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A MANUAL

of

ANATOMY

By

HENRY ERDMANN RAt)ASCH, M. Sc, M. D.

ASSISTANT PROFESSOR OF HISTOLOGY AND EMBRYOLOGY IN
JEFFERSON MEDICAL COLLEGE; INSTRUCTOR IN ANATOMY IN
THE PENNSYLVANIA ACADEMY OF FINE ARTS, PHILADELPHIA

WITH 329 ILLUSTRATION'S

PHILADELPHIA AND LONDON

W. B. SAUNDERS COMPANY

1917

il

Copyright, iqit, by W. B. Saunders Company

DEDICATED
TO

MR. DANIEL BAUGH

PREFACE

This book was originally intended as a Visceral Anatomy for the
use of first-year medical students. Although there are numerous and
excellent anatomies published, they are all large and voluminous.
There being a need for an anatomy of intermediate size, the original
manuscript has been enlarged at the suggestion of the publishers.
Chapters in Osteology, Syndesmology, and Myology have been
added and the chapters on the Blood-Vascular and Nerve Systems
have been extended so as to include the appendages and their
plexuses, thereby making this work desirable for medical students,
medical preparatory students and nurses.

The anatomy and histology of the nerve system is taken up in a
manner different from that used in most anatomies. The external
anatomy is continued from one segment to another, uninterruptedly,
and the histology is taken up in the same manner. In this way the
student has a more connected idea of the parts and their relations
to one another. In addition the various pathways are given sepa-
rate and rather full consideration, so that impulses may be traced,
in a connected manner, from origin to termination.

The semilunar valves of the aorta and pulmonary artery are
described in all anatomies under the ventricles, without justification
from a standpoint of anatomy and embryology. In this work they
are described in their respective vessels, where they should be
taken up.

Although the B. N. A., as a whole, is not all that could be desired
this nomenclature is given in parentheses. The author has used the
terms ventral and dorsal instead of anterior and posterior, respec-
tively, in order to avoid confusion arising between anatomists
and embryologists. The latter use the terms anterior and posterior
exclusively for head and tail directions, and not synonymously with
ventral and dorsal. For this reason the author uses cephalad and
caudad for headward and tailward, discarding anterior and posterior
altogether and avoiding confusion arising in comparative anatomy.

The illustrations of the first three chapters are from Sobotta and
McMurrich's work. Many of those of the visceral portion are
adapted from standard works as Cunningham, Gray, Piersol, Morris
and Rauber-Kopsch. A number of the illustrations were made
from photographs of organs and preparations at the Daniel Baugh
Institute of Anatomy and Biology.
13

14 PREFACE

The author desires to thank Dr. J. J. Fauz for his assistance in
the preparation of the photographs and some of the drawings and
Mr. Smoczynski for his assistance in the preparation of the outlines
of the organs; also the publishers for their suggestions and many
courtesies.

H. E. Radasch.

Malvern, Pa.,

July, 191 7.

CONTENTS

CHAPTER I

Page
Osteology 17

CHAPTER II
Syndesmology 108

CHAPTER III
Myology 143

CHAPTER IV
Blood-Vascular System 211

CHAPTER V
Lymph-Vascular System • 252

CHAPTER VI
Respiratory System 271

CHAPTER VII

Alimentary Tract 282

CHAPTER VIII
Urinary System 316

CHAPTER IX
Male Organs of Reproduction .... 324

CHAPTER X
Female Organs of Reproduction 330

CHAPTER XI

Ductless Glands 338

IS

CONTENTS.
10

CHAPTER XII

Eyeball and Lacrimal Apparatus.

CHAPTER XIII

Page

■ 341

CHAPTER XIV

358

\i 1 \ 1 System

A MANUAL OF ANATOMY

CHAPTER I
OSTEOLOGY

The skeleton is a framework of bone and cartilage that serves for
the attachment of the muscles. The axial portion comprises the
head and trunk and is comparatively rigid or fixed, while the appen-
dicular portions, the appendages, are extremely mobile; the bones of
the extremities represent a system of levers actuated by the muscles
and acting upon the joints, which constitute the fulcra. The human
skeleton is an endoskeleton which is more or less completely invested
by the muscles and completely covered by the skin.

The adult skeleton comprises 206 individual bones arranged as
follows:

Single bones Pairs Total
f The vertebral column 26 . . 26

The ribs 12 24

Axial Skeleton j The sternum 1 1

The skull 6 822

I The hyoid bone 1 1

/ Pectoral appendage 32 64

Appendicular Skeleton' D , . ,

rr l Pelvic appendage 31 62

Auditors- Ossicles 366

206

Bone is a derivative of the mesoderm and represents the most
highly differentiated of the connective tissues. It is mainly a sec-
ondary tissue as in most instances it is derived from cartilage. It
consists of cells and intercellular substance. The latter is a hard,
tough resistant, yet elastic substance to which the peculiar charac-
teristics of bone are due. Osseous tissue consists of about 66 per
cent, of inorganic, or earth salts and of 34 per cent, of organic mate-
rial. The inorganic salts comprise phosphates, carbonates and
fluorid of calcium, also chlorid of sodium and phosphate of mag-
nesium. The organic material includes fats, collagen, etc. If a
fresh bone be burned or calcined, the organic material will be re-

l8 OSTEOLOGY

moved and a porous cast of the bone, representing the earthy salts,
will remain. If a bone be subjected to the action of a mineral acid,
the earthy material is removed and flexible bone, representing the
organic substances, remains. The elasticity and toughness of the
bone is due to the organic substance while the inorganic salts impart
hardness to it.

. *■<

Fig. I. — Portion of a cross-section of a decalcified human radius. X about 4.8.
(Sobotta and Huber, " Atlas of Human Histology.) The figure shows the lamellar systems of
compact bone, as well as some trabecular of spongy bone, agl, periosteal lamellar; igl, peri-
medullary lamellae; il. interstitial lamellar, hi. Haversian lamellar; p, periosteum; sp, trabec-
ular of spongy bone.

Fresh bone upon examination shows the presence of an enveloping
membrane, the periosteum. This is tough, does not strip readily
and serves for the attachment of muscles and tendons. The articu-
lar portions of a bone are covered with hyalin cartilage. Cleaned
specimens are devoid of these two structures.

In order to study bone under the microscope it must be decalcified
and sectioned, or pieces must be ground so thin that their structure
is readily discernible.

STRUCTURE OF BONE 19

There are t-dio varieties of bone, compact and cancellous.

The compact variety is the more abundant and exhibits a char-
acteristic structure. Surrounding all bones there is a fibrous sheath,
the periosteum. This consists of white fibrous connective tissue and
its deep layer is rich in blood-vessels and cells, the future osteoblasts.
From its inner layer bundles of fibers (Sharpey's) penetrate the
bone. The real osseous tissue is arranged in four varieties of
lamellae and between the lamellae are the lacunae and canaliculi.

1. The periosteal lamella are few in number and lie just beneath
the periosteum. These constitute the circumference of the bone
and between them are the lacunae, containing osteoblasts, and the
canaliculi. Howship's lacuna are on the surface and canals (Volk-
mann's) pierce the layers and transmit blood-vessels for a short
distance.

2. The Haversian lamella are hollow cylinders of bone that fit
into one another, the central one containing the Haversian canal.
The number in a system varies from three to eight. Between the
layers are the lacunae and canaliculi. The Haversian canals of the
various systems anastomose with one another. These canals are
for the transmission of blood-vessels.

3. The intermediate lamella fill in the areas between the cylindrical
Haversian systems. They are irregular in course and contain
lacunae and canaliculi.

4. The perimedullary lamella are irregular in number and extent
and when present they are seen on the marrow-cavity surface of the
bone and are comparable to the periosteal lamellae.

The lacuna are irregular, stellate spaces and contain the osteo-
blasts. The canaliculi serve to connect the various lacunae together
and to support the processes of the osteoblasts.

An osteoblast is an irregular, stellate cell with a flattened body.
Its processes are numerous, but short and heavy. These cells have
to do with the formation of osseous tissue, but in what manner they
do it is unknown.

Compact bone constitutes the shafts of the long bones, covers their
extremities and forms the outer portion of the short, irregular and
flat bones.

Cancellous bone consists of delicate bars of osseous tissue that
form a network resembling a sponge. Lacunae, canaliculi and osteo-
blasts are present but Haversian systems are absent. This variety
is found in the ends of the marrow-cavity of the long bones, forms
the bulk of the extremities of these bones and of the flat, short and
irregular bones. This variety imparts lightness and permits of an
increase in size without sacrificing strength.

The medullary, or marrow-cavity, is long, narrow and contains the
marrow; it is found in the shafts of the long bones. It is lined by

20 OSTEOLOGY

the endosteum which serves as an internal periosteum and a covering
for the marrow.

Bone Marrow. — In the adult there are two varieties of bone marrow,
red and yellow. In early life only red marrow is found. The red
marrow consists of a delicate network of reticulum connected with
the endosteum. It supports various cellular elements and blood-
vessels, nerves and lymphatics. The cellular elements are as follows:

i. Myelocytes are large, nucleated masses of granular protoplasm
that exhibit ameboid movements. These are seen only in marrow
under normal conditions.

Fig. 2. — Blood. Elements of the bone-marrow of a mouse. X 700. {Sobotta and
Huber. "Atlas of Human Histology.") The preparation was taken from the femur of a full-
grown mouse. 1. Polynuclear giant-cell (myeloplax); 2-7, marrow-cells; 2, marrow-cell
with annular nucleus (goes through the nuclear stage of 4 into that of 3 — that is. into the
ordinary polymorphonuclear cell") ; 4 and 5. acidophile cells; 6 and 7, mitoses; 8, ordinary ery-
throcyte; o and io, nucleated erythrocytes.

2. Erythroblasts are nucleated red blood cells and are very numer-
ous as the red marrow is practically the only tissue in which they
are formed.

3. Erythrocytes are normal red blood cells that have just been
formed from the preceding and are ready to go into the blood stream.

4. Leukocytes are white blood cells and are of the finely and
coarsely granular eosinophilic and basophilic types.

5. Myeloplaxes, or osteoclasts, are large, irregular masses of proto-
plasm that may contain one or more nuclei. They are bone-destroy-
ing cells and are of great importance in the growth and repair of
bone. They are capable of ameboid motion and are also phagocytic
in action.

6. Osteoblasts are mentioned in bone marrow but they are chiefly
at the periphery and are not essential to the marrow.

Fat is seen in small quantities in red marrow but predominates in
yellow marrow.

In the adult, red marrow is found in the extremities of the long

BONE DEVELOPMENT 21

bones and in the centers of the flat and irregular bones, or wherever
cancellous bone is found.

Yellow bone marrow is the result of the deposition of a great quan-
tity of fat in the red marrow of the shafts of the long bones. As a
result the cellular elements are greatly reduced and its function as
a seat of blood-cell formation is practically nil. It is found only in
adults.

Serous, or mucoid marrow results when the fat and cellular elements
are absorbed and replaced by a serous infiltrate, as in old age, starva-
tion and certain diseases. It thereby loses its function of making
blood cells.

Bone Development. — There are two methods, endochondral and
mtramembranous.

In the endochondral form the hyalin cartilage is replaced by osseous
tissue. All of the bones of the body except those of the face and
vault of the cranium are said to be formed by this method but the
endochondral bones are really formed by a combination of the two
methods, as will be seen. The point at which bone formation first
begins is called the center of ossification. There are several of these
centers for each of the bones and these will be considered later.

At the center of a ossification the cartilage cells reproduce rapidly
and arrange themselves in rows parallel to the long axis of the bone
(proliferation). Calcareous salts are deposited in the cartilage
partitions and most of the cartilage cells disappear (calcification).
New cells, chondroclasts , appear and destroy some of the partitions,
forming a series of small spaces called primary areola. Osteoblasts
gain access to these spaces and lay down a thin veneer of osseous
tissue upon the cartilaginous and calcareous partitions. The peri-
chondrium becomes the periosteum and its cells form a layer of
periosteal bone. Blood-vessels and osteoblasts penetrate the little
bone and enter the areolae which have been converted into a fewer
number of larger spaces by the destruction of many of the partitions
(vascularization). The first, or primary marrow, is then formed.
The blood-vessels and osteoblasts proceed toward the extremities
of the little shaft, almost to the area of proliferation. Gradually
all of the calcareous material of all of the partitions is removed and
replaced by osseous tissue. After this no more cartilage appears in
the changed area. Each extremity is ossified from an independent
center at a later date so that a pad of cartilage, the epiphyseal disc,
intervenes between the shaft and each extremity until the bone has
reached its full length. Then this disc ossifies and the parts are
united so that this area can no longer be distinguished. The bone
continues to grow in length by cartilage being formed a little more
rapidly, in the epiphyseal disc, than it is converted into bone. The
bone grows in diameter by the continual addition of new layers of

OSTEOLOGY

periosteal bone. After a number of periosteal lamellae have been
formed, osteoclasts destroy all of the central cancellous bone and
establish the primary adult marrow-cavity. They continue to de-
stroy the oldest or innermost periosteal lamellae but less rapidly
than the new ones are formed upon the outside. As a result the
marrow-cavity is formed and continues to grow at the expense of
the compact bone but never as rapidly as the bone is formed. In
the meantime Haversian systems are being formed from the perios-
teal lamellae, and the remnants of the latter constitute the irregular
lamella;.

PK

Fig. 3. — Bone development. Portion of a longitudinal section of a metacarpal bone of a
five-month embryo. X so. (Sobolta and Huber. "Alius of Human Histology.") Outside
in the perichondrium (periosteum) is a layer of periosteal bone. eK, bone formed by endo-
chondral ossification; A"». cartilage; Km, zone in which the cartilage cells are arranged in
rows; Km, zone of enlarged cartilage cells and calcification of ground substance; KnR,
remains of calcified cartilaginous matrix. M, marrow; pK, bone formed by periosteal ossi-
fication; Rz, giant-cells (osteoclasts).

In the extremities of the long bones and in the flat and irregular
bones no marrow cavity is formed. The cancellous tissue practi-
cally remains and is added to by the constant honeycombing action
of the osteoclasts upon the innermost periosteal lamellae. In this
manner the central portions of these bones always remain cancellous
and are covered by only a thin layer of compact bone.

In intramembranous bone formation ossification occurs without the
intervention of cartilage. At the- center of ossification (say of a
skull bone) the mesodermal cells form a membrane from which
fibers radiate in all directions and upon which calcareous material is
deposited. The inner and outer boundary layers of this membrane
become somewhat denser and constitute the periosteum. These

CLASSES OF BONES 23

layers give rise to the osteoblasts that secrete osseous tissue as above,
forming periosteal lamellae and a veneer for the calcareous trabeculae.
More periosteal lamellae are added and the process spreads gradually
in all directions. The calcific material is removed and replaced with
bone and osteoclasts honeycomb the innermost or oldest layers of
periosteal bone thereby increasing the amount of cancellous bone.
The thin covering of compact bone constitutes the tables of the skull
bones.

Bones are usually classified, as to shape, as long, flat, short and
irregular. The long bones (ninety) are found in the extremities and
include the femur, tibia, fibula, humerus, radius, ulna, clavicle, meta-
carpal and metatarsal bones and the phalanges. The name indi-
cates the presence of a central, more or less cylindrical portion called
the diaphysis, or shaft, and two more or less expanded portions the
epiphyses, or extremities. The diaphysis is a hollow cylinder of
compact bone that contains the yellow marrow in the adult. In the
longer examples of this class the shaft is not straight but curved,
thereby greatly strengthening the bone. The epiphyses are usually
enlarged for articulation and muscle attachment. Each consists of
a thin covering of compact bone surrounding a mass of cancellous
bone that contains red marrow throughout life.

The flat bones (thirty-eight) are the scapulas, ossa coxae, sternum,
ribs, frontal, vomer, parietals, nasals, lacrimals and patellae. These
are adapted for protection and consist mainly of a central mass of
cancellous bone covered by a thin layer of compact bone. In the
cancellous bone red marrow is found throughout life.

The short bones (thirty) are the carpal and tarsal bones. These
serve to give strength to the parts and yet permit limited motion.
Each consists of a central mass of cancellous bone, containing red
marrow, surrounded by a layer of compact bone.

The irregular bones (thirty-eight) comprise the vertebrae, tem-
porals, sphenoid, zygomatics, maxillae, palatals, conchals, ethmoid,
hyoid and sacrum. These are very irregular in shape and also con-
sist of a mass of cancellous bone, containing red marrow, surrounded
by a layer of compact bone. Some parts of these bones, however,
are so thin as to be nearly transparent and these portions contain
no cancellous bone.

Some place the patellae and hyoid bones and the auditory ossicles
(incus, malleus, and stapes) as unclassified bones. Wormian bones
are found along the cranial sutures but are inconstant. Sesamoid
bones are found in certain tendons of the muscles of the extremities;
they are variable in number.

Very few of the bones show extensive smooth areas, but lines,
crests, ridges, spines, tubercles, processes, protuberances and the like
are seen. On the other hand, depressions of various kinds, as pits,

24 OSTEOLOGY

fossa, cavities, furrows, grooves, fissures, and foramina, or canals,
sinuses, or air spaces are seen. Each serves its purpose as will be
pointed out in each bone.

THE VERTEBRAL COLUMN (COLUMNA VERTEBRALIS)

The vertebral column comprises twenty-six individual bones in
the adult; in early life thirty-three are present but certain ones fuse
as will be indicated later. These bones are the vertebrae and they
are classified as true, or movable and false, or fixed.

True, or movable False, or fixed

Cervical 7 Sacrum (5 fused)

Thoracic 12 Coccyx (4 fused)

Lumbar 5

A typical vertebra comprises the body (ventral segment ), the neural
arch (dorsal segment) and a number of processes.

The body [corpus vertebra-) is the largest part but varies in size and
form in the different segments of the vertebral column. It is nearly

-spinous process

transverse process

„ „ ■ „ /. < superior t'crlebral notch
Superior articular pv'rv

SupfrwrSL7ac\Yjl^\!rarS ""' /""'

Fig. 4. — A vertebra seen from above.
(Sobotta and McMurrich.)

Inferior Ami -fa, it hifi
forkeud of rib

Fir., s. — A vertebra seen from the side.
(Sobotta and McMurrich.)

cylindrical in shape and its superior and inferior surfaces are flattened
or slightly concave, to accommodate the intervertebral discs. Ven-
trally and at the sides the body is concave from above downward,
as well as from side to side. The dorsal surface is concave from side
to side. All parts exhibit numerous foramina that transmit the
nutrient vessels of the bones.

The neural arch (arcus vertebra) is formed by the two roots of the
vertebra and two lamina. The pedicles, or roots of the vertebral arch
(radix arcus vertebra ) are two flattened bars of bone that pass dorsally
from the body to the points of attachment of the articular processes.
As these processes are not of the same height as the body, a distinct

VERTEBRAL COLUMN 25

notch is formed between the body and the articular processes, above
and below these roots. These are the superior and inferior inter-
vertebral notches {incisurce vertebra superior et inferior). In the articu-
lated vertebral column these become the intervertebral foramina for
the transmission of the spinal nerves and vessels.

The lamina are two, flat, rather broad, sloping plates of bone which
extend dorsally, converge toward the midline and fuse with the root
of the spinous process. These serve to complete the neural arch
which, with the body, forms the vertebral or spinal foramen.

The processes are muscular and articular. The muscular processes
are as follows: The transverse processes, two in number, vary in size
and function in the different vertebrae. They extend laterally from
the junction of the root of the arch and the lamina of each side. The
spinous process is that mass of bone that extends dorsally, in the
median plane of the body, from the junction of the fused laminae.
Its shape, size and direction varies in the different segments of the
vertebral column.

The articular processes (zygapophyses) are four in number, two
superior and two inferior. These are placed upon the upper and
lower parts of the neural arch at the junction of the roots of the
arch and laminae. Each superior process (processus articularis supe-
rior) projects superiorly and faces, generally, dorsally. Each inferior
process (processus articularis inferior) project interiorly and faces,
generally, in a ventral direction. These directions, however, differ
in the various regions.

THE CERVICAL VERTEBRAE

The cervical vertebras are seven in number and are the smallest
of the true vertebrae. The first and second are considerably modi-
fied and the seventh somewhat so. In all, the transverse processes
are perforated by a foramen.

The body is oblong and the dorsoventral dimension is greater than
the transverse. The superior surface is markedly concave from side
to side and slopes dorsoventrally. The lateral margins are sharp
and project superiorly while the ventral edge is rounded and smooth.
The inferior surface is concave, dorsoventrally, and convex from side
to side. The ventral edge overlaps the vertebra beneath. The
ventral surface of the body is mainly flat but becomes concave at the
sides. The dorsal surface is flat and rough and presents numerous
foramina. At the superior part of the lateral surface of the body is
attached the transverse process. Each is pierced by the transvi
foramen {foramen transversarium) and consists of two parts, one
dorsal and the other ventral to the foramen. The dorsal portion
arises from the vertebral arch and represents the true transverse
process; the ventral portion represents the ribs of the thoracic region.

26 OSTEOLOGY

These are united by a small bar of bone that completes the foramen
and each division terminates in a small tubercle called tubcrcula
a ntcr ins et posterius. These processes are grooved for the accommoda-
tion of the spinal nerve trunks. The vertebral artery and vein pass
through the transverse foramina of the superior six cervical verte-
brae. The roots of the vertebral arches arise from the middle of the
side (dorsal portion) of the body and are directed dorsally and later-
ally, in a horizontal direction. Above and below these are the
intervertebral notches. The lamina are rather long and broad;
they fuse in the midline dorsally. The spinous processes are short,
bifid, flattened from above downward and are dorsally directed.
The articular processes are dorsal to the transverse processes. The

Fig. 6. — The fifth cervical vertebra seen from above. (Sobolla and MrMurrich.)

facets are circular and the superior face upward and dorsally, while
the inferior face downward and ventrally.

The Atlas. — This is the first cervical vertebra and it possesses
neither body nor spinous process. It consists of two lateral masses con-
nected to each other by a ventral and a dorsal arch. Each lateral mass
is irregular and its ventral end is closer to the midline than the dorsal
end. Superiorly it possesses an oval articular facet {fovea articular is
superior) that receives a condyle of the occipital bone. Each facet is
concave and slopes dorsally and toward the midline. The inferior
articular facets (fovea artiadares inferior •&?) are circular and nearly
flat. Each surface faces downward and toward the midline. Upon
the medial surface of each lateral mass there is a small tubercle to
which the transverse ligament of the atlas is attached. Behind each
tubercle is a nutrient foramen. The ventral arch (arcus anterior) is
thickest in the middle forming here, on its ventral surface, the ventral
tubercle (tuberculum anterior) ; its dorsal surface exhibits a facet {fovea
dentis) for articulation with the dens of the epistropheus or axis.
The dorsal arch (arcus posterior) arises from the lateral mass and
transverse processes. At its origin it is flattened from above down-
ward and bounds a groove, dorsal to the articular facet, that extends

VERTEBRAL COLUMN

27

to the transverse foramen. This groove is occupied by the vertebral
artery and suboccipital nerve. The dorsomedian part of the arch
may present a small tubercle (tuberculum posterior) which represents
a rudimentary spinous process. Each transverse process arises from
the lateral mass by two roots that are united, enclosing the trans-
verse foramen. The anterior and posterior tubercles are usually
fused into one. The extremely large vertebral foramen of the atlas is

Posterior tubercle

Transverse process

Foramen transv

divided into two portions by the transverse ligament that extends
between the two median tubercles. The smaller ventral division
contains the dens of the epistropheus while the larger dorsal portion
accommodates the spinal cord.

The Epistropheus. — This is the second cervical vertebra and it

Odontoid process

(anterior articular
facet)

(epistropheus), fr.

. front. (Sohotta and McMurrich.)

possesses a tooth-like process called the dens. The superior part of
its body is continued as the dens. The apex of this process is blunt,
and to it are attached the alar ligaments. Where it joins the body
of the vertebra, the process is constricted and its dorsal surface at this
region is smooth and grooved to accommodate the transverse liga-
ment. The ventral surface of the dens has a facet for articulation

28 OSTEOLOGY

with the dorsal surface of the ventral arch of the atlas. The inferior
surface is somewhat concave and slopes sharply downward and over-
laps the body of the third cervical vertebra. The ventral surface of
the body is irregular and has a ridge that extends onto the neck of
the dens. The dorsal surface is flattened and presents numerous
foramina. The roots of the vertebral an lies are deeply grooved, in-
feriorly, but superiorly they support the superior articular facets.
The laminae are short and thick and form the short, bifid spinous
process. Each transverse process slopes downward and has but one
terminal tubercle. The superior articular processes cover the roots of
the vertebral arches. They are nearly circular, flattened or slightly
concave; they face upward and a little laterally. Dorsal to each is
a groove in which the second cervical nerve courses. The inferior
articular facets are nearly circular and face inferiorly and forward or
ventrally. These lie dorsal to the transverse processes.

The seventh cervical vertebra is called the vertebra prominens
because its spinous process projects beyond the level of the other
vertebras. This process is not bifid. The transverse processes are
wider and more prominent than those of the sixth vertebra. The
foramen does not usually transmit the vertebral artery as it is too
small. The ventral tubercle is small and the costal element may be
separate, constituting a cervical rib.

THE THORACIC VERTEBRjE (VERTEBRA THORACALES)

The thoracic vertebrae are twelve in number and they articulate
with the ribs. The body of a thoracic vertebra is usually described
as heart-shaped. The superior and inferior surfaces are slightly
concave or flattened, smooth and rimmed. The ventral and lateral
surfaces are concave from above downward and rough. The body is
thicker behind than in front, thus forming the thoracic curve of the
vertebral column (concavity ventrally directed). Dorsally it is
concave and shows numerous foramina. Near the junctions of the
roots of the arches and the body (along the superior and inferior
margins) there are four costal facets (fovea costales) two superior and
two inferior. In two successive vertebrae the contiguous facets
accommodate the head of a rib.

The roots of the vertebral arches slope upward and backward so that
the superior intervertebral notch is slight and the inferior notch is
deep. The laminae are flat and broad and slope downward and out-
ward, thus overlapping those of the vertebra below. The vertebral
foramen is circular and smallest in this portion of the vertebral
column as this portion of the spinal cord is smallest in diameter.
The spinous processes vary; in the upper part of the thoracic region
they are short and nearly horizontal, while in the lower part they are

VERTEBRAL COLUMN 20.

longer, heavier and successively more oblique. Each may possess a
tubercle at its extremity.

The transverse processes are larger in the upper thoracic vertebra?
and gradually decrease in length. They are directed laterally and
dorsallv. Near the extremity of each there is a concave facet for
articulation with the tubercle of the rib.

The superior articular facets are nearly vertical, facing dorsallv
and a little laterally. The inferior facets are directed downward
and face ventrally and a little medially.

The first thoracic vertebra resembles, somewhat, a cervical verte-
bra. The superior costal facet is more on the side of the body; the

Inferior facet for.head of rib

)

Spinous process
Fir,. o. — The sixth thoracic vertebra from the side. (Sobotta and McMurrich.)

transverse processes are quite long and the superior intervertebral
notches are well marked. The superior articular facets are more
sloping and are directed upward and dorsallv.

The ninth thoracic vertebra has usually no inferior costal facets.

The tenth thoracic vertebra has only a superior costal facet and the
facet upon the transverse process is small or absent.

The eleventh thoracic vertebra has one costal facet below the
superior margin and none upon the short transverse process.

The twelfth thoracic vertebra has one costal facet upon the root
of the vertebral arch. The transverse process is thick and presents
a number of tubercles resembling those of the lumbar vertebrae.
Its inferior articular processes face laterallv.

THE LUMBAR VERTEBRA (VERTEBRAE LUMBALES)

The lumbar vertebrae are the largest of the true vertebrae and are
five in number.

The body is reniform and the ventrodorsal dimension is about
half the transverse dimension. The superior and inferior surfaces
are smooth and somewhat concave and rimmed. The ventral and

3°

OSTEOLOGY

lateral surfaces are quite concave from above downward and show
numerous foramina. The dorsal surface is concave from side to side
as well as from above downward. The body is slightly thicker
behind than in front giving a curve to this part of the column, with
the convexity forward. The roots of the vertebral arches are directed
dorsally and are short and thick. Both intervertebral notches are
well marked. The laminas are broad and nearly vertical. The
vertebral foramen is large and triangular. The spinous process is
short, flat and broad; each is directed dorsally and slightly down-
ward. The transverse processes are somewhat slender and are directed
laterally and horizontally. In the successive vertebra? the lamina?

Superior articular process

Transverse process

Fig. io. — The third lumbar vertebra seen from above. (Sobotta and McMurrich.)

arise at a more ventral level from the roots of the vertebral arches.
They apparently represent the costal elements of the thoracic ver-
tebrae. Upon the dorsal surface of each transverse process are the
accessory tubercles. The superior articular processes are oval and lie
at the junction of the roots of the arches and the lamina. The
articular facets are concave, vertical and face medially. The inferior
articular processes are at the inferior margin of each lamina at the
root of the spinous process. The oval and nearly flat facets face
laterally. These processes are nearer the median plane than are
the superior ones and so are overlapped by these when articulated.
The fifth lumbar vertebra has the largest body. Its ventral
vertical dimension is much greater than the dorsal vertical measure-
ment and so assists the sacrum in forming the sacrovertebral angle.
The transverse processes are pyramidal in shape and arise from the
sides of the body and the vertebral arches. The superior articular
facets are directed more dorsally than medially. The inferior facets
face ventrally and laterally and are in a line with the superior pro-
cesses. The spinous process is short and narrow.

THE SACRUM 3 1

Ossification. — The vertebra are of endochondral origin and each develops
irom four primary (two for the lamina and two for the body) and three secondary
centers, usually. The centers for the lamina appears during the sixth week of
fetal life and spread into the base of the spinous process, the roots of the arches
and the transverse processes. The centers for the body appear during the
eighth week and these centers soon fuse. At birth the vertebra consists of three
parts. During the first year the laminae fuse dorsally (in the lumbar region
first and then upward) and during the third year the body and laminae fuse.
The secondary centers appear at about the sixteenth year. There is one for the
tip of each transverse process and one for the tip of the spinous process. All parts
are fused into one mass by the twenty-fifth to the thirtieth years.

The number of centers for the atlas is variable (two to five). Usually three
centers appear, one for each lateral mass (sixth week of fetal fife) and one for the
ventral arch (end of the first year).

The epistropheus is usually developed iromfive or six primary and two secondary
centers. The primary centers are one for each lamina (seventh to eighth week),
one (or two) for the body (fourth month) and two for the dens (sixth month).
During the second year a secondary center appears for the apex of the dens and
this unites with the main mass at about the twelfth year. The oilier center is
for a thin epiphyseal disc on the inferior surface of the body.

THE FIXED OR FALSE VERTEBRjE

The sacrum represents the fusion of five vertebrae. It is said to be
roughly triangular in shape (better like a curved wedge). Its ventral
or pelvic surface is smooth, concave from side to side as well as from
above downward. It presents four transverse ridges that terminate
at the ventral sacral foramina. These foramina extend laterally as
shallow grooves and dorsally they communicate with the vertebral
canal. That portion on each side lateral to the foramina constitutes
the lateral mass (pars lateralis). Its lateral surface (upper part) is
large and ear-shaped (articular surface) and articulates with the os
innominatum on each side. Dorsal to this area is the sacral tuber-
osity. The superior surface articulates with the fifth lumbar verte-
bra; it resembles that vertebra in this part and possesses superior
articular processes.

The dorsal surface is rough, convex from above downward and
shows a median as well as two pairs of lateral ridges and four pairs of
dorsal sacral foramina. The crest (crista sacralis media) is in the
midline and consists of the spinous processes of the upper four sacral
vertebra;. The fifth spinous process is absent and the lamina; sepa-
rated so that the vertebral canal is exposed. This gap is the hiatus
sacralis. Lateral to the crest is the sacral groove on each side. This
groove is bounded laterally by a crista sacralis articularis, which is
formed by the row of fused articular processes. Lateral to each
crest is a row of dorsal sacral foramina through which pass the dorsal
branches of the sacral spinal nerves. Lateral to the foramina is a
row of tubercles forming the lateral ridge (crista sacralis lateralis) of
each side. This represents the transverse processes of the true

32

OSTEOLOGY

Superior articular iirja-a

Fig. ii. — The sacrum seen fr

\

Apex of sacrum

front (pelvic surface). (Sobotta and McMurrich.)

Superior articular process Sacral canal

FlG. 12. — The sacrum seen from behind (dorsal surface). (Sobotta ami McMurrich.)

THE COCCYX 33

vertebrae. The sacral cornua are the downward-projecting inferior
articular processes of the last sacral vertebra. The apex of the
sacrum represents the oval body of the fifth sacral vertebra.

The sacral canal is flattened dorsoventrally and curves with the
bone. It communicates with the dorsal and ventral sacral foramina.

The sacrum of the. female is shorter, broader and less curved than
in the male. In the male it is directed more obliquely backward.

Ossification. — The sacrum has thirty-five centers of ossification. The body
of each segment has three centers, each arch two, the lateral mass has six (two for
each of the first three segments) and each of the lateral surfaces has two centers.
The first centers appear during the eighth or ninth week of fetal life and all are
fused between the twenty-fifth and thirtieth years.

Muscles Attached. — To the ventral surface the mm. pyriformis, the coccygeus
and part of the iliacus. To the dorsal surface the mm. gluteus maximus, the
latissimus dorsi. sacrospinalis and multifidus.

THE COCCYX (OS COCCYGIS)

The coccyx represents the fusion of four rudimentary vertebrae.
The first segment is the largest and the others are successively smaller.
The superior surface of the first segment shows an oval concave facet

First coccygeal vertebra
Second coccygeal vertebra

Fig. 13. — The coccyx seen from in front. (Sobotta and McMurrich.)

that articulates with the sacrum. The dorsal surface presents two
upward-projecting processes [cornua coccygea) representing articular
processes for articulation with the cornua sacralis. These assist in
forming two foramina for the fifth pair of sacral nerves. Laterally
this segment presents a rudimentary transverse process on each side.
The second may also present such processes but the remaining seg-
ments are rudimentary nodules of bone.

Ossification. — The coccyx is developed from four centers, one for each segment.
That for the first segment appears during the first to the fourth years, the
second, from the fifth to the tenth years, the third, from the tenth to the fifteenth
and the fourth, from the fourteenth to the twentieth years. The fusion of the
parts is complete about the thirtieth year.

Muscles Attached. — To the dorsal surface the m. gluteus maximus; to the
lateral margin the mm. coccygeus and levator ani on each side; to the tip the
m. sphincter ani externus.

34

OSTEOLOGY

THE VERTEBRAL COLUMN AS A WHOLE

When the vertebrae are articulated a peculiarly curved, and for
the most part movable, column is formed. The adult vertebral
column averages from 27J-2 inches to
28% inches (70 to 73 cm.) in length,
in the male, and in the female about
23% inches (60 cm.). The individual
parts in the male are as follows: cervical,
13 to 14cm.; thoracic 27 to 29 cm.;
lumbar, 17 to 18 cm.; sacrococcygeal,
12 to 15 cm.

The ventral part consists of the bodies
of the vertebrae that serve as a support
for the head and trunk. The verte-
bral arches and laminae form the ver-
tebral canal that contains the spinal
cord and its membranes. This canal
is largest in the cervical and lumbar
regions and is open at the last sacral
segment. At the side of the column
the intervertebral notches now form the
intervertebral foramina through which
the roots of the spinal nerves pass.
The first two cervical foramina are
dorsal to the articular processes and
the remainder (as far as the sacrum)
are ventral to these processes. Dor-
sally the spinous processes produce a
dorsal median ridge and the transverse
processes a lateral ridge, on each side.
As a result a groove is formed on each
side of the median ridge called the ver-
tebral grooves and these are occupied by
the muscle that operate the vertebral
column.

Curves are also noted. When viewed
from the ventral surface the vertebral
column may have a slight lateral curve
in the thoracic region with the con-
vexity to the right; this is due, prob-
ably, to the greater use of the right side
and right upper extremity or by pressure
exerted by the thoracic aorta upon the thoracic vertebrae. Viewed
from the side the vertebral column presents four dorsoventral curves,

Fig. 14. — The vertebral colu
seen from the left side. (Sobolta
and UcMurrich.)

THE STERNUM 35

cervical, thoracic, lumbar and sacral. The thoracic and sacral are
primary curves, existing during fetal life, while the other two are
acquired curves; they are formed after the child begins to walk. The
cervical curve is slight and has its convexity ventral; the thoracic
curve is marked and its concavity is ventrally directed. The lower
part of this curve becomes continuous with the lumbar curve which
is also marked and has its convexity ventrally directed. The sacral
curve has its concavity ventrally directed and from its length is the
deepest and most marked curve. The sudden dorsal curve of the
first segment of the sacrum causes the fifth lumbar vertebra to form
a prominent projection called the sacrovertebral angle.

THE STERNUM

The sternum constitutes the middle portion of the ventral bound-
ary of the thorax and is a fairly long, flat and thin bone; it is pointed
at its inferior extremity, constricted near its middle and consists of
three parts, the manubrium, body and xyphoid process.

The manubrium, or handle, is the superior portion and its ventral
surface is smooth and somewhat saddle-shaped. To it are attached
the mm. pectoralis major and sternomastoideus. Its superior margin
is thickened and uneven exhibiting a median notch, the suprasternal
notch, or incisura jugularis, that is more pronounced when the clav-
icles are in position. On each side of this notch there is an oblique
facet for articulation with the clavicle, the incisura clavicularis.
Just inferior to this another facet is noted, on the lateral margin,
for articulation with the cartilage of the first rib. Inferior to this
the bone becomes narrower.and the inferior corner is absent, forming
a facet with a like area upon the next portion of the sternum, for
the second costal cartilage. The inferior margin of the manubrium
is connected with the second segment by cartilage or it may be fused
with it. The dorsal surface is smooth and slightly concave and shows
numerous foramina. It affords attachment to the mm. sterno-
hyoideus and sternothyroideus.

The body (corpus sterni) is the middle and longest segment. It is
nearly flat from side to side and convex from above downward.
Its superior portion is narrower than the inferior part. The ventral
surface (planum sternale) is smooth but shows three more or less
marked transverse ridges that indicate the four segments that fuse
to form this portion of the sternum. It affords attachments to the
m. pectoralis major upon each side. The superior margin is attached
or fused to the manubrium forming an angle at the junction that is
usually appreciable to the touch. This is the sternal angle (angulus
sterni). The lateral portions of this margin complete the facet for
the second costal cartilage. The inferior margin is convex and its

3°

OSTEOLOGY

middle part is connected to the xyphoxd process. Latera to th
the sixth and seventh costal cartilages are attached. Each lateral
margin is thick and irregular presenting facets at the extremities
of the ridges that accommodate the third, fourth and fifth costal
cartilages The dorsal surface is concave from above downward and
may exhibit the transverse ridges. Its superior portion affords
attachment to the m. transversus thoracis, or triangularis sterm,
while the remainder is in relation with the pericardium and pleura.
The xvPlwid process (processus xyphoideus) is the smallest segment
and variable in form. Its base is attached to the body of the sternum

Jugular notch

Clavicular

notch " -^ x

■

first rib I

Manubrium

Notch for >— -^yar
second rib - ^Bi iiJx.

Notch for _ ).£'.

third rib V

{

Notch for

fourth rib .'«g \

Body of sternum

> -

Notch for EM /

fifth rib

Notch for lSjC"' g

sixth rib ^W^ k 1

Notch for yvS

seventh 'rib ' jPIrl

Xiphoid process

Fic. IS— The sternum seer, from in front. 'SoboUa and McMurrich.)

while its apex affords attachment to the linea alba of the abdomen.
The process slopes dorsally forming the pit of the stomach, or ,n,r-
sterZl depression. To its lateral margins the aponeuroses o the
abdominal muscles are attached, while the dorsal surface .afford, at-
tachment to a portion of the m. transversus thoracis and diaphragm.

In the male the sternum is longer and broader than m the female
its direction is more oblique and variations of the different segments
are also noted.

Ossification -The sternum is an endochondral bone and the cartilaginous
stem mf formed bv the fusion of two lateral bars. Ossification begms dunng
™h month of fetal life with the appearance of the center for the manubrium.

THE RIBS 37

Secondary centers may appear for the clavicular facets. The body develops
from four single, or double centers (one for each segment) and their appearance
usually follows that for the manubrium; the last one appears just before birth.
One center appears for the xyphoid process during the third year. The seg-
ments of the body fuse between early childhood and the twentieth to the twenty-
fifth years. The manubrium and body may never fuse while the body and
xyphoid process fuse at about the fortieth to fiftieth years.

Muscles Attached. — The mm. pectoralis major, sternohyoidens, sternothy-
roideus, transversus thoracis the diaphragm and the aponeuroses of the mm.
obliquus internus abdominis, obliquus externus abdominis and transversalis
abdominis — nine pairs.

THE WBS (COSTE)

The ribs, or hemal arches, twelve in number on each side, form a
bony protection for the thoracic contents. They are movable as
they articulate with the thoracic vertebrae, dorsallv, and with the
costal cartilages, ventrally; by means of the latter they are connected
with the sternum. The first seven constitute the true ribs [costm
vera) as their cartilages articulate individually with the sternum.
The remainder are called false ribs (costm spuria); of these the carti-
lages of the eighth, ninth and tenth ribs join that of the seventh rib
[vertebrochondral ribs) while the costal cartilages of the eleventh and
twelfth ribs are free at their ventral extremities [floating ribs).

A typical rib presents a head, neck, tubercle, shaft and angle. The
head (capitullum costae) is slightly enlarged and represents the dorsal
or vertebral extremity of the rib. Its medial surface has an articular
facet divided by a ridge [crista capituli) into a larger inferior portion
that rests in the superior facet of the body of a thoracic vertebras
(from which it takes its number) ; the smaller superior facet articu-
lates with the inferior facet of the body above. -To the crista is
attached the interarticular ligament. The neck (collum) is a nar-
row part of the rib connecting the head to the shaft and here a
tubercle is seen dorsally. The ventral surface of the neck is smooth
and the dorsal surface roughened for the attachment of the ligaments
of the neck. The superior margin may present a ridge for the attach-
ment of the ventral costotransverse ligament. The inferior margin
is smooth and continuous with the costal groove.

The tubercle is on the dorsal surface of the rib at the junction of
the neck and shaft. It presents an oval articular portion that faces
inferiorly and dorsally. It articulates with the facet on the trans-
verse process of a thoracic vertebra. The nonarticular portion
affords attachment to the fibers of the ligament of the tubercle. A
groove, occupied by the lateral division of the dorsal branch of a
thoracic spinal nerve, separates tubercle from shaft and neck.

The shaft is thin, curved and band-like. It varies in length in the
different ribs. The seventh and eighth are the longest and the first

3§

OSTEOLOGY

the shortest. The curvature is not uniform but varies in the different
regions and gives the peculiar shape of the thorax. From the tuber-
cle the rib proceed first laterally and at a variable distance in the
different ribs, then it turns rather sharply in a ventral direction.
This change of direction produces the angle (angulus costa). The
distance from tubercle to angle is greater in the eighth rib and nil in
the first rib. The rib is also twisted so that the ventral end is at a
lower level than the head, when the rib is placed upon a plane surface.
This is most noticable in the seventh and eight ribs and least in the
first and last ribs.

The shaft is flattened and has two surfaces, lateral and medial.
The lateral surface is smooth and convex and faces according to the
part of the thorax in which it is placed, i.e. , superiorly in the upper part,
laterally in the middle of the thorax and slightly downward in the
lower part. The medial surface is smooth and faces in the opposite

Fig. i 6.— The

nth rib of the left

from within. (Sobolta and McMurrich.)

direction. The superior margin is thick and rounded and affords
attachments to the mm. intercostales externus et internus. The
inferior margin is sharp and dorsally it is grooved; here it forms the
costal groove {sulcus costalis) which disappears ventrally. The in-
ferior margin, between the angle and the tubercle, is ridged and
affords attachment to the m. iliocostalis. The costal groove contains
the intercostal vessels and the lip affords attachment to the external
and internal intercostal muscles. In the groove are seen the nutrient
foramina that are directed toward the vertebral extremity.

Peculiar Ribs. — The first rib is the smallest. The head is small
and the head articulates with only one vertebral body, the first. The
neck is short and flattened from above downward. The tubercle,
at the junction of the neck and shaft, is prominent and bears a small
facet, on its under surface, for articulation with the transverse process
of the first thoracic vertebra. The angle and tubercle are coincident.
The medial margin is thin and presents, near its middle, the tubercu-
lum scaleni; this margin affords attachment to Sibson's fascia. The
superior surface is uneven and at the tubercle area a ridge passes ven-.
trally and laterally separating two grooves; the ventral, deeper, one
is for the subclavian vein, while the dorsal one is for the subclavian

THE COSTAL CARTILAGES

39

artery and ventral division of the first thoracic nerve (sulcus sub-
clavian). Dorsal to the latter groove the surface is roughed for the
attachment of the m. scalenius medius. The inferior surface is
smooth and covered with pleura. The lateral margin is thickened
and rough dorsally for attachment of the first digitation of the m.
serratus anterior.

In the second rib there is no twist and the surfaces are turned so
that they are obliquely directed. The head presents two facets and
the angle is distinct from the tubercle. The lateral surface presents
a roughened area for the attachment of part of the first and the entire
second digitation of the m. serratus anterior. The margin likewise
affords attachment to the external and internal intercostal muscles.

On the tenth rib there is only one facet on the head and usually
none on the tubercle.

Fig. 17. — The first ri
and McMurrich.)

Fig. 18. — The second
and McMurrich.)

Tubers-
Tubercle

b of the right side seen from above and from the side. (Sobotta
rib of the right side seen from above and from the side. (Sobotta

On the eleventh and twelfth ribs the heads show only one facet; the
tubercles and angles are faint. The ventral ends are pointed and
tipped with cartilage. Both ribs are short.

Ossification. — The ribs are of endochondral origin and each rib is developed
from three centers, except the last two pairs. The center for the shaft appears
during the ninth or tenth week of fetal life. The centers for the head and the
tubercle appear about the sixteenth to the twentieth years. Fusion is complete
about the twenty-fifth year. The last two ribs have tuv centers each, one for
the shaft and one for the head.

Muscles Attached. — The mm. intercostales interna et externi, scalenus an-
terior, scalenus medius. scalenus posterior, pectoralis minor, serratus anterior,
latissimus dorsi, diaphragma, quadratus lumborum, obliquus externus ab-
dominis, serratus posterior superior, serratus posterior inferior, iliocostalis lum-
borum, iliocostalis dorsi, iliocostalis cervicis, longissimus, levatores costorum
and infracostales (nineteen).

THE COSTAL CARTILAGES

The costal cartilages are the bars of cartilage attached to the ribs,
on the one hand, and on the other directly or indirectly to the

}o

OSTEOLOGY

sternum, except the eleventh and twelfth pairs. The first seven pairs
articulate with the sternum at the designated notches and usually a
synovial membrane exists at the joints. The eighth, joined by the
ninth and tenth cartilages, on each side, is attached to the seventh
cartilage. The eleventh and twelfth are small and merely tip these
ribs. The cartilages increase in length from the first to the seventh
and then again shorten. Their direction and obliquity vary as can
be noted in the illustration.

THE THORAX AS A WHOLE

The thorax or chest consists of a framework of bones and cartilages.
Between the ribs lie the intercostal muscles and membranes com-

Fig. 19. — Ventral

pletely closing these intervals. The thorax has the shape of a trun-
cated cone, flattened from before backward, shorter in front than
behind. It presents four walls, or boundaries, dorsal, two lateral and
ventral ; it has two apertures, superior and inferior.

The dorsal wall consists of the twelve thoracic vertebra; and the

THE FRONTAL BONE 41

ribs to their angles. On each side of the midline is seen a deep groove,
the vertebral groove. The bodies of the vertebra? project into the
cavity of the thorax and reduce its dorsoventral dimension markedly.
The lateral walls consist of the shafts of the ribs. The ventral wall
consists of the sternum and the costal cartilages. This wall is the
shortest and slopes downward and forward.

The superior, or cephalic aperture, is kidney-shaped, about 4 inches
(10 cm.) from side to side and about 2 inches (5 cm.) dorsoventrally.
Its boundaries are as follows: dorsally, the body of the first thoracic
vertebra; laterally, the first ribs; vent rally, the upper margin of the
sternum. This aperture slopes downward and forward so that its
ventral margin is on a level with lower border of the body of the
second thoracic vertebra, in the male, and in the female at the lower
border of the third thoracic vertebra. The main structures trans-
mitted are the esophagus, trachea, thoracic duct, the innominate,
left common carotid and left subclavian arteries, the right and left
innominate veins, the vagal, phrenic and sympathetic nerves and the
apex of each lung covered by the cervical extension of the parietal
pleura.

The inferior, or caudal aperture is not a true aperture as it is closed
in by the diaphragm. Its boundaries are as follows: dorsally the
body of the twelfth thoracic vertebra; laterally the twelfth ribs;
ventrally the eleventh, tenth, ninth, eighth and seventh costal carti-
lages. These joined cartilages sloping upward and inward form with
their fellows of the opposite side the subcostal angle at the midline.

The thorax is widest at the level of the eight or ninth ribs, deeper
behind than in front and deeper on the left than on the right side.
In the female the capacity is less, the ribs more movable, the inlet has
a greater slant and the sternum is shorter than in the male. Upon
transverse section the thorax is kidney-shaped.

THE BONES OF THE SKULL (OSSA CRANII)

This portion of the skeleton, comprising the entire head, is made
up of twenty-two bones; it is divided into cranium cerebrate and
cranium viscerate. The cranium cerebrale consists of fifteen bones,
the occipital, sphenoid, ethmoid, frontal, parietal (two), temporal
(two), inferior nasal conchas (two), lacrimal (two), nasal (two), and
vomer. The cranium viscerale consists of the ossa faciei which are
the mandible, maxillae (two), zygomatic (two), palatal bones (two).
The hyoid bone will be described in this section.

THE FRONTAL BONE (OS FRONTALE)

The frontal bone constitutes the front part of the cerebral cranium
and consists of frontal, orbital and nasal portions.

OSTEOLOGY

and convex ventrally. Upon ea h -ronta, luberosity. The

marked part of the convex^onsntute, £ ^ ^ ^

tyertor HMrxM presents an arch on m ^supraorbital

b>' r Ted rStSSSX^ Processesf laterally
„„/(•/; or A"*"™. Each arch i si o . ]ls arches upward

is the zygomatic process from which the hm at mpo _

and backward upon the temporal portion of the bone <g £

dfa). This surface is smooth and ~ncave and conrtr ut- P
of the temporal fossa and here the «^?S2iSS articulates
the arch is bounded by the ««feri ^f^^X processes lies
with the nasal bone. Between the two -ed.aUngular^

Frontal eminence

Supercilt

arch

Nasal portion Frontal spine
Fig. 20.— The frontal bone seen from in front.

Zygomatic
'process
Supraorbital margin
Supraorbital notch
(Snbotta awi McMurriM

From this the supcrcilhary arch {anus stipercunan* ,

S - o^tal portion £ars orb i^compri ^ — L
arched part on each ^ f the m ^ Jn Q^A and sepa

ra^t^t^

to this is the nasal notch from ^."^^Satea with the
projects downward as the rontal #g **ef™*n each side
(two) nasal and ethmoidal bones. %^*Jf ^ Jusl wlthin
of the nasal process constitutes the roof of a nasal a a
the medial part of the orbital margin ,, the ^ ^ £ . J

(g r * ^ ''^ thl" ^ utt w!^ th^Lal part of the
obliquus superior of the eyeoan. j u

THE PARIETAL BONES

43

orbital margin is the lacrimal fossa for the lacrimal gland (fossa
glandule lacrimalis).

The cerebral surface is concave and accommodates the frontal
lobes of the cerebrum. It is smooth but uneven due to the pressure
of the meningeal vessels and the gyri of the frontal lobes. From
the center of the upper margin a groove {sulcus sagittalis) descends
and terminates in a crest at the end of which is the foramen cecum.
Here the superior sagittal sinus begins.

Articulations. — Dorsally, with the parietals and sphenoid; laterally, with the
zygomatic bones; inferiorly and medially, with the nasals, maxilla;, lacrimals and
ethmoid bones.

Sagittal groove

Cerebral
surface of
frontal
portion

Cerebral surface (of orbital portion)

Foramen i

Fig. 21. — The frontal bone seen from behind (ce

^?

Zygomatic
process

Frontal crest

Orifice of frontal sinus
•Frontal spine

bral surface). {Sobotta t

nd XlcMurrich.)

Ossification. — Tuv lateral primary centers and three pairs of secondary centers.
The primary centers appear about the sixth or seventh week of fetal life and
form the bulk of the bone. The secondary centers appear later, one pair for the
frontal spine, one center for each zygomatic process and a center on each side
at the region of the trochlear pit. These centers fuse on each side by the sixth
or seventh month of fetal life and the two halves are usually fused by the seventh
year.

Muscles Attached. — Mm. corrugator supercilii, orbicularis palpebral and tem-
poralis (three pairs).

THE PARIETAL BONES (OSSA PARLETALES

The two parietal bones form the lateral portions of the vault of the
cranium. Each has two surfaces, parietal and visceral, and four
margins and four angles.

The parietal surface is smooth and convex in both directions; its

44

OSTEOLOGY

middle portion is quite bulged constituting the parietal tuberosity
{tuber parietale). Between this and the inferior margin are two

Sagittal border
Parietal foramen

Mastoid angle

Sphenoidal angle

Sulci arteriosi Squamosal border

Fig. 23. Sigmoid groove

Fig. 22. — The right parietal bone, outer surface. (Sobotta and McMurrich.)
Fig. 23. — Right parietal bone, inner (cerebral) surface. {Sobotta and McMurrich.

nearly parallel curved lines, the superior and inferior temporal lines
{linea temporalis superior et inferior). The upper one serves for the

THE OCCIPITAL BONE 45

attachment of the temporal fascia and the lower limits the attach-
ment of the m. temporalis. The bone below the inferior line (planum
temporale) forms a part of the floor of the temporal fossa and may
show arterial grooves. Near the occipital part of the superior mar-
gin is the parietal foramen, for the transmission of a small artery and
vein.

The cerebral surface is concave in both directions and may show
impressions of the gyri of the parts of the brain covered. The sur-
face is smooth but uneven due to the well-marked blood-vessel
grooves and arachnoideal granulations. Along the superior margin
is a half groove (completed by the other parietal bone) constituting,
when completed, the sagittal sulcus [sulcus sagittal is) in which is
lodged the superior sagittal sinus; to the edges of the groove the falx
cerebri is attached. At the mastoid angle is a portion of the trans-
verse sulcus.

The ventral (frontal), superior (medial) and dorsal (occipital) mar-
gins are deeply serrated and articulate with the bones indicated.
The inferior margin (tnargo squamosus) is the shortest and most
irregular; it is beveled and overlapped by the squamous portion of
the temporal bone. The angles are the frontal, occipital, mastoid
and sphenoidal and indicate the bones with which they articulate.

Articulations. — Frontally, with the frontal; medially with the opposite parietal;
occipitally, with the occipital; inferiorly, with the squamous portion of the tem-
poral and the sphenoid bone frontally.

Ossification. — This bone is purely of intramembranous origin. Ossification
starts at two centers near the middle of the bone at about the eighth week of
fetal life. During the fourth month these centers become confluent at the tuber
parietale area. At the angles ossification is not so rapid foreshadowing the
fontanelles.

Muscle Attached. — Each affords attachment to the m. temporalis.

OCCIPITAL BONE (OS OCCIPITALE)

The occipital bone forms the dorsoinferior portion of the cranium
and its four parts are arranged around the foramen magnum. The
four parts are the tabular, basilar and exoccipiials.

The tabular part 1 squama occipitalis) is convex in both directions.
It consists of two parts, the occipital plane (planum occipitalc) which
is nearly vertical and the nuchal plane (planum nuchale) which is
horizontal. The dividing line between these parts is represented
by the external occipital protuberance (protnbercntia occipitalis ex-
terna) which is near the middle of the bone; the superior curved line
(liuca nucha- superior) extends laterally from the protuberance, on
each side. To the protuberance is attached the ligamentum nucha?.
To the superior curved line are attached the galea aponeurotica, the
mm. trapezius, occipitalis, sternomastoideus and the splenius cap-

46

OSTEOLOGY

itis. The surface of the planum occipitale is smooth and bulging.
The planum nuchale is irregular, rough and divided into lateral
halves by a central crest {crista occipitalis externa) that extends from
the protuberance to the foramen magnum. Each area is trans-
versely bisected by the inferior nuchal line. Each area gives attach-
ment to the mm. semispinalis capitis, the obliquus capitus superior
and the rectus capitis posterior major and minor.

The cerebral surface is concave, smooth but irregular. A cross-
like arrangement of ridges form the eminentia cruciata at the center
of which is the internal occipital protuberance. From the upper part
of this extends the superior sagittal sulcus. At right angles to the
protuberance extend the two transverse grooves {sulci transversi) in

Planum occipitale

External occipital protuberance
nuchae suprcma
Planum nuchale

Condyloid canal

Hypoglossal

Foramen magnum
:ipital bone seen

Planum nuchale
Lateral port/o
Condyloid fossa
Jugular process

'--- Occipital condyle?
External occipital crest
behind. (Sobotta and McMurrich.)

which are lodged the transverse sinuses and to the edges of which is
attached the tentorium cerebelli. Extending from the protuber-
ance to the foramen magnum is seen the internal occipital crest to
which the falx cerebelli is attached. The area of junction of the
sinuses constitutes the confluens sinuum.

Of the angles the superior is somewhat pointed and is inserted be-
tween the parietal bones (posterior fontanelle region); the lateral
angle articulates with the petrous portion of the temporal bone.
The two serrated superior or parietal margins form with the parietal
bones the lamdoidal suture. The lateral margins are irregular and
extend from the lateral angle on each side to the corresponding
jugular process and they articulate with the mastoid portion of the
temporal bone.

THE OCCIPITAL BOXE

47

The lateral, or exoccipital parts bound the foramen magnum later-
ally. The inferior surface of each bears a large condyle which serves
for articulation with the atlas of the vertebral column. Each con-
dyle is oval or reniform and obliquely placed; the articular surface
is convex- dorsoventrally and flattened from side to side and faces
downward and a little laterally. Each is raised from the main mass
of the exoccipital and this supporting mass is pierced by the hypo-
glossal canal (canalis hypoglossi) which transmits the hypoglossal
nerve, the meningeal branch of the ascending pharyngeal artery and
its accompanying vein. The canal terminates laterally at the ven-
tral side of the condyle. Dorsal to the condyle is the condyloid fossa

Sagittal groove

Lambdoid border

Transverse groovi

Internal occipital crest

_ Condyloid canal
Jugular tubercle

Hypoglossal canal

Basilar portion -r

jipital bone seen from in front (cerebral surface). (Sobotta
McMurrich.)

(fossa condyloidea) that may continue through the bone as the con-
dyloid canal [canalis condyioideus). Projecting from the bone at
the side of each condyle is the jugular process (processus jugularis)
which is notched ventrally to assist in forming the jugular foramen.
The cerebral surface of the exoccipital is smooth but uneven, exhibit-
ing a projection, the jugular tubercle (tuberculwn jugulare) at the side
of the foramen magnum. This is just over the orifice of the hypo-
glossal canal and it may be grooved for the glossopharyngeal, vagal
ami accessory nerves.

The basilar portion forms the ventral boundary of the foramen
magnum and extends to the sphenoid bone; to this it is attached by a
firm osseous union. Its inferior surface is horizontal, irregular and

46 OSTEOLOGY

roughened. In the median line is the pharyngeal tubercle for the
attachment of the pharyngeal aponeurosis. Laterally the roughened
surface gives attachment to the mm. longus capitis and rectus capitis
anterior. The cerebral surface slants upward and forward and is
smooth and concave, contains the basilar groove and supports the
(medulla) oblongata.

The foramen magnum is oval and variable in size. It is narrower
ventrally than dorsally (condylic encroachment) and faces inferior
and somewhat ventrally. To its margins are attached the cerebral
meninges and the ligaments that connect it to the atlas and epi-
stropheus. It transmits the (medulla) oblongata, the cranial end of
the spinal cord, the accessory nerves, the vertebral arteries and men-
ingeal vessels.

Articulations. — With the parietals, temporals, sphenoid and atlas — six bones.

Ossification. — It is mainly of endochondral origin, the squamous portion,
above the occipital crest, developing intramembranously. The basilar portion
develops from two renters (sixth week; which soon fuse. Each exocripital portion
ossifies from one renter (about the eighth week). The endochondral portion of
the squamous part ossifies from several centers (two to four during the sixth or
seventh week). The superior part of the bone arises in membrane from four
centers, two near the midline (sixth to seventh week) and two more lateral to
these (third month). These two lateral masses fuse about the fourth month of
fetal life. The exocripital and squamous parts are united by about the third
year; the exoccipitals and the basilar portion are united by the fourth or fifth
year; the basilar part and the sphenoid bone fuse about the twenty-fifth year.

Muscle Attached. — To the superior nuchal line the mm. occipitalis, the
trapezius and sternomastoideus; to the space below this line the mm. semispinalis
capitis, the splenius capitis and the obliquus capitis superior; to the inferior
curved line and the space below, mm. the rectus capitis posterior major and minor;
to the jugular process the mm. rectus capitis anterior and the superior constrictor
of the pharynx.

THE SPHENOID BONE (OS SPHENOIDALE)

The sphenoid bone is in the base of the skull and assists in forming a
number of fossa?. It consists of a body, two greater, two lesser wings and
two pterygoid processes. The body (corpus) is a hollow, cuboidal mass
of bone placed in the median line. It contains two air sinuses sepa-
rated by a nearly vertical median septum; these are extensive and
communicate with the nasal fosss. The cerebral surface is saddle-
shaped and contains a deep depression, the sella turcica (fossa iiy-
pophyseos) that serves for the lodgment of the hypophysis. The
dorsal limit of the fossa is a ridge of bone, the dorsum sella:, which is
continuous with the basilar part of the occipital bone. This is
smooth and supports the pons and the basilar artery. The lateral
portions of the dorsum sella project laterally as the posterior cli-
noidal processes (processi clinoidci posteriores) and to these the tento-
rium cerebelli is attached. The ventral boundary ridge is the tuber-

THE SPHENOID BONE

49

culum sella in front of which is the sulcus chiasmatis that continues on
each side into the optic foramen. In front of the sulcus the bone is
smooth and continues for a short distance and then articulates with
the ethmoid. On the irregular articular area there is often a pro-
jection in the midline called the spine of the sphenoid. Most of each
lateral surface is fused with the greater wing and pterygoid process,
but curving above the root of the greater wing there is an S-shaped
groove for the internal carotid artery (sulcus caroticus). This
groove is bounded dorsally by the petrous process (for articulation
with that portion of the temporal bone) ; above this there may be
a groove for the abducens nerve. The nonarticular portion of the
anterior part is smooth and somewhat concave on each side of the
midline due to the presence of the median sphenoidal crest [crista

Infratemporal surf ace

Sphenomaxillary surf

Interna! pterygoid phl>
Fig. 26. — The sphenoid bone

Pterygoid fist

ft niiutar process

from in front. (Sobotta and McMurrtch.)

sphenoidalis); this articulates with the perpendicular plate of the
ethmoid. The crest ends in the sphenoidal rostrum. At the lateral
limit of each depression is seen an opening that leads into the air
sinus of each side. The remainder of this surface articulates with
the ethmoid and palatal bones. The inferior surface presents a ridge-
like continuation of the sphenoidal rostrum and this ridge fits between
the alas of the vomer. The dorsal end of this surface is rougher and
serves for the attachment of the mucosa of the roof of the pharynx.
The posterior surface of the body is fused with the basilar portion of
the occipital bone.

The greater, or temporal wing (ala magna) is nearly horizontal and
the cerebral surface forms a considerable portion of each middle fossa
of the skull. The lateral, or squamosal margin, starts at the parietal
angle and downward and then backward and medially to end at the

5°

OSTEOLOGY

spina angularis where the bone is grooved for the cartilaginous por-
tion of the auditory tube (sulcus tuba). The more extensive margin
starts at the parietal angle, passes downward and medially to the
body; the first half (frontal) articulates with the frontal bone while
the medial half is free and forms the inferior margin of the superior
orbital fissure, which transmits the oculomotor, trochlear, ophthal-
mic division of the trigeminal and the abducens nerves and the
ophthalmic veins. The margin then continues backward along the
body of the bone forming, posteriorly, the lingula that constitutes
the lateral boundary of the carotid groove; this is fused underneath
with the root of the pterygoid process. The remaining portion of
this margin is directed laterally; its first part is free, forming the
anterior boundary of the foramen lacerum; the rest (petrosal) is

-The sphenoid bone <

External /itnygoid plate
Htuiititur process
l from behind. (Sobotta and McMurrich

rough for articulation with the petrous part of the temporal bone and
ends as the spina angularis. In the broad root of origin of the greater
wing are seen three foramina, the foramen rotundum (for the trans-
mission of the maxillary division of the trigeminal nerve); the large
foramen ovale (for the transmission of the mandibular division of the
trigeminal nerve and a branch of the middle meningeal artery) ; the
foramen spinosum (for the transmission of the middle meningeal artery
and vein and the nervus spinosum, from the mandibular division of
the trigeminal nerve). The cerebral surface of this wing is concave
and exhibits the foregoing foramina and may also show impressions
of the gyri of the temporal lobe of the brain and a sulcus arteriosus.
Its orbital surface {fades orbitalis) is smooth and forms a part of the
orbital fossa and lies below and lateral to the superior orbital fissure;
near this there may be the spina recti lateralis to which is attached

THE SPHENOID BONE 5 1

the common ligament of the ocular muscles. Its inferior margin
or orbital crest, is free and assists in bounding the inferior orbital
fissure (fissura orbital is inferior). Below this is seen the opening of
the foramen rotundum.

The concavo-convex temporal surface (fades temporalis) is the
largest and is separated from the preceding by the zygomatic margin.
The nearly horizontal infratemporal crest (crista infratemporalis) sepa-
rates the planum temporale (above) from the infratemporal surface
(below). The infratemporal surface is divided by the low spheno-
maxillary ridge into a lateral, infratemporal surface proper (showing
the openings of the foramina ovale and spinosum) and an anterior,
medial spenomaxillary surface. The entire temporal surface enters
into the formation of the infratemporal, and pterygopalatine (spheno-
maxillary) fossae.

The lesser, or orbital wings (alas parvae) are narrow, triangular and
nearly horizontally placed. Each arises by two roots that embrace
the optic foramen. The posterior root forms the anterior clinoidal
process on each side (processus clinoideus anterior). The cerebral
surface forms a part of the anterior cranial fossa; the inferior surface
forms a part of the orbit and the upper boundary of the superior
orbital fissure. Its anterior margin articulates with the frontal bone
and its posterior, sickle-shaped margin is sharp and separates the
anterior and middle cranial fossae.

The pterygoid processes (processus pterygoidei) are two vertical
processes that project downward from the under surface of the bone
at the junction of the greater wings and body. Each consists of two
lamina, (lamina: processus pterygoidei lateralis et medialis) between
the roots of which extends the pterygoid canal for the pterygoid nerve
and artery. The two plates are almost at right angles to each other,
fused behind (except below at the pterygoid notch) and separated in
front where they form the pterygoid fossa. Thd medial pterygoid
plate is narrow and stout; its posterior free margin forms, below, the
pterygoid hook (hamulus pterygoideus) and, above, it divides to en-
close the scaphoid fossa. This fossa gives origin to the m. tensor veli
palati. This margin affords attachment to the pharyngobasilar
fascia, pharyngeal aponeurosis, superior constrictor of the pharynx
and the m. pharyngopalatinus. At the root of this plate are the
vaginal processes (processus vaginalis) and the pterygopalatine groove.
The lateral pterygoid plate is thin and broad and is directed laterally.
It affords attachment to the inferior head of the m. pterygoideus
lateral and to the m. pterygoideus medialis. The anterior surface of
the root of the pterygoid process forms a part of the pterygopala-
tine fossa.

The sphenoidal concha (concha' s phenoidales) are hollow and each
is shaped like a three-sided pyramid. The apex is in contact with the

52 OSTEOLOGY

vaginal process of the medial plate while the base is attached to the
lateral mass of the ethmoid bone. The superior surface is in contact
with the inferior surface of the front part of the body of the sphenoid
and the apposed walls have been absorbed to form the sphenoidal
sinus of each side. The inferior surfaces assist in forming the roof of
each nasal fossa and a part of the pterygopalatine fossa. They are
separate bones up to the fifth year at which time fusion, as above
given, takes place.

Articulations. — With the frontal, parietals, temporals, occipital, ethmoid,
vomer, palatals and zygomatic bones (twelve).

Ossification. — This bone is mainly of endochondral origin, the medial pterygoid
plate developing in membrane. There are fourteen centers of which six form the
presphenoid (the lesser wings and the front part of the body); the other eight
centers form the postsphenoid, or remainder of the bone, except the medial
pterygoid plates. The first center on each side are for the greater wing and it
appears about the eighth week of fetal life and the last ones are for the hamular
processes and appear during the fourth fetal month. The centers are great
wings two, pot sphenoid body two. lingular two, lesser wings two, presphenoid
body two, medial pterygoid plates two, hamular processes two. The presphe-
noid and main part of the body unite about the eighth month of fetal life so that
at birth the greater wings with the pterygoid processes are still separate from
the body; they are all united usually by the end of the first year.

Muscle Attached. — Mm. temporalis, pterygoideus lateralis, pterygoideus
medialis, constrictor pharyngeus superior, tensor veli palati, levator palpebrae,
obliquus superior and the four recti of the eyeball (eleven pairs).

THE TEMPORAL BONES (OSSA TEMPORALLY)

The temporal bones form the middle portion of the base of the
cranium. Each consists of three parts — the squamous, tympanic
and petromastoid portions.

The squamous part (squama temporalis) is the vertical portion
that forms part of the lateral boundary of the cranium. The cere-
bral surface is smooth but bears the impressions of the gyri of the
temporal lobe of the brain and the middle meningeal artery. The
temporal surface is smooth and assists in forming a part of the tem-
poral fossa; here it gives attachment to the m. temporalis. At the
anteroinferior part of this surface is the zygomatic process (processus
zygomaticus). This is a twisted bar of bone that at its anterior ex-
tremity articulates with the zygomatic bone; its inferior and medial
aspects give attachment to the m. masseter. Its superior margin
continues backward over the external acoustic meatus as the superior
root of the zygomatic process and becomes continuous with the supra-
mastoid crest. The inferior margin turns medially and constitutes
the anterior root. About half way along this margin is the lubcrcu-
lum articulate that bounds the mandibular fossa (fossa mandibularis)
in front. Just in front of the external auditory meatus the anterior
root has another projection, the postglenokl tubercle. In the depths

THE TEMPORAL BONES

53

of this fossa is the partly closed petrotympanic fissure, the middle
portion of which transmits the tympanic branch of the internal max-
illary artery and also lodges the anterior process of malleus. Near%
this is a canaliculus that transmits the chorda tympani nerve. That
portion of the mandibular fossa behind the fissure is nonarticular
and lodges a portion of the parotid gland (which becomes enlarged
in mumps and causes the pain when the mandible is lowered). The
anterior part is articular and with the articular tubercle and the
condyle of the mandible forms the temperomandibular articulation;
this contains an interarticular fibrocartilage. The posteroinjerior
surface of the squamosa forms a part of the posterior wall of the ex-
ternal auditory canal. The superior margin is convex and beveled
at expense of the cerebral surface. The posterior, inferior and medial

Parietal border
% Squamous portion

Groove for middle temporal artery

Parietal
Supramental

Sphenoidal border

from the outer (lateral)
ilc.Murricli.)

margins of the squama are fused with the petrous part. Inferiorly
and in front is the petrotympanic fissure separating it from the cor-
responding part of the bone.

The tympanic portion (pars tympanica) forms the posterior part
of the mandibular fossa, the anterior and inferior walls and a part
of the posterior wall of the external auditory canal. Its lower edge
embraces the styloid process as the vagina! process. Although fused
with the other parts of the bone it is separated, laterally, from the
mastoid and squamous divisions by the tympanomastoid fissure. To
that part bounding the canal the cartilaginous portion of the external
ear is attached.

The external auditory canal {meatus audilorius externus) is slightly
curved, oval on section and twisted upon its long axis. For details
see page 350.

54 OSTEOLOGY

The petromastoid portion (pars petrosa et pars mastoidia) is the
most massive division and is pyramidal in form. The petrous part
(pyramis) is a long, three.-sided pyramid with an apex, a base, three
surfaces and three margins. The apex is near the middle line of the
base of the cranium at the body of the sphenoid. The base is fused
with the squamous and tympanic portions. The anterior surface
forms a part of the floor of the middle cranial fossa and is smooth but
irregular; it may show impressions of the gyri of the temporal lobe of
the cerebrum. Near the apex is the impressio trigemina which
lodges the semilunar ganglion of the trigeminal nerve. On this
surface are seen the eminentia arcuata, made by the superior semi-
circular canal; near this is the slit-like hiatus canalis facialis, for the
facial nerve; a little lateral to the hiatus may be a small opening, the

Sulcus arteriosus 4
Sphenoidal border

,. Parietal border

Cerebral sar/at

Subarcuate Jossa
Internal auditory meatus

Inferior petrosal groove

Styloid proa

Fig. 20. — The right temporal bone

seen from the cerebral surface. (Sobotta and
\L Murrich.)

apcrtura superior canalis tympani. The posterior surface forms part
of the posterior cranial fossa and is concave, smooth but uneven.
Here the following are seen: (i) Internal auditory meatus (meatus
auditorius internus) a long, oval opening in the depths of which the
opening of the canalis facialis may often be noted. The meatus
transmits the acoustic nerve and vessels. (2) The aqueduct of the
vestibule (apertura externa aqueduclus vestibuli) is in front of the pre-
ceding; this lodges the saccus endolymphaticus. (3) The ridge of
the posterior semicircular canal is above this. The inferior surface
is very irregular and mostly rough. The most prominent structure
is the styloid process (processus styloideus) that gives attachment to
the mm. styloglossus, stylohyoideus and stylopharyngeus and the

THE TEMPORAL BOXES

55

stylohyoid and stylomaxillary ligaments. Behind the process is the
foramen styloideum, for the facial nerve and the mastoid artery. The
jugular fossa (fossa jugularis) is medial to the process and assists in
forming the jugular foramen. In the jugular fossa is the canalis
mastoideus for the auricular branch of the vagus. In front of and
lateral to the fossa is the carotid canal (canalis caroticus) for the trans-
mission of the internal carotid artery and the sympathetic plexus.
Upon the ridge separating the fossa and canal is the canaliculus
tympanicus for the transmission of the tympanic branch of the glosso-
pharyngeal nerve. The fossula fenestra cochlea, with the opening of
the aqueduct of the cochlea (apertura externa aqueductus cochlea),
are seen anteromedial to the jugular fossa. In the fossula is lodged

•--.^Sphenoidal border

Fig. 30. — Right temporal bone seen from below. {Sobolta and McMurrich.)

the petrous ganglion of the glossopharyngeal nerve. From the
roughened bone near the apex the m. tensor veli palatini arises.

The superior angle, or margin, separates the anterior -and posterior
surfaces and also separates the middle and posterior cranial fossae
from each other. It is grooved for the superior petrosal si?ius and to
it is attached the tentorium cerebelli. The posterior angle, or mar-
gin, is in part free or nonarticular where it forms a part of the jugular
foramen; the remainder is articular and usually presents a groove
for the inferior petrosal sinus. The anterior angle, or margin, is the
shortest and extends from the apex to the squamous part. Near
the squama is seen the osseous portion of the auditory tube (canalis
musculotubarius). This is divided by a bony septum into a smaller
division (semicanalism. tensor tympani) for the tensor tympani muscle;

56 OSTEOLOGY

the larger portion {semicanalis tubes auditiva) is the osseous portion
of the pharyngotympanic, or auditory tube.

The mastoid portion of the temporal bone lies posterior to the ex-
ternal auditory meatus and forms a nipple-like process that is vari-
able in size. Its lateral surface is rough and with the inferior margin
affords insertion to the mm. sternomastoideus, splenius capitis and
longissimus capitis. Its inferior surface shows a groove (incisura
mastoidea) along the root of the apex which gives origin to the pos-
terior belly of the m. digastricus. Medial to this groove is another
for the occipital artery. The cerebral surface of the mastoid division
forms a part of the floor of the posterior cranial fossa; on it are seen
a deep wide groove for the transverse, or sigmoid sinus which leads
to the jugular fossa; the mastoid foramen for a small artery and vein.

Articulations. — Each articulates with the occipital, parietal, sphenoid, man-
dible and zygomatic bones (5).

Ossifications. — It is mainly of endochondral origin and develops from ten
centers, as follows: (a) the center for the squamozygomatic part appears at about
the end of the second month of fetal life; (b) one for the tympanic plate during the
third month; (f) six for the petromastoid portion during the fifth to the sixth
months; (d) two for the styloid process, one just before and the other just after
birth. The squamozygomatic portion develops in membrane. The mastoid
process develops during the second year and toward the age of puberty it be-
comes cellular. The squamous and tympanic parts fuse just before birth and
the petromastoid and the squama during the first year. The base of the mastoid
process fuses with the rest about the same time and the lower end of the styloid
process and the basal end unite about the age of puberty.

Muscles Attached. — To the squama, the m. temporalis; to the zygomatic
process, the m. masseter; to the mastoid portion, mm. sternomastoideus, splenius
capitis, longissimus capitis, digastricus and auricularis posterior; to the styloid
process; the mm. styloglossus, stylohyoideus and stylopharyngeus; to the
petrous portion the mm. tensor veli palatini, stapedius, the tensor tympani and
levator veli palatini (fifteen).

THE ETHMOID BONE (OS ETHMOIDALE)

The ethmoid bone is alight, thin-walled, honeycombed bone that
forms a part of the floor of the anterior cranial fossa and fits in be-
tween the orbital parts of the frontal bone. The bone is T-like and
consists of a median vertical plate that is topped by the cribriform
plate. From this the ethmoidal labyrinth of each side is suspended.

The perpendicular plate {lamina perpendicularis) is irregular and
pentagonal in form and projects into the cranial cavity as a sharp,
median crest (crista galli); to this is attached the falx cerebri, at its
frontal extremity is a notch forming the foramen cecum with the
frontal bone. This plate is usually deflected to one or the other side
and has smooth surfaces. Its posteroinferior surface is fused with the
vomer while its anterior margin articulates with the cartilaginous
nasal septum.

THE ETHMOID BONE

57

The cribriform plate (lamina cribrosa) bridges the space between
the two orbital plates of the frontal bone and is pierced by numer-
ous foramina for the passage of the olfactory nerves. On each side of
the midline the cerebral surface shows a groove for the olfactory lobe.
Along each lateral edge are notches that become the ethmoidal for-
amina upon articulation. Anteriorly, there is a slit that transmits
the nasociliary nerve into the nose. The inferior surface forms the
roof of the nasal fossa?.

The ethmoidal labyrinths (labyrinthi cthmoidaJes) are two thin-
walled masses enclosing numerous air cells, anterior, middle and pos-
terior. The lateral, or orbital wall (lamina papyracea) forms a part

Lamina papyracea

dtcular

Middle

'"" } * turbinated

Ethmoidal

cell

Perpen-

Uncinate

dicular

process

plate

Fig. 31. — The ethmoid bone seen from
above. (Sobolta and McMurrich.)

12. — The ethmoid bone seen from the
;ide. (Sobolta and McMurrich.)

of the medial wall of the orbit. The anterior and posterior ethmoidal
foramina are seen here; these transmit small ethmoidal vessels
and the anterior nasociliary nerves. Upon the medial surface, that
forms a part of the lateral wall of each nasal fossa, are seen the two
ethmoidal turbinals [concha ethmoidales). These are two thin, con-
voluted plates of bone of which the middles is much the larger.
Between the middle and superior concha? is the superior meatus of
the nasal fossa and into this the posterior ethmoidal cells open. The
middle meatus lies between the middle and inferior conchas and
into it open the middle and anterior ethmoidal cells and the frontal
sinus (see "Nasal Fossaa, page 272).

Articulations. — With the sphenoid frontal, two nasal, two palatal, two lacrimal,
two maxilkc, two inferior concha? and vomer bones (thirteen).

Ossification. — It is of endochondral origin and is developed for jour centers,
one for each labyrinth and two for the perpendicular plate. The centers for the
labyrinths appear at about the fifth month of fetal life and also form the lateral
part of the perpendicular plate. The centers for the perpendicular plate appear
at the end of the first year; they form this plate and the medial portion of the

58 OSTEOLOGY

cribriform plate. Fusion of all parts is complete by the sixth year. The sphe-
noidal fusion is complete by about the twenty-fifth year but vomerine fusion is
not completed until the fortieth or fiftieth year. The ethmoidal cells are usually
completed at birth.
Muscles Attached. — Xone.

THE INFERIOR CONCHiE (CONCHA NASALES INFERIOR)

Each inferior concha is a scroll-shaped bone located on the lateral
wall of the inferior part of the nasal fossa. The superior margin is
thin and articulates with the maxilla and the palatal bone and by a
process {processus lacrimalis) with the lacrimal bone. Here it assists
in forming the nasolacrimal canal. Its posterior edge unites with the
ethmoid bone by means of the ethmoidal process (processus ethmoid-
alis). From this margin the maxillary process extends forming a part

Ethmoidal process

Lachrymal process

Maxillary process

Fig. 33. — The inferior turbinated (conchal) bone seen from its lateral surface. (Sobotta and
M< Murrich.)

of the medial wall of the maxillary sinus. The medial margin is free
and slightly curved. The medial surface is convex from above down-
ward, projects into the nasal fossa and forms the floor of the middle
meatus. The lateral surface is concave and overhangs the inferior
meatus.

Articulations. — With the maxilla, lacrimal, ethmoidal and palatal bones (four).
Ossification. — It is developed in cartilage and from a single center. This
appears at about the fifth montli of fetal life.
Muscles Attached. — None.

LACRIMAL BONES (OSSA LACRLMALIA)

The lacrimal bones are thin bones that form a part of the orbital
fossas. Each has two surfaces and four margins and is quadrilateral
in shape.

The lateral, or orbital surface, is smooth and is divided by a vertical
ridge (crista, lacrimalis posterior) into two areas; the anterior is the
lacrimal groove (sulcus lacrimalis) for the lacrimal sac; the posterior
area is the orbital surface proper. The ridge ends below in a hooklet
(hamulus lacrimalis) that forms part of the upper boundary of the
nasolacrimal duct. The medial wall of the lacrimal groove ends as
the descending process. Part of the crest gives attachment to the

THE VOMER 59

tendo oculi and lacrimal part of the m. orbicularis oculi. The
medial surface is uneven and closes in the anterior ethmoidal cells and
forms a part of the lateral boundary of the middle meatus of the nose.
The margins are uneven and articulate with various bones.

Articulations. — With the frontal, ethmoidal, maxilla and inferior concha (four).
Ossification. — Of intramembranous origin and from one center that appears
during the eighth or ninth week of fetal life.

Muscles Attached. — M. orbicularis oculi (lacrimal part).

'X.

Posterior

lachrymal

crest

Alae vomeris

Depression for
lachrymal sac

Hamulus lacrimalis

Fig. 34. — Left lacrimal bone seen PlG. !5. — The vomer seen from the side,

from its median surface. (Sobotta fScbotta and McMurrich.)

and McMurrich.)

THE VOMER

The vomer is an irregular, quadrilateral bone that forms the pos-
terior portion of the nasal septum. It is usually deflected to one or
the other side. The right and left surfaces are smooth. The superior
margin possesses two lips, or alee by means of which it is held fixedly
in position. The posterior, or free margin is the posterior margin of
the nasal septum and separates the two choanae. The inferior
margin is irregular for articulation with the palatal bones and the
maxillae. The anterior (longest) margin is sloping and articulates
with the ethmoidal bone and the cartilaginous nasal septum. Its
anterior extremity is irregular and articulates with the maxillae.

Articulations. — With the maxilla?, palatals, sphenoid and ethmoid bones (six.)

Ossification. — It is of intramembranous origin and developes from two centers

(one on each side of the midline). These appear during the end of the second

month. These centers begin to fuse during the third fetal month and fusion is

usually completed at the age of puberty.

Muscles Attached. — None.

NASAL BONES (OSSA NASALES)

The two nasal bones form the bridge of the nose. Each has two
surfaces a.nd four fnargins. The lateral surface is convex from side to
side, concave from above downward and constricted near the middle.
Upon this surface is seen a small opening for the nutrient vessel.

6o

OSTEOLOGY

The medial surface is small, concave from side to side and forms a
part of the lateral boundary of the nasal fossa. It is traversed bv a
narrow groove (sulcus ethmoidalis) in which is lodged a branch of the
nasociliary nerve. The margins are roughened and irregular for
articulation with the neighboring bones.

Articulations. — With the opposite nasal, the frontal, ethmoidal and maxilla
(four).

Ossification. — It is of intramembranous origin and is developed from one
center that appears about the eighth week of fetal life.

Muscles Attached. — Xone.

Nasal foramen •

Fig. 36. — The left nasal bone seen
:rom the lateral surface. {Sobolla
md McMurrich.)

■ Ethmoidal groove

[Nasal foramen

Fig. 37. — The left nasal bone seen
rom its medial surface. (Sobotta
nd McMurrich.)

THE FACIAL BONES (OSSA FACIEI)

These comprise the two maxillae, two palatals, two zygomatics and
the mandible.

THE MAXILLAE

The maxilla? (two) form the front of the face and constitute the
upper jaw. The main portion is the body, and from this extend four
processes. The body (corpus) although apparently massive is light
and hollow (maxillary sinus). It has four surfaces. The lateral, or
anterior surface [fades anterior) although smooth is irregular showing
ridges that correspond to the sockets of the teeth (processus
alveolaris). Of these ridges that for the canine tooth is the most
prominent separating two fossae, incisor fossa (medially) and canine
fossa (laterally). Its superior oblique margin (margo infraorbital is)
is free and beneath it is the infraorbital foramen. The medial margin
has the nasal notch limited below by the anterior nasal spine.

The orbital surface (planum orbitale) is smooth and nearly horizon-
tal. Posteriorly it forms part of the posterior boundary of the in-
ferior orbital fissure. The first part of the medial margin is notched
forming the lacrimal groove (sulcus lacrimalis) . Through the planum
extends the infraorbital canal which may be open for a variable dis-
tance. The canal has two openings (invisible unless the canal is laid

THE MAXILL.*

6l

open) that lead into the maxillary sinus and these transmit vessels to
the anterior and middle teeth.

The infratemporal surface is posteriorly and laterally placed, convex
from side to side and smooth. The upper margin, with the posterior
margin of the orbital surface, forms the anterior boundary of the
inferior orbital fissure. Near the middle of the posterior portion it is
pierced by several alveolar canals (foramina aheolaria) that trans-
mit vessels and nerves to the molar teeth. That part of the bone

Frontamaxiltary suture

Frontal process

%

Fig. 38. — The right maxilla seen from the
medial surface. (Sobotla and McMurrich.)

FlG. 39. — The right maxilla seen from
the lateral surface. (Sobotta and Mc-
Murrich.)

that extends beyond the last molar tooth is called the maxillary
tuberosity (tuber maxillare).

The nasal, or medial surface (fades nasalis) forms a part of the
lateral wall of the nasal fossa. It exhibits the nasal notch, in front,
the lacrimal groove, above, and along the posterior margin the ptery-
gopalatine groove, which becomes a canal upon articulation (for the
posterior palatine nerve and the great palatine artery). Near the
upper and back part of this surface is the opening into the maxillary
sinus which is smaller in the articulated skull. The sinus is pyra-
midal in shape (as is the body) and communicates with the middle
meatus of the nasal fossa. Its walls, the surfaces of the body, are
for the most part thin, especially over the sockets of the teeth. In

62 OSTEOLOGY

the recent state it is lined with a mucous membrane which is con-
tinuous with that of the nasal fossa.

The palatal process is a horizontal shelf of bone at the lower margin
of the nasal surface of the body and extends as far back as the second
molar tooth. Its superior surface forms most of the floor of the nasal
fossa. The rough inferior surface is concave from side to side and,
with its fellow, forms the anterior three-fourths of the vault of the
hard palate and about one-half of the roof of the oral cavity. It is
grooved by the pterygopalatine groove. Its medial margin helps
form the nasal crest {crista nasalis) for articulation with the vomer.
In front the nasal crest forms the incisor crest that ends in the anterior
nasal spine. Back of the nasal spine the medial margin is grooved
and with its fellow forms the incisive foramen (foramen incisivum).
Into this open the foramina of Stenscn and Scarpa.

The alveolar process (processus alveolaris) is that part below the
level of the palatal process. It represents half of the superior dental
arch and bears the teeth of its respective side. It is present only
when the teeth are present, being absorbed when the permanent
teeth are lost.

The zygomatic process (processus zygomaticus) is concave behind,
in keeping with the infratemporal surface, and flattened anteriorly.
It separates the facial and infratemporal surfaces and is attached
to the body above the first molar tooth. Its extremity is irregular
for articulation with the zygomatic bone.

The frontal process (processus frontalis) is a thin plate of bone ex-
tending above the level of the orbital surface. The infraorbital
margin is continued upon it as the crista lacrimalis anterior, behind
which the grooved area forms a part of the fossa for the lacrimal sac.
The tendo oculi is attached in front of the groove. The medial sur-
face is smooth but uneven forming part of the lateral boundary of
the nasal fossa. Upon it is seen the oblique ethmoidal crest (agger
nasi). Its edges are roughened for articulation with the neighboring
bones.

Articulations. — It articulates, above, with the nasal, frontal, lacrimal and
ethmoidal bones; posteriorly and medially with the palatal and opposite maxilla;
laterally with the zygomatic bone; it also articulates with the inferior concha and
the vomer (nine).

Ossification. — It is of intramembranous origin and is developed from six
centers. These are the orbitonasal, zygomatic, palatal, nasal, injrawmerine and
prcmaxillary (probably two). These centers appear about the eighth week and
by the tenth week the first five have fused into one mass. Later these two fuse
but the suture between them is noted on the -palate up to middle life. The
maxillary sinus begins to form during the fourth month and reaches its full
size after the second dentition.

Muscles Attached. — Mm. orbicularis oculi, obliquus inferior, caput angulare,
caput infraorbitale, caninus, nasalis, depressor alae nasi, dilatator naris posterior,
masseter, buccinator, orbicularis oris and pterygoideus medialis (twelve).

THE PALATAL BONES

63

PALATAL BONES (OSSA PALATLNA)

Each palatal bone is very delicate and of irregular shape. It
assists in forming the following fossae: nasal, orbital, pterygopalatine,
infratemporal and pterygoid. It has two main portions, horizontal
and vertical.

The horizontal portion (pars horizontalis) forms about one-third
of the hard palate. Its superior surface, smooth and concave, con-
stitutes a part of the floor of the nasal cavity. The inferior surface
is rougher and forms part of the roof of the mouth. The medial
and anterior margins articulate with the neighboring bones while the
lateral margin fuses with the pars perpendicularis. The posterior
margin is free and has the aponeurosis of the palate attached to it.

Orbital process —

Sphenoidal process

Orbital
process
Horizontal plate^

Pterygopalatine groove
Perpendicular plate

Orbital process

Pterygopalatine groove Lesser palatine

(greater palatine foramen) foramen

Fig. 41. Fig. 42.

Fig. 40. — The right palate bone seen from behind. (Sobotla and McMurrich.)
Fig. 41. — The right palate bone seen from lateral surface. (Sobotta and McMurrich.')
Fig. 42. — The right palate bone seen from the medial surface. *, Surface which completes
the pterygoid fossa. (Sobotla and McMurrich.)

The posterior part of the medial margin constitutes the posterior
nasal spine.

The perpendicular portion (pars perpendicularis) is narrow below.
Its medial surface forms the back of the lateral wall of the nasal fossa
and is crossed by the conchal crest (crista conchalis) ; above this crest
is the middle meatus and below it is the inferior meatus. Near its
upper part is the ethmoidal crest. The lateral wall is a part of the
pterygopalatine fossa wall. It is quite irregular and shows the ptery-
gopalatine groove. Its front part constitutes the maxillary process.
The anterior margin is irregular for articulation. The posterior mar-
gin exhibits, below, the pyramidal process. The inferior margin joins

64 OSTEOLOGY

the horizontal part. The superior margin supports two processes,
the sphenoidal and orbital.

The sphenoidal process (processus sphenoidalis) is small and dor-
sally directed. Its superior surface is smooth and assists in forming
the pharyngeal canal for the pharyngeal artery and the pharyngeal
branch of the sphenopalatine ganglion. Its medial surface forms a
part of the nasal fossa. Its lateral surface forms a part of the wall
of the pterygopalatine fossa.

The hollow orbital process (processus orbitalis) is the highest part
of the bone and its medially directed opening communicates with
the sphenoidal sinus. The nonarticular surfaces are as follows:
superior, that forms a part of the floor of the orbit; medial, that
forms a part of the lateral nasal wall; lateral, that forms a part of
the wall of the pterygopalatine fossa.

The pyramidal process (processus pyramidalis) is at the antero-
inferior extremity of the bone. A smooth, V-shaped groove forms
a part of the pterygoid fossa. A small part of the lateral surface
enters into the formation of the infratemporal fossa. Through this
process pass, vertically, the lesser palatine foramina for the trans-
mission of the lesser palatine nerves and vessels.

Articulations. — With the ethmoid, vomer, sphenoid, maxilla, inferior concha
and the opposite palatal bones (six).

Ossification. — It is of intramembranous origin and usually from one center,
which appears in the second fetal month. The orbital process may have a
separate center.

Muscle Attached. — The mm. tensor veli palatini, constrictor pharyngeus
superior, pterygoideus medialis and uvula; (four).

THE ZYGOMATIC BONES (OSSA ZYGOMATIC A)

The zygomatic bones are irregular, constituting the cheek bones
and assisting in forming the orbital, infratemporal and temporal
fossa?.

The lateral surface (fades malaris) of each is convex, smooth and
exhibits the zygomaticofacial canal. The most prominent part of
this surface is the malar tuberosity. The surface is roughly quad-
rilateral in form and the angles are represented by processes. The
femporal process is broad and is posteriorly directed. The fronto-
sphenoidal process is the most prominent and is superiorly directed.
The marginal process is anterior and somewhat curved. The in-
ferior process is the least marked. The margins connecting these
processes are mostly thin and sharp. The temporal margin has a
projection, the processus marginalis, and with the orbital and masset-
eric margins is free. To the latter is attached the m. masseter.
The maxillary margin is articular.

The medial surface is divided by the orbital process which sepa-

THE MANDIBLE

rates the concave infratemporal from the orbital areas (also called
surfaces). Part of the orbital process is nonarticular and forms the
anterior boundary of the inferior orbital fissure. The orbital area
of the medial surface exhibits two foramina (zygomaticoorbitale) one
of which is the internal opening of the zygomaticofacial canal (for
the zygomaticofacial branch of the zygomatic nerve) ; the other is
the zygomaticotemporal canal (for the zygomaticotemporal nerve).
The former canal opens upon the lateral surface of the bone and the
latter in the temporal fossa.

Fig. 43. — The right i
from the lateral surfac
McMurrich.)

ar bones seen
(Sobotta and

Fig. 44. — The right malar bone seen
from the media! or temporal surface.
(Sobotta and Sdciiurrich.)

Articulations. — With the temporal, frontal, sphenoidal and maxillary bones
(four).

Ossification. — It is of intramembranous origin and is developed from three
centers. The center for the orbital portion appears about the eighth to the tenth
week and forms the bulk of the body and the temporal process; a second center
forms the temporal fossa part of the body and the third forms the lower part of
the body. These fuse at about the fifth month of fetal life but sutures may persist
between these throughout life.

Muscle Attached. — Mm. caput infraorbitale, zygomaticus, caput zygomaticum
and masse ter (foun.

THE MANDIBLE (MANDIBULA)

The mandible is V-shaped with its extremities turned upward.
It constitutes the entire lower jaw and is the strongest bone of the
face. It supports the lower teeth and consists of a body and two rami.

The body (corpus mandibular) has two surfaces and two margins.
The lateral surface is convex from side to side and concave from above
downward. In the median line is a vertical ridge, the symphysis,
below which is the mental protuberance (protuberantia mentalis) which
is divided into two tubercles (tubera mentalia). The sockets of the
front teeth project somewhat. At each side of the symphysis is the
incisor fossa and in line with the second premolar tooth is the mental
foramen, for the mental nerve and vessels. The oblique line (linea
obliqua) extends upward and backward from the mental tubercle.
The medial surface is convex from above downward and concave

66

OSTEOLOGY

from side to side. Upon each side of the median line are the menial
spines (spina mentales) the upper giving attachment to the mm.
genioglossus and the lower to the geniohyoideus. Above the spine
is a nutrient foramen. Below and to the side is the digastric fossa
(fossa digastrica) for the attachment of the anterior belly of the m.
digastricus. This surface is traversed and divided by an oblique
line below and in front over the digastric fossa. This is the mylo-
hyoid line (linea mylohyoidea) to which the mm. mylohyoideus and
constrictor pharyngeus superior are attached. The bone below this

Notch of the mandibte

Pterygoid depression

Mead of condyloid process

Mental foramen
Fig. 45. — The mandible !

Angle {masseteric tttbovsityt

. from the lateral surface. (Sobotta and McMurrich.)

line is hollow (fossa submaxillar is) for the submaxillary gland and in
front is another hollow area the fossa sublingualis.

The superior, or alveolar margin, supports the lower teeth. The
inferior margin (basis mandibulce) is thicker than at the junction of
the alveolar margin and the body. This margin is longer than the
superior, rounded and grooved near the junction with the ramus for
the external maxillary artery.

The rami (rami mandibulae) are flat and nearly vertical in direc-
tion. The lateral surface of each is smooth but uneven due to ridges
for muscle attachment (masseter). The medial surface is smooth
and irregular. Near the middle is the foramen mandibular e that
leads into the inferior alveolar canal (for the vessels and nerves of the
same name). The shelf of bone overhanging the opening is the
lingula mandibulce. An oblique groove (sulcus mylohyoideus) extends
downward from the foramen lodges the mylohyoid artery and nerve.
The angle (angulus mandibulce) represents the junction of the base and
rami. The anterior margin is free and continuous with the oblique
line. The posterior margin is thick, smooth and covered by the paro-

THE SKULL AS A WHOLE

67

ticl gland. The inferior margin represents the fusion of ramus and
body. The superior margin is thin and presents the coronoid and
condyloid processes with an intervening mandibular notch (incisura
mandibular).

The coronoid process {processus coronoideus) is a flat triangular proc-
ess that affords attachment, laterally, to the mm. masseter and
temporalis, and medially to the m. temporalis. The condyloid
process (processus condyloideus) is more massive and presents a
condyle and a neck. The condyle (capitulum mandibular) is oblong
with its long axis transversely placed. Its surface is convex and

Mental Spine Sublingual

depression

One-half of the mandibl.

Mylohyoid groov,
Submaxillary depression

1 from the medial surface. (Sobotta and McMurrich.)

mainly articular. The neck (collum mandibular) is flattened from
before backward and ridged. Upon its medial surface, anteriorly,
there is a deep depression {fovea pterygoidea) for insertion of the m.
pterygoideus medialis.

Articulations. — With the temporal bones (two).

Ossification. — It is of intramembranous origin and develops from two centers,
one for each half. These centers appear about the forty-fifth day of fetal life.
At birth the mandible consists of two halves that fuse, usually, by the end of the
first year.

Muscles Attached. — The mm. mentalis, quadratus labii inferioris, triangularis,
platysma, buccinator, masseter, orbicularis oris, geniohyoglossus, geniohyoideus,
mylohyoideus, digastricus, constrictor pharyngeus superior, temporalis and
pterygoidei medialis and lateralis (sixteen pairs).

THE SKULL AS A WHOLE

Only a general description of the skull in various views will be
given, as frontal, lateral, occipital, basal, medial and internal.

The frontal aspect {norma frontalis) exhibits the following impor-
tant features for consideration: The frontal region, the orbital fossa,
pyriform aperture and dental arches.

68

OSTEOLOGV

The frontal region, above the level of the orbits, is convex in both
directions and its breadth and height vary in the different races.
The lower border is sharply outlined, on each side, by the supraorbi-
tal margins, each of which shows the supraorbital notch (incisura
supraorbitalis). In the median line, near the lower margin is the
and passing to each side from this are the superciliary arches.

Fig. 47.— The skul! seen from in front. (Sobotta anil McMwrich.)

The lateral borders of the frontal region are sharp, below, but not
above; no superior border is present as the curve of the bone blends
with the vertex.

The orbital fossae (two) are pyramidal in shape with the base
(orbital aperture) at the face and the apex directed backward and
medially. The apex is practically the optic foramen (for the optic
nerve and ophthalmic artery); below and medial to this is the
superior orbital fissure, for the oculomotor, trochlear, ophthalmic
division of the trigeminal, and the abducens nerves and the ophthal-
mic veins. In the temporal part of the orbit is the fossa for the lacri-
mal gland. The roof is formed by the orbital portion of the frontal

THE SKULL AS A WHOLE 69

bone and the small wing of the sphenoid. The floor is formed by the
orbital surfaces of the maxilla and zygomatic bones and the orbital
process of the palatal bone. Here is seen the inferior orbital fissure
that transmits the maxillary division of the trigeminal nerve, the
zygomatic branch of that division, the infraorbital vessels and some
branches from the palatine ganglion. Through the floor passes the
infraorbital canal. The lateral wall is formed by the great wing of
the sphenoid and the orbital surface of the zygomatic bone. It is
bounded by the two orbital fissures, behind. In it are seen two open-
ings, the foramina zygomaticoorbitalis, for the transmission of the
zygomaticofacial and zygomaticotemporal nerves from the maxillary
division of the trigeminal nerve. The medial wall is formed by the
frontal process of the maxilla, the lamina papyracea of the ethmoid
and the body of the sphenoid bones. ' At the inferior and medial
part (in front) is seen the fossa for the lacrimal sac.

The pyriform aperture {aperture pyriformis) lies below and between
the orbits and varies in the different races. It is bounded by the nasal
bones and the frontal processes of the maxillae. In the medial line
is seen the anterior nasal spine and, deeper in, the vomer. The
middle and inferior concha? are seen upon each lateral wall.

The dental arches are transversely placed and the upper overlaps
the lower, slightly. In the mandible, on each side of the midline, is
seen the mental foramen for the transmission of the mental vessels
and nerves.

The lateral aspect (norma lateralis) is mainly cranial. This por-
tion is bounded by the frontal, temporal, parietal and occipital bones,
and lies above a line drawn from the tip of the mastoid process to the
nasofrontal suture. The temporal fossa lies above the level of the
zygomatic process and extends upward to the superior temporal line.
The fossa contains the m. temporalis, with its nerves, vessels and
fascia, and the zygomaticotemporal nerve. Below the level of the
zygomatic arch the temporal fossa continues as the infratemporal
fossa, under cover of the ramus of the mandible. Into this fossa open
the foramina ovale and spinosum which are best seen on the basal
view. Under the root of the zygomatic arch is the mandibular fossa,
for the condyle of the mandible, and behind this is the external
auditory meatus. The pterygopalatine fossa is small and somewhat
hidden. It lies between the maxilla, in front, and the root of the
pterygoid process, behind. It communicates with the infratemporal
fossa through the pterygomaxillary fissure.

The occipital aspect (norma occipitalis) is formed by the squamous
portion of the occipital bone and the lower part of each parietal bone.
Its lower limit is the superior curved line and in the middle of this is
the external occipital protuberance, or inion.

The vertex (norma verticalis) is the superior aspect of the skull

7°

OSTEOLOGY

and varies greatly. The sutures are quite pronounced. In the
midline is the sagittal suture between the parietal bones. This joins
the lamboidal suture, between the occipital and parietal bones, be-
hind. This junction indicates the posterior fontanelle of the fetus.
In front, the sagittal suture meets the coronal suture, between the
parietal and frontal bones. This junction corresponds to the
anterior fontanelle of the fetus.

The basalar aspect (norma basalts), with the mandible off, is quite
complicated. In front are seen the superior dental arch and the hard
palate with its foramen incisivum. Back of the hard palate are' the
choanal, or posterior nares to the side of which are the pterygoid and

vertex

^ jm Occiput

scaphoid fossce. At about the middle of the base is seen the foramen
magnum (for the spinal cord and vertebral arteries) with the two con-
dyles and condyloid foramina (for the hypoglossal nerve) at each side.
Back of the foramen magnum is the external occipital crest with the
external occipital protuberance at its superior end, from the latter
the superior nuchal lines extend laterally.

Lateral to the midline the following are seen, from before back-
ward: The infraorbital fissure, the infratemporal fossa, foramen ovale
(for mandibular branch of the trigeminal nerve) for. spinosum (for
middle meningeal artery and vein) and the mandibular fossa; the fora-

THE SKULLL AS A WHOLE 7 1

men lacerum (for the carotid artery and great superficial petrosal
nerve), the auditory tube, the carotid canal, the jugular foramen (for
the jugular vein and the glossopharyngeal, vagal and hypoglossal
nerves), the styloid process and the external auditory meatus; the
stylomastoid foramen (for the facial nerve), the mastoid notch, the
mastoid process and the mastoid foramen.

The basis cranii interna is exposed by removing the vault of the
cranium. Three fossae, anterior, middle and posterior are then seen.
The anterior, the smallest, lies at the highest level. It is bounded,
in front, by the vertical portion of the frontal bone and behind, by the
edges of the small wings of the sphenoid bone. In the middle are
seen the foramen cecum and the crista galli; at the sides of the latter
are the olfactory grooves (for the olfactory lobes) and the cribriform
plate, of the ethmoid. This plate is pierced for the transmission of
the olfactory nerves. The frontal lobes of the cerebrum lie in this
fossa.

The middle fossa lies between the edges of the small wings of the
sphenoid bone and the superior margins of the petrous portions of the
two temporal bones. This is narrow in the midline and here is seen
the pituitary fossa for lodgment of the pituitary gland. This fossa
contains in addition the cruri cerebri and the temporal lobes of the
cerebrum. At each side, and from before backward, are the optic
foramen, internal opening of the carotid canal, and the carotid groove.
Far to the side the foramina rotundum, ovale, spinosum and lacerum,
the depression for the semilunar ganglion and the hiatus facialis.
The superior orbital fissure is here but it is hidden by the overhang-
ing posterior edge of the small wing of the sphenoid.

The posterior fossa is the largest, deepest and at the lowest level.
It contains the cerebellum. It lies between the superior margins
of the petrous portions of the two temporal bones, in front, and the
vertical portion of the occipital bone, behind. It is roofed over by
the tentorium cerebelli. In the midline are the foramen magnum
with the canal is hypoglossi upon each side; then follow the internal
occipital crest and internal occipital protuberance. At the sides of the
midline are seen the internal acoustic meatus, the jugular foramen and
grooves for the superior and inferior petrosal sinuses and the lateral
and sigmoid sinuses.

