore-brain, are derivatives from its alar region, and the interlaminar sulcus
(big. 978) reaches its lowest or most cephalic point between the optic pouch
and the infundibulum. This sulcus is here the hypothalamic sulcus, but the
continuation of the ‘ sulcus of Monro ’ towards the foramen is a secondary effec t
produced by the growth of the thalamus.
 
For development of the eye, see next chapter.
 
The thalamus begins early in the second month as an enlargement in
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
i 59 i
 
 
the anterior part of the dorsal lamina due to growth of the mantle cells. It
increases rapidly and narrows the ventricle, so that in the fourth or fifth month
the two bodies come into contact and fuse to a small extent, leaving as an attachment between them when they draw apart again the connexus thalami or massa
intermedia.
 
 
 
 
Fig. 980. —Schemes to show how the Corpus Striatum alters by
its Growth the Shape of the Cavity.
 
occ, occipital growth, with formation of posterior horn; i.c., line in which
pyramidal motor fibres issue through corpus striatum.
 
 
Later, in the fourth to fifth month, growth of the alar laminae farther back
than the thalamic formation makes the pulvinar and geniculate bodies, and
becomes secondarily continuous with the thalamus.
 
Telencephalon. —This (Fig. 979) is an outgrowth or forward bulging of the
terminal part of the thalamencephalon; it gives off on each side the two cerebral
vesicles. These hollow vesicles have cavities
widely open into that of the telencephalon, and
thus into the third ventricle, of which the telencephalon makes the most anterior part ..
 
The cerebral vesicles, growing fairly rapidly,
stand up above the general level of the fore-brain,
being separated from each other by the rudiment
of the great longitudinal fissure. The direction of
their main growth is upwards and backwards from
the interventricular foramen, which is the opening
from the telencephalon into a vesicle. They also
grow forward for a little distance in front of the
foramen, and of course their increasing size leads
to an increasing prominence laterally. Thus they
cover successively the diencephalon, the mid-bram,
and finally the hind-brain and its formations, so
that these are not to be seen from above. The
vesicles begin to cover the mid-brain (Fig. 981)
during the third month, and grow over the cerebellum in the fifth month. .
 
The interventricular foramen does not increase
in size pari passti with the growing brain, hence
 
becomes relatively very small.
 
The anterior wall of the central unpaired or
original telencephalic growth is the lamina terminalis. This is the direct path from one cerebral
 
fn the other whence it becomes the path .
 
Ilong which commissural fibres between the hemispheres will proceed in their
 
P " Thl V w fl S n a s S of'the cerebral vesicles are very thin at first, and thicken slowly.
But the thkkening of the corpus striatum is visible at an early stage m each
vesicle bednrdng to stand up into the cavity as a growthi ofthe floor and lower
partof the outer wall. It grows rapidly, so that in the third month (Fig. 981)
 
 
 
Fig. 981. —Brain of Embryo in Middle of
Third Month seen from
 
ABOVE, THE UPPER PART
of the Right Cerebral
Vesicle being removed
to expose the Corpus
Striatum (CS), Thalamus (OT), Midbrain
(MB).
 
 
 
 
 
 
 
1592
 
 
A MANUAL OF ANATOMY
 
 
it makes a marked prominence, while the greater part of the remaining wall of
the vesicle is still thin. The corpus striatum, thus forming a floor for the lateral
ventricle, is the cause, by its further growth, of alteration in the shape of that
cavity. This is shown in Fig. 980. The mass, at first low, grows in an upward
and backward direction, projecting into the cavity, and thus leading to the
formation of an inferior horn ; the forward-turned end of this horn is the result
of further growth of the body. The deep cleft seen on the inner side of the
mass in Fig. 981 is obliterated by fusion following on growth of the corpus on
one side and of the thalamus on the other, and the floor of the ‘ body ’ of the
cavity is raised accordingly.
 
The corpus striatum is one of the primitive formations in the brain connected
with its primitive functions. A section across the fore-brain and vesicles in the
second month is represented diagrammatically in Fig. 982, where the thick
mass of the corpus striatum is in contrast with the thin wall of the rest of the
vesicle. This thin wall is the rudimentary neopallium, that part of the cerebrum
which in man is associated with the higher functions of the brain, and will, when
it begins to grow, completely overshadow in size the original portion. The result
of neopallial growth is shown in the second diagram; the mass of the corpus
is not affected, while the rapid increase of the area of the neopallium leads to
its overlapping the inert striate mass. Overlapping cannot take place on the
inner and basal aspects, but growth outwards and backwards and downwards
 
 
 
Fig. 982. —Schematic Sections to show how the Corpus Striatum (CS) is
 
OVERLAPPED BY THE GROWTH OF THE NEOPALLIUM, AND IS DIVIDED INTO CAUDATE and Lenticular Parts by the Pyramidal Fibres. OT, thalamus.
 
is unrestricted, so we find the surface area corresponding with the corpus striatum
is overlapped by opercula from behind and above and in front. The surface
area corresponding with the striate body is the insula, and the opercula covering
it in make by their presence the lateral fissure.
 
Growth of the neopallial area implies formation of processes from its nervecells, and during the third month the pyramidal motor fibres begin to extend down
toward the lower regions. They pass, as indicated in Fig. 982, through the
corpus striatum to reach the marginal region beside the thalamus, and
m doing so divide the corpus into caudate and lentiform masses, the caudate
mass lying between them (1 internal capsule) and the ventricular cavity, the lentiform ganglion between them and the surface; hence the lentiform and caudate
nuclei are always separated from one another by fibres of the internal capsule,
and these fibres are always separated from the lateral ventricle by the caudate
mass, and from the surface by the lentiform body. The mass of fibres, however,
passing out of the striate body below and behind, come to separate the lenticular
part here from the thalamus, with which they are coming into relation.
 
The capsular fibres, passing through the corpus striatum, are affected by its
upward growth, and thus make their passage and exit in a line (Fig. 980) curved
like the surface of the striate body; this being so, it is easily understood that a
section downwards, as along the arrow, would cut, in order from above, neopallium, cavity, caudate nucleus, internal capsule, lentiform nucleus, capsule,
caudate nucleus, cavity, and finally neopallium again,
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1593
 
 
In tig. 982 the medial wall of the cavity of the vesicle is seen to remain thin.
This wall is invaginated into the cavity as the ependymal covering of the choroid
plexus of the lateral ventricle. The line of this thin wall lies just above the floor
thickening of the corpus striatum, and is affected by the growth of this body,
so that it assumes a curve corresponding with the curved shape of the ventricle,
being invaginated into this throughout its length. This thin inner wall is continuous with the roof-plate of the third ventricle at the interventricular foramen,
and the invaginations which cover the plexuses of the ventricles thus become
continuous at this point.
 
The anterior part of the hemisphere vesicle corresponds to the frontal lobe;
the lower part, as far forwards as the stem of the lateral fissure, becomes the
temporal lobe ; and the upper and posterior part represents the parietal lobe.
 
 
 
Fig. 983.—Side Views of Left Hemisphere at Beginning of Fifth and
End of Sixth and Seventh Months (modified from Koli.mann).
 
The occipital lobe is formed at a later period as the hemisphere grows backwards.
The limbic lobe is developed in connection with the medial surface of the hemisphere. The olfactory lobe is developed as a hollow protrusion from the ventral
aspect of the frontal portion of the hemisphere vesicle.
 
The surface of each hemisphere becomes very much broken up into gyri or
convolutions, this being effected bv means of fissures. I he fissures are of two
kinds—complete and incomplete/ The incomplete fissures are merely sulci
produced by the growth of the gyri, and they do not involve the entire thickness
of the walls of the cerebral hemispheres. The complete or primary fissures are
infoldings of the walls of the cerebral hemispheres, and involve their entire
thickness. They consequently give rise internally to certain prominences upon
the wall of each lateral ventricle—namely, the lateral choroid plexus, hippo
 
 
1594 A MANUAL OF ANATOMY
 
campus, calcar avis, and eminentia collaterals. The primary fissures are as
follows:
 
Lateral. Calcarine (anterior part).
 
Choroidal. Parieto-occipital.
 
Hippocampal. Collateral (central part).
 
With the exception of the lateral fissure, already described, the other complete fissures appear on the medial surface of the vesicle of the cerebral hemisphere.
 
The choroidal fissure is not really a fissure, but merely a groove or sulcus
produced by an infolding of the vesicular wall, which is here composed entirely of
ependyma. It commences above and behind the interventricular foramen of the
corresponding side, and it terminates close to the tip of the temporal pole, where
the inferior or descending horn of the lateral ventricle ends. Between these
two points it passes backwards, downwards, and then forwards into the future
temporal lobe in a crescentic manner, so as to embrace the stalk of the cerebral
hemisphere. After the ependymal infolding has taken place, vascular mesenchyme dips in between its two folds, and so a plica chorioidea is formed. From
this choroidal fold the lateral choroid plexus of the corresponding side is formed.
This plexus projects into the lateral ventricle, but is excluded from the ventricular
cavity by the ependyma of the wall, previously infolded. When the lateral
choroid plexus is withdrawn, the thin ependymal covering of the plexus comes
away with it, or is broken down. Under "these circumstances the choroidal
fissure is really a fissure, inasmuch as the lateral ventricle now opens upon the
surface through it. The internal prominence produced by the choroidal fissure
is the lateral choroid plexus covered by ependyma, this prominence being verv
conspicuous.
 
The other complete fissures will be found described in connection with the
cerebral hemispheres. All the primary fissures are formed before the fourth month.
 
The incomplete fissures are very numerous. The first two to make their
appearance are the calloso-marginal fissure, or sulcus cinguli, on the medial
surface of the cerebral hemisphere, and the central sulcus, or fissure of Rolando,
on the external surface. These, along with the other incomplete fissures, will
be found described in connection with the cerebral hemispheres. - These are
developed in the later foetal months, and inconstant tertiary fissures appear
for years after birth.
 
The cavity of the vesicle of the cerebral hemisphere forms on either side the
lateral ventricle, which is very much curtailed by the thickening undergone
by the vesicular walls, and the internal prominences produced by the complete
fissures. As the frontal lobe undergoes development the body of the ventricle
extends forwards into it, and so the anterior horn of the ventricle is formed.
As the occipital lobe becomes developed at a later period the body of the ventricle
extends backwards into it, and so the posterior horn is formed. Meanwhile
the interventricular foramen on either side, originally large, is being gradually
much diminished in size.
 
Basal Ganglia. —The basal ganglia of each cerebral hemisphere are as follows:
 
Corpus striatum.
 
Claustrum.
 
Amygdaloid nucleus.
 
ihey are all developed from the deep part of the much thickened cortical
substance which forms the floor of the lateral fossa. The claustrum and amygdaloid nucleus remain of small size, but the nucleus caudatus of the corpus striatum
forms a conspicuous prominence in the lateral ventricle as it bulges into that
cavity.
 
Commissures. —The commissures are as follows:
 
1. Corpus callosum. 4. Anterior.
 
2. Fornix. 5. Posterior.
 
3. Hippocampal. 6. Middle.
 
 
7. Habenular.
 
 
THE NERVOUS SYSTEM
 
 
1595
 
 
At an early period in the development of the cerebral hemispheres the interhemispherical (great longitudinal) fissure leads directly down to the roof of the
diencephalon. At a later period the roof of the diencephalon is separated from
the great longitudinal fissure by two commissures placed one above the other.
The upper commissure is the corpus callosum, and the lower one is the fornix.
These may be looked on as drawn back from the lamina terminalis by the growing
vesicles, although this is not quite an accurate statement of their formation.
 
 
 
Fig. 984.—Schematic Figure to show the General Formation of
 
the Main Commissures.
 
The thalamus (OT) is supposed to be cut away in part, exposing the region
of the corpus striatum; this has grown up "(producing the curved form of
ventricle already described), and the choroidal fissure (, ch.f .) is therefore
a curved line. Fibres of the internal capsule ( i.c.) also come through the
mass of the corpus striatum in a curved line, and lie between the
thalamus and lenticular part of corpus striatum. Hippocampal formations
lie on the other side of the choroidal fissure, and association fibres here make
the fimbria ( fimb .) and fornix (/). Commissural fibres cross the middle line
and are cut at h (hippocampal commissure) and ac (anterior commissure) ;
these are in the lamina terminalis. As the neopallium grows, its commissure, the corpus callosum, begins to form; it is at first in the lamina
terminalis (cc.), but with increasing growth it extends forwards (A) and
backwards (P). The rostrum, shown by the dotted line, is subsequently
formed by fusion of the walls of the two'vesicles, the septum lucidum being
that part of the wall between this and A. The backward extension carries
with it the hippocampal commissure; these backward movements, involving
also the hippocampus, are associated with great growth of the front part
of the brain.
 
Fornix—Anterior Commissure— These appear in the third month. In
Fig 984 is shown the inner aspect of a cerebral vesicle in which the lamina
terminalis is visible. Thickenings begin in this from fibres crossing between
the olfactory and insular regions', these make the anterior commissure. . A
little later fibres extend from each hippocampus to the sides of the lamina,
where they turn into the side walls of the telencephalon, and reach much
later the basal laminae of the thalamencephalon, constituting the anterior
 
 
 
 
 
 
 
1.596 A MANUAL OF ANATOMY
 
pillars of the fornix. The rest of the fornix is carried back with the growing
vesicle.
 
Corpus Callosum. —Some time later, as the neopallium grows, its commissural
fibres begin to become evident as the corpus callosum. These at first make use
of the path already utilized by the earlier commissural fibres, and are found
crossing at and above the upper part of the lamina terminalis as far back as the
level of the interventricular foramen, as seen in the figure. As the neopallium
grows, however, its commissural fibres become too numerous to be confined to
this area, and their line of crossing extends backwards and forwards. The
hinder extension necessarily lies with the fornix above the choroidal fissure, while
the forward extension is between the two anterior expansions of the vesicles or
hemispheres. These anterior fibres of the corpus callosum come from the frontal
lobe above the anterior horn of the ventricle, hence that part of the wall of the
hemisphere below these fibres is the medial wall of this horn. The hemispheres
become approximated and fused below this small area of medial wall as the result
of growth of neopallium round it, and commissural fibres now find their way
through the line of fusion below the medial wall of the anterior horn. This makes
the rostrum, and its continuity in front and above with the original forward
extension of the corpus callosum cuts off the two areas of medial wall from the
rest of this wall in the longitudinal fissure; they now form the two layers of the
septum lucidum, and the cavity between them is only the corresponding part
of the space of the fissure, similarly cut off. The fusion between the medial walls
is not confined to the region just considered, but is found behind this in the
neighbourhood of the callosal fibres and the fornix; this explains the posterior
extension of the region of the septum lucidum.
 
The hippocampal commissure appears on the back part of the ventral aspect
of the plate formed by the fused areas of the cerebral hemispheres, to which
position it has been carried by the backgrowth of the corpus callosum. Its
fibres pass across from one hippocampus to the other, and they correspond to
the region known as the lyra or psalterium.
 
The posterior commissure is formed in connection with the back part of the
roof of the diencephalon behind the pineal diverticulum.
 
The so-called middle commissure is not a commissure properly so called,
but is formed by the fusion over a limited area of the grey matter of the medial
surfaces of the thalami, and properly termed connexus thalami.
 
The habenular commissure is produced by the decussating fibres of the
thalamic stria?, these fibres, as they decussate, forming the dorsal part of the
pedicle of the pineal body.
 
Meninges of the Encephalon. —The walls of all the cerebral vesicles are invested by mesoderm, and this tissue becomes differentiated into the three
meninges—namely, the dura mater, arachnoid, and pia mater.
 
Choroid Plexuses. —The choroid plexuses of the two lateral, third, and fourth
ventricles are developed as infoldings of the ependymal walls of the ventricles.
Vascular mesenchyme (mesoderm) dips in between the two layers of each infolding, and in this manner plicce c-horioidece are formed. These choroidal folds
give rise to the choroid plexuses, which as they project into the ventricles carry
the ependymal walls, already infolded, before them.
 
Tela Chorioidea. —The vascular mesoderm ( pia mater) investing the neural
tube is converted into a double layer interposed between fore-brain and cerebral
vesicles as a result of the backgrowth of the latter. It is clear that this velum
interpositum extends to the interventricular foramen, where its two layers are
continuous, and where vessels of the cerebral layer can join those of the earlier
one. The dotted lines in Fig. 982 show the position of these two layers on
section; it can be seen that the ‘ cerebral ’ layer reaches out to the thin medial
wall of the vesicle, and its marginal vessels can invaginate this to form the
choroid plexus of the lateral ventricle, while the deeper layer rests on the roof
of the third ventricle, and makes its choroid plexus. The continuity of the two
layers at the foramen explains why the lateral vein runs there to join the internal
cerebral vein, which is in the lower layer.
 
 
THE NERVOUS SYSTEM
 
 
1597
 
 
Development of the Peripheral Nervous System.
 
The peripheral nerves are arranged in two groups—namely, spinal, which
are derived from the spinal cord; and cranial, which arise from the brain.
 
The spinal nerves are composed of two kinds of fibres—efferent, centrifugal,
or motor; and afferent, centripetal, or sensory.
 
A motor spinal nerve-fibre arises as the axon of a neuroblast or nerve-cell in
the mantle layer of the neural tube (see Development of the Spinal Cord).
 
A sensory spinal nerve-fibre is developed from a cell of a spinal ganglion,
and these ganglia are developed from the corresponding neural crest.
 
Neural Crests. —The neural or ganglionic crests, right and left, are ridges of
ectodermic cells which lie on either side of the neural tube. They are derived
from a single crest of ectoderm, which is formed by the fusion of the ectoderm
over each neural fold, this single crest being situated medially on the dorsal
aspect of the neural tube along che line of fusion of the neural folds to close the
tube. Subsequently the medial
crest divides into right and left
halves, which cover the dorsolateral aspects of the neural tube.
 
Each neural crest becomes
broken up into a number of segments, or ganglia, there being
four pairs for the head region,
and thirty-one pairs for the
region of the trunk.
 
Spinal Ganglia. —The spinal
ganglia are arranged in thirtyone pairs, right and left.
 
Each cell of a ganglion acquires two poles — afferent or
centripetal, and efferent or centrifugal—and at this stage it is
consequently a bipolar cell.
 
The centripetal or proximal
pole, which is the axon of a
ganglionic cell, grows into the
dorsal part of the wall of the
neural tube and forms part of
the dorsal or posterior root of a
spinal nerve. Within the marginal layer of the neural tube the centripetal
pole or nerve-fibre divides into tw r o branches, ascending and descending, which
give off collaterals and terminate in arborizations. The centrifugal or distal pole
joins the ventral or anterior nerve-root of the same segment of the spinal cord
on the distal side of the ganglion to form a spinal nerve.
 
Though the cells of a spinal ganglion are originally bipolar, they become m
the course of growth unipolar, the single pole having a T-shape. d his is brought
about by an excessive growth of one wall of the bipolar cell, which biings the
two original poles into contact, when they fuse, and are now connected with the
cell by one stalk or pole, which divides into a centripetal and a centrifugal process.
 
Whilst the fibres of the dorsal or posterior roots of the spinal nerves grow
into the mantle layer of the neural tube from the cells of the spinal ganglia, the
fibres of the ventral or anterior roots arise within the mantle lacei as the axons
of its neuroblasts or nerve-cells. The fibres of the anterior roots therefore grow
out from the neural tube.
 
Cranial Nerves. _The development of the cranial nerves, with the exception
 
of the olfactory and optic nerves, corresponds for the most part with the development of the spinal nerves. The motor cranial nerve-fibres arise as the axons of
nerve-cells of the brain, and groiv into the brain, whereas the sensory cranial
nerve-fibres grow into the brain from the cells of the cephalic ganglia.
 
 
Neural Crest (Ectoderm)
 
 
 
Fig. 985. —Development of the Neural
or Ganglion Crest (Keibel and Mall)
(after Von Lenhossek and Koi.lmann).
 
 
 
 
 
 
1598
 
 
A MANUAL OF ANATOMY
 
 
Cephalic Ganglia. —The cephalic ganglia, like the spinal ganglia, are developed
from the neural crests, and they constitute four pairs of ganglionic groups—
namely, trigeminal, acoustico-facial, glosso-pharyngeal, and vagal. They are
all comparable to the spinal ganglia.
 
The trigeminal ganglion is connected with the sensory root of the fifth
cranial nerve. The centripetal poles of its nerve-cells pass inwards into
the brain, forming the large sensory root of the nerve, and the centrifugal
poles of its cells pass peripherally, forming the ophthalmic, superior maxillary,
and sensory part of the inferior maxillary nerves. The trigeminal ganglion
is thus clearly comparable to a spinal ganglion. The small motor root of the
fifth nerve is homologous to the motor or anterior root of a spinal nerve, inasmuch
as its fibres arise as the axons of nerve-cells within the brain.
 
The acoustico-facial ganglion resolves itself into facial and acoustic parts.
 
The facial ganglion, known as the geniculate ganglion, is connected with
the genu of the facial nerve in the aqueduct of Fallopius. The centripetal poles
of the nerve-cells of this ganglion form the sensory root of the facial nerve—the
pars intermedia of Wrisberg —which passes inwards to the fasciculus solitarius
and upper part of the glosso-pharyngeal nucleus. Many of the centrifugal poles
of the cells issue from the ganglion as the chorda tympani nerve, which passes
to the anterior two-thirds of the tongue as a nerve of special sense.
 
The acoustic ganglion is represented by the vestibular and cochlear ganglia
in connection with the auditory nerve.
 
The vestibular ganglion is connected with the vestibular division of the
auditory nerve in the internal auditory meatus. As in the other ganglia, the
centripetal poles of the cells of this ganglion form the centripetal fibres of the
vestibular nerve, which pass inwards to the brain. The centrifugal poles of
the cells leave the ganglion, and form the peripheral part of the nerve as regards
its distribution.
 
The cochlear ganglion, known as the ganglion spirale, is connected with
the cochlear division of the auditory nerve, and is situated in the spiral canal
of the modiolus. Its nerve-cells are related to nerve-fibres, as in the case of
the vestibular ganglion.
 
The glosso-pharyngeal ganglion, which is broken up into a superior (jugular)
ganglion and an inferior (petrous) ganglion, is comparable to a spinal ganglion.
The centripetal poles of the nerve-cells, which issue from the ganglion, represent
the centripetal sensory fibres of the glosso-pharyngeal nerve, passing into the
brain. The centrifugal poles of the nerve-cells, issuing from the ganglion, represent the peripheral sensory fibres of the nerve.
 
The vagal ganglion, which is broken up into the upper ganglion (of the root)
and the lower ganglion (of the trunk), is disposed towards the sensory fibres
of the vagus nerve, as in the case of the other ganglia.
 
MENINGES OF THE ENCEPHALON.
 
Dura Mater.
 
The dura mater is a strong fibrous membrane which surrounds the
encephalon, and is composed of two layers—outer and inner. The
outer or endosteal layer serves as the internal periosteum or endocranium of the cranial bones, and the inner or sustentacular layer supports the encephalon. It is more firmly adherent to the bones forming
the base of the skull than to those over the cranial vault, and it is also
firmly attached along the course of the sutures. At the various openings it is prolonged outwards, blending with the sheaths of the transmitted nerves, and also becoming continuous with the external periosteum or pericranium. At the sphenoidal fissure it passes into the orbit
 
 
THE NERVOUS SYSTEM
 
 
1599
 
 
to form the orbital periosteum. At the lower margin of the foramen
magnum the two layers of which the dura mater is composed separate.
The external layer blends with the periosteum of the occipital bone
around the margin of the foramen magnum. The internal layer is
prolonged into the spinal canal, and forms the theca of the spinal cord.
The outer surface of the dura mater is rough and flocculent, owing to
fibrous processes which connect it to the inner surfaces of the cranial
bones. Its inner surface is smooth and covered by endothelium.
Superiorly, on either side of the superior longitudinal sinus there are
several small granular nodules, called arachnoid granulations, which
are best marked in old age. They indent the parietal bone, and protrude into the superior longitudinal sinus, carrying with them prolongations from the endothelial lining of the sinus, which separate them
from the blood.
 
The bodies are enlargements of the villi of the arachnoid membrane
(see p. 1609).
 
Structure. —The dura mater consists of fibrous and elastic tissues arranged as
parallel bundles.
 
The intracranial dura mater differs from the dura mater of the
spinal cord in the following respects: (1) it consists of two layers—
outer or periosteal, and inner or sustentacular—whereas the spinal
dura mater has only one layer, representing the sustentacular layer;
(2) it furnishes certain processes or septa, which project into the cranial
cavity, and separate parts of the encephalon from each other, whereas
the spinal dura mater sends no septa into the spinal cord; and (3) it
contains venous sinuses, which are absent in the spinal dura mater, or
are represented by the extradural venous plexuses (see p. 1434) •
 
Subdural Space.—This is the interval between the dura mater and
the arachnoid membrane. There is really no space, but simply sufficient interval to contain a minute quantity of serous fluid for lubricating
purposes. The dura mater and the arachnoid are therefore practically
in contact with each other.
 
Blood-supply. —The cranial dura mater is supplied by the meningeal arteries,
which are extradural and supply the inner table of the cranial bones. These
vessels are very numerous, and the chief are as follows on either side, from before
backwards: (1) anterior meningeal, two in number, from the anterior and posterior
ethmoidal arteries; (2) meningeal, from the cavernous part of the internal carotid
artery; (3) small meningeal, from the middle meningeal, or from the first part
of the maxillary artery; (4) middle meningeal, from the first part of the internal
maxillary; (5) meningeal branches of the ascending pharyngeal artery, (6) posterior meningeal branch of the occipital artery; and (7) posterior meningeal, from
 
the vertebral artery. . , . ,
 
The anterior meningeal branch of the anterior ethmoidal artery arises from
that vessel as it accompanies the nasal nerve on the cribriform plate of the
ethmoid bone, and it takes part in the supply of the dura mater of the anterior
 
fossa
 
The anterior meningeal branch of the posterior ethmoidal artery arises from
that vessel after it has entered the cranial cavity through a minute foramen
between the cribriform plate of the ethmoid and the sphenoid. It has a limited
distribution to the dura mater in this region.
 
 
i 6 oo
 
 
A MANUAL OF ANATOMY
 
 
The meningeal branch of the internal carotid artery arises from the cavernous
part of that vessel, and enters the middle fossa to supply the dura mater.
 
The small meningeal artery is usually a branch of the middle meningeal, but it
may arise from the first part of the maxillary artery. It enters the cranial cavity
through the foramen ovale, and supplies the adjacent dura mater and the
trigeminal ganglion.
 
The middle meningeal artery, as stated, is a branch of the first part of the
maxillary artery. Its diameter is that of the foramen spinosum, through which
it enters the cranial cavity. After passing into the cranium it divides into two
branches, anterior and posterior. The anterior branch passes forwards, outwards,
and upwards in a groove on the upper surface of the great wing of the sphenoid
bone to the inner aspect of the antero-inferior angle of the parietal bone, where
there is a groove, or sometimes a short canal. The position of the middle
meningeal artery at this level is ascertained by taking a point on the exterior
of the skull ii inches behind the zygomatic process of the frontal bone and
inches above the zygomatic arch. From this point the artery ascends in a
 
 
Frontal
 
Diploic
 
Vein
 
 
 
T rx.
 
Anterior Temporal Diploic Vein
 
 
Posterior Temporal
Diploic Vein
 
 
Occipital Diploic
Vein
 
 
Fig. 986.— The Veins of the Diploe.
 
 
The outer tables of the cranial bones have been removed.
 
 
branching meningeal groove near the anterior border of the parietal bone as
high as the superior longitudinal sinus. In this part of its course it furnishes
numerous branches forwards and backwards.
 
The posterior branch passes backwards on the squamous part of the temporal
bone, and then on to the inner aspect of the inferior border of the parietal bone,
where there is a meningeal groove about the centre. From this point it ascends
in a branching groove as high as the superior longitudinal sinus, giving off
branches forwards and backwards.
 
The distribution of the middle meningeal artery extends as high as the
superior longitudinal sinus forwards on to the frontal bone, and backwards
on to the occipital bone. Besides supplying the dura mater and the inner
table and diploe of the bones, the vessel furnishes the following branches:
(1) Ganglionic to the trigeminal ganglion; (2) a petrosal brcinch, which passes
through the hiatus (hallopii) to supply the facial nerve in its canal, and anastomose with the stylo-mastoid branch of the posterior auricular artery; and (3) an
orbital branch, which enters the orbit through the sphenoidal fissure, and anastomoses with the ophthalmic artery.
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1601
 
 
The meningeal branches of the ascending pharyngeal artery, which is a
branch of the external carotid, are three in number: One passes through
the foramen lacerum into the middle fossa; another passes through the jugular
foramen into' the posterior fossa; and the third passes through the anterior
condylar foramen, likewise into the posterior fossa.
 
The posterior meningeal branch of the occipital artery passes through the
jugular or mastoid foramen into the posterior fossa.
 
The posterior meningeal branch of the vertebral artery passes through the
foramen magnum into the cerebellar fossa of the occipital bone.
 
As a rule, only one of these various posterior meningeal arteries is large
enough to carry injection. .#•
 
Meningeal Veins. —The sinuses or veins with the middle meningeal artery are
two in number. They pass through the foramen ovale, and terminate in the
pterygoid plexus of veins. The other meningeal veins are disposed in one of
two ways. Some of them accompany the corresponding arteries and terminate
in extracranial veins; whilst others end in the various intracranial venous sinuses,
in part directly and in part by means of venous lacunae.
 
Veins of the Diploe. —These vessels are situated in the cancellous tissue
between the outer and inner plates of the cranial bones, and are exposed after
removal of the outer plate. They are destitute of valves, and are arranged
in the form of a network, from which the blood is returned by four diploic veins
on either side—namely, frontal, anterior temporal, posterior temporal, and
occipital. These terminate partly in extracranial veins, and partly in the intracranial venous sinuses and meningeal veins.
 
The frontal diploic vein passes downwards and escapes through an opening
in the outer plate of the frontal bone at the supra-orbital notch, where it joins
the communicating vein which passes between the supra-orbital and ophthalmic
veins. It receives radicles from the frontal air-sinus of the same side.
 
The anterior temporal diploic vein is confined to the back part of the frontal
and anterior part of the parietal regions, and descends to terminate in two ways.
It partly joins one of the extracranial deep temporal veins by passing through
an opening in the outer plate of the great wing of the sphenoid, and in part it
ends in a meningeal vein, or in the spheno-parietal, or it may be the cavernous
 
sinus. „ , . , - ,
 
The posterior temporal diploic vein is confined to the parietal region, and
descends to the postero-inferior angle of the parietal bone, where it pierces the
inner plate of that bone, and terminates in the transverse sinus..
 
The occipital diploic vein occupies the occipital region, and pierces the inner
table of the occipital bone, to terminate in the transverse or sigmoid sinus.
 
Nerves of the Dura Mater— The dura mater receives nerves from (i) the
sympathetic plexuses which accompany the arteries; (2) the three divisions o
the fifth cranial nerve; (3) the ganglion of the root of the va gus nerve , an
(4) the hypoglossal nerve. Headache is said to be due to irritation of these nerves,
especially to one of the branches of the fifth, known as the nervus tentorn.
 
Processes of the Dura Mater.— It has been already explained that
the dura mater is composed of two layers outer or periosteal, and
inner or sustentacular. The processes are formed by the inner or
sustentacular layer, and are four in number the faix cerebri, tentorium
cerebelli, falx cerebelli, and diaphragma sellse.
 
The falx cerebri is an extensive sickle-shaped process, which occupies
the great longitudinal fissure, where it lies between the two cerebral
hemispheres. Anteriorly it is almost pointed, and is attached to the
crista salli of the ethmoid bone. Posteriorly it is broad, and is attached
to the upper surface of the tentorium cerebelli along the median line
the straight sinus being situated at the place of junction The supenor
border is convex, and is attached m the median line to the frontal,
 
IOI
 
 
1602 A MANUAL OF ANATOMY
 
parietal, and occipital bones, extending upon the latter bone only as
low as the internal occipital protuberance. The superior sagittal sinus
is situated along this border. The inferior border is concave and free.
It overhangs the upper surface of the corpus callosum, from which it
is separated by a slight interval. The inferior sagittal sinus is situated
within this border. The lateral surfaces face the medial surface of the
cerebral hemispheres.
 
The tentorium cerebelli is an extensive crescentic sheet which covers
the cerebellum. Superiorly it supports the posterior parts of the
cerebral hemispheres, and is elevated along the median line, whence it
slopes towards the attached borders. Anteriorly it presents a free,
 
Falx Cerebri
 
9
 
I
 
 
 
Fig. 987.—The Falx Cerebri, Tentorium Cerebelli, and Venous Sinuses
 
of the Dura Mater (Left View).
 
i- Superior Sagittal Sinus 4. Transverse Sinus
 
2. Inferior Sagittal Sinus 5. Superior Petrosal Sinus
 
3. Straight Sinus 6. Internal Jugular Vein
 
sharp, concave border, which forms, with the dorsum sellae of the
sphenoid bone anteriorly, an oval opening, called the foramen ovale
tentorii , within which the mesencephalon is placed. Posteriorly and
laterally the tentorium cerebelli is convex, and is attached as follows,
from behind forwards: (i) to the horizontal ridge on the inner surface
of the tabular part of the occipital bone, where the process contains
the transverse sinus; (2) to the inner aspect of the postero-inferior angle
of the parietal bone, where the process also contains this sinus; and
(3) 1° the superior border of the petrous part of the temporal bone,
where the process contains the superior petrosal sinus. Close to the
apex of th e pars petrosa the outer and anterior borders of the tentorium
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1603
 
 
cerebelli cross, the outer border passing inwards to be attached to the
posterior clinoid process of the sphenoid bone, and the anterior border
passing forwards to be attached to the anterior clinoid process of that
bone.
 
In all the carnivora the tentorium is ossified.
 
 
The falx cerebelli extends forwards into the posterior cerebellar
notch, where it lies between the two cerebellar hemispheres. It is
falciform in outline. Superiorly it is attached to the posterior part
of the inferior surface of the tentorium cerebelli in the median line.
Posteriorly it is attached to the internal occipital crest, and this portion
bifurcates interiorly, the two divisions being connected to the lateral
margins of the vermiform fossa. Along this posterior attachment it
contains the occipital sinus and its two divisions. Anteriorly it ends
in a free border.
 
In the ornithorhynchus and many cetacea the falx is ossified.
 
 
The diaphragma sellse is a small circular fold horizontally placed,
which forms a roof for the sella turcica or hypophysial fossa of the
sphenoid bone, and almost entirely covers the hypophysis. At its
centre there is a small opening for the passage of the infundibulum.
 
Venous Sinuses of the Dura Mater.—These are blood-channels or
spaces situated between the two layers of the dura mater, and lined
with endothelium. They are as follows:
 
 
Superior sagittal sinus.
Inferior sagittal sinus.
Straight sinus.
 
Transverse sinuses (two).
Occipital sinus.
Cavernous sinuses (two).
 
 
Spheno-parietal sinuses (two).
Circular sinus.
 
Superior petrosal sinuses (two).
Inferior petrosal sinuses (two).
Basilar sinus.
 
Petro-squamous sinuses (two).
 
 
The superior sagittal sinus is situated in the median line within the
superior convex border of the falx cerebri. It extends from the crista
galli of the ethmoid bone to the internal occipital protuberance, where
as a rule it turns sharply to the right, and opens into the right transverse
sinus. It sometimes, however, turns to the left, and opens into the
left transverse sinus. Its posterior extremity is dilated, and forms the
confluens sinuum, which usually occupies a depression on the right side
of the internal occipital protuberance, and is connected with the
dilatation at the posterior extremity of the straight sinus by a transverse vessel. It increases in size as it passes backwards, and its shape
is triangular in section, the base being directed towards the cranial
vault. The apex is directed downwards, and in this region the sinus
is crossed by a number of delicate fibrous bands. Opening into the
sinus on either side there are venous spaces, called lacunae laterales,
which are situated within the dura mater, and projecting into these
lacunae from below, or into the sinus itself, there are seveial arachnoid
granulations, covered by the endothelial lining. The sinus receives
the superior cerebral veins and some of the meningeal veins of the falx
 
 
A MANUAL OF ANATOMY
 
 
1604
 
cerebri. The former open into it from behind forwards, so far at least
as the more posterior vessels are concerned, so that the blood-flow in
these veins is opposed to the current of blood in the sinus, which is
from before backwards.
 
The superior sagittal sinus sometimes communicates anteriorly
with the veins of the roof of the nose through the foramen ccecum, and
 
 
Frontal Air-Sinus
 
 
 
Anterior Fossa
 
/
 
 
'' Cerebellar Fossa
 
 
Accessory Nerv
Hypoglossal Nerve
 
 
Spinal Cord '
Occipital Sinus
 
 
Optic Nerve ^
Ophthalmic Artery
 
 
Third Nerve
 
Fourth Nerve
 
Region of
Meckel’s Cave
 
Fifth Nerve
 
Facial Nerve’
 
Auditory Nerve
 
Glosso-pharyngeal
Nerve
 
Vagus Nerve
 
 
Transverse Sinus
 
 
Cerebral Fossa
 
^ Confluens Sinuum
 
 
Border of Small Wing
✓ ' of Sphenoid
 
 
Ant. Pt. of Circ. Sinus
^ (Ant. Intercav. Sinus)
 
Hypophysis
 
 
Cavernous Sinus
Sixth Nerve
 
 
Middle Fossa
 
 
Basilar Sinus
Sup. Petrosal
Sinus
- Inf. Petrosal
Sinus
 
Sigmoid Sinus
 
 
Fig. 988.—Ihe Internal Uase or- the Skull, showing the Cranial
 
Nerves and Venous Sinuses.
 
 
it communicates with the veins of the scalp by means of an emissary
vein, which passes through the parietal foramen of each side, when
that is present.
 
The inferior sagittal sinus (vein) is of small size, and is situated in
the lower free border of the falx cerebri over its posterior two-thirds.
Its direction is backwards, and it opens into the front part of the straight
sinus at the anterior margin of the tentorium cerebelli. It is circular,
and increases in size as it passes backwards. Its tributaries are derived
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1605
 
from the lower part of the falx cerebri, and from the adjacent parts
of the medial surfaces of the cerebral hemispheres.
 
The straight sinus is situated at the junction of the falx cerebri
with the tentorium cerebelli, and is formed by the union between the
inferior longitudinal sinus and the great (internal) cerebral vein at
the anterior margin of the tentorium. It is triangular in section, and
increases in size from before backwards. Its course is downwards
and backwards in the median line to the left side, as a rule, of the
internal occipital protuberance, where it becomes slightly dilated, and
is continued into the left transverse sinus. Its terminal dilatation is
connected with the confluens sinuum by a transverse vessel. In
those cases where the superior longitudinal sinus passes into the left
transverse sinus the straight sinus passes into the right transverse sinus.
In addition to the inferior longitudinal sinus and the great cerebral vein,
the straight sinus receives some of the superior cerebellar veins and
tributaries from the falx cerebri and tentorium cerebelli.
 
The transverse sinuses extend on each side from the internal occipital
protuberance to the postero-lateral compartment of the jugular foramen,
through which it passes, to terminate in the bulb of the internal jugular
vein. The sinus pursues a curved course. It passes outwards in the
transverse groove on the inner surface of the tabular part of the occipital
bone as far as the inner surface of the postero-inferior angle of the
parietal bone. Here it ascends for a little in a groove, and, having
described a sharp curve, it passes downwards and medially in the
sigmoid groove on the inner surface of the mastoid portion of the temporal bone. Finally, it turns forwards in the groove on the upper
surface of the jugular process of the occipital bone to the jugular foramen. As far as the postero-inferior angle of the parietal bone the
transverse sinus is contained within the attached border of the tentorium cerebelli, and just before leaving this it receives the superior
petrosal sinus. The right transverse sinus is, as a rule, formed by the
superior longitudinal sinus, and in these circumstances is larger than
the left, which is usually formed by the straight sinus. The reverse,
however, may be the case. Before leaving the torcular the two sinuses
communicate freely.
 
The transverse sinus of each side, in addition to the superior petrosal
sinus, receives tributaries from the posterior part of the cerebrum and
the superior and inferior surfaces of the cerebellum. It also receives
the posterior temporal and occipital diploic veins, and the petrosquamous sinus, when that sinus is present. Near its termination it
communicates with the marginal sinus of the same side. The sinus
communicates with extracranial veins by means of two large emissary
veins, posterior condylar and mastoid, which pass through the corresponding foramina. These foramina, however, being inconstant, the
 
emissary veins are sometimes wanting.
 
The name ‘ transverse ’ is strictly applicable only to that part ot
the sinus which is contained within the attached border of the tentorium
cerebelli , and extends from the internal occipital protuberance to the
 
 
i6o6
 
 
A MANUAL OF ANATOMY
 
 
postero-inferior angle of the parietal bone. Beyond this latter point
the sinus is known as the sigmoid sinus.
 
The occipital sinus is situated within the falx cerebelli along its
attachment to the internal occipital crest. It is of small size, and is
formed inferiorly by the union of the two marginal sinuses (inferior
occipital) which lie on either side of the vermiform fossa and foramen
magnum, where they communicate with the posterior intraspinal veins
and the terminal part of each lateral sinus. Superiorly it opens into
the confluens sinuum. In certain cases the marginal or inferior occipital
sinuses remain separate, and then each opens into the corresponding
transverse sinus. The occipital sinus receives tributaries from the
falx cerebelli and the inferior surface of the cerebellum, and it establishes a communication between the beginning and end of the transverse
sinuses.
 
The cavernous sinuses are so named because the interior of each is
broken up by fibrous filaments, which impart to it a reticular appearance. Each sinus is situated on the side of the body of the sphenoid
bone, and extends from the inner extremity of the sphenoidal fissure
to the apex of the petrous part of the temporal bone. Anteriorly it
receives the ophthalmic vein or veins from the orbit, and posteriorly it
terminates by dividing into the superior and inferior petrosal sinuses.
In addition to the ophthalmic vein or veins, the cavernous sinus
receives the spheno-parietal sinus and some of the inferior cerebral
veins. It communicates with the angular vein of the face through the
superior ophthalmic vein; with its fellow of the opposite side through
the circular sinus; with the transverse sinus by the superior petrosal
sinus; with the internal jugular vein by the inferior petrosal sinus;
with the pterygoid plexus through the inferior ophthalmic vein, and
by an emissary vein which passes through the foramen ovale, or through
the foramen Vesalii ’; and with the pharyngeal plexus by an emissary
vein which passes through the foramen lacerum medium. The internal
carotid artery, with the cavernous sympathetic plexus, lies within the
sinus, and the sixth cranial nerve (Fig. 989) is close to the outer side of
the artery. In connection with the roof and outer wall of the sinus
there are the third and fourth, as well as the ophthalmic and superior
maxillary divisions of the fifth cranial nerves.
 
The spheno-parietal sinus is of small size, and is situated on the
inferior surface of the lesser wing of the sphenoid bone. It generally
begins in connection with the anterior temporal diploic vein, and ends
in the anterior part of the cavernous sinus.
 
The circular sinus fills any small part of the hypophysial fossa which
 
is not occupied by the gland; on each side it opens freely into the
cavernous sinus.
 
The superior petrosal sinus is situated along the superior border
of the petrous part of the temporal bone, and lies within the attached
margin of the tentorium cerebelli. It begins at the back part of the
cavernous sinus, and, having passed laterally and backwards, it opens
into the transverse sinus as that is about to enter the sigmoid groove
 
 
/
 
 
THE NERVOUS SYSTEM 1607
 
of the pars mastoidea. It receives tributaries from the cerebellum and
tympanum.
 
The inferior petrosal sinus occupies the groove at the junction of
the basilar process of the occipital bone with the petrous part of the
temporal bone. It begins at the back part of the cavernous sinus, and,
passing backwards and slightly laterally, it leaves the cranial cavity
through the antero-medial compartment of the jugular foramen, to
terminate in the bulb of the internal jugular vein. It receives tributaries from the inferior surface of the cerebellum, and from the internal
ear.
 
 
 
Fig. 989._Right Internal Carotid put in Position on Base of Skull and
 
Crossed by Sixth Nerve.
 
Greater superficial petrosal nerve is also seen entering foramen lacerum.
 
The basilar sinus is really a plexus of veins situated within the dura
mater over the basilar process of the occipital bone, extending as low
as the anterior margin of the foramen magnum, where it communicates
with the anterior intraspinal veins. It connects the anterior ends of
the inferior petrosal sinuses with each other.
 
The petrosquamous sinus is situated along the junction of the
petrous and squamous parts of the temporal bone. Its direction is
backwards, and it opens into the transverse sinus as that is entering the
 
siermoid fossa of the pars mastoidea.
 
Each petro-squamous sinus represents the continuation of the
transverse sinus in early life, to terminate in the primitive jugular vein.
Often there are no traces of the petro-squamous sinus.
 
 
 
 
 
 
 
i6o8
 
 
A MANUAL OF ANATOMY
 
 
Emissary Veins. —These are vessels which pass through foramina in the
cranial wall, and establish communications between the intracranial venous
sinuses and the extracranial veins. The principal emissary veins are mastoid,
nasal, posterior condylar, parietal, and occipital. In addition to these there
are emissary veins, which pass through (i) the foramen ovale, (2) the foramen
Vesalii (when present), and (3) the foramen lacerum and the carotid canal.
 
The transverse sinus in many cases has two emissary veins, mastoid and
posterior condylar.
 
The mastoid emissary vein is of large size. It passes through the mastoid
foramen, and usuallv opens into the posterior auricular vein.
 
The posterior condylar emissary vein passes through the posterior condylar
foramen, and opens into the suboccipital plexus, from which the blood is carried
away by the vertebral and deep cervical veins.
 
The mastoid and posterior condylar veins are not constant.
 
The superior sagittal sinus may have three emissary veins—parietal and
occipital and nasal.
 
The parietal emissary vein passes through the parietal foramen, and opens
into the occipital plexus, or into radicles of the superficial temporal vein.
 
The occipital emissary vein passes from the confluens sinuum to the occipital
plexus, being transmitted through a minute foramen which pierces the external
occipital protuberance.
 
The nasal emissary vein passes through the foramen caecum; like all other
emissary veins it is often absent.
It has been seen already that the cavernous sinus communicates with (1) the
angular vein of the face, (2) the pterygoid plexus, and (3) the pharyngeal plexus.
The marginal or inferior occipital sinus communicates with the posterior intraspinal veins, and the basilar sinus communicates with the anterior intraspinal
veins.
 
 
Arachnoid Membrane.
 
This is a very delicate membrane which loosely surrounds the
encephalon, and is situated between the dura mater and pia mater.
It does not dip into the fissures, except in the case of the great longitudinal fissure, its general course being over the gyri and other eminences and depressions of the encephalon. It is conspicuous at the base
of the encephalon in the region of the interpeduncular space, pons, and
medulla oblongata. Its outer surface is practically in close contact
with the inner surface of the dura mater, the extremely slight interval
containing a very little lubricating serous fluid, and being known as
the subdural space. Between the arachnoid and the pia mater there
is the interval known as the subarachnoid space. The membrane
furnishes sheaths to the various cranial nerves.
 
Subarachnoid Space.—This space lies between the arachnoid and
the pia mater. It is crossed by delicate trabeculae of connective tissue,
which pass between the two membranes, in a reticular manner. The
meshes of this reticulum contain the cerebro-spinal fluid.
 
The subarachnoid space communicates with the ventricles of the
brain by one main opening, the median aperture of the ventricle or
foramen of Magendie, which is situated in the median line of the roof
of the ventricle a little above the lower angle.* In some situations—
as, for example, over the gyri—the arachnoid and pia mater are in close
 
* The modern view is that there are also foramina at the lateral angles of the
ventricle, lateral apertures.
 
 
/
 
 
THE NERVOUS SYSTEM
 
 
1609
 
 
contact, but in other localities the two membranes are more or less
widely separated by intervals, called cisternas. The most important of
these are the cisterna magna, cisterna pontis, cisterna basalis, and
cisterna venae magnae.
 
The cisterna cerebello-medullaris (or magna) lies between the posterior
part of the inferior surface of the cerebellum and the medulla oblongata.
It is of large size, the arachnoid, which here passes from cerebellum to
medulla, being widely separated from the pia mater. It is continuous
through the foramen magnum with the posterior part of the subarachnoid space of the spinal cord.
 
The cisterna pontis is situated on the ventral aspect of the pons.
Interiorly it is continuous with the anterior part of the subarachnoid
space of the spinal cord, and in the region of the medulla oblongata
it is continuous otherwise with the previous cisterna and interpeduncularis. It contains the basilar artery.
 
The cisterna basalis or interpeduncularis is situated in front of the
pons, in which situation the arachnoid extends over the interpeduncular space from one temporal lobe to the other. It contains the
arteries which form the circulus arteriosus. This cisterna is prolonged
outwards on each side into the stem of the lateral fissure, each of these
prolongations containing the middle cerebral artery. Anteriorly it
extends in front of the optic commissure into the great longitudinal
fissure over the upper surface of the corpus callosum, this prolongation
containing the anterior cerebral arteries.
 
The cisterna venae magnae lies just behind the entrance of the great
transverse fissure, between the splenium and the corpora quadrigemina,
where the great cerebral vein comes out.
 
The subarachnoid fluid can be drained away in two directions. It
can enter the lymph-spaces of the cranial nerves upon which the arachnoid is prolonged outwards in the form of sheaths; and it can enter the
lacunae laterales, and through the intervention of the Pacchionian bodies
make its way into the superior longitudinal sinus.
 
Structure of the Arachnoid Membrane. —The arachnoid consists of fine
fibrous tissue arranged in interlacing bundles, the intervals between these
bundles being occupied by delicate cellular membranes. Several such layers,
intimately blended together, form the membrane.
 
Beneath the arachnoid, and constituting a part of it, there is a reticulum
of subarachnoid trabeculce. These trabeculae consist, as in the case of the arachnoid proper, of fine fibrous tissue, but the intertrabecular spaces, instead of
being occupied by cellular membranes, contain cerebro-spinal (subarachnoid)
fluid. The trabecular reticulum connects the arachnoid with the subjacent pia
mater. The superficial surface of the arachnoid is covered with a delicate layer
 
of endothelium.
 
Arachnoid Granulations— These are small granular bodies which
are situated along the course of the superior longitudinal sinus, into
which some of them project. They are seldom met with in adults
in other sinuses— e.g., the lateral and straight sinuses. Each body is
a villous projection of the arachnoid membrane, with which it is connected by a narrow pedicle. Some bodies project into the superior
 
 
i6io
 
 
A MANUAL OF ANATOMY
 
 
longitudinal sinus; others project from below into the lacunae laterales.
In all cases the bodies pierce the dura mater and carry before them
the lining of the sinus. Superficially the bodies give rise to the depressions on the internal surface of the parietal bone near the superior
border. Each body contains a prolongation of the subarachnoid space
and reticulum. This is surrounded by a prolongation of the arachnoid
membrane, and external to this is the endothelial lining of the sinus or
of the lacuna. The granulations probably are channels through which
the subarachnoid fluid can be drained away from the subarachnoid
space into the lacunae laterales, and thence into the superior sagittal
sinus, as well as into the other sinuses— e.g., the transverse and straight
sinuses. They are rarely met with in children under twelve, and then
most commonly in the transverse sinus.
 
Pia Mater.
 
The pia mater is the most internal covering of the encephalon. It
is a very vascular membrane, which invests and is closely adherent to
the entire surface. From its internal surface delicate processes pass
into the cerebral substance, which represent the minute bloodvessels,
surrounded by pia-matral sheaths. The pia mater not only invests the
external surface, but also dips into the sulci, and covers the opposed
surfaces of the gyri. It also furnishes sheaths to the various cranial
nerves, which blend with their perineurium. It gives rise to two weblike expansions—namely, the tela chorioidea inferior and tela chorioidea
superior.
 
The tela chorioidea inferior is situated in the lower part of the roof
of the fourth ventricle, and from it are derived the choroid plexuses
of that ventricle. The tela chorioidea superior (or velum interpositum)
is an invagination of the pia mater through the transverse fissure beneath the splenium of the corpus callosum. It lies underneath the
body of the fornix, and its lower surface is covered by the ependymal
lining of the third ventricle, the latter forming the roof of that cavity.
The tela chorioidea superior furnishes the choroid plexuses of the two
lateral and third ventricles.
 
The pia mater of the encephalon differs from the pia mater of the
spinal cord in being thinner and less adherent to the nervous substance.
The greater thinness is due to the fact that it is destitute of the outer
layer which characterizes the spinal pia mater.
 
Structure. —The pia mater of the encephalon consists of a single layer of
areolar tissue, which contains a great many small bloodvessels, these being
derived from the larger vessels lying in the subarachnoid space.
 
The Cranial Nerves.
 
The cranial nerves are arranged in twelve pairs. They have received numerical names according to the order in which they leave
the cranial cavity from before backwards, and they also have descrip
 
THE NERVOUS SYSTEM
 
 
1611
 
 
tive names. The different pairs of nerves are as follows, in order from
before backwards:
 
 
First, or olfactory.
 
Second, or optic.
 
Third, or oculo-motor.
 
Fourth, or trochlear (pathetic).
Fifth, or trigeminal (trifacial).
Sixth, or abducent.
 
 
Seventh, or facial.
 
Eighth, or auditory.
 
Ninth, or glosso-pharyngeal.
Tenth, or vagus.
 
Eleventh, or accessory.
Twelfth, or hypoglossal.
 
 
The cranial nerves are connected to certain parts of the encephalon,
and these connections constitute their superficial or apparent origins.
The fibres, however, can be traced to certain collections of grey matter,
which are called nuclei. From the deep positions occupied by these
nuclei they constitute the deep origins of the nerves.
 
First or olfactory nerve consists of the olfactory filaments or nerves,
which are about twenty in number.
 
The olfactory nerves are non-medullated. They arise as the axons
of the olfactory cells of the olfactory mucous membrane of the nasal
fossa; and enter the cranial cavity through the foramina of one half
of the cribriform plate of the ethmoid bone. Thereafter they enter
the grey matter on the ventral or inferior aspect of the olfactory bulb,
and terminate in arborizations which intermingle with the arborizations
formed by the dendrites of the mitral cells situated in the granular layer
of the bulb (see p. 1570).
 
Second or Optic Nerve.—This nerve arises from the brain by means
of the optic tract, the deep connections of which have been already
described (p. 1545). Each optic tract passes forwards and inwards to
the optic commissure or chiasma, which is situated in front of the interpeduncular space. 1 he optic nerve of each side arises from the anterior
part of the optic chiasma. It courses forwards and outwards to the
optic foramen, through which it passes into the orbit, piercing the dura
mater, and receiving a sheath from it, as well as from the arachnoid
membrane. Having reached the back part of the eyeball, it pierces the
sclerotic and choroid coats ^ inch to the nasal or inner side of the axis
of the eyeball, and terminates in an expansion which forms the most
internal layer of the retina, called the nerve-fibre or optic layer.
 
Neither this nor the preceding is, strictly speaking, a nerve at all.
 
Third or Oculo-motor Nerve.—The fibres of this nerve arise from
the oculo-motor nucleus, which is situated in the grey matter of the
ventral aspect (floor) of the aqueduct on a level with the upper quadrigeminal body, and extends superiorly for a short distance on to the
lateral wall of the third ventricle. The nucleus is intimately related
to the medial longitudinal bundle, by means of which it is connected
with the trochlear and abducent nuclei. All three nuclei receive collaterals from the bundle; and in this manner a functional association
between these nuclei is maintained, and harmonious action is insure
on the part of the muscles which are supplied by the nerves arising from
them. It consists of several groups of cells. As many as seven groups
are ascribed to each oculo-motor nucleus by Perlia, which correspond
 
 
1612
 
 
A MANUAL OF ANATOMY
 
 
to the seven muscles supplied by the oculo-motor nerve, and are disposed symmetrically. In addition to these, there is a medially-placed
group, the cells of which furnish fibres to both oculo-motor nerves.
The fibres which arise from the individual groups of each nucleus are
regarded as supplying particular orbital muscles. Certain of the
oculo-motor fibres of one side arise from the nucleus of the opposite
side, the fibres from either side decussating at the median line. Moreover, each oculo-motor nerve is said to receive fibres from the abducent
 
 
Olfactory Bulb
 
 
 
Lateral Fissure
Gyrus Rectus
 
 
Ant. Perforated
Substance
 
 
Tuber Cinereum
 
 
Corpus
Mamillare
Crus Cerebri
 
 
Post. Perforated
Substance
 
 
Pons
 
 
Olfactory Tract
 
 
Optic Nerve
 
 
'.Medulla Oblongata
 
 
Spinal Cord
 
 
Optic Chiasm a
 
 
Optic Tract
Third Nerve
 
 
Fourth Nerve
 
 
Fifth Nerve
Sixth Nerve
Facial Nerve
 
Sensory Root ol VIJ.
 
Auditory Nerve
Glosso-pharyngeal Nerve Vagus Nerve '
Accessory Nerve
 
Hypoglossal Nerve
 
 
Fig. 990. —The Base of the Encephalon, and the - Cranial Nerves.
1, frontal lobe (orbital surface); 2, temporal lobe; 3, cerebellum.
 
 
nucleus of the opposite side, which ascend in the posterior longitudinal
bundle and cross to the other side.
 
Two views are entertained in regard to the nerve-supply of the
medial rectus muscle. According to one view, the muscle of one side
is supplied by those fibres which have crossed from the oculo-motor
nucleus of the opposite side. The other view is that the muscle of
one side is supplied by those fibres which have crossed from the abducent nucleus of the opposite side. According to this latter view,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1613
 
 
the nerve-fibres which supply the lateral rectus muscle of one side and
those which supply the medial rectus muscle of the opposite side arise
from the same nucleus—namely, the abducent nucleus—and vice
versa.
 
Probably the whole of the oculo-motor nucleus is not in series with
the medial somatic group to which the fourth, sixth, and twelfth nuclei
belong, but that some of it corresponds to the more lateral group containing the seventh, ninth, and tenth nuclei. Fibres from this part
probably go to the ciliary muscle and iris.
 
 
 
Fig qqi._Scheme showing the Different Cell-groups which constitute,
 
'according to Perlia, the Nucleus of Origin of the Third Cranial
 
OR OCULO-MOTOR NERVE (FROM TESTUT, AFTER PERLIA).
 
 
1. Posterior Dorsal Nucleus
1'. Posterior Ventral Nucleus
 
2. Anterior Dorsal Nucleus
2'. Anterior Ventral Nucleus
 
 
3
 
4
 
5
 
 
Central Nucleus ,
 
Jucleus of Edinger and Westphal
Lntero-medial Nucleus
 
 
6. Antero-lateral Nucleus
 
7. Trunk of Oculo-Motor Nerve
 
8. Crossed Fibres
 
9. Nucleus of Origin of Fourth Nerve
 
g'. Intercrossing of Fourth Cranial Nerves
 
10. Third Ventricle
M. Middle Line.
 
 
The old view, that the orbicularis oculi is supplied from this nucleus,
by the medial longitudinal bundle and the facial trunk, is no longer
held by anatomists.
 
Course of the Fibres o£ the Third Nerve.— The fibres pass forwards
from their origin through the tegmentum, the red nucleus, and the
medial portion of the substantia nigra, and afterwards make their superficial appearance at the oculo-motor sulcus on the medial aspect of
 
the crus cerebri. .
 
The third or oculo-motor nerve supplies the following seven muscles.
 
the levator palpebne superioris; the superior, inferior, and internal
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1614
 
recti; the inferior oblique; the sphincter pupillae; and the ciliary
muscle.
 
Fourth (Trochlear, or Pathetic) Nerve. —The fibres of this nerve arise
from the trochlear nucleus, which is situated in the grey matter of the
ventral aspect (floor) of the aqueduct on a level with the upper part
of the lower quadrigeminal body. The nucleus is intimately related
to the medial longitudinal bundle, by means of which it is connected
with the oculo-motor nucleus.
 
The fibres are at first directed laterally and backwards, and then
medially to the upper part of the superior medullary velum, which
they enter. Here the nerve crosses to the opposite side, decussating
 
 
 
Fig. 992.—Deep Origins of Third, Fourth, and Fifth Cranial Nerves.
 
with its fellow, after which it emerges from the upper end of the
superior medullary velum close below the lower quadrigeminal body,
and by the side of the frenulum veli. After this the nerve turns
over the superior peduncle of the cerebellum, and is then directed
forwards, round the outer aspect of the crus cerebri, between which
and the temporal lobe it makes its superficial appearance.
 
The fourth nerve supplies the superior oblique muscle of the eyeball.
 
Fifth Cranial, Trigeminal (or Trifacial) Nerve. —The fifth cranial
nerve resembles a spinal nerve in having two roots—sensory and motor
 
the former being large, and having a ganglion, called the trigeminal
ganglion.
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1615
 
Sensory Root. —The fibres of this root are derived from the central
poles of the bipolar cells of the trigeminal ganglion. After entering the
pons each fibre divides into two branches, ascending and descending,
as in the case of the fibres of the dorsal or sensory root of a spinal nerve.
The terminal nuclei of these ascending and descending sensory fibres
are two in number—upper and lower.
 
♦The upper sensory nucleus is situated in the outer portion of the
dorsal part of the pons, where it lies close to the lateral side of the
pontine or principal motor nucleus of the nerve. The ascending sensory
fibres, after a short course, enter this nucleus and terminate in arborizations around its cells.
 
The lower sensory nucleus, continuing the line of the upper sensory
nucleus, is an upward prolongation of the substantia gelatinosa from
the tubercle and funiculus gelatinosus in the medulla oblongata. The
nucleus is traceable as low as the dorsal grey horn of the spinal cord
on a level with the second cervical spinal nerve, where it is close to
the substantia gelatinosa. The descending sensory fibres, which are
numerous, and constitute the spinal root of the fifth nerve, pass downwards through the pons and medulla oblongata into the spinal cord as
low as the level of the second cervical spinal nerve. They are accompanied by the lower sensory nucleus, and at different levels they enter
this nucleus and terminate in arborizations around its cells.
 
The disposition of the fibres and cells within the spinal root
is of a reversed order—that is, the ophthalmic nerve is associated
with the lower part of the spinal root, above this the maxillary,
with the mandibular at the upper end.
 
The ascending or mesencephalic nucleus of the fifth extends along
the grey matter on the side of the aqueduct as far as the level of the
lower part of the upper corpus quadrigeminum. Its lower limit is
lateral to the substantia coerulea in the upper part of the fourth ventricle.
The mesencephalic root has only been recognized as sensory within the
last few years, and there is reason to suppose that it receives proprioceptive impulses from certain muscles.
 
Motor Nucleus. —This nucleus is placed in the lateral part of the
tegmental region of the pons, deep to the floor of the upper or pontine
portion of the fourth ventricle, and immediately medial to the upper
sensory nucleus of the nerve. Its fibres run ventro-laterally to emerge
as the small motor root of the nerve.
 
Most of the axons of the cells of the terminal sensory nuclei
pass inwards to the raphe and cross to the opposite side. They
then become longitudinal and ascend in company with the
medial lemniscus or chief sensory tract, their destination being
the thalamus of the side to which they have crossed. They
thus constitute a trigemino-thalamic ascending tract. From these
fibres collaterals are furnished to (1) the facial nucleus, and
(2) the ventral vago-glosso-pharyngeal nucleus, or nucleus am
 
i6i6
 
 
A MANUAL OF ANATOMY
 
 
biguus, from the cells of which latter the efferent or motor fibres
of the pneumogastric or vagus nerve arise.
 
A few of the axons, however, enter the pontine or chief motor
nucleus, and also the mesencephalic sensory nucleus, of the nerve,
and terminate in arborizations around its cells.
 
The large sensory and small motor roots appear close together, on
the lateral aspect of the ventral surface of the pons, the motor root
lying above and slightly internal to the sensory root. The sensory root
enters and the motor root leaves the pons.
 
Distribution. —The fifth cranial nerve has an extensive distribution
by means of its three divisions—ophthalmic, superior maxillary, and
inferior maxillary.
 
Ophthalmic Nerve (Sensory). —(i) The front part of the cranium;
(2) the integument of (a) the upper eyelid, and ( b ) the root and tip of
the nose; (3) the anterior part of the nasal mucous membrane, and the
conjunctiva; (4) the eyeball; and (5) the lacrimal gland.
 
Maxillary Nerve (Sensory). —(1) The integument of the zygomatic
and anterior part of the temporal regions; (2) the integument of
(, a) part of the lower eyelid, ( b) the side of the nose, (c) the upper lip,
and (d) that part of the face between the lower eyelid and the upper
lip; (3) the upper teeth, and the mucous membrane of the upper gum;
 
(4) a large part of the nasal mucous membrane; (5) the mucous membrane of the maxillary air-sinus (or antrum of Highmore); (6) the
mucous membrane of (a) the naso-pharynx, and ( b ) the soft and hard
palate and the tonsil.
 
Mandibular Nerve (Sensory and Motor). —The sensory distribution
 
of this nerve is as follows: (1) the integument of (a) the temporal region,
( b ) the outer surface of the pinna, and (c) the external auditory meatus;
 
(2) the integument of the lower lip, and that which covers the mandible;
a recurrent branch runs along the petro-squamous suture, supplying
the mucous membrane of the tympanum and of the mastoid antrum;
 
(3) the temporo-mandibular joint; (4) the parotid salivary gland;
 
(5) the mucous membrane lining the buccinator muscle, and the integument covering that muscle (by means of the long or sensory buccal
nerve ); (6) the mucous membrane (fungiform and conical papillae) of the
anterior two-thirds of the tongue (common sensation); (7) the submandibular and sublingual salivary glands; and (8) the pulps of the
lower teeth, and the mucous membrane of the lower gum.
 
The motor distribution of the mandibular nerve is as follows:
(1) The muscles of mastication—namely, (a) the masseter, ( b ) the
temporal, and (c) the pterygoid muscles; (2) the mylo-hyoid muscle
and anterior belly of the digastric; (3) the tensor tympani muscle by
means of a branch from the otic ganglion; and (4) the tensor palati
muscle through the otic ganglion.
 
Sixth or Abducent Nerve. —The fibres of this nerve arise from the
abducent nucleus, which is situated in the dorsal part of the pons close
to the median line. It lies above the striae acusticae on the floor of the
 
 
THE NERVOUS SYSTEM
 
 
1617
 
fourth ventricle subjacent to the eminentia teres. The fibres emerge
from the inner part of the nucleus, and pass through the lower part
of the pons in a forward and slightly downward and lateral direction
to the lower border of the pons just lateral to the pyramid of the
medulla oblongata, where the nerve makes its superficial appearance.
 
The abducent nucleus receives collaterals from the medial or
posterior longitudinal bundle, and a functional connection is thereby
established between that nucleus and the oculo-motor nucleus. The
medial rectus muscle of one side and the lateral rectus of the other side
are thus associated muscles.
 
The sixth nerve supplies the lateral rectus muscle of the eyeball.
 
 
 
Fig. 993. —Deep Origins of Sixth, Seventh, and Eighth
 
Cranial Nerves.
 
Seventh or Facial Nerve.— The facial nerve is composed of two
parts. One of these consists of efferent or motor fibres, and is known
as the facial nerve proper. The other part, of small size, consists of
afferent or sensory fibres. The facial nerve proper arises from the
facial nucleus , which is situated deeply in the dorsal part of the lower
portion of the pons. The fibres of the nerve pursue an intricate course
before appearing superficially. They at first pass backwards and
inwards to the floor of the fourth ventricle. Here they turn upwards,
lying close to the median line in the form of a single bundle. The
nerve then makes a sharp bend laterally, and passes forwards through
the pons in a downward and outward direction to its place of emergence.
 
T02
 
 
 
 
 
 
 
 
 
 
 
i6i8
 
 
A MANUAL OF ANATOMY
 
 
In its course within the pons the nerve is intimately related to the
dorsal aspect of the abducent nucleus.
 
1 he intrapontine part of the facial nerve proper is intimately related
to the following structures:
 
1. The abducent nucleus. 4. The spinal root of the fifth
 
2. The superior olive. nerve.
 
3. The corpus trapezoides. 5. The medial or posterior
 
longitudinal bundle.
 
The motor facial nucleus receives fibres from the following sources:
(1) The corpus trapezoides, being thereby brought into connection with
the cochlear division of the auditory nerve; (2) the spinal root of the
 
 
sup?- cerebellar^
peduncle.
 
 
emmeniia,
teres.
 
nucleus of".,
sixth n.
 
medial longitudbundle.
 
stalk of olive"'
mediul fillet -
 
 
\- -V-inferiori cerebellar
-ymiddle j peduncle.
 
_\_lai- vestibular
 
nucleus.
 
 
-/-spinal root of V f - h n.
 
 
facial nucleus
 
-facial nerve
 
^vestibular part
'"''of 8 f h nerve.
 
s . "'-corpus trapezoides
 
"'Supr. olivary nucleus
 
abducens nerve
pyramidal tract.
 
Fig. 994.— Diagrammatic Section through the Pons, to show Deep
Origins of Sixth (Red) and Seventh (Black) Cranial Nerves.
 
 
fifth cranial or trigeminal nerve, which is the sensory nerve of the face;
and (3) the pyramidal tract of the opposite side, being thereby brought
into connection with the precentral motor area of the cerebral cortex.
 
All the foregoing fibres terminate within the nucleus in arborizations around its component cells.
 
The sensory portion of the facial nerve arises from the central poles
of the bipolar cells of the geniculate ganglion on the facial nerve in the
facial canal. This ganglion resembles the ganglion of the fifth nerve
and the spinal ganglia, and most of the peripheral poles of its bipolar
cells give rise to the chorda tympani nerve. The pars intermedia passes
from the facial canal into the internal auditory meatus, after leaving
which it runs to the lower border of the pons, where it lies between the
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1619
 
 
facial nerve proper and the auditory nerve. The nerve then enters
the medulla oblongata, and passes downwards to the upper part of the
nucleus of the fasciculus solitarius (see Glosso-pharyngeal Nerve), and
its fibres terminate in arborizations around the cells of the upper part
of that nucleus. In this situation it is closely associated with the
terminal afferent or sensory fibres of the glosso-pharyngeal nerve.
 
The facial nerve proper emerges from the brain at the lower border of
the pons in front of, and internal to, the auditory nerve; and the
sensory part enters between the facial nerve proper and the auditory
nerve.
 
 
 
Fig. 995.—Terminal Nuclei of the Vestibular Nerve, with their
Superior Connections (Schematic) (L. Testut’s * Anatomie Humaine ’).
 
 
x. Cochlear Root, with its Two Nuclei
 
2. Accessory Nucleus
 
3. Lateral Nucleus (or Tuberculum Acusticum)
 
4. Vestibular Root
 
5. Medial Nucleus
 
6. Lateral Vestibular Nucleus (or Nucleus of
 
Deiters)
 
7. Superior Nucleus (of Bechterew)
 
8. Inferior Root or Nucleus of Auditory Nerve
 
9. Ascending Cerebellar Fibres
 
 
10. Fibres passing to Raphe
 
11. Oblique Fibres
 
12. Lemniscus
 
13. Inferior Sensory Root of Fifth Cranial Nerve
 
14. Pyramidal Fibres
 
15. Raph6
 
16. Fourth Ventricle
 
17. Inferior Peduncle of Cerebellum (Restiform
 
Body)
 
18. Origin of Auditory Striae
 
 
Distribution—Motor Part (Facial Nerve Proper).— (1) The muscles
of the face, including the buccinator ; (2) the occipito-frontalis; (3) the
muscles of the auricle; (4) the posterior belly of the digastric and the
stylo-hyoid; (5) the platysma myoides; and (6) the stapedius muscle
within the tympanic cavity.
 
Sensory Part (Sensory Root and Chorda Tympani). —The anterior
two-thirds of the tongue (sense of taste).
 
The chorda tympani nerve conveys secretory and vaso-dilator fibres
from the facial nerve proper to the submandibular and sublingual salivary glands. .
 
The large superficial petrosal nerve from the geniculate ganglion
 
of the facial nerve is concerned in the supply of the mucous membrane
 
 
 
 
1620
 
 
A MANUAL OF ANATOMY
 
 
of the palate, the path being as follows: (i) Large superficial petrosal
nerve (facial fibres); (2) the nerve of pterygoid canal; (3) spheno-palatine
ganglion; and (4) the descending palatine nerves.
 
Eighth, Auditory, or Acoustic Nerve. —The auditory nerve is the
nerve of hearing and of equilibrium. It is an afferent or centripetal
nerve which conducts impressions from the membranous labyrinth
(cochlea and vestibule) to the medulla oblongata and pons, and thence
to the cerebrum and cerebellum. It consists of two divisions—namely,
the cochlear nerve or root, and the vestibular nerve or root.
 
. The fibres of the cochlear nerve arise from the bipolar cells of the
spiral ganglion in the spiral canal of the modiolus, the modiolus being
the central pillar of the osseous cochlea. The fibres of the vestibular
nerve arise from the bipolar cells of the vestibular ganglion (or ganglion
of Scarpa) at the deep end of the internal auditory meatus.
 
The two nerves or roots reach the brain at the lower border of the
pons lateral to the facial nerve and ventral to the restiform body.
They have different central connections, and consequently take different
courses. The cochlear nerve passes round the outer side of the restiform body, whilst the vestibular nerve passes backwards medial to that
body, and each root has special terminal nuclei.
 
Cochlear Nerve. —The terminal nuclei of the cochlear nerve, which
is the nerve of hearing, are two in number—ventral and lateral.
 
The ventral or accessory nucleus lies on the ventral aspect of the
inferior peduncle between the cochlear and vestibular nerves. The
lateral or dorsal nucleus, or tuberculum acusticum , is situated on the
lateral and dorsal aspects of the peduncle. The fibres of the cochlear
nerve or root enter these two nuclei, and terminate in arborizations
around their component cells.
 
Central Connections of the Ventral and Lateral Cochlear Nuclei.—
 
The ventral and lateral nuclei constitute cell-stations in the path of
the fibres of the cochlear nerve, and from these cell-stations two fresh
nerve-tracts arise, one being ventral, which constitutes the corpus
trapezoides, and the other dorsal, which forms the auditory striae.
 
Ventral Cochlear Tract. —The relays, or fresh supplies, of nervefibres for this tract are furnished by the cells of the ventral nucleus.
The axons of these cells give rise to the trapezium, or corpus trapezoides, which is reinforced by the axons of the cells of the nucleus
trapezoides, and fibres from the superior olive of the same side. The
trapezoidal fibres cross the median plane, and thereafter constitute
the lateral lemniscus, being further reinforced by fibres from the superior
olive of the side to which they have crossed, and from the nucleus of
the lateral lemniscus. The fibres of this fillet terminate in the lower
 
quadrigeminal body and internal geniculate body, both of the same
side.
 
Dorsal Cochlear Tract. —The relays of fibres for this tract are furnished by the cells of the lateral nucleus. The axons of its cells form
the auditory striae, which cross the dorsal aspect of the restiform body
and the floor of the fourth ventricle. At the median line they pass
 
 
THE NERVOUS SYSTEM
 
 
1621
 
 
forwards, and then cross to the opposite side. Thereafter they join
the lateral or acoustic lemniscus of the side to which they have
crossed.
 
The lateral or acoustic lemniscus (see p. 1557) derives its fibres from
the following sources: (1) The corpus trapezoides; (2) the auditory
striae; (3) the superior olive of both sides; and (4) the nucleus of the
 
 
 
Fig. 996. —Terminal Nuclei of the Cochlear Nerve, with their Superior
Connections (Schematic) (L. Testut’s ‘ Anatomie Humaine ’).
 
The vestibular root and its terminal nuclei, with the efferent fibres of these
latter, have been suppressed. In order not to obscure the trapezoid body,
the efferent fibres of the terminal nuclei of the right side have been in a
great part of their extent resected. The trapezoid body is consequently
composed of only half of its fibres—namely, those which come from the
left.
 
 
t. Vestibular Root of Auditory Nerve
 
2. Cochlear Root
 
3. Ventral Nucleus of Auditory Nerve
 
4. Lateral Nucleus (or Tuberculum Acusticum)
 
5. Efferent Fibres of Ventral Nucleus
 
6. Efferent Fibres of Lateral Nucleus, forming
 
the Auditory Striae
 
6'. Direct Fibres of the Striae going to the
Superior Olivary Body of the same side
 
 
6 ". Crossed Fibres of the Striae going to the
Superior Olivary Body of the opposite side.
 
7. Superior Olivary Body
 
8. Corpus Trapezoides
 
9. Trapezoid Nucleus
 
10. Lateral Lemniscus 11. Raphe
 
12. Pyramidal Tract 13. Fourth Ventricle
 
14, Inferior Peduncle of Cerebellum (Restiform
Body)
 
 
lateral lemniscus. It serves as a path of connection between the
ventral and lateral cochlear nuclei of one side, and the lower Quadrigeminal body and medial geniculate body of the opposite side.
 
It is to be noted that the ventral and lateral cochlear nuclei are
slightly connected with the lower quadrigeminal body of the same
side but not with the corresponding medial geniculate body.
 
The axons of the cells of the medial geniculate body form a cork
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1622
 
 
A MANUAL OF ANATOMY
 
 
cipetal tract, which passes to the cortex of the first or superior temporal
gyrus of the temporal lobe of the brain.
 
The complex nervous chain associated with the cochlear nerve may
be tabulated as follows:
 
1. The bipolar cells of the spiral ganglion.
 
2. The fibres of the cochlear nerve.
 
3. The ventral and lateral cochlear nuclei.
 
4. The fibres of the corpus trapezoides, reinforced as stated.
 
5. The auditory striae.
 
6 . The medial geniculate body.
 
7. The corticipetal tract from the medial geniculate body to the
 
superior temporal gyrus.
 
The cell-stations connected with this nervous chain are as follows:
 
1. The ventral cochlear nucleus. 5. The nucleus of the lateral lemnis
2. The lateral cochlear nucleus. cus.
 
3. The nucleus trapezoides. 6. The lower quadrigeminal body.
 
4. The superior olive of each side. 7. The medial geniculate body.
 
Some of the fibres of the chain terminate in these cell-stations,
and others are derived from the axons of the cells which compose
the stations.
 
Vestibular Nerve. —The terminal nuclei of the vestibular nerve,
which is the nerve of equilibrium, are three in number—namely,
(1) the dorsal or principal nucleus, (2) the descending nucleus, and
 
(3) the nucleus of Deiters, associated with which there is the
nucleus of Bechterew.
 
The medial or principal nucleus is situated in the floor of
the fourth ventricle underneath
the area acustica and stria (see
Fig. 995, 5). The inferior nucleus
is continuous with the lower end
of the dorsal nucleus, and it accompanies the descending fibres
of the vestibular nerve into the
medulla oblongata. The lateral
nucleus (nucleus of Deiters) is
situated lateral to the dorsal
and descending nuclei, and the
superior nucleus (nucleus of
Bechterew) represents the upper
and outer part of the nucleus of
Deiters.
 
As the vestibular nerve passes backwards medial to the inferior
peduncle, some of its fibres, to be presently described, turn downwards.
The majority, however, pass to the principal nucleus, the lateral
nucleus, and the superior nucleus, and terminate in arborizations
around the cells of these nuclei. A few of the vestibular fibres are
regarded as passing directly to the cerebellum (superior vermis).
 
 
 
Superior N.
Lateral N.
Medial N.
 
 
Fig. 997.—The Position of the Vestibular Nuclei in Relation to Floor
of Fourth Ventricle (Semi-schematic).
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1623
 
 
Central Connections of the Nuclei of the Vestibular Nerve. —The
 
fibres of the vestibular nerve terminate in the nuclei just stated. The
medial or principal nucleus and the other vestibular nuclei are intimately related to the superior vermis of the cerebellum, and especially
to the roof-nucleus, by means of cerebellar fibres. This communication represents the direct sensory cerebellar tract of Edinger, and it is
contained within the inferior peduncle of the cerebellum. The axons
of many of the cells of the lateral nucleus and superior nucleus pass
into the medial or posterior longitudinal bundle, within which they
divide into ascending and descending branches. In this manner the
medial longitudinal bundle is brought into communication with the
vestibular nerve. By means of the medial longitudinal bundle, which
represents the ground-bundles in the spinal cord, the nucleus of Deiters
is brought into communication with the anterior or motor horns of the
spinal cord. By means of this bundle the nucleus is also brought into
communication with the nuclei which control the ocular muscles—
namely, the oculo-motor, trochlear, and abducent nuclei.
 
The complex nervous chains associated with the vestibular nerve
may be tabulated as follows:
 
 
Cerebellar Chain.
 
 
1. The bipolar cells of the vestibular ganglion.
 
2. The fibres of the vestibular nerve.
 
3. The medial vestibular nucleus, lateral nucleus, and superior nucleus.
 
4. The secondary cerebellar vestibular tract or the direct sensory cerebellar
 
tract of Edinger, leading to the superior vermis and roof-nucleus of
the cerebellum.
 
 
Spinal and Oculo-motor Chains.
 
 
1. The bipolar cells of the vestibular ganglion.
 
2. The fibres of the vestibular nerve.
 
3. The lateral and superior vestibular nuclei. , . . .
 
4 The secondary vestibular tract from the nuclei to the posterior longitudinal
 
bundle, and thence to the motor horns of the spinal cord and the motor
nuclei of the ocular muscles.
 
The lateral nucleus thus has important connections as follows:
 
1. The membranous 3 - The motor horns of the
 
 
spinal cord.
 
 
vestibule.
 
2. The cerebellum.
 
 
4. The motor nuclei of the
ocular muscles.
 
 
nncnnnrfinff Fibres of the Vestibular Nerve. —As the vestibular nerve
 
 
 
usually regarded as terminating in arborizations around the cells of
 
 
1624
 
 
A MANUAL OF ANATOMY
 
 
that nucleus. Superiorly they are related to the lateral vestibular
nucleus, and some authorities have regarded them as fibres passing
between the nucleus and the cuneate nucleus.
 
The cochlear and vestibular nuclei originally form one acoustic or auditory
nucleus, which is developed from the rhombic lip.
 
Ninth or Glosso-pharyngeal Nerve. —This nerve consists chiefly of
afferent or sensory fibres, which grow into the medulla oblongata,
but it also contains a few efferent or motor fibres, which arise within
the medulla oblongata.
 
Afferent or Sensory Fibres. —These fibres arise from the central
poles of the bipolar cells of the ganglia which are situated on the
 
 
 
Fig. 998.— Deep Origins of Ninth and Tenth Cranial Nerves.
 
glosso-pharyngeal nerve as it passes through the jugular foramen.
These ganglia resemble the ganglion of the fifth nerve and the spinal
ganglia. Having entered the medulla oblongata, the afferent fibres
end in two terminal sensory nuclei—namely, the dorsal vago-pharyngeal
nucleus, and the nucleus of the fasciculus solitarius.
 
The dorsal vago-pharyngeal nucleus consists of two parts—upper
and lower. The upper part is situated in the grey matter of the floor
of the lower or bulbar part of the fourth ventricle, underneath the superficial area known as the trigonum vagi , and immediately external to the
hypoglossal nucleus. The lower part is situated in the lower or closed
part of the bulb, and lies in the grey matter which forms the lateral
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM 1625
 
wall of the central canal of the bulb, being here situated behind the
hypoglossal nucleus.
 
The highest part of the dorsal vago-glosso-pharyngeal nucleus
represents the portion associated with the glosso-pharyngeal nerve,
and the remaining and greater part belongs to the vagus nerve.
 
The nucleus of the fasciculus solitarius is a column of grey matter
and nerve-cells which accompanies the fasciculus solitarius, to be
presently described, throughout the whole length of the medulla
oblongata (Figs. 889 and 998).
 
A few of the afferent fibres of the glosso-pharyngeal nerve enter
the highest part of the dorsal vago-glosso-pharyngeal nucleus, and
terminate in arborizations around its cells. Most of the afferent fibres,
however, descend along with a few of the afferent fibres of the vagus
nerve, the two sets of descending fibres constituting a strand, called
the fasciculus solitarius (tractus solitarius). This strand descends
throughout the whole length of the medulla oblongata. It lies lateral
to the dorsal vago-glosso-pharyngeal nucleus, inclining towards the
ventral aspect of the upper part of that nucleus, and towards the
dorsal aspect of its lower part. It is accompanied throughout by the
nucleus of the fasciculus solitarius, and the glosso-pharyngeal afferent
fibres of the fasciculus solitarius terminate at different levels in arborizations around its cells. The fasciculus solitarius is formed chiefly, not
entirely, by glosso-pharyngeal fibres: fibres from facial enter its upper
end.
 
Efferent or Motor Fibres. —These fibres arise within the medulla
oblongata as the axons of some of the cells of the ventral vago-glossopharyngeal nucleus or nucleus ambiguus. This nucleus is situated
in the formatio reticularis grisea of the medulla oblongata, and is in
line with the facial motor nucleus, which is placed in the dorsal part
of the lower portion of the pons. The nucleus ambiguus is ventral
in position to the dorsal vago-glosso-pharyngeal nucleus, and the
axons of its cells, some of which form the glosso-pharyngeal efferent
or motor fibres, pass dorsal wards towards the last named. They
then alter their course, and, passing forwards and laterally, associate
themselves with the afferent or sensory glosso-pharyngeal fibres.
 
The funiculi of the glosso-pharyngeal nerve appear in the dorsolateral sulcus of the medulla oblongata, between the olivary and restiform bodies, and immediately below the facial nerve.
 
Distribution.— The glosso-pharyngeal nerve is distributed to (1) the
mucous membrane of the posterior third of the tongue, of which part
it is the nerve of taste, as well as of common sensation; (2) the mucous
membrane of the pharynx, tonsil, and fauces, (3) the mucous membrane of the tympanum; and (4) the stylo-pharyngeus muscle. It
also furnishes secretory and vaso-dilator fibres to the parotid gland
by means of (1) its tympanic branch (Jacobson’s nerve), (2) the tympanic plexus, (3) the small superficial petrosal nerve, (4) the otic ganglion, and (5) the auriculo-temporal nerve.
 
Tenth or Vagus Nerve. —This nerve consists of afferent or sensory
 
 
1626
 
 
A MANUAL OF ANATOMY
 
 
\
 
 
fibres, which grow into the medulla oblongata; and efferent or motor
fibres, which arise within the medulla oblongata.
 
Afferent or Sensory Fibres. —These fibres arise from the central
poles of the bipolar cells of the ganglion of the root and the ganglion
of the trunk of the nerve, which resemble the glosso-pharyngeal ganglia,
the ganglion of the fifth nerve, and the spinal ganglia. Having entered
the medulla oblongata, the afferent fibres pass to the same two terminal
sensory nuclei as do the afferent fibres of the glosso-pharyngeal nerve—
namely, the dorsal vago-glosso-pharyngeal nucleus and the nucleus
of the fasciculus solitarius —which have just been described in connection with the glosso-pharyngeal nerve. Most of the afferent fibres
of the vagus nerve pass to the vagal portion of the dorsal vago-glossopharyngeal nucleus, which represents its greater and lower part, the
highest part of the nucleus receiving, as stated, a few of the afferent
fibres of the glosso-pharyngeal nerve. Within the vagal part of the
nucleus the afferent fibres of the vagus terminate in arborizations
around its cells. A few of the afferent fibres, however, descend along
with most of the afferent fibres of the glosso-pharyngeal nerve, the
two sets of descending fibres constituting the strand called the fasciculus
solitarius, already described in connection with the glosso-pharyngeal
nerve. These descending afferent vagal fibres terminate, like the
corresponding glosso-pharyngeal fibres, in the nucleus of the fasciculus
solitarius, which has been described in connection with the glossopharyngeal nerve.
 
The dorsal vago-glosso-pharyngeal sensory nucleus, and the nucleus
of the fasciculus solitarius, also sensory, are therefore shared in
common by the afferent or sensory fibres of the glosso-pharyngeal
and vagus nerves, but in unequal proportions. Only a few glossopharyngeal afferent fibres go to the dorsal vago-glosso-pharyngeal
nucleus, whereas most of the vagal afferent fibres pass to that nucleus.
In the case of the nucleus of the fasciculus solitarius it is the reverse.
 
Efferent or Motor Fibres. —These fibres arise within the medulla
oblongata as the axons of most of the cells of the ventral vago-glossopharyngeal nucleus or nucleus ambiguus, which has been described in
connection with the glosso-pharyngeal nerve. The fibres pass dorsalwards to the more superficially placed dorsal vago-glosso-pharyngeal
nucleus. They then alter their course, and, passing forwards and outwards, associate themselves with the afferent or sensory vagal fibres.
 
The ventral vago-glosso-pharyngeal nucleus or nucleus ambiguus,
which is a motor nucleus, is shared in common by the efferent or motor
fibres of the glosso-pharyngeal and spinal accessory nerves, especially
the latter. The fibres from this nucleus join the vagus, and leave it as
the pharyngeal and laryngeal branches.
 
The funiculi of the vagus nerve appear in the dorso-lateral sulcus
of the medulla oblongata, between the olivary and restiform bodies,
and immediately below the funiculi of the glosso-pharyngeal nerve.
 
Distribution. —The vagus nerve has a very extensive distribution on
either side, of which the following is a summary:
 
 
THE NERVOUS SYSTEM
 
 
1627
 
 
Motor Distribution. —(1) The muscles of the soft palate (except
the tensor palati) ; (2) the constrictor muscles of the pharynx; (3) the
intrinsic muscles of the larynx; (4) the muscular tissue of the oesophagus
and stomach; and (5) the muscular tissue of (a) the trachea, (b) the
bronchi, and (c) the bronchial tubes.
 
Sensory Distribution. —(1) The pharynx, oesophagus, and stomach;
(2) the larynx, trachea, and bronchial tubes to their terminal ramifications; and (3) the skin on the cranial aspect of the pinna, as well
as of the lower and back part of the external auditory meatus.
 
Cardiac Fibres. —The cardiac fibres of the nerve are inhibitory
(efferent) and depressor (afferent).
 
The most important connection of the vagus nerve is that which is
established with the bulbar or accessory portion of the accessory nerve.
 
Glosso-pharyngeal and Vagal Nuclei. —These two nerves, as stated,
consist of afferent or sensory and efferent or motor fibres. The afferent
fibres of both nerves share in common two terminal nuclei —namely, the
dorsal vago-glosso-pharyngeal nucleus and the nucleus of the fasciculus
solitarius. Most of the glosso-pharyngeal afferent fibres terminate
in the nucleus of the fasciculus solitarius, and most of the vagal afferent
fibres terminate in the dorsal vago-glosso-pharyngeal nucleus. According to the description which has been given of the dorsal vagoglosso-pharyngeal nucleus, it is a nucleus of termination , or sensory
nucleus. According to certain authorities, however, it is a mixed
nucleus —that is to say, it is both a nucleus of termination, or sensory
nucleus, and a nucleus of origin, or motor nucleus. In accordance
with this view, the nucleus contains two sets of cells —sensory and
motor —some of the afferent glosso-pharyngeal and most of the afferent
vagal fibres terminating in arborizations around the sensory cells,
and some of the efferent fibres of each nerve arising as the axons of the
motor cells.
 
The nucleus of the fasciculus solitarius is a nucleus of termination,
 
or sensory nucleus.
 
The fibres of the sensory portion of the facial nerve terminate m
the upper part of the nucleus of the fasciculus solitarius.
 
The efferent or motor fibres of the glosso-pharyngeal and vagus
nerves arise as the axons of the motor cells of the ventral vago-glossopharyngeal nucleus, or nucleus ambiguus, which is a nucleus of origin,
or motor nucleus. According to the description which has been given
of this nucleus, it gives origin to all the motor fibres of the two nerves.
If, however, the dorsal vago-glosso-pharyngeal nucleus is a mixed
nucleus, then some of the efferent or motor fibres of the two neives
 
arise as the axons of its motor cells.
 
