ELEMENTS OF

MAMMALIAN ANATOMY

DAVISON.

MAMMALIAN ANATOMY

WITH SPECIAL REFERENCE TO

THE CAT

BY

ALVIN DAVISON, PH.D.

EX-FELLOW OF PRINCETON UNIVERSITY ; PROFESSOR OF BIOLOGY IN LAFAYETTE COLLEGE

WITH OVER ONE HUNDRED ILLUSTRATIONS MADE BY
W. H. REESE, A.M., FROM THE AUTHOR'S DISSECTIONS

Study nature, not books."

— Agassiz.

PHILADELPHIA
P. BLAKISTON'S SON & CO.

1012 WALNUT STREET
1903

COPYRIGHT, 1903, BY P. BLAKISTON'S SON & Co.

COM PAN Y
i, PRINTERS
PHI LAOEUPHIA, PA.

PREFACE.

Huxley after years of pedagogical experience reached
the conclusion that it is unwise to introduce the beginner
at once to new and strange forms of microscopic life when
it is possible to use a subject of which the student is
bound to know something, — the elementary anatomy of
a vertebrate animal. The late T. Jeffrey Parker and
numerous other eminent zoologists likewise advocate be-
ginning zoological work by studying one of the higher
animals. Since the majority of college students have
time for only one year of zoological work, they cannot
acquire a fruitful knowledge of both vertebrates and
invertebrates. A study of the former enables one not
only to become familiar with the anatomy and physi-
ology of his own body, — a matter of vital importance, -
but throws a clear light on the significant problem of
organic evolution such as is not to be derived from a
study of invertebrate forms. Inasmuch as the genea-
logical histories are best worked out among the Mam-
malia, and since a careful study of the anatomy of the
cat familiarizes one with the anatomy of the human
body, as is evidenced by the fact that our best medical
schools now advise their prospective students to dissect
either a dog, a cat, or a rabbit as a preparation for their
later work, it is apparent that a knowledge of the mam-
mals is of the greatest worth.

This brief work is intended to acquaint the student

Vi PREFACE.

with the general structure of the cat, and at the same
time introduce him to some of the most important mor-
phologic features of the Mammalia. The following works
are useful for reference: "Anatomical Technology,"
Wilder and Gage; "Anatomy of the Cat," Reighard and
Jennings; "Mammals Living and Extinct," Flower and
Leydekker; "Primary Factors of Organic Evolution,"
E. D. Cope; "Vertebrate Zoology," J. S. Kingsley;
"Anatomic des Hundes," Ellenberger and Baum;
"Human Physiology," Schenck and Giirber; 'Osteology
of the Mammalia," Flower; " Human Histology," Piersol.
In the preparation of this book I have consulted a
large number of works on human and comparative
anatomy and physiology. Those giving most assistance
are the works mentioned above, in addition to 'Mam-
malian Anatomy' by Jayne, 'Anatomic Descriptive et
Comparative' by Strauss-Durckheim, ' Nervose Central-
organe' by Edinger, and "Vertebrate Palaeontology' by
Woodward. I am especially indebted to my artist, Mr.
W. H. Reese, of the Phillipsburg High School, for the
care and patience exercised in making the drawings
from my own dissections. Mr. D. S. Hartline, of the
Bloomsburgh State Normal School, has read the entire
manuscript and made valuable criticisms. Above all, I
have to thank Prof. J. S. Kingsley for numerous valuable
suggestions and important corrections in the manuscript.

ALVIN DAVISON.

EASTON, PA., September,

CONTENTS.

PAGE

INTRODUCTION, __17

The Biological Sciences, _ -- 17

Classification of the Animal Kingdom,- 18

Preparation and Preservation of Material,- — 20

GENERAL STRUCTURE OF A VERTEBRATE,

External Features, -- 32

THE SKELETON, -- 36

General Terms Used in Description of Bones,- 36

Tabulation of Bones, _ -- 37

Structure of Bone,_ 40

Bones of the Skull,- 41

Vertebral Column, 57

Sternum, -- 63

Ribs, 65

Thoracic Limb, _ -- 67

Pelvic Limb,__ 79

THE JOINTS, 89

THE MUSCLES, _ _ . 93

ORGANS OF DIGESTION, — 117

Alimentary Canal,-: 117

Accessory Glands of Digestion, 131

Peritoneum, 135

THE VASCULAR SYSTEM,- 140

Heart,- 140

Arteries of Trunk.

Arteries of Neck and Head, 145

Arteries of Thoracic Limb, — 148

Arteries of Pelvic Limb, -- 151

Venous System, 153

Lymphatic System, 161

Ductless Glands, _ 165

RESPIRATORY SYSTEM,.- 168

EXCRETORY AND REPRODUCTIVE SYSTEMS, 174

Glands of the Skin,_ 174

vii

Vlll CONTENTS.

PAGE

Urinary Organs, 174

Female Organs of Reproduction, __ __ 177

Male Organs of Reproduction,- 180

NERVOUS SYSTEM, _ __ 186

Brain, 186

External Features,- 187

Internal Structure, _ 192

Spinal Cord, __ 205

Fiber Tracts of the Central Nervous System, __ 210

Peripheral Nerves, ; 216

Cranial Nerves, 216

Spinal Nerves,_ 218

Sympathetic System, 226

Organs of Sense, . 231

Cutaneous, 231

Olfactory,- 232

Gustatory, __ __ 232

Visual, 233

Auditory, _. 237

INDEX, 243

LIST OF ILLUSTRATIONS.

FIG. PAGE

1. Specimen Jar, 20

2. Injecting Syringe, 21

3. Diagrammatic View of Operation for Injection, 22

4. Method of Making Incision in the Carotid Artery for Injection. __ 22

5. Method of Inserting the Cannula into a Vessel, 23

6. Palmar Aspect of Cat's Paw with Cannula Inserted, 24

7. Flat Epithelium Cells from the Mouth, 28

8. Involuntary Muscle, 28

9. Cells of Cartilage,. 29

10. Fibers of Voluntary Muscle, 29

11. Fibers of Connective Tissue, 30

12. Longitudinal Section of the Humerus of a Kitten, 38

13. Longitudinal Section of the Femur, 39

14. Cross-section of Cat's Femur, 40

15. Diagram of the Bones of the Mammalian Skull Viewed Laterally, 42

16. Dorsal Aspect of the Cat's Skull, 43

17. Ventral Aspect of the Skull with the Left Auditory Bulla Re-

moved, 47

18. Cut Surface of a Sagittally Bisected Skull, 50

19. Mesal or Inner Aspect of the Mandible, 54

20. Ventral Aspect of Larynx, Hyoid Bones, and Tongue, 55

21. Lateral Aspect of the Skeleton, 58

22. Plan of a Vertebra,. 59

23. Dorsocaudal Aspect of Atlas, __ 59

24. Lateral Aspect of the Axis, 60

25. Latero-caudal Aspect of a Thoracic Vertebra, — __ 60

26. Caudal Aspect of Fourth Lumbar Vertebra, 61

27. Dorsal Aspect of the Sacrum, 61

28. Ventral Aspect of the Bones of the Thorax, 64

29. Caudal Aspect of Sixth Rib, 65

30. Lateral Aspect of the Scapula, — 68

31. Caudal Aspect of the Clavicle, 68

32. Cephalic Aspect of the Humerus, -- 69

ix

X LIST OF ILLUSTRATIONS.

FIG. PAGE

33. Lateral Aspect of the Ulna, 70

34. Mesal Aspect of the Radius, 71

35. Genealogy of the Horse, 73

36A. Dorsal Aspect of Cat's Manus, 74

36s. Generalized Type of Carpus, 74

37. Lateral Aspect of Forelimb of Equus, 75

38. Lateral Aspect of Innominate Bone, 80

39. Ventral Aspect of Innominate Bones, __ 80

40. Caudal Aspect of Femur, 81

41. Cephalic Aspect of Tibia,___ 82

42. Mesal Aspect of Fibula, _ __ 83

43. Dorsal Aspect of Hind-foot, __ 85

44. Diagram of a Diarthrodial Joint, 89

45. Lateral Aspect of Dissected Knee-joint, 90

46. Caudal Aspect of Knee-joint, 91

47. Ventral Aspect of Trunk and Neck Muscles,-- 99

48. Lateral Aspect of the Muscles of the Cat, __ 104

49. Lateral Aspect of the Muscles of the Thoracic Limb, 105

50. Mesal Aspect of the Muscles of Thoracic Limb, __ __ 112

51. Ventral Aspect of the Muscles of Trunk and Thigh, __ 113

52. Lateral Aspect of the Muscles of the Leg, __ 113

53. Caudal Aspect of the Muscles of Crus and Foot, 114

54 Diagram of the Chief Organs of the Cat,___. 118

55. Dorsal Aspect of the Tongue and Larynx, 119

56. Longitudinal Section of the Canine Tooth, 120

57. Lateral Aspect of the Permanent Dentition, 121

58. Ventral Aspect of the Alimentary Canal, 127

59. Transverse Section of the Cat, 128

60. Cross-section of the Cardiac End of the Stomach, 128

61. Gastric Glands, 129

62. Cross-section of the Small Intestine, 130

63 A. Villi and Glands of Intestine,- 131

63B. Photomicrograph of Intestine with Blood-vessels Injected, — 131

64. Salivary Glands, 132

65. Photomicrograph of Section of the Liver, 134

66. Diagram of the Stomach of a Ruminant,. 137

67. Heart Viewed Ventrally, 141

68. Heart Viewed Ventrally with Caudal Third Cut off,___ 142

69. Heart Viewed Dorsally, 142

70. Chief Arteries of the Trunk, ___ 144

71. Ventral Aspect of the Arteries of the Head and Neck, 146

72. Arteries of the Forelimb, 149

73. Arteries of the Leg, 152

LIST OF ILLUSTRATIONS. XI

FIG. PAGE

74. Cross-section of Artery and Vein, 153

75. Vein with Valves, 154

76. Veins of Cat, 155

77A. ' Arterial System of a Rabbit, 158

77B. Arterial System of a Man, 158

78. Ventral Aspect of Chief Lymphatic Vessels of the Cat, 163

79. Photograph of the Lymphatic Capillaries and Vessels of Cat's Ear, 164

80. Diagrammatic Transverse Section of the Chest, 170

81. Photograph of a Lung Corrosion of a Puma, 171

82. Termination of a Bronchiole, 172

83. Ventral Aspect of Female Urogenital System, _ 175

84. Median Longitudinal Section of a Kidney; 176

85. Diagram of Structure of Kidney, 176

86. Section of Ovary, _ 179

87. Ventral Aspect of Male Reproductive Organs, 181

88. Spermatozoa, _ 182

89. Dorsal Aspect of the Brain, 189

90. Ventral Aspect of the Brain, _ 190

91. Diagram of the Ventricles, 192

92. Sagittal Section of the Brain, 194

93. Dorsal Aspect of the Brain with the Cerebellum and Portion of

Cerebrum Removed, 197

94. Cross-section of the Brain Caudad of the Optic Chiasm, 199

95. Cross-section of the Brain through Anterior Commissure, 201

96. Diagrammatic Section of Spinal Cord, 207

97. Nerve-cell, 208

98. Diagram of the Relation of Cells and Fibers in the Spinal Cord, 209

99. Diagram of Some Fiber-tracts, 211

100. Diagram of Chief Fiber-tracts of the Mammalian Brain, 214

101. Ventral Aspect of the Brachial Plexus, 220

102. Ventral Aspect of the Nerves of the Pelvic Limb, 225

103. Cephalic Half of Sympathetic System, __ 228

104. Caudal Half of Sympathetic System, _ 229

105. Pacinian Corpuscle, 232

106. Longitudinal Section of the Eye, 235

107. Diagram of the Mammalian Ear, 238

108. Section of the Cochlea of the Calf, 239

ELEMENTS

OF

MAMMALIAN ANATOMY

INTRODUCTION.

Since this book is designed for the use not only of
students who have pursued the study of biology for some
time, but also for those making their first aetual acquaint-
ance with the subject, it may be well to call attention
to the fact that any animal or plant may be considered
from several different standpoints. A general study of
structure and of the relations of the various systems and
organs is known as Anatomy. Histology concerns itself
with the cell and cell aggregates or tissues composing
the organs. These two sciences are included in Mor-
phology, a term which by many is made to include also
Embryology or Ontogeny, treating of the development of
an organism from the egg, or its vegetable homologue,
to the period of assuming adult characteristics. Since
ontogeny deals not only with the growth of structure
but also the process of growth, it may likewise be in-
cluded under Physiology, a science which has for its
province the investigation of the functions of the organs
and systems. A special field of physiology having for
its consideration the operations, especially the conscious
2 17

1 8 ELEMENTS OF MAMMALIAN ANATOMY.

operations of the nervous system, constitutes the science
of Psychology.

The same species of animals are not found in all parts
of the world. The lion and tiger are found wild only in
the old world, while the opossum is confined to the new
world. Again, many species of animals whose fossil re-
mains indicate their existence on earth several millions
of years ago, have at present no living representatives.
A consideration of this geographical and stratigraphical
location of organisms forms the science of Distribution.
The science of Phytogeny seeks to discover the geological
ancestral history of an organism.

A casual glance shows at once striking similarities and
differences between the common cat, the lion, and the
tiger. All have retractile claws, the same number and
kind of teeth, and the same number of toes. On the
other hand, the resemblances between these cat-like ani-
mals and the dogs are less marked, while the differences
are more striking. The cats and dogs resemble each
other more closely than either does a horse. Horses,
dogs, and cats have numerous characters in common
which are not present in birds. The recognition of such
resemblances and differences furnishes a basis of classifi-
cation, the treatment of which forms the science of
Taxonomy.

The following is a brief classification of the animal
kingdom :

Invertebrata : Animals with no skeletal axis and without a central
nervous system entirely dorsal of the alimentary
canal.

Protochordata : Small marine forms having, during part of their life
at least, a rudimentary skeletal axis and other features
marking them as a connecting-link between the inver-
tebrates and vertebrates. Tunicates or sea squirts,
Amphioxus.

INTRODUCTION. 1 9

Vertebrata : Forms with i\ skeletal axis and dorsal nerve-cord whose

anterior end is dilated into a brain.
PISCES (fish).

AMPHIBIA (frogs, toads, and salamanders).
REPTILIA (snakes and lizards).
AYES (birds).
MAMMALIA (vertebrates suckling their young).

I'rutothcria: Oviparous mammals. Ornithorhynchus.
Euthcria: Viviparous mammals with anus and

urogenital opening distinct.
Marsupialia (opossums and kangaroos).
Insectivora (moles, shrews, and hedge-
hogs).

Edentata (sloths and ant-eaters).
Chiroptera (bats and flying foxes).
Rodentia (rabbits, squirrels, mice, and

rats).

Cetacea (whales, porpoises, and dol-
phins).

Sirenia (sea co\\ ).
Ungulata (the hoofed mammals).
Carnivora (dogs, cats, wolves, and

foxes).
Primates (monkeys and man).

A glance at the above outline shows that the class
Mammalia is divided into two subclasses, the latter of
which includes ten orders. Each of these orders consists
of several families which in turn are composed of genera
made up of species. The order Carnivora includes eleven
families, of which Canidae (the dogs), Felidae (the cats),
and Ursidae (the bears) are the most frequently seen in
America. The family Felidae is represented by only two
living genera, Cynaelurus and Felis. The genus Felis
includes several species, of which Felis leo (the lion),
Felis tigris (the tiger), and Felis domestica (the cat)
are the most familiar. Of the last species, there are sev-
eral varieties, such as Maltese, Angora, and Manx cats.

Linnaeus, born in Sweden, 1702, invented the system

20 ELEMENTS OF MAMMALIAN ANATOMY.

of binomial nomenclature in accordance with which the
scientific name of every plant and animal is composed of
two parts, the generic and specific. Thus the house cat
is designated Felis domestica; the lion, Felis leo; the
dog, Canis familiaris; the wolf, Canis lupus; the pig,
Sus scrofa; the red deer, Cervas elephas; the elephant,
Elephas Africanus; the ourang-outang, Simia satyrus;
and man, Homo sapiens.

METHODS OF PRESERVING MATERIAL.

Alcohol has been widely used as a preservative, but
owing to the fact that it is expensive and quickly evap-
orates from the specimen exposed to the air, thereby

rendering the parts dry and brittle, its
use has been largely supplanted by for-
malin. Formalin, CH2O, is often sold
under the names of formose, formol,
formine, formalosa, and formaldehyd.
It can be purchased for about thirty
cents a pound. For preserving any ani-
mal or plant, the concentrated 40% for-

FIG. 1.-— SPECIMEN 11 i i • 1-1 i •,-, ,1

JAR maldehyd is diluted with water in the

proportion of ninety-five parts of the
latter to five parts of the former. It is evident, there-,
fore, that one pound of formaldehyd will make about
ten liters of preserving fluid.

The specimens may be kept a year or two without
changing the formalin in ordinary stone jars with covers,
but for permanent preservation the glass jar with the
ground-glass cover should be used (Fig. i).

Preparation of Vascular System.- -To render the vessels
plainly visible and distinguish the arteries from the
veins, it is advisable to inject the former with a red

INTRODUCTION.

21

mass and the latter with a blue mass. These fluid masses
should be of such a character as to harden in a short
time after injection, so that they will
not run out when the vessels are cut
during dissection.

A syringe of hard rubber, having a
capacity of about two ounces, serves
very well for injection. A cannula of
correct size may be had by asking the
druggist for the filling cannula of the
Parke Davis serum syringe. The end
to be inserted into the blood-vessel
should be ground off obliquely and
smoothly on a whetstone. The connec-

•/

tion between the cannula and nozle is
formed by stiff rubber tubing which
should be securely tied to the cannula
(Fig. 2).

The injecting mass is prepared by
thoroughly mixing TOO c.c. of water, 20
c.c. of glycerin, 20 c.c. of concentrated
formalin, and 85 gm. of common laun-
dry starch. One-half should be colored
red by adding to it one or two grams
of powdered carmin made into a paste
with a few drops of ammonia, and the
other colored blue by dissolving in it a
gram or twTo of soluble Berlin blue.
These liquid masses, after being passed
through a fine wire strainer or a coarse

o

piece of cheese-cloth stretched across a

funnel, may be preserved for any length of time in covered

jars.

The animal may be anesthetized by placing it in a

FIG. 2. — INJECTING
SYRINGE. : £.

p, Plunger handle;
b, barrel ; pi,
nozle ; c, cannula ;
r, rubber tube ; <it,
point of detach-
ment; s, string.

22

ELEMENTS OF MAMMALIAN ANATOMY.

tight box with a cloth or absorbent cotton wet with 30
c.c. of ether or chloroform. If only the arteries are to

be injected, the cat may re-
main in the box until dead ;
but if the veins are also to
be injected, it is preferable
to use ether for the anes-
thetic and then remove the
animal to the tray as soon
as it is unconscious, and re-
flect a portion of skin, ex-
posing the external jugular
veins (Fig. 3). With the
curved forceps thrust be-
neath the vein a cord may
be pulled through and tied
in a loose knot. One-half
inch from the latter a
second cord should be tied

FIG. 3. — DIAGRAMMATIC View OF
OPERATION FOR INJECTION.

d, Broken line showing course of the
carotid artery beneath ; b, string
loosely tied; c, transverse vein
uniting external jugulars; a,
points of curved forceps con-
taining string.

around the vein loosely. An
oblique cut (Fig. 4) with the
point of the scissors directed
caudad is then made in the vein between the cords. The
incision should extend about
half-way through the vessel.
Absorbing the blood with ab-
sorbent cotton as it runs from
the vessel will prevent clog-
ging. If too much ether has
not been used, the blood will
continue running fifteen min-
utes. When it has nearly
ceased flowing, the carotid
artery must be found by making a slit in the muscle

FIG. 4. — METHOD OF MAKING IN-
CISION IN THE CAROTID AR-
TERY FOR INJECTION.

INTRODUCTION.

23

alongside of the trachea just mesad of the jugular, as
indicated by the line d (Fig. 3). Having cut through
the muscle, two white cords are seen along either side
of the trachea. The mesal one may be red, as it is the
carotid artery. The lateral one, lying in the same sheath
with the preceding, is the vagus or tenth cranial nerve.
Separate the artery from the nerve and tie two cords
loosely around the vessel as in the case of the jugular.
Lift up the artery with the index finger (Fig. 4), and
make an oblique incision with the
scissors. The cannula with the con-
necting tube attached should then be
inserted caudad in the oblique cut of
the artery (Fig. 5), and the string s
drawn tight so as to hold the cannula
in place. The string st should then
be tightened to prevent the injection
mass from running out where the can-
nula is inserted. After stirring the red
mass, filling the syringe, and slipping
the nozle into the connecting tube the
operator should press slowly but con-
tinuously on the plunger until that
portion of the carotid cephalad of the
string st is w^ell distended. In a large
cat this will not occur until the syringe is nearly or quite
empty. When the vessels are full, the cannula is with-
drawn while the operator pulls on both ends of the string s.
The syringe must be washed out immediately, after which
the blue mass is well stirred and injected caudad into the
external jugular in the same manner as described for the
arteries.

By making a slit about three inches long in the ab-
dominal wall a fold of the intestine may be pulled out

FIG. 5. — METHOD OF
INSERTING THE CAN-
NULA INTO A VES-
SEL.

24 ELEMENTS OF MAMMALIAN ANATOMY.

so that its lumen can be filled with about 200 c.c. of
15% formalin. The same amount should be injected
into the lungs by inserting the cannula caudad into
the ventral wall of the trachea. If the cat is not to
be used at once, it may be preserved several months
by wrapping it in a piece of muslin saturated with a
solution of thymol (thymol, 5 gin., dissolved in 200
c.c. of hot water). Thymol is a fungicide. An outer
wrapping of well-vaselined cloth prevents evaporation
in case the specimen is kept in a dry room.

The portal system is not injected through the jugular

vein. The portal trunk just caudad of
where it enters the liver may be found
by cutting a piece from the abdominal
wall on the right ventral aspect just
caudad of the last rib. After two loose
knots are tied around this trunk as
directed for the jugular, the cut is made
and the cannula inserted caudad. About

FIG 6 -PALM\R T5 c-c- °f ^ie ^ue mass maY be injected

ASPECT OF CAT'S into the portal system of a large speci-

PAW WITH CAN- ^ t . . j ,-i

NULA INSERTED. men. This should not be injected until

the other systems have been filled.
The lymphatic system must likewise be injected for
demonstration. While the cat is being anesthetized, 5
gm. of soluble Berlin blue are dissolved in 100 gm. of
water, and the solution warmed to about the tempera-
ture of the body. As soon as the cat is unconscious
the syringe should be warmed by filling it with hot
water, and the point of the cannula pushed obliquely
proximad under the thick skin on the palm (Fig. 6)
of the paw. The syringe after being half filled with
Berlin blue solution is attached to the cannula and the
plunger pushed in very slowly so that one-fourth of the

INTRODUCTION. 25

amount in the syringe is forced out in ten minutes.
While the injection is being made the limb should be
gently massaged by pinching and rubbing from the
foot toward the body. This facilitates the flow of the

j

liquid in the lymph-vessels. In this manner the lymph-
atics of each limb are filled. The author has been
able to fill the left thoracic duct by continuing the in-
jection for about twenty minutes in the palm of the
left paw. The lymphatics of the head and neck may
be injected in a similar manner by inserting the cannula
beneath the skin on the tip of the ear, the tip of the
tongue, the tip of the nose, and the lips.

In order to inject the lacteals the abdominal cavity
must be opened, and the cannula inserted very obliquely
into the wrall of the small intestine so that its point is
between the mucous and muscular coats. The half-
filled syringe being attached, very gentle pressure should
then be exerted on the plunger, until the blue solution
appears in the lacteals. To inject all the lacteals it is
necessary to insert the cannula into the wall of the
intestine at a dozen different places. To fill the thoracic
duct injection may be made into the large lymphatic
gland lying at the point where the converging blood-
vessels of the mesentery meet. The best solution for
injecting the thoracic duct is made by dissolving 7
gm. of gelatin in a warm Berlin blue solution (4 gm.
of Berlin blue to 100 c.c. water). This should be filtered
through a single layer of absorbent cotton and then
injected while still quite warm. In all cases injections
to fill the lymphatics must be warm and must be pushed
in very slowly. These lymphatic injections are best
preserved by injecting the trachea and intestine with
95% alcohol and immersing the cat in a jar of 70%
alcohol.

26 ELEMENTS OF MAMMALIAN ANATOMY.

Preparation of a Mammal for Dissection of the Muscles,
Peripheral Nerves, and Viscera.- -The simplest method
is to anesthetize the animal as before described, remove
the skin, make a slit throughout the entire ventral
body- wall, and immerse the specimen in a jar of 5%
formalin. A better method is to inject into the carotid
artery 200 c.c. of glycerinated formalin (water 140
c.c., glycerin 30 c.c., formalin 30 c.c.), and half that
amount into the intestine and trachea. The specimen
may then be preserved in the thymol and vaselin cloths
as previously described, or put into formalin.

Preparation of the Central Nervous System.- The
animal may be killed either with chloroform or ether.
About 200 c.c. of formal-bichromate (170 c.c. of 5%
potassium bichromate and 30 c.c. of formalin) are then
injected slowly cephalad into the carotid artery (Figs. 3, 4,
and 5). After skinning, the eyes should be cut out
and the flesh removed from the head and dorsal side
of the vertebral column. On a line connecting the
caudal borders of the orbits, cut through the skull to
the brain with the bone cutters and remove piece by
piece the roof of the skull. Next cut away the lateral
walls down to the base of the brain. Care must be
exercised in laying bare the cerebellum, and cutting
loose the tentorium cerebelli, the plate of bone separating
the cerebrum from the cerebellum. The spinal cord
is next laid bare dorsally, beginning with the atlas, by
cutting through the pedicles of the neural arches on
either side. With a sharp knife or a pair of scissors
the spinal nerves may then be cut and the cord lifted
from behind forward out of its bed, until the brain is
reached. The latter must be carefully raised while the
nerves at its base are cut, and the dura mater loosened.

To further harden them the brain and cord should
be placed in weak formal-bichromate (5% formalin, 500

INTRODUCTION. 27

c.c. + 5% potassium bichromate, 500 c.c.) one week
in the dark. Light causes a precipitate. At the end
of one week the specimen should be placed in 1000
c.c. of 5% formalin for another week, after which it is
ready for dissection. In case brains of calves or sheep
are used a hammer and bone chisel are necessary for
opening the skull. The head should first be nailed to the
tray. As soon as the brain is removed it should be
placed in a large pan of water and the dura mater care-
fully cut away, the clotted blood washed off and a
syringeful of strong formal-bichromate injected into the
third ventricle by pushing the cannula about half an
inch through the infundibulum (Fig. 94). The brain
of a sheep or calf will be very soft when removed, as it
cannot be hardened previously by injecting the harden-
ing fluid into the arteries. Therefore it is necessary
to lay the specimen on absorbent cotton in the jar
of formal-bichromate, which must be exchanged for
fresh fluid on the second and third days. At least two
weeks are required for hardening the brain of a sheep or
calf, after which it is placed in 5r(' formalin for a week
or more to wash out the bichromate before dissection.
Brains are best preserved permanently in 85 c[ alcohol.

Preparation of the Osseous System. — A mounted skele-
ton of the cat may be purchased for about eight dollars.
A partially articulated skeleton may be easily prepared in
the laboratory by cutting most of the flesh from a speci-
men soaked in formalin two weeks. After drying a few
days the remaining tissue is easily removed from the
bones, which will remain articulated if the ligaments at
the joints are not cut. Clean disarticulated bones are
best secured by following directions given in the " Ana-
tomical Technology " bv Wilder and Ga^e. A beautifully

O _/ _/ O J

cleaned set of bones may also be obtained by exposing
to the weather during the summer the skinned carcass.

GENERAL STRUCTURE.

The study of any vertebrate reveals the presence of
numerous organs, each of which is for the performance
of a particular function. Thus the heart is the organ
for the propulsion of the blood, the kidney for the elim-
ination of the nitrogenous waste. Several organs com-
bined for a common purpose constitute a system. The
heart, with the various vessels for conveying the blood,
forms the circulatory system. The following eight
systems are found in all Mammalia : Osseous or bony,

n

FIG. 7. — FLAT EPITHELIUM CELLS FIG. 8. — INVOLUNTARY MUSCLE-
FROM THE MOUTH. X 150. CELLS. X 250.

n, Nucleus of the cell. n, Nucleus of a cell.

muscular, digestive, respiratory, vascular, excretory, re-
productive, and nervous.

The relative locations of the various systems are
represented diagrammatically in Fig. 54. The organs
have the same arrangement throughout all the orders
of mammals. Moreover, the minute structure of the
same organ is so similar in the different species that in
most cases one can scarcely distinguish them by micro-
scopic examination. The organs are composed of four

28

GENERAL STRUCTURE.

FIG. 9.— CELLS OF
CARTILAGE.
150.

classes of tissues: Epithelial, which covers all free sur-
faces; connective, forming the bones, binding together
the muscular fibers and elements of the nervous system
and making up cartilage and ligaments (Fig. 1 1 ) ; mus-
cular, composing the greater part of the
muscular system; and nervous, consti-
tuting the nervous system (Fig. 85).

The naked eye is unable to distin-
guish the elements of the tissues, but
the microscope reveals the fact that
each kind of tissue is formed of either
cells or fibers or, as is most frequently
the case, a combination of both.

The different relative arrangements of these anatomic
elements, together with their morphology, permit one
to. know from what organ any particular section of
tissue under consideration has been taken.

These ultimate units of structure are still further

resolved into parts by the chemist, who
has shown that they are composed
largely of carbon, hydrogen, oxygen,
and nitrogen. Since there can be no
energy developed in the body without
the disintegration and consequent death
of some of the particles composing the
millions of tiny cells, it is plain that
they must have their losses replaced in
order to continue their existence. There-
fore a method of preparing the food for
the use of the cells, and a way of transporting it to each
of them are necessary.

The former is accomplished by the digestive system,
which, through the agency of the salivary, gastric,
pancreatic, and other glands, transforms the food into

FIG. 10. - -FIBERS
OF VOLUNTARY
MUSCLE. : 100.

n, Fiber; /, tendon.

ELEMENTS OF MAMMALIAN ANATOMY.

a special liquid state capable of being absorbed by the
millions of minute finger-like villi of the small intestine
( Fig. 63). Thence it is transferred by the lacteal vessels
and veins to the heart, whence it is conveyed by the
arteries to their capillary distribution in the neighbor-
hood of every cell in the body.

The dead matter or waste material resulting from the
cell activity is of two kinds, gaseous and liquid. Both
diffuse through the capillary walls into the blood. The

FIG. 11. — FIBERS OF CONNECTIVE TISSUE. X 300.

former, which is carbon dioxid, is carried to the heart
and thence by the pulmonary arteries to the lungs, where
it passes into the terminal branches of the trachea, and
finally by expiration reaches the exterior. The liquid
excretion is transported by means of the veins and arte-
ries to the kidneys, where it diffuses through the walls
of the capillaries into the minute tubules opening into
the ureters leading to the bladder. It must be remem-
bered that the material known as feces passed out of
the alimentary canal through the anus is not an excretion

GENERAL STRUCTURE. 31

of the cells of the body, but merely that portion of the
food not transformed into a condition permitting it to be
absorbed by the villi.

In addition to these systems necessary for the main-
tenance of life, the cat requires a means for supporting
the body and moving about, furnished by the osseous
and muscular systems. The osseous system serves not
only for support and locomotion, but also for the pro-
tection of the delicate vital organs. The skull and spinal
column contain the brain and spinal cord, while the
heart and lungs are well shielded by the dorsal vertebrae,
the ribs, and sternum. Likewise the muscles ward off
serious injuries from the blood-vessels, as they cover to
a considerable depth nearly all large arteries, and also
aid by their contraction in moving the lymph through
the numerous lymphatic vessels extending from the
extremities to the jugular veins.

These systems previously described are capable of per-
forming their functions only when supplied with nerves
through which impulses can be transmitted from the
brain and spinal cord. Stimuli sent by the brain or cord
through the nerves cause the gastric juice to flow into
the stomach, the bile and pancreatic secretions to be
formed and poured forth into the intestines, the kidneys
to eliminate the waste from the blood, the heart to beat,
and the muscles to contract and relax.

The only system which is not absolutely necessary to
the life of the cat is the reproductive; but this is required
for the continuance of the species. It is not, however,
functional during the entire life, but as a rule only from
the end of the first to the tenth year.

""

<-»—"

*

32 ELEMENTS OF MAMMALIAN ANATOMY.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. What advantages are derived from the study of mammalian anat-
omy?

2. Define morphology and state a fact from that science.

3. What two sciences does biology include?

4. What five sciences are included in zoology?

5. Make a physiologic statement concerning the heart.

6. State five facts belonging to the science of distribution.

7. What is taxonomy?

8. Name five classes of vertebrates.

9. By examining specimens discover what external feature distin-
guishes a reptile from an amphibian.

10. Do all mammals have hair?

11. What habit is common to no other vertebrates except mammals?

12. Give two points of difference between the two subclasses of Mam-
malia.

13. Name the ten orders of Eutheria and give an example of each.

14. Which orders derive their names from the habits of the animals?

15. Which orders derive their names from anatomic features?

16. Which orders are aquatic?

17. What is the ultimate syllable of all family names?

18. Explain what is meant by binomial nomenclature.

19. Name three families of Carnivora.

20. Examine specimens and determine wherein the teeth of Canidae
differ from those of Felidae.

21. What two rank names constitute the scientific name of an animal?

22. Give the scientific name of five Carnivora, two Ungulata, and two
Primates.

23. Define organ, system, tissue, and cell.

24. Name two organs belonging to each system.

25. How do the elements of the four kinds of tissue differ?

EXTERNAL FEATURES.

The cat, like all other mammals, possesses two well-
defined skeletons, the endoskeleton, consisting of the true
bones, and the exoskeleton, composed of the skin and its
appendages. The skin invests the body completely and
is continuous with the lining of the digestive and uro-
genital canals. It varies in thickness in different regions,
being very thin on the lips, ears, and eyelids, and ex-

GENERAL STRUCTURE. 33

ceedingly thick on the pads of the feet and on the ventral
neck region, where, in contest with an enemy, it is most
likely to be seized. A fibrous connective tissue binds the
skin to the subjacent structures. In some places the
union is very firm, as on the distal parts of the limbs
and the head, while in other regions it is loose, as on
the lateral aspect of the trunk.

The skin consists of an external layer, the epidermis,
and, beneath this, the dermis or true skin, designated the
corium. The epidermis is composed of numerous strata
of epithelial cells. Those on or near the surface are
much flattened while the deeper ones are more or less
cubical. As the superficial layer desquamates in minute
fragments, forming what is commonly called dandruff,
it is replaced by cells developed from the deeper layers.

The portion of the epidermis adjacent to the corium
or cutis vera contains the coloring-matter of the skin,
and is known as the rete mucosum. At the orifices of
the internal passages, such as the digestive and genital
tracts, the epithelium changes to a soft delicate nature,
and is then known throughout these passages as mucous
membrane.

The corium or dermis is a form of fibrous connective
tissue whose deepest portion forms the white fluffy
areolar substance cut in removing the skin. In many
regions just below the true skin is a layer of adipose
tissue, which when examined under the microscope is
seen to be composed of numerous globular fat-cells sup-
ported by fibrous areolar tissue. The seven pads on the
forepaw and the five on the hind one consist of greatly
thickened epidermis, the corium, and masses of fibrous
connective tissue enveloping many fat-cells.

The sebaceous or oil glands lie in the corium, and by
means of a duct open into the hair follicle near the sur-
3

34 ELEMENTS OF MAMMALIAN ANATOMY.

face. The sudoriparous or sweat glands, composed of
coiled tubes, are present in the subcutaneous tissue, from
whence a duct extends to the surface. Although there
are no blood-vessels in the epidermis, numerous nerve
terminations are present in the deeper portions. The
true skin is richly supplied with both nerves and blood-
vessels.

The claws produced by a special modification of the
epidermis are among the most important appendages of
the skin. Five of these are present on each forefoot,
while only four occur on the hind one. At the root of
each claw, the dermis forms a crescentic fold over it, and
beneath is a number of papillae richly supplied with
blood-vessels. This entire structure forms the matrix of
the claw, which is set around the terminal part of the
distal phalanx of each digit. Claws, or some similar
structures, such as nails or hoofs, are present in all
mammals except the Cetacea.

Another important appendage of the skin is the hair,
which covers the entire body except the tip of the nose
and the pads of the feet. Its length and color vary
with the variety of the cat. The Mombus cat of Africa
has short stiff hair, while the Angora or Persian cat is
remarkable for the length and delicacy of its soft fur.
The hair, like the nails, is an extreme modification of
the epidermis. Bach hair grows from a papilla at the
bottom of a small sac, the follicle, which is a depression
in the corium. The central part of the hair is the pith,
and the external portion, formed of thin overlapping
scales, the cuticle. The coloring-matter lies in the super-
ficial scales, and may be disposed in such an irregular
manner that one-half of a hair is white, and the other
half yellow.

The large hairs on either side of the nose are known

GENERAL STRUCTURE. 35

as vibrissae. Their roots are provided with delicate nerve-
endings of touch, so that the animal may find its way
with ease through dark narrow passages. There are a
few long hairs above the eyes, forming the eyebrows, but
no eyelashes are present.

Most of the hairs are inserted obliquely into the skin,
but when angered the cat can erect them by the con-
traction of a small muscle passing from the skin to the
hair-bulb.

On some mammals the hairy covering is partial and
limited to particular regions ; in others, as the hippopota-
mus and the Sirenia, it is very scanty, but scattered over
the whole surface; while in the Cetacea it is reduced to a
few small bristles about the mouth.

Some kinds of hair, as those of the mane and tail of
the horse, are shed and renewed annually. Most mam-
mals have a long hairy coat in winter which gives place
in spring to a short coat. The Arctic fox, hare, ermine,
and numerous other animals of the colder regions undergo
a complete change of color in the two seasons, being
white in winter and brown or gray in summer. By this
protective coloration they escape many of their enemies.

THE SKELETON.

The number of bones in the skeleton of the cat varies
with its age, since two or more bones separate in the
young may form one mass in the old animal. The three
portions of the innominate bone which are distinct (Fig.
38) in the young, become fused in the adult. In very old
age many sutures of the skull become partially or wholly
obliterated. In the young adult cat the number of bones,
exclusive of the teeth, ear bones, chevron bones, and
sesamoid bones, is about 233. The sacrum is reckoned
as one bone, though composed of three coalesced verte-
brae. The structure and embryology of the teeth show
that they belong to a different category from the bones.
The ossicula auditus, or ear bones, are the malleus, incus,
and stapes of the middle ear. The chevron bones are
eight in number, attached to the ventral side of the
vertebrae of the tail. The sesamoid bones number about
forty, of wrhich the patella, or knee-cap, is the largest.
They are formed in the tendons where there is much
pressure or friction, as upon the volar surface of the
metacarpus. The outline on page 37 gives the classifica-
tion, names, and number of the different bones of the
skeleton.

GENERAL TERMS USED IN DESCRIPTION OF BONES.

In reference to shape the bones are spoken of as long,
short, flat, and irregular. Long bones are those having a
shaft or diaphysis in which is a cavity filled with marrow,
and two enlarged extremities or epiphyses (Fig. 13):

36

Frontal, 2

Ethmoid, I

Temporal,

Cranium Parietal, 2

Interparietal, . . . . i

Occipital, i

Sphenoid, i

, Skull

Premaxillary, ... 2

Maxillary, 2

Palatine, 2

Vomer, i

Maxilloturbinal, . . 2

Nasal, 2

Head Lachrymal, . .

Malar or Jugal, ... 2

Mandible, i

iTympanohyal, . . 2

Stylohyal, 2

Epihyal, 2

AXIAL SKKLK- iijuiu^.,« \Ceratohval,

TON / Basihyaf, i

\ Thyrohyal, 2

Cervical vertebrae, . 7

Thoracic vertebrae, . 13

Vertebral column Lumbar vertebrse, . 7

Sacral vertebrae, . . i

Trunk Caudal, . 21

f Ribs, 26

rhorax t Sternum, i

Shoulder girdle { Scapula,

( Clavicle, 2

Arm Humerus, 2

Forearm f Ulna, 2

( Radius, 2

/ Thoracic limb

Scapholunar, .... 2

Cuneiform, 2

Pisiform, 2

Trapezium, 2

Trapezoid 2

Magnum 2

Unciform, ... 2
Hand /

Metacarpus 10

APPENDICULAR / x Phalanges f Pfox'maK i°

SKELETON \ Middle, 10

I Distal, 8

Pelvic girdle Innominate, .... 2

Femur, 2

po. j Patella, 2

i Tibia 2

Fibula, 2

\ Pelvic limb Astragalus,

Calcaneum, . . .

Scaphoid, 2

Entocuneiform, . . 2

Mesocuneiform, . . 2

Ectocuneiform, ... 2

Cuboid, 2

Foot

Metatarsus 10

( Proximal, 8

Phalanges Middle, 8

( Distal

37

ELEMENTS OF MAMMALIAN ANATOMY.

femur, fibula, metacarpals, and phalanges. Short bones
are those not elongated and with no medullary cavity:
tarsus and carpus. Flat bones are plate-like, with a layer

of cancellous tissue between two
layers of compact tissue : parietal,
scapula, and innominate. Irregular
bones are those which have an ex-
ceedingly irregular shape: ethmoid
and vertebrae. The aspect of a bone
is the portion seen when viewed from
a given direction. The border of a
bone is the margin, edge, or ridge at
the juncture of two surfaces. Proxi-
mal is used to designate the portion
of a structure nearer the axis or spinal
column, in distinction to distal, which
signifies the part farther removed
from the axis. Cephalic indicates the
part of an organ nearer to the plane
passing just beyond the head and per-
pendicular to the spinal axis, while
caudal is applied to the other part of
the organ nearer to the perpendicular
plane at the end of the extended tail.
Sagittal refers to the plane bisecting
the animal in a vertical and longitu-
dinal direction. Mesal and lateral are
adjectives, the former meaning nearer
to the sagittal plane and the latter
more remote on either side of that
plane. Proximad, distad, cephalad,
caudad, mesad, and later ad are adverbs

indicating direction in accordance with the adjectives to
which they are related.