In a median sagittal section of the skull, the bulk is represented
by the cavity of the cranium, for the brain. In the frontal bone is
seen the frontal sinus; within the body of the sphenoid is the sphe-
noidal sinus and in the superior surface of the body is the pituitary
fossa. In the posterior fossa is the internal acoustic meatus. The
facial portion of this section presents the nasal cavity (cavum nasi).
This and its connections are described on page 271.

At birth the facial portion of the skull represents only about one-

72 OSTEOLOGY

eighth the mass of the cranial portion. The median line junction of
the frontal and parietal bones is incomplete, constituting the frontal
fontanelle (fonliculus frontalis); this is diamond-shaped, covered in by
membrane and is closed by bone by about the middle of the second
year. Between -the parietal and occipital bones there is also an area
where the bones are incomplete and this is the posterior fontanelle
(fonticulis occipitalis). This is closed usually by the second month
after birth. Lateral fontanelles are usually present at the sphenoidal
angles of the parietal bones. The parietal eminences are unusually
prominent at birth and represent the less-marked tubera parietalia
of the adult.

The forehead bulges prominently at the regions of the frontal

Frontal fontanelle

Frontal eminence

Sphenoid fontanelle

Occipital fontanelle

Parietal eminence

Fig. 49. — Skull of a new-born child seen from the left side. (Sobolla and McMurrich.)

tuberosities. The apertura pyriformis is relatively wider than in the
adult, the maxilla? are low and the alveolar margins poorly marked.
The maxillary sinus is merely indicated by a groove. The mastoid
process is barely noticeable. The mandible consists of lateral halves
united by fibrous tissue and the alveolar margin is poorly marked.
The ramus is wide and the angle is obtuse.

In the adult the face constitutes about one-half of the mass of the
cranium. This is mainly due to the eruption of the teeth and the
development of the air sinuses.

As regards sex, the skull of the average female is smaller than that
of the average male by about one-tenth. It is lighter, smoother and
less well marked in regard to ridges for muscle attachment. The
forehead is usually more vertical though the frontal and occipital

THK CLAVICLE

73

regions are less capacious
more oval.

The vertex is usuallv flatter and the face

BONES OF THE SUPERIOR ( PECTORAL ) EXTREMITY

The bones of each pectoral appendage are the clavicle, scapula (form-
ing one-half of the shoulder girdle) the humerus (arm), the radius and
ulna (forearm), carpal bones (wrist), metacarpal bones (palm) and
the phalanges (fingers).

THE CLAVICLE

The clavicle, or collar bone, is a ~-shaped bone that forms the
ventral portion of the pectoral girdle on each side. It consists of a
shaft and two extremities.

(.Subotta and McMurrich.)

The sternal extremity (ertremitas sternalis) is enlarged, oval and
somewhat concave, from above downward. Its articular surface is
smooth, and articulate with the manubrium sterni; from this bone,
however, it is separated by the interarticular fibrocartilage. This
extremity also rests upon the first costal cartilage. The edge of the
articular area serves for the attachment of the capsular ligament.

The shaft has a double curve. The sternal two-thirds is cylindrical

'Sternal articular —
tuberosity

[Sobotta ami McMurrich.

and convex in front, and the acromial one-third is flattened and con-
cave in front. The shaft has two surfaces and two margins. The
superior surface is smooth and subcutaneous. The inferior surface
shows, near the sternal extremity, a depression (tuberositas costalis)
for the attachment of the costoclavicular ligament. Beyond this a
groove extends to the acromial extremity and here the m. subclavius
is inserted. The ventral, or anterior margin, is roughened and from
its sternal portion arises the clavicular part of the m. pectoralis
major; from its acromial end a portion of the m. deltoideus arises.

74 OSTEOLOGY

The dorsal, or posterior margin is broad at its sternal end and here the
clavicular portion of the m. sternomastoideus arises; immediately
below this the m. sternohyoideus has its origin. Near the acromial
end of this margin is a small projection, the coracoid process {tuber-
ositas coracoidea) for attachment of the conoid ligament.

The acromial extremity presents, at its end, an oval facet for
articulation with the acromion of the scapula; to the edges of this
area is attached the capsular ligament. Its superior surface is
roughened and mainly subcutaneous. The inferior surface shows
the oblique trapezoid ridge at the dorsal end of which is the tuberositas
coracoidea. These are for the attachment of the trapezoid and
conoid portions of the coracoclavicular ligament, respectively.
The ventral, or anterior margin is thin and gives origin to the m.
deltoideus. The dorsal, or posterior margin is roughened for the
insertion of the m. trapezius.

The nutrient foramina are large and on the dorsal margin.

Articulations. — With the scapula and sternum (indirectly).

Ossification. — It is endochondral in origin and develops from ti,o centers, one
for the shaft and acromial extremity (fifth to sixth week) and one for the sternal
extremity (fifteenth to twentieth year). It is the first bone to ossify and fusion of
the two parts is completed by about the twenty-fifth year.

Muscles Attached. — Origins. — Mm. sternomastoideus, deltoideus, pectoralis
major, and sternohyoideus. Insertions. — 11m. trapezius and subclavius (six).

THE SCAPULA

The scapula, or shoulder blade forms the dorsal half of the pectoral
girdle on each side. It is flat, somewhat triangular and presents
a body, a spine and two processes.

The body is triangular and thin and presents two surfaces, three
margins and three angles. The ventral, or costal sulfate {fades
costalis) is concave in both directions and forms a fossa. Along
its medial, or vertebra! margin the m. serratus anterior is inserted.
The superior half of the lateral, or axillary margin is thick deepen-
ing the fossa in this area. The surface of the bone shows several
ridges that converge toward the neck. The fossa and ridges give
origin to the m. subscapularis.

The dorsal surface (fades dorsalis) is crossed, almost horizontally,
by the spine, which divides this surface into two portions or fossa?.
The upper, smaller supraspinous fossa is above the spine and the
latter forms its floor. From the outer part arises the m. supra-
spinatus. This fossa communicates with the infraspinous fossa
by means of the great scapular notch that transmits the transverse
scapular artery and suprascapular nerve. The infraspinous fossa
is triangular and roofed by the inferior surface of the spine. The
bulk of this area gives origin to the m. infraspinatus. Along the
vertebral margin the m. rhomboidei is inserted; along the upper

THE SCAPULA

75

Acromion
Glenoid cavity

'

External

Neck

Axillary bordt

Inferior angle
Fig. 52. — The dorsal surface of the left scapula. (Sobotta and McMurrich.)

Subscapular ft
Internal angle

Acromion Articular surface of
Coracoid

Inferior angle
PlC. 53. — The costal surface of the left scapula. (Sobotta and McMurrich.)

76 OSTEOLOGY

two-thirds of the axillary margin the m. teres major arises while
from the lower third the m. teres minor takes origin. Occasionally
the m. latissimus dorsi has an origin at the inferior angle.

The superior margin is thin, sharp and presents the scapular
notch. Usually this notch is bridged by a ligament and through
the foramen thus formed passes the suprascapular nerve while
above the ligament courses the transverse scapular artery. The
posterior belly of the m. omohyoideus arises near the notch. The
vertebral margin (margo vertebralis) is the longest. It is irregular
and to it are inserted the mm. levator scapulae, and rhomboideus
major et minor (from above downward). The axillary margin is
thick. The part just below the glenoid fossa is roughened (tuberositas
infraglenoidalis) and from this arises the long head of the m. triceps.

The angles are medial, inferior and lateral. The medial and in-
ferior angles are rather blunt. The lateral angle, occasionally called
the head, supports the glenoid cavity and coracoid process. The
glenoid cavity is oval and concave in both directions; its edge affords
attachment to the capsular ligament. Below the cavity is the infra-
glenoid tuberosity and above is the supraglenoid tubercle (tuberositas
supraglenoidialis) from which arises the long head of the m. biceps
brachii. The neck (collum scapula) connects the glenoid cavity
to the body. It is constricted and is indicated by a line connecting
the scapular notch and the infraglenoid tuberosity.

The spine (spina scapula) is on the dorsal surface and arises near
the vertebral margin and passes obliquely upward and laterally
toward the glenoid cavity; here the spine twists and leaves the dorsal
surface to form a free projecting mass of bone called the acromion.
At its glenoid edge it forms the great scapular notch. The main
part of the spine separates the supra- and infraspinous fossae, from
each other. Its ventral margin is fused to the body of the bone
while its dorsal margin is free and subcutaneous; to the upper lip of
this margin the m. trapezius is inserted and from the inferior lip the
m. deltoideus arises.

The acromion, one of the processes, is a continuation of the spine.
It is flattened from above downward and overhangs the glenoid
cavity. It presents superior and inferior surfaces and medial and
lateral margins. The superior surface slopes upward, faces dorsally
and is subcutaneous. The inferior surface is smooth. The medial
margin presents a facet (facies articularis acromii) for articulation
with the acromial extremity of the clavicle. The m. trapezius is
inserted to the medial margin while the m. deltoideus arises from the
lateral margin.

The coracoid process (processus coracoideus) is attached to the
upper part of the head just lateral to the scapular notch. It is bent
in such a manner so as to overhang the glenoid cavity. To the

THE HUMERUS 77

upper surface, near the bend, are attached the trapezoid and conoid
ligaments. Its dorsal margin affords attachment to the coraco-
acromial ligament and near its apex the m. pectoralis minor is in-
serted. From the apex the mm. coracobrachialis and short head of
the biceps arise.

Nutrient foramina are numerous around the glenoid cavity and upon the
surfaces of the spine.

Articulations. — With the clavicle and humerus (two).

Ossification. — It is of endochondral origin and is developed from seven
centers. The center for the body appears about the seventh to eighth week of
fetal life; two centers appear for the coracoid process, one during the first year and
the other about the tenth year; two centers appear for the acromion at about the
age of puberty; one center appears for the inferior angle about the sixteenth year
and one for the vertebral margin at about the seventeenth year. All parts are
usually fused by the twenty-fifth year.

Muscles Attached. — Origin. — Mm. subscapularis, omohyoideus, supraspinatus,
infraspinatus, teres major, teres minor, deltoideus, coracobrachialis, long head of
the triceps, short head of the biceps and occasionally the latissimus dorsi.

Insertions. — Mm. trapezius, levator scapulae, rhomboidei major et minor,
serratus anterior and pectoralis minor (seventeen).

THE HUMERUS

The humerus constitutes the support of the arm muscles. It con-
sists of a proximal extremity, a shaft and a distal extremity.

The proximal extremity comprises the head, neck and two tubercles.
The head {caput humeri) forms about one-third of a sphere and is
articular, resting in the glenoid cavity of the scapula. Its dorsal
half is the more convex, and the whole surface faces medially and
somewhat upward and dorsallv. It is set off from the rest of the
bone by a constriction, the anatomical neck (collum anatomicum) to
which the capsular ligament is attached. The tubercles are large and
small. The larger (tuberculum majus) seems to be a projection of
the shaft and presents three facets for the insertion of the mm. supra-
spinatus, infraspinatus and teres minor (from above downward).
It has numerous nutrient foramina. The smaller tubercle (tuberculum
minor) is attached to the front of the proximal extremity and is
separated from the preceding by the bicipital groove (sulcus inter-
tuber cularis). The two tubercles are connected by the transverse
humeral ligament. To the small tubercle the m. subscapularis is
inserted. The part of the bone succeeding these parts is the surgical
neck (collum chirurgicum) and is the part most liable to fracture.

The shaft (corpus humeri) is partly cylindrical and partly flattened
(distally). It presents ventral and dorsal surfaces and medial and
lateral margins. The proximal half of the ventral surface is divided
into lateral and medial portions by the intertubercular groove. The
tips of this groove are the crests of the larger and smaller tubercle;
(they are called the crista tuberculi majoris (lateral) and minoris

78

OSTEOLOGY

medial). The muscles inserted here are the mm. pectoralis major
(lateral lip), latissimus dorsi (floor of groove), teres major (medial
lip). At the end of the lateral part of the ventral surface is the V-
shaped deltoid tuberosity (tuberositas deltoidea) for the insertion of the
m. deltoideus. The medial ventral surface, near the middle of the
shaft, receives the fibers of the m. coracobrachialis. The distal por-

Greatcr tubercle

Upper

extremity

Anatomical neck

'ntertubtrntlar grccrt t

. Greater tubercle

Lower
extre-
mity

FIG. 54— The left h

behind. (Sobotta and MtMurrith.)

Fig. S5-— The left hu

front. {Sobotta and AIcAlurrich.)

tion of the ventral surface presents a ridge that begins at the deltoid
tubercle that forms two sloping surfaces from which the m. brachialis
anterior arises. The dorsal surface is divided into proximal and distal
(greater) portions by the oblique groove for the radial nerve (sulcus
nervus radialis). The nerve is accompanied by the profunda brachii
artery. Its course is downward and laterally. Upon the upper

THE HUMERUS

79

part there is a ridge from which the lateral (small) head of the m.
triceps arises. Distal to the groove the surface is smooth, extensive
and gives origin to the medial head of the m. triceps. The medial
margin {margo medialis) is rounded and indistinct, proximally, while
distally its prominent epicondylic ridgs ends at the medial epicondyle.
At about the middle of this margin is seen the insertion of the m.
coracobrachialia. The lateral margin {margo lateralis) is more
prominent, especially at its distal extremity where it is grooved for
the radial nerve and the profunda brachii artery. This distal por-
tion constitutes the lateral epicondylic ridge from which arise the
mm. brachioradialis (proximal two-thirds) and extensor carpi
radialis longus (distal one-third).

The distal extremity comprises the epicondyles, trochlea and capi-
tal urn. The lateral epicondyle (epicondylus lateralis) is small and
from it arises the m. anconeus and the common tendon of origin
of the extensor muscles. The medial epicondyle (condylus medialis)
is more prominent and affords origin to the m. pronator teres and
the superficial flexor muscles of the forearm.

The trochlea is a spool-shaped articular surface for the proximal
extremity of the ulna. Its ventral surface is more extensive than
the dorsal surface. It is placed obliquely to the long axis of the
bone. The coronoid fossa (fossa coronoidea) is just proximal to the
trochlea on the ventral surface of the bone. This receives the
coronoid process of the ulna during flexion of the forearm. In a
corresponding position upon the dorsal surface is the deeper ole-
cranon fossa (fossa olecrani) for the reception of the olecranon
process of the ulna during extension of the forearm.

The capilulum is lateral to the trochlea and articulates with the
head of the radius. It is separated from the trochlea by a groove.
Its articular portion is rounded ventrally and distally but not
dorsally. It is attached to the ventral surface of the humerus.
Just proximal to the capitullum is the radial fossa (fossa radialis)
for the reception of the head of the radius during flexion of the
forearm.

Nutrient foramina are numerous; the two largest (distally directed) are near
the insertions of the mm. deltoideus and coracobrachialis. The smaller ones
are in the region of the anatomical neck.

Articulations. — With the scapula, radius and ulna (three).

Ossification.— It is of endochondral origin and is developed from six centers.
One for the shaft appears during the seventh week of fetal life; one for the head
appears during the fifth or sixth month (postnatal); one for the large tubercle
during the second or third year; one for the small tubercle at the end of the third
year. The first three are fused by the seventh year and this epiphysis is fused
with the shaft by the twenty-fifth year. The center for the capilulum and
lateral half of the trochlea appears during the second or third years; that for the
medial pari of the trochlea about the sixth year; that for the lateral condyle about
the twelfth year. The medial condyle fuses with the shaft at about the nine-
teenth year and the others by about the seventeenth year.

80 OSTEOLOGY

Muscles Attached. — Origin. — Mm. triceps, brachialis, pronator teres, flexor
carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum sublimis,
brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis.
extensor digitorum communis, extensor digiti quinti proprius, extensor carpi
ulnaris, anconeus and supinator (brevis).

Insertions. — Mm. subscapularis, supraspinatus, infraspinatus, teres minor,
pectoralis major, latissimus dorsi, teres major, coracobrachialis and deltoideus.

THE ULNA

The ulna constitutes the medial bone of the forearm and consists
of a proximal extremity, shaft and a distal extremity.

The proximal extremity comprises the olecranon and coronoid
processes. The olecranon process is a direct continuation of the
shaft and represents the dorsal part of the extremity. Its dorsal
surface is triangular, covered with a bursa and subcutaneous. The
superior (proximal) surface is nearly at a right angle with the dorsal
surface and forms at this junction the tip of the elbow where the
tendon of the m. triceps is inserted. The ventral, or volar surface,
is smooth and concave, from above downward, and convex, from
side to side. It articulates with the trochlea of the humerus. The
sharp margin between these two surfaces serves for attachment of
the ligaments of the elbow joint.

The coronoid process (processus coronoideus) projects, shelf-like,
from the ventral surface of the bone. The proximal surface, with
the ventral surface of the olecranon, forms the semilunar notch for
articulation with the trochlea of the humerus. The ventral or volar
surface of the coronoid process is rough, triangular and continuous
with the corresponding surface of the shaft. It usually presents
a tubercle (tuberositas ulna) for insertion of the tendon of the m.
brachialis. The margin affords attachment to ligaments of the
elbow joint. The ventral surface also affords origin to the mm.
flexor digitorum sublimis and pronator teres and occasionally to the
flexor pollicis longus.

The semilunar notch {incisura semilunaris) articulates with the
trochlea of the humerus. This notch is narrowest across the
middle and is uneven so as to approximate closely to the trochlear
surface.

The radial notch (incisura radialis) is at the lateral margin of the
coronoid process. It is concave dorsoventrally and comparatively
small, accommodating the head of the radius. Medially it joins
the semilunar notch and all of its other margins serve for attachment
of ligaments.

The shaft (corpus ulna) is tapering and its distal extremity is
slightly curved, laterally. It presents three surfaces and three
margins. The ventral, or volar surface, is smooth and concavo-
convex. It affords origin for the mm. supinator, flexor digitorum

THE ULNA » I

profundus, pronator teres and pronator quadratus (from above
downward). The medial surface is smooth and not sharply defined
from the ventral surface; it affords origin to the m. flexor digitorum
profundus and is often described with the ventral surface. The
dorsal surface is quite well defined and faces somewhat laterally.

Dorsal border
Internal stir/the

Fig. 56.— The left ulna seen from be-
hind. (Sobolta ami McMurrich.)

Fig. 57. — The left ulna seen from ;
front. (Sobolta and McMurrich.)

It is smooth and concave in its proximal two-thirds and the distal
portion is rounded and not sharply separated from the medial
surface. Its proximal portion affords origin to the mm. anconeus
and then in order (but along its lateral margin) the abductor pollicis
longus, extensor pollicis longus and extensor indicis proprius.

82 OSTEOLOGY

The ventral, or volar margin is rounded extending from the tuber-
osity to the styloid process and affords origin to the m. flexor digito-
rum profundus. The dorsal margin (margo dorsalis) is sharp and
subcutaneous. To it is attached the aponeurosis of the mm. flexor
carpi ulnaris, extensor carpi ulnaris and flexor digitorum profundus.
The lateral margin, or interosseous crest {crista interossei), is sharp
and well defined in its proximal three-fourths. To almost its entire
extent it affords attachment to the interosseous membrane.

The distal extremity comprises a head and a styloid process. The
head (capitulum ulna:) in its ventrolateral portion is smooth,
convex, narrow and articulates with the ulnar notch of the radius.
Its distal, flat, semilunar surface rests upon the interarticular car-
tilage of the wrist joint. The margin affords attachment to the
ligament that holds this bone to the radius. The styloid process
is a small projection of bone medial and dorsal to the head from
which it is separated by a small groove. This groove extends upon
the dorsal surface of the bone and lodges the tendon of the m.
extensor carpi ulnaris.

Nutrient foramina are numerous. The main ones (distally directed) is on the
ventral surface near the middle. Others are seen near the radial notch and near
the groove at the distal extremity of the bone.

Articulations. — With the radius (at both ends) and the humerus.

Ossification. — It is of endochondral origin and develops from three centers.
The coiler for the shaft appears about the eighth week of fetal life; that for the
distal extremity appears during the fourth year (sixth to the eighth year (Pryor)
and for the proximal extremity about the tenth year. The shaft and proximal
extremity fuse about the sixteenth year and the distal extremity fuses with the
shaft at about the twentieth year.

Muscles Attached. — Origin. — Mm. supinator, pronator teres, flexor digitorum
sublimis, flexor digitorum profundus, pronator quadratus, flexor carpi ulnaris,
extensor carpi ulnaris, flexor pollicis longus, extensor pollicis brevis, extensor
indicis proprius, extensor pollicis longus.

Insertions. — Mm. triceps, anconeus and brachialis (fourteen).

THE RADIUS

The radius is the shorter bone of the forearm and is laterally
placed. It consists of a proximal extremity, shaft and distal extremity.

The proximal extremity comprises the head, neck and tuberosity.
The head (capitulum radii) is disc-like and its surface concave and
articular (fovea capituli radii). Its margin is broad and smooth and
its medial portion articulates with the radial notch of the ulna. The
remainder of the margin is enclosed by the annular ligament of this
joint. The neck (folium radii) is the smooth, constricted portion
of bone between the head and shaft. The tuberosity (tuberositas
radii) is an oval projection on the medial and proximal part of the
radius. Its dorsal surface is roughened for the insertion of the
tendon of the m. biceps brachii; its ventral surface is smooth and
covered by a bursa.

THE RADIUS

83

The shaft {corpus radii) is larger distally than proximally and has
a lateral convex curve. It has three surfaces and one well-marked
margin. The ventral, or volar surface is smooth and slightly convex
proximally and broad and flat distally. It is crossed by the ventral
oblique line, from which the m. flexor digitorum sublimis takes
origin, and proximal to which the m. supinator is inserted. The
bulk of this surface gives origin to the m. flexor pollicis longus;

Styloid process

Styloid process

-The left radius seen from i
(Sobolta and McMurrich.)

Fig. 50. — The left radius seen from be-
hind. (Sobotta and McMurrich.)

to the distal part the m. pronator quadratus is inserted. The lateral
surface {margin) is broader proximally than distally where it is more
ridge-like passing into the base of the styloid process. The m.
supinator is inserted to the proximal portion (as well as the neck);
the m. pronator teres to the middle part and the distal part is
covered by muscles. The dorsal surface {fades dorsalis) is broadest at

84 OSTEOLOGY

its distal portion and narrow proximally. It is crossed by the dorsal
oblique line proximal to which the m. supinator is inserted. Distal
to the line the mm. extensor pollicis longus and extensor pollicis
brevis respectively arise. The distal quarter of the surface is
subcutaneous and has several grooves that continue onto the ex-
tremitv. The interosseous crest (crista interossei) is the lateral
margin and is the only one that is well defined. It begins proximally
at the tuberosity and distally divides to embrace the ulnar notch
of the distal extremity. To the triangular area so formed the m.
pronator quadratus is inserted. The crest gives attachment to
the interosseous membrane.

The distal extremity has two articular surfaces and a styloid process.
The distal surface (carpal articular) is slightly concave and divided
into two facets. The lateral of these surfaces is triangular and for
articulation with the navicular (scaphoid) and the medial is quadri-
lateral and articulates with the lunate (semilunar) bones of the
carpus. The concave ulnar notch (incisura ulnaris) is on the medial
margin of the distal extremity of the head of the radius and to its
distal edge is attached the articular cartilage that supports the
head of the ulna and prevents it from participating in the formation
of the wrist joint. To the ventral and dorsal edges ligaments are
attached. The ventral margin of the distal extremity gives attach-
ment to the capsular ligament of the wrist Joint. The dorsal
margin is irregular and grooved for tendons and also gives attach-
ment to the capsular ligament. The broad medial groove contains
the tendons of the mm. extensor digitorum communis and extensor
indicis proprius. The next one accommodates the tendon of the
m. extensor pollicis longus; the last groove accommodates the
tendons of the mm. extensores carpi radialis longus and brevis.

The styloid process is the pointed projection of the lateral surface of
the distal extremity. The lateral surface of its proximal end is
grooved and the tendon of the m. brachioradialis is here inserted.
The remainder of the groove accommodates the tendons of the mm.
abductor pollicis longus and extensor pollicis brevis. The medial
surface of the process is smooth and articular and enters into the
formation of the wrist joint.

Nutrient foramina are numerous around the neck. The main one for the shaft
is in the proximal third and is proximally directed. Small foramina are also
present in the distal extremity.

Articulations. — With the humerus, ulna (both ends) and the navicular and
lunate carpal bones.

Ossification. — It is of endochondral origin and is developed from four centers.
Tlhil for the shaft appears about the eighth week; that for the distal, extremity
during the second or third year (eighth to the fifteenth month (Pryor); thai for
the head from the fifth to the seventh year; that for the tuberosity during the
fourteenth year. By the twenty-third year all are fused with the shaft.

THE CARPI'S S 5

Muscles Attached. — Origins. — Mm. flexor digitorum sublimis, flexor pollicis
longus, abductor pollicis longus, extensor pollicis brevis.

Insertions. — Mm. biceps brachii, supinator, pronator teres, pronator quadratus
and brachioradialis (nine).

THE BONES OF THE HAND

The hand comprises the wrist (carpus, eight bones), the palm
(metacarpus, five bones) and the digits (phalanges, fourteen bones).

THE CARPUS

The carpal bones are arranged in two rows of which the first, or
proximal row contains the navicular (scaphoid), os I una turn (semi-
lunar), os triquctrum [cuneiform) and the os pisiforme. The
second, or distal row contains the greater multangular (trapezium),
the lesser multangular (trapezoid), the os capitatum (os magnum) and
the os hamatum (unciform) bones. These are given from radial to
ulnar side. They are all irregular bones. The dorsal surfaces
form an irregular convex surface and are rough for the attachment
of ligaments. The ventral surfaces are irregular and together form
a concave or groove-like area which is bridged by the transverse
carpal ligament and constitutes thus a canal for the flexor tendons
of the fingers. The oilier surfaces are articular except for those bones
that form the ends of the rows and here the exposed surface of each
is nonarticular. The navicular and os lunatum articulate with the
distal extremity of the radius and the distal row articulates distally
with the metacarpal bones.

These bones are of endochondral origin and are usually carti-
laginous at birth. According to J. N. Pryor the centers appear
earlier than formerly supposed. They appear earlier in the female
than in the male. Each has one center of ossification that appears
as follows:

Usually given Pryor

Capitatum appears about 12th mo. (1). 3d to 10th mo.

Os hamatum

Os triquetrum

Os lunatum

Greater multangular

Navicular

Lesser multangular

Os pisiforme

14th mo. (2). 5th to the i2mo.

3d year (3). 2nd to 3d year

5th to 6th year (4). 3d to 4th year

6th year (7). 4th to 6th year

6th year (5). 4th to 5th year

6th to 7th year (6). 4th to 6th year
nth to 12th year (8). 9th to 13th year

Ossification is completed about the 15th year.

Muscles Attached. —

Navicular. — M. Abductor pollicis brevis (origin).

Os Pisiforme. — Abductor quinti digiti (origin), flexor carpi ulnaris (insertion).
Great Multangular. — Abductor pollicis brevis, opponens pollicis, flexor pollicis
brevis (deep head) (all origins).

Lesser Multangular. — Deep head of flexor pollicis brevis (origin)

86

OSTEOLOGY

THE PHALANGES 87

Os Capitation. — Deep head of flexor pollicis brevis, adductor pollicis (origins).
Os Hamatum — Opponens quinti digiti, flexor quinti digiti brevis (origins),
flexor carpi ulnaris (insertion).

THE METACARPAL BONES (OSSA METACARPALIA)

The metacarpal bones are five in number and articulate with the
distal carpal bones and each other, proximally, and with the first
row of phalanges, distally. The first, or thumb metacarpal, is the
most mobile. Each consists of a base, shaft and head.

The base is the carpal extremity, each is wedge-shaped and the
articular surface varies with the joint that it forms. The first
{thumb) is the shortest and strongest. The second (index finger)
is the longest. The shaft of each is smooth and narrow in the middle.
The dorsal surface is triangular and broad distally. The ventral
surface is narrow and more like a ridge. The medial and lateral
surfaces are concave and afford origin for the mm. interossei. The
head (capituium) has an articular surface for the base of the proximal
phalanx. This surface is rounded and more extensive ventrallv
than dorsally. The ventral edge is grooved for the passage of
tendons. To the margins of the head ligaments are attached.

Nutrient Foramina. — There is one for each bone. In the first it is directed
distally while in the others it is proximally directed.

Ossification. — Each of the four medial metacarpal bones has one center for
the shaft and base and one for the head. The shaft and base center appears
(successively and in order) during the ninth or tenth week of fetal life; the
center for each head appears during the third year and fuses completely with
the shaft by the twentieth year. The center for the shaft and head of the first
metacarpal bone appears after the tenth week and for the base during the third
year. Fusion with the shaft takes place about the twentieth year.

Muscle Attached. — First Metacarpal. — Jim. First dorsal interosseous (origin).
flexor pollicis brevis, opponens pollicis, abductor pollicis longus (insertions)
(four).

Second Metacarpal. — First and second dorsal interossei, first palmar interos-
seous, adductor pollicis (origins); flexor carpi radialis, extensor carpi radialis
longus (insertions) (six).

Third Metacarpal. — Second and third dorsal interossei, adductor pollicis
transversus and obliquus (origins); extensor carpi radialis brevis, flexor carpi
radialis (insertions) (six).

Fourth Metacarpal. — Third and fourth dorsal interossei and second palmar
interosseous (origins) (three).

Fifth Metacarpal. — Extensor carpi ulnaris, flexor carpi ulnaris, opponens
quinti digiti (insertions) (three).

THE PHALANGES (PHALANGES DIGITORUM MANTJS)

The phalanges are fourteen in number, three for each finger and
two for the thumb. The first, or proximal phalanges, are the
longest and the distal are the smallest. The proximal end of each
first phalanx is rather large and bears a concave articular facet for
the head of the metacarpal bone. The shaft is somewhat flattened

OSTEOLOGY

THE PELVIC APPENDAGES 89

and presents a smooth convex dorsal surface; the ventral surface is
smooth and concave for the accommodation of the flexor tendons.
The head bears a convex articular facet for the second phalanx.
The second phalanges resembles the first generally. The proximal
facet, however, is convex. The third phalanges are the smallest and
shortest. The proximal extremity is large and its articular surface
is convex. Its distal extremity is flattened for the support of the
nail.

Nutrient Foramina. — There are usually two nutrient foramina for each phalanx,
distally directed and upon the ventral, or palmar surface.

Ossification. — These are of endochondral origin and each is developed from
two 11 titers. The center for the shaft and distal extremity appears during the ninth
to the tenth week of fetal life and that for the proximal extremity during the third
year. According to Prvor most of these centers appear between the first and
early part of the third years. Fusion of these parts occurs at the eighteenth or
twentieth year.

Muscles Attached. — These are all insertions.
Thumb. —

Fir>l Phalanx. — Mm. Extensor pollicis brevis, flexor pollicis brevis, adductor
pollicis, abductor pollicis brevis, adductores pollicis obliquus
and transversus (five).
Set ond Phalanx. — Mm. Flexor pollicis longus, extensor pollicis longus (two).
Index Finger. —

First Phalanx. — First dorsal and first palmar interossei (two).
Second Phalanx. — Mm. Flexor digitorum sublimis, extensor digitorum com-
munis, extensor indicis (three).
Third Phalanx. — Mm. Flexor digitorum profundus, extensor digitorum
communis (two).
Middle Finger. —

First Phalanx. — Second and third dorsal interossei (two).

Second Phalanx. — Mm. Flexor digitorum sublimis, extensor digitorum

communis (two).
Third Phalanx. — Mm. Flexor digitorum profundus, extensor digitorum
communis (two).
Ring Finger. —

First Phalanx. — Fourth dorsal and second palmar interossei (two).
Second Phalanx. — Mm. Flexor digitorum sublimis, extensor digitorum com-
munis (two).
Third Phalanx. — Mm. Flexor digitorum profundus, extensor digitorum
communis (two).
Little Finger. —

First Phalanx. — Third palmar interosseus, flexor quinti digiti brevis, abductor

quinti digiti (three).
Second Phalanx. — Mm. Flexor digitorum sublimis, extensor digitorum

communis (two).
Third Phalanx. — Mm. Flexor digitorum profundus, extensor digitorum
communis, extensor digiti quinti (three).

THE LOWER LIMB (PELVIC APPENDAGES)
The pelvic appendages comprises the pelvic girdle and the append-
ages proper. The girdle is formed by the two innominate bones, articu-
lating with each other ventrally and with the sacrum dorsally.

90 OSTEOLOGY

THE HIP BONE (OS COXjE)

The hip bone is classed as a flat bone; it is shaped like a propeller,
one blade of which is perforated by a foramen (obturator). It
represents the fusion of three segments, the ilium, ischium and os
pubis. These surround and form the acetabular cavity.

The ilium is the largest division and presents two surfaces, three
margins and four spines. The lateral surface is divided into a
larger (gluteal) and a smaller (acetabular) portion. The gluteal
portion is large, concavoconvex and is marked by the three gluteal
lines. The inferior gluteal line (linea glutece inferior) lies just over
the acetabular margin and between these two the reflected head
of the m. rectus femoris arises. The ventral {anterior) line is the
largest and starts near the ventral end of the iliac crest and arches
dorsally to the greater sciatic notch. The dorsal {posterior) gluteal
line is a short curved line near the dorsal portion of the lateral sur-
face; dorsal to this line the m. gluteus maximus arises. The m.
gluteus medius arises between the ventral and dorsal lines and the
iliac crest. The medial surface is divided into dorsal and ventral por-
tions. The dorsal part is partly articular (fades articular is) for articu-
lation with the sacrum. Superiorly and dorsally the bone is rough-
ened and presents a tuberosity {tuberositas iliaca) and serves for the
attachment of ligaments. The superior edge here gives origin to
the mm. multifidus, sacrospinalis and quadratus lumborum. The
ventral portion is mainly concave, smooth and presents the extensive
iliac fossa from which the m. iliacus arises. The oblique iliopectineal
line {linea arcuala), which bounds the fossa inferiorly, ends ventrally
in the iliopectineal eminence. The dorsosuperior portion of this
surface gives origin to the m. obturator internus.

The iliac crest {crista iliaca) has a lateral lip (labrum lateralis),
a medial lip (labrum medialis) and an intervening area (linea inter-
media). The crest is in the form of a quarter circle and extends
from the ventral superior spine to the dorsal superior spine in a
double curve. From the dorsal part of the crest the mm. quadratus
lumborum, latissimus dorsi and sacrospinalis arise; on the ventral
part the mm. obliquus abdominis internus and transversus ab-
dominis arise and the oblique abdominis externus is inserted. The
ventral superior spine (spina ilia-ca anterior superior) is a blunt process
that affords origin to the m. sartorius and laterally to the m. tensor
fascia? lata? and the inguinal ligament. The ventral inferior spine
(spina iliaca anterior inferior) is below the preceding and gives
origin to the m. rectus femoris and the iliofemoral ligament. The
ventral margin connects the two ventral spines. The dorsal superior
spine is at the termination of the iliac crest. From it the dorsal
margin starts and a short distance below its origin it presents the

THE HIP BONE

91

92 OSTEOLOGY

dorsal inferior spine; below this the margin is deeply notched; this
constitutes the greater sciatic notch (incisura ischiadica major).

The ischium, the dorsoinferior portion of the os coxae, presents
a body and two rami. The body {corpus) is the superior part of the
bone. Its lateral surface is irregular, presenting a deep acetabular
notch that forms two-fifths of the acetabular cavity. The bone
beyond this slopes from the margin of the cavity and is smooth.
The medial surface is smooth, concave and forms a part of the wall
of the pelvic cavity. The short ventral margin assists in forming the
obturator foramen. The medial margin presents the ischial spine
(spina ischiadica); this bounds the lesser sciatic notch superiorly
and affords origin to the m. gemellus superior and the sacrospinous
ligament; laterally it gives origin to the m. coccygeus and medially
to the m. levator ani. The rami are two wedge-shaped bars of bone
that join each other at nearly a right angle. The ventral surface of
each is concave and the inferior affords origin to the mm. obturator
externus, and adductor magnus. The medial surfaces are flat and
afford an origin to the crus penis (or clitoridis) and mm. ischiocavern-
osus, obturator internus and transversus perinei. The medial
margin of each ramus is thin and assists in forming the boundary of
the obturator foramen. The dorsolateral margin of the superior
ramus presents a rough irregular mass of bone, the tuberosity (tuber
ischiadicum); from this arise the mm. semitendinosus (superiorly
and laterally) and the biceps femoris and semimembranosus
(inferiorly and medially).

The pubis (os pubis) is the smallest division and is ventrally
placed. It comprises a body and two rami.

The body (corpus) presents two surfaces. The dorsoinferior surface
is smooth and affords origin to the m. levator ani and the pubo-
prostatic ligament. The ventroiuferior surface is rough and affords
origin to the mm. gracilis, adductores longus et brevis and the
obturator externus. The medial margin (fades symphyseos) is oval,
covered with cartilage and joins its fellow of the opposite side to form
the symphysis pubis. The superior margin is thick and extends so
as to form the crest and tubercle. The crest gives origin to the mm.
rectus abdominus and pyramidalis and the tubercle affords attach-
ment to the inguinal ligament. The superior ramus slopes superiorly
and laterallv and its lateral extremity forms a part of the acetabular
cavity. Its ventrosuperior surface affords origin to the m. pectineus.
The dorsosuperior (medial) surface is concave and forms a part of the
pelvic wall. The ventroiuferior surface is concave. The inferior
margin (crista obturatoria) forms a part of the boundary of the obtu-
rator foramen. The dorsosuperior margin is a continuation of the
iliopectineal line and is called the pecten ossis pubis. The interior
ramus is flattened and has a downward and lateral direction; it

THE PELVIS 93

completes the boundary of the obturator foramen and with its fellow-
forms the pubic arch. Its ventral surface gives origin to the mm.
gracilis and adductores magnus et brevis. Its smooth medial sur-
ace and inferior margin give attachment to the crus penis or clito-
ritis and the arcuate ligament.

The obturator foramen (foramen obturation) is the opening between
the above bones. This is closed in by a membrane in the fresh
condition.

The acetabulum is a deep cavity formed by the above bones; the
ilium forms a little less than two-fifths, the ischium a little more than
two-fifths and the pubis one-fifth. Opposite the obturator foramen
the margin, to which the capsular ligament is attached, is interrupted
and this is the acetabular notch (incisura acetabuli). The articular
portion of the floor is horseshoe-shaped and the central depressed
area (fossa acetabuli) is continuous with the acetabular notch.

Nutrient foramina are numerous; for the ilium in the iliac fossa and pelvic and
gluteal areas; for the ischium near the acetabulum and upon the pelvic portion;
for the pubis in the acetabular fossa and in the body.

Articulations. — With the femur, sacrum and fellow of the opposite side.

Ossification. — It is of endochondral origin. The primary centers appear early;
the center for the ilium about the ninth week of fetal life; for the ischium about
the fourth month; for the pubis about the fifth to the sixth month of fetal life.
Up to the twelfth year these bones are still separated from one another by car-
tilage in the acetabular cavity; at that time about three centers appear here and
fusion is completed by the sixteenth year. At about the age of puberty other
centers appear; one for the ventroinferior spine, twelfth year; one for the ventral
two-thirds of the iliac era! and superior spine, fifteenth year; one for the dorsal
one-third of the iliac crest and the dorsal superior spine, fifteenth year; one for the
tuberosity of the ischium, fifteenth year: one or two for the tubercle and angle of
the pubis. These all fuse with the body by the twenty-fifth year.

Muscle Attached. — Origins. — Mm. tensor fascia? lata?, latissimus dorsi, trans-
versa abdominis, quadratus lumborum, sacrospinalis, obliquus abdominis
internus, gluteus maximus, gluteus medius, gluteus minimus, rectus femoris,
iliacus, pyriformis, rectus abdominis, pyramidalis, obturator internus, obturator
externus, ischiocavernosus. transversus perinei, gemelli superior and inferior,
levator ani, coccygeus, biceps femoris, semitendinosus, semimembranosus,
adductores magnus and brevis, pectineus, gracilis and adductor longus.

Insertion. — M. obliquus abdominis externus.

THE PELVIS

The pelvis consists of the two ossa coxa-, sacrum and coccyx. That
portion superior to the iliopectineal lines constitutes the false pelvis
(pelvis major) and that below the true pelvis (pelvis minor). The
pelvis minor is bounded, ventral! y, by the symphysis pubis, the bodies
and superior rami of the pubic bones; laterally by the body of the
ischium and its rami and dorsally by the sacrum and coccyx. The
superior aperture, or brim, slopes downward and forward at an
angle of 6o° to the horizontal plane; it is bounded, ventral! y, by the

94 OSTEOLOGY

bodies of the ossa pubes, laterally by the iliopectineal lines and
dorsally by the promontory of the sacrum. The inferior aperture,
or outlet, is bounded, venlrally and superiorly, by the bodies of the
ossa pubes, laterally by the rami of pubes and ischii and ischial
tuberosity and dorsally by the tip of the coccyx and sacrotuberous
ligaments. The ventral wall is only i>2 to 2 inches vertically and
the dorsal wall 5 to 6 inches in extent.

The female pelvis is lighter and smoother and the iliac bones do
not flare out as much as in the male. The cavity is more capacious,
the sacrum shorter and wider, the sacral curve less uniform and the
pelvic arch is wider in the female. The superior aperture is large
and more oval; the outlet is larger and the ischial tuberosities are
farther apart in the female.

THE FEMUR

The femur is the longest bone in the body and comprises a proxi-
mal extremity, shaft and a distal extremity.

The proximal extremity consists of head, neck and two trochanters.
The head (caput femoris) is the articular portion. It is hemispherical
in shape, fits into the acetabular cavity and near its summit exhibits
a depression (fovea capitas femoris) in which the ligamentum teres
is attached. The neck (folium femoris) is shaped like an old-fash-
ioned mortar, supports the head and is attached by its base to the
shaft, at an angle of 1250. Ventrally and dorsally its junction with
the shaft is marked by oblique ridges; the ventral ridge is the superior
portion of the intertrochanteric line and to it is attached the ilio-
femoral ligament. The dorsal ridge connects the two trochanters
and is called the intertrochanteric crest; part of this, the quad rat or
tubercle, affords insertion to the m. quadratus femoris. Vascular
foramina are numerous in the neck.

The greater trochanter (trochanter major) is a quadrilateral mass of
bone that projects from the shaft above the level of the neck. Its
medial surface is quite concave, forming the trochanteric fossa where
the m. obturator externus is inserted. The lateral surface is some-
what convex and presents an oblique ridge into which the m. gluteus
minimus is inserted. To its proximal, or superior margin the mm.
obturator internus and gemelli are inserted (ventrally) and the
pyriformis (dorsally). The dorsal margin is the superior portion of
the intertrochanteric crest.

The lesser trochanter (trochanter minor) is a blunt, cone-shaped
mass of bone upon the dorsal surface at the junction of the shaft and
neck and at a lower level than the greater trochanter. Here the
intertrochanteric crest ends. To this trochanter the m. iliopsoas is
inserted.

The shaft is cylindrical and curved from above downward with

1HE FEMUR

95

the convexity ventrally directed. It becomes broader where it
supports the distal extremity. Margins are not present as the gen-
eral curvature of the circumference causes the surfaces to blend
insensible with one another. Upon the dorsal surface is a narrow

Great trochanter

Oreat trochanter

Internal epicondyle

Internal

condyle i

Intercondyloid line

\ External condyle
Intercondyloid ft

Fig. 66. — The right femur seen from
behind. (Soboila and AlcMurrich.)

FlG. 67. — The right femur see
front. (.Sobotta and McMu

1 from i
rich.)

rough area called the linca aspera. The medial edge, or lip, of the
linea aspera continues, superiorly, around the base of the trochanter
minor where it becomes continuous with the ventral intertrochanteric
line; these two constitute the spiral line from which the m. vastus
medialis arises. The lateral Up of the linea aspera is continued,
superiorly, to the level of the trochanter minor as the gluteal tuber-

96 OSTEOLOGY

osity. This is rough and serves for the insertion of the m. gluteus
maximus. The pectineal line lies between these two and serves for
the insertion of the m. pectineus. In the middle of the shaft the
lips of the linea aspera are most prominent. The mm. adductores
magnus, longus and brevis are inserted into the proximal portion
between the mm. gluteus maximus and pectineus. In the distal
third the lips diverge and end at the corresponding epicondyles as
the epicondylic lines. The triangular area between these lines is the
popliteal plane (planum poplitcum) which is part of the floor of the
popliteal fossa. The adductor tubercle is a small eminence at the end
of the medial epicondylic line; to its medial surface the tendon of
the m. adductor magnus is inserted and from its dorsal surface the
m. gastrocnemius (medial head) arises. The medial lip and the
adjoining medial surface of the shaft afford origin for the m. vastus
medialis; the lateral lip and lateral surface afford origin for the m.
vastus lateralis; the ventral surface of the shaft affords origin to the
mm. vastus intermedius and articularis genu. The m. biceps fe-
moris arises from the lateral lip distal to the m. gluteus maximus
and also from the lateral epicondylic line. The distal portion of the
same line gives origin (dorsally) to the m. plantaris.

The distal extremity consists of the two condyles and two epicondyles.
The condyles are two rocker-like articular processes of the bone;
the articular surface of the two condyles are connected ventrally
(patellar area) and are separated dorsally by the intcrcondylic notch
or fossa. When the bone is held vertically the medial condyle
projects farther distally but is narrower and less extensive dorso-
ventrally than the lateral condyle. The intercondylic notch is quite
deep and broad. To the medial wall is attached the dorsal cruciate
ligament and on its lateral wall is attached the ventral cruciate
ligament. Where the floor of the notch joins the popliteal plane
there is a ridge to which the dorsal part of the capsular ligament
is attached. The medial epicondyle affords attachment to the
tibial collateral ligament of the knee joint. The lateral epicondyle
is less prominent and presents a dorsal groove {popliteal) that ends
in a pit ventrally. Here the m. popliteus arises. The dorsal por-
tion of the epicondyle affords attachment to the fibular collateral
ligament of the knee joint and to the lateral head of the m.
gastrocnemius.

The articular surface consists of the patellar and condylic portions.
The patellar part (jacies patellaris) is concave in the middle and is
separated from each condylar surface by an oblique groove. The
lateral condylic surfaces are convex in both directions and are on
the distal and dorsal portions of the condyle. The medial is
narrower than the lateral.

THE PATELLA QJ

Nutrient foramina are found in the fossa for the ligamentum teres, the neck,
on the great trochanter, on the linea aspera (proximally directed) and in the
intercondylic fossa.

Articulations. — With the hip bone, tibia and patella.

Ossification. — It is of endochondral origin and is developed from five centers.
The centers for the shaft appears during the second fetal month; that for the distal
extremity during the ninth month; that for the head during the first year; the
center for the greater trochanter about the second to the third year; that for the
lesser trochanter about the twelfth to the thirteenth year. All fuse with the shaft
by the twentieth to the twenty-second year.

Muscles Attached. — Origins. — Mm. vasti medialis, lateralis and intermedius.
short head of biceps femoris, gastrocnemius, popliteus, plantaris and articularis
genu.

Insertions. — Mm. glutei maximus, medius and minimus, gemelli superior and
inferior, pyriformis, obtutatores internus and externus, psoas, iliacus, quadratus
femoris, adductores magnus, brevis. and longus, and pectineus (twenty-three).

THE PATELLA

The patella is a sessamoid bone, that is one that is developed in
a tendon. It protects the knee joint ventrally. It is flattened, of
a triangular outline (inverted) and possesses an apex, a base, two
surfaces and two margins.

The apex (apex palel/ce) is distal and affords attachment to the
ligamentum patellae. The base (basis patella) is broad and thick and

Base Base

Apex Apex

Fig. 68. — The patella seen from in front. Fig. 69. — The patella seen from behind.

-■■•iia ami McMurrich.) (Sobotta and McMurrich.)

receives, ventrally, the insertion of the tendon of the m. quadriceps
extensor. The ventral surface is convex, somewhat rough, subcu-
taneous and has numerous foramina. The dorsal surface is mainly
articular. A vertical ridge divides it into a larger, concave lateral
facet, for the lateral condyle of the femur, and a smaller, concave
medial facet for the medial condyle of the femur. The nonarticular
portion is the dorsal surface of the apex and here the synovial mem-
brane of the knee joint is attached. The medial and lateral margins
are convex and afford insertion to the mm. vasti medialis and
lateralis, respectively.

90 OSTEOLOGY

Nutrient foramina are seen upon the ventral surface.

Articulations. — With the femur.

Ossification. — It is of endochondral origin and develops from one. or two
centers, which appear during the third year. Ossification is usually com-
pleted by the age of puberty.

Muscles Attached. — Insertions. — Mm. vasti medialis, lateralis and intermedins
and the rectus femoris (four).

THE TIBIA

The tibia or shin bone is the larger and stronger bone of the leg.
It consists of a proximal extremity, shaft and distal extremity.

The proximal extremity comprises the condyles, the intercondylic
eminence and the tuberosity. The condyles constitute a flat mass
that caps the proximal end of the shaft. The proximal surface of each
condyle is concave and articular. The lateral is the smaller and
nearly circular in outline. Near the middle of the intercondylic

Anterior intereondyloid fossa

^ Tuberosity of tibia

cimal extremities of the right tibia ;
(Sobot'a and McMurrich.)

area is the intercondylic eminence [cmincntia intcrcondyloidea);
this presents two peaks, or tubercles, the tubcrculum inter condyloideum
lalerale and tub. inter, mediate. The depression ventral and dorsal
to the eminence constitute the ventral and dorsal intercondyloid
fossce. Here are attached the ventral and dorsal cruciate liga-
ments and the menisci of the knee joint. The lateral condyle
projects well beyond the side of the shaft and presents a small
dorsolateral facet for articulation with the proximal extremity of
the fibula. Ventrally the iliotib al band (trackis iliotibialis) is
attached, the tendon of the m. biceps femoris is inserted and the
mm. extensor digitorum longus and peroneus longus arise. The
dorsomedial margin of the medial condyle is grooved for the inser-
tion of the m. semimembranosus. The tuberosity is slightly distal
to the condyles; its proximal portion is covered by a bursa while
the distal part receives the insertion of the ligamentum patella?.

The shaft (corpus tibia') presents three surfaces and three margins.
Its proximal three-fourths is wedge-shaped (triangular in section)

THE TIBIA

99

and its distal one-fourth is somewhat flattened. The medial surface,
flat or convex, is extensive but mainly subcutaneous. On its
proximal portion the mm. gracilis and semitendinosus are inserted.

Fig. 71. — The right tibia seen from
front. (Sobolta and McMumch.)

Inferior extremity

Fig. 7^- — The right tibia, seen from
behind. (Sobotta and McMurrich.)

The proximal portion of the lateral surface is quite extensive and
affords an extensive origin to the m. tibialis anterior; distally it
turns and blends with the medial surface a sort of ventral surface.
This is covered by the tendons of the mm. tibialis anterior, extensor
hallucis proprius and the ext. digitorum communis. The dorsal

IOO OSTEOLOGY

surface is extensive and is usually convex proximally and flat distally.
The convex portion is crossed by the oblique popliteal line proximal
to which the m. popliteus is inserted; from the oblique line the m.
soleus arises. From the bulk of the remainder of the surface the
mm. tibialis posterior (laterally) and the flexor digitorum longus
(medially) arise. The distal portion is merely covered by these
tendons and the tendon of the m. flexor hallucis proprius. A nutrient
canal (distally directed) is present on this surface. The ventral
margin, or crest is prominent in the proximal three-fourths and subcu-
taneous. The medial margin is prominent in its middle third only.
The lateral margin, or interosseous crest (crista inter ossea) is sharp
and to it the interosseous membrane is attached. Distally it is
divided into two lines that diverge and enclose the articular surface
for the distal extremity of the fibula and the area for the attachment
of the ligaments of this joint.

The distal extremity is quite large and exhibits an articular surface
and a malleolus. The articular surface is on the inferior, or distal
portion; this is triangular and saddle-shaped and rests upon the
articular surface of the astragalus (talus). Upon the lateral margin
of the extremity (base of the triangle) there is a notch (incisura
fibularis) for articulation with the fibula and the articular cartilage
lines the notch. The medial angle of this extremity projects in-
feriorly as the medial malleolus. The medial aspect of the malleolus
is subcutaneous and its lateral aspect is articular forming a part of
the ankle joint. It also serves for the attachment of the tibial
collateral ligament. Its dorsal surface has two grooves, one for
the tendons of the mm. tibialis posterior and the flexor digitorum
longus and the other for the tendon of the m. flexor hallucis longus.

Nutrient foramina are numerous in the condylar portion, the intercondyloid
fossae and the eminence; the main one for the shaft is on the dorsal surface and
is distally directed. The margins of the distal extremity also shows numerous
foramina.

Articulations. — With the femur, fibula and astragalus.

Ossification. — This is of endochondral origin and develops from three or four
centers. The center for the shaft appears during the second fetal month. The
renter for the proximal extremity appears before birth and for the distal extremity
between the first and second years. The center for the tuberosity, when independ-
ent, appears at about the eleventh year. Complete fusion with the shaft takes
place by the twentieth to the twenty-fourth year.

Muscle Attached. — Origins. — Mm. tibialis anterior, extensor digitorum longus,
soleus, flexor digitorum longus, tibialis posterior, peroneus longus.

Insertions. — Mm. biceps femoris, semimembranosus, semitendinosus, sartorius,
gracilis, popliteus, quadriceps extensor (thirteen).

THE FIBULA

The fibula is the slender bone on the lateral side of the leg but it
does not support the body. It consists of two extremities and a
shaft.

THE FIBULA

The proximal extremity or head (capitulum fibula) is broad, flat,
and pointed. This point is the apex to which the fibular collateral
ligament is attached and the m. biceps femoris is inserted. The
medial surface slopes medially and distally and has an articular
facet that fits against the articular facet upon the lateral condyle
of the tibia. The lateral surface is somewhat roughened. The

- Anterior crest

Inferior extremity —>

Peroneal

Fic. 73. — The right fibula, seen from
the medial surface. (Sobolta and Mc-

FlG. 74. — The right fibula, seen from
he lateral surface. (Sobotla and Mc-

tendon of the m. biceps femoris is inserted to the ventral and
proximal surface and below this the m. peroneus longus arises; its
dorsal part gives origin to the m. soleus. The next portion of the
bone is somewhat constricted and is called the neck.

The shaft (corpus fibula) is exceedingly variable as to shape and
form. It has three surfaces, three margins and an interosseous crest.
The medial surface is divided into ventral and dorsal areas by the
interosseous crest to which the interosseous membrane is attached.
The ventral part of this surface is variable in width and affords origin
to the mm. extensor digitorum communis, extensor hallucis longus
and peroneus tertius. The dorsal part of this surface is less exten-

OSTEOLOGY

sive, lies dorsal to the interosseous crest and affords origin to the
m. tibialis posterior. The lateral, or peroneal surface, in its proximal
part, faces ventrally and in its distal part faces dorsally. It gives
origin to the mm. peronei longus and brevis. The dorsal surface is
fairly extensive but irregular. Proximally the m. soleus arises while
distally the m. flexor hallucis longus arises.

The ventral margin, or crest, separates the
medial and lateral surfaces and to it the in-
termuscular fascia that separates the peroneal
from the ventral muscles is attached. The
lateral margin, or crest is fairly well marked
(distally) and separates the lateral and dorsal
surfaces. From its proximal end the m.
soleus arises. The medial margin, or crest, is
a curved ridge dorsal to the interosseous crest
and serves to separate the smaller dorsal part
of the medial surface (from which the m.
tibialis posterior arises) from the larger dorsal
surface of the shaft. The crest gives at-
tachment to the deep fascia that covers the
m. tibialis posterior.

The distal extremity is called the lateral
malleolus (malleolus lateralis). It is an ir-
regular mass of bone with a blunt point.
The lateral surface is convex and mainly
subcutaneous. The medial surface exhibits
a facet for articulation with the astragalus
(talus). Dorsal to this is a pit for the at-
tachment of the astragulofibular ligament,
and proximally the roughened surface gives
attachment to the interosseous ligaments.
The dorsal surface shows a groove (sulcus
malleolaris) for the passage of the tendons of
the mm. peronei longus and brevis. The
ventral margin gives attachment to the astrag-
alofibular and calcaneofibular ligaments.

Arterial Foramina. — These are numerous, some in the head and some in the
malleolus. The largest is on the dorsal surface of the shaft and is distally directed .

Articulations. — With the tibia (proximally and distally) and with the as-
tragalus (talus).

Ossification. — It is of endochondral origin and arises from three centers.
The center for the shaft appears during the middle of the second month of fetal
life. The center for the distal extremity appears during the second year and for
the proximal extremity during the third or fourth year. Fusion with the shaft
is completed between the twentieth and twenty-fourth years.

Muscles Attached. — Origins. — Mm. soleus, peronei longus, brevis and tertius,

Fie. 75.— The tibia and
fibula seen from behind.
(Sobotta and McMurrich.)

THE TARSUS IOJ

tibialis anterior and posterior, flexor hallucis longus. extensor digitorum com-
munis and extensor hallucis longus.
Insertions. — M. biceps femoris.

THE BONES OF THE FOOT

The foot comprises the tarsus, metatarsus and the phalanges.
THE TARSUS

The tarsal bones (ossa tarsi) are the astragalus, calcaneum, scaphoid,
three cuneiform and cuboid bones. All are irregular in shape.

The astragalus (talus) forms the tarsal part of the ankle and
supports the tibia. It consists of a body, head and neck.

The body presents a superior, saddle-shaped facet for articulation
with the tibia. The articular surface extends laterally for articula-
tion with the malleolus of the fibula and medially for articulation
with the malleolus of the tibia. Around these areas ligaments of the
joint are attached. The distal surface presents two articular facets;
the dorsal one (dorsal calcaneal facet) is concave for articulation
with the dorsal facet upon the calcaneus. The ventral facet (middle
calcaneal facet) is slightly convex for articulation with the facet upon
the sustentaculum tali of the calcaneum. Between the two there is
a deep groove {sulcus tali). The oval head presents a convex articular
facet on its ventral surface; this articulates with the scaphoid
(navicular) bone. Ventral and lateral to the middle calcaneal facet
is the ventral calcaneal facet. Upon the infer omedial surface of the
head is another facet that rests upon the plantar calcaneonavicular
ligament. The neck is a groove and is best marked dorsally where it
separates the body and head.

Articulations. — With the tibia, fibula, calcaneum and scaphoid (navicular).
Muscles Attached. — Xone.

The calcaneum, or heel bone, is the largest of the tarsal bones. It
is an irregular mass the dorsal portion of which projects as the heel
and is called the tuberosity (tuber calcanei). To the middie of its
dorsal surface the tendo Achillis (calcaneus) is attached. The medial
surface of the main part of the bone presents a heavy shelf of bone,
the sustentaculum tali the plantar surface of which is grooved for the
tendons of the m. flexor hallucis longus. Its superior surface pre-
sents the middle calcaneal facet (for the astragalus). The superior
surface of the main portion of the bone presents a large dorsal cal-
caneal facet and a small ventral calcaneal facet in front of the middle
one. These are for articulation with the corresponding facets upon
the astragalus. The dorsal facet is separated from the others by a
deep groove (sulcus calcanei). The lateral surface is somewhat con-
cave. The ventral extremity is a concave articular facet for articula-
tion with the scaphoid (navicular) bone.

104

.OSTEOLOGY

Articulations. — With the astragalus (talus) and the scaphoid (navicular) hones.

Muscles Attached. — Origins. — Jim. flexor digitorum brevis, abductores
hallucis and digiti quinti. flexor quadratus plants and extensor digitorum brevis.

Insertions. — Mm. plantaris, tibialis posterior and tendo Achillis (calcaneus)
(eight).

The scaphoid bone (os naviculare) is somewhat concavoconvex.
Its proximal (correctly dorsal) surface is a concave articular facet

f^ Pkatm i ill o/ digit ii

l'h,ilnni II a; tllgft ll
I 9) dipt II

FtG. 76. — A frozen preparation of the bones
of the foot seen from the plantar surface.
(Scholia and McMurrich.)

Fig.
McMu

• dorsal
ch.)

for the head of the astragulus. The distal (ventral) surface presents
three confluent quadrate facets for articulation with the three
cuneiform bones. The medial space projects as the tuberosity. The
other surfaces are roughened.

Articulations. — With the astragalus and three cuneiform bones (four).
Muscles Attached.— M. tibialis posterior (inserted).

THE METATARSI'S IOj

The cuboid (os cuboideumj is laterally placed and is roughly
cuboidai in form. Its medial surface presents a facet for articulation
with the lateral cuneiform bone and occasionally with the navicular
bone. The proximal surface has a concave facet for articulation with
the calcaneum. The distal surface presents two articular facets for
the fourth and fifth metatarsal bones. The plantar surface bears a
groove (sulcus peronei) for the tendon of the m. peroneus longus.

Articulations. — With the calcaneum, lateral cuneiform, fifth and fourth meta-
tarsal bones and occasionally with the navicular bone.
Muscle Attached. — Origin. — M. flexor hallucis brevis.
Insertion. — Part of the m. tibialis posterior.

The three cuneiform bones are wedge-shaped and form with the
cuboid the distal row of tarsal bones.

The first or medial cuneiform bone is the largest and articulates
with the first metatarsal bone, distally, the navicular, proximally and
the second metatarsal and second cuneiform bones, laterally.

Muscles Attached. — Mm. tibialis anterior, tibialis posterior and peroneus
longus (inserted).

The second (middle) cuneiform bone is the smallest. It articu-
lates distally, with the second metatarsal bone, laterally, with the
third cuneiform bone and medially, with the first cuneiform and
proximally with the navicular bone.

Muscles Attached. — Part of the tendon of the m. tibialis posterior is inserted.

The third (lateral) cuneiform bone articulates distally with the
third metatarsal bone laterally with the fourth metatarsal and
cuboid, proximally with the navicular and medially with the second
cuneiform and second metatarsal bones.

Muscle Attached. — Origin. — M. flexor hallucis brevis.

Insertion. — M. tibialis posterior.

Ossification. — The tarsal bones are of endochondral origin. The calcaneum
develops from two centers and the others from one each. The centers appear in
the following order:

Calcaneum (body) sixth month of fetal life

Astragalus (talus) seventh month of fetal life

Cuboid ninth month of fetal life

Lateral cuneiform first year

Medial cuneiform third year

Scaphoid and middle cuneiform fourth year

Tuberosity of the calcaneum about the tenth year and fuses with
the body about the age of puberty.

THE METATARSUS

The metatarsus, like the palm, consists of Jive bones. Each
presents a proximal extremity or base, a shaft and a distal extremity, or
head. The proximal extremities articulate with the distal row of
tarsal bones and with each other. The first is the shortest and

Io6 OSTEOLOGY

stoutest and the second the longest. The fifth presents a tuberosity
at the lateral part of the proximal extremity to which the tendon of
the m. peroneus tertius is attached.

Ossification. — These are of endochondral origin and each develops from two
centers, one for the shaft and one for the digital extremity of the four outer meta
tarsals and one for the shaft and one for the base of the first metatarsal. The
center for the shaft appears during the ninth week of fetal life; the center for the
base of the first metatarsal appears during the third year; the centers for the
distal extremities of the others appear between the fifth and eighth years. Fusion
of shaft and epiphysis is usually completed by the eighteenth to the twentieth
years.

Muscles Attached. —
First Metatarsal. — Origin. — First dorsal interosseous. Insertions. — .Mm. tibialis

posterior, peroneus longus (three).
Second Metatarsal. — Origin. — Mm. adductor hallucis obliquus, first and second

dorsal interossei. Insertions. — Mm. tibialis posterior, peroneus longus

(five).
Third Metatarsal. — Origins. — Mm. adductor obliquus hallucis, second and third

dorsal interossei, first plantar interosseous. Insertions. — M. tibialis pos-
terior (five).
Fourth Metatarsal. — Origins. — Mm. adductor hallucis obliquus, third and fourth

dorsal interossei, second plantar interosseous. Insertions. — M. tibialis

posterior (five).
Fifth Metatarsal. — Origins. — Mm. flexor quinti digiti brevis, adductor hallucis

transversus. fourth dorsal and third plantar interossei. Insertions. — Mm.

peroneus brevis and peroneus tertius (six).

THE PHALANGES

The phalanges of the foot resemble those of the hand in number,
form and arrangement. Their nutrient foramina are similar.
Each consists of a proximal extremity, shaft and distal extremity.
Their articulations are also similar.

Ossification. — These are of endochondral origin and each is developed from
two centers. The center for the shaft appears during the tenth week of fetal life
and those for the proximal extremities appear between the fourth and tenth years.
Fusion between these parts occurs about the eighteenth year.

Muscles Attached. — All are insertions.
First Phalanx of the Great Toe. — Mm. extensor digitorum brevis (innermost

tendon), abductor hallucis. adductores hallucis transversus and obliquus,

flexor hallucis brevis (five).
First Phalanx of the Second Toe. — First and second dorsal interossei, first lum-

bricale (three).
First Phalanx of Third Toe. — Third dorsal interosseous, first plantar interosseous,

second lumbricale (three).
First Phalanx of the Fourth Toe. — Fourth dorsal interosseous, second plantar

interosseous, third lumbricale (three).
First Phalanx of the Little Toe. — Mm. flexor digitorum quinti brevis, abductor

digiti quinti brevis, third plantar interosseous, fourth lumbricale (four).
Second Phalanx of the Great Toe. — Mm. extensor hallucis longus, flexor hallucis

longus (two).

THE FOOT AS A WHOLE

107

Second Phalanx of the Other Toes. — Mm. flexor digitorum brevis, one slip of the
common tendon of the extensor digitorum longus and the extensor digitorum
brevis (except the fifth toe).

Third Phalanges. — Two slips of the common tendon of the extensor digitorum
longus, the extensor digitorum brevis and flexor digitorum longus.

THE FOOT AS A WHOLE

The bones of the foot are arranged in the form of an arch and this
supports the weight of the body in the erect position. The foot is
placed at a right angle to the leg. There are two arches, longitudinal
and transverse.

Tarsus Sinus ft

Navicular bonr

Middle cuneiform bone
/ External cuneiform bone

calcaneus

-A frozen preparation of the bones of the right foot :
(Sobctie. and McMun

1 from the outer side.

The longitudinal arch is the larger and the longer; the curvature
of the arch is greater on the medial aspect than it is on the lateral
aspect. The heel (back) part of the arch is made up of the calcaneum
and the proximal part of the astragalus and is about 3 inches in
length; the front part of the arch consists of the other tarsal and the
metatarsal bones and measures about 7 inches in length. The
weakest part of the arch is at the joint between the astragalus and
scaphoid bones. It is especially supported here by ligaments (the
calcaneoscaphoid and the tendon of the m. tibialis posterior).
Whenever these give, the arch becomes lower and causes Hat-foot.

The transverse arch of each foot is only a half arch and the whole
is formed when the two feet are placed in apposition. This half
arch represents the difference in height of the longitudinal arch at
its lateral and medial aspects.

CHAPTER II

SYNDESMOLOGY

THE JOINTS

A joint, when movable, is the fulcrum at which the levers (bones)
are moved by the muscles. There are two main divisions of joints,
the immovable and the movable.

i. Synarthroses, or immovable articulations, are those in which
no motion is perceptible. In these the apposed edges of the bones
are irregular and fit, or dove-tail, into one another. There is a
small amount of white fibrous tissue separating the bones, but no
joint cavity exists. There are four varieties.

(a) Suture (sutura) is that form found in the skull. • When the
irregularities of the connecting bones are well marked they form a
true suture (sutura vera), otherwise a false suture (sutura notka).
When the sutural projections are tooth-like they form a sutura
dentata; when saw-like they constitute a sutura serrata; when
ridge-like they form a sutura limbosa. The false suture may be
a sutura squamosa (squamoparietal), a sutura harmona (palatal
processes of the maxillae).

(b) Schindylesis is that variety in which a bone is placed in a
cleft between two lamellae of another, as the articulation of the
vomer with the maxilla1.

(c) Gomphosis is that form in which a conical process fits into a
special socket, as the articulation of the teeth with the mandible
and maxillae.

(d) Synchondrosis is that variety in which hyalin cartilage
intervenes between the articular surfaces of certain bones, early
in life, to be later ossified. This is represented by the epiphyseal
cartilage separating shaft and extremities of long bones, before adult
life.

Movable joints comprise two classes, partly movable, or amphi-
arthroses and freely movable, or diarthroses.

i. Amphiarthroses exhibit slight movement and they resemble
somewhat in structure the diarthroses. Two varieties are noted.

(a) Symphysis, that form in which the two articular surfaces of
the bones are connected by an intervening plate of fibrocartilage.
All parts are held together by ligaments and a rudimentary joint
cavity may be present. Examples are the symphysis pubis and the
articulations between the bodies of the true vertebrae.
1 08

STRUCTURE OF A JOINT IOq

(b) Syndesmosis, that form in which the bony surfaces are con-
nected by an interosseous ligament, as the inferior tibiofibular
articulation.

2. Diarthroses. — Most of the articulations come under this class
and a number of varieties are given.

(a) Arthrodia is that variety in which there is a somewhat limited
gliding movement, as between the bones of the carpus, the tarsus
and the articular processes of the vertebra.

(b) Ginglimus, or hinge joint, is that form in which motion occurs
only in one plane, that is at right angles to the long axis of the bones
taking part (as in a hinge). The best examples are the interpha-
langeal articulations and the elbow joint. The knee and ankle
joints belong to this variety but permit of some lateral movement.

(c) Condyloid, or biaxial articulations, permit of movement in
two planes, at right angles to each other, permitting flexion, exten-
sion, abduction and adduction and circumduction, as in the
radiocarpal articulation.

((/) Trochoid, or rotary joint, is that variety iri which there is
rotation only, as in the proximal and distal radioulnar articulations,
as well as that between the dens of the epistropheus with the atlas
and transverse ligament.

(c) Reciprocal reception, or saddle joint, is a term applied to the
carpometacarpal articulation of the thumb. Such permits of
flexion, extension, abduction, adduction and circumduction.

(/) Enarthrosis, or ball and socket joint, is the variety that per-
mits of motion about practically any number of axes from a common
center, as the hip and the shoulder joints.

A number of structures are required in order to have a diarthrodial joint, as
bones, cartilage, ligaments and synovial membrane. Two bones are necessary
and their articular surfaces are so formed and adapted to each other so as to
permit of certain movements. The parts of these bones that actually rub against
each other are covered with a layer. of hyalin cartilage. Ligaments connect
the bones together so as to prevent them from separating. A synovial membrane
lines the inner surface of the capsular ligament and covers all parts of the bones
within the joint cavity except that part covered with hyalin cartilage (real articular
surfaces).

The structure of bone has been discussed in the chapter on "Osteology."

Cartilage. — There are three varieties: (a) hyalin, (b) fibrocartilage,
(c) elastic cartilage.

Cartilage is surrounded by an investing, genetic membrane called
the perichondrium, which is analogous to the periosteum of bones.
From it the cartilage cells, or chondroblasts, arise. Within the peri-
chondrium is the matrix containing the cartilage cells. In hyalin
cartilage this matrix is apparently homogeneous. In special prepa-
rations, however, a groundwork of white fibrous tissue may be
recognized. The cartilage cells beneath the perichondrium are

110 SYNDESMOLOGY

small, elongated and close together. Near the middle of the cartilage
they are larger, oval and each usually lies in a distinct space, or
lacuna.

Hyalin cartilage is found covering the articular surfaces of bones,
and as the costal, tracheal, bronchial and the larger laryngeal car-
tilages. It may calcify or even ossify.

In fibrocartilage the matrix is chiefly white fibrous tissue in which
the fibers are mostly parallel to one another. The cartilage cells lie
in little scattered islands of hvalin matrix.

T^

J -r

■-■■■ : —-

B

C

Fig. 79. — Sections of cartilage. A. Hyalin cartilage, a. Fibrous layer of peri-
chondrium; 6, genetic layer of perichondrium; c, youngest chondroblasts; d, older chondro-
blasts; e, capsule; /, cells; g, lacuna. B. Elastic cartilage. C. White fibro-cartilage.
(Radasch's Histology.)

Fibrocartilage is found as the intervertebral discs, interarticular
cartilages and deepening joint cavities. It may calcify in old age.

Elastic cartilage does not concern us here.

Ligaments are those bands of dense white fibrous tissue that hold
the bones together. They resemble the fascia? in structure and con-
sist of bundles of white fibrous tissue, most of which are parallel to
one another; other bundles pass obliquely or transversely to the
preceding and bind all together into a firm sheet or band. A variable
quantity of elastic tissue is present. The connective-tissue cells lie
between the bundles of fibers and are comparatively few in number.
Ligaments are whitish and shiny in appearance and are arranged as

STRUCTURE OF A JOINT III

capsules with accessory strengthening portions, or as individual
bands or intraarticular ligaments.

A synovial membrane is a thin, delicate serous membrane that lines
the joint cavity. It consists of a single layer of endothelial cells that
are flat and plate-like with irregular edges that fit into one another.
At intervals small gaps or stomata exist. These cells rest upon a thin
layer of fibroelastic subendothelial tissue. This membrane does not
extend over the hyalin cartilage of the articular surfaces in the adult.
These membranes transude {not secrete) a thick, viscid substance,
called synovia, that lubricates the joint. Synovial membranes are
found elsewhere as in bursae, and vaginal synovial membranes.

Bursae are sacs of white fibrous tissue lined with a synovial mem-
brane; they may be cutaneous, as those placed between the skin
and a prominent bony process (over the patella, olecranon and
malleoli). The subtendinous bursee are those intervening between
a tendon and a bone or cartilage, facilitating the action of the muscle.
Some bursae are over joints.

A vaginal synovial membrane (synovial sheath) is one that lines
a groove or canal in the bone, through which a tendon passes, thus
facilitating its action. These are seen in connection with the flexor
and extensor tendons of the fingers and toes, especially.

ARTICULATIONS OF THE VERTEBRAL COLUMN AND HEAD

The articulations of the vertebral column are those between the
bodies and those between the articular processes. In addition there
are ligaments connecting the spinous processes, transverse processes
and laminae.

Bodies. — These articulations are amphiarthrodial and the liga-
ments are intervertebral, ventral longitudinal and dorsal longitudinal.

The intervertebral discs vary in thickness in the various parts of the
vertebral column. Each conforms in shape to the surfaces of the
bodies to which it is firmly attached. Its peripheral portion (annu-
lus fibrosus) is dense and tough white fibrocartilage, while its central
portion {nucleus pulposus) is soft, pulpy and elastic.

The ventral longitudinal ligament (lig. longitudinale anterius) is a
broad, fibrous band that extends from the epistropheus to the
superior segment of the sacrum. It is attached to the projecting
superior and inferior edges of the ventral portion of each body and the
intervertebral disc. Some of its fibers are of short course and others
extend over three or four vertebrae.

The dorsal longitudinal ligament (lig. longitudinale poster ius) con-
nects the dorsal surfaces of the bodies in the same manner. It lies
in the vertebral canal.

Articular Processes. — The articular processes form arlhrodial
articulations. Each contiguous pair of processes is surrounded by

SYXDESMOLOGY

Fig. 80. — The ventral longitudinal lig-
ament in the lower thoracic portion of
the vertebral column, together with the
costo-vertebral ligaments seen from in
front. (Sobotta and McMurrich.)

Fig. 81.— The dorsal longitudinal liga-
ment in the lower thoracic and upper
lumbar portions of the vertebral column.
The vertebral arches have been removed.
(Sobotta and McMurruh.)

Inten-ertebral foramen

Intervertebral fibrocartitage

Fig. 82. — Two thoracic vertebrae divided longitudinally in the medu
ligamenta flava. {Sobotta and McMurrn In

and showing the

LIGAMENTS OF THE VERTEBRAL COLUMN II3

a thin capsular ligament (capsula articularis) that is usually com-
pleted by the ligamenta flava. These ligaments are loosest in the
cervical region, where movement is most extensive, and are attached
to the bone adjoining the articular surfaces.

Other ligaments are as follows:

Ligamenta Flava. — The laminae of adjoining vertebrae are connected
to each other by the short, yellow, elastic ligamenta flava. These
close in gaps in the osseous vertebral canal.

Ligamenta intertransversaria are short ligaments that connect the
transverse process of the vertebrae, except in the cervical and upper
thoracic region.

Ligamenta supraspinaUa form a strong band that connects the
tips of the spinous processes together. In the neck it is usually
more highly developed and consists, mainly, of yellow elastic tissue.
This part is called the ligamenlum nucha and is important and highly
developed in quadrupeds.

Ligamenta inter spinalia are the short, thin bands that connect
one spine with another, and extend dorsoventrally from the supra-
spinous ligaments to the ligamenta flava.

The lumbosacral articulation is similar to that of the typical
vertebrae. Two accessory lumbosacral ligaments are present. Each
extends from the transverse process of the last lumbar vertebra to
the ventral aspect of the ala of the sacrum; occasionally there is an
extension from the lateral part of the body of the last lumbar ver-
tebra to each ala.

The sacrococcygeal articulation is a symphysis. The last seg-
ment of the sacrum and the first of the coccyx are connected by
strong ventral, dorsal and lateral sacrococcygeal ligaments. An
intervetebral Jibrocartilage is present.

The vertebral column is capable of flexion, extension, lateral flexion,
rotation and some circumduction. The movements are most exten-
sive in the cervical and lumbar regions and while the movement of
one vertebra upon its neighbor may be small, the motion as a whole
becomes considerable.

ATLAS AND AXIS

This articulation (atlantoepistrophica) comprises those of the
articular processes and that between the dens and atlas.

The articulation between the processes are arthrodial. Each
joint possesses a capsular ligament and an accessory ligament; the
latter is located in the vertebral canal and represents a thickening
of the capsular ligament.

The ventral atlantoepistropheal ligament connects the ventral sur-
face of the body of the epistropheus to the ventral surface of the
ventral arch of the atlas. This is reinforced bv the fibers of the

H4

SYXDESMOLOGY

ventral longitudinal ligament. The dorsal atlantoepistropheal liga-
ment extends from the dorsal arch of the atlas to the lamina; of the
epistropheus (like a ligamentum flavum).

The transverse ligament (lig. transversum atlantis) extends trans-
versely between the two tubercles of the atlas and dorsal to the
neck of the dens of the epistropheus; between these two structures
there exists a synovial sac. The cruciform ligament (lig. cruciatum
atlantis) is formed by the transverse ligament sending fibers from
its superior margin to the ventral margin of the foramen magnum

Alar Cmriatt ligament

Fig. 83. — The atlanto-odontoid articula-
tion. The odontoid process {den, epis-
trophei) and the ventral arch of the atlas
have been cut. (Sobotla and McMurrich.)

Fig. 84. — The cruciate ligament after re-
moval of the tectorial membrane. The artic-
ular capsules have also been removed on the
right side. (Sobolla and McMurrich.)

and fibers from its inferior margin to the dorsal surface of the body
of the axis.

Movements. — The head and the atlas rotate upon the axis or
epistropheus.

ATLAS AND OCCIPITAL BONE

The atlantooccipital articulation (articnlatio atlantooccipitalis) is

a d {arthrosis. The ligaments are as follows:

1. A capsular ligament that surrounds each condyle of the
occipital bone and corresponding facet of the atlas.

2. The ventral atlantooccipital membrane imcmbrana atlantooccip-
italis anterior) extends from the ventral arch of the atlas to the
ventral margin of the foramen magnum and is thickened in the
median line.

3. The dorsal atlantooccipital membrane extends from the dorsal
arch to the dorsal margin of the foramen magnum. Both are
continuous with the capsular ligaments.

4. The alar, or check, ligaments (ligg. alaria) are two short, strong

THE MANDIBULAR ARTICULATION 115

oords extending right and left from the sides of the apex of the dens
to the condylar portions of the occipital bone.

5. The ligament of the apex (lig. apicis dentis) extends from the
apex of the dens to the ventral margin of the foramen magnum.

Occipital bone

Fig. 85. — A portion of the occipital bone together with the atlas and axis (epistropheus)
and their ligaments seen from behind. On the left side the capsule of the atlanto-
epistropheal articulation has been removed. (Sobotta and McXIurrkh.)

Movements. — Between the occipital bone and the atlas, a rocking
motion is accomplished (nodding) as well as a limited amount of
oblique motion.

THE MANDIBULAR ARTICULATION

The mandibular articulation {articulatio mandibularis) is a
ginglymo-arthrosis and the parts concerned are the condyles of the
mandible and the mandibular fossa; of the temporal bones. An
intraarticular cartilage (disc) intervenes between these bones, however.

1. The loose capsular ligament is attached to the edges of the
fossa and to the neck of each condyle.

2. The temporomandibular ligament (lig. tern poromandibulare) is a
vthickening of the lateral wall of the capsule and extends between

the inferior margin of the zygoma and the neck of the mandible
(dorsally and laterally).

3. The articular disc (discus articularis) is a concavo-convex mass
of fibrocartilage that is attached, peripherally, to the capsule so as
to divide the joint cavity into two compartments, each of which
has its own synovial membrane.

4. The sphcnomandibular ligament (lig. sphenomandibulare) is a
thin, fiat band extending between the spine of the sphenoid bone and
lingula of the mandible. It is an accessory ligament.

5. The stylomandibular ligament (lig. stylomaudibulare) extends
from the styloid process of the temporal bone to the dorsal margin
of the angle of the mandible. It is an accessory ligament.

Movements. — Depression, elevation, forward, backward, lateral
(grinding).

n6

SYXDESMOLOGY

ARTICULATIONS OF THE THORAX

Two articulations exist between each rib and the vertebral column.
The head articulates with the bodies and the tubercle with a transverse
process.

COSTOVERTEBRAL ARTICULATIONS

The articulations of the heads of the ribs (articulatianes capitu-
lorum) are of the ginglynwid variety of diarthrosis. The head articu-

remporomamiibuLir ligament

Zygomatic arch

Pterygoid process

Temporal bone

Sphenoid bone

/ Sphertot.nindt-

1

butar ligament

Fig. 86. — The right temporomandib-
ular articulation seen from the outer
side., (Sobotta and McMurrich.)

Fig. 87. — The right temporo-mandibu-
lar articulation seen from the inner side.
{Sobotta and McMurrich.)

lates with the demifacet of the two adjoining vertebral bodies.
A capsular ligament surrounds these parts. The ventral portion of
the capsule is reinforced by three radiating bundles of fibers called
the radiate ligaments of the head (fig. capituli costce radiation).
These start at the head; the middle one is attached to the inter-
vertebral disc and the others to the vertebral bodies.

The intraarticular ligament (lig. capituli costce intraarticulare) is
within the joint; it is attached to the ridge on the head, between the
two facets, and to the intervertebral disc.

ARTICULATION OF THE RIBS

117

The costotransverse articulations {articidationes coslotransversarice)
of the typical ribs are those between the tubercles of the ribs and
the transverse processes of the lower vertebra with which the head

articulates. These are arthrodial joints. The capsular ligament
is thin but is not found on the eleventh and twelfth ribs.

The ventral costotransverse ligament {Kg. costotransversarium an-
terior) is short and strong; it connects the neck and tubercle of the

n8

^VNDKSMOLOGY

rib with the transverse process above and to its costotransverse
capsular ligament.

The dorsal costotransverse ligament is a short and oblique fasciculus
that connects the transverse process with the nonarticular portion
of the tubercle. Such ligaments are absent on the eleventh and
twelfth ribs.

The ligament of the neck of the rib (lig. colli costce) consists of short
fibers that connect the dorsal surface of the neck with the ventral
surface of the transverse process, though some of the fibers pass to
the inferior articular process of the upper vertebra.

STERNOCOSTAL ARTICULATIONS

The articulations of the costal cartilages of the true ribs, except
the first, are of the arthrodial variety.

i

i

■• ' A/

Fir.. 90. — A frontal longitudinal section of the sternum and costal cartilages. (Sobotta and
.1/, Murrich.)

A thin capsular ligament surrounds each joint.

The ventral sternocostal, or radiate ligaments pass from the ventral
surfaces of the costal cartilages to the ventral surface of the sternum,
interlacing with those of the opposite side forming the membrana
sterni.

STERNOCLAVICULAR ARTICULATION IIQ

The dorsal sternocostal ligaments are like the preceding but less
prominent.

The intraarticular sternocostal ligaments (Jig. sternocostal intra-
articulare) are inconstant in all except the second sternocostal articu-
lation. When these are present, they extend transversely between
the costal cartilage and the sternum and divide the joint cavity
into two distinct (superior and inferior) portions.

The xiphoid ligament passes from the ventral surface of the xiphi-
sternum to the ventral surface of the seventh and sometimes the
sixth costal cartilage.

INTERCHONDRAL ARTICULATIONS

The cartilages of the sixth, seventh and eighth (ninth and tenth
sometimes) ribs articulate with each other forming arlkrodial joints.
Each joint is surrounded by a thin capsule. The ventral and dorsal
portions of the capsule are thickened by fibers connecting the
adjacent cartilages. These constitute the external and internal
inter chondral ligaments.

Each costal cartilage fits into a depression on the sternal end of
the shaft of a rib. There is no true joint as these structures are
held together by the blending of the periosteum and perichondrium.

ARTICULATIONS OF THE STERNUM

The sternal synchondrosis is the amphiarthrodial articulation
between the manubrium and body of the sternum. Ventrally and
dorsally are found the interstemal ligaments supported by the
membrana sterni.

THE ARTICULATIONS OF THE SUPERIOR EXTREMITY

The superior extremity, or pectoral appendage comprises the
pectoral girdle (clavicles and scapula;) and the appendages proper.
The pectoral girdle articulates with the axial skeleton ventrally, only,
at the sternum. Each clavicle articulates with its corresponding
scapula.

THE STERNOCLAVICULAR ARTICULATION

The sternoclavicular articulation (articulatio sternoclavictdaris) is
of the arthrodial variety. The parts concerned are the enlarged
sternal end of the clavicle, a facet upon the superolateral angle of the
manubrium, the superior surface of the first rib and an intraarticular
fibrocartilage.

A capsular ligament encloses the joint.

The intraarticular cartilage (discus intraarticularis) is thinner in
the middle than at its circumference. It is attached peripherally

120 SYNDESMOLOGY

to the capsular ligament, as well as to the clavicle superiorly and
the first costal cartilage inferiorly.

The ventral sternoclavicular ligament {lig. sternoclavicular e anterius)
consists of fibers strengthening the capsule and connecting the
ventral surfaces of the clavicle, sternum and first costal cartilage.

The dorsal sternoclavicular ligament is similar to the preceding.

The interclavicular ligament (lig. interclavicularc) is a strong acces-
sory ligament connecting the sternal ends of the two clavicles across
the interclavicular notch; this ligament is attached to the upper
margin of the sternum also.

Costoclavicular
ligament
Articular capsule

Costal cartilage I — "

Costal cartilage II

Sternal synchondrosis

Fig. 91. — The two sternoclavicular joints, together with the costosternal articulations of
the two upper ribs seen from in front. The right sternoclavicular joint has been opened by a
saggital section. (Sobclta and McMurrich.)

The costoclavicular ligament (lig. costoclaviculare), also accessory,
is a strong, oblique band connecting the first costal cartilage with
the inferior aspect of the sternal end of the clavicle.

THE ACROMIOCLAVICULAR ARTICULATION

The acromioclavicular articulation (articulalio acromioclavicul-
aris) is also an arthrodial joint.

A capsular ligament is present.

The superior and inferior acromioclavicular ligaments are thickened
portions of the capsule connecting adjoining portions of the clavicle
and acromion of the scapula.

An intraarticular cartilage is inconstant and when present it is
obliquely placed and is attached by its circumference to the capsule.

The coracoclavicular ligament (lig. coracoclavicularis) is an acces-
sory ligament and connects the coracoid process of the scapula and
the acromial end of the clavicle; it consists of two parts.

THE SHOULDER JOINT

The trapezoid ligament (lig. trapezoidcum) is attached, inferiorly,
to the basal half of the superior surface of the coracoid process and
superiorly to the inferior surface of the acromial end of the clavicle.

The conoid ligament (lig. conoideum) is somewhat triangular; its
blunt apex is attached to the base of the coracoid process (near the
scapular notch) and its base is attached to the coracoid tuberosity of
the clavicle. It lies medial to the preceding ligament.

Coracoclav cular ligament
(Conoid portion)
Superior transverse ligament

Coracoelavicalar ligament (Trapezoid portion)
Coracoid process

Coraco-acromial ligament
Acromion

\ , Intertubercular mucous

^ Long head of biceps

-The left shoulder and acromioclavicular joints seen f
inner surface. (Sobotta and McMurrich.)

above and from the

The scapula has several intrinsic ligaments that are not articular.
The coracoacromial ligament (lig. coracoacromialc) is attached, in-
feriorly, to the apical half of the dorsolateral margin of the coracoid
process and, superiorly, to the tip of the acromion. It is tense and
tends to protect the shoulder joint.

The superior transverse ligament (lig. transversum scapula: superius)
bridges the scapular notch.

The inferior transverse scapular ligament connects the lateral
margin of the scapular spine with the dorsal aspect of the head of
the scapula.

THE SHOULDER JOINT (ARTICULATIO HUMERI)

The shoulder joint is of the enarthrodial variety and permits of the
widest range of movement of any joint of the body. It is formed by
the glenoid fossa of the scapula and the head of the humerus.

122 SYNDESMOLOGY

The glenoid ligament (labrum glenoidale) is a ring-like mass of
dense white fibrous tissue that deepens the glenoid fossa. It is
firmly attached to the margin of that fossa.

The capsule (capsula articularis) is attached, proximally, to the
circumference of the glenoid fossa and the labrum glenoidale; distally
it is attached to the anatomical neck of the humerus. It is strongest
superiorly. It is strengthened by fusion with the tendons of the
mm. subscapularis, supraspinatus and infraspinatus, near their
insertions.

The transverse humeral ligament is a portion of the capsular liga-
ment that bridges the groove between the tubercles of the humerus.

Acromioclavicular ligament
Coraco-acromial ligament
Supraspinal

1

Fig. 93. — The left shoulder joint seen from behind, the long head of the triceps being
cut and the terminal portions of the supraspinatus, infraspinatus, and teres minor muscles
cut and turned outward. (Sobolta and McMurrick.)

The coracohumeral ligament (lig. coracohumerale) is an accessory
ligament that extends the base of the coracoid process and the base
of the greater tubercle of the humerus. It is partially fused with
the capsular ligament.

The glenoJiumeral ligament consists of three bands of fibers that
strengthen the ventral part of the capsule and are seen only upon its
inner aspect. They extend from the ventral margin of the glenoid
fossa to the ventral part of the neck of the humerus.

The head of the humerus is held against the glenoid fossa by mus-
cular action and atmospheric pressure as the ligaments themselves
are too lax to do this.

The synovial membrane lines the capsule and extends over the
nonarticular portions of the bones within the capsular ligament.
The proximal end of the tendon of the long head of the m. biceps
brachii arise within and passes through the joint cavity and leaves

THE ELBOW JOIN 1

123

at the groove between the tubercles. The tendon is enclosed within
the synovial membrane which is prolonged upon it into the groove
but the cavity here is closed. Where the subscapularis tendon lies
over the capsule there is a bursa and its cavity and synovial mem-
brane are continuous with the joint cavity. The subdeltoid, or
subacromial bursa does not communicate with the joint cavity.

Movements. — This joint is capable of flexion, extension, abduction,
adduction, rotation and circumduction.

Tendon of iong fiend of biceps

Coracohumeral ligament

Inteiiubereular mucous shealh

Tendon of long head of biceps

Fig. 04. — A frontal longitudinal section of the shoulder joint, parallel to the tendon of
the long head o! 5 Jwlla and McMurrich.)

THE ELBOW JOINT (ARTICULATIO CUBITI)

The elbow joint is of the ginglymus, or hinge variety. The bones
concerned are the humerus, ulna and radius. The humeroulnar
articulation comprises the trochlea of the humerus and the semilunar
notch of the ulna. The humeroradial articulation comprises the
capitulum of the humerus and the head of the radius.

The capsule surrounds the joint and is made up of individual
ligaments of varying thickness that join so as to make a complete
investment of the joint.

The ventral ligament (Jig. anlerius) consists of vertical, oblique and
transverse fibers. It is attached, proximally, to the bone just
beyond the coronoid and radial fossa? of the humerus and, distally,
to the margin of the coronoid process of the ulna and the annular
ligament of the radioulnar articulation. The middle portion is the
strongest.

The thin dorsal ligament (lig. posterius) is attached, proximally, to
the margin of the olecranon fossa and capitulum of the humerus and,

124

>YNDESMOLOGY

distally, to the margins and tip of the olecranon process of the ulna
and the dorsal aspect of the radial notch of the ulna.

The ulnar collateral ligament (lig. collaterale ulnare) is triangular
and fills in the medial part of the capsule between the two preceding
ligaments. It is attached, proximally, to the edge of the medial
epicondyle and, distally, to the medial margin of the semilunar
notch of the ulna. Its fibers are formed into three bands that are
called ventral, dorsal and transverse.

A synovial membrane lines the capsule and is reflected over the
nonarticular portions of the bones within the joint cavity. Pads

Internal
epkondyL

Articular capsule
Internal
epicondyle

Fig. 95-— The left elbow joint seen from
front. 'Sobotta and McMurrich.)

Fig. 96. — The left elbow joint seer
from behind and from the radial side
{Sobotta and McMurrich.)

of fat separate it from the capsule in the coronoid and olecranno
fossae.

The movements of the elbow joint are of flexion and extension.

RADIOULNAR ARTICULATIONS

There are two radioulnar articulations, one between the proximal
extremities of the two bones and the other between their distal
extremities. They both represent the rotary, or lateral ginglymus
variety.

The proximal radioulnar articulation (articulatio radioulnaris
proximalis) consists of the radial notch of the ulna and the head of the
radius.

RADIOCARPAL ARTICULATION

The annular ligament (lig. annulare radii) holds these bones in
apposition. It is attached to the ventral and dorsal margins of the
radial notch and is obliquely placed so as to form a funnel. Its
synovial membrane is continuous with that of the elbow joint.

The distal radioulnar articulation
{articulatio radioulnaris distalis)
comprises the head of the ulna and
the ulnar notch of the radius. The
ventral and dorsal radioulnar ligaments
are transverse bands of fibrous tissue
that connect the adjoining nonartic-
ular surfaces of the bones. A dis-
tinct capsular ligament does not exist.

The triangular articular disc is
important in binding these bones
together. Its apex is attached to
the depression at the root of the
styloid process of the ulna and its
base to the ridge between the ulnar
notch and the distal carpal articular
surface of the radius.

A synovial membrane closes the
joint cavity and, covering the ar-
ticular surfaces of the bones extends
proximally between the ulna and
radius as the recessus sacciformis.

Accessory Ligaments. — The oblique
ligament (chorda obliqua) is an ob-
lique band connecting the coronoid
process of the ulna and the tuber-
osity of the radius.

The interosseous membrane (mem-
brana interossea anlebrachii) is a
strong, sheet-like band that connects
the adjacent margins of the ulna and
radius, distal to the oblique chord.
Between these two ligaments there
is a gap, the hiatus interosseus.

Movements are of pronation and
supination.
THE RADIOCARPAL ARTICULATION (ARTICULATIO RADIOCARPEA)

The radiocarpal articulation is of the condyloid, or biaxial variety.
It comprises the distal extremity of the radius, the discus articularis,
on the one side, and the scaphoid (os naviculare), semilunar (os
lunatum), and cuneiform (os triquetrum) bones, on the other.

Fig. 97. — The bones of the left fore-
arm with the interosseous membrane;
the annular ligament has been divided.
(Sobotta and McMurrich.)

126 SYNDES1I0L0GY

The capsule is loose and its thickened portions constitute the
following ligaments.

The lateral radiocarpal ligament (Jig. radiocarpeum laterale) extends
from the tip of the styloid process of the radius to the tuberosity of
the navicular bone.

The medial ulnocarpal ligament (lig. ulnocarpeum mediale) is cord-
like and extends from the styloid process of the ulna to the triquetral
and pisiform bones.

The ventral radiocarpal ligament {lig. radiocarpeum volarc) extends
between the ventral margin of the distal end of the radius and the
styloid process of the ulna to the ventral surfaces of the navicular,
lunate and triquetral bones and sometimes to the os capitatum
(magnum). -

The dorsal radiocarpal ligament [lig. radiocarpeum dorsale) extends
from the dorsal margin of the distal end of the radius to the dorsal
surfaces of the first row of carpal bones.

A synovial membrane lines the joint.

The movements are of flexion and extension, abduction and
adduction.

THE CARPAL ARTICULATIONS tARTICDLATIONES INTERCARPE^J

The carpal articulations are all of the arthrodial variety.

First Row. — The dorsal ligaments run transversely and connect
the navicular and lunate bones and the lunate and triquetral bones.

The ventral, or volar ligaments, are thinner but and similarly placed.

The interosseous ligaments are two in number, one connecting the
lunate and the navicular bones and the other the lunate and tri-
quetral bones. These are at the proximal ends of the bones and
extend from ventral to dorsal surfaces and shut out the wrist joint
from the intercarpal joints.

The pisiform bone has three ligaments. The capsule connects it
with the triquetral bone and it has its own synovial membrane. Its
two palmar ligaments connect it with the hamate and fifth meta-
carpal bones.

Second Row. — The dorsal ligaments connect the great multangular
(trapezium) with the lesser multangular (trapezoid), the latter with
the os capitatum (magnum) and this with theoshamatum (unciform).

The ventral, or volar ligaments are similarly arranged.

The interosseous ligaments are three in number and connect the
bones somewhat as in the first row, but not so completely.

The articulation between the first and second rows of carpal bones
is surrounded by a short capsular ligament.

The ventral, or volar ligament (lig. carpi radiatum), extends between
the two rows on their ventral surfaces.

The dorsal ligament is thinner but similarly arranged.

THE CARPAL ARTICULATION

127

The radial collateral carpal ligament extends between the lateral
surfaces of the navicular and greater multangular bones.

The ulnar collateral ligament extends between the medial surfaces
of the triquetral and hamate bones.

Two synovial membranes are present, one between the pisiform
and triquetral bones (already mentioned) and the other is between
the two rows with extensions between the various bones forming a
labyrinthine cavity.

Movements. — Between the first and second rows, flexion, extension
and slight rotation.

1 28 SYNDESMOLOGY

CARPOMETACARPAL ARTICULATIONS

The articulation of the first (thumb) metacarpal with the great
multangular bone is one of reciprocal reception. It permits of the
greatest movement of any of these joints and a loose capsule
surrounds the joint.

Movements. — Flexion, extension, abduction, adduction and circum-
duction.

The articulations between the other metacarpal and carpal bones
are of the arthrodial variety.

The dorsal ligaments are quite distinct and extend between the
dorsal surfaces of the bones concerned.

The ventral, or volar ligaments are similarly arranged.

Interosseous ligaments extend between the capitate and hamate
bones and the adjacent surfaces of the third and fourth metacarpal
bones.

The synovial membrane is continuous with that between the first
and second row of carpal bones.

Movements. — A slight gliding movement, only, is permitted.

INTERMETACARPAL ARTICULATIONS

The four inner metacarpal bones articulate with each other on
their adjacent sides (bases). Dorsal (ligg. basalia oss. metacarp.
dorsalia) and ventral (ligg. basalia oss. metacarp. volaria) ligaments
connect their bases transversely. The synovial membranes are all
extensions of and continuous with that between the two rows of
metacarpal bones.

The transverse metacarpal ligament (lig. capitulorum oss. mcta-
carpalium fpansversum) is a strong band that connects the heads of
the four inner metacarpal bones (ventral surfaces). It blends,
distally, with the metacarpophalangeal ligaments and, proximally
with the fascia of the interosseous muscles.

THE METACARPOPHALANGEAL ARTICULATIONS

These joints are of the condyloid variety.

A capsule surrounds each joint and this is strengthened dorsally
by the expansions of the tendons of the m. extensor digitorum
communis.

The ventral, or volar ligament (lig. vaginale) is thick, strong and
grooved for the flexor tendons.

The collateral ligaments (ligg. collateral ia) are cord-like thickenings
of the lateral parts of the capsule.

Movements. — Flexion, extension and some abduction, adduction
and circumduction.

TIIE SACROILIAC ARTICULATION"

129

ARTICULATIONS OF THE PHALANGES (ARTICULATIONES DIGITORUM

MANUSi

These joints are of the ginglymus variety.

A capsule is present and is strengthened by a ventral, or volar,
and two collateral ligaments arranged similarly
to those in the preceding articulations.

Each of these joints has a complete sy-
novial membrane lining the joint cavity.

Movements. — Flexion and extension.

THE ARTICULATIONS OF THE INFERIOR EX-
TREMITY (PELVIS APPENDAGE)

This appendage comprises one-half of the
pelvic girdle and the appendage proper.
The pelvic girdle comprises the two ossa
coxae (innominate bones), that articulate
with each other ventrally at the symphysis
pubis, and with the sacrum dorsally. Upon
each side the girdle articulates with the
proximal extremity of the femur. Accessory
ligaments are also present.

THE SACROILIAC ARTICULATION (ARTICU-
LATIO SACROLLIACA)

This articulation is of the amphiarthrodial
variety. A joint cavity is barely preceptiblc.

A capsule is formed by the following ligament.

The ventral sacroiliac ligament is short, thin but strong and extends
between the ala of the sacrum and the iliac fossa of the hip bone.

The dorsal sacroiliac, or interosseous ligament extends from the
supraauricular area of the ilium to the tubercles of the first and
second sacral segments and the adjacent bone. There are two parts,
as follows:

The short dorsal sacroiliac ligament extends from the dorsal superior
spine of the ilium to the first and second transverse tubercles of the
sacrum.

The long dorsal sacroiliac ligament extends from the dorsal superior
spine of the ilium to the transverse tubercles of the third and fourth
sacral segments.

Accessory Ligaments. — The sacrotuberous , or great sacrosciatic,
ligament (lig. sacrotuberosum) is of a triangular outline but narrow
in the middle; it extends from the dorsal inferior spine of the ilium
to the transverse tubercles and the lateral margins of the third,
fourth and fifth sacral and first coccygeal segments and to the
tuberosity of the ischium, inferior to the groove for the m. obturator
internus. From this attachment a portion passes along the medial
aspect of the ramus of the ischium as the processus falciformis.

Fig. 100. — Articulations
of the middle finger seen
from theside. {Sobotta and
McMurrick.)

13°

SYNDESMOLOGV

The sacrospinous, or small sacrosciatic ligament (lig. sacrospinosum )
is of a triangular outline and lies ventral to the preceding ligament.
It extends from the last two sacral and the first coccygeal segments
to the spine of the ischium.

These ligaments convert the sciatic notches of the hip bone into
foramina; the greater foramen (foramen ischiadicum majiis) lies
superior to the sacrospinous ligament and the lesser foramen (foramen
ischiudicum minus) lies inferior to the same ligament.

Lumbar vertebra l\
Anterior sacro-iliae lig.

Anterior longitudinal ligament
Iliolumbar lig.

Articular capsule
of hip joint
Iliofemoral

pubic lig.
Fig. ioi. — The male pelvis with its ligaments

fibrocartilage membrane

front. (Sobotta and McMurricli.)

THE SYMPHYSIS PUBIS (SYMPHYSIS OSSIUM PUBIS j

This articulation is of the amphiarthrodial variety and completes
the pelvic girdle ventrally.

The ventral pubic ligament {lig. pubicum anterius) is short and
thick and extends between the adjacent surfaces of the two pubic
bones. Its superficial surface is strengthened by the interlacement
of fibers from the tendons and aponeuroses of the adjacent muscles.

The dorsal pubic ligament {lig, pubicum poster ins) is similarly
arranged but weaker.

The superior pubic ligament {lig. pubicum su peri us) is weak and
extends from one pubic crest to the other.

The arcuate, or inferior ligament (lig. arcualum pubis), is quite
strong and extends from the descending ramus of the one pubic
bone across the inferior surface of the joint to the inferior ramus
of the other pubic bone.

THE HIP JOINT

131

The inter pubic disc {lamina fibrocartUaginea inter pubica) is covered
with hyalin cartilage and is attached to the adjacent surfaces of the
two pubic bones. It may contain a cleft-like cavity which, however,
does not contain a synovial membrane.

The obturator membrane almost completely fills in the obturator
foramen of the hip bone. At its highest part there is a U-shaped
gap that completes the obturator canal.

Short post, sacn-iliac I

WjS Iliolumbar ligament

<^ ■/ 5 ."'iliac tig.

■

;heroit$

■

Fig. 102. — The female pelvis

from behind. (Sobotla 1

THE HIP JOINT ARTICULATIO COXjE)

The hip joint is of the enarthrodial variety. It comprises the head
of the femur and the acetabular cavity of the hip bone.

The labrum glenoidale, or cotyloid ligament is a C-shaped mass of
fibrocartilage that is attached to the rim of the acetabular cavity
to deepen it and to make it narrower. The gap is at the acetabular
notch and here the two ends of the labrum are connected by the
transverse ligament (lig. transversantm acetabuli). This ligament
converts the notch into a foramen through which the vessels and
nerves pass into and out of the acetabular cavity. The inner surface
of the labrum is articular.

The capsule is a hollow cylinder. It is attached, proximally, to
the labrum glenoidale and the transverse ligament and the adjoin-
ing bone; distally, it is attached, above, to the medial aspect of the

132

SYNDESHOLOGY

Pubocapsalar ligament

■ator membrane

Fig. 103. — The right hip joint seen from in front. (Sobotta and McMurrich.)

FlG. 104. — The right hip joint seen from behind. (Sobotta and McMurrich,)

THE HIP JOINT 133

greater trochanter; ventrally, to the intertrochanteric line; dorsally,
to the junction of the middle and lateral third of the neck and
inferior]}- to the region of the lesser trochanter. Most of the dorsal
surface of the neck is not intrascapular while all of the remainder is.

The iliofemoral ligament (lig. iliofemorale) is j^-shaped and sup-
ports the capsule ventrally. It extends between the inferior margin
of the superior spine of the ilium to the intertrochanteric line of the
femur, splitting as it descends.

The pubocapsular ligament (lig. pubocapsularis) extends from the
superior ramus of the pubis and obturator crest to the capsule, with
which it blends.

The ischiocapstilar ligament {lig. ischiocapsularis) consists of fibers

Tendon of
rectus femoris

i

Fossa of acetabulum
Round ligament X

ligament of acetabulum

Fig. 105. — Socket of the right hip joint after cutting through the articular capsule and the
round ligament. The head of the femur has been removed. (Sobotla and McMurrich.)

that extend from the region of the lesser sciatic notch to the
acetabular portion of the capsule to blend therewith.

The round ligament (lig. teres femoris) is a flattened band extend-
ing from the superior portion of the depression in the head of the
femur to the lower margin of the transverse ligament and to the
adjacent margins of the acetabular notch.

The fossa in the acetabular cavity contains a mass of fat that is
called the Haversian gland. This is covered by the synovial mem-
brane so that it lies external to this membrane.

