DISSECTION OF THE DOG
AS A BASIS FOR THE STUDY OF PHYSIOLOGY
BY
W. H. HOWELL, A.B., Ph.D.
X.ECT.HEH m PHVSIOLOGV AXD H.STOLOGV .N THE UN.VERS.TV OP MICH.OAK, KORMERLV
ASSOCIATB IN BIOLOGY, JOHNS HOPKINS UNIVERSITY
NEW YORK
HENRY HOLT AND COMPANY
1889
Copyright, iSSflj
Henry Holt & Co.
0^ HS'^.i. JuN e. ■^■.
TABLE OF CONTENTS.
INTRODUCTION.
PAGB
Method of killing and preparing the dog — Necessary dissecting
instruments — Method of injecting and of making cannulas... . 9
CHAPTER I.
Muscles of the abdomen — The abdominal viscera — External and
internal anatomy of the alimentary canal and connected
organs — The urinary system — Female reproductive organs —
Male reproductive organs — The diaphragm 15
CHAPTER II.
Muscles of the shoulder — Muscles of the arm 30
CHAPTER III.
The thoracic viscera— Dissection of the heart and great blood-
vessels— Dissection of the mouth ; of the nasal cavity ; of the
salivary glands ; of the cartilages of the larynx 37
CHAPTER IV.
Injection of the blood-vessels — Dissection of the vascular system
— Branches of the descending aorta; of the post-cava; of the
portal system; of the prae-cava — Arteries of the anterior
portion of the body 49
CHAPTER V.
Muscles of the thorax — Dissection of the neck; of the thoracic
vagus; of the thoracic sympathetic; of the brachial plexus;
of the muscles of the larynx 61
CHAPTER VI.
Dissection of the brain — Directions for the removal of the brain
— External characters — Internal structure 75
CHAPTER VII.
Dissection of the eye — Accessory organs of the eye — Muscles of
the eyeball — Dissection of the eyeball S6
PREFACE.
It is admitted beyond all question that even an
elementary study of human physiology ought to be
preceded by a more or less thorough dissection of
some mammal. This little book, prepared originally
for the author's own class, is intended to give this
necessary anatomical basis to those who have not the
opportunity of dissecting the human body. With this
purpose in view, attention has been directed to those
organs which are the chief objects of physiological
study, rather than to those which have mainly an ana-
tomical interest. One chapter has been inserted
treating of the anatomy of the muscles of the shoulder
and arm, but the author does not think it advisable to
require this of a class unless there is abundance of
time at the teacher's disposal. The anatomy of these
muscles is of no particular importance in general phy-
siology, and even from the standpoint of comparative
anatomy it has but little value owing to the incom-
plete knowledge possessed with regard to muscle
homologies among the mammalia. With reference to
the muscles of the abdomen and the thorax the case
is very different : these muscles play an important part
in the performance of the respiratory movements, and
their position and relations ought to be known by the
student. Descriptions of these muscles, therefore,
PREFACE.
have been inserted in connection with the chapters on
the abdominal and thoracic viscera.
The dog has been selected in preference to the rab-
bit or the cat, the other animals usually employed for
such purposes, for several reasons. In most respects
its anatomy corresponds very closely to that of man ;
the size of the blood-vessels and other organs is rela-
tively large, and this is especially true of the thoracic
viscera and the neck region, which can be dissected
with more success by the beginner upon the dog than
upon the rabbit or the cat ; if small dogs are se-
lected, they will be found to be of a convenient size
for general laboratory use ; finally, most of the usual
physiological experiments and demonstrations are
made upon the dog, and a knowledge of its anatomy
will therefore prove particularly valuable to those who
intend to make a special study of physiology.
The directions for dissection have been divided into
seven chapters, with the idea that a fresh dog would be
used for each chapter with the exception of those upon
the muscles of the shoulder and arm, the brain, and
the eye, requiring therefore four dogs for the entire
work, though a smaller number may be made to
answer. To obtain the most satisfactory results, how-
ever, one must be careful not to attempt to dissect too
much upon a single animal. When the student is at
work upon the blood-vessels he should not be required
to dissect at the same time the peripheral nervous
system. A much better knowledge of the circulatory
organs, especially of their relations to each other, will
be obtained if they are dissected as a whole. After
learning the anatomy of the blood-vessels the nerves
can be dissected with greater success, and their rela-
tions to the arteries and veins determined more easily.
PREFACE. 7
The same remarks apply of course to other groups of
organs. Each chapter, therefore, with the exceptions
named, has been arranged so as to include a number
of regions or sets of organs which can be conveniently
dissected upon one animal. If there is not sufficient
time for a class to do the whole chapter, there is no
obstacle in the way to prevent the teacher from select-
ing the most important parts and omitting the others.
In the use of terms denoting directions and relations
it has been thought best to employ the usual nomen-
clature rather than to adopt the more recent and more
exact designations proposed by various authors. These
latter are not as yet current in general anatomical
literature or standard anatomies; indeed it remains to
be seen which of those proposed will prove "the fittest."
It did not seem wise, then, to burden the beginner with
a discussion as to the use of terms, when in the great
majority of cases the terms in ordinary use are suffi-
ciently definite. The terms of direction made use of are:
anterior, meaning toward the head ; posterior, toward
the tail ; dorsal and ventral, with the usual significance ;
and right and left, inner and outer, with reference to
the mid-line of the body.
In the directions for dissecting and in the descrip-
tive part of the text an effort has been made to avoid
unnecessary minuteness in the instructions. To a per-
son altogether ignorant of the methods of dissecting a
written description cannot fully supply the place of an
instructor; it is necessary and indeed better for him to
learn some things from experience. To students with
some little experience in the art of dissection, or work-
ing under the guidance of an instructor, it is a hin-
drance rather than an advantage to attempt to describe
just the direction and extent of each cut, the way in
o PREFACE.
which the instruments should be held, etc., or to point
out all the numerous possible mistakes which may be
made. It is better to leave something to the intelli-
gence and discretion of the teacher or the pupil, if the
dissecting is to prove a healthy discipline.
It is but proper to say that the general idea of the
arrangement of the directions for dissection was taken
from the very excellent book on " Practical Zoology"
by Marshall and Hurst.
I take pleasure also in expressing my thanks to my
friend Mr. T. D. Coleman, Assistant in Physiology in
this laboratory, for his kindness in helping me in the
dissections and in the preparation of the diagrams.
W. H. Howell.
Johns Hopkins University,
Baltimore, Md.
INTRODUCTION.
The following brief description of methods and
instruments may contain some useful practical hints
for those whose experience in such matters is limited.
Method of Killing and Preparing the Dog. — The
quickest and most merciful method of killinsf the dopf
is to chloroform him. For this purpose it is only
necessary to have a tight box or metal can with a
well-fitting cover. In the bottom of this box place
a sponge saturated with chloroform, put in the dog
and close the lid. After a short time the animal
becomes quiet, but it should not be removed from the
box until all respiratory movements have ceased. For
convenience in dissecting the dog should then be
tied down upon some form of dog-holder. Perhaps
the simplest and most economical form, one which
can be readily made and answers every purpose, is
shown in I, Fig. i. It consists of a board about 30
inches long and 12 inches wide, supported upon two
blocks, and having at one end a piece of bent iron
rod which can be fastened into the mouth, and serves
to hold the head. On the sides of the board are six
cleats by means of which the limbs of the animal can
be fastened in any desired position.
With regard to the preservation of the animal,
if the dogs are to be kept only a few days, or
even a week, the simplest and least injurious method
is to leave them on ice in an ice-box when they
I O IN TROD UCTION.
are not being dissected. A number of dogs can
be kept in good condition in tliis way with but
little expense, especially if it is possible to remove
the intestines, or at least the large intestine and rec-
tum, after the first day. This method of preserving
the animal has the great advantage of not decolorizing
any of the tissues, and furthermore prevents the sour
odor which soon comes on after using preservative
liquids. If it is not possible to make use of this
method, and it is necessary to keep the animal for
some time, recourse must be had to some of the usual
preservative liquids. Immersing the dog in alcohol
will keep it from decomposing, but leaves it in such a
bad condition for dissecting that it is not to be recom-
mended. Wickerscheimer's liquid injected into the
arteries after having previously washed out the blood
with 0.6^ sol. of NaCl is highly recommended, though
my experience with it has been unsatisfactory. The
formula for this liquid is as follows : Dissolve in 3
litres of boiling water 100 grms. of alum, 25 grms. of
common salt, 1 2 grms, of potassium nitrate, 60 grms.
of potassium carbonate, and 20 grms. of arsenious acid ;
after cooling add i^ litres of glycerme and \ litre of
alcohol. A liquid which I have tried but few times,
but which has given satisfaction, is made by mixing
one part of glycerine with two parts of a 2% solution
of corrosive sublimate, and adding to this mixture
crystals of chloral hydrate in the proportion of 2 grms.
of chloral to each 100 cc. of the liquid. This liquid
keeps the animal pliant, does not destroy the color,
and seems to bring out the nerves more distinctly.
Necessary Dissecting Instr2imc7its. — Each student
should be provided with a small case of dissecting in-
struments containing at least the following things:
Zrrs
Fig. I. — Instruments.
12 IN TROD UC TION.
Two dissecting scalpels, one large and one small.
Two dissecting forceps, one large with blunt ends,
and one small with fine points for more delicate work.
Two pairs of scissors, one with large blades for
coarse work and one small pair for fine dissection.
One seeker, an instrument of the form shown in II,
Figo ic This will be found very useful in dissecting
nerves, blood-vessels, etc., when by careful tearing with
the seeker instead of cutting with the scalpel or scis-
sors structures may be revealed which otherwise would
be destroyed.
Several weighted hooks of the kind shown in IV,
Fig. lo These consist simply of a strong hook to
which is attached a cord about two feet in length, car-
rymg at its other end a lead weight. The most con-
venient weight to use is about 125 grammes, though
it is well to have some lighter and some heavier than
this. These weighted hooks are useful for holding
back the skin, muscles, etc., while dissecting, and are
much preferable to the ordinary chain-hooks sold with
dissecting cases.
In addition to these instruments there should be at
hand for general use several artery-clamps or " serre-
fines," either of the form usually sold by instrument
makers, or preferably like that shown in V, Fig. i, hav-
ing longer and narrower points ; several aneurism
needles of the form shown in III, Fig. i, for passing
ligature threads round blood-vessels, etc.; one or more
pairs of strong bone forceps such as can be obtained
from any instrument-maker ; a number of small sponges
and a small saw.
Cannulas and Injecting' Syringe. The cannulas
used in injecting can readily be made of any desired
size from ordinary glass tubing. The steps in the pro-
IN TROD UCTION: 1 3
cess are represented in Fig. i. The glass tubing is
first held in the Bunsen flame until softened, and then
pulled out gently to the form shown in A. After
cooling a scratch is made with a file at the point indi-
cated by the dotted line, the tube broken, and the end
ground down obliquely to the form shown in B, upon
a grindstone or a piece of ground glass. The narrow
neck given to the cannula in this way is necessary in
order to hold it firmly when tied in the blood-vessel.
The two ends of the cannula should be slightly
rounded by heating in the flame. If cannulas are
needed for the smaller arteries, for ducts of the salivary
gland, etc., the glass tube after being softened in the
flame is pulled out to the proper diameter and then
this narrowed portion is treated as above.
The requisite features of a good cannula, especially
if it is to be used in experiments upon a living animal,
are that the neck should be as short as possible, and
not any narrower than is necessary to enable the
cannula to be tied firmly in the vessel ; and secondly,
the lip of the cannula should not be made too oblique,
not more so than will facilitate its introduction into
the vessel. Three of these cannulas will be required
in the injection of the blood-vessels as described in
Chapter IV., one for the aorta and two for the venae
cavge. As these must all be of large size they can
easily be made.
With reference to the syringe, the best form un-
doubtedly is the usual brass injection syringe provided
with several brass cannulas and a stop-cock ; it can be
obtained from any of the instrument-makers. These
syringes, however, are very expensive, and those who
cannot afl"ord to buy them will find the common
white-metal syrmges with double leather piston a
14 INTRODUCTION.
cheap and serviceable substitute. These latter can be
obtained from Whitall, Tatum & Co. of Philadelphia,
of different sizes and at very small cost. The best
size to use for the dog is one holding six or eight
ounces. Before using this syringe the piston must be
left in water for some time to swell, otherwise it will
not work tight in the barrel; though if left too long in
the water the trouble will be in the other direction.
The method of using the syringe in injecting is de-
scribed in Chapter IV.
CHAPTER I.
MUSCLES OF THE ABDOMEN AND AB
DOMINAL VISCERA.
MUSCLES OF THE ABDOMEN.
Make a median incision through the skin and fat
extending from the middle of the sternum to the sym
physis piibis ; at the two ends of this make lateral in
cisions on each side, and reflect the flaps of skin to-
gether with the subjacent fat. The muscular portion
of the abdomijial wall will be exposed.
I. The Linea Alba is the white line extending
along the ventral mid-line of the abdomen ; it is
formed by the fusion of the tendons of the muscles
of the two sides.
2o The External Oblique Muscle arises by fleshy
slips from the posterior ribs, from the fourth to the
thirteenth, and in part from the fascia below the
thirteenth rib ; the fibres pass obliquely inward and
posteriorly, and end in a broad, thin aponeurosis lying
along the middle of the abdominal wall and fusing
with its fellow of the opposite side.
Make an incision through the aponeurosis at its ju7ic-
tion with the muscle fbres, and reflect the muscle out-
ward, separating it carefully from the muscles beneatlh
l6 MUSCLES OF THE ABDOMEN
3. The Internal Oblique Muscle arises from the
crest of the iHum, from Poujjart's ligament, and
from the aponeurosis of the transversalis muscle
anterior to the ilium ; its fibres pass obliquely inward
and anferiorly to end in a thin aponeurosis which meets
its fellow in the mid-line, and lies immediately below
that of the external oblique, the two being separated
with some difficulty.
4. The Rectus Abdominis Muscle is a straight
band of fibres arising anteriorly from the sternum
and the cartilaginous portions of the posterior ribs,
and inserted at the symphysis pubis. Several zigzag
lines of fibrous tissue pass transversely across the band
of fibres in their course, making it in reality a poly-
gastric muscle.
5. The Transversalis Abdominis arises by fleshy
slips from the under surface of the posterior ribs
and from the region of the lumbar vertebrae ; the
fibres pass transversely inward, and end in a thin
aponeurosis lying beneath the rectus abdominis.
Dissect off very carefully the 1-ectiis abdominis and
the transversalis ; a thin 7nembrane, the peritoneum,
will be exposed covering over the abdominal organs.
THE ABDOMINAL VISCERA.
After removal of the peritoneum the abdominal
viscera are exposed in situ. The intestines are con-
cealed by a special fold of the peritoneum, the great
omentum, which hangs down from the stomach. The
omentum is loaded with fat, and if held up against
the light it will be found to be penetrated by a num-
ber of minute holes.
AND ABDOMINAL VISCERA. 1 7
A. THE ALIMENTARY CANAL.
1. The CEsophagus. The posterior end of the
oesophagus as it enters the stomach can be seen by
pressing aside the lobes of the Hver ; it penetrates the
diaphragm below the middle.
2. The Stomach may be studied in situ by lift-
ing up the lobes of the liver so as to expose it fully.
When empty it lies obliquely in the body, having a
marked bend at the posterior end ; when filled it lies
more transversely.
a. The Fundus. The left or cardiac end of the
stomach is much dilated ; the enlarged portion which
lies to the left of the entrance of the oesophagus is the
fundus.
b. The Great Curvature is the line from the
fundus along the posterior margin of the stomach to
the beginning of the intestines.
c. The Small Curvature is the line from the
opening of the oesophagus along the anterior margin
of the stomach to the beginning of the intestine.
d. The Pylorus is the opening of the stomach into
the intestines. The position of the pylorus is marked
externally by a shallow constriction. This region of
the stomach is spoken of as the pyloric end as dis-
tinguished from the cardiac end in the neighborhood
of the oesophagus.
3. The Intestines.
a. The Duodenum is the first portion of the small
intestine. It begins at the pylorus, bends suddenly
to the posterior for several inches, and then forward
again for some distance, making a U-shaped loop,
which continues directly into the remainder of the
small intestine. The glandular organ lying in the
1 8 MUSCLES OF THE ABDOMEN
curvature of the duodenum is the pancreas ; its at-
tachments must not be disturbed.
b. The Small Intestine is several feet in length,
and forms a very much convoluted tube which is at-
tached to the dorsal wall of the body by a membrane,
the mesentery. Starting from the duodenum, follow
the small intestine to its ending in the large intestine.
c. The Mesentery is a double layer of the peri-
toneum which is reflected from the dorsal wall of the
abdomen, and encloses the stomach and intestines.
