JOHNA.SEAVERNS

3 9090 013 413 493

Webster Family Library of Veterinary Medicine
Cummings School of Veterinary Medi.L jo at
Tufts University
200 yv'estboro Road

OUTLINES

EQUINE ANATOMY,

OUTLINES

EQUINE ANATOMY

A MANUAL

FOR THE USE OF VETERINARY STUDENTS IN THE
DISSECTING ROOM.

JOHN HENRY STEEL, M.R.C.V.S.,

ASSISTANT-KKMONSTRATOR OF ANATOMY, EOyAT, VKTERINART COLI.EOK.

NEW YORK:

WILLIAM WOOD AND CO, PUBLISHERS.

27, GREAT JONES STREET.

t >^ I

5-74

PREFACE.

This sketcli of tlie Structure of the Horse is but an out-
line; the same subject indifferent aspects bas been treated
by Chauveau (rendered available to us by Fleming's
Translation), and by Gamgee and Law ; and tbe manner
in which it has been executed by them, in both cases,
betrays the hand and touch of the master. In those works,
however, the outline has been filled up, and into the bach-
ground have been introduced figures of other domesticated
a,nimals, the beauty of which draws the attention away
from the main object. The anatomical works of Pro-
fessor Strangeways and of Percivall are fully appreciated
by the Author, but he has found that a concise work with
an arrangement illustrating the sequence of structures in
the course of dissection is much required to introduce the
student to more complete and pretentious records.

A tribute of respect to Professor Pritchard the Author
feels to be a duty ; his sound anatomical knowledge, and
his skill and eloquence in communication of information to
those who have the pleasure of studying under him, have
indelibly impressed the mind of the Author as of numerous
other members of the veterinary profession.

The Author has hoped, therefore, by these outlines to
introduce the student of veterinary comparative anatomy
to his standard of comparison, for only by first gain-
ing a knowledge of this can he qualify himself for the
study. In the dissecting room the student's investiga-
tions are in the first place confined to the Eorse, after-
wards he may avail himself of opportunities of ex-
amining other animals. It is, therefore, in the dissecting
room, during this first stage of his study, this work
is designed to render him assistance. In his study and
at his leisure he will fully aj)i3reciate the beauties and
the solid value of the works above alluded to ; but the
student in the dissecting room requires conciseness, a
quality which the Author believes he has been successful in
harmonising with truth.

And if, in the course of his examination of Nahire, th.e
student observes errors in this work of ari, let him re-
member "Varium et mutabile semper natura;" let him
see whether he has not discovered one of those exceptions
which but serve to prove Nature's rules.

A work of this kind necessarily omits important facts,
but the author has endeavoured to insert all the leading
facts of his subject, almost all of which he has himself
seen in the dissecting room. When obliged to trust to the
observations of others, he has referred to our leading
authorities ; ho has not, however, hesitated to confirm his
own observations by comparison with those recorded by
others. If he has failed in supplying to veterinary litera-
ture a work of which he himself not very long ago, as a
student, felt the need, he hopes his failure will stir up

PREFACE. Vll

some abler hand to the work ; and that the boldness of
this attempt will be pardoned in consideration that the
aim of the author is to facilitate the acquisition of a
knowledge of Veterinary Anatomy, and thus slightly to
serve that profession to which it is at once his pride and
his honour to belong.

J. H. S.

Royal Yet£ei>^aet College,
Nov., 1S7C.

OUTLINES

OP

EQUINE ANATOMY,

PART I.— INTRODUCTORY.

Anatomy is the examination by means of dissection
(cutting up) of organized bodies, and the scientific ar-
rangement and appreciation of the parts thus separated
with regard to their character and relative position.

The science of anatomy is therefore very extensive ; it is
primarily divided into animal and vegetable anatomy ; and
animal anatomy is called Anthropotomy when man is the
object of investigation, Hippotomy when the horse is
being examined. In the study of Comparative Anatomy
some particular species of animal is taken as the standard,
and the points in which other species differ from this are
noted : it is the search for diversity. Transcendental or
Philosophical Anatomy is the search for analogies between
different species and the endeavour to reduce them all to
a general type.

Investigation demonstrates that all the organs of the
body are made up by the various combinations of a few
primary tissues produced by union of anatomical elements.
The study of these tissues, irrespective of their situation,
is termed General Anatomy, while the investigation of
their component elements by the aid of the microscope is
Histology.

An organ of the body is a collection of definitely
arranged tissues for the performance of some function useful

2 OUTLINES OF EQUINE ANATOMY.

to the animal economy ; the lowest forms of animal life
consist of but one organ, a simple cell ; but in ascending
the animal scale we find organ after organ superadded,
until in the vertebrata we find a most complex collection
of mutually dependent organs ; the study of the characters
and relative positions of these and the arrangements of the
tissues of which they are composed is termed Descriptive
Anatomy.

The examination of healthy organs is Physiological, of
diseased, morbid or Pathological Anatomy. A knowledge
of anatomy enables the physician to diagnose (distinguish)
disease ; the surgeon to diagnose, appreciate the extent of,
and apply the best means of remedy for injuries and mal-
formations ; and the natural historian to arrange the various
beings, and so to suggest those most fit for economic
purposes. An anatomist only can duly appreciate the
importance of the ever varying points constituting " un-
soundness " in the domesticated animals.

The instruments required in the pursuit of descriptive
anatomy of the horse are not numerous. ScaJjoels are the
agents used in the separation of the soft organs one from
the other, a firm grasp being maintained upon the most
pliable by means oi forceps, while, if necessary, the oppos-
ing tissue is retained in position by hooks and chains. The
cutting instruments require to be kept sharp by means of
an oil-stone. In some cases scissors may be substituted for
scalpels with advantage, as in clearing arteries and in dis-
secting the eye. A hloivjnpe is a useful accessory for the
inflation of hollow organs with thin walls ; a saiv is abso-
lutely necessary for the proper demonstration of the various
bony cavities and of the structures contained in them,
while a chisel and hammer serve to raise the separated
portions of bone.

The vessels require to be filled with some substance
which will distend them as they naturally exist in the
livino- animal, and thus render them more apparent.
Arteries and veins for temporary use are generally dis-
tended with coloured size or tallow, which solidify as the
body cools, but more permanent specimens require coloured
wax"; mercury is useful for injecting lymphatics. The
substance is forced into the vessels by means of an injecting
syringe which has stopcocJcs. These stopcocks require to
be introduced into the large arterial trunks, when the

INTRODUCTORY. 3

material will fill the arteries of the bodj, but the valves
of the veins prevent fluid from passing from their larger to
their smaller branches, so it is here necessary to com-
mence at the smaller vessels. Lymphatics are injected
by introducing the point of the syringe into the areolar
tissue beside the arteries and veins of an organ, when
the mercury will generally find its way to the lym-
phatics ; they are, however, but seldom dissected, and
being valvular like the veins, cannot be injected from the
larger vessels.

Solutions of nitric and other acids and alcohol are used
for hardening the softer organs, as the brain and the
eye, while by maceration or boiling the bones may be
cleaned, and thus rendered fit for demonstration of their
peculiarities ; by boiling also we render apparent the
arrangement of the muscular fasciculi of the heart. The
age of the subject influences its value for dissecting
purposes. Young animals, in consequence of the tender-
ness of their areolar tissue, do not present that similarity
between bands of white fibrous tissue and the nerves
which we find in the older subject. They also present
well-marked separations between the bones, and in many
cases the various ossific centres from which these bones
originate ; the muscles, though more easily separable, are
less marked and more liable to tear ; an older subject is,
therefore, preferable for dissection of muscles. Fat sub-
jects are said to keep better than lean, but this advantage
is more than counterbalanced by the difficulty of removal
of the adipose tissue from some parts. Coarse lymphatic
animals present bulky but soft muscles, while well-bred
horses and asses afford firm well-defined muscles. Since
also they occupy less space and are less expensive, asses are
generally dissected by the veterinary student. They do
not difler essentially in structure from the horse. The
value of an animal for dissection may, after death, be
judged by taking into consideration the period before
accession of rigor mortis or death stiffening and the length
of its duration. When death has ensued from nervous
prostration the vital powers soon lose their control over the
tissues. Coagulation of the albuminoid matter in the
muscles occurs, constituting rigor mortis, but soon decom-
position commences as a result of the substitution of
chemical for vital force in the tissues. Such a subject,

4 OUTLINES OF EQUINE ANATOMY.

therefore, is liable to decompose sooner than one of oppo-
site characteristics. Human bodies are preserved by injec-
tion of the vessels with solution of arsenic, carbolic acid,
and other preservative fluids, but such a precaution is not
necessary in veterinary anatomy, since our subjects are
destroyed when in a state of health, are cheaper, and will
keep for three weeks with care. The bodies of animals
which have died or been destroyed when suffering from
disease are deficient in tone or firmness of the tissues in
general. Death from hsemorrhage or bleeding causes a
general want of colour of the parts, and therefore of one of
the most useful guides in separation, while puncture of
the brain by the poleaxe or " pithing " produces satis-
factory results with instant death.

When placed on the dissecting-room table the subject is
generally rested on its right or left side for the convenience
of the dissectors, six of whom work at the same subject,
dividing it among themselves into six parts — head, neck,
abdomen (including the pelvis), back (including the
thorax), fore and hind extremities. Such a division,
though extremely artificial, is advantageous, though it
requires cordial co-operation at the boundaries of the
various regions ; thus, the longus colli lies for the most
part in the neck, but extends into the thorax ; the proper
demonstration of this muscle, therefore, requires the
action of two individuals. The subject should be placed
with the abdomen towards the light, as the organs con-
tained in it are of much importance and require careful
dissection. We may here observe that some art is re-
quired in the distinction of the different structures in
different positions of the subject ; diversity in this respect,
therefore, while it renders the student proficient in prac-
tical anatomical knowledge, but ill accords with that
" cramming" for examination which consists in the reten-
tion verbatim of passages from books, and the fixture of
pictures of the subject in definite positions on the mind.
The pritnary lines of incision through the shin are —
I. From the root of the ear to the throat just behind

the angle of the jaw.
n. From the withers to the point of the shoulder and

on to the centre of the chest.
III. From the commencement of the back to the under

surface of the chest near the elbow.

INTRODUCTORY. 5

IV. From the posterior part of the loins to the central

line of the abdomen against the stifle.
V. From the centre of line No. Ill to the centre of

line No. IV.
VI. Along the central line of the under surface of the

body from the lower lip to the anus.
In making these incisions care must be taken to cut the
8kin only, for under it in some places important structures
are superficially situated. The skin having been punc-
tured by a slight incision at first, the knife (this work takes
the edge off an ordinary scalpel) should be introduced,
and the remainder of the skin divided from within out-
wards. From the primary incisions the dissectors then
commence to separate the skin from the neighbouring
parts, being careful to cut only through areolar tissue, the
great connecting medium of the other tissues ; the free
flaps in a short time produced may be then drawn away
from the subject, whereby the areolar tissue is rendered
tense and thus more easily perceptible and divisible. Any
blood effused by accidental or intentional incision into
veins is to be removed with a sponge, and only such parts
as are to be immediately dissected are to be denuded of
skin, for on exposure the areolar tissue becomes dry and
tough, assuming the appearance of dried ligament or
tendon in some places, and hence becoming liable to mis-
lead. All portions of separated skin should be imme-
diately removed, as being liable to cover the subject with
loose hairs.' The bare portions may be kept moist by damp
cloths, which also serve to keep off dust, &c. After one
side of the animal has been duly investigated much
information may be gained by turning it over and examin-
ing the other side by a similar but somewhat modified
process, each dissector exchanging his region for some
other, whereby the most satisfactory amount of informa-
tion gained from each subject by each individual is
attained.

Finally, we will recommend that, while acquiring that
superficial knowledge of the situation and peculiarities of
the bones which is requisite to the due appreciation of the
anatomical position of organs, the student avail himself of
the opportunity of learning practically the handling of the
scalpels, skinning, cleaning, &c., for the first subject of a
student generally yields him hut little more information than

6 OUTLINES OP EQUINE ANATOMY.

this. Never cut througli anytliiug but areolar tissue with-
out having examined its nature. In the separation of
the skin the edge of the knife must be always turned
towards the skin from the unknown tissues, this is a
primary rule in dissection ; always cut towards known
structures when dividing areolar tissue, any slip of the
knife will then do no damage.

Where possible, have the basement structure of the
part, as the bones or cartilages, cleaned to show its points
of muscular attachment, &c., near at hand for constant
reference, and during dissection take advantage of the
guidance of some authentic work on anatomy read aloud,
or better, of a good anatomist \i\ 'propria persona. Care-
fully note any point in which the subject under examina-
tion differs from the description.

The different portions of the subject may be altered in
position, irrespective of the position of the subject in
general, by means of hloclis placed under parts which
require to be elevated, iron-forTced bars tirmly fixed in
the table by penetration with one sharp extremity, which
form a prop for limbs, and cords either from pulleys or
from fixed points, these may be tightened at convenience.

By the separation of organs one from the other in the
dead body the hand and the eye are trained for operations
upon the living subject ; the student therefore should not
regret the time expended in the mechanical pursuit of
anatomy, nor consider that examination of preparations,
plates, or recent specimens prepared by others, will render
him proficient in anatomy ; it is only men who work on
this system who fear the ])ractical anatomical examination
recommended as a test by the highest authorities.

One of the most prominent characteristics of the highest
subkingdom of animals is the possession of an internal
skeleton or basement structure. This consists of a number
of definitely but diversely shaped masses of a hard white
substance composed of a mixture of earthy and animal
matter. Submit a bone to combustion in a fire with a free
supply of air, it first turns black in consequence of the
carbon contained in its animal matter, and when this is
completely burnt a white friable mass, in shape resem-
bling the bone, remains, being the earthy matter which
entered into its formation. Subject another bone to the
action of dilute hydrochloric acid, this will remove th<?

INTRODUCTORY. 7

earthy matter, and tlie animal matter will remain in the
shape of the bone, but extremely flexible.

In the extremely young subject all the bones are
cartilaginous, being elastic and pliable, but afterwards, by
the deposit of earthy matter in their substance and by
alteration in the arrangement of their component ele-
ments, they change to bono. This process of ossifica-
tion (bone makings), commencing at fixed points, involves
gradually the surrounding cartilage. These points are
termed centres of ossification. Some cartilages remain of
fixed structure throughout life, and are termed "|jerma-
7ient,^' They with the bones therefore form the skeleton,
which is composed of many portions brought into mov-
able contact with each other, whereby the various motions
of the body are possible and concussion from motion
modified, and thus shock to internal organs prevented.
Where firm power of support and resistance is required
bone is situated ; where yielding with protection to other
parts, cartilage. When these structures are placed in
position and maintained there by artificial means we have
an artificial skeleton, but in the natural sheleton they are
bound together by bands or layers of a strong glistening
fibrous substance (tvhite fibrous tissue) or of a yellow elastic
tissue, the characters of which are expressed by its name.
These are ligaments. The white fibrous tissue under the
microscope is found to be composed of collections of
parallel bands of wavy fibres with a single outline, which
bands cross each other irregularly. Yellow elastic tissue
consists of fibres with a double outline, which are irregu-
larly arranged, but send branches to the neighbouring
fibres, and are curled at their extremities in consequence of
their elastic recoil.

Cartilage consists essentially of cells (circumscribed sacs,
each containing smaller sacs or nuclei, which contain a cen-
tral spot or nucleolus) with an ijiter cellular substance or
matrix. In the true or hyaline cartilage this matrix is
devoid of structure, being slightly granular ; but when
cartilage requires increased strength we find the matrix
assuming the characters of white fibrous tissue ; where it
requires elasticity, yellow elastic tissue ; thus, white fibro-
cartilage and yellow elastic fibro-cartilage are formed.
These three forms of permanent cartilage present cells
collected in groups of about three or four, which have been

8 OUTLINES OF EQUINE ANATOMY.

produced by division of one cell, but tbe cells in temporary
cartilage are more evenly diffused througb the mass.
Another form of cartilage is found in the foetus, which is
termed cellular, since it consists of cells collected together
with no apparent intercellular substance.

Bones are composed of compact and cancellated structure.
The former is the dense external layer which they present.
In the cancellated, which is situated more internally, the
bony structure is arranged in a trabeculated manner,
whereby spaces are left which are termed cancelli. Small
near the compact substance, these gradually increase in
size until in the centre of the bone we frequently find a
large open space or medullary canal, so named from its
containing the medulla or marrow, a greasy substance,
which in the young subject is of a red colour, but in the
adult yellow ; it consists of areolar tissue, in the meshes of
which are fat and peculiar cells (or myeloplaxes) ; it also fills
the cancelli.

The intimate structure of bones is complex ; through its
substance run canals for blood-vessels, and arranged con-
centrically around these canals are bony layers termed
lamince, between which at intervals are irregular spaces
containing the special cells of bone, or lacunce. From each
of these lacunae, towards the central or Haversian canal,
and towards the other lacunae, run minute passages or
canalicuU, through which only the fluid portion or nutritive
plasma of the blood is supposed to pass. An arrangement
such as that just described is termed an Haversian system,
and the Haversian canal of one system is frequently
brought into communication with that of another by means
of a transverse branch, all the Haversian systems com-
posing a bone are not uniform in size.

Bones are of three kinds, long, flat, and irregular. Long
bones (or long round bones), as the femur, radius, &c., have
one axis (as a rule) much longer than the others and have
a distinct medullary canal. They present a central ossific
centre or diaphysis forming the body of the bone, and at
each end of this an epiphysis forming an extremity. From
either part processes or apophyses may j^roject. Their
Haversian canals run parallel to the long axis of the bone,
and the different Haversian systems are connected together
by connecting laminae, which are concentric with the medul-
lary canal of the bone.

INTRODUCTORY. 9

Flat bones have one axis mucli shorter than the others,
whence the bone assumes an expanded form and serves for
the attachment of large muscles or for forming the walls of
cavities. They present no medullary canal, but between
the outer compact layers is cancellated substance, which in
the cranial bones is termed diploe. Examples of flat bones
— scapula, parietal bones. They have a centrally situated
centre of ossification, with others for their processes, and
their Haversian canals are perpendicular to their flat sur-
faces. Some parts of them seem to result from ossific
deposit in fibrous membrane, and not from change of car-
tilage.

Irregular bones are those in which no marked difference
exists between the length of their axes. They consist of
cancellated structure surrounded by a thin layer of com-
pact substance. The centres of ossification are related to
the peculiarities of each bone. Examples— petrous, temporal
bones, os pedis, &c. In this class are included " short hones."

Bones derive their supply of blood from the arteries which
run nearest to them ; they are surrounded by a strong
membrane composed of white fibrous tissue, periosteum,
which is very vascular, and from which minute vessels pass
to foramina on the surface of the bone in connection with
the Haversian canals. In addition to this long bones
generally present a small opening {foramen medullare),
which pierces the shaft of the bone, and through which
passes a branch from the nearest important artery which
runs to the medullary canal, and breaks up to supply the
medulla and to send small branches, corresponding with
those from the periosteum, into the bone ; and a third
source of supply is derived from small articulatory foramina
surrounding those surfaces by which these bones come into
indirect contact with each other. These articulatory sur-
faces being covered with cartilage, are not covered by
periosteum, which also is absent from some places where
tendons become directly attached to the bone, and from
bones, like the ethmoidal cells and the ossa turbinata, which
are intimately clothed with highly vascular mucous mem-
brane. Bones are but slightly supplied with nerve-
force, their lymphatics have not been satisfactorily de-
monstrated. Bones present eminences and cavities, either
of which may be articulatory or no n- articulatory.

10

OUTLINES OF EQUINE ANATOMY.

Articulatory . ^

Eminences •{

I Non-articulatory <

Articulatory

^Seads. — Separated from main por-
tion of bone by a circumscribed
neck, being rounded, cf. Head of
femur.

Condyles. — Oval -rounded projecting
surfaces, cf. Condyles ot femur.

Both these form synovial or di-
arthrodial or free-moving joints ;
others serve to form fixed or im-
perfectly movable joints, but have
no definite names.
f Imprints. — Rough, irregular, and
small prominences for attachment
of muscles, tendons, or ligaments.

Processes. — Lnrge eminences arising
from separate centre of os^ifi(•atiou,
variously named from their figures.

Ridges t Eminences with elongated

or crests j bupis of attachment.

Tuberosities. — Large eminences with
l^ extremely \^ ide ba^e.
r Glenoid, or saucer-like, shallow.
'\ Cotyloid, or cup-like, deep.
{'Channels or furrows. — Wide, deep,
and smooth.

Grooves. — Long, narrow, and even at
bottom.

Fissures. — Narrow and rough.

Digital impressions. — Look as if made
by the finger when the bones were
in a plastic condition.

FosscB. — Smooth and shallow.
Non-articulatory ^ Simises. — Cavities divided by imper-
fect septa or bony partition.

Notches. — Grooves scooped at the
edge of a bone.

Foramina. — Cavities passing through
bones.

Canals. — Long foramina.

Fissures. — Narrow torumina.

Hiatus. — Wide openings with irre-
gular outlines.

The epiplijses of long bones consist mainlv of cancellated
tissue, the compact portion forming but a thin external
layer ; that under the cartilage (articular laiimia) is most
dense, and from its vessels the cartilage-cells draw nutriment.
This enlargement of the extremities of the bone is for the
purpose of affording increased surface for ligamentous and
other attachments without increasing the weight of the bone.

Cavities •{

INTRODUCTORY. 11

For convenience of description anatomists, wlien possible,
distinguish surfaces of hones, and the lines of union of the
surfaces constitute the borders.

We have mentioned ligaments of various kinds entering
into the formation or perfection of joints. These are gene-
rally composed mainly of white fibrous tissue ; some contain
a small amount of yellow elastic tissue ; others mainly con-
sist of yellow elastic tissue, as ligamentum nuchse. We
have seen, too, that the ligaments are either broad expan-
sions or dense bands. Analogous in structure are the
fascise, which are found in particular regions ; they con-
sist of widespread membranous layers of white fibrous
tissue, which form sheaths to bind down muscles in their
situations and to brace them for action ; they are generally
attached to the most prominent portions of the basement
structures in the neighbourhood. They present channels
and foramina through which vessels and nerves pass, and
in some cases have muscles acting upon them, as tensor
vaginae femoris. They are most marked in those situa-
tions in which the muscles are long, as in the limbs. On
approaching an annular or a capsular ligament they blend
with it. The most important are fascia lata of the fore-
arm, the lumbar, psoas, and gluteal fascise, and the fascia
of the thigh. The gluteal presents a considerable amount
of yellow elastic tissue. Fascia superficialis abdominis is
wholly elastic. The several portions of the skeleton are
caused to move upon each other by the action of muscles.
The motion found in other parts of the body, with the
single exception of that produced by ciliae, is also due to the
peculiar property of muscular fibres ; this motion may be
voluntary or uncontrolled hy the ivill, and is brought about
by the contractility of two forms of fibres, voluntary or
striated, involuntary or unstriated. Involuntary muscular
fibre is that which produces the motion of most of the
internal organs by which nutrition and reproduction are
brought about ; it is generally arranged so as to form a
thin coating to a hollow organ or a tube or a vesicle, and
consists of a number of fusiform or spindle shaped nuclea-
ted cells overlapping each other at their extremities where
they meet. The double wall of separation becomes ab-
sorbed and thus a plain fibre is produced, distended at
intervals in consequence of the presence of the nucleus;
these fibres are collected together to form fasciculi, which

12 OUTLINES OF EQUINE ANATOMY.

are generally spread out, forming layers, but sometimes, as
in the large intestine, are collected to form bands. When
in mass they are white in colour. Voluntary, striated,
or red muscular fibre is that which is under the control of
the will under ordinary circumstances. It consists pri-
marily of certain minute globular cells, sarcous elements,
which are arranged so as to form elongated chains or
jibrillcB. When examined under any but the highest
powers of the microscope the lines of junction of the cells
seem like black lines or stri(B extending across the fibrillse.
A number of fibrillae become collected into a bundle, sur-
rounded and connected together by a layer of simple mem-
brane, the sarcolemma, to form a fibre ; and the fibres are
collected into fasciculi, which vary in size, may be seen with
the naked eye, and are surrounded by perimysium. These
fasciculi are united together to form masses of various
shapes, red in colour, vulgarly known as "flesh." These
are the muscles of anatomists ; the study of them consti-
tutes myology. Muscles vary much in form, being in some
cases fusiform, in others flat, and in others irregular ; they
are attached to the basement structures in most cases, and
sometimes consist wholly of red muscular fibre, in others
the red muscular portion, belly, is continued by a white
ligamentous band, which may be cordiform, or expanded
and flat (aponeurotic). This band is termed a tendon; it
consists of dense, slightly modified, white fibrous tissue, and
in some places becomes firmly blended with the periosteum
of the bones to which it runs, in others becomes continuous
with ligaments. When the muscular fibres of a muscle
meet the tendon in a direction obliquely to its course on
one side the muscle is termed penniform ; if on both sides,
hijpenniform ; sometimes two fleshy bellies of a muscle are
connected by a central tendon, such a muscle is said to be
digastric. Muscles, as a rule, cover the surfaces of bones
and form grooves and channels through which the nerves
and blood-vessels pass, and as they are marked more or
less distinctly in different cases by prominences or depres-
sions on the surface of the body of the living animal, they
afford valuable surs^ical i^ruides. Vessels and nerves which
run in contact with a muscle are termed its satellites. The
muscles are extremely numerous, they vary in size from the
huge longissimus dorsi to the minute muscles of the middle
ear. The tendons of some muscles extend throughout

INTRODUCTORY. 13

their whole length, performing the function of a ligament
in addition to their motorial value. Muscles are gene-
rally connected together by areolar tissue, in dissecting
them the knife should be always used in the direction of
their fibres, their attachments more particularly investi-
gated, but their relations and figure also taken into account.
Nerve-tissue next demands notice, as being the source of
all muscular action, sensation, and intellect. The nervous
system is primarily divided into the cerebro-spinal and
sympathetic systems, each of which consists of nerves and
nerve-centres ; the two are intimately blended. The cerebro-
spinal nervous system is that which regulates animal
life, i. e. sensation, voluntary motion, and intellect. Its
centres are the brainand spinal cord ; its nerves are marked
by whiteness, they are given off from the above-mentioned
centres, as a rule, in pairs, one from each side of the centre.
Those of the spinal cord originate hy two sets of fibres, a
superior or sensory, from the supero-lateral part of the cord ;
each of these has a ganglion upon it and subsequently
unites with the inferior or motor root. After this the sen-
sory cannot be distinguished in any way from the motor
fibres ; the difference lies not in the fibres, but in the parts
to and from which they run. The sympathetic, gang^lionic,
or vegetative system superintends those organs which
provide directly for the maintenance of the individual or
the perpetuation of the species. Its centra consist of a
number of grey nodular bodies, enlargements of the nerves,
found in various parts of the body (termed ganglia) . Thus,
they exist as a chain of ganglia connected together by
fibres on either side of the spine, as special ganglia existing
in certain organs as the heart, as the ganglia on the sensory
roots of the cerebro-spinal nerves, and as certain ganglia
situated in certain irregular but constant parts of the body,
as those of the fifth cranial nerve. From these fibres run,
collected into nerves distinguishable by their darker colour
than those of the animal system. These and the cerebro-
spinal nerves communicate in every possible manner.
Two classes of histological elements are distinguishable in
nerve-tissue, fibres and cells. The nerves are composed only
of fibres which are of two kinds, grey and white. The grey
fibres so much resemble unstriated muscular fibre that
their nervous nature has been doubted. They are found
most largely in the sympathetic nerves, of which they form

14 OUTLINES or EQUINE ANATOMY.

the greater part, and consist of transparent fibres marked
by a number of nuclei ; they are smaller in calibre and
their nuclei more crowded than those of unstriated muscular
fibre. The white fibres in the living and very fresh subject
are transparent, resembling extremely minute glass threads,
but shortly after death they undergo change and exhibit a
central transparent but tough substance, axis cylinder,
surrounded by a thin layer of simple membrane, medullary
sheath, or neurilemma, while between the two is a quantity
of white albuminoid matter, which undergoes coagulation,
and is termed the ivhite substance of Schivann. These fibres,
with a few grey fibres, are united together to form those
white bands commonly known as nerves. Some of them seem
to commence in the tissues by free extremities, others by
loops, many in cells which will be found most marked
in the organs of special sense and in voluntary muscles.
In the latter we find these cells under the form of expanded
plates termed the motorial 'plates ; the rods and cones of
the eye, fibres of Corti of the ear, and Pacinian corpuscles
of the skin, are cells of special sense. Nerve-cells are found
in the nerve-centres, they are sometimes spheroidal, but
frequently present one, two, or more prolongations from
which the axis cylinders of the nerves pass. They are
termed polar cells {multi-, hi-, according to whether they
have many or but two prolongations). They abound in
the grey portions of the centres, the white being mainly
composed of nerve-fibres, connective tissue, and granular
matter. Nerve-cells present each a nucleus with one or
more nucleoli surrounded by granular matter sometimes of
a dark colour.*

We have seen examples of pure membrane or lemma in
the investing layers of the nerve and muscular elements
termed respectively neurilemma and sarcolemma. A third
form is brought under our notice in investigating the com-
plex membranes of the body. It is termed basement mem-
brane, and consists of a thin structureless or slightly
granular fibre on one side in contact with connective tissue
with numerous vessels, on the other with cells with more
or less marked walls, nuclei, and nucleoli, termed epithelial

* When a number of nerves passing from different parts of a centre
become mixed at one part, and from this nerves, each composed of
fibres from several parts uf the centre, run to distinct organs, we term
the arrangement a plexus.

INTRODUCTORY. 15

cells. The compound membranes are together made up
therefore of internally a vasculo-areolar layer, centrally
basement membrane, externally epithelial cells. They
are of four kinds — serous, synovial, mucous, and cuticular.

Serous membranes are the most simple. They line
closed sacs, do not secrete fluid from the blood, but merely
are moistened by some halitus or vapour which serves to
allow them to move freely upon each other without friction,
for two layers of serous membrane generally come in
contact whereby motion of the contents of a cavity without
motion of its walls is admissible. The epithelium of this
form of membrane consists of a single layer of cells spread
over the surface of the basement membrane, closely fitted
together, whereby each assumes the hexagonal form charac-
teristic of tessellated epithelimn. The pleura, pericardium,
and arachnoid are good examples of serous membranes. It
is supposed that they are merely dilated extremities of
lymphatics. Synovial membranes differ from serous in their
greater complexity and in the nature of their secretion, for
they separate from the blood a fluid which, in consequence
of the fatty matter it contains, serves to lubricate freely mov-
able joints. They therefore line the cavities of such joints
covering the inner surface of its ligaments, and in young
animals even extending over the cartilage of the articular
surfaces of the bones. In some parts, either to fill up space
or to afford increased secreting surface, the vascular layer
of the membrane is thickened, rendering it prominent and
heightened in colour, forming the synovial fring'es. Besides
lining the cavities of joints synovial membranes form the
thecae or sheaths of tendons, lining the channels through
which they pass, and being reflected over the tendons,the two
portions being connected by double folds of membrane
termed /roe?^a. Whenever a tendon plays over a prominent
surface whereby the direction of its action is altered it has
placed between it and the prominence a small synovial
closed sac termed a bursa, the third form of synovial cavity ;
a marked bursa is situated between extensor pedis tendon
and the antero-inferior part of metacarpi magnum, the
synovial apparatus between flexor brachii and the humerus
is intermediate in character between a theca and a bursa.
Sometimes two or even three of the different forms of
synovial cavity communicate. Synovial membranes always
present simple tessellated epithelium. It is on the Mucous

16 OUTLINES OF EqUINE ANATOMY.

membranes that we find it gaining its greatest complexity,
in some cases consisting of several superimposed layers, the
most internal of which, drawing nutriment from the blood,
''hands it on" to those more externally placed. This is
stratified epithelium. In some cases, however, as in the
guttural pouch, we find the mucous membrane resembling
a serous membrane in the simplicity of its component
elements. The vascular layer of mucous membrane is
termed corium, and is sometimes thick, presenting numerous
and large blood-vessels, as in the case of the mucous mem-
. brane of the hard palate. In some situations it is extremely
attenuated or even, as in the corneal conjuctiva, completely
absent. Epithelium of mucous membrane is of two kinds,
ciliated or non-ciliated. Non-ciliated epithelium may be
either tessellated (above described) or, the mutual compres-
sion of the cells not being so great, they may retain the
spheroidal figure (as in the bladder, ureters, and pelvis of
the kidney) , or the cells may be cylindrical, fitting in closely
together, having one extremity free, the other in contact
with the basement membrane. This is columnar epithe-
lium ; it lines the greater portion of the digestive tract.
Either columnar or spheroidal cells may present on their
free surface a number of small pointed prolongations
which, by some peculiar power independent of nerve in-
fluence, wave to and fro. These are ciliae, their presence
is manifest in the respiratory tract, where their action serves
to waft upwards mucus for expectoratiou ; and also in the
Fallopian tube, where they waft the sperm- cell upwards,
the germ-cell downwards. Mucous membrane lines all
those great cavities of the body which communicate with the
external air, but the distinction hetween the mucous and serous
membranes is very artificial. Thus, the alimentary, respira-
tory, genito-uriimry and lachrymal tracts are all lined by
mucous membrane, and as this insensibly blends with the
skin at the external openings of the body, we may look
upon the structures of the body already described as con-
tained in a large sac of compound membrane. In some
parts the corium of mucous membranes presents unstriated
muscular fibre, in others it is thickened at certain points
producing papillce, such as those found on the tongue
and the intestinal mucous membrane. Other peculiarities
in the mucous membranes will be noticed in the descrip-
tions of different parts ; thus, the teeth, as will be shown,

INTRODUCTORY.

17

are modified mucous memhrane. The skin consists of
exactly the same component elements as other membranes,
but they are generally more complex. It is in many
parts continuous with the larger mucous membrane, and
all over its surface presents openings leading into glands.
It presents modifications under the form of hair and hoof.
It consists of two parts separated by basement membrane,
dermis and ejiidermis. The dermis corresponds to the
corium of mucous membrane, and consists of a more or
less thick layer of reticulated yellow elastic and white
fibres, containing in their meshes vessels and nerves. It
presents two layers, the reticulated and papillated. The
reticulated layer internally situated, its deep-seated surface
is continuous with the subcutaneous areolar tissue, its
superficial with the papillated layer, which is externally
raised into a number of finger-like prominences (covered
with basement membrane), on to which the epidermis is
moulded. The subcutaneous areolar tissue varies in its
density in different parts of the body, being in some places
very loose, as in the intermaxillary space, on the chest, &c.
These parts are most liable to dropsical collections and
most readily admit insertion of setons. It contains col-
lections of fat, the terminations of the hair-follicles and of
the sudoriparous glands. Portions of these also, and the
sebaceous glands, are embedded in the dermis. The
epidermis consists of epithelial cells moulded upon the
external surface of the dermis ; the most deep-seated are
spheroidal and contain pigment-granules, forming the rete
mucosum. The superficial layers become hard, dry, and
scaly ; as they are subjected to external influences, they are
gradually worn away.

Hairs are produced from depressions on the surface of
the skin termed hair-follicles. These are filled with
spheroidal epithelium, and into each of them open gene-
rally the ducts of two sebaceous glands. At its deep-
seated extremity, where it forms a cul-de-sac, each follicle
presents a papilla from which the hair is produced. The
hair is the epithelium of the papilla (which is of the same
nature as the dermis). It consists of a hulh, apex, and
shaft. The hulb immediately surmounts the papilla, and
is the largest portion of the hair, consisting of the softest
and most recently formed spheroidal cells. The shaft is
the cylindrical portion which runs outwards, emerges from

18 OUTLINES or EQUINE ANATOMY.

the follicle, and terminates in the apsx. It consists of an
external or cortical layer, the cells of which are imbricated
(arranged like tiles upon a honse), and a central medul-
lary portion, consisting of soft, spheroidal cells. The
sebaceous glands pour their secretion into the follicle ; it
is an oily substance, and permeates the hair, rendering it
pliable. These glands are small fiask-shaped bodies of the
racemose class. The sudoriparous glands produce the
sudor or sweat, which thej pour out upon the surface of
the skin. Each gland consists of a single elongated tube,
which is ver J much twisted upon itself in the subcutaneous
areolar tissue so as to form a small, rounded mass per-
meated by blood-vessels. It takes a slightly wavy course
through the dermis, and in passing through the epidermis
becomes cork-screw like. Hairs are either short and glossy,
as those covering the surface of the body in general, or
long and coarse, with their bulbs deeply imbedded in the
subcutaneous tissue, forming horsehair, found in the mane,
tajl, eyebrows, eyelashes, and tentaculse of the lips, which
in the upper lip of some coarse-bred horses become long
and wavy like the human mustachois. Fineness and
scantiness of hair is a mark of a well-bred horse. It varies
in colour in horses from white to black. In the ass it gene-
rally assumes a brownish-white mouse colour, and a dark
line of hair extending down the back assists in distin-
guishing Equus asinus from E. caballus. The modifica-
tion which hair undergoes in forming horn will be
described in its proper place.

We must now examine those complex arrangements of
mucous membrane which produce glands. All glands are
depressions in mucous membrane, and these depressions
may assume either the tubular or the follicular form, and
either of these may be simple or compound. Simple tubu-
lar glands are those which consist of a single undivided
tubular depression of mucous membrane : examples are the
follicles of Lieberkiihn, and the sudoriparous glands — the
former of which are extremely shallow, the latter much
elongated. Sometimes these tubes divide at their deep-
seated extremities, and each part may again subdivide, and
thus, by continuation of this process, compound tubular
glands, such as the testes or the kidneys, are produced ;
the latter organ has dilated extremities of its tubules, and
thus resembles compound follicular glands.

INTRODUCTORY. 19

Simple follicular glands are flask-shaped bodies openini,^
on to the surface bj a small duct ; when several of these
pour their secretion into a compound duct, we see the first
example of a compound follicular or racemose gland,
which consists of a number of flask-shaped or vesicular
bodies, which pour their secretions through a number of
ducts, which unite and reunite until at last thej form a
more or less elongated canal, the duct of the gland, which
opens on to the surface of the mucous membrane lining
the cavity to which the gland is appended. The secreting
vesicles or acini thus bear to the ducts the relation which
grapes bear to their stalks, hence the name racemose.
The several parts of the gland are closely invested by
areolar tissue, whereby they are united to form lobules,
which by their union complete the gland. As examples of
compound follicular glands, may be adduced the salivary,
pancreas, lachrymal, and mammary glands, while the
meibomian, brunners, and the sebaceous glands present
this type under a much less complex form.

The so-called ductless glands present peculiar charac-
ters, which will be specially noticed. All the above-
mentioned structures are supplied with matter for growth
and for rej)air by the blood, and the same fluid also re-
moves matters for which they have no longer use. It is
conveyed from the heart throughout the system by cer-
tain vessels found in all parts of the body more or less.
It must, however, be clearly understood that in all cases
the special cells of a tissue are externally placed to the
blood-vessels, so that all nutriment obtained by any but
blood-cells must be obtained through the walls of the
vessels and through the wall of the cell. The vascularity
of a part consists in the close relation of its cells to its
vessels. Thus the capillaries run between the muscular
fibrillae of voluntary muscle ; they are separated from the
cells by basement membrane in the complex membranes ;
in stratified epithelium the outer layers are separated by
basement membrane and a number of cells which hand on
the nutritive portion or plasma of the blood from within
outwards. The same condition obtains in cartilage except
that the cells are separated by intercellular substance of
variable nature and amount ; while in bone the plasma
passes through an elongated but extremely minute canal
m its course from the vessel to the cell. The vessels from

20 OUTLINES OP EQUINE ANATOMY.

whicli the cells directly derive the plasma are the capil-
laries, extremely minute vessels, uniform in size, forming
an intricate network, varying in the figure of its inter-
spaces in the different tissues, which in muscle are elon-
gated parallelograms, in lungs smaller than the vessels
themselves. These vessels connect the terminal extremi-
ties of the arteries with the commencement twigs of the
veins ; the blood does not take any definite course
through them. The wall of the capillary consists of
simple membrane with more or less numerous nuclei
imbedded in its substance. When the vessels are large
they present nuclei elongated both longitudinally and
transversely ; the smaller vessels have only longitudinal
nuclei, which are widely scattered. The brain and the
mucous membrane of the bowels present extremely minute
capillaries, those of the skin are very large (as may be
well seen in that part modified to form the hoof) . In the
spleen, corpus cavernosum penis, and in the chorion, the
arteries open directly into veins usually modified to form
venous sinuses.

The arteries carry blood from the heart to the tissues.
They vary in size in proportion to their distance from the
heart. They may be distinguished from the veins by
their elasticity, which enables them to remain open after
death, and also to expel the blood which they contained
when the heart's action ceased, whence they are found
empty. The sum of the areas of the arteries at a distance
from the heart is greater than the area of the aorta, and
the size of this sum is great in proportion to the distance
from the heart, so that the arterial system has fancifully
been described as a cone, the apex of which is at the
aorta, the base at the capillaries, in which the smallest
arteries terminate. Arteries may be given off at right
angles or at an acute angle from a large trunk ; as the
pressure of fluids in closed vessels is equal in all directions,
this arrangement will scarcely influence the flow of blood to
particular parts. Some arteries run directly to the organs
which they supply, others, especially the spermatic artery
in the horse, assume a peculiar convoluted character ;
while in some cases several vessels unite to form a more
or less intricate plexus termed rete mirabile, examples of
which may be seen in the circle of Willis and the circular
arteriosus of the foot. Arteries possess three coats. The

INTRODUCTORY.

21

external or fihro -areolar coat consists of more or less con-
densed areolar tissue, with a slight predominance of elastic
fibres ; it serves to protect the vessels and to form the
nidus in which the small nutrient vessels of the arterial
coats (vasa vasorum) break up into capillaries. It is
directly continuous with the areolar tissue of the channel
through which the artery runs, which sometimes becomes
developed into a marked sheath enclosing other structures
in addition to the artery ; the carotid sheath is an example.
The middle or musculo -elastic coat consists of unstriated
muscular fibre in union with yellow elastic tissue. The
muscular fibres assume a direction transverse to the longi-
tudinal axis of the vessel ; they predominate in the smallest
arteries, those most distant from the heart. The elastic
fibres mainly take a longitudinal direction, but are
arranged in the form of a network ; in the largest arteries,
as the aorta, they form the major portion of the arterial
wall. The internal coat is of a serous nature, presenting
an internal layer of tessellated epithelium and a peculiarly
modified basement membrane. The latter, termed the fenes-
trated membrane of Henle, shows a peculiar tendency to
curl up when removed from its situation, and it has
numerous perforations. These characters seem to indi-
cate its intermediate nature between common basement
membrane and ordinary yellow elastic tissue with
which in some vessels its external surface intimately blends.
This coat of the artery is continuous centrally with the
endocardium, peripherally with the constituent membrane
of the capillaries. The course of arteries is in some cases
irregular, either as a result of disease or of original
formation. Descriptions of these cannot be accurate /or
all cases. When arteries run near one another they
almost always anastomose or inosculate, communicate
more or less closely, either directly or by branches.
Hence provision is made for continuance of supply of
blood after obliteration of one source ; the collateral sources
after injury resulting in obliteration of an important
artery generally prove equal to the emergency— a point of
great value in surgery.