The synovia! membrane lines the capsule and covers all parts of
the bones within the joint except the actually articulating portions.
Occasionally a bursa is found communicating with the ventral part
of the synovial sac. This is beneath the tendon of the m. iliopsoas.

Movements. — This joint is capable of flexion, extension, abduction,
adduction, rotation and circumduction.

134

SYNDESMOLOGY
THE KNEE JOINT (ARTICULATIO GENU)

The knee joint is the largest joint in the body and is of the
lynius variety. Three bones, the femur, tibia and patella enter
into its formation. The condyles of the femur articulate ventrally

Fig. 106. — The right knee joint in
tension seen from in front. (Sobotta
McMurrich.)

G. 107.— The right knee joint seen f
behind. {Sobotta and McMurrich.)

with the patella and distally with the condylar facets upon the head
of the tibia.

The capsule in itself is not a complete investment nor are the
special portions sufficient to form a complete capsule. The latter
is completed and strengthened by expansions from the various
tendons about it.

THE KNEE JOINT

135

The patellar ligament {lig. patella;), a. ventral ligament, connects
the apex of the patella with the tuberosity of the tibia.

The dorsal ligament (lig. posterius) is thin laterally and thick
medially. It extends from the margins of the femoral condyles and
popliteal surface just superior to the intercondylic notch to the
dorsal margin of the head of the tibia. The tendon of the m.
semimembranosus contributes the oblique popliteal ligament (lig.
popliteum obliquum).

The tibial collateral ligament (lig. collaterale tibiale), or internal

Patellar surface

Anterior
ligament
Anterior capitular

pi w*»

Tuberosity 0/ tibia

ight knee joint in flexion after m
lateral ligaments. {Sobolta a

moval or' the articular capsule and the
,:J McMurrich.)

lateral ligament, is short and strong, extending from the medial
condyle of the femur, inferior to the adductor tubercle, to the
medial surface of the head of the tibia.

The fibular collateral, or externa! lateral ligament (lig. collaterale
libidare), is a cord-like band extending from the lateral condyle of
the femur to the head of the fibula, ventral to the styloid process.
It is split by the tendon of the m. biceps femoris.

Within the joint cavity a number of important ligaments will be
found.

The cruciate ligaments (lig. crnciata genu) are ventral and dorsal.
The ventral one (lig. cruciatum anterius) extends obliquely (laterally
and dorsallv) from the front of the intercondylic eminence of the

136 SYNDESMOLOGY

tibia to the dorsal part of the lateral condyle and the intercondylic
notch.

The dorsal one (lig. cruciatum posterius) is shorter than and dorsal
to the preceding. It extends obliquely (ventrally and medially)
from the area dorsal to the intercondylic eminence of the tibia to
the medial condyle near the ventral end of the intercondylic notch.

Two fibrocartilagcs deepen the facets upon the head of the tibia.

The medial meniscus (meniscus medialis), or internal semilunar
cartilage, is C-shaped. Its ends, or cornua are attached to the head
of the tibia in front of and behind the ventral cruciate ligament.
Its margin is attached to the margin of the head of the tibia by the
short coronary ligament.

Transverse ligament
Anterior crucial Deep infrapatellar bursa

Patellar lig.
Internal

Posterior crucial lig.

Fig. 109. — The condyles of the tibia with the two menisci and the origins of the crucial liga-
ments. (Sobotta and McMitrrich.)

The lateral meniscus (meniscus lateralis), or external semilunar
cartilage, is roughly semilunar. Its cornua are attached to the
superior surface of the head of the tibia but are farther apart than
the cornua of the other cartilage. It is also attached to the margin
of the head of the tibia by a coronary ligament.

The transverse ligament (lig. transversum genu) binds the ventral
margins of the menisci together.

The synovial membrane lines the capsule, covers the bones within
the capsule and also invests the intraarticular ligaments. Between
it and the patellar ligament is the infrapatellar pad. In this region
the synovial membrane forms folds, the plica synovialis patellaris
and the plicce alares (two). Bursce exist in relation with the joint.
The prepatellar bursa lies between the patella and the skin. The
deep infrapatellar bursa lies between the ligamentum patellar and
the tuberosity of the tibia. The suprapatellar bursa lies between
the femur and the tendon of the m. quadriceps extensor. The
subcutaneous tibial bursa lies between the tuberosity of the tibia and
the skin.

THE TIBIOFIBULAR ARTICULATIONS

137

Anterior capitular ligament

Movements. — This joint permits of flexion and extension. Under
certain conditions a slight rotation is permitted.

THE TIBIOFIBULAR ARTICULATIONS

An articulation of the arthrodial variety exists between the proximal
extremities and another between the
distal extremities of the tibia and hbula.

The proximal tibiofibular articulation
is the smaller and less important. A
capsule surrounds the joint and this is
strengthened by additional ligaments.

The ventral ligament of the head of the
fibula (lig. capituli fibula anterius) ex-
tends between the head of the fibula and
the adjacent part of the lateral tibial
condyle.

The dorsal ligament of the head of the
fibula (lig. capituli fibidoz posterius) is
similarly placed but thinner.

A synovial membrane is present and
may connect with that of the knee joint.

The distal tibiofibular articulation, a
synchondrosis, is merely a lateral support
to ankle joint.

The ventral ligament of the lateral mal-
leolus, or anterior inferior tibiofibular
ligament, extends between the ventral
surfaces of the distal end of the tibia and
the lateral malleolus of the fibula.

The dorsal ligament of the lateral mal-
leolus, or posterior inferior tibiofibular
ligament is similar in position.

The distal ligament of the lateral mal-
leolus, or transverse inferior tibiofibular
ligament extends from the dorsal margin
of the tibia to the pit on the dorsomedial
portion of the lateral malleolus.

The interosseous ligament is strong and
connects the adjacent surfaces of the
distal extremities of the tibia and fibula.
It is continuous superiorly with the interosseous membrane.

The interosseous membrane, like that of the forearm, connects the
adjacent margins of the two bones and separates ventral and
dorsal muscles. Superiorly there is a gap for the anterior tibial
vessels and inferiorly another opening for the peroneal vessels.

FlC. IIO. — The right tibia
and fibula with their ] igaments.
(Sobotta and McMurrich.)

138

SYNDESMOLOGY

The synovial membrane of the joint is an extension of that of the
ankle joint.

THE ANKLE JOINT (ARTICULATIO TALOCRURALIS I

The ankle joint, or tibiotarsal articulation is of the ginglymus
variety. The bones concerned are the tibia, fibula and talus
(astragalus).

A capsule is formed by the various ligaments and these vary in

strength.

Fig. III. — The ankle joint :

from behind. (Sobolta and \Ii.\lu

The ventral ligament is thin and connects the margin of the head
of the tibia with the margin of the head of the talus.

The dorsal ligament is very strong and consists of three parts.
The ventral fasciculus (lig. talofibular e anterius) is the shortest and
connects the ventral margin of the lateral malleolus with the talus
in front of its articular surface. The medial fasciculus (lig. calcaneo-
fibulare) is cord-like and connects the tip of the malleolus with the
side of the calcaneum. The dorsal fasciculus (lig. talofibulare
poslcrius) is the strongest and is transversely placed. It extends
from the fibular fossa of the malleolus to the dorsal surface of the
talus.

The deltoid ligament (lig. deltoideum) , or medial ligament, is tri-
angular in shape and the strongest ligament of the ankle joint. It
extends from the medial malleolus to the navicular, talal and

THE INTKRTAKSAL ARTICULATIONS

139

calcaneal bones. It has a number of divisions, as anterior, posterior
and deep (all talotibial) and tibionavicular and tibiocalcaneal.

The synovial membrane that lines the capsule and invests the non-
articular portions of the bones within the joint sends an extension
into the inferior tibiofibular articulation. Pads of fat separate it
from the bones at the front and back of the joint.

Movements. — These are of flexion and extension.

THE INTERTARSAL ARTICULATIONS (ARTICULATIONES
INTERTARSEiE)

The intertarsal articulations are of the arthrodial variety.
The talocalcaneal joint is formed by the talus and the calcaneum.
In addition to a capsule there are the anterior, posterior, lateral,

Deltoid ligament
Tendon of tibialis (inter

Dorsal
tarsometatarsal lig.

Tendon of tibialis
Sustentaculum tali

Calcaneus

Calcaneal tendon

(.Sobotta and McMurrich.)

medial and interosseous talocalcaneal ligaments, which connect
corresponding areas of the two bones.

The talocalcaneonavicular joint is formed by the talus, calcaneum
and naviculare. It is at the summit of the anteroposterior arch of
the foot. The most important ligament is the plantar calcaneona-
vicular ligament as it gives support to the arch and forms part of the
articulation. It blends with the deltoid ligament of the ankle joint.
Other ligaments are, the calcaneonavicular part of the bifurcate liga-
ment and the posterior talonavicular ligament.

The calcaneocuboid articulation is surrounded by a capsule which
is supported by other ligaments as, the medial calcaneocuboid (the
calcaneocuboid part of the bifurcate ligament), dorsal, lateral and
inferior calcaneocuboid ligaments.

140

SYNDESMOLOGY

The cuneonavicular articulation concerns the navicular and three
cuneiform bones. In addition to the capsule there are the dorsal
and plantar cuneonavicular ligaments.

The intercuneiform articulations are two in number, the middle
bone taking part in both. The ligaments are the dorsal and plantar
intercuneiform ligaments.

The cuneocuboid articulation is between the cuboid and the third
cuneiform bones. The ligaments are the dorsal, plantar and interos-
seous cuneocuboid ligaments.

Anterior

talo-fibidar

%

-The ligaments of the foot

tmts Upmaia Transverse capitular tig.

from above and from the outer side. (Sobotta

THE TARSOMETATARSAL ARTICULATIONS (ARTICULATIONES TAR-
SOMETATARSEjE)

These joints are formed by the cuboid and three cuneiform bones,
proximal]}-, and the bases of the five metatarsal bones, distally.
There are three joints and they are of the arthrodial variety.

The medial tarsometatarsal articulation comprises the internal
cuneiform bone and the base of the first metatarsal bone (great toe).
The ligaments are the capsule, and dorsal and plantar tarsometatarsal
ligaments.

The intermediate tarsometatarsal joint comprises the three
cuneiform bones and the bases of the second, third and a part of the
fourth metatarsal bones. The ligaments are dorsal, plantar and
interosseous.

The lateral tarsometatarsal articulation involves the cuboid and

THE IXTERUETATARSAL ARTICULATIONS

141

the bases of the fourth and fifth metatarsal bones. The ligaments
are dorsal and plantar.

Each of the three joints has a separate synovial membrane.

Movements. — The intertarsal and tarsometatarsal articulations
permit of a gliding movement. In the tarsus inversion, eversion and
a slight rotation may be produced.

Sesamoid bone

Tendon of peronaeus longits
Plantar tarsometatarsal ligts.

14. — The ligaments of the foot seen from the plantar surface.
McMurrich.)

THE INTERMETATARSAL ARTICULATIONS

These joints comprise the adjacent surfaces of the outer four
metatarsal bones only. The ligaments are the dorsal, ventral (plantar |
and interosseous ligaments of the bases. In addition transverse meta-
tarsal ligaments bind the bases on their plantar surfaces. The syno-
vial membrane is an extension of the preceding joints.

142 SYNDESMOLOGY

THE METATARSOPHALANGEAL ARTICULATIONS

These joints are of the condyloid variety. They resemble those
of the hand and each is provided with a modified capsule, a plantar
(accessory) and two lateral (collateral) ligaments. The dorsal liga-
ment is supplied by the expansion of the extensor tendon as it passes
over the joint.

Movements. — Flexion, extension, abduction and adduction.

THE INTERPHALANGEAL ARTICULATIONS (ARTICULATIONES
DIGITORUM PEDIS)

These joints also resemble those of the hand. The capsule is thin.
The other ligaments are the plantar (accessory) and two lateral
(collateral). The dorsal ligament is supplied by the extensor tendon.
Each capsule has its own synovial membrane.

Movements. — These are of fle-xion and extension.

CHAPTER III
MYOLOGY

Muscle tissues are those that produce the various movements of
the different parts and organs of the body. Myology is that division
of Anatomy that treats of the origin, insertion and actions of the
muscles. There are three varieties of muscle tissue, voluntary
striated, involuntary nonstriated and involuntary striated.

Voluntary striated, or skeletal muscle tissue consists of units
called muscle cells. These are cylindrical in shape, vary in length
from 2.5 cm. to 12 cm. and in from 25^ to 80/u in diameter. Each cell
or fiber shows longitudinal and cross-striations. Each fiber consists
of a large number of delicate fibrillar, or sarcostyles, imbedded in the
homogeneous sarcoplasm and is surrounded by a delicate membrane
called the sarcolenima. The fibrillar are composed of sarcous sub-
stance which stains deeply while the sarcoplasm stains faintly,
thereby causing the longitudinal striations. Each fibril is not an
uninterrupted thread but consists of segments (sarcous elements) of
equal length and separated from one another by an interval filled
in with sarcoplasm. These segments are all at the same level at
any given part of the fiber causing, thus, the cross-striations or
alternating dark and dim discs. In special preparations the dim
discs are seen to be crossed by a fine dark line called the membrane
of Kraiise, or Dobie's line. The nuclei are numerous and are located
at the periphery of the sarcous substance just beneath the
sarcolenima.

A muscle consists of a collection of muscle fibers and exhibits a
definite structure. Each muscle is surrounded by a sheath of white
fibrous tissue called the epimysium. From this septa are sent in
which divide the muscle into large secondary bundles; these are
further subdivided into primary bundles, or fasciculi each of which
is surrounded by a sheath called the perimysium. Incomplete
septa extend into the primary fasciculi and ultimately give rise
to a delicate meshwork all of which constitutes the endomysium;
this supports the muscle fibers, smaller nerves and vessels.

This variety of muscle is found as the skeletal, and external ocular
muscles, in the tongue, pharynx, upper part of the esophagus, anus,
diaphragm, larynx and external ear.

The involuntary, or smooth muscle tissue, consists of small
spindle-shaped cells. Each cell measures from 25// to 200/^ in length
143

144

fff

0 "■ ■ * .'

r/

—A

D

Fig. 115. — A, Longitudinal section of smooth muscle fibers, a. Muscle fiber; 6, nucleus;

c, fibrous tissue between fibers. B, Cross-section of smooth muscle fibers, a. Perimysial
connective tissue; b, blood-vessel; c, nucleated fiber; d, nonnucleated fiber. C, Longitud-
inal section of voluntary muscle fibers, a, Sarcotemma; b, nucleus; c, end of muscle fiber;

d, dark bands; e, intermediate disc;/, nucleus; g, lateral disc. D, Diagrammatic section of
cross and long striations. a. Dark disc; b, lateral discs; c, intermediate disc. £, Cross-
section of voluntary muscle, a. Perimysium; b, endomysium; c, nucleus of perimysium; d,
fibrillar; e, nucleus of muscle; /, sarcolemma. F, Longitudinal section of cardiac muscle
fiber, a. Muscle fiber; 6, nucleus; c, branch. G. Cross-section of cardiac muscle fibers, a.
Perimysial sheath; b, nucleus of sheath; c, muscle fiber; d, nucleus; e, radial plates of fibrillae.
(Radasch, Histology.)

MUSCLE TISSUE 145

and 5M to 7M in diameter; each fiber contains a single, long, slender,
centrally placed nucleus. The fibers are arranged in bundles that
form layers in the hollow organs. It is found in the gastrointestinal
tract, trachea, bronchial tubes, within the eyeball, in the genitouri-
nary system, in the blood vascular and lymph vascular systems and
the capsules of some organs.

The involuntary striated, or cardiac muscle tissue, is found in the
heart only. Each cell is a short, stubby cylinder measuring from
25M to 200ju in length and 25/z to 40^ in diameter. According to
some the heart muscle is considered a syncytium. Each cell has
cross- and longitudinal striations; the fibrillar are radially arranged
but are not present in the nuclear area. A single, broad, oval
nucleus is found near the center of each fiber. The cells are arranged
in bundles that do not form muscle masses as in the first variety,
nor are they arranged in regular layers as in the second variety. For
their general arrangement see "The Heart."

A muscle has two points of attachment; that which usually acts
as the fixed point (the part from which the muscle usually acts) is
called its origin, while the point acted upon (moved) is called the
insertion. Muscles are usually attached to the periosteum of the
bone (but may be attached to the bone directly, to ligaments or to
the skin) by means of tendons, or aponeuroses. The main mass of
the muscle (between the tendons) constitutes the venter or belly.

Movements are not the result of the action of a single muscle but of a
variable number. While one (or more) muscle is concerned directly
with the action produced other muscles (fixation muscles) steady
various joints during the action. The actions of muscles are of im-
portance in the displacement of fractured bones and the deformities
in dislocations.

Muscles are often named from their action (extensors, flexors,
pronators, supinators); number of heads (biceps, triceps); points of
attachments (sternomastoid, sternohyoid); shape (deltoid, trapezius,
rhomboideus) ; situation (ulnaris, radialis, tibialis) ; direction (rectus,
obliquus, transversal is) ; course (orbicular, or sphincter).

The fibers of the muscles are arranged in various ways. When
parallel, or nearly so, they form quadrilateral and fusiform muscles.
When they converge toward a common point, they form triangular
muscles (temporalis). When arranged obliquely and attached to one
or both sides of the tendon, they constitute penniform muscles. On
one side they are called unipennate (peronei); on both sides, they
constitute bipennate muscles (rectus femoris); when the tendinous
bands are numerous and the fibers are obliquely attached, the result
is a multipennate muscle (deltoid).

More or less directly connected with the muscles are the fascia.
The superficial fascia {fascia superficialis), or panniculus adiposus

146 MYOLOGY

is that loose areolar tissue just beneath the skin where the fat is
deposited. It supports the cutaneous nerves and vessels and is the
one affected in dropsical conditions.

The deep fascia (fascia profunda) is in close relation with the bones,
ligaments and muscles. It is of variable thickness in the various
regions of the body. It envelops the entire extremities and sends in
septa, the intermuscular fascia?, that separates the muscles from one
another. It assists in strengthening joints and as aponeuroses
affords attachment to muscles.

There are said to be 347 pairs of muscle and two single muscles
in the body.

THE MUSCLES OF THE HEAD

The muscles of the head comprise those of the scalp and auricular,
nasal, oral and orbital regions as well as those of mastication.

THE MUSCLES OF THE SCALP

The superficial fascia of the scalp is firm and dense and is attached
to the skin; it contains the superficial vessels, nerves and considerable
fat.

The m. epicranius (occipitofrontalis) consists of two bellies with
an intervening tendon. The frontal portion [frontalis) arises from
the galea aponeurotica (epicranial aponeurosis) and at the orbital
arch blends with the mm. orbicularis oculi and corrugator supercilii.
The occipital portion [occipitalis) arises from the lateral two-thirds
of the superior nuchal line of the occipital bone and terminates in the
galea aponeurotica. The galea aponeurotica is a broad and extensive
mass of dense fibrous tissue that connects the two bellies together;
it is attached laterally to the temporal ridges and dorsally, between
the dorsal bellies, to the middle of the superior nuchal line.

Actions. — The frontal portion draws the scalp forward and elevates
the skin over the root of the nose and the eyebrows. This action is
increased in fright and terror. The occipital portion draws the
scalp backward.

Nerves. — Occipitalis. — Posterior auricular branch of the facial
nerve.

Frontalis. — Temporal branch of the same nerve.

THE EXTRINSIC MUSCLES OF THE EAR

The m. auricularis anterior, the smallest, arises from the temporal
fascia and is inserted into the top of the root of the auricle.

The m. auricularis superior, the largest, is fan-shaped and arises
from the temporal fascia and is inserted into the top of the auricle.

The m. auricularis posterior arises from the surface of the
mastoid process and is inserted into the cranial surface of the auricle.

MUSCLES OF THE NASAL REGION

147

Actions. — Practically functionless.

Nerves. — Auricularis anterior and superior. — Temporal branch of
the facial nerve. — Auricularis posterior. — Posterior auricular branch
of the same nerve

Frontal,
Orbicularis oculi

(Palpebrdl portion)

L16. palpebrals mediate
Procerus . , .
Nasaiis s^&J

Galea aponeurotica

Auricularis superior

Orbicularis OCul't
orbital portion)

Occipitalis

Can in us
Orbicularis oris

Transversus ment

Plalysma

116. — The superficial layer of the facial muscles;
neck seen from the side and slightly from in front.

domastoideus

id the neighboring muscles of the
{Sohotta and McMurrich.)

THE NASAL REGION

The m. procerus, or pyramidalis nasi, arises from the frontalis
muscle and the skin of the glabella and is inserted into the membrane
that stretches over the nose.

The m. nasaiis, or compressor naris, arises from the maxilla above
the incisor fossa and is inserted into the above membrane.

The mm. dilatatores nasi are attached to the margin of the nostril,
one anterior to the other.

The m. depressor alae nasi arises from the upper part of the incisor
fossa of the maxilla; it divides, one part being inserted into the ala
and the other into the septum of the nose.

The caput angulare, or levator labii superioris et alaeque nasi,
arises from the root of the frontal process of the maxilla and is
inserted into the ala of the nose and joins the m. orbicularis oris.

Actions. — The procerus wrinkles the skin over the bridge of the
nose. The caput annulare elevates the upper lip (disdain and con-
tempt). The other muscles act as indicated by their names.

Nerves. — All are supplied by the facial nerve.

148

THE ORAL REGION

The m. orbicularis oris is a sphincter muscle connected with the
other muscles that converge at the mouth. The superior part is
attached to the nasal septum (nasolabial band) and the incisor
fossa (superior incisive fasciculus which is continuous with the
mm. buccinator and caninus); the inferior part is attached to the
mandible at each side of the symphysis (inferior incisive fasciculis
which is continuous with the mm. buccinator and caninus) ; laterally
it is joined by the buccinator, the elevators and depressors of the
lower lip at the angle of the mouth.

The m. quadratus labii superioris consists of the three following
muscles:

The caput infraorbitale, or levator labii superioris, arises from the
maxilla just above the infraorbital foramen and joins the orbicularis
oris muscle.

Fig. 117. — The oral musculature seen from behind. The muscles, together with the
integument, have been separated from the bones, and the mucous membrane covering the
muscles has been removed. (Scbotla ami McMitrrich.)

The caput angulare has been described above.

The caput zygomaticus, or zygomaticus minor arises from the
zygomatic bone and is inserted into the margin of the orbicularis oris
muscle.

The m. caninus, or levator anguli oris, arises from the canine fossa
of the maxilla and is inserted into the orbicularis oris and the skin of
the angle of the mouth.

The m. zygomaticus (major) arises from the zygomatic arch and is
inserted into the skin and into the orbicularis oris muscle.

The m. triangularis, or depressor anguli oris, arises from the
oblique line of the mandible and is inserted into the skin and the
orbicularis oris muscle.

The m. risorius is a portion of the platysma muscle arising from
the fascia over the parotid gland; it is inserted into the skin of the
angle of the mouth.

The m. quadratus labii inferioris, or depressor, arises from the

THE MUSCLES OF THE ORBITAL REGION I49

mandible close to the triangularis; it is inserted into the skin of the
lower lip and into the orbicularis oris.

The m. mentalis, or levator menti arises from the incisor fossa of
the mandible and is inserted into the skin of the chin.

The m. buccinator forms the bulk of the cheek. It arises from the
pterygomandibular raphe and the alveolar processes of the mandible
and maxilla. At the angle of the mouth its fibers blend with those
of the muscles there.

Actions. — These are the muscles of expression and by their actions
produce the effect of emotions upon the face. The m. orbicularis
oris causes the lips to pout, protrude unevenly, or compresses the
lips in various degrees. The mm. quadratics superioris and zygomati-
cus draw the lips upward; the mm. zygomalicus, risorius, buccinator
and triangularis draw the angle of the mouth laterally; the mm.
triangularis and quadratus inferioris draw the lips downward. The
m. buccinator flattens the cheek and draws the angle laterally and
the in. mentalis protrudes the lower lip.

Nerve Supply — All are supplied by the facial nerve.

THE ORBITAL REGION

The external muscles include three.

The m. orbicularis oculi is a sphincter muscle of the eyelids. Its
orbital portion spreads over the cheek, temple and forehead (pars
orbital is) and the palpebral portion (pars palpebral- is) is contained
in the eyelid. Medially the palpebral portion is attacked to the
medial palpebral ligament and the borders of the nasolacrimal
groove.

The pars lacrimalis, or tensor tarsi, is a portion of the above muscle
that lies behind the lacrimal sac and extend from the nasolacrimal
groove to the tarsal ligaments. It closes the eyelids.

The m. corrugator supercilii arises from the medial portion of the
superciliary arch and blends with the deep fibers of the orbicularis
oculi. It throws the skin of the forehead into vertical folds.

Nerve Supply. — All are supplied by the facial nerve.

Within the orbit are the orbital muscles, the fascia bulbi and the
eyeball, vessels and nerves. These structures are embedded in the
orbital fat. The fascia bulbi, or capsule of Tenon, represents a
bursa upon which the eyeball moves. One layer is attached to the
posterior surface of the eyeball while the other is applied to the
adjacent fat. The layers are continuous at the conjunctival region.
This fascia is pierced by the optic nerve and the tendons of the
ocular muscles upon which it is prolonged in the form of sheathes.

The m. levator palpebrae superioris arises from the upper part
of the optic foramen and as it passes forward it spreads out and is
inserted into the lid, mainly into the superior border of the superior

150 MYOLOGY

tarsal plate. It is also inserted into the conjunctiva, the orbicularis
oculi and skin of the upper lid.

Action. — Elevates the upper lid.

Nerve Supply. — Superior division of the oculomotor nerve.

The mm. recti are the superior, inferior, lateral and medial, and
they all arise from a ring of fibrous tissue that surrounds the optic
foramen. The superior, medial and superior head of the lateral
rectus all arise from the upper part of this ring while the inferior
rectus and the inferior head of the lateral rectus arise from the
inferior portion of this ring. The medial and lateral recti are in-
serted into the transverse plane of the eyeball about 8 mm. behind
the corneoscleral junction. The superior and inferior recti are

18. — Muscles of the right orbit.

inserted a little medial to the vertical axis of the eyeball about 8
mm. behind the corneoscleral junction.

The m. obliquus superior arises from the lateral margin of the
optic foramen, passes obliquely to the superomedial part of the
orbit where its middle tendon passes through a fibrous pulley that
is here attached. It then turns laterally and passes between the
superior rectus and the eyeball to be inserted into the sclera at the
equator of the eyeball between the lateral and superior recti muscles.

The m. obliquus inferior arises from the anteromedial part of the
floor of the orbit at the margin of the nasolacrimal groove. It
passes laterally between the inferior rectus and the floor of the orbit
and then between the lateral rectus and the eyeball to be
inserted into the sclera between the superior and lateral recti
muscles but at a more posterior level than the superior oblique.

Actions. — The medial and lateral recti muscles move the eyeball
medially and laterally in the horizontal plane. The superior and
inferior recti tend to move the eyeball in the vertical plane but their

THE MUSCLES OF MASTICATION 151

insertion and oblique direction cause them to produce some inward
movement as well as some rotation. This action of the superior
rectus is corrected by the inferior oblique while the same action of
the inferior oblique is corrected by the superior oblique muscle.
Diagonal movements are produced by the two contiguous recti
muscles acting at the same time. The oblique muscles acting alone
produce movements upon the anteroposterior axis of the eyeball.

Nerve Supply. — The lateral rectus by the abducent nerve.

The superior oblique by the trochlear nerve.

The remainder of the orbital muscles by the oculomotor nerve.

The m. orbitalis, or Mueller's muscle consists of smooth muscle
tissue and spans the inferior orbital fissure and infraorbital groove.

Action. — Probably assists in protrusion of the eyeball.

Nerve Supply. — Sympathetic nerves.

MUSCLES OF MASTICATION

The m. temporalis arises as a fan-shaped mass from the temporal
fossa and the temporal fascia. It is inserted into the coronoid proc-
ess and the anterior margin of the ramus of the mandible.

Action. — Closes the mouth, protrudes and retracts the mandible.

Nerve Supply. — Mandibular division of the trigeminal nerve.

The m. masseter arises superficially from the anterior two-thirds
of the inferior margin of the zygomatic arch and deeply from the
medial surface of the entire zygomatic arch; it is inserted into the
lateral surface of the coronoid process, ramus and angle of the
mandible.

Action. — Closes the mouth.

Nerve Supply. — Mandibular division of the trigeminal nerve.

The m. pterygoideus externus arises from the infratemporal sur-
face of the greater wing of the sphenoid bone (superficial head), and
from the lateral surface of the lateral plate of the pterygoid process
of the same bone (deep head). It is inserted into the anterior part of
the neck of the mandible just below the condyle and into the capsule
of the joint and the articular disc.

Action. — Protrusion and lateral movements of the mandible.

Nerve Supply. — Mandibular division of the trigeminal nerve.

The m. pterygoideus internus arises from the medial surface of
the lateral pterygoid plate and from the tuberosity of the maxilla;
it is inserted into the medial surface of the angle and ramus of the
mandible behind the mylohyoid groove.

Action. — Closes the mouth and assists in protrusion and lateral
movements of the mandible.

Nerve Supply. — Mandibular division of the trigeminal nerve.

'5-

Galea aponeuroses

Temporalis

Occipitalis

ularis

Trapezius
Splenius capitis
Parotid oland
Sternocleidomastoideus
Alasseter x

Fig. no. — The deepest layer of the facial muscles and the temporalis. . The caninus, the
zygomatic arch, a portion of the zygomatic bone with the origin of the masseter and the tem-
poral fascia? have been removed. (Sobotla and McMurrich.)

Palatine mucous^^

Hamulus of
pterygoid p,

lohuoideus x

^(Ant. belly)

Fig. 120. — The two pterygoidei seen from the
skull has been divided in the sagittal pi.
tongue and soft palate have been remo1

K indicates that the structures so marked, in the muscle illustrations, have
been cut.

irface. The anterior portion of the
and the temporal bone in an oblique plane; the
(Sobotta and McMurrich.)

THE CERVICAL MUSCLES 1 53

THE MUSCLES AND FASCIA OF THE NECK

The superficial fascia is very thin and invests the m. platysma.

The m. platysma is a broad thin sheet of muscle that (irises from
the pectoral and deltoid fascia; and passes obliquely upward and
inward over the neck; some of its fibers are inserted into the mandible
while the remainder pass onto the lower part of the face to be inserted
into the skin and to blend with the other muscles at the angle of the
mouth.

Action. — Wrinkles the skin of the neck, assists in depressing the
angles of the mouth arid may assist in depressing the mandible.

Nerve Supply. — Facial nerve.

The deep fascia (fascia colli) surrounds all of the muscles of the
neck, forms the carotid sheath and sends in septa that have received
special names. Dorsally it is attached to the ligamentum nuchse
and as it passes ventrally it splits at the dorsal margin of the sterno-
mastoid muscle to envelop it, uniting again at the ventral margin of
this muscle to envelop the infrahyoid muscles and then passes to
the midline of the neck. It is attached, superiorly, to the inferior
nuchal line of the occipital bone and the entire length of the body of
the mandible; inferiorly, it is attached to the sternum, the clavicle,
first rib and to the acromial process of the scapula.

The prevertebral fascia (fascia prevertebralis) is the transverse
septum that passes in front of the vertebral column and the preverte-
bral muscles. The pretracheal fascia is a septum that arches across
the neck ventral to the trachea and thyroid gland, assisting in form-
ing the carotid sheath on each side. These two septal fasciae form
a compartment containing the larynx, trachea, thyroid gland,
esophagus and pharynx. The carotid sheath forms a tubular com-
partment that encloses the carotid artery, the jugular vein, the vagal
and descendens hypoglossi nerves. The prevertebral fascia lies dorsal
to the parotid gland and assists in forming the stylomandibu-
lar, sphenomandibular and pterygomandibular ligaments.

The m. sternomastoideus arises from the ventral surface of the
manubrium sterni (sternal head) and from the medial third of the
superior surface of the clavicle (clavicular head). It passes supe-
riorly and dorsally in an oblique manner to be inserted into the lateral
surface of the mastoid process of the temporal bone and the superior
nuchal line of the occipital bone.

Action. — Flexes the head laterally and rotates it toward the opposite
side if acting alone. Both acting flex the head upon the neck and
assist in raising the clavicle and sternum in forced inspiration.

Nerve Supply. — Accessory nerve and a branch from the second
cervical nerve through the cervical plexus.

154

MYOLOGY
INFRAHYOID MUSCLES

The m. omohyoideus consists of two bellies; the dorsal one arises
from the superior margin of the scapula and the transverse scapular
ligament and ends in a tendon that continues as the ventral belly

that is inserted into the body of the hyoid bone along its inferior
margin. The muscle has an oblique direction and the middle tendon
is held in position by a process of cervical fascia that is attached
to the clavicle and first rib.

Action. — Depresses hyoid bone (after elevation) and draws it to
one side and backward if one alone is acting.

THE SUPRAHYOID MUSCLES 155

Nerve Supply. — Ansa cervicalis formed by the first three cervical
nerves.

The m. sternohyoideus is narrow and arises from the dorsal surface
of the manubrium sterni, the first costal cartilage and the adjacent
part of the clavicle. It is inserted into the inferior margin of the
body of the hyoid bone.

Action. — Depressor of the larynx and hyoid bone after elevation in
deglutition.

Nerve Supply. — Ansa cervicalis.

The m. sternothyreoideus arises from the dorsal surface of the
manubrium sterni and the first costal cartilage and is inserted into
the oblique line of the thyreoid cartilage of the larynx.

Action. — Depressor of the larynx and hyoid bone.

Nerve Supply. — Ansa cervicalis.

The m. thyreohyoideus, apparently a continuation of the preced-
ing, arises from the oblique line of the thyreoid cartilage and is
inserted into the body and greater cornu of the hyoid bone.

Action. — Depressor of the hyoid bone and elevator of the thyreoid
cartilage.

Nerve Supply. — Ansa cervicalis.

SUPRAHYOID MUSCLES

The m. digastricus consists of two bellies, the dorsal one of which
arises from the digastric notch of the mastoid process. This is
directed toward the hyoid bone where the middle tendon is held in
place by a band of cervical fascia. The ventral belly continues from
this tendon and is inserted into the digastric fossa of the mandible
(near the symphysis on the medial surface).

Actions. — Elevator of the hyoid bone and the ventral belly depresses
the mandible.

-Xii-cc Supply. — Ventral belly by the mylohyoid branch of the
inferior alveolar division of the trigeminal nerve; dorsal belly by the
facial nerve.

The m. srylohyoideus arises from the dorsolateral portion of the
base of the styloid process of the temporal bone and is inserted into
the body of the hyoid bone near the omohyoideus.

Action. — -Elevator of the hyoid bone.

Nerve Supply. — Facial nerve.

The m. mylohyoideus is broad and extensive forming the floor of
the buccal cavity. It arises from mylohyoid ridge of the mandible
and is inserted into the body of the hyoid bone and a fibrous median
raphe that extends from the hyoid bone toward the chin.

Actions. — Elevates the hyoid bone and depresses the mandible.

Nerve Supply. — Mylohyoid branch of the inferior dental nerve
(trigeminal).

156 MYOLOGY

The m. geniohyoideus arises from the inferior mental spines (me-
dial surface of the symphysis menti) and is inserted into the ventral
surface of the body of the hyoid bone.

Actions. — Elevates the hyoid bone and depresses the mandible.

Nerve Supply. — First and second cervical nerves through the
hypoglossal nerve.

LINGUAL MUSCLES

The intrinsic muscles are given in the description of the "Tongue"
(page 288). The extrinsic muscles are given below.

The m. genioglossus is a fan-shaped muscle arising from the supe-
rior mental spines; its inferior fibers are inserted into the body of the
hyoid bone while the remainder are inserted into the tongue from its
tip to the base.

Body of tono'ue
filiate papilla I L 0„^tadinsl;s i;n6uae inferior
Root o/tono'- /LXJ Oral mucous membrane X

G/ossopalatir.

Sty/o -

pbaruno'eus

w~ x Cenioolossus
Gen'tohuoideus
*S< ' ' !j'i ''il *5 ^ riyoolossus
Greater comu of Vfl;||'l'| \M^~^Hyoid bone (body)
" * — -v — * ^^Huothureoid membrane

Thureohuoideus

Fig. 123. — The superficial layer of the musculature of the tongue seen from the right side.
The mandible has been divided immediately to the right of the median line. (Sobotto-
and McMurrich.)

Actions. — Elevates the hyoid bone, depresses the mandible and
assists in protracting, retracting and depressing the tongue.

Nerve Supply. — Hypoglossal nerve.

The m. hyoglossus arises from the body and greater cornu of the
hyoid bone and is inserted into the side of the tongue.

Actions. — Elevates the hyoid bone and depresses the tongue.

Nerve Supply. — Hypoglossal nerve.

The m. styloglossus arises from the tip of the styloid process and
the stylohyoid ligament and is inserted into the side and inferior
surface of the tongue, decussating with the mm. hyoglossus and the
glossopalatinus.

Actions. — Elevates the tongue and assists in retracting the tongue.

Nerve Supply. — Hypoglossal nerve.

MUSCLES OF THE PHARYNX AND PALATE 157

The m. glossopalatinus arises from the inferior surface of the soft
palate and is inserted into the side of the tongue blending with the
m. styloglossus and intrinsic muscles.

Action. — Elevates the base of the tongue.

Nerve Supply. — Accessory nerve through the pharyngeal plexus.

The m. chondroglossus is a variable muscle and when present it
arises from the lesser cornu of the hyoid bone and blends with the
intrinsic muscles of the tongue.

Action. — Negligible.

Nerve Supply. — Hypoglossal nerve.

PHARYNGEAL AND PALATAL MUSCLES

The m. constrictor pharyngeus superior is thin and arises from the
inferior portion of the dorsal margin of the medial pterygoid plate,
from the pterygomandibular ligament, the mylohyoid line and the
mucous membrane of the floor of the mouth. Its fibers radiate
dorsally and are inserted into the pharyngeal tubercle of the occipital
bone and the median raphe. Its inferior portion is overlapped by
the middle constrictor.

The m. constrictor pharyngeus medius arises from the stylohyoid
ligament and both cornua of the hyoid bone. It is inserted into the
dorsal median raphe. It is overlapped by the inferior constrictor.

The m. constrictor pharyngeus inferior arises from the oblique
line of the thyreoid cartilage and cricoid cartilage and is inserted into
the dorsal median raphe.

Actions. — These are the muscles of deglutition.

Nerve Supply. — Accessory nerve through the pharyngeal plexus.
The inferior receives branches from the vagal nerve in addition.

The m. stylopharyngeus arises from the root of the styloid process
and is inserted into the wall of the pharynx and the superior and
dorsal margins of the thyreoid cartilage of the larynx.

Actions. — Elevates and draws laterally the wall of the pharynx.

Nerve Supply. — Glossopharyngeal nerve.

The m. pharyngopalatinus arises from the soft palate and is
■inserted into the dorsal margin of the thyreoid cartilage near the
m. stylopharyngeus.

Action. — Draws the pharynx over the bolus of food in deglutition.

Nerve Supply. — Accessory through the pharyngeal plexus.

The m. salpingopharyngeus is a small muscle that arises from the
inferior part of the auditory (Eustachian) tube and blends with the
m. pharyngopalatinus.

The m. levator veli palatini arises from the inferior part of the
cartilaginous auditory tube and from the apex of the petrous portion

of the temporal bone. It is inserted into the aponeurosis of the
soft palate.

Action. — Elevates the soft palate.

Nerve Supply. — Accessory nerve through the pharyngeal plexus.

The m. tensor veli palatini arises from the cartilaginous portion
of the auditory tube and from the scaphoid fossa of the pterygoid
process and the spine of the sphenoid bone. It is inserted into the
dorsal margin of the soft palate and into the palatal aponeurosis.

pharynoobasilar

Stylopharyndeus

Stylohuotdeus

Constrictor
pharuno'is medi

pheryno'eal raph

pharuno'eal o'/ands
— styloid process
V parotid o'land

Constrictor
pharuno'is superior

Pteryo'oideus internus

Submaxillary o'land

Fig. 124. — The constrictors o- the pharynx seen from behind. The posterior part of the
skull has been removed. *, A bundle of the superior constrictor arising from the base of
the skull. (Sobotta and McMurrich.)

Action. — Renders the palate tense.

Nerve Supply. — Trigeminal nerve through the otic ganglion.

The m. glossopalatinus (see lingual muscles).

The m. uvulae is really a pair of muscles and these are the only
intrinsic muscles of the palate. Each arises from the posterior
nasal spine and palatal aponeurosis and is inserted into the tissues
of the uvula.

LATERAL AND PREVERTEBRAL CERVICAL MUSCLES

!59

Action. — Elevates the uvula.

Nerve Supply. — Accessory nerve through the pharyngeal plexus.

THE LATERAL AND PREVERTEBRAL CERVICAL MUSCLES

The m. scalenus anterior arises from the anterior tubercles of the
transverse processes of the third, fourth, fifth and sixth cervical

vertebra?. It is inserted into the scalene tubercle and ridge of the
first rib.

The m. scalenus medius arises from the posterior tubercles of the

l6o MYOLOGY

transverse processes of the inferior six cervical vertebra and is
inserted into the first rib dorsal to the subclavian groove.

The m. scalenus posterior arises from the posterior tubercles of
the transverse processes of the fourth, fifth and sixth ribs and is
inserted into the lateral surface of the second rib.

Actions. — Lateral flexion of the vertebral column and accessory
to respiration.

Nerve Supply. — Ventral rami of the lowest four cervical nerves.

The m. longus capitis, or rectus capitis anticus major arises from
the anterior tubercles of the transverse processes of the third, fourth,
fifth and sixth cervical vertebrae and is inserted into the basilar
portion of the occipital bone.

Action. — Flexes the head and the cervical vertebrae.

Nerve Supply. — Ventral rami of the first four cervical nerves.

The m. rectus capitis anterior, or rectus capitis anterior minor
arises from the lateral mass of the atlas and is inserted into the
basilar portion of the occipital bone.

Action. — Flexes the head upon the vertebral column.

Nerve Supply. — From the loop between the first and second
cervical nerves.

The m. longus colli is divisible into three portions. The vertical
part arises from the bodies of the last three cervical and the first
three thoracic vertebrae and is inserted into the bodies of the second,
third and fourth cervical vertebrae. The superior oblique part
arises from the anterior tubercles of the third, fourth and fifth
cervical vertebrae and is inserted into the anterior tubercle of the
atlas. The inferior oblique portion arises from the bodies of the
first three thoracic vertebrae and is inserted into the anterior tubercles
of the fifth and sixth cervical vertebrae.

Action. — Flexes the vertebral column.

Nerve Supply. — Ventral rami of ' the second, third and fourth
cervical nerves.

The m. rectus capitis lateralis arises from the transverse process
of the atlas and is inserted into the jugular process of the occipital
bone.

Action. — Flexes the head laterally upon the vertebral column.

Nerve Supply. — The loop between the first and second cervical
nerves.

MUSCLES OF THE BACK

The superficial fascia is thin and contains a variable quantity
of fat. The deep fascia is usually more prominent. It is attached,
superiorly, to the superior nuchal line of the occipital bone and is
continuous with the cervical fascia. It is continuous with the
axillary fascia and the fascia of the abdomen and thus covers the

THE MUSCLES OF THE BACK

161

superficial muscles and even ensheathes them. In the middorsal
line it is attached to the ligamentum nuchas and the vertebral
spines; it is also attached to the spine of the scapula and to the crest
of the ilium. The muscles are superficial and deep and are usually
described under four layers.

The mm. trapezius and the latissimus dorsi form the superficial
layer.

The m. trapezius is broad, thin, flat and of a triangular form. It
arises from the medial portion of the superior nuchal line of the

Semispinal''^ capit

Splenius capitis

Sternocleidomastoideus

Sacrospinalis

fc I posterior layer)

Gluteal fascia

Fig. i 2- . — The superficial layer of the flat muscles of the back together with the neighbor-
ing muscles of the head, neck, abdomen, and buttock. Upon the right side the rhomboideus
major and the teres major are represented covered by fascia. (Sobotta and McMurrich.)

occipital bone, from the ligamentum nucha; and from the spines of
the seventh cervical and all of the thoracic vertebrae as well as the
supraspinous ligaments. The superior fibers are inserted into lateral
third of the dorsal margin of the clavicle; the middle fibers are inserted
into the medial margin of the acromion and the superior margin
of the spine of the scapula; the inferior fibers are inserted into the base
of the spine of the scapula.

I 62 MYOLOGY

Action. — The whole muscle rotates the scapula. The superior
portion elevates the shoulder girdle while the inferior fibers depress
the vertebral margin.

Nerve Supply. — The accessory nerve and the third and fourth
cervical nerves through the cervical plexus.

The m. latissimus dorsi is also a flat, triangular muscle. It
arises from the lumbosacral fascia, from the lower three or four ribs
(interdigitating with the m. obliquus abdominis externus) and occa-
sionally from the inferior angle of the scapula. Toward its inser-
tion the muscle becomes narrow and thick and its ribbon-like tendon
is inserted into the floor of the intertubercular sulcus (bicipital
groove).

Action. — Depresses and rotates the humerus medially and as a
muscle of extraordinary inspiration it elevates the inferior ribs.

Nerve Supply. — The thoracodorsal nerve from the dorsal cord of
the brachial plexus (representing sixth, seventh and eighth cervical
nerves).

SECOND LAYER

The m. levator scapula is a narrow muscle that arises from pos-
terior tubercles of the transverse processes of the first three or four
cervical vertebra and is inserted into the superior angle and vertebral
margin of the scapula.

Action. — Elevates the superior angle and vertebral margin of the
scapula.

Nerve Supply. — Dorsal scapular nerve of the brachial plexus (fifth
cer.) and branches from the third and fourth cervical nerves.

The m. rhomboideus minor arises from the ligamentum nucha?
and the spines of the seventh cervical and first thoracic vertebra?.
It is inserted into vertebral margin of the scapula at the base of the
spine.

The m. rhomboideus major arises from the spines of the second,
third, fourth and fifth thoracic vertebra; and supraspinous ligaments.
It is inserted into the vertebral margin of the scapula at the base of
the spine and at the inferior angle.

Actions. — They elevate and draw toward the median line the
vertebral margin of the scapula.

Nerve Supply. — Dorsal scapular nerve of the brachial plexus
(fifth cer.).

THIRD LAYER

The m. serratus posticus superior arises from the ligamentum
nuchas and the spines of the seventh cervical and first three thoracic
vertebra;. It is inserted into the second, third, fourth and fifth
ribs.

The m. serratus posticus inferior arises from the lumbosacral

THE MUSCLES OF THE BACK

163

fascia attached to the last two thoracic and first two lumbar spines;
after a horizontal course it is inserted into the last four ribs.

Actions. — Extensors of the vertebral column and accessory muscles
of respiration.

Nerve Supply. — Dorsal rami of the superior and inferior thoracic
nerves, respectively.

The m. splenius is a band-like muscle that arises from the lig.
nuchae, the last cervical and the first six thoracic spines and the

Splenius capitis
Levator scapulae
Rhomboideus minor
tSupraspinatus)

Rhomboideus
major

Occipitalis
Semispinalis capitis
Sternocleidomastoideus
Splenius cervicis
Levator scapulae
^Trapezius y

Latissimus X

Latissimus x

Serratus

§;'.\ posterior inferior

.umbodorsal fascia
I posterior layer)

Gluteal fascia

(Glutaeus maximus)

Fig. 1 28. — The deeper layers of the flat muscles of the back. On the left side the trape-
zius and latissimus have been cut away; on the right side the rhomboidei have also been cut
' 1 and the lumbodorsal fascia has been retained only where it is in relation with
the origin of the serratus posterior inferior and below. (Sobolla and Ml Murrich.)

supraspinous ligaments. The superior portion is inserted, as the
splenius capitis into the mastoid process and the superior nuchal line.
The inferior portion, as the splenius cervicis, is inserted into dorsal
tubercles of the first three or four cervical vertebra?.

Actions. — Extension and lateral movement of the vertebral column.
The splenius capitis assists in flexion, rotation and raising the head.

1 64

MYOLOGY

Nerve Supply. — Dorsal rami of the cervical and superior thoracic
nerves.

FOURTH LAYER

The m. sacrospinalis, or erector spinse, is the large muscle mass
that tills the vertebral groove on each side of the spinous processes.
It arises from the iliac crest, from the dorsal sacral ligament and
from the dorsum of the sacrum and the spinous processes of the

Iliocostalis
turn bo rum

FlG. 129. — The deeper layers of the lo
spinalis has been partly removed and the i
anil McMurrich.)

'spinalis capitis X

Rectus capitis
major

Splenius capitis X
ObUquus
capitis super.

longissimus capitis X
Obliquus capitis inferior
Spinalis cervicis
Semispinalis capitis X
fnterspinales
~ 5 err at us
poster, super, X

Semispinalis ceroids
et dorsi X

Multifidus dorsi

Legator costae

Levator costae

fono'us

5 er rat us
posterior inf

Semispinalis X

:he back. On the left side
pinalis has been cut and reflected.

lumbar and superior sacral vertebrae. Near the last rib the muscle
divides into several portions, as follows:

The m. iliocostalis lumborum, or lateral portion, is inserted into the
six inferior ribs.

The m. iliocostalis dorsi, or accessorius, is the successor of the
preceding in the upper thoracic region. It arises from the inferior
six ribs, medial to the iliocostalis lumborum and is inserted into the
six superior ribs.

THE MUSCLES OF THE BACK 165

The m. iliocostalis cervicis, or cervicis ascendens, succeeds the
m. iliocostalis dorsi in the cervical region. It arises from the
superior six ribs medial to the insertion of the preceding muscle and
is inserted into the dorsal tubercles of the fourth, fifth and sixth
cervical vertebra?.

The m. longisimus is the medial and largest portion of the m.
sacrospinalis. It is inserted into all of the ribs and into the trans-
verse processes of the thoracic and lumbar vertebra?.

The m. longisimus cervicis, or transversalis cervicis, arises from
the transverse processes of the first six thoracic vertebra? and is
inserted into the dorsal tubercles of the transverse processes of the
third, fourth, fifth and sixth cervical vertebra?.

The m. longisimus capitis, or trachelomastoideus, arises in com-
mon with the preceding and from the articular processes of the lower
four cervical vertebra?. It is inserted into mastoid process of the
temporal bone.

The m. spinalis dorsi lies just lateral to the midline in the thoracic
region. It arises from the spinous processes of the first two lumbar
and the last two thoracic vertebra? and is inserted into the spines of
the first four, or more, thoracic vertebra?.

The m. semispinalis capitis, or complexus, is a broad muscle that
arises from the transverse processes of the first six thoracic and the
articular processes of the last four cervical vertebra?. It is inserted
into the occipital bone between the superior and inferior nuchal lines.

Actions. — Assists in extension and lateral movements of the pelvis
and vertebral column. Extension, lateral movement and rotation
of the head (mm. long, capitis and semispinalis capitis). Accessory
to inspiration (mm. longisimus and iliocostales).

Nerve Supply. — Dorsal rami of the spinal nerves.

FIFTH LAYER

The m. semispinalis comprises two portions.

The m. semispinalis dorsi arises from the transverse processes of
the last six thoracic vertebra? and is inserted into the spines of the
first four thoracic and last two cervical vertebra?.

The m. semispinalis cervicis, or colli, arises from the transverse
processes of the first six thoracic and the articular processes of the last
four cervical vertebra? and is inserted into the spines of the second to
the fifth cervical vertebra?.

Actions. — Extension, rotation and lateral movement of the vertebral
column.

Nerve Supply. — Dorsal rami of the spinal nerves.

The m. rotatores are eleven pairs of small, thoracic muscles. Each
arises from the transverse process and is inserted into the lamina of
the vertebra superior to it.

l66 MYOLOGY

Action. — Extension and rotation of the vertebral column.

Nerve Supply. — Dorsal rami of the thoracic spinal nerves.

The mm. interspinals are paired muscles connecting the trans-
verse processes of the vertebrae. They extend the vertebral column
and are supplied by the dorsal rami of the spinal nerves.

The mm. intertransversarii, or intertransversales, are small mus-
cles connecting the adjacent transverse processes. In the neck and
lumbar region they are paired on each side of the midline. These
assist in lateral movement and rotation of the vertebral column and
are supplied by the ventral rami of the spinal nerves.

The m. rectus capitis posterior major arises from the spine of the
second cervical vertebra and is inserted into the occipital bone below
the middle of the inferior nuchal line.

The m. rectus capitis posterior minor arises from the dorsal tu-
bercle of the atlas and is inserted into the occipital bone medial to the
preceding muscle.

Actions. — Both muscles assist in elevation, rotation and lateral
movement of the head.

Nerve Supply. — Dorsal ramus of the suboccipital, or first cervical,
nerve.

The m. obliquus capitis superior arises from the transverse process
of the atlas and is inserted into the lateral portion of the occipital bone
between the superior nuchal line and the jugular process.

The m. obliquus inferior arises from the spine of the epistropheus
(axis) and is inserted into the transverse process of the atlas.

Actions. — The superior produces elevation, rotation and lateral
movement of the head upon the atlas. The inferior produces extens ion ,
lateral movement and rotation of the atlas in the axis.

Nerve Supply. — Posterior ramus of the suboccipital or first cervical
nerve.

The m. rectus capitis lateralis connects the jugular process of the
occipital bone with the transverse process of the atlas. It assists in
lateral movement and rotation of the head and is supplied by the sub-
occipital nerve.

MUSCLES OF THE THORAX, OF RESPIRATION

The mm. intercostales are placed between the ribs and are eleven
pairs in number on each side.

Each external intercostal muscle (m. intcrcostalis externus) arises
from the inferior margin of a rib, passes downward and ventrally to
be inserted into the superior margin of the rib beneath. It does not
quite reach the sternum in front and the space is spanned by the
ventral intercostal aponeurosis.

Each internal intercostal muscle (m. intercostalis interims) arises
from the costal cartilage and the medial margin of the costal groove

THE DIAPHRAGM

167

and passes downward and dorsally to be inserted into the superior
margin of the costal cartilage and rib beneath. It extends to the
angle of the rib only and the remainder of the intercostal space is
spanned by the dorsal intercostal aponeurosis.

The mm. levatores costarum are twelve in number arising from
the transverse processes of the seventh cervical and the first eleven
thoracic vertebrae; each is inserted into the rib dorsal to the angle.

The mm. subcostales are on the medial surfaces of the inferior ribs
near their angles. These are in series with the internal intercostal
muscles.

Anterior fanaitudinal //'{foment

Intercostales extern?

SUrnothyreoide! X

Rib XI

RibXIl Lumbar vertebra I Subcostales
Fig. 131.
lavicles and the ribs, with the intercostales.

Fig. 130.

Fig. 130. — The sternum, sternal ends of the
and the transversus thoracis, seen from behind. (Sobotta and McMurrich.)

Fig. 131, — The fifth to the twelfth thoracic vertebra: and the vertebral extremities of the
corresponding ribs, with the intercostales and subcostales seen from in front. On the left side
the intercostal ligaments have been removed. {Sobotta and McMurrich.)

The m. transversus thoracis, or triangularis sterni, is within the
thoracic cavity. It arises from the dorsal surface of the xiphoid
process and most of the body of the sternum and is inserted into the
second, third, fourth, fifth and sixth costal cartilages of both sides.

The diaphragm (diaphragma) is a musculomembranous partition
between the thorax and abdomen. The muscular portion arises as
follows: dorsally by two crura (pars lumbal is) the rig/it crus arising
from the first, second and third lumbar vertebras and the left from
the first and second lumbar vertebra;; from the middle arcuate liga-
ment in front of the aorta; from the internal arcuate ligament (arcus
lumbocostalis medialis) that stretches from the body of the first
lumbar vertebra to its transverse process; from the external arcuate

1 68

/ i game at (arc its lumbocostal is lateralis) that stretches from the
transverse process of the first lumbar vertebra to the apex and
lower margin of the twelfth rib. Ventrally, the diaphragm arises
from the dorsal surface of the ensiform cartilage of the sternum
{pars sternalis) and from the dorsal surface of the six lower costal
cartilages; laterally, it arises from the lower six ribs (pars costalis).
The muscle fibers are all inserted into the central tendon.

The centra! tendon (centrum tendincum) consists of three leaflets
of which the right is the largest and the left the smallest. There are
three chief openings in the diaphragm. The aortic orifice (hiatus
aorticus) is the lowest and most dorsal; it transmits the aorta, the

Fig. 132. — The abdominal surface of the diaphragm. .4, Middle arcuate ligament and
aortic orifice; B. esophageal orifice; C, caval orifice; D. right crus; E, medial arcuate ligament;
F, lateral arcuate ligament.

vena azygos major and the thoracic duct. The esophageal orifice
(hiatus esophageus) is to the left of the preceding and at a more
ventral level; it transmits the esophagus and vagal nerves. The
caval orifice (foramen vena cavce) is the highest and is situated to the
right of the midline. It is quadrate in form and transmits the
inferior vena cava.

The diaphragm is dome-shaped and when viewed from the side
shows that the ventral attachment is at a higher level than the dorsal;
when viewed from the front it exhibits two domes of which the right
is the higher, reaching the level of the fifth interspace in the mid-

THE MUSCLES OF THE ABDOMEN 169

clavicular line; the left dome reaches the level of the sixth left
sternochondral junction. The position varies with inspiration and
expiration, its excursion at times being as great as 2 inches.

Actions. — Inspiration is accomplished mainly by the diaphragm
and intercostal muscles assisted by the mm. scalenei, serrati pos-
teriores, levatores costarum and the subcostal muscles. The dia-
phragm depresses its central tendon and elevates the inferior ribs.
The external intercostal muscles elevate the ribs. The internal inter-
costal muscles are supposed to do the same. The accessory muscles
of inspiration are the mm. pectorales, quadratus lumborum sterno-
mastoideus, latissimus dorsi, infrahyoid muscles and extensors of
the vertebral column.

Expiration is accomplished by the relaxation of the above muscles
and elevation of the diaphragm causing the thoracic cavity to be-
come smaller, by the elasticity of the lungs and by the contraction
of the abdominal muscles.

THE MUSCLES AND FASCIA OF THE ABDOMEN

The superficial fascia of the abdomen contains a variable quantity
of fat and consist of a single layer in the superior portion of the
abdominal wall. In the groin region it is separable into two layers,
the superficial one of which is continuous with that of the thigh; the
deeper layer is attached to the inguinal ligament and fascia lata of
the thigh thus preventing the passage of fluids from the abdominal
wall to the thigh. These fascial layers also pass along the spermatic
cord and form part of the scrotum.

The deep fascia is closely applied to the muscles even investing
some. It is variable in its thickness in different regions.

The abdominal cavity side of the muscles is covered by fascia
that is named according to the muscle covered (transversalis, quad-
ratus lumborum, psoas, diaphragmatic). At the thigh it forms the
femoral sheath for the femoral vessels and at the inguinal ring the
i nf u nd ibul i/orm fascia. Upon the deep surface of this fascia are the
extraperitoneal tissue and the peritoneum.

The extraperitoneal tissue usually contains a great quantity of
fat in which are embedded the extraperitoneal abdominal organs.
The peritoneum is a serous membrane that lines the abdominal cav-
ity and invests some organs completely, some incompletely and
others not at all.

The m. obliquus externus abdominis is broad and thin and arises
from the eight inferior ribs interdigitating with the mm. serratus
anterior and latissimus dorsi. It is inserted into the ventral half of
the external iliac crest and aponeurosis by means of which it is
attached to the xyphoid process, the linea alba and the symphysis

170 MYOLOGY

pubis. This aponeurosis is extensive forming various ligaments
and assisting in forming the external abdominal ring.

The inguinal ligament (lig. inguinale Pouparf) is the inferior
margin of the aponeurosis of the m. obliquus externus abdominis
and extends from the ventral superior spine of the ilium to the tuber-
cle of the pubis. It affords attachment to some muscles and also
forms the floor of the inguinal canal.

Oelto'deus
'Clavicular portion of pecmaj

Sternocostal
portion of pec ma)

Abdominal portion of pec rnaj
Serratus anterior

Cremaster
Reflected inguinal lig

of penis
Superior pillar Inferior pillar.

Fig. 133. — Superficial and second layers of the abdominal and pectoral muscles seen from
in front. On the right side the pectoralis major and the obliquus abdominis externus have
been removed. {Sobotta and McMurrich.)

The lig. lacunare, or Gimbernat' s lig., is a triangular reflection of
the medial extremity of the inguinal ligament toward the iliopec-
tineal line.

The subcutaneous inguinal ring, or external abdominal ring, is
just over the tubercle of the pubis and through it pass the spermatic
cord, or round ligament of the uterus, and the cremaster muscle and

THE MUSCLES OF THE ABDOMEN

171

its fascia. The margins of the ring are called the crura and these
are thin. From the margins of the ring a thin tubular sheath of
fascia, the inter columnar, or external spermatic fascia, passes over the
spermatic cord.

The reflex inguinal ligament of Colles, or the triangular fascia,
consists of fascial fibers from the opposite side that are attached
to the crest and tubercle of the pubis.

Omohyoid
Scalenus medius
Sternohyoid * *,
+ Sternothyreoid/l.

Fig. 134. — The superficial layer of the abdominal muscles and the serratus anterior seen
from the left side. The pectoralis major and minor and the inner portion of the clavicle have
been removed and the arm has been drawn backward. (Sobotta and McMurrich.)

The m. obliquus internus abdominis, broad and thin, arises
from the lumbodorsal fascia, the ventral two-thirds of the iliac crest
and from the lateral portion of the inguinal ligament. Its fibers
are directed superiorly and medially, the superior ones are inserted
into the three lower ribs and the remainder are inserted into an apo-
neurosis that joins that of the external oblique and transversalis
muscles. This conjoined fascia splits to envelop the rectus abdominis

muscle forming, at the lateral margin of the muscle the linea semi-
lunaris and at the medial margin the linea alba. The inferior margin
of the aponeuroses is joined by fibers from the transversalis fascia
forming the conjoined tendon, or falx aponeiaotica ingiiinalis; this is
attached to the pubic crest and iliopectineal line.

The m. cremaster arises from the inferior margin of the internal
oblique muscle and is inserted, in part, to the tubercle of the pubis.

The m. transversus abdominis arises from the deep surfaces of
the lower six costal cartilages, the lumbosacral fascia, the medial

External intercostal /tots.

Sternal membrane
Rectus abdomin
Rib VI

Intercostales interni

Serratus anterior

'ntercostales exterm

Semicircular line
Transversalis fascia

Inouinal lid.
Cremaster x

Pyramidalis X

Fk;. 135. — The deeper layers of the abdominal muscles. On the left side the anterior
layer of the sheath of the rectus abdominis and the obliquus abdominis externus have been
removed; on the right side, in addition, the rectus abdominis, the pyramidalis. and the ob-
liquus abdominis internus. The external intercostal ligaments have been removed on the
left side. (Soboita and McMurrich.)

crest of the ilium and from the lateral part of the inguinal ligament.
After a horizontal course the fibers are inserted into an aponeurosis
that joins that of the internal oblique to form the sheath of the
rectus muscle; this aponeurosis is inserted into the xyphoid cartilage,
the linea alba and the crest of the pubis. The inferior fibers form
the conjoined tendon described above.

The m. pyramidalis abdominis is small and arises from the pubic
crest and is inserted into the ilea alba.

THE INGUINAL CANAL

173

The m. rectus abdominis arises from the symphysis and crest of
the pubis and is inserted into the ventral surface of the xyphoid
process and of the fifth, sixth and seventh costal cartilages. The
muscle is divided transversely by three or more tendinous bands,
the inscriptiones tendineee. The lateral margin of the muscle is indi-
cated by the lined semilunaris. At this line the abdominal apo-
neurosis splits to form the two layers of the rectus sheath. The in-

Fig. 136. — The diaphragm and the muscles of the dorsal abdominal wall. The ven-
tral abdominal wall and the abdominal viscera have been removed; the thorax has been
bent backward so that the lumbar vertebra are strongly convex forward. (Sobctta and
McMurrich.)

ferior portion of the dorsal layer of the sheath is not present and the
linea semicirctdaris marks the inferior limit of the layer.

The inguinal canal (canalis ingninalis) begins at the abdominal
inguinal ring and continues to the subcutaneous inguinal ring. The
abdominal, or internal ring, lies about 1 cm. superior to the middle
of the inguinal ligament. The floor of the canal is formed by the
inguinal ligament; the ventral vail by the aponeurosis of the external

174 MYOLOGY

oblique and the muscle fibers of the internal oblique; the dorsal wall
consists of the transversalis fascia and falx aponeurotica inguinalis
(conjoined tendon). At the abdominal ring is the infundibuliform,
or internal spermatic fascia. In the canal lies the spermatic cord
and it is invested by the infundibuliform, cremasteric and inter-
columnar fascia?.

The triangular area between the inguinal ligament, inferiorly,
the rectus abdominis, medially, and the inferior epigastic artery,
laterally is called Hesselback's triangle. A hernia at this point is
called a directing ing. hernia, whereas when the intestine traverses
the inguinal canal and appears at the subcutaneous ring then it
is an oblique ing. hernia.

Actions. — To compress the abdominal wall as in defecation, vomit-
ing, micturition, parturition and deep respiration. They also act as
flexors of the vertebral column and pelvis.

Nerve Supply. — Pyramidalis from the last thoracic nerve; the cre-
master from the genitofemoral (L. i, 2); the remainder are supplied
by the ventral rami of the last six thoracic nerves.

The m. quadratus lumborum arises from the dorsal portion of the
iliac crest from the transverse processes of the lower lumbar verte-
bras and from the iliolumbar ligament; it is inserted into the inferior
margin of the last ribs and the transverse processes of the upper
lumbar vertebra;.

Ad ion. — Assists in inspiration and flexion and extension of the
vertebral column.

Nerve Supply. — Branches from the ventral rami of the first three
lumbar nerves.

FASCIA AND MUSCLES OF THE PERINEUM AND PELVIS

The superficial fascia extends into the scrotum to form there the
dartos fascia and the scrotal septum, in the male, while in the female it
assists in forming the mons veneris and labia majora, containing con-
siderable fat in the latter places. It also passes over the penis and
connects with the superficial fascia of the thigh, buttocks and abdom-
inal wall. In the dorsal part of the perineum there is a considerable
space between the rectum and ischium on each side and this consti-
tutes the ischiorectal fossa which is filled with a mass of fat contained
in the superficial fascia here. Ventrally, the superficial fascia com-
prises two layers as in the groin. The superficial layer is continuous
with that of abdomen and thigh. The deeper layer is attached to the
pubic arch, the fascia of the urinogenital diaphragm and to the root
of the penis and the scrotal septum. The attachment of this layer
prevents the urine that extravasates, when the perineal portion of
the urethra is ruptured, from entering the thigh and the ischiorectal
fossa.

THE MUSCLES OF THE PERINEUM 1 75

The deep fascia is thin and tends to invest the muscles. In the
midline of the perineum about i cm. ventral to the anal canal, there is
a fibrous area called the central tendinous point of the perineum and
four muscles are here attached.

The m. sphincter ani externus is a flattened, spindle-shaped muscle
around the anus and anal canal connected ventrally with other mus-
cles at the central tendinous point and dorsallv it is connected with
anococcygeal ligament.

Action. — Closes the anus voluntarily.

Nerve Supply. — By the third and fourth sacral nerves through the
pudendal and perineal nerves.

The m. corrugator cutis ani are radiating bundles of smooth mus-
cle tissues at the margin of the anal opening and superficial to the
external sphincter.

The m. transversus perinei superficialis is a variable muscle.
When present, it arises from the inferior ramus of the ischium and the
fascia of the urinogenital diaphragm: it is inserted into the central
point of the perineum.

Action. — They_/f.v the central tendinous point of the perineum.

Nerve Supply. — Deep perineal branch of the pudendal nerve (S.

3,4)-

The m. bulbocavernosus, or accelerator urlnas of the male, sur-
rounds the root of the penis, the bulb of the urethra and the corpus
spongiosum, in the male. It arises from the central point of the
perineum and median raphe and the fibers are inserted into the
fascia of the urinogenital diaphragm, the dorsal surface of the
corpus cavernosum and into the fascia of the dorsum of the penis.

The bulbocavernosus, or sphincter vaginae of the female arises
from the central point of the perineum and is inserted into the root of
the clitoris somewhat as in the male.

Ail ion. — Compresses the urethra in the emission of semen and urine
and assists in the erection of the penis in the male. In the female it
contracts the vaginal orifice and compresses the bulb of the vestibule.

Nerve Supply. — Deep branch of the perineal nerve (S. 3, 4).

The m. ischiocavernosus, or erector penis, invests the crus penis
of the male. It arises from the tuberosity of the ischium and is
inserted to the fascia of the crus penis and to the corpus cavernosum
of the penis.

The m. ischiocavernosus, or erector clitoridis, of the female is
smaller and similar in attachments.

Action. — Erection of penis or clitoris.

Nerve Supply. — Deep branch of the perineal nerve (S. 3, 4).

The urinogenital diaphragm comprises several muscles and two
layers of fascia.

176

The m. sphincter urethras membranaceae arises from the inferior
pubic ramus and is inserted into the median raphe partly ventral and
partly dorsal to the urethra.

The m. transversus perinei profundus arises from the inferior
ramus of the ischium and is inserted into the median raphe.

The m. sphincter urethras in the female is smaller and some of the
fibers are inserted into the side of the vagina with the transversus
perinei profunda.

Action. — Slight compression of the urethra and slight constriction
of the vagina.

/ coccyx

occygeal
ligament

scrotum
corpus cavernosum of urethra ^corpora cavernosa of pen*

Fig. 137. — Superficial muscles of the male perineum. (Sobottu and McMur

The fascial portion constitutes the fascia urinogenitalis diaphrag-
matis inferior et superior. The inferior fascia, or superficial layer of
the triangular ligament, tills in the pubic arch and is about 3.5 cm. in
height. Between its apex and the subpubic ligament passes the
dorsal vein of the penis. Laterally the fascia is attached to the rami
of ischium and pubis. This fascial layer is perforated by the ure-
thra, ducts of Cowper's glands and various arteries, veins and nerves.
In the female this fascia is not as strong and it is pierced by the
vagina. The deep layer, or fascia diaphragmatis urinogenitalis
superior is a portion of the pelvic fascia and is perforated by the
urethra. Between its two layers are found the dorsal vein of the

THE MUSCLES OF THE SUPERIOR EXTREMITY 177

penis, the membranous part of the urethra, the bulbocavernosus
muscle, the glands of Cowper and their ducts and arteries, veins and
nerves in the male. In the female the dorsal nerve and vessels of the
clitoris, a part of the urethra, the bulbocavernosus muscle, the glands
of Bartholin, the vestibular bulbs and arteries, veins and nerves.

The pelvic fascia (fascia pelvina) forms a lining for the pelvic
cavity and an investment for the muscles here. It is connected,
superiorly, with the fascia of the abdominal cavity while inferiorly,
it is attached to the bony and ligamentous boundary of the inferior
pelvic outlet. Different portions have been given special names ; that
portion in relation with the pyriformis muscle is the pyriformis fascia
while the obturator fascia is in relation with the m. obturator internus.
The fascia diaphragmatis urinogenitalis superior has already been
discussed, and with the various muscles previously discussed con-
stitutes the ventral portion of the pelvic floor. The dorsal part of the
floor consists of the mm. levatores ani and the anal fascia, the perineal
body and the anococcygeal body. The white line, or tendinous arch,
is a taut band of fascia that extends from the dorsal surface of the
symphysis pubis to the ischial spine. The pelvic fascia also forms
the true ligaments of the bladder and the sheath of the prostate
gland.

The m. levator ani arises from the dorsal surface of the body of the
pubis, the tendinous arch and the spine of the ischium. It is inserted
into central tendon of the perineum into the external sphincter, to
the anococcygeal ligament and to the sides of the lower coccygeal
segments.

Actions. — Supports and raises the pelvic floor; assists in defecation;
elevates the prostate gland, or contracts the vagina; assists in child-
birth.

Nerve Supply. — Directly by the third and fourth sacral nerves and
by branches from the perineal nerve.

The m. coccygeus arises from the spine of the ischium and the
sacrospinous ligament. It is inserted into the lateral aspect of the
inferior portion of the sacrum and the superior part of the coccyx.

Action. — Mainly to assist the levator ani in supporting the pelvic
floor.

Nerve Supply. — By the third and fourth sacral nerves.

THE SUPERIOR EXTREMITY OR PECTORAL APPENDAGE

Fascia and Muscles of the Pectoral Region. — The superficial fascia
is thin and contains a variable quantity of fat and the mammary
glands.

The deep fascia invests the pectoral muscles and connects with the
abdominal fascia. Medially, it is attached to the sternum, superiorly,

178 MYOLOGY

to the clavicle and laterally, forms the axillary fascia. This fascia
forms the costocoracoid membrane and ligament. The costocoracoid
membrane is a layer of the deep fascia extending from the superior
margin of the m. pectoralis minor to the clavicle. This layer, before
it reaches the clavicle, splits to envelop the m. subclavius and
then it is attached to the inferior surface of the clavicle. Medially,

Deltoideus
Clavicular portion ofpecmaj

Sternocostal
portion of pec mat

Cremaster
Reflected inguinal lig

Superior pillar Inferior pillar.

Fig. 138. — Superficial and second layers of the abdominal and pectoral muscles seen
from in front. On the right side the pectoralis major and the obliquus abdominis externus
have been removed. (Sobotta and McMurrich.)

this membrane is attached to the first costal cartilage and laterally
to the coracoid process and as this part of the membrane is quite
well developed it is called the costocoracoid ligament. The membrane
is pierced by the cephalic vein, the branches of the lateral ventral
thoracic nerve and thoracoacromial artery and vein.

The m. pectoralis major is large and fan-shaped, arises from the
sternal half of the ventral margin of the clavicle, from the ventral

THE MUSCLES OF THE SHOULDER REGION 1 79

surface of the sternum and the first six costal cartilages and, a small
part, from the aponeurosis of the external oblique muscle. It is
inserted as a rather broad thick tendon into the lateral margin of
the intertubercular sulcus, or bicipital groove. The clavicular part
of the muscle forms the inferior part of the tendon while the costo-
sternal portion forms the superior part.

Action. — Assists in drawing the arm to the side of the thorax; adduc-
tion and medial, or inward rotation while bringing the arm across
the ventral part of the thorax.

Nerve Supply. — Lateral ventral thoracic nerve, from the lateral
cord of the brachial plexus (C. 5, 6, 7) and the medial ventral thoracic
nerve from the medial cord of the brachial plexus (C. 8, T. 1).

The m. pectoralis minor, small and triangular, arises from the
ventral surfaces of the chondral extremities of the third, fourth and
fifth ribs and the third and fourth intercostal fasciae; it is inserted
into the margin of the coracoid process near the origin of the mm.
biceps and coracobrachialis.

Action. — Depresses and draws the shoulder forward.

Nerve Supply. — Same as pectoralis major.

The m. subclavius arises from the superior surface of the first
costal cartilage and sternal end of the first rib and is inserted into
the subclavian groove on the inferior surface of the clavicle.

Action. — Depresses the clavicle and shoulder and assists in inspira-
tion by fixing the first rib.

Nerve Supply. — Branch from the brachial plexus (C. 5, 6).

The m. serrarus anterior, or serratus magnus, arises by eight or
nine digitations from the first eight ribs and is inserted into the verte-
bral margin and ventral surfaces of the superior and inferior angles
of the scapula.

Action. — Draws the scapula forward, assists in rotating the scapula
and is an important muscle in inspiration.

Nerve Supply. — The long thoracic nerve (from the ventral rami
of the fifth, sixth and seventh cervical nerves).

MUSCLES OF THE SHOULDER REGION

The m. deltoideus, a large multipennate muscle, arises from the
lateral third of the ventral margin of the clavicle, from the lateral
margin of the acromion, from the inferior margin of the spine of the
scapula and from the fascia covering the infraspinatus muscle. It
is inserted into the deltoid tubercle of the shaft of the humerus.

Action. — Abducts the humerus to a right angle with the glenoid
fossa of the scapula. Assists in drawing the arm forward (ventrally)
and backward (dorsally).

Nerve Supply. — Axillary, or circumflex nerve (C. 5, 6).

i8o

The m. supraspinatus arises from the bulk of the supraspinous
fossa and the fascia covering the muscle and is inserted into the
proximal facet of the greater tubercle of the humerus and into the
capsular ligament.

Action. — Assists the deltoid in abducting the arm.

Nerve Supply. — Suprascapular nerve (C. 5, 6).

The m. infraspinatus arises from the bulk of the infraspinous
fossa and the fascia covering it and is inserted into the middle facet
of the greater tubercle of the humerus.

Trapezius

raspinatus
'fascia

Teres major

■issimus X
head of triceps brachii

brachii

Outer head of triceps brachii
Inner head of triceps brachii

picondy/e

3 Antibrachial
1 fascia

Fig. i3g. — The deltoid and muscles of the upper arm see
Mc Munich.)

from the side. 'Sobotta i

Action. — Assists in abducting the arm and when raised assists in
drawing the arm dorsally.

Nerve Supply. — Suprascapular nerve (C. 5, 6).

The m. teres minor arises from the dorsal surface of the axillary
margin of the scapula (proximal two-thirds) and the intermuscular
septa and is inserted into the distal facet of the greater tubercle of
the humerus.

Action. — Rotates the humerus laterally.

THE FASCIA AND MUSCLES OF THE ASM 151

Nerve Supply. — Axillary, or circumflex nerve (C. 5, 6).

The m. teres major arises from the inferior third of the dorsal
aspect of the axillary margin of the scapula and from the intermus-
cular septa and is inserted into the medial margin of the intertuber-
cular sulcus (bicipital groove) of the humerus.

With the margins of the teres minor and subscapularis muscles
and the neck of the humerus, the teres major forms a triangular
space. The long head of the triceps muscle divides this into a
medial, quadrilateral space, transmitting the axillary nerve and the
posterior circumflex artery and a lateral, triangular sp^c, transmit-
ting the circumflex scapula artery.

Action. — Rotates the humerus medially.

Nerve Supply. — Lower scapular nerve (C. 5, 6).

Levator scapulae X

/JV R homboideus minor X

Infraspinatus
Rhomboideus majo

Deltoideus
Subdeltoid bursa
Pect oralis maj>

Fig. 140. — The muscles of the dorsal surface of the left scapula and the neighboring
portion of the extensor surface of the upper arm. The deltoid has been removed with the
exception of its origin and insertion; portions of the dorsal muscles inserting into the verte-
bral border of the scapula and also of the latissimus dorsi and pectoralis major have been
retained. (Sobottu an J McMurrich.)

The m. subscapularis arises from the entire subscapular fossa and
is inserted into the lesser tubercle of the humerus and into the cap-
sular ligament and even into the surgical neck of the bone.

Action. — Medial rotator of the humerus and assists in drawing the
arm ventrally.

Nerve Supply. — Long and short subscapular nerves (both C. 5, 6).

FASCIA AND MUSCLES OF THE ARM

The superficial fascia is thin and presents a bursa over the
olecranon.

The deep fascia is continuous with that of the shoulder muscles

182

and the axilla and with that of the forearm. It sends in a medial
septum, that separates the brachialis muscle from the medial head
of the triceps, and a thin lateral septum, that separates the brachialis
and brachioradialis muscles from the triceps, behind. These septa
are only, in the distal half of the arm and are attached to the epicon-
dyles distally.

OmohuoideuB X

~ -Clavicle

Coracoid

process.

Subscapular,

Subclavivsx

Bursa of latissirrtus
Tendon of larissimus

pecrora/i's major
Deltoideus x

> head of biceps

-The muscles of the flexor surface of the upper arm, superficial layer. The deltoid
has been removed. (Sobotta and .1/. Murrich.)

The m. coracobrachialis arises in common with the short head of
the biceps muscle, from the tip of the coracoid process of the scapula
and is inserted about the middle of the medial margin of the humerus.

A ction. — A ssists the biceps in ra ising and drawing the arm medially.

Nerve Supply. — Musculocutaneous nerve (C. 7).

The m. biceps brachii arises from the tip of the coracoid process
(short head, or caput breve) and from the supraglenoid tuberosity
and glenoid ligament (long head, or caput longum). The latter tendon
passes through the shoulder joint and into the bicipital groove and
then forms a fleshy belly that lies beside the belly from the short

VENTRAL MUSCLES OF THE FOREARM AND HAND 1 83

head; these form a common tendon that is inserted into the dorsal
surface of the tubercle of the radius. The bicipital fascia (laccrtus
fibrosus) is a strong fascial band that arises from the tendon in front
of the elbow joint and passes medially to join the deep fascia of the
forearm.

Action. — Draws the humerus forward at the shoulder joint, flexes
the elbow joint and supinates the forearm.

Nerve Supply. — The musculocutaneous nerve (C. 5, 6).

The m. brachialis (anterior) arises from the distal two-thirds of
the ventral surface of the humerus and the intermuscular septa and
is inserted into the ventral ligament of the elbow joint and the coro-
noid process of the ulna.

Action. — Flexes the forearm at the elbow.

Nerve Supply. — Musculocutaneous nerve (C. 5, 6) and radial
nerve (C. 5, 6).

The m. triceps brachii, the only dorsal muscle of the arm, arises
by three heads. The long head (caput longum) arises from the infra-
glenoid tuberosity of the scapula; the lateral head arises from the
lateral margin (proximal one-third) and the intermuscular septa;
the medial head has the most extensive origin from the dorsal sur-
face of the shaft of the humerus and the intermuscular septa. The
common tendon is inserted- into the tip of the olecranon process of
the ulna and into the deep fascia of the forearm on each side of this.

Action. — Mainly an extensor of the forearm; the long head may
assist in adducting the humerus at the shoulder-joint.

Nerve Supply. — Branches from the radial nerve of the dorsal cord
of the brachial plexus (C. 6, 7, 8).

FASCUE AND VENTRAL MUSCLES OF THE FOREARM AND HAND

The superficial fascia is as usual containing fat and the superficial
vessels and nerves. It contains one muscle in the palm.

The m. palmaris brevis, in the medial side of the palm, arises
from the medial margin of the central palmar aponeurosis and is
inserted into the skin of the medial border of the hand. It wrinkles
the skin here, when acting, and deepens the hollow of the hand.

The deep fascia is quite strong at the elbow region due 'to reinforce-
ment from the tendon of the biceps and triceps muscles. It sends
in intermuscular septa one of which is attached to the dorsal margin
of the ulna. At the wrist it is strengthened by transverse bands
that form important ligaments. The transverse carpal, or anterior
annular ligament (lig. carpi transvcrsum). is a broad band stretching
between the navicular and greater multangular bones, laterally, and
the pisiform and hamate bones, medially. This holds the flexor
tendons and median nerve in place. The space between the bones

184 MYOLOGY

and the ligament is divided into two compartments, the larger for
the flexor tendons of the digits and the median nerve, and the smaller
for the flexor carpi radialis ' tendon. Three synovial sheaths lie
beneath this ligament.

The dorsal carpal, or posterior annular ligament (lig. carpi dor sale),
is another broad ligamentous band upon the dorsal surface of the
wrist joint. Beneath it are six compartments each lined with a syn-
ovial membrane. These are, lateromedially, as follows: (a) mm. ab-
ductor pollicis longus and extensor pollicis brevis; (b) mm. extensores
carpi radialis longus and brevis; (c) m. extensor pollicis longus; (d)
mm. extensores digitorum communis and indicis proprius; (e) m.
extensor digiti quinti proprius; (/) m. extensor carpi ulnaris.

In the palm the deep fascia constitutes the palmar aponeurosis.
The medial part of this is the largest and most extensive as well as
the strongest portion. It is triangular in shape with its apex blending
with lig. carpi transversum; its base is opposite the bases of the four
medial digits and here a slip is given off for each finger; each slip
divides into two slips that are attached to the sides of the metacar-
pophalangeal joints and the first phalanx of each finger. The digital
sheaths are continuations of the palmar aponeurosis upon the ventral
surface of each finger. Each sheath is attached to the sides of the
phalanges and serves to keep the flexor tendons in place. Each is
lined with a synovial membrane. The synovial space of the little finger
is continuous with the large synovial sac of the palm that also extends
into the forearm under the transverse carpal ligament. The synovial
spaces of the outer three fingers are independent of one another.
The synovial space, or sheath of the thumb extends through the
palm and under the transverse carpal ligament into the forearm.

SUPERFICIAL MUSCLES OF THE FOREARM

The m. pronator teres arises from the medial epicondylic ridge and
its intermuscular septum, from the medial epicondyle of the humerus
and the fascia over it and from intermuscular septa here; this con-
stitutes the caput humeralc. The caput ulnare, or deep head arises from
the medial surface of the coronoid process of the ulna. The muscle
is inserted into the middle of the lateral surface of the shaft of the
radius.

. 1 1 lion. — Flexes the elbow joint and pronates the forearm.

Nerve Supply. — Median nerve (C. 6).

The m. flexor carpi radialis arises from the medial condyle through
the common tendon, from the intermuscular septa and fascia over it
and is inserted into the proximal extremities of the second and third
metacarpal bones.

Action. — Flexes the elbow and wrist joints and assists in pronating
the forearm.

THE VENTRAL MUSCLES OF THE FOREARM

I85

Nerve Supply. — Median nerve (C. 6).

The m. palmaris longis arises from the common tendon of the
medial epicondyle, the fascia over it and the intermuscular septa and
is inserted into the transverse carpal ligament and the apex of the
palmar aponeurosis.

Action. — Assists inflexion of the elbow and wrist joints and makes
the palmar fascia tense.

Nerve Supply. — Median nerve (C. 6).

Brack /o radial is

Tendon of biceps

Fig. 142. Fig. 143.

Fig. 142. — The superficial layer of the muscles of the flexor surface of the forearm to-
gether with the brachioradialis. seen from in front. 'Sobotto and M, Murrich.)

Fig. 143. — The superficial layer of the muscles of the flexor surface of the forearm after
removal of the palmaris longus and the flexor carpi radialis. seen from in front and slightly
from the radial side. The brachioradialis is drawn outward to show e supinator and the
insertion of the tendon of the biceps. (Sobotta and McMurrich.)

The m. flexor carpi ulnaris arises from the common tendon of the
medial epicondyle of the humerus, the fascia over it and the inter-
muscular septa and from the medial margin of the olecranon and the
first two-thirds of the dorsal margin of the ulna. The muscle is in-
serted into the pisiform and hamate bones and the proximal extremity
of the fifth metacarpal bone.

l86 MYOLOGY

Action. — Flexes and addticts the wrist and assists in flexing the
elbow joint.

Nerve Supply. — Ulnar nerve (C. 8, Th. i).

The m. flexor digitorum sublimis has three heads. The caput
humerale arises from the common tendon, the ulnar collateral liga-
ment and from the intermuscular septa. The caput radiale arises
from the first two-thirds of the ventral surface of the radius. The
caput ulnare arises from the medial margin of the coronoid process
of the ulna. All join to form a common belly that divides in the
distal third of the forearm and continues as four tendons which at the
wrist are arranged in pairs, middle and ring fingers (superficial) and
index and little fingers (deep). Here these tendons are contained in
a common synovial sheath with the tendons of the profundus muscle.
In the palm the four tendons separate and over the base of the first
phalanx of each finger the tendons split to give passage to the cor-
responding tendon of the flexor digitorum profundus muscle. Dor-
sal to the latter tendon these slips partially reunite to be inserted
into the sides of the second phalanges of the fingers. The vincida
longa and brevia. are delicate accessory portions of each tendon.

Action. — Flexes the elbow, wrist, metacarpophalangeal and first
interphalangeal joints.

Nerve Supply. — Median nerve (C. 6).

DEEP LAYER

The m. flexor digitorum profundus arises from the ventral and
medial surfaces of the ulna and olecranon (first two-thirds) and
from the middle third of the medial half of the interosseous mem-
brane and the deep fascia. Its broad tendon passes beneath the
transverse carpal ligament and in the palm divides into four tendons
for the four fingers. Each tendon passes through the split in the
corresponding tendon of the m. flexor digitorum sublimis and
is inserted into the ventral surface of the base of the distal phalanx.
Each tendon also gives off vinculo longa and brevia.

The mm. lumbricales are four small muscles connected with the
tendons of the preceding muscle in the palm. Each of the two lateral
muscles arises by a single head from the radial side of the tendon for
the index and middle fingers and is inserted into the side of the cap-
sule of the metacarpophalangeal articulation and into the side of the
corresponding extensor tendon dorsally. Each of the two medial
muscles arises by two heads from the adjacent sides of the second,
third and fourth tendons and is inserted in the same manner.

Action. — The flexor digitorum profundus flexes the wrist and the
fingers at all of their joints. The lumbricales flex the fingers at the
metacarpophalangeal joints and assist in extending the fingers at their
interphalangeal joints.

THE VENTRAL MUSCLES OF THE FOREARM

I87

Nerve Supply. — Flexor digitorum profundus: Volar interosseous
branch of the median nerve (C. 7, 8, Th. 1) and the ulnar nerve
(C. 8, Th. 1). The two lateral lumbricales: Median nerve (C. 6, 7).
The two medial lumbricales: Ulnar nerve (C. 8, Th. 1).

The m. flexor pollicis longus arises from the middle third of the ven-
tral surface of the shaft of the radius and from the medial margin of
the coronoid process of the ulna. It is inserted by means of a long
tendon that passes beneath the carpal ligament, in its own synovial
sheath, to the base of the distal phalanx of the thumb.

Bicipito- radial bursa

Supinator

-r- Radial head of flexor

pollicis lonous

Tendon of extensor
Tendon of flexor _LIIIK|i. Ill carpi radial, lonous
carpi ulnaris J > W.V ^1,', Tondon 0f flexor

idialis
i
Tendon of patmaris lonous

Fig. 144. — The deep layer of the muscles of the flexor surface of the forearm after removal of
the superficial layer, seen from in front. (Sobotta and McMurrich.)

Action. — Flexes the wrist and the thumb.

Nerve Supply. — Volar interosseous branch of the median nerve
(C. 7, 8, Th. 1.).

The m. pronator quadratus arises from the ventral surface and me-
dial margin of the distal quarter of the ulna and passing transversely
across the forearm is inserted into the distal quarter of the ventral
surface of the radius.

Action. — Assists in pronating the forearm.

Nerve Supply.- — Volar interosseous branch of the median nerve
(C. 7, 8, Th. 1).

SHORT MUSCLES OF THE THUMB

The m. abductor pollicis brevis arises from the tubercle of the
navicular and the greater multangular bones and from the transverse
carpal ligament. It is inserted into the first phalanx of the thumb
(radial side) and into the capsule of the metacarpophalangeal joint.

Action. — Abducts the thumb.

Xcrve Supply. — Median nerve (C. 6, 7).

The m. opponens pollicis arises from the transverse carpal ligament
and the ridge of the greater multangular bone. It is inserted into the
ventral surface and lateral margin of the first metacarpal bone.

An+ibrachiat
fascia

Tendon of palrnaris hnous

r aponeurosis and the palma
■ shown covered by the fasci:

brevis. The thenar and hypothenar
(Sobotlo. and McMurrich.)

Action. — Draws the metacarpal bone over the palm.

Nerve Supply. — Median nerve (C. 6, 7).

The m. flexor pollicis brevis consists of two parts of which the
superficial portion arises chiefly from the transverse carpal ligament
and is inserted into the radial side of the base of the first phalanx of
the thumb. The deep portion, or first palmar interosseous muscle,
arises from the base of the first metacarpal bone (medial side). It
is inserted into the medial side of the base of the first phalanx of the
thumb.

Action. — Flexes the thumb and assists in opposing it to the fingers.

Nerve Supply. — Median nerve (C. 6, 7).

The m. adductor pollicis also consists of two parts. The oblique

THE MUSCLES OF THE LITTLE FINGER 189

head- arises from the ventral surface of the greater and lesser mult-
angular and the capitate bones and from the bases of the second,
third and fourth metacarpal bones and their ligaments. It is in-
serted into the medial side of the base of the first phalanx of the
thumb.

The transverse head arises from the median ridge of the ventral
aspect of the third metacarpal bone and the fascia covering the
adjacent interosseous muscles. It is inserted into the medial side of
the base of the first phalanx of the thumb.

Action. — Adducts the thumb and assists in opposing it to the
fingers.

Nerve Supply. — Deep branch of the ulnar nerve (C. 8, Th. i).

MUSCLES OF THE LITTLE FINGER

The m. abductor digiti quinti arises from the pisiform bone and the
tendon of the flexor carpi ulnaris muscle. It is inserted into the
medial side of the base of the first phalanx of the little finger.

Action. — Draws the little finger from the ring finger and flexes it
at the metacarpophalangeal joint.

Nerve Supply. — Deep branch of the ulnar nerve (C. 8, Th. i).

The m. opponens digiti quinti arises from the transverse carpal liga-
ment and the hamate bone. It is inserted into the medial margin
and medial half of the ventral surface of the fifth metacarpal bone.

. 1 1 lion. — Draws the metacarpal forward so as to deepen the
hollow of the hand.

Nerve Supply. — Deep branch of the ulnar nerve (C. 8, Th. i).

The m. flexor digiti quinti brevis arises from the transverse carpal
ligament and the hamate bone and is inserted into the medial side
of the first phalanx of the little finger.

Action. — Flexes the proximal phalanx of the little finger.

Nerve Supply. — Deep branch of the ulnar nerve (C. 8, Th. i).

There are two sets of interosseous muscles, palmar and dorsal.

The mm. interossei volares, or palmar interossei, are three in num-
ber. Each arises by one head: the first arises from the medial side
of the second metacarpal bone, the second and third from the lateral
sides of the fourth and fifth metacarpal bones. The first is inserted
into the extensor tendon, the capsule of the metacarpophalangeal
joint and the medial side of the first phalanx of the second finger.
The second and third are inserted into the lateral sides of the first
phalanges of the fourth and fifth fingers and their respective extensor
iendons and capsular ligaments.

The mm. interossei dorsales axe jour in number. Each arises by
a head from each of the two bones that bound its interosseous space.
The first is inserted into lateral side of the first phalanx of the index

190 MYOLOGY

finger and its extensor tendon. The second is inserted in the same
manner to the middle linger. The third is inserted into the medial
side of the same finger and the fourth into the medial side of the ring
finger.

Action. — The dorsal intcrossei abduct the fingers from a line through
the middle finger while the palmar muscles adduct the fingers to this
line. The interossei also assist the lumbricales to flex the first
phalanges at the metacarpophalangeal joint and extend the second

Tendon of fle/tor oto prof.

Annular fibres

<f<>3 '

•Flexor dqit.V
Ooponens di<f.V
Transverse carpal
ligarnenrlf
Abductor c/ifVX
Pisiform bone
Tendon of flexor
~<lrpi ulndr/iX

Tendon of- flexor
carpi nsdra/a

subhmh

Fig. 14-

aponeurosis,
(.Sobolta and McMurri

The tendo
■h.)

Fig. 146.

Fig. 146. — The palmar muscles after removal of the pain
sheath of the middle finger has been split lengthwi:

Fig. 147. — The deep layer of the palmar muscles. The transverse carpal ligament and
the abductores digiti V and pollicis brevis have been removed. The tendons of the long
flexors have been removed from the carpal canal and. after splitting the tendon-sheaths of
the fingers, have been partly removed and partly drawn aside. (Sobolta and McMurrich.)

and third phalanges through their attachment to the extensor
tendons.

Nerve Supply. — Deep branch of the ulnar nerve (C. 8, Th. 1).

DORSAL AND LATERAL MUSCLES OF THE FOREARM

The superficial muscles are seven in number.

The m. brachioradialis arises from the lateral epicondylic ridge
(proximal two-thirds) and from the intermuscular septum. It is
■inserted at the beginning of the groove upon the lateral side of the
distal extremity of the radius.

Action. — Flexes the elbow joint, assists the pronators and supina-
tors and is a semipronator and a semisupinator.

THE DORSAL MUSCLES OF THE FOREARM

I9I

Nerve Supply. — Branch from the radial nerve (C. 5, 6).

The m. extensor carpi radialis longus arises from the distal third
of the lateral epicondylic ridge, from the intermuscular septum and
from the common tendon of the lateral epicondyle. It is inserted
into the radial side dorsal surface of the base of the second meta-
carpal bone.

Action. — Extends the wrist and assists in flexing the elbow.

Fie

Fig. 148.
-The superficial layer of

1 carpi radial, brevis
Tendon of exrensori$ carpi radial, hnpi

Fig. 149.
nuscles of the extensor surface of the forearm

(Sobotla

148.-
and McMurrich.)

Fig. 140. — The deep layer of muscles of the extensor surface of the forearm. The super-
ficial layer of the extensors has been removed, the cavities of the dorsal carpal ligament have
been opened and the tendons of the superficial muscles removed. (Sobotla and McMurrich.)

Nerve Supply. — Radial nerve (C. 5, 6, 7, 8).

The m. extensor digitorum communis arises from the common
tendon, from the lateral epicondyle of the humerus, from the fascia
of the region and the intermuscular septa. Near the wrist it con-
tinues as four tendons that pass beneath the dorsal carpal ligament
with the tendon of the extensor indicis proprius. Upon the dorsum
of the palm the tendons separate and pass toward the dorsal surface

192 MYOLOGY

of each finger. Over the first phalanx of each finger the tendon
receives the tendons of the interossei and lumbricales muscles. At
the distal extremity of the first phalanx each tendon separates into
three portions, the median of which is inserted into the base of the
second phalanx. The lateral slips unite and are inserted into the
base of the third phalanx. Upon the dorsum of the palm the second
and third, and the third and fourth tendon are connected to each
other bv an oblique tendinous slip, which interferes with the indi-
vidual extension of these fingers.

Action. — Extends the elbow, wrist and fingers.

Nerve Supply. — Dorsal interosseous nerve (C. 5, 6, 7, 8).

The m. extensor carpi radialis brevis arises from the common ten-
don, the intermuscular septa and fascia and the radial collateral
ligament. It is inserted into the dorsal surface of the bases of the
second and third metacarpal bones.

Action. — Extends the wrist and assists in flexing the elbow.

Nerve Supply. — Deep branch of the radial nerve (C. 5, 6).

The m. extensor digiti quinti proprius arises from the common
tendon, the fascia over it and the intermuscular septa. It is in-
serted into the expansion of the tendon of the extensor digitorum
communis over the first phalanx of the little finger.

Action. — Extends, elbow, wrist and little finger.

Nerve Supply. — Dorsal interosseous nerve (C. 6, 7, 8).

The m. extensor carpi ulnaris arises from the common tendon,
the fascia over the muscle, the intermuscular septa and from the
middle half of the deep fascia attached to the dorsal margin of the
ulna. It is inserted into the medial surface of the base of the fifth
metacarpal bone.

Action. — Extends and adducts the wrist and assists in extension of
the elbow joint.

Nerve Supply. — Dorsal interosseous nerve (C. 5, 6, 7, 8).

The m. anconeus, a small triangular muscle, arises from the dorsal
surface of the lateral epicondyle of the humerus and the capsular
ligament and is inserted into the lateral surface of the olecranon and
the dorsal surface of the proximal part of the ulna to the oblique line.

Action. — Extends the elbow joint.

Nerve Supply. — Radial nerve (C. 7, 8).

The deep muscles are Jive in number.

The m. supinator (brevis) arises from the lateral epicondyle of
the humerus, the collateral and annular ligaments of the joint, the
fascia over it and from the surface of the ulna just distal to the radial
notch. It is inserted to the lateral and ventral surface of the radius
from the neck to the oblique line.

Action. — Main supinator of the forearm and extends the elbow.

Nerve Supply. — ^eep branch of the radial nerve (C. 7, 8).

THE DORSAL MUSCLES OF THE FOREARM

193

The in. abductor pollicis longus, or extensor ossi metacarpi pollicis,

arises from the proximal part of the lateral half of the dorsal surface
of the ulna, from the middle part of the dorsal surface of the radius
and from the intervening part of the interosseous membrane. It is
inserted into the lateral side of the base of the first metacarpal bone.

Action. — Abducts the metacarpal bone of the thumb, and assists
in abducting and extending the wrist.

Nerve Supply. — Dorsal interosseous nerve (C. 6, 7, 8).

The m. extensor pollicis longus arises from the middle part of the
dorsal surface of the ulna and the interosseous membrane and is
inserted into the dorsal surface of the second phalanx of the thumb.

Action. — Extends and abducts the thumb and wrist.

Tendon of extensor
pollicis tono'us

Tendon of extensor
carpi radiaiis brevis

Fig. 150. — Tendons and muscles (interossei dorsales) of the dorsum of the hand. The dor-
sal carpal ligament is retained, the rest of the dorsal fascia being removed. {Sobotta and
Mc Munich.)

Nerve Supply. — Dorsal interosseous nerve (C. 5, 6, 7, 8).

The m. extensor pollicis brevis arises from the distal part of the
dorsal surface of the radius and from the adjoining portion of the
interosseous membrane. It is inserted into the dorsal surface of the
base of the first phalanx of the thumb.

Action. — Extends and abducts the thumb and wrist.

Nerve Supply. — Dorsal interosseous nerve (C. 5, 6, 7, 8).

The m. extensor indicis proprius arises from the dorsal surface of
the ulna (just distal to the extensor pollicis longus) and from the
interosseous membrane. It is inserted into the index finger by join-
ing the tendon of the m. extensor communis digitorum.

Action. — Extends the index finger and the wrist.

Nerve Supply. — Dorsal interosseous nerve (C. 5, 6, 7, 8).

194 MYOLOGY

THE INFERIOR EXTREMITY, OR PELVIC APPENDAGE
FASCLE AND MUSCLES OF THE BUTTOCK AND THIGH

The superficial fascia of the buttock and thigh is continuous with
the fascia of the adjoining parts of the body. In the buttocks it
contains a large quantity of fat which gives these parts their full
appearance. In the inguinal region, or groin, the superficial fascia
consists of a superficial and a deep layer; the superficial layer contains
considerable fat and the superficial vessels and nerves. The deep
layer is attached to the medial half of the inguinal ligament, to the
pubic arch (medially) to the deep fascia of the thigh (laterally) and
below, it joins the superficial layer. By its attachment to the
inguinal ligament and pubic arch fluids of the perineum and
abdominal wall are prevented from passing into the thigh. Between
these two layers of superficial fascia are seen the superficial inguinal
lymph nodes, the great saphenous vein and its tributaries.

The deep fascia, or fascia lata, invests the muscles and vessels of
the thigh and buttock. Superiorly (proximally) it is attached to
the pubic symphysis and crest, the inguinal ligament, the iliac crest,
the sacrotuberous ligament, the ischium and the pubic arch ; inf eriorly
(distally) it is attached to the patella, the condyles of the tibia, the
head of the fibula, forms the collateral ligaments of the patella and
is continuous with the deep fascia of the leg. The ventral and lateral
portions of this fascia are thick and strong and in the distal part of
the thigh it sends in muscular septa. Near the pubic region the
fascia is pierced by the great saphenous vein and this area constitutes
the fossa ovalis, or saphenous opening. This is oval in shape and cov-
ered by the fascia cribrosa and superficial fascia. The lateral margin
of the fossa, margo falciformis, is sharp, while the medial margin is
shelf-like and is called the fascia pectinea. This is attached, supe-
riorly, to the iliopectineal line and capsule of the hip joint after pass-
ing dorsal to the femoral sheath and over the muscles here. The
distal margin of the fossa is called the inferior cornu. The proximal
margin is the superior cornu. The lateral portion of the fascia shows
a band-like thickening that is called the tractus iliotibialis, or ilio-
tibial band into which the m. tensor fascia? lata; and part of the m.
gluteus maximus are inserted. The distal portion of this band
strengthens the knee joint laterally. The lateral intermuscular sep-
tum extends medially from the fascia lata, separates the ventral and
dorsal muscles and is attached to the linea aspera and the lateral
epicondylic line. The medial intermuscular septum passes laterally
and is attached to the linea aspera and the medial epicondylic line
and forms the ventral wall, or roof of the adductor canal. Over
most of the buttock this fascia is thick.

The femoral sheath is a cone-shaped prolongation of the iliac

THE VENTRAL MUSCLES OF THE THIGH I95

(dorsaily) and transversalis fasciae (ventrally) into the thigh. It
contains the femoral vessels and is divided into three compartments:
the medial compartment, or femoral canal contains some fat, the inter-
mediate the femoral vein and the lateral one the femoral artery.
The abdominal opening of the femoral canal constitutes the femoral
ring. That portion of the inguinal ligament ventral to the ring is
called the superficial femoral arch, while the thickened part of the
femoral sheath under cover of the inguinal ligament is called the deep
femoral arch. The tissues that fill the ring constitute the femoral
septum. The femoral sheath is about 1V2 inches in length.

VENTRAL MUSCLES OF THE THIGH

The m. sartorius arises from the ventral superior spine of the ilium
and the notch below, passes to the medial side of the thigh and is
inserted into the superior extremity of the tibia just below the medial
condyle; it also is attached to the capsular ligament and the fascia
lata. It is a strap-like muscle and forms the lateral boundary of the
femoral triangle.

Action. — Flexes the knee and everts the thigh.

Nerve Supply. — The two intermediate cutaneous branches of the
femoral nerve (L. 2, 3).

The m. quadriceps femoris is composed of four muscles.

The m. rectus femoris arises by two heads, one from the ventral
inferior spine of the ilium and the other from the roughened area of
the acetabulum. The two heads join and ultimately form a tendon
that is inserted into the superior or proximal margin of the patella.

The m. vastus lateralis, or externus, has an extensive origin from
the capsule, the hip joint, tubercle of the femur, from the margin of
the great trochanter, from the gluteal tuberosity, part of the linea
aspera, from the fascia lata and the intermuscular septum. It is
inserted into the lateral margin of the patella and tendon of the rectus
femoris and into the capsular ligament of the knee joint.

The m. vastus medialis, or interims, arises from the spiral line, the
linea aspera, the part of the line leading from this to the medial con-
dyle, from the membranous roof of the adductor canal, from the in-
termuscular septum and from the tendon of the adductor magnus.
It is inserted into the medial margin of the patella and the rectus
femoris tendon and the capsular and lateral ligaments of the knee
joint.

The m. vastus intermedius, or crureus, arises from the ventral and
lateral surfaces (proximal two-thirds) of the femur, the intermuscular
septum and from the end of the linea aspera and line leading to the
lateral condyle. It is inserted into the deep surfaces of the preceding
three tendons.

196 MYOLOGY

The m. articularis genu, or subcrureus, arises from the distal por-
tion of the ventral surface of the femur and is inserted into the capsule
of the knee joint.

The real insertion of the quadriceps femoris is the tubercle of the
tibia by means of ligamentum patellae, the patella being a sessamoid
bone.

Action. — The muscle as a whole extends the leg. The rectus femoris
also flexes the hip joint. The articularis genu draws the capsule and
synovial sheaths out of the way during extension of the leg.

Patellar /ig. — 3
Tuberosity of tibia

Pes
anserinus

Fig. i si. Fig. 152.

Fig. 151, — The superficial layer of muscles of the ventral surface of the thigh. (Sobotta
and McMurrich.)