Blood-vessels, nerves, and lymphatics pass to the in-
testines between its two layers.
d. The C^cum is seen at the point where the small
intestine passes into the large ; it is a coiled diverticu-
lum of the intestine two or more inches in length.
e. The Large Intestine commences at the caecum.
The first portion is known as the colon ; it passes an-
teriorly for a short distance as the ascending colon,
then transversely, the transverse colon, and finally
posteriorly as the descending colon, which is continued
directly into
f. The Rectum. This is the terminal portion of the
large intestine ; it lies within the pelvis, and opens
to the exterior through the anus.
or. Peyer's Patches. At intervals alonp^ the lower
portion of the small intestine, on the border oppo-
site the attachment of the mesentery, a number of
small oval bodies will be seen, the Peyer's patches.
They are masses of lymphoid tissue imbedded in
the intestinal wall.
h. Lymph Glands. Enclosed within the layers of
the mesentery will be found a number of lymph glands,
flattened oval bodies varying in size. Where the
AND ABDOMINAL VISCERA. jg
caecum joins the intestine tiiere is a collection of
these glands known as the Pancreas Asselli.
B. INTERNAL ANATOMY OF THE ALIMENTARY
CANAL AND APPENDICULAR ORGANS.
Ligature the stomach about one inch to the left of
the Pylorus, and at the oesophagus. Remove the
stomach from the body, cutting through its walls just
beyond the ligatures; open it along the great curvature,
wash with zvatcr and examine.
1. The Stomach. The walls of the stomach con-
sist of an outer layer of peritoneum, a middle
layer of muscle which is thicker at the pyloric end
than elsewhere, and an internal layer of mucous
membrane. The last layer is connected to the mus-
cular wall by sub-mucous areolar tissue, and can easily
be pulled or dissected away. The mucous mem-
brane is thrown into numerous folds which are es-
pecially marked in the cardiac region.
Cut out a piece of the small intestine, selecting a
portion which contains 07ie or more Peyers patches,
open along the line of the mesentery, wash thoroughly
and examine.
2. The Small Intestine. The walls of the small
intestine are composed of the same layers as those of
the stomach. The mucous membrane is not thrown
into folds, but is raised into a number of minute pro-
cesses which can be seen better with a magnifying-
glass. These processes are set closely together like
the pile of velvet ; they are known as the Villi.
Examine the appearance of a Peyer's patch when
seen from the inside.
20 MUSCLES OF THE ABDOMEN
3. The Caecum.
Cut out the ccectim together with the adjoining p07'-
tions of the small and large intestine, lay open, and
wash with water.
The boundary line between the small and the
large intestine is marked by a circular thickening of
the mucous membrane — representing the ilco-colic
valve. On one side the mucous membrane of the
small intestine is shaggy with villi ; on the other, the
colon, the membrane is smooth. The mucous mem-
brane of the caecum is thickly studded with small
lymph follicles.
4. The Colon. The mucous membrane is smooth
throughout, showing no villi, but in some places it is
thrown into irregular folds or rugae.
5. The Pancreas lies in the loop of the duo-
denum ; it is an elongated glandular body of pinkish
color.
6. The Pancreatic Ducts. In the dog there are
two main ducts ; one, the smaller, opens into the
duodenum about an inch beyond the pylorus, close to
or in connection with the bile duct ; the other, larger
duct opens into the duodenum about i or i| inches
lower down. (The close attachment of the pancreas
to the duodenum conceals these ducts. They can
be demonstrated most easily by tearing away care-
fully the pancreas from the duodenal wall with a
blunt-pointed instrument, commencing at the pylorus.
The ducts are tougher than the loose connective tissue
attaching the rest of the pancreas, and can be ex-
posed easily in this way.)
7. The Spleen is an elongated, flattened, dark-
red body lying to the left of the stomach, and con-
nected to it by a fold of the peritoneum, the gastro-
AND ABDOMINAL VISCERA. 21
splenic omentum. It is wider at the upper end ; the
blood-vessels enter it along the line of attachment of
the omentum.
8. The Liver. The anterior surface is convex, and
fits against the arched diaphragm to which it is at-
tached by a median fold of peritoneum, the suspen-
sory ligament. The organ is relatively large in the
dog, and, as in other mammals, may be divided into
two principal lobes, the right and the left. Each of
these is again subdivided into smaller lobes, the left
into two and the right into four, the homologies of
which are not properly known. They may be named
as follows :
a. The Left Central Lobe lies against the left
half of the diaphragm.
b. The Left Lateral Lobe, the largest lobe of
the liver, lies between the left central and the cardiac
end of the stomach.
c. The Right Central Lobe lies aorainst the rieht
half of the diaphragm ; it has a deep groove on its
under surface for the reception of the gall-bladder.
d. The Right Lateral Lobe is just posterior to
the right central.
e. The Caudate Lobe, posterior to the last, lies to
the right of and dorsal to the pyloric end of the stom-
ach, extending backward to the right kidney.
f. The Spigelian Lobe, the smallest lobe of the
liver, projects into the small curvature of the stomach ;
it lies dorsal to a fold of the peritoneum connect-
ing the liver to the stomach, the Jicpato-gustric
omentttm.
g. The Gall-bladder is a large, thin-walled oval
sac imbedded in the right central lobe.
h. The Bile-duct has the arraneement shown in
22
MUSCLES OF THE ABDOMEN
Fig. 2. It opens into the duodenum about an inch
below the pylorus. The duct leading directly from
the gall-bladder is known as the cystic duct. In the
dog it is very short.
L. CENTRAL,
L. LATERAL
L. LATERAL
SPIGELIAN,
CAUDATE
AND R LATERAL^
Fig. 2. Diagram of the Bile-duct and its Branches.
C. THE URINARY SYSTEM.
Remove the liver, splee7i, and intestines from the
abdomen, taking care not to disturb the reprodtictive
or the urinary organs. In removing the liver it
will prove most convenient to double-ligatnre the large
inferior cava above and below the liver, a7id cut be-
tween the ligatures. In removing the intestines double-
ligatui'e the rectum as near the anus as possible, and
cnt between the ligatures.
I. The Kidneys are a pair of dark-red oval
bodies lying against the dorsal wall of the abdomen,
outside of the peritoneum. Each is usually im-
bedded in fat. If this is carefully removed, the hilus
will be exposed as a notch on the inner border where
the blood-vessels and ureter enter the kidney.
AND ABDOMINAL VISCERA. 23
2. Adrenal Bodies — one on each side. They lie in-
ternal to the upper portion of the kidney, and are
surrounded by fat. Each is an elongated, yellowish
body about f in. in length.
3. The Ureter emerges from the hilus of the
kidney, passes backward and inward to reach the
under surface of the bladder, into which it opens, well
down toward the neck. Make an opening in the
ureter about an inch from the bladder, and through
this opening pass a bristle or probe into the bladder.
Notice that the ureter runs obliquely in the wall of
the bladder some distance before it reaches the in-
terior.
4. The Bladder is a thin-walled muscular sac
which when filled with urine projects some distance
above the symphysis pubis.
Cut open the bladder and remove any urine that
may be present with a sponge.
Determine the position of the opening of the
ureters internally. From each a white thickening of
the mucous membrane passes downward to the
urethra, inclosing a triangular area, the trigojie.
5. The Urethra, the duct of the bladder arises
from the lowest portion of the bladder. Its further
course will be seen in the dissection of the repro-
ductive system.
6. The Internal Structure of the Kidneys.
Remove one from the body and slice it open along
its long diameter, preferably a little to one side of the
mid-line.
Each kidney has externally a fibrous investment
which can be peeled off easily with the forceps. The
proper substance of the kidney is divided into a cor-
tical and a medullary layer.
24 MUSCLES OF THE ABDOMEN
a. The Cortical Substance forms the external
layer. It is of a darker color, and somewhat mottled
owing to the presence of the Malpighian bodies.
b. The Medullary Substance forms the internal
layer. It is of a lighter color, and striated owing to
the peculiar arrangement of the uriniferous tubules and
blood-vessels. The uriniferous tubules are united into
a number of groups, each of a pyramidal form, and
known as the Malpighian pyrainids. The apices of
these pyramids unite to form a ridge lying in the long
axis of the kidney. The openings of the uriniferous
tubules are found upon this ridge.
c. The Sinus. The medullary substance encloses a
cavity, the sinus, which is a continuation inward of
the hilus. It is filled with connective tissue, blood-
vessels, and the greatly expanded ureter, which here is
known as \\\& pelvis. The expanded pelvis clasps the
ridge described above, receiving thus the excreted
urine. The cavity of the pelvis also extends outward
for some distance along each pyramid.
D. THE DIAPHRAGM.
The diaphragm is the muscular septum between the
abdomen and the thorax, and can now be examined
from the abdominal side. It is a dome-shaped parti-
tion, partly muscular, partly membranous.
1. The Central Tendon lies at the top of the dome.
It is a thin membrane passing into muscular substance
at all points of its circumference.
2. The Muscular Substance has three origins :
a. Posteriorly from the bodies of several of the
lumbar vertebrae by two thick muscular slips or crura.
b. From the ensiform cartilage.
c. From the cartilages of the posterior ribs.
AND ABDOMINAL VISCERA. 2$
From these points the muscular substance passes
up along the walls of the thorax for some distance, and
then bends inward somewhat abruptly to end in the
central tendon.
£. FEMALE REPRODUCTIVE ORGANS.
If dissected 2ipon a new dog, open the abdomen as in
the dissection of the abdominal viscera, and remove the
stomach, intestines and liver. Then cut through the
skin and muscles above the pubis symphysis so as to ex-
pose this and the rami running from, it above and
below for a short distance. Cut throtigh the sym-
physis with bone forceps, and the rami above and
beloiv the obturator foramen at a distance of about
one-half inch on each side of the symphysis. Remove
carefully the pieces of bone thus isolated.
1. The Ovaries. A pair of oval bodies of a pale
color, lying posterior and dorsal to the kidneys, at the
termination of the oviducts. Each, in the small dogs,
is less than one one-half inch long, and is concealed
in a membranous capsule, which must be cut open to
fully expose the ovary.
2. The Oviducts. Each consists of two parts : pos-
teriorly a thick-walled tube, which unites with its
fellow of the opposite side to form the body of
the uterus ; anteriorly a very small convoluted tube
lying close to the ovary — the Fallopian tube. The
oviduct is connected to the dorsal wall of the
abdomen throughout its whole length by a broad
fold of peritoneum, the broad ligament.
a. The Fallopian Tube is very narrow and
slightly convoluted. It lies close to the ovary ; its
anterior end expands into a capsule surrounding the
26 MUSCLES OF THE ABDOMEN
ovary and communicating with the abdominal cavity
by a small opening ; its posterior end suddenly ex-
pands into a horn of the uterus.
b. The Uterus consists of two horns, each begin-
ning from the posterior end of the Fallopian tube, and
a body formed by the fusion of the posterior portions
of the horns. The body of the uterus is directly con-
tinuous with the vagina.
3. The Vagina is quite wide, and passes directly to
the posterior to end in the vestibule or urino-genital
canal.
4. The Urethra. Immediately ventral to the vagi-
na lie the bladder and urethra. The latter runs
along the ventral wall of the vagina, and finally the
two unite within the pelvis to form the vestibule or
urino-genital canal.
5. The Vestibule formed as stated above, lies ventral
to the rectum, and opens to the exterior. It has
very vascular walls.
Lay open the vestibule carefully, beghuiing at the
exterior, and cutting along the dorsal mid-line.
6. The Clitoris, a small organ homologous with the
penis of the male, is found just within the vestibule on
its ventral wall. It possesses essentially the same
structure as the penis, though on a smaller scale. It
has a glans clitoridis and two corpora cavernosa con-
nected with the ischia.
7. Note the connection of the urethra and vagina
with the vestibule.
AND ABDOMINAL VISCERA. 2J
F. THE MALE REPRODUCTIVE ORGANS.
If dissected upon a nezv dog, open the abdomen as in
the dissectio7i of tJie abdomi7ial viscera. Remove the
stomach, liver and intestines without disturbing the
urinary or reproductive organs.
1. The Scrotal Sac is a pouch-like diverticulum
of the skin of the abdomen lying posterior to the
symphysis pubis. It contains the testes.
2. The Testes. Dissect the skin from the scrotal
sac and the proximal half of the penis ; the two testes
will be exposed. Each is enclosed in a thin sheath of
peritoneum, the tunica vaginalis. Within this lies a
firm white sheath of connective tissue, the tunica al-
buginea, forming the proper capsule of the organ. At
the anterior end of each testis is the spermatic cord
enclosed in its sheath, and consisting of the spermatic
artery and vein and the vas deferens bound into one
cord. It may be followed forward to the abdominal
wall which it penetrates through an oblique opening,
the inguinal canal. Along the dorsal side of the
spermatic cord is a thin band of muscle fibres, the
cremaster muscle ; it arises from Poupart's ligament
at the symphysis and passes to the testes, over which
its fibres spread.
Slit ope7i the tunic of the testis and spermatic cord.
The testis will be fully exposed as an oval pinkish
body about an inch long (in small dogs), and sus-
pended by the spermatic cord.
3. The Epididymis is an irregular convoluted mass
lying along the inner and dorsal border of the testis.
It is divisible into several portions.
a. The Caput Epididymis is the enlarged por-
28 MUSCLES OF THE ABDOMEN
tion lying in contact with the anterior end of the tes-
tis.
b. The Cauda Epididymis forms the posterior
narrower portion. It is connected with the testis by a
ihort licjament, the ptibernaciihim.
4. The Vas Deferens — the narrow tube forming
the continuation of the cauda epididymis. It passes
along the spermatic cord, enters the abdomen, and
finally opens into the urethra — as will be seen in the
later dissection.
5. The Spermatic Artery and Vein, found also in
the spermatic cord. They supply the testis with blood.
C^it tJiroitgJi tJie pubis as directed i7i the dissection
of the female organs. Ligature the rectum, and re-
viove it if not done in the previous dissection. Clear
azvay the fat, etc., from the neck of the bladder to the
root of the penis.
6. The Vas Deferens. After passing through the
ing-uinal canal it turns inward to the dorsal sur-
face of the neck of the bladder lying internal to the
ureter. The two vasa deferentia open close together
into the dorsal surface of the urethra a short distance
beyond its origin from the bladder.
7. The Prostate Gland is a large glandular mass
encircling the urethra at the same point. Its ducts
open into the floor of the urethra.
8. The Urethra after leaving the prostate gland
continues under the symphysis pubis to reach the
penis. This portion is known as the urino-genital
canal, and has very vascular walls.
9. Cowper's Glands are very small in the dog.
Each opens into the urino-genital canal by a small
duct as it passes under the symphysis.
10. The Penis. At its root the lower aspect is
AND ABDOMINAL VISCERA. 29
iormed by the corpus spongiosum, in the middle of
which Hes the urethra. The sides and upper surface
are formed by the two corpora cavernosa, wtiite tough
bodies which are very vascular, and are attached to
the ischial bones. At the distal end of the penis these
bodies end in the long xS\\q}^ glans penis, which forms
the terminal portion of the corpus spongiosum. A
cross-section through the penis will give a good view
of the arrangement of the three corpora of which it is
composed.
11. The Os Penis. In the glans penis and for a
short distance between the corpora cavernosa is found
the large penis bone. It lies over the urethra, and is
grooved on the under side.
12. The Prepuce. The end of the glans penis is
covered by a movable fold of the integument, the
prepuce.
CHAPTER II.
MUSCLES OF THE SHOULDER AND ARM,
MUSCLES OF THE SHOULDER.
Dissect off the skin together with the underlying skin
mtcscles from the neck, shoulder and arm. Begin to
dissect from the dorsal side, placing the aimnal upon
its right or left side.