The axons of the cells of the terminal sensory nuclei are disposed
like those of the cells of the terminal sensory nuclei of the fifth nerve.
They cross to the opposite side, become longitudinal, and ascend m
company with the medial lemniscus or chief sensory tract to the
thalamus of the side to which they have crossed. They constitute the
vago-glosso-pharyngeal ascending thalamic tract.
 
 
1628
 
 
A MANUAL OF ANATOMY
 
 
Eleventh or Accessory (Spinal Accessory) Nerve. —This is a motor
nerve, which is partly a continuation of the vagus. Its spinal fibres
arise from the accessory nucleus, which is situated to a small extent
within the medulla oblongata or bulb, and mostly within the cervical
part of the spinal cord. This nucleus consists of a column of large
cells which is continuous with the dorsafivago-glosso-pharyngeal nucleus
at the medullary level. The column extends from the level of the
lower part of the olivary body to the level of the sixth cervical nerve.
The bulbar termination of the nucleus is situated on the dorso-lateral
aspect of the hypoglossal nucleus. The spinal portion is situated in
the lateral part of the anterior grey horn of the cervical spinal cord,
and its cells lie directly behind the motor cells which give origin to
the anterior roots of the upper five cervical nerves.
 
The fibres which emerge superficially from the bulb constitute the
bulbar part of the accessory nerve, and are accessory to the vagus
nerve. The fibres which arise from the spinal cord constitute the
spinal part of the accessory nerve, and are really distinct from the
bulbar fibres.
 
Bulbar Part.— The fibres of this part arise as the axons of the cells
of the nucleus ambiguus. They are directed at first dorsalwards, and
then outwards through the lateral part of the medulla oblongata or
bulb, from which they emerge, behind the olive, in the form of about
five funiculi, placed below, and in line with the funiculi of the vagus
nerve. They then pass outwards, lying within the cranial cavity,
and join the spinal part of the accessory nerve (which has entered the
cranial cavity through the foramen magnum). The accessory nerve
afterwards leaves the cranial cavity through the jugular foramen.
 
Spinal Part.— The fibres of this part arise as the axons of the cells
of the accessory nucleus in the cervical cord. They are directed at
first backwards, and then outwards through the lateral column of
the spinal cord, from which they emerge as a series of funiculi which
succeed to the funiculi of the bulbar part, the lowest spinal funiculus
being on a level with the fifth cervical nerve. The funiculi of the spinal
part ascend, lying in the subdural space between the ligamentum
denticulatum and the posterior roots of the upper five cervical nerves.
They enter the cranial cavity through the foramen magnum, and join
the bundles of the bulbar part, to form the accessory nerve.
 
Distribution of Accessory Nerve.— After leaving the jugular foramen,
the accessory nerve divides into two branches—internal and external—
the internal branch containing the fibres of the bulbar part, whilst the
external branch contains the fibres of the spinal part.
 
Spinal Distribution.— The external or spinal branch supplies the
sterno-cleido-mastoid and trapezius muscles.
 
Bulbar Distribution. —The internal or bulbar branch passes over,
and in close contact with, the ganglion of the trunk of the vagus nerve.
Its fibres are continued into (1) the pharyngeal and superior laryngeal
branches of the ganglion of the trunk of the vagus, and (2) the trunk
of the vagus beyond the ganglion.
 
 
THE NERVOUS SYSTEM
 
 
1629
 
 
The bulbar fibres, through their connection with the vagus nerve,
are probably distributed to (1) the muscles of the soft palate, excluding
the tensor palati; (2) the constrictor muscles of the pharynx; and
(3) the intrinsic muscles of the larynx. The bulbar fibres may also
furnish (a) the inhibitory fibres to the heart, (b) the motor fibres to the
oesophagus, and (c) the motor fibres to the stomach.
 
The bulbar fibres of the accessory nerve are regarded by some
authorities as arising from the column of cells which constitutes the
ventral vago-glosso-pharyngeal nucleus, or nucleus ambiguus.
 
Twelfth or Hypoglossal Nerve.—The fibres of the hypoglossal nerve
arise from the axons of the cells of the hypoglossal nucleus, which is
situated within the medulla oblongata This nucleus represents a
column of large multipolar motor-cells, which extends from the level
of the auditory striae superiorly to the level of the upper part of the
decussation of the pyramids inferiorly. The lower part of the nucleus
is situated within the lower or closed part of the medulla oblongata,
and its upper part lies within the upper, open, or ventricular part.
The lower part lies in the grey matter which forms the ventro-lateral
aspect of the central canal of the medulla oblongata. The upper part
lies in the grey matter which covers the bulbar part of the floor of the
fourth ventricle, and is underneath the area known as the trigonum
hypoglossi.
 
The nerve-fibres issue from the ventral aspect of the nucleus, and
the nerve-funiculi pass through the medulla oblongata in a dorsoventral direction, lying between its anterior and lateral areas, and
between the formatio reticularis alba and formatio reticularis grisea.
Having reached the bottom of the ventro-lateral sulcus between the
pyramid and the olive, they emerge from the medulla oblongata in
line with the sixth cranial nerve superiorly.
 
The two hypoglossal nuclei, right and left, are connected with
each other by commissural dendrons; and each nucleus receives
collaterals from the pyramidal tract of the opposite side, being thereby
brought into connection with the precentral motor area of the opposite
cerebral hemisphere.
 
Distribution.—The hypoglossal nerve is the motor nerve of the
 
tongue, and supplies (1) the stylo-glossus, (2) the hyo-glossus, (3) the
genio-hyo-glossus, and (4) the intrinsic muscles of the tongue.
 
Cranio-cerebral Topography (see Figs. 999 and 1000).
 
The auricular point is the centre of the orifice of the meatus auditorius externus.
 
The pre-auricular point is situated in the depression between the
tragus of the auricle and the condyle of the mandible.
 
The bregma, or point of junction of the sagittal and coronal sutures,
corresponds to the centre of a line connecting the two auricular points
(the centre of the orifice of the meatus auditorius externus).
 
The lambda, or meeting of the sagittal and lamboidal sutures, is
 
 
T63o
 
 
A MANUAL OF ANATOMY
 
 
situated about 2§ inches or four fingers' breadth above the inion, or
external occipital protuberance.
 
The pterion, or region of the spheno-parietal suture, is situated
about i| inches behind the external angular process of the frontal
bone, and about if inches above the zygomatic arch. Two fingers’
breadth above the middle of the zygoma forms quite a useful indication to it.
 
the asterion, or point where the parieto-mastoid, occipito-mastoid,
and lambdoid sutures meet, is situated about 2 inches behind the
 
 
 
Fig. 999.— Diagram showing the Relations of the Chief Cerebral
Fissures to the Exterior of the Head (Reid).
 
 
A. Glabella B. Inion C. Auricular Point
 
E. Pre-auricular Point
 
F. Superior Rolandic Point
 
G. Posterior Border of Root of Mastoid Process
 
H. Inferior Rolandic Point
B.C. Transverse Fissure
 
 
D.E., F.G. Reid’s Perpendicular Lines
Sy.Fis. Lateral Fissure
Sy.a.Fis. Anterior Limb of Fissure
Sy.h.Fis. Posterior Horizontal Limb of Fissure
p.o.Fis. External Parieto-occipital Fissure
+ Parietal Eminence
 
 
auricular point very nearly in line with the upper border of the zvgomatic arch. J
 
The sagittal line represents the line which connects the nasion,
or meeting of the two fronto-nasal sutures, with the inion.
 
The sagittal suture corresponds to that part of the sagittal line
which extends from the lambda to the bregma.
 
The coronal suture is indicated on either side by a line extending
from the bregma to the pterion.
 
The lambdoid suture (occipito-parietal) corresponds to a line extending from the lambda to the asterion.
 
The squamo-parietal suture, and its continuation backwards as the
parieto-mastoid suture, are indicated by a curved line, with the con
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM 163!
 
vexity upwards, extending from the pterion to the asterion, the highest
part of the curve being about 2 inches above the zygomatic arch.
 
The superior sagittal sinus corresponds to a line drawn from the
glabella to the inion, or external occipital protuberance. For the
most part it occupies the median line, but as it grooves the upper
portion of the tabular part of the occipital bone it deviates to one side,
most commonly the right side.
 
The confluens sinuum (or torcular Herophili) is usually situated on
the right side of the inion.
 
The occipital sinus corresponds to a line drawn downwards from
the inion.
 
 
 
Fig. 1000.—The Relations of the Brain to the Surface (modified
 
from Hermann).
 
 
The transverse sinus on either side is indicated by a line drawn
outwards from a point immediately above, and external to, the inion
to a point immediately above the asterion. This line is slightly curved,
the convexity being upwards. The sinus grooves the inner surface of
one-half of the tabular portion of the occipital bone, along the line of
attachment of the tentorium cerebelli ; and in the region of the asterion,
where the sinus, in altering its course, describes a curve, it grooves the
inner aspect of the parietal bone, close to the postero-inferior angle, for
a very short distance.
 
Inasmuch as the superior sagittal sinus usually opens into the
right transverse sinus, the right sinus is usually larger than that of the
 
left side. . . ,
 
The sigmoid part of the transverse sinus grooves the inner surface
 
of the mastoid portion of the temporal bone, and the superior surface
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1632
 
of the jugular process of the occipital bone. The following line indicates approximately the course of the sinus: (1) Draw a line horizontally forwards from the asterion for fully f inch to a point on the
root of the mastoid process in line with the upper part of the meatus
auditorius externus; (2) the line now curves and passes downwards and
forwards on the front part of the mastoid process towards its tip for
f inch, lying close to the groove between the back of the pinna and the
mastoid process (the level to which this line descends is J inch below
the lower margin of the orifice of the meatus auditorius externus);
and (3) the line finally passes forwards for inch to meet the jugular
foramen, through which the sigmoid part of the transverse sinus leaves
the cranial cavity to become the internal jugular vein.
 
The sigmoid sinus lies directly behind the mastoid or tympanic
antrum, being separated from it only by a very thin plate of bone. In
pyogenic affections of the tympanum and antrum the sinus is consequently liable to become affected with thrombosis.
 
The convexity of the genu of the sigmoid sinus is on a level with
the temporo-mandibular joint, and lies from J to J inch behind the
base of the suprameatal triangle or £ inch behind the pre-auricular
point.
 
The right sigmoid sinus is usually larger than the left. In many
cases the genu is scarcely perceptible, and the horizontal and vertical
limbs under these circumstances are practically almost in direct continuity with each other. The genu lies at a depth from the surface
varying from J to J inch.
 
The middle meningeal artery corresponds to the centre of the zygomatic arch. At a point from \ to £ inch above the centre of the arch
it divides into its two terminal branches—anterior and posterior.
 
The large anterior division of the middle meningeal artery, as it
lies in the groove, or, it may be, short canal, on the internal aspect
of the antero-inferior angle of the parietal bone, is indicated by taking
a point i-J inches behind the external angular process of the frontal
bone, and ij inches above the zygomatic arch. From this point it
ascends almost vertically towards the sagittal suture, lying about
| inch behind the coronal suture.
 
The Sylvian point coincides with the pterion, and is situated about
ij inches behind the external angular process of the frontal bone, and
about 2 inches above the zygomatic arch. It indicates the division of
the stem of the lateral fissure into its three limbs—anterior, ascending,
and posterior. The anterior limb of the fissure passes horizontally
forwards for about 1 inch, and the ascending limb upwards and slightly
forwards for a variable distance, from the pterion.
 
The posterior limb of the fissure is long, and is directed for the most
part horizontally backwards for fully 2 inches, after which it turns
upwards into the parietal lobe for a short distance. The line which indicates the course of the posterior limb is called the Sylvian or lateral
line. It extends from the pterion backwards and slightly upwards
towards the lambda for about 2 inches until it lies below the parietal
 
 
THE NERVOUS SYSTEM
 
 
1633
 
eminence, when it turns directly upwards for J inch. The parietal lobe
and a small portion of the frontal lobe lie above the Sylvian line, and
the temporal lobe lies below it.
 
The superior Rolandic point is situated ^ inch behind the centre
of the sagittal line, which connects the nasion and the inion. This
point approximately represents the upper extremity of the central
fissure.
 
The inferior Rolandic point is situated on the Sylvian line about
1 inch behind the Sylvian point, and 2 inches above the pre-auricular
point. It indicates the point where the central fissure, if sufficiently
prolonged, would meet the posterior limb of the stem of the lateral
fissure.
 
The line of the central fissure is represented by a line connecting the
superior and inferior Rolandic points.
 
The Rolandic angle is the angle which this line forms with the
sagittal line. It ranges from 65 to 70 degrees. The line, if sufficiently prolonged, would cross the zygomatic arch at its centre. It
indicates in a general way the course of the central fissure, but this
fissure usually ceases at a point J inch above the Sylvian line. The
cerebral convolutions directly in front of, and behind, the central line
are (1) the precentral, or ascending frontal, convolution (motor area)
in front; and (2) the postcentral, or ascending parietal, convolution
(sensory area) behind. The line represents the boundary-line between
the frontal and parietal lobes of the cerebral hemisphere.
 
The base-line of Reid is represented by a line drawn backwards from
the centre of the infra-orbital margin through the pre-auricular and
auricular points to the inion. The central fissure may be determined
from Reid’s base-line in the following manner: Two lines are drawn
upwards to the sagittal line perpendicular to the base-line, one from
the pre-auricular point and the other from the posterior border of the
mastoid process close to its root. These two lines, together with the
sagittal and Sylvian lines, enclose a quadrilateral area, and the diagonal
connecting the postero-superior and antero-inferior angles represents
the fissure except at its superior and inferior limits.
 
The parietal eminence may usually be felt, if it cannot be seen, as
the point of maximal convexity in the parietal region. If it cannot
be felt, its position may be estimated by localizing the four angles of
the parietal bone, bregma, lambda, pterion, and asterion, and taking
the point where the diagonals joining them meet. It indicates the
position of the supramarginal gyrus of the parietal lobe of the cerebral
hemisphere.
 
The frontal eminence corresponds to the middle frontal convolution.
 
The foramen magnum, through which the medulla oblongata is
continuous with the spinal cord, lies midway between the mastoid
processes. Its posterior margin is 2 inches from the inion in a downward and forward direction.
 
The tentorium cerebelli and superior surface of the cerebellum
 
103
 
 
1634
 
 
A MANUAL OF ANATOMY
 
 
practically coincide with the level of the transverse sinus, as indicated by a line slightly curved upwards connecting the inion and
asterion.
 
The lower level of the cerebral hemisphere may be indicated by the
following line: Commencing at a point \ inch external to the nasion,
the line passes laterally in an arched manner, with the convexity
upwards, lying about J inch above the centre of the supra-orbital arch.
It then inclines downwards and crosses the temporal ridge of the
frontal bone about \ inch above the fronto-malar suture, which is
easily felt. After this the line passes backwards and slightly downwards to the pterion, and thence to the upper border of the posterior part of the zygomatic arch. From this point the line passes
backwards, lying about \ inch above the upper margin of the orifice
of the meatus auditorius externus. It then crosses the supramastoid
crest (posterior root of the zygoma), and passes to the asterion. From
this it nearly follows the line of the transverse sinus from the asterion
to a point a little above and external to the inion. In other words,
speaking generally, the cerebral hemisphere extends as low as the
superior nuchal line of the occipital bone posteriorly , the upper border
of the zygomatic arch laterally , and the upper part of the eyebrow
anteriorly. The frontal lobe of the cerebral hemisphere is to a large
extent in contact with the frontal portion of the frontal bone, but it is
also related to the anterior part of the parietal bone as far back as
the central fissural line.
 
The parietal lobe is related to the part of the parietal bone which
lies behind the central line. The lobe extends as far back as the
parieto-occipital fissure, which is usually situated opposite the lambda.
 
The occipital lobe occupies the cerebral fossa of the tabular part
of the occipital bone, its limits being the level of the lambda superiorly
and the level of the inion inferiorly.
 
The temporal lobe is under cover of the squamous portion of the
temporal bone and the postero-inferior part of the parietal bone.
The parallel sulcus, which separates the first and second temporal
convolutions, is indicated by a line drawn from the lambda to the
marginal tubercle on the posterior border of the malar bone about
J inch below the fronto-malar suture.
 
Below it is the middle temporal gyrus, the centre of which corresponds to the inferior horn of the lateral ventricle. A perforation
\ inch below the line just mentioned and ij inches behind the middle
of the external auditory meatus would strike it with certainty if it were
distended.
 
Autonomic System.
 
The autonomic nervous system, mentioned at the beginning of this
chapter, was then stated to be composed of two differentiated groups
of fibres which were termed sympathetic and parasympathetic, the
former known by that name to generations of anatomists, but the latter
including within its limits a more modern conception of certain fibres
 
 
/
 
 
THE NERVOUS SYSTEM
 
 
1635
 
and functions which were not grouped in any way with the sympathetic
by the older observers.
 
The sympathetic system comprises all that chain of nerve cords and
ganglia which lies on each side and front of the vertebral column, with
its connections and distributions. The detailed descriptions of the
system in the different regions of the body have been given in previous
chapters of this book, where they can be perused. It is not necessary,
therefore, to enter on these details again, but something can be said
about the system in its general aspect.
 
The ganglia which, with the connecting cords, make up the ‘ sympathetic chain ’ are probably modified in number from an original set
which corresponded with the number of spinal nerves. This original
number of ganglia has been lessened, however, by fusion of neighbouring masses, and sometimes by actual loss; for example, in the cervical
region, the four uppermost ganglia have been fused into the single
superior cervical ganglion, and the lower two have joined in the inferior
ganglion—which itself shows signs of joining with the first thoracic—
while the ‘ middle cervical ganglion ’ is frequently, if not usually,
absent or very small. In the thoracic region the number is decreased
frequently by fusion, and in the lumbar and sacral portions of the
chain is very variable.
 
Both afferent and efferent (secretory and motor) impulses pass
through the sympathetic system. The afferent fibres run through it
without interruption, arising from the cells in the posterior root ganglia.
Efferent fibres arise from the lateral grey matter of the spinal cord,
and leave the cord through the anterior nerve roots of the thoracic
and upper two or three lumbar nerves. They pass from these to the
sympathetic chain by fine branches (white rami communicantes), and
run in this chain to the particular ganglia with which they are concerned.
 
Rami communicantes are of two sorts, white (medullated) and grey
(non-medullated). White rami bring the medullated fibres to the
sympathetic chain from the nerves within which they emerged from
the spinal cord, and are therefore confined to the thoracic and upper
lumbar regions. Grey rami are fibres of sympathetic origin, arising
from cells in the ganglia in which the white fibres have been interrupted,
and passing for convenience of distribution to any and all of the spinal
nerves; in this way they reach their objectives, and are found connecting the sympathetic chain with all the spinal nerves—not limited
to particular regions like the white rami.
 
The rami are thus of two sorts, and both sorts are present in
the thoracic and upper lumbar region, but it must not be
imagined that a ramus of either sort to a nerve is always a single
branch; it may be doubled or even trebled, and may reach a
ganglion or the interganglionic trunk, but there are only two
kinds of fibres represented at the most, and the white fibres,
wherever they join the sympatheitc trunk, run in it until they
reach the appropriate ganglia—which may be near, or far away.
 
 
1636
 
 
A MANUAL OF ANATOMY
 
 
Afferent fibres from visceral structures pass from these through the
sympathetic system, and through white rami to the spinal nerve and
spinal ganglion concerned; some are said to go through grey rami.
Those from the body-wall and limbs, and from the head and neck,
run their courses within the spinal nerves themselves.
 
Efferent fibres are always interrupted once in their course, so that
there are two relays of the efferent impulse. The first is represented
 
anatomically by the course of the issuing
white fibre from the cord to its appropriate
ganglion, the second by the course of the
non-myelinated fibre arising in this ganglion
and passing to its objective.
 
The ganglionic cell which interrupts the
efferent impulse, and relays it secondarily,
may be one of those in the sympathetic
chain ganglia, or may lie at some distance
from the chain, in one of the great plexuses
(cardiac, cceliac, hypogastric), or even in
some more remote and minute collection of
nerve-cells in the wall of a viscus or on a
bloodvessel. Wherever this ganglionic cell
may be, the first relay of the impulse is
carried by a fibre which is not interrupted
before reaching it; this fibre is termed preganglionic. The second relay is carried by
a postganglionic fibre, which is the axon of
this ganglion cell, and is non-medullated.
 
From what has been said it can be
understood that the efferent fibres, in white
rami communicantes, may run even to the
extreme end of the sympathetic chain, or
to a distant plexus, before losing their preganglionic status, so that they will pass
through any intervening ganglia without
interruption. Afferent fibres always pass
through such ganglia without interruption,
to reach the posterior root ganglia. Thus
the level of exit of an efferent preganglionic
fibre has little to do with the level or
position of its terminal ganglion, and the
postganglionic fibres in a grey ramus may
have come from a sympathetic ganglion some distance away.
 
 
 
Fig. iooi.—Approximate
Levels in Cord of
Centres of Origin of
Sweat - fibres (Pre ganglionic) supplying
(A) Head, Neck, and
Upper Part of Thorax;
B, Upper Limb ; C,
Lower Limb ; D, External Genitals and Anal
Region.
 
 
Course of Sympathetic Efferent Impulses.
 
Central Origin.—The cells of the intermedio-lateral region of the
cord, approximately corresponding with the nerve-levels which give
passage to the fibres issuing from the cord, and considered generally to
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE NERVOUS SYSTEM
 
 
1637
 
be those from which these fibres take origin. There are probably
higher centres in the nervous axis which exercise some controlling
influence over these thoraco-lumbar cells; such centres are presumed
to lie in the hypothalamus, their scattered fibres passing down in
the tegmentum and formatio reticularis of the pons and medulla.
Other control centres in the floor of the fourth ventricle are more
doubtful.
 
Dilatation of Pupil. — Preganglionic fibres emerge through upper
(? three) thoracic nerves and run up the gangliated cord. Cell-station ,
superior cervical ganglion. Postganglionic fibres pass through ciliary
ganglion without interruption and enter short ciliary nerves. Their
course to the ganglion is curious. They pass up in the plexus on the
internal carotid, leave this by the carotico-tympanic filaments, and
 
 
 
Fig. 1002.—To show Course of Sympathetic (Red) and Parasympathetic
(Blue) Fibres concerned in Certain Infra-orbital Actions (Preganglionic Fibres, Dotted; Postganglionic, Solid Lines).
 
A, the routes followed in the case of the pupil; B, those in the case of lacrimal
secretion; G, superior cervical ganglion; T, C, tympanic and cavernous
plexuses; N, naso-ciliary nerve; S, spheno-palatine ganglion; Z, zygomaticomalar nerve; L, lacrimal nerve; F, facial ganglion.
 
enter the middle ear. From this they pass up through the foramen
lacerum and join the cavernous plexus, from which they find their
way into the orbit with some of the branches of the fifth nerve, or
on the ophthalmic artery (Fig. 1002).
 
Lacrimal Gland— Preganglionic to superior cervical ganglion.
Postganglionic along internal carotid, and probably through ophthalmic
nerve and its lacrimal branch.
 
Salivary Glands (Fig. 1003).— Submandibular.— Preganglionic from
upper thoracic nerves. Cell-station , superior cervical ganglion. Postganglionic along external carotid and facial, fibres passing unchanged
through submandibular ganglion.
 
Parotid. —Preganglionic and cell-station as last.
 
Postganglionic along external carotid and maxillary arteries, through
otic ganglion unchanged, into auriculo-temporal nerve.
 
 
 
 
 
 
 
 
 
1638
 
 
A MANUAL OF ANATOMY
 
 
Sweating.—The preganglionic fibres leave the spinal cord at varying
levels according (Fig. 1001) to their final destinations. The cellstations are in the sympathetic ganglia appropriate to the levels to be
supplied. The postganglionic fibres, arising in these ganglia, are distributed through the cutaneous nerves; they reach these usually
through grey rami communicantes and the nerves concerned, but in
the case of the head and face they reach the cutaneous nerves by
passing first through the arterial plexuses.
 
The mammary gland, being a modified sweat-gland, is supplied
in a similar way, the postganglionic fibres reaching the gland
along the fourth, fifth, and sixth intercostal nerves.
 
The cardiac sympathetic preganglionic fibres leave the cord by the
upper four or five thoracic nerves, and end in the corresponding
thoracic ganglia; these are therefore the cell-stations. Postganglionic
 
 
 
Fig. 1003.—To show the Paths of Sympathetic and Parasympathetic
Fibres to Salivary Glands (Colour Plans as Last Figure).
 
FA, M, facial and maxillary arteries; CH, chorda tympani; AT, auriculo-temporal; O, otic ganglion; G, superior cervical ganglion; T, tympanic plexus.
 
fibres arise from the cells in these ganglia, pass upwards through the
cervical chain to come off as cervical cardiac branches, or run more
directly from the thoracic ganglia to the deep cardiac plexus. All
these fibres pass through the plexus without interruption to reach the
heart.
 
It may be added, although it does not come under this heading,
that afferent fibres from the heart probably run in all these
cardiac sympathetic nerves except the superior cervical branch.
 
It follows from this description of the course of the sympathetic
cardiac fibres that the cell-collections which form the scattered cardiac
ganglia are cell-stations for the parasympathetic only (see later).
 
The splanchnic nerves, which arise from the lower six ganglia of
the thoracic gangliated cord, carry mainly medullated preganglionic
fibres which have left the spinal cord through the lower seven or
eight thoracic nerves. Their cell-stations are in the coeliac ganglion.
 
 
 
 
THE NERVOUS SYSTEM 1639
 
The postganglionic fibres arise here, and are distributed in the branches
of the coeliac plexus.
 
Many afferent fibres run up through the plexus into the
splanchnic nerves.
 
The bladder is supplied by sympathetic fibres which arise in the
upper lumbar segments. Some of the preganglionic fibres appear to
end in lumbar ganglia, but most of them go into the aortic plexus or
lie lateral to this, cross the bifurcation of the aorta and the common
iliac vessels, pass through their own side of the hypogastric plexus
(presacral nerve), where some of them terminate, while others pass on
into the vesical part of the pelvic plexus. The cell-stations are therefore in the lumbar ganglia, in the hypogastric plexus, and in the vesical
plexus, and from these cells the postganglionic fibres run, in the course
indicated, to the bladder wall.
 
The Parasympathetic System.
 
This system, connected in distribution and in some structural points
with the sympathetic, is distinguished from it by separate origin from
the central axis, and by different and largely opposed function. The
fibres come from the central axis at its extremities, while the sympathetic has a limited output in its middle part; in both cases the fibres
emerge among the ordinary fibres of an efferent nerve, but whereas
they leave this almost at once (white rami) in the case of the sympathetic, they run to their distribution (for a considerable distance
usually) in the parasympathetic in the nerve within which they emerge.
 
The cranial parasympathetic is comprised in an outflow of special
fibres running in the third , seventh , ninth , and tenth nerves.
 
The third or oculo-motor nerve has fibres which run to the ciliary
muscle and pupillary sphincter, being concerned in contraction of the
pupil and accommodation. The preganglionic fibres, arising in the
mid-brain, probably from the Edinger-Westphal nucleus, pass out
in the third nerve into its inferior division, to reach their terminations
in the ciliary ganglion' this is therefore the cell-station. Postganglionic
fibres arise in the ganglion and pass forward in the short ciliary nerves.
 
The seventh or facial nerve contains parasympathetic fibres which
reach the lacrimal, submandibular, and sublingual glands (Figs. 1002
 
and 1003). *
 
Those to the lacrimal gland arise from nuclear material (? upper
 
salivatory nucleus) in the reticular formation of the pons, run in the
issuing nerve, and leave it by the greater superficial petrosal branch,
they pass in this to the pterygoid canal, and so to the spheno-palatine
ganglion * this is therefore the cell-station. Postganglionic fibres, arising
here, pass into the maxillary nerve, enter its zygomatico-temporal
offset, and run through the junction between this nerve and the lacrimal
 
into this last-named nerve.
 
Those to the submandibular and sublingual glands come as pre
0
 
 
1640
 
 
A MANUAL OF ANATOMY
 
 
ganglionic fibres from the upper salivatory nucleus, pass into the facial
nerve, and leave it in the chorda tympani. The cell-station comprises
the submandibular ganglion (for sublingual) and ganglion cells embedded
in the submandibular gland (for this gland). The postganglionic fibres
are short, arising from these ganglia.
 
The ninth or glossopharyngeal carries preganglionic fibres (which
have arisen from the lower salivatory nucleus) to end in the otic
ganglion; they reach this ganglion by passing through the tympanic
branch and tympanic plexus, then through the lesser superficial
petrosal nerve. The cell-station is in the otic ganglion. Postganglionic
fibres run in the auriculo-temporal nerve.
 
The tenth or vagus nerve has a large number of visceral branches
which belong to the parasympathetic system. The preganglionic fibres
arise mainly (apparently) from the dorsal nucleus of the vagus, run
in the nerve, and leave it by various visceral branches. They end
in [a) microscopic ganglia in the viscera, or (b) more apparent but
scattered ganglia, as in the cardiac plexus.
 
The sacral parasympathetic outflow takes place in the second and
third sacral nerves; the fourth nerve apparently contributes sometimes to the outflow. Visceral preganglionic fibres issue with these
nerves as the pelvic splanchnic nerves, and pass through the pelvic
plexuses. The cell-stations are generally in the visceral walls of the
pelvic viscera, but may lie in minute ganglia in the plexuses. Postganglionic fibres are short, arising from these cells.
 
 
Development of the Sympathetic Nervous System.
 
The sympathetic ganglia may be regarded as being developed from the
ventral aspects of the neural crests and spinal ganglia, and they are therefore
of ectodermic origin, according to this view. Certain cells become detached
from the neural crests and spinal ganglia, and migrate ventralwards towards the
 
 
 
Neural Crest
 
Neural Tube
- Spinal Ganglion
 
 
Migratory Cells
from Ganglion
 
Motor Root of
Spinal Nerve
 
o
 
... Sympathetic
Ganglion
 
 
Aorta
 
Fig. 1004.—Development of Sympathetic Ganglia (Schematic).
 
region of the aorta, where they form the ganglionic sympathetic chain. The
ganglionic cells proliferate, and are furnished with processes which become
fibrillar. These fibrillar processes give rise to the chain which connects the
ganglia, and also to the grey rami communicantes and the various visceral
branches.
 
 
 
 
 
 
 
 
CHAPTER XVI
 
 
THE EYE
 
 
The eyeball is almost spherical. It consists of the segments of two
spheres—namely, a large posterior or sclerotic segment, which is
opaque, and a small anterior or corneal segment, which is transparent.
The sclerotic segment forms five-sixths of the eyeball, and the corneal
segment one-sixth. The centre of the corneal segment is called the
anterior pole, and the centre of the sclerotic segment is known as
the posterior pole. The sagittal (antero-posterior) axis, or axis of
vision, of the eyeball is represented by a line connecting the anterior
and posterior poles. The equator is represented by a line encircling
the centre of the eyeball in a coronal plane, the diameter of the circle
being about I inch. The plane of this circle would therefore divide
the eyeball into two halves—an anterior half, consisting of the corneal
and the front part of the sclerotic segment, and a posterior half, consisting of the back part of the sclerotic segment. The meridian is
represented by a line encircling the eyeball horizontally at right
angles to the equator, and passing through the anterior and posterior
poles.
 
Posteriorly the eyeball receives the optic nerve, which pierces
the sclerotic coat at a point about J inch to the inner side of and
about -f T inch below the posterior pole.
 
The eyeball is composed of three coats concentrically arranged:
(i) an external coat, consisting of an opaque part, called the sclera,
and a transparent part, called the cornea; (2) a middle coat, which is
vascular, pigmented, and muscular, and consists of (a) a posterior
part, called the choroid coat, (b) an anterior part, the iris, and (c) an
intermediate part, representing the ciliary body; and (3) an internal
 
coat , called the retina. .
 
These three coats enclose the following refracting media : (1) a fluid,
called the aqueous humour, which lies between the cornea and the
crystalline lens, where it occupies the anterior and posterior chambers,
into which this region is divided by the iris; (2) a solid body, called
the crystalline lens, which lies behind the aqueous humour, and (3) a
soft gelatinous body, called the vitreous body, which occupies the laige
space behind the crystalline lens.
 
 
Coats of the Eyeball.
 
External=sclera and cornea.
 
Middle =choroid, ciliary body, and iris.
Internal = retina.
 
 
Refracting Media.
 
Aqueous humour.
Crystalline lens.
Vitreous body.
 
 
T64T
 
 
1642
 
 
A MANUAL OF ANATOMY
 
 
External Coat.
 
Sclera (or Sclerotic Coat).—The sclera (white of the eye) is a strong
white fibrous coat of great density, which surrounds the posterior
five-sixths of the eyeball, and maintains the shape of the organ. Anteriorly it unites, and becomes continuous with the cornea, which it
slightly overlaps. The junction of the two is indicated by a slight
groove, called the sulcus sclerce, and the union is known as the corneoscleral junction . Posteriorly, as has been shown above, the sclera is
pierced by the optic nerve a little below and to' the inner side of the
centre. The part of the sclera corresponding to the optic entrance
 
Levatoi Palpebras Superioris
 
 
Fornix Conjunctive
 
Fig. 1005.—Vertical Sagittal Section of the Eye and its
Appendages (Hirschfeld and Leveille).
 
is pierced by a number of openings for the passage of the fasciculi
of the optic nerve, and hence is called the lamina cribrosa.
 
Around the optic entrance there are numerous minute openings
for the ciliary vessels and nerves, and here the dura matral sheath of
the optic nerve blends with the sclerotic coat. About midway between
the optic entrance and the corneo-scleral junction the sclera is pierced
by four openings for the passage of the vence vorticosce of the choroid.
 
The sclera is thickest posteriorly around the optic entrance. It
is also thick near the sclero-corneal junction, where it receives the
insertions of the recti muscles.
 
The outer surface of the sclera is covered by a membranous investment, called the fascial sheath of the eyeball (fascia bulbi or capsule
of Tenon), and between the two there is the episcleral lymph-space (or
 
 
Hyaloid Canal
(Canal of Cloquet)
 
 
Hyaloid Membrane
 
 
Retina
 
>
 
 
Sinus Venosus Sclera?
 
 
Anterior
Chamber \
 
 
. Choroid
 
 
Rectus Superior
i „--Sclera
 
 
Arteria
z Centralis
 
 
 
/ Retinas
 
 
Cornea
 
Ciliary / y.
Processes'’ ft
 
Zonuiar Space
 
 
Rectus Inferior
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1643
 
 
Tenon’s space), which is broken up into a reticulum by processes of
connective tissue which pass between the sheath and the sclera.
This space communicates with the subdural and subarachnoid spaces.
The inner surface of the sclerotic coat is dark brown, and has grooves
for the ciliary vessels and nerves. It is lined with connective tissue
containing pigment-cells, forming the lamina fusca. Processes from
this layer pass to the choroid coat, and these, together with vessels
and nerves, traverse an interval, which represents the perichoroidal
lymph-space. This space communicates with the episcleral lymphspace through the vascular openings in the sclera. Anteriorly the sclera
blends with the cornea at the sclero-corneal junction, the sclera slightly
overlapping the cornea. Posteriorly around the optic entrance the
sclera blends with the dura matral sheath of the optic nerve.
 
Structure.—The sclera is composed of fibrous tissue mixed with
elastic fibres, and contains many connective-tissue corpuscles. The
fibres are arranged in bundles, which are disposed longitudinally and
transversely, and interlace with one another. The connective-tissue
corpuscles occupy spaces between the fibres, which may be regarded
as lymph-spaces.
 
Arteries.—These are the short ciliary group of posterior ciliary
arteries, and the anterior ciliary arteries, which are branches of the
ophthalmic. The vessels belonging to the former group are disposed
in the form of capillary networks; whilst the vessels derived from the
latter form a ring near the sclero-corneal junction beneath the conjunctiva, to which ring they converge in the substance of the
sclerotic coat.
 
The sclerotic veins open into the anterior ciliary veins, and into
the vencB vorticosce of the choroid. There is also a slight drainage
into the sinus venosus sclerce , a minute channel running deeply at the
sclero-corneal junction.
 
Nerve-supply.—The ciliary nerves.
 
Cornea.—The cornea is the transparent part of the external coat
of the eyeball, of which it forms the anterior sixth, and serves to
transmit light. It is almost circular, its transverse measurement being
slightly greater than the vertical. At its circumference it is continuous with the sclera, by which it is slightly overlapped. The anterior
surface is convex. The posterior surface is concave, and forms the
anterior boundary of the anterior chamber of the eye.
 
Structure.— The cornea consists of the following five layers, from
 
before backwards: .
 
1. The conjunctival epithelium.
 
2. The anterior elastic lamina.
 
3. The substantia propria.
 
4. The posterior elastic lamina.
 
5. A layer of endothelium.
 
The conjunctival epithelium is stratified, there being not less than
five strata of cells, and is continuous with the epithelium, which covers
 
 
1644
 
 
A MANUAL OF ANATOMY
 
 
^ \ Stratified Epithelium of
/ Conjunctiva
Membrane of Bowman
or Anterior Elastic
Lamina
 
 
the free surface of the conjunctiva. The cells of the deepest stratum
are columnar; succeeding these there are layers of polygonal cells;
and these in turn are overlaid by layers of squamous cells.
 
The anterior elastic lamina (Bowman) is probably of the same
nature as the fibrous portion of the substantia propria. It is closely
connected with the substantia propria, is thin, and contains no
corpuscles.
 
The substantia propria is composed of modified connective tissue
arranged in bundles which form superimposed laminae. These laminae
amount in number to about sixty. The fibres of alternate laminae
cross each other at right angles, and at the circumference of the cornea
 
they are continuous with
 
 
the fibres of the sclerotic.
The successive laminae are
connected by cement substance, and within this
substance are branched
spaces, called the corneal
spaces or lacunae, which
communicate with each
other by very delicate
canaliculi. Each of these
spaces contains a nucleated connective-tissue corpuscle, called the corneal
corpuscle. These corpuscles, like the spaces which
they occupy, are branched,
and the offsets of adjacent
corpuscles communicate
with one another. As seen
in vertical sections of the
cornea, the corpuscles are
spindle - shaped, but in
 
 
 
Substantia Propria
 
 
Posterior Elastic
Lamina or
 
Membrane of Descemet
'Single Layer of Squamous
Epithelium lining
Descemet’s Membrane
 
 
Fig. 1006.—Vertical Section of the Cornea
 
(magnified) .
 
 
horizontal sections they appear flattened out, and give off their
branches.
 
The posterior elastic lamina (or membrane of Descemet) covers
the posterior surface of the substantia propria. It is thicker than the
anterior elastic lamina, and .is composed of an elastic homogeneous
membrane, which is very brittle. When stripped from the substantia
propria it comes away in shreds, and these curl up at their ends in
such a manner that the anterior or attached surface of each shred is
turned inwards. At the circumference of the cornea the posterior
elastic lamina becomes broken up into fibres. The most posterior of
these fibres pass in a radiating manner into the iris, and they form the
ligamentum pectinatum iridis, the intervals between the fibres of
which represent the spaces of the irido-corneal angle.
 
The layer of endothelium lines the posterior surface of the posterior
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE 1645
 
elastic lamina, and consists of one stratum of cells. It is continued
over the front of the iris, and into the spaces of the angle.
 
The cornea in the adult is non-vascular, except at the circumference, in which situation there are the conjunctival and sclerotic
capillaries, which terminate in loops. Being destitute of blood-vessels,
the nourishment of the cornea is maintained by the flow of lymph
through its surface. It is about 1 mm. thick, slightly more peripherally.
 
Nerve-supply.—The nerves are derived from the ciliary nerves,
and are very numerous. They enter the deep surface of the anterior
part of the sclera, and form a plexus round the corneo-scleral junction.
Offsets from this plexus enter the cornea, and form what is known
as the plexus annularis. From this plexus delicate offsets are given
off, which traverse the substance of the cornea and pass through
the anterior elastic lamina. They then give rise to a fine plexus upon
the surface of that lamina, called the subepithelial plexus. From
this plexus, in turn, minute fibrils are given off, which pass amongst
the cells of the conjunctival epithelium, and almost reach the surface,
forming an intra-epithelial plexus.
 
Pectinate Ligament of Iris.—It has been seen that the posterior
elastic lamina at its circumference breaks up into fibres. The most
posterior of these pass in a radiating manner into the iris, constitute
the ligamentum pectinatum iridis, and are covered by a prolongation
of the endothelial layer of the cornea.
 
Spaces of Irido-corneal Angle (or Spaces of Fontana).—These spaces
represent the irregular intervals which lie between the radiating fibres
of the pectinate ligament. They are lined by a prolongation of the
endothelial layer of the cornea, and they communicate internally with
the anterior chamber and the lymph-spaces within the iris, and
externally with the sinus venosus sclerae.
 
Sinus Venosus Sclerse.—This canal (formerly known as the canal
of Schlemm) is situated deeply in the sclerotic, close to the corneo-scleral
junction. It communicates internally with the anterior chamber
through the spaces of the irido-corneal angle, and externally with
anterior ciliary veins of the sclera. It encircles the outer margin of
the cornea, and has a little projecting rim of sclerotic on its deep
surface, called the ‘ scleral spur/ from which the ciliary muscle takes
 
origin.
 
Middle Coat.
 
1. Choroid Coat.— This is a very vascular, deeply pigmented tunic
of a dark brown colour, which lies between the sclera and the retina.
It extends over the posterior five-sixths of the eyeball, and reaches as
far forwards as the ora serrata of the retina. Anteriorly it is connected
with the circumference of the iris, and posteriorly it is pierced by the
optic nerve. Its outer surface is connected to the inner surface of the
sclera by means of the lamina fusca and its processes, as well as by
vessels and nerves which cross the ‘ perichoroidal lymph-space.
Its inner surface is in contact with the pigmentary- layer of the retina.
 
 
1646
 
 
A MANUAL OF ANATOMY
 
 
Structure.—The choroid coat consists of connective tissue, bloodvessels, and branched pigment-cells. It is composed of three layers,
which are as follows, from without inwards: (1) the lamina supra choroidea; (2) the choroid proper; and (3) the lamina basalis, or
membrane of Bruch.
 
The suprachoroid lamina is composed of delicate, non-vascular
lamellae, each of which is made up of elastic fibres arranged in a reticular
manner, and of branched pigment-cells.
 
The choroid proper consists principally of bloodvessels and pigmentcells supported by connective tissue. The bloodvessels are arranged
partly as arteries and veins, and partly as capillaries. The choroid
proper is therefore composed of two layers—external or lamina vasculosa, and internal or lamina chorio-capillaris.
 
The lamina vasculosa (arterio-venous layer) is composed of
(1) branches of the short ciliary group of the posterior ciliary arteries,
which pass forwards before they turn inwards to end in capillaries;
 
Suprachoroid Lamina
 
 
Arterio-Venous Layer
 
 
Membrana
Chorio-capillaris
 
Basal Lamina (Bruch’s Memb.)
 
Pigmentary Layer of the Retina
 
Fig. 1007.—Vertical Section of the Choroid Coat.
 
The pigmentary layer of the retina is also shown.
 
and (2) veins, which form the chief part of the lamina vasculosa,
and are called the vense vorticosae. These veins are very closely set,
and are arranged in a whorled manner. They ultimately converge
and form four or five vessels, which pierce the sclerotic nearly midway
between the optic entrance and the corneo-scleral junction at points
equally distant from each other. Scattered throughout the lamina
vasculosa are branched pigment-cells.
 
The lamina chorio-capillaris is composed of a plexus of capillary
bloodvessels, the arteries leading to it being derived from the short
ciliary arteries.
 
The lamina vasculosa and lamina chorio-capillaris are connected
by fine elastic fibres, which form what is known as the stratum intermedium.
 
The lamina basalis, or membrane of Bruch, is situated on the inner
surface of the lamina chorio-capillaris, which it separates from the
pigmentary layer of the retina. It is a very delicate membrane without any very definite structure.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1647
 
 
Tapetum. —This is present in certain animals. It lies between the lamina
vaseulosa and the lamina chorio-capillaris in the stratum intermedium, and it
gives rise to an iridescent or rainbow-like appearance. In some animals it is
fibrous in structure, and in others cellular.
 
2. Ciliary Body.—The ciliary body connects the anterior part of
the choroid to the circumference of the iris. It is composed of
(1) the orbicularis ciliaris, (2) the ciliary processes, and (3) the
ciliary muscle.
 
The orbicularis ciliaris, or ciliary ring, is a narrow zone which lies
immediately in front of the anterior part of the choroid, with which
it is continuous. In it are folds which are radially disposed, and it
separates the ciliary processes from the ora serrata of the retina.
 
The ciliary processes, about seventy in number, are infoldings
(Fig. 1005) of the anterior part of the choroid, and consist of the choroid
proper and the basal membrane (of Bruch). They constitute a series
 
 
Conjunctiva
 
Choroid
 
Sclera
 
 
Optic Nerve
 
 
 
Retina
 
 
Ciliary Body
Iris
 
Cornea
" Lens
 
'Anterior Chamber
Posterior Chamber
 
— Sinus Venosus Scleras
. Ora Serrata
 
 
Vitreous
 
 
Fig. 1008.—Diagram of Section through the Eyeball to show
the Main Layers mentioned in the Description.
 
S, S, suspensory ligament of lens.
 
 
of rays arranged in a circular manner, and converge as they pass inwards and forwards to the periphery of the crystalline lens on its
anterior aspect. They are somewhat conical in outline.. Their bases
or free extremities, which are round and prominent, lie behind the
circumference of the iris upon the anterior aspect of the periphery of
the crystalline lens. Their apices are connected with the orbicularis
ciliaris Anteriorly they are related to the posterior chamber of the
eyeball at its circumference. Posteriorly they are related to and
connected with the suspensory ligament of the lens.
 
Structure._The ciliary processes are similar in structure to the
 
choroid, but the pigment-cells are not so numerous. On their deep
or posterior surfaces the processes are covered by the ciliary part
of the retina, which is prolonged from the pigmentary layer of the
retina, and is continuous with the pars iridica retinae (uvea) on the
posterior surface of the iris.
 
 
 
 
 
 
 
 
 
 
 
 
 
1648
 
 
A MANUAL OF ANATOMY
 
 
The arteries of the ciliary processes are derived from those of the
anterior part of the choroid, and from the anterior ciliary arteries.
The veins pass to those of the choroid.
 
Ciliary Muscle. —This muscle is composed of unstriped fibres. It
forms a greyish-white ring, about T V inch broad, which is situated at
the anterior part of the choroid opposite the ciliary processes. The
fibres are arranged in two sets—radial and circular. The radial
fibres arise from the calcar sclerae close to the corneo-scleral junction
and behind the sinus venosus of the sclera. From this origin they
pass backwards in a radiating manner, and are inserted into the
orbicularis ciliaris and the attached ends of the ciliary processes. The
circular fibres form a ring around the circumference of the iris internal
to the radial fibres.
 
 
Pupil
 
 
 
Fig. 1009.—The Iris and Ciliary Processes (Posterior View)
 
(Hirschfeld and Leveille).
 
The ciliary muscle is supplied by the short ciliary nerves, which are
branches of the ciliary ganglion, and derive their fibres from the
motor oculi nerve.
 
Action. —The ciliary muscle is the muscle of accommodation , and
adjusts the eye to the vision of near objects. When it contracts it
draws forwards the choroid and the ciliary processes; the suspensory
ligament of the crystalline lens is thereby relaxed, and, as a consequence, the anterior surface of the lens is rendered convex.
 
The circular fibres of the ciliary muscle are well developed in
cases of hypermetropia, but are deficient in cases of myopia.
 
3. Iris. —The iris forms the anterior part of the middle coat of the
eyeball. It is a coloured contractile diaphragm, which is suspended
in the aqueous humour between the cornea and the crystalline lens.
It is perforated by an almost circular aperture, called the pupil, which
is situated slightly to the nasal or inner side of its centre, and serves
for the transmission of light. The margin which surrounds the pupil
is known as the pupillary margin. Its circumference is continuous
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1649
 
with the ciliary body, and is connected with the posterior elastic
lamina of the cornea by means of the ligamentum pectinatum iridis
 
 
Anterior Wall of Capsule of Lens..(I
 
 
Sphincter Pupillae ...
 
 
Membrane
of Descemet —
 
 
Epithelium .
of Cornea
 
 
Sinus Venosus
Scleras
 
 
Suspensory
Ligament
Middle Portion of
Suspensory Ligament
 
Posterior Portion of
Suspensory Ligament
 
 
Margin of Cornea
 
Conjunctiva —
 
 
 
Ciliary Muscle
"Radiating Fibres)
 
 
Fig. ioio.—Meridional Section through the Anterior Portion of
 
the Eye (magnified 16X1) (Fuchs).
 
C.P., C.P., zonular spaces.
 
at the iridial angle. The circumference is known as the ciliary margin.
The surfaces of the iris are anterior and posterior. The anterior
 
TO4
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1650
 
 
A MANUAL OF ANATOMY
 
 
surface is directed towards the cornea. Its colour varies in different
individuals, and it presents a striated appearance, the striae converging
towards the margin of the pupil, and being produced by the underlying vessels. The posterior surface is directed towards the crystalline
lens and ciliary processes. It has a purple colour, and is covered by
two layers of columnar epithelium, the cells of which contain dark
pigment. These two layers of pigmented cells constitute the pars
iridica retinae (uvea), which is continuous with the pars ciliaris retinae.
 
_ The iris divides the space between the cornea and the crystalline lens
into two compartments, the anterior chamber and posterior chamber,
both of which contain the aqueous humour.
 
Structure. —The component parts of the iris are (1) a layer of
endothelium; (2) a connective-tissue stroma, with branched pigmentcells; (3) muscular tissue; and (4) pigment.
 
The layer of endothelium covers the anterior surface of the iris,
and is continuous with the endothelium which lines the posterior
elastic lamina of the cornea.
 
 
Long Ciliary Artery
 
 
 
Fig. ioii.—The Arteries of the Choroid and Iris (Lateral View).
 
The connective-tissue stroma is composed of fibres which for the
most part pass in a radiating manner towards the pupillary margin.
Some, however, are disposed circularly at the ciliary margin. They
support the bloodvessels and nerves, and scattered between their
bundles there are branched cells. These cells contain pigment in darkcoloured eyes, but in blue eyes there is little pigment here.
 
The muscular tissue is of the unstriped variety, and its fibres are
arranged in two sets, circular and radiating. The circular fibres form
a ring round the pupil, and are nearer the posterior surface than the
anterior. They are known as the sphincter pupillse. The radiating
fibres converge from the ciliary margin of the iris towards the pupillary
margin, where they blend with the circular fibres. The radiating
fibres constitute the dilator pupillse. Some authorities regard the
radiating fibres as elastic, and not muscular.
 
The pigment of the iris is variously situated, according to the
colour of the eye. In the eyes of albinos there is no pigment. In
other eyes pigment is contained in the cells of the two layers of columnar
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1651
 
epithelium which line the posterior surface of the iris, and form the
pars iridica retinae (uvea). In blue eyes the pigment is largely confined to this region, but in other coloured eyes it is also present in the
branched cells of the connective-tissue stroma.
 
Blood-supply—Arteries. —The arteries of the iris are derived from
(1) the long ciliary, and (2) the anterior ciliary vessels.
 
The long ciliary arteries are two in number, and belong to the
posterior ciliary group of branches from the ophthalmic artery. They
pierce the back part of the sclera, one on each side of the optic
nerve, and pass forwards between the sclera and the choroid towards
the ciliary margin of the iris. Here each vessel divides into two
branches, upper and lower, which anastomose with those of the
opposite side to form an arterial ring round the ciliary margin of the
iris, called the circuius arteriosus major. This ring is joined by some
of the anterior ciliary arteries, and it gives offsets to the ciliary muscle
 
 
Pupil
 
; Iris
 
 
 
Fig. 1012. —The Choroid and Iris, showing the Ven,e Vorticose
and Ciliary Nerves (after Hirschfeld and Leveille).
 
The sclera and cornea have been removed.
 
and iris. The branches which enter the iris are supported by the
connective-tissue stroma, and converge towards the pupillary margin,
near which they form by their anastomoses another arterial ring,'
called the circulus minor.
 
The anterior ciliary arteries are about six in number, and are
derived from the muscular and lacrimal branches of the ophthalmic
artery. They are of small size, and pierce the anterior part of the
sclera close to the corneo-scleral junction. Some of them supply the
ciliary processes, and others join the circulus major (see Fig. ion).
 
The veins of the iris accompany the arteries, and are in communication with the sinus venosus sclerse.
 
Nerves of the Choroid Coat and Iris. —These are derived from the
ciliary nerves, short and long, the former coming from the ciliary
ganglion, and the latter from the naso-ciliary branch of the ophthalmic
or first division of the fifth cranial nerve. They are about sixteen
 
 
 
 
 
 
 
 
1652
 
 
A MANUAL OF ANATOMY
 
 
in number, and pierce the back part of the sclera around the optic
nerve. They then pass forwards between the sclerotic and choroid,
giving branches to the latter coat, which become disposed in a plexiform manner amongst the bloodvessels. Having reached the corneoscleral junction, the nerves enter the ciliary muscle, in which they form
a plexus. From this plexus branches enter the iris at the ciliary
margin. These branches accompany the vessels, and by their subdivisions and communications they form a copious plexus of nonmedullated fibres in the connective-tissue stroma of the iris. The
sphincter pupillse is supplied by fibres which are derived from the oculomotor or third cranial nerve by means of the motor root of the ciliary
ganglion. The dilator pupillae is supplied by fibres which may be
traced to the second thoracic ganglion through the sympathetic root
of the ciliary ganglion (see p. 1637).
 
Membrana Pupillaris. —During intra-uterine life the pupil is closed by a
delicate membrane, called the membrana pupillaris. This disappears shortly
before birth, but remnants of it are sometimes found.
 
 
Internal Coat.
 
Retina.—The retina is the internal or nervous tunic of the eyeball. It is soft in consistence, translucent, and of a pinkish colour.
Its internal surface is in contact with the hyaloid membrane, which
 
 
 
Fig. 1013.—The Posterior Portion of the Right Retina
 
(Anterior View).
 
 
encloses the vitreous body, and its external surface is in contact with
the choroid coat. Posteriorly it receives the fibres of the optic
nerve. Anteriorly it extends almost to the ciliary body, where there
is a notched border, called the ora serrata. Here its nervous elements
cease, but its pigmentary layer is continued over the deep or posterior
 
 
 
 
 
 
 
 
THE EYE
 
 
1653
 
 
surfaces of the ciliary processes on to the posterior surface of the iris,
forming, with the addition of a layer of columnar epithelial cells,
the pars ciliaris retinae and pars iridica retinae (uvea) respectively.
The retina diminishes in thickness from behind forwards.
 
The external surface is formed by a stratum of hexagonal pigmentcells, which send processes into the adjacent layer. When the choroid
is separated from the retina these processes are torn, and the stratum
of pigment-cells remains attached to the choroid, being apparently
a part of it. The pigmentary layer, however, really belongs to the
retina.
 
The internal surface shows, in the line of the visual axis of the
eyeball, the macula lutea or yellow spot, where vision is most distinct.
This spot is transversely oval, and measures about X V inch from side
 
 
 
Fig. 1014.—Longitudinal Section through the Head of the Optic
 
Nerve (14X1)
 
 
r. Retina
 
b. Centre of Porus Opticus
ch. Choroid
 
s. Sclera
 
so. Outer Part of Sclera
si. Inner part of Sclera
ci. Ciliary Artery (in longitudinal section)
sd. Subdural Space
 
nasal, Medial Side
 
 
(Fuchs).
 
sa. Subarachnoid Space
n. Bundles of Nerve-fibres
se. Septa between the Nerve-bundles
a. Arteria Centralis Retinae
v. Vena Centralis Retinae
p. Sheath formed by Pia Mater
ar. Sheath formed by Arachnoid
du. Sheath formed by Dura Mater
 
temporal, Lateral Side
 
 
to side. At its centre is a slight depression, called the fovea centralis.
In this situation the retina is thinnest, and the dark colour of the
hexagonal pigment-cells is visible through it, giving it the appearance
of a foramen. About inch to the inner side of the posterior pole
of the eyeball, and about iucb below its level, is the porus opticus,
or optic disc. This is circular in outline, and its circumference is
slightly elevated. It is the point of entrance of the fibres of the optic
nerve, and the centre of the disc is pierced by the arteria centralis
retinae which immediately divides into two branches upper and
lower. * The optic disc consists entirely of nerve-fibres, and is known
as the ‘ blind spot,’ vision being absent in this situation.
 
Structure of the Retina.— The retina consists of eight superimposed layers, seven of which are nervous and one pigmentary.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1654
 
 
In addition to these, there are sustentacular fibres. The eight layers
are as follows, from within outwards:
 
 
1. Stratum opticum, or layer of nerve-fibres.
 
2. Ganglionic layer, or layer of nerve-cells.
 
3. Inner plexiform (inner molecular) layer.
 
4. Inner nuclear or granular layer.
 
5. Outer plexiform (outer molecular) layer.
 
6. Outer nuclear or granular layer.
 
7. Layer of rods and cones.
 
8. Pigmentary layer.
 
 
 
Pigmentary Layer
 
 
1 Layer of Rods and Cones
 
 
A. Membrana Limitans Externa
 
 
> Outer Nuclear Layer
 
 
„_Outer Plexiform Layer
 
 
. Inner Nuclear Layer
 
 
In addition to the foregoing layers, there are two very delicate
membranes, which really belong to the sustentacular fibres of the
 
retina, but are known
as the membrana limitans interna and externa. The membrana
limitans interna covers
the retina on its internal surface, and the
membrana limitans externa intervenes between the outer nuclear
layer and that of the
rods and cones. The
layers of the retina
are supported by fibres
called the sustentacular
fibres.
 
1. Stratum Opticum.
 
—This layer consists of
the fibres of the optic
nerve, and it extends
from the optic disc to
the ora serrata. The
fibres are non-medullated, and are chiefly
centripetal, but some
are centrifugal. The
 
centripetal fibres arise
Fus ioi 5. Diagrammatic Section of the Human mainly as the axons of
 
• R =mIT LTZE) COPIED FR0M QUAIN ’ S the “ lls of the S an 8
lionic layer. The centrifugal fibres pass towards the inner plexiform and inner nuclear
layers.
 
2. Ganglionic Layer.—This consists of large, somewhat flaskshaped, multipolar ganglion-cells, which for the most part form a
single layer. In the macula lutea, however, they form several layers.
 
 
> Inner Plexiform Layer
 
 
Layer of Nerve-cells
(Ganglionic Layer)
 
I Layer of Nerve-fibres
 
Membrana Limitans Interna
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1655
 
 
The round ends of the cells rest upon the stratum opticum, and from
each of these ends an axon is given off, which enters the stratum
opticum obliquely, and forms one of its component fibres. The
tapering end of each cell sends off several dendrites, which enter the
inner plexiform layer, within which they arborize.
 
3. Inner Plexiform (Inner Molecular) Layer contains the arborizations of the dendrites of (1) the cells of the ganglionic layer, and
(2) the bipolar cells of the inner nuclear layer. The intercommunications between these two sets of dendrites give rise to five strata, according to Ramon y Cajal. Besides these, there are the arborizations. of
the processes of the spongioblasts of the inner nuclear layer, which
are likewise arranged in strata.
 
4. Inner Nuclear or Granular Layer.—This layer consists of cells
which are arranged in three groups: (1) bipolar cells, (2) horizontal
cells, and (3) spongioblasts, or amacrine cells. The bipolar cells are
the most numerous, and are nucleated. Each cell gives off two processes—internal and external. The internal processes of the cells enter
the inner plexiform layer, and end at different levels in arborizations.
The external processes pass into the outer plexiform layer, and form
arborizations in its outermost part, which are closely related to the
terminal parts of the rods and cones of the bacillary layer. According to Cajal, the bipolar cells are of two kinds—rod-bipolars and conebipolars. The external processes of the rod-bipolars ramify round the
terminal parts of the rod-fibres, and the internal processes arborize
round the cells of the ganglionic layer. The external processes of
the cone-bipolars form horizontal arborizations round the ends of
the cone-fibres, and the internal processes terminate in arborizations
in the inner plexiform layer at different levels.
 
The horizontal cells occupy the outer part of the inner nuclear
layer. Their dendrites enter the outer plexiform layer, and come
into relation with the terminal parts of the cone-fibres, whilst their
 
axons run in a horizontal direction. .
 
The spongioblasts are situated in the innermost part of the inner
nuclear layer. They are destitute of axons, and ha\ e been called
amacrine cells, because each cell is ‘ without a long fibre or process.
Their dendrites enter the inner plexiform layer, and end in arboriza
 
tions, which are arranged in strata.
 
=; Outer Plexiform (Outer Molecular) Layer.—This layer is composed of the following structures: (i) the external processes of the
rod-bipolars and cone-bipolars of the inner nuclear layer; (2) the
dendrites of the horizontal cells of the inner nuclear layer; and (3) the
terminal parts of the rod-fibres, and filaments from the foot-plates
 
of the cone-fibres. ,
 
6 Outer Nuclear or Granular Layer.—This consists of granules,
 
which are of two kinds—rod-granules and cone-granules. The rodgranules are the more numerous, and are oval enlargements m the course
of the rod-fibres, as these pass to the outer plexiform layer'• Each
rod-fibre has only one rod-granule, and the granules lie at different
 
 
1656
 
 
A MANUAT, OF ANATOMY
 
 
levels. Each granule has a nucleus, which has transverse striations,
there being at least two clear bands. The external process of each
rod-granule is continuous with one of the rods of the bacillary layer,
and the internal process passes into the outer plexiform layer, where
it comes into relation with the arborizations of the external process of
a rod-bipolar.
 
The cone-granules are larger than the rod-granules, but not so
numerous, and each contains an oval nucleus. Situated in the outermost part of the outer nuclear layer, they lie close to the membrana
limitans externa. The outer end of each granule is continuous with
one of the cones of the bacillary layer. The inner end is prolonged
into a cone-fibre, which passes into the outermost part of the outer
 
 
 
Fig. 1016. —Scheme of the Horizontal Cells and Spongioblasts of the
 
Retina (Ramon y Cajal).
 
 
A. Rod-fibres
 
B. Cone-fibres
 
1. Outer Plexiform Layer
a, b. Horizontal Cells, with arborizations
c. Horizontal Cell, with deep processes
 
 
2. Inner Plexiform Layer
/» S, h , f Spongioblasts extending to
j, l. 1 different depths
m, n. Spongioblasts with diffuse processes
o. Ganglionic Nerve-cell
 
 
plexiform layer, where it expands into a foot-plate, from which filaments are given off. These filaments come into relation with the
arborizations of the external process of a cone-bipolar cell.
 
7. Layer of Rods and Cones consists of rods and cones, the former
being cylindrical, and the latter flask-shaped. The rods are much
more numerous, longer, and narrower than the cones, and both are
placed perpendicularly.
 
Each rod and cone consists of two segments—outer and inner.
In the case of the rods the two segments are of almost equal length the
inner segment being rather larger than the outer. The outer segment
is the only seat of the colouring matter known as visual purple or
rhodopsin In the case of the flask-shaped cones, the inner segment
of each forms two-thirds of the cone, and is of large size; whilst the
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1657
 
outer forms one-third, is narrow, and represents the tapering part of
the flask. The outer segments of both rods and cones have faint
transverse striations. The inner segments of both are subdivided.
The outer part is composed of delicate fibrils longitudinally arranged,
and therefore presents a longitudinally striated appearance. The
inner part is faintly granular. The rods and cones are continued at
their inner ends through the membrana limitans externa into the
rod-fibres and cone-fibres, which belong to the outer nuclear layer.
The outer ends of the rods project into the pigmentary layer.
 
8 . Pigmentary Layer.—The most external layer of the retina is
in close contact with the choroid coat. It consists of a single layer
of hexagonal epithelial cells, which contain pigment. The deep
surfaces of the cells
give off processes which
extend into the intervals between the outer
ends of the rods and
 
 
 
Layer of Rods and Cones
 
 
Membrana Limitans Externa
 
 
Outer Nuclear Layer
 
 
Outer Plexiform Layer
Inner Nuclear Layer
 
 
Inne’ Plexiform Layer
 
 
Ganglionic Layer
 
 
1 1 Nerve-fibre Layer
■/.Membrana Limitans Interna
 
Fig. 1017.—Section of the Retina as seen
 
UNDER THE MICROSCOPE (MAGNIFIED).
 
 
 
 
 
cones.
 
Sustentacular Fibres
(or Fibres of Muller).—
 
These fibres form the
supporting tissue of the
retina, and extend from
its internal surface to
the boundary-line between the outer nuclear
layer and the layer of
rods and cones. The
inner ends of the fibres
are expanded, and blend
at their edges to present
the appearance of a
distinct retinal layer,
which is called the membrana limitans interna. Their outer ends,
which are very numerous owing to the breaking up of the fibres,
also expand and form the membrana limitans externa, which lies
between the outer nuclear layer and the layer of rods and cones.
(The membrana limitans interna and externa are sometimes considered layers of the retina, under which circumstances the retinal
layers would be ten in number, instead of eight.) From the membrana
limitans externa delicate offsets enter the layer of rods and cones,
in the innermost part of which they form fibre-baskets in connection
with the deep ends of the rods and cones. As the sustentacular fibres
pass through the inner nuclear layer each has an oval nucleus, which
contains a nucleolus. This nucleus is variously described as being
situated on one side of the fibre, or as involving its whole circumference. Throughout their course the sustentacular fibres give off
lateral offsets, which increase in number from within outwards.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1658
 
 
A MANUAL OF ANATOMY
 
 
Structure of the Macula Lutea and Fovea Centralis.—The chief
structural characters of the macula lutea and fovea centralis may
be stated in the following tabular manner:
 
 
Macula Lutea.
 
1. Cones only.
 
2. Outer nuclear layer has only cone
fibres disposed obliquely.
 
3. Ganglionic layer very thick, cells being
 
several layers deep.
 
4. Stratum opticum not continuously
 
disposed.
 
B
 
 
Fovea Centralis.
 
1. Thinnest part of the retina.
 
2. Pigmentary layer thick.
 
3. Cones only.
 
4. Outer nuclear layer has only
 
cone-fibres.
 
5. Ganglionic layer absent.
 
6. Stratum opticum absent.
 
A
 
 
Membrana Limitansv
Externa N, “
 
 
Fibrous Basket-work
 
 
Outer Plexiform
Layer
 
 
Nucleus of one of
Sustentacular Fibres
 
 
Inner Plexiform_
 
Layer
 
 
Sustentacular Fibres'
Limitans Interna 1 '
Membrana
 
 
 
Centrifugal Nerve-fibre
 
 
Rods and Cones
 
 
Outer Nuclear
Layer
 
 
Subepithelial
 
Ganglion-cell
 
Stellate Ganglioncell
 
Bipolar Q.anglioncell
 
Multipolar
 
Ganglion-cell
 
 
Multipolar
Ganglion-cell
Layer of Nervefibres
 
 
Fig. 1018.—Diagram of the Elements of the Retina (Wiedersheim,
 
AFTER PH. StoHR).
 
A, nervous elements; B, supporting elements.
 
 
Structure of the Ora Serrata.—At the ora serrata the nervous
elements of the retina end, and its pigmentary layer is continued over
the deep or posterior surfaces of the ciliary processes. Here is added
to its deep or posterior surface a layer of columnar epithelial cells,
and the two layers form the pars ciliaris retinas, which is continued
into the pars iridica retinae (uvea). In the latter the cells of both
layers are pigmented.
 
Blood-supply of the Retina.—The retina is supplied with blood by
the arteria centralis retinae, a branch of the ophthalmic artery. Within
the orbit the artery pierces the under aspect of the optic nerve a little
behind the eyeball, and passes forwards in the centre of the nerve.
At the centre of the optic disc it divides into two branches, upper
and lower. Each of these breaks up into two branches, nasal or medial,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1659
 
 
and temporal or lateral. The temporal branches keep clear of the
macula lutea, but give small twigs to it, which, however, do not enter
the fovea centralis, this part being non-vascular. As the branches
pass inwards and outwards respectively towards the periphery of the
retina they ramify freely, and end at last in capillary networks.
The arteries do not extend farther outwards than the inner nuclear
layer. No anastomoses take place between the branches of the arteria
centralis retinae.
 
 
 
Fig. 1019._Scheme of the Retina, showing the Connection between
 
the Layer of Rods and Cones and the Ganglionic Layer (Ramon
 
 
y Cajal).
 
A. Layer of Rods and Cones
 
B. Outer Nuclear Layer
 
C. Outer Plexiform Layer
 
E. Inner Nuclear Layer
 
F. Inner Plexiform Layer
 
G. Ganglionic Layer
 
H. Layer of Nerve-fibres
M. Sustentacular fibre
 
a. Rods
 
b. Cones
 
c. Granule of Cones
 
d. Granule of Rods
 
 
e. Bipolar Cells of Rods
 
f. Bipolar Cells of Cones
 
g, h, i, \ Ganglionic Corpuscles ramifying at different
j, k. f levels in Inner Plexiform Layer
r, r'. Deep arborizations of Bipolar Cells
 
s. Centrifugal Nerve-fibre
 
t. Nucleus of Sustentacular Fibre
 
X. Deep ends of Rod-fibres amongst superficial
arborizations of Bipolar Cells
Z. Meeting of arborizations of Cones and Bipolar
Cells
 
 
In the foetus the arteria centralis retinae sends a branch to the
posterior part of the capsule of the crystalline lens, which reaches it
through the ‘ canal of Cloquet in the vitreous body.
 
The veins are ultimately collected into two vessels, upper and
lower, which pass through the optic disc, one above and the other
below' the artery. They then form one vessel which opens into the
superior ophthalmic vein. The veins of the retina are destitute of
muscular tissue, the wall of each being formed by a single layer of
endothelial cells, external to which there is a perivascular lymph
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
i66o
 
 
A MANUAL OF ANATOMY
 
 
space, this in turn being limited by another layer of endothelial cells.
These lymph-spaces are in communication with those of the optic
nerve.
 
Relation of the Retinal Layers to One Another.—The only two
layers which are in direct continuity are the stratum opticum and
ganglionic layer, some fibres of the former being the axons of the
cells of the latter. As regards most of the strata, the constituent
elements of successive layers are brought into communication by
means of the interlacements which take place between the arborizations formed by their various processes. These interlacements occur
in the inner and outer plexiform layers.
 
 
Levator Palpebrae Superioris
 
Hyaloid Canal >
 
(Canal of Cloquet)
 
 
Hyaloid Membrane
 
 
Retina
 
 
Sinus Venosus
S clerae
 
Posterior
Chamber
 
Anterior
Chamber
 
 
Choroid
 
 
Rectus Superior
s „ Sclera
 
 
Arteria
 
, l /Centralis
*' '■ / Retinae
 
 
 
Cornea
 
Ciliary / y.
 
Processes'
 
Zonular Space
 
 
Rectus Inferior
 
 
Fornix Conjunctivas
 
Fig. 1020.—Vertical Sagittal Section of the Eye and its
Appendages (Hirschfeld and Leveille).
 
 
In the inner plexiform layer there are several strata of interlacements, by means of which the dendrites of the cells of the ganglionic
layer are brought into communication with the internal processes of
the bipolar cells of the inner nuclear layer. In the outer plexi orm
layer there is a free intermingling between the external processes of
the bipolar cells of the inner nuclear layer and the rod-fibres and conefibres.
 
Nerve-cells of the Retina.—These are arranged in three strata,
and communicate with one another through interlacing arborizations.
The outermost stratum consists of the rods and cones; the middle
stratum is formed by the bipolar cells; and the innermost stratum
represents the cells of the ganglionic layer. The axons of the gang
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EYE
 
 
1661
 
 
lionic cells enter the stratum opticum as centripetal fibres, which pass
in the optic nerve to the brain. The centrifugal fibres of the stratum
opticum ramify in the inner plexiform or inner nuclear layer.
 
Refracting Media.
 
Aqueous Humour and Chambers of the Eye.—The aqueous humour
occupies the space between the cornea and the front of the crystalline
lens, which is divided by the iris into two chambers, anterior and
posterior. It is a clear fluid having an alkaline reaction, and is
composed of H ? 0 , holding in solution a very small amount of sodium
chloride and traces of albumen.
 
The anterior chamber is bounded anteriorly by the cornea, and
posteriorly by the iris and the central portion of the crystalline lens
enclosed within its capsule. The anterior
chamber communicates with the irido-corneal
spaces, through them with the sinus venosus
sclerae, and through this canal with the veins
of the sclera.
 
The posterior chamber, which is of limited
extent, is bounded anteriorly by the iris, and
posteriorly by the peripheral part of the
crystalline lens and its suspensory ligament,
and by the ciliary processes. The anterior and
posterior chambers communicate with each
other through the pupil; with lymph-spaces in
the iris; and through the latter spaces with
the perichoroidal lymph-space.
 
Crystalline Lens.—The crystalline lens is
situated directly behind the pupil and iris, from
which latter it is separated by the posterior
chamber. It is a solid, transparent, biconvex
disc, the posterior surface being more convex
than the anterior, and is enclosed within a A ’ 0 fi n br e e 4° e f ) . th ^°L ( man
homogeneous, transparent envelope, called the fibres (seen on end).
capsule of the lens. The centre of the anterior
 
surface is called the anterior pole, and that of the posterior surface
the posterior pole. The line connecting these two poles constitutes
the axis of the lens, and a line surrounding the periphery represents
the equator. The transverse measurement of the lens, is about
•it inch, and its axis measures about inch. The . anterior surface
at its central part faces the pupil. External to this, the pupillary
margin of the iris rests upon it, and external to this again is the
posterior chamber, with part of the aqueous humour. The posterior
surface is received into the ‘ patellar fossa on the anterior aspect
of the vitreous body. The periphery is related to the suspensory
ligament, the zonular spaces present in this ligament, and the ciliary
processes. From the anterior and posterior poles delicate lines radiate
 
 
 
Fig. 1021.—Fibres of
the Crystalline
Lens (highly magnified) (after Kolliker).
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1662
 
 
A MANUAL OF ANATOMY
 
 
towards the equator. In early life these are three on each surface.
Those on the posterior surface form an inverted while those on
the anterior form an erect Y. These lines represent the free margins
of septa within the lens upon which the ends of the lens-fibres terminate.
 
Structure.—The lens is laminar in structure. The outer laminae
are soft in consistence, but the succeeding ones gradually become
firmer, and the central portion, which constitutes the nucleus, is
very firm and hard. The laminae are arranged concentrically, and
after boiling or immersion in alcohol they may be peeled off, like
the coats of an onion. The fibres of which the laminae are composed
terminate upon septa within the lens, of which the radiating lines on
the surfaces, already referred to, are the free margins. The concentric laminae are therefore not continuous all round, but are split
up along these lines. The lens-fibres, which are disposed in a curved
manner, are of small size, and have serrated edges, which fit closely
to each other. In transverse section the fibres appear as hexagonal
prisms. The fibres are the elongated cells which line the posterior
part of the ectodermal vesicle (lens vesicle) from which the lens is
developed. In early life each fibre has a nucleus, but after the lens has
attained its full development only the outermost fibres are nucleated.
 
Capsule of the Lens.—This is a transparent, homogeneous, elastic
and brittle membrane, which surrounds and encloses the lens. Its
anterior wall is thicker and more elastic than the posterior. In the
adult the lens and its capsule are non-vascular, but in the foetus they
receive the hyaloid branch of the arteria centralis retinae, which reaches
it through the hyaloid canal in the vitreous body.
 
Epithelium of the Lens.—The posterior surface of the lens is devoid
of epithelium, and is in direct contact with the posterior wall of the
capsule. The anterior surface is covered by a single layer of columnar
cells, which intervenes between the anterior surface and the anterior
wall of the capsule. Towards the equator these cells become elongated,
and pass into short fibres, which become continuous with the superficial
lens-fibres.
 
Crystalline Lens at Different Ages.—The characters of the lens at
different ages are as follows:
 
 
Foetal Lens.
 
Almost spherical.
Pinkish colour.
Semitransparent.
Soft in consistence.
 
 
Adult Lens.
 
Biconvex
 
Colourless.
 
Transparent.
 
Firm in consistence.
 
 
Lens in Old Age.
 
Flattened.
 
Amber colour.
 
Opaque, more or less.
Very firm in consistence.
 
 
Vitreous Body.—This body occupies about four-fifths of the space
within the eyeball, and is situated between the crystalline lens and the
retina. It is transparent and gelatinous, and is composed of water,
holding in solution a small quantity of sodium chloride and albuminous
matter. It is surrounded by a transparent, homogeneous envelope,
called the hyaloid membrane. This membrane is in contact with the
retina, except anteriorly, where there is an excavation called the fossa
 
 
/
 
 
THE EYE 1663
 
patellaris , into which the posterior surface of the crystalline lens is
received.
 
 
Anterior Wall of Capsule of Lens __I
 
 
Sphincter Pupillae_
 
 
Membrane
of Descemet
 
 
Epithelium
of Cornea
 
 
Suspensory
Ligament
Middle Portion of
Suspensory Ligament
 
Posterior Portion of
Suspensory Ligament
 
 
Sinus Venosus
Sclera
 
Margin of
Cornea
 
 
Conjunctiva
 
 
Ciliary Muscle
'Radiating Fibres)
 
 
Fig. 1022.—Meridional Section through the Anterior Portion of
 
the Eye (magnified 16X1) (Fuchs).
 
C.P., C.P., zonular spaces.
 
 
Towards its circumference the vitreous body is laminated, the
laminae being arranged concentrically. Laminae are also said to radiate
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1664
 
 
A MANUAL OF ANATOMY
 
 
from its antero-posterior axis towards the circumference. Scattered
throughout the vitreous body there are some amoeboid corpuscles,
and it is traversed from behind forwards by a minute passage called
the hyaloid canal (canal of Cloquet, canal of Stilling). This extends
from the centre of the optic disc to the posterior wall of the capsule
of the lens, and posteriorly it communicates with the lymph-spaces of
the optic nerve. In the foetus the canal transmits a branch of the
arteria centralis retinae, called the hyaloid artery , which supplies the lens.
 
No vessels enter the vitreous body, its nutrition being derived
from the vessels of the retina and ciliary processes.
 
Zonula ciliaris, or zonule of Zinn, is the thickened portion of the
hyaloid membrane which is situated in front of the ora serrata of the
retina. From this point it extends inwards behind the ciliary processes towards the periphery of the crystalline lens. Behind the
ciliary processes are radial folds with intervening depressions. The
depressions receive the ciliary processes, and the radial folds are
separated from the intervals between the ciliary processes by lymphspaces, which communicate with the posterior chamber of the eye.
 
Suspensory Ligament of the Lens, and Zonular Spaces.—The ciliary
zonule, as it approaches the periphery of the lens, divides into three
layers—posterior, middle, and anterior. The posterior layer lines the
fossa patellaris in front of the hyaloid membrane. The middle layer
consists of a few scattered fibres which pass to the equator of the lens.
The anterior layer is the thickest, and forms the suspensory ligament
of the lens, which is attached to the anterior wall of its capsule not
far from the equator (see Fig. 1022). When the radiating fibres of
the ciliary muscle contract the suspensory ligament is relaxed, and
the convexity of the anterior surface of the lens is increased.
 
Behind the suspensory ligament of the lens there is a sacculated
lymph-space, called the zonular space, which surrounds the equator
of the lens.
 
Development of the Eye.
 
The retina, optic nerve, and crystalline lens are developed from the ectoderm,
the retina and optic nerve being derived from the ectoderm of the anterior
primary cerebral vesicle, whilst the crystalline lens is developed from the ectoderm of the side of the head. The accessories of the eye— e.g., the sclera, cornea,
choroid, ciliary body, and iris—are all developed in mesoderm, but ectoderm, as
will be seen, is also employed in some of these. The vitreous body, though
developed to a certain extent from the mesoderm, is principally formed from the
ectoderm.
 
The earliest indication of the future eye is in the form of a shallow marginal
groove on each side in the widely open cerebral plate of embryos with a few
somites. As the region grows these grooves become deepened by the upgrowth
of the lateral margins, which ultimately fuse in the middle line, in continuity
with the fusion of the edges of the medullary folds further back. In this way
the open grooves are converted into recesses or lateral pockets of the closed
fore-brain, each pocket being in contact from the beginning with the ectoderm
of the surface.
 
The pocket formed in this way is termed the optic recess, and becomes the
optic vesicle very soon by its rounded enlargement under the surface ectoderm;
such enlargement is mainly at its distal part, its connection with the brain
 
 
THE EYE 1665
 
being slightly constricted, forming a ' neck ' for the vesicle. As the development
goes on this neck is drawn out into a definite stalk, which connects the vesicle
with the fore-brain. Stages in these changes can be seen in Fig. 1025. The
vesicle is hollow, its cavity being carried into the stalk, and, through this, communicating with that of the fore-brain, which will be the third ventricle. The
 
 
Lens Pit
 
 
Ectoderm
 
srjer
 
Optic Stalk
 
 
Optic Vesicle
 
prifT&yKS-'Ka.
 
ilM /
 
 
Lens
 
Cavity of Vesicle
a?- m
 
6i ; w'sn'j.;!'' . ..£31 «
 
 
Optic Stalk
 
 
Pigmentary
Layer of I
Optic Cup Retinal Layer
of Optic Cup
 
 
Fig. 1023.—Development of Crystalline Lens and Optic Vesicle
 
(Scheme).
 
The lens is lying in the optic cup.
 
 
enlargement formed by the optic vesicle lies deep to, and in contact with, the
ectoderm of the lateral surface of the head (Fig. 1025).
 
The ectoderm in relation with the optic vesicle becomes thickened and
depressed, this depressed portion constituting the lens area. The depressed
ectoderm is deepened and converted into a kind of cup, and, the mouth of the
fossa becoming constricted, its lips unite. In this manner the lens area becomes
transformed into a closed ectodermic sac, called the lens vesicle, from which the
 
 
 
Fig. 1024.—Diagram showing (see Text) the Conversion of Optic
 
Vesicle into Optic Cup.
 
crystalline lens is differentiated. The lens vesicle now becomes completely
separated from the surface ectoderm, with which it was originally continuous
 
^ Fl The outer wall of the vesicle, facing the rudiment of the lens, is invaginated
so as to obliterate the cavity of the vesicle, which is now converted into the
oi>tic cut> Fig 1024 gives diagrammatic sections which may help in the comprehension of this change. The middle vertical row of figures here shows sections
 
105
 
 
 
1666
 
 
A MANUAL OF ANATOMY
 
 
along the length of the optic outgrowth; the simple optic vesicle is seen at the
top, the commencing invagination of its lower lateral wall is seen next, while
the completed invagination is shown in the lowest section. It can be seen that the
invagination extends into the optic stalk also. On the left side the invagination
is shown by transverse sections of the vesicle, corresponding more or less with
the stages of the middle column. Observe that the cavity (V) of the optic
 
 
 
 
Fig. 1025.—Different Stages in the Development of the Eye
(from Reconstruction Models at St. Mary’s Hospital).
 
A piece of the wall of the optic vesicle has been removed in the first specimen,
showing the cavity of the vesicle ; the lens thickening of the ectoderm is
beginning to be depressed. In the second the optic outgrowth is entire,
and the lens depression is projecting into the cavity of the optic cup. In the
third figure removal of part of the wall has opened the cavity of the vesicle,and also the cavity of the cup, in which the lens vesicle is lying, still attached
to the ectoderm, its cavity opened by the section. The figures also show
the formation of the stalk of the vesicle and the extension into it of the cleft
continuous with the cavity of the optic cup.
 
vesicle is being obliterated, replaced by the cavity (C) of the optic cup, which is
still open in front and below; the last section in the middle column has gone
along this interval between the two sides of the cup. The interval is termed
the choroidal or foetal fissure, and extends into the stalk. It closes later by the
apposition and rapid fusion of its lips, so completing the optic cup. The righthand column of sections is made from the distal end towards the brain; they show
the concavity in the vesicle, and in the stalk, lost in the last section.
 
 
 
 
 
 
THE EYE
 
 
1667
 
The lens vesicle, when it separates from the surface ectoderm, lies in the
opening of the optic cup. Vascular mesoderm extends into the cavity of the
cup through the choroidal fissure, behind and below the lens vesicle; when the
fissure closes, the mesoderm within the cavity of the cup loses its connection
with the outer mesoderm, except at the end of the fissure, where a relatively
large vessel persists, and becomes ultimately the central artery of the retina.
Since the end of the fissure is in the optic stalk, which becomes the optic nerve,
this artery passes in the terminal piece of the nerve to enter the eye. The artery,
when first formed, is known as the hyaloid artery, and is distributed over the
posterior surface of the lens.
 
In cases of non-closure of the choroidal fissure the region of the fissure
remains unpigmented, and one of two congenital deficiencies in the eye is met
with, each being known by the general term coloboma. If the patent fissure
affects the ventral wall of the optic cup, then the deficiency in pigment affects
the choroid, and the condition is known as coloboma choroidea. If the patent
fissure affects the lower margin of the optic cup, then the deficiency affects the
lower part of the iris, and the condition is known as coloboma iridis.
 
As stated, the wall of the optic cup consists of two layers. The outer layer,
which is comparatively simple, gives rise to the pigmentary layer of the retina.
The inner layer is, on the other hand, very complicated. After much differentiation it gives rise to all the other layers of the retina. The mesodermic tissue,
which invests the optic cup, gives rise to the sclera, cornea, choroid, ciliary
body (including the ciliary processes and ciliary muscle), and iris. The ciliary
processes are covered by layers from the (ectodermal) walls of the cup.
 
Crystalline Lens. —The lens is of ectodermic origin. The surface ectoderm
on the lateral aspect of the head opposite the optic vesicle becomes thickened
and depressed to form, as stated, the lens area. The depressed ectoderm is
deepened and converted into a kind of cup. The mouth of the cup becomes
constricted, and its lips unite. In this manner the lens area becomes transformed into a closed ectodermic sac, called the lens vesicle, from which the
crystalline lens is differentiated. The lens vesicle becomes completely separated
from the surface ectoderm, with which it was originally continuous. It is now
received into the optic cup, which has been formed in connection with the optic
vesicle, its position being just within the mouth of the cup, the circumference
of the margin projecting slightly in advance of the vesicle.
 
The anterior and posterior walls of the lens vesicle at this stage consist of
several layers of cylindrical cells, and the vesicle contains a small central cavity.
The anterior wall becomes gradually thin, and is ultimately formed of one layer
of flattened cells, these cells constituting the anterior epithelium of the adult
crystalline lens. The cells of the posterior wall become elongated in a forward
direction, obliterating the cavity of the vesicle, and coming into contact with
the anterior wall. By this process of cell elongation the lens-fibres are formed.
At the equator of the lens the cells of the anterior and posterior walls merge
gradually into one another through the medium of a transitional zone of columnar
cells.
 
At this stage in its development the crystalline lens consists of (1) an anterior
epithelial wall, and (2) a posterior wall composed of elongated cells forming
the lens-fibres.
 
As development proceeds, additional lens-fibres are formed by the proliferation of cells at the equator of the lens. These fibres are laid down in successive
layers, which are arranged concentrically.
 
Capsule of the Crystalline Lens.— At an early period in its development the
lens becomes invested by a mesodermic capsule, freely supplied with bloodvessels derived from the hyaloid artery and anterior ciliary arteries. This
capsule is known as the tunica vasculosa. It persists throughout the period of
active growth of the lens, and then undergoes retrogression to form the permanent lens capsule. The portion of the tunica vasculosa which covers the
front part of the lens is called the membrana papillaris, but this usually disappears
prior to birth. It may, however, be present at birth, giving rise to the condition
 
 
i668
 
 
A MANUAL OF ANATOMY
 
 
known as atresia pupillce. Towards the end of intra-uterine life the tunica
vasculosa undergoes retrogression and becomes transformed, as stated, into the
permanent lens capsule, which is a transparent, homogeneous, elastic membrane.
 
This mesodermal pupillary membrane is a continuation across the open
mouth of the cup of the plane of the choroidal layer. It is, therefore, on the
outer surface of the developing iris, of which it forms the mesodermal base, the
muscles being derived from the actual ectodermal or retinal layer itself.
 
Development of the Optic Cup and Optic Stalk. —The optic cup, as stated, is
formed by the invagination of the distal or outer wall of the optic vesicle, the
invagination also affecting the ventral wall of the optic vesicle and the ventral
wall of the part of the optic stalk which is adjacent to the optic vesicle, thereby
giving rise to the choroidal fissure. The mouth of the optic cup is directed
towards the lateral aspect of the head, and the lens vesicle lies just within the
mouth. That the invagination of the optic cup is not caused by the growth
of the lens vesicle has been proved by experimental transplantations on amphibian
embryos. The margin of the cup projects slightly over the lens vesicle, and the
circumference of this margin represents the outline of the pupil. The wall of the
cup consists of two layers —namely, inner and outer, the inner representing the
distal or outer wall of the optic vesicle, which has now become invaginated, or
folded inwards. The cup is divisible into two regions—namely, (i) the ciliary
region, adjoining the margin of the cup; and (2) the fundus. The line of separation between these two regions corresponds to the ora serrata of the adult eye.
 
The ciliary region of the optic cup is associated with the ciliary body (including the ciliary processes and ciliary muscle) and the iris, which are developed
from the thickened anterior part of the choroid. The outer layer of the ciliary
portion, as elsewhere, forms the pigmentary layer of the retina. The inner
layer of the ciliary portion, which is very thin, forms (1) the pars ciliaris retinae
on the posterior surfaces of the ciliary processes, and (2) the pigmented pars
iridica retinae [uvea) on the posterior surface of the iris.
 
The fundus of the optic cup is the proper retinal region. The outer layer
forms, as in the ciliary region, the pigmentary layer of the retina. The inner
or retinal layer becomes differentiated into all the layers of the retina except the
pigmentary layer. The changes which it undergoes are very complicated.
Its thickness is considerably increased, and it subdivides into two layers—
outer and inner—from which the various retinal strata (except the outer pigmentary layer) are specialized.
 
The optic stalk is transformed into the optic nerve. The stalk is at first
hollow, its cavity communicating with that of the optic vesicle on the one hand,
and with the third ventricle of the brain on the other. As stated, the choroidal
fissure involves the under surface of the optic stalk near the optic vesicle, as
well as the under surface of the optic vesicle itself. When the choroidal fissure
undergoes closure, the hyaloid artery, which passed through that fissure, becomes
enclosed within the optic stalk, and forms the arteria centralis retincc of adult
life. By the closure of the choroidal fissure, and the consequent enclosure of
the hyaloid artery, the cavity of the distal portion of the optic stalk becomes
obliterated. Inasmuch as the ventral or lower wall of this part of the stalk
has been previously invaginated, the wall of the stalk is now composed of two
layers—outer and inner—the inner being formed by the invaginated ventral
or lower wall. The outer layer of the optic stalk is now continuous with the
outer layer of the optic cup, whilst the inner layer of the optic stalk is continuous
with the inner layer of the optic cup. As regards the proximal part of the optic
stalk, its cavity becomes gradually closed. The wall of the optic stalk becomes
thickened, its cells proliferate, and they give rise to the neuroglial or sustentacular
tissue of the future nerve. The nerve-fibres which build up the optic nerve are
regarded as having two sources. The majority of them represent the axons of
the ganglion cells of the retina, which pass in the optic stalk to the diencephalon
and mesencephalon. These are therefore centripetal fibres. Other fibres are
regarded as being centrifugal, these arising in connection with the diencephalon
and mesencephalon.
 
