Difference between revisions of "Book - An Atlas of the Medulla and Midbrain"

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VIII. View of the Midbraiu from Above, showing Relations of Fibre Tracts.  
 
VIII. View of the Midbraiu from Above, showing Relations of Fibre Tracts.  
 
 
==Chapter VII. The Inferior and Accessoey Olives==
 
 
1. NUCLEUS OLIVARIS INFERIOE.
 
 
inferior " Position. The surface form of the olive, as seen on the uncut
 
medulla, is shown in all text-books (Fig. 33). Its position in the
 
reconstruction is seen on Plates n, in and iv. The nucleus itself
 
extends from the proximal limit of the decussatio pyramidum to
 
the pons (Fig. 20). It lies in the ventral portion of the medulla
 
oblongata, lateral to the stratum interolivare lemnisci, from which
 
it is separated by the root-fibres of the N. hypoglossus and the
 
median accessory olive. Dorsal to the olive lies the large area of
 
formatio reticularis in the medulla oblongata, but the lateral and
 
ventral aspects of the olive are superficial. Opposite the distal half
 
of the lateral surface is a considerable mass of medullated fibres
 
belonging to the lateral funiculus of the spinal cord, but only one
 
small bundle of these fibres extends opposite the proximal half of
 
the olive (Plate iv).
 
 
The dimensions of the olive are as follows: The dorsoventral
 
diameter 4.48 mm., the transverse 6.5 mm., and the anteroposterior
 
7.5 mm.
 
 
The gray matter of the olive forms a hollow shell with a wrinkled
 
wall (Fig. 35). In the model it is made nearly solid inasmuch as,
 
with the magnification used, its walls made strips of wax too thin
 
to handle. It presents for examination six surfaces dorsolateral,
 
lateral, ventral, proximal, distal and medial the last surface including the hilus. The dorsolateral surface, as its name indicates,
 
slopes toward the lateral surface and passes over into it by a gradual
 
curve. On the other hand, the ventral surface is practically level,
 
but likewise rounds onto the lateral surface. This corresponds to
 
the familiar form of the olive in cross-section (Fig. 35).
 
 
In Plate i, Fig. 1, is shown a lateral view, including the dorsolateral surface. The general outline of this view is of interest.
 
The dorsal border is practically level. Starting from the distal
 
 
 
 
THE INTEBIOB AND ACCESSORY OLIVES 87
 
 
end of the nucleus, the outline passes ventralward and forward by
 
a gradual curve which reaches its most ventral point at the proximal
 
end of the ventral surface. This will be recognized as the curve
 
of the olive seen on the uncut medulla. The proximal border is
 
slightly curved and represents the edge that faces the pons.
 
 
The surface of the olive is marked by deep sulci and more shallow grooves, so that the whole suggests the surface of a brain.
 
From the view of the lateral surface it will be noted that all of these
 
grooves run in an approximately dorsoventral direction.
 
 
The dorsal or dorsolateral surface shows three sulci. They are
 
approximately parallel and divide the dorsal part of the olive into
 
four lobes. These sulci are distinguishable from the other grooves
 
on this surface in being deeper, for they reach down to the opening
 
of the hilus, as can be seen in Fig. 19. The sulci do not pass
 
over onto the curve of the lateral surface, which is marked by
 
comparatively shallow grooves that more or less alternate with the
 
deep sulci of the dorsolateral surface. From this fact it follows
 
that the lobes are well marked only in the dorsal portion. It is
 
evident that transverse sections of the olive would be all comparatively similar over the lateral curve, but would differ on the dorsolateral surface, according as the section passed through a sulcus or
 
a lobe. This will be clear by comparing Figs. 31 and 32.
 
 
Of the four lobes, the first or proximal is the largest (Plate i,
 
Fig. 1, L. p.). It is subdivided in the dorsal portion by two or
 
three fairly deep grooves. The first sulcus runs a little obliquely,
 
the dorsal end being further spinalward than the ventral. The
 
first lobe has three surfaces (1) a dorsolateral, (2) a proximal and
 
(3) a mesial. In other words, the first lobe curves around the
 
proximal end of the nucleus to the mesial surface, so as to enclose
 
a portion of the hilus. This explains why a cross-section of the
 
proximal lobe shows the gray matter as a complete ring (Fig. 36).
 
The first lobe is made up of three convolutions, or gyri, two of
 
which are seen from the lateral view and the other from the mesial.
 
 
The second and third lobes consist each of a single convolution,
 
or gyrus. They present but one surface, directed dorsolaterally.
 
At the dorsal border they are comparatively narrow, but broaden
 
out in joining the lateral surface.
 
 
The fourth lobe forms the distal end of the olive and is the
 
smallest of all, consisting, like the second and third, of a single convolution or gyms. It does not curve around the hilus as does
 
the first lobe (Fig. 20). Nevertheless, the lobe is placed obliquely,
 
so that a cross-section of the extreme distal part is a small closed
 
ring, the same as the cross-section of the proximal lobe.
 
 
The surface of the lobes and the sides of the sulci are marked by
 
small grooves which run in a dorsoventral direction. Indeed, in the
 
depth of the sulci are small folds in the nuclear wall. These can
 
be seen in longitudinal section (Fig. 19).
 
 
The lateral surface forms the curve of the shell. Its dorsal
 
margin (Plate i, Fig. 1) is an indistinct line where it curves onto
 
the dorsolateral surface. Its ventral border makes the curve of
 
the surface form. This curve or ventral border is so placed that
 
the distal part of the lateral surface is narrow, that is, the part
 
opposite the fourth lobe. The greatest breadth of the lateral surface is at the proximal end. The entire surface is covered by
 
shallow grooves, of which the deepest alternates with the first and
 
second sulci. It is worthy of note that all of the grooves of this
 
surface run in a dorsolateral direction, as do those of the dorsolateral surface.
 
 
The ventral surface is smaller than the dorsal (Plate i, Fig. 2).
 
It is for the most part horizontal, but at the spinal end it passes
 
by a gradual curve onto the distal surface (Fig. 33). In its surface
 
markings it contrasts with the dorsolateral and lateral surfaces, for
 
instead of taking a dorsoventral direction, its grooves all radiate out
 
from a point in the ventral border of the hilus (Plate i, Fig. 2).
 
This point is opposite the word mesial in the figure. Thus it
 
happens that while the distal groove runs transversely, as do those
 
of the dorsolateral surface, the proximal groove runs longitudinally
 
parallel to the raphe and at right angles to the grooves of the dorsolateral surface.
 
 
The grooves of the ventral surface are not marked by secondary
 
furrows, as are the sulci of the dorsolateral surface. As has been
 
said, these grooves appear to radiate from a point about the middle
 
of the ventral border of the hilus. The first or most medial of these
 
grooves (S. p.) runs directly parallel to the long axis of the olive,
 
that is, in an anteroposterior direction. It is a deep groove and
 
extends far dorsalward on the median surface, separating off a
 
small gyrus from the main lobe. This is seen only on a view of the
 
mesial surface which, unfortunately, is not given. The second (S. s.) passes obliquely toward the cerebrum and becomes continuous with one of the grooves of the lateral surface. The third (S. t.)
 
lies still more obliquely and does not leave the ventral surface.
 
The distal part of the ventral surface is somewhat damaged, inasmuch as the sections were here a little too much decolorized in
 
preparation, but enough can be made out to say that the grooves
 
run transversely and are the continuation of the grooves of the
 
lateral surface.
 
 
The medial surface is not given in the plates. It shows the hilus.
 
From this aspect it can be seen that the ventral part of the olive
 
makes a floor for the hilus and the dorsal part, a roof (Fig. 33).
 
The proximal end of the hilus is closed in by the first lobe (Fig. 20).
 
Opposite each lobe of the surface is a deep groove in the cavity to
 
which the hilus leads, and the sides of these main grooves are
 
marked again by grooves which correspond each to one convolution
 
of the external surface. In brief, the essential points of the form
 
of the olive are (1) its general shape as a hollow shell, (2) its hilus,
 
(3) its transverse grooves on the dorsolateral surface, and (4) its
 
radiating grooves on the ventral surface.
 
 
The olives of both sides were modelled in the effort to see if the
 
fissures above described offered a basis of symmetry. The symmetry proved to be sufficiently apparent to lead one to an emphasis of the differences. The three deep fissures of the external
 
surface, as well as the three radiating grooves of the ventral aspect,
 
corresponded in the two lines. The differences consisted in the
 
relative size of two of the lobes. The first lobe of the right olive
 
was larger than the corresponding lobe of the other side, while the
 
fourth lobe of the right side was proportionately smaller. The
 
term proportionately is accurate, inasmuch as the two olives are of
 
the same length and the second and third lobes correspond in size
 
on the two sides. The symmetry of the two olives is shown in
 
Fig. 19. At this level the fourth lobe of the right side is but a
 
single fold in the nuclear wall.
 
 
It is now necessary to relate the appearance of the sections to the Inferior olive
 
form of the olive in the model. A typical cross-section, so to speak, in sections,
 
shows the thin folded wall and the open hilus (Fig 1 . 33). Attention has
 
already been called to the fact that the form of the wall varies according as a section passes through a sulcus or a lobe (Figs. 32 and 33). It
 
will be noticed that, inasmuch as the sulci run slightly obliquely, no
 
one section passes through the entire length of one sulcus. The sulci can be used in determining the symmetry of an olive cut in crosssection. In tracing the olive of the cross series of the same stage, it
 
is found that the first lobe of one side is larger and the fourth smaller
 
than the corresponding lobes of the other side, the same peculiarity
 
that has been noted in the model. I have, however, no method of determining right and left side of either series as compared with a real
 
medulla.
 
 
Sections in a longitudinal direction differ widely from those of the
 
transverse series; they illustrate the symmetry of the olive, that is they
 
show the relation of the lobes and sulci and the varying depth of the
 
sulci and grooves far better than the transverse series (Figs. 16 to 23).
 
The first section shows the dorsal border of the olive. In the next three
 
sections the symmetry can be traced, and note made of the relative size
 
of the first and fourth lobes. The relation of the wall of these two
 
lobes to cross-sections is evident, that is, the obliquity of the fourth
 
lobe and the curve of the wall of the first account for the closed circles
 
at either end in the transverse series. The last three sections pass
 
through the ventral wall and the direction of the sulci is the point of
 
special interest.
 
 
In the various longitudinal sections it will be noted that there are
 
groups of cells either as rings or as irregular figures, that are wholly
 
separate from the main wall; some of these lie within and some without
 
the hilus (Fig. 19). These can be understood by reference to the transverse series. If, for example, in Fig. 33, a transverse line is drawn
 
across the dorsal wall of the olive, it will cut off rings of cells, and these
 
rings will be of two types: (1) a ring from a fold that projects on the
 
lateral surface, and (2) a ring from a fold that projects into the hilus.
 
The rings of the first type lie without the hilus and have their outer
 
margin corresponding to the surface of the olive; the rings of the
 
second type lie within the hilus and have their inner margin corresponding to the surface of the olive. This is a practical point in modeling
 
the olive.
 
 
Fibres of From this study of the sections it is clear that the fibres of the olive
 
inferior olive. are non-medullated at birth and hence are not in the model.
 
 
3Pf
 
 
Median Nucleus oUvaris accessorius medialis. The medial accessory
 
' olive is an irregular nucleus, much broken by bands of fibres running through it. It lies opposite the main olive, between the interolivary layer of the lemniscus and the root-bundle of the !N".
 
hypoglossus (Plate v). Its inferior limit extends farther spinalward than the nucleus olivaris inferior, but its proximal does not
 
reach as far cerebralward. From the view of the lateral surface
 
(Fig. 2), it consists of. three columns of cells running in a dorsoventral direction. Each of the columns has small separate masses
 
of cells opposite its dorsal border. The first or distal column is
 
by far the largest. Its ventral portion is thick and a prominent
 
process from the distal ventral angle curves around the distal border
 
of the N". hypoglossus and the main olive (Plate vn). It makes an indentation in the ventral part of the medulla sheet (Plate YI).
 