Fig. 152. — The muscles of the ventral surface of the thigh after removal of the sartorius.
The inguinal ligament has also been removed. (Sobotta and McMurrich.)

Nerve Supply. — Branches of the femoral nerve supply each indi-
vidual division (L. 3, 4).

The m. iliopsoas consists of three parts.

The m. psoas major arises from the last thoracic and the first four
lumbar intervertebral discs and the margins of the adjacent verte-
brae, from tendinous arches over the bodies of the first four lumbar

THE MEDIAL MUSCLES OF THE THIGH 197

vertebrae and from the transverse processes of all of the lumbar ver-
tebras. A spindle-shaped muscle is formed the tendon of which is
inserted into the apex of the lesser trochanter of the femur.

The m. psoas minor is often absent but when present it arises from
the last thoracic intervertebral discs and the margins of the adjacent
vertebras and is inserted into the iliopectineal line.

The m. iliacus is a fan-shaped muscle that arises from the margin
of the iliac fossa, the ala of the sacrum and the neighboring pelvic
ligaments and from the capsule of the hip joint. It is inserted into
the lateral portion of the psoas tendon, the lesser trochanter and the
neighboring part of the shaft of the femur and into the capsule of the
hip joint (m. iliocapsularis).

Actions. — The psoas muscles flexes the vertebral column ventrally
and laterally. The iliopsoas flexes the thigh upon the pelvis, or vice
versa.

Nerve Supply. — Psoas minor, first and second lumbar nerves; psoas
major, second and third lumbar nerves; iliacus, femoral nerve (L.

2, 3, 4)-

The m. pectineus arises from the iliopectineal line and bony surface
adjacent, from the lig. lacunare (Gimbernat's) and the fascia over the
muscle. It is inserted into the proximal half of the line from the lesser
trochanter to the linea aspera.

Actions. — Adducts and assists in flexing the thigh.

Nerve Supply. — Femoral nerve (L. 2, 3) and obturator nerve (L.
2, 3)-

MEDIAL MUSCLES OF THE THIGH

The m. gracilis, long and slender, arises from the inferior half of the
pubic symphysis and the margin of the pubic arch. It is inserted
into the proximal and medial extremity of the shaft of the tibia dorsal
to the m. sartorius and ventral to the m. semitendinosis.

Actions. — Adducts, flexes and rotates the thigh medially.

Nerve Supply. — Obturator nerve (L. 2, 3).

The m. adductor longus arises from the ventral surface of the body
of the pubic bone between the crest and symphysis. It is inserted
into the medial lip of the linea aspera (medial two-fourths).

Actions. — Adducts and assists in flexing the thigh.

Nerve Supply. — Obturator nerve (L. 2, 3).

The m. adductor brevis arises from the body and first portion of the
inferior ramus of the pubic bone. It is inserted into the distal por-
tion of the line from the lesser trochanter to the linea aspera, dorsal to
the pectineus.

Actions. — Addicts and flexes the thigh.

Nerve Supply. — Obturator nerve (L. 2, 3, 4).

The m. adductor magnus is the largest of this group and arises

from the lateral margin and inferior surface of the tuberosity of the
ischium, from the margin of the inferior ramus of the ischium and the
ventral surface of the inferior ramus of the pubic bone. It is in-
serted into the femur superior to the linea aspera and continues all
along the linea aspera and the line leading to the medial epicondyle of
the femur and its adductor tubercle; is is also attached to the medial
intermuscular septum. Where the medial epicondylic line begins

Iliopsoas X

Pectineus X

Sacrotuberous ho.
Adductor lonous X
Gracilis X

Tendon of sartoriuS

Tendon of Gracilis ■

Tendon of semitendinosus

Pes anserinus
Fig. 153- — The deep layer of n
sartorius, rectus femoris, pectineus, add
{Sobotta and McMurrich.)

Semimembranosus

Internal intermuscular
septum

Sartorial bursa

Anserine bursa

Gastrocnemius

the medial surface of the thigh. The iliopsoas,
:tor longus, and gracilis have been removed.

there is a gap in the insertion for the transmission of the femoral
vessels.

Actions. — Adducts and extends the thigh.

Nerve Supply. — Medial portion, tibial, or internal popliteal nerve
(L. 4, 5, S. i). Lateral portion, obturator nerve (L. 3, 4).

The m. obturator externus arises from the inferior half of the mar-
gin of the obturator foramen (ischium and pubis) and from the ad-

THE MUSCLES OF THE BUTTOCK 199

jacent portion of the obturator membrane. It is inserted into the
fossa on the medial side of the greater trochanter.

Actions. — Rotates the thigh laterally and assists inflexion and ad-
duction of the thigh.

Nerve Supply. — Obturatur nerve (L. 3, 4).

The trigonum femorale, or Scarpa's triangle, is located on the ven-
tral surface of the proximal portion of the thigh. Its base is formed
by the inguinal ligament, its lateral boundary by the sartorius muscle
and the media! boundary by the adductor longus muscle. Its floor
is formed by the iliopsoas, pectineus, the adductor longus and some-
times a part of the adductor brevis muscles. It contains the femoral
vessels and nerve.

The adductor, or Hunter's canal (canalis adductorius Hunteri), is in
the medial side of the middle third of the thigh and is bounded ven-
trally, or superficially by the sartorius muscle and fascia between the
vastus medialis and the adductor muscles; dorsally and medially by
the vastus medialis. It contains the femoral artery and vein and the
saphenous nerve.

MUSCLES OF THE BUTTOCK

The m. gluteus maximus is a large quadrilateral muscle composed
of very coarse fibers. It arises from the iliac bone above the dorsal
gluteal line, from the dorsal surfaces of the sacrum and coccyx and
the sacrotuberous ligament and from the tendon of the sacrospinalis
muscle. It is inserted into the gluteal tuberosity of the femur but
mainly into the fascia lata.

Actions. — Extends the thigh and assists in adduction and lateral ro-
tation (inferior fibers).

Nerve Supply. — Inferior gluteal nerve from the sacral plexus (L.
5, S. 1, 2).

The m. tensor fasciae latas arises from iliac crest near the ventral
superior spine and the fascia covering it and is inserted into the fascia
lata at the level of the greater trochanter.

Actions. — Assists in abduction and rotation of the thigh and in sup-
porting the knee joint when in extension.

Nerve Supply. — Superior gluteal nerve of the sacral plexus (L.
4, 5. S. 1).

The m. gluteus medius arises from the ilium between the dorsal
and ventral gluteal lines and the iliac crest and the fascia over it.
It is inserted into the dorsosuperior portion of the greater trochanter.

Actions. — Abducts and rotates the thigh medially.

Nerve Supply. — Superior gluteal nerve from the sacral plexus
(L. 4, 5, S. 1).

The m. gluteus minimus arises from the ilium between the ventral
and inferior gluteal lines. It is inserted into the ventral surface of
the greater trochanter.

Actions. — Abducts the thigh. The ventral fibers produce medial
rotation and the dorsal fibers lateral rotation.

Nerve Supply. — The superior gluteal nerve from the sacral plexus.

The m. pyriformis arises from the ventral surface of the roots of
the vertebral arches of the second, third and fourth sacral segments
and from the grooves here, from the superior margin of the sacro-
sciatic notch and ligament. It is inserted into the depression on the
medial surface of the greater trochanter of the femur.

Actions. — Abducts and rotates the thigh laterally.

Ghtaeus medius
(Gluteal fascia)

Sacrospinous Piriformis

Glutaeofemoral

lliotibial band

Fig. 154-

Fig. 154- — Superficial layer of the dorsal muscles of the hip.
ficial layer of the fascia lata which covers the tensor fasciae
X. position of greater trochanter. (Sobotta and McMurrich.)

Fig. 155. — Middle layer of the dorsal muscles of the thigh,
been divided and reflected. (Sobotta and McMurrich.)

Nerve Supply. — Branches from the ventral rami of the first and
second sacral nerves.

The m. obturator internus arises from the margin of the obturator
foramen (pelvic side), form the hip bone superior and dorsal to the
foramen, from the obturator membrane and the fascia over the mus-
cle. It is inserted into a small facet upon the medial surface of the
greater trochanter.

The m. gemelus superior arises from the lateral surface of the
ischial spine and is inserted into the superior margin of the tendon
of the obturator internus muscle.

The m. gemellus inferior arises from the superior aspect of the

THE DORSAL MUSCLES OF THE THIGH 201

ischial tuberosity and is inserted into the inferior margin of the tendon
of the obturator internus muscle.

Actions. — Abduct and rotate the thigh laterally.

Nerve Supply. — Obturator internus and superior gemellus, special
branch of the sacral plexus (S. i, 2, 3). The inferior gemellus, a
branch from the nerve to the quadratus femoris muscle from the
sacral plexus (L. 4, 5, S. 1).

The m. quadratus femoris arises from lateral margin of the ischial
tuberosity and is inserted into the quadrate line and tubercle of the
dorsal aspect of the femur.

Actions. — Add nets and rotates the thigh laterally.
Nero Supply. — Special nerve from the sacral plexus (L. 4, 5, S. 1).

MUSCLES (HAMSTRING) ON THE DORSAL PART OF THE THIGH

The m. biceps femoris has two heads of which the long one arises
from inferomedial facet of the ischial tuberosity in conjunction with
the semitendinosis. The short head arises from the entire lateral lip
of the linea aspera and the bulk of the lateral epicondylic line and
from the lateral intermuscular septum. The fibers of the short
head join the tendon of the long head and this tendon is inserted into
the head of the fibula and the lateral condyle of the tibia.

Actions. — Flexes the leg and rotates it laterally when semiflexed
and when acting from the fibula assists in extending the pelvis upon
the thigh (raises it from a stooping position).

Nerve Supply. — Sciatic nerve through the tibial division (L. 5,
S. 1, 2).

The m. semitendinosis arises in conjunction with the- long head
of the biceps from the tuberosity of the ischium (medial facet). It
is inserted into the medial surface of the proximal extremity of the
tibia dorsal to the sartorius and below the gracilis; it is also attached
to the deep fascia of the leg.

Actions. — Flexes and rotates the leg medially and extends the pelvis.

Nerve Supply. — Tibial nerve (L. 5, S. 1. 2).

The m. semimembranosus arises from the lateral facet of the
tuberosity of the ischium and is inserted into the groove upon the
medial side of the medial condyle of the tibia and by extensions to
the tibial collateral ligament, the popliteal fascia and the dorsal sur-
face of the lateral condyle of the femur (oblique popliteal ligament).

Actions. — Flexes and rotates the leg medially and assists in exten-
sion of the pelvis.

Nerve Supply. — Tibial nerve (L. 5, S. 1, 2).

THE FASCLE AND MUSCLES OF THE LEG AND FOOT

The superficial fascia is the same as elsewhere, in the leg, but in
the foot pads of fat are placed under the heel and the balls of the toes.

The deep fascia is continuous with that of the thigh and around
the knee joint it is especially well developed. Here it forms the
collateral patellar ligaments and the (dorsal) popliteal fascia which is
reinforced by the expansions of the various neighboring tendons.
In the leg two intermuscular septa are found laterally and these en-
close the peronei muscles separating them from the extensor, ven-
trally, and the flexors, dorsally. At the ankle the deep fascia is also
strengthened forming the annular ligaments.

Glutaeus maximus

Gemellus super.

Sacrotuberous
Sacrospinal
Obturator inte,
Bursa of- obturator int.

Glutaeus mediuS

Glutaeus minimus
Tendon of
bturator internuS X

Middle oluteal

bursa
Glutaeus medius a

Gemellus infei
Quadratic fem
'Adductor min

Glutaeu
Adductor mao'nus
Kastus lateralis

Popliteal fossa

Tendon of bleep*
Gastrocnemius

Fig. 156. — The deep layer of the dorsal hip muscles and the superficial layer of the
flegors of the thigh region. The gluteus maximus) and mediusand the obturator internus
have been removed. (.Sobotta and McMurrich.)

The ligamenhim transversum cruris, or ventral annular ligament is
broad and extends between the two malleoli. It holds the tendons
of the tibialis anterior and extensor muscles of the toes in place.

The ligamentum crucial urn cruris, or lower band of the ventral annular
ligament is a fascial band upon the dorsum of the foot. A part of this
band holds the tendons of the tibialis anterior, the extensor longus
hallucis and the extensor digitorum longus and peroneus tertius

THE VENTRAL MUSCLES OF THE LEG 203

muscles in place. A synovial sheath surrounds each of these tendons
except the last which is included with the third tendon.

The superior peroneal retinaculum, or lateral annular ligament con-
nects the lateral malleolus and the calcaneus. This holds the pero-
neal tendons in place and has one synovial sheath.

The ligamentum laciniatum, or medial annular ligament connects
the medial malleolus with the tuberosity of the calcaneus. It gives
attachment to certain muscles, is pierced by the calcaneal vessels
and nerves and the dorsal tibial vessels and nerve; it also holds the
tendons of the tibialis posterior, flexor digitorum longus and flexor
hallucis longus muscles in place. Each tendon has a separate syno-
vial sheath.

In the sole of the fool the deep fascia forms the plantar aponeurosis.
The central portion is the largest and strongest part. It is triangular
in shape and is attached dorsally, to the tuberosity of the calcaneus;
near the toes the base of the triangle gives off five slips, one for each
toe. Each slip joins the digital sheath and splits into two portions
each of which is attached to the opposite side of the first phalanx of
the same toe. This central aponeurosis is of assistance in maintaining
the arch of the foot. The deep fascia on each side of the central
part is thin and at the junction of each with the central portion an
intermuscular septum is sent into the depths separating the various
muscles and forming sheaths for others. The digital sheaths are
arranged like those of the hand.

MUSCLES OF THE VENTRAL PART OF THE LEG AND OF THE DORSUM
OF THE FOOT

The m. tibialis anterior arises from the lateral condyle of the tibia,
from the upper two-thirds of the lateral surface of the shaft, from
the interosseous membrane and intermuscular fascia. The long
tendon passes over the medial side of the dorsum of the foot and is
inserted on the medial side of the first cuneiform and first metatarsal
bones.

Actions.- — Flexes the foot dorsally and assists in inverting the foot.

Nerve Supply. — Deep peroneal nerve (L. 4, 5, S. 1).

The m. extensor digitorum longus arises from the lateral condyle
of the tibia, from the medial surface of the shaft of the fibula (ventral
part) and from the fascia and intermuscular septum. It is inserted
into the four lesser toes. Over the first phalanx of each toe each
tendon is joined by tendons from the lumbricales, interossei and the
extensor digitorum brevis. This conjoined tendon splits into three
portions, the central one of which is inserted into the distal phalanx
and the two side tendons into the middle phalanx.

Actions. — Flexes the foot dorsally and extends the four lesser toes.

204

Nerve Supply. — Deep peroneal nerve (L. 4, 5, S. 1).

The m. peroneus tertius arises with the preceding from the medial
surface of the shaft of the tibia and the intermuscular septum and is
inserted into the dorsal surface of the base of the fifth metatarsal
bone.

Actions. — Flexes the foot dorsally and raises the lateral margin of
the foot.

CapXulum of fibula - P

Tibialis anten

Perortaeus landus

Patellar Hi.
Pes anserinus

Tuberosity of tibia

Tendo
of peronaeus III

Tendon of ext
hall. lono.

Fig. 157. — The muscles of the ventral surface of the lower leg and of the dorsum of the foot.
The transverse crural ligament has been removed. (Sobolta and McMurrich.)

The m. extensor hallucis longus rises from the middle two-thirds
of the medial surface (ventral part) of the fibula and from the inter-
osseous membrane. The tendon passes over the dorsum of the foot
and is inserted into the base of the distal phalanx of the great toe.

Actions. — Extends the great toe and flexes the foot dorsally.

Nerve Supply. — Deep peroneal nerve.

The m. extensor digitorum brevis arises from the dorsal surface of
the calcaneus and from the lig. cruciatum cruris. Its four tendons
are inserted into the four inner toes. The innermost tendon is in-
serted into the base of the first phalanx of the great toe while the

THE DORSAL MUSCLES OF THE LEG 205

other three tendons join the long extensor tendons of the next three
toes.

Action. — Extends the four inner toes.

Nerve Supply. — Deep peroneal nerve.

LATERAL MUSCLES OF THE LEG

The m. peroneus longus arises from the head and upper two-thirds
of the lateral surface of the fibula and from the intermuscular septa.
It is inserted into the first cuneiform bone and the base of the fifth
metacarpal bone (lateral aspect). The tendon passes behind the lat-
eral malleolus, over the side of the calcaneus and through a groove
in the cuboid bone on its way to the sole of the foot.

Actions. — Everts the foot, extends the foot and strengthens the
arch.

Nerve Supply. — Superficial peroneal nerve (L. 4, 5, S. 1).

The m. peroneus brevis arises from the distal half of the lateral
surface of the fibula and intermuscular septum. It is inserted into
the tuberosity on the base of the fifth metatarsal bone.
■ Actions. — Extends and everts the foot.

Nerve Supply. — Superficial peroneal nerve.

DORSAL MUSCLES OF THE LEG

The superficial muscles are three in number the gastrocnemius,
the soleus, constituting the m. triceps suraz, and the plantaris.

The m. plantaris arises from the lateral epicondyle of the femur and
the adjacent part of the popliteal surface and is inserted into the tendo
calcaneus (Achillis) or the tuberosity of the calcaneus.

Ac/ions. — Assists in flexing the leg and extending the foot.

Nerve Supply. — Tibial nerve (L. 4, 5, S. 1).

The m. gastrocnemius arises by two heads. The medial head
arises from the politeal surface of the femur close to the medial
epicondyle and from the capsular ligament of the knee joint. The
lateral head arises from the dorsolateral portion of the lateral con-
dyle of the femur and the epicondylic line and from the capsular
ligament. Each head is inserted into a broad membrane that forms
the tendo calcanea (Achillis) which is inserted into the dorsal surface of
the calcaneus.

Actions. — Flexes the leg and extends the foot.

Nerve Supply. — Tibial nerve (S. 1, 2).

The m. soleus arises from the upper dorsal surface of the head and
shaft of the fibula, from the tendinous arch over the popliteal vessels
and tibial nerve and from the oblique line of the tibia. It is inserted
into the tendo calcanea, not far from the heel.

206

MYOLOGY

Actions. — Extends the foot.

Nerve Supply. — Tibial nerve by two branches; that to the super-
ficial surface is from the first and second sacral nerves; that for the
deep surface is from the fifth lumbar and first and second sacral
nerves.

The deep muscles are four in number.

158. Fig. 159. Fig. 160.

Fig. 158. — The superficial muscles of the calf of the leg. {Sobotla and McMurrich.)
Fig. 159. — The second layer of the calf muscles. The gastrocnemius has been removed.

(.Sobotla and McMurrich.)

Fig. 160. — The deep musculature of the calf, seen from behind and from the inner side.

The triceps sune has been removed. (Sobolta and McMurrich.)

The m. politeus arises from the lateral epicondyle of the femur and
is inserted into the dorsal surface of the tibial proximal to the oblique
line.

Actions. — Flexes and rotates the leg medially.

Nerve Supply. — Tibial nerve (L. 4, 5, S. 1).

The m. flexor digitorum longus arises from the medial part of the
dorsal surface of the tibia below the oblique line and from the in-
termuscular septa. It is inserted into the base of the last phalanx of

THE MUSCLES OF THE SOLE OF THE FOOT 207

the four outer toes. The tendons pass through the split tendons of
the flexor digitorum brevis. With this muscle the lumbricales and
the quadratus plantae, or accessorius muscles are associated.

Actions. — Flexes the four outer toes and extends the foot.

Nerve Supply. — Tibial nerve (L. 5, S. 1).

The m. flexor hallucis longus arises from the lower or distal half of
the dorsal surface of the fibula and from the fascia and intermuscular
septa. It is inserted into the base of the last phalanx of the great toe.

Actions. — Flexes the great toe, extends the foot and assists in
supporting the arch of the foot.

Nerve Supply. — Tibial nerve (L. 5, S. 1, 2).

The m. tibialis posterior arises from the lateral part of the dorsal
surface of the tibia, from the interosseous membrane, from the medial
surface of the fibula and from the intermuscular septa. The tendon
passes into the sole of the foot and has a very extensive insertion as
follows: into the plantar surfaces of the navicular, first and second
cuneiform bones; into the plantar surfaces of the second, third and
fourth metatarsal bones; the groove of the cuboid and the medial
margin of the sustentaculum tali of the calcaneus.

Actions. — Extends and inverts the foot.

Nerve Supply. — Tibial nerve (L. 5, S. 1).

THE MUSCLES OF THE SOLE OF THE FOOT

The plantar muscles are usually described as arranged in four
layers.

First Layer. — The m. abductor hallucis arises from the medial
surface of the tuberosity of the calcaneus, from the lig. laciniatum
(internalannularlig.), the plantar aponeurosis and intermuscular sep-
tum. It is inserted into the medial side of the first phalanx of the
great toe.

Actions. — Flexes and abducts the great toe.

Nerve Supply. — Medial plantar nerve (L. 4, 5, S. 1).

The m. flexor digitorum brevis arises from the ventral part of the
medial process of the tuberosity of the calcaneus and from the central
plantar aponeurosis and intermuscular septa. It is inserted by four
tendons into the sides of the second phalanges of the four lesser
toes. Each tendon splits to permit the corresponding tendon of the
m. flexor digitorum longus to pass through.

Actions. — Flexes the toes.

Nerve Supply. — Medial plantar nerve (L. 4, 5, S. 1).

The m. abductor digiti quinti arises from the tuberosity of the cal-
caneus, from the lateral part of the plantar aponeurosis and inter-
muscular septum. It is inserted into the lateral surface of the base
of the first phalanx of the little toe.

Actions. — Flexes and abducts the little toe.

208 MYOLOGY

Nerve Supply. — Lateral plantar nerve (S. i, 2).

Second Layer. — The mm. lumbricales are jour muscles associated
with the flexor digitorum longus tendons. The first arises from the
medial side of the tendon for the second toe and the others arise from
the adjacent side of all four tendons. Each muscle is inserted into
the extensor tendon and the base of the first phalanx of the four
outer toes, as in the hand.

Actions. — Flex the metatarsophalangeal joints and extend the
interphalangeal joints of the four outer toes.

Nerve Supply. — The first or medial lumbricale, medial plantar
nerve (L. 4, 5, S. 1); the other three, lateral plantar nerve (S. 1, 3).

Pig. 161. — The plantar aponeurosis
(Sobotta and McMvrrich.)

Fig. 162. — -The superficial layer
of the plantar muscles. The plantar
fascia has been largely removed from
the surface of the flexor digitorum
brevis. (Sobotta and McMurrkh.)

The m. quadratus plantae or accessorius, arises from the lateral
margin of the plantar ligament and the adjacent portion of the plan-
tar surface of the calcaneus; a medial head arises from the medial
margin of the long plantar ligament and from the medial surface of
the calcaneus. Its flattened tendon is inserted into the tendons of
the flexor digitorum longus (mainly for the second, third and fourth
toes) .

Actions. — Assists in flexing the toes and draws the long tendons
into the middle of the sole of the foot.

Nerve Supply. — Lateral plantar nerve (S. 1, 2).

The tendons of the mm. flexor hallucis longus and flexor digitorum
longus are included in this layer.

Third Layer. — The m. flexor hallucis brevis arises from the tendon

THE MUSCLES OF THE FOOT

209

of the tibialis posterior and the plantar surface of the cuboid bone.
It forms two tendons (between which the tendon of the m. flexor
hallucis longus passes) which are inserted into the medial and lateral
surfaces of the base of the first phalanx of the great toe, blending with
the other tendons inserted here.

Action. — Flexes the great toe at the metatarsophalangeal joint.

Nerve Supply. — Medial plantar nerve (L. 4, 5, S. 1).

The m. adductor hallucis arises by two heads. The oblique head
arises from the plantar surfaces of the second, third and fourth meta-

Vaoinol lip

Tendons of flexor
dio. lohg.

Adductor dig. 1/
Interczset
r/exor dig. V-

Abduclor did V
Fle*.or dig. bre\
Abductor iiallucis \

,. f. Abductor did V
tibialis post. Flexor d.fbre
Tendon of flexor Abductor M/uc,
hallucis Ion dus

of plantar mus-
is, the abductor

Tendon of abductor ha/locisc
Adductor hallucis
(oblique head)

Flexor ha/luc/s
bre/i's

Tendon off/exor
'torum londusX

Tendon of flexor
hallucis IbniJusX

Fie, H)j.— The middle laj
cles. The flexor digitorum b:
hallucis, and the abductor digiti quinti havt
been removed; the tendon-sheaths of the digit:
and of the peronasus longus have been opened
(Sobotta and Mc Munich.)

Fig. 164. — The deep layer of plantar muscles.
The tendons of the flexor digitorum longus, the
flexor hallucis longus, and the quadratus
plantse have been removed. (Sobotta and
McMurrich.)

tarsal bones and from the sheath of the m. peroneus longus and is
inserted into the lateral surface of the base of the phalanx of the great
toe. The transverse head arises from the transverse metatarsal liga-
ments and the capsules of the metatarsophalangeal joints (outer
four). It is inserted with the oblique head.

Actions. — Adducts and flexes the great toe.

Nerve Supply. — Lateral plantar nerve.

The m. flexor digiti quinti brevis arises from the base of the fifth
metatarsal bone and the sheath of the m. peroneus longus. It is
inserted into the lateral surface of the base of the first phalanx of the
little toe.

Action. — Flexes the little toe.

Nerve Supply. — Lateral plantar nerve.

Fourth Layer. — The mm. interossei are seven in number, four dorsal
and three plantar.

The dorsal muscles occupy the four interosseous spaces and each
arises from the adjacent surfaces of two metatarsal bones. The
tendons of the first and second are inserted into the first phalanx of the
second toe (medial and lateral surface). The third and fourth are
inserted into the lateral surfaces of the first phalanges of the third
and fourth toes.

The three plantar interossei are located in the three lateral spaces.
Each arises from the medial surface of the third, fourth and fifth
metatarsal bones and is inserted into the medial surface of the first
phalanges of the third, fourth and fifth toes.

Actions. — Flex the metatarsophalangeal joints and extend the in-
terphalangeal joints.

The plantar interossei adduct the toes toward the second toe; the
dorsal interossei abduct their respective toes from the middle line
of the second toe.

Nerve Supply. — Lateral plantar nerve (S. 1,2).

CHAPTER IV

THE BLOOD-VASCULAR SYSTEM

The chief organs found in the thorax are the heart with its peri-
cardium and the great vessels as the aorta, pulmonary arteries, in-
nominate, left common carotid and subclavian arteries, the innom-
inate veins and the superior and inferior venae cavae; the lungs and
pleurae; the esophagus, trachea and bronchi; the vagal, phrenic and
sympathetic nerves, the thoracic duct and part of the thymus body.

In order to comprehend that an organ is enlarged or displaced it is
necessary to know its normal size, position and outline upon the
body wall. In order to facilitate physical diagnosis certain lines
are drawn upon the body and these bound certain definite regions.
Bony landmarks are used wherever possible. The various lines and
regions of the thorax will be first considered.

Lines of the Thorax. — For the convenience of outlining the organs
upon the body surface, a number of vertical and transverse lines
are drawn. The chief vertical lines are the midst ernal, midclavicular,
lateral sternal, parasternal, midaxillary, scapidar and midverlebral.

The midsternal line (one) is drawn from the midsternal notch
and if continued upon the abdominal wall would pass through the
umbilicus and symphysis pubis.

The midclavicular lines (two) are drawn from the middle of the
clavicle through the nipple of the male and if continued upon the
abdomen would pass through the middle of the inguinal ligament.

The lateral sternal lines are two lines at the right and left borders
of the sternum.

The parasternal lines are two vertical lines midway between the
midsternal and midclavicular lines. Some place these lines midway
between the lateral sternal and the midclavicular lines.

The midaxillary lines (two) are drawn from the apex of the axilla
(armpit) with the arms extended at a right angle to the body.

The scapular lines (two) are drawn vertically through the inferior
angle of each scapula.

The midverlebral line (one) is drawn along the spinous processes
of the thoracic vertebrae.

The horizontal lines upon the ventral surface are as follows:

i. At the lower border of the cricoid cartilage.

2. Through the clavicles.

CHE BLOOD-VASCULAR SYSTEM

3. Through the third chondrosternal junction.

4. Through the sixth chondrosternal junction.

With the two lines at the sternal borders the following regions are
outlined:

I. Suprasternal, containing the trachea, thyreoid gland and the
esophagus.

Fig. 165. — Lines and regions of the
ventral thoracic and abdominal walls.
{From a Photograph.) a, Midsternal;
b, b, parasternal; c, (-.midclavicularlines;
e, subcostal line; /, intertubercular lines;
g, subcostal angle; hd, ltd, midinguinal
lines. RL right and left hypochondriac
regions; RL, LL, right and left lumbar
regions; RI, LI, right and left inguinal
regions; E, epigastric; U, umbilical; H
hypogastric regions; M, McBurney's
point.

Fig. 166. — Outline of regions on the
ventral thoracic wall. {From a Photo-
graph.) a. Line through cricoid cartilage;
b, line through clavicles; c. line through
third chondrosternal articulation; d, line
through sixth chondrosternal articula-
tion; e, e lateral sternal lines; /, angle of
Ludovicius. 1, Suprasternal region; 2,2,
supraclavicular regions; 3, upper sternal
region; 4, 4, infraclavicular regions; 5,
lower sternal region; 6, 6. mammary
regions; 7, 7, inframammary regions.

2, 2. The supraclavicular regions containing the apex of each lung
and the cervical pleura.

3, Upper sternal region containing the thymus, the arch of the
aorta and the medial border of the upper border of each lung.

4, 4. The infraclavicular regions containing the upper lobe of each
lung where tuberculous bronchopneumonia is first manifested.

5, Lower sternal region containing the ventral border of the right
lung and the uncovered area of the heart.

6, 6. The mammary regions containing the bulk of the lungs and
the bulk of the heart.

LINES OF THE THORAX

213

7, 7. The inframammary regions containing the lower portions of the
lungs and the costophrenic sinuses. These regions overlap the right
lobe of the liver upon the right side and on the left side the left lobe
of the liver, the fundus of the stomach and the spleen. Upon the
left is Traube's semilunar space.

The horizontal lines upon the dorsal surface are as follow

1. At the upper borders of the scapulae.

2. Through the spines of the scapulae.

3. Through the inferior angles of the scapulas.

Fig. 167. — Lines and regions on the dorsal thoracic wall. a. Midvertebral line; b, b. scapu-
lar lines prolonged headward; c, a line at the upper borders of the scapula?; d. a line through
the spines (bases) of the scapula?; e, a line at the apex of the inferior angles of the scapula?.
1,1, Suprascapular regions; 2, 2, supraspinous regions; 3,3, infraspinous regions; 4, 4, inter-

scapular regions; 5, 5, infrascapular regions. (Fn

■ photograph.)

In conjunction with the midvertebral and the scapular lines pro-
longed upward to the shoulder the following regions are outlined:

1, 1. Scapular regions.

2, 2. Supraspinous regions.
7,, 7,. Infraspinous regions.

4, 4. Interscapular regions.

5, 5. Infrascapular regions.

Occupying the bulk of each side of the thoracic cavity are seen
the lung and pleural membranes. The region between the two
pleural sacs is called the interpleural space, or septum mediastinale.
This region is not a space in the true sense as it is occupied by various
organs and structures.

214

THE BLOOD-VASCULAR SYSTEM

The mediastinal septum is divided into two main portions, supe-
rior and inferior. The superior mediastinum lies above the level of
the pericardium, extending from the junction of the manubrium and

Fig. 169. — The ventral, middle and dorsal mediastinal spaces (at the level of the disc
between ninth and tenth thoracic vertebrae).

gladiolus sterni to the lower border of the fourth thoracic vertebra.
In this region lie the arch of the aorta and its three branches, the
upper part of the superior vena cava and the innominate veins, the
esophagus, trachea, thoracic duct, the vagal, phrenic, cardiac, re-
current laryngeal and sympathetic nerves and the thymus gland.

THE HEART

215

The inferior mediastinum is the widest portion and is divided into
ventral, middle and dorsal portions. The ventral lies between the
sternum and the pericardium and contains some lymph nodes,
branches of the internal mammary artery and areolar tissue.

The middle portion is the largest and is bounded by the pericar-
dium. Its contents are the pericardium, heart, roots of the great
vessels and the phrenic nerves.

The dorsal mediastinum lies behind the pericardium. Its contents
are the descending thoracic aorta, the thoracic duct, vena azygos
major, vagal nerves and esophagus.

The blood vascular system consists of the heart, arteries, that carry
the blood away from the heart, veins, that carry the blood toward the
heart and capillaries that connect the arteries and veins. There are
two main circulations, the systemic and the pulmonary. The systemic
is farther divided into the general systemic and the portal circulations.

Fig. 170. — Ventral

of the heart. (From a photograph.)

THE HEART

The heart (cor) is a hollow muscular organ of a flattened, conical
shape situated in the thoracic cavity. It is contained in a serous
sac called the pericardium. About one-third lies to the right of the
midsternal line and two-thirds to the left. Its long axis is directed
downward (caudad) to the left and forward (ventrad). Its dimen-

2l6 THE BLOOD-VASCULAR SYSTEM

sions are 5 inches (12.5 cm.) long, 3.5 inches (8.75 cm.) wide and 2.5
inches (6.25 cm.) thick. It weighs 10 to 12 ounces in the male and
8 to 10 ounces in the female.

It presents a base, an apex, two surfaces and two margins. The
base (basis cordis) is directed upward (cephalad) and backward
(dorsad) and is formed by the atria, chiefly the left. It lies ventral
to the bodies of the fifth, sixth, seventh and eighth thoracic vertebrae
but separated from them, mainly, by the esophagus and the thoracic
aorta. It presents the openings of the pulmonary veins and the
superior and inferior venae cava;, the oblique vein and fold of Marshal.

Ate fc»* ,

Fig. 171. — Dorsal view (base and diaphragmatic surface) of the heart. The vessels are
filled with cotton to make them stand open. (.From a photograph.) L.P.A.. R.P.A.. Left and
right pulmonary arteries; P.\'.. pulmonary veins; V.A.M., venaazygos major. P.I.G., dorsal
(inferior) interventricular sulcus.

The base is limited below by the atrioventricular groove which con-
tains the coronary sinus.

The apex (apex cordis) is blunt and rounded representing the left
ventricle; it is situated in the fifth left intercostal space 8 cm. from
the midline.

The sternocostal surface (facies sternocostal is) looks upward
(cephalad) and forward (ventrad) and to the left. It lies dorsal to
the sternum and the third, fourth, fifth and sixth costal cartilages,
mainly of the left side. The upper part consists of the two atria and

THE CHAMBERS OF THE HEART 21 7

roots of the pulmonary artery and aorta. The greater part of the
surface consists of the ventricles separated incompletely from the
preceding by the ventral atrioventricular groove. This ventricular
area is convex and is divided into a larger, right, and smaller, left,
portion by the ventral (superior) interventricular sulcus which goes to
the right of the apex.

The diaphragmatic surface (fades diaphragmatica) is flattened and
rests chiefly upon the central tendon of the diaphragm. It consists
of the ventricles and is divided into a greater, left ventricle, and
smaller, right ventricle portions by the dorsal interventricular sulcus.

The right margin consists of a vertical and a horizontal portion.
The vertical part is curved and is formed by the right atrium; it is
marked by the sulcus tcrminalis. The horizontal portion is thin and
sharp and is formed by the right ventricle; this latter part is called
also the inferior margin, or margo acutus.

The left margin is convex and is formed mainly by the left ventri-
cle. It is rounded and is called the margo obtusus. It is obliquelv
directed with its convexity to the left.

The chambers of the heart are four in number: right and left atria
and right and left ventriculi. The right atrium communicates with
the right ventriculus and the left atrium with the left ventriculus.
The capacity of each ventricle is about 100 c.c. and that of each
atrium slightly less.

Right Atrium. — Make an incision with the scissors connecting the inferior and
superior cava?; from the middle of this incision make another into the auricular
appendage. By these incisions the atrium is laid open and the various points
of interest may be readily examined.

Right Ventricle. — From the right atrium cut into the right ventricle along the
inferior margin of the chamber to the apex. From the middle of this incision
carry another to the interventricular groove and follow the interventricular
septum into the pulmonary artery.

Left Atrium. — Make an incision connecting the right and left superior pul-
monary veins; make another from the left superior pulmonary vein into the
appendage.

Left Ventricle. — Make an incision from the left atrium into the left ventricle
following the left border of the heart to the apex; then continue along the in-
terventricular sulcus into the aorta using a finger of the left hand as a guide to
the scissors.

The right atrium (atrium dextrum) consists of the main chamber
and the auricle (auricula dextra). The points of interest in the
interior are as follows:

1. Crista tcrminalis, a ridge running from in front (ventral margin)
of the superior vena cava to in front of the inferior vena cava. This
ridge is marked externally by a groove, the sulcus tcrminalis.

2. The tricuspid (right atrioventricular) orifice leading into the
right ventricle.

2l8 THE BLOOD-VASCULAR SYSTEM

3. The orifice of the superior vena cava at the upper (cephalad) and
back (dorsal) part of the atrium.

4. The orifice of the inferior vena cava at the lowest part of the
atrium.

5. The Eustachian valve {valvida vena cava inferioris) situated in
front of (ventral to) the orifice of the inferior vena cava and extend-
ing to the fossa ovalis.

6. The coronary sinus (sinus coronarius) opening between the
orifice of the inferior vena cava and the tricuspid orifice.

7. The coronary valve (valvula sinus coro-narii) that protects the
orifice of the coronary sinus.

8. Foramina thebesii (vena cordis minima) openings of small veins
in the walls of the atrium.

9. Fossa ovalis, a depression in the lower part of the interatrial
septum.

10. Annulus ovalis (limbus fossa ovalis) the incomplete ridge form-
ing the boundary of the fossa ovalis.

n. The musculi pectinati, the muscle columns in the auricle.

12. The openings of the anterior cardiac veins at the lower part of
the front (ventral) wall of the atrium.

13. The tubercle of Lower (tuberadum intervenosum) a small pro-
jection between the fossa ovalis and the superior and inferior venae
cavae, not prominent in man.

The right ventricle (ventricuhts dexter) is pyramidal in form and the
cavity consists of the main part, or body, and the conus arteriosus,
that leads into the pulmonary artery. These two parts are separated
by a slight ridge, the supraventricularcrest. The walls in the body
portion are thinner than those of the left ventricle and are irregular,
due to the presence of the trabecula cornea. The walls of the conus
arteriosus are smooth. The points of interest are as follows:

1. The tricuspid orifice communicating with the right atrium,
guarded by the tricuspid valve. It is oval and is directed obliquely
downward (caudad) and to the right.

2. The pulmonary artery orifice at the upper (cephalic) and front
(ventral) part of the chamber and at the end of the conus arteriosus.

3. Vena cordis minima, the openings of small veins in the walls.

4. Trabecula carnea, or muscle columns of three varieties, ridges,
arches and papillary muscles. The last, musculi papillares, are more
or less massive projections attached to the ventricular wall by their
bases. The papillary muscles usually number three: (1) a large
ventral, (2) a smaller dorsal, (3) a single, or group of papilla; (septal)
attached to the interventricular septum. To the summit of each are
attached the chordae tendineas.

5. The moderator band, a modified column attached at one end to
the interventricular septum and at the other to the base of the ventral

THE CHAMBERS OF THE HEART

219

papillary muscle. It tends to prevent over-distention of the ven-
tricle and is prominent in lower animals.

6. The tricuspid valve (valvule trims pidalis) consists of three some-
what triangular leaflets. The base of each is attached to the atrio-
ventricular orifice and the free edges are serrated; from the serrations
delicate tendinous threads, the chorda tendinea, pass to the papillary
muscles. The left, or infundibular cusp, is the largest and is situated
over the conus arteriosus. The right, or marginal cusp, is in rela-
tion with the right part of the ventral wall; the medial, or septal cusp,

— Heart dissected
entricle. A, Chordae tend

B, eustachian valve; C. coronary vaK

and the right

is in relation with the interventricular septum. This valve guards
the atrioventricular orifice.

7. The chorda; tendineaz are delicate cords that attach the valve
edges and central parts of the valve leaflets to the papillary muscles
and prevent the leaflets from passing into the atrium.

The left atrium (atrium sinistrum) consists of the body and the
auricle. The body is smooth-walled while the auricular wall is
roughened. The points of interest are as follows:

1. Orifice of the four pulmonaxy veins opening into the upper
(cephalic) part of the dorsal wall.

220 THE BLOOD-VASCULAR SYSTEM

2. The atrioventricular orifice communicating with left ventricle.

3. Vena cordis minima.

4. Musculi pectinati in the auricula.

The left ventricle (ventriculus sinister) has thicker walls than the
right ventricle (3 to 1) and is somewhat cylindrical in form. The
cavity is divided into body (irregular wall) and vestibule (smooth-
walled) that leads to the aorta. The points of interest are as
follows:

1. Bicuspid orifice that communicates with the left atrium and is
guarded by the bicuspid valve.

2. The aortic orifi.ce that leads into the aorta and is situated at the
upper, front part at the summit of the vestibule. It is circular in
outline and lies ventral to the preceding orifice.

3. Vena cordis minima.

4. Trabecula cornea: ridges, arches and papillary muscles. The
papillary muscles (musculi papillares) are two in number, ventral and
dorsal, or inferior and they are much larger than those of the right
ventricle. To these the chorda; tendinea; are attached.

5. The bicuspid valve (valvula mitralis) consists of two leaflets, the
ventral, or aortic cusp is the larger, the inferior, or marginal cusp is
the smaller. Usually two smaller cusps are found at the angles of
junction of the larger cusps. The free edges of the leaflets are ser-
rated and have the chordae tendinea; attached here as well as to the
under surfaces of the valve leaflets.

6. The chorda tendinea are attached like those of the right ven-
tricle but are thicker and stronger.

The interventricular septum (septum ventriculorum) separates the
two ventricles. It corresponds to the interventricular sulcus and has
an oblique position. The bulk of it consists of muscle tissue, the
upper (cephalic) and ventral part in membranous and is, therefore,
called the pars membranacea.

The muscle tissue of the heart is arranged differently in the atria
than in the ventricles. In the atria two layers are noted. The
superficial layer runs transversely and is common to both chambers.
The deep layer consists of fibers that loop over each atrium from front
to back (dorsoventrally) and form circular bands around the auricula;
and orifices of the veins. In the ventricles the arrangement is more
complex. The superficial set consists of fibers that arise from the
conus arteriosus and pass across the right ventricle around the apex
and thence to the papillary muscles of the left ventricle. Other
fibers arise from the right atrioventricular ring, pass beneath the
preceding, around the apex to the dorsal papillary muscle of the left
ventricle. Some fibers arise from the left atrioventricular ring and
pass to the right ventricle and its papillary muscles. The deep set
(larger) consists of fibers that arise in the papillary muscles of one

THE PERICARDIUM 221

ventricle, describe an S-shaped course and pass under the papillary
muscles of the other ventricle. There are three sets of these and
the course is very complicated.

The atrioventricular bundle (His) connects the right atrium
directly with the ventricles. This bundle of muscle fiber arises near
the fossa ovalis as small bundles of fibers that converge to form its
node; it then continues as a single bundle in the lower part of the pars
membranacea to the muscular portion of the interventricular septum.
Here the bundle divides into right and left portions one for each
ventricle. Each passes down its respective side of the interventricu-
lar septum, beneath the endocardial lining, to ultimately divide
to numerous bundles that pass to the papillary muscles and then
spread out over the entire ventricular muscle.

The heart receives its blood supply through the rigid and left
coronary arteries that arise from the aorta in the sinuses of Valsalva.
The blood is returned to the right atrium through the coronary sinus
and the anterior cardiac veins. The tributaries of the coronary
sinus are the small, or right cardiac vein and the middle, or posterior
cardiac veins. The lymph drains into the right lymphatic and thor-
acic ducts.

The nerve supply is from the vagal, accessory and sympathetic
nerves.

The pericardium is a fibrous sac lined by a serous membrane. It
is conical in shape with its base downward (caudad) and apex up-
ward (cephalad). The base is attached to the central tendon of the
diaphragm while the apex is continuous with the cervical fascia.
The sac contains the heart and the cardiac ends of the great vessels.
Its ventral wall gives attachment to the superior and inferior sterno-
pericardial ligaments. It constitutes the boundary of the middle
mediastinal space as well as assists in bounding the ventral and
dorsal mediastinal spaces. At its base it is pierced by the inferior
vena cava and at its apex (dorsally) it is pierced by, and its fibrous
part also ensheaths the superior vena cava, pulmonary veins,
right and left pulmonary arteries and aorta.

The serous portion consists of a visceral layer, upon the heart, and
a parietal layer, lining the fibrous sac. These two are continuous
over the great vessels of the heart but all of the vessels do not receive
a complete investment. As a result recesses, or sinuses, are formed.
The great transverse sinus lies between the pulmonary artery and the
aorta (ventrally) and the two atria (dorsally). The great oblique
sinus lies between the inferior vena cava (to the right and below)
and the left inferior pulmonary vein (to the left and above).

The vestigial fold of Marshall is a fold of serous pericardium en-
closing the ligamcutum vena cava sinistra. It passes from the left
pulmonary artery region to the left superior pulmonary vein.

22 2 THE BLOOD-VASCULAR SYSTEM

To outline the heart upon the ventral thoracic wall the following
points are used: (i) 3 cm. from the midsternal line upon the upper
margin of the third right costal cartilage; (2) 2.5 cm. from the mid-
sternal line at the sixth chondrosternal junction; (3) 8 cm. from the
midsternal line in the left fifth interspace (apex point); (4) 4.5 cm.
from the midsternal line in the second left interspace. The line 1, 2
should be curved to the right so as to be 3.5 cm. from the midsternal
line at the fourth interspace. This line represents the right atrium.

Fig. 173. — Outline of the heart upon the ventral thoracic wall. {From a photograph .
P, Pulmonary valve; A, aortic valve; M, mitral valve; T tricuspid valve, i, 2, 3, 4, point
for outlining the heart.

The line 2, 3 represents the right ventricle. The line 3, 4 should be
curved a little to the left and represents the left border and mainly
left ventricle. The line 1, 4 represents the base line. The valves
are located as follows: The pulmonary valve is placed horizontally
beneath the middle of the third left chondrosternal junction. The
aortic valve is below this and toward the midline and at an angle.
The mitral valve is opposite the third left interspace and nearly
horizontal, while the tricuspid valve is below this near the midline
and at an angle, slightly overlapping the mitral valve. These areas
indicate the position of the valves but do not indicate the regions
where the valve sounds are best heard. These latter are called the
puncta maxima and are as follows:

THE ARTERIES

223

i. Pulmonary punctum maximum (p. m.) is at the sternal end of
the second left intercostal space.

2. Aortic p. m. is at the second right costal cartilage.

3. Mitral p. m. is just above the area of the apex point.

4. Tricuspid p. m. is at the sternal ends of the fifth and sixth
costal cartilages.

That portion of the heart that lies immediately beneath the ven-
tral thoracic wall and separated from it by- only the pericardium and

Fig. 174. — Diagram of the heart and valves in relation to the skeleton of the ventral
thoracic wall. PC, Superior vena cava; RA, right atrium; RV, right ventricle; LA, left
atrium; LV, left ventricle; P, pulmonary valve; A, aortic valve; M, mitral valve; T, tri-
cuspid valve.

pleurae is called the area of superficial cardiac dulness and is chiefly
ventricular; the remainder is overlapped by the lungs and gives the
deep cardiac dulness.

THE ARTERIES

The circulations are the pulmonary and systemic; the systemic is
divided into general systemic and portal.

The pulmonary circulation comprises the right ventricle, the pul-
monary aorta and the pulmonary arteries, the lungs, pulmonary
veins and the left atrium.

224

THE BLOOD-VASCULAR SYSTEM

The pulmonary aorta, or artery (artcria pulmonalis) , leaves the
right ventricle at the summit of the conus arteriosus. The vessel
is about 2 inches (5 cm.) long and 1 ii inches (30 mm.) in diameter.
It passes upward (cephalad) and dorsally and under the arch of the
aorta it divides into right and left pulmonary arteries which further
divide and ramify the lungs. The base of the pulmonary aorta
has three dilatations called the sinuses of Valsalva, two ventral and
one dorsal. Here are seen the semilunar valves, three in number;
each valve is semilunar in shape and is attached by its peripheral

1 -RCm.CMrt, IMjIV0'1*

Lisflrt

ch of the aorta and its branches; the superior '
the pulmonary arteries and vein:

. and its tributaries;

margin to the base of the pulmonary artery (annul us Jibrosus) . The
inner, or free edge, near its middle possesses a nodule called the
cor pits aranlii (modulus valvules semilunaris). From each side of this
a minute semilunar fold extends and is called lunule (lunula). The
right pulmonary artery is larger and longer than the left. Its first
branch lies below the first branch bronchus. The first branch of
the left pulmonary artery passes above the first branch bronchus.

The pulmonary veins (vena pulmonales) are four in number. The
lobular divisions unite to form one vein for each lobe, three in the
right lung and two in the left lung. The middle vessel on the right
side joins that of the upper lobe so that two veins leave each lung
to empty into the left atrium. No valves are present.

In the pulmonary circulation the venous or deoxygenated blood

THE ARTERIES OF THE HEAD AND NECK 225

passes from the right ventricle into the pulmonary artery, through
its right and left branches to the lungs where it is oxygenated in the
capillaries. The blood then continues into the radicals of the pul-
monary veins and through these veins to the left atrium.

The systemic circulation is more extensive and more complicated;
it comprises the left ventricle, the aorta and its branches, the sys-
temic capillaries, the superior and inferior venae cavae and their
tributaries and the right atrium.

The aorta consists of an ascending portion, arch and descending
portion; the last is divided into thoracic and abdominal parts.

The ascending portion (aorta ascendens) arises from the summit
of the vestibule of the left ventricle. It is about 2 inches (5 cm.)
in length and i'6 inches (28 mm.) in diameter. At its root (bulb us
aorta) it possesses three dilatations, the sinuses of Valsalva, two
dorsal and one ventral. Here are seen the semilunar valves and
these are the same in structure as those of the pulmonary artery.
From the ventral sinus arises the right coronary artery and from the
left dorsal sinus arises the left coronary artery. These arteries nour-
ish the heart.

The ascending aorta passes obliquely upward (cephalad), ventrally
and to the right, to the level of the upper border of the second right
costal cartilage. Here the arched part (arcus aorta) continues up-
ward (cephalad), dorsally and to the left across the trachea and
thence downward (caudad) to the level of the lower border of the
fourth thoracic vertebra; here it constitutes the beginning of the
descending aorta. The arch has three branches, the innominate, left
common carotid, and left subclavian arteries.

The innominate artery (arteria innomyna) is the largest branch
.of the aorta and measures i'2 to 2 inches (3.5 to 5 cm.) in length.
It lies in the posterior mediastinum and extends to the root of the
neck, where it divides into the right common carotid and right
subclavian arteries.

THE ARTERIES OF THE HEAD AND NECK

The right common carotid (arteria carotid is communis dexter)
arises in the root of the neck and extends to the upper margin of the
thyreoid cartilage; it is about 3'2 inches (8.5 cm.) in length. It lies
in the carotid sheath with the internal jugular vein and the vagal
nerve and divides into the right internal and external carotid arteries.

The left common carotid artery (arteria carotidis communis
sinister) arises from the arch of the aorta and extends to the upper
margin of the thyreoid cartilage. It consists of a thoracic and a cervi-
cal portion. The thoracic part is about 1 to ili inches (2.5 to 3.5 cm.)
in length and extends to the left sternoclavicular articulation. The
cervical portion starts here and continues as on the right side.

2 26 THE BLOOD-VASCULAR SYSTEM

The course of either common carotid artery is indicated as follows:
Draw a line from the sternal end of the clavicle to a point midway
between the mastoid process and the angle of the mandible. That
portion of the line inferior to the upper margin of the thyreoid car-
tilage lies over the artery.

The external carotid artery (artcria carotis externa) is the smaller
of the two branches of the common carotid and extends from the
upper margin of the thyreoid cartilage to the back of the neck of the
mandible, where it divides into the internal maxillary and super-
ficial temporal arteries. It is about 2J2 inches (6.1 cm.) in length.
It gives off the following branches:

1. The superior thyreoid (art. thyreoidea superior) is the first
branch and arises on a level with the tip of the greater cornu of the
hyoid bone. It passes to the superior portion of the thyreoid
gland, which it supplies, and in addition gives branches to the larynx
and sternomastoid muscle.

2. The lingual artery {artcria lingua! is) is the second branch
mainly for the supply of the tongue. Its chief branches are the
hyoid, dorsal lingual and sublingual (for the sublingual gland) arteries.

3. The external maxillary, or facial artery (artcria maxillaris
externa) arises just above the lingual artery, passes up the neck, over
the body of the mandible and terminates at the angle of the mouth
as the angular artery. In the neck this artery gives off the following
arteries: (a) The ascending palatine, for the soft palate, tonsil,
pharynx wall and the auditory tube, (b) The tonsillar artery, for
the tonsil and constrictor muscles of the pharynx, (c) The sub-
maxillary artery, for the submaxillary gland, (d) The submental
artery, for the submaxillary and sublingual glands and the mylohyoid
muscle.

In the face the following branches are given off: (a) The superior
labial, or coronary artery, that supplies the upper lip and part of the
septum of the nose, (b) The masseteric branch, for the masseter
muscle, (c) The lateral nasal artery, that arises near the angle of
the mouth and supplies the ala of the nose, (d) The angular artery
is the terminal part of the external maxillary artery and runs along
the side of the nose to the medial commissure of the eyelids.

4. The occipital artery (art. occipitalis) arises near the inferior
margin of the posterior belly of the digastric muscle and extends to
the inferior nuchal line where it divides into its terminal branches.
This gives off a number of branches, (a) Muscular branches to the
neighboring muscles, (b) Meningeal branches that enter the skull
through the hypoglossal canal and jugular foramen and supply the
meninges here, (c) The descending branch, or prince psccrvicis artery,
supplies muscles of the dorsal vertebral region. ((/) The terminal
branches (medial and lateral) supply the scalp of the neighborhood.

THE ARTERIES OF THE HEAD AND NECK

227

5. The posterior auricular artery (art. auricularis posterior) arises
above the level of the posterior belly of the digastric muscle and ends
back of the auricle. This has a number of branches, (a) The
muscular branches supply the sternomastoid, digastric and styloid
muscles, (b) The parotid branches pass to the parotid gland, (c)
The stylomastoid artery enters the stylomastoid foramen and supplies
the external auditory canal, the tympanum, vestibule, semicircular
canals and mastoid cells, (d) The auricular branch supplies the

-Ramification of the external carotid artery in the head (diagrammatic).
(Sobotta and McMurrich.)

posterior auricular muscle, the auricle and scalp of the region, (e)
The occipital branch supplies the sternomastoid and occipitalis
muscles and the scalp here.

6. The ascending pharyngeal artery (art. pharyngea ascendens)
arises from the lower part of the carotid artery and passes to the
pharynx and soft palate. Its branches are as follows: (a) Pharyn-
geal branches to the wall of the pharynx and tonsil, (b) The pre-
vertebral branches for the prevertebral muscles, deep lymph nodes and

228 THE BLOOD-VASCULAK SYSTEM

large nerves, (c) The posterior meningeal for the meninges;
these enter the skull through the hypoglossal canal and jugular
foramen. (</) The inferior tympanic for the tympanum.

7. The superficial temporal artery (art. temporalis superficialis),
one of the terminal branches of the external carotid artery, is about
1 to 2 inches (2.5 to 5 cm.) in length. Its branches are numerous.
(a) Parotid branches, for the parotid gland, (b) Articular, for the
temporomandibular articulation, (c) Anterior auricular, for the
auricle and external auditory canal, (d) Transverse facial, for the
parotid gland and duct, masseter muscle and skin, (e) Middle
temporal, for the temporal muscle. (/) The zygomaticoorbital, for
the orbicularis oculi muscle, (g) The frontal branch, for the frontalis
and orbicularis oculi muscles, (k) The parietal branch for the au-
ricular muscles, fascia and skin.

8. The internal maxillary artery (art. maxittaris interna) is the
other terminal branch of the external carotid artery. This is under
cover of the parotid gland and the ramus of the mandible. The
first part extends from the neck of the mandible to the lower margin
of external pterygoid muscle. Its main branches are as follows:
(a) Deep auricular, for the mandibular articulation, parotid gland,
external auditory meatus and the tympanic membrane, (b) The
middle meningeal artery, the largest branch, enters the middle fossa of
the skull through the foramen spinosum. It gives off a number of
branches before and after it enters the skull. These are mainly for
the supply of the meninges, tympanic cavity, semilunar ganglion of
the trigeminal nerve, and structures in the orbit, (c) The inferior
alveolar artery enters the mandible at the mandibular foramen, passes
along the mandibular canal and ends at the mental foramen by
dividing into mental and incisive branches. This gives rise to
branches that supply the mucous membrane of the cheek, the
mylohyoid muscle, all of the teeth and the quadratus labii inferior
muscle.

The second part extends from the lower margin of the external
pyterygoid muscle to upper head of the external pterygoid muscle.
Its branches are as follows: (a) The masseteric artery, for that mus-
cle, (b) The two deep temporal arteries, for the temporal muscle.
(c) The pterygoid branches, for these muscles, (d) The buccinator
branch, for that muscle, the mucosa and skin of the cheek.

The third part extends from the interval between the two heads of
the external pterygoid muscle through the pterygomaxillary fissure
into the pterygopalatine fossa. Its branches are as follows: (a)
The infraorbital branch passes through the orbit in the infraorbital
canal and appears upon the face at the infraorbital foramen. It
supplies branches to the incisor teeth, the maxillary sinus, some of the
ocular muscles, the lacrimal gland, the lower eyelid, lacrimal sac and

THE SUBCLAVIAN ARTERY 229

skin of this region, (b) The posterior superior alveolar artery sup-
plies the molar and premolar teeth, the gums and maxillary sinus.
(c) The descending palatine supplies the mucosa of the roof of the
mouth, (d) The pharyngeal branch supplies the roof of the nose
and pharynx, the sphenoidal sinus and the auditory tube, (e)
The sphenopalatine branch supplies the sphenoidal sinus and the
nasal cavity.

The course of the external carotid artery is indicated by a line drawn
from the posterior end of the greater cornu of the hyoid bone to the
lobule of the ear.

The internal carotid artery (arteria carotis interna) extends from
the end of the common carotid artery to the middle fossa of the skull;
it enters the skull through the carotid canal and foramen lacerum
and divides into the middle and anterior cerebral arteries. These
are considered under the "Circulation of the Brain," page 430, with
the exception of the ophthalmic artery (arteria ophthalmica). This
artery passes into the orbit through the optic foramen and gives off
a number of branches. Some of these are for the muscle of the eye-
ball, others for the lacrimal gland and tissues of the orbit, nasal
cavity, eyelid, ethmoidal cells and meninges. One of its most im-
portant branches is the central retinal artery that enters the eyeball
through the optic nerve and supplies the retina. The supraorbital
branch reaches the forehead through the supraorbital foramen and
supplies the frontalis muscle and skin. The frontal artery is the
terminal branch of the ophthalmic artery and supplies the scalp.

The subclavian arteries {arteria: subclavian). The right subclavian
artery is shorter than the left as it arises from the innominate artery
while the left arises from the arch of the aorta. The right one is
about 3 inches (7.5 cm. ) in length while the left is about 4 inches (10
cm.) in length. Each consists of three parts. The first part of each
extends from the origin to the medial margin of the scalenus ante-
rior muscle. The second part extends from the medial to the lateral
margin of the scalenus anterior muscle. The third part extends from
this point to the outer margin of the first rib.

The branches are as follows: (a) The vertebral artery (art. verte-
bralis) is the first branch and it passes up through the foramina in the
upper six cervical vertebra, enters the skull through the foramen
magnum and anastomoses with the vertebral artery of the other side
to form the basilar artery. The branches are given under the "Cir-
culation of the ''Brain," page 430.

(b) The thyrocervical trunk (truncus thyreoccrvicalis) is only a few
millimeters in length and divides into three branches: (1) The inferior
thyreoid artery, that gives branches to the thyreoid gland, muscles of
the neighborhood, esophagus, larynx, trachea and the structures
within the vertebral canal. (2) The transverse cervical artery (art.

230

THE BLOOD-VASCULAR SYSTEM

transversus colli) that terminates as the ramus ascendens, or super-
ficial cervical artery and the ramus descendens, or posterior scapular
artery. These vessels supply the neighboring muscles. (3) The
transverse scapular artery (art. transversa scapula) terminates in the
infraspinous fossa of the scapula. It gives off a number of branches
that supply the dorsal and ventral scapular, sternomastoid and sub-

Fig. 177.- — The branches of the subclavian artery and the course of the vertebral artery
in the neck (schematic). (Sobotta and McMurrich.)

clavius muscles, the acromioclavicular, sternoclavicular and shoulder
joints.

(c) The internal mammary artery [art. mammaris interna) extends
from its origin to the sixth intercostal space where it divides into the
musculophrenic and superior epigastric arteries. This lies within the
thorax and gives off branches to the diaphragm, thymus, medias-
tinum, intercostal spaces and the skin. The musculophrenic artery
is one of its terminal branches and this supplies the diaphragm and

THE AXILLARY ARTERY 23 1

the lower intercostal spaces. The superior epigastric artery continues
into the abdominal wall and anastomoses with the inferior epigastric
artery. It gives branches mainly to the muscles and skin along its
course.

(d) The costocervical trunk (truncus costocervicalis) gives rise to
two branches, (i) The deep cervical artery {art. cervicis profunda)
passes to the back of the neck, supplies muscles there and sends
branches into the vertebral canal. (2) The superior intercostal
artery (art. intercostalis supremo) gives rise to the first two dorsal
intercostal arteries that pass ventrally in the intercostal spaces, anas-
tomose with the branches from the internal mammary artery and
give nutrient branches to the ribs.

THE AXILLARY ARTERY (ARTERIA AXILLARIS) AND AXILLA

The axillary artery, the continuation of the subclavian artery, lies
in the axillary space and extends from the outer margin of the first
rib to the lower margin of the tendon of the teres major muscle. It
is described under three parts, the first lying above the upper margin
of the pectoralis minor muscle, the second part lying under cover of
that muscle and the third part constituting the remainder.

The branches of the first part are the (a) superior thoracic artery
(art. thoracis suprema) that supplies the pectoralis major and minor,
subclavius, serratus anterior and intercostal muscles, (b) The
thoracoacromial artery (art. thoracoacromialis) a short trunk that
gives off four branches; the clavicular branch supplies the sterno-
clavicular articulation and adjacent muscles; the pectoral branch
supplies the pectoral and deltoid muscles and the skin; the deltoid
branch supplies the deltoid muscle and skin; the acromial branch
supplies the deltoid muscle and completes the circulation around
the shoulder.

(c) The lateral, or long thoracic artery (art. thoracis lateralis) is
a branch of the second part. It passes along the lower margin of
the pectoralis minor muscle and supplies this and adjacent muscles.

The remaining branches are from the third part of the artery.

(d) The subscapular artery (art. subscapulars) is about iJ-2 inches
(3.7 cm.) long and divides into two branches, the circumflex scapula:,
or dorsalis scapulcB artery is the larger and gives branches to the in-
fraspinatus, teres major and minor, triceps and deltoid muscles.
The thoracodorsal, or long subscapular artery, is the continuation of
the main stem and supplies the muscles at the lateral wall of the
thorax.

(e) The posterior circumflex artery (art. circumflexa humeri
posterior) passes to the back of the neck of the humerus and supplies
the teres major and minor, the triceps and deltoid muscles, the
shoulder joint and the head of the humerus.

232 THE BLOOD-VASCULAR SYSTEM

(/) The anterior circumflex artery (art. circumflexa humeri anterior)
is small and passes toward the bicipital groove supplying the long
head of the biceps and the adjacent muscles.

The course of the axillary artery is indicated by drawing a line from
the middle of clavicle to the lower margin of the pectoralis major
muscle where it crosses the prominence caused by thecoracobrachialis
muscle. The arm must be extended at a right angle.

The axillary space, or axilla is a pyramidal space situated between
the upper part of the arm and the side of the thorax. Its apex is
directed toward the root of the neck between the first rib, clavicle
and scapula and here the various structures enter the space. The
base, formed by the skin and axillary fascia, is directed downward
and outward. The ventral wall is formed by the pectoral major
and minor muscles, the clavicle, the costocoracoid membrane and
the subclavius muscle. The dorsal wall is formed by the sub-
scapularis, teres major and latissimus dorsi muscles. The medial
boundary consists of the first four ribs and their intercostal muscles
and the serratus anterior muscle. The lateral boundary is narrow
and consists of the humerus, coracobrachialis and biceps muscle.
The contents are the axillary artery and vein, the brachial plexus of
nerves and its branches, some branches of the intercostal nerves,
lymph nodes and fat.

The brachial artery {art. brachialis) is the continuation of the axil-
lary artery and extends to the neck of the radius. It courses along
the medial side of the arm and gives rise to several branches, (a)
The profunda artery (art. profunda brachii) accompanies the radial,
or musculospiral nerve. It supplies the triceps and shaft of the
humerus and assists in forming the anastomosis around the elbow
joint.

(b) The superior ulnar collateral, or inferior profunda artery (art.
collateralis ulnaris superior) mainly assists in the anastomosis
around the elbow joint.

(c) The inferior ulnar collateral, or anastomotic artery (art. col-
lateralis ulnaris inferior) supplies the triceps and brachialis muscles
and aids in forming the anastomosis around the elbow joint.

The course of the brachial artery is indicated by drawing a line
along the medial margin of the biceps (at the junction of the anterior
and middle thirds of the outlet of the axilla) to the middle of the
elbow.

At the neck of the radius the brachial artery divides into radial
and ulnar arteries.

The radial artery {art. radialis) is the smaller and extends into
the palm of the hand forming there the deep palmar arch. Its first
part extends from the elbow to the apex of the styloid process of the
radius; the second part extends around the side of the wrist to the first

THE ULNAR ARTERY 233

interosseous space; the third part passes into the palm of the hand to
join the deep branch of the ulnar artery.

The branches of the first part are the radial recurrent, that supplies
the brachioradialis, supinator, extensores carpi radialis longus and
brevis muscles and assists in the anastomosis around the elbow
joint; the muscular branches for the muscles of the radial (ventral)
side of the forearm; the superficial volar artery is small and arises
near the end of the first part, passes through the muscles of the ball
of the thumb and joins the main part of the ulnar artery to form the
superficial palmar arch. The volar carpal branch helps form the
volar carpal arch for the wrist joint.

The branches of the second part are, the dorsalis pollicis (two)
that pass along the sides (dorsally) of the thumb to supply the skin,
tendons, ligaments and joints. The dorsalis indicts radialis artery
is small and passes along the radial margin of the index finger for
the skin, tendon and joints. The first dorsal metacarpal and dorsal
radial carpal arteries are small and pass to the dorsal aspect of the palm.

The branches of the third part are, the princeps pollicis which
passes to the distal end of the metacarpal bone of the thumb and
divides into two branches (collateral) that pass along the sides of the
thumb. The volaris radialis indicts runs along the radial side of
the index finger.

The course of the radial artery is indicated by drawing a line from
the hollow of the center of the elbow to the side of the styloid process
of the radius.

The ulnar artery extends from the neck of the- radius to the palm
of the hand where it forms the superficial palmar arch and assists
in forming the deep palmar arch. It has a number of branches.
(a) The volar ulnar recurrent is small and assists in forming the anas-
tomosis around the elbow joint, (b) The dorsal ulnar recurrent
supplies the brachialis and adjacent muscles and assists in the elbow
joint anastomosis, (c) The common interosseous artery extends to
the superior edge of the interosseous membrane and then divides
into dorsal and ventral interosseous arteries. The ventral, or volar
artery, runs between the deep muscles of the forearm giving branches
to these, to the radius and the ulna, the median artery and other
small branches. The dorsal artery gives off the interosseous recurrent
artery (elbow- joint anastomosis), muscular branches to the deep
muscles of the back of the forearm and branches to the skin of this
region and the wrist, (d) The volar carpal artery is small and assists
in the carpal arch formation, (e) The dorsal carpal artery passes
to the back of the wrist and assists in forming the dorsal carpal arch.
(/) The profunda artery is the last branch of the ulnar artery and
passes into the depths of the palm to assist in forming the deep
palmar arch.

234 THE BLOOD-VASCULAR SYSTEM

The course of the ulnar artery is indicated by two lines, as the
arterv curves. Draw a line from the medial epicondyle of the hum-
erus to the medial surface of the pisiform bone; the distal two-thirds
represents the distal two-thirds of the ulnar artery. From the center
of the cubital fossa draw another line to the junction of the upper
and middle thirds of the first line and that new line will indicate
the course of the first part of the ulnar artery.

In front of the elbow joint there is a triangular, somewhat de-
pressed area called the cubital fossa, or antecubital space. Here
the brachial artery sinks in quite deeply. The base, directed up-
ward, is a line connecting the two epicondyles of the humerus.; the
medial boundary is the lateral margin of the pronator teres; the
lateral boundary is the medial margin of the brachioradialis; the floor
consists of the supinator and brachioradialis. This space contains
the brachial artery and its vena? commites, the radial and ulnar
arteries, the median and radial nerves and the tendon of the biceps
muscle.

Upon the ventral aspect of the ligaments of the wrist lies the
ventral or volar carpal arch. This is formed by the volar carpal
branches of the radial and ulnar arteries assisted by branches from
the deep palmar arch and volar interosseous artery. It supplies
the ligaments and synovial membranes of the joints here.

The dorsal carpal arch is similar and formed by the dorsal carpal
branches of the ulnar and radial arteries assisted by branches from
the interosseous arteries.

The superficial palmar arch (areas volaris superficialis) is formed
by the main portion of the ulnar artery and the superficialis volae
branch of the radial artery. It lies just beneath the deep palmar
aponeurosis. It gives off four volar cow won digital arteries of which
the one on the ulnar side passes to the ulnar side of the little finger.
The other three pass to the clefts between the fingers where each
divides into two branches (proper digital arteries) that go to the
adjacent sides of index, middle, ring and little fingers.

The position of the superficial palmar arch is indicated by a curved
line extending from the pisiform bone to the base of the cleft between
the thumb and index finger. The convexity should extend to about
the middle third of the palm.

The deep palmar arch (arcus volaris profunda) is deeeply placed.
It lies upon the bases of the metacarpal bones and their ligaments.
It gives rise to recurrent branches for the volar carpal arch; articular
branches of the adjacent joints; volar carpal arteries that pass to the
dorsum of the hand and form the digital branches; and communicating
branches that connect with the proper volar digital arteries.

The course of the deep palwar arch is indicated by a line parallel to the
line of the superficial arch about >£ to % inch nearer the wrist.

THE DESCENDING AORTA 235

THE DESCENDING AORTA

The descending aorta (aorta descendens) begins at the lower
border of the fourth thoracic vertebra, passes downward (caudad)
to the left of the midline, through the diaphragm into the abdominal
cavity where it divides ventral to the body of the fourth lumbar
vertebra into right and left common iliac arteries. That portion
(prediaphragmatic) above the diaphragm (above the twelfth thoracic
vertebra) constitutes the thoracic aorta while that below (post-
diaphragmatic) constitutes the abdominal aorta.

The thoracic aorta (aorta thoracalis) is 7 to 8 inches (17.5 to 20
cm.) in length and is reduced in diameter from 23 mm., at the
beginning, to 21 mm., at the diaphragm. The branches are:

( Intercostal, nine pairs, for the lower nine intercostal spaces that

I supply the intercostal muscles, the vertebral column and the skin

v ■ , , of the back and sides of the thorax,

ranetai J 0 , .

I subcostal, one pair.

Superior phrenic, one pair; that supply the superior surface of the

L diaphragm.

(Esophageal, one pair.
Bronchial, four to five pairs.
Pericardial, three to four pairs.
Mediastinal, several.

The abdominal artery (arteria abdominalis) extends from the
twelfth thoracic vertebra to the fourth lumbar vertebra, is from 7 to
8 inches (17.5 to 20 cm.) in length and lies in the epigastric and
umbilical regions. Its branches may be divided into parietal and
visceral but they will be given in order of origin.

1. Inferior phrenic (two) parietal.

\ Gastric.

2. Celiac axis (one) visceral \ Hepatic.

[ Splenic.

3. Suprarenal (two) visceral.

4. First lumbar (two) parietal.

5. Superior mesenteric (one) visceral.

6. Renal (two) visceral.

7. Spermatic, or ovarian (two) visceral.

8. Second lumbar (two) parietal.

9. Inferior mesenteric (one) visceral.

10. Third lumbar (two) parietal.

11. Fourth lumbar (two) parietal.

r> -,. ,. -, f External (two) parietal.

12. Common mac (two) { T % . , . ,

( Internal (two) parietal and visceral.

13. Middle sacral (one) parietal.

The inferior phrenic arteries supply the inferior, or abdominal
surface of the diaphragm and give off a pair of superior adrenal
arteries.

236

THE BLOOD-VASCULAR SYSTEM

The celiac axis is only V2 inch in length but is of large caliber.
It supplies the liver, stomach, spleen, pancreas and part of the duo-
denum. Its branches are as follows: the left gastric, or coronary;
the splenic, which gives off the pancreatic, short gastric (vasa brevia)
and left gastroepiploic branches; the hepatic artery that gives off the
right gastric, gastroduodenal, right gastroepiploic and superior
pancreaticoduodenale arteries.

The suprarenal arteries supply the adrenal glands and represent
the middle suprarenal arteries.

The superior mesenteric artery supplies the duodenum, jejunum,
ileum, cecum, appendix, ascending and transverse colons. Its
branches are intestinal (ten to sixteen) for the jejunum and ileum;
the inferior pancreaticoduodenale; the middle colic; right colic, ileo-
colic and terminal, for the end of the ileum, cecum, appendix,
ascending and transverse colons.

THE BRANCHES OF THE ABDOMINAL AORTA 237

The renal arteries are two large arteries that supply the kidneys.
Each gives off the inferior suprarenals , ureteral, perinephric branches
and some branches to the lumbar lymph nodes.

The spermatic (testicular) arteries accompany the vas and pass
to the testes in the spermatic cords. Each gives off branches to the
ureter, peritoneum and lumbar lymph nodes.

The ovarian arteries, of the female, pass to the ovaries and uterus
through the broad ligament. Each gives off branches to the ureter,
peritoneum, lumbar lymph nodes to the uterine tubes, uterus and
its round ligament.

The inferior mesenteric artery is a large branch that supplies the
descending colon, iliac and pelvic colons and the upper third of the
rectum. Its branches are the left colic, sigmoid branches and the
superior hemorrhoidal arteries.

The four pairs of lumbar arteries correspond to the intercostal
arteries of the thorax. They supply the muscles and skin of the
dorsal and lateral portions of the abdominal wall.

The middle sacral artery is a small artery that passes along the
sacrum and coccyx and ends in the coccygeal gland.

The common iliac arteries represent the terminal branches of the
aorta and start at the middle of the fourth lumbar vertebra to the
left of the midline. The right artery is about 2 inches (5 cm.) in
length and the left is about 1% inches (4.3 cm.) in length. Each
divides into external and internal iliac arteries.

The internal iliac, or hypogastric artery (arteria hypogastrica),
arises opposite the sacroiliac articulation and passes into the pelvis
for about 1J-2 inches (3.7 cm.) before dividing into its terminal
branches. These arteries supply the greater part of the pelvic wall
and viscera, the buttocks, thighs and the external organs of repro-
duction. Each gives rise to parietal and visceral branches. The
parietal branches are as follows: The iliolumbar artery supplies
the iliacus, psoas and quadratus lumborum muscles and also the
vertebral canal. The lateral sacral artery supplies the pyriformis
muscle and also sends branches to the sacral canal and sacral nerves.
The superior gluteal artery leaves the pelvis and passes into the
buttock and lies on the deep surface of the gluteus maximus. It
gives off a number of muscular branches to the glutei, obturator
internus and tensor fascia; lata; muscles and nutrient vessels to the
hip bone. The obturator artery passes into the buttock and gives
off a number of muscular branches to the obturator internus, iliopsoas
and levator ani muscles; nutrient branches to the ilium; vesical
branches to the bladder; pudic branch that is mainly for collateral
circulation. These branches all arise within the pelvis. The
terminal part of the artery gives off branches to the obturator
externus and adjacent muscles, to the hip joint, head of the femur

238 THE BLOOD-VASCULAR SYSTEM

and ligaments. The internal pudic artery is a large branch that
enters the buttock and passes to the perineum. In the buttock it
supplies the neighboring muscles. In the perineum it gives off the
inferior hemorrhoidal artery that supplies the lower part of the rectum
and the anal canal; the perineal artery for the scrotum of the male,
or the labia of the female; the transverse perineal artery supplies the
sphincter ani, the sphincter vagina;, or bulbocavernosus muscle, the
bulb of the urethra, the corpus spongiosum and penile portion of
the urethra (in the male) and the bulb of the vestibule (in the
female) ; the profunda artery of the penis or elitoris supplies the corpus
cavernosum of the penis or clitoris; the dorsal artery of the penis or
of the elitoris supplies the dorsal portion of the penis or clitoris as
well as the corpus cavernosum and glans penis, or clitoris. The
inferior gluteal, or sciatic artery passes into the buttock and then
the upper part of the thigh. It gives of muscular branches for the
proximal parts of the hamstring muscles; coccygeal branch; cutaneous
branches to the skin; a branch that accompanies the sciatic nerve.

The visceral branches are as follows: (a) The superior vesical
artery supplies the upper part of the bladder. (b) The inferior
vesical artery supplies the base of the bladder, the seminal vesicles,
vas and prostate gland, (c) The artery of the ductus deferens accom-
panies the vas, supplies it and extends to the testicle, (d) The
middle hemorrhoidal artery gives branches to the seminal vesicles,
vas, prostate and terminates in the rectum where it supplies the
middle third, (e) The vaginal artery supplies the vagina and also
the rectum, bulb of the vestibule and base of the bladder. (J)
The uterine artery supplies the uterus, round ligament and the
vagina.

The external iliac artery (art. iliaca externa) is about 3^ to 4
inches (8.7 to 10 cm.) in length and ends at the thigh side of the
inguinal ligament. It gives rise to two main branches. The
inferior epigastric artery (art. epigastrica inferior) passes along the
medial side of the abdominal inguinal ring into the ventral ab-
dominal wall to the umbilical region where it anastomoses with
branches from the superior epigastric branch of the internal mam-
mary artery. It gives rise to muscular branches, an external spermatic
artery, cutaneous branches and a pudic branch. The deep circum-
flex iliac artery (art. circumtlcxa ilium profunda) passes toward the
ventral superior spine of the ilium and gives off muscular and
cutaneous branches.

The femoral artery (arteria femoralis) is the continuation of the
external iliac artery and extends from the inguinal ligament to the
lower part of the thigh where it passes through the adductor magnus
muscle. The first inch and a half was called the common femoral
and the remainder the deep and superficial portions. Its branches

THE POPLITEAL ARTERY AND SPACE 239

are as follows: (a) The superficial circumflex iliac artery (art.
circumflex ilium superficialis) supplies the lymph nodes of the
groin and the skin here, (b) The superficial epigastric artery (art.
epigastrica superficialis) passes to the ventral abdominal wall and
supplies the superficial fascia and skin in its course, (c) The super-
ficial external pudic artery (art. pudenda externa superficialis) sup-
plies the skin of the pubis, scrotal, or labial regions, (d) The
muscular branches pass to the adductors, pectineus, sartorius and
vastus medialis muscles, (e) The deep external pudic artery (art.
pudendar externa profunda) passes to the scrotum or labium majus.
(f) The deep femoral artery (art. profunda femoralis) is the largest
branch of the femoral artery and passes in between the deep muscles
of the thigh and gives rise to numerous branches. These are the
lateral circumflex, medial circumflex, muscular and four perforating
arteries. These are for the supply of the deep muscles of the thigh
and the perforating arteries pass to the dorsal part of the thigh and
anastomose with vessels there, (g) The anastomotic artery, or arteria
genu suprema, supplies the skin of the medial side of the leg muscles
near the knee and the knee joint.

The course of the femoral artery is indicated by a line drawn from
a point midway between the ventral superior spine of the ilium
and the symphysis pubis to the adductor tubercle on the medial
condyle of the femur. The superior two-thirds of this line represents
the femoral artery. The thigh should be abducted and rotated
laterally.

The popliteal artery (art. poplitea) is the continuation of the
femoral artery back of the knee; it lies in the popliteal fossa at the
distal end of which it divides into anterior and posterior tibial arteries.
It is deeply placed and gives rise to the following branches: Muscular
branches to the hamstring and upper leg muscles; articular (five)
branches to the knee joint; cutaneous branches to the skin of the
popliteal space.

The popliteal fossa, or space, is back of the knee joint and is of a
diamond shape. It is bounded superolaterally by the biceps;
inferolaterally by the lateral head of the gastrocnemius and plantaris;
supermedially by the semimembranosus, semitendinosus, sartorius
and gracilis; infcromedially by the medial head of the gastrocnemius.
The floor is formed by the popliteal plane of the femur, the dorsal
ligament of the knee joint and the fascia covering the popliteus
muscle. It contains the popliteal artery and its branches, the
popliteal vein, the termination of the external saphenous vein, the
common peroneal (external popliteal) and tibial (internal popliteal)
nerves, some lymph nodes and fat.

The course of the popliteal artery i^ indicated by a line drawn from
the outer margin of the semimembranosus muscle (at the beginning

240 THE BLOOD-VASCULAR SYSTEM

of the lower third of the thigh) to the middle of the popliteal space;
this indicates the upper part of the artery. The lower part Is repre-
sented by a line drawn from this point vertically downward to the
level of the tuberosity of the tibia.

The anterior tibial artery (art. tibialis anterior) is the smaller
branch of the popliteal artery and passes distally upon the ventral
surface of the interosseous membrane. It gives off the following
branches: (a) Fibular branch that supplies the soleus, peroneus
longus and skin of this region, (b) The posterior tibial recurrent
branch for anastomosis around the knee joint, (e) The anterior
tibial recurrent is for the same purpose and also supplies the tibialis
anterior and the tibiofibular articulation, (d) Muscular branches
for the muscles of the front of the leg. (e) Cutaneous branches for
the skin of the front of the leg. (/) Medial anterior malleolar branch
for the skin of the lateral malleolus and the ankle joint, (g) The
lateral anterior malleolar branch for the skin of that region and the
ankle joint and adjoining articulations.

The dorsalis pedis artery is the direct continuation of the anterior
tibial artery. It extends from the front of the ankle joint to the
base of the first interosseous space. Its branches are as follows:
(a) Cutaneous branches for the skin of the dorsum and medial side
of the foot, (b) Medial and lateral tarsal branches that supply the
extensor digitorum brevis and the articulations here, (c) The
arcuate artery arches across the bases of the metatarsal bones and
gives off first three metatarsal arteries; each of these divides into
digital arteries that supply the adjacent sides of the outer four toes.
(</) The first dorsal metatarsal artery arises from the dorsalis pedis
artery and supplies the two sides of the great toe and the medial
side of the next toe. (e) The profunda artery passes through the
foot to the plantar part and anastomoses with vessels there.

The course of the anterior tibial artery is indicated by drawing a
line from the inner side of the head of the fibula to a point midway
between the two malleoli. All of this line, except the first i>4
inches, represents the artery.

The course of the dorsalis pedis artery is indicated by drawing a
line from the point midway between the two malleoli to the base
of the first interosseous space.

The posterior tibial artery is the larger branch of the popliteal
artery. It lies between the superficial and deep muscles of the back
of the leg and extends from the lower margin of the popliteus muscle
to a point midway between the medial malleolus and the most
prominent part of the heel, where it divides into medial and lateral
plantar arteries.

It gives off the following branches: (a) Muscular brandies to the
soleus, tibialis posterior, flexor digitorum longus and flexor hallucis

THE PLANTAR ARTERIES 24.I

longus. (b) A fibular branch to the adjacent muscles and for
anastomosis around the knee joint, (c) The peroneal artery is its
largest branch and passes to the dorsal part of the lateral malleolus.
It gives off muscular branches to the muscles along its course; a
nutrient branch to the fibula; a communicating branch to the posterior
tibial artery; a perforating artery that passes along the inferior margin
of the interosseous membrane to the front of the ankle and anas-
tomoses with the vessels here. (</) The nutrient artery supplies the
tibia, (e) The communicating branch that communicates with the
peroneal artery. (/) Cutaneous branches for the skin of the medial
and dorsal surfaces of the leg. (g) The posterior medial malleolar
branch anastomoses with the corresponding branch of the anterior
tibial artery.

The course of the posterior tibial artery is indicated by drawing a
line from a point i inch below the center of the popliteal space to a
point midway between the medial malleolus and the most prominent
part of the heel.

The plantar arteries are medial and lateral.

The medial plantar artery ( art. plantar is medialis) is the smaller,
passes along the medial side of the foot to the head of the metatarsal
bone of the great toe; here it is joined by a branch of the dorsalis
pedis artery and supplies the medial side of the great toe and the
muscles, skin and articulations along its course. It also gives off
three branches that join the metatarsal branches of the lateral
plantar artery.

The lateral plantar artery (art. plantaris lateralis) is deeply placed,
courses toward the lateral side of the foot and at the base of the fifth
metatarsal bone it arches medially to the base of the first metatarsal
bone where it anastomoses with the dorsalis pedis artery. The
arched part constitutes the plantar arch.

The branches of the main vessel are as follows: (a) Muscular
branches to the muscles of the foot, (b) Cutaneous branches to
the, lateral side of the foot, (c) The media! calcaneal branch to the
skin and tissues of the heel. The arch gives off the following
branches: (d) Four plantar metatarsal arteries that form the digital
arteries that supply the adjacent sides of the four inner toes, (e)
Three perforating arteries that join the dorsal metatarsal arteries.
(/ Articular branches to the tarsal joints, (g) The fifth metatarsal
branch supplies the outer side of the little toe, the joints and tendon
sheathes along its course.

The course of the medial plantar artery is indicated by a line drawn
from the point midway between the medial malleolus and the promi-
nence of the heel to a point at the middle of the under surface of the
great toe. The course of the lateral plantar artery is indicated by a
line from the same starting point to a point about }2 inch internal

242

THE BLOOD-VASCULAR SYSTEM

to the tuberosity of the little toe. The plantar arch is indicated by
a line drawn from this point transversely across the foot to the base
of the first interosseous space.

VEINS (VEN.fi)

The blood passes from the arteries to the capillaries and then is
carried by the veins to the heart. The main veins are the superior

Superficial Temporal Vein Middle Temporal re/'n

Occip,tal

Posterior Huricu/ar V
Posterior Tac'al V.

Posterior Externa I Jufu/arV '.
External Jugular K

Fig. 179. — The

i o£ the right side of the head and neck.

and inferior venae cavae, the pulmonary veins and the azygos system.
The blood is returned from the head and neck chiefly by the
internal jugular veins (right and left) which correspond to the com-
mon carotid arteries. The blood that enters the cranial cavity by
means of the internal carotid and vertebral arteries is carried to the
venous sinuses of the skull (see the "Circulation of the Brain").
Of these sinuses the transverse sinus on each side continues as the

THE VEINS OF THE SUPERIOR EXTREMITY 243

internal jugular vein. This vein passes down the neck, in the carotid
sheath, and behind the sternoclavicular articulation each is joined
by the corresponding subclavian vein forming the innominate vein
of each side. The tributaries to each internal jugular vein are the
common facial, lingual, pharyngeal, superior and middle thyreoid
veins.

The common facial vein receives the blood from parts supplied
by several of the branches of the external carotid artery. The
anterior facial division corresponds to the external maxillary artery
while the posterior facial vein corresponds to the temporal and in-
ternal maxillary branches of the external carotid artery.

The lingual vein corresponds to the lingual artery.

The pharyngeal veins start at the venous plexus of the pharynx
and represent the various branches distributed to the pharynx.

The occipital vein corresponds to the occipital artery.

The superior and middle thyreoid veins correspond to the branches
of the superior thyreoid artery.

The external jugular vein is in the neck but it is a tributary of the
subclavian vein. This vein is formed, back of the angle of the
mandible, by a branch of the posterior facial and the posterior au-
ricular veins. This receives the transverse cervical, transverse scapu-
lar and anterior jugular veins and is usually quite large.

The blood of the superior extremity is returned ultimately by the
subclavian vein.

In the hand the blood is returned from the fingers by the superficial
volar and dorsal digital veins (a pair of each to each finger). These
vessels anastomose with each other on the dorsal and ventral por-
tions of the palm and through the palm and carry the blood to the
vessels of the forearm.

In the forearm there are two main (superficial) longitudinal venous
channels, the cephalic vein on the radial side and the basilic vein
on the ulnar side and occasionally a median vein on the ventral
surface. The cephalic vein starts from the radial side of the dorsal
venous arch of the palm and turns to the radial side of the ventral
surface; it continues to the cubital fossa and from there continues
up the arm on the lateral margin of the biceps muscle to the interval
between the deltoid and pectoralis major muscles, near the clavicle;
here it turns in and empties into the axillary vein of which it is a
tributary. In the cubital fossa it is connected to the basilic vein by
the median cubital vein which also connects it with the deep veins
of the forearm.

The basilic vein begins on the ulnar side of the dorsal venous
plexus of the hand and continues along the dorsal surface of the
forearm to the upper third of the forearm where it turns to the
ventral surface; it continues into the arm along the medial margin

244

THE BLOOD-VASCULAR SYSTEM

s

^\

of the biceps muscle, and at about the middle it pierces the fascia
and accompanies the branchial artery and in the axilla continues as
the axillary vein. The median cubital vein connects it to the cephalic

and deep veins of the forearm.
The median vein, when pres-
ent, starts at the plexus in the
palm, continues along the ven-
tral surface of the forearm and
at the cubital region receives
the deep median vein and then
divides into median cephalic
and median basilic veins that
empty into the corresponding
veins. The median cubital
vein is then absent.

Deep veins accompany the
various arteries (as vena com-
mites) and carry the blood to
the axillary vein.
""" The axillary vein {vena axil-
laris) starts at the lower mar-
i,-c v. gin of the teres major muscle
and is the direct continuation
v"" of the basilic vein. At the
lower margin of the first rib it
continues as the subclavian
vein. Its tributaries are the
cephalic vein and the vena com-
mites of the brachial artery.

The subclavian vein {vena
subclavia) extends from the
lower margin of the first rib to
the dorsal surface of the sternal
end of the clavicle where it is
joined by the internal jugular
vein to form the innominate.
Its main tributary is the ex-
ternal jugular vein.

The innominate veins are
spect right and left.

The right innominate vein
{vena innomyna dexter) is about
i inch (2.5 cm.) in length and extends from the medial extremity
of the right clavicle to a little inferior to the cartilage of the first
(right) rib. Its course is almost vertical and close to the right
margin of the sternum.

Median CephaJ/c
Ve,n r

Lateral Cutanea

CephaJia Vein -

-Superficial veins of the flexor
of the upper extremity.

THE SUPERIOR VENA CAVA

245

The left innominate vein (vena itmomyna sinister) is about 2j^
inches (6 cm.) in length and extends from the medial extremity of
the left clavicle obliquely downward and to the right to join the
right innominate vein to form the superior vena cava. This junc-
tion is just inferior to the first right costal cartilage. The tributaries
to the innominate veins are the vertebral, inferior thyreoid and internal
mammary veins.

The superior vena cava, or precava (vena cava superior), is about 3
inches (7.5 cm.) in length and extends from the inferior margin of

"RC<m. Co- flrt

"R Safari

Ih}.Tl««"'<1^

Lisflrt

181. — Arch of the aorta and its branches; the superior vei
the pulmonary arteries and veins.

id its tributaries;

the first right costal cartilage to the level of the upper margin of the
third right costal cartilage, where it empties into the right atrium
of the heart. Its course is vertical and its inferior half is within
the pericardium. In addition to the innominate veins it also
receives the vena azygos major.-

The superficial veins of the inferior extremity are the great and
small saphenous veins.

The great saphenous vein (vena saphena magna) begins at the
dorsal venous arch which is formed by the dorsal digital veins of
the foot. From the medial side of this arch the great saphenous
vein passes in front of the medial malleolus, along the medial margin
of the tibia to the back of the medial condyle of the femur; it then
gradually turns to the ventral surface of the thigh and at the fossa

246

THE BLOOD-VASCULAR SYSTEM

ovalis (saphenous opening) it passes through the deep fascia and
empties into the femoral vein. It receives tributaries from the
dorsum of the foot, the front and back of the leg, from the front and

femora/ rfrfery

Superficial fyi'fastrictfetr,

FemoraJ Vein

FlG. 182. — The superficial veins of the lower extremity
its tributaries. B, the small saphenous *

back of the thigh (the superficial femoral veins) and the superficial
circumflex iliac, superficial epigastric and superficial external pudic
veins.

The small saphenous vein (vena saphena parva) starts at the lateral

THE INFERIOR VENA CAVA 247

portion of the venous arch of the foot, passes back of the lateral
malleolus, up the dorsal surface of the calf to about its middle where
it pierces the fascia and passes to the popliteal space to empty
into the popliteal vein It receives tributaries from the back and
lateral surfaces of the heel and leg.

The deep veins of the foot and leg are two in number for each
artery and are called vena commitcs. In the popliteal space the
venae commites of the anterior and posterior tibial veins join to
form the popliteal vein. This vein receives the small saphenous
vein and tributaries that correspond to the branches of the popli-
teal artery.

The femoral vein accompanies the femoral artery and is the
continuation of the popliteal- vein. Its tributaries are the great
saphenous vein and vessels that correspond to branches of the
femoral artery.

The external iliac vein is the direct continuation of the femoral
vein and at the level of the lumbosacral articulation it is joined by
the internal iliac or hypogastric vein to form the common iliac vein
of each side. Its tributaries are the deep circumflex Viae and inferior
epigastric veins.

The internal iliac or hypogastric vein (vena hypogastrica) is short
and is formed by the junction of vessels that correspond to the
branches of the hypogastric artery. Its tributaries are superior and
inferior gluteal, inferior hemorrhoidal, lateral sacral, middle hemor-
rhoidal, uterine (two veins from the uterine plexus), vaginal (one
vein from the vaginal plexus), veins from the superior and inferior
vesical plexuses and the vesicoprostatic plexus, and the dorsal veins
of the penis, or clitoris.

The common iliac veins are right and left.

The right common iliac vein (vena iliaca communis dexter) is
smaller and more vertical in direction than the left. The tributaries
to each common iliac vein are the middle sacral (to the left) and the
iliolumbar s to both.

The inferior vena cava, or postcava (vena cava inferior) is formed
by the junction of the two common iliac veins on the right side of
the body of the fifth lumbar vertebra. It passes through the ab-
domen, through the diaphragm, enters the pericardium and empties
into dorsoinferior portion of the right atrium of the heart. Its
tributaries are the inferior phrenic, suprarenal, renal, spermatic, or
ovarian, lumbar and hepatic veins. (See Fig. 178.)

The inferior phrenic veins (two) return a part of the blood from
the diaphragm.

The suprarenal veins (two) return the blood from those glands.

The renal veins (two) return the blood from the kidneys. The
right renal vein is about 1 inch (2.5 cm.) in length and the left is about
3 inches (7.5 cm.) in length.

248

THE BLOOD-VASCULAR SYSTEM

The lumbar veins are four pairs of veins that correspond to the
four pairs of lumbar arteries.

The spermatic, or testicular veins (two) return the blood from the
testes. Each vein begins at the pampiniform plexus of veins upon
the spermatic cord, passes through the inguinal canal, enters the
abdomen and that of the right side empties into the inferior cava
while that of the left side empties into the left renal vein.

The ovarian vein of each side starts at the pampiniform plexus of
veins and terminates like the corresponding vein of the male.

-RCo» -Car. /Ire Ui-p*"**

_ L "Phrenic M

a Subclo*

\ fin.

Lisflrt

Fig. 183. — Arch of the aorta and its branches; the superior vena cava and its tribu-
taries; the pulmonary arteries and veins.

The blood that passes from the aorta through the celiac axis,
superior and inferior mesenteric arteries does not pass directly to the
inferior cava but passes first through the liver (through the portal
vein). The blood, after passing through the liver, leaves this organ
through two vessels called the hepatic veins; these open into the
inferior vena cava just before this vessel passes through the
diaphragm. This peculiar course constitutes the portal circulation.

The pulmonary veins are usually five in number, three right and
two left. These start at the root of the lung and the two left proceed
directly to the left atrium where they empty their blood. On the
right side the veins from the superior and middle lobes of the lung
usually unite to form one vessel and this and the vein from the inferior
lobe proceed directly to the left atrium where they empty their
blood.

THE AZYGOS VEINS

249

The azygos veins, three in number, collect the blood from most
of the intercostal spaces and serve to connect the superior and
inferior venae cava?.

The azygos major (vena azygos major) arises opposite the first
or second lumbar vertebra by a branch from the right lumbars,
right renals or inferior vena cava. It passes up the right side of
the vertebral column, through the aortic orifice in the diaphragm

Fig. 184. — The portal vein and its tributaries.

to the fourth thoracic vertebra where it arches over the root of the
right lung to empty into the superior vena cava. Its tributaries
are the lower ten posterior intercostal veins of the right side, the
right superior intercostal vein, the azygos minor veins, the right
bronchial vein and several veins from the esophagus, mediastinum
and pericardium.

The vena azygos minor inferior (vena hemiazygos) arises in the
abdomen by a branch from one of the left lumbar veins or from the

25°

THE BLOOD-VASCULAR SYSTEM

left renal vein. It enters the thorax through the left crus of the
diaphragm and passes upward to the ninth or eighth thoracic
vertebra where it passes across to the right and terminates in the
vena azygos major. Its tributaries are the lower one or two inter-
costals and veins from the esophagus and mediastinum.

MaJor: n J'

Fig. 185. — The azygos system of veins.

The vena azygos minor superior (vena azygos accessoria) is usually
small and joins the vena azygos major or the preceding vessel.

THE SYSTEMIC CIRCULATION

The general systemic circulation is as follows: The blood leaves
the left ventricle through the aorta and through the branches at

THE PORTAL CIRCULATION 25 1

the arch is distributed to the head, neck and upper extremities.
From the thoracic aorta it is distributed to the lesser organs and
walls of the thorax and partly to the lungs, from the abdominal aorta
to the walls and viscera of the abdomen and pelvis, and lastly to the
lower extremities. The blood from the head and upper extremities
is returned upon each side through the internal jugular and sub-
clavian veins respectively. On each side these form the innomi-
nate or brachiocephalic veins which join to form the superior vena
cava that empties the blood into the right atrium. From the lower
extremities the blood is returned by the two common femoral veins,
which continue as the external iliac veins in the abdomen and are
joined by the internal iliac veins to form the common iliac vein of
each side. The common iliac veins unite to form the inferior vena
cava which then receives the blood through the tributaries above
mentioned. The blood is then emptied into the right atrium.

The portal circulation is as follows: The blood leaves the aorta
through the celiac axis, superior and inferior mesenteric arteries.
From the celiac axis the blood passes to the liver, stomach, spleen,
pancreas and duodenum. From the inferior mesenteric artery it
passes to the pancreas, duodenum, jejunum, ileum, cecum, appendix,
ascending and transverse colons. From the inferior mesenteric
artery the blood passes to the descending colon, sigmoid flexure and
upper part of the rectum. The blood from the spleen, most of
that from the stomach, pancreas and duodenum is returned by the
splenic vein; that from the distribution of the superior mesenteric
artery by the superior mesenteric vein; that from the distribution
of the inferior mesenteric artery by the inferior mesenteric vein.
The inferior mesenteric vein joins the splenic vein and the splenic
vein then joins the superior mesenteric vein to form the portal
vein.

The portal vein (vena porta) is about 3 inches (7.5 cm.) long, passes
upward and to the left, enters the transverse fissure of the liver where
it divides into two main branches, the right and left lobar branches.

CHAPTER V
THE LYMPH VASCULAR SYSTEM

The lymp vascular system is in close relation to the blood vascular
system and through it the liquor sanguinis of the blood, as lymph,
comes into direct contact with the cells of the body. It differs from
the blood vascular system in several ways: (i) It contains no blood
but lymph. (2) The flow is in one direction, from the periphery
toward the center. (3) It is no true circulatory system as it has no
separate organ to force the lymph along. (4) Like the veins, many
of the lymph vessels possess valves but unlike veins these lymph
vessels are interrupted at frequent intervals by lymph nodes through
which the lymph must filter before it can course onward. These
lymph vessels communicate directly with the large serous cavities
of the body (peritoneal, pleural, pericardial, joint cavities, bursa?
and tendon sheaths) by means of stornata. These serous cavities
are really enormously dilated lymph spaces lined with endothelial
cells.

This system consists of lymph spares, lymph vessels, lymphatic
organs and the lymph.

Lymph spaces do not represent the beginning of the lymph vessel
system but here the lymph has its origin and passes from these
spaces into the vessels. They are mere tissue spaces and are not
lined with endothelial cells except in a few isolated instances, as
those around the ganglion cells of the sensor ganglia, and the large
lymph space above mentioned. There are three sets of these spaces:
(1) the intercellular, or pericellular; (2) the perineural, around the
nerves; (3) the perivascular, around the blood-vessels.

The lymph vessels (vasa lympkatica) vary in size, the smallest
being capillarics'tha.t are mere tubes of endothelial cells and varicose
in form. It is into these that the lymph passes directly from the
intercellular spaces. The next vessels are thin-walled and resemble
venules, and lastly, the largest are the lymphatic and thoracic ducts.
Certain structures as the brain, cartilage, epidermis, nails and avas-
cular structures are devoid of lymphatic vessels.

The lymphatic organs are the cistcrna chvli, lymph nodes, spleen,
thymus and tonsils, and lymphoid tissue comprising the diffuse form,
solitary nodules and Pcyer's patches.

Lymph nodes are collections of lymphoid tissue varying in size
from that of a pin head to that of a lima bean. They are scattered
152

CISTERNA CHYLI

L.J««V

ThorCcrf

throughout the body, being usually arranged in groups. The
lymph must filter through one or more groups before it enters the
blood vascular system.

The lymph is practically the liquor sanguinis of the blood con-
taining only the leukocytes, or white blood cells. It passes out of
the blood capillaries into the tis-
sue spaces, bathes the tissues
and cells, giving up its nutritive
elements and receiving effete ma-
terial in return. It then passes
through the walls of the lymph
capillaries entering here the real
vessel system. It then passes
into the larger vessels, through
one or more node groups and is
ultimately returned to the blood
vascular system by the right
lymphatic and thoracic ducts.
These empty into the right and
left subclavian-internal jugular
vein junctions, respectively.

Throughout the body the lym-
phatics are divided into a super-
ficial and a deep set. The super-
ficial set drains the outside of the
organs and the body, while the
deep set drains the muscles, bones
and deeper parts of the organs.
This will be further explained as
the various structures are dis-
cussed.

The receptaculum chyli (cis-
tema chyli) is a delicate, thin-
walled reservoir, 5 to 7.5 cm.
long and 6 to 8 mm. wide. It is
located in the abdominal cavity
on the right side of the first or
second lumbar vertebra between
the aorta and the vena azygos
major. This thin-walled struc-
ture is difficult to find when empty. It receives the lymph from
various regions through the following tributaries: two ascend-
ing lumbar trunks, two descending (lumbar) trunks, one com-
mon intestinal trunk and occasionally one retroaortic trunk. It is
drained by the thoracic duct.

CsChyH

-Cisterna chyli and thoracic
1L. first lumbar vertebra.

254 THE LYMPH VASCULAR SYSTEM

The thoracic duct is 15 to 18 inches (37.5 to 45 cm.) long and
starts from the cisterna chyli at about the first lumbar vertebra.
It passes up (cephalad) through the aortic orifice of the diaphragm
into the thoracic cavity (dorsal mediastinum) in the midline to the
level of the fifth or fourth thoracic vertebra where it crosses to the
left side of the vertebral column. It continues through the superior
mediastinum into the neck to the level of the seventh cervical verte-
bra where it curves downward over the subclavian artery and
empties into the angle formed by the left subclavian-internal jugular
vein junction. Its orifice is guarded by a valve and valves are
numerous along its course. The thoracic duct receives the lymph
from the lower extremities, the abdomen and its contents, the left
thorax, left lung and the left side of the heart, from part of the lower
half of the right thorax and from the left side of the head and neck
and the left upper extremity.

The right lymphatic duct (ductus lymphaticus dexter) is about
% inch in length. It is formed by the junction of the right sub-
clavian, the right jugular and right bronchomediastinal trunks and
empties into the right subclavian-internal jugular vein junction.
Its orifice is guarded by a valve. The right lymphatic duct receives
the lymph from the right side of the head and neck, the right upper
extremity, the right thorax (upper half), the right lung, the right
side of the heart and from part of the convex surface of the liver.

For the sake of convenience the lymphatic drainage of the body
will be considered in regions, as head and neck, upper extremity,
lower extremity, abdomen and thorax.

LYMPHATICS OF THE HEAD AND NECK

The lymphatics of the outside of the head and neck are divided
into superficial and deep. The node groups of the head are as follows
(those marked (S) are superficial and those marked (D) are deep):

1. Occipital (Lym phoglandulo? occipitalcs) (S). — This group con-
sists of one to three nodes in the occipital region on the upper part
of the trapezius muscle; these drain the occipital portion of the
scalp and their efferents carry the lymph to the upper deep cervical
nodes.

2. Postauricular (Lym phoglandula: auricularcs posteriores) (S). —
This group comprises usually two or three nodes near the mastoid
process of the temporal bone. These drain the posterior temporo-
parietal region, part of the pinna of the ear and the posterior wall of
the external auditory canal. Their efferents carry the lymph to
the upper deep cervical nodes.

3. Preauricular (L. auricularcs antcriores) (S and D). — The
superficial nodes are placed over the parotid gland and the deep are
within its substance. The latter are the more numerous. These

LYMPHATICS OF THE HEAD

255

nodes drain the eyelids, eyebrows, frontotemporal part of the scalp,
root of the nose, the front wall of the external auditory canal, part
of the pinna, the middle ear, soft palate, deep portion of the cheek
and back part of the nasal fossae. Their efferents drain into the
upper deep cervical nodes.

4. The superficial facial (L. facialis superficialis) (S). — This group
consists of three subgroups: (a) the infraorbital, or maxillary nodes

Su\j mental
Cerv

Jug Trim K

Fig. 187. — Lymph nodes and lymphatic drainage of the head and neck. Superficial nodes
indicated as circles and deep nodes in solid black.

in the infraorbital region; (b) the buccal or buccinator group in the
cheek; (c) the supramandibular group upon the mandible at the
anterior edge of the masseter muscle. These groups drain the eye-
lid, conjunctiva, skin and mucous membrane of the nose and cheek.
Their efferents carry the lymph to the submaxillary nodes and to
the upper deep cervical nodes.