0

FIG. 12. - - LONGITU-
DINAL SECTION OF
THE HUMERUS OP A
KITTEN.

li, Epiphysis for head;
c, cartilage ; b, bone ;
m, medullary sub-
stance; o, epiphysis
for olecranon pro-
cess.

THE SKELETON.

39

A process is a projection or elevation.

A tuberosity is a rough obtuse pro-
cess.

A tubercle is a small and usually more
or less pointed process.

A condyle is a rounded and somewhat
elongated smooth articular process. The
distal end of the femur presents a pair
of condyles (Fig. 40).

A fossa is an irregular depressed area

(Fig. 30).

A foramen is an aperture for the pas-
sage of vessels or nerves.

The shaft is the body or middle por-
tion of an elongated bone.

The head is a spheroidal prominence
at one end of an elongated bone (Fig.
40).

The epiphysis is a small process of
bone ossified from a separate center. In
the young animal it is attached to the
main bone by cartilage, but in the adult
becomes a part of the main bone (Fig.
12). The femur has four epiphyses, one
for the head, one for the distal extremity,
and one for each trochanter process (Fig.
40). With the exception of the pha-
langes, metacarpals, and metatarsals, all
of the long bones have an epiphysis at
each extremity. In the human, these
epiphyses do not unite with the shaft
before the sixteenth year. Diploe is
the spongy layer of bone between the
layers of the flat bones (Fig. 18).

FIG. 13. — LONGITU-
DINAL SECTION
OF THE FEMUR.

w<l, Medullary cav-
ity; d and h, can-
cellous tissue ; tr.
cancellous tissue
of trochanter pro-
cess ; b, compact
bony tissue.

compact surface

40 ELEMENTS OF MAMMALIAN ANATOMY.

The articulation of a bone has reference to its contact
with other bones by means of joints.

STRUCTURE OF BONE.

Every bone is completely covered except on its articu-
lating surfaces with a tough membrane, the periosteum,
which serves for the attachment of muscles, and the
renewal of bony tissue in case of injury. The long bones
contain a cavity, the medullary cavity, filled with marrow

FIG. 14. — CROSS-SECTION OF CAT'S FEMUR. ( 5.

cp, Compact tissue; en, cancellous tissue; en, endosteum; me, medullary

canal; /><?, periosteum.

(Fig. 12). This cavity is lined with endosteum, a mem-
brane similar to the periosteum.

The shaft of the long bone is composed mainly of
compact bony tissue through which extend longitudin-
ally intercommunicating microscopic channels, Haversian
canals, for the conveyance of blood-vessels, nerves, and
lymphatics.

The lacuna, or spaces for the bone cells during life,
are arranged concentrically about the Haversian canals.
The canaliculi, or processes of the lacunae, communicate

THE SKELETON. 4!

with one another. At the extremities of the bones the
place of the medullary canal is taken up by cancellous
tissue (Fig. 13, d), the compact tissue being very thin.
The flat bones have no medullary canal, but the diploe
or cancellous tissue lying between the outer compact
tissue has its spaces rilled with a red marrow of the same
nature as that in the cancellous tissue of the long bones,
wherein the red blood-corpuscles are formed. The large
medullary cavity or canal is filled with yellow or fatty
marrow.

BONES OF THE SKULL.

The skull is usually considered in two parts, the
cranium and face. The former is composed of nine
bones, which will be described in order.

•The frontal bones (Figs. 15 and 16) are two in number,
lying between the orbits, and articulating with one
another in the median line. They form the roof of the
cephalic part of the brain cavity and the caudal portion
of the roof of the nasal chamber. A lateral projection
(po, Fig. 1 6) is known as the postorbital process. Within
the frontal bone is a cavity, the frontal sinus (Fig. 18),
which contains air and is lined with mucous membrane.
It communicates with the nasal cavity. The lateral
descending portion of the bone, articulating with the
palatine and orbitosphenoid, is the orbital plate of the
frontal.

In the majority of the Mammalia the frontal is a
paired bone, but in man the two portions become anchy-
losed during the fifth or sixth year. The horns of
ruminants are outgrowths of these bones. Among the
Cervidae (deer) horns are usually developed only on the
male, and are shed every year. In the Bovidae (cattle)
the horns are permanent when present.

4

ELEMENTS OF MAMMALIAN ANATOMY.

The ethmoid (Fig. 18) is a single bone lying ventral
to the frontals and nasals. It separates the cranial
cavity from the nasal cavity and projects into the latter
in the form of two thin scroll-like plates of bone and a
median vertical plate. In order to see the relations of
this bone, three skulls must be used, one of which should

FIG. 15. — DIAGRAM OF THE BONES OF THE MAMMAUAN SKULU VIEWED

LATERALLY.

1, 2, 3, etc., indicate the places of exit of the twelve cranial nerves, pmx,
Premaxillary ; ty, tympanic, 7 and 8 are on periotic; thy, tympano-
hyal; shy, stylohyal; ehy, epihyal; chy, ceratohyal; bhy, basihyal;
thhy, thyrohyal. The cartilage bones are shaded. — (From Flower,
after Huxley.)

be bisected sagittally, a second should have the roof
of the cranial and nasal cavities removed, and the third
should be cut transversely on a line joining the middle
of the orbits. The ethmoid is usually visible externally
as a small rhomboid plate on the mesal wall of the orbit
between the frontal, lachrymal, and palatine bones. It
consists of four parts: the paired ethmoturbinals or

THE SKELETON.

43

lateral ethmoids (Fig. 18), the mesethmoid, and the cribri-
form plate. The ethmoturbinals are in the form of
scroll-like laminae which project forward from the trans-
verse cribriform plate into the nasal cavities. The portion
which appears externally in the mesal wall of the orbit

oc

FIG. 16. — DORSAL, ASPECT OF THE CAT'S SKULL.

ap, Anterior palatine foramen ; c, canine tooth ; co, coronal suture ; /, for-
amina in palatine bone, the lateral one is the posterior palatine and
the mesal one is the sphenopalatine ; fr, frontal; if, infraorbital fora-
men; in, interparietal ; Ic, lachrymal canal at the anterior border of
the lachrymal bone; Id, lambdoidal crest; ml, malar; mx, maxillary;
na, nasal; oc, occipital; p, vertical plate of the palatine; po, post-
orbital process of the frontal; pm, postorbital process of the malar;
par, parietal; px, premaxillary ; sq, squamosal part of the temporal;
sg, sagittal suture; sp, alisphenoid part of the sphenoid; tp, temporal
fossa; zg, zygomatic process of the squamosal.

is the os planum. In the recent state, the surfaces of
these bones within the nasal cavity are covered with a
mucous membrane over which the first pair of cranial
nerves (olfactory) are distributed. The delicacy of the
sense of smell is proportional to the development of the

44 ELEMENTS OF MAMMALIAN ANATOMY.

ethmoturbinals. In most orders of animals five scrolls are
present, but in Echidna there are six and in some Ungu-
lates there are eight, while in adult Primates there are
only from one to three, more, however, being present
in the embryo.

The mesethmoid is the perpendicular plate of bone
which, prolonged cephalad by cartilage, separates the
nasal cavity into two portions. Caudad it is united to
the cribriform plate, dorsally it articulates with the
median descending plates of the frontals and the nasals,
and ventrally it articulates with the vomer and pre-
sphenoid. The cribriform plate is the caudal portion
of the ethmoid (Fig. 18), which, extending transversely
between the frontals, separates the cranial cavity from
the nasal cavity. It is pierced by many pinhole foramina
for the exit of the olfactory nerve. In Ornithorynchus
(duck-bill of Australia) there is a single large foramen
in the cribriform plate, as is also the case in birds.

The temporal is a paired bone lying at the base and
side of the skull. It contains the organs of hearing.
It consists of four parts: the squamous or expanded
portion (Fig. 16), to which the zygomatic process is
attached; the mastoid (Fig. 17), which is the part caudad
of the squamosal and dorsal to the bulla; the tympanic,
which forms the auditory bulla; and the petrous (Figs.
17 and 1 8), which contains the internal ear. The
squamous portion overlaps the parietal dorsally in a
scale-like manner and is limited ventrally by a clearly
defined projecting ridge extending above the external
auditory meatus as the dorsal border of the zygoma.

The zygomatic process extends cephalad to join the
zygomatic process of the malar, the two together forming
the zygomatic arch, or zygoma, to which the masseter
muscle is attached. Ventral of the root of the zygomatic

THE SKELETON. 45

process is the glenoid cavity for the articulation of the
condyle of the mandible. Immediately caudad of this
cavity is the postglenoid process. The mastoid portion
of the bone is somewhat triangular in shape, about two
centimeters long, and lies caudad of the external meatus.

The tympanic portion appears on the base of the skull
as the auditory bulla. Its cavity is divided into two
unequal chambers by a bony septum rising from the
floor and reaching almost to the roof. The cephalic
or true tympanic chamber, sometimes called the middle
ear, is the smaller, and has on its lateral wall a horseshoe-
shaped prominence known as the tympanic ring, to
which the tympanic membrane of the drum of the ear
is attached. There are four apertures in the walls of
the cephalic tympanic chamber: The meatus auditorius
externus, or the external auditory canal; the Eustachian
tube, leading from the cephalic dorsal angle of the
chamber to the pharynx; the fenestra ovalis and the
fenestra rotundum, opening into the internal ear. The
caudal or mesal chamber of the bulla is larger than the
cephalic, but has no special features worthy of consider-
ation.

The petrous portion of the temporal bone is not visible on
the external surface of the skull, but may be seen by look-
ing into the external auditory meatus. It forms the mesal
wall of the tympanic cavity. The foramen seen in its dorsal
part is the fenestra ovalis. In a sagittally bisected skull the
petrous (Fig. 17) may be recognized by the internal audi-
tory meatus entering it. By removing the bulla, a large
portion of the petrous bone may be seen from its ventral
aspect. A central prominence, the promontory, con-
tains the foramen rotundum opening into the base of
the cochlea. The apex of the promontory, mesad of
the fenestra rotundum, forms the wall of the first whorl

46 ELEMENTS OF MAMMALIAN ANATOMY.

of the cochlea. Dorsal to the fenestra rotundum is the
fenestra ovalis, opening into the vestibule of the internal
ear. In the recent state this opening is closed by a
membrane in which is imbedded the foot of the stapes.
The cochlea in the interior of the bone may be displayed
by cutting away the bony rim of the fenestra rotundum
and then chipping off a crust of bone in a line from
this foramen to the juncture of the basioccipital and
basisphenoid bones.

The petrous bone, viewed dorsally in a bisected skull,
appears in the floor of the brain cavity ventrad of the
tentorium. Its surface is pierced by the internal auditory
meatus, which gives passage to the auditory nerve.
Close examination reveals a division of the canal into
two parts, a ventral for the eighth nerve and a dorsal,
the aqueductus Fallopii, for the facial nerve. This
aqueduct twists through the petrous laterad, and thence
between the petrous, squamosal, and mastoid to the
stylomastoid foramen.

The parietal bone is paired and joins its fellow in the
median line, forming the caudal half of the sagittal
suture. Its point of greatest convexity is the parietal
eminence. Its cerebral or internal surface presents
slight arborescent grooves which in the recent state
sheltered the meningeal artery. The plate of bone pro-
jecting obliquely cephalad from the caudal border of
the parietal is the tentorium, an ossification of the dura
mater separating the cerebrum from the cerebellum.

The interparietal is a triangular bone situated at the
junction of the two parietals and occipital bones. Its
sutures are usually obliterated quite early.

The occipital (Figs. 16, 17, and 18) is a single bone
surrounding the foramen magnum and articulating with
the interparietal, parietals, temporals, and sphenoid. In

FIG. 17. — VENTRAL ASPECT OF THE SKULL WITH THE LEFT AUDITORY

BULLA REMOVED.

asp, Alisphenoid; ap, anterior palatine foramina; bs, basisphenoid ; bl,
auditory bulla; bo, basioccipital ; c, canine tooth; e, petrous portion
of the temporal; en, occipital condyle; ea, external auditory meatus;
eh, opening of the Eustachian tube; fr, frontal; fm, foramen mag-
num; gc, glenoid cavity; gn, postglenoid process; hm, hamular pro-
cess of the pterygoid; ic, incisor tooth; if, infraorbital foramen; in,
incus; jg, jugular foramen; Id, lambdoidal ridge; mx, maxilla; ml,
molar tooth; mp, mastoid process; ms, mastoid portion of the tem-
poral ; ma, malar ; m, malleus ; osp, orbitosphenoid ; ov, foramen ovale ;
pi, palatine; pt, pterygoid; pn, promontory of the petrous; po, post-
orbital process ; pr, premolar teeth ; pm, premaxillary ; rd, fenestra
rotundum ; rt, foramen rotundum ; st, stapes ; sg, squamosal ; sf, stylo-
mastoid foramen ; tc, carotid foramen, or foramen lacerum medius ;
vm, vomer, forming the septum between the posterior nares; zg,
zygomatic process of squamosal.

THE SKELETON.

47

the young kitten it is composed of four parts : the supra-
occipital, lying dorsal to the foramen magnum, the two

FIG. 17.

exoccipitals , lying laterad of it, and a basioccipital,
bounding it ventrally. The crescentic elevation on the

48 ELEMENTS OF MAMMALIAN ANATOMY.

supraoccipital near its parietal margin is the lambdoidal
ridge, to which the cephalohumeral muscle is attached
(Fig. 48).

The exoccipitols bound the cerebellum laterally and
support the occipital condyles, which articulate with the
atlas or first vertebra. Immediately caudad of the bulla
is the paroccipital process. There are two foramina,
one of which, the anterior condyloid, opens ventrally
with the jugular foramen adjacent to the bulla, while
the other, the posterior condyloid, opens more dorsally
at the side of the condyle. The former transmits the
twelfth (hypoglossal) cranial nerve, supplying the larynx,
hyoid bone, and tongue. The jugular foramen, or
foramen lacerum posterius, is at the juncture of the
bulla, exoccipital, and basioccipital. The internal jugular
vein and the ninth, tenth, and eleventh nerves pass
through it. The basioccipital portion of this bone lies
entirely on the ventral aspect of the skull. It articu-
lates cephalad with the basisphenoid by a suture which
is generally obliterated in cats three or four years old.

The sphenoid bone lies in the center of the base of the
skull. It is composed of eight parts, corresponding to
eight distinct bones in the lower vertebrates : the basi-
sphenoid, articulating caudad with the basioccipital;
two alisphenoids, extending dorsad from the basisphenoid
and articulating caudad with the temporals (Figs. 17
and 1 8); two pterygoids, projecting ventrally from the
basisphenoid and terminating in sharp processes; a
presphenoid in the midventral line cephalad of the
basisphenoid ; two orbito sphenoids, extending dorso-later-
ally from the presphenoid and articulating cephalad with
the frontals. In an old cat, the sutures between these
eight parts become more or less obliterated. The basi-
sphenoid together with the alisphenoids is sometimes

THE SKELETON.

49

called the posterior sphenoid in distinction to the anierior
sphenoid, composed of the presphenoid and orbito-
sphenoids.

TABLE OF THE FORAMINA OF THE SKULL.

FORAMINA.

Infraorbital.

Anterior palatine.

Sphenopalatine.

Posterior palatine.
Olfactory foramina.
Optic.

Lacerum anterius,
or sphenoidal fis-
sure.

Rotundum.

Ovale.

Lacerum medium.

Internal auditory
meatus.

Aqueduct of Fallo-

pius.
Stylomastoid.

Jugular or posterior
lacerated.

Anterior condyloid.

BONES SURRMI xniNc, THE
FORAMINA.

Superior maxillary.

Maxillary and pre-
maxillary.

Palatine.

Palatine.

Ethmoid.

Orbitosphenoid.

Alisphenoid and
orbitosphenoid.

Alisphenoid.

Alisphenoid.

Petrous and basi-

sphenoid.
Petrous.

Petrous, mastoid,
and tympanic.

Tympanic and mas-
toid.

Occipital and tem-
poral.

Exoccipital.

STRUCTURES TRAVERSING THE FORA-
MINA.

Infraorbital nerve of the supe-
rior maxillary division of the

fifth.
Nasopalatine branch of the

fifth cranial nerve and nasal

artery.
Sphenopalatine nerve and

sphenopalatine artery.
Palatine nerve and artery.
Olfactory nerve.
Optic nerve and meningeal

artery.
Third, fourth, and sixth cranial

nerves and first division of

fifth cranial nerve.
Second division of fifth cranial

nerve.
Third division of fifth cranial

nerve.
Internal carotid artery.

Eighth cranial nerve.
Seventh cranial nerve.
Seventh cranial nerve.

Ninth, tenth, and eleventh
cranial nerves and jugular
vein.

Twelfth cranial nerve.

The basisphcnoid presents on its dorsal or cerebral
surface the sella turcica, or pituitary fossa, which lodges
the pituitary body of the brain (Fig. 90). The posterior
boundary of this fossa is the clinoid plate, and its lateral
projections are the posterior clinoid processes. On each
side of the basisphenoid there extends dorsally in a

5°

ELEMENTS OF MAMMALIAN ANATOMY.

narrow strip to the parietal the alisphenoid, at the base
of which, cephalad of the auditory bulla, are three
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is the sphenoidal fissure, or anterior lacerated foramen,
which transmits the third, fourth, and sixth cranial
nerves supplying the eyeball muscles, and the first

THE SKELETON. 51

branch of the fifth nerve. This foramen is between the
alisphenoid and the orbitosphenoid. The other two
foramina, rotundum and ovale, transmit the second and
third divisions of the fifth nerve.

The pterygoid portion of the sphenoid is a paired bone
(Figs. 17 and 18) lying on either side of the cephalic
half of the basisphenoid and the caudal half of the
presphenoid. In the adult cat the sutures are some-
times obliterated so that this bone appears as a caudal
continuation of the palatine. The two pterygoid bones
or plates form the descending walls, and, together with
the median portion of the sphenoid, the roof of the
mesopterygoid fossa, whose cephalic continuation is the
posterior nares. From the ventral posterior angle of
each projects the hamular process, dorsal of which is
seen the small external pterygoid process. Between the
bases of the hamular and the external pterygoid processes
is the small external pterygoid fossa.

The presphenoid bone is the narrow median bone ex-
tending from the basisphenoid to the vomer. It contains
within it two large sinuses into which project the ventral
scrolls of the ethmoturbinal bones. The alisphenoids
enter into the formation of the mesal walls of the orbits
and are perforated at their bases by the optic foramina,
through which pass the optic nerves.

BONES OF THE FACE.

There are seven paired bones in the face and two
single ones, making in all sixteen.

The premaxillary, with its fellow, extends ventrad and
laterad of the anterior nares. These bones bear the six
incisor teeth. The anterior palatine or incisor foramina
connect the oral cavity with that of the anterior nares.

C2 ELEMENTS OF MAMMALIAN ANATOMY.

V '

In life, these foramina transmit the naso-palatine nerves.
In the Primates, the premaxillary is anchylosed to the
maxillary although it arises from a separate center of
ossification.

The maxillary is a paired bone which meets its fellow
in the median line in the roof of the mouth. All its
articulations are visible externally except those with the
maxilloturbinal, ethmoid, and vomer. Five teeth, a
canine, three premolars, and a molar, are present in this
bone of the adult cat. The molar is wanting to the
young. The several portions of the bone are as follows:
the palatine plate, appearing in the roof of the mouth;
the nasal process, extending dorso-caudad to the frontal;
the malar process, extending ventrad to the orbit to
articulate with the malar bone; and the orbital plate,
which is the root of the malar process, forming a partial
floor to the orbital cavity. The large foramen leading
from the orbital cavity through the orbital plate is the
infraorbital foramen for the passage of the infraorbital
branch of the superior maxillary branch of the fifth
nerve.

The palatine bone with its fellow helps to form the
roof of the oral cavity and the floor of the nasal cavity.
It is composed of two plates: one, vertical, forming the
lateral walls of the posterior nares and the cephalic part
of the walls of the median pterygoid fossa, and a portion
of the nasal wall of the orbital cavity; the other, hori-
zontal, forming part of the roof of the mouth. The ver-
tical plate is pierced by two foramina, the posterior pala-
tine and the sphenopalatine, each of which transmits a
palatine nerve and artery (Fig. 16).

The vomer is a single narrow bone which in the nasal
cavity articulates dorsally with the mesethmoid and
ventrally with the palatines and the palatine plates of

THE SKELETON. 53

the maxillary, in the median line. This bone, with the
mesethmoid and its cartilage, forms the nasal septum,
dividing the nasal cavity into two chambers. It is best
demonstrated by removing the palatines, when it may
be seen extending cephalad from its bifurcated articula-
tion with the presphenoid to its articulation with the
premaxillaries. The caudal portion of the bone is ex-
panded horizontally and articulates with the ventral eth-
moturbinals. Its dorsal margin is bifurcated for articu-
lation with the mesethmoid.

The maxilloturbinal is a paired bone occupying the
anterior portion of the nasal cavity (Fig. 18). It is com-
posed of a few scrolls which, when the nasal bone is
removed, may be seen attached to the maxillary. It
consists of a horizontal longitudinal plate, wiiose lateral
border is fixed to the maxillary wliile the mesal border
bifurcates into a dorsal curved plate and a ventral scroll.
The space between the maxilloturbinal and cephalic por-
tion of the lateral ethmoid is the middle nasal meatus.
The maxilloturbinal bone in man receives the name of
the inferior turbinated, in distinction to the middle and
superior turbinated bones, constituting the lateral eth-
moid.

The nasal bone, joining with its fellow in the median
line, forms a large part of the roof of the nasal chamber.
It articulates with the premaxillary, maxillary, and
frontal on the surface, and the ethmoid within the nasal
chamber.

The lachrymal bones are two in number and lie in the
cephalic part of the nasal walls of the orbits. Each
articulates with the maxillary, frontal, os planum of
the ethmoid, and the malar. The bone has about half
of the area of the finger-nail. The lachrymal canal is
bounded by the lachrymal and the maxilla. This canal,

54

ELEMENTS OF MAMMALIAN ANATOMY.

beginning in a vertical groove, the lachrymal groove, car-
ries the duct permitting the tears to pass from the eye
into the nasal chamber (Fig. 16).

The malar bone is paired. It forms the cheek as well
as the lateral and cephalic border of the orbit. The arch
largely formed by this bone is the zygoma. The process
projecting dorsad toward the postorbital process of the
frontal bone is the postorbital process of the malar. The
masseter muscle originates on the border of the malar.

FIG. 19. — MESAL OR INNER ASPECT OF THE MANDIBLE.

ang, Angle ; cndyl, condyle ; cor pr, coronoid process ; can, canine tooth ;
inc, incisor teeth; inf. d. fm, inferior dental foramen; in, inferior
notch ; mol, molar tooth ; prm, premolar teeth ; dt, diastema ; sm, sur-
face of symphysis ; up, superior notch.

The mandible or inferior maxillary is the single bone
forming the lower jaw (Figs. 17 and 21). It is made up
of two halves which are united by an immovable articula-
tion or symphysis (Fig. 19) at the chin. Each half con-
sists of a horizontal and an ascending ramus. On its
alveolar border the horizontal ramus bears three incisor
teeth, a canine, two premolars, and a molar tooth. In
the caudal part of the oral surface of this ramus is the in-

THE SKELETON.

55

ferior dental foramen, which transmits the inferior dental
nerve and artery traversing the dental canal extending
within the bone to the mental foramen on the lateral sur-
face near the base of the canine tooth. The space on the
dorsal border between the canine
and the first premolar tooth is
called the diastema.

The ascending ramus or por-
tion of the bone caudad of the
inferior tooth is marked by six
features: (i) the fossa on the
outer or lateral surface which
gives insertion to the masseter
muscle ; (2) the angle which is the
caudoventral termination of the
'bone; (3) the inferior notch im-
mediately dorsal of the angle ; (4)
the condyle for the articulation
with the glenoid cavity of the
temporal; (5) the superior notch
dorsal of the condyle; (6) the
coronoid process, which is the
dorsal termination of the ascend-
ing ramus and gives insertion to
the temporal muscle.

FIG. 20. — CENTRAL ASPECT
OF LARYNX, HYOID BONES,
AND TONGUE. The tongue
has been cut transversely
near its middle and its mus-
cles fixing it to the hyoid
have been removed.

bh, Basihyal; ch, ceratohyal;
cr, cricoid cartilage of the
larynx; eh, epihyal; ep,
epiglottis; /g, cricothyroid
ligament; lyk, thyrohyal;
rg, rings of cartilage in the
trachea; tc, thyroid cartil-
age of the larynx ; tm, tym-
panohyal; sh, stylohyal.

THE HYOID BONES OR HYOID
APPARATUS.

The hyoid bones consist of two
jointed rods, one on either side

(Figs. 20 and 21), hanging from the temporal bone, and
supporting the larynx. Each rod is composed of six
parts : the epihyal ; the ceratohyal ; the tympanohyal ; the

56 ELEMENTS OF MAMMALIAN ANATOMY.

basihyal ; and the thyrohyal. The dorsal end of the thyro-
lival is prolonged by a piece of cartilage, the chondrohyal.
The hyoid apparatus varies greatly among mammals.
In man it consists of a single bone composed of the body
or basihyal, two small cornua representing the cerato-
hyals, and two large cornua representing the thyrohyals.
The bone is suspended from the skull by ligaments cor-
responding to the bony chain in the cat.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. How many more bones present in the cat than in man?

2. In what two parts of the skeleton does the number of bones in
the cat exceed those in man?

3. What is a sesamoid bone?

4. Find on a specimen a sesamoid bone and describe it.

5. Draw a lateral aspect of the skull and label all parts

6. What are the paired bones of the cranium?

7. Name the single bones of the face.

8. Draw the caudal aspect of the skull and label all parts.

9. Which bones of the skull derive their names from their location?

10. Which bones of the skull are pierced by more than two foramina?

11. Write a description of the orbital cavity.

12. Which foramina of the skull derive their names from their shape
or size?

13. Which foramina derive their names from their location?

14. Which foramina transmit important blood-vessels?

15. Draw figures representing relative shapes and sizes of all foramina
of the skull.

16. What bones enter into the formation of the brain cavity?

17. Write about 200 words describing the nasal cavity.

18. Draw a ventro-lateral aspect of the auditory bulla and label all
features.

19. Write a description of the auditory bulla and name some mam-
mals in which it is absent.

20. Which bones of the skull are composed of more parts in the young
than in the adult?

21. Name the principal sutures of the skull.

22. Name the parts of the sphenoid bone in the order of size.

23. Name the bones of the skull visible from the dorsal aspect.

24. Name the bones of the skull visible from the cephalic aspect.

25. What bone of cranium paired in the cat is single in man?

THE SKELETON. 57

26. What bone present in face of the cat is wanting as a separate ele-
ment in man?

27. Draw lateral aspect of mandible and label all features.

28. Name the bones bearing the teeth.

29. Name the elements of hyoid apparatus in order.

30. Draw a section of the frontal bone showing diploe.

31. Describe the difference between the relative locations of the cranial
and facial portions of the skull in cat and man.

32. Name five membrane bones and five cartilage bones.

VERTEBRAE.

The vertebral column is composed of the following five
groups of vertebrae: seven cervical, thirteen thoracic,
seven lumbar, three sacral, and caudal varying from
four to twenty-six. The following six features are com-
mon to all of the vertebrae in the first four groups except
•the atlas: (i) the body of the vertebra (Fig. 22), which
forms the floor of the neural canal and articulates with
the adjacent vertebrae by means of interposed discs of
cartilage; (2) the transverse processes, which project
laterad from the body or from the walls of the neural
canal; (3) a spinous process, which projects dorsad from
the roof of the neural canal; (4) the neural arch, com-
posed of a pedicle on either side, forming the ventro-
lateral walls of the neural canal, and the laminae, extend-
ing dorsad from the pedicles to complete the dorsal wall
of the neural canal; (5) the inter-vertebral notch, which,
with the notch of the succeeding vertebra, forms the
intervertebral foramen for the exit of a spinal nerve; (6)
the articular processes or zygapophyses, two of which pro-
ject cephalad and two caudad from each vertebra. The
former are called the anterior zygapophyses, and the
latter posterior zygapophyses.

The first cervical vertebra, or atlas, is characterized by
its large horizontally expanded transverse processes, the
5

ELEMENTS OF MAMMALIAN ANATOMY.

absence of a spinous process, and its rudimentary body.
Its true body in the embryo, becomes united to the axis

as the odontoid process. The cephalic margin of the
neural arch is prolonged at each side into a process or

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THE SKELETON.

59

FIG. 22. — PLAN OF A VER-
TEBRA.

sp>, Spinous process; ar,
articular process; us,
transverse process; nc,
neural canal; pd, pedi-
cle ; lm, lamina ; en, cen-
trum or body.

articulation with the occipital condyles (Fig. 17) of the
skull. The root of this articular process is pierced by a
foramen giving passage to the first
spinal nerve and the vertebral ar-
tery and vein (Fig. 23, }r). From
the lateral opening of this foramen
(fr) a groove is continued ventrad
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cess, where it leads into the longi-
tudinal vertebrarterial canal com-
mon to the first six cervical verte-
brae. The vertebral artery and vein
course through this canal (Fig. 23).
The axis, or second vertebra, is
characterized by its odontoid pro-
cess, which projects within the at-
las, and also by its elongated spi-

nous process, which projects both cephalad and caudad.

The transverse process projects
caudad from the body, which is
flattened dorsoventrally. This
.« process is pierced at its base by

>^ iH I the vertebrarterial canal.

The remaining five cervicals
are very similar to one another.
The seventh has no vertebrar-
terial canal. The spinous pro-
cesses grow successively longer
from the third to the seventh
(Fig. 21). The transverse pro-
cesses of the fourth and fifth are
bifurcated, the dorsal branch be-
ing called the transverse element
and the ventral one the costal element, since it is really the

FIG. 23. — DORSOCAUDAL AS-
PECT OF ATLAS.

fr, Transverse process; tic,
neural canal; sp>, spinous
process ; fr, aperture of the
transverse part of the ver-
tebrarterial canal which
enters the atlas at vf; azg,
anterior zygapophysis ; zg,
posterior zygapophysis.

6o

ELEMENTS OF MAMMALIAN ANATOMY.

rudiment of a rib. The transverse process of the fifth ends

nl

FIG. 24. — LATERAL ASPECT OF THE Axis.

ar st, Anterior zygapophyses ; od pr, odontoid process ; nl sp, neural spine
or spinous process; p zg, posterior zygapophysis ; trs pr, transverse
process; vrt c, vertebrarterial canal.

in three branches. The following features are common to

all thirteen thoracic vertebrae : a
spinous process, projecting from
the dorsum of the neural arch ;
two cephalic articular processes or
anterior zygapophyses, facing
dorsad or dorsolaterad ; two cau-
dal articular processes or posterior
zygapophyses, facing ventrad or
ventromesad; a body whose
transverse diameter is greater
than the vertical diameter; and
transverse processes. There are
two half facets on each side of
the body of every thoracic verte-
bra except the first, eleventh,
twelfth, and thirteenth. The
head of a rib thus articulates
with two vertebrae (Fig. 28).
The body of the first vertebra

bears on each side a whole facet and a half facet. The

ce n

FIG. 25. - - LATEROCAUDAL
ASPECT OF THE SECOND
THORACIC VERTEBRA.

tr, Transverse process; nc,
neural canal; ce, facet for
tubercle of rib ; ar, poste-
rior zygapophysis; s, spi-
nous process ; c, centrum ;
n, intervertebral notch ; e,
pedicle; /, lamina.

THE SKELETON.

6l

eleventh, twelfth, and thirteenth bear a whole facet on
each side of the body.

The transverse processes of the first eleven bear facets
for the articulation with the tubercles (Fig. 25) of the
ribs. The last three thoracic vertebrae are characterized
by mammillary processes springing from the dorsolateral
portion of the roots of the anterior zygapophyses.

a

Fi<;. 26. --CAUDAL ASPECT OF
FOURTH LUMBAR VERTEBRA.

Accessory process; cr, centrum
or body; pa, pedicle; tr, trans-
verse process ; s, neural canal ; sf>,
spinous process ; zg, the mammil-
lary process of the anterior zyga-
pophysis; am, lamina; pz, poste-
rior zygapophysis.

FIG. 27. — DORSAL ASPECT OF THE
SACRUM.

ft, Floor of the neural canal ; fr, dor-
sal aperture of the intervertebral
foramen; //, lateral mass; pzg,
posterior zygapophysis; sp, spi-
nous process ; si, auricular surface
for articulation with the ilium ; // ,
transverse process; zgt, tubercle
formed by fusion of the zygapoph-
yses ; zg, anterior zygapophysis.

The following features are common to all of the lumbar
vertebra: a spinous process projecting dorsocephalad
(Fig. 26) ; a transverse process projecting ventrocephalad
on either side from the body; anterior zygapophyses and
posterior zygapophyses. A mammillary process or meta-
pophysis is present on the root of the anterior zygapoph-

62 ELEMENTS OF MAMMALIAN ANATOMY.

ysis of the first five bones, and an accessory process or
anapophysis occurs on the caudal margin of the wall of
the neural arch of all except the last vertebra. The
transverse processes increase in length and curvature
caudally. The spinous processes increase in length in
the same order, and the neural canal likewise enlarges
caudally.

The sacrum is a single bone (Fig. 27) formed by the
union of three sacral vertebrae. The limit of each element
is marked by the dorsal and ventral intervertebral fora-
mina which furnish passage for the dorsal and ventral
branches of the spinal nerves. The two tubercles on
either side of each of the three median spinous processes
are the result of the fusion of the articular processes.
The cephalic portion of the bone presents on its lateral
aspect the auricular surfaces for articulation with the
ilium. This expansion appears to be a modified transverse
process. Prominent transverse processes #lso project from
the caudal angles.

The caudal vertebrae vary greatly in number. Accord-
ing to Mivart, there are only four in the Manx cat; and
according to Jayne, there may be as many as twenty-six
in some varieties of the common cat. The transverse
processes and zygapophyses become less prominent from
the third vertebra to the eighth or ninth, where they are
present only as slight ridges. The spinous process is
present in the first three, but dwindles to a ridge in the
fourth. The first six or seven elements possess a neural
arch which' more distally loses its roof, making the neural
canal a mere groove. The groove becomes fainter dis-
tally and finally disappears entirely. The chevron bones
are the paired ossicles projecting ventrad from the
cephalic ends of the bodies of the vertebrae, from the
second or third to the thirteenth vertebra. In the sixth,

THE SKELETON. 63

seventh, and eighth vertebrae the chevron bones unite
ventrally in the middle line, forming an arch. The last
ten caudal vertebrae are scarcely more than cylinders of
bone representing the bodies of the vertebrae.

The number of vertebrae in the different species of
mammals varies widely. As a rule, there are seven
elements in the cervical region. The sea cow (Manatus)
has only six cervical vertebrae, while the three-toed sloth
has nine. The number of thoracico-lumbar varies from
sixteen in the orang to thirty-six in the cetacean Del-
phinus. The elements composing the sacrum likewise
vary from one in the ape, Cercopithecus, to nine in some
of the Edentata. The human sacrum is composed of
from four to six vertebrae. The same is true of the
gorilla, chimpanzee, and orang. The caudal vertebrae
vary greatly in number in the different forms. In the
adult human there are present only four or five vertebrae,
which form a single bone, the coccyx, while in the embryo
eight segments make up the caudal region. Ossification
takes place, however, in only five or six segments.

THE STERNUM.

The sternum of the cat is composed of eight pieces,
called sternebrae, which lie in the median line on the
ventral side of the chest (Fig. 21). The sternum serves
for the attachment of the cartilaginous portions of nine
pairs of ribs. The first sternebra (Fig. 28), which ends
cephalad in a laterally compressed pointed process, is the
manubrium. The six succeeding sternebrae form the body
or gladiolus ; the caudal piece is called the ensiform or
xiphoid process. It is terminated by a flat piece of carti-
lage. The cartilaginous portion of the first rib articulates
with the manubrium near its middle. The ribs from the

64

ELEMENTS OF MAMMALIAN ANATOMY.

FIG. 28. — VENTRAL ASPECT OF THE BONES OF THE THORAX. The num-
bers on the vertebral or bony portions of the ribs indicate the names
of the ribs. The numbers of the last four ribs are placed just ceph-
alad of them.

c, Cartilaginous part of first rib ; cr, cartilaginous disc between the bodies
of the vertebrae ; en, ensiform process ; hd, heads or capitula of ribs ;
ra, manubrium; mr, attachment of twelfth to the eleventh rib; n, free
termination of thirteenth rib; r, attachment of the eleventh to the
tenth rib ; //>, tubercle of first rib ; tn, transverse process of first thoracic
vertebra; v, body of vertebra.

THE SKELETON.

second to the seventh inclusive are attached at the
junctions of the sternebrae. The eighth and ninth ribs
are attached near together on the caudal end of the
seventh sternebra.

RIBS.

There are thirteen pairs of ribs in the cat. The nine
cephalic are called true ribs because they articulate dor-
sally with the spinal column and ventrally with the
sternum. The other four (Fig. 28) are
false ribs, three of which articulate
ventrally with other ribs, while the
fourth has no ventral articulation, and
is therefore called a floating rib. Each
rib is composed of two parts, the ver-
tebral or bony portion and the sternal
or cartilaginous.

The following description of the
sixth will serve to give a correct idea
in general of the anatomy of a rib.
Its vertebral portion (Fig. 29) presents
four features: a head or capitulum,
which articulates with the bodies of
the fifth and sixth thoracic vertebrae;
a tubercle, which articulates writh the
transverse process of the sixth thor-
acic vertebra ; a neck, which is the con-
stricted portion between the capitu-
lum and tubercle; and the shaft, in-
cluding the portion of the rib between
the tubercle and its articulation with
the sternal or cartilaginous portion. The bend in the shaft
beyond the tubercle is the angle. The sternal portion of
the rib, consisting of cartilage, is sometimes called the cos-

6

FIG. 29.— CAUDAL AS-
PECT OF SIXTH RIB.

ag, Angle; cr, pit for
articulation with
cartilaginous por-
tion; h, capitulum;
tik, neck; sh, shaft;
tb, tubercle with fa-
cet for articulation
with transverse pro-
cess.

66 ELEMENTS OF MAMMALIAN ANATOMY.

tal rib. In the sixth rib the costal portion is about half as
long as the vertebral portion.

Certain ribs present marked features varying from the
sixth. The first rib is stout and flat and has no distinct
ande. The articular surface of its head is not divided

O

into two facets, as is the case in all the others except
the three caudal ones. The lengths of the ribs increase
from the first to the ninth. The last three ribs have no
necks and no tubercles for articulation with the transverse
processes of the vertebrae.

The number of ribs varies from nine pairs in the
cetacean Hyperoodon to twenty-four in the two-toed
sloth (Choloepus). In most fishes and snakes, ribs are
present throughout both the trunk and tail regions, but
with the assumption of life on land, and the development
of limbs, the vertebrates have suffered a degeneration of
the ribs in all parts except the middle portion of the
trunk. In the embryo, however, anlage of ribs occurs
in all regions of the trunk, but they early coalesce with
the vertebrae except in the thorax.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Draw caudal aspect of third thoracic vertebra and label all features.

2. Describe the differences between the first and last thoracic ver-
tebrae.

3. What feature common to all thoracic vertebras not present on any
of the other vertebrae?

4. Draw the caudal aspect of the fourth cervical vertebra.

5. What feature common to all cervical vertebrae except seventh
but not present in any other vertebrae?

6. Draw cephalic aspect of atlas and label all features.

7. Compare the third and seventh cervical vertebrae.

8. What two features serve to distinguish the lumbar from all other
vertebrae?

9. Draw the cephalic aspect of the second lumbar vertebra and label
all features.

10. Wherein does the seventh lumbar vertebra differ from the first?

THE SKELETON. 67

11. How do you distinguish the caudal from the cephalic aspect of
any vertebra?

12. Draw ventral aspect of sacrum and label all features.

13. Give the two features distinguishing the caudal vertebrae from
all others.

14. Note the size and direction of the spinous process throughout
the column.

15. Describe the variation in number of the different groups of ver-
tebrae in other mammals.

16. Draw lateral aspect of sternum and label all features.

17. Describe the attachment of ribs to sternum.

18. What features common to all the ribs?

19. Name ribs having a tubercle.

20. Draw first rib and label all features.

21. Draw cephalic aspect of ninth rib and label all features.

22. How do you distinguish a false rib from a true rib?

23. What features mark the caudal aspect of a rib?

24. Make a drawing showing the articulation of a rib with the spinal
column and label all parts.

25. How do ribs vary as to number in mammals?

THE THORACIC LIMB.

The thoracic or fore-limb of the cat is composed of a
scapula, clavicle, humerus, ulna, radius, seven carpals,
five metacarpals, and fourteen phalanges (Fig. 20). The
scapula and clavicle form the shoulder girdle.

The scapula, commonly called the shoulder-blade (Fig.
30), is not articulated with the bones of the trunk, but
is held in position by the serratus magnus, levator anguli
scapulae, and other less important muscles. It articulates
with the head of the humerus by the glenoid cavity. It
presents three well-marked borders: the cephalic or an-
terior, the vertebral, and the axillary adjacent to the
vertebrae on the side near the axilla or armpit. The
outer surface of this bone is divided by a strong spine
into two nearly equal fossae, the cephalic of which is the
supraspinous, and the caudal one the infraspinous, fossa.

68

ELEMENTS OF MAMMALIAN ANATOMY.

From the lower part of the spine project the acromion
and metucronn'on processes. The subscapular fossa occu-
pies the entire inner or mesal surface.

*• <?/

^J

FIG. 30. — LATERAL OR OUTER ASPECT OF THE SCAPULA.

ac, Acromion process ; ax, axillary border ; c, coracoid process ; gl, glenoid
cavity ; m, metacromion process ; sc, suprascapular notch ; sp, spine ;
sup. fos, supraspinous fossa ; vr, vertebral border ; n, neck.

A slight constriction between the base of the spine and
the margin of the glenoid cavity is termed the neck.
From the cephalic side of the latter the coracoid process

curves mesad.

The clavicle is a slender
curved bone, about one inch
long, imbedded in the mus-
cle between the manubrium
and the coracoid process
(Fig. 21). It does not ar-
ticulate with any bone, but

is held in place by the cephalohumeral and cleidomastoid
muscles (Fig. 48).

The shoulder girdle varies somewhat among the Mam-

FIG. 31. — CAUDAL ASPECT OF LEFT

CLAVICLE.
/>, Mesal end ; a, lateral end.

THE SKELETON.