I. The Trapezius Muscle arises from the occipital
bone, and from the dorsal mid-line above the spi-
nous processes of the cervical and anterior thoracic
vertebrtC. From this extensive line of origin the
fibres converge toward the scapula and humerus. Care-
fully cleaning the muscle from fat, fascia, etc., it will
be found to be composed of three divisions.
a. The Anterior Trapezius is the most anterior
division ; it arises from the occipital bone, and from
the dorsal mid-line of the neck above the spinous pro-
cesses of all but the last cervical vertebrae. The mus-
cular fibres converge toward the humerus, where they
fuse with a long muscle, the levator humeri, and are
inserted with it into the lower part of the shaft of the
humerus.
b. The Middle Trapezius arises from the dorsal
mid-line above the spinous processes of the posterior cer-
vical and anterior thoracic vertebrae in a continuous line
with the insertion of the anterior trapezius. Its fibres
MUSCLES OF THE SHOULDER AND ARM. '\l
pass to the spine of the scapula, and are inserted along
the greater portion of its anterior edge. There is usually
a space between this and the anterior division near the
origin of the fibres, which is filled up with fat, connec-
tive tissue, lymphatic glands, etc.
c. The Posterior Trapezius arises above the spi-
nous processes of the anterior thoracic vertebrae in a
continuous line with the middle trapezius. The fibres
pass obliquely forward to be inserted along the pos-
terior edge of the outer or vertebral portion of the
spine of the scapula.
In man these three divisions are more completely
united to form a single trapezius muscle.
Cttt the three divisions of the trapezius at their in-
sertions and reflect the C2it ends dor sally to their origins.
The follozuing ninscles zuill be exposed.
2. The Rhomboideus Minor. It arises from the
dorsal mid-line above the spinous processes of the
posterior cervical vertebrae, just beneath the origin of
the trapezius. The fibres pass obliquely to the scapula
and are inserted into the anterior angle of the vertebral
margin.
a. TheOccipito Scapularis. Lying along the inner
margin of the rhomboideus minor is a narrow band of
muscle, the occipito scapularis, which arises from the
occipital bone and is inserted into the scapula along
with the rhomboideus, the two forming one muscle at
the insertion. This muscle is known also as the rhom-
boideus capitis or rhomboideus occipitalis in human
anatomy.
3. The Rhomboideus Major arises from the spi-
nous processes of the four or five most anterior tho-
racic vertebrge — its origin being in a continuous line
with that of the rhomboideus minor, from which
32 MUSCLES OF THE SHOULDER A AW ARM.
indeed it is not separate in the dog. The fibres pass
straight to the scapula, to be inserted along the verte-
bral edge.
4. The Levator Anguli Scapulae arises from the
transverse processes of the posterior cervical verte-
brae. The fibres form a broad sheet of muscle, and are
inserted into the under or ventral side of the scapula
near the anterior angle of the vertebral margin. Its
insertion is just to the inside of that of the rhom-
boideus minor.
5. The Levator Scapulae is a narrow flat band
of muscle which has its origin from the transverse
process of the atlas, and is inserted into the acromion
process of the scapula and a small extent of the neigh-
boring portion of the spine. Its insertion is just to the
inner side of that of the middle trapezius. This
muscle corresponds to the levator claviciilcE of the cat.
6. The Levator Humeri is a muscle similar in
shape to the last, lying nearer to the ventral mid-line.
It arises from the skull posterior to the external audi-
tory meatus, and is inserted below the middle of the
humerus, on its ventral face. Just before the muscle
passes over the shoulder-joint it is intersected by a
transverse line of tendon dividing it into two portions,
the anterior of which corresponds to the clavo-mastoid
of the cat, while the posterior division represents the
clavo-deltoid.
7. The Sterno-mastoid lies to the inner side of
the last-mentioned muscle ; it will be described in
connection with the dissection of the neck.
8. The Supra-spinatus is a large muscle occupy-
ing the whole of the supra-spinous fossa, from which
its fibres originate. They pass outward to be inserted
into the great tubercle of the humerus.
MUSCLES OF THE SHOULDER AND ARM. 33
9. The Deltoid Muscle. In the dog it is divided
into two separate museles, not including the portion
of the levator humeri which corresponds to the clavo-
deltoid.
a. The acromio-deltoid, the smaller division, takes
its origin from the acromion process, and is inserted
into a ridge along the outer surface of the proximal
third of the humerus.
b. The spino-deltoid arises by a strong fascia from
the posterior border of the spine of the scapula along
most of its extent, and is inserted into the humerus to-
gether with the acromio-deltoid.
Cut through the bellies of the deltoid muscles, and
reflect the cut ends.
10. The Infra-spinatus Muscle fills up the infra-
spinous fossa from which it arises. Its fibres end
in a strong tendon which is inserted into the great
tuberosity of the humerus just below the insertion of
the supra-spinatus.
11. The Teres Minor is seen just posterior to the
infra-spinatus near its insertion. When dissected out
it will be found to arise along the posterior margin of
the scapula by a tendinous expansion lying beneath
the infra-spinatus. It is inserted into the humerus
below the great tuberosity.
12. The Latissimus Dorsi is a very large muscle
arising by a fascia from the spinous processes of the
lumbar and posteroir thoracic vertebrae. From this
origin the fibres form a wide sheet of muscle lying on
the dorso-lateral wall of the thorax, and converge
anteriorly toward the humerus. It ends in a tendinous
expansion which fuses with the sheath of the triceps
medius and teres major, through which its action on
the humerus takes place. Just before its insertion the
34 MUSCLES OF THE SHOULDER AND ARM.
latissimus gives off a muscular slip, which passes along-
the arm, superficial to the triceps, to be inserted into
the olecranon process of the ulna. It might be called
the latisshnus extensor muscle.
Cut through the latissimus dorsi at its insertion.
Cut across also the pectoralis group of muscles and the
loose connective tissue, nerves, blood-vessels, etc., which
bind the arm to the side of the thorax. The scapula
zuill then fall outzvard, displaying the folloiuing mus-
cles.
13. The Teres Major — the muscular band lying
along the posterior margin of the scapula. It is in-
serted by a flat tendon into the upper part of the
humerus, between the biceps and coraco-brachialis
muscles.
14. The Sub-scapular Muscle is the large mass of
muscle filling up the sub-scapular fossa. It has three
or four tendinous lines separating the muscle in-
completely into fasciculi. The fibres converge to-
ward the head of the humerus, into which they are
inserted, the tendon passing through the capsular
ligament of the shoulder-joint. At the anterior
margin of the scapula the sub-scapular muscle fuses
more or less with the supra-spinatus.
15. The Serratus Magnus is the large muscle con-
necting the vertebral margin of the scapula to the
wall of the thorax. Anteriorly it fuses with the leva-
tor anguli scapuli, the two constituting in this animal
in reality but one muscle. The portion which arises
from the transverse processes of the cervical vertebrae
may be called the levator anguli scapuli, while the
portion arising from the ribs is the serratus magnus.
It springs from the first eight ribs by fleshy slips, and
is inserted alons^ the vertebral margin of the scapula.
MUSCLES OF THE SHOULDER AND ARM. 35
MUSCLES OF THE ARM.
i6. The Biceps Muscle lies on the inner and ven-
tral face of the humerus. Its anterior end is covered
over by the insertion of the pectoralis muscles upon
the humerus. The biceps arises by a single strong
tendon from the edge of the glenoid fossa (coracoid
process), the tendon passing through the capsular liga-
ment of the joint. The muscle is inserted by a strono-
tendon chiefly into the ulna, though it is attached also
to the radius by a smaller slip,
17. The Coraco-brachialis is a small muscle lying
to the inner side of the proximal end of the biceps.
It arises by a single tendon from the coracoid
process, passes over the head of the humerus, and is
inserted into the inner side of the humerus just
beneath the tendon of the teres major.
18. The Triceps Brachialis is the large mass of
muscle lying along the dorsal aspect of the humerus.
It serves to extend the forearm. In the dog it has
four divisions.
a. The largest division is an irregular muscle,
formed apparently by the fusion of two muscles ; it
arises along the posterior margin of the scapula, the
attachment being especially strong near the glenoid
fossa, and is inserted into the olecranon process of the
ulna. The other three divisions lie between this one
and the humerus, and agree pretty well in position
with the three heads of the triceps in man.
b. The most internal of these three divisions arises
from the humerus at the insertion of the coraco-
brachialis, and also by a line of fascia along the middle
third of the humerus.
36 MUSCLES OF THE SHOULDER AND ARM.
c. The most external of the three divisions arises
from the head of the humerus just beneath the inser-
tion of the teres minor, and from fascia along the outer
part of the humerus.
d. The middle division arises, in common with the
last, just beyond the head of the humerus.
The divisions b, c and d are inserted into the ole-
cranon process along with a.
Cut tliroiigh the bellies of the ti^iceps, and reflect the
cut ends.
19. The Brachialis Anticus is a flat muscle closely
adherent to the humerus ; it arises from the dorsal
and external aspect of the humerus throughout most
of its extent. The fibres pass over to the anterior or
ventral face 0/ the humerus, and at the elbow end in a
tendon which is inserted into the ulna. The tendon
passes between the two terminal tendons of the
biceps, fusing with them.
20. The Sub-anconeus is a very small muscle
which arises from the dorsal surface of the distal
end of the humerus round the margins of the ole-
cranon fossa. The muscle adheres closely to the hu-
merus, and is inserted into the olecranon process and
outer side of the ulna.
CHAPTER III.
THE THORACIC VISCERA, BUCCAL CAV-
ITY, PHARYNX AND LARYNX.
THE THORACIC VISCERA.
Dissect off the skin and muscles from the thorax.
With tJie 'bone forceps cut carefully tJiroiLgh all the
bony ribs at a distance of several inches on each side of
the sternum. Remove the triangular piece of the
thoracic wall thus isolated.
A. In removing this piece notice the vertical fold
of serous membrane passing from the heart
to the sternum ; it is a portion of the pleural
membrane known as the anterior mediastinum.
1. The Thymus Gland lies in the anterior part of
the thorax anterior to the heart. It varies in size with
the age of the animal, being larger in the young and
decreasing in size as the animal grows older.
2. The Lungs will be found collapsed when the
thorax is opened ; in the closed thorax they filled all
the space not occupied by the heart, great blood-
vessels, etc. They lie quite free in the cavity, except
at the roots, i.e., where the blood-vessels and bronchi
enter them.
The left lung is divided into two lobes, the upper of
which is incompletely subdivided by a deep notch.
38 THE THORACIC VISCERA, BUCCAL CAVITY,
The right lung is divided into four lobes. The
most posterior of these, the infra-cardiac lobe, pro-
jects between the heart and the diaphragm, enclosed
in a special fold of the right pleura.
3. The Pleurae. Each side of the thorax is lined
by a delicate membrane, the parietal pleura, which
at the anterior end of the thorax bends backward
along the great blood-vessels to the root of the lungs,
and thence is reflected over the external surface of the
lungs, forming the visceral pleura. In the unopened
thorax the lungs fill the whole cavity, and the
parietal and visceral layers of the pleura come into
contact, forming a smooth sliding-surface for the ex-
pansion and collapse of the lungs. The right and
left pleural sacs meet in the mid-line to form a double-
walled septum, the mediastiniDn. The portion of this
extending from the heart to the sternum is the an-
terior mediastinum. The portion between the dorsal
surface of the heart and the vertebral column is the
posterior m'cdiastinitm, it encloses between its layers
the oesophagus, the descending aorta, the low^er por-
tion of the trachea, etc.
4. The Phrenic Nerves, one on each side, lying be-
tween the heart and the lung. Follow each to its
termination in the diaphragm.
5. The Trachea can be seen passing into the thorax
from the neck. Its further dissection should be made
after that of the heart.
6. The CEsophagus is a wide muscular tube lying
along the dorsal wall of the thorax. It is easily seen
by lifting up the right lung.
PHARYNX AND LARYNX. 39
B. DISSECTION OF THE HEART AND GREAT
BLOOD-VESSELS OF THE THORAX.
I. The Pericardium is the membranous sac in which
the heart is enclosed. Like the pleura and the perito-
neum it is a double-walled sac. One layer, the visceral,
is attached closely to the muscular substance of the
heart ; the other, the parietal, lies loosely round the
heart. The two layers meet at the roots of the great
blood-vessels, and hold between them a little serous
liquid, the pericardial liquid. Notice the attachment
of the pericardium, the parietal layer, to the dia-
phragm.
Cut aiuay the pericardium, aud clean as carefully as
possible the roots of the large veins and arteries aris-
ing from the heart.
The greater portion of the surface of the heart
facing ventrally is made up of the right ventricle.
Anterior and to the right lies the right auricle. The
tip of the heart — the apex — is formed by the left
ventricle alone. The left ventricle makes up also the
greater portion of the dorsal surface of the heart.
The position of the internal septum between the two
ventricles is marked externally by a groov^e, contain-
ing a coronary artery and vein, which begins down
toward the apex on the ventral surface, and runs
obliquely around to the dorsal side.
Determine the positions of the right and left ven-
tricles, and the right and left auricles. Each of the
auricles consists of a main cavity, the atrium, into
which the veins open, and an auricular appendix,
usually the most conspicuous portion of the auricle.
40 THE THORACIC VISCERA, BUCCAL CAVITY,
1. The Veins opening into the Right Auricle.
a. The Superior Vena Cava (picE-cava) opens
into the anterior end of the auricle, and brings back
venous blood from the head, neck, upper limbs and
thorax.
b. Just above the root of the right lung the su-
perior cava receives the large azygos vein. Lift up
the right lung and follow the azygos along the dorsal
wall of the thorax to the diaphragm. Notice the side
branches, the intercostal veins, which it receives from
the walls of the thorax.
c. The Inferior Vena Cava (post-cava) empties
into the posterior end of the auricle. Follow it to the
diaphragm.
2. Arteries arising from the Right Ventricle.
a. The Pulmonary Artery arises from the an-
terior and dorsal corner of the ventricle, passes
dorsally for a short distance, and then divides into
the right and left pulmonary arteries which go to the
two lungs, entering each at its root. They carry
venous blood from the heart to the lungs.
3. Veins opening into the Left Auricle.
a. The Pulmonary Veins. There are two prin-
cipal veins on each side : on the left side, one from
each lobe ; on the right side, one from the two upper
and one from the two lower lobes. These four veins
converge to enter the auricle, the two from the right
lung passing directly underneath the right auricle to
reach their destination. These veins bring back
arterial blood from the lungs to the heart.
4. Arteries arising from the Left Ventricle.
a. The Aorta arises from the anterior end of the
ventricle, immediately dorsal to the origin of the
pulmonary artery. It passes for a short distance
anteriorly, the ascending aoi'ta, then curves posteriorly
PHARYNX AND LARYNX. 4 1
and dorsally, forming the arcJi of the aoi^ia, from
which the arteries for the head, upper Hmbs, etc., are
given off, and finally passes posteriorly along the
dorsal wall of the thorax, the descending aorta, lying
dorsal to the oesophagus.
This portion gives off side branches — the intercostal
arteries — to the ribs, durins; its course in the thorax.
5. The Ductus Arteriosus may be found as a liga-
ment connecting the pulmonary artery, just before its
division into right and left pulmonary arteries, with
the aorta. In embryonic life it is a vessel forming a
communication between these two vessels, and in
adult life is occasionally found patent. It is a rem-
nant of the connection between the fourth and fifth
arterial arches of the embryo.
C. THE INTERNAL ANATOMY OF THE HEART.
Cut across the great vessels about half an inch from
the heart, and remove the heart from the body,
I. The Auricles.
Cut away the outer zvall of both auricles and wash
out the contained blood.
a. The Right Auricle. The wall of the auricle
is thin ; that of the appendix is thicker and marked
internally by muscular ridges, as is also the wall of
the auricle in part.
b. The Septum Auricularum is the thin parti-
tion between the two auricles. An oval depression
in it is known as the fossa ovalis ; it marks the posi-
tion of the foetal foramen ovale. If the dog is young
this may still be found open.
c. The Coronary Vein. The opening of this
vein into the auricle is seen just posterior to the
42 THE THORACIC VISCERA, BUCCAL CAVITY,
opening of the inferior cava, lying between it and the
opening of the auricle into the ventricle. Follow
its course back along the groove between the auricle
and the ventricle.
d. The Auriculo-ventricular Orifice. The
crescentic opening leading into the right v^entricle.
e. The Left Auricle has thin walls like the right.
The walls of the appendix are thicker and marked in-
ternally by muscular ridges.
f. The Left Auriculo-ventricular Orifice. The
circular opening leading into the left ventricle.
2. The Ventricles.
Cut across the two ventricles at some distance from
the apex — in the lower third of the right ventricle.
The cavity of the right ventricle has a crescentic
shape ; the wall is relatively thin. The cavity of the
left ventricle is circular ; its walls are quite thick. The
ventricular septum is very thick and arched, with the
convexity projecting into the cavity of the right ven-
tricle. The cavity of the left ventricle extends into
the apex, while that of the right ventricle terminates
some distance anterior to it.