5. Deep facial (L. faciales profunda) (D). — This group consists of
several nodes along the lateral wall of the pharynx near the internal

256 THE LYMPH VASCULAR SYSTEM

maxillary artery. These drain orbit, temporal fossa, the naso-
pharynx, palate, nasal fossa; and the cerebral meninges. Their
efferents pass to the upper deep cervical nodes.

6. Lingual (L. linguales) (D) nodes are at the base of the tongue
and are intervening nodes in the tongue drainage. Their lymph
passes into the upper deep cervical nodes.

The node groups of the neck are as follows:

Superficial cervical (L. cervicales superficiales) (S). — These com-
prise the external jugular group that lies upon the external jugular
vein just a little below the parotid gland. These nodes drain the
lower part of the pinna of the ear, the parotid region, the occipital
and mastoid regions and their efferents pass to the upper deep cervical
and supraclavicular nodes.

2. Submaxillary (L. submaxillares) (D). — This consists of three
to six nodes located in the submaxillary triangle. These drain the
superficial part of the nose, lower and front part of the face, upper
and lower lips, gums, anterior part of the margin of the tongue and
the floor of the mouth, either directly or through the facial and
submental nodes. Their efferents carry the lymph to the upper
deep cervical nodes.

3. The submental, or suprahyoid nodes (S) lie beneath the fascia
just within the symphysis of the mandible; they drain the skin of
the chin, skin and mucous membrane of the middle of the lower
lip, the gums, the floor of the mouth and the tip of the tongue.
Their efferents pass to the submaxillary and upper deep cervical
nodes.

4. The prelaryngeal nodes (D) are variable and when present are
found in front of the lower (tracheal) end of the larynx. They drain
the lower part of the larynx, the upper part of the trachea and the
thyreoid body. Their efferents carry the lymph to the upper deep
cervical nodes.

5. The pretracheal nodes (D) lie upon the front of the trachea
and receive the lymph from the trachea and thyreoid body. Their
efferents pass to the upper deep cervical nodes.

6. The retropharyngeal nodes (L. retropharyngeal) (D) lie behind
the upper part of the dorsal wall of the pharynx and drain the nasal
fossae, the nasopharynx and the auditory tubes. Their efferents
pass to the upper deep cervical nodes.

7. The deep cervical nodes, although the}- form an almost con-
tinuous chain, are divided into two sets, the upper and the lower.
Each group may be divided into medial and lateral subgroups.
The upper lie beneath the sternomastoid muscle (the lateral sub-
group) and upon the internal jugular vein (the medial subgroup).
These drain the occipital region of the scalp, the back of the neck,
the pinna of the ear, the tongue, larynx, trachea, thyreoid body,

THE LYMPHATICS OF UPPER EXTREMITY 257

nasopharynx, palate, nasal fossae, esophagus and face through the
above-mentioned node groups. The lower group lies in relation with
the lower part of the internal jugular vein (medial subgroup) and in
relation with the brachial plexus and the subclavian artery (lateral
subgroup). This group drains the back of the neck, scalp, the super-
ficial pectoral region in addition to receiving lymph from the upper
deep nodes. The lymph from the upper nodes passes partly to the
lower nodes and partly into a trunk that joins a similar trunk from
the lower nodes. These two trunks unite to form the jugular lymph
trunk upon each side of the neck. Upon the right side of the body
this trunk joins the subclavian trunk to form the right lymphatic
duct, while upon the left side it empties into the thoracic duct, or
directly into the subclavian-jugular vein junction.

THE UPPER EXTREMITY

The nodes and vessels of the upper extremity are superficial and
deep. They are as follows:

The superficial cubital nodes (L. cubitales superficiales) (S) are
the first nodes of the extremity. These are located upon the medial
side of the basilic vein just above the medial epicondyle. They
drain both surfaces of the hand and forearm and also its ulnar border.
Their efferents pass to the deep cubital or the lateral axillary nodes.

2. The Deep Cubital Nodes (L. cubitales profunda) (D). — Occa-
sionally some small nodes are found along the ulnar and radial
arteries. The deep cubital nodes, however, lie at the terminal part
of the brachial artery upon the volar side of the elbow; they drain
the deep structures of the hand and forearm. The efferents pass
to the lateral axillary nodes.

3. The axillary group \L. axillares) (D) comprises the following
subgroups:

(a) The lateral axillary nodes (one to six) lie along the axillary
vein. They receive the lymph, both superficial and deep, from
the ventral and dorsal pectoral regions either directly or through
the node groups previously mentioned. Their efferents pass to the
central axillary nodes and the subclavian group and even to the
lower deep cervical nodes.

(b) The ventral axillary, or pectoral nodes (two to four) lie
along the lower border of the pectoralis major muscle from the third
to the sixth intercostal spaces; they receive the lymph from the
superficial part of the ventral and lateral thoracic walls above the
umbilicus and the lateral two-thirds of the mammary gland. Their
efferents pass to the central, lateral and subclavian nodes.

(c) The dorsal axillary, or subscapular nodes lie upon the dorsal
wall of the axilla near the subscapular artery. They drain the

258

THE LYMPH VASCULAR SYSTEM

superficial parts of the dorsal and lateral walls of the thorax above
the level of the umbilicus and the lower part of the neck. Their
efferents carry the lymph to the central group, or to the subclavian
nodes, or even to the jugular trunk.

(d) The central axillary group consists of three to six large nodes
near the base of the axilla. They drain more or less completely the

bctav
VartlC

-Lymph nodes and lymphatic drainage of the upper i
and thoracic wall. RLD, Right lymphati

preceding groups. Their efferents carry the lymph to the subclavian
group.

4. The deltopectoral nodes (S) lie in the interval between the
pectoralis major and the deltoid muscles. They receive the lymph
from the outer side of the shoulder and arm. Their efferents pass
to the lateral axillary nodes, or the lower deep cervical group.

5. The subclavian nodes (infraclavicular) (D) lie upon the axillary
artery between the pectoralis minor muscle and the clavicle. They

THE LYMPHATICS OF LOWER EXTREMITY

259

HP&tecrj'c

receive the lymph from the upper extremity, ventral, lateral, and
dorsal thoracic walls and mammary gland. From these nodes the
subclavian trunk carries the lymph ir—
though some efferents may pass
to the lower deep cervical nodes.

Upon the right side the jugular and
subclavian trunks unite to form the
shortright lymphatic duct that empties
into the junction of the right sub-
clavian and internal jugular veins.
Upon the left side they may empty
into the thoracic duct, or into the
left subclavian-internal jugular vein
junction.

THE LOWER EXTREMITY

The lymphatics of the lower ex-
tremity are superficial and deep.
The node groups are as follows:

1. The anterior tibial nodes (D) is
inconstant and when the present is
located at the upper part of the
anterior surface of the interosseous
membrane. It receives the lymph
from the deep parts of the sole, the
dorsum of the foot and deep struc-
tures of the front of the leg. The
efferents pass to the popliteal nodes.

2. The popliteal nodes (L. poplitea)
(D) are four or five in number and
lie in the popliteal space around the
popliteal artery. They receive lymph
from the deep parts of the foot, deep
structures of back of the calf and from
the anterior tibial node, also from the
superficial structures of the lateral
part of the foot and heel and back 1
of the leg (parts drained by the ex-
ternal saphenous vein). The efferents
carry the lymph to the deep femoral
nodes. Occasionally a node is found where the small saphenous
vein pierces the deep fascia.

3. The inguinal nodes are divided into two sets, the superficial
and deep. The superficial inguinal nodes (L. ingninales superficiales)

9. — Lymph nodes and lymphatic
nage of the lower extremity.

260 THE LYMPH VASCULAR SYSTEM

consist of two sets, proximal and distal and they lie superficial
to the deep fascia. The superior, or proximal superficial inguinal
nodes, four to seven in number, lie just below the inguinal ligament
and above a horizontal line drawn through the middle of the
saphenous opening in the deep fascia. They receive the lymph
from the outer and back part of the thigh and buttock, the super-
ficial part of the abdominal wall (below the umbilicus), the anal
canal, the perineum, scrotum and penis of the male and the labia,
vestibule and vagina of the female. The lymph then passes into
the deep inguinal nodes.

The inferior, or distal superficial inguinal nodes lie below the
above nodes around the internal saphenous vein and number three
to six. They receive the lymph from the superficial parts of the
foot (not lateral), the sole (except the heel), inner, front and sides
of the calf, and all the superficial parts of the thigh except the upper
and outer parts. The efferents pass to the deep inguinal nodes.

The deep inguinal nodes (L. subinguinales profunda?), three to
seven, lie along the femoral vein. They receive the lymph from the
popliteal and superficial inguinal nodes as well as from the deep
structures of the outer and front portions of the thigh, also deep
parts of the clitoris and penis. The efferents carry the lymph
to the external iliac nodes of the abdomen.

THE LYMPH NODES OF THE ABDOMEN

The lymph nodes of the abdomen are divided into two groups, the
parietal and visceral. The parietal drain the deep structures of
the walls and extremities, while the visceral drain the viscera.
The groups are as follows:

Parietal Visceral

i. External iliac [ i. Celiac

2. Internal iliac Preaortic j 2. Superior mesenteric

3. Common iliac 1 3. Inferior mesenteric

4. Subaortic.

5. Lateral aortic

6. Retroaortic

1. The external iliac nodes consist of three chains, one lateral,
one intermediate and one medial to the external iliac artery. These
nodes receive the lymph from the lower extremity through the
various inguinal nodes, from the glans penis or the glans clitoris,
the deeper structures of the abdominal wall (below the umbilicus),
from the upper part of the vagina, cervix of the uterus, prostate,
bladder, membranous urethra, some from the internal iliac nodes
and from the structures along the course of the obturator artery.
The efferents carry the lymph to the common iliac nodes.

THE LYMPHATICS OF THE ABDOMEN

26l

2. The internal iliac, or hypogastric nodes (L. hypogastrica), sur-
round the internal iliac artery. They receive the lymph from the
pelvic viscera and the deeper structures of the perineum, buttocks,
posterior part of the thigh and urethra. The efferents carry the
lymph to the common iliac nodes.

A special group, the sacral nodes (L. sacrales) lies in the hollow of
the sacrum and drain the rectum, prostate and dorsal pelvic wall.
The efferent pass to the subaortic and lateral aortic nodes.

3. The common iliac nodes are arranged in groups in front, lateral
and medial to the common iliac artery. They receive the lymph
from the external and internal iliac nodes and send it to the lateral
aortic nodes.

4. The subaortic nodes (L. subaortic^) lie upon the ventral sur-
face of the fifth lumbar vertebra and receive part of the lymph from
the sacral and hypogastric nodes and pass the lymph to the lateral
aortic nodes.

5. The lateral aortic or lumbar nodes (L. lambales) comprise two
seis right and left, at the respective sides of the aorta. On each side
the nodes receive the lymph from the corresponding common iliac,
subaortic and hypogastric nodes; from the testicle, or ovary, oviduct
and body of the uterus; from the lateral abdominal muscles; from
the kidneys and adrenals. The chief vessels from these nodes are
the right and left ascending {common) lumbar trunks that empty the
lymph into the cisterna chyli.

262 THE LYMPH VASCULAR SYSTEM

6. The retroaortic nodes lie behind the aorta on the third and
fourth lumbar vertebrae. They receive lymph from the lateral and
preaortic nodes and the chief vessel from this group is the retroaortic
trunk that empties into the cisterna chyli.

The visceral nodes of the abdomen proper are the preaortic nodes
consisting of three main groups and a large number of subsidiary
groups.

1. The celiac, or middle suprapancreatic group consists of nodes
around the origin of the celiac axis artery. In addition there are
several subsidiary groups.

(a) The gastric group (L. gastricce) comprise the left ventral
gastric nodes that lie between the layers of the lesser omentum along
the left gastric artery; they drain most of the lesser curvature and
the neighboring parts of the ventral and dorsal surfaces of the stomach
and empty into the left dorsal gastric nodes.

(b) The dorsal paracardial nodes {right and left) lie around the
cardiac orifice and drain the cardiac end of the stomach and the
efferents pass to the left dorsal gastric nodes.

(c) The left dorsal gastric nodes lie upon the left gastric artery
and receive lymph from the cardiac part of the stomach and from
the above nodes. The efferents pass to the middle suprapancreatic
(celiac) nodes.

(d) The right gastroepiploic nodes lie along the right part of the
greater curvature of the stomach, receive lymph from that part and
pass the lymph to the subpyloric nodes.

(e) The subpyloric nodes are located at the end of the first part
of the duodenum and drain the pyloric part of the stomach and
receive lymph from the right gastroepiploic nodes. Their efferents
pass to the celiac group.

(/) The left suprapancreatic, or the pancreaticosplenic nodes are
distributed along the course of the splenic artery and drain the spleen
and the left portion of the stomach and empty into the middle
suprapancreatic or celiac group.

(g) The right suprapancreatic nodes lie upon the hepatic artery
and drain a part of the liver and the pyloric portion of the stomach.
The lymph then passes to the middle suprapancreatic or celiac
group.

(//) The biliary nodes lie along the bile duct and receive lymph
from the gall-bladder and liver and pass it to the celiac nodes.

(0 The hepatic nodes lie at the portal fissure of the liver, receive
lymph from the liver and pass it to the celiac nodes.

From the celiac, or middle suprapancreatic nodes the lymph is
carried by the celiac trunk to the common intestinal trunk and also
common lumbar trunks.

2. The superior mesenteric group is found around the origin of

THE LYMPHATICS OF THE INTESTINES 263

the superior mesenteric artery. Its subsidiary groups are: (a)
mesenteric, (b) ileocolic and (c) mesocolic nodes.

(a) The mesenteric nodes, comprising from 100 to 150, lie between
the layers of the mesentery. One group lies close to the intestinal
wall, another around the loops and primary branches of the artery
and a third along the main stem of the artery. The lymph from the
small intestine drains through the first group, then into and through
the second and then through the third group and is then carried
to the superior mesenteric nodes.

RPul-aC»<-iKl1

GaStric
■R CaStric

Supra|>o.n.

&

=*t m vV\°v

Fig. 191. — Lymph nodes and lymphatic drainage of the stomach.

(b) The ileocolic nodes, about twenty to thirty, form a chain along
the ileocolic artery. The main subgroups are the ileal, along the
ileal branch of the superior mesenteric artery; the ventral ileocolic
near the front of the cecum; the dorsal ileocolic, in the angle between
the ileum and the colon; the appendicular along the appendix and
paracolic along the medial side of the ascending and transverse colons.
These nodes drain the lower part of the ileum, cecum, appendix and
ascending colon and empty the lymph into the superior mesenteric
nodes.

(c ) The mesocolic nodes (part of the paracolic chain) are numerous
and lie in relation with the transverse colon. The lymph from the

264

THE LYMPH VASCULAR SYSTEM

transverse colon passes through these nodes and thence to the
superior mesenteric nodes. From the superior mesenteric group
the Ivmph is drained by the superior mesenteric trunk that helps to
form the common intestinal trunk.

3. The inferior mesenteric group lies at the origin of the inferior
mesenteric artery. The subsidiary groups are the (a) left colic,
(b) sigmoid, (c) pararectal.

(a) The left colic -nodes lie along the branches of the left colic
artery and drain the descending colon and empty into the inferior
mesenteric group.

(b) The sigmoid nodes lie along the branches of the sigmoid and
superior hemorrhoidal arteries and drain the sigmoid flexure of the
colon. The efferents carry the lymph to the inferior mesenteric
nodes.

J>uc*L

f

192. — Lymph nodes of the pancreas.

(c) The pararectal, or superior hemorrhoidal nodes lie in contact
with the muscle coat of the rectum and drain the upper part of the
rectum. The lymph then passes to the inferior mesenteric nodes.

From the inferior mesenteric nodes the lymph is carried by the
inferior mesenteric trunk to the common intestinal trunk.

The common intestinal trunk is the main tributary of the cisterna
chyli and receives the lymph from the above organs through the
celiac, superior and inferior mesenteric nodes and trunks.

The lymphatic drainage of the liver is quite complicated and
will therefore be given special consideration. There are two sets
of vessels superficial and deep. The superficial vessels of the convex
surface drain in three directions. Those of the left side drain into
the paracardial nodes of the gastric group; those of the middle pass

THE LYMPHATICS OF THE THORAX

26?

through the caval orifice of the diaphragm and empty into nodes at
the termination of the inferior vena cava; from the right side the
vessels drain into the celiac nodes. In addition some of the lymph
passes to the hepatic nodes; some into the inferior diaphragmatic
nodes to the internal mammary nodes and some to the dorsal
mediastinal nodes.

The superficial vessels of the visceral surface carry the lymph
chiefly to the hepatic nodes; some of the lymph from the dorsal part
of this surface is carried to the caval nodes above mentioned.

Fig. 193. — Ileal and ile

lymph nodes and lymphatic drainage.

The deep lymphatic vessels are the ascending that accompany the
hepatic veins and empty the lymph into the caval nodes, and the
descending that emerge at the portal fissure and empty the lymph
into the hepatic nodes.

THE THORAX

The lymph nodes of the thorax comprise two wain sets, parietal and
visceral.

Parietal. Visceral.

1. Internal mammary. 1. Ventral mediastinal.

2. Intercostal 2. Dorsal mediastinal.

3. Diaphragmatic. 3. Tracheobronchial.

266 THE LYMPH VASCULAR SYSTEM

Parietal. — I. The internal mammary, or sternal nodes (four to
eighteen) lie along the course of the internal mammary artery.
These receive lymph from mammary gland, the deeper structures of
the ventral thoracic and abdominal walls (to umbilicus) and dia-
phragm, from the liver through the ventral diaphragmatic nodes
and from the medial part of the mammary gland. The lymph then
passes through the internal mammary trunk that empties either into
the subclavian-internal jugular vein junction, or upon the right
side into the right lymphatic duct, or the right bronchomediastinal
trunk, and upon the left side into the thoracic duct.

2. The intercostal nodes (L. intercostales) lie at the lateral and
dorsal part of the intercostal spaces. They receive the lymph from
the deeper structures of the dorsal and lateral walls of the thorax.
The vessels from the lower four or five intercostal spaces usually
form a trunk on each side that descends into the abdomen to empty
into the cisterna chyli, or into the first part of the thoracic duct.
These are the descending lumbar trunks. The lymph of the left
upper intercostal spaces drains into the dorsal mediastinal nodes,
or into the thoracic duct, while upon the right side the lymph from
the corresponding spaces is emptied into the right lymphatic duct.

3. The diaphragmatic nodes comprise three groups, (a) ventral,
(b) middle and (c) dorsal.

(a) The ventral nodes lie behind the ensiform cartilage of the
sternum and receive lymph from the convex surface of the liver
and the ventral part of the diaphragm. The lymph then passes
into the internal mammary nodes.

(b) The middle nodes {right and left) lie where the phrenic nerves
enter the diaphragm. Some of the right nodes lie within the fibrous
pericardium. They receive lymph from the middle of the diaphragm
and some from the convex surface of the liver (and the right nodes).
The lymph then passes to the dorsal mediastinal nodes.

(c) The dorsal nodes lies at the dorsal part of the diaphragm and
receive lymph from the adjacent regions. The lymph then passes
partly to the lateral aortic nodes and partly to the dorsal mediastinal
nodes.

The visceral nodes are (1) ventral mediastinal, (2) dorsal mediastinal
and (3) tracheobronchial.

1. The ventral mediastinal (superior) nodes lie in front of the
arch of the aorta in the superior mediastinum. They receive lymph
from the thymus body through the thymic nodes and the lymph
vessels passing from these nodes assist in forming the right and left
bronchomediastinal trunk.

2. The dorsal mediastinal nodes (eight to twelve) lie behind the
pericardium near the esophagus and descending thoracic aorta.
They receive lymph from the esophagus, dorsal surface of the peri-

THE TRACHEOBRONCHIAL LYMPHATICS

267

cardium, diaphragm and the convex surface of the liver. Most
of the lymph passes to the thoracic duct and the remainder to the
tracheobronchial nodes.

3. The tracheobronchial nodes comprise jour groups, the right
and left tracheal and the intertracheobronchial, the bronchopulmonary
and the pulmonary.

Fig. 194. — Tracheobronchial lymph nodes.

(a) The right and left tracheal nodes lie upon the right and left
sides of the trachea.

(6) The intertracheobronchial nodes are found in the angle of the
bifurcation of the trachea.

(c) The bronchopulmonary nodes lie at the hilus of the lung.

(d) The pulmonary nodes are in the lungs in the angles where the
bronchial tube branches arise.

These nodes receive the lymph from the trachea, bronchi, lungs

268

THE LYMPH VASCULAR SYSTEM

and heart and some from the dorsal mediastinal nodes. The lymph
passes into vessels that unite with the vessels from the internal
mammary and ventral mediastinal nodes to form the right and left
bronchomediastinal trunks. These trunks usually empty into the
subclavian and internal jugular vein junction, of their respective
sides, but may empty into the right lymphatic and thoracic ducts,
respectively.

THE SPLEEN AND THYMUS BODY

Although the spleen and thymus are not usually described under
the lymphatic system the fact that they consist mainly of lymphoid
tissue seems to warrant their description here. They are usually
described under ductless glands but they are not of epithelial
structure.

The Spleen, Lien. — The spleen, usually called a ductless gland,
is located deeply in the left side of the abdominal cavity. It lies

ycntra-L bord-er

PlG. [95. — The visceral surface of the spleen showing its various areas. (From a photo-
graph.) a. Intermediate angle; 6, dorsal angle; c, ventral angle.

partly in the epigastric but mainly in the left hypochondriac regions.
It is about 5 inches (12.5 cm.) in length, 3 inches (7.5 cm.) wide and
i'4 inches (3 cm.) thick. It weighs about bl2 ounces (195 grams).
Its long axis usually conforms to th'e obliquity of the tenth rib. It
is irregular in shape but is said to be tetrahedral in form. It is
soft, of a dark brown color and very vascular.

The spleen has an apex, a base, two surfaces and three borders.
The apex is somewhat pointed and is about 1J2 inches (3.75 cm.)
from the midvertebral line. The base corresponds to the colic area
of the visceral surface and extends usually to the midaxillarv line.

^

THE SPLEEN 269

The parietal, or diaphragmatic surface is smooth and convex and
is in contact with the diaphragm. The visceral surface is irregular
and is divided into three areas by three ridges. The longest ridge
starts below the apex and extends nearly to the base. It separates
the larger, concave gastric area (above) from the smaller and flatter
renal area (below). On the gastric area is seen the hilus where the
vessels, nerve and lymph vessels, enter and leave. The triangular
base, or colic area, is the smallest and is bounded by the medial,
ventral and dorsal angles.

The ventral border is thin and notched and separates the dia-
phragm a t i c surface from the r
gastric area. The dorsal border is
thin and separates the diaphrag-
matic surface from the renal area.
This border corresponds approxi-
mately to the eleventh intercostal
space. The inferior border sepa-
rates the diaphragmatic surface
from the colic area.

The spleen is practically com-
pletely invested by peritoneum is
connected with the stomach by a
fold of peritoneum called the
gastrosplenic omentum. A fold of
peritoneum passes from the spleen
to the peritoneum ventral to the
left kidney; this is the licnorenal
ligament and through this the
splenic artery reaches the organ.
Another fold, the phrenicocolic
ligament, connects it with the
diaphragm. _ Fig 1Q0._0utl„

The spleen is outlined upon the body wail.

body as follows: Three points are

first determined: (i) i}^2 inches to the left of the tenth thoracic
spine; (2) in the eleventh intercostal space on a level with the first
lumbar spine and i inch medial to the level of the center of the crest
of the ilium; (3) in the ninth interspace in the midaxillary line. Join
the points one and two by a slightly curved line with the convexity
downward following the eleventh interspace (renal line) ; join points
two and three by a curved line with the convexity outward (colic
line); then continue the curved line from three to the upper border
of the ninth rib and follow this to the scapular line, then horizontally
across to the upper border of the tenth rib and then in a sharp curve
proceed to point one. It must be remembered that this gives the

270

THE LYMPH VASCULAR SYSTEM

anatomic outline, but this entire area does not give dulness upon
percussion as approximately the apical one-fifth is deeply placed.

The artery that supplies the spleen is the splenic artery. The
splenic vein returns the blood to the portal vein. The nerves are
from the splenic plexus derived from the solar plexus of the
sympathetic system.

The Thymus Body. — The thymus body, or gland is essentially an
organ of fetal life and early childhood. It is located in the lower
cervical and upper thoracic regions and in the latter place lies upon
the pericardium and great vessels. It weighs about 1 ounce (28

Fig. 197. — Ventral

child at birth.

grams) at birth but this is quite variable; it measures at that time
about 2 inches (5 cm.) in length, iH inches (3.75 cm.) in breadth
and ij£ inches (30 mm.) in thickness. It is pinkish in color and
consists of two unequal lobes. After the second year it does not
grow in proportion to the other organs of the body and gradually
loses its lymphoid structure and becomes more adipose in character.
Usually at puberty it is very small though it may be very large.

The arteries are usually from the inferior thyroid and internal
mammary arteries and its veins join the corresponding veins. The
nerves are derived from the sympathetic and vagal nerves.

CHAPTER VI

THE RESPIRATORY SYSTEM

The respiratory system comprises the nasal cavities, the pharynx,
larynx, trachea, bronchi, lungs and pleura.

THE NASAL CAVITIES

The nasal cavities (Fig. 198), two in number, extend from the an-
terior nares to the posterior nares, or choanee. The anterior nares, or
nostrils, lead into the vestibule. The lower part of the vestibule
is lined with heavy hairs, the vibrism, that protect the entrance.
The upper part of the vestibule is smooth and represents that
part of the nasal fossae lined by an extension of the skin, beyond
this area a mucous membrane exists. ' That part of the nasal cavity
above the vestibule is the olfactory portion as it is concerned with
the sense of smell. This portion is narrow and slit-like. The
remainder is expanded and constitutes the respiratory portion.

The floor of each cavity is formed by the palatal process of the
maxilla and palate bone and the soft palate. The lateral wall is
formed by the nasal bone, frontal process of the maxilla, lacrimal
bone, labyrinth of the ethmoid with its superior and middle conchal
processes, the vertical plate of the palate bone and the medial surface
of the medial pterygoid plate. The roof consists of the nasal and
frontal bones, the cribriform plate of the ethmoid, the body of the
sphenoid and the sphenoidal concha?, the sphenoidal process of
the palate bone and the ala of the vomer. The medial wall, or septum,
consists of the crests of the palate bones, below, the vomer, the per-
pendicular plate of the ethmoid, the nasal spine of the frontal bone,
and the cartilaginous septum, in front. The cavity is deepest in
the middle (going from front to back).

Upon the outer or lateral wall are three projections; the inferior
concha (the largest), the middle and superior (smallest) conchal
processes. The space between the floor and the inferior concha con-
stitutes the inferior meatus and has the nasal duct opening into it.
The space between the inferior concha and the middle conchal
processes is the middle meatus. As its front extremity is the iufun-
dibulum that leads into the frontal sinus and anterior ethmoidal
cells. In the middle of the outer wall is an opening that leads into
the maxillary sinus. Between the middle and superior conchal

272

THE RESPIRATORY SYSTEM

processes lies the superior meatus that communicates with the pos-
terior ethmoidal cells. Above the superior conchal process is a
small space called the sphenoethmoidal recess that communicates with
the sphenoidal sinus.

The choanae, or posterior nares, are the openings by which the
nasal cavities communicate with the pharynx. They are larger than
the nostrils.

Fig. 108. — Median sagittal section through the head and neck, a, Superior meatus of the
nose; 6, middle meatus of the nose; c. inferior meatus of the nose; d. Eustachian (torus tuba-
rius) cushion; e, orifice of auditory tube; /, palatoglossal fold; g. tonsil; h, palatopharyngeal
fold; k, arycpiglottic fold; /, ventricle of the larynx; in. vocal cord; K, vestibule of nose.

The pharynx connects the nasal and oral cavities with the larynx.
For a description see page 290.

THE LARYNX

The larynx, or organ of voice is situated at the lower part of the
pharynx between the trachea, below, and the base of the tongue,

Male

Female

44 mm.

36 mm.

43 mm.

41 mm.

36 mm.

26 mm.

136 mm.

112 mm.

THE LARYNX 273

above. It lies in the upper and front part of the neck where it causes
a projection in the midline that will be described later. It extends
from the lower border of the third cervical vertebra to the lower
border of the sixth cervical vertebra separated therefrom by the
pharynx. Its position depends upon the movements of the head and
neck during deglutition and singing. In the fetus it lies at a higher
level than in the adult. Up to puberty the larynx of the male is simi-
lar to that of the female. After this time the increase in the male
is greater, the cartilages enlarging, the thyreoid cartilage becoming
more prominent and the glottis nearly doubling its length. At this
time the voice of the male is uncertain and likely to break at un-
expected moments. The dimensions of the larynx are as follows:

Vertical
Transverse
Dorsoventral
Circumference

The larynx at its upper extremity is somewhat triangular in out-
line (base dorsally directed) and below, almost cylindric. It consists
of nine cartilages connected by ligaments and intrinsic and extrinsic
muscles. The cartilages are:

Single Paired

f Thyreoid ( Arytenoid

j Cricoid < Cuneiform

I Epiglottis [ Cornicula laryngis

The thyreoid cartilage (cartilage thyreoidea) is the largest and
consists of two lamella?, or ala?. The ventral borders of the als
meet, in their lower portions in front, at an angle of about 90°, in
the male and 1200 in the female. This junction produces a promi-
nence in the midline called the prominentia laryngca, or Adam's
apple, which is more noticeable in the male then in the female.
Above, these borders are separated by a V-shaped notch, the incisura
thyreoidea. The dorsal borders are thick and each extends upward as
a long cylindrical process, the superior cornu, and downward in a
shorter, heavier process, the inferior cornu. The superior cornua are
connected to the greater cornua of the hyoid bone, while the inferior
cornua articulate with the lateral surface of the cricoid cartilage.
Upon the outer surface of each ala is an oblique line that divides this
surface into two unequal portions. The inner surface of each is
smooth and to it is attached the mucous membrane of the larynx.
At the angle, on this medial surface, are attached, from above
downward, the epiglottis, the thyreoepiglottis ligament, the plica
ventrindaris, plica vocalis and lastly the thyreoepiglottic and thy-
reoarytenoideus muscles. To the curved upper border is attached

274

THE RESPIRATOR'S SYSTEM

the tkyreokyoid membrane and to the slightly curved lower border the
cricothyreoid membrane.

The cricoid cartilage, or signet ring {cartilago cricoidea), is smaller
but heavier and stronger than the thyreoid cartilage. It consists
of the lamina and arch. The lamina, nearly 2.5 cm. in height, is
dorsally placed and lies between the two alas of the thyreoid cartilage;
it exhibits a ridge in the midline that gives attachment to the esoph-
agus. On each side of this line is a shallow depression for attachment
of the cricoarytenoideus posterior muscle.

The arch constitutes the sides and front of the cartilage and is
about 5 to 6 mm. in height. It gives
attachment to the cricothyreoideus
muscle, in front, and the inferior con-
strictor of the pharynx, behind. At
the junction of the arch portion with
the lamina on each side is a facet for
articulation with the inferior cornua
i of the thyreoid cartilage.
If ' - II The upper border of the cricoid

I cartilages gives attachment to the
cricothyreoid membrane, n front
and at the sides and at the side
also to the cricoarytenoideus lateralis
muscle. The back part presents a
facet on each side of the midline for
articulation with the arytenoid carti-
lages. The lower border of the cricoid
cartilage is connected with the first
ring of the trachea.

The epiglottic cartilage {cartilago
cpiglottica) is somewhat leafshaped
and is attached by its lower smaller
end to the alar angle (upper part) by
the thyroepiglottic ligament. The
ventral surface is attached to the base of the tongue by the medial
and two lateral glossoepiglottic folds. Two little depressions are thus
produced one on each side of the medial fold and these are the
vallecula. The epiglottis protects the glottis of the larynx during
deglutition. From the side of the epiglottis the arye pi glottic folds
extend backward, on each side, to the arytenoid cartilage.

The arytenoid cartilages (cartilagines arytenoidew), two in number,
are small and articulate with the upper part of the cricoid cartilage.
Each has the form of a three-sided pyramid, having an apex, base
and three small surfaces. The apex is pointed and is in relation with,
or may be articulated with, the corniculum laryngis. The base

THE LARYNX

275

articulates with the cricoid cartilage. Two of the basal angles are
important. The lateral angle, or muscular process, gives attachment
to the cricoartenoideus posterior muscle. The ventral angle, or
vocal process, gives attachment to the inferior thyreoarytenoid
ligament, or the true vocal band. The dorsal surface gives attach-
ment to the arytenoideus muscle. Upon the ventrolateral surface
are attached the superior thyreoarytenoid ligament, or the false
vocal bands and the thyreoartenoideus muscle. The medial surface
forms the lateral boundary of the respiratory glottis.

The cornicula larynges (cartilagines corniculata) are two small
cone-shaped cartilages that surmount the
arytenoid cartilages at the dorsal end of the
aryepiglottic folds.

The cuneiform cartilages (cartilagines
cunciformes) are two, long, flat structures
located in the aryepiglottic fold.

Ligaments. — The larynx is connected to the
hyoid bone and the trachea by the extrinsic
ligaments. The cartilages are connected to
one another by the intrinsic ligaments. The
most important of the former is the thyreohyoid
membrane that extends between the thyreoid
cartilage and the hyoid bone. Its variation
in thickness gives rise to several subsidiary
ligaments. Of the intrinsic ligaments the
most important, from a surgical standpoint,
is the cricothyroid membrane. This extends
between the medial portion of the arch of the
cricoid and the thyreoid cartilages. It is not
of the same thickness throughout, thus giving
rise to subsidiary ligaments. It is here that the larynx is opened
in cases of obstruction of the glottis.

The interior of the larynx (cavum laryngis) is lined by a mucous
membrane. At the upper end of the larynx is located the superior
aperture (aditus laryngis) which is triangular in outline with its base
at the epiglottis and its apex at the apices of the arytenoid cartilages.
The aperture extends dorsally and downward and is bounded laterally
by the aryepiglottis folds. A short distance beneath the aperture
are seen the vocal bands. There are two on each side; the superior
fold is called the false vocal band, or plica ventricularis and contains
the superior thyreoarytenoid ligament. The inferior fold is the true
vocal band, or plica vocalis and contains the inferior thyreoarytenoid
ligament. On each side of the larynx between each pair of folds is a
depression or pouch called the ventricle of the larynx (ventriculus
laryngis). An extension upward and forward from each ventricle,

Interior of the
from the left.
entricularis; b,
plica vocalis.

276

THE RESPIRATORY SYSTEM

between the false vocal band and the thyreoid cartilage constitutes
the saccule (appendix ventriculi laryngis). That part of the cavity
between the true bands and the aperture is the vestibule of the larynx.
The rima glottidis is the narrow dorsoventral slit between the
true vocal folds. In the male this measures about 23 mm. in length
and in the female about 16 to 20 mm. The ventral three-fifths
constitutes the vocal portion (pars intermembranacea) and the dorsal
two-fifths is the respiratory part (pars intercartilaginea) . The shape
of each portion depends upon the movements of the vocal folds

during respiration and phona-
tion. The lower portion of the
cavity of the larynx constitutes
the body and this is nearly
cylindrical in shape.

The muscles of the larynx
are intrinsic and extrinsic. The
former serve to move the larynx
up and down while the latter are
connected with the processes of
phonation and respiration. The
intrinsic muscles are as follows:

Mm. cricothyreoidei (two) render

the cords tense.
Mm. thyreoarytenoidei (two)

relax the cords.
Mm. cricoarytenoidci posticuj

(two) open the glottis.
Mm. cricoarytenoidei lateralis

(two) close the glottis.
M. arytenoideus (one).

THE TRACHEA AND BRONCHI

The trachea or windpipe, extends from the lower border of the
sixth cervical vertebra to the upper border of the fifth thoracic verte-
bra where it divides into right and left stem bronchi. It is about 4}$
inches (11 cm.) long in the male and from 3^ to 4 inches (8.75 cm.)
in length in the female. It consists of two portions, cervical and
thoracic. It is nearly cylindrical in shape with the dorsal part
flattened. Its caliber in the living is 12.5 mm. transversely and 11
mm. dorsoventrally; in the cadaver it measures from 19 to 25 mm.
transversely. Its caliber is slightly greater in the middle than at
either end. It is composed of fifteen to twenty C-shaped plates of
cartilage separated from one another by white fibrous tissue and
mucous membrane.

The bronchi are two in number, right and left. That part to the

THE LUNGS AND PLEUR.-E 277

first branch constitutes the stem bronchus and the divisions are the
branch bronchi.

The right stem bronchus is about 1 inch (2.5 cm.) in length, makes
an angle of about 250 with the midline of bifurcation and enters the
right lung at the level of the fifth thoracic vertebra. It has a greater
diameter than the left and gives off three branches, one for each lobe
of the right lung. The first branch is called the eparterial bronchus.

The left bronchus is about 2 inches (5 cm.) in length and makes an
angle of about 460 with the midline of bifurcation. It enters the
lung at the level of the sixth thoracic vertebra. It gives off but two
branch bronchi, one for each of the two lobes of the left lung. The
first branch is called the hyparterial bronchus.

THE LUNGS AND PLEURA

The lungs (puhnoncs) two in number, are the real organs of respira-
tion. They occupy the bulk of the thoracic cavity and extend into
the neck; each lies in a completely closed serous sac, or space.
The right lung weighs about 22 ounces and the left lung about 20
ounces in the cadaver. In the bloodless condition, after electro-
cution, the weights are 8l2 ounces and 71; ounces, respectively.
Each lung is smooth and glistening and, at birth, of a pinkish color.
In adult life it is usually mottled, becoming darker as age advances.
Each lung is somewhat conical in shape and presents an apex, a
base, two surfaces and three borders.

The apex is blunt and projects out of the thoracic cavity into
the root of the neck to the extent of about 1 inch above the first
rib. The medial and ventral part is grooved by the subclavian
artery.

The base, or diaphragmatic surface is smooth, semilunar in shape
and concave fitting upon the dome of the diaphragm on each side.
The right dome of the diaphragm ascends higher than does the left
so that the concavity is deeper in the right lung.

The costal surface is smooth and convex and may show grooves,
corresponding to the ribs, in specimens hardened in situ. It is the
most extensive surface.

The mediastinal surface is triangular in shape and concave for the
accommodation of the heart and pericardium. A special part where
the vessels, nerves, lymph vessels and bronchi enter and leave is
noted and this is the root, or hilus. This surface differs in the two
lungs.

In the left lung the concavity is deeper. The root (radix pul-
monis) occupies a position a little behind and above the middle of
the surface. It is outlined by the reflections of the pleura and con-
sists of the bronchus and its branches, the pulmonary artery and

278 THE RESPIRATORY SYSTEM

veins, the bronchial artery and vein, nerves and lymphatics. In the
root the order of the chief structures is, from above downward, artery,
bronchus, vein. At the lower part of the root the two layers of
pleura that bound the root come together, continue to the base and
extend from the lung to the mediastinal pleura as a band called
ligamentum latum pulmonis. Above the root is seen the aortic groove
caused by the arch of the aorta; from this groove the subclavian
groove extends upon the apex; ventral to this groove is seen another
made by the left innominate vein. The aortic groove is seen extend-
ing downward along the dorsal part of this surface.

In the right lung the root has the same general position, appear-
ance and structures. The order, however is different; from above

Fig. 202. — Medial surface of the luntrs. A. Right lung; B. left lung, a. Groove for the
right innominate vein; b, groove for the innominate artery; c groove for left subclavian
artery; d, groove for left innominate vein; e, e, lig. latum pulmonis; /, /, pulmonary arteries;
g. g. bronchi; h, h, pulmonary veins.

downward we find bronchus, artery and vein. The ligamentum
latum pulmonis is present. Above the root is a deep groove that is
formed by the vena azygos major as it hooks over the root to empty
into the superior vena cava; above and passing outward is a deep
groove for the superior vena cava and right innominate vein;
behind the latter the innominate artery may form a groove. At the
dorsal part of this surface may be a long groove formed by the
esophagus.

The borders are ventral, dorsal and inferior, or basal. The ventral
border is thin and sharp and upon the left lung presents a notch
called the incisura cardiaca. The dorsal border is rounded, thick

THE PLEURAL REFLECTIONS 279

and rests in the deep concavity at the side of the vertebral column.
The basal border is sharp and thin, separates the base from the other
surfaces and extends into the costophrenic sinus.

The right lung contains three lobes, the upper, middle and lower
and two fissures while the left lung presents two lobes, upper and lower
separated by the one fissure. The lines for the fissures will be given
later.

As previously mentioned each lung is in a closed serous cavity the
pleural cavity. The serous membrane bounding this space is called
the pleura. The pleura is divided into portions according to parts
invested, as visceral, that investing the lung, and parietal, that
attached to the ribs, diaphragm and pericardium, thus bounding
each pleural cavity. The visceral pleura invests the lungs except at
the root where the layers are separated by the structures entering
and leaving the lung. At the lower limit of the root the layers
approximate and constitute the ligamentum latum pulmonis. The
visceral pleura extends into the fissures and completely separates
the lobes from each other.

The parietal pleura consists of several subdivisions: that covering
the inner surfaces of the ribs, cartilages and intercostal muscles
and membranes constitutes the costal pleura; that upon the dia-
phragm is the diaphragmatic pleura; that toward the midline upon
the pericardium constitutes the mediastinal pleura, while that portion
that covers the apex of the lung in the neck is the cervical pleura.
These pleural reflections forming a closed sac constitute a continuous
layer of endothelium and it is possible to start at any point and
return after passing over the various divisions without an interrup-
tion in the serous membrane. The surface is constantly kept moist
with lymph so as to prevent friction.

As will be seen later the lungs do not extend down completely
into the cleft between the diaphragm and body wall; this serous
space unoccupied by lung is called the costophrenic sinus. It is
deepest in the midaxillary line.

The outline of the pleura upon the body wall is as follows: From
a point '2 to 1 inch (1 to 2.5 cm.) above the clavicle over
the sternal end of the first rib, draw a line to the midsternal line to
pass under the sternoclavicular articulation. On the right side
continue this line down to the level of the sixth ehondrosternal junc-
tion, then obliquely outward to the tenth rib, or interspace on the
midaxillary line and then horizontally across to a point between
the spine of the twelfth thoracic vertebra and the transverse process
of the first lumbar vertebra. From this point carry a line verti-
cally to the upper border of the third thoracic vertebra and then
arch across to the apex point. The right apex is about \ ■> inch higher
than the left apex.

28o

THE RESPIRATOR'S SYSTEM

On the left side where the apex line reaches the midsternal line
continue down to the level of the junction of the fourth cartilage

Fig. 203. — Outline of pleura? aid lun^s upon the ventral thoracic wall.
i/» !»! a photograph.) A, Area of superficial cardiac dullness.

Fu;. J04.— Outline of pleura and lungs upon the dorsal thoracic wall. (From a photograph.)

with the sternum then turn out to the edge of the sternum and down
to the level of the sixth chondrosternal junction, then outward
to the upper border of the tenth rib in the midaxillary line, thence

THE PLEURAL REFLECTIONS 26l

across to a point midway between the twelfth thoracic spine and
the transverse process of the first lumbar vertebra. Then continue
vertically upward to the level of the upper border of the third
thoracic vertebra and then arch across to the apex point.

To outline the lungs draw a line from the apex point to the mid-
sternal line passing beneath the sternoclavicular articulation and
just within the pleural line. On the right side the edge of the lung
follows the pleural line to the sixth chondrosternal junction, then
passes obliquely downward and outward to cross the eighth rib
on the midaxillary line, then horizontally across to the level of the
tenth thoracic spine and up along the vertical pleural line to the
apex point. On the left side follow the pleural line from the apex
point to the midsternal line, then down parallel to the pleural
reflection to the level of the fourth chondrosternal junction, then
outward in a curved line so that the deviation is about 5 cm. from
the midsternal line in the fourth interspace; then curve toward the
sternum for about 2.5 cm. thence downward and outward to cross
the eighth rib in the midaxillary line, across to the level of the tenth
thoracic spine, up parallel to the pleural line to the apex point.

To outline the main fissure start on the back at the level of the
transverse process of the third thoracic vertebra, pass obliquely
down so as to reach the lower border of the lung at the parasternal
line. This separates the upper from the lower lobe. On the right
side the intermediate fissure starts from the main fissure at the
midaxillary line and crosses the front of the thorax practically hori-
zontally to the junction of the fourth cartilage with the sternum.
This fissure separates the upper from the middle lobe.

CHAPTER VII

THE ALIMENTARY TRACT (APPARATUS DIGESTORIUS)

The alimentary tract is a tube-like structure about 30 feet in length
extending from the lips to the anus. Here the food is mechanically
and chemically treated (digested) so that it is capable of absorp-
tion. The caudal portion of the apparatus receives and expels the
undigestible portions of the food. In addition to the tube are
various organs that lie in the wall of the tube or lie outside and are
connected to the tract; these are the accessory organs. All of the
tract caudal to the pharynx is called the tubus digestorius. The
parts of the alimentary tract are as follows:

f Aperture
Mouth \ Vestibule

I Oral cavity proper

Pharynx

Esophagus

Stomach

Small intestine

C Duodenum
\ Jejunum
[ Ileum

Accessory organs
(■ Teeth

Gums
\ Tongue

Salivary glands
I Tonsils' (?)

/ Liver
I Pancreas

Large intestine

Colon

Cecum and appendix
ascending
transverse
descending
I sigmoid

Rectum

Anal canal

Anus

THE MOUTH

The mouth comprises the aperture, vestibule and oral cavity proper
and here are found the accessory organs, the teeth, tongue, gums and
oral salivary glands.

The aperture (rima oris) is the narrow slit between the lips (labia
oris). It is placed transversely and is bow-shaped. It is about 2
inches (5 cm.) in length and extends from the first premolar of one
side to the corresponding premolar of the opposite side.

THE VESTIBULE

283

The vestibule (vestibulum oris) in a state of rest is a narrow, slit-
like cavity that lies between the lips and cheeks (buccal) externally,

■Fig. 20s. — A diagram of th

ntary tract.

and the teeth and gums, internally. The lips bounding the aperture
and vestibule consist of skin externally and mucous membrane

THE ALIMENTARY TRACT

internally. Between these lie the muscles, fat and white fibrous
tissue supporting blood-vessels, nerves and lymphatics. In the
mucous-membrane side lie numerous small labial salivary glands.
Internally, each lip is connected to the gum by a delicate fold of
mucous membrane, the frenum; that of the upper lip is the larger.

The cheeks (buccal) consist of skin externally and mucous mem-
brane internally. Between these lie the muscles, fat and white
fibrous tissue and the buccal salivary glands, besides blood-vessels,
nerves and lymphatics. In the infant, in the superficial fascia, is
an encapsulated mass of fat called the corpus adiposum bucccr, or
sucking pad. It is of great importance as it strengthens the cheek
during nursing. In the adult it is less prominent.

The gums ( gingiva) constitute the
mucous membrane covering the
alveolar portions of the maxillae and
mandible. They consist of a firm
red tissue about i or 2 mm. thick.
They are quite vascular, are firmly
attached to the periosteum and ex-
tend about the base of the crown of
each tooth in the form of a collar.

The vestibule communicates with
the mouth cavity by the small spaces
between the teeth and a large space
behind the last molar teeth. On the
inside of the cheek, opposite to the
second upper molar tooth, is a papilla
where the parotid duct empties its
secretion into this vestibule.

The oral cavity proper is bounded
above by the palate, below by the
tongue and floor, or sublingual region
and laterally and in front by the teeth and gums. The dorsal wall
is wanting, constituting the communication with the pharynx.

The palate (palatum) consists of two portions, hard and soft.
The hard palate (palatum durum) constitutes the ventral two-thirds
of the roof and is nearly horizontal in direction. It is formed by
the palatal processes of the maxillae and the palate bones and is
covered by a mucous membrane and shows a ridge in the midline
called the raphe; some transverse folds, the ruga: [plica palatina-)
are seen. The soft tissues contain the palatal salivary glands.

The soft palate {palatum molle) constitutes the dorsal one-third .
of the roof and it slopes downward (caudad) and backward. The
dorsal free edge consists of two lateral arches produced by the
downward projecting, cone-like process of the middle of the soft

Fig. 206. — Mouthopened. ,1.1'alat
oglossal fold; B. palatopharyngeal fold
c, tonsil; D, uvula.

THE TEETH 285

palate called the uvula. This part varies in length in different
individuals. The ventral edge of the soft palate is attached to the
hard palate the upper and lower surfaces are covered by mucous
membranes that become continuous at the free edge. Between
these mucous membranes lie the palatal aponeurosis (attached to the
hard palate) and the muscles of the palate (in the posterior two-
thirds of the soft palate). Extending downward from the palate,
are two folds on each side, the arches, that will be described later.

The muscles of the soft palate are the mm. tensor veil palatini,
levator veil palatini, glossopalatinus, pkaryngopalatinus and uvula, all
paired.

The blood supply of the palate is from the descending palatine
branch of the internal maxillary artery, the ascending palatine
artery and branches from the ascending pharyngeal and dorsalis
lingua? arteries.

The sensor nerves are from the sphenopalatine ganglion. These
are the anterior, middle and posterior palatine nerves; the motor
nerves for all muscles, except the tensor veli palatini, come from the
spinal accessory nerve through the pharyngeal plexus. The tensor
veli palatini is supplied by the motor portion of the trigeminal nerve
through the otic ganglion.

The floor of the mouth consists of the tongue and the sublingual
region. The sublingual region, or true floor, consists of the tissues
between the anterior part of the base of the tongue and the mandible.
Connecting the tongue to the floor in the midline is a small fold of
mucous membrane, the frenulum lingua;. On each side of this fold
is a little papilla (caruncula sublingualis) in which is the orifice of
the submaxillary duct.

Extending from the papilla on each side is a fold of mucous mem-
brane, the plica sublingualis, in which are seen numerous openings
representing the orifices of the sublingual ducts.

The teeth (denies) are the organs of mastication. During life
there are two sets, temporary and permanent. The temporary, or
deciduous teeth (denies decidui), are twenty in number and begin
to erupt about the sixth or seventh month and are all present at
about the twenty-fourth to the thirtieth month. In each jaw are
found central incisors (two), lateral incisors (two), canines (two) and
molars (four). In the permanent set (denies permanentes) there are
thirty-two teeth. In each jaw are found two central incisors, two
lateral incisors, two canines, four premolars and six molars. These
teeth begin to erupt at about the sixth year and all are present at
about the twenty-first to the twenty-fifth year.

Each tooth consists of a central cavity (cavum dentis) surrounded
by the dentin (substantia cburnea) that gives the form to and consti-
tutes the bulk of the tooth. That portion of the tooth projecting

286

THE ALIMENTARY TRACT

beyond the line of the alveolar socket of the jaw is the crown (corona
dentis) and is covered by the enamel (substantia adamantina); that
portion covered by the gum is the neck (collum dentis) while that part

\ » —Enamel

Fig. 20S. — Mandible with the permanent teeth
canine; D. premolar

1, Ce
, mola

within the alveolar process constitutes the root {radix dentis). The
root is held in the alveolar socket by the peridental membrane (peri-
osteum aheolare). At the apex of the root is an opening (foramen
apicis) that leads into the root canal (canalis radicis) that terminates

THE TONGUE 287

in the pulp cavity (cavum dent is). The latter is occupied by the
tooth pulp (pulpa dentis). The part of the tooth that opposes that
of the other jaw is called the fades masticatoria.

The incisors (denies incisivi) are chisel-like teeth and those of
the upper jaw are larger and stronger than those of the mandible.
The root of each tooth is flattened laterally.

The canines (denies canini) are pointed, or conical in shape and
are stronger than the incisors. They represent the holding and
tearing teeth of the lower animals. The rcot of each is nearly conical
and longer than that of the incisor tooth.

The premolars (denies premolares) exhibit two little projections
or cusps upon the crown the latter being more massive than in the
preceding teeth. The root of each tooth is usually single and
flattened from side to side.

The molars (denies molares) are the most massive teeth; the crowns
are cuboidal and the cusps three to five in number. Each upper
tooth possesses three roots while each lower but two roots. The
third molar, or wisdom tooth, is called the dens serotinus.

In the normal condition the teeth form an arch in each jaw the
dental arch (arcus dental is). The upper is slightly the larger and
therefore slightly overlaps the lower arch.

The tongue (lingua) is the most mobile organ in the body. It
has the following important functions: Mastication, insalivation,
deglutition, taste and speech. In order to get the proper shape and
dimensions of the tongue it must be hardened in situ. It is about 9
cm. ($li inches) in length and lies in the oral cavity proper and
oropharynx. It consists of apex, base, dorsum, inferior surface and
margin.

The apex, or tip (apex lingua) is the free extremity and is usually
narrow and thin, resting against the incisor teeth.

The base, or root (radix lingua) is the attached portion and is
broad and massive. It is directed downward (caudad) and back-
ward and is attached to the hyoid bone, mandible and floor of the
mouth.

The dorsum (dorsum lingua:) consists of two parts, the anterior,
or apical two-thirds and posterior, or basal one-third. The apical
two-thirds, or oral part, is nearly horizontal and slightly arched from
before backward and from side to side. It may show a slight
median, longitudinal groove (sulcus mediants) that ends posteriorly
in the foramen cecum. The apical two-thirds is separated from the
basal one-third by a slight V-shaped groove, the sulcus lerminalis,
the apex of which is the foramen cecum. In front of the sulcus is a
V-shaped collection of papilla, eight to ten in number, below the
surface, called the vallate papilla:. These contain the taste-buds.
Scattered over the dorsum are smaller, conical projections, the

THE ALIMENTARY TRACT

tUUfonn papilla'; a third variety, the fungiform papilla are less
numerous than the filliform and are found chiefly at the sides and
apex.

The basal one-third, or pharyngeal part of the tongue, is nearly
vertical in direction. Papilla? are not found here but rounded ele-
vations, that represent masses of lymphoid tissue below the mucosa,
are present. These constitute the lingual tonsil (tonsilla lingual is).

The dorsum of the base is connected to the epiglottis by three folds,
two lateral (plica; pharyngoepiglotticm) and one median (plica glosso-
epiglottica), the glossoepiglottic folds. Between the median and each
lateral fold a little fossa is formed, the vallecula.

The inferior surface (fascies inferior) of the tongue is not extensive.
Here is seen a part of the frenulum lingua? and upon each side of

Fie. 209. — Do

ith the epiglottis

this a slight fold of mucous membrane, the plica fimbriata. Near
the tip there may be a slight elevation that indicates the presence
of the apical gland.

The margin (margo lateralis) of the tongue is free in front of the
anterior arches of the fauces and separates the dorsum from the
inferior surface. The tongue is covered by a mucous membrane.
The bulk of the organ consists of voluntary striated muscle tissue.
The muscles comprise two sets, the intrinsic and the extrinsic.
The intrinsic muscles are the superior and inferior longitudinal,
the transverse and the vertical lingual muscles. The extrinsic are
the hyoglossus, genioglossus, glossopalatinus, styloglossus and choudro-
glossus. In the tongue are numerous small glands, the lingual
salivary glands (gland nice linguales).

THE ORAL SALIVARY GLANDS

289

The arteries are the lingual, external maxillary and ascending
pharyngeal. The nerves are the hypoglossal, glossopharyngeal,
chorda tympani, the lingual branch of the mandibular division of the
trigeminal and the internal laryngeal branch of the vagus.

The principal oral salivary glands {glandule salivares) are six
in number, two parotid, two submaxillary and two sublingual.

The parotid gland (glandula parotis) is the largest and weighs from
20 to 30 grams. It lies upon the side of the face and chiefly in front
of the ear. It is bounded above by the zygomatic arch, below by the
angle of the mandible and a line extending back to the mastoid

Fig. 210. — The oral salivary glands in their normal positions.

process. In front it extends a little distance over the masseter
muscle, behind to the external auditory canal and sternomastoid
muscle. The deepest and thickest part is wedge-shaped and in
close relation with the great vessels of the neck. This constitutes
the processus retromandibularis and occupies the so-called parotid
fossa. Within the gland are important vessels and the facial nerve
and its branches.

The parotid duct {ductus parotideus) extends from the upper
anterior part of the gland, is 5 to 6 cm. in length and empties into
the vestibule opposite the second upper molar tooth. This duct

290 THE ALIMENTARY TRACT

corresponds approximately to the middle third of a line drawn from
the lower margin of the external auditory meatus to the middle of
the upper lip.

The blood supply of the parotid gland consists of branches from
the external carotid artery and other arteries in relation with the
gland.

The nerves are from the great auricular, facial, auriculotemporal
(from otic ganglion) nerves and the external carotid plexus of the
sympathetic system (the latter are chiefly vasomotor).

The submaxillary gland (glandula submaxillaris) weighs 8 to 10
grams and is located under the middle of the body of the mandible
in the submaxillary triangle. A process of the gland usually extend
forward and medially.

The submaxillary duct (ductus submaxillaris) is about 5 cm. long
and empties into the oral cavity at the side of the frenum lingua
at the apex of the caruncula sublingualis.

The submaxillary gland receives its blood supply from the external
maxillary artery. The nerves are from the chorda tympani and the
lingual nerves, from the submaxillary ganglion and the external
maxillary plexus.

The sublingual gland (glandula sublingualis,) 3 to 4 grams in
weight, is a collection of glands in the floor of the oral cavity upon
each side of the frenum. They form a mass from 35 to 45 mm. in
length. The ducts (ducti sublinguales minor es) may be fifteen to
twenty in number upon each side and empty into the oral cavity on
the plica sublingualis.

The blood supply of the sublingual glands consists of the sublingual
(from the lingual), the submental (from the external maxillary)
arteries. The nerves are derived from the lingual and chorda tym-
pani nerves through the submaxillary ganglion and from the
external maxillary plexus.

In the mouth cavity the processes of digestion that take place
are mastication and insalivation.

The pharynx is somewhat funnel-shaped but flattened from before
backward. It extends from the base of the skull to the sixth cervical
vertebra, behind, and the cricoid cartilage, in front. It is 5 to 5H
inches (12.5 to 14 cm.) in length and widest in the upper part behind
the orifices of the auditory tubes. The nasopharynx is about 3 cm.
long, the oropharynx 5 cm. and the laryngopharynx about 7 cm.
long. From the incisor teeth to the esophagus is about 5^ to 6>£
inches. Dorsoventrally the nasopharynx is 15 to 18 mm., from the
septum of the nose to the dorsal wall; from the glossopalatal arches
to the dorsal wall about 10 mm.; below this the wall approach each
other. The transverse dimension at the lateral recesses is 35 mm.;
opposite the middle of the soft palate 25 mm.; opposite the inferior

THE PHARYNX

29I

margin of the laryngeal opening 45 mm.; below this it narrows to
the esophagus.

The pharynx is attached from above downward to the pharyngeal
spine, basioccipital, petrous portion of the temporal bone, auditory
tube, internal pterygoid plate, pterygomaxillary ligament, mylohyoid
ridge, mucous membrane of the mouth, base of the tongue, hyoid

Fig. 211. — Median sagittal section through the head and ncek. a, Superior meatus of the
nose; b, middle meatus of the nose; c, inferior meatus of the nose; d, torus tubarius (eusta-
chian cushion); e, orifice of auditory tube;/, palatoglossal fold; g. tonsil; h. palatopharyn-
geal fold; k, aryepiglottic fold; e, ventricle of the larynx; m, vocal cord; n, vestibule of nose.

bone and thyreoid and cricoid cartilages of the larynx and below it
becomes continuous with the esophagus.

The pharynx is divided into the nasopharynx, oropharynx and
laryngopharynx.

The nasopharynx (pars nasalis) extends from the base of the skull
to the dorsal border of the soft palate. It lies behind the nasal
cavities and is an accessory portion of the respiratory system. Its
ventral wall is wanting and here are seen the two choanal. Upon

292 THE ALIMENTARY TRACT

each lateral wall are several points of interest. Here is seen the
pharyngeal orifice of the auditory tube (tuba auditiva) bounded by a
hook-shaped prominence, the torus tubarius, which is open below.
The anterior limb of the cushion continues to the soft palate and is
called the salpingo palatal fold [plica salpingopalatina). The
posterior limb is the longer and continues down the pharynx wall and
constitutes the salpingopharyngeal fold (plica salpingopharyngea).
Behind the cushion is quite a deep recess called the lateral recess
of the pharynx (recessus pharyngeiis). In the middle of the roof is a
small recess called the pharyngeal bursa (bursa pharyngea). In the
dorsal wall are collections of lymphoid tissue, the pharyngeal tonsils.
In infancy and childhood these masses frequently hypertrophy
constituting adenoids.

The floor is formed by the sloping soft palate the dorsal border of
which almost touches the dorsal wall of the pharynx. The narrow
space intervening is called the isthmus of the pharynx (isthmus
pharyngonasalis).

The oropharynx (pars oralis) extends from the lower border of
the soft palate to the level of the hyoid bone. The ventral wall is
partly wanting representing the communication with the oral
cavity. The remainder of the wall is made by the base of the tongue.
Here are seen the glossoepiglottic folds and the valleculas. Upon
each lateral wall are seen two folds that start at the soft palate and
diverge, the anterior passing to the tongue as the glosso palatine
fold (arcus glossopalatinus) which contains the glossopalatinus
muscle. The posterior extends for some distance upon the lateral
pharyngeal wall and is called the pharyngopalatine fold (arcus
pharyngopalatinus) which contains the pharyngopalatinus muscle.
The wedge-shaped area between these folds extending across the
cavity constitutes the isthmus of the fauces {isthmus faucium).
In this area is seen the tonsil (palatal). Above the tonsil is the sup-
ratonsillar fossa (fossa supratonsiUaris).

The tonsils (tonsillaz palatini) are situated between the above folds.
Each is about 1 inch (2 to 2.5 cm.) long, 3j inch (18mm.) wide and
]j inch (12 to 15 mm.) thick. Its pharyngeal surface is covered by
mucous membrane and exhibits a number of pits, or crypts (twelve
to fifteen in number).

The tonsil is not concerned in the process of digestion but belongs
to the great group of lymphatic organs. Its arteries are derived from
the ascending palatine and tonsillar branches of the external maxillary
artery; the dorsalis lingua; of the lingual and the ascending pharyn-
geal of the external carotid artery. Its nerves are from the glosso-
pharyngeal and the pharyngeal plexus.

The laryngopharynx (pars laryngea) extends from the hyoid bone
to the cricoid cartilage, or to the level of the sixth cervical vertebra,

THE ABDOMEN 293

behind. Here are seen the opening into the larynx, in front, and the
opening into the esophagus, behind. The epiglottis is seen here as
well as the recessus pyriformis. Each recess lies at the side of the
laryngeal aperture and is bounded laterally by the thyreoid cartilage
and medially by the aryepiglottic fold.

The pharynx has seven communications; two nasal, two auditory
tubes, one oral, one laryngeal and one esophageal.

The muscles of the pharynx are the superior, middle and inferior
constrictors, the stylopharyngeus and the pharyngopalatinus.

The blood supply of the pharynx is from the ascending pharyngeal,
the ascending palatine (from the external maxillary) descending
palatine (from the internal maxillary) dorsalis lingua? and pterygo-
palatine (from the internal maxillary). The nerves are from the
pharyngeal plexus of the vaga?, glossopharyngeal and sympathetic
nerves.

THE ESOPHAGUS

The esophagus (Fig. 205) is the narrowest part of the alimentary
tract and extends from the sixth cervical vertebra to the eleventh
thoracic vertebra. It is about 10 inches (25 cm.) long and consists
of cervical, thoracic and abdominal portions. Its diameter varies,
its widest part being about r2' inch (12 mm.), in the resting condition,
and then its ventral and dorsal walls are in contact. Distended, it
measures 25 to 30 mm. It is not quite vertical, deviating in certain
regions from the midline.

The blood supply of the esophagus is derived from the inferior
thyroid, descending thoracic aorta, bronchial, left gastric and
inferior phrenic arteries. The nerves are derived from the vagi
and the sympathetic system.

THE ABDOMEN

The abdomen comprises the largest portion of the trunk. In the
male it is somewhat barrel-shaped and flattened from before backward.
In the female it has the shape of a flattened, truncated cone. In
the midline the ventral wall is only 21-; to 3 inches from the vertebral
column.

The abdomen represents the largest serous cavity of the body and
consists of two divisions, the abdominal cavity proper and the pelvic
cavity. The abdominal cavity proper is bounded above by the dia-
phragm and below is continuous with pelvic cavity. Dorsally it is
bounded by the lumbar vertebra? and iliac bones, laterally by the
muscles, fascia? and skin and ventrally by muscles, fascia? and skin.
The upper part of the abdominal cavity is under cover of the ribs
due to the doming of the diaphragm.

2g4 THE ALIMENTARY TRACT

The pelvic cavity is bounded dorsally by the sacrum and coccyx,
laterally by the body of the ischium and part of the ilium, ventrally
by the symphysis pubis. It has an inlet that gives communication
with the thoracic cavity and its boundaries are as follows: Dorsally
the margin of the base of the sacrum, laterally the iliopectineal lines,
ventrally the crests of the pubic bones. It slants downward and
forward and is heart-shaped. The outlet is irregular and is bounded
dorsally by the tip of the coccyx, laterally by the tuberosities of the
ischia and ventrally by the pubic arches and symphysis. "It slants
slightly downward and forward.
This is not a true aperture but is
closed in by the pelvic diaphragm
consisting mainly of the levatores
ani and the ischiococcygei muscles
and pelvic fascia. This diaphragm
is pierced by the anal canal, in the
male, and the anal canal and the
vagina in the female.

In the female the pelvis is more
delicate, wider and shallower than
in the male. The inlet is larger,
the sacrum shorter and less curved,
the outlet larger and the coccyx
more movable, the pubic arch
larger and less angular.

The apertures of the abdominal
walls are the three openings in the
diaphragm, the openings in the
pelvic floor for the rectum the
urethra and in the female the
vagina; the inguinal canal for the
spermatic cord in the male, or the
round ligament in the female, and
the crural or femoral canal that
leads into the thigh.
The abdomen is divided into
nine regions by four lines or planes, two horizontal and two vertical.
A line drawn about the trunk at the lower border of the tenth
costal cartilage and the superior part of third lumbar vertebra is
called the subcostal line. A second line drawn at the level of the
highest points of the iliac crests and through the middle of the
fifth lumbar vertebra is the intertubercular line. The two vertical
lines are drawn parallel to the long axis of the body from the
midpoint of the inguinal ligament (one on each side). The three
transverse zones formed by the horizontal lines are the costal, the

Pig. 212. — Lines and regions of the abdo-
men and the viscera in each, i. Subcostal
line; 2, intertubercular line; 3, 3, midingui-
nal lines; A, A, right and left hypochondriac
regions; B. B, right and left lumbar regions;
C, C. right and left inguinal regions; D,
epigastric region; E, umbilical region; F,
hypogastric region.

THE CONTENTS OF THE ABDOMEN

295

umbilical and the hypogastric. The two vertical lines divide these
zones into nine regions. In the costal zone the regions are right
hypochondriac, epigastric and left hypochondriac. In the umbilical
zone they are right lumbar, umbilical and left lumbar regions. In the
hypogastric zone lie the right iliac, hypogastric and left iliac regions.

A horizontal line drawn about the trunk at a point midway
between the superior border of the crest of the pubis and the inferior
margin of the sternum and at the level of the first lumbar vertebra,
behind, is the transpyloric line.

The contents of the abdomen are the stomach, intestines, liver,
pancreas, spleen, kidneys, ureters, bladder, adrenals, seminal vesicles,
prostate and vasa deferentia (in the male) and the ovaries, oviducts,

213. — Outline of some of the organsof the thorax Fig. 214. — Outline of some of the

and abdomen, on the ventral body wall. (From a photo- organs of the thorax and abdomen, on
graph. 1 the dorsal body wall. (From a photo-

graph.)

uterus and vagina (in the female) nerves, sympathetic ganglia, blood-
vessels, lymph channels and lymph nodes. These are located in the
various regions as follows:

Right Hypochondrium. — Right lobe of the liver, gall-bladder,
duodenum, hepatic flexure of the colon and the upper part of the
right kidney.

Epigastrium. — Part of right and left lobes of the liver, the pylorus
and bulk of the stomach, aorta, celiac axis, celiac ganglia and
pancreas.

Left Hypochondrium. — Spleen, tail of the pancreas, splenic flexure
of the colon, upper part of left kidney and the left portion of the
greater curvature of the stomach.

296 THE ALIMENTARY TRACT

Rig/it Lumbar Region. — Liver, part of the right kidney, coils of
the small intestine and ascending colon.

Umbilical Region. — The transverse colon, the greater curvature of
the stomach, coils of the small intestine, the mesentery and great
omentum.

Left Lumbar Region. — Lower part of the left kidney, descending
colon and coils of the small intestine.

Right Iliac Region. — Cecum, appendix, ileocecal junction and
right ureter.

Hypogastric Region. — Coils of the small intestine, fundus of bladder
(when distended) uterus (during pregnancy).

Left Iliac Region. — Descending colon and left ureter.

THE PERITONEUM

The peritoneum is a serous membrane that lines the abdominal
cavity and more or less completely invests the various organs. In
the male this is a closed sac, but in the female the oviducts open into
the peritoneal cavity. The tunica vaginalis of the testes and the
serous lining of the scrotal compartments are derived from the peri-
toneum. That portion lining the walls of the peritoneal cavity is
the peritoneum parietale and that upon the organs is the peritoneum
viscerale.

Peritoneal folds are of three kinds:

1. Omenta, those folds that connect the stomach to other organs.
These are the gastrocolic, or great omentum {omentum majus), which
extends from the greater curvature of the stomach to the transverse
colon. The gaslrohepalic, or lesser omentum (omentum minus),
extends from the lesser curvature of the stomach to the transverse
fissure of the liver. The gastrosplenic omentum extends from the
greater curvature of the stomach to the spleen.

2. Mesenteries that connect parts of the intestine to the dorsal
body wall. These are the mesentery proper ( mesenterium) compris-
ing the mesojejunum and mesoileum, the transverse mesocolon
(mesocolon transversum) mesosigmoid (mesocolon pehinum) and
mesoappendix.

3. Ligaments, folds of peritoneum that connect organs other
than the gastrointestinal tract to the body wall. These are the
falciform, the right and left lateral ligaments of the liver, broad
ligament of the uterus, false ligaments of the bladder, etc.

Owing to the peculiarity in development of the greater and lesser
omenta of the stomach a portion of the general peritoneal cavity,
the lesser sac (bursa omentalis) is cut off from the remainder which
then constitutes the greater sac. These two sacs communicate
with each other underneath the liver through the foramen of Winslow
(foramen epiploicum).

THE PERITONEUM

297

The lesser sac is bounded by two layers of peritoneum, ventral
and dorsal. The ventral layer invests the caudate lobe of the liver
and continues to the dorsal edge of the portal fissure and from here,
and from the fissure for the ligamentum venosum it passes to
the lesser curvature of the stomach as the dorsal layer of the gas-
trohepatic omentum. It invests about the entire dorsoinferior
surface of the stomach, being continued as the dorsal layer of the
great omentum to the lower border of
this fold where it becomes continuous
with the dorsal layer of the lesser sac.
From the upper part of the greater
curvature of the stomach it continues
to the spleen as the dorsal layer of the
gastrosplenic omentum.

The dorsal layer of the lesser sac passes
from the foramen of Winslow over the
inferior vena cava and the celiac axis,
covers a small area of the diaphragm
behind the caudate lobe, thence passing
to the left, it covers the upper surface
of the pancreas, the left adrenal and
superior pole of the left kidney and part
of the gastric area of the spleen. From
the pancreas it continues as the ventral
layer of the transverse mesocolon, over
the colon and from this region it con-
tinues as the ventral layer of the dorsal
fold of the great omentum to its lower
border, where it becomes continuous
with the dorsal layer of the ventral fold
previously described.

The greater sac constitutes the bulk
of the peritoneal cavity. The ventral
layer starts at the uncovered area of the
liver (upper margin) and continues on
to the under surface of the diaphragm
down the ventral body wall to the pelvis.
a fold attached to the ventral body wall and the under surface of the
diaphragm is reflected upon the ventral and superior surface of the
liver as the falciform ligament of the liver. In the free edge of this
fold is the round ligament of the liver.

The dorsal layer starts at the upper margin of the uncovered
area of the liver, forming here the upper leaflet of the coronary
ligament; it invests the superior, right and ventral surfaces of the
right and left lobes and passes to the inferior surface at the ventral

Fig. 215. — Medial sagittal section
of female showing the reflections of
the peritoneum (digrammatic). .4,
Foramen epiploicum; B, bladder; C,
transverse colon; D. duodenum; E.
rectum; Mt's, mesentery; P, pan-
creas; SI, small intestine; V , uterus.

From the umbilical region

298

THE ALIMENTARY TRACT

margin of the liver. Here it passes backward and upward over the
right and left lobes to the portal fissure while lateral to this fissure
the peritoneum spreads upon the remainder of the inferior surface
(except the caudate lobe and the inferior vena cava) to the lower
margin of the uncovered area forming here the lower leaflet of the
coronary ligament; upon the left it continues to the diaphragm as
part of the left lateral ligament and upon the right side as part of
the right lateral ligament. The portion extending to the left covers
the dorsal abdominal wall lying ventral to the outer and upper part
of the left kidney and extending from here to the spleen as the li-
enorenal ligament. This layer then passes around and invests the
spleen covering the renal, colic and part of the gastric areas con-
tinues to the greater curvature of the stomach as the ventral layer

FiG. 216. — Transverse section of the abdomen, at the level of the foramen epiploicum,
showing the reflections of the peritoneum (diagrammatic). A, Aorta; B, inferior vena cava;
C. gastrohepatic omentum; K, K. kidneys.

of the gastrosplenic omentum. Upon the right side the peritoneum
passes upon the diaphragm as far to the left as the esophagus, form-
ing here the fold called the gastrophrenic ligament. It also con-
tinues downward over the right adrenal and kidney, to the duodenum
and hepatic flexure of the colon, both of which it partially invests.
From the portal fissure the dorsal layer of the greater sac continues
down to the lesser curvature of the stomach as the ventral layer of
the gastrohepatic omentum; from the. lesser curvature it invests
the superior surface of the stomach and the greater curvature,
from which it is continuous with the ventral layer of the ventral fold
of the great omentum to the lower border of that fold. From the
lower border of the great omentum it continues upward to the
transverse colon as the dorsal layer of the dorsal fold of the great
omentum and from the colon up to the dorsal body wall it forms the

THE PERITONEUM

299

dorsal layer of the transverse mesocolon to the pancreas. At the
pancreas the peritoneum passes downward over the third part of
the duodenum to the oblique mesentery of the small intestines.
Here it forms the right layer of the mesentery, invests the bowel and
then passes to the dorsal body wall as the left layer of the mesentery;
it then continues down along the dorsal body wall to the left and
right, investing the sides and ventral walls of the ascending and
descending colons (with cecum and appendix). In the left iliac
fossa it completely invests the sigmoid colon forming for it a mesen-
tery that shortens as the pelvic cavity is reached and ending at the
beginning of the rectum. In the pelvic cavity the dorsal layer
descends upon the front and sides of the rectum lessening at the
sides so that at about the middle of this organ the entire peritoneum
leaves the rectum to be carried forward, in the male, to the back of

■ section of the abdomen at a more caudal level (diagrammatic),
nferior vena cava; C, ascending colon; C descending colon.

the bladder and sides of the pelvis, forming the rectovesical pouch.
It then continues over the superior part and lateral surfaces of the
bladder to the ventral abdominal wall, becoming here continuous
with the ventral layer.

In the female the peritoneum is reflected from the rectum to the
upper part of the dorsal wall of the vagina and then to the dorsal
wall of the uterus and broad ligament, over the fundus and the ovi-
ducts to the ventral surface of fundus and body of the uterus and
the broad ligament; it then continues to the back of the bladder, up
over the superior part of the lateral surfaces of this organ to the
ventral body wall. In the female the fossa between the rectum,
behind, and uterus and vagina, in front, is the pouch of Douglas
(rectouterine) and between the uterus, behind, and the bladder,
in front, the space is called the uterovesical pouch.

300 THE ALIMENTARY TRACT

At the sides of the body wall the ventral and dorsal layers of the
greater sac are continuous with each other.

The organs completely invested by the peritoneum are as foliows:
Spleen, jejunum, ileum, cecum, appendix, transverse colon, sigmoid
colon and the oviducts (in the female).

Those partially invested are: Liver, stomach, duodenum, ascending
and descending colons, rectum (upper part), bladder, uterus and
vagina (in the female).

Those uninvested are: Kidneys, adrenals, ureters, rectum (lower
part), anal canal, pancreas, seminal vesicles, vas and prostate (in the
male), and the urethra.

THE STOMACH (VENTRICULUS)

The stomach (ventriculus) lies in the epigastric, umbilical and left
hypochondriac regions. The direction of its long axis varies
from oblique to nearly horizontal, depending upon the quantity of
its contents. The space occupied is called the stomach-chamber.
When viewed from the side this space is somewhat triangular with
curved sides. The floor slants downward (caudad) and ventrally;
it is formed by the upper surface of the pancreas, the transverse
mesocolon, transverse colon, spleen, right adrenal, and the upper
pole of the left kidney. The roof is formed by the inferior surface
of the left lobe of the liver and the diaphragm. The ventral wall
is formed by the ventral abdominal wall and the diaphragm.

When empty and contracted the stomach is sausage-shaped and
almost vertical. As the stomach fills it dilates at the fundus first
and at the pyloric portion last.

The stomach presents two orifices, cardia and pylorus, two surfaces,
ventral and dorsal, and two borders, the greater and lesser curvatures.
It is divided into fundus, body and pyloric portion.

The cardiac orifice (cardia) is situated about 2 inches (5 cm.)
to the left of the midline at the level of the eleventh thoracic vertebra,
behind, or 1 inch to the left of the seventh sternochondral junction,
in front. It is fixed in position.

The pyloric orifice (pylorus) is situated about 12 to 1 inch (i1.,
to 2.5 cm.) to the right of the midline at the level of the first lumbar
vertebra. In the distended stomach the pylorus moves an inch or
so to the right. It opens into the duodenum.

The ventral surface (paries anterior) is convex and is in contact
with the roof and ventral wall of the stomach chamber when the
organ is distended. When empty, the transverse colon lies ventral
to it. It is more extensive than the dorsal surface.

The dorsal surface (paries posterior) is more flattened and less
extensive than the preceding and is in contact with the floor of the

THE STOMACH

30I

stomach chamber. This surface may be divided by a slight ridge
into an upper and a lower area.

The greater curvature (curvatura venlriculus major) is convex and
starts to the left of the esophagus in the incisura cardiaca and extends
to the pylorus. This margin is 12 to 16 inches long in the distended
stomach (three to four times that of the lesser curvature) and has
the great omentum attached along the greater part of its extent.

The lesser curvature (curvatura ventriculus minor) is somewhat
concave, extends from the cardiac region to the pylorus; it is only
3 to 4 inches in length and has the gastrohepatic omentum attached
to it. Near the pylorus is the incisura. annularis.

The fundus (fundus ventriculi) is the dilatation to the left of the
esophagus and it extends 1 to 2 inches (2.5 to 5 cm.) above the level
of the cardiac orifice. It constitutes a little less than one-third of
the stomach. The body (corpus ventriadi) is the next portion and

ltU3u.|o,r

-The parts of the stomach shown
in the distended organ.

Fig. 219. — Form and position of the
empty contracted stomach.

connects the fundus and pyloric portions. It constitutes a little
over one-third of the stomach. The pyloric end (pars pylori, a\
constitutes about one-third and is separated from the body by the
incisura annularis. It is sometimes separated into a dilated first
part, the pyloric vestibule (antrum pyloricum) and a second tubular
portion, the pyloric canal.

The measurements of the distended stomach are, length 10 to 12
inches (25 to 30 cm.), lateral 4 to 5 inches (10 to 12.5 cm.), and dorso-
ventral 3 to 4 inches (7.5 to 10 cm.). Its capacity is usually 1 quart
(40 ounces) though some give 4 to 5 pints as the capacity. Its
weight is 41., ounces (135 grams).

The stomach is almost completely invested with peritoneum, the
uncovered area being just behind and to the left of the cardia. It is
triangular in shape, measures about 2 inches along the base and \V^
inches high. The stomach is connected to the liver by the gastro-

302 THE ALIMENTARY TRACT

hepatic omentum; to the colon by the gastrocolic omentum and to
the diaphragm by a small fold, the gastrophrenic ligament.

The interior of the stomach exhibits many folds chiefly longi-
tudinal in direction, consisting of mucous and submucous coats.
These folds are the ruga;. Minute orifices representing the gastric
pits, or crypts, are seen throughout the entire surface. At the pyloric
orifice a distinct fold is seen, constituting the pyloric valve. Within
this fold is a strong ring of circularly disposed smooth muscle tissue,
the sphincter pylori muscle.

The stomach is supplied by the following arteries (branches of
the celiac axis): The gastric (from celiac axis direct), pyloric (from
the hepatic), right gastroepiploic (gastroduodenale), left gastro-
epiploic (splenic), vasa brevia (splenic). The veins empty into the
superior mesenteric and splenic veins.

The nerves are derived from the vagals and the solar plexus
(ganglion celiaca) of the sympathetic; branches from these form the
plexuses of Auerbach (plexus myentcricus) and Meissner (plexus
submucosce) in the walls of the organ.

SMALL INTESTINE (INTESTINI TENTJE)

The small intestine consists of duodenum, jejunum and ileum and
is, after death, 20 to 22 feet in length (22.5 feet in the male and 23
feet in the female). The diameter varies from 2 inches (5 cm.) at
the duodenum, to a little over 1 inch (27 mm.) at the ileum.

The duodenum is n inches (27.5 cm.) in length and starts at the
right side of the first lumbar vertebra and ends at the left of the
second lumbar vertebra having a C-, U- or V-shape. Its two ex-
tremities are only about 2 inches (5 cm.) apart. It is the largest part
of the small intestine. It consists of superior (pars superior),
descending (pars descendens) , transverse (pars horizontal is) and ascend-
ing (pars ascendens) portions. In the cavity of the duodenal loop
is placed the head of the pancreas. All parts do not lie in the same
plane. The first part is slightly movable being almost invested by
peritoneum while the remainder is fixed being only partially invested.
In this it is readily distinguished from the remainder of the intestine.
At its termination as it turns ventrally to continue as jejunum
(duodenojejunal junction) it is bound to the body wall by a fold, the
suspensory ligament of Treitz, containing some smooth muscle tissue,
the suspensory muscle (m. suspensorius duodeni). As a whole the
duodenum is incompletely invested with peritoneum.

The interior of the duodenum varies in appearance. The first
part is smooth but this condition is soon changed by the appearance
of circular folds, the plica; eircidares, or valvules conniventes. In
the descending portion is a longitudinal fold representing the course

THE DUODENUM

3°3

of the bile and pancreatic ducts. At the lower end of this fold is
a papilla (papilla duodeni) at which the above ducts empty into the

4

Fig. 220. — A diagram of the alimentary tract.

duodenum. This papilla is usually 3J-2 to 4 inches from the pyloric
orifice.

3°4

THE ALIMENTARY TRACT

The jejunum (intestinum jejunum) represents about two-fifths
(8 feet) of the small intestine. It has a greater diameter, ij^ to
ili inches (3.75 to 3 cm.) than the ileum, its walls are thicker and

Bi\1wTWlrlV Hc.-t.cfl

Fig. 221. — Ventral view of the duodenum, pancreas and the neighboring organs.

redder, the plica; circulares are larger and more numerous than
in the ileum and the villi are more numerous and broader.

-Interior of the jejunum showing the plica? circula

iFrotn a photograph.)

The ileum (intestinum ileum) constitutes about three-fifths (12
feet) of the small intestine. It is about 1 inch (2.5 cm.) in diameter,
its walls are thin and pale, the plicae circulares are few and small and
the villi few and slender. Both of these portions of the small in-

THE CECUM 305

testine are completely invested with peritoneum and are suspended
from the dorsal body wall by the mesentery. The coils of the
jejunum lie chiefly in the upper and left part of the abdominal cavity,
the first third of the ileum in the left iliac fossa, and the remainder
in the lower right portion of the abdominal cavity and even in the
pelvic cavity.

The small intestine receives its blood supply from the following
vessels: Duodenum from the pyloric and superior pancreatico-
duodenale (branches of the hepatic artery) and inferior pancreatico-
duodenale (from the superior mesenteric artery). The veins return
the blood to the superior mesenteric and portal veins.

The jejunum and bulk of the ileum receive their blood from the vasa
intestini tenuis (from the superior mesenteric artery) and the re-
mainder of the ileum from the ileal vessels (ileocolic branch of the
superior mesenteric artery). The veins return the blood to the
superior mesenteric vein.

The nerves are derived from the celiac plexus of the sympathetic-
system. Branches from this plexus form the plexuses of Auerbach
(plexus myentericus) and Meissncr (pi. submucosa) in the walls of the
intestine. Some branches of the right vagus join the latter plexuses.

THE LARGE INTESTINE (INTESTINTJM CRASSUM)

The large intestine consists of cecum, colon, rectum, anal canal
and anus (Fig. 220).

The large bowel presents a sacculated appearance. This condi-
tion is due to the three longitudinal bands, or tenia coli. These
bands represent the longitudinal muscle tissue of the large intestine
and as these bands are about one-sixth shorter than the intestine
they cause the sacculations. They arise at the base of the appendix
and are nearly equidistant from one another. They extend to the
rectum where they end by spreading out to form a complete longi-
tudinal layer. If the tenia? be removed the sacculations disappear
and the bowel is of a cylindrical form. All along the large intestine
are seen little tabs of fat surrounded by peritoneum called the
appendices epiploic^.

The cecum (intestinum cecum) is the blind portion of the large
intestine. It is about 2.5 inches (6.5 cm.) long and 3 inches (7.5
cm.) wide. It lies in the right iliac fossa and extends as high as
the intertubercular plane. The interior of the cecum shows some
folds of the mucosa and submucosa. The superior end is continuous
with the colon. The opening of the ileum is guarded by the ileo-
cecal valve (valvula coli) that consists of two segments, upper (labium
supcrius) and lower (labium inferius). About 1 li inches below the
ileocecal orifice is the appendiculer orifice and this may be guarded
by a valve.

306

THE ALIMENTARY TRACT

The cecum is usually entirely invested with peritoneum but it has
no mesentery.

The appendix (processus vermiformis) is the smallest part of the
intestine. It has been known to be absent and in other cases as
long as 9 inches ("22. 5 cm.). Its average is about 3 inches (7.5 cm.)
in length and }-i inch (6 mm.) in diameter. Its orifice, guarded by a
valve (valvula processus vermiformis) usually is considered half way
on a line between the anterior superior spine of the ilium and the
umbilicus; this is called McBurney's point. The appendix is com-
pletely surrounded by peritoneum and possesses a mesentery, the
mesoappendix.

The colon (Figs. 213 and 220) consists of four parts, ascending,
transverse, descending and sigmoid flexure.

The ascending colon (colon ascendens)
is 5 to 8 inches (.12.5 to 20 cm.) long
and extends from the intertubercular
plane to the under surface of the liver,
where it turns ventrally and to the left
Jg SL as the hepatic flexure. It is wider and

K^s^^^gS^^^ more prominent than the descending

colon; it is usually invested upon its
ventral and two lateral surfaces with
peritoneum and is, therefore, fixed in
position. It lies in the right lumbar and
partly in the right hypochondriac
regions.

Fig. 223.— Cecum with part of At the liver the colon bends sharply
the ventral wall removed, a, to the left and ventrallv and this part

Ileocecal valve and orifice; B, . .. . . . , ., • \ n /n

appendicular orifice. is called theriglit (hepatic) flexure (nexura

coli dextra) and produces the colic im-
pressions upon the visceral surface of the liver.

The transverse colon (colon transversum) is from 15 to 20 inches
(37-5 to 50 cm.) long; it begins at the hepatic flexure and extends
across the body in an arched manner (convexity downward) to the
spleen where it ends at the splenic flexure. The first and last por-
tions are fixed in position, but the intervening portion is freely
movable possessing a long mesentery, the transverse mesocolon.
Its extremities lie in the right and left hypochondriac regions while
the middle portion lies in the umbilical and even in the hypogastric
region.

At the spleen the transverse colon turns sharply downward
(caudad), forming the left (splenic) flexure (flexura coli sinistra).
This lies at a higher level than the right flexure.

The descending colon (colon descendens) is about 4 to 6 inches
(10 to 15 cm.) long and starts at the splenic flexure and extends to

THE ANAL CANAL 307

the left iliac crest. It is about i}2 inches (3.75 cm.) in diameter and
is partly invested with peritoneum; it is fixed in position. It lies
in the left hypochondriac and lumbar regions and bends slightly
toward the midline at the level of the left kidney.

The sigmoid flexure, 17 to 20 inches (42.5 to 50 cm.) in length,
consists of two parts, the iliac and pelvic colons. The iliac colon,
about 5 to 6 inches (12.5 to 15 cm.) long, extends from the crest of
the ilium to the brim of the pelvis. It is completely invested with
peritoneum but has no mesentery. It lies in the left iliac and the
hypogastric regions. The pelvic colon, about 12 to 17 inches (30
to 42.5 cm.) in length, extends from the brim of the pelvis to the
third sacral segment in an irregular loop. This constitutes a large
coil that is completely invested with peritoneum and has a well-
developed mesentery that shortens as the end of this portion of the
bowel is reached. This mesentery is referred to as the mesosigmoid
for both parts as a whole, or pelvic mesocolon.

The rectum (iutestinum rectum) about 5 to 6 inches (12.5 to 15
mm.), extends from the third segment of the sacrum to a point
about 1*2 inches (3.75 cm.) in front of the tip of the coccyx. The
first part is only partially invested by peritoneum and the last por-
tion not at all. Its diameter varies, being smallest at the beginning
and largest nearest the anal canal. This dilated portion is called
the ampulla (ampulla recti). When empty the diameter is about
1 inch (2.5 cm.) but when distended it may be 3 inches (7.5 cm.).

The rectum is not straight, as its name indicates, but shows a
curve from before backward as it follows the curve of the sacrum.
Viewed from the front it shows usually three curves; the upper and
the lower have the concavity to the left and the middle curve to
the right. These are not sacculations but are due to the projection
of the coats into the lumen of the organ forming, thus, three well-
marked shelves, the rectal valves (plicce transvcrsales recti). These
valves extend from a half to two-thirds of the way across the lumen
and serve to support the weight of the fecal matter.

The anal canal (pars Orudis recti) is the slit-like continuation of
the bowel. It is from 1 to i'2 inches (2.5 to 3.75 cm.) in length
and '_> to 34 inch (12 to 18 mm.) dorsoventrally. It lies between
the levatores ani muscles and extends backward and downward at
an angle of about 45° to the horizontal plane, from the end of the
rectum to the anal orifice. The circularly disposed smooth muscle
fibers extend from the beginning to about }i inch from its end and
constitute the internal sphincter muscle. Around the lower two-
thirds is a strong band of circularly arranged voluntary striated
muscle called the external sph 'ncter.

The interior of the anal canal shows, in its upper and middle
thirds, a number (five to ten) of vertical folds called the columns of

308 THE ALIMENTARY TRACT

Morgagni {eolumnce rectales). Between these are little depressions
{sinuses rectales) bounded below by crescentic folds called the anal
valves.

The anal orifice is the lower aperture of the alimentary tract.
This orifice is irregular and is usually surrounded by hairs, sebaceous
and modified sweat glands (glandule? circumanales). At the orifice
the mucous membrane of the rectum passes into the skin without
any sharp line of demarcation.

The blood-vessels that supply the large bowel are as follows:
Cecum and appendix by the ileocecal artery (from the ileocolic branch
of the superior mesenteric artery) ; the ascending colon by the right
colic (from the superior mesenteric) ; the transverse colon by the mid-
dle colic (from the superior mesenteric) and the left colic (from the
inferior mesenteric) ; sigmoid colon by the sigmoid branches of the

Fig. 224. — Lower part of the rectum and the anal canal. C, C, columns of Morgagni; Vj
anal valves.

inferior mesenteric artery; the rectum by the superior hemorrhoidal
(from the superior mesenteric), the middle hemorrhoidal (from the
internal iliac) and the inferior hemorrhoidal (from the internal
pudic).

The venous blood of the rectum passes in two directions. There
are two venous plexuses in the rectum, internal and external. The
internal hemorrhoidal plexus gives rise to the inferior hemorrhoidal
veins that empty into the internal pudic vein which is a tributary
to the inferior vena cava through the internal and common iliac
veins. The external hemorrhoidal plexus gives rise to the superior
hemorrhoidal vein that empties into the inferior mesenteric vein
which is a tributary to the portal vein. The blood that is distrib-
uted by the inferior mesenteric artery is returned by venous channels
that correspond to the arterial branches; these ultimately form the
inferior mesenteric vein that empties into the splenic vein, a tribu-

THE LIVER 309

tary to the portal vein. Corresponding venous channels return the
blood from the distribution of the superior mesenteric artery to
form the superior mesenteric vein. This vein unites with the splenic
vein to form the portal vein that enters the portal fissure of the liver.
The nerves of the great bowel to the rectum are derived from the
sympathetic plexuses around the roots of the superior and inferior
mesenteric arteries. Their distribution is similar to that of the
small intestine. The rectum receives its sympathetic fibers from
the inferior and hypogastric plexuses. Its cerebrospinal nerves are
derived from the second, third and fourth sacral segments of the
spinal cord.

THE LIVER (HEPARi

The liver is the largest gland in the body, weighing from 50 to 55
ounces (1500 to 1650 grams) in the male, and from 43 to 48 ounces
(1290 to 1440 grams) in the female. It represents one-eighteenth to
one-twentieth of the body weight at birth and about one-fortieth
in the adult. The bulk of the liver lies in the right hypochondriac
region, the remainder extending across the epigastric into the left
hypochondriac region. It is soft, of a reddish-brown color and quite
friable. It is not completely invested with peritoneum, having a
large area, the uncovered area, uninvested. Its shape is irregular
and inconstant in the same body varying under different conditions.
It is usually described as a "right angle triangular prism with the
basal angles rounded." Its measurements are as follows: greatest
transverse 7 to 8 inches (17.5 to 20 cm.) ; vertical (near the right side)
6 to 7 inches (15 to 17.5 cm.); dorsoventral (in the thickest part)
4 to 5 inches (10 to 12.5 cm.).

It presents five surfaces, superior, ventral, right, dorsal (these four
constituting the parietal surface) and inferior [visceral) surface and
an inferior border.

The superior surface (fades superior) is convex from before
backward and slightly concave, to the left of the midline, from
side to side. This depressed area is the cardiac impression, for
here the heart rests upon the liver separated therefrom by the central
tendon of the diaphragm. The convexity of the two sides is due to
the doming of the diaphragm. This surface is divided by the sus-
pensory ligament into a greater, right, and a lesser, left portion.

The ventral surface is extensive and of a triangular shape; it
is slightly convex, or flattened, resting against the diaphragm and
the ventral abdominal wall. It is divided by the suspensory liga-
ment as above stated. The right lateral surface is convex and
triangular in shape and rests against the diaphragm.

The dorsal surface ( fades posterior) is convex, the greater right
portion being broad while the lesser left portion is narrow and comes

310 THE ALIMENTARY TRACT

to a point. To the left of the midline of the liver is the deep vertebral
groove where the liver is moulded around the protruding vertebra
column. The greater portion of this surface is uninvested with
peritoneum and is called the uncovered area. This area is from 2 to 3
inches (5 to 7.5 cm.) from above downward to 4 to 5 inches (10 to
12.5 cm.) from side to side. This surface presents from right to
left, the uncovered area with the adrenal impression (impressio
suprarenalis), the fossa for the inferior vena cava (fossa vena cava:),
the base of the caudate lobe, the fissure for the ligamcntum venosum and
the esophageal groove (impressio esophagea).

The inferior, or visceral surface (fades inferior), presents from
right to left the following: Starting across the upper part is seen first

. - I Suspensory ligament

V." ^^^^7 Round ligament

^H Wm^ J Umbilical notch

^^1 jf^r Gall-bladder

Fig. 225. — Ventral and right surfaces of the liver. {From a photograph.)

the large renal impression (impressio renalis), then the transverse, or
portal fissure with the processus caudatus of the caudate lobe above it ;
then the fissure for the ligamentum venosum (fossa ductus venosi) ;
next the omental tuberosity (tuber omentalc) that fits into the lesser
curvature of the stomach; lastly, the gastric impression (impressio
gaslrica) that accommodates the ventral surface of the stomach.
Across the lower part of this surface (right to left) are seen: first, the
colic depression (impressio colica) below the renal impression; the
duodenal depression (impressio duodenalis) above and to the left;
next, the gall-bladder in its fossa (fossa vesica fellea); then, the quad-
rate lobe with the pyloric depression (impressio pyloris); the umbilical
fissure for the round ligament; and lastly, the end of the gastric
impression.

THE LIVER

3"

The inferior border, or margin of the liver is sharp and thin.
Where the falciform ligament reaches it there is a deep notch called
the umbilical notch (incisure umbilicalis) which represents the begin-
ning of the umbilical fissure. A little to the right of the notch is
seen the base of the gall-bladder.

The lobes of the liver are four in number, right (lobus dexter) with
its subdivisions the quadrate (lobus quadratus) , caudate (lobus cauda-
tus) and lastly the left lobe (lobus sinister). The fissures a.re five in
number and form a broken letter H. Upon the left are the continu-
ous umbilical ( fossa umbilicalis) and ligamentum venosum (fossa
ligamentum venosum) fissures that constitute the great longitudinal
fissure. On the right are the fissure (fossa) for the ga'l bladder

Inferior i
Caudate lobe
. Esophageal groove \ Uncovered

Fissure for the 1

Gastric
pression

Omental tuberosit

Hepatic arcerv

// '
Fissure for the round lig.

Quadrate lobe

Gall-bladder

gall-bladder
Portal fissure

Common duct

Fig. 226. — Dorsal and inferior surfaces of the liver. {From a photograph.)

(fossa vesica fellece) and the fissure for the inferior vena cava (fossa
vena- cava-) interrupted by the caudate process; connecting the longi-
tudinal fissure with the fossa for the gall-bladder is the transverse,
or portal fissure (porta hepatica). At the portal fissure the hepatic
artery, nerves and portal vein enter and the hepatic ducts and lymph
channels pass out.

The ligaments are the suspensory, coronary, right and left lateral,
umbilical and ligamentum venosum. The falciform, or suspensory
ligament (ligamentum falciforme hepalis), is a sickle-shaped fold of
peritoneum that connects the liver to the diaphragm and ventral
abdominal wall. It starts at the umbilicus, passes upward to the
diaphragm and liver and then back to the dorsal surface where its

312

THE ALIMENTARY TRACT

two layers separate, one going to the right and the other to the left
as the upper leaflets of the coronary ligament. It passes over the
ventral surfaces and superior wall to the left of the midline of the
liver and separated the right from the left lobes here.

The coronary ligament (lig. corinarium hcpatis) consists of upper

and lower leaflets. The upper have been mentioned above. The

lower leaflet represents the peritoneum from the visceral surface of the

liver and it bounds the inferior margin of the uncovered area. At the

right edge of the uncovered area the two leaflets unite and pass to the

^^^mmmm^ . diaphragm as the right triangular

ligament dig. triangular e dextrum).

^djMkfe To the left of the caudate lobe the

two leaflets unite and extend along

the dorsal edge of the left lobe to

its end and then to the diaphragm

as the left triangular ligament (lig.

triangulate sinistrum).

The round ligament (lig. teres
hepalis) represents the impervious
umbilical vein of the fetus and it
lies in the free edge of the falciform
ligament and enters and lies in
the fissure for the round ligament
in the inferior surface.

The ligamentum venosum lies in
the fissure of that name and ex-
tends from the portal fissure dor-
sally to the inferior vena cava. It
represents the impervious ductus
i*J venosus.
«r upon The blood-vessels entering the

{From a .

liver are the hepatic artery and
the portal vein. The latter is the
real nutrient vessel of the liver as it is laden with the nutritious sub-
stances absorbed from the gastrointestinal tract and comes into
very intimate relation with the hepatic cells.

The several hepatic veins drain the liver and empty the blood into
the inferior vena cava at the dorsal surface of the liver. Two of
these veins are usually of considerable size.

The nerves are chiefly sympathetic from the celiac plexus; the
cerebrospinal nerve assisting is the left vagus.

To outline the liver upon the ventral abdominal wall four points
are taken: (i) in the middle of the fifth interspace on the right mid-
clavicular line; (3) the upper margin of the sixth left rib li inch
(1 cm.) medially from the midclavicular line; (2) >£ inch (12.5 mm.)

Fig. 227. — Outline of th
the ventral abdominal wa
photograph.)

THE GALL-BLADDER AND DUCTS

313

below the tip of the tenth right rib; (4) a point midway be-
between the lower end of the gladiolus sterni and the umbilicus in
the midsternal line. The line connecting (1) and (3) should be
depressed in the midsternal area representing the cardiac depression.
The line connecting (1) and (2) should describe a curve to the right.
The line connecting (3) and (2) is concavoconvex, passes through
the midsternal point (4) and is like a reversed italic /. The posi-
tion of the liver varies with the movements of respiration, ascending
during expiration and descending during inspiration.

THE GALL-BLADDER AND DUCTS

The gall-bladder (vesica fellea) lies in a fossa on the visceral surface
of the right lobe of the liver. It is pear-shaped, measures about 3

X

C«Si«£uit t V N f /fcCir,c

- ?• - u,„, »»«r

V. \_'_ Omen.

aie- —

Fig. 228.— Structures in the lesser omentum (liver raised). The duodenum is laid open to
show where the conjoined ducts empty. PV, Portal vein.

inches (7.5 cm.) in length and 1 to i}4 inches (2.5 to 3.5 cm.) in
diameter. Its capacity is from 1 to ixi ounces (30 to 45c. a). Itcon-
sists of a. fundus, body (corpus) and neck (collum). The neck presents
a peculiar curve with the convexity directed toward the right.

The hepatic duct (ductus hepaticus) is made up of the right and
smaller left lobar ducts. It measures usually 1 to i}i inches (2.5
to 3 cm.) in length and 3 to 4 mm. in diameter and joins the cystic
duct.

The cystic duct (ductus cysticus) begins at the neck of the gall-
bladder and is from 1% to iH inches (3 to 3.75 cm.) in length and

3M

THE ALIMENTARY TRACT

3 to 4 mm. in diameter. It joins the hepatic duct to form the com-
mon bile duct.

The common bile duct (ductus cholidochus) is about $y2 to 4 inches
(8.5 to 10 cm.) in length, 6 to 7 mm. in diameter and passes into the
duodenal wall where it joins the pancreatic duct. These ducts pass
obliquely through the coats of the duodenum and before opening
into the lumen of this organ there is a dilatation of this combined
duct called the ampulla of Voter. The orifice of the common duct is
2,Vi to 4 inches from the pylorus along the dorsomedial wall.

The gall-bladder receives its blood from the cystic artery, a branch
of the hepatic artery. Its veins empty directly into the portal vein.
The nerves are derived from the sympathetic plexus upon the hepatic
artery.

THE PANCREAS

The pancreas is often referred to as the abdominal salivary gland.
When fixed in situ it measures from 5 to 6 inches (12.5 to 15 cm.) in

Fig. 229. — Ventral

, pancreas and the neighboring organs.

length. Its weight is from 85 to 90 grams. Most of the organ lies in
the epigastrium and the remainder in the left hypochondrium. It
consists of head, neck, body and tail.

The head (caput) is the largest portion, measures about 2 inches
(5 cm.) across. It lies in the concavity of the duodenum. The neck
(collum) is the narrow, constricted portion between the head and the
body. It is about 1 inch (2.5 cm.) long and \'2 inch (12 mm.) thick.

THE PANCREAS 315

The body (corpus) is the longest and thickest division and is somewhat
wedge-shaped. It presents three surfaces, ventral, inferior and dorsal,
and three borders, ventral, superior and inferior. The tail (cauda) is
the pointed extremity that extends to the spleen. The pancreas is
classed as a retroperitoneal organ.

The pancreatic duct {ductus pancreaticus) begins near the tip of
the tail and continues in a zigzag manner through the long axis of
the organ; near the head it bends downward to join the common bile
duct.

Occasionally an accessory duct (ductus pancreaticus accessorius) is
found. This is small and opens independently into the duodenum
about 3i inch above and a little ventral to the preceding duct.

The arteries are the superior pancreaticoduodenale (from the
gastroduodenale of the hepatic artery), the inferior pancreaticoduo-
denale (from the superior mesenteric artery) and pancreatic branches
from the splenic and hepatic arteries. The veins empty into the
superior mesenteric, splenic and portal veins. The nerves are mainly
sympathetic from the solar plexus by way of the celiac, splenic and
superior mesenteric plexuses.

CHAPTER VIII

THE URINARY SYSTEM

The urinary system comprises the ti
bladder and the urethra.

THE KIDNEYS

'ii kidneys, two ureters, the

Each kidney (re») is a large, bean-shaped organ, measuring 4>2
inches (11.5 cm.) in length, 2 inches (5 cm.) in width and about 1 ' 2
inches (3 cm.) in thickness. In the male the kidney weighs from
41-2' to 6 ounces (135 to 180 grams) and in the female from 4 to 5!^
ounces (120 to 165 grams). It is rather solid in texture and of a
reddish-brown color.

Surfaces. — The kidney presents ventral and dorsal surfaces, media!
and lateral borders and superior and inferior poles.

Fig. 230. — Ventral surfaces of the kidneys showing the areas of each.

The ventral, or visceral surface (fades ventralis), is convex and
looks forward (ventrally) and outward. Upon each kidney are areas
as follows: Right kidney: adrenal, duodenal, hepatic and colic.
Left kidney: adrenal, gastric, pancreatic, splenic, jejunal and colic.

The dorsal, or parietal surface (fades dorsalis) is directed backward
(dorsally) and inward and is flatter than the ventral surface. The
dorsal surface is in contact with muscles. The areas are diaphrag-
316

THE KIDNEYS

317

matic, transversalis, quadratus lumborum and psoas; these are on
both kidneys but not to the same extent. In addition to these,
upon the left kidney may be seen two grooves formed by the eleventh
and twelfth ribs and two little depressions near the medial border
formed by the transverse processes of the first and second lumbar
vertebrae, respectively. On the right kidney there is one groove
formed by the twelfth rib and one depression formed by the trans-
verse process of the first lumbar vertebra.

The lateral border {mar go lateralis) is convex in both directions and
belongs more to the dorsal surface. The medial border {margo
medialis) is concave presenting a deep notch, the kilns, seen mainly
from the front. The vessels here are the renal vein, in front, the
renal artery, above and in the middle, and the ureter behind and
below.

Fig. 231. — Dorsal surfaces of the kidneys showing the areas of each.

The superior pole, or extremity is thick and broad and about 4 cm.
from the midline. It is capped by the adrenal. The inferior pole,
or extremity is usually thinner and more pointed than the preceding
and is about 5J2 cm. from the midline of the body.