69

malia. The clavicle is never fully developed in any of
the Carnivora . Primates , Chir op ter a ,
Edentata, and Monotremata are the
only orders in which all the species
possess clavicles. A third element of
the shoulder girdle, known as the cora-
coid, is a fully developed bone only in
the Monotremata, where it articulates
at one end with the scapula, forming
part of the glenoid cavity, and at the
other end with the presternum. In
the other mammals the coracoid is
represented by the coracoid process
of the scapula, which ossifies from a
separate center. In many of the lower
vertebrates a distinct coracoid is pres-
ent.

The humerus is the bone of the arm
or brachium. It articulates proxi-
mally with the glenoid cavity of the
scapula (Fig. 2 1 ) and distally with the
ulna and radius. It consists of three
parts : the proximal extremity bearing
the head, the middle portion or shaft,
and the distal extremity (Fig. 32). The
greater and lesser tuberosities separated
by the bicipital groove lodging the
tendon of the biceps muscle, are the
two processes on the proximal ex-
tremity. The former is the larger
and more cephalic, and serves for the
insertion of the supraspinatus muscle
(Fig. 49). The distal extremity is marked by two im-
portant projections, the external and internal condyles.

FIG. 32. --CEPHALIC
ASPECT OF RIGHT
HUMERUS.

bl, Bicipital groove ; cr,
supracondyloid
ridge ; cp, capitellum
for articulation with
the radius; dr, del-
toid ridge; et, ex-
ternal condyle ; gt,
greater tuberosity ;
it, internal condyle;
It, lesser tuberosity;
sp, supracondyloid
foramen or entepi-
condylar foramen ;
sr, supinator ridge;
tr, trochlea for ar-
ticulation with ulna.

ELEMENTS OF MAMMALIAN ANATOMY.

Extending proximad from the external condyle is the
supinator ridge. Proximad of the internal condyle is

the supracondyloid foramen transmit-
ting the median nerve and brachial artery
(Figs. 72 and 89). The olecranon fossa
is the deep cavity on the caudal aspect
of the bone, opposite the coronoid fossa.
The articular surface of the distal ex-
tremity consists of the capitellum, for ar-
ticulation with the head of the radius,
and the trochlea, for articulation with the
sigmoid cavity of the ulna. On the
cephalic side of the proximal third of
the bone is the rough deltoid ridge for the
insertion of the deltoid muscle which
arises from the shoulder girdle.

The ulna is the longest bone of the
forearm or antebrachium, and is caudad
of the radius. It articulates in the greater
sigmoid cavity with the trochlea of the
humerus and in the lesser sigmoid cavity
with the head of the radius. The distal
articulation is with the radius, cuneiform
and pisiform (Fig. 21). The olecranon
process forms the proximal termination
of the bone and serves for the insertion
of the triceps muscle. Distad of the sig-
-fnoid cavity is a projection known as the
coronoid process. The styloid process
forms a small projection on the distal
extremity of the bone.

The radius is the preaxial or cephalic
bone of the antebrachium. It articulates proximally with
the capitellum of the humerus and the lesser sigmoid cavity

or-

J

st

FIG. 33. — LATERAL
OR OUTER AS-
PECT OF THE
RIGHT ULNA.

ar, Articular facet
for radius ; cr,
coronoid process ;
gs, greater sig-
moid cavity ; Is,
lesser sigmoid
cavity; on, olec-
ranon process ;
st, styloid pro-
cess.

THE SKELETON.

of the ulna, and distally with the scapholunar and radius.
It bears but two processes, the tubercle and the siyloid pro-
cess. The tubercle (Fig. 34) is a slight
knot near the proximal end on the ulnar
side. Proximal from the tubercle is the
neck which supports the head bearing a
concave crown for articulation with the
capitellum of the humerus. The styloid
process projects from the distal end par-
allel with the process of the same name
on the ulna.

The bones of the antebrachium in
many mammals are more or less coal-
esced. In the Chiroptera and many of
the Ungulates the radius is enlarged at
the expense of the ulna, whose proximal
third only remains. The primitive Un-
gulates of the lower tertiary period pos-
sessed a complete ulna as well as radius.
The phylogeny of the horse's limb illus-
trates the gradual development of the
antebrachium of the Equidae (Fig. 35).
Fossil remains reveal the fact that mam-
mals existed as early as the triassic pe-
riod, when the sedimentary rock forming
the triassic strata wras laid down. This
probably occurred 10,000,000 years ago.

According to palseontological investi-
gations, the Ungulata arose from the
Condylarthra, a group of small five-toed
mammals of the lower Eocene, best rep-
resented by the typical genus Phenaco-
dus. In this genus and its successor, Hyracotherinm, the
ulna and radius are well developed and distinct. Orohip-

FIG. 34. - - MESAL
OR INNER AS-
PECT OF RIGHT
RADIUS.

fc, Articulatory sur-
face for capitel-
lum of humerus;
hd, head, - - the
point of the ar-
row is on the ar-
ticulating surface
for the lesser sig-
moid cavity; nk,
neck; sc, articu-
latory surface for
scapholunar ; st,
styloid process ;
tb, tubercle ; ul,
facet for ulna.

~2 ELEMENTS OF MAMMALIAN ANATOMY.

pus, the descendant of Hyracotherium, also shows a dis-
tinct radius and ulna, but in the later forms of the horse
line the ulna gradually diminishes in size and becomes

me

F{

z

24

FIG. 35. — (See opposite page for explanation.}

more and more coalesced with the radius, until in Equus
scarcely more than the proximal third remains (Fig. 37).
Carpus.- -The carpus consists of seven bones arranged

THE SKELETON.

73

in two rows (Fig. 36). Beginning on the pollex side, the
scapholunar, cuneiform, and pisiform compose the proxi-

F

H

A L

V

FIG. 35. — GENEALOGY OF THE HORSE.

F, Forefoot; H, hindfoot; A, forearm; L, leg; I, Orohippus or Pachyno-
lophus; II, Mesohippus; ///, Miohippus; IV, Protohippus; V, Plio-
hippus; VI, Equus; 2, 3, 4, and 5 are the second, third, fourth, and
fifth digits respectively; me, metacarpus; mt, metatarsus; p, pha-
langes; u, ulna; r, radius; /, tibia; /, fibula. — (After Marsh.}

mal row, and the trapezium, trapezoid, magnum, and

74

ELEMENTS OF MAMMALIAN ANATOMY.

unciform form the distal row. The scapholunar, easily
distinguished because of its large size, articulates with the
radius, cuneiform, unciform, magnum, trapezoid, and tra-
pezium. The cuneiform articulates with the ulna, unci-
form, pisiform, and scapho-
lunar. The pisiform is next
to the scapholunar in size.
It projects prominently
laterad from the cuneiform
and articulates with the
radius, ulna, and cuneiform.
The trapezium is the small-
est bone of the carpus. It is

A. B.

FIG. 36.

A, Dorsal aspect of left manus of cat : a, First phalanx of the pollex ; b,

second or terminal phalanx ; en, cuneiform ; h, head of fourth meta-
carpal ; m, magnum ; mt, metacarpal 4 ; n, claw ; pi, pisiform ; .9,
sesamoid bone; st, scapholunar; td, trapezoid; tm, trapezium; u, unci-
form ',1,2, and 3, first, second, and third phalanges of the middle digit.

B, Generalized type of carpus as found in lower vertebrates : c, Centrale ;

1, intermedium or lunare ; r, radiale or scaphoid ; ra, radius ; m, meta-
carpals; u, ulnare or cuneiform; ?</, ulna; 1, carpalia 1, or trapezium;

2, carpalia 2, or trapezoid; 3, carpalia 3, or magnum; 4 and 5, car-
palia 4 and 5, or unciform.

crescentic in shape and articulates with the scapholunar,
trapezoid, and first and second metacarpals. The trap-
ezoid is almost as small as the trapezium. It is distin-
guished by its flatness. It articulates with the scapho-

THE SKELETON.

75

<sc

lunar, magnum, second metacarpal, and trapezium. This
bone, is not visible on the palmar surface of the wrist.
The magnum articulates with the
scapholunar, trapezoid, unciform,
and second, third, and fourth meta-
carpals. The unciform can be recog-
nized by its wredge shape. It articu-
lates with the scapholunar, cunei-
form, magnum, and fourth and fifth
metacarpals. Each carpal bone de-
velops from a single center except
the scapholunar, which develops
from two centers.

The typical arrangement of the
vertebrate carpus is shown in figure
36, B. The pisiform does not be-
long to the cartilaginous skeleton,
butisasesamoidbone. In all mam-
mals possessing five digits the an-
lage of three bones in the proximal
row, five bones in the distal row,
and a central element occurs in the
embryo, but through fusion of ele-
ments a less number is present in
most adults. Thus, in the cat the
radiale and intermedium and cen-
trale unite to form the scapholunar.
In all forms carpalia 4 and 5 coal-
esce to form the unciform.

Metacarpus. - There are five
metacarpal bones forming the mid-
dle region of the forefoot. They
are named, beginning on the pollex side, first, second,
third, fourth, and fifth metacarpals respectively. Each

FIG. 37. — LATERAL AS-
PECT OF LEFT FORE-
LIMB OF EQUUS.

//, Hiimerus; ms, third
metacarpal; w4, fourth
metacarpal; p, phalan-
ges; r, radius; s, sesa-
moid; sc, scapula; u,
ulna; a, scaphoid; c,
semilunar; m, cunei-
form; n, pisiform; w,
magnum; 11, unciform.

76 ELEMENTS OF MAMMALIAN ANATOMY.

bone consists of a proximal extremity or base, a middle
portion or shaft, and a distal extremity or head (Fig. 36).
These bones are curved so as to be slightly convex on the
dorsal aspect.

The number of metacarpals in mammals varies from
one in Equus to five which are present in most orders.
Nearly all the species of every order, except the Edentata
and Ungulata, possess five metacarpals. In the pig and
hippopotamus there are four metacarpals, in the rhi-
noceros three, and in the camel, deer, sheep, and cow
two. In the last three forms the metacarpals present are
the third and fourth, which in the adult are coalesced
into a single bone known as the cannon-bone. Remnants
of the second and fifth metacarpals are present in the
deer, sheep, and cow, as the small caudo-lateral hoofs
indicate. The functional metacarpal present in the horse
is the third. The reduction of metacarpals in the ances-
tral forms of the horse is shown in figure 35, and will be
referred to again in the description of the phalanges.

Phalanges.- -The cat has five toes or digits on the fore-
foot, called pollex, index, medius, annulus, and minimus.
Each digit, except the pollex, consists of three phalanges
(Fig. 36). The pollex or thumb has only two phalanges.
The row of phalanges articulating with the metacarpals
is called the proximal, the terminal row the distal, and
the remaining row the middle phalanges. Two small sesa-
moid bones are attached on the volar side of the junction
of each proximal phalanx with the metacarpal. Each
distal phalanx has its proximal end produced caudal on
the palmar aspect so that its articular surface faces
dorsal. The distal phalanges terminate in claws which
are retractile.

The number of digits in the forefoot of Mammalia varies
from one to five. Nearly all the species of every order

THE SKELETON. 77

except the Endentata and Ungulata possess five digits.
The tapir has four functional digits. The cow, deer,
sheep, and pig also have four digits, but only two are
functional, the second and the fifth being atrophied and
terminating in the small caudo-lateral hoofs which do not
touch the ground. The rhinoceros has three functional
digits, and the Equidae possess only one digit (Fig. 37),
the third, though the atrophied remnants of the second
and fourth metacarpals are present as splint bones which
do not support phalanges.

As before stated, the Ungulates are undoubtedly de-
scendants of a five-toed ancestor of Eocene times. The
evolution of the horse's limb and the reduction in the
number of digits are shown in figure 35. Fossil remains
of the ancestors of the horse have been found in western
United States, Europe, and South America. Orohippus
lived in the region of Wyoming, Montana, and Idaho
probably more than 5,000,000 years ago, when that
country was more or less marshy, and it was necessary
that the mammals should possess a spreading foot which
would not permit them to sink too deep into the mud.
As the ground became firmer and preying Carnivora
more numerous, the foot of the horse adapted itself to
rapid flight over solid ground. Thus, through use and
natural selection the third digit was enlarged at the
expense of the other digits. Confirmation of this ances-
tral history of the horse is found by an examination of
the early embryonic stages. According to Ewart, a
horse embryo 35 cm. long possesses quite well-developed
second and fourth metacarpals terminating with pha-
langeal structures. The ulna and radius of an embryo
50 mm. long are strikingly similar to these same bones
in Mesohippus. In a still younger embryo the ulna is
complete and correspondingly as large as in Orohippus.

78 ELEMENTS OF MAMMALIAN ANATOMY.

As to the method of walking, mammals are spoken of
as plantigrade, digitigrade, and unguligrade. The first
mode of progression is exemplified by the bear, which
place's its metacarpals and phalanges flat on the ground
in walking. The cat is digitigrade, walking on its toes.
The horse and cow are unguligrade, as they walk upon
the hoof. In some cases, as in the Cetacea, the forefoot
is adapted for swimming instead of walking, and the
number of phalanges to each digit is more than three.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. What bones compose the shoulder girdle?

2. How is the thoracic limb attached to the trunk?

3. What does the condition of the clavicle in the cat indicate as to
its past history?

4. Draw the mesal aspect of the scapula and label all parts.

5. What is the significance of the coracoid process?

6. Which processes of the scapula derive their names from their
location and which from their shape?

7. How do you distinguish the right from the left scapula?

8. Draw the caudal aspect of the humerus and label all features.

9. Describe what is seen in looking directly at the distal articulating
surfaces of the humerus.

10. How do you distinguish the right from the left humerus?

11. What features of the humerus derive their names from their shape?

12. Draw the mesal or inner aspect of the ulna and label all features.

13. What features of the ulna derive their names from their form?

14. How do you distinguish the right from the left ulna?

15. Describe the articulations of the radius.

16. Draw lateral aspect of radius and label all features.

17. Describe the condition of the bones of forearm in the horse and
its ancestors.

18. In a five-month fetus of the horse the ulna is distinct from radius
and complete, while in the mature animal but little more than the distal
third remains, and is anchylosed to the radius. Explain significance
of this fact.

19. Draw ventral aspect of carpus and label all parts.

20. Wherein is the chief difference between carpus of cat and man.

21. Draw the lateral aspect of the third metacarpal and label all fea-
tures.

THE SKELETON. 79

22. How do you distinguish the distal from the proximal end of the
metacarpals?

23. Describe the variation in the number of metacarpals in mammals.

24. Describe the usual arrangement of the phalanges in mammals
having five digits.

25. How do you distinguish a phalanx from a metacarpal?

26. Give the number of functional digits in forelimb of dog, pig, cow,
sheep, horse, and rabbit.

27. Name some mammals with atrophied digits.

28. What is the significance of these?

29. In the evolution of the perissodactyls (odd-toed ungulates) de-
scribe the order in which the digits are lost.

30. In the Bovidae and Cervidae which two digits are functional?

THE PELVIC LIMB.

The pelvic or hind-limb of the cat is composed of the
innominate bone, femur, patella, tibia, fibula, seven
tarsals, five metatarsals, and twelve phalanges.

The innominate bone is composed of four parts, the
ilium, ischium, pubis (Figs. 21 and 38), and the small
cotyloid bone. The ilium is the dorsal portion, extending
down to and occupying about one-third of the acetabu-
lum. The ischium includes the caudal portion of the
bone, extending ventral and forming two-thirds of the
boundary of the obturator foramen. The pubis is the
ventral portion, possessing two rami, one projecting
laterad to unite with the ilium, cotyloid, and ischium,
and the other projecting caudad along the mid-ventral
line, joining its fellow and the ischium. In young kittens
the junction of these parts is plainly visible, but in adult
specimens it is wholly obliterated. In old specimens the
ischium and pubis become more or less anchylosed with
their fellows in the mid-ventral line. The cephalic and
dorsal border of the ilium is the crest (Fig. 39). The
rough crescentic area on the mesal aspect is the auricular
surface for articulation with the sacrum. The cephalic

So

ELEMENTS OF MAMMALIAN ANATOMY.

rounded angle of the crest is the anterior superior spine.
The anterior inferior spine is the small prominence
cephalad from the ventral termination of the auricular
surface. The posterior superior spine is the mesal pro-
jection on the mid-dorsal border of the ilium, forming
part of the auricular surface.

ass.

FIG. 38. — LATERAL ASPECT OF LEFT
INNOMINATE BONE.

ct, Cotyloid bone; ac, acetabulum;
il, ileo-pectineal eminence; as,
anterior inferior spine; a^, an-
terior superior spine. — (Modified
after Jayne.)

FIG. 39. — VENTRAL ASPECT OF THE
INNOMINATE BONES.

ac, Acetabulum ; ai, posterior infer-
ior spine ; ar, auricular surface ; cr,
crest ; ct, cotyloid notch ; ip, ileo-
pectineal eminence; is, body of
ischium; ob, obturator foramen;
pb, body of pubis; s, spine; sm,
symphysis pubis ; sp, spine of
pubis; sr, surface of ilium for
attachment of spinal muscles;
tb, tuberosity of the ischium.

The ischium presents a spine on its dorsal border near
the acetabulum. Between this spine and the posterior
inferior spine of the ilium, is a shallow concavity termed
the greater sciatic notch in distinction to the lesser sciatic
notch between the spine of the ischium and the tuber-

THE SKELETON.

8l

(96

^V-^- trch.
*inlch.r.

l.trch -«

n.a 5.-U*

osity. The acetabulum or cotyloid cavity forms the cup
for the articulation of the femur. The interruption in its
ventral border is the cotyloid
notch, at whose base there is
a depression for the attach-
ment of the ligamentum teres
holding the femur in place.
The junction of the pubis with
its fellow is known as the sym-
physis. The cephalic portion
of the bone lying on either side
of this is called the body, the
caudal part taking the name
of ramus. The latter forms
part of the boundary of the
obturator foramen and meets
the ramus of the ischium. This
foramen gives passage to the
obturator nerve and vessels.

In the Sirenia, which have
no pelvic limbs, the innomi-
nate bones are rudimentary.
In the Cetacea these bones are
also rudimentary, which fact
indicates that the ancestors of
these forms possessed func-
tional hind -limbs.

The femur, or thigh-bone,
may be recognized by its
spherical head with a pit for
the attachment of the liga-
mentum teres wliich aids in holding the head in the ace-
tabulum.

The greater trochanter projects from the proximal end of

7

FIG. 40. — CAUDAL ASPECT OF
FEMUR.

ex tub, External tuberosity; int
tub, internal tuberosity; ex
end, external condyle; int end,
internal condyle; i end t, in-
tercondylar notch or fossa ;
intch r, intertro chanter ic
ridge ; g trch, greater trochan-
ter; hd, head; lin as, linea as-
pera; / trch, lesser trochanter;
nk, neck; pit, pit for the liga-
mentum teres ; tr fos, trochan-
teric fossa or digital fossa.

82

ELEMENTS OF MAMMALIAN ANATOMY.

the bone to a level

-itn

FIG. 41.-- ANTERIOR
OR CEPHALIC AS-
PECT OF RIGHT
TIBIA.

at, Articulatory sur-
face for the astrag-
alus ; cr, crest ; et, ex-
ternal tuberosity ; fc,
facet for articulation
with the fibula; im,
internal malleolus ;
*/, internal tuberos-
ity; /g, ligament of
the patella cut off;
tb, tubercle.

nia have any trace

with the head. On this process are
inserted the pyriformis, gluteus me-
dius, and gluteus minimus muscles, all
of which originate on the innominate
bone. The lesser trochanter is the small
projection on the caudal aspect of the
proximal portion of the bone (Fig. 40).
The inter trochanter ic ridge or posterior
intertrochanteric line extends be-
tween the two trochanters, and lying
between this line and the neck is the
digital fossa. The external and in-
ternal condyles are the articulatory
processes on the distal end of the bone.
The blunt projections at their roots
are the external and internal tuberos-
ities. The inter condyloid notch forms
the depression on the caudal aspect
between the condyles. On the ceph-
alic aspect is the trochlear surface for
articulation with the patella. Two
small sesamoid bones, the fabellae, are
present on the caudal aspect of the
condyles, but they are usually re-
moved in preparing the skeleton. The
linea aspera is the slightly roughened
line beginning on the caudal side, dis-
tal to the middle and extending proxi-
mally a short distance, where it bifur-
cates.

The form of the femur varies but
little among mammals having func-
tional posterior limbs. No living Sire-
of a femur, but a vestigial femur is

THE SKELETON.

present in Halitherium, a fossil form. The hind-limbs are

wanting among the Cetacea, but in a few forms nodules

of bone or cartilage may represent the

femur. In most Perissodactyla and Ro-

dentia, and in some Insectivora and a

few fossil Carnivora, a third trochanter

is present.

The patella, or knee-cap (Fig. 21), is
a sesamoid bone developed in the tendon
of the quadriceps extensor muscle (Fig.
52). It is somewhat the shape of an al-
mond and about half its size. It articu-
lates with the trochlea of the femur.

The tibia is the larger bone of the crus.
It presents two enlarged extremities and
a shaft whose cross-section is triangular.
It articulates with the femur and fibula
proximally and the fibula and astragalus
distally (Fig. 21). This is the longest
bone in the cat's skeleton. Between the
concave condyles on the proximal end is
a notch giving attachment to the crucial
ligament of the knee-joint (Figs. 41, 46).

The prominences of the lateral and
mesal aspects of the proximal extremity
are the external and internal tuberosities
respectively. Beneath the former is the
facet for articulation with the fibula (Fig.
41). The tubercle, a prominence on the
cephalic side of this extremity, is for
the insertion of the ligamentum patellcz,
which is really the termination of the
tendon of the quadriceps extensor muscle (Fig. 52). On
the caudal aspect between the condyles is the popliteal

ar

FIG. 42. — INNER OR
MESAL ASPECT
OF RIGHT FIB-
ULA.

Facet for tibia;
ar, facet for as-
tragalus; ex, ex-
ternal malleolus;
h, head ; s, shaft ;
/, articular sur-
face for tibia ; gr,
groove for pero-
neus longus mus-
cle.

a

84 ELEMENTS OF MAMMALIAN ANATOMY.

notch. The sharp cephalic border of the bone forms the
crest. On the distal extremity is a process, the internal
mallcolus, bearing two grooves, the more caudal of which
shelters the tendon of the flexor longus digitorum muscle
while the other is for the tibialis posticus (Fig. 52). A
facet is present on the lateral aspect of this extremity for
articulation with the fibula.

The fibula in proportion to its length is the slenderest
bone in the skeleton. It is the outer or lateral bone
of the crus, and articulates proximally with the tibia
and distally with the tibia and astragalus (Fig. 21).
The proximal extremity is the head, upon which is a
circular facet for articulation with the tibia. The sharp
edge along the cephalic aspect of the shaft furnishes
attachment to the interosseous membrane uniting the
two bones of the crus. The mesal aspect of the distal
extremity shows a prominent facet for articulation with
the astragalus. Immediately proximal to this is the
articular surface for the tibia. From the lateral aspect
projects the external malleolus, on the caudal side of
which is a groove for the peroneus brevis muscle, and
on the cephalic side is a slight depression for the pero-
neous longus (Fig. 52).

In many of the Mammalia the two bones of the crus
are more or less united. In most of the Chiroptera and
Ungulata the fibula is rudimentary. The middle portion
of the fibula is absent in the horse and its distal portion
is fused with the tibia (Fig. 35). The ancestor of the
Equidae in Eocene times had a well-developed fibula, but
in the evolution of the horse this bone has gradually
diminished in size, as shown in the figure.

The tarsus is composed of seven bones in two rows.
The proximal row contains the os calcis, astragalus, and
navicular or scaphoid; the distal row the cuboid, ecto-

THE SKELETON.

cuneiform, mesocuneiform, and entocuneiform. The os
calcis, or calcaneum, is the largest
bone of the tarsus, being twice as
long as broad (Fig. 43). Its caudal
end presents a groove for the ten-
don of the plantaris muscle. The
peroneal tubercle is on the outer
side of the distal extremity. The
sustentaculum, a shelf-like pro-
cess projecting from near the
middle of the inner side, supports
a facet for the tendon of the
flexor longus digitorum muscle

(Fig. 53)-
The astragalus lies on the inner

or mesal side of the calcaneum and
articulates with the tibia, fibula, cal-
caneum, and navicular. The bone
is composed of a body, neck, and
head. The body is proximal and
bears a trochlear surface for articu-
lation with the tibia. The head
bears a convex surface for articu-
lation with the navicular. The neck
is the constricted portion between
the body and the head.

The navicular lies on the mesal
side of the foot and articulates with
the remaining six bones of the tar-
sus. It may be recognized by its
deep concave surface for articula-
tion with the astragalus, and also

by the tuberosity, a process on its mesal plantar angle
(Fig. 43)-

FIG. 43. — DORSAL ASPECT
OF LEFT HIND-FOOT.

ag, Astragalus; ar, articu-
lar surface of the tibia ;
cb, cuboid; cc, ectocu-
neiform; gr, groove for
the tendon of the plan-
taris; h, head of the
fourth metatarsal ; ic,
entocuneiform ; me,
mesocuneiform ; m} , hal-
lux or first metatarsal ;
w2) w3, m4, and rw5, sec-
ond, third, fourth, and
fifth metatarsals ; nv,
navicular or scaphoid;
oc, os calcis, or calca-
neum; 3, proximal row
of phalanges; 2, middle
row of phalanges ; 1 , dis-
tal row of phalanges.

86 ELEMENTS OF MAMMALIAN ANATOMY.

The entocuneijorm is next to the smallest bone of the
tarsus. It articulates with the navicular, mesocuneiform,
and first and second metatarsals. The mesocuneiform is
a wedge-shaped bone and the smallest element of the
tarsus. It articulates with the other two cuneiforms,
the navicular and second metatarsal. The ectocuneiform
may be recognized by a strong hook-like process on its
plantar surface. It articulates with the navicular, meso-
cuneiform, cuboid, and second and third metatarsals.

The cuboid is the lateral bone of the distal row. It
may be recognized by the deep groove on its plantar
surface which shelters the tendon of the peroneus longus
muscle.

The typical arrangement of the tarsal elements in ver-
tebrates is similar to that of the carpus. Three bones,
a tibiale, intermedium, and fibulare, compose the proximal
row, while five tarsalia form the distal row. The centrale
occupies the center of the tarsal region. In the adult
mammal fusion of some of these elements occurs, so that
not more than seven distinct bones are present in any
form. The astragalus contains the tibiale and inter-
medium, while the fourth and fifth tarsalia form the
cuboid.

The metatarsus consists of five bones, the first of which
is rudimentary, while the other four are longer than the
metacarpus, which they resemble (Fig. 43). The first
metatarsal is smaller than any bone of the tarsus. It
articulates with the entocuneiform and is also in contact
with the second metatarsal. The four long metatarsals
have a slight dorsal convexity, each one consisting of a
base or enlarged proximal part, a shaft or middle portion,
and a head or distal rounded articular process. On the
plantar surface of the head of each metatarsal is a median
spine, on each side of which is a concavity for a sesamoid

THE SKELETON. 87

bone. These sesamoid bones are frequently lost in clean-
ing the skeleton.

The number of functional metatarsals in mammals
varies from one to five. Usually the number of meta-
carpals and metatarsals is the same, but in the tapir
there are four metacarpals and but three metatarsals.
All Monotremata, Carnivora, and Primates have five
metatarsals, but in the cats, dogs, and hyenas the first
metacarpal is vestigial. In early geological times all
mammals possessed five metatarsals, the number of
which in many cases has gradually diminished owing to
environment, as is shown in the phylogeny of the horse

(Fig. 35)-

The Kquidae possess but one functional metatarsal
and two rudimentary ones, although Orohippus, the an-
'cestor of the horse, had three functional metatarsals.

The phalanges of the cat's foot are twelve in number.
Each metatarsal except the first supports three phalanges.
The proximal phalanges are the stoutest, and the distal
the smallest. Each distal phalanx bears a claw.

In all five-toed mammals, such as Primates, there are
fourteen phalanges, each digit being composed of three,
except the hallux, which has two.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Describe the articulations of the innominate bone.

2. How do you distinguish the cephalic from the caudal aspect of
the os innominatum?

3. Which processes derive their names from their location?

4. Draw the lateral aspect of the os innominatum and label all fea-
tures.

5. Name the four parts of the bone in order of size.

6. What two orders of mammals have no pelvic limbs?

7. Describe what is seen in viewing the femur from the cephalic
aspect.

8. Name the processes of the femur.

9. Draw the distal aspect of the femur.

ELEMENTS OF MAMMALIAN ANATOMY.

10. How do you distinguish the right from the left femur?

1 1 . Describe the patella.

12. Draw the caudal aspect of the tibia and label all features.

13. How do you distinguish the right from the left tibia?

14. Describe the articulations of the fibula.

15. What features distinguish the proximal from the distal extremities
of the fibula?

16. Write 100 words describing the crus in other mammals than the
cat.

17. Draw the ventral aspect of the tarsus and label all parts.

18. Which of the tarsals support metatarsals?

19. Name the tarsals in order of size.

20. Draw the lateral aspect of the third metatarsal.

21. How do you distinguish a metatarsal from a metacarpal?

22. How do you distinguish the proximal from the distal end of a
metatarsal?

23. Describe the condition of the metatarsals in various mammals.

24. In most mammals how many phalanges to each digit?

25. What artiodactyls have you seen with only two functional digits
on the posterior limbs?

THE JOINTS.

The study of the articulation of the bones and the
ligaments holding them in place is known as syndesmol-
ogy. There are three general classes of articulations :
Synarthroses, or immovable joints; amphiarthroses, or
joints with slight motion; and diarthroses, or joints freely
movable. A synarthrodal joint is exemplified in the
sutures between the bones of the skull. The two surfaces
of bone are separated by fibrous membrane only. An
amphiarthrodal articulation occurs between the bodies
•of the vertebrae and also in the union of the sacrum
with the ilium. In the articula-
tion of the vertebrae the con-
tiguous surfaces of the bone are
faced by flattened discs of fibro-
cartilage (Fig. 21).

The diarthrodal articulation is
exemplified in all joints allowing
free motion. Such joints are
composed of the following parts :
the ends of two bones having
their contiguous surfaces covered
with cartilage; a synovial mem-
brane forming a short tube whose
ends are closed by the cartilagin-
ous articulating surfaces; and

several ligaments varying in number from two or three to
a dozen (Fig. 44). There are four kinds of the diarthrosis :

the arthrodia, or gliding joint, which occurs between the
8 89

FIG. 44. - - DIAGRAM OF A
DIARTHRODAL JOINT.

ar, Afticulatory cartilage ; Ig,
ligament ; sn, synovial
membrane ; sy, synovial
fluid in synovial cavity; /,
tibia ; -v, femur.

9o

ELEMENTS OF MAMMALIAN ANATOMY.

bones of the carpus; the enarthrosis, or ball-and-socket
joint, such as at the hip or shoulder; the ginglymus, or
hinge joint, exemplified at the elbow and knee; and the
rotatoria, or pivot joint, formed by the articulation of

the axis and atlas.

As the knee-joint can be
readily dissected and the
parts well displayed, it is
here described somewhat in
detail. The leg should be
detached at the hip-joint
and the muscles largely re-
moved, taking care in the
immediate neighborhood of
the knee that the ligaments
are not cut. There are eight
ligaments to this joint. The
anterior ligament, or liga-
ment of the patella (Fig. 45),
extending from the patella
to the anterior tubercle on
the tibia, is the strongest
ligament of the knee-joint,
and is really a continuation
of the tendon of the quadri-
ceps extensor muscle. The
capsular ligament, which
entirely surrounds the joint
except in the places occu-
pied by the anterior and lateral ligaments, consists of
two parts, a cephalic and a caudal. The former is seen
on either side of the anterior ligament, extending from
the femur to the tibia as a thick membrane, and more
laterally being attached to the menisci. The caudal

FIG. 45. — LATERAL ASPECT OF DIS-
SECTED KNEE-JOINT.

ad, Adipose tissue; ax, antero-in-
ternal ligament of the meniscus ;
cp, capsular ligament cut and re-
flected mesad; bi, tendon of the
popliteus muscle pulled proximad
to display sc; en, caudal projec-
tion of condyle of tibia ; ex, an-
tero-external ligament of the
meniscus ; ex, external lateral liga-
ment; fb, fibula; fm, femur; Ig,
ligament of the quadriceps exten-
sor muscle ; pt, patella ; sc, exter-
nal or lateral meniscus ; scm, mesal
or internal meniscus ; tf, tibiofibu-
lar ligament ; tb, tibia.

THE JOINTS.

91

m

part extends from the fabellae and the femur to the tibia
and menisci.

The external lateral ligament proceeds from the exter-
nal tuberosity of the femur to the
head of the fibula. The internal
lateral ligament, much shorter than
the external one, extends from the
internal tuberosity of the femur to
the internal tuberosity of the tibia.
The anterior and capsular ligaments
must be cut in order to see the cru-
cial ligaments, which are short, and
cross each other in the region of the
intercondylar notch. The posterior
crucial extends from the caudal
margin of the head of the tibia to
the mesal cephalic angle of the in-
tercondyloid notch of the femur.
The anterior crucial extends from
the summit of the tibia to the cau-
dolateral angle of the intercondy-
loid notch. The tibiofibular liga-
ment is very short, extending from
the head of the fibula to the outer
tuberosity of the tibia. In addition
to these ligaments, there are four
bands uniting the menisci to the
bones. The menisci or semilunar
cartilages are two biconcave cartila-
ginous plates, about one millimeter
thick) interposed between the con-
dyles of the femur and tibia.

The synovial membrane is a very thin transparent
sheet lying within the capsular sheath of the joint. It

FIG. 46. — CAUDAL ASPECT
OF KNEE-JOINT WITH
CAPSULAR LIGAMENT
CUT.

ac, Anterior crucial liga-
ment ; ar, articular sur-
face of condyle of tibia ;
en, condyle of femur ; cp,
capsular ligament cut
along the line Ig and re-
flected proximad ; ex,
external lateral liga-
ment; fb, fibula; fin,
femur; in, internal lat-
eral ligament; Ig, cut
edge of capsular liga-
ment ; pc, posterior cru-
cial ligament; pi, pos-
terior external ligament
of the meniscus; sm,
mesal or internal men-
iscus ; sme, lateral or ex-
ternal meniscus; tf, tib-
iofibular ligament ; tb,
tibia.

92 ELEMENTS OF MAMMALIAN ANATOMY.

secretes the white glairy synovia for lubricating the joint.
The synovial fluid and membrane may be demonstrated
by cutting open a fresh joint obtained from the butcher-
shop (Fig. 4).

All other freely movable joints are similar in structure
to the knee-joint, but have no menisci and fewer liga-
ments. The shoulder-joint has only two or three liga-
ments, the most important of which is the capsular. The
elbow- joint has four ligaments and the hip- joint only two.
In the ankle-joint there are eight ligaments in addition
to the capsular.

These ligaments which bind the joints consist of white
fibrous connective tissue which under the microscope is
seen to be composed of parallel and interlacing fibers.
They are very tough and have but little elasticity, so
that the joints are seldom dislocated (Fig. n).

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Give three examples of each of the three general classes of joints.

2. Explain difference in anatomy of the three classes of joints.

3. Without aid of the microscope can you detect any differences
between a ligament and a tendon?

4. By removing the capsular ligament describe the ligaments that
can be displayed on the lateral and caudal aspects of the knee-joint.

5. After bringing to view by dissection as many ligaments as possible
on inner aspect of knee-joint, draw and label all parts.

6. Draw the menisci.

7. By careful dissection note the ligaments present in the hip-joint.

8. How many ligaments can you find in the shoulder-joint?

9. In what joints is synovia present?

10. Cut a very thin slice of articular cartilage about a millimeter square,
mount in dilute acetic acid, and make drawing as seen under the micro-
scope.

THE MUSCLES.

The study of the muscular system is known as myology.
The muscles are of two kinds : voluntary, which are under
the control of the will; and involuntary, which cannot be
controlled by the will. All muscles moving the bones are
voluntary and are supplied with branches of the cerebro-
spinal nerves. Examples of involuntary muscles are
found in the walls of the alimentary canal, the ureter,
bronchial tubes, and blood-vessels. These are supplied
with nerves from the sympathetic nervous system (Fig.
91). The structure of a voluntary muscle may be seen
by teasing a small piece on a slide in a drop of water,
covering with a cover-glass, and examining with the
compound microscope. It is composed of striated fibers
from one to fifteen centimeters in length, wrhile involun-
tary muscle is composed of cells more or less spindle-
shaped and non-striated, except in the heart (Figs. 8
and 10).

There are over five hundred voluntary muscles in the
cat, each of which is usually attached at either end to
the periosteum of a bone. That point of attachment
which is the center of motion is known as the origin of
the muscle, and is usually more proximad than the
insertion of the muscle. In the case of the biceps, its
origin is on the scapula and its insertion on the radius.
Usually a muscle originates and terminates in a white
glistening cord called a tendon, composed for the most part
of white fibrous tissue (Fig. n).

Each muscle-fiber is surrounded by a transparent

93

94 ELEMENTS OF MAMMALIAN ANATOMY.

clastic sheath, the sarcolemma. A number of fibers
bound together by a loose connective tissue, and the
whole enveloped by an extension of the same, is a fascic-
ulus. The tissue connecting the fibers is the endomy-
sium, while that enveloping the fasciculus is the peri-
mysium. A number of fasciculi bound together in a
sheath, the epimysium, constitutes the entire muscle.
The epimysium is merely a deflected portion of the
sheath enveloping the fasciculus. It is visible to the
naked eye as a thin shining sheath beneath the fascia
which covers the muscles and binds them together.

According to function, muscles are spoken of as flexors,
extensors, adductors, abductors, rotators, elevators, depres-
sors, and sphincters. A flexor muscle is one which by its
contraction bends a limb or any portion of it. An
extensor muscle is the antagonist of a flexor and serves
to bring the two long bones into line. An abductor
muscle is the one inserted on a long bone, which it draws
laterad from the axis of the limb or the sagittal plane
of the body. An adductor muscle is the antagonist of
an abductor. The pectoral muscles are adductors of the
forelimb. A rotator muscle is one which produces more
or less of a rotatory motion in the bone upon which it
is inserted. A rotator muscle is exemplified in the obtu-
rators, which arise on tfie innominate bone and are
inserted in the digital fossa of the femur. An elevator
muscle is represented by the temporal, extending from
the temporal bone to the mandible, which it elevates.
A depressor muscle is the antagonist of an elevator.
The digastric is a depressor of the mandible. A sphincter
muscle is one surrounding an orifice which it closes by
contraction. The orbicularis oris in the lips is an ex-
ample.

Muscles are named according to their function, shape,

THE MUSCLES. 95

or part to which they are attached. Thus the sterno-
mastoid muscle arises on the sternum and is inserted on
the mastoid process of the skull. The latissimus dorsi is
so named because it is a very broad muscle (Fig. 47)
and occupies the dorsal part of the cat's body. The
extensor communis digitorum muscle signifies by its
name that it is the common extensor of the digits.

DISSECTION OF THE MUSCLES.

Since the other systems are of more importance from
the standpoint of comparative anatomy and physiology
than the muscular, only the more important muscles will
be described. Great care should be exercised in removing
the skin of the cat, in order that such superficial muscles
as the platysma myoides on the neck and side of the
face, and occipitofrontalis, may not be cut away. The
skin is attached to the underlying muscles by the super-
ficial fascia, a fibrous areolar tissue, which contains the
subcutaneous fat more or less abundant in all specimens.
The deep fascia is the fibrous and membranous layer
of dense tissue lying close against the muscles and dipping
down between them. The stronger parts of this fascia
are called aponeuroses.

Directions for Dissection.- -Dissection does not mean
the cutting up, but the intelligent separation of one
organ from another without removing the same. The
muscles should not be cut loose from their origin or
insertion, but merely separated from each other by cut-
ting the deep fascia in the longitudinal direction of the
muscle. If it is necessary to remove a muscle for dis-
playing those beneath, it should be cut transversely in
the middle and the two parts reflected. No portion of a
muscle or other tissue should be removed without know-

96 ELEMENTS OF MAMMALIAN ANATOMY.

ing what it is and noticing carefully its relation to the
surrounding parts. The specimen under dissection
should be securely nailed to the tray so that the muscles
are made tense. When the parts become dry, they
should be thoroughly wet with water. If the formalin
in which the specimen has been preserved is irritating
to the mucous membrane of the dissector, a half liter
of 5% ammonium hydrate should be poured over the
specimen.

The muscles of the following table are arranged accord-
ing to location, but they need not be dissected in the
order named. Some classes having time for the study
of one-half or even one-third of the muscles here de-
scribed will be able by the use of the table and the illus-
trations to become familiar with the functions and the
relations of any muscles the instructor may wish to
assign for study. The student should note carefully the
muscles which together effect a certain motion, such as
the flexion of the forearm or the extension of the digits.

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98

FIG. 47. — VENTRAL ASPECT OF THE CEPHAUC HALF OF THE CAT. The
superficial muscles have been removed from the left side and the
scapula reflected laterad to display the serratus and adjacent muscles.

a, Triceps; b, triceps; car, carotid artery; c, clt and c.2, scalene muscles;
cph, cephalohumeral ; ere, coracobrachialis ; dg, digastric; ds, cut end
of the digastric; ext, external oblique; /, inferior constrictor; gh,
geniohyoid; h, humerus; i, scalene; ic, triangularis sterni; int, in-
ternal oblique; j, hyoglossus; k, styloglossus ; /, rectus lateralis; Id,
latissimus dorsi reflected lateral and much of the reflected portion
cut off; lv, levator anguli scapulae; m, longus colli; man, mandible;
mas, masseter; mh, mylohyoid; md, median ventral line; n, fascial
aponeurosis of the external oblique; pc1} pc.,, pc3, and pc4, first, second,
third, and fourth parts of the pectoralis muscle; pet, portion of the
pectoral muscle of the left side ; ret, left rectus abdominalis ; sh, sterno-
hyoid ; shlt sternohyoid of the left side with its middle portion removed ;
std, sternothyroid ; stm, sternomastoid ; st, portion of left sterno-
mastoid; sub, subscapularis ; sps, suprascapularis ; tm, teres major;
tr, triceps; x, cleidomastoid ; 1, 2, 3, 7, 8, and 9, ribs; 5, trachea.

