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PRINCIPLES OF FUNCTIONAL
ANATOMY OF THE RABBIT

Principles

of Functional Anatomy of

the Rabbit

BY

EDWARD DRANE CRABB, Ph.D.

FORMERLY INSTRUCTOR IN MAMMALIAN AND COMPARATIVE ANATOMY IN THE
DEPARTMENT OF ZOOLOGY, UNIVERSITY OF PENNSYLVANIA

WITH THIRTY-THREE ILLUSTRATIONS

PHILADELPHIA

P. BLAKISTON'S SON & CO., Inc.

IOI2 WALNUT STREET
i

Copyright, 1931, by P. Blakiston's Son & Co., Inc.

PRINTED IN U. S. A.
BY THE MAPLE PRESS COMPANY, YORK, PA.

PREFACE

This elementary work on dissection of the rabbit was pre-
pared to meet the needs of laboratory courses in mammahan
anatomy designed for students who wish to obtain a background
for advanced human physiology, for those majoring in physical
education and for premedical and other students who wish to
learn the technique of mammalian dissection and the basic
principles of descriptive and functional anatomy. An effort
has been made to keep the subject matter down to such a point
that the entire outline may be covered in one hundred, or less,
laboratory hours.

In teaching mammalian anatomy the writer finds that the
most nearly ideal method is that employed by Professor J.
Percy Moore, in the University of Pennsylvania who discourages
the student from committing the descriptions to memory,
with the idea of reciting them by rote, and stimulates him to
learn anatomy from the functional, rather than the purely
descriptive point of view. The student is required to be able
to demonstrate on his specimen and explain the relations and
functions of structures at any time the laboratory instructor
may make such requests and at written examinations.

The method of using the consecutive numbers of muscles,
arteries, and nerves in the descriptions and cross references
is an elaboration of a similar system employed in mimeographed
outlines for dissecting the cat, at the University of Pennsylvania.

The books which have been consulted to any considerable
extent during the preparation of this work are: Addison,
W. H. F. 1927, Piersol's Normal Histology, 13 ed. J. B. Lippin-
cott Co. ; Bensley, B. A. 1926, Practical Anatomy of the Rabbit,
4 ed. P. Blakiston's Son & Co. Inc.; Hyman, L. H. 1922, A
Laboratory Manual for Comparative Vertebrate Anatomy,

VI PREFACE

The University of Chicago Press; Lewis, W. H. 1924, Gray's
Anatomy of the Human Body, 21 ed. Lea & Febiger; Martin,

E. G. 1928, The Human Body, 11 ed. Henry Holt and Company;
Metheny, D. G. 19 15, Potter's Compend of Human Anatomy,
8 ed., P. Blakiston's Son & Co. Inc.; Mivart, St. G. 1895, The
Cat, Charles Scribner's Sons; Pratt, H. S. 1925, A Course in
Vertebrate Zoology, pp. 272-328, Ginn and Company;
Reighard, J. and H. S. Jennings, 1901, Anatomy of the Cat,
2 ed. Henry Holt and Company; Scott, R. J. E. 1928, Gould's
Medical Dictionary, 2 ed., P. Blakiston's Son & Co. Inc.;
Spalteholtz, W., 5 ed. EngUsh, J. B. Lippincott Co.; Stromsten,

F. A. 1923, Davison's Mammalian Anatomy, 4 ed., P. Blakis-
ton's Son and Co. Inc., and Sutton, H. A. and C. K. Drinker,
1910, Osteology and Syndesmology, P. Blakiston's Son and Co.
Inc.

The drawings in this manual and the material from which
they were drawn were prepared in the Biology Laboratory of
the University of Colorado.

The writer takes pleasure in acknowledging his indebtedness
to Hugo G. Rodeck, Instructor in Biology, University of
Colorado, for figures 30, 32, and t,^; to Miss Eleanor A. Kinney
for drawing figures 1-9 and 12-18 and for typing the preHm-
inary and final drafts of the manuscript ;■ to Thurman M.
Rogers for figures 10 and 12; and to Wm. C. Denson for figure

31-

Edward Drane Crabb.

CONTENTS

Page

L.\BORATORY EQUIPMENT AND MATERIALS I

Chapter

I. The Elementary Tissues 5

A. Connective tissue 6

B. Epithelial tissue 8

C. Muscular tissue 9

D. Nervous tissue 12

E. Fluid tissue 13

II. The Skeleton 14

A. The skeleton as a whole 15

B. Development and classification of bones 18

C. Relations and topography of some of the bones 19

a. Skull 19

b. Vertebral column 23

c. Ribs and sternum 26

d. Pectoral girdle and superior limb . . ' 28

e. Pelvic girdle and inferior limb 31

III. Articulations 36

A. Synarthroses 36

B. Amphiarthroses 2>1

C. Diarthroses 2>1

IV. Work Preliminary to Dissection 38

A. External characters of the rabbit 38

B. General description of the body 38

C. Topographical terms used 39

D. Myological terms 41

E. Namds of muscles 42

F. Skinning the rabbit 42

G. Subcutaneous muscles 43

H. Preparing the skinned surface for dissection of muscles 44

V. Muscles of the Right Superior Limb 46

A. Muscles which attach the superior limb to the body 47

B. The four major functional groups 52

C. Muscles of the shoulder joint 53

D. Muscles which move the forearm 54

E. Muscles which move the hand 55

VI. Muscles of the Right Inferior Limb 60

A. Muscles of the thigh 61

vii

37159

VIU CONTENTS

Chapter Page

B. Muscles of the cms and foot 65

VII. Veins, Lymphatics, Arteries, and Nerves and Their Relations,

Left Superior Limb 70

A. Veins and lymphatics 73

B. Arteries of the left shoulder and arm 74

C. Nerves of the left superior limb 76

D. Arteries of the forearm and hand 79

VIII. Veins, Lymphatics, Arteries, and Nerves and Their Relations,

Left Inferior Limb 81

A. Veins and lymphatics 81

B. Arteries of the thigh 83

C. Nerves of the thigh, leg, and foot 85

D. Arteries of the leg and foot 86

IX. Muscles of Right Side of Trunk ant) Head; Salpv^ary, Thyroid,

AND Lymph Glan-ds and Vessels of the Head and Neck. ... 88

A. External muscles of the trunk 88

B. Muscles of the head 91

C. Glands of head and neck 92

D. Veins and arteries of head and neck 93

X. The Thorax and Its Contents 95

A. Thoracic viscera 96

B. Heart and great blood vessels 97

C. The venae cavae 100

XL The Abdomen and Its Contents 102

A. Abdominal aorta and principal branches 104

B. Postcava 107

C. Hepatic portal system 107

D. Digestive system iii

E. The Endocrine System 114

F. Urinogenital system, 115; psoas muscles 119

XII. The Nervous System 120

A. Cranial nerves, page, 121. Table of ' 121

B. Brain 125

Method of removing brain 126

C. Spinal cord and spinal nerves 127

Index 129

LIST OF ILLUSTRATIONS

Figure Page

1. Relative position of the various bones of the cranial half of the skeleton 15

2. Skull, caudolateral view 20

3. Right mandibular ramus, lateral view 22

4. Diagram of a typical vertebra, caudolateral view 23

5. A, fifth cervical vertebra, cranial view, and B, Axis, right lateral view 24

6. Fifth thoracic vertebra, right side 24

7. The sacrum and first caudal vertebra, ventral view, and last lumbar

vertebra, ventrolateral view 25

8. Sternum and costal ribs of left side, dorsal view 27

9. Proximal two-thirds of fourth right rib 27

10. Right scapula, A, lateral; and B, glenoid view = 29

11. Right humerus, caudal view 30

12. Right humerus, cranial view 30

13. Bones of right antibrachium, craniolateral view 30

14. Right innominate bone, slightly twisted to show structures 32

15. Femur, A, cranial; and B, caudal view ^^

16. Right tibio fibula, laterocranial view 34

17. Tarsals and metatarsals of right foot, dorsal view 34

18. Superficial muscles of shoulder and arm 47

19. Cross section proximal end of distal third of right arm 55

20. Cross section of proximal third of antibrachium and insertion of flexors

of digits 56

21. Cross section through proximal third of right thigh 62

22. Cross section through middle of proximal third of right leg 66

23. Left subclavian artery and principal branches 75

24. Principal nerves of left brachial plexus 77

25. Principal branches of the femoral artery 84

26. Principal branches of thoracic aorta 98

27. Principal veins of the precaval system, dorsal view loi

28. Principal branches of abdominal aorta 105

29. Principal branches of postcava, and relations of small saphenous and iliac

veins, ventral view 108

30. Disfribution of the hepatic portal vein, ventral view 109

31. Hepatic branches of hepatic and portal veins no

32. Brain of rabbit, dorsal view 120

33. Brain of rabbit, ventral view, to show relations of principal arteries and

origin of cranial nerves 122

ANATOMY OF THE RABBIT

LABORATORY EQUIPMENT AND MATERIALS

The student should provide himself with the following
equipment :

I scalpel, medium size, preferably with metal handle rounded
at the end for probing under muscles

I cartilage knife, with milled metal handle

I pair dissecting scissors, large, straight, four to six inches
long

I pair forceps, stout, straight, with milled points

I pair forceps, small, four to six inches long, with fine milled
points, curved or straight

I grooved director

1 seeker, or probe

2 dissecting needles, plain, straight, stiff
I small, fine carborundum stone

I or more cheap hand towels, or cloths, which may be dis-
carded when greasy or dirty.

The dissecting instruments must be of good quality and must
be kept sharp and in good order. The student may supply
himself with any additional equipment for dissection, especially
a small scalpel which will hold a very sharp edge and a pair of
small elbow or straight scissors, and may wear any sort of
dissecting apron, laboratory coat, or smock, with or without
cloth or rubber sleeve protectors. Most students prefer to roll
up the sleeves to being handicapped by bunglesome sleeve
protectors. Rubber gloves are almost useless. A good grease-
cutting soap, such as "lava soap," "klex," or "skat" is a boon
to those whose hands will bear such rough treatment.

2 ANATOMY OF THE RABBIT

One notebook, taking large loose leaf fillers (pages about
S}yi X II inches), ruled for notes and plain linen ledger for
sketches, will suffice for recitation and laboratory purposes.
The student should cultivate the habit of making hasty, though
essentially accurate, sketches of structural relations and of
writing terse, to-the-point notes, to help him visualize the
functional relations of structures. Long, tedious notes usually
benumb the brain while they are being written and are seldom
useful for reference because of the relatively great amount of
time required to read them.

Drawings or sketches should be made with the dorsal side of
the figure toward the top, or the bound edge if the figure is large,
of the page. The name of the figure should be placed under it,
as is done in books and published articles; and the labeling
should be written in full (abbreviations may be used judiciously)
on one or both sides of the figure and parallel to the name. Do
not use numbers, letters, or other symbols which require a list of
explanations. This admonition applies to both lecture and
laboratory work. The legend, or any other indirect method
of labehng is objectionable in the laboratory notebook where
there is ample space for direct labeling, for the following reasons :
(i) It increases the amount of time required to label the drawing
accurately. (2) It increases the percentage of errors in labeling.
(3) It inhibits ready reference to the finished drawings. (4) It
takes nearly twice as long to grade drawings labeled indirectly
as it does those labeled directly.

One injected rabbit (correctly speaking, a hare) will be
furnished each student, and all the dissection work will be done
on this one specimen. If the student mutilates his rabbit or
allows it to dessicate or mold, he will be obliged to purchase
another specimen with which to finish the course. In addition
to the expense of a new specimen a considerable amount of
additional work will also be incurred, for the area to be dissected
must be exposed before the parts are available for study. Then
too, the discarded material is no longer available for review for
practical laboratory examinations.

LABORATORY EQUIPMENT AND MATERIALS 3

The rabbits may be obtained, already prepared, from dealers,
either as ''wet preserved" or ''dry embalmed" material. The
"wet preserved" rabbits are skinned before being preserved
and should be kept in a preserving solution to prevent desiccat-
ing between laboratory periods. The only satisfactory way to
handle such material is to furnish each student with a covered
container of solution in which to keep his rabbit and a water-
tight tray in which to dissect it. The embalmed rabbits reach
the laboratory "dry" and unskinned; and if properly cared for,
they are much nicer to work with than the "wet" material.
The rabbits for the class may be kept in a nearly air-tight metal
box or rolled up in a tarpaulin, about six rabbits to each roll.
In either case the stored rabbits may require heavy sprinkling
with water which has been boiled to kill mold spores; or the
muslin cloths, with which each rabbit should be wrapped, may
be dipped in boiled water before the rabbit is wrapped up in it,
from time to time. A very satisfactory storage box, which will
hold twenty to twenty-four rabbits, can be made of galvanized
iron by any sheet metal worker. It should he ^6 X iS X iS
inches and have a tight-fitting lid. A layer of wet excelsior
in which the rabbits were packed for shipment should be spread
over the bottom of the box and covered with a piece of burlap
or other cloth to prevent the excelsior from getting into the
rabbit fur. After each rabbit has been tagged with the student's
name, wrapped in muslin and placed in the box, a large piece
of sackcloth and more of the wet excelsior may be placed on
top of them. Since the wetness of this excelsior is due to
embalming fluid, it is not conductive to growth of molds. The
rabbits thus packed may be sprinkled with boiled water once
each week, if necessary. If the directions on the care of
individual material (p. 43) are carefully followed and the hd
kept on the box, there will be little or no danger of the material
molding or dessicating during the entire term. However, the
instructor must watch the material closely for early signs of
dessication or mold.

4 ANATOMY OF THE RABBIT

A solution which will retard dessication of exposed surfaces
of the rabbit and relieve the tingUng sensation in the dissector's
fingers, due to phenol in the embalming fluid, is made as follows:

Water, preferably distilled 600 ml.

Gum tragacanth 35 gni-

Let soak about twelve hours in a half-gallon fruit jar, and then
add, stirring well,

Glycerin 400 ml.

Ethyl alcohol 500 ml.

Oil of cloves o . s ml.

Water, to fill the jar

This much stock solution will make about two gallons, when
diluted with water, and should last a class of fifteen students an
entire semester.

Directions for injecting the arteries and veins and for pre-
serving fresh laboratory material may be found in Stromsten's
book, pp. 9-16.

Bones may be cleaned for laboratory use by removing most of
the flesh and then boiling them in a solution of 150 grammes of
'' Gold Dust" washing powder in seven liters of water until the
flesh can be brushed off, as directed by Stromsten, p. 15. Fresh
material is best. However, good representative bones may be
salvaged from dissected material at the end of the semester.
Such bones require more cooking than those from fresh material .
Only old rabbits with well ossified bones should be selected for
skeletal material for general class use.

CHAPTER I
THE ELEMENTARY TISSUES

A brief introduction to the histology, or cellular architecture,
of mammalian tissues should aid the student to grasp functional
anatomy, for the cell is the unit of structure and of function.
Groups of cells of the same kind form a tissue ; two or more tissues
form an organ, or functional unit such as a muscle with its parts
and attachments; and the necessary organs form the organism.

There are five kinds of elementary (primary) tissues: Con-
nective, epithelial, muscular, nervous, and fluid or circulat-
ing tissues. The first four are often referred to as fixed tissues,
and some histologists do not accord the fluid tissues (blood and
lymph) the rank of an elementary tissue (chiefly because the
cell elements, the corpuscles, are independent of each other and
are suspended in a fluid medium) , but place them in the group
of connective tissues with which they develop from the mesen-
chyme of the mesoderm, which, as its name implies, is the
middle one of the three blastodermic layers of early embryonic
stages and which also gives rise to the muscles.

Prepared slides of mammaHan tissues belonging to the five
elementary groups will be furnished for this study. At this
time the instructor should explain briefly the process of fixing,
dehydrating, infiltrating, and cutting the tissues into sections
about S}JL (0.008 mm.) thick; how these thin sections are fastened
to the 1X3 inch glass slip, stained, dehydrated, and covered
with a very thin slip of glass, dried and made ready for class use.

In studying the cellular structure of tissues with the com-
pound microscope, the student should always locate the struc-
tures he wishes to study with the low power (16 mm.) objective
before turning the high power (4 mm.) objective onto the object
to study the finer structure. It is a good plan to be certain

S

6 ANATOMY OF THE RABBIT

that the low power objective is in position before: {a) A shde is
placed under the microscope, (b) a shde is taken from under the
microscope, and (c) the microscope is put away. In short,
always keep the low power in position when the high power is not
in actual use. Failure to observe this rule will result in broken
slides and possibly a scratched lens. Draw, or sketch, three or
more tangent cells of representative tissues of the first four
elementary groups. In drawing the cells, all three of them
should lie in the same focal plane, for the drawing is the student's
interpretation of the structure of the tissue he is studying;
therefore he should not attempt merely "to draw what he sees."
The instructor should give further directions when he supplies
the class with slides and posts the list of required drawings.

A. CONNECTIVE TISSUE

A common characteristic of connective tissue is the presence
of few cells and of much intercellular material, especially in
adults where the cells become inconspicuous. The principal
functions of connective tissue are those of connection and sup-
port. It enters into the structure and attachment of every
organ in the body. Martin gives an idea of the very wide
distribution of this tissue when he states that if all the tissues
of the human body except connective tissue could be dissolved
out, the original form of the entire body and of each organ would
remain.

Some of the more common kinds of adult connective tissue
are : (a) White fibrous, {b) yellow elastic, (c) adipose, (d) reticu-
lar, (e) cartilaginous, (/) osseous, (g) dentinal, {h) lymphoid,
and (/) corneous tissue.

(a) White fibrous tissue fibers are very fine, transparent,
and are not elastic. Fascia, periosteum, muscle sheaths,
tendons, hgaments are composed mostly of white fibrous tissue.

(b) Yellow elastic tissue is very elastic and forms an impor-
tant portion of the ligamentum nuchae, vocal cords, arteries,
and respiratory tubes.

THE ELEMENTARY TISSUES 7

(c) Adipose tissue is composed of modified connective tissue
cells, known as fat cells which occur in the meshes of areolar
tissue. Adipose tissue is essentially a '' packing substance,"
for it accumulates in the spaces between structures of the body
very much as bric-a-brac is packed in excelsior. The greatest
quantities of this tissue occur in the lumbar region in the areolar
tissue around the kidneys, in the marrow of long bones, in the
omentum, in the subcutaneous areolar tissue, and in other
places. However, that lying between the skeletal muscles will
be most often noticed in dissecting the rabbit.

(d) Reticular (retiform) tissue consists essentially of branch-
ing cells which form a network containing fluid and other
cellular elements. It occurs as supporting framework in lymph
glands, spleen, mucosa of the intestine, in interstitial tissues of
kidneys, Hver, and in the framework of bone marrow.

(e) Cartilaginous tissue is nonvascular and is comparatively
brittle. It is usually divided into three kinds according to
differences in its intercellular matrix: (i) Hyahne cartilage
(gristle) has an opalescent blue-like tint, is brittle, and forms
the articular surfaces of bones, the larger cartilages of the nose,
larynx, trachea, and bronchi, the costal and xiphoid cartilages,
and enters into numerous other structures. (2) Elastic (yellow
elastic fibrocartilage, reticular) cartilage is yellowish in color,
comparatively tough and pliable, and is limited in distribution.
It occurs in the Eustachian tube, cartilages of the external ear,
epiglottis, and other parts of the larynx. (3) Fibrous cartilage
(white fibrocartilage) occurs mainly between articulating sur-
faces in certain joints, such as the knee (menisci or interarticular
plates), the vertebral centra (connecting fibrocartilage), as
lining of osseous grooves through which a tendon passes (strati-
form fibrocartilage), e.g., bicipital groove of humerus (Fig. 12)
and peroneal groove of tibiofibula (Fig. 16) and forms the
fibrocartilaginous rim to certain joints (circumferential fibro-
cartilages) such as the hip joint.

(f) Osseous, or bone tissue is the densest and hardest tissue
in the body, except the dentin and enamel of the teeth. The

8 ANATOMY OF THE RABBIT

development of bones is considered in section II, B. A cross
section of the compact shaft of a dried long bone which has been
prepared for microscopic study shows an outer layer of circum-
ferential lamellae which Hes next to the periosteum and a
similar layer which lies next to the hollow, or narrow cavity,
of the bone. Both of these layers lie parallel to the internal and
external surfaces of the shaft, and thus their lacunae appear
in rows rather than in concentric (Haversian, Haver's) arrange-
ment, as is the case in the tissue lying between these two areas.
The interstitial (ground) lamellae are irregularly disposed plates
which, for the most part, fill the areas between the concentric
lamellae of the Haversian systems. In each of these cases the
lamellate appearance is due largely to the arrangement of the
cavities (lacunae) which were occupied by the cells while
the bone was alive. The Haversian (Haver's) system is essen-
tially a group of two or more concentric lamellae, alternating
with concentric rings of lacunae arranged around a central
cavity. Haversian canal.

Haversian canals enclose blood and lymph vessels and thread-
like processes of marrow tissue. Lacunae are ovoid spaces,
"about 20 ji long, io^jl wide, and 6/x thick" (Addison), lying
between the rings of lamellae, and from which minute canals,
canaliculi, radiate to join other lacunae so that in life communi-
cation was established between all the cells of a Haversian
system.

B. EPITHELIAL TISSUE

EpitheUal tissues are primarily covering or protecting tissues,
such as the epidermis, the lining of the digestive tract and body
cavity; in short, the lining of all natural tubes and cavities in
the body is epithelial tissue. The predominating form of the
component cells of the various kinds of epithelial tissue are of
two chief groups, or types : Squamous and columnar. Each of
these two groups is again divided into simple and stratified epi-
thelium, depending upon whether it is composed of a single layer

THE ELEMENTARY TISSUES 9

or of several layers of cells. The cells in modified epithelium are
adapted or specialized to meet particular uses, such as glandular
and ciliated epithehal cells. The term neuroepithelium is
applied to the perceptive apparatus of the special senses which
are found in such structures as the taste buds of the tongue,
rods and cones of the retina, and in the organ of Corti in the
ear. Skin glands, hair, and nails arise from the epidermis.
Membranes and glands are the more common adult epithelial
tissues.

Squamous (pavement) epithelium occurs in single layers,
simple squamous, and in two or more superimposed layers,
stratified squamous epitheHum. The stratified type is more
common than the simple squamous type. In sectioned tissue
the surface layer is often very much flattened, as in the simple
type, while the next layer is irregularly columnar. This
arrangement is correlated with nutrition to a great extent, for
the deeper columnar (formative) cells are the more recent and
the squamous surface cells are senescent and are being ehmi-
nated. The outer layer of the cornea is composed of classical
stratified squamous epithelium, while the simple type is usually
obtained for laboratory use from the outer capsule of the
crystalHne lense.

Columnar epithelium may be simple, consisting of a single
layer of tall, or prismoidal cells, as in the lining of the small
intestine; stratified, when it is more than one layer of cells
thick, as in the luminal walls of the epididymis, vas deferens
and trachea.

Modified epithelium commonly occurs in the lining of the
larger respiratory tubes as cilliated stratified collumnar
epithelium.

C. MUSCULAR TISSUE

(a) Striated (striped, skeletal, voluntary) muscle tissue
is characterized by its cells having alternating dark and light
bands extending across the diameter of the cell. The term
voluntary, although in general use, is misleading when applied

lO ANATOMY OF THE RABBIT

to Striated muscle, for most all striated muscles are subject
to reflex action and others, such as those which have to do
with the act of swallowing, the intercostals and diaphragm,
which function in breathing, function both voluntarily and
involuntarily.

The structural unit of striated muscle tissue is the cylindric
or prismatic fiber or multinucleated cell, which is about o.oi
mm. in diameter and seldom exceeds 4-5 cm. in length; however,
fibers over 12 cm. long have been found in the sartorius muscle
(Addison). Usually the greatest diameter is near the middle
of the fiber and grows less toward either end. Each fiber, or
cell is composed of cytoplasm, called sarcous substance,
within which are several nuclei and which is enveloped by a thin,
often indistinguishable, sheath, the sarcolemma. The sarcous
substance consists of two principal parts, the passive sarco-
plasm and the highly speciahzed contractile fibrHlae. The
cross striations of alternating dark and light bands depend
upon the arrangement and constitution of the long, threadlike
contractile fibrillae, and, in the final analysis, are probably only
regions of different densities; the less dense, or optically lighter,
are singly refracting regions and are called isotropic while the
denser, or optically darker, region is double refracting and is
called anisotropic (Addison).

A skeletal muscle is composed of a great number of multi-
nucleated cells or fibers, which are held together by an areolar
connective tissue sheath, the endomysium, and thus constitute
the small secondary bundle, or fasciculus. Varying numbers
of secondary bundles are enveloped by a connettive tissue
sheath, the perimysium, and thus constitute the primary
bundle. Primary bundles are in turn grouped together and
enveloped with a connective sheath, the epimysium, to form
the skeletal muscle. The epimysium (muscle sheath) is con-
nected with the perimysium (sheath of primary bundles) and the
endomysium and sarcolemma, so that there is a continuous
connection between the sheath enveloping the entire muscle,
the primary and secondary bundles and the fibers. However,

THE ELEMENTARY TISSUES II

the primary function of the perimysium appears to be to
serve as a support for the blood vessels and nerves ramifying
between the primary bundles and only incidentally serves as
a support for the secondary bundles which constitute the
primary bundle.

Drawings Suggested, (i) A part of the cross section of a
small striated muscle showing a primary bundle at least one
inch in diameter, with the tangent sides of two or more other
primary bundles included; then fill in the primary bundle
with secondary bundles in outline and complete three of the
secondary bundles by diagramatically representing the con-
tained muscle fibers. The tiny, more or less prismatic struc-
tures within the muscle fiber are groups or bundles of contractile
fibrillae and are called sarcostyles or muscle-columns. Name
and label, (ii) Study fibers or fasciculi which have been
teased out and mounted on slides and slides showing longitudi-
nal sections of fibers so that the striations and general form of
fibers and fascicuH can be appreciated. Draw longitudinal
view of entire, or parts of, one or more fibers and fasciculi.
Name and label.

(b) Smooth (non-striated, involuntary, plain, pale) muscle
tissue is characterized by its cells (fibers or fiber-cells) lacking
the cross-striations, being essentially fusiform or spindle-shaped,
having a single, nearly central nucleus, a diameter of ^-S/jl and
a length of from 50-2 2 5;u. The smooth muscle cells in the skin
and walls of blood vessels are broad and short (15-20/x), in the
wall of the small intestine long (215-220/z) and delicate, and
in the gravid uterus they may attain a length of 500M and a
width of 30)U (Addison). Each cell has a single elongate,
cylindrical nucleus with rounded ends which is imbedded in
cytoplasm. The extremely delicate contractile fibrillae often
pass through the cell lengthwise and on into the next cell, thus
forming intercellular bridges. The blood supply of these cells
is meagre compared with that of striated cells, but, as in the
latter, they pass through the endomysium as capillaries of
larger vessels which course through the perimysium. The

12 ANATOMY OF THE RABBIT

lymphatics also follow this course. The nerve supply is by
fibers of the sympathetic system. Since smooth muscles are
nowhere massive as are striated muscles, it follows that this
kind of muscle occurs only in small bundles and thin sheets.
Smooth muscle is common to the walls of tubes, such as the
digestive tract, blood vessels, and uterus.