At the proximal ventral angle the first column connects with the
 
second. The dorsal border of the first column shows a spur of
 
cells from the distal half, while corresponding to the proximal half
 
is a small separate group of cells. The spur corresponds to the
 
second indentation on the medulla sheet (Plate vi). The second
 
column is thin and flat; opposite its dorsal border are two small
 
masses of cells. The third column is about one-third as broad as
 
the others; it makes a narrow column of cells, opposite the dorsal
 
end of which is still another small nucleus.
 
 
Dorsal
 
 
 
 
 
in sections.
 
 
 
 
Ventral.
 
 
FIG. 2. Diagram of Nucleus olivaris accessorius medialis.
 
 
In longitudinal sections these relations are clear. Fig". 20 passes Median
 
through the three columns near the ventral border. The first, which is accessory olive
 
clearly the largest, appears curving around the inferior border of the
 
main olive. The root-fibres of the N. hypoglossus cut through it. The
 
second and third columns need only be mentioned. Passing dorsalward,
 
we have the three columns, making groups of cells between the fibres
 
of the N. hypoglossus and the stratum interolivare lemnisci (Fig. 19).
 
Fig. 17 shows the scattered groups of cells of the medial-accessory olive.
 
Cross-section. In Fig. 29, is seen the ventral part of the first column.
 
This is, however, much better developed in Figs. 30 and 31. In Fig. 32
 
the second column is present, while in Figs. 33 and 35 the third column
 
is seen.
 
 
The nucleus olivaris accessorius dorsalis is not shown in the
 
model, but Fig. 15 skows its shape. It varies in shape on the two
 
sides. The distal portion lies dorsal to the third lobe of the nucleus
 
olivaris inferior, and the proximal portion corresponds to the second
 
lobe.
 
 
  
  

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Sabin FR. and Knower H. An atlas of the medulla and midbrain, a laboratory manual (1901) Baltimore: Friedenwald.

Online Editor  
Mark Hill.jpg
This 1901 book by Florence Rena Sabin (1871 - 1953) and her collaborator presents one of the very earliest atlases of the human central nervous system, describing the midbrain and brainstem. This atlas was extremely useful for later researchers attempting to both understand the development and mapping of the midbrain and medulla. Florence Sabin later work was as a key historic researcher in early 1900's establishing our early understanding of both vascular and lymphatic development in the embryo.



Modern Notes: Medulla | Mesencephalon | Florence Sabin

Neural Links: ectoderm | neural | neural crest | ventricular | sensory | Stage 22 | gliogenesis | neural fetal | Medicine Lecture - Neural | Lecture - Ectoderm | Lecture - Neural Crest | Lab - Early Neural | neural abnormalities | folic acid | iodine deficiency | Fetal Alcohol Syndrome | neural postnatal | neural examination | Histology | Historic Neural | Category:Neural


Neural Tube Development
Neural Tube Primary Vesicles Secondary Vesicles Adult Structures
week 3 week 4 week 5 adult
neural plate
neural groove
neural tube

Brain
prosencephalon (forebrain) telencephalon Rhinencephalon, Amygdala, hippocampus, cerebrum (cortex), hypothalamus‎, pituitary | Basal Ganglia, lateral ventricles
diencephalon epithalamus, thalamus, Subthalamus, pineal, posterior commissure, pretectum, third ventricle
mesencephalon (midbrain) mesencephalon tectum, Cerebral peduncle, cerebral aqueduct, pons
rhombencephalon (hindbrain) metencephalon cerebellum
myelencephalon medulla oblongata, isthmus
spinal cord, pyramidal decussation, central canal
Historic Disclaimer - information about historic embryology pages 
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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)


AN ATLAS OF THE MEDULLA AND MIDBRAIN

By Florence R. Sabin


A LABORATORY MANUAL

ILLUSTRATED WITH SEVEN COLORED PLATES, ONE BLACK PLATE AND FIFTY-TWO FIGURES


EDITED BY


Henry McE. Knower, PH.D.

Instructor in Anatomy in the Johns Hopkins University, Baltimore, Md.


BALTIMORE, MD., U. S. A.

THE FRIEDENWALD COMPANY

PUBLISHERS

1901


COPYRIGHT, 1901, BY FLORENCE R. SABIN


THE FRIEDENWALD COMPANY BALTIMORE, MD M U. S. A.

Historic Disclaimer - information about historic embryology pages 
Mark Hill.jpg
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Editor's Preface

This Atlas is planned to meet the practical need of some quick and simple, yet full and reliable, means of aiding the student to obtain, from a few sections (or from a series of sections), a reasonably clear idea of the important central relay-station of the brain here presented. (Though representing the human brain, the atlas can be applied to the study of the brains of lower mammals.)

The time allotted to a course in Neurology is generally so short; the sections to be studied exhibit such great special complexity of structure, due to the presence and association of many different centres in the narrow limits of the region; and the descriptions in text-books or lectures are commonly so detailed, or so general or diagrammatic; that many students get but hazy ideas of what is shown in their preparations, without spending more time in the effort than is reasonable.

We believe, and a number of well-known teachers in several of our large universities have agreed in this opinion, that this little Atlas will offer a valuable and new remedy for the difficulties stated above; and will save the student much time for real study, now often spent in getting started.

Supplied with these excellent drawings of the reconstruction, showing for the first time accurately and satisfactorily structures to be studied, the student can quickly compare his own sections with the figures of the Atlas and find the parts there clearly designated and explained.

Again, if, as is usually the case, a student has only a few cross -J-Tiio -narnrvn + Vi a A+laa with if.a 4-8 fiomrPS of


At the urgent solicitation of Professor Ph. Stohr, of Wiirzburg, Germany, Dr. F Ziegler, of Freiburg, Germany, is considering the reduplication of the model on which this atlas is based. It is expected that such models, from his studio, will be available within the year .



Florence R. Sabin, M. D


May 31, 1901.



Editor's Preface

This Atlas is planned to meet the practical need of some quick The need of and simple, yet full and reliable, means of aiding the student to obtain, from a few sections (or from a series of sections), a reasonably clear idea of the important central relay-station of the brain here presented. (Though representing the human brain, the atlas can be applied to the study of the brains of lower mammals.)

The time allotted to a course in Neurology is generally so short; the sections to be studied exhibit such great special complexity of structure, due to the presence and association of many different centres in the narrow limits of the region; and the descriptions in text-books or lectures are commonly so detailed, or so general or diagrammatic; that many students get but hazy ideas of what is shown in their preparations, without spending more time in the effort than is reasonable.

We believe, and a number of well-known teachers in several of our large universities have agreed in this opinion, that this little Atlas will offer a valuable and new remedy for the difficulties stated above; and will save the student much time for real study, now often spent in getting started.

Supplied with these excellent drawings of the reconstruction, its use with , sections.

showing for the first time accurately and satisiactorily structures to be studied, the student can quickly compare his own sections with the figures of the Atlas and find the parts there clearly designated and explained.

Again, if, as is usually the case, a student has only a few crosssections through this region, the Atlas, with its 48 figures of sections cut in two planes and drawn to resemble actual preparations, furnishes a good supplementary series of sections for comparison.

It is thus easy to understand the many sections which are not through particularly well-marked points usually figured in textbooks; and it is possible to get a very satisfactory idea of any structure, by turning to the two series figured, to the colored plates and to the index, with sections of Tracts in the Spinal Cord may be more readily understood and Spinal Cord. 'traced forward into the brain with the aid of this manual. The arrangement The text not only describes, in a convenient manner and fully, ' everything figured in the reconstruction; but the paragraphs of small print, and others referred to in the headings and index, explain just how to compare sections with the model, and how to trace nerve-fibre tracts or masses of gray matter, from section to section through this region.

The importance When it is realized that this model represents that part of the f the Braku brain in which the nuclei of origin of all the true cranial nerves are found; that association tracts between these centres are here included; that the cells and fibre-tracts are brought into intimate association, from their central position, with those of the Spinal Cord, Cerebellum, and Forebrain; the usefulness of the Atlas to the Anatomist, Physiologist, Pathologist, and Psychologist, whether in the laboratory or in connection with lectures and demonstrations, may be seen.

supplementary A short list of text-books and journals has been included, to " permit the tracing of certain tracts of nerve-fibres further up into the higher brain centres or down into the cord, and to encourage the student to seek information as to the many and varied sides of Neurology from reliable sources where more extensive references are to be found.

The Editor wishes to explain that his participation in this Atlas is confined to the suggestion of publishing the original research in the present modified new form, and to assistance in a considerable rearrangement of the text and index to facilitate ready reference. He has urged this publication in order to furnish the student, in a new and especially available form, a valuable guide to the ready

interpretation of his preparations.

HENRY Mo E. KNOWER. ANATOMICAL LABORATORY,

JOHNS HOPKINS UNIVERSITY.


AUTHOR'S PREFACE.

A description and the plates of a reconstruction of the medulla oblongata of the new-born babe was published in the " Contributions to the Science of Medicine," dedicated to William Henry Welch. 1 The model was built in the Anatomical Laboratory of the Johns Hopkins University at the suggestion of Dr. Franklin P. Mall and Dr. Lewellys F. Barker. It was the original thought that such a reconstruction would not only show graphically for the first time the form and relations of the tracts and nuclei, but that it would simplify for the student of anatomy a region both complex and difficult. The shape of the tracts in the cord was well known, the forms of the internal capsule in the brain could be fairly well imagined, but the tracts between the cord and brain were too complex to give mental pictures without the aid of a model. The suggestion has been made by Dr. H. Me E. Knower, of the Anatomical Laboratory of the Johns Hopkins Medical School, that the description of the model be put into a more convenient form for the student; by means of fuller references to the plates and sections; by a rearrangement of contents to make the location in the model of any set of serial sections or any single section of the region an easy matter; by adding a full index; and by a list of literature containing a few of the most important references valuable to the student at the beginning of a study of the central nervous system of man or the mammals. I am indebted to him for the arrangements for this edition.

I wish to thank Dr. John Hewetson for the material which made the model possible. Both series were unbroken, and so admirably prepared that any omissions in the model are due not to the material, but to the nature of the structures in question. I am greatly indebted to Mr. Max Broedel for the beautiful illustrations of the model. They are so accurate and clear as to be equal in value to the model itself. It is through the kindness of Dr. Henry M. Hurd that the plates of these drawings can be used for the present edition. Dr. Franklin P. Mall controlled the construction of the model, Dr. Lewellys F. Barker its study. I acknowledge with thanks their unfailing help and interest.


1 Model of the Medulla, Pons and Midbrain of a New-born Babe, by Florence R. Sabin. Contributions to the Science of Medicine, and vol. ix of the Johns Hopkins Hospital Reports.


Contents

Chapter I.

Introductory

Method Of Using Atlas

Chapter Ii. The Long Tracts.

A. In The Medulla (Medulla Sheet)

B. In The Pons And Midbrain (Lemnisci And Formatio Reticularis)

Chapter Iii. The Columns Of The Spinal Cord.

A. Ventrolateral Column

(A) Ventral Part

(&) Dorsal Part

B. Dorsal Column

Chapter Iv. Cerebellar Peduncles.

Inferior Peduncle, Or Corpus Restiforme

Superior Peduncle, Or Brachium Conjunctivum

Chapter V. The Cerebral Nerves And Their Nuclei. Median Group (Red In Model).

(A) N. Hypoglossus, XII

Nucleus N., XII

(&) N. Abducens, VI

Nucleus N., VI

(C) N. Trochlearis, IV

Nucleus N., Iv 56

(D) N. Oculomotorius, III

Nucleus N., III

Chapter Vi. The Cerebral Nerves And Their Nuclei (Continued). Lateral Group.