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FIG. 49. — LATERAL OR OUTER ASPECT OF MUSCLES OF THE PECTORAL

LIMB.

a, Cephalic part of the ento-triceps ; an, annular ligament; am, abductor
minimi digiti; c, extensor carpi radialis brevior; del, acromiodeltoid ;
dl, biceps; ecd, extensor communis digitorum; ecrl, extensor carpi
radialis longior, whose tendon is marked m; emd, extensor minimi
digiti ; ei, extensor indicis ; exul, extensor carpi ulnaris ; eom, extensor
ossis metacarpi pollicis; ex, ulnar head of the flexor carpi ulnaris;
fu, flexor profundus digitorum; hu, humerus; i, caudal part of the
ento-triceps; o, olecranon process of the ulna; p, claw of first digit;
pect, portion of the pectoralis; r, region of the head of the radius;
sp, spine of the scapula ; trlt ecto-triceps with its middle portion cut
out.

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Tuberosity of the os calcis.

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erects the trunk on the h
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FIG. 50.

112

FIG. 50. — MESAL OR INNER ASPECT OF THE MUSCLES OF THE FORELIMB.

a, Supracondyloid ridge of humerus; ab, abductor pollicis; b, humerus;
c, humeral head of the flexor carpi ulnaris; cp, ento-triceps ; d, in-
sertion of a tendon of flexor sublimis digitorum; e, ulnar head of
flexor carpi ulnaris; ec,, -extensor carpi radialis longior; ec.,, extensor
carpi radialis brevior; /, portion of the flexor sublimis digitorum
arising from the flexor profundus digitorum ; fs, the portion of the
flexor sublimis arising from the palmaris longus; //>, common tendon
of the flexor profundus digitorum; flx, flexor profundus digitorum;
h, flexor profundus digitorum; k, pronator quadratus; /, flexor carpi
radialis; o, short part of the ento-triceps; ol, olecranon process; ot,
tendinous loops; pect, pectoralis cut off; pi, origin of the palmaris
longus which is reflected caudad; pt, pronator teres; r, ento-triceps;
ro, coracobrachialis ; s, split in the tendon of the flexor sublimis re-
vealed by cutting away the tendinous loop; ss, supraspinatus ; si,
supinator longus; tm, teres major; tb, the head of the humerus; x,
a tendon of the flexor profundus digitorum whose portion between
the two letters is cut out to display the insertion of d.

FIG. 51. — VENTRAL ASPECT OF MUSCLES OF CAUDAL PORTION OF TRUNK

AND THIGH.

a, Transversalis abdominis becoming aponeurotic; adct, adductor mag-
nus; c, pectineus; ex ob, external oblique, whose aponeurosis on the
left side is removed; /, aponeurosis of external oblique; grc, gracilis
with its middle part cut out on the left side ; m, median ventral line ;
ps, psoas magnus ; p, penis ; rcf, rectus f emoris ; ret, rectus abdominis ;
sar, sartorius with its middle part cut out on the left side; smb, semi-
membranosus; smt, semitendinosus ; spmc, spermatic cord; /, apo-
neurosis; trs, internal oblique with a rectangular piece cut out to
show the rectus and transversalis ; tug, tensor vaginae femoris; ts,
testicle; m, vastus internus; x, external abdominal ring.

FIG. 52. — LATERAL ASPECT OF THE MUSCLES OF THE LEG WITH THE GLU-
TEI, TENSOR VAGINA FEMORIS, SEMITENDINOSUS, AND BICEPS FEM-
ORIS REMOVED.

a, Portion of semimembranosus ; ab, adductor magnus; b, peroneus ter-
tius; c, abductor ossis metatarsi; ct, cut surface of the vastus ex-
ternus ; d, peroneus brevis ; eld, extensor longus digitorum pedis ;
gas, gastrocnemius ; /, tendinous loop; Ip, annular ligament; //, ex-
ternal lateral ligament of the knee-joint; Ig, tendon of the extensor
longus digitorum pedis; o, tendinous arch of the peroneus longus;
oc, os calcis ; pi, peroneus longus ; ret, rectus femoris ; t, ligamentum
patellae ; tr, greater trochanter ; ts, soleus ; tg, tendon of gastrocnemius ;
tpl, tendon of the plantaris ; tb, tibialis anticus ; vex, vastus externus
with a piece cut out.

I '

FIG. 51.

ret

10

ELEMENTS OF MAMMALIAN ANATOMY.

.

The muscles in the different orders of mammals have
the same general arrangement. Over four hundred mus-
cles occurring in the cat are found in
man and have approximately the same
relative location and function, and the

/•\^ same nerve-supply. The size and the

,-A shape of the muscles may vary some-
what in accordance with the habits of
the animal. The pectoralis in the cat
consists of five parts, while in man there
are only two parts. The biceps is a sim-
ple muscle in the cat, but in man it has
two well-defined heads. The muscles for
moving the ear, which are well developed
in the horse, cow, and cat, are exceed-
ingly rudimentary in man. The Ceta-
cea and Sirenia possess fewer muscles
than the other orders of mammals, as
they have no hind-limbs. These few re-
marks serve to show that a familiarity

-ac

flexor
orum

FIG. 53. — CAUDAL ASPECT OF THE MUSCLES OF THE
CRUS AND FOOT WITH THE GASTROCNEMIUS, SOL-
Eus, AND PLANTARIS REMOVED.

ad, Adductor ; ac, tendon of Achilles ; ab, abductor
ossis metatarsi ; eg, external head of gastrocne-
mius; fb, flexor brevis digitorum cut at x and
turned aside ; fd, flexor longus digitorum ; ft, flexor
longus hallucis ; i, peroneus longus ; /. peroneus
brevis ; Ip, tendinous loop through which pass the
tendons of the flexor brevis digitorum and the
flexor longus digitorum ; n, cut tendons of fb;
o, plantaris over the tuberosity of the os calcis ;
p, tendon of the peroneus brevis ; pi, tendon of
the plantaris, whose proximal portion is cut away ;
r, tendon of the flexor longus digitorum pedis cut
off as it passes through the slit in the flexor brevis
digitorum ; s, tendon of the flexor brevis digitorum
split for the transmission of the tendon of the
longus digitorum pedis ; s, soleus ; /, tendon of the flexor longus digit-
pedis; x, plantaris giving origin to the flexor brevis digitorum.

THE MUSCLES. 115

with the muscles of any one mammal guarantees a general
knowledge of the muscular system of all mammals.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Describe the two kinds of muscles.

2. Draw a diagrammatic cross-section of the palmaris longus muscle
representing the relation of the fibers, fasciculi, sarcolemma, endomy-
sium, and epimysium.

3. Describe an example of each class of muscles as to function.

4. Which muscles of the head and neck region derive their names
from their function?

5. Describe the chief muscles moving the mandible.

6. Describe the muscles lying ventral to the trachea.

7. Name three important muscles attaching the thoracic limb to
the trunk.

8. Draw the caudal aspect of the triceps muscle.
9 What muscles flex the forearm on the arm?

10. Name the chief extensors and flexors of the digits.

11. On what process of the humerus do several of the flexors of the
manus arise?

12. On what process of the humerus do most of the extensors of the
manus arise?

13. Draw the outline of the ventral aspect of the flexor profundus
digitorum as it would appear detached from limb and with origins slightly
separated.

14. Draw cephalic aspect of the radius and mark the areas to which
the muscles are attached and the names of the same.

15. What muscles flex the manus on the forearm?

16. Describe the muscles extending the manus on the forearm.

17. What muscles in the forearm region derive their names from their
function and location?

18. Describe the large adductor of the thoracic limb.

19. Describe the muscles serving to move the humerus in four direc-
tions.

20. Describe the location and the use of the tendinous loops in the
manus.

21. What muscles form the ventral and lateral walls of the abdomen?

22. Describe from your dissection four muscles causing the movement
of the ribs.

23. After removing the biceps femoris and sartorius, and dissecting
the muscles on the lateral aspect of the thigh, draw the muscles visible
on the lateral aspect, and label.

24. Name the muscles flexing the crus on the thigh.

Il6 ELEMENTS OF MAMMALIAN ANATOMY.

25. Describe from your dissection the muscles extending the crus on
the thigh.

26. Describe the muscles forming the calf of the leg.

27. What muscles are the opponents of the adductor magnus?

28. Draw the plantar aspect of pes showing the superficial muscles, and
label all the features.

29. Describe three muscles moving the digits.

30. Show by drawing the location of the muscles flexing the pes on
the tibia and label all the features.

ORGANS OF DIGESTION,

A young lean cat which has had no food for twenty-
four hours is the best subject for the demonstration of
the digestive system. Directions for preparing the
specimen are given in the chapter on technique.

The digestive system (Figs. 54 and 55) consists of
the alimentary canal and the accessory glands of diges-
tion. The canal is made up of the mouth, pharynx,
esophagus, stomach, small intestine, and large intestine.
Its entire length is about five times that of the cat from
the tip of the nose to the root of the tail. The accessory
glands consist of five pairs of salivary glands, the liver,
and the pancreas.

THE MOUTH.

The mouth is bounded cephalad by the lips, laterally
by the cheeks, and dorsally by the palate, where the
mucous membrane lies in seven or eight transverse
ridges or rugae, and caudally depends from the palatine
bones forming the velum palati. To display the anatomy
of the mouth, one should remove the right half of the
mandible. From either side of the velum palati two
folds of membrane diverge as they extend to the floor
of the mouth at the root of the tongue. The cephalic
fold is the anterior pillar and the caudal one is the poste-
rior pillar of the fauces (Fig. 55). The caudal portion
of the mouth between these folds is known as the fauces.
It opens into the pharynx. On either side of the tongue

between the two pillars is a crescentic depression holding

117

-o

118

ORGANS OF DIGESTION.

119

cc

cd

a tonsil. In man, the tonsils sometimes become in-
flamed and enlarged, giving
rise to a disease called tonsil-
litis. The tonsil is a compound
lymphatic gland whose func-
tion is unknown.

Folds of mucous membrane
called f rena bind the lips to the
gums, which are composed of
dense fibrous tissue investing
the alveolar margins of the
jaw-bones. The mucous lining
of the mouth contains many
simple mucous glands invisi-
ble to the naked eye. Those
of the lips are called labial, of
the cheeks, buccal, and of the
palate, palatine glands.

The tongue lying in the floor
of the mouth is a muscular
mass composed of the genio-
hyoglossus, lingualis superfici-
alis superior and inferior, sty-
loglossus, and hyoglossus mus-
cles. Caudally it is attached
to the hyoid bone. Its invest-
ment of mucous membrane is
formed into a fold beneath it,
called the frenum linguae. The
dorsal surface of the tongue
displays four kinds of papillae

FIG. 55. — DORSAL ASPECT OF
THE TONGUE AND LARYNX.

at, Arytenoid cartilage; a/, an-
terior pillar of the fauces ; cc,
crico-epiglottic ligament; cd,
true vocal cords; cv, circum-
vallate papilla; ep, epiglottis;
fl, flat papilla; fg, fungiform
papilla ; fr, filiform papilla ; gl,
glottis; hy, epihyal bone cut
off ; i, false vocal cord ; oe, lu-
men of the esophagus, which
is cut off just as it opens into
the pharynx ; pf, posterior pil-
lar of the fauces; tn, tonsil.

(Fig. 55): The circumvallate,

numbering from six to eight arranged in a V shape near

the root; the flat, very numerous at the root; the conical,

120

ELEMENTS OF MAMMALIAN ANATOMY.

most numerous and thickly set over the entire dorsal
aspect; and the fungiform, which are blunt and located
more thickly on the sides and near the tip of the tongue

(Fig. 55)-

The Teeth.- -During the first year the cat develops
twenty-six teeth, known as the deciduous or temporary
set, as they are later replaced by a permanent set. The
three parts of a tooth are the crown, neck, and fang (Fig.
57). The crown may be divided into several portions
called cusps. A tooth split longitudinally presents the

following four features (Fig. 56) : the
enamel, a hard glistening substance
covering the entire crown of the tooth
down to the neck; the cement, a bony
substance investing the fang ; the den-
tine, forming the interior hard portion
of the tooth ; and the pulp cavity, con-
taining in the recent state the nerve-
and blood-vessels. The enamel con-
sists mostly of the phosphate of lime.
It is the covering which when broken
permits the tooth to decay.

In an adult cat there are in each

half of the upper jaw three incisors, one canine, three pre-
molars, and one molar (Fig. 57). In each half of the lower
jaw there are three incisors, one canine, two premolars,
and one molar. The permanent dentition of the cat is
therefore expressed by the formula i -|, c \, pm J, m -J-.

The upper incisor teeth are small and undivided both
as to root and crown. They are scarcely one-third as
long as the canine and are planted in the alveoli or
sockets of the premaxillary. The remaining teeth of
this jaw are in the maxilla. The canine or eye tooth
is the longest and likewise is undivided as to root and

FIG. 56. - - LONGITU-
DINAL SECTION OF
THE CANINE TOOTH.

c, Crown ; cr, cement ;
d, dentine; c, en-
amel; /, fang; m,
pulp-cavity ; n, neck.

ORGANS OF DIGESTION.

121

crown. The next three teeth are known as the pre-
molars. They vary much in size. The anterior one
is the smallest, being about the size of the incisors. Its
crown is usually simple, although occasionally there is
seen a small posterior cusp, called triticone, in distinction
to the main cusp or protocone. The root is usually
composed of only one fang. The second premolar is
much larger than the first. Its crown presents a large
median cusp, or protocone; a very small cusp, triticone,

FIG. 57. — LATERAL ASPECT OF THE PERMANENT DENTITION OF THE CAT.

ilt i,2, i{, First, second, and third incisors of the upper jaw; c, canine; />,,
p.2, and />:i, first, second, and third premolars; m, molar; 1, 2, 3, the
incisors of the lower jaw; 4, canine; 5 and 6, first and second pre-
molars; 7, molar; c, cingulum; d, deuterocone ; m, metaconid; m, mo-
l.ir; pt, protoconid; re, protocone; td, talonid ; /, talon; tr, triticone.

on the posterior side of the protocone half-way between
its base and apex; and a basal cusp, the talon, on the
posterior side of the base of the tooth. The prominent
ridge encircling the tooth at its base is the cingulum.
The root is composed of two fangs.

The third premolar or carnassial tooth is fully twice
as large as the second premolar. Its protocone is the
large central cusp, posterior to which is the large triti-
cone. At the mesal anterior angle is the deuterocone.

122 ELEMENTS OF MAMMALIAN ANATOMY.

The small projection at the lateral anterior angle is the
protostyle. The root of the tooth usually consists of
three fangs. The posterior tooth in the maxilla is
called the molar, since it is the only one not preceded
by a milk tooth. It is very small and its crown presents
a grinding surface instead of a cutting one. Its root
consists of two fangs.

Each half of the mandible holds three incisors, one
canine, two premolars, and one molar. The incisors and
canine are so similar to the upper ones that they need
no further description. The first premolar presents a
principal cusp or protoconid, a lower small cusp or
metaconid, and a projection, on the posterior side of
the base, known as the talonid. A cingulum or encircling
ridge is also present at the base of the tooth. The root
consists of two fangs.

The second premolar is very similar to the first except
that it is larger and presents an anterior basal cusp in
addition to the others. The lower molar, sometimes
called the sectorial, because it shears against the upper
sectorial or carnassial premolar, presents two nearly
equal cusps, the protoconid and the paraconid. The
root consists of two fangs, the anterior of which is the
larger.

The deciduous or milk teeth begin to appear above the
gums when the kitten is two weeks old. The incisors
and the canine appear first, then the second and third
molars. The first upper molars do not appear till the
kitten is about six weeks old. According to Jayne, the
deciduous dentition is complete at the end of the second
month. At the end of the fourth month the milk incisors
are being displaced by the permanent teeth. The
formula for the temporary set is di f , dc J-, dm f .

Teeth are present in nearly all adult mammals. The

ORGANS OF DIGESTION. 123

whalebone whales, the duck-bill, and some of the ant-
eaters have no teeth in the adult state, but teeth are
present during their embryonic life. The Echidna shows
no evidence of teeth at any time. Most mammals have
two distinct sets of teeth, known as the milk or deciduous
set, and the permanent set. In the Marsupialia, the
milk dentition is in a degenerate condition. The milk
teeth are present, but none become sufficiently developed
to appear above the gums, except the last premolar, and
in some cases the canine and the incisors. The sloths
have only one set of teeth and are therefore Monophy-
dont. Mammals having both a milk and a permanent
set are termed Diphydont.

In the majority of mammals the teeth are divided
according to form and function into four groups: incisors,
canines, premolars, and molars. Such a dentition is
known as Heterodont, in distinction to the Homodont
dentition, in which all the teeth have the same form, as
is the case in the dolphins. In mammals with a hetero-
dont dentition the number of teeth in the different genera
varies considerably, as seen by the following formula :

m I =44

m \ -- 42

m ^ = 30

P I, m | =20
f , m = 32
?, m =44
|, m | =50

f» P I, m f

The elephant presents a very specialized dentition. It
has no canines nor any lower incisors. The single pair
of upper incisors is developed into long tusks, much
prized for ivory. They continue to grow throughout
the entire life of the animal. Six molars are present
on each side, only one or two of which are functional at

Pig,

i

3.

c p

Dog,

i

:<

p ' r>

^o» •

Cat,

i

c , P

Porcupine,

i

1

c ; p

Sheep,

i

0

c V, P

Horse,

i

::

1 ' tr

c p

Opossum,

i

c p

Man,

2

1 ' I
C p

124 ELEMENTS OF MAMMALIAN ANATOMY.

once. The posterior ones move forward to take the
place of the anterior as these become worn out. The
tusks of the walrus are its canines greatly developed.
None of the typical modern Ruminants have incisors
in the adult state, though they are present in the embryo.
Palaeontology has demonstrated that the ancestors of
the Ruminants had well-developed upper incisors in the
later Eocene times. The occurrence of the rudimentary
upper incisors in the embryo furnishes evidence of a full
dentition in the ancestors of the ruminants, since the
individual embryological history is somewhat of a
recapitulation of the ancestral history of the race.

THE PHARYNX.

The pharynx is that portion of the alimentary canal
between the mouth and the esophagus. The structure
is well shown by making a sagittal section through the
head and neck. This is best done with a saw, after the
specimen is frozen by placing it out-of-doors during one
or two days of cold winter weather.

There are seven openings into the pharynx : the two
posterior nares (Fig. 18), opening anteriorly from the
roof; a Eustachian tube on each side; the esophagus;
and the larynx, leading into the trachea. The mucous
membrane lining the pharynx contains many simple
microscopic mucous glands.

VISCERA.

The body cavity must be opened before the rest of the
alimentary canal can be displayed. The entire ventral
wall of the thoracic and abdominal cavities should be
cut away with the bone forceps and scalpel. The body

ORGANS OF DIGESTION. 125

cavity is divided into two parts by the diaphragm (Fig.
54). The cephalic portion, the thoracic cavity, contains
the esophagus, heart, blood-vessels, thoracic duct, trachea,
and lungs. In the young cat there is present also the
thymus gland, stretching cephalad several centimeters
from the base of the heart. The transparent membrane
lining this cavity and investing the lungs is the pleura.

The caudal part of the body cavity, or coelom, is the
abdominal cavity containing the abdominal viscera,
which are here briefly described. The liver, a large
brownish-red organ, is adjacent to the diaphragm on the
right side, while the stomach (Fig. 54) lies close to the
diaphragm on the left. The spleen is the dark red, flat,
elongated organ caudad of the stomach on the left side.
T]ie sheet of thin transparent tissue more or less laden
with fat, depending from the stomach and covering the
intestines like an apron, is the greater omentum. It is
a portion of the peritoneum which lines the abdominal
cavity and invests most of the organs therein. The
pancreas is a pinkish elongate body, bent at a right
angle near its middle, so that one portion lies in the
bend of the duodenum and the other dorsal to the stom-
ach. The kidneys may be recognized by their well-
known shape and dorsal location in the cephalic lumbar
region. The ovaries are small pinkish bodies lying near
the kidneys, adjacent to the dorsal abdominal wall.
The uterus is easily known by its two horns extending
caudad from the ovaries to their junction at the body
of the uterus. The bladder, if full of urine, is at once
recognized; and if empty, appears as a small pear-

shaped mass ventrad to the rectum (Fig. 54).

>

126 ELEMENTS OF MAMMALIAN ANATOMY.

ESOPHAGUS.

The esophagus or gullet is that portion of the ali-
mentary canal leading from the pharynx to the stomach.
In the thoracic cavity it lies dorsal to the heart (Fig. 54)
by the side of the aorta. Immediately caudad of the
diaphragm it opens into the cardiac end of the stomach
(Fig. 58).

STOMACH.

The stomach is that dilated portion of the canal
lying immediately caudad of the diaphragm on the left
side. The esophageal end of the stomach is known as
the cardiac portion, and the intestinal end is the pyloric
portion (Fig. 58). Here a circular fold of mucous mem-
brane embraced by a sphincter muscle serves as a valve
to open and close the pylorus or gateway to the intes-
tine. The dorsal surface of the stomach is its lesser
curvature and the ventral convex surface is its greater
curvature. The structure of the walls of the stomach
is described below.

INTESTINE.

The intestine is that much contorted portion of the
canal leading from the stomach to the external aperture
or anus. The first portion, the small intestine (Fig. 58),
is about three feet long in a large cat, and is less in
diameter and much more convoluted than the second
portion, or large intestine.

The small intestine consists of three parts: the duo-
denum, the jejunum, and the ileum. The duodenum is
the first twelve or fifteen centimeters. A duct from the
liver and the gall-bladder and two ducts from the pan-
creas, empty into it. The former is the ductus com-

ORGANS OF DIGESTION.

127

munis choledochus and the latter are the pancreatic
ducts. The jejunum is the portion of the small intestine
next to the duodenum. It is about twenty-five centi-

vc//

FIG. 58. — VENTRAL ASPECT OF THE ALIMENTARY CANAL WITH THE ILEUM

PULLED TO ONE SIDE.

ac, Small intestine opening into the large intestine ; a, anus ; ao, ascending
colon; bd, hepatic duct; ce, cecum; cd, cystic duct; cs, bile-cyst or
gall-bladder; cr, cardiac portion of the stomach; di, diaphragm;
du, duodenum ; do, caudal part of the descending colon ; dc, ductus
communis choledochus ; gc, greater curvature of the stomach ; il,
ileum; je. jejunum; lc, lesser curvature of the stomach; ce, esophagus;
pn, pancreas; f>y, pyloric portion; pa, mesenteric gland; pd, pan-
creatic duct ; r, rectum ; sp, spleen ; tc, transverse colon.

128

ELEMENTS OF MAMMALIAN ANATOMY.

meters long. No special mark indicates its limits. It
is so called because that portion of the canal in man is
frequently empty after death. The ileum constitutes
more than two-thirds of the small intestine, is much
convoluted, and extends from the jejunum to the large
intestine on the right side of the abdominal cavity, near
the iliac bone. The intestine is supported by the folds

of the peritoneum known as
the mesenteries.

The large intestine con-

FIG. 59. — TRANSVERSE SECTION OF
THE CAT.

i, Sections of the intestine ; d, duo-
denum ; a, aorta ; pan, pancreas ;
pa, pancreas Aselli ; spl, spleen ;
sp, spinous process of the lumbar
vertebra; tr, transverse process;
v, post-cava or inferior vena cava ;
om, greater omentum ; the broken
line is the peritoneum.

FIG. 60. — CROSS-SECTION OF THE
CARDIAC END OF THE STOMACH.
X 3.

cav, Cavity of the stomach; ex, ex-
ternal muscular coat ; in, internal
muscular coat; m, mucous coat;
mm, muscularis mucosae; s, sub-
mucous or areolar coat ; se, serous
or peritoneal coat.

sists of the cecum, colon, and rectum. The cecum is the blind
conical projection at the beginning of the large intestine.
It is only one or two centimeters long. The ileum opens
into the large intestine at the junction of the cecum and
colon. An annular fold of mucous membrane, strengthened
by a sphincter muscle, forms the ileocecal valve, which re-

ORGANS OF DIGESTION.

129

tains the food in the small intestine until the nutriment
is absorbed (Fig. 58).

The colon, extending from the cecum to the rectum, is
composed of the ascending, trans-
verse, and descending parts. The as-
cending colon lies on the right side;
the transverse extends crosswise, con-
necting the ascending with the de-
scending, which lies on the left side.
The descending colon terminates in
the rectum, which is five or six centi-
meters long.

The wall of the alimentary canal is
composed of three chief coats-
mucous, areolar, and muscular. These
coats may be seen by cutting trans-
versely, with a sharp scalpel, a portion
of the stomach hardened in formalin.
The mucous coat (Fig. 60) lines the
lumen and contains the numerous
glands which vary much in the differ-
ent portions of the canal. The esopha-
gus contains the esophageal glands,
whose secretion probably has no other
effect on the food than to facilitate its
passage. The mucous coat of the
stomach contains the gastric glands,
which yield pepsin and hydrochloric
acid, the chief agents of the gastric
digestive fluid (Fig. 61). The glands
in the cardiac end of the stomach

differ from those in the pyloric end in containing numerous
parietal or acid cells which probably secrete the hydro-
chloric acid for digestion.

dT

FIG. 61. - - A CROSS-
SECTION OF THE Mu-
cous COAT OF THE
STOMACH BETWEEN

THE LINES a AND C IN

FIG. 60 SHOWS Two
GASTRIC GLANDS. X
250. Diagrammatic

a, Mouth of gastric
gland ; e, columnar
epithelial cells on
the food surface of
the stomach ; /, lu-
men of a gland; o,
oxyntic or acid cell.

II

130

ELEMENTS OF MAMMALIAN ANATOMY.

The mucous coat of the small intestine contains tube-
like glands, the glands of Ljeberktihn, whose secretion
changes starch into sugar. In the duodenum and
jejunum the mucous membrane is thrown into numerous
transverse folds, vahuli conniventes, which increase the
surface for absorption. The villi are minute finger-like
processes (Fig. 62), barely apparent to the naked eye,
projecting into the lumen for the purpose of absorbing
the nutriment from the chyle. They consist of a covering

of columnar epithelial cells (Fig.
63), within which ends a chyle ves-
sel or lacteal surrounded by small
blood-vessels held in place by con-
nective tissue. The fatty portions
of the food are carried by the lac-
teals (Fig. 78) to the left thoracic
duct, and thence to the jugular vein,
while other portions of the food are
taken up by the capillaries of the
portal system, which begin in the
villi (Fig. 63). The mucous mem-
brane of the large intestine like-
wise contains tube-like glands sim-
ilar to the glands of Lieberkiihn,
but no villi.

The submucous or areolar coat is adjacent to the mucous
coat of the intestine, but in the stomach the muscularis
mucosae intervenes. Next to the submucous coat is
the muscular coat, composed of two layers, one of circular
fibers, the other of longitudinal fibers. An additional
layer of oblique fibers is present in the cardiac end of
the stomach, which aid in giving that organ the peculiar
churning or peristaltic motion necessary for chymifica-
tion of the food. A fourth coat or serous covering sur-

FIG. 62 — CROSS-SECTION
OF THE SMALL INTES-
TINE. X 5.

ex, Longitudinal muscular
coat ; m, circular muscu-
lar coat; mu, mucous
coat; Ib, glands of Lie-
berkuhn; se, serous or
peritoneal coat ; sm,
submucous or areolar
coat.

ORGANS OF DIGESTION.

rounds the muscular coat of the stomach and intestines.
It is merely a reflected portion of the peritoneum which

lines the entire abdominal cavity.

THE ACCESSORY GLANDS OF DI-
GESTION.

The salivary glands are five in
number on each side of the head.
They secrete the saliva, certain

FIG. 63. — A, CROSS-SECTION OF THE Mucous COAT OF THE INTESTINE
BETWEEN a AND c, IN FIG. 62. ' 200. Diagrammatic.

i'il, Two villi projecting into the lumen of the intestine; <?/>, columnar
epithelial cells; /, lacteal; a artery; r, vein; Ib, gland of Lieberkiihn;
m, mouth of gland of Lieberkiihn; ar, location of areolar or sub-
mucous coat.

B, PHOTOMICROGRAPH OF SECTION OF INTESTINE WITH BLOOD-VESSELS

INJECTED.

b, Large artery; mu, muscular coat; s, submucous or areolar coat.

elements of which have the power of changing starch
into sugar.

132

ELEMENTS OF MAMMALIAN ANATOMY.

The parotid gland is the largest of the salivary group
and lies just ventrad to the base of the external ear
(Fig. 64) beneath the skin. It is about two centimeters
in diameter. Its secretion is poured into the mouth
through Stenson's duct, which may be seen extending
from the cephalic margin of the gland over the masseter
muscle, to near the angle of the mouth, where it per-
forates the buccinator muscle, and opens within the
mouth on the cheek, opposite the prominent cusp of the

last premolar. The duct
and gland may be injected
with Berlin blue by insert-
ing the cannula into the
orifice of the duct (Fig. 64).
The submaxillary gland is
near the angle of the man-
dible and ventrad to the
parotid. Wharton's duct
extends from its anterior
surface, between the digas-
tric and masseter muscles,
to its orifice on the floor of
the mouth, opposite the last
tooth of the mandible.

The sublingual gland is

quite small, elongated, and lies cephalad of the submaxil-
lary. Its duct extends parallel with that of the submaxil-
lary and opens within the mouth upon the same papilla
beneath the tongue. The malar gland is very small and
lies near the angle of the mouth ventrad of Stenson's duct.
Its several ducts, which are not easily demonstrated, pass
through the cheek to open within the mouth. The zygo-
matic or infraorbital gland lies on the lateral part of the
orbit on the ventro-lateral surface of the eyeball. It may

FIG. 64. — LATERAL ASPECT OF THE
HEAD WITH THE SKIN REMOVED.

cr, Carotid artery ; c s, esophagus ; Im,
lymphatic gland ; nr, vagus and
sympathetic nerves; sm, sub-
maxillary gland; tr, trachea; v,
cervical vertebra.

ORGANS OF DIGESTION. 133

be seen by cutting away the zygomatic arch and the mas-
seter muscle. From near the ventral angle of the gland
a duct leads to the roof of the mouth posterior to the
molar tooth.

The liver is the largest gland in the body and is situated
immediately caudad of the diaphragm (Fig. 54), and in
contact with the right lateral and cephalic surfaces of
the stomach. It is composed of five lobes: the caudate,
right lateral, right central, left central, and Spigelian. If
the abdominal wall is removed, a ventral view of the
liver shows the caudate lobe to be the most caudal part
of the organ on the right side. Its dorsal surface is
in contact with the kidney. Cephalad of this is the
right lateral lobe in contact with the diaphragm. These
two lobes are of about the same size. The right central
lobe is much larger than the two preceding ones and
presents a deep cleft in which is lodged the green gall-
bladder or cyst. The left central lobe is small, lies in
contact with the diaphragm, and is separated from the
right central lobe by the broad or falciform ligament,
which is a double layer of peritoneum, apparently pending
from the diaphragm. The left lateral lobe is about the size
of the right central lobe and is in contact with the dia-
phragm, stomach, and right central lobe. The Spigelian
lobe is seen by raising the liver from the stomach. It
is the smallest lobe and lies adjacent to the esophagus.

The right lateral fissure is between the right lateral
and right central lobes. The cystic notch shelters the
gall-bladder. The umbilical fissure is between the two
central lobes. The round ligament lies in this fissure.
The left lateral fissure is between the left central and
left lateral lobes. The transverse fissure separates the
ventral from the Spigelian lobe and lodges the portal
vein, hepatic artery, and the main bile-ducts.

134 ELEMENTS OF MAMMALIAN ANATOMY.

The bile secreted by the liver passes through the
several ducts from the various lobes, to the main hepatic
duct, which may be seen by cutting away the liver from
the right side of the gall-cyst, and carefully picking off
the peritoneum ensheathing the vessels between the
Spigelian lobe and the cystic duct. The latter is some-
what convoluted in its course from the deeply imbedded
end of the cyst, to a point on the duodenum about three
centimeters from the pylorus. The main hepatic duct

'• • , v v «

A

V

FIG. 65. — PHOTOMICROGRAPH OF SECTION OF THE LIVER. X 300

b, Blood-vessel.

joins the cystic duct (Fig. 58) near its middle. The
common duct thus formed is the ductus communis
choledochus. When the bile is secreted faster than it
is permitted to enter the intestine, it passes backward
from the ductus communis choledochus into the cyst.

The bile aids in the absorption of the fats by the
villi, and renders the chyme alkaline so that the pan-
creatic juice may act more strongly. The formation of
red blood-corpuscles takes place in the liver of the

ORGANS OF DIGESTION. 135

embryo, while in the adult the liver destroys these
corpuscles. The chief function of this organ, however,
is the formation of glycogen from the sugars and starches
eaten and the gradual transformation of this glycogen
into sugar as demanded for the nutrition of the body.
Diabetes mellitus is caused by a diseased liver which
permits sugar to accumulate in the blood.

The pancreas (Fig. 58) is an elongated gland bent at
a right angle near its middle. The body of it lies dorsal
to the pyloric portion of the stomach, and the head lies
close along the concavity of the duodenum. It has two
ducts, one of which enters the duodenum in common
with the ductus communis choledochus, while the other
enters about three centimeters further caudad. The
pancreatic juice acts on the starches, proteids, and fats.

THE PERITONEUM.

The peritoneum (Fig. 59) is the serous sac lining the
abdominal cavity and investing most of the organs
therein contained. The four portions of the peritoneum
are known as the omenta, the mesenteries, parietes, and
ligaments. The omenta are three in number, the largest
of which is the great or gastrocolic omentum, stretching
caudad from the dorsal abdominal wall and the greater
curvature of the stomach, so as to cover the intestine
like an apron. It is composed of four layers of peri-
toneum forming a closed sac, and bearing more or less
fat. Two layers form the ventral wall of the sac attached
to the stomach, and two layers are also present in the
dorsal wall of the sac which invests the pancreas.

The lesser omentum, or gastrohepatic omentum, ex-
tends caudad from the liver to the pyloric part of the
stomach and duodenum. Its two folds extend from the

136 ELEMENTS OF MAMMALIAN ANATOMY.

two sides of the portal fissure, ensheathing the portal
vein, hepatic artery, and cystic duct. The gastrosplenic
omentum stretches from the cardiac region of the stomach
to the spleen, which it embraces, and then proceeds to
the diaphragm.

The mesenteries are the two layers of peritoneum
suspending the intestine from the dorsal abdominal wall.
There are four mesenteries : the true mesentery, sus-
pending the jejunum and ileum; the mesoduodenum,
suspending the duodenum; the mesocolon, suspending
the colon; and the mesorectum, suspending the rectum.

The parietes or parietal peritoneum is that portion
lining the walls of the abdominal cavity. It is a closed
sac in the male, but in the female the Fallopian tubes
open into it.

The ligaments are the layers of the peritoneum sus-
pending other organs than parts of the alimentary
canal. The falciform ligament extends from the caudal
surface of the diaphragm and the abdominal wall, to
the surface of the liver, which its line of attachment
divides into halves. The round ligament is a fetal relic
extending from the umbilicus to the longitudinal fissure
on the caudal surface of the liver. A third ligament
connects the dorsal border of the liver with the dia-
phragm. The broad ligaments of the uterus are the folds
of peritoneum which embrace the uterus, the Fallopian
tubes, and the ovaries. The ovarian ligaments are short
cords extending from the ends of the uterine cornua to
the ovaries. The round ligaments of the uterus pass
from the sides of the uterus to the brim of the pelvis.

The peritoneum is called a serous membrane because
of the colorless serum secreted by it. Other serous
membranes are the pericardium of the heart, the pleura
lining the thoracic cavity and investing the lungs, and

ORGANS OF DIGESTION.

137

the synovial membranes of the joints. Serous mem-
branes invest only such cavities as are not exposed to
the air. All other cavities are lined by mucous mem-
brane. A serous membrane consists of a layer of fibrous
connective tissue covered by plate-like endothelial cells.

REMARKS ON THE MAMMALIAN DIGESTIVE SYSTEM.

The digestive system of mammals varies somewhat

among the different groups. In carnivorous animals, as

a rule, the alimentary canal is much shorter than in

FIG. 66. — DIAGRAM OF THE STOMACH OF A RUMINANT.

a, Dotted line showing the direction of the food in the process of diges-
tion; abom, abomasutn ; tin, duodenum; ce, esophagus; ps, psalterium ;
rt, reticulum.

herbivorous. In the wildcat the canal is four times the
length of the body, while the canal of the sheep is twenty
times as long as the body. In man it is about nine
times as long as the distance from the crown of the
head to the coccyx. In Ruminants, such as the cow and
the sheep, the stomach is very large and divided into
four chambers — the rumen or paunch, reticulum, psal-
terium or many plies, and abomasum. (Fig. 66). The
rumen and reticulum serve as mere storage cavities,
from which the food returns to the mouth for thorough

12

138 ELKMI«:NTS OF MAMMALIAN ANATOMY.

mastication, and then passes direct, by means of a
groove in the esophagus, into the psalterium, and finally
on to the abomasum. The latter is the true stomach,
and is provided with gastric glands. In the camels the
rumen and reticulum have connected with them pouch-
like diverticula for the storage of water. The con-
stricted openings of the pouches into the rumen or
reticulum may be entirely closed by sphincter muscles.

In man and the higher apes there is present an at-
tenuated extension of the cecutn known as the vermi-
form appendix. In the fetus of man it is proportionally
longer than in the adult. In the herbivorous mammals,
such as the cow and rabbit, the cecum is greatly enlarged,
so as to play an important part in digestion. In a few
forms, such as the sloths, some Cetacea, and a few
Carnivora, the cecum is absent.

The lowest mammals, the Monotremata, resemble
birds and reptiles in possessing a cloaca into which open
the rectum and the urinary and genital ducts. The cloaca
opens externally beneath the tail. Salivary and thyroid
glands, pancreas, and liver are present in all mammals,
but the gall-cyst is absent in Cetacea, the Perissodactyla,
Hyracoidea, and a few Rodentia. The liver is usually
relatively larger in fat-eating animals.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1 . Describe the fauces.

2. Describe in detail every feature visible on the dorsal surface of
the tongue.

3. Give the number "of fangs in each tooth of the permanent set.

4. Give the number of each kind of teeth in the two sets.

5. Draw two aspects of the sectorial tooth.

6. How thick is the enamel of the teeth?

7. Name some mammals which do not have enamel on the teeth.

8. Name some toothless mammals.

9. Name some mammals having only one set of teeth.

ORGANS OF DIGESTION. 139

10. Give the dental formulae for three ungulates.

11. In what animals are some of the teeth greatly enlarged?

12. Do any runfinants have upper incisors?

13. Name the important features of the pharynx.

14. Name every organ in the abdominal cavity, telling with what other
organs it is in contact.

15. Describe as much of the peritoneum as you can see in your specimen.

16. Draw the alimentary canal in its natural position, showing all
ducts leading into it, and label all parts.

17. How much longer is the small intestine than the large one?

18. On what does the length of the canal in different mammals largely
depend?

19. Make a section of a portion of the wall of the stomach and draw
what is seen, labeling all parts.

20. Make a section of the small intestine, draw what can be seen by
naked eye or simple microscope.

21. About how many villi to each square millimeter?

22. Describe the two channels through which the food passes from
the intestines to the heart.

23. Make a somewhat diagrammatic drawing representing that part
of the venous system conveying the food from the intestines to the heart.

24. What is the size of the cecum in other mammals than the cat?

25. Give the location, size, and form of the salivary glands

26. Name the lobes of the liver in order of their size.

27. How is the liver held in place?

28. Draw the pancreas, showing ducts leading to the intestine.

29. Draw the complex stomach characteristic of many ruminants.

30. What is the cloaca and in what mammals is it present?

THE VASCULAR SYSTEM.

The vascular system is composed of the central forcing
muscular organ, the heart; a system of vessels, the
arteries, carrying the blood from the ventricles to the
lungs and all parts of the body; a system of vessels, the
veins, returning the blood to the auricles; and numerous
microscopic vessels, the capillaries, connecting the
termination of the arteries with the origin of the veins.

THE HEART.

The location of the heart in the cat may be seen by
removing the ventral thoracic wall, but for the study
of the parts, the heart of an ox or a sheep will be found
more satisfactory. The heart of the cat lies between
the lungs (Fig. 80) in the thoracic cavity a little to the
left of the median line. The caudal end is the apex, and
the cephalic end is the base. The entire organ is in-
vested by a tough membrane, the pericardium, which
when cut permits the pericardial fluid to run out. All
the blood-vessels originate from the dorsocephalic aspect
of the heart.

It is composed of a right and left half, each of which
consists of an auricle and a ventricle. The separation
between the two halves is apparent on the ventral
surface. The auricles receive the blood from the veins
and pass it to the ventricles, which disperse it through
the arteries. There is no aperture between the auricles
or the ventricles. The aperture between the right

auricle and the right ventricle is guarded by the tricuspid

140

THE VASCULAR SYSTEM.

141

valve which prevents the blood from returning into the
auricle when the systole or contraction pushes the blood
into the pulmonary artery. The opening between the
left auricle and left ventricle
is guarded by the bicuspid or
mitral valve. These valves
may be displayed by cut-
ting away the caudal half of
the ventral wall of the ven-
tricles, when the chorda)
tendinese, delicate tendin-
ous cords, will be seen ex-
tending from the margins of
the translucent membran-
ous valves to the columnar
carneae or muscular projec-
tions on the walls of the
ventricles. The walls of the
auricles are thin in compari-
son with the wralls of the left
ventricle, which are twice as
thick as the walls of the
right ventricle (Fig. 68).

The auricles are very
small when not injected,
and may by the beginner be
cut away with the pericar-
dium and surrounding adi-
pose tissue. The right auri-
cle receives three veins, the
precava, postcava, and cor-
onary veins, all of which enter its dorsal aspect. The por-
tion of the auricle into which the above veins open is the
sinus venosus. At the dorsal part of the septum which

FIG. 67. — HEART VIEWED YEN-
TRALLY, WITH YKXTRAL HALF OF
THE AURICLES AND VENTRICLES
CUT AWAY AND THE AURICLES
DRAWN LATERAD. Partly dia-
grammatic.

n, Orifice of the aorta; ao, aorta;
aao, arch of the aorta ; ap, orifice
of the precava ; as, orifice of the
postcava; h, left pulmonary-
veins; fan, left ventricle; mt, mi-
tral or bicuspid valve; la, left
auricle ; p, orifice of the pulmon-
ary veins ; pc, postcava ; prc, pre-
cava; ba, orifice of the pulmonary
artery; prv, right pulmonary
veins ; rv, right ventricle and one
of the right pulmonary veins; ra,
right auricle ; rp, right pulmonary
artery; tr, tricuspid valve; xp,
left pulmonary artery.