Remove the aiiricles close to the base of the ven-
tricles, and cnt short the aorta and pulmonary artery.
A good view of the relative positions of the four open-
ings into the ventricles is tints obtained.
a. The Tricuspid Valve of the right ventricle.
It guards the right auriculo-ventricular orifice, and is
formed by three membranous flaps attached round
the margin of the orifice. The free borders project
into the ventricle, and are connected to its wall by
tendinous cords, the chordce tendinecE, which end in
papillarv elevations of the ventricular wall known as
tht papillary muscles. Some of the chorda^; tendineae
PHARYNX AND LARYNX. 43
go to two flaps, or one flap may have chordoc from
two papillary muscles.
CiU through the right ventricular zvall between two
of the flaps to get a better view of their attachments.
Note the rcticnlated strnctiire of the ventricular
walls — the coiumnas carneae.
b. The Pulmonary Artery. The portion of
the right ventricular cavity leading into the pulmonary
artery is known as the conus arteriosus and forms a
funnel-like recess. The opening into the artery is
guarded by three pocket-valves, the semi-lunar valves,
which can be exposed easily with a probe from the
opening of the artery above. Cut through the
conus and artery longitudinally to get a better view
of the valves.
c. The Mitral Valve of the left ventricle
guards the left auriculo-ventricular orifice. It resem-
bles the tricuspid, with the exception that there are
only two flaps or cusps.
d. The Aortic Semi-lunar Valves, three in
number, have the same structure as those of the pul-
monary artery.
e. The Coronary Arteries. Behind two of
the aortic semi-lunar valves will be found the open-
ings of the two coronary arteries arising from the base
of the aorta. Run a probe into each and follow its
course for some distance.
3. The Trachea and Bronchi. Find the trachea as
it enters the thorax. Dissect it toward the lungs. It
divides into two large branches, the bronchi, one for
each lung. If one of the bronchi is followed into the
lung to which it is distributed it will be found to give
off smaller bronchi at intervals, and these in turn give
off still smaller branches, the whole system forming
44 THE THORACIC VISCERA, BUCCAL CAVITY,
what is known as the bronchial tree. The terminal
twigs of this system end in the air-sacs or alveoH, little
membranous bags, in the walls of which the capillaries
of the pulmonary artery are distributed.
D. DISSECTION OF THE BUCCAL CAVITY.
Remove the skin from the head. Lay open the
mouth on one side by cutting tJiroiLgJi the cheek with a
pair of scissors, and contimnng the cttt backward
across the bone with bone forceps or saw.
1. The Roof of the Mouth.
a. The Hard Palate, formed by the palatine
processes of the maxillary and palatine bones. It is
covered by pigmented mucous membrane which is
raised into a number of transverse ridges. The soft
palate is continued backward from this and ends in a
free notched border.
b. The Tonsils are two pinkish-gray eminences
lying lateral to the soft palate and above the root of
the tongue.
c. The Teeth. Verify the dental formula i. |,
c. |, pm. f , m. |.
2. The Floor of the Mouth.
a. The Tongue is attached along the greater
part of its length to the floor of the mouth. The
mucous membrane covering the upper surface shows
three different kinds of papillae : the circu^nvallate,
four in number, arranged along two converging lines
at the root, of the tongue ; the ftmgiform, found
generally over the dorsal surface and especially thick
at the tip ; the filiform, which toward the root are
larger than in front, and end in free notched borders.
They are thickly scattered over the whole dorsal surface.
/'//AA'i'iVX A AD LARYNX. 45
3. The Pharynx is the continuation backward of the
buccal cavity beyond the soft palate. The nasal cavity
also opens into it above the palate. To expose it
better the symphysis of the mandibles may be cut
through, allowing one side of the lower jaw to be de-
pressed,
a. The Epiglottis is the conspicuous V-shaped
lobe of cartilage projecting into the pharynx.
b. The Glottis, or Rima Glottidis. Posteriorly
the pharynx ends in two openings. One of these is
slit-like and placed ventrally ; the inconspicuous folds
bounding it are the false vocal cords, while immedi-
ately below or posterior to these are two more dis-
tinct folds, the tnte vocal cords. The slit between the
true cords is the glottis ; it leads into the larynx. The
epiglottis projects over this opening and covers it
during the act of swallowing.
c. The QisoPHAGus. The second opening at the
posterior of the pharynx is the beginning of the
oesophagus. It lies dorsal to the glottis,
d. The Eustachian Tubes. Slit open the soft
palate. The openings of the Eustachian tubes will be
seen in the anterior portion of the dorsal wall of the
pharynx, on a level with the nasal cavity.
To expose the nasal cavity insert the blade of the
scissors into the anterior nares of one side and cut
back close to the septum, ttsing the bone forceps if
necessary. Remove also the external wall of this side
of the nasal cavity. The structure of this side is de-
stroyed, but now by carefully removing as muck of
the septum, as possible the nasal chamber of the other
side will be exposed.
4. The Nasal Cavity. Note the arrangement of
the turbinate bones. The respiratory passage lies
46 THE THORACIC VISCERA, BUCCAL CAVITY,
between the lower turbinate and the palate, while the
olfactory passages proper lie between the upper
ethmoidal turbinates.
a. The Schneiderian Membrane is the mucous
membrane covering the upper turbinates. It is usually
of a darker color than the rest of the nasal mucous
membrane, and contains the end organs or cells of
the olfactory nerve-fibres.
5. The Salivary Glands.
Dissect on the side not previously used. No especial
directions are required.
a. The Parotid Gland is not very prominent in the
dog. It lies posterior to and somewhat in front of
the ear, and forms a somewhat indefinite pinkish mass.
b. Stenson's Duct, the duct of the parotid, arises
from the ventral margin of the gland, runs across
the middle of the masseter muscle, bends inward at
the border of the muscle, and opens into the mouth by
a small aperture on the inside of the cheek opposite
the posterior portion of the last premolar of the
maxilla. Insert a probe into the duct and demon-
strate the opening into the mouth.
c. The Sub-maxillary Gland forms on each side
a compact mass lying just posterior to the angle of
the mandible and concealed by connective tissue,
which must be cleared away.
d. Wharton's Duct. The duct of the sub-maxil-
liary will be exposed best if the attachment of the
digastric (see page 65) to the mandible is cut, and
this muscle reflected backward as far as possible. If
the thin sheet of muscle (mylo-hyoid) lying in the
floor of the mouth is now carefully cut the duct will be
exposed, and can be traced back to the gland and for-
ward to its opening upon the floor of the mouth.
PHARYNX AND LARYNX.
47
e. The Chorda Tympani, the nerve of the sub-
maxillary, is also shown in this dissection. Coming
out from underneath the mandible and passing to-
ward the ventral mid-line will be seen the large
lingual nerve. Just at the point it comes into view
it gives off a minute branch, the chorda, which runs
Fig. 3. — Diagram of the Sub-Maxillary Gland.
to the duct and thence to the gland. The relations of
these parts is shown in Fig. 3.
f. The Sub-lingual Gland lies along the outer
side of the duct of Wharton, and is crossed by the
lingual nerve. It is a small narrow glandular body
which opens upon the floor of the mouth by several
small ducts.
6. The Larynx. Remove the larynx and the hyoid
bone with its processes from the body for more care-
ful examination. The larynx consists of four princi-
pal cartilages, a. The thyroid, the largest and most
anterior ; the sides or wings are widely open behind.
b. The cricoid, having somewhat the shape of a sea/
ring, being narrow on the ventral surface and ex-
panded dorsally. It is connected to the thyroid by
ligaments and muscles, c. The ^7'j'/^7^(?2rt' cartilages are
48 THE THORACIC VISCERA, BUCCAL CAVITY. ETC.
two small triangular cartilages attached to the anterior
end of the dorsal side of the cricoid. The vocal cords
are connected with these cartilages.
7. The Hyoid Bone consists of the body or basi-
hyal connected with the thyroid, the two long an-
terior cornua, each composed of three pieces, the
cerato-hyal united with the basi-hyal, the epi-hyal and
the stylo-hyal, the last being connected with the base
of the skull by a flexible cartilage, and the two shorter
posterior horns each composed of a single bone, the
thyro-hyal, which unites with the lateral portion of the
thyroid.
CHATER IV.
DISSECTION OF THE VASCULAR
SYSTEM.
Injection. In dissecting the blood-vessels it will be
found most convenient to inject the arteries and veins
with different colors, using coarse injection, which will
not pass beyond the capillaries. The injection material
recommended is plaster of Paris. The dry powder
should be mixed with water, stirring all the time,
until the liquid has the consistency of a very thin
paste ; the coloring matter is then added. This mix-
ture should not be made until it is ready to be ttsed,
since it sets quickly. For the veins the best coloring
matter to use is a saturated aqzieous sohition of
Prussian blue ; for the arteries, freshly prepared
chromate of lead held in suspension in water. To
prepare this latter make a ifo solution of am-
mo7iiiim or potassium bichromate and a strong
solution of acetate of lead, add the latter solution to
the former, stirring all the while, until the bichromate
solution is all precipitated as ycllozu chromate of lead.
Allow the liq2cid to stand until the precipitate settles
to the bottoin, then decant the supernatant liquid.
Wash the precipitate several times with water, de-
50 DISSECTION OF THE VASCULAR SYSTEM.
canting the excess, a7id finally mix the chr ornate held
in suspension in a little water with the plaster-of-Paris
solution.
The injection of the vessels is best done as folloivs :
Dissect off the skill and mnscles fi^oui the ventral sur-
face of the thorax. Open the thorax by cutting
througJi the cartilaginous ribs at tJieir junction with
the bo7iy ribs on each side of the steimuni fro7n above
the diaphragm to the third rib, then cut transversely
across the stei-num and remove the piece of thorax
thus isolated. On the under side of the piece of the
sternum left at the anterior end of the thorax ru7i the
two sternal arteries and veins ; these must be Heated
either by dissecting thcTn out aiid tyiiig each separately,
or by passing a thread round the piece of sterniim
and bijiding firmly.
Take a large cannula, to which a bit of rubber tub-
ing is attached, fill it with o.b^c solution of NaCl,
clamp the tubing, and then insert the cannula
into the aorta zvhere it springs from the heart and
ligature it firmly. Fill the syringe with the o. ti solution
of NaCl and inject it into the aorta, making mean-
while a cut in the right aui'icle throitgh which the blood
can escape. Continue the injection of NaCl solution
until all the blood is washed out. Then make the
yellow mixttire of plaster of Paris and inject it 7cntil
the arteries are tJioroiighly filled. If any escape takes
place from the small arteries C7it in opening the thorax,
these arteries can easily be ligated. In this as in all other
injections care must be taken not to let air get into
the vessel. The rubber tubing on the cannula should be
clamped each time the syringe is removed to be filled ;
ivhile in filling the syringe one must be careful alsa
to remove all air by holding it in an inverted position
DISSECTION OF THE VASCULAR SYSTEM. 5 1
aftei' it is filled, and pushing tip the piston-i'-od until
the injection fiows from the end.
To inject the veins it will be more convenie7it to in-
ject the superior cava and inferior cava separately, hi-
tr educe a cannula filled with the blue injcctioji into each,
and then force in the injection as in the arteries until
the veins are well filled. A sponge should be at ha7td
during the ivhole process to sop up any liquid or injec-
tion material zvhich may escape into the thoracic cavity.
By this process of injection the heart is not left in good
condition for dissecting, but this is supposed to have
beeit done before.
The injectio7i of the arteries and veins can be made
also from the femoral artery and vein of one of the legs,
injecting in each case tozuard the heart and first wash-
ing out the blood with salt solution. This method,
however, is not so likely, in inexperienced hands at least,
to give good results. After injecting the animal must
be left some little time before using to allow the plaster
to set.
A. THE DESCENDING AORTA.
Find the aorta just beyond the arch, and dissect
toward the posterior. Turn the heart and lungs
toward the right, dissecting along the left side of the
thorax. If necessary cut off the ribs on this side nearer
to the vertebral column.
1. The Intercostal Arteries come off from the aorta
in pairs in the spaces between the ribs ; they pass out-
ward alono^ the lower or posterior margins of the ribs.
The first intercostal from the aorta supplies the 5th
or sometimes the 4th rib, giving- a branch to the rib
above. The ist, 2d and 3d ribs are supplied by the
superior intercostal artery (see below).
2. The Bronchial Arteries arise either from the 3d
$2 DISSECTION OF THE VASCULAR SYSTEM.
aortic intercostal or from tlie aorta at that level, pass
beneath the oesophagus to reach the root of the
lungs, and thence penetrate the lungs, following the
bronchi.
3. The Cceliac Axis is a large branch given off from
the aorta as it pierces the diaphragm ; it passes for a
short distance into the abdominal cavity, and then di-
vides into three branches, as follows :
a. The Hepatic Artery, the most anterior
branch, passes beneath the oesophagus at its junction
with the stomach, sends one or two large branches to
the liver, the true hepatic artery, one branch to the
duodenum, and finally is distributed to the pancreas.
b. The Coronary Artery, the smallest of the
three branches, is distributed chiefly along the small
curvature of the stomach.
c. The Splenic Artery, the most posterior divi-
sion, splits into two main branches distributed chiefly
to the spleen. Each sends branches to the stomach
along the great curvature, and some smaller branches
are given off to the pancreas also.
4. The Superior Mesenteric Artery arises from the
aorta a short distance posterior to the coeliac axis. It
gives off a number of branches which supply the small
intestine and the greater portion of the large intes-
tine. Follow its course in the mesentery.
5- Posterior to the last two small arteries are given
off, that on the left side being somewhat anterior to
the other. Each divides into two branches, one of
which passes anteriorly, the phre^iic arteiy, to supply
the diaphragm, while the other is distributed to the
muscles of the abdominal wall. This latter branch
supplies also the adrenal bodies.
6. The Renal Arteries are two large trunks, one on
iriT. MAXILLARY
TEMPORAL
POST. AURICULAR
BRANCH TO 5UBMX
LEFT
SUBCLAVIAN
TO ABDOMINAL WALL
Fig. 4. — Arterial System of the Dor,.
DISSECTION OF THE VASCULAR SYSTEM. 53
each side, going directly to the kidneys. The artery
on the left side is somewhat posterior to that on the
right. Each artery as it enters the hilus of the kidney
splits into two or more branches.
7. Muscular Branches. Posterior to the renal arteries
several muscular branches may arise which are dis-
tributed to the muscles of the abdominal wall.
8. The Spermatic Arteries. In the male they form
two small branches of the aorta arising some distance
posterior to the renals and going to the testes. They
pass to the inguinal canal, and reach the testes in the
spermatic cords. In the female they are known as the
0: criini arteries, and pass more directly outward to
reach these bodies, being distributed to them and to
the anterior portion of the oviducts.
9. The Inferior Mesenteric Artery comes off from the
aorta some distance posterior to the spermatics, and is
distributed to the rectum and to the lower portion
of the large intestine.
10. The Iliac Arteries. Below the inferior mesenteric
the aorta divides into three branches, the two external
iliacs and a median trunk ; this latter soon divides again
into three branches, the two internal iliacs and a
median sacral or caudal artery.
11. The Internal Iliacs. Open the pelvis as directed
in the dissection of the reproductive organs. Each
internal iliac gives off just beyond its origin a small
branch, the superior vesical, which passes to the blad-
der ; each iliac then divides into two main branches,
the pudic and the sciatic. The pudic lies more to the
outer side ; followed out it breaks into two branches,
one of which, the internal pjidic, is distributed to
the genital organs in the pelvis — in the female to
the vagina, vestibule, and uterus ; the other seems to
54 DISSECTION OF THE VASCULAR SYSTEM.
correspond to the external pudic, beino;- distributed to
the external i^enital organs. This arrangement is dif-
ferent from that in man.
The second chief division of the internal iliac, the
sciatic, after giving off two large branches, t\\Q gluteals ^
which supply the muscles on the back of the pelvis,
passes along with the sciatic nerve through the sacro-
sciatic foramen to reach the exterior of the pelvis,
where it is distributed chiefly to muscles.
12. The External Iliacs pass beneath Poupart's liga-
ment to reach the front of the thigh, where they are
known as the femoral arteries. Before leaving the
abdomen each gives off a large branch, which seems
to have no homologue in human anatomy. This
branch in turn gives off one or two branches, the
epigastric artery, which is distributed to the muscles
of the anterior abdominal wall, and then passes be-
neath Poupart's ligament to reach the inner portion
of the thigh, where it is distributed chiefly to the large
adductor muscles.