The veins carry blood from the capillaries to the heart
with exception of the portal veins, which convey it from
the alimentary organs of the abdomen to the liver, where it
is purified prior to admission into the general round of

2^ OUTLINES OF EQUJNE ANATOMY.

the circulation. Arteries inosculate or anastomose in some
situations freely, but veins rarely approach each other
without communication ; they are also more numerouSj
much less regular, and larger than arteries. A portion of
vein removed from the body will be found more or less
coloured by blood which has remained in it after death.
The thinness of its walls will allow it to collapse when
placed upon a flat surface. Like arteries veins have three
coats, which differ from those of the arteries in the paucity
of their component elements. The internal or seroid coat,
however, requires notice, for, in addition to lining the
vessel, it projects into the cavity, double folds constituting
valves of a semilunar form. These always have their free
margins and concave surfaces directed towards the heart,
for they perform an important function in promoting the
circulation. According to the size of the vessel from one
to three valves may coexist at one particular part. Only
two arteries, aorta and pulmonary artery, possess valves,
and they look from the heart. Some veins, as those of the
foot, portal system, and several components of the ante-
rior and posterior venae cavse, have no valves ; in other
situations the valves are few in number. When not in use
during the forcible rush of blood through the vessels, the
valves lie against the sides of the vessel. This is their ordi-
nary situation in the jugulars, in which they come into
action only when the animal's head is lowered, as in
grazing ; under other circumstances the blood passes to the
heart in virtue of its own weight. Certain modifications
of veins, termed venous simises, will be noticed in due
course.

In addition to blood-vessels we find other vessels which
convey a fluid from which blood is prepared. The free
spaces of the body, and, according to some authorities,
even the serous cavities, are lined by an epithelial mem-
brane, continuous with that lining certain vessels termed
lymphatics, which unite and reunite until at length they
pour their contents into the blood-vessels. These vessels
probably run from all parts of the body ; the largest trunks
which they form are the tJioracic duct and the great right
lymphatic, which open into the large veins at the anterior
part of the chest. The smallest lymphatics resemble
the capillaries in structure, the largest closely resemble
veins, presenting valves, and passing towards the centre of

INTRODUCTORY. 23

circulation, but they anastomose less freely, tlieir valves
are less numerous, the fluid they contain is colourless, and
sooner or later almost all of them pass through certain
dark grey nodular bodies, found in various parts of
the body, termed lymphatic glands. These produce a
change in the nature of the contained fluid, and seem to
be mere means of economy of space, since some of the
lower animals in place of glands present extreme elonga-
tion and tortuosity of the lymph vessels. In these lower
aniniEfels the lymph vessels present in some parts dilata-
tions with thick muscular walls, lymph hearts, which
drive the lymph into the blood-vascular system in several
situations. In the higher vertebrata the communication
between the blood and lymph systems seems to occur only
at the anterior part of the thorax. Some authorities have
described these large lymph vessels as contractile.

Lymphatic glands consist of a special investing coat
with trabeculse passing inwards, dividing the contained
space into cavities, of which the external are most marked,
all of which are lined with epithelium. The external por-
tion, therefore, is softest, and is termed the cortical portion ;
the firmer central structure is the medullary structure. A
number of beaded afferent lymphatics converge and pass
into a gland ; they seem primarily to pass to the medullary
portion in which they are arranged in a convoluted mass.
They are supposed to open into the cavities of the gland,
lymph spaces, and the lymph to pass irregularly through
these until it arrives at the commencement portion of the
efferent lymphatics, which, larger and less numerous than
the afferent vessels, on emerging from the gland pass
towards the main lymphatic trunks.

The lymph vessels of the bowels are distinctively called
the lacteals, for the fluid they convey is rendered opaque
and milky in appearance by the presence of fatty globules
taken up from the contents of the intestines by these
vessels. They differ in no respect from other lymphatics ;
th,ey commence in the villi of the intestines either in blind
extremities, in loops, or in plexuses.

21* OUTLINES OF EQUINE ANATOM^

PART II— OSTEOLOGY.

THE SKULL,

with a few cartilaginous accessory structures, forras tlie
basement structure of the head. It is composed of modi-
fied vertebrae, united together in such a manner as to form
numerous cavities, mostly for the purpose of protecting
important organs. It is a conical body, the apex part or
muzzle, of which we shall consider as being directed for-
wards, the base towards the trunk to which it is united by
the neck. It is divided into the cranium, which corre-
sponds to the neural portion of the other vertebrae, and the
face, which is antero-inferiorly placed, and corresponds to
the haemal ring. The latter much predominates in size.

THE CRANIITM

consists of twelve bones, four pairs and four single. The
cavity formed by these bones will be considered when its
contents are to be examined ; we shall here examine as
distinct bones those osseous masses which, in the adult,
are firmly united into a single mass with those of the face
forming the upper jaw. The lower jaw is formed by a
special bone of the face (the inferior maxillary bone).
The union between the upper and lower jaws, and that
])etween the cranium and the first cervical vertebra, are
the only examples of synovial articulations to be found
in the skull. The union of os hyoides (the tongue bone)
with the base of the skull is fibro-cartilaginous. All the
other joints are immoveable, and sooner or later become
obliterated.

OS OCCIPITIS is the postero- superior bone of the
cranium, that which articulates with the atlas, and which
forms the "poll." It is divided into hody, condyles, basilar
procesSf and styloid 'processes. It is a single bone lying

OSTEOLOGY. 25

along the middle line of tlie body, and its basilar process
forms the posterior part of the base of the cranium. It is
elongated from behind, where it blends with the condyles,
forwards, where it is roughened, coming in apposition
with OS sphenoides. It widens posteriorly in extending
upwards towards the roots of the styloid processes, exter-
nally to the condyles, and in these parts we see a large
foramen on each side, condyloid, through which the lingual
nerve passes. We shall simply in future note the position
of the foramina of the skull, as a more detailed description
may be found elsewhere.

The under surface is convex, and anteriorly presents
roughened depressions for attachment of rectus capitis
anticus minor. Posteriorly it presents a small smooth
process, extending between the condyles, expanding poste-
riorly to blend with the upper surface in forming the
inferior part of foramen magnum. The upj^er j^ci'^t is con-
cave in all parts, most so posteriorly, where laterally it
presents the upper openings of the condyloid foramina ;
while anteriorly its external margins are sharpened, each
forming the inner boundary oi foramen lacerum basis cranii.
The condyles are two in number, forming the lateral
boundaries of foramen magnum. They are articulatory
prominences, convex in all parts, superiorly looking
upwards and slightly outwards, inferiorly downwards and
outwards. Their inner aspect is upwards and inwards ;
superiorly they join the body of the bone. From their
external angles run the styloid processes ; inferiorly they
are continued on to the basilar processes, converging, but
separated by a smooth concave surface. They are mainly
separated from the styloid processes by deep fossse, which
present the condyloid foramina. The styloid processes
are long, and extend in a downward direction, being
slightly curled inwards, and flattened from without in-
wards. They afford attachment to stylo-hyoideus, stylo-
maxillaris, digastricus, and obliqui capitis superior and
anticus, and one of the attoido-occipital ligaments. Their
anterior sarface at the superior part is roughened for
articulation with os temporale petrosum, and superiorly
their margin is continued upwards as the mastoid ridge to
the true crest of the bone. The body of the occiput is
continued upwards from the superior part of the condyles
and styloid processes laterally, centrally from the superior

26 OUTLINES OF EQUINE ANATOMY.

margin of foramen magnum, which it forms by means of a
concave, somewhat sharp margin. It presents three sur-
faces : the anterior internal surface is firm, and presents a
number of depressions for accommodation of the cerebellar
convolutions, from which it is separated by the membranes
of the brain. The posterior Surface is bound on either side
by the mastoid ridges, and meets the superior in forming a
prominent ridge with a backward inclination, crest or crista.
This surface is divided into two parts by a roughened line
extending from the centre of the crest towards foramen
magnum. To this the cordiform portion of ligamentum
nuchse is attached ; the concave roughened surfaces on
either side of it, scabrous pits, afford attachment to com-
plex! major and minor and recti capitis major and minor
postici. To the crest and mastoid ridges are attached
temporalis, obliquus capitis superior, levator humeri,
trachelo mastoideus, splenius, and (to the crest) some of
the auricular muscles. The superior surface of the bone
forms the posterior part of the forehead, and is roughened,
for from it commence the parietal ridges. Thus it affords
attachment slightly to temporalis on either side, and ante-
riorly presents an irregular margin dentated centrally
for union with os triquatrum, squamous laterally for union
with the parietal and more externally with the squamous
temporal bone.

OS TRiaUATRUM is a small shield-shaped portion of
bone, with a smooth and flat superior surface and dentated
margins ; ant ero -laterally convex, meeting at a rounded
point anteriorly for union with the parietals. Posteriorly
concave, thus presenting two prominent posterior angles,
articulating here with os occipitis. Its iiuier surface
presents the ossific tentorium, a remarkable bony promi-
nence, with three concave surfaces, uniting to form three
sharp margins, one at each side, giving attachment to the
membranous tentorium, one anteriorly for attachment of
the posterior margin of falx cerebri.

The PARIETAL BONES are flat and thin, presenting
two surfaces and five margins. The external surface is
convex, looking upwards and outwards. At its posterior
part it presents a few foramina for the passage of men-
ingeal arteries to the coverings of the brain. It is divided
into two parts by the parietal ridge, a slightly prominent
line of bone passing obliquely outwards from the anterior

OSTEOLOGY.

27

part of tlie crest of tlie occiput towards tlie orbital process
of the frontal bone, and whicb gives attachment to auri-
cular muscles. The outer division helps to form the
temporal fossa, and affords attachment to temporalis ; it is
continued by a thin, very rough squamous surface, on
which the squamous temporal bone rests. The inner
portion of the external surface is immediately subcu-
taneous. The poster 0 -internal margin articulates by suture
with OS triquatrum, the inner margin similarly with its
fellow. The anterior margin inwardly presents a rough
surface for squamous articulation with os frontis, out-
wardly the outer layer of the bone projects, so that \t rests
on OS frontis. The external margin forms the thin jagged
edge of the squamous suture with the squamous temporal
bone, as also does the postero-external margin, which meets
with the postero -internal, forming a point which articulates
with OS occipitis. The inner surface of the bone is mostly
covered with digital impressions for accommodation of the
cerebral convolutions, but along the postero-external
margin has a smooth groove through which a large vein
runs to torcular herophili, from a small foramen just
above the mastoid process of squamous temporal bone.
Below this groove, at its outer part, is a rough surface for
union with the petrous temporal bone.

OS FRONTIS (one of which is found on each side of
the cranium) forms part of the anterior and of the
superior portion of the cranium. It also forms^ the
supero-posterior part of the nasal chamber and a consider-
able portion of the inner wall of the orbit. So it presents
a cranial, a facial, and an orbital plate. The facial plate
is quadrilateral, smooth externally, internally^ at its pos-
terior part, blends with the cranial plate, at its anterior
is roughened, helping to form the frontal sinus. The outer
surface is flat, in parts convex, and subcutaneous with
exception of its outer margin which is covered by orbicu-
laris palpebrarum. From the posterior part of this
margin projects the orbital process, a long prominence,
flattened from above downwards, externally convex in
contact with the orbicularis palpebrarum, intei-nally con-
cave in contact with the lachrymal gland, having periorbi-
tale attached to its posterior margin. Its outer extremity
articulates with the zygomatic process of the squamous
temporal bone; its anterior margin forms the superior

28 OUTLINES OF EQUINE ANATOMY.

part of the rim of the orbit, its root becomes expanded in
becoming attached to the outer edge of the facial plate,
and presents the supra-orbital foramen. The anterior part
of this edge forms the inner part of the rim of the orbit,
and is continuous downwards with the orbital plate. The
anterior margin presents a laminated squamous surface to
the outer part of which the lachrymal, to the inner the
nasal bone becomes attached. The inner margin presents
a roughened edge for apposition with its fellow, from the
anterior part of which a thin plate of bone is reflected
downwards to form the inner boundary of the frontal sinus
lying in contact with its fellow. The posterior boundary is
squamous, most so on the outer side, for articulation with
the parietal bone. The cranial plate blends superiorly
with the posterior part of the under surface of the facial
plate, and presents digital depression for the cerebral
convolutions. Its inner margin is serrated and lies in
contact with its fellow. Its inferior margin joins the
upper part of the crista galli and cribriform plates of the
ethmoid. Its outer margin joins the orbital plate. The
anterior surface helps to form the frontal sinus, and from
the inner margin of the surface runs the vertical bony
septum which inf eriorly is reflected to form a narrow ledge
of bone running obliquely forwards and upwards in
blending anteriorly with the facial plate in a sharp point.
The orbital plate externally is concave, forming the inner
part of the orbit. Near the root of the orbital process it
presents the iibro-cartilaginous loop through which the
superior oblique muscle of the eye plays. Posteriorly it is
continued below the orbital j^rocess, helping to form the
temporal fossa, and articulating with the squamous tem-
poral bone. This plate presents a deep indentation, in-
feriorly extending upwards towards the orbital loop. It
terminates in a point, and accommodates the orbital surface
of OS ethmoides, which, by the older anatomists, was
termed os planum. The anterior margin inferiorly gives
attachment to os palati ; centrally to the superior maxil-
lary bone ; superiorly to the lachrymal bone. The inner
surface of this plate posteriorly is separated by a remark-
able groove from the cranial surface, and has a squamous
suture with the ala of the ethmoid ; centrally it gives attach-
ment to the cranial plate ; anteriorly forms the convex outer
wall of the frontal sinus. At the extreme postero-inferior

OSTEOLOGY. 29

part this plate in articulating witli os etlimoides forms
foramen orbitale internum.

OS ETHMOIDES forms a considerable part of the an-
terior boundary of the cranium, and consists mainly of a
body, from which an ala projects on either side, and a re-
markable process projects upwards anteriorly. The body
articulates posteriorly with the body of os sphenoides :
here it is rounded and solid, but anteriorly it presents two
large cavities, ethmoidal sinuses, indirectly continuous with
the nasal chamber. The under surface presents centrally
a small convex smooth surface, on either side of which is
roughened for squamous suture with the vomer. Each of
the sides of the body anteriorly is occupied with a squamous
surface for os palati, posteriorly by a continuation of that
on the posterior part for os sphenoides. The upper surface
looks in an upward and slightly backward direction, and
is concave. Posteriorly it i:)resents a peculiar depression
separated from the rest of this surface by a sharp ridge,
optic fossa, from which the two foramina optici pass through
the substance of the bone, for passage of the optic nerves,
running from the optic decussation, which rests in the fossa.
The wings look inward and slightly upwards. Their upper
surfaces are completely occupied in formation of the cere-
bral cavity ; they therefore present digital impressions. At
the line of junction of the u?ider surface with the body of the
bone posteriorly is the opening (inferior) of the optic fora-
men, and in front of this is a smooth groove, which by union
with a similar depression in os sphenoides forms foramen
lacerum orbitale. The outer margin of this surface of the ala
is mainly occupied by a squamous suture for union with the
special groove in os frontis ; and the smooth space be-
tween, by some anatomists described as a distinct bone, os
planum, serves to form a considerable part of the inner
wall of the orbit, fitting into the deep depression extending
from the inferior margin of the orbital plate of os frontis.
From the antero-superior part of the body crista galli pro-
cess runs in an upward direction, to join superiorly the
infero- central part of the cranial plates of ossa frontis.
Its superior extremity is enlarged, and presents a concave
triangular surface for os frontis. Its posterior margin is
sharp, smooth on either side and affords attachment
to the anterior extremity of falx cerebri. Anteriorly
it presents a more or less prominent ridge, extend-

30 OUTLINES OF EQUINE ANATOMY.

ing from above downwards, continuous anteriorly as
septum nasi. On either side it is jagged, and continues
as far as the anterior margin of the Avings by the cribri-
form pjates, perforated thin layers of bone through
which the fibres of the olfactory nerves pass, and which
posteriorly form the boundaries of depressions olfactory
fossa, in which the olfactory bulbs rest ; anteriorly have
attached to them certain thin plates of bone curled upon
one another in a complex manner, forming the ethmoid
cells, a direct continuation of the ethmoidal sinuses in the
body. These are portions of bone which derive their nutri-
ment directly from the mucous membrane which covers
them, having no special periosteum. In that mucous
membrane (and also that of the superior turbinated bone)
the fibres of the olfactory nerve are distributed, rendering
it the organ of the special sense of smell.

OS SPHENOIDES forms the major portion of the floor
of the cranium, and is situated between the occiput and
OS ethmoides. It consists of a body and two wings with two
crura or legs. The upper surface of the body is irregularly
concave, receiving the name sella turcica. Centrally it
supports the pituitary body, and on either side of this is a
depression in which rests the cavernous sinus, while extend-
ing on to the upper surface of each wing on each side we
see a groove for the superior maxillary division of the fifth
cranial nerve, running forwards to join the suhsphenoid
foramen i7i forming foramen rotundum. This is separated
anteriorly by a thin j)late of bone from a smooth groove,
which unites with another on os ethmoides to ioYv^ foramen
lacerum orhitale. The posterior extremity presents a rough-
ened ovoid surface for articulation with the anterior ex-
tremity of the basilar process of the occiput. Anteriorly is
a similar surface for apposition with the posterior part of
the body of the ethmoid, which is separated on each side
from foramen rotundum by a thin plate of bone, which
presents a small squamous surface for the antero -internal
part of the wing of the ethmoid. The under surface of
the body is convex, tending to become smooth anteriorly.
Posteriorly it is rough for insertion of a rectus capitis
anticus major on either side. The wing of os sphenoides
superiorly is concave and presents an irregular surface,
helping to form the cerebral cavity. Its posterior margin
is internally sharp, externally rounded, forming the anterior

OSTEOLOGY. ' 31

boundary of foramen lacerum basis cranii. Its superior
margin presents externally a squaiaous serrated surface for
the squamous temporal bone. In the angle which it forms
with the anterior margin is foramen pathetici. The anterior
margin, on its inner edge, articulates with the wing of os
ethmoides, superiorly presenting the smooth groove which
forms foramen lacerum orbitale, more externally foramen
rotundum, and on its outer edge a ridge to which peri-
orbitale is attached, which terminates inferiorly in an elon-
gated process, flattened from side to side. This is the
crus of the bone. Its siqjerior margin and anterior extre-
mity articulate with os palati ; its inner surface posteriorly
with OS pterygoideum, and to its inferior margin are
attached masseter internus and pterygoideus.

OS TEMPORALE SaUAMOSUM (one on each side of
the head) is situated at the postero-lateral part of the
head, and is so named because its main portion is almost
wholly occupied in squamosal connection with the neigh-
bouring bones. It is divided into two parts — body and
zygoma. The inner surface of the body superiorly along
its whole length articulates with the parietal bone. Its
anterior margin joins os frontis ; antero- inferiorly it joins
the wing of os sphenoides ; postero -inferiorly it presents a
deep notch, into which the petrous temporal bone with the
external auditory process fits. The posterior margin unites
with the petrous temporal bone, and at its extreme posterior
part with os occipitis. The central part of the inner surface
is smooth, and assists to form the wall of the cranium. The
external surface is divided into two almost equal parts by
a line running from the postero-superior to the antero-
inferior angle, from the anterior part of which the zygoma
commences. The space above this line helps to form the
temporal fossa, having temporalis attached to it, while
superiorly it presents some foramina. The inferior division
of this surface is smooth and centrally presents a groove,
the inferior opening of the canal between this and the
parietal bone. Just in front of this is a small rounded
prominence, the mastoid process, to which is attached one
of the ligaments of the temporo -maxillary articulation.
The zygoma is a large process, which is very thin, flattened
from above downwards, running directly outwards at its
origin. It is then twisted from below upwards (so that its
outer margin becomes superiorly placed), and runs in a

32 OUTLINES OF EQUINE ANATOMY.

forward direction. Its superior margin anteriorly presents
a roughened prominence, to whicli the outer extremity of
the orbital process of os frontis is united. In front of
this, the inner surface, is concave, forming part of the orbit ;
the outer surface presents a squamous suture, terminating
anteriorly in a point for the zygomatic or malar bone.
The rest of the outer surface affords attachment to masseter
externus. The superior surface, at its junction with the
body, forms a deep, smooth, rounded groove, in which the
coracoid process of the inferior maxilla fits. The under
surface presents the glenoid cavity coate i with articular
cartilage, extending from without inwards on to the body,
rounded posteriorly by the mastoid process ; it articulates
with the condyle of the inferior maxilla through the medium
of a disc of cartilage.

OS TEMPORAL PETROSTJM (Pair) is an extremely
irregular bone, wedged in between the occipital, parietal,
and squamous temporal bones. Its posterior surface lies in
contact with os occipitis, its anterior superior with the
parietal, inferiorly with the squamous temporal bone. It
is the hardest bone in the body, and co7itains the organ of
hearing (as will be afterwards described). Its inner sur-
face helps to form the inner surface of the cranium, and
presents digital impressions, with centrally /oramew audi-
torium internum. The external surface is very rough and
irregular ; superiorly it assists in forming the mastoid
ridge, giving attachments to several of the cervical muscles ;
centrally it presents the external auditory process, to
which the annular cartilage of the ear is attached, and
which is perforated by the external auditory hiatus, which
extends inwards as far as the tympanum. Below and in
front of this there is a prominence, which looks as if a
round peg had been driven into the bone ; this is the
hyoid process, to which the antero-superior angle of the
long cornu of os hyoides is united by fibro- cartilage.
Immediately below this is a rounded, roughened protu-
berance, denoting the situation of the mastoid cells inside
the bone ; hence it is termed the mastoid process. In front
of it is an elongated, sharp process, the styloid process, to
which tensor palati and stylo-pharyngeus are attached, and
just below and behind it is the styloid foramen, from which
the Eustachian tube passes to the pharynx.

OSTEOLOGY. 33

BONES OF THE FACE

are nine pairs and two single bones. We sliall first examine
the pairs.

OS NASI is a fiat bone, forming tbe major part of the
roof of the nasal chamber; presents two surfaces, two
margins, a base, and an apex. The lase of this bone has a
squamous laminated surface for union with os frontis.
The inner margin is straight, and lies in apposition with the
corresponding part of its fellow. The outer margin meets
it at an extremely acute angle, and as the anterior part of
the outer margin is free, the two points coming together
produce a remarkable prominence, to which the nasal car-
tilages are attached, and which is termed the nasal peak.
From the external surface of the bone, near the outer margin
of the nasal peak, dilator naris superior arises ; behind this
the margin is in apposition with the upper extremity of
the superior process of the anterior maxillary bone. It
then presents thin horizontal plates fitting into os niaxil-
lare superius, and at the outer angle of the base is a line of
union with os lachrymale. The superior surface is convex ;
inclined obliquely outwards over it passes nasalis longus
labii superioris. The inner surface, correspondingly con-
cave, is partly occupied by the expanded upper portion of
septum nasi, but inclined to its outer side it presents a
ridge to which is attached OS turbinatum superius. The
turbinated bones are extremely thin and friable in the
dried subject, but when fresh they are coated on both sides
by mucous membrane, which renders them elastic. Each
of them consists of two portions, one anteriorly placed,
belonging to the nasal chamber, the other to the sinuses of
the head. These bones are supplied with nutriment by
their investing mucous membrane ; they therefore have no
periosteum. They will be noticed more particularly in our
description of the nasal chambers and the sinuses of the
head.

Os turbinatum inferius is attached to the nasal surface
of the facial plate of the superior maxillary bone.

Os maxillare anterius is situated at the anterior part of
the upper jaw, lodges the superior incisors, and forms the
outer and inferior boundary of the anterior opening into
the nasal fossae of the skeleton ; it consists of a body and

3

34 OUTLINES OF EQUINE ANATOMY.

two processes. The body is externally convex, affording
attachment to levator labii superioris. Its internal surface
lies in contact with its fellow by a broad roughened surface,
and the two bones here together form foramen incisiorum,
running from the roof of the mouth at its extreme ante-
rior part. The anterior attachment of septum nasi extends
on the bone as far as this foramen. The inferior margin
of the body presents on each side three alveolar cavities,
into which the incisors lit. These are conical depressions,
separated from each other by thin bony plates ; thus the
two central incisors have between them two bony laminae.
Behind the convex alveolar line is a smooth portion of
the lower margin of the bone, and behind this is a ^portion
of the alveolar cavity for the tush, which is completed by the
superior maxillary bone. From the supero-posterior part
of the body an elongated process passes obliquely upwards
and backwards. It^ superior margin Y\m^ irom the upper
portion of the symjjhysis, first outwards, then upwards, as
far as os naris. It is rounded, to its external surface
dilator naris inferior is attached, and it winds round
towards the false nostril. Its posterior margin, inferiorly
by squamous suture, superiorly by schindylesis, is in con-
nection with the superior maxillary bone. The up^er
margin is united to the anterior part of the roughed por-
tion of the outer margin of the os nasi. The inner surface
forms the anterior margin of the lateral boundary of the
nasal chamber. The inferior surface of the body of this
bone slopes obliquely upwards and backwards, and centrally
terminates in a thin process, the p>alatine, running back-
wards towards the palatine process of the superior maxillary
bone. It is flattened from above downwards ; its extreme
postero-superior parts in some cases is in apposition with
the anterior extremity of the vomer ; it forms the inner
boundary of a space, incisive opening, which is generally
filled with cartilaginous matter continuous superiorly with
septum nasi, embedded in which is the organ of Jacobson.
Os maxillare superius is a large bone, with its fellow
forming a very considerable portion of the face. It assists
in forming several cavities, and completely forms one of
the facial sinuses, the inferior maxillary. These sinuses,
however, are only found markedly developed in the adult.
It presents two surfaces and four margins. The superior
margin is irregular, being in apposition with the outer

OSTEOLOGY. 35

margin of the os nasi ; it is but half the length of the
inferior. The anterior margin slopes obliquely downwards
and forwards, and joins the posterior margin of the nasal
process of the anterior maxilla. It meets the inferior margin
at an acute angle in forming the posterior boundary of the
alveolar cavity for the tush. The posterior margin presents
an irregular concavity looking upwards. It is a rough
squamosal surface extending into the outer part of the bone,
increasing in width from above downwards, superiorly in ap-
position with the lachrymal, inferiorly with the malar bone.
This surface terminates above in a projecting point, which
slightly meets the squamous temporal bone. The inferior
surface of the projection is smooth for the passage of the
superior varicose vein of the face ; below, and slightly
behind, is an irregular prominence, tuberosity, to which
buccinator and retractor labii inferiosis are attached. The
inferior margin along the greater part of its length is occu-
pied by the alveolar cavities for the upper molars. These
consist of a series of deep square cavities, separating the
bone into two plates, and separated from one another by
thin bony septa. Their walls correspond to the external
surface of the teeth, into the grooves of which the bony
matter is moulded. They are six in number ; the first and
last cavities of the series are triangular, and sometimes at
the anterior angle of the first is a small alveolar cavity in
which the premolar or " wolf's tooth " is situated. In
front of this the inferior margin is smooth and rounded to
its anterior extremity. The external surface slopes obliquely
downwards and outwards. From about the centre of the
articulatory surface of the posterior margin (which en-
croaches considerably upon the surface) the anterior ex-
tremity of the zygomatic ridge runs forward for a short
distance. It terminates about opposite the second molar
tooth ; to its under surface are attached masseter externus
and zygomaticus, just in front of its anterior extremity
retractor labii superioris arises. Buccinator posteriorly and
caninus anteriorly arise from this surface just above the
inferior margin ; and between the former muscle and the
zygomatic spine is the superior varicose vein of the face.
The superior maxillary or infra-orhitar foramen is situated
above and in front of the zygomatic spine ; through it the
major portion of the dental branch of the superior maxillary
division of the fifth nerve (after passing through the

36 OUTLINES OF EQUINE ANATOMY.

canalis infra orbitale, a special chanuel of the "bone which
runs through the maxillary sinus) emerges with an accom- •
panying artery, both run forwards concealed from view by
levator labii superioris alseque nasi. From the point of
junction of the malar, lachrymal, and superior maxillary
bones, nasalis longus labii superioris arises. A considerable
portion of the inner surface of this bone is occupied in
forming the outer wall of the nasal chamber. Along the
central line extending from before backwards is a ridge to
which the inferior turbinated bone is attached. At about
the centre of the bone this terminates in bifurcating, form-
ing two lines, one of which runs upwards and backwards,
the other downwards and backwards, mapping out that
portion of bone which forms the inferior maxillary sinus.
The extreme inferior margin affords attachment to the
gums of the roof of the mouth ; higher up is a groove
running forwards for the palatine artery, and above this a
horizontal process, palatine process, projects inwards. It
extends neither as far as the anterior nor as the posterior
extremity of the bone, but anteriorly, gradually diminishes
in size to terminate imperceptibly ; posteriorly presents a
squamous surface extending on to the small part of the
tuberosity for union with the palate bone. This surface
presents a smooth groove, which helps to form the palatine
canal. The free margin presents numerous spiculse of bone,
which serve to keep it closely in apposition with the palatine
process of its fellow, and the two together form a groove
into which the anterior part of the inferior margin of the
vomer fits. The iij)per surface of this process helps to form
the floor of the nasal chamber, the inferior surface is
covered by the mucous membrane of the hard palate, with
its rich venous plexus. This bone assists in forming the
superior maxillary sinus through which two bony canals
pass, the canalis infra orbitale, and the bony covering of the
ductus ad nasum.

OS LACHRYMALE forms the antero -internal part of
the orbit, assisting in forming its margin, thus being bent
upon itself in such a manner as to present two plates,
separated by the concave marginal border, which is for tbe
most part smooth, but centrally rather rough. The exter-
nal surface, therefore, as a whole, is convex, but it consists
of two concave plates. The anterior is the facial plate. It
presents at about its centre a tubercle (lachrymal) to which

OSTEOLOGY. O /

the orbicularis palpebrarum is attached. Above this it
gives partial attachment to labii superioris alseque nasi,
below to nasalis longus labii superioris. The posterior or
orbital plate is funnel-shaped, converging from all points
to towards the lachrymal foramen^ situated just behind the
centre of the marginal border. To this bone near this
foramen is attached the inferior oblique muscle of the eye-
ball, and in it rests the lachrymal sac from which the
ductus ad nasum is continued forwards through a bony
canal, running along and attached to the internal surface
of the facial plate of the bone. The i7iner surface of the
bone assists in forming the superior maxillary sinus, and is
therefore covered with mucous membrane. The anterior
margin is in contact with os nasi and also with the supe-
rior maxillary bone, which extends along the whole length
of the inferior margin, along the inner edge, while the
malar bone has a squamous union with a considerable por-
tion of the outer edge. The extreme posterior part of this
margin is smooth. The superior margin has a squamous
union with os f rontis, but at the posterior angle, where this
margin and the inferior meet, the lachrymal bone comes in
contact with os palati.

OS PALATI forms the anterior, posterior, and outer
boundary of the posterior naris. It is very irregular, but
mainly consists of a bony plate elongated from behind
forwards. This plate is convex on its internal surface, and
posteriorly is divided into two equal parts by a prominent
ridge. The upper part is articulatory supero-posteriorly
for union with the lateral part of the body of ethmoides ;
in front of this os f rontis occupies a small space ; os
lachrymale, a still smaller ni front of that ; but the greater
part of this division is covered with mucous membrane,
assisting to form the ethmoid sinus. Below the articula-
tion with OS f rontis is foramen spheno-palati7ium, which is
continued by a groove on to the inferior part, which, with
the inferior part of the ridge, posteriorly is united to the
])terygoid and (more inwardly) the vomer. Anteriorly
this part becomes much prolonged and is smooth and
concave, forming the posterior boundary of the posterior
nares. It becomes twisted from below upwards at its
anterior extremity, thus forming a peculiar process,
palatine, the inner margin of which is smooth, rounded,
concave, and coated with mucous membrane forming the

38 OUTLINES OF EQUINE ANATOMY.

anterior and external boundary of tlie posterior naris in
the skeleton. Its free extremity unites with its fellow ante-
riorly at a symphysis, and thus the two bones form a
''■ jpalatine arcli,'^ to which, in the fresh subject, the fibrous
layer of the fixed portion of the soft palate is attached.
The free margin of the ridge on the inner surface of the
bone is united to the vomer, and by the groove of that bone
separated from its fellow. The external margin of the
palatine process is convex, and presents a serrated edge for
union with the palatine process of the superior maxilla.
Posteriorly this roughened surface increases in size, pre-
senting a very wide squamous surface for union with the
inner surface of the tuberosity of the superior maxilla.
This surface is rough in all parts except at a central
groove running forwards, which combines with a similar
depression on the maxillary surface to form the palatine
canal. Behind this the bone is smooth ; it is over here the
superior maxillary division of the sixth nerve and the
internal maxillary artery course in their way from the
sphenoidal to the maxillary hiatus. The extreme posterior
part of the inferior margin articulates with the crus of os
sphenoides, assisting to form the pterygoid ridge, to the
superior part of the internal surface of which is attached
the pterygoid bone.

OS PTERYGOIDEUM is a small plate of bone attached
to the under surface of the cranium at its junction with the
face ; consists of two parts, the anterior of which is flattened
from side to side, the posterior from above downwards
and is the widest and thinnest. The anterior iorms a small
tuberous prominence, attached to the inner surface of the
palatine bone, curved slightly outwards at its extremity,
thus producing a groove through which tensor palati plays
(bound down by the pterygoid ligament) . The superior sur-
face of the posterior part articulates with ossa sphenoides
and palati, and its inner margin meets the vomer. To its
under surface masseter internus and pterygoideus gain
either direct or indirect attachment.

OS ZYGOMATICUM OR THE MALAR BONE forms the
major portion of the outer boundary of the orbit. It is
pyramidal, presenting three surfaces, three margins, a base
and an apex. The external surface is for the most part
convex, anteriorly it is flat, affording attachment to
nasalis longus labii superioris. Its inferior margin is

OSTEOLOGY. 39

surmounted by the middle portion of the zygomatic ridge,
to which masseter externus is attached. The superior
surface is concave, occupies the centre of the bone, being
continued neither to the superior extremity nor to the
inferior, and assists in foruiing the orbit. The internal
surface is concave, and wholly occupied by a squamous
surface ; the major portion lies in apposition with the
superior maxillary bone, but at the antero-superior angle it
unites with the lachrymal bone. The base, external and
internal margins are the sharpened edges of the squamous
surface. The superior margin anteriorly is serrated for
union with os lachrymale, centrally smooth, rounded, and
concave, forming the outer margin of the orbit ; pos-
teriorly it is continuous at the apex on to the superior
surface, forming a squamous facet for the antero-external
part of the zygomatic process of the squamous temporal
bone.

The VOMER, so named from the resemblance of the
corresponding bone in man to a ploughshare, is the only
single bone in the facial portion of the upper jaw.
It presents two margins, two extremities, and two surfaces.
This bone posteriorly forms the line of division of the
posterior nares ; anteriorly it is continued almost as far as
the anterior naris on the floor of the nasal cavity between
the two chambers. Its inferior border anteriorly presents
a roughened articulatory surface, which fits into a groove
formed by the junction of the palatine processes of the
superior and anterior maxillae of one side with the corre-
sponding parts of the other, being an example of the form
of joint known as schindylesis. The posterior part of th^
inferior border is covered by mucous membrane ; centrally
it is sharp, dividing the posterior nares, posteriorly expands,
terminating on either side in a sharp point, which is con-
cealed by the pterygoid bone. The superior margin con-
sists of two thin plates of bone passing upwards one on
each side to form a groove into which septum nasi fits.
These plates gradually increase in length (and the groove
accordingly in depth) from before backwards to about the
anterior part of the posterior third of the bone, where they
become widened, presenting on their external surfaces
concave squamous articulations for the inner ridges of the
palatine bones. At the extreme posterior part they meet
the under surface of the ethmoid and sometimes extend as

40 outlitntes of equine anatomy.

far as os spHenoides. The groove also becomes wider here,
receiving the postero -inferior thickened angle of septum
nasi. The apex of the hone rests on the palatine processes
of the anterior maxillae. The hase is formed by the pos-
terior angular prolongations with their separating depres-
sion. It consists of a sharp concave ridge. The surfaces
are the outer surfaces of the thin plates, and are covered
by the Schneiderian mucous membrane.

THE LOWER JAW

is formed by a single bone, the INFERIOR MAXILLA,
which articulates with the upper jaw only at the glenoid
cavities of the squamous temporal bones, though connected
with it by soft structures in many parts in the fresh sub-
ject. It consists of two exactly similar halves united to-
gether by the symphysis at the interior part. Between these
anteriorly is situated the tongue, postero- superiorly the
l)harynx and guttural pouches. Each side of the bone
presents two surfaces, two margins, and two extremities.
The superior extremity is divided into two parts by a deep
notch through which a branch of nerve passes.

The anterior part is the coracoid process, which runs
upwards for a considerable distance, inclined backwards.
It is flattened from side to side and rests in the temjDoral
fossa. Its inner surface affords attachment to temporalis .
The posterior part is the condyle ; it is elongated from side
to side, convex in every direction, with a slight oblique
inclination inwards. It is coated with articular cartilage,
and through the medium of the inter-articular disc of car-
tilage, articulates with the glenoid cavity of the squamous
temporal bone. The condyle affords attachment to the
capsular ligament around its margin, externally also to its
strengthening accessory band. Below the condyle on the
inner side pterygoideus is inserted, and here the external
carotid artery terminates its temporal branch, winding round
the posterior margin of the jaw. The anterior extremity or
body is flattened from above downwards, presenting two
surfaces and two margins. The superior surface is concave,
sloping from without inwards, covered by the mucous
membrane of the mouth, from which internally frsenum
linguse passes. The inferior surface is convex, sloping
from the external to the internal margin and backwards.

OSTEOLOGY. 41

Superiorly it is covered by tlie gums ; below tliis depressor
labii inferioris lias its origin. The external margin presents
three alveolar cavities for the lower incisors, slightly
smaller than those in the upper jaw, and behind these,
after a short interval, the alveolar cavitij for the tush, which
is more anteriorly placed than its superior corresponding
cavity. The internal "mar gin is rough, and by uniting
with its fellow forms the symphysis. Behind the body
the bone is constricted, forming the neck, which partly lies
in contact with the buccal mucous membrane. Its external
surface superiorly presents the curved line of attachment
of carinus ; below this is the anterior maxillary foramen or
foramen menti. Below this the bone is subcutaneous.
Both its superior and its inferior margins are rounded.
The latter to its inner side has digastricus attached as far
forward as the symphysis. The neck terminates posteriorly
where the alveolar cavities of the molars commence. They
resemble iu general cliaracters and number those of the
upper jaw, and occupy a considerable portion of the superior
margin of the bone, which extends gradually backwards
and upwards, and which from the last alveolar cavity
curves upwards to join the anterior margin of the coracoid
process, aifording attachment to buccinator and to re-
tractor labii inferioris. Buccinator also becomes attached
to the bone up against the alveolar cavities on the external
surface ; below this retractor labii inferioris runs forwards,
the rest of the anterior part of this surface is separated from
the skin only by retractor anguli oris. But behind the
molars the bone becomes much expanded, in consequence
of increased convexity of the inferior margin, which pro-
trudes postero-inferiorly forming the angle of the jaw to
which sterno-and stylo-maxillaris are attached, the latter
to the inner, the former to the outer edge. The margin
above this is thickened and tuberous. The parotid gland
is in contact with it. The expanded portion is termed the
ramus or branch, and being concave both externally and
internally its central portion is very thin. On both sur-
faces it presents roughened ridges extending from above
downwards which on the external surface serve to give
attachment to masseter externus, on the inner side to
masseter internus, which latter muscle hides the posterior
maxillary foramen to which the inferior dental artery and
nerve pass, and having entered it course along below the

42 OUTLINES OF EQUiyE ANATOMY.

fangs of tlie molars as far as the anterior maxillary fora-
men, where each sends a branch outwards, while the main
portion continues on in the bone to supply the incisors
and tush. The upper edge of the internal surface up
against the molar teeth is termed the alveolar ridge, and
affords attachment to mylo-hyoideus, the external surface
of which muscle lies in contact with the bone as far down
as the inferior margin, where the submental branch of the
submaxillary artery passes forwards, just abovethe attach-
ment of digastricus. Below this the inferior margin of the
bone is rounded and covered with panniculus ; at the com-
mencement of the ramus it presents one or more promi-
nences, which serve to mark where the submaxillary vessels
and the parotid duct wind round the jaw.

THE VERTEBRA.

The distinctive characteristic of vertebrata is the pos-
session of a central chain of bones forming a spinal column.
The chain is composed of vertebrae, and to the vertebrae
all the other bones of the body are appended, so that each
vertebra with its bony appendages constitutes a vertebral
segment of the body. These vertebral segments differ in
number in different animals, and frequently vary in animals
of the same species. They are between fifty and sixty in
number in the horse. A complete or typical vertebral
segment consists of two similar arches united in forming
a rounded body or centrum. One is placed superiorly to
the centrum, and as it encloses the nerve-centres of animal
life is termed the neural arch; the other is inferiorly
placed, and is termed the hcemal arch, — it encloses the
organs of vegetative life, including circulation, respiration,
digestion, and involuntary motion. Each arch may be
divided into five parts ; those of the neural arch are :
pedicles, running upwards from the supero-lateral parts
of the body ; lamince, running from the upper extremities
of the pedicles to meet in the central line, and from the
point of junction the neural or superior spinous process runs
upwards. These parts may be found in almost all the
vertebral segments, though only in a rudimentary con-
dition in the coccygeal region. The haemal arch can be
recognised only in the dorsal, though found under ex-
treme modification in most of the other regions. Here

OSTEOLOGY. 43

we see the ribs running downwards from tlie lateral parts
of the body, continued by the sterno - costal cartilages,
between which, at their lower extremities, is the sternum or
hcemal spine. From various parts of the arches processes
project ; thus at the anterior and posterior extremity of
each lamina is an articular or oblique process, with a syno-
vial facet for union with the neighbouring vertebrae, A
process is also found on the point of union of the neural
laminae and pedicles which generally unites with another
from the point of junction of the pedicles and the centrum,
forming the transverse processes of the cervical and dorsal
vertebrce. The lumbar transverse processes consist simply
pf the inferior process, the superior in this region being
blended with the anterior oblique. The two in the cervical
region are distinct at their commencement, but united at
their free extremities ; thus they form, the vertebral fora-
mina. From the under surface of the centrum, in some
parts, a process arises and passes in a downward direction ;
this is generally termed the inferior spinous process.

The spinal vertebrae, as a rule, present the centrum with
the neural arch and its processes. The centrum has a
flattened superior surface, from each extremity of which
triangular roughened surfaces extend towards the centre,
where their apices are slightly separated by a smooth
channel which connects other channels situated between
the roughened surfaces and the inferior extremities of the
laminae. The anterior surface of the body is convex, and
is attached by means of a disc of fibro-cartilage to the
posterior surface of the vertebra in front, which is corre-
spondingly concave. The extremities of the body are its
widest parts, so that its central portion is smallest ; it
presents two surfaces converging to form a prominent line
extending from before backwards along the under surface.
It is this line which, in some cases, forms the inferior
spinous process. The ring or arch of the vertebra is formed
by the lamince and pedicles ; the latter present grooves on
their anterior and posterior margins, and the anterior
groove of the vertebra, uniting with the posterior groove
of the vertebra in front of it, forms an intervertebral
foramen or gap, by means of which nerves escape from,
and vessels pass into, the spinal canal. The vertebrae of
the spinal column may be true or false, the true vertebrae,
or those which are capable of more or less extensive motion

4-1 OUTLINES OF EQUINE ANATOMY.

upon tlie neiglibouring vertebrae, and wliicTi present a
regular set of the processes of the neural arch, including
spinous (superior and inferior), oblique (anterior and pos-
terior), transverse (simple or compound). True vertebrae
are found in the cervical, dorsal, and lumbar regions ; they
do not all present all the processes above named, but their
processes present a certain amount of regularity. This
is different in the coccygeal vertebrae, and as the sacral
bones coalesce the vertebrae in these two regions are termed
false. The distinction between true and false vertebrae is
very artificial. The vertebrae in these different regions
present peculiarities which are distinctive, but it will be
observed that the characters are gradually assumed ; thus,
the vertebrae in the posterior part of a region tend to
assume the figure of those of the anterior part of the next.
The specific characters are, therefore, best marked in
the central vertebrae of a region. We shall, therefore,
describe the third cervical, ninth dorsal, and third lumbar
vertebrae as typical of their several regions. The sacrum
will be examined as a whole, the coccygeal vertebrae will
require but slight notice.