142

ELEMENTS OF MAMMALIAN ANATOMY.

divides this auricle from the adjoining one is an oval
depression, the fossa ovalis, where, in the embryo, the
two auricles communicated. The left auricle is in con-
tact with the right dorsally, and receives three pulmonary
veins (Fig. 69).

FIG. 68. — VENTRAL ASPECT OF THE
HEART WITH ITS CAUDAL THIRD
CUT OFF TRANSVERSELY.

a, Adipose tissue; be, brachioceph-
alic artery ; la, left auricle ; Iv, left
ventricle; Ic, left carotid artery;
o, ductus arteriosus ; pv, pulmon-
ary vein ; ba, pulmonary artery ;
pc, precava; psc, postcava; ra,
right auricle ; re, right carotid ar-
tery ; rs, right subclavian artery ;
rv, right ventricle; sb, left subcla-
vian artery; tr, trachea.

FIG. 69. — DORSAL ASPECT OF THE
HEART OF THE CAT.

ao, Aorta ; ap, apex ; as, azygos vein ;
be, brachiocephalic artery; ca,
coronary artery; cv, coronary
vein; /, left auricle; Ic, left caro-
tid artery; Isb, left subclavian ar-
tery ; p, postcava ; pc, precava ; pa,
pulmonary artery dividing into
its right and left branches ; ra,
right auricle; re, right carotid;
rs, right subclavian ; v, pulmonary
veins.

From the right ventricle arises the pulmonary artery
which carries the impure blood to both lungs. Its
mouth is guarded by three semilunar valves which
prevent the return of the blood. The left ventricle gives
origin to only one important vessel, the aorta, which
arches dorsally around the left auricle, and at the apex

THE VASCULAR SYSTEM. 143

of the arch gives off two branches, the brachiocephalic
or innominate, and the left subclavian. Three semilunar
valves also guard the mouth of the aorta. The arteries
of the heart may easily be distinguished from the veins
by the fact that the walls of the former are much thicker.

THE ARTERIES OF THE TRUNK.

The blood-vessels form two systems of circulation;
the one known as the pulmonary circulation includes the
arteries carrying blopd from the right ventricle to the
lungs, and the veins returning the blood from the lungs
to the left auricle; the other, known as the systemic
circulation, includes the arteries conveying the blood
from the left ventricle to all parts of the body, and the
veins returning the blood to the right auricle.

The main artery of the systemic circulation is the
aorta, which, beginning in the left ventricle, arches
dorsad to the heart and extends along the spinal column
to the tail. That portion in the thoracic cavity is termed
the thoracic aorta, while that portion in the abdominal
cavity is the abdominal aorta. Three semilunar valves
guard the mouth of the aorta at its opening from the
ventricle, in order that the blood may not be forced
back into the heart by the contraction of the muscular
coat of the arteries.

The branches of the thoracic aorta are as follows : the
right and left coronary, arising from the aorta immediately
beyond its exit from the ventricle, are distributed to
the walls of the heart. From the arch of the aorta arise
two large branches: first, the brachiocephalic, giving
origin to the right subclaman supplying blood to the
arm, and the right and left carotids supplying the head
and neck; and, second, the left subclaman, supplying

144

ELEMENTS OF MAMMALIAN ANATOMY.

the left arm, brain, and sternum (Fig. 70). Ten pairs
of intercostal arteries supply the intercostal spaces,
muscles of the back, and the spinal cord. Two bronchial
arteries go to the lung tissue. Two to four esophageal

arteries are distributed to the
esophagus. Two or three pairs
of lumbar arteries pierce the
muscles of the back.

The abdominal aorta gives
off the following branches : the
cceliac axis, the superior mes-
enteric, the adrenolumbalis, a
pair of renal, a pair of genital,
an inferior mesenteric, a pair
of iliolumbar, seven or eight
pairs of lumbar, a pair of ex-
ternal iliacs, a pair of internal
iliacs, and a caudal artery
(Fig. 70).

The coeliac axis is a large
branch arising just caudad to
the diaphragm and gives off
the hepatic branch to the liver,
pancreas, and duodenum, the

FIG. 70. — CHIEF ARTERIES OF THE
TRUNK, VENTRAL ASPECT.

ar, Arch of the aorta; be, brachioceph-
alic; cc, coeliac axis; cd, caudal; c,
coronary; /, gastric; gr, gastric; gas,
gastroduodenalis ; hp, hepatic; ht,
location of heart ; icn, intercostals ;
ic, external iliac; it, internal iliac;
il, iliolumbar; im, inferior mesen-
teric ; Is, left subclavian ; //>/, left

pulmonary; m, splenic; o, splenic; r, right pulmonary; re, renal; sp, splenic
trunk ; sms, superior mesenteric; sm, spermatic or ovarian; s, adrenolum-
balis; 1, 2, 3, 4, 5, and 6, lumbar arteries.

THE VASCULAR SYSTEM. 145

coronary to the stomach, and is continued as the splenic,
supplying the stomach and the spleen. The phrenic artery,
supplying the diaphragm, sometimes arises from the coeliac
axis, but usually from the adrenolumbalis.

The superior mesenteric is about the same size as the
coeliac axis, and arises within one centimeter caudad. It
sends branches to the pancreas and both intestines. The
tidrenolumbalis is a small branch on the left side dividing
into the adrenal, phrenic, and muscular. The renal
arteries supply the kidneys and usually the suprarenal
bodies. The genital arteries are small, and arise from
one to two centimeters caudad of the renal arteries.
They pass obliquely caudad to the ovaries in the female,
and the testes in the male. The inferior mesenteric is
.almost as large as the superior mesenteric. It is dis-
tributed to the large intestine. The pair of iliolumbai
arteries are small branches supplying the muscles of tin-
iliac region.

Four or five pairs of lumbar arteries are given off from
the dorsal side of the aorta at regular intervals between
the diaphragm and the origin of the external iliac arteries.
They supply the muscles of the back and spinal cord.
The external iliac arteries are the largest branches of the
abdominal aorta and carry blood to the hind-limbs. The
internal iliac arteries arise more than a centimeter caudad
to the external iliacs and furnish blood to the pelvic
viscera and the muscles of the innominate region. The
caudal artery is the continuation of the aorta beyond the
origin of the internal iliacs. It extends into the tail
(Fig. 70).

ARTERIES OF THE HEAD AND NECK.

From the arch of the aorta arise the brachio cephalic
and left subclaman, which supply the sternum, neck,

ELEMENTS OF MAMMALIAN ANATOMY.

head, and anterior extremities with blood. The brachio-
cephalic gives off the left carotid and then divides into
the right carotid and right subclavian (Fig. 71). Some-
times the two carotids arise as a single trunk from the

FIG. 71. — VENTRAL ASPECT OF THE ARTERIES OF THE HEAD AND NECK
The carotids with their branches have been drawn laterad.

a, Internal maxillary ; ac, anterior cerebellar ; cc, median cerebral ; cr,
posterior cerebral ; cp, posterior cerebellar ; ex, carotid plexus, many
of whose branches reunite into one, ex', which is cut off; ex, external
carotid; em, external maxillary; inc, origin of internal carotid; inc.',
union of internal carotid with circle of Willis; ia, inferior alveolar;
if, infraorbital; i, optic chiasma; li, lingual; mn, middle meningeal;
ms, muscular; oc, occipital; ol, anterior cerebral; pi, palatine; pa,
posterior auricular; s, anterior spinal; th, thyroid; x, hypophysis;
1, 2, 3, 4, 5, and 6, canal in cervical vertebrae.

THE VASCULAR SYSTEM. 147

brachiocephalic, which is then continued as the right
subclavian. In this case the common trunk of the ca-
rotid usually bifurcates within one or two centimeters of
its origin, forming the right common carotid and the
left common carotid, lying on the respective sides of the
trachea beneath the sternomastoid and the sternohyoid
muscles. The vagus or tenth cranial nerve and the
sympathetic trunk lie in the same sheath with the
carotid (Fig. 64).

Each carotid artery in the neck region gives off the
following branches : a thyroid to the thyroid cartilage and
gland, and a muscular to the muscles of the neck. At
the base of the skull, about the middle of the bulla of
the temporal bone, a slight enlargement of the vessel is
seen, from which arises the very small internal carotid,
leading through the foramen lacerum medius to the base
of the brain, where it joins the circle of Willis. The con-
tinuation of the common carotid is now known as the
external carotid. This, after giving off a lingual branch
to the tongue, an external maxillary branch to the lower
jaw, a post-auricular branch, and a temporal branch,
turns to pass along the mesal aspect of the mandible,
where it is named the internal maxillary, whose main
branches are the inferior alveolar, the middle meningeal
supplying the dura mater, several branches to form the
carotid plexus, a palatine, spheno palatine, and infraor-
bital. The latter is the direct continuation of the internal
maxillary. It supplies the upper teeth, lower eyelid,
parts of the nose, and upper lip. An ophthalmic branch,
supplying structures in the orbit, may arise from the
carotid plexus or the internal maxillary.

The -vertebral artery is the first branch given off by
either subclavian. It proceeds dorsad and cephalad to
the sixth cervical vertebra, whence it extends through

148 ELEMENTS OF MAMMALIAN ANATOMY.

the vertebrarterial canal and foramen magnum, to a
junction with its fellow in the median line on the ventral
aspect of the medulla oblongata. The union of the two
vertebral arteries forms the basilar artery, which, after
giving off several branches to the medulla and cerebel-
lum, divides cephalad of the pons Varolii, forming the
circle of Willis around the infundibulum and the optic
chiasma. The circle of Willis receives the internal ca-
rotid and gives off several arteries to the cerebrum. In
man the internal carotid is much larger proportionately
than in the cat (Fig. 71).

THE ARTERIES OF THE THORACIC LIMB.

There is more or less variation in the branching of the
arteries in the limbs. No two cats are found exactly
alike as to their arteries or veins. The same is true of
all other mammals.

The subclavian artery, which on the right side springs
from, or is merely a continuation of, the brachiocephalic,
and on the left side arises from the arch of the aorta,
supplies the forelimbs with blood (Figs. 71 and 72).
When the subclavian reaches the armpit, it is called the
axillary artery, and its continuation along the humerus
is the brachial artery. A continuation of the same artery
along the radius is the radial artery, furnishing a large
part of the blood to the fingers.

Four branches arise from the subclavian: the vertebral
artery, extending to the brain through the vertebrarterial
canal; the internal mammary artery, arising from the
ventral side of the subclavian opposite the origin of the
vertebral, and extending along the visceral surface of
the sternum, and sometimes supplying the pericardium
of the heart; the superior intercostal, arising near the

THE VASCULAR SYSTEM.

[49

vertebral artery and supplying the first and second
intercostal spaces, the deep muscles of the back, and
the serratus magnus; and the thyroid axis, extend-
ing cephalad to supply some muscles of the neck and
the lateral aspect of the scapula (Fig. 72).

The axillary artery gives origin
to three branches: the anterior
thoracic, the long thoracic, and
the circumflex. The anterior tho-
racic supplies the pectoral mus-
cles. The long thoracic is distrib-
uted chiefly to the latissimus
dorsi. The circumflex artery is
almost as large as the continua-
tion of the axillary, which be-
yond this point is called the bra-
chial. The circumflex, about a
centimeter from its origin, after
giving off the subscapular, which
is distributed mainly to struc-
tures in the subscapular fossa,
winds around the neck of the

FIG. 72.— ARTERIES OF THE FOREUMB.
VENTRAL ASPECT.

a, Digital artery ; an, anastomotica magna ;
ac, anterior circumflex; ai, anterior in-
terosseous; ax, axillary; at, anterior
thoracic; b, digital artery; be, brachio-
cephalic; br, brachial; c, dorsal branch
of the radial where it passes between the
second and third metacarpals to the

palmar side; ex, circumflex; is, superior intercostal; Is, left subclavian;
It, long thoracic; m, branch to extensor muscles; nt, nutrient; pi, pos-
terior interosseous ; r, radial; rd, radial recurrent; sf, supracondyloid
foramen of the humerus; spr, superior profunda; sb, subscapularis ; sp,
suprascapularis ; st, sternal; th, thyroid axis; ul, ulnar; ur, ulnar recur-
rent ; vt, vertebral.

150 ELEMENTS OF MAMMALIAN ANATOMY.

limiKTUs to its distribution in the triceps and deltoid
muscles.

The brachial artery, in addition to several muscular
branches, gives origin to the anterior circumflex, superior
profunda, the nutrient, and anastomotica magna. The
anterior circumflex supplies the biceps and head of the
humerus. The superior profunda is distributed to the
muscles on the caudal aspect of the humerus. The
nutrient artery enters the nutrient foramen of the humerus.
The anastomotica magna is the small branch supplying
the convexity of the elbow. The brachial artery after
passing through the supracondyloid foramen takes the
name of radial.

The radial artery, which lies deep beneath the flexor
muscles on the caudal aspect of the proximal half of the
radius (Fig. 72), becomes superficial along its distal half,
where the vessel is covered by skin and fascia only. In
the region of the wrist, it curves dorsad and then pierces
between the second and third metacarpals to the palmar
side, where it sends branches to each of the digits, and
forms the palmar arch by anastomosing with the ulnar
artery beneath the flexor muscles. In addition to a few
small branches, the radial gives off the following: the
radial recurrens, supplying the concavity of the elbow;
the ulnar recurrens, supplying the convexity of the elbow;
the posterior inter osseous, passing caudad between the
radius and the ulna to the extensor muscles; the anterior
interosseous, passing along the cephalic side of the inter-
osseous membrane; the ulnar, extending beneath the
flexor muscles, which it supplies, to the palm, where it
anastomoses with the radial to form the palmar arch;
and the volar branch, supplying the superficial palmar
region. The ulnar and anterior interosseous frequently
arise from the same trunk, as shown in the figure. The

THE VASCULAR SYSTEM. 151

ulnar artery in the cat is so small that it is frequently
not filled by the starch injection, but in man it is larger
than the radial.

THE ARTERIES OF THE HIND-LIMB.

As in the forelimb, the branching of the arteries in the
hind-limb varies considerably in different specimens.
The main artery of the leg lies on the ventral or mesal
aspect of the femur, passing obliquely to the caudal side
of the knee-joint, where it divides into two branches (Fig.
73), one extending along the cephalic, the other along
the caudal aspect of the crus. The cat, or at least the
caudal half of a cat, should be fastened to the dissecting
tray on its back, the abdominal wall removed, and the
viscera pushed laterad to demonstrate the origin of the
artery of this limb. As in the forelimb, the main artery
in different portions of the leg takes the name of the
corresponding region.

The external iliac is the largest artery arising from the
aorta in the lumbar region. It gives off but one im-
portant branch, the profunda, which, extending caudad,
soon gives off a large epigastric artery to the abdominal
wall, then smaller branches to the external genital
organs, and numerous branches to the muscles on the
caudal aspect of the femur.

The femoral artery, which is a continuation of the
external iliac, extends along the mesal aspect of the
femur. In the proximal half of its course it is quite
superficial, but the distal portion is covered by the
gracilis, sartorius, and semimembranosus muscles. It
furnishes four important branches: the anterior femoral,
supplying mainly the quadriceps extensor muscle; the
superior posterior femoral, supplying the adductor and

152

ELEMENTS OF MAMMALIAN ANATOMY.

hamstring muscles; the saphenous, accompanying the
saphenous nerve and vein to the foot, where it branches
and anastomoses with the plantar artery; and the pos-
terior inferior femoral, supplying mainly the gastrocne-
mius group of muscles (Fig. 52).

The popliteal artery is the continuation of the femoral

FIG. 73. — ARTERIES OF THE RIGHT LEG. VENTRAL ASPECT.

a, Aorta ; at, anterior tibial ; af, anterior femoral ; cd, caudal ; eg, epigastric ;
em, external malleolar; fern, femoral; im, internal malleolar; il, ex-
ternal iliac; it, internal iliac; lu, iliolumbar; m, digital; n, digital;
o, digital; p, peroneal; pa, profunda; />/, posterior superior femoral;
pi, posterior inferior femoral; pn, plantar; pp, popliteal; pt, posterior
tibial; ps, saphenous.

artery in the popliteal region on the caudal aspect of
the knee-joint. One or two articular branches are given
off here to the joint, in addition to the posterior tibial,
which supplies the deep muscles of the crus.

The anterior tibial artery is the continuation of the pop-
liteal on the lateral cephalic aspect of the tibia, adjacent

THE VASCULAR SYSTEM.

to the bone. By separating the tibialis anticus and ex-
tensor longus digitorum muscles, this artery is well
displayed. Near the knee-joint a small branch, the
peroneal, is given off, and passes to the dorsal aspect
of the foot, where it anas-
tomoses with the dorsal
branch of the saphenous,
forming a superficial arch
sending branches to the dig-
its. The peroneal is so small
that it is frequently not in-
jected. In the tarsal region
two branches, an external
malleolar and an internal
malleolar, are given off. A
centimeter or two distal to
the latter branch, the main
artery passes between the
second and third metatar-
sals to the deep plantar re-
gion, where it receives an
anastomosing branch from
the saphenous, and sends
off branches to the digits.

en

FIG. 74. — CROSS-SECTION OF AR-
TERY AND VEIN. X 350.

V, Vein; .4, artery; 01, inner coat;
cp, epithelium lining the vessels ;
et, middle or muscular coat of
vein ; ex, muscular coat of artery ;
fb, fibro-areolar coat. - - (From
Martin's "Human Body.")

THE VENOUS SYSTEM.

The veins are the vessels
returning the blood to the

heart. As a rule, veins carry only impure blood, but
the pulmonary veins returning blood from the lungs to
the left auricle carry pure blood. After death the veins
can readily be distinguished from the arteries by the
fact that they have much thinner walls than the arteries

154 ELEMENTS OF MAMMALIAN ANATOMY.

and are usually full of blood, while the arteries are
empty (Fig. 74). This is due to the fact that the thick
muscular coat of the arteries, by its contraction tends
to drive the blood into the veins, whose muscular coat
is very thin. The three coats composing the walls of
the veins are the epithelial, or tunica intima; the middle,
or muscular; and the tunica adventitia, or outer elastic
coat of fibro-areolar tissue. The veins of the central ner-
vous system and its membranes have no muscular coat.
While the only valves in the arteries are found at their

origin from the heart, the veins of the
limbs, neck, and head possess numerous
valves. These valves are formed by
semilunar folds of the epithelial coat,
strengthened by fibrous tissue (Fig.

75).

The main deep veins of the limbs ac-
company the arteries and take the same
FIC 75 --VEIN CUT names as the arteries. A superficial set
OPEN. ARROW of veins is present also in the limbs. The

SHOWS THE Dl- 1 ~ . - ,11 i

RECTION OF THE large superficial vein on the lateral aspect
BLOOD. Of the forelimb is the cephalic. The

v, Semilunar valves; <- . , . ...

i, free edge of the superficial vein extending along the
valve- mesal aspect of the hind-limb is the

saphenous.

The Veins of the Trunk, Head, and Neck.- -There are
two chief venous trunks: the precava, or superior vena
cava, and the postcava, or inferior vena cava. Both vessels
open into the dorsal aspect of the right ventricle. The
veins received by the postcava are thirteen in number.
The phrenic veins collect the blood from the diaphragm
and empty into the vena cava immediately caudad of
the diaphragm. The several hepatic veins collect the
blood from the liver, which must be partly dissected

THE VASCULAR SYSTEM.

155

away to see their en-
trance into the vena cava.
The two suprarenal veins
return the blood from the
suprarenal bodies and
two renal veins carry the
blood from the kidneys.
The left ovarian or sper-
matic vein is a tributary
to the left renal, but the
right ovarian empties
directly into the vena
cava. A pair of small
iliolumbar veins collect-
ing blood from the lum-

FIG. 76. — VENTRAL VIEW OF THE
CHIEF VEINS OF THE TRUNK,
NECK, AND HEAD.

az, Azygos; au, anterior auricu-
lar ; br, brachiocephalic ; cd,
caudal; cph, cephalic; em, ex-
ternal maxillary; ex, external
jugular; eic, external iliac; hp,
hepatic; im, internal maxil-
lary; ij, internal jugular; ims,
inferior mesenteric; Urn, ilio-
lumbar ; ilc, common iliac ; tie,
internal iliac; na, nasal; ov,
ovarian or spermatic; pan,
posterior auricular; pd, pan-
creato-duodenalis ; pcv, pre-
cava; pst, postcava; prt, por-
tal; phrn, phrenic; rn, renal;
ste, superficial temporal; st,
gastro-epiploica and coro-
nary; sr, suprarenal; sir, ster-
nal; sp, gastrosplenic ; sm, su-
perior mesenteric; sbcl, sub-
clavian ; tr, transverse ; tg, lin-
gual; vtr, vertebral; 1, 2, 3, 4,
5, 6, the vertebrarterial canal
of the first six cervical verte-
bra? ; u>, intercostals ; x, supe-
rior intercostals.

fie

156 ELEMENTS OF MAMMALIAN ANATOMY.

bar muscles empty into the vena cava a centimeter or more
cephalad to the large common iliacs. The union of the com-
mon iliac veins collecting the blood from the hind-limbs and
the pelvic region, and the caudal vein, forms the begin-
ning of the postcava. The common iliac is formed by
the union of the external and internal iliac veins in the
pelvis. The former is much the larger of the two.

The portal system begins with the veins collecting the
blood from the intestines, pancreas, spleen, and stomach,
and terminates where the hepatic veins enter the vena
cava. The inferior mesenteric vein collects the blood
from the large intestine; the superior mesenteric, from the
small intestines; the g astro splenic, from the spleen,
stomach, and pancreas; the coronary, from the lesser
curvature of the stomach; the gastro-epiploica, from the
greater curvature of the stomach; and the pancreato-
duodenalis, from the pancreas and duodenum. The last
three may empty directly into the portal vein or into
one of the three branches first named (Fig. 76).

The superior vena cava extends from the union of the
brachiocephalic veins to the right auricle. Three im-
portant veins empty into the precava: the azygos, col-
lecting blood from the intercostal spaces; the sternal,
lying on the visceral surface of the sternum; and the
right vertebral, which, with its fellow, collects the blood
from the deep muscles and spinal cord in the region of
the atlas, and after making a strong anastomosis with
the internal jugular vein, descends in company with the
vertebral artery through the vertebrarterial canal of the
first six cervical vertebrae. The left vertebral vein is a
tributary of the left brachiocephalic (Fig. 76).

The brachiocephalic vein is formed by the union of the
subclavian and the external jugular. Sometimes the ver-
tebral vein joins also in the union instead of emptying

THE VASCULAR SYSTEM. 157

into the precava. The subclavian -vein returns the blood
from the arm, and accompanies the subclavian artery.
The external jugular veins are large vessels lying on either
side of the neck beneath the platysma myoides muscle.
When the skin is removed, the veins are plainly seen
through this very thin muscle. The external jugular is
formed ventral to the angle of the mandible by the
union of the internal and external maxillary veins. The
external maxillaries are united by a large transverse vein.
The two tributaries of the external jugular are the
cephalic and the internal jugular. The former is the
superficial vein on the lateral aspect of the arm, and
the latter is the small vein returning blood from the
brain.

A system of tube-like spaces, called sinuses, whose
walls are formed by the dura mater lined with epithelium,
takes the place of the large venous trunks within the
cranial cavity. These sinuses are usually not filled by a
starch injection, but may be filled by a gelatin mass.
They cannot be dissected by the beginner. The superior
longitudinal sinus extends in the median line beneath the
roof of the skull, from the ethmoid region to the tentorium
cerebelli, where it bifurcates to form the lateral sinuses,
which proceed laterad and ventrad in the substance of
the tentorium. The lateral sinus emerges from the ten-
torium just caudad to the petrosal bone, where it follows
the groove to the jugular foramen. This groove may be
seen in a bisected or unroofed skull.

The superior petrosal sinus lies in the angle formed
by the junction of the tentorium and the petrosal bone,
and unites with the lateral sinus just before it reaches
the jugular foramen. The inferior petrosal sinus, col-
lecting blood from the base of the brain, lies in the
groove ventral to the petrosal bone, and unites with the

158

ELEMENTS OF MAMMALIAN ANATOMY.

lateral sinus at the jugular foramen. The union of these
sinuses at this foramen forms the internal jugular vein,
which extends deep beneath the muscles of the neck

r.c

sb.

5pm

A

sm

im

rr -

sb

sm

FIG. 77. — A, VENTRAL VIEW OF HEART AND MAIN ARTERIES IN THE TRUNK
OF THE RABBIT. 11, ARTERIES OF MAN.

a, Right auricle; ca, left carotid; c ax, coeliac axis; i n, innominate or
brachiocephalic ; il, common iliac; i m, inferior mesenteric ; / r, left
renal; r r, right renal; re, right intercostals ; sm, superior mesen-
teric; spm, spermatic; sa, sacral; sb, left subclavian.

with the carotid artery. It joins the external jugular
opposite the shoulder-joint. At the base of the skull the
internal jugular gives off a large transverse anastomosing

THE VASCULAR SYSTEM. 159

vein to the vertebral, so that the blood from the vein
may return partly by the latter vessel.

The pulmonary veins convey the pure blood from the
lungs to the left auricle. There are three main trunks
from each lung. These six veins are arranged in pairs
(Fig. 69), constituting a left pair from the left lung; a
median pair, composed of one branch from the right and
one from the left lung; and a right pair from the right
lung. Each pair forms a common trunk before entering
the auricle. In order to demonstrate these veins one
must remove the heart and lungs from an injected cat,
and carefully dissect away the fatty and connective
tissues enveloping the vessels.

The peripheral connection between the arteries and
veins is by means of capillaries, which are microscopic
vessels with an extremely thin wall composed of a single
layer of epithelial cells. These capillaries are so abun-
dant everywhere in the flesh that a needle cannot be
inserted without penetrating some. They form a kind of
mesh or network, so that every cell may be supplied
with oxygen and food and discharge its waste matter.
All the blood carried to any portion of the body by the
arteries is not returned by the veins, as a considerable
amount of the plasma and some of the white corpuscles
escape through the thin capillary walls and are returned
to the circulation by a system of vessels called lymphatics
(Fig. 78).

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. What holds the heart in place?

2. Draw the ventral aspect of the heart with the pericardium re-
moved and label all features.

3. When the heart is detached from the body, how do you distin-
guish the dorsal from the ventral aspect?

4. How many veins open into each auricle?

5. What arteries lead from each ventricle?

l6o ELEMENTS OF MAMMALIAN ANATOMY.

6. After dissecting write a detailed description of the valves of the
heart.

7. Describe the differences in the appearance of the walls of the aorta

and vena cava.

8. From your dissection write a description of the features seen in
each cavity of the heart.

9. Name the branches of the thoracic aorta in order.

10. Name the branches of the abdominal aorta and tell what organs
each supplies.

1 1 . Draw the creliac axis and its branches throughout their course
and label all parts.

12. Show by a drawing the relations of the aorta and venae cavae
throughout.

13. Make a diagrammatic cross-section of the neck, showing location
of arteries and veins.

14. Describe the three routes by which blood may reach the brain
and the two routes by which it may be returned to the heart.

15. Name the arteries arising from the arch of the aorta.

16. Draw the inner or mesal aspect of your dissection of the arteries
of the thoracic limb and label all parts.

17. Draw cross-section of arm at middle of humerus to show location
of main artery and vein.

18. Draw cross-section of the middle region of the forearm to show
location of chief arteries.

19. Draw outline of the bones of the manus and show relation of ar-
teries to bones as seen from palmar aspect.

20. Draw outline of femur and show course of main artery in relation
to the bone as seen from mesal aspect.

21. Draw outline of bones of the pes and show relations of the arteries
to the bones as seen from the plantar aspect.

22. At what joints in its course is the chief artery of the pelvic limb
most superficial?

23. Describe the difference in structure of a vein and an artery.

24. What veins open into each auricle of the heart?

25. Name the veins returning the blood from each organ of the ab-
dominal cavity.

26. Draw the portal system and label all vessels.

27. Describe the veins returning the blood from the head.

28. Describe the chief blood sinuses in the skull.

29. Where are the valves found in the blood-vessels?

30. If the brachial vein were cut, how could the blood from the manus
reach the heart?

THE VASCULAR SYSTEM. l6l

THE LYMPHATIC SYSTEM.

The lymphatics constitute that part of the vascular
system which collects the colorless fluid called lymph
from the tissues, and the chyle from the small intestine,
and conveys them to the external jugular veins. The
portion of the lymphatic system originating in the villi
of the small intestine and conveying the chyle to the
left thoracic duct is known as the lacteals.

The lymphatic system consists of four parts: (i) the
lymphatic spaces between the skin and muscles in all
parts of the body, the spaces between the muscles adjacent
to the bones, and internal spaces such as those enclosed
by the peritoneum and pleura; (2) minute thin-walled
vessels beginning by capillary mouths in the spaces just
described and leading to larger vessels which empty into
the tracheal trunks or thoracic duct ; (3) the glands, which
vary in size from a mustard-seed to two centimeters in
diameter, and are located chiefly on the side of the neck, in
the axillary region, at the bifurcation of the trachea; in
the inguinal region, lumbar region, and mesentery; (4)
the two tracheal trunks and thoracic duct (Fig. 78).

One of the largest of the lymphatic spaces is the
greater cavity of the peritoneum. The cavity of the
lesser peritoneum, a large lymphatic space, may be
shown by separating the layers of the great omentum
carefully. The cavity of the pleura within the chest is
also a large lymphatic space. Numerous small lymph
spaces are present in all parts of the body. The lym-
phatic capillaries originating in these spaces are invisible
to the naked eye, but their union into larger vessels may
be demonstrated satisfactorily in a cat just killed, by
pulling forward the tongue, and injecting very slowly
beneath the skin, on its ventral aspect, five or ten centi-
14

1 62 ELEMENTS OF MAMMALIAN ANATOMY.

meters of a two per cent, solution of Berlin blue in warm
water.

The lymph glands (Fig. 78) of the cat are not nearly
so numerous as in man. The largest lymph gland is
the pancreas Aselli in the mesentery. It is considerably
flattened and about two centimeters long. A few other
very small lymphatic glands are also present in the
mesentery. The two largest lymph glands of the head
are just beneath the skin cephalad of the submaxillary
gland. On the side of the neck beneath the cephalo-
humeral muscle are three large lymph glands at the
cephalic border of the scapula. A small axillary gland
lies on the caudal side of the axillary vein beneath the
scapula. A single popliteal gland is in the popliteal
space, an inguinal gland lies on each side of the penis,
two or three iliac glands are near the origin of the
femoral artery, and a few small lumbar glands lie in
the lumbar region of the abdominal cavity.

All parts of the body have communication with the
lymphatic vessels, which for the most part are so small
as to be invisible unless injected, when they are easily
recognized by their beaded appearance caused by the
numerous valves within them. There are two systems
of vessels in the head and extremities — the superficial
and the deep. The former accompany mainly the super-
ficial veins, and the latter follow the deep veins. On the
outer aspect of the thoracic limb just beneath the skin
two vessels are present, which flow into the cervical
glands. They carry the lymph from the ball of the foot
and the skin of the foot and forearm. One or two deep
lymph-vessels are found accompanying the brachial vein
and artery, which convey the lymph from the bones and
muscles of the arm to the axillary gland.

In the pelvic limb two or three superficial vessels are

THE VASCULAR SYSTEM.

163

present transmitting the lymph from the foot to the
popliteal gland, whence two ves-
sels proceed to the deep lympha-
tic system. The lymph from the
bones and muscles of the leg
reaches the iliac glands through
two or three deep vessels lying
near the femoral vein and artery.
The inguinal glands receive most
of the lymph from the skin of
the leg.

The lymph from the superfi-
cial parts of the head flows
largely into the submaxillary
glands, while that from the brain,
tongue, esophagus, and larynx
empties into the laryngeal
glands.

The lymph of the right fore-
limb, right side of the neck and

th

FIG. 78. — VENTRAL ASPECT OF CHIEF
LYMPHATIC VESSELS OF THE CAT.

a, Axillary gland ; as, pancreas Aselli ; an,
superficial lymphatics from the head;
b, bronchial glands receiving lymph
from lungs; c, lymphatic trunk; cr, cer-
vical glands; cv, laryngeal glands; d,
vessel from diaphragm; ej, external jug-
ular vein ; in, inguinal glands ; il, iliac
glands; ju, junction of thoracic duct
with tracheal trunk ; /, lumbar glands ;
li, large intestine ; Iv, lymph-vessel from
liver; m, lacteal vessel and glands of
mesentery; n, superficial lymphatics
from limb; o, deep lymph-vessels from
limb ; on, lymphatics from thoracic wall ;
ol, vessel from abdominal wall ; oc, ves-
sels from limb ; rec, receptaculum chyli ;
s, subclavian vein; t, lymphatics from
skin of leg ; tr, tl, tracheal trunks ; va, lymph trunk from pancreas Aselli
to thoracic duct; v, precava; 1 and 2, submaxillary lymph_glands.

1 64

ELEMENTS OF MAMMALIAN ANATOMY.

head, and right side of the thoracic wall is received by
the right tracheal trunk. The left tracheal trunk re-
ceives the lymph from the left side of the head, neck
and thoracic wall, and the left forelimb. The thoracic

•

V ' ' ' l_.'-

1

FIG. 79. — PHOTOGRAPH OP LYMPHATIC CAPILLARIES INJECTED WITH
BERLIN BLUE. They lie immediately beneath the skin on the outer
aspect of the ear.

a, Point of injection; the black area is Berlin blue lying in the connec-
tive-tissue spaces from which the capillaries arise; n, injection escaped
from ruptured vessel.

duct receives the lymph from the lungs, heart, all the
abdominal viscera, and muscles, and the hind-limbs.
With but few exceptions, all the main lymphatic vessels
pass through lymphatic glands before reaching one of the

THE VASCULAR SYSTEM. 165

three main trunks. In fact, the vessels bringing the
lymph to the glands may be said to terminate there.
They are called afferent lymphatics. The lymph moves
free through the tissue of the gland, and on the opposite
side is taken up by the efferent lymphatics.

The right and left tracheal trunks lie on their respective
sides of the trachea and empty into the external jugular
vein just before its junction with the subclavian. The
opening is guarded by a valve which prevents the blood
from entering the lymphatic trunk.

The thoracic duct (Fig. 78) is the largest vessel of the
lymphatic system, but is usually invisible unless injected.
It extends from the region of the kidneys on the dorsal
aspect of the body cavity, along the left side of the
spinal column, to its opening into the external jugular
vein near where the latter joins the subclavian vein.
The caudal end of the thoracic duct is expanded, forming
the receptaculum chyli. Numerous valves are present
in the duct, and give to it a moniliform appearance. It
receives all the lymph from the left abdominal wall, both
pelvic extremities, a large part of the thoracic wall, and
the thoracic and abdominal viscera.

DUCTLESS GLANDS.

The spleen, thyroid gland, thymus gland, and suprarenal
bodies are ductless glands whose functions are imper-
fectly knowrn. The largest of these is the spleen, which
is of a deep red color in a fresh specimen, and lies in
the abdominal cavity on the left side caudad to the
stomach (Fig. 54). It is about five centimeters long,
two centimeters wide, and less than a centimeter thick.
It is composed of lymphoid tissue of two forms, sup-
ported by connective-tissue trabeculae which are merely

1 66 ELEMENTS OF MAMMALIAN ANATOMY.

prolongations of the enveloping capsule. The two
forms of tissue can be seen by cutting the organ trans-
versely. The dense lymphoid tissue appears as white
spots less than the size of a pin-head. They are the
Malpighian corpuscles. The intervening looser lymphoid
tissue forms the greater part of the spleen, and is
known as the splenic pulp. The splenic artery, a branch
of the cceliac axis, enters the spleen at its hilus and
divides into capillaries which terminate in irregular
spaces, thus permitting the blood to flow freely through
the splenic pulp, whence it is taken up by the capil-
laries of the splenic vein leading to the portal vein. In
embryonic life the spleen forms blood-corpuscles, but in
postnatal life it seems to destroy blood-corpuscles. An
animal from which the spleen has been removed may
live many years in good health.

The thyroid gland is composed of two parts lying on
the lateral aspects of the trachea, just caudad to the
larynx. Each part is less than two centimeters long.
The two parts are sometimes connected by a small isth-
mus extending ventrally across the trachea, as in man.
An enlargement of this gland in man is called goiter.
An animal can live only a short time after the removal
of the thyroid unless it is fed thyroids or an extract
of thyroid gland. The function of the gland is to supply
iodin compounds to the system.

The thymus gland is a median structure varying in
size according to age. In a cat about one-third grown
it is very large, extending cephalad from the heart along
the ventral aspect of the trachea three or four centi-
meters. As the cat grows older, it gradually dwindles,
and is entirely absent in aged specimens. Its function is
unknown. It persists throughout life in the lower ver-
tebrates.

THE VASCULAR SYSTEM. 1 67

The suprarenal bodies are small, somewhat bean-shaped
organs lying cephalad to the kidneys. An animal from
which they have been removed can live but a short
time. Their function is not known. They are sometimes
spoken of as suprarenal capsules.

The above-named ductless glands occur in all mammals
in the same relative ocations. The anatomy of the
lymphatic system is also exceedingly similar throughout
the various orders of mammals. In some animals, espe-
cially man, the lymphatic glands are more numerous than
in the cat. The tracheal trunks are also wanting in man
and a right thoracic duct about two centimeters long is
usually present. A failure of the lymphatics to do their
work results in dropsy.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Which of the four parts of the lymphatic system are visible in
your specimen?

2. Describe size and number of lymphatic glands in the mesentery.

3. Describe the location of lymph glands present in any other portion
of your specimen.

4. How do you distinguish a lymph gland from other glands?

5. What causes the lymph to flow in one direction only?

6. WThat is meant by afferent and efferent lymphatics?

7. Which kind of blood-corpuscles are found within the lymph-vessels?

8. From what regions does the thoracic duct receive the lymph?

9. What glands receive the lymph from the thoracic limb?

10. What glands receive the lymph from the pelvic limb?

11. Describe location of spleen, thyroid and thymus glands, and
suprarenal capsules by naming the organs with which they are in contact.

12. Draw a cross-section of the spleen and label all features visible.

13. Draw a cross-section of the suprarenal body and label parts.

14. Tell what you know of the functions of the ductless glands.

15. What is a gland?

THE RESPIRATORY SYSTEM.

Respiration is the process whereby the tissues are sup-
plied with oxygen and relieved of their carbon dioxid. In
mammals, the special organs of respiration are the lungs,
wherein the carbon dioxid is received from the blood,
while at the same time the oxygen of the air passes
through the thin-walled capillaries to the red blood-
corpuscles capable of conveying it to the cells throughout
the body. Each cell is composed largely of carbon,
hydrogen, oxygen, and nitrogen, and any activity on the
part of the cell is the result of the chemical union of
some of its elements, whereby several waste products are
formed, one of which is the gas, CO2 (carbon dioxid).
This gas is a poison and therefore must be eliminated.
It passes through the thin walls of the capillaries adjacent
to every cell, and is transferred through the veins to the
heart and thence to the lungs. Here the pulmonary
artery divides up into capillaries ramifying over the air
sacs (Fig. 82), thus permitting the carbon dioxid to
escape into the air sacs. Other waste products resulting
from chemical activity within the cells are carried away
by the kidneys and sweat glands.

The respiratory system consists of the nasal passages,
pharynx, larynx, trachea, and lungs. The air taken in at
the anterior nares is warmed in passing over the mucous
membrane of the turbinated bones, after which it goes
on through the posterior nares (Fig. 18) to the pharynx,
and thence into the larynx.

The larynx is the cartilaginous expansion of the cephalic

1 68

THE RESPIRATORY SYSTEM. 169

end of the trachea, at the base of the tongue. The basi-
hyal bone is attached to the cephalic ventral margin of
the larynx and on each side is a thyrohyal bone (Fig. 20).
Dorsal to the larynx is the esophagus. By removing
carefully the muscles and fibrous tissue from the cartilage
the larynx is seen to be composed of five pieces: the
epiglottis, thyroid cartilage, two arytenoid cartilages, and
the cricoid cartilage (Fig. 20). The epiglottis is the
small triangular cartilage that closes the glottis when
food passes into the esophagus (Fig. 55). The thyroid
cartilage constitutes the largest part of the larynx. In
man it forms the prominence known as Adam's apple.
Dorsally the two halves of the thyroid cartilage are
separated, each projecting cephalad into a process known
as a cornu. The arytenoid cartilages are the two small
paired pieces caudad to the thyroid, on the dorsal side.
The cricoid cartilage forms a complete ring at the caudal
end of the larynx (Fig. 20).

There are a number of ligaments connecting the various
parts of the larynx, the most important of which are the
vocal cords. These are of two kinds — true and false.
They are best demonstrated by dividing the larynx
sagittally. The superior or false vocal cords are the two
superior thyro-arytenoid ligaments passing from the
arytenoid to the thyroid cartilage, at the base of the
epiglottis. The cat is said to use these cords in purring.
The inferior or true vocal cords are the inferior thyro-
arytenoid ligaments, consisting, as in man, of a fold of
mucous membrane on either side, just caudad to the
false vocal cords (Fig. 55). The depression on either side
between the true and false vocal cords is the ventricle.
By means of the muscles attached to the arytenoid
and thyroid cartilages, the tenseness of the vocal cords
is regulated, and the various pitches of voice produced.

T7°

ELEMENTS OF MAMMALIAN ANATOMY.

The trachea, or windpipe, is the tube leading from the
larynx to the lungs (Fig. 54). Its walls are prevented
from collapsing by the presence of about forty-five carti-
laginous rings which are incomplete dorsally. Before
passing into the lungs the trachea bifurcates into a right
and a left bronchus. The trachea and bronchi are lined by
ciliated columnar epithelium. The cilia project freely

/*

Wft/,^ PC

peck*

FIG. 80. — DIAGRAMMATIC TRANSVERSE SECTION OF THE CHEST.

ao, Aorta ; br, bronchus ; crd, spinal cord ; esoph, esophagus ; hd, head of
rib; pa, parietal pleura; pc, cavity of the pleura; sp, spinous process;
st, sternum ; tb, tubercle of rib ; tr, transverse process ; vp, visceral
pleura; t, thoracic duct; n, sympathetic nerve cord; az, azygos vein;
trc, trachea; v, pulmonary veins.

into the lumen from the columnar walls, and are always
waving in such a manner as to carry the secreted mucus
lodged thereon toward the mouth, thereby preventing
the lungs from becoming clogged with foreign material.
Ciliated cells with the cilia in action may be easily demon-
strated by scraping very lightly a little mucus from the
posterior part of the roof of the frog's mouth, and mount-

THE RESPIRATORY SYSTEM.