(c) Cardiac muscle tissue, although possessing striated
fibrillae, similar to striated muscle tissue, is essentially involun-
tary in its action. The cells are peculiar in having protoplasmic
connections with each other.

D. NERVOUS TISSUE

The laboratory work will be confined chiefly to the study of
cross sections of the spinal cord with special reference to the
origin of spinal nerves and the spinal reflex paths and to cross
sections of a peripheral nerve trunk. However, the student
should study the descriptions and figures of nerve cells and their
component parts, as well as those of the structure of the spinal
cord and the peripheral nerves, in a textbook of histology,
physiology, or anatomy.

(a) The spinal cord should be studied from a slide having
several consecutive cross sections and one having consecutive
longitudinal sections which pass through the dorsal and ventral
roots of a spinal nerve. The middle thoracic spinal cord of a
small mammal, such as the mouse, is better than that of a
rabbit. A cross section through the spinal cord, which also
passes lengthwise through the roots of a pair of spinal nerves,
should be located on the sHde and studied carefully. Such a
section will present to the unaided eye, or under a low power
hand lens, a circular outHne of the spinal cord with a large
structure, which roughly resembles the letter ''H," extending
nearly across the section. This section of the spinal cord is
easily oriented under the low power of the microscope by
noting the fact that the larger cleft, the ventral (anterior)
median fissure, which extends from the periphery of the

THE ELEMENTARY TISSUES 1 3

section between the sides and nearly to the cross piece of the
''H/' is in the ventral side of the spinal cord. The smaller
cleft, which is more difficult to find, is the dorsal (posterior)
median sulcus and is in the dorsal side of the cord. The ends
of either side of the ''H" are called dorsal (posterior) and
ventral (anterior) horns. These horns are the beginning of
the dorsal sensory, and of the ventral motor roots of the spinal
nerve and contain the principal synapse involved in spinal
reflex movements. The neurons, which consist of the nerve
cell and its various processes, are sensory or afferent in the
dorsal root; that is, they convey stimuli from the periphery
(skin usually) to the central nervous system; while the neurons
in the ventral root are motor or efferent, that is, they convey
impulses from the central nervous system to the muscles.

(b) The peripheral nerve trunks have both myelinated
(sheathed) and unmyelinated nerve fibers. A cross section
of such a nerve trunk shows numerous circles with a deeply
stained center, the myelinated nerve fibers, and much smaller
deeply stained independent centers, the unmyehnated fibers,
intersperced between the myehnated fibers.

E. LIQUID TISSUES

Prepared slides of adult and embryonal rabbit blood or of
amphibian or avian blood should be available. Blood cells are
of two primary types: The erythrocytes (red or colored cells)
and leukocytes (white or colorless cells). Blood platelets will
not be considered here.

Erythrocytes of the adult rabbit do not have a nucleus
normally, but are nucleated in the embryo. Young mammalian
red blood cells (erythroblasts) are nucleated and may appear
in blood of adults after severe hemorrhage. In adult amphib-
ians and birds the erythrocytes are normally nucleated.

Leukocytes are of several kinds, but are usually much
larger than red blood cells, have one or more nuclei, which m.ay
be almost any form, and stain deeply.

CHAPTER II
THE SKELETON

The material for the study of the skeleton in this course
should comprise articulated and disarticulated skeletal material
of both rabbit and man. It is an excellent plan to supply each
student with a box containing the disarticulated skeleton of a
rabbit. The student should master the skeleton as a whole in
order to get the relation of the principal groups of bones and
the principal bones themselves to each other and to the osseous
framework of the body. Students often make the mistake of
beginning the study of the skeleton by concentrating on single
bones instead of mastering a whole group and then the various
bones which comprise that group. Although there is some
difference of opinion concerning the grouping of certain
bones, anatomists are in agreement on the basis for the major
groups. Spalteholtz considers the bones in five major groups:
Head, trunk, pelvis, superior extremity (superior Hmb and
girdle), and inferior limb and girdle); while Gray groups the
bones into an axial skeleton (including the hyoid) , appendicular
skeleton, and auditory ossicles. The method employed in this
work is intended to give the student the relation of the various
bones in each group to each other as well as the relation of the
various groups to each other and to the entire skeleton. More
of the details of the topography of the bones and their functional
relations will be considered under C of this chapter.

The principal functions of the skeleton are support, by
furnishing attachment for muscles and ligaments, and protec-
tion, by covering or overlying vital structures, such as, the
brain, thoracic viscera, and arteries.

14

THE SKELETON

15

Fig. I. — Relative positions of the various bones of the cranial half of the
skeleton. AT, atlas; AX, axis (epistropheus); C, clavicle; CA, carpus; D,
digits II-V; H, humerus; IF, intervertebral foramen; L, first lumbar vertebra;
MC, metacarpals II-V; OC, occiput; OP, olecronal process of ulna; P, pollex,
PB, pisiform bone; R, radius; S, scapula; SP, spinous process; ST, sternum, TP,
transverse process; U, ulna.

A. THE SKELETON AS A WHOLE

The adult skeleton is conveniently divided into an axial
and an appendicular part which are subdivided for convenience
in studying.

i6

ANATOMY OF THE RABBIT

.^xiAL Skeleton

i. SKULL

{a) Cranium

R.VBBIT

(Common terminology)
2 frontals
2 parietals

1 interparietal

2 temporals
I occipital

I sphenoid (6 parts)

1 ethmoid

2 nasals
2 premaxillaries

{b) Facial Bones

Man
(BNA terminology)

1 OS frontale

2 ossa parietales

2 ossa temporales

I OS occipitale

I sphenoidale (7 parts)

1 ethmoidal

2 ossa nasales

2 maxillaries

2 maxillae

2 maxilloturbinals

■ 2 conchae nasalis inferiores

2 lachrymals

2 ossa lachrymales

2 malars

2 ossa zygomatica

I vomer

I vomer

2 palatines

2 ossa palatina

I mandible

I mandibula

(c) Hyoid Bones

I hyoid bone (basihyal)

Hyoideum (including 2 greater

2 greater cornua

and 2 lesser cornua)

2 lesser cornua

(d) Auditory Ossicles

malleus

malleus

incus

incus

stapes

stapes

ii. TRUNK

(a) Vertebral Column

7 cervical vertebrae

7 vertebrae cervicales

12 thoracic

12 vertebrae thoracales

8 lumbar

5 vertebrae lumbales

3 sacral

5 vertebrae sacrales

20 caudal

4 vertebrae coccyges

24 ribs

I manubrium

4 sternebrae

I xiphoid process

(b) Ribs

(c) Sternum

24 costae

I manubrium sterni

I corpus sterni

I processus xiphoideus

THE SKELETON

17

II. Appendicular Skeleton

1. PECTORAL GIRDLE

2 scapulae

2 scapulae

2 clavicles

ii. SUPERIOR LIMB

(a) Brachium

2 claviculae

I humerus

(b) Antibrachium

I humerus

I radius

I radius

I ulna

(c) Carpus

I ulna

9 carpals

8

ossa carpalia

I navicular

(radiale)

I OS naviculare manus

I lunate

(intermedium)

I OS lunatum

I triquetral

(ulnare)

I OS triquetrum

I pisiform

I OS piciforme

I trapezius

(carpale I)

I multangulum majus

I trapezoid

(carpale II)

I multangulum minus

I central

I OS magnum

(carpale III)

I OS capitatum

I unciform

(carpale IV, V)

{d) Metacarpus

I OS hamatum

5 metacarpals

{e) Digits

5 ossa metacarpalia

S digits

5-

digites

14 phalanges

14 phalanges digitorum manus

5 proximal phalanges

5 phalanges d. m. prima

4 middle phalanges

4 phalanges d. m. secunda

5 distal phalanges

5 phalanges d. m. tertia

iii. PELVIC GIRDLE

2 innominate bones

2

ossa coxae

2 ilia

2 ossa iHa

2 pubes

2 ossa pubes

2 ischia

iv. INFERIOR LIMB

(a) Thigh

2 ossa ischies

I femur

I femur

I patella (one of the sesamoid bones)

I patella

(b) Leg (crus;
I tibiofibula (i tibia and i fibula) i tibia

I fibula

i8

ANATOMY OF THE RABBIT

(c) Tarsus

6 tarsals

I calcaneum
I astragalus
I navicular (scaphoid)

I second cuneiform
I third cuneiform
I cuboid

4 metatarsals

4 digits

12 phalanges
4 proximal
4 middle
4 distal (ungual)

7 ossa tarsaha
I calcaneus
I talus

I OS naviculare pedis
I OS cuneiforme primum
I OS cuneiforme secundum
I OS cuneiforme tertium
I OS cuboideum

(d) Metatarsus

5 ossa metatarsalia

(e) Digits

5 digites

14 phalanges digitorum-pedis
5 phalanges d.p. prima

4 phalanges d.p. secunda

5 phalanges d.p. tertia

B. DEVELOPMENT AND CLASSIFICATION OF BONES

The process of ossification is essentially one of impregnating
connective tissue with calcium salts by the activity of special-
ized connective tissue cells, called osteoblasts. From the
manner of calcification, bones are of two principal kinds: (i)
Direct, intermembranous or dermal bones are thin bones,
such as form most of the sides and top of the cranium and the
greater part of the face. In this type osteoblasts deposit the
calcium salts directly in young connective tissue without
the bone being first preformed in cartilage. These are called
membrane bones because they are developed within sheets of
embryonal connective tissue membrane. They are sometimes
called dermal bones because they are represented in some of the
lower vertebrates by dermal plates. (2) Indirect, endochronal,
cartilage or replacing bones are preformed in fetal cartilage and
this cartilage is in turn replaced by calcium salts to form the
bone. Areas of calcium deposition are called centers of
ossification. There are often three or more centers of ossifica-
tion in each developing bone, the carpals and tarsals have only

THE SKELETON 1 9

one, and the metacarpals, metatarsals, arid phalanges two
centers of ossification in man. This probably holds for the
rabbit also. By far most of the bones are formed by the process
of replacement.

Bones are classified according to their form, as a means of
ready reference. Although this method of classification
suggests the function, it is limited in application to the bones
themselves. Thus, in reference to the shape of the bones, the
four classes are: (i) Long bones, those having a diaphysis
(shaft) , which is usually filled with yellow marrow, and typically
two epiphyses (separately ossified ends) which ultimately
fuse with the extremities of the diaphyses. Some noteworthy
exceptions are found in the metacarpals, metatarsals, and
phalanges which have only one epiphysis. Examples of
typical long bones are the clavicle, humerus, radius, ulna,
metacarpals, phalanges, and femur. (2) Short bones have
little cancellous tissue and no cavity, e.g., carpals and tarsals.
(3) Flat bones have a layer of cancellous tissue between the
two other layers of very compact tissue, e.g., innominate bone,
scapula, and parietals. (4) Irregular bones are of various
forms and structure, e.g., vertebrae, temporals, mandible, and
practically all others which do not fit into the preceding groups
readily.

C. RELATIONS AND TOPOGRAPHY OF SOME OF
THE BONES

a. THE SKULL

The skull of the rabbit (Figs. 2, 3) does not usually lend
itself to intensive study due to the fact that in laboratory
material it is seldom well ossified. However, the general form
and relations of the principal bones may be seen readily.

The occipital bone forms the base of the skull; furnishes
two processes, occipital condyles, for the articulation of the
atlas; articulates with the sphenoid ventrally and with the
interparietal cranially; and surrounds the foramen magnum.

20

ANATOMY OF THE RABBIT

This bone develops from four parts, the names of which are
retained for descriptive purposes after the parts have fused
to form a single bone. The basioccipital forms the floor of
the foramen magnum, the supraoccipital the roof and the two
exoccipitals the two sides of this foramen.

The two parietal bones form most of the vault of the
cranium. These bones articulate with each other, with the

Fig. 2. — Skull, caudolateral view. C, condyle of occipital bone (occipital
condyle); EA, external auditory meatus, osseous portion; F, frontal; G, pie-
molars and molars; I, interparietal; IF, infraorbital foramen; IN, incisors; L,
lachrymal bone; M, malar bone; MP, mastoid process of temporal; MX, maxil-
lary; N, nasal; NP, nasal process of premaxillary; PM, premaxillary ; SE,
styloid process of exoccipital; SF, stylomastoid foramen; SO, supraoccipital;
SP. squamous portion of temporal; TP, tympanic bulla.

interparietal caudad, the temporals laterad and the frontals
craniad.

The two temporal bones form the major portion of the
sides of the cranium, contain the auditory organs, furnish
attachment for muscles and contribute to the structure of the
zygomatic arches. The temporal bone (temporal complex)
is made up of three (4, Bensley, 5 in man, Gray) portions
(squamous, tympanic, and petrous), which are fused together
in well ossified skulls. These portions of the temporal are

THE SKELETON 21

often designated as bones (e.g., squamous bone) probably
because these portions are separate in young mammals and are
actually distinct bones in lower vertebrates. The tympanic
portion contains the external and middle parts of the auditory
organ and presents two striking external structures. One of
these, the mastoid process, is a large protuberance of spongy
bone which occupies most of the caudolateral side of the skull
craniad to the occipital bone and dorsad to the tympanic
bulla. The other, the tympanic bulla, is a large, bulbus,
sacuiate bone with a large external foramen, the external
auditory meatus. The petrous portion of the temporal is a
very solid, stone-like bone which lies mediad to the bulla and
contains the meatus, semicircular canals, cochlea, vestibule,
foramen for the eighth cranial nerve and other structures of
the internal ear. Its medial margin is visible through the
foramen magnum. The squamous portion of the temporal
bone forms most of the side of the cranium and gives off the
zygomatic process, which articulates with the malar bone to
form the zygomatic arch.

The two frontal bones articulate with each other, with the
parietals and squamous portion of temporals caudad, the
nasals, premaxillaries, maxillaries, and lachrymals craniad and
with other bones. The frontal bones form part of the vault
of the cranium and of the nares and nearly the entire superior
portion of the orbits, where each gives off a prominent supra-
orbital process.

The two nasal bones form the major part of the roof of the
nares, and form visible articulations with the frontals and
frontal process of the premaxillaries.

The premaxillaries bear the two large and two small
incisors, articulate dorsally with the nasals and frontals,
caudally with the maxillaries and internally with the vomer and
maxiloturbinals.

The maxillaries bear the grinding teeth, form the caudal
half of the incisive foramen and articulate medially with the
palatines and lachrymals, laterally with the malar bones (which

22

ANATOMY OF THE RABBIT

form the major portion of the zygomatic arches) and with the
premaxillaries and frontals. The major portion of the max-
illoturbinals (inferior nasal conchae) is attached to the pre-
maxillaries. The premaxillaries and maxillaries form the
maxillae or upper jaws.

The floor of the cranium and interorbital bony structures
are formed mainly by the basal portion of the occipital, and
by the various parts of the sphenoid bones.

MF

Fig. 3.- — Right mandular ramus, lateral view. A, angle; AS ascending (con-
dyloid process); B, body (horizontal ramus); C, condjde; D, diastema; I, incisors;
MF, mental foramen ; MN, mandibular notch; SN, supra-angular notch.

The mandible (lower jaw, inferior maxilla; Fig. 3) comprises
a right and a left mandibular ramus which bear the teeth. The
cranial ends of these two rami articulate with each other and
form the mandibular symphysis. On the medial side of the
body of the mandibular ramus there is a rough area, the
mylohyoid Hne, for the attachment of the mylohyoid muscle.
The mandibular (inferior dental) foramen, which is caudoven-
trad to the last tooth, permits entrance of the inferior alveolar
artery and mandibular nerve to the roots of the inferior teeth.
Branches of this artery and nerve pass out of the bone through
the mental foramina. The medial side of the angle and of the

THE SKELETON 23

ascending part of the mandible have wide depressions for
muscle insertion.

The hyoid apparatus is craniad to the larynx to which it is
mobily attached. The osseous portions are the heavy basal
part (basihyal, hyoid bone) and its two pairs of cornua, which
extend mainly dorsolaterad. The lesser cornu of either side
is attached to the cranial, and the greater cornu to the caudal
end of the hyoid bone.

b. VERTEBRAL COLUMN

In all vertebrate animals, from fish to man, the individual
vertebrae are formed on the same general plan. Thus, the

Fig. 4. — Diagram of a typical vertebra, caudolateral view. AA, anterior
articulating process; C, centrum (body); IN, intervertebral notch; LM, lamina;
NC, neural canal; P, pedicle; PA, posterior articulating process; SP, spinous
(neural) process; TP, transverse process,

differences in the vertebrae of various animals and in the
different sections of the vertebral column of a single animal are
primarily due to modifications of the type- vertebra. A
typical vertebra (Fig. 4) has eight primary parts: a centrum
(body), a neural canal, two intervertebral notches, a
spinous process (neural spine), two pedicles, two laminae,
two transverse processes, two anterior (superior) articular
processes (prezygapophyses), and two posterior (inferior)
articular processes (postzygapophyses) . The pedicles of a
vertebra are the sides of the neural canal, and the laminae form
the roof or arch of this canal. The intervertebral notch with

24

ANATOMY OF THE R.\BBIT

the cranial margin of the pedicle of the next vertebra caudad,
forms the intervertebral foramina through which the vertebral
nerves pass. The cranial, or anterior, end of a mammalian

Fig. 5. — A, fifth cervical vertebra, cranial view, and B, Axis, right latera
view. AA, anterior articulating process; AS, articulating surface of AA;
C, centriun (body); CE, costal element of TP; LM, lamina; NC, neural canal;
OP, odontoid process (dens); P, pedicle; PA, posterior articulating process;
SP, spinous process; TE, transverse element of TP; TP, transverse process;
V, vertebrarterial canal (transverse foramen).

vertebra can be distinguished from the caudal end by the fact
that the articulating surfaces of the anterior articular processes
look dorsomediad while those of the posterior articular processes
look ventrolaterad.

Fig. 6. — Fifth thoracic vertebra, right side. AAS, anterior articulating
surface of anterior articulating process; C, centrum; CDF, costal demifacet;
IN, intervertebral notch; PAS, posterior articulating surface of posterior articu-
lating process; SP, spinous process; TAF, tubercular articulating facet.

Any one of the five sections of the vertebral column has one,
or more, vertebrae which is characteristic of that particular
group, while the others of that group show a marked tendency

THE SKELETON

25

to more nearly conform to the type of the vertebrae of the
preceding or the next group. This is especially true with

Pig. 7. — The sacrum and first caudal vertebra, ventral view, and last lumbar
vertebra, ventrolateral view. AA, anterior articulating process; AP, auricular
process; CI, first caudal vertebra; IN, intervertebral notch; L8, last lumbar
vertebra; MP, mammillary process of AA; PAS, posterior articulating surface of
posterior articulating process; Si, 2, 3, first, second, and third sacral vertebrae;
SP, spinous process; TP, transverse process; VF, ventral foramen for ventral
root of spinal nerves.

regard to certain points of such structures as neural spines,
transverse processes or centra, but there are certain other
points of structure which are pecuhar to the vertebrae of only

26 ANATOMY OF THE RABBIT

one group and thus serve as criteria for determining to which
group any single vertebra of a disarticulated skeleton belongs.
The distinguishing character of the cervical vertebrae
(Fig. 5) is the presence of the vertebrarterial (transverse)
foramen in the transverse processes of all seven of these
vertebrae; that for the thoracic vertebrae (Fig. 6) is the pres-
ence of costal demifacets on the centra, for articulation with
the head (capitulum) of the ribs, and tubercular facets on the
transverse processes, for articulation with the tubercle of the
ribs. The costal demifacets are represented by a whole facet
entirely on the cranial ends of the vertebrae of the last three,
or four, centra. Definite tubercular facets are absent on the
transverse processes of these vertebrae. The distinguishing
characters of the lumbar vertebrae (Fig. 7) are absence of
costal and tubercular facets. The transverse processes are
long and extend craniolaterad, and the centra are very heavy.
The three sacral vertebrae (Fig. 7) are fused together and the
intervertebral foramina are divided into a small dorsal and a
large ventral foramen. The first two vertebrae contribute to
the formation of the auricular processes, by means of which
the sacrum articulates with the innominate bones. The
caudal vertebrae progressively degenerate; the neural canal
is lost first, then the processes, so that the last eight vertebrae
are little more than cylindrical centra.

C. RIBS AND STERNUM

The rabbit commonly has twelve pairs of ribs, but, as in man,
a thirteenth pair is sometimes found. The ribs are curved,
flattened bones which articulate with the vertebrae dorsally
and the first seven with the sternum ventrally by means of
costal cartilages. The last five are ''floating" ribs, that is,
they are not directly attached to the sternum.

A typical rib (Fig. 9) has a head (capitulum) with which it
articulates with the costal demifacets of two contiguous thoracic
vertebrae, a tubercle, with which it articulates with the trans-

THE SKELETON

27

verse process of a thoracic vertebra (except as noted above in the
last three or four thoracic vertebrae) and a body or shaft.

Fig. 8. Fig. 9.

Fig. 8. — Sternum and costal ribs of left side, dorsal view. Cartilage is repre-
sented by stippling; bone, white. I-VIII, costal cartilages and ends of first
eight ribs; EC, ensiform (xiphoid) cartilage; M, manubrium; S 1-4, sternebrae;
XP, xiphoid process.

Fig. 9. — Proximal two-thirds of fourth right rib. A, angle; H, head (capitu-
lum); N, neck; S, shaft; T, tubercule and articulating facet.

The constricted area between the head and the tubercle is the
neck, and the sharpest bend in the shaft forms the angle of the
rib. The sternal portion of all the ribs is cartilaginous; how-

28 ANATOMY OF THE RABBIT

ever, only the first seven of these costal cartilages articulate
with the sternum.

The sternum (breastbone, Fig. 8) of the rabbit is comprised
of six bones; a manubrium, four sternebrae and a xiphoid
process (ensiform cartilage). In man the four sternebrae
(segments) fuse to form the body of the sternum. The cartilag-
inous ends of the first pair of ribs articulate directly with the
sides of the manubrium; the second to fifth pairs articulate
with the intersternebral cartilages of the manubrium and the
first to third sternebrae and the sixth and seventh pairs articu-
late with the cartilage between the fourth sternebra and
xiphoid process.

d. THE PECTORAL GIRDLE AND SUPERIOR LIMB

The pectoral (shoulder) girdle is comprised of two paired
bones, the scapula and clavicle. Right and left clavicles are
attached to the manubrium and scapula by ligaments, thus the
right and left halves are united to form the ventral portion of
the girdle.

The scapula is attached to the trunk by muscles, except for
the ligaments and clavicle. The general topography of the
lateral and glenoid regions of the scapula is sufficiently well
show^n in figure lo to serve as a guide in studying this bone.
The medial side* of the fiat portion of this bone forms the
subscapular fossa, and the spine divides the lateral side of
the blade into a supraspinous and an infraspinous fossa. These
three fossae furnish surfaces for the attachment of three large
muscles which are named after the respective fossae. The
clavicle is rudimentary.

The brachium has a single bone, the humerus (Figs, ii,
12). Its proximal end bears five important topographical
points for articulation or for muscle attachment. The large
head which articulates with the glenoid cavity of the scapula,
the lesser (medial) tuberosity, the greater (lateral) tuberos-
ity, from which the deltoid ridge extends along the laterocranial

THE SKELETON

29

surface of the proximal third of the humerus, and the bicipital
groove for the tendon of the biceps muscle lies on the cranio-
medial surface between the greater and lesser tuberosities.

The antibrachium is comprised of two slightly curved bones,
the radius and ulna (Fig. 13). As in man, the radius is
shorter than the ulna and forms the major part of the anti-
brachial articulation with the carpus. However, in the
rabbit there is very httle rotation of the hand, due to the

Fig. 10. — Right scapula, A, lateral; and B, glenoid view. C, coracoid process;
CB, coracoid (cranial) border; GB, glenoid (axillary) border; GC, glenoid
cavity; lA, inferior (glenovertebral angle; IF, infraspinous fossa; IG, infra-
glenoid tubercle; MP, metacromial process; S, spine; SA, superior (coracocranial,
craniovertebral) angle; SF, supraspinous fossa; SG, supraglenoidal tubercle;
VB, vertebral border.

manner of articulation of the radius at the semilunar notch
where it is flattened against the ulna instead of having a
rotating head, as in man and the cat. The proximal end
of the radius is concave and grooved to fit the medial trochlea
on the distal end of the humerus. The ulna is the longer of the
two bones and plays a more important part in the articulation
of the brachial and antibrachial bones. There is a distinct
nutrient foramen on the medial side near the distal end of the
proximal third of the ulna.

The carpus has nine bones roughly arranged in two rows.
From the radial side the bones of the proximal row are the

30

ANATOMY OF THE RABBIT

navicular, lunate, triquetral, and pisiform. Those of the
distal row, from the radial side, are the trapezius, trapezoid,
central, os magnum, and unciform. The presence of the

Fig. II.

Fig. 12.

Fig. 13.

Fig. II. — Right humertis, caudal view. EL, epiphyseal line; LT, greater
tubercle; LE, lateral epicondyle; GT, lesser tuberosity; ME, medial epicondyle;
OF, olecranon fossa; T, trochlea.

Fig. 12. — Right humerus, cranial view. BG, bicipital groove; GT, greater
tuberosity (tubercle); H, head; LE, lateral epicondyle; LER, lateral epicondylar
ridge; LT, lesser tuberosity; ME, medial epicondyle; RF, radial fossa; T, trochlea.

Fig. 13. — Bones of right antibrachium, craniolateral view. CP, coronoid
process of radius; EOF, epiphysis of olecranal process; OP, olecranal process;
R, radius; SN, semilunar notch; SP, styloid process of radius; SPU, styloid proc-
ess of ulna; U, ulna.

ninth carpal and the general arrangement of all the bones in
two rows with five bones in the distal row, indicates that the
carpus of the rabbit belongs to a low vertebrate type in which
pronation and supination are impossible or very limited.

THE SKELETON 3 1

In the lower vertebrate generalized carpus two of the carpal
bones are alhgned with the antibrachial, and five with the
metacarpal bones, and there are the two indifferently placed
bones (lunate and central), which form the ''middle row" of
some authors. The proximal row is comprised of the radiale
(navicular) which Ues at the end of the ulna, and the inter-
medium and the centrale (central). The bones of the second,
or distal row are given the same ordinal name as that of the
metacarpal with which each articulates. Thus, the first carpal
(beginning on the radial side) articulates with the first meta-
carpal and it and the other four are known as carpale I (trape-
zius), carpale II (trapezoid), carpale III (os magnum),
carpalia IV and V (unciform). A study of the generalized
low vertebrate type will aid the student greatly in mastering
the carpus and its relations in the rabbit and in man. The
pisiform bone forms a conspicuous protuberance on the
caudal side of the carpus, for the insertion of the flexor carpi
ulnaris m. (29), articulates with the proximocaudal surface
of the triquetral and with the caudal surface of the styloid
process of the ulna. It is not visible on the cranial surface of
the carpus.

