Chapter V: Muscles of the Leg and Foot (29)

The arrangement of the muscles should be noted, since the space
inclosed by the divergence of the sterno-cephalici and the convergence
of the omo-hyoidei is the area of election for the operation of
tracheotomy.

Footnote 126:

The student should bear in mind that these terms are employed simply
as a matter of convenience in description; all the parts, though
differently named, form a continuous whole.

Footnote 127:

The apertures do not exist in the fœtus, and are sometimes absent in
the adult subject. Some of them may be produced in dissection by the
necessary disturbance of the parts. Clinicians state that a serous
exudate formed in one pleural sac usually passes through to the other
side in the horse.

Footnote 128:

A correct idea of the natural form and size of the lung cannot be
obtained from a specimen in this state. The lungs should be hardened
_in situ_ for this purpose.

Footnote 129:

Some authors consider each lung to be divided into anterior and
posterior lobes by the cardiac notch, so that the right lung would
have three lobes and the left lung two lobes.

Footnote 130:

In fœtal lung the lobulation is much more distinct. Pigmentation of
the lung is sometimes seen in horses, and in such cases the pigment is
deposited mainly in the interlobular tissue, thus mapping out the
lobules.

Footnote 131:

It must not be inferred from the necessarily brief account here given
that the two sets of vessels are quite distinct. On the contrary,
competent observers state that numerous small branches of the
bronchial arteries anastomose with pulmonary vessels. Part of the
blood conveyed to the lungs by the bronchial arteries is returned by
the pulmonary veins. In the horse bronchial veins are absent or
inconstant.

Footnote 132:

The cervical part of the gland is very variable. The thoracic lobe of
one side may have no cervical continuation; the other lobe may then
give off a single prolongation which bifurcates. The thoracic part in
the new-born foal occupies most of the space which is later taken up
by the apices of the lungs. Its two lobes are in contact, and its deep
surface is molded on the anterior part of the pericardium and the
large vessels.

Footnote 133:

It is therefore often termed the precardiac lobe.

Footnote 134:

The arrangement here is one of the most striking features of the pig’s
larynx. The short, thick middle hyo-epiglottic ligament and the
anterior part of the thyro-hyoid membrane are inelastic, while the
posterior part of the membrane is thin and elastic and allows the
epiglottis to be separated by a considerable interval from the thyroid
cartilage. Moreover, the borders of the epiglottis are connected with
the thyroid cornua of the hyoid bone by lateral hyo-epiglottic
ligaments.

Footnote 135:

The kidneys are soft, plastic organs, and hence an accurate knowledge
of their form can be gained only from a study of specimens which have
been hardened _in situ_. The description here given is based on this
method. For this purpose subjects should be hardened in the standing
position to avoid artefacts.

Footnote 136:

The most instructive sections are those made in the horizontal and
transverse planes, through the pelvis in each case.

Footnote 137:

The fœtal kidney is divided by furrows into a number of polygonal
areas, each of which is the base of a pyramidal lobe or renculus.
These furrows usually disappear before or soon after birth in the
foal, although traces of them are sometimes seen in the adult.

Footnote 138:

In the kidney of the horse the renal columns dip in between the
pyramids very superficially as compared with the arrangement in the
human kidney. Breuer states that the pyramids are 40 to 64 in number,
and are arranged in four rows. Only the middle ones are distinct.

Footnote 139:

The crest is the result of fusion of the papillæ or apices of the
pyramids in the embryo.

Footnote 140:

This is commonly termed the fundus by veterinarians, but is not the
homologue of the fundus of the human bladder.

Footnote 141:

This would correspond to the fundus vesicæ of man.

Footnote 142:

From the standpoint of comparative anatomy the term “adrenal” seems
decidedly preferable to “suprarenal.”

Footnote 143:

This is a remnant of the gubernaculum testis of the fœtus.

Footnote 144:

The tunica vaginalis is not a part of the scrotum in the strict or
narrow sense of that term, but is included here on practical grounds.

Footnote 145:

Sometimes one vesicula or both are very large in the gelding. The
writer has seen four cases in the dissecting room, three of which were
bilateral, the other unilateral. The vesicula resembled the urinary
bladder in appearance and contained about a quart of thick,
amber-colored secretion.

Footnote 146:

It has been customary to divide the pelvic part of the urethra into
prostatic and membranous parts. These terms apply well in human
anatomy, but have no special value in comparative anatomy. In the
horse a prostatic part hardly exists, unless we assume that it and the
neck of the bladder together are only about an inch in length. There
is no membranous part in the sense in which that term is used in
regard to man.