171

FIG. 81. — PHOTOGRAPH OF A LUNG CORROSION OF A PUMA IN MORPHO-
LOGIC MUSEUM OF PRINCETON UNIVERSITY. The specimen was
prepared by Mr. Sylvester. The trachea with all its ramifications
was injected with white paraffin, and the pulmonary artery^with red
paraffin, after which the lung substance was eaten away with acid.

tr, Trachea; br, bronchus; b, bronchia; c, bronchiole. The pulmonary
artery and its branches are much darker than the air tubes.

172

ELEMENTS OF MAMMALIAN ANATOMY.

ing the same in a drop of saliva on a glass slip, which
is then to be examined with a microscope magnifying
about 300 diameters. The diaphragm of the microscope
should be arranged so as to admit but little light.

The lungs together with the heart fill up the greater
part of the thoracic cavity. In a cat recently killed the
lungs may be expanded by tying a piece of glass tubing
on the trachea and blowing into it strongly for a few
seconds. Each lung is completely invested by a sac of

delicate transparent serous mem-
brane called pleura (Fig. 80).
Each sac is reflected at the root
of the lung, where the blood-
vessels and bronchus enter, so as
to form a parietal layer lining its
half of the thoracic cavity. The
median space between the two
sacs is called the mediastinum.
The anterior or ventral medias-
tinum contains the heart. The
dorsal or posterior mediastinum
contains the esophagus and
aorta.

Each lung is divided by deep clefts into several lobes.
The left lung is composed of two large lobes and a small
one. The right lung consists of four unequal lobes. The
cephalic end of the lung is the apex and the caudal end,
resting against the diaphragm, is the base. The bronchi,
as they are continued into the lungs, subdivide into
smaller tubes, whose later subdivisions are the bron-
chioles. The latter, dividing like the branches of a tree,
finally terminate in blind pouches known as infundibulo
or alveoli, the walls of wThich are thickly beset with
microscopic sac-like evaginations named air sacs (Figs.

FIG. 82. — THE TERMINATION
OF THE BRONCHIOLE c IN
FIG. 81.

br, Bronchiole; al, alveolus
showing about a dozen air
sacs or air cells. — (From
Martin's " Human Body.")

THE RESPIRATORY SYSTEM. 173

8 1 and 82). The walls of these air sacs are very thin,
somewhat like the peritoneum. Over them course numer-
ous thin- walled capillaries, so that the carbon dioxid of
the blood passes out into the air as the oxygen passes
into the blood. Expiration is the process of forcing the
air out of the lungs which have been filled by an inspira-
tion chiefly effected by depressing the diaphragm and
elevating the ribs. The two processes together are
spoken of as a respiration.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Of what four elements are the soft parts of the body largely com-
posed ?

2. What waste* gas is formed in every part of the body exercised?

3. Through what three channels do waste materials pass from the
-blood?

4. Describe the manner in which the oxygen of the air reaches the
blood.

5. Write a description of the pharynx.

6. Bisect the larynx in the sagittal plane, make a drawing of the cut
aspect, and label all features.

7. How many cartilaginous rings in the trachea and what is their
use?

8. Describe as much of the pleura as can be seen in your specimen.

9. Do the right and left bronchi have the same number of main
branches?

10. Why do the air cells seldom become clogged?

11. What muscles are largely used in respiration?

12. Describe the hyoid bone as seen from your dissection.

13. What part of this bone can you feel beneath your mandible?

14. How does the carbon dioxid given off by the cells in the foot reach
the lungs?

15. What causes the air to enter the lungs?

16. Innate the lungs of a freshly killed animal by forcing air from
your lungs into a glass tube tied into its trachea.

17. After retaining a full inspiration of air as long as possible, expire
it through a glass tube into the bottom of a two-liter bottle and insert
into the bottle a lighted splinter.

18. Describe the pulmonary circulation.

THE EXCRETORY AND REPRODUCTIVE

SYSTEMS.

As explained in the last section, a portion of the waste
products produced by the activity of the cells of the
body is passed off through the lungs, but some other
outlet must be provided for the excretions that are not
in the form of gases. These liquid excretions, containing
various salts and urea, pass off through the kidneys and
the glands of the skin.

The latter are of two kinds, sudoriparous or sweat
glands, and sebaceous or oil glands, with ducts opening into
the hair follicles near the surface. The sweat glands lie
deeper than the sebaceous glands. The former are sub-
cutaneous and consist of a more or less coiled tube with
a straight duct opening on the surface. They are most
abundant on the tip of the nose and the balls of the
feet. The sebaceous glands are very numerous all over
the body. Both are of microscopic size.

A still more important part of the excretory system is
the urinary system, consisting of the kidneys, two ureters
leading from the kidneys to the bladder, the bladder, and
the urethra.

The student should note that the kidney is not en-
veloped by the peritoneum, like the other abdominal
organs, but lies dorsad to it and is encased by a fibrous
covering known as the capsule. The hilus is that portion
of the concave surface where the renal artery and vein
and ureter enter. A median longitudinal section of the
kidney will show that the ureter within the kidney

174

THE EXCRETORY AND REPRODUCTIVE SYSTEMS.

175

enlarges, forming the pelvis, into which projects the renal
papilla (Fig. 84). This is better demonstrated in a
transverse section.

The substance of the kid-
ney is composed of an outer
cortical layer, about a half
centimeter thick, and an
inner medullary substance
adjacent to the pelvis, and
projecting into the latter in
the form of a papilla. In
the cortical substance are
hundreds of Malpighian
bodies, each composed of a
ball of capillaries (Fig. 84)
enveloped by the invagin-
ated enlarged extremity of
a tubule which carries away
the urine by a tortuous
course to the papilla (Fig.
85). In the Malpighian
bodies the water and other
mineral substances of the
urine are extracted from the
blood by means of the epi-
thelial cells forming the
inner wall of the capsule of
Bowman. These urinary
products pass through the
proximal convoluted tubule

cl

FIG. 83. — VENTRAL ASPECT OF FE-
MALE URINO-GENITAL SYSTEM
WITH THE BLADDER PULLED TO
ONE SIDE.

a, Entrance of the urethra into the
vestibule; ao, aorta; bl, bladder;
cl, clitoris; en, cornu or horn of
the uterus ; ft, Fallopian tube, the
left one is cut off ; fm, fimbriated
extremity of the Fallopian tube ;
kd, kidney; /, ovarian ligament;
crv, ovary; ra, renal artery; rv,
renal vein ; re, rectum ; ur, ureter ;
ut, body of the uterus; uth, ure-
thra; ye, vena cava; vg, vagina;
•vs, vestibule.

and the loop of Henle to the

distal convoluted tubule, where they are mingled with the
urea extracted from the blood by the columnar epithelial
cells of the tubule. From this point the excretions flow

ELEMENTS OF MAMMALIAN ANATOMY.

into the collecting tube which empties into the pelvis at
the papilla. In a prepared micro-
scopic section of the kidney,
these Malpighian bodies and
uriniferous tubules may be seen
with a microscope magnifying
about 200 diameters.

The ureter is a small tube lead-
ing from the pelvis of each kid-
ney along the dorsal aspect of the

FIG. 84. — MEDIAN LONGITUDINAL SECTION
OF A KIDNEY.

cor, Cortical substance ; hi, hilus ; med, me-
dullary portion; p, papilla; pi, pelvis;
•u, pyramids; ur, ureter.

abdominal cavity to the dorsal
and caudal end of the bladder.
The bladder, or urocyst, is the
sac for retaining the urine. It
lies ventrad to the rectum, a little
to the right of the median line,
being held in place by the liga-
mentum suspensorium, a fold of
the peritoneum attached to the
mid-ventral line. It is also at-
tached by lateral ligaments. On

FIG. 85. — DIAGRAM OF THE
STRUCTURE OF THE KID-
NEY BETWEEN THE LINES
a AND c IN FIG. 84.

ar, Arteries leading to the
Malpighian capsules, only
one capsule being shown;
b, veins leading from the
capillary network about a
convoluted tubule as at
n; ex, line marking the
boundary between the cor-
tical and medullary por-
tions of the kidney ; cp, cap-
sule of Bowman enveloping
the bunch of capillaries ; d,
distal convoluted tubule;
hi, Henle's loop; n, capil-
lary network about the
tubule; t, the bunch of
capillaries or Malpighian
tuft; ur, portions of urin-
iferous tubules emptying
into the collecting tubule
c; xc, proximal convoluted
tubule.

its dorsocauclal aspect,

THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 177

near where the ureters empty, the urethra originates and
passes along the ventral surface of the vagina to the vesti-
bule, within which it opens (Fig. 83). In the male it passes
directly from the bladder along the ventral surface of the
rectum to the root of the penis at the pubic symphysis,
and thence on through the corpus spongiosum to the point
of the penis. The ureter, bladder, and urethra consist
largely of muscular tissue, the lining being formed by
mucous membrane.

THE FEMALE REPRODUCTIVE SYSTEM.

The female reproductive organs are the two ovaries, a
pair of Fallopian tubes, a uterus, and a vagina. To
demonstrate these, the entire ventral abdominal wall
must be removed and the pubic symphysis severed with
the bone-cutters. The ovaries are the small yellowish
oval bodies about one centimeter long lying just caudad
of the kidneys, against the dorsal abdominal wall. From
the vicinity of each extends a tube caudad to join its
fellow in the median line ventrad to the rectum (Figs. 54
and 83). The cephalic portions of these are the Fallopian
tubes, and the larger caudal portions are the cornua of
the uterus. The junction of the cornua in the median
line forms the body of the uterus.

The Fallopian tube is smaller in diameter than the
cornu of the uterus, generally more or less contorted, and
terminates by a fimbriated expansion or mouth opening
freely into the abdominal cavity.

The Fallopian tubes and uterus are suspended by the
broad ligament, or ligamentum latum, which is a fold of
the peritoneum attached to the dorsal abdominal wall.
The round ligament, or ligamentum rotundum, also aids
in keeping the uterus in place. This appears as a thicken-
15

178 ELEMENTS OF MAMMALIAN ANATOMY.

ing of the broad ligament when the latter is looked
through toward the light. The round ligament extends
from about the middle of the horn or cornu of the uterus
ventrad of Poupart's ligament, and through the muscles
of the abdominal wall beneath the skin of the inguinal
region, where it gradually loses itself. It is exceedingly
delicate and thread-like.

The vagina extends from the uterus to the vestibule,
opening on the surface ventrad to the anus. The small
papilla just caudad of the orifice of the urethra on the
ventral surface of the vestibule is the clitoris, the homo-
logue of a part of the penis in the male. The prominent
circular fold of mucous membrane cephalad of the orifice
of the urethra represents the hymen, which marks the
separation between the vagina and vestibule. This struc-
ture may be shown by making a median longitudinal
section through the vagina. Bartholin's glands lie on the
lateral aspect of the vestibule, into which their ducts
open. Each one is about the size of a small pea. The
vagina, uterus, and Fallopian tubes are lined with mucous
membrane in which are many glands. The mucous lining
is surrounded by a muscular coat especially thick in the
uterus.

The ovaries are the organs producing the female germ
cells or ova which when fertilized are known as the eggs
(Figs. 54 and 83). One lies caudad of the kidney on each
side and is invested by peritoneum, which should be care-
fully dissected away. A microscopically prepared section
of the adult ovary magnified about 100 diameters will
reveal a number of ova in a more or less mature state.
Usually a peripheral ring of very young ova is present,
more mature ones are near the center, while one or two
quite ripe ova are very near the circumference. As the
ova develop, a follicle or sac known as the Qraafian

THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 179

follicle is formed about them. This is lined with several
layers of epithelial cells forming the membrana granulosa.
At one side of the follicle the membrana granulosa
thickens and envelops the ovum, forming the discus
proligerus. The cavity of the follicle is filled with liquor
folliculi. When the ovum becomes almost mature, the
walls of the follicle have grown peripherad, so as to cause
a pin-head protuberance on the surface of the ovary
clearly visible to the naked eye. In a fresh specimen this
protuberance may be picked open and the ovum expelled

9*

Mp:'- f° j*

' :- * ' '"

nii • '- '/'

^v — _> r

;.

FIG. 86. — SECTION OF OVARY. X 40.

sr, Surface of the ovary; gr, Graafian follicle with mature ovum; o, ovum;
c, cavity of the follicle; un, undeveloped ova; strm, stroma or con-
nective elements of the ovary; m, membrana granulosa; d, discus
proligerus.

on a slide for examination with the microscope. The
ovum is scarcely visible to the unaided eye. The human
ovum is still smaller.

The ova of all mammals, except the Ornithodelphia
(Monotremata), are very small. When the ovum becomes
mature, the protruding wall of the follicle bursts, per-
mitting its contents to be received by the expanded end
of the Fallopian tube, whence it passes to the uterus.
If the male element, the spermatozoon, enters the ovum,
the latter is soon enveloped by a growth of mucous mem-
brane and retained in the uterus for development. Ripe

l8o ELEMENTS OF MAMMALIAN ANATOMY.

ova occur near the close of the first year of the cat's life
and new ones probably continue to mature during the
next ten years. The discharge of the ova from the ovary
is accompanied by a constitutional disturbance, during
which an extra amount of blood is sent to the sexual
organs, and the sexual appetite becomes very marked.
In the human species this disturbance occurs about every
twenty-eight days. Mature ova occur in the human ovary
between the thirteenth and forty-eighth years.

The mammary glands of the adult female cat reach
their full development when it gives birth to young.
They may be seen by carefully removing the skin from
the ventral aspect of the body, when they will appear
somewhat like a thin layer of adipose tissue extending
from near the axilla to the pubic symphysis. There are
four teats or nipples on each side. In some mammals the
nipples are less numerous and confined either to the
thoracic or inguinal region. In the elephant, Chiroptera,
and Primates there are but two nipples, and they are
thoracic. In most Ungulates the nipples are inguinal.

THE MALE REPRODUCTIVE SYSTEM.

The organs of generation in the male consist of the
testes, the ducts leading from the testes to the urethra,
the prostate gland, Cowper's gland, and the penis.

The testes are two in number, contained in a pouch of
integument called the scrotum, which hangs beneath the
anus. Internally the scrotum is divided into two cham-
bers. By dissecting away the adipose tissue covering
the spermatic cord in the inguinal region (Fig. 51) it
may be seen that the cord and the testes are enveloped
by a tough sheath. This is composed of cremasteric
fascia derived from the aponeurosis of the external ob-

THE EXCRETORY AND REPRODUCTIVE SYSTEMS.

181

lique muscle, and of the tunica 'vaginalis. On the testis
between these two coats is a
thin layer of fibers forming
the levator scroti muscle.
The tunica vaginalis is com-
posed of three layers, the
outer of which is the fascia
propria, derived from the
transversalis fascia. The
other two are derived from
the peritoneum.

During fetal life the testes
lie in the abdominal cavity,
and when they descend into
the scrotum about the time
of birth, a double layer of
peritoneum is pushed down
before them through the in-
guinal canal, forming a di-
verticulum whose blind end
lies within the scrotum,
while the constricted por-
tion forms a channel for
the vas deferens, spermatic
nerve, and vessels. These
three structures form the
spermatic cord (Fig. 51).
The fascia propria (tunica
vaginalis communis) is in-
separably united with the
adjacent parietal layer of
the peritoneum. The vis-
ceral layer of peritoneum is
quite delicate and trans-

FIG. 87. — VENTRAL ASPECT OF THE
MALE REPRODUCTIVE ORGANS.

cr, One of the crura of the penis ;
ep, epididymis revealed by cut-
ting and reflecting vg, a piece of
the tunica vaginalis and albu-
ginea; et, external abdominal
ring; it, internal abdominal ring;
in, inguinal canal ; g, glans penis ;
gd, Cowper's glands; pe, penis;
pr, prostate gland; re, rectum;
/, testis from which the tough
sheath composed of the levator
scroti muscle and cremaster fascia
has been removed, leaving it en-
veloped by the tunica vaginalis;
is, testicle from which a portion
of the tunica vaginalis has been
reflected; nth, urethra; ur, ure-
ters ; vd, spermatic cord ; vdd, vas
deferens within the abdominal
cavity; vg, tunica vaginalis re-
flected; i'g2, tunica vaginalis; v,
spermatic vein.

1 82 ELEMENTS OF MAMMALIAN ANATOMY.

parent and lies close to the testis. Immediately sur-
rounding the latter is a dense capsule, the tunica albu-
ginea, sending septa into the interior. Within the tunica
vaginalis is the tunica albuginea, closely investing the
testicle, and adjacent to the epididymis penetrating the
substance of the gland, forming a septum known as the
mediastinum testis or corpus Highmorianum (Fig. 87).

The testis is about i J centimeters long by i centimeter
thick. On its dorsal surface lies the epididymis, an
elongated body composed of an enlarged extremity, the
globus major, and an attenuated portion, the globus minor.

The main portion of a testicle is
composed of many minute coiled
tubules, tubuli seminiferi, which
unite into a few tubules near the
surface of the testis beneath the
globus major, into which they ex-
tend. These tubules are the i)asa
\ ' efferentia. The epididymis is com-

FIG. 88. - - SPERMATOZOA posed of a single greatly convoluted
x* 5^0 IvE GERM CELLS' tubule of which the vas def erens is
h, Head; t, tail. a continuation. The latter pro-

ceeds cephalad to the external ab-
dominal ring, which it enters to traverse the inguinal canal
into the abdominal cavity. It then curves caudad and
enters the urethra on its dorsal aspect in the region of the
prostate gland.

The inguinal canal begins with the external abdominal
ring, which is an opening in the tendon of the external
oblique muscle, and ends with the internal abdominal
ring, which is an opening in the fascia of the transver-
salis muscle (Fig. 51). By accident, a fold of the small
intestine sometimes descends through the inguinal canal,
which condition is known as hernia or rupture.

THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 183

The penis is a cylindrical pointed body about three
centimeters long when in repose. It is composed of two
kinds of tissues arranged in three bundles. The corpus
spongiosum is the median ventral bundle, extending
throughout the length of the organ, and at the end
forms the glans or head. The two dorsal lateral bundles
are the corpora cavernosa. They form the greater part
of the penis proximad of the glans, and by diverging
somewhat before their attachment on either side to the
pubis and ischium form the crura. The penis is sus-
pended from the wall of the abdomen by a fold of in-
tegument inserted at the base of the glans, and forming
the prepuce. The latter is a free projection of skin
covering the glans. In the midst of the penis is a small
bone. The penis is the organ of copulation, and is com-
posed of a spongy mass of elastic and muscular fibers
richly supplied with highly distensible blood-vessels
which when filled render the organ erect.

The prostate gland surrounds the urethra dorsally and
laterally about two or three centimeters from the bladder.
This gland secretes a milky fluid which is poured into
the urethra through many ducts, during copulation, and
serves as a medium for the spermatozoa (Fig. 87).

Cowper's glands are two in number, about the size of
a pea, and lie in the angles formed by the urethra and
the crura of the corpora cavernosa. These glands secrete
a vfscid fluid of unknown function. One duct from each
gland opens into the urethra.

184 ELEMENTS OF MAMMALIAN ANATOMY.

REMARKS ON THE MAMMALIAN URO GENITAL

SYSTEM.

The urogenital system is subject to some variations in
the different orders of Mammalia. In the Ornithodelphia,
the mammary glands are devoid of teats and the oviducts
corresponding to the Fallopian tubes and horns of the
uterus do not unite in the median line to form the body
of the uterus, but unite with the urethra, forming the
urogenital canal. The latter opens into an enlarged
terminal portion of the rectum, called the cloaca. The
ureters also open directly into the cloaca, so that there
is but one external opening for the genital and excretory
products. In the above features the Monotremes resem-
ble the Amphibia and reptiles. All mammals are vivip-
arous except the Monotremata, which are oviparous,
laying eggs as large as those of the robin. The Orni-
thorhynchus incubates its eggs in an underground nest,
while the Echidna carries hers in a temporary abdominal
pouch.

The Marsupialia bring forth their young in a very
immature condition. They are then carried for several
months in an abdominal integumentary pouch, the
marsupium, within which are the nipples. In the Mono-
tremata, Cetacea, Sirenia, and elephant the testes do not
descend into a scrotum, but are retained in the primitive
location within the abdomen. In Primates and some
Edentates, the uterus is merely a pear-shaped body
without any cornua, the Fallopian tubes leading directly
into the body of the uterus.

In the ox, bears, seals, and cetaceans the kidneys are
distinctly lobulated. Internal evidence of lobulation is
presented in most mammals by the renal papillae. In the
embryo the kidneys of all mammals are lobulated.

THE EXCRETORY AND REPRODUCTIVE SYSTEMS. 185

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. What other waste products besides CO._, result from the chemical
action in the tissues of the body?

2. Write a description of all parts of the urinary system visible in
your dissection.

3. Bisect a kidney longitudinally in the horizontal plane, draw the
cut surface, and label all features.

4. Explain the parts of a uriniferous tubule.

5. Wherein does the male urinary system differ from the female?

6. Make a drawing of the Fallopian tubes and uterus and label all
parts.

7. Describe location, size, external appearance, etc., of the ovary
as seen in your specimen.

8. How are the female reproductive organs held in place?

9. Can you distinguish externally the termination of the uterus and
the beginning of the vagina?

10. Are there any eggs protruding from the ovary or any cavities
from which eggs have been recently discharged?

1 1 . Describe a Graafian follicle.

12. What must be added to the ovum to produce another animal?

13. Name the parts of the male reproductive system present in your
specimen and locate them.

14. Describe the course of the spermatozoon from the testis to the
exterior.

15. Do all mammals nourish their young in the same manner?

16. What mammals incubate their eggs externally?

THE NERVOUS SYSTEM.

The nervous elements of the cat form three systems,
known as the central, peripheral, and sympathetic. The
central nervous system includes the brain and spinal cord.
The peripheral system includes the twelve pairs of nerves
emanating from the brain and the forty pairs of nerves
emanating from the spinal cord to supply the extremities
and trunk. The sympathetic system is composed of two
ganglionated nerve cords extending throughout the
trunk within the body cavity, one on either side of the
vertebral column, and their various branches to all the
viscera, blood-vessels, etc., of the body (Figs. 91 and 92).

THE BRAIN.

The central nervous system is known as the cerebro-
spinal axis. It is composed of the brain and spinal cord.
The brain lies within the cranial cavity and is protected
by three membranes called the meninges. These may be
demonstrated by cutting away the roof of the skull with
the bone forceps. The dura mater is the tough fibrous
membrane lining the interior of the skull. It dips down
between the two halves of the cerebrum, forming the
falx cerebri. Between the cerebrum and cerebellum in
the cat it is ossified, thus forming the bony shelf or ten-
torium cerebelli (Fig. 18). The dura mater adheres
closely to the inner surface of the cranial cavity, forming
the internal periosteum. The second membrane of the
brain is the arachnoid. Between the dura mater and the

186

THE NERVOUS SYSTEM. 187

arachnoid is the subdural space, containing a fluid having
the nature of lymph. The arachnoid is a very delicate
membrane which does not dip down into the sulci between
the convolutions of the brain, as is the case with the
pia mater, but passes across these depressions, where it
may be easily demonstrated (Fig. 100).

The subarachnoidal space lies between the arachnoid
and pia mater. The pia mater is the delicate vascular
membrane following so closely the convolutions and sulci
of the brain that it becomes apparent only when lifted
carefully by the forceps.

In order to study the brain satisfactorily each student
should have a specimen hardened according to directions
in the section on technique, and also should be permitted
to examine a series of sections cut transversely about a
centimeter thick. These sections may be mounted for
permanent use in pasteur dishes, according to the method
described in the "Journal of Applied Microscopy," Octo-
ber, 1902. The brain of a calf or sheep serves the learner's
purpose better than that of a cat, as the parts are larger,
and they are also easier to procure. An additional ad-
vantage is also found in the fact that there is some
difference between the brains of the cat and calf, and
the student must therefore rely more on his own observa-
tions.

External Features.- -The brain is composed of five
parts : the medulla oblongata, or myelencephalon; the pons
Varolii and cerebellum, forming the metencephalon; the
corpora quadrigemina and crura cerebri, composing the
mesencephalon; the diencephalon, including the optic
thalami and other parts bounding the third ventricle;
and the telencephalon, or cerebral hemispheres. The
medulla oblongata, sometimes called the bulb or stem
of the brain, is the expansion of the spinal cord as it

ELEMENTS OF MAMMALIAN ANATOMY.

passes through the foramen magnum. The pons Varolii
is the bridge of transverse fibers seen on the ventral
aspect of the brain just cephalad of the medulla (Fig. 94).
The cerebellum or little brain lies on the dorsal side of
the medulla and is partly covered by the caudal part of
the cerebrum. The mesencephalon is not visible exter-
nally on the dorsal aspect, but may be seen immediately
cephalad of the cerebellum by cutting away the cerebrum
(Fig. 98). The diencephalon is visible externally only
on the ventral aspect of the uncut brain, where it forms
the floor of the third ventricle. It may be viewed as a
whole if the dorsal half of the cerebrum including the
corpus callosum is cut away. The telencephalon is com-
posed of the two large hemispheres partially surrounding
the diencephalon and mesencephalon.

The brain is composed of two kinds of matter, white
and gray. The former is constructed for the most part
of fibers, while the latter is formed largely of cells. The
outer or cortical portion of the cerebrum and cerebellum
is a layer of gray matter less than a half centimeter
thick, and is disposed in folds called gyri or convolutions
with intervening depressions termed sulci, the more im-
portant of which are called fissures.

The four different portions of the cerebrum are known
as frontal, parietal, occipital, and temporal lobes, which
occupy the respective regions of the cranial cavity. The
frontal and parietal lobes are separated by the crucial
fissure, extending transversely between them. The ol-
factory lobe (usually torn off in removing the brain
from the skull) projects from the cephalic portion of the
frontal lobe. The parietal lobe is marked by three gyri,
named according to location gyrus marginalis, gyrus
suprasylvius, and gyrus ectosylvius (Figs. 89 and 90).
The caudal portions of the gyri marginalis and supra-

THE NERVOUS SYSTEM.

189

sylvius constitute a portion of the occipital lobe. These
two gyri are separated by the lateral sulcus. The supra-
sylvian sulcus extends between the gyrus suprasylvius
and the gyrus ectosylvius. The splenial sulcus (Fig. 92)
separates the gyrus marginalis
from the gyrus fornicatus on
the mesal aspect of the parie-
tal and occipital lobes. There
are no definite sulci or fissures
separating the parietal, occipi-
tal, and temporal lobes. The
postrhinal fissure, extending
caudad from the fissure of Syl-
vius, divides the temporal lobe
into two portions on the ven-
tral aspect.

The ventral surface (Fig. 90)
of the brain also presents im-
portant features which should
be noted by the student before
investigating the internal
structure. The anterior pyra-
mids, two indistinctly differ-
entiated bundles of fibers, oc-
cupy the mesoventral region
of the medulla, and cephalad
of the pons help form the crura
cerebri. Laterad of each pyra-
mid is the olivary projection.
A broad band of transverse
fibers appearing just caudad

of the pons Varolii and laterad of the anterior pyramids
is the corpus trapezoideum.

The pons Varolii is itself composed of a band of

FIG.

89. — DORSAL ASPECT OF
THE BRAIN.

Gyrus marginalis; ac, white
matter of the cord; ad, gray
matter of the cord; b, gyrus
suprasylvius ; c, gyrus ectosyl-
vius ; cr, crucial fissure ; ce, lat-
eral lobe of cerebellum ; d, lat-
eral sulcus; e, suprasylvian
sulcus; Ig, great longitudinal
fissure; md, medulla oblon-
gata ; n, first spinal nerve ; ol,
olfactory lobe; p, posterior
pyramids; sp, spinal cord; v,
vermis of cerebellum.

FIG. 90. — VENTRAL ASPECT OF THE BRAIN.

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, The cranial nerves; a, ophthalmic branch
of the trigeminal nerve; an, anterior pyramids; at, anterior horn of
gray matter; b, superior maxillary branch of the trigeminal nerve;
1 la, eleventh cranial nerve with roots from the spinal cord ; c, mandib-
ular branch of the trigeminal nerve; ca, corpus albicans; cb, cere-
bellum ; cc, canalis centralis ; en, cornea ; ct, cut surface of spinal cord ;
ex, external rectus muscle; cr, crus cerebri; g, Gasserian ganglion
of the trigeminal nerve ; hi, pyriform lobe ; in, opening into the tuber
cinereum revealed by removal of the infundibulum and pituitary
body ; i, internal rectus ; io, inferior oblique ; ir, inferior rectus ; n} and
n.2l first and second spinal nerves; ol, olfactory lobe; op, optic com-
missure ; ot, optic tract ; p, posterior horn of gray matter ; pt, anterior
perforated space ; pv, pons Varolii ; r, mesal or inner root of olfactory
nerve ; rt, lateral root of olfactory nerve ; pr, postrhinal fissure ; sy,
Sylvian fissure ; s, superior rectus muscle ; tz, corpus trapezoideum ;
x, external arciform fibers.

190

THE NERVOUS SYSTEM. IQl

transverse fibers which on either side forms the middle
peduncle of the cerebellum, commonly called the crus
cerebelli ad pontem medullse. The fibers originate either
in cells of the medulla or those of the cerebellum.

The crura cerebri, or peduncles of the cerebrum, the
ventral portions of which are continued as the anterior
pyramids (Fig. 90), are seen just cephalad of the pons.
Their fibers unite the cerebrum to the rest of the brain
and the spinal cord. In the space between the crura
and the optic chiasm is a prominent projection, the
terminal nodular portion of which is the pituitary body
or hypophysis. It occupies the pituitary fossa of the
skull and is usually torn off in removing the brain.
Caudad of the hypophysis are two small rounded white
bodies, the corpora albicantia. The tuber cinereum, a
slightly elevated mass of gray matter behind the optic
chiasm, bears on its surface the funnel-shaped stalk, the
infundibulum , to which the hypophysis is attached. If
the two latter parts are removed, there is seen a small
elongated aperture through the tuber cinereum into the
third ventricle (Figs. 90 and 92).

The optic commissure, or optic chiasm, is the commissure
formed by the crossing of the optic nerves just cephalad
of the tuber cinereum. The prolongation of the optic
nerves dorsad from the optic commissure forms the
optic tracts, partly covered by the temporal lobes. On
either side of the median fissure just cephalad of the
optic chiasm is a somewhat triangular area known as
the anterior perforated space because of the numerous
vessels that enter the brain in this region. Laterally this
space is bounded by the lateral olfactory tract or lateral
root of the olfactory nerve, which presents the appearance
of a band of white fibers extending from the olfactory
lobe into the temporal lobe. The mesal or inner root of

ELEMENTS OF MAMMALIAN ANATOMY.

ab.

mi

the olfactory nerve is seen adjacent to the median ventral
line cephalad of the anterior perforated space. The
olfactory lobes project from the cephalic ventral portion
of the cerebrum and give origin to the first pair of cranial
nerves.

Internal Structure.- -The canalis centralis, a small canal
extending throughout the center of the spinal cord,

enlarges in the region of the brain,
forming four cavities or ventricles
communicating with each other by
narrow channels. The brain is there-
fore to be considered as a hollow
structure. The first and second ven-
tricles, also known as lateral ventricles,
occupy the cerebral hemispheres (Fig.
91). The third and fourth ventricles
lie in the median line, and are there-
fore well seen in a sagittal section of
the brain (Fig. 92).

The Ventricles of the Brain.- -The
fourth ventricle is visible on the dorsal
aspect of the medulla oblongata (Fig.
92). It is about three centimeters
long by one centimeter wide, and lies
ventral to the cerebellum. This ven-
tricle is merely an expansion of the
canalis centralis of the spinal cord. Its roof is very thin
and consists of two portions, one of which, the superior
medullary velum, sometimes called the valve of Vieussens,
covers the cephalic half of the ventricle ; the other portion
is the inferior medullary velum, lying over the caudal
half. The latter velum is composed of a fold of pia
mater tucked in between the cerebellum and medulla,
in addition to a layer of epithelial cells on the ventricular

FIG. 91. — DIAGRAM OP
VENTRICLES OF THE
BRAIN VIEWED
DORSALLY.

ah, Anterior horn of
the right lateral ven-
tricle; as, aqueduct
of Sylvius ; cc, can-
alis centralis of the
spinal cord; 3 and
4, third and fourth
ventricles ; m, fora-
men of Monro ; mi,
middle horn or cor-
nu of the ventricle.

THE NERVOUS SYSTEM. 193

aspect of the pia mater. Some nervous matter in addi-
tion to the pia mater and epithelium forms the superior
velum. Two longitudinal vascular fringes, hanging from
the roof of the ventricle on either side of the mid-line,
form the choroid plexus, which is merely a network of
blood-vessels carried by a reflected portion of the pia
mater.

Cephalad the fourth ventricle is continued as a small
canal, the iter, or aqueduct of Sylvius, which lies ventrad
to the corpora quadrigemina and opens into the third
ventricle (Fig. 92). The latter is a narrow, vertical,
cleft-like space between the optic thalami. The two
thalami are united by the soft or middle commissure,
better designated as the massa intermedia, extending
through the ventricle. Unless this ventricle has been
injected with a starch mass through the infundibulum
before the brain was hardened, its cavity will not exceed
a millimeter in width. The roof is formed much in the
same manner as that of the fourth ventricle, by a re-
flection of the pia mater lined with epithelium (Figs. 92
and 94). A sagittal section of the brain placed in a pan
of water will show the fold of pia mater called velum
interpositum extending cephalad from the pineal gland.
Two folds of the pia mater hanging on either side from
near the median line form the choroid plexus as in the
fourth ventricle. The body of the fornix lies dorsad of
the membranous roof of the ventricle. In the floor lie
the corpora albicantia, the infundibulum, the tuber
cinereum, and the optic commissure. Cephalad the
third ventricle communicates with the lateral ventricles
by slit-like apertures, the foramina of Monro, passing
laterad and ventrad of the anterior pillars of the fornix.

The lateral ventricles are found in the cerebral hemi-
spheres ventrad to the corpus callosum. They are the

194

ELEMENTS OF MAMMALIAN ANATOMY.

largest ventricles of the brain. In order to view them
satisfactorily, the entire dorsal portion of the brain down
to the corpus callosum must be cut away, and a hole
cut through the corpus callosum. A number of cross-
sections of the cerebral hemispheres should also be
studied.

FIG. 92. —SAGITTAL SECTION OF THE BRAIN.

ac, Anterior commissure ; ai), arbor vitae ; c, habena ; cc, canalis centralis ;
cb, cerebellum; cm, middle commissure or massa intermedia; cr,
sulcus crucialis; cpq, corpus quadrigemina ; ex, choroid plexus of
third ventricle — the dark line dorsad of ex is the velum interpositum ;
/, sulcus splenialis ; fr, frontal lobe of cerebrum ; fn, anterior pillars
of the fornix; in, infundibulum ; it, iter, or aqueduct of Sylvius; k,
genu of corpus callosum; Imx, lamina terminalis; m, splenium; mr,
sulcus marginalis ; med, medulla ; op, optic chiasm ; oc, occipital lobe ;
ol, olfactory lobe; pn, pineal gland; po, pons Varolii; pc, posterior
commissure; pv, inferior medullary velum; pvv, superior medullary
velum or valve of Vieussens ; 3 and 4, third and fourth ventricles.

Each ventricle is composed of a body from which pro-
jects an anterior cornu and a middle or descending cornu.
The former extends into the frontal lobe and thence into
the olfactory lobe, and the latter descends into the
temporal lobe. The roof of the body of the lateral ven-
tricle is formed by the corpus callosum (Figs. 92, 93,
and 94) and the mesal wall by the septum lucidum, a

THE NERVOUS SYSTEM. 1 95

mass of gray matter lying between the fornix and the
corpus callosum. A fringe of pia mater projects through
the foramen of Monro into the lateral ventricle, where it
forms the choroid plexus. The lateral ventricles are lined
with the epithelial layer common to the other ventricles.

These cavities within the central nervous system result
from the manner in which the brain and cord are formed.
In the embryonic life of most vertebrates the nervous
system appears as a trough of matter extending dorsally
throughout the length of the body. The sides of this
trough grow dorso-mesad, thus forming a roof and
thereby converting the trough into a canal which in the
spinal cord becomes the canalis centralis, and in the
brain the ventricles. This continuous cavity of the
central nervous system contains a fluid having the nature
of lymph.

The Commissures of the Brain.- -The paired portions of
the brain are united across the median line by bands of
fibers known as commissures, two of which are visible
on the ventral surface of the brain, and the others may
be seen in a sagittal section (Fig. 92).

The pans Varolii is the commissure on the ventral
aspect of the medulla. Its fibers pass into the cerebellum
on either side, forming the middle peduncle or crus cerebelli
ad pontem. The optic commissure or optic chiasm is
formed by the crossing of the optic nerves, cephalad of the
tuber cinereum. Some of the fibers originating in the cells
of the retina of one eye pass by this commissure directly
to the cells in the retina of the other eye, while a second
set passes from the eye to the optic tract on the opposite
side of the brain, and still a third set, originating in one
corpus quadrigeminum, passes by the optic commissure
direct to the opposite corpus quadrigeminum (Figs. 92,
TOO).

196 ELEMENTS OF MAMMALIAN ANATOMY.

The corpus callosum is the largest commissure of the
brain. It joins the two cerebral hemispheres, and forms
the roof of the lateral ventricles. This broad plate of
fibers (Figs. 92, 93, 94, 95), which may be seen at the
bottom of the great longitudinal fissure by pressing the
hemispheres slightly apart, is about one millimeter thick
and three centimeters wide. Laterally the fibers radiate
in all directions to the gray matter of the cortex. The
ventral bend of the median cephalic portion of the
callosum is the genu or knee. The caudal border is the
splenium.

The fornix lies ventral to the callosum (Figs. 92 and
94) and consists of a median plate of fibers, the body,
two posterior columns, and two anterior columns or pillars.
The median plate or body of the fornix sends some fibers
into the ventral surface of the callosum. From the
cephalic border of the body near the median line the
two anterior columns, or pillars, descend in a curve,
forming the cephalic boundary of the third ventricle as
far ventrad as the anterior commissure. Here the two
columns diverge slightly from the median line, but con-
tinue their descent, curving caudad to their termination
in the corpora albicantia. The posterior columns, or
crura, descend from the caudal border of the body,
curving laterad into the median cornu of the lateral ven-
tricle, and gradually unite with the cornu ammonis.
The cornu ammonis, or hippocampus major, is a thickened
projecting fold of the wall of the median cornu (Fig. 93).
The free lateral margin of the posterior pillar or crus of
the fornix is the fimbria, or tcznia hippocampi. Adjacent
to the median line in either hemisphere, a thick lamina of
matter, the septum lucidum, stretches from the cephalic
part of the fornix dorsad to the callosum. The very
narrow cavity formed by the adherence of the margins

THE NERVOUS SYSTEM.

197

of the septum of one hemisphere to those of the septum
in the other hemisphere is sometimes called the fifth
ventricle. Between each anterior pillar of the fornix and

FIG. 93. — DORSAL ASPECT OF THE BRAIN WITH THE CEREBELLUM AND
THE DORSAL THIRD OF THE CEREBRUM REMOVED AND MOST OF THE
CORPUS CALLOSUM CUT AWAY FROM THE RIGHT HALF.

ac, Right anterior corpus quadrigeminum ; c, commissure of the quadri-
gemina; ca, the united superior and inferior peduncles of the cere-
bellum ; cr, the middle peduncle or crus cerebelli ad pontem ; cs, corpus
striatum; ct, edge of corpus callosum cut slightly to the left of the
median line; cal, dorsal surface of the callosum into which a hole
has been cut; lip, hippocampus major, or cornu ammonis, in the
median cornu of the lateral ventricle; h, hippocampus major near
where it is joined by the fibers of the crus of the fornix; i, uncut
portion of the callosum ; md, medulla oblongata ; n, anterior columns
or pillars of the fornix ; o, gray cortex of the cerebrum ; p, posterior
crus of the fornix; pn, pineal gland, cephalad to which is the heavy
white line, the commissure of the habenae or taeniae thalami; pp,
funiculus gracilis; re, funiculus of Rolando; 1, funiculus cuneatus;
ts, one of the testes or posterior corpora quadrigemina ; x, body of
the fornix.

the optic thalamus is a cleft, the foramen of Monro,
leading from the third ventricle, laterad of the septum
lucidum, into the lateral ventricle.

198 ELEMENTS OF MAMMALIAN ANATOMY.

The three remaining commissures are known according
to their location as the anterior, middle, and posterior.
The anterior commissure (Figs. 92 and 95) perforates the
corpora striata, extending across the median line imme-
diately cephalad of the anterior pillars of the fornix. It
is about two millimeters in diameter. The middle com-
missure, or massa intermedia, lies between the optic
thalami. It is sometimes called the soft or gray com-
missure. It is nearly one centimeter in diameter and
passes through the third ventricle (Fig. 92). The pos-
terior commissure is a cord of fibers about a millimeter
in diameter connecting the caudal portions of the optic
thalami.

The Basal Ganglia. — A semi-independent group of nerve
cells forming a definite mass is known as a ganglion.
In the ventral portion of the brain lie three pairs of
large ganglia, called corpora quadrigemina, optic thalami,
and corpora striata. To study them, the entire dorsal
surface of the brain down to and including the corpus
callosum should be removed.

The corpora quadrigemina (Fig. 93) lie cephalad of the
medulla, and consist of an anterior pair, the nates, and
a posterior pair, the testes. A narrow canal, the iter,
or aqueduct of Sylvius, leads from the fourth ventricle
through the corpora quadrigemina (Fig. 92) from the
fourth ventricle to the third ventricle. The nates lie
nearer to the midline than the testes, which are slightly
separated by a depression occupied by the middle portion
of the central lobe of the cerebellum. The testes are
united by a white commissure. The posterior commis-
sure of the brain unites the cephalic portions of the nates
(Fig. 92). Its cut end may be seen ventrad to the base
of the pineal gland.