13. The Femoral Artery runs for some distance just
below the sartorius muscle, giving off several
branches to the muscles, and one long branch, the
sapJicii02is artery, which passes to the leg, lying
below the skin. The femoral next bends sharply
inward to reach the back of the knee-joint, where it is
named the popliteal artery; this divides into two
branches, one rather large which passes into the leg
between the tibia and fibula, and finally reaches the
front of the leg. It corresponds to the anterior tibial
of human anatomy, and may be followed down upon
the dorsum of the foot. The second, smaller division
sends branches to the lower portions of the muscles
DISSECTION OF THE VASCULAR SYSTEM. 55
of the thigh and the gastrocnemius ; it represents the
postei^ior tibial.
B. VEINS BELONGING TO THE SYSTEM OF
THE FOST-CAVA.
1. The Post-cava {inferior vena-cava). Follow its
course to the diaphragm. It receives no branches in
the thoracic cavity.
2. The Hepatic Veins. Where the cava pierces the
diaphragm it receives two hepatic veins, one usually-
larger than the other.
3. The Phrenic Veins empty into the cava at about
the same level as the hepatic veins. They bring back
blood from the diaphragm.
4. The Renal Veins. Follow the post-cava along the
dorsal wall of the abdomen. At first it is partly im-
bedded in the liver ; just below the liver it receives the
two large renal veins coming directly from the kid-
neys. The left is slightly posterior to the right.
5. The Spermatic (<9zv?7-/(7;/) Veins, corresponding to
the spermatic arteries. The one on the left side empties
into the left renal vein, the one on the right side di-
rectly into the cava.
6. The Iliac Veins. Below the renal the cava re-
ceives several veins from the muscles of the abdominal
wall, and finally divides into two large branches, the
C0VWW71 iliac veins. Each of these in turn divides
into an external and an internal iliac vein which brins"
back blood from the regions supplied by the arteries of
the same name.
56 DISSECTION OF THE VASCULAR SYSTEM.
C. THE HEPATIC PORTAL SYSTEM OF VEINS.
The Portal Vein is the large vein lying in the mes-
entery which collects venous blood from the stomach,
pancreas, spleen and intestines, and passes into the
under side, of the liver. Within this organ it again
breaks up into capillaries, the blood from which is
finally collected into the hepatic veins which empty
into the post-cava. The portal can easily be found on
the under side of the liver; it is formed from two
large branches, one from the intestines and one from
the spleen, pancreas and stomach. It breaks up into
branches which enter the diflferent lobes of the liver.
D. VEINS BELONGING TO THE SYSTEM QF
THE PRyE-CAVA.
1. The Pras-cava {superior vcna-cavd). A descrip-
tion of this vein has been given in the chapter on the
dissection of the thoracic viscera.
2. The Vena Azygos. Make out again the course
of this vein, and the point where it opens into the
prae-cava.
3. The Vertebral Veins. The vein on the right
side opens into the cava anterior to the azygos. Trace
it back to its emergence from the vertebral canal of
the spinal column. The vein on the left side opens
into the left brachio-cephalic or innominate vein.
They bring back blood from the brain, etc.
4. The Sternal Veins. The vein on the right side
opens into the pr?e-cava anterior to the vertebral.
On the left side it opens into the brachio-cephalic be-
yond the vertebral. They bring back blood from the
sternum and the anterior wall of the thorax.
TEMPORAL'
PHRENIC
HEPATIC<
TO ABDOMINAL WALL I
SPERMATIC
ILIO LUMBAR
y
* HEPATIC
NF. VENA CAVA
SPERMATIC
pio. 5. —Venous System of the Dcc\
DISSECTION OF THE VASCULAR SYSTEM. 57
5. The Brachio-cephalic {innominate) Veins- The
two large veins which unite to form the prae-cava.
Each after a short course divides into the sub-clavian
and external jugular.
6. The Sub-clavian Vein brings back blood from
the arm, shoulder, etc. Beyond the point where it
joins the external jugular it receives the siib.-scapular
vein. Followed into the arm it will be found to re-
ceive a number of muscular branches.
7. The External Jugular passes toward the head,
lying just below the skin in its course through the
neck. Near the level of the larynx the jugular
divides into two branches, t\\Q facial "mx^ the temporal,
brincringf back blood from the head. The sub-maxil-
lary gland lies between these two veins and sends a
small vein to each of them. The facial veins of the
two sides are united by a wide cross-branch — the
tra7isvcrse vein.
8. The Internal Jugular. Near the junction of the
external jugular and s.ub-clavian the former receives
the internal jugular, which has a deeper course along
the side of the trachea. It brings back blood from
the brain.
E. THE ARTERIES OF THE ANTERIOR POR-
TION OF THE BODY.
1. The Arch of the Aorta. Clean the fat, etc., from
the arch. The following branches are given off from it :
2. The Brachio-cephalic {innominate) Artery, given
off nearest to the heart.
3. The Left Sub-clavian Artery, given off separately,
and distributed to the left arm, shoulder, etc.
4. The Common Carotid Arteries. Dissect out the
brachio-cephalic trunk. The two common carotids
58 DISSECTION OF THE VASCULAR SYSTEIu.
are given off separately though close together, and
pass forward in the neck, one on each side of the
trachea.
Make a median mcision along the ventral stirface
of the neck from the larynx to the sternum. Clear
away the muscles lying on the trachea and the common
caj'otids luill be exposed. Each gives off the following
brandies :
5. The Superior Thyroid Artery, given off at the
level of the thyroid body, to which it is chiefly dis-
tributed.
6. The Internal Carotid. At the level of the larynx
the common carotid divides into the internal and ex-
ternal carotid. The former is much smaller and
passes to the base of the skull, which it enters through
the carotid foramen, being one of the arteries which
supplies the brain with blood.
7. The External Carotid seems to be the direct
continuation of the common carotid. It gives off the
following branches :
8. The Occipital Artery is a small branch arising
close to the internal carotid and running parallel to it.
It is distributed to the exterior of the skull in the
occipital region.
9. The Lingual Artery, the third branch of the ex-
ternal carotid, is a large artery distributed chiefly to
the tongue.
10. The Facial Artery is a small branch given off a
short distance beyond the lingual. It usually gives a
branch to the submaxillary gland.
11. The Posterior Auricular, the next branch, is given
off from the outer side of the carotid, supplying the
tissues on the posterior side of the ear. A short dis-
tance from its origin it may give a branch to the sub-
maxillary gland.
DISSECTION OF THE VASCULAR SYSTEM. 59
12. The Internal Maxillary Artery. Just beyond the
orifrin of the facial the external carotid divides into
two branches, the larger being the internal maxillary,
distributed to the inner side of the mandible, maxilla,
etc.; the smaller branch is
13. The Temporal Artery, distributed to the mus-
cles and integument of the side of the head.
14. The Right Sub-clavian Artery. Beyond the ori-
gin of the two common carotids the brachio-cephalic
artery is known as the right sub-clavian artery. The
chief branches are as follows :
15. The Vertebral Artery, a branch which passes
dorsally to reach the vertebral canal of the spinal
column, through which it reaches the interior of the
skull to supply the brain.
16. The Superior Intercostal Artery comes off quite
close to the vertebral, sometimes forming a branch of
it. It is distributed to the three anterior ribs.
17. The Sternal {intcnial mainuiary>) Artery, given
off a little beyond the last. In company with the
artery of the other side it passes along the under sur-
face of the sternum, supplying it and the adjacent por-
tions of the ribs.
18. The Thyroid Axis arises usually somewhat
nearer the heart than the last, but from the anterior
border of the sub-clavian. It seems to be homologous
with the thyroid axis of human anatomy, but has a
different distribution. It divides into branches which
supply the muscles of the root of the neck and of
the supra-scapular region.
19. The Pectoral Branches. Beyond the thyroid
axis the sub-clavian artery, now known as the axillary,
gives off one or two branches which are distributed
chiefly to the pectoral muscle.
6o DISSECTION OF THE VASCULAR SYSTEM.
20. Near the point where the axillary artery enters
the arm it gives off a large branch from its posterior
border which divides into three arteries :
a. The Long Thoracic Artery, a small branch
passing along the side of the thorax and distributed
chiefly to the pectoral and latissimus dorsi muscles.
b. The Sub-scapular Artery, a large branch dis-
tributed to the sub-scapular muscles.
c. The Circumflex Artery, passing obliquely
round the humerus and distributed chiefly to the
triceps extensor muscle of the arm.
21. The Brachial Artery. After reaching the arm
the axillary artery is known as the brachial. It gives
off muscular branches in the arm, and at the elbow
divides into two branches for the fore-arm.
CHAPTER V.
MUSCLES OF THE THORAX— DISSEC-
TION OF THE NECK— THE SYMPA-
THETIC SYSTEM— THE BRACHIAL
PLEXUS AND THE LARYNX.
MUSCLES OF THE THORAX.
Make a median incision throngh the skin of the
thorax along the line of the sternum, and transverse
incisions at the shoulders. Dissect off the flaps of skin
from the thorax, shoulder, and npper part of the ab-
domen. In removing the skin notice the thin skin-nms-
cle extending over the posterior and outer portion of the
thorax and the abdomen. Remove the fat and fascia
from the thorax, and the group of pectoralis muscles
will be exposed.
I. Pectoralis Major Muscle. This name is applied
to the large muscle arising from the sternum and ribs,
and inserted into the humerus. In reality the muscle
can be divided into five or more separate divisions or
muscles, whose origin and insertion extend along the
lines named. The two or three most anterior of these
divisions arise from the anterior end of the sternum
as far back as the junction of the 3d rib. They form a
group of fibres which pass nearly transversely outward
to be inserted into the middle and lower third of the
shaft of the humerus. Cut across the fibres of this
62 MUSCLES OF THE THORAX.
band and reflect the cut ends ; the remaining divisions
of the pectoralis will be fully exposed. The fibres
arise along the whole length of the sternum, pass
obliquely forward and outward to be inserted into the
head and upper part of the shaft of the humerus, and
partly also into the fascia covering the biceps muscle
of the arm.
C2tt across the pectoralis unisclc and rejiect the cut
ends.
2. The Sternalis Muscle is a small fan-shaped mus-
cle lying lateral to the anterior end of the sternum.
The muscular fibres arise at the level of the cartilagi-
nous portion of the 2d and 3d ribs from a strong
fascia ; they pass obliquely forward and outward to be
inserted into the ist rib.
3. The Scaleni Muscles arise from the transverse
processes of the last four cervical vertebrae, and are
inserted into the ribs. In the dog four scaleni may
be distinguished lying close to one another :
a. The Scalenus Primus lies nearest to the ven-
tral mid-line ; it arises from the transverse processes
of the 5th and 6th cervical vertebrae, and is inserted
into the ist rib where the bony and cartilaginous por-
tions meet.
b. The Scalenus Secundus is much longer; it
arises from the transverse processes of the 4th and 5th
cervical vertebrge by two tendons, and is inserted into
the bony ribs from the 3d to the 7th.
c. The Scalenus Tertius lies dorsal to the ante-
rior end of the secundus ; it arises in common with it,
but is inserted into the bony portion of the ist rib to
the outer side of the insertion of the primus.
d. The Scalenus Ouartus is a very small muscle
inserted into the ist rib between the primus and
DISSECTION OF THE NECK. 63
tertius ; it arises from the transverse process of the
7th cervical vertebra.
4. The Intercostal Muscles. Remove the above-
named muscles and fat, etc., from the thorax ; the in-
tercostal muscles lying between the ribs will be ex-
posed.
a. The External Intercostals form the external
layer passing from the posterior margin of one bony
rib to the anterior margin of the succeeding one ; the
fibres have an inclination inward and to the posterior.
This layer ceases at the cartilaginous ribs. The layer
of muscle between these portions of the ribs forms
the mtercartilagmoiis muscles, and their fibres have an
inclination in the opposite direction.
b. The Internal Intercostals. Dissect off the
external intercostals between two or three of the ribs,
and the internal intercostals will be exposed ; these
also pass from one bony rib to the other, but have an
inclination outw^ard and to the posterior.
DISSECTION OF THE NECK.
Make ail incision along the mid-line of the neck
tJiJ'oiigh the skin, and the necessary transverse incis-
ions at the shoulder. Lay back the flaps of skin o?i
both sides.
I. The Platysma Myoides is a skin-muscle found
in the neck which may have been reflected with the
skin. The chief bundle of fibres in it arises from the
dorsal wall of the anterior portion of the thorax, and
comes obliquely around to the ventral surface of the
neck, and continues forward to the head. Scattered
muscular fibres pass transversely from this during its
course toward the ventral mid-line of the neck. The
muscle is attached only to the skin.
64 DISSECTION OF THE NECK.
2. The Hyoid Bone lies just anterior to the larynx.
Determine its shape by feeling through the muscles
covering it. The body is a short transverse bar of
bone, and from it two horns — posterior cornua —
may be felt passing posteriorly to the thyroid cartil-
age of the larynx. Two longer anterior horns pass
to the base of the skull to be attached to the temporal
bone.
3. The Sterno-mastoid Muscles form a pair of broad
muscular bands arising from the anterior end of the
sternum, and passing obliquely forward, diverging
from each other, to be inserted into the mastoid por-
tion of the temporal bone.
Cut these muscles at the sternal insertion, and re-
flect them fo7^ivard.
4. The Sterno-hyoid Muscles, one on each side, lie
along the ventral mid-line of the neck. Separate the
two along the mid-line, and the trachea will be ex-
posed. Each is a flat band arising from the anterior
end of the sternum and the ist rib, and inserted into
the hyoid bone.
Cut the sterno-hyoids at the anterior end and reflect
backwards.
5. Sterno-thyroid Muscles, one on each side of the
neck. Each is a slender band of muscle arising from
the anterior end of the sternum with the sterno-hyoids,
and passing obliquely forward to be inserted into the
side of the thyroid cartilage of the larynx.
Cut the ste^mo-thyroids at the anterior end and re-
flect backwards ; the trachea will be fully exposed.
6. The Thyroid Glands are two oval bodies lying
one on each side of the trachea just posterior to the
larynx. Usually these are entirely separated from each
other (differing in this respect from the same struct-
DISSECTION OF THE KECK. 65
ures in man), but occasionally the posterior ends are
connected by a slender band or isthmus passing across
the trachea.
7. The Mylo-hyoid Muscle lies anterior to the hyoid
bone, between the rami of the mandible It is a
thin muscular sheet which arises from the hyoid bone
on each side, and is inserted along the inner side of
the mandible ; it meets its fellow in the mid-line and
forms the floor of the mouth.
8. The Digastric Muscle is the thick muscle cover-
ing the angle and part of the body of the mandible.
It arises from the occipital bone of the skull, and is
inserted into the mandible, serving to depress the
jaw. In the dog it is not truly a digastric muscle,
though a tendinous line may be observed running
across its belly somew^hat posterior to the middle.
9. The Vago-sympathetic Nerve. The combined
trunk of the vagus and sympathetic nerves lies along
the trachea on each side, in the same sheath with the
carotid artery and internal jugular vein. Expose it
on the left side at the middle of the neck, and dis-
sect it anteriorly. To expose its origin from the
skull, cut the digastric muscle at its mandibular inser-
tion and reflect it backward. When the parts are a
little more dissected it will be well to remov^e this
muscle entirely, taking care not to cut the hypoglossal
nerve.
10. The Superior Laryngeal Nerve is a branch of
the vagus ; it arises far forward, somewhat beyond the
anterior end of the larynx. At its origin from the
vagus there is an enlargement of that nerve known as
the ganglion of the trunk of the vagus. Trace the
superior laryngeal to the larynx, which it enters and
supplies with sensory fibres, giving also motor fibres to
(>^ DISSECTION OF THE NECK.
one of the intrinsic muscles of the larynx, the crico-
thyroid. The superior laryngeal anastomoses with
the inferior laryngeal by a large branch passing be-
neath the wing of the thyroid cartilage.
11. Somewhat posterior to the origin of the superior
laryngeal the sympathetic trunk separates from the
vagus. Follow it forward a short distance until it
ends in the super i 07^ cervical ganglion.
Just anterior to its ganglionic enlargement the vagus
enters the skull. Emerging at about the same point
the following cranial nerves can be found :
12. The Hypoglossal, or 12th Cranial Nerve, is very
large ; it runs forward beneath the digastric and mylo-
hyoid muscles to enter the tongue, to which it supplies
motor fibres. It leaves the skull through the anterior
condylar foramen.
a. The Descendens Hypoglossi, a branch of the
hypoglossal, arises from the convex border of the
loop made by the hypoglossal and passes posteriorly
along the neck superficial to the vagus and carotid ;
in its course it soon unites with a branch of the first
cervical spinal nerve, and from the common trunk
branches are given to the sterno-thyroid and sterno-
hyoid muscles. The nerve is very long, reaching to
the posterior third of the neck.