If the kidney be sectioned longitudinally, and parallel to the sur-
faces, a number of important points are noted. The peripheral one-
third is distinctly demarcated from the inner two-thirds and these
constitute the cortex and medulla, respectively. The cortex (sub-
stantia (corticalis) shows striations perpendicular to the surface.
These alternating dark and light stripes are due to the difference in
vascularity of these two parts: the dark ones constitute the labyrinth
(pars convoluta) and are the more vascular; the lighter ones are the
medullary rays (pars rod iota). The rays are continuous with the
medullary portion of the kidney while the labyrinth extends a dis-

3i*

THE URINARY SYSTEM

tance into the medulla between the medullary pyramids, forming here
the cortical ends of the columns of Berlin or columna renales.

The medulla {substantia medidlaris) is seen to consist of a number
of pyramids (pyramides renales) the apices of which are directed
toward the sinus and the bases (bases pyramides) toward the cortex.
The basal areas constitute the boundary zone of the kidney. Between
the pyramids are the incomplete fibrous columns of Berlin (columna;
renales) the pathways of the vessels to and from the boundary
zone.

Just within the hilus is seen an area called the sinus. This is
occupied by the pelvis of the ureter and the branches of the renal
artery, the tributaries of the renal vein and some adipose tissue.
Here are also seen the apices of the
medullary pyramids that project
into the sinus a short distance con-
stituting the papilla renales.

The kidneys are retroperitoneal,
that is, not in any way or part in-
vested with peritoneum. Each is
usually imbedded in considerable fat,
Hi/u*s the fatty capsule (capsitla adiposa)
wihch is usually thicker at the
margins of the organ. In this fatty
tissue is seen the fascia renalis, a
sheet of white fibrous tissue with
some fat interposed between it and
the kidney (the perirenal fat).
That portion of the fatty capsule
outside of the renal fascia is the
pararenal fat. The organ is held in
position by the surrounding organs,
chiefly, and somewhat by the renal
fascia.

The vessels of the kidney are the renal artery and the renal vein.
The nerves are about fifteen in number and are derived from the
renal plexus. This plexus is formed by branches from the solar
plexus, celiac ganglion, aortic plexus and lesser and least splanchnic
nerves. Branches from the tenth, eleventh and twelfth thoracic
nerves also reach the kidneys.

The kidneys lie mainly in the epigastric and umbilical regions but
extend somewhat into the lumbar and hypochondriac regions. The
left is usually higher than the right. The left kidney extends from
the middle of the eleventh thoracic vertebra to the upper border of
the third lumbar vertebra. The right kidney extends from the lower
border of the eleventh thoracic vertebra to the middle of the third

Fig. 232. — Median longitudinal section
of the right kidney. A. A, Calyces
minores; B, B, calyces majores; C, pelvis
of the ureter; 5, hilus of the kidney.

THE URETERS

319

lumbar vertebra. In the female they are somewhat lower than in the
male. The inferior poles are il4, to 2 inches (3.75 to 5 cm.) above
the crests of the ilium. The upper pole of each is 4 cm. from the mid-
line while the lower pole is 5^ cm. from the midline.

THE URETERS

The ureters are the tubes by means of which the urine is con-
veyed from the kidneys to the bladder. Each consists of a pelvis
and ureter proper. The pelvis lies in the sinus and consists of a num-
ber of small divisions, the calyces minores eight to ten in number.

• of a corrosion preparation of the
(From a photograph.)

ssels and ureter of the kidney.

These calyces minores surround and are completely attached to
two or three pyramid apices and join to form two or three tubular
structures, the calyces major es. The junction is somewhat enlarged
and constitutes the pelvis. At the level of the disc between first and
second lumbar vertebne it continues as the ureter proper.

The ureter proper is a small tube about 4 mm. thick and 10 to
12 inches (25 to 30 cm.) in length. It extends from the upper border
of the second lumbar vertebra to the bladder. The first part (pars
abdominalis) lies in the abdominal cavity and corresponds nearly to
the midinguinal line. The second half (pars pelvina) lies in the pel-
vic cavity. When it reaches the bladder, it enters that structure
obliquely and proceeds for nearly an inch (2.5 cm.) between the mus-
cular and mucous coats. Its opening in the bladder is guarded by
mucous folds.

320

THE URINARY SYSTEM

Its blood supply is from the renal, spermatic, ovarian, middle
hemorrhoidal and superior vesical arteries. Its nerves are derived
from the renal, spermatic and hypogastric plexuses of the sympa-
thetic system.

THE BLADDER

The bladder (vesica urinaria), located in the pelvic cavity just
behind the symphysis pubis, is the reservoir for the urine. When

Fig. 234. — Medii

prostate, urethr.

empty and contracted the bladder is almost spherical in shape. Its
shape in the infant is somewhat conical. In the empty collapsed
state, as in the cadaver, it is somewhat cup-shaped. When dis-
tended, it is about $}$ inches (14 cm.) in height, 44 inches (11. 5 cm.)
in width and nearly 4 inches (10 cm.) dorsoventrally, and then
extends into the abdominal cavity. In the female the width is
greater and the dorsoventral dimension less. Its capacity is about 1
pint (500 to 700 c.c.) but is usually emptied when it contains 8 to 10
ounces (about 300 c.c).

THE BLADDER

321

The bladder presents an apex, a base, a superior and ventroinferior

and two lateral surfaces and illy defined borders.

The apex (vertex veskce) is best seen in the nearly empty bladder
and lies just behind the symphysis pubis. From this the urachus
extends to the umbilicus. The base (fundus vesica) is directed
downward and backward (dorsally) and is partly in relation with
rectum and seminal vesicles of the male and vagina of the female.
It is partially invested by peritoneum. The superior surface is
directed toward the abdominal cavity and its shape varies with the
state of distention. It is invested with peritoneum. The ventro-
inferior surface is directed downward and forward (ventrally) and

Fig. 23s. — Bladder laid open showing the trigo

when the bladder is distended it is partially invested with perito-
neum. The so-called neck of the bladder is at the lowest part of the
organ, at the junction of the base and ventroinferior surface. Here
the urethra begins and it represents the most fixed part of the blad-
der. The lateral surfaces are directed downward and outward and
meet in front at the urethral orifice. Each is partially invested with
peritoneum.

When the empty contracted bladder is opened the mucosa exhib-
its folds, or rugae except at the trigone. In the distended bladder
these folds disappear. The trigone (trigonum vesica) is a triangular
area at the neck; at the basal angles are the two ureteral orifices and

3 2 2 THE URINARY SYSTEM

at the apical angle is the urethral orifice. The sides are of equal
length and measure about i!4 inches (3 cm.) in the empty bladder
and i'2 inches (3.75 cm.) in the distended condition. The ureteral
orifices are usually guarded by small folds of the mucosa. Extend-
ing upward and outward from each ureteral orifice is seen a short
ridge the ureteral fold (plica ureterica) formed by the ureter in its
oblique course through the bladder wall. Connecting the ureteral
orifices is another fold (basal side of the trigone) the intcrurcteral fold
{torus ureterica), extending from the middle of the fold across the
trigone, and on into the urethra, is a ridge the uvula of the bladder
{uvula vesica).

The ligaments are ten in number, five true and five false. The
true ligaments are mainly fascial bands and are the two ventral, the
two lateral and the middle. The ventral ligaments (puboprostatic)
extend from the neck of the bladder to the prostate gland and then
to each side of the symphysis pubis. The lateral ligaments extend
from the side of the bladder and prostate gland to the lateral walls
of the pelvis. The middle, or umbilical ligament dig. umbilicales
medium), consists of the impervious urachus and extends from the
summit of the bladder to the umbilicus.

The false ligaments are peritoneal folds and are five in number,
two dorsal, two lateral and one ventral. The dorsal false ligaments
extend from the dorsolateral region of the bladder to the side of the
rectum in the male; between the two there is a depression called
the rectovesical pouch. In the female these ligaments extend from
the dorsolateral region of the bladder to the sides of the uterus bound-
ing thus, the uterovesical pouch. The lateral false ligaments extend
from the sides of the bladder to the lateral pelvic walls and iliac
fossae. The ventral false ligament extends from the apex of the bladder
to the umbilicus and lies over the urachus. Extending from the
sides of the bladder and converging at the umbilicus are two addi-
tional folds of peritoneum that cover the two impervious hypo-
gastric, or umbilical arteries. These folds are the plica umbilicales
laterales and the impervious arteries are sometimes referred to as
the round ligaments of the bladder.

The arterial supply of the bladder is from the superior, middle
and inferior vesical arteries in the male; in the female other branches
are received from the uterine and vaginal arteries. The veins carry
the blood to the tributaries of the hypogastric veins and anastomose
with the pudendal venous plexus.

The lymphatics are few and empty into the intern aliliac, hypo-
gastric and sacral nodes.

The nerves are from the third and fourth sacral cerebrospinal
nerves through the vesical plexus and from the upper lumbar nerves
through the hypogastric plexus.

THE URETHRA 323

THE URETHRA

The urethra varies in the male and female. The female urethra
(urethra muliebris) is about i'-2 inches (3.75 cm.) in length extending
from the neck of the bladder (orificium urethra internum) to the
external urinary meatus (orificium urethra; externum) in the vestibule.
It may be dilated to about li inch (6 mm.) and lies imbedded in the
ventral wall of the vagina. It is directed downward and forward.

The male urethra (urethra virilis), 7 to 8 inches (17.5 to 20 cm.) in
length, extends from the neck of the bladder to the end of the penis.
It consists of three parts, prostatic, membranous and penile portions.
The prostatic portion (pars prostatica) is about 1 inch (2.5 cm.) in
length and courses through the prostate from its base to its apex.
It presents the most dilated part of the urethra; its greatest caliber
is 12 mm. Upon its dorsal wall or floor is seen a ridge the urethral
crest (crista urcthralis) which represents a continuation of the uvula
of the bladder. The middle part of this ridge is slightly thickened
and shows a depression in the center, the sinus pocularis (utriculus
proslaticus) upon each side of which is to be seen the opening of the
ejaculatory duct. At each side of the crest is a linear depression, the
prostatic sinuses, into which open the prostatic ducts.

The membranous portion (pars membranacea) is about' M inch
(12 mm.) in length and lies beneath the symphysis pubis. It is
firmly fixed in position and not easily dilated. Its caliber is about
8 mm. ; its distal part has thin walls and is the part that is most liable
to rupture.

The spongy, or penile portion, is about 6 inches (15 cm.) in length
and lies in the spongy portion of the penis and glans penis. Its
caliber is about 9 mm. except near the end where it is dilated to
from 12 to 14 mm., the fossa navicularis. Its termination is called
the external urinary meatus (orificium urethra; externum) and repre-
sents a vertical slit about Vi inch (6 mm.) in extent.

CHAPTER IX
THE MALE ORGANS OF REPRODUCTION

The male organs of reproduction comprise the two testes, two
vasa deferentia, two seminal vesicles, two ejaculatory ducts, a
prostate, two glands of Cowper, the penis and the scrotum.

The testes, two in number, lie in the scrotum. The scrotum is a
pouch-like structure of skin at the dorsal side of the root of the penis.

Spermo/tic
Cord.

Tunica.

/? / buy ii"-^

Dmitri

T poss«-

Fig. 236. — The left testis in situ with the
tunica vaginalis partly removed.

Fig. 237. — Frontal section of testis, epi
didymis and spermatic cord:

It is divided into two compartments by a septum {septum scroti) which
corresponds to the ridge, or raphe upon the outside. Internally
each compartment is lined by a serous membrane, the parietal layer
oj the tunica vaginalis testis. This was derived from the peritoneum

324

THE SPERMATIC CORD 325

during intrauterine life. Between the serous membrane and skin
is the dartos (tunica dartos) which contains some smooth muscle
tissue.

Each testis occupies a compartment and is suspended by the
spermatic cord. Each organ is about i'2 to 2 inches (4 to 5 cm.) in
length, 1J-4 inches (3 cm.) dorsoventrally and 1 inch (2.5 cm.) in
width. It weighs about 1 ounce (30 grams) and its parenchyma is
yellowish in color. The long axis is directed forward, upward and
outward.

The testis presents two surfaces, two borders and two poles. The
lateral (fascies lateralis) and the medial (fades medialis) surfaces are
convex and smooth. The ventral border (mar go ventralis) is convex
and free. The dorsal border (margo dorsalis) is somewhat flattened
and has the epididymis attached to it. The superior pole, or ex-
tremity is rounded and to it is attached the head of the epididymis;
to the inferior pole, or extremity and lower part of the dorsal border
is attached the gubernaculum that connects the testis to the scrotum.
The testis is invested by the tunica vaginalis testis except along the
dorsal border where the epididymis is attached. Along the outer
side of the organ the serous tunic passes in between the testis and
epididymis forming the digital fossa (sinus cpididymi).

The epididymis consists of the head (caput epididymis), the body
(corpus epididymis) and the tail (caiida epididymis). The head and
tail are attached to the testis by the superior and inferior epididymal
ligaments. At the head the excretory ducts of the testicle enter
and form that portion of the epididymis. The body and tail portions
consist of the convolutions of one tubule; if this tubule be straight-
ened it would measure about 20 feet in length.

The spermatic cord (funiculus spcrmaticus) suspends the testicle
in the scrotum and serves as pathway for vessels, nerves, lymphatics
and the vas. It consists of numerous vessels, white fibrous tissue
and some muscle tissue, the cremaster muscle. It contains the vas,
the spermatic, cremasteric and deferential arteries, the pampiniform
plexus of veins, nerves and lymphatics. It extends from the back of
the testis through the so-called inguinal canal to the internal abdomi-
nal ring, measuring about 5 inches (12.5 cm.) in length.

The artery of the testicle is the spermatic artery, that is, a branch
of the abdominal aorta. The venous channels form the internal
spermatic vein which then forms a complicated plexus upon the
spermatic cord, the pampiniform plexus. This plexus reforms the
spermatic vein that enters the abdomial cavity at the internal ab-
dominal ring; the right one empties directly into the inferior vena
cava while that of the left side empties into the left renal vein.

The nerves are derived chiefly from the tenth thoracic nerve
through the spermatic plexus of the sympathetic system.

326

THE MALE ORGANS OF REPRODUCTION

THE VAS DEFERENS

The vas deferens (ductus deferens) the continuation of the epididy-
mis, is about 18 inches (45 cm.) in length, but the first 6 inches are
coiled in a small area at the end of the epididymis. The vas, one on
each side, joins the spermatic cord and continues in this through the
inguinal canal to the internal abdominal ring; here it enters the ab-
dominal cavity and continues into the pelvic cavity, passes to the
under surface of the bladder and near the prostate gland is it joined
by the seminal duct. Near its end it dilates constituting the ampulla
(ampulla ductus deferens). It then becomes smaller and joining the
seminal duct forms the ejaculatory duct.

THE SEMINAL VESICLES

The seminal vesicles (vesciculce seminales) are two rather wide,
convoluted tubes beneath the base of the bladder. Each is about

Fig. 238. — Dorsal view of distended bladder and neighboring organs of reproductic

2l2 inches (6 cm.) in length, 10 mm. in breadth and 5 mm. in thick-
ness. If straightened each would measure about 5 inches (12.5 cm.)
in length. The duct (ductus excretorius) is short and joins the vas
to form the ejaculatory duct.

THE PROSTATE

32/

Theejaculatory duct {ductus ejaculatorius) is about 3iinch (18 mm.)
in length and enters the prostate gland near the inferior basal angle,
converges with its fellow of the opposite side to the dorsal wall of the
urethra where each empties upon the urethral crest.

THE PROSTATE

The prostate gland {prostata) is a pyramidal-shaped organ situated
at the so-called neck of the bladder. It is of a dark red color and

Fig. 239. — Median sagittal section through the bladder, prostate, urethra and penis
of the male.

musculoglandular in structure. It is about il-i inches (3.5 cm.)
wide, 1 inch (2.5 cm.) thick and 1 '4 inches (3.5 cm.) high. It weighs
about y2 ounce (15 grams.)

It consists of apex, base, ventral, dorsal and lateral surfaces. The
apex (apex prostata-) is directed downward and forward and rests
upon the deep layer of the urinogenital diaphragm. The base (basis
prostata1) is directed upward and backward and is in contact with the
bladder. Near the middle of the base the urethra enters the organ
and courses through it to the apex. At the inferior angles of the

328 THE MALE ORGANS OF REPRODUCTION

base the ejaculatory ducts enter the organ and converge at the
urethra. That portion of the prostate between these ducts and the
urethra constitutes the so-called middle lobe of the prostate.

The dorsal surface (fades posterior) is in contact with the rectum.
The ventral surface (fades anterior) is directed toward the symphysis
pubis and is connected to it by the two puboprostatic ligaments.
The lateral surfaces (fades laterales) are in contact with the leva-
tores ani muscles with only a venous plexus intervening.

The visceral layer of the pelvic fascia invests the prostate upon its
lateral and dorsal surfaces; this is called the sheath of the prostate.
It is continuous at the apex of the gland with the urinogenital dia-
phragm and from its ventral part two bands continue to the pubis as
the puboprostatic ligaments.

The arteries of the prostate are derived from the middle hemor-
rhoidal, internal pudic and inferior vesical arteries. The veins form
a plexus around the gland and then empty into the hypogastric
(internal iliac) veins. In elderly male these veins are usually en-
larged. The nerves are from the hypogastric plexus of the sympa-
thetic system.

COWPER'S GLANDS

The glands of Cowper are located between the layers of the tri-
angular ligament and their ducts empty into the penile urethra.
They are small organs about 6 to 8 mm. in diameter. The duct of
each is about 1 inch (2.5 cm.) in length.

THE PENIS

The penis is attached to the pubic arch. It is composed chiefly of
erectile tissue. In the pendulous state the surfaces are under, or
urethral, and the opposite surface is the dorsum. It consists of root,
bodv and glans penis. The root (radix penis) consists of two crura
and a bulb. Each crus arises from the side of the pubic arch, gradu-
ally increasing in size and continuing as the corpus cavernosum.
Each crus is surrounded by the ischiocavernosus muscle and con-
verges to meet its fellow at the midline. The bulb (bulbus urethra:)
is the beginning of the corpus spongiosum and lies behind the point
at which the urethra enters the corpus spongiosum.

The body (corpus penis) of the penis consists of two corpora cav-
ernosa (corpora cavernosa penis) and the corpus spongiosum (corpus
cavernosum urethra?). Each corpus cavernosum lies to the side of the
midline of the organ in the dorsal part of the penis and consists of
erectile tissue. The corpus spongiosum lies in a groove upon the
under surface of the corpora cavernosa. It is traversed by the
urethra and consists of erectile tissue. These three structures are
surrounded by white fibrous tissue and the loose skin.

THE PENIS

329

The glans penis is the continuation of the corpus spongiosum and
is an expanded, cap-like structure that covers the ends of the corpora
cavernosa, where its edge is raised forming the corona gland is. At its
end is a slit-like orifice the external urinary meatus. On the glans the
skin forms a free covering, or hood, the prepuce (prcputinm ) that is
attached to the glands beneath the urinary meatus by a delicate
fold, the frenulum {frenulum prcputii). From the fibrous capsule of

Fig. 240. — Male organs of
(except testes).

Fig. 241. — Male urethra laid open. A,
Urethral crest; B, prostate; C. glands of
Cowper; D, bulb; E. fossa navicularis; F,
external urinary meatus.

the penis a triangular fold of fibrous tissue is attached to the sym-
physis pubis; it is the suspensory ligament (ligamentum suspensorium
penis) of the penis. Between the capsule and the corpora cavernosa
lie the dorsal vein and dorsal arteries of the penis.

The arteries that supply the penis are deep dorsal arteries and the
artery to the bulb. The veins empty into the prostatic plexus or into
the dorsal vein.

The nerves are from the pudenal nerve and hypogastric and
pelvic plexuses of the sympathetic system.

CHAPTER X
THE FEMALE ORGANS OF REPRODUCTION

The female organs consist of the two ovaries, two oviducts, uterus,
vagina, internally, and the two glands of Bartholin, the vestibule,
clitoris, hymen, two labia minora and two labia majora and mons
veneris, externally.

The ovaries lie at the side of the pelvic cavity in a little depression
called the ovarian fossa (fossa ovarica). They lie behind the broad
ligament of the uterus and are attached thereto. Each organ is
about ili inches (3.75 cm.) long, *i inch (18 mm.) wide and \i inch

Body

Fimbriated extremity

Fig. 242. — Dorsal

and broad ligament sho
n (i photograph.)

(8 mm. ) thick. It weighs about 4 to 8 grams. Each presents two
surfaces, two borders and two poles. The long axis is directed down-
ward (caudad) and medially.

The pelvic, or lateral (fades lateralis) and visceral, or medial sur-
faces (fades medialis) are convex and nodular; the latter condition is
due to the projecting Graafian follicles, between the age of puberty
and the menopause. The dorsal border (margo liber) is convex and
free. The ventral border (margo mesovaricus) is not free and repre-
sents the attached border; it is connected to the broad ligament by a
double sheet of peritoneum, the mesovarium. The superior, or
tubal pole (e.xlremilas tubaria) is rounded and covered by the fim-
330

THE OVIDUCTS 33 I

briated extremity of the oviduct; one of the largest fimbria? is
attached to the ovary and is called the ovarian fimbria {fimbria
ovarica). The inferior, or uterine pole {extremitas uterina) is directed
toward the uterus and is connected to it by a cylindric band of
fibrous tissue, the uteroovarian ligament (ligamcntum ovarii proprium).
The ovary is connected to the lateral pelvic wall by a triangular fold
of peritoneum, the suspensory ligament (ligament sitspensorium
ovarii) through which the vessels gain access to the ovary.

The ligaments of the ovary are the mesovarium, suspensory,
uteroovarian and the fimbria ovarica.

The arteries of the ovaries are the ovarian from the abdominal
aorta. These enter at the hilus with the branches of the uterine
artery. The veins form first a plexus similar to the pampiniform
plexus of the male, near the ovary, and then form the ovarian vein
upon each side. The right one empties into the inferior vena
cava while the left one empties into the left renal vein.

The nerves are from the ovarian plexus continuous with the renal
and aortic plexuses of the sympathetic system; sensor fibers from
the ovary pass through the dorsal root of the tenth thoracic nerve.

THE OVIDUCTS

Each oviduct {tuba uterina) is about 4 inches (10 cm.) long and
extends from the ovary to the uterus. It is situated at the upper
border of the broad ligament in the pelvic cavity and is not straight
in course. Each consists of an infundibulum. the ampulla and
isthmus.

The infundibulum {infundibulum tuba: uterina) or fimbriated
extremity is funnel-shaped and fringed; this fringe constitutes the
fimbriae and one of these fimbria? is attached to the ovary. Its
opening {ostium abdominale) is about 2 mm. in diameter. The
ampulla (ampulla tuba uterina;) is the longest, widest and most tor-
tuous portion; its first part is hooked over the superior pole of the
ovary. The isthmus (isthmus tuba uterina), the narrowest part, is
straight and horizontal in its course and ends at the lateral angle of
the uterus. Its opening (ostium uterinum tuba) is 1 mm. in diameter.
It has a thick wall.

The oviduct is connected to the upper part of the broad ligament
of the uterus by a thin band of peritoneum, the mesosalpinx. The
tube is entirely invested with peritoneum.

The blood supply is from the ovarian and mainly the uterine
arteries. The veins empty into the uterine and ovarian veins. The
nerves are from the ovarian and uterine plexuses of the sympathetic
system. Its sensor fibers enter the dorsal roots of the eleventh and
twelfth thoracic and first lumbar nerves.

332

THE FEMALE ORGANS OF REPRODUCTION

THE UTERUS

The uterus, or womb, is a muscular organ with a very small cavity.
It is situated in the pelvic cavity. It is of a flattened pear-shape
and its walls are very thick. Its position varies with the position
of the body and the state of the bladder and the rectum. It meas-
ures (in the virgin) 3 inches (7.5 cm.) in length, 2 inches (5 cm.) in
width and 1 inch (2.5 cm.) in thickness. In the virgin it weighs
about 1 V2 ounces (45 grams) and in those that have borne children
about 2H ounces (75 grams). It consists of fundus, body, cervix and
lateral border.

-Dorsal view of the uterus ;
broad ligament.

nd left half of the

Fig. 244. — Frontal section
tirough the uterus showing its
avity (diagrammatic), C,
licse palmatae.

The fundus (Jundus uteri) is the upper, broad and convex extrem-
ity above the level of the openings of the oviducts and represents
about li inch of the length. The body {corpus uteri) is somewhat
triangular in shape, broad above and narrower below. Its ventral
surface {fades vesicalis) is flattened while the dorsal surface {fades
intestinalis) is convex. At the sides the broad ligaments of the
uterus are attached. It represents about 1% inches of the length
of the uterus. The cervix, or neck {cervix uteri) about 1 inch in
length, is cylindrical in shape. It connects the body of the uterus
with the vagina. The lower end projects into the vagina and consti-
tutes the vaginal portion {portio vaginalis), while the upper end is
called the supravaginal part {portio supravaginalis).

The cavity of the uterus when seen from the side represents a
mere slit. Viewed from the front, that part in the body is triangular
in outline and the cervical portion (canal) is spindle-shaped. The
upper end of the cervical canal {canal is cervicis uteri) represents the
internal OS (orijicium internum uteri) while the vaginal end repre-
sents the external os {orificium externum uteri). The mucosa of the
cervical canal shows a large number of oblique folds, the plicce

THE PARAMETRIUM 333

palmatcB, while the mucosa in the- body is smooth. The mucosa at
the external os is usually pouched forming the ventral and dorsal
lips {labium anterius et labium posterius. The fundus, the ventral
surface of the cervix and the entire dorsal surface and cervix are
invested with peritoneum.

The lateral border (margo lateralis) separates the two surfaces and
here the broad ligament is attached.

The uterus is supported by a number of ligaments. The two broad
ligaments (ligamenta lata uteri) extend from the side of the uterus
to the lateral pelvic wall and are covered by the peritoneum. From
the free edge of each extends the mesosalpinx. Each round liga-
ment {ligamentum teres uteri) extends from the junction of the oviduct
and the fundus, under the peritoneum, to the internal abdominal
ring; from here it passes through the inguinal canal and is lost in
the tissues of the labium majus. The two ventral, or uterovesical
ligaments, extend from the uterus to the bladder. The two dorsal
ligaments, or rectovaginal folds, extends from the uterus and vagina
to the rectum. The uterorectal folds {plica rectouterine?) extend from
the uterus to the rectum and contain the utcrosacral ligaments.

The position of the uterus varies with the position of the body and
the condition of the neighboring organs. In a ventral view it is
seen bent usually toward the right side; in the erect position, when
the bladder is empty, the uterus usually rests upon the bladder and
is then bent forward and downward on the cervix so that the axis
of the organ is not a straight line. This is called anteflexion. If the
uterus as a whole is tilted forward it constitutes anleversion; as the
bladder fills the uterus becomes more erect. When the bladder is
full and the rectum empty the organ may be bent backward and be
either retroverted, or retroflexed.

The parametrium is that rather thick layer of loose tissue between
the two layers of peritoneum of the broad ligament, below the level of
the mesosalpinx. Where the broad ligament joins the pelvic dia-
phragm will be found the ureter and the uterine vessels. Below
these vessels the fibrous and muscle tissue form the lateral cervical
ligament, on each side.

In the female at birth the cervical portion of the uterus predomi-
nates and the plica; extend through the cavity. The organ grows
slowly until just before puberty when it rapidly increases in size and
the plica; in the body disappear. In old age the uterus becomes
harder and paler.

During the child-bearing period the uterus undergoes periodic
changes, called menstrual changes. The menstrual flow recurs every
twenty-eight days.

The arteries of the uterus are the uterine and ovarian arteries, the
branches of which form an extensive anastomosis.

334

THE FEMALE ORGAN'S OF REPRODUCTION

The veins form a plexus that empties into the tributaries of the
internal iliac veins.

The nerves are derived from the uterovaginal plexus connected
with the hypogastric and vesical plexuses of the sympathetic system
and branches are received from the third and fourth sacral nerves.
THE VAGINA

The vagina is a flattened, musculomembranous tube that connects
the external genitalia with the uterus. Its ventral and dorsal walls
are in contact and the cavity is a transverse or H-shaped slit that
extends ventrodorsally. The ventral wall is about 3 inches (7.5 cm.)
in length, while the dorsal wall is about 3J-2 inches (8.75 cm.) long.

Fig. 245. — Medi;

:ittal section of the female pelvis.

The cervix projects into the vagina and as a result the vaginal cavity
projects around the end of the cervix, constituting the ventral and
dorsal fomices, respectively; at the sides of the cervix are the lateral
forn ices. In the ventral wall lies the urethra.

The arteries are derived from the uterine, vaginal branches of
the hypogastric (internal iliac) and branches from the internal puden-
dal and middle hemorrhoidal arteries. The veins form a dense
plexus and empty into the hypogastric veins. The nerves are
derived from the uterovaginal and vesical plexuses of the sympa-
thetic system and from the third and fourth sacral nerves.
THE EXTERNAL GENITALIA

The external genitalia (pudendum muliebre) comprise the mans
veneris, the labia majora, the labia minora, the vestibule, elitoris,
glands of Bartholin and the hymen.

THE EXTERNAL GENITALIA

335

The mons veneris {commissura labiorum anterior) is the pad of
fat covered with skin and hairs over the symphysis pubis.

The labia majora are two linear folds of skin extend-
ing from the mons veneris toward the anus. In the midline they lie
in contact and this line of contact constitutes the pudendal slit (rima
pudendi). The adjacent surfaces of the labia are covered by mucous
membrane. Just in front of the anal region the folds are quite low
and are connected by a transverse -
fold called the posterior commissure
{commissura labiorum posterior).

When the labia majora are
separated two smaller folds, the
labia minora are exposed. At
their pubic extremities they are
united and surround the clitoris,
forming its prepuce (preputium
clitoridis) and frenulum {frenulum
clitoridis); anally they diverge
and fuse with labia majora.
Near this region a transverse fold,
the fourchette {frenulum labiorum
pudendi) connects the labia minora
and forms the posterior boundary
of the vaginal orifice. The de-
pression between the fourchette
and dorsal commissure is the fossa
navicular is. The long triangular
area between the labia minora is
the vestibule {vest ibul urn vagina).
Here are seen the vaginal and
urethral orifices and the opening
of the ducts of the vestibular
glands.

The vaginal Orifice {orificium G. hymen; If . fourchette

vagina) is the larger and occupies

the dorsal part of the vestibule or basal part of the triangle. Between
the orifice of the vagina and the converged labia minora (pubically)
is a triangular area near the middle of which is seen the urethral
orifice {orijicum urethra: externum). Upon each side of the vaginal
orifice, beneath the mucous membrane and extending to the clitoris
region, is a bulb-like mass of erectile tissue, the bulbus vestibuli.

The hymen is a variable fold of tissue which tends to cover the
vaginal orifice. It is usually crescentic in shape but may be absent.

The glands of Bartholin {gland ul a: vestibularis ma fores) are in
relation with the triangular ligament and their ducts empty into the

Fig. 246. — External organs of reproduc-
tion of the female. A, Anterior commis-
sure; B. clitoris; C, labium minus; P. ves-
tibule; E, urethral orifice; F, vaginal orifice;

336

THE FEMALE ORGANS OF REPRODUCTION

space between the vaginal orifice and the labia minora. Each is
elongated and about the size of a bean. They represent the glands
of Covvper of the male.

The clitoris is the analog of the penis minus a corpus spongiosum.
It arises by two crura from the sides of the pubic arch and these con-
tinue as the corpora cavernosa clitoridis that meet and form the body
of the clitoris (corpus clitoridis); this is connected to the symphysis

Fig. 247. — Female perineum dissected. .-1. Clitoris; B, crus of the clitoris; C, bulb of the
vestibule; D, urethral orifice; E. vagina.

by a suspensory ligament (ligament siispensorium clitoridis). At
the end of the body is a small rounded mass of erectile tissue the
glans clitoridis, that is very sensitive. The glans is covered by, the
prepuce (preputium clitoridis) derived from the labia minora. The
body of the clitoris is about ijjj inches (3 cm.) long.

Arteries — The artery of the clitoris is the deep artery of the clit-
oris from the internal pudendal. Its nerves are derived from the
hypogastric plexus of the sympathetic system and the internal pudic
nerve. The glans is supplied by the dorsal artery of the clitoris. The
bulbits vestibuli is supplied by the artery of the bulb from the internal
pudendal artery. The nerves are from the hypogastric plexus and
branches from the pudendal nerves.

THE MAMMARY GLANDS

The mammary glands (mamma) although not directly connected
with the reproductive organs are best considered here as they are
accessories. Each is a hemispherical mass in the superficial fascial of
the upper, ventral thoracic wall, extending, usually, from the second

THE MAMMARY GLAND

337

to the sixth rib. Each is surmounted by a nipple (papilla mamma)
which is of variable size and shape; it is usually in the lower, outer
quadrant of the gland. The nipple is darker in color than the gland
proper and is surrounded by a circular area of darkened skin. This
area is the areola. The amount of pigment in the areola and nipple
varies. On the summit of the nipple are seen small depressions into
which the milk ducts empty. During lactation the organ consists
mainly of glandular tissue and is firmer and larger than in the non-

mary gland through the nipple

lactating period. During this latter period the glandular tissue is
reduced to a minimum and the organ consists chiefly of adipose and
white fibrous tissues and gland ducts. In early childhood there is
very little or no difference between the mammae of the male and
female. Toward the age of puberty, in the female, the mamma;
begin to grow rapidly.

The arteries of the mammary gland are the internal mammary
artery and branches from the lateral thoracic and intercostal arteries.
The veins empty the blood into the internal mammary and axillary
veins. The nerves are from the thoracic sympathetics and from the
fourth, fifth and sixth intercostal nerves.

CHAPTER XI

THE DUCTLESS GLANDS

The ductless glands comprise the spleen, thymus, thyreoid, para-
thyreoids, adrenals, carotid bodies, coccygeal body, parasympathetic
bodies, pituitary and pineal bodies.

THE THYREOID BODY

The thvreoid bodv, or gland is located in the neck at the sides of
the larynx and over the upper part of the trachea. It weighs about
25 grams and measures 2 inches (5 cm.) in width and 2.4 inches (6
cm.) in height. It consists of tuo
lateral lobes and a middle lobe, or
isthmus. This is not always the case
as it may be horseshoe-shaped, or
have the form of a notched sphere, or
may be in two distinct parts. Each
lateral lobe is somewhat conical in
shape, its apex resting upon the side
of the ala of the thyreoid cartilage
and the base extending down to the
fifth or sixth tracheal ring. The
isthmus is a narrow band of gland-
ular tissue that connects the two
lateral lobes across the second, third
and fourth of the trachea rings.
Occasionally a pyramidal lobe (said
to occur in 40 per cent.) is seen
extending upward from the upper
margin of the isthmus. Being firmly attached to the underlying
structures the thyreoid follows the larynx in its movements.

The arteries are the superior and inferior thyreoid arteries. The
superior and middle thyreoid veins emptv into the internal jugular
vein of each side; the inferior thyreoid vein joins its fellow of the
opposite side to empty into the left innominate vein.

The nerves are derived from the middle and inferior cervical
ganglia of the sympathetic system.

THE PARATHYREOIDS

The parathyreoids are usually four in number, two superior and
iuv inferior, although as many as twelve may be present. Each
338

Fig. 249. — Thy

oid gland, ventral
1 a photograph.)

THE CHROMAPHYL SYSTEM

339

weighs from o.oi gram to 3 grams and is about J4 inch (6 mm.) in
length and about % inch [3 mm.) in diameter. They are yellowish
brown in color and may be lenticular, or nearly spherical in shape.
The superior are behind the lateral lobes of the thyreoid body at the
level of the lower border of the cricoid cartilage. The inferior are
variable in position and may be found behind
the lower part of the lateral lobes and at a
distance below. Each is supplied by a branch
from the inferior thyreoid artery.

CHROMAPHYL SYSTEM

A number of small organs in the body stain
peculiarly when treated with chromium salts;
they secrete adrenalin and are classed under
the chromaphyl system. The adrenals are the
largest and the others comprise the carotid
bodies, aortic bodies and paraganglia; all are
closely associated with the sympathetic
system.

THE ADRENALS

The adrenals, or suprarenal glands {glandula-
suprarcnales) are two in number. Each is of
a yellowish color externally, and darkish
brown (chromaphvl tissue) internally. Each

lies in the epigast'ric region and is in relation ^^"^ inf^
with the upper part of the kidney. Each parathyroids, respectively,
organ weighs about 6 to 7 grams and meas-
ures 2 inches (5 cm.) in height, i'2 inches (3.75 cm.) in width and
about '-4 to *2 inch (6 to 12 mm.) in thickness.

The right adrenal is triangular in outline and its base rests
upon the superior extremity of the right kidney. Upon its
ventral surface is seen a furrow, the hilus, at which the supra-
renal vein emerges.

The left adrenal is semilunar in shape and its base rests upon the
upper part of the medial border and a part of the superior extremity
of the kidney. Upon its ventral surface is seen the hilus.

The adrenals are retroperitoneal.

The arteries are the suprarenal arteries from the aorta, and
branches from the renal and inferior phrenic arteries. The right
suprarenal vein empties into the inferior vena cava while the left
empties into the left renal vein.

The nerves are derived from the suprarenal plexus and branches
from the solar and renal plexuses of the sympathetic system and from
the greater splanchnic, vagal and phrenic nerves.

Fig. 250. — Dorsal view of
the parathyreoids and the

.HO

THE DUCTLESS GLANDS
CAROTID BODIES

The intercarotid bodies (glomus caroticum) are two small bodies
structures situated at the bifurcation of each common carotid artery.
Each is about the size of a grain of wheat (3 mm. by 1 mm.). Each
is closely connected with the carotid sympathetics and is grayish-
reddish brown, or yellowish in color.

Rig h 1~Jlclrena. /

Fig. 2si.— The adrenals, ventral view. (From a fholograph.)

COCCYGEAL GLAND

The coccygeal gland is located in front of the tip of the coccyx and
is smaller than the preceding gland. It is in close relation with the
middle sacral artery.

PARASYMPATHETIC BODIES

The parasympathetic bodies (aortic bodies) are two to three in num-
ber and are seen in the fetus and in early childhood. They are retro-
peritoneal and are found in front of the aorta in the neighborhood
of the third and fourth lumbar vertebra; at the origin of the inferior
mesenteric artery. Their blood supply is from the aorta. Each is
brownish in color, about 8 to 11 mm. long and 3 mm. in diameter.

The pituitary body, or hypophysis and the pineal body, or epiphysis
will be described under the "Nerve System." The spleen and thy-
mus have already been described under the "Lymphatic System."

CHAPTER XII
THE EYEBALL AND LACRIMAL APPARATUS

The eyeball and part of the lacrimal apparatus lie in each orbital
fossa.

The orbital fossae are pyramidal cavities on each side of the bridge
of the nose and below the frontal bone, in the upper part of the face
region. Each is about 2 inches (5 cm.) deep. The base, or orbital
aperture is forward on the face while the apex is directed backward
and medially and is represented by the optic foramen. It has a roof,
floor, and two walls, a lateral and a medial. The bones that form the
boundaries of each fossa are the frontal, lacrimal, ethmoid, sphenoid,
malar, maxilla and palate bones. At the front of the orbit at the
junction of the floor and medial wall is seen a groove, the lacrimal
fossa (fossa sacci lacrimalis) and an opening extending into a bony
canal. The fossa and opening lodge the lacrimal sac, while the bony
canal is for the nasal duct. At the upper and inner portion of the
front of the orbit is a spine, or a depression (spina vel fovea trocfdearis)
for the attachment of the pulley of the superior oblique muscle. In
the temporal portion of the orbit is a depression wherein is lodged
the lacrimal gland.

Within the orbit is lodged the eyeball, the muscles that operate
it, the capsule of Tenon and the orbital fat, vessels and nerves.

The capsule of Tenon (fascia bulbi) is a lymph space of bursa
wherein the eyeball moves as free from friction as possible. This is
a double layer of serous membrane that covers the posterior portion
of the eyeball and extends as far forward as the reflection of the con-
junctiva. The layers are practically in apposition. It is pierced
posteriorly by the optic nerve and continues thereon. It is likewise
pierced further forward by the tendons of the ocular muscles and
prolonged upon each in the form of a tubular sheath. That portion
of the fascia under the eyeball is formed like a sling, or hammock and
seems to support the eyeball and has, therefore, been called the s«s-
peusory ligament.

The extrinsic muscles are the rectus superior, rectus inferior, rectus
lateralis, rectus medialis, obliquus superior and obliquus inferior.
The four recti muscles arise from a tendinous ring around the optic
foramen, the lateralis having two heads. These muscles pass for-
ward and are inserted into the sclera at about 8 mm. from the cor-
neoscleral junction. The superior and inferior recti are inserted
into the vertical plane a little medial to the axis of the eyeball while
341

342

THE EYEBALL AND LACRIMAL APPARATUS

the lateral and medial recti are inserted in the horizontal plane. The
superior oblique, a digastric muscle, arises a little above and medial
to the ring and passes forward to the upper and inner angle of the
orbit to pass through the pulley and then turns outward between the
superior rectus and the eyeball to be inserted into the sclera between
the superior and lateral recti muscle midway between the cornea and
optic nerve area, behind the equator of the eyeball.

The inferior oblique arises at the front of the orbit just lateral to
the lacrimal fossa. It passes outward between the eyeball and the
floor of the orbit, then upward between the lateral rectus and the
eyeball to be inserted into the sclera between the lateral and superior
recti muscles, a little further back than the superior oblique.

252. — Muscles of the right orbit.

The lateral and medial recti muscles move the eyeball horizontally
outward and inward. The superior rectus moves the eyeball ver-
tically upward when assisted by the inferior oblique, while the in-
ferior rectus moves the eyeball vertically downward when assisted
by the superior oblique. The inferior oblique rotates the eyeball
laterally, while the superior oblique rotates the eyeball medially.

The orbital fat, usually considerable, serves as a cushion for the
eyeball. It varies in quantity in different individuals and in health
and sickness. It fills in the orbital fossa around the eyeball and is
most abundant behind that organ.

THE EYEBALL

The eyeball {bulbus oculi) occupies the anterior portion of the orbit
being protected by the orbital margins and the eyelids. The antero-
posterior and the transverse diameters are 24 mm. while the vertical
diameter is 23.5 mm. so that the eyeball is not quite a sphere at the
equator. At birth the eyeball is about 17.5 mm. in diameter and is

THE CORNEA

343

nearly spherical in shape. It increases about 3 mm. between birth
and puberty and soon thereafter attains its adult size and shape.

The apparent difference in the size of the eyeballs of different
individuals is not due to a real difference in size but to a difference
in the prominence of the eyeball and width of the palpebral fissure.
When viewed from the side the eyeball is seen to consist of parts of
two spheres. The smaller, anterior, corneal portion (about one-
sixth) represents part of a sphere of 14 mm. diameter, while the
larger, posterior portion (five-sixths), represents the greater part of

a sphere of 24 mm. diameter. The optic axis is represented by a
line connecting the anterior and posterior poles, that is the central
points of anterior and posterior curvatures, respectively. The
equator is the line around the eyeball midway between the poles.
The visual axis is a line that passes from the first nodal point of the
cornea to the fovea centralis of the retina.

The eyeball is called the organ of vision {organon visits). In
reality it makes an image like a camera, while nerve impulses that
are generated by the cells of the retina travel to the brain and these
impulses are then translated into photic impressions.

The eyeball consists of three coats, or tunics: (1) the corneoscleral
(tunica fibrosa ocitli); (2) the choroid, ciliary body and iris, or the
uveal tract; (3) the retina.

1. The cornea constitutes about one-sixth of the circumference of
the eyeball and is transparent. It represents one of the important

344 THE EYEBALL AND LACRIMAL APPARATUS

refractive media of the eyeball. It is composed mainly of white
fibrous tissue arranged in layers, covered externally by epithelium
and internally by endothelium. It is thinner in the axial region
(0.9 mm.) and at the corneoscleral region is about 1.2 mm. thick.
The curvature is greater in youth than in old age.

The sclera, or white of the eyeball consists of about five-sixths of
the circumference and is composed of dense white fibrous tissue.
It is the protective coat and serves for the attachment of the ocular
muscles. That portion of the sclera where the optic nerve passes out
is sieve-like and is called the lamina cribrosa. Between the sclera
and the capsule of Tenon is the episcleral lymph space. Between
the sclera and the choroid is the sitbsclcral lymph space. Besides
being pierced by the optic nerve fila it is perforated by the posterior
ciliary arteries and the vena; vorticosas. It is thinnest at the
equator.

2. The uveal tract, consisting of choroid, ciliary body and iris, is
also called the vascular coat (tunica vasculosa oculi).

The choroid (chorioidea) is the most extensive of the three divi-
sions. It lies between the sclera, externally, and the retina, inter-
nally and extends forward to the ora serrata. It is a loose coat and
contains the large blood-vessel trunks of the eyeball, in its outer
part, and a capillary plexus near its inner border. The pigment
layer of the retina adheres firmly to it. Between it and the sclera
is a meshwork (lamina suprachorioidea) covered with endothelium,
constituting the suprachoroidal, or subscleral lymph space. It is the
posterolateral part of the choroid coat that gives the peculiar
metallic reflex of the lower animals.

The ciliary body (corpus ciliarc) comprises the ciliary ring, ciliary
muscle and the ciliary processes. The ciliary ring is indicated upon
the outside of the eyeball by a 4-mm. area encircling the eyeball at
the edge of the cornea. It is mainly fibrous tissue supporting the
blood-vessels of that region.

The ciliary processes (processes ciliarcs) are sixty to seventy radially
placed ridges that start at the end of the choroid and extend to the
base of the iris where they end abruptly at about 1 mm. in height,
They vary in length from 2 to 5 mm. and they are not all of the same
height. They contain blood-vessels and are covered by the pig-
mented layer of the retina (pars ciliaris retincc).

The ciliary muscle (m. ciliaris) consists of smooth muscle and is
arranged chiefly in two sets, radial and circular. The radial fibers
arise at the corneoscleral junction, radiate backward to be attached
to the processes and ciliary ring. They constitute the tensor chor-
ioidea; muscle. These fibers are usually the more numerous. The
cirt ular fibers lie under the radial fibers near the base of the iris.
These muscles are part of the intrinsic muscles of the eyeball.

THE RETINA 345

The iris is the automatic curtain of the eyeball regulating the
amount of light that enters the organ. In its center is the pupillary
aperture which varies in size under varying amounts of light. The
iris consists mainly of white fibrous tissue, covered anteriorly by
endothelium and posteriorly by the pigmented layer of the retina
(pars iridica retina). It contains two sets of smooth muscle, one,
the circular fibers, arranged circularly near the pupillary aperture.
This is called the sphincter pupilla muscle, for by contraction it
diminishes the pupillary aperture. The second set or radial fibers
extend outward from the circular fibers to the base of the iris and
constitute the dilatator papilla muscle, for by contraction they in-
crease the size of the pupillary aperture. In the center of the iris
are found also the blood-vessels (to be described later) and varying
quantities of pigmented connective-tissue cells that give the color
to the eyeball.

The retina is the neural, or image-making coat of the eyeball, i.e.,
concerned with the formation of an image. It is usually called the
expanded portion of the optic nerve but it is more than that and
very complex in structure. It consists of two main parts, the pig-
mented layer and the true neural portion (consisting of nine complete
layers). The pigmented layer is composed of pigmented columnar
epithelial cells that are firmly attached to the glassy membrane of
the choroid and continue over the ciliary region and iris as pars
ciliaris and pars iridica retina, respectively. The neural portion-
extends only to the end of the choroid where it ends in a serrated
edge, the ora serrata. This part of the retina constitutes the pars
optica retina. . Its cellular elements are the layer of rods and cones,
the outer and inner ganglionic layers. The layer of nerve fibers
ultimately forms the optic nerve. The important regions of the
retina are the blind spot, yellow spot and the ora serrata.

The blind spot (optic disc) is so-called because no image can be
formed there. It is whitish in color. It represents the area of
convergence of nerve fibers that constitute the optic nerve. It is
situated about 3 mm. to the nasal side and about 2 mm. below the
posterior pole of the eyeball. It is about 1.5 mm. in diameter and is
usually slightly depressed in the center, the excavatio papilla nervi
optici.

The macula lutea, or yellow spot is oval in shape and 2 by 3 mm.
in its diameters and lies in the visual axis. Its central part is slightly-
depressed and is called the fovea centralis.

The ora serrata is the region at which the pars optica retinae
ends. Here the retina is about 0.1 mm. thick while at the optic
nerve region it is about 0.4 mm. in thickness.

In the eyeball are the crystalline lens, aqueous and vitreous humors,
the anterior, posterior and vitreous chambers.

346 THE EYEBALL AND LACRIMAL APPARATUS

The crystalline lens (lefts crystal! iua) is a transparent, biconvex
lens in which the posterior curvature is greater than the anterior.
The posterior curvature, however, is practically fixed while the
anterior curvature is variable. It lies just behind and in contact
with the iris (at the pupillary region) and rests in a depression in the
vitreous humor called the patellar fossa (fossa patellaris). It is about
4 mm. in thickness and 9 to 10 mm. in its transverse diameter. It
is surrounded by a capsule the anterior layer of which, at the edge or
equator of the lens, is continuous with the anterior layer of the zonule
of Zinn. This zonule represents a thick and plicated portion of the
hyaloid membrane of the vitreous humor that is moulded around the
ciliary processes and intervening depressions. This anterior layer is
called the suspensory ligament of the lens. The bulk of the lens con-
sists of lens fibers. The lens represents the most important refract-
ive medium of the eyeball.

The vitreous humor (corpus vitreum) is the largest structure of
the eyeball and occupies the vitreous chamber, or optic cup, that repre-
sents the posterior four-fifths of the eyeball. The jelly-like sub-
stance is surrounded by the hyaloid membrane (membrana hyaloidea).
On the anterior surface is the patellar fossa for the posterior surface
of the lens. At the ora serrata region the hyaloid membrane
becomes thickened and strengthened by radial fibers and this con-
stitutes the zonule of Zinn (zonula ciliaris). As the zonule advances
over the ciliary processes toward the lens, it is moulded over and
attached to the processes and invaginated into but not attached to
the depressions. As the equator of the lens is approached, the zonule
splits into two layers, the anterior and thicker blending mainly with
the anterior layer of the lens capsule and sending fibers to the
posterior layer (that lines the patellar fossa). The vitreous humor
represents one of the refractive media but is usually disregarded in
ophthalmology.

The aqueous humor is merely lymph that occupies the anterior
and posterior chambers.

The anterior chamber [camera oculi anterior) is the space between
the back of the cornea and the front of the iris and is filled with
aqueous humor. The angle formed at the junction of iris and cornea
is the infiltration angle.

The posterior chamber (camera oculi posterior) is the space
between the back of the iris and the front of the lens and suspensory
ligament. It is filled with aqueous humor and communicates with
the anterior chamber through the pupillary aperture.

The optic nerve (nervits opticus) is 1 ' L. to 2 inches (3.75 to 5 cm.)
in length, from the eyeball to the chiasm. It begins as the nerve-
fiber layer of the retina, mainly, but also contains fibers that have a
centrifugal course. It traverses the orbital fat and leaves the orbit
through the optic foramen.

THE EYELID AND CONJUNCTIVA 347

The blood-vessels of the eyeball are the central retinal artery
(arteria centralis retina:) the short and long posterior ciliary arteries
and the anterior ciliary arteries. The central retinal artery enters the
optic nerve near the eyeball and passes into the eyeball to supply the
retina. Its blood is returned by the central vein that has a cor-
responding course.

The short posterior ciliary arteries, about six to twelve in number,
pierce the sclera near the optic nerve region to enter the choroid. In
the choroid they form the layer of large vessels and then the choroidal
capillaries and these branches anastomose with those of the other
arteries. They supply a part of the sclera.

The long posterior ciliary arteries, two in number, pierce the sclera
at some distance from the optic nerve and pass between the sclera
and choroid to the ciliary muscle where they form the cir cuius
arteriosus major, at the base of the iris, by anastomosis. From this
circle vessels pass to the pupillary margin to form the cir cuius arte-
riosus minor.

The anterior ciliary arteries, four in number, form a plexus at the
edge of the cornea. Branches pierce the sclera and connect with the
circulus iridicus major.

The blood from the long and short ciliary arteries is carried to the
veno? vorticosa and then to the ophthalmic vein. Most of the blood
from the anterior ciliary arteries is returned by the anterior ciliary
veins.

The lymphatic spaces of the eyeball are intercommunicating. The
anterior chamber communicates with the posterior and with the
spaces in the sclera and cornea and with the venous canal of Schlemm,
by means of the spaces of Fontana. The posterior chamber com-
municates with the spaces in the choroid and retina and through
these with the subarachnoidean space around the optic nerve. The
capsule of Tenon receives lymph from the subscleral space and from
the choroid by means of the vessels around the venae vorticosae and
the lymph is then transmitted to the subarachnoidean space around
the optic nerve.

The nerves comprise the long and short ciliary nerves and ciliary
ganglion.

THE EYELIDS AND CONJUNCTIVA

The eyelids (palpebral) are two transverse folds of skin, attached
to the upper and lower orbital regions, that protect the eyeball.
The cleft between the two eyelids is called the palpebral fissure and
measures about 30 mm. though this varies in the different races.
The outer surface is covered with skin while the inner surface is a
mucous membrane called the conjunctiva. Between these two layers
are fibrous and muscle tissues and the tarsal plate containing the
tarsal glands. At the margin are seen two rows of heavy hairs the

348 THE EYEBALL AND LACRIMAL APPARATUS

eyelashes, or cilia. The medial and lateral angles at which the lids
meet are called the medial and lateral canthi, or commissures, respect-
ively. Near the medial canthus of each lid is a minute elevation,
the papilla lacrimalis; the minute orifice, or punctum, found therein is
the beginning of the lacrimal duct system. Medial to the papilla is
seen the caruncida lacrimalis.

The conjunctiva (tunica conjunctiva palpebro?) is a mucous mem-
brane that lines the inner surface of each lid and is reflected onto the
sclera of the eyeball {tunica conjunctiva bulbi) just in front of the
insertion of the ocular muscles. It continues to the edge of the
cornea where its epithelium only passes onto that part of the eyeball.
The region where the conjunctiva is reflected from the lid to the
sclera is called the fornix conjunctiva; (superior and inferior). When
the lids are in apposition the conjunctiva represents a closed sac.

THE LACRIMAL APPARATUS

The lacrimal apparatus comprises the lacrimal glands, the puncta,
canalicidi, lacrimal sacs and nasal ducts.

Fig. 254. — The lacrimal 'apparatus of the right

The lacrimal glands (glandulm lacrimales) one in each orbital
fossa, is located in the upper and lateral (temporal) part of the orbit
in the lacrimal fossa. It is flattened and the main portion measures
about 12 by 20 mm. The ducts, three to nine in number, empty into
the conjunctival sac between the upper edge of the eyelid and the
fornix.

The punctum, one in each eyelid, is located near the inner canthus
upon the summit of a little papilla. It leads into a canaliculus. The
canaliculus (ductus lacrimalis) one in each eyelid, of which that in

THE NASAL DUCT 349

the upper eyelid is the shorter, connects each punctum with the
lacrimal sac.

The lacrimal sac (sacus lacrimalis) represents the dilated upper
extremity of the nasal duct. It is about 12 to 15 mm. long, 4 to 5
mm. wide and 7 mm. thick. It lies in the lacrimal groove and re-
ceives the canaliculi.

The nasal duct (ductus nasolacrimalis) is about 18 mm. long and
3 to 4 mm. in diameter. It passes inward and backward and opens
into the inferior meatus of the nasal cavity under cover of the inferior
conchal bone.

CHAPTER XIII

THE EAR (ORGANON AUDITUS)

The car, or auditory apparatus consists of three parts the external,
middle, or tympanum and internal or labyrinth portions.

THE EXTERNAL EAR

The external portion comprises the pinna and external auditory
canal. The pinna, or auricle, is a peculiarly moulded mass of elastic
cartilage covered with skin and adapted to catch the sound waves
and conduct them into the external auditory canal. It is of an oval
form and is located midway between the forehead and the occiput.
It is attached to the side of the head and its cartilage continues as a
tube that forms a part of the external auditory canal. Its parts
are the helix and antihelix, the tragus and antitragus and the lobule.
The latter contains no cartilage and is very vascular. The muscles
of the pinna are intrinsic and extrinsic. The extrinsic muscles are
the atlrahens aurem {m. auricularis anterior) which is the smallest
and is in front; the atolens aurem (m. auricularis superior) which is
the largest and is above; the retrahens aurem [m. auricularis poste-
rior) which is behind the pinna. These muscles are of very little
importance in man. The intrinsic muscles are the mm. helicis major,
helicis minor, tragicus, antitragicus and the transversus and obliquus
auricular (B.

The external auditory canal [canal is auditorius extcrnus) is about
i inch (2.5 cm.) in length when measured, as it should be, from the
bottom of the concha. It is like an elongated S in shape and its
general direction is forward and inward. It makes an angle of about
45° with the sagittal plane and its diameter varies in the different
parts. Its anterior and inferior walls are longer than the posterior
and superior walls on account of the slope of the tympanic membrane.
The lateral one-third is called the cartilaginous portion (pars carti-
laginea) and is formed by the tube-like continuation of the pinna;
the medial two-thirds is called the osseous portion (pars ossea) because
its walls are formed by bone (temporal). This canal is lined by skin
continued from the pinna and in it are found the ceruminous, or
wax glands (glandulce ceruminosa) and many hairs (barbula hirci).

THE MIDDLE EAR

The middle portion, or tympanum (cavum tympani) consists of the
tympanic cavity proper, the attic, the membraua tympani, the ossicles
and its connection with the pharynx, the auditory tube.
35°

THE TYMPANIC CAVITY

351

The tympanic cavity proper, or atrium lies just medial to
the tympanic membrane and is a narrow space, quadrilateral in
shape. It is placed practically parallel to the sagittal plane of the
body. Its length and height are 15 mm. each. The distance
between the lateral and medial walls varies; at the top it is 6 mm., in
the middle about 2 mm. and at the bottom about 4 mm. Above the
level of the tympanic membrane the tympanic cavity forms a recess
called the attic (recessus epitympanicus) , or epitympanum. This
recess contains most of the incus and half of the handle of the mal-
leus and communicates with the mastoid antrum. In the anterior

Fig. 255. — Vertical section through the external auditory canal and tympanum. At
Epitympanic recess; B. tympanum; C, fenestra oralis closed by foot of the stapes; Mem..
tympanic membrane.

wall {paries carotica) of this cavity are two openings; the upper
represents the orifice of the canal that transmits the tensor tympani
muscle (semicanalis m. tenso'ris tympani) while the lower represents
the orifice of the auditory tube. The medial wall \ paries labyrinthica)
has an oval opening, the fenestra vestibuli; its long axis, 3 mm., is
directed horizontally while its shorter axis is directed vertically and
measures about 1.5 mm. In the recent slate this orjening is closed
by the foot of the stapes held in position by the annular ligament
{ligamentum annulare). In the dried bone this opening leads into
the vestibule of the internal portion of the ear. Below the fenestra
vestibuli is another opening (in the dried bone) that leads into the
cochlea and is termed the fenestra cochlea. In the recent state it is
closed by the membrana tympani secundaria.

352

THE EAR

The tympanic antrum {antrum tympanicum) is a cavity in the
temporal bone that is about 8 by 10 mm. and connects the epitym-
panum with the mastoid cells. The mastoid cells (cellules mastoidece)
vary in number and size and are said not to be developed until the
sixth year. In the adult they are usually quite numerous.

The tympanic membrane (membra na tympani) is an elliptical,
disc-shaped membrane that slopes downward, medially and back-
ward, thus accounting for the difference in the length of the walls of
the external auditory canal. It is about 10 mm. in its vertical
dimension and 9 mm. from side to side. Its circumference is thick-
ened by circularly directed fibers of the annidus fibrocartilagineus ,
that attaches it to the circumference of the medial end of the external
auditory canal. Above the malleolar prominence (formed by the
handle of the malleus) is the pars flaccida. The bulk of the mem-
brane is tense, constituting the pars tensa. The central part of the
membrane is drawn slightly inward by the attached handle of the
malleus and is called the umbo.

The lateral surface of the membrane is covered by a thin skin
and the medial surface by a delicate mucous membrane. The cir-
cular and radial fibers between these two layers are .thinner in the
middle than at the circumference.

The muscles of the middle ear are the m. tensor tympani and the
m. stapedius. The insertion of the tensor tympani upon the medial
edge of the anterior surface of the handle of the malleus is such that
when the muscle contracts the handle is drawn medially and the
membrane is rendered tense. The stapedius is inserted into the
neck of the stapes and by its contraction the anterior end of the
base of the stapes is tilted laterally and the posterior end medially,
thus, probably, compressing the lymph in the vestibule.

The tympanic ossicles (ossicula auditus) or ear bones (Fig. 255) are
three in number upon each side. These are the malleus, incus and
stapes.

The malleus is the largest having a length of 8 to 9 mm. It
is composed of head, neck, handle, long and short processes. The
head (caput) articulates with the body of the incus. The handle
(manubrium) is directed downward, medially and backward and is
attached along its entire length to the tympanic membrane.

The incus consists of a body and two processes. The body (corpus)
has a facet for articulation with the head of the malleus. The long
process (crus longum) is directed almost perpendicularly downward
and at its low extremity it articulates with the head of the stapes.

The stapes consists of the head, neck, two crura and a base. The
head (caput) articulates with the long process of the incus. The
oval base (basis) rests in the fenestra vestibuli and is held in position
by the ligamciitum annulare.

THE INTERNAL EAR 353

The auditory tube (tuba auditiva) connects the tympanic cavity
with the pharynx. The air which it transmits to the tympanic
cavity serves to maintain an equilibrium of pressure upon both sides
of the tvmpanic membrane. The lateral end opens upon the
anterior wall of the tympanic cavity. The tube is about i ] 2' inches
(36 mm.) in length and is directed downward at an angle of about
30° to 40° to the horizontal plane and forward and medially at an
angle of about 450 to the sagittal plane. It opens into the naso-
pharvnx. Its lateral one-third is the osseous portion (pars ossea)
and the medial two-thirds the cartilaginous portion (pars carlilaginea) .
The cartilage is in the form of a T-shaped hook in which the anterior
wall is completed by fibrous tissue. The cartilage projects into the
nasopharynx (covered by mucosa) constituting the eustachian
cushion (torus tubarius). Some of the fibers of the tensor veli
palatini muscle take origin from the upper end of the hook and have
been called the dilatator tuba- muscle.

THE INTERNAL EAR

The internal portion of the ear, or labyrinth is the most important
portion of the- auditory apparatus. It is located in the petrous
portion of the temporal bone and comprises the osseous and mem-
branous labyrinths .

The bony labyrinth (labyrinthus osseus) consists of the vestibule,
the semicircular canals and the cochlea.

The vestibule (vcstibulum) lies between the semicircular canals,
behind, and the cochlea, in front. It is about 6 mm. anteroposte-
riorly and 4 to 5 mm. from above downward and 3 mm. from without
inward. In its lateral wall is seen the fenestra vestibuli closed by the
base of the stapes and its ligament. It lodges the sacculus (recessus
sphcricus) and the itlricnlus (recessus cllipticus) and numerous
foramina that transmit nerve fibers from the sacculus and utriculus
and lower end of the cochlear duct, are noted here.

The semicircular canals (canales semicircular es ossei) are behind and
above the vestibule. They are three in number in each ear
and are called superior, lateral and posterior. Each forms about two-
thirds of a circle and is about 1 to 1.5 mm. in diameter. One
extremity of each is dilated and this is the ampulla which is 2 mm.
in diameter. These canals communicate with the vestibule by
five openings. The superior canal is vertical and is placed trans-
versely to the long axis of the petrous portion of the temporal bone.
Its length is about 18 mm. The lateral canal is placed almost hori-
zontally and measures 12 to 15 mm. in length. The posterior canal
is about 20 mm. in length. The opposite lateral canals lie in the
same plane while the superior canal of one ear is parallel to the poste-
rior canal of the other ear.

354 THE EAR

The cochlea represents a tapering tube, of 28 to 30 mm. length,
spirally wound for nearly 234 turns about a bony axis, the modiolus.
The broad portion is the base that measures about 9 mm. across and
is in relation with inferior fossula of the internal auditory meatus.
The end of the coil is the apex, or cupola; it is about 5 mm. above
the base and about 2 mm. above the apex of the modiolus. The
basal portion of the tube is about 2 mm. in diameter.

The modiolus, or axis is a conical mass about 3 mm. high and is
pierced by many foramina for the transmission of nerve fibers.
Upon the tube side the modiolus sends out a bony shelf that extends

Fig. 256. — Isolated membranous labyrinth of the

A, ductus endolymphaticus.

about halfway across the tube and is called the lamina spiralis
(ossea). The division of the tube is completed by the basilar
membrane that extends from the spiral lamina to the lateral wall of
the osseous tube. As a result two passage-ways are formed, the
upper the scala veslibuli and the lower the scala iympani. At the
modiolus end of the spiral lamina is a canal that extends the length
of the shelf and in this spiral canal is lodged the spiral ganglion of
Corti {ganglion spirale). The spiral lamina and basilar membrane
extends to within a short distance of the end of the tube and here
the two scalae communicate with each other. This communication
is called the helicotrema.

Within the bony labyrinth is a membranous cast called the mem-
branous labyrinth (labyrinlhicus membranaceous). This cast is
separated from the bony walls by the perilymph. Within the mem-
branous labyrinth is the endolymph. The parts are the sacculus,
utriculus, the semicircular canals and the cochlear duct.

The sacculus and utriculus lie in the osseous vestibule. The saccu-
lus lies in the lower and front part, is oval in shape and measures

THE MEMBRANOUS LABYRINTH

355

2 by 3 mm. It is smaller than the utriculus. It presents a thick-
ened neuroepithelial area, the macula acuslica sacculi. The saccule
communicates with the cochlear duct by means of a small canal, the
ductus reuniens. Another canal, the ductus endolymphaticus , passes
through the aqueductus vestibuli to end in a small sac under the
dura, in the cranial cavity. This duct is met by a canal from the
utriculus, the ductus utriculosaccular is, thereby giving an indirect
communication between these two structures.

The utriculus lies in the posterior and superior part of the bony
vestibule. It is larger than the preceding and its highest part com-
municates with the ampullae of the superior and lateral membranous

semicircular canals. The lower medial part communicates with the
ampulla of the posterior canal. The central part communicates with
the lateral canal and above this with the common opening of the
posterior and superior canals. The utriculus possesses a whitish,
neuroepithelial area, the macula acustica utriculi. From the utriculus
the ductus utriculosaccularis passes to the ductus endolymphaticus.

The membranous semicircular canals (ducti circulates) represent
casts of the osseous canals, but are only one-fourth the diameter
of the latter. In the ampullae are found neuroepithelial areas, the
crista acustica. The semicircular canals seem to be the organs of
equilibrium, the canals being arranged, apparently, in the three
dimensions of space.

The membranous cochlea (ductus cochlcaris) cochlear duct, or

356 THE EAR

scala media is a limited portion of the scala vestibuli. From the
spiral lamina the thin membrane of Reissner {membrana vestibularis)
passes upward and laterally at an angle of about 450 to be attached
to the lateral wall of the scala vestibuli. This forms a tube, triangu-
lar in section, the scala media, or cochlear duct, which is closed at its
apical end, constituting the lagena. The basal end of the cochlear
duct lies in the vestibule and communicates by means of the ductus
reuniens with the saccule. Upon the medial end of the basilar mem-
brane is the important part of the auditory apparatus, the organ of
Corti (organum spirale). This consists of supporting and neuroepi-
thelial (hair) cells that form a mass that has a spiral course upon the
basilar membrane and extends the length of the scala media. The
hair cells are about 15,000 in number and constitute the neuroepithe-
lial elements that translate the lymph waves into nerve impulses.
These impulses are transmitted to the brain and there translated into
auditory impressions.

The blood supply of the pinna and external auditory canal is from
the posterior auricular and superficial temporal arteries, chiefly;
the veins from the former empty into corresponding veins while the
veins from the latter empty into the external jugular and external
maxillary veins.

The nerves of the pinna are the auriculotemporal, the small
occipital and the great auricular. Those of the external canal are
the auriculotemporal and auricular branch of the vagus.

The blood supply of the tympanum is as follows: The membrana
tympani is supplied laterally by the deep auricular branch of the
internal maxillary while the medial side receives its blood from the
tympanic branch of the internal maxillary mainly. The veins
laterally empty into the external jugular and medially into the plexus
of the auditory tube or into the lateral sinus. The nerves are later-
ally from the trigeminus and medially from the glossopharyngeus.

The arteries that supply the tympanic cavity are branches of the pos-
terior auricular, internal maxillary, middle meningeal, internal car-
otid and ascending pharyngeal arteries. The veins empty into the
superior petrosal sinus, the pterygoid plexus and the middle menin-
geal vein. The nerves are from the pharyngeal plexus. The tensor
tympani muscle is supplied by the trigeminus (through the otic gang-
lion) and the stapedius by the facial nerve.

The blood supply of the labyrinth is the auditory artery from the
basilar artery. This gives rise to three branches, the anterior ves-
tibular, the cochlear and the vestibulocochlear arteries. The audi-
tory veins return the blood to the inferior petrosal sinus, or to the
lateral sinus.

The nerve of the labyrinth is t he auditory nerve. This consists
of two portions, vestibular and cochlear. The vestibular division con-

THE NERVES OF THE LABYRINTH 357

sists of three portions, one from the utriculus, one each from the
ampullae of the superior and lateral semicircular canals. The coch-
lear division consists of three parts, one from the sacculus, one from
the posterior semicircular canal and the third, the bulk of this divi-
sion, from the organ of Corti.

CHAPTER XIV

THE NERVE SYSTEM

The nerve system (systema nervorum) is the most important and

most complicated apparatus in the body. It serves, through various

sensations and impressions, to make us cognizant of our surroundings

and give us the power to adapt ourselves to our environments. It

presides over motion and sensation

and the functions of the various

organs are subjected to its control.

It is most highly developed in

man and consists of two kinds of

nerve tissue, gray and white.

It is composed of units called
neurons that are linked together
in such a manner so as to give
direct and indirect connections
between the central system and
the periphery of the body. Each
neuron consists of a cell and its
processes.

Gray nerve tissue is composed
of nerve cells, their processes, nerve
fibers a.nd a distinctive supportive
tissue, the neuroglia. A neuron is
a nerve cell and its processes. The
cell body, or cytom, comprises a
mass of protoplasm varying from
4M to 1 20M in diameter and exhibits
a granular and fibrilar structure.
The basophilic granules are large
but inconstant depending upon
the state of the cell. These
granules are called the corpuscles
of Nissl, or tigroid bodies. Their
position, size and number depends
upon the functional activity of the
cell; they may be diffusely scattered and small, or arranged in groups
around the nucleus, or near the periphery and extend into the minor
processes, or dendrites. In fatigued cells they disintegrate and dis-
appear. The fibrillar character is due to the neurofibrils that extend
throughout the protoplasm forming an apparent network but the
358

TdereuntB

Fig. 258.— Nerve cells. A, Multipolar; B.
bipolar; C. diagram of a neuron.

NERVE FIBERS 359

fibrils do not really form junctions with one another. These fib-
rils pass into all of the processes and form the most important part
thereof. They are brought out by intravitam, or silver nitrate staining.

The nucleus is usually large, spherical and pale in appearance as it
contains but little chromatin. It is usually eccentrically placed.
The nucleolus is large and stains darkly.

If but one process is present it is the axone, the other processes,
when present, being called dendrites. The axone is the main process
and consists of a number of neurofibrils embedded in neuroplasm
and surrounded by a delicate sheath called the axilemma. This proc-
ess may go but a short distance in the gray substance and terminate
in a brush-like manner near the processes of another cell (second type
cell). When the axone leaves the gray substance and becomes sur-
rounded by a myelin sheath and a neurilemma it constitutes a mye-
linated fiber and the cell is called a Dieter's cell, or cell of the first type.

The dendrites are the minor processes and consist mainly of neuro-
fibrils that extend but a short distance from the cell before they
branch and form a large number of twigs that terminate in a brush-
like manner near the processes of another cell. These are the telo-
dendrites and these processes serve an associative function. Some
dendrites are quite long, leave the gray substance and become in-
vested with a myelin sheath and a neurilemma and serve as a nerve
fiber.

The cells that possess but one process, as those of the ganglia of
the dorsal roots of the spinal nerves and certain of the cerebral
nerves, are called unipolar. When two processes are present, as in
the cochlear and vestibular ganglia and the Purkinje cells of the
cerebellum, they are called bipolar cells. When more than two
processes are present, they are called multipolar cells, as are seen in
the cerebral cortex and the ventral horns of the spinal cord espe-
cially. The latter are the largest cells of the nerve system.

The neuroglia is the special supportive tissue of the nerve system
and comprises glial cells and glial fibers. The cells are chiefly stel-
late, possessing many processes that may be short and thick, or long
and slender. The fibers form a meshwork that supports the func-
tionating nerve cells.

Nerve fibers may be myelinated, as seen in the cerebrospinal sys-
tem, or amyelinated, as seen in the sympathetic system. A myelin-
ated nerve fiber, on cross-section, is seen to consist of a central axis,
the axis-cylinder, or axons; this consists of neurofibrils embedded in
neuroplasm and surrounded by an axilemma. This is surrounded by
the myelin sheath that is composed of a framework of neurokeratin
containing the myelin substance [phosphorized fat) in its meshwork.
It is apparently an insulating sheath and is surrounded by the
neurilemma, a delicate connective-tissue sheath. Upon longitudinal

360 THE NERVE SYSTEM

section a nerve fiber shows constrictions (nodes of Ranvier) at regular
intervals; here the myelin substance is wanting and the neurilemma
dips in and touches the axilemma. Here only may collaterals arise.
Nerve fibers vary from 2^ to 20ju in diameter.

A nerve consists of a number of nerve fibers in one mass of
variable size. The number of nerve fibers varies from a few to
450,000 to 800,000, as in the optic nerve. The nerve is surrounded
by a connective-tissue sheath called the epinemium. This sends in
septa that divides the nerve into large secondary bundles and these
septa send in others that form sheaths for the primary bundles, or
fasciculi. These latter sheaths are the perineural sheaths. Fibers
of the perineurium pass into the bundles and form a mesh work, the
endoneurium, that supports the nerve fibers, blood-vessels and
nerves of the nerve.

Nerve fibers are sensor and motor and an entire nerve as the hypo-
glossal, accessory, oculomotor, trochlearis and abducens may be
composed entirely of motor fibers and each is then called a motor
nerve. A nerve may be composed entirely of sensor fibers, as the
acoustic, olfactory and optic nerves and are then called sensor.
Some nerves, mixed, have both sensor and motor fibers as the spinal,
vagal, glossopharyngeal, trigeminal and facial nerves. Each main
division of such a nerve is distinguished as the motor root and the
sensor root.

Although there are two divisions, the cerebrospinal and the sym-
pathetic, they are not isolated from each other, but are intimately
connected by intercommunicating fibers, the rami communicantes.

The cerebrospinal system comprises the centra! portion, i.e., brain,
spinal cord and their meninges, and a peripheral portion, the cerebral
and spinal nerves and their ganglia.

The central nerve system is surrounded and protected by the
bones of the skull and the vertebral column. The cranial part fits
rather snugly into the cranium and the bones surrounding it are
immovable, thus affording greater protection. The spinal portion
is situated in the jointed vertebral column but the vertebral canal
is of sufficient diameter to admit of all normal movements without
injuring the spinal cord. The central nerve system is not solid but
possesses a central cavity system throughout, the cavity varying in
the different parts. This canal system is a characteristic of the
nerve system of the vertebrates only. It comprises the ventricles
and spinal canal and contains the cerebrospinal fluid. It communi-
cates at several points with the subarachnoid lymph spaces around
the central system and by means of these communications the intra-
neural and the extraneural pressure are balanced. Interference with
these openings, as in certain diseases, causes a disturbance of the
balance with certain attendant symptoms.

THE MENINGES

361

The meninges comprise three membranes the dura, arachnoid and
the pia. The dura {dura mater) is a thick and tough white fibrous
tissue membrane. In the cranial cavity it is attached to the bones
and acts as the inner periosteum thereof as well as a protection to
the brain. It also forms the falx cerebri which is a vertical, sickle-
shaped membrane that separates the cerebral hemispheres from each
other in the sagittal plane. The dura forms the walls of the venous
sinuses and the tentorium cerebelli. The latter lies above the cere-

PlG. -'Mj. — Dried spt

ie falx cerebri and the tentorium cerebelli. (From a
photographs

bellum, serves to support the weight of the occipital portion of the
cerebrum and joins the falx cerebri and the falx cerebelli. The dura
also forms a sheath about the cerebral nerves for a short distance.
The falx cerebelli is a vertical septum of dura that lies between the
two cerebellar hemispheres. The diaphragma sella is a portion of
the dura that stretches over the top of the sella turcica of the sphe-
noid bone and thus converts that depression into a fossa in which the
hypophysis is situated. The diaphragm is pierced by a small open-
ing through which the stalk of the hypophysis passes.

In the vertebral canal the dura does not serve as a periosteum but
is suspended as a loose bag that extends from the foramen magnum
to the third division of the sacrum. Within this bag is the spinal

362 THE NERVE SYSTEM

cord. Between the dura and the arachnoid is a lymph space called
the subdural lymph space.

The arachnoid (arachnoidea) is a delicate, web-like membrane
that lies between the dura and pia, and though closely applied to
the latter does not follow it into the fissures and sulci except in the
case of the longitudinal and lateral cerebral fissures. Between the
arachnoid and the pia is the subarachnoid lymph space (cavum sub-
arachnoideale) which does not communicate with the subdural space.
The arachnoid forms a number of reddish bodies that project into
the venous sinuses. These are the Pacchionian bodies {granulationes
arachnoideales) and although they may appear to lie within the sinu-
ses they are covered by a thin layer of the dura. In certain regions
the arachnoid and pia are separated from each other forming spaces,
the cisterna subarachnoidcales. The cisterna cerebellomedularis is the
largest and is situated between the cerebellum and the roof of the
oblongatal portion of the fourth ventricle. The cisterna pontis is
in relation with the pons. The cisterna inter peduncularis is in the
interpeduncular space. The cisterna chiastnatis is an extension of
the preceding in front of the optic chiasm.

The pia {pia mater) is the vascular membrane of the brain and spinal
cord. It is closely applied to the surface of these and enters all of
the fissures and sulci, more so in the cerebrum than in the cerebellum.
The larger vessels project into the subarachnoid space while the
smaller ones ramify the pia and then pierce the nerve tissue.

THE SPINAL CORD

The spinal cord (medulla spinalis) is that portion of the central
nerve system located in the vertebral canal. It is somewhat cylin-
drical in shape and extends from the margin of the foramen magnum
to the lower border of the first or upper border of the second lumbar
vertebra. In the male it measures about 18 inches (45 cm.) and in
the female about 17 inches (43 cm.). Its weight, when stripped, is
about 30 grams and with the nerve roots about 45 grams. Two
enlargements are present, one in the cervical portion and the other in
the lumbar portion of the cord. The former {intumescentia cervi-
calis) is at its maximum at the sixth cervical vertebra (12 to 14 mm.)
and the latter {intumescentia lumbal is) reaches its maximum at the
twelfth thoracic vertebra (n to 13 mm.). This increase is due to the
added cells and fibers for the appendages. These enlargements vary
in size according to the use of the appendages; in man, ourang and
gibbon the cervical enlargement is the larger. In the kangaroo and
ostrich the lumbar enlargement is the larger. In animals without
appendages these enlargements are barely perceptible.

The terminal portion of the spinal cord is cone-shaped and is called
the conus medullaris. This includes the three lower sacral and the

THE SPINAL CORD

363

coccygeal segments. Its formation is due to the reduction in
quantity of the gray and white substances.

Extending from the conus is a thread, the filum terminale, that

Fig. 260. — Dorsal view of the
spinal cord and membranes in situ.
The vertebral arches have been re-
moved. {From a photograph.)

Fig. 261. — Model of the pons, ob-
longata and spinal cord in situ (ventral
view), a. Pons; b, cervical enlarge-
ment; c, brachial plexus, d, thoracic
nerves (ventral divisions) ; t, lumbar
enlargement and conus; /, Cauda
equina; g, lumbosacral plexus; h*
cervical sympathetic ganglia;*, tho-
racic sympathetic ganglia ; k, I.
splanchnic

is nearly 10 inches (25 cm.) in length. It consists chiefly of the pia
and about one-half lies within the dural sac and its remainder exter-
nal to the sac. Its peripheral end is attached to the coccyx. In
the early months of fetal life, the spinal cord is as long as the verte-

364 THE NERVE SYSTEM

bral canal. As the cord grows less rapidly than does the vertebral
column, it recedes from the bottom so that at birth it extends to the
lower border of the fourth lumbar vertebra and in the adult to the
upper border of the second lumbar vertebra. In the earliest condi-
tion the nerves pass out at right angles to the cord while in the adult,
in order to continue out of the proper foramen of exit, each of the
lower nerves lengthens as the cord recedes and forms a more acute
angle. As a result the lower end of the cord is surrounded by bundles
of nerve fibers resembling, thus, a horse's tail; this constitutes the
cauda equina.

The spinal cord presents a number of fissures and grooves. Yen-
trally in the midline is the ventromcdian fissure {Jissura mcdiana
anterior) the depth of which is about one-third the dorsoventral
diameter of the cord. Dorsally in the midline is the dorsomedian
groove {sulcus mcdiana posterior) . Where the dorsal roots of the spinal
nerves enter there is a groove, upon each side of the cord called the
dorsolateral groove {sulcus lateralis posterior) ; midway between this and
the dorsomedian groove lies the dorso paramedian groove {sulcus inter-
medins posterior) upon each side of the cord. The cord is divided
into halves, longitudinally, by the ventromedian fissure and the
dorsomedian septum. The latter extends all of the way from the
surface to the gray commissure.

Upon transverse section, the spinal cord is seen to consist of
internal gray and external while nerve tissues.

The gray substance is arranged in the form of an H-shaped column,
the dorsoventral bars representing the horns, or cornua and the
transverse bar the gray commissure {commissure grisea). In the gray
commissure is the central canal {caualis centralis). That portion
of each horn ventral to the level of the canal is the ventral horn
{columua anterior) and that behind is the dorsal horn {columna
posterior). The ventral horns are the larger, are blunt and do not
extend to the periphery of the cord; the dorsal horns are more slender
and usually extend to the periphery of the cord. The cornua con-
tain the functionating cells of the spinal cord.

The gray nerve tissue consists of nerve cells their processes, neurog-
lia and nerve fibers. The nerve cells are arranged in groups in the
ventral horns but these groups vary in size and number of cells in
the various segments of the cord. The ventral horn cells are the
largest nerve cells in the body. The various groups are as follows:

1. The ventromedian group is found in nearly all segments of the
cord (except the fifth lumbar and the first sacral). This apparently
represents the nuclei of origin of the fibers of the nerves that supply
the long trunk muscles.

2. The dorsomedian group is found in the upper cervical segments,
the thoracic and first lumbar segments, in other words where no limb
muscles are represented.

THE SPINAL CORD 365

3, 4. The ventrolateral and dorsolateral groups are the largest and
represent the nuclei of origin of the nerves to the muscles of the limbs.
These groups are not continuous throughout the cord but are found
in the cervical and lumbar enlargements and the upper sacral
segments.

5. The central group is found chiefly in the lumbar and sacral
segments.

6. The intermediate, or lateral group, is a thin, continuous column of
cells in the thoracic and first two lumbar segments with recrudes-
cences in the upper cervical and third and fourth sacral segments.
The axones from these cells pass to the sympathetic ganglia and
represent the white rami rommunii antes; they are splanchnic efferent
fibers representing motor connections between cerebrospinal and
sympathetic systems.

Although many axones of the above cells form the nerve fibers
of the ventral roots of the spinal nerves, the axones of the other cells
have a different course and function. Some of these axones as well
as myelinated dendrites pass to the medial and lateral sides of the
ventral horns and form the medial and lateral ground bundles.
Upon entering these bundles the fibers branch T-like and the divi-
sions pass up and down for one or two, and occasionally more,
segments and then turn into the gray substance and end around the
cells of the ventral horns of those segments. These fibers represent
intersegmental association fibers and serve to connect several seg-
ments together for coordination of action of several muscles, or mus-
cle groups. Other cells, especially those along the medial side of the
ventral horns, send their axones and dendrites through the gray com-
missure to the other side of the cord as commissural fibers. The
dendrites pass to the ventral horn cells of the same level and they do
not leave the gray substance. The axones enter the white substance
of the ground bundle of the opposite side, branch T-like and the
ascending and descending branches ultimately end in the gray a
few segments above and below to terminate around the cells of the
ventral horn.

These cells ventral to the intermediate group represent somato-
motor cells while those of the intermediate group region to the trans-
verse line through the canal represent the visceromotor cells.

In the dorsal horn there is only one distinct group of large cells, the
other cells being somewhat scattered and small. This main- group
is the nucleus of Clarke (nucleus thoracis) and is an unbroken column
from the eighth cervical segment to the second lumbar segment; it
lies at the dorsal side of the cervix of the dorsal horn (the junction of
this horn with the gray commissure). Most of the axones of these
cells pass to the dorsolateral columns of the same side forming the
superficial dorsolateral spinocerebellar tract. The other axones pass

366 THE NERVE SYSTEM

through the gray commissure to the opposite side (possibly to the
white substance) constituting axones of commissural cells.

The other cells of the dorsal horn are classified as marginal, stellate
and spindle cells. The marginal cells are near the extremity of the
dorsal horn and the axones enter the lateral columns as intersegmen-
tal association and other fibers. The stellate cells send their mye-
linated dendrites to the funiculus cuneatus of the dorsal column.
The spindle cells, the smallest, send their axones to the dorsal col-
umns. Some of these cells also send their myelinated axones
through the dorsal portion of the gray commissure to the opposite
side to form there the two spinothalamic tracts, the spinotectal and
superficial ventrolateral spinocerebellar tracts.

These cells near the transverse midline of the dorsal horns repre-
sent viscerosensor cells while those farther dorsad represent somato-
sensor cells.

The neuroglia consists of spider-like cells that possess a small, flat
body and many, long, slender processes. In addition there are many
glial fibers that form a meshwork for the support of the nerve cells
and vessels. In the region of the spinal canal there is an especially
dense meshwork of these fibers called the substantia grisea centralis;
around the peripheral end of each dorsal horn is a cap of neuroglia
called the substantia gelatinosa, or caput cornualis. This contains a
few nerve cells that send their axones into the marginal tract.

The white nerve tissue consists mainly of myelinated nerve fibers
supported by neuroglia and a little white fibrous tissue. These are
divided into columns and tracts. In each half of the cord there are
three columns, ventral, lateral and dorsal. The ventral column lies
between the ventral median fissure and the ventral nerve roots; the
lateral column lies between the ventral and dorsal nerve roots; the
dorsal column lies between the dorsal nerve root and the dorsomedian
septum. Connecting the ventral columns across the midline is the
white commissure (commissura alba) that lies between the ventral
median fissure (ventrally) and the gray commissure (dorsally).

Each column consists of tracts, some of which, however, do not
extend the full length of the spinal cord. The ventral columns are
the following:

1. The sulcomarginal tract (fasciculus lectospinalis) borders the
ventromedian fissure, consists of descending fibers from the corpora
quadrigemina of the opposite side and is seen in the cervical part of
the cord.

2. The direct pyramidal tract {fasciculus cerebrospinalis anterior)
lies lateral to the preceding and consists of descending fibers from the
motor cells of the cerebral cortex. It represents undecussated
fibers (10 to 15 per cent.) of the oblongata but they ultimately cross
to the opposite ventral horn through the white commissure at vari-

THE SPINAL CORD

367

ous levels. It does not extend below the midthoracic segments of
the cord.

3. The vestibulospinal tract (fas. vestibulospinalis) consists of
descending fibers from the vestibular nuclei of the brain stem, that
end in the ventral horn of the cord as far as the sacral region.

4. The ventral ground bundle (fasc. anterior proprius) lies at the
medial side of the ventral horn. It consists of intersegmental asso-
ciation fibers of the ventral cells of the same and opposite sides
(ascending and descending).

5. The ventral spinothalamic tract (fasc. spinothalamicus anterior)
lies in the intermediate zone of the ventral columns, consists of

Fig. 262. — Diagram of the

tracts of the spinal

origin or termination.

ascending axones of the cells of the opposite dorsal horn that pass
through the white commissure and ascend to end in the thalamus.
These fibers convey touch and pressure impressions from the opposite
side of the body.

The lateral column is more extensive and contains more tracts.

1. The olivospinal tract (fasc. olivospinalis) lies at the side of, or in
the ventral root region and consists of descending axones from
the cells of the olivary nucleus (in the oblongata) ; they end around
the ventral horn cells. This tract is found in the cervical segments.

2. The superficial ventrolateral spinocerebellar tract (of Gowers')
(fasc. spinocerebellaris anterior) is at the periphery of the cord and
consists of axones from the cells of the dorsal horn of the opposite

368 THE NERVE SYSTEM

side that cross through the white commissure and ventral horn to
form this tract. These fibers ascend to the cerebellum through its
brachium conjunctivum and constitute ascending fibers that convey
muscle sense impressions, chiefly from the opposite side of the body;
they are concerned with reflex actions.

3. The superficial dorsolateral spinocerebellar tract (fasc. spino-
cerebellarls posterior) extends from the preceding to the dorsal root
zone. It consists of the axones of the nucleus of Clarke from (he
same and opposite sides. These ascend and enter the cerebellum
through the restiform body and convey also muscle sense impressions
and are concerned with reflexes.

4. The crossed pyramidal tract (fasc. cerebrospinal is lateralis) is
very extensive and lies medial to the preceding. This consists of the
descending axones (85 to 90 per cent.) of the motor cells of the cerebral
cortex that have decussated in the oblongata. They enter the ven-
tral horn at various levels and terminate about the cells there that
form the ventral roots of the spinal nerves especially. This tract
continues to the fourth sacral segment.

5. The lateral ground bundle (fasc. lateralis proplus) lies along the
lateral margin of the ventral and dorsal horns. It consists of
intersegmental association fibers (ascending and descending) that
arise in the cells of both horns and end at various levels above and
below their origin.

Between the above-mentioned tracts is an area called the mixed
lateral tract. Here several tracts have been isolated.

6. The rubrospinal tract (fasc. rubrospinalis) consists of axones
that descend from the cells of the red nucleus of the midbrain to end
about the cells of the ventral horn.

7. The tectospinal tract (fasc. tcctospinalis) consists of descending
axones from the cells of the corpora quadrigemina that end about the
cells of the ventral horn.

8. The fasciculus spinotectalis consists of ascending axones of the
cells of the dorsal horn and ends in the corpora quadrigemina.

9. Ventral and dorsal spinothalamic tracts (fasciculi spinothalamics
anterior el posterior) comprise ascending axones of cells of the dorsal
horn of the opposite side that end in the thalamus. The ventral one
conveys impressions of touch and pressure from the opposite side
while the dorsal ones (mixed with the fibers of Govvers' tract) convey
impressions of heat, cold and pain from the opposite side.

The tracts of the dorsal column are as follows:

1. The fasciculus gracilis (Colli) occupies the medial portion of the
column along the dorsal septum. It consists almost entirely of the
axones of the cells in the ganglia of the dorsal roots of the spinal
nerves. It comprises those fibers representing the sacral, the lum-
bar and last eight thoracic nerves. The sacral fibers are nearest

SPINAL CORD 369

the dorsal septum and the highest thoracic are nearest fasciculus
cuneatus. There is really no functional difference between the
fibers of this tract and the fasciculus cuneatus, the latter represent-
ing fibers that enter the cord merely at a higher level. Most of
these fibers ascend some of them terminating in the gray substance
of the dorsal horn at various levels; others, representing fibers from
all the spinal nerve roots of this tract, extend the length of the cord
and end in the nucleus gracilis of the oblongata. The descending
fibers will be considered under the tracts of Schultze, Flechsig and
septomarginal of Bruce.

2. The fasciculus cuneatus (Burdachi) lies lateral to the preceding
and represents axones of the cells in the ganglia of the upper thoracic
and cervical nerves. They correspond to the preceding and are
merely of a higher level.

3. The dorsal ground bundle (fasc. posterior proprius) is another
intersegmental association tract. It consists of the axones of some
of the cells in the dorsal horn that pass to the tract and branch
T-like and so ascend and descend for a short distance and reenter
the gray substance.

4. The comma tract of Schultze (fasc. inlcrlascicularis) lies deep
between the fasciculis gracilis and cuneatus. It consists of the short
descending branches of the fibers that form the two above fasciculi.
These descend for a short distance and enter the gray of the dorsal
horn.

5. The oval tract of Flechsig {tractus cervicolumbalis of Edmger) is
another such tract situated in the fasciculus gracilis at the dorsal
median septum. This is best seen in the lumbar region of the cord.

6. The septomarginal tract (fasc. septomarginal of Bruce) is
another group of descending fibers along the dorsal septum but close
to the gray commissure. These tracts, four, five and six, are con-
sidered to be of an associative nature.

7. The marginal tract (fasc. posterolateral is of Spitzka arid Lissauer)
is a small bundle of fibers among the dorsal root fibers just after
they enter the cord. It consists of the axones of some of the cells of
the ganglia, that do not enter the dorsal fasciculi proper but continue
up the spinal cord as the marginal tract to end around the cells of
the substantia gelatinosa after a course of only three or four seg-
ments; some of these fibers may possibly end around the cells of the
ventral and dorsal horns.

The dorsal columns are the most complex of the cord. It will sim-
plify them to consider the course of the fibers that enter the dorsal
roots of the spinal nerves.

1. Most of these latter fibers form the fasciculi cuneatus and
gracilis; these fibers divide into ascending and descending branches.
The ascending branches are of variable length some ending soon in

370 THE MERYE SYSTEM

the gray of the dorsal horn and others ending in the same way at
higher levels. Some ascending fibers of each spinal nerve continue
to the oblongata and end in the nuclei cuneatus and gracilis. The
descending branches that form the oval, comma and septomarginal
tracts end in the gray substance of the dorsal horn.

2. Many fibers after entering the dorsal root zone course along
the medial side of the gray of the dorsal horn and enter it to terminate
around the cells of the same level. These latter cells represent
neurons that form various tracts of the lateral column and are also
concerned in the reflex arc.

3. Some fibers of the dorsal roots enter into the formation of the
marginal tract and terminate about the cells of the substantia
gelatinosa and perhaps around other cells of the ventral and dorsal
horns.

The various cell groups and the formation of the various tracts of
the spinal cord are diagrammatically represented in Fig. 262.

The fiber tracts consist of extrinsic fibers: (a) that arise outside
of the cord and traverse it or end in it; (b) fibers that arise in the
cord and pass out of it. Under (a) are the tracts of Goll and Bur-
dach, the crossed and direct pyramidal tracts, vestibulospinal, olivo-
spinal, some of the mixed lateral and marginal tracts; the direct
cerebellar and Gowers' tracts, and parts of the mixed lateral tracts
come under (b).

The intrinsic fibers are those that arise and end in the cord as the
three ground bundles.

THE BRAIN

The brain, or encephalon, is an ovoid mass of gray and white nerve
tissues that occupies the cranial cavity. It reaches its highest de-
velopment in man. It is the seat of the intellect and special senses
and presides over motion, respiration, circulation, etc. Its measure-
ments are as follows: Frontooccipitally 6.4 to 6.8 inches (16 to 17
cm.), laterally 5.2 to 5.6 inches (13 to 14 cm.); height 5 inches
(12.5 cm.). The average weight of the adult male brain is 1400
grams and of the female 1250 grams. At birth the weight in the
male is 400 grams and in the female 380 grams. It usually doubles
by the end of the first year and trebles by the end of the fourth or
fifth year; it almost reaches its maximum by the end of the eighth
or ninth year. From that time the growth in weight is slow and
ceases about the eighteenth or twentieth year. The brain begins
to lose weight after the sixtieth year and very rapidly from seventy
to eighty years. The important factors that affect brain weight are
age, sex, race, intelligence, skull form and body weight.

In regard to race the Caucasians have the heaviest and the Aus-
tralians the lightest. There is considerable variation in the Cau-

THE BRAIN

371

casian race. In regard to intelligence, the brains of the highly in-
tellectual individuals will weigh on the average 100 grams more.
Brains weighing under 1000 grams in the male and 900 grams in the
female are usually considered too low for mental integrity.

The brain consists of a number of divisions: (1) the cerebrum,
comprising the cerebral hemispheres and a number of lesser structures;
second, the cerebellum; third, the brain stem, comprising the midbrain,
the pons and tegmental portion and the oblongata. The brain as a
whole when viewed from above, exhibits two lateral masses, the hemi-

h

Olfactory tract Ot

showing the attachn
From a photograph. )

spheres, separated by a deep cleft, the longitudinal fissure {fissura
longitudinalis cerebri). The frontal pole is rather narrow but not
pointed. The parietooccipital region in the broadest and most
massive, while the occipital pole is rather sharply pointed. The
superior and lateral surfaces show severalrather deep clefts or fissures
and a number of smaller clefts or sulci; these separate the various
lobes and convolutions from one another. The size and number of
these convolutions depends upon the degree of intelligence. When
the hemispheres are separated a whitish band, quite extensive fronto-
occipitally, is seen at the bottom of the fissure connecting the two
hemispheres; this is the corpus callosum, or intercerebral commissure.
The cerebellum is not visible in this view.

The under, or ventral surface (basis cerebri), is also called the

372 THE NERVE SYSTEM

base. Going from before backward the following parts are seen: the
frontal lobes separated by the longitudinal fissure and upon each side
of the fissure an olfactory bulb and tract. Just behind the tracts,
across the midline, lies the optic chiasm and farther to the side the
temporal lobes which are separated from the frontal lobes by the
sylvian fissure. Just behind the chiasm is the tuber and stalk of the
pituitary body; to the rear of the tuber lie the two corpora albican-
tia, one upon each side of the midline. This represents the extent of
the cerebrum upon the basal surface.

Behind the corpora albicantia is a rather deep, triangular space,
the posterior perforated space, bounded laterally by two large diverg-
ing whitish masses, the crura cerebri. Appearing from the medial
side of each crus (in the above space) is a nerve, the oculomotor, or
third cerebral nerve. These structures constitute the midbrain por-
tion of the brain stem.

Behind the posterior perforated space and partially covering the
crura cerebri is a broad mass of transversely coursing fibers, the
pons; at its lateral boundaries in front is seen a large nerve upon each
side, the trigeminus, or fifth cerebral nerve; at its posterolateral
boundary are noted two nerves, the facial, or seventh and the audi-
tory, or eighth nerves. Coming out between the pons and the crus
on each side is the trochlearis, or fourth nerve; at the inferior border
of the pons and near the midline is seen the abducens, or sixth nerve.
On each side, the pons continues as a thick rope-like mass that
enters the corresponding cerebellar hemisphere; these two masses
constitute the middle cerebellar peduncles or brachia pontis.

Behind the pons is a tapering structure that is continuous with the
spinal cord. This is the oblongata. Out of the first fissure to the
side of the median groove the hypoglossus, or twelfth nerve, is seen to
emerge, while farther to the side are seen the roots of the glosso-
pharyugcus (ninth), vagus (tenth )and accessorius (eleventh) nerves.

At the sides of the oblongata and completely covered by the occip-
ital pole of the cerebrum are the two hemispheres of the cerebellum,
separated from each other in the midline by a fissure.

The dorsal surface of the midbrain, pons and oblongata region are
completely hidden by the cerebrum and cerebellum.

When the cerebellum is raised and the pia removed a shallow,
diamond-shaped fossa, the fourth ventricle is exposed. This is
bounded below by the diverging inferior cerebellar peduncles and
above by the converging superior cerebellar peduncles.

When the cerebral hemispheres are raised from the cerebellum the
pineal body and the corpora quadrigemina are exposed. The pineal
body lies in front of and between the two anterior quadrigeminal
bodies. These will all be considered under the midbrain.

It is customary to give the external anatomy of each part with its

THE BRAIN

373

Olfactory bulb.

Optic N. -
Oculomotor II.

IriyeminaJ 'M.
Facial fj.

Vagal N.
Accessory N

Optic chiasm

Trochlear//,
-tons

fibcluce/15 A/.
Auditor}/ N.
Glossopharyngeal 'IV.
HypojIossaJ N-

OblonyaJa

Cerebellum

Fig. 264. — Diagram of the ventral surface of brain showing the attachments of the cerebral

X

y&

C -^ ,

A

*2

-w-**

Fig. 265. — Left lateral aspect of the brain with the arachnoid, pia and vessels intact. (From
a photograph).

374

THE NERVE SYSTEM

internal anatomy immediately following. It seems more practical
to give the external anatomy of each part in sequence connecting the
external landmarks as much as possible, and then to give the internal
anatomy and carry it through in the same connected manner.

The parts of the brain are often described as forebrain, midbrain
and hindbrain. It seems more practical to describe the parts under
cerebrum, cerebellum and brain stem and will be taken up in that way.

THE BRAIN STEM

The brain stem is continuous with the spinal cord and as it shows
less differentiation and is the next direct part it will be first con-

optic chiasma

interpeduncular

accessory nerve
medulla oblongata
of the pyramids

(.Sobotla and McMu

sidered. Its parts from below, upward are oblongata, pons and teg-
mental portion of the pons and the midbrain.

The oblongata (medulla oblongata) is about i inch (2.5 cm.) in
length and is a connecting link between the spinal cord and higher
centers. It is smallest at the spinal cord end and gradually increases
in its dimensions toward its base. At the spinal cord end it meas-

THE OBLONGATA

375

ures about 10 mm. in both dimensions; at the pontile end it measures
17 to 18 mm., transversely, and about 15 mm. dorsoventrallv. It is
flattened from before backward and is directed nearly vertically,
resembling an inverted, flattened, truncated cone. It presents
ventral, lateral and dorsal areas and certain grooves.

The ventral area contains only the pyramid [pyramis, or fasciculus
cerebrospinalis anterior) and is divided longitudinally by the ventro-

•mediate portion)

root filaments of vagus, ri
and glossopharyngeal * " \?^i

restiform body
pyramid

taberadam cineream' t",'"\ fl
root filaments of accessary ner\-»

if

J) *„

anterior root filaments of * \ i H %fu

cervical nerve II '(j^^^H

anterior lateral sulcus-' ^^^^HS

posterior lateral salens spinal

'§ . ainea te tubercle
M fasciculus euneatas
1. posterior intermediate salens
1 posterior root filaments
of cervical nerve II

Fig. 2^7. — Brain stem, lateral view

. (Sobotta and McMurrich.)

median groove (fissura mediana anterior) that terminates at the fora-
men cecum. This groove is not continuous as it is crossed and in-
terrupted by bundles of fibers passing from one side to the other
constituting the pyramidal decussation (decussatio pyramidiun). At a
little distance to the side of the ventromedian groove is another, the
ventrolateral sulcus (sulcus lateralis anterior). The mass of fibers be-
tween these two grooves is the pyramid. Those fibers of the pyra-
mid that cross, or decussate (85 to 90 per cent.) constitute the
crossed pyramidal tract of the spinal cord. The remaining fibers
continue down the same side to the appropriate levels, then cross to

376

THE NERVE SYSTEM

the opposite side through the white commissure of the cord; these
libers constitute the direct pyramidal tract of the spinal cord. Be-
tween the pons and the upper end of the pyramid the abducens nerve
is seen to emerge.

The lateral area of the oblongata contains the olivary body, the
lateral column and certain nerve roots. The olivary body (oliva)
is about the size and shape of an olive pit, that is, about ]2 inch
(12 mm.) long; it is situated at the upper end of the lateral area
and represents the position of the inferior olivary nucleus.

Dorsal groove
Fig 268 — Dissei tion showing the dorsal aspect of the brain stem with the corpora striata
and dentate nuclei intact. (From a photograph.)

The lateral column is in part the continuation of some of the lateral
tracts of the spinal cord, i.e., the direct cerebellar, Gowers' and the
lateral ground bundle. Below (caudad) the olive it is well marked,
being located between the ventrolateral and dorsolateral grooves.
Near the olive it is crossed and hidden by the external arcuate fibers
that pass to the dorsal area.

Between the olive and the pyramid are seen the roots of the hypo-
glossal nerve emerging from the ventrolateral groove. In the dorso-
lateral groove are seen the roots of the vagal and glossopharyngeal
nerves, above, and the roots of the accessory nerve, below.

THE PONS 377

The dorsal area is more complicated. In its lower (caudal) two-
thirds in the midline, is the dorsomedian groove (fissura mediana
posterior), which ends above at the lower angle of the fourth ventricle.
This is bounded upon each side by a club-shaped elevation, the nu-
cleus gracilis; the upper end of this is expanded and is called the clava.
The nucleus gracilis is bounded laterally by the dorsal paramedian
groove (sulcus intermedins) to the outside of which is the nucleus cune-
atus; this is bounded laterally by the dorsolateral groove (sulcus
lateralis posterior). These two nuclei occupy the lower two-thirds of
the dorsal area. Between the upper end of the nucleus cuneatus and
the lateral area lies an eminence the tuberculum rolandi (tuboculum
cincreum); this eminence lies in the dorsolateral groove and causes it
to fork at this point. The upper part of the dorsal area in the midline
is the lower part of the fourth ventricle, while the lateral part of the
area is represented by quite a mass of fibers called the restiform body,
or inferior cerebellar peduncle (corpus rest i forme); these two peduncles
constitute the lateral boundaries of the lower half of the fourth ven-
tricle. This peduncle consists of the direct cerebellar tract of the
spinal cord and the superficial and deep arcuate fibers of the oblongata.
The superficial arcuate fibers appear from the ventromedian groove
and sweep laterally and dorsally over the olive in a sheet-like manner
occasionally covering the entire olive. The}- continue dorsally and
assist in the formation of the restiform body.

THE PONS AND THE TEGMENTAL PART OF THE PONS

The pons, or bridge (Fig. 266), represents the broad band of fibers
on the ventral surface of the middle part of the brain stem. It is
not sharply demarcated from the tegmental part upon section. It
represents the transverse fibers that connect the cerebellar hemi-
spheres with each other through the nuclei pontis and constitutes
a cerebellar commissure. It is about 1 inch (2.5 cm.) from side to
side and also from above downward; it extends laterally to the root
of the trigeminus nerve on each side. Along the midline its presents
the basilar groove (sulcus basilaris) in which lies the basilar artery.
Along the lower border of the pons three cerebral nerves are seen;
near the midline is the abducens and at the side the facial and audi-
tory nerves, at the upper edge of the restiform body. At the sides
the pons fibers become massed into a cylindrical band that passes
into each cerebellar hemisphere; these are the middle cerebellar
peduncles (brachia pontis). Emerging through the lateral border of
the pons is the trigeminal nerve constituting the arbitrary lateral
boundary of the pons and the beginning of the brachium pontis.