THIHD CEHVIGAL VEHTEBRA

presents a regular ring and set of processes. The body
is long, enlarged at each extremity. The anterior extremity
is heart-shaped, looks downwards and forwards, is convex,
and has its base superiorly placed. It is convex in all
directions, and by a disc of cartilage is connected to the
posterior sarface of the body of the second cervical vertebrae.
The posterior extremity is mainly occupied by a large con-
cave surface, to which the intervertebral disc is attached.
Its margin is slightly flat superiorly, and it looks upwards
and backwards. Its outer circumferent margin is a sharp
ridge ; its upward aspect serves to prevent dislocation
downwards. The upper surface of the body presents the
arrangement already noticed, and through the lateral and the
transverse grooves run venous sinuses. The roughened sur-
faces are for attachment of the superior vertebral ligament,
and are large in corresponding proportion to the size of the
body. T\iQ lateral surfaces of the body are somewhat rough,
and converge towards the central line of the inferior part
where they meet, in forming a ridge extending from the apex

OSTEOLOGY. 45

of the anterior articular surface, to a roughened tubercle
situated below the centre of the posterior articulatory
surface. This is the inferior spinous processes, and to
them, as well as to the lateral surfaces, which are slightly
concave, longiis colli is attached. The pedicles present
the superior root of the transverse process arising from
their external surface, extending obliquely from the an-
terior oblique process downwards and backwards. The
superior spinous process arises as a sharp ridge, becoming
expanded, rough, and blended with the posterior oblique
processes posteriorly ; to it are attached ligamentum nuchse
and the superior spinous ligament. On either side of this
the superior surface of the laminae is concave and rough,
anteriorly presenting a groove circumscribing the anterior
oblique process, posteriorly a circular line, marking the
commencement of the roughened upper surface of the pos-
terior oblique process. The anterior, and posterior margins
of the laminae between the oblique processes are concave,
and afford attachment to the interlaminal ligaments. The
oblique processes are all very large, present extensive
roughened surfaces for muscular attachment, and large
circular articulatory surfaces. The anterior articulatory
facets look upwards and inwards, and are slightly convex,
the posterior downwards and outwards, and are slightly
concave. The two anterior oblique processes are connected
by the above-mentioned sharp anterior margin of the
laminae, the posterior processes by a thick concave roughened
line, which is the posterior margin of the laminse, and
serves to unite two roughened prominences separated from
the articulatory surfaces by a slight groove. The trans-
verse processes each present two roots separated by a
canal, through which the vertebral artery vein and branch
of the sympathetic nerve pass. The upper root is derived
from the outer surface of the pedicle at a line extending
obliquely from its antero- superior to its postero-inferior
angle. The other root commences at the supero- lateral part
of the body of the vertebra. The vertebral canal is con-
tinued backwards to the posterior part of the body by a
smooth groove ; anteriorly it commences at a funnel-shaped
opening just behind the anterior articulatory surface. The
process has two tubercles on its free margin, both of which
are rough and tuberous. The anterior extends obliquely
downwards and forwards, the posterior runs horizontally

4Q OUTLINES OF EQUINE ANATOMY.

backwards, slightly curled upwards at its roughened free
margin. Both of these tubercles a^ord attachment to
muscles. The inferior surface of the process is concave
and rough ; the superior surface convex. Its anterior margin
is concave, smooth, and rounded ; its posterior margin con-
cave and sharj).

CEEVICAL VEETEBRJE

in general are remarkable for their size, for the large size
of their foramina magna and intervertebral gaps, for the
regularity and uniform length of their processes, and for
their general roughnesses, and the facilities they afford for
muscular attachment. Each of them, however, presents
modifications. The first two, atlas and dentata, approxi-
mate the characters of the vertebrae which are modified
to form the skull ; the last two tend to assume the dorsal
type. The third, fourth, and fifth are with difilculty dis-
tinguishable. The following modifications will he observed in
examining the vertebroe from the third to the seventh.

The posterior part of the superior spinous processes
becomes more separated from the posterior oblique pro-
cesses. The anterior and posterior oblique processes in
the third are separate, in fourth united by a thin ridge,
in fifth by a roughened ridge. The concavity between the
superior spinous process and the anterior oblique processes
becomes more and more marked to the sixth. The articula-
tory surfaces on both oblique processes increase in size from
before backwards, as do also the vertebral foramina, and
the articulatory surfaces gradually change from the vertical
to the horizontal position. The inferior spinous process
decreases in size to the sixth, where it is almost imper-
ceptible; it becomes larger m the seventh and very irregular.
The posterior tubercle from before backwards manifests a
tendency to division, which in the sixth is very marked, so
that the superior and inferior parts foim distinct promi-
nences, of which the superior is triangular, concave pos-
teriorly. From the dentata to the sixth the superior
spinous processes decrease in size, but the seventh has a
broad superior spinous process terminating superiorly in
a point. This is the shortest of the cervical vertebrae. Its
transverse process is square, undivided, and has only one
root. Its posterior oblique processes present much smaller

OSTEOLOGY. 47

articulatory surfaces than the anterior, but not the smallest
in the neck. They come into contact with the anterior
oblique processes of the first dorsal vertebra. This ver-
tebra, at the supero-posterior and lateral parts of the body,
has a concave synovial facet on each side for the head of
the first ribs. The first and second cervical vertebrae
require more detailed description.

ATLAS is the first cervical vertebra, and in it we see a
manifestation of analogy with the cephalic vertebrae in the
expansion of its parts. Its ring is very large, ovoid from
side to side anteriorly, circular posteriorly. It accommo-
dates the commencement portion of the spinal cord with
its membranes, the commencement portion of the basilar
and of some meningeal arteries, the spinal accessory nerve,
some venous sinuses and fat. Also posteriorly the odontoid
process of the dentata, with its ligaments. The body is very
small, flattened from above downwards. Its superior sur-
face anteriorly has a roughened groove, extending on either
side outwards and backwards for attachment of the odon-
toid ligaments. Posteriorly it presents an articulatory
surface concave from side to side, surrounded by a ridge,
continuous with the articulatory surface upon the posterior
part of the bone. The inferior surface is convex. Anteriorly
it has the lower part of the articulatory surfaces for the
condyles of the occiput, converging inferiorly, where they
are separated by a groove to which their synovial mem-
branes are attached, and which is continuous with a small
triangular space on the antero -inferior part, which is occu-
pied by a ligament. At the postero-inferior part of the
body is a prominence looking backwards, tubercle or in-
ferior spinous process, to which longus colli (and the
inferior vertebral ligament) is attached. On either side of
this the bone is rough for attachment of obliquus capitis
anticus. Opposite the articulatory surfaces it is convex
and bulging, between these somewhat concave and smooth.
The pedicles run obliquely upwards and outwards from the
lateral parts of the body of the bone, being concave and
rough internally, convex externally, and expanded at either
extremity, forming those portions of this vertebra which
correspond to oblique processes of others. Anteriorly the
expanded part presents an articulatory facet for union with
a condyle of the occiput. It superiorly looks downwards
and slightly forwards, running outwards. It then becomes

48 OUTLINES OF EQUINE ANATOMY.

reflected inwards and looks upwards ; inferiorly, a small
portion looks directly inwards and converges tow^ards, but
does not quite meet, its fellow. Thus we have formed an
irregular cotyloid cavity.

The posterior expanded portion of the pedicle presents a
convex triangular facet, having its apex at the postero-
external angle of the lamina sharp and acute, its infero-
external angle rounded, its infero-internal angle continuous
with the smooth postero- superior part of the body. It
looks inwards and backwards, and comes into connection
with the anterior surface of the body and with the odontoid
process of the dentata. The laminae internally are concave
and rough ; exiernally convex, having a small ridge centrally
at the anterior part, a rounded and roughened promi-
nence for attachment of the superior spinous ligament and
rectus capitis posticus minor posteriorly. The anterior
margin is a sharp ridge, forming a concavity affording
attachment to the capsular and lateral ligaments of the
attoido-occipital joint, extending from the articular surface
for one condyle to that for the other. At the antero-
external angle the point of junction of the lamina and
pedicles is pierced by a foramen extending into the spinal
canal, continuous with one in the anterior part of the wing.
This gives passage to the suboccipital nerve, and to a
branch of artery going inwards to assist in forming the
basilar. The transverse process ala, or wing, extends from
above downwards and backwards, obliquely to the infero-
external angle of the posterior articular surface. It is a
thin plate of bone, extending downwards and outwards ;
since its surfaces are concave it is thinnest at its centre, and
here it is pierced by a foramen leading from a groove, through
which the vertebral artery passes from above downwards.
Its outer margin is convex, thick, and rough, and extends
obliquely downwards and outwards, posteriorly a little
behind the rest of the bone at its most convex part. It
affords attachment to several muscles of the neck, levator
humeri, splenius, trachelo-mastoideus, also to obliquus
capitis superior and obliquus capitis inferior. In the con-
cavity beneath the wing the union of the vertebral artery
with ramus anastomoticus takes place, and the resulting
branch passes through the anterior foramen, thus gaining
the superior surface, sending one branch into the spinal
canal, the other to the poll. The superior cervical ganglion

OSTEOLOGY. 49

is also situated in tlie concavity of tlie under surface of the
wing.

The DENTATA OR AXIS is tlie largest and tlie longest
of the true vertebrae, and has the largest superior spinous
process ; it is the second cervical vertebra. Its body is
very long, but superiorly presents the usual arrangement
for venous sinuses and the attachment of the superior
vertebral ligament. Anteriorly it presents a synovial sur-
face for union with atlas, and centrally the odontoid
process : superiorly this process is separated from the rest
of the upper surface of the body by a rough line from
which another runs forward to the anterior margin. The
space on either side between the ridges is concave ; to the-
transverse ridge is attached the broad, to the concavities
the short odontoid ligaments. The anterior margin is
convex, the lateral margins sharp and elevated. Theinfero-
lateral surface of the process is convex and articulatory,.
coming into connection with the postero-superior part o£
the body of the atlas. It is most prominent at the centre
of the posterior part, forming a small tubercle. It is con-
tinued on either side on to the antero-extornal part of the
body as a rounded synovial surface, looking obliquely
upwards and outwards. The under surface of the body
centrally presents a prominent ridge, sharp posteriorlyy
roughened anteriorly. It affords attachment to longus colli
and to the inferior vertebral ligament. Anteriorly it does
not extend as far as the odontoid process, from which it is
separated by a groove, which extends completely round the
anterior part, affording attachment to the capsular' liga-
ment of the atlo-axoid articulation, separating the inferior
spinous ridge from the outer circumferent margin of the
anterior articulatory' surfaces, which here cause expansion
of the bone. Posteriorly the body laterally presents tv/o sur-
faces, converging towards the inferior ridge roughened for
attachment of longus colli. From the supero-lateral part,
of the body the transverse processes run obliquely upwards
outwards, and backwards ; they have two roots, a broad
concave one, inferiorly separated by the vertebral foramen
from a smaller one superiorly situated. This process is
undivided at its free extremity. The pedicles are long and
high, thus rendering the foramen magnum longest verti-
cally ; their inner surface is rough and concave, their outer
roiicjli and straight. The posterior margin is concave, assist-

4

50 OUTLINES OF EQUINE ANATOMY.

ing tlie third cervical vertebra to form an intervertebral
gap. The anterior margin is very deeiDlj indented, generally
forming a large foramen, bounded anteriorly by a small
thin jn-ocess of'bone or of white fibrous tissue ; from this a
smooth broad grove runs downwards to the vertebral fora-
men ; it gives exit to the second cervical nerve, and also
gives passage to vessels. The ]josterior surface of the body
and the oblique processes (of which there are but two, pos-
teriorly placed) resemble those of the following cervical
vertebrae already described. The laminaB inferiorly form
the superior part of the ring, superiorly are wholly occupied
by the superior spinous process, which is very thick, and
from before backwards increases in height, thickness, and
roughness of its superior margin. This margin <x?iferior%
affords attachment to rectus capitis posticus major and to
the superior spinous ligament, j)osteriorly to ligamentuni
nuchte and complexus minor. It bifurcates posteriorly,
and its divisions blend with the oblicpie jn'ocesses. To the
sides of this process obliquus capitis inferior is attached
along its whole length.

THE BOESAL VERTEBR-ffi

are eighteen in number, and are characterised by the length
of their superior spinous processes, and by the synovial
articulatory surfaces on the supero -lateral parts of their
bodies for union with the heads of the ribs, also by articu-
latory surfaces on their transverse processes for union with
the tubercles of the ribs. They are the smallest of the true
vertebrae. In the anterior part they tend to assume the
cervical, in the posterior the lumbar type.

NINTH DOESAL VERTEBRA.

The body, on the upper surface, presents the usual
arrangement. Its two sides present superiorly at the
anterior and posterior parts concave synovial facets, ex-
tending on to the external surfaces of the pedicles. The
anterior facet looks forAvards and outwards, and comes into
connection with the posterior facet of the rib in front. The
posterior facet looks backwards, and slightly outwards, ana
is for the anterior facet of the head of the rib behind.
■ Below this the sides are concave from before backwards,

OSTEOLOGY. 51

and meet inferiorly in forming a median ridge (wliicli in
some of the vertebrae of tlie dorsal region is elongated to
form tlie inferior spinous process). Eacli of the sides at its
centre, though inclined to the anterior part, presents a
medullary foramen, through which a branch of the inter-
costal artery passes. The under surface of the bodies of the
anterior six dorsal vertebrae is covered by longus colli, of
the posterior three by psose parvi, of the central ones by the
vena azygos on the right side, thoracic duct centrally,
posterior aorta on the left. The anterior surface is convex
and circular, somewhat flattened superiorly. It gives
attachment to the intervertebral disc, and is adaj)ted to
the posterior surface of the body of the vertebra imme-
diately in front of it. The posterior surface is correspond-
ingly concave. The pedicles are internally smooth and
concave, externally rough, slightly encroached upon by the
facets for the heads of the ribs. Anteriorly and posteriorly
they have grooves for the intervertebral gaps scarcely per-
ceptible anteriorly, posteriorly, in some cases, converted
into a foramen. Centrally, at the point of junction with
the lamina, is a tuberous process, rough for muscular
attachment (of longissimus dorsi and levatores cos-
tarum). This is the transverse process, and has on its
external surface a small irregular convex synovial facet for
the tubercle of the rib, having between it and the posterior
facet on the body a smooth groove, extending from the
intervertebral gap. The laminae are concave inferiorly,
forming the roof of foramen magmini, supero-posteriorly,
wholly occupied by the superior spinous process, supero-
anteriorly presenting a small synovial facet od each side,
representing the anterior oblique processes ; the posterior
oblique processes are on the postero-inferior part. The
superior spinous process, remarkable for its length, runs
obhquely upwards and backwards. Superiorly it is tuberous,
affording attachment to the superior spinous ligament, and
so indirectly to muscles. Its anterior margin is sharp,
especially inferiorly, affording attachment to the inter-
spinous ligament. It is much longer than the posterior
margin, which is centrally sharp, having on either side
a groove, deepest inferiorly, bounded externally by a
roughened margin. They terminate just above the pos-
terior oblique processes. The central sharp ridge bifurcates
inferiorly, one division running to each oblique process.

52 OUTLINES OF EQUINE ANATOMY.

To fhis margin also is attached the interspinous liga-
ment.

Deferences in the Dorsal Vertebrae.

Superior spinous jrrocesses increase in length to fifth, then
decrease to thirteenth, the rest being about uniform ; they
are inclined backwards to the sixteenth, which is upright ;-
the seventeenth and eighteenth incline slightly forwards.
First comes to a point superiorly ; the rest increase in rough-
ness and thickness to the sixth, and in width from before
backwards in the twelve posterior vertebrae, in which also'
may be noticed a concavity just below the anterior part of the
superior extremity. In the central vertebrae the anterior
margin is rough about at its middle. The transverse p-o-
cesses are large and mainly articulatory in the first, and gra-
dually become modified in the last until each of them con-
sists of two portions, the superior of which is blended mth
the anterior oblique process, the inferior, articulatory, con-
tinuous with the anterior facet on the lateral part of the
body of the vertebra in the case of the last two. The
articulatory facets for the heads of the ribs gradually decrease
in depth from before backwards. The intervertehral notches'
on the ijosterior part of the pedicles are in the fourth to the
sixteenth vertebrae converted into foramina ; hence the fifth
to the seventeenth have no anterior notches. The articu-
atory surfaces on the anterior ohlique processes are larger than
those on the posterior. The former look outwards, the
latter inwards ; their tendency in this is increased from
before backwards. The ohlique processes of the first four
vertebrae are distinct ; in the other vertebrae the articular
surfaces are continued on to the laminae. Inferior spinous
processes are marked only in the six anterior and three pos-
terior vertebrae. The foramina magna are largest m the
anterior, smallest in the central^ vertebrae. The smooth
grooves on the iipper surface of the body are most marked
anteriorly. The last dorsal vertebra has no posterior arti-
culatory surfaces for the heads of the ribs, and its anterior
surfaces are blended with those of its transverse processes.

THE LUMBAR VERTEBRA

are the vertebrae forming the basement structure of the
loins,, situated between the dorsal and the sacral regions.

OSTEOLOGY. 53

In general characters tliey resemble tlie dorsal vertebrae ;
we shall, therefore, only notice their peculiarities. These
vertebrre are five or six in number, are larger than the
dorsal, and each presents a large foramen magnum and
transverse processes ; also has no articulatory surfaces for
the heads of the ribs. The superior spinous processes
resemble those of the posterior dorsal ; all look forwards ;
are- short and stout, elongated from above downwards,
tuberous at their upper extremities, anteriorly presenting a
sharp margin, posteriorly a double margin, both for attach-
ment of the interspinous ligaments. The oblique processes
tend to assume a peculiar rounded hinge-like character;
those on the posterior part present a rounded convexity,
elongated from behind forwards, looking outwards and
' downwards . The anterior ohlique pirocesses have articulatory
surfaces looking upwards and inwards. The intervertebral
gaps are large, the transverse processes, formed by a single
root, extend directly outwards, those of the anterior ver-
tebrae having a slight inclination backwards, those of the
posterior forwards. Their length is characteristic of the
vertebrae of this region. They are flattened from above
downwards, and of the first five vertebrae are tuberous at
their free extremities, affording attachment to quadratus
lumborum, psoas magnus, and indirectly to some of the
.abdominal muscles.

The anterior and posterior margins are sharp, affording
.attachment to intertransversales lumborum ; the upper and
under surf axes are smooth ; the former affords attachment
to longissimus dorsi, which occupies the space between
this and the superior spinous process ; the latter to the
ipsoae muscles. When six lumbar vertebrae exist the trans-
verse process of the sixth is much shorter than the rest,
.and presents articular synovial facets^hoth on its anterior and
its posterior margins, ovoid and elongated from side to side,
separated by grooves from the amphiarthrodial facets of
the body. These present special ligaments, and the poste-
rior one slants from without inwards and backwards, being
in connection with the first sacral transverse process.
The anterior slopes in a similar direction, articulating
vwith a corresponding facet on the posterior part of
rthe fifth lumbar transverse process. The latter, where
there are only five lumbar vertebrae, is modified to join the
.sacrum. Most horses present six, most asses five, lumbar

54 OUTLINES OF EQUINE ANATOMY.

vertebrae. The bodies of tbese vertebrae are larger and
more prisuiatic than those of the dorsal, terminating iiife-
riorly in somewhat marked ridges, inferior spinous pro-
cesses, for attachment of the inferior vertebral ligament, to
which the crura of the diaphragm are attached. To their
lateral surfaces] the psose parvi muscles are attached; their
anterior and posterior surfaces present but shallow concavi-
ties and convexities. The bodies and foramina magna
decrease in height from before backwards ; so at the poste-
rior part of the last lumbar the body presents a shallow
surface, very much elongated transversely.

THE SACRUM

in early life, consists of five distinct vertebrae, which in the
adult become firmly united by healthy bony union, whereby
a firm basis for attachment of the hind limb is afforded.
We therefore shall view it as a single bone, since it acts as
such. It is situated at the j^osterior part of the spinal
column, between the lumbar and coccygeal vertebrae. It
articulates laterally with the venter ilii. It is pyramidal
in figure, its base being anteriorly placed ; sometimes it is
composed of six bones, in consequence of coalescence of the
first coccygeal vertebra with its ajjex. It is a false ver-
tebra, as its segments are not capable of moving upon each
other. The base presents laterally foramen magnum coming
to a point superiorly at the root of the superior spinous
process, broad inferiorly. It leads mto a canal which
gradually and regularly decreases in size from before back-
wards, being extremely small posteriorly. The spinal cord
extends into this about as far as opposite the second sacral
bone ; the membranes of the cord are continued farther.
Below this opening is an articulatory surface, the transverse
diameter of which is about twice as long as the vertical ; it
is slightly convex in all directions. At the sui3ero -lateral
parts of the foramen are the oblique processes, which are
roughened externally, and internally present concave facets
looking uj^wards and inwards. From the inferior part of
the anterior margin of each of these a thin ridge runs to
meet its fellow at the root of the superior sj^inous j^rocess
of the first bone. Below the oblique processes are the
intervertebral notches, which lead into grooves running
from the upper to the under surface of the transverse pro-

OSTEOLOGY. 55

cess of tlie first bone, separating the articulatory surface of
the body from those on the anterior margins of the transverse
processes, wliicli overhang the grooves inferiorly in a re-
markable manner. These surfaces come into contact with
those on the posterior margin of the transverse processes
of the last lumbar, of which they are the exact counterparts,
being almost flat, looking inwards and slightly upwards.
They extend to the outei' extremity of this transverse pro-
cess, which is sharp, and at its superior surface form
angles with rounded roughened surfaces which extend to the
extremity on the postero-external part, much expanded,
looking upwards, backwards, and outwards, for union with
the venter surface of the ilium. They do not occupy the
whole of the upper surface, but are continued by a rough-
ened ridge, which extends along the lateral part of the
bone, becoming smaller and sharper posteriorly, formed by
union of the transverse processes of the other sacral bones ;
it affords attachment to the sacro-sciatic ligament. Both
above and below this ridge is a series of foramina, four in
number, decreasing in size from before backwards for
passage of the branches of the sacral nerves, the superior
branches through the superior foramina, the inferior
branches through the inferior foramina, through which
also pass branches of the lateral sacral arteries and veins.
Above the superior foramina (supersacral) are a series of
small prominences, decreasing in size from before back-
wards, produced by the oblique processes of the bones.
Higher up are the superior spinous processes, more or less
completely united by ossification of the interspinous and
interlaminal ligaments, presenting a series of five tuberous
prominences, to which triceps abductor femoris, biceps
rotator tibialis, ischio -tibialis, and some of the coccygeal
muscles, also the lateral sacral ligament and longissimus
dorsi are attached. The first spinous process looks almost
directly upwards ; the rest have a marked direction back-
wards, and decrease in length posteriorly. The inferior
surface of the bone anteriorly, on either side, presents a
remarkable smooth, irregular concavity, being the under
surface of the transverse process ; a rounded neck, extend-
ing inwards and backwards, serves to unite this to the
main portion, which is formed by the under surfaces of
the bodies, as denoted by transverse, irregular ridges,
which serve to divide this portion into five flattened parts.

56 OUTLINES OF EQUINE ANATOMY.

It is slightly concave from before backwards, is widest
anteriorly, and decreases in size posteriorly ; on either side
it slopes upwards and outwards, presenting the inferior roiv
cf foramina (subsacral), which are much larger than the
.superior. Internally placed to the foramina the lateral
sacral, arteries run along this portion of the bone. The
apex consists of a somewhat rounded and slightly concave
.articular surface, surmounted by a small ring, presenting on
either side a small transverse, superiorlj^ a superior spinous
process. It articulates with the first coccygeal vertebra.

THE COCCYGEAL VERTEBRiS

from thirteen to eighteen in number, occupy the pos-
jterior part of the vertebral column, and are small
bones in which the different parts of a vertebra assume a
more and more rudimentary form from before backwards,
so that while the first presents a body, ring, and small
2)rocesses, the sixth presents only a body with two pedicles
and small transverse processes ; the posterior coccygeal hones
..are merely small bony masses, elongated from before back-
wards, enlarged at each extremity, where they become
united with their fellows by fibro- cartilage. The pos-
terior bones only become ossified late in life, so that the
number of these vertebrae varies with age. They all
present both anteriorly and posteriorly convex articulatory
surfaces to their bodies. In consequence of this, mobility
of the vertebral column here attains its maximum, but the
want of a regular set of processes renders these false
Tertebrse ; superiorly they afford attachment to the
levatores coccygis ; inferiorly to the clepressores ; laterally
to the curvatores. The anterior bones also afford attach-
ment to ischio-tibialis and to compressor coccygis.

THE RIBS, COST^,

together with the sternum and the cartilages of elongation
.form the haemal arch of the dorsal vertebral segments.
They are elongated bones, extending from above down-
wards from the lateral parts of the dorsal vertebrae.
Though they have a longitudinal axis greatly exceeding
either of the transverse axes, yet as they present no medul-
lary canal nor marked distinction of shaft and extremities,

OSTEOLOGY. 57

they are not included in the class " long round bones."
Each rib presents a body and an upper extremity. The
extremity is divided into head, connected to the rest of the
bone by the nech, and tubercle. The head is a more or less
spherical process, with two convex, synovial, articulatory
surfaces, separated by a roughened groove. The anterior
surface articulates with the posterior facet on the body
of- the vertebra in front ; the posterior, with the anterior
facet of the vertebra behind ; the groove corresponds to the
intervertebral disc of cartilage and affords attachment to
ligamentum teres. Around each of the articulatory sur-
faces is a slight groove for attachment of a capsular liga-
ment. In the two last ribs the posterior articulatory
surface is continuous with the facet of the tubercle. The
neck varies in thickness and rotundity in the different
ribs ; its inner surface is roughened for attachment of the
stellate ligament. The tubercle seems to be the superior
part of the body, and is posteriorly placed to the head.
That of the first rib is largest ; it gradually decreases in
size in the bones from before backwards, so that it is ex-
tremely small in the two last. From this process arises
levator costse, and to it is attached longissimus dorsi. It
presents on its internal surface, becoming more anteriorly
placed in the posterior vertebras, a small articulatory facet
for union with the transverse process of the dorsal verte-
brae ; the outer circumferent margin of this is rough for
attachment of the capsular ligament, and on either side
for the costo-trans verse ligaments. The body is more or
less flattened irregularly from without inwards, and in the
central ribs is so twisted upon itself that the two extremi-
ties will not rest upon a plane surface at the same time.
The eighth rib takes the following course from its upper
extremity : at first, outwards, backwards, and downwards ;
centrally, more directly downwards ; inferiorly slightly
inwards and backwards. The body therefore presents two
margins and two surfaces. The internal surf ace is smooth,
convex from before backwards, concave from above down-
wards. It is covered by the pleura costalis, through which
it may be seen on laying open the thorax of a fresh sub-
ject. At its extreme superior part the sympathetic gan-
-gliated cord may be seen. To the extreme inferior part of
this surface of the posterior ribs are attached the diaphragm
.and transversalis abdominis. The external surface is convex

58 OUTLINES OF EQUINE ANATOMY.

ill all directions ; in the anterior ribs its lower part affords
attacliment to serratus magnns, in tlie fourteen posterior
ribs to obliquus abdominis externus, in the four or five
posterior ribs to obliquus abdominis internus. To about
the inferior part of the superior third of the last two ribs
a line of prominences extend, one on each rib, from the
tubercle of the second ; to this transversalis costarum is
attached, while a corresponding superior line of promi-
nences runs from the fourth tubercle to meet the former in
the sixteenth rib ; it marks out the inferior limit of longis-
simus dorsi, and opposite to it the bone makes its most
marked curve downwards, which is termed the angle of
the rib. Superficialis costarum is attached below the
inferior row of prominences. The anterior margin affords
attachment to the intercostales externi at its outer edge,
superiorly to levatores costarum, at its inner edge to inter-
costales interni. In the fourteenth rib a small groove runs
along this margin from the head of the bone ; it gradually
increases in length in the ribs in front of this, so that in
the second, third, and fourth the external margin seems
bevelled off from behind forwards, affording extensive
surface for attachment. The posterior margin presents a
corresponding arrangement on the inner side. It affords
attachment to the intercostales in a similar manner to the
anterior margin. Towards their inferior extremities the
ribs tend to become rounded, the ninth being most so.
The posterior ribs assume the character of thin long bones
composed of two rounded surfaces meeting by sharp
margins. They increase in width from before backwards
to the sixth, after which they decrease. In length they
decrease from the eighth both backwards and forwards,
the first being the shortest. The inferior extremity of the
body is continuous with the cartilage of elongation, the
union being more or less gomphotic. The cartilage has a
considerable tendency to undergo ossification, thus as-
suming the normal character of the inferior costa as found in
birds ; the bone therefore extends downwards in the centre
of the cartilage to a degree varying with the age of the
animals. Some of these cartilages are directly attached
to the sternum, others indirectly through the medium
of their fellows. Those of the first class belong to the
first eight ribs, which therefore are said to be true ribs,
behind these, on each side, are generally ten false ribs^

OSTEOLOGY. 59

sometimes nine or eleven, with tlie inferior extremity of
tlie cartilage pointed, and more or less firmly united to the
neighbouring cartilages by a small elastic ligament. The
union of the posterior cartilages is most lax, and in some
cases the last rib is wholly unconnected to the last but one ;
it is then said to be floating. The floating rib is generally
found when nineteen ribs exist on each side ; sometimes it
is -a mere cartilaginous elongated body extending from the
transverse process of the first lumbar vertebra imbedded
in the abdominal muscles. The external surface of the
fourteen posterior cartilages is connected with the external
oblique abdominal muscle. To that of the four or five
jDOsterior true ribs rectus abdominis is attached, and ante-
riorly is blended with lateralis sterni, which is continued
obliquely forwards and upwards over the second and third
to become attached to the first, from which also sterno-
thyro-hyoideus partly derives its inferior attachment. The
cartilages decrease in thickness from before backwards ;
they increase in length from behind and from before to
the ninth and tenth. They are connected together by the
inferior thickened portion of the intercostales interni, for
the external intercostales terminate opposite the inferior
extremity of the rib. The inferior extremity of the
cartilages of the false and floating ribs terminates in a
point, that of the true ribs is convex, coated with ar-
ticular cartilage, articulating with the cartilage of the
sternum.

The first rib is the shortest and strongest, and is also
the straightest. Its head articulates with the last cervical
and first dorsal vertebrae. Its tuhercle is large and very
rough externally for attachment of transversalis costarum,
and longissimus dorsi. It is irregularly rounded, to the
inner surface is attached the pleura at its reflection to
form the mediastinum. And many of the important
structures which pass through the entrance of the thorax
lie in contact with this bone. The posterior margin
affords attachment to the first intercostals. The ante-
rior margin presents at the inferior part of the superior
third, a prominence to which the short or upper head
of scalenius is attached. Below this the bone is smooth
for the passage of the axillary plexus of nerves. On
the external surface at the superior part of the inferior
third the lower head of scalenius is attached, and

-GO OUTLINES OF EQUINE ANATOMY.

under it are two smooth grooves for tlie passage of the
axillary artery, and (below it) the axillary vein. The rest
of this surface is occupied by the attachuient of serratus
magnus. The cartilage of the first rib is the shortest and
stoutest, and very closely approximates its fellow of the
■opposite side.

The last rib is the smallest, and its ])osterior margi7i
gives attachment to quadratus lumborum. To the inner
surface of the last two ribs the psoas magnus attached.
We have seen that the anterior ribs are strongest, broadest,
and most firmly connected together ; they are thus admir-
ably adapted to the formation of the thorax, which not
only serves to protect important viscera, but also affords
an extensive base for attachment of the fore limbs to the
trunk. This cavity is completed below by the STERNUM,
which consists of "^the haemal spines of six vertebral seg-
ments embedded in a cartilaginous mass, so that they may
be viewed as one bone. Each of these bones presents
seven surfaces. The superior surface is smooth, forms the
floor of the thorax, where it gives attachment to ligaments,
and to the sterno-costales interni. That of the sixth bone
on either side presents the articulatory surfaces for the
cartilages of the last two true ribs, of the fifth bone for
the sixth sterno-costal cartilage. ThQ anterior im^ posterior
surfaces are rough for attachment of the cartilage, while
the superior and inferior lateral surfaces, scarcely distin-
guishable in the first bone, assist in forming the lateral
and inferior surfaces of the bone taken as a whole. These
bones decrease in depth and increase in width from before
backwards. They are prolonged anteriorly and posteriorly
by cartilages. The anterior cartilage i^resents a rounded
supero-anterior extremity from which a short concave
superior margin runs to the antero- superior part of the
first bone. An inferior margin convex, rounded smooth
along the central line of the under surface, blending with
the inferior margins of the bone almost as far backwards
as the posterior cartilage. It is flattened from side to side,
though growing broader posteriorly, and thus it gives
the sternum a keel-shape ; it is the cariniform cartilage.
Its prominent antero-superior part would form the prow.
The ensiform, posterior or xiphoid cartilage is a mem-
braniform piece of cartilage, flattened from above down-
wards, widest at its attachment to the posterior part of

OSTEOLOGY. 61

the last bone, decreasing in size posteriorly to form tlie
neck, subsequently again expanded in forming an aiypendix
portion. To its under surface are attached the abdominal
oblique and rectus muscles, also pectoralis magnus, to the
upper surface the diaphragm and trans versalis abdominis
and the fibrous pericardium. The sternum thus presents three
surfaces and two extremities. The anterior extremity is the
prow of the carinif orm cartilage ; to it sterno-maxillaris
and sterno-thyro-hyoideus are attached. The jjosfer /or ex-
tremity is formed by the ensiform cartilage. The lateral
surfaces anteriorly give attachment to pectoralis anticus,
posteriorly to pectoralis magnus and trausversus. The
inferior margin is anteriorly smooth and rounded ; it here
presents a spurious bursa, over which pectoralis traus-
versus plays. The tipper surface is slightly concave, both,
longitudinally and transversely. Centrally it affords at-
tachment to the mediastinum. Anteriorly the thymus
gland rests on it, posteriorly the fibrous pericardium is
attached. Laterally it presents the articulatory surfaces
for the inferior extremities of the sterno-costal cartilages,
and internally placed to this the internal thoracic artery
runs from before backwards, with its accompanying vein.
The first- sterno-costal cartilage articulates with the sternum
just in front of the first bone, the second, third, fourth,
and fifth with the intervals between the following bones,
the sixth with the fifth bone, the seventh and eighth witk
the last.

BONES OF THE FORE LIMB.

The SCAPULA is a flat triangular bone, placed on the
antero-lateral part of the thorax, having its apex inferiorly
opposite the first rib, its base extending oblicjuely down-
wards as far as the angle of the sixth rib. A. fiat bone is
required in this position to aftbrd sufficient surface for
attachment of the large muscles which connect the fore
limb to the trunk, for in the horse two bones (coracoid and
clavicle) which perform this function in many other animals
are rudimentary. It presents two surfaces, three borders,
and three angles. The anterior border is superiorly convex
and roughened, inferiorly concave and smooth, and at its
extreme inferior part presents a large roughened process,
coracoid (a rudiment of a distinct bone). This process
externally presents, superiorly a groove for a blood-vessel

62 OUTLI^ES OF EQUINE ANATOMY.

running obliquely downwards and backwards ; below, and
almost parallel to this a roughened ridge, mapping out tlie
line of attachment of flexor brachii, may be traced in a cir-
cular manner around the whole anterior part of the process.
On the inner surface is a ridge with a slight inclination
backwards, terminating inferiorly in a small process to which
coraco-humeralis is attached. Around the anterior margin
of the bone, just above the coracoid process, runs arteria
dorsalis scapulae with its accompanying vein and nerve
from within outwards, protected by a hand of white fibrous
tissue {cor aco- scapular ligament), which extends from the
process to about the middle of this margin of the bone ;
antea spinatus becomes attached to this ligament exter-
nally; subscapularis internally. The roughened anterior
margin at its superior part affords attachment to pectoralis
anticus and antea spinatus. The postero-superior margin
of the bone is rough and cancellous for attachment of the
scapular cartilage of elongation. This is a thin piece of
fibro-cartilage, extending upwards for about three inches,
having a tendency to ossification at its attached margin.
It becomes very thin superiorly, and curls inwards. Ante-
riorly its margin has a backward inclination, posteriorly it
is continued as a thin piece of cartilage beyond the pos-
terior angle of the bone. Its external surf ace affords attach-
ment, anteriorly to antea spinatus, centrally to postea
spinatus, and posteriorly to serratus magnus. To its inner
surface the rhomboidei are attached. The postero-supeiior
margin anteriorly forms an obtuse angle with the anterior
margin. Posteriorly, in a corresponding manner, it joins
the postero -inferior margin, at the extreme superior part
of which is a triangular surface roughened for attachment
of serratus magnus. From this the posterior margin of the
bone makes a curve in a downward direction to the inferior
angle. Superiorly this curve presents a sharp edge, to
which teres externus and internus, caput magnum of the
triceps extensor brachii and scapulo-ulnaris are attached.
Inferiorly it is more rounded, but still, for the most part,
roughened ; centrally for attachment of caput magnum,
around which the attachment of scapulo-humeralis extends
in a peculiar manner, at the extreme inferior part of
scapulo-humeralis posticus, externally of scapulo-humeralis
externus, internally of subscapularis. About four inches
from its inferior part, in some cases, we find a groove

OSTEOLOGY. 63

running on to tlie external surface of the bone, marking
the course of branclies of the iDOsterior scapular vessels.
The portion of the bone opposite this is more rounded than
the rest, and is termed the neck. Below it are the cora-
coid process anteriorly, the articulatory surface for the
humerus posteriorly. This articulatory surface occupies
the inferior angle. It is termed the glenoid cavity, and
is much smaller than the head of the humerus on which
it fits, thus allowing great range of action of the joint. It
looks slightly downwards and backwards, is shallow, and
presents a sharp margin, but at its antero-external part
manifests a slight tendency to extend on to the external
surface of the bone. At its anterior part it is divided mto
two by a groove into which, Avhen the limb is extremely
bent, coraco-humeralis tendon may fit. Externally to this
is a roughened prominence, near the articulatory surface.
The rest of the space between the coracoid process and
the glenoid cavity is smooth, and presents a large foramen
for a blood-vessel to pass into the bone. The sharp outer
circumferent margin of the glenoid cavity affords attach-
ment to the capsular ligament of the shoulder- joint.

The external surface of the scapula is termed the
dorsum. It is convex in all directions, but ia hollowed out
in some parts in such a manner as to produce a very pro-
minent ridge, extending from the superior margin to the
neck, separating the anterior third from the posterior two
thirds of this surface. This is the spine, and separates
this surface into fossa antea sjnnatus anteriorly and fossa
])ostea sinnatus posteriorly. At its attached margin, and
superiorly and inferiorly, this spine gradually blends with
the surface of the bone. Its free margin presents infe-
riorly a roughened prominence (corresponding to the acro-
mion i^rocess in man with which the clavicle articulates).
More superiorly the ridge presents a roughness which
culminates in an elongated prominence with a backward
curve, the tubercle, to which the inferior anglo^ of tra-
pezius is attached. The spine anteriorly affords attachment
to antea spinatus, posteriorly to postea spinatus ; also
levator humeri, teres externus, and (indirectly) pectoralis
anticus gain attachment to its edge. Fossa antea spinatus
is bounded anteriorly by the anterior margin, posteriorly,
for the most part, by the spine, superiorly by the postero-
superior margin, inferiorly it becomes widened in forming

64 OUTLINES OP EQUINE ANATOMY.

the anterior part of tlie neck ; to its wliole extent is
attaclied autea spinatus. This surface is increased by the
addition of the space, bounded anteriorly by the coraco-
scapular ligament, under which the dorsalis scapulae vessels
and nerve wind round the neck of the bone in passing to
or from this fossa. Fossa postea spinatus occupies two
thirds of the dorsum. It is bounded posteriorly by the
postero-inferior margin, superiorly by the postero- superior
margin, anteriorly by the spine. Superiorly it is smooth,
affording attachment to postea spinatus muscle, while the
inferior part, forming the posterior part of the neck, pre-
sents roughened lines extending obliquely upwards and
backwards from the inferior extremity of the spine. This
part gives attachment to scapulo-humeralis externus, and
presents grooves running from the posterior margin of the
bone to the inferior extremity of the spine, in which a
branch of the j^osterior scapular artery runs, sending off
the medullary artery of the hone through a foramen in this
region. The inner surface of the scapula is termed the
venter. It is concave from before backwards, the concavity
being most marked along the central line opposite the
spine. It is widest centrally, and superiorly terminates in
a point on reaching the cartilage of elongation. Inferiorly
it becomes flat in forming the neck, and again concave at
the inner surface of the coracoid process. Across the neck
of the bone, from behind forwards, run branching grooves
for arteries ; in other respects this concavity is smooth,
and it is continuous at its .upper part, anteriorly and
posteriorly with two other smooth surfaces, the anterior
of which is smallest and bounded by a roughened line
running downwards and backwards from the anterior edge
of the bone ; the posterior is bounded by a curved and
much rougher line extending from the posterior margin of
the bone up against the posterior angle. This smooth
surface, therefore, presents superiorly three points ; infe-
riorly it terminates at the margin of the glenoid cavity,
the inner surface of the coracoid process, and posteriorly
the roughened line which affords attachment to scapulo-
humeralis externus. It affords attachment to subscapularis,
between which, therefore, superiorly are two roughened
triangular surfaces, to which are attached the anterior and
posterior parts of serratus magnus. Along the inner
edge of the postero - superior roughened margin, and to

OSTEOLOGY.

65

tlie inner surface of tlie cartilage of elongation, are attached
the rliomboidei muscles.