13. The Spinal Accessory, or nth Cranial Nerve,
leaves the skull through the jugular foramen in com-
pany with the vagus and glosso-pharyngeal ; it runs
posteriorly upon the sterno-mastoid muscle, within
which it soon disappears. It supplies this and other
muscles of the neck with motor fibres.
14. The Glosso-pharyngeal, or 9th Cranial Nerve,
appears in the same place close to the vagus; it turns
inward to the mid-line and disappears in the muscles
DISSECTION OF THE NECK. 6/
enveloping the pharynx. It supplies the tongue and
pharynx with sensory fibres, and gives some motor
fibres also to the pharynx.
15. The Lingual Nerve. If not previously done,
cut through the mylo-hyoid muscle ; the lingual will
be exposed coming out from under the mandible. It
runs toward the mid-line and disappears in the tongue,
which it supplies with gustatory fibres. This nerve is
a branch of the inferior maxillary division of the 5th
or trigeminal nerve.
Co7itimie the dissection of the vagosympathetic
trunk posterioi'ly. In ordei" to show the relations of
this trinik at the root of the neck and in the thorax,
open the latter freely, as in the dissection of the thoracic
viscera, double-ligature the large veins at the root of
the neck, divide thc7n between the ligatures, and then
dissect out the vagosympathetic trunk.
16. Inferior Cervical Ganglion. At the root of the
neck the vago-sympathetic ends in a large ganglion,
the inferior cervical ganglion, from which several
small branches are given off, passing toward the heart
and entering the cardiac plexus. At the ganglion
the two nerves separate as shown in Fig. 6.
17. The Thoracic Vagus continues posteriorly from
the ganglion, giving off also some small branches to
join the cardiac plexus. Near the base of the heart it
gives ofT a large branch, the recurrent or inferior laryn-
geal, which on the left side curves round the aorta and
passes anteriorly along the side of the trachea in the
neck, where it can easily be found and followed to its
termination in the larynx, to the muscles of which it
gives motor fibres. Dissect out the communicating
branch to the superior laryngeal which passes beneath
the wing of the thyroid cartilage. On the right side
VAGO-SYMPATHETIC,
INFERIOR CERVK
HEART BRANCHES. '
RECURRENT LARYNgI
RIGHT VAGUS,
COELIAC
GANG
AND SOLAiR-
PLEXU,S
BRANCHES TO
ABDOMINAL
ORGANS.
XII. R.C.
XIII. RAMUS COMMUNICANS.
.LUMBAR GANGLION.
Fig. 6 — Diagram of titf. Vagv^ and Sympathetic Nerves.
DISSECTIOX OF THE NECK. 69
this nerve curves round the sub-clavian artery, and
then continues forward into the neck as described.
After giving off other branches to the lungs, the
vagus descends along the oesophagus, and finally
divides into two branches, one of which passes to the
dorsal side of the oesophagus, and is there joined by a
similar branch from the right vague ; the other division
passes to the ventral side of the oesophagus, where it
joins the similar ventral branch of the right vagus.
The two new trunks thus formed can be traced to the
stomach ; each ends in a plexus of nerve-fibres, which
are distributed to the stomach and make connections
also with the solar plexus of the cfjeliac ganglia.
18. The Thoracic Sympathetic Trunk. From the
inferior cervical ganglion two branches pass to the
large \st thoracic ganglion, one above and one
below the sub-clavian artery, forming a ring known as
the '' annulus of Vietissensi' From this annulus one
or more small branches may be given off toward the
heart to join the cardiac plexus.
The I St thoracic ganglion is very large, and besides
its connections with the inferior cervical gives off the
following branches : a. A large branch, the vertebral,
passing forward to join with the two lower cervical
spinal nerves, b. A branch to the ist thoracic spinal
nerve, c. A branch to the 2d thoracic spinal, d. A
branch to the 3d thoracic spinal, and sometimes, e, a
branch to the 4th thoracic spinal.
From the ist thoracic ganglion the sympathetic
trunk continues backward along the spinal column,
and at intervals shows ganglionic swellings, usually one
for each rib after the 3d or 4th ; but this is sometimes
irregular. From each ganglion a branch passes to the
70 DISSECTION OF THE NECK
corresponding spinal nerve. These branches of com-
munication are known as the rami commiinicaiites.
In the posterior portion of the thorax, just after
c:ivino: off a ramus communicans to the 12th or the
13th thoracic spinal nerve, the sympathetic sends off a
large branch to the inner side, known as the splanchnic
nerve. This nerve passes through the diaphragm and
(in the dog) ends in a ganglionic enlargement, the
splanchnic ganglion. From this ganglion small
branches can be traced inward and forward, ending in
a larger nerve-mass, the cceliac ganglion, which lies just
posterior to the coeliac axis and on the ventral aspect
of the aorta. There is a similar arrangement on the
other side, the two coeliac ganglia being connected
with each other by cross-branches and sending very
numerous fine branches to the surrounding abdominal
organs, which form what is called the solar plcxns.
The solar plexus, as before mentioned, is connected
with the terminal plexuses of the vagi.
After giving off the splanchnic the sympathetic
may have one more ganglion in the thorax, from which
a ramus communicans is given to the 13th thoracic
spinal nerve, and a small branch, \\\t small splanchnic,
which joins the splanchnic ganglion. It then passes
through the diaphragm and continues as the abdomi-
nal sympathetic, which also has ganglionic enlargements
as in the thorax. From these ganglia branches arise
which form plexuses, similar to the solar plexus, for
the abdominal and pelvic organs. The two sympa-
thetic trunks finally unite at the posterior end of the
sacrum in an unpaired ganglion lying in the mid-line.
19. The Brachial Plexus in the dog is formed from
the 6th, 7th and 8th cervical spinal nerves and the
I St thoracic spinal nerve, and usually receives a small
DISSECTION OF THE NECK.
71
branch from the 2d thoracic spinal nerve. Shortly
after emerging from the vertebral canal these nerves
branch to form a complicated plexus, represented in
Fig. 7, from which branches are given off to the
arm, fore-arm, shoulder, etc. The plexus should be
dissected upon the side the least injured by previous
dissection ; in this case probably the right side. Cat
TO CLAVO-DELTOID
SUPRA-SCAPULAR
3 SUB-SCAPULAR
MUSCULO-CUTANEOUS
CIRCUMFLEX
JMUSCULO-SPIRAL
EDIAN
ULNAR
* ^S^RES MAJOR
'fOOs
Fig. 7. — Diagram of the Brachial Plexus of the Dog.
carefully through the muscles on the side of the verte-
bral column where the neck and thorax meet until some
of the nerves are exposed, and then from this trace
out the other members of the plexus. In order to
expose the plexus fully one must take great care not
to cut small branches, and must dissect slowly. The
following are the chief terminal branches of the plexus.
From which of the spinal nerves they are derived can
be seen from the figure, although the arrangement of
the plexus varies somewhat in different individuals,
a. Branch distributed chiefly to the clavo-deltoid.
']2 DISSECTION OF THE NECK.
b. Supra-scapular Nerve to muscles on the dorsal
side of the scapula.
c. Sub-scapular Nerve to muscles on the ventral
side of the scapula.
d. Musculo-cutaneous Nerve supplies the biceps
and may be traced finally to the elbow, where it breaks
up into fibres distributed to the skin of the elbow and
fore-arm.
e. Circumflex Nerve sends some branches to
the teres major and the sub-scapular muscles, and then
passes dorsally between the insertion of the teres major
and the triceps, giving off branches to the triceps and
the anterior deltoid muscles.
f. Musculo-spiral Nerve passes obliquely round
the humerus to the dorsal side to reach the radial side
of the fore-arm, where it divides into two branches, the
radial and posterior inter-osseus nerves. It supplies
the muscles and skin of the back of the arm, and in
the fore-arm is distributed to the muscles and the
digits of the radial side.
g. The Median Nerve.
h. The Ulnar Nerve. These two nerves arise
together from the 8th cervical and ist thoracic nerve ;
they pass to the fore-arm and hand, to which they are
distributed.
i. A branch to the teres major and latissimus dorsi
muscles.
k. The Interal Cutaneous Nerve. Besides giv-
ing some branches to the pectoral muscles this is dis-
tributed to the skin on the inner side of the arm.
20. The Intrinsic Muscles of the Larnyx.
To dissect these muscles it is better to remove the
larynx and epiglottis entirely from the body. Cut
DISSECTION OF THE NECK. ^l
through the trachea below the larynx and through the
pharynx above the hyoid bone ; in taking out the larynx
dissect it free from the cesophagits, zuhich adheres to its
dorsal side. The intrinsic laryngeal muscles form six
pairs, and with the exception of the arytenoid muscles
correspond very zvell to those of human anatomy. The
illustrations in the text-book of human anatomy may
therefore be consulted if necessary.
a. The Crico-thyroid Muscle is a short trianfrular
muscle arising from the ventral and lateral faces of the
cricoid, and is inserted into the posterior border of the
thyroid and its posterior cornu.
b. The Posterior Crico-arytenoid Muscle arises
from the flattened dorsal surface of the cricoid, and
is inserted into the arytenoid cartilages, the fibres
passing obliquely forward and outward.
c. The Lateral Crico-arytenoid is concealed by
the wing of the thyroid. Cut through the posterior
horn of the thyroid where it joins the cricoid and
lift up the wing of the thyroid. The muscle is seen as
a band of fibres arising from the lateral surface of the
cricoid, and passing obliquely toward the dorsal side
to be inserted into the arytenoid.
d. The Thyro-arytenoid Muscle is anterior to
the last, the fibres having somewhat the same general
direction. It consists of two nearly separate muscular
bands which arise from the internal face of the ventral
portion of the thyroid and pass dorsally to be inserted
into the arytenoid.
e. The ARYTENO-EPicLOTTiDEANlies anterior to the
last and nearly parallel with it. It arises from the
arytenoid cartilage and passes ventrally and forward
to end in the aryteno-epiglottidean fold. The muscles
74 DISSECTION OF THE NECK.
of the two sides at their origin are connected by a
cross-shp of muscular fibres.
f. The Arytenoid Muscle. The fleshy portion
arises from the arytenoid cartilage just anterior to the
insertion of the posterior crico-arytenoid, and is in-
serted into the inner angle of the arytenoid of the
opposite side.
CHAPTER VT.
DISSECTION OF THE BRAIN.
The brain should be removed immediately after kill-
ing the dog, and placed in alcohol for a week or longer
before dissecting. To prevent flattening wrap the brain
in raw cotton before placing it in the alcohol.
To remove the brain, first skin the head, and citt off
the muscles attached to the sknll especially in the occipi-
tal region. Then zvith a small hand-saw carefully sazu
tJirougJi the bone in a horizontal plane round the skull
so as to isolate the cap of the skull. U^ith a little care
this can be done without tearing the brain at all. Re-
move the cap and with bone forceps chip off as much
of the sides of the skull as is necessary to fully uncover
the brain. Take out the brain by lifting it up care-
fully from either end, and cutting the nerves that come
off from the ventral surface. Cut the nerves so as to
leave as much of a stump as possible adhering to the
brain.
In addition to the brain hardened in alcohol it will
be convenient to harden tivo other brains in JllUllers or
'j6 DISSECTION OF THE BRAIN.
E^dicki s^ liquid for a month or more, then wash them
well in water and keep in 8or« alcohol. One should be
divided longitudinally by a cut through the great longi-
tudinal fissure and the corpus callosum, and the other
should be divided into a series of cross-sections, each
aboiU \ in. thick, from the anterior to the pos-
terior end of the brain. After having dissected an
alcohol brain according to the following directions the
study of these cross and longitudinal sections zuill prove
very instructive in giving the proper relations of the
different parts to one another.
A. THE BRAIN MEMBRANES.
1. The Dura Mater will be exposed in removing the
brain. It is the tough membrane lining the inside of
the skull. It projects in between the lobes of the
cerebrum as a vertical fold, the falx cerebri, and as a
transverse fold, the tentorium, between the cerebrum
and cerebellum.
2. The Pia Mater is a much thinner membrane,
closely investing the brain ; it is very vascular, since the
blood-vessels supplying the brain are carried in it.
* The composition of these liquids is as follows :
muller's liquid.
Water lOO parts.
Potassium bichromate 2 parts.
Sodium sulphate i part.
ERLICKl'S LIQUID.
Water lOO parts.
Potassium bichromate 2^ parts.
Copper sulphate -J part.
The brains should be immersed in a relatively large quantity of these
liquids, and during the first week of the hardening the liquid should be
changed either every day or every second day. The Erlicki's liquid acts
more quickly and is probably the better one of the two to use.
DISSECTION OF THE BRAIN. 77
B. EXTERNAL CHARACTERS OF THE BRAIN.
I. The Dorsal Surface of the Brain.
a. The Cerebral Hemispheres occupy the greater
portion of the dorsal surface. They show a number of
well-marked fissures and convolutions (sulci and gyri).
The two hemispheres are connected by a broad white
commissure, the corpus caliosiciu, which may be seen
by gently separating the two hemispheres and tearing
or cutting away the pia mater which stretches across
from one to the other. The corpus lies well toward
the ventral surface of the hemispheres.
b. The Olfactory Lobes are a pair of large flat
tened triangular lobes projecting from the ventral sur-
face of the brain, but visible in a dorsal view.
c. The Corpora Quadrigemina may be exposed
by pressing apart the cerebellum and the cerebrum, and
tearing away the intervening pia mater. They consist
of two pairs of rounded elevations, of which the pos-
terior pair are the larger.
d. The Cerebellum. The whole surface is marked
with narrow folds which run both in a transverse and
a longitudinal direction. They are seen better if the
pia mater is stripped off". The cerebellum is divided
into a large median lobe, the vermis, in which the
folds run transversely, and two lateral lobes or hemi-
spheres in which the folds have a general longitudinal
direction. On the outer and under sides of the hemi-
spheres the \oosQjioccular lobes will be seen if the brain
has been carefully removed.
IViih a pair of forceps tear away carefully the pia
mater beneath and posterior to the cerebellum to bring
into view the medzilla oblonp-ata.
e. The Medulla Oblongata lies beneath and
78 DISSECTION OF THE BRAIN.
posterior to the cerebellum, and posteriorly passes into
the spinal cord. Anteriorly the medulla widens out to
form l\\QfoiLrtJivcntricle, which lies immediately under
the cerebellum. This lozenge-shaped or oval cavity is
covered over anteriorly by a thin sheet of nervous mat-
ter, the valve of Vieiisscns or the anterior medullary
vehim, easily seen, by pressing backward the cerebel-
lum, as a thin membrane running from the posterior
border of the corpora quadrigemina over the anterior
part of the fourth ventricle. Posteriorly the fourth
ventricle is roofed in by a similar membrane lyings
immediately under the cerebellum and probably re-
moved in exposing the ventricle, the posterior medul-
lary velum.
f. Floor of the Fourth Ventricle. About the
middle are seen two transverse bands of fibres — medul-
lary or auditojy strict — the origin of the auditory
nerve. The posterior end of the ventricle where the
lateral walls converge is known as the calai7ius scrip-
torius.
g. Fasciculi of the Medulla Oblongata. Pos-
terior to the calamus scriptorius the dorsal surface of
the medulla shows a median fissure continuous with
the posterior median fissure of the cord. On each
side of this lies a rounded eminence, the fascicuhis
gracilis (posterior pyramid). Just exterior to this on
each side is the small fasciculus cuueatus. If these
two fasciculi are followed forward they run into a
rounded eminence on each side, forming the lateral
boundary of the fourth ventricle, the restiform bodies,
and these followed anteriorly are seen to pass up into
the cerebellum, forming the posterior peduncles of the
cerebellum, making a connection between the cere-
bellum and cord.
DISSECTION OF THE BRAIN. 79
2. The Ventral Surface of the Brain.
a. The Cekehral Hemispheres meet in front, but
diverge posteriorly. The vertical fissure separating the
hemispheres (on the dorsal side) is continued around
for some distance on the ventral surface. Note the
large olfactory lobes lying along the ventral surface.
b. The Optic Chiasma. Lying at the end of the fis-
sure is a transverse band of nerve-fibres, the chiasma.