A. Motor Nerves (Red In Model)

(A) N. Accessprius, XI

Nucleus N., XI.


(B) N. Glossopharyngeus Et N. Vagus, Ix And X

Nucleus N., Ix And X

(C) N. Facialis, VII

Nucleus N., VII

(D) N. Trigeminus, V

Nucleus N., V

B. Sensory Nerves (Blue In Model)

(A) N. Glossopharyngeus Et N. Vagus, Ix And X

Nucleus N. , Ix And X

(&) N. Trigeminus, V

Nucleus N., V

(C) N. Vestibuli, Viii

Nuclei N. Vestibuli

(D) N. Cochleae, Viii

Nuclei N. Cochlese

Chapter Vii. The Inferior And Accessory Olives 86

Chapter Viii. The Midbrain.

1. Relation Of Its Structures To The Central Fibre Mass

2. The Nucleus Ruber (Red Nucleus) And Its Capsule

3. The Fasciculus Retroflexus (Meynerti)

4. The Decussatio Tegmenti Dorsalis (Meynerti)

5. The Decussatio Tegmenti Ventralis Of Forel

6. Stratum Album Prof Undum (Deep White Layer)

7. Substantia Centralis Grisea (Central Gray Matter)

8. The Pyramidal Tract

9. Substantia Nigra

Chapter Ix. The Formatio Reticularis Alba And Grisea

General Summary of what Is shown In Reconstruction

References To Literature

List of Illustrations

FIGURES : PAGE

1. Transverse Section of the Spinal Cord. Outline 36

2. Diagram of Medial Accessory Olive 91

3-24. Series of Horizontal (frontal) Sections, including Medulla and Midbrain 125-132

25-51. Series of Transverse Sections from the Cord to the Midbrain. .133-145

52. Diagram of the Model giving Levels of Sections here Figured 146

PLATES following page 146

I. The Inferior Olive. II. View of the Lateral Surface of the Reconstruction.

III. View of the Dorsal Surface of the Reconstruction.

IV. First Dissection of the Reconstruction. Lateral view, showing

Fibre Tracts, &c., and the Sensory Nuclei of Cerebral Nerves. V. Second Dissection of the Reconstruction. Lateral view, showing

Fibre Tracts, &c., and Motor Nuclei of Cerebral Nerves. VI. Third Dissection of the Reconstruction. Lateral view, showing

the Long Tracts of the Medulla.

VII. Fourth Dissection of the Reconstruction. Dorsomedian view, showing the Long Fibre Tracts as Related to Nuclei of Cerebral Nerves and to other Structures.

VIII. View of the Midbraiu from Above, showing Relations of Fibre Tracts.


Chapter VIII. The Midbrain

1. THE RELATION OF ITS STRUCTURES TO THE CENTRAL FIBRE MASS.

The midbrain has been difficult to model, inasmuch as it is not easy to give definite outlines to all of its nuclei and fibre-bundles. The key to the form relations of the region was given in the description of the medial lemniscus. The central fibre mass, including the medial lemniscus, the superior lemniscus and the lateral part of the capsule of the red nucleus, is placed obliquely in the midbrain and divides it into two areas. The medial area contains the red nucleus, a formatio reticularis area, the nuclei of the oculomotor and trochlear nerves and the fasciculus longitudinalis medialis (Plates ni, vn, vni), while the lateral area contains the substantia nigra, and, later in course of development, the pyramidal tract (Plate n). In the view from the lateral surface given in Plate n, the midbrain sheet is shown, with the substantia nigra in place. In Plate v the substantia nigra has been removed and the complete fibre-sheet is thus revealed. In a third view (Plate iv) the fibre-sheet itself has been removed and the whole midbrain medial to it is visible. In the ventral portion is seen the nucleus ruber and its capsule; dorsal to it is the space for the formatio reticularis, while toward the median line can be seen the fasciculus longitudinalis medialis, the stratum profundum album of the superior colliculus, together with the nucleus and root-fibres of the oculomotor nerve. These three views give a general idea of the whole area. Plate vni shows the midbrain seen from above. The form relations of the region are (1) the great size of its nuclei, namely, the nucleus ruber and the substantia nigra and (2) the deflection of the medial lemniscus, apparently due to the development of the nucleus ruber. In describing the midbrain, then, the relations of the fibre-sheet will first be considered; secondly, the structures that lie medial to it; and finally, those that lie lateral to it.

The fibre-sheet as a whole has been described in connection with the medial lemniseus, and reference will be made here only to those parts of it that belong essentially to the midbrain, namely, the lemniscus superior and the lateral capsule of the red nucleus. The latter will be considered in connection with that nucleus.

The lemniscus superior is best seen in a lateral view (Plates n superior and v). Its shape has already been described; it is a triangular sheet of fibres placed upon the lemniscus medial is. In the model the only means of distinguishing it from the medial lemniscus lies (1) in the thinness of the sheet and (2) in the fact that, while the medial lemniscus passes on beyond the region of the model, and is therefore shown with a square-cut edge, the lemniscus superior ends within the limits of the model and has a rounded edge.

The lemniscus superior appears to begin opposite the proximal part of the pons, where a few of the fibres of the medial lemniscus seem to radiate from the main bundle, making a fairly thick sheet at the start, which, however, grows thinner as it becomes wider. A further point of interest is that the dorsal border of the superior lemniscus comes to lie adjacent to the capsule of the nucleus colliculi inferioris.

The transverse series shows many interesting points in regard to the g uper i or lemniscus superior. In Fig. 40 there is no distinction to be made be- lemniscus tween the medial and the lateral lemnisci; but by passing farther cere- insectlons bralward to Fig. 42, it becomes evident that the two separate; between them is an area of fine fibres, those of the lemniscus superior. In Fig. 43 the fibres of the lemniscus superior are passing farther dorsalward. This shows clearly on the model. The lemniscus superior lies even farther lateral than the lemniscus lateralis itself. The next section (Fig. 44) shows interesting relations. The nucleus colliculi inferioris has almost disappeared. The lemniscus medialis is gradually curving into its characteristic midbrain position and the superior lemniscus is making its way to the region just lateral from the capsule of the nucleus of the inferior colliculus. Figs. 46, 47 and 48 take the superior lemniscus well into the region of the superior colliculus, and here the fibres are few, fine, and cut in cross-section. The transverse series is not complete enough to show the proximal limit of the lemniscus superior. In the longitudinal series, on the other hand, the lemniscus superior is apparently complete and the sections show that it does not pass beyond the midbrain (Fig. 12). Three sections will show the relative widths of the lemniscus medialis and the lemniscus superior: (1) Fig. 16, which shows the lemniscus medialis; (2) Fig. 13, a transition, and (3) Fig. 12, which shows the lemniscus superior. In this last section, as well as in Fig. 9, the superior lemniscus borders the large area of gray matter in the superior colliculus and, indeed, appears to have some relation with its cells. Indeed, there is a closely packed group of cells, almost a definite nucleus, opposite the end of the tract. 1 In passing still farther dorsalward it becomes impossible to distinguish the superior lemniscus from the capsule of the nucleus colliculi inf erioris (Fig. 7) ; but in the next section (Fig. 6) is seen the area of the nuclear capsule without question.

The model bears out closely the description of the relations of the lemniscus superior given by Forel. 2 If any of its fibres pass on, it must be those in the ventral part, where the bundle lies adjacent to the lemniscus medialis. On the other hand, the view of Elechsig, that the superior lemniscus ends in the superior colliculus, is well sustained.

The end of the tract, as seen in the model, is about opposite the point at which the fasciculus retroflexus of Meynert plunges into the nucleus ruber.

2. THE NUCLEUS RUBER AND ITS CAPSULE (PLATE iv).

Red nucleus. The nucleus ruber has a capsule of cells and fibres on its dorsal, lateral and superior surfaces. The spinal surface of the nucleus, on the other hand, is related (1) to the fibres of the !N". oculomotorius, (2) to the brachium conjunctivum, (3) possibly to some fibres of the lemniscus medialis. The ventral surface at this stage lies in a mass of cells which underlies both the nucleus ruber and the substantia nigra (Plates iv, v and vm). This mass I have called the lectus or bed of the two nuclei.

The red nucleus will be described first, inasmuch as it makes so prominent a feature of the midbrain. It is seen from the side in Plate iv, and from a mesial aspect, in Plate vn. In the latter view a portion of the superior capsule of the red nucleus has been removed, as can be seen by comparing with Plates v and vm. The connection of the brachium conjunctivum with the red nucleus is seen in part on Plate iv, but far better in Plate vin. where other Red nucleus, structures have been sacrificed to show this relation on the right side of the view. The position of the nucleus ruber in this view is judged by the shape of its capsule.


1 This is in accord with v. Monakow, C., Experimentelle und pathologisch-anatomische Untersuchungen ueber die Haubenregion, den Sehhuegel und die Regio subthalmica, nebst Beitragen zur Kenntniss friih erworbener Gross- und Kleinhirn defecte. Arch. f. Psychiat., Berl., Bd. 27 (1895), S. 1-128. On S. 452 in the same volume, he refers to what I have termed the proximal limit of the lemniscus superior, as the place where the superior lemniscus and the chief part of the lemniscus fuse.

2 Forel, A., Untersuchungen iiber die Haubenregion un ihre oberen Verkniipfungen im Gehirne des Menschen und einiger Sangethiere mit Beitragen zu den Methoden der Gehirnuntersuchung. Arch. f. Psychiat., Berl., Bd. VII (1877), S. 393-495.




The nucleus is roughly oval but not regular in shape. It is placed in the ventral portion of the midbrain, surrounded on its dorsal, lateral and superior surfaces by a capsule of cells and fibres. The lemniscus medialis, in passing toward the thalamus, lies adjacent to the dorsolateral angle of the capsule, where the two fibre masses are practically indistinguishable. Just distal to the red nucleus, or at least to its dorsal portion, is situated the decussation of the brachium conjunctivum. In order to study the relations of the brachium conjunctivum to the red nucleus, it will be necessary to recall the various decussations of the tegmeiitum. In the description of the brachium conjunctivum, note was made of three decussations : (1) a commissure between Bechterew's nuclei, (2) the dorsal bundle of the brachium conjunctivum and (3) the ventral or main part of the brachium conjunctivum (Plate vin).

In regard to the relations of the brachium conjunctivum to the nucleus ruber, the model makes three points clear: first, that some of the fibres of the brachium conjunctivum pass into the dorsal capsule of the nucleus ; second, that some of the fibres pass through the nucleus ; and third, that others end in the nucleus. The fibres entering the dorsal capsule are distinctly visible on the left side of Plate vin, where they appear to spread out over the nucleus. The relation is evident in section (Fig. 16) which is taken just dorsal to the level of the nucleus ruber. The fibres that pass through the nucleus appear as a bundle cut in cross-section at the lateral, proximal angle of the dorsal capsule (Plate vin, left side). In regard to this bundle, a comparison of the two sides of the model will show three points: (1) that the bundle passes obliquely through the dorsal portion of the nucleus and leaves its dorsolateral portion ; (2) that it enters the lateral region of the capsule, which is Forel's x Feld BATh; (3) that it comes to lie immediately adjacent to the lemniscus medialis. The fibres that end in the red nucleus enter the dorsomedian portion and the space has been left vacant in

1 Forel says that BATh. consists mainly of an upward continuation of the brachium conjunctivum. Forel, op. cit., S. 426.


Plate vin to show their position. A single section will make these relations plain (Fig. 19). In passing ventralward through the nucleus, the fibres become much fewer and more scattered (Figs. 20 to 23). In fact, there are no medullated fibres in the ventral portion.

Capsule of the The capsule of the nucleus ruber is peculiar in being a complex

  • of cells as well as fibres. The dorsal capsule is almost wholly made

up of fibres; in the proximal capsule, however, cells predominate,

while the ventral capsule at this stage of development is made up

of cells with no medullated fibres.