 
THE EYE
 
 
1669
 
 
Vitreous Body. —This body is formed within the optic cup, for the most part
posterior to the lens vesicle. It is principally developed from the ectoderm, but
the mesoderm also takes part in its formation. The ectodermic fibres are derived
from those cells which pertain to the sustentacular fibres of the retina.
 
These ectodermal fibres form a very delicate reticulum (Fig. 1026) connecting
the lens vesicle and the inner layer of the optic cup. Mesodermal ingrowth
through the choroidal fissure brings in vessels which ramify to some extent
between the ectodermal connecting strands, but for the most part pass forward
to the back of the growing lens, over which the vessels spread, with their thin
mesodermal surrounding. The main vessel thus reaching the lens is the hyaloid
artery, and this with its surrounding fine mesoderm occupies at first a large part
of the small cavity of the cup, enclosed by ectodermal processes, more or less
avascular in the more peripheral parts of the cup. This is the state known as
the primary vitreous, characterized by
ectodermal formations connected in
origin with both retina and lens, and
associated fairly intimately with vascular mesoderm. The central hyaloid
artery is distributed over the back of
the lens, its terminal branches meeting, at the periphery of this structure,
vessels which enter the cup from the
outside, turning round its rim.
 
The primary vitreous is gradually
succeeded and replaced by the secondary vitreous. The time of the beginning of the change is usually considered to be about the fifth to sixth
week, when the posterior hyaloid
capsule of the lens makes its appearance; after this the slowly increasing
ectodermal element can be produced
only by the retina. It is this element
which, by its growth, occupies the extra
space resulting from the increasing size
of the eyeball, so that it gradually
comes about that the original vascu- C, wall of fore-brain ; OP.V., points to
lar mesodermo-ectodermal formation cavity of optic vesicle; OC, to cavity
 
 
 
Fig. 1026.—Vertical Section through
Eye in 5 Mm. Embryo.
 
 
of optic cup; L.P., lens pit; ECT., surface ectoderm. Protoplasmic processes
connect the lens pit with the inner
wall of the cup.
 
 
(primary vitreous) is surrounded and
enclosed by an increasing mass of ectodermal secondary vitreous ; this is
largely non-vascular, but does not
become completely avascular until the
hyaloid artery atrophies. The vessels are contained in a central funnel-shaped
‘ space ’ in this stage, surrounded by the secondary vitreous, which does not
compress them in any way; the broad end of the funnel is behind the lens, over
which the vessels extend as before, making a vascular capsule for the structure,
and joining round the periphery with vessels reaching its anterior surface. The
anterior part of this tunica vasculosa has been seen already to form the pupillary
 
m The bloodvessels atrophy and disappear in the latter part of foetal life, when the
interval in which they lay persists as the hyaloid (or vitreous) canal, or canal
of Cloquet, the remaining ectodermal substance, now avascular, being the
 
definite vitreous. r , r J ,
 
About the end of the third month the growth forward of the nm of the optic
 
cup (to form the ectodermal portion of the iris) is accompanied by the appearance
of a more fibrillar vitreous formation corresponding with it; this is sometimes
referred to as the tertiary vitreous, and the fibrils of the suspensory ligament of
the lens are developed in this formation.
 
 
1670
 
 
A MANUAL OF ANATOMY
 
 
That part of the hyaloid artery which lies in the fissure in the optic stalk
remains as the extra-ocular part of the arteria retinae centralis. The actual
arteries of the retina are secondary and late branches which extend into that
layer from the hyaloid artery as this enters the eyeball; when the lentine part of
the vessel atrophies, these retinal branches remain and enlarge.
 
Derivatives of the Mesodermic Envelope of the Optic Cup. —These are as
follows: (1) Sclera, (2) cornea, (3) choroid, (4) ciliary body (including the ciliary
processes and ciliary muscle), and (5) iris.
 
The mesoderm which invests the outer surface of the optic cup is disposed in
two layers —outer and inner. The outer layer has a fibrous character, and gives
rise to the sclera, of which the cornea is a forward extension. The inner layer
is vascular, and gives rise to the choroid, and mesodermal bases of the ciliary
body and iris. The outer dense fibrous layer of the mesoderm of the outer
surface of the optic cup, as stated, gives rise to the sclera. From its anterior
margin a thick lamina of mesoderm is prolonged between the lens vesicle and the
surface ectoderm. This lamina shows two layers—superficial and deep. The
superficial layer becomes differentiated into the cornea, which is thus genetically
continuous with the sclera. The deep layer becomes the pupillary membrane
(see above). Between these two layers there is an interval, which represents the
aqueous chamber.
 
The inner vascular layer of the mesoderm of the outer surface of the optic
cup, as stated, gives rise to the choroid. The anterior margin of the choroid,
which adjoins the margin of the optic cup (ciliary region) becomes thickened,
and gives rise to the ciliary body, in connection with which the ciliary processes
and ciliary muscle are developed. The ciliary processes become covered posteriorly
by the pars ciliaris retince, which is a thin retinal expansion from the ciliary
region of the optic cup. The iris is also developed at the anterior margin of the
choroid in the form of a ring of mesoderm. In this mesoderm the fibres forming
the dilator pupillce and sphincter pupillce muscles are formed by proliferation
of the ectodermal cells of the edge of the optic cup, which has extended forward
in front of the lens, and the back of the iris receives a pigmentary covering {uvea)
from the pars iridica retince.
 
 
/
 
 
CHAPTER XVII
 
THE EAR
 
 
The organ of hearing is divided into three parts—the external,
middle, and internal ear.
 
 
External Ear.
 
The external ear consists of the auricle (or pinna) and the external
auditory meatus. The former has been already described (see p. 1294)*
The external auditory meatus extends from the bottom of the
concha to the membrana tympani, and is about 1 inch in length.
It consists of two parts—outer, or cartilaginous, and inner, or osseous.
The cartilaginous part, which is also fibrous, is about J inch in length,
and the osseous part, which lies within the petrous portion of the
temporal bone, is about § inch long. The widest part of the meatus
is its orifice, which is oval, the long measurement being vertica .
The narrowest part is situated in its osseous portion, about T mch
from the tympanic membrane, and it is known as the isthmus. There
is another constriction of the canal situated near the deep end of t e
cartilaginous part, and produced by a projection which is placed
antero-inferiorly. The chief direction of the canal is inwards and
slightly forwards. At first it is also inclined upwards, then backwards,
 
and finally downwards. . ,
 
The cartilaginous part is continuous with the cartilage of the auricle,
and is attached to the external auditory process of the temporal bone.
Its cartilage is folded so as to form a deep groove which is open at its
upper and back part, the cartilaginous deficiency being completed
by fibrous tissue. In the anterior wall of the cartilaginous part are
two clefts (called the fissures of Santorini ) which are occupied by fibrous
Ssuf In important and close inferior relation of the cartilaginous
 
meatus is the parotid gland (see Fig. 1027). ,
 
The osseous part has been described in connection with the temporal
hone (d IQ4) At its deep end there is a narrow groove, called the
sulcus tvmianicus, which forms about five-sixths of a circle, the
 
deficiency being placed superiorly, at the V^femporaf^The
rinp- ic completed by the squamous part of the temporal bone, me
 
tympanic membrane is set obliquely within the tympanic sulcus
being inclined in such a way that its front part is nearer the nudd
line of the body than its back, and its lower part nearer the middle
line than the upper. The floor and anterior wall of the meatus
consequently longer than the roof and posterior wall.
 
^ 1671
 
 
 
1672
 
 
A MANUAL OF ANATOMY
 
 
The meatus is lined with skin, which is continuous with that of
the auricle. In the osseous part of the canal the skin is very thin,
and is provided with vascular papillae, but is destitute of glands and
hairs.. It is reflected over the outer surface of the membrana tympani,
of which it forms the outer layer. In the cartilaginous part of the canal
the skin is thicker, and is provided with hairs, connected with the
follicles of which are sebaceous glands. In addition to these there are
convoluted tubular glands, similar in structure to sweat-glands, and
called the ceruminous glands, which secrete the ear-wax.
 
Blood-supply.—The arteries are derived from the posterior auricular
of the external carotid, the deep auricular of the first part of the maxil
 
Upper Part ofHelix
 
 
Lateral Ligament of the Malleus
 
1
 
Incus
 
 
Semicircular Canals
 
 
Concha
 
 
External Auditory
Meatus
 
 
 
Malleus
Vestibule
__ Cochlea
x , Tympanum
 
Tensor Tympani Muscle
 
Apex of Pet. Portion
of Temporal Bone
 
_Anterior Lig. of
 
the Malleus
 
-Internal Carotid
 
Artery
 
 
Lobule
 
Pharyngotympanic Tube
 
 
Parotid Gland
 
 
Tip of Styloid Process of
Temporal Bone
 
 
Tympanic Membrane
 
Iug. 1027. General View of the Right Organ of Hearing (after
 
Hirschfeld and Leveill£).
 
The external ear and middle ear are seen in section.
 
 
iary, and the anterior auricular branches of the superficial temporal.
The veins follow the course of the arteries.
 
Lymphatics. These pass to the mastoid glands and to the preauricular lymphatic glands.
 
Nerves. The auriculo-temporal nerve gives two branches to the
meatus, upper and lower, which enter it by passing between the
cartilaginous and osseous walls. The upper branch supplies the skin
covering the upper part of the membrana tympani, while the auricular
branch (Arnold s nerve) of the vagus supplies that of the osseous
part of the canal in its lower and back part, and also that covering
the lower part of the membrana tympani.
 
Early Condition of the Meatus.—At birth the osseous part of the
 
canal is represented by the tympanic annulus and a small portion of
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EAR
 
 
1673
 
the squamous part of the temporal bone. It is connected by fibrous
tissue to the cartilaginous framework of the auricle, and within this
fibrous tissue the osseous canal is formed by two outgrowths from the
tympanic annulus.
 
 
Middle Ear.
 
I he middle ear, or tympanum, is an irregular space within the
petrous part of the temporal bone, which lies between the membrana
tympani externally and the outer osseous wall of the internal ear or
labyrinth internally. It is lined with mucous membrane, and it
communicates with the naso-pharynx by means of the pharyngotympanic tube, through which it receives air. It has three parts:
(1) the tympanum proper, or cavum tympani; (2) the attic, or epitympanic recess; and (3) the tympanic or mastoid antrum.
 
The tympanum proper (or cavum tympani) is situated between the
tympanic membrane and the outer wall of the internal ear. Its
contents are as follows:
 
1. A chain of ossicles (malleus,
 
incus, and stapes), with
their ligaments.
 
2. Muscles.
 
The vertical and antero-posterior diameters (inclusive of the attic)
are fully \ inch. The transverse measurement is from | to £ inch,
except opposite the centre of the membrana tympani, where it is
only T V inch, and the shape of its cavity may, perhaps, be visualized
by likening a cast of it to a biconcave disc about the size of a threepenny piece.
 
The tympanic cavity has six walls—lateral, medial, roof, floor,
anterior, and posterior.
 
The lateral wall is formed chiefly by the tympanic membrane,
which has the handle of the malleus fixed to it, and slightly by the
tympanic annulus, within the circumference of which there is a groove,
called the tympanic sulcus, in which the membrane is set. The tympanic annulus and sulcus are interrupted superiorly by a notch, called
the tympanic notch. In front of the tympanic annulus is the open,
inner extremity of the squamo-tympanic fissure, which lodges the
processus gracilis of the malleus, and transmits the tympanic branch
of the internal maxillary artery. At the inner end of the fissure is
the opening of the iter chordce anterius, by which the chorda tympani
nerve leaves the tympanum.
 
The (medial) wall (see Fig. 1028) separates the tympanum from the
internal ear or labyrinth. It is very irregular, and is formed by the
following parts :
 
1 The fenestra vestibuli. 3 - The promontory.
 
2. Projection of the facial canal. 4 - The fenestra cochleae.
 
5. The sinus tympani.
 
 
3. Nerves.
 
4. Bloodvessels.
 
5. Air.
 
 
A MANUAL OF ANATOMY
 
 
^74
 
 
The fenestra vestibuli is situated in a depression, called the fossa
ovalis, at the upper part of the inner wall, and it leads into the cavity
of the vestibule. It is irregularly oval, and is elongated from before
backwards. It is occupied by the foot-piece of the stapes, and the
annular ligament which connects the circumference of the foot-piece
to the margin of the opening, the margin being covered by cartilage.
 
The projection of the facial canal lies above the fenestra ovalis.
The canal, which contains the facial nerve, is here directed backwards,
and has walls of a paper-like thinness.
 
The promontory is seen below the fossa ovalis, between it and the
fossa rotunda, and slightly in front of both. It is a rounded promin
 
Mastoid
 
Antrum
 
 
 
Sinus Tympam Outlet of Facial Canal at
Stylo-mastoid Foramen
 
kiG. 1028. Section through the Petrous and Mastoid Portions of the
Temporal Bone, showing the Tympanum and Mastoid Cells.
 
ence made by the first turn of the cochlea, and is grooved by the nerves
of the tympanic plexus.
 
The fenestra cochlese is situated in a funnel-shaped depression
called the fossa rotunda, below and behind the promontory. It leads
into the scala tympani of the cochlea, and in the recent state is closed
by the secondary membrane of the tympanum.
 
1 he sinus tympani is a depression behind the promontory, and
between the fossa ovalis and fossa rotunda. In close relation to this
is the ampulla of the posterior semicircular canal.
 
The roof of the tympanum is a thin plate of bone, called the tegmen
tympani, which forms part of the anterior surface of the petrous part
of the temporal bone.
 
The floor, narrower than the roof, is a thin plate of bone which
separates the tympanum from the jugular fossa.
 
 
 
 
 
 
 
 
 
 
 
 
THE EAR
 
 
1675
 
 
The anterior wall is narrow, owing to the descent of the roof, and
the inclination towards each other of the outer and inner walls. In
it are the openings of two canals, the upper of which lodges the tensor
tympani muscle, whilst the lower is the osseous part of the pharyngotympanic tube. The two orifices are separated by the margin of the
processus cochleariformis. The carotid canal lies just in front of the
lower part of the anterior wall.
 
 
 
Fig. 1029.—Diagrammatic Outline of Tympanum and Associated
 
Recesses.
 
 
The posterior wall is formed by the anterior or tympanic surface
of the petrous part of the temporal bone. From above downwards
the following parts are seen: (1) the opening of the mastoid antrum,
which communicates with the attic of the tympanum, or epitympanic
recess; (2) a depression called the fossa incudis, receiving the short
process of the incus* (3) a small conical projection, called the pyramid,
at the summit of which is an opening for the tendon of the stapedius
muscle (posteriorly the canal within the pyramid, which contains the
 
 
 
Mastoid Antrum
 
 
Lateral Semicirc.C. ~ *
Pyramid •
Sinus Tympanum —
 
 
-Epitympanic Recess
 
-Site of Geniculate Ganglion
 
Fenestra Vestibuli
 
Promontory
 
Fenestra Cochleae
 
 
Fir jo^o_ Diagram to show Course and Relations of Facial Canal on
 
' 'the Medial and Posterior Walls of the Tympanum.
 
 
stapedius muscle, passes downwards in the posterior wall of the
tympanum, and communicates with the descending part of the canal
which contains the facial nerve; this explains how the branch of that
nerve to the stapedius reaches the muscle); and (4) the iter chordae
 
posterius, for the chorda tympani nerve. .
 
Tympanic Membrane.-This is the membrane which closes the
inner extremity of the external auditory meatus. It is situated on
the outer wall of the tympanum, of which it forms the chief part, and
it is set for the most part in the sulcus tympamcus, which marks the
 
 
 
 
 
 
 
 
1676
 
 
A MANUAL OF ANATOMY
 
 
inner surface of the tympanic annulus. Superiorly, however, where
the ring is wanting, the membrane is attached to the tympanic notch
(of Rivinus). This part of it is thinner and looser than the rest, and
is called the membrana flaccida, or Shrapnell’s membrane. The
attachment of the membrana tympani to the sulcus is by a thickened
ring of fibres, called the annulus fibrosus. This annulus passes from
the extremities of the notch to the short process of the malleus in the
form of two bands, the anterior and lateral ligaments of the malleus,
which form the lower boundary of the membrana flaccida. The membrane is set obliquely in the tympanic sulcus, so that its lower part
forms an acute angle with the floor of the meatus externus, and its
upper part an obtuse angle with the roof of the passage.
 
 
Superior Ligament of Malleus
 
 
Head of Malleus
Insertion of Tensor Tympani
 
Chorda Tympani Nerve
 
 
Pharyngo-tympanic
Tube
 
 
 
Superior Ligament of Incus
Body of Incus
 
Attic of Tympanum
 
^ Short Process of
Incus
 
L ’\ST ^Posterior Liga^ ment of Incus
 
s ^_Long Process of
 
 
_Processus Orbicu
1 & • laris of Incus
 
y ' 0 _Handle of Malleus
 
—
 
_Membrana Tympani
 
 
 
 
Fig. 1031.—The Right Membrana Tympani, Malleus, and Incus
(Internal, Posterior, and Superior View) (Spalteholz).
 
 
The tympanic membrane is somewhat oval. In the vertical
direction it measures about 10 mm., and horizontally from 8 to 9 mm.
The handle of the malleus lies between the mucous and fibrous layers
of the membrane, and descends to a point a little below its centre,
where it ends in a small knob, from which the radiating fibres of the
membrane proceed. This knob is firmly attached, and, being directed
inwards, the membrane is consequently drawn inwards at that point,
and its outer surface presents a slight conical depression, the deepest
part of which is called the umbo.
 
Structure.— The membrane consists of three layers—external,
middle, and internal.
 
The external or cutaneous layer is very thin, and is derived from
the skin of the external meatus. It contains no glands, is freely provided with bloodvessels and nerves, and is covered by stratified
squamous epithelium.
 
 
/
 
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EAR
 
 
1677
 
The middle or fibrous layer forms the proper substance of the
membrane, and consists of fibrous tissue. The fibres are radial and
circular. The radial fibres lie beneath the cutaneous layer, and radiate
from the handle of the malleus to the annulus fibrosus. The circular
fibres are deep to the radial fibres, and are most numerous towards the
circumference of the membrane. Both sets of fibres are absent from
the membrana flaccida.
 
The internal or mucous layer is continuous with the mucous membrane of the tympanum, and is covered by a single layer of squamous
epithelium.
 
The membrana flaccida, pars flaccida, or Shrapnell’s membrane, has
cutaneous and mucous layers only. These are united by connective
tissue, which is so loosely arranged that the membrane is flaccid. This
part is very liable to perforation.
 
Cone of Light.—Extending from the knob, in which the handle of
the malleus terminates, downwards and inwards to the antero-inferior
margin of the membrana tympani there is seen a specially bright
reflection, triangular in outline, with the apex towards the umbo.
This is called the cone of light.
 
Arterial Supply of the Tympanic Membrane.—(1) Deep auricular
branch of the maxillary artery. This vessel, which passes through the
anterior wall of the external meatus, supplies the cutaneous layer. It
descends from the skin of the roof of the meatus along the course of the
handle of the malleus to the umbo, where it divides into branches
which radiate towards the circumference of the membrane. (2) The
stylo-mastoid branch of the posterior auricular; and (3) the tympanic
branch of the maxillary. The former artery enters the tympanum from
the facial canal, and the latter through the squamo-tympanic fissure.
Branches from them supply the mucous layer, and form an anastomotic
ring around the circumference of the membrane. The fibrous layer
receives its arterial supply from the vessels of the cutaneous and
mucous layers.
 
The veins join the external and internal jugular.
 
Nerve-supply.—(1) The auriculo-temporal of the mandibular, (2) the
auricular branch of the vagus, and (3) branches from the tympanic
plexus.
 
Secondary Membrane of the Tympanum.—This membrane closes
the fenestra cochleae on the inner wall of the tympanum, and separates
the tympanic cavity from the scala tympani of the cochlea. It is
concave towards the tympanum, and, like the membrana tympani,
consists of three layers. The external layer is formed by the tympanic
mucous membrane; the middle layer is fibrous; and the internal layer is
formed by the lining membrane of the cochlea.
 
The mastoid antrum and mastoid air-cells are described with the
temporal bone on p. 188, while the Eustachian or pharyngo-tympanic
tube is dealt with on p. 1378.
 
 
1678
 
 
A MANUAL OF ANATOMY
 
 
Lateral Process
Long Process
 
 
 
Ant.
 
Process
 
 
Plandie
 
 
Fig. 1032.—The Malleus.
 
1. anterior view; 2, posterior view.
 
 
Ossicles of the Tympanum.
 
The tympanum contains three small bones, arranged in the form
of a chain which extends from the membrana tympani to the fenestra
vestibuli. The bones are the malleus, the incus, and the stapes. The
malleus is related to the membrana tympani, the stapes to the fenestra,
and the incus occupies an intermediate position between these two.
 
The malleus is so named from its resemblance to a hammer. It is
composed of a head, neck, handle, and two processes, long and short.
 
T 2 The head is the upper, enlarged,
 
Facet for incus rounded end. Posteriorly it has
 
a saddle-shaped facet, directed
obliquely downwards and inwards,
for articulation with the incus in a
synovial joint. The neck is the
constricted part below the head.
The handle (; manubrium) is directed
downwards, inwards, and backwards
from the neck; it is compressed
from before backwards, slightly
curved, and ends in a knob. It
lies between the fibrous and mucous layers of the membrana tympani,
descending to a point a little below the centre of the membrane. It
is firmly attached to the fibrous layer by its periosteum. The tensor
tympani muscle is inserted into the inner part close to its root. The
long or anterior process (processus gracilis ), which is slender, springs
from the front of the neck, and is directed forwards and downwards to
the petro-tympanic fissure, where it is embedded in fibres which form
part of the anterior ligament of the malleus, and connect it to the
margins of the fissure. The long process is in the adult for the most
part replaced by fibrous tissue except close to the neck of the malleus.
In early life it is continuous with Meckel’s cartilage. The short or
lateral process is situated immediately below the long process. It is
directed laterally to the upper part of the
membrana tympani, with which it is connected by the annulus fibrosus. It is also
connected with the extremities of the notch
by the anterior and posterior malleolar
ligaments.
 
Ihe incus resembles an anvil. It consists
of a body and two processes—short and
 
long. The body is thick, somewhat four- ^ ~ Head ° f Sta fu
 
sided, and laterally compressed. Anteriorly y^ 08 '
 
it presents a saddle-shaped articular surface
 
for the head of the malleus, with which it forms a synovial joint.
The short process is directed backwards, is tipped with cartilage, and
articulates with the fossa incudis on the posterior wall of the tympanum. The long process is directed downwards and medially, behind
 
 
Facet
 
for Malleus
 
/ Short Process
 
/
 
 
 
Long Process
 
 
'*■' Lentiform Nodule for
Head of Stapes
 
 
THE EAR
 
 
1679
 
 
and parallel to the handle of the malleus. Its lower extremity is bent
inwards, and becomes narrowed into a neck, upon which is placed a
disc-like knob of bone, called the os orbiculare, which is covered by
cartilage for articulation with the head of the stapes. In early life,
and up to the sixth month of intra-uterine life, this process forms a
separate ossicle.
 
The stapes resembles a stirrup. It has a head, neck, two crura,
and a foot-piece or base. The head is directed laterally, is concave
and covered by cartilage, and articulates with the processus lenticularis
of the incus. The neck is the constricted part which lies immediately
internal to the head. Posteriorly it gives
insertion to the stapedius muscle. The
crura are anterior and posterior respectively,
and spring from the neck. They diverge as
they pass inwards, and are attached to the
foot-piece near its extremities. The anterior
crus is straighter and shorter than the
 
posterior. The foot-piece or base is some- Malleus
what oval, is directed medially, and occupies incus,,
the fenestra ovalis, which it almost completely fills; its circumference is covered by
cartilage, being attached to the margins of
the fenestra by annular ligamentous fibres. Stapes-
The arch formed by the crura and foot-piece _ ~
 
is occupied by a delicate membrane, which tympanic Os
is attached to a slight groove on the inner sicles in Position.
aspect of the arch.
 
Development of the Tympanic Ossicles— The malleus and incus are usually
regarded as being developed from the proximal end of Meckel’s cartilage,
which forms the cartilaginous bar of the first or mandibular arch. According to
some authorities, however, the incus is developed from the hyoid bar. The stapes
is developed from the dorsal part of the hyoid bar of the second visceral arch.
 
Ligaments of the Ossicles.—The synovial joints between the malleus
and incus and between the incus and stapes are provided with thin
capsular ligaments. The ligaments which connect the ossicles to the
walls of the tympanic cavity are five in number, three of them belonging
to the malleus, one to the incus, and one to the stapes.
 
The ligaments of the malleus are anterior, lateral, posterior, and
superior. The anterior ligament is arranged as a fibrous band which
extends from the root of the long process to the petro-tympanic fissure,
through which it passes to be attached to the spine of the sphenoid
bone. The lateral ligament (or malleolar fold) extends from the
short process to the anterior extremity of the tympanic notch. The
posterior ligament extends from the short process to the posterior
extremity of the notch. The superior ligament extends from the head
of the malleus to the roof of the attic or epitympanic recess.
 
The ligament of the incus connects the short process, near its
posterior extremity, to the fossa incudis.
 
 
 
 
i68o
 
 
A MANUAL OF ANATOMY
 
 
The annular ligament of the stapes connects the circumference of
the foot-piece, which is covered by cartilage, to the margin of the
fenestra vestibuli, which is also covered by cartilage.
 
Muscles of the tympanum are the tensor tympani and the stapedius.
 
Tensor Tympani— Origin .—(i) The cartilaginous part of the
pharyngo-tympanic tube; (2) the apex of the petrous part of the
temporal bone; and (3) the wall of the osseous canal through which
the muscle passes.
 
Insertion, —The medial aspect of the handle of the malleus close to
its root.
 
Nerve-supply.—A branch from the otic ganglion, and through it
from the internal pterygoid branch of the mandibular division of the
fifth cranial nerve.
 
The muscle consists of a fleshy belly, about inch long, and a
delicate tendon. In passing backwards to the tympanum it lies in a
canal, the entrance to which is situated within the petro-squamous
angle of the temporal bone. The canal is placed above the osseous
part of the tube, from which it is separated by the processus cochlearifor mis. On entering the tympanum the tendon of the muscle bends
sharply over the edge of the processus cochleariformis, and then passes
laterally to reach its insertion. The tendon forms very nearly a
right angle with the fleshly belly.
 
Action. —To render tense the membrana tympani by drawing
inwards the handle of the malleus, and along with it the membrane.
 
Stapedius Origin. —The wall of the canal within the pyramid, and
of the continuation of this canal in front of the descending part of the
facial canal.
 
The tendon emerges from the canal within the pyramid through a
small orifice on the apex.
 
Insertion. —The posterior aspect of the neck of the stapes.
 
Nerve-supply. —The facial nerve.
 
Action. To draw the head of the stapes backwards. The result
is that the front part of the foot-piece of the stapes is tilted away
 
from the vestibule, and its back part is pressed inwards towards the
vestibule.
 
Movements of the Ossicles.—The malleus and incus both act as
levers of the first kind, the fulcra of which are represented by an axis
passing backwards from the slender process of the malleus. When a
sound-wave presses the tympanic membrane inward, the handle of the
malleus travels inward with it, and the head of the malleus, or short
arm of the lever, moves outward. The upper part, or short arm of
the incus lever, must move out too, since it is attached to the head
of the malleus, and the long process moves inward, thus pressing the
 
stapes into the fenestra ovalis and compressing the perilymph in the
cochlea.
 
Ihe secondary membrane of the tympanum, stretched across the
fenestra rotunda, is bulged outward by the perilymph, thus allowing
vibrations to travel through that fluid.
 
 
/
 
 
THE EAR
 
 
1681
 
Mucous Membrane of the Tympanum.—The tympanic mucous
membrane is continuous anteriorly with that of the naso-pharynx
through the pharyngo-tympanic (or Eustachian) tube. Posteriorly it is
prolonged into the mastoid antrum, and thence into the mastoid cells.
It forms the internal layer of the tympanic membrane, and the external
layer of the secondary membrane of the tympanum. It also furnishes
sheaths for the tendons of the tensor tympani and stepedius muscles,
and for the chorda tympani nerve. Two folds extend downwards from
the roof of the attic or epitympanic recess, one in front of and the other
behind the superior ligament of the malleus. The former is connected
with the head of the malleus, and the latter (sometimes described as
the superior ligament of the incus) with the incus.
 
Attic or Epitympanic Recess and its Pouches.—The part of the
tympanic cavity which lies above the level of the upper margin of the
tympanic membrane is called the attic or epitympanic recess, as distinguished from the atrium or tympanum proper. It contains the
head and neck of the malleus, and the body and short process of the
incus. These divide it incompletely into two compartments—outer
and inner. The outer attic is subdivided into two pouches—superior
and inferior. The superior pouch is partially separated from the
inner attic by the two mucous folds which have been already referred
to as descending from the roof of the attic in front of and behind the
superior ligament of the malleus. The inferior pouch of the outer attic
is known as the pouch of Prussak. It is bounded laterally by the
membrana flaccida, superiorly by the lateral ligament of the malleus,
which partially separates it from the superior pouch, and internally
by the neck of the malleus. The pouch communicates posteriorly
with the tympanic cavity by an opening which is situated a little above
the level of the bottom of the pouch. If fluid, therefore, should
accumulate in Prussak’s pouch, it may readily lead to perforation of
the membrana flaccida.
 
Two other pouches are present—namely, the anterior and posterior
recesses or pouches of Troltsch. These lie one in front of and the other
behind the handle of the malleus, and are produced by the fold of
mucous membrane which invests the chorda tympani nerve.
 
The tympanic mucous membrane is covered for the most part by
columnar ciliated epithelium, except over the ossicles and membrana
tympani, where the epithelium consists of a single layer of squamous,
non-ciliated cells.
 
The tympanic or mastoid antrum is supplementary to the tympanum proper, or cavum tympani, behind which it is situated. It
communicates by a large irregular opening with the attic, and is
lined with mucous membrane, which is continuous with that of the
attic and cavum tympani. Opening from the antrum there are the
mastoid cells, which are lined with mucous membrane, continuous
with that of the antrum.
 
The average measurements of the antrum are as follows: vertical,
about Q millimetres; antero-posterior, about n millimetres; and
 
106
 
 
1682
 
 
A MANUAL OF ANATOMY
 
 
transverse, about 8 millimetres. The roof is formed by the thin
tegmen tympani, which enters into the formation of the middle fossa
of the base of the skull, and is consequently related to the temporal
lobe of the cerebrum and its meninges. The genu and descending
limb of the sigmoid sinus lie behind the antrum, and a little farther
back is the cerebullum. The facial nerve, as it traverses the descending part of its canal, lies in the posterior wall of the cavum tympani,
close to the medial wall and in front of the mastoid antrum. This
part of the nerve is on a plane anterior to the mastoid process, and is
nearly flush with the opening of the antrum. The ampulla of the
lateral semicircular canal of the internal ear gives rise to a slight
eminence on the medial wall at its anterior part.
 
The lateral wall corresponds on the surface with the area of the
suprameatal triangle of Macewen, and is formed by the postmeatal
plate of the squamous portion of the temporal bone. For a description
of this triangle, which is the region selected for mastoidectomy , and also
for the mastoid cells, see the description of the temporal bone.
 
Summary of Important Structures closely related to the Mastoid Antrum.
 
1. Temporal lobe of cerebrum and its meninges (roof).
 
2. Genu and descending limb of sigmoid sinus, and farther back the cerebellum (posterior wall).
 
3 - Facial nerve (posterior wall of cavum tympani, close to medial wall and
nearly flush with antral opening).
 
4 - Lateral semicircular canal (anterior part of medial wall).
 
The upper part of the antrum communicates, as stated, with the
attic of the cavum tympani, but the lower part is shut off by bone from
the cavity of the cavum tympani.
 
The mucous membrane of the mastoid antrum is continuous with
that which lines the mastoid cells. Anteriorly it is also continuous
with the mucous membrane of the attic and cavum tympani or tympanum proper. The mucous membrane of the cavum tympani is
continuous anteriorly with that of the pharyngo-tympanic tube, and
the mucous membrane of the tube is continuous with that of the
naso-pharynx. This extensive and continuous tract of mucous
membrane is covered by columnar ciliated epithelium except in the
following regions: (1) the promontory; (2) the tympanic ossicles;
(3) the tympanic membrane; (4) the mastoid antrum; and (5) the
mastoid cells. In these regions the epithelium consists of a single
layer of squamous, non-ciliated cells.
 
It is of considerable importance to note that micro-organisms
may pass from the naso-pharynx through the tube into the cavum
tympani and attic, and thence into the mastoid antrum and mastoid
cells. Purulent affections of these regions may therefore readily be
caused in this manner. Such affections may subsequently involve
(1) the temporal lobe of the cerebrum and its meninges, (2) the genu
and descending limb of the sigmoid sinus, and (3) the internal ear or
labyrinth.
 
 
/
 
 
THE EAR
 
 
1683
 
Arteries of the Tympanum. —The principal arteries are: (1) the tympanic
branch of the maxillary, and (2) the stylo-mastoid branch of the posterior
auricular. The tympanic artery enters through the petro-tympanic fissure, and
supplies the membrana tympani and front part of the tympanum. The stylomastoid artery enters the facial canal through the stylo-mastoid foramen, and
passes from the descending part of the canal into the tympanum. It supplies
the back part of the cavity and the mastoid cells, and it forms, with the tympanic
artery, a ring round the circumference of the membrana tympani.
 
In addition to the foregoing two arteries, the following three arteries enter
the tympanic cavity: (1) the petrosal branch of the middle meningeal, which
enters from the facial canal, into which it passes through the hiatus; (2) the
tympanic branch of the ascending pharyngeal, which accompanies the nerve
through the tympanic canaliculus; and (3) the tympanic branch of the internal
carotid, which enters by a minute foramen on the posterior wall of the ascending
part of the carotid canal in company with a sympathetic twig from the carotid
plexus.
 
The veins of the tympanum pass to the pterygoid plexus, the superior petrosal
sinus, the internal jugular vein, and the pharyngeal plexus.
 
Nerves of the tympanum are described on pp. 1325 and 1400.
 
Internal Ear.
 
The internal ear is the essential part of the organ of hearing, and
is known as the labyrinth from its remarkable complexity. It consists
of two parts—namely, the osseous labyrinth and the membranous
labyrinth.
 
Osseous Labyrinth.
 
The osseous labyrinth is a cavity situated within the petrous part
of the temporal bone, and is divided into three parts—namely, the
vestibule, the semicircular canals, and the cochlea. These divisions
are lined with a delicate periosteum, between which and the contained
membranous labyrinth there is a clear fluid, called the perilymph.
 
Vestibule.—The vestibule is the central division of the osseous
labyrinth. The semicircular canals lie behind it, and the cochlea is
situated in front of it. In the lateral wall is the fenestra vestibuii, which
is occupied by the foot-piece of the stapes and its annular ligament.
The medial wall has anteriorly a depression called the fovea spherica
or spherical recess, which corresponds to the lamina cribrosa at the
deep end of the meatus auditorius internus. It is pierced by apertures
for the passage of filaments of the auditory nerve to the saccule.
Behind and above the fovea spherica there is a ridge, called the vestibular crest, which lies obliquely. Posteriorly it bifurcates, and
between its two divisions there is a small depression, called the cochlear
recess, in which are openings for nerve filaments to the canalis cochlese.
Anteriorly it becomes somewhat triangular, and forms a pyramid,
which is pierced by nerves to the utricle.
 
The roof of the vestibule, behind and above the crista vestibuii,
has an oval depression, called the elliptical recess, which encroaches on
the inner wall and lodges the recess of the utricle. It is pierced by
nerves to the ampulke of the superior and external semicircular canals.
Below the fovea elliptica is the opening of the aqueduct of the vesti
 
1684
 
 
A MANUAL OF ANATOMY
 
 
bule, which leads to the posterior surface of the petrous part of the
temporal bone about J inch external to the orifice of the meatus
auditorius internus. It transmits the ductus endolymphaticus and
a minute vein.
 
Anteriorly the vestibule communicates with the scala vestibuli
of the cochlea, and posteriorly are the five openings of the semicircular
canals.
 
Semicircular Canals.—The osseous semicircular canals are situated
behind the vestibule. They are three in number—superior, posterior,
 
 
Cupola of Cochlea
Petrous part of Tern- 5
 
poral Bone
 
 
Facial Canal
A
 
 
 
Superior Semicircular Canal
 
 
Fenestra Vestibuli
 
Lateral Semicircular
Canal
 
 
Posterior Semicircular
Canal
 
Vestibule
 
 
Fenestra Cochleae
 
 
_ Superior Semicircular Canal
 
 
Inner Wall of Canal '
of Cochlea
 
Helicotrema
 
 
Lamina Spiralis
 
 
Crus Commune of Sup. and
Post. SemicircularCanals
 
 
Posterior Semicircular
Canal
 
Lateral Semicircular
Canal
Elliptical Recess
\ Crista Vestibuli
Spherical Recess
 
 
1 \ .
 
1 '
 
> Orifice of Aqueductus Vestibuli
Recessus Cochlearis
 
 
Fenestra Cochleae
Scala T.ympani Scala Vestibuli
 
Fig. 1035. —The Osseous Labyrinth of the Left Side (Lateral View).
A, entire; B opened (Hirschfeld and Leveille; B, modified).
 
 
and lateral—and they open into the vestibule by five circular apertures,
the contiguous ends of the superior and posterior canals having a
common orifice. Each canal forms about two-thirds of a circle, and
each presents at one end an enlargement, called the ampulla. The
superior semicircular canal occupies a vertical position, and lies transversely as regards the long axis of the petrous part of the temporal
bone, giving rise to the eminentia arcuata on its superior surface.
Its ampullary end (antero-external) opens independently into the upper
part of the vestibule above the ampullary orifice of the external canal.
 
 
 
 
 
 
 
 
 
 
 
 
 
THE EAR
 
 
1685
 
 
Its non-ampullary end unites with the non-ampullary end of the
posterior canal to form the crus commune, and the two open by a
common orifice into the vestibule. The posterior semicircular canal
arches backwards towards the posterior surface of the pars petrosa,
with which it is almost parallel, and, like the superior, it occupies a
vertical position. Its ampullary end (inferior) opens independently
into the lower and back part of the vestibule, and its non-ampullary
end, as just stated, joins that of the superior canal. The lateral
semicircular canal arches outwards, and occupies a horizontal position.
Its extremities are independent of those of the other two canals,
and they open by separate apertures into the upper and back part
of the vestibule. Its ampullary end is in front.
 
Cochlea.—The osseous cochlea is situated in front of the vestibule.
It consists of a tube coiled spirally upon itself, like a snail s shell,
 
 
 
Fig. 1036. _Median Section of the Left Osseous Cochlea of Man
 
from Apex to Base (Arnold).
 
 
S.V. Scala Vestibuli
S.T. Scala Tympani
 
 
L.S.O. Lamina Spiralis Ossea
C.C. Central Canal of Modiolus
 
 
M.A.I. Internal Auditory Meatus
 
 
and is conical. Its base is opposite the lamina cribrosa at the deep
end of the meatus auditorius interims; and its apex, known as the
cupola is directed outwards and slightly forwards towards the canal
which contains the tensor tympani muscle. Its length from base to
apex is about i inch. It consists of (1) a winding tube, called the
spiral canal of the cochlea ; (2) a central pillar, called the modiolus,
round which the spiral canal turns; and (3) a thin plate of bone, called
the osseous spiral lamina, which winds spirally round the modiolus
and projects into the spiral canal of the cochlea. . .
 
The spiral canal of the cochlea (cochlear canal or tube) winds round
the modiolus which forms its inner wall. It describes two and threenuarter turns, and its basal turn or coil gives rise to the promontory on
the inner wall of the tympanum. At the cupola it ends in a blind
extremity. It gradually diminishes in size from base to cupola; its
 
 
 
i686
 
 
A MANUAL OF ANATOMY
 
 
length is about 32 millimetres; and its diameter is about 2 millimetres
at the base, where it is greatest.
 
The modiolus is the central pillar round which the spiral canal of
the cochlea turns, and it forms the inner wall of that canal. It commences at the cochlear area of the lamina cribosa at the deep end of the
internal auditory meatus, and extends almost to the cupola, gradually
tapering. It is traversed by minute canals for branches of the cochlear
division of the auditory nerve. One of these canals occupies the
centre of the modiolus, and is called the central canal of the modiolus.
This canal begins at the foramen centrale of the cochlear area of the
lamina cribrosa, and it transmits the nerve-filaments for the apical
coil. The other canals, which have no special name, commence at
the tractus spiralis foraminosus of the cochlear area of the lamina
cribrosa, and they transmit the nerve-filaments for the other coils—
middle and basal. At successive levels these canals change their
direction, and pass outwards to the attached margin of the lamina
spiralis, to be presently described. Here they coalesce and form a
winding canal, called the spiral canal of the modiolus, which lodges
the spiral ganglion or ganglion of Corti. From this canal secondary
canals for nerve-filaments pass into the lamina spiralis.
 
The osseous spiral lamina is a thin plate of bone, which winds
spirally round the modiolus, to which it is attached. It projects from
the modiolus into the spiral canal of the cochlea throughout the windings
of the latter, and it extends for about half-way towards the outer wall
of the cochlear canal. It divides that canal incompletely into two
passages or scalar —an upper or scala vestibuli, and a lower or scala
tympani, the commencement of which is at the fenestra cochleae.
Close to the cupola the lamina spiralis terminates in a hook-like process,
called the hamulus. The spiral lamina consists of two plates of bone,
between which there are canals for nerve-filaments, these canals being
offsets of the spiral canal of the modiolus, which, as has been said,
contains the spiral ganglion or ganglion of Corti. They extend to the
free margin of the spiral lamina. The free margin of the lamina
spiralis is, in the recent state, attached to the outer wall of the spiral
canal of the cochlea by means of the basilar membrane or basilar
lamina, and the scala vestibuli and scala tympani are now completely
separated, except in the region of the hamulus, where they communicate
through an opening, called the helicotrema.
 
The lamina cribrosa, at the deep end of the internal auditory
meatus, will be found described in connection with the temporal
bone (p. 190).
 
At the lower end of the scala tympani is the upper opening of the
aqueductus cochleae, which passes downwards and medially to the
posterior border of the petrous part of the temporal bone. It transmits
a small vein to the inferior petrosal sinus, and establishes a communication between the scala tympani and the subarachnoid space.
 
 
 
THE EAR
 
 
1687
 
 
Membranous Labyrinth.
 
The membranous labyrinth is situated within the osseous labyrinth,
and its constituent parts receive the terminal branches of the auditory
nerve. It is separated from the periosteal lining of the osseous labyrinth by the perilymph, and it contains the fluid known as the endolymph. In the case of the vestibule and the osseous semicircular
canals the. membranous labyrinth corresponds more or less with
them; but in the case of the osseous cochlea it forms part of the septum
between the scala tympani and scala vestibuli, and contains a passage
called the membranous canal of the cochlea (ductus cochleae).
 
 
 
Fig. 1037. —Diagram of Membranous Labyrinth.
 
Vestibular Part of the Membranous Labyrinth.—The vestibule
contains two membranous sacs—namely, the utricle and the saccule
 
_which are in close contact, but do not communicate with each other
 
directly. These sacs contain endolymph.
 
The utricle is the larger of the two sacs, and into it the membranous
semicircular ducts open. It occupies the upper and back part of the
vestibule, a portion of it, known as the recessus utriculi, lying in the
fovea elliptica. Near the crista vestibuli the wall of this recess receives
fibres of the auditory nerve and is thickened, this part of it being called
the macula utriculi. From the anterior and medial part of the utricle
a minute canal, called the ductus utriculi («ductus utriculo-saccularis ),
passes to join the ductus sacculi, and so form the ductus endolymphaticus (see Fig. 1037).
 
 
 
 
 
 
 
 
1688
 
 
A MANUAL OF ANATOMY
 
 
The saccule, which is somewhat oval, lies in front of the utricle,
and occupies the fovea spherica, where it is near the opening leading
into the scala vestibuli of the cochlea. Through the openings of the
fovea spherica it receives filaments of the auditory nerve, and this
portion of the saccule, being thickened, is known as the macula sacculi.
Interiorly the saccule is connected with a small canal, called the
ductus reuniens, which opens into the canal of the cochlea, or ductus
cochlearis, not far from its closed vestibular end. From the posterior
part of the saccule a minute canal, called the ductus sacculi, passes off,
which is soon joined by the ductus utriculi, and so the ductus endolymphaticus is formed. This latter duct traverses the aqueductus
vestibuli, and, having reached the posterior surface of the petrous
part of the temporal bone, it ends in a small blind dilatation, called the
saccus endolymphaticus , which lies beneath the dura mater. The saccule
and utricle are thus indirectly connected by means of the ductus sacculi
and ductus utriculi; and the saccule communicates with the ductus
cochlearis by means of the ductus reuniens.
 
Semicircular Ducts.—The membranous semicircular ducts correspond in outline to the osseous semicircular canals, within which they
lie; they form about two-thirds of a circle, and each has an ampulla
at one end, which is situated within the ampulla of the osseous canal.
They are elliptical in transverse section, and open into the utricle by
five orifices, the non-ampullated ends of the superior and posterior
canals being united, so that these two open by a common orifice
forming the crus commune. The convex wall of each canal is attached
to the periosteal lining of the osseous canal, whilst the concave wall is
practically free from the osseous wall, and is bathed by the perilymph.
These canals contain endolymph.
 
Structure.—The walls of the utricle, saccule, and membranous
semicircular canals consist of three layers: an outer or fibrous layer,
which is vascular; a middle layer, or membrana propria, which is translucent; and an inner or epithelial layer. In each ampulla the middle
layer, or membrana propria, projects into the cavity of the canal from
the peripheral wall, this projecting part being known as the septum
transversum. It partially divides the interior of the ampulla into two
compartments, and its free margin, which is covered by the auditory
epithelium, is called the crista acustica or ampullaris. The epithelial
layer consists of a single stratum of squamous cells, except in those
regions to which the filaments of the auditory nerve are distributed. These regions are as follows: (i) the macula (acustica)
utriculi; (2) the macula (acustica) sacculi; and (3) the crista of each
ampulla.
 
The macula utriculi is the thickened part of the antero-inferior wall
of the recessus utriculi, and is lined with auditory epithelium. The
macula is covered by calcareous particles, called otoconia, which
consist of crystals of calcium carbonate. The macula sacculi is the
thickened part of the anterior wall of the saccule, and is also lined with
auditory epithelium covered by otoconia. The crista ampullaris, as
 
 
THE EAR
 
 
1689
 
 
we have seen, is the free margin of the septum trailsversum in each
ampulla, and is covered by auditory epithelium.
 
The auditory epithelium is of the columnar variety, and consists of
two kinds of cells, auditory and sustentacular. The auditory cells are
nucleated, and each is provided at its free extremity with a slender,
tapering, hair-like filament, which projects into the cavity. These
filaments are sometimes spoken of collectively as auditory hairs, and
the cells are hence called hair-cells. Their deep extremities fall short
of the membrana propria. The sustentacular cells lie between the haircells, and are elongated and nucleated. Their deep extremities are
attached to the membrana propria, and their free extremities give rise
to a kind of limiting membrane. The auditory nerve-fibres pierce
the membrana propria, and, having lost their medullary sheaths, the
axons end in arborizations round the deep ends of the auditory or
hair cells.
 
Superior Semicircular Duct
 
 
Lateral Semicircular Duct i
 
 
Posterior Semicircular Duct
 
 
 
Facial Nerve
 
 
Crus Commune of Superior and
' l Posterior Semicircular Ducts
 
j r Ampulla
 
_ l Nerve to Ampulla
Nerve to Utricle
~ . Nerve to Saccule
_ Cochlear Nerve
 
 
Fig. 1038. —The Membranous Semicircular Ducts, showing the Distribution of the Branches of the Auditory Nerve to their Ampullae
 
(Breschet).
 
Membranous Cochlea.—The membranous cochlea is situated within
the osseous cochlea, and fills the gap which is left by the lamina
spiralis. It consists of two membranes, the basilar membrane and the
vestibular membrane (membrane of Reissner, Fig. 1040), which enclose
between them the ductus cochlearis, or scala media. 1 he osseous
cochlea in the recent state is therefore divided into three spiral
passages—the scala tympani, the scala vestibuli, and the ductus
cochlearis. The scala vestibuli is continuous with the scala tympani
at the cupola through an aperture, called the helicotrema ; and at the
base of the cochlea it opens upon the anterior wall of the vestibule.
The scala tympani begins at the fenestra cochleae, and in the recent
state is separated from the tympanic cavity by the secondary membrane of the tympanum. The scala media, or ductus cochlearis,
communicates near its lower end with the saccule by means of the ductus
reuniens. The scala vestibuli and scala tympani contain perilymph,
which is continuous with the perilymph of the vestibule and osseous
semicircular canals. The scala media contains endolymph, which is
continuous with that of the saccule,
 
 
 
 
1690
 
 
A MANUAL OF ANATOMY
 
 
Basilar Membrane.—The basilar membrane extends from the free
margin of the lamina spiralis to the crista basilaris, or lower part of
the spiral ligament, a thickening of the periosteum of that part of the
outer wall of the cochlea which forms the outer wall of the scala media,
or ductus cochlearis. It separates the ductus cochlearis from the scala
tympani, and is divisible into two zones, inner and outer. The inner
is called the zona arcuata, and supports the spiral organ. The outer
is known as the zona pectinata, and extends from the foot-plates of
the outer rods of this organ to the crista basilaris. The basilar membrane consists of a homogeneous membrana propria, with fibres embedded in it, the fibres being most numerous in the zona pectinata.
 
Vestibular Membrane, or Membrane of Reissner.—This is a delicate
membrane which extends from the upper surface of the lamina spiralis
a short distance from its free margin to the outer wall of the cochlea,
where it is attached to the periosteum a little above the outer attachment of the basilar membrane. It separates the cochlear duct from the
scala vestibuli, and consists of very delicate connective tissue lined on
each side with a single layer of squamous epithelium.
 
 
Osseous Spiral Lamina
 
 
Vestibular Membrane
Basilar Membiane
 
 
Scala Vestibuli
 
Ductus Cochlearis
 
 
Sc' NYll ESy/: ,'-.;
 
| Scala Tympan*
 
 
 
 
Fig. 1039.
 
 
-Vertical Section of the Cochlea of a Fcetal Calf, showing
THE SCALAE AND MODIOLUS (KoLLIKER).
 
 
The scala media, or ductus cochlearis, is situated between the
basilar membrane and the vestibular membrane. It is triangular in
transverse section, and has a roof, an outer wall, and a floor. The
roof is formed by the vestibular membrane (see Fig. 1040). The
outer wall is the wall of the cochlea and its periosteum, between the
external attachments of the basilar membrane and the vestibular
membrane. The periosteum in this region is much thickened, and
forms the spiral ligament of the cochlea, the lower part of which gives
rise to the crista basilaris. The floor is formed by the basilar membrane, and a part of the upper surface of the lamina spiralis. It has
been seen that the basilar membrane separates the ductus cochlearis
from the scala tympani. The ductus ends above in a closed extremity
at the cupola, and it has a similar ending at the base of the cochlea.
Near its lower blind extremity it receives the ductus reuniens, by
which it communicates with the saccule.
 
It has just been shown that part of the floor of the cochlear duct
is formed by some of the lamina spiralis. In the recent state it is
of some thickness, which is due to a thickening of its periosteal
 
 
/
 
 
 
 
THE EAR
 
 
1691
 
 
covering. This fibrous thickening forms the limbus laminae spiralis
(see Fig. 1040).
 
Its outer margin is crescentic, the deep notch being called the sulcus lamince
spiralis. The sulcus has two lips, upper and lower. The upper is called the
labium vestibulare, the upper surface of which is marked by several interlacing
prominences and grooves. At the free margin of this labium the prominences
assume the form of tooth-like projections, which are known as the auditory
teeth. The lower lip of the sulcus is called the labium tympanicum. It is continued into the basilar membrane, and is perforated by a great number of apertures
for the branches of the cochlear division of the auditory nerve.
 
Spiral Organ (of Corti).—Over the upper surface of the inner part
(zona arcuata) of the basilar membrane the epithelium undergoes
 
 
 
Fig. 1040.—The Organ of Corti (Wiedersheim, after Lavdowsky).
 
 
1. Spiral Ligament
 
2. Limbus
 
3. Sulcus Spiralis
 
4. Inner Rod of Corti
 
5. Outer Rod of Corti
 
6. Tunnel of Corti
 
7. Phalangeal Process of Outer Rod
 
8. Inner Hair-cells
 
 
9. Outer Hair-cells
 
10. Cells of Deiters
 
11. Lamina Reticularis
 
12. Cells of Hensen
 
13. Cells o Claudius
 
14. Spiral Ganglion
 
15. Cochlear Nerve
 
16. Nerve-fibres to Hair-cells
 
 
remarkable modification, and gives rise to the spiral organ or organ
of Corti. The constituent parts of this very complicated organ are as
 
follows:
 
1 The rods of Corti. 4. The cells of Hensen and of Claudius.
 
2 The auditory or hair cells. 5 - The lamina reticularis.
 
3! The cells of Deiters. 6. The membrana tectona.
 
The rods of Corti are arranged in two rows, inner and outer (see
Fig 1041). Each rod consists of a foot-plate or base, an intermediate
portion, and a head. The foot-plate, which is expanded, rests upon
the zona arcuata of the basilar membrane, and the foot-plates of the
inner rods are separated from those of the outer rods by a slight
interval. As the rods rise the intermediate portions of the inner and
 
 
 
 
 
 
1692
 
 
A MANUAL OF ANATOMY
 
 
outer rods incline towards each other, and the heads of the two sets
of rods come into contact. In this manner a triangular tunnel is
enclosed between the two sets of rods and the basilar membrane,
which is called the tunnel of Corti. This extends along the entire
length of the ductus cochlearis.
 
 
phalangeal
 
PROCESS
 
 
IfSNER ROD
 
 
 
BASILAR. MEMBRANE
 
 
The inner rods are more numerous than the outer, there being from
5,000 to 6,000 of the former and about 4,000 of the latter. They
incline upwards and outwards. The head of each has a concavity on
its outer side, above and below which there is a projecting portion, so
 
that it resembles the upper extremity
of the ulna, with its great sigmoid
cavity and olecranon and coronoid
processes. The concavity on the head
of the inner rod receives the round
head of the outer rod. Finally, the
tic. 1041. A Pair of Rods of inner rods are shorter than the outer.
Corti from the Rabbit’s Coch- The ou + pr rn d<? lpcc nnmprrmQ
 
lea (Side View, highly mag- An ? ouler * oas j ^ re . Aess nui ? e 5 , 0US
 
nified) (Schafer, in Quain’s ? nd lon § er than the inner, and they
 
‘Anatomy’). ~ incline upwards and inwards. The
 
head of each is divisible into two
parts—inner and outer. Ihe inner part is round, and is received
mto the concavity on the outer aspect of the head of the inner rod.
The outer part is prolonged into a beak-like projection, called the
phalangeal process, which forms part of the lamina reticularis, to be
presently described.
 
The auditory or hair cells are arranged in two sets—inner and
outer. Ihe inner hair-cells lie internal to the row of inner rods, and
form a single row. They are from 3,000 to in number. Their
 
free extremities, which lie close to the heads of the inner rods, are each
provided with a tuft of short, hair-like filaments. The deep, nucleated
ends of the cells are related to the terminal arborizations of nervefibres. Internal to the row of inner hair-cells there are two or more
rows of columnar cells, which are continuous with the columnar
epithelium of the sulcus spiralis laminae. The outer hair-cells are
disposed in three or four rows external to the outer row of rods. They
are much more numerous than the inner hair-cells. Their free extremities, like those of the inner cells, are each provided with a tuft
of short, hair-like filaments, and their deep, nucleated ends are related
to the terminal arborizations of nerve-fibres.
 
 
1 he cells of Deiters, which are sustentacular, are situated between
the rows of outer hair-cells. Each cell is nucleated and contains a
slender filament, known as the sustentacular filament or phalangeal
process. This filament is attached by its base to the basilar membrane, and is prolonged into the tapering upper end of the cell. It
terminates in an expansion, which forms a phalanx of the lamina
reticularis, to be presently described.
 
The cells of Hensen are disposed as a continuous layer external
to the lamina reticularis.
 
 
 
 
THE EAR 1693
 
External to the cells of Hensen there are the cubical or columnar
cells of Claudius: these are merely an epithelial lining layer.
 
The reticular lamina extends between the heads of the rods of
Corti and the cells of Hensen. It consists of phalanges, which are
arranged in two (or more) rows—inner and outer. The phalanges of
the inner row are formed by the phalangeal processes of the heads of the
outer rods of Corti. The phalanges of the outer row (or rows) are
formed by the phalangeal processes of the cells of Deiters. Between
the phalanges there are openings through which the outer ends of
the outer hair-cells, with their crescentic tufts of hair-like filaments,
project.
 
The membrana tectoria, or membrane of Corti, which is elastic,
is the most superficial structure in connection with the spiral organ.
It extends from the limbus spiralis near, and external to, the attachment of the vestibular membrane to the region of the outer hair-cells.
It covers (1) the limbus laminae spiralis; (2) the labium vestibulare,
 
 
 
 
- Hehcotrema
 
 
Scala Vestibuli
 
 
Membranous Spiral
Lamina
 
 
Scala Tympani
 
 
1
 
1
 
Expansion of Cochlear Nerve
 
Fig. 1042.—Section of the Cochlea, showing the Distribution of the
Cochlea Branch of the Auditory Nerve (magnified) (Hirschfeld
and Reveille).
 
and the auditory teeth; (3) the sulcus laminae spiralis; (4) the inner
hair-cells; (5) the inner and outer rods of Corti; (6) the cells of Deiters;
and (7) the lamina reticularis.
 
Auditory Nerve.—The auditory nerve, within the meatus auditorius
internus, breaks up into two divisions—vestibular and cochlear.
 
The vestibular nerve, as it traverses the meatus auditorius internus, has a gangliform enlargement, the vestibular ganglion, and
divides into three branches. These enter the vestibule through the
foramina in the superior vestibular area of the lamina cribrosa at the
deep end of the internal meatus. They are distributed to the macula
utriculi and to the cristae acusticas of the ampullae of the superior
and external semicircular canals.
 
The cochlear nerve in the meatus auditorius internus divides into
two branches—one to the macula sacculi, and the other to the crista
of the ampulla of the posterior semicircular canal. The filaments of
the former, which has a gangliform enlargement, pass through the foramina in the inferior vestibular area of the lamina cribrosa, and the
 
 
 
 
 
 
 
 
 
 
 
 
A MANUAL OF ANATOMY
 
 
1694
 
latter passes through the foramen singulare in the lamina cribrosa.
The cochlear nerve, having parted with these two branches, breaks
up into filaments which pass through the foramina of the cochlear
area of the lamina cribrosa, and so reach the base of the modiolus
of the cochlea. They traverse the canals of the modiolus, from which
they pass into the canals between the two layers of the lamina spiralis.
In doing so they have to cross the spiral canal of the modiolus, which
is situated close to the attached margin of the lamina spiralis. This
canal contains a ganglion, called the spiral ganglion, which follows
the windings of the canal, and contains bipolar nerve-cells. As the
auditory fibres pass from the canals of the modiolus into those of
the lamina spiralis the course of each fibre is probably interrupted
by a bipolar cell of the spiral ganglion. The nerve-fibres, leaving
these bipolar cells, traverse the canals between the two layers of the
lamina spiralis. Having lost their medullary sheaths, they pass
through the foramina of the labium tympanicum on the outer margin
of the limbus spiralis, and enter the basilar membrane, where they
end in arborizations which are connected with the inner and outer
hair-cells.
 
Blood-supply of the Labyrinth.—The labyrinth derives its blood
from the internal auditory, which is a branch of the basilar artery
or of the anterior inferior cerebellar. The vessel traverses the meatus
auditorius internus, and divides at its deep end into two branches—
vestibular and cochlear. The vestibular artery supplies the utricle,
saccule, and semicircular canals, and the cochlear artery supplies the
cochlea.
 
The veins of the labyrinth ultimately join to form one vessel, called
the internal auditory vein, which opens into the inferior petrosal
sinus. The aqueductus cochleae and the aqueductus vestibuli each
transmit a vein; that which passes through the former joins the inferior
petrosal sinus or the bulb of the internal jugular vein, and that which
passes through the latter opens into the superior petrosal sinus.
 
 
Development of the Ear.
 
Internal Ear—Membranous Labyrinth. —The membranous labyrinth is
developed from the surface ectoderm in a manner similar to the development
of the crystalline lens. Over a circumscribed area, corresponding to the upper
end of the first visceral cleft, and upon the side of the hind-brain, the ectoderm
becomes thickened and invaginated. A depression is thus formed, which is
called the auditory pit. This pit becomes deepened, its mouth becomes constricted, and its lips, coming together, unite. The auditory pit then becomes
transformed into a closed sac, called the auditory or otic vesicle, or otocyst.
The auditory vesicle now becomes isolated from the surface ectoderm, and sinks
into the adjacent mesoderm, taking up a position close to the side of the hindbrain.
 
The auditory vesicle, which is at first almost spherical, soon becomes pyriform, this being due to the formation of a process, called the recess of the labyrinth
or vestibule, which is prolonged from its dorsal wall. As this process lengthens
it gives rise to the ductus endolymphaticus, which occupies the aqueductus
vestibuli of the petrous portion of the temporal bone. The expanded terminal
 
 
 
THE EAR
 
 
1695
 
part of the ductus endolymphaticus is called the saccus endolymphaticus, and it
lies underneath the dura mater. The ventral aspect of the vesicle gives off a
tapering diverticulum, which gives rise to the ductus cochlearis, or scala media,
of the cochlea. This duct describes a bend, within which lies the cochlear
ganglion of the cochlear division of the auditory nerve. As the duct elongates
it continues to bend in a spiral manner, and so the ductus cochlearis is formed.
The cochlear ganglion elongates, and follows the spiral turns of the duct, from
which circumstance the ganglion is known as the ganglion spirale.
 
The three semicircular ducts are developed from the upper or cephalic part
of the auditory vesicle, this part representing the future utricle. This portion
of the vesicle presents two folds—vertical and horizontal. From the vertical
fold the superior and posterior semicircular canals are formed, whilst the horizontal fold gives rise to the lateral semicircular canal.
 
The auditory vesicle now becomes transversely constricted, and is divided
into two sacs—large and small. The large sac is called the utricle, from which
the semicircular ducts have just been developed. The small sac is called the
saccule, from which the ductus cochlearis has been developed. The portion
of this duct which communicates with the saccule becomes constricted, and
forms the canalis reuniens of Hensen.
 
The constriction which completely divides the auditory vesicle into utricle
and saccule also involves the vesicular end of the ductus endolymphaticus, and
divides it into two ducts, called the ductus utriculi and ductus sacculi. This
arrangement constitutes the only communication which now exists between the
utricle and the saccule.
 
As stated, the cochlear ganglion, or ganglion spirale, of the cochlear division
of the auditory nerve lies within the spiral turns of the ductus cochlearis. As
the osseous cochlea becomes formed, the ganglion spirale comes to occupy the
spiral canal of the modiolus. The vestibular ganglion of the vestibular division
of the auditory nerve lies in the internal auditory meatus after the completion
of ossification.
 
The membranous labyrinth, hitherto considered, is entirely epithelial.
Certain of its epithelial cells undergo important specializations to fit them for
sensorial purposes. These cells form six groups in definite regions. These groups
are as follows: (1) The crista acustica ampullaris, of which there are three, one in
the ampulla of each of the three epithelial semicircular canals; (4) the macula
(1 acustica) utriculi’, (5) the macula ( acustica) sacculi', and (6) the spiral organ {of
Corti), specialized from the epithelial ductus cochlearis. The groups connected
with the ampullae of the semicircular canals, the utricle, and the saccule, receive
their nerve-fibres from the vestibular ganglion of the vestibular division of the
auditory nerve. The organ of Corti receives its nerve-fibres from the cochlear
ganglion, or ganglion spirale, of the cochlear division of the auditory nerve.
 
Osseous Labyrinth. —The membranous labyrinth is surrounded by mesodermic
tissue, which becomes disposed in four layers. These layers, from within outwards,
may be spoken of as (1) the connective-tissue layer, (2) the gelatinous layer,
(3) the perichondrial layer, and (4) the cartilaginous layer. The connectivetissue layer forms the connective tissue of the various parts of the epithelial
labyrinth. The fibrous tissue of the gelatinous layer acquires vacuoles, and gives
place to the various perilymphatic spaces, which contain a fluid called the perilymph. In the case of the cochlea, the scala vestibuli and scala tympani alone
contain perilymph, the cochlear duct containing endolymph. The perichondrial
layer forms the lining perichondrium of the periotic cartilaginous capsule, and
subsequently becomes the lining periosteum of the osseous labyrinth. The
cartilaginous layer forms the periotic cartilaginous capsule, which undergoes
ossification, and gives rise, amongst other parts, to the osseous labyrinth, which
jg q£ i ar ger size than the membranous labyrinth. The osseous semicircular canals
conform in shape to the membranous semicircular ducts, but are of larger size.
The osseous vestibule differs from the membranous vestibule in being a single
osseous case, whereas its contents are the utricle and the saccule.
 
Whilst the perilymph lies external to the membranous labyrinth, the interior
 
 
1696
 
 
A MANUAL OF ANATOMY
 
 
of the semicircular ducts, utricle, saccule, and scala media contain endolymph,
the latter being in communication with the saccule by means of the canal is
reuniens.
 
The middle ear or tympanum and pharyngo-tympanic tube (see p. 73 et seq.)
 
are developed from the tubo-tympartic recess of the pharynx. This is the widest
part of the early pharynx, opposite the second and third arches, and by the
time the embryo has reached the second month of development the recess is
definitely indicated; it projects laterally with its contained cavity, compressed
dorso-ventrally, widely open into the general pharyngeal cavity. Its roof
supports the otic capsule, while the outer parts of the first two visceral grooves
are seen in its floor, with the second arch between them. It is bounded in
front by the first arch, and caudally by the third arch. The first lateral pouch,
on its lateral edge, is in contact with the persistent upper end of the first outer
groove; the second pouch, which has lost contact, is at its postero-lateral angle.
The recess deepens, and the third arch grows forward, cutting off the outer part
of the cavity from the pharynx and narrowing the anterior part, which still
remains continuous with the pharynx; the outer and larger part is the early
tympanum, and the constricted front portion becomes the tube.
 
The otic capsule enlarges and chondrifies, and as it grows depresses the
inner part of the tympanum, slightly rotating it, so that its former roof now
becomes its inner wall, applied to the surface of the capsule. Its floor, also
rotated, now slopes downwards and medially, and is in close relation with the
meatal plate, a cellular ingrowth from the upper end of the first outer groove;
this has grown in below the tympanum, and by a later process of hollowing
forms the ectodermal lining of the outer meatus and membrane.
 
Meckel’s cartilage develops in the mesoderm of the first arch, therefore
antero-lateral to the recess, in front of the position of the first pouch. It sends
an extension over the pouch to invade the second arch area behind this, passing
under the floor between the endoderm and the meatal plate; this extension forms
the basis of the tympanic membrane and the manubrium, and its upper part probably also forms the incus. The hyoid bar (Reichert’s cartilage), the bar of the
second arch, is behind this, immediately in front of the second pouch; an exten
sion from its upper end over the roof gives rise to the stapes. The stapes becomes
associated with the cartilaginous capsule, which has enlarged considerably; the
enlargement extends postero-laterally, and leads to the fusion of Reichert’s bar
with the capsule (tympano-hyal) and the position of the remnant of the second
pouch in the fossula rotunda (fenestra cochleae).
 
The chorda tympani crosses the first pouch; the level of the early tympanum
might roughly be taken as extending up to this nerve. The higher level of the
adult cavity is attained by a later extension. In the early condition of the
tympanum, the malleus, incus, stapes, and chorda tympani nerve lie embedded
in the mesodermic tissue which intervenes between the epithelial or mucous
roof of the membranous tympanum and its osseous roof. This mesodermic
tissue disappears, and the mucous (originally epithelial) lining of the tympanum
now comes into direct contact with the malleus, incus, stapes, and chorda
tympani nerve, all of which it encloses within folds. Though these structures
apparently lie within the tympanic cavity, this is not their actual position. They
are really outside the cavity, inasmuch as they lie external to the mucous lining of
the cavity. This may be illustrated by stating that the handle or manubrium
of the malleus and the chorda tympani nerve do not lie in the tympanic cavity,
but are placed between the middle, or fibrous, layer and the internal, or mucous,
layer of the membrana tympani.
 
External Ear.— AThe external ear consists of (1) the external auditory meatus,
including the membrana tympani, and (2) the pinna.
 
The external auditory meatus is developed from the upper part of the first
external or ectodermic furrow, which corresponds in position to the first
internal visceral cleft.
 
The membrana tympani is developed from the closing membrane which
separates the first internal visceral cleft from the first external ectodermic furrow.
 
 
THE EAR
 
 
1697
 
This closing membrane is a trilaminar structure. Its inner layer consists of
entoderm; its middle layer of mesoderm; and its outer layer of ectoderm. The
membrana tympani, which is developed from it, is therefore trilaminar. The
outer layer is ectodermic, and is continuous with the cuticular lining of the external
auditory meatus; the middle layer is mesodermic, or fibrous; and the inner layer
is entodermic, or mucous, and is continuous with the mucous lining of the
tympanic cavity.
 
The component parts of the pinna are developed from six projections, consisting of mesoderm, covered by ectoderm. These appear on the upper ends
of the first and second visceral arches, where these bound the upper part of
the first external ectodermic furrow, which gives rise to the external auditory
meatus. The helix is developed from two of these tubercles, and each of the
other four gives rise to the antihelix, tragus, antitragus, and lobule. The mesodermic tissue of the projections becomes differentiated into connective tissue
and cartilage, and the ectoderm covers these.
 
 
107
 
 
GLOSSARY
 
 
Terms still in common use, though now ‘discardedare included in this list,
with a certain number of proper names coming in the same category.
 
 
Abdomen, a word of uncertain derivation, but possibly from abdo,
I hide or conceal.
 
Aberrant, wandering from the normal
source.
 
Acervulus, a little heap.
 
Acervulus cerebri, brain-sand.
 
Acetabulum, a vessel for holding
vinegar; a juggler’s cup. But
used by Pliny to signify hipsocket.
 
Acinus, any juicy berry with stones
— e.g., the grape; the kernel in the
berry.
 
Acrocephalous, having a pointed or
conical head.
 
Acromion, the point or summit of
the shoulder.
 
Acusticus, a, um, pertaining to sound,
or to the sense of hearing.
 
Adamantoblast, enamel germ cell.
 
Adductor canal, subsartorial canal.
 
Adenoid, glandular.
 
Aditus, an approach or access.
 
Adrenal, near to the kidney.
 
Advehens, carrying to.
 
Afferent, carrying to.
 
Agger, a mound or rampart.
 
Agminated, disposed in columns.
 
Ala, a wing.
 
Ala cinera, vagal triangle.
 
Albicans, white.
 
Albuginea, whitish.
 
Alcock’s canal, pudendal canal.
 
Allantois, sausage-like.
 
Alveolus, a little trough.
 
Alveus, a trough.
 
Amacrine, without a long fibre.
 
Ambiguus, dark, obscure.
 
Ameloblast, enamel germ.
 
Ammonis, cornu, horn of Ammon,
who was represented as having
the head of a ram.
 
 
Amphiarthrosis, literally, articulation on both sides. Secondary
cartilaginous joint (fibro-cartilage).
 
Ampulla, a flask.
 
Amygdala, an almond.
 
Anastomosis, literally, an outlet; the
communication of branches of
vessels with one another.
 
Anconeus, pertaining to the elbow.
 
Ankylosis, bony union between two
bones which are normally separate.
 
Annulus, a little ring.
 
Ansa, a handle, loop, or brace.
 
Ansa cervicis, ansa hypoglossi.
 
Anserinus, pertaining to a goose.
 
Antecubital, in front of the elbow.
 
Antibrachium, forearm.
 
Anticubital fossa, cubital fossa.
 
Anticus, in front, anterior.
 
Antinion, opposite to the inion.
 
Antrum, a cave or cavity.
 
Antrum of Highmore, maxillary
sinus.
 
Antrum, mastoid, tympanic antrum.
 
Anus, a ring.
 
Aorta, literally, the lower end of the
trachea; a carrier.
 
Apertura piriformis, anterior aspect
of nose.
 
Aponeurosis, an expansion from a
tendon.
 
Aponeurosis, lumbar, lumbar fascia.
 
Aponeurosis, pharyngeal, pharyngobasilar fascia.
 
Apophysis (‘ grow from ’), a process
or swelling on a bone.
 
Appendix ventriculi laryngis, saccule.
 
Aqueductus cerebri, aqueduct of
 
 
mid-brain.
 
Aqueductus Fallopii, facial canal.
Arachnoid, like a spider’s web.
 
1698
 
 
 
 
GLOSSARY 1699
 
 
Arantii, corpus, nodule (in cusps of
aortic and pulmonary valves).
 
Archenteron, primitive intestine.
 
Arcuatus, curved.
 
Area acustica, vestibular area.
 
Areola, a small open place.
 
Arnold’s ganglion, otic ganglion.
 
Arnold’s nerve, tympanic nerve.
 
Artery, literally, an air vessel; the
trachea was known as the arteria
aspera; a bloodvessel which carries
the blood from the heart.
 
Arthrodia, from the Greek word
meaning * a joint ’; applied to a
gliding joint.
 
Arthrosis, plane joint.
 
Arytenoid, pitcher-like.
 
Ascending frontal convolution, precentral convolution.
 
Ascending parietal convolution, postcentral convolution.
 
Aspera, rough.
 
Asterion, a star.
 
Astragalus, the ankle-bone; a die
(pi. dice); talus.
 
Atlas, a support; refers to Atlas,
who carried the earth on his
neck.
 
Atresia, imperforation.
 
Atrium, the hall in a Roman house.
 
Attic, epitympanic recess.
 
Attollens, raising up, elevating.
 
Attrahens, drawing to or towards.
 
Auditory, pertaining to the organ, or
sense, of hearing.
 
Auerbach’s plexus, myenteric plexus.
 
Auricle, the external ear.
 
Auricle (O.T.), atrium (heart).
 
Auricular appendix (O.T.), auricle.
 
Azygos, without a pair, single.
 
Bacillary, pertaining to a small staff
or rod.
 
Balanus, an acorn.
 
Barba, a beard.
 
Bartholin’s duct (great duct of Rivini),
 
principal sublingual duct.
 
Basilar, belonging to the base.
 
Basilic, royal, important.
 
Basion, base.
 
 
Bechterew, nucleus of, superior
vestibular nucleus.
 
Bell, nerve of, nerve to serratus
anterior.
 
Bellini, ducts of, terminal collecting
tubules of kidney.
 
Biceps, having two heads.
 
Bicornis, two-horned.
 
Bicuspid (teeth), pre-molar.
 
Bigelow, Y-shaped ligament of, iliofemoral ligament.
 
Biventer, having two bellies.
 
Bowman’s capsule, capsule of glomerulus.
 
Bowman’s membrane, anterior elastic lamina of cornea.
 
Brachium, the arm.
 
Brachium conjunctivum, superior
cerebellar peduncle.
 
Brachium pontis, middle cerebellar
peduncle.
 
Brachycephalic, short-headed.
 
Bregma, from a Greek verb meaning
‘ to moisten/
 
Broca, area of, parolfactory area.
 
Broca, band of, diagonal band.
 
Bronchiole, a little bronchus.
 
Bronchus, literally, a draught; the
windpipe.
 
Bryant’s triangle, (1) horizontal line
from anterior superior spine;
(2) vertical line from top of great
trochanter; (3) line joining anterior superior spine to top of
great trochanter.
 
Bubonocele, a variety of tumour in
the groin.
 
Buccinator, a trumpeter.
 
Bulla, a knob; a bubble.
 
Burdach, fasciculus of, fasciculus
cuneatus.
 
Burns, falciform process of (ligament
of Hey), superior cornu of saphenous opening.
 
Burns’ space, suprasternal space.
 
Bursa, a sac containing fluid.
 
Bursa omentalis, lesser sac.
 
Cacumen, tip, peak, or end.
 
Caecum, blind.
 
 
 
 
 
 
 
GLOSSARY
 
 
1700
 
Caeruleus, dark blue.
 
Calamus, a reed-pen.
 
Calcaneum, the heel.
 
Calcar, a spur.
 
Calcination, reduction to a powder
(or line) by heat.
 
Calcis, of the heel.
 
Calix, a cup or goblet.
 
Callosal convolution, gyrus cinguli.
 
Calloso-marginal fissure, sulcus cinguli.
 
Callosum, hard, thick.
 
Calvaria ( calva , the bald scalp), the
upper part of the skull.
 
Canalis reuniens, ductus reuniens.
 
Cancellated, lattice-formed, reticulated.
 
Canthus, the angle of the eye.
 
Capillary, pertaining to the hair;
a vessel of hair-like minuteness.
 
Capitellum, a small head.
 
Capsular, suprarenal.
 
Caput gallinaginis, urethral crest.
 
Caput medusae, varicose veins radiating from umbilicus in portal
obstruction.
 
Cardia, the opening of the stomach;
the heart.
 
Cardiac, pertaining to the heart
(originally to the stomach).
 
Cardinal, principal or chief.
 
Carina, a keel.
 
Carneae, pertaining to flesh.
 
Carotid, stupefying; or perhaps from
two Greek words meaning ‘ head ’
and ‘ ear.’
 
Carpus, the wrist.
 
Cartilages, alar, lower lateral cartilage.
 
Cartilages, lateral, upper lateral cartilage (of nose).
 
Cartilages, Santorini, of, corniculate
cartilage.
 
Cartilages, Wrisberg, of, cuneiform
cartilage.
 
Caruncula, a little piece of flesh.
 
Caruncula sublingualis, sublingual
papilla.
 
Carunculae myrtiformes, carunculae
hymenales.
 
 
Cauda, a tail.
 
Caudate, tailed.
 
Caudate lobe (O.T.), tail of caudate
lobe.
 
Cavernous, full of hollows or cavities.
 
Centimetre (cm.), § of an English
inch.
 
Cephalic, pertaining to the head.
Cerato, horny.
 
Ceruminous, pertaining to wax.
Chiasma, two lines placed like an X.
Choana, a funnel.
 
Choanse, posterior apertures of nose.
Choledochus, bile-receiving.
Chondral, pertaining to cartilage.
 
Choroid (Chorioid), like skin.
Cinereus, ash-coloured.
 
Cingulum, a small girdle.
Circumflexus, bent around.
Circumvallate papillae, vallate papillae.
 
Cisterna, a cistern or reservoir.
Clarke, posterior vesicular column of,
 
thoracic (dorsal) nucleus.
Claustrum, a bulwark, barrier, or
inclosure.
 
Clava, a club; gracile tubercle.
Clavicle, from clavis, a key, or possibly a hoop-stick.
 
Cleido-, pertaining to the clavicle.
Clinoid, like the knob of a bedpost.
Clitoris, from a Greek verb meaning
‘ I shut up ’ or ‘ enclose.’
 
Clivus, a slope.
 
Cloaca, a sewer or drain.
 
Coccyx, a cuckoo.
 
Cochlea, a snail.
 
Cochlea, membranous, duct of cochlea.
 
Cochleariformis, spoon-like.
 
Coeliac, pertaining to the belly.
Colliculus, a little hill.
 
Colliculus, quadrigeminal body.
Colliculus seminalis, urethral crest.
Colon, the great gut.
 
Columns, rectal (Morgagni), anal
columns.
 
Comes, a companion.
 
Comma tract, semilunar tract.
 
 
 
 
 
 
GLOSSARY
 
 
Complexus, literally, folded together;
encompassing.
 
Concatenatae, chained together.
Concatenate glands, deep cervical
(lymph) glands.
 
Concha, a shell.
 
Condyle (‘ knuckle ’), a small round
prominence covered by cartilage.
Coni vasculosi, lobules of epididymis.
Conjunctiva, connecting.
Conniventes, winking or blinking.
Conoid, cone-like.
 
Conoid tubercle, coracoid tuberosity.
Conus arteriosus, infundibulum.
Conus elasticus, crico-vocal membrane.
 
Convoluta, rolled together.
 
Coracoid, like a crow or raven.
 
Cord, vocal, false, vestibular folds.
Cord, vocal, true, vocal fold.
Cordiform, heart-shaped.
 
Cords (gangliated, lumbo-sacral,
etc.), trunks.
 
Cornea, horny.
 
Corniculum, a little horn.
 
Cornu ammonis, hippocampus.
Coronal, literally, pertaining to a
crown; transverse.
 
Coronary, encircling.
 
Coronoid, like a crooked beak.
Corpora albicantia (brain), corpora
mamillaria.
 
Corpus (of long bone), shaft.
 
Corpus adiposum buccae, buccal pad.
Corpus arantii, nodule (aortic and
pulmonary valves).
 
Corpus cavernosum penis, corpus
cavernosum.
 
Corpus cavernosum urethrae, corpus
spongiosum.
 
Corrugator, a wrinkler.
 
Cortex, the bark or outer covering.
Costal, pertaining to a rib.
 
Cotyloid, cup-like.
 
Cowper’s gland, bulbo-urethral gland.
Coxa, the hip.
 
Cranium, the skull.
 
Crassum, thick, dense, or bulky.
Cremaster, a suspender.
 
Cribriform, sieve-like.
 
 
1701
 
Cribrosa, perforated with sieve-like
pores.
 
Cricoid, like a ring.
 
Crista tuberculi majoris, lateral lip
of bicipital groove.
 
Crista tuberculi minoris, medial lip
of bicipital groove.
 
Crucial, pertaining to, or shaped like,
a cross.
 
Crural, pertaining to the leg.
 
Crural canal, femoral canal.
 
Crural ring, femoral ring.
 
Crural septum, femoral septum.
 
Crus, cerebral peduncle.
 
Crusta, basis pedunculi.
 
Cryptorchismus, concealment of the
testis.
 
Cryptozygous, hidden arches.
 
Cubitum, the elbow.
 
Cucullaris, pertaining to a cowl or
hood.
 
Culmen, the top or summit.
 
Cuneate, wedge-shaped.
 
Cuneiform bone (hand), triquetrum.
 
Cuneus, a wedge.
 
Cupola, a dome.
 
Cymba, a boat or skiff.
 
Cystic, pertaining to the gall-bladder.
The condition of a thin-walled
swelling containing fluid or semifluid.
 
Cytoplasm, formative yolk; protoplasm in a cell.
 
Dacryon, a tear.
 
Dartos, skinned or flayed.
 
Deciduous, falling away.
 
Decussation of lemnisci (fillet), sensory decussation.
 
Deferens, carrying away.
 
Deiters, nucleus of, lateral vestibular
nucleus.
 
Dens, odontoid process.
 
Dens serotinus, wisdom tooth.
 
Dentate fascia, dentate gyrus.
 
Descemet’s membrane, posterior elastic lamina of cornea.
 
Detrusor, from detrudo, I drive away.
 
Deutoplasm, literally, wet plasm;
nutritive yolk.
 
 
 
 
 
 
1702
 
 
GLOSSARY
 
 
Dia-, through or between.
 
Diaphragm, a partition.
 
Diaphysis grow between ’), the
shaft of a bone, or the part which
grows between the epiphyses.
 
Diarthrosis, an ‘ apart ’ joint— i.e.,
a ‘ free ’ joint (the articular surfaces being free to play upon each
other); synovial joint.
 
Diencephalon, the ’tween-brain or
inter-brain; thalamencephalon.
 
Digastric, having two bellies.
 
Diploe, a doubling.
 
Discus proligerus, cumulus ovaricus.
 
Diverticulum, from diverto, ‘ I separate/ or ‘ part/ or ‘ go a different
way.’
 
Dolichocephalic, long-headed.
 
Dorsal, pertaining to the back
aspect.
 
Dorsum, the back.
 
Douglas, pouch of, recto-uterine or
recto-vaginal pouch.
 
Douglas, semilunar fold of, arcuate
line.
 
Duct, nasal, naso-lacrimal duct.
 
Ductus deferens, vas deferens.
 
Ductus perilymphaticus, aqueduct of
cochlea.
 
Duodenum, twelve (probably fingerbreadths) .
 
Ebur, -oris, ivory.
 
Eburnea, pertaining to ivory.
 
Ectopia, a displacement.
 
Efferent, carrying out.
 
Embolif ormis, beak-shaped or wedgeshaped.
 
Emissary, sent out.
 
Emulgent, milking, straining out.
 
Enarthrosis, ball-and-socket joint.
 
Encephalon, the contents of the head
or skull.
 
Endocardium, ‘ within the heart ’;
the lining membrane of the cardiac
chambers.
 
Endognathion, literally, inner jaw.
 
Endosteum, ‘ within a bone ’; the
medullary membrane.
 
Ensiform, sword-like.
 
 
Ensiform process, xiphoid process.
 
Entomion, a notch.
 
Ependyma, from Greek words meaning ' clothing upon/
 
Ephippium, a saddle.
 
Epi-, upon or over, above.
 
Epicardium, upon the heart.
 
Epididymis, upon the testicle.
 
Epiglottis, cushion of, tubercle of
epiglottis.
 
Epiotic, upon or over the ear.
 
Epiphysis (‘ grow upon ’); a process
of a bone which has a secondary
centre of ossification.
 
Epiploon, from a Greek verb meaning
‘ to float upon/
 
Epipteric, upon a wing.
 
Epipteric bone, sutural bone at
pterion.
 
Epistropheus, axis.
 
Epoophoron, above the egg-bearing
organ.
 
Erythroblast, red (cell) germ.
 
Ethmoid, like a strainer.
 
Eustachian cushion, tubal elevation.
 
Eustachian spine (of medial pterygoid plate), processus tubarius.
 
Eustachian tube, pharyngo-tympanic
tube.
 
Eustachian valve, valve of inferior
 
vena cava.
 
Exognathion, literally, outer jaw.
 
Exomphalos, out of the navel.
 
Facet (French, facette, a little face),
a small plane surface, usually
articular.
 
Falciform, sickle-like.
 
Fallopian tube, uterine tube.
 
Falx, a sickle.
 
Falx aponeurotica inguinalis, conjoint tendon.
 
Fascia, a bandage, or a bundle of
reeds.
 
Fascia bulbi, fascial sheath of eyeball.
 
Fascia, Camper’s, superficial layer of
superficial fascia of anterior abdominal wall.
 
Fascia, Colies’, deep layer of superficial fascia of perineum.
 
 
 
 
/
 
 
 
 
GLOSSARY
 
 
1703
 
 
Fascia, coraco-clavicular, clavi-pec
toral fascia.
 
Fascia infundibular, internal spermatic fascia.
 
Fascia intercolumnar, external spermatic fascia.
 
Fascia, Scarpa’s, deep layer of superficial fascia of anterior abdominal
wall.
 
Fascia, Sibson’s, suprapleural membrane.
 
Fasciculus, a small bundle.
 
Fasciola cinerea, splenial gyrus.
 
Fastigium, a roof.
 
Fauces, the throat.
 
Fauces, anterior pillar, glosso-palatine arch.
 
Fauces, posterior pillar, pharyngopalatine arch.
 
Fel, the gall-bladder.
 
Femur, the thigh.
 
Fenestra, an opening, a window.
 
Fenestra ovalis, fenestra vestibuli.
 
Fenestra rotunda, fenestra cochleae.
 
Ferruginea, pertaining to iron-rust.
 
Fibula, a buckle, clasp, or brace.
 
Fillet, lemniscus.
 
Filum, a thread.
 
Fimbria, a fringe.
 
Fimbriatum, fringed.
 
Fissure, a cleft or slit.
 
Fistula, .a pipe or tube.
 
Flechsig, tract of, posterior spinocerebellar tract.
 
Flocculus, a little lock of wool.
 
Fold, bloodless (Treves), ileo-caecal
fold.
 
Fold, ileo-colic, vascular fold of
caecum.
 
Fold, recto-vesical, sacro-genital fold.
 
Follicle, a small bag or sac.
 
Fontana, spaces of, spaces of iridocorneal angle.
 
Fontanelle, a small spring.
 
Foramen, an aperture or a hole.
 
Forceps, a claw of a beetle.
 
Fornicatus, pertaining to an arch.
 
Fornix, an arch or a vault.
 
Fossa, a ditch or trench.
 
Fossa, antecubital, cubital.
 
 
Fossa ovalis, saphenous opening.
 
Fossa, rhomboid, floor of fourth
ventricle.
 
Fossa, spheno-maxillary, pterygopalatine fossa.
 
Fourchette, a fork.
 
Fovea, a small pit.
 
Foveola, a very small pit.
 
Frenulum, a small bridle.
 
Frenum, a bridle.
 
Frontal, pertaining to the forehead.
 
Frontal spine (of frontal), nasal spine.
 
Fundiform, sling-like.
 
Funicular, pertaining to a cord.
 
Funiculus, a slender rope, a cord.
 
Furcalis, pertaining to a two-pronged
fork.
 
Furcula, a small two-pronged fork.
 
Fusca, dark or dusky.
 
Galactophorous, milk-carrying.
 
Galea, a helmet.
 
Galea aponeurotica, epicranial aponeurosis.
 
Galen, great vein of, great cerebral
vein.
 
Galen, veins of, internal cerebral
veins.
 
Gallinaginis, of a woodcock.
 
Gallus, a cock.
 
Ganglion, a swelling or excrescence.
 
Ganglion, aortico-renal, lower part
of coeliac ganglion.
 
Ganglion, Gasserian, trigeminal ganglion.
 
Ganglion, jugular (O.T.), superior
ganglion of ninth.
 
Ganglion, jugular (B.N.A.), superior
ganglion of tenth.
 
Ganglion, lenticular, ciliary ganglion.
 
Ganglion, Meckel’s, spheno-palatine
ganglion.
 
Ganglion nodosum (B.N.A.), inferior ganglion of tenth.
 
Ganglion, ophthalmic, ciliary ganglion.
 
Ganglion, petrous (O.T. and B.N.A.),
 
inferior ganglion of ninth.
 
Ganglion, semilunar, trigeminal ganglion.
 
 
 
 
 
 
 
 
1704
 
 
GLOSSARY
 
 
Ganglion, stellate, first thoracic
ganglion.
 
Ganglion, submaxillary, submandibular ganglion.
 
Gartner’s duct, duct of epoophoron.
Gastric, pertaining to the stomach.
 
Gastrocnemius, the belly of the
leg.
 
Gemellus, paired or double.
 
Geminus, twin or twofold.
 
Geniculate, knee-like.
 
Genio-, pertaining to the chin.
Gennari, stria of, visual stria.
 
Genu, the knee.
 
Gerota’s capsule, renal fascia.
Giacomini, banderella or frenulum,
tail of dentate gyrus.
 
Gimbernat’s ligament, pectineal part
of inguinal ligament.
 
Ginglymus, a hinge.
 
Ginglymus, hinge-joint.
 
Giraldes, organ of, paradidymis.
Glabella, without hair; smooth.
Gladiolus, a small sword.
 
Gladiolus, body of sternum.
 
Gland, Bartholin’s, greater vestibular
gland.
 
Gland, Cowper’s, bulbo-urethral
gland.
 
Glenoid, like a shallow socket.
Glisson’s capsule, hepato-biliary capsule.
 
Globosus, round or spherical.
Globus, a globe or sphere.
Glomerulus, a small ball of thread.
Glosso-, pertaining to the tongue.
Glottis, the mouthpiece of a flute.
Gluteal, pertaining to the buttock.
 
Gnathic, pertaining to the jaw.
Gnathion, the jaw.
 