The tegmental part of the pons, or pars dorsalis pontis, cannot
be seen from the ventral surface. If a knife be passed fron tally,
dorsal to the pons and this structure lifted off, the tegmental

378 THE NERVE SYSTEM

part approximately, will be exposed; it seems to be a continuation
of the oblongata and by some is well called the preoblongata. The
dorsal part of this portion of the brain stem shows the upper half of
the fourth ventricle. At the lateral angles of this space are seen the
massive middle cerebellar peduncles; the lateral boundaries, above,
are the converging superior cerebellar peduncles (brachia conjunctiva)
that also overhang and form a part of the roof of the fourth ventricle.
The fourth ventricle, or rhomboidal fossa (ventriculus quart us),
represents the canal of the spinal cord laid open and the walls at
the sides stretched so as to form
a diamond-shaped fossa. It is
nearly vertical in direction. The
roof is very thin, possessing prac-
tically no nerve tissue, and is rein-
forced by the pia; that portion over
the lower half of the ventricle is
called the inferior medullary velum
(velum medullare inferius), while that
over the upper half constitutes the
superior medullary velum, or valvule
(velum medullare superius). Ordi-
narily the cerebellum hides the fourth
ventricle completely.

The so-called floor is nearly verti-
cal in direction and represents the
dorsal surface of the pars dorsalis
pontis and oblongata; it consists of
gray nerve tissue. It shows a median
longitudinal furrow and is divided
into upper and lower triangles by
some nerve fibers that cross the middle of the space transversely
to pass into the median furrow; these fibers, the acoustic strice
(strim medullaris) may be absent, but when present approximately
separate the oblongatal part of the ventricle from the tegmental,
or pontile potion.

In the upper triangle near the midline and the acoustic striae is
an eminence, the collicidus facialis (cmincntia mediana); just below
and lateral is a depressed area, the superior fovea. Above the emi-
nence, toward the apex of the triangle, is a slate-colored, slightly
depressed area, the locus carnleus; the cells in this area are pig-
mented by the substantia fcrruginea.

In the lower triangle just below the acoustic striae is the area acus-
tica (better area vestibularis). Medially and below this is a triangu-
lar depression, the trigonum vagi (ala ciuerca) and between this and
the median groove is seen a tapering elevation, the trigonum hypo-

-The so-called "flo

fourth ventricle.

THE MIDBRAIN 379

glossi. These tapering elevations, at the lower angle of the ventricle,
constitute the calamus scriptorius (point of a pen).

Between the lower margin of the trigonum vagi and the lower
boundary of the ventricle is a narrow space, the area postrema; this
is separated from the trigonum vagi by the funiculus separans, a
clear ridge.

The lower lateral boundaries of the fourth ventricle are the diverg-
ing restiform bodies; at the lateral angles are the two middle pedun-
cles; the upper lateral boundaries are the converging superior
peduncles that also form a small part of the roof in this region.

The fourth ventricle communicates caudally with the spinal canal
and above it is continuous with the aqueduct of Sylvius, or iter. It
represents a lymph space and communicates with the subarach-
noid space by means of an opening in the roof of the lower triangle,
the foramen of Majendie. The roof at the lateral angles possesses
small openings called the foramina of Luschka. At the sides of the
ventricle are the lateral recesses (recessi lateralcs) that communicate
with the subarachnoid space upon the ventral surface (at the sides)
between the acoustic and hypoglossal nerves by means of the
apertura lateralis ventriculi quarti.

THE MIDBRAIN

The midbrain, the upper part of the brain stem, comprises the
crura cerebri, the posterior perforated space, the corpora quadrigemina,
the medial geniculate bodies, the brachia and the aqueduct of Sylvius.
It is about % inch (18 mm.) in length.

The crura cerebri (pedunculi cerebri) are seen upon the ventral
surface; each crus is a large, whitish, cylindric mass of nerve fibers
which starts at the upper border of the pons, but at a more dorsal
level, and passes upward (frontally) and laterally into the cerebrum.
It represents the chief bulk of the midbrain. Between the diverging
crura is a triangular depressed area called the posterior perforated
space (interpeduncular space). This is so called because of the large
number of small openings that transmit vessels into the interior of
the brain of this region. Along the medial side of each crus is the
oculomotor sulcus (sulcus oculomotorius) from which emerges the
oculomotor nerve. Near the pontile border of the lateral margin
of each crus is the trochlear nerve.

Upon each side of the midbrain are seen the crus, the medial
geniculate body, and the superior and inferior brachia.

The internal geniculate body (corpus geniculatum mediale) is a
small oval eminence on the side of the midbrain. It is connected
with its fellow of the opposite side by the commissure of Gudden.
It also represents an intermediate nucleus in the auditory pathway.

The superior brachium (brachium quadrigeminum superius) is a

38o

THE NERVE SYSTEM

band of libers at the upper, medial part of the midbrain . It consists
of fibers of the optic tract that terminate in the superior quad-rigem-
inal body and also of fibers that pass to the lateral geniculate body.
The inferior brachium (brachium quadrigeminum inferius) lies at
the side of the upper quadrigeminal body and disappears under the
medial geniculate body. It represents fibers of the auditory path-
way from the inferior quadrigeminal body.

mammillary hotly

optic chiasma )

(Sobotla and McMur

The dorsal surface of the midbrain exhibits the corpora quadrigemina,
or colliculi; of these there are four, two superior and two inferior, and
they are separated from one another by a transverse and a longi-
tudinal furrow. The latter is in the midline.

The superior quadrigemina are oval in shape, yellowish gray in
color and are the larger. Above, in the median groove that sepa-
rates them, lies the pineal body. They are centers connected with
eye-muscle reflexes, resulting from optic and auditory impulses.

The inferior quadrigemina are nearly hemispherical in shape and
lighter in color than the preceding. They are nuclei in the pathway
of auditory impulses.

THE CEREBELLUM

38l

The superior and inferior quadrigemina rest upon the lamina
quadrigemina which really constitutes the dorsal wall of the mid-
brain.

The iter, or aqueduct (aqueduct us cerebri), is a narrow canal con-
necting the third and fourth ventricles. Its shape varies somewhat
in different parts and it lies nearer the dorsal than the ventral sur-
face of the midbrain.

\

^^__

1

\^

Lenticular nucleus
Caudate nucleus
Internal capsule

Thalamus
Corpora quadrigem
Valvula
Brachiu::;

Dentate nucleus
Fourth ventricle

Dorsal groove

Fig. 271. — Dissection showing the dorsal aspect of the brain stem with the copora striata
and dentate nuclei intact. (From a photograph.)

THE CEREBELLUM

The cerebellum lies in the posterior fossa of the skull under cover
of the occipital pole of the cerebrum from which it is separated by
the shelf of dura called the tentorium cerebelli. It averages 165
grams in the male and 155 grams in the female, reaching its greatest
weight between the twenty-fifth and thirty-fifth years. It repre-
sents a coordinating center and might well be called the balancing
brain.

The cerebellum consists of two lateral lobes, or hemispheres, and
a middle lobe, or vermis. The two hemispheres are separated from
each other ventrally by a groove, the vallecula, into which the oblon-
gata, tegmental portion of the pons and the midbrain fit. Dorsally
the hemispheres are less widely separated.

382

THE NERVE SYSTEM

The vermis and each hemisphere present a superior and an inferior
surface. The superior surface of the vermis consists of the following
lobes, from before backward: (a) Hngula cerebelli; (b) lobus centralis;

Fig. 272. — Superior surface of the cerebellum. {From a pnoiograpli.)

(c) c id men; (d) declive. The lobes of the superior surface of each
hemisphere represents a continuation of these with the exception of
the lingula. The central lobe is continued into each hemisphere as

Fig. 273. — Frontal '

' of the cerebellu

(From a photograph.)

the ali lobidi centralis. The admen continues as the lobus culminis.
The declive continues as the lobus lunatus. In addition to these
lobes the last of those of the superior surface is the posteroinjcrior
lobe.

Upon the inferior surface of the vermis the following lobes are

THE CEREBRUM 383

noted from behind forward: (a) tuber; (b) pyramis; (c) uvula; (d)
nodulus. Upon each hemisphere in the same order are the (a)
posteroinferior lobule; {b) biveniral lobule; (c) tonsilla; (d) flocculus.

The fissures of the cerebellum all run, in general, transversely
and are eight in number forming, thus, nine lobes.

The cerebellum is connected to the rest of the nerve system by
its three pairs of peduncles. The inferior peduncles (corpora resti-
forme) connect the cerebellum with the spinal cord, the oblongata
and the cerebral nerve nuclei. The middle peduncles (brachia pontis)
the largest, consist mainly of fibers that connect one cerebellar
hemisphere with the other through the nuclei pontis. The superior
peduncles [brachia conjunctiva) are the smallest and consist chiefly
of fibers that connect the cerebellar cortex with the midbrain,
especially.

THE CEREBRUM

The cerebrum comprises the cerebral hemispheres, the corpora
striata, the callosum, olfactory tracts and bulbs and the following
structures usually classified as diencephalon: the thalami, the epiphy-
sis, the corpora albicantia, tuber, hypophysis, optic chiasm and tracts
and the lateral geniculate bodies.

Viewed dorsally only the cerebral hemispheres are seen. When
these are separated in the midline, the callosum is exposed. If the
cerebral hemispheres are raised, then the epiphysis and velum inter-
positum are shown covering the thalami and third ventricle. The
lateral geniculate bodies are also seen laterally placed. Ventrally
are seen from behind forward, the corpora albicantia, the tuber
cinereum and hypophysis, the optic chiasm and tracts, and the ol-
factory tracts and bulbs.

The ventral structures will be considered first.

The corpora albicantia are two small, whitish bodies situated close
together, one on each side of the midline in the interpeduncular
space. These are nuclei in the olfactory pathway.

The tuber cinereum is a hollow, conical structure lying just in
front of the corpora albicantia. Its cavity constitutes the infun-
dibular recess of the third ventricle. Connected with the lower end
of the tuber is the hypophysis.

The hypophysis, or pituitary body, is a small glandular structure
suspended from the lower end of the tuber by means of a small
stalk. It consists of two divisions the, anterior lobe, or prehypophysis,
and a posterior portion, the posthypophysis. The former is epithelial
in structure and is derived from the oral epithelium; the posthypophy-
sis is a direct derivative of the nerve system. These two parts are
bound together by a common capsule.

The optic chiasm lies just in front of the tuber and is formed by

3»4

THE NERVE SYSTEM

the convergence of the optic nerves here, attended by a decussation
of some of their fibers. The nerve fibers from the nasal portion of
each retina cross to the opposite side of the brain while those from
the temporal side of the retina continue on the same side. This
produces the chiasm and decussation. The fibers on each side then
continue as a flattened band called the optic tract of which some of
the fibers pass to the lateral geniculate body, others to the puhinar
of the thalamus and the remainder to the superior quadrigemina.
These fibers constitute the lateral root of the optic nerve. The

Olfactory bulb

•r

Olfactory tract

Oculomotor__JM(

m ■

nerve ^^^E

Abducens__H^H

lirrvt' K. *»

Glossopharyn- j^^\
geal and ^^ \
vagal nerves

th

Hypoglossal nerve ^

bv H <

/Opt..

A^

-Ventral aspect of the brain showing the attachment of the cerebral
Ft >»i a photograph.)

medial root, or infracomtnissure of Gudden, are independent of these
fibers and connect one medial geniculate bod}- with the other through
the chiasm but constitute no part of the true optic pathway.

The lamine tenninalis is a thin layer of gray nerve tissue just
behind the optic chiasm, extending upward into the cerebrum in
front of the optic thalami and anterior commissure; it separates
these from the cerebral hemisphere in front. It represents the fron-
tal end of the original neural tube. The preceding structures con-
stitute the hypothalamus.

The lateral geniculate body (corpus geniculatum laterale) is seen
in a lateral view and lies just in front of the medial geniculate body
of the midbrain and represents a way-station of visual impulses in
the optic pathway. It represents a part of the thalamus. These
bodies constitute the metathalamus.

THE THALAMI AND EPIPHYSIS

385

The thalami lie under cover of the cerebral hemispheres and velum
interpositum. When exposed each is a large, ovoid mass of gray
nerve tissue separated from its fellow, in the midline, by a vertical
cleft, the third ventricle. The posteromedial part constitutes the
puhinar. The ventricular surface is smooth and shows an area
where the two thalami are united across the midline, making the
middle commissure (massa intermedia). Above this and arching over
the entire surface is a narrow ridge showing where the dorsal and

Septum pellucidu

Posterior commissure

Optic chiasm

Hypophysi
Corpus mammil:

th ventricle
medullar;

Oblongata

-Median sagittal section of the brain showing the medial surface of the right half.
{From a photograph.)

medial surfaces meet and where the velum interpositum is attached.
The thalamus is a nucleus in the optic pathway as well as in the
general sensor pathway, from the tegmentum to the cerebral cortex
(touch pain, temperature, muscle sense and emotional).

The epiphysis, or pineal body, is a small, reddish body lying between
the superior quadrigeminal bodies at the caudal end of the roof of the
third ventricle. Its cavity is called the epiphyseal recess and is an
extension of the third ventricle.

The velum interpositum is a thin membrane roofing the third ven-
tricle and covering the dorsal surface of the thalami. This repre-
sents the bulk of the roof of the third ventricle and no nerve tissue
develops here. It is a thin epithelial layer and is reinforced by pia
with its blood-vessels called the tela ckorioidea. The tela forces this
epithelial layer in as two ridges with blood-vessels and these consti-
tute a part of the chorioidal plexuses.

386 THE NERVE SYSTEM

Just in front of the superior quadrigemina and between the caudal
ends of the thalami is a small triangular area called the trigonum
babe u nice. This contains some nerve cells, the ganglion habenuliB.
The axones from these cells form the fasciculus retroflexus and termi-
nate in the ganglion inlerpeduncidare of the interpeduncular space.
The ganglion habenula? is a way-station in the olfactory pathway.

The epiphysis, velum and trigonum habenulae constitute the
cpithalamus.

The third ventricle (vcntriculus tcrtius) is a vertical, cleft-like
space between the two thalami. It communicates caudally with the
iter and frontally and laterally with the lateral ventricles, in the
cerebral hemispheres, by means of the foramina of Monro.
CEREBRAL HEMISPHERES

The cerebral hemispheres constitute about six-sevenths of the
brain weight. The hemicerebri are separated from each other, in
the midline, by the median longitudinal fissure [fissura longitudinalis
cerebri) at the bottom of which is seen the callosum which connects
these hemispheres with each other. The cerebral hemispheres are
connected with the rest of the brain mass by means of the internal
capsule.

Upon examining each hemicerebrum the lateral, or external surface
is seen to be convex while the media! surface is flattened above and
hollowed out below in the temporal lobe region. Each of these
exhibits little folds called convolutions which are separated form each
other by fissures, or sulci. The main fissures are important land
marks in the cerebral topography and serve to separate more or less
completely the various lobes from one another.

The lobes are frontal, parietal, occipital, temporal and central in each
hemisphere. The interlobar fissures bound these lobes fairly well.

Fissures. — Upon the lateral surface are seen the following inter-
lobar fissures:

i. The Sylvian fissure (fissura cerebri lateralis) is about 2}<i inches
(6 cm.) long and is seen at the base and side of the frontal end of the
cerebrum. It is the deepest fissure and varies from 15 mm. at its
beginning to 2$ to 30 mm., at its deepest part. It extends back-
ward and upward and serves to separate the frontal and parietal
lobes, above, from the temporal lobe, below. It consists of stem,
posterior, ascending and anterior horizontal rami. When its lips are
separated, the insula, or island of Rcil (central lobe) is exposed. The
insula is surrounded by the circuminsular fissure (sulcus circidares).

2. The central fissure (fissura centralis) starts upon the medial sur-
face and then extends obliquely downward and forward on the lateral
surface, in a sinuous manner, for about 4 inches (10 cm). It makes
an angle of about 710 with the midline and separates the frontal
from the parietal lobe.

THE FISSURES AND LOBES OF THE CEREBRUM 387

V^'

^.Occipital lobe

Temporal lobe

Lateral cerebral fissure (Sttviusl Oblongata

Fig. ^76. — Left lateral aspect of the brain with the membranes removed. (Fr

Fig. 277- — Main Assures and lobes of the lateral erebral hemisphere.

388 THE NERVE SYSTEM

3. The occipital fissure (sulcus parietooccipitalis) is seen about 5
cm. above the occipital pole and is only partly represented upon the
lateral surface. It indicates the separation between the occipital
and parietal lobes.

Upon the media! surface the following interlobar fissures are seen:

1. The central fissure which extends for about 1 cm. upon this
surface.

2. The occipital fissure, or fossa, has its main portion on this sur-
face. It extends downward and forward for 3 to 3.5 cm. and meets
the following fissure. It is usually quite deep and separates the
medial surface of the parietal and occipital lobes completely from
each other.

3. The calcariuc fissure (sulcus calcarinus) arises upon the medial
surface about 1 cm. above the base of the cerebrum just internal to
the occipital pole. It passes upward and inward from 3.5 to 4 cm.
and joins the occipital fissure; these continue forward for about 3 cm.
as the occipitocalcarinc fissure. The calcarine fissure separates the
occipital lobe completely from the temporal lobe while the occipito-
calcarine fissure separates parietal and temporal lobes incompletely.
The occipital lobe, or cuneus is embraced by the occipital and cal-
carine fissures.

4. The collateral fissure (sulcus collateral is) starts near the occipital
pole on the temporal lobe and continues frontally into the temporal
pole where it may join the rhinal fissure, one of the minor fissures.

The super callosal fissure (sulcus cinguli) starts in the frontal lobe
beneath the genu of the callosum a short distance and then curves
over the callosum following its curvature to the parietal lobe where
it is usually continued under the same name; this latter part was
formerly called the paracentral fissure and surrounds the paracentral
gyre. Between the collosal and cingular fissures is the gyrus cinguli.

Other lesser fissures or sulci are as follows:

1. Frontal Lobe. — Superior, middle and inferior frontal, precentral,
rostral and paracingular sulci.

2. Parietal Lobe. — Postcentral, angular, paroccipital, intermedial
and precuneal sulci.

3. Occipital Lobe. — Lateral occipital and lunatal sulci.

4. Temporal Lobe. — Superior, middle and inferior temporal sulci.
Each lobe is divided into gyres or convolutions by the above

secondary fissures.

The insula, or island of Reil, or central lobe is concealed by the
lips of the sylvian fissure. It is tetrahedral in shape and its apex
is pointed downward and forward. It is surrounded by the circum-
insular or circular fissure. Those parts of the cerebrum that cover
in the insula are called opercula, as temporal operculum, superior
operculum (frontal and parietal) and orbital operculum.

THE OLFACTORY BULB AND TRACT

389

The olfactory lobes are located upon the ventral surface of each
frontal lobe. Each consists of the olfactory bulb and tract. The
olfactory bulb (bulbus olfactorius) is a flattened, oval mass of a red-

Central fissur

Cingular fissure
\

>Vx<Yv

/ Rai-/ ^ Paracentral fissu

FlG. 278. — Medial aspect of the right cerebral hemisphere showing the lobes and main fis-
sures. {From a photograph.)

Fig. -70. — Lobes

n fissures of the medial surface of the right cerebral hemisphe

dish-gray color in relation with the cribriform plate of the ethmoid
bone. Through the latter pass the various olfactory nla from the
nasal mucosa to end in the bulb.

Each olfactory tract {tr actus olfactorius) is a flattened band of
nerve fibers extending backward from the bulb toward the optic

390 THE NERVE SYSTEM

chiasm and then separating into a medial, an intermediate and a
lateral root. The area at which these arise is called the trigonum.
The intermediate root is short and passes to the anterior perforated
substance. The lateral root passes to the uncus, gyrus ambiens and
gyrus semilunaris. The medial root passes but a short distance to
the area parolfactoria and subcallosal gyre, fornix and fimbria and
hippocampal gyre.

The corpus callosum (Fig. 278) is the broad mass of nerve fibers
bridging the bottom of the intercerebral cleft and connecting the
two cerebral hemispheres together. This represents a commissure.
It serves to connect areas of the opposite sides of the cerebrum with
each other. Upon the dorsal surface of the callosum lies a very
thin layer of gray nerve tissue continuous with the cortex of the
hemispheres. In this are some longitudinal fiber bands called the
stria longitudinalis and stria medialis. The gray tissue and fibers
represent a poorly developed supercallosal gyre.

When the callosum is cut parallel to the longitudinal fissure, its
flattened arch is noted. It consists of the thickened frontal end
called the genu, next a thinner, band-like part, the body, and lastly
a large occipital end called the splenium. The genu curves down-
ward and then sharply backward, tapering rapidly to form the ros-
trum that joins the lamina terminalis. The genu contains frontal
fibers. The body is much longer and narrower than either extrem-
ity and contains the parietal fibers. The splenium is the thickest
portion and forms the occipital end of the callosum. It contains
the occipitotemporal fibers. It overlaps the midbrain but is sepa-
rated from it by the velum interpositum.

The callosum measures from 7 to 10 cm. in length and varies in
thickness. The genu is 9 mm., the body 5 mm. and the splenium
13 to 15 mm. in thickness. The square surface is about 5.5 sq. cm.
in the average brain but runs up to 10.5 sq. cm. in the brain of
highly intellectual individuals.

The fornix lies underneath the callosum. This consists of a
bundle of longitudinally directed fibers that describes a longitudinal
arch on each side of the midline. At the top of the arch the bundles
are side by side and constitute the body of the fornix. As they pro-
ceed frontally the bundles diverge and descend, each terminating
in the corpus albicans of the same side. Occipitally the bundles
diverge more widely and descend and then bend frontally continuing
to the uncus of the same side as the fimbria. These separated bun-
dles constitute the anterior and posterior pillars, respectively, of the
fornix. This structure is a part of the olfactory pathway. The
fibers of the fornix originate in the hippocampus, form the fimbria
which continue as the posterior pillars, then the body and then the
anterior pillars to finally terminate in the corpus albicans of that side.

CORTICAL LOCALIZATION

391

The septum lucidum {septum pellucidum) lies between the callo-
sum, above, and the body of the fornix, below. It consists of two
layers that enclose a space called the fifth ventricle, or pseudocele.
This represents a part of the original longitudinal fissure that lies
subcallosal and the thin walls of the septum constitute the medial
walls of the hemispheres of this area where nerve tissues fail to
develop in any great quantity.

The hippocampus is an elevation in the lateral ventricle and is in
relation with the fimbria as above described. It constitutes a part
of the rhinencephalon.

Within each hemicerebrum is an extensive and irregular cavity
called the lateral ventricle (ventrical us lateralis). Each consists of
a body, frontal, occipital and temporal extensions, or horns. Each
ventricle is in connection with the third ventricle by an opening
situated between the frontal end of the thalamus and the under-
surface of the anterior pillar of the fornix. The opening is called
the foramen of Monro I foramen iiiteneutriculus). The ventricles are
reservoirs for the cerebrospinal fluid.

CORTICAL LOCALIZATION

The various areas of cortical representation of the special senses
and other functional areas are indicated in Figs. 280 and 281.

280. — Lateral surface of the left cerebral hemisphere showing cortical localization of

i. The motor area occupies the posterior portion of the lateral
surface of the frontal lobe just in front of the central fissure; it ex-
tends over upon the medial surface as indicated.

2. The general sensor area [tactile, temperature and pain) lies in
frontal portion of the lateral surface of the parietal lobe just behind

392

THE NERVE SYSTEM

the central fissure. It has a marked extension upon the medial
surface also.

3. The auditory area is located in the upper part of the lateral
surface of the temporal lobe just below the sylvian fissure.

4. The visual area is located in the occipital lobe partially upon
the lateral surface but mainly upon the medial surface, occupying
the entire lobe (aniens) here.

5. The olfactory area is upon the medial surface surrounding the
callosum, including the fornix, fimbria and hippocampal portion of
the temporal lobe.

6. The gustatory area is located upon the medial surface of the
temporal lobe just beneath the olfactory area.

showing cortical localization of

TOPOGRAPHY OF THE BRAIN

1. The longitudinal fissure is indicated by drawing a line from the
external occipital protuberance (inion) to the root of the nose
(glabella).

2. The Central Fissure. — Start at a point upon the longitudinal
fissure line 1 cm. behind its midpoint; from this point draw a line
downward and forward for 9 to 10 cm. at an angle of 700 to 71°.

3. The lateral (sylvian) fissure starts i1.-; inches (3 cm.) behind
the external angular process of the frontal bone and extends upward
and backward to a point f$ inch (2 cm.) below the most prominent
part of the parietal eminence.

4. Transverse Fissure. — Draw a line from the inion to the external
auditory meatus.

Kronlein's Method. — (1) The base line is a horizontal line from

INTERNAL ANATOMY OF THE BRAIN

393

the lower border of the orbit to the upper border of the external
auditory meatus. (2) Draw a horizontal line parallel to (1) at the
level of the supraorbital ridge. (3) Erect a vertical line AB, at
the middle of the zygoma. (4) Draw a vertical line CD, from the
posterior border of the mastoid process to the midline of the skull.
(5) Connect B and D. (6) Draw a vertical line E. G. from the articu-
lation of the mandible to BD. (7) Bisect the angle DBH with the
line BI.

Fig. 282. — Diagram of Kronl

The line DB represents the central fissure. BI represents the
sylvian fissure. At B the anterior branch of the middle meningeal
artery may be reached and at H the posterior branch. In abscess of
the temporal lobe trephine in the square E, C, H.

THE INTERNAL ANATOMY OF THE BRAIN

Having considered the external anatomy of the parts of the brain
consecutively the internal anatomy will now be considered in the
same manner by means of trans-sections at certain levels.

In the spinal cord the gray nerve tissue is placed internally in the
form of a flitted H-shaped column and the white nerve tissue surrounds
it. At the lower part of the oblongata the relation is about the same
but certain alterations are noticeable due to the presence of the motor
and sensor decussations, etc. The gray nerve tissue continues in

394

THE NERVE SYSTEM

relation with the canal and as the canal opens out dorsally to become
the fourth ventricle, the gray of the roof fails to develop, so that we
find only the floor composed of gray nerve tissue called the ventricular
gray. It is as though the cord had been split along the dorsal median
septum and the two halves spread out and the canal exposed as a
diamond-shaped fossa. As a result of this the motor cells are still
ventrally placed but mainly near the midline and the dorsal sensor

Nuclei

"■ CerebroA
Nerves

0>ive_,_| ' ' f

IV } Ventricular
Gray

Fir.. 2R3. — Diagram of the

.Spino-l
Cr«wj I

gangl

cells have been moved to the side. This will be noticed when the
cerebral nerve nuclei are considered. This peculiar condition of the
fourth ventricle being at the dorsal surface of the pons-oblongata is
due to the failure of development of nerve tissue in the dorsal wall
of the neural tube at this region. Hence all nuclei of this part and
the liber tracts that pass centrifugally and centripetally must pass
ventral to the cavity, thus placing this ventricle at the dorsal surface.
It is to be remembered that the nerve cells ventral to a line drawn

INTERNAL ANATOMY OF THE BRAIN STEM 395

through the spinal canal from side to side are motor and those dorsal
are sensor. As the fourth ventricle passes frontal into the aqueduct
it is as though the slit cord had been returned to its original condition
and gray nerve tissue surrounds the entire aqueduct. The ventral,
or floor part represents the seat of the cerebral nerve nuclei.

The motor nerve cells do not form continuous columns as in the
spinal cord but are grouped forming three interrupted columns, con-
stituting the nuclei of the cerebral nerves. One column [medial
somatic column) is along the median groove of the fourth ventricle
and aqueduct and comprises the hypoglossal, and abduccns nuclei.
Another column {lateral somatic column) slightly lateral to the pre-
ceding, comprises the accessory, part of the vagal, the facial, and tri-
geminal nuclei. These two go to voluntary, or skeletal muscle, in-
cluding tongue, pharynx and larynx. A third column (splanchnic
or visceromotor) is located further from the midline and comprises
part of the vagal, glossopharyngeal and facial nuclei. These cells
are concerned with the movements of involuntary nonstriated mus-
cles of the viscera and their axones go to sympathetic ganglia.
These cells represent the intermedio-lateral group of the spinal
cord.

The sensor cells do not form a continuous column either but form
isolated groups of nuclei that lie furthest from the midline. These
nuclei of termination are for both ordinary and special senses. The
olivary, pontile and arcuate nuclei are connecting links between the
cerebellum and the rest of the nerve system.

In the third ventricle that lies frontad of and is continuous with
the aqueduct, the gray substance is practically lacking so that this
part of the brain lies beyond the region of the cerebral nerve nuclei.
In addition to this central gray there are numerous nuclei scattered
in the white nerve tissue, giving thus a mixed character that does
not exist in the cord. In the cerebellum and the cerebrum the rela-
tion is again more distinct, but the gray here is superficial or cortical
while the white is central or medullary.

THE BRAIN STEM

Oblongata. — In studying the internal structure of the oblongata
sections at the motor decussation, sensor decussation and midolivary
levels will be utilized. These sections are from ascending levels in
the order named.

Motor Decussation (Figs. 284 and 285). — In the upper or pontile
part of the oblongata the motor fibers all lie in a compact bundle in the
ventral area constituting the pyramid. At the lower (spinal cord)
part of the oblongata these fibers are seen crossing the ventral
median groove in bundles constituting the pyramidal, or motor de-
cussation. Upon examining a section at this level these fibers are

39^

THE NERVE SYSTEM

Nucleus Cuneatus

rasciculus Spmo-
'ercbellaris Ventrahs

Mixed lateral Tracts

Vestibule* -Spinal and
Spmo-tna/amic Tracts Hyramtdal

Vhvo Spinal Tract
Ventral Horn

Decussation
Fig. 284. — Section of the oblongata at the level of the motor or pyramidal decussation.

Vcritro'mcd'zn < r^mmid

ra/horn
effh* T\

FlG. 285. — Section of the oblongata at the level of the motor decussation (Weigert's stain).
The right half shows the various fasciculi and nuclei in outline.

THE SENSOR DECUSSATION' 7)91

seen sweeping, obliquely dorsolaterally, from one side of the ventral
fissure to the opposite side of the oblongata, cutting through the
ventral horn of gray tissue to the dorsolateral region. These fibers
constitute here the crossed pyramidal tract of the spinal cord and
comprise 85 to 90 per cent, of the motor fibers. The remaining
15 to 10 per cent, continue down on the same side as the direct
pyramidal tract in the cervical and upper portion of the thoracic
part of the spinal cord, where they cross at various levels in the
white commissure so that all fibers ultimately end in the opposite of
ihe cord from which they originate in the cerebrum. The motor
area of gray represented by the ventral horn of the spinal cord is
thus cut into two parts: (i) the isolated ventral mass that is gradually
pushed more laterally and is diminished in size at higher levels; (2)
the basal portion (that near the canal) which represents the motor
gray of the floor of the fourth ventricle higher up.

Dorsally a change is also noticeable on the peripheral part of the
dorsal horn — the substantia gelalinosa has become much increased
and forms a projection on the lateral surface of the oblongata called
the tuberculum cinereum. The remainder of the dorsal gray also
shows alterations. Near the dorsal median septum an elongated
aggregation of cells, the nucleus gracilis, appears among the fibers
of the fasciculus gracilis. This ultimately produces an elevation
upon the dorsal surface of the oblongata called the nucleus gracilis.
A little lateral to this another aggregation, the nucleus cuneatus,
appears; this also forms an elevation upon the dorsal surface. It will
be remembered that the fasciculi gracilis and cuneatus (the tracts of
Goll and Burdach) occupy the dorsomedian area in the spinal cord
but at this level of the oblongata they are quite a bit smaller as their
fibers are terminating in their respective nuclei; in the next level
these tracts will have ceased to exist being replaced by these nuclei.
The bulk of the fiber tracts of the lateral area of the oblongata pass
upward uninterruptedly into the cerebellum, quadrigemina or thal-
amus as the case may be. These tracts comprise the several spino-
cerebellar, spinothalamic, rubrospinal, vestibulospinal, spinotectalis
and converse tracts. They will be considered later.

Sensor Decussation (Fig. 286). — Just above the motor decussa-
tion lies the sensor decussation. In the ventral part of the section
are seen all of the motor fibers in two compact bundles, the pyramid,
one upon each side of the ventromedian groove. Just dorsal to
these are seen first, a thin flattened bundle, the beginning lemniscus,
or fillet (lemniscus medial is) and dorsal to that the decussating sensor
fibers arising from the nuclei gracilis and cuneatus of the opposite
sides. These added fibers here have raised the canal to a slightly
higher (dorsal) level; between the decussating fibers and the canal
lie the wedge-shaped remains of the filaments of the hypoglossal

398 THE NERVE SYSTEM

nerve sweeping ventrally close to the pyramid. Lateral to these
nerve fibers are seen the remains of the isolated portion of the ventral
horns somewhat smaller than in the preceding section. In the dorsal
half of the section the gray has a peculiar arrangement. Near the
midline is the slender nucleus gracilis and just lateral the more
massive nucleus cuneatus and then the tuberculum cincreum. Here
the nuclei form elevations upon the dorsal surface and the tracts of
Goll and Burdach are almost ended. Superficial to the tuberculum
cinereum, in both sections, are seen some nerve cells and nerve fibers
constituting the descending nucleus and root of the trigeminal nerve

::<ic-jr">a'' ft.~c .C.//1.5

Fig. 286. Section of the oblongata at the level of the sensor decussation (Weigerfs stain).

The right half shows the various fasciculi and nuclei in outline.

{nucleus traclus spinalis nervi trigemini and tractus spinalis ncrvi
trigemini).

Between this and the next section the nuclei gracilis and cuneatus
disappear, several. new nuclear masses, olivary nuclei, appear and
the addition of a great mass of nerve fibers (formatio reticularis)
between the canal and the lemnisci raises the canal to such a level
dorsally that it is practically exposed and constitutes the fourth
ventricle. This is due to the fact that the dorsal wall of this part
of the neural tube develops no nerve tissue and that nerve tissue
which does form is ventrally placed.

The Midolivary Region (Fig. 287).— This section shows a marked
change. The ventral median groove is broad but shallow and is
flanked by the large motor tracts, the pyramids; these are covered
externally (superficially) by some gray nerve tissue, the arcuate

THE MIDOLIVARY REGION

399

nucleus and some nerve fibers, the external, or superficial arcuate
fibers. Of these arcuate fibers some arise in the nuclei gracilis and
cuneatus of the same side and pass to the cerebellum; others arise
from the nuclei of the opposite side, decussate in the raphe, course
ventrally and pass over the surface of the pyramid. Many of these
fibers are interrupted in the arcuate nuclei and then pass on to the
cerebellum by way of the restiform body. Just dorsal to the pyra-
mids lie the medial lemnisci forming quite a thick bundle of longi-
tudinally coursing fibers. These are separated from each other in the

Nucleus of Hypoglossal
Fourth UenTr/clr
Mrjiart lonyitudmat Tascir'i
TectcspirtaJ

\ 7ff/*t choi-oiifott inferior

^Tractus satitetrius.

Descendma roof of vestibu

Jf eti form body

, ^eK/P° 3Ci

Pig. 287. — Sec

of the oblongata at the level of the midolivary region ( Weigert's stain).
The right half shows the various fasciculi, nuclei and nerves in outline.

midline by the median raphe that extends dorsally to the ventricular
gray. The raphe consists of a few nerve cells and fibers. Some of
the fibers run longitudinally, others obliquely (internal arcuate fibers)
and still others run dorsoventrally (belonging to the external arcuate
fibers).

Between each lemniscus and the floor of the fourth ventricle on
each side of the raphe are seen bundles of fibers running longitudi-
nally, transversely and some gray nerve tissue; this constitutes the
mass mentioned above as the formatio reticularis. This field is
divided by the hypoglossal nerve roots into a median area (formatio
reticularis alba) as it contains little gray nerve tissue; the lateral
part is the formation reticularis grisea as it contains considerable

4<DO THE NERVE SYSTEM

gray nerve tissue. The transverse fibers are chiefly internal arcuate
and olivocerebellar, while the longitudinal are chiefly association
fibers (short course) of the centers of respiration (nuclei of the facial,
phrenic and vagal nerves) derived from the cells of the grisea. One
especial group of longitudinal fibers just beneath the ventricular
gray is called the median longitudinal bundle (fasciculus lougiludinalis
medialis). This is a set of longer association fibers that serves to
connect the various cerebral nerve nuclei together and corresponds
to the ventral and ventrolateral ground bundles of the spinal cord.
The fibers just ventral to this bundle constitute the fasciculus tecto-
spinalis.

Just dorsal to and a little to the side of the pyramid lies a crinkled
mass of gray containing white fibers and surrounded by white fibers.
This is the inferior olivary nucleus (nucleus olivius inferior) which
produces the elevation upon the lateral surface of the oblongata
called the olive. Its opening, or hilus, is directed toward the raphe
and of the fibers seen entering and leaving some pass to the olive
of the other side while others pass to the cerebellum of the opposite
side through the restiform body and vice versa. In addition, fibers
pass to and from the olive to the spinal cord and thalami. The
dorsal and medial olivary nuclei are detached parts of the main
nucleus.

In the dorsal region of this section is seen the lower end of the
fourth ventricle. The roof is thin and devoid of nerve tissue and con-
stitutes the tela choroidea inferior. The floor of the ventricle con-
sists of gray nerve tissue showing several aggregations of cells, or
cerebral nerve nuclei. On each side of the midline lies the nucleus
of the hypoglossal nerve; just lateral lies a small group of cells, the
nucleus iutercalatus (function not known). At the side of this lies
one of the nuclei of the vagal nerve. That part of the vagal nucleus
near the midline is motor (to the heart) and the lateral portion is
sensor. In the lateral dorsal mass is seen a large group of fibers, the
descending root of the auditory nerve; just beneath this are the nucleus
and fasciculus solitarius; at the extreme dorsal portion is seen the
restiform body'. The latter structure contains the fibers of the direct
spinocerebellar and cerebellospinal tracts of the spinal cord and the
internal and external arcuate fibers of the oblongata region. Be-
neath these structures is seen another nucleus of the vagus, the nucleus
ambiguus and the fibers of the vagus. This nucleus probably repre-
sents the remains of the isolated portion of the ventral horn of the
cord from lower sections. Near the side are seen the nucleus and
fibers of the spinal root of the trigeminal nerve.

Pons and Pars Dorsalis Pontis. — This portion of the brain stem is
equivalent to the oblongatal part plus a broad and thick band of
transverse fibers ventrally placed; the latter fibers constitute the

THE INTERNAL ANATOMY OF THE PONS REGION

4OI

pons. This part of the brain will be considered in three sections:
(1) lower, (2) middle and (3) tipper.

1. If a section at the lower end be examined the ventral part
will be seen to consist of a rather thick mass {pars basalis pontis)
of transversely coursing fibers, the pons, and two large bundles of
longitudinal fibers, the pyramids. In among these fibers are seen
collections of nerve cells called the nuclei pontis. The transverse
fibers are more abundant in man than in any other animal. Most of
them lie ventral to the pyramidal tracts and serve to connect the
cerebellar hemispheres with each other. At the lateral boundaries

Nucleus globosus

Nucleus emboliformls

Nucleus dentatus

Beehterew's nucl

Deiter's nucleus
Spinal root of V nerve

Nucleus of VII

conjunctivun
Corpus
restiforme

Nucleus VI ni

Pyramid Medial 1.

Fig. 288. — Section of the lower part of the pons region.

of the pons these fibers are collected into a compact bundle that
enters the corresponding cerebellar hemisphere as the middle pedun-
cle (brachium pontis). Some of the pons fibers end around the cells
of the pontile nuclei of the same side and some go to the opposite side ;
new fibers then arise from these cells and continue to the cerebellar
hemisphere. Some of the cells of the nuclei pontis are also way-sta-
tions in the pathway of cerebropontile fibers and new fibers arising
here pass to the cerebellar hemispheres. These cerebropontile fibers
have a longitudinal course.

In the area just dorsal to the pons fibers are the pyramids, two
large compact bundles of longitudinal fibers on their way to the
oblongata. Some of these fibers terminate in the nuclei pontis
representing cerebropontile fibers. Dorsal to the pyramids are seen a
variable number of deeper transverse pontile fibers. The arcuate
fibers and nuclei of the oblongata are analogous to the pons fibers and
pontile nuclei.

Dorsal to the pons lie the fibers of the medial lemniscus forming a

4-02

THE NERVE SYSTEM

rather compact bundle upon each side of the raphe. In higher sec-
tions these lemnisci diverge from the midline to make room for
the trapezium.

Pars Dorsalis Pontis. — The lemnisci separate the pons proper from
the pars dorsalis pontis (preoblongata). Dorsal to the outer side
of the lemniscus is seen the central tegmental trad and the superior
olivary nucleus connected with the fibers of the trapezium (acoustic
fibers). Between the superior olivary nucleus and the formatio

reticularis lies a bundle of fibers (trapezia!) that form the trapezium
of the next level. This portion shows also the formatio reticularis on
each side of the raphe with the median longitudinal bundle in its dor-
sal area; between the formatio reticularis and the cavity of the ven-
tricle is the ventricular gray substance in which are seen certain cere-
bral nerve nuclei.

Near the midline is seen the nucleus inscrtus (Streeter) that con-
tinues up to the aqueduct. To the side of this lies the nucleus of the
abducens nerve; lateral to this the principal vestibular nucleus is noted
and beneath the gray the descending root of the vestibular nerve; at
the dorsal margin lies the upper end of the rcstiform body. Deeper

THE INTERNAL ANATOMY OF THE PONS REGION

403

ventrad and over the superior olivary nucleus is the nucleus of the
facial nerve, while lateral thereto are some of the fibers of this nerve.
Between the facial nerve and the restiform body are found the sub-
stantia rolandi and the descending root of the trigeminal nerve.

2. Upon examining a section through the trigeminal nerve (middle
section) the ventral part of the section exhibits superficial and deep
fibers of the pons embracing the two pyramids. At the sides the
brachia pontis are still present. At the junction of the pons with the

Fourth

Dorsal longitu-
dinal fasciculus
Median longi-
tudinal fascic-
ulus

Deep fibers of
pons

r~

^k.

M

_.

-^/_

<

-J^ieH*!

- '*— 4-

Brachium con-
junctivum

Desc. motor
root of the tri-
geminal nerve

Sensor nucleus
of trig, nerve

Motor nucleus
of trig, nerve

Thalmoolivary
tract

Lateral lemnis-

Brachium

Fig. 290. — Section of the pons at the level of the origin of the trigeminal nerve.

tegmental part the media) lemnisci have been pushed to the side and
replaced by the trapezium, a set of transversely directed fibers (decus-
sating) intersperced with nerve cells (the trapezia] nucleus). These
fibers arise from the ventral and some from the dorsal cochlear
•nuclei of the fourth ventricle and pass to the trapezium where some
end in the nucleus trapezoideus of the same, or opposite side while
others end in the olivary nucleus of the same, or opposite side. The
new fibers from the cells of these nuclei then cross to the opposite side
(if the preceding have not) making the decussation complete; they
are then joined by the new fibers from the cells of the opposite side
and constitute the lateral lemniscus, which will be described later.
The trapezium is a part of the auditory pathway. Between the
trapezium and the lateral surface of the section are seen the superior
olivary nucleus, the fibers of the motor root of the trigeminal nerve,
while more ventrally are the brachia pontis and the sensor root of the
trigeminal nerve; near the surface lies the sensor nucleus of the latter
nerve.

404

THE NERVE SYSTEM

Dorsal to the trapezium and in the midline is the raphe with the
for mat io reticularis forming a large field on each side. Lateral to the
formatio is the motor nucleus of the trigeminal nerve, next the mesen-
cephalic root of the same nerve and upon the surface the superior cere-
bellar peduncle {brachium conjunctivum) forming also the dorsal
wall of the section in this area. The peduncle is semilunar in shape
and consists chiefly of fibers from the cells of the dentate nucleus of
the cerebellum, while the remainder are probably from the cerebellar
cortex of the opposite side, decussating to reach this side. These
fibers pass chiefly to the red nucleus of the midbrain and some con-
tinue to the thalamus.

In the dorsal portion of the section the fourth ventricle is seen
becoming narrower and is roofed by the valvula, or anterior medullary

Fig. 291. — Diagram of the nuclei of the cerebral nerves in the brain stem (lateral
Motor nuclei in solid block, sensor nuclei dotted. '

velum. Beneath the ventricular gray and near the midline is the
median longitudinal fasciculus .

3. A section through the upper part of the pons is more compact
and smaller. In the ventral area the pyramids are separated into
many small bundles by the transverse pontile fibers. At the side of
the field is seen the trigeminal nerve. In the tegmental portion
changes have occurred. In the midline just dorsal to the pons fibers
the trapezium has been replaced by the decussating fibers of the bra-
chia conjunctiva while the medial lemniscus is now seen at the side
and somewhat flattened. Dorsal to the decussating fibers is seen the
formatio reticularis, lateral to which is placed the brachium conjunc-
tivum no longer superficial, as in the preceding section, but rather
deeply placed and covered by the flattened band, the lateral
lemniscus. The lateral lemniscus previously mentioned consists of
the ventral cochlear fibers and nerve cells comprising the nucleus of

THE INTERNAL ANATOMY OF THE MIDBRAIN 405

the lateral lemniscus, apparently a continuation of the superior olive.
Here some of the fibers of the lemniscus end and new ones arise from
the cells of the nucleus and continue, to end in the inferior quadri-
geminum and medial geniculate body and possibly in the superior
quadrigeminum. The dorsal median area of the formatio reticularis
is occupied by the median longitudinal fasciculus. Dorsal to this area
is the ventricular gray substance. In this section the fourth ventricle
is small and entirely roofed over by the valvula that contains a
little nerve tissue. At the lateral boundary of the ventricular gray
is noted the mesencephalic root of the trigeminal nerve.

THE MIDBRAIN

In this portion of the brain stem two sections will be described,
one through the inferior quadrigeminal bodies and the other at the
level of the superior quadrigeminal bodies.

Transverse section of the midbrain through the inferior quadrigeminal bodies.

The section through the inferior bodies shows a marked change
over the preceding sections. Ventrally are seen the two crura cerebri
(pedunculi cerebri) separated from each other by the interpeduncular
space. Each cms consists of a ventral area called the crusta (basis
pedunculi) containing only motor fibers in three groups: (1) the
lateral one-fifth consisting of fibers from the cortex of the temporal
lobe of the cerebrum to the nuclei pontis and called the temporo-
pontile tract; (2) the middle three-fifths consists of the fibers from the
pyramidal cells of the motor area of the frontal lobe passing to the
cerebral nerve nuclei and to the spinal cord constituting the pyram-
idal tract previously mentioned; (3) the medial one-fifth consist of
fibers from the cells of the frontal lobe passing to the nuclei pontis
and called the frontopontile tract. Dorsally the crusta is bounded
by a crescentic mass of pigmented gray substance called the sub-
stantia nigra. This separates the tegmentum from the crusta and

406

THE NERVE SYSTEM

its cells send their axones in various directions but their function is
unknown. The substantia nigra extends throughout the midbrain.
The tegmentum consists of transverse and longitudinal fibers with
collections of nerve cells here and there. It represents a continua-
tion of the tegmental portion of the pons. In the midline is seen the
raphe and at the side, above the substantia nigra, lies each brachium
conjunctivum completing its decussation. Lateral to this is the
medial lemniscus. Dorsal to the superior cerebellar peduncle, near
the midline, is seen the median longitudinal fasciculus, while near the
surface is located the lateral lemniscus covered by the inferior
brachium. Dorsal to the raphe is the aqueduct gray substance, con-
taining a small canal, the iter, or aqueduct (aqueduclus cerebri). The

through the superior quadri^c-minal bodit

gray substance surrounds the canal completely; in its floor, resting
upon the median longitudinal fasciculus, is a collection of nerve
cells, the nucleus of the trochlear nerve. At the side of the gray is the
ftiesencep/ialis root of the trigeminal nerve. Dorsal to the aqueduct
gray, on each side of the midline, is a rounded mass of gray nerve
tissue covered by white fibers, the inferior quadrigcminal body
[colliculus inferior). The nucleus of each body is separated from the
aqueduct gray by the stratum lemnisci. The nucleus ■ receives
fibers chiefly from the lateral lemniscus. Its cells send fibers to the
thalamus and the nucleus represents a way-station in the auditory
pathway.

In the pregeminal region the crusta and substantia nigra are
substantially the same. Medially, at the junction of the tegmentum
and crusta, is a groove (sulcus oculomotorius) from which the oculo-
motor nerve emerges. In the tegmentum an important change has
occurred. Near the midline is a large, reddish, circular collection of
nerve cells called the red nucleus. The fibers of the oculomotor
nerve course around and through it. This nucleus receives fibers
from the cerebral cortex, the corpus striatum and from the cere-

INTERNAL ANATOMY OF THE PBEGEMTNAL REGION

407

bellum through its brachia conjunctiva; most of the fibers of the
latter end here. From its cells fibers extend: (1) to the thalamus and
the cerebral cortex; (2) to the spinal cord as the rubrospinal tract.
These latter fibers decussate almost immediately and pass down the
opposite tegmentum.

To the side of the red nucleus lies the medial lemniscus and it is
smaller as many of its fibers terminate in the superior quadrigeminal

Fig. 294. — Diagram of the formation and components of the
of the brain stem.

edian longitudinal fasciculu

body and the remainder pass to the thalamus (general sensor path-
way); at the side of the lemniscus lies the inferior bracliium. Be-
tween the two red nuclei is seen a mass of decussating fibers called
the fountain decussation. These fibers are derived from the superior
quadrigeminal bodies and the cells in the aqueduct gray, cross the
midline and join the median longitudinal fasciculus and pass to the
nuclei for the nerves of the eye muscles and to the spinal centers for
movements of the head and neck.

40S THE NERVE SYSTEM

The median longitudinal fasciculus (Fig. 294) occupies, relatively,
the same position as in previous sections. It corresponds to the.
ventral ground bundle of the spinal cord. Its fibers are associative
with regard to many cerebral and spinal nerve centers. It connects
especially the quadrigeminal bodies and the sensor cerebral nerve
nuclei with the oculomotor, trochlear, abducens and facial cerebral
nerves. A special nucleus is located in the floor of the third ventricle
at its junction with the aqueduct. The fibers from this nucleus
decussate immediately and cross through the posterior commissure.

In the dorsal part of the section are the aqueduct, surrounded by
the aqueduct gray, in the ventral part of which is the nucleus for the
oculomotor nerve. Dorsal to the gray are the two superior quadri-
geminal bodies (colliculi superiores). Each body consists of four
layers of alternating white and gray. The white layers represent
fibers of the optic tract and some from the occipital cortex. Other
fibers enter from the lateral and medial lemnisci (part of the optico-
acoustic reflex pathway).

INTERNAL ANATOMY OF THE CEREBELLUM

As previously mentioned, the cerebellum consists of two lateral
hemispheres with an intermediate vermiform lobe (vermis). Most of
the gray substance is externally located and the white is internal.
The remaining gray is found in the white as certain nuclei, to be
mentioned later. In the vermis the gray predominates while in the
lateral hemispheres the white predominates. As the main fissures
and sulci run transversely and as the gray is comparatively thin
the cut edge of the cerebellum exhibits a peculiar arborescent ap-
pearance; this is called the arbor vita" ccrebelli.

In the white substance of each lateral hemisphere is a crinkled
layer of gray with a white core called the dentate nucleus (nucleus
denial us). It resembles the olivary nucleus of the oblongata and
like it has a hilus for the entrance and exit of nerve fibers. Its cells
give rise to most of the fibers of the brachia conjunctiva and it repre-
sents a way-station in the indirect motor pathway.

The nucleus embolis is small, lies just medial to the preceding and
is analogous to the accessory olivary nucleus.

The nucleus globosus lies a little medial and ventral to the embolis
while the nucleus fastigii lies in the white substance of the vermis
close to the midline.

There are three pairs of cerebellar peduncles, inferior, middle and
superior. The inferior peduncles, or restiform bodies, enter the
cerebellum beneath the other two. Each consists of afferent and
efferent fibers; the afferent fibers comprise: (1) the dorsolateral
superficial spinocerebellar tract (direct cerebellar) derived from the
column of Clark (nucleus thoracis) of the spinal cord and ending

THE INTERNAL ANATOMY OF THE CEREBELLUM

409

in the gray of the vermis of both (but chiefly the opposite) sides; (2)
the olivocerebellar fibers (internal arcuate of oblongata) that arise
in the olivary nucleus and end in the cortex of the vermis and hemi-
spheres and also in the dentate nucleus; (3) the external arcuate
fibers from the nuclei gracilis and cuneatus of both sides; (4) fibers
from the vestibular and trigeminal nuclei; (5) cerebellospinal fibers
arising in the cerebellum and ending in the ventral horns of the
spinal cord {efferent).

The middle peduncle {brachium ppntis) the largest consists of
fibers running in opposite directions across the midline and consti-

FlG. 205. — Section of the right cerebellar hemisphere showing the dentate nucleus. (From
a photograph.)

tuting a commissure connecting the two lateral cerebellar hemispheres
with each other. Most of these fibers end in the nuclei pontis of
the same or opposite side and new fibers from these cells complete
the circuit. In addition, some of the fibers connect the cerebellar
hemispheres with certain cerebral nerve nuclei, especially the oculo-
motor, trochlear and abducens nuclei.

The superior peduncles (brachia conjunctiva) the smallest, form
an oval or concavoconvex band; the fibers arise in the dentate
nucleus of the same side, chiefly, with additional fibers from the
nuclei fastigii of both sides. The fibers decussate in the midbrain
where most of them end in the red nucleus, while a few continue to
the thalamus. This peduncle also contains the ventrolateral super-
ficial spinocerebellar tract (Gowers'). Its fibers instead of entering
the cerebellum through the inferior peduncles continue into the
pars dorsalis pontis and enter the cerebellum through the superior-
peduncles.

4io

THE NERVE SYSTEM

The cerebellum contains other fibers than the above, called the
fibrrn proprm. These are commissural and association fibers; the
commissural fibers connect the hemispheres with each other across
the midline and pass through the vermis. The association fibers do
not cross the midline but connect adjacent laminae with one another.
THE INTERNAL ANATOMY OF THE CEREBRUM
A section of the cerebrum shows that like the cerebellum it con-
sists chiefly of gray nerve substance externally {cortex) and white
■ ^ .,„ nerve tissue internally (medulla). In

■"V ' addition, masses of gray tissue are

seen near the ventral part of the
cerebral hemispheres and are there-
fore called basal ganglia. The in-
ternal anatomy is best represented
with two sections one horizontal, or
flatwise (side to side) about midway
between dorsal and ventral sur-
faces; the other a frontal {vertical)
section at the level of the anterior
commissure.

The horizontal section shows the
bulk of the gray externally and the
white internally placed, while toward
the center are seen various basal
ganglia. Just within the lateral
margin, near the frontal end, is the
island of Reil, or central lobe {insula).
Medial to this is the periclaustral
{white) lamina covering the irregular
strip of gray, the claustrum. This is
one of the basal ganglia and probably
represents an isolated portion of the
cortex of the insula. Medial to the
claustrum lies a narrow strip of
white nerve tissue the external
capsule and frontally, caudally, and
dorsally it connects with the internal
capsule and represents fibers of an associative nature for the cortical
regions around the insula. It contains a few fibers that pass to and
from the thalamus.

The next medially placed structure is the corpus striatum consist-
ing of two masses of gray, the lenticular and caudate nuclei, separated
from each other by the frontal limb of the internal capsule. The
caudal limb of the internal capsule separates the lenticular nucleus
from the thalamus.

Fig. 296. — Horizontal section of the
Tight cerebral hemisphere through the
corpus striatum. (From a photograph.)
C, Caudate nucleus; /, internal capsule
(anterior limb) ; c, posterior limb; Ins,
insula; CI, claustrum; OR, optic radia-
tion; Th, thalamus.

THE STRUCTURE OF THE CORPUS STRIATUM

411

The lenticular nucleus {nucleus lent if or mis) is surrounded by white
substance and is shaped like a triangular pyramid, or on section it
resembles a biconvex lens, hence the name. It is divided into three
main masses and each of these has fine bands of white giving a stri-
ated appearance to the mass. The largest and lateral segment is
called the putamcn while the other two constitute the globus pallidus.

The caudate nucleus (nucleus caudatus) as the diagram shows, is a

/?mysdu,/<:

/flmySiA

Fig. 297. — Model of the corpus striatun
A, Lateral view; B, medial view.

Fig. 298. — Drawing of the left internal
capsule, viewed from above, showing its
component fibers.

tail-shaped mass of gray nerve tissue. Owing to its arched course
its sections present different appearances at different levels.

The amygdaloid nucleus (nucleus amygdala) represents an isolated
part of the temporal cortical gray substance connected with the end
of the caudate nucleus. It is not shown at this level.

The interna! capsule lin this section represents a knee-bent mass
of white nerve tissue situated between the lenticular nucleus, later-
ally and the caudate nucleus and thalamus, medially. It represents
the only pathway for fibers from the cerebral cortex to brain stem
and cerebellum and vice versa. In the early stage of development of

412

THE NERVE SYSTEM

the nerve system the cerebral vesicles are connected to the primitive
forebrain vesicle around the future foramen of Monro which later
becomes unimportant functionally. Soon the ventromedial surface
of each cerebral vesicle rests upon the dorsolateral surface of each
thalamus and a fusion takes place, the striatothalamic fusion. This
fusion area is the later internal capsule. The frontal limb contains
the thalamofrontal and striatofrontal fibers. These fibers arise

from the cells of the thalamus
and end in the lenticular and
caudate nuclei of the corpus
striatum and frontal lobes of
the cerebrum. These are the
corticipetal fibers. In addition
there are the fibers running in
the opposite direction as the
frontopontile (frontal cortex
to pontile nuclei); fronto-
thalamic (frontal cortex to the
thalamic nuclei); striatothala-
mic fibers (from striate nuclei
to the thalamic nuclei). These
are corticifugal fibers.

The knee portion, or genu
contains the fibers of the
pyramidal tract, voluntary
motor fibers that arise from
the pyramidal cells of the
cortex of the frontal lobe in
front of the central fissure and
pass through the internal
capsule to form the pyramids
previously mentioned. The motor portion takes in about half of
the occipital limb of the internal capsule. The remainder of this
limb contains the sensor fibers that pass from the thalamus to the
cortex of the parietal lobe, to the general somatic sensor area. At
the extreme occipital part of this limb are: (i) fibers of the optic
radiation that course in both directions between the pulvinar of
the thalamus, the lateral geniculate body and the superior quad-
rigeminal bodies (on the one hand) and the occipital cortex (visual
area) on the other; (2) fibers of the auditory radiation passing
both ways between the medial geniculate and inferior quadrigem-
inal body, on the one hand, and the cortex of the temporal lobe
(auditory area) on the other; (3) occipitopontile and temporopontile
fibers from the cortex of these lobes to the nuclei pontis.

The thalamus (Fig. 296) is an important way-station in the sensor

Fig. 299. — Frontal section of the Tight cere-
bral hemisphere through the corpus striatum
and internal capsule. (From a photograph.) C.
Caudate nucleus; CI, claustrum; 1. internal
capsule; L, lenticular nucleus.

THE VENTRICULAR SYSTEM 413

and optic pathways. It receives impulses of muscle sense, pain,
temperature and touch and transmits them to the cerebral cortex
and receives in return impulses from the various parts of the cerebral
cortex. It is an emotional center under control of the cerebral cortex.
Its fibers constitute the thalamocortical and corticothalamal groups.
These represent fibers to and from the frontal, parietal and occipital
lobes and ventral fibers to and from the temporal lobe, island of Reil,
and lenticular nucleus.

The thalamus lies between the occipital limb of the internal cap-
sule and the midline. It consists of three chief nuclei separated from
one another by white nerve tissue; these are the nucleus anterior,
nucleus medialis and the nucleus lateralis (largest).

A vertical or frontal section shows the above structures, but
in a slightly different relation. The internal capsule shows no bend
but has a regular course that is oblique in direction, converging
toward the midline. Beneath the lenticular nucleus is seen the cor-
pus callosum that represents a commissure connecting the cerebral
hemispheres with each other.

THE VENTRICULAR SYSTEM

The ventricular system comprises the two lateral ventricles, the fo-
ramina of Monro, the third ventricle, the aqueduct, the fourth ventricle,
the foramen of Magendie and the spinal canal.

Each lateral ventricle (ventricidus lateralis) lies in a cerebral hem-
isphere and comprises a body, and three horns, anterior, middle and
posterior. The body (pars centralis) is situated underneath the
body of the corpus callosum and over the caudate nucleus and part
of the thalamus; it communicates at its frontal end with the third
ventricle by means of the foramen of Monro (foramen intervmtri-
culare). The anterior, or frontal horn (pars anterior) is short and
extends from the foramen of Monro, forward and outward into the
frontal lobe. The middle, descending, or temporal horn (pars inferior)
is the largest and passes backward, outward, downward, forward and
inward in the temporal lobe. The posterior, or occipital horn (pars
posterior) passes backward and inward from the body of the ventricle
into the occipital lobe.

The third ventricle (ventriculus tcrtius) is a vertical cleft in the mid-
line between the two thalami and dorsal to the chiasm, tuber cin-
ereum, corpora albicantia and part of the tegmentum of the crura
cerebri. It is covered, or roofed by the velum interpositum. It
continues frontally as a slight evagination, the optic recess; ventrally,
it gives rise to the infundibular recess and dorsallv, to the epiphyseal,
or pineal recess. It communicates with each lateral ventricle by a
foramen of Monro and caudally with the fourth ventricle by means
of the aqueduct.

4M

THE NERVE SYSTEM

The aqueduct or iter (aquedudus cerebri) lies in the midbrain; its
roof is the lamina quadrigemina and its floor the tegmental part
of the crura cerebri. It is a short, narrow canal that communi-
cates caudally with the fourth ventricle and frontally with the third
ventricle.

The fourth ventricle (vcntriculus quartiis) is a shallow, diamond-
shaped fossa in the pons oblongata region. Its floor (better ventral

Occipital horn
Fig. 300. — Horizontal section of the brain through the lateral ventricles.

wall) is the tegmental part of the pons and oblongata; in the oblon-
gata region it is roofed by the tela chorioidea inferior and in the
pons region by the valvula and the brachia conjunctiva. At the
frontal and caudal angles the fossa becomes canal-like to continue as
the aqueduct and spinal canal, respectively. At the lateral angles
the cavity continues as a narrow recess over each corresponding resti-
form body and these prolongations are called the lateral recesses.
Openings here lead into the subarachnoid lymph space and these are
the foramina Lusckkce (apertura latcralcs). The upper and lower parts
of the roof do not form a flat structure but a gable, or peak under
the cerebellum, so that the ventricle has the greatest depth here.
The tela chorioidea inferior has an opening near its spinal cord end
called the foramen of Magendie, which communicates with the sub-
arachnoid space. This with the foramina of Luschka permits an

THE WHITE SUBSTANCE OF THE CEREBRUM

415

interchange of cerebrospinal fluid between the ventricular system
and the lymph spaces of the membranes covering the brain. By this
means an equilibrium of pressure is established inside and outside of
the brain and spinal cord.

The spinal canal is a narrow, tube-like space extending the length
of the spinal cord; it is located in the gray commissure. It tends
to become obliterated more or less after the prime of life.

The entire ventricular system is lined with ependymal cells that in
the spinal cord are chiefly simple ciliated cells and in the ventricles
simple squamous, or simple ciliated elements.

The white substance of the cerebrum (medulla) consists of my-
elinated nerve fibers that are classified according to their connections,
into three groups: (1) projection, (2) association, (3) commissural.

Fig. 301. — The ventricular system of the brain represented in situ.

i. The projection fibers are those that pass from the cortex to
lower centers (thalamus, midbrain, pons, oblongata) and are centrifu-
gal in direction; to these are added the fibers from the lower centers
to the cerebral cortex, the corticipetal fibers. These fibers form the
bulk of the corona radiata. This is nothing more nor less than the
fan-shaped form assumed by the fibers from the various cerebral
convolutions as they pass to, or ascend from, the internal capsule.
It is the fan-shaped collection of fibers dorsal to the internal capsule
that at a more ventral level constitute the internal capsule.

The corticifugal fibers are the pyramidal, or great voluntary motor
pathway, the corticothalamic, frontopontile, temporopontile, and
the corticifugal fibers of the optic radiation. All of these indicate
by the name the origin and termination, and their respective posi-
tions have been discussed in the internal capsule and the crura cere-
bri; the pyramidal tract has been discussed in the pons, oblongata
and spinal cord.

416 THE NERVE SYSTEM

The corticipctal fibers comprise the thalamocortical, the auditory
radiation and the optic radiation.

2. The association fibers are short and long. The short ones con-
nect areas in adjacent convolutions with one another, or gyri rather
close together (arcuate and tangential fibers). The long association
fibers connect areas remote from one another in the same cerebral
hemisphere as the cingulum, uncinate, superior longitudinal and
fasciculus rectus.

3. The commissural fibers are those that pass across the midline
to connect areas of the opposite sides together. Under this head are
found the corpus callosum, the hippocampal commissure and the
anterior commissure.

The corpus callosum is the largest commissure and consists of
fibers that cross the midline in both directions at the bottom of the
intercerebral cleft. The fibers form a compact structure already
considered and these fibers spread out in all directions, but unequally,
so that all parts of the cortex do not receive the same number of
fibers. These fibers may be direct axones of cells, or collateral of
the association, or projection fibers. It connects all parts of the
cerebral cortex with one another, except parts of the temporal lobes
and the olfactory bulbs.

The hippocampal commissure is part of the olfactory pathway.
It connects the cornu ammonis of the two sides together.

The anterior commissure is also a part of the olfactory pathway,
connecting the two olfactory bulbs with each other and also con-
necting the olfactory bulb of one side with the temporal lobe of the
other side. Most of the fibers of the commissure pass from one tem-
poral lobe to the other, but the exact point of termination is not
known.

The various pathways will now be considered.

The Direct Motor Pathway. — This comprises but two neurons.
The parts concerned are the two pyramidal tracts and the motor por-
tions of the cerebral and spinal nerves.

The pyramidal tract of each side consists of afferent fibers that arise
from the large and small pyramidal cells of the motor area of the
cerebral cortex. They pass down through the corona radiala into
the internal capsule occupying the middle portion thereof; the}' enter
the crusta of the crus cerebri, then the tegmentum of the pons and
the ventral area of the oblongata; in these three regions some of its
fibers pass to the cerebral nerve nuclei of origin. At the caudal end
of the oblongata 85 to 90 per cent, of the fibers decussate to the op-
posite side of the spinal cord as the crossed pyramidal tract and then
end at various levels around the cells of the ventral horn. The
remaining fibers continue down the same side of the spinal cord, as
the direct pyramidal tract, to various levels in the cervical and upper

THE MOTOR PATHWAY

417

thoracic region and then pass through the ventral, or white com-
missure, to end in the ventral horn of the opposite side. Ultimately
all fibers decussate before they end. This ends the first neuron. The
second neuron comprises the cells of the ventral horn and their
processes that form the motor root of the spinal nerves, on the one

FlG. .^02. — Diagram of the neurons in the direct and indirect motor pathways and the con-
nections of the cerebellum with the brain stem and the spinal cord. Direct. — Neuron 1, .4 to
B\ neuron 2. B to C. Indirect. — Neuron 1. A (cerebral cortex) to D; 2, D to E; 3, E to F; 4,
F to g; 5, « to B\ 6, B to C.

hand, and in the case of the cerebral nerves comprises the cells of
the various nuclei of origin and their processes that form the motor
portion of the cerebral nerves. These axones pass out of the gray
substance, become myelinated and ultimately end directly in a vol-
untary striated muscle fiber. This is the em! of the second neuron.
First neuron, a pyramidal cell in the motor cortex of the cerebrum

4 1.

THE NERVE SYSTEM

and its axone that forms a part of the pyramidal tract and that
ends in a cerebral nerve nucleus, or the ventral gray of the spinal
cord.

Second neuron, the cell in the nucleus of origin or in the ventral

Fig. 303. — The origins, decussat

i and courses of the fibers forming the media! and lateral
i. Direct sensor pathway.

gray of the spinal cord, and its axone that ends in a voluntary
striated muscle fiber.

The Indirect Motor Pathway. — This is more complex and com-
prises six neurons. First, from the motor area of the cerebrum (say
right side) through the pyramidal tract, as above, to the nuclei
pontis of the same side (right) ; second, from the nuclei pontis through

THE SENSOR PATHWAY 419

the brachium pontis to the cerebellar cortex of the opposite (left) side;
third, from the cerebellar cortex to the dentate nucleus of the cere-
bellum of the same (left) side; fourth, from the dentate nucleus
through the brachium conjunctivum to the red nucleus of the opposite
(right) side; fifth, from the red nucleus of that side through the
rubrospinal tract to the cerebral nerve nucleus, or ventral horn of
the spinal cord of the opposite (left) side. (The fibers of the rubro-
spinal tract cross to the opposite side almost immediately after leav-
ing the red nucleus.) Sixth, from the cerebral nerve nucleus, or the
ventral horn gray to the voluntary striated muscle fiber. As seen
above there are three crossings, or decussations, the next to the last
neuron terminating upon the opposite side of the body.

The Direct Sensor Pathway. — In the trunk the impulses arise at
the periphery and are conveyed by the sensor spinal nerves to the
ganglia on the dorsal roots. From there they are conveyed into the
dorsal column of the spinal cord to end in the nuclei gracilis and
cuneatus of the oblongata of the same side. Some collaterals are
sent into the dorsal horn gray. New fibers arise in the nuclei cune-
atus and gracilis and immediately cross, or decussate to the opposite
side, forming the sensor decussation, that lies just above, or cephalad
of the motor (pyramidal) decussation. These decussated fibers
form the medial lemniscus that continue through the oblongata, pons
and midbrain to end in the thalamus of that sine. From the thalamus
new fibers convey the impulses through the internal capsule (posterior
limb) to the somatic sensor area of the cerebral cortex (postcentral
gyre). In this pathway three neurons are recjuired, the first, from
the surface to the nuclei gracilis, or cuneatus (the cell body lying in
the dorsal ganglion); the second, from these nuclei to the thalamus;
and the third, from the thalamus to the cerebral cortex.

Reflex conduction may occur in two ways:

(1) Direct. — The impulse is conveyed into the cord in the above
manner but the fiber as it enters the cord gives off collaterals of two
kinds:

(a) A collateral that passes to the ventral horn of the same
and opposite sides where it ends. The impulse then originates from
the motor cells in that area and is conveyed to the muscle which
moves unconsciously.

(b) As the sensor fibers enter the spinal cord they divide into
ascending and descending fibers. The ascending pass to the nuclei
gracilis and cuneatus and give off collaterals at various levels. The
descending fibers end at various segments in the dorsal horn and new
fibers arise from the cells here to pass to the ventral horn of the same
and opposite sides. New impulses arise from the motor cells here
and are conveyed to the muscles.

(2) An indirect reflex path is as follows: First neuron, from the peri-

420

THE NERVE SYSTEM

pherv to the nuclei cuneatus and gracilis through the dorsal column
of the spinal cord. Second neuron, from these nuclei to the cerebellar
cortex through the restiform body. Third neuron, from the cere-
bellar cortex to the dentate nucleus of the cerebellum (same side).
Fourth neuron, from the dentate nucleus to the red nucleus through
the brachium conjunctivum. Fifth neuron, from the red nucleus
through the rubrospinal tract to the ventral horn of the spinal cord.
Sixth neuron, through the ventral motor roots to the muscle. In

Fig. 304. — Diagram of the structures involved in a reflex action. .4, receptive surface;
B, skeletal muscle; C. blood-vessel and sympathetic ganglion; D. a viscus and sympathetic
ganglion; E, spinal nerve attached to spinal cord. Red indicates motor and blue tensor
impulses.

both varieties of reflex action the cerebral cortex is not brought
into the action.

The neurons involved in the movements of the involuntary muscu-
lature of the body and secretions of glands are complicated by con-
nection with the sympathetic system.

Optic Pathway (Fig. 305). — The axones of the first neuron arise
from the inner ganglion cells of the retina and form the optic nerve;
at the chiasm those fibers from the temporal half of the retina con-
tinue on the same side and those from the nasal half cross to the oppo-
site side through the chiasm. These crossed and uncrossed fibers of
each side form the optic tracts that curve over the ventral surface of
each cerebral peduncle to end as follows: (1) in the pulvinar of the
thalamus; (2) in the lateral geniculate body; (3) a few fibers pass to

THE GUSTATORY PATHWAY

421

the superior quadrigeminal body (eye muscle movements). The
axones of the second neurons start from the pulvinar and lateral gen-
iculate body, form the optic radiation at the caudal and most ven-
tral part of the internal capsule and end in the occipital cortex (visual
area).

The neuron that ends in the superior quadrigeminal body is con-
cerned in the action of the sphincter pupilte muscle of the iris; it is

Fig. 305. — Diagram of the optic pathway.

succeeded by a second neuron that connects the superior quadrige-
minal body with the nucleus of the oculomotor nerve. A third
neuron connects this nucleus with the ciliary ganglion and a, fourth
neuron connects this ganglion with the sphincter pupillae muscle.

Gustatory Pathway. — This pathway comprises two nerves, the
nervi intermedins and the glossopharyngens. The first neuron cell of
the nervi intermedins lies in the geniculate ganglion (of the facial
nerve, so called) and the peripheral fiber (dendrite) ends within the
tongue; the central fiber (axone) ends in the nucleus solitarius of the

422

THE NERVE SYSTEM

Fig. 306. — A diagram of the probable pathways of gustatory impulses.

RESTBODY

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DE/TERS
NUC.

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WRQOT 1 ■

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Fig. 307. — Diagram of the nuclei of termination of the vestibular nerve, and their higher
connections.

THE AUDITORY PATHWAY

423

glossopharyngeal and vagal nerves. The first neuron of the glosso-
pharyngeal nerve lies in the ganglia jugulare and nodosum and the
peripheral fiber (dendrite) ends in the tongue; the central fiber
(axone) ends in the nucleus solitarius of the oblongata (as in the pre-
ceding). The second neuron lies in this nucleus and the axon ends in
the thalamus. The third neuron starts in the thalamus and ends in
the gustatory area of the temporal lobe of the cerebral cortex (medial
surface).

Auditory Pathway. — The auditory nerve consists of the cochlear
and vestibular divisions. The first neuron cells of the cochlear nerve
lie in the ganglion spirale of the organ of Corti. The peripheral fibers

Fig. 308. — Diagram of the cochle

clei of terminate

nd their higher connection

(dendrites) end in relation with the hair cells of the organ of Corti
while the central fibers (axones) pass to the dorsal and ventral coch-
lear nuclei of the oblongata (floor of the fourth ventricle). The
second neuron cells lie in these nuclei; the axones from the dorsal
cochlear nucleus pass over the floor of the ventricle (as the acoustic
stria?) to the median sulcus, then pass ventrally into the oblongata
cross the midline and most of the fibers pass obliquely to join the
lateral lemniscus to end in the medial geniculate body.

The fibers from the ventral cochlear nucleus pass toward the mid-
line, just dorsal to the pyramids, and form here the trapezium.
They continue across the midline and sweep dorsally to join the
lateral lemniscus and end in the medial geniculate body and the
inferior quadrigeminal body. Fibers pass to and end in the superior
olivary nucleus. Some fibers end in the nucleus of the lateral lem-
niscus and are replaced by new fibers. Others may end in the
nucleus of the trapezium to be succeeded by new fibers from the
cells here.

424 THE NERVE SYSTEM

The third natron cells lie in the medial geniculate body and their
axones then pass to the auditory center which is in the superior
portion of the cortex of the temporal lobe.

The first neuron cells of the vestibular nerve (the nerve of equilibra-
tion) lie in the vestibular ganglion in the internal auditory canal.
The peripheral fibers (dendrites) end in the neuroepithelial areas of
the utriculus, sacculus and semicircular canals of the internal ear.
The central fibers (axones) pass to the brain stem where they divide
into ascending and descending branches. These branches end in the
various vestibular nuclei. The second neuron cells lie in these nuclei
and the axones of these cells pass to the vermis of the cerebellum, to
the nucleus fastigii of the cerebellum, to the various cerebral nerve
nuclei through the median longitudinal fasciculus (from Deiter's
nucleus), to the superior olive, to the spinal cord (through the ves-
tibulospinal tract) and possibly to the thalamus. Third to cortex.
Pathway for Touch, Temperature and Pain. — In the trunk and
extremities, the first neuron cells lie in the ganglia of the dorsal roots
of the spinal nerves. The peripheral fibers (dendrites) bring the
impulses from the periphery (organ or skin) and it is then conveyed
by the axone into the spinal cord through the dorsal root; the axones
end in the gray substance of the dorsal horn. The second neuron cells
lie here and their axones cross through the ventral gray commissure
to the opposite side and form the spinothalamic tracts in the spinal
cord and in the oblongata they join the medial lemniscus to end in
the thalamus. The third neuron cells lie in the thalamus and the
axones pass through the internal capsule (sensor limb) to the cortical
area of somatic sensibility (postcentral gyre). Some of the impulses
of touch and contact sensibility are conveyed through the dorsal
column of the spinal cord (same side) to the nucleus cuneatus and
gracilis. The new fibers from these nuclei decussate and join the
opposite medial lemniscus to end in the thalamus of that side; thus
some of the sensibility fibers cross in the spinal cord at their entrance
and others do not cross until the above nuclei have been reached.

In the head most of the impulses are conducted to the nuclei of
the trigeminus, glossopharyngeal and vagal nerves of each side to
the ganglia of the sensor divisions; then they are conducted to the
nuclei of termination of these nerves, in the fourth ventricle. This
course constitutes the first neuron. The second neurons connect
these nuclei with the thalamus by way of the medial lemniscus. The
third neurons connect the thalamus with the cerebral cortex as above.

The muscle sense (deep sensibility) impulses of the trunk and
extremities are conveyed as follows: The first natron connects the
periphery with the spinal cord where some of the fibers continue
on the same side through the dorsal column to the nuclei cuneatus
and gracilis. From here the fibers of the second neuron convey the

TRACTS CONCERNED IN RESPIRATION

425

impulses by way of the opposite medial lemniscus to the thalamus.
The third neuron connects the thalamus with the cortical area.
Some fibers pass from the nuclei gracilis and cuneatus to the cere-
bellar cortex; new fibers pass from here to the dentate nucleus of
the cerebellum from which new fibers pass to the thalamus through
the brachia conjunctiva.

Some of the fibers, only, of the first neuron, have the above course.
Others, after entering the dorsal roots of the spinal nerves, do not
enter the dorsal column but join the spinocerebellar tracts (ventral
and dorsal superficial) to end in the cerebellar cortex of the
same side. The impulses are then carried to the dentate nucleus
and from here through the brachium conjunctivum to the thalamus;
from the thalamus the impulses are conveyed to the cerebral cortex.

Fig. 309. — Diagn

; and tracts concerned in respiration.

Respiration. — Although respiration is apparently controlled by
the respiratory nucleus that lies in the formatio reticularis of the
oblongata, it is maintained by stimuli carried to this center by the
blood vascular system and reflex impulses from the sensor portion
of the vagus through cells in the nucleus of termination of the vagal
nerve and by impulses from the higher respiratory centers. The
respiratory nucleus is connected with the following motor nuclei:
Facial, vagal, accessory, cervical plexus, phrenic, brachial plexus
and thoracic nerves. Axones from the higher centers and from the

426

THE NERVE SYSTEM

sensor vagal nucleus end in the respiratory nucleus. The cells of the
respiratory nucleus send their axones directly, or by means of col-
laterals, in the formatio reticularis, to the nuclei of the above-
mentioned motor nerves so that through this connection a number
of cerebral and spinal nerves are caused to act.

Olfactory Nerves and Pathway. — Each so-called olfactory nerve
consists of about twelve separate nerves called the olfactory fila. These
arise in the olfactory mucosa of the nose, pass through the openings
in the cribriform plate of the ethmoid bone and terminate in the
olfactory bulb.

Medial stria.

Lateral stria.

Inlermedictte sit

Bulb

Tract

Trigone

Gyrus ambiens

Gyrus semilunaris-

Uncus

-Schematic representation of the olfactory pathway upon the '
the brain.

ntral surface of

The olfactory path-way comprises the olfactory fila and the rhinen-
cephalon, the parts of which will be considered under peripheral and
central, or cortical portions.

The peripheral portion comprises the following:

The olfactory bulb (biilbus olfactorius) that receives the olfactory
fila. Each lies upon the cribriform plate of the ethmoid bone. It
is oval in outline, flattened and of a reddish color. It is continued
toward the cerebrum as the olfactory tract.

The olfactory tract (tractits olfactorius) is a wedge-shaped band of
nerve fibers and passes from the bulb toward the cerebrum. After
a course of about 3.5 cm. it forms the olfactory tubercle {tuberculiim
olfactorium) the base of which is seen in the ventral surface of this
region and is called the trigonum olfactorium (gray nerve tissue).

From the trigonum three tracts, or striae, continue, called the lateral,

THE OLFACTORY PATHWAY 427

intermediate and medial roots, or stria, of which each has a different
course and termination. Each lateral root (stria olfacloria lateralis)
passes to the sylvian fissure where it is continuous with the limen
insula and then continues to the gyri ambiens and semilunaris.

The intermediate root (stria olfacloria intermedins) extends from
the olfactory tract over the trigonum to the gray substance of the
anterior perforated substance.

The medial root (stria olfacloria medialis) passes to and merges
with the area parolfactoria.

Broca's diagonal band is seen ventrally in the anterior perforated
space. This comes from the uncus and courses obliquely along the
outer side of the optic tract, converging with its fellow of the oppo-
site side to the base of the intercerebral cleft where they pass dor-
sally into the gyrus subcallosus under the genu of the corpus callosum.
From here each continues in the indusium of that side forming the
medial and lateral longitudinal stria?.

The anterior perforated substance lies just behind (caudad of) the
trigonum between this and the optic chiasm. It is somewhat quad-
rilateral in shape. In the lateral and caudal part of this area is
Broca's diagonal line.

The area parolfactoria lies in the base of the intercerebral cleft
under the genu of the corpus callosum.

The gyrus ambiens and gyrus semilunaris are seen upon the ventral
surface to the side of the corpora albicantia, bounding the anterior
perforated space caudolaterally. They represent, apparently, a
portion of the uncus separated therefrom by the end of the dentate
gyre, called the. frenulum Giacomini. They are a part of the hippo-
campal gyre.

The central portions are sometimes called the limbic lobe and are
as follows:

The gyrus subcallosum lies just behind the area parolfactoria
under the genu of the corpus callosum continuing as the indusium.

The indusium (gyrus epicallosus) is a thin band of gray nerve
tissue extending over the dorsal surface of the corpus callosum.
Through it ran the medial and lateral longitudinal stria;, or roots,
forming two ridges. The indusium continues ventrally as the gyrus
dentatus. The medial and lateral longitudinal stria are continuations
of Broca's diagonal band.

The hippocampus is a portion of the temporal lobe that projects
into the middle horn of the lateral ventricle. Upon it lies a white
band, the fimbria, a portion of the fornix.

The uncus is a hook-like, isolated portion of the hippocampal
gyre just behind the gyrus ambiens upon the ventral surface of the
brain just lateral to the frontal portion of the pons.

The dentate gyre is a notched band of gray nerve tissue in the

428

TlIK MO RYE SYSTEM

depths of the hippochampal fissure that separates it from the hippo-
campal gYre. On the other side is a fissure that separates it from
the fimbria, in the depths of which is a narrow band, the fasciola
cinerca; this is a narrow extension of the uncus to the splenial portion
of the callosum, where it fuses with the dentate gyre. The dentate
gyre seems to be a continuation of the indusium that extends ven-
trally around the uncus as the frenulum Giacomini.

The gyrus Andres Retzii is a small, oval, corrugated portion of the
hippochampal gyre just behind the splenium of the corpus callosum.

The corpora albicantia are two, small, rounded, white structures,
on the ventral surface of the brain just caudad of the optic chiasm

Sub calhsal ay>
^rea parolfactory

'Frenulum GicLcommi .
Tra.ci' lntesmea'>aJ*\'_f ' Frenulum gyrus arnbienS
jtrta. j . Gyrvs semilunaris.

-Schematic representation of the olfactory pathway.

(intercrural space) and near the midline. Their white color is due
to the myelinated nerve fibers of the fornix that end here in the
central gray nerve tissue. This gray tissue is usually arranged as
two nuclear masses in each body.

The anterior commissure is seen in the frontal wall of the third
ventricle, as it courses from side to side. It is usually a small bundle
of nerve fibers of which the frontal portion belongs to the olfactory
pathway. It connects the uncus of the two sides with each other in
addition to containing the pathway fibers from the bulb.

The septum pellucidum consists of two layers enclosing a portion of
the early intercerebral cleft, during the formation of the callosum.
This space is the so-called fifth ventricle but is not a part of the true
ventricular system of the brain. The septum is enclosed in the arch
of the corpus callosum and extends from it to the fornix. Its frontal
part contains some gray nerve tissue that is a part of the olfactory
pathway. Occasionally an opening is seen in the septum permitting

THE OLFACTORY PATHWAY 429

communication between the two lateral ventricles. Also, in two
instances the writer has noticed that the septum extended all the way
from the genu to the splenium and w^as twice as long as in the usual
specimens.

The fornix is a paired structure consisting of longitudinally cours-
ing fibers connecting the uncus and corpus albicans of each side.
It consists of a body and a pair of anterior (frontal) and a pair of pos-
terior (occipital) pillars. The body is that portion ventral of the
body of the callosum where the two tracts lie side by side. Fron-
tally, at the region of the anterior commissure, the two tracts diverge
and course ventrally, as the anterior pillars, to end in the corpus
albicans of each side. Occipitally, at the splenium of the callosum,
these tracts diverge as the posterior pillars and pass first ventrally and
then frontally in a hook-like manner to end in the uncus of each side.
As the pillars pass ventrally they project into the inferior (temporal)
horn of the lateral ventricle and lie upon the hippocampus, here
constituting a band of fibers called the fimbria; this dwindles in size
as the uncus is approached.

Impulses arising in the olfactory portion of the nasal mucosa pass
to the olfactory bulb by way of the olfactory fila. This constitutes
the peripheral tract (first neuron). From the bulb the impulses are
conducted by another neuron system, by way of the olfactory tract,
to the primary centers, i.e., the gray substance of the tractus olfactor-
ium, trigonum, anterior perforated substance and the gray substance
of the septum lucidum. The impulses are then conducted to the cor-
tical centers by a third neuron.

The lateral olfactory stria carries the impulses to the gyrus ambiens
and gyrus semilunaris from the trigonum. The intermediate stria
carries the impulses to the gray substance of the anterior perforated
space; from the trigonum, the anterior perforated substance and the
septum lucidum impulses pass to the hippocampus by way of the
fornix.

The medial olfactory stria consists of fibers from the trigonum that
pass toward the gyrus subcallosus and then over the corpus callosum
through the dentate gyre to end in the hippocampus.

Other fibers pass from the anterior perforated substance and the
septum pellucidum to the nucleus amygdala and the thalamus.

The hippochampus is connected with the corpus albicans of each
side by the fornix fibers that arise from the cells of the hippocampus
and the dentate gyre. As the fornix passes ventral to the corpus
callosum it receives fibers from the medial longitudinal stria3, dorsal
to the callosum, that pass to this body and constitute the fibres
perforantcs. While most of the fornix fibers pass to the corpus albi-
cans some pass to the ganglion habenula (a small nucleus between the
epiphysis and the caudal end of the thalamus).

43°

THE NERVE SYSTEM

The corpus albicans of each side is further connected with the thal-
amus and the tegmentum of the crus cerebri, where there is a small
ganglion, the ganglion pro/ionium tegmcnti.

THE CIRCULATION OF THE BRAIN

The arteries (Fig. 312) that supply the brain are the two vertebral
(arteries vertebrates) and the two internal carotid arteries (arteries
carol ides internee). The latter enter the cranial cavity through the

Olfactory bulb

SG^neri/e

Int. carotid artery
^nerve

Vertebral art.

Spmat cord \ ^\^t'n f. Cere6e//*r art
Fig. 312. — The arteries of the base of the brain. (After Sobotta and McMurrich.)

carotid canals while the former enter through the foramen magnum.
The vertebral arteries join to form the basilar artery (arteria basilaris)
the largest branches of which are the two posterior cerebral arteries
(arteria; cerebri posteriores) . The internal carotid arteries give rise
to a branch, the posterior communicating artery, that passes back
and anastomoses with the posterior cerebral artery on each side.
In front each internal carotid artery gives rise to an anterior cerebral
artery (arteria cerebri anterior) which is connected to its fellow on the
opposite side across the midline by the anterior communicating
artery. Thus a so-called circle is formed at the base of the brain
called the circle of Willis (circulus adenosis).

VEINS 431

The other branches of each vertebral artery are the following:
The posterior meningeal.

The ventral spinal, one on each side, which unite to form a single
vessel that lies at the front of the ventral median fissure of
the spinal cord.
The dorsal spinal artery, one descending upon each side behind

the dorsal roots of the spinal nerves.
The posterior inferior cerebellar.
Bulbar.
The basilar artery gives the following branches:
Internal auditory.
Anterior inferior cerebellar.
Superior cerebellar.
Posterior cerebral.
The internal carotid gives rise to the following branches:
Posterior communicating.
Middle cerebral (in the sylvian fissure).

The anterior cerebral that winds over the callosum and lies in
the longitudinal fissure.
The central ganglionic masses are supplied by branches of the circle
of Willis, or trunks close to it.

Veins. — The blood is returned from the cerebrum by the super-
ficial and the deep cerebral veins {vena? cerebri). The superficial veins
receive the blood from the convolutions and deeper parts and empty
into the sinuses. The deep veins, or internal cerebral veins (Galen)
unite to form a short trunk, the vena magna Galeni, that ends in the
straight sinus.

The blood from the cerebellum is returned by the superficial and
deep cerebellar veins which return the blood to the transverse, superior
and inferior petrosal and the occipital sinuses.

The blood from the pons is returned to the cerebellar veins, or the
superior petrosal sinus.

From the oblongata the blood is returned to the inferior petrosal
sinus, or the basilar plexus.

The sinuses in the dura that receive the blood from the brain are
the following:
Single:

Superior sagittal sinus.
Inferior sagittal sinus.
Straight sinus.
Occipital sinus.
Circular sinus.
Basilar sinus.
Paired:
Lateral sinuses.

432 THE NERVE SYSTEM

Sphenoparietal sinuses.
Superior petrosal sinuses.
Inferior petrosal.
Cavernous.

The superior sagittal sinus (si)nis sagittalis superior) lies in the up-
per edge of the falx cerebri and extends from the foramen cecum, in
front, to the torcular Herophili (confluens sinuum), behind.

The inferior sagittal sinus {sinus sagittalis inferior) lies in the
lower edge of the falx cerebri and extends backward to the frontal
edge of the tentorium cerebelli to end by joining the deep cerebral
vein (Galen) to form the straight sinus.

The straight sinus (sinus rectus) extends along the upper surface
of the tentorium cerebelli, from the end of the inferior sagittal sinus
to the torcular Herophili.

The occipital sinus, the smallest, is formed from veins around the
margin of the foramen magnum and terminates in the torcular
Herophili.

The circular sinus (anterior and posterior intercavernous sinuses)
is situated in the pituitary fossa and surrounds the pituitary body
and is connected on each side with the cavernous sinus.

The basilar sinus (plexus basilaris) extends across the basilar por-
tion of the occipital bone and connects the ends of the cavernous,
or the ends of the superior petrosal sinuses to each other.

The lateral sinuses (sinus transversi) begin at the torcular and
pass outward and then downward to the jugular foramen of the skull;
here each ends in the internal jugular vein of that side. They are
the largest sinuses and carry most of the blood out of the skull.

The sphenoparietal sinuses (sinus sphenoparietalcs) lie under the
lesser wings of the sphenoid bone and each terminates in the ante-
rior end of the corresponding cavernous sinus.

The cavernous sinus (sinus cavemosi) lie upon the side of the
body of the sphenoid bone and extend from the sphenoidal fissure
to the apex of the petrous portion of the temporal bone. These
communicate with each other through the circular sinus and receive
the blood from the sphenoparietal sinuses and send the blood into
the superior and inferior petrosal sinuses.

The superior petrosal sinuses (sinus petrosi superiores) start at
the same regions, pass downward and outward along the lower
margin of the petrous portion of the temporal bone; each ends in
the lateral sinus of that side.

The inferior petrosal sinuses (sinus petrosi inferiores) begin at
the posterior end of the cavernous sinus of each side and pass down-
ward, backward and laterally in the posterior fossa of the skull and
empty into the internal jugular vein of that side.

The veins of the spinal cord form a plexus in the pia and from this

THE CEREBRAL NERVES 433

plexus six main longitudinal and radicular veins are formed. The
longitudinal veins are one ventromedial!, two ventrolateral, two dorso-
lateral and one dorsomedian.

The radicular veins pass around the nerve roots to terminate in
the ventral and dorsal spinal "veins.

The venlromedian and dorsomedian veins empty into veins of the
oblongata; the lateral veins empty partly into the preceding but
chiefly into the two radicular veins that carry their blood to the
ventral and dorsal spinal veins of the vertebral column.

The intracranial lymphatics are meningeal and cerebral. The
meningeal lymphatics start in the spaces of the dura, follow the
blood-vessels and empty into the internal maxillary and upper deep
cervical lymph nodes.

The Peripheral Nerve System

The peripheral nerve system comprises the cerebral and spinal
nerves and their associated ganglia.

THE CEREBRAL OR ENCEPHALIC NERVES
The term cerebral nerves is poorly chosen as the first two pairs,
only, are connected with the cerebrum and these are not considered
true nerves but outgrowths of the cerebral vesicles; the others
are connected with the brain stem. The term encephalic nerves
would be more satisfactory as the distinction from spinal nerves would
be maintained and the origin from the brain, as a whole, would
be expressed.

The cerebral nerves are twelve pairs in number and ten pairs are
directly connected with the brain stem in which lie their nuclei of
origin, or termination. These nerves vary, some are purely motor,
others purely sensor (special senses) and others are mixed.
These nerves are classified as follows:
i. Olfactory. Pure sensor, special sense (smell).

2. Optic. Pure sensor, special sense (vision).

3. Oculomotor. Pure motor.

4. Trochlear. Pure motor.

5. Trigeminus. Mixed.

6. Abducens. Pure motor.

7. Facial. Mixed. Special sense (taste).

8. Auditory. Pure sensor, special sense (hearing).

9. Glossopharyngeal. Mixed. General and special sense (taste).
10. Vagus. Mixed.

n. Spinal accessory. Pure motor.
12. Hypoglossal. Pure motor.

For the sake of convenience these will be taken up in reverse order
just as the brain was considered from the oblongata to the cerebrum.

434

THE XERYE SYSTEM

Hypoglossal Nerve (Nervus Hypoglossus). — This is the motor
nerve of the tongue and its nucleus lies in the lower, or caudal end
of the gray substance of the fourth ventricle. This nucleus is about
18 mm. long and quite narrow; it extends from the upper level of the
pyramidal decussation to the stria; acusticae and close to the mid-
line. It represents a continuation of the motor gray of the spinal
cord. The upper end of the nucleus lies beneath the trigonum

Fig. 313. — The hypoglossal

and distribution.

hypoglossi of the fourth ventricle. The two nuclei are connected
across the midline by commissural fibers and fibers from the opposite
pyramid end in each nucleus, completing thus the connection with
the cerebral cortex. The nerve cells are large and their myelinated
axis-cylinders pass ventrally through the formatio reticularis, be-
tween the olivary nucleus and the pyramid, to emerge (superficial
origin) in the groove between these two structures on the ventral
surface of the oblongata.

THE ACCESSORY NERVE 435

The hypoglossal nerve leaves the cranial cavity through the hypo-
glossal canal, enters the neck, passes downward, ventrally and medi-
ally to the tongue. It gives off the recurrent, descending, thyreo-
hyoid and lingual branches.

The recurrent branch (ramus rccurrens) is given off in the cranial
cavity and supplies the dura of the posterior fossa. The descending
branch (ramus descendens) forms the hypoglossal loop with a branch
from the second and third cervical nerves and supplies the mm.
omohyoideus, sternohyoideus and sternothyreoideus. The thyreoid
branch (ramus thyreoidens) supplies the m. thyreohyoideus. The
lingual branches (rami lingualcs) supply the mm. hyoglossus,
genioglossus, geniohyoideus and the intrinsic muscles of the tongue.

The hypoglossal nerve communicates with the superior cervical
ganglion (sympathetic), the ganglion nodosum of the vagal nerve,
the upper cervical nerves, the pharyngeal plexus and the lingual
branch of the mandibular nerve (trigeminal).

The Spinal Accessory Nerve (Xervus Accessories). — This is a pure
motor nerve consisting of a spinal division (representing a spinal
nerve) and an accessory portion arising from the oblongata (bulbar
part). The spinal part arises from the dorsolateral nerve cells in
the ventral horn of the first four cervical segments of the spinal cord.
These myelinated axones pass ultimately to the surface of the spinal
cord, emerge at the lateral column and pass up through the foramen
magnum to join the bulbar portion. The accessory, or bulbar root,
arises from nerve cells in the ventricular gray at the upper (cephalic)
end of the spinal nucleus and is practically a continuation of the
lower, or caudal end of the nucleus ambiguus of the vagal and glosso-
pharyngeal nerves. It is lateral to the lower end of the hypoglossal
nucleus and is called the nidus laryngci, because its fibers later join
the vagus and though this nerve pass to the intrinsic muscles of the
larynx, except the cricothyreoid muscle. The spinal root supplies
the trapezius and sternomastoid muscles.

Fibers from the opposite pyramids end in each nucleus (cortical
connections) as do also fibers from the dorsal (sensor) roots of the
spinal nerves (establishing a reflex arc).

The superficial origin of the bulbar portion of the accessory nerve
is the side of the oblongata, at the head end of the restiform body.
The spinal portion arises from the side of the spinal cord as low as
the sixth cervical nerves. These two portions join and leave the
cranial cavity through the jugular foramen. The bulbar root sends
a branch to the ganglion nodosum of the vagal nerve and the re-
mainder joins the vagal nerve and ultimately supplies the intrinsic
muscles of the larynx (except the m. cricothyreoideus), and furnishes
cardioinhibitory nerves to the vagus. The spinal portion (ramus
extcrnus) passes into the neck and supplies the mm. sternomastoideus
and trapezius.

436 THE NERVE SYSTEM

The spinal portion communicates with the cervical plexus.

Vagal and Glossopharyngeal Nerves (Nervus Vagus et Nervus
Glossopharyngeus) . — These nerves, though mixed, are mainly sensor
and as their nuclei of origin and termination are so close together and
so intimately associated they will be considered together. It is

highly probable that the glossopharyngeal nerve is purely sensor.
The nuclei are the dorsal (mixed) nucleus, nucleus ambiguus and
nucleus of the fasciculus solitarius.

The dorsal {mixed) nucleus, long and rod-shaped, lies at the upper
end of the hypoglossal nucleus and the motor part comprises that
portion nearest the midline. The axones of the cells in this portion

THE VAGAL AND GLOSSOPHARYNGEAL NERVES

437

pass obliquely ventrolateral between the olivary nucleus and the
restiform body, emerging from the oblongata between the olive and
the end of the lateral column. The fibers belong to the vagus and
pass to the esophagus, stomach, trachea and bronchi. This is a
nucleus of origin and the sensor part will be discussed later.

The nucleus ambiguus is deeply placed in the formatio reticularis
and the substantia gelatinosa; it seems to be a continuation of the
bulbar part of the accessory nerve. The axones pass first dorsally,
then bend ventrally and join the preceding, supplying the esophagus,

-Diagram of the course of the trigeminal, glossopharyngeal and vagal
the brain stem. Motor nuclei solid black, sensor nuclei dotted.

pharynx and the m. cricothyreoideus of the larynx. Apparently a por-
tion of this nucleus is cardiq-inkibitory. This is also a nucleus oj origin.

The sensor fibers arise from cells in the ganglia. Connected with
the vagus are the jugular gang! inn (ganglion jugulare) and the gang-
lion nodosum. Connected with the glossopharyngeus are the gang-
lion superior and the ganglion pclrosum. These ganglia are compar-
able to the ganglia connected with the dorsal (sensor) roots of the
spinal nerves. The axones of the cells in these ganglia enter the
oblongata, branch into ascending and descending fibers that ter-
minate in the nucleus ala cinerea and the nucleus of the tractus soli-
tarius, or trineural fasciculus, respectively. These are the nuclei of
termination.

The nucleus ala cinerea is the sensor part of the previously men-
tioned dorsal nucleus and it receives ascending branches, above-
mentioned; these are chiefly vagal so that the bulk of this nucleus
belongs to the vagus.

438 THE NERVE SYSTEM

The nucleus and Iraclus solitarius form a spindle-shaped column in
the dorsal area of the oblongata between the descending root of the
trigeminal nerve and the fibers are mainly of the glossopharyngeal
nerve. Only a few vagal fibers enter this nucleus and there are
reasons to believe that all of the glossopharyngeal fibers terminate
here. This nucleus and tract extend from the upper limit of ob-
longata into the spinal cord as far as the fourth cervical segment.
From the cells of all of these sensor nuclei axones pass to the opposite
side of the oblongata, join the lemniscus and pass to the thalamus
and ultimately establish a connection with the cerebral cortex.

The vagal and glossopharyngeal nerves arise from the oblongata
between the olivary and the restiform bodies (superficial origin).
They leave the cranial cavity through the jugular foramen.

In the jugular foramen the vagus has two ganglia, jugular and
nodosum. The nerve passes through the neck in the carotid sheath,
passes through the thorax and enters the abdomen. The jugular
ganglion gives off branches to the meninges and to the auricle and
the external auditory canal. The ganglion nodosum gives off the
pharyngeal and superior laryngeal nerves. The pharyngeal nerve
assists in forming the pharyngeal plexus that supplies most of the
muscles of the pharynx and soft palate. The superior laryngeal
nerve divides into external and internal branches. The external
branch supplies the m. cricothyreoideus. The internal branch sup-
plies the mucous membrane of the larynx.

In the neck the vagus gives off the cardiac branches, and recurrent
laryngeal nerves.

The superior and inferior cardiac nerves of the right side join the
deep cardiac plexus of the thorax. The left superior cardiac nerve
joins the deep cardiac plexus while the left inferior cardiac nerve
joins the superficial cardiac plexus. The recurrent laryngeal nerve
gives off muscular branches to the trachea and esophagus and then
ends in the larynx to supply all of the muscles except the m. crico-
thyreoideus. This is the bulbar portion of the accessory nerve.

In the thorax the vagus assist in forming the cardiac, pulmonary
and coronary plexuses. These are described on page 470.

In the abdomen the vagi give branches to the stomach and to the
celiac, splenic, renal and hepatic plexuses.

The glossopharyngeal nerve arises just behind the vagus. As it
passes through the jugular foramen it exhibits two ganglia, the
superior and petrous ganglia. The superior gives off no branches.
The petrous ganglion gives off the tympanic branch that assists in
forming the tympanic plexus that supplies the mucosa of the tym-
panum, mastoid cells and auditory tube. It also forms a part of the
superficial petrosal nerve.

In the neck the glossopharyngeal nerve gives a branch to the m.

THE AUDITORY NERVE 439

stylopharyngeus and branches that pass to the mucosa of the
pharynx directly and others indirectly (through the pharyngeal
plexus). Terminal brandies pass to the tonsil and mucosa of the
dorsal one-third of the tongue.

Auditory Nerve (Nervus Acusticus). — This nerve comprises really
two distinct nerves called cochlear and vestibular divisions of the
auditory nerve; these are both connected with special sense, the
former hearing, and the latter, the sense of equilibrium, if this term
might be used. As in the case with all of the real cerebral sensor
nerves there is a ganglion connected with each division comparable
to the ganglion on the sensor divisions of the spinal nerves. The
fibers of the cochlear division, the real nerve of hearing, arise from
the bipolar cells of the ganglion spiralc located in the internal ear.
These myelinated axones pass into the ventral surface of the brain
stem, in connection with the vestibular division, at the lower (caudal)
border of the pons at its junction with the brachium pontis. After a
short course the fibers terminate in the ventral and dorsal cochlear
nuclei. These nuclei lie upon the lateral and ventral aspect of the
restiform body, respectively.

The fibers arising from the cells of the ventral cochlear nucleus
pass transversely through the ventral part of the tegmentum, just
dorsal to the pons fibers, and form here the trapezium; here fibers are
added from the superior olive of both sides and from the cells of the
trapezial nuclei. All of these fibers cross the midline and form the
lateral lemniscus that ends in the inferior quadrigeminal and medial
geniculate bodies. From these structures new fibers continue to
the auditory center in the cortex of the temporal lobe.

In the lateral lemniscus are cells constituting the nucleus of the
lateral lemniscus (a way-station in the auditory pathway). Here
some of the lemniscal fibers may end and then new ones replace
them.

The fibers from the dorsal, or lateral cochlear nucleus have a dif-
ferent course. They pass over the restiform body to the floor of
the fourth ventricle, where most of them continue superficially as
the strim acusticce, to the median sulcus, cross the midline, pass
ventrally in an oblique manner and join the lateral lemniscus of the
opposite side. Some of the fibers pass to the lemniscal nucleus of
the same side from which new fibers join the trapezium and pass to
the lemniscus of the opposite side. All of the fibers terminate as
those of the ventral nucleus do.

The fibers of the vestibular division arise from the bipolar cells of
the ganglion vestibnlare that lies in the internal auditory meatus.
They enter the brain stem with the cochlear division. Some of the
fibers ascending end in the medial vestibular nucleus; others descend-
ing end in the spinal vestibular nucleus; still others terminate within

440

THE NERVE SYSTEM

the lateral vestibular nucleus [Deiter's) and the remainder pass to the
superior nucleus of Beckterew. From these nuclei fibers pass in
various directions to the dentate nucleus and nucleus fastigii of the

IN f ROOT ^

ft£OL LEM.

Fin. 316. — Diagram of the nuclei of termination of the vestibula
connections.

nd their higher

Pic. 317. — Diagram of the

nuclei of termination and their higher connections.

cerebellum, to the nuclei of the oculomotor, trochlear, trigeminus and
abducens nerve, to the temporal lobe of the cerebral cortex, to the
thalamus and to the ventral horns of the spinal cord (cervical
portion).

THE FACIAL NERVE 441

The lateral lemniscus contains all of the auditory fibers but they
reach this tract by different routes as shown above.

The auditory nerve is attached to the brain at the inferolateral
margin of the pons lateral to the facial nerve. It consists of ves-
tibular and cochlear roots. It passes into the internal acoustic meatus.
The vestibular root, or nerve communicates with the nervus inter-
medius and the geniculate ganglion of the facial nerve and sends its
three branches to the utriculus and ampulla? of the superior and
lateral semicircular canals. The cochlear root, or nerve sends
branches to ampulla of the posterior semicircular canal, to the
sacculus and the cochlea. The vestibular nerve has the vestibular
ganglion and the cochlear nerve the spiral, or cochlear ganglion.