The metacarpus has five metacarpal bones and five paired
sesamoid bones, one pair on the ventral side of each meta-
carpophalangeal articulation, which form grooves through
which flexor tendons pass.

The phalangeal bones are five in the proximal, four in the
middle, and five in the distal rov/. The distal (ungual) phalan-
ges terminate in claw-shaped bony processes which, in life, are
covered by the nail or claw.

e. THE PELVIC GIRDLE AND INFERIOR LIMB

The pelvic girdle (Fig. 14) is formed by a right and a left
innominate bone which are firmly articulated with the auricular
processes of the sacrum and with each other through the pubio-
ischial symphysis. The three major component parts of the

32

ANATOMY OF THE RABBIT

innominate bone are separate in young individuals, but fuse
together solidly in old adults. The three major parts of this
bone are the ilium, ischium, and pubis. The cotyloid or

LSN

LIT

IT—

-ISCH

Fig. 14. — Right innominate bone, slightly twisted to show structures. AC,
acetabulum; C, crest of ilium; CAP, caudoventral margin of auricular surface;
IAS, inferior anterior spine; IE, iliopectineal eminence; ILI, ilium, IPS, inferior
posterior spine (caudodorsal margin of auricular surface) ; IS, ischial spine (on
dorsomedial surface); ISCH, ischium; ISY, ischial symphysis, which is con-
tinuous with PS; IT, ischial tuberosity; LIT, lateral ischial tuberosity; LSN,
lesser sciatic notch; OB, obturator foramen; P, pubis; PS, pubic symphysis;
SAS, anterior superior spine.

acetabular bone is insignificant in point of size. The Hnes
of union (sutures) of the parts of the innominate bone all
unite in, or near, the acetabulum. The ilium is the cranial
part which articulates with the sacrum; the pubis is the ventro-

THE SKELETON

33

cranial, and the ischium is the ventrocaudal portions of the
innominate bone. The last two form the symphysis by which
the right and left innominate bones are joined ventrally. The
ischiopubic suture passes through the ventral rim of the obtura-
tor foramen.

Fig. 15. — Femur, A, cranial; and B, caudal view. GT, greater trochanter;
H, head; LC, lateral condyle; LER, lateral epicondylar ridge; LT, lesser tro-
chanter; MC, medial condyle; MER, medial epicondylar ridge; N, neck; PG,
patellar groove; S, shaft; IF, trochanteric fossa; TT, third (lateral) trochanter.

The proximal third of the femur (Fig. 15) presents eight out-
standing anatomical points: The ball-shaped head, which articu-
lates with the acetabulum; the neck, a constriction distad to the
head; the lesser trochanter; nutrient foramen and linea aspera
are on the medial side. The great trochanter, a heavy, beak-
Hke process, surmounts the end of the femur and the lateral
(third) trochanter is opposite the lesser (medial) trochanter.
The trochanteric fossa, a deep pit for insertion of the tendon of

34

ANATOMY OF THE RABBIT

the inferior gemellus muscle, is on the caudal side of the femur
between the great and lateral trochanters on the lateral side
and the head and lesser trochanter on the medial side. The
distal end of the femur presents two articulating surfaces:

Fig. i6. Fig. 17.

Fig. 16. — Right tibiofibula, laterocranial view. C, crest of tibia; EL, epi-
physeal line; F, fibula; LM, lateral malleolus; MM, medial malleolus; PN,
peroneal notch in LM; T, tibia.

Fig. 17. — Tarsals and metatarsals of right foot, dorsal view. A, astragalus;
C, cuboid; CA, calcaneus (os calcis) ; G, groove for tendon of plantaris m. (45);
N, navicular; PT, proximolateral tuberosity for insertion of peroneus brevis m.
(50c); SC, second cuneiform; TA, trochlea of astragalus; TC, third cuneiform;
TOC, trochlea of calcaneum; II, III, IV, V, second to fifth metatarsals.

The patellar groove is on the cranial, and the lateral and
medial condyles are on the caudal sides mainly. The inter-
condylar fossa is between the two condyles, and the prominence
above each condyle forms the lateral and the medial epicon-
dyles (supracondyles, supracondyloid ridges).

THE SKELETON 35

The patella is formed within the tendon of the quadriceps
femoris m. (42) (patellar ligament) and is, therefore, a sesa-
moid bone; but most anatomists enumerate it with the bones
of the human skeleton.

The tibia and fibula are fused together and thus form the
tibiofibula (Fig. 16). The proximal end of the tibia is tri-
angular in cross section with the articulating surface greatly
expanded. The apex of the triangle is directed craniad and
forms the crest of the tibia. The distal end of the tibia articu-
lates with the calcaneum and astragalus and presents two
eminences; the medial (internal) malleolus and the lateral
(external) malleolus. The lateral malleolus has a groove on
the caudal side, the peroneal notch, through which the tendons
of the peroneal muscles (50) pass.

The tarsus (Fig. 17) has only six bones, which indicates a
marked advance from the generaUzed vertebrate type. The
reduction in number and increase in relative size of other
tarsals, as compared with man, are correlated with development
of leaping.

There are four metatarsals; the first is absent, as is also
the hallux. Each of the four digits has three phalanges.

CHAPTER III
ARTICULATIONS

It must be borne in mind that in osteology an articulation
is merely a union of two or more bones and may, or may not,
permit movement between the bones which form the articula-
tion; while the term joint usually refers to a movable articula-
tion. Unfortunately, there is seldom any distinction made
between the terms articulation and joint.

The essential component parts of a movable joint are: (i)
Two or more bones. (2) Ligaments, usually with some kind of
cartilage. (3) Synovial membrane and synovial fluid. At
points of great friction, such as the knee joint, there are purse-
like sacs of connective tissue filled with fluid called bursae,
which are interposed between the articulating surfaces of the
bones and cartilaginous discs. The capsule of a joint is a
covering of fibrous connective tissue and is found in all joints,
except in some of the intracarpal and intratarsal, of man
(Sutton and Drinker). Man has thirteen bursae and ten
ligaments in his knee (Gray). The inner lining of the capsule
is formed by the synovial membrane which secretes synovial
fluid ("joint water") for lubricating and preventing friction
in the joint.

All of the various kinds of articulations fall into three grand
divisions or classes: Synarthroses, immovable; amphiarthroses,
slightly movable; and diarthroses, freely movable joints.

A. SYNARTHROSES, immovable articulations

(a) Sutura, suture-hke, e.g., skull bones.

(b) Gomphosis, conical process in socket, e.g., teeth.
(Gray, describes nine other types or sub-types of synarthroses.)

36

ARTICULATIONS 37

B. AMPHIARTHROSES, slightly movable articulations

(a) Symphysis, connected by broad flattened discs of com-
plex fibrocartilage, e.g., bodies of vertebrae, pubic bones, rami
of mandible.

(b) Syndesmosis, connected by interosseous ligaments,
e.g., inferior tibiofibular articulation.

C. DIARTHROSES, freely movable articulations

(a) Ball-and-Socket Joint, a globular head fits into a
cup-like cavity, free movement, e.g., hip and shoulder joints.

(b) Condyloid Joint, a condyle fits into an eliptical cavity,
free movement except rotation, e.g., articulation of head and
neck, mandible, wrist.

(c) Gliding Joint, two plane surfaces, or one slightly con-
vex and the other slightly concave, movement considerably
restricted by bony extension or by ligaments, e.g., articular
processes of vertebrae.

(d) Saddle Joint, reciprocal concavoconvex surfaces, free
movement, except axial rotation, e.g., carpometacarpal joint of
the thumb in man.

(e) Pivot Joint, a pivot within a ring of bone and ligament,
e.g., atlanto-axial articulation in neck, and radius-ulnar
articulation in man.

(J) Hinge Joint, essentially concavoconvex surfaces having
in addition a median projection which fits into a shallow groove,
or other osseous projections, which allow only flexion and
extension. The interphalangeal joints are the true type, the
humeroulnar-, knee-, and ankle joints are typical in the rabbit,
but not in man, because in man they permit a certain amount
of rotation or of side-to-side movement.

CHAPTER IV

WORK PRELIMINARY TO DISSECTION

The student should be given his injected rabbit at this time
so that he can follow outlines A and B. He should locate the
place where the preparator incised the skin in order to insert
the canula into a large artery for the purposes of injecting
embalming fluid and the colored mass which distends and colors
the arteries (usually red, sometimes yellow) so that these
vessels may be easily followed.

A. EXTERNAL CHARACTERS

Note the general appearance, form, and proportion of the
rabbit, the character of its fur, vibrissae (^'whiskers"), incisors
(front teeth), mouth, eyes, two Hds, and conjunctival fold
(third eyehd), external ears, external auditory meatus, hands
(fore feet), feet (how many fingers? toes?), mammary glands,
nipples, vagina, or scrotum and penis, caudal appendage, anus
and any other normal or anomalous external structures.

B. GENERAL DESCRIPTION OF THE BODY

Locate as accurately as possible the axilla (arm pit), ole-
cranal process (elbow point, formed by proximal end of ulna
(Fig. 13), volar or caudal surface of hand (palm), radial side
of hand (side on which the poUex and radius are), ulnar side of
hand (side on which the Httle finger and ulna are), cranial
or dorsal side of hand (back side, opposite of volar) , the poplit-
eus or popliteal space (concave region behind knee), plantar
or caudal surface of foot (sole); external, lateral, or peroneal
side of foot (side on which the little toe and fibula are) , medial

38

WORK PRELIMINARY TO DISSECTION 39

or internal side of foot (side on which tibia is and the hallux or
great toe should be), and the cranial or dorsal side of the foot.
The digits (fingers and toes), metacarpals and metatarsals
are designated by ordinals (I, II, III, IV, and V) and the pollex
and hallux (of man) are designated the first digits (digit I).

C. TOPOGRAPHICAL TERMS

Difficulties with terms of direction or terms used in locating
anatomical structures in man and four-footed mammals will
be reduced if the four-footed animal is stood up on its hind feet
or if it is assumed that man walks on all fours. Since the
rabbit happens to be the material with which this laboratory
work is being done, instead of the human cadaver, it will
necessitate the student's being able to recognize the fact that
certain terms employed in mammalian anatomy, although
equally applicable to human anatomy, are supplanted by
synonomous terms in most of the text books of human anatomy.
Thus, in combinations each of the three following groups of
topographical terms mean essentially the same thing: (i)
Anterior, superior, and cranial (e.g., articulating processes of
vertebrae); (2) ventral, of rabbit; and anterior, of man (e.g.,
abdominal region); (3) dorsal, of rabbit; and posterior, of man
(e.g., region of back). Thus, the liberties of anatomists in.
employing a dual system of terminology, to say nothing of the
vast number of purely synonomous terms, make it necessary
for the student to master both sets of terminology so that he
can translate one to the other.

It would save much confusion if such terms as superior and
inferior, anterior and posterior, which are commonly used in
human anatomy, were not employed at all and the more
concise terms cranial and caudal, ventral and dorsal (including
their adverbial forms) were used in their stead. In order to
simplify the meaning and application of these terms the writer
has employed the use of an anatomical position for the rabbit
in which the axial skeleton is extended in as nearly a straight

40 ANATOMY OF THE RABBIT

line as possible and the limbs are extended as nearly at right
angles to the axial skeleton as possible with the radial and
tibial sides mediad. Thus only four topographic terms,
cranial, caudal, medial, and lateral, are essential and the
confusing terms, dorsal and ventral need be applied only to
the trunk, head, and tail. However, it is easier, although not
necessary, to refer to the back of the hand or foot as the dorsal
side than as the cranial side, but the dorsal side of the humerus
would be the caudal side while the dorsal side of the femur
would actually be the cranial side if these terms are applied to
the limbs. The anatomical position employed in studying
human anatomy is that in which the human cadaver is laid on
its back with the arms straight along the sides and the palms
of the hands turned up (supinated) and with the heels resting
on the table.

Although the following rules on the use of the various forms
of the different terms are often violated by good anatomists
their validity remains unshaken. The -al ending denotes
the adjectival use of the term, e.g., caudal appendage, caudal
region; the -ad ending denotes the adverbial use of the term,
usually as an adverb of direction or of location (cf. Reighard
and Jennings, p. viii), as one structure or region is caudad to
another, e.g., the pelvis is caudad to the sternum. Both forms
of this term are derived from the Latin noun cauda, the tail.
The other three terms are derived from the Latin nouns cranium,
the bony case surrounding the brain; ventrum, the external
surface of the thorax and abdomen and dorsum, the region of
the back. These terms are often compounded with each
other and with other terms such as medial or mesial (middle)
and lateral (side) to indicate a position or plane. Just as the
cardinal directions. North, South, East, and West are com-
pounded into Northeast, Northwest, etc. to designate the
direction of points between, so also in anatomy topographical
terms are compounded to designate intermediate positions.
These terms are equally as applicable to the dissected as to the
entire animal. As an example, the kidneys are later oventr ad

WORK PRELIMINARY TO DISSECTION 4 1

to the spinal column, and the tip of the nose is craniad to the
spinal column and craniad to the cranium. Also, curiously
enough, if the tail of the rabfiit is flexed onto its body, the last
caudal vertebra is caudad to the next to the last caudal vertebra
which in turn is craniad to the last caudal vertebra, just as if
the tail were extended straight out from the body.

D. MYOLOGICAL TERMS

Muscles are spoken of as being '^voluntary," the striated or
skeletal muscles; or ''involuntary," the nonstriated pale or
smooth muscles. Involuntary muscles occur chiefly in the
walls of tubes, such as blood vessels and the digestive tract,
while most all of the other muscles are striated. Striated or
skeletal muscles are attached to bones or other muscles by
tendons. The terms ''voluntary" and "involuntary" are
misleading, for all "voluntary" muscles are subject to some
form of involuntary action, such as reflex movements of the
hmbs and automatic, or purely involuntary, acti\dty such as
occurs in the "voluntary" muscles which have to do with
swallowing and those which have to do with respiration.

The origin of a muscle is its more central or fixed or, in case
of muscles of the extremities, the end attached nearest the body,
while the insertion of a muscle is the distal or movable attached
end. However, these terms are more or less arbitrary, for they
are true in point of function only when the origin is fixed.
Thus, if the muscles of the head and neck are contracted so that
the head is fixed, contraction of the basioclavicular muscle (No.
4, p. 49) will draw the shoulder craniad and thus will conform
to the definition of the terms origin and insertion. Contrarily,
if the muscles which attach the shoulder to the body are
contracted in such a way as to fix the shoulder, while the head
is not fixed, then contraction of the basioclavicular muscle
will move the head but not the shoulder. Thus, it is apparent
that these are dogmatic terms, the use of which is intended as a
means of saving time in readily referring to one of two ends of a

42 ANATOMY OF THE RABBIT

muscle and that in order to be used intelligibly there must be
a common agreement on the applications of the two terms. If
the student will recall having seen screen doors closed by means
of a long, coiled spring, or piece of strong elastic (which he will
assume is a muscle), one end of which was attached to the
doorpost and the other to a point on the door near the latch,
he will be able to comprehend the rules underlying the distinc-
tion between origin and insertion of muscles in man and the
rabbit. In this explanation the door post (to which the
hinges of the screen door are fastened) furnishes the fixed, or
proximal attachment for one end of the '^ muscle " (the spring) —
the origin, while the freely moving edge of the door furnishes
the distal or movable attachment for the '' muscle" (the
spring) — the insertion. The term attachment may mean
either origin or insertion, but does not differentiate between
these terms. The free sides, or edges, of a muscle are called
margins or borders and the area between the two margins, the
bulging part, is called the belly of the muscle.

E. THE NAMES OF MUSCLES

The names of muscles are usually derived from the origin,
insertion, situation, direction of fibers, form, or function of
the muscle, and for this reason, the name designates not only
the muscle, but often also suggests its relations and functions.

F. SKINNING THE RABBIT

The skin is a natural protection for the soft tissues, and
since several days will be spent in dissecting the muscles, it is a
good plan to remove the skin from only the region in which the
dissection is being done and to leave it in place on the remaining
regions of the specimen so as to delay exposure of those parts to
active dessication as long as possible. For this reason, it is the
best plan to remove the skin from the various parts of the body
as directed in the following instructions.

WORK PRELIMINARY TO DISSECTION 43

Make a midventral incision through the skin from the larynx
to about one inch of the anus. Starting at a point on this
incision midway between the arms, cut through the skin along
the medial side of the right arm to a point just beyond the
elbow where the forearm is completely encircled by the incision.
Now, beginning at a point on the midventral incision near the
region of the navel make an incision through the skin dorsad
to the vertebral column. Each one of these incisions through
the skin should be as nearly straight as possible and should
be at right angles to the preceeding one. Crooked incisions
will detract from the neatness of the dissection and increase
the difficulties encountered in replacing the reflexed skin at the
close of each laboratory period. It will be necessary to cut
through the subcutaneous muscles. Without making addi-
tional incisions through the skin reflex this delimited portion
of the skin so as to expose the muscles of the right shoulder,
neck, and side of the thorax. The skin of the right hand and
distal two-thirds of the antibrachium will remain, thus forming
a ''glove" protecting the muscles and tendons of the forearm,
wrist, and hand from drying rapidly, while the other three-
quarters of the rabbit will remain unskinned until these regions
are to be dissected. Do not loosen the skin on any other region
of the body at this time, for if left in place it will greatly
retard dessication, and too, a fresh surface is much easier to
dissect than an old, dirty one. Before leaving the laboratory
be certain to apply some of the glycerine — gum mixture to the
skinned areas, to replace the skin, wrap the specimen in muslin
and place it in the receptacle provided for that purpose.

G. SUBCUTANEOUS MUSCLES

The major portion of the two subcutaneous muscles is usually
removed with the skin. On account of the thin structure and
diffuse nature of insertion the subcutaneous muscles are gener-
ally difficult to study. The largest of these muscles is the
cutaneous maximus which arises principally from the latissimus

44 ANATOMY or THE RABBIT

dorsi muscle (No. 2, p. 49) in the axilla, sternum amd linea
alba and inserts in the skin along the dorsolateral body region.
The platysma muscle covers much of the side of the head and
neck. It arises mainly from the ventrum of the head and neck,
whence its fibers are distributed dorsocaudad to the skin. The
platisma is sometimes described as two muscles, the "super-
cervicocutaneous " and the ''cervicofacial" which approximates
the platisma of man. The function of the subcutaneous
muscles is principally to move the skin. In removing the
cutaneous maximus m. it is best to leave it attached to the
distal end of the latissimus dorsi m. until after the limb has
been removed from the body.

H. PREPARING THE SKINNED SURFACE FOR
DISSECTION OF THE MUSCLES

Before beginning the actual dissection of the muscles (Chapter
V) the superficial fascia and fat must be cleared away from the
region to be dissected so that the borders of the muscles can be
accurately distinguished. This is best accomplished with the
thumb nail and forefinger, or with the cartilage knife and
thumb, by means of which the tissue is stripped off the muscles.
Avoid the practice common to many beginners of picking up
the fascia with forceps and then cutting it off, for this invariably
results in nicks being cut out of the muscles instead of a smooth
uniform surface. After the surface has been cleared properly
the border of a muscle will stand out as a line of demarkation
which may be indicated simply as a line of inaction when the
member is manipulated, or as a definite line of tangency
between fibers of a muscle running in one direction and those
of another muscle passing in a different direction. That is,
the fibers of one muscle are all parallel, usually. Of course there
are exceptions to the rule. Often the margin of a muscle is
dehmited by fat lying between it and the next muscle. When
the border of the muscle has been definitely determined probe
under it with the grooved director to determine the depth of

WORK PRELIMINARY TO DISSECTION 45

the muscle, so that an underlying muscle will not be injured;
then, after the muscle is fairly well freed to near its origin and
insertion, pass the grooved director under it and hold the
instrument in such a way that it passes under the middle of the
belly of the muscle and at right angles to the fibers (Fig. i8);
then, running the scissors blade along the groove of the director,
transect the muscle neatly. There are a few exceptions to this
rule for transecting muscles and also to the rule that each
muscle should be transected before it is completely dissected
to its origin and insertion. Muscles properly transected can be
reconstructed for study by simply approximating the two ends
at the transection.

CHAPTER V
MUSCLES OF THE RIGHT SUPERIOR LIMB

Attention should be directed primarily to the anatomy,
relations, and mechanics of muscles and bones in this section.
Their innervation and blood supply will be studied in Chapter
VII, for which this dissected hmb will serve as a guide. A
thorough review of the general anatomy and relations of the
back of the skull, cervical, thoracic, and lumbar vertebrae,
ribs, sternum and bones of the pectoral girdle and limb should
be made at this time and special stress should be placed on
the topography of the scapula, humerus, radius, and ulna.
Although there is a marked difference in the form of these
bones in the rabbit and in man most of the elevations, depres-
sions, and other points of contour are comparable and subserve
similar purposes, such as, the spine of the scapula. Failure to
learn the topography of these bones is certain to result in the
explanations of origin, insertion, relations, and functions of the
muscles being quite unintelUgible to the student.

An attempt has been made in this work to give the main
origin and insertion and principal functions of the muscles in
concrete form for the convenience of ready reference. The
student should deduce the various possible functions of each
muscle from its relations as he dissects it, but he should by all
means avoid committing the descriptions to memory. If he
will remember that a muscle, Uke a piece of elastic, functions
only by contracting — never by extending — he can readily grasp
the mechanical relation between the two attachments (origin
and insertion), the course of the muscle or its tendons and the
function of the muscle. The order of dissection of the muscles
selected in this manual is based upon the availability of the

46

MUSCLES OF THE RIGHT SUPERIOR LIMB

47

muscles and their importance in interpreting the major motions
and locomotion. The more superficial muscles are dissected
first, then transected and the two ends reflected before an
attempt is made to dissect out the next underlying muscle.
Thus, if the student will intelligently follow the consecutive
arrangement for these dissections he will save time.

Fig. i8. — Superficial muscles of shoulder and arm. AD, acromiodeltoid (13);
AT, anterior trapezius (la); B, biceps brachii (20); BC, basioclavicularis (4);
C, costal attachments of external oblique (51); CD, clavodeltoid; CM, cleido-
mastoid; E, external auditory meatus; ECRL, extensor carpi radialis longus (27);
EDC, extensor digitorum communis; ET, ectotriceps (caput laterale, 22a);
FCU, flexor carpi ulnaris (29); GD, grooved director in position for transecting-
AT (la) ; I A, interscapular aponeurosis (often more extensive than is shown here) ;
L, levator scapulae ventralis (3); LDF, lumbodorsal fascia; M, masseter muscle
(63); MT, meditriceps (caput longum); PM, pectoralis minor; PT, posterior
trapezius; S, serratus magnus (10); SM, sternomastoid (7).

A. MUSCLES WHICH ATTACH LIMB TO BODY

(Nos. i-ii, Fig. 18)

I. Trapezius muscles (Fig. i8): Arise continuously from
the occiput along the spinous processes and lumbodorsal fascia ;
to spine and metacromion of scapula. This muscle is sub-

48 ANATOMY OF THE RABBIT

divided, by the interscapular aponeurosis, into cranial, (la) and
caudal portions (ib) which are separated between the scapulae
by a ghstening, wide, thin, tendonous membrane, the inter-
scapular aponeurosis. The trapezius is very thin and wide,
consequently it is very easily, mutilated.

la. Anterior trapezius (acromio-, superior trapezius) m:
Occipital bone, vertebral spines and dorsal ligament of neck and
interscapular aponeurosis. Draws glenoid end of scapula
dorsocraniad. Method: Clear all fat and fascia off the side of
the neck so that the space between the ventral border of the
anterior trapezius m. and the dorsal border of the levator
scapulae ventralis m. (3) will be plainly visible, about midway
between the shoulder joint and the base of the ear. This inter-
muscular space is usually filled with fat and consequently
readily located. Begin at this point to probe under the muscle
with the grooved director. After ha\dng explored this region,
by probing, force the point of the grooved director through the
fascia at a point midway between the first long neural spine
(second thoracic) and the superior angle of the scapula, as shown
in figure 18. With the point of the scissors gliding along in the
groove of the director transect this muscle through its middle
and complete the dissection, but do not try to separate the two
trapezius muscles from each other.

lb. Posterior trapezius (spino-, inferior trapezius) m:
Spinous processes of last six to ten thoracic vertebrae and
lumbodorsal fascia; to dorsal half of spine of scapula. Draws
scapula dorsocaudad. Method: Begin probing by inserting
the grooved director under the cranial margin of this muscle at
the point where the transection of the anterior trapezius m.
ended. The ventral margin of the belly of this muscle is more
or less fused with the belly of the latissimus dorsi m. (2) . Using
the grooved director and scissors transect this muscle from the
point of entrance between the scapulae ventrocaudad and com-
plete the dissection. Do not attempt to separate the proximal
half from the latissimus dorsi, but the distal half must be sepa-
rated from the latissimus dorsi muscle.

MUSCLES OF THE RIGHT SUPERIOR LIMB 49

2. Latissimus dorsi m.: Lumbodorsal fascia mainly; to
proximal end of humerus. Flexes brachium. The tendons of
the latissimus dorsi and those of the cutaneous maximus and
epitrochearis (a thin, superficial m. which inserts in the olecronal
process, Fig. 19) fuse and with the pectoralis minor form the
tendinous bicipital arch, through which the biceps muscle (20)
and principal vessels and nerves of the arm pass. Method:
Insert the grooved director dorsad under the belly of the latissi-
mus dorsi, in the triangle formed by the margins of this and
the pectoral muscles, and probe a considerable area of the
muscle free. Then push the grooved director dorsad through
the post axillary triangle between the posterior trapezius m.
(i^) and the latissimus dorsi. Transect near the vertebral end
of the scapula leaving the proximal portion fused with that of
the posterior trapezius {ih).

3. Levator scapulae ventralis (Ls. major) m.: Basioccipital
bone, dorsad of basioclavicularis m. (4) ; to metacromial process.
Draws shoulder and brachium craniad. Transect. This is a
long slender muscle. It arises with the basioclavicularis m.
(4) and is fused with the anterior trapezius m. (la) the distal
third of its length. This (3) and the next muscle (4) arise under
and ventrad to the cleido- (6) and sternomastoid (7) mm. and
lie nearly parallel to each other.

4. Basioclavicularis : Basiocciput, ventrad of levator scapu-
lae ventralis (3) ; to clavicle. Draws shoulder craniad or may
depress head or extend arm. Transect. This muscle continues
onto the arm as the clavodeltoid (12), and both muscles (4, 12)
form the basiohumeralis.