The spinal surface of the nucleus is related to three groups of fibres; first, to the brachium conjunctivum ; second, to the fibres of the jSL oculomotorius, and third, to a few fibres that enter the midbrain from the lemniscus medialis (Plate iv).

The medial wall of the capsule is incomplete and consists of a few fine fibres adjacent to the dorsal capsule. Besides these, the fasciculus retroflexus of Meynert bounds a part of this surface (Plate vn). The dorsal capsule consists mainly, as has been said, of fibres from the brachium conjunctivum (Plates iv and vm). It covers the dorsal surface of the nucleus, and its lateral border lies adjacent to the medial lemniscus. Dorsal to this capsule is the formatio reticularis region of the midbrain, and medial to it is the fasciculus longitudinalis medialis. According to Forel, 1 the capsule receives fibres from each of these structures.

The dorsal capsule passes immediately into the superior capsule. Plate vm shows well the superior capsule with its relations to the fasciculus longitudinalis medialis, the fasciculus retroflexus Meynerti and the lemniscus medialis.

The area adjacent to the lemniscus medialis, including a portion of the dorsal and superior walls of the capsule, corresponds to Forel's 2 Feld BATh.


1 Forel, op. cit., S. 424.

2 Forel describes the area BATh as being dorsolateral to the nucleus ruber. Op. cit., S. 415.


The proximal capsule of the model will serve to illustrate in part ForeFs description of the area between the nucleus ruber and the thalamus, though the model includes but the lower border of the region. The dorsal part of the proximal capsule is rich in fibres, which it receives from the dorsal capsule. The middle part consists of mixed fibres and cells, while the ventral part has more cells than fibres; indeed, toward the lateral border there is a fairly definite nucleus. 1

In the centre of the dorsal edge of the proximal capsule the fasciculus retroflexus of Meynert plunges through the capsule and into the nucleus ruber (Plates iv and vm). The capsule is thickest at its lateral border. The relation of the fasciculus longitudinalis medialis to the capsule is an interesting one. In Plate vm will be seen the trough of the fasciculus longitudinalis medialis ' and the groove for the nucleus of Darkschewitsch. This groove opens out onto the surface of the superior capsule. "While the main bulk of the fibres of the fasciculus longitudinalis medialis do not pass beyond the nucleus, yet a small bundle of fine fibres passes onward into the medial border of the superior capsule and is gradually lost among its cells and fibres. This relation has been demonstrated already by Forel. 2

Reference has already been made to the lateral capsule as a part of the midbrain sheet. The lemniscus medialis itself forms a part of the lateral wall of the nucleus. The part of the capsule adjacent to the lemniscus medialis is by far its densest portion and its fibres enter Forel's B Feld BATh, and Flechsig's Haubenstralilung. The fibres of the ventral part are few and scattered.

The origin of the fibres of the lateral capsule deserves consideration. (1) The lemniscus medialis, as has been said, forms a part of the capsule; (2) fibres of the medial and ventral portion of the pontal sheet enter the midbrain and spread out over the lateral surface of the nucleus. In the sections it is hard to separate these fibres from those of the brachium conjunctivum (Fig. 20). (3) Fibres of the brachium conjunctivum appear in some sections to enter the lateral capsule. (4) In Plate v of the model can be seen a small nucleus lying in a lateral capsule and in the corresponding sections, certain fibres appear to be definitely related to this nucleus (Fig. 21). According to Fore], the capsule receives fibres from the nucleus ruber.

1 This agrees exactly with Forel, who has divided the area into three zones: a dorsal or Forel's Feld H, a middle or the zona incerta, and a ventral, or Liiy's body. Forel, op. cit., S. 415.

2 Forel, op. cit., S. 420.

3 Forel, op. cit., S. 425; v. Monakow, op. cit., S. 28. 7


The description of the lateral capsule as given in For el's article appears to me to apply more to its dorsal portion. Their origin is hard to trace. In passing farther ventralward (Fig. 20), there is a great thinning out of the capsular fibres. In the first place, the lateral wall has become reduced to a few scattered fibres. By following carefully between the last two sections, it seems clear that some of the fibres of the lateral wall come from the pontal sheet and the brachium conjunctivum. At the level of Fig. 21, however, its fibres appear to be directly related to a small mass of cells lying distal to the nucleus ruber and surrounded by the fibres of the root of the 1ST. oculomotorius (K\i. x. of 1. c. of N"u. r., Plate iv). Forel's Feld H shows clearly in Fig. 21. The fasciculus retroflexus on the medial border will be described later. In passing through Figs. 22 and 23, it is evident that the fibres around the nucleus are becoming fewer, while the cells become more and more numerous, especially in the proximal and adjacent lateral capsules. In Fig. 24 are the cell masses that underlie both the nucleus ruber and the substantia nigra.

The longitudinal series is better than the transverse for obtaining a clear idea of the relations described above. Starting from, the dorsal aspect, in Fig. 13, is seen the area of the formatio reticularis which lies dorsal to the nucleus ruber; from this, one passes into the area of the definite dorsal capsule in Fig. 16. The relation of the fasciculus longitudinalis medialis to the nucleus of Darkschewitsch and the superior capsule of the nucleus ruber may be followed at the same time as far as Fig. 21. In Fig. 19 are seen, (1) the lemniscus medialis as a part of the lateral capsule; (2) the brachium conjunctivum just distal to the nucleus; (3) the relations of the N. oculomotorius; (4) Feld BATh of Forel; and (5) the fibres of the fasciculus longitudinalis medialis passing into the nucleus of Darkschewitsch (Nu. f. 1. m.). In this section it will be noted that there are a few fibres making a medial capsule.

3. FASCICULUS EETROFLEXUS OF MEYKEKT.

Fasciculus The f asciculus retroflexus of Meynert is easy to follow in sections t 8 (Fig. 19). Its position and relation to the nucleus ruber are clear in the illustrations (Plates iv, vn and vm). Its nucleus of origin is outside of the limits of the model. The bundle enters on the proximal aspect of the model as a band 1 mm. wide, and passes obliquely medialward and ventralward, and plunges through the nucleus ruber and its capsule. It both enters and leaves the medial surface of the nucleus entering near the proximal border just dorsal to the middle of the nucleus and leaving near the distal border at about the middle of the dorsoventral diameter. On emerging from the nucleus the bundle immediately spreads out into a sheet more than twice as broad as the entering bundle (Plate vn). The fibres end in the borders of the fossa interpedunculare just distal to the nucleus ruber. Between the fibres are to be seen a few scattered cells, the remains of the ganglion interpedunculare. The root-fibres of the !N". oculomotorius pass through the area of the bundle as it emerges from the nucleus ruber.

In longitudinal sections the bundle is easily traced. In Fig. 16 are seen a few fibres just entering* the edge of the section. It will be noted that only the peripheral fibres of the bundle are medullated. Figs. 19 and 20 carry the bundle to the edge of the nucleus ruber, while Figs. 21 and 22 take it through the nucleus. The last trace of the bundle is seen in Fig. 23, and here the cells of the ganglion are especially clear. The transverse series does not go entirely through the nucleus ruber, so the entrance of the bundle can not be seen; however, Fig. 50 shows its fibres near the region of the ganglion interpedunculare.

4. DECUSSATIO TEGMENTI DORSALIS MEYNEKTI.

The decussatio tegmenti dorsalis Meynerti shows in Plate vm Dorsal tegmentai (Fig. 47). It lies proximal to the ventral part of the brachium conjunctivum. The course of the fibres to the decussatio is indicated in Plate iv. If the bundle in Plate iv be imagined as continued to the level of the radix descendens (m.) 1ST. trigemini, the tract can be well traced. The fibres are difficult to follow in the longitudinal series in this part of their course, but easy to trace in transverse sections. The bundle then starts just lateral to the radix descendens (m.) E". trigemini, 1 and curves across the midbrain between the brachium conjunctivum and the stratum album profundum.

1 Meynert believed that the bundle has a definite relation to this nerve. Cf. Forel, op. cit., S. 442.


The decussation is just ventral to the fasciculus longitudinalis medialis. In Plate vm it can be made out that the decussation curves so that the fibres on leaving it turn toward the spinal cord. In the longitudinal sections these fibres can be seen to pass through the brachium conjunctivum and to enter the longitudinal bundles of the formatio reticularis alba of the pars dorsalis pontis. These fibres have not been differentiated in the model from the other longitudinal bundles of the middle region of the tegmentum. 1

In tracing the fibres of this bundle in the longitudinal series, it will be easiest to begin with the decussation (Fig 1 . 19). By passing dorsalward, one can trace at the same time the fibres coming- to the decussation from the level of the radix descendens (m.) N. trigemini, and the fibres leaving the decussation to form a longitudinal path in the pons. In Figs. 16 and 18 are seen the fibres turning toward the pons. The bundles passing to the decussation do not come out in these drawings, since the fibres are delicate and are mixed with the bundles of the root of the N. oculomotorius. In Fig. 13 (D. t.), however, these fine fibres are plain.

In the transverse series the decussation is seen just ventral to the nucleus of the N. oculomotorius (Fig. 48), while the fibres passing to it are plain on Fig. 47. In this section the fibres show a broad curve and there is a space between them and the stratum profunduin album.

5. DECUSSATIO TEGMENTI VENTBALIS or FOEEL.

ventral tegmentai The decussatio tegmenti ventralis of Forel is represented at this VonL stage by a few delicate fibres ventral to the decussatio tegmenti dorsalis Meynerti. They show in Plate vm, and in Fig. 48 and in Fig. 20 (D. t).

6. STBATUM ALBUM PBOFTJNDTJM.

Deep white layer The stratum album profundum of the superior colliculus is conn ' spicuous in the model of the midbrain (Plates in, iv, v and vm). The deep white fibre layer is, in reality, a composite of fibre systems, but its shape as a whole will be considered first. It is a hollow shell that outlines the central gray matter of the midbrain (Plate m). Through the centre of the cavity of the shell passes the central canal describing the midbrain curve; the sides of the shell rest upon the fasciculus longitudinalis medialis as a base (Plate iv). As seen in Plate m, the shell is open on its distal and dorsal aspects, while at the proximal end it is completed across the midline by an arch. The arch is placed vertically (Plate vm). The side view is of value in studying its relations (Plate iv). This view shows the curve of the fasciculus longitudinalis medialis through which passes the radix N. oculomotorii. Dorsal to the


1 The fibres from Meynert's decussation have been called the descending bundle of the tegmentum, and are pictured by Eamon y Cajal. Ramon y Cajal, op. cit., S. 114.


fasciculus longitudinalis medialis stretches the lateral wall of the deep white shell. In this wall is an oval space, the distal end of which is just dorsal to the opening for the root of the oculomotor nerve. The wall is divided into two parts by a curved ridge that runs in a dorsoventral direction. This ridge lies at the junction of the middle and proximal thirds of the wall and extends dorsalward from the proximal end of the space just mentioned. Distal to the ridge is a depression, which is due simply to the prominence of the ridge. This ridge appears to mark a difference in structure between the two parts, for distal to it the wall consists of a thin flat sheet in which the fibres run longitudinally, while proximal to it is the arch of the shell in which the fibres curve across the midline. This arch, in contrast to the thin sheet below the ridge, is thick and densely packed, at least in its ventral portion. The details of the direction of the fibres are to be considered later. The distal margin of the flat sheet is marked on the external surface by a dorsoventral groove, below which pass the fibres of the radix descendens (m.) !N". trigemini. This root of the trigeminal nerve passes spinalward in about the same plane as that occupied by the deep white sheet.