Laterally each pair of the corpora quadrigemina is

THE NERVOUS SYSTEM.

prolonged into two white bands, the anterior and pos-
terior brachia. The latter are about a half centimeter
long, and pass forward beneath a pisiform ganglion, the
corpus geniculatum internum or mediate. The anterior
brachia pass from the cephalic end of the nates laterad
beneath the caudal projections of the optic thalami,
where they join the optic tracts.

FIG. 94. — CROSS-SECTION OF THE BRAIN IN THE PLANE x IN FIG. 92
The plane is just caudad of the optic chiasm.

1 and 2, First and second or lateral ventricles; cr, corpus callosum; cm,
anterior pillars of fornix; ex, choroid plexus of lateral ventricle; ex',
choroid plexus of third ventricle; cxt, gray cortex; ca, ependyma or
endyma lining the ventricles; /, median longitudinal fissure; h,
habena, or taenia thalami; me, middle commissure, or massa inter-
media; n, fibers of the optic tract as they enter the external genic-
ulate body s; o, fornix ; r, caudal portion of nucleus lenticularis ;
op, optic thalamus ; oc, optic tract as it leaves the chiasm ; si, septum
lucidum; im, part of third ventricle dorsad to the commissure; v,
third ventricle ; /, fibers of optic tract.

Homologues of the corpora quadrigemina exist in all
vertebrates. In them originate largely the optic nerves,
and therefore their size is in proportion to the animal's
power of sight. In the mole, which has little use for
eyes, the anterior pair is rudimentary.

The optic thalami form the largest pair of basal ganglia,
and lie cephalad of the corpora quadrigemina and form

200 ELEMENTS OF MAMMALIAN ANATOMY.

the lateral walls of the third ventricle, across which they
meet, forming the massa intermedia, or middle com-
missure.

On the dorsal aspect of each thalamus, near the median
line, is a longitudinal band of white fibers called the
habena, or t&nia thalami, which at its caudal limit is
united to its fellow by the commissura habenae. The
thalamus is composed largely of gray matter, but there
are two important bundles of fibers, known as the optic
tract and internal capsule (Fig. 94), appearing on its
lateral surface. The optic tract, of which the optic nerve
is a continuation, arises by two roots, the larger of which
comes from the cells forming the lateral geniculate body,
which is the lateral and caudal projection of the thalamus.
The internal capsule, well shown in a transverse section,
is composed mainly of the fibers descending from the
cells of the parietal region of the cortex.

The pineal gland, or pineal body (Fig. 92), is a conical
projection about a half centimeter long, from the caudal
part of the dorsal surface of the thalamus. It is a ves-
tigial structure which in some of the lower vertebrates
in early geological time functioned as a third eye. In
Hatteria, a New Zealand lizard about a foot long, the
eye is present, projecting slightly through a foramen in
the parietal bone. Traces of this third eye with a lens
have also been noticed in the embryo of the viper and
some of the lizards.

The corpora striata are the most cephalic of the basal
ganglia and are somewhat pear-shaped, the larger ends
being cephalad and nearer the median line than the
caudal portions, which curve laterad around the optic
thalami (Fig. 93). They form a part of the floor of the
lateral ventricles, and are pierced by the anterior com-
missure (Fig. 95), a small cord of white fibers.

THE NERVOUS SYSTEM.

2OI

The corpus striatum consists of both white and gray
matter. The latter, composed of cells, is disposed in
two chief nuclei or masses, known as the nucleus cauda-
tus, lying median and cephalic, and the nucleus lenticu-
laris, which is more lateral and caudal (Fig. 95). The
center of the nucleus lenticularis is laterad of the optic
thalamus and dorsad of the crus cerebri. A thin layer
of white matter, the lamina semicircular is, separates the

vn cm

FIG. 95. — CROSS-SECTION OF THE BRAIN THROUGH THE ANTERIOR COM-
MISSURE.

an, Arachnoid; ce, external capsule; d, corpus callosum; cm, anterior
commissure ; /.re, falx cerebri ; /, great longitudinal fissure ; fx, anterior
pillars of the fornix; ic, internal capsule; n, radiating fibers of cal-
losum ; in, septum lucidum ; nc, nucleus caudatus of corpus striatum ;
/, nucleus lenticularis; p, pia mater; vis, superior longitudinal sinus;
vn, third ventricle; v, lateral ventricle.

optic thalamus from the nucleus caudatus. A few fibers
from the crus cerebri form the lamina semicircularis,
whose edge may be seen in the floor of the lateral ven-
tricle on the lateral boundary of the nucleus caudatus.
A group of fibers, known as the internal capsule, separates
the optic thalamus from the nucleus lenticularis, laterad
of which is the external capsule, a group of fibers probably
descending from the cells of the cerebral cortex. The two
nuclei of the corpus striatum are connected by fibers,
17

202 ELEMENTS OF MAMMALIAN ANATOMY.

and other fibers connect these nuclei with the cortex of
the cerebrum and the optic thalamus.

The Medulla Oblongata.- -The medulla oblongata, or
myelencephalon, is the stem of the true brain and extends
from the point of origin of the first spinal nerve to the
pons Varolii. The cerebellum must be removed in order
to study carefully the features of the medulla, and as
it is cut away the student should notice just ventrad to
it the very thin roof of the fourth ventricle. Its caudal
portion, composed of a reflection of the pia mater lined
with epithelium, takes the name of inferior medullary
velum, and the cephalic part, formed of pia and a thin
layer of nervous matter, is called the anterior medullary
-velum, or valve of Vieussens (Fig. 92).

The fourth ventricle (Figs. 92 and 93) is an enlargement
of the canalis centralis of the cord. The clavae, or expan-
sions of the funiculi graciles, the three peduncles or crura
of the cerebellum, and the testes or colliculi inferiores
form its lateral boundaries. Its cavity is shallow and
pointed at either extremity. The floor, called fossa
rhomboidea, is formed by the continuation of the gray
matter of the spinal cord. Where the ventricle is widest
a tract of fibers, the stria medullaris, arises from the
midline and proceeds laterad to help form the auditory
nerve.

Laterad of the clava a larger band of fibers, the
funiculus cuneatus, runs parallel with a more lateral
lying bundle, the funiculus cuneatus later alis, or funiculus
of Rolando. These three bands of fibers compose the
restiform body, or inferior peduncle of the cerebellum.
On the ventral aspect of the medulla may be seen the
anterior pyramids, composed of a band of fibers lying
on either side of the median line and apparently emerging
from the pons. They form a section of the crossed

THE NERVOUS SYSTEM. 203

pyramidal or motor tract connecting the brain with the
cord. The olivary eminence lies just laterad of the
pyramid. The fact that seven posterior cranial nerves
originate from the medulla shows the importance of this
part of the brain. The destruction of the respiratory
centers, or vital knot, lying ventrad to the caudal end
of the fourth ventricle causes instant death.

The Cerebellum, or Little Brain.- -The cerebellum,
which in the cat lies caudad of the cerebrum and dorsad
of the medulla, resembles the cerebrum in being com-
posed of an outer layer of gray matter or cells and an
inner mass of white matter made up of fibers. While
within the cerebrum there are several important ganglia
or masses of gray matter, in the cerebellum only one
chief mass of gray matter, the corpus dentatum, is present
in each hemisphere.

The outer layer of gray matter, known as the cortex,
is folded into numerous convolutions, between which are
deep sulci (Fig. 92). The central core of white matter
forms an arborescence known as the arbor mtcE.

The cerebellum (Fig. 89) is seen to consist externally
of two lateral portions, the cerebellar hemispheres, a
median vermiform process and three pairs of peduncles
or bands of fibers uniting it with other parts of the
brain and cord (Fig. 93). The separation between the
hemispheres and vermis or vermiform process is most
marked on the cephalic aspect.

The peduncles are named, according to their location,
superior, middle, and inferior. The middle peduncle, or
cms ad pontum, is a dorsal prolongation of the fibers of
the pons Varolii (Fig. 90). In order to display the other
peduncles a portion of the cerebellum must be cut or
picked away with the forceps. The superior one, known
also as the brachium conjunctivum, extends as a cord

204 ELEMENTS OF MAMMALIAN ANATOMY.

of fibers along the cephalic half of the fourth ventricle
beneath the corpus quadrigeminum. The inferior pedun-
cle, or restiform body, forms part of the boundary of
the caudal half of the fourth ventricle and enters the
cerebellum between the other two peduncles. It is com-
posed largely of fibers from the spinal cord.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Describe the meninges of the central nervous system.

2. Which of the five parts of the brain are exposed dorsally?

3. Draw the lateral aspect of the brain and label all features.

4. Draw the ventral aspect of the brain and label all features.

5. Draw the dorsal aspect of the brain after the dorsal portion, in-
cluding corpus callosum and fornix, has been removed.

6. Describe the differences existing between the gyri and sulci of
your specimen and the one described in the text.

7. Write a description of the ventricles, giving dimensions and bound-
aries.

8. Describe the attachment of the pineal body.

9. Which of the cranial nerves derive their name from their function?

10. Name the foramina giving passage to one or more of the cranial
nerves.

1 1 . From which of the five parts of the brain do most of the cranial
nerves originate?

12. Describe the choroid plexus.

13. What is the internal capsule?

14. Draw a cross-section of the brain made by cutting through the
optic commissure and label all parts.

15. Draw a cross-section of the brain made by cutting through the
middle commissure and label all parts.

16. Draw a cross-section of the brain made by cutting through the
corpora quadrigemina and label all parts.

17. Write a description of the corpus callosum.

18. Which is the smallest commissure of the brain?

19. Explain the difference in structure between the white and gray
matter.

20. Describe the cerebellum.

THE NERVOUS SYSTEM. 205

THE SPINAL CORD.

The spinal cord extends from the foramen magnum
through the vertebral canal. It is more or less cylindrical
throughout and has a diameter of about one centimeter
except in the lumbosacral region, where it grows gradu-
ally smaller until it is only one or two millimeters in
diameter. In order to study the cord, one should have
a mounted transverse microscopic section, an entire cord
in situ with the dorsal wall of the vertebral canal re-
moved, so that the exit of the spinal nerves may be seen.

The membranes which envelop the spinal cord are the
same as those that envelop the brain. The dura mater
is the external tough coat; the pia mater, the internal
delicate vascular coat sending a process deep into the
anterior fissure on the ventral side; and the arachnoid,
the very thin membrane between the two preceding.
The arachnoid lies close against the dura mater, but is
separated from the pia mater by the subarachnoid space,
which is filled with a serous fluid called the cerebrospinal
fluid. It is apparently the same as that in the ventricles
of the brain, and seems to be of a lymphoid nature.
In fact, the subarachnoidean space is merely a large
lymph space similar to the cavities of the pleura and
peritoneum. This lymph, or cerebrospinal fluid, proba-
bly escapes from the thin walls of the capillaries covering
the pia mater and is taken up by lymphatic vessels which
begin in open mouths on the walls of the space.

The cord presents two enlargements, the cervical,
whence issue the nerves of the forelimbs, and the lumbar,
giving origin to the nerves of the posterior limbs. Twro
deep fissures, the anterior median and the posterior
median, penetrate about one-third through the cord,
incompletely dividing it into halves longitudinally. The

206 ELEMENTS OF MAMMALIAN ANATOMY.

pia mater is prolonged into the anterior fissure, but not
into the posterior fissure. Slightly laterad of the anterior
median fissure issue the anterior roots of the spinal
nerves, and at about the same distance from the posterior
median fissure are the posterior roots of the spinal nerves.
These two roots unite about one centimeter from their
origin (Fig. 90). On the posterior or sensory root is a
small ganglion located very near the junction of the two
roots. The common spinal nerve, formed by the union
of the two roots, almost immediately divides into four
branches, one of which, the dorsal, supplies the muscles
and skin along the vertebral column; a second, the ven-
tral branch, supplies the limbs or intercostal spaces;
while the other two branches, rami communicantes, join
the adjacent ganglion of the sympathetic cord (Fig. 103).
Each of the four branches contains both motor and sen-
sory fibers, or, in other words, fibers from both roots.

The exit and entrance of the nerve roots divide the
white matter of the lateral half into three columns named,
according to their location, the anterior column, the
lateral column, and the posterior column. The first is
ventral to the anterior nerve roots, the last is dorsal to
the posterior nerve roots, while the lateral column is
between the roots.

The elements of the spinal cord, like those of the
brain, are of two kinds — the cells composing the gray
matter and the fibers composing the white matter.
While in the brain the gray matter is largely on the
surface, forming the cortex, in the cord it occupies the
central region. A canal, the canalis centralis, about one-
half a millimeter in diameter, extends throughout the
cord, opening into the fourth ventricle of the brain. A
cross-section of the cord shows the gray matter arranged
in the shape of a letter H . The ventral columns of gray

THE NERVOUS SYSTEM.

207

matter are the anterior horns, and the posterior columns,
the posterior horns (Fig. 96).

Many of the fibers extend in a longitudinal direction
throughout the cord, but the roots of the spinal nerves
upon entering the cord run transversely a longer or
shorter distance, and in many cases cross to the opposite
side. It is thought that the anterior root fibers are, for

FIG. 96. — DIAGRAMMATIC CROSS-SECTION OF THE SPINAL CORD. The cells
and fibers are represented too few and too large in proportion to the
size of the cord.

ag, Anterior horn or column of gray matter; a, nerve process of the cell
c; an, anterior root ; cc, canalis centralis ; c, one of many cells forming
the ganglion on the posterior root; d, posterior fissure; e, cell giving
off an axis-cylinder process into the anterior root ; dn, dorsal branch ;
/, cut-off fibers; gn, ganglion of posterior root; i, axis-cylinder pro-
cess of the cell io; nc, junction of anterior and posterior roots; ps,
posterior root of nerve; pg, posterior horn of gray matter; s, terminal
arborization of part of fiber from c , v, anterior median fissure; in,
ventral branch of nerve; van, axis-cylinder process of anterior horn
cells ; x, the part of the posterior root fiber extending caudad in the
cord.

the most part, the axis-cylinder processes of the cells in
the anterior horn (Fig. 98).

Each posterior root fiber after passing into the cord
separates into two parts one of which extends cephalad,
the other caudad (Fig. 98). Both give off branches at
right angles, called collaterals, which terminate in arbori-
zations about the cells of the cord.

208

ELEMENTS OF MAMMALIAN ANATOMY.

Each nerve cell presents two kinds of processes, proto=
plasmic processes or dendrites and an axis=cylinder pro=

cess (Fig. 97). The dendrites, except in the ganglia
outside of the central nervous system, are usually several
in number and comparatively short, while there is but

FIG. 97. — CELL FROM THE CENTRAL NERVOUS SYSTEM. 100.

a, Dendrites or protoplasmic processes; ax, axis-cylinder process; n,

nucleus of the cell body.

one axis-cylinder process from each cell, which may
be more than a foot in length. A number of axis-cylin-
ders (nerve fibers), each of which is surrounded by a
sheath, the neurilemma, constitutes a nerve bundle
or nerve. Every axis-cylinder or nerve fiber originates
in a cell, but terminates freely either within the central

FIG. 98. — DIAGRAM SHOWING THE RELATION OF SOME OF THE CELLS AND
FIBERS OF THE SPINAL CORD. Lateral aspect of the cord.

a, Anterior median fissure; ac, cells of the anterior horn; an, anterior root
of spinal nerve ; c, axis-cylinder process ; co, collateral fibers ; e, fibers
connecting higher brain centers with cerebellum ; fi, sensory fibers
of fillet to the brain; g, gn, go, ganglion of posterior root; gr, gray
matter ; ir, fibers of the posterior sensory tract ; /, fibers to cerebellum ;
777, cells in the anterior horn or column of gray matter ; n, spinal nerves ;
o, cells in the posterior horn or column of gray matter; nc, nucleus
gracilis and nucleus cuneatus; nr, nucleus ruber; r, a fiber of pos-
terior root ; rb, ganglion cells of medulla ; s, tract of fillet to the brain ;
sp, fibers of superior peduncle of the cerebellum; tf , fiber of crossed
pyramidal tract ; is, point of decussation ; v, division of fiber x into
its cephalic and caudal extensions ; w, a collateral of the longitudinal
fiber ir.

18

209

210 ELEMENTS OF MAMMALIAN ANATOMY.

nervous system or in some other part of the body (Figs.
97, 98). Within the central nervous system a fiber
usually ends in an arborescence which may be contiguous
but not continuous with the dendrites of another cell.
The nerve processes have the power of conducting
impulses whether derived from the cell itself or an
external stimulus. The dendrites conduct impulses to-
ward the cell, while the axis-cylinder conducts them
from the cell.

The sensory fiber r (Fig. 98) leads from the dermis
of the cat's paw. A pin-prick in the paw causes an
impulse to be transmitted along the fiber to the cell
g, and thence by its axis-cylinder, x, to the point v
within the cord where the fiber splits. From the point
v the impulse will proceed both through the ascending
portion of the fiber, ir, and the collateral, w. By the
latter route it will stimulate the cell m, whose axis-
cylinder terminates in the foreleg muscles, which are
thereby made to contract and pull the paw away from
the irritating object. This process may take place
without consciousness, and is then known as reflex action.
If, however, the impulse travels along the fiber ir, and
thence through the fiber s to the brain, whence an im-
pulse descends through the fiber t' , is, the process is known
as voluntary reaction.

THE FIBER TRACTS OF THE CENTRAL NERVOUS

SYSTEM.

As before stated, the white matter of each half of the
cord is divided by the exit and entrance of the nerve
roots into three columns — anterior, lateral, and posterior.
Each of these columns is subdivided into tracts which
have special names and special functions (Fig. 99).

THE NERVOUS SYSTEM.

211

In the posterior column two tracts are recognized:
the fasciculus of Goll, occupying the mesal third of the
column, and the fasciculus of Bur-
dach, composing the remainder. In
the medulla of the cat these two
tracts may be distinguished by the
unaided eye (Fig. 93). They are
here called the funiculi of Goll and
Burdach, or funiculi gracilis and
cuneatus. Their fibers are largely,
if not entirely, the axis-cylinder
processes of the ganglion cells on
the posterior roots of the spinal
nerves. They terminate in the nu-
clei gracilis and cuneatus, two small
masses of nerve cells in the medulla
laterad of the fourth ventricle (Fig.
98) . That these fibers are processes
of the spinal ganglion cells is proved
by the fact that they degenerate
if the posterior nerve roots are
severed close to the cord. In
whales, where the pelvic extremi-
ties are wanting, the fasciculi of
Goll and Burdach are very small.

The lateral column is composed
of five tracts : the direct cerebellar
tract, the antero-lateral descending
cerebellar tract, the antero-lateral
ascending cerebellar tract or Gow-
ers's tract, the lateral ground bun-
dle, and the crossed pyramidal tract.

The direct cerebellar tract occupies the superficial re-
gion of the cord laterad of the posterior cornu of gray

FIG. 99. - - DIAGRAM OF
SOME FIBER TRACTS.
DORSAL ASPECT.

a/, Antero-lateral ascend-
ing cerebellar tract; c,
posterior corpus quad-
rigeminum; cer, lateral
lobe of cerebellum,
whose median portion
is removed ; eg, the two
fasciculi of Goll and
Burdach represented as
one; cp, crossed pyra-
midal or chief motor
tract; cp' , crossed pyra-
midal tract in the region
of the cerebral pedun-
cle ; dc, direct cerebellar
tract; fi, the large part
of the fillet derived from
tic: nc, nuclei gracilis
and cuneatus ; s, decus-
sation of pyramidal
tracts; x, sensory or
superior pyramidal de-
cussation; sp, superior
peduncle of cerebel-
lum.

212 ELEMENTS OF MAMMALIAN ANATOMY.

matter. Its fibers originate from the cells of the more
central portion of the gray matter throughout the cord
and terminate in the cerebellum. Its fibers help to
form the inferior peduncle of the cerebellum.

The ant ero -lateral descending cerebellar tract occupies
the superficial area ventrad of the anterior horn of gray
matter. Its fibers originate in the cells of the cerebellum
and extend caudad in the cord.

The antero-lateral ascending cerebellar or Gowers's
tract occupies the superficial area laterad of the anterior
horn. Its fibers probably originate in the cells of central
gray matter throughout the cord, and largely terminate
in the cerebellum. The lateral ground bundle consists
largely of fibers with a short course, many of which are
commissural, connecting the two halves of the spinal cord.

The crossed pyramidal tract contains the longest
fibers of any of the tracts of the central nervous system
and occupies a large area just laterad of the posterior
horn of gray matter. Its fibers originate in the cortical
cells of the brain near the crucial sulcus (Fig. 89), and
descend as part of the internal capsule, through the
corpus striatum and laterad of the optic thalamus to the
base of the brain. Here it is one of the three main tracts
forming the crus or peduncle of the cerebrum, whence
it extends through the pons Varolii, appearing along the
median ventral line of the medulla as the pyramid (Fig.
90). At the caudal end of the medulla it crosses dorsad
to the opposite side of the cord to occupy the area laterad
of the posterior horn of gray matter. Its fibers terminate
largely in arborizations around motor cells of the cranial
nerves in the brain, and the cells in the anterior horn
of gray matter, from which originate the motor fibers
for the muscles of the body. Therefore it is apparent
that this tract controls largely the muscular activities

THE NERVOUS SYSTEM. 213

of the entire body (Figs. 98, 99, and 100). The crossing
of the fibers of this tract in the caudal region of the
medulla is known as the motor decussation or the de-
cussation of the pyramidal tract.

The limits of these various fiber tracts of the central
nervous svstem cannot be determined by dissection.

j */

They have been worked out largely by experimental
physiology and pathology, and by studying their embry-
onic development when the fibers of different tracts
are seen to acquire their sheaths (neurilemmae) at differ-
ent periods. The portion of a nerve fiber separated from
its cell degenerates, so that if the fibers of the crossed
pyramidal tract were injured by accident or disease in
the region of the medulla, all that part of the tract in
the cord would degenerate, in consequence of which the
subject would suffer paralysis.

The larger portions of the tracts thus far described
have been confined to the cord, while the remaining
tracts to be discussed concern chiefly the brain. In
order to understand these it is necessary to remember
that the cortex of the brain is composed of millions of
nerve cells which give origin to nerve fibers extending
to other portions of the cortex, to the basal ganglia, the
cerebellum, medulla, and spinal cord (Fig. 100). Like-
wise some of the fibers originating in the cells of the cord,
medulla, cerebellum, and basal ganglia terminate about
the cells of the cortex. The cord, medulla, and cere-
bellum are connected with the higher brain centers by
the fibers of the cerebral peduncles (Figs. 90 and 100),
which are separated into two parts by an elongated mass
of gray matter, the substantia nigra. The dorsal part
is known as the tegmentum, while the ventral part is the
crusta .

The fibers of the brain are of three kinds — the com-

214

ELEMENTS OF MAMMALIAN ANATOMY.

missural fibers, the projection fibers, and the association
fibers.

The first-named constitute the commissures of the
brain previously described (Figs. 90, 92). In addition
to these commissures, numerous other fibers cross to the
opposite half in that portion of the brain caudad of the
optic thalami. The internal portion of the medulla

FIG. 100.- — DIAGRAM OF CHIEF FIBER TRACTS OF THE MAMMALIAN BRAIN.

LATERAL, ASPECT.

a, 6, c, d, e, Fibers forming internal capsule; ac, anterior corpus quad-
rigeminum; cb, direct cerebellar tract; cr, crossed pyramidal or
chief motor tract; cs, cortico-pontine or secondary motor tract; m,
middle peduncle of cerebellum; ng, nuclei gracilis and cuneatus; n,
decussation of crossed pyramidal tract; o, optic thalamus; oc, optic
chiasm; pc, posterior corpus quadrigeminum ; pons, transverse fibers
of pons Varolii ; py, pyramids formed by pyramidal tract ; pi, posterior
longitudinal bundle; rn, nucleus ruber; s, antero-lateral cerebellar
tract; sn, substantia nigra; sp, superior cerebellar peduncle; st,
corpus striatum ; t, fibers of the fillet or great sensory tract.

oblongata possesses numerous transverse fibers which,
with the longitudinal fibers, form a kind of reticulum
in the midst of the gray matter, known as the formatio
reticularis.

The projection fibers (Fig. 100) are those connecting
the cortex with the lower brain centers and the cord.
The chief motor tract is the crossed pyramidal tract

THE NERVOUS SYSTEM. 215

already described in the cord. It may be traced from
the pyramids to its origin in the cortex in the region of
the crucial sulcus (Fig. 89), by slicing away the ventral
portion of the brain obliquely in a plane joining the
cephalic margin of the pons and the crucial sulcus. Num-
erous fibers are given off by this tract to the motor roots
of the cranial as well as the spinal nerves.

The secondary motor tract, cortico pontine tract, carries
motor impulses from the frontal cortex to the medulla,
whence other fibers convey them to the opposite half of
the cerebellum. The axis-cylinders of the cells here
transmit the impulses through the inferior peduncle to
the cells in the anterior horn of gray matter of the cord.

The great sensory tract of the brain is the fillet. Its
fibers originate largely in the cells of the nuclei gracilis
and cuneatus of the medulla (Figs. 98, 99, 100) and cross
over to the opposite side of the medulla, forming the
sensory or superior pyramidal decussation. This tract
receives also fibers from the spinal cord, the cerebellum,
and the medulla oblongata.

These projection fibers, after leaving the peduncular
region, turn dorsad to pass with others through the
corpus striatum and laterad of the optic thalamus. In
this part of their course they form what is known as the
internal capsule (Fig. 95). The spreading out of the
projection fibers just beneath the cortex of the cerebrum
forms the corona radiata.

The association fibers are those which connect different
portions of the same cerebral hemisphere. Two kinds
are recognized. The short fibers connect adjacent
convolutions, while the long ones place in communication
two remote portions of a hemisphere.

2l6 ELEMENTS OF MAMMALIAN ANATOMY.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Describe the membranes of the cord.

2. What difference in the size of the nerve roots in the various regions
of the cord ?

3. Draw a cross-section of the cord showing all features visible to
the naked eye.

4. How does the arrangement of the gray matter of the cord and
brain differ?

5. Describe the processes of nerve cells.

6. In what portions of the body are nerve cells found ?

7. What is the location of the cells whose protoplasmic processes
largely make up the tracts of Goll and Burdach?

8. WThat part of the cord is occupied by the chief motor tract?

9. What tracts of the cord originate or terminate within the cere-
bellum?

10. Describe the course of the crossed pyramidal tract throughout
the axial nervous system.

1 1 . Describe three bundles of commissural fibers in the brain.

12. Which tract of the projection fibers contains the longest axis-
cylinder processes?

1 3 . Describe the great sensory tract of the brain.

14. What do the association fibers connect?

15. Tell what is known of the functions of various regions of the cortex.

16. Explain why paralysis of the left side of the body would result
from an injury to the right motor region of the cortex.

17. Procure a piece of spinal cord from the butcher-shop. Smear
a bit of the gray matter on a glass slip, dry, then stain in hematoxylin,
wash, and after drying mount in balsam. Draw and describe nerve cells
thus found.

THE PERIPHERAL NERVES.

All portions of the head, trunk, and limbs of the cat
are supplied with nerve fibers which are in communication
with the central nervous system by means of fifty-two
pairs of nerve bundles, forming what are known in the
brain region as the cranial nerves and in the region of
the cord as the spinal nerves.

The Cranial Nerves.- -There are twelve pairs of cranial
nerves, all of which pass through foramina in the base
of the skull, and all except one, the tenth or vagus, are

CRANIAL NERVES.

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217

2l8 ELEMENTS OF MAMMALIAN ANATOMY.

distributed to structures of the head and neck. They
are divided according to function into motor and sensory.
Some of the nerves communicate with the brain by more
than one root, and in such cases the same nerve may have
sensory fibers in one root and motor fibers in another.
For example, the trigeminal nerve transmits a stimulus
causing the muscles of mastication to contract and also
supplies the teeth with sensory fibers (Fig. 90).

The olfactory, optic, auditory and glossopharyngeal
are the only cranial nerves wholly sensory. The oculo-
motor, patheticus or trochlearis, abducens, facial, spinal
accessory, and hypoglossal are wholly motor. The
trigeminal and pneumogastric contain both motor and
sensory fibers.

The dissection of the cranial nerves is very difficult.
A head, containing a brain hardened by a formalin in-
jection, should be placed in 500 c.c. of 5% nitric acid,
which will decalcify the bone in about a week. After
washing out the acid by soaking the specimen in running
water tw^enty-four hours, the dissector may with much
care follow the course of the nerves peripherad from their
origin at the base of the brain. The vagus nerve must
of course be traced in an entire specimen, where it may
be easily followed in the neck region along with the
carotid artery, whence it passes to the lungs and stomach
(Fig. 64).

Some of the sensory nerve roots bear ganglia, the
largest of which is the Gasserian ganglion, more than
a half centimeter in diameter, forming a knot on the
sensory root of the trigeminal, within the cranial cavity
(Fig. 90).

The Spinal Nerves.- -There are forty pairs of nerves
connected with the spinal cord. They issue from the
vertebral canal through the intervertebral foramina.

THE NERVOUS SYSTEM. 2 19

Each nerve is connected to the cord by a ventral and
dorsal root (Figs. 90 and 98). The former is also known
as the motor root, since its fibers are almost entirely
motor, while the latter is the sensory root, as it is com-
posed of fibers transmitting impulses to the central
nervous system. A ganglion about the size of a pin-
head is located on the dorsal root immediately proximad
of its junction with the ventral root, within the inter-
vertebral foramen. This anatomy can be displayed by
cutting away the dorsal muscles on either side of the
column, and then, with the bone-cutters, severing the
laminae of several of the arches of the vertebrae, so that
the roof may be removed from the vertebral canal (Fig.
22).

Immediately beyond the intervertebral foramen each
nerve gives off a dorsal branch to the muscles of the
back, and a small connecting twig to the sympathetic
system. The main nerve is then spoken of as the ventral
branch. These main nerves or ventral branches, in
various regions of the trunk, anastomose with each other,
forming plexuses. In the region of the neck there is
formed the cervical plexus; in the region of the shoulder,
the brachial plexus; in the region of the loins, the lumbar
plexus; and in the region of the sacrum, the sacral plexus
(Figs. 101 and 102).

There are eight cervical nerves, the first of which does
not make its exit through the intervertebral foramen,
as do all the other spinal nerves, but traverses a foramen
in the atlas. The first five cervical nerves, the three
posterior cranial nerves, and branches from the sym-
pathetic trunk, form the cervical plexus. These five
cervical nerves supply mainly the structures of the neck.

There are thirteen pairs of thoracic nerves. The
ventral branches of the sixth, seventh, and eighth cervical

22O

ELEMENTS OF MAMMALIAN ANATOMY.

nerves and the first thoracic nerve form the brachial
plexus. This may be displayed by removing the cephalo-
humeral muscle and cutting through the pectoral muscles

:

FIG. 101. — VENTRAL ASPECT OF THE BRACHIAL PLEXUS AND CHIEF NERVES

OF THE ARM.

6, 7, 8, and 1, Sixth, seventh, and eighth cervical and first dorsal nerves;
at, ath, anterior thoracic nerves ; a and b, to muscles of the forearm ;
c and d, to the joint; ex, circumflex nerve; cu, internal cutaneous;
de, to the deltoid ; g, to the digits ; /, to the digits ; fo, supracondyloid
foramen ; It, long thoracic ; me, musculocutaneous ; me, median nerve ;
pi, posterior interosseous ; pth, posterior thoracic ; sp, musculospiral ;
sp, to suprascapular region ; sb, to subscapular region ; ex, subscapular ;
ra, radial ; un, ulnar nerve.

THE NERVOUS SYSTEM. 221

about two centimeters from their origin (Fig. 47). The
manner in which the nerves anastomose varies some-
what, but the following will be found approximately
correct :

The sixth cervical nerve gives off a small branch to
the rhomboideus and levator anguli muscles of the
shoulder, and then divides into two nearly equal
branches, one of which supplies the muscles on the
lateral aspect of the scapula, and the other joins with
the seventh cervical nerve. Small branches from the
fifth and sixth cervical nerves unite to form the phrenic
nerve supplying the diaphragm.

The seventh cervical nerve gives off three small
branches at about the same point, one of which is the
..posterior thoracic supplying the serratus magnus muscle,
a second helps to form the musculocutaneous, and the
third forms part of the median and anterior thoracic.
The main portion of the seventh cervical unites with the
eighth and first thoracic, to form the musculospiral nerve.
The circumflex and subscapular branches supplying the
deltoid and subscapular muscles are also derived from the
seventh.

The eighth cervical nerve, after giving off a small
branch to the pectoral muscle, a small twig to the median
nerve, and a large branch to the first thoracic nerve,
is continued as the main part of the musculospiral nerve.

The first thoracic nerve gives first a large branch
to the musculospiral nerve, a second small branch to
the anterior thoracic, and a third branch forming the
internal cutaneous nerve supplying the skin of the arm
and forearm on the caudal aspect. The main portion
of the first thoracic nerve then continues as the main part
of the ulnar nerve.

The nerves of the forelimb are five in number (Fig.

222 ELEMENTS OF MAMMALIAN ANATOMY.

101): the external cutaneous, the internal cutaneous,
the musculospiral, the median, and the ulnar. The
external cutaneous arises from the sixth and seventh
cervical nerves and passes distad along the caudal aspect
of the biceps to the cephalic aspect of the forearm, where
it becomes subcutaneous. It supplies the biceps and
coracoid muscles and the skin of the forearm. The
internal cutaneous arises from the first thoracic and
passes along the ventral side of the arm, becoming
subcutaneous just proximad of the elbow, where it is
distributed to the skin of the arm and forearm on the
caudal and ventral aspects.

The musculospiral arises from the seventh and eighth
cervical and first thoracic nerves. It is the largest
component of the brachial plexus. It winds obliquely
around the humerus to the cephalic aspect, where it
divides into two branches, the radial and the posterior
interosseous. The radial nerve is the smaller and be-
comes subcutaneous near the elbow, and passes along
the radial region. The posterior interosseous proceeds
along the dorsal aspect of the forearm to the wrist,
where it divides into branches supplying the digits.

The median nerve arises from the seventh and eighth
cervical and first thoracic. It follows the course of
the brachial artery, passing through the supracondylar
foramen to the elbow, where it passes beneath the pro-
nator teres to the carpal region, and supplies the first,
second, and third digits. It also supplies the pronator
teres and flexor muscles of the forearm.

The ulnar nerve (Fig. 101) is derived from the eighth
cervical and first thoracic. It courses with the brachial
artery to the middle of the humerus, where it turns
caudad to pass between the olecranon process and
internal condyle of the humerus. It is here sub-

THE NERVOUS SYSTEM. 223

cutaneous and furnishes the sensation experienced when
one strikes what is popularly called his 'funny bone,"
but what is really the ulnar nerve. It then passes
down the ulnar side of the forearm, supplying some
of the flexor muscles, and finally divides to supply
the fourth and fifth digits. The ventral branches
of the remaining thoracic nerves encircle the body,
supplying the muscles and skin of those regions.

The lumbar plexus (Fig. 102) is composed of the
anastomosing of the ventral branches of the seven
lumbar nerves. As in the cervical and thoracic nerves,
the lumbar nerves divide into dorsal and ventral branches
immediately without the intervertebral foramen. The
former supply the muscles and skin of the back. The
first five ventral branches are joined to each other by
a delicate nerve-cord. In order to display this plexus,
the entire ventral and lateral abdominal wall should
be cut away and the specimen securely nailed to the
tray on its back. The adipose tissue and muscles lying
on either side of the bodies of the lumbar vertebrae
must be carefully picked away until the roots of the
nerves are apparent. They may then be easily followed
distad.

The iliohypogastric nerve is the ventral branch of
the first lumbar nerve. It supplies the muscles of
the abdomen. This nerve and the two next described
are scarcely as large in diameter as an ordinary pin.
The ilio-inguinal nerve is the ventral branch of the
second lumbar nerve. Within two centimeters of its
origin it divides into two branches, the cephalic of
which supplies the rectus and transverse muscles and
the caudal supplies structures in the inguinal region.
The lumbo -inguinal nerve is the ventral branch of the
third lumbar nerve. Its cephalic branch supplies the

224 ELEMENTS OF MAMMALIAN ANATOMY.

lumbar region and its caudal branch is distributed
to the superficial structures of the inguinal region. The
fourth lumbar nerve divides into two parts, one of which
is the external cutaneous nerve, supplying the skin and
other structures of the hip region, and the other is the
external spermatic, supplying the external genital organs.

The anterior crural nerve is composed mainly of branches
of the fifth and sixth lumbar. It receives a small branch
from the fourth. It supplies the psoas muscles, which
it pierces, and then divides into several branches, one
of which is the saphenous, passing subcutaneously along
the mesal aspect of the leg. The other nerves supply
the muscles of the thigh on the cephalic and mesal
aspect. The obturator nerve is composed of branches
from the sixth and seventh lumbar. It is smaller than
the preceding, and passes through the obturator foramen
to supply the obturator and adductor muscles.

The great sciatic nerve is composed mainly of the
ventral branches of the seventh lumbar and first sacral
nerves. It usually receives accessions from the other
sacral nerves and the sixth lumbar. The great sciatic
is the largest peripheral nerve in the body. It passes
caudad from its origin around the greater sciatic notch
and thence along the caudal aspect of the thigh to the
popliteal space, where it divides into the internal and
external popliteal nerves. The former continues down
the caudal side of the tibia as the posterior tibial nerve
to the internal malleolus, where it divides into internal
and external plantar nerves, which supply the digits.
The external popliteal or peroneal nerve extends to
the outer cephalic aspect of the leg, where it divides
into the musculocutaneous and anterior tibial nerves. The
former extends between the extensor longus digitorum
and peronei muscles to its ramification on the dorsum

THE NERVOUS SYSTEM.

225

FIG. 102 — VENTRAL ASPECT OF THE NERVES OF HIND-LIMB.
4, 5, 6, 7, 1, 2, and 3, Fourth, fifth, sixth, and seventh lumbar, and first,
second, and third sacral nerves ; a, branch from the fourth to the fifth ;
ac, anterior crural; cu, saphenous; d, anterior tibial; e, peroneal or
musculocutaneous ; ex, external popliteal or peroneal; ef, external
plantar; fo, obturator foramen; gs, greater sciatic; g, external sper-
matic ; it, internal popliteal ; ip, internal plantar ; kn, knee ; /, external
cutaneous; Is, lumbosacral cord; t, posterior tibial; s, small sciatic.

19

226 ELEMENTS OF MAMMALIAN ANATOMY.

of the foot. It supplies the skin along its course and
the peronei muscles. The anterior tibial nerve passes
down on the cephalic aspect of the tibia beneath the
extensor longus digitorum muscle to the tarsal region,
where it anastomoses with a branch of the external
cutaneous, and supplies the skin, tibialis anticus, and
the extensor muscles.

The lesser sciatic nerve is a branch of the greater
sciatic in the buttock region. The pyriformis, obturator,
gemelli, quadratus femoris, semitendinosus, and semi-
membranosus muscles are innervated by the greater
sciatic nerve (Figs. 48 and 102).

The sacral plexus is an irregular network composed
of the ventral branches of the three sacral nerves and
two or more small twigs from the seventh lumbar (Fig.
102). This plexus is seldom the same in any two cats.
From it are given off the internal pudic and glutei nerves.
The former supplies the prostate and anal glands, the
sphincter muscle, and the penis. The latter supplies
the glutei and pyriformis muscle.

THE SYMPATHETIC NERVOUS SYSTEM.

The sympathetic nervous system is composed chiefly
of a pair of nerve-cords extending from the base of the
skull to the root of the tail, a number of ganglia and
branches supplying the thoracic and abdominal viscera,
and numerous minute fibers supplying the muscular
walls of the blood-vessels in all parts of the body. The
sympathetic system supplies all non-striped or involun-
tary muscles in any part of the body.

In order to demonstrate this system successfully, one
should use a lean injected specimen. After the cat has
been securely nailed on its back to the tray, the entire

THE NERVOUS SYSTEM. 227

ventral half of the thoracic and abdominal walls should
be removed. By pushing the heart and lungs to the
left side a white cord about one millimeter in diameter
may be seen lying near the median dorsal line (Fig. 103).
The left cord may be found in a similar manner and
both followed cephalad and caudad, noting their numer-
ous branches in accordance with the following descrip-
tion.

The sympathetic nerve=cord begins in the superior cervi-
cal ganglion lying near the angle of the mandible, beneath
the submaxillary and lymphatic glands. This ganglion
is about the shape of a grain of wheat, but not more
than half so large, and is adjacent to the small vagus
ganglion on the dorsal side of the carotid artery. The
ganglia are masses of large nerve cells and occur at regular
intervals on the sympathetic cords in the body cavity,
and are present also on some of the branches of the
cords (Fig. 104). On the cords there are three pairs
of cervical ganglia, thirteen pairs of thoracic ganglia,
seven pairs of lumbar ganglia, and one or two pairs of
sacral ganglia, in addition to two median unpaired
sacral ganglia.

In the cervical region the sympathetic and pneumo-
gastric, or tenth cranial nerve, are bound in a common
sheath lying along the lateral aspect of the carotid
artery. One or two centimeters cephalad of the first
rib is the thyroid or middle cervical ganglion, whence the
nerve proceeds in two cords, enclosing the subclavian
artery, to the large inferior cervical ganglion just caudad
of the first rib. From the cervical portions of the sym-
pathetic cord are given off numerous delicate branches,
forming the carotid plexus on the carotid artery, and
uniting with the eight posterior cranial nerves and the
first spinal nerve. From the inferior cervical ganglion

228

ELEMENTS OF MAMMALIAN ANATOMY.

a branch goes to the vagus nerve, several branches

to the brachial plexus, and
a branch to the heart, form-
ing the cardiac plexus, while
the main sympathetic cord
continues along the dorsal
thoracic wall. A ganglion
occurs opposite each verte-
bral body, from which it
gives off a branch to the
corresponding spinal nerve.
The great splanchnic arises
from the main cord just
cephalad of the diaphragm
and extends to a group of
ganglia in the region of the
trunk of the coeliac axis

FIG. 103.— CHIEF PART OP LEFT
HALF OF SYMPATHETIC SYSTEM
CEPHALAD OF THE DIAPHRAGM.
Semidiagrammatic.