5. Occipitoscapularis (levator scapulae minor, l.s. dorsalis,
rhomboideus capitis) m.: Supraoccipital region and mastoid
process to medial surface of inferior angle of scapula. Draws
vertebral border of scapula dorsocraniad. Transect. This is a
long ribbon-hke muscle lying immediately ventrad of the
anterior trapezius m. (la) from its origin to the cranial border
of the rhomboideus m. (9), where it passes over the levator

50 ANATOMY OF THE RABBIT

scapulae m. (ii), then between the rhomboideus major and
minor mm. (9) and on to insert into the scapula.

6. Cleidomastoid m.: Mastoid process, fused with occipito-
scapularis (5); to clavicle. Rotates head, or depresses snout
when clavicle is fixed, or may raise sternum when head is fixed.
Transect. This and the next muscle (7) lie parallel, have
similar functions and represent the sternocleidomastoid m. of
man.

7 . Sternomastoid m. : Manubrium sterni ; to mastoid process.
Transect.

8. Pectoral mm.: All of the sternal bones; to superior limb.
Adduct and rotate superior limb. Probe, but do not attempt
to establish the insertions definitely until the clavodeltoid m.
(12) has been transected. Transect each muscle at a different
level or angle. This group of muscles is so loose in texture that
the probe will readily pass through at any point. However,
only three (Hyman) to five (Bensley) separate muscles are
described as comprising the entire group. In origin and in other
ways these muscles do not agree with the pectorals of man.

8a. Pectoralis primus (p. tenuis) m.: Manubrium sterni,
with platysma m. (p. 72) and sternomastoid m. (7); to deltoid
ridge and cranial side of humerus, under clavodeltoid m. (12).
This narrow slip of muscle covers the cranial border of the
pectoraHs major (86). It is easily identified by being very
narrow, superficial, most anterior of the group, and usually more
reddish in color.

8b. Pectoralis major (p. secundus) m.: Manubrium and
first two sternebrae; to proximal two-thirds of craniolateral
side of humerus, with pectoralis primus (8a). Adducts and
rotates superior limb.

8c. Pectoralis minor (p. tertius) m.: Entire ventrolateral
surface of sternum; to proximal third of humerus and fascia
around shoulder joint and clavicle. Adducts superior limb.
This muscle forms the deep portion of the bicipital arch. As
here described it includes the pectoralis quartus of Bensley
(p. 211), and is much the largest of the group.

MUSCLES OF THE RIGHT SUPERIOR LI]VIB 5 1

Sd. Pectoscapularis m.: Manubrium and first three sterne-
brae; to entire length of spine of scapula and craniomedial
surface of vertebral border of scapula. Rotates scapula
craniad. It is firmly, although indirectly, attached to the
clavicle by tendonous fibers. (Cf. method, m. 14.)

9. Rhomboideus m.: Spinous processes of vertebrae from
second cervical to ninth thoracic; to vertebral border of scapula.
Draws vertebral end of scapula toward spinal column. This
muscle has an anterior (rhomboideus minor) and a posterior
part (rhomboideus major) as in man. Transect both parts.

10. Serratus magnus (s. ventralis, s. anterior) m.: Sternal
ends of second to seventh or eighth ribs, by six, (sometimes
seven) fleshy digitations; to inferior angle of scapula, with
rhomboideus major m. (9). Draws vertebral end of scapula
ventrad and, with levator scapulae (11), forms a sort of sHng
which supports most of the weight of the anterior part of the
body on the superior limbs. Transect.

11. Levator scapulae (levator anguli scapulae of man) m.:
Transverse processes of last five cervical vertebrae and first two
ribs, under scalenus muscle; to vertebral border of scapula.
Draws scapula cranioventrad and, with serratus magnus
(10), supports much of the weight of the body. Transect.

Method of removing superior Hmb: The attachments of the
clavicle to the sternum should be severed so that the clavicle is
permanently attached by ligaments to the muscles of the
shoulder joint. Failure to provide this attachment for the
clavicle will result in loss of parts of four muscles (Nos. 4, 5, Sc,
and 12) and of the clavicle itself, unless it has been left attached
to the sternum. The student must remember that the right
superior is the only limb which will be removed from his rabbit
and that this limb must be preserved until the end of the
term.

A check at this time should show that every muscle which
helps to attach the superior limb to the body has been transected
so that this limb is free from the trunk. It is a good plan to
place the limb in its normal position and identify the proximal

52 ANATOMY OF THE RABBIT

and distal ends of all dissected muscles while they are fresh in
mind. The body should be carefully put away so that it will not
dessicate before the other required muscles of the superior limb
have been dissected and mastered.

B. THE FOUR MAJOR FUNCTIONAL GROUPS

Now that the superior limb has been removed from the trunk,
it is clear that its musculature falls into four major functional
groups which are comparable in the superior limb of both rabbit
and man. (i) Muscles which move the pectoral girdle (Nos.
1-5, 6-1 1) . Most of these muscles arise from the axial skeleton,
insert on the pectoral girdle and thus attach the scapula and
clavicle to the trunk. (2) Muscles which move the arm (Nos.
2, 8, 12-20). These muscles arise from the pectoral girdle,
or axial skeleton, and insert on the humerus (or antibrachium,
e.g., biceps brachii m., 20) and control various movements of the
arm at the scapulohumeral articulation (shoulder joint). (3)
Muscles which move the antibrachium. This group is sub-
divided into those muscles which (a) flex (Nos. 20, 21); (b)
extend (No. 22) and (c) rotate (especially in man) the distal
half of the forearm and hand and are divided into two antagonis-
tic groups in man. (i) Pronators, muscles which turn the radial
side of the forearm mediad and the palm caudad, or downward
if the forearm is in an extended position, (ii) Supinators which
do the opposite, that is, turn the palms craniad or up and the
radius laterad, when the Hmb is extended, so that the radius
and ulna lie parallel instead of the radius crossing the ulna as in
(i). (4) Extensors (Nos. 23-28) and flexors (Nos. 29-32) of the
carpals, metacarpals, and digits.

Further dissection and study will show conclusively that the
functions of many individual muscles cannot be readily delim-
ited, for they are modified by the action of other muscles. For
example, the pectorals (8), latissimus dorsi (2) and basiohumer-
ahs (4, 1 2) muscles have their origins on the axial skeleton but
are inserted on the humerus instead of the pectoral girdle.

MUSCLES or THE RIGHT SUPERIOR LIMB 53

These muscles can function in such a fashion as to justify their
being placed in first one and then in the other of functional
groups I and 2 and groups A and C. The biceps brachii m.
(20) is a good example of such a muscle, and there are numerous
other such examples.

C. MUSCLES OF THE SHOULDER JOINT

(Nos. 12-19; Figs. 10-12, 18)

12. Clavodeltoid (cleidohumeralis, clavobrachialis) m.:
Clavicle and cleidohumeral ligament mainly; to craniolateral
border of middle two-thirds of humerus. Draws arm craniad.
This is the continuation of the basioclavicularis m. (4).

13. Acromiodeltoid m.: Acromion and metacromial process;
to deltoid ridge of humerus. Draws humerus caudad and
laterad.

14. Supraspinatus m. : Most of spine and body surfaces of the
supraspinous fossa of scapula, which it fills completely and over-
laps the cranial border of the scapula; to greater tuberosity of
humerus. Draws humerus craniad. Method: Since the distal
end of the pectoscapularis m. (8^) completely envelops the
supraspinatus the pectoscapularis will have to be probed and
transected about at its middle to expose the supraspinatus,
which may be explored by inserting a small probe or stout
dissecting needle under it at the cranial margin of the acromion.
It need not be transected.

15. Infraspinatus m.: Spine and body surfaces of infra-
spinous fossa; to greater tuberosity of humerus. Rotates
humerus. Probe, but do not transect.

16. Teres major m.: Vertebral third of axillary border of
scapula; to craniomedial surface of humerus, distad of greater
tuberosity, with tendon of latissimus dorsi m. (2). Draws
humerus caudad and rotates it mediad.

17. Teres minor m.: Axillary border of scapula and sub-
scapularis m. (18); to humerus with t. major. This muscle
lies between the teres major m. (16) and the infraspinatus m.

54 ANATOMY OF THE R.ABBIT

(15) and the subscapularis m. (18). In man the teres are
antagonistic rotators of the arm, but in the rabbit they are
fused and have a common insertion. Transect both.

18. Subscapularis m.: Entire medial surface of scapula; to
lesser tuberosity of humerus. Draws humerus mediad. Probe
only.

19. Coracobrachialis m.: Coracoid process of scapula; to
craniomedial surface of humerus. Draws humerus mediad.
Do not transect. This muscle is usually short, but it is often
variable in length and point of insertion since it is homologous
with the second or coracoid head of the biceps brachii in man.
(Cf. biceps brachii, 20.)

The student should now have a clear conception of the com-
plicated muscle and tendon, as well as ligament, relations of
diarthrodial joints in general and of a ball-and-socket joint (the
shoulder joint) in particular, so that attention may be centered
on the broader aspects of functional relations of muscles and
bones in the following descriptions of muscles.

D. MUSCLES WHICH MOVE THE FOREARM

(Nos. 20-22; Figs. 18, 19)

20. Biceps brachii (b. flexor cubiti) m.: Cranial border
of glenoid fossa (supraglenoidal tubercle) of scapula; to proximo-
medial surface of radius and ulna. Draws forearm craniad.
Transect. This muscle has various functions besides flexing
the antibrachium. For instance, if the elbow joint is fixed by
antagonistic muscles it draws the limb craniad. Its functions,
though similar, are more varied in man than in rabbit. The
biceps Hes over and inserts with the brachialis m. (21).

21. Brachialis (b. anticus) m.: Lateral, and cranial middle
third of humerus; to radius and ulna w^ith biceps m. (20).
Draws antibrachium craniad. The wide inserting tendons of
the clavodeltoid m. (12) and pectoralis major and minor mm.
(86, 8c) divide this muscle into an anterior and a posterior
portion.

MUSCLES OF THE RIGHT SUPERIOR LIMB

55

Cranial Side

'MSN

22. Triceps brachii (t. extensor cubiti) m.: Scapula and
humerus; to olecronal process of ulna. Extends antibrachium
and thus is antagonistic to the biceps and brachialis muscles
(20, 21).

22^. Caput laterale (ectotriceps) :
Arises from the region of greater tuber-
cle of humerus.

2 2&. Caput longum (meditriceps,
anconeus longus) : Arises from the axil-
lary border of scapula.

22c. Caput mediale (entotriceps,
anconeus medialis, anconeus poster-
ior) : Arises from the dorsal surface of
humerus.

E. MUSCLES WHICH MOVE
THE HAND

(Nos. 23-31; Fig. 20)

There are some ten flexors and exten-
sors of the wrist and hand which arise Fig.iq.— Crosssectionprox-
from the humerus or radius and ulna r! ^1; Whl^u't^l "et

near the elbow, in addition to those brachial a.; BI, biceps brachii;
, . , . r .1 1 1 1 BV, brachial v.; C, clavodel-

which arise from the carpals and meta- toid, inserting end of; cv, ce-
carpals and insert on the phalanges. p^^IJ'^^:;;:^^^' f . epitrochiearis

^ / \ rn';ECT,ectotricepsm.;ENT,

In general the extensors (Nos. 23-27) entotriceps; H, humerus;

J ,-i . , J T ,1 • 1 MET, meditriceps; MN, me-

and their tendons he on the cranial or ^^^^ ^ . ^sn, muscuiospirai
dorsal side of the antibrachium and n.; sr, superficial radial n.;

, . UN, ulnar n.

hand while the flexors (Nos. 28-31) and

their tendons lie on the volar or caudal side. The tendons of
both groups of muscles are held firmly in place at the wrist and
finger joints by bands of tough connective tissue, forming annu-
lar ligaments, through which these tendons ghde freely. In
order to understand the functions and general mechanical rela-
tions of annular ligaments and tendon sheaths, the student
should expose the one on the dorsum of the carpus (Fig. 20, AL)

S6

ANATOMY OF THE RABBIT

FCUM
UN

Volar Side

Fig. 20. — Cross section of proximal third of antibrachium and insertion of
flexors of digits. AL, annular ligament (ligamentvrai carpi dorsale) ; CV, cephalic
vein; ECRL, extensor carpi radialis longus m.; EDC, extensor digitorum com-
munis m.; EDL, extensor digitorum lateralis m.; EIP, extensor indicis et pollicis
m,; EPB, extensor policis brevis; FCR, flexor carpi radialis m.; ECU, flexor
carpi ulnaris m.; FCUM, flexor carpi ulnaris minor m.; FSD, flexor sublimis
digitorum m.; MN, median nerve; P, flexor profundus digitorum m.; PV, palmar
branch of cephalic vein; R, radius; RA, radial a.; RN, radial n.; RV, radial v.;
SRA, superficial radial a.; SRN, superficial radial n.; U, ulna; UA, ulnar a.;
UN, ulnar n.

MUSCLES OF THE RIGHT SUPERIOR LIMB 57

and one or more on the volar side of the digits. This is best
accompKshed after the extensor communis digitorum (23) and
flexor sublimis (29) muscles have been transected so that their
tendons can be manipulated freely through the tendon sheaths.
Method: Remove the skin entirely from the hand and digits
including every hair. The best way to do this is to insert the
grooved director along the medial side of the carpus and pollex,
then cut through the skin mediad. Do the same thing on the
fifth digit and cut through the skin laterad; then carefully
dissect the skin off the back and volar sides of the hand. The
tendons of the extensor muscles of the hand lie just under
the skin, while those of the flexors are better protected. Clear
the remaining superficial fascia off of the back and volar sides
of the hand so as to expose the glistening tendons clearly. The
antibrachial fascia (homologue of crural fascia, p. 63) is a tough
sheet of tendonous tissue which envelops the antibrachium,
dipping between the muscles, especially on the extensor side.
It will have to be removed.

23. Extensor communis digitorum m. : Lateral epicondyle
of humerus and adjacent region of ulna and other fascia; to all
digits except the pollex. Draws hand, especially the digits,
craniad. Method: After the back of the hand has been cleared
of superficial fascia so that the tendons and annular ligaments
are clearly visible pick up the tendons of this muscle just
proximad to the ligamentum carpi dorsale (Fig. 20, AL) with
the forceps and manipulate it, by flexing and extending the
hand, so as to demonstrate the insertion of the various tendons.
Transect, but be careful not to cut the next muscle (24) which
passes along the index tendon and under the belly of the
extensor digitorum communis m. (23).

24. Extensor pollicis et indicis m.: Craniolateral region
of ulna near elbow joint; to pollex and index finger. Extensor
and abductor of pollex. Do not transect. This muscle
respresents and is sometimes separated to form the extensor
longus polhcis and extensor indicis mm. as in man.

58 ANATOMY OF THE RABBIT

25. Extensor digitorum lateralis m.: Lateral epicondyle of
humerus and proximal region of ulna; to fourth and fifth digits.
Extends and abducts these digits. Method: Be careful to
separate this from the next muscle (26) before transecting. It
is essentially the homologue of the extensor digiti quinti
proprius of man.

26. Flexor carpi ulnaris minor m.: Olecronal process and
laterocaudal side of head of radius; to triquetral bone, or
possibly to proximoventral surface of fifth metacarpal. Flexes
and adducts carpus. Do not transect.

27. Extensor carpi radialis longus m.: Medial supracon-
dyloid ridge of humerus; to proximal ends of second and third
metacarpals. Extends digits. Do not transect. The two
tendons of this muscle pass under the tendon of the next (28)
near the distal end of the radius.

28. Extensor pollicis brevis m. : Laterocranial side of distal
half of radius; to first metacarpal. Adducts and extends the
poUex. Do not transect.

29. Flexor carpi ulnaris m.: Superficial head, mediocaudal
side of olecronal process; and deep head, medial epicondyle of
humerus, fused with a head of flexor profundus m. (31) and the
sublimis m. (30) ; to pisiform bone. Flexes carpus. Transect
distad of the two heads. This is the most superficial of the
flexor group and is easily identified before the brachial fascia
has been removed by its inserting into the prominent pisiform
bone.

30. Flexor sublimis digitorum m.: Medial epicondyle of
humerus, with deep head of Nos. 29 and 31;. to all the digits,
except, usually, the pollex. Flexes digits. Method: Probe the
mass of tendons between the pisiform bone and the first meta-
carpal free. The more superficial tendon is that of the subhmis;
the deeper and larger tendon is comprised of the tendons of the
various heads of the flexor profundus (31). The main insertion
of the tendons of this muscle is onto the metacarpophalangeal
joint where a large sheath is formed through which the tendon of
the profundus m. (31) passes.

MUSCLES OF THE RIGHT SUPERIOR LIMB 59

31. Flexor profundus digitorum m.: Three heads from
region of medial epicondyle of humerus and elbow joint and
two from middle third of ulna and radius; to the distal phalanges
of all digits. Do not transect. The tendons of this muscle
perforate those of the subUmis m. (30) at the metacarpophalan-
geal articulations.

32. Flexor carpi radialis m. : Medial epicondyle of humerus;
to volar side of proximal end of third metacarpal. Flexes
carpus. This is a long slender muscle with a long round tendon
which passes along the caudal side of the radius, between the
first metacarpal and os magnum to its insertion on the third
metacarpal. The entire tendon is covered and firmly held in
place by tendonous material. Method: It is a tedious task to
demonstrate the insertion of the tendon of this muscle. How-
ever, it is best accompHshed after the pollicis tendon of the
flexor profundus m. (31) has been severed. Only experience
can suggest the best method of digging this tendon out of its
sheath.

CHAPTER VI
MUSCLES OF THE RIGHT INFERIOR LIMB

Despite the fact that the pelvic girdle and inferior limb are
essentially homologous with the pectoral girdle and superior
limb, the attachment of the two girdles is decidedly different,
for the pelvic girdle is attached to the axial skeleton primarily
by ligaments which allow limited movement. The psoas
major m. (65a) plays a relatively indirect part in attaching the
innominate bone to the vertebrae, for it is essentially related to
the thigh and hip joint. The musculature of the hip joint is
far more complicated than that of the shoulder joint. Among
the more striking differences in the musculature of the hip of
man and rabbit should be mentioned that of the gluteus max-
imus m. (;^6) which is very large in man and forms most of the
bulk of the natis, or buttock; while in the rabbit this muscle is
insignificant in bulk and is placed mainly mediad to the greater
trochanter of the femur. Since the student has already dis-
sected the muscles of the shoulder in considerable detail, and
because of the limited amount of time available for this work,
it is not advisable to follow the more nearly complete outline
employed in Chapter V in the dissection of the muscles of the
inferior Hmb.

Method: Continue the median incision through the skin cau-
dad, passing about half an inch to the right of the genitalia and
anus, to a point laterad of the anus. Also make a cut from
the mid- ventral incision at a point about one inch craniad to the
mons pubis, along the medial side of the limb just well past
the knee; then free the crus at this point by cutting the skin
around the leg so that the distal two-thirds of the leg and foot will
remain covered by intact skin. Reflex the skin of the thigh
dorsolaterad to the mid-dorsal line.

60

MUSCLES OF THE RIGHT INFERIOR LIMB 6 1

A. MUSCLES OF THE THIGH

(Nos. S3-42e; Fig. 21)

33. Biceps femoris (biceps flexor cruris) muscle: The
long or posterior head, ischial tuberosity, caudal and three
sacral vertebrae; the short (caput brevis, smaller, or anterior)
head, first caudal and last three sacral spinous processes,
mainly; to crural fascia. Flexes and abducts cms. The origin
of each is somewhat involved with that of other muscles and
the two heads have a common insertion into the wide crural
fascia, extending over the crus and into the tendon of Achilles.
The biceps femoris is a large muscle, covers more than half the
lateral side of the thigh, and is antagonistic to the quadriceps
m. (42) and tensor fascia latae m. (34).

Method: Remove the mass of fat, including the large lymph
gland, from the pophteal space, insert the fingers and use the
handle of the scalpel or grooved director to force the biceps
femoris m. {3;^^) laterad and the semitendinosus (41) and semi-
membranosus (39) mm. mediad until the sciatic nerve and
tenuismus muscle (34) are located. The tenuissimus m.
(34) will probably be found lying along the caudomedial border
of the biceps femoris. Insert the grooved director craniad
under the biceps and transect it, then the tenuismus (34), but
at different levels to show the instructor that it was not inad-
vertently cut both at one time. Leave the distal end of the
tenuissimus attached with the common insertion of the biceps
femoris.

34. Tenuissimus (tensor fasciae cruris, abductor cruris) m. :
Transverse process of first caudal vertebra, by a long thread-
like tendon, at the caudal border of the gluteus maximus m.
(36) and under the long head of the biceps m. {33) ; to crural
fascia, with tendons of biceps femoris.

35. Tensor fasciae latae (tensor femoris vaginae) m.:
Ventral border of ilium fused with the gluteus medius, and wide
lumbar fascia; to fascia lata and cranial side of femur. Pri-

62

ANATOMY OF THE RABBIT

marily, it is a tensor of the lateral fascia (which is a thin tendon-
ous sheath covering most of the vastus lateraUs m., 42a) but
also helps to extend the leg since it functions with the quadriceps
(42). The craniomedial portion of the tensor m. (35) is usually

Caudal Side

Fig. 21, — Cross section through proximal third of right thigh. ALB, adduc-
tors longus and brevis; AM, adductor magnus; BL, biceps, long head; BS,
biceps, short head; C, crureus m.; F, femur; FL, fascia lata; FA, femoral a.;
FV, femoral v.; G, gracilis m.; R, rectus femoris; S, sciatic n.; SA, sartorius m.;
SM, semimembranosus; ST, semitendinosus; T, tenuissimus m.; TFL, tensor
fasciae latae m.; VI, vastus intermedius m.; VL, vastus lateralis m.; VM, vastus
medialis.

more or less fused with the gluteus medius and vastus lateralis
(42a) muscles. Method: A Y-shaped incision is necessary to
give access to the quadriceps femoris (42) and gluteus maximus
(36) muscles. Make a small opening in the fascia lata just
above the knee, insert the grooved director and, after exploring
the fascia lata, push the grooved director dorsad until it meets

MUSCLES OF THE RIGHT INFERIOR LIMB 63

resistance from the gluteus medius muscle, adjust this instru-
ment to a point about midway of the rectus femoris muscle
(42c), then slit open the fascia lata and the tensor muscle
(35) to the belly of the gluteus medius (which is a large, thick
triangular muscle arising on the ilium and sacrum and inserting
onto the greater trochanter of the femur) . Explore the region
and continue one leg of the Y-shaped incision craniad along the
belly of the gluteus medius and the other leg of the Y caudad
about one inch, but not quite to a point dorsad of the greater
trochanter. The gluteus maximus m. (36) will be mutilated
unless care is used in making the caudal leg of the Y-shaped
incision. Transect over the midcranial border of ^he vastus
lateralis m. (42a).

7^6. Gluteus. maximus m.: Sacrocaudal vertebrae; to lateral
trochanter. The caudal head draws the thigh caudad and lat-
erad in both man and the rabbit, while the cranial head draws
the thigh craniodorsad. The wide, thin cranial head of this
muscle arises with the tensor fasciae latae m. (35) from the
lumbar fascia, and a thin fan-shaped caudal portion, which
lies under the cranial margin of the long head of the biceps
femoris m. (^^) and over the caudal end of the gluteus medius,
and arises from the sacrum and first caudal vertebra. The
gluteus maximus forms most of the buttock in man, notwith-
standing the fact that its origin and insertion are very much as
in the rabbit.

37. Sartorius m.: Inguinal hgament; to patellar ligament
and crural fascia, with the broad tendon of the gracihs muscle.
The sartorius is fused with the cranial border of the distal half of
the gracihs m. {t,S) which it assists in adducting and possibly in
flexing the thigh.

38. Gracilis (adductor gracihs) m.: Ventral surface of
ischiopubal symphysis and ventrum of ischium with fibers of
adductor femoris mm. (40) ; to crural fascia on proximomedial
side of leg. Adducts thigh. This is a thin, wide, subcutaneous
muscle and is the homologue of the epitrochlearis of the superior
limb (p. 55).

64 ANATOMY OF THE RABBIT

39. Semimembranosus m.: Dorsolateral region of ischial
tuberosity (Fig. 14, IT); to proximal end of anterior crest of
tibia. Flexes crus. It has two parts; the superficial one arises
from the general dorsal fascia of the sacrocaudal region and that
covering the origin of the adductor longus (40b) ; to crural fascia
on medial side of leg, anterior crest of tibia and by a large tendon
to the tendon of Achilles. The superficial origin is separated
from the deep by the caudal head of the biceps which passes
between the two parts of this muscle near its origin on the
ischial tuberosity. Transect at a level different from that of the
biceps or gracilis.

40. Adductor femoris mm.: Nearly the whole of the
lateroventral surface of pubis and ischium; to femur and knee.
The three adductors draw the thigh mediad and caudad, but
function principally in propulsion.

40a. Adductor magnus m.: Ventral part of ischial tuber-
osity; to mediodistal end of femur and medial region of knee
over the origin of the medial head of gastrocnemius muscle
(43). Extends the thigh. Do not transect. This muscle is
the most caudad of the adductors. It and the adductor
brevis (40c) are usually considered together and called ''adduc-
tor femoris" or ''adductor magnus et brevis" in man. The
semitendinosus m. (41) is entirely embedded in this muscle.

40b. Adductor longus m.: Ventral ramus of ischium and
caudal portion of symphysis ; to caudal region of distal third of
femur, inserting laterad of the origin of the medial head of the
gastrocnemius m. (43). Do not transect.

40c. Adductor brevis m.: Cranial region of symphysis
pubis and pubis; to caudomedial part of femur, mainly distad of
the lesser trochanter. Do not transect.

41. Semitendinous m.: Region of ischial tuberosity, within
head of adductor magnus (40a); to medial condyle of tibia.
Flexes and adducts leg. Method: Expose this muscle by opening
the medial side of the adductor magnus m. with the grooved direc-
tor, beginning at the insertion tendon of the semitendinosus. Do
not transect either the semitendinosus or the adductor magnus.

MUSCLES OF THE RIGHT INFERIOR LIMB 65

42. Quadriceps femoris m.: Proximal end of femur and
ilium; to tibia, by ligamentum patellae. Extends the leg;
therefore it is comparable to the triceps brachii m. (22). The
quadriceps is composed of five heads, or parts (four in man and
cat) which practically surround the femur and, with the tensor
fascia latae m. (34), form the bulk of the muscular part of the
thigh anterior to the femur.

42a. Vastus lateralis (v. externus) m.: Origin, greater tro-
chanter of femur mainly. It lies along the craniolateral side of
the thigh, under the fascia latae and laterad to the rectus femoris
m. (42b). It is the largest of the quadriceps. Method: Sepa-
rate the vastus from the rectus (42^) by exerting lateromediad
strain with two fingers on the proximocranial border of the
vastus lateralis. Be careful not to transect the rectus femoris
(42b) or the vastus intermedins (426^) with the vastus lateralis.