The internal wall of the shell is practically the converse of the external (Plate m), for opposite the external ridge is a concavity, while just distal to it is an internal ridge. Passing spinalward from this internal ridge is the flat sheet, which runs down to a second ridge on the internal surface. This ridge lies in the lower part of the midbrain and practically limits the deep white layer. Distal to it runs the radix descendens 1ST. trigemini. The exact point at which the deep white ends and the root of the ~N. trigeminus begins has never been determined, but the model at least suggests that this ridge is the junction of two different fibre systems. The arch or commissure is to be seen in Figs. 5 and 12. In the latter the inner wall of the base of the arch comes into sight. Just at the junction of the pillars of the commissure with the fasciculus longitudinalis medialis and the proximal capsule of the nucleus ruber is the groove for the nucleus of Darkschewitsch. This groove has already been noted as opening out upon the superior capsule. The relative thickness of parts of the arch varies markedly. The ventral part contains most of the fibres. Dorsal to it is an area which shows no medullated fibres at all. The sections in this area, however, are decolorized more than the rest of the series. Just dorsal to this space is a narrow band of a few, fine, decussating fibres.

Deep white layer These form relations, namely, the external and internal ridges and the in sections. i ower limiting ridge, together with the arch over the canal, will make clear the direction of the fibres, as seen in sections. For example, between the proximal, internal ridge and the lower limiting ridge, the fibres run in a longitudinal direction and form a definitely circumscribed, though narrow bundle (Figs. 5 and 6). At the limiting groove these fibres appear to break, and distal to the groove is situated the radix descendens (m) N. trigemini. This can be traced in Fig. 5 directly to the level of the main root of the N. trigeminus, a point which is seen clearly in the model (Plate v). In section (Fig. 6) the descending root of the nerve is more broken, inasmuch as this is the level of its nucleus, of origin, which is situated in the locus cseruleus.

To return to the midbrain shell, the same two sections (Figs. 5 and 6) will show that the external ridge is made up of fibres running in a wholly different direction. Indeed, they slant into the deep white from the formatio reticularis, so that while the internal border of the deep white is definite, the external border is extremely indefinite. These fibres from (or to) the formatio reticularis slant into the ridge and decussate in the commissure.

Passing Tentralwa'rd we come to a level in which no decussating fibres can be seen, but the external ridge continues to have the same structure (Fig. 9). The next few sections, however, enter into the area of the decussation and the pillars of the arch (Figs. 11, 12 and 13). The section in Fig. 16 passes through the nucleus of Darkschewitsch at the base of the pillars of the arch. In the transverse series the stratum album profundum can be traced through Figs. 43 to 51. Certain points are brought out more clearly here than in the longitudinal series: (I) the fibres that slant into the ridge (Figs. 47 and 48), (2) the posterior commissure and its relation to the nucleus of Darkschewitsch (Figs. 50 and 51) (Nu. c. p.).

In regard to the course of these fibres the model confirms the findings of Held rather than those of Ramon y Cajal, the former stating that the fibres slant into the posterior commissure from the superior colliculus. These fibres decussate in the arch and pass down in the pillars to the nucleus of Darkschewitsch.

The fibre relations of the deep white layer have now been completed, except the fact that the space left in the lateral wall really contains fibres (Plate iv). A single section will show, however, why this space was left in the model (Fig. 12). The contrast between this section and Fig. 6 is marked, for instead of having the narrow band between the medial ridge and the N. trigeminus, as in Fig. 6, the corresponding area in Fig. 12 is evidently a place where fibres of the fonnatio reticularis alba end (or begin) in the central gray matter of the midbrain. This stratum profundum album forms the boundary of the central gray matter, and the area just described shows that at least some of its fibres are connected with the cells within. The contents of the midbrain shell are: (1) the nuclei of the oculomotor and trochlear nerves and the roots of these nerves, (2) the central gray matter, and (3) the central canal.

7. SUBSTANTIA CENTRALIS GRISEA.

The shape of the central gray matter, substantia centralis grisea, central gray is worthy of mention. Its outline is given in the model only in the m region of the midbrain, where the stratum album profundum forms a definite border for it (Fig. 6). In the medulla oblongata, however, it can be readily constructed from the shape of the floor of the fourth ventricle. Certain structures in the central gray matter have already been considered, namely, the various nuclei of the cerebral nerves. These can be divided into two groups, first, the median motor groups of nuclei, that is, of the Nn. hypoglossi, abducentes, trochleares et oculomotorii, which lie embedded in the fasciculus longitudinalis medialis on the border of the central gray matter (Figs. 6 and 12); second, certain of the sensory nuclei, namely, the superior and medial, vestibular nuclei, the nucleus tractus solitarii and the nucleus alse cinerese (Figs. 6 and 7).

Besides these nuclei connected with the cerebral nerves, there is a definite and clearly defined nucleus in the pons region. It corresponds to the descriptions of the substantia ferruginea and lies opposite the decussation of the brachium conjunctivum (Plate m, Fig. 7). In both series, and in the model as well, this nucleus is situated in the central gray matter, exactly dorsal to the fasciculus longitudinalis medialis, whereas, in ForeFs picture, it is placed slightly dorsolateral (Figs. 7 and 41).

The central gray matter of the midbrain is better developed than that elsewhere. Its shape is outlined by the stratum album profundum and the fasciculus longitudinalis medialis; it contains the nuclei of the oculomotor and trochlear nerves, as well as the nucleus of Darkschewitsch. It has been mentioned that certain of the fibres of the formatio reticularis appear to be connected with it.

To complete the description of the area of the midbrain medial to the midbrain fibre-sheet, there is left the large area which lies between the stratum album profundum and the lemniscus superior and dorsal to the nucleus ruber (Plate vm). This area contains, first, the nucleus colliculi inferioris, which has already been described, and second, the formatio reticularis of the inferior and superior colliculi. The formatio reticularis of the entire model, however, is to be considered later.

These structures, lateral from the midbrain sheet, are the substantia nigra (together with a small nucleus possibly derived from it) and the pyramidal tract.

8. THE PYRAMIDAL TRACT.

The pyramidal The pyramidal tract is non-medullated at birth, but its position ' can be related as follows: In Plate n it lies just external to the substantia nigra. (This is best seen in Quain's Anatomy, op. cit., Vol. in, Pt. i, page 42, Fig. 33; also see other text-books). It plunges through the pons (Fig. 22) and lies on the ventral surface of the medulla oblongata. Its decussation at the junction of the cord and medulla is on Fig. 21.

9. SUBSTANTIA NIGRA.

substantia nigra. The substantia nigra lies in the ventral part of the midbrain (Plate n). It is larger than the nucleus ruber. It is oblong in shape and is placed against the lateral surface of the lemniscus medialis and lateral capsule of the nucleus ruber. It lies at an angle to the long axis of the model, so that its proximal edge is farther from the midline than the distal. Just lateral to it is the area in which the pyramidal tract develops at a later stage, and though the model does not show the tract, it can readily be imagined plunging into the pons in this region.

The shape of the nucleus is fairly regular. The ventral border a straight line in the model rests upon the cellular area which the substantia nigra and the nucleus ruber have in common. The nucleus ruber can be easily outlined from this cell-mass by its color, but it is practically impossible to make a definite ventral limit in these sections for the substantia nigra. The dorsal border of the substantia nigra is curved, and, at the distal dorsal angle, the nucleus is notched to receive a bundle of fibres from the lemniscus medialis (Plate n). This bundle is shown in Plate v.


The substantia nigra is familiar in the sections ; it is to be seen in all Substantia nigrs the cross-sections of the midbrain and in all the longitudinal sections in sections. of the ventral part of the same. Its relations to the lemniscus medialis and the nucleus ruber are brought out well in both series (Figs. 19 to 24). The first two sections of the series show the bundle of fibres of the lemniscus medialis, that enters the substantia nigra. The last section shows the cell-area common to the two large nuclei of the midbrain. (Lectus substantia nigrse et nuclei rubri.) The absence of fibres except the small bundle from the lemniscus medialis is to be noted in the sections. The transverse series (Fig. 49) may be taken as a type of the nucleus. The angle, at which this section is cut, readily explains itself on the model. A cross-section taken at the extreme spinal end of the nucleus shows the bundle entering from the lemniscus medialis (Fig. 46). The connection appears to be much more intimate from this aspect than the longitudinal series showed.


Chapter IX. Formation Reticulaeis Alba et Geisea

Formatio Though the formatio reticularis is represented in the model for a ' the most part merely by a space, nevertheless certain of its relations can be made quite clear. In considering the three regions of the model, each is characterized, first, by a special form of the sensory or central fibre-mass, and second, by nuclei limited to the region. For example, the medulla oblongata has the vertical medial sheet and the olive; the pons has the horizontal sheet and the pontal nuclei, while the midbrain has the oblique-lateral sheet and the nucleus ruber and substantia nigra, which have, as has been said, a common bed of cells.

The position of the formatio reticularis has a definite relation to these main structures. It lies dorsal to the large nucleus of the region in every case. In the medulla oblongata it lies dorsal to the inferior olive and lateral to the vertical sheet; in the pons, it lies dorsal both to the pontal nuclei and to the pontal sheet, that is, the sheet forms a boundary between the pontal nuclei and the formatio reticularis. In the midbrain, the formatio reticularis lies dorsal to the nucleus ruber and the substantia nigra, but here the fibre-sheet is reversed in position as compared with the medulla oblongata, for it lies lateral rather than medial.

The reticular area of the medulla oblongata is best seen from the side (Plate v); the pontal and midbrain reticular areas from the dorsal aspect in Plate vn, and the midbrain area in Plate vm.

The intrinsic structures of the formatio reticularis are its long and short fibre-tracts and its cells, both the diffuse areas and the more or less definite nuclei.

The longitudinal section in Fig. 9 gives a comprehensive view of the entire formatio reticularis. It is bounded medially by the fasciculus longitudinalis medialis and the stratum profundum album; laterally by the nucleus funiculi gracilis and the nucleus funiculi cuneati, the corpus restiforme, the sensory cerebral nuclei and the lemniscus lateralis. In this section several points are to be noted: (1) the large number of longitudinal fibres, some of which seem to run the entire length of the formatio reticularis; (2) the comparatively even distribution of these fibres; (3) the large number of cells, and (4) the absence at this level of special groups or nuclei, for the whole area seems to be one continuous nucleus. This section may be taken as a type of the dorsal area of the formatio reticularis.

This level of the formatio reticularis is in contrast to a level farther ventral (Fig. 13). Here we have the longitudinal fibres and the cells again ; but the fibres run in fairly definite bundles and the cells form fairly definite nuclei. The first level was undifferentiated and showed fibres extending through the whole length of the medulla oblongata, pons and midbrain, while this level is distinctly differentiated and shows shorter tracts breaking up into nuclei. For example, distal to the radix 1ST. abducentis is the middle part of the medulla sheet, namely, its formatio reticularis Bundle; and proximal to the root of the E". abducens the fibrebundle turns lateral ward and splits into two parts, a medial and a lateral.

These two longitudinal fibre-bundles can be traced from the region just proximal to the E". abducens through the pons and into the midbrain; the fibres pass directly through the brachium conjunctivum. The more centrally placed of these longitudinal fibres run to the border of the central gray masses and there end abruptly, while the more lateral fibres end indefinitely in a great cell area in the midbrain, namely, the nucleus lateralis superior of Flechsig. The fibres from the decussatio tegmenti dorsalis of Meynert turn spinalward and pass through the formatio reticularis of the pons. They cannot be separated as a distinct bundle.