The Facial Nerve (Nervus Facialis). — The facial nerve consists of
two distinct nerves, the facial proper (motor) and the nervus intermedins
(sensor).

The nucleus of origin of the motor portion is deeply placed and
lies in the ventral part of the tegmental part of the pons well to the
side of the midline. It is just above (cephalad of) the boundary
between the oblongata and pons. The axones of these cells have
a decidedly peculiar course. They pass first dorsally almost to
the ventricular surface, then arch over the nucleus of the abducens
nerve (toward the midline), then pass ventrally and emerge from the
brain stem at the lower border of the pons at the medial side of the
auditory nerve.

The fibers of the nervus intermedius are both motor and sensor
fibers; the sensor portion arises from the unipolar cells of the gen-
iculate ganglion in the facial canal. The dendrites, that pass per-
ipherally, constitute the chorda tympani nerve (taste) and the central
fibers (axones) constitute the intermediate nerve. They enter the
brain stem between the facial and auditory nerves and terminate in
the upper end of the nucleus of the fasciculus solitarius (glossopharyn-
geus). The motor fibers are said to arise from the cells in a nucleus
near the midline and beneath the ventricular gray substance (nucleus
salivatorius) . This is said to extend from the level of the facial
nerve to the level of the lower end of the motor nucleus of the
trigeminal nerve. These represent excito glandular fibers.

The facial nerve arises from the brain at the inferolateral margin
of the pons just medial to the auditory nerve. It passes into the
internal acoustic meatus with the acoustic nerve, then through the
facial canal of the petrous portion of the temporal bone and appears
upon the base of the skull through the stylomastoid foramen. It
then passes through the parotid gland (branching here) to supply the
muscles of the face. The geniculate ganglion is situated upon the
facial nerve in the facial canal and gives off the greater superficial
petrosal, deep petrosal and externa! superficial petrosal nerves; the
deep nerve passes to the sphenopalatine ganglion.

44 -1

THE XERVE SYSTEM

In the facial canal the nerve gives off a branch to the m. stapedius
and the chorda tympani nerve. The latter passes through the
tympanic cavity and petrotympanic fissure to join the lingual
branch of the mandibular nerve.

In the neck the facial nerve gives branches to the mm. stylohyoideus
and digastricus (posterior belly), auricularis posterior and occipitalis
and the intrinsic muscles of the auricle.

In the parotid gland the facial nerve forms the parotid plexus con-
stituting cervicofacial and temporofacial divisions. The cervicofacial

Nucleus Salivatori us
, Motor part of M Intermedins _
Meryus Intermedius

Geniculate Garty/>o" Maxi llary Mei

Posterior /luricularh.

To Dioastnc^
To Stylohyoid.

Fig. 318. — Diagram of the facial and intermediate nerves and their connections.

division gives off the following branches: Buccal branches to the
m. buccinator and muscles at the angle of the mouth; the marginal,
or supramandibidar. branch of the mandible that supplies the mm.
orbicularis oris and the quadratus labii inferioris. The cervical, or
iniramandibular, branch supplies the m. platysma.

The temporofacial division gives off the temporal branches that
supply the mm. orbicularis oculi, corrugator supercilii, frontalis and
auricularis anterior and posterior. The zygomatic branches supply
the mm. orbicularis oculi and zygomaticus.

The Abducens Nerve (Nervus Abdmois). — This is a small motor
nerve the fibers of which arise from the cells of the nucleus located
under the dorsal part of the tegmental portion of the pons near the
midline. The axones pass ventrally and laterally and emerge from

THE TRIGEMINAL NERVE 443

the brain stem along the lower border of the pons near the midline
(superficial origin).

The abducent nerve passes through the middle fossa along the
carotid artery and enters the orbital fossa through the superior
orbital fissure to supply the m. rectus lateralis.

The Trigeminal Nerve {Nerous Trigeminus). — This represents a
mixed nerve and is the largest of the cerebral nerves. Its nuclei
of origin and termination are the most widely distributed and longest
of all the nerves, extending from the midbrain through the pars
dorsalis pontis and the oblongata into the spinal cord.

The nucleus of origin of the motor portion consists of two parts, a
principal nucleus that lies close to the sensor nucleus, though dorsal
thereto, near the lateral aspect of the pars dorsalis pontis. The
mesencephalic nucleus starts just a little above (cephalad of) the
preceding and extends throughout the midbrain and is seen at the
extreme lateral limit of the gray substance of the aqueduct. Where
it starts it is quite large but the midbrain portion gradually tapers.
The fibers arising from these two nuclei pass ventrally and emerge
from the brain stem at the junction of the pons and brachium pontis
of each side serving, thus, as an arbitrary boundary between these
two structures. The greater part of the motor root consists of the
axones of the principal nucleus. The two nuclei are connected to
each other by collateral fibers. These nuclei receive fibers from the
motor area of the cerebral cortex through the opposite pyramid.

The sensor portion consists of the axones of the cells in the semi-
lunar ganglion (ganglion scmilunare) located upon the apex of the
petrous portion of the temporal bone. It is larger than the motor
root and enters the brain stem where the motor root emerges. In
the brain stem the fibers bifurcate, one branch ascending and ending
in the main sensor nucleus that lies near the surface of the tegmental
part of the pons, ventral to the brachium conjunctivum. This
nucleus, like the corresponding motor nucleus, extends into the
midbrain, tapering as it ascends. The descending branches form a
large tract called the descending root of the trigeminal nerve. The
tract lies just lateral to the substantia gelatinosa; at intervals the
fibers end around the cells of the substantia gelatinosa and they
represent the nucleus of termination of the descending root. This
descending root decreases in size as it approaches the spinal cord and
ends at the level of the first or second cervical nerve. From these
terminal nuclei fibers (arcuata) pass through the raphe to the oppo-
site side and proceed upward to the thalamus where new fibers arise
and pass to the sensor area of the cerebral cortex. Some fibers pass
from the sensor to the motor nucleus thus establishing a simple
reflex arc.

The trigeminal nerve is attached to the brain at the middle of the

444

THE NERVE SYSTEM

lateral border of the pons. It consists of two roots, the larger, sensor
and the smaller, motor. As these two roots pass forward and reach
the apex of the petrous portion of the temporal hone the sensor root
exhibits an enlargement, the semilunar, or Gasserian ganglion.
From this ganglion Hirer roots, or nerves, are seen to arise, the ophthal-
mic, maxillary and mandibular nerves. The motor root is hidden by
the ganglion and it joins the mandibular nerve.

The ophthalmic nerve passes through the middle fossa to enter
the orbital fossa through the superior orbital fissure It gives rise

Trigeminal Gasserian Ophthalmic nerve
or 5th nerve ganglion

Sphenopa

Inf. alveolar nerve

Fig. 319. — The trigeminal nerve and its communications with the facial and glosso-
pharyngeal nerves. {After Sobotta and Mc&turrich.) The exposed nerves are black, the
concealed ones shaded.

lo three, main branches. The lacrimal nerve gives branches to the
lacrimal gland, the conjunctiva and skin at the lateral commissure of
the eyelids. The frontal nerve, through its supratrochlear branch,
supplies the skin of the root of the nose, the medial commissure of the
eyelids and the medial part of the forehead. Through its larger
supraorbital branch it supplies the frontal sinus, the skin of the
upper eyelid and of the forehead and scalp to the vertex. The
nasoi iliary nerve, in the orbit, gives a branch to the ciliary ganglion,
gives off the infratrochlear nerve, that supplies the skin of the root of
the nose and the eyelids. In the nose it gives off the lateral and
medial nasal branches that supply the mucosa of the lateral wall and
septum of the nose. On the face the external nasal branch supplies
the skin of the lower half of the tip of the nose.

The ciliary ganglion, connected with this division of the trigeminal
nerve, is a small reddish ganglion in the orbit. It has three roots;

THE TRIGEMINAL NERVE 445

the long, or sensory root, is derived from the nasociliary nerve; the
short, or motor root is derived from the oculomotor nerve; the sym-
pathetic root is derived from the cavernous plexus of the sympathetic
system upon the internal carotid artery. This ganglion gives rise
to about fifteen short ciliary nerves that supply the coats of the eyeball
and the muscles of the ciliary body and iris.

The maxillary nerve, the largest division, leaves the middle fossa
of the skull through the foramen rotundum, passes through the
pterygopalatine fossa where it gives off a number of branches. The
remainder of the nerve enters the orbit as the infraorbital nerve,
passes through the infraorbital canal (giving off branches) and
appears upon the face through the infraorbital foramen.

In the pterygopalatine fossa it gives off the following branches:
Two branches to the sphenopalatine ganglion; posterior superior
alveolar nerves, for the molar teeth and the neighboring parts of the
gum. The zygomatic, or orbital branch, that divides into zygomatico-
temporal or temporal nerve (for the skin of the temple) and the
zygomaticofai ial, or malar nerve (for the skin over the zygomatic bone) .

In the infraorbital canal the infraorbital nerve gives off the middle
and anterior superior alveolar nerves that supply the premolar, canine
and incisor teeth, the gum and the mucosa of the maxillary sinus.

Upon the face the infraorbital nerve gives off the inferior palpebral
branches, for the lower eyelid; the external nasal, for the skin of the
side of the nose; the superior labial, for cheek and upper lip.

The sphenopalatine ganglion is connected with this division of the
trigeminal nerve, in the pterygopalatine fossa, by the two spheno-
palatine (sensor) roots. The motor root comes from the geniculate
ganglion of the facial nerve (through the greater superficial petrosal
nerve) and the sympathetic root comes from the cavernous plexus
(through the deep petrosal nerve). These last two named nerves
form the nerve of the pterygoid canal. This ganglion gives off the
following branches: Pharyngeal branches, to the mucosa of the roof
of the pharynx. The anterior palatine nerves, for the mucous mem-
brane of the mucosa of the soft and hard palate and a part of the
lateral wall of the nasal fossa. The middle palatine nerve, for the
mucosa of the uvula, soft palate and palatal tonsil. The posterior
palatine nerve supplies the mucosa of the same region. The posterior
superior nasal nerve, for that portion of the lateral wall of the nasal
fossa. The nasopalatine nerve, for the mucous membrane of the
roof and nasal septum and the hard palate. Orbital branches, to the
periosteum of the orbit.

The mandibular nerve contains all of the motor fibers and some
sensor fibers. These two parts are separate and leave the middle
fossa of the skull through the foramen ovale, enter the infratemporal
fossa, fuse and divide into anterior and posterior divisions.

446 THE NERVE SYSTEM

The branches of the undivided nerve are the spinous, or recurrent
nerve, that supplies the dura and a branch to the m. pterygoideus
internus.

The masticator nerve, or anterior branch, gives off a branch to the
m. pterygoideus externus; one, to the m. masseter; two, to the m.
temporalis; a buccinator branch (sensor) that supplies the skin and
mucosa of the cheek.

The Larger posterior branch gives off the following branches: The
auriculotemporal nerve (by two roots) that supplies the skin and
scalp of the temporal region, the mandibular articulation, the paro-
tid gland, the skin of the external auditory canal and the tympanic
membrane.

The Lingual nerve is one of the terminal branches of the mandibular
nerve. It supplies the mucosa of the apical two-thirds of the tongue,
the floor and lateral walls of the mouth and sends a branch to the
submaxillary ganglion. It is joined by the chorda tympani and
branches from the hypoglossal nerve.

The inferior alveolar, or dental nerve, is the larger terminal branch
of the mandibular nerve. This gives off the mylohyoid nerve, for
the muscle of the same name and the anterior belly of the digastricus.
It then enters the mandibular canal, through the mandibular
foramen. Here it gives off branches to the molar and premolar teeth
and the mental nerve and then terminates in branches for the canine
and incisor teeth. The mental nerve leaves the mandibular canal
through the mental foramen and supplies the chin and lower lip.

The submaxillary ganglion is connected with the lingual nerve.
Its motor root is derived from the chorda tympani; its sensor root is
derived from the lingual nerve; its sympathetic root is derived from
the sympathetic plexus of the external maxillary artery. Its
branches are distributed to the submaxillary gland and duct.

The otic ganglion is situated near the mandibular nerve as it
emerges from the foramen ovale. Its motor root is derived from the
nerve to the m. pterygoideus internus; its sensor root is derived from
the tympanic plexus (through the smaller superficial petrosal nerve);
the sympathetic root is derived from the sympathetic plexus upon the
middle meningeal artery. It sends branches to the nerve of the
pterygoid canal, the chorda tympani and roots of the auriculotem-
poral nerves; its two motor branches supply the mm. tensor veli pala-
tini and tensor tympani.

The Trochlear Nerve (Nerous Trochlearis). — This is a pure motor
nerve that has its nucleus of origin in the midbrain. This nucleus
is small and oval and lies in the gray substance of the floor of the
aqueduct beneath the inferior quadrigeminal body of each side. It
rests upon the median longitudinal fasciculus and lies close to the
midline. The axones arising from these cells pass downward (cau-

THE OCVLOMOTOR XERVE

447

dally) and laterally along the edge of the aqueduct gray which they
follow to the midline; here the nerves decussate at the upper edge
of the superior medullar}- velum and emerge at the medial border
of the brachia conjunctiva. They are the smallest of the cerebral
nerves. These nuclei receive fibers from the motor area of the
opposite cerebral cortex through the pyramid. Fibers of the median
longitudinal fasciculus also end here.

The trochlear nerve arises from the midbrain just behind the cor-
pora quadrigemina. It passes to the ventral surface of the brain
stem and through the middle fossa of the skull to enter the orbital
fossa through the superior orbital fissure. It supplies the m. ob-
liquus superior.

The Oculomotor Nerve (Nervus Ocidomotorius). — This is also a
pure motor nerve and its nucleus of origin is also in the midbrain.

Fig. 320. — Xuclei of origin of the motor cerebral nerves (lateral view)

The nucleus is quite large, 5 to 6 mm. long and lies in the floor of
the aqueduct gray substance under the superior quadrigeminal
bodies just ahead of the preceding nucleus; it rests upon the median
longitudinal fasciculus. The cells do not form a single mass but
are arranged into a number of fairly distinct groups (at least seven)
in each nucleus and a common small nucleus in the midline, the
central nucleus. Most of the fibers of each nerve arise from the
nucleus of the same side and pass ventrally in bundles; when the red
nucleus is reached they spread out and pass through it, to be gathered
into compact bundles at its ventral limit. These bundles are then
collected into a single mass that emerges upon the medial aspect of
each cerebral peduncle (intercrural space) in the oculomotor sulcus
(the groove between the crusta and tegmentum of the crus).

448 THE NERVE SYSTEM

The fibers from the central nucleus, and possibly other nuclei, de-
cussate immediately and join the opposite nerve. These fibers are
probably those that innervate the medial rectus muscle.

The oculomotor nucleus is connected to the occipital cortex
(visual area) through the optic radiation; with other cerebral nerves
through the median longitudinal fasciculus; with the motor area of
the cerebral cortex through the pyramid; with the visual apparatus
through fibers from the superior quadrigeminal body.

The oculomotor nerve emerges from the ventral surface of the mid-
brain in the oculomotor sulcus and passes forward to enter the orbital
fossa through the superior orbital fissure. It supplies the mm. recti
superior, inferior, medialis, the levator palpebrae and obliquus in-
ferior; it also sends a branch to the ciliary ganglion.

The Optic Nerve (X err us Opticus). — As previously mentioned this
is not considered as a true cerebral nerve and is best considered as
the optic tract. This tract comprises the optic nerves and the optic
chiasm as the peripheral parts and the pulvinar (of thalamus) the
lateral geniculate body, the superior quadrigeminal body and the
occipital cortex as the central parts.

The optic nerve arises in the retina of the eyeball. The fibers
proceed in a peculiar manner. Upon reaching the ventral part of
the brain in the region of the thalamus, the fibers from the nasal side
of each retina (about two-thirds) cross the midline, decussate, form-
ing the optic chiasm and those parts usually called the optic tracts.
In addition the caudal side of the chiasm contains added fibers the
commissure of Gudden, a group of fibers that connect one medial
geniculate body with the other; so far as is known these fibers have
no part in the visual pathway but form the so-called medial root of
the optic tract.

The optic tract after leaving the chiasm bends dorsally around the
crus cerebri of each side and divides into a medial and a lateral root.
The medial root ends in the medial geniculate body and represents, the
commissure of Gudden above mentioned. The lateral root is the real
continuation of the visual portion of the chiasm and ends in the lower,
or primary optic centers, i.e., the lateral geniculate body, the pulvinar
and the superior quadrigeminal body of that side. The first named
receives the most of the fibers and the last the least, as it is concerned
only with muscle reflexes and not with light, or color perception.
From its cells fibers join the optic nerve and end in the retina.

The lateral geniculate body and pulvinar of the thalamus are im-
portant subcenters for vision. From these centers new fibers arise
and pass in a compact bundle toward the occipital cortex (cuueus)
where they end around the occipital cells. In addition, fibers pass
from these occipital cells and end in the superior quadrigeminal body
and pulvinar of the same side. All of these fibers and the caudal
part of the internal capsule constitute the optic radiation.

THE SPINAL NERVES 449

The superior quad ri gem inal body is connected with the nuclei
of the motor nerves of the eyeball by means of fibers that arise from
its cells and enter the median longitudinal fasciculus. This body is
also connected with the oblongata and the spinal cord through the
medial lemniscus.

From the optic chiasm the optic nerve may be followed through
the optic foramen to the dorsal portion of the eyeball. Its connec-
tion with the eyeball is described under that organ.

Olfactory Nerve (Nervus Olfactorius). — This is not a single nerve
upon each side but about twenty nerves, or fila; these arise from the
cells of the nasal mucosa, pass through the cribriform plate of the
ethmoid bone and terminate in the olfactory bulb. The details
of the remainder of the tract have been considered under the
"Olfactory Pathway."

THE SPINAL NERVES

The spinal nerves are arranged in pairs of which there are usually
thirtv-one. Each nerve consists of two portions, or roots called
ventral, or motor and sensor, or dorsal. These nerves pass from the
vertebral canal through the intervertebral foramina. Within the
vertebral canal the roots are distinct and separate, but peripheral to
the foramina the roots are united together into a single mass, the
nerve proper. These nerves are named according to the vertebra
between which they pass. Each nerve passes beneath its correspond-
ing vertebra except the first cervical pair that emerges between the
occipital bone and the atlas and should really be called the suboc-
cipital nerve. Occasionally the thirty-first pair is absent, or two
additional pairs may be present. These latter are small and do not
emerge from the vertebral canal; they represent rudimentary caudal
nerves.

The nerves are as follows:

Cervical . . 8 pairs.

Thoracic. . . 12 pairs.

Lumbar 5 pairs.

Sacral .... 5 pairs.

Coccygeal . . i pair.

Each spinal nerve consists of a ventral and a dorsal root. The
ventral, or motor root consists of myelinated axones of the cells in
the ventral horns of the spinal gray substance. The roots emerge
from the ventrolateral region in a linear formation, indicating a
segmentation of the cord. The ventral roots are smaller than the
dorsal but the individual fibers are larger. These fibers are both
somatomotor and visceromotor.

Within each intervertebral foramen lies a ganglion connected with
each dorsal root. The central end of the root (that which enters

450 THE NERVE SYSTEM

the cord) is made up of the myelinated axones of the ganglion cells
in these ganglia; the peripheral part of the root (that which joins the
motor root to form the nerve proper) consists of the myelinated
dendrites of the cells in the ganglia.

Each spinal nerve, after the junction of its two roots, is a mixed
nerve; a short distance from this junction each nerve divides into a
dorsal and a ventral primary division, or ramus, each of which con-
sists of motor and sensor fibers. Each dorsal ramus divides into a
medial and a lateral trunk. The medial branches, in the upper half
of the body contain the cutaneous nerves while the lateral branches
contain the muscular nerves; in the lower half of the body the reverse
condition prevails. Certain spinal nerves send branches to the sym-
pathetic system and these constitute the white rami communicantes.

Those spinal nerves that are intended for the appendages are the
largest, as the lower cervical and first thoracic for the pectoral
appendage and the lower lumbar and upper sacral for the pelvic
appendage. These nerves form the great brachial and lumbar plexuses
upon each side, for the pectoral and pelvic appendages, respectively.

THE DORSAL RAMI OF THE SPINAL NERVES
THE CERVICAL NERVES

The first cervical, or suboccipital nerve has a rudimentary dorsal
root usually. Its dorsal ramus is large. The nerve passes into the
neck and gives off muscular branches to the mm. semispinalis capitis,
recti capitis posterior major and minor and the obliqui capitis
superior and inferior. It sends a communicating branch to the second
cervical nerve.

The dorsal ramus of the second cervical nerve is larger than its
ventral ramus and passes into the neck. It distributes muscular
branches to the mm. semispinales capitis and cervicis, the obliquus
inferior and the multifidus. It sends communicating branches to help
form the dorsal cervical plexus. A large part of this ramus accom-
panies the occipital artery as the great occipital nerve which is the
chief cutaneous nerve of the back of the scalp.

The third cervical nerve is small and its dorsal ramus divides into
medial branch that becomes the third occipital nerve and supplies the
skin of the scalp and neck. The lateral, or muscular branch, supplies
contiguous muscles.

The dorsal rami of the rest of the cervical nerves are quite small.
Their medial branches are cutaneous for the skin of the back of the
neck and their lateral branches supply the surrounding muscles.

THE THORACIC REGION

Each dorsal ramus divides into medial and lateral branches. The
medial branches of the first seven thoracic nerves are chiefly cuta-
neous for the scapular region. The lateral branches supply branches

THE SPINAL NERVES 45I

to the longitudinal muscles of the back. In the lower thoracic
region the lateral branches are cutaneous, supplying the skin of the
back as low as the buttock. The medial branches, here, supply
branches to the longitudinal muscles of the back.

THE LUMBAR REGION

The dorsal rami of the first, second and third lumbar nerves divide
into medial and lateral branches. The medial branches innervate
the deep muscles of the back while the lateral branches are chiefly
cutaneous and supply the skin of the buttock.

The dorsal rami of the fourth and fifth lumbar nerves are chiefly
muscular and send branches to the longitudinal muscles of the back.

THE SACRAL AND COCCYGEAL REGIONS

The dorsal rami of the first, second and third sacral nerves supply the
m. multifidus through their medial muscular branches, and the skin of
the sacral and adjoining buttock region, through their lateral
cutaneous branches.

The dorsal rami of the fourth and fifth sacral nerves and that of the
coccygeal nerve form the posterior anococcygeal nerve, which is a
cutaneous nerve for the skin of the coccyx region.

THE VENTRAL RAMI OF THE SPINAL NERVES

The ventral rami of the spinal nerves are, with the exception of those
of the thoracic region, concerned in the formation of extensive plex-
uses. Each usually receives a gray ramus communicans from the
sympathetic system and many give off a delicate white ramus com-
munis ans to the sympathetic system.

Each thoracic nerve passes ventrally between the intercostal
muscles, supplying branches to these muscles. At the side of the
thorax each gives off a lateral branch that passes to the subcutaneous
tissues and branches into ventral and dorsal divisions, for the supply
of the skin of the side of the thorax. The remainder of the ventral
ramus continues ventrally between the intercostal muscles to the
margin of the sternum where it passes to the subcutaneous tissues
to be distributed to the skin of the ventral thoracic region.

THE CERVICAL PLEXUS (PLEXUS CERVICALIS1

The ventral rami of the first four cervical nerves form the cervical
plexus, under cover of the m. sternomastoideus. These nerves form
irregular loops with one another and from these loops superficial
(cutaneous) ascending and descending and deep ( muscular and com-
municating) branches are given off.

The Superficial Cutaneous Branches. — Ascending Branches. — The
smaller occipital nerve (C. 2, 3) passes toward the occiput and gives

452

THE XERVE SYSTEM

off the mastoid, auricular and occipital branches for the skin of the
ear and mastoid and occipital regions.

The great auricular nerve (C. 2, 3) passes toward the ear and gives
off mastoid, auricular and facial branches to the skin of those regions;
the facial branch supplies the skin of the cheek and over the masseter
muscle and parotid gland.

The cutaneous cervical nerve (C. 2, 3) supplies the skin of the
anterior triangle of the neck.

N.hypoyhssas
to m.rectus capitis latcraJi

N occipitalis minor it-*^-*
Ramus descendens n. hypoqlosii
N auncularis maynus
N. cutaneus colii

N.dorsolii,7°mU"at°r*C/VX'1'
SCapulat\ja„Mrnomo,

M cutane,
medial'!
A/n. mtercosfobrachiales

(After P. Eisler.)

Descending Branches. — The descending roots of the second and
third cervical nerves unite to form a single trunk that divides into
ventral, middle and dorsal branches. The ventral, or suprasternal
branches supply the skin of the neck and upper sternal region. The
middle, or suprascapular branches supply the skin of the over the
middle third of the clavicle to the nipple. The dorsal, or supra-
acromial, branches supply the skin over the lateral third of the clavicle
and the deltoid region.

THE BRACHIAL PLEXUS 453

The Deep Branches. — These are lateral and medial. The muscular
branches of the lateral division are to the mm. sternomastoideus (C. 2),
trapezius (C. 3, 4), levator scapulae (C. 3, 4), scaleni medius and
posterior (C. 3, 4). The communicating branches are given to the
accessory nerve.

The medial division gives muscular branches to the prevertebral
muscles as follows: mm. rectus capitis lateralis, longus capitis, rectus
capitis anterior (C. 1, 2), the mm. intertransversarium, longus colli
and longus capitis (C. 2, 3, 4), the m. scalenius anterior (C. 4).

The descending cervical nerve is formed by small branches from
the second and third cervical nerves. With the descendens or com-
municans hypoglossi (derived from the first and second cervical
nerves) the descending cervical nerve forms the ansi hypoglossi,
which sends branches to the mm. sternohyoideus, sternothyreoideus
and omohyoideus. The mm. thyreoihyoideus and geniohyoideus
are also supplied by the first and second cervical nerves by a branch
that accompanies the hypoglossal nerve.

The phrenic nerve (11. phrcnicus) is also derived from the descend-
ing branches of the third, fourth (mainly) and fifth cervical nerves.
This nerve passes down through the neck and thorax and at the
diaphragm supplies this organ with muscular branches. It also
gives branches to the pleura, pericardium, inferior vena cava, supra-
renal gland and liver. The last two are not direct, however, but
through the diaphragmatic sympathetic plexus.

The communications of the descending cervical branches are with
the superior cervical sympathetic ganglia, the vagal and the hypo-
glossal nerves. The communications of the phrenic nerve are with
the cervical sympathetics and the celiac and diaphragmatic plexuses.

THE BRACHIAL PLEXUS .PLEXUS BRACHIALIS)

The brachial plexus is the extensive plexus from which are derived
the nerves for the superior extremity. It is formed by the ventral
rami of the fifth, sixth, seventh cervical and first thoracic nerves. This
plexus lies in the neck and axillary space and gives rise to a large
number of branches.

The brachial plexus communicates with the cervical sympathetic
ganglia.

The second thoracic nerve sends a branch, the intercoslohumeral ,
or intcrcostobrachial nerve, directly to the arm.

The primary cords of the plexus are formed as follows: The fifth
and sixth nerves form the first cord; the seventh constitutes the. second
cord; the eighth cervical and first thoracic nerves form the third cord.
At the same time each of the nerves divides into ventral and dorsal
trunks.

The secondary cords of the plexus are formed as follows: The

454 THE NERVE SYSTEM

ventral trunks of the fifth, sixth and seventh nerves form the lateral
cord; the ventral trunks of the eighth cervical and first thoracic
form the medial cord; the dorsal cord is formed by the union of all of
the dorsal trunks of the nerves of the plexus. These cords are
lateral, medial and dorsal to the axillary artery and from this rela-
tion receive their names.

The branches of the brachial plexus are usually described under
supraclavicular and infraclavicular branches.

The supraclavicular portion (pars supradavicularis) represents the
branches given off above the level of the clavicle and these are an-
terior and posterior.

The Anterior Branches. — Muscular branches to the mm. scalenus
anterior and longus colli (C. 5, 6, 7, 8).

The communicating branch to the phrenic nerve (C. 5).

The nerve to the m. subclavius (C. 5, 6).

The posterior branches are as follows: Branches to the mm. scaleni
medius and posterior (C. 5, 6, 7, 8).

The dorsal, or posterior scapular nerve (n. dorsalis scapula) is
distributed to the mm. levator scapula;, rhomboidei major and minor
(C 5).

The long, or posterior thoracic nerve (n. thoracal is longus) passes
through the neck into the axilla to the m. serratus anterior (C. 5,

6, 7)-

The suprascapular nerve (n. suprascapularis) passes from the neck
to the superior margin of the scapula, through the scapular notch
and supplies the mm. supraspinatus and infraspinatus (C. 5, 6).

The infraclavicular portion (pars infraclavicularis) is distributed
to the shoulder, ventral part of the thorax and the extremity proper.
It has ventral and dorsal branches. Some of the* ventral branches
are from the lateral cord and some from the medial cord. The
dorsal branches are all from the dorsal cord.

The Ventral Branches. — The ventral, or anterior thoracic nerves, are
lateral and medial and arise from the corresponding cords. The
lateral nerve is derived from the fifth, sixth and seventh cervical
nerves and the medial nerve from the eighth cervical and first thor-
acic nerves. These supply the mm. pectorales major and minor.

The musculocutaneous nerve (n. musculocutancus) is derived from
the lateral cord (C. 5, 6) and is usually accompanied by the nerve
to the m. coracobrachialis (C. 6, 7). This nerve passes through the
axilla into the arm (between the biceps and brachialis muscles) to
elbow where it continues as the lateral cutaneous nerve of the forearm, •
this divides into ventral and dorsal branches. The ventral branch sup-
plies the skin of the lateral half of the ventral surface of the forearm
to the ball of the thumb. The dorsal branch supplies the skin of
the first three-fourths of the lateral half of the dorsal surface of the

THE MEDIAN NERVE

455

forearm. The only muscular branches are to the biceps and brachialis
muscles.

The medial, or internal cutaneous nerve (n. cutaneous antibrachii
medialis), is derived from the medial cord of the brachial plexus
(C. 8, Th. i). It passes from the axilla into the arm, in the distal
part of which it divides into ventral and ulnar branches. The ventral
branch supplies the medial half of the ventral surface of the forearm
to the wrist. The ulnar branch supplies the first three-fourths of
the medial half of the dorsal surface of the forearm.

-

Fig. 322. — Infracla

■ portion of the brachial plexus after i
toralis major and minor muscles.

The medial cutaneous, or lesser internal cutaneous nerve of the
arm is derived from the median cord of the brachial plexus (Th. i).
It supplies the first half of the skin of the medial surface of the arm.

The median nerve («. medianus) is derived from the medial
(C. 8, Th. i) and lateral (C. 5, 6, 7) cords by two heads. It passes
from the axilla through the arm and forearm (between the superficial
and deep muscles) to the wrist and enters the palm.

[ts first branches are given off in the forearm to the elbow joint.
The next branches are muscular for the mm. pronator teres, flexor
carpi radialis, palmaris longus, flexor digitorum sublimis. The

456 THE XERVE SYSTEM

ventral, or volar interosseous nerve, accompanies the ventral in-
terosseous artery and gives off muscular branches to the mm. flexor
longus pollicis, pronator quadratus and lateral half of the flexor digi-
torum sublimis; it gives branches to the radiocarpal articulation.

In the palm the median nerve supplies the skin.

In the hand it gives off its terminal branches which are muscular
and cutaneous. The muscular branches are for the mm. abductor
pollicis brevis, the opponens pollicis and the flexor pollicis brevis.
The cutaneous branches are five in number; the first three supply suc-
cessively the lateral and medial sides of the thumb and the lateral
side of the index finger; the other two branches divide into two each
for the adjacent sides of the index and middle and the middle and
ring fingers, respectively.

The ulnar nerve (nervus ulnaris) is derived from the medial cord
of the brachial plexus (C. 8, Th. 1). It passes from the axilla through
the arm, behind the medial epicondyle into the forearm where it
lies between the superficial and deep muscles of the ulnar side. It
accompanies the ulnar artery into the palm and there divides into
its terminal branches.

Its first branches are in the forearm. The articular branch supplies
the elbow joint. The muscular branches are for the mm. flexor carpi
ulnaris and medial half of the flexor digitorum profundus. It gives
off cutaneous branches that extend into the hand. The ventral or
palmar cutaneous branch supplies the distal third of the ventral sur-
face of the forearm (medial half) and the skin of the hypothenar
eminence. The dorsal cutaneous branch supplies the skin of the
distal third of the dorsal surface of the forearm (medial half) and the
back of the palm and also gives off the dorsal digital branches for the
little finger and the adjacent sides of little and ring fingers.

In the palm the ulnar nerve supplies the palmaris brevis muscle
and divides into a superficial and a deep branch. The superficial
branch (cutaneous) divides into two digital branches for the medial
side of the little finger and the adjacent sides of the little and ring
fingers. The deep branch supplies the mm. flexor brevis and abductor
quinti digiti, opponens quinti digiti, interossei, lumbricales (third
and fourth), adductor pollicis and flexor pollicis brevis (deep part).

The axillary, or circumflex nerve («. axillaris), is derived from the
dorsal cord (C. 5, 6). It is large and passes from the axilla, winds
around the surgical neck of the humerus and ends by giving branches
to the m. deltoideus. It also gives muscular branches to the m. teres
minor, articular branches to the shoulder joint and a large cutaneous
branch to the skin of the proximal half of the lateral surface of the
arm.

The radial, or musculospiral nerve (n. radialis), is derived from all
of the nerves of the dorsal cord. It leaves the axilla and passes to

THE RADIAL NERVE

457

the bend of the elbow along the radial groove on the dorsal surface
of the humerus. It divides into superficial and deep terminal
branches. In its course through the arm it gives off a number of
branches. The muscular branches are distributed to the mm. triceps,

Fig. 323- — Ne

; of the left upper extremity.

anconeus, brachialis, brachioradialis, extensor carpi radialis longus
and at times the brevis. The posterior cutaneous brachial nerve {the
upper internal cutaneous branch of the musculospiral) supplies the
skin of the first third of the medial surface of the arm. The dorsal

458 THE NERVE SYSTEM

cutaneous nerve of the forearm supplies the skin of the dorsal surface
of the arm (last third) and of the first two-thirds of the forearm.

The terminal branches are the superficial and deep rami. The
superficial ramus, or old radial nerve arises near the elbow, passes
along the lateral part of the forearm and in the lower third it passes
to the dorsal surface to end in branches that supply the skin of the
back of the wrist and some of the fingers. Its digital branches are
five in number; the first three supply both sides of the thumb and the
radial side of the index finger. The other two branches divide into
two each for the contiguous sides of the index and middle and the
middle and ring fingers.

The deep ramus, or posterior interosseous nerve, supplies the
muscles of the forearm and the carpal articulations. The nerve lies
between the superficial and deep muscles and supplies the following:
mm. carpi radialis brevis, supinator, extensores digitorum communis,
digiti quinti proprius, carpi ulnaris, the abductor pollicis longus,
extensores pollicis longus and brevis and extensor indicis proprius.

The first, or short subscapular nerve in. subscapularis), is derived
from the fifth and sixth cervical nerves (dorsal cord) and supplies
the subscapularis muscle.

The second, or lower subscapular nerve, has the same origin and
passes to the teres major and subscapularis muscles.

The thoracodorsal, or long subscapular, nerve arises from the sixth
and seventh and eighth cervical nerves (dorsal cord). It supplies
the latissimus dorsi muscle.

THE LUMBOSACRAL PLEXUS (PLEXUS LUMBOSACRALIS)

The lumbosacral plexus is formed by the ventral rami of the five
lumbar, the five sacral and one coccygeal nerves. It is usually
divided into lumbar, sacral and pudendal plexuses.

The lumbar plexus is formed by the ventral rami of the first, second,
third and a branch of the fourth lumbar nerves. It is formed within
the substance of the psoas muscles and also divides into its branches
here. The first two nerves divide into superior and inferior branches.
The superior branch of the first lumbar nerve divides into the ilio-
hypogastric and ilioinguinal nerves. The inferior branch of the first
and the superior branch of the second nerve form the genitofemoral
nerve. The inferior branch of the second, the whole third and the
branch of the fourth lumbar nerves divide into smaller ventral and
larger dorsal divisions. The ventral divisions form the obturator
nerve; the dorsal divisions form the femoral, and lateral, or external
cutaneous, or anterior crural nerves. In addition independent
muscular branches are given off. The branches are as follows:

Muscular branches pass to the m. quadrat us lumborum (L.i, 2,3,4),
psoas major (L. 2, 3), psoas minor (L. 1).

THE LUMBAR PLEXUS

459

The iliohypogastric nerve (w. iliohypogastrics) passes into the loin
along the crest of the ilium into the groin and gives off muscular
branches (to the muscles of the abdominal wall) and the lateral and
ventral cutaneous branches. These cutaneous branches supply the

Lai. cutaneous branch of

ilioliypogastric
Genitofemoral
Ilioinguinal

Muscular branches
to the Mop,
External spermatic nerve**
tat. femoral cut.
Lumbj-:

Tibial

ifu:-f

long head of

bieeps and

semitendinosus

inter r.us
Posterior femoral cutaneous nave

Medial infer, cluneal
Perineal nerve-rdors. nerve of penis
Infer, hemorrhoidal

Muse, branches t,

Fig. 324-

■ d axcygeui

-Lumbosacral pies

{.After P. Eisler.)

skin of the superolateral part of the buttock and the ventral abdom-
inal wall.

The ilioinguinal nerve (n. ilutinguinalis) passes along the iliac
fossa to the external abdominal ring and supplies branches to the
skin of the pubic region, scrotum and root of the penis (or mons
veneris and labia majora) and the superomedial portion of the thigh.

460

THE NERVE SYSTEM

-lateral Cutaneous M

'^rme^a/e CuHuiems ^ 4

Superficial Perorrea! /V—

Fig. 325. — Nerves of the ventral part of the right lower extremity,

THE SACRAL PLEXUS 461

The genitofemoral nerve (n. genilofemoralis) passes across the
iliac fossa and gives off an external spermatic branch that supplies
a part of the scrotum and thigh; the remainder passes into the thigh
along side of the femoral artery and supplies the skin of the ventral
and proximal part of the thigh.

The lateral cutaneous nerve (n. cutaneous femoralis lateralis)
passes into the thigh and supplies the skin of the ventrolateral and
lateral aspects of the thigh and buttocks.

The obturator nerve («. obtnratorius) (L. 2, 3, 4) passes into the
thigh through the obturator groove. Its ventral, or superficial
branch supplies muscular branches to the adductores longus and
brevis, the gracilis and occasionally the pectineus; an articular
branch to the hip joint; a cutaneous branch to the skin of the medial
surface of the thigh (distal two-thirds); a branch to the femoral
artery. The dorsal, or deep branches pass into the thigh and give
muscular branches to the obturator externus, adductores magnus
and brevis; an articular branch to the knee joint.

The femoral, or anterior crural, nerve («. femoralis) is a large
nerve derived from the second, third and fourth lumbar nerves. It
passes through the iliac fossa and into the thigh at the side of the
femoral sheath and in the femoral triangle gives off a number of
branches. The muscular branches are distributed to the mm. pec-
tineus, sartorius, rectus femoris, vasti lateralis, medialis and inter-
medins; articular branches to the hip and knee joints; cutaneous
branches, the intermediate and medial cutaneous branches, that supply
the skin of the ventral part of the thigh to the knee.

The saphenous nerve (n. saphenus) is the terminal part of the
femoral nerve. It passes into the leg and supplies the medial side
of the knee and patellar regions, the medial side of the leg and foot.

THE SACRAL PLEXUS (PLEXUS SACRALIS)

The sacral plexus is formed by the remainder of the fourth, all
of the fifth lumbar and all of the first and part of the second and third
sacral nerves. The fourth and fifth lumbar and the first and second
sacral nerves divide into ventral and dorsal divisions. The third
sacral nerve divides into superior and inferior divisions, the latter
forming the pudendal plexus. The ventral divisions of the fourth
and fifth lumbar and first, second and the superior part of the
third sacral nerves form the tibial nerve. The dorsal divisions form
the common peroneal nerve. The branches of distribution are
dorsal and ventral.

The sciatic nerve is really the tibial and common peroneal nerves
with extra nerves for the hamstring muscles. This large nerve
passes through the greater sciatic foramen into the buttock and then
into the thigh where it divides into the tibial and common peroneal

462

THE NERVE SYSTEM

•Super/or GJuteal M

Pudendal N
Small Sciatic N- %.

Common Peroneal N.

oneal Ana5.br.

PlonTar Cutaneous M-

Fig. 326. — Nerves of the dorsal part of the right lower extremity.

THE PLANTAR NERVES 463

nerves at almost any level. In its course the sciatic nerve gives
branches to the mm. biceps, semitendinosus, semimembranosus and
the adductor magnus.

Collateral branches of the sacral plexus are given off as follows:
muscular branches to the mm. quadratus femoris, obturator internus,
gemelli superior and inferior, pyriformis, glutei maximus, medius,
minimus; articular branches to the hip joint.

The tibial, or internal popliteal, nerve (». tibialis) is derived from
the fourth and fifth lumbar and first three sacral nerves. It is a
part of the sciatic nerve to various levels of the thigh but is usually
individual before the popliteal space is reached. It continues
through the back of the leg to the back of the ankle and passes into
the foot where it divides into medial and lateral plantar nerves.

In the popliteal space it gives branches to the knee and proximal
tibiofibular joints; muscular branches to the mm. plantaris, gastroc-
nemius (both heads) popliteus; the medial cutaneous sural nerve
(tibial communicating nerve) is joined by the peroneal anastomotic
branch of the common peroneal nerve and these form the sural nerve
that accompanies the small saphenous vein and supplies the skin of
the lateral and back parts of the calf, ankle and heel and the side of
the foot; it also gives branches to the ankle and tarsal joints. In
the back of the leg the tibial nerve distributes muscular branches to
the mm. tibialis posterior, flexor digitorum longus, flexor hallucis
longus; cutaneous branches to the skin of the medial malleolus and
the heel and posterior part of the sole of the foot; articular branches
to the ankle joint.

The medial plantar nerve is the larger of the two terminal branches
and accompanies the medial plantar artery. Its collateral branches
are muscular to the mm. abductor hallucis and flexor digitorum
brevis; cutaneous to the skin of the medial part of the sole of the foot;
articular branches to the tarsal and metatarsal joints.

The common digital plantar nerves are four in number. The first
(medial) supplies the m. flexor hallucis brevis, and the skin of the
medial side of the foot and great toe. The second supplies the first
lumbricale muscle and then divides into two proper digital nerves
for the adjacent sides of the great and second toes. The third and
fourth divide into proper digital branches for the skin of the adjacent
sides of the second and third and the third and fourth toes.

The lateral plantar nerve accompanies the lateral plantar artery.
It distributes collateral branches to the quadratus plantae and ab-
ductor digiti cjuinti muscles; cutaneous branches to the sides of the
foot. Its terminal branches are the superficial and deep rami. The
superficial ramus [lateral branch) supplies the flexor digiti quinti
1)K \ is and the two interossei of the fourth space and the skin of the
sole and of the lateral surface of the little toe. The medial branch

464

THE NERVE SYSTEM

divides into proper digital nerves for the adjacent sides of the little
and fourth toes. The deep ramies gives off muscular branches to the
interossei muscles (except those of the fourth space) to the adductor
hallucis and the three lateral lumbricale muscles; articular branches
to the tarsal and metatarsal joints.

The common peroneal, or external popliteal nerve (n. peroneus
communis), passes through the popliteal space to the back of the
head of the fibula. It gives off collateral branches as follows: a mus-
cular branch to the short head of the biceps; articular to the knee

Fir,. 327. — The plantar

joint; two cutaneous branches, the lateral sural branch and the anasto-
motic branch. The lateral sural branch arises in the popliteal space
and supplies the skin of the lateral surface and back of the leg in
the first two-thirds. The peroneal anastomotic nerve (fibular com-
municating nerve) joins the corresponding branch of the tibial nerve
the distribution of which has been given.

The terminal branches of the common peroneal nerve are the
following:

The tibial recurrent nerve supplies the proximal part of the tibialis
anterior muscle, the knee and tibiofibular joints.

THE PUDENDAL PLEXUS 465

The deep peroneal, or anterior tibial, nerve (». peroneus profundus)
passes to the front of the leg and accompanies the anterior tibial
artery to the dorsum of the foot. In the leg it gives off muscular
branches to the mm. tibialis anterior, extensores hallucis longus,
digitorum longus and peroneus tertius; a branch to the ankle joint.
Its terminal branches in the foot are medial and lateral. The medial
branch that accompanies the dorsalis pedis artery and supplies the
first dorsal interosseous muscle and the skin of the medial side of
the great toe and the adjacent sides of the great and second toes,
also the adjacent joints. The lateral branch gives off muscular
branches to the extensor digitorum brevis muscle, the tarsal and
metatarsal joints and branches (sensor probably) to the second and
third dorsal interossei.

The superficial peroneal, or musculocutaneous nerve is the last
branch of the common peroneal nerve and lies between the peroneus
longus and extensor digitorum longus muscles. It gives collateral
muscular branches to the peronei longus and brevis muscles and
divides into dorsal medial and intermediate cutaneous nerves. The
former ultimately divides into two branches that supply the adjacent
sides of the second and third toes. The latter divides into two
branches each of which divides into two for the supply of the skin
of the adjacent sides of the third and fourth and the fourth and
fifth toes.

THE PUDENDAL PLEXUS (PLEXUS PUDENDUSl

The pudendal plexus is formed by fibers from the first three sacral
nerves and by the anterior rami of the fourth and fifth sacral and
first coccygeal nerves. It receives gray rami communicantes from
the sympathetic system. It gives rise to a number of branches.

The posterior cutaneous nerve of the thigh (small sciatic nerve) is
derived from the first three sacral nerves. It is a cutaneous nerve
and its branches are as follows: Perineal branches supply the scrotum
and root of the penis, or the labium majus and clitoris and part of
the skin of the perineum. The inferior gluteal branches supply the
skin of the lower half of the buttock and back of the thigh. The
perforating cutaneous nerve supplies the skin of the lower part of the
buttock and the medial surface of the nates.

The muscular branches pass to the levator ani, coccygeus and ex-
ternal sphincter muscles. The nerve to the external sphincter mus-
cle also supplies cutaneous branches to the skin of the ischiorectal
fossa and the fold of the nates behind the anus.

The anococcygeal nerve is derived from a plexus formed by the
remainder of the fourth and fifth sacral and coccygeal nerves; it
supplies the skin of the coccyx region and that back of the anus.

The pudendal, or pudic nerve arises in the pelvis from the second,

466 THE NERVE SYSTEM

third and fourth sacral nerves. It passes to the buttock through
the greater sacrosciatic foramen and in the ischiorectal fossa divides
into its terminal branches. The inferior hemorrhoidal nerve accom-
panies the inferior hemorrhoidal artery and gives off muscular
branches to the external sphincter ani muscle; cutaneous branches to
the skin around the anus; communicating nerves to the surrounding
nerves. The perineal nerve consists of superficial and deep portions.
The superficial portion is cutaneous and as its lateral and medial
divisions supplies the skin of the scrotum, or labium majus. The
deep branch gives off muscular branches to the anterior portion of
the mm. levator ani, and external sphincter, the transversus perinei
(superficialis et profundus), ischiocavernosus (or sphincter vaginas),
ischiobulbosus, sphincter urethra; membranaceae. It also supplies
the erectile tissue of the bulb and corpus cavernosum and the mucosa
of the urethra as far as the glans.

The dorsal nerve of the penis, or clitoris accompanies the internal
pudendal artery. It passes under the pubic arch and along the
dorsum of the penis or clitoris. It sends branches into and around
the corpus cavernosum.

THE SYMPATHETIC NERVE SYSTEM

The sympathetic nerve system (systema nervorum sympathicum),
although seemingly an independent structure, is intimately con-
nected with the cerebrospinal system. Owing to its peculiar ar-
rangement and appearance it is called the ganglionatcd cord and ex-
tends from the base of the skull to the coccyx. It rearranges and
distributes fibers of the cerebrospinal system to the viscera; it trans-
mits sensor impulses from the viscera to the cerebrospinal system;
it sends motor fibers to vessels and organs through the cerebrospinal
nerves.

This system consists of a series of central ganglia, collateral ganglia
and terminal ganglia. The central ganglia (ganglia trunci sympa-
thies) are arranged in pairs on each side of the midline from the
base of the skull to the coccyx; they are connected with one another
up and down (on the same side only). The fibers are gray in color
and constitute the gray rami communicantes; these are connecting
and distributor^- in function.

Each ganglion consists of a variable number of large, multipolar
nerve cells surrounded by a capsule of white fibrous tissue. In addi-
tion neuroglia, myelinated and amyelinated nerve fibers are present.
Each cell possesses a main process, the axone, that may be associative
in function, or may pass to the cerebrospinal system as the gray
ramus communicans, or it may pass to the periphery, or to ganglia
farther out. The dendrites are usually numerous and serve an
associative function in the immediate neighborhood. The white

THE SYMPATHETIC NERVE SYSTEM 467

rami communicantes are from two main sections of the spinal cord,
the thoracicolumbar (from the second thoracic to the second lumbar
nerve levels) and the pelvic, or sacral (from the second to the fourth
sacral nerve levels). Both ventral and dorsal roots of the spinal
nerves are concerned.

The small fibers {white rami communicantes) from the ventral
roots of the spinal nerves may end in the central ganglia of that
level; they may pass through that ganglion and up or down to
another one of the central ganglia; they may pass through the
central ganglion and terminate in a collateral ganglion. All of these
fibers are the splanchnic efferent fibers. The sensor fibers are the
splanchnic afferent*; and the cells lie in the dorsal root.

Although in early fetal life there are as many pairs of ganglia as vertebral seg-
ments, at birth this condition does not prevail. The central ganglia are ar-
ranged as follows:

Cervical 3 pairs. s

Thoracic 10 to 12 pairs.

Lumbar 4 pairs.

Sacra! 4 to 5 pairs.

Coccygeal a single one.
These communicate with one another up and down.

Fibers from the spinal nerves that pass to the sympathetic ganglia are wkite
and constitute the white rami communicantes. Those from the sympathetic
system to the spinal cord are gray and constitute the gray rami communicantes.
These are the communicating fibers.

I In libers of distribution are chiefly gray and pass from the various sympathetic
ganglia to vessels and organs of the thoracic and abdominal cavities, that is, the
muscles and epithelium thereof representing both motor and sensor fibers.

The collateral ganglia, or ganglionated plexuses are the cardiac,
solar and hypogastric plexuses.

The terminal ganglia are in the various organs, as in the plexuses
of Auerback and Meissner of the gastrointestinal tract.

The cervical portion (pars cephalica el cervical is) of the central sys-
tem comprises three pairs of ganglia, the superior, middle and in-
ferior cervical ganglia. No white rami communicantes are found
here.

The branches of these ganglia are either central communicating
branches for the other nerves, or peripheral branches that pass
directly, or through plexuses to the viscera and vessels of the head,
neck and thorax.

The superior cervical ganglia (ganglia cervicalcs superiores) are the
largest; each lies opposite the second and third cervical vertebra?.
Each is broad, fiat and spindle-shaped, of a reddish color and repre-
sents a fusion of the first four conical ganglia. From its superior
(cephalic) end a branch ascends along the internal carotid artery
and in the skull its two branches form the internal carotid and cavern-

468

THE NERVE SYSTEM

ous plexuses. The carotid plexus communicates with the semilunar
(Gasserian) and sphenopalatine ganglia and the abducens and glosso-
pharyngeal nerves. The cavernous plexus, in the cavernous sinus,
communicates with the oculomotor, trochlear, the ophthalmic divi-
sion of the trigeminus and abducens nerves and the ciliary ganglion.
Other branches of these plexuses follow the anterior, middle cerebral
and ophthalmic arteries.

Fig. 328. — Diagram of the sympathetic ganglia and their connections

Other branches of the superior cervical ganglion communicate
with the middle ganglion, the first four cervical nerves (ventral
roots) vagal, glossopharyngeal (forming the pharyngeal plexus), and
hypoglossal nerves, while others pass to the larynx, pharynx and
heart; the latter form the superficial cardiac nerve, the right one join-
ing the deep cardiac plexus and the left the superior cardiac plexus.

The middle cervical ganglia {ganglia cervicales mediates) are the
smallest and lie in front of the sixth cervical vertebra and represent
the fifth and sixth ganglia fused.

Each sends branches, gray rami communicantes, to the fifth and

THE CENTRAL SVMPATHETHIC GANGLIA 469

sixth cervical nerves and to the subclavian artery. Peripheral
branches pass to the thyreoid gland and heart, as the middle cardiac
nerve to the deep cardiac plexus. This ganglion may be absent and
when this occurs these branches arise direct from the cord in that
region.

The inferior cervical ganglia {ganglia cervicales inferiores) lie upon
a level with the seventh cervical vertebra and are irregular in shape.
Each usually represents a fusion of the seventh cervical and the first
thoracic ganglia and each sends branches, gray rami, to the seventh
and eighth cervical nerves and the subclavian artery; it also gives
off the inferior cardiac nerve that joins the deep cardiac plexus.
Other branches follow the vertebral artery into the skull and these
continue along the cerebral and cerebellar arteries.

The thoracic ganglia (pars thoracalis) are ten to twelve pairs in
number. They rest against the heads of the ribs, behind the pleura.
The first often fuses with the last cervical and the eleventh and
twelfth are usually fused. All of the spinal thoracic nerves (except
the first) send white rami to these ganglia. Branches from the first
five pairs of thoracic ganglia go to the aorta and its branches and
from the second, third and fourth others go to the posterior pulmon-
ary plexus. From the lower ganglia branches go to the aorta and
others form the splanchnic nerves.

The great splanchnic nerve (n. splanchnicus major), on each side,
is formed by branches from the fifth, sixth, seventh, eighth and
ninth ganglia and is whitish in color. It passes through the crus of
the diaphragm and joins the celiac ganglion of the solar plexus and
ultimately the renal and adrenal plexuses. In the thorax branches
pass to the aorta and esophagus.

The lesser splanchnic nerve (n. splanchnicus minor) is formed by
branches from the ninth and tenth ganglia, passes through the dia-
phragm to join the aorticorenal ganglion of the solar plexus.

The least splanchnic nerve (n. splanchnicus imus) is made up of
fibers from the eleventh thoracic ganglion, pierces the diaphragm
and ends in the renal plexus.

The lumbar ganglia are usually four in number upon each side,
small and placed near the midline. They receive white rami from
the first two lumbar nerves. They send branches to the lumbar
nerves and to the abdominal aorta and aortic plexus.

The sacral ganglia (pars pclviua) are four or five in number on
each side on the front of the sacrum; branches pass to the sacral
nerves. Some of the sacral nerves send branches through the gang-
lia. Other branches pass to the pelvic plexus and the vessels and
pelvic organs, as bladder, rectum, uterus (motor and inhibitor
fibers) prostate (secretor fibers) and vasodilatator fibers to the geni-
tal organs.

47° THE NERVE SYSTEM

In front of the coccyx the two cords join to form a single coccygeal
ganglion, or ganglion impar.

The cardiac plexus (plexus cardiac us) comprises the superficial and
deep portions and lies at the base of the heart. The superficial plexus,
under the arch of the aorta, is formed by the left superior cardiac
nerve, the left inferior cervical cardiac, a branch from the vagus and
some fibers from the deep plexus. The ganglion of Wrisberg may
be present. From this plexus branches pass to the left half of the
deep plexus and to the anterior coronary and left anterior pulmonary
plexuses.

The deep portion (plexus cardiacus profundus) is situated in front
of the tracheal bifurcation. It is the larger and is formed by the
cardiac branches of the cervical ganglia (except left superior)
branches of the recurrent laryngeal and vagal nerves. Branches
pass to the anterior and posterior coronary plexuses. The left cor-
onary plexus sends branches to the left atrium and ventricle and the
right coronary plexus to the right atrium and ventricle. Branches
also pass to the pulmonary plexuses.

The pulmonary plexuses (plexus puhnonaJes) are ventral and
dorsal. The ventral plexus on each side lies upon the structures at
the ventral part of the root of the lung, which structures it supplies.
Each receives fibers from the deep cardiac plexus and the left from
the superficial cardiac plexus also. The dorsal plexus lies behind
the root of the lung and is formed by branches from the second,
third and fourth thoracic sympathetic ganglia, but chiefly branches
from the vagal nerve. Branches therefrom pass along the vessels
and bronchi.

The esophageal plexuses (plexus esophagei) are ventral and dorsal
and are formed, chiefly, by the vagal nerves through the pulmonary
plexuses; branches from these plexuses pass into the esophagus and
pericardium. The lower part of the esophagus also receives fibers
from the greater splanchnic nerve.

The solar, or celiac plexus (plexus celiacus) is a great network of
sympathetic nerves and ganglia situated in front (.ventrad) of the
aorta and crura of the diaphragm and behind the pancreas; it is
in relation with the celiac axis and superior mesenteric arteries. To
this plexus pass all of the splanchnic nerves and branches from the
right vagus. From it pass branches to the viscera of the abdomen
and along the branches of the aorta. It consists of the celiac plexus
and two main ganglionic masses, the celiac ganglia. This plexus is
connected with the renal, diaphragmatic, adrenal, aortic and supe-
rior mesenteric plexuses and others lower down.

The most important ganglia are the celiac; these are the largest

THE ABDOMINAL SYMPATHETIC PLEXUSES 47 1

in the body. Each is large and irregular, situated in front of the
cms of the diaphragm and consists of a collection of smaller ganglia.
The upper end of each receives the great splanchnic nerve while
the lower part constitutes the aorticorenal ganglion that receives the
lesser splanchnic nerves.

The solar plexus gives rise to a number of plexuses.

1. The phrenic plexuses receive branches from the phrenic nerves.
The right is the larger and may possess a ganglion. From each
branches pass to the diaphragm and (on the right side) to the inferior
vena cava and to the suprarenal and hepatic plexuses.

2. The coronary plexus sends branches to the esophagus and along
the lesser curvature of the stomach that join branches of the vagus.

3. The splenic plexus, chiefly from the left celiac ganglion, accom-
panies the splenic artery to the spleen, likewise giving branches to
the pancreas and the greater curvature of the stomach. Branches
of the right vagus join the plexus.

4. The hepatic plexus is the largest and receives branches from the
left vagal and phrenic nerves. Its branches go to the liver and
pyloric portion of the stomach, duodenum, pancreas, greater curva-
ture of the stomach and to the gall-bladder. These branches form
plexuses along the arteries and take their names therefrom.

5. The suprarenal plexus, on each side, contains a ganglion at the
junction of branches of the celiac ganglion, great splanchnic and
phrenic nerves and renal plexus that form this plexus. It sends
branches to the adrenal, or suprarenal glands.

6. The superior mesenteric plexus surrounds the superior mesen-
teric artery and receives branches from the right vagal nerve, the
celiac and aorticorenal ganglia. As it passes into the mesentery it
gives rise to subplcxuses that follow the branches of this artery, as
the pancreatic, intestinal, iliocolic, right colic and middle colic. It has
a ganglion at the root of the artery.

7. The renal plexuses consist of branches of the solar plexus,
aorticorenal, adrenal and aortic plexuses and the least splanchnic
nerves; branches pass to the kidneys and to the spermatic plexuses.

8. (a) The spermatic plexuses are formed by branches from the
renal and aortic plexuses; branches pass to the testes.

(b) The ovarian plexuses are formed in the same manner and send
branches to the ovaries, oviducts and borders of the uterus. They
communicate with the uterine plexus.

9. The aortic plexus is situated upon the front and sides of the
abdominal aorta between the superior and inferior mesenteric
arteries. It is made up of branches from the solar plexus and the
lumbar sympathetic ganglia. It distributes branches to the sper-
matic, inferior mesenteric, suprarenal, renal, and hypogastric plexuses
and to the inferior vena cava.

472

THE NERVE SYSTEM

The inferior mesenteric plexuses is situated at the root of the infe-
rior mesenteric artery where a ganglion is found. It is derived,
chiefly, from the left side of the aortic plexus and gives rise to sub-
plexuses that follow the branches of the artery, as the left colic and

Lefl greater splanchnic r,
Left celiac gang/ion
Sup mesenteric artery
left renal gonolion •
Sup mesenteric ganglia

Left,

x/artery

left sympathetic cord

In? mesenteric ganctlic

Left Com. //lac artery

Left com iliac vein
Hypogastric plexus

Fig. 329. — Abdominal portion of the sympathi tic trunk.

sigmoid plexuses that distribute branches to the corresponding parts
of the large intestine (descending, iliac, pelvic colons and the upper
part of the rectum).

The hypogastric plexus is located in front of the promontory of the
sacrum and is composed of branches of the aortic plexus (the hypo-

THE HYPOGASTRIC PLEXUS 473

gastric nerves) and the lumbar ganglia. Below it divides into right
and left pelvic plexuses to supply the pelvic viscera.

The pelvic plexuses receive branches from the second, third, and
fourth sacral nerves and a few from the first two sacral sympathetic
ganglia. Small ganglia are present. Subplexuses follow the
branches of the internal iliac artery (hypogastric). The subdivisions
are as follows:

1. The vesical plexus contains a large number of spinal nerve
fibers and accompanies the branches of the vesical arteries. Its
branches pass to the bladder and ureter and, in the male, to the
seminal vesicles and vasa deferentia and some branches join the
spermatic plexus on the spermatic cord.

2. (a) The prostatic plexus is large and sends branches to the
prostate, neck of the bladder, seminal vesicles and penis of the male.
In the latter they constitute the small and large cavernous nerves
that accompany branches of the internal pudic (pudendal) artery.

(b) The uterovaginal plexus sends branches to the uterus along
the uterine artery and these join those of the ovarian plexus. The
branches to the vagina, vestibule and clitoris contain quite a few
spinal nerve fibers.

3. The inferior hemorrhoidal plexus sends branches to the lower
part of the rectum and these join the branches from the superior
hemorrhoidal plexus.

INDEX

Abdomen, 293

apertures of, 294

boundaries of, 293

cavities of, 293

lines of, 294

lymphatics of, 260

muscles of, 169

regions of, 294

viscera of, 293
Abdominal aorta, 235
branches, 235

rings, 1 70
Abducens nerve, 442
Acetabulum, 93
Acromion, 73
Air cells, ethmoidal, 57

sinuses, frontal, 71
mastoid, 352
maxillary, 61
sphenoidal, 57
Ala cinerea, 378
Alimentary tract, 282
Alisphenoids, 49, 50
Alveolar process, 62
Amphiarthroses, 10S
Ampulla, rectal, 307

semicircular canals, 353

uterine tube, 331

vas, 326
Amygdala, 41 1
Anal canal, 307

columns, 307

valves, 307
Angle of mandible, 16

of scapula, ;i,

of sternum, 35

sacrovertebral, 35

subcostal, 41
Ankle joint, [38
Annulus ovalis, 218
Anococcygeal body, 177
Ansa hypoglossi, 433
Antecubital nodes, 25 7
Anterior rami of spinal nerves, 451
Antihelix, 350
Antitragus, 35

Antrum, maxillary, 61

pyloric, 301

tympanic, 312
Anus, 308
Aorta, 225

abdominal, 236

arch of, 225

branches of, 235

great sinus of, 235

thoracic, 235

valves, 225
Aortico-renal plexus, 471
Aperture of larynx, 275

of mouth, 282

pyriform, 69
Apertures of diaphragm, 168

of fourth ventricle, 379, 414

of pelvis, 93

of thorax, 167
Aponeurosis, epicranial, 146

intercostal, 166, 167

palatal, 283

palmar, 1X4

plantar, 206
Apparatus digestorius, 282

lacrimal, 34S

respiratory, 271

urinogenital, 316, 324
Appendage, pectoral, 73

pelvic, 89
Appendices epiploica, 305
Appendix of larynx, 276

vermiform, 306
Aqueduct of cerebrum, 3S1
Aqueous chamber, 346

humor, 346
Arachnoid, 362

granulations, 362

villi, 362
Arbor vita; of cerebellum, 408
Arch, alveolar, <•:

aortic, 223

arterial of hand, 234
of wrist, 234

carpal, 234

dental, 69

476

Arch, glossopalatal, 292
neural, 24

pharyngopalatal, 292
plantar, 107
Arcuate fibers, external, 409

internal, 409
Arteries, ascending pharyngeal, 228
axillary, 231
brachial. 232
bronchial, 232
of brain, 431
carotid, common, 225

external, 226

internal, 229
celiac, 236
cerebral, anterior, 430

middle, 431

posterior, 4.51
cervical ascending, 230

deep, 231

transverse, 229
ciliary, long, 347

posterior, 347

short, 347
circumflex of humerus, 231, 232

iliac, 239

of thigh, 239
colic left, 237

middle, 236

right, 236
common digital, 234, 240
communicating anterior, 430

peroneal, 241

tibial, 241
coronary of heart, 225

of maxillary, 236

of stomach, 236
costocervical trunk, 231
deferential, 23S.
digital of foot, 241

of hand, 234
dorsal lingual, 236

of clitoris, 238

of penis, 238
dorsalis pedis, 240

pollicis, 240
epigastric inferior, 238

superficial, 239

superior, 230
esophageal, 235
external iliac, 238
branches of, 238
maxillary, 226
branches of, 226
facial, 226

Arteries, femoral, 238

circumflex deep, 239
lateral, 239
medial, 239
fibular, 240
frontal, 229
gastric, 236
gastroduodenale, 236
gastroepiploic left, 236

right, 236
gluteal, 237
hemorrhoidal inferior, 238

middle, 238

superior, 237
hepatic, 236

branches of, 236
hypogastric, 237
ileocolic, 236
iliac common, 237

external, 238

internal, 237
iliolumbar, 237
infraorbital, 228
innominate, 225
intercostal, 233
intestinal, 236
labial, 226
lingual, 226
lumbar, 237
malleolar, 241
mammary, 230
maxillary external, 226

internal, 228
median, 233
mediastinal, 235
meningeal, middle, 228
mesenteric inferior, 237

superior, 236
metacarpal, 233
metatarsal, 240
musculophrenic, 230
nasal, 226
obturator, 237
occipital, 226
of eyeball, 347
of peni-

ophthalmic, 229
ovarian, 237
palatal ascending, 226

descending, 229
pancreatic, 236
pancreaticoduodenale, 236
perforating of foot, 241

of femoral, 239

of hand, 234

477

Arteries, perforating, of peroneal, 241
pericardial, 235
peroneal, 241
pharyngeal, 227
phrenic, 23s
plantar lateral, 241

medial, 241
popliteal, 239
posterior auricular, 227
pudendal, 238, 239
pulmonary, 224
radial, 232
branches, 234
indicis, 233
renal, 237
retinal, 229
sacral, 237
scapular, 230
spermatic, 237
spinal, 431
subclavian, 229
subcostal, 235
sublingual, 226
submaxillary, 226
subscapular, 231
superior thyreoid, 226
supraorbital, 229
suprarenal, 23G
temporal, 228
thoracoacromial, 231
thoracodorsal, 231
thyrocervical trunk, 229
thyreoid inferior, 229

superior, 226
tibial anterior, 240

posterior, 240
tonsillar, 226
ulnar, 233
uterine, 238
vaginal, 238
vertebral, 229
vesical inferior, 238
middle, 238
superior, 238
Arthrodia, 109
\rti. ular discs, in

processes, 25
Articulations, 108

acromioclavicular, 126
ankle, 138

atlantoepistropheal, 113
atlantooccipital, 114
calcaneocuboid, 139
carpal, 1 26
carpometacarpal, 128

Articulations, costochondral, 11
costotransverse, 117
costovertebral, 116
humeroradial, 123
humeroulnar, 123
interchondral, 119
intermetacarpal, 128
intermetatarsal, 141
interphalangeal, 129, 142
intertarsal, 139
lumbosacral, 113
mandibular, 115
metacarpophalangeal, 128
of elbow, 1 23
of hip, 131
of knee, 134
of pelvis, 129
of pubis, 130
of shoulder, 127
of vertebrae, in
radiocarpal, 125
radioulnar, 124
sacrococcygeal, 113
sacroiliac, 129
sternoclavicular, 119
sternocostal, 118
tarsometatarsal, 140
tibiofibular, 137
tibiotarsal, 138
Aryepiglottic folds, 274
Arytenoid cartilages, 224
Association fibers of cerebrum, 416
of oblongata, 400
of spinal cord, 367, 368, 369
Atrioventricular apertures, 217, 220

bundle, 221
Atrium left, 219

right, 217
Attic, tympanic, 351
Auditory area, 392
canal, 350
labyrinth, 353, 354
meatus, 350
nerve, 356
ossicles, 352
tube, 353
Auricle, 217, 219, 350
Axilla, 232
Axis cylinder, 359

Bartholin, glands of, 335
Basal ganglia, 410
Base of brain, 371

of heart, 216

of skull, 70

4?S

Basilar groove, 377

Bicipital groove, 77

Bile ducts, 314

Bladder, 319

Blind spot, 345

Blood vascular system, 2IJ

Bone or bones, atlas, 26

axi>. 2;

calcaneus, 103

cancellous, 19

carpal, S5

clavicle, 73

coccyx, 33

compact, 19

composition, 17

conchal, 58

development of, 21

diaphysis, 27

ear, 352

epiphysis, 27

ethmoid, 56

facial, 60

flat, 23

frontal, 41

haversian canals, 19
systems, 19

hip, 90

humerus, 77

ilium, 90

incus. 352

innominate, 90

irregular, 23

ischium. 92

lacrimal, 58

lacunae, 19

lamellae, 19

long, 23

malleus, 352

mandible, 65

marrow. :o

maxilla, 60

metacarpal. 87

metatarsal, 103

nasal, 59

occipital. 4-

of foot, 107

of hand, 85

palate, 63

parietal, 43

patella, 97

pelvis, 89

periosteum, 17

phalanges, 87, 106

pubis, 92

radius, 82

Bone or bones, sacrum, 31

scapula, 74

sesamoid, 23

short, 23

sphenoid, 4S

stapes, 352

sternum, 35

structure of, 17

tarsus, 103

temporal, 52

thigh, 94

tibia, 9S

ulna, 80

vertebrae, 24

Wormian, 23

zygomatic, 64
Brachia conjunctiva, 379, 410

of midbrain, 379

pontis, 377, 409
Brain, 370

base of, 371

circulation of, 430

fissures of, 386

hemispheres of, 386

lobes of, 386

parts of, 371

stem, 374, 393

topography of, 392

ventricles of, 413

weight of, 369
Broad ligament of uterus, 333
Bronchi, 277
Buccae, 2S4
Bulb of corpus spongiosum, 328

of urethra, 328

of vestibule, 335

olfactory, 389, 426
Bursae, 111

Cai Virus scriptorius. 379
Calyces renales, 319
Canal, anal, 308

hypoglossal, 47

inguinal. 175
Canine fossa, 60
Capsule, external, 410

internal, 411

of joints, in

of Tenon, 341
Cardia, 300
Carotid body, 340
Cartilage. 109
Caruncula lacrimalis, 348
Cauda equina, 364
Cavernous plexus, 470

479

Cavernous sinus, 432

Cecum, 305

Cells, ethmoidal. 57

mastoid, 352
Cerebellum, 3S1, 40S
Cerebrospinal nerve system, 360
Cerebrum, 386, 410
Cerumen, 350
Ceruminous glands, 350
Chambers of eyeball, 346
Cheeks, 284
Chest, 40
Choame, 274
Chordae tendineae, 219
Choroid, 344

plexus, 385
Chromaphyl system, 339
Ciliary body, 344

ganglion, 444

processes, 344

ring, 344
Cingulum, 388
Circular sinus of brain, 430

of eyeball, 347
Circulation, portal, 251

pulmonary, 224

systemic, 250
Circumanal glands, 30S
Cisterna eerebellomedullaris, 362

chiasmatis, 362

chyli, 253

interpeduncularis, 362

magna, 362

subarachnoideales, 362
Claustrum, 410
Clava, 37 1

Clinoid processes, 48
Clitoris, 336
Coccygeal ganglion, 470

gland, 340
Cochlea, 354
Cochlear duct, 355
Colliculi, 380
( lolon, 306

ascending, 306

descending, 306

lie'. II res of, 306

pelvic. 306

sigmoid, 307

transverse, 306
Columnae 1 arneae, 210
Columns of Bertin, 317

of rectum. 307

of spinal cord, ; 16
Comma tract, 309

Commissure, anterior, 410, 42S

gray, 364

hippocampal, 416

of Gudden, 448

posterior, 33s

white, 366
Cones, retinal, 345
Confluens sinuum, 461, 432
Conjunctiva, 348
Conus arteriosus, 218

medullaris, 362
Coracoid process, 76
Cord, ganglionated, 466
Cords of brachial plexus, 453
Cornea, 343
Cornicula laryngis, 275
Corona dentis, 286

glandis, 329

radiata, 415
Coronal suture, 70
Coronoid fossa, 79

process, 66, 80
Corpora albicantia, 383, 428

quadrigemina, 380
Corpus adiposum buccae, 284

callosum, 390, 416

cavernosum, 328

geniculatum, 379, 384

spongiosum, 328

striatum, 411
Cortex, cerebral, 410
Corti, organ of, 356

spiral ganglion of, 354
Cortical localization, 391
Corticifugal projection libers, 415
Costal cartilages, 39
Cowper's glands, 328
Cranial fossa-, 71
Craniocerebral topography, 392
Cricoid cartilage, 274
Crura ci rebri, 379, 405
Crusta, 403
Crystalline lens, 346
Cuneale fasciculus, 319

nucleu
Cuneiform cartilages, 275
Cuneus, 388, 392
Cupola of cochlea, 354

Dartos fascia. 325

Decussation, brachia conjunctiva, 4o£

fountain, 407

lemnisci, 397

motor, 375, 39s

optic, 284

480

Decussation, sensor, 397

Deiter's nucleus, 440

Dendrites, 359

Dens, 27

Dental arches, 287

Dentate gyre, 427

nucleus, 408
Diaphragm sella;, 361

urinogenitale, 176
Diarthroses, 109
Digastric fossa, 66
Digestive system, 282
Dorsum sellae, 4S
Ductless glands, 338
Ductus endolymphaticus, 355
Duodenum, 302
Dura mater, 361

Ear, external, 350

internal, 353

middle, 350
Ejaculatory duct, 327
Enarthrodial joints, 109
Encephalon, 370
Endolymph, 354
Ependyma, 415
Epididymis, 325
Epigastrium, 295
Epiglottic cartilage, 274
Epiglottis, 274
Epiphyseal line, 21
Epiphysis, 27, 385
Epithalamus, 386
Epitympanic recess, 352
Eruption of teeth, 2S5
Esophagus, 293
External auditory canal, 350
meatus, 350

genitalia, 334
Eyeball, 341
Eyelids, 347

Face, 71
Facial bones, 60
Falx cerebelli, 361

cerebri, 361
Fasciculus, or fasciculi, anterior pro-
prius, 367

anterolateral superficial, 367

cerebropontile, 401

cerebrospinal, 366, 36S

cervicolumbalis, 369

cuneatus, 369

gracilis, 368

interfascicularis, 369

lateralis proprius, 368

Fasciculus, or fasciculi, longitudinalis
medialis, 400, 40S

olivospinal, 367

posterior proprius, 369

posterolateralis, 369

pyramidal, 416

retroflexus, 3S6

rubrospinal, 36S

septomarginal, 369

solitarius, 400

spinocerebellar, 367, 368

spinotectal, 36S

spinothalamic, 367, 368

striatothalamic, 412

tectospinal, 366, 368, 400

vestibulospinal, 367
Fauces, 292

Female reproductive organs, 330
Femoral canal, 195

ring, 195
Fenestra cochlea;, 351

vestibularis, 351
Fibers, arcuate, external, 39S, 409
internal, 409, 410

association, 416

commissural, 4r6

corticostriate, 413

corticothalamic, 413

projection, 415

thalamocortical, 4r2
Fibrocartilage, 109
Filiform papillae, 28S
Filtration angle, 346
Filum terminale, 363
Fimbria of uterine tube, 331
Fissure or fissures, calcarine, 388

central, 386

cingular, 3SS

circular, 386

collateral, 388

frontal, 3S8 »

hippocampal, 3S8

lateral, 3S6

longitudinal, 386

occipital, 3SS

of cerebellum, 3S3

of cerebrum, 386

of liver, 311

of lung, 280

of oblongata, 375

of spinal cord, 364

orbital, 51, 6S, 388

palpebral, 347

parietal, 388

portal, 311

48 1

Fissure or fissures, sphenoidal, 5 i . 68

sylvian, 386

temporal, 388
Flexures, cervical, 35

lumbar, 35

of colon, 300

of rectum, 307

of sacrum, 35

of vertebral column, 34

thoracic, 35
Folds, peritoneal, 296
Fontanelles, 70
Foot, arteries of, 139

bones of, 103

muscles of, 207
Foramen or foramina, alveolaria, 61

cecum, 43, 287

condyloid, 70

epiploic, 296

incisive, 62

infraorbital, 61

interventricular, 413

intervertebral, 34

jugular, 71

lacerum, 70, 71

magnum, 48, 70

mastoid, 70

mental, 65

obturator, 93

of Luschka, 414

of Magendie, 379, 414

optic, 68

ovale, 70

rotundum, 71

spinosum, 70

stylomastoid, 70

supraorbital, 42

vena cava?, 168

vertebral, 25

Winslowi, 296
Formatio reticularis, 398
Fornix, 390, 429
Fossa, or fossx, anterior, 71

canine, 60

condyloid, 47

coronoid, 80

cranial, 71

digastric, 66

digital, 323

for gall-bladder, 311

glenoid, 76

iliac, 96

incisor, 6o, 63

infraspinous, 74

infratemporal, 69, 70
3i

Fossa or fossa?, interpeduncular, 379

ischiorectal, 174

jugular, 55

lacrimal, 43, 68

middle, 71

nasal, 99, 271

orbital, 38, 341

ovarian, 330

popliteal, 239

pterygoid, 51, 70

pterygopalatine. 51, 70

radial, 80

scaphoid, 70

submaxillary, 66

supraspinous, 74

supratonsillar, 292

temporal, 69

trochanteric, 94
Fourchette, 335
Fourth ventricle, 378, 414
Fovea centralis, 345
Frenulum linguae, 288

labii, 284

preputii, 329
Frontal tuberosity, 42
Fundus of stomach, 301

of uterus, 332
Fungiform papillae, 288

Galea aponeurotica, r46

Gall ducts, 314

Gall-bladder, 313

Ganglion or ganglia, aorticorenal, 471

basal, 410

cardiac, 470

celiac, 470

cervical, 467

ciliary, 444

coccygeal, 470

cochlear, 438

Gasserian, 443

geniculate, 441

habenulx', 386, 429

interpedunculare 386

jugular, 438

lumbar, 469

nodosum, 438

of Corti, 438

otic, 446

petrous, 438

sacral, 469

semilunar, 443

sphenopalatine, 445

spinal, 449

submaxillary, 446

48 2 in

Ganglion or ganglia, sympathetic, 466,
467 _

thoracic, 469

vestibular, 438
Ganglionated cord, 400
Geniculate bodies, 379, 384

ganglion, 441
Genu of corpus callosum, 390

of facial nerve, 441

of internal capsule, 412
Giacomini, 427, 428
Gingiva;, 284
Ginglymus, 109
Girdle, pectoral, 73

pelvic, 89
Glabella, 42
Glans clitoris, 336

penis, 329
Globus pallidus, 44
Glomus caroticum, 340
Glossopalatal arch, 292
Glottis, 276
Goll, tract of, 36S
Gowers' tract, 367
Gracilis, funiculus, 368

nucleus, 397
Gums, 2S4
Gustatory, 392

Habenula, ganglion of, 386
Hair cells, auditory, 356
Hard palate, 284
Haversian canals, 19

systems, 19
Heart, 215

outline of, 222
Helicotrcma, 354
Helix, 350
Hemispheres, cerebellar, 381

cerebral, 386
Hilus of kidney, 317

of lungs, 278

of nucleus dentatus, 408
olivarius, 400

of spleen, 269

suprarenal gland, 339
Hip joint, 131
Hippocampal fissure, 3S8
Hippocampus, 391, 427, 429
Humor, aqueous, 346

vitreous, 346
Hyalin cartilage, 109
Hymen, 335
IIvpoi hondrium, 295
Hypogastrium, 295

Hypophysis, 383
Hypothalamus, 3S4

Ileocecal valve, 305
Ileopectineal eminence, 92

line, 92
Ileum, 304
Iliac crest, 90

spines, 90
Impression, cardiac, 309

colic, 310

gastric, 269

hepatic, 269

renal, 310

splenic, 269
Incisura angularis, 301

cardiaca, 278
Indusium, 427
Inframammary region, 213
Inguinal canal, 173

ligament, 170

ring, 170
Insula, 388

Intercondylic fossa, 96
Intercostal aponeuroses, 166, 167
Internal capsule, 411
Interosseous membrane, 124, 137
Interpleural space, 213
Interscapular region, 313
Intertubercular plane, 294
Interventricular foramen, 413

grooves, 217
Intervertebral cartilages, in
Intestine, large, 305

small, 302
Intumescentia cervicalis, 362

lumbalis, 362
Ins. 345

Island of Reil, 3S8
Isthmus of fauces, 292

of pharynx, 292

of uterine tube, 331
Iter, 3S1

Jaw, mandible, 65

maxilla, 60
Jejunum, 305
Joints, 108
Jugular foramen, 7c

process, 47

Kidneys, 316
Kronlein's methods, 392

Labia majora, 335
minora, 335

Labia oris, 2S2
Labrum glenoidale, 122
Labyrinth ethmoidal, 57
membranous, 354
osseous, 353
Lacrimal apparatus, 348
duct, 340
fossa, 42, 68
gland, ,us
Lamina terminalis, 384
Larynx, 272

interior of, 274
Lateral or transverse sinus, 432
of fourth ventricle, 414
of pharynx, 292
ventricles, 391, 413
Lemniscus, lateral, 403

medial, 307, 308, 406, 4rg
Lens, crystalline, 346, 423
Lenticular nucleus, 411
Ligaments, 109

peritoneal folds, 296
Line or lines, aspera, 95
intertubercular, 294
lateral sternal, 211
midaxillary, 211
midclavicular, 211
midsternal, 211
midvertebral, 211
mylohyoid, 66
of abdomen, 294
of thorax, 211
parasternal, 21 r
Poupart, 294
scapular, 211
subcostal, 294
transpyloric, 294
Lips, 283

Lobe or lobes, caudate, 311
central, 388
cerebellar, 3S1, 382
cerebral, 388
frontal, 388
oi cipital, 3S8
of liver, 311
of lungs, 279
olfactory, 38S
parietal, 388
temporal, 388
Locus cceruleus, 378
Lumbar plexus, 458

regions, 295
Lungs, 277

outline of, 281
Lymph, 253

Lymph nodes, 253
aortic, 261

axillary, 257

cervii al, 256

fai ial, 255

gastric, 263

hypogastric, 261

inguinal, 259

lingual, 250

lumbar, 261

mesenteric, 262, 264

occipital, 234

of abdomen, 260

of head and neck, 254

of liver, 264

of lower extremity, 259

of neck, 256

of thorax, 265

of upper extremity, 257

parotid, 254

popliteal, 259

subclavian, 259

submaxillary, 256

suprapancreatic, 262

tracheobronchial, 267
trunks, 254
vascular system, 252

Macula acustica, 355

lutea, 343
Malleolus, 100, 102
Mammary gland, 366
Mammillary bodies, 383, 428
Marrow, 20
Marshall, fold of, 221
Mastoid cells, 352
Maxillary sinus, 61
Meatus, acoustic, 350

of nose, inferior, 271
middle, 271
superior, 271
Median longitudinal bundle, 400,
Mediastinum, 213
Membrana tympani, 352
Membranes of brain, 361

of Reissner, 356
Membranous labyrinth, 354
Meninges, .i'11
Mesem ephalon, 378
Mesentery, 296
Metathalamus, 384
Midbrain. 378
Middle ear, 351

Mitral valve, 220
Moderator band, 218

484

Modiolus, 354
Mons veneris. 335
Motor area, 3gi

decussation, 305

pathway, direct, 416
indirect, 418
Mouth, 282
Muscles, 140

movements of, 145

of abdomen, 169

of arm, 181

of back, 160

of buttock, iog

of cervical region, 153, 159

of ear, 146, 352

of eyeball, 341, 149

of foot, 207

of forearm and hand, 1S3
dorsal, 190
ventral, 184

of infrahyoid region, 154

of larynx, 276

of leg, dorsal, 205
lateral, 205
ventral, 203

of little finger, 189

of mastication, I5r

of nasal region, 148
of neck, 153, 159

of oral region, 148

of orbital region, 149, 341

of pectoral region, 177

of pelvis, 174

of perineum, 1 74

of pharynx and palate, 157

of scalp, 146

of shoulder region, 179

of suprahyoid region, 165

of thigh, dorsal, 201
medial, 197
ventral, 195 •

of thorax, 166

of thumb, 188

of tongue, 156, 288

structure of, 143

tissue, 143
Myocardium, 220
Myology, 143

Nasal aperture, 271

cavity, 271

fossa, 271
Nasal cavity, 271
Nasolacrimal duct, 349
Nerve or nerves, abducens, 442

Nerve or nerves, accessory, 435
acustic, 439
alveolar, 445, 446
anococcygeal, 465
ansa hypoglossi, 453
auricular, 452
auriculotemporal, 446
axillary, 456
cardiac, 468, 438
cerebral, 433
cervical, 450
chorda tympani, 441
circumflex, 456
coccygeal, 45 r
cochlear, 439
common peroneal, 464
deep peroneal, 465
descendens hypoglossi, 453
digital of foot, 463

of hand, 435
encephalic, 433
facial, 441
femoral, 461
frontal, 444
genitofemoral, 466
glossopharyngeal, 436
gluteal, 465
hypoglossal, 434
iliohypogastric, 459
ilioinguinal, 459
inferior maxillary, 445
infraorbital, 445
intercostobrachial, 453
intermedius, 441
laryngeal, internal, 438

external, 438

recurrent, 438

superior, 438
lingual, 446
lumbar, 451
mandibular, 445
masticatory, 446
maxillary, 445
mental, 446
musculocutaneous, 434
musculospiral, 456
nasociliary, 444
nasopalatine, 445
obturator, 460
occipital, 450
oculomotor, 447
olfactory, 449
ophthalmic,' 444
optic, 447
palatine, 445

Nerve or nerves, perineal, 465, 466
peroneal common, 41. 4

deep, 465

superficial, 465
petrosal, 441
pharyngeal, 438
phrenic, 453
plantar, 463
popliteal external, 464

internal, 463
pudendal, 465
pulmonary, 470
radial, 456
sacral, 451
saphenous, 451
scapular, 454
sciatic, 461
spinal, 449

dorsal rami of, 450

ganglion of, 440

ventral rami of, 451
splanchnic, 469
superficial peroneal, 465
superior maxillary, 445
supraorbital, 444
sural, 464
sympathetic, 466
thoracic, 450
thoracodorsal, 437
tibial, 463, 465

recurrent, 464
trigeminal, 443
trochlear, 446
ulnar, 456
vagal, 436
vestibular, 439
zygomatic, 445
zygomaticofacial, 445
zygomaticotemporal, 445
Nerve cells, 35S
fibers, 359
system, 358

peripheral, 433
Neurilemma, 359
Neuroglia, 359
Neuron, 358
Nipple, 337

Nucleus or nuclei, ambiguus, 400
amygdala-, 411
caudate, 411
cochlear, 439
cuneus, 397
dentate, 408
dorsalis, 465
emboliform, 408

Nucleus or nuclei, fastigii, 408

globosus, 408

gracilis, 397

hypoglossal, 434

insertus, 402

intercallatus, 402

laryngeal (nidus), 433

lateral of thalamus, 431

lenticular, 411

medial of thalamus, 413

of abducens nerve, 402

of accessory nerve, 440

of Bechterevv, 440

of Clarke, 365

of Deiter, 440

of facial nerve, 403, 439

of funiculus solitarius, 400

of glossopharyngeal nerve, 436

of lateral lemniscus, 405

of median longitudinal bundle, 408

of mesencephalon, 408

of oculomotor nerve, 406, 447

of tegmentum, 406

of thalamus, 413

of tractus solitarius, 400

of trapezoid body, 403

of trigeminal nerve, 443

olivary, 400

pontis, 400

red, 406

thoracalis, 365

trochlear, 406, 446

vagal, 436, 437

vestibular, 402, 439
Nymphse, 335

Oblongata, 374, 395
Olecranon, 80
Olfactory area, 392

bulb, 389, 426

lobe, 389

mucosa, 271

stria.', 426, 429

tract, 389, 426
Olivary nucleus, 400
Olive, 375, 400
Omental bursa, 297

tuberosity, 310
Omentum, 296
Opercula insula?, 388
Optic axis, 343

chiasm, 383, 448

commissure, 44S

foramen, 68

nerve, 340, 448

486

Optic radiation, 448

thalami, 385

tract. 448
Ora serrata, 345
Oral cavity, 284
Orbit, 68, 341
Organ of Corti, 356
Ossicles, auditory, 352
Ossification of bone, 21
Otic ganglion, 446
Ovary, 330
Oviduct, 331

Palatal aponeurosis, 285
Palate, 284
Palpebral, 347
Pampiniform plexus, 325
Pancreas, 314
Papillae, lingual, 287
Parametrium, 3^3
Parasympathetics, 340
Paratliyreoid bodies, 338
Parotid gland, 289
Pathway, auditory, 423
gustatory, 421

motor, direct, 416
indirect, 418

muscle sense, 424

olfactory, 426

optic, 420

reflex, 419

respiration, 425

sensor, 419

touch and pressure, 424
Peduncles of cerebellum, 383, 408

of cerebrum, 370, 405
Pelvic cavity, 294
Pelvis, 93
Penis, 328

Perforated substance, 427
Pericardium, 221
Perichondrium, 109
Perilymph, 354
Perimysium, 143
Perineurium, 360
Periosteum, 18
Peritoneal cavity, 296
Peritoneum, 296
Perivascular lymph spaces, 252
Permanent teeth, 285
Pharynx, 290
Philtrum, 283
Pia, 362

Pillars of fornix, 390
Pineal body, 3S5

Plantar arch, 241
Pleura1, 279
Pleural cavity, 279

outline, 279
Plexus or plexuses, aortic, 471

brachial, 453

cardiac, 470

carotid, 470

cavernous, 470

celiac, 470

cervical, 451

choroidal, 385

coronary, 471

esophageal, 470

hemorrhoidal, 473

hepatic, 471

hypogastric, 472

lumbar, 458

mesenteric, 471

ovarian. 471

pampiniform, 325

pelvic, 473

pharyngeal, 438

phrenic, 471, 472

prostatic, 473

pudendal, 465

pulmonary, 470

renal, 471

sacral, 470

sigmoid, 472

splenic, 471

suprarenal, 471

uterine, 473

vaginal, 473

vesical, 473
Plica or plicae, circulares, 302

fimbriata, 288

glossocpiglottic, 2S8

palmate, 322

salpingopalatal, 292

salpingopharyngeal, 292

sublingual, 2S5

umbilical, 322

ureteric, 322

ventricularis, 275

vocalis, 275
Pons (varolii), 377, 400
Portal circulation, 25 j
Posterior chamber, 346

commissure, 335
Prepuce, 329
Pudendum, 334
Pulmonary circulation, 224
Pulvinar, 384
Puncta lacrimalia, 348

487

Puncta maxima, 222
Pupil, 345
Putamen, 41 1
Pyloric antrum. 301
I\ lorus, 300
Pyramidal colls, 416
Pyramids, 375, 395, 401
Pyriform aperture, 60

QUADRIGEMINAL bodies, 380, 405

Radiation, auditory, 412

of corpus striatum, 412

optic. 448
Rami communicantes, gray, 466

white, 467
Raphe of oblongata, 398

of palate. 284

of pons, 402

of scrotum, 384
Recess, epitympanic, 351

lateral of fourth ventricle, 414

of infundibulum, 413

of pharynx, 292

optic. 413

pineal, 413
Rectal ampulla, 307

valves, 307
Rectum, 307
Red marrow, 20

Refracting media of the eyeball, 346
Regions of abdomen, 294

of thorax, 21 2
Respiratory system, 271
Restiform body, 377, 408
Retina, 345
Ring, inguinal, 170

Saccule, 354
Sclera, 344
Scrotum, 324
Sella turcica, 48
Semicircular canais, bony, 353

membranous, 355
Semilunar ganglion, 443
Seminal vesicles, 326
Sensor area of brain, 391

decussation, 397

pathway, 419
Septomarginal tract, 369
Septum lucidum, 391, 428
Sigmoid colon, 307

mesocolon, 307
Sinus cavernosus, 432

circular, 432

Sinus coronary, 218

frontal, 71

great oblique, 221
transverse, 221

intercavernous, 432

lateral, 432

longitudinal, 432

maxillary, 61

of cranium, 432

of dura, 432

petrosal, inferior, 432
superior, 432

phrenicocostal, 270

rectal, 308

sagittal, inferior, 432
superior, 432

sphenoidal, 71

sphenoparietal, 432

squamopetrosal, 432

straight, 432

transverse, 432
Skeleton, appendicular, 17

axial, 17
Skull, 41

as a whole, 67
Sounds of the heart, 222
Space, axillary, 232

interpleural, 213

mediastinal, 213

subarachnoid, 362

subdural, 362
Spaces, lymph, 232

of Fontana, 347
Spermatic cord, 325
Spinal canal, 415

cord, 362

ganglia, 449

nerves, 449
Splanchnic nerves, 469
Spleen, 268

Splenium of corpus callosum, 416
Spongy bone, 19
Sternal angle, 35
Stomach, 300

bed, 300

chamber, 300
Stria? mcdulares, 378, 423
Subarachnoid space, 362
Subcostal angle, 41
Subdural space, 362
Sublingual gland, 290
Submaxillary ganglion, 446

gland, ?qo
Substantia ferruginea, 378

gelatinosa, 366, 397

Substantia nigra, 405

Sulci. See Fissures.

Suprarenal gland, 339

Supratonsillar fossa, 292

Sutures, 108

Sympathetic nerve system, 466

Symphysis of mandible, 65

pubis, 93
Synarthrosis, 108
Synchondrosis, 108
Syndesmology, 10S
Synovial bursae, 1 1 1

membrane, 1 1 1
Systemic circulation, 250

Tarsus, 103
Taste buds, 287
Teeth, 285

Tegmentum of pons, 377, 406
Tela choroidea, 400
Temporal fossa, 69
Temporopontile tract, 412
Tentorium cerebelli, 361
Testes, 324

Thalamocortical fibers. 412
Thalamostriate fibers, 412
Thalamus, 385, 412
Thebesius, foramina of, 218
Third ventricle, 413
Thoracic duct, 252
Thorax. 42

boundaries of, 42

lines of. 211
Thymus gland, 270
Thyreoid cartilage, 273

gland, 338
Tongue, 287
Tonsil, lingual, 288

palatal, 292

pharyngeal, 292
Trachea, 276
Tract. See Fasciculus.

olfactory, 389, 426

optic, 418
Tragus, 350
Transpyloric line, 295
Trapezium, 403
Trigonum habenuhe, 386

hypoglossi, 378

olfactory, 426

vagi, 378

vesicae, 322
Trochanter, 94

Trunks of brachial plexus, 453
Tube, auditory, 353

Tube, uterine, 331
Tuber cinereum. 383

omentale, 310
Tunnel of Corti, 356
Tympanic antrum, 352

atrium, 351

attic, 351

cavity, 351

membrane, 352

ossicles, 352
Tympanum, 352

Umbo membranae, 352
Uncus, 427
Urachus, 322
Ureter, 319
Urethra, crest of, 323

female, 323

male, 323
Urinary bladder, 319
Uterine tube, 331
Uterus, 332
Utricle, 354
Uvula cerebelli, 383

palatina, 285

vesicae, 322

Vagina, 334
Vallate papillce, 288
Vallecula, 228
Valves aortic, 229

bicuspid, 220

colic, 305

pulmonary, 224

pyloric, 302

rectal, 307

sinus coronarii, 218

tricuspid, 217
Valvula, 404
Vas deferens, 326
Vascular system, 211
Vein, or veins, azygos, 249

cardiac, 221

cava, inferior, 247
superior, 245

internal jugular, 242

of abdomen, 247

of brain, 431

of extremities, lower, 245
upper, 24.5

of head, 243

of spinal cord, 432

portal, 251

pulmonary, '248
Velum interpositum, 385

489

Ventrii les, cerebral, 413

fourth, 378, 413

lateral, 391, 413

of heart, 218, 220

of larynx, 275

third, 3S6, 413
Vertebra, 24

cervical, 25

coccygeal, 33

lumbar, 29

prominens, 28

sacral, 31

thoracic, 28

Vertebral column, 24

as a whole. 34

curves of, 34

Vestibular ganglion, j (8

Vestibule, aortic, 220

bulb of, 335

Vestibule, of labyrinth, 353

of larynx, 275

of mouth, 283

of nose, 271

of vagina, 335
Vibrissas, 271
Villi arachnoideale, 362

of intestine, 304
Visual area, 392

axis, 343
Vitreous body, 346
Vocal cords, 275
Vulva, 334

Willis, circle of, 430

Womb, 332
Wrist, 85

Xyphoid process, 36

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Norris'
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Coolidg'e on Nose and Throat

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This new book furnishes the student and practitioner a guide and ready reference to the
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DISEASES OF THE EYE,

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Bass and Johns' Alveolodental Pyorrhea

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of 168 pages, illustrated. Cloth, $2.50 net.

Drs. Bass and Johns present their subject from the viewpoint of infection by
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Theobald's Prevalent Eye Diseases

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Cluneal Professor of Ophthalmology, Woman's Medical College of Pennsylvania.

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DISEASES OF THE EYE.

Haab and DeSchweinitz's
External Diseases qf the Eye

Atlas and Epitome of External Diseases of the Eye. By Dr. O.

Haab, of Zurich. Edited, with additions, by G. E. DeSchweinitz,
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IOI colored illustrations on 46 lithographic plates and 244 pages of
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The Medical Record, New York

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Haab and DeSchweinitz V
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Atlas and Epitome of Ophthalmoscopy and Ophthalmoscopic
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of Pennsylvania. With 152 colored lithographic illustrations and 92
pages of text. Cloth, S3.00 net. In Saunders' Hand-Atlas Series.
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The Lancet, London

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Kyle's
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URINE AND IMPOTENCE.

Og'den on the Urine

Clinical Examination of Urine and Urinary Diagnosis. A Clinical
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Haab and deSchweinitz's
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Atlas and Epitome of Operative Ophthalmology. By Dr. C

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GENITO-URINARY AND NOSE, THROAT, ETC. u

Greene and Brooks'
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Diseases of the Genito-Urinary Organs and the Kidney. By

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Gleason on Nose, Throat,
and Car

A Manual of Diseases of the Nose, Throat, and Ear. By E.

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Ivy's Applied Anatomy and

Oral Surgery for Dental Students

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FOR DENTAL STUDENTS

This work is just what dental students have long wanted — a concise, practical
work on applied anatomy and oral surgery, written with their needs solely in
mind. No one could be better fitted for this task than Dr. Ivy, who is a graduate
in both dentistry and medicine. Having gone through the dental school, he
knows precisely the dental student's needs and just how to meet them. His
medical training assures you that his anatomy is accurate and his technic modern.
The text is well illustrated with pictures that you will find extremely helpful.

H. P. Kuhn, M.D., Western Dental College, Kansas City.

" I am delighted with this compact little treatise. It seems to me just to fill the bill."

CHEMISTRY, SKIN, AXD VENEREAL DISEASES. IJ

American Pocket Dictionary New 9th i Edition

The American Pocket Medical Dictionary. Edited by W. A.
Newman Dorland, M. D., Editor "American Illustrated Medical
Dictionary." Containing the pronunciation and definition of the
principal words used in medicine and kindred sciences. 693 pages.
Flexible leather, with gold edges, $1.25 net; with thumb index,
$1.50 net.

James W. Holland. M. D.,
■ Professor of Medical Chemistry and Toxicology, and Dean, Jefferson Medical College

Philadelphia,
" I am struck at once with admiration at the compact size and attractive exteripr. )
rtmend it to our students without reserve."

Stelwagon's Essentials of Skin 7th Edition

Essentials of Diseases of the Skin. By Henry W. Stel-
WAGON, M. D., Ph.D., Professor of Dermatology in the Jeffer-
son Medical College, Philadelphia. Post-octavo of 291 pages,
with 72 text-illustrations and 8 plates. Cloth, $1.25 net. In
Saunders' Question- Compend Series.

The Medical News

" In line with our present knowledge of diseases of the skin. . . . Continues to main-
tain the high standard of excellence for which these question compends have been noted."

Wolffs Medical Chemistry seventh Edition

Essentials of Medical Chemistry, Organic and Inorganic.
Containing also Questions on Medical Physics, Chemical Physiol-
ogy, Analytical Processes, Urinalysis, and Toxicology. By Law-
rence Wolff, M. D., Late Demonstrator of Chemistry, Jefferson
Medical College. Revised by A. Ferree Wit.mer, Ph. G., M. D.,
Formerly Assistant Demonstrator of Physiology, University of
Pennsylvania. Post-octavo of 222 pages. Cloth, §1.25 net. In
Saunders' Question-Compeud Series.

Vecki's Sexual Impotence New sth Edition

Sexual Impotence. By Victor G. Vecki, M. D., Consulting
Genito-Urinary Surgeon to Mt. Zion Hospital, San Francisco.
i2mo of 405 pages. Cloth, $2.25 net.

Johns Hopkins Hospital Bulletin

"A scientific treatise upon an important and much neglected subject. ... The
treatment of impotence in general and of sexual neurasthenia is discriminating and
judicious."

Wilcox on Genito-Urinary and Venereal Diseases

Second Edition

Essentials of Genito-Urinary and Venereal Diseases. By
Starling S. Wilcox, M. D., Lecturer on Genito-Urinary Diseases
and Syphilology, Starling-Ohio Medical College, Columbus. 121110
of 321 pages, illustrated. Cloth, $1.25 net. Saunders' Compends.

SA UN VERS' BOOKS ON

Second
Edition

Wells' Chemical Pathology

Chemical Pathology. Being a discussion o< General Path-
ology from the Standpoint of the Chemical Processes Involved.
By H. Gideon Wells, Ph. D., M. D., Assistant Professor of
Pathology in the University of Chicago. Octavo of 616 pages.
Cloth, $3.25 net.

Wm. H. Welch, M. D.. Professor of Pathology, Johns Hopkins University.

"The work fills a real need in Ihe English literature of a very important subject, and
I shall be glad to recommend it to my students."

Fourth
Revised Edition

Jackson's Essentials of Eye

Essentials of Refraction and of Diseases of the Eye. By

Edward Jackson, A. M., M. D., Emeritus Professor of Diseases of
the Eye, Philadelphia Polyclinic. Post-octavo of 261 pages, 82 illus-
trations. Cloth, $1.25 net. In Saunders' Question-Corn pend Series.

Johns Hopkins Hospital Bulletin

" The entire ground is covered, and the points that most need careful elucidation are.
made clear and easy."

Gleason's Nose and Throat Fourth SSS

Essentials of Diseases of the Nose and Throat. By E. B.

Gleason, S. B., M. D., Clinical Professor of Otology, Medico-
Chirurgical College ; Graduate School of Medicine, University of
Pennsylvania. Post-octavo, 241 pages, 1 12 illustrations. Cloth.
$1.25 net. /;/ Saunders' Question Compends.

The Lancet, London

" The careful description which is given of the various procedures would be sufficient
to enable most people of average intelligence and of slight anatomical knowledge to make
a very good attempt at laryngoscopy."

Grunwald and Grayson on the Larynx

Atlas and Epitome of Diseases of the Larynx. By Dr. L.

Grunwald, of Munich. Edited, with additions, by Charles P.
Grayson, M.D., University of Pennsylvania. With 107 colored
figures on 44 plates, 25 text-cuts, and 103 pages of text. Cloth,
$2.50 net. In Saunders' Hand-Atlas Series.

Second
Edition

Mracek and Stelwagon's Atlas of Skin

Atlas and Epitome of Diseases of the Skin. By Prof. Dr.
Franz Mracek, of Vienna. Edited, with additions, by Henry
W. Stelwagon, M.D., Jefferson Medical College. With 77 col-
ored plates, 50 half-tone illustrations, and 280 pages of text. In
Saunders' Hand-Atlas Series. Cloth, $4 .00 net.

EYE, EAR, NOSE, AND THROAT.

deSchweinitz and Holloway on Pulsating Exoph-
thalmos

Pulsating Exophthalmos. An analysis of sixty-nine cases not pre-
viously analyzed. By George E. deSchweinitz, M. D., and Thomas
B. Holloway, M. D. Octavo of 125 pages. Cloth, $2.00 net.

This monograph consists of an analysis of sixty-nine cases of this affection
not previously analyzed. The therapeutic measures, surgical and otherwise,
which have been employed are compared, and an endeavor has been made
to determine from these analyses which procedures seem likely to prove of
the greatest value. It is the most valuable contribution to ophthalmic liter-
ature within recent years.

British Medical Journal

ith the whole subject and in it the most complete account of

Jackson on the Eye Preparin(, New (3d) Edition

A Manual of the Diagnosis and Treatment of Diseases of the
Eye. By Edward Jackson, A. M., M. D., Professor of Ophthalmology,
University of Colorado. i2mo volume of 615 pages, with 1S4 beautiful
illustrations.

The Medical Record, New York

" It is truly an admirable work. . . . Written in a clear, concise manner, it bears evidence of the
author's comprehensive grasp of the subject. The term ' multum in parvo' is an appropriate one to
apply to this work."

Grant on Face, Mouth, and Jaws

A Text-Book of the Surgical Principles and Surgical Diseases
of the Face, Mouth, and Jaws. For Dental Students. By H. Horace
Grant, A. M., M. 1)., Professor of Surgery and of Clinical Surgery,
Hospital College of Medicine, Louisville. Octavo of 231 pages, with
6S illustrations. Cloth, $2.50 net.

Preiswerk and Warren's Dentistry

Atlas and Epitome of Dentistry. By Prof. G. Preiswerk, of
Basil. Edited, with additions, by George W. Warren, D.D.S., Pro-
fessor of Operative Dentistry, Pennsylvania College of Dental Surgery,
Philadelphia. With 44 lithographic plates, 152 text-cuts, and 343 page3
of text. Cloth. $3. 50 net. In Saunders* Atlas Series,

Asher's Chemistry and Toxicology

Chemistry and Toxicology for Nurses. By l'mi ir Asher, Ph.G.,
M. D., Dean and Professor of Chemistry, New Orleans College of Phar-
macy. i2mo of 190 pages. Cloth, $1.25 net.

Date

Due

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7

DEC

MARS »

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946

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