42b. Rectus femoris m.: Origin, superior anterior spine
and ventral border of ilium mainly. The rectus is a long cylin-
droid muscle which is intimately covered by the cranial border
of the vastus lateralis m. Transect.

42c. Vastus medialis m. : Neck of femur to fascia at knee.
The vastus mediaUs lies caudad to the rectus femoris (42^),
craniad to the femoral artery (18) and laterad to the gracilis
m. (38).

42 J. Vastus intermedius m.: Greater trochanter; to patella.
This triangular muscle lies on the craniolateral side of the femur
and crureus muscle (42^) with the apex of the triangle directed
toward the rectus m. {42b).

426. Crureus m. (second head of vastus intermedius) : Dis-
tal four-fifths of cranial surface of femur; to deep fascia of knee.

B. MUSCLES OF THE CRUS AND FOOT

(Nos. 43-50^; Fig. 22)

43. Gastrocnemius m.: Caput laterale, condyles of lateral
side of tibia and femur; caput mediale, condyle of medial side
of femur and sesamoid bone. Extends foot. This muscle

66

ANATOMY OF THE RABBIT

forms the bulk of the calf of the leg. Tendons of the two heads
fuse together and with tendon fibers of the soleus m. (44) insert
into the end of the os calcis so as to form a tubular sheath
through which the tendon of the plantaris m. (45) glides freely
to insert on the plantar surface of the phalanges. Each head
may be separated into two or more divisions, and a strong
muscle slip of the lateral head, which arises under the peroneal

Cranial Side

5AP

MED

Fig, 22. — Cross section through middle of proximal third of right leg. ATA,
anterior tibial a.; B, biceps femoris m.; CF, crural fascia; CPN, common peroneal
n.; EDL, extensor digitorum longus (49); F, fibula; FDP, flexor digitorum longus
(46) and three peroneals fused; LG, lateral head of gastrocnemius m.; MG,
medial head of gastrocnemius; P, plantaris m.; PA, peroneus longus anterior
(50a); S, semimembranosus m.; SAP, saphenous artery, vein, and nerve; SH,
small head of lateral gastrocnemius m.; SSV, small saphenous vein; T, tibia;
TA, tibialis anterior m.

nerve, is usually present. Method: Separate the two heads
from the plantaris muscle (45) and transect the medial head to
give access to the plantaris and soleus mm. The tendons of
these three muscles form the tendon of Achilles.

44. Soleus m.: Proximolateral side of fibula and lateral
condyle of tibia; to os calcis. A small portion of this muscle is
visible proximad of and between the heads of the gastrocnemius,

MUSCLES OF THE RIGHT INFERIOR LIMB 67

with which it is intimately fused, so that it and the two heads of
the gastrocnemius are sometimes described as one muscle under
the name triceps surae.

45. Plantaris m.: Lateral epi condyle of femur mainly; to
middle phalanges of all the toes. Flexes phalanges and extends
foot. Do not transect. This muscle lies caudad to the soleus
and between the heads of the gastrocnemius. Its tendon, after
passing mediad and then caudad to those of the triceps surae,
passes over the end of the heel (os calcis) and spreading on the
plantar region inserts into the middle phalanges of the digits.
In man it inserts into the os calcis with the tendons of the soleus
and gastrocnemius.

46. Flexor digitorum longus m.: Caudomedial surface of
proximal half of tibia and fibula, mainly; to proximal ends of all
four of the distal phalanges. Flexes phalanges and extends
foot. Probe but do not transect. This muscle lies along the
caudal side of the leg, and its strong tendon passes mediad to
the OS calcis and through a groove on the caudal surface of the
talus (astragulus. Fig. 17) onto the plantar side of the foot where
it separates into four tendons, which perforate the plantaris
tendons before inserting into the distal phalanges. Since the
hallux and first metatarsal have disappeared in the rabbit, the
tendon of the flexor longus hallucis m. joins with the tendons of
the flexor longus digitorum.

47. Tibialis anterior (tibiaHs anticus) m.: Lateral tuber-
osity, condyle, and anterior crest of tibia; to proximomedial end
of second metatarsal. Flexor of foot. Method: Slit the crural
fascia along the caudal margin of the biceps femoris m. then
down the lateral side of the crus to near the external maleolus
of the tibia; flex the crural fascia, with biceps attached, craniad
to give access to this and the next muscles. Begin probing
between the tibia and the muscle just proximad to the transverse
crural ligament. This is a superficial muscle and lies on the
anterolateral side of the tibia. Its tendon passes with those
of the extensor digitorum longus m. (49) under the transverse
crural (tarsal) ligament (which is similar to the annular ligament

68 ANATOMY OF THE RABBIT

of the carpus) to insert on the second metatarsal. Transect,
but do not mutilate the muscle under it.

48. Tibialis posterior (t. posticus) m.: Proximal third of
medial side of tibia; to first two phalanges of second digit,
mainly. Extends foot and second digit. This is a flat, thin
muscle and lies closely along the medial side of the tibia. The
tendon of insertion begins about the middle of the tibia, passes
through a shallow groove in the medial maleolus of the tibia
and under the proximal end of the second metatarsal to its
insertion on the second digit.

49. Extensor digitorum longus m.: Lateral condyle of tibia ;
to middle and distal phalanges of digits. Extends toes and
flexes foot. This muscle is fusiform. Its proximal attachment
is by a single round tendon ; its belly is flat and wide and rapidly
narrows to the tendons which pass through the transverse
crural ligament with the tendon of the anterior tibial m. (47) ;
then passes unaccompanied through the cruciate crural ligament
(on the dorsum of the tarsus) before diverging to insert into
the four digits. Thus, this muscle is remarkably similar to the
extensor digitorum communis m. (23) of the antibrachium.

50. Peroneal mm. : Lateral side of proximal end of tibia and
fibula; to lateral side of foot, mainly. The four peroneal
muscles lie along the lateral side of the tibiofibula, mainly
between the extensor digitorum longus m. (49) and the flexor
digitorum longus m. (46), and their tendons pass through the
peroneal notch (Fig. 16, PN), which lies on the caudal side of
the lateral maleolus of the tibia. The proximal ends of all four
muscles are more or less fused with each other and with the
flexor digitorum longus m. (46). The long anterior peroneal m.
(50a) is the least involved since it is free except for a narrow slip
which passes from its proximal end over the peroneal nerve and
joins the fibers of the flexor digitorum longus m. (46). The
peroneal tendons are held within the grooves through which
they glide by broad tendonous structures each of which is called
a retinaculum peroneum. The one over the peroneal groove is
the superior retinaculum peroneum.

MUSCLES OF THE RIGHT INFERIOR LIMB 69

50a. Peroneus longus anterior m.: Lateral condyle of the
tibia and ligaments of knee; to proximal end of second metatar-
sal. Everts and extends foot. The inserting tendon of this
muscle begins about the middle of the crus, extends along the
lateral side of the tarsus to the proximal end of the fifth metatar-
sal then traverses the foot to its insertion. This muscle lies
under the caudal margin of the anterior tibial m. (47), caudad to
the extensor digitorum longus m. (49) and between it and the
peroneus longus posterior m. (506). Method: To demonstrate
the insertion of this muscle transect the tendons of the plantaris
m. (45) and flexor digitorum longus m. (46) in the plantar
region of the foot, but at different levels; then follow the tendon
across the foot at the tarsometatarsal articulations to the base
of the second metatarsal. Transect near the origin.

5o5. Peroneus longus posterior m.: Lateral condyle of
tibia, fibula and fascia of knee mainly; to proximolateral side of
first phalanx of fifth digit, also attached to fourth digital tendon
of extensor digitorum longus m. (49) dorsad to fifth metatarsal.
Extends and abducts fourth and fifth digits.

50c. Peroneus brevis m.: Lateral condyle and proximal
third of shaft of tibia laterad of the crest; to proximolateral
tuberosity of fifth metatarsal (Fig. 17, PT). Extends fifth
metatarsal. The proximal third of this muscle lies under the
extensor digitorum longus m. (49) .

50 J. Peroneus tertius m.: Fibula mainly; to proximolateral
side of first phalanx of fourth digit. Abducts and extends digit
and helps to flex foot. The proximal part of this muscle is
intimately fused with the plantaris m. (45) and peroneus
longus posterior m. (506).

CHAPTER VII

VEINS, LYMPHATICS, ARTERIES, AND NERVES AND
THEIR RELATIONS, LEFT SUPERIOR LIMB

The student will endeavor to preserve arteries, veins, and
nerves at the expense of the muscles in the work in this and
Chapter VIII. However, the muscles, especially Nos. isod
inclusive, must be dissected out and preserved to such a degree
that they are readily recognized, for the anatomy and functions
of these muscles cannot be mastered until knowledge of their
blood supply and innervation has been added to that of their
morphology and general relations. At this time it is quite
possible and often necessary, to transect the muscles which
have been dissected out in the other limb in unusual places and
in more than one place without mutilating them beyond recogni-
tion and without injuring their principal vessels and nerves.

Since, for the most part, the veins parallel the arteries and
usually take the same name as the corresponding artery, only
the exceptions will be studied in any detail. Thus most of
the work of Chapters VII and VIII will be to trace the arteries
and nerves in order to determine the structures which they
supply. It often happens that students dissect out the arteries,
and even other structures, with no more purpose in mind than a
pick-and-shovel man has while he is digging up a pipe Hne on the
campus. He does not know or care whether the pipe line con-
ducts gas, water, steam, oil, air, or soil, or whether removing
it will inconvenience anyone or not, and if it does, why and how.
Since the function of the arteries is to conduct material neces-
sary for the proper function and even Hfe, of the structures,
the student should learn their relations to the structures
and organs which they subserve. The veins have as important
functions to perform as do the arteries, for they convey the

70

VEINS, LYMPHATICS, ARTERIES, AND NERVES 7 1

waste products away from the cells and carbohydrate and
protein foods from the digestive tract to the liver, thence to the
arterial system. Unfortunately, the injection of veins meets
with mechanical difhculties, in the form of valves, which mark-
edly inhibit studying these vessels. The general plan and
course of the systemic and pulmonary veins is essentially
the same as that of the arteries. Some of striking exceptions
to the rule that veins and arteries usually take parallel courses
and the same name are the azygos (p. loi), cephalic (p. 73),
small saphenous (p. 82), and hepatic portal (p. 107, Fig. 30)
veins. Veins anastomose more freely than do arteries. The
student will get much more information out of his dissections
if he will remember an earlier admonition that the arteries,
veins, and lymphatics constitute the essential transportation
system of the body and as such they convey nutrient materials
to each muscle, bone, or other organ or structure in the body
and waste materials away from each and all of them, and that
the nerves and their specialized structures constitute a system
of communication by means of which the various activities of
muscles, vessels, other structures, and organs in general are
directed and coordinated.

There are two important cautions to bear in mind in dissect-
ing the axillary region: (i) In transecting the sternal ends of the
pectoral muscles do not accidentally cut the axillary vessels or
the branchial plexus. (2) In dissecting the axillary region, and
at all subsequent times, be careful not to break the axial artery
or axial vein. After the pectoral muscles have been transected,
these vessels and the nerves are exposed to any strain which
may be exerted on the superior Hmb. To prepare for the first
incision lay the rabbit on its back with its right side toward the
operator and support it in this position by placing the fingers
of the left hand on its shoulder and neck region in such way that
the pectoral muscles are exposed. The contour of the latero-
ventral skeletal structure of the thorax must be recalled so
that the student will know exactly where the knife must pass

72 ANATOMY OF THE RABBIT

in order to avoid severing the vessels and nerves in the axilla,
as stated in warning i, above.

Method: Beginning at the pectoral region peel the cutaneous
maximus muscle laterad and caudad, transecting it along the
mid-ventral line to the umbilical region, then laterodorsad to
near the mid-dorsal line. The cutaneous maximus should
also be transected from the xiphoid process to the axilla of the
left superior limb. When the cutaneous maximus is lying in its
normal position this incision should begin at the xiphoid process
and pass dorsocraniad to that region which is not covered by
this muscle and lies at the dorsocaudal margin of the axilla.
Its artery, which passes laterad between the pectorals and
latissimus dorsi muscle and a group of lymph glands should
remain in the proximal end of the transected cutaneous maxi-
mus muscle. Remove any remaining fascia and fat and the
platysma muscle (a cutaneous muscle extending from the jaws
and throat to clavicle and sternum) so that the neck, thorax,
and cranial half of the abdomen have the muscles well exposed.
Insert a finger under the caudal margin of the pectoral muscles,
to explore them; then insert the grooved director and transect
all the pectorals, except the cranial portion. The levator
scapulae ventralis m. (3) should be transected later when it
comes convenient to do so, for this muscle limits the operator's
freedom while he is working in the axillary region.

After the pectoral muscles have been transected, the tangent
margins of the pectoraHs major (86) and the pectoralis minor
(8c) are separated and all the pectorals reflected in order to
expose the vessels and nerves in the axilla. Clear the fat and
fascia away from these structures, but be careful not to injure
the trunk or branches of the vessels and nerves. The first of the
axillary structures exposed is the axillary vein, a thin-walled
flaccid vessel partly filled with very dark coagulated blood
(if the veins are not empty or have not been injected) , into which
the basilic and cephalic veins empty. The axillary artery
(i), a thick- walled vessel, which will be filled with injection
mass, lies between the axillary vein and the two most caudal

VEINS, LYMPHATICS, ARTERIES, AND NERVES 73

cords of the brachial plexus (C) which arise from vertebral
nerves T.I, and C.VIII, and C.VII.

A. VEINS AND LYMPHATICS OF THE LEFT SUPERIOR

LIMB

(Fig. 27)

The blood of the superior limb is returned by two venous
systems, the cephalic, or superficial, and the basilic, or deep
veins essentially as in man. The basilic system parallels, with
some modifications, the brachial artery and its branches, but
there is no artery in the arm comparable to the cephahc vein.
These two venous systems are united by anastomosis of a num-
ber of smaller veins, especially in the forearm and hand. The
cephalic empties into the axillary vein, which is merely the
continuation of the brachial, and is known as the subclavian
after entering the body cavity.

The cephalic vein originates in the dorsum of the hand from
digital branches of three interosseous veins which unite on the
mid-dorsum of the metacarpus, between the second and third
metacarpals, and between the skin and tendons of the extensor
digitorum communis m. (23). Thus is formed a subcutaneous
venous arch which is the beginning of the main branch of the
cephahc vein. A fourth interosseous vein from the pollex and
index finger joins the cephahc on the mid-dorsum of the carpus.
A large palmar branch passes along the radial side of the fore-
arm and joins the cephalic in the concavity of the elbow. There
is no typical vena mediana cubiti, connecting the cephalic
and brachial systems at the concavity of the elbow as in man.
Thus, in its subcutaneous course the cephahc vein passes
along the cranial side of the superior limb from the venous arch
to the middle of the humerus, then by a wide spiral over the
lateral surface of the brachium, along the acromiodeltoid
muscle and at the metacromial process passes between the long
and lateral heads of the triceps m., caudad of the humerus, to
join the brachial vein. At this point it receives an anastomos-

74 ANATOMY OF THE RABBIT

ing branch from the postauricular branch of the external jugu-
lar vein. This anastomosing branch often joins the cephahc
vein directly with the external jugular instead of with its
postauricular branch.

The lymphatic system is essentially like that of man, inas-
much as the numerous lymph vessels of the superior limb pass
through several lymph glands, or nodes, before converging to
form a trunk which empties into the thoracic duct near the
subclavian vein. However, the axillary and post axillary
lymph nodes, and possibly the epicondylar node, will be all
of this system the student can find unless he has specially
prepared material.

Since the veins, lymphatics, arteries, and nerves of a region
are described separately, the student will be obliged to keep the
description of each and the structures which they serve in mind
while he is dissecting the arteries and nerves.

B. ARTERIES OF THE LEFT SHOULDER AND ARM

(Nos. i-ii, Fig. 23)

N.B. Before beginning dissection of the arteries, the student
must acquire a working knowledge of the veins (A) and the
nerves (C) of the shoulder and arm regions, otherwise he will
mutilate these structures while dissecting the arteries.

1. Axillary artery: Subclavian; in the course of the trunk
artery which supphes the superior limb, the first rib (Figs. 23,
26, I) mark the distal designation of the subclavian a. and the
beginning of the axillary artery. Thus the axillary is the con-
tinuation of the subclavian and as such is merely that portion
of the main trunk which lies in the axilla.

2. Anterior thoracic (acromio thoracic) a.: Axillary; to
proximal ends of the pectorals, subscapular region and possibly
to the deltoid mm. (There may be two arteries instead or one
or other anomalies.)

3. Long thoracic a.: Axillary, with thoracicodorsalis (4); to
latissimus dorsi and distal ends of pectoral muscles.

VEINS, LYMPHATICS, ARTERIES, AND NERVES 75

Fig. 23. — Left subclavian artery and principal branches. I-V, relations of
digits to interosseous arteries; AA, arch of aorta; AT, anterior thoracic; AC,
anterior cervical; AX, axillary; B, brachial; BB, branch to belly of biceps;
BBB, branch to distal ends of biceps and brachiaiis; BBS, branch to proximal
end of biceps and region of shoulder joint; BE, branch to elbow joint; BM,
branches to medial and lateral heads of triceps; BR, branch to brachiaiis; CA,
cervical axis; I, first rib; ICU, inferior collateral ulnar; IM, internal mammary;
IP, inferior profunda; LT, long (lateral) thoracic; P, profunda; PHC, posterior
humeral circumflex (7); PP, princeps pollicis; R, radial; RR, radial recurrent;
S, subscapularis; SUC, superior ulnar collateral; TA, thoracic aorta; TD, thoraci-
codorsaHs (thoracoacromial); UL, ulnar; UN, ulnar nutrient; UR, ulnar recur-
rent; VA, vertebral; VI, volar interosseous.

76 ANATOMY OF THE RABBIT

4. Thoracicodorsalis a.: Axillary, with long thoracic a.; to
sternal ends of pectorals and clavodeltoid muscles and becomes
superficial.

5. Brachial a.: That portion of the trunk artery extending
from the axilla to the origin of the ulnar and radial arteries is
the brachial.

6. Subscapularis a.: Brachial; to shoulder region. One of
the branches passes through to the teres major, subscapularis,
and another (thoracicodorsalis a., cf. 4) perforates the belly of
the teres major and becoming superficial at the dorsal margin
of the latissimus dorsi m. sends branches to the deltoids and
triceps mm. (posterior circumflex a.); to the subscapular,
latissimus dorsi, trapezius, supra- and infraspinatus muscles
(posterior suprascapular a.) ; to the infraspinatus and latissimus
dorsi mm. (circumflex scapulae a.).

7. Posterior humeral circumflex (postcircumflex) : Dorsal
side of axillary near subscapularis; to shoulder region. The
main branch passes caudad of the neck of the humerus to the
deltoid mm.; branches pass to the coracobrachialis m., medial
region of shoulder joint, and long and lateral heads of triceps m.
This is probably the homologue of the profunda brachii (sup.
profunda a.) of man. Anastomoses and various anomalous
origins are found in the elbow region.

8. Profunda (superior profunda) brachii a.: Brachial; to
latissimus dorsi and triceps mm.

9. Inferior profunda a.: Brachial; to distal end of biceps
brachii.

10. Nutrient a.: Brachial, or inferior ulnar collateral; to
nutrient foramen of humerus.

11. Inferior collateral ulnar (anastomotica magna) a.:
Brachial; to meditriceps and elbow region.

C. NERVES OF THE LEFT SUPERIOR LIMB

(Nos. 1-9)
The brachial plexus (Fig. 24) is formed by fibers from six
spinal nerves (cervicals IV-VIII and thoracic I, hereafter

VEINS, LYMPHATICS, ARTERIES, AND NERVES

77

referred to as CIV, C.V, C.VIII, and T.I). As in man, the
relations of the nerves comprising the plexus are often very
variable and additional fibers from the more craniad cervical and
more caudad thoracic spinal nerves usually enter it. Fibers of
C.V and CIV join the brachial plexus, but most of the branches
of these vertebral nerves pass to the cleidomastoid and other
muscles and integument of the neck. All nerves from the
superior limb communicate with the central nervous system
through this plexus, and most of the nerve trunks supplying the

Fig. 24. — Principal nerves of left brachial plexus. I, first rib; IV-VIII,
cervical spinal nerves; AA, axillary artery; AT, anterior thoracic; AX, axillary;
LAT, long anterior thoracic; M, median; MBC, Wrisberg's n. (6); MC, musculo-
cutaneous; MS, musculospiral ; R, radial; SR, superficial radial; SP, suprascap-
ular; T, branches to triceps (n.8); TI, first thoracic spinal nerve; TD,
thoracodorsal; U, ulnar; VA, vertebral a.

brachium and antibrachium converge with the cord formed by
T.I and C.VIII. This cord is easily recognized since it is the
most caudad of the three great nerve cords in the axillary region
and arises on two sides of the first rib. At least twenty impor-
tant nerves supply the muscles of the superior limb, but all of
those described here supply, in general, the same regions in the
rabbit as in man. Commonly, the larger nerves follow the gen-
eral course of the arteries and are often given the same name as
that of the corresponding artery. The origin, course, and
distribution furnish the necessary information for identifying

78 ANATOMY OF THE RABBIT

the nerves. It is not necessary nor desirable to attempt to find
the dorsal and ventral roots of the spinal nerves which form the
brachial plexus at this time, for this would entail cutting away
portions of the vertebrae, whereas the spinal nerves may be
identified easily and more safely by simply tracing them to
the point of emergence.

Method: Clear away the superficial material in the axilla and
dissect the tissue away from the ventral surface of each nerve
cord with the grooved director and fine-pointed forceps, making
the strokes peripherad, and beginning with the cord formed by
spinal nerves T.I and C.VIII, for T.I passes from caudad of the
first rib to join C.VIII craniad to this landmark. The student
should determine definitely through which of the intervertebral
foramina each spinal nerve of the brachial plexus emerges. The
nerves of the antibrachium and hand are described at this time
merely for convenience; the student should dissect out the
arteries and nerves of this region at the same time.

1. Anterior thoracic nerve: C.VII; to proximal end of
pectoral muscles, entering with the anterior thoracic artery (2).
There are sometimes more than one of these nerves.

2. Long anterior thoracic n.: Fibers from T. I, C.VIII,
and C.VII by two or more nerves; to distal end of the pectorals
and latissimus dorsi. (Intercostals, especially the first, also
send branches to this region.)

3. Suprascapular n.: C.VI, chiefly; to medial part of
supraspinatus and supraglenoid region, pectoral mm. and prob-
ably to the skin on medial surface of arm. This nerve also
sends branches over the cranial border of the scapula to the
supraspinatus m.

4. Axillary (circumflex) n.: C.VII, C.VI; to teres minor,
subscapularis and deltoid muscles, other structures in the region
dorsocaudad to the shoulder joint and lateral integument.
There is an anterior and a posterior branch, similar to that in man.

5. Musculocutaneous n.: C.VII principally; to biceps bra-
chii, coracobrachiaHs, brachialis anticus mm. and integument of
radial side of forearm, very much as in man. It pierces the

VEINS, LYMPHATICS, ARTERIES, AND NERVES 79

coracoid muscle craniad of the posterior humeral circumflex
artery (7) to pass to the lateral side of the arm.

6. Medial brachial cutaneous (lesser internal cutaneous,
Wrisberg's) n.: T.I mainly; to integument and fascia on caudal
side of brachium and proximal third of antibrachium. A long,
slender nerve.

7. Median n.: TI, C.VIII, and C.VII; to middle and radial
flexors of forearm and branches to digits II, III, and IV. This
nerve is easily recognized as the largest craniad of the three
trunks in the brachial region and it accompanies the brachial
and radial arteries to the carpus.

8. Musculospiral n.: T.I, C.VIII, and C.VII mainly; to
triceps m., antibrachium and integument; by two important
medial branches to triceps brachii and perforating the medi-
triceps it gives off a branch, the superficial radial (lateral anti-
brachial cutaneous) n. which accompanies the cephaUc vein
to the dorsum of the hand. The radial nerve passes between
the extensor carpiradialis m. and distal end of humerus, sends
branches to the extensors of the forearm, to other muscles and
passes into the volar surface of the hand.

9. Ulnar n.: T.I and C.VIII; to skin and muscles of fore-
arm and hand; branches go to the elbow region and to several of
the flexors of the forearm. It passes along the medial side of the
arm, between the long and medial heads of the triceps muscle,
distad to the medial epicondyle of the humerus and mediad to
the olecronal process along the ulnar side between the flexor
carpi ulnaris m. (29) and the flexor profundus m. (31) : crossing
under the tendon of the former it passes craniad to the pisiform
bone and into the palm. Usually it is not practical to follow
the distribution of the ulnar, median, and radial nerves to the
digits.

D. ARTERIES OF THE FOREARM AND HAND

(Nos. 12-17; Fig. 23)
About the middle of the proximal third of the radius the bra-
chial artery divides to form the radial and ulnar arteries. The

8o ANATOMY OF THE RABBIT

radial artery courses along the medioproximal third of the
radius, then along the ventral side to the base of the pollex,
thence, as the palmar arch, across the palm, giving off four pal-
mar interosii, which bifurcating send a branch to the adjacent
sides of each two digits, at a point about the middle of the second
ulnar metacarpal where it gives off the fourth palmar inter-
osseous a. which supplies the radial side of the fifth and ulnar
side of the fourth digits. The last important branch of the
radial artery is the princeps policis which passes over the base
of, and to the ulnar and dorsal sides of the pollex.

12. Ulnar a. : Brachial, to flexor mm. and hand. Its general
course, for most of its length, is between the radius and ulna;
however, Bensley (p.. 218) found that it passes along the flexor
carpi ulnaris m. (29) to join the palmar arch on the volar side of
the fifth digit. The ulnar is small and seldom sufficiently well
injected to be followed to the hand.

13. Radial recurrent a.: Radial; to proximal ends of
extensor communis digitorum m., extensor carpi radialis m.
and anastomoses freely with the brachial and radial branches,
but is sometimes very small.

14. Ulnar recurrent a.: Ulnar, as in man; to flexor carpi
radialis, flexor profundus digitorum and other muscles.

15. Volar interosseous a.: Base of ulnar; to interosseous
and carpal regions, passing along the caudal side of the inter-
osseous membrane. It is very small for its length.

16. Nutrient a.: Base of ulnar; through nutrient foramen
into ulna, about three cm. from the semilunar notch.

17. Palmar arch: Radial a.; to digits by four or five pal-
mar interosseous branches. This arch is formed mainly by the
radial, although the ulnar a. (12) and volar interosseous a. (15)
usually contributes to it. It gives off five interosseous branches
to the digits.

CHAPTER VIII

VEINS, LYMPHATICS, ARTERIES, AND NERVES AND
THEIR RELATIONS, LEFT INFERIOR LIMB

The procedure for dissecting the inferior limb is essentially
the same as that for the superior limb. It is a good plan to
study figures 28 and 29 before beginning dissection in order to
get the relations of the trunk veins and artery to the inferior
vena cava (postcava) and aorta. Do not open the abdominal
cavity until work is begun on Chapter XI, or X, as directed
by the instructor.