HUMERUS is a long round bone, wliicli is situated
below the scapula, running obliquely from above down-
wards and backwards, forming with the scapula an obtuse
angle posteriorly. It is a very stout bone, and its superior
extremity is much larger than its inferior. The superior
extremity presents a head and four tubercles. The latter
form a continuous chain occupying the anterior part of
this extremity. The head is situated at the posterior part
and is convex. Since it looks directly upwards in the
natural position of the bone it seems to be inclined to the
posterior part. It extends slightly on to the fourth
tubercle, and between it and the other tubercles is a space
elongated from side to side with numerous large foramina ;
this is occupied by fat in the fresh subject. On the inner
side of the upper extremity is a roughened process, broad
posteriorly, terminating in a point anteriorly in joining the
internal tubercle ; to this subscapularis is attached. The
three tubercles on the anterior part are termed respectively
external, middle, and internal. The internal tuhercle is the
smallest, receiving the termination of the roughened spot
just mentioned, posteriorly, and externally presents the
commencement of a synovial surface coated with fibro-
cartilage which dips down into the shallow fossa between
the internal and middle tubercles and then, after com-
pletely covering the middle tuhercle, dips into the deep fossa
between this and the external tubercle, terminating after
investing the inner surface of the latter. Over this sur-
face the tendon of flexor brachii plays ; hence it is lubricated
with synovia, and presents a large and important bursa,
which is separated from the capsular ligament of the
joint by the fat in the perforated space in front of the
head. Below this surface may be seen a series of small
articular foramina. Both the external and internal
tubercles afford attachment to antea spinatus and pectomlis
magnus which serve to bind flexor brachii in its situation,
but the external tubercle gives the most extensive attach-
ment and is continued inferiorly as a stout ridge much
roughened, especially above and below, superiorly for
attachment of one tendon of postea spinatus, inferiorly it
presents a tubercular termination roughened and curved
slightly backwards where teres externus is attached. Just

5

66 OUTLINES OF EQUIXE ANATOMY.

beliiud tlie ridge is a tria,ugular roiigliened space extending
to tlie fonrtli tubercle. To the anterior part of this the in-
ferior extremity of scapnlo-humeralis externus is attached,
while its inferior margin marks out the limit of humeralis
externus and the line of attachment of caput medium of
triceps extensor brachii. The foiirth tuhercle, situated ex-
ternally to the head, is continuous with the antero- external
tubercle. It has the articulatory surface for the scapula
extending on to its internal surface, while its external sur-
face affords attachment to one head of postea spinatus, over,
which the other head plays, with a bursa intervening, to
become inserted into the upper part of the ridge. Just
below the fourth tubercle is a row of articulatory foramina.
The shaft of this bone presents four surfaces ; the internal
is straight ; superiorly, just below the roughened surface
for attachment of subscapularis, the upper head of coraco-
humeralis becomes attached. Centrally, at the superior
part of the middle third, elongated from above downwards,
is a roughened ovoid space for insertion of the common
tendon of teres internus and latissimus dorsi. Below this,
inclined to the anterior surface, is the attachment of the
lower head of coraco-humeralis ; between the two heads
runs a branch of the humeral artery with its satellite vein
and nerve to flexor brachii, from behind forwards, but the
attachment of teres internus is a little posteriorly placed
to their connecting line. Straight down the limb, but in
consequence of the position of the bone, oblicjuely over its
inner surface, the humeral artery runs from the inner sur-
face of the shoulder-joint downwards to the inner part of
the elbow-joint. At the superior part of the inferior third
of the bone it gives off the medullary artery, which pierces
the medullary foramen here situated. The goiTesponding
vein is more posteriorly placed. The anterior surface is
superiorly smooth, mainly occupied by flexor brachii run-
ning downwards, slightly inclined inwards, after passing
over the tubercles of the humerus. The roughened attach-
ment of the long head of coraco-humeralis encroaches
upon this surface at the superior part of the inferior third,
and is separated by a prominent line running downwards
from the ridge on the external surface, from a deep de-
pression just above the lower articulatory surface which
almost (in some species of animals quite) extends through
the bone as far as the supra- condyloid fossa. This is the

OSTEOLOGY. 67

anterior fossa of the humerus. It presents many foramina,
and affords attachment to levator hnmeri and pectoralis
tra-nsversus. Externally placed to this the surface at the
inferior part is very rough, bounded ^posteriorly by a ridge
which runs upwards and backwards from the outer condyle.
This ridge is most prominent inferiorly, and there affords
attachment to extensor pedis at its lowest part, while
superiorly, and to the roughened surface in front of it, is
attached extensor metacarpi magnus ; from the inferior
part to the inferior prominent extremity of the humeral
ridge runs a hand of mixed luhite and elastic fibres which
gives attachment to panniculus carnosus, levator humeri,
and pectoralis transversus, and seems to bind down hume-
ralis externus in the twisted, wide, smooth groove which
we may trace from this around the external surface of the
bone bounded superiorly by the head and the line running
from this to the ridge, inferiorly by a much less prominent
roughened line winding round from the attachment of
subscapularis at the inner surface of the superior extremity
as far down as the external part of the outer condyle.
The lower part of the posterior surface presents two ridges
running upwards from the condyles of which the inner is
largest at its inferior extremity and runs straight upwards,
while the outer, at first insignificant, proceeds obliquely
inwards and upwards, becoming imperceptibly blended
with the middle third of the bone. It was the external
margin of this ridge we saw on the outer side of the bone.
Between the ridges is the supra-condyloid fossa, deepest in-
feriorly, which serves to accommodate the hamular process
of the ulna, and in the fresh subject contains some fat.
Inferiorly it presents an articulatory surface concave from
side to side continuous with that of the condyles. To
the upper part of the outer ridge anconeus is attached,
while caput parvum arises from the extreme superior part
of the inner ridge. From the inferior extremity of the
outer, flexor metacarpi externus arises, while the internal
ridge inferiorly gives attachment to the common originat-
ing tendon of perforans and perforatus, and externally is
rough for attachment of one head of flexor metacarpi
medius and flexor metacarpi internus. The rest of the
inferior extremity of the bone is occupied by the articula-
tory surface of the elbow-joint. It consists of two parts
or condyles. The inner condyle is much larger than the

68 OUTLINES OF EQUINE ANATOMY.

outer, andpreseuts one prominent convex surface, decreas-
ing in size towards the outer condyle whicli consists of two
convexities. These condyles are connected together by a
slight articulatory concavity, which extends posteriorly into
the supra- condyloid fossa. On either side of this extremity
is a depression for attachment of a lateral ligament of the
elbow-joint. In the centre of the articulatory surface is a
peculiar roughened depression with rounded edges ; this
must not be mistaken for ulceration.

RADIUS AND ULNA.

The basement structure of the forearm comprises two
bones, both of which, in the ox and other animals, extend
to the knee. In the horse, however, the posterior bone or
ulna terminates about opposite the superior part of the
inferior third of the radius or anterior bone, though traces
of it may sometimes be seen united to the inferior extremity
at the postero-extemal part. The RADIUS is a long round
bone, extending from the elbow to the knee, presenting a
shaft, a superior and an inferior extremity. The shaft
centrally is convex from side to side, and oJso from above
downwards. It is smooth anteriorly, and over it play
extensor metacarpi and extensor pedis. From the outer
margin of the middle third extensor metacarpi obliquus
runs obliquely over this surface downwards and inwards.
The jJosterior surface is slightly concave from side to side,
and to its outer margin the inferior part of the ulna is
attached to an extremely elongated triangular roughened
surface. The rest of the central part of this surface affords
attachment to radialis accessorius and the superior sus-
pensory ligament. The external and internal sharp margins
-afford attachment to the faschia which sustains the muscles
of the forearm, while more externally placed than the ulna,
extensor suffraginis is situated, enclosed between two
layers of faschia, one of which is attached in front, the
other behmd it. The ?/jjper extremity of the radius, at the
-extreme superior part, presents an articulatory surface
corresponding to that of the inferior extremity of the
humerus. It consists of an inner and an outer part, almost
separated by a roughened groove, extending forward from
the posterior margin of the bone to within about one quarter
qI an inch of the anterior margin, which is here slightly in-

OSTEOLOGY. 69

dented backwards. The in7ier surface for tlie large internal
condyle is concave in all directions, larger than the outer
surface, and posteriorly continuous with a synovial facet
on the posterior surface of the bone, which is in apposition
with the inner synovial facet of the ulna. The outer surface-
is divided into two parts ; the inner part is largest in every
way, and is continuous inwards at the anterior part with
the outer half of the articular surface ; outwardly it is con-
tinuous with the outer small division. The posterior margin
of this surface is continuous with the outer facet, which is
on the posterior surface, and articulates with the ulna. The
outer circumf erent margin of the whole articulatoiy surface
is prominent for attachment of the capsular ligament of
the elbow-joint, and both internally and externally below
it is a roughened surface (of which the outer is largest) for
attachment of the lateral ligaments ; from the outer runs
extensor suffraginis, while the inner is separated by a
smooth portion of bone with slight transverse grooves,
from a roughness on the shaft, to which also the inner
lateral ligament is attached, while the tendon of humeralis
externus runs under this prolongation of the ligament over
the smooth surface to become attached to a roughened
space on the posterior surface, which extends as far as the
inner margin of the union with the ulna. The anterior
surface of this extremity presents a prominent roughened
tubercle continuous with the roughened space on the inner
part for attachment of flexor brachii. Externally to this is
a smooth surface with a few foramina. On the posterior
part of the bone, inclined to the outer side below the syno-
vial facets for the ulna, is a roughened space, to which
the fibrous band between the bones is attached spreading
beyond the line of the ulna, on either side, in its attachment
to the radius. Below this is the radio-ulnar arch formed
by the approximation of smooth parts of the two bones,
through which a branch of the radial artery (vein and
nerve) passes to flexor metacarpi externus from within out-
wards. This space presents below the medullary foramen of
the radius, for the artery during its passage gives off the
nutritive vessel of that bone. Below this the union of the
bones is ossific, except in the young animal, in which it is
fibrous. The inferior extremity of the radius articulates
with the upper row of bones of the knee, and for this
purpose presents three continuous articular facets. The

70 OUTLINES OF EQUINE ANATOMY.

inner is the largest in every respect. Viewed from behind
forwards it is posteriorly convex, anteriorly concave. It
posteriorly slightly extends on to the back of the bone.
It articulates with os scaphoides. Its anterior, posterior,
and inner margins aiford attachment to the radio-carpal
capsular ligament. Its outer abruptly bends upwards
posteriorly in commencing the articulatory surface for os
hmare or middle sujface, which, after running upwards for
a short distance at the posterior pp.rt, bends outwards, thus
producing a convexity posteriorly, a concavity anteriorly,
separated from the anterior concavity of the scaphoid sur-
face by a slightly prominent articular ridge. It decreases
in size from its inner to its older margin, and is there con-
tinuous with the small convex articulatory surface which
extends on to the posterior surface of the bone, awd comes
anteriorly in contact with the cuneiform bone posteriorly
with trapezium. The posterior surface of the bone above
this articulatory portion presents a roughened prominence,
separated from the middle articulatory facet by a deep
fossa. This affords attachment to the thick posterior
annular ligament of the knee. Each side presents a pro-
minence, the inner is the largest, for attachment of a
lateral ligament of the knee. The outer prominence is
divided into two parts by a groove running from above
downwards, through which extensor suffraginis plays,
bound down by the annular ligament. The anterior sur-
face inferiorly presents four prominences for attachment
of the annular ligament, and three intervening grooves. The
outer groove gives passage to extensor pedis tendon, the
central to extensor metacarpi magnus, the internal runs
obliquely inwards and downwards as far as the articular
surface, and gives passage to extensor metacarpi obliquus.
The ULTTA is attached (as above described) to the pos-
tero-external ])art of the radius, superiorly by two small
synovial articulatory facets connected with the synovial sur-
face of the elbow- joint. Below this by a fibrous articulation,
and at the lowest part by an ossific union, and between the
ossific and the fibrous portion is the radio-ulnar arch. The
ulna is divided into a free and an attached portion. The
attached portion is prismatic, largest superiorly, and from
this tapers downwards, terminating insensibly, blending
with the outer edge of the posterior surface of the radius at
the superior part of the inferior third. The outer surface

OSTEOLOGY. 71

affords attacliment to extensor suffragiuis, and slightly
to extensor pedis. The inner at the radio-ulnar arch to
humeralis externns. Its anterior surface is that attached
to the radius, while its external and internal surfaces meet
in forming a rounded border posteriorly. The free portion
or olecranon presents two surfaces, three borders. The
anterior border is articulatory, concave from above down-
wards, convex from within outwards. It extends most on
to the onter surface. Inferiorly it widens, terminating
externally and internally in the synovial surfaces of the
attached portion of the bone. Frecjuently only the superior
part of this border is smooth, roughness extending com-
pletely across it at the inferior part. This surface articu-
lates with the supra-condyloid portion of the articulatory
surface of the humerus, thus assisting to form the elbow-
joint. Superiorly it forms an acute angle with the antero-
■superior margin which is sharp, and extends obliquely
upwards and backwards. This angle is termed the hook-
like or hamular process. The antero- superior margin
posteriorly widens in joining the tuberous superior margin,
which anteriorly presents a smooth surface where rests a
bursa, and the tendon of triceps extensor brachii playing
over this becomes attached to the roughened part. The
external surface is convex, and roughened along its central
line from above downwards for attachment of some of
the muscular fibres of caput medium, and more anteriorly
of anconeus. Inferiorly it is smooth on becoming con-
tinous with the external surface of the attached portion of
the bone. The inner surface is smooth and concave. At
its junction with the superior margin it affords attachment
to one head of flexor metacarpi medius and to scapulo-
nlnaris. It blends with the external surface in forming the
rounded j^osterior margin, which is continuous with the
corresponding part of the attached portion, and which, at
its junction with the superior margin, affords attachment
to ulnaris accessorius.

The CAHPITS—^' wrist" of human subject, ''knee" of
horse—

■consists of seven or eight small bones arranged in two rows
between the radius and metacarpus. The bones composing

72 OUTLINES OF EQUINE ANATOMY.

the two i*ows are connected together by inter-osseous liga-
ments, and by other connecting ligaments. The upper row
is formed of four bones, which form the radio-carpal articu-
lation with the radius ; between this and the lower row,
which is composed of three, sometimes four, bones is the
carpal ginglymoid or hinge-like joint, while the lower row
forms with the metacarpus an arthrodial or gliding joint,
carpo-metacarpal. The four hones of the ujp^er row are
the scaphoid, lunar, cuneiform, and trapezium ; those of the
lower ro2v, trapezoides, magnum, and unciforme, and
sometimes the pisiform bone.

OS SCAPHOIDES is irregularly cubical, presenting,
six surfaces. It is the inner bone of the upper row and
articulates with radius, lunare, trapezoides, and magnum.
Both its inferior and superior surfaces are articulatory,
presenting anteriorly a convexity, continued anteriorly
on to the outer surface, posteriorly a concavity. But the
concavity is most marked on the inferior surface, and.
while that of the superior surface is continued for a short
distance on to the posterior surface of the bone, that of
the inferior surface does not completely cover that surface,
which posteriorly presents a roughened part, projecting,
inwards. The tq)i)er surface articulates with the inner
prominent portion of the radius. The inferior surface
anteriorly (the convex part) with os magnum, posteriorly
(the concave part) with os trapezoides. The space between,
the reflections of these synovial surfaces which articulate
with OS lunare into the outer surface of the bone is flat but
rough for attachment of inter-osseous ligaments, as also is
a concavity behind it, separated into a deep superior part,
and an inferior part by a sharp ridge. Posteriorly the con-
cavity is bounded by a roughened ridge, a continuation of
the posterior roughened surface of the bone, which is tuberous,
below and superiorly presents a continuation of the superior
articular surface. This surface is continuous inwardly
with the interior and anterior surfaces, both of which are.
roughened for attachment of connecting ligaments supe-
riorly and inf eriorly, and of the annular ligament centrally.

OS LUNARE is the centre bone of the upper row. It. is
elongated from before backwards, and widest superiorly^
It articulates with the radius, scaphoides, cuneiformCj^
magnum, and unciforme. It presents six surfaces. The^
superior surface is articulatory, convex anteriorly, concave-

OSTEOLOGY. /o

posteriorly, terminating behind in a point wliicli extends
upwards. Its outer margin also anteriorly terminates in a
point. This surface articulates with the central part of the
inferior articulatorj surface of the radius, the vertical por-
tion of which corresponds to a continuation of this smooth
articulatory surface on to the inner surface of os lunare,
which surface, at its antero- superior part, also comes in ap-
position with OS scaphoides. This surface, too, is continued
on to the external part of the bone anteriorly, where it plays
on OS cuneif orme. The inferior surface presents two parts,
inner of which is convex anteriorly, concave posteriorly,
extending from the anterior to the posterior margin of the
bone. It articulates with os magnum, and anteriorly is.
continued on to the internal surface, forming a small
articulatory facet for os scaphoides. The outer portion of
the inferior surface is convex, anteriorly placed and comes
into connection with os unciforme. It is continuous with
the lower facet on the outer surface, on which os cunei-
forme plays. The anterior surface is slightly roughened^
for attachment of connecting and the annular ligaments
The imsterior surface superiorly is concave, inferiorly pro-
minent ; it also gives attachment to the annular ligament.
The outer surface presents posteriorly, the outer surface of
this roughened prominence antero-superiorly, and antero-
inf eriorly are the articulatory facets for os cuneif orme. The
space between them is concave and rough for attachment
of interosseous ligaments. The inner surface superiorly along
its whole length presents the vertical articulation for the
radius, which anteriorly is continuous with a small surface
for OS scaphoides, which is also in contact with a corre-
sponding facet at the antero -mferior part continued from
the inferior surface. The space between these is rough for
attachment of interosseous ligaments.

OS CTJNEIFORME is situated at the outer part of the
upper row. It articulates with radius, lunare, unciforme,
and trapezium. It presents two surfaces and four borders^-
The external surface is convex in every direction, and is-
roughened for attachment of the annular, connecting, and
outer lateral ligaments. Along its postero-superior margin it
presents a roughened groove for attachment of the capsular
ligament of its articulation with trapezium. The internal
surface presents anteriorly two smooth articulatory facets,
one superiorly continued as far as the anterior margin, con-

74 OUTLINES OF EQUINE ANATOMY.

tinuous with the articulatoiy surface on its superior margin ;
one inferioiiy, separated by a roughened space from the
anterior margin, continuous with the articulatorj surface
of the inferior margin. Between and behind these this
surface is roughened for attachment of interosseous liga-
ments, posteriorly it terminates in a point. The superior
margin presents a smooth triangular concave surface for
articulation with the radius continuous with the superior
one on the internal surface for lunare. T]iq inferior surface
or margin presents an articulatory surface with the unciform,
which anteriorly is concave, posteriorly at the external side
convex. It is continuous with the inferior facet on the
inner surface for lunare. It is separated by a roughened
space from the ]30sterior margin, which presents a concave
ovoid articulatory surface extending obliquely forwards
and u^^wards ; with this the inferior articulatory surface of
trapezium comes in contact. It is separated from the
inferior articulation by a roughened dexn'ession, to which
its capsular ligament is attached. The anterior margin of
the bone is also roughened for ligamentous attachment.

OS TRAPEZIUM is situated at the postero-external part
of the upper row. It is flattened from side to side, and
slightly curved inwards. It presents two surfaces and four
margins. The anterior margin has two articulatory facets,
the superior concave for articulation with the radius, and
extending on to the internal surface of the bone. It is sepa-
rated by a deep perforated groove from the inferior facet,
which is below and slightly externally placed, convex for
articulation with cuueforme ; internally placed to this the
anterior margin is rough. The superior and inferior margins
are rough, and extend from the anterior to the posterior
margin. The superior is sharpest, and from about its centre
over the external surface of the bone a roughened groove
extends towards the infero- anterior articulatory facet.
Flexores metacarpi externus et medius are attached to the
upper margin, and through the groove on the external sur-
face a rounded tendon of flexor metacarpi externus runs to
the outer small metacarpal bone. This groove presents a
prominent roughened edge, separating it from a depression ;
the rest of the external surface is convex and roughened for
attachment of the annular ligament, which is also attached
to the inferior margin and to the posterior margin, which
is rounded and rough. The internal surface is concave and

OSTEOLOGY.

75

sligMly rougli for attacliment of the annular ligament.
At'^its antero-superior part it presents a small articulatory
facet continuous with the superior facet on the anterior
margin. From this a ridge runs downwards and backwards
obliquely to the inferior margin.

- OS TRAPEZOIDES is the inner bone of the lower row,
and articulates with magnum, scaphoides, metacarpi mag-
num, and parvum internum (sometimes with pisiform).
It presents three surfaces. The supero-iuternal surf ace pre-
sents superiorly a rounded convexity, which commencing
in a point at the outer margin anteriorly occupies the whole
upper part of the bone, and passes to the postero-internal
part, extending about halfway down to the lower surface.
Around it runs a narrow groove, exce^Dt at the outer part,
where it is continuous with a small elongated facet, articu-
latory for OS magnum. The rest of this surface is roughened
for attachment of the annular, inner lateral, and connecting
ligaments. Along the inferior margin is a groove which
bounds the inferior articulatory surface. The inferior surface
is mainly occupied by a flat facet for articulation with the
inner small metacarpal bone, elongated from before back-
wards, posteriorly continuous with a smaller facet for os
metacarpi magnum, and this in turn is continuous with a
still smaller facet for os magnum. This articulatory sur-
face is bounded on every side by a groove, except on the
outer, where it is reflected on to the outer surface for arti-
culation with OS magnum. Between the superior facet
(continuous with the upper surface) and the inferior facet
(continuous with the lower surface) the outer part of the
bone is roughened for attachment of interosseous ligaments.
Postero-inferiorly is a peculiar prominence presenting a
sharp point inwards, bounded by the posterior surface for
OS magnum posteriorly, inferiorly by the facet for os meta-
carpi magnum.

OS MAGNUM is the central bone of the lower row, and
articulates with lunare, scaphoides, trapezoides, unciforme,
metacarpi magnum, et parvum internum. It has five
surfaces, which give it a triangular appearance, and is flat-
tened from above downwards, having a base or anterior
surface, and an apex or posterior angle which is rounded.
The superior surface is triangular and presents two articu-
latory portions which blend anteriorly. The outer consists
of two triangular portions united at their apices, occu-

76 OUTLINES OF EQUINE ANATOMY.

pying tlie inner half of tlie surface, extending from tlie
anterior margin to the posterior angle. The posterior
triangle, convex and rounded, extends on to the posterior
angle of the bone. The anterior triangle is continuous on.
its outer margin with a facet, on the anterior part of the
outer surface for os unciforme. Internally it is con-
tinuous with the inner articulatory part of this surface,
which is triangular, occupying the inner angle of the
surface, separated postero-externally from the other part
by a perforated concavity. It is slightly continued on to-
the inner surface of the bone for articulation with trape-
zoides. "With this part os scaphoides comes in contact, while
OS lunare occupies the outer part. The inferior surface is
flattened, slightly convex anteriorly, slightly concave pos-
teriorly, and has four margins. The anterior margin is.
convex, extending farthest backward on the inner side.
The posterior is not half the length of this, and is perfectly
straight. The outer margin is straight, but centrally pre-
sents a deep depression, roughened, and extending towards
the centre of the surface. Along the inner margin, at its
anterior part, is a small facet for articulation with the
inner small metacarpal bone ; this is continuous with the
main surface for os metacarpi magnum, and is continued on
to the inner surface, forming a small facet for the trape-
zoid. The inner surface presents three facets for trape-
zoides — one antero-superiorly elongated, one antero-infe-
riorly, shorter but deeper, and one posteriorly extending^
from the posterior part of the inner concavity of the
inferior surface ; this looks forwards. The rest of the
surface presents irregular roughened concavities and
convexities for attachment of interosseous ligaments. _ The
outer surface presents articulatory facets for union with os-
unciform, between which the bone is rough for attach-
ment of interosseous ligaments. The anterior surface or
base forms an irregular parallelogram extended from side
to side, which centrally presents a roughened prominence
for attachment of the annular ligaments, superiorly and
inferiorly a groove bounded by the articular facets of the
upper and lower surfaces,

OS UNCIFORME.— The outer bone of the lower row
articulates with cuneiforme, lunare, magnum, metacarpi
magnum, et parvum externum. It presents four surfaces,,
and a posterior very prominent angle. The su])ero- external

OSTEOLOGY. 77

surface presents an articulately convexity extending obli-
quely downwards, outwards, and backwards. The outer
part of this articulates with cuneiforme, the inner with
lunare and extends to a superior facet on the inner surface
for articulation with magnum. The inferior s?M/ace presents
three articular parts, the anterior, extending obliquely
outwards and backwards, internally continuous with the
inferior facet for magnum on the internal surface. It
articulates with metacarpi magnum, as also does the
posterior part, which slightly meets the former by its
anterior angle, but is separated from it inwardly by an
indentation on its inner margin, externally by the middle
part of the surface, which articulates with the outer small
metacarpal bone. This surface presents a semicircular
figure, and a groove extends round its outer margin. The
in7ier surface so exactly corresponds with the outer surface
of OS magnum that one description will suffice for both.
The posterior facet is on the inner side of the process, the
outer, posterior, and superior parts of which are rough, as
also is the anterior surface, affording attachment to the
annular ligaments, bounded on every side by grooves
mapping out the articulatory facets of the neighbouring
surfaces.

OS PISIFORME is a small osseous nodule found on the
inner side of the lower row, articulating with trapezoides,
and the inner small metacarpal bone, for which it presents
small articulatory facets. Its presence is by no means
constant ; it is relatively larger in the ass than in the
horse.

THE METACARPUS

is formed of three bones, the largest of which is centrally
placed, with a smaller one on each side of it. It extends
from the knee to the fetlock, but the small bones only
proceed downwards part of this distance.

OS METACARPI MAGNUM (CANON OR SHANK
BONE) is a long, round bone, extending from the knee to
the fetlock, having two extremities and a shaft. The
shaft is flattened from behind forwards, and presents two
surfaces connected by Iwo rounded margins. The anterior
surface extends in a straight line from above downwards,
is convex and rounded from side to side, becoming flat-
tened, and li^.ore expanded superiorly and inferiorly. It is

78 OUTLINES OF EQUINE ANATOMY.

for tlie most part smooth, and is separated from tlie skin
only by tlie expanded tendons of extensor pedis and
extensor snffraginis, wliicli run from above downwards
inclined to the outer side, and are closely connected to-
gether. At its extreme superior part it presents a groove
marking out the limit of the superior articulatory surface,
and below this is roughened, especially on the inner side,
where is a roughened prominence for attachment of ex-
tensor metacarpi magnus. The j^osterior surface is flattened,
and on either side presents a roughened surface for attach-
ment of the metacarpal interosseous ligaments, binding the
small to the large bone. These surfaces are widest supe-
riorly and inferiorly, taper to a point slightly con-
verging, extendmg to about the inferior part of the middle
third of the bone. The space between them is concave,
and at the inferior part of the superior third inclined to
the inner side presents the medullary foramen, through
which a branch of the small metacarpal artery runs to
supply the bone. The extreme superior part of this
surface affords attachment to the superior extremity of the
superior sesamoideal ligament, the anterior surface of
which lies in contact with the greater part of the rest of
this surface, which, superiorly convex, at the lower part of
the middle third becomes concave centrally, agam be-
coming 2:>romment, especially along the middle line in
reaching the inferior articulatory surface. Here it is
pierced by a row of articular foramina. The margins of
the bone superiorly are roughened for attachment of the
capsular (car po -metacarpal) and annular ligaments of the
knee, centrally are smooth, forming with the small meta-
carpals grooves running from above downwards. Infe-
riorly they are rough for attachment of a ligament from
the inferior extremity of the small metacarpal bone, and
one from the lateral part of the sesamoid bone, and below
this present each side a rounded concavity for attachment
of the lateral ligaments of the fetlock. The tijpper surface
of the bone presents four distinct articulatory facets. One
is by far the largest and slants obliquely inwards, and
occupies the inner two -thirds of the surface. It articu-
lates with OS magnum and presents four margins. The
anterior margin has two convexities and extends farthest
backwards on the inner side, and there meets the inner
margin which runs obliquely from within outwards

OSTEOLOGY. 79

and backwards. It is divided into an anterior and a
posterior part by a break in tlie margin. The anterior
part is continued on to tke posterior surface in forming the
small anterior articulatory facet for the inner small meta-
carpal bone. The posterior part is continuous with a small
facet for os trapezoides which, in its turn, joins an ex-
tremely small one for os metacarpi parvum internum. The
posterior margin is perfectly straight and about half the
size of the anterior. The outer margin anteriorly and
posteriorly is continuous with circulatory facets sloping
outwards, separated by a deep roughened dejDression,
These articulate with os unciforme, and are each con-
tinuous with an articulatory facet on the posterior surface
for the external small metacarpal bone. The iiiferior arti-
culatory surface is convex in every direction, and consists
of three prominences running from behind forwards. The
central prominence is most marked, narrowest, and extends
farthest both anteriorly and posteriorly. It is wholly
articulatory. The inner and outer prominences consist
of surfaces sloping towards the central ridge. They are
coated with cartilage continuous with that of the central
ridge. In most cases the inner is larger than the outer
articulatory surfaces.

OSS A METACARPI' PARVA are extremely elongated
small bones, placed at the lateral, inclined to the posterior,
part of the large metacarpal bone. They decrease in size
from above downwards, terminating iv/eriorly oj^posite the
inferior part of the middle third of the large bone in small
rounded bulbs, from which the superior ligament of the
pad, and a small ligament to the infero-lateral part of the
large bone, run downwards. The siq^erior extremity is rough
and tuberous for the most part, while superiorly it is more
or less occupied by ai'ticulatory surfaces, which extend
slightly on to the attached part as two synovial facets
for OS metacarpi magnum. Below this the whole attached
surface is roughened for the white fibrous connection with
the large bone. The inner and otder surfaces are smooth,
and from the inner runs the anterior lumbricus muscle,
while the outer, with the large bone, forms a smooth
groove.

The inner small metacarjKil hone at its upper extremity is
for the most part flat for articulation with os trapezoides.
Its outer margin anteriorly presents an almost vertical

80 OUTLINES OF EQUINE ANATOMY.

aTticulatory facet to blend witli that of tlie large bone,
wbicb articulates with os magnum, while postero-externally
is a small facet for connection with os pisiforme. It gives
attachment to extensor metacarpi obliquus and flexores
nietacarpi internus and medius, the latter through the
medium of the annular ligament of the knee. To it also
is attached the inner lateral ligament of that joint. It is
larger and longer than the outer small bone.

The outer small metacarjxil hone supero-externally is
rough for attachment of the outer lateral, and the annular
ligament of the knee, also of flexor metacarpi externus.
Supero-internally it presents an articulatory surface, flat
and slanting inwards, on which os unciforme glides.

SESAMOID BONES, two in number in each limb, are
situated at the fetlock behind the inferior extremity of the
large metacarpal bone on which they play, f .)r their anterior
surfaces are articulatory, and they are so united together
that the surfaces of the two bones form the counterpart
of the posterior part of the inferior extremity of the large
metacarpal bone. Each bone presents four surfaces. The
anterior surface is triangular and articulatory, consists ex-
ternally of a large smooth surface, which inwardly becomes
reflected backwards in forming with its fellow the counter-
part of the central ridge of the inferior extremity of the
large metacarpal bone. This surface inwardly is connected
by the inner margin to \\iq ]josterior surface. This margin
gives attachment to the intersesamoid ligament which
binds the bones together, and thus renders their posterior
surfaces which are coated with fibro-cartilage, a convenient
groove for the flexor tendons to play over. The inferior
surface is rough, triangular, and presents foramina ; from
it the inferior sesamoid ligaments extend. The outer sur-
face inclines obliquely upwards and inwards in such a
manner as to form a point superiorly in meeting the anterior
and posterior surfaces. The posterior margin of this sur-
face presents a prominent ridge, and anteriorly some large
foramina. From the ridge the lateral sessamoid ligaments
run, and also to the ridge are attached those portions of
the superior sesamoideal ligament which pass to extensor
pedis, and also the annular ligaments of the fetlock.

OS SDEFRAGINIS is the long roimd bone which extends
from the fetlock to the pastern joint. Its shaft is short and
slightly compressed from before backwards. The anterior

OSTEOLOGY. 81

surface is convex from side to side, and is mainly occupied
by tlie extensor pedis tendon with the bands running to it
from the superior- sessamoideal ligament. It is, therefore,
smooth for the most part, but above and below it becomes
roughened. Superiorly it is ]3rominent for attachment of
the tendon of extensor suffraginis (or ligamentum exten-
sorum). This prominence is slightly inclined to the outer
side. The ijosterior surface is also convex, and superiorly
presents externally and internally two prominent angles
from which two ridges converge to form a prominent rough
surface at the central part, to which the short part of the
inferior sessamoideal ligaments is attached. To the angles,
are attached white fibrous bands, which converge in be-
coming attached to the posterior surface of the perforatus
tendon ; they are parts of the annular ligament of the fet-
loch. The margins of this bone lie in contact with the plantar
vessels and nerves, and inferiorly present a roughened line,
to which the superior ligament of the navicular bone is at-
tached in blending with the lateral hgament of the pastern
joint. The superior articulatory surface of the bone is in
every respect concave, and presents three concavities, the
inner and outer of which are triangular; the inner is shghtly
the largest. The central concavity is deepest and narrowest,
extending from the anterior to the posterior surface, while
between "it and the above-mentioned ridges is a rougher
space perforated by numerous foramina. The inferior ex-
tremity is much smaller than the superior, and presents an
irregularly heart-shaped articulation, which, by uniting
with the upper extremity of os coronse, fonus the pastern
joint. This is obtusely rounded anteriorly, extending
shghtly on to the anterior surface, and consists of two
roimded convexities, which meet forming a shallow groove.
They extend considerably on to the posterior surface, and
are here separated by a roughened indentation ; the inner
is slightly the largest. On either side, slightly inclined to
the anterior part, just above the articulation, the lateral
ligaments of the pastern are attached. Posteriorly, above
the articulatory surface, are numerous foramina.

Ossa coronse, pedis, and naviciilare will be examined in
dissection of the foot.

82 OUTLINES OF EQUINE ANATOMY.

BONES OF THE HIND LIMB.

The posterior cavity of tlie "body is termed ttie pelvis. It
is most marked in tlie skeleton for in tlie fresli subject it is
anteriorly confounded witli the posterior part of the abdo-
men. Its basement structure consists of two bones (each
composed of smaller portions connected together by liga-
ments), superiorly is the sacrum which has been described as
part of the spinal column. Inferiorly and lateral^ are the
ossa innominata.

OSSA INNOMINATA are two in number, one on each
side, and these are united at the inferior part centrally
forming the symjohysis. These bones originally consist
each of three parts, but in the adult these parts are firmly
united to form one bone. Supero-anteriorly is the ilium
forming the lateral boundary of the pelvis at the ante-
rior part; antero-inferiorly is os pubis; postero -inferiorly
OS ischium. The three unite in forming a cotyloid cavity
termed the acetabulum, coated with articular cartilage
with a gap extending from its inner and anterior part
towards the centre, where ligamentum teres which serves
to maintain the cavity in contact with the head of the
femur, is attached. It is deep in all parts and is rendered
more so by a band of fibro-cartilage (circumferential or
cotyloid) which is attached around its margin, and is con-
tinued across the gap forming the transverse ligament,
and binding down the pubio-femoral ligament in its
passage to the head of the femur. The ischium forms
the major portion of this cavity (about three-fifths), while
the pubis forms the least, a little less than one-fifth, os
ilium forming a little more than one-fifth ; but a consider-
able j)art of the pubis is occupied by the roughened
groove extending inwards. The acetabulum looks outwards
and slightly downwards and backwards.

OS ILIUM is a flat bone, triangular in shape, placed
obliquely from above downwards and outwards. It is tri-
angular, and presents two surfaces, three margins, and three
angles. The antero -inferior angle is termed the antero-
inferior spinous process, it is rough and tuberous, elongated
from above downwards presenting four prominences, two
superiorly, two inferiorly. It affords attachment internally
to iliacus, longissimus dorsi, obliquus abdominis externus,
obliquus abdominis internus, transversalis abdominis, and

OSTEOLOGY. S3

quadratus luuiborum. Externally gluteus maximus is
attached to it, and from its inferior tubercles runs the
common tendon of tensor vaginae and gluteus externus.
The siqjerior angle is the supero-posterior spinous process,
it is elongated, flattened from within outwards, and sujdo-
riorly is curled slightly outvvards. To it runs the superior
ilio-sacral ligament, from its posterior margin the inferior
ilio-sacral ligament. To its inner surface is attached
longissimus dorsi, and to its external surface gluteus
maximus ; while gluteus externus, in some cases, seems to
arise from its summit. The inferior angle becomes rounded
in forming the neck, which is convex, and below dilates to
form the anterior part of the acetabulum inferiorly, the
union with the neck of the ischium, externo- superiorly, the
junction with the os pubis antero-internally. The external
surface of the ilium is called the dorsum, and is concave,
looking upwards, outwards, and backwards. It becomes
convex in forming the neck. Superiorly to the upper
margin it affords attachment to gluteus maximus, and this
muscle is firmly attached to it as far as a crescentic groove,
running across its neck where gluteus internus commences,
and becomes attached as far down as the acetabulum. The
margin connecting the anterior and superior angles is slightly
concave, and is rough and thickened. It is termed the
crista, and affords firm attachment to the tendinous struc-
ture of longissimus dorsi. The anterior 7nargin is concave,
and looks downwards and outwards, it is smooth, affords
internally attachment to iliacus, externally to the glutei
muscles, and inferiorly at the neck becomes widened,
forming two roughened fossae separated by a smooth space.
To these, one of which is inclined to the dorsum, the other
to the venter surface, are attached the two heads of rectus
f emoris ; between them is a small quantity of fat. Below this
ilio-femoralis arises, above it psoas parvus is inserted. The
jposterior margin is divided into three parts. The superior
third gives attachment to the inferior ilio-sacral ligament,
the middle is smooth for passage of gluteal vessels and
nerves round it from within outwards, the inferior forms
a very sharp prominent ridge continued on to the neck of
the ischium, to which the sacro- sciatic ligament is attached.
This is the ischiatic spine, and externally is continuous with
a small but very rough space for attachment of part of
gluteus internus. The internal surface of the ilium is

84 OUTLINES OF EQUINE ANATOMY.

termed the venter. It is convex for tlie most part, and is
•divided into two portions by a roughened articulatory
surface for the transverse process of the first sacral bone.
This articular surface {auricular facet) looks obliquely
downwards and forwards, and is smoothest centrally,
where is sometimes found a small synovial cavity. Its
outer margin is very rough for attachment of the sacro-
iliac ligament. The surface anteriorly placed to this, which
)liel23S to form the brim of the pelvis, is triangular, termi-
jjating in a point inferiorly. It gives attachment to the
iliacus, and that portion of it which forms the anterior
l>art of the neck presents transverse grooves, through
which runs the arteria innominata from behind forwards
in its course to the triceps cruralis. This surface is sej^a-
a-ated from the posterior surface, which is much narrower,
and gives origin to pyriformis, by grooves running directly
•downwards to the obturator foramen, through which the
obturator vessels and nerve pass. In contact with this
surface superiorly and under the first sacral transverse pro-
cesses are the iliac arteries andtheir commencing branches,
also the external, internal, and common iliac veins.

OS ISCHIUM occupies the postero -inferior part of the
pelvis, and consists of three processes with the body
at which they join. The antero-exiernal jjrocess runs for-
wards to help to form the acetabulum, consequently the
superior part of its anterior surface is roughened for
articulation with the ilium and its infero-anterior j^art for
union with os pubis. It is smooth, both externally and
internally ; externally, in forming the neck of the ischium,
over which obturator internus and pyriformis play, the latter
muscle is attached to a roughened line on the upper part of
Ihe process ; internally in forming with the ant ero -internal
process an arch with rounded margin, which looks forwards
and gives attachment to obturator externus, and assists in
forming the obturator foramen. The anterior extremity
of the last-mentioned process joins os pubis, while its inner
margin, meeting its fellow, assists the corresponding part
of the body in forming symphysis ischii, the union becom-
ing strengthened below by a connecting ligament, particu-
larly thick opposite the posterior margin of obturator
foramen, in becoming reflected down to form the triangular
■ligament of the penis of the male. The superior margin of
(Symphysis pubis et ischii affords attachment along almost

OSTEOLOGY. 85

its whole length to a reflection inwards of the sacro-sciatic
ligament, which covers the origin of obturator internus
from the superior part of the margins of the foramen of
the same name, separating it from the pelvic viscera. The
posterior 2)rocess of the ischium is triangular and tuberous -
at its extremity, which extends outwards and backwards,,
and is termed the tuberosity of the ischium. It presents
a .small rough ridge, extending forwards along its outer ■
margin to the neck, from which ischio-femoralis arises. -
To the posterior tuberous part triceps abductor femoris,
biceps rotator tibialis, ischio tibialis and erector penis are
attached. The inner margin of this process slopes inwards
towards its fellow, which it joins at an oblique angle at the
symphysis. This is the ischial arch, and round it the urethra
passes from the pelvis into the penis. In so doing it is bound ■
down by a small ligament and by the crura, which, being
attached on either side,converge to form corpus cavernosum.

OS PUBIS consists of three sides and three angles ; its
inner margin lies in contact with its fellow, and thus forms
symphysis pubis, continuous with and analogous to sym-
physis ischii. The posterior angle is united to the antero-
internal process of the ischium, and from it the outer
margin forms an arch running forwards and outwards^
which, after completing the obturator foramen, terminates
in the junction with os ischium and os ilium, forming the
acetabulum. The anterior margin, forming the brim of the
floor of the pelvis, is at first smooth, centrally presents a
rough prominence, pectineal! tubercle, to which pectineus
is attached, and inwardly these two pectinean tubercles are
connected by a dense fibrous band, which affords attach-
ment to the abdominal muscles anteriorly, and posteriorly
is partly continuous with the connecting ligament of the
symphysis, while the rest of it passes through a groove,
which occupies the under surface of os pubis, extending
outwards to the pubic notch of the acetabulum. Sym-
physis pubis superiorly forms a smooth concave surface for
the bladder to rest upon, and externally to this the inward
reflection of the sacro-sciatic ligament is attached. To the'
under surface of the whole symphysis the common tendon
of the graciles is attached centrally, and on either side a
biceps adductor femoris.