The optic nerves arise from it anteriorly, and poste-
riorly it passes backward and outward, forming the
optic tracts, which finally end in the corpora quadri-
gemina. By carefully lifting up the side of the cere-
bral hemisphere each tract may be followed as it passes
over the optic thalamus, in which some of the fibres
end, until it reaches the corpora quadrigemina.
c. The Lamina Cinerea is exposed by turning
back the optic chiasma. As will be seen later, it forms
the anterior wall of the third ventricle. If gently torn,
the third ventricle will be exposed.
d. The Infundibulum lies immediately behind the
chiasma. It is a median prolongation of the ventral
surface of the brain : at its apex is \\\^ pituitary body.
The infundibulum is hollow within, the cavity being
a prolongation of the third ventricle.
e. The Corpora Albicantia are two small white
eminences posterior to the infundibulum.
f. The Crura Cerebri are the two eminences
lying outside of and posterior to the corpora albicantia.
They pass forward and upward into the cerebral
hemispheres, diverging from each other ; they form
the connection between the cerebral hemispheres and
the medulla. (To expose them clearly the pia mater
must be cleaned off, taking care not to injure the
cranial nerves.)
80 DISSECTION OF THE BRAIN.
g. The Pons Varolii is the large band of trans-
verse fibres lying back of the crura cerebri. It con-
sists of transverse commissural fibres connecting the
two sides of the cerebellum. Followed up toward
the dorsal side it will be seen to pass into the cere-
bellum on each siae, forming the middle peduncles of
the cerebellum.
h. Corpus Trapezoideum, a band of similar trans-
verse fibres lying posterior to the pons, and inter-
rupted in the mid-line by the anterior pyramids.
i. The Anterior Pyramids, the two bands of
longitudinal fibres lying on the ventral surface of the
medulla and ending (apparently) anteriorly in the
pons. The anterior median fissure also ends at the
pons.
3. The Roots of the Twelve Cranial Nerves.
a. The Olfactor\ or I. cranial nerves arise from
the under side of the olfactory lobes; most probably
they were torn off in removing the brain.
b. The Optic or II. cranial nerves arise from the
anterior border of the optic chiasma.
c. The Oculo-motor or III. cranial nerves arise in
the space between the' two crura cerebri.
d. The Patheticus or IV. cranial nerve is very
small, and on the ventral surface appears in the space
between the cerebral hemisphere and the crus cerebi
on each side. The real origin is from the valve of
Vieussens on the dorsal side of the brain. It may be
followed back easily to this point.
e. The Trigeminal or V. cranial nerve is very
large, and arises from the sides of the pons by two
roots. The smaller, inner one is the motor root ; the
larger, outer one the sensory root.
f. The Abducens or VI. cranial nerve is small, and
DISSECTION OF THE BRAIN. 8 1
arises from the ventral surface of the medulla back of
the pons,
g. The Facial or VII. cranial nerve arises from the
outer side of the anterior border of the corpus trape-
zoideum behind the origin of the trigeminal.
h. The Auditory or VIII. cranial nerve arises just
outside of and behind the facial nerve. It is laro-er
than the facial.
i. The Glossopharyngeal and the Vagus, the
IX. and the X. cranial nerves, arise together by a num-
ber of slender roots from the side of the medulla behind
and to the outer side of the origin of the auditory nerve.
j. The Spinal Accessory or XI. cranial nerve
arises by a number of roots from the side of the cord
and medulla, extending forward as far as the origin of
the vagus nerve.
k. The Hypoglossal or XII. cranial nerve arises
from the ventral surface of the medulla close to the
mid-line and just outside of the anterior pyramids.
C. THE INTERNAL STRUCTURE OF THE BRAIN.
1. The Cerebral Hemispheres (^Fore-brain or pros-
encephaloii).
With a razor kept wet with alcohol take off hori-
zontal slices of the cerebral hemispheres, cutting care-
fully tmtil the corpus callosum is reached.
a. Note the structure of the cerebral hemispheres:
the outer cortical layer of gray matter folded into the
interior at the sulci, and the inner or medullary por-
tion of white matter — nerve-fibres.
b. Notice the direction of the fibres of the corpus
callosum, running transversely from one hemisphere
to the other.
82 DISSECTION OF THE BRAIN.
Remove carcfitlly with forceps and knife the corpus
callosiini lentil the lateral ventricles are exposed, taking-
care not to injure the fornix, which lies immediately
beneath.
c. The Lateral Ventricles, one on each side,
fully exposed after complete removal of the corpus
callosum. In each three chambers or horns may be
distinguished ; the anterior cornu, a narrow slit run-
ning forward and separated from the anterior cornu
of the other side by a vertical partition — the septum
lucidum ; the descending cormi, situated posteriorly
and curving downward and outward ; the posterior
cornu, situated at the most posterior end of the ven-
tricle, a small diverticulum running backward, very
inconspicuous in the dog.
d. The Septum Lucidum is the vertical partition
lying between the anterior cornua of the two ventricles.
It contains within its walls a small cavity, the so-
called 5th ventricle, not formed by the closing in of
the embryonic medullary tube like the other true
ventricles of the brain.
e. The Corpus Striatum is the oval mass pro-
jecting into each anterior cornu from the side of the
cerebral hemisphere. Only a part of the corpus
striatum is seen in the dissection ; the remainder is
concealed in the walls of the hemisphere. It is
originally an outgrowth from the floor of the vesicle
of the cerebral hemispheres, and contains two nuclei of
gray matter in its interior — the 7tticle7ts caudatus, con-
tained within the part which projects into the ven-
tricle, and the nuclezis lenticularis, contained within
the part buried in the wall of the hemisphere.
Lay open the descending cornu on one side by care-
fully cutting away the sides of the cerebral hemisphere.
DISSECTION OF THE BRAIN. 83
Note its extensive cotu^se, sweeping around ciownivai'd
and forzuard to the bottom of the temporal lobe of the
hemisphere.
f. The Hippocampus Major is the prominent con-
vex ridge lying along the floor of the descending
cornu.
g. The Fornix. T\\t posterior pillar of the fornix
is the narrow band of white fibres lying along the
anterior border of the hippocampus major. The pos-
terior pillars on each side followed forward meet just
at the posterior edge of the septum lucidum, and unite
for a short distance to form the body of the fornix ;
then bending downward they diverge again, forming
the anterior pillars of the fornix, which run toward
the base of the brain.
Ciit aivay the outer ivall of the anterior cornn on
the sajne side on zuhich the zuall of the posterior cornn
was removed.
h. The Foramen of Monro, one on each side, is
the slit-like opening underneath the body and anterior
pillar of the fornix. It leads into the 3d ventricle,
and is the passage of communication between the 3d
and the lateral ventricles.
To expose the 2id ventricle lift 7ip carefully the pos-
terior pillars of the fornix zvhcre they co7iverge and
tear tJiem azuay with the forceps Remove in the same
way the portion of the corp^is callosnm still left be-
tween the posterior pillars of the fornix and forming
the roof of the 3c/ ventricle.
Properly speaking, the corpus callosum does not
form the roof of the 3d ventricle. The true roof of
the ventricle is a portion of the pia mater known as
the vehtm interpositum which lies immediately be-
neath the corpus callosum. The velum interpositum
84 DISSECTION OF THE BRAIN.
gets into the interior through the great transverse
fissure of the brain between the cerebrum and cere-
bellum. At the anterior end of the ventricle it con-
tinues on through the foramen of Monro on each
side into the lateral ventricles, forming the choroid
plexuses. Each choroid plexus is a thin vascular fold
of membrane which passes backward into the descend-
ing horn of the lateral ventricle upon the hippocampus
major. If the corpus callosum is removed with suffi-
cient care these relations of the pia mater can easily
be demonstrated upon the dog's brain.
i. The 3D Ventricle is seen as a narrow slit begin-
ning just back of the anterior pillars of the fornix,
and extending posteriorly as far as the corpora
quadrigemina. While narrow from side to side, it is
quite deep.
2. The Optic Thalami {thalamencephaloii) are the
two oval masses forming the sides of the 3d ventricle.
a. The Pineal Gland is connected by a stalk to
the upper and posterior end of the 3d ventricle. It
was originally a diverticulum from this ventricle.
b. The Commissures of the 3D Ventricle.
The Middle Commiss7ire is very large, but delicate
and easily broken. It passes across the middle of the
ventricle between the optic thalami.
The Posterior Commissure is at the extreme pos-
terior end of the 3d ventricle, lying beneath the stalk
of the pineal gland ; It is a narrow band of white fibres.
The AnteiHor Commissure lies at the extreme ante-
rior end of the 3d ventricle, just where the anterior
pillars begin to diverge from each other. By cutting
the body of the fornix open vertically this commis-
sure can be brought into full view. It is a narrow
band of white fibres.
DISSECTION OF THE BRAIN. 85
Cutting through the middle commissure, the 3d
ventricle can be seen to pass downward and forward
toward the base of the brain, ending finally in the in-
fundil)ulum. This can be seen best in a median longi-
tudinal section of the brain. Posteriorly the 3d ven-
tricle passes into the aqttedttct of Sylvms just beneath
the posterior commissure. A bristle can be passed
backward easily along the aqueduct into the 4th ven-
tricle.
By scparatijig the posterior portion of the cerebral
hemisphere completely from the optic thalamus a good
view of the latter can be obtained, and the zuay i7i
wJiich the optic tract comes around from the ventral
surface of the brain to end partly in the tJialamtis and
partly in the corpora quadrigemina is nicely shown.
3. The Mid-brain or Mesencephalon.
a. The Corpora Quadrigemina. They form the
dorsal surface of the mid-brain, and surround the aque-
duct of Sylvius.
b. The Crura Cerebri form the base of the mid-
brain. They can be seen passing forward from the
anterior border of the pons to the optic thalamus.
The Anterior Crura of the Cerebellum pass
forward along the sides of the 4th ventricle from the
cerebellum to the corpora quadrigemina. The middle
and posterior crura have already been seen, but ought
to be located again at this point to get a complete
idea of all the connections of the cerebellum.
CHAPTER VII.
DISSECTION OF THE EYE.
ACCESSORY ORGANS OF THE EYE.
With a moistened sponge clean the exposed portion of
the eyeball and the eyelids from dirt.
1. The Eyelids. The upper and lower eyelids di-
verge from each other, leaving an oval space through
which the front of the eyeball is seen. The points at
which the two lids meet are known as the inner and
outer angles or canthi of the eye.
2. The Meibomian Glands. On the inner margin
of the edge of each lid will be seen a number of short
yellowish lines passing inward for a short distance,
arranged at right angles to the free edge : these are
the Meibomian glands.
3. The Conjunctiva. The under or inner surface of
each lid is covered by a loose mucous membrane, the
conjunctiva. Follow this backward into the orbit ; it
is soon reflected upon the surface of the e3'eball,
covering over the whole of the exposed portion. The
conjunctival mucous membrane consists then of two
parts, one covering the inner surface of the eyelids
and one the external surface of the eyeball. The line
along which the mucous membrane is reflected from
DISSECTION OF THE EYE. 8/
the eyelids to the eyeball is known as \\\(^ fornix con-
jimctivcs. The portion of the conjunctiva upon the
eyeball can be followed forward easily as far as the
cornea. Upon the cornea itself it is reduced to a
simple layer of stratified epithelial cells firmly adherent
to the proper substance of the cornea, and visible only
in microscopic sections.
4. The Membrana Nictitans. The third eyelid or
nictitating membrane is very conspicuous in the doo-.
It is formed by a fold of the conjunctiva strengthened
by a lamina of cartilage, and projects from the inner
angle of the eye. In the dead animal it may extend
over one third or one half of the exposed portion of
the eyeball. In the human eye this membrane is re-
duced to a comparatively inconspicuous fold, t\\^ plica
seinihinaris.
5.. The Harderian Gland. This gland lies on the
'.nner face of the nictitating membrane. It is easily
exposed by everting the membrane. It is not present
in man.
6. The Puncta Lacrymalia. On the free edo-e of
each eyelid, about 2 mm. or more from the inner
canthus of the eye, are the mouths of two small ducts.
Each begins as a small opening on the edge of the
lid which leads into a short canal. The two canals
end in an expanded portion known as the lachrymal
sac, from which the nasal died is continued downward
to open into the lower portion of the nasal cavity.
By means of this apparatus the tears which moisten
the front of the eyeball are drained off into the nose,
and thence into the pharynx.
7. The Lachrymal Gland. To expose the tear-gland
cut through the skin and conjunctiva outward from
the outer canthus for a short distance, and then
88 DISSECTION OF THE EYE.
through the conjunctiva along the line of the fornix
conjunctivae of the upper lid. The lachrymal gland
will be exposed lying on the upper and outer surface
of the eyeball, between it and the tendinous margin
of the orbit. Its ducts open upon the eyeball along
the fornix conjunctivae.
MUSCLES OF THE EYEBALL.
Remove the skin from the head. To expose the
orbital cavity remove the zygomatic arch by sawing
through it at its two ends and dissecting it off from
the underlying parts. Next dissect azvay the imiscu-
lar mass lying beneath the zygoma and on the side of
the skull ; in doing this it will be necessary to cut
through and remove the coronoid process oj the man-
dible, tising the bone forceps. The eyeball zvith its cone-
shaped mass of muscles r turning backzvard from it will
noiv be exposed ; all other tissues, muscle, fat, etc., must
be dissected azvay as carefully as possible.
Six eye-muscles are usually described, namely,
the internal and external rectus, the superior and in-
ferior rectus, and the superior and inferior oblique.
The dog has in addition a representative of the large
retractor bulbi lying beneath the six muscles men-
tioned. No special directions can be given for dis-
sectinofout these various muscles. The student should
read over first the descriptions of all of them, and then
dissect as neatly as possible. None of the muscles
will be difficult to expose except the superior oblique,
which is very liable to be injured or overlooked ; the
upper and inner angle of the orbit, therefore, where its
tendon is reflected to the eyeball must be dissected
with particular care.
DISSECTIOA' OF THE EYE. 89
1. The External Rectus Muscle lies on the outer
surface of the eyeball ; it arises from the bony portion
of the orbit round the optic foramen, and is inserted
by a flat tendon into the outer surface of the eyeball
beneath the conjunctiva.
2. The Inferior Rectus Muscle lies alona: the lower
surface of the eyeball, and has the same general inser-
tion and origin as the internal rectus, arising also
from the bone round the optic foramen where the op-
tic nerve enters the orbit. Its fibres do not lie exactly
along the vertical meridian of the eyeball, so that its
contraction will not rotate the eyeball directly down-
ward.
3. The Superior Rectus Muscle lies along the upper
surface of the eyeball ; it arises also from the bone
round the optic foramen, and is inserted into the eye-
ball on its upper surface. Owing to the direction of
its fibres its pull will not rotate the eyeball directly up-
wards. Along the inner edge of this muscle a muscular
slip may be seen, passing to the inner and upper angle
of the orbit ; this slip forms part of the levator palpe-
brse superioris, not one of the muscles of the eyeball.
4. The Internal Rectus Muscle lies along the inner
side of the eyeball. It arises from the bone round
the optic foramen, and passes forward to be inserted
into the inner aspect of the eyeball.
5. The Inferior Oblique Muscle will be found along
the lower and outer side of the front of the eyeball.
Its fibres arise from the front portion of the floor of
the orbit, from the orbital portion of the maxillary
bone, and passing outward obliquely round the eye-
ball are inserted over the tendon of the external rectus
muscle.
6. The Superior Oblique Muscle. The muscular
90 DISSECTION OF THE EYE.
portion of this muscle lies to the inside of the internal
rectus, between it and the inner wall of the orbit ; its
fibres arise round the optic foramen with the recti mus-
cles, pass outward along the inner wall of the orbit to
its upper and outer angle, where they end in a slender
tendon which lies in a orroove in a piece of cartilage
(the trochlea) found at this point. After passing
throucrh the g-roove the tendon bends backward to the
eyeball, and is inserted just beneath the tendon of the
superior rectus muscle. The trochlea serves as a pul-
ley to change the direction of the pull of the muscle.
7. The Retractor Bulbi. Lifting up the four recti
muscles, or removing them altogether, there will be
found beneath four slips of much paler muscle, having
the same general direction as the recti muscles. Taken
together they form the retractor bulbi, and in some
mammals are united to form a single hollow muscle
inserted round the circumference of the eyeball.
DISSECTION OF THE EYEBALL.