Method: Cut through the skin from the mid-ventral incision
along the medial side of the thigh and leg to about the middle of
the tibia; then continue the incision around the leg so that the
skin is separated in the middle region in such a way that the
undisturbed skin envelops the distal half of the leg and foot like
a stocking. Without making additional incisions in the skin,
loosen the skin from the proximal half of the leg and thigh and
reflex this free flap dorsad. It probably will be desirable to
continue the median abdominal incision caudad, passing to the
left of genitalia and anus, to the I'oot of the tail. Prepare the
thigh for dissection by removing the superficial fat and fascia
from the medial side and inguinal region.

A. VEINS AND LYMPHATICS OF THE LEFT INFERIOR

LIMB

(Fig. 29)

It is not necessary for the student to study the veins and
lymphatics distad to the proximal third of the crus at this time,
but, because the blood in the veins flows toward the heart, it is

81

82 ANATOMY OF THE RABBIT

impractical to limit the description of these vessels to the proxi-
mal region of the limb. The deep veins should be dissected out
while the arteries of that region are being dissected and studied.

The venous system of the inferior limb resembles that of the
superior in having a superficial and a deep trunk in which many
of the tributaries anastomose. The branches of the deep system
generally parallel the arteries, while the superficial system is
comprised essentially of the great and the small saphenous
veins and their tributaries.

The small saphenous vein (Fig. 29) is not accompanied by
an artery and differs from that of man in being larger than the
great saphenous and in emptying into the internal iliac instead
of into the femoral vein. Thus, the larger vessel, the saphena
parva, of the superficial venous system of the inferior limb of the
rabbit arises as three interdigital veins which converge to form a
subcutaneous venous arch on the mid-dorsum of the proximal
third of the metatarsals, passes over the transverse crural
ligament, diagonally over the crus to the caudal margin of the
biceps femoris muscle and laterad of the semimembranosus, in
which relation it continues and passes over the caudal head of
the biceps to pierce the fascia between the proximal ends of the
two heads of the biceps and continuing craniad until it reaches a
point nearly dorsad of the acetabulum and mediad of the caudal
border of the gluteus maximus m. (36), it passes mediad through
the obturator foramen into the pelvis where it is known as the
internal iliac vein. Important anastomoses with the deep
system occur in the foot, popliteal space, and trunk.

The saphena magna vein, which is much smaller than the
saphena parva, arises mainly on the medial and plantar surfaces
of the foot where it anastomoses with branches from the deep
and the small saphenous veins. The principal branch passes
over the medial maleolus of the tibia and closely parallels the
saphenous artery (24) and saphenous nerve (12) to empty into
the femoral vein.

The lymphatic system of the inferior Hmb is essentially
the same as that of man. The principal lymph glands, or nodes,

VEINS, LYMPHATICS, ARTERIES, AND NERVES 83

are the inguinal group and the large popliteal gland. Practi-
cally all the lymph passes through these glands enroute to the
thoracic duct.

Method: Force an entrance between the biceps femoris m.
{2)^) and semimembranosus m. (as directed in Chap. VI, Method)
and transect the biceps femoris just proximad of the branch of
the sural a. (26) so that the insertion end of the biceps with its
branch of the sural artery will remain intact. Note the artery
(25) supplying, and the mass of fat enclosing, the popliteal
lymph gland. Separate the lateral from the medial head of the
gastrocnemius muscle and transect the lateral head and also
the superficial vein which passes over it in order to gain ready
access to the popliteal artery (25).

B. ARTERIES OF THE THIGH

(Nos. 18-25; Fig. 25)

Read the description of the nerves of the thigh, C, before
beginning dissection of the arteries of this part of the limb,
which are essentially branches of the femoral.

18. Femoral artery: The external ihac artery (Fig. 28, EI)
becomes the femoral after passing out of the abdominal cavity
dorsad to Poupart's (inguinal) ligament, which is the landmark
for distinguishing these two arteries. Note its parallel relation
to the femoral vein and femoral (anterior crural) nerve. Ready
access to the femoral artery is gained by entering at a point on
the middle medial surface of the thigh between the sartorius
(37) and gracilis (38) muscles. Be careful not to injure the
superficial epigastric artery (21). Numerous "rami muscu-
lares" pass from the femoral trunk to various muscles.

19. Pudic (superficial external and deep external' pudic)
aa. : Femoral; to the pubic, or hypogastric and iliac regions of the
abdominal wall, scrotum, in the male, or labia majora, in the
female.

20. Profunda femoris a.: Caudolateral side of femoral; to
proximal portion of thigh, adductores magnus and longus and

84

ANATOMY OF THE RABBIT

other muscles. It is usually the second, occasionally the first,
branch of the femoral after it passes the inguinal ligament;
anastomoses freely and is subject to many variations.

Fig. 25. — Principal branches of the femoral artery. AT, anterior tibial; DI,
dorsal interosseous; FEM, femoral; IG, inferior genicular; IL, inguinal ligament;
LC, lateral circumflex; M, malleolar; P, peroneal; PA, plantar arch; PF, pro-
funda femoris; PG, posterior genicular; PT, posterior tibial; PUD, pudendals;
S, saphenous, cut in two to save space; SG, supreme genicular; SIE, superficial
inferior epigastric; SU, sural; II, III, IV, relation of digits and interosseous
arteries.

21. Epigastric (superficial epigastric) a.: Femoral; to inferior
abdominal wall, anastomoses with a branch of the internal
mammary artery (39).

VEINS, LYMPHATICS, ARTERIES, AND NERVES 85

2 2. Lateral circumflex (lateral femoral circumflex) a.:
Femoral (or profunda, as in man); to sartorius, quadriceps,
region of hip joint, tensor fasciae latae and other muscles;
anastomoses freely.

23. Supreme genicular (genu suprema, highest genicular,
anastomotica magna) a. : Femoral, close to saphenous (24) and
popliteal (25), under sartorius m. at distal end of middle third of
femur; to medial and caudal regions of knee; anastomoses freely
but is rather small in size.

24. Saphenous (saphena magna) a.: Femoral, caudad to,
with or near, supreme genicular (23); to ankle and os calcis
(malleolar a.) and continues as the posterior tibial a. along the
plantar surface of the foot.

25. Popliteal a.: Femoral; by twigs to soleus and plantaris
muscles in popliteal region ; other important branches are given
off; then, passing through the interosseous membrane (between
the tibia and fibula), it gives off the anterior tibial a. (27).

C. NERVES OF THE THIGH, LEG, AND FOOT

(Nos. 11-16)

The lumbosacral plexus is formed by fibers from eight or
more spinal nerves; 4-5 Lumbar (L.IV or V-VII) and 3-4
Sacrals (S.I-IV). Since the body cavity is not to be opened
at this time, it is impractical to trace out this plexus; therefore
the student will be obliged to depend largely upon location,
course, and distribution as criteria for indentifying the nerves of
the inferior limb.

II. Femoral (anterior crural) nerve: Lumbar plexus,
mainly L.V; to abdominal wall, psoas muscles, thigh and integu-
ment. Just before leaving the abdominal cavity, in company
with the femoral artery, it gives off a large branch which divides
into several rami musculares nn. after entering the quadriceps
muscle with branches of the lateral circumflex artery (22).
Several other smaller muscular and cutaneous branches are

86 ANATOMY OF THE RABBIT

given off from the anterior division of the femoral n. into the
thigh.

12. Saphenous (great-, long-, internal saphenous) n.: Con-
tinuation of the posterior division of the femoral ; to medial side
of limb and ankle, primarily cutaneous. This nerve lies along
the craniomedial side of the femoral artery from the inguinal
Hgament to the origin of the saphenous artery (24) which it
follows closely until it is lost in the crural fascia, or medial
region of the tarsus.

13. Sciatic (ischiadicus; great sciatic) n.: Mainly L.VII
and S.I; general cutaneous; sends branches to the muscles
caudad of the femur and passes along the caudal side of the
femur to near the popliteal space where its component halves
separate to form the common peroneal n. (14) and the tibial n.
(15) which send branches to various muscles of the leg, foot,
toes, and integument.

14. Common peroneal (external popliteal, peroneal) n.:
Lateral branch of sciatic; to tibialis anterior and extensor com-
munis digitorum mm., dorsum of foot, skin, and toes.

15. Tibial (internal popliteal) n.: Medial branch of sci-
atic; along the calf under the soleus muscle to sole of foot and
toes; gives off numerous muscular and cutaneous branches. It
is the medial half of the sciatic and mediad of the os calcis it
becomes the posterior tibial.

16. Posterior femoral cutaneous (small sciatic) n.: S.II
and S.III mainly; to skin, adductores and biceps mm. and other
structures in the caudolateral region of the thigh.

D. ARTERIES OF THE LEG AND FOOT

(Nos. 26-29)

The arteries of this region are branches of the popliteal
(25) and the saphenous (24). Method: The remaining skin
should be removed at this time and not even a hair should be
left attached to the base of a toe nail. At the end of the
laboratory period the foot and crus should be wrapped in a small

VEINS, LYMPHATICS, ARTERIES, AND NERVES 87

wet cloth, preferably one which has been saturated with the
glycerin — gum mixture, to prevent dessication.

26. Sural artery: Pophteal; by branches to popKteal
lymph node and fat and to both heads of the biceps femoris;
other branches go to the triceps surae m. (44), one of which
(small saphenous a.) continues along the lateral surface of the
lateral head of the gastrocnemius and tendon of Achilles to the
OS calcis, thence along the lateral and dorsal surface of the foot
and fifth digit and probably joins the plantar arch (29).

27. Anterior tibial a.: Popliteal; to plantaris m. and dor-
sum of foot. Passes from the popliteal region craniad between
the tibia and fibula, along the interosseous membrane and on the
lateral side of the tibia; gives off a branch which passes through
the distal end of the interosseous membrane to the plantaris
m. (45), thence along the tibia and tendons of the anterior
tibial muscle (47), through the transverse crural ligament and
onto the dorsum of the foot. Frequently arteries 27 and 28 are
not injected.

28. Peroneal a.: Anterior tibial, craniad of the inter-
osseous membrane; to toes. This artery passes along the inter-
osseous membrane (visible on lateral side of tibia), gives off a
branch which goes through the distal end of the space between
the tibia and fibula to the plantaris muscle (45), thence along
the tibia and, with the tendons of the anterior tibial muscle,
through the transverse crural ligament onto the dorsum of the
foot where it anastomoses with the dorsal interosseous branch
of the plantar arch.

29. Plantar arch. The saphenous artery, through its con-
tinuation, the posterior tibial, forms the major portion of the
plantar arch, although the peroneal a. (cf. 27), anterior tibial
(27) or small saphenous (cf. 26), any one, or all three, may
contribute to the formation of this arch.

CHAPTER IX

MUSCLES OF RIGHT SIDE OF TRUNK AND HEAD;

SALIVARY, THYROID, AND LYMPH GLANDS

AND VESSELS OF THE HEAD AND NECK

A. EXTERNAL MUSCLES OF THE TRUNK

(Nos. 51-62)

Those muscles which He outside of the body cavity may be
considered in two groups according to generaUzed functions: (i)
Respiratory muscles and (2) Supporting muscles. Most of
these are both supporting and respiratory, such as, those in the
abdominal wall, but certain others are primarily respiratory in
function, such as, the intercostals (56, 57) and serratus posticus
(55) groups, while others are primarily supporting in functions,
such as, the muscles of the back. The student should consider
the possible as well as the obvious functions of each muscle and
of each group of muscles while he is doing the dissection.

The musculature of the abdominal wall is comprised of
muscles 51-54. Method: See that the cutaneous maximus
muscle and all superficial fascia have been removed so that the
fibers of the muscles are clearly visible. Because the abdominal
wall is very thin in the rabbit, it is scarcely worth while for the
student to do more dissection than is necessary to clearly
identify the first three muscles (51-53). The student must
remember that only muscles of the right side of the rabbit will
be dissected, as directed in this chapter. However, it is permis-
sible to dissect the sternothyroid (61) and sternohyoid (62)
muscles on the left side since these will have to be transected in
dissecting the vessels of the neck. Do not open the abdominal
cavity until directed to do so (Chap. X).

88

MUSCLES OF RIGHT SIDE OF TRUNK AND HEAD 89

51. Obliquus externus (o.e. abdominis) muscle: Lumbo-
dorsal fascia, xiphoid process and last ten ribs; to linea alba and
inguinal ligament. Constricts abdomen. Method: Insert the
grooved director through a small incision, made with a sharp
scalpel in the middle of the muscle, between the external and the
internal obhque m. (52) and transect craniad, then reverse the
grooved director and transect caudad. Reflexing the two ends
of the transected muscle will reveal the internal oblique m. (52).

52. Obliquus internus (o.i. abdominis) m.: Last four ribs,
inguinal ligament and lumbar vertebrae; to linea alba, by an
aponeurosis which is involved with the rectus abdominis m.
(54). Compresses abdomen. Transect, to expose the trans-
versalis m. (53).

53. Transversalis abdominis m.: Last seven ribs and apo-
neurosis with internal oblique m. (52) ; to linea alba. Constricts
abdomen. Do not cut through this muscle, for to do so will
open the abdominal cavity.

54. Rectus abdominis m.: Pubis; to sternum and costal
cartilages II- VII. Compresses abdomen. The rectus is closely
associated with the inserting tendonous sheaths (aponeuroses)
of the external and internal obhque mm. (51, 52).

55. Serratus posticus m.: Vertebral spines from the middle
cervicals to lumbars; to last eight ribs. Probably elevates the
first four to six ribs (inspiration) and depresses the others
(expiration) . This muscle is divided into a superior (anterior)
and an inferior (posterior) part in man and in the cat, but in the
rabbit both parts are fused into one continuous broad sheet of
tendon and short muscle belly. The broad aponeurosis from
which it arises is fused with the splenius capitis m. (58) on the
neck and with the lumbodorsal fascia caudad. Method: Do not
injure the tendon of this muscle, but make the transection
through its belly close to the ribs, leaving part of the muscle
attached to its broad tendon.

56. External intercostal mm.: Caudal surface of each of
first eleven ribs; to the cranial surface of the next rib caudad.
Raise the ribs; therefore these are muscles of inspiration. The

90 ANATOMY OF THE RABBIT

course of the fibers is craniodorsad and caudoventrad. Method:
Insert the grooved director under the ventral margin between
and two ribs, near the sternal cartilages (preferably fourth to
eighth ribs) and transect the muscle in order to expose the
internal intercostal mm. (57).

57. Internal intercostal mm. Mediocaudal surface of each
of the first eleven ribs and costal cartilages; to mediocranial
border of each succeeding rib. The function is not clearly
understood, for, as in the externals, it depends upon '^ fixation."
Most probably they raise the ribs. The fibers extend ventro-
craniad and dorsocaudad, thus crossing obliquely under those
of the externals (56). Do not transect.

58. Splenius capitis et colli m.: Ligamentum nachae and
possibly spines of first three thoracic vertebrae; to mastoid
process and base of skull. Turns head sidewise and inclines
face, both muscles acting raise the face. The caudal portion
forms the splenius colli in man. Do not transect.

59. Sacrolumbalis (sacrospinaHs, erector spinae) mm.:Lum-
bodorsal tendon, sacrum, ihum, mammillary processes of last
six lumbar vertebrae ; by seven to nine subdivisions to proximal
portion of ribs and to all the vertebrae caudad to the second
cervical. Thus, including all its parts, this is the largest,
longest, and strongest muscle in the body. It is antagonistic
to the psoas muscles (65) and is divided into three major
divisions each of which is subdivided into three major parts.
Method: Insert the grooved director under the lumbar fascia,
transect and reflex it laterad and mediad so as to expose the
sacrolumbalis group. It is not necessary to transect any
muscles of this group.

59a. Iliocostal (lateral division of erector spinae) mm. : Inserts
into all the ribs.

596. Longissimus dorsi (middle division of erector spinae) m. :
Inserts mainly on transverse and accessory processes of vertebrae
and proximodorsal regions of all but the first two to four ribs.

59c. Spinalis dorsi (medial division of erector spinae)
m.: Spines of first two lumbar to last two or three thoracic

MUSCLES OF RIGHT SIDE OF TRUNK AND HEAD 9 1

vertebrae; to spinous process of the next four or more thoracic
vertebrae.

60. Levatores costarum mm. : Ends of transverse processes
of thoracic vertebrae; caudoventrally to lateral surface, near
angle, of next rib caudad. Elevates the ribs ; therefore functions
in inspiration. Method: To get at these muscles it is necessary
to cut a '' window" about an inch long through the longissimus
m. (596) in the region of the fourth to eighth thoracic vertebrae
and probe the levator m.

61. Sternothyroid (sternothyroideus) m.: Sternum; to
lateral side of thyroid of larynx. A narrow, slip of a muscle.
Transect.

62. Sternohyoid (sternohyoideus) m.: Dorsal surface of
manubrium and first pair of costal cartilages; to greater cornu
of hyoid. Right and left muscles are fused together for most
of their length and thus form a wide ribbon-like muscle which
envelops the ventrolateral surfaces of the trachea from the
sternum to the cranial margin of the thyroid cartilage. At this
point the muscle bifurcates, each limb narrowing to its insertion
onto a greater cornu of the hyoid bone. Do not transect this
muscle.

B. MUSCLES OF THE HEAD

(Nos. 63-64)
Only two muscles of this very difficult region will be required ;
however, the student should spend some time studying the
muscles of mastication in reference books.

63. Masseter muscle: Zygomatic arch mainly; to margin and
lateral side of angle and ramus of mandible. Elevates the
mandible. Note the relations of the parotid duct, p. 92 and
facial nerve, p. 122. Method: Make an incision from the
external auditory meatus cranioventrad through the belly of
the masseter to the mandibular ramus with the cartilage knife.

64. Digastric (digastricus) m.: Occipital bone and mastoid
process ; to ventromedial margin of mandible near the symphysis.
Depresses the mandible. Transect.

92 . ANATOMY OF THE RABBIT

C. GLANDS OF HEAD AND NECK

The glands of this region are of three kinds: Sahvary, lym-
phatic, and ductless.

SALIV^ARY GLANDS

Three pairs of glands comprise the salivary, or "oral diges-
tive" glands.

The parotid is a large, somewhat diffuse gland which lies
ventrad of the ear and immediately caudad of the ascending
ramus of the mandible. Its duct (ductus parotideus parotid-,
Stenno's-, or Stenson's duct) passes craniad over the masseter
muscle (6^) to open into the mouth through the cheek near the
diastema of the mandible.

The submaxillary gland Hes ventrad to the parotid and
caudoventrad to the angle of the mandible. Its duct (ductus
submaxillaris, submaxillary-, or Whartons duct) leaves the
dorsal side of the gland, and accompanied by the duct of the
sublingual gland, passes between the digastric (64) and masseter
(67,) muscles, dorsocraniad along the muscle under the tongue
and enters the mouth through the lateroventral side of the
tongue (frenulum) near the beginning of its anterior third.
The anterior facial branch of the external jugular vein partly
separates the submaxillary from the sublingual gland.

The sublingual gland is about the same size as the submaxil-
lary gland and lies immediately craniad to it and ventrad to the
angle of the jaw. Its duct accompanies that of the submaxillary
gland to the mouth.

Lymph Glands : There are several small, subcutaneous
lymph glands along the neck and throat and between the
mandibular rami. The student should locate some of these
and the two large deep cervicals which he, one on either side
laterad to the common carotid artery (30) and caudad to the
tympanic bulla. This gland is about two cm. long and is usually
stained red by carmine from the injection mass in the common
carotid artery. There are numerous smaller lymph glands in
this region.

MUSCLES OF RIGHT SIDE OF TRUNK AND HEAD 93

Ductless Glands : The available endocrine glands of the
cervical region are limited to the thyroid and parathyroids.

The thyroid gland is the only ductless gland required to be
dissected at this time. This is a large bilobed gland with each
lobe lying on the lateral side of the trachea, just caudad to the
larynx. The two lobes are connected by an isthmus which
passes over the ventral side of the trachea and connects the two
lobes of the thyroid gland at the caudal ends and lies dorsad to
the sternohyoid muscle (62).

The parathyroid glands are four small bodies more or less
imbedded in the medial border, one at either end, of the two
lobes of the thyroid gland. They will probably be quite
invisible except in sectioned tissue.

The pineal body and pituitary gland are described in Chapter
XII, B.

D. VEINS AND ARTERIES OF THE HEAD AND NECK

(Fig. 26, 27)

Method: Clear the skin and subcutaneous muscle (platysma)
away, but do not remove the skin entirely from the head unless
it is found to be absolutely necessary, for this region must be kept
from dessicating until the work in Chapter XII is completed.
The student should locate the large vessels of the neck, on that
side of the neck which was not mutilated by the preparator
when he injected the arterial system, and dissect craniad.

The external jugular vein (Fig. 27, EJ) is readily seen after
the superficial fascia and platysma muscle have been removed.
It receives two important branches from the head, the anterior
facial, which drains the suborbital, maxillary and mandibular
regions and the posterior facial, which drains the temporal,
and occipital regions of the head. The external jugulars are
joined together by an anastomosing branch, the transverse
jugular, which is sometimes nearly as large as either of the
external jugulars. After the external jugular vein has been
exposed, the operator may proceed safely with the dissection.

94 ANATOMY OF THE RABBIT

Method: Transect the sternomastoid (7) and sternothyroid (61)
muscles, if these muscles were dissected on the other side
earlier, but it is not necessary to transect the sternohyoid
muscle (62) since simply pushing it to the right side of the
trachea will give ample working room.

The internal jugular vein, the common carotid artery
(30) and the tenth cranial (pneumogastric or vagus) nerve lie
closely parallel along the trachea. The pneumogastric nerve
may be stained red from dye diffused out of the common carotid
artery.

30. Common carotid artery (Fig. 26): Innominate;
branches to head and neck. The origin of the common carotid
will be studied when the thorax is opened (Chapter X).

31. Internal carotid a.: Common carotid; to internal
structures of cranium. This branch leaves the common carotid
at a point near the base of the skull and passes into the cranium
through the lacerum medium foramen.

32. External carotid, a.: Common carotid; to soft struc-
tures outside of cranium and to bones of skull. The external
and internal carotids anastomose with each other and with
branches of the vertebral a. {^^) within the cranium (Fig. ^^.

CHAPTER X
THE THORAX AND ITS CONTENTS

The body cavity must be opened in a manner which will
destroy the least number of important structures, guard against
dessication of the contents and at the same time permit ready
access to the internal structures. Great care must be exercised
in opening the body cavity to prevent mutilating the thoracic,
or abdominal, viscera. It is also imperative that the wall of the
thorax be excised in a single piece which is left attached to the
abdominal wall, as directed under method. All of the ribs,
except the first, of the left side are to be cut free at their sternal
and vertebral ends and the second rib must be freed from the
first so that this mass, containing the major portion of the
second to twelfth ribs and comprising almost the entire left
thoracic wall, can be flexed onto the abdomen, thus exposing
the thoracic viscera.

Method: (a) Make an incision through the abdominal cavity
near the diaphragm and about 3 cm. to the left of the linea alba,
explore with the finger and then continue the incision craniad
through the margin of the diaphragm and last two true costal
cartilages. Insert the grooved director craniad through this
opening and push its point through the muscles between the
first and second ribs at a point about two cm. laterad to the
sternum and with the scissors transect all the costal cartilages
craniad including the first. It is now possible to insert the
fingers into the thoracic cavity and explore the region for the
next two incisions which will complete the excision of the left
thoracic wall.

{h) Transect the muscles binding the second rib to the first
from the sternal incision (a) to the dorsal margin of the thoracic
cavity, which is determined by digital exploration. (The

95

96 ANATOMY OF THE RABBIT

scalenus muscle passes over the first rib to the cervical
vertebrae.)

(c) The vertebral ends of the ribs will now be transected.
Insert the fingers of the left hand under the ribs and with the
cartilage knife cut through the lateral musculature to the ribs in
a straight line from between the first and second ribs (the first is
later to be broken and left in situ as a land mark) almost even
with the dorsal surface of the thoracic cavity (which is deter-
mined by digital exploration, and lies about even with the costal
border of the iliocostal muscle, 59a) to the caudal margin of the
thirteenth rib, or two cm. farther caudad than this. In com-
pleting this incision it will be necessary to use bone cutters
(preferably heavy scissors type) to cut through the ribs. (A
heavy pair of "Wiss" j'jyi inch shears having blades with two-
inch cutting edges has served the writer for twenty years.)
The second and third ribs are cut first and the others in suc-
cession including the last. After the ribs have been cut it is
necessary to transect the diaphragm so that the section of the
thoracic wall can be flexed onto the abdomen where it will be
entirely out of the operator's way and may be returned to its
original position at the end of the laboratory period.

(d) Beginning at the region of the xiphoid process reflex the
mass of excised ribs and transect the diaphragm leaving about
two cm. of its costal insertion attached to the reflected section
of the thoracic wall. Continue this incision dorsad through the
crus of the diaphragm (Fig. 28, CD) to the aorta. Be certain
to get the form and relations of the diaphragm well in mind,
for besides being an important motor organ of respiration it is
a most important landmark and bears relations to several other
organs and structures.

A. THORACIC VISCERA

The contents of the thoracic cavity should be studied in
situ, that is, as they lie without their position and relations being
disturbed noticeably.

THE THORAX AND ITS CONTENTS 97

Thymus gland: In young, and often in adult rabbits, the
thymus gland, a fatty-appearing pink mass, occupies much of
the sternal wall of the thoracic cavity craniad to the heart and
may extend onto the neck in young, and often in adult rabbits,
while in old adults it is usually small or quite indistinguishable.
Leave the thymus gland loosely attached by its right side until
actual dissection necessitates further dissection or its complete
removal.

Mediastinum : Determine the position, extent, form, and
relations of the mediastinum, with as little cutting as possible.
It is essentially a chambered septum with translucent walls
composed primarily of two layers of serous membrane, the
pleura, which separates the thorax into right and left pulmonary
portions, and a central portion. What important structures
occur in each portion of the thorax?

Pericardium : Note the attachments, structure and relations
of the pericardium and then slit this sac open on the ventral side
to expose the heart.

B. HEART AND GREAT BLOOD VESSELS

(Figs. 26, 27)

Clear the fat, and, if necessary, the thymus gland and other
tissues away in order to expose the heart and great blood
vessels for study.

Heart: Note the form and position of the heart, the thick-
walled ventricles and the collapsed thin-walled auricles, which as
previously stated, usually contain a quantity of blood clot.
The wall of the left ventricle is much firmer than that of the
right, due to the differences in actual thickness which in turn is
correlated with the functions of the two ventricles.