Gomphosis, a bolting together.
Gonion, an angle.
 
Gracilis, slender.
 
Grisea, grey.
 
Gubernaculum, a rudder.
 
Gula, the gullet.
 
Gustatory, pertaining to taste.
Guttural, pertaining to the throat.
Gyrus, a circle; a crook.
 
 
Habenula, a small thong or rein.
Hsemorrhoidal, associated with
haemorrhoids.
 
Hallux, the great toe.
 
Ham, a thing bent or crooked.
Hamular, hook-shaped.
 
Harmonia, a fitting together.
Hartmann’s pouch, sacculation at
junction of neck and body of gallbladder.
 
Hassall, corpuscles of (thymus), concentric corpuscles.
 
Haustrum, a machine for drawing
water.
 
Heister’s valves, spiral valve.
Helicine, spiral.
 
Helicotrema, hole of a spiral.
 
Helix, a coil or spiral.
 
Hepar, the liver.
 
Hepatic, pertaining to the liver.
Hernia, a sprout; a rupture.
Hesselbach’s triangle, inguinal triangle.
 
Hiatus, a gap.
 
Hiatus Fallopii, hiatus for superficial
petrosal nerve.
 
Highmore, antrum of, maxillary
sinus.
 
Hilum, a little thing; a trifle.
 
Hippocampus, a seahorse.
Hippocampus major, hippocampus.
Hippocampus minor, calcar avis.
Hircina, pertaining to a goat.
 
His, bundle of, atrio-ventricular
bundle.
 
Homodynamic]
 
Homogenesis see Chapter I.
Homologous )
 
Houston’s valves, horizontal folds of
rectum.
 
Huguier, canal of, anterior canaliculus for chorda tympani.
 
Humerus, the upper part of the arm;
the shoulder.
 
Hunter’s canal, subsartorial canal.
Hyaline, glassv.
 
Hyaloid, like glass.
 
Hydatid, a watery vesicle.
 
Hydrocele, a watery tumour.
 
Hymen, the marriage deity.
 
 
/
 
 
 
 
 
 
 
GLOSSARY
 
 
1705
 
 
Hyoid, like the Greek letter upsilon.
 
Hypo-, beneath or under.
 
Hypophysis, ‘ grow beneath.’
 
Hypothenar, beneath the palm of the
hand.
 
Ileum, implying twists or coils.
 
Ilium, literally of the soft parts—
i.e., of the flank; os ilium, the bone
of the flank.
 
Ima, lowest.
 
Impar, dissimilar (in number), unequal.
 
Incisivus, cutting into.
 
Incisura jugularis, suprasternal notch.
 
Incisura scapularis, suprascapular
notch.
 
Incisura semilunaris (ulna), trochlear
notch.
 
Infundibuliform, funnel-shaped.
 
Infundibulum, a funnel.
 
Inguinal, pertaining to the groin.
 
Inion, literally, the occiput.
 
Innominatum, unnamed.
 
Insula, an island.
 
Intercalary, inserted.
 
Internodium, the space between two
knots or joints.
 
Interparietal bone, membranous part
of occipital as a separate bone.
 
Interpositum, placed between.
 
Interstitial, belonging to interstices
or small parts between the main
parts of bodies.
 
Intertubercular sulcus, bicipital
groove.
 
Intumescentia, enlargement (spinal
cord).
 
Iris, the rainbow.
 
Ischiatic, pertaining to the hip.
 
Ischium, the hip.
 
Isthmus, faucium, oro-pharyngeal
isthmus.
 
Isthmus rhombencephali, upper constricted end of fourth ventricle.
 
Iter, a passage or road.
 
Jacobson, cartilage of, sub-vomerine
cartilage.
 
Jacobson, organ of, vomero-nasal
organ.
 
 
Jacobson’s nerve, tympanic nerve.
 
Jejunum, empty or hungry.
 
Jugal, yolking.
 
Jugular, pertaining to the throat.
 
Jugular notch (B.N.A.), suprasternal
notch.
 
Jugum, a yolk.
 
Kerckring, ossicle, occasional centre
in posterior margin of foramen
magnum.
 
Key and Retzius, foramina of
 
(Luschka), lateral apertures of
fourth ventricle.
 
Kobelt’s tubes, epoophoron.
 
Labbe, vein of, inferior anastomotic
vein (connects superficial middle
cerebral with transverse sinus).
 
Labrum, a basin.
 
Lacertus fibrosus, bicipital aponeurosis.
 
Laciniosum, full of folds, indented,
jagged.
 
Lacrimal, pertaining to tears.
 
Lacteal, pertaining to milk.
 
Lactiferous, milk-carrying.
 
Lacuna, a hollow or cavity.
 
Lacunee (of sagittal sinus), lacunae
laterales.
 
Lacunar, pertaining to a hollow or
gap.
 
Lacunar ligament, pectineal part of
inguinal ligament.
 
Lamella, a small plate.
 
Lamina, a plate.
 
Lamina cinerea, lamina terminalis.
 
Lamina cribrosa, medial boundary
of internal auditory meatus.
 
Lamina papyracea, orbital plate of
ethmoid.
 
Lamina quadrigemina, tectum.
 
Lateral, on the side of. Used in
reference to the sagittal plane of
the body.
 
Lateral mass (ethmoid), labyrinth.
 
Lateral sinus, transverse sinus.
 
Latissimus, broadest.
 
Latum, broad.
 
Lemniscus, a ribbon.
 
 
 
 
 
 
 
1706
 
 
GLOSSARY
 
 
Leptorhine, having small narrow
nostrils.
 
Levator, a lifter or raiser.
 
Lien, the spleen.
 
Lieno-, pertaining to the spleen.
Ligament, a band or bandage.
 
Ligula, a little tongue.
 
Limbic lobe, gyrus fornicatus.
Limbous, pertaining to a border.
Limbus, a border.
 
Limbus fossae ovalis (or limbus
ovalis), annulus ovalis.
 
Limen, a threshold.
 
Linea, a line.
 
Lines, oblique (tibia), soleal line.
Lines, oblique internal (jaw), mylohyoid line.
 
Lines (occiput), nuchal lines.
 
Lines, popliteal, soleal line.
 
Lingual, pertaining to the tongue.
Lingula, a little tongue.
 
Lister’s tubercle, dorsal tubercle of
radius.
 
Longissimus, longest.
 
Longitudinal sinus, sagittal sinus.
Lower, tubercle of, intervenous
tubercle (heart).
 
Lumbar, pertaining to the loin.
Lumbricalis, like an earth-worm.
Lunar, pertaining to the moon.
Lunula, a little moon; a crescent.
Luteum, of a yellow colour.
 
Luys’ nucleus, subthalamic body.
Lymphatic, from lympha, pure or
spring water; lymph.
 
Lyra, a lyre; hippocampal commissure.
 
McBurney’s point (base of appendix),
 
junction of lower and middle
thirds of spino-umbilical line.
Macula, a spot.
 
Magendie, foramen, median aperture
of fourth ventricle.
 
Magnum, os, capitate bone.
 
Malar, pertaining to the cheek.
 
Malar bone, zygomatic bone.
Malleolus, a small hammer or mallet.
 
Malleus, a hammer or mallet.
 
 
Mamma, a breast or pap.
 
Mammilla, a little breast or pap.
Properly spelt mamilla.
 
Mandible, the chewing bone— i.e.,
lower jaw.
 
Manubrium, a handle or hilt.
 
Marshall, oblique vein, oblique vein
of left atrium.
 
Massa intermedia, interthalamic
 
connexus.
 
Masseter, the chewing muscle.
 
Mastoid, breast- or pap-like (nipplelike).
 
Maxilla, jaw.
 
Meatus (pi. Meatfis), a passage or
canal.
 
Meckel’s cave, cavum trigeminale.
 
Meckel’s diverticulum, diverticulum
ilei.
 
Mediastinum, standing in the middle;
a partition.
 
Medulla, marrow.
 
Megacephalic, having a large head.
 
Megaseme, having a large index.
 
Meibomian glands, tarsal glands.
 
Meissner’s plexus, plexus of the submucosa.
 
Membrane, costo-coracoid, clavi
pectoral fascia.
 
Meninges, membranes.
 
Meniscus, a crescent.
 
Meniscus (knee), semilunar cartilage.
 
Mental, pertaining to the chin.
 
Mesaticephalic, having a head with
an index of mean value.
 
Mesencephalon, the mid-brain.
 
Mesentery, in the middle of, or
among, the intestines.
 
Mesial, nearer to the sagittal plane
of the body.
 
Meso-, in the midst of. In compounds usually implies a structure
like a mesentery, a peritoneal attachment fold.
 
Mesocephalic, pertaining to a head
of mean capacity.
 
Mesogastrium=meso- (q.v.) and
stomach.
 
Mesognathion, middle jaw.
 
 
 
 
 
 
 
 
GLOSSARY
 
 
Mesometrium=meso- [q-v.) and
womb.
 
Mesonephros, mid-kidney.
 
Mesorhine, pertaining to an intermediate nasal index; a condition
intermediate between broad-nosed
and narrow-nosed.
 
Mesosalpinx =meso- (q.v.) and tube.
 
Mesoseme, intermediate index.
 
Meta-, after or beyond.
 
Meta-nephros, hind-kidney.
 
Metencephalon, the after-brain.
 
Metopic, pertaining to the forehead.
 
Metopism, persistence of the metopic
or frontal suture.
 
Microcephalic, pertaining to a small
head.
 
Microseme, small index.
 
Middle commissure, interthalamic
connexus.
 
Millimetre (mm.), slightly less than
2V of an English inch.
 
Minimae, least, smallest.
 
Mitral, resembling an Asiatic headdress, or mitre.
 
Modiolus, the nave of a wheel.
 
Molar, pertaining to a mill, or to
grinding.
 
Monro, foramen, interventricular
foramen.
 
Mons veneris, mons pubis.
 
Montanum, pertaining to a mountain.
 
Monticulus, a small mountain.
 
Morbus, a disease.
 
Muliebris, pertaining to a woman,
feminine.
 
Miillerian duct, para-mesonephric
duct.
 
Multangulum majus, os, trapezium.
 
Multifidus, many cleft; divided into
many parts.
 
Musculo-spiral nerve, radial nerve.
 
Myelencephalon, marrow-brain.
 
Myeloplaxes, marrow-plates.
 
Myentericus, pertaining to the muscular tissue of the bowel.
 
Mylo-, pertaining to a mill.
 
Myocardium, the muscular tissue of
the heart.
 
Myrtiform, like a myrtle-berry.
 
 
1707
 
Nares, posterior, posterior apertures
of nose.
 
Naris (pi. nares), a nostril.
 
Nasal, pertaining to the nose.
 
Natal, pertaining to the buttock.
Natis (pi. nates), the buttock.
Navicular, pertaining to a boat.
Nephros, a kidney.
 
Neural, pertaining to a nerve.
Neuroglia, literally ‘ nerve glue.’
Nictitans, winking.
 
Norma, a rule or measure (aspect).
Notochord, string or cord of the back.
Nucha, the nape of the neck.
 
Nuck, canal, vaginal process.
Nucleus, a kernel.
 
Nuhn, glands, anterior lingual (seromucous) glands.
 
Nymphae, nymphs or goddesses of
the fountains, woods, trees, etc.;
labia minora.
 
Obelion, a horizontal line (perhaps
a little spit).
 
Obex, a bolt; a barrier.
 
Obturator, one who closes or stops
up.
 
Occipital, pertaining to the back
part of the head.
 
Odontoblast, a tooth-germ.
 
Odontoid, tooth-like.
 
Odoriferae, carrying odours.
(Esophagus, food-carrier.
 
Olecranon, head or point of the
forearm.
 
Olfactory, pertaining to smell.
Olfactory trigone, olfactory pyramid.
Olivary, pertaining to an olive.
Omentum, that which is drawn over.
 
Omentum, gastro - hepatic, lesser
omentum.
 
Omentum, gastro-splenic, gastrosplenic ligament.
 
Omo-, pertaining to the shoulder.
Omphalo-, pertaining to the navel.
Operculum, a cover or lid.
 
Ophryon, the eyebrow.
 
Ophthalmic, pertaining to the eye.
Opisthion, hinder or rear.
 
Opisthotic, behind the ear.
 
 
 
 
1708
 
 
GLOSSARY
 
 
Optic, pertaining to sight.
 
Optic thalamus, thalamus.
 
Ora, a border or margin.
Orthognathous pertaining to a
straight (non-projecting) jaw.
 
Os incae, interparietal bone.
 
Os japonicum, bi-partite zygomatic
bone.
 
Os magnum, capitate bone.
 
Os, oris, a mouth.
 
Os, ossis, a bone.
 
Os tincae, external os of uterus.
Ossicle of Kerckring, occasional
centre in posterior margin of
foramen magnum.
 
Osteoblast, bone-germ.
 
Osteoclast, bone-destroyer.
Osteogenetic, bone-forming.
 
Ostium, a door, entrance, or exit.
Otic, pertaining to the ear.
 
Otoconia, ear-dust.
 
Otoliths, ear-stones.
 
Ovary, egg-forming organ.
 
Oxyntic, producing acid.
 
Pacchionian bodies, arachnoid granulations.
 
Pacinian corpuscles, lamellated corpuscles.
 
Palatum, the palate.
 
Pallium, a covering.
 
Palmar, pertaining to the palm.
Palpebra, an eyelid.
 
Pampiniform, tendril-like.
 
Pancreas, literally, all or completely
flesh.
 
Para-, near, by the side of.
Paradidymis, near the testis.
Parametrium, near the womb.
Parietal, pertaining to a wall.
Paroophoron, near the egg-bearing
organ; medial mesonephric tubules.
 
Parbtid, near the ear.
 
Parovarium, epoophoron.
 
Pars intermedia (Wrisberg), sensory
root of facial nerve.
 
Patella, a small dish; a plate.
 
Pecten, another name for the os
pubis; a comb.
 
 
Pectinatus, pertaining to a comb.
 
Pectineal or Pectineus, associated
with the pecten bone or os pubis.
 
Pectiniform, comb-like.
 
Pectoralis, pertaining to the breast.
 
Peduncle of corpus callosum, paraterminal gyrus.
 
Pelvis, a basin.
 
Penicillus, a painter’s brush or pencil.
 
Penis, a tail, or pendant process.
 
Peri-, around, about, or near.
 
Pericardium, around the heart.
 
Perineum, from a Greek verb meaning ‘ I dwell, or am situated,
around/
 
Perineum, central point of, perineal
 
body.
 
Periosteum, around bone.
 
Periotic, around the ear.
 
Peritoneum, from a Greek word
meaning ‘ stretched around/
 
Peroneal or Peroneus, ‘ pertaining
to the peronee/ the Greek name for
fibula.
 
Petit’s canal, zonular spaces.
 
Petit’s triangle, lumbar triangle.
 
Petrous, rocky.
 
Phalanx, a rank of soldiers.
 
Pharynx, the throat.
 
Phenozygous, having visible arches.
 
Philtrum, a love potion.
 
Phrenic, pertaining to the diaphragm.
 
Pineal, belonging to, or like, a pinenut or pine-cone.
 
Pinna, a kind of shell-fish; a feather
or wing.
 
Pisiform, like a pea.
 
Pituitary, pertaining to phlegm or
mucus; hypophysis.
 
Placenta, a flat cake.
 
Plagiocephalous, pertaining to an
oblique or twisted head.
 
Planta, the sole of the foot.
 
Plantar, pertaining to the sole of the
foot.
 
Platycnemism, broadness of leg.
 
Platyrhine, having a broad nose.
 
Platysma, a broad sheet.
 
Pleura, a rib.
 
 
 
 
 
 
 
 
 
 
 
iyog
 
 
GLOSSARY
 
i
 
 
Plexus, a twining or network.
 
Plexus, Auerbach’s, myenteric plexus.
Plexus, gulae, cesophageal plexus.
Plexus, Meissner’s, plexus of the
submucosa.
 
 
Plica, a fold.
 
Plica hypogastrica, lateral umbilical
 
 
fold.
 
Plica urachi, median umbilical fold.
Plicae palmatae (uterus), arbor vitae.
Pneumogastric, pertaining to the
breathing organs and stomach.
Pocularis, pertaining to a cup.
 
 
Pollex, the thumb.
 
Pomum Adami, laryngeal prominence.
 
Pons, a bridge.
 
Popliteal or Popliteus, pertaining to
the ham.
 
Porta, a gate.
 
Portal, pertaining to a gate.
 
Portio major and minor, sensory and
motor roots of trigeminal nerve.
 
Postaxiah r , , T
Preaxial / see Cha P ter L
 
Posterior vesicular column (Clarke),
thoracic (or dorsal) nucleus.
 
Posticus, posterior.
 
Poupart’s ligament, inguinal liga
 
ment.
 
Primary divisions (of spinal nerves),
 
anterior and posterior rami.
Proctodaeum, the threshold of the
 
 
anus.
 
Prognathous, having a projecting
lower jaw.
 
Proligerus, bearing offspring; germinating.
 
Pro-nephros, fore-kidney.
 
Pro-otic, before the ear.
 
Prosencephalon, the fore-brain.
 
Prostate, standing before; or, more
probably, pertaining to a porch
or vestibule.
 
Psalterium, a psaltery or instrument
of the lute kind.
 
Psalterium (lyra), hippocampal commissure.
 
Psoas, from a Greek word meaning
* the muscles of the loins,’ and
secondarily ‘ the loins themselves.’
 
 
Pterion, a wing.
 
Pterotic, pertaining to a wing.
Pterygoid, wing-like.
 
Pubes, the hair which appears on the
external genital organs at the age
of puberty.
 
Pubic, pertaining to the os pubis.
Pudendal, pertaining to the pudendum.
 
Pudendum, ‘ of which one ought to
be ashamed.’
 
Pudic, modest or chaste.
 
Pulmo, a lung.
 
Pulmonary, belonging to the lungs.
Pulvinar, a couch or cushion,
Putamen, trimmings or clippings.
Pyloric vestibule, pyloric antrum.
Pylorus, literally, a gate-keeper.
Pyriformis, pear-shaped.
 
Quadratus, square.
 
Quadriceps, having four heads.
Quadrigeminus, fourfold, four.
 
Racemose, pertaining to a cluster of
grapes; full of clusters; clustering.
Radius, a staff or rod; the spoke of
a wheel.
 
Ramus, a branch.
 
Ranine, pertaining to a frog.
 
Raphe, a seam.
 
Receptaculum, a receptacle.
Receptaculum chyli, cisterna chyli.
Rectus, straight.
 
Recurrent, running back.
 
Refractory, breaking up.
 
Reil, island of, insula.
 
Ren, a kidney.
 
Restiform, like a rope or cord.
Restiform body, inferior cerebellar
peduncle.
 
Rete, a net.
 
Retina, from rete, a net.
 
Retrahens, drawing back.
 
Retzius, cave, retro-pubic space.
Revehens, carrying back.
 
Rhinencephalon, the ‘ nose ’ or olfactory brain.
 
Rhinion, a nose.
 
Rhombencephalon, the rhomb-brain
(hind-brain).
 
 
 
 
 
 
 
 
 
 
1710
 
 
GLOSSARY
 
 
Rhomboid ligament, costoclavicular
ligament.
 
Riedel’s lobe, an elongation of lower
margin of right lobe of liver (due
to pressure).
 
Rima, a cleft or chink.
 
Risorius, laughing.
 
Rivini, ducts, sublingual ducts.
 
Rolando, fissure, central sulcus.
 
Rostrum, a beak.
 
Rotula, a little wheel.
 
Rugae, wrinkles.
 
Saccus reuniens, sinus venosus
(heart).
 
Sacrum, sacred; derivation and original meaning very doubtful.
 
Sagittal, pertaining to an arrow;
antero-posterior.
 
Salpinx, a trumpet or tube.
 
Salvatella, saving, or making well.
 
Santorini, cartilages, corniculate cartilages.
 
Santorini, duct, accessory pancreatic
duct.
 
Santorini, fissures, clefts in cartilage
of exterior auditory meatus.
 
Saphenous, apparent, manifest.
 
Sartorius, pertaining to a tailor.
 
Scala, a ladder, flight of steps, or
staircase.
 
Scala media, duct of cochlea.
 
Scalenus, of unequal sides.
 
Scansorius, of, or for, climbing.
 
Scaphocephalous, having a head like
a boat.
 
Scaphoid, like a boat.
 
Scapula, a spade; probably from a
Greek verb meaning ‘ I dig/
 
Scarpa’s triangle, femoral triangle.
 
Schlemm, canal, sinus venosus
sclerae.
 
Schindylesis, a splitting or cleavage.
 
Sciatic (identical with Ischiatic),
pertaining to the hip.
 
Sclera, hard.
 
Sclerotic, hard; sclera.
 
Scrobiculus, a little ditch or trench.
 
Scrotum, a skin bag or pouch; a hide
(probably originally ‘ scortum J ).
 
 
Sebaceous, pertaining to grease.
Sella, a seat; a saddle.
 
Semilunar bone, lunate.
 
Semilunar fold of Douglas, arcuate
line.
 
Seminalis, pertaining to semen.
Septum, a fence or barrier.
 
Serotinus, that comes or happens
late.
 
Serratus, jagged like a saw.
 
Sesamoid, like sesame (a kind of
grain).
 
Shrapnell’s membrane, flaccid part
of membrana tympani.
 
Sibson’s fascia, suprapleural membrane.
 
Sigmoid, like the Greek letter S
 
(sigma).
 
Sigmoid cavity, greater, trochlear
notch.
 
Sigmoid cavity, lesser, radial notch.
Sigmoid cavity (of radius), ulnar
 
notch.
 
Sigmoid notch (mandible), mandibular notch.
 
Sinus, a cavity or hollow.
 
Sinus, Valsalva, of, sinuses of aorta.
Smegma, a cleanser.
 
Solar, relating to the sun.
 
Solar plexus, coeliac plexus.
 
Soleus, a sole or sandal; a sole-fish.
Sperma, seed or semen.
 
Spermatic, pertaining to semen.
Spermatoblast, a seminal bud.
Spermatozoa (plural), seminal
animals.
 
Sphenoid, wedge-like.
Spheno-maxillary fossa, pterygopalatine fossa.
 
Sphenotic, pertaining to the sphenoid
bone and ear-capsule.
 
Sphincter, binding or closing tight.
Spigelian lobe, caudate lobe.
Splanchnic, pertaining to viscera.
Splenium, a bandage or compress.
Splenius, pertaining to a bandage.
Squamous, scaly.
 
Stapes, a stirrup.
 
Stellatum, starry.
 
Stensen’s duct, parotid duct.
 
 
/
 
 
 
 
 
 
GLOSSARY
 
 
Stephanion, a crown or wreath.
 
Sternebra, a segment of the sternum.
 
Sternum, the breast or chest.
 
Stomata, mouths or pores.
 
Stomatodaeum or Stomodaeum, the
threshold of the mouth.
 
Stria medullaris, stria habenularis.
 
Striae acusticae, auditory striae.
 
Striae medullares, auditory striae.
 
Styloid, pen-like.
 
Subflava, somewhat yellow.
 
Subiculum, an under layer or support.
 
Submaxillary, submandibular.
 
Substantia gelatinosa (Roland), gelatinous matter.
 
Sudoriferous, sweat-carrying.
 
Sulcus, a furrow.
 
Supercilium, an eyebrow.
 
Supracallosal gyrus, indusium griseum.
 
Sural, pertaining to the calf of the
leg.
 
Sustentaculum, a prop or support.
 
Sustentaculum lienis, phrenico-colic
ligament.
 
Suture, a sewing together, a seam.
 
Sylvius, aqueduct, aqueduct of midbrain.
 
Symphysis, growth together.
 
Syn-, with; together with (union or
harmony may be implied).
 
Synarthrosis, literally, a * together
with ' (direct) joint; fibrous joint.
 
Synchondrosis, bound together with
cartilage; cartilaginous joint.
 
Syndesmosis, bound together with
bands or bonds.
 
Synovia, resemblance to the white
of an egg.
 
Taenia, a band or ribbon.
 
Talus, a die (pi. dice); the ankle-bone.
 
Tapetum, a carpet or coverlet.
 
Tarsus, a broad flat surface; the
instep.
 
Tectorius, pertaining to a cover.
 
Tegmen, a covering.
 
Tegmentum, a covering.
 
Tela, a web.
 
Telencephalon, the end-brain.
 
 
1711
 
Temporal, pertaining to the temples
of the head.
 
Tendo Achillis, tendo calcaneus.
 
Tendon, from tendo, ‘ I stretch.’
 
Tenon’s capsule, fascial sheath of
eyeball.
 
Tentorium, a tent.
 
Tenuis, slender, small.
 
Teres, rounded.
 
Testis, a witness.
 
Thalamencephalon, the bedchamberbrain, or inter-brain.
 
Thalamus, a bedchamber; a marriage-bed.
 
Thebesian valve, valve of coronary
sinus.
 
Thebesian veins, venae cordis minimae.
 
Theca, a cover, case, or sheath.
 
Thenar, the flat of the hand.
 
Thorax, the breast or chest; a breastplate.
 
Thymus, thyme.
 
Thyroid, like a shield.
 
Tibia, a pipe or flute; the shin-bone.
 
Tinea, a small fish, perhaps the tench.
 
Tonsil, palatine, tonsil.
 
Tonsil, pharyngeal, naso-pharyngeal
tonsil.
 
Torcular, a wine-press (twisting is
implied).
 
Torcular Herophili, confluens sinuum.
 
Torus, a protuberance.
 
Torus tubarius, tubal elevation.
 
Trabecula, a little beam.
 
Trachea (‘ rough ’), the wind-pipe.
 
Trachelo-, belonging to the neck.
 
Tragus, a goat.
 
Trapezium, a table; a four-sided,
figure, no two sides of which are
parallel to one another.
 
Trefoil, having three leaves.
 
Treitz, muscle, suspensory muscle of
duodenum.
 
Treves, bloodless fold of, ileo-csecal
fold.
 
Triangular fascia, reflected part of
inguinal ligament.
 
Triangular fibro-cartilage, articular
disc.
 
 
 
1712
 
 
GLOSSARY
 
 
Triangular ligament, inferior or superficial layer; perineal membrane.
 
Triceps, having three heads.
 
Trigeminus, threefold, triple.
 
Trigdnocephalus, a triangular head.
 
Trigonum, a triangle; triangular.
 
Triquetrum, three-cornered; triangular.
 
Triticea, wheaten, or like a grain of
wheat.
 
Trochanter, from a Greek verb meaning ‘ I roll, turn, or revolve.'
 
Trochlea, the wheel of a pulley.
 
Trochlear, pulley-shaped.
 
Trochlearthrosis, a pulley-joint.
 
Trochoides, wheel-like.
 
Trolard, vein of, superior anastomotic
vein.
 
Tuba, a trumpet.
 
Tubarius, pertaining to a trumpet.
 
Tube, auditory, pharyngo-tympanic
tube.
 
Tube, Eustachian, pharyngo-tympanic tube.
 
Tubercle, a small swelling.
 
Tubercle, articular, articular eminence.
 
Tubercle, greater multangular, of,
 
crest of trapezium.
 
Tubercle, Lister’s, dorsal tubercle of
radius.
 
Tubercle, Lower, of, intervenous
tubercle (heart).
 
Tubercle, radial, dorsal tubercle of
radius.
 
Tuberosity, an exaggerated tubercle.
 
Turbinals or turbinate bones, conchse.
 
Turbinate, whirled or coiled; like a
top.
 
Turbo, a whirl or coil; a top.
 
Turcica, Turkish.
 
Tympanum, a drum.
 
Ulna, the elbow, but more usually
the forearm.
 
Umbilicus, the navel.
 
Umbo, a boss or knob.
 
Unciform, hook-like.
 
Unciform bone, hamate.
 
Uncinate, furnished with a hook.
 
 
Ungual, relating to a nail.
 
Unguis, a nail.
 
Unicornis, one-horned.
 
Urachus, urine-holder.
 
Ureter, from a Greek verb meaning
‘ I pass urine.'
 
Urethra, the canal by which urine is
passed.
 
Uriniferous, urine-carrying.
 
Uterus, the womb or matrix.
 
Uterus masculinus, prostatic utricle.
Utricle, a little womb or matrix.
Uvea, from uva, a bunch of grapes;
a cluster.
 
Uvula, a small bunch of grapes.
 
Vagina, a scabbard or sheath.
 
Vagus, strolling about, wandering,
vagrant.
 
Valgus, bow-legged.
 
Vallecula, a little valley.
 
Vallecula Sylvii, vallecula cerebri.
Vallum, a rampart.
 
Valsalva, sinuses, sinuses of aorta.
Valve, bicuspid, left atrio-ventricular
valve.
 
Valve, Eustachian, valve of inferior
 
vena cava.
 
Valve, ileo-caecal, ileo-colic valve.
Valve, mitral, left atrio-ventricular
 
valve.
 
Valve, Thebesian, valve of coronary
sinus.
 
Valve, tricuspid, right atrio-ventricular valve (cusps are anterior
inferior medial).
 
Valve, Vieussens, superior medullary
velum.
 
Varus, bent or turned inwards.
 
Vas (pi. vasa), a vessel.
 
Velum, a curtain or veil.
 
Velum interpositum, tela choroidea.
Velum palatinum, soft palate.
Veneris, ' of Venus.’
 
Ventral, pertaining to the belly.
Ventricle of larynx, sinus of larynx.
Vermiform, like a worm.
 
Vertebra, primarily means a joint,
but more particularly a joint of
the spine.
 
 
 
 
 
 
 
 
GLOSSARY
 
 
Vertex, the top or crown of the head.
 
Veru, a dart, javelin, or spear.
 
Verumontanum, urethral crest.
 
Vesalii, foramen, emissary sphenoidal
foramen.
 
Vesica, the urinary bladder.
 
Vesical, pertaining to the urinary
bladder.
 
Vespertilio, a bat.
 
Vestibular nucleus, principal or
dorsal; medial nucleus.
 
Vestigial, pertaining to a trace.
 
Vestigium, a trace or vestige.
 
Vibrissa, a stiff hair of the nostril.
 
Vicq d’Azyr, bundle of, mamillothalamic tract.
 
Vidian canal, pterygoid canal.
 
Vidian nerve, nerve of pterygoid
canal.
 
Vieussens, ansa of, ansa subclavia.
 
Vieussens, valve, superior medullary
velum.
 
Villus, shaggy hair; a tuft of hair.
 
Vinculum, a band or bond.
 
Vitelline, pertaining to the yolk of
an egg.
 
Vitellus, the yolk of an egg.
 
Vitreous, like glass, glassy.
 
Vola, the palm of the hand.
 
Volar, pertaining to the palm; palmar, or anterior.
 
Vomer, a ploughshare.
 
 
I 7 I 3
 
Vorticosse, full of whirlpools, eddying, coiled.
 
Vulva, a wrapper or covering.
 
Wharton’s duct, submandibular
duct.
 
Willis, circle of, circulus arteriosus.
 
Winslow, foramen, opening of lesser
sac.
 
Winslow, ligament, oblique posterior
ligament of knee.
 
Wirsung, duct, pancreatic duct.
 
Wolffian duct, mesonephric duct.
 
Wood’s muscle, abductor metatarsi
quinti.
 
Wormian bones, sutural bones.
 
Wrisberg, cartilage, cuneiform cartilage.
 
Wrisberg, ligament, accessory attachment of lateral semilunar cartilage.
 
Wrisberg, nerve, medial cutaneous
nerve of arm.
 
Xiphoid, like a sword.
 
Y-shaped ligament of Bigelow, iliofemoral ligament.
 
Zinn, inferior tendon or ligament
 
(eye), lower part of common tendinous ring.
 
Zinn, zonule, ciliary zonule.
 
Zygoma, a yoke.
 
 
108
 
 
 
 
INDEX
 
 
Arteries, nerves, ligaments, joints, muscles, and veins are classified under corresponding
headings. Where a number is given in heavy type, the principal reference is indicated.
 
 
Abapical pole of ovum, 25
Abdomen, 674, 754
 
division into regions, 755
Abdominal cavity, 756
pregnancy, 19
wall, 704
 
landmarks of, 704
Abducent nerve, 1166, 1447, 1616
in orbit, 1254
 
Abductor digiti minimi (foot), 646
(hand), 496
hallucis, 644
 
ossis metatarsi quinti, 643
pollicis brevis, 493
longus, 505
 
Abernethy, fascia of, 854
Aberrant ductules, 751
Abnormal definition, 5
Accessory bile-ducts, 779
 
nerve. See Cranial nerves
obturator nerve, 580, 847
process, 140
Acervulus cerebri, 1590
Acetabulum, 340
 
ossification of, 341
Acrocephaly, 270
Acromial anastomosis, 443
Acromion, 296 , 298
Acromio-clavicular joint, 444
Acromio-thoracic artery, 426
Adamantoblasts, 287
Addison's lines, 755
Adductor brevis, 577
hallucis, 649
longus, 576
magnus, 577
minimus, 578
pollicis, 494, 496
Adenoids, 1373
Agger nasi, 214
Aggregated nodules, 868
Air-cells, mastoid, i88
sphenoidal, 199
Akinesis, 9
Ala cinerea, 1490
 
of frontal bone, 181
orbitalis, 273
of sacrum, 148
temporalis, 275
 
 
Alae of ethmoid, 207
of vomer, 228
Alar thoracic artery, 427
Alimentary canal (embryonic), 23
Allantoic diverticulum, 31
Allantois, 31, 32, 33, 954
Alveolar arches, 1337
index, 269
point, 244, 268
process of maxilla, 214
Alveoli, pulmonary, 1028
Alveus, 1525, 1569
Ambiguus nucleus, 1625 , 1626, 1627
Ameloblasts, 287
Amitosis, 9, 12
Amnion, 27, 30, 32, 106
Amniotic cavity, 25, 26, 32
duct, 32
fluid, 106
folds, 31, 32
 
Amphioxus gastrulation, 35
mesoderm, 36
Ampulla of duodenum, 865
of ear, 1684
of rectum, 944
of vas deferens, 935
Amygdaloid nucleus, 1524, 1532
tubercle, 1524
 
Anal canal, development of, 965
of female, 978
lymphatics of, 964
of male, 945
structure of, 961
columns, 961
fascia, 922
membrane, 965
valves, 962
Analogy, 122
Anaphase, 10
 
Anastomosis, acromial, 443
cruciate, 538, 585 , 587
round, elbow-joint, 479
knee-joint, 548
scapular, 441
trochanteric, 585
Anatomical description, 2
snuff-box, 484
textbooks, 2
Anatomy, 1
 
 
1714
 
 
 
 
 
 
INDEX
 
 
1715
 
 
Anconeus muscle, 500
Angle, cranio-facial, 260
of eye, 1289
of mandible, 232
pubic, 339, 552
sacro-vertebral, 151
sternal, 102, 1013
subcostal, 165
subpubic, 344
 
Angles of pharyngeal lateral pouches. 70,76
Angular process, medial, 181
Animal cell, 8
Ankle-joint, 661
 
Annular-ligament of radius, 520
Annulus fibrosus—
 
of intervertebral disc, 1107
of tympanic membrane, 1676
ovalis, 1055
 
Ano-coccygeal body, 675
Ansa hypoglossi, 1206
 
lenticularis, 1531, 1539 , 1567
peduncularis, 1565, 1567
subclavia, 1239, 1335
Antecubital lymphatic glands, 452, 514
Antihelix, 1295
Antinion, 268
Antitragicus muscle, 1296
Antrum, definition, 115
pyloric, 760
tympanic, 188, 1681
Anus, 674
 
development of, 965
imperforate, 965
lymphatics of, 964
Aorta, abdominal, 825
 
branches of, 825
guides to bifurcation of, 708
arch of, 1037
 
development of, 1041
ascending, 1033
 
branches of, 1036
development of, 1037
great sinus of, 1036
descending, 1089
 
development of, 1094
embryonic, 51, 68
thoracic, 1033
varieties of, 1040
Aortic arches, 68, 91, 1118
isthmus, 1038
lymphatic glands, 832
nodule, 1063
orifice, 1062
 
position of, 1064
plexus, 811
sinuses, 1063
spindle, 1038
valve, 1062
vestibule, 1060
Aortico-renal ganglion, 809
Aperture, bony, of nose, anterior, 244
posterior, 251
 
median, of fourth ventricle, 1492, 1608
Apex of lung, 1021
Apical pole of ovum, 25
 
 
Aponeurosis, bicipital, 453
epicranial, 1156
palatine, 1351
palmar, 484
plantar, 642
Apophysis, 114
 
Appendices epiploicae, 768, 871
Appendix, vermiform, 764
 
development of, 63, 872, 883
mesentery of, 764, 787 , 884
Aquatic respiration, 1377
Aqueduct of mid-brain, 1488, 1560
 
development of, 58, 1561, 1589
of vestibule, 191, 264
Aqueductus cochleae, 193, 1165, 1686
Aqueous humour, 1661
Arachnoid granulations, 1599, 1609
membrane, cranial, 1608
spinal, 1413
 
Arbor vitae cerebelli, 1485
of uterus, 977
 
Arc, longitudinal, of skull, 269
Arch, coraco-acromial, 445
crico-thyroid, 1215
femoral, deep, 719, 734
jugular, 1175
nasal, 1154
palato-glossal, 1350
palato-pharyngeal, 1350
palmar, deep, 484, 497 , 499
superficial, 483, 487, 498
plantar, 614, 657
subpubic, 344
superciliary, 181
Archenteric cavity, 25
Archenteron, 27, 30
Arches, arterial, 1118
dental, 281
of foot, 672
visceral, 66, 278
 
metamorphosis of, 1376
Archoplasm, 9
 
Arcuate eminence, 189, 263, 1684
fibres of medulla, 1465
ligaments of knee-joint, 631
of diaphragm, 836
line, 727
 
Arcus parieto-occipitalis, 1501
tendineus, 947
Area, bucco-pharyngeal, 34
cochlear, 190
embryonic, 33
orbital, 1493
proto-cardiac, 34
tentorial, 1493
vestibular, 1491
Areas of Broca, 1446
of cortex, 1569
of Flechsig, 1467
 
vestibular, superior and inferior, 190
Areola of nipple, 414
Arm, landmarks of, 446
Arteria, centralis retinae, 1260
rectae, 906
 
thyroidea ima, 1038, 1204, 1221
 
 
 
 
 
 
 
1716
 
 
INDEX
 
 
Artery or arteries—
 
acromio-thoracic, 426
alar thoracic, 427
anastomosis, cruciate, 538, 585 , 87
round, elbow-joint, 479
knee-joint, 548
scapular, 441
aorta, abdominal, 825
 
branches of, 825
development of, 1041, 1118
guides to bifurcation, 708
arch of, 1037
 
development of, 1041
ascending, 1033
 
branches of, 1036
development of, 1037
great sinus of, 1036
descending, 1089
 
development of, 1094
embryonic, 51, 68
primitive dorsal, 1118
ventral, 1118
thoracic, 1033
varieties of, 1040
aortic arches (emb.), 68, 91
appendicular, 797
arch, crico-thyroid, 1215
 
palmar, deep, 484, 497 , 499
superficial, 483, 487, 498
plantar, 614, 657
arcuate, 612
 
ascending pharyngeal, 1219
auditory, internal, 1448, 1576
of auricle, 1672
auricular, deep, 1305
 
posterior, 1161, 1219
axillary, 425
 
varieties of, 428
azygos, of vaginal, 980
basilar, 1447, 1575
brachial, 454
 
collateral circulation after ligature, 457
profunda, 455
varieties of, 456
bronchial, 1090, 1029
buccal, 1282, 1307
of bulb, female, 703
male, 688
 
bulbar, of vertebral, 1575
caecal, 797
 
calcaneal, lateral, of peroneal, 626
medial, of post-tibial, 627
calcarine, 1577
capsular, of liver, 885
carotid, common, 1207
 
left, in thorax, 1039
ligation of, 1210
surgical compression, 1210
internal, 1323
 
at base of brain, 1449
cavernous part of, 1169
cerebral part of, 1570
development of, 91, 1118,
1122, 1324
 
 
Artery or arteries ( continued )—
 
carotid, internal, petrous part of, 1399
carpal, anterior, of radial, 475
of ulnar, 479
 
arch, posterior, 478, 508, 511
posterior, of radial, 511
of ulnar, 478
 
rete, anterior, 478, 479, 498
centralis, retinae, 1260, 1658
cerebellar, anterior inferior, 1448, 1576
posterior inferior, 1575
superior, 1448, 1576
cerebral, anterior, 1449, 1572
middle, 1449, 1573
posterior, 1448, 1576
 
cerebral areas of, 1577
cervical, ascending, 1242
deep, 1148, 1244
transverse, 1193, 1243
 
deep branch of, 402, 1192,
1243
 
superficial branch of, 1142,
 
1243
 
of uterine, 980
 
choroidal, anterior, 1449, 1571
posterior, 1577
ciliary, anterior, 1260, 1651
long, 1260, 1651
posterior, 1260
short, 1260
 
circulus arteriosus, 1449, 1577
major, 1651
minor, 1651
 
circumflex, anterior humeral, 427
fibular, 609
iliac, deep, 732
 
superficial, 508, 712
lateral femoral, 585, 588
medial femoral, 585, 589
posterior humeral, 427, 428
scapular, 427
 
clitoris, dorsal artery of, 703
cochlear, 1694
coeliac, 811
colic, left, 801
middle, 797
right, 797
 
communicating, anterior, 1449, 1573
posterior, 1449, 1571
companion artery of sciatic nerve,
538
 
coronary, of heart, 1036
of uterine, 980
of corpus callosum, 1573
cremasteric, 731
crico-thyroid arch, 1215
 
branch of superior thyroid, 1214
dental, anterior superior, 1308
inferior, 1307
posterior superior, 1307
dorsalis, indicis, 511
linguae, 1216
pedis, 611
 
varieties of, 614
pollicis, 511
 
 
 
 
 
 
 
INDEX
 
 
1717
 
 
Artery or arteries ( continued )—
epigastric, inferior, 729
 
branches of, 731
guide to, 708
superficial, 584, 711
superior, 731, 1000
 
ethmoidal, anterior, 1261, 1281,
 
1362
 
posterior, 1261
facial, on face, 1278
in neck, 1217
transverse, 1158, 1281
femoral, 563, 581 » 587
 
profunda of, 584, 588
fibular, circumflex, 609
 
of frenulum linguae, 1216
ganglionic, 1449, 1573 , 1577
gastric, left, 812
right, 814
 
gastro-duodenal, 814
gastro-epiploic, left, 812
right, 814
 
genicular, of popliteal, 548
gluteal, inferior, 538, 926
superior, 536, 927
helicine, 953
hepatic, 813, 885
 
varieties of, 815
hyaloid, 1664
ileal, 796
ileo-colic, 787
iliac, circumflex deep, 732
superficial, 712
common, 849
 
branches of, 851
collateral circulation after
ligature of, 852
guide to, 708
varieties of, 852
external, 853
 
branches of, 854
collateral circulation after
ligature of, 854
guide to, 708
varieties of branches, 854
internal, 923
 
branches of, 924
foetal condition of, 923
varieties of, 923
ilio-lumbar, 926
indicis, dorsalis, 511
radialis, 487, 498
infra-hyoid, 1214
infra-orbital, 1282 , 1307
innominate, 1038
 
varieties of, 1039
intercostal, 997
 
anterior, 998, 1000
collateral, 1093
lower two, 732, 999
posterior, 998, 1091
superior, 997, 1093, 1243
interlobar, of kidney, 904
interlobular, of kidney, 905
of liver, 885
 
 
Artery or arteries ( continued )—
interosseous, anterior, 478
common, 478
posterior, 506, 507
recurrent, 508
of iris, 1651
jejunal, 796
of kidney, 904
labial, inferior, 1279
 
superior, 1280, 1362
of labyrinth, 1694
lacrimal, 1260
laryngeal, inferior, 1243
superior, 1214
of larynx, 1396
lenticular, 1573
lenticulo-striate, 1573
lenticulo-thalamic, 1573
of ligamentum teres of uterus, 731
lingual, 1215
lumbar, 847
 
abdominal branches of, 732
branches of, 847
malleolar, lateral anterior, 609
medial anterior, 609
of posterior tibial, 627
mammary, external branches of
lateral thoracic artery, 426
internal, cervical part of, 1242
thoracic part of, 999
branches of, 1000
masseteric, 1307
mastoid of occipital, 1146, 1219
maxillary, 1304
 
branches of, 1305
median, 478 , 498, 5 1 ^>
meningeal, accessory, 1306, 1600
anterior of ethmoidal, 1599
of ascending pharyngeal, 1220,
1601
 
of internal carotid, 1600
middle, 1306, 1600
of occipital, 1146, 1219, 1601
of vertebral, 1575, 1601
mental, of facial, 1279
 
of inferior dental, 1283, 1307
mesenteric inferior, 801
branches of, 801
superior, 796
 
branches of, 796
metacarpal, dorsal, 511
palmar, 498
metatarsal, dorsal, 613
first plantar, 657
musculo-phrenic, 1000
mylo-hyoid, of inferior dental, 1307
nasal, dorsal, 1261, 1281
lateral, of facial, 1280
nutrient arteries—
of femur, 587
of fibula, 626
of humerus, 455, 456
of radius, 478
of tibia, 626
of ulna, 478
 
 
 
 
 
 
 
 
 
 
INDEX
 
 
1718
 
Artery or arteries [continued )—
obturator, 589, 925, 927
abnormal, 566
occipital, first part, 1218
 
descending branch of, 1218
second and third parts, 1146
olecanon rete, 479
ophthalmic, 1170, 1259
ovarian, 830
 
in pelvis, 978
of palate, soft, 1354
palatine, ascending, of facial, 1217
of ascending pharyngeal, 1220
greater, 1308 , 1338, 1362
lesser, 1308
 
palmar arch, deep, 484, 497, 499
superficial, 483, 487, 498
palpebral, lateral, 1260, 1281
medial, 1261, 1281
pancreatica magna, 812
pancreatico-duodenal, inferior, 798
superior, 814
pedis, dorsalis, 611
varieties of, 614
perforating, foot, 613, 657
hand, 498
 
of profunda femoris, 586
pericardiaco-phrenic, 1000
perineal, superficial, of female, 703
of male, 687
transverse, 687
peroneal, 610, 626
branches of, 626
communicating branch of, 627
varieties, 626
 
pharyngeal, ascending, 1219
of maxillary, 1308
of pharynx, 1373
phrenic, 827
placental, 51
plantar arch, 655, 657
lateral, 655 , 657
medial, 654 , 657
pollicis, dorsalis, 511
princeps, 487, 497
pontine, 1448, 1575
popliteal, 541, 546
varieties of, 548
princeps pollicis, 487, 497
profunda, of brachial, 455
femoris, 584 , 588
linguae, 1216, 1346
of pterygoid canal, 1308, 1362
pterygoid, of maxillary, 1307
pubic, 731
 
of obturator, 589
pudendal, accessory, 689
deep external, 584
internal, 925
female, 703
in gluteal region, 539
male, 686
 
superficial external, 584, 710
pulmonary, 1028, 1042
development of, 1042
 
 
Artery or arteries [continued )—
pulmonary, trunk, 1042
 
development of, 1042
radial, 473
 
first part, 474
 
recurrent branch of, 475
second part, 509
third part, 497
varieties of, 475, 498
radialis indicis, 487, 498
rectal, 906
 
inferior, 963
middle, 925, 963
superior, 802, 963
recurrent, anterior tibial, 609
ulnar, 477
 
posterior interosseous, 508
tibial, 609
ulnar, 477
radial, 475
renal, 827
 
aberrant, 828
accessory, 828
varieties, 828
rete, olecranon, 479
retinal, 1658
sacral, lateral, 926
median, 946
 
saphenous, of descending genicular,
 
587, 589
 
of scalp, 1153
scapular, circumflex, 427
of sclera, 1643
septal, of facial, 1280
 
of spheno-palatine, 1308, 1339,
1362
 
spheno-palatine, 1308, 1361
spinal, anterior, 1447, 1575
lateral, 1434
 
posterior, 1434, 1447, 1575
of posterior intercostals, 1093,
1411
splenic, 812
striate, 1573
stylo-mastoid, 1219
subclavian, 1237
 
development of, 1240
left, first part of, 1240
in thorax, 1040
right, first part of, 1237
second part of, 1240
third part of, 1191
 
guide to, 1192
subcostal, 732, 848, 1093
sublingual, 1216
submental, 1218
subscapular, 427
suprahyoid, 1216
supra-orbital, 1154, 1260
suprarenal, inferior, 828
middle, 827
 
superior, of phrenic, 827
suprascapular, 402, 438 , ii 93 ; 1243
suprasternal of suprascapular,
 
43 8 . 1243
 
 
 
 
 
 
 
 
 
INDEX
 
 
1719
 
 
Artery or arteries ( continued )—
supratrochlear (brachial), 456
of ophthalmic, 1154, 1261
sural cutaneous, 548
tarsal, 612
 
temporal, anterior deep, 1307
middle, 1158
posterior deep, 1307
superficial, 1158
testicular, 829
 
terminal part of, 738
varieties, 829
thoracic, alar, 427
lateral, 427
somatic, 1244
superior, 426
 
thyro-cervical trunk, 1242
thyroid, inferior, 1242
superior, 1213 , 1242
thyroidea ima, 1038, 1204, 1221
tibial, anterior, 607
 
guide to, 599
recurrent, 609
posterior, 624
guide to, 599
recurrent, 609
varieties, 627
of tongue, 1346
of tonsils, 1215, 1355
tonsillar, of facial, 1217
transverse facial, 1158
tympanic, anterior, 1306
inferior, 1220
 
of tympanic membrane, 1677
ulnar, 475
 
collateral, 456
first part, 476
 
recurrent branches of, 477
second part, 480
third part, 487
varieties, 479. 49$
umbilical, 51, 9 2 3> io8 3
urachal, of superior vesical, 924
ureteric, of superior vesical, 924
uterine, 979
vaginal, 980
 
azygos, 980
of liver, 885
of uterine, 980
 
vas aberrans, brachial, 456, 475
to vas deferens, 738, 925
vertebral, at base of brain, 1447
development of, 1121, 1242
first part, 1241
fourth part, 1574
second part, 1241
third part, 1151
varieties of, 1242
vesical, inferior, 925
superior, 924
vestibular, 1694
zygomatic, 115 8
Articular discs— . .
 
of acromio-clavicular joint, 444
of mandibular joint, 1318
 
 
| Articular discs ( continued )—
of radio-ulnar joint, 520
of sterno-clavicular joint, 444
Articularis genu muscle, 573
Articular nerves—
 
ankle-joint, 610, 615, 627, 663
calcaneo-cuboid, 654
carpal joints, 507, 525
carpo-metacarpal, 526
elbow-joint, 461, 480, 519
hip-joint, 545, 574, 580, 597
intermetacarpal, 526
interphalangeal, foot. 653, 654
shoulder-joint, 432, 464
talo-calcanean, 615
tarsal, 614, 652, 654
tarso-metatarsal, 614, 652, 654
tibio-fibular, inferior, 550, 610, 660
intermediate, 660
superior, 550, 659
wrist-joint, 489, 507, 523
Aryepiglottic fold, 1386
development of, 73
Arytenoid cartilages, 1382
development of, 1383
Arytenoideus muscle, 1393
Aspera, linea, 350
 
Association fibres of cerebrum, 1568
Aster, 9, 10
 
Asterion, 180, 239, 251, 268, 1630
Atavism, 6
 
Atlanto-axial joints, 1404 , 1408
Atlanto-occipital joints, 1406, 1409
Atlas, 128
 
development of, 170
ossification of, 142
Atresia ani, 955
Atria of heart, left, 1052
 
interior of, 1059
right, 1051
 
interior of, 1054
of lung, 1027
 
Atrio-ventricular bundle, 1071
node, 1071
 
Atrium of middle meatus, 1357
Attraction particles, 9
sphere, 9
 
Atypical, definition, 6
Auditory artery, internal, 1448, 1576
cells, 1689, 1692
epithelium, 1689
hairs, 1689
 
meatus, external, 193 , 1671
internal, 190, 264
nerve, 1165, 1404, 1447, 1620
process, external, 194
radiation, 1531, 1568
striae, 1471, 1489, 1620
teeth, 1691
Auricle, 1294
 
blood-supply of, 1297
lymphatics of, 1297
muscles of, extrinsic, 1160
intrinsic, 1296
nerve-supply of, 1297
 
 
 
 
 
INDEX
 
 
1720
 
Auricle, structure of, 1295
veins of, 1297
Auricles of heart, left, 1052
right, 1051
 
Auricular artery, deep, 1305
posterior, 1219
nerve, great, 1142 , 1278
posterior, 1160, 1272
point, 251, 268, 1629
surface of sacrum, 147
tubercle, 1295
tubercles (emb.), 68
vein, posterior, 1161
Auricularis anterior muscle, 1160
posterior, 1160
superior, 1160
 
Auriculo-temporal nerve, 1157, 1277
Auscultation triangle, 400
Autonomic nervous system, 1634
parasympathetic, 1639
cranial, 1639
sacral, 1640
sympathetic, 1635
 
course of efferent impulses, 1636
development of, 1640
ganglia, 1635
 
rami communicantes, 1635
Axial filament in spermatozoon, 13
skeleton, 23
Axillary artery, 425
 
varieties of, 428
fascia, 414
folds, 412
 
lymphatic glands, 416, 424, 434 , 514
sheath, 429
space, 412, 422
vein, 428 , 451
Axis, 131
 
odontoid process of, 131
ossification of, 143
Azygos arteries of vagina, 890
veins, 839
 
Back, landmarks of, 397
of scalp and neck, 1141
Baillarger, bands of, 1565
Balfour’s cell-chain theory, 55
Ball-and-socket joint, 393
Band, diagonal, 1515
ilio-trochanteric, 593
moderator, 1057
pudendal, 929
sciatic, 929
 
Basal cartilaginous plate in skull, 89
ganglia, 1526
Base of brain, 1443
Base-line of Reid, 1633
Basi-bregmatic axis, 260
Basi-cranial axis, 260
Basi-facial axis, 260
Basi-hyal, 236
Basilar artery, 1447, 1575
 
branches of, 1447, 1575
groove, 174
membrane, 1690
 
 
Basilar, part of occipital bone, 174
vein, 1521, 1579
Basilic vein, 450, 451
Basi-occipital, 275
Basion, 258, 268
Basket cells of cerebellum, 1487
Beak of ulna, 312
Bechterew, band of, 1565
Bellini, duct of, 903
Bergmann, fibres of, 1487
Biceps brachii, 452 , 463
third head, 454
femoris, 542
 
Bicipital aponeurosis, 453
groove, 300
synovial sheath, 465
Bifurcated ligament—•
 
calcaneo-cuboid part, 666
calcaneo-navicular part, 665
Bile canaliculi, 886
capillaries, 886
ducts, 779
 
accessory ducts, 779
interlobular ducts, 886
Birth of foetus, 107
Biventer cervicis muscle, 407
Bladder, urinary, blood-supply of, 952
development of, 955
female, 977
infantile, 952
 
ligaments of, false, 918, 952
true, 952
 
lumen of empty bladder, 951
male, 932
 
nerve-supply of, 953
orifices of, 951
peritoneal relations of, 934
structure of, 949
trigone, external, of, 934
internal, of, 951
 
Blastocele, 24
Blastocyst, 24
Blastoderm, 24
Blastodermic vesicle, 24
Blastomere, 21
Blastopore, 35
Blastula, 24
Blind spot, 1653
 
Blood circulation, development of, so, s
islands, 51
 
Bochdalek, ganglion of, 1320
Body, ano-coccygeal, 675
carotid, 1211
cavity, primitive, 23, 42
ciliary, 1647
geniculate, lateral, 1538
medial, 1538
Pacinian, 490, 653
perineal, female, 701
male, 681
pineal, 1540
ponto-bulbar, 1584
stalk, circulation in, 51, 52
morphology, 31 "
relation to umbilicus, 65
 
 
 
 
 
 
 
 
 
 
INDEX
 
 
1721
 
 
Body, ultimo-branchial, 76
vitreous, 1662
wall, development of, 59
split by pleurae, 78
Bone, canaliculi, 117
cell, 117
chemical, 115
lacunae, 117
marrow, 121
Bones, cancellated, 118
classification of, 118
compact, 116
of head, 172
ossification, 119
Borders, post- and pre-axial, 5
Bowman, capsule of, 901, 906
Brachia of corpora quadrigemina, 1538,
 
1548
 
Brachial artery, 454, 456
 
collateral circulation after ligature, 457
profunda, 455
varieties of, 456
plexus, 439
 
infraclavicular branches, 431
in neck, 1193
 
supraclavicular branches, 430,
1194
 
Brachialis muscle, 454
Brachio-radialis, 501
Brachycephalic skulls, 243, 267, 269
Brain, 1442
 
development of, 55, 15 81
superior surface of, 1433
weight of, 1570
 
Bregma, 180, 237, 238, 268, 1629
Bregmatic bone, 265
Broca, area of, 1446
Bronchioles, 1027
 
development of, 1030
Bronchus, eparterial, 1027, 1030
hyparterial, 1027
 
development of, 1030
left, 1086
right, 1086
 
Bruch, membrane of, 1646
Bryant’s triangle, 552
Buccal mucous glands, 1272
Buccinator muscle, 1269
Bucco-pharyngeal area, 34, 44
 
fascia, 1179, I 3 68
membrane, 44, 56. 69
Bulb, olfactory, 1165, 1510 , 157 °
of penis, 682
of posterior horn, i 5 2 4
Bulbar ridges, 1079
Bulbo-urethral glands, 685
Bulbs of vestibule, 696
Bulla ethmoidalis, 1357
Bundle, atrio-ventricular, I ° 7 I
 
medial longitudinal, 1464, 1555
of Munzer, 1588
Bursa of biceps brachii, 453
femoris, 542, 641
 
of coraco-clavicular ligament, 405
 
 
Bursa, under gastrocnemius, 544, 619, 640
gluteal muscles, 598
of infraspinatus, 465
under obturator internus, 535
olecranon, 447
of popliteal tendon, 641
prepatellar, 554, 640
under semimembranosus, 544, 64°
subacromial, 436, 464
subhyoid, 235
subpsoas, 598
subscapular, 464
suprapatellar, 574, 640
of teres major, 465
Bursae at elbow-joint, 519
at hip-joint, 598
at knee-joint, 640
at shoulder-joint, 464
 
Caecum, 762
 
development of, 63, 882
peritoneal relations of, 763
varieties of, 764
vascular fold of, 792
Cajal, horizontal cells of, 1562
moss fibres of, 1488
Calamus scriptorius, 1452
Calcaneal arteries—
 
lateral of peroneal, 626
medial of post-tibial, 627
Calcaneo-cuboid joint, 666
Calcaneo-navicular ligament, plantar, 665,
673
 
part of bifurcated ligament, 665
Calcaneum, 370
 
ossification of, 378
peroneal tubercle, 372, 388
structure of, 372
 
sustentaculum tali of, 371, 388, 390
tubercles on, 370, 386
tuberosity of, 370
varieties of, 372
Calcar avis, 1524
femorale, 354
 
Calcarine area of cortex, 1569
artery, 1577
Callosal radiation, 1568
Calvaria, 260
Canal or canals—
anal, 945, 97 8
carotid, 189, 191, 258, 263
central, of cord, 1422
condylar, 175, 258
cranio-pharyngeal, 197, 206
dental, 212, 213
facial, 190
femoral, 566
Haversian, 116
hepatic, 886
hyaloid, 1664
incisive, 248
infra-orbital, 245
inguinal, 708, 735
innominate, 201
 
 
 
 
 
 
 
 
 
1722
 
 
INDEX
 
 
Canal or canals—( continued )
intestinal, 761
lacrimal, 245
mandibular, 231
naso-lacrimal, 248
neural, 40
 
of Nuck, 743, 744, 969
obturator, 993
 
palatine, greater and lesser, 255
palato-vaginal, 199, 255
palmar, 332
 
pharyngo-tympanic, 257
portal, 885
 
pterygoid, 204, 255, 263
pterygo-palatine, 227
pudendal, 688
pyloric, 760
of sacrum, 148
semicircular, 1684
spiral, of cochlea, 1685
subsartorial, 580
vertebral, 154
Volkmann's, 117
zygomatico-facial, 219
zygomatico-temporal, 219
Canaliculus for chorda tympani, anterior,
187, 1673
 
posterior, 190, 1675
lacrimal, 1287
mastoid, 191, 258
tympanic, 258
Cancellated bone, 118
Canine fossa, 212
ridge, 211
teeth, 280
Capitate bone, 320
 
ossification of, 322
Capitellum, definition, 114
Capitulum of humerus, 304
Capsular decidua, 104, 106
Capsule, external, of brain, 1531
internal, of brain, 1528
Caput cornu, 1421
 
gyri hippocampi, 1507
medusae, 712
 
Cardiac nerves of sympathetic cervical,
1334 . 1335
 
of vagus, cervical, 1330
thoracic, 1045
plexus, 1046
deep, 1046
superficial, 1046
 
Cardinal veins, 51, 1127, 1132, 1136
Carotico-clinoid foramen, 200
Carotid artery, common, 1207
 
left, in thorax, 1039
external, 1212
 
development of, 1119, 1213
internal, 1169, 1323, 1324, 1399'
1449
 
development of, 91, 1118,
1122, 1324
 
body, 1211
 
canal, 189, 191, 258, 263
groove of sphenoid, 200
 
 
Carotid notch of sphenoid, 200
plexus, 1333
sheath, 1207
triangle, 1196
tubercle, 134, 1172
Carpal arch, posterior, 478, 508, 511
arteries—
 
anterior, of radial, 475
posterior, of radial, 511
of ulnar, 479
joints, 524
 
rete, anterior, 478, 479, 498
Carpo-metacarpal joints, 525
Carpus, 315
 
morphology, 323
ossification of, 322
varieties of, 322
as a whole, 321
Cartilage or cartilages—
arytenoid, 1382
corniculate, 1383
costal, 160
cuneiform, 1383
of larynx, 1379
 
of mandibular arch, 74, 75, 232
nasal, 1298
of second arch, 75
semilunar, 632
thyroid, 1380
 
Cartilaginous base of skull, 89, 270, 275
Cartilago triticea, 1384
Caruncula lacrimalis, 1289, 1292
Carunculae hymenales, 696
Cauda equina, 1417
Caudal, definition, 122
Caudate nucleus, 1526
Cave of Retzius, 339
Cavernous sinus, 1169, 1606
Cavity, glenoid, 294 , 461
of larynx, 1386
nasal, 1356
 
of septum lucidum, 1520
thoracic, 1002
Cavum trigeminale, 1167
Cell, animal, 8
 
of Cajal, 1562
division, 9
germ, 12
of Golgi, 1564
membrane, 8
pyramidal, 1562
Cement, 285
 
Centra, vertebral development, 59
Central artery of retina, 1260, 1658
canal of cord, 1422
lobule of cerebullum, 1478
tendon of diaphragm, 835
Centrale, os, 322
 
Centro-acinar cells of Langerhans, 891
Centrosome, 9, 10, 21
in spermatozoa, 13
Centrum of vertebrae, 125
Cephalic, definition, 122
vein, 450, 451
Cerg,to-hyal, 76, 23$
 
 
 
/
 
 
 
 
 
 
 
 
INDEX
 
 
I 7 2 3
 
 
Cerebellar fossae, 264
 
Cerebelli, tentorium, 1163, 1602, 1633
 
Cerebellum, 1475
 
arbor vitae of, 1485
association and commissural fibres
of, 1485
 
basal surface, 1443
development of, 1488, 1586
lobes and lobules of under surface
of, 1480
 
of upper surface, 1478
medullary vela, 1485
morphology of, 1481
nuclei of, i486
peduncles, inferior, 1484
middle, 1484
superior, 1483 , 1553
structure of, i486
under surface of, 1479
upper surface of, 1476
Cerebral commissure, anterior, 1518, 1568
hippocampal, 1518, 1568
posterior, 1542
cortex, 1561
 
development, 1510, 1591
fissures of, 1495
 
calcarine, 1503
choroidal, 1525
collateral, 1497
dentate, 1508
ecto-rhinal, 1508
lateral, 1495
parieto-occipital, 1496
postcalcarine, 1503
precalcarine, 1503
ganglia, basal, of, 1526
gyri of, 1493. See under Gyri
hemispheres, 1493
lobes of—
 
frontal, 1497
insula, 1505
limbic, 1506
occipital, 1502
olfactory, 1510
parietal, 1499
pyriform, 1508
 
temporal, 1504
lobules of—
 
cuneus, 1504
paracentral, 1499
parietal, 1501
postcentral, 1506
prsecuneus, 1502
precentral, 1506
quadrate, 1502
pole, frontal, of, 1451
 
occipital, of, 1451, i 5°3
temporal, of, 1444
veins, 1578
vesicles, primary, 58
Cerebri, crura, 1445. 1551
Cerebro-spinal axis, 1410
Cerebrum, the, 1493
Ceruminous glands, 1672
Cervical canal in pregnancy, 104
 
 
Cervical fascia, deep, 1178
 
compartments of, 1180
 
fistula, 1377
 
lymphatic glands, deep, 1189, H 99
superficial, 1178
plexus, 1185
 
branches, deep, 1188
 
superficial, 1141, 1187
spinal nerves, origins of, 1418
vertebrae, 126
Cervix cornu of cord, 1421
of uterus, 973
 
Check ligaments of eyeball, 1253
Cheeks, 1337
Chiasma, optic, 1545
Chondrocranium, 89, 270, 275
Chorda tympani nerve, 1347, 1402
Chordae tendineae, 1057
Chorio-decidual vessels, 109
Chorion, 29, 106
Chorionic ectoderm 29
mesoderm, 29
villus, 29
 
Choroid coat of eyeball, 1645
nerves of, 1651
structure of, 1646
plexus of fourth ventricle, 1492
of lateral ventricle, 1521
 
of inferior horn of, 1525
of third ventricle, 1521
Choroidal fissure, 1525
Chromatin, 9
 
discharged from nucleus, 18
Chromosomes, 10, 17, 18
Chyli, cisterna, 838, 1100
Ciliary body of eye, 1647
ganglion, 1257
margin, 1649
nerves, long, 1256
short, 1258
processes, 1647
vessels, 1260, 1651
Cinereum, tuber, 1445* 1544
Cingulate sulcus, 1496
Circular folds of small intestine, 864
sinus, 1606
sulcus, 1497
 
Circulation, course of, 1050
embryonic, 51
 
Circulus arteriosus, 1449, 1 577
major, 1651
minor, 1651
Circumduction, 395
 
Circumflex artery, anterior humeral, 427
fibular, 609
 
lateral femoral, 585, 588
medial femoral, 585, 589
posterior humeral, 427, 428
scapular, 427
iliac artery, deep, 732
 
superficial, 584, 712
nerve, 432 , 436
Cisterna basalis, 1609
 
cerebello-medullaris, 1609
chyli, 838, 1100
 
 
 
 
 
 
INDEX
 
 
1724
 
 
Cisterna pontis, 1609
venae magnae, 1609
Classification of joints, 394
of movements, 395
Claustrum, 1531
 
Clava of medulla oblongata, 1455
Clavicle, 289
 
in female, 291
ossification of, 292
structure of, 291
varieties of, 291
Clavi-pectoral fascia, 420
Cleavage nucleus, 21
Cleft, intratonsillar, 1354
palate, varieties of, 218
uro-genital, 693
 
Clinoid process, anterior, 200 , 261
middle, 200 , 261
posterior, 198 , 261
Clitoris, 694
 
arteries of, 703
development of, 698
frenulum, 694
glans, 695
lymphatics of, 695
prepuce, 695
Clivus monticuli, 1478
of sphenoid, 197, 264
Cloaca, 45, 99, 954
division of, 98
Cloacalfossa, 956
 
membrane, 45, 955, 956
septum, 99, 954
Closing membrane, 66
Coats of eyeball, 1641
Coccygeal plexus, 531
Coccygeus muscle, 948
Coccyx, 149
 
cornua of, 150
ossification of, 151
varieties, 151
Cochlea, 1685, 1689
 
aqueduct of, 193, 1165, 1686
Coeliac artery, 811
ganglia, 809
plexus, 807, 809
Coelom, 23, 29, 65
 
extra-embryonic, obliterated,
106
 
Coils of intestine, formation, 63
Collateral fissure, 1497
Colliculus facialis, 1491
Colon, ascending, 766
descending, 767
 
iliac part of, 767
left flexure of, 767
pelvic, 943
right flexure of, 766
taeniae of, 768, 870
transverse, 766
Column, vertebral, 124
as a whole, 151
Columnae rugarum, 986
Columns, anal, 961
renal, 900
 
 
Commissures of brain—
 
anterior, 1518, 1568
corpus callosum, 1513 * 1568
Gudden, of, 1545, 1547
habenular, 1541
hippocampal, 1518, 1568
posterior, 1542
of female perinaeum, 692
of spinal cord, 1418, 1420, 1426
Communicating artery, anterior, 1449,
1573
 
posterior, 1449, 1571
Companion artery of sciatic nerve, 538
Comparative anatomy, 1
embryology, 23
 
Compressor venae dorsalis penis, 680
Conchae, nasal, inferior, 223
middle, 209
superior, 209
sphenoidal, 204
Condylar canals, 176, 258, 264
fossa, 176, 258
tubercle, 234
Condyles of femur, 352
occipital, 175, 258
of tibia, 357
 
Condyloid process of mandible, 232
Cone-bipolar cells of retina, 1655
Cone of light, 1677
Cones of retina, 1656
 
Confluence of the sinuses, 174, 1603, 1631
Congenital cystic kidney, 95
Conjoint tendon, 725
Conjugation of pronuclei, 20
Conjunctiva, 1291, 1292
Conoid impression, 297
ligament, 444
tubercle, 289
 
Constrictor muscles of pharynx, 1368,
1369
 
Contrahentes, 515
 
Conus medullaris of spinal cord, 1416
Convoluted tubules of kidney, 901,903
Convolutions of brain. See Gyri
Coraco-acromial arch, 445
ligament, 445
 
Coraco-brachialis muscle, 452
Coraco-clavicular ligament, 444
Coracoid process and bone, 296 , 298
Cord, spermatic, 736
Cornea of eyeball, 1643
Corneal corpuscles, 1644
spaces, 1644
 
Corniculate cartilages, 1383
Corona glandis, 715
 
radiata, 1515, 1531
of ovum, 14, 19
Coronal, definition, 5
suture, 238, 1630
Coronary arteries of heart, 1036
of uterine, 980
ligaments of knee, 623
plexuses, 1048
sinus, 1065
Coronoid fossa, 304
 
 
 
 
 
INDEX
 
 
I7 2 5
 
 
Coronoid process of mandible, 232
of ulna, 312
Corpora bigemina, 58
geniculata, 1538
mamillaria, 1543
 
peduncles of, 1544
quadrigemina, 1547
 
development of, 58
Corpus albicans of ovary, 982
callosum, 1513
 
development of, 1531, 1596
forceps major, 1516
minor, 1515
genu,1514
peduncles of, 1514
radiatio corporis callosi,
 
1515
 
fimbriatum, 972
luteum, 982
striatum, 1526
 
development of, 58, 1591
trapezoides of cerebellum, 1484
of pons, 1470
Corrugator cutis ani, 675
supercilii muscle, 1266
Cortex, cerebral, 1561
Corti, rods of, 1691
tunnel of, 1692
 
Cortical branches of cerebral arteries,
1572, 1574, 1577
 
Cortico-medullary, arterial arches of
kidney, 904
venous arches, 907
Cortico-pontine fibres, 1552
Cortico-thalamic tract, 1566
Costal cartilages, 160
 
extensions from sclerotomes, 59
groove, 156
zone, 755
 
Costo-capitular facets, 134, 153
Costo-clavicular ligament, 443
Costo-coracoid ligament, 420
Costo-transverse lamella, 128
Costo-tubercular facets, 136
Cotyledons, no
Cranial capacity, 268
fossae, 260, 261, 263
index, 269
Cranial nerves, 1610
 
at base of brain, 1446
of skull, 1165
superficial origin of, 1446
abducent, at base of skull, 1166
distribution, 1166, 1447, 1616
nucleus of, 1473, 1616
in orbit, 1254
superficial origin, 1447
accessory, at base of skull, 1166
bulbar part, 1628
course, 1331, 1447, 1628
cranial root, 1331
distribution of, 1331, 1628
origin of, deep, 1628
superficial, 1447
spinal part, 1628
 
 
Cranial nerves {continued )—
 
auditory, at base of skull, 1166
 
cochlear nerve, 1404, 1620, 1693
in internal ear, 1693
meatus, 1404
nuclei of, 1620
spiral ganglion, 1620, 1694
superficial origin, 1447
vestibular ganglion, 1404, 1620,
1693
 
nerve, 1404, 1622, 1693
facial, at base of skull, 1166
 
distribution, 1157, 1272, 1401,
1447, 1682
 
after emerging from facial canal,
1272
 
in facial canal, 1400
ganglion of, 1403 , 1618
meatal portion of, 1400
nuclei of, motor, 1472, 1617
sensory, 1619
origin of, deep, 1617
superficial, 1447
petrous portion, 1400
sensory root, 1403
glosso-pharyngeal, at base of skull,
1166
 
distribution of, 1325, 1626
extracranial portion of, 1324,
1447, 1625
ganglia of, 1325
origin of, deep, 1619, 1624
superficial, 1447
 
hypoglossal, at base of skull, 1167
distribution of, 1322, 1629
extracranial portion of, 1332,
1447
 
origin of, deep, 1458, 1629
superficial, 1447
 
oculo-motor, at base of skull, 1165
nucleus of, 1561, 1611
in orbit, 1253
superficial origin, 1446
olfactory, 1165, 1360 , 1611
optic, at base of skull, 1165
development of, 1668
in orbit, 1253
origin, deep, 1611
superficial, 1446
 
trigeminal, at base of skull, 1165
distribution of, 1446
ganglion, 1167
 
mandibular nerve, 1168, 1309,
1616
 
maxillary nerve, 1168, 1616
mesencephalic root, nucleus of,
1561
 
motor root, nuclei of, 1474, 1615
ophthalmic nerve, 1168, 1254
 
1616
 
origin, deep, 1614
superficial, 1446
sensory root of, 1472
 
nuclei of, 1472, 1474,
1615
 
 
 
 
INDEX
 
 
1726
 
Cranial nerves ( continued )—
vagus, in abdomen, 861
 
auricular branch of, 1161, 1328,
1672, 1677
 
at base of skull, 1166
cardiac branches of, 1330
cervical cardiac branches of, 1330
portion of, 1327, 1330, 1447
distribution of, 1626
ganglia of, inferior, 1328 , 1626
superior, 1328 , 1626
nuclei of, motor, 1626
sensory, 1626
origin, deep, 1625
superficial, 1447
pharyngeal branch of, 1329
pulmonary plexuses of, 1029,
1043, 1045
 
thoracic portion of left, 1044
of right, 1043
 
Cranio-cerebral lobes of cerebrum, 1634
topography, 1629
Cranio-facial angle, 260
Cranio-metrical terms, 268
Cranio-pharyngeal canal, 197, 206
Cranium, 172
 
development of, 91, 270
interior of, 259
Cremaster muscle, 723
Cremasteric fascia, 716, 723
reflex, 724
 
Crest, conchal, of maxilla, 213
ethmoidal, of palatine, 225
external occipital, 259
of ilium, 334
incisive, of maxilla, 216
incisor, of maxilla, 216
infratemporal, 202
internal occipital, 264
lacrimal, 222
nasal, of maxilla, 216
of palatine, 225
obturator, 340
pubic, 399
 
relations of structures at, 728
sphenoidal, 199
supramastoid, 185
of tibia, 1359
 
transverse, of internal auditory
meatus, 190
of trapezium, 319, 333
urethral, female, 988
male, 939
vestibular, 1683
Cretinism, 270
Cribriform fascia, 561 , 568
plate of ethmoid, 207
Crico-arytenoideus posterior, 1392
lateralis, 1392
Crico-arytenoid joint, 1385
Cricoid cartilage, 1382
 
development of, 73, 1382
Crico-thyroideus, 1390
Crico-thyroid joint, 1385
Crico-vocal membrane, 1384
 
 
Crista ampullaris, 1688
galli, 207, 261
 
Cruciate anastomosis, 538, 585 , 587
ligaments of knee, 634
occipito-axial, 1405
 
transverse part, 1405,1408
vertical part, 1407
Crura cerebri, 1445, 1551
 
development of, 1589
Crus commune, 1688
of helix, 1295
Crusta-petrosa, 285, 287
Cryptorchismus, 743
Cryptozygous skull, 243
Crystalline lens, 1661
 
development of, 1667
Cubital fossa, 458
Cuboid bone, 377
 
ossification of, 378
 
peroneal groove of, 378 , 388, 390
 
varieties, 378
 
Cuboideo-metatarsal joint, 669
Culmen monticuli, 1478
Cuneate tubercle, 1455
Cuneatus, fasciculus, 1429
funiculus, 1455
nucleus, 1460
 
Cuneiform bones of tarsus, 373
intermediate, 375
lateral, 375
medial, 374
ossification of, 378
cartilages, 1383
Cuneo-cuboid joint, 669
Cuneo-navicular joint, 668
Cuneus of brain, 1504
Cupola of cochlea, 1695
Curved form of embryo, 48
Curves of vertebral column, 151
Cutaneous nerves. See also under Nerves,
cutaneous
of arm, 447
of back, 397
of forearm, back of, 449
front of, 465
of gluteal region, 529
of hand, 449, 465
of leg, outer side of, 614
of pectoral region, 412
of perinaeum, male, 675
of scapular region, 436
of sole of foot, 644
of trunk, 710
 
Cuvier, ducts of, 51, 92, 1127
Cystic duct, 778
 
development of, 891
structure of, 890
notch, 756, 777
Cytomicrosomes, 9
Cytoplasm, 8
Cytotrophoblast, 27, 29
 
Dachryon, 244, 268
Dartos muscle, 709, 713, 716
Daughter cells, 12
 
 
 
 
 
INDEX
 
 
1727
 
 
Daughter chromosomes, 10
nuclei, 12
 
Decidua basalis, 104
capsularis, 104, 106
parietalis, 104
Decidual cells, 107
 
change in pregnancy, 107
Decussation, fountain, 1433, 1551
of lemnisci, 1465
of pyramids, 1453
Deferens, vas, 737
 
development of, 738 , 753
in pelvis, 935
structure of, 737
Deiters, cells of, 1692
Deltoid, 436
 
tuberosity, 300
Dental arches, 281
canaliculi, 284
 
canals, anterior and middle, 213
posterior, 212, 253
groove, 218
lamina, true, 286
papilla, 285, 287
pulp, 283, 287
sac, 285, 287
Dentate fissure, 1508
nucleus, 1485
Dentatum, os, 133
Dentine, 284
 
Depressor alae nasi muscle, 1268
anguli oris muscle, 1270
labii inferioris muscle, 1270
Descent of testis, 739
 
abnormal conditions of, 743
positions of, 743
gubernaculum testis, 740
mesorchium, 740
plica gubernatrix, 740
uro-genital mesentery, 740
Descriptive terms, 1
Deutoplasm, 9, 15
Development—
 
of anal canal, 965
of anus, 965
 
of appendix, vermiform, 63, 872, 883
of aqueduct of mid-brain, 58, 1561
of arteries, principal, 1118
 
aorta, arch of, 1018, 1041
ascending, 1037
descending, 1094
carotid, common, ni 9 > I2I 3
external, 1119. I2I 3
internal, 91, 1118,1122, 1324
central, of retina, 1667, 1668
femoral, 1123
hyaloid, 1667, 1669
innominate, 1119
of limbs, 1123
upper, 516
pulmonary, 91, 1042
subclavian, 1119. 1121
tibial, 1123
umbilical, 151
vertebral, 1121
 
 
Development ( continued )—
of ary epiglottic folds, 73
of arytenoid cartilages, 1383
of atlas vertebra, 170
of atria of heart, 1075
of atrial septa, 1075
of atrio-ventricular valves, 1081
of auditory meatus, external, 68,
1696
 
of ossicles, 1679
of auricle of ear, 1697
of basal ganglia, 1594
of bile-duct, 868
of bladder, urinary, 955
of blood, 51
 
of body cavities, 47, 48
wall, 59
 
of brain, 55, 1581
of bronchi, 1030
of bronchioles, 1030
of bulbo-urethral glands, 686
of bulbs of vestibule, 699
of caecum, 882
of calyces, 95
 
of cartilages of larynx, 1397
of caruncula lacrimalis, 1292
of cement of teeth, 287
of cephalic ganglia, 1598
of cerebellum, 58, 1488, 1586
of cerebral hemispheres, 1510, 1591
peduncles, 1588, 1589
vesicles, 58, 1591
of choroid plexuses, 1596
of circulatory system, 51, 5 2
of cisterna chyli, 1138
of clitoris, 698
 
of commissures of brain, 1594
of conchae of nose, 1363
of conjunctiva, 1292
of cornea, 1670
of corniculate cartilages, 1383
of coronary sinus, 1076
of corpora mamillaria, 58, 1590
quadrigemina, 58, 1589
of corpus callosum, 1531, I 59 ^
striatum, 58, 1591
of cranial nerves, 1597
of cranium, 91, 270
of cricoid cartilage, 73, 1382
of crura cerebri, 1598
of cuneiform cartilages, 1383
of cystic duct, 891
of decidua, 104
of dentine, 287
of diaphragm, 837
of diencephalon, 58, 1589
of duodenum, 80
of dura mater, 90
of ear, external, 1696
internal, 1694
 
membranous labyrinth, 1694
middle, 1694
osseous labyrinth, 1695
of ejaculatory duct, 102, 959
of endolymphatic duct, 1694
 
 
 
 
 
 
 
 
 
INDEX
 
 
1728
 
Development ( continued )—
of epididymis, 753
of epoophoron, 753, 987
of ethmoid bone, 276
of excretory system, 92
of eye, 1664
of eyelids, 1292
of face, 88
 
of facial musculature, 68
skeleton, 277
of flocculus, 1586
of fore-brain, 56
of fore-gut, 44
of fornix, 1518, 1595
of frontal bone, 277
of gall-bladder, 891
of geniculate bodies, 1591
of genital organs, external, female,
698
 
male, 699
 
of genito-urinary system, 92
of gonads, 100
of gums, 1339
of heart, 90, 1073
of hind-brain, 55, 57
 
metamorphosis of, 1581
of hind-gut, 44
 
of hippocampal commissure, 1596
of hymen, 696, 699
of hyoid bone, 76, 278
of hypophysis cerebri, 58, 87,1171
of infundibulum cerebri, 58, 87, 1171,
1590
 
of insula, 1510, 1592
of interventricular foramen, 1535
of intervertebral disc, 59, 169
of intestine, large, 872
small, 870
 
of intrinsic muscles of hand, 515
of iris,. 1670
 
of islets of Langerhans, 895
of kidney, 92-97, 910
of labia pudendi, 699
of labyrinth of ear, 1695
of lacrimal bone, 277
of lamina terminalis, 1510, 1595
of laminae of cord, 54, 1438
of larynx, 1397
of lens, 1667
of lesser omentum, 80
sac, 79, 81
of lips, 1339
of liver, 79, 888
of lungs, 70, 77, 1029
of lymphatic glands, 1139
system, 1137
vessels, 1138
of malleus, 74, 1679
of mammary gland, 417
of mandible, 234
of massa intermedia, 1591
of medulla oblongata, 1581
of medullary vela, 1597
of meninges of brain, 1596
of cord, 1442
 
 
Development ( continued )—
 
of mesonephros, 92, 94, 914
of metanephros, 92, 94, 910
of metencephalon, 1585
of mid-brain, 56, 1589
of middle ear, 1696
of mitral valve, 1081
of mouth, 84, 1339
of myelencephalon, 1581
of nasal apertures, 84, 1363
bone, 277
cartilages, 1363
chonchas, 1363
of naso-lacrimal duct, 1294
of neopallium, 1592
of nervous system, 53
of nose, 1363
 
external, 1365
 
of notochord, 23, 39 , 134, 167
of nucleus, arcuate, 1585
caudate, 1592
cuneate, 1584
gracilis, 1584
hypoglossal, 1581
lentiformis, 1592
oculo-motor, 1581
pontis, 1584
red, 1589
trigeminal, 1589
trochlear, 1589
of oesophagus, 66, 78, 108
of olfactory, apparatus, 1511
bulb, 1512, 1570
epithelium, 1364, 1512
lobe, 1511
nerves, 1512
organ, 1364
tract, 1570
 
of omental bursa, 79, 81
of omentum, greater, 81
lesser, 80
 
of opercula insulae, 1510
of optic nerve, 1668
of otocyst, 74
of ovary, 100, 753
of palate, 86
of palatine bone, 277
of pancreas, 80, 894
of pancreatic ducts, 81, 894
of paramesonephric (Mullerian) duct,
101 , 987
 
of paranasal sinuses, 1363
of parathyroid glands, 76
of paroophoron, 754
of parotid gland, 1289
of penis, 700
 
of pericardium, 43, 46, 1019
of peripheral nervous system, 1597
of peritoneum, 795
of pharyngo-tympanic tube, 73, 74,
1378 ‘
 
of pharynx, 1373
of philtrum, 1341
of pineal body, 58, 1590
of pinna, 67, 1697
 
 
 
 
 
 
 
 
 
INDEX
 
 
1729
 
 
Development ( continued )—
of placenta, 106
of pleura, 78, 1011
of pleural sac, 78
of pons, 1586
 
of position of intestinal canal, 874
of stomach, 874
of pronephros, 92, 94
of prostate, 960
of prostatic utricle, 101
of pulmonary valve, 1081
of pulvinar, 1591
of pyramid of brain, 1584
of Rathke’s pouch, 87 , 206, 1171
of rectum, 99, 965
of respiratory system, 752
of rete testis, 752
of retina, 1667
of ribs, 59, 170
of saccule, 1695
of salivary glands, 1289
of sclera, 1670
of scrotum, 700
of semicircular canals, 1695
ducts, 1695
 
of seminal vesicles, 102, 959
of seminiferous tubules, 752
of septal cartilage, 1363
of septum lucidum, 1520
of skull, 270
of soft palate, 1354
of spinal cord, 53, 1436
ganglia, 54, 1597
nerves, 55
of spleen, 80, 897
of stapes, 75, 1679
of sternum, 170
of stomach, 861
of sublingual gland, 1235
of submandibular duct, 1234
gland, 1234
 
of suprarenal glands, 899
of sympathetic system, 1640
of tarsal glands, 1292
of teeth, 285
of tela choroidea, 1596
of telencephalon, 58, 1591
of tentorium cerebelli, 90, 273
of testis, 100, 752
of thalamus, 1539, 159°
of thoracic duct, 1138
of thymus, 76, 1020
of thyroid cartilage, 1381, 1387
gland, 70, 76, 1222
of tongue, 72, 1348
of tonsil, 76, 1356
of trachea, 70, 1029
of transverse processes of vertebrae,
 
59
 
of tricuspid valve, 1081
of tuber cinereum, 58, 1589
of tympanic cavity, 73, 74, 1696
membrane, 75, 1696
of umbilical cord, 31/32
of umbilicus, 63
 
 
Development [continued )—
of ureter, 910
of urethra, female, 988
male, 700, 956
of urinary bladder, 955
of uterine tubes, 987
of uterus, 101, 987
of utricle of ear, 1695
prostatic, 101
of vagina, 101, 987
of valve of heart, arterial, 1081
of vas deferens, 100, 102, 738, 753
of veins, principal, 1123
 
azygos veins, 1098, 1136
cardinal, 51, 1127
anterior, 1127
posterior, 1131
thoracic formation, 1136
cerebral, 1128
of gonads, 1135
iliac, common, 1132
innominate, 1032
portal, 817, 1124, 1125
primitive jugular, 51, 1127
renal, 1132, 1135
subcardinal, 1133
supracardinal, 1132, 1133
suprarenal, 1135
umbilical, 51, 1125, 1126
of upper limb, 516
vena cava, inferior, 1033
superior, 1032
vitelline, 51, 63, 1124
of venous system, 91
of ventricles of brain—
fourth, 1493
lateral, 1594
third, 1535
 
of vermiform appendix, 63, 872, 883
of vermis, 1587
of vertebrae, 59
of vertebral column, 168
of vestibular glands, 699
of visceral arches, 1373
of vitreous body, 1669
of vocal folds, 1397
of vomero-nasal organ, 1366
of xiphoid process, 170
of zygomatic bone, 277
Diaphragm, 883
 
arcuate ligaments of, 836
blood-supply, 833
central tendon of, 835
crura of, 835
lymphatics of, 834
openings of, 835
Diaphragma sellae, 1163, 1603
Diaphragmatic plexus of nerves, 809
Diencephalon, 58
Digastric fossa, 230
muscle, 1127
triangle, 1198
 
Digital arteries, palmar, 488
plantar, 655, 657
nerves of foot, 652, 654
 
 
109
 
 
 
 
 
1730
 
 
INDEX
 
 
Digital nerves of hand, 489, 499
 
processes, palmar aponeurosis, 485
plantar, 643
veins, foot, 644
hand, 467
 
Digitate impressions, 181
Dilator naris muscle, 1268
 
papillae muscle, 1650, 1652
Diploe, 119, 260
 
veins of, 1154, - i 6 oi
Diploid number of chromosomes, 18
Disc, .embryonic, 33, 39
Discs, intervertebral, 1107
Discus proligerus, 18, 982
Diverticula of ischio-rectal fossa, 676,
677
 
Diverticulum, amniotic, 31
ilei (Meckel's), 63, 762
Dolichocephalic skull, 243, 269
Dorsal aortae, 68
concavity, 50
convexity, 122
laminae of cord, 54
mesentery, 79
venous plexus of foot, 610
hand,467
 
Dorsalis indicis artery, 511
pedis artery, 611 , 614
pollicis artery, 511
Dorsum sellae of sphenoid, 197, 261
Duct or ducts—
bile, 779
 
of Cuvier, 51, 92, 1127
cystic, 778
efferent, 751
ejaculatory, 936
endolymphatic, 191, 1688, 1694
of Gaertner, 102
hepatic, 778
lactiferous, 415, 417
lymphatic, right, 1246
mesonephric, 94, 102
naso-lacrimal, 1294
pancreatic, 892
 
paramesonephric (Mullerian),
 
101 , 987
parotid, 1287
perilymphatic, 193
pronephric, 94
prostatic, 939
semicircular, 1688
sublingual, 1235
submandibular, 1233
thoracic, in abdomen, 838
in neck, 1246
in thorax, 1100
thyro-glossal, 1222
vitelline, 762
vitello-intestinal, 61, 762
Ductus arteriosus, 1043', 1082
cochlearis, 1689, 1690
reuniens, 1688
sacculi, 1688
utriculi, 1687
venosus, 1126
 
 
Duodenal curves, formation of, 81
glands, 867
papilla, 865
recesses, 791
 
Duodeno-ieiunal flexure, 762
fold, 805
 
Duodenum, 761, 803
ampulla of, 865
first part of, 803
fourth part of, 805
glands of, 867
second part of, 804
suspensory muscle of, 805
third part of, 804
Dura mater at base of skull, 1162
blood-supply of, 1599
of brain, 1598
nerves of, 1601
 
processes of, 1601
sinuses of, 1163, 1603
of spinal cord, 1410
 
blood-supply of, 1412
 
Ear, development of, 73, 1694
external, 1671
internal, 1683
middle, 1673
 
Earliest known stage of human embryo,
 
26
 
Ectoderm, primitive, 25
 
structures formed from, in
Ectognathion, 218
Ectopia testis, 743
Efferent ducts, 751
Ejaculatory duct, 936
 
development of, 959
structure of, 959
Elastic laminae of cornea, 1644
Elbow-joint, 516
bursae of, 519
ligaments of, 517, 518
nerves of, 519
relations of, 519
synovial membrane, 519
Elliptical recess of labyrinth, 1683
Embedding of ovum, 28, 104
Emboliformis, nucleus, 1485
Embryo, the, 39
 
formation of, 26
general form of, 48
Embryological terminology, 4
Embryology, general, 1, 8
Embryonic area, 33
disc, 39
 
plate, 26, 33, 36
 
Eminence, arcuate, 189, 263, 1684
frontal, 181, 1633
ilio-pubic, 335
parietal, 178, 1633
Eminentia medialis, 1491
saccularis, 1544
Emissary veins, 1608
Enamel, 285
cells, 287
cuticle, 285
 