The FEMUR is a long, round bone, extending from the
hip to the stifle. It is the largest bone in the body, and

86 OUTLINES OF EQUINE ANATOMY.

centrally is rounded, but superiorly becomes flattened from
behind forwards. It consists of a sliaft and two extremi-
ties. Tlie shaft presents four surfaces. The anterior
surface is in all parts convex and rounded, though in blend-
ing with the upper extremity it is inclined to become flat.
It is directly continuous with the inner and outer surfaces.
The inner surface is rounded. Supero-posteriorly it pre-
sents a roughened prominence, elongated from above down-
wards, continuous by two roughened sharp lines with the
head. The anterior of these sharp lines marks out the
attachment of vastus iuternus. This prominence is tro-
chanter minor internus. To it are attached psoas
magnus and iliacus. Below it the surface is roughened
for attachment of pectineus and of one head of biceps
adductor femoris ; still lower down is an oblique smooth
surface, extending from above downwards and backwards
for passage of the femoral artery and vein, at the upper
part of which, opposite the centre of the bone postero-
internally is the medullary foramen. Still lower down this
surface is very rough for attachment of the other head of
biceps adductor femoris. The jjosterior surface of the bone
superiorly is very wide, j^resenting a fiat surface between
the two small trochanters. Slightly inclined to the outer'
side of the centre of this part is a roughened surface for
attachment of ischio-femoralis and a portion of triceps
abductor femoris. From the upper part of trochanter
minor externus a thick ridge runs upwards towards the
posterior part of trochanter major; this forms the outer
boundary of the trochanteric fossa, a deep depression on
the supero-posterior and external part of the bone, into which
are inserted the two obturator muscles and pyriformis,
with gemini or ischio-trochanterius. The middle third
of this surface is roughened and continuous with that on
the inner surf ace for pectineus and biceps adductor femoris ;
below this, separated by the smooth oblique groove for the
femoral artery, is a triangular space extending as far as
the outer condyle for attachment of the lower head of
biceps adductor femoris. The external surface presents
superiorly the ridge running from trochanter major to
trochanter minor externus, to which the posterior head of
gluteus maximus is attached. This culminates in a long
process flattened from before backwards, curled forwards,
and tuberous at its free margin, trochanter minor externus,

OSTEOLOGY. 87

to wliicli gluteus externus is attaclied. Below this for a
short distance it is smooth, and still lower down is a deep
fossa which looks outwards and backwards, and is rough-
ened for attachment of gastrocnemius internus. It is
bounded by ridges, of which the outer is most prominent
and roughened for origin of the outer head of gastrocne-
mius externus ; while the other head arises from near the
lower insertion of biceps adductor, separated from the
former and from internus by the femoral artery. The
inner ridge is smooth. The superior extremity is divided
into two parts — head and trochanter major. The head
IS internally placed, and consists of a rounded articular
surface, convex in every direction, with a break in its
margin at the internal part, which, running upwards, leads
into a deep groove extending to the centre of the head,
roughened for attachment of ligamentum teres and the
pubio -femoral tendon of rectus abdominis. Around the
outer margin of this surface is attached the capsular liga-
ment of the hip-joint. From the head outwards, bounded
posteriorly by the trochanteric fossa, anteriorly by the
dilated upper extremity of the anterior surface, is a ridge
of bone, which externally becomes much expanded in form-
ing an irregularly concave surface, looking inwards, per-
forated by numerous foramina, to which gluteus internus
becomes attached. This is the inner surface of trochanter
major, which consists of two parts, the anterior one
rounded and rough, presenting on its external surface
centrally a smooth spot for a bursa, below which is a ridge
for insertion of the anterior head of gluteus maximus.
The ijosterior ]jart is much larger, and superiorly presents
a roughened extremity for attachment of another head of
gluteus maximus, and from this a roughened ridge forming
the outer boundary of the trochanteric fossa runs to tro-
chanter minor externus, to which ridge the third head of
gluteus maximus is attached. At the smooth surface between
trochanter major and the head ilio-femoralis is attached to
a thin roughed line running from above downwards.
The inferior limit of trochanter major and the anterior
margin of the ridge running to the external small trochan-
ter mark out the superior attachment of vastus externus.

The inferior extremity of the femur may be divided
into an anterior and a posterior part. The anterior con-
sists of two articular ridges, which look downwards and

88 OUTLINES OF EQUINE ANATOMY.

forwards, wliicli form a continuous articulatory surface
for tlie patella to play over. The inner is mucli tlie largest,
especially suj^ero-anteriorly, where it becomes bulbous, with
an inclination inwards. The outer decreases slightly in
size posteriorly. The non-articulatory parts of these ridges
are rough for attachment of the capsular ligament of the
stifle. The ijosterior part of the inferior extremity consists
of two condyles separated by the intercondyloid fossa,
which runs from behind forwards. It is roughened for
attachment at its postero-internal part of the postero-
superior ligament of the outer interarticular disc of car-
tilage. Just in front of this the outer condyle is under-
mined for attachment of the superior extremity of one
crucial ligament, while the inner similarly affords attacil-
ment to the other. Anteriorly are numerous foramina.
The outer condyle is the largest, and in front of its inferior
extremity is a deep depression, whence arises the common
tendon of flexor metatarsi and extensor pedis. Behind an^
above this is a ridge running backwards, to the anteria*
part of which the tendon of popliteus is attached, to ths
posterior parts the outer lateral ligaments of the patella,
and of the stifle joint. The inner surface of the interna},
condyle is roughened, and presents a prominence to which
are attached the corresponding inner lateral ligaments.
The articulatory surface of the inner condyle is continuous
with that of the inner ridge.

PATELLA is a floating bone, situated at the infero-
anterior part of the femur. It is the " knee cap " of the
human subject, and has three surfaces and three angles.
The superior surface looks slightly backwards, it is bicon-
.cave (slightly) affords attachment to triceps cruralis, and
is bounded anteriorly by a prominent margin, posteriorly
by a line, convex externally, concave internally. These
meet at a rounded angle outwardly, from which run the
outer patellar lateral and straight ligaments, and at an acute
angle inwards, where the bone is continued by a fibre -car-
tilaginous prolongation, from the extremities of which pass
the inner lateral and inner sti'aight patellar ligaments. The
cmtenor surface is rough and convex, affording attachment
outwardly to triceps abductor femoris. Its superior mar-
gin is rounded. Its inferior margin comes to a point cen-
trally ; just above this is a smooth spot for a bursa and
still higher up is roughened for attachment of the central

OSTEOLOGY. 89

straight ligament. Externally to this is the attachment of
the outer straight ligament. The posterior surface of the
bone is articulatory, consisting of an outer small part con-
nected by a broad prominent ridge with the inner large
part, which superiorly is concave and extends downwards,
inferiorly inclines forwards, terminating internally in a
point. The outer part plays over the outer ridge of the
femur, the inner over the inner ridge, the surface being
completed by the cartilaginous prolongation inwardly.
Around this surface the capsular ligament is attached ex-
ternally and internally.

The TIBIA is a long round bone extending from the
stifle to the hock. It articulates superiorly with the femur
through the medium of the semilunar discs of cartilage,
and directly inferiorly with the astragalus; outwardly
with the fibula. It consists of a shaft and two extremities.
The shaft is prismatic presenting three surfaces, antero-
external, antero-internal, and posterior. The anterior sur-
faces centrally blend, forming a rounded margin, but
superiorly become expanded and unite in forming a sharp
ridge, which increases in size as it proceeds upwards. To
the internal surface of this ridge the expanded tendinous
layer common to ischio-tibialis, sartorius, and gracilis is
attached along its whole length, while biceps rotator
tibialis, after playing over a bursa on this sur-
face is attached to its prominent edge about the
centre. Along the sharp anterior margin externally is
attached the aponeurosis of triceps abductor femoris,
while to the external surface of the ridge, the free margin
of which slightly bends outwards, is attached the muscular
portion of flexor metatarsi. The superior extremity of the
ridge is triangular, bifurcating in forming two prominences
separated by a smooth groove. To the upper part of these
j)rominences the inner aud outer straight ligaments of the
patella are attached. While the central straight ligament,
after playing over a bursa situated in the groove, becomes
attached to the point of bifurcation. The inner prominence
is much the largest. The antero-internal surface is imme-
diately subcutaneous, and over it runs vena saphena from
before backwards and upwards. The anter a -external surface
is occupied by the passage of flexor metatarsi and extensor
pedis and is smooth. Inferiorly this surface^ becomes
wider on approaching the inferior extremity and internally

90 OUTLINES OF EQUINE ANATOMY.

it presents a small prominence roughened for attacliment
of tlie snpero-anterior annular ligament of the liock,
which runs obliquely downwards and outwards, over the
tendons of flexor metatarsi and extensor pedis towards the
infero- external part of the hone. The j^osterior surface
is divided into two parts. One superiorly placed, bounded
superiorly by the superior margin of the bone, internally
by the superior half of the inner margin, externally by a
line running from without inwards, obliquely downwards.
These enclose a triangular space to which popliteus is
attached. The rest of this surface is roughened by ridges
running obliquely inwards and downwards, to the outer
part of which is attached flexor pedis perforans to the
inner flexor pedis accessorius ; these two muscles are sepa-
rated by the posterior tibial artery, which runs through a
smooth groove, which at the inferior part of the superior
third of this surface presents the medullary foramen. The
inner margin of the bone is inferiorly unoccupied. Its
superior part affords attachment to popliteus and about the
centre of this half is a remarkable prominence serving to
mark out the course of the tendon of biceps rotator
tibialis. Superiorly this margin gives attachment to the
inner lateral ligament of the stifle joint. The oute^^ mar-
gin superiorly is roughened, affording attachment to the
outer lateral ligament ; below this is a roughened line to
which the upj^er extremity of the fibula is attached by
white fibrous tissue ; below this a smooth surface helping
to form the fibular arch through which the anterior tibial
vessels pass. This margin as far down as the inferior
extremity gives attachment to the white fibrous tissue
which connects it to the fibula. Its superior part is sepa-
rated from the anterior ridge of the bone by a deep smooth
rounded groove, in which lies a bursa for passage of the
tendon common to flexor metatarsi and extensor pedis.
Flexor pedis perforans extends as far up as the posterior
2:)art of the expanded superior extremity of this margin.

The superior surface of the bone is divided into two
articular surfaces by a spine which runs from behind for-
wards, presenting an irregular groove extending from the
perforated line which separates the anterior ridges from
this superior surface, to the posterior margin. It is rough
and prominent, anteriorly affording attachment to one of
the crucial ligaments, and to the anterior ligaments of the

OSTEOLOGY. 91

semilunar cartilages. Beliind this it is concave and per-
forated, affording attachment to the posterior ligament of
the inner cartilage, while to its junction with the posterior
margin are^ attached the postero -inferior ligament of the
outer cartilage and the other crucial ligament. The inner
side of the spine is by far the most prominent, and its
external surface is articulatory continuous v/ith the inner
articulator y facet, which is ovoid, bounded by a roughened
margin and lying in contact with the under surface of the
inner cartilage and with the inner condyle of the femur.
The outer articulatory surface is triangular, concave, and
looks slightly backwards, and is in contact with the under
surface of the outer cartilage and with the outer condyle.
The inferior extremity is c^uadrilateral and consists of two
articular grooves running obliquely from within outwards
and forwards, which come in contact with the sujDcrior
articulatory surface of astragalus. The inner groove is the
deepest and the narrowest and extends farthest backwards.
The outer in some cases consists of two portions of bone con-
nected by fibrous tissue, tlie outer of tJiem being the inferior
extremity of the fibula. The outer margin is rough and pro-
minent, being termed the outer malleolus, over which a
groove for peroneus runs downwards. It affords attach-
ment to the capsular, outer lateral and supero-anterior
annular ligament of the hock. The ijosterior margin is
rough for attachment of the capsular ligament, and
comes to a point centrally. The inner margin is
rough, and posteriorly presents a groove running
from above downwards for flexor pedis accessorius,
anteriorly the internal malleolus, larger than the outer,
which gives attachment to the inner lateral and capsular
ligaments. The anterior margin is straight, and rough for
attachment of the capsular ligament.

The FIBULA is a small very much elongated piece
of bone, situated at the external part of the tibia,
rounded for the most part and by its inner part con-
nected with the tibia by white fibrous tissue, some-
times continued as far as the true hock joint. Some-
times its middle part degenerates into a white
fibrous band. Superiorly it slightly expands in forming
a button-like extremity flattened from without inwards,
the inner surface of which is roughened for attachment
of white fibrous tissue connecting it to the suj)ero- external

92 OUTLINES OF EQUIN'E ANATOMY.

part of the tibia. Below this the surface (internaT) is-
smooth, forming (with the tibia) the fibular arch through
which the anterior tibial vessels pass. The external sur-
face of the button-like superior extremity is occupied by
the attachment of the outer lateral ligament of the patella.
The greater part of fhe remainder of the external surface
gives attachment to peroneus.

TARSUS, HOCK (ANKLE OF HUMAN SUBJECT),

consists of a number of small bones resembling to a certain
extent those of the knee. It occupies the space between
the tibia and the metatarsus, and consists of two roivs of
hones, of which the superior is formed by two somewhat
large bones, astragalus and calcis, while the inferior con^
sists of four smaller bones, and is split into two rows on
its inner side, so that while cuboides occupies the whole
depth of the row on the outer side, cuneiforme magnum
forms the upper and cuneifoiTae medium and parvum
f oi-m the lower subdivision on the inner side. It is between
these bones on the inner side that " spavin " generally
first manifests itself.

OS CALCIS is the postero-external bone of the upper
row, and articulates by three facets anteriorly mth astra-
galus, inferiorly with cuboides. It consists of a hocly and
a process. The hodij consists of a large portion externally
placed, which presents externally a roughened surface to
which ligaments are attached. Internally a very irregular
aspect, having at its postero-inferior part a somewhat
square projection which superiorly is roughed for attach-
ment of the capsular ligament of the hock, posteriorly has
a groove coated with fibro cartilage, over which flexor pedis
perforans'plays, internally and inferiorly roughened surfaces
for ligamentous attachment. Anteriorly a slightly concave
oblong aiiiculatory facet extending from above down-
wards obliquely inwards for articulation with astragalus.
The main portion of the body just above this process on
the inner surface presents a small elongated facet looking
upwards, inwards, and forwards, which is continuous round
an acute articular margin with another facet looking
downwards and slightly forwards. The rest of the inner
surface running to a point inferiorly is roughened for

OSTEOLOGY. 93

attacliment of interosseous ligaments. Along tlie anterior
margin may be seen a small facet looking inwards, con-
tinuous with a large one upon the margin looking forwards,
the rest of this margin is rough. The inferior margin is
mainly occupied by an irregular slightly concave articu-
latory surface for os cuboides, this is continued slightly
on to the internal surface at its inferior point as a small
facet for union with astragalus. From the siq^erior mar-
gin the process runs upwards. The loosterior margin is
continuous with the posterior margin of the process and
both are rounded and roughened for attachment of the
€alcaneo- cuboid ligament. The sujjerior extremity of the
process is tuberous, slightly inclined forwards. Anteriorly
it presents a smooth surface for a bursa, over which gastro-
cnemius extemus plays, becoming inserted just behind,
while still farther back this surface is smooth for the
bursa situated on the point of the hock, where the expanded
tendon of gastrocnemius internus forms a cap for it, be-
coming attached by a fibrous band running to the process
on either side. The anterior margin is thinner than the
posterior but rounded. The external surface is subcu-
taneous. The internal surface coated with fibro-cartilage,
continuous with that on the oblique posterior part of the
inner prommence of the body, over which the perforans
tendon plays, bound down by the posterior annular ligament.
OS ASTRAGALUS is a square bone at the inner part of
the upper row of the hock bones. It articulates superiorly
with the tibia, posteriorly with calcis, inferiorly with
cuneiforme magnum and cuboides. It has five surfaces. The
antero-superior surface presents two prominent rounded
articular ridges, running obliquely downwards and out-
wards. The inner ridge is the longest, and its inner side
the straightest, and completely coated with cartilage. It
extends beyond the outer, both anteriorly and posteriorly.
The outer ridge curls slightly outwards at its inferior
extremity, and is separated from the inner by a deep syno-
vial fossa, which is shorter than either of the grooves, and
generally presents a break in the articular cartilage cen-
trally. Between it, the grooves, and the inferior surface,
is a triangular depression, roughened for attachment
of extensor pedis accessorius. The ]}osterior surface of
the bone is extremely irregular. Internally it presents
superiorly a roughened prominence, and below this the

94 OUTLINES OF EQUINE ANATOMY.

posterior surface of the tubercle. More outwardly, sepa-
rated from tlie ridge by a deep perforated fossa, is an
ovoid articulately surface for os calcis, extending directly
downwards ; and more outwards, inclined to the outer sur-
face and extending obliquely forwards, is an articulatory
facet consisting of two parts, one of wbicb is vertical, the
other horizontal. A little lower down, on the outer side, is
another small facet, elongated from above downwards. We
see a third at the inf ero-external angle of the bone con-
tinuous with that on the inferior surface of the bone. The
interarticular space is rough and perforated. The outer sur-
face is small, rough, and concave, giving attachment to one of
the lateral ligaments. The inner surface is roughened and
flat superiorly, inferiorly forms a prominent tubercle ; to-
the whole of it ligamentous substance is attached. The an-
terior margm of both the inner and outer surfaces is occupied
by the outer margin of the supero- anterior articular ridges.
The inferior surface is mainly articulatory, consisting of a
slightly convex surface, elongated from side to side, ex-
ternally continuous with a small triangular facet for os
cuboides, which is continuous with one on the posterior
part for os calcis. Anteriorly it almost reaches the internal
ridge, and at the under surface of the tubercle is reflected
backwards, extending to about the centre of the posterior
part of the bone, where it terminates in becoming continu-
ous with the inner articulatory facet for os calcis of the
posterior part. The anterior and reflected portions are
separated by a gap in the articular cartilage, which presents
numerous foramina. This portion internally is more con-
cave than the rest of the surface, being separated from its
outer extremity by a prominent point. This large articu-
latory surface comes in apposition with cuneif orme magnum.
OS CUNEIFORME MAGNUM is a flat bone with two
surfaces and four margins. The sujyerior surface is concave
in most parts, and is prominent at the outer j^art of its
anterior margin. It is the exact counterpart of the infe-
rior extremity of astragalus (with exception of its small
surface for os cuboides), and therefore requires no detailed
description. Its posterior part is most prominent, espe-
cially inwardly ; inferiorly it articulates with ossa cunei-
forme parvum and medium. For medium it presents a
large articulatory surface, extending along the anterior
border, having a convex anterior, concave posterior margin

OSTEOLOGY. 95

almost flat, witli its inner and larger half inclined slightly
inwards. At the postero- external angle is another facet
for mediuna, which is rounded, slightly concave, continuous
with a small facet on the outer margin at the posterior part
for OS cuboides. For parvum there are two small round
facets, continuous with each other at the antero-internal
angle, the outer being concave, almost continuous with the
anterior surface for medium, the inner convex looking
downwards and backwards. The rest of this surface is
extremely rough for attachment of interosseous liga-
ments; in some places it is perforated by foramina.
The miteriov and internal margins of the bone are rough-
ened for attachment of ligaments, and the imsterior margin
presents two very irregular prominences separated by an
irregular groove, which is continuous with the roughened
groove upon the inferior surface. The posterior surface
for articulation with cuneiforme parvum encroaches upon
the inner prominence below. The outer prominence inclines
slightly outwards, and on its postero-external part presents
a concavo-convex surface, extending obliquely upwards and
backwards for union with os cuboides. In connection with
the external extremity of the anterior articulatory part of
the upper surface is a facet elongated from before back-
wards, also coming into connection with os cuboides.
Behind this is a groove extending upwards and backwards
to the break in the superior surface. The rest of the
surface is rough for attachment of interosseous ligaments.
CUNEIFORME MEDIUM is a flat bone, situated at the
lower, inclined to the inner, part of the hock. It may be
distinguished from cuneiforme magnum by a projection
from the centre of its posterior margin, which is inclined
slightly inwards. The u])jper surface is for the most part
articulatory, presenting two distinct facets for union with
magnum. The first is oblong with a notch in its posterior
margin. It presents an anterior and a posterior rounded
margin ; the surface slants from the former to. the latter ;
it is, therefore, concave. The posterior notch is separated
by a roughened perforated space from an ovoid facets
extending obliquely inwards on the superior surface of the
process. The under surface much resembles this, but the
articulatory facets are convex and less regular, and the
posterior facet is elongated from side to side, inclining out-
wards and backwards, also the intervening roughened

96 OUTLINES OF EQUINE ANATOMY.

space is larger. It articulates with os metatarsi inagnum,
and posteriorly with the inner splint bone. The anterior
margin is convex, most prominent along its central line,
and on the inner side, near both the upper and the lower
surfaces are rows of foramina. The inner margin is a
deep groove, the sides of which meet at an oblique angle.
It is everywhere roughened, except at its antero-iuferior
angle, where is a small articulatory surface for union with
cuneifonne parvum. The external margin presents a shal-
lower groove than the internal, and a larger articulatory
surface at the antero-inferior part for cuboides. The
posterior angle at w^hich these two surfaces meet looks
obliquely downwards and backwards, being prolonged su-
periorly into a very thin process, with the superior part of
which cuneiforme magnum articulates, and os cuboides
with the external lateral part.

CUNEIFORME PARVUM is situated at the postero-
internal and inferior part of the hock. It has two surfaces
and a process. The superior surface is mainly occupied
by a smooth concave articulatory surface looking inwards,
bounded anteriorly by a roughened ridge, for articulation
with magnum. The inferior surface presents three articu-
latory facets. The posterior facet is ovoid and distinct,
and articulates with the inner small metatarsal bone, as
also does the central facet, which is continuous with the
anterior facet for metatarsi magnum, and that in its turn
with a small surface for medium on the antero-internal
part of the bone. The process is continued from the
posterior margin, is flat from side, tuberous, has rounded
margins, and curls inwards. It is roughened externally
for attachment of ligamentous structure (especially a band
running to os cuboides) as are also the interarticular
spaces. The roughened depression on the inferior surface
is sometimes so deep as to divide the bone into two dis-
tinct parts.

OS CUBOIDES occupies the outer part of the lower
row of hock bones, and is equal in thickness to the sum
of the two cuneiforme bones (magnum and medium).
This thickness is characteristic, and serves to distinguish
this from all other bones except os scaphoides of the
knee, from which it may be distinguished by the greater
number and the smaller size of its articulatory surfaces. It
has six surfaces. The anterior smd j)osterior are roughened

OSTEOLOGY. 97

for ligamentous attacliment, more especially the anterior
for the middle anterior annular ligament for which there
is a slight depression. The external surface presents a
groove running from below upwards, separating the rough-
ened anterior and posterior parts. This leads upwards to a
roughened line which tends to separate the upper surface
into two articulatory parts and after reaching the inner
surface curves in a direction backwards. Thus at the pos-
tero-external angle it cuts off a convex, ovoid facet sloping
obliquely downwards, outwards, and forwards for union
with OS calcis. The anterior articulatory facet is divided
into two parts, the outer largest, quadrilateral at the
antero-external angle of the surface, slanting slightly
outwards and forwards, continuous along its internal
margin with the inner part which is pyriform (broadest
posteriorly) for union with astragalus. It does not reach
to the anterior margin of the bone, but along its inner
edge blends with a pyriform facet, with its base anteriorly
placed at the antero- superior angle of the internal surface
for cuneiforme magnum. The inter^ial surface at its
postero- central part has a prominence, smooth and articu-
latory both above and below. The superior facet looks
upwards and inwards meeting os cuneiforme magnum.
The inferior, downwards and inwards for cuneiforme
medium. At the antero-inferior angle is a facet elongated
from before backwards continuous with one for metatarsi
magnum on the inferior surf ace, it articulates with medium.
The space between these is roughened for ligamentous
attachment, but around the posterior and superior part of
the last mentioned facet is a deep smooth groove extending
to below the articulatory prominence posteriorly, through
which the communicating branches between the anterior
and posterior tibial veins run. The inferior surface presents-
two facets, one at the antero-external angle, the other at
the postero- external angle for union with os metatarsi
parvum externum. The former is largest and continuous
inferiorly with a surface sloping upwards and inwards for
metatarsi magnum, which joins one on the inner surface
for cuneiforme medium. The superior surface is occupied
by a smooth articulatory surface elongated from before
backwards with the greater portion of which os calcis
comes in contact.

The remainder of the bones of the hind limb resemble

7

98 OUTLINES OF EQUINE ANATOMY.

tlie corresponding bones of the fore, thongli each presents
certain points of difference which will be noticed.

OS METATARSI MAGNUM differs from the large meta-
carpal hone. — In being about one and one-third times as
long, in being rounder, in having the articular surfaces for
the splint bones more posteriorly placed. In a tendency
to the production of a sharp ridge running from the upper
surface of the bone downwards over the central line of
of the antero-superior part. In the arrangements of its
upper surface, which presents two distinct articulatory
surfaces, one anteriorly crescent-shaped, one posteriorly
placed rounded. These are separated by a roughened
groove. Supero-externally is a groove running obliquely
downwards and backwards for the metatarsal artery.

OS METATARSI PARVUM EXTERNUM is much the
largest of the four splint bones. Its upper extremity
presents at the antero-external part a facet for os cuboides,
but the rest of this extremity which is rough and tuberous
as well as its size renders it readily distinguishable.

OS METATARSI PARVUM INTERNUM is distin-
guishable by its upper extremity, which has two articu-
latory facets (continuous with that for union with os
metatarsi magnum) for os cuneif orme parvum, and one on
its outer side for cuneiforme medium. These facets with
the rest of the surface which is rough, render the extreme
upper part somewhat pointed.

OS SUFFRAGINIS is larger at its superior extremity,
smaller at its inferior than that of the fore limb.

OSSA SESAMOIDEA, OS CORON-ffi present no marked
difference ; OS NAVICULARE is smaller.

OS PEDIS may be distinguished: — By the slight ob-
liquity of its antero-lateral surface ; by the greater con-
cavity, less circular, more regularly semilunar shape of
its plantar surface, which is widest at the toe and gradually
decreases in size towards the heels, while that of the fore
limb present an indentation into the central part of its
posterior crescentic margin.

AETHEOLOGY. 99

PART III— ARTHROLOGY.

Articulations are tlie unions of the component parts
of the basement structures, the means by which such parts
are enabled to play on one another in adaptation to the
various movements of the individual. These are of three
kinds, moveable, imrtially moveable, and fixed. The fixed or
synarthrotic joints are those which in the young animal
are moveable, but become obliterated later on in life ; they
mainly serve for connection ; motion between the parts
forming them is but slight, it is impossible after full
development of the bones. They are of four hinds, the most
marked examples of which may be found in the cranium.
They consist of the coaptation of edges or surfaces of
bones with the intervention only of periosteum. The sim-
plest forms afford the most firm centres of connection.

Sutura is the apposition of two edges or surfaces, more
or less complete, by the adajDtation of prominences on one
piece to depressions on the other. This adaptation may be
by the juxtaposition of irregular surfaces, sutura squamosa,
which may be more or less rough ; examples of this may
be seen in the union of the malar with the frontal bone ;
or it may be by the dovetailing of two jagged edges, sutura
serrata vel dentata. The latter name is applied when the
jagged margins resemble the line formed by the edges of a
dog's molars.

Harmonia is the apposition of two edges of bone, which
may be roughened, but are not jagged ; they therefore
simply are in contact, and connection between the bones is
simply by continuity of periosteum, as in the union between
two ossa nasi.

Gompliosis is the insertion of a peglike process of one
l>one into a corresponding cavity of another. It is rare ;
the connection of the teeth with the jaws and of the rib
with its cartilage are examples.

Schindylesis is the union of three l)ones, by the attach-

100 OUTLINES OF EQUINE ANATOMY.

ment of the edge of one Lone into a groove formed by part
of the edges of the others, the rest of the union between
the other two being by suture. Such is the attachment of
the vomer to the palatine processes.

Partially moveable or ampMarthrotic joints are those
which, while admitting a small amount of motion, also
afford firm union. This is brought about by insertion
betv^een two roughened surfaces or edges of bone of a piece
of fibro -cartilage, the perichondrium of which is con-
tinuous with the periosteum of the bones connected.
Sooner or later, in different individuals, the cartilage
becomes ossified and the union complete. Such is the
connection of the ossa innominata by means of the sym-
physis, and of the two halves of the inferior maxilla,
which " grow together," forming the symphysis inferioris
maxillae. In the case of the articulations between the
bodies of the vertebrae we see permanent amphiarthrotic
joints. Some of these joints are strengthened by connecting
ligaments.

Diarthrotic, synovial, or freely moveable joints are those
in which the component parts glide more or less upon each
other. They present cavities lined by synovial membranes,
the surfaces of the bones in apposition are coated with
articular cartilage, and are maintained in apposition by
ligaments. These ligaments may be interosseous, situated
between the bones, running from a roughened spot on the
surface of one bone to a corresponding part of its fellow ;
examples may be seen between many of the bones of the
hock and knee ; connecting, running from the outer surface
of one bone to that of the other. Capsular, broad, expanded
bands of white fibrous tissue serving to strengthen and
protect the synovial membranes of a diarthrodial joint.
Annular, extending round a complex joint attached to all
the prominent bony points it presents, keeping in position
its surrounding structures ; generally consists of a broad
ligamentous expansion, sometimes simply of a small white
fibrous band ; examples of both these forms may be seen in
the hock. The motion between synovial surfaces may be
simply an almost imperceptible gliding ; where this is the case
the joint is arthrodial. Others admit of more or less exten-
sive motion in two ways — either abduction and adduction
(motion from or towards the longitudinal vertical plane of
the body), or elevation and depression (motion to or from

ARTHROLOGY. 101

the ground surface). These are gin glymoid joints, and in
them motion may be limited by bony in'ominences sooner
or later in either direction ; the elbow-joint is an apposite
example. Axonoides or pivot-like motion is motion on the
longitudinal axis of the joint, as ginglymus is on_ the
transverse axis ; the union between atlas and axis is of
this nature. Rotatorial or ball-and-socket joints allow
flexion, extension, abduction, and adduction, axonoidal
motion, and circumduction (whereby the above movements
are manifested in combination) ; examples are the hip and
shoulder- joints, in which a more or less globular head fits
into a corresponding cavity. Joints are by no means con-
stant ; thus sometimes a small synovial sac may be found
in the centre of a symphysis ; some bones are united together
by two kinds of joints; thus most of the vertebrae are
united to their fellows both by amphiarthrosis and by
diarthrosis.

The ARTICULATIONS OF THE HEAD are synarthro-
dial with few exceptions. They present every variety of
this class, while the petrous temporal bone and os hyoides
are united by amphiarthrosis, and the upper to the lower
jaw by diarthrosis. The latter only presents unusual
characters.

Temporo-maxillary articulation is the apposition and
connection of the glenoid cavity of the scjuamous temporal
bone with the condyle of the inferior maxilla. In birds
there is an intervening bone, OS qnadratum, but in mam-
malia this is only represented by an inter- articular disc of
fihro -cartilage, which serves to separate the cavity of the
joint into two distinct parts, each lined by a synovial mem-
brane, so that both surfaces of this cartilage are lubricated
by synovia. It is a flattened piece of cartilage, elongated
from side to side, and all around its outer margin is
attached the capsular ligament of the joint, which extends
from the outer circumferent margin of the glenoid cavity
to that of the condyle. It is strengthened by £i fibrous hand
running from the outer part of the condyle to the outer
part of the cavity, and by another running from the pos-
terior part of the condyle to the mastoid process of the
squamous temporal bone, and continued from this up to
the base of the external auditory process, covering a small
synovial cavity. This joint internally is covered by
pterygoideus, externally by masseter externus.

lO'Z OUTLINES OF EQUINE ANATOMY.

In examining tlie synarthrodia! articulations of the skull
we notice several sutures, one of whicli divides the bone
into two parts longitudinally, only noticeable superiorly
and not extending to the posterior extremity ; this is the
saggittal suture between the nasal, frontal, and parietal
bones of the two sides of the head, forming the " plume " of
the arrow posteriorly between the parietal and triquatral
bones. Other sutures serve to mark the division of the
skull into four vertebral segments ; they are the

Lambdoidal, between os occipitis and os parietale, so
called from its likeness to the Greek lambda (A), which is
caused by protrusion of the mastoid ridge of the petrous
temporal between these two bones.

Coronal, between the frontal and parietal bones.

Great transverse, between the frontal and nasal, malar,
lachrymal bones, extending into the orbit. All these
extend downwards on either side towards the base of the
skull.

Atloido -occipital articulation

is the union of the condyles of the occiput with the
anterior ai*ticulatory surfaces of the atlas. Each of these
condyles has a proper synovial membrane, and the two lie
together on their inner and inferior parts. Their outer
surfaces are strengthened by accessor}/ fih-es, which are con-
tinued superiorly, extending from the anterior margins of
the laminae of the Atlas to the superior part of foramen mag-
num of the occiput, forming the capsular ligament. Two flat,
white, fibrous bands extend from the styloid processes of the
occiput to the anterior margins of the laminae. This joint
is ginglymoid, admitting motion upwards and downwards.

Atlo-axoid articulation

is the union of the posterior part of the body of the atlas
and the posterior part of its superior surface with the
under surface of the odontoid jDrocess, and its antero-lateral
continuations on the dentata. These have one synovial
membrane attached to the outer circumferent margin of
both surfaces. Inferiorly along the central line this is
strengthened by a small band of yellow elastic tissue (a con-
tinuation of the inferior vertebral ligament). Laterally it
has accessory fibres, which are continued upivards, connecting
the anterior laminal margin of the axis with the posterior

ARTHHOLOGY. 103

laminal margin of the atlas. The superior spinous process
of the dentata is connected to the upper surface of the
laminae of the atlas by yellow elastic hands lying together
along the middle line expanded in becoming blended with
the interlaminal ligament outwardly. The superior surface
of the synovial membrane is in contact with the odontoid
lig^aments, three in number : — The hroad ligament runs
from the transverse ridge on the upper surface of the
odontoid process, the two small ligaments are beneath
this just visible, one on either side, running from the
depressions on the upper surface of the odontoid process.
The three run to the roughened surface at the antero-
superior part of the body of the atlas. This is a specimen
of an axonoides articulation ; it allows motion of the head
from side to side, whereby the muzzle may be made to
describe a circle.

Vertebral articulations.

The rest of the vertebral articulations have many
characters in common. The anterior convex surface of the
body is united to the posterior concavity of the body in
front of it, through the medium of an intervertebral disc of
cartilage, which is soft and cartilaginous centrally, hard
and fibrous externally. Inferiorly its fibres in some cases
take a marked direction from before backwards along the
central line, forming the inferior vertebral ligament, most
marked in the lumbar region, where it affords attachment
to the crura of the diaphragm. The superior vertebral
ligament serves to strengthen this union superiorly, for it
runs along the floor of the spinal canal, its whole length
consisting of a series of bands attached to the roughened
upper surfaces of the vertebral centra, widest in becoming
attached to the intervertebral discs, growing narrow oj^po-
site the centres of the vertebral bodies, in forming a small
band passing over the transverse groove for a venous
sinus.

The anterior oblique processes of the vertebrae are
united to the posterior oblique processes of the vertebrae
in front, each by means of a synovial membrane with a
strengthening capsular ligament. This articulation is ar^Aro-
dial, and is separated inferiorly by the intervertebral gap
from the amphiarthrodial union of the bodies, supero-inter-
nally from its fellow by the interlaminal ligaments which,

104^ OUTLINES OF EQUINE ANATOMY.

running from the posterior margin of the laminae of the
anterior vertebra, gain the anterior margin of the laminae
of the posterior vertebra, extending inwards as far as the
i7iter spinous ligame7it, which runs from the posterior margin
of the superior spinous process of one vertebra to the
anterior margin of the spine of the next bone. This is not
found in the cervical and coccygeal regions, and with the
interlaminal becomes converted into bone in the sacral.

The sujiersjnnous ligament is a dense band of white
fibrous tissue extending along the upper extremities of
the superior spinous processes from the sixth dorsal to the
coccygeal vertebra. Posteriorly it becomes gradually lost.
In the sacral region it affords attachment to the important
muscles of the quarter, triceps abductor femoris, biceps
rotator tibialis, and ischio tibialis ; and in extending down-
wards on either side of the spinous processes forming that
flattened band which becomes attached to the oblique
processes termed the sacral ligament, gives attachment to
longissimus dorsi and to some of the muscles of the tail.
It is very intimately blended with the superior ilio-sacral
ligament and with the tendinous layer of longissimus dorsi
against the posterior spine of the ilium. In front of
this it gives attachment laterally to longissimus and latis-
simus dorsi and to other muscles through the medium of
the lumbar faschia. In the cervical region it is repre-
sented by

Ligamentum nuchse. This is a remarkable body, wholly
composed of yellow elastic tissue, situated in the middle
plane of the neck, consisting of three portions, super-
spinous, cordiform, and membraniform. The superspinous
portion consists of double bands extending between the
superior spinous processes of the cervical and four an-
terior dorsal vertebrae ; they are expanded inferiorly,
blending with the interlaminal ligaments. Superiorly
they blend with the memhraniform portion which consists
of two thin layers of closely and somewhat irregularly in-
terlaced elastic fibres. These layers rest against each
other by their inner surfaces, inferiorly are formed by a
nuaiber of bands running upwards and backwards from
the cervical and anterior dorsal spinous processes. Thus
the muscles which occupy the spaces between the superior
spinous processes in this region lie in contact with their
fellows along the central plane, but those more superiorly

AETHROLOGY. 105

placed are separated by tlie two layers of the membranif orm
portion of this ligament. The muscles mainly thus sei)a-
rated are the complexi majores. The superior margin of
this portion blends with the cordiform portion, which is a
rounded band of yellow elastic tissue, extending from the
superior extremity of the spine of the fifth dorsal ver-
tebra (where it is directly continuous with the superspinous
ligament) to the postero-inferior part of the crest of the
occiput and the line between its scabrous pits. To its
upper surface, which is flattened, is attached the fatty mane,
and on either side it affords more or less direct attach-
ment to panniculus carnosus, levator humeri, splenius, tra-
pezius, rhomboideus and complexus major. This elastic
ligament serves to support the head without muscular
exertion.

COSTAL ARTICULATIONS.

The upper extremity of the rib presents three synovial
surfaces for union with the spine. The tubercle articu-
lates with the transverse process of the vertebra behind, by one
facet which has a synovial membrane (strengthened to form
a capsular ligament) and tivo costo-transverse lateral
strengtheriincj bands, one externally, the other internally
placed. The head of the rib presents two facets separated
by a roughened groove. The facets unite by diarthrosis
with corresponding facets, one on the postero-superior and
lateral part of the body of the vertebra in front, the other
with the antero-superior and lateral part of the vertebra
behind. Each of these facets has a synovial membrane
strengthened to form a capsular ligament, and from the
groove between ligamentum teres runs to the intervertebral
disc. From the inner surface of the neck of the rib the
stellate ligament runs, and divides into three parts, one of
which runs to the body of the vertebra in front, another to
the body of the vertebra behind, the third to the inter-
vertebral disc of cartilage.

The gomphotic union of the inferior extremity of the
rib with the sterno-costal cartilage is maintained by con-
tinuity of the costal periosteum with the investing peri-
chondrium of the cartilage. The inferior extremity of the
cartilage of elongatio7i has a diarthrodial union with the
sternal cartilage or bones in the case of all the true ribs ;
it presents a synovial membrane and tivo lateral ligaments,

lOo OUTLINES OF EQUINE ANATOMY.

the superior of wliicli blends with a fibrous hand ivhicJi runs
from one extremity of the sternum to the other, and posteriorly
is continuous with the ligament by which the inferior
sharpened extremities of the false ribs are connected
together.

ARTICULATIONS OF THE FORE EXTREMITY.

Shoulder or scapulo-humeral articulation

is the union of the glenoid cavity of the scapula with
the head of the humerus ; presents only a capsular ligament,
directly connecting the outer circumferent margins of these
two articular surfaces. It is lined by synovial membrane.
Anteriorly its external surface is separated by fat from
the tendon of flexor brachii, and the bursa between it and
the antero-superior part of the humerus. The muscles in
contact with this surface are : —

Internally — subscapularis ; posteriorly, caput magnum,
scapulo-humeralis posticus ; externally, scapulo-humeralis
externus, postea-spinatus, and antea spinatus.

This is a good example of a rotatorial joint.

Elbow or brachio-humeral articulation

is the union of the condyles of the humerus with the
articulatory superior surface of the radius and that of the
hamular process of the ulna. This articulation has a
break in the articular cartilage of both of the articular
surfaces. It presents a capsular ligament and two lateral.
The outer lateral ligament is the shortest but stoutest.
It runs from the depression on the external surface of the
outer condyle to a slight prominence at the superior part
of the outer margin of the radius. The inner lateral
ligament superiorly is attached to a depression on the
inner surface of the inner condyle, runs downwards, is
attached to a prominence at the superior part of the inner
margin of the radius, passes over the tendon of humeralis
externus, which it binds down, and becomes attached
below it.

It is a ginglymoid articulation.

Radio-ulnar articulation

has been necessarily somewhat minutely described in our
examination of its component bones.

ARTHROLOGY. 107

The knee-joint, carpus, wrist of human subject,

consists of four distinct joints, all synovial and having
distinct capsular ligaments. The radio-carpal joint is
between the inferior extremity of the radius and the sca-
phoid, lunar, and cuneiform bones and trapezium. These four
bones are united together by interosseous and connecting
ligaments, which it is unnecessary to specify. The carpal
joint is between the row thus formed, and the lower row
formed by trapezoides, magnum, and unciforme united
together in a corresponding manner, which by their under
surfaces come into connection with the upper surface
of the metacarpus, thus forming the carpo-metacarpal
joint. The last joint is arthrodial; the two former ginglymoid;
each has a synovial membrane, which in every case dips
down between the small facets presented by their small
bones for union with one another, which have been already
minutely described. The fourth capsular ligament is found
surrounding the synovial joint which trapezium makes
with the cuneiform bone. These different joints are con-
nected by lateral ligaments and the annular ligaments. The
outer lateral ligament may be divided into four, the inner
into three parts. The annular ligament is attached
anteriorly to the roughened anterior surfaces of all the
small bones of the knee, also to the roughened supero-
anterior part of the metacarpus. It anteriorhj presents
three channels running from above downwards with special
synovial thecse ; the inner one extends obliquely downwards
to the inner small metacarpal bone and gives passage to
extensor metacarpi obliquus. The outer one runs straight
downwards for passage of extensor pedis. The central is
broadest and terminates opposite the supero- anterior part
of metacarpi magnum, where the extensor metacarpi
magnus, to which it gives passage, is attached. A continu-
ation of the annular ligament surrounds extensor suffra-
ginis in the major portion of its course from the elbow
to the knee, and after it has passed through a sheath
formed by the outer part of this ligament, from which it
receives a reinforcing land, it is termed ligamentum exten-
sorum. On the surface of trapezium it forms a groove
with a theca for the lower tendon of flexor metacarpi
externus. The arrangement of the posterior part of the
annular ligament with its synovial membranes, and its

108 OUTLINES OF EQUINE ANATOMY.

superior stisjjensory and suhcarpal limiting hands lias been
ininutely described in connection with the tendons of the
flexor es pedis.

Fetlock joint
is the union of the inferior extremity of the cannon
bone superiorly with the ossa sesamoidea and os suffra-
ginis inferiorly. We, therefore, must examine how the
four bones are united together. The sesamoid bones
are covered posteriorly by fibro-cartilage, for they form
a groove over which the flexor tendons play. This cartilage
serves to connect the two sesamoids together in passing
between them, forming the intersesamoid ligament, and
superiorly it is prolonged above the bones, continuous with
two small bands of a decidedly elastic nature running to
the postero-inferior part of the large metatarsal bone. The
sesamoids are connected to os suif raginis laterally by broad
bands of white fibrous tissue, lateral sesamoid ligaments^
inferiorly by several ligaments, the inferior sesamoideal.

The superficial inferior sesamoid ligament consists of two
lateral and a central portion, all of which extends from
the supero-posterior part of os suffraginis to the inferior
part of the mass formed by the sesamoids and their fibro-
cartilage. The middle ligament has a widespread triangular
attachment to the posterior surface of os suffraginis and
extends to the inferior part of the sesamoid mass. The
deep ligament rises from the small triangular space at the
supero-posterior part of os suffraginis, sends fibres which
cross each other before reaching the sesamoid mass. , The
combined sesamoid and sufFraginis bones are attached to
the large metacarpal bone by the

Superior sesamoideal or suspensory ligament which ex-
tends from the supero-posterior part of os metacarpi
magnum and as a firm fibrous cord, with more or less
numerous muscular fibres interspersed, inns down the
back of the limb in the groove formed by the posterior
surface of os metacarpi magnum and the small metacarpal
bones on either side. Opposite the superior part of the
inferior third it bifurcates, one division running to the
outer part of each sesamoid, and from this being continued
onwards over the lateral parts of os suffraginis to blend
with extensor pedis on the anterior part. This hgament
corresponds to a number of muscles found in this situ-
ation in animals which have five digits ; sometimes

ARTHROLOGY. 109

these miiscles are found so marked in the horse as to receive
the name lumbrici. The lateral ligaments of the fetlock
extend from the infero-lateral jmrt of metacarpi magnum
almost as high up as the inferior bulbous i^rominence of
the splint bone, downwards to the supero-lateral part of
OS suffraginis. They are connected together by the capsular
ligament, a thick layer of white fibrous tissue attached to
the • large metacarpal and suffraginis bones close to their
articulatory surfaces ; internally it is lined by the synovial
membrane of the joint, externally in contact with extensor
pedis tendon, and extensor suffraginis. The annular liga-
ment passes from the lateral ligaments behind the flexor
tendons, and inferiorly has two bands which blend with
perforatus tendon at its bifurcation.