Footnote 147:

The statement often made that it acts as a sphincter of the bladder is
a hypothesis of doubtful plausibility. In material hardened _in situ_,
in which the internal urethral orifice is tightly closed, the urethral
muscle apparently takes no part in the closure.

Footnote 148:

This is clinically important, since enlargement of the prostate may
interfere with micturition.

Footnote 149:

These terms apply properly only when the adjacent viscera are removed
and the ovaries are actually “suspended” by the broad ligaments. When
the ovary is in its natural position, the surfaces are dorsal and
ventral, the former corresponding to the “external” surface if the
free border is directed outward, to the “internal” if the free edge is
medial.

Footnote 150:

The Fallopian tubes may be regarded, both in structure and morphology,
as prolongations of the uterus (McMurrich).

Footnote 151:

The arrangement is the only exception to the general rule that the
serous cavities are closed. In this case the mucous membrane of the
fimbriated extremity is continuous with the adjacent peritoneum, a
persistence of the embryonic relations of the Müllerian duct.

Footnote 152:

In formalin-hardened subjects there is frequently a pronounced
ring-like constriction at the beginning of the vulva.

Footnote 153:

The term vulva is used here in the sense in which it is understood
generally by English and French veterinarians. In the German works it
is applied only to the labia and other structures around the external
orifice of the urogenital sinus, while the sinus itself is termed the
vestibule of the vagina (Vestibulum vaginæ).

Footnote 154:

Lesbre states that the cornua may attain a length of 45 to 50 cm.

Footnote 155:

The pericardium is described before the heart since it must be
examined first in the laboratory.

Footnote 156:

This is termed the tubercle of Lower in human anatomy and the
tuberculum intervenosum by German veterinary anatomists.

Footnote 157:

These vessels will be described later in their systematic order.

Footnote 158:

The relation to the guttural pouch is not constant. In some
cases—especially when the head and neck are extended—the artery lies
behind the pouch. The backward extension of the latter is variable.

Footnote 159:

By some authors the term facial is applied to the artery only after it
turns around the lower border of the jaw.

Footnote 160:

The artery is conveniently placed at its inflection for taking the
pulse, since it is superficial and lies directly on the bone.

Footnote 161:

This vessel appears to represent both the supraorbital and frontal of
man.

Footnote 162:

The term axillary is often applied to the artery from the first rib to
the point of origin of the subscapular branch.

Footnote 163:

The pulse can be taken where the artery lies on the lateral ligament,
since the pectoral muscle is thin here.

Footnote 164:

This vessel is also termed the A. metacarpea volaris superficialis or
the palmar metacarpal artery.

Footnote 165:

In the great majority of subjects this vessel and some of its branches
are the seat of more or less extensive verminous aneurysm, produced by
the Sclerostomum armatum. In the author’s experience an entirely
normal specimen is quite exceptional in adult horses.

Footnote 166:

The left branch is a descriptive convention rather than a reality,
since the arteries of the small intestines spring from the mesenteric
trunk either directly or by short common stems with an adjacent
vessel.

Footnote 167:

The obliteration in the adult extends a variable distance from the
vesical end toward the origin, but usually involves only a small part.

Footnote 168:

Most of the veins are depicted in the illustrations of the section on
the arteries, to which reference is to be made.

Footnote 169:

Chauveau says “the bronchial veins, which ramify on the bronchi like
the arteries of which they are satellites, open into the great
coronary vein very near its mouth, after having united to form a
single vessel, which sometimes opens directly into the atrium.”
Ellenberger and Baum state that the bronchial and œsophageal veins
open into the vena azygos separately or by a common trunk. Martin
describes a short broncho-œsophageal trunk, but the vein which he
figures as the bronchial does not come from the lungs, but is a small
mediastinal vessel. The author finds such a vessel entering the
terminal part of the œsophageal vein, but no distinct bronchial vein
in the horse.

Footnote 170:

M’Fadyean records a case in which the vein lay on the deep face of the
omo-hyoideus with the carotid artery.

Footnote 171:

The venous angle formed by this junction indicates the position of the
thyroid gland.

Footnote 172:

These are termed by Chauveau and M’Fadyean the subsphenoidal
confluents.

Footnote 173:

The place and mode of termination is quite variable. It may disappear
from the surface of the thigh at any point above the distal third. In
some cases it passes through the anterior part of the gracilis instead
of dipping in between that muscle and the sartorius.

Footnote 174:

This often joins the posterior femoral or the popliteal vein.

Footnote 175:

The term chyle is often applied to the lymph carried by the efferent
vessels of the intestine when it contains products of digestion, and
these vessels may be designated as lacteals or chyle vessels.