 
/
 
 
 
 
 
INDEX
 
 
173
 
 
Enamel, organ, 285, 287
prism, 287
Encephalon, 1442
base of, 1443
 
arteries at base of, 1447
development of, 55, 1581
flexures of primitive, 57
Endocardium, 1068
Endognathion, 218
Endolymph of internal ear, 1697
Endolymphatic duct, 191, 1688, 1694
Endoskeleton, 113
Endosteum, 122
Endothelium, 112
Entoderm derivatives, 112
Entomion, 251, 268
Ependymal layer of cord, 54
Epiblast, 25
Epibolic growth, 35
Epicardium, 1018, 1068
Epicondyles of femur, 352, 353
of humerus, 304
Epicoracoid bone, 299
Epididymis, 749
 
development of, 753
structure of, 750
Epigastric artery, inferior, 729
superficial, 584, 711
superior, 731, 1000
depression, 705
Epiglottis, 1379
 
development of, 73
Epi-hyal, 76, 237
 
Epiotic centres of temporal bone, 196
Epiphyses, 114
 
and ossification, 305
Epiploicae, appendices, 768, 871
Epipteric bone, 180, 253, 265
Episternal bones, 162, 165
Epithalamus, 1540
Epitympanic recess, 188, 1681
pouches of, 1681
Epoophoron, 971
 
development of, 753, 987
Equator of eye, 1641
Equina, cauda, 1417
Eruption of teeth, 288
Erythroblasts, 51, 121
Ethmoid bone, 207
alae of, 207
labyrinth, 208
ossification of, 211
Ethmoidal crest of palatine, 225
 
foramina, 183, 210, 247, 248 * 261
notch, 182
 
process of inferior nasal concha, 223
spine, 197
 
Evolution of embryo, 23
Excretory organs, connection with
splanchnocoele, 93
development, 92
Exoskeleton, 113
Expulsion of foetus, 107
Extensor carpi radialis brevis, 502
longus, 501
 
 
Extensor carpi ulnaris, 503
digiti minimi, 503
digitorum, 502
brevis, 611
longus, 607
hallucis brevis, 611
longus, 606
indicis, 506
pollicis brevis, 505
longus, 505
retinacula of foot, 603
of hand, 508
Extra-dural space, 1412
Extra-embryonic coelom, 29
obliterated, 106
mesoderm, 26
 
Extra-peritoneal tissue, 743
Extravasation of urine, 678
Eye, 1641
 
chambers of, 1661
coats of, 1641
development of, 1664
equator of, 1641
movements of, 1231
Eyelashes, 1290
Eyelids, 1289
 
development of, 1292
structure of, 1290
 
Face, arteries of, 1278
bones of, 172
development of, 88
landmarks of, 1263
Facet, 115
 
Facial artery on face, 1278
in neck, 1217
transverse, 1158, 1281
canal, 190
ganglion, 1403
 
lymphatic glands, deep, 1309
nerve. See Cranial nerves
skeleton, development of, 277
vein, anterior, 1218, 1280
common, 1218
deep, 1308
transverse, 1281
Falx cerebelli, 1602
cerebri, 1601
anal, 675
 
Fascia of abdominal wall, anterior, deep,
7°9
 
superficial, 709
posterior, 839
of Abernethy, 854
of arm, deep, 451
axillary, 414
of back, deep, 397
bucco-pharyngeal, 1179, 1368
bulbi, 1252
cervical, deep, 1178
clavi-pectoral, 420
cremasteric, 716, 723
cribriform, 561, 568
of dorsum of foot, deep, 611
superficial, 610
 
 
 
 
 
 
 
 
 
 
INDEX
 
 
1732
 
Fascia of forearm, deep, 468
of gluteal region, 531
of hand, back of, 509
iliac, 839
 
infundibuliform, 716, 739
lata, 560
 
iliac portion, 561
pubic portion, 561
of leg, deep, 600
lumbar, 840, 841
 
posterior lamella of, 403
thoracic part of, 404
masseteric, 1337
obturator, 920
orbital, 1252
of palm, superficial, 484
of pectoral region, 414, 420
pelvic, parietal, 919
visceral, 921
perineal, deep, 677
superficial, 677
pharyngo-basilar, 1371
popliteal, 546
pretracheal, 1179
prevertebral, 1179
propia of Cooper, 716
psoas sheath, 839
of pyriformis, 919
of scapular region, deep, 436
spermatic, external, 716
internal, 716
temporal, 1161
transversalis, 733
 
Fascial compartments of neck, 1180
Fasciculus cuneatus, 1418, 1429
gracilis, 1418, 1429
longitudinal, inferior, 1569
superior, 1569
occipito-frontal, 1569
perpendicular, 1569
postero-lateral, 1430
retroflexus, 1541, 1558, 1561
solitarius, 1625, 1626
uncinate, 1569
Fasciola cinerea, 1513
Fastigii, nucleus, 1485
Fecundation, 20
Femoral artery, 563, 581 , 587
profunda of, 584, 588
canal, 566
 
cutaneous veins, 559
 
hernia, parts concerned in, 568
 
ring, 566
 
septum, 743
 
sheath, 565, 568
 
triangle, 552, 563
 
vein, 563, 589
 
Femoro-patellar joint, 628, 639
Femur, 345
 
adductor tubercle, 350, 354, 553
calcar femorale, 354
condyles, 352
epicondyles, 352, 353
fossa hypotrochanterica, 354
gluteal tuberosity, 350
 
 
Femur head, 345
 
intercondylar notch, 353
linea aspera, 350
neck, 346
ossification of, 355
patellar surface, 351
pectineal line, 350
pilastered, 354
popliteal groove, 352
surface, 358
quadrate line, 350
tubercle, 350
relation to stature, 354
sexual differences, 354
shaft, 348
structure, 353
trochanteric fossa, 348
line, 346
 
trochanters, 346, 348
tubercles of neck, 346
varieties, 354
Fenestra cochleae, 1674
vestibuli, 1674
Fertilization of ovum, 20
Fertilized ovum, 20
 
developmental stages, 22
segmentation, 21
Fibrinoid, 108
Fibula, 364
head, 364
 
malleolar fossa, 364
malleolus, 364
 
guide to, 599
oblique line, 366
ossification of, 367
structure of, 367
varieties, 367
 
Fibular circumflex artery, 609
intermuscular septa, 601
Fifth arch, rudimentary, 70
month foetus, no
Filum terminale of cord, 1417
Fimbria of brain, 1510, 1518, 1525
ovarian, 972
Fimbriae, 972
 
Fimbriata, plica, of tongue, 1343
Fimbriatum, corpus, 972
Fimbrio-dentate sulcus, 1509
First pharyngeal groove obliterated, 74
Fissure for ligamentum teres, 775
venosum, 776
longitudinal, 1450
orbital, inferior, 247, 253 , 1262
superior, 247, 263 , 1262
palpebral, 1289
pterygoid, 203
pterygo-maxillary, 253
squamo-tympanic, 187, 1673
tympano-mastoid, 192
1 Fissures of brain—
calcarine, 1503
choroidal, 1523
collateral, 1497
ecto-rhinal, 1508
lateral, 1495
 
 
 
 
 
 
INDEX
 
 
1733
 
 
fissures of brain ( continued )—
parieto-occipital, 1496
postcalcarine, 1^03
postclival, 1477
precalcarine, 1503
primary, of cerebellum, 1477
transverse, 1520
Fistula in ano, 677
 
umbilical urinary, 954
Fixation villi, 109
Fixed terms in anatomy, 3
Flaccida, membrana, 1676, 1677
Flagellum in spermatozoon, 13
Flava, ligamenta, 1108
Flexor—
 
accessorius, 647
carpi radialis, 470
ulnaris, 473
digiti minimi, 496
 
brevis, 650
digitorum brevis, 645
longus, 621
profundus, 481
sublimis, 470
hallucis brevis, 648
longus, 623
pollicis brevis, 494
longus, 482, 496
retinacula of ankle, 602
of hand, 493
Flexures of brain, 57, 58
of colon, left, 767
right, 766
Floor plate, 53
Foetal circulation, 1082
 
changes in, at birth, 1083
peculiarities of, 1082
membranes, 106
Foetus, 4, no
 
general growth of, no
maternal connections, 104
monthly growth, no
Fold or folds—
 
ary epiglottic, 73
glosso-epiglottic, 1380
lacrimal, 1294
peritoneal, 744
pharyngo-epiglottic, 1380
recto-uterine, 967
of Treeves, 792
vesico-uterine, 967
vestibular, 1385, 1387
vocal, 1388
 
Fontanelles, 180, 237, 239, 265, 266
sagittal, 180, 266
Foot, arches of, 672
as a whole, 386
Foramen or foramina—
 
caecum of frontal bone, 181, 261, 1604
of medulla oblongata, 1451
of tongue, 72, 1222
carotico-clinoid, 200
definition, 115
 
emissary, sphenoidal, 201, 263
of Hiischke, 194, 197
 
 
Foramen or foramina ( continued )—
incisive, 216, 255
infra-orbital, 212, 245
interventricular, of brain, 1535
of heart, 1081
jugular, 258, 264, 1166
lacerum, 258, 263
magnum, 176, 258, 264, 1167, 1633
 
structures passing through, 1167
mandibular, 231
mastoid, 187
mental, 229, 245
obturator, 340
optic, 229, 245, 247, 261
ovale, 201 , 253, 257, 263
 
of capsule of shoulder - joint,
461
 
in heart, 1065
tentorii, 1602
palatine, 226, 257
parietal, 243
pterygo-spinous, 203
rotundum, 201 , 255, 263
sacral, anterior, 144
sciatic, greater, 993
lesser, 535, 993
singulare, 190
spheno-palatine, 255
spinosum, 201 , 253, 263
sternal, 164, 171
stylo-mastoid, 192
supra-orbital, 244
supra-trochlear, 304
transversarium, 128
vertebral, 128
zygomatic, 219
 
zygomatico-facial, 219, 245, 247
zygomatico-temporal, 219, 247
Forceps major, 1516
minor, 1515
Fore-brain, 46, 56, 57
Fore-gut, 44, 62, 65
Formal position, the, 21
Formatio-reticularis alba, 1459
grisea, 1458
 
Formative cell-mass, 24
Fornix of brain, 1516, 1569
of conjunctive, 1292
Fossa or fosse—•
 
at base of skull, anterior, 260
middle, 261
posterior, 263
canine, 212
cerebellar, 264
condylar, 176, 258
coronoid, 304
cubital, 458
digastric, 230
digital, 744
for gall-bladder, 774
guttural, 257
hypophysial, 197, 261
iliac, 336, 708
incudis, 1675
incisive, of mandible, 229
 
 
 
 
 
 
I 734
 
 
INDEX
 
 
Fossa or fossae ( continued )—
 
incisive, of maxilla, 211, 216, 255
infraclavicular, 412
infraspinous, 292
infratemporal, 253
interpeduncular, 1561
intrabulbar, 941
ischio-rectal, 676
jugular, 191, 258
for lacrimal gland, 183, 245
nasal, 248
olecranon, 304
ovalis of heart, 1055
 
of middle ear, 1674
parafloccular, 191, 264
popliteal, 541, 545
pterygoid, 203, 257
pyriform, 76, 1376, 1386
radial, 304
retro-duodenal, 791
rotunda, 1674
scaphoid, 204
subarcuate, 191, 264
sublingual, 230
submandibular, 230
subnasal, 244
supraspinous, 292
temporal, 251
terminal, 941
tonsillar, 76
trochanteric, 348
trochlear, 183, 245, 1251
for vena cava, 777
vermian, 176, 264
vestibular, 696
 
Fountain decussation, 1433, 1551
Fovea-centralis, 1652
 
structure of, 1658
inferior, of fourth ventricle, 1490
spherica, 1683
 
superior, of fourth ventricle, 1491
Foveola of kidney, 903
Frankfurt plane, 242
Frenulum clitoridis, 695
labiorum, 696
linguae, 1336, 1343
lingulae of cerebellum, 1478
praeputii, 713
 
veli of superior medullary velum
1485, 1548
Frontal bone, 180
 
development of, 275
ossification of, 184
varieties of, 184
eminence, 181, 1633
lobe of brain, 1497
nerve, 1254
 
process of zygomatic, 220
sinus, 184, 250
suture, 238
 
Fronto-nasal process, 83, 88
Fronto-pontine tract, 1529, 1566
Funiculus, cuneatus, 1455
gelatinosus, 145 s
gracilis, 1455
 
 
Gaertner’s duct, 102
Galactophorous ducts, 415, 417
Gall-bladder, 778
 
development of, 891
lymphatics of, 891
spiral valve, 890
structure of, 890
Ganglia, basal, 1526
Gangliform enlargement on anterior
tibial nerve, 614
on median nerve, 489
on nerve to anconeus, 461
to teres minor, 432
on posterior interosseous nerve,
507
 
Ganglion, aortico-renal, 809
basal, 1526
of Bochdalek, 1320
cardiac, 1046
cervical, inferior, 1335
middle, 1334
superior, 1333
ciliary, 1257
coccygeal, 946
coeliac, 809
 
diaphragmaticum, 833
of facial nerve, 1403, 1618
of glosso-pharyngeal nerve,
inferior, 1325
superior, 1325
habenulae, 1541
impar, 946
 
interpedunculare, 1541, 1561
mesenteric, inferior, 811
superior, 809
otic, 1314
phrenic, 1016
spheno-palatine, 1320
spinal, 1419, 1428
spiral, 1694
splanchnic, 1105
stellate, 1104
submandibular, 1315
sympathetic, 1655
lumbar, 838
sacral, 922
trigeminal, 1167
of vagus nerve, inferior, 1328
superior, 1328
vestibular, 1404, 1693
Ganglionic layer of retina, 1654
Gastral mesoderm, 36
Gastrocnemius, 617
Gastro-phrenic ligament, 789
Gastrulation, 38
Gemellus, inferior, 535
superior, 535
Genial tubercles, 230
Genicular arteries, 548, 587, 589
nerves, 550, 580, 637
Geniculate bodies, 1538 , 1621
gyrus, 1514
 
Genio-glossus muscle, 1230
Genio-hyoid muscle, 1230
Genital cord, ioj
 
 
 
 
 
 
 
INDEX
 
 
Genital eminence, 99, 694, 698
swellings, 694, 698
Genito-femoral nerve, 554, 846
Genito-iirinary development, 92
Gennari, band of, 1547
Genu of central sulcus, 1496
of corpus callosum, 1514
of internal capsule, 1528
of sigmoid sinus, 1632
Gerlach, valve of, 764
Germ-cells, female, 14, 16
male, 12
origin, 13
 
Germinal cells in developing cord, 54
epithelium, 13, 16
layers, structures derived from, 111
vesicle, 15
Gill-slits, 66, 70
Glabella, 181, 244, 268
Gland or glands. See also Lymphatic
glands
buccal, 1272
bulbo-urethral, 685
cardiac, of stomach, 858
ceruminous, 1672
ciliary, 1290
duodenal, 867
gastric, 858
Haversian, 596, 598
intestinal, 867
labial, 1271
lacrimal, 1247
lingual, anterior, 1345
mammary, 412, 414 , 416
molar, 1272
of Montgomery, 415
nasal, 1359
palatal, 1351
parathyroid, 1223
parotid, 1284
prostate, 937
pyloric, 859
sublingual, 1234
submandibular, 1233
tarsal, 1291, 1292
thymus, 1019
thyroid, 1204, 1220
accessory, 1221
of tongue, 1344, 1345
urethral, 942
vestibular, greater, 697
Glandis, corona, 715
Gians clitoridis, 695
penis, 715
 
Gleno-humeral ligaments, 462
Glenoid cavity, 294 , 298
Glenoidale, labrum, 463
Glia cells of cerebellum, 1487
Glisson, capsule-*>f, 884
Globosus, nucleus, 1485
Globus pallidus, 1528
Glomeruli, external and internal, 93
Glomerulus of kidney, 905
Glomus coccygeum, 946
Glosso-epiglottic fold, 1343, 1380
 
 
1735
 
Glosso-pharyngeal nerve. See Cranial
nerves
 
Glottidis, rima, 1388
Gluteal artery, inferior, 538, 926
superior, 537, 927
fascia, 531
 
fold, 529 1
 
lines, 336
 
nerve, inferior, 539, 930
superior, 539, 930
region, 529
tuberosity, 350
reins, inferior, 538
superior, 536
Gluteus maximus, 531
medius, 532
minimus, 534
quartus, 534
Gnathic index, 269
Gnathion, 244, 268
Golgi, cells of, 1487, 1564
Gomphosis, 242 , 285
Gonads, 100
Gonion, 251, 268
Gracilis, fasciculus, 1418, 1429
funiculus, 1455
muscle, 516
nucleus, 1459
 
Granulations, arachnoid, 1599, 1609
Granulosa, membrana, 982
Grey matter—•
 
central, of medulla, 1459
of mid-brain, 1560 ” '
of cerebellum, 1484
of cerebral hemispheres, 1561
of spinal cord, 1420, 1424
of tegmentum, 1533
Groove, bicipital, 300
carotid, 200, 261
costal, 156
 
dental, of maxilla, 218
infra-orbital, 213
lacrimal, 222, 247
of maxilla, 213
medullary, 34
meningeal, anterior, 180
mylo-hyoid, 232
nasal, of ethmoid, 208
nuchal, 397
 
obturator, 340 *
 
olfactory, of ethmoid, 207
of sphenoid, 197
optic, 197, 261
 
peroneal, of cuboid, 377, 388, 390
 
for pharyngo-tympanic tube, 257
 
popliteal, 352 -- L
 
pulmonary, of thorax, 166
 
sacral, 146, 153
 
sigmoid, 188
 
spinal, 397
 
spiral, 300
 
subclavian, 290
 
of trapezium, 319, 333
 
vertebral, 153
 
Growth, embryonic, 48 ■
 
 
 
 
 
 
1736
 
 
INDEX
 
 
Growth, foetal, no
Gubernaculum of testis, 103, 740
Guerin, valvule of, 942
Gums, 1338
 
development of, 1339
Gustatory cells, 1348
organs, 1347
pore, 1348
Guttural fossa, 257
Gyrus or gyri—
angular, 1501
annectant, 1498
breves, 1506
cinguli, 1507
dentatus, 1509
frontal, 1498
geniculate, 1514
hippocampal, 1507
lingual, 1504
longus, 1506
marginal, 1499
occipito-temporal, 1505
orbital, 1499
precentral, 1497
postcentral, 1501
postparietal, 1502
rectus, 1499
subcallosal, 1514
supracallosal, 1514
supramarginal, 1501
temporal, 1505
 
Habenula, 1541
Habenulae, ganglion, 1541
striae, 1541
trigonum, 1541
Habenular commissure, 1541
Hair-cells, auditory, 1689, 1692
Hallucis, abductor, 644
adductor, 649
extensor brevis, 611
longus, 606
flexor brevis, 648
longus, 623
 
tendon of, 646
Hamate bone, 320
 
hook of, 321, 333
ossification of, 322
Hamstring muscles, 542, 544
Hamulus of lacrimal, 222
pterygoid, 203
of spiral lamina, 1686
Hand as a whole, 330
Hand-plates, no
 
Haploid number of chromosomes, 18
Harmonic suture, 394
Hassall, concentric corpuscles of, 1020
Haversian canals, 116
 
gland of hip-joint, 340, 596, 598
system, 117
Head, bones of, 173
process, 36
Heart, 1048
 
apex of, 1052, 1059
atrial portion of, 1051
 
 
Heart atrium, left, 1052, 1059
right, 1051, 1054
auricles of, 1051, 1052
base of, 1048, 1053
block, 1072
bloodvessels of, 1064
course of circulation, 1050
development of, 1073
exterior of, 1050
interior of, 1054
Latham’s circle, 1048
lymphatics of, 1067
nerves of, 1068
size of, 1073
topography of, 1048
of orifices of, 1064
tube, 90
 
ventricle, left, 1060
right, 1055
 
ventricular portion of, 1052
weight of, 1073
Helicine arteries, 953
Helicis major muscle, 1296
minor muscle, 1296
Helicotrema, 1686, 1689
Helix, 1294
 
spine of, 1295
tail of, 1295
 
Hemisternal cartilages, 170
Henle, loop of, 901, 903
Hensen, cells of, 1692
 
continuity theory of, 55
Hepatic artery, 813, 885
canals, 886
cells, 886
cylinders, 889
duct, 778
lobule, 884
plexus, 809
veins, 885
 
Hepatis, pons, 775, 777
porta, 775
sustentaculum, 789
Hernia, appendicular, 787
congenital, 747
diaphragmatic, 838
encysted, 747
femoral, 568
infantile, 747
 
inguinal, direct, medial, 746
oblique, lateral, 745
medial, 746
 
mesenteric, 786 s
 
meso-colic, 787
retro-peritoneal, 791
umbilical, 748
 
congenital, 748
Hertwig, sheath of, 287
Heterotypical mitosis, 17
Hiatus, definition, 115
 
for greater superficial petrosal nerve,
189, 190, 263
 
for lesser superficial petrosal nerve,
189, 263
 
semilunaris, 1357
 
 
 
 
 
 
 
INDEX
 
 
1737
 
 
Hilton, white line of, 962
Hilton’s law, 433
Hilum of lung, 1022
Hind-brain, ss, =>7
Hind-gut, 44, 45
Hinge-joint, 393
Hip bone, 334
 
ossification of, 341
joint, 590
 
arterial supply of, 596
bursae of, 598
capsular ligament, 590
Haversian gland, 596, 598
ilio-femoral ligament, 591
ischio-femoral ligament, 591
nerves of, 596
pubo-femoral ligament, 592
relations of, 596
synovial membrane, 595
Hippocampal commissure, 1518, 1568
gyrus, 1507
 
Hippocampus, 1509, 1532
His’ theory of nerve growth, 35
Histology, 1
 
Holden’s guide to greater trochanter, 552
Holoblastic ova, 25
Homodynamy, 6, 122
Homogeneity, 6
Homology, 6, 122
serial, 6, 122
 
Horns of cord, 1421, 1422
 
of lateral ventricle, 1523, 1524
Horseshoe kidney, 822
Humeral lymphatic glands, 424
Humerus, 299
 
anatomical neck of, 299
bicipital groove, 300
capitulum, 304
epicondyles, 304
greater tuberosity, 299
lesser tuberosity, 300
nutrient foramen, 300
ossification of, 305
shaft, 300
spiral groove, 300
structure, 304
supracondylar process, 302
surgical neck of, 300
trochlea, 304
varieties, 305
Humphry’s ligament, 633
Hiischke, foramen of, 194, 197
Hyaloid artery, 1664
canal of eye, 1664
membrane, 1662
Hyaloplasm, 8
 
Hydroccele, encysted, of spermatic cord,
743
 
Hymen, 695
 
development of, 696, 699
Hyo-glossus muscle, 1231
Hyoid arch, 75, 278
bone, 235
 
body, 235
horns, 236
 
 
Hyoid bone, development of, 278
ossification of, 236
tubercle of, 235
Hyperchordal bar, 143
Hypoblast, 25
 
Hypobranchial eminence, 70
Hypochordal bar, 168
Hypogastric sympathetic plexus, 811
zone, 755
 
subdivisions of, 755
Hypoglossal nerve. See Cranial
nerves
 
triangle, 1490
Hypophysial fossa, 197
Hypophysis cerebri, 1171
 
development of, 58, 87, 1171
infundibulum, 1171
structure of, 1171
Hypospadias, 700
Hypothalamus, 1543
 
.
 
Ichthyopsida, 23, 69
Ileo-caecal fold, 792
Ileo-colic valve, 873
 
frenula of, 873
Ileum, 762, 869
 
peritoneal relations of, 786
Iliac arteries. See Arteries
fossa, 336
 
left, contents of, 708
right, contents of, 708
veins. See Veins
Ilio-costalis muscle, 404
Ilio-costo-cervicalis muscles, 404
Ilio-femoral ligament, 591
Ilio-hypogastric nerve, 531, 710, 728, 845
Ilio-inguinal nerve, 554, 729, 845
Ilio-pectineal septum, 856
Ilio-psoas muscle, 571, 842
Ilio-pubic eminence, 335
Ilio-tibial tract, 531, 560 , 57 °
Ilio-trochanteric band, 593
Ilium, 334
 
anterior inferior spine, 334
superior spine, 334
auricular area, 336
groove, 346
crest, 334
gluteal lines, 336
surface, 336
ligamentous area, 336
muscular area, 336
posterior spines, 334, 336
Impar, ganglion, 946
tuberculum, 70
Impregnation, 20
Impression, trigeminal, 189, 263
Incisive canal, 248
crest, 248
foramina, 216, 255
fossa of mandible, 229
Incisor crest, 216
teeth, 278
 
Incisura semilunaris cerebelli, 1475
temporalis, 1507
 
 
 
 
 
 
INDEX
 
 
1738
 
Incus, 1678
 
ligament of, 1679
Index, alveolar, 269
cranial, 269
gnathic, 269
nasal, 269
orbital, 269
vertical, of skull, 269
Indicis, dorsalis, artery, 511
extensor, muscle, 506
radialis, artery, 487, 498
Indusium griseum, 1510
Infarcts, red and white, 109
Infraclavicular fossa, 412
 
lymphatic glands, 416, 434
Infrahyoid muscles, 1200
region, 1203
 
Infra-orbital canal, 245, 247
foramen, 212, 245
groove, 213
nerve, 1276, 1319
plexus, 1274, 1276
process of zygomatic, 220
Infrapatellar tendon, 574
Infraspinatus muscle, 437
Infratemporal crest of sphenoid, 202
Infundibuliform fascia, 716, 739
Infundibulum of ethmoid, 209
of frontal, 184
of heart, 1056
 
of hypophysis cerebri, 1171, 1544
of lung, 1028
of nasal fossa, 250, 1357
of uterine tube, 972
Inguinal canal, 735
 
position of, 708
hernia, 745-748
ligament, 551, 707, 719
lymphatic glands, 558
recesses, 745
triangle, 708, 736
Inion, 243, 268
Inner cell mass, 24, 25
Innominate canal, 201
Intercellular passages of liver, 886
Interclavicular ligament, 443
Intercostal arteries, 411, 997
membranes, 994, 995
muscles, 994, 995
nerves, 728, 996, 1099
spaces, 167
 
Intercosto-brachial nerve, 433 , 447
Intercrural fibres, 718
Intercuneiform joints, 669
Interfoveolar ligament, 726
Interglobular spaces, 285, 287
Interior of cranium, 259
Interlamina sulcus, 54
Interlobar notch of liver, 777
Interlobular plexuses of liver, 885
Intermediate cell mass, 42
 
formation from, 92, 93
Intermetacarpal joints, 526
Intermetatarsal joints, 671
Interosseous artery, anterior, 478
 
 
Interosseous artery, common, 478
posterior, 506, 507
recurrent, 508
membrane of forearm, 521
of leg, 660
muscles of foot, 650
dorsal, 651
plantar, 650
of hand, 512
dorsal, 512
palmar, 494, 512
nerve, anterior, 481
posterior, 506
Interparietal bone, 177
Interpeduncular fossa, 1561
space, 1445
 
Interphalangeal joints, foot, 572
hand, 528
 
Interspinales muscles, 410
Intertragic notch, 1294
Intertransversales muscles, 410
Intertubercular line, 755
plane, 755
 
Interventricular foramen, 1535
Intervertebral discs, 1107
 
development of, 59, 169
Intervillous space, 105, 108
Intestinal canal, 761
 
blood-supply of, 795
development of, 870
glands, 867
lymphatic trunk, 832
Intestine, large, 762
 
appendices epiploicae, 871
blood-supply of, 871
character of, 871
development of, 872
of position of, 874
lymphatics of, 799, 802
nerves of, 871
structure of, 870
small, blood-supply of, 869
 
characteristics of different parts
of, 869
 
circular folds of, 864
development of, 870
 
of positions of, 874
glands of, 867
lacteal vessels, 866
lymphatics of, 869
structure of, 863
villi of, 865
 
Intra-embryonic coelom, 42, 46
Intralobular plexuses of liver, 885
Intratonsillar cleft, 1354
Intra-uterine conditions in pregnancy,
104
 
Iris, 1648
 
blood-supply, 1651
development of, 1670
muscles of, 1650
nerves of, 1651
structure, 1650
 
Ischio-cavernosus, female, 702
male, 679
 
 
 
 
 
 
 
 
 
 
INDEX
 
 
1739
 
 
Ischiofemoral ligament, 591
Ischiorectal fossa, 676
contents of, 677
diverticula of, 676, 677
Ischium, 347
body, 337
ramus, 338 *
spine of, 338
tuberosity of, 338, 529
Islets of Langerhans, 892
Isolecithal eggs, 23
 
Isthmus of external auditory meatus, 194
of gyrus cinguli, 1507
oropharyngeal, 1330
pharyngeal, 1371
of rhombencephalon, 38
 
Japonicum, os, 221
Jejunum, 762, 869
Joints, acromio-clavicular, 444
ankle, 661
 
atlantoaxial, 1404, 1408
altanto-occipitai, 1406, 1409
ball-and-socket, 393
calcaneo-cuboid, 675
carpometacarpal, 325
of thumb, 523
cartilaginous, 393
classification of, 394
condyloid, 393
costochondral, 1112
costotransverse, 1112
costovertebral, mo
cricoarytenoid, 1383
crico-thyroid, 1385
cuboideometatarsal, 669
cuneo-cuboid, 669
cuneo-navicular. 668
elbow, 316
 
femoropatellar. 628, 639
fibrous, 393
of foot, 664
general, 393
of hand, 522
hinge, 303
hip, 590
intercarpal, 324
xnterchondral, 1114
intercoccygeal, 989
intercuneiform, 669
mtermetacarpal, 526
intermetatarsal, 671
interphalangeal, of foot. 672
of hand, 528
knee, 62S
lumbosacral, 988
mandibular, 1316
metacarpophalangeal, 327
metatarsophalangeal, 671
mid-tarsal, 663
movements of joints, 393
naviculo-cuboid, 668
obstetrical, 177
of occipital bone, 1406, 1409
of pelvis, 988
 
 
Joints, pisiform, 324
pivot, 393
plane, 393
 
pubic symphysis, 092
radioulnar, 520
of ribs, mo
sacro-coccygeal, 989
sacroiliac, 990
saddle, 393
shoulder, 461
sternal, 1114
stemo-clavicular, 443
stemo-costal, 1113
suture, 394
syndesmosis. 393
synovial, 393
talo-calcaneal 664
talo-ca lcaneonavicula r 663
tarsometatarsal, 669
tibiofibular, inferior. 639
intermediate, 660
superior, 639
transverse carpal, 323
of vertebral column, 1105
wrist, 322
Jugular arch, 1175
facet, 192
 
foramen, 258, 264, 1166
fossa of temporal, 191, 238
lymphatic trunk, 1199
notch of occipital, 1 76
process of occipital. 176. 258
vein, anterior, 1173
external, 1176
 
development of, 1177
internal, 1211
 
posterior external 1142, 1178
Jugum sphenoidale 197, 206
 
Karyokinesis, 9
Karyoplasm, 8, 9. 13
Karyosomes, 9
Kata phase, 10
Kidneys, 817
 
arteries of, 904
calyces of, 907, 908
cortex of, 901
development of, 95. 910
early condition of, 909
glomerulus, 903
hilum of, 821
lymphatics of, 907
medulla of, 900
pelvis of, 907
sinus of, 821
structure of, 900
uriniierous tubules 901
varieties of, S22
veins of, 906
Knee-joint, 628
 
arterial supply. 637
bursae of, 640
ligaments of. arcuate. 631
capsular. 622
cruciate, 634
 
 
174 ° INDEX
 
 
Knee-joint, ligaments, Humphry’s, 633
lateral, 630
medial, 629
oblique posterior, 631
patellae, 629
transverse, 633
Wrisberg’s, 633
movements of, 637
nerve supply, 637
semilunar cartilages, 632
synovial membrane, 634
 
Labia majora, 692
 
development of, 694
minora, 693
 
development of, 694
Labial mucous glands, 1271
Labrum, acetabulare, 594, 597
glenoidale, 463
 
Labyrinth of ear, membranous, 1687
blood-supply of, 1694
of themoid, 208
of kidney, 901
osseous, 1683
Lacrimal apparatus, 1293
artery, 1260
bone, 222
 
development of, 277
hamulus of, 222
ossification, 223
structure, 223
varieties, 223
canal, 245
canaliculi, 1293
crest, 222
fold, 1294
fossa, 183, 245
gland, 1247
groove, 247
 
of lacrimal, 222
of maxilla, 213
nerve, 1254, 1276
notch of maxilla, 213
process of inferior nasal concha, 223
sac, 1293
 
Lacrimalis, caruncula, 1289, 1292
lacus, 1289
Lacteal vessels, 866
Lactiferous ducts, 415, 417
Lacuna or lacunae—
laterales, 1603
magna, 942
muscular, 856
urethales, 942
vascular, 856
Lacunar region, 855
Lacus lacrimalis, 1289
Lambda, 180, 237 , 242, 268, 1629
Lambdoid suture, 237 , 1630
Lamina basalis, 1646
 
chorio-capillaris, 1646
cribrosa of internal auditory
meatus, 190 , 1686
of sclera, 1643
dorsal, of cord, 54, 1440
 
 
Lamina elastic, of cornea, 1644
fusca, 1643
labio-dental, 286
osseous spiral, 1685
reticular, 1693
suprachoroid, 1646
terminalis of brain, 1510, 1544
vasculosa of choroid, 1646
ventral, of cord, 54, 1439
vertebral, 127
 
Landmarks of abdominal wall, 704
of arm, 446
axilla, 412
of back, 397
 
of scalp and neck, 1141
of thigh and popliteal space, 540
of face, 1263
 
of front and inner side of thigh, 551
of wrist and palm, 482
of gluteal region, 529
of leg, 598
 
of male perinaeum, 674
of pectoral region, 412
of side of neck, 1172
of sole of foot, 641
 
Langerhans, centro-acinar cells of, 891
islets of, 892
 
Laryngeal artery, inferior, 1243
superior, 1214
nerve, external, 1329, 1395
internal, 1329, 1395
recurrent, 1044, 1045, 1330 * 1395
superior, 1329, 1395
Larynx, cartilages of, 1379
development of, 73, 1397
epiglottis, 1379
inlet, 1386
lymphatics of, 1396
mucous membrane of, 1399
muscles, intrinsic, of, 1390
 
actions of, summary of,
1394
 
nerves of, 1395
 
pyriform fossa, 76, 1373, 1386
rima glottidis, 1388
vestibuli, 1388
saccule of, 1387
sinus of, 1387
structure of, 1379
vessels of, 1396
vestibular folds, 1385, 1387
ligaments, 1387
vestibule of, 1387
vocal folds, 1388
ligaments, 1385
Latham, circle of, 1048
Latissimus dorsi muscle, 399
nerve to, 431
Law of ossification, 305
Lemniscus, decussation of, 1465
lateral, in mid-brain, 1557
in pons, 1471, 1475
medial, in medulla, 1465, 1466
in mid-brain, 1556
in pons, 1473
 
 
 
 
 
 
 
INDEX
 
 
I 74 I
 
 
Lens, crystalline, 1661
 
capsule of, 1662
development of, 1667
at different ages, 1662
vesicle, 1665, 1667
Lenticularis, ansa, 1531, 1539, 1567
Lentiformis, nucleus, 1526
Leptorhine skulls, 269
Lesser, triangle of, 1228
Levator anguli oris, 1268
ani, 947
 
glandulae thyroidae, 1221
labii superioris, 1268
alaeque nasi, 1267
palati, 1353, 1378
palpebrae, superioris, 1247
scapulae, 400
Levatores costarum, 410
longiores, 411
Lienis, sustentaculum, 767
Ligament or ligaments—
 
accessory, of atlas and axis, 1405
of knee, 629
acromio-clavicular, 444
alar, of odontoid process, 1408
of ankle-joint, 661
annular, of stapes, 1690
 
of superior radio-ulnar joint,
520
 
apical, of odontoid process, 1408
arcuate, of diaphragm, 836
of knee, 631
 
atlanto-axial, posterior, 1406
atlanto-occipital, 1406
of auricle, 1296
bifurcated, 665
of bladder, false, 918, 952
true, 952
 
brachial, medial, 452
of calcaneo-cuboid joint, 666
calcaneo-navicular, plantar, 665, 673
of carpo-metacarpal joints, 525
check, of orbit, 1253
conoid, 444
 
Cooper, oblique ligament of, 518
coraco-acromial, 445
coraco-clavicular, 444
coraco-humeral, 462
coronary, of knee, 628
costo-clavicular, 443
costo-coracoid, 420
costo-transverse, 112
cruciate, of atlas and axis, 1407, 1408
of knee, 634
 
of cuboideo-metatarsal joint, 671
of cuneo-cuboid joint, 669
of cuneo-navicular joint, 669
digital vaginal, of hand, 492
of elbow, 517, 518
fundiform, of Retzius, 604
gastro-phrenic, 789
gastro-splenic, 789
gleno-humeral, 462
of head of femur, 593
of hip-joint, 590
 
 
Ligament or ligaments (< continued )—
of knee-joint, capsular, 590
of head of femur, 593
ilio-femoral, 590
ischio-femoral, 592
transverse, 595
Humphry’s 633
hyo-epiglottic, 1380
ilio-femoral, 590
ilio-lumbar, 988
inguinal, 551, 707, 719
pectineal part of, 719
reflected part of, 720
relations of, 718
of intercarpal joints, 524
interclavicular, 443
interclinoid, 1163
of intercuneiform joints, 669
interfoveolar, 725
of intermetacarpal joints, 526
of intermetatarsal joints, 671
of interphalangeal joints of hand, 528
of foot, 672
 
interspinous, of vertebrae, 1109
intertransverse, of vertebrae, mo
intra - articular, of costo - vertebral
joints, 1111
 
of sterno-costal joints, 1113
of knee-joint, 628
accessory, 629
arcuate, 631
capsular, 628
coronary, 628
cruciate, 634
Humphry’s, 633
lateral, 630
medial, 629
oblique posterior, 613
patellae, 574, 629
transverse, 633
of Wrisberg, 633
of laminae of vertebrae, 1108
of larynx, 1384
of left vena cava, 1018
lieno-phrenic, 789
lieno-renal, 789
of liver, 788
 
coronary, 788
falciform, 788
triangular, 788
 
longitudinal, anterior, 1105, 1406
posterior, 1106
lumbo-sacral, 988
of malleus, 1679
of mandibular joint, 1316
of metacarpo-phalangeal joints, 527
of metatarso-phalangeal joints, 671
oblique posterior, of knee, 631
occipito-axial, 1407
of ovary, 982
palpebral, lateral, 1291
medial, 1265, 1291
pectinate, of iris, 1644, 1645
pectineal, 856
peritoneal, 78S
 
 
 
 
 
 
 
1742
 
Ligament or ligaments [continued)
petro-sphenoidal, 193
phrenico-colic, 789
phrenico-splenic, 789
piso-hamate, 473, 524
piso-metacarpal, 473, 524
plantar, long, 667
short, 667
 
pterygo-mandibular, 1181
pterygo-spinous, 1181
of pubic symphysis, inferior, 682, 98
pubo-femoral, 592
pubo-prostatic, 922
pulmonary, 1005
quadrate, 520
radiate, mi
 
radio-carpal, posterior, 522
radio-ulnar, 520
sacro-coccygeal, 989
sacro-iliac, 990
sacro-spinous, 991
sacro-tuberous, 542, 990
 
falciform process of, 991
of the scapula, 445
of shoulder-joint, 461
spheno-mandibular, 234, 1181, 1316
spino-glenoid, 445
spiral, of cochlea, 1690
of spleen, 789
of sternal joints, 1114
sterno-clavicular, 443
sterno-costal, 1113
sterno-pericardial, 1018
stylo-hyoid, 1232
stylo-mandibular, 1181, 1317
suprascapular, 445
supraspinous, 1109
suspensory, of axilla, 420
of eye, 1252
of lens, 1664
of ovary, 970
of penis, 713
talo-calcaneal, 664
of talo-calcaneo-navicular joint, 605
of tarso-metatarsal joints, 669
temporo-mandibular, 1316
thyro-epiglottic, 1380
thyro-hyoid, 1384
of tibio-fibular joints, 659
transverse, of atlas, 1405
deep, of palm, 526
of foot, 671
of hip-joint, 595
 
of inferior tibio-fibular joint, 660
of perinaeum, 682
of shoulder-joint, 453, 463
superficial, of palm, 484
trapezoid, 444
of uterus, broad, 968
of vertebrae, 1105
vestibular, 1385
vocal, 1385
of Wrisberg, 633
of wrist-joint, 522
of Zinn, 1250
 
 
INDEX
 
Ligamentum or ligamenta—*
arteriosum, 1043
denticulata, 1413, 1415
flava, 1108
nuchae, 399, 1144
patellae, 574, 629
pectinatum iridis, 1644, 1655
suspensoria of mammary gland,
414
 
teres of liver, 788, 1126
of uterus, 986
venosum, 1127
 
Ligula of fourth ventricle, 1492
Limb buds, no
lower, 529
upper, 397
Limbic lobe, 1506
Limbous suture, 237
Limbus, lamina spiralis, 1691
sphenoidalis, 197, 261
Limen insulae, 1506
Line or lines—
 
Addison’s, 755
arcuate, 340
gluteal, 336
intertubercular, 755
lateral, of abdomen, 755
mylo-hyoid, 230
Nelaton’s, 552
nuchal, 172, 250
oblique, of mandible, 231
of ulna, 314
pectineal, 350
quadrate, 350
soleal, 361
spino-umbilical, 707
subcostal, 755
Sylvian, 1632
temporal, 178
trapezoid, 290, 297
vertical, of tibia, 361
Linea alba, 704
aspera, 350
splendens, 1415
Lineae semilunares, 705
Lingual artery, 1215
glands, 1345
nerve, 1313
 
Lingula of cerebellum, 1477
of mandible, 231
of sphenoid, 200, 276
Linin, 9
Lips, 1336
 
Liquor folliculi, 19, 982
Lithotomy, lateral, structures divided in,
692
 
Liver, 771
 
borders of, 777
cells of, 886
component parts, 771
connections of, 771
cystic notch, 777
development of, 79, 888
duct of, 778
 
excretory apparatus of, 778
 
 
 
 
 
 
 
 
INDEX
 
 
17 43
 
 
Liver fissures or fossae of—
 
for gall-bladder, 774
for ligamentum teres, 775
venosum, 776
for vena cava, 777
impression, cardiac, 773
colic, 775
duodenal, 775
oesophageal, 776
renal, 775
suprarenal, 777
interlobar notch, 777
ligaments of, 788
lobes of—
 
caudate, 777
left, 773
quadrate, 774
right, 773
lobules of, 884
lymphatics of, 887
nerves of, 868
peritoneal relations of, 777
porta hepatis, 775, 777
position of, 771
structure of, 884
surface of, 773
topography of, 771
tuber omentale, 774
Lobes of cerebral hemispheres—
frontal, 1497
insula, 1505
limbic, 1506
occipital, 1502
olfactory, 1510
parietal, 1499
pyriform, 1508
temporal, 1504
 
of cerebellum. See Cerebellum
of testis, 750
Lobule of ear, 1294
Lobules of cerebral hemispheres—cuneus, 1504
paracentral, 1499
parietal, 1501
postcentral, 1506
praecuneus, 1502
precentral, 1506
quadrate, 1502
 
of cerebellum, See Cerebellum
of epididymis, 751, 752
Locus caerulus, 1491
Longissimus capitis muscle, 406
cervicis muscle, 406
thoracis muscle, 406
Lucidum, septum, 1518
cavity of, 1520
Lumbar arteries, 847
 
fascia, 403, 404, 840, 841
lymphatic trunk, 833
plexus, 844
puncture, 154
triangle, 400, 708
vertebrae, 138
Lumbo-sacral trunk, 847
Lumbrical muscles of foot, 649 .
 
 
Lumbrical muscles of hand, 492
Lunate bone, 317
 
ossification, 322
Lung buds, 77, 1029
Lungs, 1021
 
cervical part of, 1246
development of, 77, 1028
difference between lungs, 1025
in foetus, 1031
lobes of, 1023
lymphatics of, 1029
nerves of, 1029
root of, 1025
structure of, 1027
Lunules of aortic valve, 1063
Luteum, corpus, 982
Lymphatic duct, right, 1246
Lymphatic glands—
antecubital, 452
aortic, 832
apical, 424
 
axillary, 416, 424, 434
buccinator, 1284
caval, 1104
central, of axilla, 434
cervical, deep, 1189, 1199
superficial, 1178
coeliac, 815
colic, 803
facial, 1280
 
deep, 1309
gastric, 815
hepatic, 816
humeral, 424, 434
ileo-colic, 800
iliac, common, 849, 852
external, 855
internal, 927
infraclavicular, 416, 434
inguinal, 558
deep, 559
superficial, 558
innominate, 1101
intercostal, 1095, 1101
of intestine, large, 803
small, 799
juxta-aortic, 833
lingual, 1217
 
mammary, internal (or sternal),
1101
 
mastoid, 1161
 
mediastinal, anterior, 1014.
 
See also Innominate
posterior, 1101
mesentric, inferior, 802
superior, 789
obturator, 855
occipital, 1148
pancreatic, 815
pararectal, 964
paratracheal, 1199, 1227
parotid (pre-auricular), 1285
pectoral, 424, 434
popliteal, 551
pre-aortic, 832
 
 
 
 
 
 
 
 
 
*744
 
 
INDEX
 
 
Lymphatic glands ( continued ,)—
pre-laryngeal, 1199, 1386
pretracheal, 1199, 1225
pubic, 558
retro-aortic, 833
retro-femoral, 855
sacral, 946
splenic, 815
submandibular, 1198
submental, 1199, 1203
subscapular, 424, 434
supratrochlear, 452
thoracic, 1101
tibial, anterior, 610
tracheo-bronchial, 1103
Lymphatic nodules of spleen, 896
system, development of, 1377
trunk, intestinal, 832
lumbar, 833
vessels of—
 
abdominal wall, deep, 733
superficial, 558, 712
anal canal, 964
antebrachial, 514
anus, 964
auricle, 1672
bladder, 952
brachial, 514
buttock, 658
carpal, 513
clitoris, 695, 715
colon, ascending, 800
descending, 802
pelvic, 802, 943
transverse, 800
diaphragm, 834
digital, foot, 658
hand, 513
epididymis, 750
face, 1283
gall-bladder, 891
genitals, external, 558
gluteal region, 540, 558
gums, 1338
heart, 1067
inguinal region, 558
intercostal spaces, 999
intestine, large, 800, 802, 943
small, 799, 869
kidney, 907
larynx, 1396
lips, 1336
liver, 887
 
lower limb, 558, 658
lungs, 1029
mammary gland, 416
nasal cavity, 1363
nose, 1298
oesophagus, 1088
ovary, 982
 
palate, mucous membrane, of
hard, 1338
palm, 513
pancreas, 893
parotid gland, 1288
 
 
Lymphatic vessels ( continued )—
penis, 715
pericardium, 1019
perineum, female, 693
male, deep, 690
superficial, 558, 690
pharynx, 1373
pleura, ion
rectum, 964
scalp, 1162
scrotum, 717
seminal vesicles, 959
spleen, 897
stomach, 860
suprarenals, 898
testis, 750
thyroid gland, 1222
tongue, 1347
tonsils, 1355
trachea, 1225
upper limb, 513
ureter, 909
urethra, female, 988
male, 942, 943
uterine tubes, 983
uterus, 986
vagina, 986
vulva, 704
Lymph sacs, 1137
 
jugular, 1137
posterior, 1137
retro-peritoneal, 1137
 
McBurney, point of, 708
Macrocephaly, 268
Macrosomes, 25
Macula, lutea, 1653
sacculi, 1688
utricli, 1688
Magma reticulare, 32
Malleolar arteries, 609, 627
Malleolus, lateral, 364
medial, 361
Malleus, 1678
 
development of, 74, 1678
Mamillo-thalamic tract, 1517, 1543
Mammalia, 23
 
Mammary artery, internal —•
 
cervical part, 1242
thoracic part, 999
gland, 412, 414
accessory, 416
blood-supply, 415
development of, 417
lymphatics of, 416
nerves, 416
structure of, 416
lymphatic glands, 11 or
Mammillary process, 139
Mandibular arch, 66
canal, 231
foramen, 231
fossa, 186
joint, 1316
notch, 232
 
 
 
 
 
 
 
INDEX
 
 
1745
 
 
Mandible, 229
angle of, 232
base, 231
body, 229
changes in age, 234
condyloid process, 233
coronoid process, 232
development, 234
lingula, 231
ossification of, 234
structure, 234
symphysis of, 229
Mantle layer of cord, 54, 1437
Manubrium sterni, 161
Marginal layer of cord, 54, 1437
sinus of placenta, 106, no
tubercle of zygomatic, 220
Marrow, 121
Massa intermedia, 1534
Masseter muscle, 1301
Masseteric artery, 1307
nerve, 1309
Mastoid air-cells, 188
emissary vein, 1608
foramen, 187, 259
lymphatic glands, 1161
notch, 187, 258
process of temporal, 187
Maternal connections of foetus, 104
Maturation of ovum, 19
Maxilla, 211
 
alveolar process, 214
body, 211
 
development of, 277
frontal process, 214
ossification of, 218
palatine process, 215
structure of, 217
zygomatic process, 214
Maxillary processes—
 
of inferior nasal concha, 223
of palatine, 226
of zygomatic, 220
sinus, 217
 
Meatus, auditory, external, 193,
1671
 
bloodvessels of, 1672
early condition of, 1672
lymphatics, 1672
nerves of, 1672
internal, 190, 264
definition, 115
inferior, 1357
middle, 1357
of nasal fossae, 250
superior, 1356
 
Medial and median, definition, 122
Median artery, 478 , 498, 516
basilic vein, 450
cephalic vein, 450
nerve in arm, 458
 
digital branches of, 489
in forearm, 480
in hand, 489
lateral root of, 432
 
 
Median artery, medial root of, 423
 
palmar cutaneous branch of, 466,
481
 
summary of, 490
vein, 448
 
deep, 450
 
Mediastinal space, ion
Mediastinum, 1003, ion
anterior, 1006, 1013
middle, 1006, 1015
superior, 1006, 1012
testis, 750
 
Medulla oblongata, 1443, 1451
central canal of, 1446
development of, 1581
grey matter of, 1456
structure, internal, of, 1456
white matter of, 1462
Medullary cords in gonads, 100
groove, 34
 
laminae of nucleus lentiformis, 1528 *
1538
 
rays of kidney, 901
ridges, 34
spaces, 118
vela, 1485, 1491
Megakaryocytes, 121
Megaseme, 269
Membrana eboris, 284, 287
flaccida, 1676, 1677
granulosa, 982
limitans retinae, 1654
nictitans, 1292
propria, 1688
pupillaris, 1652
sacciformis, 315, 521
tectoria, 1407
 
of cochlea, 1693
Membrane or membranes—
 
atlanto-occipital, 1406, 1407
basilar, 1690
cell, 9
 
crico-vocal, 1384
intercostal, 994, 995
interosseous, of arm, 521
of leg, 660
nuclear, 8, 9
obturator, 993
perineal, 683
 
secondary, of tympanum, 1677
suprapleural, 1007, 1246
thyro-hyoid, 1384
tympanic, 1675
vestibular, 1690
Membranous labyrinth, 1687
Meningeal arteries, 1599
veins, 1601
 
Meninges of brain, 1598
 
of spinal cord, 1410 •*»
 
Menstruation, 19
Mental foramen, 229, 245
nerve, 1277 , 1313
point, 244, 268
protuberance, 229
tubercle, 229
 
 
no
 
 
 
 
 
 
 
 
 
1746
 
 
INDEX
 
 
Mentalis muscle, 1271
Mercier, bar of, 951
Meridian of eyeball, 1641
Meroblastic ova, 25
Mesaticephalic skulls, 243, 269
Mesencephalon, 1547
Mesenchyme, 112
Mesenteric artery, inferior, 801
superior, 796
hernia, 786
 
lymphatic glands, inferior, 802
superior, 789
plexus, inferior, 811
superior, 809
vein, inferior, 802
superior, 798
windows, 787
 
Mesentery, definition of, 780
primitive dorsal, 79, 793
ventral, 61, 79
proper, 786
 
ventral gastro-duodenal, 793
of vermiform appendix, 787
Mesoblast, 22, 26
Mesocardium, 90
Mesocephalic skulls, 268
Meso-colon, pelvic, 787
transverse, 787, 794
Mesoderm, 22
 
chorionic, 30, 33
covering fore-brain, 56
of visceral arches, 68
embryonic, 33
formation of, 26
gastral, 36
intra-embryonic, 30
lateral sheet of, 40, 41
paraxial, 40, 41
primitive, 26
prostomial, 36
somatic, 41
splanchnic, 41
 
structures derived from, 112
Meso-gastrium, 793
Mesognathion, 218
Mesognathous skulls, 244, 269
Mesonephros, 92, 94, 91^
Mesorchium, 740
Mesorhine skulls, 269
Meso-salpinx, 968
Mesoseme, 269
Mesothelium, 112
Mesovarium, 968
Metacarpal arteries, dorsal, 511
palmar, 498
bone, first, 323
 
Metacarpo-phalangeal joints, 527
Metacarpus, 323
 
ossification of, 329
as a whole, 327
Metakinesis, 10
Metanephros, 92, 94, 910
Metatarsal arteries, dorsal, 613
first plantar, 657
Metatarso-phalangeal joints, 671
 
 
Metatarsus, 378
 
ossification of, 386
varieties of, 384
as a whole, 384
Metathalamus, 1538
Metopic suture, 238
Meynert, ganglion of, 1544
Microcephalic skulls, 268
Microseme, 269
Mid-gut, 45, 61
Mid-tarsal joints, 665
Mitral cells, 1570
orifice, 1156
 
position of, 1064
valve, 1061
 
Moderator band of heart, 1057
Modiolus, 1686
Molar glands, 1272
teeth, 280
 
Molecular layer of cerebellum, "i486
Mons pubis, 692
Montgomery, glands of, 415
Morbus cseruleus, 1085
Morgagni, sinus of, 1370
Morphology, 1
 
of intrinsic muscles of hand, 515
Morula, 22
 
Moss-fibres of Cajal, 1488
Mouth cavity, 1335
 
development of, 86
I proper, 1336
 
vestibule of, 1336
Movable kidney, 822
Movements of joints, 395
Multifidus muscle, 409
Munzer, bundle of, 1558
Muscles—
 
abductor digiti minimi—
foot, 646
hand, 496
hallucis, 644
 
ossis metatarsi quinti, 643
pollicis brevis, 493
longus, 505
adductor brevis, 577
hallucis, 649
longus, 576
magnus, 577
minimus, 578
pollicis, 494, 496
anconeus, 500
antitragicus, 1296
articularis genu, 573
ary-epiglotticus, 1394
arytenoideus, 1393
obliquus, 1393
transversus, 1394
auricularis, anterior, 1160
posterior, 1160
superior, 1160
of Bell, 951
biceps brachii, 452
femoris, 542
biventer cervicis, 407
brachialis, 452
 
 
 
 
 
INDEX
 
 
17 47
 
 
Muscles ( continued )—
brachio-radialis, 501
buccinator, 1269
bulbo-spongiosus, of female, 702
of male, 680
ciliary, 1648
coccygeus, 948
compressor naris, 1267
sacculi laryngis, 1394
venae dorsalis penis, 680
constrictor inferior, of pharynx, 1368
middle, of pharynx, 1368
radicis penis, 680
superior, of pharynx, 1369
coraco-brachialis, 452
corrugator cutis ani, 675
supercilii, 1266
costalis, 405
cremaster, 723
 
crico-arytenoideus lateralis, T392
posterior, 1392
crico-thyroideus, 1390
dartos, 716
deltoid, 436
 
depressor alae nasi, 1268
anguli oris, 1270
labii inferioris, 1270
detrusor urnae, 950
diaphragm, 1833
 
central tendon of, 833
development of, 837
orifices of, 835
digastric, 1227
dilator naris, anterior, 1268
posterior, 1268
pupillae, 1650, 1652
extensor carpi radialis brevis, 502
longus, 501
ulnaris, 503
digiti minimi, 303
digitorum, 302
brevis, 611
longus, 607
hallucis brevis, 611
longus, 606
indicis, 506
pollicis brevis, 305
longus, 505
flexor accessorius, 647
carpi radialis, 470
ulnaris, 470
digiti minimi, 496
 
brevis, 650
digitorum brevis, 645
longus, 621
profundus, 481
sublimis, 470
hallucis brevis, 648
longus, 623
pollicis brevis, 494
longus, 482, 496
gastrocnemius, 617
gemellus inferior, 535
superior, 535
genio-glossus, 1230
 
 
Muscles ( continued )—
genio-hyoid, 1230
gluteus maximus, 531
medius, 532
minimus, 334
quartus, 534
gracilis, 376
hamstring, 542, 544
helicis major, 1296
minor, 1296
hyo-glossus, 1231
iliacus, 842
ilio-capsularis, 842
ilio-costalis, 404
ilio-costo-cervicalis, 404
ilio-psoas, 571
infraspinatus, 437
intercostal, external, 994
internal, 995
intercostales intimi, 996
interosseous, of foot, 650
of hand, 494, 512
interspinales, 410
intertransversales, 410
ischio-cavernosus, of female, 702
of male, 679
 
of larynx, intrinsic, 1390
latissimus dorsi, 399 » 439
levator anguli oris, 1268
ani, 947
 
glandulae thyroidae, 1221
labii superioris, 1268
 
alaeque nasi, 1267
palati, 1353, 1378
palpebrae superioris, 1247
prostatae, 947
scapulae, 400
levatores costarum, 410
longiores, 411
longissimus, 406
capitis, 406
cervicis, 406
 
longitudinalis linguae inferior, 1346
superior, 1346
longus, capitis, 1397
cervicis, 1398
lumbricales, of foot, 648
of hand, 492
masseter, 1301
of mastication, 1301
mentaiis, 1271
multifidus, 409
mylo-hyoid, 1229
obliquus auriculae, 1297
capitis inferior, 1150
superior, 1150
externus abdominis, 717
inferior, of eye, 1251
internus abdominis, 722
superior, of eye, 1250
obturator externus, 579
internus, 535, 949
occipito-frontalis, 1154
omo-hyoid, 1200
 
inferior belly of, 402, 437
 
 
 
 
 
 
 
 
1748
 
 
INDEX
 
 
Muscles ( continued )—
 
opponens digiti minimi, 496
pollicis, 494
orbicularis ciliaris, 1647
oculi, 1264
 
lacrimal part, 1265
orbital part, 1264
palpebral part, 1265
oris, 1271
 
palato-glossus, 1351
palato-pharyngeus, 1352
palmaris brevis, 484
longus, 470, 487
papillary, 1057
pectineus, 571
pectoralis major, 418
minor, 420
 
perinaeum, deep, transverse
muscle of, 681
peroneus brevis, 617
longus, 613
tertius, 607
plantaris, 620
platysma, 1175
popliteus, 621
prevertebral, 1397
procerus, 1267
pronator quadratus, 482
teres, 469, 470
psoas major, 841
minor, 842
 
pterygoid, lateral, 1302
medial, 1304
pubo-vesical, 922
pyramidalis, 727
pyriformis, 534, 948
quadratus femoris, 535
lumborum, 843
quadriceps femoris, 572, 573
rectus abdominis, 726
capitis anterior, 1397
lateralis, 1397
posterior major, 1149
minor, 1150
femoris, 572
inferior, of eye, 1249
lateralis, of eye, 1249
medialis, of eye, 1249
superior, of eye, 1249
of respiration, 1115
rhomboideus major, 401
minor, 401
risorius, 1269
rotatores, 410
sacro-spinalis, 404
salpingo-pharyngeus, 1378
sartorius, 568
scalenus anterior, 1235
medius, 1236
posterior, 1236
scansorius, 534
semimembranosus, 543
semispinalis capitis, 407
cervicis, 408
thoracis, 408
 
 
Muscles ( continued )—
semitendinosus, 543
serratus anterior, 401, 434
posterior inferior, 403
superior, 402
of soft palate, 1351
soleus, 619
 
sphincter ani externus, 675
internus, 961, 963
pupillae, 1650, 1652
urethrae, female, 702
male, 680
vesicae, 950
spinalis, 406
 
thoracis, 406
splenius, 404
capitis, 404
cervicis, 404
stapedius, 1680
sternalis, 420
sterno-costalis, 1002
sterno-hyoid, 1201
sterno-mastoid, 1145, 1182
sterno-thyroid, 1201
stylo-glossus, 1232
stylo-hyoid, 1228 , 1272
stylo-pharyngeus, 1323
subanconeus, 459
subclavius, 421
subcostal, 995
subscapularis, 440
supinator, 504
supraspinatus, 437
temporalis, 1302
tensor fasciae latae, 570
palati, 1353 , 1378
tympani, 1680
teres major, 439
minor, 438
 
thyro-arytenoideus, 1392
thyro-epiglotticus, 1392, 1394
thyro-hyoid, 1201
tibialis anterior, 606
posterior, 622
of tongue, intrinsic, 1346
tragicus, 1296
transversus abdominis, 724
auriculae, 1296
linguae, 1346
superficialis perinaei, 678
thoracis, 996
trapezius, 398
 
in neck, 1144
triceps brachii, 458 , 501
vastus intermedius, 573
lateralis, 572
medialis, 573
verticalis linguae, 1346
vocalis, 1392
zygomaticus major, 1269
minor, 1268
Musculi pectinati, 1054
Musculo-cutaneous nerve of arm, 432, 458
of leg, 604
 
Musculus-uvulae, 1352
 
 
 
 
 
 
 
 
 
INDEX
 
 
1749
 
 
Myelinization in cord, 1440
Myeloplasm, 53
Myenteric plexus, 863, 869
Mylo-hyoid groove, 232
line, 231
muscle, 1229
Myocardium, 1068
structure of, 1072
Myotomes of visceral arches, 1375
 
Nabothi, ovula, 985
Nasal bones, 221
crest, 222
 
development of, 277
ossification of, 222
capsule, 86, 1363
conchse, inferior, 223
middle, 209
superior, 209
crest of maxilla, 216
of palatine, 225
folds, 83
fossae, 248, 1356
 
arteries of, 1361
development of, 83, 85, 1363
lymphatics of, 1363
nerves of, 1360
groove, 208
index, 269
 
mucous membrane, 1359
notch of frontal, 181
part of maxilla, 212
of pharynx, 1371
pits, 83
 
process of frontal, 181
septum, osseous, 248
slit, 207, 250, 261
spine of frontal, 181
posterior, 225
Nasion, 240, 244, 268
Naso-lacrimal canal, 248
duct, 1294
 
Naso-pharyngeal tonsil, 1373
Natal cleft, 529
Navicular bone, 372
 
ossification, 378
tuberosity of, 373, 388, 641
varieties, 373
 
Naviculo-cuboid joint, 668
Neck, landmarks of, 1172
N 41 aton's line, 552
Neopallium, 1592
Nephric tubules, 93
Nephrocoele, 93
Nephrostome, 93
Nerves—
 
of abdominal wall, deep, 728
abducent. See Cranial nerves
accessory. See Cranial nerves
accessory obturator, 580, 847
to anconeus, 461
ansa hypoglossi, 1206
subclavia, 1335
auditory. See Cranial nerves
auricular, great, 1142 , 1278
 
 
Nerves ( continued )—
 
auricular, posterior, 1160, 1272
of vagus, 1161 , 1328, 1672,
 
1677
 
auriculo-temporal, 1157, 1277,
 
1311
 
bigeminus, 928
brachial plexus, 439, 1193
 
infraclavicular branches, 431
in neck, 1193
 
supraclavicular branches,
 
43 °> 1194
buccal, 1277, 1310
of facial, 1274
carotico-tympanic, 1404
cervical branches of facial, 1275
plexus, 1185
branches, deep, 1188
 
superficial, 1141, 1187
spinal, posterior rami, 1142,
1152
 
chorda tympani, 1347, 1402 , 1619
as pretrematic nerve, 69
ciliary, long, 1256
circumflex, 432 , 436
coccygeal, 530, 928, 929
cochlear, 1404, 1693
cutaneous nerves. See also Cutaneous
nerves
 
of arm, lateral, 448
 
medial, 432, 448, 457
posterior, 448, 460
of calf, lateral, 551
of forearm, lateral, 448
medial, 432, 448 , 457
posterior, 448
 
of ilio-hypogastric, anterior, 710
lateral, 531, 728
of neck, anterior, 1143, 1187
palmar, of median, 466, 481
of ulnar, 466, 477
perforating, of sacral plexus, 931
of subcostal, lateral, 531, 728
of thigh, intermediate, 555
lateral, 534, 564, 846
medial, 556
of ulnar, 448, 466, 499
dental, inferior, 1311
of maxillary—
 
anterior superior, 1319,1361
middle, 1320
posterior, 1320
digastric, 1272
digital, of foot, 652, 654
of hand, 489, 499
dorsal, of penis, 691
dorso-lumbar, 844
of dura mater, 1601
ethmoidal, anterior, 1361
posterior, 1257
of face, 1272
 
facial. See Cranial nerves
femoral, 575, 846
branches of, 576
frontal, 1254
 
 
 
 
 
175 o
 
 
INDEX
 
 
Nerves ( continued )—
 
furcalis, 847, 928, 931
genicular, 550, 580, 637
genito-femoral, 554, 846
 
femoral branch of, 554 , 846
genital branch of, 846
glosso-pharyngeal. See Cranial
nerves
 
gluteal, inferior, 539, 930
superior, 539, 930
haemorrhoidal, inferior, 675, 691
hypoglossal. See Cranial nerves
ilio-hypogastric, 728, 845
cutaneous branches—anterior, 710
lateral, 531, 728
ilio-inguinal, 554, 845, 729
incisive, of inferior dental, 1313
infra-orbital, 1276, 1319
infratrochlear, 1256, 1276
intercostal, 996, 1099
branches of, 997
lower five, 728
intercosto-brachial, 433 , 447
interosseous, anterior, 481
 
of nerve to popliteus, 550
posterior, 506
lacrimal, 1254 , 1276
laryngeal, external, 1329, 1395
internal, 1329, 1395
recurrent, 1044, 1045, 1330,1395
superior, 1329, 1395
to latissimus, dorsi, 431
lingual, 1313 , 1347
lumbo-sacral trunk, 847
mandibular, 1168, 1309
distribution, 1616
summary of, 1316
masseteric, 1309
maxillary, 1168, 1319
 
branches of, 1259, 1319
distribution of, 1616
summary of, 1323
median, in arm, 458
 
branches of, 459, 481
digital branches of, 489
in forearm, 480
in hand, 489
lateral root of, 432 .
medial root of, 432
palmar cutaneous branch of, 466,
481
 
summary of, 490
meningeal, 1168
mental, 1277 , 1313
musculo-cutaneous, of arm, 432, 458
of leg, 604
mylo-hyoid, 1312
nasal nerves—
 
of greater palatine, 1361
of infra-orbital, 1276
of spheno-palatine ganglion, 1360
naso-ciliary, 1255
nutrient, to fibula, 627
to radius, 481
 
 
Nerves ( continued )—
 
nutrient, to tibia, 550
to ulna, 481
 
obturator, 557, 579, 846
accessory, 580, 847
genicular branch of, 580
to obturator internus, 539, 930
occipital, greater, 1141, 1152
lesser, 1142
third, 1142, 1152
ophthalmic, 1254, 1258
distribution, 1616
optic. See Cranial nerves
palatine, greater, 1322, 1338,
lesser, 1322
 
palmar cutaneous, of median, 466,
481
 
of ulnar, 466, 477
patellar plexus, 557
pectoral, 431
 
pelvic splanchnics, 930, 947
of penis, dorsal, 691
perforating cutaneous, 931
perineal, 691
 
deep branch of, 691
of fourth sacral, 675, 932
long, 691
 
to peroneus tertius, 610
petrosal, deep, 1404
 
external, 1169, 1402, 1403
superficial, greater, 1168, 1401
lesser, 1169, 1402, 1403
pharyngeal plexus, 1329
 
of spheno-palatine ganglion, 1321
of vagus, 1329
phrenic, in neck, 430, 1189
in thorax, 1015
plantar, lateral, 653
medial, 652
 
popliteal, lateral, 550 , 931
medial, 550 , 931
to popliteus, 550
post- and pre-trematic, 69
of pterygoid canal, 1321, 1360
pudendal, 690, 704, 931
to pyriformis, 930
to quadratus femoris, 540, 930
radial, 433
 
in arm, 459
 
cutaneous branches of, 433, 460,
467
 
in forearm, 475
 
muscular branches of, 433, 460,
461
 
rami communicantes, 1635
in abdomen, 838
cervicales, 1189, 1206
in neck, 1334
in pelvis, 947
in thorax, 1104
 
ramus descendens hypoglossi, 1189,
 
1205
 
to rhomboids, 402, 430 , 1194
sacral, 928, 929
 
posterior rami, 529, 530
 
 
 
 
 
 
 
INDEX
 
 
i75i
 
 
Nerves ( continued )—
saphenous, 557
sciatic, 540, 544, 931
scrotal, posterior, 691
to serratus anterior, 430, 1194
spinal nerves, origins of, 1418
 
posterior primary rami of,
 
4 11 , I 4 1 9
roots of, 1419
 
thoracic, 1099
spinosus, 1168, 1399
splanchnic, 1105
pelvic, 930, 947
to stapedius, 1402
stylo-hyoid, 1272
to subclavius, 431, 1195
subcostal, 728, 849
 
lateral cutaneous branch of, 531,
728
 
suboccipital, 1141, 1152
subsartorial plexus, 431
subscapular, 431
subtrapezial plexus, 399
supraclavicular, 412, 1144
supra-orbital, 1153 , 1254, 1276
suprascapular, 431, 438, 1195
supratrochlear, 1154 , 1254, 1276
sural, 550, 615
 
communicating, 551
sympathetic trunk in abdomen, 838
ganglia of—
 
cervical, inferior, 1335
middle, 1334
superior, 1333
impar, 946
in neck, 1333 , 1335
 
cardiac branches, 1334,
1335
 
constitution of, 1335
in pelvis, 946
plexuses—
 
aortic, 811
cardiac, 1046
carotid, internal, 1170
coeliac, 807, 809
coronary, 1048
diaphragmatic, 809
gastric, 809
hepatic, 809
hypogastric, 811, 922
mesenteric, inferior, 811
superior, 809
ovarian, 811
pelvic, 922
phrenic, 809
renal, 809
splenic, 809
suprarenal, 809
testicular, 811
in thorax, 1104
temporal, deep, 1309, 1311
tentorii, 1168
thoracic, spinal, 1099
 
anterior rami, 996
to thyro-hyoid, 1206
 
 
Nerves ( continued )—
 
tibial, anterior, 610, 614
posterior, 627
of tongue, 1347
trochlear. See Cranial nerves
tympanic, 1325
ulnar, 432
 
in arm, 458
 
cutaneous branches of, 448, 466,
499
 
deep division of, 499
digital branches of, 499
dorsal branch of, 467
in forearm, 480
in hand, 499
 
palmar cutaneous branch of, 466,
 
477
 
vagus. See Cranial nerves
vestibular, 1404, 1622, 1693
in visceral arches, 69, 1121
zygomatic, 1319
zygomatico-facial, 1259, 1277
zygomatico - temporal, 1158, 1259,
 
1276
 
Nerve-plexuses—
 
annularis, of cornea, 1645
 
aortic, 811
 
brachial, 429, 1193
 
buccal, 1275, 1277
 
cardiac, deep and superficial, 1046
 
carotid, internal, 1170
 
cervical, 1185
 
coccygeal, 531, 931
 
coeliac, 807, 809
 
coronary, 1048
 
diaphragmatic, 809
 
gastric, 809
 
hepatic, 809
 
hypogastric, 811, 922
 
infra-orbital, 1274, 1276
 
intra-epithelial, of eye, 1645
 
lumbar, 844
 
mesenteric, inferior, 811
superior, 809
myenteric, 863, 869
oesophageal, 1043, 1087
ovarian, 811
parotid, 1273
patellar, 557
pelvic, 922
pharyngeal, 1329
phrenic, 809 , t
 
pudendal, 929
pulmonary, 1043, 1045
renal, 809
sacral, 928
splenic, 809
 
subepithelial, of eye, 1645
of submucosa of small intestine,
 
863, 869
 
subsartorial, 558
subtrapezial, 399
suprarenal, 809
testicular, 811
tympanic, 1325
 
 
 
 
 
 
 
 
T 75 2
 
 
INDEX
 
 
Nerve-roots, 1419
Nervous system, 1410
 
development, 53
Neural canal, 40
crest, 54
groove, 34, 40
tube, 42, 53
 
Neurenteric canal, 34, 35, 37
Neuroblasts, 54, 1438
Neuro-central lip, 126
synchondrosis, 142
Neuroglia of spinal cord, 1410
Nictitans, membrana, 1292
Nigra, substantia, 1539, 1560
Node, atrio-ventricular, 1071
sino-atrial, 1070
Nodules of aortic valve, 1063
Normal, definition of, 5
Nose, 1298
 
cartilages of, 1298
development of, 83, 1363
lymphatics of, 1298, 1363
nerves of, 1360
Notch or notches—
acetabular, 340
carotid, 200
 
cystic, of liver, 756, 777
ethmoidal, of frontal, 182
fibular, of tibia, 363
frontal, 181
intercondylar, 353
interlobar, of liver, 777
jugular, 176
mandibular, 232
mastoid, 187, 258
nasal, 212
 
of frontal, 181
of maxilla, 221
parietal, 188
pre-occipital, 1499
sciatic, greater and lesser, 340
spheno-palatine, 228
spino-glenoid, 294
supra-orbital, 181, 247
suprasternal, 162
trochlear, of ulnar, 312
tympanic, 1673
umbilical, of liver, 777
Notochord, 23, 39 , 167
in vertebras, 59
Notochordal groove, 35, 167
Nuchae, ligamentum, 399, 1144
Nuchal flexure, 58
furrow, 1141
groove, 397
 
Nuck, canal of, 743, 744, 969
Nuclear membrane, 9, 15
reticulum, 9, 15
Nuclein, 9
Nucleolus, 9, 15
Nucleoplasm, 8
Nucleus or nuclei—
abducent, 1473
accessory, 1628
ambiguous, 1626 , 1626, 1627
 
 
Nucleus or nuclei ( continued )—
amygdaloid, 1524, 1632
arcuate, 1462
caudatus, 1526
of cell, 9, 15
cochlear, 1620
cuneatus, 1460
dentate, 1485
emboliformis, 1485
of facial nerve, motor, 1472, 1617
sensory, 1619
 
of fasciculis solitarius, 1619, 1626
 
globosus, 1485
 
gracilis, 1459
 
hypoglossal, 1629
 
of lateral lemniscus, 1475
 
lateralis, 1462
 
lentiformis, 1526
 
oculo-motor, 1561, 1611
 
olivary, 1461, 1472
 
pontis, 1469, 1470
 
pulposus, 1107, 1108
 
red, 1539, 1553
 
subthalamic, 1540
 
thoracici, 1424, 1425
 
of trapezium, 1471
 
of trigeminal nerve —
 
mesencephalic root of, 1561, 1615
motor of, 1474, 1615
pontine, 1474
 
sensory of, 1472, 1474, 1615
trochlear, 1561 , 1614
vago-pharyngeal, dorsal, 1624
vestibular, 1622
Nutrient arteries—
of femur, 587
of fibula, 626
of humerus, 455, 456
of radius, 478
of tibia, 626
of ulna, 478
Nutrient foramina—
of clavicle, 290
of fibula, 366
of humerus, 300
of radius, 307, 311
of ribs, 157
of scapula, 295
of tibia, 361
of ulna, 314
nutrient nerves—
to fibula, 627
to radius, 481
to tibia, 550 '
to ulna, 481
 
Obelion, 238, 243, 268
Obex, 1490
 
Oblique cord of forearm, 521
ligament of Cooper, 518
Obliquus capitis inferior, 1150
superior, 1150
externus abdominis, 717
inferior, of eye, 1251
internus abdominis, 722
 
 
 
 
 
 
 
 
 
INDEX
 
 
1753
 
 
Obliquus, superior, of eye, 1250
Oblongata, medulla, 1443, 1451
Obstetrical hinge-joint, 177
Obturator artery, 589, 925 , 927
abnormal, 566
canal, 579, 993
crest, 340
 
externus muscle, 579
fascia, 920
foramen, 340
groove, 340
 
internus muscle, 535, 949
nerve to, 539, 93°
membrane, 993
nerve, 557, 579, 846
accessory, 580 , 847
Occipital artery, first part, 1218
second part, 1146
third part, 1146
bone, 172
 
condyles, 175, 258
crests of, 174, 259, 264
ossification of, 177
point, 243, 268
 
protuberance, 172, 174, 243, 1141
varieties, 176
groove, 258
lobe of brain, 1148
lymphatic glands, 1148
nerve, greater, 1141 , 1152
lesser, 1142
third, 1142 , 1152
point, 243, 268
 
protuberance, external, 172, 243, 1141
sinus, 1606
triangle, 1184
veins, 1148
venous plexus, 1147
Occipito-axial ligaments, 1407
Occipito-frontalis, 1154
Ocular appendages, 1289
Oculo-motor nerve, 1165, 1253, 1446
nucleus, 1561, 1611
Odontoblasts, 284, 287
Odontoid process of axis, 131
(Esophagus, cervical part of, 1227
development of, 66, 78, 1088
lymphatics of, 1088
structure of, 1088
thoracic part of, 1087
Olecranon, 312
bursa, 447
fossa, 304
rete, 479
 
Olfactorium, trigonum, 1511
Olfactory apparatus, development of, 1511
bulb, 1165, 1510 , 1570
structure of, 1570
capsule, 271, 276
foramina; 261
groove of ethmoid, 207
of sphenoid, 197
lobe, 1510
 
mucous membrane, 1359
nerves, 1165, 1360 ? i6ji
 
 
[ Olfactory organ, 271
 
tract, 1445, 1511 , 1570
Olivary nuclei, 1461, 1472
Olive of medulla, 1453, 1454
Omentale, tuber, of liver, 774
of pancreas, 807
Omentalis, bursa, 79, 81
Omentum, definition of, 779
greater, 756, 784
lesser, 785
Omo-hyoid, 1200
 
inferior belly of, 402, 437
Ontogeny, 7
Oocyte, 13, 14, 16, 17
Oogenesis, 16
Oogonia, 13, 16
Opening into lesser sac, 790
saphenous, 551, 561 , 707
to tympanic antrum, 188, 1681
Openings in diaphragm, 835
Opercula insulae, 1506
Operculum, frontal, 1498
fronto-parietal, 1498
orbital, 1498
Ophryon, 244, 268
Ophthalmic artery, 1170, 1259
 
nerve, 1168, 1254, 1258, 1616
veins, 1261
Opisthion, 258, 268
Opisthotic centre, 195
Opponens digiti minimi, 496
pollicis, 494
Optic chiasma, 1545
cup, 1666, 1668
disc of retina, 1653
foramen, 200, 245, 247, 261
groove, 197, 261
nerve, 1545
 
development of, 1668
in orbit, 1253
origin, deep, 1611
superficial, 1446
radiation, 1547 , 1566, 1568
recess, 1545
stalk, 1665, 1668
tract, 1445, 1545
vesicle, 1664
Oral fissure, 1337
Ora serrata of retina, 1652
structure of, 1658
Orbicularis ciliaris, 1647
oculi, 1264, 1265
oris, 1271
Orbit, 245
 
contents of, 1247
fascia of, 1252
 
Orbital area of cerebrum, 1493
fascia, 1252
fissure, inferior, 247
superior, 247
index, 269
 
plate of ethmoid, 208
of frontal, 182
of maxilla, 213
process of zygomatic, 219
 
 
 
 
 
1754
 
 
INDEX
 
 
Organ, spiral, 1691
Organogeny, 48
Orifice or orifices—
aortic, 1062
of bladder, 951
cardiac, topography of, 1064
of coronary sinus, 1055
mitral, 1061
 
oesophageal, of stomach, 760, 761
pulmonary, 1059
pyloric, 760
tricuspid, 1055, 1057
urethral—
 
female, 695
male, 715, 938
of vagina, external, 695
vena cava, inferior, 1054
superior, 1054
 
Oropharyngeal isthmus, 1350
Orthognathous skulls, 244, 269
Os centrale, 322
dentatum, 133
japonicum, 221
pubis, 331
trigonum, 370
of uterus, external, 974
internal, 976
Ossa suturarum, 265
Ossification of bones, 119
centres, 119
law of, 304
of named bones—of atlas, 142
of axis, 143
of carpal bones, 322
of clavicle, 292
of coccyx, 151
of ethmoid, 211
of femur, 354
of fibula, 367
of hip bone, 341
of humerus, 305
of lacrimal, 223
of maxillae, 218
of metacarpals, 329
of metatarsals, 386
of nasal, 222
 
concha, inferior, 224
of occipital, 177
of palatine, 228
of phalanges of foot, 386
of hand, 386
of radius, 311
of sacrum, 149
of scapula, 298
of sphenoid, 205
of sternum, 164
of tarsal bones, 378
of temporal, 195
of tibia, 363
of ulna, 315
of vomer, 229
of zygomatic, 221
 
Osteoblasts and osteoclasts, 120, 121
Osteogenic fibres, 120
 
 
Ostium abdominale, 19, 972
Otic capsule, 75, 272
ganglion, 1314
Otoconia, 1688
 
Ovarian follicles, vesicular, 982
plexus, nervous, 811
venous, 979
pregnancy, 19
Ovary, 969
 
abnormal positions of, 104, 971
descent of, 970
development of, 100, 980
ligament of, 970, 982
suspensory, of, 970
ovulation in, 18, 19
structure of, 98
Ovocentre, 21
Ovulation, 18, 19
Ovum, 8, 14 , 16
 
fertilization of, 20
growth in pregnancy, 105
maturation of, 19
segmentation of, 21
transit to uterus, 19
 
 
Pacinian bodies of foot, 653
of hand, 490
Palate folds, 84
soft, 1350
 
development of, 86, 1354
glands of, 1351
muscles of, 1351
nerves of, 1354
relation to structures in, 1354
Palatine arteries—
 
ascending, 1217
of ascending pharyngeal, 1220
greater, 1308 , 1338, 1362
lesser, 1308
bones, 224
 
development of, 277
foramina of, 226
ossification of, 228
tubercle of, 226
nerves, 1322, 1338
Palatino-vaginal canal, 199
Palato-glossal arches, 1350
Palato-glossus, 1351
Palato-pharyngeal arches, 1350
Palato-pharyngeus, 1351
Pallidus, globus, 1528
Palmar aponeurosis, 484
 
arch, deep, 484, 497, 499
 
superficial, 483, 484, 498
cutaneous branch of median, 466, 481
of ulnar, 466, 477
metacarpal arteries, '498
space, 492
 
Palmaris brevis, 484
longus, 470, 487
Palpebral arteries, 1260, 1281
Pampiniform plexus, 738
Pancreas, 806
 
blood^supply, 893
 
 
 
 
 
 
 
 
 
INDEX
 
 
1755
 
 
Pancreas connections, position and relations of, 806
development of, 80, 894
lymphatics of, 893
structure of, 891
tuber omentale of, 807
Pancreatic duct, 892
 
accessory, 892
Panniculus carnosus, 1175
Papilla, duodena], 865
lacrimalis, 1289
Papillae of tongue, 1344
Paracentral lobule, 1499
Parachordal cartilages, 271
Paradidymis, 750
Parafloccular fossa, 191
Paraflocculus, 1481
Paraganglia, 1105
Paramesonephric duct, 101, 987
Parametrium, 974
Paranasal sinuses, 250
 
development of, 1364
Pararectal recess, 919
Parasympathetic system, 1410, 1639
cranial, 1639
sacral, 1640
 
Parathyroid glands, 1223
 
development of, 76
Paravesical recess, 919
Paraxial mesoderm, 40, 41
Parietal bones, 178
 
ossification of, 180
varieties of, 180
eminence, 178, 1633
foramen, 179, 243
notch of temporal, 188
Paroccipital process, 176
Paroophoron, 971
 
development of, 754, 987
Parotid duct, 1287
gland, 1284
 
development of, 1289
structure of, 1288
lymphatic glands, 1283
plexus, 1273
Pars iridica retinae, 1650
Patella, 355
 
ossification of, 357
structure, 356
Patellar plexus, 557
retinacula, 629
Pectineus muscle, 571
Pectoral lymphatic glands, 424, 434
nerves, 431
region, 412
ridge, 300
 
Pectoralis major, 418
minor, 420
 
Pedicles of vertebrae, 128
Pelvic fascia in female, visceral, 968
in male, parietal, 919
visceral, 921
 
Pelvis, 914
 
axes of, 344
 
bony, 342
 
 
Pelvis, brim of, 342
of child, 345
contents of, 915
diameters, 342
false, 342
female, 965
 
peritoneum, 966
viscera, position of, 966
inclination, 344
inlet, 342
of kidney, 907
male, 916
 
peritoneum of, 917
viscera, position of, 916
measurements of, 345
outlet, 344
 
sexual differences of, 345
true, 342
Penis, 712
 
angle of, 942
bulb of, 682, 953
composition of, 714
corona glandis, 712, 715
corpora cavernosa, 953
corpus spongiosum, 953
coverings of, 712
crus, 682
 
fascial sheath of, 713
frenulum of, 713
glans, 715
prepuce, 713
septum of, 953
structure of, 953
suspensory ligament of, 713
Perforaculum, 13
 
Perforating arteries of foot, 613, 657
of hand, 498
of profunda femoris, 586
cutaneous nerve, 931
Pericardium, 1017
 
development of, 46, 67, 1019
lymphatics of, 1019
sinus, transverse, of, 1018
structure of, 1019
Perichoroidal lymph space, 1643
Pericranium, 1157
Perilymph of internal ear, 1687
Perilymphatic duct, 193
Perineal body, female, 701
male, 681
fascia, 675
fold, 957
 
membrane, 683, 701
pouch, 679
triangle, deep, 682
Perineum, female, 692, 701
male, 674
 
Periodontal membrane, 287
Periosteum, 121
 
Periotic cartilaginous capsules, 195
Perirenal capsule, 818
Peritoneum, 779
 
course of transverse, 782
vertical, 780
development of, 81, 795
 
 
 
 
 
1756
 
 
x INDEX
 
 
Peritoneum in foetus, 793
folds of, 744, 792
ligaments, 788
mesenteries, 786
omenta, 784
fossae, 744, 791
parietal, 744
pelvic, in female, 966
in male, 917
primitive, of testis, 741
recesses of, 791, 919
sac, greater, 789
 
lesser, 81, 785, 790
structure of, 795
Perivascular spaces, 1436
Peroneal artery, 610, 626
retinaculum, 601
tubercle, 372, 388
Peroneus brevis, 617
longus, 615
tertius, 607
 
Perpendicular plate, ethmoid, 208
of palatine, 214
Pes hippocampi, 1525
Petrosal process, posterior, 198
sinus, inferior, 1607
superior, 1606
 
Petro-sphenoid ligament, 193
Pfliiger, cords of, 753
Phalanges of foot, 384, 385
ossification of, 386
of hand, 329
 
ossification of, 329
Pharyngeal artery, ascending, 1219
bursa, 168, 1373
plexus, 1329
pouches, 70, 76, 1373
recess, 1372
tubercle, 258
 
Pharyngo-basilar fascia, 1371
Pharyngo-epiglottic folds, 73, 1380
Pharyngo-tympanic canal, 257 "
groove, 257
tube, 1378
 
development of, 73, 74, 1378
Pharynx, 1366
 
blood-supply of, 1373
development of, 1373
laryngeal part of, 1373
lymphatics of, 1373
muscles of (constrictor), 1368
nasal part of, 1371
oral part of, 1373
Phenozygous skulls, 243
Philtrum, 1336
Phrenic artery, 827
 
nerve in neck, 430, 1189
in thorax, 1015
Phylogeny, 7
Pia mater, cranial, 1610
spinal, 1414
 
Pigmentary layer of retina, 1657
Pillars of fornix, 1516, 1517
Pineal body, 1540
 
development of, 58, 1390
 
 
1 Pineal recess, 1534
Pinna, development of, 67, 1697
Pisiform bone, 318, 333
 
ossification of, 322
joint, 524
 
Piso-hamate ligament, 473, 524
Piso-metacarpal ligament, 473, 524
Pit for ligament of head of femur, 346
Placenta, 24, 108
 
formation of, 106
separation of, 107
septa, 109
 
sinus, marginal, of, 106, no
structure of, 108
Plagiocephalus, 270
Plane, intertubercular, 755
subcostal, 755
Plantar aponeurosis, 642
arch, 655, 657
artery, lateral, 655 , 657
medial, 654 , 657
ligament, long, 667
short, 667
nerve, lateral, 653
medial, 652
triangle, 650
Plantaris, 620
Planum temporale, 178
Plasmodi-trophoblast, 27
Plasmodium in embedding of ovum, 27
Platycnemism, 363
Platymeria, 354
Platyrhine skulls, 269
Platysma, 1175
Pleura, 1005
 
development of, 78, ion
lymphatics of, ion
reflection of, 1005
lines of, 1007
 
Pleural sacs, development of, 78
differences between, ion
Plexus, choroid, of fourth ventricle, 1492
of lateral ventricle, 1521
 
of inferior horn of, 1525
 
of nerves—
 
annularis, of cornea, 1645
aortic, 811
brachial, 429, 1193
buccal, 1275, 1277
cardiac, deep and superficial,
1046
 
carotid, internal, 1170
cervical, 1185
coccygeal, 531, 931
coeliac, 807, 809
coronary, 1048
diaphragmatic, 809
gastric, 809
hepatic, 809
hypogastric, 811, 922
infra-orbital, 1274, 1276
intra-epithelial, of eye, 1645
lumbar, 844
 
mesenteric, inferior, 811
superior, 809
 
 
 
 
 
 
 
 
INDEX
 
 
1757
 
 
Plexus of nerves ( continued )—
myenteric, 863, 869
oesophageal, 1043, 1087
ovarian, 811
parotid, 1273
patellar, 557
pelvic, 922
pharyngeal, 1329
phrenic, 809
pudendal, 929
pulmonary, 1043, 1045
renal, 809
sacral, 928
splenic, 809
 
subepithelial, of eye, 1645
of submucosa of small intestine, 863, 869
subsartorial, 558
subtrapezial, 399
suprarenal, 809
testicular, 811
tympanic, 1325
of veins—
 
dorsal, of foot, 610
of hand, 467
spinous, 1435
occipital, 1147
ovarian, 979
pampiniform, 738
prostatic, 952
pterygoid, 1308
suboccipital, 1152
vesical, 952
Plica fimbriata, 1343
 
semilunaris of conjunctiva, 1289,
1292
 
sublingualis, 1336
Plicae villosae, 858
Point, alveolar, 244, 268
auricular, 251, 268
jugal, 251, 268
mental, 244, 268
nasal, 240, 244, 268
occipital, 243, 268
pre-auricular, 1629
Rolandic, inferior, 1633
superior, 1633
subnasal, 244, 268
Sylvian, 1632
Polar bodies, 16, 17
Pollicis, abductor brevis, 493
longus, 505
adductor, 494, 496
dorsalis artery, 511
extensor brevis, 505
longus, 505
flexor brevis, 494
longus, 482, 496
opponens, 494
princeps artery, 487, 497
Pons of brain, 1444, 1468
hepatis, 775, 777
Pontine flexure, 57
Pontis, cisterna, 1609
Poto-bulbar body, 1584
 