PASTERN JOINT.

The inferior articular surface of os suffraginis is main-
tained in apposition with the superior surface of os coronse,
anteriorly by the tendon of extensor pedis, posteriorly by
the long inferior sesamoideal ligament. On each side is
a stout lateral ligament, superiorly extending almost half
way round the bone from underneath extensor pedis, an-
teriorly to the external part of the posterior surface. Its
fibres run downwards and backwards, and after covering
the inferior attachment of flexor pedis perforatus become
attached to the supero-lateral parts of os coronse, some
of them being continued on to form one of the divisions
of the stellate navicular ligament, others joining with
similar fibres from the other side to form a thin fibrous
layer, the superior surface of which intimately blends with
the perforans tendon ; the inferior gives attachment to the
fibrous frog.

The coffin or pedal joint will hereafter be described.
(See Foot.) It has only two ligaments, lateral.

LIGAMENTS OF THE PELVIS.

The superspinous ligament in the sacral region is very
thick and strong, and anteriorly expands, becoming
attached to the postero-superior spinous process of the
ilium. It is here continuous with the tendinous structure
of longissimus dorsi, and is termed the superior ilio-sacral
ligament. Becoming attached along the posterior margin
of the ilium, extending from the postero-superior spinous

110 OUTLINES OF EQUINE ANATOMY.

process about three inches downwards, is the inferior ilio-
sacral ligarnent, the fibres of which run obliquely down-
wards and backwards, to become attached inferiorly to the
transverse ridge of the sacrum, and to become continuous
onwards, blending with the substance of the sacrosciatic
ligament, after forming with that ligament below the trans-
verse ridge a canal extending from before, backwards,
through which an important branch of the gluteal artery,
with its accompanying vein and nerve, pass. The space on
the lateral part of the sacinim bounded outwardly by the
inferior ilio-sacral ligament and by the superior part of the
venter ilii is occupied by the posterior part of longissimus
dorsi, and when this is removed, a continuation of the
superior spinous ligament, under the form of a thick layer
of fibres running downwards and backwards over the lateral
surface of the sacral spines, is exposed. It is termed the
sacral ligament.

The sacro-iliac ligament consists of a number of stout
ligamentous fibres, diverging in all directions from the
roughened surface around the auricular facet of the first
sacral transverse process. They run to the roughened
surface of venter ilii, and externally blend with the inferior
ilio-sacral ligament, internally being continuous with a stout
ligamentous band running towards the articulatory margin
on the anterior part of the last lumbar transverse process,
to the summit of which also a few scattered fibres run.

The sacro-sciatic ligament forms the postero -lateral
boundary of the pelvis. Superiorly it is attached firmly
along the whole length of the transverse ridge of the
sacrum, inferiorly it becomes attached to the ischiatic spine,
and to the tuberosity of the ischium, from the line between
these two prominences becoming reflected inwards as a
fibrous layer between the jpelvic viscera, and the internal ohtu-
rator and pyriformis muscles becoming attached to the
superior edge of the posterior margin of the ischium and
along the upper part of the inner edge of the os innomi-
natum. Thus between the ligament and the bone are two
spaces ; the superior-ischiatic notch is between the anterior
margin of the ligament and the posterior margin of the
ilium, and gives passage to the gluteal vessels and nerve
and the sciatic nerve. The inferior-ischiatic notch between
the neck of the ischium and this ligament, where it is
reflected inwards, gives passage to the obturator internus

ARTHROLOGY. Ill

and pyriformis tendons ; the external surface of this liga-
ment gives attachment to some of the large muscles of the
quarter and over it, almost embedded in it, runs the great
sciatic nerve. Its inner surface affords attachment to re-
tractor ani and compressor coccygis. The obturator
ligament is an extremely thin layer of white fibrous tissue,
with difficnlty demonstrable, situated between the internal
and external obturator muscles, attached to the margins of
the foramen, deficient at the antero-external part, where
the obturator vessels and nerve gain passage.

ARTICULATIONS OF THE HIND EXTREMITY.

Hip -joint

is formed by the head of the femur and the acetabulum,
maintained in apposition by ligaments. The acetabulum
is increased in depth by the circumfere^itial or cotyloid
ligament, a ring of fibro-cartilaginous substance attached
around its margin, it passes over the deficiency on the
inner side of the cavity, and here is termed the trans-
verse ligament; thus it leaves a space through which a
dense ligamentous band of a tendinous nature runs to
become attached to the break in the articular cartilage on
the head of the femur. This is the puhio -femoral ligament,
a continuation of the common tendon of the abdominal
muscles ; it runs from the anterior part of symphysis pubis
outwards through a groove on the under surface of os
pubis ; some of the muscular fibres of rectus abdominis
are directly inserted into it ; at its attachment to the
head of the femur it blends with ligamentum tenses, which
passes from here to the internal roughened part of the
acetabulum. From the free margin of the cotyloid liga-
ment the capsular ligament extends downwards, to become
attached around the outer margin of the articulatory
surface of the head of the femur ; it is lined by synovial
membrane, which also invests the pubio-femoral and teres
ligaments.

Stifle joint

corresponds to the knee of the human subject ; the pa-
tella, tibia, fibula, and femur assist to form it. Between
the condyles of the femur and the upper articulatory
surface of the tibia on either side is a semilunar disc of
fibro-cartilage. These are convex and thick externally

112 OUTLINES OF EQUINE ANATOMY.

and decrease in size to form a tliin edge at tlie internal
margin around wliich the synovial membrane is reflected
from the upper to the under surface ; to the outer
margin the capsular ligament is firmly attached. The
anterior extremity of each cartilage is attached by a liga-
ment to the anterior part of the spine on the upper ex-
tremity of the tibia. The posterior extremity of each by
a ligament to the upper extremity of the tibia behind the
spine, but the outer cartilage in addition has a ligament
extending to the posterior part of the inter-condyloid
fossa of the femur. The femur is also connected to the
tibia directly by the crucial and the lateral ligaments.
The crucial ligaments, two in number, can only be exposed
by removal of one of the condyles of the femur. One
of them runs from the anterior part of the groove on the
tibial spine, to become attached supero- posteriorly to the
inner surface of the outer condyle in the intercondyloid
fossa ; its fibres cross at right angles, the other crucial liga-
ment, which runs from the anterior part of the intercondy-
loid fossa downwards and backwards to the superior ex-
tremity of the tibia behind the spine.

The Older lateral ligament is superiorly attached to the
depression on the outer surface of the outer condyle of the
femur ; it crosses the tendon of popliteus which plays
through a sheath between this and the capsular ligament,
and then passes on to the femur. This ligament becomes
attached below to the upper extremity of the fibula ; from it
peroneus mainly arises.

The inner lateral ligament is lomgeY smd narrower than the
outer, extending from the internal surface of the inner
condyle downwards to the supero-internal j^art of the tibia.

The patella is connected to the femur by two lateral
ligaments. The inner extremity of the patella is continued
as a piece of fibro-cartilage which plays over the inner
condyle, and from this the inner ligament runs to the inner
surface of the internal femoral ridge. It is smaller than
the outer, which runs from the outer extremity of the
patella to the corresponding part of the outer ridge.

The patella is connected to the tibia by three straight
ligaments. The inner runs from the complementary car-
tilage on the inner side of the patella to the supero-internal
angle of the ridge on the antero- superior part of the tibia.
The outer, which is composed of two portions, extends from

AETHROLOGY. 1 ] 3

the outer extremity of tlie patella to the supero-external
angle of the same ridge. The capsular ligament, after con-
necting together the two articulatory surfaces posteriorly
and laterally, and internally becoming attached to the
semilunar cartilages, externally to the lateral ligaments
(partially separated from the outer by the tendon of pop-
liteus), blends with the inner and the outer straight
ligaments of the patella, connecting them together, and
covering the central straigJit ligament, which commences
about the centre of the anterior surface of the patella,
plays over a bursa on that bone, is separated from the main
joint by a quantity of fat, plays over another bursa at the
central part of the superior extremity of the tibial ridge,
and becomes attached below it.

The synovial membranes of this joint are two or three in
number, for in some cases we see the cavity of the joint
between the femur and the patella communicating with that
of the inner condyle of the femur. The cavity of the outer
condyle always remains distinct. These cavities frequently
communicate with the important bursae in the neighbour-
hood. The condyles come directly into contact with the la-
teral parts of the spine of the tibia, the upper surfaces of the
semilunar cartilages are concave 1o accommodate the con-
vex surfaces of the condyles, their under surfaces are plane.

The mode of union of the fibula to the tibia has been
already described.

HOCK JOINT.

The small bones of the hock, like those of the
knee, are united together by interosseous and connectincj
ligaments, thus producing two rows, the superior formed
by astragalus and calcis, the inferior by the cuboid
and three cuneiform bones. These, together with the
metatarsus, form the tarsal and tar so -metatarsal gliding
joints, lubricated with synovia secreted by membranes,
which extend to the facets situated between the several
small bones ; generally a distinct synovial sac may be dis-
tinguished between the component bony layers of the
lower row.

The true hock-joint is the ginglymoid articulation formed
by the apposition of the inferior grooves of the tibia with
the superior ridges of astragalus. This joint presents a
capsular ligament, attached around the edge of the articu-

8

114 OUTLINES OF EQUINE ANATOMY.

latory surfaces, which at the postero-internal part is
thickened and fibro-cartilaginous, its external surface being
here concave and lubricated with synovia, forming part
of that theca in which the perforans tendon glides.

The lateral ligaments of the JiocTc are two in number, and
extend from the malleoli of the tibia to the supero- lateral
l^arts of the large and respective small metatarsal bones ;
the outer is the largest. Both of them may be divided into
several parts.

The posterior annular ligament is thickened in covering
the bones on the postero-internal part of the joint in the
groove, in which the perforans tendon plays ; it likewise
becomes reflected from the posterior border of os calcis to
blend with the posterior margin of the inner lateral liga-
ment, binding down the perforans tendon and continued on
to retain the tendon of flexor pedis accessorius in its groove
behind the internal malleolus.

The anterior annular ligament becomes marked as three
hands. The superior extends across the antero-inferior part
of the tibia, over the flat surf ace, binding down the tendons
of flexor metatarsi and extensor pedis, inclined obliquely
from within outwards and downwards, and continued on to
retain the tendon of peroneus in its groove on the outer
malleolus of the tibia. The middle hand, extending from
the cuboid, winds round extensor pedis tendon, and then
blends with that division of the flexor metatarsi tendon
which passes to the same bone. The inferior hand, closely
connected in the fresh subject with the middle, runs from
the superior extremity of the outer small metatarsal bone
over extensor pedis tendon to the central line of the supero-
anterior part of the large metatarsal bone.

The calcaneo-euboid ligament extends from the posterior
border of os calcis along its whole length downwards to the
superior part of the outer small metatarsal bone. Exter-
nally it blends with the external lateral ligament, internally
with the posterior annular ligament. A large and impor-
tant synovial membrane covers the inner surface of the
capsular ligament.

None of the other ligaments of the hock require special
notification.

The other articulations of the hind limb resemble
those of the fore limb, to the description of which reference
may be made when the dissection arrives at this stage.

SPECIAL ANATOMY. 115

PART lY.— SPECIAL ANATOMY.
The Head.

From the angle formed at the meeting of the incisions
through the skin downwards from the ear, and backwards
from the lower lip, the operator commences to remove the
skin in the antero-superior direction as far as the root of
the ear, the eyelids, and the central line of the face ; this
done he works forward towards the lips and the nostril,
where the muscular fibres are found closely in contact with
the skin, in some places being inserted into it. The roots
of some of the long hairs which form the " feelers " will be
also cut through in removing the skin from the lips. From
the zygomatic ridge to the centre of the submaxillary
space the panniculus in a thin layer lies immediately in
contact with the skin, and through it may be seen the
branches of the facial nerve, and the masseter externus
muscle. Its fibres converge from here towards the angle
of the mouth, where they blend with other muscles, especi-
ally orbicularis oris, forming the muscular band termed
retractor anguli oris.

To the same point, and to the upper lip above it, run
fibres forming a thin layer extending from the zygomatic
ridge, and some from the muscles of the lower eyelid. This
is zygomaticus, which muscle forms the central part of the
superficial subcutaneous layer of the face.

The upper part of this layer is formed by levator labii
superioris alseque nasi, which is attached superiorly to the
nasal, frontal, and lachrymal bones at their point of
junction, and runs downwards and forwards to be inserted
into the point of the false nostril, the wing of the nostil,
and the upper lip, blending with the other muscles of this
part.

The fibres of this muscle are separated inferiorly into two

116 OUTLINES OF EQUINE ANATOMY.

portions by the passage of the insertion portion of retractor
labii superioris, which spread out in their course towards
the ala of the nostril and the upper lip, while their origin
from the superior maxillary bone in front of the termina-
tion of the zygomatic ridge is hidden by zygomaticus.

Extending round the free margin of the lips are a number
of fibres of red muscular substance into which all the mus-
cles running to these organs seem to pass ; this is orbicu-
laris oris, the muscle by which the lips are closed and the
animal enabled to grasp small articles (as oat grains) on a
flat surface. This muscle is nowhere intimately attached
to the bone, but is composed of a series of short fibres
encircling the oral opening.

The frontal and nasal bones are immediately in contact
with the skin on the forehead and nose, but about opposite
to the nasal peak the tendon of nasalis longus labii
superioris emerges from beneath lev. labii sup. alseque
nasi, and running over the cartilaginous prolongation of
the nasal bones, where it is lubricated with synovia, it gains
the anterior surface of the alse of the nostril, which are
here to be seen covered by dilator naris anterior (which
runs from the external surface of one ala to that of the
other) ; here the tendon blends with the corresponding
tendon from the other side of the face, and from the point
of union the fibres radiate to blend with orbicular oris, and
become inserted into the skin of the upper lip.

The false nostril fills the angle formed between this
tendon and the levator labii sup. alseque nasi. From the
anterior edge of the nasal bones, extending as far back as
where this bone meets the anterior maxillary bone, the
dilator naris superior arises, and runs to be inserted into
the false nostril along its whole superior margin.

Below retractor anguli oris the terminal portion of
retractor labii inferioris with a small round tendon is
found going to blend with orbicularis oris in the lower lip
(this tendon is connected to the inferior maxillary bone
below the corner incisor by a distinct band of muscular
fibres in some subjects), and below this the bone is sub-
cutaneous.

On removal of the superficial muscular layer of the face
we expose the masseter externus, a huge square mass of
muscle arising along the whole length of the under surface
of the zygomatic process, and passing to the whole external

SPECIAL ANATOMY. ]17

surface of the branch of the inferior maxilla. At its origin
it is tendinous, and through its substance run strong tendi-
nous bands, which are inserted below into irregular ridges ;
these bands are a provision for the constant closure of the
jaws when not required to be separated in mastication or
otherwise, for this muscle, with temporalis, pterygoideus,
and masseter internus serve to close the month. In many
other- situations we shall observe tendinous bands running
throughout the whole length of auiscles to support weight,
without the active contraction of muscular fibre which
would weary.

Along the posterior part of the superior margin of mas-
seter externus we see the temporal artery with an
accompanying vein, which vein is sujDeriorly placed. This
artery is one of the three terminal trunks of the external
carotid, and after winding round the angle of the jaw
posteriorly, proceeds for about two inches on the external
surface of this muscle, and then dips down into its sub-
stance ; the pulse is frequently taken at this artery. Along
the anterior margin of the masseter externus run the
submaxillary artery and vein, with the duct of the parotid
salivary gland. The artery is almost invariably the most
anteriorly situated, but the position of the vein and duct is
not constant. At first in contact with the inferior maxillary
bone they next pass over retractor labii inf erioris, when the
artery gives off a branch running forwards, the inferior
labial and several branches, the anterior masseteric, which
run from it posteriorly to the masseter muscle. They then
run on to buccinator and caninus, the muscles which form
the cheek ; about the centre of this muscular mass the duct
dips between the muscular fibres, and having proceeded a
short distance beneath the buccal mucous membrane, opens
into the mouth at a small eminence or papilla situated
opposite the space between the second and third molar
teeth (but the position of this opening is not constant). At
the anterior extremity of the zygomatic spine the sub-
maxillary artery divides into the superior labial and facial.
This division occurs just after the vessel has passed over
the originating tendon of retractor labii superioris ; the
superior labial branch runs forward, being mingled with
the fibres of the superior maxillary division of the fifth
cranial nerve, which here emerge from the infra-orbital
foramen, and run to the upper lip. With these it pierces

lis OUTLINES OF EQUINE ANATOMY.

the lip, and so gains tlie incisive foramen, where it combines
with the corresponding artery from the opposite side, and
the trunk thus formed joins with the arch formed by the
union of the two palatine arteries, which run along the
sides of the roof of the mouth. The facial artery runs
upwards, anastomosing with branches of the ocular arteries,
which bend round the margin of the orbit. At its upper
part it passes over the origin of nasalis longns labii
superioris (which arises from about the point of junction
of the nasal, malar, and lachrymal bones).

By removal of zygomaticus and retractor anguli oris we
expose buccinator and caninus. These two muscles are
intimately blended ; buccinator anteriorly blends with
orbicularis oris, its fibres run directly backwards to become
inserted into the anterior margin of the ramus of the lower
jaw, posteriorly to the alveolar cavities ; it is also attached
slightly to the alveolar ridges and to the tuberosity of the
superior maxilla. To show this an incision must be made
through masseter externus, whereby it will be found to
cover superiorly a varicose vein situated immediately
beneath the zygomatic spine, running from the submaxil-
lary vein on the cheek through the foi-amen lacerum orbi-
tale to the cavernous sinus ; below this is one of the buccal
salivary glands from two to three inches in length, similar
in structure to the parotid gland, the secretion of which is
poured into the mouth through numerous foramina opening
upon a line of papillary eminences of the buccal mucous mem-
brane, opposite to the upper molar teeth. Below this gland
is seen buccinator intimately blended with retractor labii
inferioris, inserted as above mentioned. Caninus is com-
posed of two distinct layers of arched fibres, which arise
from the superior and inferior maxillary bones respectively
at the interdental spaces, run towards the central line of
the anterior part of buccinator, where they blend together
and with that muscle, sending some straight fibres to blend
with it posteriorly. By raising the infero-anterior part of
buccinator, just in front of masseter externus, we expose
the inferior buccal glands, in every respect, except situa-
tion, resembling the superior ; they lie in immediate con-
tact with the buccal mucous membrane, with which the
internal surface of buccinator is intimately attached
throughout the rest of the cheek. Passing around the
anterior margin of the coracoid process of the inferior max-

SPECIAL ANATOMY. 119

illary bone is the buccal hrancJi of the inferior maxillarij
division of the fifth cranial nerve; it sends some large fibres
to the buccal glands, and runs onwards to supply buc-
cinator and caninus as far forwards as the angle of the
mouth. The facial hranch of the same nerve winds round
the posterior margin of the lower jaw just below the con-
dyle, combines with the seventh nerve or portio dura, and
proceeds over the cheek on the external surface of masseter
externus. One of its portions runs with the temporal
artery, the inferior branch passes to the lower lip, and
there unites with that portion of the dental branch of the
inferior maxillary nerve, which passes out of foramen
nienti (or the anterior maxillary foramen). The middle
and largest branch proceeds over the cheek, and sends
communicating fibres to the nerve which passes out of the
infra-orbital foramen; these pass in a curved manner
around the origin of retractor labii superioris, but the
greater number of the fibres blend with the infra-orbital
fibres, and run to the nostril and upper lip. Some small
muscles on the muzzle remain yet to be noticed.

Dilator naris inferior arises from the superior process
of the anterior maxillary bone, winds round its smooth
superior margin, and becomes inserted into the cartilagi-
nous anterior extremity of the inferior turbinated bone
into the skin of the false nostril. From the superior ex-
tremity of the false nostril a small muscle running to the
superior maxillary hone just above the termination of the
zygomatic ridge may frequently he found.

Depressor labii superioris arises from the external sur-
face of the body of the anterior maxilla around the alveolae
of the incisors, and extending back to the canines : it
becomes inserted into the mucous membrane lining the
upper lip, and may be exposed by removing this mem-
brane and the labial glands. It will be found to blend
centrally with its fellow. In the lower lip we find a
corresponding muscle, levator labii inferioris. Internally
to these muscles is a layer of salivary glandular substance
from which run numerous ducts which pierce the mucous
membrane of the lips, by inversion of which their openings
may be rendered visible to the naked eye. The structure
of the lower lip is completed by a mass of fatty matter
throughout which many muscular fibres are interspersed.
The lips, therefore, consistof skin, muscle, glandular struc-

12Q OUTLINES OF EQUINE ANATOMY.

ture, and mucous membrane, witli veins, arteries, lymph-
atics, and especially nerves, the large size of which renders
the " twitch " such an effectual " sedative ?" It is orbi-
cularis oris which forms the greater part of the lij^s, and
which brings the two lips into close connection at their
extremities, whereby the commissures, or angles of the mouth,
are formed. The lips are the organs of prehension of the
horse, and present an external surface from which long
hairs, ''feelers,'' project, more especially from the inferior
central prominent portion commonly called the chin. The
internal surface of the lips is concave, moulded upon the
anterior surfaces of the inferior and anterior maxillary
bones (which is covered by the dense mucous membrane
which forms the gum) and upon the anterior surfaces of
the crowns of the incisors. The free margins of the lips
are in contact with each other, or sej^arated according as
the mouth is shut or open.

The remainder of the skin may now be removed, when
another orbicularis muscle will be exposed in the eyelids,
which it tends to approximate and to maintain in appo-
sition. This is orbicularis palpebrarum, which is attached
by a small tendon to the lachrymal tubercle situated on
the facial surface of the lachrymal bone. Its fibres extend
into the upper and the lower lids, and meet at the o^der
angle, commissure, or canthus of the eye. It is exter-
nally in contact with the skin, which is thin and smooth
in this neighbourhood. Internally it is fixed to the bones
which form the rim of the orbit by loose areolar tissue,
and in the substance of the upper eyelid is attached to
the tarsal cartilage or ligament, a small semilunar portion
of yellow elastic cartilage which is thickest in the centre,
and grows narrower and thinner until it terminates in a
point at either extremity in becoming continuous with the
white fibrous tissue of the eyelid. It is sometimes found
in the lower lid, but is then mostly fibrous. On the
internal SLirface of this cartilage, and running in small
parallel lines visible through the mucous membrane lining
the eyelid, in a direction perpendicular to its free margin,
are the meibomian glands, specially modified sebaceous
glands, the product of which serves to prevent overflow
of tears on to the external surface of the lids. To orbi-
cularis palpebrarum run several muscles.

Levator palpebrae superioris externus runs from the

SPECIAL ANATOMY.

121

root of the orbital process of the frontal bone to the npper
eyelid, where it blends with orbicularis, from the lower
part of which muscle levator labii superioris alseque nasi
and zjgomaticus in part take their origin. The eyelids,
therefore, are two semilunar folds which are adapted to
cover the anterior surface of the eyeball. They are com-
posed externally of skin, internally of mucous membrane,
nam-ed the conjunctiva, which becomes reflected over the
tunica albuginea and the cornea, thus covering all that
portion of the eye which is naturally visible, and serving
to retain the eyeball in its proper relation with the palpe-
bral fissure, by its smooth surface to facilitate the move-
ments of the eyelids, and to protect the eye. That portion
of it which lines the eyelids and covers the tunica albu-
ginea is vascular, but its continuation ovei' the cornea is
simjjly a basement membrane, with a single layer of tesse-
lated epithelial cells, which is transparent and thus causes
no obstruction to vision. Between these two layers of the
eyelid are situated muscular structure, vessels, nerves, the
meibomian glands and the tarsal ligament. ^ The free
borders of the eyelids are broad and only come into appo-
sition by their outer edges when the lids meet ; thus a trian-
gular canal is formed by which the tears are directed
towards the inner angle of the palpehral fissure, the space
between the eyelids. Along the outer edge of this margin
we see the eyelashes, cilise ; long curved hairs, those of
the upper lid, the strongest and longest, run in an upward
direction, those of the lower lid downwards. This margin
also presents in each eyelid a row of openings of the
meibomian glands, and at the inner extremity a much larger
opening ; these latter are the puncta lachrymalia, through
which the tears pass on their way from the front of the
eye to the nasal chamber. The points at which the eye-
lids meet are termed the cantM ; the outer or temporal
cantlius is in the form of an acute angle, and here the
eyelids are in direct contact with the eyeball ; the inner
or nasal canthus presents a rounded diverticulum in which
is situated a small rounded nodular body covered by a
very thin dark skin which presents a few short and fine
hairs. This is the canincula lachrymalis, which is merely
a mass of connective tissue and vessels, and is situated
between the puncta lachrymalia into which it serves to
direct the tears. Before departing from consideration of

122 OUTLINES OF EQUINE ANATOMY.

the eyelids we may notice that into the inner surface of
the tarsal ligament is inserted by a broad tendon the

Levator palpebrse superioris internus, a muscle which
arises from the upper part of the orbital hiatus above
rectus superior, and passes within the periorbital membrane
to become inserted as described. By playing over the eye-
ball it is enabled to raise the eyelid.

The eyelids receive blood from the ophthalmic artery,
from the facial artery, and from the ocular and supra-
orbital branches of the internal maxillary artery. Their
nerves are derived from the ophthalmic division of the
fifth cranial nerve, the supra-orbital branch of which is
remarkable as passing to the foramen of that name from
the foramen lacerum orbitale externally to the periorbital.

On the supero-posterior part of the head, on either side
of the poll, are situated the structures which compose
the external ear. These consist of three cartilages on each
side, of the muscles which act upon them, and of the skin
which covers one of them extending inwards to line the
external ear. Situated nearest to the orbit, resting on the
rounded mass which is named the temporal muscle, is an irre-
gularly triangular shaped cartilage, which seems to be con-
nected to the other cartilages by muscle alone : this is the
scutiform cartilag'e. From its external surface the external
scuto- auricular es muscles run to theconchial cartilage, and
similar muscles may be found attached to its internal sur-
face. The conchial cartilage is a portion of membraniform
cartilage twisted upon itself in such a manner as superiorly
to present a sharp point, externally a wide broad slit,
infero-posteriorly a cup-shaped diverticulum, infero-
anteriorly a tubular portion along one side of which we
see an irregular slit running outwards, filled with fibrous
tissue (and from the other side a thin process runs
to be attached below to the guttural pouch), which
is connected to the external auditory process by a ring-
shaped piece of cartilage, the annular cartilage. This
cartilage is connected to the external auditory process by
yellow elastic tissue, and similarly to the conchial cartilage ;
the circular portion of the conchial will fit on the annular,
and the annular on the bony process like the joints of a tele-
scope, but this action is regulated by muscles which run
from one cartilage to the other, which with those running
from the scutiform cartilage constitute the intrinsic

SPECIAL ANATOMY. 123

muscles of the external ear. To the conchial cartilage
run the extrinsic auricular muscles ; those anteriorly
situated are the attrahentes, and are attached to the zygo-
matic process and to the parietal ridges. The retrahentes
are attached to the liganientum nuchse, and by areolar
tissue to the muscles situated externally to the muscles
of the poll. The adductor muscles run from the crest of
the occiput ; debility of these causes the animal to
become " lop-eared." Parotideo auricularis is the abductor ;
it runs from the external part of the base of the conchial
cartilage, to become attached below to the external surface
of the parotid gland. It is not directly subcutaneous, but
covered by a thin layer of panniculus. Around the base
of the conchial cartilage is a quantity of fat, which facili-
tates its movements. The common integument covering
the external surface of this cartilage at its upper third is
reflected over its margin at the meatus auditorius exter-
nus (or slit) to line the conchial and annular cartilages,
and the external auditory canal, at the bottom of which it
covers the external surf ace of membrana tympani. It is
very fine and at the internal surface of the conchial
cartilage presents long hairs which seem to close up
the external opening ; they serve to prevent the ingress of
foreign matters. More internally it presents sebaceous
glands modified for the production of the cerumen or wax
of the ear, ceruminous glands. We notice that the external
ear of the ass is more developed than that of the horse.
The external ear receives blood by the anterior and pos-
terior auricular branches of the external carotid artery ;
the latter sends a large branch, middle auricular, to the in-
ternal surface of the conchial cartilage. The nerves of the
external ear are derived from the facial, fifth cranial, and first
cervical nerves.

The inferior maxilla must now be partially removed
by incision through the interdental space and through its
neck after masseter externus has been separated from its
inferior attachment, and thrown upwards over the zygo-
matic spine. By removing the piece of bone thus separated
we expose the anterior attachment of digastricus inf eriorly,
and above tbis we cut through the attachment of

Mylo-hyoideus, which arises from the alveolar ridge at
the superior part of the internal surface of the inferior
maxilla. Its fibres run towards the centre of the inter-

12-i OUTLINES OF EQUINE ANATOMY.

maxillary space, where they blend witli tliose of its fellow,
thus forming a sling for the tongue and a central raphe,
which posteriorly is attached to the inferior margin of the
spur process of os hyoides. To the internal surface of the
ramus of the inferior maxilla is attached

Masseter interims, which arises from the under surface
of the crus of the sphenoid bone and of the palatine bone,
and becomes attached below to the greater part of the
internal surface of the ramus.

By division of its inferior attachment we expose the
inferior maxillary division of the fifth cranial nerve,
which emerges from the cranium through the anterior part
of the foramen lacerum basis cranii. It sends a large
bunch of fibres to join with the seventh nerve, and pass
over the cheek to form the facial ; just before arriving at
the posterior maxillary foramen it breaks up into three
parts — the buccal^, gustatory, and inferior dental branches.
The buccal branch winds round the front of the coracoid
process of the bone and then passes over buccinator and
caninus, sending large branches to the molar salivary
glands. Just within its origin and firmly attached to it by
nerve-fibres is the otic ganglion, which receives motor
fibres from the seventh and sends different branches to the
middle ear. The gustatory branch receives an extremely
important branch (chorda tympani) , which passes from the
seventh nerve during its course through the middle ear.
It then passes between masseter internus and pterygoideus,
and goes to supply the posterior and lateral parts of the
tongue with common sensation and with the special sense
of taste. It also sends a very distinct branch to the
sub-lingual salivary gland. The inferior dental branch
at once passes through the posterior maxillary foramen ;
it then runs along below the fangs of the inferior molar -
teeth, between the two plates of the bone, taking a curved
direction downwards and forwards ; it sends a large branch
to each molar tooth, and at the anterior maxillary foramen
divides, one portion running onwards between the plates
of the bone, to be expended in supplying the canine and
three incisor teeth of that side, while the other runs
through the foramen to the lower lip, blending with a few
fibres from the facial nerve. The two last-mentioned
nerves are separated from the buccal branch by

Pterygoideus, which arises from the under surface of the

SPECIAL ANATOMY. 125

pterygoid bone and tlie crus of the sphenoid, and becomes
inserted into the internal surface of the neck of the inferior
maxillary condyle. The upper extremity of the inferior
maxilla should now be removed by disarticulation of the
joint, and sweeping a knife around the coracoid process
in the temporal fossa. It will be thus shown that a con-
siderable amount of fat assists in filling up this fossa,
thus allowing play of the coracoid process. Deficiency of
this fat causes that depression above the eyes noticeable
in old or emaciated horses. In addition we also see in this
fossa the

Temporalis, a muscle which passes from its attachment
to the superior bony boundary of the temporal fossa, ex-
tending as far as the parietal ridges to become inserted
into the inner surface of the coracoid process of the inferior
maxilla. It is sometimes composed of two distinct parts,
and serves when acting alternately with its fellow to
give the jaw the lateral motion necessary for the grinding
of the food ; when acting in conjunction with its fellow it
aids in closing the mouth.

Muscles which close the mouth : — Masseter externus,
masseter internus, temporalis, pterygoideus. We have
now exposed the posterior part of the orbit, which in the
horse consists of fibrous membrane, the periorhitale ; below
this is the internal maxillary artery. Commencing at
the termination of the external carotid, at the inner sur-
face of the temporo -maxillary articulation, this vessel
takes a direct course towards the sphenoideal foramen,
and having passed through it gains foramen rotundum,
and thus becomes again visible just below the orbit. It
takes a straight course towards the maxillary hiatus, where
it breaks up into three branches which adopt the names of
the foramina of the hiatus through which they pass.
Before arriving at the sphenoideal foramen this artery gives
of£ deep temporal branches upwards and branches doivn-
wards to masseter internus. Also the inferior maxillary
artery which passes through the posterior maxillary fora-
men, and courses with the corresponding nerve between
the plates of the inferior maxilla supplying the lower teeth,
and sending a small branch outwards through foramen
menti. In its course below the orbit the internal maxil-
lary artery gives off branches upiuards to the temporal
muscle, and ocular branches, which run to the eyeball and

126 OUTLINES OF EQUINE ANATOMY.

to the appendages of the eye, also the su;pra-or'bital artery,
which passes iu a direction upwards to the root of the
orbital process of the frontal bone ; after passing through
the supra-orbital foramen it breaks up in sup"plying the
muscles of the forehead. A remarkable branch of this
artery, the lateral nasal makes a peculiar twist before
piercing the internal orbital foramen. By passing
through this it is described as gaiiiingthe nasal chamber, from
which it passes through the cribriform plate of the eth-
moid bone into the olfactory sinus, and after supplying
the olfactory bulb it passes again through the cribri-
form plate and supplies the mucous membrane of the
superior meatus of the nasal chamber. Some of the
ocular branches passing over the lower margin of the
orbit anatomose with branches of the facial artery. The
internal maxillary artery sends branches downward to
supply the soft palate, and the buccal branch to the cheek
and the molar glands ; it then breaks up into the spheno-
palatine, palato-maxillary, and superior dental branches.

The spheno-palatine artery, passing through the foramen
of the same name, gains the nasal chamber, where it sup-
plies the inferior and middle meatus. The palato-maxillary
artery, on emerging from the palatine canal through the
palatine foramen, courses its way along the lateral part of
the hard palate, and bending inwards anteriorly is retained
in position by a small cartilaginous hook, and anastomoses
with its fellow, the arch so formed giving off a branch
which passes through foramen incisivum to anastomose
with the terminal parts of the superior labial arteries. The
superior dental artery passes through canalis infra orbitale,
and sends a branch to each molar ; it sends a small branch
through the infra-orbital foramen to anastomose with the
arteries of the face, but the main trunk runs between the
plates of the bones to supply the tush and the incisors.

The fifth cranial nerve, pars trigemini, arises by two
roots from the lateral part of the pons Varolii at the
base of the brain. One of these is sensory, the other is
motor ; in this respect the nerve resembles those given off
from the spinal cord ; it is hence sometimes called the spinal
nerve of the brain, and the analogy is increased by the
presence of a large ganglion, the Gasserian, on the sensory
root. This ganglion is situated between the two folds of
dura mater, which constitute the membranous tentorium,

SPECIAL ANATOMY. 127

and tlie motor root runs over its under surface. From the
ganglion three branches pass : — One runs to combine with
the motor tract to form the inferior maxillary division,
which passes through foramen lacerum basis cranii, as
ah'eady noticed ; another, the ophthalmic division, passes
through foramen lacerum orbitale, in company with the
third, fourth, and sixth cranial nerves and the ophthalmic
artery, and thus gains the orbit. The third, or superior
maxillary division, passes from the cranium, and emerges
with the internal maxillary artery through foramen rotun-
dum. It may be seen with this vessel passing to the maxil-
lary hiatus, prior to gaining which it divides into three parts,
corresponding to the terminal branches of the artery. The
superior dental hranch passes through canalis infra-orbitale,
and, like the artery, supplies the upper teeth ; but a very
large branch passes through the infra-orbital foramen,
where it is covered by levator labii superioris alaeque nasi.
It blends with a large branch from the facial nerve, forming
the superior labial nerve, and the plexus of 7ierves over the
lateral part of the muzzle formed hy the union of the infra-
orbital, anterior maxillary, and facial nerves corresponds to
the "pes anserinus " of the human subject The palato-
maxillary nerve, passing with the artery of the same through
the palatine canal, gains the hard palate, which it supplies
with sensation ; it also sends fibres to the soft palate. The
spheno-palatine nerve, passing with the spheno -palatine
artery through the foramen of the same name, gains the
nasal chamber, the inferior and middle meatus of which it
supplies with common sensation. At its origin it forms a
close connection by means of numerous fibres with the
spheno-palatine or Meckel's ganglion, a collection of nerve-
cells, which receives motor fibres through the vidian branch
of the seventh cranial nerve, and is supposed to send
efferent fibres to the palate.

We have now exposed the mouth, a cylindrical cavity
elongated in an antero-posterior direction, presenting four
surfaces and two extremities. The anterior extremity is
guarded by the lips, between which is the labial fissure.
The posterior extremity presents the anterior opening of the
fauces, bounded on either side by the reflections of mucous
membrane from the palate to the base of the tongue, the
posterior pillars of the tongue. Through this opening the
pendulous palate and the cavities of the tonsils are visible.

128 OUTLINES OF EQUINE ANATOMY.

The lateral surfaces of the mouth are formed by the cheeks,
the mucous membrane lining these presents j^erforated
papillse, on which the ducts of the buccal glands pour the
secretions of those glands ; varying in position in different
subjects, but generally about opposite the space between
the second and third molar teeth, we may distinguish the
opening of the parotid duct with a larger papilla. The
mucous membrane posteriorly is reflected inwards behind
the molar teeth to join the posterior pillars of the tongue ;
in some places it is coloured by pigmentary deposit. On
the roof of the mouth, centrally, it is thick, and presents
dense stratified epithelium and a plentiful submucous
tissue, in which is situated a remarkable plexus of veins con-
gestion of which from dental or other irritation causes that
prominence of this part termed "lampas" by individuals
who ignorantly considered it a primary diseased condition ;
on either side of this runs a palatine artery, as has been
described. That portion of the mucous membrane which
is attached to the bony palate is termed the hard palate,
and inferiorly presents a central groove, from which
crescentic prominences, seventeen to eighteen in number
on each side, run in an oblique direction outwards. These
are termed the "bars," and are straightest and closest
posteriorly, where they blend with the

Soft palate, the mucous membrane of which is redder
and less dense, and which runs in a backward direction
from the posterior crescentic margin of the x^a^latine bones.

Occupying the outer circumferent margin of the roof
and of the floor of the mouth at particular parts we see the
teeth. These are products of mucous membrane. They
are hard organs ; by some anatomists considered as bones,
but are merely the result of special development of mucous
membrane. They are firmly fixed in cavities in bone
termed alveolar cavities, and are surrounded by mucous
membrane termed the gums. They present three parts : —
A fang, th^it part enclosed in the alveolar cavity; crown,
that visible on inspection of the mouth after the teeth are
fully developed ; neck, that part connecting the fang and
the crown, and to which the mucous membrane formmg
the gum is attached. Teeth are composed of three sub-
stances (two of which closely resemble bone in histo-
logical structure), dentine, enamel, and crusta petrosa or
cement. They surround a central cavity, which is called

SPECIAL ANATOMY. 129

the pulp cavity, for it contains a small papilla to wliicli an
artery and a nerve run and from wliicli a vein proceeds ;
this is the pulp. It is immediately surrounded by dentine,
which is formed continuously from its outer part, so that
the pulp cavity, which is large in the young animal, in the
adult becomes almost obliterated ; on the outer surface of
the dentine rests a layer of very dense white substance of a
petrous nature, enamel. It is deficient on the lower part
of the fang. Externally placed to this we see a yellowish-
brown matter, crusta petrosa or cementum.* The upper
surface of the tooth generally presents one or more depres-
sions, the infundibuli, into which dip the three layers of
substance of which the tooth is composed, and which are
frequently filled with crusta petrosa. When a tooth is
wholly covered on its external surface with enamel it is
termed a simple tooth, all other teeth are compound. We
see simple teeth in the dog ; the canines of the horse are
by some considered simyjle. Teeth are named according to
their function, grinders and pincers. These are arranged
in rows, each of which consists of six teeth, and between
the rows of grinders and pincers in the horse are situated
solitary teeth, the canines, cuspidati, or tushes, which in the
mare are rudimentary; they are weapons of offence or of
defence, and are well developed in stallions. The incisors
or pincers are situated in the mouth, anteriorly in contact
with the inner surface of the lips, arranged along the
anterior crescentic margin of the hard palate ; a corre-
sponding number being placed in the upper margin of the
lower jaw, three incisors on each side of the symphysis.
The upper incisors are larger, longer, and put in their
appearance later than those of the lower jaw. The cutting
surface of the teeth is ovoid, with an acute angle at either
extremity ; the anterior edge is higher than the posterior,
and the tooth, taken as a whole, presents a curve the con-
cavity of which is posteriorly situated. There are two
complete sets of incisors, temporary or milk, and perma-

* Crusta petrosa in structure exactly resembles bone presenting
laminse, lacunse, and canaliculi, and, where it is very thick, Haversian
canals. Dentine consists of an earthy matrix, through which branch-
ing and wavy canaliculi run from the pulp cavity, and near its outer
surface terminate in lacunse. Enamel consists of prismatic hexagonal
bodies, which have their margins jagged to enable them to fit closely
together. One extremity of these looks towards the pulp cavity, the
other towards the surface of the tooth.

9

130 OUTLINES or EQUINE ANATOMY.

nent. These are distinguisliable by the following charac-
teristics : — Milk teeth are snialler and whiter than perma-
nent, and their infundibuluin is more shallow ; they have a
marked neck, and are smooth on the anterior surface of the
crown ; permanent incisors decrease in size gradually from
the nipping surface to the extremity of the fang, and pre-
sent grooves on their anterior surface, running in a direc-
tion from above downwards. At an early period of foetal
life there may be distinguished the smooth margin of the
jaw covered by mucous membrane. A longitudinal groove
shortly presents itself, and at the bottom of this "primitive
dental groove " mucous papillse appear. These are pro-
duced by a thickening of the mucous corium, which causes
an elevation of the epithelial and basement layers. Trans-
verse partitions (which subsequently become converted
into bone) are thrown across the groove, whereby il is
separated into as many cavities as it subsequently produces
teeth {follicular stage) . Then by gradual closure of the upper
part of the groove, by approximation of the margins, each
papilla becomes enclosed in a sac {saccular stage), which is
lined by epithelial cells. The parietal portion of the
epithelial layer is said to produce the crusta petrosa,
the visceral* (that clothing the papilla) epithelium is
converted into enamel, and the corium is continuously
developed into dentine, that part which has not yet been
changed being termed the dental pulp. The papilla thus
altered becomes too large for its cavity and forces its way
through the gum which forms the upper wall of the sac
{eruptive stage or " cutting the teeth''). Small portions of
the dental sac are separated from the main cavity at an
early stage of the developmental process, in those cases
where' a second or permanent set of teeth will be required
to replace the temporary organs. These small sacs are
termed cavities of reserve, and slowly undergo the changes
above described in connection with the parent sac, a papilla
being produced which subsequently becomes developed
into a permanent tooth, by the growth of which absorption
of the fangs of the temporary teeth is brought about, and
they, being deprived of their source of nutriment, fall from
the mouth {''shedding the milh teeth''). Of the molars,
the three anterior of each row only are replaced, for in the
jaw of the young animal there is not room enough for six
molars. Those teeth which occupy the three posterior

SPECIA.L ANATOMY.