5, 6, 7, 8, 9, and 10, Fifth, sixth,
seventh, and eighth cervical
nerves, and first and second
thoracic spinal nerves; a, the
dorsal branch of the left vagus
In; an, dorsal branch of the right
vagus ; ax, common dorsal vagus
formed by a and an; avb, ventral
vagus ; be, cardiac branch of sg, cr,
carotid plexus; car, carotid ar-
tery ; cm, rami communicantes ; cp,
cardiac plexus; dia, diaphragm;
g, ganglia in the thoracic cavity ;
ig, middle cervical ganglion; Ig,
portion of left lung ; In, left vagus
nerve; nv, cranial nerve; pn,
phrenic nerve; pp, pulmonary

I plexus ; sn, sympathetic cord ; sm,

superior cervical ganglion ; sb, left
subclavian artery; sg, stellate ganglion or inferior cervical; spm, splanch-
nic major nerve ; vg, vagus ganglion ; v, vagus nerve.

THE NERVOUS SYSTEM.

229

(Figs. 103 and 104). These ganglia and anastomosing
branches constitute the solar or epigastric plexus, lying

FIG. 104. — CHIEF PART OF LEFT HALF OF SYMPATHETIC SYSTEM CAUDAD
OF THE DIAPHRAGM. Semidiagrammatic.

bl, Bladder; ce, cceliac axis; du, duodenum cut off; dia, diaphragm; gr,
anterior gastric plexus; g, ganglion; im, inferior mesenteric artery;
il, external iliac artery; ng, dorsal branch of vagus (Fig. 103, ax);
nl, ventral branch of vagus ; oe, esophagus cut off ; p, superior mesen-
teric plexus; plx, inferior mesenteric plexus; px, branches to dorsal
gastric plexus ; rn, renal plexus ; sm, superior mesenteric artery ; spn,
splanchnic major or greater splanchnic nerve from the sympathetic
cord ; sg, semilunar ganglion ; spc, sympathetic cord of left side.

dorsad of the stomach, to which it sends numerous
branches. This plexus also receives the lesser splanchnic
nerve coming from the sympathetic cord just cephalad

230 ELEMENTS OF MAMMALIAN ANATOMY.

of the diaphragm, and branches from the tenth cranial
nerve.

The largest ganglion of the solar plexus is the semi-
lunar. The solar and its allied plexuses send nerves
to the diaphragm, suprarenal bodies, many of the blood-
vessels of the abdominal cavity, stomach, kidneys,
ureters, testes or ovaries, uterus, liver, gall-bladder,
spleen, pancreas, and intestines.

The hypogastric plexus is the third great sympathetic
plexus. It lies on the ventral aspect of the two caudal
lumbar vertebrae and is formed by branches from the
solar plexus and a few twigs from the sympathetic
cords. It supplies the blood-vessels of the pelvic region
and all the organs of the pelvis. The sympathetic cords
in the lumbar region lie near together and the com-
municating branches between them and the spinal
nerves are longer than in the thoracic region. In the
sacral region there are no rami communicantes, and the
ganglia are irregularly arranged. A median ganglion
in the sacral region is known as the ganglion impar.
There may be two median ganglia. The sympathetic
cords terminate in the tail.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. Name the foramina of the skull giving passage to one or more
cranial nerves.

2. From a study of one or more specimens and the description in the
book make a diagrammatic drawing of each cranial nerve.

3. Which cranial nerves have their roots in the medulla?

4. Name the cranial nerves which are wholly motor.

5. Which of the cranial nerves do not supply structures of the head?

6. Of what are ganglia composed ?

7. Make a drawing of your dissection showing the connection between
the spinal and sympathetic nerves.

8. Which spinal nerves form the several plexuses?

9. Make a drawing showing wherein the brachial plexus in your
specimen differs from that described in the text.

THE NERVOUS SYSTEM. 231

10. Write a description of your dissection of the nerves of the thoracic
limb.

11. Mention in what way the lumbar plexus differs from the descrip-
tion in the book.

12. Draw the great sciatic nerve and its branches as seen from the
caudal aspect.

13. What nerves supply the digits?

14. Describe the chief plexuses of the sympathetic system.

15. How do stimuli from the viscera reach the brain?

16. What portion of the body is not supplied with nerves from the
sympathetic system?

THE ORGANS OF SENSE.

The organs of sense are the specialized peripheral
terminations of the sensory nerves, and are so constructed
as to be capable of receiving only a certain kind of
stimulus. The stimuli for the eye are ether vibrations;
those for the ear are vibrations of the air. The stimu-
lation of the sensory nerves produces sensations in the
cells of the cerebral cortex to which they lead.

The external stimuli giving rise to the internal sen-
sations of seeing, hearing, smelling, and tasting are
transmitted by only four pairs of cranial nerves, while
the stimuli of cutaneous sensations are transmitted
by three pairs of cranial nerves and all the spinal nerves.

Cutaneous Sense Organs.- -The cutaneous sense organs
are composed of the endings of the sensory nerves in
all parts of the skin and the mucous membrane of the
mouth, nose, arms, vagina, and urethra. One kind of
sense organs, those of pain, are present in every organ of
the body. The sense organ of pain is probably an
unmodified free nerve-ending.

While all portions of the skin and perhaps other
parts of the body are supplied with organs capable of
receiving stimuli giving rise to tactile sensation, the
soles of the feet and the skin at the base of the vibrissae

232

ELEMENTS OF MAMMALIAN ANATOMY.

are specially sensitive regions. The nerves terminate
in a kind of wreath formation about the base of the
vibrissae.

All of these sense organs are invisible to the naked
eye except the Pacinian corpuscles, whose function is
unknown. If the mesentery is held up and looked
through toward the light, the Pacinian corpuscles or
sensory nerve terminations appear as translucent oval
bulbs about two millimeters long. If a piece of the

mesentery containing a corpuscle is
pinned tense on a piece of cork and
then cut out and placed ten minutes
in 3% acetic acid, the termination of
the nerve within the corpuscle may
be seen with a microscope magnifying
thirty diameters. All the spinal sen-
sory nerve fibers enter the cord by the
posterior root (Figs. 90 and 96).

The Olfactory Organ.- -The organ of
smell lies in that part of the mucous
membrane lining the caudal part of
the nasal cavity and the basal third of
the ethmoturbinal bones (Fig. 18).
That part of the mucous membrane
containing the olfactory cells is known
as the Schneiderian membrane. In a fresh specimen it is
of a grayish color while the other mucous membrane is
red. The first pair of cranial nerves convey the olfactory
impulse to the brain. They pass through the foramina in
the cribriform plate of the ethmoid bone, to the olfactory
bulbs, from each of which two roots extend to the base
of the cerebrum (Fig. 90).

The Gustatory Organ.- -The organ of taste is located
chiefly in the mucous membrane on the dorsum of the

FIG. 105.-- PACINIAN
CORPUSCLE FROM
THE MESENTERY. X
20.

ax, Axis-cylinder ; n,
neurilemma ; m, the
white substance of
Schwann; e, epithe-
lial cell.

THE NERVOUS SYSTEM. 233

tongue, the soft palate, the pillars of the fauces, epi-
glottis, and part of the cheek. On the dorsum of the
tongue are seen four kinds of papillae — the circumvallate,
the fungiform, the filiform, and flat. The circumvallate
papillae are from eight to twelve in number, forming two
sides of a triangle on the caudal portion of the dorsum
of the tongue. The fungiform are blunt papillae scattered
sparsely in the midst of the numerous filiform or pointed
papillae (Fig. 55). The special organs of taste, known
as taste-buds, are very numerous in the fungiform and
circumvallate papillae of most mammals, but in the cat
they are few and not well differentiated. These taste-
buds occur in many parts of the mucous membrane of
the mouth cavity, each being supplied with a branch
of the glossopharyngeal nerve.

The Visual Organ.- -The special organ of sight is
the eye, which occupies the orbital cavity of the skull.
The ball of the eye is protected above and below by
extensions of skin called the eyelids or palpebrae, which
are lined with mucous membrane, a transparent layer
of which, known as the conjunctiva, extends over the
front of the eyeball between the two lids. The dorsal
lid is raised by the levator palpebrae muscle, which
has its origin in the occipitofrontalis muscle. A sphincter
muscle, the orbicularis palpebrarum, lies on the margin
of the lids, and by its contraction closes the eye.

The point on either side where the two eyelids meet
is termed the canthus or angle. At the mesal or inner
canthus are two minute apertures, the puncta lachry-
malia, leading into two short canals which unite to
form the nasal duct. The lachrymal canal, wrhich forms
the channel for this duct, is clearly visible in the lach-
rymal bone of the dried skull. At the mesal canthus
there is a prominent fold of mucous membrane, the

20

234 ELEMENTS OF MAMMALIAN ANATOMY.

membrana nictitans, or plica semilunaris, which is a
rudimentary structure in the cat, but is found well
developed in birds, which have the power of sweeping
it rapidly across the eyeball, thereby removing dust.

On the inner surface of each lid are the Meibomian
glands. The lachrymal gland lies in the dorso-lateral
region of the orbit, and its ducts open on the ventral
surface of the upper lid, whence the tears flow over
the conjunctiva ventrad to the puncta lachrymalia.
The Harderian gland is the very small gland at the mesal
canthus.

The muscles controlling the movements of the eye-
ball are seven in number: four are recti muscles, two
are oblique, and one is a retractor. The recti muscles
(Fig. 90) originate on the bone around the optic for-
amen, and are inserted on the sclerotic coat, caudad
of the equatorial ring. The external rectus is inserted
on the lateral aspect; the internal rectus, on the mesal
aspect; the superior rectus, on the dorsal aspect; and
the inferior rectus on the ventral aspect. The superior
oblique muscle arises from the sphenoid bone mesad
of the optic foramen, extends along the mesal wall of
the orbital cavity to its dorso-mesal margin, where
it passes through a tendinous loop fastened to the frontal
bone and then turns laterad to its insertion in the sclerotic
beneath the superior rectus. The inferior oblique arises
from the lachrymal bone and is inserted on the sclerotic
between the external and inferior recti muscles. The
above muscles may be demonstrated by cutting away
the lateral and dorsal walls of the orbital cavity. The
retractor oculi originates on the boundary of the optic
foramen and is inserted into the sclerotic around the
entrance of the optic nerve. This muscle is completely
hidden by the recti muscles.

THE NERVOUS SYSTEM.

235

The eyeball is composed of three membranes and
three humors. The outer coat, the sclerotic, consists
of the opaque portion forming the caudal two-thirds,
and the transparent portion, or cornea, forming the
remainder (Fig. 106). The optic nerve pierces the
sclerotic a little mesad of the longitudinal axis of the
eye. The surface of the cornea is more strongly curved
than that of the opaque portion of the sclerotic, and

a

FIG. 106. — LONGITUDINAL SECTION OF THE EYE.

aq, Aqueous humor; c, cornea; cp, capsule of the lens; ch, choroid; ci,
ciliary process; i, iris; Ig, ligament of lens; m, ciliary muscle; opn,
optic nerve ; rt, retina ; sc, sclerotic coat ; os, ora serrata.

contains no blood-vessels. The second or middle coat
of the eye is formed by the choroid membrane and its
extension, the iris. This coat is incomplete, as there
is an aperture, the pupil, through the iris for the ad-
mission of light. The choroid appears as a jet-black
membrane, less than half as thick as the sclerotic, lying
closely appressed to the latter. The choroid is lined
internally by dark pigment cells, except in the caudal
area around the optic nerve, which has a metallic luster.

236 ELEMENTS OF MAMMALIAN ANATOMY.

This portion is called the tapetum. It causes the shining
appearance of the cat's eyes in the dark. The choroid
is a vascular membrane, being supplied by the ophthalmic
artery, a branch of the internal carotid.

The iris is attached by its peripheral margin to the
sclerotic and choroid coats, and hangs free in the aqueous
humor. It gives color to the eye. In the cat it is
yellowish, while in man it is frequently blue or black.
The iris is merely a curtain to regulate the amount of
light admitted to the retina. There is a sphincter
muscle lying in it, which by contraction renders the
pupil very small. There is probably no dilating muscle
of the iris present in the cat. The short, thickened,
radial projecting folds of the choroid are the ciliary
processes, which contain numerous blood-vessels, and
in some mammals a gland. The ciliary muscle arises
from the sclerotic coat near its junction with the cornea,
and is inserted into the cephalic part of the choroid coat.

The inner membrane of the eye is the retina, which is
of a light gray color in a fresh specimen and seems quite
free from the choroid. It is thickest in the caudal
two-thirds of the cavity of the eyeball (Fig. 106). At
the base of the ciliary bodies it seems to end with a
free margin, called the ora serrata. In reality it becomes
very thin here and is prolonged over the ciliary bodies
and covers the caudal aspect of the iris. The blind
spot is the point of entrance of the optic nerve, laterad
of which is the yellow spot, or macula lutea, containing
the fovea centralis, or acute point of vision. This is
the point on which the rays of light are focused when
the cat sees distinctly.

The three humors of the eye are the aqueous, the
crystalline lens, and the vitreous humor. The aqueous
humor is a watery fluid occupying the anterior chamber

THE NERVOUS SYSTEM. 237

between the cornea and crystalline lens. It always
escapes as soon as the cornea is punctured. The vitreous
humor is of a jelly-like consistency, filling the large pos-
terior chamber caudad of the lens. It is perfectly trans-
parent and is surrounded by a delicate capsule, the
hyaline membrane.

The crystalline lens is a transparent biconvex tissue
having a vertical diameter of about one centimeter
and a shorter diameter through its optical axis. It
is enclosed in a transparent elastic capsule, some of
whose fibers are continued peripherad as the suspensory
ligament which is inserted in the choroid coat (Fig. 106).

The Auditory Organ.- -The organ of hearing is com-
posed of three parts — the external ear, middle ear, and
internal ear. The first consists of the pinna and the
auditorius meatus externus. The pinna is the pro-
jecting portion of the ear capable of being moved by
muscles, and is composed of integument strengthened
by fibrocartilage. The auditorius meatus externus ex-
tends from the base of the pinna to the tympanic mem-
brane (Fig. 107). Its outer or lateral third is formed
by cartilage, and the remainder by the tympanic por-
tion of the temporal bone (Fig. 17). The meatus is
lined with mucous membrane in which are numerous
sebaceous and oleaginous glands. The latter secrete
the wax of the ear.

The middle ear, or tympanum, is an irregular cavity
about one centimeter in diameter contained in the
lateral chamber of the bulla (Fig. 107). It is separated
from the external auditory meatus by the delicate
translucent membrane, the membrana tympani. The
petrous bone containing the internal ear forms part of
the inner or nasal wall. In the petrous bone are two
foramina which may be seen in a dry skull by looking

238

ELEMENTS OF MAMMALIAN ANATOMY.

through the external auditory meatus. The more dor-
sal foramen is the fenestra ova Us, which in the recent
state is closed by a membrane to which the foot of the
stapes is attached. The ventral one is the fenestra
rotundum, also closed by a membrane in the recent
state. In the dry skull the fenestra ovalis opens into
the first or basal whorl of the cochlea, and the fenestra

rotundum opens into the vesti-
bule of the internal ear. The
Eustachian tube (Fig. 18), whose
opening may be seen cephalad of
the auditory bulla, connects the
middle ear with the posterior
nares and thus admits air to the
tympanic cavity.

To demonstrate further the
anatomy of the middle ear, one
should clean the flesh from a
fresh or preserved head and care-
fully cut away the ventral walls
of both chambers of the auditory
bulla (Fig. 17).

In the middle ear are three
bones, the malleus, incus, and
stapes, commonly called ham-
mer, anvil, and stirrup. They

form a crooked chain across the cavity. The long process
of the malleus is fastened throughout nearly its whole
length to the inner or mesal surface of the membrana
tympani, and its enlarged extremity articulates with the
body of the incus. The latter has two legs, to one of
which the stapes is attached. The base of the stapes is
inserted in the membrane closing the fenestra ovalis (Figs.
17 and 107).

FIG. 107. — DIAGRAM OF THE
MAMMALIAN EAR.

The internal ear is repre-
sented removed about a
centimeter from the mid-
dle ear and slightly rotated
to the left. The base of the
stapes, s, in nature, covers
the fenestra ovalis, o-v; c,
basal whorl of the cochlea ;
ea, external auditory meat-
us ; e u, opening of the Eu-
stachian tube ; i, incus ; in ,
malleus ; sc, semicircular
canals ; ve, vestibule ; /,
tympanum.

THE NERVOUS SYSTEM.

239

The internal ear, or labyrinth, consists of three parts-
the vestibule, cochlea, and semicircular canals (Figs.
1 8 and 107). All of these parts are of membrane and
lie in cavities of corresponding shape within the petrous
bone. A lymphoid fluid, the perilymph, floats the deli-
cate membranous internal ear within its bony cavity,
while within the membrane is a similar fluid, the endo-
lymph. The 'vestibule is a small sac adjacent to the
tympanum, and may be seen by looking through the

FIG. 108. — SECTION OF THE COCHLEA OF THE CALF. 10. — (From

Ellenberger, after Kolliker.}

a, Modiolus; c, scala tympani; v, scala vestibuli; Im, lamina spiralis; pt,
portion of the petrous bone; r, scala media, or ductus cochlearis.

fenestra ovalis. From the dorso-caudal aspect of the
vestibule, arch three semicircular canals at nearly right
angles to one another. The external semicircular canal
is in a horizontal plane and surrounds a small fossa
almost caudad of the fenestra ovalis. The superior
semicircular canal lies in a transverse plane caudad
to the preceding. The posterior semicircular canal
lies in a vertical longitudinal plane, immediately laterad
from the jugular foramen.

The cochlea is a coiled canal lying within the coiled

240 ELEMENTS OF MAMMALIAN ANATOMY.

cavity, the bony cochlea, extending cephalad from the
vestibule. If both chambers of the auditory bulla are
removed and a bristle thrust into the fenestra rotundum
(Fig. 17), it will enter the basal whorl of the bony cochlea.
A line drawn from the lateral margin of the foramen
ovale to the mesal margin of the fenestra rotundum
passes through the apex and middle of the base of the
cochlea, which may be rendered visible by carefully
clipping off with the bone-forceps the ventral portion
of the petrous bone along the line indicated. This
coiled canal, the cochlea, is divided into two channels
by a shelf of bone, the lamina spiralis, projecting from
the central axis or modiolus of the coil (Fig. 109). The
bony lamina extends but partly across the canal, the
remaining distance being bridged by membrane. The
cephalic channel, or the one nearer the apex of the
cochlea, is called the scala vestibuli. The other is
the scala tympani.

The semicircular canals probably have nothing to do
with hearing, as they are well developed in fishes, wThich
do not hear at all. They may aid in helping the cat to
maintain its equilibrium. The auditory nerve, how-
ever, is distributed to the vestibule and semicircular
canals as well as to the cochlea upon the lamina spiralis,
where the organ of Corti, the essential organ of hearing,
is located.

REMARKS ON THE MAMMALIAN NERVOUS SYSTEM.
So far as known, the relation of the sympathetic to the
peripheral and central nervous systems is the same in
all mammals. The number of spinal nerves varies with
the number of vertebrae. The distribution of these
nerves, however, is approximately the same in all forms

THE NERVOUS SYSTEM. 241

«

with five digits. In those having a less number of digits
the nerve branch corresponding to the lacking digit
or digits is wanting. The arrangement of the columns
or tracts of fibers in the spinal cord is very similar in
all the orders. The anterior or direct pyramidal tract,
however, is absent in most orders below the Primates.
It is best developed in man, although in a number of
cases it has been found entirely wanting in the human.
The number of the cranial nerves is always twelve and
their distribution is the same in all forms investigated.

The structure of the brain in the Ornithodelphia and
Didelphia differs considerably from that of the Mono-
delphia. In the two former subclasses the corpus
callosum and fornix are very rudimentary, but the
anterior commissure piercing the corpora striata is un-
usually large. The fibers, which in the Monodelphia
arise from the cells of the hippocampus, and extend
cephalad to form the fornix, cross transversely to the
opposite hippocampus in the two lower subclasses.

In all higher mammals the cerebrum is greatly con-
voluted, but in the lower ones the convolutions are
few or almost absent, as in Ornithorhynchus. The
above-mentioned features show that the ornithodelphian
brain presents a striking similarity to the brains of
reptiles and birds. The brains of Rodentia possess but
few convolutions, while the brain of man is the most
highly convoluted.

The size of the brain varies widely. As a rule, the
larger the brain in proportion to the size of the animal,
the greater is its intelligence. However, in man this
statement does not hold true, as an individual with a
small brain may be much more capable mentally than
one with a large brain. Mental power in man seems
to depend upon the development of the cells and fibers
of the brain.

242 ELEMENTS OF MAMMALIAN ANATOMY.

The average weight of a male human brain is about
three pounds; of a female, about two and two-thirds
pounds. The human brain is -£% the weight of the body;
the ape's, ^V; the rat's, -^ ; the sheep's, o4-T; and the ele-
phant's, 5-^0 . The brain of man is larger than that of
any other mammal except the whale and elephant. The
brain of a large whale weighs over four pounds, while
that of a large elephant will weigh about ten pounds.

PRACTICAL QUESTIONS AND SUGGESTIONS.

1. How many nerves transmit the stimuli received by the organs of
special sense?

2. Where are the sense organs of pain located ?

3. How many sense organs are visible in the mesentery of your
specimen?

4. Describe the path of a stimulus from the index finger to the brain.

5. Through which nerve roots would the stimuli received by the
cutaneous sense organs pass into the cord?

6. Describe the nerves transmitting the stimuli from the olfactory
organ.

7. Describe the gland secreting the tears and how they reach the
nasal cavity.

8. By cutting away the lateral and dorsal walls of the orbit dissect
the muscles of the eyeball and make a drawing of them, labeling all parts.

9. What nerves control the movements of the eyeball?

10. Procure the eyes of any mammal from the butcher-shop or slaughter-
house; bisect one in the meridional and the other in the equatorial direc-
tion. Make a drawing of the features seen and label.

11. Remove the crystalline lens from a fresh eye, describe its size,
shape, structure, length of focus, and power of magnification.

12. Describe the path of a stimulus from the retina to the area of
sight in the brain.

13. Name every feature visible in the eyes you have dissected.

14. What nerve supplies the auditory organ?

15. Describe the middle ear.

16. In what part of the temporal bone is the internal ear located?

17. By looking into the auditorius meatus of the dried skull two open-
ings are seen. Into which portions of the internal ear do these lead?

18. Write a description of the internal ear.

19. Mention some important points of difference in the nervous system
of various mammals.

20. What relation, if any, between intellectual ability and brain devel-
opment?

INDEX

A.

Abdominal aorta, 144

arteries, 145

cavity, 125

muscles, 104, 106

veins, 154

Accessory glands, 131
Acetabulum, 79, 81
Adipose tissue, 33
Air sacs, 172

Alcohol as a preservative, 27
Alimentary canal, 124

length of, in mammals, 137
Alveoli, 172
Amphiarthroses, 89
Amphibia, 19
Anesthetization, 21, 22
Anatomy, 17

Anterior perforated space, 191
Aorta, 143
Aponeuroses, 95
Aqueduct of Sylvius, 193
Arachnoid, 186, 205
Arbor vita?, 203
Arm, arteries of, 148

bones of, 67

muscles of, 100

nerves of, 222
Arteries, 143

abdomen, 144

arm, 148

brain, 146

injection of, 20

leg, 151

neck, 145

thorax, 143

valves of, 154
Artery, adrenolumbalis, 145

anastomotica magna, 150

axillary, 148

basilar, 146

brachial, 148, 150

Artery, bronchial, 144
carotid, 143, 146
cerebellar, 146
cerebral, 146
circumflex anterior, 150
coeliac, 144
coronary, 143, 145
epigastric, 151
femoral, 151

anterior, 151

posterior inferior, 152

superior posterior, 151
hepatic, 144
iliac, 145
iliolumbar, 145
inferior alveolar, 147
infraorbital, 147
intercostal, 148
interosseous, 150
lingual, 147
lumbar, 144
malleolar, 153
mammary, 148
maxillary, 147
meningeal, 147
mesenteric, 145
ophthalmic, 147
phrenic, 145
popliteal, 152
profunda, 151

superior, 150
pulmonary, 142
radial, 148, 150
renal, 145
saphenous, 152
spermatic, 144
subclavian, 143, 148
subscapular, 149
temporal, 147
thoracic, 149
thyroid, 147

axis, 149
tibial, 152

243

244

INDEX.

Artery, ulnar, 150

vertebral, 147

volar, 150
Articulation, 40
Arytenoid cartilage, 169
Association fibers, 215
Astragalus. 85, 86
Atlas^S?
Auditory bulla, 45

nerve, 240

organ, 237
Aves, 19
Axis, 59
Axis-cylinder process, 208

B.

Basal ganglia, 198
Bicuspid valve, 141
Bile, 134

Binomial nomenclature, 20
Bladder, 176
Blood-vessels, 143

injection of, 21
Body of vertebra, 59
Bone structure, 39
Bones, 41

ear, 238

head, 41

kinds of, 36, 38

pelvic limb, 79

preparation of, 27

sesamoid, 36

table of, 37

terms used in describing, 36, 38

thoracic limb, 67
Brachia, 199
Brachial plexus, 220
Brachio-cephalic artery, 143
Brachium conjunctivum, 201
Brain, 186

arteries of, 146

external features, 187

fiber-tracts of, 213

fissures, 188

internal structure, 192

ventricles of, 197
Broad ligament, 13'i
Bronchus, 170
Buccal cavity, 1 1 7

C.

Calcaneum, 85
Canalis centralis, 206

Canidse, 19
Cannon bone, 76
Cannula, 21
Capillaries, 30, 159
Capsular ligament, 90
Cardiac plexus, 128
Carnivora, 19
Carotid artery, 143
Carpalia, 74
Carpus, 72, 75
Cartilage, 29

semilunar, 91
Caudad, 38
Caudal, 38
Cells, 28, 29

gastric glands, 129

nerve, 208
Central nervous system, 186

preparation for dissection, 26
Cephalad, 38
Cephalic, 38
Cerebellum, 203
Cerebrum, 188
Chevron bones, 62
Chief motor tract, 214
Choroid membrane, 235

plexus, 193
Cilia, 170

Circle of Willis, 147
Circulatory system, 140
Classes of vertebrates, 19
Classification of animals, 18
Clavae, 202
Clavicle, 68
Claws, 34
Clinoid plate, 49

processes, 49
Clitoris, 178
Cloaca, 184
Coccyx, 63
Cochlea, 40, 239
Cceliac axis, 144
Colon, 128

Columns of spinal cord, 206
Commissures of brain, 194
Condyle, 39
Conjunctiva, 233
Connective tissue, 29
Convolutions of brain, 188
Coracoid process, 68, 69
Cornu Ammonis, 196
Corona radiata, 215
Corpora albicantia, 191

quadrigemina, 198

striata, 200

INDEX.

245

Corpus callosum, 196

dentatum, 203

geniculatum, 199
Cotyloid bone, 79
Cranial nerves, 215
Cranium, 41
Cribriform plate, 43, 44
Cricoid cartilage, 169
Crossed pyramidal tract, 212
Crucial ligaments, 91
Crura cerebelli, 203

cerebri, 191
Crus, 83, 84

ad pontem, 203
Crystalline lens, 236
Cuboid, 86
Cuneiform, 74

Cutaneous sense organs, 231
Cystic duct, 134

D.

Deciduous teeth, 122
Decussation of pyramidal tract, 212
Dendrites, 208
Dentition, deciduous, 122

mammalian, 123

of cat, 120
Dermis, 33
Diarthroses, 89
Diastema, 55
Diencephalon, 187
Digestion, organs of, 117
Digestive system of mammals, 137
Digitigrade, 78
Digits, 76, 81, 86
Dissection, directions for, 95
Distad, 38
Distal, 38
Distribution, 18
Ductless glands, 165
Ductus communis choledochus, 128,

134

Duodenum, 126
Dura mater, 186, 205

E.

Ear, 237

Ectocuneiform, 86
Embryology, 17
Endomysium, 93
Endoskeleton, 32
Entocuneiform, 86
Epidermis. 33

Epididymis, 182
Epiglottis, 169
Epimysium, 93
Epiphysis, 39
Epithelium, 28, 29
Esophagus, 126
Ethmoid bone, 42
Ethmoturbinal, 42, 44
Eustachian tube, 45, 124
Excretion, 30
Excretory system, 174
Exoskeleton, 32
External capsule, 201
Eye, 233

F.

Face, 41

Falciform ligament, 133

Fallopian tubes, 177

Falx cerebri, 186

Families, 19

Fascia, 94

Fasciculus of Burdach, 211

of Goll, 211

of muscle, 94
Fauces, 117
Female organs, 177
Femur, 81
Fenestra ovalis, 45

rotundum, 45

Fiber tracts of nervous system, 210
Fibers, 29, 30

of brain, 213
Fibula, 84
Fillet, 215

Fissures of brain, 188
Foot, arteries of, 153

bones of, 85

muscles of, 109, 111

nerves of, 224
Foramen, 39

anterior palatine, 51

infraorbital, 52

intervertebral, 62

jugular, 48

lacerum, 48, 50

magnum, 46

mental, 55

obturator, 81

of Monro, 193

optic, 51

ovale, 51

Foramina, table of, 49
Formaldehyde, 20, 96
Fossa. 39

246

INDEX.

Frena, 1 1 9
Frontal bones, 41
Funiculi gracilis, 2 1 1

of Goll and Burdach, 211
Funiculus cuneatus, 202

of Rolando, 202

G.

Gall-bladder, 126
Gall-cyst in mammals, 138
Ganglia, 218, 219, 227
Gasserian ganglion, 218
Gastric glands, 129
Genera, 19
Ginglymus, 90
Gland, Cowper's, 183

lachrymal, 234

mammary, 180

parotid, 132

prostate, 183

salivary, 131

thymus, 166

thyroid, 166
Glands, accessory, 131

Harderian, 234

lymph, 162

Meibomian, 234

of mouth, 119

of small intestine, 130

of stomach, 129

sebaceous, 33, 174

sudoriparous, 34, 174
Glenoid cavity, 55, 67
Graafian follicle, 179
Great splanchnic nerve, 228
Gustatory organ, 232
Gyri of brain, 188

H.

Habena, 200

Hair, 34

Haversian canals, 40

Heart, 140

Hepatic duct, 134

Hippocampus major, 196

Histology, 17

Horns of mammals, 41

Humerus, 69

Humors of eye, 236

Hymen, 178

Hyoid bones, 55

Hypogastric plexus, 230

Hypophysis, 191

I.

Ileuin, 128
Ilium, 79
Infundibula, 172

Infundibulum, 191

Inguinal canal, 182

Injection of vessels, 20

Innominate bone, 79, 81

Integument, 33

Internal capsule, 201, 205, 212

malleolus, 84
Interparietal, 46
Intestine, 126
Iris, 235
Ischium, 79
Iter or aqueduct of Sylvius, 193

J-

Jar, preservation, 20
jejunum, 126, 128
Joints, 89

K.

Kidney of cat, 175
of mammals, 184
Knee-joint, 90

L.

Lachrymal bone, 53
Lacteals, 130, 161

injection of, 25
Lacunae, 40
Lambdoidal ridge, 48
Larynx, 55, 168
Laterad, 38
Leg, arteries of, 151

bones of, 79

muscles of, 108

nerves of, 224
Ligaments, 29

of knee-joint, 91

of larynx, 135
Linea aspera, 82
Liver, 133
Lumbar plexus, 223
Lungs, 172
Lymph, injection of, 24

system, 161

M.

Malar bone, 54

gland, 132
Male organs, 180

INDEX.

247

Malpighian bodies, 175
Mandible, 54
Marrow, 40
Marsupialia, 19

urogenital system of, 184
Mastoid portion of temporal, 45
Maxilla or maxillary, 52
Maxilloturbinal, 53
Meatus auditorius externus, 45, 237

internus, 46
Median nerve, 222
Mediastinum, 172
Medulla oblongata, 202
Membranes, mucous, 129, 137, 232

of brain, 186

of cord, 205

serous, 136
Meninges, 186, 205
Meniscus, 90
Mesad, 38
Mesal, 38

Mesencephalon, 187, 188
Mesenteries, 135
Mesethmoid, 43
Mesocuneiform, 86
Metacarpus, 75
Metatarsus, 86
Mitral valve, 141
Morphology, 17
Motor decussation, 213
Mouth, 117

Mucous membrane, 129, 137, 232
Muscles, dissection of, 95

eye, 233

head and neck, 97

kinds, 93

naming of, 94

pelvic limb, 108

table of, 97

thoracic limb, 100
Musculospiral nerve, 221

N.

Names, scientific, of animals, 20
Nares, 124
Nasal bone, 53

chamber, 53

duct, 233

septum, 43
Navicular, 85
Nerve, abducens, 217

anterior crural, 224

auditory, 217

facial, 217

Nerve, glossopharyngeal, 217

hypoglossal, 217

iliohypogastric, 223

interosseous, 222

lumbo-inguinal, 223

mandibular, 217

maxillary, 217

median, 222

musculocutaneous, 224

musculospiral, 220, 222

obturator, 224

oculomotor, 217

olfactory, 217

ophthalmic, 217

optic, 217

pathetic or trochlear, 217

peroneal, 225

phrenic, 228

plantar, 224

radial, 222

saphenous, 224

sciatic, 224, 226

splanchnic, 228

subscapular, 221

thoracic, 221

tibial, 224

trigeminal, 217

ulnar, 222

vagus, 217, 228
Neural arch, 57

canal, 59

Nomenclature, 20
Nucleus caudatus, 201

cuneatus, 21 1

gracilis, 211

lenticularis, 201

O.

Obturator foramen, 81

nerve, 224
Occipital bone, 46
Olfactory organ, 232
Omentum, 135
Ontogeny, 17

Optic commissure (chiasm), 191
195

nerve, 217

thalami, 199
Orbital plate, 52
Orders of mammals 19
Organ, 28

of Corti, 240
Organs of sense, 231
Ornithodelphia, 19

248

INDEX.

Ornithodelphia, brain of, 241
urogenital system, 184

Os calcis, 85
magnum, 75
planuni, 43

Osseous system, 31

Ova of mammals, 179

( ) varies, 178

Oviparous, 19

P.

Pacinian corpuscle, 232
Palatine bone, 52

plate, 52
Pancreas, 135
Papillae of tongue, 233
Parietal bone, 46
Parotid gland, 132
Patella, 83

ligaments of, 90
Peduncles of cerebellum, 203

of cerebrum. 191, 213
Penis, 183
Pericardium, 140
Perimysium, 94
Periosteum, 40
Peripheral nerves, 216
Peritoneum, 135
Petrous bone, 45
Phalanges, 76, 87
Pharynx, 124
Phylogeny, 18
Physiology, 17
Pia mater, 186, 205
Pillar of fauces, 1 1 7
Pineal body, 200
Pisces, 19
Pisiform bone, 74
Pituitary body, 191
Plantigrade, 78
Pleura, 172
Plexus, brachial, 220

cardiac, 228

cervical, 219

choroid, 193, 194

lumbar, 223

pulmonary, 228

sacral, 226

solar, 229

Pons Varolii, 188, 195
Portal system, 156
Premaxillary (premaxilla), 51
Preservation of material, 20
Primates, 19

Process, acromion, 68

clinoid, 49

coracoid, 68

coronoid, 70

hamular, 51

mammillary, 61

mastoid, 47

odontoid, 60

postorbital, 41

pterygoid, 51

spinous, 57

styloid, 70, 71

transverse, 57

trochanter, 81, 82
Projection fibers, 213
Prostate gland, 183
Proximad, 38
Psychology, 18
Pterygoid bone, 48, 51
Pulmonary arteries, 142

circulation, 143

veins, 159

Q.

Quadriceps extensor muscle, 110

R.

Radius, 70

Rectum, 128

Reproductive system, 174

Reptilia, 19

Restiform body, 202, 204

Retina, 236

Ribs, 65

Rodentia, 19

Roots of spinal nerves, 206

Rotatoria, 90

Round ligament, 136

S.

Sacral plexus, 226

Sacrum, 62

Sagittal, 38

Salivary glands, 131

Saphenous nerve, 224

Sarcolemma, 93

Scapholunar, 74

Scapula, 67

Schneiderian membrane, 239

Sciatic nerve, 224, 226

notch, 80
Scrotum, 180
Sebaceous glands, 174

INDEX.

249

Secondary motor tract, 215
Semicircular canals, 239
Semilunar ganglion, 230

valves, 142

Sensory tract of brain, 215
Septum lucidum, 196
Serous membrane, 136
Sesamoid bones, 36, 76
Shaft, 39

Shoulder girdle of mammals, 69
Sigmoid cavity, 70
Sinuses, blood, 157
Sirenia, 19
Skeleton, 36
Skin, 32

Solar plexus, 229
Species, 19
Spermatic cord, 181
Sphenoid bone, 48
Sphincter muscle, 194
Spinal cord, 205

preparation for dissection, 26

nerves, 218
Spleen, 165
Stenson's duct, 132
Sternebra, 63
Sternum, 63
Stomach, 126

of ruminant, 137
Subclasses of mammalia, 19
Subclavian artery, 143

vein, 156

Sublingual gland, 132
Submaxillary gland, 132
Sudoriparous glands, 174
Sulci of brain, 188
Superior pyramidal decussation,

215

Suprarenal bodies (capsules), 167
Sutures, 89

Sympathetic nervous system, 226
Symphysis of mandible, 54

pubis, 80
Synarthroses, 89
Synovia, 90

Synovial membrane, 91
Syringe, injecting, 21
Systemic circulation, 143
Systems of mammals, 28

T.

Tarsalia, 86
Tarsus, 84
Taste-buds, 233

.Taxonomy, 18
Teeth, 120

of mandible, 54

of maxillary, 52

of premaxillary, 51
Telencephalon, 187
Temporal bone, 44
Tendon, 93
Tentorium, 46
Testes, 180
Thoracic aorta, 143

cavity, 125

duct, 165

nerves, 219

Thymus gland, 125, 166
Thyroid cartilage, 169

gland, 166
Tibia, 83
Tissues, 29

A|A <-i -,

Iocs, 8/
Tongue, 119
Tonsil, 119
Trachea, 170
Tracts of spinal cord, 215
Trapezium, 74
Trapezoid, 74
Tricuspid valve, 141
Tuber cinereum, 191
Tuberosity, 39
Turbinated bones, 53
Tympanum, 237

U.

Ulna, 70, 71, 72
Ulnar nerve, 222
Unciform, 75
Ungulata, 19

digits of, 77

origin of, 71
Unguligrade, 78
Ureter, 176

Urogenital system of mammals, 184
Ursidae, 19
Uterus, 177

Vagina, 178
Valves, heart, 141

of arteries, 143, 154

of veins, 154
Varieties, 19
Vas deferens, 182
Vascular system, 140

250

INDEX.

Vascular system, preparation of,

for dissection, 20
Vein, azygos, 156

brachiocephalic, 156

cephalic, 154

coronary, 156

gastroepiploica, 156

gastrosplenic, 156

hepatic, 154

iliac, 156

iliolumbar, 155

jugular, 157

maxillary, 157

mesenteric, 156

ovarian, 155

pancreatoduodenalis, 156

phrenic, 154

portal, 156

postcava, 154

precava, 154

pulmonary, 159

saphenous, 154

spermatic, 155

sternal, 156

subclavian, 157

suprarenal, 155

vertebral, 156
Veins, structure of, 154

trunk, head, and neck, 155

valves of, 154
Velum interpositum, 193

palati, 1 1 7

Vena cava, 156
Venous sinuses, 157

system, 153

Ventricles of brain, 192
Vertebrae, 57

caudal, 62

cervical, 58

lumbar, 61

thoracic, 60

Vertebrarterial canal, 59
Vertebrata, 19
Villi, 130
Viscera, 124
Visual organ, 233
Vital knot, 202
Viviparous, 184
Vocal cords, 169
Vomer, 52

W.

Wharton's duct, 132
Willis, circle of, 147

X.

Xiphoid process, 63

Z.

Zygoma, 44, 54
Zygomatic gland, 132
process, 44

Note Subjectjlndex, Page 6

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MEDICAL BOOKS. 15

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27

DA COSTA

Clinical Hematology

A Practical Guide to the Examination of the Blood by
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*#* A new, thorough, systematic, and comprehensive
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OERTEL

Medical Microscopy

JUST READY

A GUIDE TO DIAGNOSIS, ELEMEN-
TARY LABORATORY METHODS,
AND MICROSCOPIC TECHNIC

By T. E. OERTEL, M.D.,

Professor of Pathology and Clinical Microscopy, Medical Depart-
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WITH 131 ILLUSTRATIONS. 1 21110. Cloth, $2.00

28

The Pocket Cyclopedic of
Medicine and Surgery

Full Limp Leather, Round Corners, Gilt Edges, $1.00
With Thumb Index, $1.25

Uniform 'with " Gould's Pocket Dictionary "

A concise practical volume of nearly 600
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By Drs. Gould and Pyle

Based upon their large "Cyclopedia of
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29

A NEW EDITION

CROCKER ON THE SKIN

The Diseases of the Skin. Their Description, Pathology,
Diagnosis, and Treatment, with Special Reference to the
Skin Eruptions of Children. By H. RADCLIFFE CROCKER,
M.D., Physician to the Department of Skin Diseases, Uni-
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Third Edition, Rewritten and Enlarged

OCTAVO. JUST READY t CLOTH, $5.00

*#* This new edition will easily hold the high position
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STURGIS— MANUAL OF
VENEREAL DISEASES

By F. R. STURGIS, M.D., Sometime Clinical Professor of
Venereal Diseases in the Medical Department of the Uni-
versity of the City of New York. Seventh Edition, Revised
and in Part Rewritten by the Author and FOLLEN CABOT,
M.D., Instructor in Genito-Urinary and Venereal Diseases
in the Cornell University Medical College. I2mo. 216
pages. Cloth, $1.25

*V* This manual was originally written for students'
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remedies.

30

FOR THE DISSECTING ROOM

Holden's Anatomy — Seventh Edition
320 Illustrations

A Manual of the Dissections of the Human Body. By JOHN
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Hughes ajvd Keith- -Dissections
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31

EDGAR'S

OBSTETRICS

A NEW TEXT -BOOK
1 22 i Illustrations

Edgar's Obstetrics excels all
other works on this subject
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formity and consistency in
arrangement, thoroughness
and clearness in handling
details, and in the number
and usefulness of its illus-
trations.

OCTAVO. CLOTH, $6.00; SHEEP, $7.00

mVH

..i

I); l|

fljjm I I : '

11

lllti.'ll

I