 
Popliteal artery, 541, 546
 
genicular branches, 548
fascia, 546
fossa, 541, 545
groove, 352
lymphatic glands, 551
nerve, lateral, 550 , 931
Popliteal nerve, medial, 550 , 93 i
vein, 546, 549
Popliteus, 621
nerve to, 550
Porta hepatis, 775
Portal canals, 885
sinus, 816
vein, 816 , 885
Porus opticus, 1653
Position, formal, 3
Post-anal gut, 98
Post-auditory process, 193
Post-axial, definition, 5, 122
Post-glenoid tubercle, 183
Post-trematic nerves, 69
Pouch or pouches—
 
of epitympanic recess, 1681
perineal, 679
of Rathke, 87 , 206, 1171
recto-uterine, 966
recto-vesical, 918
vesico-uterine, 967
Praecuneus of brain, 1502
Pre-auricular, 1629
Pre-axial, definition, 5, 122
Precervical sinus, 67
Preglenoid tubercle, 186
Pregnancy, extra-uterine, 19
Pre-interparietal bone, 265
Prelaryngeal lymphatic glands, 1199,
1386
 
Premaxilla, 218, 277
Prepatellar bursa, 554, 640
rete, 548
 
Prepuce of clitoris, 695
of penis, 713
 
Pretracheal lymphatic glands, 1199, 1225
Pretrematic nerves, 69
Primitive jugular, 51, 1127
mesoderm, 26
oesophagus, 66
pharynx, 44, 65, 66
floor, 70
segments, 40
streak, 33 , 34
 
Princeps pollicis artery, 487, 497
Process or processes—
 
alveolar, of maxilla, 214
angular, medial, 181
articular, 139
 
auditory, external, of temporal, 194
clinoid, anterior and middle, 200, 261
posterior, 198, 261
condyloid, of mandible, 233
coracoid, 296
coronoid, of mandible, 232
of ulna, 312
 
costal, of cervical vertebrae, 128
 
 
 
 
 
 
 
 
 
1758
 
 
INDEX
 
 
Process or processes ( continued )—
 
ethmoidal, of inferior nasal concha,
223
 
frontal, of maxilla, 214
of zygomatic, 220
infra-orbital, of zygomatic, 220
jugular, of occipital, 176 , 258
of lacrimal, descending, 222
 
of inferior nasal concha, 223
mamillary, 139
maxillary—
 
of inferior nasal concha, 223
of palatine, 226
of zygomatic, 220
nasal, of frontal, 181
odontoid, 131
orbital, of zygomatic, 219
palatine, of maxilla, 215
paroccipital, 176
petrosal, posterior, 198
post-auditory, 195
pterygoid, of sphenoid, 203
sphenoidal, of palatine, 227
spinous, of cervical vertebrae, 127
styloid, of fibula, 364
of radius, 309
of temporal, 194, 257
of ulna, 315
supracondylar, 302
temporal, of zygomatic, 220
transverse, of cervical vertebrae, 128
uncinate, of ethmoid, 210
of pancreas, 806
vaginal, of sphenoid, 198
of temporal, 192, 194
xiphoid, 163
 
zygomatic, of frontal, 181
of maxilla, 214
of temporal, 185
 
Processus cochleariformis, 193, 1675
reticularis of spinal cord, 1421
tubarius, 204
Proctodaeum, 698
Profunda brachial artery, 455
femoris artery, 584 , 588
Prognathous skulls, 244, 269
Projection of facial canal, 1674
fibres of cerebrum, 1565
Proligerus, discus, 18, 982
Promontory of middle ear, 1674
of sacrum, 144
Pronator quadratus, 482
teres, 469, 470
Prone, definition, 5
Pronephros, 92, 94 , 912
Pronucleus, female, 8, 16
male, 8
 
Pro-otic centre, 196
Prostate gland, 937
 
blood-supply of, 960
development of, 960
lymphatics of, 960
structure of, 959
Prostatic fissure, 937
sinus, 939
 
 
Prostatic utricle, 939
Prostomial mesoderm, 36
Protocardiac area, 34
Protoplasm, 8
. Protuberance, mental, 229
occipital, external, 172
internal, 174
 
Pseudo-ganglion. See Gangliform enlargement
Psoas major, 841
minor, 842
sheath, 839
 
Pterion, 180, 239, 253, 268, 1631
Pterotic centre, 196
Pterygoid canal, 204, 255, 263
artery of, 1308, 1362
nerve of, 1321, 1360
fissure, 203
fossa, 203, 257
hamulus, 204
muscle, lateral, 1302
medial, 1304
 
plates of sphenoid, 203, 204
development, 277
plexus of veins, 1308
processes, 203
tubercle of sphenoid, 204
Pterygo-mandibular ligament, 1181
Pterygo-maxillary fissure, 253
Pterygo-palatine canal, 227
fissure, 253
fossa, 254
 
Pterygo-spinous foramen, 203
ligament, 1181
Pubic angle, 339, 552
artery, 731
crest, 339, 552
guide to, 707
 
relation of structures at, 728
lymphatic glands, 558
symphysis, 992
tubercle, 339
 
guides to, 551, 706
Pubis, os, 339
 
Pubo-femoral ligament, 599
Pudendal arteries—
 
external, deep, 584
 
superficial, 548, 710
internal, 539, 686, 703, 925
accessory, 689
band, 929
canal, 688
nerve, 690, 704, 931
Pulmonary alveoli, 1028
groove of thorax, 166
orifice of heart, 1059
 
position of, 1064
outgrowth from foregut, 70, 77
valve of heart, 1059, 1064
Pulvinar of thalamus, 1537
Punctum lacrimale, 1289
Pupil, 1648
 
Pupillaris, membrana, 1652
Purkinje, cells of, i486
fibres of, 1070
 
 
/
 
 
 
 
 
INDEX
 
 
1759
 
 
Pyloric antrum, 760
glands, 859
sphincter, 857, 861
valve, 861
Pylorus, 861
 
position of, 761
Pyramid of cerebellum, 1480
of medulla, 1452 , 1470
of middle ear, 190, 1765
Pyramidal fibres in mid-brain, 1559
layer of cortex, 1562
lobe of thyroid, 1221
tract, 1565
 
Pyramids, decussation of, T451, T433
Pyriform fossa, 76, 1373, 1386
Pyriformis, 534, 948
 
Quadrate lobe of liver, 774
lobule of brain, 1502
Quadratus femoris, 535
 
nerve to, 540, 930
lumborum, 843
Quadriceps femoris, 572, 573
Quadrigemina, corpora, 1547
Quadrilateral space, 441
 
Radial artery, 473
 
first part, 474
 
recurrent branch of, 475
second part, 509
third part, 497
varieties of, 475, 498
nerve, 433
 
in arm, 459
 
cutaneous branches of, 433, 460,
467
 
in forearm, 475
 
muscular branches of, 433,
 
460, 461
vein, 450
 
Radiata, corona, 1515, I 53 1
of ovum, 14, 19
Radiatio corporis callosi, 1513
Radiation, auditory, 1568
callosal, 1568
optic, 1566, 1568
thalamic, 1567
Radius, 306
 
grooves of, 309
head of, 306
lines, 307
ossification of, 311
styloid process, 309
tubercle, dorsal, of, 309
tuberosity of, 307
Rami communicantes, 1635
in abdomen, 838
cervicales, 1189, 1206
in neck, 1334
in pelvis, 947
of pubis, 339
in thorax, 1104
 
Ramus descendens hypoglossi, 1205
of ischium, 338
of mandible, 231
 
 
Raphe, palpebral lateral, 1265
scrotal, 716
 
Rathke, pouch of, 87 , 206, 1171
Rays, medullary, of kidney, 901
Receptive cone, 21
Recess or recesses—
cochlear, 1683
elliptical, 1683
epitympanic, 1681
 
infundibular, of third ventricle, 1533
lateral, of fourth ventricle, 1489
optic, of third ventricle, 1533
peritoneal, duodenal, 791
duodeno-jejunal, 792
inguinal, 745
pararectal, 919
paravesical, 919
pericaecal, 792
sphero-ethmoidal, 1337
suprapineal, 1334
tubo-tympanic, 73
of the utricle, 1687
Rectal arteries, inferior, 963
middle, 925, 963
superior, 802, 963
pits, 961
 
Recti muscles of eyeball, 1249
Recto-uterine folds, 967
pouch, 966
 
Recto-vesical pouch, 918
Rectum, ampulla of, 944
blood-supply of, 963
development of, 965
female, 978
flexures of, 944
horizontal folds of, 961
lymphatics of, 964
male, 943
 
peritoneal relations of, 944
structure of, 960
Rectus abdominis, 726
sheath of, 727
capitis anterior, 1397
lateralis, 1397
posterior major, 1149
minor, 1150
femoris, 572
 
Recurrent artery, anterior tibial, 609
ulnar, 477
 
interosseous, posterior, 508
radial, 475
 
laryngeal nerve, 1044, 1045, 1330 ,
1395
 
Red nucleus, 1539, 1553
Reduction division, 14, 16, 17
Refracting media of eyeball, 1661
Reichert’s cartilage (of second arch), 74,
75, 273, 278
scar, 104
 
Reid, base line of, 1633
Renal artery, 827
 
sympathetic plexus, 809
vein, 828
 
Respiratory apparatus, development of,
1029
 
 
 
 
 
 
 
INDEX
 
 
1760
 
 
Rete, carpal, anterior, 478, 479 , 498
cords, 100, 752
olecranon, 479
prepatellar, 548
testis, 751
Retina, 1652
 
central artery of, 1260, 1658
ciliary part of, 1647
development of, 1667
fovea centralis, 1653, 1658
macula lutea, 1653, 1658
nerve cells of, 1660
optic disc, 1653
ora serrata, 1652, 1658
rods and cones layer, 1656
structure of, 1653
sustentacular fibres of, 1657
Retinaculum or retinacula—
of ankle, 601
extensor, of ankle, 603
of hand, 508
flexor, of ankle, 602
of hand, 493
of hip-joint, 393
patella, 629
peroneal, 601
 
Retro-pharyngeal space, 1179
Retro-pubic cellular tissue, 919
Retzius, cave of, 339
Rhinencephalon, 1512
Rhinion, 240, 244, 268
Rhombencephalon, 1451
Rhomboideus major, 401
minor, 401
 
Rhomboids, nerve to, 402, 430
Rib, first, 157
second, 158
Ribs, 154
 
development of, 59, 170
ossification of, 160
varieties, 159
Rider’s bone, 354
Ridge, pectoral, 300
 
pelvic, transverse, 101
supinator, of ulna, 314
teres, 300
 
Rima glottidis, 1388
Ring, femoral, 551, 566
guide to, 707
inguinal, deep, 735
 
guide to, 708
superficial, 551, 720
guide to, 707
Risorius, 1269
Rods of retina, 1656
Rolandic angle, 1633
points, 1633
Roof-plate, 53
Roots of spinal nerves, 1419
 
development of, 54
Rostrum of corpus callosum, 1514
Rotatores, 410
Rotunda, fossa, 1674
Rotundum, foramen, 201 , 255, 263
Rugarum, columnae, of vagina, 986
 
 
Sac, lacrimal, 1293
 
development of, 1294
peritoneal, greater, 786, 789
lesser, 785, 790
 
opening into, 790
Saccule of internal ear, 1688
of larynx, 1387
 
Sacculus endolymphaticus, 1688
Sacral groove, 153
 
nerves, posterior rami, 528, 530
plexus, 928
spina bifida, 154
Sacro-spinous ligament, 991
Sacro-tuberous ligament, 542, 990
Sacro-vertebral angle, 15T
Sacrum, 144
alae, 148
apex, 148
canal of, 148
ossification, 149
promontory of, 144
sexual characteristics, 149
varieties, 148
Sagittal line, 1630
suture, 237, 1630
 
Saphenous branch of descending genicular
artery, 587, 589
nerve, 557
 
opening, 551, 552, 561
guide to, 707
vein, long, 559, 600
short, 600, 615
Sartorius, 568
Sauropsida, 23, 33
Scala tympani, 1689
vestibuli, 1689
Scalene tubercle, 157
Scalenus anterior, 1235
medius, 1236
posterior, 1236
Scalp, anterior part of, 1153
fascia of, 1153
 
superficial veins and nerves of, 1153'
as a whole, 1162
Scansorius, 534
Scaphocephalus, 270
Scaphoid bone, 316
 
ossification of, 322
tubercle of, 316, 332
fossa of auricle, 1295
of sphenoid, 204
Scapula, 292
 
acromion, 296
coracoid process, 296
glenoid cavity, 294
ossification, 298
spine, 295
varieties, 298
Scapular anastomosis, 441
circumflex artery, 427
ligaments, 445
Schindylesis, 242 , 394
Sciatic band, 929
 
nerve, 540, 544, 931
notch, greater, 340
 
 
 
 
 
 
INDEX
 
 
1761
 
 
Sciatic notch, lesser, 340
Sclera, 1642
Scrotum, 715
 
arteries of, 717
development of, 700, 717
lymphatics of, 717
nerves of, 717
septum, 716
skin of, 716
 
structures forming wall, 716
Segmentation, 40
cavity, 24
 
in archenteron, 38
cells, 21, 22
nucleus, 21
in ovum, 21
 
Sella turcica of sphenoid, 197, 261
Sellae, diaphragma, 1163, 1603
Semicircular canals, 1684
ducts, 1688
 
Semicircularis stria, 1532
Semilunar cartilages of knee, 632
tract of cord, 1430
Semilunaris, hiatus, 1357
Semimembranosus, 543
Seminal vesicles, 936
 
blood-supply of, 959
development of, 959
lymphatics of, 959
structure of, 958
Seminiferous tubules 752
Semispinalis capitis, 407
cervicis, 408
thoracis, 408
Septum of clitoris, 694
ilio-pectineal, 856
linguae, 1346
lucidum, 1518
of nose, 248
 
formation of, 85
of penis, 953
primum, 1075
* secundum, 1076
 
transversum, 46, 78, 79
of ear, 1688
 
Serial homology, 6, 41, 122
Serosa, 32
 
Serrata, ora, of retina, 1652, 1658
Serratus anterior, 401, 434
posterior, inferior, 403
superior, 402
 
Sesamoid bones, foot, 386
 
gastrocnemius, 618
great toe, 648
hand, 329
patella, 574
 
in peroneus longus, 617
thumb, 494
 
in tibialis posterior, 623
Sheath, axillary, 429
carotid, 1207
femoral, 565 , 568
of Hertwig, 287
of rectus, 727
 
Shoulder-girdle generalized, 298
 
 
Shoulder-joint, 4&1
ligaments of, 461
Sigmoid groove of temporal, 188
sinus, 1606
 
guide to, 1632
Sino-atrial node, 1070
Sinus, annularis, 1124
basilar, 1607
cavernous, 1169, 1606
cervicalis, 1377
circular, 1606
of epididymis, 748
ethmoidal, 210
frontal, 184
of larynx, 1387
marginal, 1606
 
of placenta, 106, no
maxillary, 217
of Morgagni, 1370
occipital, 1606
 
guide to, 1631
petrosal, inferior, 1607
superior, 1606
 
petro-squamosal, of foetus, 241
petro-squamous, 1607
portal, 816
precervical, 67
prostatic, 939
sagittal, inferior, 1604
superior, 1603
 
guide to, 1631
sigmoid, 1606
 
guide to, 1632
spheno-parietal, 1606
straight, 1605
tarsi, 370, 390
tonsillaris, 1355
transverse, 1605
guide to, 1631
of pericardium, 1018
tympani, 1674
uro-genital, 99
venosus, 46, 52, 90, 1124
sclerae, 1645
 
Sinuses of dura mater, 1163, 1603
paranasal, 250
Sinusoids, 1125
Skeleton, 113
 
general principles, 122
Skull at birth, 265
 
deformities of, 269
development of, 270
of female, 267
racial peculiarities of, 268
sexual characters, 267
as a whole, 237
Smegma, prseputii, 713
Snuff-box, anatomical, 484
Sockets of mandible, 231
of maxilla, 214
Sole of foot, 641
Soleal line, 361
Soleus, 619
 
Solitarius, fasciculus, 1625, 1626
nucleus of, 1619, 1625
 
 
in
 
 
 
 
 
 
 
 
 
1762
 
 
INDEX
 
 
Solitary lymphatic nodules, 868
Somatopleure, 40
Somites, mesodermal, 40
Space or spaces—
 
interglobular, 285
intervillous, 105, 108
of irido-corneal angle, 1645
middle palmar, 492
perivitelline, 14
quadrilateral, 441
retropharyngeal, 1179
suprasternal, 1179
thenar, 492
triangular, 441
zonular, 1664
Spermatic cord, 736
 
coverings of, 739
fascia, external, 739
internal, 739
 
Spermatids, 12, 14, 16, 752
Spermatocytes, 13 , 1 7 > 752
Spermatogenesis, 13, 14
Spermatozoa, 8 , 12 , 14. 752
Sphenodon, 302
Spheno-ethmoidal plate, 90
recess, 1357
 
Spheno-mandibular ligament, 234, 1181,
1316
 
Spheno-palatine artery, 1308, 1361
foramen, 255
ganglion, 1320
nerves, 1322, 1338, 1361
notch, 228
Sphenoid bone, 197
lingula, 200
openings in, 204
ossification of, 205
spine of, 201, 257
 
ethmoidal, of, 197
varieties 205
wing, greater, 201
lesser, 200
Sphenoidal air-cells, 199
chonchae, 204
crest, 199
 
process of palatine, 227
Sphincter ani externus, 675
internus, 961, 963
pupillae, 1650, 1652
pyloric, 857, 861
vesicae, 950
 
Spinal arteries, anterior, 1434, 1447, 1575
posterior, 1434, 1447, 1575
cord, 1410
cauda equina, 1417
caudal end of, 1440
central canal of, 1422
columns of, 1418
commissures of, 1418
conus medullaris, 1416
development of, 53, 1436
enlargements of, 1416
fibres, association of, 1425
filum terminale of, 1417
grey matter of, 1420
 
 
Spinal arteries, growth of, 1442
horns of, 1421, 1422
ligamenta denticulata of, 1415
meninges of, 1410
nerve fibres of, course of, 1426
processus reticularis, 1421
sections of, 1423
structure of, internal, 1420
minute, 1424
sulci of, 1418
surfaces of, 1420
tracts of, 1429
white matter of, 1423, 1426
ganglia, 1419, 1428
groove, 397
nerves, 1418
 
origin of, 1418
 
relation of vertebrae to, 1420
posterior primary rami of, 411,
1419
 
roots of, 1419
Spinalis, 406
 
thoracis, 406
Spindle, 10
Spine or spines —
definition, 115
ethmoidal, of sphenoid, 197
iliac, anterior, 334, 335, 551, 707
posterior, 335
of ischium, 338
 
nasal, anterior, of maxilla, 221
of frontal, 181
posterior, 225
of scapula, 295
of sphenoid, 201, 257
suprameatal, 187
Spino-glenoid ligament, 445
notch, 294
 
Spino-thalamic tract, 1432
Spino-umbilical lines, 707
Spiral ganglion, 1694
 
groove of humerus, 300
organ, 1691
Spireme, 10
 
Splanchnic ganglion, 1105
nerves, pelvic, 930, 947
thoracic, 1105
Splanchnopleure, 41
Spleen, 768
 
accessory, 771
 
component parts, connections and
position of, 768
development of, 81, 897
ligaments of, 771, 789
lymphatic nodules of, 896
lymphatics of, 897
nerves of, 897
peritoneal relations of, 771
structure of, 895
Splendens, linea, 1415
“ Splenic dulness, area of, 771
sympathetic plexus, 809
Splenium of corpus callosum, 1514
Splenius, 404
capitis, 404
 
 
/
 
/
 
 
 
 
 
 
 
 
 
INDEX
 
 
i 7 6 3
 
 
Splenius cervicis, 404
Spongioblasts, 54
Spongioplasm, 8
Squamo-mastoid suture, 241
Squamosal suture, 239, 1631
Squamo-tympanic fissure, 1673
Stapedius, 1680
Stapes, 1679
 
development of, 75, 1679
Stellate ganglion, 1104
Stephanion, 251, 268
Sternal angle, 162, 1013
plate, 170
Sternalis, 420
Sternebrae, 161
Sterno-clavicular joint, 443
Sterno-costalis, 1002
Sterno-hyoid, 1201
Sterno-mastoid, 1145, 1182
Sterno-pericardial ligaments, 1018
Sterno-thyroid, 1201
Sternum, 160
 
angle of, 162
body,162
 
development of, 164, 170
foramen of, 164, 171
manubrium, 161
ossification of, 164
sexual characteristics, 164
varieties, 163
xiphoid process, 163
Stomach, 758
 
blood-supply of, 860
component parts, connections and
position of, 758
curvatures of, 759
development of, 79, 862
divisions of, 760
gastro-phrenic ligament, 789
gastro-splenic ligament, 789
glands of, 858
lymphatics of, 860
nerves of, 860
orifices of, 760
peritoneal relations of, 761
structure of, 856
topography of, 761
trigone or uncovered area of, 761
Stomodaeum, 46, 81, 1339
Straight sinus, 1605 ,
 
Stratum cinereum, 1550
granulosum, 1570
laciniosum, 1569
lemnisci, 1550
opticum, 1550, 1564
radiatum, 1569
zonale, 155°
 
Stria longitudinalis and medialis, 1510,
 
1513, 1514
 
Striae, auditory, 1471, 1489, 1620
habenulae, 1534, 1541
Striatum, corpus, 1526
Strio-frontal fibres, 1529
Stylo-glossus, 1232
Stylo-hyal, 75, 197
 
 
Stylo-hyoid ligament, 1232
muscle, 1228
 
Stylo-mandibular ligament, 1181, 1317
Stylo-mastoid foramen, 192
Stylo-pharyngeus, 1323
Styloid, definition of, 115
pr^pess of fibula, 364
of radius, 309
of temporal, 194, 257
of ulna, 315
 
Subacromial bursa, 436, 464
Subanconeus, 459
Subarachnoid space of brain, 1608
of spinal cord, 1413
Subarcuate fossa, 191, 264
Subcallosal gyrus, 1514
Subclavian artery, 1237
 
development of, 1240
left, first part of, 1240
in thorax, 1040
right, first part of, 1237
second part of, 1240
third part of, 1191
 
guide to, 1192
 
groove, 290
triangle, 1190
vein, 1192, 1244
Subclavius, 421
 
nerve to, 431, 1195
Subcostal angle, 165
line, 755
nerve, 728, 849
 
lateral cutaneous branch of, 531,
728
 
plane, 755
 
Subdural space of brain, 1599, 1608
of spinal cord, 1412
Sublingua, 1343
Sublingual artery, 1216
ducts, 1235
fossa, 230
gland, 1234
 
development of, 1235
Submandibular duct, 1233
fossa, 230
ganglion, 1315
gland, 1233
 
development of, 1234
lymphatic glands, 1198
triangle, 1196
 
Submental lymphatic glands, 1199, 1203
triangle, 1202
Subnasal fossa, 244
point, 244, 268
 
Suboccipital nerve, 1141, 1153
region, 1149
triangle, 1150
venous plexus, 1152
Subpubic angle, 344
arch, 344
 
Subsartorial canal, 580
plexus, 558
 
Subscapular artery, 427
nerves, 431
Subscapularis, 440
 
 
 
 
 
 
 
 
 
INDEX
 
 
1764
 
Substance, perforated, anterior, 1445, 1511
posterior, 1445, 1561
Substantia ferruginea, 1491
 
gelatinosa, 1421, 1426, 1459
nigra, 1539, 1560
reticularis of medulla, 1458
Subthalamic nuclei, 1540
region, 1539
tegmental region, 1558
Subtrapezial plexus, 399
Suctorial pad of fat, 1270, 1337
Sulcus, callosal, 1507
central, 1495
centralis insulae, 1506
cingulate, 1496
circular, 1497
ethmoidal, of nose, 221
fimbrio-dentate, 1509
frontal, 1498
hypothalamic, 1533
interaminar, 54
intermedius, 759
intraparietal, 1500
lateralis, of mid-brain, 1551
occipital, lateral, 1503
transverse, 1503
occipito-temporal, 1505
oculo-motor, 1551
olfactorius, 214
olfactory, 1498
orbital, 1498
postcentral, 1500
 
postero-lateral, of spinal cord, 1418
precentral, 1500
sagittal, 181
temporal, 1505
 
terminalis, of right atrium, 1052
of tongue, 1342
tympanic, 1673
Superciliary arch, 181
Supination, 5
 
Supinator ridge of ulna, 314
Supracallosal gyrus, 1514
Supraclavicular branches of brachial
plexus, 430, 1194 *
 
nerves, 412, 1144
 
Supracondylar process of humerus, 302
Suprahyoid muscles, 1227
region, 1202
Supramastoid crest, 185
Suprameatal spine, 187
triangle, 187, 1682
Supra-occipital bone, 275
Supra-orbital artery, 1154, 1260
foramen, 244
margin, 181
 
nerve, 1153, 1254, 1276
notch, 181, 247
vein, 1154
 
Suprapatellar tendon, 574
Suprapineal recess, 1534
Suprapleural membrane, 1007, 1246
Suprarenal glands, 823
 
blood-supply of, 898
development of, 899
 
 
Suprarenal glands, lymphatics of, 898
nerves of, 899
structure of, 897
plexus, 809
 
Suprascapular artery, 402, 438, 1193, 1243
nerve, 431, 438, 1195
notch, 294
vein, 1193
 
Supraspinatus, 437
 
Suprasternal bones, 165
 
branch of suprascapular atrery, 438,
 
1243
 
notch, 162
space, 1179
 
Supratrochlear arteries,—
of brachial, 456
ophthalmic, 1154, 1261
nerve, 1154, 1254, 1276
vein, 1154
 
Sural cutaneous arteries, 548
nerve, 550, 616
 
communicating, 551
 
Suspensoria, ligamenta, of mammary
gland, 414
 
Suspensory ligament of lens, 1664
of penis, 713
 
Sustentacular cells of testis, 14, 752
fibres of retina, 1657
 
Sustentaculum hepatis, 789
lienis, 767
tali, 371, 388
 
Sutural bones, 180, 237, 265
 
Sutures, 237, 394
closure of, 240
coronal, 238
frontal, 238
fronto-maxillary, 240
fronto-nasal, 240
fronto-parietal, 239
fronto-squamosal, 240
harmonic, 394
intermaxillary, 240
internasal, 240
interpalatine, 241
lambdoid, 237
limbous, 238
maxillo-maxillary, 255
metopic or frontal, 238
naso-maxillary, 240
occipito-mastoid, 237
palato-maxillary, 241
parieto-mastoid, 238
petro-basilar, 242
petro-sphenoid, 241
petro-squamosal, 241
premaxillary, 216, 218
sagittal, 237, 1630
schindylesis, 242, 394
serrated, 394
spheno-parietal, 239
spheno-squamosal, 240
squamo-mastoid, 240
squamosal, 239, 1631
zygomatico-maxillary, 240
zygomatico-temporal, 240
 
 
 
 
 
 
 
 
INDEX
 
 
1765
 
 
Sylvian line, 1632
point, 1632
 
Sympathetic ganglia, 1635
 
cervical, inferior, 1335
middle, 1334
superior, 1333
 
plexuses. See Nerves or Plexus
system, 1410, 1635
trunk in abdomen, 838
in neck, 1335
in pelvis, 946
in thorax, 1104
Symphysis of mandible, 229
pubis, 992
 
Synapsis in reduction division, 18
Synchondroses, 242
 
petro-occipital, 242
spheno-occipital, 242
spheno-petrosal, 242
Syndesmosis, 392
Synovia, 393
Synovial bursae, 395
joints, 393
membrane, 393, 395
 
of ankle-joints, 663
of elbow-joint, 519
of hip-joint, 595
of knee-joint, 553, 634
of radio-ulnar joint, 520
inferior, 521
superior, 520
of shoulder-joint, 463
of tibio-fibular joint, 659
superior, 659
of wrist-joint, 523
sheaths at ankle, 602, 603 ^ .
 
of biceps tendon, 465
of extensor tendons of hand, 509
of flexor digitorum longus, 622
hallucis longus, 624
tendons in hand, 491
of toes, 646
of hand, 490
palmar, great, 332
of peroneal tendons, 617
of tibialis posterior, 623
at wrist, 490
 
Taeniae coli, 768
Tali-sustentaculum, 371, 388
Talo-calcaneal joint, 664
Talo-calcaneo-navicular joint, 665
Talus, 367
 
ossification of, 378
os trigonum of, 370
varieties of, 370
Tapetum of choroid, 1647
 
of corpus callosum, 1515
Tarsal arteries, 612
tunnel, 370, 390
Tarso-metatarsal joints, 669
Tarsus, 367
 
of conjunctiva, 1290
varieties of, 378
as a whole, 378
 
 
Taste-buds, 1347
 
Tectoria, membrana, of occipital joint,
1407
 
of spiral organ, 1693
Teeth, 278
 
auditory, 1691
canine, 280
development of, 285
eruption of, 282, 288
incisor, 279
molar, 280
premolar, 280
present at birth, 288
sockets of, 214, 231
structure of, 283
temporary or milk, 282
Tegmen tympani, 187, 189, 263, 1674
Tegmentum of brain, 1552
Tela choroidea of fourth ventricle, 1492*
1610
 
of third ventricle, 1553, 1610
Telencephalon, 1493
Telolecithal eggs, 25
Telophase, 11
 
Temporal arteries, deep, 1307
 
artery, superficial, 1158
bone, 184
 
mastoid portion of, 187
process of, 187
ossification of, 195
petrous portion of, 188
squamous portion of, 185
structure of, 195
styloid process, 194, 257
varieties, 195
zygomatic process, 185
fascia, 1161
fossa, 251
 
gyn of cerebrum, 1505
line, 178
 
lobe of cerebrum, 1504
nerves, deep, 1309, 1311
pole of cerebrum, 1444
process of zygomatic, 220
region, 1153
sula of cerebrum, 1505
vein, superficial, 1159
veins, deep, 1308
Temporalis, 1302
 
Tendinous intersections of rectus abdominis, 726
 
Tendo calcaneus, 599, 619
Tendon, conjoint, 725
suprapatellar, 574
Tensor fasciae latae, 570
palati, 1353, 1378
tympani, 1680
 
Tentorium cerebelli, 1163, 1602, 1633
development of, 90
Teres major, 439
minor, 438
ridge, 300
 
Terminale, filum, of cord, 1417
Terms, embryological, 4
position, 2
 
 
 
 
1766
 
 
INDEX
 
 
Testicular artery, 738, 829
plexus, 811
vein, 829, 830
Testis, 749
 
abnormal positions of, 104, 743
descent of, 103, no, 739
development of, 100, 752
lymphatics of, 750
structure of, 750
Thalamencephalon, 58
Thalamic radiation, 1539, 1567
Thalamo-frontal fibres, 1529
Thalamo-striate fibres, 1529
Thalamus, 1535
 
connections of, 1539
development of, 58, 1539
pulvinar of, 1537
structure of, 1538
Theca folliculi, 982
 
of spinal cord, 1410
Thenar space, 492
Theories of nerve growth, 55
Thoracic artery, alar, 427
lateral, 427
superior, 426
cavity, 1002
 
contents of, 1002
diameters of, 1114, 1115
duct, abdominal part of, 838
cervical part of, 1246
cisterna chyli, 838, 1100
thoracic part of, 1100
vertebras, 134
wall, 994
Thorax, 165
 
apertures of, 165
boundaries of, 165
in different animals, 78
sexual characteristics, 167
as a whole, 165
Thymus, 1019
 
in adult, 1019
development of, 76, 1020
structure of, 1020
Thyro-arytenoideus, 1392
Thyro-epiglottic ligament, 1380
Thyro-epiglotticus, 1392, 1394
Ihyro-glossal duct, 1222
Thyro-hyals, 236
Thyro-hyoid arch, 278
ligaments, 1384
membrane, 1384
muscle, 1201
 
Thyroid artery, inferior, 1242
superior, 1213, 1242
cartilage, 1380
 
development of, 1381
gland, 1204, 1220
accessory, 1221
blood-supply of, 1221
development of, 70, 76, 1222
pyramidal lobe of, 1221
structure, 1222
veins, 1222, 1215, 1245
Ihyroidea ima artery, 1038, 1204, 1221
 
 
Tibia, 357
 
condyles of, 357
crest of, 359
head of, 357
 
retroverted, 363
intercondylar eminence, 358
medial malleolus, 361
guide to, 599
notch, fibular, 363
ossification of, 363
pressure (squatting) facet, 363
shaft, 359
structure, 363
torsion of shaft, 363
tubercle of, 357, 553
guide to, 598
varieties of, 363
Tibial artery, anterior, 607
guide to, 599
posterior, 624
 
guide to, 599
nerve, anterior, 610, 614
posterior, 627
recurrent arteries, 609
Tibialis anterior, 602
posterior, 622
 
Tibio-fibular joints, 659, 660
Tomes, fibres of, 284
Tongue, 1342
 
arteries of, 1347
development of, 72, 1348
lymphatics of, 1347
mucous membrane of, 1343
muscles of, intrinsic, 1346
nerves of, 1347
veins of, 1347
 
Tonsil, naso-pharyngeal, 1373
Tonsils, 1354
 
development of, 76
structure of, 1355
Tooth, structure of, 283
Topography, cranio-cerebral, 1629
Torticollis, 1183
 
Torus occipitalis transversus, 177
palatinus, 216, 1338
Trabeculae carneae, 1056
Trachea, cervical part of, 1223, 1224
development of, 77, 1226
lymphatics of, 1225
thoracic part of, 1085
Tracheotomy, 1205
Tract, arcuate, 1464
 
cortico-thalamic, 1566
fronto-pontine, 1529, 1566
fronto-striate, 1529
fronto-thalamic, 1529
ilio-tibial, 560
 
mamillo-thalamic, 1517, 1543
olfactory, 1445, 1511, 157°
olivo-cerebellar, 1484
 
optic, 1445, 1545
 
pallido-rubro-olivary, 1556
pyramidal, 1565
strio-thalamic, 1529
temporo-pontine, 1566
 
 
 
 
INDEX
 
 
1767
 
 
Tract, trigemino-thalamic, 1615
 
vago-glosso-pharyngeal, ascending
thalamic, 1627
 
Tracts of spinal cord. See also Fasciculi
cerebro-spinal, anterior, 1431
lateral, 1430
intersegmental, 1431
olivo-spinal, 1432
ponto-spinal, 1464
rubro-spinal, 1432, 1553
semilunar, 1430
spino-cerebellar, dorsal, 1432
ventral, 1432
spino-thalamic, 1432
spino-tectal, 1433
 
tecto-spinal, 1432, 1464. 1353. 1555
vestibulo-spinal, 1431
Tractus spiralis foraminosus, 1686
Tragicus, 1296
Transversalis fascia, 733
Transverse carpal joints, 525
ligament of atlas, 1405
of foot, deep, 671
of hip-joint, 595
of knee-joint, 633
of palm, deep, 526
of perinaeum, 682
of shoulder-joint, 453, 463
of tibio-fibular joint, inferior, 660
pelvic ridge, 101
processes, development of, 59
sinus of dura mater, 1605
of pericardium, 1018
 
development of, 90
Transversus abdominis, 724
nuchae, 1145
 
perinaei, superficialis, 678
Trapezium, 318
crest of, 319
groove of, 319, 333
ossification of, 322
of pons, 1470, 1620
Trapezius, 398
 
cervical portion of, 1144
Trapezoid bone, 319
 
ossification of, 322
line, 290, 297
 
Trapezoides, corpus, of cerebellum, 1484
Triangle or triangles—
 
anterior, of neck, 1196
of auscultation, 400
Bryants’, 552
carotid, of neck, 1196
digastric, of neck, 1198
femoral, 552, 563
inguinal, 708, 736
of Lesser, 1228
lumbar, 400, 708, 772
muscular, of neck, 1196
occipital, of neck, 1184
perineal, deep, 682
plantar, 650
posterior, of neck, 1183
subclavian, of neck, 1190
submandibular, 1196
 
 
Triangle or triangles ( continued )—submental, 1202
suboccipital, 1150
suprameatal, 187
vagal, 1490
 
Triangular spaces (shoulder), 441
Triceps brachii, 458, 501
Tricuspid orifice, 1057
 
position of, 1064
valve, 1057
 
Trigeminal ganglion, 1167
impression, 189, 263
nerve. See Cranial nerves
Trigone, external, of bladder, 934
internal, of bladder, 951
Trigonocephaly, 270
Trigonum, habenulae, 1541
olfactorium, 1511
Trilaminar blastoderm, 34
Triquetral bone, 317
 
ossification of, 322
Trochanter, definition, 115
greater, 346, 529
guide to, 552
lesser, 348
third, 354
 
Trochanteric anastomosis, 585
fossa, 348
 
Trochlea, definition, 115
of humerus, 304
Trochlear fossa, 183, 245, 1251
notch of ulna, 312
Trophoblast, 26, 27, 28
Tubal pregnancy, 19
Tube, pharyngo-tympanic, 1378
 
development of, 73, 1378
muscles connected with, 1378
uterine, 971
 
development of, 987
Tuber cinereum, 1445, 1544
 
development of, 58, 1589
omentale, of liver, 774
of pancreas, 807
valvulae, 1480
 
Tubercle, adductor, 350, 354, 553
amygdaloid, 1524
anterior, of thalamus, 1537
articular, of temporal, 185
auricular, 1295
carotid, 134, 1172
condylar, 235
conoid, 289
cuneate, 1455
dorsal, of radius, 309
of epiglottis, 1380
of fifth metacarpal, 327
genial, 230
hyoid, 235
infraglenoid, 294
mental, 229
of palatine, 226
peroneal, 372, 388
pharyngeal, 174
post-glenoid, 185
pre-glenoid, 186
 
 
 
1768
 
 
INDEX
 
 
Tubercle, pterygoid, 204
pubic, 339, 551, 706
quadrate, 350
of rib, 156
scalene, 157
of scaphoid, 316, 332
of talus, 368
of tibia, 357, 553, 598
vestibular, 1491
Tuberculum impar, 70
sellae, 197
 
Tuberosity of calcaneum, 370
deltoid, 300
gluteal, 350
 
greater, of humerus, 299
of ischium, 338, 529
lesser, of humerus, 300
of maxilla, 213
of navicular, 373, 388
of radius, 307
of ulna, 312
 
Tubo-tympanic recess, 73
Tubules, seminiferous, 752
uriniferous, 901
Tunica albuginea, 750
vaginalis, 748
vasculosa, 750
Tympani, sinus, 1674
Tympanic annulus, 1672
antium, 188, 1681
canaliculus, 191, 258
cavity, 1673
membrane, 1675
 
arterial supply, 1677
nerves of, 1677
secondary, 1677
structure of, 1676
part of temporal, 194, 195
ring, 195
sulcus, 1673
 
Tympano-hyal, 75, 197, 276
Tympano-mastoid fissure, 192
Tympanum, 1673
arteries of, 1683
 
development of, 73, 74, 75, 1696
mucous membrane of, 1681
muscles of, 1680
nerves of, 1325, 1400
ossicles of, 1678
 
ligaments of, 1679
movements of, 1680
Typical, definition of, 6
 
Ulna, 312
 
beak, 312
 
coronoid process, 312
oblique line, 314
olecranon, 312
ossification, 315
radial notch, 313
shaft, 313
structure of, 315
styloid process, 315
supinator ridge, 314
trochlear notch, 313
 
 
Ulnar artery, 475
 
first part, 476
 
recurrent branches of, 477
second part, 480
third part, 487
varieties, 479, 498
collateral artery, 456
nerve, 433
nerve, 432
 
in arm, 458
 
cutaneous branches of, 448, 466,
499
 
deep division of, 499
digital branches of, 499
dorsal branch of, 467
in forearm, 480
in hand, 499
 
palmar cutaneous branch of, 466,
 
477 .
 
vein, anterior, 451
posterior, 451
U-loop, 62, 64, 875
Ultimo-branchial body, 76
Umbilical cord, 65, 105, 108, 110
hernia, 748
notch of liver, 756
sac with gut, 62
vessels, 51, 923, 1083
zone of abdomen, 755
subdivisions of, 755
Umbilicus, 63, 65, 705
Umbo, 1676
 
Uncinate process of ethmoid, 210
of pancreas, 806
Uncus of brain, 1507
Urachus, 65, 933
Ureter in abdomen, 822, 907
blood-supply of, 909
development of, 95, 910
lymphatics of, 909
nerves of, 909
structure of, 908
varieties, 823
Urethra, female; 978
 
development of, 988
external orifice of, 978
lymphatics of, 988
male, 938
 
bulb of, 941
development of, 956
external orifice of, 938
lymphatics of, 942
membranous part of, 940
prostatic part of, 939
spongy part of, 941
structure of, 940, 941, 942
Urethral crest, 939
glands, 942
 
Uriniferous tubules, 901
structure of, 901
summary of, 903
 
Uro-genital division of perinseum—
female, 692
male, 677
sinus, 99, 700
 
 
 
 
 
 
 
INDEX
 
 
1769
 
 
Uterine tube, 971
 
development of, 987
fimbriae, 972
lymphatics of, 983
ostia, 972
structure of, 982
Uterus, 972
 
anteflexion of, 975
anteversion of, 975
at birth, 977
body of, 973
 
cavity of, 976
broad ligament of, 968
cervix of, 973
 
arbor vitae of, 977
canal of, 976
development of, 101, 987
fundus of, 973
glands of, 985
gravid, 104
 
iigamentum teres of, 968
lymphatics of, 986
parametrium, 974
position of, 974
relations, general, of, 974
peritoneal, 974
structure of, 983
varieties of, 977
Utricle of internal ear, 1687
prostatic, 939
Uvula of cerebellum, 1480
of soft palate, 1350
vesicae, 951
 
Uvulae, musculus, 1352
 
Vagina, 977
 
arteries of, 986
development of, 101, 987
fornices of, 974
lymphatics of, 986
orifice, external, of, 695
structure of, 986
Vaginal process, 741
 
abnormal conditions of, 743
metamorphosis of, 742
of sphenoid bone, 198
of temporal bone, 192, 194, 257
vestige of, 969
 
Vagus nerve. See Cranial nerves
Valentin, ganglion of, 1320
Vallecula of cerebellum, 1479
cerebri, 1444, 1495
of tongue, 1343, 13 80
Value of anatomy in medicine, 1
Valve or valves—
anal, 962
aortic, 1062
of coronary sinus, 1055
of Gerlach, 872
of Guerin, 942
ileo-colic, 873
mitral, 1061
pulmonary, 1059, 1064
pyloric, 861
spiral, 890
 
 
I Valve, tricuspid, 1057
Valvulae, tuber, 1480
Valvule of Guerin, 942
Variable terms, descriptive, 4
Varieties of joints, 394
Vas aberrans of brachial artery, 456, 475
deferens, 757
 
ampulla of, 935
blood-supply of, 738
development of, 100, 102, 753
pelvic portion of, 935
structure, of 737
Vasa recta, false, of kidney, 905
Vastus intermedius, 573
lateralis, 572
medialis, 573
 
Vegetative pole of ovum, 25
Veins—
 
auricular, posterior, 1161, 1219
axillary, 428, 451
azygos. See Vena azygos
basilar, 1521, 1579
basilic, 450, 451
median, 450
of brain, 1578
bronchial, 1029, 1091
capsular, of liver, 885
cardiac, 1065, 1066
cardinal, 51, 92, 1127
central, of liver, 885
cephalic, 450, 451
median, 450
cerebellar, 1579
cerebral, 1578
 
anterior, 1521
deep middle, 1521
superficial middle, 1578
cervical, deep, 1149
 
transverse, 1193, 1245
chorionic, 51
choroid, 1521, 1578
clitoris, dorsal, of, 704
condylar, emissary, 1608
coronary sinus, 1065
of corpus striatum, 1521, 1578
cystic, 815, 891
 
development of principal veins, 1123
digital, of foot, 644
hand, 467
diploic, 1154, 1601
dorsal plexus of foot, 610
of hand, 467
emissary, 1608
epigastric, inferior, 731
superficial, 712
superior, 731
 
extraspinal, anterior, 1435
facial, anterior, 1218, 1280
common, 1218
deep, 1308
transverse, 1281
femoral, 563, 589
cutaneous, 559
profunda, 589
frontal, diploic, 1601
 
 
 
 
 
 
 
 
 
 
INDEX
 
 
1770
 
 
Veins [continued )—
gastric, left, 813
gastro-epiploic, left, 813
right, 815
 
gluteal, inferior, 538
superior, 536
hepatic, 885
 
iliac, circumflex, deep, 732
common, 852
external, 854
internal, 927
infra-orbital, 1282
innominate, 1031, 1032
development, 927
intercostal, 999
anterior, 999
collateral, 999, 1094
posterior, 999, 1094
superior, 1094
intralobular, of liver, 885
intraspinal, 1435
jugular, anterior, 1175
arch, 1175
external, 1x76
internal, 1211
 
posterior, external, 1148, 1178
primitive, 51, 92
lingual, 1217
lumbar, 848
 
ascending, 839, 848
mammary, internal, 1001
mastoid, emissary, 1608
maxillary, 1308
median, 448
deep, 450
meningeal, 1601
mental, 1283
mesenteric, inferior, 802
superior, 798
nasal arch, 1154
emissary, 1608
 
oblique, of left atrium, 1052, 1066
occipital, 1148
diploic, 1601
emissary, 1148, 1608
ophthalmic, 1261
ovarian, 830, 979
plexus, 979
 
palpebral, lateral, 1281
pampiniform plexus, 738
pancreatico-duodenal, superior, 815
parietal emissary, 1147, 1608
parumbilical, 712, 789
penis, dorsal, of, 714
pharyngeal, descending, 1220
phrenic, 827
popliteal, 549
portal, 816, 885, 886
prepyloric, 815
prostatic plexus, 952
pudendal, internal, 689
pulmonary, 1028, 1043
radial, 450
 
rectal, inferior, 698, 964
middle, 964
 
 
Veins ( continued )—
 
rectal, superior, 964
renal, 828
sacral, median, 946
saphenous, long, 559, 600
short, 615
 
of spinal cord, 1436
spinous plexus, dorsal, 1435
splenic, 813
 
subcardinal, 1132, 1133
subclavian, 1192, 1244
subcostal, 848, 1098
sublobular, of liver, 885
suboccipital plexus, 1152
supracardinal, 1132, 1133
supra-orbital, 1154
suprarenal, 827
suprascapular, 1193, 1245
supratrochlear, 1154
temporal, diploic, anterior, 1601
superficial, 1159
testicular, 738, 829, 830
thyroid, 1222
 
inferior, 1245
superior, 1215
ulnar, anterior, 451
posterior, 451
umbilical, 51, 92, 1083
uterine, 980
vaginal, 980
 
of liver, 885
of vas deferens, 738
vertebral, 1244
 
anterior, 1245
 
4 vitelline, 46, 63, 79, 91, 1124
Veli frenulum, 1485, 1548
Velum, medullary, inferior, 1485, 1491
superior, 1485, 1491
Vena azygos, 839, 1096
 
cava, inferior, 830, 1033
 
development of, 92, 1133
tributaries of, 831
superior, 1032
 
development of, 92, 1130
comitans hypoglossi, 1217
hemiazygos, inferior, 839, 1097
superior, 1097
magna cerebri, 1521
Venae advehentes, 1125
comites, brachial, 455
 
pudendal, internal, 689
radial, 474
tibial, anterior, 608
posterior, 624
ulnar, 477
 
cordis minimae, 1067
rectae of kidney, 907
revehentes, 1125
stellatae of kidney, 907
vorticosae, 1643
Venous plexuses—
 
dorsal, of foot, 610
of hand, 467
spinous, 1435
occipital, 1147
 
 
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Latest revision as of 23:00, 29 June 2020

CHAPTER XII THE THORAX


Thoracic Wall.

Muscles—Intercostal Muscles.—The classic description of t muscles gives them as two in number in each space, external internal, arranged as thin sheets of obliquely-disposed muscular hi with a large admixture of tendinous fibres.

External Intercostal Muscles— Origin .—The lower border of upper rib bounding an intercostal space.

Insertion .—The outer margin of the upper border of the lower

Nerve-supply .—The intercostal nerve of the corresponding spat



Interosseous Part of Internal Intercostal Muscle

Fig. 577. —Diagram of the Intercostal Muscles and Intercostal Arte:

A small portion of the external intercostal muscle has been divided and

reflected.

The fibres of each muscle are directed downwards and forwc and in this respect coincide with those of the obliquus exte abdominis. The muscles, as a rule, extend as far forwards as junction of the ribs with their cartilages, but sometimes they short of this point, especially in the upper spaces. From the p where the fibres cease the upper six muscles are continued inw to the side of the sternum by a thin delicate membrane, called anterior intercostal membrane. This occupies the spaces between true costal cartilages. Posteriorly the muscles extend as far as tubercles of the ribs.



[nternal Intercostal Muscles.— Origin. —The upper margin of the al groove of the upper rib.

Insertion. —The inner margin of the upper border of the lower rib. Serve-supply. —The intercostal nerve of the corresponding space, rhe fibres of each muscle are directed downwards and backwards, and lis respect coincide with those of the obliquus internus abdominis, upper six muscles extend as far inwards as the side of the sternum, the lower two are continuous anteriorly with the obliquus internus )minis. Posteriorly the muscles extend as far back as the angles le ribs. In this situation each is replaced by a delicate membrane id the posterior intercostal membrane , which lines the adjacent ion of the external intercostal muscle, and ds behind with the superior costo-transverse nent. The internal intercostal muscles are ired internally by the parietal pleura.

4 ction of the Intercostal Muscles. —This subhas given rise to much discussion and irence of opinion. Three views are entered: (i) According to Haller, the external internal intercostal muscles both act as ators of the ribs, and are therefore muscles ispiration. Inasmuch as the fibres of the muscles decussate, they must, according to view, act on the principle of the parallelon of forces. The common nerve-supply of Fig. 578. —Diagram of two muscles tends to favour this view. Section across an According to Hamberger, the external inter- ntercostal pace.

al muscles are elevators of the ribs, and El, I, external and in 'efore muscles of inspiration; whilst the inLal intercostal muscles are depressors of

ribs, and therefore muscles of expiration.

According to Hutchinson, the external inter:al muscles and the interchondral portions of internal intercostal muscles act as elevators the ribs, and are therefore muscles of ination; whilst the interosseous portions of the internal intercostal scles act as depressors of the ribs, and are therefore muscles of iration.

When a rib is elevated, its lower border is at the same time

rted.


ternal intercostal muscles ; INT, intercost, intimus, or intracostal. Pleura represented by interrupted line. Lateral cutaneous nerve shown between El and I.


Subcostal Muscles.—Deep to the internal intercostal muscles the lains of a third sheet of muscular fibres can often be demonstrated, i sheet is best developed dorsally and in connection with the lower ces. The direction of the fibres is similar to that taken by the cs of the internal intercostal, but unlike these last the fibres, tead of passing between adjacent ribs, pass between ribs some ces apart. The fibres constitute the subcostal muscles, which are the same plane as the sterno-costalis and the costal fibres of the






A MANUAL OF ANATOMY


996

diaphragm, and represent in the thoracic wall the transversus mus of the abdominal wall.

For the levatores costarum muscles, see Index.

It is customary, in modern descriptions of the intercostal muscu ture, to speak of three layers of muscles in this situation. 1 additional fibres are referred to as intercostales intimi: they w described and figured many years ago by Henle, and are usually tal to be partly detached fibres of the internal intercostals. Their fib have the same direction as those of the internal intercostals, from wh they are separated by the intercostal vessels and nerves (Fig. 57 They form a very thin layer, aponeurotic in some places, and tra lucent, better developed in the lower part of the thoracic wall, a more particularly in the middle portions of the spaces.

They are frequently considered to be parts of the same sh as the sterno-costalis (triangularis sterni) and subcostal fibi but this does not seem to be at all certain. If this view is tak the three kinds of muscle are grouped together as the transver thoracis, implying their general continuity with the sheet of abdominal transversus.

Intercostal Nerves.—These are eleven in number on each side, a are the anterior primary divisions of the upper eleven thoracic spi nerves. The anterior primary division of the twelfth thoracic spi nerve is not an intercostal nerve, but lies along the lower border the twelfth rib, and is known as the subcostal nerve (‘ last doi nerve ’).

The lower five intercostal nerves ultimately leave the intercom spaces, and pass into the anterior abdominal wall.

Upper Six Intercostal Nerves .—Each of these nerves, as it ent the back part of an intercostal space, lies between the posterior ini costal membrane and the parietal pleura. About the level of the an of the rib it pierces the posterior intercostal membrane, and pas forwards in the costal groove of the upper rib, lying between intercostal muscles. It continues its forward course in this posit in company with the intercostal artery and intercostal vein, the or of these from above downwards being intercostal vein, intercom artery, and intercostal nerve. The nerve is concealed by the ov lapping lower border of the upper rib.

At (or just beyond) the angles of the ribs between which it is pass the intercostal nerve gives off a collateral branch and, a little furt on, its lateral cutaneous branch. The collateral branch runs forw; along the upper surface of the rib below the space, supplying muscles and terminating either in them or by forming a connect loop with the main nerve some distance from the sternum. The late cutaneous branch pierces the internal intercostal muscle to run forw: between this and the external muscle: it pierces this to reach the surfa the actual site of the perforation varying, of course, according to level of the nerve. The main intercostal nerves themselves run


THE THORAX


997


reen the intercostales interni and intimi after they have given off branches described.

laving arrived at the anterior extremity of the osseous rib, each r e, still internal to the internal intercostal muscle, passes inwards ts deep surface, lying at first upon the parietal pleura, and sublently upon the sterno-costalis muscle, crossing in its course the rnal mammary vessels. On reaching the side of the sternum it es straight forwards, to become an anterior cutaneous nerve, cing in succession the following structures: the interchondral ion of the internal intercostal muscle; the anterior intercostal ibrane; the pectoralis major muscle; and the deep fascia.

Branches.—These are muscular, lateral cutaneous, and anterior ineous.

rhe muscular branches supply the following muscles: the levatores arum, serratus posterior superior, subcostal muscles, intercostal


internal mammary artery; AOR, aorta; RA, anterior primary ramus of thoracic spinal nerve; COLL, collateral branch; LC, lateral cutaneous branch; P, anterior terminal perforating, passing in front of internal mammary.

scles, the sterno-costalis, the serratus posterior inferior, and the scles of the anterior abdominal wall.

The lateral cutaneous nerves arise just beyond the costal angles, 1 run as described above. They pierce the external intercostal scles, and make their appearance under fibrous arches connecting

costal slips of origin of the serratus anterior. The first intercostal

ve, as a rule, gives off no lateral cutaneous branch, and that of the ond is known as the intercosto-brachial nerve.

The anterior cutaneous nerves are the terminal branches of the upper intercostals, that of the first being sometimes absent. For their

criptions, see Index.

Intercostal Arteries.—These vessels are arranged in two sets derior and anterior.

Posterior Series.—The intercostal arteries of the first two spaces ! derived from the superior intercostal artery (see Index). The







998


A MANUAL OF ANATOMY


intercostal arteries of the lower nine spaces are branches of the < scending thoracic aorta, and are called the posterior intercostal arten Each at first lies between the posterior intercostal membrane and 1 parietal pleura. About the level of the angle of the rib it pierces i posterior intercostal membrane, and gives off its collateral intercos branch, which inclines downwards. These two arteries now p; forwards between the two intercostal muscles, the main poster intercostal lying in the costal groove of the upper rib, where it 1 the intercostal vein above it and the intercostal nerve below it, a the collateral intercostal lying along the upper border of the lov rib. These two vessels, in the case of the upper nine spaces, termin; by anastomosing with the anterior intercostal arteries, which are t in number in each of these spaces, and will be presently describi These anastomoses take place a little in front of the mid-point betwe the vertebral column and the side of the sternum.

Branches.—These are posterior, collateral intercostal, and late cutaneous.

The posterior branch passes backwards to the muscles and inte^ ment of the back, giving off in its course a spinal branch, which ent< the vertebral canal through the intervertebral foramen.

The collateral intercostal branch, as stated, arises about the le^ of the angle of the rib, and inclines downwards to the upper border the lower rib, along which it passes between the intercostal muscles.

The lateral cutaneous branch accompanies the corresponding latei cutaneous nerve.

The posterior intercostal and collateral intercostal arteries gi branches to the intercostal muscles and ribs. Those of the thii fourth, and fifth spaces, at least, furnish branches to the mamma gland and pectoral muscles, anastomosing with the thoracic brand of the acromio-thoracic artery from the first part of the axillary, a with the lateral thoracic from the second part of that vessel. T first posterior intercostal artery, as it enters the third intercostal spa< gives off a branch which ascends to the back part of the second int< costal space, and anastomoses with the branch of the superior intercos artery to that space.

Anterior Series. — The internal mammary artery furnishes t' anterior intercostal arteries to each of the upper six intercostal spac and the musculo-phrenic branch of the internal mammary furnisl two anterior intercostal arteries to each of the seventh, eighth, a ninth intercostal spaces. The arteries of the upper six spaces lie first upon the sterno-costalis muscle, and then upon the parietal pleu being under cover of the internal intercostal muscle. Afterwards the anterior intercostal arteries pass between the external and inter] intercostal muscles. In each space they anastomose with the poster intercostal and collateral intercostal arteries, and also with the c responding intercostal arteries of the upper two spaces.

Branches.—These are distributed to the intercostal muscles, ri mammary gland, and pectoral muscles. %


t




THE THORAX


999


The lower two intercostal spaces are not furnished with anterior srcostal arteries. The posterior intercostal arteries of these spaces, sr leaving them, enter the abdominal wall, and pass forwards ween the internal oblique and transversalis muscles to the rectus lominis, in which they anastomose with the superior epigastric 1 inferior epigastric arteries.

Intercostal Veins.—These veins accompany the corresponding


enes.

The posterior intercostal vein passes backwards in the costal iove of the upper rib in company with the posterior intercostal ery, above which it lies. In the region of the angle of the rib it is ned by the collateral intercostal vein , which accompanies the corremding artery. Close to the vertebral column the posterior intercostal n receives a large posterior branch, which returns blood from the iscles and skin of the back, the vertebral venous plexus, and the -tebral canal. The mode of termination of the posterior intercostal ns differs on the two sides, and will be described in connection

h the dissection of the posterior wall of the thorax.

The anterior intercostal veins accompany the anterior intercostal cries. Those of the upper six intercostal spaces pass to the internal immary, and those of the succeeding three spaces pass to the musculo

renic veins.

Intercostal Lymphatics.—The lymphatic vessels of the intercostal ices pass partly to the posterior intercostal glands, which lie at the ck parts of the intercostal ices, and partly to the anter intercostal or sternal glands, rich lie along the course of 3 internal mammary artery.

Internal Mammary Artery.— ris vessel arises from the lower .e of the first part of the bclavian artery, and passes wnwards, forwards, and inirds behind the inner part of 3 clavicle and the first costal F IG - 580. To show the Interrelations

of the Right Internal Mammary Artery and Phrenic Nerve, and their Relations to Subclavian and Innominate Veins (Interrupted Lines) and to Pleura.


AP, anterior margin of pleura (PL). The mediastinal surface is stippled.


rtilage. It then descends verbally behind the succeeding stal cartilages as low as the

th intercostal space, where it
minates by dividing into two

anches—namely, the superior igastric and the musculorenic. The artery lies about ■§ inch from the margin of the sternum.

Cervical Relations— Anterior. —The clavicular portion of the sternoistoid muscle, and the internal jugular and subclavian veins. The aenic nerve crosses it superficially from without inwards. Posterior. The dome of the pleura.


IOOO


A MANUAL OF ANATOMY


Thoracic Relations — Anterior. —The pectoralis major; upper costal cartilages; anterior intercostal membrane; internal intercos muscles; and upper six intercostal nerves. Posterior. —The plei above, and subsequently the sterno-costalis muscle. Lateral .—1 artery has a vena comes on either side of it. The anterior intercos or sternal glands lie along the course of the vessel.

Branches. —The artery gives off no branches in the neck. In i thoracic part of its course it furnishes the following branches:


Pericardiaco-phrenic.

Mediastinal.

Pericardial.

Sternal.


Anterior intercostal. Perforating. Musculo-phrenic. Superior epigastric.


The pericardiaco-phrenic artery , long and slender, arises high up, a accompanies the phrenic nerve to the diaphragm. It gives twigs the pericardium and pleura, and in the diaphragm it anastomoses w the phrenic branch of the abdominal aorta and with the muscr phrenic branch of the internal mammary. The mediastinal branc are distributed to the contents of the mediastinum—namely, remains of the thymus body, mediastinal glands, and areolar tiss The pericardial branches supply the front part of the pericardium. 1 sternal branches are distributed to the sternum and the sterno-cost; muscle. The anterior intercostal arteries . are two in number to each the upper six intercostal spaces. For their description, see Ind The perforating branches are six in number, one arising opposite e£ of the upper six intercostal spaces. Each vessel pierces the inter intercostal muscle, anterior intercostal membrane, and pectoralis maj It then gives a few twigs to the front of the sternum, and turns o wards to supply the skin of the pectoral region. The second, thi fourth, and fifth perforating branches give offsets to the inner port; of the mammary gland.

The musculo-phrenic artery is one of the terminal branches of 1 internal mammary. It arises from that vessel in the sixth intercos space, and passes obliquely downwards and outwards behind 1 seventh, eighth, and ninth costal cartilages. About the level of 1 tenth rib it perforates the diaphragm, and terminates in the late wall of the abdomen, where it anastomoses with the ascending brar of the deep circumflex iliac artery. It gives off anterior intercos and muscular branches. The anterior intercostal arteries are two number to each of the seventh, eighth, and ninth intercostal spac in which they are disposed in a manner similar to the anterior intercos branches of the internal mammary. The muscular branches c distributed to the diaphragm and lateral wall of the abdomen, the diaphragm they anastomose with the phrenic branch of t abdominal aorta and the pericardiaco-phrenic branch of the interi mammary.

The superior epigastric artery is the other terminal branch of i internal mammary, of which it is the continuation. It descer


THE THORAX


IOOI


nd the seventh costal cartilage, and passes through the areolar val between the sternal and costal portions of the diaphragm. In manner it enters the sheath of the rectus abdominis, lying at first nd the muscle, but afterwards entering it. In the muscle it tomoses with the inferior epigastric artery, which is a branch of external iliac.

'he branches of the superior epigastric artery will be found deed on p. 731.

'he internal mammary veins (venee comites) are two in number, lie one on each side of the artery. They are formed respectively


Sterno-hyoid Muscle Sterno-thyroid Muscle.


Subclavian Artery (First Part)


Internal Mammary Artery


,. m Anterior Intercostal Arteries


Sternal Glands


V

__ Rectus Superior

Abdominis Abdominis Epigastric j

Artery Musculo-phrenic Artery

Fig. 581. —Dissection of the Anterior Wall of the Thorax

(Posterior View).


he union of the venae comites of the musculo-phrenic and superior astric arteries. In their course they receive tributaries correspondto the branches of the artery. About the level of the first rcostal space the outer vein crosses over the artery and joins the r vein to form a single vessel, which opens into the corresponding 'inmate vein. The internal mammary veins are provided with ns at intervals.

►ternal or Internal Mammary Lymphatic Glands. —These glands } a chain along the internal mammary vessels. They are usually ined, however, to the first three spaces, there being one, or it may









1002


A MANUAL OF ANATOMY


be two, in each of these spaces. They usually lie in front of the inter mammary vessels.

They receive their afferent vessels from (i) the inner third of mammary gland, (2) the anterior half of the costal pleura, (3) anterior halves of the external and internal intercostal muse (4) the lymphatics which accompany the superior epigastric arte and (5) the anterior group of superior diaphragmatic glands. T 1 efferent vessels pass to the thoracic duct , or to the right lymphatic d\ according to the side on which the glands lio. Frequently one more of these vessels drain to the supraclavicular group of gland? fact which explains the infection (which sometimes occurs) of th glands in malignant disease of certain abdominal viscera.

Sterno-costalis (Triangularis Sterni) — Origin. —(1) The deep surf; of the xiphoid process and body of the sternum close to the late border, and extending as high as the level of the third costal cartila and (2) the deep surfaces of the lower two or three true costal cartila at their sternal ends.

Insertion. —The deep surfaces and lower borders of the co? cartilages from the sixth to the second. The insertion takes pi by separate slips, and one or two of the upper slips may be partk attached to the rib itself.

Nerve-supply. —The intercostal nerves of the adjacent spaces.

The lowest fibres of the muscle are horizontal; the succeeding fit pass obliquely upwards and outwards; and the upper fibres are aim vertical.

Action. —To depress the anterior extremities of the ribs, and take part in expiration. It fixes the anterior part of the chest w and so assists the actions of the muscles, particularly those of pectoral group, attached to that region.

The muscle forms a thin musculo-tendinous sheet, which is situa on the deep surfaces of the costal cartilages and side of the sterni and is serially continuous with the transversalis abdominis mus< It supports the internal mammary vessels, sternal glands, and cert of the intercostal nerves, whilst its deep surface rests upon the park pleura.

Thoracic Cavity.

Contents and their General Position. —The thoracic cavity is chk occupied by the lungs and heart. The lungs are situated one in e; half of the cavity, and each lung is provided with a serous membra called the pleura. The heart lies obliquely between the lungs, project more to the left of the sternum than to the right, and is enclosed wit a fibro-serous sac, called the pericardium. Each lung is free to exp; except at the hilum, which is situated on its inner surface. Throi this hilum the bronchus, pulmonary artery, and pulmonary v( pass, along with other structures, and the pedicle so formed is ca the root of the lung. The upper part, or apex, of the lung rises i the root of the neck, where it is covered by the cupola of the plei




THE THORAX


1003


in turn being covered by the suprapleural membrane. The lower , or base, of the lung rests upon the corresponding half of the hragm, the heart lying upon the central tendon of that muscle, rhe two pleural sacs fill the spaces enclosed by the ribs of their sides, but an interval exists between them; this is the mediastinum s. 582 and 583). Nearly all the contents of the thorax (other than lungs and pleurae) lie in the iastinal space, which, as will be ., is arbitrarily divided for conience and description, rhe pulmonary artery springs a the base of the right ventricle

he heart, and the aorta from

base of the left ventricle. The innominate vein courses along upper aspect of the arch of the

a in front of the origins of the

)minate, left common carotid, left subclavian arteries, and

es with the right innominate

1 behind the sternal end of the

right costal cartilage to form

superior vena cava. This latter sel opens into the posteroerior angle of the right atrium he heart, and, just before piercthe pericardium, receives the a azygos which arches forwards r the right bronchus. The inor vena cava, having entered thorax through the foramen for a cava in the central tendon the diaphragm, almost lmmetely opens into the postero:rior angle of the right atrium of heart.

The phrenic nerve on each side cends in front of the root of lung, and is intimately related the pericardium, especially on left side. The small anterior monary plexus of nerves lies in

it of the root of each lung. The vagus nerve on each side descends ind the root of the lung, and forms in that part of its course the ch larger posterior pulmonary plexus. The following important ves descend in front of the arch of the aorta: the left phrenic, the vagus, the superior cervical cardiac branch of the left sympathetic, !■ the lower cervical cardiac branch of the left vagus. The left


LEADING TO A COSTOPHRENIC SUL cus of Pleura (Dotted Line).

TH is placed in the mediastinum between the pleural sacs.


d











1004


A MANUAL OF ANATOMY


superior intercostal vein lies in front of the back part of the a arch, usually intervening between the phrenic in front and the v behind. The superficial cardiac plexus of nerves lies within concavity of the arch of the aorta, and the deep cardiac plexus behind the arch and in front of the trachea close to its bifurcc into the two bronchi. The left recurrent laryngeal nerve p; backwards under the arch, and then ascends behind it. Withir


F 1G - 583-—Diagrams showing, in the First Figure, how the Mediasti IS SIMPLY THE INTERVAL BETWEEN THE TWO PLEURAL SACS, A DEFINI WHICH HOLDS EVEN WHEN, AS IN THE SECOND FIGURE, IT IS MUCH TENDED BY PERICARDIUM, ETC.

The lower figure shows how the space between the pleural sacs can be div into a superior (S) mediastinum and an ‘ inferior ’; this term, howeve not commonly used, the lower space being subdivided, by the subver planes of the front and back walls of the pericardium, into a posterior (J middle (M), and a rather doubtful anterior space.

concavity of the aortic arch the trunk of the pulmonary artery bn up into its right and left divisions, and the ligamentum arterioi extends from the root of the left pulmonary artery to the back ] of the concavity of the aortic arch immediately beyond the origii the left subclavian artery; the recurrent laryngeal nerve winds ro its left side prior to passing upwards behind the arch of the ao The gangliated trunk of the sympathetic lies very deeply, and desce











THE THORAX


1005


the heads of the ribs close behind the parietal pleura, and the or three splanchnic nerves lie obliquely on the sides of the bodies ie lower thoracic vertebrae.

'he oesophagus lies in contact with the front of the vertebral mi, and the trachea is anterior to it. The descending thoracic a lies very deeply, being situated at first on the left side of the T>ral column, but subsequently in front of it. The thoracic duct ads on its right side, and the vena azygos ascends on the right of the thoracic duct, both structures being under cover of the )hagus. The superior and inferior venae hemiazygos, upper and

r, as well as the two transverse azygos veins, upper and lower, fiosely related to the vertebral column.

'he thoracic cavity contains the following sets of lymphatic glands : anterior mediastinal or anterior group of superior diaphragmatic ds in front of the pericardium; the superior mediastinal above pericardium, along the arch of the aorta and innominate veins; posterior mediastinal behind the pericardium; the posterior rcostal in the back parts of the intercostal spaces; and the bronchial tie interval between the diverging bronchi, and also at the root ach lung. In early life a portion of the thymus body, which is l of large size, lies behind the upper part of the sternum, whence fiends into the lower part of the neck.

fleurse. —The pleurae are the two serous sacs which invest the

s, and line the adjacent parietes. Each forms a closed sac, which uite distinct from its fellow. Like other serous membranes, the ra consists of two portions—parietal and visceral—which, however, continuous with one another.

rhe parietal pleura lines the parietes, and is divisible into five ions—namely, costal, diaphragmatic, pericardial, cervical, and iastinal. The costal pleur alines the inner surfaces of the ribs and rnal intercostal muscles. The diaphragmatic pleura covers the er surface of one half of the diaphragm. The pericardial pleura 1 intimate contact with the pericardium, the phrenic nerve and •mpanying vessels alone intervening. The cervical pleura forms t is known as the cupola (dome ), and rises into the neck for about ch above the clavicle, being a little higher on the right side than file left, on account of the projection formed by the liver. The iastinal pleura of each side bounds the mediastinum. rhe viscera pleural closely invests the lung, and is known as the nonary pleura. It is intimately connected with the lung substance, extends into the fissure, or fissures, which map out the lung into s. Below the root of each lung it forms a fold, called the pulmonary went, which descends to the diaphragm; medianly the fold is icted in front on to the pericardium, and behind on to the cesogus..

Continuity and Reflections of the Pleura —(1) In the Transverse action .—Commencing at the deep surface of the sternum, the etal pleura of each side passes backwards to the pericardium, the


/


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A MANUAL OF ANATOMY


two being in contact except for a little inferiorly. They form lateral boundaries of the space which is called the anterior mediastin When they reach the pericardium the two pleurae separate, each keep to its own side of that sac, and so forming the pericardial plei which bounds laterally the space known as the middle mediastin Each pleura in this manner reaches the anterior aspect of the i of the corresponding lung, where it becomes the visceral pleura. 1 covers the front of the root of the lung, and then invests the en organ, dipping into its fissure or fissures, as the case may be, and gi\ a covering to the posterior aspect of the root. On leaving the b of the root of each lung, the two pleurae pass backwards slightly c the pericardium, trachea, and oesophagus, and over the descenc thoracic aorta, to the lateral aspects of the bodies of the thor; vertebrae. These portions form the lateral boundaries of the sp which is called the posterior mediastinum. From the vertebral coir each pleura passes outwards over the gangliated trunk of the s^


Fig. 584. —Schemes to show Pleural Conditions above, through,

BELOW THE ROOT OF LUNG (L).

P, parietal pleura; V, visceral pleura.

pathetic, and then lines the inner surfaces of the ribs, as well as internal intercostal muscles. In this manner it reaches the d surface of the sternum.

From the foregoing description it will be evident that the plei in passing from the deep surface of the sternum to the vertebral colui meets with, and is reflected over, the lung and its root. At the If of the manubrium sterni the pleura passes uninterruptedly backwa to the vertebral column. That of the right side passes over the 1 of the superior vena cava, innominate artery, right innominate v and trachea; whilst that of the left side passes over the side of left common carotid and left subclavian arteries, (esophagus, ; thoracic duct. The two pleurae, as they pass backwards at this le form the lateral boundaries of the space which is called the supe\ mediastinum.

Below the level of the root of the lung the antero-posterior reflect of the pleura is complicated by a triangular fold, called the pulmon ligament. This fold consists of two layers of pleura in close appositi


THE THORAX


1007

h are continuous superiorly with the anterior and posterior pleural
stments of the root of the lung. It extends, on the one hand,

veen the lower border of the root of the lung and the diaphragm i vhich latter it is attached, and, on the other hand, between the cardium and the inner surface of the lung below the level of the

. In the last-named situation its two layers separate to encase

lung at that level. Its lower border is free and concave.

[2) In the Vertical Direction.—Superiorly the parietal pleura of 1 side rises in the form of a cupola into the root of the neck for about ch above the clavicle, where it is covered by suprapleural membrane sons fascia). This fascia is derived from the scalene group of teles, and is attached, on the one hand, to the medial border of the rib, and, on the other, to the front of the transverse process of the


STERNUM


Fig. 585.—Diagram showing the Reflections of the Pleurae

(Transverse Section).

Hith cervical vertebra. The subclavian artery and innominate 1 are intimately related to the cupola of the pleura internally and eriorly, the artery being the higher of the two. Immediately in it of the artery the phrenic and vagus nerves and the internal umary vessels lie in contact with the pleura. Inf eriorly the ietal pleura of each side is reflected from the thoracic wall on to upper surface of the corresponding portion of the diaphragm, ch it covers where the base of the lung rests upon it. The intering portion of the diaphragm (central tendon) is covered by the )us portion of the pericardium. Medially the diaphragmatic pleura omes continuous with the mediastinal pleura.

Lines of Reflection of the Pleurae — Sternal Reflection.- —Behind the ■lubrium sterni the right and left pleurae are separated from each er by an interspace which represents the superior mediastinum .








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A MANUAL OF ANATOMY


At the level of the junction of the manubrium and body of the steri they meet each other, and descend behind the body of the bon close contact and inclining slightly to the left of the median line, the level of the lower border of the fourth costal cartilage the pleura parts company with the right, and passes outwards downwards close to the left border of the sternum, and in intin


Fig. 586. —Surface Markings on Front of Thorax.

Thick black lines mark pleura; dotted lines within these show lungs and ' fissures; fine lines heart and main vessels and lower edge of liver medi interrupted line shows transpyloric plane.

relation with the pericardium. There is, however, a small triang area of that sac which is uncovered by the pleura, and lies in di relation to the anterior thoracic wall. The left pleura continues downward course as far as the inner surface of the sixth costal cartil lying not far from the left border of the sternum. At this leve again passes outwards and downwards, to be reflected on to diaphragm. The right pleura pursues an undeviating course downw;


















THE THORAX


1009


nd the sternum as far as the junction of the body and xiphoid ess. At this level it leaves the bone, and passes obliquely outwards, iwards, and backwards over the inner surface of the seventh costal lage, from which it is reflected on to the diaphragm.

'osto-diaphragmatic Reflection .—The level of this reflection may be idered, in the first place, as it affects certain definite vertical lines, he left sternal line it takes place at the level of the sixth costal


Fig. 587. —Surface Markings on Back of Thorax.

ira, thick line; lungs and fissures, dotted lines within these; uppermost level of diaphragm and liver on right side, interrupted line, hirst, sixth, and twelfth thoracic spines marked. Roots of lungs indicated.

tilage, and in the right sternal line at the level of the seventh costal tilage. In the left mammary line it takes place at the level of the ith costal cartilage, where it joins the osseous part of the rib, and the right side at a similar level. In the left mid-axillary line it es place on a level with the lower border of the tenth rib, this being lowest point to which the pleura descends. In the right midllary line it takes place on a level with the upper border of the tenth , or, it may be, the lower border. Posteriorly, in the scapular line










IOIO


A MANUAL OF ANATOMY


(inferior angle of the scapula) on each side it takes place at the k of the lower border of the twelfth rib. From this point inwards the vertebral column the line of pleural reflection is a little below adjacent border of the twelfth rib, and is very nearly midway betw the vertebral end of that rib and the first lumbar transverse proces

From the foregoing description it will be evident that the pie descends lowest in the mid-axillary line, and that posteriorly, d to the vertebral column, it actually descends below the level of lower border of the twelfth rib. The direction of the line of cos diaphragmatic reflection, from before backwards, is at first obliqr downwards and outwards until the level of the tenth rib is reach The line then passes backwards and upwards to the vertebral colui The costo-diaphragmatic pleural line is on a distinctly lower le than the margin of the base of the lung, but it is a little above the ] of the costal attachment of the diaphragm. The portion of diaphragm below the line is therefore in direct contact with the thoiz wall and adjacent internal intercostal muscles, without the intervent of the pleura, and the costo-diaphragmatic reflection is connected these structures by a fascial expansion.

The free surfaces of the parietal and visceral pleurae are in hea in close contact. They are polished, and moistened by a slight amoi of serous fluid, so that they glide smoothly upon each other. In ca of pleurisy, however, certain changes take place. The free surfa become roughened by the deposit of lymph, and the movement of lung is accompanied by the sound known as pleuritic fricti Adhesions are also frequently formed, and a serous exudation tai place into the pleural sac, which tends to compress the lung injurious the condition being known as pleurisy with effusion. In cases serous exudation the cavity of the pleura, which is a shut sac, is clea demonstrable, but in health no such cavity exists, the parietal a visceral pleurae being at all times in intimate contact with each oth The attached surfaces of the parietal and visceral pleurae are rougher by fibrous processes, by means of which they are connected to 1 parts which they cover.

The costal pleura is the thickest, and can readily be stripped fr< the inner surfaces of the ribs and internal intercostal muscles. Tb is a fairly thick layer of subserous areolar tissue on its attached surfa The diaphragmatic and pericardial pleurae are thinner than the cos pleura, and are more adherent to the subjacent structures. 1 diaphragmatic pleura follows closely the upper surface of the diaphraj in its antero-posterior curvature, with the result that though in 1 mammary line it is attached anteriorly to the eighth costal cartila it ascends when traced backwards to the level of the fifth costal cartik prior to turning downwards to the level of the twelfth rib. 1 pulmonary pleura is the thinnest and most adherent. Beneath there is a layer of subserous areolar tissue containing much elas tissue, and this is in continuity with the areolar tissue which perva( the lung.



THE THORAX


ioii


ifferences between the Two Pleural Sacs. —The right pleural sac rises higher

he root of the neck, and is shorter and wider than the left. These differences

ue partly to the projection formed by the liver on the right side, and partly 3 greater inclination of the heart to the left of the sternum than to the right.

Ilood-supply. —The parietal pleura receives its arteries from the rior and posterior intercostals, and from the various branches of internal mammary. The visceral pleura receives its blood from bronchial arteries.

'he veins pursue courses corresponding to the arteries, ferve-supply. —The nerves are derived from the sympathetic, nic, vagus, and intercostal nerves.

lymphatics—Visceral or Pulmonary Pleura. —The lymphatic vessels lis part of the pleura open into the superficial lymphatics of the s. Parietal Pleura. —The lymphatics of the costal pleura open the lymphatics of the internal intercostal muscles , which terminate ) the sternal or internal mammary glands, and (2) the intercostal ds. The lymphatics of the diaphragmatic pleura open into the )hatics of the diaphragm. The lymphatics of the mediastinal pleura into (1) the anterior mediastinal glands, and (2) the posterior iastinal glands.

'here are some costal pleural areas, however, which have particular lages. The ‘ apical ’ or cervical pleura, including that part below niddle of the first rib, drains into glands in the bottom of the neck, nd the lower end of the jugular, or it may be into the subclavian k; occasionally it seems to have some drainage into the uppermost of the axillary glands. Just below this area, and extending 1 to about the fourth rib, is a second region which, beside the lary drainage into posterior intercostal and internal mammary ds, usually has some drainage through the thoracic wall into the ary glands, accompanying the lateral intercostal nerves and vessels, drainage into axillary glands may even (but unusually) extend down r as the sixth rib.

iructure. —The pleura is a typical serous membrane like the serous portion le pericardium, the peritoneum, and the tunica vaginalis. Such mem*s are called serous because their free surfaces are moistened by a small tity of serous fluid. Briefly stated, the pleura consists of a homogeneous, sctive-tissue basement membrane, containing elastic tissue, and lined endothelium.

evelopment. —The pleura is developed from the walls of the coelom, or -cavity, which is the cleft in the mesoderm separating the splanchnopleure >omatopleure (see p. 78).

'he Mediastinum. —The mediastinum is formed by the approxion of the two pleural sacs in the region of the median anteroerior line of the thorax. The interval between the two sacs is d the mediastinal space , and its boundaries are as follows: in front, sternum; behind, the bodies of the thoracic vertebra; and on either the corresponding pleural sac. The mediastinal space contains dures so numerous as to necessitate its subdivision into four parts perior, anterior, middle, and posterior.


1012


A MANUAL OF ANATOMY


Fig. 588. —Mediastinal Contents exposed by pulling back the Ante

Parts of the Pleural Sacs.

Smaller mediastinal vessels are not shown.

and laterally, the mediastinal pleura of each side as it extends from deep surface of the manubrium sterni to the vertebral column.

Contents.—These are as follows: (1) the arch of the aorta; (2) innominate artery, and the thoracic portions of the left common car and left subclavian arteries; (3) the right and left innominate ve and the upper half, or extra-pericardial portion, of the superior \ cava; (4) the phrenic, vagus, left recurrent laryngeal, and can nerves; (5) the trachea, oesophagus, and thoracic duct; (6) the supe mediastinal glands; and (7) the remains of the thymus.

In studying the topographical anatomy of the thorax it wT


The superior mediastinum is situated above the pericardium, its boundaries are as follows: in front, the deep surface of the manub: sterni, with the origins of the sterno-hyoid and sterno-thyroid mus behind, the bodies of the upper four thoracic vertebrse and the I portions of the longus cervicis muscles; above, an imaginary \ corresponding to the superior aperture of the thorax; below imaginary plane passing from the lower border of the manub: sterni to the lower border of the body of *the fourth thoracic verte


Inf. Thyroid vein L. Innominate V. Thymus

Bulmonary A.




THE THORAX


1013


d convenient to use as a landmark the manubrio-sternal joint,

h is often sufficiently superficial to be apparent as a transverse

3 known as the sternal angle (angle of Louis). The angle is in the 3 horizontal plane as the disc between the bodies of the fourth and thoracic vertebrae, and therefore indicates the level of the imaginary e separating the superior from the other divisions of the mediasti. The angle marks the level at which the ascending aorta ends and descending aorta begins: the superior limit of the pericardium-and


L. Vagus N.

L. Phrenic N.

Sup. Intercostal Vein


Recurrent Laryngeal N. going to turn round Lig.


L. Appendix Infundibulum


R. Vagus


Cardiac Nerves

R. Phrenic N. Sup. V. Cav.

Ascending Aorta


Fig. 589. —Main Mediastinal Structures seen from the Front

(Heart exposed).


he left side of the heart. At this same level the two pleural sacs meet ront, the trachea bifurcates, the vena azygos enters the superior a. cava, the left recurrent laryngeal nerve winds round the ligaitum arteriosum, the thoracic duct crosses the middle line, and the phagus reaches the middle line.

the anterior mediastinum is situated behind the body of the num, and its boundaries are as follows: in front, the deep surface he body of the sternum, and the left sterno-costalis muscle; behind, pericardium; and laterally, the mediastinal pleura of each side as








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A MANUAL OF ANATOMY


it extends from the deep surface of the body of the sternum to lateral aspects of the pericardium. Its direction is downwards an the left. At its upper part there is no interspace, because the pleural sacs come into contact behind the first piece of the bod] the sternum. Below this level, however, the left pleural sac dive: from its fellow, so as to leave an interspace. *

Contents.— These are the anterior mediastinal glands, s< lymphatic vessels, the anterior mediastinal branches of the inte mammary artery, and areolar tissue.


Parietal Pleura


Internal Mammary Vessels


Pleural Interval


Pulmonary Pleura


Left

Oblique

Fissure


Left Vagus Nerve


Right

Oblique

Fissure


Nerve


Vena Azygos

Fig. 59 °* Transverse Section of the Thorax through the Sec Sternal Segment in Front and the Body of the Ninth Thor \ ERTEBRA BEHIND, SHOWING THE REFLECTIONS OF THE PLEURAE AND

Position of the Viscera.


S. Sternum

A.M. Anterior Mediastinum A. A. Ascending Aorta P.A. Pulmonary Artery R.A.A. Right Appendix R.A. Right Atrium M.M. Middle Mediastinum L.A. Left Atrium


P.M. Posterior Mediastinum O. (Esophagus

D.A. Descending Thoracic Aorta T.V. Thoracic Vertebra M. Middle Lobe of Right Lung R.U. Right Upper Lobe R.L. Right Lower Lobe L.U. Left Upper Lobe L.L. Left Lower Lobe


Anterior Mediastinal Glands. —These glands are situated within areolar tissue of the lower part of the anterior mediastinum, between lower part of the body of the sternum and the front of the pericardii u re f e * ve ^eir a ff went vessels from (i) the antero-median port

ot the diaphragm, corresponding to the xiphoid process of the sternii (2) the supero-anterior surface of the liver on either side of the falcifc ligament (3) the anterior part of the pericardium; (4) the antei P 3 , 1 ^ Pr . e mec hastinal pleura. Their efferent vessels ascend and oj into the internal mammary and superior mediastinal glands.









THE THORAX


1015


he middle mediastinum lies behind the anterior and below the rior mediastinum, and is the widest part of the interpleural space, ontents. —These are as follows: (1) the heart, enclosed in the ardium; (2) the ascending aorta; (3) the pulmonary trunk; ie lower half or intrapericardial portion of the superior vena cava ; he phrenic nerves and the pericardiaco-phrenic vessels; (6) the cation of the trachea; and (7) the roots of the lungs, he posterior mediastinum is situated behind the pericardium, and v the posterior part of the superior mediastinum, with which r it is continuous. Its boundaries are as follows: in front , the ardium, and below this the posterior part of the diaphragm;


Pericardium and CEsoph.


Aorta

Sympathetic Chain


Subclavian A.


CEsoph. and Thoracic D. Sup. Intercostal V.


Vagus N. Phrenic N.


591. —Structures in Posterior Mediastinum, seen from the Left.


id, the bodies of the thoracic vertebrae below the level of the lower ier of the body of the fourth; and laterally, the mediastinal pleura ich side as it extends from the back of the root of the lung to side of the vertebral column.

Contents. —These are as follows: (1) the descending thoracic aorta;

he oesophagus, and the two vagus nerves; (3) the thoracic duct;

he vena azygos; (5) the superior and inferior venae hemiazygos, with corresponding transverse azygos veins; (6) the greater splanchnic r es, right and left; and (7) the posterior mediastinal glands.

Phrenic Nerve. —The nerve arises chiefly from the anterior primary sion of the fourth cervical nerve. It usually receives a small root









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A MANUAL OF ANATOMY


from the anterior primary division of the third cervical, and, a rule, an additional root from that of the fifth cervical. Hat descended on the superficial surface of the scalenus anterior mu: to the root of the neck, it crosses the internal mammary artery su] ficially from without inwards. It then enters the thorax and desce in front of the root of the lung in close contact with the side of pericardium, and under cover of the mediastinal pleura. Ha\ reached the diaphragm, the nerve divides into several branches, wl pierce that muscle, to be distributed to its abdominal surface, terminal branches of each nerve are connected in the diaphragm v filaments of the corresponding phrenic plexus of the sympathe which is an offshoot from the coeliac plexus. At the place of junct

of the two sets of fibres on right side there is a small gangli called the phrenic ganglion. the thorax the phrenic ne occupies the superior and mid mediastinal spaces. The n phrenic nerve lies in success on the outer side of the ri innominate vein and superior v< cava, and then descends in fr< of the root of the right lu Certain filaments from this ne not infrequently reach the un surface of the diaphragm passing through the vena ca aperture. The left phrenic ne: descends in the interval betw< the left common carotid £ left subclavian arteries, where crosses the vagus nerve fr without inwards. It then pas behind the left innominate vc and crosses over the arch of aorta separated from the vagus by the left superior intercostal ve after which it descends in front of the root of the left lung. E; nerve is accompanied by the pericardiaco-phrenic artery, which i branch of the internal mammary artery.

Branches.— The nerve of each side furnishes twigs to the p< cardium, the mediastinal pleura, the inferior vena cava, peritonei liver, and suprarenal glands; its principal branches are, howet distributed to the diaphragm.

Differences between the Two Phrenic Nerves. —(i) The right nerve is shoi, than the left, because the right half of the diaphragm, having the bulk of liver below it, is higher than the left half. (2) The right nerve is straighter til the left, because the heart, enclosed in the pericardium, projects less to the ri side than to the left. (3) The right nerve occupies a deeper position in the upl part of the thorax than the left. " }


Fig. 592. —Structures in Posterior Mediastinum, seen from the Right.

PH.N., phrenic nerve.





THE THORAX


1017


Pericardium.—The pericardium is the fibro-serous sac which loosely ounds the heart in the middle mediastinum. It is somewhat cal, being wide below, where it is in contact with the diaphragm, narrow above, where it surrounds the great vessels connected 1 the base of the heart. On each side it is intimately related to mediastinal pleura, and is embraced by the anterior portions of inner surfaces of the lungs. The phrenic nerve on each side descends ery close contact with it. In front of it are the body of the sternum the sternal ends of the corresponding costal cartilages. Its anterior ace is to a greater or less extent encroached upon by the adjacent


Fig. 593. —The Heart (Anterior View) and Pericardium. The anterior part of the pericardium has been removed.


•tions of the anterior margins of the lungs and by the two pleurae, ere is, however, a small portion of this surface which is immediately ited to the sternum below the level of the lower border of the fourth

costal cartilage at its sternal end. Posteriorly, the pericardium
in front of the posterior mediastinum, and the oesophagus is here

ited to it opposite the posterior aspect of the left auricle of the heart. The pericardium consists of two portions—an external or fibrous, I an internal or serous. The fibrous pericardium is strong and dense, eriorly it is attached to the middle lobe of the central tendon of ! diaphragm, and slightly to its muscular part, more particularly









ioi8 A MANUAL OF ANATOMY

on the left side. Superiorly it ensheathes the great vessels connec with the base of the heart, with the single exception of the infei vena cava.