The formatio reticularis area of the entire section is one large nucleus; nevertheless five fairly distinct groups of cells can be differentiated within it. The first of these is the nucleus centralis inferior, which lies in the medulla sheet distal to the radix N". abducentis (Plate vi, Fig. 35). The second, the nucleus reticularis tegmenti, lies between the formatio reticularis fibres just proximal to the E". abducens (Plate vm, Fig. 40). The third, the nucleus centralis superior medialis, lies between the two medial fibrebundles in the proximal part of the pons (Plate vm, Fig. 42). In Plate vin the curve of the formatio reticularis bundle corresponds to this nucleus. The fourth nucleus is the nucleus centralis superior lateralis, which lies at the same level as the third but farther lateral. It occupies the hollow of the brachium conjunctivum (Plate vm, Fig. 42). The fifth is the nucleus lateralis superior, or formatio reticularis grisea of the midbrain (Plate vm).

As has been said, besides these fibre-bundles and nuclei, the section in Fig. 13 shows a diffuse formatio reticularis area extending throughout the section and lying lateral from the tracts just considered. This lateral area is in contrast to the lateral area of the more dorsal level. The longitudinal fibres are almost entirely wanting, their place being taken by transverse fibres or internal arcuates. These fibres are so delicate that they show better in transverse section (cf. Fig. 30). Beside the definite arcuate bunbles from the dorsal funiculi of the cord and the decussating fibres of the brachium conjunctivum, the entire area from the proximal limit of the fasciculus cuneatus to the level of the motor root of the ~N. trigeminus shows numbers of delicate arcuate fibres cut in cross-section. This area corresponds in extent to that of the tractus spinalis IN", trigemini, and doubtless many of these fibres come from its nucleus.

It will make the formatio reticularis more interesting to compare with two sections, one taken dorsal to the level of the formatio reticularis and the other ventral. In the first place Fig. 6 lies dorsal to the formatio reticularis. This might be called the level of the dorsal cerebral nuclei or the level of the central gray matter and its differentiated nuclei. The longitudinal fibres of the formatio reticularis have disappeared, and the following nuclei of the cerebral nerves are visible, the !N". glossopharyngeus, 1ST. vagus, E". acusticus, "N. facialis and "N. trigeminus. Moreover, the central area of the section is a mass of cells around the central canal. The ventral level, on the other hand, as seen in Fig. 20, is the level of the main regional nuclei, the olive, the pontal nuclei, the substantia nigra and nucleus ruber. At this level there are no nuclei of cerebral nerves nor fibres of the formatio reticularis. It is, in fact, a non-medullated area in which the motor fibres, that are soon to characterize this level (i. e., pyramidal tract), can just be seen, as lines of brown stain on the sections.

In the reticular area of the medulla are two longitudinal tracts, first, the descending bundle from Deiters' nucleus to the spinal cord (Plate v), and second, the tract described as extending from Burdach's nucleus up to the region of the nucleus ambiguus (Plate vii, Fig. 12) (Tr. fr. Nu. D. and F. c. to F. r.).

It will be noted in both of the sections (Figs. 9 and 13) that the formatio reticularis region does not reach either the proximal or the distal limit of the section; that is to say, the formatio reticularis of the model region is not connected with the cord, nor yet with the hypothalamic region at so dorsal a level. This is due to the cervical and the midbrain curves. The model shows this point well. A cross-section of the spinal cord, showing its reticular area is to be seen in Plate v. The fibres of this area must curve over the dorsal surface of the olive to enter the formatio reticularis area of the medulla oblongata. On the other hand, the proximal connection shows best in Plate vm, where the transition is made just over the dorsal capsule of the nucleus ruber. It is not necessary to say that it is impossible to limit exactly the dorsal capsule from the formatio reticularis; indeed, Forel says that the formatio reticularis enters into the formation of the capsule of the nucleus ruber. Fig. 16 shows these relations clearly, for at either end of the section is to be seen an area of formatio reticularis.

Beside the large diffuse cell-masses of the formatio reticularis and the more definite cell-groups connected with the longitudinal tracts, there are scattered in the formatio reticularis certain definite little masses of cells. They are situated on either side of the brachium conjuiictivum sheet in its ventral course from the cerebellum to the decussation (Plates in and iv).

CONCLUSION.

GENERAL SUMMARY.

It will now be possible, I think, to reduce the model to simple summary of terms, even though it may seem to be complex. As viewed from the side, the model consists, in general, of two levels a ventral J and a dorsal. The ventral level is characterized, first, by a remarkable absence of medullated fibres at this stage of development, and second, by the presence of large definite nuclei. These nuclei characterize the regions they occupy; the olive of the medulla,

Comparison the pontal nuclei, the nucleus ruber and substantia nigra in the withcSS! midbrain. This is the level and these the structures by which the medulla oblongata, pons and midbrain differ from the cord. The absence of medullated fibres speaks for the later development of these structures. This level is eventually occupied by the brachium pontis and the pyramidal tract, the fibres of which have long been laid down at this period. 1

The pyramidal tract, which develops in this level, lies wholly on the surface of this region, save where it plunges through the pontal nuclei. It lies far from the dorsal area, which represents the more developed part of the model and has no form relation to it save that the decussation makes a slight impression on the trough for the ventral horn; that is to say, the pyramidal tract has no influence in moulding the shape of other structures; it rather adjusts itself to structures already formed. In this it is in contrast to the sensory tract, which is so closely related in form to adjacent structures. This illustrates well the point which His has made, that the difference in time development determines the relative positions of structure. 2

Continuation The dorsal half of the model, on the other hand, corresponds structures, rather to the spinal cord. The easy transition of the cord into the dorsal part of the model is clear in the view of the lateral surface of the model. This level, with all its complexity, is in reality simple. It consists (1) of long tracts on the way to the cortex, (2) of long tracts to the cerebellum, namely, the brachium conjunctivum and corpus restiforme; (3) of the cerebral nuclei, their root-bundles and paths; (4) the association areas or formatio reticularis alba and grisea.

The central fibre mass is a structural unit in the form of three sheets, the medulla, pontal and midbrain, which contain the medial and lateral lemniscus, or the main sensory path toward the cortex. It contains also certain shorter tracts, the fasciculus longitudinalis medialis, the lemniscus superior and unnamed formatio reticularis fibres. Of the tracts to the cerebellum, the corpus restiforme lies on the lateral surface of the medulla oblongata, while the brachium conjunctivum, being related to the nucleus ruber, lies within the pons and midbrain.


1 Flechsig. Die Leitungsbahnen im Geblrn und Kiickenmark des Menschen, Leipzig, 1876, S. 192.

2 Die Neuroblasten und deren Entstehung im embryonalen Mark, Abhandl. d. math.-phys. Cl. d. k. sachs. Gesellsch. d. Wissensch., Bd. xv, Leipzig, 1889, S. 292.


SUMMARY: GROUPING OF CEREBRAL NERVES, ETC. Ill


The cerebral nerves are divided into two groups, a medial and a Grouping of lateral. The motor nuclei are definite, compact masses, with the C( exception of the nucleus ~N. accessorii, which represents the transition from the type of the nuclei to the spinal cord. The motor nuclei correspond to the ventral-horn cells. They are related to f ormatio reticularis areas ; the median group to the fasciculus longitudinalis medialis, the lateral to the formatio reticularis alba. The root-fibres of the lateral group, with one exception, take an indirect course to the surface, showing that they have developed in an area of complex growth. The sensory nuclei all belong to the lateral group. They correspond, in the main, to the dorsal horn of the spinal cord, and thus occupy a dorsal level. They are diffuse and cover a wide area. All but two of them, namely, the nuclei of the !N". trigeminus and !N". cochleae, lie in the substantia centralis grisea. With the exception of the nuclei N. cochleae, they border the formatio reticularis. In general, they are characterized by long descending tracts accompanied by nuclei. The nerves of the special senses do not conform wholly to the general type, for the !N". vestibuli is peculiar in its relations to the cerebellum, and the "N. cochleae in its well-developed and complex central path.

The formatio reticularis consists of mixed cells and fibres. The Formatio dorsal level represents the longer association paths of the model, rt and its cells are diffuse. In the ventral level the fibres are grouped into shorter paths and then the cells form nuclei in connection with these short bundles.

The model brings out the fact that the region is divided into four levels, as has been shown by His from a study of earlier embryos. I wish to emphasize the large number of nerves represented by nuclei in the first layer, or the substantia centralis grisea. They are (1) all of the spinal nerves through the nuclei of the dorsal funiculi, (2) the nuclei of the four motor nerves of the median group, and (3) all of the sensory cerebral nuclei of the model except the nucleus of the !N". trigeminus and the N. cochleae. The second layer, that of the formatio reticularis, includes the remaining four motor nuclei of the cerebral nerves. That this position is not primary for these nuclei, but is rather the result of development, is suggested by courses of their fibres. The third layer includes the olive, pontal nuclei, substantia nigra and red nucleus, the fourth the pyramidal tract.

The question of the origin of these four layers is one of great interest. According to His, the motor nuclei, both of the median and lateral groups, come from the ground plate, while the sensory nuclei come from the medial part of the wing plates. 1 The third layer offers an attractive field for study.

Three of its nuclei, namely, the olive, the pontal nuclei and the red nucleus, are connected with the cerebellum. In the spinal cord the cells related to the cerebellum are in the nucleus dorsalis Clarkii which lies between the dorsal and ventral horns. The origin of the olive, according to His, is from the cells of the Rautenlippe, which forms the lateral part of the wing plate adjacent to the cells which form the sensory nuclei. This serves to open up the question of the origin and relations of this ventral nuclear layer. Have these nuclei a common origin, and what is the relation of the substantia nigra to the other three?

A part of this question is being studied in this laboratory. Problems along this line have been opened up by the work of His, and I can but believe that the application of the wax-plate method to the study of the development of the central nervous system has a promising future. With a series of models, the course of development may become a matter of sight and not a theory. Moreover, all those individual differences which may be misleading in any one model can be easily eliminated when each model is but one of a series.

1 His, W., Die Entwickehing des menschlichen EautenWms. Abhandl. d. math.-phys. Cl. d. k. sachs. Gesell. d. Wissensch., Leipz., 1891, S. 1-74.

Literature

This list is designed to meet the needs of the student beginning the Study of the Central Nervous System. (It does not represent the full bibliography considered in writing the original article.)

For the development of the Central Nervous System:

His, W. Arch. f. Anat. u. Physiol., Anat. Abth., Leipz., 1893.

For a comprehensive text-book on the Nervous System:

VAN GEHUCHTEN, A. Anatome du Systeme Nerveux De L'Homme. 1897.

For general text-books :

Nervensystem. Prof. Dr. H. Ziehen (Jena), 1899; from Dr. Karl von Bardeleben's Anatomie des Menschen. OBERSTEINER, H. Anleitung beim Studium der Nervosen Centralorgane. 1896.

QUAIN'S Anatomy. Vol. in, Pt. i. The Spinal Cord and Brain. Edited by Schafer and Thane. 1895. Also Quain's Anatomy. Vol. m, Pt. n. The Peripheral Nerves.

For the development and scope of the Neurone Conception, with a full review of modern investigation and with complete literature :

BARKER, L. F. The Nervous System. 1899.

For a detailed Anatomy of the Cord and Brain :

v. KOELLIKER, A. Handbuch der Gewebelehre, Bd. n.

Leipz., 1896. For the Anatomy of the Spinal Cord :

VON LENHOSSE'K, M.

For the Tracts as studied by the Method of Successive Myelenization:

FLECHSIG, P. Die Leitungsbahnen im Gehirn und Eiickenmark. Leipzig (1876).

For the Midbrain :

FOREL, A. Arch. f. Psychiat., Berl., Bd. vn (1877), S. 393495.

For a study of the details of the Medulla Oblongata by the Golgi Method:

RAMO'N Y CAJAL. Beitrag zur Studium der Medulla Oblongata. Deutsche Uebersetz. von Bresler, Leipzig (1896). For the Acustic Nerve and its central path :

HELD. Arch. f. Anat. u. Phys., Anat. Abth., Leipzig (1891). For the paths in the cord and brain, especially Medulla and Midbrain :

v. BECHTEREW, W. Die Leitungsbahnen im Gehirn und

TMickenmark. Leipzig (1894). For Comparative Anatomy:

EDINGER, L. Yorlesungen iiber den Bau der Nervb'sen Cen tralorgane. Leipzig, 1893. Journals of Current Contributions:

Le Neuraxe, Van Gehuchten, Lou vain.