Footnote 176:

The lymph vessels of these organs appear to vary considerably in their
mode of termination, and the arrangement needs further study. Some
ducts from the stomach, liver, and spleen open directly into the
cistern.

Footnote 177:

Abscess here can be reached readily by an incision between the vein
and the omo-hyoideus.

Footnote 178:

It is, of course, only the pericardium which comes in contact with the
wall, but it is customary as a matter of convenience to speak of the
relation of the heart as though it were direct.

Footnote 179:

Only the most important differential features of the arrangement of
the vessels as compared with those of the horse will be considered.

Footnote 180:

The homologies of the vessels of the lower parts of the limbs are
still uncertain. The account given here is mainly based on the views
of Sussdorf and Baum.

Footnote 181:

It is difficult to make the arrangement of these vessels clear in a
brief textual description, but a reference to the schematic figure
will explain the main facts.

Footnote 182:

Most of the differences in the veins of the ox are correlated with
those of the arteries of which they are satellites and will not be
described. The account here given consists chiefly of those
differential features which could not be deduced from a knowledge of
the arteries.

Footnote 183:

The upper series is continuous with the posterior mediastinal
(œsophageal) glands and the lower or tracheal glands with the
bronchial. Hence we might well designate the mediastinal glands as
œsophageal (anterior and posterior) and tracheo-bronchial.

Footnote 184:

When enlarged, as is often the case in tuberculosis, this gland
frequently causes difficulty in swallowing and in rumination and
produces chronic or recurrent bloating.

Footnote 185:

The relative weight is subject to wide variation. It is large in
hunting dogs and such as are trained for speed or worked.

Footnote 186:

Limitations of space and the purpose of this work preclude
consideration of the finer structure of the nervous system, for which
ample literature is available.

Footnote 187:

The description given here is intended to present the chief facts in
regard to the brain as they may be studied in the dissecting room. The
vessels and membranes which must be examined first have been
described.

Footnote 188:

Unless care is used in removing the brain the infundibulum is likely
to be torn and the pituitary body left in the cranium. In this case
there is a small opening which communicates with the third ventricle.

Footnote 189:

The fossa corresponds in position to the locus perforatus anticus of
the human brain, but is not pierced by numerous openings for vessels
in the horse.

Footnote 190:

The decussation varies superficially in different specimens. In some
there is a distinct superficial crossing of fibers so that the median
fissure is practically effaced at this point.

Footnote 191:

In the new nomenclature the term lamina quadrigemina is applied to the
dorsal mass of the mid-brain, and the four eminences which it bears
are the corpora quadrigemina.

Footnote 192:

In man a distinct superior brachium connects the superior pair with
the lateral geniculate body, but in the domesticated animals the union
with the optic thalamus is too direct to allow of any definite arm
being recognized.

Footnote 193:

On a strictly embryological basis the optic part of the hypothalamus,
comprising the anterior part of the third ventricle and the structures
associated with it, belong to the telencephalon, but will be
considered here as a matter of convenience.

Footnote 194:

This backward projection of the thalamus is equivalent to the pulvinar
and lateral geniculate body of man, which are not superficially
divided in the domestic animals.

Footnote 195:

In order to study the configuration of the hemisphere it should be
separated from its fellow by median section and from the brain stem by
cutting across the mid-brain. Material for this purpose should be
hardened _in situ_.

Footnote 196:

Termed by Lesbre the parietal fissure and by M’Fadyean the great
oblique fissure.

Footnote 197:

Just above this point is a lobe which is homologous with the insula of
man. When the overhanging gyri which partly conceal it—forming the
operculum—are removed, there are disclosed several short, deeply
placed gyri (Gyri breves).

Footnote 198:

By some authors this is regarded as the homologue of the cruciate
fissure of the dog, but it seems likely that the latter is represented
by a short and inconstant sulcus situated further forward.

Footnote 199:

From the morphological point of view other structures should be
included, but in descriptive anatomy it is usual to limit the
application of the term to the parts enumerated above.

Footnote 200:

It is generally believed that these constitute an olfactory path.

Footnote 201:

It is hardly possible to get an accurate idea of the shape of the
ventricle except by studying a cast of it. The size of the ventricles
varies in different subjects, and it is not rare to find more or less
disparity between the two ventricles of the same brain.

Footnote 202:

The term arose from the striated appearance of the mass in sections
cut in certain planes, the gray matter being cut up into strands by
tracts of white fibers.

Footnote 203:

Although this nerve springs directly from the ganglion, it contains
motor as well as sensory fibers.