The fibrous layer is attached to the sternum by two fibrous ban which are known as the superior and inferior sterno-pericara ligaments of Luschka, the former being attached to the deep surf; of the manubrium, and the latter to the deep surface of the xiph process.

The serous pericardium is a typical serous membrane, and consi of two layers, parietal and visceral, which together form a closed sa

The parietal portion lii the inner surface of 1 fibrous part, to which it closely adherent, and a intimately covers the up] surface of the central tend of the diaphragm.

The visceral portu known as the epicardiu closely invests the heart, a! also the great vessels at base more or less complete The continuity between t parietal and serous portic is established inferiorly alo the inferior vena ca^ Superiorly the continuity established along the gre vessels at the base of t heart about ij inches abo it. In this situation t serous portion forms an c terial sheath which enclos within it the ascending aor and pulmonary trunk 1 about ij inches, this bei the only complete shea formed by the serous portic Behind this sheath, with its contents, and in front of the atrial port! of the heart, there is a passage, called the transverse sinus of t pericardium, which leads from the right to the left side of the sero sac. The serous portion is also related to the superior vena cava ai the pulmonary veins, but it only covers them in front and at t sides.

The serous portion of the pericardium forms a triangular fo, called the ligament of the left vena cava (vestigial fold of Marshal

which is situated between the left pulmonary artery and the upper 1< pulmonary vein. Its base is directed towards the left, and its surfac


Fig. 594. —Scheme of Disposition of Arterial (A) and Venous Mesocardia (V) on Posterior Wall of Pericardium.

The dotted arrow lies in transverse sinus.







THE THORAX


1019


anterior and posterior. Between its two delicate layers there is nail fibrous cord, a vestige of the left duct of Cuvier; this, like the apericardial part of the superior vena cava on the right side,

es down in front of the pulmonary vessels.

The free surfaces of the parietal and visceral layers of the serous don are smooth, polished, and lubricated by serous fluid to allow of movement on the part of the heart. In the course of pericarditis y become at first dry, and then roughened by deposits of lymph, s giving rise to the pericarditic friction sound, and, it may be, to esions. They may also become separated from each other by an sion into the pericardial sac.

Blood-supply.—The fibrous portion of the pericardium and the ietal layer of the serous portion receive their arteries from (1) the icardial and pericardiaco-phrenic branches of the internal mammary, (2) the descending thoracic aorta. The visceral layer of the >us portion receives arterial twigs from the coronary arteries of the rt.

The veins pass to the internal mammary, pericardiaco-phrenic, and gos veins.

Nerve-supply.—The phrenic, vagus, and sympathetic nerves. Lymphatics.—These pass to the anterior, superior, and posterior liastinal glands.

Structure. —The fibrous portion of the pericardium is composed of fibrous lie, and is very dense, but not very extensible. The serous portion consists a homogeneous, connective-tissue basement membrane containing some tic fibres, and lined with endothelium. The parietal layer is much thicker n the visceral; the latter is intimately connected with the cardiac muscular ue, except along the grooves, which are occupied by adipose tissue and 3 d vessels.

Development. —The serous portion of the pericardium is developed from walls of the coelom, or body-cavity, which is the cleft in the mesoderm arating the splanchnopleure and somatopleure.

The fibrous walls have various origins; the antero-lateral parts come from deep layers of the body-wall, split off by the extension of the pleural cavities, l the lower or diaphragmatic part is derived from the septum transversum.

} cavity is at first continuous with the pleural sacs, but the openings, which dorsal and medial to the ducts of Cuvier, are closed by the end of the first nth.

The Thymus.—This is present in the foetus and young child, a.nd ms a very conspicuous object in the dissection of a child during J first year or two of life. It attains its greatest size at puberty, er which, as a rule, it slowly atrophies, although traces of it are to found even in advanced age. The atrophic process which it under-S is, however, extremely variable. In its fully-developed condition is situated partly in the thorax and partly in the neck. In the mer situation it occupies the superior and anterior mediastinal ices, extending as low as about the level of the fourth costal cartilages, d lying in front of the great bloodvessels and upper part of the perirdium, the upper part of the sternum being in front of it. In the ck it extends as high as the lower part of the thyroid gland, being


1020


A MANUAL OF ANATOMY


under cover of the sterno-hyoid and sterno-thyroid muscles. In situation it embraces the front and sides of the trachea, complel concealing it from view, and encroaches upon the carotid sheath

either side. Its length is ab


Two Follicles


Trabecula


Medulla


Cortex


Fig. 595. —Transverse Section of a Lobule of the Thymus Gland of a Kitten.


The concentric corpuscles of Hassall are shown in the medulla.


2w inches, and its breadth, wt


is greatest inferiorly, is about inches. Its colour is pinkish is soft in consistence; and surface shows indications of lo lation. It consists of two as} metrical lateral lobes, each of wh is pyramidal. In some cases left lobe is the larger, and other cases the right. These lo are in close contact, but are s quite distinct. Sometimes a th lobe is present, occupying an termediate position between other two.

Blood-supply.—The arteries chiefly derived from the inter mammary, inferior thyroid, s superior thyroid.

The veins open into the rij and left innominate and thyr veins.

Nerve-supply.—The nerves ; derived from the sympathetic a vagus.


Structure. —Each lobe has a capsule of fibrous tissue, from which traben pass into the interior. These trabeculae map out each lobe into large and sn lobules. Each lobule consists of an outer cortical and an inner medull portion. The cortex is composed of lymphoid tissue, the lymphoid elem predominating over the retiform, and it is surrounded by a capillary r work of bloodvessels which contains many lymph corpuscles. The lymph tissue of the cortex is incompletely subdivided into nodules by means trabeculae.

The medulla is more transparent than the cortex, the retiform element the lymphoid tissue is more conspicuous, and the lymph corpuscles are \ numerous. In addition, the medulla contains small groups of cells, more less concentrically arranged, which are known as the concentric corpuscles Hassall. According to one view, these cells are remains of the diverticula fr which the thymus body is developed; but another view is that they are conceri with the formation of bloodvessels and connective tissue.

Development. —The thymus body is developed in two lateral parts from entodermic epithelium of the pharyngeal portion of the primitive gut. 1 epithelium of the third visceral cleft on either side becomes evaginated early the second month, and gives rise to dorsal and ventral diverticula. The vent diverticulum, which forms the thymic growth, has a thick epithelial wall, bu small lumen, and grows in a downward direction. Its distal end, which ] ventral to the pericardium, forms a solid enlargement, and the proximal d loses its connection with the third visceral cleft. The enlarged distal end grj




THE THORAX


1021


umerous solid epithelial buds, which are invested with mesoderm. This ing gradually extends to the proximal part of the diverticulum. The solid and cords of each side ramify freely, and give rise to the corresponding lobe e thymus. The original diverticulum thus assumes a lobulated appearance, resembles a racemose gland. The buds or acini, however, are solid, and not w, as in racemose or acinous glands. The acini are separated by connective s and bloodvessels, which are developed from the surrounding mesoderm, phoid tissue is also developed from the mesoderm around the acini, and tissue forms the greater part of the adult thymus. The epithelial elements ch lobe are subordinate to the lymphoid tissue, and are ultimately represented le concentric corpuscles of Hassall.

jungs.—The lungs are two in number—right and left. They are lgy in consistence, float in water, and are readily compressed, m pressed between the fingers crepitation is elicited, this being to the displacement of air. When the lung is incised, similar litation is heard, and a muco-serous fluid, mixed with air, exudes, y possess considerable elasticity, their colour is that of a dark slate, they are usually mottled, this being due to carbonaceous matter, larly life, however, the colour is rose-pink.

rhe lungs occupy the greater part of the thoracic cavity. Normally / are at all times in close contact with the thoracic walls, the pleurae rvening. Unless adhesions have formed during life between the

eral and parietal pleurae, the surface of each lung is quite free

spt in two situations—namely, at the root, which occupies a limited i of the inner surface, and at the attachment of the pulmonary ment. Each lung is conical, the base being directed downwards. >resents for consideration an apex, a base, two surfaces, and two iers.

The apex is blunt, and rises out of the thoracic cavity into the t of the neck for about inches. It is here covered by the cupola he pleura, and a little below its highest point it presents a groove its medial and anterior aspects. In the case of the right lung > groove is produced by the innominate and right subclavian arteries, l in the case of the left lung by the subclavian artery of that side, ow this groove there is another groove, produced on either side by innominate and subclavian veins.

The base is extensive, semilunar in outline, and concave in adaptai to the upper arched surface of the diaphragm, upon which it ts, with the intervention of the pleura. The base of the right g is related to the right lobe of the liver, and that of the left lung [he left lobe of the liver, the stomach, and the spleen, the diaphragm srvening in each case. The margin of the base is thin and sharp, 1 it extends into the costo-diaphragmatic recess, reaching lowest lind, but nowhere as low as the line of the costo-diaphragmatic ection of the pleura.

The costal surface is extensive and convex, and in health it is sely applied to the inner surfaces of the ribs and of the internal ercostal and subcostal muscles.

The medial surface is of much more limited extent than the outer


1022


A MANUAL OF ANATOMY


Fig. 596.—Mediastinal Aspect of Right Lung.


part (DA) of the aortic groove, vertically placed and produced 1 the descending thoracic aorta. Anterior to the lower part of tf groove the left lung is related to the oesophagus, but less intimate than the right lung. The inner surface of the right lung presen above the level of the hilum grooves for the following structures: tl vena azygos (AZ), the superior vena cava (SVC) and right innomina vein, the innominate artery, the trachea (T) and oesophagus. Tl inner surface of the left lung presents above the level of the hilu grooves for the following: the arch of the aorta (A), the left subclavb


(Figs. 596 and 597 )- The greater part of it is concave (P) in adaptat to the heart, enclosed in the pericardium, the concavity being grea in the case of the left lung on account of the projection of the he to the left side. About the junction of the anterior two-thirds c posterior third this surface presents a vertical fissure, called the hilt at which the root of the lung is situated. The medial surface of right lung, behind the hilum, is related ((E) to the oesophagus, and corresponding portion of the inner surface of the left lung prese


CE

p

ivc

A R




THE THORAX


1023


jry (S), the left innominate vein, the oesophagus and thoracic

t ((E) The borders are anterior and posterior. The anterior border is 1 and short, and overlaps the pericardium, more so during inspiral than expiration, but leaving an area of the pericardium uncovered, wn as the area of precordial dulness. The anterior border of right lung keeps behind the sternum as low as the sixth right

al cartilage. The corresponding border of the left lung, beyond

lower border of the fourth left costal cartilage, presents a deep


Fig. 597. —Mediastinal Aspect of Left Lung.


laped notch, called the cardiac notch , for the reception of the al portion of the heart enclosed in the pericardium. The posterior ier is elongated, thick, and round, and occupies the groove by side of the vertebral column.

Each lung is divided into two lobes, upper and lower, by an exten> oblique, and deep fissure, which penetrates to the hilum. So ) is this fissure that, unless adhesions have formed, the lung appears onsist of two halves. The fissure commences on the inner surface,

■ the posterior border, about 3 inches below the apex. It then



1024


A MANUAL OF ANATOMY


turns round the posterior border, and passes obliquely downwa and forwards over the outer surface to the basal margin. In case of the right lung the fissure joins the basal margin some li distance from the lower end of the anterior border; but in the c of the left lung the fissure joins the basal margin distinctly fart forwards. A good ready guide to this fissure is the lower bordei the pectoralis major muscle, as it forms the anterior fold of the axi The upper lobe is comparatively small, and includes the ap about the upper 3 inches of the posterior border, the anterior bon and in the case of the left lung practically all that can be ausculta anteriorly. The lower lobe is of large size, and lies behind and be the oblique fissure. It includes the base, the posterior border exc


Fig. 598.—Diagram showing the Heart and Lungs in -Situ.

1. Tricuspid Orifice 2. Pulmonary Orifice 3. Mitral Orifice

4. Aortic Orifice x> Region of Latham’s Circle

the upper 3 inches, and practically all that can be ausculta posteriorly.

By means of the oblique fissure each lung, as stated, is divided ii two lobes. In the case of the left lung the division proceeds no fartf In the case of the right lung, however, there is an additional fissr which extends from near the mid-point of the chief fissure at 1 posterior border horizontally forwards over the outer surface to anterior border. This additional fissure cuts off from the upper 1 ( a triangular or wedge-shaped portion, which is called the middle lo

A fourth or even a fifth lobe may be present on the right side. Tb accessory lobes are usually found in the region of the hilum or of the infeij vena cava. If in the former position, the accessory lobe appears to be due t ! lateral displacement of the vena azygos, which in these cases lies in the obit fissure; if in the latter position, the accessory lobe represents the azygos lob( many animals.






THE THORAX


1025


)ifferences between the Two Lungs.—(1) The right lung has two res and three lobes, whilst the left lung has only one fissure and two 3. (2) The anterior border of the right lung is uninterrupted whilst

of the left lung presents interiorly the cardiac notch. (3) The right rger and heavier than the left, the weight of the right being about unces and that of the left about 18 ounces. (4) The right lung orter than the left, this being due to the fact that the liver causes right half of the diaphragm to rise higher than the left half, rhe right lung is broader than the left, because the heart projects e to the left side than to the right.

Vertical Extent of the Lungs.—In the mammary line the right lung ends as low as the sixth rib; in the mid-axillary line as low as the


Groove for Subclavian Artery. Groove for Innominate V in


Upper Lobe .


B


Groove for Subclavian Artery , Groove for Innominate Vein


Upper Lobe


Lower Lobe Oblique Fissure


Cardiac N otch i

Obliaue Fissure


Lower Lobe


Fig. 599. —The Lungs (Anterior View), A, the right lung; B, the left lung.


ith rib; and in the scapular line (inferior angle of the scapula) as as the tenth rib. The lower limits of the left lung exceed those he right by about the depth of a rib. It should be borne in mind, /ever, that owing to respiratory changes the vertical extent of the gs is extremely variable.

Root of the Lung.—The root is situated at the hilum on the inner face. Its chief constituents are as follows: (1) the bronchus or tube; (2) the pulmonary artery, which conveys venous blood to lung; and (3) the two pulmonary veins, which convey the arterial oxygenated blood from the lung to the left atrium of the heart, addition to these constituents there are (a) the bronchial arteries and ns, (b) the pulmonary lymphatic vessels, (c) the pulmonary nerves, 1 (d) the bronchial lymphatic glands. All these constituents are

65






1026


A MANUAL OF ANATOMY


connected by areolar tissue, and the entire root is invested by t pleura.


Right Bronchus


Right Pulmonary^ Artery


Right

Pulmonary

Veins


Left Pulmonary Artery


Left Bronchus


Left Pulmonary Veins


Fig. 600.—The Roots of the Lungs (Anterior View).


Relations. —The following relations are common to both root in front, the phrenic nerve, with the pericardiaco-phrenic artery ai


Fig. 6oi.—Mediastinal Views of Roots of Lungs, to show Relations of Bronchi, Arteries, and Veins.


the anterior pulmonary plex of nerves; behind, the vag nerve and the posterior pi monary plexus of nerves; ai below, the pulmonary ligament

Special Relations—Right Ro — Anterior. —The superior vei cava and the upper part of tl right atrium of the heart. S perior. —The vena azygos as arches forwards over the rig bronchus and right vagus open into the superior vena cav Posterior. — The vena azygc Left Root — Superior. —The ar of the aorta. Posterior. —T. descending thoracic aorta.

Relative Position of the Chi


Constituents. —The relation fn

before backwards is the same on each side, and is as follows: (i) t upper of the two pulmonary veins; (2) the pulmonary artery; ai









THE THORAX


1027


the bronchus. The relation from above downwards differs on the sides. On the right side a division of the bronchus, known as eparterial bronchus, occupies the highest position at the hilum, reas on the left side a branch of the pulmonary artery is usually highest structure. The inferior angle of the somewhat pearled hilum is occupied by the lowest tributary of the pulmonary is.

rhe larger portion of the right bronchus and the whole of the left ichus are hyp arterial.

Itructure of the Lungs. —The trachea divides into two bronchi, right and left, structure of which is similar to that of the trachea. The right bronchus, at it | inch from its origin, gives off superiorly a branch, called the eparterial


Fig. 602. _Scheme of a Pulmonary Lobule (after I.. Testut’s

‘ Anatomie Humaine ’).

ichus, for the upper lobe of the right lung, and beyond this point, where it 3w hyparterial, it divides into two branches, one for the middle and the other the lower lobe. The left bronchus is entirely hyparterial, and divides into branches, one for the upper and the other for the lower lobe of the left lung, structure of these primary divisions of the bronchi is similar to that of the ichi themselves. Within each lung these primary divisions undergo subsions to a certain extent dichotomously, but the ramifications are chiefly due ranches being given off laterally, and these never anastomose. The ramificas of the air-tubes within the lungs are called the inter pulmonary hvorichi , and r ultimate subdivisions within the lobules are known as the bronchioles. h bronchiole transmits air to and from a group of infundibula.

Each lobular bronchial tube, after entering a lobule, divides into as many nchioles as there are groups of infundibula. Each bronchiole, on approaching luster of, say, two or three infundibula, presents a dilatation, called the ibule, and from this vestibule reception chambers, known as the atria, proceed he infundibula.





1028


A MANUAL OF ANATOMY


An infundibulum is an irregular, funnel-shaped passage closed at one e; and having its walls and closed extremity beset with pulmonary alveoli, wh also beset, though more sparsely, the walls of the atria.

The interpulmonary bronchi are destitute of membranous walls posterioi and are cylindrical. This is due to the fact that their irregular plates of cartik are disposed round the circumference of the wall. The muscular fibres «  arranged in complete rings round the bronchi, and the elastic tissue for: longitudinal bundles. The mucous membrane is freely provided with racemi mucous glands, and is covered with stratified ciliated columnar epitheliu When the branches of the bronchi, by division, have attained a diameter of abc 2 1 - inch, the cartilaginous plates disappear, and the walls consist of a fibro-elas membrane and circularly-disposed muscular fibres, with a thin mucous coat des tute of mucous glands, and covered with simple ciliated columnar epithelium, th< being here and there patches of squamous, non-ciliated cells. The walls of f vestibule, atria, and alveoli are very thin, and consist of areolar, elastic, a muscular tissues, the elastic element being specially developed at the marg; of the orifices of the cells. This elastic tissue enables the alveoli to recoil at distension. The interior of the vestibule, atria, and alveoli is lined with a sin

layer of squamous, non-ciliated epitheliu which is of extreme delicacy in the alvec Upon the outer walls of the cells there e dense networks of capillary bloodvesse which also pervade the septa between t cells, these septa being formed by infoldir of the contiguous cell-walls. Each septu contains only one capillary layer. T venous blood is thus brought into the me intimate relation with the air, all that sep< ates the two being the very thin walls the cells and the very delicate walls of t capillary bloodvessels. Moreover, there bei only one capillary layer in each intercellu] septum, the blood in the septal capillaries exposed to the air on each side.

Bloodvessels of the Lungs. —Tv

sets of arteries are associated wi each lung—namely, pulmonary ai bronchial, the former having to ( with the respiratory function of the organ, and the latter with nutrition of its component tissues. The pulmonary arteries are tv in number, right and left. They result from the bifurcation of tl pulmonary trunk, and convey venous blood to the lungs. Each arte ramifies freely within the lung, its branches closely accompanying t bronchial tubes, but never anastomosing with one another. Ultimate! they terminate in dense capillary networks which lie upon the wails the alveoli, and also in the septa between adjacent cells. The arteri are somewhat more capacious than the veins.

The pulmonary veins commence as radicles in the capillary ne works already referred to, and they pass to the root of each lun where they give rise to two pulmonary veins, which proceed to tl left atrium of the heart and convey to it arterial or oxygenated bloo The pulmonary veins and their tributaries are destitute of valve Unlike the branches of the pulmonary artery, the tributaries of tl pulmonary veins freely anastomose. Within the lung the arteri)


Fig. 603. —Section of Lung (injected).









THE THORAX


1029


ally lie above and behind the corresponding interpulmonary nchi, the veins below and in front. It is to be noted that the nonary arteries carry venous blood, whilst the pulmonary veins •y arterial blood.

The bronchial arteries convey arterial blood to the lungs for the rition of their component tissues. They will be described in aection with the descending thoracic aorta, with which they are )ciated.

The bronchial veins return their blood chiefly into the vena azygos superior vena hemiazygos respectively. They are not so large he corresponding arteries, since some of the blood conveyed by the nchial arteries is returned by the pulmonary veins.

Lymphatics. —The lymphatic vessels of each lung are arranged wo sets— superficial and deep. At the hilum these two sets open > the interbronchial glands. The superficial set receives the lymtics of the visceral or pulmonary pleura.

Nerves. —These are derived from the anterior and posterior pullary plexuses, which are formed by the vagi nerves, aided by iches from the sympathetic. The nerves penetrate as far as alveoli, upon the walls of which they are regarded as terminating arborizations. The anterior and posterior pulmonary plexuses be found described on p. 1044.

Development of the Respiratory Apparatus.

rhe respiratory apparatus consists of the larynx, trachea, and lungs. The est indication of it is a median longitudinal groove, appearing in the third c on the inner aspect of the ventral wall of the oesophageal part of the foreThis groove is called the laryngo-tracheal groove, and it produces an evaginn of the ventral wall of the oesophagus. It consists of entoderm derived 1 that of the fore-gut, and it is covered by splanchnic 'mesoderm. This groove lually deepens, and gives off the two lung-buds from its caudal end; these then carried caudally by elongation of the recess to form a trachea. The ngo-tracheal tube consists of (1) entoderm derived from that of the fore-gut, (2) mesoderm, which invests it.

rhe condition of matters now is that there are two tubes, dorsal or pharyngophageal, and ventral or laryngo-tracheal, which communicate freely cephalad. Larynx. —The larynx is developed from the cephalic or proximal part of the nonary diverticulum, with coincident modification of the pharyngeal floor

the Larynx).

rrachea. —The trachea is developed from the caudal or distal part of the ngo-tracheal tube, the cartilaginous rings, connective tissue, and muscular ie of the trachea being developed from the mesodermic investment of the litive tube and becoming evident after the middle of the second month. Lungs. —The simple lung-buds of early stages (Fig. 604) are hollow club-shaped >dermal extensions from the caudal end of the laryngo-tracheal tube, which v into the small rounded mesodermal masses already prepared for them; e project into the upper end of the pericardio-peritoneal channels, rhe buds are asymmetrical, and grow rapidly. Various stages of this growth, 0 the middle of the second month, are given in the figure, also the outward earance of a lung a little older than this, in which the early lobulation is seen, enlarging lung, with its surrounding pleura, gains room for its growth by thing the body-wall and extending (p. 78) in this, splitting it cranially, bally, and to a smaller extent caudally. The entoderm of each lung-bud and


A MANUAL OF ANATOMY


1030

of its various ramifications furnishes all the epithelial elements, bronchial ; alveolar, of the corresponding lung. The mesoderm of the bud and of its vari ramifications gives rise to the bloodvessels, connectiye and muscular tissues,; cartilages of the bronchial tubes, as well as to the visceral pleura. The pedi

of the lung-buds give rise to the bronchi. The right lung-bud gives off ti processes or vesicles, and the left lung-bud gives off two processes, and in manner the three-lobed condition of the adult right lung and the two-lo condition of the adult left lung are indicated.

Each of these processes gives rise by budding to secondary processes, : these in turn give rise successively to other processes. This budding goes very freely, and the ramifications constitute the pulmonary lobes. All the b


Fig. 604.— Entodermal Lung-Buds of Embryos of 5-7 and 8 mm.

Below, at a smaller magnification, the same from embryos of fifth and si: weeks. Also outer aspect of right lung (18 mm.)

or processes, which carry along with them an investment of mesoderm, give 1 to the ramifying system of interpulmonary bronchi. The terminal ramificati* form the bronchioles and infundibula. The air-cells or pulmonary alveoli ;

formed as hollow sessile buds or evaginations of the walls of the infundibula, w the cavities of which they communicate freely.

As stated, the epithelial cells of the lung-buds and of all their ramificatic as well as the epithelial cells of the pulmonary diverticulum, are developed fr the entoderm of the fore-gut.

The eparterial bronchus is often said to be an additional bronchial outgrow The condition, however, is due in all probability to the enlargement of a si si diary arterial anastomosis; an ordinary epibronchial pulmonary artery deveL and enlarges in the second month, comparable with that on the left side, but wa



THE THORAX


i°3 T


lisappears in the latter part of this month, leaving the hypobronchial artery rry on the supply to the lung.

jungs of the Foetus. —The lungs prior to birth, having been imious to air, feel solid, like liver, and at once sink if placed in a el containing water.

luperior Mediastinal or Cardiac Glands. —These glands, which are Lerous and important, are situated in the superior mediastinum, g the upper aspect of the arch of the aorta, in front of the lower of the trachea, and along the right and left innominate veins, rhey receive their afferent vessels from (i) the anterior mediastinal ds, (2) the upper part of the pericardium, (3) the heart, (4) the hea, (5) the oesophagus, and (6) the thymus. Their efferent vessels


Fig. 605. —The Roots of the Lungs, etc.


ninate in the thoracic duct and in the right lymphatic duct, or into of the main vessels opening into or forming these ducts.

Innominate Veins.— These vessels are two in number, right and , and each is formed by the junction of the internal jugular and clavian veins behind the inner end of the clavicle. They both in the superior mediastinum.

The right innominate vein is about an inch in length, and passes vnwards with a slight inclination inwards. At the level of the lower der of the first right costal cartilage, close to the sternum, it unites ft the left innominate vein to form the superior vena cava. Laterally s closely related to the right phrenic nerve and right pleura; its dial relation is the upper part of the innominate artery, and behind s the right vagus nerve.






1032


A MANUAL OF ANATOMY


The left innominate vein is about 3 inches in length, and pas obliquely inwards and downwards from left to right. As stated, joins its fellow of the right side to form the superior vena cava, front of it there are the upper part of the manubrium sterni, origins of the sterno-hyoid and sterno-thyroid muscles, and the rema of the thymus. Behind it are the origins of the innominate, left comir carotid, and left subclavian arteries; the left vagus and left phre nerves; and two superficial cardiac nerves from the cervical porti( of the left vagus and left sympathetic. Below it there is the arch of 1 aorta.

There are no valves in the innominate veins.

Tributaries. —Each vein receives the following tributaries: (1) 1 vertebral vein; (2) the inferior thyroid vein; (3) the internal mamm: vein; and (4) the first posterior intercostal vein. The last-nan vessel, however, sometimes opens into the vertebral vein, and 00 sionally the right inferior thyroid vein opens into the left innomin; vein. The left innominate vein receives, as an additional tributa the left superior intercostal vein.

Development. —The right innominate vein is developed from that port of the right primitive jugular vein which intervenes between the place wh it receives the right subclavian vein and the place where the transverse v joins it.

The left innominate vein is developed from the venous network between primitive jugulars.

Superior Vena Cava. —This vessel is formed by the union of the rig and left innominate veins behind the lotver border of the first rig costal cartilage close to the sternum. It is about 3 inches in lengi and descends almost vertically to the level of the upper border of t third right costal cartilage, where it opens into the postero-super: angle of the right atrium of the heart. In its course it pierces t fibrous pericardium. The upper half of the vessel is extrapericardi and lies in the superior mediastinum; but the lower half is intrape cardial, and lies in the middle mediastinum.

Relations—Upper Half— Lateral. —The right phrenic nerve a: the right pleura. Medial. —The lower part of the innominate artei Lower Half— Internal. —The ascending aorta. Posterior. —The root the right lung. The serous pericardium covers the lower part the vessel except over about its posterior fourth.

The superior vena cava is destitute of valves.

Tributaries. —The chief tributary is the vena azygos after it h arched forwards over the right bronchus. It opens into the superi vena cava immediately before that vessel pierces the fibrous pe: cardium. Other minute tributaries are pericardial and mediastin veins.

Development. —The portion of the superior vena cava above the vena azyg is developed from that part of the right primitive jugular vein which lies beh the point where it is joined by the transverse jugular vein; and the portion bel the vena azygos is developed from the right duct of Cuvier.



THE THORAX


1033


nferior Vena Cava. —This vessel enters the thorax by perforatingcentral tendon of the diaphragm, and immediately afterwards

ceived within the fibrous pericardium. Its course in the thorax

-actically nil, as it may be said to open at once into the posteroior angle of the right atrium of the heart.

Phoracic Aorta. —The thoracic aorta extends from the base of the ventricle of the heart to the level of the lower border of the body le twelfth thoracic vertebra. At this point it passes through the ic opening of the diaphragm, and enters upon the abdominal part

s course. It passes at first upwards and to the right; it then


606. —Vena Azygos and Right Sympathetic Chain, showing Ganglia and the Greater and Lesser Splanchnic Nerves arising from it.

Ph.N., phrenic nerve.

T s in an arched manner upwards, backwards, and to the left, over root of the left lung; and finally descends in close contact with vertebral column, lying at first upon its left side, but subsequently ■ont of it. It is therefore conveniently divided into three parts— ely, the ascending aorta, the arch of the aorta, and the descending a.

Mcending Aorta. —The ascending aorta commences at the base lie left ventricle of the heart, behind the left border of the sternum, level with the lower margin of the third left costal cartilage, and -minates at a point behind the right border of the sternum on a level












1034


A MANUAL OF ANATOMY


Fig. 607.—Transverse Section through Fourth Thoracic Vertebra (after Symington).

























THE THORAX


io35



















A MANUAL OF ANATOMY


1036

with the upper margin of the second right costal cartilage. Its co is upwards and to the right, with an inclination forwards. It lk the middle mediastinum, and within the fibrous pericardium, w ensheathes it, and for about the first i| inches of its course it is enclc

along with the adjacent portion of the pulmoi trunk, in a sheath formed by the serous par the pericardium. The ascending aorta meas about 2 inches in length. At its commencen it presents three dilatations, which corresp to the aortic sinuses in the interior, and opposite the segments of the aortic valve, sinuses are situated one' in front and behind. Along the right side of the vessel t] is a somewhat extensive dilatation, called great sinus of the aorta.

Relations — A nterior. —The infundibulum the right ventricle, the pulmonary trunk, the right auricle at first, and subsequently first piece of the body of the sternum, f] which it is separated by the pericardium, ri pleura, and anterior margin of the right li Posterior .—The right pulmonary artery, fi Fig. 609.— Ascending which it is separated by the fibrous pericardii

(Intrapericardial) an q the j e ft a trium, from which it is separa

with its Three by the transverse smus. Right. — I he supe:

Large Branches. vena cava and the right atrium. Left .—'

pulmonary trunk.

Branches. —These are the two coronary arteries, right and left.

The right coronary artery arises from the anterior aortic sir Passing forwards between the right auricle and the pulmonary tru it enters the right atrio-ventricular groove, which it traverses fr front to back as far as the commencement of the inferior interv tricular groove. At this point it gives off the inferior interventricr branch. It then enters the posterior part of the left atrio-ventrici groove, in which it anastomoses with a branch of the left coron; artery. The inferior interventricular artery traverses the inferior ini ventricular groove as far as the region of the apex, where it anas moses with the anterior interventricular artery from the left coron; artery.

The right coronary artery furnishes branches to the right atri and to both ventricles. One, of large size, called the right margi artery, passes along the right border, towards the apex.

1 he left coronary artery arises from the left posterior aor sinus, and is at first concealed by the pulmonary trunk. It pas forward between the pulmonary trunk and the left auricle, and gn off the anterior interventricular branch. It then enters the left atr ventricular groove, which it traverses from front to back, anastomosi posteriorly with a branch of the right coronary artery. The anter



THE THORAX


1037


jentricular artery traverses the anterior interventricular groove r as the region of the apex, where it anastomoses with the inferior ventricular branch of the right coronary artery, he left coronary artery furnishes branches to the left atrium and )th ventricles. One, of large size, called the left marginal artery,

s along the left border, towards the apex.

svelopment. —The ascending aorta, along with the pulmonary trunk, is aped from the truncus arteriosus, in which the bulbus cordis teminates. ls divided by a spiral septum into aorta and pulmonary trunk.

rch of the Aorta. —The arch of the aorta commences behind the border of the sternum on a level with the upper margin of the id right costal cartilage, and terminates on the left side of the body


Fig. 610.—The Arteries of the Heart seen from in Front, the Heart being supposed to be Semi-Transparent.

Le fourth thoracic vertebra, at the lower border of which it becomes iescending aorta. It passes upwards, backwards, and to the left, ping over the root of the left lung, and when it reaches the left of the body of the fourth thoracic vertebra it descends. The ht to which the arch reaches corresponds to the centre of the ubrium sterni, which is about 1 inch below the upper border of manubrium. It lies in the superior mediastinum, and its left is in close relation with the left pleura.

delations — Anterior .—The left phrenic and left vagus nerves, the ler being anterior to the latter. Between these two nerves are the

rior cervical cardiac branch of the left sympathetic, and the inferior

ical cardiac branch of the left vagus, both on their way to the super1 cardiac plexus, which they form; and the left superior intercostal




A MANUAL OF ANATOMY


1038

vein on its way to join the left innominate vein. All these structu are overlaid by the left pleura. The remains of the thymus constit an additional anterior relation. Posterior. —The trachea, deep card plexus of nerves, oesophagus, thoracic duct, and left recurrent laryng nerve. Superior .— The left innominate vein, and the origins of following three great arteries, named in order from right to left, £ also from before backwards: the innominate, the left common carol and the left subclavian. Inferior .— The left bronchus, the bifurcat of the pulmonary trunk, the superficial cardiac plexus of nerves, left recurrent laryngeal nerve, and the ligamentum arteriosum. 1 last-named.fibrous cord is attached to the back part of the concav of the arch immediately beyond the level of the origin of the ] subclavian artery.

The arch presents a constriction immediately beyond the ori of the left subclavian artery, called the aortic isthmus , and this succeeded by a short fusiform dilatation, known as the aortic spin (of His). These features are best marked in the foetus.

Branches. —These are three in number—namely, the innomina left common carotid, and left subclavian arteries. They arise in the on named, proceeding from before backwards, and also from right to le

Innominate Artery.— This vessel is the first and largest of the th branches which arise from the arch of the aorta. It springs from 1 upper aspect of the arch rather above the level of the upper bon of the second right costal cartilage, and it terminates behind 1 upper border of the right sterno-clavicular joint by dividing into 1 right common carotid and right subclavian arteries. It is from to 2 inches in length, its direction is upwards and outwards, and lies in the superior mediastinum.

Relations — Anterior .— The right half of the manubrium ster with the origins of the right sterno-hyoid and sterno-thyroid muscl the left innominate and the right inferior thyroid veins; the ri£ sterno-clavicular joint; and some remains of the thymus. Posterior The trachea at first, but as the artery ascends obliquely to the ri£ it leaves the front of the trachea and is placed on the right side. 1 three cervical cardiac branches of the right sympathetic also lie behi the artery on their way to the deep cardiac plexus. Right. —The ri£ pleura; the innominate vein, with the right vagus nerve behind the superior vena cav^; and the right phrenic nerve. Left. —The 1 common carotid artery and the trachea, in this order from bet upwards.

Branches.— These are terminal, and are two in number—name the right common carotid and the right subclavian. The artery, a rule, gives off no branches in its course. Occasionally, however, gives origin to a vessel of variable size, called the arteria thyroidea i'i (lowest thyroid artery). The interest attached to this occasioi branch is that, in ascending to the isthmus of the thyroid gland in i neck, it lies in front of the trachea, and would be endangered in 1 operation of tracheotomy.


THE THORAX


1039


arieties. —(1) The innominate artery may be shorter or longer than usual, n cases of high bifurcation the artery may so encroach upon the trachea as

endangered in tracheotomy.

jeft Common Carotid Artery in the Thorax. —This vessel arises from ipper aspect of the arch of the aorta, just to the left of, and posterior


Trachea


Innominate

Artery


Rt. Superior Intercostal Artery

Arch of._, Aorta


Left Common Carotid Artery — Scalenus Anterior Muscle

... Left Vagus Nerve

Left Subclavian Artery (Third Part)

Left Phrenic Nerve

Left Superior Intercostal Artery


Cardiac Branches of Vagus and Sup. Cervic. Symp. Ganglio 1

Superficial Cardiac Plexus


Left Bronchus


Descending

Thoracic

Aorta


CEsophagus


Intercostal Vessels and Nerve


. Abdominal Aorta


Fig. 611.—Dissection of the Posterior Wall of the Thorax.


the origin of the innominate artery. It lies in the superior mediasim, and its direction is upwards and to the left. Having reached posterior aspect of the left sterno-clavicular joint, it enters upon cervical part of its course.

Relations — Anterior .—The left half of the manubrium sterni, 1 the origins of the left sterno-hyoid and sterno-thyroid muscles,













1040


A MANUAL OF ANATOMY


but these structures lie at a little distance from the vessel; the L innominate vein; and some remains of the thymus. Posterior. —T trachea at first, and subsequently the left recurrent laryngeal nen the oesophagus (which here deviates slightly to the left of the trache; and the thoracic duct. Right.- —The innominate artery at first, ai later the trachea. Left. —The left vagus and left phrenic nerves, wi the superior cervical cardiac branch of the left sympathetic and t inferior cervical cardiac branch of the left vagus; the first and the 1< superior intercostal veins as they pass to the left innominate vei and the left pleura and lung.

The thoracic portion of the left subclavian artery is on the left < and posterior to, the vessel, but at a little distance from it.

The thoracic portion of the left common carotid artery gives < no branches.

First Part of the Left Subclavian Artery in the Thorax. —This ves< arises from the upper aspect of the arch of the aorta a little to the 1( of, and posterior to, the origin of the left common carotid artery, lies deeply in the superior mediastinum, and is almost parallel to t thoracic portion of the left common carotid, its course being neai vertical.

Relations— Anterior. —The left common carotid artery; the left vag and left phrenic nerves, with the superior cervical cardiac branch of t left sympathetic and the inferior cervical cardiac branch of the 1( vagus, all these nerves lying between it and the left common carol artery; and the left innominate vein. Posterior. —The oesophagus a] the thoracic duct. Right. —The trachea and the left recurrent larynge nerve. Left. —The left pleura and the inner aspect of the left lur the latter being grooved by the vessel.

The thoracic portion of the left subclavian artery gives off branches.

Varieties of the Aorta —1. Position.— (a) The arch of the aorta may rise high as the upper border of the manubrium sterni, or it may stop short of t level of the centre of the manubrium, (b) It may have been derived from a rh aortic arch instead of a left.

2. Branches of the Arch and their Positions. —Varieties in these respects ; very numerous. The normal number of branches arising from the arch is thr There may be, however, only one branch, or, on the other hand, there may as many as six. When there is a reduction in the number of branches, it usually due to the left common carotid arising with the innominate from a comm trunk. The most common additional branch is the left vertebral artery, its pl< of origin being between the left common carotid and left subclavian arteri The right vertebral artery sometimes arises from the arch, but this is somewl rare. An arteria thyroidea ima may arise from the arch between the innomin; and left common carotid arteries. In rare cases the internal mammary arte or the inferior thyroid, may spring from the arch. The innominate artery n be absent, in which cases the right subclavian and right common carotid he independent origins. Under these circumstances the right subclavian art may be the last of the branches from the arch, and, when this is so, in order reach the right side of the neck, it crosses in front of the vertebral colur lying behind the oesophagus, or more rarely between the trachea and oesophagus.




THE THORAX


1041


velopment of the Arch of the Aorta and its Branches. —The arch of t>rta, between the innominate artery and the left subclavian, is the ed fourth aortic arch of the embryo. It is thus of the same develop


4


ig. 612.—The Aorta in the Thorax, and the Principal Arteries

of the Head and Neck.


^rch of the Aorta Aortic Isthmus Aortic Spindle descending Aorta -oronary Arteries (from Ascend' ing Aorta) nnominate Artery ^eft Common Carotid -eft Subclavian ^ight Common Carotid


10. Right Subclavian

11. External Carotid

12. Internal Carotid

13. Maxillary

14. Superficial Temporal

15. Vertebral

16. Internal Mammary

17. Thyro-cervical Trunk

18. Inferior Thyroid

19. Transverse Cervical


20. Suprascapular

21. Superior Thyroid

22. Lingual

23. Facial

24. Occipital

25. Posterior Auricular

26. Ascending Pharyngeal

27. Transverse Facial

28. Posterior Intercostals

29. Lig. Arteriosum


d value as the innominate and first part of the right subclavian. Beyond ft subclavian origin it is formed from a part of the left dorsal aorta. The unate, as said above, is a portion of the right fourth aortic arch, and the

66






1042


A MANUAL OF ANATOMY


left common carotid is a forward-running branch from this fourth arch, as i common carotid on the right side; these two vessels, although their actual a is in doubt, are frequently said to represent the ventral aortce of lower form interpretation of some practical value even if not absolutely correct (see p. et seq.). The left subclavian is an intersegmental artery, enlarged because < relation to the limb; its origin was from the dorsal aorta opposite to the enti of the fourth aortic arch. The ligamentum arteriosum is the remnant o: sixth aortic arch .

For the description of the descending aorta, see p. 1089.

Pulmonary Trunk. —This is the great vessel which, by mean its right and left divisions, carries the venous blood from the r ventricle of the heart to the lungs. It is therefore an exampl an artery which conveys venous blood, and in this respect resem the umbilical arteries of the foetus. It arises from the infundibu of the right ventricle of the heart, on a level with the upper ma of the third left costal cartilage at its junction with the stern It is directed upwards and backwards, and after a course of al 2 inches breaks up into two divisions, right and left, within the < cavity of the arch of the aorta. The vessel lies in the middle mec tinum, and along with the ascending aorta it is contained within pericardium, the serous portion of which forms one common shi for the two arteries over about the first ij inches of their course

Relations — Anterior .—The sternal extremity of the second intercostal space and second left costal cartilage, and the left pL and left lung. Posterior .—The root of the ascending aorta; the c mencement of the left coronary artery; and the left atrium of heart. Right .—The right coronary artery; the right auricle the ascending aorta. Left .—The left coronary artery and the auricle.

The only branches of the trunk are the two terminal divisions.

The right pulmonary artery passes outwards to the right, be. the ascending aorta and superior vena cava, to the root of the 1 lung, where it divides into two branches, upper and lower. The u; branch is distributed to the upper lobe, and the lower branch, w is the larger of the two, is distributed to the middle and 1< lobes.

The left pulmonary artery passes outwards to the left, in f of the left bronchus and descending aorta, to the root of the left 1 where it divides into two branches, one for the upper and the c for the lower lobe. The ligamentum arteriosum is attached to upper aspect of its root.

The right pulmonary artery is larger and longer than the left.

Development. —The pulmonary trunk, along with the ascending aon chiefly developed from the truncus arteriosus, but a small portion of it is foj by the commencement of the sixth left arterial arch, which remains connected that portion of the truncus which becomes partitioned off to form the pulmc trunk.

The right and left pulmonary arteries are developed as branches fror sixth left aortic arch near its commencement, the remainder of that arch g rise to the ductus arteriosus of the foetus. I


!




THE THORAX


1043


igamentum Arteriosum.— This is a fibrous cord which is the remains important vessel peculiar to foetal life, called the ductus arteriosus. [tends from the upper aspect of the root of the left pulmonary y to the under surface of the arch of the aorta immediately nd the level of the origin of the left subclavian artery. Its tion is upwards, backwards, and slightly to the left.

uring foetal life the right and left pulmonary arteries are of small size, and uctus arteriosus conveys the greater part of the venous blood from the ventricle of the heart into the aorta at a point beyond the origin of the left avian artery. None of this blood, therefore, can pass into the great vessels 1 spring from the upper aspect of the arch of the aorta, evelopment. —The ductus arteriosus is developed from the dorsal part of xth left aortic arch.

'ulmonary Veins. —These vessels carry the arterial or oxygenated I from the lungs to the left atrium of the heart. Though they

alled veins, they contain arterial blood, and in this respect rede the umbilical vein of the foetus. They are four in number,

right and two left, and at the root of each lung the upper of the is on a more anterior plane than the lower. The right veins pass nd the superior vena cava and the right atrium, and the left > pass in front of the descending aorta. All four vessels open into eft atrium on its posterior aspect. On leaving the roots of the lungs veins are said to receive small bronchial tributaries from the cent interpulmonary bronchi and glands.

rhe right pulmonary veins are larger and longer than those of the side.

Tagus Nerves in the Thorax.— These nerves, right and left, differ luch from each other in their course and relations as to require rate descriptions.

rhe right vagus nerve, having descended in front of the first part he right subclavian artery, and having given off its recurrent ngeal branch at the lower border of that vessel, enters the thoracic ty. It then descends in the superior mediastinum behind the >minate vein, and, inclining backwards, it reaches the right of the trachea, along which it courses to the posterior aspect of the of the right lung. Behind the root of the right lung the nerve )mes flattened out and breaks up into numerous branches, which disposed in a plexiform manner, and constitute the right posterior nonary plexus, from which branches are given off to the right lung, m. the lower part of this plexus the nerve issues in the form of two Is, which descend in the posterior mediastinum upon the right side he oesophagus, or gullet, and communicate freely with the corrending cords of the left side. In this manner a plexus is formed, ch is called the oesophageal plexus. Subsequently the two cords he right side unite to form a single nerve, which descends on the ‘erior surface of the oesophagus, and enters the abdomen through oesophageal opening of the diaphragm to be distributed to the -wior surface of the stomach.


1044 A MANUAL OF ANATOMY

The left vagus nerve enters the thoracic cavity between the common carotid and left subclavian arteries, and descends in superior mediastinum behind the left innominate vein. It passes in front of the arch of the aorta, having the left phrenic n on its right side and anterior to it, with the intervention of the supi cardiac nerve from the left superior cervical sympathetic gan^ and its own inferior cardiac branch. At the lower border of the it gives off its recurrent laryngeal branch, and then passes to

posterior aspect of the root of the lung. Behind the root of the lung the nerve, as on the right : becomes flattened out and br up into numerous branches, w are disposed in a plexiform mar and constitute the left posterior monary plexus, from which bran are given off to the left lung. F the lower part of this plexus nerve, as on the right side, is; in the form of two cords, w] descend in the posterior mediastii upon the left side of the oesopha, or gullet, and communicate fr with the corresponding cords of right side. In this manner, as sta a plexus is formed, which is ca the oesophageal plexus. Subsequei the two cords of the left side u to form a single nerve, which scends on the anterior surface of oesophagus, and enters the abdor through the oesophageal opening the diaphragm to be distributed the anterior surface of the stomac Branches. —These are as folio the left recurrent laryngeal; card from the right nerve; pulmona pleural; oesophageal; and p cardial.

The left recurrent laryngeal nerve arises from the left vagus in fr of the arch of the aorta on a level with its lower border. It pas backwards within the arch at the place of attachment of the li mentum arteriosum, and then turns upwards behind the arch. Hav reached the groove between the trachea and the oesophagus, it asce: therein to the neck, where its subsequent course and distribution will described. In the thorax the nerve, which contains fibres derived fr the cranial root of the accessory nerve, furnishes a few cardiac branc to the deep cardiac plexus as it winds round the arch of the aorta.


Fig. 613. — Scheme of Vagus Nerve in Thorax and Abdomen (Flower).

C.P. Branches to Cardiac Plexus P.P.P. Branches to Posterior Pulmonary Plexus

A.P.P. Branches to Anterior Pulmonary Plexus

T.S.G. Branches from Upper Thoracic Ganglia of Sympathetic P.G. (Esophageal Plexus G.B. Gastric Branches





THE THORAX


1045


ie right recurrent laryngeal nerve is extra-thoracic, inasmuch as

es from the right vagus at the root of the neck, and it winds

[ the first part of the right subclavian artery.

e left recurrent laryngeal nerve turns round the ligamentum arteriosum

e this structure is the remnant of the arterial arch within the sixth

il arch, of which the recurrent laryngeal is the nerve. Among the visceral

in front of this the nerves are in the anterior parts of their arches, in

f the arterial stems, but in the sixth visceral arch the vessel, having to >ack to reach the arch, lies in it in front of the nerve. Thus the nerve is t round the ligament when the heart and large vessels assume a more 1 position with reference to the head and neck. On the right the sixth il arch disappears early, and as the fifth artery is a very short-lived ure, the nerve catches against the fourth artery, the first part of the right tvian. It is interesting to observe that in those cases in which the right ivian arises from the left end of the arch of aorta, and passes to the right d the oesophagus, there is no right fourth aortic arch; the nerve consequently es against the third arch, internal carotid, running thus directly to the v.

he cardiac branches of the right vagus are two or three in number, they descend upon the trachea to the deep cardiac plexus. (The iac branches on the left side are derived, as stated, from the recurrent laryngeal nerve as it winds round the arch of the 1.)

he pulmonary branches are arranged in two sets, anterior and erior. The anterior pulmonary branches are two or three in her, and arise from the parent trunk before it disappears behind root of the lung. They pass to the anterior aspect of the root, being joined by sympathetic twigs, they form the anterior pulary plexus, which is reinforced by twigs from the deep cardiac us, and in the case of the left anterior pulmonary plexus by twigs 1 the superficial cardiac plexus. The branches of the anterior nonary plexus enter the lung, and accompany the ramifications he interpulmonary bronchi.

rhe posterior pulmonary branches arise from the vagus nerve ind the root of the lung. They are larger and more numerous 1 the anterior branches, and, being joined by twigs from the >nd, third, and fourth thoracic sympathetic ganglia, they form posterior pulmonary plexus. The branches of this plexus, like those he anterior, enter the lung, and accompany the ramifications of interpulmonary bronchi. The pleural branches are distributed to mediastinal and visceral pleurae, particularly in the region of the im.

The oesophageal branches arise chiefly from the oesophageal plexus dw the level of the roots of the lungs, and they are distributed to the tion of the oesophagus which occupies the posterior mediastinum ler oesophageal branches, however, arise above the level of the ts of the lungs, and are distributed to the portion of the oesophagus ich occupies the superior mediastinum.

The pericardial branches arise from the oesophageal plexus, and are tributed to the pericardium, which they enter from behind.


A MANUAL OF ANATOMY


1046


Cardiac Plexus. —The cardiac plexus is one of three large prew bral plexuses associated with the sympathetic system, the other —namely, the cceliac and the hypogastric—being situated in abdominal cavity. The plexus is situated partly in the conca of the arch of the aorta, and partly upon the trachea above the bifu tion and behind the aortic arch. It is formed by branches of vagi and sympathetic nerves, and consists of two portions, super! and deep, which communicate with each other.

The superficial cardiac plexus, which is comparatively smal situated in the concavity of the arch of the aorta between the ! mentum arteriosum and the right pulmonary artery. It is for by (1) the superior cardiac nerve from the left superior cervical s pathetic ganglion, and (2) the inferior cervical cardiac branch of left vagus nerve. These two nerves descend over the arch of aorta, lying between the left phrenic and left vagus nerves. At place where the two nerves join there may be a small ganglion, w is known as the cardiac ganglion (ganglion of Wrisberg).

Branches. —The plexus gives branches to the left anterior monary plexus, and, having received a considerable accession of fi from the right half of the deep cardiac plexus, it is prolonged into right coronary plexus.

The deep cardiac plexus, of larger size than the superficial situated upon the trachea immediately above the bifurcation behind the arch of the aorta. It is formed by (1) all the car branches of the right cervical sympathetic ganglia—namely, supe: middle and inferior—and of the right vagus—namely, superior inferior; (2) one or two cardiac branches from the right recur laryngeal nerve; (3) one or two cardiac branches from the right va in the thorax; (4) the middle and inferior cardiac branches of the cervical sympathetic trunk; (5) the superior cervical cardiac bra of the left vagus; and (6) the cardiac branches of the left recuri laryngeal nerve. It is arranged in two halves, right and left, wl communicate with each other. Each half receives the follov branches:


Right Half.


Left Half.


1. The three cardiac branches of

the right cervical sympathetic.

2. The two cardiac branches of the

right vagus, in the neck.

3. The cardiac branches of the right

recurrent laryngeal.

4. The cardiac branches of the right

vagus, in the thorax.


1. The middle and inferior cai

branches of the left cer sympathetic.

2. The superior cardiac brand

the left vagus, in the neck.

3. The cardiac branches of the

recurrent laryngeal.


Branches. —The right half of the deep cardiac plexus gives (1) branches to the right anterior pulmonary plexus; (2) bran< to the right coronary plexus. The left half of the deep cardiac pkj gives off (1) branches to the left anterior pulmonary plexus; (2) bran( to the left coronary plexus. j


THE THORAX


1047


$.R


Fig. 614.—Scheme of the Sympathetic Trunk in the Neck, and

of the Cardiac Plexus (Flower).


S.C.G. Superior Cervical Ganglion.

md G.P. Branches to Vagus and Glosso-pharyngeal , 3c, 4c. Branches to Upper Four Cervical Nerves .P Carotid Plexus P. Cavernous Plexus •G. Branch to Ciliary Ganglion '.P. Deep Petrosal •P. Greater Superficial Petrosal .N. Nerve of Pterygoid Canal •N. To In f erior Ganglion of Vagus H. To Hypoglossal -.P. To External Carotid Plexus •P. To Pharyngeal Plexus •N. Superior Cardiac Nerve

M.C.G. Middle Cervical Ganglion.

5c. To Fifth and Sixth Cervical Nerves •P. To Inferior Thyroid Plexus •N. Middle Cardiac Nerve


I.C.G. Inferior Cervical Ganglion.

7c, 8c. To Seventh and Eighth Cervical Nerves V.P. To Vertebral Plexus S.P. To Subclavian Plexus I.C.N. Inferior Cardiac Nerve


F.T.G. First Thoracic Ganglion


Cardiac Plexus.

C.B.Pn. Cardiac Branches of Vagus S C P Superficial Cardiac Plexus G.W. Cardiac Ganglion D C.P. Deep Cardiac Plexus R A.P.P. Right Anterior Pulmonary Plexus L.A.P.P. Left Anterior Pulmonary Plexus R.C.P. Right Coronary Plexus L.C.P. Left Coronary Plexus








1048


A MANUAL OF ANATOMY


Coronary Plexuses. —These are two in number, right and left.

The right coronary plexus is formed by branches from (1) superficial cardiac plexus, and (2) the right half of the deep card plexus. It accompanies the right coronary artery, and furnis branches to the right atrium and right ventricle of the heart.

The left coronary plexus is formed by branches which are derh chiefly from the left half of the deep cardiac plexus. It accompar the left coronary artery, and furnishes branches to the left atrium a left ventricle of the heart.

Ganglia are met with in the coronary plexuses, and in the cou of the fibres which supply the walls of" the auricles. They are a present on the fibres which supply the walls of the ventricles the region of the atrio-ventricular groove, but nowhere else. In heart of the calf the nerves are easily recognized beneath the visce pericardium, as they pass across the muscular fibres in an obli( manner.

Heart. —The heart is a hollow muscular organ, which, enclo: within the pericardium, is situated in the middle mediastinum, wh it lies obliquely between the two lungs. It is conical in shape, a is free to move within its pericardial sac, except at the base, wh it is connected with the great bloodvessels. Its relation to the thora wall during life is influenced by posture and by the respiratory mo merits. When a person lies upon the left side, or when the prc position is assumed, the organ is more intimately related to the thora wall than in the opposite postures; and during inspiration it is 1 intimately connected with the thoracic wall than during expiration.

General Relations and Topography. —The heart lies obliqu behind the lower three-fourths of the body of the sternum. Ab( two-thirds of the organ are contained in the left half of the thora cavity, and about one-third in the right half. The base is direcl upwards, backwards, and to the right, and lies opposite the bod of the middle four thoracic vertebrae—namely, the fifth, sixth, seven and eighth. The apex is directed downwards, forwards, and to 1 left, and during life it strikes the thoracic wall in the fifth left int costal space if inches below the left nipple, and about £ inch witl the left mammillary line. This point represents the apex-beat, and about 3I inches from the median line of the sternum. The sten costal surface , which is convex, lies behind the lower three-fourths of 1 body of the sternum and the corresponding costal cartilages, right a namely, the third, fourth, fifth, and sixth—more particularly the of the left side. This surface is encroached upon by the pleurae a the thin anterior margins of the lungs. Opposite the cardiac not on the anterior margin of the left lung there is a small portion which uncovered by lung, unless during deep inspiration, and this cor: sponds with the area of precordial dulness. Latham’s circle is tak as defining this area, and the directions for describing the circle a as follows: Make a circle of 2 inches in diameter round a point nr way between the left nipple and the end of the sternum/ Strict


THE THORAX


1049


.king, the area of precordial dulness is triangular in conformity to V-shaped cardiac notch on the anterior margin of the left lung, it may be mapped out by the following lines: one drawn from the tion of the apex-beat to the median lines of the sternum on a level 1 the fourth left costal cartilage; another drawn from the position he apex-beat to the median line of the sternum at the junction he body and xiphoid process; and a third connecting the inner 5 of these two lines, and extending along the middle of the sternum.


>rax, may be indicated with approximate accuracy in the following nner:

Base .—Draw a line across the sternum on a level with the upper rder of the third right and the lower border of the second left costal

















1050


A MANUAL OF ANATOMY


cartilages, and prolong this line for § inch to the right of the sterm and i inch to the left of it.

Inferior Border , or Acute Margin .—Draw a line from the steri end of the sixth right costal cartilage to the position of the apex-be; This line corresponds to the lower limit of the heart.

Right Limit .—Draw a line from the upper border of the third rig costal cartilage, \ inch from the sternum, to the sternal end of t

sixth right costal cartilage. This line shoi be curved outwards to such an extent tf its greatest convexity will be i J inches dista from the median line of the sternum, corresponds with the right limit of the rig atrium.

Left Border, or Obtuse Margin .—Draw line from the lower border of the second 1< costal cartilage, i inch from the sternum, the position of the apex-beat. This line shor be slightly curved outwards, but it must n include the left nipple. It corresponds to t left limit of the heart.

Course of the Circulation. —The interior the heart is divided by two septa (atrial ai ventricular) into two halves, right and le and each half is subdivided by a transvei constriction into two chambers, an upper atrium, and a lower or ventricle, right ai left respectively. The atria, except in t foetus, are completely separated from ea other by a septum, and so also are t ventricles; but the atrium and ventricle each side communicate freely with each oth by the atrio-ventricular orifice. The rig atrium receives the venous blood chiefly fro the superior and inferior venae cavae and t coronary sinus. From the right atrium t blood passes into the right ventricle, ai thence into the pulmonary trunk. The rig and left pulmonary arteries convey it to t lungs, and in passing through the pulmona capillaries it is oxygenated and beeom arterial blood. It is then taken up by the pulmonary venous radick and conveyed to the pulmonary veins, which carry it to the left atriu of the heart. From the left atrium it passes into the left ventric whence it is driven into the aorta. The aorta and its various ran fications convey the arterial blood to the different parts of the bod and thereafter it is returned as venous blood to the right atrium the heart.

Exterior of the Heart. —The exterior of the heart presents distinj


Fig. 616.—To show the Parts of Heart as

SEEN FROM THE FRONT,

when Pericardium is

REMOVED.

VD is the right ventricle, narrowing upwards (infundibulum) to reach pulmonary artery (P). The prominent anterior part of left ventricle (VS) is seen along its left border, and forms the actual apex; the left auricle (AS) shows just above this. The ascending part of aorta (A) comes from the left ventricle, and therefore appears from behind P. AD is the anterior aspect of the right auricle.


THE THORAX


IQ5 1


cations of its division internally into four chambers. These take form of grooves—namely, atrio-ventricular, interatrial, and inter tricular.

The atrio-ventricular groove , which is deep, divides the heart into al and ventricular portions, and surrounds the organ except in it, where the root of the aorta and the pulmonary trunk are situated.

atrial portion is posterior and superior in position, whilst the

itricular portion is anterior and inferior. The right half of the io-ventricular groove contains (i) the right coronary artery, and the small cardiac vein, which latter lies chiefly in its posterior •t. The left half of the atrio-ventricular groove contains (i) the

coronary artery; (2) the right coronary

ery, which lies in its posterior part; a portion of the great cardiac vein, ich lies in its anterior part, and also jhtly in its posterior part; and (4) the unary sinus, which lies in its posterior

rt. ! '

The atrial portion of the heart has the m of a crescent, the horns of which present the auricles, and are directed 'wards. The concavity of the crescent also directed forwards, and lodges the ot of the aorta and the pulmonary ink, the latter being the more anterior the two. Its walls are thin, and it is vided into two atria, right and left. The ternal indication of this division is the ter atrial groove, which is situated verbify on the posterior surface to the left the openings of the superior and inferior mae cavse. This groove corresponds to Le posterior attachment of the atrial ptum in the interior. The greater part

the posterior surface of the atrial portion .

formed by the left atrium. Projecting forwards from the anterior id upper part of each atrium is the auricle (auricular appendix). I ho vo auricles embrace between them the root of the aorta and the

ulmonary trunk. .

The right atrium (right auricle) forms the anterior and right part

f the base of the heart, and is triangular in outline as seen from ie front. The superior vena cava enters its atrium at the posteroiperior angle, and the inferior vena cava at the postero-mferior ngle. Near the latter vein the coronary sinus also opens into the trium. The right auricle (auricular appendix) is prolonged forwards rom the antero-superior angle of the atrium, and inclines to the e t 1 front of the root of the ascending aorta. It is shorter, broader, an ^ss curved than the left auricle, and its margin is notched, but no so


Fig. 617.—A Posterior View of the Heart, showing Left Atrium (LA) receiving Pulmonary Veins (PV).

This is the highest and most posterior cavity. The right atrium (RA) is seen beside it, "and the left ventricle (LV) is visible below and in front on its left side. The coronary sinus (SV) runs transversely between the atrium and the ventricle.



1052


A MANUAL OF ANATOMY


much so as is that of the left auricle. The right atrium is travers< by a groove, called the sulcus terminalis , which extends from the fro: of the termination of the superior vena cava to the front and rig] side of the termination of the inferior vena cava. This groove sho\ where the sinus venosus of embryonic life meets the primitive atrium.

The left atrium (left auricle) forms the posterior part and left the base of the heart. It is quadrilateral, and the greater part it lies flattened behind the ascending aorta and the pulmonary trun The pulmonary veins, two right and two left, open into the posteri part of the atrium. The left auricle (auricular appendix) is prolongi forwards from its left aspect, and inclines to the right over the le side of the pulmonary trunk. It is longer, narrower, and more curvi


than the right auricle, and its margin is more deeply notched. T] back of the left atrium is related to the oesophagus, with the inte vention of the pericardium; the small oblique vein of left atrium (ve of Marshall) passes downwards and inwards upon it, to open into tl coronary sinus.

The ventricular portion of the heart is conical, its walls are thic and it is divisible into two ventricles, right and left. The extern indication of this division is the interventricular groove, which co responds to the attachment of the ventricular septum in the interio This groove consists of two parts, anterior and posterior. The anteri interventricular groove extends over the sterno-costal surface of tl heart from the left side of the pulmonary trunk to the inferior bord




THE THORAX


ic>53


he right of, and near, the apex. At this point it becomes continuous

h the inferior interventricular groove. It contains, besides fat, the anterior branch of the left coronary artery, and (2) a part of great cardiac vein. The inferior interventricular groove is situated the inferior surface of the heart, and, as stated, is continuous with preceding. It contains, besides fat, (1) the inferior interven:ular branch of the right coronary artery, and (2) the middle cardiac n.

The ventricular portion of the heart presents an apex, a base, ) surfaces, and two borders. The apex is directed downwards, wards, and to the left, and forms the apex of the heart. The left


Great Cardiac Vein


Left Ventricle


Apex


Arch of Aorta

Superior Vena Cava


Right Pulmonary Veins *

'• Right Atrium


Inferior Vena Cava


Coronary Sinus


Right Coronary Arteiy


Right Ventricle


Pulmonary Trunk


Left Pulmonary Veins


Fig. 619. —The Heart (Posterior View.)


itricle alone enters into its formation. The base is directed upwards,

kwards, and to the right, and is connected with the atria and the

gins of the aorta and pulmonary trunk, the former being behind I the latter in front.

The surfaces are sterno-costal and diaphragmatic. The sternotal surface is convex, and is traversed by the anterior interventricular >ove. As this groove lies near the left border, the greater part of s -surface (about two-thirds) is formed by the right ventricle, and ' remainder b}^ the left ventricle. In post-mortem examinations, before, when the pericardium is opened, the right ventricle is chiefly xised for inspection. On this aspect of the right ventricle there

the anterior cardiac veins. Its upper and left part is somewhat









1054


A MANUAL OF ANATOMY


conical, and is called the infundibulum (conus arteriosus). It gr origin superiorly to the pulmonary trunk. The diaphragmatic surf is flat, and is traversed by the inferior interventricular groove, this groove lies near the inferior border, the greater part of this surf; (about two-thirds) is formed by the left ventricle, and the remaim by the right ventricle. On this aspect of the left ventricle there ; the posterior cardiac veins.

The borders are inferior (right) and left. The inferior border comparatively long, and extends from right to left. It is formed the right ventricle, and is sharp in outline, from which circumstai it is known as the acute margin. The marginal branch of the ri^ coronary artery and one of the anterior cardiac veins lie along

The left border is shorter th the inferior, and is blunt a round, from which circu stances it is known as 1 obtuse margin. The margi] branch of the left corom artery lies along it.

Interior of the Heari Right Atrium (Right Auric —The wall of the auricle marked by a number muscular elevations arran^ as closely-set, vertical, par lei bands, like the teeth a comb, from which circu stance they are called 1 musculi pectanati. Th bands, relatively to ez other, are more or less r icular. They are also presi on the right wall of 1 atrium, being more comb-1 here than in the auric and they terminate posteriorly at a vertical ridge, called the cn termmalis. This crest corresponds in position to the sulcus termini externally, and it has the same significance. Internally and posterio the walls of the atrium are destitute of musculi pectinati, and p sent a smooth appearance. The right atrium presents the follow: openings : the opening of the superior vena cava; the opening of' inferior vena cava; the opening of the coronary sinus; the openings the venae cordis minimae; and the tricuspid orifice.

The orifice of the superior vena cava, which is destitute of a val is situated at the postero-superior angle of the atrium. It is direc downwards and forwards, and the upper part of the crista termin; is continuous with its anterior margin.

The orifice of the inferior vena cava is situated at the poste


Fig. 620.—Diagrammatic Section along Right Side of Heart.

AV, atrio-ventricular valve ; C, trabeculae carneae; E, valve of I VC; FO, fossa ovalis; P, papillary muscle; SV, supraventricular crest; T, opening of coronary sinus.





THE THORAX


1055


erior angle of the atrium, and is directed upwards and inwards,

front of the orifice, and to a certain extent overlapping it, there a crescentic fold of endocardium, which is the remains of the valve the inferior vena cava (Eustachian valve) of foetal life. The conxity of the crescent is continuous with the anterior margin of the fice of the vein, and the inner horn of the crescent is continuous th the anterior limb of the annulus ovalis, to be presently described. ie fold is a somewhat indefinite structure in the adult, being subject much variety as regards size, and sometimes presenting several ■all openings. During foetal fife, however, the valve is of the utmost portance, inasmuch as it directs the blood entering by the inferior na cava through the foramen ovale into the left atrium.

The orifice of the coronary sinus is situated between the valve of 3 inferior vena cava and the tricuspid orifice. It is guarded by a licate semicircular fold of the endocardium, called the valve of the ■onary sinus (Thebesian valve), which, however, is functionally

ompetent.

The foramina venarum minimse (foramina Thebesii) represents Tral minute openings on the wall of the atrium. Some of these are lply blind recesses, whilst others are the orifices of minute veins, led the vence cordis minimce, which return the blood from the wall the atrium.

The atrio-ventricular or tricuspid orifice is situated in the lower i anterior part of the atrium in front of the orifice of the inferior 1a cava, with the intervention of that of the coronary sinus. It is il and in health will admit three fingers. Through this opening s blood passes from the right atrium into the right ventricle, its urn being prevented by the tricuspid valve, which will be described connection with the right ventricle.

The posterior wall of the atrium corresponds to the atrial septum,

I presents for consideration the fossa ovalis and the annulus ovalis. The fossa ovalis is an oval depression which is situated upon the rer part of the atrial septum a little above and to the left of the free of the inferior vena cava. It indicates the position of the amen ovale of the foetal heart, which is a communication between ! two atria through which the blood entering the right atrium by • inferior vena cava passes into the left atrium. The floor of the sa ovalis is very thin, and is bounded above and at the sides by a >minent crescentic margin, called the annulus ovalis. The annulus ieficient below, and the concavity of the crescent is directed downrds. Its anterior limb is continuous with the valve of the inferior ia cava. In some cases a minute oblique communication between

two atria persists in the adult, being situated under cover of the

^er portion of the annulus ovalis.

Interior of the Right Ventricle. —When exposed to view in the ■inary way, the interior of the right ventricle is pyramidal, the

e being directed backwards and to the right, and the apex forwards,

the left, and a little downwards. It is completely separated from


A MANUAL OF ANATOMY


1056


the left ventricle by the ventricular septum, which forms the poster wall of the ventricle, and bulges into it so as to be convex towards In transverse section, therefore, the right ventricle is semilunar, wall, which is about three times thinner than that of the left ventri( is thickest at the base, and becomes thinner towards the apex. 1


\


L. Atriiin


“A. V. orifi


Aortic

Vestibule


Septum


tiG. 621 .—-Longitudinal Section through Heart, opening the Four

Cavities.

Shows the deep situation of the aortic vestibule, between the left A.V. openi and the interventricular septum. The thin upper part of this septum the pars membranacea, which is partly between the aortic vestibule a each of the right-sided cavities. Based on a section given by Tandler.

capacity of the ventricle is about 4 ounces. Its upper and left pz form the infundibulum [conus arteriosus), from the upper part of whi the pulmonary trunk springs. The walls of the infundibulum 2 smooth, but elsewhere the walls of the ventricle are elevated in muscular bands, called trabeculce carnece . These project into t






THE THORAX


1057


y, and from their reticular arrangement they render the wall

irregular. According to the manner in which the trabeculse ese are attached to the wall, they are arranged in three sets: (1) some simple elevations, which are attached to the wall by their entire th, as well as by their extremities; (2) some are attached to the only by their extremities, being free elsewhere; and (3) others ittached only by one extremity. These latter are called papillary

les. They are conical, and their bases are attached to the wall

le ventricle. Their free extremities are connected with a number iform processes, called chordce tendinece, which pass to the margins ventricular surfaces of the segments of the atrio-ventricular e. When the ventricle contracts, the papillary muscles also ract, and by tightening the chordae tendineae they prevent the >s of the atrio-ventricular valve from being swept back into the im. The cusps are therefore maintained in contact during the

ricular systole, and no regurgitation of blood from the ventricle

the atrium is allowed in health. The papillary muscles are ,nged in three groups—anterior, inferior, and septal—and their

s are attached to the walls of the ventricle in the region of the

t of the cavity. The anterior papillary muscle is of large size, inferior is usually broken up into two or more secondary papillary

cles, while the septal muscles are variable both in number and

In most hearts a fleshy column, called the moderator band , is met 1 in the right ventricle, which extends from the ventricular septum he base of the anterior papillary muscle. The term moderator band applied to this bundle in the mistaken belief that it moderated ension of the right ventricle. It is now known to serve for the sage of an important slip of the atrio-ventricular bundle. (The d was noted and drawn by Leonardo da Vinci more than four hunI years ago, and the name of bundle of Leonardo has been suggested it.)

The openings. connected with the right ventricle are two in number amely, the tricuspid and pulmonary, Ihey are situated at the e of the cavity, and are guarded by most important valves. The uspid orifice is situated on the right and posteriorly, whilst the monary orifice is situated on the left and anteriorly, being also on igher level than the other. Vence minimce cordis are said to open

i the right ventricle. . .

The right atrio-ventricular or tricuspid orifice is oval, and admits passage of three fingers. It allows the venous blood to flow from right atrium into the right ventricle, and in order to prevent urgitation of blood from the ventricle into the atrium during the itricular systole it is guarded by an important valve, called the lit atrio-ventricular or tricuspid valve. This valve is composed of ee segments or cusps , which are covered with endocaidium. These >ject into the cavity of the ventricle, and are triangular. The bases the cusps are continuous with one another, and form a ring, which


A MANUAL OF ANATOMY


1058

is attached to the margin of the tricuspid orifice. The largest cus situated in front and to the left of the tricuspid orifice. It interv< between that orifice and the infundibulum, and is known as the ante cusp. Another cusp is situated behind the tricuspid orifice, and i contact with the ventricular septum. It is called the medial c The third cusp is situated to the right near the acute margin, an called the inferior cusp. In the angular intervals between the b parts of the three large cusps there are usually three small cusps.

Each cusp consists of two layers of endocardium, with fibi tissue between them, especially at their central parts. The mi< portion of each cusp is therefore thicker than the marginal porti these latter being thin and transparent. The margins themse


Superior Vena Cava .


Aorta


Annulus Ovahs


Fossa Ovalis


Valve of Inferior Vena Cava


✓ Pulmonary Trunk (opened)


§N — Pulmonary Valves


Orifice of Coronary Sinus

Valve of Coronary &§§!!

Sinus / Inferior Vena Cava

Tricuspid Valve


- Left Coronary Artei j


Ventricular Septun


Left Ventricle


Chordas Tendineae

I

Papillary Muscle

Fig. 622.—The Interior of the Right Auricle and Right Ventrici


are notched. The atrial surfaces of the cusps are smooth, but t ventricular surfaces are roughened by the chordae tendineae, wl are also attached to the margins.

The chordae tendineae are filiform, fibrous processes which connected on the one hand with the wall of the ventricle, and the other with the cusps of the tricuspid valve. Most of them sp from the anterior and inferior papillary muscles, but a few of ti arise from the ventricular septum and from the small papillary t nences upon it. Those which are connected with the anterior papil muscle pass to the interval between the anterior and inferior cu: those which are connected with the inferior papillary muscle and subdivisions pass to the interval between the medial and infe









THE THORAX


1059


>s; and those which are connected with the ventricular septum

to the interval between the anterior and medial cusps. The

lection of the chordae tendineae with the cusps of the valve is of reef old nature as follows: (1) most are connected with the marginal

s of the cusps; (2) others are connected with the thickened central
ion of each cusp; and (3) a few pass to the basal portion of each

), where they are connected with the fibrous ring around the uspid orifice.

rhe pulmonary valve guards the orifice of the pulmonary trunk, prevents regurgitation of blood from the trunk into the right tricle during the elastic recoil of the arterial wall. It is composed

hree semilunar cusps, and the wall of the artery opposite each


Ascending Aorta (opened)


Aortic Semilunar Valves —


Ventricular Septum


Pulmonary Trunk Lunule


Pulmonary Veins


Atrial Septum


Mitral Valve

%

%\ t ',!■/

- Chord® Tendineae


r Papillary Muscle


Trabeculae Carneae <

Apex


Fig. 623. —The Interior of the Left Atrium and Left Ventricle.


ment presents a recess, these recesses being called sinuses. The ve and the sinuses are similar to corresponding structures in mection with the aortic orifice, and will be fully described along h that orifice.

Interior of the Left Atrium.— The musculi pectinati are present V in the auricle, whereas in the right atrium they are present both be auricle and on the right wall of the atrium. The wall of the left him is entirely smooth. The atrium presents five openings— nely, the openings of the four pulmonary veins, and the mitral ice.

The orifices of the four pulmonary veins are situated on the posterior h of either side, two right and two left, and are destitute of valves.










io6o


A MANUAL OF ANATOMY


The auriculo-ventricular or mitral orifice is situated in the ante: part of the floor of the atrium. It is oval, and in health admits i passage of two fingers.

Venee minima cordis are said to open into the left atrium.

The atrial septum presents a slight depression, limited inferio by a faint crescentic ridge, the concavity of which is directed upwar These indicate the position of the foramen ovale of the foetal heart

Interior of the Left Ventricle.—The cavity of the left ventri extends quite to the apex of the heart, and is longer and narrow than that of the right ventricle. It is somewhat conical, the base bei directed backwards and upwards. The ventricular septum rece<

from the cavity, and is cones towards it. In transverse secti<


Left

Ventricle


Right Ventricle


Left Ventricle


therefore, the left ventricle is o\ or nearly circular. The wall of 1 left ventricle is about three tin thicker than that of the right, 1 difference being readily accounl for by the fact that the left ventri is concerned with the systemic c culation, whilst the right ventri has to do with the pulmonary c culation, the latter involving a mr shorter circuit. The wall of 1 left ventricle attains its maximi thickness about the junction the upper fourth and lower thr fourths, and is thinnest in 1 region of the apex. The capac of the ventricle is about 4 ounc


Ventricular Septum

Fig. 624. Transverse Sections of 'ppg portion of the cavity imme

. ateiy below the aortic orifice

A. through apex .(superior view). known as the aortic vestibule, i

B, through ventricles (inferior view). .. . . . . *

walls 01 which are fibrous.

The left ventricle, like the right, is provided with trabeculae carnt They are arranged in a very intricate manner, more particularly the region of the apex and over the posterior wall. The aor vestibule and the ventricular septum, at least over its upper pa are destitute of trabeculae carneae, and present a smooth appearan The papillary muscles are much larger than those in the right ventric they are two in number, anterior and posterior, and they are attaci by their bases to the respective walls of the ventricle, whilst th free ends are connected with the chordae tendineae.

The openings connected with the left ventricle are two in numl —namely, mitral and aortic. They are situated at the base of 1 ventricle in close proximity to each other, and are guarded by imports valves. The mitral orifice is situated on the left and posterior whilst the aortic orifice is situated on the right and anteriorly. 1





THE THORAX


1061


ic orifice is also considerably the higher of the two. Vence minima

lis are said to open into the left ventricle.

The auriculo-ventricular or mitral orifice is oval, and in health fits two fingers. It allows the arterial blood to flow from the left um into the left ventricle, and in order to prevent regurgitation blood from the ventricle into the atrium during the ventricular tole it is guarded by an important valve. This valve is called the auriculo-ventricular, mitral, or bicuspid valve. It is composed two large segments or cusps , with two small cusps in the angular irvals between their basal parts. The cusps are similar in shape


L.


'ig. 625. —Dissection (viewed from above) of the Basal Part of the

Heart.

3 two arterial stems have been removed close to their origins, exposing their valves, while the atria have been cut away a little distance above the atrio-ventricular valves. The coronary arteries are thus exposed for some extent after their origins, the aortic sinuses are partly visible, the coronary sinus is seen opening into the right atrium, and the atrioventricular valves, mitral and tricuspid, are seen closed.


Pulmon. Art.


Coron. Art.


Coron. Sinus Left Atrium


d structure to those of the tricuspid valve, but on account of 3 nature of their work they are thicker and stronger. They 5 disposed obliquely, and are of unequal size. The larger of 3 two is placed in front and to the right of the orifice. It internes between the mitral and aortic orifices, and is known as the terior cusp. The smaller cusp is placed behind and to the left of 3 orifice, and is known as the posterior cusp.

The chordae tendineae are attached to the cusps, as in the case of e tricuspid valve. They are, however, fewer in number, and of safer thickness and strength than on the right side.




1062


A MANUAL OF ANATOMY


Function of the Tricuspid and Mitral Valves. —These valves serve to prev regurgitation of blood from the ventricles into the atria during the ventrici systole. Whilst the ventricle is being filled, some of the blood gets beh the segments of the atrio-ventricular valve—that is to say, between each segm and the wall of the ventricle—and the segments are thus carried towards atrio-ventricular orifice. When the ventricle is filled with blood the segme are in contact, and the ventricular systole now takes place. At the same t: the papillary muscles contract. Blood is forced against the segments of the va' but it cannot in health enter the atrium, because the segments are maintai in close contact, and are prevented from being swept back into the auricle by chordae tendineae, which are under the control of the papillary muscles. If tl were no papillary muscles, in which case the chordae tendineae would spi directly from the wall of the ventricle, then the segments of the valve would be held tight, but would, under the pressure of the blood, be driven back into atrium, and regurgitation of blood would of necessity occur. The explanai of this lies in the fact that when the ventricle contracts a kind of screwing or wringing movement takes plac§ in its wall, as, so to speak, in wringing a towel. The effect of this peculiar action is to approximate successive part: the ventricular wall to the atrio-ventricular orifice, and this would have effect of relaxing the chordae tendineae, and so allowing the segments of the va to be driven back into the atrium. The chordae tendineae, however, spring fi papillary muscles, and these are elevations of the wall of the ventricle direc

Orifice of Nodule Orifice of

Coronary Artery { Lunule Coronary Artery


Fig. 626.—Cusps of the Aortic Valve.


towards the atrio-ventricular orifice. During the wringing movement, theref( of the ventricular wall in systole the papillary muscles, as stated, contract, ; so maintain the chordae tendineae taut, or tightly drawn.

When the mitral valve opposes the entrance of blood into the left ventr the cardiac affection is known as mitral obstruction (stenosis). When mitral valve is incompetent, and allows regurgitation of blood to take place fi the left ventricle into the left atrium, the cardiac affection is known as mi regurgitation (incompetence).

The aortic orifice is circular, and is separated from the mitral ori: by the anterior cusp of the mitral valve. It is guarded by the ao; valve, which by means of its cusp prevents regurgitation of bl( from the aorta into the left ventricle during the elastic coil of arterial wall. It is composed of three semilunar cusps or segmei consisting of fibrous tissue, covered on their ventricular surfaces endocardium, and on their arterial surfaces by the endothelial lin of the artery. Each cusp is attached by its convex border to wall of the artery at the place where it springs from the ventri The other border of the cusp is free, and is directed away from ventricle. Each cusp, therefore, is so disposed as to allow the bl<























THE THORAX


1063


)ass freely into the aorta from the left ventricle. The free border

ach cusp is strengthened by a band of fibrous tissue, and at the

tre of the border there is a small swelling, called the nodule [corpus ntii). This gives rise to a slight projection, and on either side of he border is concave. The attached convex border of each cusp Iso strengthened by fibrous tissue. In addition to these fibrous

kenings, fibrous tissue pervades each cusp from the nodule to the

iched border, with the exception of the portions immediately )w the lateral concave parts of the free border. These portions in ti cusp are semilunar, and are called the lunules. They are the mest parts of the cusp, and are transparent, consisting practically udocardium and the endothelial lining of the artery.

The interior of the wall of the aorta presents three well-marked jsses, each of which is placed opposite a segment of the valve. These isses are called the aortic sinuses (sinuses of Valsalva), and they are dised as anterior, left posterior, and right posterior respectively. The erior sinus presents the orifice of the right coronary artery, and the posterior sinus presents the orifice of the left coronary artery. Each is, together with the corresponding cusp of the aortic valve, forms nail pocket, and the three pockets open away from the left ventricle hat is to say, in a direction corresponding to the normal blood-flow.

Function of the Aortic Valve— This valve serves to prevent regurgitation of )d from the aorta into the left ventricle during the elastic recoil of the arterial i close to the heart. During the ventricular systole, when the blood is being r en through the aortic orifice, the aortic valve assive, and its three segments are applied to arterial wall. During the elastic recoil of the

rial wall, however, the valve is in action. The
effect of the elastic recoil is to force sufficient

)d backwards towards the left ventricle to close aortic valve. This blood enters the pockets ned by the aortic sinuses and the cusps of the ^e. The cusps are pressed towards the centre of aortic orifice, and they come into contact in following manner: the three nodules come into

e contact at the centre of the aortic orifice, and

dose what would otherwise be a small space, and respective lunules are closely pressed against another. In this manner the aortic orifice is lpletely closed, and regurgitation of blood into left ventricle is in health effectually guarded inst. It will be evident that the strain of the kward pressure of blood must be borne by those tions of the segments which are strengthened fibrous tissue extending from each nodule to attached border of each cusp. Though the ules are thin and weak, nevertheless, being, so to speak, doubled up against ! another, the more they are pressed upon the more closely they fit together. When the aortic valve offers opposition to the entrance of blood into the fa, the cardiac affection is called aortic obstruction (stenosis). On the other id, when the aortic valve is incompetent, and allows regurgitation of blood take place into the left ventricle, the cardiac affection is called aortic regurgiion (incompetence).


Fig. 627. —The Aortic Sinuses and the Aortic Valves, seen from above.

The right coronary artery (left in figure) is seen coming from the anterior sinus; the left artery is arising from the left posterior sinus.


A MANUAL OF ANATOMY


1064

The pulmonary valve, which guards the orifice of the pulmon; trunk, is similar to the aortic valve, and the preceding descript is for the most part applicable to it. The cusps of the pulmon; valve are, however, weaker than those of the aortic valve, and 1 sinuses are destitute of any arterial orifices. These sinuses are dispo: as posterior, right anterior, and left anterior respectively.

The function of the pulmonary valve is similar to that of 1 aortic valve.

Ventricular Septum. —This septum completely separates the ri^ and left ventricles. The external indications of its attachments ; the anterior and inferior interventricular grooves. It is thick, and for i most part fleshy. It is thickest in the region of the apex, and becon thinner towards the base of the ventricles. It bulges into the ri^ ventricle, so as to be convex on that aspect, whilst it recedes from 1 left ventricle, so as to be concave towards it. The upper or ba part of the septum presents anteriorly a small portion which is destiti of muscular fibres. This portion is thin (see Fig. 621) and consi of fibrous tissue, covered on either side by endocardium.

It is known as the membranous part of the septum, and is develop from the fused A.V. cushions of embryonic life. It forms the ri^ and posterior part of the wall of the aortic vestibule immediat< below the aortic valves. Its upper part separates the cavity of 1 vestibule from the right atrium, while its lower part is between ventricles', these relations can be seen in Fig. 621.

Topography of the Orifices of the Heart.-r— The pulmonary orif is situated on a level with the upper margin of the third left cos cartilage at its junction with the sternum. The aortic orifice, whi is more deeply placed than the pulmonary, is situated behind the 1 border of the sternum on a level with the lower margin of the th costal cartilage.

The tricuspid orifice lies behind the body of the sternum oppos the fourth intercostal spaces and fourth and fifth costal cartilag The mitral orifice, which is placed very deeply, is situated behind 1 left border of the sternum on a level with the fourth left costal cartila The anterior atrio-ventricular groove corresponds with a line dra from the third left to the sixth right costal cartilage, and it is on t line that the two atrio-ventricular orifices are necessarily found.

Cardiac Bloodvessels—Arteries. —The nutrient vessels of the he are the coronary arteries, right and left, which arise from the root the ascending aorta. For a description of these vessels, see p. 1036

Veins. —The cardiac veins are as follows: the great cardiac ve the coronary sinus; the posterior cardiac veins; the middle card vein; the small cardiac vein; the anterior cardiac veins; the oblic vein of left atrium; and the venae cordis minimae or smallest card veins. With the exception of the last-named cardiac veins (ve cordis minimae), all the others are seen upon the exterior of the hee

The great cardiac vein commences at the apex of the heart, 2 ascends in the anterior interventricular groove alongside of the antei



THE THORAX


1065


ventricular branch of the left coronary artery. In this part of its se it is more properly called the anterior interventric.ular vein. of large size, and receives tributaries from both ventricles and the ventricular septum. On reaching the atrio-ventricular ye it enters the left division of that groove, in which it courses y with the left coronary artery. Having turned round the left of the heart, it joins the left extremity of the coronary sinus, which it is continuous. The name coronary, which was sometimes 1 to this vessel, is strictly applicable to it only where it lies in the atrio-ventricular groove.


Fig. 628. _Heart viewed from below and behind, showing the

Arterial and Venous Distributions here.

The coronary sinus is the dilated terminal part of the great cardiac 1. It is about 1 inch in length, and occupies a portion of the terior part of the left atrio-ventricular groove. Its left extremity Dntinuous with the great cardiac vein, and its right extremity opens > the right atrium between the valve of the inferior vena cava and tricuspid orifice, the opening being guarded by the valve of the Dnary sinus. At the place where the coronary sinus is continuous h the great cardiac vein there is a valve, which is composed of two nents.

The coronary sinus is the persistent left horn of the sinus venosus. The posterior cardiac veins ascend upon the posterior surface of left ventricle, and open partly into the coronary sinus, and partly



io66


A MANUAL OF ANATOMY


into the contiguous portion of the great cardiac vein. One of tl is known as the left marginal vein.

The middle cardiac vein, which is of large size, commences at apex of the heart, and passes along the inferior interventric groove with the inferior interventricular branch of the right coror artery. It receives tributaries from the adjacent surface of the ri ventricle and from the ventricular septum, as well as a few f: the left ventricle, and opens into the right extremity of the coror sinus.


Fig. 629. —Diagram showing the Position of the Heart and its Valvl Orifices in Relation to the Anterior Wall of the Thorax.


R.A. Right Atrium R.V. Right Ventricle L.A. Left Atrium L.V. Left Ventricle A.A. Arch of Aorta In. Innominate Artery


R.S. Right Subclavian Artery

R. C.C. Right Common Carotid Artery L.C.C. Left Common Carotid Artery L.S. Left Subclavian Artery

S. V.C. Superior Vena Cava


Numbers on Sternum.

1. Tricuspid Orifice 3. Mitral Orifice

2. Pulmonary Orifice 4. Aortic Orifice


The small cardiac vein occupies the right atrio-ventricular gro in company with the right coronary artery, and opens into the ri extremity of the coronary sinus. It is subject to some variat but it usually receives tributaries from the contiguous parts of the ri atrium and right ventricle, including the anterior cardiac veins.

The anterior cardiac veins ascend on the front of the right ventri and open into the small cardiac vein. One of them is known as right marginal vein.

The oblique vein of left atrium (oblique vein of Marshall), whic

a persistent part of the left duct of Cuvier, passes downwards and inw;





THE THORAX


1067

the posterior aspect of the left atrium, and opens into the left emity of the coronary sinus, its orifice being destitute of a valve.

evelopment. —The oblique vein of left atrium represents the terminal portion e left duct of Cuvier.

rributaries of the Coronary Sinus. —These are as follows: (1) the t cardiac vein; (2) some of the posterior cardiac veins, others of e veins opening into the great cardiac vein; (3) the middle cardiac

(4) the small cardiac vein; and (5) the oblique vein of left atrium,

h the exception of the last-named tributary, all the others are dded with valves at their terminal orifices, but elsewhere they destitute of valves.


Fig. 630. —The Veins of the Heart as seen from in Front.

The heart is supposed- to be semi-transparent.

The venee cordis minimae (smallest cardiac veins) are not visible >n the exterior of the heart. They are very minute, and they open ) the right atrium, their orifices constituting some of the foramina arum minimarum. Similar minute veins are said to open into the atrium, and also into both ventricles.

Lymphatics.—The lymphatic vessels of the heart form two netks—subendocardial and subpericardial. The vessels are ultitely collected into two trunks, right or posterior, and left or erior. The right trunk receives the lymphatics of the right side he heart, and the left trunk takes up those of the left side. Each tik accompanies the corresponding coronary artery, and both pass kwards on either side of the pulmonary trunk. Having pierced pericardium, they terminate in the superior mediastinal or cardiac nds.






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A MANUAL OF ANATOMY


Nerves.—The nerves of the heart are derived from the super and deep cardiac plexuses, and through these from the vagus svmpathetic nerves. The branches do the atria are derived p from the deep cardiac plexus, and partly from the coronary plex They form a gangliated plexus on the surface of each atrium her the epicardium, and from this plexus branches proceed to the mus wall. The branches to the ventricles are derived from the right left coronary plexuses. These branches lie upon the surface of ventricle beneath the epicardium, and in the heart of the calf the; readily recognizable as delicate, thread-like streaks. Minute ga are met with at intervals on these nerves in the region of the ba the ventricles, but none on those nerves which lie over the lower thirds of each ventricle. The branches which enter the mus^ substance of the ventricular walls form plexuses, but are dest of ganglia.


Fig. 631. —The Superficial Muscular Fibres of the Heart in the Region of the Apex (C. Gegenbaur).