Journal of Comparative Neurology, C. J. Herrick, Granville,

Ohio, U. S. A. Brain, London, England.

Arch, fiir Psychiatric und Nervenkrankheiten, Berlin, Germany.


Abbreviations

o, Fibres running from region of lemniscus lateralis toward the dorsal border of brachium conjunctivum.

A. c. (or Aq. c., or Aq. cer.), Aquaeductus cerebri. Silvian.

  1. , Decussating portion of root of N. trigeminus. N. V.

B. c. (or Br. conj., or Brach. conj.), Brachium conjunctivum. Superior cerebellar peduncle.

B. c. (d.), Brachium conjunctivum (dorsal bundle).

C. a., Columna anterior (Columna ventralis). Ventral column. C. c., Canalis centralis.

C. i. (or Coll. inf.), Colliculus inferior. Inferior Corpora Quadrigemina.

C. p., Cornmissura posterior cerebri.

C. r. (or Corp. rest.), Corpus restiforme. Inferior peduncle.

C. s. (or Coll. s., or Coll. sup.), Colliculus superior. Superior Corpora Quadrigemina.

C. t., Corpus trapezoideum.

D. b. c. (or Dec. B. c., or Dec. Br. Conj.), Decussatio brachii conjunctivi. Decussation of superior cerebellar peduncle.

D. betw. nu. c. i., Decussation between nuclei colliculi inferioris.

D. c. n. r., Capsula dorsalis of the nucleus ruber. (Red nucleus.)

Dec. Beet., Commissure between Bechterew's nuclei. (Superior vestibular nucleus.)

Dec. 1., Decussatio lemniscorum.

D. p., Decussatio pyramidum.

D. rel. to N. V. (Same as /?.), Decussation related to N. trigeminus.

D. t. v. F., Decussatio tegmenti ventralis, of Forel.

D. t. Vide F. to d. M.

D. t. d. M., Decussatio tegmenti dorsalis Meynerti.

F. a. i., Fibrae areuatse internae.

F. a. i. (d.) (or F. a. i. (Dec. 1.)), Fibrse arcuatae internae (distal bundle) or Decussatio lemniscorum.

F. a. i. (p.) (or F. a. i. (cun.)), Fibrae arcuatae internae (proximal bundle).

F. a. i. (vest.) , Fibrae arcuatae internae, pertaining to central vestibular paths.

F. a. e., Fibrae arcuatae externae.

F. betw. B. c. & h. 1. Vide a.

F. B. c. d. Vide B. c. (d.).

F. c. (or F. cu., or Fa. cun.), Fasciculus cuneatus. Column of Burdach.

F. c. s. (or F. do.), Fasciculus cerebellospinalis. Direct cerebellar tract.

F. c. to Fr., Fibres from fasciculus cuneatus to forma tio reticularis. Column of Burdach.

F. fr. d. M., Fibres from Decussatio tegmenti dorsalis Meynerti.

F. fr. f. 1. (1.), Fibres from fasciculus lateralis (lateral group). Lateral column.

F. fr. f. 1. (m.), Fibres from fasciculus lateralis (medial group).

F. fr. 1. m. to s. n., Fibres from lemniscus medialis to substantia nigra.

F. g. (or Fa. gr.), Fasciculus gracilis. Column of Goll.

F. L, Fossa interpedunculare.

Fib. arc. int. Vide F. a. i. (p.).

F. 1., Fasciculus lateralis.

F. 1. m. (or Fasc. 1. med.), Fasciculus longitudinalis medialis. Posterior longitudinal bundle.

F. 1. p., Fasciculus lateralis proprius. Lateral ground bundle.

F. 1. p. (d.), (or F. 1. p. (4)), Bundle continuous with fasciculus lateralis of the cord.

F. p. (or F. Py.), Fasciculi longitudinales pyramidales. (In Fig. 36 F. p. is Fibrse pontis.) Pyramidal tract.

F. r. a., Formatio reticularis alba.

F. r. M. (or Fasc. retrof.), Fasciculus retroflexus Meynerti.

F. sc. dl., Fasciculus cerebellospinalis dorsolateralis. Direct cerebellar tract.

F. to d. M. (or F. to d. t. d.), Fibres to decussatio tegmenti dorsalis Meynerti.

F. v. c. (i.), Fibres connecting vestibular area with cerebellum (inner or medial group).

F. v. c. (o.), Fibres relating the vestibular area with the cerebellum (outer or lateral bundle).

F. v. 1., Fasciculus ventrolateralis. Ventrolateral column.

F. v. p., Fasciculus ventralis proprius. Ventral ground bundle.

L. c. nu. r., Capsula lateralis nuclei rubri.

L. 1. (or Lemn. lat.), Lemniscus lateralis.

L. m., Lemniscus medialis.

L. nu. r., Lectus nuclei rubri. Bed of red nucleus.

L. s., Lemniscus superior.

Med. obi., Medulla oblongata.

Mesenc., Mesencephalon.

Mot. V. Vide N. V (m.).

N. c. Vide N. VIII (Coch.).

N. 1. 1., Nucleus lemnisci lateralis.

N. Ill, Eadix N. oculomotorii.

N. IV (or N. troch.), Eadix N. trochlearis.

N. V, Eadix N. trigemini.

N. V (dec.). Vide/?.

N. V (m.), or N. Mot. V, Eadix N. trigemini (motor).

N. V (s.) (or N. Sen. V), Eadix N. trigemini (sensory).

N. VI, Eadix N. abducentis.

N. VII, Eadix N. facialis.

N. VII p. p. (or VII (a.)), Eadix N. facialis, pars prima.

N. VII p. s. (or N. VII (c.)), Eadix N. facialis, pars secunda.

N. VII g. (i.) (or N. VII (b.)), Eadix N. facialis genu internuin.

N. VIII (coch.) (or N. c.), Eadix N. cochleae.

N. VIII (vest.) (or N. vest.), Eadix N. vestibuli.

N. IX & X, Eadices N. glossopharyngei et vagi.

N. XI, Eadix N. accessorii.

N. XI p. p., Eadix N. accessorii, pars prima.

N. XI p. s., Eadix N. accessorii, pars secunda.

N. XII, Eadix N. hypoglossi.

Nu. a., Nucleus arcuatus.

Nu. a. c., Nucleus alae cinerese.

Nu. c., Nucleus coluxnnaris.

Nu. c. i., Nucleus colliculi inferioris, Figs. 43 and 44. In Fig. 13, Nu. e. i. = Nucleus centralis inferior.

Nu. com., Nucleus commissuralis.

Nu. c. p., Nucleus commissurse posterior, or nucleus fasciculi longitudinalis medialis. Posterior longitudinal bundle.

Nu. c. s. (1.), Nucleus centralis superior, pars lateralis.

Nu. c. s. (m.), Nucleus centralis superior, pars medialis.

Nu. d., Nucleus dentatus.

Nu. f. c. (or Nu. f. cu., or Nuc. f. cun.), Nucleus funiculi cuneati.

Nu. f. c. (1.), Nucleus funiculi cuneati lateralis (Blumenau).

Nu. f. g. (or Nucl. f. gr.), Nucleus funiculi gracilis.

Nu. f. 1. m., Nucleus fasciculi longitudinalis medialis or nucleus commissurae posterioris (oberer Oculomotoriuskern or Darkschewitsch) .

Nu. g., Nucleus globosus.

Nu. 1. s., Nucleus lateralis superior of Flechsig.

Nu. N. c. d. (or Nu. N. cochl. cl.), Nucleus N. cochleae dorsalis.

Nu. N. c. v., Nucleus N. cochleae ventralis.

Nu. N. v. 1. (or Nu. N. vest. 1.), Nucleus N. vestibuli lateralis.

Nu. N. v. m. (or Nu. N. vest, m.), Nucleus N. vestibuli medialis (Schwalbe).

Nu. N. v. s. (or Nu. N. vest, s.), Nucleus N. vestibuli superior (von Bechterew).

Nu. N. Ill, Nucleus N. oculomotorii.

Nu. N. Ill, 1., (or Nu. N. Ill (a.)), Nucleus N. oculomotorii, pars lateralis.

Nu. N. Ill, m. (or Nu. N. Ill (b.)), Nucleus oculomotorii (medial nucleus).

Nu. N. IV, Nucleus N. trochlearis.

Nu. N. V, Nucleus N. trigemini.

Nu. m. m. N. V, Nuclei motorii minores N. trigemini.

Nu. m. p. N. V, Nucleus motorius princeps N. trigemini.

Nu. N. VI (or Nucl. N. abd.), Nucleus N. abducentis.

Nu. N. VII, Nucleus N. facialis.

Nu. N. XII (or Nucl. N. hyp.), Nucleus N. hypoglossi.

Nu. N. XII, a. K., Nucleus of Holler.

Nu. o. a. d., Nucleus olivaris accessorius dorsalis. Accessory olive.

Nu. of r., Nucleus of the roof.

Nu. o. a. m., Nucleus olivaris accessorius medialis.

Nu. o. i., Nucleus olivaris inferior. Olive.

Nu. o. s., Nucleus olivaris superior. Superior olive.

Nu. o. s. 2, Nucleus olivaris superior, at its junction with the nucleus lemnisci lateralis.

Nu. r., Nucleus ruber. Eed nucleus.

Nu. r. t., Nucleus reticularis tegmenti.

Nu. t. s. (or Nu. tr. sol.), Nucleus tractus solitarii.

Nu. x. of 1. c. of nu. r., Nucleus capsulse lateralis nuclei rubri.

Nu. y., Anterolateral extremity of nucleus of N. vest, medialis.

P. f., Pedunculus flocculi.

Py., Pyramis. Pyramid.

R. d. N. V, Radix descendens (mesencephalica) N. trigemini.

R. d. N. vest, (or Rad. desc. N. vest.), Radix descendens N. vestibuli.

R. 1., Recessus lateralis ventriculi quarti. Lateral recess of fourth ventricle.

S. 1., Transverse series.

S. 2., Horizontal series.

S. a., Striae acusticse.

S. a. p. (or St. a. p., or Str. alb. p., or St. alb. p.), Stratum album profundum.

Sen. V. Vide N. V. (s.).

S. f., Substantia ferruginea.

S. g. (or Sub. gel., or Sub. gel. Rolandi), Substantia gelatinosa Rolandi.

S. i. 1. (or St. i. 1.), Stratum interolivare lemnisci. (In Fig. 20 extend the line through the olive.)

S. n., Substantia nigra.

St. g. c. (or St. gr. c.), Stratum griseum centrale. Central gray matter.

T. fr. D. to c. (or Tr. fr. nu. D.), Tract from Deiters' nucleus to the funiculus lateralis to lateral column.

T. s. ( (or Tr. s., or Tr. sol.), Tractus solitarius.

T. s. N. V (or T. s. n. t., or Tr. s. n. t., or Tr. s. N. V), Tractus spinalis N. trigemini.

V. q., Ventriculus quartus.



Description of Figures and Plates

Figs. 3-24. Series of horizontal sections passing through the medulla, pons and midbrain of a new-born babe. The series is traced from the dorsal to the ventral surface. The following sections, Figs. 6, 7, 9, 12, 13, 16 and 19 are after Barker, L. F.: The Nervous System and its Constituent Neurones. D. Appleton & Co., 1899. (Preparations by Dr. John Hewetson.)

Figs. 25-51. Series of transverse sections passing through the medulla, pons and midbrain of a new-born babe. The series is traced from the spinal cord toward the cerebrum. The following sections, Figs. 25, 28, 31, 33, 35, 36, 39, 41, 42, 46 and 49 are after Barker, L. F.: Op. cit. (Preparations by Dr. John Hewetson.)