131

alveolar cavities are developed late, and remain tln'oughout
life, the sixth or posterior one not appearing until tlie
three anterior (temporary) molars have been replaced, as
the following table indicates —

Temporary.

Permanent

1st incisor

At birth

2 years 6 months

2nd „

6 weeks

3 „ 6 „

3rd „

9 months

4 „ 6

Tushes

—

4 „ 6

1st molar

At birth

2 „ 6

2ud „

,j

2 „ 9

3rd „

„

3 „ 6

4th „

—

1 year 3

5th „

—

1 „ 9

Gth „

—

4 years 6

Variations, however, occur as a result of breed, manage-
ment, &c. TJioroughhred horses date their birth from the Isf
January, all other breeds from the 1st May.

The molars are developed from compound papill?R.
Thej are found in four rows of six each, one on either side
of the upper and lower jaws. Each molar presents six
surfaces : —The anterior is smooth, in contact with the
tooth in front through the medium of the thm plate, form-
ing the anterior boundary of the alveolar cavity. But in
the first molar this margin is sharp. TlhQ posterior surf ace is
in similar contact with the tooth behind, but in the last
molar is sharp. The external surface presents two grooves
running from above downward, of which the anterior is the
deepest ; the internal surface is also grooved, but less dis-
tinctly, the outer surface of the upper, the inner surface of the
lower, molar is the largest, for the superficial or grinding
surface in both the upper and lower molars slants obliquely
downwards and outwards, so that the inner part of the
upper comes in contact with the outer part of the lower
molars, a consequence of the greater width of the superior
than of the inferior maxilla ; so in rasping a horse's teeth
the rasp must be applied to the inner edge of the lower,
the outer edge of th3 upper, grinders. The grinding
surface presents the edges of the layers of the substances
of which the tooth is composed arranged " in the form of a
Gothic B," so that, as substances of different degrees of
durability are exposed to equal attrition, an irregular
surface favorable to the comminution of the food is con-

132 OUTLINES or EQUINE ANATOMY.

stantly maintained. The superior molars present a square,
the inferior an oblong grinding surface. The deep-seated
surface presents deep pulp cavities into which the portions
of the divided pulp fit.

In some cases premolar or ^^ wolves teeth^' may be found
fixed in the jaw in contact with the anterior surface of the
first molar. They are small portions of tooth substance,
generally forced out by growth of the permanent molars,
which occupy more room than the temporary. The
canines, tushes, or cuspidati are four in number in the
male, and occupy the space between the molars and
incisors, being about equidistant from both. The inferior
canines are more anteriorly situated than the superior.
These teeth present no inf undibula, but have a single fang,
and their crown terminates in a point at its fi'ee extremity,
at which two ridges which separate it into two surfaces
terminate. The external surface is convex in every direc-
tion ; the internal surface presents a groove surrounding a
prominence. This is the condition of the unworn tooth ; in
the mouth of the old animal the crown becomes conical and
blunted. In the mare these teeth may be sometimes seen just
emerging from the gum, or simply as a papilla changed into
tooth substance on the surface of the mucous membrane.

The floor of the mouth therefore anteriorly and on either
side presents teeth, and the mucous membrane from the
lower margin of the cheeks and lower lips is reflected
upwards to form the gum, and from the teeth on the inner
side after passing for a short distance downwards it is re-
flected upwards to cover the tongue, which occupies the
central part of the floor of the mouth. In doing so it
forms a marked fold at the central line anteriorly, which
serves to prevent too free play of the tip of the tongue, run-
ning upwards from against the symphysis of the lower jaw
and enclosing a portion of the two genio-hyoglossi muscles.
This is the anterior pillar or fraenum linguae ; on either
side of it may be distinguished an opening of a submaxil-
lary salivary '(Wharton's) duct, guarded by a papilla
termed the " barb."

The tongue is the organ of the special sense of taste, and
is prismatic and thick posteriorly, and terminates in a
rounded spathulate extremity anteriorly. Its bulk consists
mainly of muscular structure mixed with the fibres of
which is much fat. Against the superior surface the fatty

SPECIAL ANATOMY. 133

and muscular structures become intimately blended with
the deep surface of the mucous membrane, thus constituting
a somewhat firm layer into which some of the more definite
muscles are inserted. The mucous membrane of the lateral
part of the tongue presents several small papillae on which
the ducts of the sublingual salivary glands open. These may
be seen as thin white threads running from the glands, on
elevation of the mucous membrane. Superiorly to these
we see somewhat large fungiform papillse, so named from
their resemblance to a mushroom in shape. These are
found only on the lateral parts of the tongue, and on their
surface present filiform papillae, larger specimens of which
may be found on the major part of the dorstim or upper
surface of the tongue to which they communicate the pecu-
liar velvety feel. They are hair-like prolongations of the
mucous membrane, and are either simple or compound. The
anterior part of the dorsum of the tongue presents a
central' fissure, the result of the frequent longitudinal
folding of this portion of the organ. The anterior edge of
this part is rounded and the inferior surface along the
central line presents the attachment of the fraenum. The
posterior part of the dorsum surface of the tongue, elevated
above the anterior part, presents two remarkable round
spots which, on examination, prove to be collections of
fungiform papillae surrounded by a deep groove (circum-
vallate papillae). These are situated centrally about an
inch from each other. A smaller one may be sometimes
seen just behind them.

We must now examine the hyoid bone or bone of the
tongue. This forms the basis of attachment of the pha-
rynx, larynx, and other structures situated in this neigh-
bourhood. It is suspended from the under surface of
the cranium, and hangs between the rami of the in-
ferior maxilla. It consists of five distinct portions : a
main portion and four cornua. The main portion closely
resembles a hunting spur, being composed of a spur
process, running in an anterior direction, and two heel
processes, which diverge from each other and run backwards
about three inches, " forming a crescentic space between
them." These two processes terminate posteriorly each in
a point which is continuous with the free extremity of the
cornu of the thyroid cartilage. They present a superior
sharpened margin for muscular attachment, and an inferior

134 OUTLINES OF EQUINE ANATOMY.

margin to which the thyro-hyoid ligament and muscle are
attached. To their outer surface posteriorly is attached
hyo-thyro-pharyngeus a constrictor of the pharynx.
The spur and heel processes are connected together
by the body of the hone, which presents two surfaces and
four borders. To the 'posterior border hyo-epig'lottideus
runs from the base of the epiglottis, and the thyro-hyoid
ligament is attached. From the anterior horder the spur
process projects. The lateral borders posteriorly give rise
to the heel processes, anteriorly present circular synovial
articulatory surfaces which look in a forward, upward, and
outward direction ; to these the inferior extremities of the
short cornua are attached. The superior surface of the body
and the upper sharpened border of the spur process afford
attachment to retractor lingualis, an obscure muscle, the
fibres of which, imbedded in the fatty substance of the
tongue, influence its movements. The inferior surface of the
body receives the superior terminal portions of suibscapulo-
hyoideus and sterno-thyro-hyoidens. The inferior sharp-
ened border of the spur process affords attachment to mylo-
hyoideus and its extremity, which is its deepest part, to

Genio hyo-glossus, the muscle which lies in contact
with its fellow at the central plane of the tongue, and
which, being attached to this point and to the symphysis
of the inferior maxilla, sends fibres in a radiating direction
upwards to become lost in the musculo-adipose matter of
the tongue as far forward as its tip.

Genio -hyoideus also runs from the anterior extremity of
the spur process of the os hyoides. It becomes attached an-
teriorly to the symphysis of the jaw, and lies in contact with
its fellow in the central line of the inter-maxillary space.

Extending in an oblique direction foi-wardsand upwards
from the synovial articulatory surfaces of the latera,l parts
of the body of the hyoid bone are the short cornua, cylin-
drical portions of bone shorter than the heel processes,
s-nallest at the centre, superiorly connected by fibro- carti-
lage {in which is generally to he found a bony nodule analo-
gous to the middle cornu of the ox) to the inferior extremity
of the long cornu. These are embedded in the base of the
tongue and are connected together by the

Hyoideus transversus, which runs from the internal
surface of one short cornu to that of the other.

Hyoglossus brevis, the fibres of this muscle arise from

SPECIAL ANATOMY. 135

tlie wliole lengtli of tlie lateral part of the main portion of
the hyoid bone, and radiate from this toward the under
surface of the mucous membrane of the base of the tongue.
Under this muscle, and so closely blended with it as to be
distinguished only by the direction of its fibres which run
in a parallel direction forwards, is

Hyoglossus parvus, arising from the junction of the long
and short cornua of the hyoid bone, and blending with hyo-
glossi magnus and brevis in the substance of the tongue.
To the posterior margin of the short cornua and of the
inferior extremity of the long cornu the

Hyoideus parvus is attached, and runs obliquely down-
wards and backwards to the superior margin of the heel
process.

The long cornu (of which there is one on each side) runs
obliquely upwards and backwards from the superior extre-
mity of the short cornu. It presents three angles, three
borders, and two surfaces. It assumes the form of an ex-
tremely acute angled isosceles triangle, with its apex down-
wards and forwards. The inferior angle is connected by
fibro-cartilage with the short cornu, the antero- superior
angle is connected by fibro-cartilage with the hyoid process
of the petrous temporal bone. From the postero-superior
angle, which is somewhat tuberous, the hyoideus magnus
and digastricus (sometimes) arise.

Hyoideus magnus becomes inserted into the supero-
lateral part of the body of os hyoides by a small tendon,
the fibres of which separate, the foramen thus formed
being lubricated with synovia for the passage of the
tendon of

Digastricus, which commences generally from the styloid
process of the occiput, being blended with the origin of
stylo-maxillaris, forms a f asiform belly, and then a thin
round tendon which plays through that of hyoideus magnus,
and terminates in the second muscular portion which runs
forwards, becoming inserted into the inferior margin of the
lower jaw as far forward as the symphysis. The concavity
of this muscle therefore is anteriorly situated. The
anterior margin of the long cornu presents a deep curve
superiorly, where the mucous membrane of the guttural
230uch is reflected from the internal surface to the external
surface of the bone. To the lower part of the internal sur-
face^ however, hyo-pharyngeus becomes attached, and from

lo6 OUTLI^vES OF EQUINE ANATOMY.

a ridge running across the lower part of the external sur-
face^ a long fusiform muscle —

Hyoglossus longus — runs forwards along the lateral part
of the tongue, immediately beneath the mucous mem-
brane.

The superior margin is the shortest, and affords attach-
ment to

Stylo -hyoideus, which arises from the styloid process of
the occiput, and becomes inserted into the superior margin,
and external surface of the extreme upper part of the long
cornu.

.The posterior margin is almost straight, between it and
hyoideus magnus the external carotid artery passes
superiorly ; and lower down the twelfth or lingual nerve,
and the submaxillary artery, which on gaining the external
surface of the long cornu gives off the

Lingual artery, which runs in a forward direction over
the external surface of the short cornu, through mylo-
hyoideus, the fibres of which separate for its passage, and
breaks up to form the ranine and sublingual branches.
The ranine runs to the tip of the tongue between the
genio-hyoglossus and genio-hyoideus muscles, taking a
wavy course, whereby it is capable of adapting itself to
temporary elongation of the tongue. It sends branches
downwards to anastomose with the superior branches of
the sublingual, which, after supplying the gland of the
same name, expends itself in the muscular structure of this
neighbourhood. The veins of the tongue correspond to
the arteries, and empty themselves into the submaxillary
vein. The nerves are the gustatory branch of the inferior
maxillary division of the fifth, and the anterior branch of the
glosso- pharyngeal {ninth), ivhich endoiv it with common sensa-
tion, and with the special sense of taste. It owes its motor
potver to the twelfth, lingual, or hypoglossal nerve, which
arises from the lateral part of the medulla oblongata,
and emerges from the cranium, through foramen condyloi-
deum. It passes over the guttural pouch, and runs in an
anterior direction between the pneumogastric and spinal
accessory nerves, over the internal and external carotid
arteries, and between hyoideus magnus and the long cornu
to the lateral part of the tongue.

By division of the amphiarthrotic joint of the hyoid
long cornu with the petrous temporal bone, and bending

SPECIAL ANATOMY. 187

downwards this process, we expose the guttural pouch.
This is a dilated pouch, lined by a transparent mucous
membrane in which we may see vessels ramifying, and
which has an opening anteriorly situated, a long slit in
the wall of the Eustachian tube, which here degenerates
into a mere groove between two cartilaginous ^prominences,
dilated inferiorly. It is visible as far as foramen sty-
loideum, and inferiorly is the only source of communi-
cation between the pharynx and the guttural pouch. The
outer and lower corner of the anterior surface of the i^ouch
is bounded by hyo-pharyngeus, situated between stylo-
pharyngeus and palato-pharyugeus ; here also we see the
parotid lymphatic g-lands. Posteriorly the guttural pouch
presents the superior attachment of the recti capitis antici
muscles, on the outer side of which are large nerves and
the internal carotid artery. The pouch along the central
line lies in contact with its fellow. It jDresents numerous
papillae on its internal surface. By cutting through the
posterior pillar of the tongue we now expose the isthmus
of the fauces. This is the passage which runs from the
base of the tongue to the epiglottis. Anteriorly it is
bounded by the opening between the posterior pillars
of the tongue, posteriorly by the opening, on either
side of which are the pillars of the fauces, which are
composed of muscular fibres running directly from the
jDterygoid process to the thyroid cornu, surrounded by
mucous membrane, much thickened by addition of salivary
glandular structure. The roof of this passage is formed by
the soft palate, which consists of a fixed and pendulous
portion. The fixed portion is attached anteriorly and late-
rally to the crescentic posterior margin of the ossa palati.
It consists of a fibrous layer, the superior surface of which
is covered by pharyngeal mucous membrane, the inferior
separated by a muscular layer and salivary glandular
structure from the mucous membrane of the fauces. This
muscular layer, palato-pharyngeus, runs from the fibrous
layer and from the pterygoid process, to blend with its
fellow at the central line of the pharynx, and to become
attached to the thyroid cornua. The fibrous layer is also
acted upon by

Tensor palati, which arises from the styloid process of
the petrous temporal bone in common with stylo-
pharyngeus, runs forwards along the side of the Eustachian

138 OUTLINES OF EQUINE ANATOMY.

tube, to wliicli it is also attached, and after passing through
the pterygoid groove, where it is bound down by a liga-
ment, and lubricated by synovia, becomes inserted into the
fibrous palate, which it serves to render tense.

The pendulous portion of the soft palate is very large in
the horse, and serves to close the posterior opening of the
fauces, except during the passage of food. Its inferior
margin is somewhat concave, and it consists simply of two
layers of mucous membrane, with an intervening glandular
layer. The floor of the fauces is that portion of mucous
membrane situated between the base of the tongue and
the epiglottis. Every portion of the mncous membrane of
the fauces presents large papillae and openings, for it is
surrounded by the palatine salivary glands. Its lateral
avails present depressions corresponding to the prominences
termed tonsils in the human subject. The pharynx is an
elongated passage of mucous membrane, into which several
muscles are inserted, and on which they act. Superiorly
the pharynx presents anteriorly the tivo posterior openings
of the nasal chamhers, separated by the inferior sharpened
margin of the vomer, closely invested by mucous mem-
brane ; on either side of these, and more posteriorly, are
elongated slit-like openings, each guarded by a cartilagi-
nous valve, the o][)enings of the Eustachian tubes, through
which air passes to the middle ears and to the guttural
pouches, more posteriorly the muscular walls of the
pharynx lie in contact superiorly with the guttural pouches.
Posteriorly the commencement of the esoplmgiis is the result
of the gradual narrowing of the cavity. The floor of the
pharynx is formed anteriorly by the upper surface of the
soft palate, posteriorly by the superior orifice of the larynx j
between the two is the posterior opening of the fauces. The
muscles of the pharynx are either constrictors or dilators.
Constrictors : Hyo-thyro pharijjigeus, runs from the posterior
23art of the heel process of os hyoides and from the thyroid
cornu. Thyro-pharyngeus, from the lateral part of the
external surface of the ala of the thyroid cartilage. Crico
pharyngeus, from the lateral part of ^he cricoid cartilage
(this muscle is directly continuous with the muscular layer
of the esophagus). These three muscles run upwards to
blend with their fellows and with each other in becoming
inserted into the central line of the upper surface of the
pharyngeal mucous membrane. Dilators : Hyo -pharyngeus,

SPECIAL ANATOMY. 139

runs from tlie internal surface of the long cornu of os
hjoides, and blends with its fellow upon the upper surface
of the pharynx. Stylo-pharyngeus arises in common with
tensor palati from the styloid process of the petrous tem-
poral bone, and also is attached to the lateral part of
the Eustachian tube ; it blends with its fellow on the
wall of the pharynx. Potato pharyngeus has been already
noticed.

The pharynx is suf)plied with blood by the ascending
pharyngeal hra^iches of the submaxillary artery, and also by
branches from the internal maxillary. It is partly supplied
with nerve force by the sympathetic, partly by the glosso-
pharyngeal, and superior laryngeal branch of the pneumo'
gastric. The glcsso-pharyngeal (or ninth) cranial nerve
arises from the lateral part of the medulla oblongata,
and in passing out of the cranium by foramen lacerum
basis cranii has a ganglion upon it. Passing over the wall
of the guttural pouch it has intimate connection with the
large nerves of this neighbourhood and with the superior
cervical ganglion. It then divides, sending one branch to
supply the posterior and lateral parts of the tongue with
common sensation and the special sense of taste ; the other
to the pharynx.

By an incision in a longitudinal direction through the
face to one side of the central line we may expose the
nasal chambers, and by remo^'al of an oblong portion of
the septum nasi we may expose the turbinated bones in
situ. The NASAL CHAMBERS are cavities elongated in
a direction from before backwards, bounded anteriorly by
the anterior nares, posteriorly by the posterior nares. The
chamber of one side is separated from its fellow inwardly
by the septum nasi, a thick layer of cartilage, which is
attached along its inferior margin into the groove of the
vomer ; posteriorly to the crista galli process of the ethmoid
bone ; superiorly it bifurcates and becomes spread out over
the lower surface of the nasal bones, beyond which it ex-
tends anteriorly, forming a point in front of the nasal peak,
to which, on either side, an inverted comma-shaped piece
of cartilage is attached, being composed of the alal and
corneal cartilages. The alal cartilage is circular, pre-
senting a superior and an inferior surface, and from its
inner margin the corneal cartilage runs in a direction
forwards, downwards, and outwards. The inferior extre-

140 OUTLINES OF EQUINE ANATOMY.

mity of the latter is continuous by means of a fold of
mucous membrane witb the inferior turbinated bone.

Dilator naris anterior runs from the external sur-
face of one ala to that of the other, while the corneal
cartilages are connected together anteriorly by a direct
continuation of it, by some anatomists termed cor-
nealis transversus. Dilatores naris superior and inferior,
levator labii superioris alseque nasi, and retractor labii
superioris, also become attached to these cartilages. The
skin extends around the margin of the nostril, as formed
by these structures, and is continued for a short distance
in the nasal chamber, where it insensibly blends with the
mucous membrane. About the point of junction at the
outer side, inclined to the superior part of the nostril (infero
internal in the horse), is the anterior- opening of the ductus ad
nasum which looks as though " punched out of the mucous
membrane," On the outer side the common integument be-
comes very thin, hairless, and prolonged in the angle between
the superior process of the anterior maxilla and the free
margin of the nasal bones, to form a blind pouch, the false
nostril, which we have found filled with epithelial layers of
cells. To the posterior extremity of this a muscle which runs
from just above the anterior termination of the zygomatic
ridge is attached, also levator labii superioris alseque nasi.
Into this cavity the air passes directly from the anterior
naris ; it has to diverge slightly inwards to gain the nasal
chamber. The roof of the nasal chamber is formed by the
inferior concave surface of the nasal bone, posteriorly by
the nasal plate of the frontal bone. The outer wall pre-
sents the two ossa turbinata, by means of which the cavity
is divided into three meatus.

The superior turbinated bone is attached to the inner
surface of the nasal bone, and consists of a. thin plate
curled from above downwards. Anteriorly it terminates
by a cartilaginous prolongation, which gradually blends
with the wall of the chamber ; posteriorly it is directly
continuous with the lateral mass of the ethmoid bone.
Its cavity is divided by a partition into two parts ; the ante-
rior helps to form the nasal chamber opening into the
middle meatus ; the posterior forms part of the superior
maxillary sinus.

The inferior turbinated bone is attached to the inner
surface of the superior maxillary nasal plate. It is smaller

SPECIAL ANATOMY. 141

than tbe superior ; posteriorly it gradually disappears ;
anteriorly it presents a bifid cartilaginous prolongation,
one of the divisions of which runs to the inner, the other
to the outer wing of the nostril. It has also an anterior
and a posterior division ; the former helps to form the
middle meatus, the latter enters into the composition of
the inferior maxillary sinus. Thus the superior meatus,
the longest and narrowest, is between the roof of the
chamber and the upper surface of the superior turbinated
bone. It extends from the anteiior naris to the cribriform
plate. The middle meatus, between the ossa turbinata,
comprises the anterior cavities of both turbinated bones,
and extends from the anterior naris to the ethmoid cells,
blending anteriorly with the superior ; j^osfei-iorZ?/ it presents
the ope7iing of the sinuses of the head. The inferior meatus
is between the lower surface of the inferior turbinated bone
and the floor of the chamber ; it extends from the anterior
to the posterior naris, blending anteriorly and posteriorly
with the middle. The Schneiderian or pituitary mucous
membrane lines every part of the nasal chamber. It is
highly vascular and thick, performs the part of periosteum
to the turbinated bones and ethmoid lateral masses, and
assumes almost an erectile character at the anterior ex-
tremity of the ossa turbinata. The superior meatus is
supplied by the lateral nasal artery and nerve, and the
inferior and middle meatus by the spheno-palatine artery
and nerve. The ethmoid cells and the posterior part of
the nasal chamber, in addition, receive the fibres of the
olfactory nerve, which afford the special sense of smell.
These pass through the foramina in the cribriform plate of
the ethmoid bone, and are not enclosed in any common
sheath, but each fibre runs its course independently after
its origin from the olfactory bulb, and terminates in a cell
on the nasal mucous membrane. These fibres, examined
under the microscope, are found to resemble sympathetic
fibres, being devoid of medullary sheath and of white sub-
stance of Schwann. The septum nasi, at its antero-
inferior part, is continuous with the cartilage which fills
the incisive openings, and in which may be found a mucous
organ resembling the duct of Stenson, which in the ox forms
a communication between the nasal chamber and the cavity
of the mouth. In the horse it only opens into the nasal
chamber. ' We have traced it backwards above the bony

142 OUTLINES OE EQUINE ANATOMY.

palate, as far as the soft palate, where it terminated in a
cul-de-sac. Some of the bones of the head present large
cavities lined by mucous membrane, which is (normally)
thin and transparent. These, the

Sinuses of the head, are five in number on each side.
They present numerous bony trabeculse projecting inwards
forming partial septa, and are best developed in old
animals, being the result of absorption of bone. By con-
tainmg rarefied air they serve to lessen the weight of the
head, and by causing bulging of the bone they afford in-
creased surface for muscular attachment. The frontal
sinus in the bone of the same name is bounded by its
cranial, nasal, and external plates. Internally it is separated
from its fellow by a bony plate. To open this sinus we
draw a line from the lower margin of the orbital process
of one frontal bone to that of the other ; bisect this line and
in the angle so formed inferiorly trephine. The sphenoid
sinus (which only appears very late in life) and the ethmoid
sinus are cavities mainly contained in the bodies of the bones
of the same names respectively. The antrum or superior
maxillary sinus is formed by the palatine, superior maxil-
lary, malar, lachrymal, and superior turbinated bones. It
presents two bony cauals running through it — one, canalis
infra-orbitale, through which the superior dental artery and
nerve run ; the other is the ductus ad nasum, which termi-
nates by piercing the nasal plate of the superior maxilla
several inches up the nasal chamber ; being continued by a
membranous duct which runs underneath the mucous mem-
brane to its opening. The above sinuses open by a common
foramen into the nasal chamber, by a very small opening at
the posterior part of the middle meatus. The inferior max-
illary sinus is more anteriorly placed, and is sej)arated
from the superior maxillary sinus by a thin but imperforate
plate which extends to the opening into the nasal chamber,
thus dividing it into two. So this sinus does not com-
municate with the rest, all of which communicate freely
among themselves. To trephine this sinus, a line is drawn
parallel to the zygomatic ridge about an inch above it, and
the point where this meets, a perpendicular line connecting
the two from the termination of the ridge, indicates the
point of incision.

The contents of the orbit may be examined by removal of
the superior and outer walls by sawing through the rest of

SPECIAL ANATOxMY. 143

tlie orbital process of the frontal bone, externally to tbe
supra-orbital foramen, and through the lower part of the
malar bone. After which the separated portion of bone must
be raised by a chisel, and removed by division of the peri-
orbita,le. We are thus enabled to examine the lachrymal
gland, a racemose glandular body flattened from above
downwards, and moulded between the under surface of the
orbital process and the structures beneath ; it has also an
accessory lobule found in the upper eyelid. It resembles one
of the salivary glands in appearance, and pours its secretion
through several small ducts upon the inner surface of the
upper eyelid. After passing over the front of the eyeball,
being diffused by the winking action of the eyelids, the
tears (or lachrymal secretion) pass through the canal formed
by approximation of their free margins towards the inner
canthus, to which it is directed by the downward and inward
inclination of the palpebral fissure. By the caruncula lach-
rymalis it is directed into the puncta lachrymalia, openings
situated one at the inner extremity of each eyelid, and
from this passes through a series of membranous canals to
the anterior naris. It first gains the lachrymal canals, one
of which runs from each punctum in a downward direction ;
they converge and just at the lachrymal foramen meet and
form the lachrymal sac, from which the ductus ad nasum
runs through a special canal in the lachrymal and superior
maxillary bones. It may be exposed by use of the hammer
and chisel and will be found to extend for about three quar-
ters of its course in the bony canal. Its anterior part is
continued onwards between the bone and the Schneiderian
membrane as far as the anterior naris, where it opens at
the point of junction of the skin and mucous membrane
at the superior part. Situated between the caruncula
lachrymalis and the eyeball is the cartilage -nictitans
(winkingjmembrane, or third eyelid). It is thickest pos-
teriorly, and at its anterior free margin is covered by
mucous membrane, which generally contains some pigment.
Internally its yellow fibro-cartilaginous substance is con-
tinuous with some yellow elastic tissue, enclosed in the
meshes of which, and running among the muscles of the
eye, is fatty matter on ivhicli the movements of the cartilage
depend, for when, by the action of its muscles, the eyeball
is retracted it presses upon this mass of fat, which in its
turn presses the cartilage over the front of the eyeball.

144 OUTLINES or EQUINE ANATOMY.

This fat is found even in tlie most emaciated subjects.
"We have already noticed the levator palpebrae superioris
internus ; by incision through the periorbital we may now
expose it : a thin layer of muscle which arises from the
upper margin of the sphenoicleal hiatus and runs to the
upper eyelid, on which it is enabled to act by gaining
leverage over the upper surface of the eyeball. The
periorbitale is a dense fibrous membrane which lines the
orbital cavity, forming the sole protection to the contained
structures at the postero-inferior and suj)erior parts, which
in the human subject are bony. Anteriorly it is attached
to the margin of the orbit, posteriorly around the sphe-
noideal hiatus ; it encloses the eyeball and its muscles.
From around this hiatus other muscles arise and run to
the eyeball.

Retractor oculi, consisting of four distinct portions,
arises from directly around it, and after passing in a
forward direction in contact with the optic nerve becomes
inserted into the posterior part of the extei'nal surface of
the sclerotic coat. The four

RECTI — externus or abductor, internus or adductor,
superior or levator, and inferior or depressor — arise from
the external, internal, superior, and inferior parts of the
spheiioideal hiatus respectively, and 2:>ass to the anterior
part of the sclerotic, and form aponeurotic expansions
which unite at their margins respectively, forming thus a
continuous layer, situated around the outer margin of the
cornea, covered anteriorly by conjunctiva, tunica albuginea
(forming the " white of the eye ").

Superior oblique muscle arises from just above the
straight muscles at the upper part of the sphenoideal
hiatus. It then runs to the root of the orbital process of
the frontal bone, where it passes through a fibro- cartilagi-
nous loop. From this it runs to the upper part of the eye-
ball, forms an aponeurotic tendon which runs beneath the
tendon of levator oculi, and becomes inserted into the
anterior part of the sclerotic between the last-mentioned
muscle and abductor oculi. Sirangeways has noticed an
accessory muscle which arises near the fibrous loop and he-
comes blended with this; we have frequently verified this
observation.

Inferior oblique muscle arises from the orbital plate of
the lachrymal bone, near the lachrymal foramen, runs

SPECIAL ANATOMY. 143

outwards and becomes aponeurotic, is inserted into the
anterior paii; of the sclerotic between the abductor and
depressor ; it passes externally to the depressor.

The structures contained within the orbit receive blood
through the ocular branches of the internal maxillary artery
and through the ophthalmic artery. The former we have
already noticed, and of these the most remarkable, which
we distinguish are the lateral nasal, taking a peculiar curve
through the bottom of the orbit, and then passing into
foramen orbitale internum, and the supra-orhital, which
runs directly to the foramen of the same name. Ciliary
arteries run from the internal maxillary to the eyeball.
The ophthalmic artery arises in the cranial cavity from the
anterior communicating or from the middle cerebral
artery. It passes through foramen lacerum orbitale in
company with several nerves, and on emerging from the
foramen gives off branches to the lachrymal gland, and to the
eyelids, also arteria centralis retinae, which gains the eye-
ball by passing through the centre of the optic nerve.
Three nerves arising from the base of the brain (nominally)
supply the muscles of the eyeball with motor power.
Motores oculorum or third cranial pair of nerves, arising
from the centre of the under surface of the crus cerebrum,
each nerve passes from the cranium through foramen
lacerum orbitale and then gives off fibres to all the muscles
except the abductor and the superior oblique (and the
external part of retractor). From this nerve also a branch
passes to the ophthalmic or lenticular ganglion, a small
collection of nerve cells found at the point where the third
nerve gives off fibres to the inferior oblique muscle. It
receives sensory fibres from the lateral nasal branch of the
ophthalmic division of the fifth, and sends ciliary branches
to the eyeball. The ophthalmic division of the fifth
cranial nerve, passing from the gasserian ganglion,
emerges from the cranium through foramen lacerum orbi-
tale, it then breaks up to supply the structures of the eye
and its appendages with common sensation. Among
others, giving off the supra-orbital and lateral nasal nerves,
which follow the course of the arteries of the same name.
The lateral nasal affords the sensory root of the ophthalmic
ganglion. The pathetic or fourth nerve arises from the
valve of Yieussens, which forms the anterior part of the roof
of the fourth ventricle of the brain. These are the

10

146 OUTLINES OF EQUINE ANATOMY.

smallest nerves at tlie base of the brain, and wind round
the outer surface of the crura cerebri, puttinsr in their
appearance just in front of the pons Varolii. They gene-
rally are found emerging from the cranium through
foramen lacerum orbitale (and not through foramen
pathetici as their name might lead us to expect, and which
only gives passage to small vessels). These nerves run
direct to the superior oblique muscles to which they give
motor power.

Abducens or sixth pair of nerves arise from the under
surface of the medulla oblongata, just behind the pons
Varolii, on either side of the inferior longitudinal fissure.
Each nerve passes through foramen lacerum orbitale in
company with the third, fourth, and ophthalmic division of
the fifth nerves, and the ophthalmic artery of the side to
which it belongs, and on gaining the orbit runs to supply
the abducens muscle.

The eyeball or globe of the eye is a spherical body,
slightly flattened from before backwards. The posterior
three fourths is formed by a white fibrous coat, the sclerotic,
its anterior part by a transparent layer, the cornea. To its
postero-inferior and internal part runs the optic nerve,
enclosed in its dense sheath of dura mater. The eyeball
presents three coats, three cavities, and three humours,
with accessory parts. The sclerotic is a fibrous coat, which
is externally situated at the posterior three fourths of the
eyeball. It is thickest posteriorly, and grows thinner to
about the centre, when again it commences to grow thick,
and anteriorly the cornea fits into it " like a watch-glass
into its case. Around the opening of the optic nerve it
becomes attached to its sheath, which becomes inflected
inwards forming a plate, lamina cribrosa, through numerous
perforations in which the fibres of the nerve pass. Through
the largest of these perforations, termed the porus opticus,
the arteria centralis retinae passes. Numerous small fora-
mina, through which the ciliary nerves and vessels pass,
are to be seen on the surface of the sclerotic. Anteriorly
it is directly continuous with the cornea, so that we cannot
distinguish between them with the microscope, though
the transparency of the cornea is sufficiently distinctive,
and seems to be due to fluid contained between its laminae,
since opacity is caused by pressure. It is a segment of a
smaller sphere than the sclerotic, which overlaps it most

SPECIAL ANATOMY. 147

superiorly and inferiorlj, so the part visible in the living
animal is markedly ovoid in shape, the largest end being
the inner. Around its outer circumferent margin we may
observe a semi-opaque ring, arcus senilis caused by the
presence of the ciliary ligament internally to this part. It
consists of two parts, cornea propria and cornea elastica ; the
former is anteriorly placed, and its structure may be divided
into several laminae ; the latter, posteriorly placed, consists
of a single lamina. The anterior surface is covered by the
transparent conjunctiva. Its posterior surface by the serous
membrane of the aqueous chamber. The sclerotic must
now be separated from the choroid or middle coat by laying
the eyeball on a flat surface, and cutting through the most
elevated portion of sclerotic with scissors, when the choroid,
which was separated by the weight of its contents will be
exposed. It is connected to the sclerotic by vessels and
nerves which form membrana fusca, distinguishable as a
few dark thread-like fibres running from one to the other.
The choroid is a dark brown membrane, on the surface of
which we see a number of light blue thread-like vessels
ramifying, forming the external layer of the choroid (venm
vorticoscE, so called from a fancied resemblance to a whirl-
pool) . The next layer mainly consists of arteries arranged
in festoons, of which the convexities are anteriorly situated,
tunica Uuyschiana. It rests upon a layer of polygonal pig-
ment cells, which constitutes the pigmentary layer, and in
which the rods and cones which form the external layer of
the retina, are imbedded. Towards the anterior part of
the sclerotic the choroid becomes reflected into the cavity
of the eyeball, to form the "setting" for the crystalline
lens ; and, as the diameter of the lens is less than that of
the chamber at this part, the choroid becomes puckered to
accommodate it to the size of the parts. The puckerings
are ciliary processes, the outer margin of which is termed
the ora serrata. The inner margin comes in contact with
the capsule of the lens to which it is attached, and between
the two is situated a triangular canal, the canal of Petit.
(Some uncertainty seems to exist as to the situation of this
canal. I have followed Huxley.) The ciliary processes
also contain some muscular fibres ; anteriorly they are
covered by the lining membrane of the aqueous chamber,
posteriorly by the retina. They are continuous with the
uvea, a layer of pigmentary matter which covers the pos-

148 OUTLINES OF EQUINE ANATOMY.

terior surface of tlie iris, and gives tlie eye its colour
(deficiency of this constitutes " wall eyes "). The

Iris is a muscular diaphragm, which projects into the
cavity of the eyeball, leaving centrally an oblong opening,
the pupillary opening or pupil. It consists of two orders
of unstriated muscular fibres : — circular, surrounding the
pupil, and which cause it to contract; radiating, which
extend from the outer circumferent margin to the pupil,
which they serve to enlarge. These are posteriorly covered
by the uvea, which overhangs the pupil above and below,
forming dark pigmentary masses visible in the living sub-
ject, corpora nigra. They are largest at the upper margin
of the pupil, and frequently are wanting below. The
anterior and posterior surfaces of the iris are covered by
serous membrane continuous around the margin of the
pupil. The outer margin of the iris is attached to the
ciliary ligament, a structure containing unstriated mus-
cular fibre, situated at the outer circumferent margin of
the posterior surface of the cornea, and serving to connect
together the cornea, sclerotic, iris, ciliary processes, and
choroid ; in its substance is the canal of Fontana. The
optic nerve runs from the optic decussation at the base of
the brain, through foramen optici, after emerging from
which it is pierced by arteria centralis retinae, a branch of
the ophthalmic. It runs through the orbit with this artery
in its centre, and invested by a stout sheath, which extends
from the dura mater to the sclerotic. After piercing the
lamina cribrosa, its fibres radiate on the inner surface of
the choroid, forming the middle layer of the retina, or
tunica nervosa, which extends as far as the outer margin
of the ciliary processes, ora serrata. On its external sur-
face it has the tunica Jacobi or bacillary layer, which con-
sists of nerve-cells (rods, cones, and ganglion cells) imbedded
in the pigmentary layer of the choroid. On its internal
surface are blood-vessels, which in the living subject may
be seen by means of the ophthalmoscope (tunica vasculosa) .
At the opening of the optic nerve into the eye, optic disc or
blind spot, visible on careful inspection of the living sub-
ject, nerve-cells are deficient, while there is a prepon-
derance of nerve-fibres. In the human subject the macula
lutea or foramen of Soemering presents exactly opposite
conditions, nerve-cells being here most numerous. We
have failed to distinguish it in the horse. The different

SPtClAL ANATOMY. 149

layers of the retina are connected together by areolar tissue,
which is continued over the posterior surface of the ciliary
processes, forming the zona ciliaris or zone of Zinn, which
extends as far as the capsule of the lens. At the inner
and upper part of the choroid we distinguish a part pre-
senting a peculiar greenish metallic lustre, tapetum
lucidum, which by reflecting instead of absorbing the rays
of light, enables the animal to " see in the darJc.''

The chambers of the eye are three in number. The
anterior chamber is situated between the cornea and the
iris. It communicates with the posterior chamber, which is
between the iris, ciliary processes, and the capsule of the
lens, through the pupillary opening (this communication
seems to be closed in the foetus by a vascular membrane,
memhrana pupillarisy which, however, is merely the vascular
anterior part of the capsule of the lens to which the iris is
attached). These two chambers are lined by the mem-
brane of Demeurs or Descemet, which, therefore, covers the
posterior surface of the cornea, invests both surfaces of
the iris, and is continued over the anterior surface of the
ciliary processes and the capsule of the lens. It secretes the
aqueous humour, a fluid consisting of water and a small
quantity of saline matter and albumen dissolved in it. It
serves to afford free play to the iris, to preserve the due
convexity of the cornea, and to (slightly) influence the
direction of the rays of light.

The dark chamber is the largest of the three, anteriorly
bounded by the capsule of the lens, m all other parts it is
circumscribed by the retina. The membrane lining it, the
hyaloid membrane, also sends trabeculse inwards, by which
the cavity is divided into numerous cells, in which we find
a fluid analogous to the aqueous humour, but which in
consequence of this arrangement does not flow freely when
the dark chamber is punctured ; this is the vitreous humour,
through its centre in the foetus, from behind forwards to
the lens runs a branch of arteria centralis retinae. Between
the aqueous and vitreous humours is situated the crystal-
line lens (or third humour of the eye) . It is enclosed in
a capsule, the outer circumferent margin of which is
attached to the free extremity of the ciliary processes and
of the zone of Zinn. Its anterior surface is covered by the
membrane of Demeurs, its posterior by the hyaloid mem-
brane, and the connective continuation of the retina is

150 OUTLINES OF EQUINE ANATOMY.

attached along its margin. The lens itself is biconvex,
being most convex posteriorly. It is composed of numerous
concentric transparent layers, which increase in density
from without inwards. In the centre is a circular nodule,
consisting of three triangular portions. The lamince con-
sist of fibres denticulated at their margins and decreasing
in size towards each extremity. By apposition of their
denticulse they form firm continuous layers, of which the
external is liquid, and serves to allow movement of the
lens in its capsule ; it is termed the liquor Morgagni, but
its liquidity is supposed to be the result of post-mortem
change.

The ciliary arteries and arteria centralis retince supply
the eyeball with blood ; the ciliary nerves endow it with
ordinary sensation ; the (yptic nerve with the special sense
of sight.

The first trace of the embryo mammal is a longitudinal
layer of cells, and from this both above and below an
arch is formed. The inferior or hcemal arch is mainly
composed of soft structures which are supported by a
bony framework ; it forms the face, thorax and abdomen.
The superior or neural arch subsequently becomes a bony
canal formed of many segments connected together by
various structures, which posteriorly comes to a point,
anteriorly four of its segments, or vertebrae form a large
ovoid cavity with continuous walls, the CRANIUM, Twelve-
bones combine to form the cranium, four pairs and four
single bones : —

Frontal, parietal, squamous and petrous temporal lx)nes.
(Pairs.)

Occipital, ethmoid, sphenoid, and os triquatrum.
(Single.)

These bones are for the most part formed of tY*-o dense
layers between which is cancellated structure. The central
portion contains large veins, and is termed the diploe,
the compact laminae are the vitreous tables. The imsterior
'j)art of the cranium is formed by the occiput through the
centre of which the foramen magnum passes. Inferiorly
on either side of this is a foramen condyloideum. The
roof of the cavity is formed posteriorly by the occiput
which is united anteriorly to os triquatrum (centrally)
and to the parietal bones on either side. The latter also
help to form the lateral ivalls of the cavity. Anteriorly

SPECIAL ANATOMY. 151

tlie roof is formed by the frontal bones from whicli a
plate projects downwards to tbe upper extremity of the
crista galli process of tbe ethmoid bone, which forms the
centre of the anterior surface and on either side of which
are found the ethmoidal fossae (or olfactory sinuses)
which are bounded by the cribriform 'plate of the ethmoid,
while the body of the ethmoid forms the lower part of
the anterior surface. In forming the lateral part of the
walls of the cranium the parietal bones articulate with the
wing of the sphenoid and with the squamous temporal, and
the latter, in its turn, is posteriorly almost completely
separated by the petrous temporal bone from the occiput.
The floor of the cranium is formed posteriorly by the
basilar process of the occiput, from which the body of the
sphenoid runs forwards to the body of the ethmoid.
From, the lateral part of the body of the sphenoid the
alae run to articulate anteriorly with the ethmoid and
frontal bones, laterally with the parietal and squamous
temporal ; posteriorly each presents a rough margin with
several notches which combines with the basilar process of
the occiput and the temporal (petrous) bone to form the
foramen lacerum basis cranii.

Foramina of the cranium. Foramen magnum, formed
wholly by the occiput. Affords attachment to the anterior
margin of the dura mater of the spinal cord and gives
passage to the spinal cord, which here commences from
the medulla oblongata, and its membranes. Also to
venous sinuses, the meningeal and basilar arteries, and the
major portion of the spinal accessory pair of nerves.
Forameyi condyloideum, formed by the occiput at the side
of foramen magnum, in front of the condyle. It gives
passage to the twelfth, lingual, or hypoglossal nerve.

Foramen lacerum basis cranii, situated at the side of the
basilar process of the occiput, formed by the occipital,
sphenoid, and petrous temporal bones. In the human sub-
ject by a bony septum is divided into two parts (in the
horse by a ligament) ; through the posterior run the glosso-
pharyngeal, pneumogastric, and spinal accessory nerves ;
through the anterior, the inferior maxillary division of the
fifth, internal carotid artery, and meningeal branches, and
a dilated vein running from the cavernous sinus to the
jugular at its commencement.

