View source for Talk:Book - Buchanan's Manual of Anatomy including Embryology 15

==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