7,7^. Pulmonary artery : Cranioventral end of right ventricle
to lungs. It lies ventrad to the aorta at its origin, but passes
to the left and bifurcating sends one branch over the dorsal sur-
face of the aorta to the right lung and the other over the dorsal
side of the left subclavian vein to the left lung. The pulmonary

98

ANATOMY OF THE RABBIT

artery is attached to the caudal region of the arch of the aorta by
the arterial (Botallo's) ligament which was a functioning
vessel in fetal Hfe and, with the foramen ovale, conducted the

^^ — p

Fig. 26. — Principal branches of thoracic aorta. AC, ascending cervical; B,
innominate; C, coronaries; CA, cervical axis; EC, external carotid; EM, external
maxillary; I, first pair of ribs; IC, intercostals; IM, internal mammary; IN,
internal carotid; IT, inferior thyroid; LCC, left common carotid; LS, left sub-
clavian; P, phrenics; RCC, right common carotid; V, vertebral.

blood from the pulmonary artery to the aorta, thus preventing
the blood from passing to the lungs. At birth this duct and the
foramen ovale normally close, and at this time pulmonary

THE THORAX AND ITS CONTENTS 99

circulation and respiration become established. The walls of
the pulmonary artery are supplied by a branch of the left
coronary artery, and probably also by branches of other
vessels.

34. Aorta: Left ventricle; to entire system. The divisions
of the aorta usually recognized are the arch (arcus aortae),
thoracic, and abdominal aorta. The arch gives off two,
rarely three, important branches, the innominate and the
left subclavian as wxll as some smaller branches.

35. Coronary a.: Aorta, just distad to the right and left
aortic semilunar valves; to the walls of the heart and probably
other structures near the auricles. In general the left coronary
supplies the left and ventral sides of the ventricular portion
of the heart while the right coronary passes along the opposite
region. The coronary arteries and coronary veins comprise the
coronary system. Method: Remove the remaining fat from the
auricles and transect the pulmonary artery near the right ven-
tricle. If the auricles contain an unusual quantity of blood
clot a portion of one or both may have to be removed in order
to gain access to the base of the coronary arteries.

36. Innominate (brachio-cephalic) a.: Arch of aorta; by two
branches (common carotids, 30) to neck and head and one
(right subclavian, cf. a. 37) to the right superior limb. The
left common carotid arises from various points on the innomi-
nate and occasionally from the aortic arch, as in man.

37. Left subclavian a.: Arch of aorta; to left superior
limb principally (cf. right subclavian artery, Fig. 26).

38. Vertebral a.: Subclavian arteries, rarely aortic arch,
commonly near the base of the left subclavian; to cranium via
the vertebrarterial (costo-transverse) foramina (Fig. 5, V). In-
side the skull the two vertebrals flow together to form the basilic
(Fig. 33). Method: Because of the amount of labor involved,
this artery is not often dissected out by the class. Determine
which of the vertebrae it enters.

39. Internal mammary (sternal) a.: Subclavian, near or
with costocervical axis; to sternal, intercostal, phrenic, and

lOO ANATOMY OF THE RABBIT

epigastric regions. Important anastomoses with epigastric,
phrenic, and intercostal arteries occur.

40. Intercostal aa. : Thoracic aorta; to parieties of thorax,
some seven pairs; the first passes between the fifth and sixth
ribs. The first, or anterior, three pairs extend decidedly laterad
and some anastomose with branches of the internal mammary
(39). The next three pairs extend much more nearly directly
laterad before entering the intercostal spaces, while the seventh
pair may loose its identity by being paired, single or branched
and passing dorsad as do the lumbars (46).

41. Phrenic a.: Aorta, usually; to diaphragm. Commonly
two pairs, sometimes additional branches pass from the last
pair of intercostals and other arteries.

C. THE VENAE CAVAE

(Figs. 27, 29)

Roughly speaking that portion of the systemic venous system
lying craniad to the heart comprises the precaval system,
while that portion of the systemic venous system lying caudad
to the heart comprises the postcaval system. Unlike man,
the rabbit has two superior venae cavae, a right and a left, which
converge with each other and the inferior vena cava at the
sinusvenosus of the right auricle.

Vena cava superior (precava; Fig. 27): Confluence of the
jugular and subclavian veins of the left side forms a trunk, the
left precava, which is comparable to the left innominate
(left brachiocephalic) vein in man, but unlike the innominate
of man it empties directly into the sinus of the right auricle
without joining the right vein to form a common trunk (vena
cava superior). The right precava is formed as is the left,
except that near the right auricle it receives the azygos vein.
Thus, the principal paired tributaries of the superior venae
cavae are the subclavian, internal, and external jugulars,
internal mammary (sternal) and supreme intercostal
veins.

THE THORAX AND ITS CONTENTS

lOI

The supreme intercostal veins emerge craniad to the
second rib and empty into the precavae near the heart; the
right emptying craniad to, or with, the azygos vein.

The azygos vein, as its name indicates, is not paired and
drains the parietal and dorsal regions of the thorax. It lies
along the right dorsolateral side of the thoracic aorta and
empties into the right superior vena cava before it enters the
right atrium. Method: This vein is readily seen through an

sic,^

Fig. 27. — Principal veins of the precaval system, dorsal view. Coronaries
are not shown. A, azygos; AT, anterior thoracic; EJ, external jugular; IJ,
internal jugular; IM, internal mammary (sternal); LPC, left precava; LS, left
subclavian; PA, posterior auricular; PC, postcava; PF, posterior facial; RPC,
right precava; RS, right subclavian; SIC, supreme intercostal; SV, sinus venosus;
TJ, transverse jugular.

opening made caudad to the heart by pressing the esophagus
ventrad and the aorta to the left side. Its confluence with
the right precava is readily seen by pushing the heart to the
left. It is often closely associated, sometimes confluent with,
the supreme intercostal vein.

Vena cava inferior (postcava): The postcava is a single
vessel which extending craniad from the confluence of the
common iliac veins passes through the diaphragm about 2
cm. ventrolaterad to the point where the esophagus passes
through it and empties into the sinus of the right atrium of the
heart. It receives no important veins in the thoracic region.

CHAPTER XI
THE ABDOMEN AND ITS CONTENTS

Method: Continue the lateroventral incision through the
abdominal wall to the pelvis. If the abdominal cavity is badly
messed up with extravasated blood or injection mass it will be
necessary to wash this material out with a stream of water.
It is a good plan to attach a piece of rubber tubing to a faucet
and, under the instructor's direction, invert the rabbit over
the sink and wash it out with a fairly strong stream of water.
Warm water, not hot enough to be uncomfortable to the hand,
is better than cold, for it is less conductive to mold forming on
the specimen. Since great care must be exercised to prevent
dislodging the viscera and thus making it impractical to study
the organs in situ it is best, if practical, to postpone washing
out the extravasated material until the abdominal organs
have been identified as directed below. Do not mutilate, or
drastically disturb, the abdominal organs at this time, for they
are to be studied in detail later in connection with the arteries
and with the digestive tract. Especial attention should be
paid to the following organs and their in situ relations at this
time:

Liver: A large reddish-brown organ covering the cranio-
ventral region of the stomach and occupying most of the
concave region of the diaphragm.

Stomach : Gently Hft the caudal margin of the Hver to see
the stomach, which when filled, is a very large sac.

Spleen: A long, narrow, dark-red organ lying along the
laterocaudal margin of the stomach. Note its attachments.

Cecum : The colic portion of the cecum is folded upon itself
three or four times and as a mass of large, thin-walled intestine
it occupies most of the superficial lateral portion of the latero-

THE ABDOMEN AND ITS CONTENTS IO3

ventral part of the right side of the abdominal cavity. The
tip of the cecum, the ''vermiform process," appears as a smooth,
cylindrical, glandular organ, about three inches of which
projects from beneath the medial loop of the colic portion
laterocraniad and just ventrad to a loop of the sacculated colon.

Small intestine : Numerous loops of the small intestine are
visible in various parts of the abdominal cavity.

Urinary bladder: The urinary bladder is a rather large,
usually empty, thin- walled sac which lies against the caudo-
ventral wall of the abdominal cavity. In the female rabbit
this organ may be easily distended with water, by inserting a
pipet into the urinogenital tract, to facilitate identifying and
studying its mesenteric attachments.

Testes : If the rabbit is a male, and has not been castrated,
the testes may happen to be within the body cavity near the
urinary bladder instead of being in the scrotum, for the living
rabbit is able to retract the testes at will.

Kidneys : Gently push the viscera to the right side of the
abdominal Cavity and note the relations of the left kidney
(the right will be studied later) to various other structures. The
left ureter is visible as it lies Hke a large white thread on
the ventral side of the psoas muscle (65) and passes laterad of
the genital, (48) mesiad to the iliolumbar (49) and common iliac
(51) arteries and enter the cervical (dorsal) end of the bladder.

Adrenal (supra-renal) glands : One of these bodies lies
between the cranial border of either kidney and the aorta,
considerably nearer the aorta than the kidney, instead of upon
the kidney as in man (Fig. 29, ARG).

Ovary, tube, and uterus: If the rabbit is a female the
ovary and cranial end of the left uterus will be found attached
to the dorsolateral side of the abdominal cavity about three
cm. caudad to the left kidney and partly enveloped by the
funnel of the Fallopian (uterine) tube, or salpinx. Caudo-
mediad this tube becomes enlarged and is known as the left
uterus (left womb) . The uterus, tube, and ovary are supported
by a mesenteric fold, the broad ligament, the regions of which

I04 ANATOMY OF THE RABBIT

are known by the names of the organs or parts which they
support.

A. ABDOMINAL AORTA AND PRINCIPAL BRANCHES

(Fig. 28)

42. Celiac artery (coeliac axis): Aorta; by branches to
the spleen (43), stomach, duodenum, and pancreas (44) and
Hver (45) . It arises from the abdominal aorta between the
crura of the diaphragm (Fig. 28, CD).

43. Splenic a.: Celiac axis, often close to aorta; to spleen
and pancreas. The celiac passes dorsad of the stomach and
sends important branches into this organ. Lift the stomach
cranioventrad in order to follow this artery.

44. Gastroduodenal a. : Celiac axis at origin of hepatic a. ;
by branches to pyloric end of stomach (right gastroepiploic a.)
duodenum and pancreas (superior pancreaticoduodenalis a.).
The gastroduodenal artery is really a continuation of the
celiac axis of which the hepatic is a branch. At the point where
the hepatic artery arises the larger artery, the celiac, now known
as the gastroduodenal, arises caudolaterad to the hepatic
branch, passes dorsad to the pyloric end of the stomach and
then follows the small intestine until it forms a very important
anastomosis (by the superior pancreaticoduodenalis a.) with
a cranial branch of the superior mesenteric a. (47) which in
turn is called the inferior pancreaticoduodenalis.

45. Hepatic a.: Celiac axis; to liver. Method: Gently
lift the caudal portion of the hver and with the grooved director
carefully dissect dorsad in the lesser curvature of the stomach
between the pyloris and the SpigeHan (caudal) lobe of the Hver
until the hepatic a., which courses along the right side of this
small lobe and ventrad to the hepatic portal vein (p. 107) is
located. Follow the hepatic a. under the stomach toward its
origin.

46. Lumbar aa.: Aorta; to muscles of back; six or more,
usually single, dorsal branches occurring from craniad to or at

THE ABDOMEN AND ITS CONTENTS

105

<i3/'* ^»-%. <y^,

E/ MS p, ^^

Fig. 28.— Principal branches of abdominal aorta. A. adrenolumbalis ; AD,
adrenal; C, celiac axis; CD, crus of diaphragm; CI, common ihac; CY,_ cystic
and uterine branch of II; D, diaphragm, aortic relations of; E, superhcial epi-
gastric; EI, external iliac; F, femoral; GA, gastric; G, genital; H, hepatic; ii,
internal iliac; IL, iliolumbar; IM, inferior mesenteric; L, lumbars; LI, large
intestinal division of SM; MS, middle sacral; P, profunda femons; R, renal; b,
small intestinal branches of SM; SM, superior mesenteric.

I06 ANATOMY OF THE RABBIT

the diaphragm to the caudal end of the aorta. The last one,
which arises from the aorta just above its bifurcation to form
the common iliacs"(52), is the middle sacral which passes along
the ventral side of the caudal vertebrae.

47. Superior mesenteric a.: Aorta; to small intestine,
cecum and colon, except last 15-25 cm., which region is supplied
by the inferior mesenteric (51); largest of the branches of the
abdominal aorta; anastomoses freely. Nearly half the blood it
carries flows to the large, and the other half to the small intes-
tines (Fig. 28 LI, S).

48. Renal a.: Aorta; to kidney. Anomalies of origin are
common to these arteries. The right commonly emerges
craniad to the left, and both often bifurcate before entering the
kidney.

49. Adrenolumbalis a.: Renal, aorta, or rarely phrenic
arteries; to adrenal (supra-renal) glands and abdominal wall
and fat craniad to the kidneys; often anastomoses with branches
of the iliolumbars (53).

50. Genital a.: Aorta, most any place between the renals
and inferior mesenteric; to ovaries (ovarian, utero-ovarian
artery) or to testes (internal spermatic arteries).

51. Inferior mesenteric a.: Aorta; chiefly to the last six
inches of the colon. Throughout most of its length it parallels
the inferior mesenteric branch of the hepatic portal vein.

52. Common iliac a.: Aorta; by branches to inferior limb
(external iliac a.), abdominal wall (epigastric a.), pelvis and
pelvic viscera (internal iliac or hypogastric, and median sacral
aa.), urinary bladder and uterus (cystic a.), testes or labia
(internal pudic a.) and other parts. The bifurcation of the
abdominal aorta forms the common iliacs and marks the
caudal end of the aorta.

53. Iliolumbar a.: Common iliacs, or aorta; to lateral
abdominal walls; often anastomosing with adrenolumbalis a.
(49). Occasionally there will be a pair from the aorta in
addition to the normal pair.

THE ABDOMEN AND ITS CONTENTS 107

B. POSTCAVA

(Vena cava inferior, Figs. 27, 29)

The postcava arises principally by the confluence of the
internal- and external iliacs, renal, and hepatic veins.
Its principal branches are essentially as in the abdominal aorta ;
however, the hepatic veins are vastly larger than the hepatic
artery, and there are no systemic venous branches to correspond
to the celiac (42) and superior mesenteric (47) arteries. The
blood carried to the portal organs by the branches of these
two arteries (42, 47) is collected by the hepatic portal system
and by this vein conveyed to the liver.

C. HEPATIC PORTAL SYSTEM

The hepatic portal vein (portal vein; Figs. 30, 31) and its
tributaries and hepatic branches (Fig. 31) comprise the hepatic
portal system. This venous system drains the portal organs
(the small intestine, large intestine, stomach, spleen, and
pancreas) and is the only instance in the rabbit, or man, in
which a vein arises by capillaries and ends in capillaries. This
arrangement makes it possible for the portal vein to convey the
digested food materials, except fats (which are conveyed by
the lymphatic system directly to the precaval system, in all
mammals) to the liver. After a sojourn in the liver, most of
the carbohydrates and proteins undergo a chemical change.
The liver receives the major portion of its blood from the
hepatic portal vein and the remainder from the hepatic artery
(45). The student should be certain to get the hepatic portal
system well in mind, for its physiological aspects are exceedingly
important.

Method: Further study of the hepatic portal vein should be
delayed until the stomach has been studied, p. 112. It is
usually possible to inject a considerable part of the hepatic
portal vein, especially that in the mesentery of the small
intestine, in a preserved rabbit with the starch mixture men-

io8

ANATOMY OF THE RABBIT

Fig. 29. — Principal branches of postcava and relations of small saphenous
and iliac veins, ventral view. AD, adrenolumbalis v.; AM, from origin of
adductor magnus m.; ARG, adrenal glands (right lies under postcava) ; AV, from
anus and side of vagina; B, from bladder; C, branch from tail and integument;
CC, from tail; CU, cutaneous branch; EI, external iHac; F, femoral; G, genital;
GA, genital v., male type; GE, from gluteus medius, etc.; GM, from gluteus
medius, g. maximus, and biceps; IG, inferior gluteal; IL, iliolumbar; INL,
inguinal ligament; K, kidney; MS, middle sacral (caudal); O, ovarian branch of
genital; R, renal v.; RK, right kidney; SO, subcutaneous branches; SIE, super-
ficial inferior epigastric; SS, small saphenous v.; U, ureter, left; UT, from uterus;
V, from vagina; VAV, from ventrum of anus and dorsum of vagina; VLV, ventro-
laterum of vagina, superficial; VR, from vagina and rectum.

THE ABDOMEN AND ITS CONTENTS

109

tioned on page 4 through the superior mesenteric vein,
which can be found readily in the mesentery of the small
intestine (Fig. 30, Intestinal). A hypodermic syringe, prefer-

Post Duodenum

Small Intestine

Fig. 30.

-Distribution of the hepatic portal vein, ventral view.
H. G. Rodeck.)

(Drawn by

ably a ten to twenty cc. Luer type, with a large needle is
satisfactory for this purpose. A ligature (a piece of wrapping
twine will do) must be put around the vein a short distance
on either side of the needle and tied before the needle is with-

no

ANATOMY OF THE RABBIT

Fig. 31. — Hepatic branches of hepatic and portal veins. (Prepared and
drawn by W. C. Denson.) C, cystic duct; CL, caudate lobe of liver; CV, cystic
vein; GS, gastrosplenic; IC, ileocolic; IM, inferior mesenteric; IPD, inferior
pancreaticoduodenal; LAL, left anterior lobe; LPL, left posterior lobe; PCV,
postcava; PV, portal vein; RAL, right anterior lobe; RPL, right posterior lobe:
SMi, main branch of superior mesenteric vein.

THE ABDOMEN AND ITS CONTENTS m

drawn, to prevent loss of the injected mass. The walls of the
portal vein appear to become thinner as it nears the liver,
consequently it is most often ruptured near the liver when the
mass is injected under too much pressure. The hepatic portal
vein courses along the right side of the Spigelhan (caudate)
lobe of the liver dorsad of the hepatic artery (45) before entering
the liver at the transverse fissure.

Diaphragm (Fig. 28) : Note the position, form relations,
structure and functions of this organ. Its tw^o crura straddle
the aorta and become tendonous before finally inserting dorsad of
the abdominal aorta near the origin of the fourth lumbar artery.

D. THE DIGESTIVE SYSTEM

The digestive system includes the digestive tract and the
digestive glands.

Digestive Tract : The mouth is the cephalic portion of the
digestive tract and extends from the lips to the pharynx.
Method: Access to the oral cavity is gained by loosening one of
the mandibular rami, by disarticulating the symphysis mandib-
ulae and the articulation, or by cutting off the coronoid
process and through the symphysis (Fig. 3) . With the cartilage
knife loosen the lateroventral side of the oral wall from the
mandibular symphysis well into the esophagus; then evert
the floor of the mouth laterad, with the tongue attached to the
intact mandibular ramus.

The teeth are of two kinds according to function: Cutters,
4 above and 2 below, and grinders, 12 above and 10 below,
making a total of twenty-eight. The location and numerical
distribution of these teeth, that is, the number of incisors,
canines, premolars, and molars are indicated by a dental
formula :

Rabbit I. ^.C.^.PM.f^,M.ff 28

I- 1 0-0 2-2 7,-2,

Man I. — , C. — ' PM. ^, M. ^ 32

2-2 i-i 2-2 2>-?>

112 ANATOMY OF THE RABBIT

The region between the teeth and the cheeks is the vestibule
(vestibulum oris). Note the hairy surface on the medial side
of the cheeks. Does this occur in man? With what is it
correlated?

The tongue is a large muscular organ attached to the hyoid
apparatus and bears numerous taste buds. The large taste
bud on either side and near the base of the tongue represents
the circumvalate papillae of man.

The pharynx is that portion of the alimentary tract into
which the mouth and two choanae (posterior nares), with two'
Eustachian tubes, empty and from which the esophagus and
glottis, or trachea proceed.

The esophagus connects the pharynx and mouth with the
stomach and lies dorsad of the trachea, that is, between the
spinal column and the trachea. Thus, food and drink pass over
the glottis during the process of swallowing, and are prevented
from passing into the trachea by a flap-like structure, the
epiglottis, which fits over the constricted glottis. The
posterior nares enter the pharynx dorsocraniad of the glottis.

The two tonsils are tubular and each is readily seen as a
thin glandular, flap-shaped structure surrounding a depression,
which is often mistaken for the Eustachian tube.

The two Eustachian (auditory) tubes do not empty into the
pharynx directly, as in man, but into the posterior nares about
two cm. craniad to the tonsils. Method: SHt through the soft
palate into the choanae craniad to a point near the hard palate
to find the Eustachian tubes.

The stomach lies in an obHque transverse position with the
greater curvature directed ventrolaterad and the pyloric end
dorsolaterad and to the right. Turn the abdominal viscera to
the left side of the rabbit and study the form and relations
of the stomach and different portions of the intestines and the
various relations of these organs. It is not necessary to
remove either the liver or the stomach at this time in order to
get at the latter. Further study of the systemic and hepatic
portal vessels should be made at this time (see Method, p. 107),

THE ABDOMEN AND ITS CONTENTS II3

but very little dissection should be done on any of the portions
of the intestine or related organs until that organ, or part, is
to be studied specifically, as later outlined.

The duodenum is the first part of the small intestine and its
ventral side is usually the outer or free edge of the compressed
intestine, when the stomach is in normal position. Turn the
stomach to the left side of the abdominal cavity, and beginning
at a point about six cm. from the pyloric end of the stomach
open the duodenum along the ventral or free side (as was
determined above) to the pyloric end of the stomach. Scrape
out the chyme with the blade or rounded end of the cartilage
knife so that a relatively large papilla, located about two cm.
from the pyloric valve, is plainly visible. This papilla is the
mouth of the common bile duct. Determine this by probing it
with the seeker. Note the plush-like lining of the intestine,
which is composed of the villi.

The small intestine is comprised of the jejunum, which is
said to have the more vascular and consequently thicker wall
of the two, and the ileum (cf. ilium. Fig. 14, ILI). The
jejunum and ileum comprise the mesenterial section of the small
intestine.

The cecum is very large in the rabbit. The outer loop of the
large intestine, as the intestines lie in situ, covers the dilated
end of the ileum, the sacculus rotundus, which forms a
vestibule before the ileocecal (ileocolic) valve. This valve
marks the caudal end of the ileac portion of the small intestine
and the beginning of the cecum and of the colon. That
portion of the intestine which continues from this valve to
end bhndly in a thick-walled vermiform process is the cecum,
while the colon is that portion of the intestine which becomes
saculated several inches from the ileocecal valve and continues
on to form the rectum and anus. Make incisions into the
various parts of the intestines in order to study the thickness
and character of the walls and other structures and pecuHarities.
In every instance (e.g., duodenum, sacculus rotundus), the
incision should be longitudinal and along the free margin of the

114 ANATOMY OF THE RABBIT

intestine. The pelvic viscera, which includes the lower
rectum and anus and a portion of the urinogenital system, will
be observed in connection with dissection of the urinogenital
system (p. 115).

Liver (Fig. 31): Note the attachments and relations of the
liver, the number and arrangement of the lobes, the gall bladder,
hepatic, cystic, and common bile ducts.

Pancreas : In man and the cat the pancreas is well formed,
but in the rabbit it is diffused throughout much of the mesentery
between the spleen and duodenum. Its duct is very difhcult
to find. In addition to its digestive functions the pancreas
has an endocrine function. There are structures in it, called
islands of Langerhans, which elaborate insulin. Hypofunction
of this part of the pancreas probably produces a form of
diabetes.

Salivary glands : The anatomy of the salivary glands was
studied in Chapter IX, C, but may be profitably reviewed at
this time.

Gastric glands : The stomach may be entirely freed from the
mesentery, duodenum (ligate and transect the duodenum
between the orifice of the common bile duct and pyloris) , and
esophagus, slit open and washed out so that the digestive glands
may be seen in the walls.

The intestines should be removed and studied. Method:
Transect the colon just craniad of the inferior mesenteric artery
(51), leaving the last three to six inches of the large intestine
in place. This study should include the length, size, and form
of the esophagus, small intestine, cecum and appendix, and
entire large intestine. How do these lengths compare with
those of man?

E. THE ENDOCRINE SYSTEM

The endocrine organs are frequently spoken of as the chemical
regulators of the body. The student has already dissected
out the more readiy accessible endocrine, or ductless glands;

THE ABDOMEN AND ITS CONTENTS II5

therefore only a summarized list of the more common of these
glands will be given here.

Pineal body (in cranium), p. 126, Fig. 32.

Pituitary gland or hypophysis cerebri (in cranium), p. 126,

Fig. 33' ^

Thyroid gland, p. 93.

Parathyroid glands, p. 93.

Thymus gland, p. 97.

Islands of Langerhans (in pancreas), p. 114.

Suprarenal glands (adrenal bodies), p. 103, Fig. 29, ARG.

Gonads (ovaries, p. 103 or testes, p. 103).

Prostate gland, p. 118.

F. THE URINOGENITAL SYSTEM

In medical parlance this is frequently spoken of as the G. U.
(genito-urinary) system, and as these terms indicate, it com-
prises the urinary and reproductive systems.

The urinary bladder lies craniad to the mons pubis. Note
the mesenteric attachments and its in situ relations. Extend
the bladder ventrad and note the ureters which are attached
to its craniodorsal (cervical) end and proceed from the kidneys.

Observe the anus and external genitalia. Probe where
advantageous and explore the entire region; then carefully
loosen the skin up to these parts, but not into them. Remove
the fat and superficial fascia from the inguinal and pubic
regions and, using the cartilage knife, carefully continue the
abdominal incision caudad through the symphysis pubis and
symphysis ischii, but be careful not to mutilate the structures
within the pelvis. Gentle, firm pressure dorsad on the two
thighs should now spread the innominate bones apart easily
so that ready access to the pelvic viscera may be had through
the incised symphysis of the innominate bones. Loosen the
pelvic viscera from the sides of the pelvis, using the grooved
director for most of this work and the scalpel only when

Il6 ANATOMY OF THE RABBIT

absolutely necessary, as in severing the crura penis or crura
clitoridis from its attachment to the caudal part of the ischia.
Directions for dissecting the male are given on page 117.

FEMALE RABBIT

The cranial end of the vagina Hes against the craniodorsal
end of the urinary bladder between the two ureters, and ventrad
of the colon. The two uteri (single in man, and having a
single OS uteri) extend from the cranial end of the vagina
laterocraniad to within three cm. of the kidneys, where the
oviduct (uterine-, Fallopian tube) ends in a fimbriated funnel
which, assisted by a membranous hood, effectively envelops the
ovary during life, so that it is almost impossible for any
of the ova to escape into the coelom during passage from the
ovary to the funnel and oviduct. The ovary, oviduct, and
uterus are suspended from the dorsum of the abdominal cavity
by the mesovarium, mesosalpinx, and mesometrium
respectively. These three mesenteries, composed mainly of
continuous folds of the peritoneum, comprise the broad liga-
ment. Note the blood supply of the ovaries, uterus, and
vagina.