Fig. 52. KEY TO PLANES OF SECTIONS.

PLATE I.

Fig. 1. View of the dorsolateral and lateral surfaces of the nucleus olivaris inferior. F. dl. Facies dorsolateralis. F. 1. Facies lateralis. F. p. Fissura prima. F. s. Fissura secunda. F. t. Fissura tertia. F. q. Fissura quarta. L. p. Lobus primus. L. s. Lobus secundus. L. t. Lobus tertius. L. q. Lobus quartus.

Fig. 2. View of the ventral surface of the nucleus olivaris superior. S. p. Sulcus primus. S. s. Sulcus secundus. S. t. Sulcus tertius.

PLATE II.

View of the model from the lateral surface. This view is designed to relate the model to the cord, the cerebellum and the cerebrum. The cut edge of the cord shows on the extreme right. The following points will make the position of the model clear: the dorsal and lateral funiculi and the dorsal horn of the spinal cord, the cerebellum, the fourth ventricle, the inferior and superior colliculi and the third ventricle.

The color system is as follows: all fibres are in white and black, all nuclei in colors. Red represents the nuclei of the motor cerebral nerves, blue the nuclei of the sensory cerebral nerves and yellow all other nuclei.

Nu. et Radix N. vestibuli: The nucleus is distinguishable from the root by its color. The ascending and descending parts of the root are to be determined by their relation to the entering root-bundle of the nerve. The part of the vestibular nucleus distal to the nucleus N. abducentis is the nucleus N. vestibuli medialis; the part proximal, is the nucleus N. vestibuli superior. The nucleus N. vestibuli lateralis (Deiters'), (pars lateralis) lies in the vestibular tract just dorsal to the corpus restiforme. 9


122 DESCRIPTION OF FIGURES AND PLATES

PLATE III.

View of the model from the dorsal surface. On the right side is shown the floor of the fourth ventricle; on the left, the structures beneath are exposed. The position of these structures can be related to the dorsal funiculi of the spinal cord, the fourth ventricle, and the inferior and superior colliculi.

Nu. et Radix N. vestibuli: To be distinguished by the colors. The ascending root is marked by the most proximal of the three lines on the figure; the descending by the most distal line, while the nucleus N. vestibuli medialis is indicated by the middle of the three lines. The nucleus N. vestibuli superior is continuous with the medial nucleus and lies opposite the ascending root. The nucleus 1ST. vestibuli lateralis consists of two parts, one between the corpus restiforme and the ascending root, the other in the notch between the medial and superior nuclei.

Nucleus N. cochlew dor sails: The more proximal of the two lines points to the striae acusticae.

Traotus solitarius et Nu. alas cinerce: The former is in black and white, the latter in blue.

PLATE IV.

View of the model from the lateral aspect. After removing from Plate i, the following structures: the corpus restiforme, the substantia nigra and the medial, lateral and superior lemnisci. The view is designed to show (1) the sensory nerves and their nuclei, and (2) the midbrain. The nuclei of the dorsal funiculi represent a way-station for the sensory fibres from the spinal cord; the sensory cerebral nerves are represented by the nuclei nervi glossopharyngei, vagi, vestibuli et trigemini. These include all of the sensory nerves of the region of the model except the N. cochleae, which was removed with the corpus restiforme.

Radix N. trigemini (Sens.) : The proximal line runs to the root bundle, the distal to the tractus spinalis N. trigemini.

Tract from Betters' nucleus to F. i. (3), and Fasciculus lateraMs (4): The numbers are explained in the text.

PLATE V.

View of the model from the lateral aspect. The sensory nerves of Plate iv have been removed and all of the motor cerebral nerves except the N. trochlearis are now shown.

Fasciculus lateralis (2), and Fasciculus lateralis (3): The numbers are explained in the text.

PLATE VI.

View of the lateral surface of the medulla sheet. The view can be related to Plates n, iv and v, by the position of the nucleus N. abducentis. Fasciculus ventrolateralis (1): The number is explained in the text.

PLATE VII.

View of the model from a dorsomedian aspect. This view is designed to show the central fibre mass, that is, the medulla, pontal and midbrain sheets, together with the corpus trapezoideum.

. Fibres running from Lemniscus lateralis to the brachium conjunctivum.


DESCRIPTION OF FIGURES AND PLATES 123

PLATE VIII.

View of the midbrain from the superior or cerebral aspect. This view can be understood by comparing 1 it with Plates n, iv and v, which show the stratum profundum album, the lemniscus superior and the capsula nuclei rubri from the lateral aspect.

7 is a space in the model, in the stratum profundum album where fibres of the formatio reticularis alba are related to the substantia centralis grisea.

Fasciculus ventrolateralis (1) : The number is explained in the text.


HORIZONTAL (Frontal) SECTIONS 38, 56 and 62.



(126)


HORIZONTAL (Frontal) SECTIONS 66, 72 and 74.



Q26)


HORIZONTAL (Frontal) SECTIONS 80, 86 and 94.



(127)


HORIZONTAL (Frontal) SECTIONS 100, 108, 114 and 116.



(128)


HORIZONTAL (Frontal) SECTIONS 122 and 126.



(129)


HOKIZONTAL (Frontal) SECTIONS 128 and 136.



J

~



(130)


HORIZONTAL (Frontal) SECTIONS 146 and 162.



(131)


HOEIZONTAL (Frontal) SECTIONS 170, 180 and 202.



be


CROSS-SECTIONS 20-84.




be



CKOSS-SECTIONS 94-146.



f



(134)


CROSS-SECTION 158.



(135)


CEOSS-SECTION 170.



N_^JJ


(136)


CROSS-SECTION 182.



(137)


CROSS-SECTION 190.



p ml


(138)


CKOSS-SECTIONS 200 and 212. Na.mp.n.T.


B.c.



C.t.


Urn.


Fig-. 38, Series II, Section No. 200.



I(SPflS)


Lm.,


Fig. 39, Series II, Section No. 212.

(139)


CKOSS-SECTIONS 254 and 268.



Fig. 40, Series II, Section No. 254.



Fig-. 41, Series II, Section No. 268.


(140)


CROSS-SECTIONS 290 and 304.


Nu.


St.gr.



Fig-. 42, Series II, Section No. 290.


D.betw.nax.L

NiLcl.



11


Fig. 43, Series II, Section No. 304. (141)


CROSS-SECTIONS 316 and 330.


S.CL.p,.

NU.C.L



Fig-. 44, Series II, Section No. 316.


a



JS.a.p A.C-.


N n

Ill .J-V


Fig. 45, Series II, Section No. 330.


(142)


CEOSS-SECT1ONS 338 and 354.



Bec.Br.Con]. J


Fig-. 46, Series II, Section No. 338.



n.m


-S.n.



Fig-. 47, Series II, Section No. 354.


(143)


CKOSS-SECT1ONS 372 and 384.


L.S,



NHL

Fig. 48, Series II, Section No. 372.


Aq.cer.


St. gr. c



Fig. 49, Series II, Section No. 384.


(144)


CROSS-SECTIONS 396 and 420.



Fig-. 50, Series II, Section No. 396.



TtM.

JUL

Fig-. 51, Series II, Section No. 420.


(145)


GUIDE TO SECTIONS IN SERIES 1 and 2.



(146)


INFERIOR OLIVE.


PLATE I.


Lateral Surface.


T.i


Dorsal



Veatrul


FIG. 1.


Ventral Surface.


Lateral



Mesial


FIG. 2.


LATERAL SURFACE a OF MODEL. |

!~


PLATE II.



s I

26

III


i o

I!


I

6" 11


DORSAL SURFACE OF MODEL.


PLATE III.


Stratum album profundum


Nucleus N. oculomotor!!


Commissurae nuclei coll;


Fasciculus retroflexus (Meynerti)


Lemniscus medialls...


Nucleus colliculi inferloris . .


Radix N. trochlearls __ A

Brachium conjunctivum

Radix descendens

N. trigemini

Locus caeruleus.

Radix N. trigemini (Mot.) Radix N. trigemini (Sens.) ,


Nucleus motorius princeps N. trigemini


Nucleus N. trigemini (Sens.)

Nucleus N.

vestibuli lateralis f|

Corpus restiforme


Nucleus et radix N. vestibuli


Nucleus N. cochleae dorsalis


Corpus restiforme


Tractus solitarius et nucleus alae cinereae ""


Nucleus funiculj cuneati .-"

Fasciculus cuneatus . Nucleus funiculi gracills ....

Fasciculus gracilis



Nucleus N.


.Substantia fei .Ventriculus qu


Brachium con;


Corpus restiforme


-Radix N. facial! --Nucleus N. abd


- fasciculus long


--Nucleus olivaris i


--Nucleus N. hypog


INTERIOR OF MODEL FROM SIDE (one layer removed).


PLATE IV.


<



FURTHER DISSECTION OF INTERIOR OF MODEL FROM SIDES.


PLATE V.



LATERAL VIEW OF MEDULLA SHEET.


PLATE VI.



RELATIONS OF LONG TRACTS.


Capsula superior nuclei rubri


PLATE VII.


Radix N. oculomotor! i Nucleus ruber


Fasciculus retroflexus (Meynerti)


Lemniscus lateralis*


Fasciculus longitudinalis medialis- Formatio reticularis alba -,Nucleus olivaris superior^

Radix N. facialiSx \

Nucleus N. abducentis -s^.-l


Striae acusticseNucleus N. cochleae dorsalis


Radix N. vestibuli

Corpus trapezoideum ,*'*'

Radix N. cochleae- ' Nucleus olivaris inferior -;

Nucleus funiculi cuneati


Fasciculus cuneatus to formatio reticularis


Nucleus funiculi gracilis



Lemniscus

medialis


Corpus ,- 'trapezoideu


^Nucleus oli' ' superior


Stratum interolivare lemnis --- Nucleus N. hypoglossi


Nucleus olivaris accessorius rr "Decussatio lemniscorum


Canalis centralis Substantia gelatinosa (Rolandi)


THE MIDBRAIN FROM ABOVE.


PLATE VIII.


Commissure between Bechterew's nuclei Corpus trapezoideum and nucleus olivaris superior,


Brachium conjunctivum (dorsal bundle)


Brachium conjunctivum


Decussatio tegmenti dorsalis .


Capsula dorsalis nuclei rubri


Decussatio tegmenti dorsalis


Decussatio tegmenti ventralis



Nucleus N. abducentis


Fasciculus longitudinalis medialis

Nucleus reticularis Kucleus colliculi inferioris


Capsula nuclei colliculi inferioris


Position of nucleus N. trochlearis Lemniscus superior V

Position of nucleus N. oculomotor!! ^Stratum album profundui

7' Lemniscus medialis Commissura posterior


Fasciculus retroflexus (Meynerti)


tiapsula superior nuclei rubrl


/ Nucleus Fasciculus longitudinalis medialis fasciculi

longitudinalis medialis


Lectus nuclei rubri


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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)


An Atlas of the Medulla and Midbrain (1901): Chapter I. Introductory | Chapter II. The Long Tracts | Chapter III. The Columns Of The Spinal Cord | Chapter IV. Cerebellar Peduncles | Chapter V. The Cerebral Nerves And Their Nuclei | Chapter VI. The Cerebral Nerves And Their Nuclei (Continued). Lateral Group | Chapter VII. The Inferior And Accessory Olives | Chapter VIII. The Midbrain | Chapter IX. The Formatio Reticularis Alba And Grisea | General Summary of what Is shown In Reconstruction | References To Literature | Abbreviations | Description of Figures and Plates


Cite this page: Hill, M.A. (2021, May 11) Embryology Book - An Atlas of the Medulla and Midbrain. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_An_Atlas_of_the_Medulla_and_Midbrain

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