Footnote 204:

This ganglion appears to be equivalent to the jugular or superior and
petrous ganglia of man.

Footnote 205:

In some cases the left vagus passes back below the junction of the
jugular veins and the termination of the left brachial vein. It then
runs backward and somewhat dorsally across the left face of the
anterior vena cava to reach its usual position.

Footnote 206:

The nerve lies here about a finger’s breadth above the thyroid gland.
If, however, the gland is enlarged it may come in contact with the
nerve. The same is true in regard to the relation to the anterior
cervical lymph glands.

Footnote 207:

In order to examine the plexus and the origins of its chief branches
conveniently and with as little disturbance of relation as possible,
the subject should be suspended in imitation of the natural position
and the fore limb abducted as much as is necessary.

Footnote 208:

Morphologically the last-named muscle belongs to the extensor group.
In man and in the dog and many other animals it is an extensor in
function.

Footnote 209:

In veterinary works these are frequently termed plantar nerves, which
is an unfortunate misnomer. The writer inclines to the use of the old
term metacarpal or common digital to designate the nerves as far as
their divisions, and the term digital beyond this.

Footnote 210:

The special statements of this description refer to the system of the
horse. A few important differential features will be mentioned in the
account of the nervous system of the other animals.

Footnote 211:

The right and left plexuses communicate with each other, so that both
lungs receive fibers from both vagi.

Footnote 212:

It has been customary to designate these in veterinary works as the
semilunar or cœliac ganglia, but in the horse they evidently include
the anterior mesenteric ganglia as well.

Footnote 213:

A good preparation of the ganglia in the horse is often difficult to
obtain on account of aneurysm of the artery and the formation of a
quantity of connective tissue about it.

Footnote 214:

Only the most salient differences as compared with the horse will be
mentioned.

Footnote 215:

The origin of the lacrimal nerve is such that Ellenberger-Baum and
Martin describe it as a branch of the maxillary nerve.

Footnote 216:

Lesbre terms this the tracheo-œsophageal branch, and considers that it
must be regarded as an accessory or internal recurrent nerve.

Footnote 217:

This belongs to the upper eyelid, but is described here on account of
its position.

Footnote 218:

According to Piersol the system of spaces and canaliculi in the
substantia propria is completely filled by the cells and their
processes, upon which the nutrition of the cornea largely depends. The
lamina elastica anterior, formerly described as a distinct layer
between the corneal epithelium and the substantia propria, does not
exist as such, but there is a condensation of the superficial part, of
the latter, which Rollett termed the anterior limiting layer; it is
not elastic.

Footnote 219:

In albinos the pigment is absent here, as elsewhere, and the iris is
pinkish in color.

Footnote 220:

For the minute structure of the retina reference must be made to
histological works.

Footnote 221:

Ellenberger and Baum regard this as the homologue of the transversus
and obliquus auriculæ of man.

Footnote 222:

There is, strictly speaking, no osseous part of the tube such as
occurs in man. In the horse the cartilage extends to the tympanic
orifice.

Footnote 223:

For the finer structure reference is to be made to the histological
literature.

Footnote 224:

This muscle has been described in the Myology.

Footnote 225:

To prevent a possible misapprehension, it may be stated that the
epidermis primarily molds the corium, and that the glands and
hair-follicles are invaginations of the epidermis.

Footnote 226:

The hoof may be loosened and removed intact by allowing the foot to
macerate or by boiling it.

Footnote 227:

The term foot is used here in the popular sense, _i. e._, to designate
the hoof and the structures inclosed within it.

Footnote 228:

The wide groove at the heels, however, contains chiefly the matrix of
the periople.

Footnote 229:

The lower punctum lacrimale is frequently absent and the corresponding
duct therefore blind. There is often a duct or its remnant which opens
below the inferior turbinal fold, but is not connected behind with the
functional duct.

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TRANSCRIBER’S NOTES

Page Changed from Changed to

149 arch; _t_, _t′_, superior arch; _t_, _t′_, superior
ischiatic spine; _n_, ischiatic spine; _u_,
acetabulum; _v_, epiphyseal line acetabulum; _v_, epiphyseal line

● Typos fixed; non-standard spelling and dialect retained. ● Used numbers for footnotes, placing them all at the end of the last chapter. ● Enclosed italics font in _underscores_. ● Enclosed bold font in =equals=. ● The caret (^) serves as a superscript indicator, applicable to individual characters (like 2^d) and even entire phrases (like 1^{st}). ● Subscripts are shown using an underscore (_) with curly braces { }, as in H_{2}O.