Method: Cut the anus free from the caudal vertebrae and
continuing craniad loosen the entire mass of pelvic viscera and
evert it ventrocraniad through the incised ischial and pubic
symphyses into the abdominal cavity, so that the rectum and
vagina may be easily slit open and examined. Note the
strong bands of muscles forming the anal valves, the sphincter
ani.

The urethra is that portion of the urinary canal between
the bladder and the vaginal orifice, while the continuation
of the urinary canal caudad to the exterior forms the urino-
genital (vestibulum, genitourinary) sinus, which conducts
products of both the urinary and the reproductive systems to
the exterior. . Insert the grooved director into the genitourinary
sinus and on into the bladder; then, with the scissors, sht the
genitourinary sinus and urethra along the right side from the

THE ABDOMEN AND ITS CONTENTS II7

exterior nearly to the bladder. This will expose a small
opening, the vaginal orifice, situated in the mid-dorsal wall of
the urinogenital sinus and about one cm. caudad to the bladder.
Probe through this opening with the seeker or grooved director.

MALE RABBIT

The method of dissecting the pelvic viscera of the male is
essentially the same as that for dissecting the female rabbit.
It is best to delay excising the pelvic viscera until a brief
examination of the external genitalia has been made (see Penis,
Method) .

The scrotum should be examined externally and by inserting
the grooved director from the abdominal cavity through the
inguinal canal into it; then slit the inguinal canal and the
scrotum open from the abdominal cavity to its caudal end.
Notice that the scrotum is essentially a continuation of the
abdominal cavity and that its muscular wall (cremaster muscle)
is covered by a continuation of the peritoneum. This wide,
persistent inguinal canal makes it possible for the rabbit to
withdraw the testes into the abdominal cavity at will. The
caudal end of the testis is attached to the cremaster muscle.
There are two systems of blood supply to the testis; the genital
artery (50) and vein, which make contact with the cranial
end, and branches of the iliac vessels, with the caudal end.
The branches from the iliac vessels parallel the vas deferens
(spermatic duct) to the extreme caudal end of the testis.
Intra-, and inter-anastomoses are common between the arteries
of the two systems as well as between the veins.

The penis is usually partly everted in embalmed rabbits.
Method: Make an incision through the skin to the pubic sym-
physis and continue this incision caudad passing between the
scrotal sacs and on either side of the penis and anus to the dorsal
side of the anus. The scrotal sacs may be freed from the
limbs at this time. Cut through the symphysis and evert
the anus and penis into the abdominal cavity, as directed for
the female, p. 116. Note the muscular attachment and blood

Il8 ANATOMY OF THE RABBIT

supply of the penis. After the rectum has been studied, it may
be probed with the grooved director and sHt open. Note the
ridges (rugae) in its Hning and the sphincter ani muscle.

Work out the relations of the ureters, urinary bladder,
seminal ducts (vasa deferentia, singular number, vas deferens)
urethra, prostate gland, and seminal vesicles. Method:
Beginning on the ventral side at the neck of the bladder
carefully separate the urethra from the seminal ducts, the
seminal ducts from the large somewhat bilobed seminal vesicle
and the vesicle and prostate gland, from the rectum about
three cm., or more, caudad. Slit the prostate gland and seminal
vesicle along the dorsolateral side in order to see the size and
urethral orifice of the seminal vesicle, the points of entrance
of the seminal ducts into this vesicle, which form two papillae
near the orifice, and the relations of the prostate gland. The
seminal vesicle is a large sac in which spermatozoa are almost
continuously stored and from which the spermatozoa are
normally forcefully ejected (ejaculated) during copulation.
The seminal vesicle occurs only in the male in any species and
must not be confused with the sperm receptacle (spermatheca)
which is a structure found in the female of many animals, such
as bees, flies, certain hermaphroditic snails and other forms,
and receives the spermatozoa from the male during copulation.
Separate the urethra from the rectum caudad to the anus.

Cowper's (bulbourethral) gland is bilobed and lies on the
dorsolateral sides of the urethra just caudad to the orifice of the
seminal vesicle. The function of the bulbourethral gland
appears to be only that of furnishing a lubricating fluid to
facihtate copulation; however, some physiologists maintain
that its chief function is to keep the seminal fluid alkaline. The
prostate gland contributes its secretions to the seminal fluid and
probably has an endocrine function.

The rectum should be slit open in order to observe the
longitudinal rugae and the circular muscles which form the
sphincter ani valve. The large anal glands lie on either side
of the anus.

THE .\BDOMEN AND ITS CONTENTS IIQ

65. Psoas muscles: Ribs, centra, and transverse processes
of vertebrae from the eighth to the last sacral; to innominate
bone and femur. These muscles flex the back and are essen-
tially antagonistic to the sacrolumbalis group (59). They
form the mass of muscle lying on either side of the abdominal
aorta.

6$a. Psoas major m.: Eighth thoracic to first sacral ver-
tebrae; to lesser trochanter of femur. Flexes the back and
flexes and rotates thigh. This is a wide flat muscle. Probe
but do not transect.

65^. Psoas minor (p. parvus) m.iLast three or four lumbar
and sacral vertebrae; to pubis. Flexes back. This muscle
inserts by a narrow tendon into the ihopectineal eminence
(Fig. 14, IE) on the cranial border of the pubis. It is a small
muscle and lies mediad to the psoas major.

CHAPTER XII

THE NERVOUS SYSTEM

The nervous system of the rabbit comprises three divisions:
The central nervous system (brain and spinal cord), the

Cerebral
Hemisph

ere

•Olfactory
Lobe

•Sagittal

Fissure

.Pineal Body

jbcllum-

..^1

^^

yi ^

Flocculus l\|\

^ ^

^•/e: Ventricle

yV

%

r/

Medulla-*'* \

1

["•/•Clava

Li

Cervical j
Nerve ^

-U

•Spinal Cord
s^ H.G.R.

Fig. 32.— Bra

in of

rab

bit, dorsal view

peripheral nervous system (cranial and spinal nerves) and the
autonomic nervous system (sympathetic, nerves controlling

129

THE NERVOUS SYSTEM

121

involuntary muscles, arterioles, and secreting glands). The
peripheral nerves which supply the limbs (brachial and lumbo-
sacral plexuses) were studied in section VII and VIII.

Method: Remove the entire skin from the head, in order to
make a general survey of the more superficial structures of the
head and neck region before beginning the introductory work
on the cranial nerves and brain.

A. CRANIAL NERVES

(Fig. 2>Z)
The rabbit has twelve pairs of cranial nerves, and the student
should familiarize himself with the various names, superficial

The Cranial Nerves
(A compilation; man, cat, and rabbit)

Names

Surface origin

General distribution

Function

I, Olfactory

Olfactory bulb

Schneiderian mem-

Smell

brane

II. Optic

Optic chiasma

Retina

Sight

Ill, Motor oculi, oculomotor.

Ventrum of cerebral

Recti mm. except ex-

Motion

crus (peduncle)

ternal, inf. oblique

IV, Trochlear, patheticus. . . .

Side of cerebral crus

m.
Superior oblique m.

Motion

V, Trigeminus, trifacial

Side of pons Varolii

(See Text) tensor

Sensation,

tympani m.

motion,
taste

VI, Abducens, abducent

Pyramid of medulla

External rectus m.

Motion

VII, Facial, portio dura

Side of trapezium

Face, palate, digastric
m., stapedius m.

Motion

VIII, Auditory, acoustic, por-

Between pons and

Internal ear

Hearing

tio mollis of VII.

medulla

IX, Glassopharyngeal

Side of trapezium cau-

Tongue, pharynx, ton-

Sensation,

dad to VIII

sil, meninges, middle

motion,

ear

taste

X, Pneumogastric, vagus. . . .

Side of trapezium cau-

Pharynx, larynx, eso-

Sensation,

dad to IX

phagus, heart, stom-
ach, liver, ear men-
inges

motion

XI, Spinal accessory, acces-

Medulla, caudad to

Sterno- and cleido-

Motion

sory.

X, by 4-5 filaments

mastoid ant. trape-
zius mm.

XII, Hypoglossal

Medulla, caudome-

Hypoglossus, hyoid
mm., larynx

Motion

diad to XI

122

ANATOMY OF THE RABBIT

origin, general distribution and gross function of all of them
(Fig. 33;p. i2i).

The seventh cranial (facial) nerve leaves the brain, in
company with the eighth and caudolaterad of the sixth, from
the lateral side of the trapezoid body and emerges from the

Fig. 33. — Brain of rabbit, ventral view, to show relations of principal arteries
and origin of cranial nerves. I-XII, cranial nerves.

cranium through the stylomastoid foramen (which is bordered
by the mastoid, tympanic, and petrous portions of the temporal
bone; Fig. 2, SF). The first important branch given off is the
posterior auricular n. which leaves the seventh as it turns
craniad, about two mm. from the stylomastoid foramen,
and passes caudolaterad to the caudolateral side of the ear.

THE NERVOUS SYSTEM 1 23

The next important branch is the anterior auricular n. which
passes to the muscles of the craniolateral side of the ear. The
seventh nerve separates into three main branches, near the
caudal margin of the masseter muscle and passes directly
toward the cornor of the mouth. Near the cranial border of
the masseter muscle all three branches break up into a plexus
of small nerves which are distributed to the muscles of the
vibrissae, upper and lower lips, and in short to the skin and
superficial structures of the entire face craniad to the orbit and
masseter muscle and a large nerve to the region of the snout.
Numerous small fibers pass from the larger nerves to the
integument and other structures. The facial nerve, as the
name implies, innervates most of the superficial structures of
the entire facial region.

Method: Beginning just ventrad of the zygomatic arch very
carefully clear the subcutaneous muscle and superficial fascia
toward the ear and toward the mouth until a white cord (part of
the VII nerve) , which extends in a straight line from under the
parotid gland over the masseter muscle toward the cornor of
the mouth, but divides into numerous fibers just before reaching
the cranial margin of the masseter muscle, is located. Follow
this cord and verify the above description of the seventh
cranial nerve and its principal branches. After the root of
the facial nerve and posterior and anterior auricular branches
have been exposed, it is a good plan to slit the craniolateral
wall of the external auditory meatus open as far as its entrance
into the cochlea (Fig. 2, EA), in order to facilitate locating the
sylomastoid foramen by probing. Great care must be used
to prevent cutting the seventh nerve or one of its auricular
branches.

The trigeminal (trigeminus, trifacial, V cranial) nerve
arises from the pons Varolii by two roots, a large sensory root,
which enlarges to form the semilunar (Gasserian) ganglion
from which three branches (a. mandibular or third, b. max-
illary or second and c. ophthalmic or first) arise and pass out
of the cranium through three different foramina. The second

124 ANATOMY OF THE RABBIT

root is a motor nerve and joins branch a. Thus the mandibular
branch (a) of the trigeminal is both sensory and motor, while
the other two branches of this nerve (b. and c.) are sensory.
Thus, it is a mixed (motor and sensory) nerve and also has
the most varied distribution of any of the cranial nerves.
Therefore, it is hoped that dissection of the fifth and seventh
will serve to illustrate the principles of functional anatomy
of the other ten cranial nerves. The student may dissect
all the cranial nerves if he so desires, but this will probably
require another rabbit.

a. Mandibular or third branch: Sends branches to the
muscles of mastication, tongue, and other structures, and
enters the mandibular ramus through the mandibular (inferior
dental) foramen, courses through the ramus, sending branches
to the pulp cavities and alveoli of the lower teeth, and emerges
through the mental foramina (Fig. 3).

b. Maxillary or second branch: Sends branches to the upper
teeth, palate, and infraorbital nerve through the infraorbital
foramen (Fig. 2, IF) to upper lip and part of face, and lower
eyelid.

c. Ophthalmic or first branch : Sends branches to the upper
eyelid, lining and end of nose, eyeball, and other structures
within and around the orbit.

Method: Push the facial nerve ventrad out of the way, locate
the zygomatic arch, and using the point of the bone cutters,
snip through the cranial end of this arch (malar bone) close to
the maxillary bone, then through the caudal end of this arch
(zygomatic process of temporal bone) close to the mandibular
articulation. Loosen the medial side of the arch with a scalpel
and then work it under the seventh nerve and turn the excised
zygomatic arch, with the attached portion of the masseter
muscle, laterad and well down onto the mandible. Note a
nerve entering the masseter muscle. With the handle of the
cartilage knife, carefully remove this muscle so as to expose
the ascending ramus of the mandible. Cut the ascending
ramus off with the point of the bone cutters, using great care

THE NERVOUS SYSTEM 1 25

not to cut the mandibular nerve (branch a) which Hes close
along the medial side of the ascending ramus. Beginning
at the cut edge of the ascending ramus free it from the muscles,
which are attached to its medial side, until it can be entirely
removed. Locate the mandibular nerve (branch a, or third
of V) , which enters the mandible near the anterior margin of the
transected ascending ramus. Then very carefully remove
all the muscle tissue in the orbit ventrad to the eyeball and
expose the floor of the orbit and the cranial nerves laterad
to the optic nerve. The largest of these, which passes craniad
across the floor of the orbit, and into the maxillary region
continuing as the supraorbital nerve through the supraorbital
foramen to the face is the maxillary nerve (branch b, or second
of the V). It emerges from the cranium through the foramen
rotundum and gives off numerous small branches to the
structures in the orbit, including a long, slender branch (the
palpebral) which leaves it at the foramen rotundum and passes
to the lower eyelid. The ophthalmic nerve (branch c, or first
of V) emerges just dorsomediad to the maxillary nerve, through
the orbital fissure (sphenoidal sinus, lacerum anterus foramen) .

B. THE BRAIN

(Figs. 32, S3)

The brain and spinal cord of the rabbit are protected by a
comparatively tough three-layered membrane, the meninges.
The three membranous layers of the meninges are the dura
mater, which is the toughest of the three and lines the internal
surface of the cranium and vertebral canal; the pia mater,
which is a delicate membrane and intimately covers the brain
and spinal cord; and the arachnoid, a loose web-like membrane
which connects the dura and pia mater. The brain is relatively
smaller than the spinal cord, and the cerebral hemispheres
are practically free from convolutions. The cerebellum is
well developed and has a queer stalked structure, the floculus
or parafloculus, on the lateral side of each hemisphere.

126 ANATOMY OF THE R.ABBIT

The conical pineal body, or gland (epiphysis cerebri), which
is the rudimentary third eye of certain lower animals, is attached
by a hollow stalk to the thalamencephalon. It Hes in the
triangle formed by the cranial margin of the cerebellum and
the two dorsal caudomedial angles of the cerebral hemispheres.
The cleft in which the stalk of the pineal gland lies is the dorsal
portion of the third ventricle of the brain.

The pituitary gland (hypophysis cerebri) is about 7 mm.
long and 4 mm. wide and Hes caudad to the optic chiasma, in
the pituitary fossa of the sella turcica which is surrounded by
the sphenoid bone. Since this gland is more firmly attached
to the pituitary fossa than to the brain, it is usually accidentally
detached from the latter. In this case the sht-like aperature
of the third ventricle, with which the pituitary gland was
connected, will appear as in figure ^,7,.

Method: The entire brain and about two inches of the spinal
cord with the roots of the cranial nerves and at least one pair of
vertebral nerves and as much of the membraneous covering
(meninges) as possible should be removed together. The
object in remo\dng the meninges with the brain is to protect
the delicate nervous tissue and to include the arteries. The
floor of the first two or three cervical vertebrae should be left
attached to the spinal cord for its protection and to show rela-
tions of vertebrae, spinal nerves and cord, and vertebral arteries.

The flesh is removed from the dorsal region of the skull and
the roof of the cranium cracked, but not crushed, by a few
sharp blows with the handle of the cartilage knife. Then,
the fragments of the bone are carefully picked off with the
cartilage knife and large forceps, and then the pedicles of both
sides of the cervical vertebrae are carefully cut through with
the bone cutters. After this is completed the brain is loosened
from the other half of the skull and very carefully removed.

After the brain has been removed and carefully examined, the
meninges may be slit with scissors along one side of the median
fissure of the cerebrum and into the olfactory tissue which
will probably have been removed with the brain.

THE NERVOUS SYSTEM 1 27

C. SPINAL CORD AND SPINAL NERVES

(Figs. 24, 32)

The spinal cord is essentially a continuation of the brain
into the spinal column, in which the proportion of white to gray
material becomes progressively less from the cranial portion
caudad. In the brain the gray substance surrounds the white,
but as the nerve fibers pass to the spinal cord the gray matter
occupies the central part, mainly the spinal crescent (capital
H) which is formed by tw^o columns (dorsal and ventral horns)
joined by a central portion (commissura grissea). The white
substance in the spinal cord is formed mainly of medulated
nerve fibers and neuroglia, while the gray substance is
formed mainly by cell bodies, dendrites, and some nonmedu-
lated axons.

The spinal nerves leave the spinal cord in about 37 pairs;
8 cervical, 12 thoracic, 8 lumbar, 3 sacral, and 6-8 caudal,
through the intervertebral foramina. The dorsal and ventral
roots of the three sacral nerves really have separate foramina
(Fig. 7, VF). A typical spinal nerve leaves the spinal cord
by two roots, or rami, which are covered by a common sheath
beginning a very short distance outside of the intervertebral
foramen. The dorsal root (radix posterior) forms an enlarge-
ment (dorsal ganglion), usually within the intervertebral
foramen, while the ventral root (radix anterior) does not have
a ganglion, but is larger than the dorsal and is connected with
the autonomic (sympathetic) nervous system by a short
communicating branch (ramus communicans) . The student
should observe these structures in one of the spinal nerves of
the thoracic group.

Method: Remove the flesh from about five thoracic vertebrae
and with the point of the bone cutters expose the dorsal sur-
face of the spinal cord by removing the arch of two or three
vertebrae.

INDEX

Page

Abdominal wall 88

Achilles, tendon of 66

-ad endings, meaning of 40

-al endings, meaning of 40

Anatomical position 39, 4o

Arm, movement of 52

Articulating facets, on ribs 26

on transverse processes 26

Aorta, divisions of 99

Arteries, adrenolumbalis 106

anterior thoracic 74

anterior tibial 87

axillary 74

basilic, (a.38) 99

brachial 76, 79

carotids 92, 94

celiac 104

common iliac 106

coronary 99

dissection of 70, 74

epigastric 84

femoral 83

gastroduodenal 104

genital 106

hepatic 104

iliolumbar 106

inferior collateral ulnar 76

inferior mesenteric 106

inferior profunda • 76

innominate 99

intercostal 100

internal mammary 99

interosseous of hand 80

of foot 84

lateral circumflex 85

left subclavian 99

long thoracic 74

lumbar 104

nutrient, of humerus 76

nutrient, of ulna 80

129

130 INDEX

Page

Arteries, ovarian 106

palmar arch 80

pancreaticoduodenalis, (a. 44) 104

peroneal 87

phrenit: 100

plantar arch 87

popliteal 85

posterior humeral circumflex 76

princeps policis 80

profunda brachii 76

profunda femoris 83

pudic 83

pulmonary 97

radial recurrent 80

renal 106

saphenous 85

small saphenous, (a.26) 82,87

spermatic, internal 106

spleenic 104

sternal 99

subscapularis 76

superior mesenteric 106

supreme genicular 85

sural 87

thoracicodorsalis 76

ulnar 80

ulnar recurrent 80

vertebral 99

volar interosseous 80

Attachment, muscular 42

Axilla, location of 38

structures in 71^ 74

Bladder, gall and duct no

urinary • 103, 105

Blood, cells of 13

Blood vessels, dissection of 70

injecting 4, 38

parallel to arteries 7o> 7i

Bones, development of 18

four classes of 19

histology of 7

humerus 28

temporal, parts of 20

Brachial plexus 7^

Brachium 28

INDEX 131

Page

Brain, blood supply of 99

method of exposing 126

Buttocks, man and rabbit 60

Carpus, generalized 31

Cartilages, costal 27

ensiform 27, 28

histology of 7

Cecum 102

Cells, drawing 6

Colon, regions of 113

Common bile duct, mouth of 113

Cranium, bones of 16, 19-21

Crural arteries 86

fascia 61, 67

muscles 65

nerves 85

Demifacets, costal 26

Diaphyses, epiphyses and 19

Dissection, preparation for 44

Drawings, method of labeling 2

value of freehand 2

Drying, injury to rabbits of 4

Ducts, Stenson's 92

Wharton's 92

Duodenum 113

Epiphyses, union of 19

Epithelium, histology of 8

Esophagus 112

Fascia lata, how to open, (m.35) 62

Fat, cells and occurrence of 7

Foramen ovale 98

Foramina, intervertebral 26

stylomastoid 122

vertebrarterial ., 26, 99

Forearm, muscles moving 52

Ganglia, Gasserian 1 23

Genitalia 115, 116, 117

Glands, cervical lymph 92

Cowper's 118

ductless 115

parathyroid 93

132 INDEX

Page

Glands, pineal 93, 126

pituitary 93, 126

salivary 92

Glottis, epiglottis and 112

Glycerin-gum mixture 4, 87

Gold dust, cleaning bones with 4

Gray matter of cord 127

Grooved director, 44, (m.ia) 48

Hand, muscles moving 52, 55

Haversian systems 8

Heart 97

Histology, tissues studied in 5

Hyoid apparatus 16, 23

Ileum, jejunum and 113

Ilium, innominate bone and 32

Inguinal ligament 84, 89, 108

Injection mass 4? 38

Instruments required i

Intestine, studying 113, 114

Joints, articulations or 36

Kidneys 103, 108

Knee, bursae and ligaments of 36

Lacunae, canaliculi and 8

Ligaments, annular (m.47) 67, 68, 87

cruciate crural 68

tarsal 67, 68, 88

transverse crural 67, 68, 88

Liver 102

blood supply 107, 1 14

Location, terms of 40

Lymph glands, inferior limb 82

superior limb 74

Mediastinum 97

Metacarpus 31

Methods, dissecting thigh 60, 83

opening abdomen 102

opening mouth ' 1 1 1

opening thorax 95

Microscopes, cautions on use of 5

Mold, danger from 3

INDEX 133

Page

Muscles, acromiodeltoid 53

adductor femoris 64

basioclavicularis 4q

basiohumeralis, (m.4) 49, 52

biceps brachii 52

biceps femoris 61

brachialis 54

clavodeltoid 53

cleidomastoid 50

coracobrachialis 54

cremaster 117

cutaneous maximus 43, 88

digastric 91

epitrochlearis, gracilis and 63

erector spinae, (m.59) 90

extensor carpi radialis longus 58

communis digitorum 57

digitorum lateralis * 58

digitorum longus 68

policis brevis 58

policis et indicis 57

external intercostal 89

flexor carpi ulnaris 58

carpi ulnaris minor 58

carpi radialis 59

digitorum longus 67

profundus digitorum 59

sublimis digitorum 58

gastrocnemius 65

gluteus maximus 63

gracilis, epitroclearis and 63

histology of 9

how named 42

iliocostal 90

inferior gamellus 34

infraspinatus 53

insertion of 41, 66

internal intercostal 90

latissimus dorsi 43, 49, 52

levator scapulae 51

scapulae minor 49

scapulae ventralis 49

levatores costarum 91

longissimus dorsi ~ 90

masseter 91

obliquus externus 89

134 INDEX

Page

Muscles, obliquus internus 89

occipitoscapularis 49

pectoral 50

peroneal 68, 69

plantaris 67

platysma 44, 72, 93

psoas 119

quadriceps femoris 65

rectus abdominis 89

respiratory 88

rhomboideus 51

sacrolumbalis 90

sartorius 63

semimembranosus 64

semitendinosus 64

serratus magnus 51

posticus 89

soleus 66

spinalis dorsi 90

splenius capitus et colli 90

sternohyoid 91

sternomastoid 50

sternothyroid 91

subcutaneous 43

subscapularis 54

supporting, of trunk 88

supraspinatus 53

tensor faciae latae 61

tenuissimus 61

teres, major-minor 53

tibialis anterior 67

tibialis posterior 68

transversalis abdominis . 89

trapezius, ant. and post 47

triceps brachii 55

triceps surae, (m.44) 67

voluntary and involuntary '. n, 41

IMyelenated nerves 13

Nerves, anterior auricular 123

anterior crural, (n.ii) 85

thoracic 7^

axillary 7^

common peroneal 86

communicating branches 127

facial 122

INDEX 135

Page

Nerves, femoral 85

ischiadicus, (n.13) 86

lumbosacral plexus 85

mandibular 124

maxillary 1 24

medial brachial cutaneous 77, 79

median 79

musculocutaneous 78

musculospiral 79

myelenated 13

names of arteries and 77

opthalmic 1 24

pneumogastric 94, 121

posterior auricular 122

posterior femoral cutaneous 86

roots of spinal 127

saphenous 86

sciatic 86

suprascapular 78

tibial 86

trifacial (trigeminal) 123

ulnar 79

vagus 94, 121

Wrisberg's , 79

Notes, method of taking 2

Ossification, process of 18

Osteoblasts, bone formation 18

Pancreas 114

Pectoral girdle, movement of 52

Pelvic girdle, pectoral and 60

viscera 114

Pericardium 97

Pharynx 112

Phenol, neutralization of 4

Plexi, brachial 76

lumbosacral 85

Popliteus, location of 38

Portal organs 107

Postcava 100, 107, 108

Poupart's ligament 84, 89, 108

Precaval system 100, loi

Pronators, supinators and ^2

136 INDEX

Page

Rabbits, storage of preserved 3

wet and dry preserved 3

Rectum 113, 118

Sacculus rotundus 113

Schneiderian membrane 121

Scrotum 38,117

Seminal vesicles 118

Skeleton, cljeaning 4

rabbit and man 16-18

Skin, incisions in 42, 43

Spinal cord, structure of 12-14

Spleen 102

Storage box for rabbits 3

Supinators, pronators and 52

Taste buds 112

Teeth, formula of in

Tendons, histology of (a) 6

perforating, (m.30) 58, (m.46) 67

Testes 38, 103, 115

Thigh, muscles of 61

Thorax, method of opening 95

Thumb, muscles of 57> 5^

Tibiofibula 17, 35

Tonsils 112

Topography, of bones i9~35

of rabbit 40

terms used in 40

Transection, method of 47? 48

Trochanters of femur 33

Tubes, Eustachian 112

uterine 116

Urethra 116, 118

Urinogenital sinus 116

Uterus 103, 116

Vagina 38, 116

blood supply of 83, 108, 116

Veins, basilic 72, 73

cephalic 7i-73

and musculospiral nerve 79

external jugular 93> ^00

hepatic portal 107

injection mass for 109

INDEX

137

Page

Veins, internal jugular 94, 100

jugulars 93, loi

names of arteries and 70 71

saphena magna g2

saphena parva 32

supreme intercostal 100 loi

transverse jugular loi

Vermiform process 103, 113

Vertebrae 23-26

distinguishing groups of 26

topography of typical 23

Wrist, types of 29-31

Zygomatic arch, bones of 21