The dissection of the eyeball can be made upon the
dog, or perhaps more conveniently upon one of the
ordinary slaughter-house animals, the eyes of which
can be obtained very easily from a butcher. Of the
animals killed by butchers the pig has the best eye
for dissection. While it is smaller than that of the
ox or sheep, it is quite large enough to make it easy to
dissect, and has the advantage of resembling the hu-
man eye more closely in size and general shape, and
besides, like the human eye, has no tapetum, so that
the anatomy of the retina is more clearly seen. The
following directions are written especially for the pig's
eye, though they can be used for the eyes of other
DISSECTION OF THE EYE. 91
mammals. Each student should be provided with two
eyes, and care should be taken to have the eyes re-
moved from the pig before it is scalded by the butcher
for the purpose of removing the hair.
No student should attempt to dissect the eyeball
before reading carefully in one of the human anato-
mies an account of its structure. The eye should be
dissected in a wide pan with a layer of bees-wax upon-
the bottom, and as much of the dissection as possible
should be done under water.
Dissect off the muscles fat, etc., adhering to the eye-
ball, leaving only the optic nerve. In cleaning the eye-
ball notice the conpinctival membrane on the anterior
portion of the eyeball, and the ease with zuhich it can be
dissected off. Notice also that the optic nerve enters the
eyeball to the inside and not at the middle point.
^ I. The Sclerotic Coat is the tough white connective-
tissue coat covering over the greater portion of the
eyeball. Anteriorly it passes suddenly into
2. The Cornea, the transparent membrane covering
the front of the eyeball. Through it can be seen the
ins, with its circular opening, the/?^///. In the dead
eye the pupil is usually very much enlarged from the
dilatation of the iris.
Fasten the eyeball to the bottom of the dissect ingfan
by passing a pin through the optic nerve. With a pair
of forceps pinch tip a piece of the sclerotic and cut
through it ivith the scissors. The sclerotic is rather
loosely attached to the underlying choroid coat, except
at the entj^ance of the optic nerve and near the cornea,
so that it can be cut throicgh without i^tjtiry to the
choroid. Starting from the hole thtcs made, dissect off
a wide strip of the sclerotic extending from the optic
7ierve to the cornea.
92 DISSECTIOX OF THE EYE.
3. The Choroid Coat lying under the sclerotic is
much thinner and very darkly pigmented. Beneath
the line of junction of the sclerotic and cornea the
choroid passes into the iris.
Pinch up a bit of tJic choroid with the forceps and
snip it off with scissors. From this opening pull or
dissect off the choroid from the zvhitish underlying
retina.
4. The Retina will be exposed as a delicate opaque
membrane lying upon the vitreous humor.
5. The Vitreous Humor. Pull off the retina with
a pair of forceps. The vitreous humor will be seen as
a transparent gelatinous mass filling up the cavity of
the eyeball. It is enclosed in a delicate membrane,
the hyaloid membrane. Through the window thus
made the interior of the eyeball can be seen.
To get a better view of the interior cut through the
eyeball in the equatorial plane with a pair of scissors,
dividing it into an anterior and a posterior half
POSTERIOR HALF.
6. The Retina. Notice the way in which the retina
curls away from the choroid. One of the layers of
the retina, the pigmentary epithelium, is left in con-
nection with the choroid.
7. The Optic Disc. The point of entrance of the
optic nerve is seen as a small white oval area, com-
posed of the nerve-fibres of the optic nerve, and not
having the structure of the retinal membrane. It is
the blind spot of the eye. The blood-vessels of the
retina enter through the optic nerve and can be seen
radiating from the middle of the optic disc. The
retina can be torn off easily with forceps as far as the
optic disc, where it is firmly attached.
DISSECTION OF THE EYE. 93
8. The Choroid Coat. After removing the retina a
good view will be obtained of the choroid. This coat
can also be torn off with but little difficulty from the
sclerotic, except at the entrance of the optic nerve.
Notice the difference in thickness between the two
coats.
THE ANTERIOR HALF.
Looking into the anterior half, the crystalline lens
will be seen through the vitreous humor, and through
it the iris and pupil.
9. The Ciliary Processes of the Choroid. Sur-
rounding the lens the anterior portion of the choroid
coat is thrown into a number of radiating folds, the
ciliary processes.
10. Ora Serrata of the Retina. The retinal coat
ends round the periphery of the ciliary processes. The
line of demarcation seems quite sharp, but if ex-
amined more closely with a lens it will be found to be
wavy. This indented margin of the retina is the
07'a serrafa. In reality there is a delicate membrane,
continuous with the retina, extending forward from
the ora serrata to the tips of the ciliary processes,
known as the " pars ciliaris retinae," which is em-
bryologically a part of the retina but does not have
the true retinal structure.
11. The Crystalline Lens. Remove as much as
possible of the vitreous humor without disturbing the
lens ; then with the point of the scissors raise the
periphery of the lens from the ciliary processes : the
delicate membrane passing from one to the other is
the suspensory ligament of the lens. Remove the
lens entirely and notice its shape. The posterior sur-
face is much more convex than the anterior surface.
94 DISSECTION OF THE EYE.
Divide this portion of the eye into a right and e
left half by a cut along the vertical meridian,
12. Junction of the Choroid and Iris. Along the cut
edge of one of these halves notice the relations of the
choroid, ciliary processes, and iris. The iris is direct-
ly continuous with the choroid, and along the line of
junction of the two the part of the choroid coat known
as the ciliary processes is partly free, projecting some-
what toward the interior of the eye.
13. The Canal of Schlemm. Find the point of
junction of choroid and iris. Between this and the
sclerotic where it joins the cornea is a rather con-
spicuous canal running circularly round the eyeball.
Insert a bristle and follow its course.
14. The Ciliary Muscle. At the posterior margin
of the canal of Schlemm the choroid coat is firmly
attached to the sclerotic by an oblique band of whit-
ish fibres, the radial fibres of the ciliary muscle.
These fibres belong to the class of involuntary muscle-
fibres. When they contract they pull forward the
choroid coat and slacken the suspensory ligament, al-
lowing the lens to become more convex.
For the following dissection a fresh eye should be
used. Do not clean off the muscles, etc., but fasten the
eye to the beeswax by the aid of pins so that the cornea
faces directly upwards and projects somewhat above
the level of the zuater in the pan.
15. The Aqueous Humor and Anterior Chamber.
Cut through the cornea at its junction with the scle-
rotic, and dissect it off completely. The liquid that
escapes is the aqueous humor. It fills up the space
between the cornea and the iris known as the anterior
chamber of the eye.
DISSECTION OF THE EYE. 95
i6. Iris and Pupil. The iris is now completely ex-
posed, and through its opening, the pupil, the anterior
surface of the lens projects somewhat. Lift up the
edge of the iris and notice its darkly pigmented pos-
terior surface. This layer of pigment on the back of
the iris is known as the uvea. It is continuous with
the pigmented epithelium of the retina which is pro-
longed over the ciliary processes to the iris in the
" pars ciliaris retinae."
Lift Mp the iris with forceps, a7id cut it away at its
junction with the choroid roitnd its whole circumfer-
ence.
17. The Ciliary Processes and the Suspensory Liga-
ment. The anterior surface of the lens is now fully
exposed, and the free edges of the ciliary processes
lying on it. With the point of a seeker turn back
the ciliary processes, and the suspensory ligament pass-
ing from the lens to the processes will be exposed.
The ligament is too delicate to be seen easily, but if
the lens is pushed somewhat outward it will be re-
vealed.
18. The Capsule of the Lens. The suspensory liga-
ment is attached directly to the capsule of the lens,
which is a rather tough though transparent mem-
brane enveloping the lens. If a bit of the anterior
surface of the lens is pinched up with the forceps the
capsule can be cut or broken through, and will peel
off easily so that the lens can be slipped out. The
capsule stays behind still attached to the ciliary pro-
cesses by the suspensory ligament, and if the opera-
tion has been successfully performed a better view of
the suspensory ligament will be obtained.
INDEX.
Abdomen, muscles of, 15
viscera, 16
Adrenal bodies, 23
Annulus of Vieussens, 69
Anterior chamber of the eye, 94
Anterior medullary velum, 78
Anterior pyramids, 80
Aqueduct of Sylvius, 85
Aqueous humor, 94
Artery, aorta, 40. 51; anterior
tibial, 54; axillary, 59; bra-
chial, 60 ; brachio-cephalic, 57 ;
bronchial, 51; circumflex, 60;
cceliac axis, 52 ; common carot-
id, 57 ; coronary, 43 ; coronary
of stomach, 52 ; epigastric, 54 ;
external carotid, 58 ; external
iliac, 54 ; facial, 58 ; femoral, 54 ;
gluteal, 54; hepatic, 52; inferi-
or mesenteric, 53 ; intercostal,
40, 51; internal carotid, 58;
internal iliac, 53; internal max-
illary, 59; lingual, 58; long
thoracic, 60; occipital, 58;
phrenic, 52; popliteal, 54; pos-
terior auricular, 58; posterior
tibial, 55; pudic, 53; pulmo-
nary, 40, 43; renal, 52 ; saphe-
nous, 54; sciatic, 53; sper-
matic, 28, 53; splenic, 52; ster-
nal, 59; superior intercostal,
59; superior mesenteric, 52;
superior thyroid, 58 ; superior
vesical, 53; sub-clavian, 57, 59;
sub-scapular, 60 ; temporal, 59
thyroid axis, 59; vertebral, 59
Arytenoid cartilage, 47
Auditory striae, 78
Bile-duct, 21
Bladder, 23
Brachial plexus, 70
Brain, 75.
Bronchi, 43
Caecum, 18, 20
Calamus scriptorius, 78
Canal of Schlemm, 94
Cannulas, 12
Capsule of the lens. 95
Cerebellum, 77
Cerebrum, T], 79, 81
Chiasma, 79
Chordae tendineae, 42
Choroid coat, 91
Choroid plexus, 84
Ciliary muscle, 94
Ciliary processes, 93, 95
Clitoris, 26
Coeliac ganglion, 70
Colon, 18, 20
Columnse carneae, 43
Commissures of the 3d ventricle,
84
Conjunctiva, 86
Cornea, 91
Corpora albicantia, 79
Corpora quadrigemina, T]-^^
98
INDEX.
Corpus callosum, 7
Corpus striatum, 82
Corpus trapezoideum,8o
Cowper's glands, 28
Cricoid cartilage, 47
Cr^^stalline lens, 93
Diaphragm, 24
Dissecting instruments, 10
Ductus arteriosus, 41
Duodenum, 17
Dura mater, 76
Epididymis, 27
Epiglottis, 45
Eustachian tubes, 45
Eye, 86
Eyelids, 86
Fallopian tube, 25
Falx cerebri, 76
Fasciculus gracilis, 78
cuneatus, 78
Foramen of Monro, 83
Fornix, 83
Fourth ventricle, ']%
Fundus, 17
Gall-bladder, 21
Ganglion, cceliac, 70
first thoracic, 69
inferior cervical, (y"]
splanchnic, 70
superior cervical, 66
Glottis, 45
Harderian gland, 87
Heart, 39, 41
Hippocampus major, 83
Hyaloid membrane, 92
Hyoid bone, 48, 64
Inferior cervical ganglion, 6"]
Infundibulum, 79
Inguinal canal, 27
Injecting, 12, 49
Instruments, 10
Intestines, 17, 19
Iris, 94
Kidney, 22
Lachrymal gland, 87
Lamina cinerea, 79
Larynx, 47
Lateral ventricles, 82
Linea alba, 15
Liver, 21
Lungs, 37
Lymph-glands, 18
Mediastinum, 37, 38
Medulla oblongata, "jf
Medullary striae, 78
Meibomian glands, 86
Membrana nictitans, 87
Mesentery, 18
Mitral valve, 43
Mouth, 44
Muscle, arytenoid, 74 ; aryteno-
epiglottidean, 73 ; biceps, 35 ;
brachialis anticus, 36 ; coraco-
brachialis, 35; cremaster, 27;
crico-thyroid, 73 ; deltoid, 33 ;
digastric, 65 ; external oblique,
1 5 ; external rectus, 89 ; inferior
oblique, 89 ; inferior rectus, 89 ;
infra-spinatus, 33, intercostal,
63 ; internal oblique, 16 ; internal
rectus, 89 ; levator anguli scap-
ulae, 32; levator humeri, 32;
levator scapulae, 32 ; laryngeal,
73 ; lateral crico-arytenoid, 73;
latissimus dorsi, 33 ; mylo-hy-
oid, 65 ; occipito-scapularis, 31 ;
papillary, 42 ; pectoralis major,
61 ; platysma myoides, 63 ; pos-
terior crico-arytenoid, 73 ; rec-
tus abdominis, 16; retractor
bulbi, 90 ; rhom.boideus major,
31; rhomboideus minor, 31;
scaleni, 62 ; serratus magnus,
34 ; sternalis, 62 ; sterno-hyoid.
INDEX.
99
64 ; sterno-mastoid, 64, 3
sterno-thyroid, 64 ; sub-anco-
neus, 36 ; superior oblique,
superior rectus. 89; sub-scapu-
lar, 34; supra-spinatus, 32
teres major, 34; teres minor
33 ; thyro-arytenoid, 73 ; trans
versalis abdominis, 16; trape-
zius, 30 ; triceps, 35.
Nasal cavity, 45.
Nerve, abducens, 80 ; auditory,
81 ; brachial plexus, 70; chorda
tympani, 47; circumflex, 72 ;
cranial, 66, 80 ; descendens hy-
poglossi, 66; facial, 81; glosso-
pharyngeal, 66, 81 ; hypoglos-
sal, 66, 81 ; inferior laryngeal,
6"] ; internal cutaneous, 72 ;
lingual; 67; median, 72; mus-
culo-cutaneous, 72 ; musculo-
spiral, 72; oculo-motor, 80
•olfactory, 80; optic, 79, 80
patheticus, 80; phrenic, 38
splanchnic, 70 ; sub-scapular,
72 ; superior laryngeal, 65 ; su-
pra-scapular, 72 ; spinal acces-
sory, 66, 81; sympathetic, 69;
trigeminal, 80; ulnar, 72; va-
gus, 81 ; vago-sympathetic, 65.
Nictitating membrane, 87.
<Esophagus. 17, 38, 45
Olfactory lobes, 77-79
Omentum, the great, 16; gastro-
splenic, 20; hepato-gastric, 21
Optic chiasma, 79
Optic disc, 92
Optic thalamus, 84
Optic tracts, 79
Ora serrata, 93
Ovaries, 25
Oviducts, 25
Palate. 44
Pancreas, 20
Pancreas Asselli, 19
Parotid gland, 46
Pericardium, 39
Peritoneum, 16
Penis, 28
Peyer's patches, 18
Pharynx, 45
Pia mater, "jd
Pineal gland, 84
Pleura, 38
Pons varolii, 80
Posterior medullary velum,
Prepuce, 29
Preservative liquids, 10
Prostate gland, 28
Puncta lacrymalia, 87
Pupil, 94
Pylorus, 17
Rectum, 18
Retina, 92
Salivary glands, 46
Schneiderian membrane, 46
Sclerotic coat, 91
Scrotum, 27
Semi-lunar valves, 43
Septum lucidum, 82
Spermatic cord, 27
Splanchnic ganglion, 70
Spleen, 20
Stenson's duct, 46
Stomach, 17, 19
Sub-lingual gland, 47
Sub-maxillary gland, 46
Superior cervical ganglion,
Suspensory ligament, 95, 93
Sympathetic, 69, 65
Syringes, 12
Teeth, 44
Tentorium, ^6
Testis, 27
Third ventricle, 83
Thoracic viscera, 37
lOO
Ih^DEX.
Thymus gland, 37
Thyroid bodies, 64
Thyroid caitilage, 47
Tongue, 44
Tonsils, 44
Trachea, 38, 43
Tricuspid valve, 42
Ureter, 23
Urethra, 23, 28
Uterus, 26
Uvea, 95
Vagina, 26
Vagus, 65, 67
Valve of Vieussens, 78
Vas deferens, 28
Vein, azygos, 40, 56; brachio-
cephalic, 57 ; coronaiy, 41 ; ex-
ternal iliac, 55 ; external jugu-
lar, 57 ; facial, 57; hepatic, 55;
internal iliac, 55 ; internal jugu-
lar, 57; intercostal, 40 ; phrenic,
55; portal, 56; post-cava, 40,
55 ; prae-cava, 40, 56 ; pulmo-
nary, 40; renal, 55; spermatic,
28, 55 ; sternal, 56; sub-clavian,
57 ; temporal, 57 ; transverse;
57 ; vertebral, 56.
Velum interpositum, 83
Vestibule, 26
Villi, 19
Vitreous humor, 92
Vocal cords, 45
Wharton's duct, 46
Wickerscheimer's liquid, 10
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