Structure of the Heart. —The cardiac wall is composed of muscular t which is known as the myocardium. This is intimately covered by the vi layer of the serous pericardium, this layer being called the epicardium, an

cavities of the heart are lined with a mem which is known as the endocardium.

The epicardium resembles a serous mem in structure, and is covered by endoth( Beneath the epicardium there is a va amount of fat, which is chiefly met with i atrio-ventricular and interventricular groov The endocardium is a smooth, delicate brane, destitute of bloodvessels, and coven its internal surface by endothelium. It co of a connective-tissue basement membram taining elastic fibres, and is continuous th: the arterial and venous orifices with the 1 intima of the vessels. It enters into the f tion of the segments of the atrio-ventricula semilunar valves.

Fibrous Tissue. — The atrio-ventriculai

arterial orifices of the heart are each surroi by a ring of fibrous tissue, and these rings, : case of the atria and ventricles, connect them together. The fibrous tiss these rings furnishes that which is met with in the segments of the various v In the triangular interval between the aortic and the two atrio-ventr orifices there is a collection of dense fibrous tissue, of the consistence of cartilage, which is connected with the fibrous rings just referred to, and ' represents the os cordis of the ox. ’When a heart is boiled the fibrous tis dissolved, and the atrial portion can be separated from the ventricular poi Myocardium. —The muscular tissue of the auricles is mostly distinct that of the ventricles, the fibrous rings at the atrio-ventricular orifices vening between the two, and serving to connect them.

Atria. —The muscular fibres of the atria are arranged in a superfici; common to both atria, and a deep set confined to each atrium. The supe fibres are disposed transversely, and some of them enter the atrial septum, are best marked in front. The deep fibres are arranged in two sets, loope< circular. The looped fibres arch vertically over the atrium, their extrei being attached to the ring of fibrous tissue which surrounds the atrio-ventr orifice. The annular fibres are present in the auricle around the venous or and around the fossa ovalis. The walls of the atria, though muscular, are


The whorled arrangement is well shown.


THE THORAX


1069


ntricles. —The muscular fibres of the ventricles are, as stated, mostly

t from those of the atria, and are disposed in a very complicated manner,

spring for the most part from the rings of fibrous tissue which surround trio-ventricular orifices. The superficial fibres descend obliquely towards jex, where they are disposed in a twisted or whorled manner, after which pass on to the inner surface of the left ventricle. Some of them become iuous with the papillary muscles of that ventricle, whilst others ascend as

ical layer on the inner surface of the ventricle to be attached to the left


632. —Anterior View of Heart of a Young Subject dissected after Long Boiling, to show the Superficial Muscular Fibres (Allen Thompson), f. (From Quain’s ‘ Anatomy.’)

figure is planned after one of Luschka’s, but its details were chiefly taken from an original preparation. The aorta, b', and pulmonary trunk, a', have been cut short close to the arterial (semilunar) valves, so as to show the anterior fibres of the atria; a, superficial layer of the fibres of the right ventricle; b, that of the left; c, c, anterior interventricular groove; d, right atrium; d' , its auricle, both showing chiefly perpendicular fibres; e, upper part of the left atrium; between e and b ', the transverse fibres which behind the aorta pass across both auricles; e', auricle of left atrium; /, superior vena cava, around which, near the atrium, circular fibres are seen; g, g / , right and left pulmonary veins with circular bands of fibres surrounding them.

)-ventricular fibrous ring. The superficial fibres are common to both

xicles.

the remaining fibres are very numerous, and must be described separately -ach ventricle. The principal fasciculi of the left ventricle spring from the atrio-ventricular fibrous ring, and they pass more or less obliquely towards apex. In their course they turn inwards, and enter the front part of the Ticular septum interiorly. Some of them now pass upwards to the base of ventricle to be attached to the collection of dense fibrous tissue, of the conTice of fibro-cartilage, already described; others pass across to the posterorior wall of the right ventricle, where they partly end in a papillary muscle,




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A MANUAL OF ANATOMY


and partly pass to be attached to the right atrio-ventricular fibrous ring; i a third set pass to the postero-inferior wall of the left ventricle, where become circular in direction. The principal fibres of the right ventricle are the superficial fibres, continuous with those of the left ventricle, and spring the fibrous rings around the atrio-ventricular and pulmonary orifices. ' on the postero-inferior surface of the right ventricle pass into the ventr: septum, and having traversed it obliquely forwards and upwards, they from it, and become continuous with the deep fibres of the left ventricle. r on the sterno-costal surface of the right ventricle also pass into the ventr: septum, and having traversed it obliquely backwards and downwards, they on to the postero-inferior wall of the left ventricle. Those from the in aspect of the right ventricle enter the lower part of the ventricular septum

sino-atriai node


Fig. 633. —The Sino-atrial Junction (after Tandler).


ascend in the septum to the collection of dense fibrous tissue of the consisten fibro-cartilage at the base. Although the ventricular muscular fibres are disj for the most part obliquely, there are some annular fibres, but these are con to the thickest part of each ventricular wall.

Fibres of Purkinje. —These fibres are situated between the endocardium the cardiac muscular tissue. They consist of elongated cells united at their so as to form chains. The central part of each cell contains granular protopl within which there are two nuclei; and the peripheral part presents trans 1 striations. These cells are probably vestiges of an early condition of ca; muscular fibres.

Sino-atrial Node. —In the region of the sulcus terminalis is a small oval (Fig. 633) measuring about 10 mm. in length and from 3 to 5 mm. in w where the muscular fibres are arranged so as to form a delicate network













THE THORAX


1071


■atrial node or the node of Keith and Flack. It is believed to be the spot

  • e the contraction of the heart begins and from where the wave of contraction

eeds over the heart.

Ltrio-ventricular Bundle (Figs. 634 and 635).—This bundle constitutes the atrio-ventricular muscular connection, and functionally is of a conducting ire. It begins in the atrio-ventricular node, which is situated in the central >us body of the heart a little below the opening of the coronary sinus into right ventricle. The node consists of an intricate network of muscular fibres rmingled with, and embedded in, fibrous tissue. Entering the node are


Sup. Vena


Fossa Ovalis


Ascending Aorta


ve of Inferior ena Cava


^alve of anary Sinus


if. Vena Cava


rio-ventricular Node


Right Fasciculus of Atrio ventr. Bundle


Pulmonary

Artery


Moderator Band


Right Ventricle


634-—The Atrio-ventricular Node and the Right Fasciculus of the Atrio-ventricular Bundle as seen from the Cavity of the Right Ventricle (after Tandler).


es of an indefinite but probably atrial origin. From it proceeds a single die, which represents the main stem of the atrio-ventricular bundle. This n passes forwards along the upper margin of the muscular portion of the tricular septum, lying immediately below the membranous part, and beneath anterior part of the base of the medial cusp of the tricuspid valve. In this ation the main stem breaks up into two fasciculi—right and left. Each of these aculi enters the septal wall of the corresponding ventricle, and divides into nches which ramify beneath the endocardium, where they form part of the tern of Purkinje’s fibres. Ultimately the terminal ramifications blend with muscular fibres of the ventricles and papillary muscles. A slip from the















1072


A MANUAL OF ANATOMY


right fasciculus passes to the anterior papillary muscle of the right vent] within the moderator band. To open this band and discover the slip is perl the simplest way of exposing the bundle.

The fibres of the atrio-ventricular bundle are pale, and are furnished i nerve-fibres and ganglia. The clinical significance of the bundle has refert to Stokes-Adams disease, or heart-block.

Structure of the Cardiac Valves. —Each segment of the tricuspid and m valves consists of two layers of endocardium, enclosing between them fib tissue which is derived from the fibrous ring around the corresponding a ventricular orifice. Each segment of the aortic and pulmonary valves


Em. 635.— The Left Fasciculus of the Atrio-ventricular Bundle

SEEN ON THE VENTRICULAR SEPTUM FROM THE CAVITY OF THE L

Ventricle (after Tandler).

consists of two layers of endocardium, enclosing between them fibrous tis which is derived from the fibrous ring around the corresponding arterial orif The segments of all the-valves are destitute of bloodvessels.

Minute Structure of the Myocardium. —Cardiac muscle is composed of tra versely striated fibres, but these differ so much from ordinary striated volunt muscular fibres as to require a special description. They possess no sarcolemr they branch freely, and adjacent branches unite, so that an intricate netw< is formed by them, and the transverse strias are fainter and less regular tl those of voluntary muscle. Each fibre and its branches are broken up inti series of short quadrangular muscle corpuscles, arranged in rows or chains, 2 separated from one another by cross-marks. Each muscle corpuscle conta













THE THORAX


1073


ucleus, which occupies the centre of the corpuscle, and the corpuscle presents tudinal striae as well as transverse. A cardiac muscular fibre, as well as anches, is therefore a chain of muscle corpuscles, each of which has a nucleus centre, and there is an absence of sarcolemma. height of the Heart. —The average weight of the

of the adult male is 10^ ounces, and of the adult

le 8 |- ounces.

ize. —The size of a normal heart has been compared ie closed hand of the individual person, development of the Heart. —In the absence of definite mation, the human heart must be considered as ig primarily from the fusion of vessels in the edges Le advancing mesoderm in the protocardiac area of embryonic plate. Moreover, these vessels must be ned to lie in the visceral portion of this mesoderm,

>ugh the presence of a pericardial split at such an ' stage is doubtful; thus the heart would be in assoDn with the roof of the yolk-sac, and, when reversal 3 place, with the floor of the fore-gut, to which it would

tached by its mesodermal covering. The single tube

ting from the fusion enlarges rapidly, standing away . the roof of the pericardium, and drawing after it Ding so a dorsal mesocardium, which ' suspends ’ it . the roof. The existence of a ventral mesocardium sry doubtful; if it does occur, it disappears at an edingly early stage.

'he single-looped cardiac tube formed in this way nds forward from the septum transversum, where its er end is continuous with the sinus venosus, which is into it. Its anterior end turns up as the aortic or rial stem or truncus arteriosus, entering the mesolal floor of the fore-gut, where it divides. The true iac tube, lying between these two fixed extremities,

. shows three primary dilatations, or primitive (single) chambers—the atrium Fig. 638), into which the sinus venosus opens directly; the ventricle (V); the bulbus cordis (B), from which the aortic stem issues. The dorsal mesoium, seen in the figure, disappears in its central area very quickly, thus


Fig. 636. — Cardiac Muscular Fibres,

SHOWING THEIR

Transverse Stride, Divisions, Junctions, and Position of the Nuclei.


• 637. —Scheme showing Four Successive Stages in the Development of the Heart (F. Testut’s ‘ Anatomie Humaine ’).

x. Arterial Bulb. 2 . Ventricle. 3* Atrium.

4. Veins opening into the Sinus Venosus.


dng a passage from one side to the other dorsal to the heart, and between arterial and venous ends; this is the transverse sinus of the adult perilium.

Sections through the heart show at this and succeeding stages that an inner ocardial tube forms a cellular structure, separated by a subendocardial

68
































































io 7 4


A MANUAL OF ANATOMY


space from an outer myocardial tube of contractile mesoderm cells. The sp is occupied by subendocardial fluid, probably contained in greatly disten< cells; it is invaded later by the growing myocardium, on which the endocan layer is then laid, the result being the intracardiac network characteristic of true cardiac tube. The three parts of the cardiac tube enlarge rapidly, atrium and ventricle particularly, the result being, as shown in the sec( diagram in the figure, that the bulbus is now directed backwards as well upwards, the large atrium is beginning to lap round it on each side from behi and the ventricle is situated ventrally between the two. Other results also fol this rapid growth; the sinus venosus is gradually drawn into the pericardial ca\ at the venous end, and the truncus arteriosus—though not nearly to so gr a degree—at the arterial end.



Fig. 638. —Schematic Figures of Early Heart.

In the first the heart tube is shown from the left in the pericardium (P), and 1 a single atrium (A), ventricle (V), and bulbus (BC). Opening into it behi is the sinus venosus (SV) embedded in the septum transversum above a in front of the liver-bud. A complete dorsal mesocardium (DM) is prese: this quickly breaks through and disappears in the dotted area. The secc figure shows the effect of growth of the tube without corresponding incre; in distance between its terminal attachments. The third diagram illustra the positions in the bent tube assumed by the dorsal (D) and ventral ( cushions in the A.V. and arterial regions. R, L, are right and left venc valves beside the opening of the sinus venosus.


The tube is narrowed into an atrio-ventricular* canal between the dilal atrium and ventricle, and here endocardial cushions (A . V. cushions) are ma (by the subendocardial tissue), which partly block the passage of the A.V. can dorsal and ventral cushions are formed first, right and left, smaller ones being add later. At the aortic orifice arterial cushions are similarly produced rather m< slowly. All these structures are concerned in the development of valves.

In the fourth week the heart, seen from the front, presents a surface appe; ance such as is shown in Fig. 642. Some of the parts of the adult heart can recognized here in a rudimentary state, but the cavity within is still undivid being a single passage from venous to arterial end. The division into ri£ and left passages must now be described; it is convenient to take the cavit


  • Frequently written A.V. for brevity.





THE THORAX


1075


itely, but it should be underthat the division goes on in rious parts more or less at the time.

Atrial Septa and Atria. —As

nus venosus is drawn out into ericardium from the septum rersum, its opening into the 1 is found to be no longer in, but on the right of the e line; this is probably due ferences in growth-rate of the des of the atrium. The opento the atrium is. guarded by s valves, right and left. As the a enlarges, a septum primum rs as a falciform edge (Fig. 640) ig round the upper wall of the r a little to the left of the left s valve. It quickly extends

the front and back walls, mg in this way the upper and

A.V. endocardial cushions, large interatrial opening enI by this septum above the )ns is the foramen primum. septum becomes deeper (Fig. and the foramen primum is ately closed by the meeting of the free edge of the septum with the A. V. cushions ; efore this occurs a foramen secundum appears as the result of breaking


g. 640. —Hearts of Embryos of 4-5 Mm. and 10 Mm. respectively.

t wall of right atrium cut away in each case to show deepening of septum )rimum (S. I.); F.i, foramen primum; F.2, foramen secundum; S.V., anus venosus. Venous valves are not shown.

gh of the upper part of the septum. This is seen at an early stage in the d figure in Fig. 640.


Fig. 639.—Section through Cardiac Tube in 2-5 Mm. Embryo, showing Endocardial Tube (E), Subendocardial Space (S), and Myocardial Tube (M).












A MANUAL OF ANATOMY


1076

The septum secundum* develops as a low, falciform, and fairly thick e on the upper wall a little distance to the right of the first septum, and after foramen secundum has appeared. Its lower and posterior end runs into left venous valve—which is not shown in Fig. 640—and its anterior end is on the upper and front wall. It overhangs the foramen secundum on the ri It increases very slightly in height, but its anterior end, extending round front wall, reaches the dorsal A.V. cushion here, and becomes continuous 1 the lower end of the joined venous valves; it will be noticed again with t! and it is only necessary to say here that it forms the annulus ovalis.

The opening of the sinus venosus, guarded by its two venous valves, li little to the right of the septal structures low down on the posterior wall, two valves, projecting into the atrial cavity, are joined above and prolongec the wall as an upper fornix; owing to the shortness of the left valve, thei no proper lower fornix. The upper fornix, large and developed early, t forward along the upper wall, and is lost on the upper front wall; it mak prominent edge, sometimes referred to as the ‘ septum spurium.’

The lower fornix, or, more truly, the lower end of the right valve, reaches hinder or ventralf A.V. cushion. The space on the back and upper walls, betv the septum primum and the sinus valves and upper fornix, is known as intersepto-valvular space ; the septum secundum projects into this from abo

The dorsal and ventral A.V. cushions fuse during the sixth week, divi< the A.V. canal into right and left channels. When this occurs, the lower fo extends and reaches the lower front end of the septum secundum, which has 1 seen to have reached the dorsal cushion.

The opening of the sinus into the atrium gets larger, the right valve stre ing out towards the right, the left coming against the septum primum obliterating the lower part of the intersepto-valvular space; it degener here, but some remnants of it may be found on the septum. The right v; forms the valve of the inferior vena cava, attached below and in front to remnant of the septum secundum, and being lost above and behind as the remr of the upper fornix, the crista terminalis . The enlargement is associated a the increasing size of the opening into the sinus of the inferior vena cava schemes in Fig. 641).

It is really the right horn of the sinus venosus that is engaged in this enla ment, which makes it become a part of the right atrium, that part into w] the venae cavae open; the original atrial cavity on this side is pushed outw by its enlargement, and forms only the auricle. The left horn of the s: venosus, forming the coronary sinus, , becomes descriptively only a seconc vessel opening into the large right horn, and the spur between the opening the two horns, at first some distance from the atrium, comes up (Fig. 641 its level, and finally becomes the part of the valve of the inferior vena cava 1 lies between the openings of the coronary sinus and inferior vena cava; corresponding part of the right venous valve makes the valve of the coroi sinus, as in the figure.

Thus the right atrium of the adult heart is developed from the right 1 of the sinus venosus so far as its atrium is concerned, the original atrium ( forming the auricle. The valve of the inferior vena cava is formed from right venous valve and the spur between the horns, the valve of the coronary s\ from the lower part of the right valve, and the septum is a compound of sep primum (septum ovale) and septum secundum (annulus or limbus ovalis).

The foramen ovale (foramen secundum) usually remains patent to a si extent for many years.

  • Two distinct structures seem to be confused in the descriptions givei

this septum. One is apparently only the upper remnant of the septum prm above the secondary foramen; the other is the one described here, and app< to be in reality the proper septal structure between the left and right sides. :

f The nomenclature of these cushions, as seen from the auricular aspect, be understood from the third diagram in Fig. 638.





THE THORAX


io 77


e cavity of the left atrium is produced in a somewhat similar manner. A common pulmonary vein, made by junction of right and left branches, ad opening into the left atrium at the end of the first month close to the n primum. It gradually enlarges, increasing in diameter, but not pronately in depth. Thus its right and left branches come to open into a r which, by its increase in diameter, is pushing the original atrium away ds the left. Still enlarging, the venous cavity takes up its right and left hes into itself, thus leading to their next two branches on each side coming


. 641. —First Figure: Atrial Cavities exposed by Removal of the Upper and Front Wall in an Embryo of 4-5 Mm.

atrio-ventricular opening; RVV, right venous valve, marking off sinus enosus, into which common cavity open the right and left horns of the inns (RHSV, LHSV). The left venous valve is not yet formed. The smaining figures, semi-diagrammatic, show the taking up of the sinus ito the atrium; the right atrial wall only is removed, leaving the septum rimum (SEPT. I.) in position, with the foramina (FOR. I. and II.) above nd below it. ISVS, intersepto-valvular space; LVV, left venous valve; VC, opening of inferior vena cava.

2n directly into the cavity. In this way the atrium is made from dilated inary veins, the auricle representing the original true atrium. ie A.V. canal, as already said, is divided into right and left A.V. openings e fusion of the dorsal and ventral endocardial cushions. The persisting ires are guarded by right and left cushiohs, with the corresponding ends ! fused central pair. The fusion occurs about the sixth week, and about ime time the foramen primum closes on their atrial aspect, and the venir septum is nearing its completion on their other side.

Ventricles and Bulbus Cordis.— In Fig. 642 the 4-5 mm. heart is viewed the front, and the common ventricle is seen to bulge somewhat to the ying to the left of the bulbus, and on the whole rather below it. The





A MANUAL OF ANATOMY


1078


companion drawing shows this heart with the front wall removed fror ventricle and bulb; the cavities of these two parts are seen to be separated j by a prominent bulbo-ventricular ‘ spur ’ or angle, which, by its presence, c the opening into the bulb to lead out of the right extremity of the ventr: cavity to the right, in front of, and rather below the atrio-ventricular ape: This aperture is seen guarded by its endocardial cushions.

The ventricular cavity is already showing an early state of division right and left ventricles, for a low septum is visible extending back to the in


Fig. 642. —Views from the Front of Hearts of Embryos of the Fo and Fifth Weeks (4*5 Mm. and 10 Mm.) (from Reconstructions)

On the right are shown the interiors of these hearts, the front walls of the tricles and bulbs, and to some extent of the atria, having been rem< l.a., l.v., left auricle and ventricle; r.v., right ventricle; r.b.r., right b ridge; art. cush., endocardial cushions at beginning of arterial trunk; sept., interventricular septum.


A.V. cushion. This septum is really little more than the original floor o cavity persisting at its original level, the two subdivisions of the cavfh larging downwards on each side of it. Thus the right ventricle starts existence as a bulging of the common ventricle; this bulging can be seen oi surface view of the heart.

Turning now to the 10 mm. embryo (Fig. 642), it is to be noticed tha bulbo-ventricular spur has decreased much in prominence; this is due to a atrophy and disappearance, so that the bulbar opening is now above the








THE THORAX


1079


e right-hand end of the A.V. aperture. The ventricles have become deeper the septum proportionately higher, but that the septum has not grown ird is evident from the fact that it retains its old level of attachment to the - A.V. cushion.

t the 15 mm. stage (not shown) the process of reduction of the bulboicular angle has gone even farther, the whole left and back wall of the having practically disappeared, so that the arterial cushions are, in this very near to the A.V. cushions. At the same time the greater part of the opening is, as a result, now brought directly under the passage into the ining bulbus.

urning back to the 10 mm. specimen (Fig. 642), certain changes within >ulb itself are to be seen. These consist in the development of two bulbar S. The right ridge is seen almost entire; it begins above just below the ial cushions (with the right one of which it is continuous), and passes down back on the right bulbar wall, to end in a blunt extremity just to the right


Fig. 643.—To show Method of Division of Bulbar Region and

Formation of Aortic Vestibule.

(Explanation in text.)

le A.V. opening. The left ridge starts below the left lateral aortic cushion, extends downwards and forwards on to the left front wall of the bulbus, his part has been cut away in the figure, the ridge is only partly seen cut ss. These two bulbar ridges thus overhang a deep channel, which can be in the figure, traceable downwards and to the left towards the left ventricle, each which its groove would be continued in front of the A.V. cushions and ve the edge of the ventricular septum, ihis channel becomes the aortic inel, or aortic vestibule of the complete heart, closed in, as will be described, he fusion of the ridges with each other, and with the edge of the septum.

In the 15 mm. stage, when the spur and the associated bulbo-ventricular - on the surface have disappeared, the atrophy affects mainly the wall of the 5 behind and below the left ridge, but this is nevertheless shorter than the t ridge, thus exhibiting the general tendency to shortening of this region.

complete division of the bulbar region and separation of the two ventricles

1 follow; the way in which this happens is schematically shown in Fig. 043.









io8o


A MANUAL OF ANATOMY


In these schemes the front wall of the right ventricle only is supposed to ] been removed with that of the bulb, so that the interventricular septum (w in the previous figures has only been seen in part) is now seen as a whol< not only reaches the lower A.V. cushion, but runs into the upper cushion corresponding situation, making a free falciform edge between these two po The free edge forms the boundary of the interventricular foramen, the d( wall of which is made by the cushions. The dorsal and ventral cushions j leaving now two lateral atrio-ventricular openings, one on each side of the p of the septum and interventricular foramen. In the first diagram the bulbar ridge is seen at a and the right at b\ these are continuous above 1 the left (/) and right (r) arterial cushions respectively; these cushions are fn so that a pulmonary orifice [pa) is between them and the ventral cushion


Fig. 644.—Bulbo-ventricular Region (15 Mm.).

The first figure shows the bulbar ridges in position, the second shows the ao channel, the ridges and parts of the walls being cut away. S, upper of interventricular septum; A, the fused (lateral) arterial cushions; D, dorsal arterial cushion.

The two small figures show how the septum between aorta and pulmon artery meets the fused lateral arterial cushions, leaving three semilu rudiments to each artery. D, V, dorsal and ventral cushions.

The second plan shows how the descriptive position of the definite cr results from a small amount of rotation from right to left.

and separated by these from the aortic orifice, which lies between them and dorsal cushion. The aortic orifice leads into the aortic channel (ao), wh overhung by the bulbar ridges, passes downwards and to the left in front of A^V. cushions, and through the interventricular foramen into the left ventri When fusion occurs between the A.V. cushions it affects those parts that m the floor of the aortic channel— i.e., the cushions bounding the transv( sht and the upper part of the right lateral slit—leaving the lower part (av) the right lateral slit as the permanent right opening.

In the second diagram the mode of closure is illustrated. The right bul ndge grows towards the left across the right lateral A.V. orifice—between closed and unclosed parts—and just reaches the attachment of the ventrici septum to the lower cushion. The left ridge, in contact from its early st;





THE THORAX


1081


the upper part of the septum, begins to extend along the free margin of this ; dent of its growth along this margin is indicated by the dotted line. The idge in this way reaches the right ridge by growth along the edge of the ventricular foramen, and by fusion between the two ridges the aortic channel fed in and separated from the (right) cavity continuous with the pulmonary 3. In the third figure the actual conditions (a little simplified) are shown embryo of the sixth week, in which the various parts are in the process iction and consolidation; it may be noted that a certain amount of extension sue from the fused arterial cushion takes place between the upper parts 3 two bulbar ridges.

Dr descriptive purposes the dorsal wall of the bulbar region has been given rth in the figure greater than it really possesses; owing to the disappearance 3 left dorsal wall with the bulbo-ventricular spur, the dorsal arterial cushion ictically next to the A.V. cushions, so that the ' floor ’ of the aortic channel >elow the aortic orifice is made by the fused A.V. cushions; this is the memus part of the ventricular septum, separating the aortic channel (aortic Dule) from the right atrium. The ventral wall of the aortic vestibule is made le fused bulbar ridges, and it is evident that the interventricular foramen, ugh it no longer affords a passage between the left and right ventricles, sts as the opening into the aortic vestibule (from the general cavity of the ventricle) to the right of the left A.V. orifice. The remnants of the A.V. ons, presenting as pouting lips in the ventricular cavities, and continuous

with the endocardial covering of the muscular network of the ventricles,

ne atrio-ventricular valves, modification in the network producing the chordce yiece and papillary muscles. On the left the cushion lips are placed vertically e the vertical slit, and the two valves derived from them lie naturally een the opening and the aortic vestibule and the left marginal wall respecy On the right the vertical lips (Figs. 643 and 644) separate the orifice from ieptum and the right marginal wall respectively, but in addition there is a >verse flap derived from (or in association with) the right bulbar ridge e this crosses the line of the orifice, and this flap separates the orifice from Dulmonary channel, and hence becomes the anterior (infundibular) cusp. umming up the description given of the formation of the parts, it may be that the infundibulum is a remnant of the bulbus cordis, but its dorsal wall oduced by fused bulbar ridges; the cavity of the aortic vestibule is also a part lat of the bulbus, with an added * ventricular ’ part brought into existence he disappearance of the bulbo-ventricular spur; the membranous part of ventricular septum marks the position of fused A.V. cushions, the interricular foramen remains as the opening into the aortic vestibule from the ral cavity of the left ventricle; and the A.V. valves are derived from the cushions, the anterior cusp of the right valve being an additional structure lected with the growth of the right bulbar ridge.

Tie arterial (semilunar) valves are developed by hollowing out of their arterial ices from the arterial cushions already mentioned. These are four m number

  • ht and left lateral, dorsal, and ventral. The lateral cushions fuse, coning the single orifice into two—ventral or pulmonary, and dorsal or aortic,

division of the bulbar region below these cushions has been described, and bulbar ridges which make the dividing wall have been seen to be continuous se with the fused lateral cushions; in a similar way the dividing wall between two arteries above them is continuous with the fused lateral cushions. I he arteries become completely separated, the separation extending through valvular region, and incompletely involving the bulbar region, thus the original cushions are divided (Fig. 645) into six, three for each orifice, these are hollowed into the arterial valves; the pulmonary orifice has the tral flap and two postero-lateral, the aortic opening has two antero-lateral the dorsal flap. Towards the end of intra-uterine life, however, the heart ergoes a rotation from right to left to such an extent as to place the root o pulmonary trunk in front and to the left of the root of the aorta. 1 he a, as well as the pulmonary trunk, is involved in this rotation, and the seg

1082


A MANUAL OF ANATOMY


ments of the pulmonary and aortic valves are now permanently alterec position. The relations of the various segments in the adult are as folic the cusps of the pulmonary valve are disposed as two anterior, right and : and one posterior ; whilst the cusps of the aortic valve are one anterior and posterior, right and left.


Fig. 645.— Schemes to show Formation of Arterial Valves froi

Arterial Cushions.

A, P, ventral and dorsal cushions. The second scheme shows the division

the four cushions into six. The third scheme shows the effect of rctai

on the descriptive positions of the valves.

The rotation just referred to also explains why the left ventricle of the ac heart is chiefly postero-inferior in position, comparatively little of it appeal on the sterno-costal surface of the adult heart.

Peculiarities of the Foetal Circulation. —The structures peculiar the foetus in connection with the circulation of the blood are follows:

1. Foramen ovale. 4. Umbilical arteries.

2. Valve of the inferior vena cava. 5. Umbilical vein.

3. Ductus arteriosus. 6. Ductus venosus.

The foramen ovale is an oval opening in the atrial septum, to the fourth month of intra-uterine life it is quite free, but af that period the valve of the foramen ovale gradually extends upwai on the left side of, and beyond, the annulus ovalis, and acts as a val during the latter months of foetal life. The blood can then only fl from the right atrium into the left, its return being prevented this valve.

The valve of the inferior vena cava is of large size during foe

life, and is associated with the orifice of the inferior vena cava at 1 postero-inferior angle of the right atrium. It is a crescentic fold of t endocardium, which extends between the anterior margin of t orifice of the inferior vena cava and the anterior horn of the annu. ovalis. Its situation is such as to direct the blood entering the ri£ atrium by the inferior vena cava to the foramen ovale.

The ductus arteriosus connects the pulmonary trunk to the ai of the aorta at a point immediately beyond the origin of the 1




THE THORAX


1083


Flavian artery, and conveys most of the blood from the right

ricle to the descending thoracic aorta.

rhe umbilical arteries (hypogastric arteries), right and left, are proved from the common iliac arteries to the umbilicus, through which ) leave the body of the foetus, and pass along the umbilical cord >e distributed to the foetal part of the placenta. They convey the ure blood of the foetus to the placenta.

rhe umbilical vein extends from the foetal part of the placenta >ugh the umbilicus to the inferior surface of the liver, where it joins left branch of the portal vein. After parting with its right and left aches the umbilical vein is prolonged, under the name of the tus venosus, to the inferior vena cava, which it joins at the fossa vena cava of the liver. The umbilical vein conveys pure blood n the placenta into the body of the foetus.

Foetal Circulation.— The right atrium receives blood from the erior and inferior vense cava 4 , and from the coronary sinus. The erior vena cava returns the venous blood from the head and neck, upper limbs, and the thoracic portion of the trunk; and the inferior 1a cava returns the blood from the lower limbs, the abdominal tion of the trunk, and the placenta. The placental blood is pure, l reaches the inferior vena cava in two ways: (1) a large quantity it is conveyed directly into the inferior vena cava by the ductus iosus; and (2) some of it circulates through the liver in the branches the portal vein, and is then conveyed to the inferior vena cava by i hepatic veins. The blood entering the right atrium by the inferior 1a cava is necessarily of a mixed nature, being partly placental and

  • tly venous.

The impure blood which enters the right atrium by the superior la cava, having received a small quantity of the mixed blood which

ers by the inferior vena cava, passes through the right atrioitricular orifice into the right ventricle, and from thence is driven

0 the pulmonary trunk. A small quantity of it is conveyed to the lgs by the right and left pulmonary arteries, which at this peiiod j of small size, and it is returned from the lungs to the left atrium the pulmonary veins. By far the greater part of the right ventricular )od, however, enters the ductus arteriosus, and is con\eyed by it the aorta immediately beyond the origin of the left subclavian artery. >ne of this blood, therefore, enters the three great vessels which ring from the arch of the aorta. The whole of it descends in the scending thoracic and abdominal portions of the aorta, and has a ofold destination. Part of it is distributed to the abdominal and lvic viscera, and the lower limbs, whence it is returned by the »rtal vein and inferior vena cava; but the greater part of it is conyed out of the bodv of the foetus to the placenta by means ot the nbilical arteries. Having been purified in the placenta, it is returned ence by the umbilical vein into the body of the foetus. This placental ood, as stated, reaches the inferior vena cava in two ways. P ar t y rectly by means of the ductus venosus, and partly indirectly by


1084


A MANUAL OF ANATOMY


means of the hepatic veins after having circulated through 1 liver.

A small quantity of the mixed blood which enters the right atrii by the inferior vena cava mingles with the venous blood which ent that cavity by the superior vena cava; but by far the greater part it is directed by the valve of the inferior vena cava to the forarr ovale, through which it passes into the left ventricle. Here it recen the blood which has been returned from the lungs by the pulmom


Internal Jugular Vein Common Carotid Artery

\fi/ o


Subclavian Vessels


Superior Vena Cava


Foramen Ovale Orifice of Inferior Vena Cava

Valve of Inferior Vena Cava Inferior Vena Cava


Ductus Arteriosus Pulmonary Artery

Left Auricle


Left Ventricle


Hepatic Veins

Aq-Right Ventricle


Inferior Vena Cava Aorta


Common Iliac Vein


External Iliac Vessels


Ductus Venosus

Left Branch of Portal Vein


— Right Branch of Portal Vein


-Portal Vein

Umbilical Vein Umbilicus


— Umbilical Arteries - Umbilical Vein


Umbilical Cord


Umbilical Arteries

Fig. 646. —Diagram of the Organs of Circulation in the Foetus The arrows indicate the course of the circulation.


veins, and then it passes through the left atrio-ventricular orifice ir the left ventricle. From the left ventricle it is driven into the aou and the greater part of it passes into the innominate, left comm carotid, and left subclavian arteries, to be distributed to the bra head and neck, and upper limbs, as well as to the substance of the he£ by the coronary arteries. A small quantity, however, of this mix blood passes into the descending thoracic aorta, and mixes with t venous blood entering by the ductus arteriosus. The blood is return to the right atrium of the heart from the brain, head and neck, ai















THE THORAX


1085


sr limbs, by the superior vena cava, and from the substance of heart by the coronary sinus.

Changes at Birth.—At birth respiration is established, and the rs perform their respiratory function; the right and left pulmonary ries undergo rapid enlargement; and the placental circulation is rely arrested. The umbilical arteries become obliterated and Lsformed into fibrous cords, except at their. roots, where they list as the internal iliac arteries. The umbilical vein becomes terated, and is now known as the ligamentum teres of the liver. ductus venosus becomes transformed into a fibrous cord, called ligamentum venosum, which occupies the fissure of that name in liver. The foramen ovale is closed by the valve of the foramen \e becoming adherent to the margin of the annulis ovalis on its left i. In some cases, however, this union is incomplete, and a minute ning persists, through which a small probe may be passed. In y rare cases a fairly large opening may remain, as in the condition ,wn as morbus cceruleus. As viewed from the interior of the left urn, the upper crescentic border of the valve of the foramen ovale isible upon the atrial septum, and above this border there is a slight session. The ductus arteriosus becomes obliterated, and persists a fibrous cord, called the ligamentum arteriosum, which passes n the root of the left pulmonary artery to the arch of the aorta nediately beyond the origin of the left subclavian artery.

The closure of all the peculiar structures associated with the

al circulation is usually complete from the eighth to the tenth day

er birth.

Trachea in the Thorax.—dhe thoracic portion of the trachea extends m the level of the upper border of the manubrium sterni to the el of the intervertebral disc between the bodies of the fourth and h thoracic vertebrae, where it divides into the two bronchi, right and 1. It occupies a median position in the superior mediastinum, and length is about 2 -| inches. As in the neck, it is cylindrical and n in front and at the sides, but posteriorly it is flattened and mem mous, where it rests upon the oesophagus. . .

Relations— Anterior. —The manubrium sterni, and the origins ot 3 sterno-hyoid and sterno-thyroid muscles; the remains of the ymus; the origins of the innominate and left common carotid series, and the left innominate vein; and the arch of the aorta, which s upon it immediately above its bifurcation into the two bronchi, th the intervention of the deep cardiac plexus of nerves. R° s ~ ior. —The oesophagus, which in an upward direction inclines rtially to the left of the trachea. Right. —The right vagus nerve; e innominate artery after it has left the front of the trachea, and e right pleural sac. Left. —The arch of the aorta and the e mmon carotid artery after these have left the front of the trachea, e left subclavian artery; and the left recurrent laryngeal nerve. Bronchi.—The bronchi, right and left, commence at the bifuica>n of the trachea, and each passes to the hilum of the coriespond

io86


A MANUAL OF ANATOMY


ing lung, where its ramifications commence. As in the trad each bronchus is cylindrical and firm in front and at the sides, posteriorly it is flattened and membranous. There being cerl differences between the bronchi, a separate description is requi for each.

The right bronchus is about i inch in length up to the point wf it gives off its first, or eparterial, branch. It has about six ca laginous rings, and is larger than the left bronchus. It is more vert:

than the left bronchus,


Epiglottis


Greater Horn of Hyoid Bone Lesser Horn of Hyoid Bone

Body of Hyoid Bone —


Thyro-hyoid Membrane - Levator Glandulae \ Thyroides Muscle /

Thyroid Cartilage -Crico-thyroid Ligament

Pyramid ” Cricoid Cartilage " Lateral Lobe of Thyroid Gland Isthmus

Right Bronchus Eparterial Bronchus,


Hyparterial Bronchus.^


Trachea

Left Bronchus


Fig. 647. —The Hyoid Bone, Larynx, Trachea, Bronchi, and Thyroid Gland (Anterior View).


therefore coincides with direction of the trachea t greater extent than its felL

Relations— Superior .—" vena azygos arches over it open into the superior v< cava. Posterior. —The ri{ vagus nerve.

About 1 inch from commencement the rij bronchus gives off a brar from its outer side wh passes to the upper lobe the right lung. This brar is known as the eparter bronchus, because it ari; above the right pulmonc artery. The rest of the ri£ bronchus is spoken of as bei hyparterial.

The left bronchus is abc

2 inches in length. It I about twelve cartilaginc rings, and is smaller than t right bronchus on account the smaller size of the 1< lung. Its course is more c lique than that of its fello


and it is directed downwards and outwards beneath the arch of aorta to the hilum of the left lung.

Relations— Anterior. —The left pulmonary artery, which sut quently lies above it. Posterior. —The oesophagus and the descend thoracic aorta.


The left bronchus has no eparterial branch.

When the interior of the trachea is viewed from above, as in usii the laryngoscope, the openings of the two bronchi are seen to 1 separated by a ridge which is situated to the left of the median lin and more of the interior of the right bronchus than of the left is visibl Partly on this account, and partly by reason of the more vertic













THE THORAX


1087


tion of the right bronchus, as well as its larger size, a foreign - getting into the trachea is more apt to descend into the right chus than into the left.

'he structure of the trachea will be described in connection with description of the windpipe in the neck.

Esophagus in the Thorax. —The oesophagus or gullet extends from pharynx to the stomach. In the first part of its course it lies ie neck, and this portion will be found described in connection with region. The thoracic part (see Fig. 651) extends from the level he upper border of the manubrium sterni to the level of the / of the eleventh thoracic vertebra, where, ng previously passed through the oesophaopening of the .diaphragm, it terminates

he cardiac orifice of the stomach. Its

se is not quite vertical. At its commencet the thoracic portion lies partially to the of the middle line, but as it descends it es to occupy a median position about the 1 of the fifth thoracic vertebra, and in>rly it again inclines partially to the left, ccupies the superior and posterior mediasI spaces, and lies in front of the verte. column, accurately following the thoracic 3ro-posterior curve.

Relations— Anterior .—The trachea as low

he intervertebral disc between the bodies

he fourth and fifth thoracic vertebrae; the it pulmonary artery; the root of the left [ichus; the posterior wall of the pericardium nsite the back of the left atrium of the rt; and the vertebral portion of the diaagm. Posterior .—The vertebral column; longus cervicis muscles, especially the left; thoracic duct and vena azygos; the right terior intercostal arteries; the upper and er transverse azygos veins; and interiorly descending aorta. Right .—The right erior and posterior mediastinal pleurae. Left. The thoracic portion the left subclavian artery; the upper part of the thoracic duct, left superior mediastinal pleura above and the left posterior iiastinal pleura just before it pierces the diaphragm, and the cending aorta, except inferiorly.

The right and left vagus nerves are intimately related to the cesoigus. They are at first disposed laterally, and their branches give i to the oesophageal plexus. Subsequently the right vagus nerve cends on the posterior surface of the oesophagus, and the left on

anterior surface, in which positions they accompany the gul et

ough the oesophageal opening of the diaphragm.


Fig. 648.—To show Relations between Aorta, Trachea and (Esophagus (from the Front).




io88


A MANUAL OF ANATOMY


Blood-supply—Arteries. —These are (i) the oesophageal brai of the descending aorta, (2) the oesophageal branches of the left gc artery, and (3) twigs from the left phrenic artery. In the necl oesophagus receives branches from the right and left inferior tin arteries.

The veins accompany the corresponding arteries, and term: in the vena azygos and the two venae hemiazygos.

Lymphatics. — These pass to posterior mediastinal glands whic mainly in front of the oesophagus.

Nerves. —These are derived fron vagus and sympathetic nerves.


S


Structure. —The wall of the oesopl consists of three coats—namely, muse submucous, and mucous.

The muscular coat is thick, and is posed in two layers, an external longitu and an internal circular.

The longitudinal muscular fibres ar< tached superiorly to the upper part o: median ridge on the posterior surface o cricoid cartilage, and from this point descend as two flattened bands, one on e side of the tube. These expand and meet, giving rise to one continuous 1 which completely surrounds the oesophe Interiorly they are continuous with longitudinal muscular fibres of the stoir Accessory fleshy slips are described as pai from this layer to the back of the trac the back of the root of the left bronc the pericardium, and the left pleura.

The circular muscular fibres are con ous superiorly with the lower fibres of


Fig. 649.— Diagram to show _ __ a __ j _

Pleural Relations (Thick inferior constrictor muscles of the pha: Black Lines) of (Esophagus and interiorly with the circular, and (Frontal Section). with the oblique, muscular fibres of

stomach.

The muscular tissue of the oesophagus is of the striated variety over abou upper third of the tube, but elsewhere it is of the plain or non-striated vai

The submucous coat consists of loose areolar tissue, which contains larger bloodvessels and the mucous glands.

The mucous membrane is thick, and is thrown into longitudinal fold account of the loose disposition of the submucous coat. The portion of it the submucous coat consists of plain muscular fibres, which are arranged 1 tudinally. This portion is known as the muscidaris mucosce, and it is marked in the lower part of the oesophagus. The inner surface of the mi coat is provided with numerous papillae, and it is covered by stratified squai epithelium, which is thrown into elevations by the papillae.

The mucous glands are racemose, and are situated in the submucous 1 Their ducts are large and long, and on their way to the free surface son them traverse small collections of lymphoid tissue.

Development. —The oesophagus is developed from that part of the for( which succeeds to the portion from which the pharynx is developed. At fh is very short, on account of the imperfect development of the neck. As, howi




THE THORAX


1089


leek becomes formed, and as the stomach descends, the oesophagus becomes rated.

descending Aorta. —The descending aorta, which is the continuaof the aortic arch, commences on the left side of the body of fourth thoracic vertebra on a level with its lower border, and linates at the lower border of the body of the twelfth thoracic ebra. At the latter level it* passes through the aortic opening lie diaphragm, and enters upon the abdominal part of its course, vessel lies in the posterior mediastinum, and its course is down

Stratified Epithelium Mucous Membrane Muscularis Mucosae

Submucosa


ircular Muscular Fibres


Longitudinal Muscular Fibres


- Mucous Gland


Fibrous Sheath


Fig. 650.—Transverse Section of the Wall of the (Esophagus.

is and medially, so that, though at first on the left side of the vertecolumn, it subsequently takes up a position in front of it. Relations — Anterior .—From above downwards, the root of the lung; the pericardium; the oesophagus; and the vertebral portion

he diaphragm. Posterior .—The bodies and intervertebral discs

tioracic vertebrae below the fourth; and the upper and lower transie azygos veins. Right .—The oesophagus superiorly; the thoracic t; and the vena azygos. Left .—The left superior and posterior Liastinal pleurae; and the upper and lower left azygos veins. In}dy the oesophagus inclines slightly to the left. It is to be noted

69





























logo


A MANUAL OF ANATOMY


that the oesophagus has a threefold relation to the descending ac At first it lies upon the right side of the vessel; then directly in f: of it; and finally it inclines slightly to its left side.

Branches. —These are as follows: bronchial, pericardial, cesopha^ mediastinal, posterior intercostal and subcostal.


Trachea


Left Common Carotid Artery Scalenus Anterior Muscle


Innominate

Artery


Left Vagus Nerve


Rt. Superior Intercostal Artery


_ Left Subclavian Artery (Third Part)

Lefi Phrenic Nerve


Arch of.., Aorta


Left Superior Intercostal Artery


Cardiac Branches of Cer Sympathetic Ganglia Vagus

- Superficial Cardiac Plexi


Left Bronchus


. Descending Thoracic Aorta


(Esophagus


Posterior Intercostal Vesiels and Nerve


- Abdominal Aorta


Fig. 651 —Dissection of the Posterior Wall of the Thorax.


The bronchial arteries supply the lungs and the bronchial lymph glands. They are usually three in number—one right and two 1 The right bronchial artery arises from the aorta in common with upper left bronchial artery, or sometimes from the first right poste intercostal artery. The two left bronchial arteries, upper and lo\
















THE THORAX


1091


directly from the aorta near each other. The arteries enter the

ective lungs behind the bronchi, and in their further course and -ibution they follow the ramifications of he bronchial tubes, fhe bronchial veins accompany the corre ponding arteries. The

vein opens into the vena azygos; and the left vein opens either

the superior vena hemiazygos or into the left superior interal vein. The bronchial veins are conrably smaller than the corresponding ries.

rhe pericardial branches supply the pos >r part of the pericardium, rhe oesophageal branches are numerous, arise at irregular intervals. Superiorly 7 spring from the right side of the aorta, inferiorly from its anterior wall. They stomose freely with one another along wall of the oesophagus: superiorly with oesophageal branches of the inferior

oid arteries, and inferiorly with the

phageal branches of the left gastric ry, the latter branches entering the ■ax through the oesophageal opening of diaphragm.

The mediastinal branches are very minute, supply the lymphatic glands and areolar le in the posterior mediastinum.

The posterior intercostal arteries are ar^ed in pairs, and are nine in number on 1 side. They are destined for the lower 5 intercostal spaces, the first two spaces lg supplied by the superior intercostal

ry, which is a branch of the second part
he subclavian on the right side, and of

first part on the left side. They arise in

s from the posterior wall of the descendaorta, and pass outwards upon the bodies
he vertebrae to the posterior extremities
he intercostal spaces. The arteries of

right side pass behind the oesophagus, thoracic duct, and the vena azygos; l those of the left side pass behind the erior and inferior venae hemiazygos acding to their level. The arteries of both sides pass behind the ipathetic trunk. The upper right posterior intercostal arteries longer than those of the left side, on account of the position of the cending aorta on the left side of the vertebral column. All the sries lie behind the parietal pleura. Each artery, on entering an ircostal space, lies at first between the parietal pleura and the


Fig. 652.—To show the Relations to Each Other of the Aorta, Thoracic Duct, Azygos Vein, and Intercostal Arteries (Anterior View).




1092


A MANUAL OF ANATOMY


posterior intercostal membrane. Its course is outwards and slig] upwards, and partly on this latter account, but chiefly on acco of the downward slope of the rib, it soon gains the lower borde: the upper rib. At a point corresponding to the angle of the rib


artery pierces the posterior intercostal membrane, and passing betw< the external and internal intercostal muscles, it enters the costal gro( of the upper rib. In this position it courses forwards, and ends anastomosing with the upper anterior intercostal branch of the inter



























THE THORAX


1093


unary artery, or of its musculo-phrenic branch, according to the

he companion intercostal vein lies above the artery, and the

sponding intercostal nerve lies below it. The order of structherefore, in the costal groove, from above downwards, is as

ws: intercostal vein, intercostal artery, and intercostal nerve, upper seven posterior intercostal arteries are confined to the costal spaces which they occupy; but the lower two—namely, 3 in the tenth and eleventh intercostal spaces—ultimately leave i spaces, and pass into the abdominal wall, where they have been

ibed in connection with the abdomen.

•ranches. —These are posterior, giving off a spinal branch; collateral costal; and lateral cutaneous.

he posterior branch arises from the posterior intercostal artery as vessel enters the posterior extremity of an intercostal space. It is backwards, in company with the posterior primary division of the isponding spinal nerve, between the adjacent transverse processes, ■e it lies internal to the superior costo-transverse ligament. Ope the intervertebral foramen it gives off its spinal branch , which

  • s the vertebral canal through the foramen to be distributed to

sseous and ligamentous walls, as well as to the spinal cord and its branes. The posterior branch, continuing its course backwards, les into a medial and lateral branch, which supply the muscles integument of the back.

he collateral intercostal artery arises from the main posterior interil opposite the angle of the rib. It passes obliquely downwards outwards to the upper border of the lower rib, along which it >es, lying between the external and internal intercostal muscles, riorly it ends by anastomosing with the lower anterior intercostal

h of the internal mammary artery, or of its musculo-phrenic

"h, according to the level.

he lateral cutaneous branches accompany the lateral cutaneous dies of the corresponding intercostal nerves to the integument, he first posterior intercostal artery—namely, that which lies in bird intercostal space—furnishes a branch, of variable size, which ids over the neck of the third rib to the second intercostal space, branch anastomoses with the second posterior intercostal artery, h is a branch of the superior intercostal, and may even replace it. he subcostal arteries , right and left, are the last branches of the ending thoracic aorta. They are serially continuous with the rior intercostal arteries above, and with the lumbar arteries below, vessel winds round the side of the body of the twelfth thoracic bra, and, passing beneath the lateral arcuate ligament of the iragm, enters the wall of the abdomen, where it lies along the lower t of the twelfth rib. These vessels will be found described in action with the abdomen (see p. 848).

he first and second intercostal spaces receive their arteries from uperior intercostal artery, which is a branch of the second part


1094


A MANUAL OF ANATOMY


of the subclavian on the right side, and of the first part on the side. Having descended in front of the neck of the first rib to posterior extremity of the first intercostal space, the vessel furni the first posterior intercostal artery to that space, and it also g off the second posterior intercostal artery, which descends in f of the neck of the second rib to the second intercostal space, stated, the second posterior intercostal artery receives a branch f the third posterior intercostal artery, which ascends over the : of the third rib.

Development of the Descending Aorta. —The upper portion of the descei

aorta is developed from that part of the left primitive dorsal aorta whicl between the fourth left aortic arch and the place of junction of the two prin dorsal aortae. The greater portion of it, however, results from the union c two primitive dorsal aortae. The posterior intercostal arteries are deve^ from thoracic intersegmental arteries.

Posterior Intercostal Veins. —The intercostal veins are eleve: number on either side, and each lies in the costal groove above corresponding posterior intercostal artery. In the region of the a of the rib each vein receives the collateral intercostal vein, which acc panies the artery of that name. At the posterior extremity o intercostal space each vein receives a large posterior branch, w returns blood from the muscles and integument of the back, external vertebral venous plexus, and the vertebral canal. Witt exception of the upper three or four veins, all the other intero veins pass inwards, behind the corresponding sympathetic cord to the bodies of the thoracic vertebrae, from which they receive s twigs. Their mode of termination differs on the two sides. On right side the veins, having passed behind the oesophagus, termi in the vena azygos. On the left side the lower four veins—namely eighth, ninth, tenth, and eleventh—open into the inferior vena h azygos; and the succeeding three (or four)—namely, the fifth, s: and seventh (and, it may be, the fourth also)—open into the sup vena hemiazygos.

The first posterior intercostal vein of each side accompanies corresponding superior intercostal artery, and terminates in innominate vein, or, it may be, in the vertebral vein, of its own si(

The second and third posterior intercostal veins (and, it may be fourth) of each side unite to form the superior intercostal vein, right superior intercostal vein, after a downward course, joins the u part of the vena azygos. The left superior intercostal vein fori loop which lies in front of the arch of the aorta, and opens intc left innominate vein. It sometimes receives the left bronchial as a tributary.

Summary of the Posterior Intercostal Veins—Right Posterior Inter Veins. —The first opens into the right innominate vein, or sometimes into the vertebra] vein. The second and third (and, it may be, the fourth also) to form the right superior intercostal vein, which opens into the vena a2 The lower eight (sometimes the lower seven) are direct tributaries of the ' azygos.


THE THORAX


1095


Left Posterior Intercostal Veins. —The first opens into the left innominate n, or sometimes into the left vertebral vein. The second and third (and, it ,y be, the fourth also) unite to form the left superior intercostal vein, which 3ns into the left innominate vein. The fifth, sixth, and seventh (and, it may the fourth also) terminate in the superior vena hemiazygos. The eighth, ith, tenth, and eleventh are tributaries of the inferior vena hemiazygos.

The left superior intercostal vein is developed from two sources. The upper vt is formed by the portion of the left anterior cardinal vein below, and jacent to, the commencement of the transverse jugular vein. The lower part 'ormed by the upper portion of the left cardinal vein.

Intercostal Glands. —These glands form a chain on either side of the vertebral umn, in line with the necks of the ribs. The main glands of each chain lie


g. 654.— Vena Azygos and Right Sympathetic Chain, showing Ganglia and the Greater and Lesser Splanchnic Nerves arising from it.

Ph. N, phrenic nerve.

the posterior parts of the intercostal spaces, and one or two glands accompany ch posterior intercostal artery for a very short distance.

The intercostal glands receive their afferent vessels from (1) the posterior half the costal pleura, (2) the posterior halves of the external and internal interstal muscles, (3) the deep muscles of the back, and (4) the vertebral canal, leir efferent vessels, on either side, pass to the thoracic duct; those from the >ver four or five spaces usually unite to form a trunk which, running vertically wnwards, pierces the diaphragm, and opens into the thoracic duct near its mmencement, or it may be into the cisterna chyli itself.

The efferents of the upper right intercostal glands sometimes open into a >ht broncho-mediastinal lymphatic trunk, which terminates in the right tnphatic duct.

The right superior intercostal vein is developed from the anastomotic channels iiich connect the upper three thoracic segmental veins of the right side. •














A MANUAL OF ANATOMY


1096


The Venae Azygos et Hemiazygos Veins.—The vena azygos (ve azygos major) commences in the abdomen as the right ascendi lumbar vein , and enters the thorax through the aortic opening of t diaphragm, lying on the right side of the aorta, the thoracic dr intervening. It then ascends, under cover of the oesophagus, up


Right Lymphatic Duct


Right Innominate Vein

Superior Vena Cava.Right Superior Intercostal Vein.


Vena Azygos —\


Thoracic Duct—A


Posterior Intercostal Glands

Cistema Chyli Right Ascending Lumbar Vein..


Inferior Vena Cava__.


Thoracic Duct


S 3 Left Innominate Vein

IT'

- Left Superior Intercostal Vein L. Arch of Aorta


- Superior Vena Hemiazygos


Upper Transverse Azygos Vein


— Lower Transverse Azygos Vein

— Ninth Posterior Intercostal Vein


- Inferior Vena Hemiazygos


-.Left Subcostal Vein


__Quadratus Lumborum —Left Ascending Lumbar Vein


--Abdominal Aorta


— Iliac Crest -Psoas Major

—.Uiacus


.'xCommon Iliac Arteries


Fig. 655.—The. Thoracic Duct, Azygos and Hemiazygos Veins, and

Posterior Intercostal Glands.


the bodies of the thoracic vertebrae, crossing in its course the rig posterior intercostal arteries. Having reached the level of the fif thoracic vertebra it leaves the vertebral column, and arching forwar over the right bronchus it opens into the superior vena cava ju! before that vessel pierces the pericardium. In the thorax the vei














THE THORAX


1097


is continues to lie on the right side of the aorta, the thoracic duct /ening.

ributaries. —These are as follows:

The right subcostal vein.

The lower seven (sometimes the lower eight) right posterior

ostal veins.

The right superior intercostal vein.

The right bronchial vein.

Some oesophageal veins.

Some pericardial veins.

The lower and upper transverse azygos veins, he inferior vena hemiazygos (vena azygos minor inferior) commences 3 abdomen as the left ascending lumbar vein, and enters the thorax iercing the left crus of the diaphragm. It ascends upon the bral column to the level of the eighth thoracic vertebra, lying in of the lower posterior intercostal arteries, and it takes up the • four left posterior intercostal veins. It then crosses the vertebral in from left to right under the name of the lower transverse azygos passing behind the descending aorta and thoracic duct, and ing into the vena azygos, ributaries. —These are as follows:

1. The left subcostal vein.

2. The lower four left posterior intercostal veins.

3. Some oesophageal veins.

he superior vena hemiazygos (vena azygos minor inferior) is formed le union of the fifth, sixth, and seventh left posterior intercostal

(sometimes also the fourth). At the level of the seventh thoracic

bra it crosses the vertebral column from left to right under the 5 of the upper transverse azygos vein, passing behind the descending 1 and thoracic duct, and opening into the vena azygos. It comicates above with the left superior intercostal vein, and below the inferior vena hemiazygos, ributaries. —These are as follows:

. The fifth, sixth, and seventh left posterior intercostal veins etimes also the fourth).

. The left bronchial vein, as a rule.

. Some oesophageal veins.

he superior and inferior venae hemiazygos, which are subject to 1 variation, sometimes unite to form one transverse azygos vein, he other hand, the hemiazygos veins are not infrequently multiple, multiple openings into the vena azygos.

unmary of the Azygos and Hemiazygos Veins—Vena Azygos. This vessel /es (1) the right subcostal vein; (2) the lower seven (sometimes the lower ) right posterior intercostal veins; (3) the right superior intercostal vein;

right bronchial vein; (5) some oesophageal veins; (6) some pericardial

and (7) the lower and upper transverse azygos veins,

iferior Vena Hemiazygos. —This vessel receives (1) the left subcostal vein; lower four left posterior intercostal veins; and (3) some oesophageal veins.


A MANUAL OF ANATOMY


1098

Superior Vena Hemiazygos. —This vessel receives (1) the fifth, sixth, seventh (sometimes also the fourth) left posterior intercostal veins; (2) tb bronchial vein, as a rule; and (3) some oesophageal veins.

The vena azygos and the inferior vena hemiazygos, through connection with the ascending lumbar veins, establish communica with the inferior vena cava and with the common iliac veins or < of their tributaries. They therefore form important channels by wh considerable quantity of blood is returned from the lower limbs abdominal wall in cases of obstruction of the inferior vena cava, vense azygos et hemiazygos frequently communicate with the renal v


Fig. 656.—To show the Derivation of the Azygos Veins.

First figure shows original symmetry, the primitive jugular (PJ) on each joining the cardinal (C) to make the duct of Cuvier (D), which enter sinus venosus (SV); the duct of Cuvier is intrapericardial. In the se figure the left innominate vein (LIV) is formed, taking over the left ju and subclavian drainage, and leading to the appearance of a f superior cava.’ Further changes on left side affect the cardinal, which is rec in size and broken in various ways, such as in the next figure. The ' sup intercostal vein ’ here is seen to be formed from cardinal (C) and terr piece of jugular (PJ), and at the junction of these parts the duct of G (D) is present as an obliterated remnant; the lower left intercostals ( to the right vein by two cross-connections. The longitudinal left vein persist, with connections, or (as in figures) the lower left veins may separately, or may join to form one large transverse vessel, or some n fication of these variations may be found.

Development. —The azygos vein is developed at its upper end from terminal part of the right cardinal vein; below the mid-thoracic level it is r by supracardinal (periganglionic) reaching the cardinal through an interme* piece of subcardinal. The hemiazygos veins (lower) are derived from the supracardinal, developing transverse retro-aortic connections. The V hemiazygos (left superior intercostal) is partly cardinal and (at its termina primitive jugular (see Fig. 656).

Subcostal Veins .—These are two in number, right and left, they are serially continuous with the intercostal veins. Each v( enters the thorax from the abdomen by passing behind the lat


THE THORAX


1099


late ligament of the diaphragm. As stated, the right vein opens 1 the vena azygos, and the left into the inferior vena hemiazygos.

Anterior Primary Rami of the Thoracic Spinal Nerves.— These are Ive in number on each side. The first eleven enter intercostal


aces, and are called the intercostal nerves. The last, which belongs the abdomen, lies along the lower border of the twelfth rib, and is Ued the subcostal nerve (‘ last dorsal nerve ). At the posterioi tremities of the intercostal spaces the intercostal nerves are near















IIOO


A MANUAL OF ANATOMY


the sympathetic trunk, and each nerve is connected with the adjace sympathetic ganglion by two rami communicantes, which are nee! sarily very short. One of these rami, being composed of spinal fibr is white, and the other, which consists of sympathetic fibres, is gr\ Each intercostal nerve lies below the corresponding artery, and, li it, lies between the parietal pleura and the posterior intercos membrane as far as the angle of the rib. Its subsequent course cor:sponds to that of the artery. The first intercostal nerve is of sm; size, because the greater part of the anterior primary ramus of tj first thoracic nerve takes part in the formation of the brachial plexij The second intercostal nerve sometimes gives off a small bran^ which ascends to join the portion of the anterior primary ramus the first thoracic nerve which takes part in the brachial plexus. Tj further course and distribution of the intercostal nerves belong to tl thoracic and abdominal walls, in connection with which they willfound described.

Thoracic Duct. —The thoracic duct commences in the abdony in a dilatation, called the cisterna chyli (receptaculum chyli), which situated in front of the bodies of the first and second lumbar vertehi! and terminates by opening into the angle of junction of the interij jugular and subclavian veins of the left side. It is about 18 inci in length, and enters the thorax from the abdomen by passing throu the aortic opening of the diaphragm, where it lies between the aoil on the left and the vena azygos. In this position it ascends in t thorax, resting upon the vertebral column, the right posterior inti costal arteries, and the lower and upper transverse azygos veil being under cover of the oesophagus. Up to the level of the four, or fifth thoracic vertebra it occupies the middle line. At this level passes behind the arch of the aorta, inclining to the left of the mid( line. It then ascends in close contact with the left side of the oesophagi and behind the thoracic portion of the left subclavian artery. In t] position it enters the root of the neck on the left side, where it ascen upon the left side of the oesophagus between the left common carol and left subclavian arteries. At about the level of the seven cervical vertebra it describes a curve, and passes outwards, forwarc and downwards in contact with the dome of the left pleura. It ne inclines inwards, and terminates by opening into the angle of junctk between the internal jugular and subclavian veins of the left sic In the lower part of the thorax the thoracic duct is of smaller calit than in the upper part. Its course is somewhat undulating, ar when distended it presents a beaded appearance, especially in t upper part, due to the number of valves with which it is provide Sometimes the duct divides into two branches in the lower part the thorax, which reunite at a higher level. The duct is freely provid with valves, especially in its upper part, and at its termination there’ an important valve, consisting of two segments, which are so direct as to prevent effectually the reflux of chyle, or the flow of blood in the duct.




THE THORAX


IIOI


he thoracic duct receives lymphatic vessels from the following es: (i) the lower limbs; (2) the abdomen and its viscera, except of the lymphatics from part of the upper surface of the liver; le left half of the thoracic wall; (4) the left lung and the left half e heart; (5) the lower right intercostal spaces; (6) the left upper

and (7) the left side of the head and neck. Most of the lymphatics

e right half of the thorax and those of the right lung and right of the heart pass to the right lymphatic duct, for the description lich see the section dealing with the neck.

horacic Lymphatic Glands. —These are arranged in several groups ollows: internal mammary; intercostal; innominate; anterior astinal; posterior mediastinal; tracheo-bronchial, and caval. he internal mammary lymph glands (sternal lymph glands) will iund described on p. 996. They receive their afferent vessels from tie anterior parts of the upper six intercostal spaces; (2) the inner on of the mammary gland; (3) the lymphatics accompanying the rior epigastric artery from the upper part of the anterior abdominal

(4) the lymphatics accompanying the musculo-phrenic artery

the anterior parts of the seventh, eighth, and ninth intercostal es, and from a portion of the diaphragm; and (5) the lymphatics . the anterior set of diaphragmatic glands. The efferent vessels le right glands terminate in the right lymphatic duct, and those

Le left glands in the thoracic duct. .

die intercostal lymph glands are situated on either side of the sbral column, where they lie in the intercostal spaces, there being l one to three in each space. They receive their afferent vessels l (1) the posterior parts of the intercostal spaces; (2) the parietal ra; (3) the vertebral canal; and (4) the deep muscles of the back, efferent vessels of the left intercostal glands open into the thoracic

. On the right side the efferent vessels from the lower glands

to the thoracic duct, but those from the upper glands open into

right lymphatic duct. ..11

rhe innominate lymph glands (superior mediastinal lymph glands)

n the superior mediastinum in relation to the arch of the aorta the innominate veins; they are continuous with the posterior iastinal and tracheo-bronchial glands below and with the chain >unph glands along the recurrent laryngeal nerves above. Ihey ive their afferent vessels from the pericardium, the heart, trachea, phagus, and the thymus in early life, and their efferent vesse s

to the thoracic duct and right lymphatic duct. .

fhe innominate lymph glands (anterior mediastinal lymph glands)

a the lower part of the anterior mediastinum in front of the penium. They receive their afferent vessels from (1) the median portions tie right and left lobes of the liver in the vicinity of the lalci orm nent; (2) the adjacent portion of the diaphragm; (3) the anterior of the pericardium. Their efferent vessels pass to the interna

unary lymph glands. . . , .

the posterior mediastinal lymph glands are situated m the posterior


1102


A MANUAL OF ANATOMY


Auriculo temporal Nerve Facial Nerve

Posterior Auricular Nerve >,

Glosso-pharyngeal Nerve Accessory Nerve


Hypoglossal Nerve

] Superior Laryngeal Nerve Vagus Nerve

Middle Cervical Sympathetic Ganglion

Recurrent Laryngeal Nerve Cardiac Branches of Vagus


Ri >ht Posterior Pulmonary Plexus

Vena Azygos Vascular Branch

Intercostal Vessels f and Nerve l

Ramus Communicans

Sympathetic Trunk


Abdominal Aorta


Right Ansa Subclavia


First Thoracic Ganglion


Phrenic Nerve


Root of Right Lui


. Right Vagus N< on (Esophagi

(Esophageal I J le:


Liver (cut)

Left Vagus Ner

Descending Aor Thoracic Duct


Lesser Splanchic Nerve Greater Splanchnic Nerve •

Lowest Splanchic Nerve


| Branches of V / on Stomac


Right Coeliac Gangl

— Coeliac Plexus

Superior Mesenteric Arl and Plexus


Greater Occipital Nerve


Hypoglossal Nerve


Sup. Cervical Symp. Ganglion External Carotid Artery Internal Carotid Artery

Sympathetic Trunk

Com. Car. Art. and Symp. Plexus Phrenic Nerve


Renal Artery and Plexus


S.V.C. Superior Vena Cava


Fig. 658.—Nerves of the Right Side of the Face, Neck, and Thor/

(Hirschfeld and Leveille). * I




















THE THORAX


1103


iastinum, along the course of the descending aorta and oesophagus. j receive their afferent vessels from the oesophagus, the posterior of the pericardium, and the vertebral portion of the diaphragm, r efferent vessels pass, for the most part, to the thoracic duct.


, 659.—A Dissection of the Right Apical Region to show the Stellate Ganglion (viewed from below after removal of the Pleura).

iddition to the subclavian vessels, the lower two brachial nerves are seen, with the ganglion and the superior intercostal artery.

The tracheo-bronchial lymph glands are very numerous, and are iated partly in the angle between the trachea and bronchi, partly ween the two bronchi, and partly at the root of each lung. They very dark in colour, and receive their afferent vessels from the lungs 1 the visceral pleurse. Their efferent vessels pass to the thoracic 't and right lymphatic duct.


t











iio4


A MANUAL OF ANATOMY


n.c.


n,C


The caval glands are situated in contact with the limited tho: portion of the inferior vena cava. They receive their afferent ve from the bare area of the posterior surface of the liver, and also t deep lymphatics of that organ which accompany the hepatic veir the fossa for inferior vena cava. Their efferent vessels pass to

thoracic duct. One of these glands often be found lying upon the inf< vena cava within the fibrous pericardi The Thoracic Part of the Sympatl System. —The sympathetic system in thorax consists of (i) two gangli: trunks, right and left; and (2) a vertebral plexus — namely, the car plexus. The latter plexus has 1 already described. The gangliated tr lies on each side of the vertebral coll behind the parietal pleura, and superf to the posterior intercostal vessels, presents, as a rule, eleven ganglia, first or stellate ganglion is situated at inner end of the first intercostal sp and probably is formed by the fusioi two originally distinct ganglia; the sec ganglion lies on the head of the third and the other ganglia follow in more less regular sequence, lying on the he of the ribs until the last two ganglia reached; these lie upon the sides of bodies of the eleventh and twelfth thor; vertebrae. The first thoracic ganglioi the largest of the thoracic series, and 1 previously known as stellate ganglion. sympathetic trunk leaves the thorax Fig. 660. — Scheme of the passing behind the inner part of


R.C.


R C,




s.s


Thoracic Part of the me dial arcuate ligament of the diaphra Flower) an d so enters the abdomen.


r to 12. Thoracic Ganglia

R. C. Rami Communicantes

B.D. Branches of Distribution from Upper Ganglia

G.S. Greater Splanchic Nerve and Ganglion

S. S. Lesser Splanchnic Nerve L. S. Lowes t Splanchnic Nerve


Branches — 1. Of Communicatioi

These are called the rami communicant Two of these, one white and the 0 grey, pass between each ganglion and adjacent intercostal nerve. The w fibres are of spinal and the grey of s pathetic origin. From the proximity of the ganglia to the intercc nerves the rami communicantes are necessarily short.

2. Of Distribution. —From the upper five ganglia small vase branches are given off, which are distributed to the coats of the thor; aorta. From the second, third, and fourth ganglia pulmor branches are given off to the posterior pulmonary plexus. From




THE THORAX


1105


^anglion downwards the three splanchnic (‘ visceral ’) nerves— »r, lesser, and lowest—are given off.

le greater splanchnic nerve arises by five separate roots from the sixth, seventh, eighth, and ninth ganglia, the fibres of the upper being traceable in the sympathetic trunk as high as the second ion. The roots arch obliquely forwards and downwards upon des of the bodies of the adjacent vertebrae, and by their union form a large nerve, which pierces the crus of the diaphragm and nates in the cceliac ganglion. The greater splanchnic nerve ins a large number of spinal fibres, which impart to it a white r and firm consistence. The right nerve presents a small ganglion before it leaves the thorax, called the splanchnic ganglion , there may be one on the left nerve. The greater splanchnic

gives vascular branches to the lower part of the thoracic

>•

he lesser splanchnic nerve arises by two roots from the ninth and l ganglia. It pierces the crus of the diaphragm, and terminates e aortico-renal ganglion of the coeliac plexus, he lowest splanchnic nerve, which is sometimes absent, arises ne root from the eleventh ganglion. It either passes behind the al arcuate ligament of the diaphragm or through the crus, and it inates in the renal plexus. When the lowest splanchnic nerve sent, its place may be taken by a branch from the lesser splanchnic

2k

araganglia. —Situated in close relationship to the sympathetic lia are small bodies to which the name of paraganglia has been 1. They consist of chromaphil tissue like that which forms the ilia of the suprarenal glands, and probably secrete a substance h is excitory to non-striped muscle.

he diaphragm will be found described in connection with the •men.


The Joints of the Vertebral Column.

. Joints of the Bodies of the Vertebrae.— These joints belong to class of secondary cartilaginous joints. Ihe ligaments are as ws: the anterior longitudinal ligament, the posterior longitudinal nent, and the intervertebral discs.

he anterior longitudinal ligament (anterior common ligament) is a

e band of white glistening fibres, which extends over the anterior ices of the bodies of the vertebrae and intervertebral discs. It nds from the axis to the first segment of the sacrum, and its fibres lisposed longitudinally. Ihe most superficial fibres extend fiom a n vertebra to the fifth below it; the intermediate fibres pass from ven vertebra to the third below it; and the deepest hbies pass 1 a given vertebra to the one immediately below it. The fibres are ly attached to the intervertebral discs and margins of the vertebial ies, but very loosely to the centres of the bodies, on account of the

70


iio6


A MANUAL OF ANATOMY


presence of bloodvessels. The anterior longitudinal ligamen broadest in the lumbar region, and thickest in the thoracic region, is thicker opposite the centres of the bodies than elsewhere, an these situations it fills up the concavities, and so renders the fror the column less undulating than it otherwise would be. Over lateral surfaces of the bodies a few scattered fibres are present, w pass from one vertebra to that below. In the sacral region the ant< longitudinal ligament is lost in the periosteum of the bone, br reappears lower down as the anterior sacro-coccygeal ligament, anterior longitudinal ligament is serially continuous superiorly with anterior atlanto-occipital membrane.


Posterior Band of Superior Costo-transverse Ligament

Anterior Band of Superior Costo-transverse Ligament


Three Slips of i Radiate Ligament p


Intra-articular Ligament"


- Anterior Longitudinal Ligament


-■-Hi— Intervertebral Disc


Fig. 66i.—Ligaments of the Bodies of the Vertebrae and Joints of

Heads of the Ribs on the Right Side.


The posterior longitudinal ligament (posterior common ligamenl

situated within the spinal canal, and extends over the poste surfaces of the bodies of the vertebrae and intervertebral discs. I broader above than below, and consists of glistening fibres, wl extend from the axis to the first coccygeal vertebra, its sacral p however, being very narrow and delicate. Its fibres are firmly attac to the intervertebral discs and margins of the vertebral bodies, but t are separated from the centres of the bodies by the transverse ven communications between the basivertebral veins. In the cerv: region the ligament is of almost uniform breadth, being expanded c the vertebral bodies, as well as over the intervertebral discs. In thoracic and lumbar regions, however, it is narrow opposite vertebral bodies, and broad opposite the intervertebral discs, margins, therefore, present dentations, which give it a denticula































THE THORAX


1107


trance. The arrangement of its fibres is similar to the arrangeof those of the anterior longitudinal ligament. The posterior

udinal ligament is serially continuous superiorly with the

Drana tectoria.

be intervertebral discs are situated between the adjacent surfaces e bodies of the vertebrae, and they constitute the chief bond of l between them. Their outline corresponds to that of the bodies sen which they are placed, and they are elastic and compressible, pt in early life, the first or highest disc is situated between the bodies e axis and the third cervical vertebra, and in the adult the last west disc is situated between the bodies of the fifth lumbar and sacral vertebrae.



l 662. —Posterior Longitudinal Fig. 663. —Intervertebral Discs

Ligament of the Bodies of the (Anterior View).

Vertebrae.

£ach disc is composed of a circumferential fibrous part, disposed le form of superimposed laminae, and a central portion, the nucleus 1 osus , which is soft and pulpy. The annulus fibrosus forms more 1 half of the disc, and is composed of fibrous tissue and fibroilage. As seen in transverse section the laminae are arranged

entrically around the nucleus pulposus , which they closely embrace

compress. The fibres of which they are composed are arranged >arallel bundles, which extend obliquely between the adjacent ices of the vertebral bodies, being attached to the layer of hyaline ilage which covers them. The fibres of successive laminae pass Tiely in opposite directions, and are disposed thus X. The outer nae consist of fibrous tissue, but the majority are composed of white )-cartilage. As seen in vertical section the outermost laminae are

















no8


A MANUAL OF ANATOMY


bent outwards, and those around the nucleus pulposus are bent inw; towards it, this arrangement contributing to the elasticity of the ve bral column. The nucleus pulposus consists of a soft, elastic, pi substance, having a lobate arrangement. Being surrounded compressed on all sides by the annulus fibrosus, when a section i disc is made the nucleus pulposus, being relieved from press projects beyond the level of the cut surface. It is composed ( cellular reticulum, supported by a delicate fibrous stroma.

The nucleus pulposus is a persistent portion of the notochord.

The intervertebral discs form about one-fourth of the lengtl the vertebral column, and are thickest in the lumbar region, the cervical and lumbar regions they are deeper in front than beh and they give rise to the curve forwards in the cervical region, wl they increase the forward curve in the lumbar region. In the thor


region they are of uniform depth. Throughout the column t are intimately connected with the anterior and posterior longitudi ligaments, and, in the thoracic region, with the radiate ligaments ; the intra-articular ligaments of the heads of most of the ribs, the cervical region the discs are not present at either lateral asf of the opposed surfaces of the bodies. In these regions there i synovial space on either side, between the projecting lateral lip of upper surface of the lower body and the bevelled lateral margin of lower surface of the upper body. The opposed surfaces are cove by cartilage, and there is an indistinct capsular ligament.

2. Ligaments of the Laminae. —These are called the ligame flava (ligamenta subflava). They are strong, thick plates of yel elastic tissue, which connect the laminse together, and they ext from the axis to the first sacral segment. They are best seen from interior of the vertebral canal, and as they extend between the vertel











THE THORAX


1109


2S they close in the canal in these situations. Each ligamentum im extends from the root of the articular process to the place e the lamina joins its fellow to form the spinous process. At point it comes into relation with the ligament of the opposite a small interval being left between the two for the passage of 3. Superiorly the ligament is attached to the anterior surface le upper lamina a little above its lower border, and inferiorly it tached to the upper border, and adjacent part of the posterior ice, of the lower lamina. The ligamenta flava are wider in the ical and lumbar regions than in the thoracic region, and over the ter part of the latter region, as viewed from the exterior, they are ealed from view by the imbricated laminae. Their importance ists in their great elasticity, which enables them to maintain the


G< 666._Ligamenta Flava in the Lumbar Region (Anterior View).

Ihe pedicles have been sawn through, and the vertebral bodies removed.

tebral column erect, and to restore it to the erect position after it

been bent forwards. . . A

3. Ligaments of the Articular Processes. —Ihe joints between the

cular processes belong to the class of synovial joints of the le variety. The articular surfaces are covered by cartilage, and joint is surrounded by a capsular ligament s lined with a synovial nbrane. These ligaments are disposed moie looselj 7 in the cervical

ion than elsewhere. . .

4. Ligaments of the Spines.— These are supraspinous and mter The supraspinous ligament consists of longitudinal fibres which nect the extremities of the spines. It extends from the spine the seventh cervical vertebra to the spine of the fourth sacral ment, and its fibres are arranged in a manner similar to those of anterior longitudinal ligament. In the cervical region the supralous ligament is replaced by the ligamentum nuchae. ihe interspinous ligaments, which are thin and membranous, are situ between adjacent spines, to the margins of which they are atta( from root to tip. They are strongest in the lumbar region, and in neck they are replaced by deep processes of the ligamentum nucl

5. The intertransverse ligaments. —These consist of scattered fil which pass between the extremities of the transverse processes in thoracic and lumbar regions. In the neck they are replaced by intertransverse muscles.

Movements. —The movements allowed in the vertebral column are fle: extension, lateral movement, rotation, and circumduction.

Flexion and extension are freely allowed in the cervical and lumbar reg: In the thoracic region these movements are very limited on account of (1) small amount of intervertebral substance, and (2) the imbrication of the lam Lateral flexion is allowed in the cervical, thoracic, and lumbar regions, bi the neck it is associated with rotation. During these combined movemeni lateral flexion and rotation in the neck one inferior articular process g upwards and forwards on that which is opposed to it, whilst the other inf< articular process glides downwards and backwards on the one opposed t< Pure rotation is allowed in the thoracic region round an axis corresponding the centre of a circle of which the surfaces of the articular processes form ments. This centre is necessarily anterior to the articular processes, corresponds pretty nearly with the centres of the bodies of the vertebra, the lumbar region rotation is impossible, for the following two reasons: (1) centre of the circle of which the articular processes form segments is poste to these processes; and (2) the articular processes are so disposed as to be loc In the lumbar region circumduction is allowed, which consists in a combina of flexion, extension, and lateral movements.

Summary of Movements—-Cervical Region. —(1) Flexion and extension;

(2) a combination of lateral flexion and rotation. Thoracic Region. —(1) Fie: and extension, but only to a limited extent; (2) lateral flexion; and (3) ] rotation. Lumbar Region. —(1) Flexion and extension; (2) lateral flexion;

(3) circumduction.

The joints of the atlas, axis, and occipital bone will be foi described in the section dealing with the head and neck.


The Joints of the Ribs, Costal Cartilages, and Sternum.

1. Ribs—Costo-vertebral Joints. —These are divided into joints

the heads of the ribs and costo-transverse joints.

The Joints of the Heads of the Ribs. —These unite the heads of ribs to the bodies of the thoracic vertebrae, and they are sometii spoken of as the capitular joints. They belong to the class of syno 1 joints of the plane variety. The articular surfaces are the facets the heads of the ribs and the costal facets on the sides of the hoc of the thoracic vertebrae—that is to say, the lower facet of the verte above and the upper facet of the vertebra below, the intervertet disc intervening between the two. In the case of the first, the ter the eleventh, and the twelfth vertebrae there is only one facet, and corresponding intervertebral discs do not enter into the joints, uni in the case of the first joint, into which the disc between the sevei cervical and first thoracic vertebrae may enter.


THE THORAX


mi


aments.—These are as follows
radiate, capsular, and intra

lar.

e radiate ligament (anterior costo-central ligament) or stellate

jnt consists of strong white fibres which are attached to the or margin of the head of the rib. From this point the fibres e inwards in three bands, one of which passes upwards to be Led to the body of the vertebra above, a second horizontally is to be attached to the intervertebral disc, and a third vards to be attached to the body of the vertebra below, e case of the first, tenth, eleventh, and twelfth joints, into }f which only one vertebra enters, the ligament is composed of ands, instead of three. In the first joint the lower band passes

body of the first thoracic vertebra, and the upper band to the


jsterior Band of Superior 'osto-transverse Ligament

Vnterior Band of Superior -osto-transverse Ligament


• Anterior Longitudinal Ligament


- Intervertebral Disc


Radiate Ligament —


>7.—Ligaments of the Bodies of the Vertebra and Joints of the Heads of the Ribs on the Right Side.


of the seventh cervical. In each of the tenth, eleventh, and th joints the lower band passes to the body with which the head e rib articulates, and the upper band to the body of the vertebra

e.

he capsular ligament is incomplete, and consists of thin loose 5, which cover the posterior, superior, and inferior aspects of

°int. ,

he intra-articular ligament consists of short stout fibres, which id from the ridge on the head of the rib, separating the two facets, ie intervertebral disc. It divides the joint into two complete vial cavities, and it is wanting in the first, tenth, eleventh, and

Eth joints. . . .

here are two distinct synovial membranes in those joints which

































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A MANUAL OF ANATOMY


are provided with an intra-articular ligament—namely, from second to the ninth inclusive—one being above the ligament and other below it. In those joints in which the intra-articular ligan is absent—namely, the first, tenth, eleventh, and twelfth—ther only one synovial membrane.

Arterial Supply. —Branches from the posterior intercostal arterie

Nerve-supply. —Branches from the intercostal nerves.

Costo-transverse Joints. —These belong to the class of sync joints of the plane variety. The articular surfaces are the facet the tubercle of the rib and the facet on the anterior aspect of extremity of the transverse process of the thoracic vertebra.

Ligaments. —These are as follows: posterior costo-transve inferior costo-transverse, superior costo-transverse, and capsular.

The lateral costo-transverse ligament (posterior costo-transv ligament) is a strong flat band, situated on the posterior aspect of joint, and extending from the extremity of the transverse process the non-articular part of the tubercle of the rib. The directior its fibres is outwards.

The inferior costo-transverse ligament (middle costo-transv

ligament) consists of short strong fibres which pass between the poste surface of the neck of the rib and the anterior surface of the adjac transverse process—namely, that with which the tubercle of the articulates. Its fibres, which are disposed horizontally, extend fi the joint of the head of the rib to the costo-transverse joint. 1 ligament is rudimentary in the eleventh and twelfth ribs.

The superior costo-transverse ligament is a broad flat band, lat< in position, the fibres of which pass from the crest on the upper bor of the neck of the rib to the lower border of the transverse pro( immediately above, in the vicinity of its tip. Its fibres are direc upwards and outwards, and its outer border is continuous with posterior intercostal membrane. A feeble band of fibres, medial the preceding, extends from the back of the neck of the rib, below crest, to the lower aspect of the transverse process immediately abc close to its base, being termed the posterior costo-transverse ligamen

The superior costo-transverse ligament is wanting in the case the first rib.

The capsular ligament is formed in part by the lateral cos transverse ligament, and elsewhere by a thin loose membrane, fibres of which are attached lateral to the articular processes, is absent in the case of the eleventh and twelfth ribs.

The synovial membrane is single and small.

Arterial and Nerve Supply. —Offsets from the posterior branc of the intercostal arteries and nerves.

The costo-transverse joints are wanting in the case of the eleven and twelfth ribs, and sometimes in the case of the tenth.

Costo-chondral Joints. —These belong to the class of fibrous joii The outer extremity of the costal cartilage is implanted in the o pit on the anterior extremity of the rib, and the union is effected




THE THORAX


1113


continuity which takes place between the periosteum of the rib the perichondrium of the cartilage.

2. Costal Cartilages—Sterno-Costal Joints. —These belong to the s of synovial joints, except in the case of the first joint, which mgs to the class of primary cartilaginous joints. The cartilages ch take part in these joints are the first seven on either side,

e being received into the costal pits or facets on the side of the

num.

The ligaments are capsular, sterno-costal, and in the case of the >nd joint at least intra-articular.

rhe Capsular Ligaments —The anterior part is a triangular band, the er fibres of which ascend upon the sternum, and the lower descend, 1 st the intervening fibres pass horizontally forwards. They de


Fig. 668. —The Sterno-costal Joints (Anterior View). rhe second, third, and fourth joints of the left side are seen in section.

sate with those of the opposite side, and blend with the tendinous 'es of origin of the pectoralis major muscle.

The posterior part of the capsular ligament is disposed in a manner Lilar to the anterior ligament.

The sterno-costal ligaments pass from the upper and lower borders

he costal cartilage to the side of the sternum.

The intra-articular ligament is present in the second joint, and may present in some of those succeeding to it. Its fibres extend horiitally between the centre of the sternal end of the second costal tilage and the plate of fibro-cartilage between the manubrium and ly of the sternum. It divides this joint into two complete synovial dties.

The first joint has no synovial membrane, the first costal cartilage ng directly united to the manubrium sterni. The second joint, as ted, has two synovial membranes, one above and the other below J intra-articular ligament. The succeeding joints have each usually






iii4


A MANUAL OF ANATOMY


one synovial membrane, but sometimes one or more of them ms have two.

Arterial Supply. —The perforating branches of the internal mammai artery.

Nerve-supply. —The intercostal nerves as they are becoming tl anterior cutaneous nerves.

Interchondral Joints. —These belong to the class of synovial join of the plane variety. The cartilages involved are usually the sixt' seventh, and eighth, but sometimes also the ninth, and it may be tl fifth, and even the tenth. The lower border of each cartilage projec downwards, and comes into contact with the upper border of tl cartilage below. Each joint is surrounded by fibres disposed in tl form of a capsule, and it is provided with a synovial membrane.

Arterial Supply. —The musculo-phrenic branch of the intern; mammary artery.

Nerve-supply. —The adjacent intercostal nerves.

3. Sternal Joints. —The joint between the manubrium and bod of the sternum belongs to the class of secondary cartilaginous joint; The opposed surfaces are covered by hyaline cartilage, and a plat or disc of fibro-cartilage is interposed between them, which is connecte at either side with the intra-articular ligaments of the second sterm costal joint. This disc may contain a small cavity. In front c and behind the joint there are ligamentous fibres which are dispose longitudinally.

The entire sternum is strengthened by its dense periosteum, b the radiating fibres of the sterno-costal ligaments, and by the tendinor fibres of origin of the pectoralis major muscles.

Movements of the Ribs. —The movement allowed at the joints of the hear of the ribs and costo-transverse joints is of a gliding nature, and takes place an upward and downward direction. During this movement the rib rotat round the costo-vertebral axis, which corresponds to a line passing obliquej through the joint of the neck of the rib, the neck of the rib, and the costo-tran verse joint. Owing to the curve and downward inclination of the rib, tl result of this rotation is that the anterior and lateral parts of the rib are elevate< Simultaneously, on account of the obliquity of the axis of rotation, the anteric part of the rib is carried forwards, and along with it the sternum, thus increasir the antero-posterior diameter of the thorax. The lateral part of the rib, and to certain extent the anterior part also, are carried outwards, thus giving rise t eversion of the lower border of the rib, and at the same time the angle betwee the rib and its costal cartilage is opened out. In this manner an increase in tl transverse diameter of the thorax is produced. During the elevation of tl anterior and lateral parts of the rib and the eversion of its lower border tl movement takes place round the costo-sternal axis, which corresponds to a lii drawn from the costo-central joint of one side to the corresponding stern< costal joint. It is usual to liken this movement to the movement of the hand of a bucket.

In the case of the first rib elevation and depression are the chief movemen allowed, the amount of eversion being trivial, inasmuch as the axis of rotatic is almost transverse. In the case of the second, third, fourth, fifth, and six! ribs elevation and depression, along with eversion, are allowed, the axis of rotatio in each case becoming successively more oblique. The seventh, eighth, nintl and tenth ribs, in which the costo-transverse articular surfaces are almost fla'


THE THORAX


n 15


ides rotating round the costo-vertebral axis, also rotate round the costonal axis. In the case of these ribs elevation is accompanied by a backward cement, and depression by a forward movement. These backward and vard movements take place more freely in the case of the eleventh and lfth ribs, which have no costo-transverse joints. At the sterno-costal joints movement is limited, and consists elevation and depression, together ti forward and backward movement.

At the interchondral joints slight ing movement is allowed.

Muscles concerned in Respiration.— jrdinary quiet inspiration the muscles cerned are as follows: (1) the diaagm; (2) the external and internal

rcostal muscles, assuming Haller’s

v to be correct; (3) the levatores tarum; (4) the serratus posterior suior; (5) the serratus posterior inferior;

. (6) the quadratus lumborum as being iliarv to the diaphragm, the serratus terior inferior being also auxiliary, inary quiet expiration is due to (1) the

tic recoil of the lungs, (2) the elastic

)il of the thoracic wall (costal cartiis and sternum), (3) the sterno-costalis scle, and (4) the muscles of the anteroral wall of the abdomen, which press Ily upon the abdominal viscera, and reby push the diaphragm upwards ards the thorax.

In forced inspiration the following scles come into play: (1) the scaleni; the sterno-mastoid; (3) the serratus srior ; (4) the pectoralis major and toralis minor; and (5) the latissimus

si. As auxiliary muscles there are the trapezius, levator scapulae, and rhom1 muscles, which, by their action upon the scapula, fix the shoulder.

In forced expiration the muscles of the antero-lateral wall of the abdomen with considerable strength, and now depress those ribs with which they connected, and necessarily also the sternum. By some authorities the atus posticus inferior is regarded as being concerned.

In inspiration the thoracic cavity is enlarged in its vertical, antero-pos terior, transverse diameters. The increase in the vertical diameter is due to the traction and descent of the diaphragm; the increase in the antero-postenor neter is caused by the anterior parts of the ribs, and along with them the num, being carried forwards; and the increase in the transverse diameter rought about by the eversion of the lower borders of the ribs, and the opening of the angles between the ribs and their costal cartilages.


Fig. 669.— Diagram showing the Axes of Rotation of the Ribs (from Halliburton’s ‘ Handbook of Physiology ').

A, B, axis passing from the joint of head of rib to chondro-sternal joint; a, b, axis passing through costotransverse and joints of heads of ribs. (The movement round the axis A, B resembles the raising of the handle of a bucket.)

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