Foramen auditorium internum. A circular opening at

153 OUTLINES OE EQUINE ANATOMY.

^"he centre of tlie cranial surface of the petrous temporal
bone. It gives passage to the seventh and eighth nerves,
aad runs to the internal ear though it gives off a portion
which passes to the middle ear. On the upper surface of the
body of the sphenoid, laterally are broad channels through
which the superior maxillary division of the fifth runs, and
thus gains the foramen rotundum, which, in proceeding to
the bottom of the orbit, unites with the sub-spherioidal fora-
men, which passes through the wing of os sphenoides, and
which gives passage to the internal maxillary artery. Thus
through the anterior part of the foramen rotundum, the
superior maxillary division of the fifth nerve and the in-
ternal maxillary artery pass. Just above this and situated
between the ethmoid and the sphenoid bones is foramen
lacerum orhitale, through which the third, fourth, ophthalmic
division of the fifth and sixth nerves, and the ophthalmic
artery and vein run (the ophthalmic vein connects the
superior varicose vein of the face with the cavernous sinus).
In front of the sella turcica or upper surface of the body
of the sphenoid, there are two foramina running forwards
through the ethmoid bone connected anteriorly by a space
which is covered by the inferior extremity of the cristagalli
process and in which the optic decussation rests. These
are the foramina optici. They give passage to the optic
nerves covered by their dense sheath of dura mater, and
open into the lower part of the orbits by a common opening,
which they share with the foramina lacera orbitale, and
rotunda. This is the sphenoideal hiatus, just above its
superior rough margin is forame7ipathetici, which only gives
passage to a few small vessels. Internally situated is fora-
men orhitale internum, which passes to the outer lateral
part of the ethmoidal fossa, thus passing directly into the
cranial cavity. Through it the lateral nasal artery and
vein run. Numerous other foramina are found passing
through the cranial walls, but are unnamed ; through them
pass vessels and nerve-fibres. Some others are generally
enumerated as cranial foramina, though they do not pass
into the cranial cavity. Foramen auditorium externum
runs through the external auditory process, and at the
middle ear, in the recent subject, presents the membrana
tympani. It is lined by common integument. Foramen styloi-
deum is that opening through which the facial nerve emerges
from the middle ear ; it is divided into two parts ; from

SPECIAL ANATOMY. 153

the superior tlie nerve emerges, througli the inferior the
Eustachian tube communicates with the middle ear. It is
just at the root of the styloid process of the petrous tem-
poral bone. The inner surface of the os triquatrum
presents an eminence (ossific tentorium) consisting of the
convergence of three irregular bony ridges from which
prominences run. On either side of the wall of the cavity
one runs to the floor of the cranium, and one runs forwards
along the central line to the crista galli process. In other
parts the roof and sides of the cranium present slight pro-
minences which separate broad shallow depressions (digital
imjpressions) which are adapted to the convolutions of the
brain.

The brain is covered by three membranes — dura mater,
arachnoid, and pia mater. The dura mater is externally
placed, and is a dense fibrous membrane, which forms the
internal periosteum of the skull. It presents processes,
some of which run outwards, others inwards. Those pass-
ing outwards establish its connection with the periosteum
of the outer surface of the bones by passing through the
immovable joints between them ; this accounts for the
difficulty experienced in separation of the dura mater from
the bones at the sutures. The processes running inwards
are two in number. Falx cerebri is a sickle-shaped fold,
running from the superior extremity of the crista galli,
and increasing in size until it terminates posteriorly in
becoming attached to the ossific tentorium. It is broadest
above and grows narrow below, forming a sharp edge. It
fits into the superior longitudinal fissure of the brain.
Along its attached margin runs the superior longitudinal
sinus, along its free margin the inferior longitudinal sinus.
These are connected together posteriorly by the straight
sinus, into the anterior part of which vena Galeni empties
itself, after running from the velum interpositum and from
the upper surface of the corpus callosum. These sinuses are
dilated veins situated in the dura mater, which splits to
accommodate them. They are lined by epithelium con-
tinuous with that of the other veins, and at various parts
we see fibrous cords (cordce Willissii), which run across
them to prevent undue distension. From the lateral parts
of the ossific tentorium run folds to the floor of the
cranium, the tentorial membrane. They are attached to
the inner ridges of the parietal bones, and project into the

154 OUTLINES OF EQUINE ANATOMY.

great transverse fissure, in which thej terminate in a sharp
edge. In their substance run the lateral sinuses from the
torcular HeropMli above to the cavernous sinus. The fifth
nerve (sensory portion) passes into them about their
centre, and they thus contain it with its gasserian ganglion.
The torcular Herophili, therefore, is a venous sinus, situated
against the ossific tentorium, which receives the straight
(and superior longitudinal) sinuses, and from which the
lateral sinuses and also the occipital sinuses run. The
latter pass backwards over the roof of the cerebellal cavity.
Between the fifth nerves, at the base of the brain, the layers
of the dura mater separate, forming the cavernous sinus, and
imbedding a peculiar reddish-black body, circular, and
flattened from above downwards, the use of which is un-
known, but which receives the inferior extremity of the
tuber cinereum — the pituitary body. Around the posterior
and lateral parts of this body is situated the cavernous sinus
lined by epithelium, to which run the lateral sinuses supe-
riorly, the anterior petrosal anteriorly, and the posterior
petrosal posteriorly, from the floor of the cranium ; the
latter blend with the sinuses of the floor of the spinal canal
posteriorly. It also receives anteriorly the posterior ex-
tremity of the superior varicose vein of the face, which
passes through foramen lacerum orbitale. Inferiorly it
sends off prolongations, which pass through foramen
lacerum basis cranii, and from which the jugular veins
commence. In the cavernous sinus run the internal
carotid arteries, covered by reflections of the epithelial
lining layer ; they pass from foramen lacerum basis cranii,
communicating by a transverse branch behind the pituitary
body, and emerging from the dura mater at the base of the
brain, opposite the commencement of the fissure of Sylvius.
The dura mater of the brain is continuous with that of the
cord through the medium of its attachment to the margin
of the foramen magnum of the occiput. It is attached to
almost all the foramina around their margins, and is con-
tinued over the optic nerve as far as the sclerotic, where it
terminates in forming the lamina cribrosa. On the outer
surface of the dura mater, especially at the attached
margin of the falx cerebri, have been distinguished minute
nodular bodies, largest in old subjects, glands of PaccMoni.
The arachnoid is a serous membrane, and presents a
parietal and a visceral portion. The parietal portion lines

SPECIAL ANATOMY. 155

the dura mater ; the visceral portion invests the pia mater.
Between these layers is a serous fluid, the arachnoid fluid ;
and between it and the pia mater is the subarachnoid
fluid. Posteriorly this membrane forms the posterior part
of the roof of the fourth ventricle, arachnoidean valve; it
becomes reflected from the different prominences of the
brain, and does not dip between into the sulci. Subarach-
noid" spaces are most marked in front of and behind the
optic decussation and below the posterior lobes of the
cerebrum in the transverse fissure. The pia mater is the
vascular membrane of the brain, the surface of which it
closely invests. It is prolonged into the cavities of the
brain in several i^laces ; thus, in passing through the trans-
verse fissure, it runs forwards under the posterior part of
the cerebrum and becomes thicker, forming the velum
interpositum, which is the roof of the third ventricle, and
which anteriorly bifurcates, forming the plexus choroides of
the lateral ventricles, which, passing through the foramina of
Munro (anterior communicating foramina) and between
the hippocampi and thalami optici, extend into the poste-
rior cornua of their respective ventricles. Underneath the
posterior part of the cerebellum it is similarly reflected
into the fourth ventricle, forming the plexus choroides of
the fourth ventricle.

The brain is primarily divided into cerebrum, cerebellum,
200ns Varolii, and medulla oblongata. The cerebrum is the
largest part, and is that ovoid mass situated in the ante-
rior part of the cranium. It presents on its external sur-
face a number of convolutions, gijri, separated by grooves,
sulci, which in the human subject are capable of division
into sets, but in the horse present no regularity, except
that at the middle line we may observe the " marginal
convolution." On each side of the superior longitudinal
fissure, and on opening the fissure, we may see a " gyrus
fornicatus " on each side of the bottom of it. The cerebrum
is separated from the cerebellum by the great transverse
flssure, which extends on either side, and also in a forward
direction, underneath the posterior lobes of the cerebrum,
where it contains the vellum interpositum. The cerebrum
is divided into two parts, hemispheres, by the superior lon-
gitudinal flssure, which runs forward from the transverse
fissure and anteriorly extends downwards, putting in its
appearance at the anterior part of the base of the brain ;

156 OUTLINES OF EQUINE ANATOMY.

and anteriorly and posteriorly presents somewhat firm union
of the hemispheres. It contains the falx cerebri, and is
terminated below by a layer of white matter, corpus cal-
losum, which connects the two hemispheres, and is com-
posed of fibres which run transversely from the white
substance of the hemispheres, the anterior fibres being
curved forwards, the posterior backwards, so that the nar-
rowest portion is that shown by separation of the two
hemispheres without incision. On its upper surface may
be distinguished a central longitudinal line, the rop/ie,
along which arteria corporis callosi passes, and on each
are the linese longitudinales laterales, while lineae trans-
versae intersect these at right angles. The corpus callosum
terminates both anteriorly and posteriorly by a rounded
extremity ; the anterior is the genu, the posterior the
splenu. From the latter the fornix runs in a forward
direction, connecting together the hippocampi. Anteriorly,
at the foramen of Munro, the fornix terminates in four
crura. The anterior run to the base of the brain, where
they terminate in the single corpus albicans (there are
two in the human subject). The posterior take the name
of corpora fimbriata, and extend into the posterior cornua
of the lateral ventricle. The upper surface of the fornix
is connected to the under surface of the corpus callosum
by the septum lucidum, a thin layer of nerve matter which
separates the lateral ventricles one from the other, and
between the two layers of which is the fifth ventricle (which
we have never found in the horse). By removing a small
layer from the upper surface of the cerebral hemispheres
we may demonstrate that they are composed externally of
grey matter, internally of white. The grey matter, cine-
ritious, is of uniform thickness throughout, but since it
invests the convolutions presents a wavy margin. The
white or medullarij matter in this section is termed the
centrum ovale minor, and presents the cut extremities of
vessels, through which, in the fresh subject, a small
quantity of blood oozes, puncta vasculosa. If sections are
now made through both hemispheres on a level with the
corpus callosum, the whole of the upper surface of that
layer or ceiitrum ovale major is exposed. By incision
through this on either side we lay open the cavity of the
lateral ventricle, a space divisible into anterior and pos-
terior cornua, bounded anteriorly and externally by the

SPECIAL ANATOMY. 157

substance of the hemispheres, superiorly by the corpus
callosum, internally separated from its fellow by the sep-
tum lucidum, in the anterior part of which is the foramen
of Monro or anterior communicating foramen. Its floor pre-
sents the following structures in order from before back-
wards : —

Corpus striatum, taenia semicircularis, plexus choroides,
corpus fimbriatum, hippocampus.

Corpus striatum is a pear-shaped body, the base of which
lies against its fellow, separated by brain substance, the
apex extends into the anterior cornu, which runs down-
wards, outwards, and foi^wards. Externally it is covered
by a thin layer of white matter, but is dark in colour, and
has a few small vessels at its posterior margin. By passing
a pin through it we shall find that it is situated just above
locus perforatus anticus at the base of the brain. It is
named from its composition of alternate layers of grey
and white matter. At its posterior margin is distinguish-
able a thin layer of white matter, tcenia semicircularis,
which is generally covered by the plexus choroides which
has been already described, and which also covers the
posterior crus of the fornix, corpus fimbriatum, a thin
layer which runs downwards into the posterior cornu,
where it terminates in a small enlargement, pes accessorius.
Immediately behind it is the hippocampus. (There are
two, major and minor, in each lateral ventricle of man.)
This is an internal convolution of the cerebral hemi-
spheres, it rests upon the velum interpositum inferiorly,
and, with the plexus choroides and corpus fimbriatum ex-
tends into the posterior cornu, where it terminates in the
pes hippocampi.

The posterior cor7iit runs backwards, outwards, and down-
wards, and then forwards and inwards. It is shaped like
a ram's horn, and its apex is situated in the mastoid lobule
at the base of the brain. The hippocampus is separated by
the velum interpositum from the thalamus opticus, a some-
what irregular, rounded body, which constitutes the deep
seated origin of the optic nerve. It presents on its upper
surface three prominences, corpora geniculata externum and
internum, and the tubercle. The inner surface of this body
is connected with its fellow by the middle or grey commissure,
anteriorly situated to which is the foramen of Monro or
anterior communicating foramen, which not only connects

158 OUTLINES OF EQUINE ANATOMY.

the cavities of tlie lateral ventricles but also extends down
to the base of the brain, where it forms the cavity of the
tuber cinereum, and the inf undibulum, and extends as far as
the pituitary body. Anteriorly it is bounded by the anterior
tvJiite commissure, which connects the two corpora striata
together. Posteriorly situated to the grey commissure is
the posterior commu7iicating foramen, which forms the com-
mencement of the iter a tertio ad quartum ventriculum.
Just above this is a small black cone-shaped body, the
pineal gland, the use of which is unknown — we sometimes
find it much enlarged. It contains pigmentaiy matter and
vessels arranged in an areolar stroma, and from it forwards
along the inner margins of the thalamic optici, above the
grey commissure, run the crura of the pineal body, which
anteriorly blend with the substance of the thalami. The
third ventricle is the cavity through which the grey com-
missure passes " like a transverse beam." Anteriorly, it is
bounded by the anterior white commissure, superiorly by
the velum interpositum, laterally by the thalami optici
and the crura of the pineal body. Inferiorly by the upper
surface of certain structures situated at the base of the
brain — tuber cinereum, corpus albicans, and locus perfora-
tus posticus. It presents three openings : inferiorly, the
infundibular ; sup ero- anteriorly, the anterior communi-
cating foramen ; supero-posteriorly, the posterior communi-
cating foramen. Its posterior boundary is the posterior
white commissure, which connects together the corpora qua-
drigemina, and forms the roof of the iter a tertio ad quartum
ventriculum. The corpora quadrigemina are four bodies
posteriorly placed to the pineal body. The anterior pair is
the roundest, largest, and darkest, and is termed the nates,
the posterior, or testes, more ovoid in form, posteriorly receive
tracts of white matter running from the cerebellum, iter
e cerehello ad testes. These tracts are connected together by a
thin membraniform layer of matter, valve of Yieussens, from
which the fourth pair of nerves arise. They circumscribe
anteriorly the fourth ventricle, "a boat-shaped cavity,"
situated at the upper part of the medulla oblongata. Its
roof is formed anteriorly by the valve of Yieussens, cen-
trally by the under surface of the cerebellum, posteriorly
by the arachnoidean valve. Its floor and lateral walls are
formed by the pillars of the medulla oblongata, anteriorly
its cavity is continuous through the aquaduct of Sylvius or

SPECIAL ANATOMY. 159

iter a tertio ad quarhim ventriculum with the third ventricle.
Its posterior part, frora its likeness to the nib of a pen, is
termed calamus scriptorius, and is continued through the
spinal cord by a canal which extends centrally between its
columns. The cerebellum is a round body, situated in a
special division of the cranium, posteriorly to the cerebrum
from which it is separated by the ossific and the mem-
branous tentoria ; and to which it is connected on each side
by the iter e cerebello ad testes. It presents, on either
side of the median line, running from behind forwards a
fissure, and thus the organ is divided into three parts.
Centrally is a " caterpillar-shaped " body, the anterior part
of which is the anterior vermiform process; the posterior
part, the posterior vermiform process, on either side of this
is a lobe. By an incision from behind forward in the median
plane we may expose the internal structure of the organ.
The surface of the cerebellum presents convolutions which
are divided into uniform parts by transverse secondary
grooves. The grey matter which the external surface
presents, is arranged with regard to the white as the leaves
of a tree are to the branches, so the white matter inferiorly
terminates in abroad base. This arrangement is the arhor
vitce, and the base of the stem is formed by three tracts of
white matter, the crura of the cerebellum. The anterior
is the iter e cerebello ad testis, the posterior is continuous
with the corpus restiforme of the medulla oblongata, the
middle passes under the medulla oblongata, joining with
its fellow to form a transverse band at the base of the
brain, the pons Varolii; this is the part which serves
to connect together the three other divisions of the brain.
It presents a longitudinal groove along its central line,
through which the basilar artery passes, and on either
side of which it becomes more prominent, for here is a
collection of nerve-cells in its substance constituting the
corpus dentatum, the special centre of the fifth pair of
nerves which arises from the lateral parts of its under
surface.

The medulla oblongata is but the commencement por-
tion of the spinal cord, from which it is distinguished by
its greater size, caused by the presence of a few extra nerve
cells collected to form the corpus olivare. In addition to
this, like the spinal cord, it presents three tracts of white
matter (externally) continuous with those of the cord

160 OUTLINES OF EQUINE ANATOMY.

respectively. Tlie corpora pyramidalia inferior are sepa-
rated from each, other by the inferior longitudinal fissure,
which, however, is slightly obscured by the decussation or
passage to the opposite side of the medulla of the motor
fibres of the corpora restiformia, the lateral tracts of the
medulla oblongata continuous with those of the spinal cord.
These divide anteriorly, one branch runs to the cerebellum
forming its posterior crus, the other passes forwards to the
cerebrum and unites with fibres from the pyramids forming
the crura cerebri. These restiform bodies are separated
from the inferior pyramids by the corpora olivaria, small
round bodies which internally present an irregular grey
nodule, corpus dentatum. Their upper surface forms the
floor of the fourth ventricle, and on either side superiorly
is situated a small corpus pyramidalium superior. The two
sides of the medulla oblongata are connected together by a
commissure formed of grey and white matter.

The base of the brain presents numerous and diverse
structures. At the anterior part centrally is the superior
longitudinal fissure, and on either side of this is an olfac-
tory bulb. This is a rounded mass of grey matter situated
in the olfactory sinus, from which grey fibres run forwards
through foramina, in the cribriform plates. This is
attached to the under j^art of a tract of white matter
which runs backwards and becomes narrower, terminating
in two parts which separate at an angle enclosing a trian-
gular space, locus perforatus anticus, or substantia perforata,
the out3r surface of the corpus striatum. These tracts of
matter contain a cavity lined by serous membrane, which
in some subjects is said to have been found continuous
with the lateral ventricle. From the lateral parts of the
thalamus opticus and from the corpora quadrigemina
tracts of white matter run round the lateral parts of the
crura cerebri. At the base of the brain they unite, and
the fibres from this union form two nervous cords, the optic
nerves which pass to the eye. This is the optic decussa-
tion, the fibres from one side pass— to the nerve of the
opposite side, to the nerve of the same side, to the other
optic tract ; fibres also run from one optic nerve to the
other. From the postero-lateral parts of the optic decus-
sation the crura cerebri run to the anterior margin of the
pons Varolii. They are broad bands of white matter, and
from their under surface the third pair of nerves, motores

SPECIAL ANATOMY. 161

oculorum, arises. Between these, anteriorly is the tuhcrr
cinereum, which is continued to the pituitary body as the
infiindibulum, and through which a canal runs. Imme-
diately behind this is the corims albicans, formed by the
anterior crura of the fornix, and more ^posteriorly, between
the crura cerebri in the human subject, is locus jjerforatus'
jposticus, ivJiicli in the horse is represented merely by a groove^
The hemispheres of the cerebrum of man are divided into
anterior, posterior, and middle lobes. At the lateral part
of the crura cerebri of the horse is a smooth, round mass,
mastoid lobule (analogous to the middle lobe of man).
From the optic decussation in front of this the fissure of
Sylvius runs outwards, tending to divide the hemisphere
into an anterior and a posterior lobe. Before running over
the under surface of pons Varolii the basilar artery gives
off the anterior, posterior, and middle cerebellal arteries, after
doing so it terminates in receiving the two posterior com-
municating arteries. These give off the posterior cerebral
arteries (which run upwards winding round the crura
cerebri) and are given off with the anterior communicating
and middle cerebral by the internal carotid after it has
pierced the dura mater. The anterior communicating artery
runs inwards and blends with its fellow in front of the
optic decussation. The middle cerebral runs outwards
through the fissure of Sylvius. From the anterior commu-
nicating or from the middle cerebral the ophthalmic arteries
pass through the foramina lacera orbitale to the orbit, and
from the centre of the anterior communicating the
anterior cerebral artery (double in the human subject)
passes around the anterior extremity of the corpus callosum
into the superior longitudinal fissure, where it terminates
in forming the arteria corporis callosi. Thus we have the
circle of Willis at the base of the brain formed anteriorly by
the anterior communicating, laterally and posteriorly by the
posterior communicating arteries ; it encloses the optic decus-
sation, tuber cinereum, infundibulum, corpus albicans, locu&
perforatus, and part of the crura cerebri, and surrounds the
pituitary body. We have always found the origin of the
third pair of nerves externally placed to it. Posteriorly at
the base of the brain we see the pons Varolii running trans-
versely, and a fifth nerve arising at either end of it. Fromj
the under surface of the medulla oblongata, just behind
the pons, on either side of the inferior longitudinal fissure,

11

162 OUTLINES OF EQUINE ANATOMY.

a sixth or cibducens nerve arises ; and more outwards and
posteriorly placed the glosso-2)haryngeal, pneumogastric,
spinal accessory, and lingual nerves, while the seventh and
eighth together arise immediately behind the fifth from the
lateral i^art of the medulla. The eleventh or spinal
accessory nerve arises from the lateral part of the spinal
cord as low down as the fifth cervical vertebrae. It runs
towards the cranium, passing between the sensory and
motor roots of the s^^inal nerves, receiving fibres from the
•lateral part of the cord. Its last fibres arise from the
medulla oblongata, it then emerges from the cranium
through the posterior part of foramen lacerum basis cranii,
and runs to supply sterno-maxillaris, levator humeri and
other muscles of the neck. It has extensive communica-
tion with the nerves near its origin and with the superior
cervical ganglion. The lingual nerve passes between it and
the glosso-pharyngeal.

In laying open the cranium to examine its contents
remove all surrounding soft structures. Saw through
the forehead transversely about three quarters of an
inch above the orbital process of the frontal bone.
From the extremity of this incision divide the bones
on either side so as to remove the superior third of the
foramen magnum of the occiput. Eaise the separated
portion, calvarinm, with the chisel, the dura mater with its
falx cerebri will be seen attached to its internal surface.
The anterior part of the spinal cord having been now cut
through, the brain may be raised, and the nerves passing
from its base divided in turn from behind forward. The
olfactory bulbs will gener^ally remain in situ. The contents
of the cranium is termed the encephalon.

The internal and middle ear may be examined by im-
mersing the petrous temporal bone in a solution of hydro-
chloric acid, three drachms of the acid to a c[uart of water.
(We have never tested this process practically, but have seen
it recommended.) After a time the bone will become dej^rived
of earthy matter so that it can be divided by a common scal-
pel. The foramina should be first stopped with w^ax, that the
©ssicula auditus may remain uninjured. The petrous temporal
lone is the hardest bone in the body ; it is, therefore, well
calculated for communication of the vibrations of the
atmosphere. In it is situated the organ of hearing, which,
like all other organs of special sense, has certain nerve-cells

SPECIAL ANATOMY. 163

to wliicli tlie fibres of tlie nerve of that special sense
run, and a special arrangement whereby those influences
which cause the impressions are best able to alter the
condition of the cells. The ear is divided into external,
middle, and internal ears. The first has been already
noticed ; the internal ear is that part in which are situated
the cells of hearing. It is divided into cochlea, vestibule,
and semicircular canals. The vestibule is the central
cavity. It has seven openings into it, those from the
semicircular canals, one from the scala vestibuli of the
cochlea, and one from the middle ear, fenestra ovalis. It
contains a membranous sac, the membranous vestibule,
which is divided into two parts. The superior, utriculus,
receives the openings of the membranous semicircular
canals. It is separated by a membranous partition from
the inferior or sacculus, which has no openings. This
membranous portion is in contact both externally and in-
ternally with a serous fluid. That surrounding it is the
]}erihjmpli, that contained inside of it is the enclolymph and
contains numerous minute calcareous particles, otoconites
or otolithes. The membranous semicircular canals ex-
actly resemble the bony cavities in which they are placed.
They contain endolymph and are surrounded by perilymph.
They are three in number, superior, internal, and p>osterior,
and each canal opens by its two extremities into the ves-
tibule, one of these extremities is dilated to form the
ampulla. The undilated extremities of the superior and
internal canals open by a common orifice into the vestibule.
To the ampullae run bi'anches of the eighth or auditory
nerve.

The cochlea is a cavity hollowed out in the substance of the
j)etrouS temporal bone, shaped like a snail's shell, consisting
of a canal arranged in a spinal manner around a central bony
tube, modiolus. This canal is largest at its commence-
ment, and superiorly comes to a point. It is divided into two
parts by a spiral plate, which is internally attached to the
modiolus and projects into the canal. The division is com-
pleted by a membrane consisting of two layers between
Tvhich is the scala media of the cochlea. The two portions
of the canal, termed respectively superior or scala vestibuli,
inferior or scala tympani, communicate superiorly. The
former inferiorly terminates in the vestibule, the latter at
the fenestra rotunda, an opening in the bone closed by a

164 OUTLINES or EQUINE ANATOMY.

double fold of membrane, wliicL serves to bring about a com-
munication between the cavities of the cochlea and of the
tympanum. On the bony plate which separates the scalce
(lamina sjnralis) the fibres of the auditory nerve are spread
out ; they terminate in cells which are situated in the scala
media (fibres or rods of Corti), " arranged like the key-
board of a piano." On reaching the internal ear, after pass-
ing through foramen auditorium internum, the auditory,
portio mollis, or eighth pair of nerves breaks up into three
parts. One runs to the ampullae, another to the membranous
vestibule, the third passing into the modiolus gives ofP
fibres outward into the lamina spiralis. The intensity of
a sound is supposed to be distinguished in the vestibule,
its " tone " in the scala media of the cochlea. The ves-
tibule is connected with the cavity of the tympanum by
the fenestra ovalis, which in the fresh subject is closed by
mucous membrane and by the base of the stapes. It will
be observed that the cochlea only of the bony labyrinth has
its membranous counterpart attached to the bony walls, the
membranous semicircular canals and vestibule being sepa-
rated from the bone by perilymph.

The middle ear or tympanic cavity is situated between
the external and internal ears. Its outer wall presents the
membrana tymimm, which closes the foramen auditorium
externum. By the foramen styloideum it is connected
■with the pharynx through the medium of the Eustachian
tube. It communicates inferiorly wdth certain cavities in
the petrous temporal bone (similar to the sinuses of the
face) the mastoid cells. Through this cavity the seventh
nerve passes ; it enters through foramen auditorium in-
ternum, and during its passage gives off the chorda tym-
pani, which runs to the gustatory branch of the inferior
maxillary division of the fifth, and also branches to the
muscles of the middle ear ; then it emerges by passing
through foramen styloideum. The inner wall of the middle
ear presents two foramina — fenestra rotunda, leading to the
scala tympani ; fenestra ovalis, leading to the vestibule.
Into the latter fits the base of the stapes, one of a chain of
bones which extends across the tympanic cavity to the
membrana tympani. This bone is " stirrup shaped," and
its arch superiorly is connected by fibro- cartilage with a
portion of the incus. In this joint an osseous nodule may
be observed, os orbiculare, commonly enumerated as " th&

SPECIAL A-NxVrOMY. 165

^smallest hone in the body.'' The incus resembles in shape a
human molar, one of the fangs of which articulates with os
orbiculare ; the other becomes attached to the bony wall of
the cavity. The crown has a synovial articulation with the
upper portion of head of the malleus, the handle of which
is attached to the inner surface of membrana tympani,
vibrations of which are thus communicated to the bony
chain, which, by the mechanical arrangement of its com-
ponent ossicles, communicates them in an increased degree
of intensity to the liquid contents of the vestibule,
which produces impressions upon the auditory cells,
made more powerful by the presence of the solid particles,
otoconites, in the liquid. The bones of the middle ear are
acted upon by muscles, of which we will only particularise
the stapedius, running from the wall of the cavity to the
stapes at its attachment to os orbiculare and tensor tympanij
running from the margin of the bony ring surrounding the
tympanum to the handle of the malleus at its attachment
to the membrana. The middle ear is lined by transparent
and thin mucous membrane, which covers all the structures
contained in it, and is continued into the mastoid cells.
It closes the foramen auditorium externum in forming the
inner lining of membrana tympani, and also fenestrae
rotunda and ovalis. It is continuous through the Eusta-
<;hian tube with that lining the guttural pouch and the
pharynx. The internal and middle ear are supplied with
blood by the styloid division of the posterior auricular
branch of the external carotid ; they receive sympathetic
fibres from the otic ganglion, a small collection of nerve-
<iells situate'l on the inner surface of the inferior maxillary
division of the fifth nerve, just after it has emerged from
sthe cranium throup^h foramen lacerum basis cranii.

166- OUTLINES OF EQUINE ANATOMY.

PAET y.— SPECIAL ANATOMY.
The Neck.

From tlie incisiou along tlie central line of tlie front of
tlie neck tlie operator dissects tbe skin from ^panniculus
carnosus in an upward direction, it being moderately firmly
attached until it arrives at the collection of cellulo-
adipose material attached to the superior margin of
the ligamentum nuchse along the greater part of its.
length, which is somewhat intimately blended with the
skin.

Extending from the root of the ear, parallel to the pos-
terior margin of the lower jaw, is parotideo-auricularis,
attached suj^eriorly to the conchial cartilage, and running
downwards to be attached to the surface of the parotid
salivary gland. It is covered by a thin layer of panniculus.
Behind the ear, along ligamentum nuchsa for about five
inches, are attached the retrahentes aurum muscles drawing
back the ear.

Along the lower part of the neck the muscular fibres of
panniculus are distinct ; anteriorly some of them assume
a somewhat peculiar arrangement, running in a different
direction to the other fibres, in a distinct band, towards
the submaxillary space, meeting with the corresponding
fibres from the opposite side ; posteriorly the muscle be-
comes much increased in thickness, and sends some mus-
cular fibres to cover the anterior part of the connection of
pectoralis transversus with the cariniform cartilage ; its
main portion, however, extends over the shoulder with
levator humeri, with the tendinous j)art of which muscle it
blends, at the superior j)art of the neck, and so the pan-
niculus carnosus becomes indirectly attached to the supe-
rior margin of ligamentum nuchse. The splenius muscle
may be seen after removal of the skin through the superior
aj)oneurosis of the levator humeri.

THE NECK. 167

On removal of panniculus we disclose, at tlie postero-
superior part, the sterno-maxillaris shortly after its origin
from the anterior extremity of the cariniform cartilage,
blended with its fellow along the middle line, thus forming
a sling underneath the trachea, about the anterior part of
the posterior third of the neck, they separate, and, becom-
ing round muscular cords, run forwards to be inserted each
by.a broad tendon, which, after separating the parotid from
the submaxillary salivary glands, i^asses over stylo-maxil-
laris, and becomes attached to posterior margin of the lower
jaw about three inches below its articulation with the
squamous temporal bone.

The ti-achea at the middle third of the neck is covered
by the sterno-thyro-hyoideus muscle, which, passing from
the anterior extremity of the cariniform cartilage, here
divides into two parts ; the thimier runs underneath sub-
scapulo-hyoideus to the lateral part of the external surface
of the ala of the thyroid cartilage, where it terminates,
being inserted between the muscles proper to the larynx :
just above this termination is situated the thyroid body, a
small dark-red body of a rounded form attached to the
lateral aspect of the anterior part of the trachea. The
thyroid body under the microscope presents a number of
vesicular cavities lined by tesselated epithelium embedded
in a somewhat soft stroma. It is one of the so-called vas-
cular glands, the use of which is not distinctly understood,
and receives a large hranch from the carotid arteri/, the only
constant one given off from that vessel in its course up
the neck ; this branch frequently sends off a twig to the
larynx which receives the name of the laryngeal artery.
The broader division of sterno-thyro-hyoideus runs to-
wards the centre of the submaxillary space, where it
becomes inserted into the under surface of the body of os
sphenoides, together with subscapulo - hyoideus, which,
however, occupies a much larger surface of attachment,
and which puts in its appearance about the anterior third
of the neck, running from rmderneath sterno-maxillaris
to meet its fellow at its attachment. By removal of
parotideo-auricularis and panniculus, the parotid gland is
exposed. It is an irregular- shaped organ of a dirty white
colour, composed of numerous minute lobules, which fit in
between the different structures it covers. Anteriorly it
extends a little on to the surface of masseter externus,

168 OUTLINES OF EQUINE ANATOMY.

being superiorly m contact with the temporal artery and
vem and facial nerve as they arise and wind round the
jaw, and then extends upwards over the muscles in front
of the ear forming one of its superior divisions, the
other being situated behind the ear. From this the j^os-
terior margin of the gland runs in a downward direction,
being separated from the wing of the atlas by tendinous
structure, and terminates at the junction of the submaxil-
lary and jugular veins, from which point its lower margin
runs forwards to the angle of the jaw. From this antero-
inferior point the duct of the gland arises, and passes over
the internal surface of the lower edge of masseter internus,
where it is covered only by panniculus and skin, and is
in company with the submaxillary artery, and the corre-
sponding vein. Through the substance of the parotid run
several large veins, among others the jugular, and by
raising it and removing the stylo-maxillaris, running from
the anterior part of the styloid process of the occiput to
the angle of the lower jaw, blending superiorily with digas-
tricus, we expose the termination of the

Carotid artery. Just oj^posite to the commencement of
the trachea it breaks up into three parts, one.

Ramus anastomoticus, runs directly upwards to the
under surface of the wing of the atlas (giving off a large
branch running to the occiput), here it rests upon obliquus
capitis anticus, and anatomoses with a vessel, the vertebral
artery, coming through the posterior foramen in the wing
,of the atlas ; the trunk so formed passes into the anterior
foramen, which has two outlets, through one of which a
branch runs to obliquus capitis inferior upon the upper
surface of the atlas, through the other a branch passes
.into the spinal canal, and after piercing the dura mater
;of the spinal cord anastomoses with its fellow from the
opposite side and runs forwards, as the basilar artery, to
supply the brain. The smallest of the three terminal
branches of the carotid, the internal carotid, runs directly
.towards the base of the cranium throughout its course
being situated with its fellow at the posterior part of the
septum formed by the contact of the internal walls of the
two guttural pouches.

The external carotid seems to be the direct continuation
/Of the carotid trunk, it passes forwards, and just before
arriving at the posterior angle of the long cornu of os

THE NECK. 169

liyoides gives off tlie submaxillary artery, wliicL, running
between the long cornu and hyoideus inagnus,.gives off the
.lingual artery running forwards, and then meets with and
accompanies the corresponding vein, and the parotid duct
over the internal surface of the inferior margin of mas-
seter internus. After reaching the external part of the
dilated superior extremity of the long cornu, the external
carotid gives off large posterior masseter Iranches anteriorly,
parotid branches and branches to stylo-maxillaris exter-
nally, and the posterior auricular posteriorly. This
latter branch gives off the middle auricular, which runs
to the external auditory opening. The external carotid is
here covered by the mucous membrane of the guttural
pouch, a transparent layer which covers both sides of the
long cornu of os hyoides ; on reaching the temporo-
maxillary joint the artery terminates in three branches, the
anterior auricular, which runs to the front of the ear to
supply the structures in that neighbourhood ; the tem-
poral, which winds round the jaw and runs along the
superior margin of masseter externus ; and the internal
maxillary, which runs to the base of the cranium.

The levator humeri must now be dissected to its attach-
ment to the crest of the occiput ; to the mastoid ridge ex-
tending downwards laterally from that ridge, the wing of
the atlas by a tendon common to it and trachelo-mas-
toideus and splenius, the transverse processes of the second,
third, and sometimes fourth cervical vertebrae. By turning
up its inferior margin we show the branches of the cervical
intervertebral nerves running directly to it. Its attachment
to the superior margin of the ligamentum nuchse by f aschia,
and its blending posteriorly with trapezius may also be
noticed ; by this time its attachments to the fore limb will
be shown, i. e. to the spine of the scapula, the point of the
shoulder, the humeral ridge with its elongating ligament,
and the antero-uiferior depression of the humerus.

By removal of levator humeri we expose a second layer
-of superior cervical muscles. Eunning from the transverse
processes of the cervical vertebrae, as far forwards as the
third to the superior margin of the scapula is serratus
magnus, and from the antero- superior angle of the scapula
rhomboideus runs in the form of an extremely elongated
triangle to within six inches of the attachment of the
•cordiform portion of the ligamentum nuchae to the occiput.

170 OUTLINES OF EQUINE ANATOMY.

Seen between tliese muscles and covered at its posterior
part by them is

Splenins, a large layer of muscle attached anteriorly, in
common with tracbelo-mastoideus, to tbe mastoid ridge, tbe
crest of tbe occiput and the- wing of tbe atlas, it also has
heads attached to the transverse processes of the second,
third, fourth and fifth cervical vertebrae. Posteriorly it is
attached to the superior spinous processes of the three
anterior dorsal vertebrae, and superiorly to the cordifomi
portion of ligamentum nuchse along its whole length. It
posteriorly sends a tendon to blend with the commence-
ment portion of the dorsal faschia. Having removed
this muscle we expose another muscular layer consisting
mainly of complexus major, covered inferiorly against the
vertebrae by

Trachelo-mastoideus, which is composed of three distinct
portions : 1st. Head is attached with splenius to the mas-
toid 2)i'ocess, and with complexus major to the oblique
processes of the fourth, fifth, sixth and seventh cervical
vertebrae, and the transverse processes of the two anterior
dorsal vertebrae : 2nd. Head with splenius to the trans-
verse processes of the two anterior and separately the
oblique processes of the second, third, fourth, fifth, sixth
and seventh ceiwical vertebrae ; 3rd. Head with splenius to
fourth ceiwical transverse process ; the second and third
heads join with the first to become attached posteriorly.
Between the superior tendons the oblique muscles of the
head are to be seen.

Obliquus capitis superior arises from the mastoid ridge
and from the styloid process of the occiput, its fibres run
obliquely downwards and backwards, being attached inter-
nally to the altoido-occipital capsular ligament, and be-
come inserted into the anterior margin of the transverse
process of the atlas, at the inferior margin of this muscle,
slightly concealed by it, is a small muscular band,

Obliquus capitis anticus, which runs from the styloid
process of the occiput to the under surface of the body of
the atlas at its lateral part — it is also attached to the cap-
sular ligament of the joint.

Obliquus capitis inferior passes from the supero-ex-
ternal part of the wdng of the atlas, over the altoido-
dentatal joint to the capsule of which it is attached, and
becomes inserted into the lateral part of the superior

THE NECK. 171

spinous process of the dentata ; posteriorly it is in contact
with the anterior semi- spinalis muscle of the neck, and on
the wing of the atlas it covers the vertebral artery, where it
passes on to the ala, and then dips down through its pos-
terior foramen to anastomose with ramus anastomoticus.
Through the anterior foramen a branch of the artery runs
from the union of these two to the muscles situated about
here, . but the main portion passes through the foramen in
the pedicle of the atlas, and after gaining the vertebral
canal, pierces the dura mater, and uniting with its fellow
forms the basilar artery, which runs to the brain.

Complexus major is attached in common with trachelo-
mastoideus to the oblicjue processes of the fourth, fifth,
sixth and seventh cervical vertebrse, and the transverse
processes of the two anterior dorsal vertebrae. It is also
attached to the oblique processes of the third, fourth, fifth
and sixth dorsal vertebrae, and to the oblic^ue process of the
third cervical vertebr£e ; anteriorly it blends with complexus
minor, and becomes inserted into the scabrous pit of the
occiput. It is attached along the greater part of the supe-
rior margin of ligamentum nuchse. Its posterior attach-
ment is covered by a muscle which seems at first sight to
be a part of longissimus dorsi, i.e. cervico- dor sails, which
is attached in common with complexus major to the
oblique processes of the six anterior dorsal vertebrae, and
runs forwards to the transverse xH'ocesses of the three pos-
terior cervical vertebrae (to the seventh it is attached by a
tendon, which it shares with longissimus dorsi).

Complexus minor arises from the posterior part of the
superior spinous processes of the dentata, and, blending
anteriorly with the complexus major, becomes inserted into
the scabrous pit of the occiput. It lies in contact with its
fellow of the opposite side, for about here the ligamentum
nuchse is deficient, there being a space between its cordif orm
and membraniform portions. By removal of it we expose

Rectus capitis posticus major, running from the ante-
rior part of the superior spinous process of the dentata,
becoming attached to the atloido-axoidal capsular ligament,
and blending in, become inserted into the scabrous pit of
the occiput with

Rectus capitis posticus minor, which arises from the
superior part of the arch of the atlas, and is attached to the
atloido- occipital capsular ligament.

17^ OUTLINES OF EQUINE ANATOMY.

The jugular vein, after 2:>assing tlirougli the parotid
gland, receives the submaxillary vein when about opposite
-the thyroid body. It then proceeds down the channel of
the neck, receiving no important branches, until it arrives
at the lower part, when the superficial hrachial vein, which
carries blood from the fore extremity opens into it, and in
some cases it receives the lymph from the thoracic duct on
the left side, the great right lymphatic on the right (often,
however, this opens into the axillary vein) . Finally, be-
tween the two first ribs the jugulars unite to form the com-
mencement portion of the anterior vena cava. By removing
the jugular vein aud subscapulo-hyoideus we expose the
trachea, and on its supero -lateral part the carotid artery
with the pneumogastric and gangliated cord of the sympa-
-thetic nerves enclosed in its sheath, and the inferiof
laryngeal branch of the pneumogastric a little lower down.

The (Esophagus is a long tube which commences an-
teriorly at the posterior part of the pharynx, and after
passing along the neck, and through the thorax, and the
foramen sinistrum of the diaphragm, terminates at the
cardiac or left opening of the stomach. At first situated
above the larynx in its course down the neck, it becomes
inclined to the left side (thus we watch the left side of the
neck to see a ball " go ") so that on entering the thorax it
is near the inner surface of the first left rib. While pass-
ing through the anterior mediastinum it becomes slightly
above the trachea inclined to the right side, and in pass-
ing over the base of the heart it crosses the right bronchus,
-then in the posterior mediastium, having rested in a special
groove in the left lung, where it is in company with the
•pneumogastrics, it passes with them through foramen
sinistrum. It consists of two coats. The external is mus-
cular, anteriorly it is directly continuous Avith crico-pharyn-
geus ; it consists of longitudinal fibres externally placed,
circular fibres internally, and until it has passed over the
base of the heart it retains its red colour, which is apt to
cause it to be mistaken for some of the cervical muscles in
the neck. Posteriorly it becomes thicker, and its fibres are
-continuous with those of the stomach. This coat is con-
nected to the internal or mucous coat by very loose areolar
'tissue, in consequence of which the latter is generally
arranged in longitudinal folds which close the cavity of
the tube. It is the termination of this mucous coat at the

THE NECK. 173^

stomach whicli is said to prevent vomition in the horse except
under extreme circumstances ; others attribute it to the
mode of entrance of the oesoj^hagus into the stomach,
while some argue the presence of a special spiral valve.
This mucous membrane is similar in structure to that of the
pharynx and to the cuticular portion of the mucous lining
of the stomach, with which it is continuous anteriorly and
posteriorly respectively.

In the upper and anterior part of the neck, perceptible
on manipulation in the living animal, is the larynx, a
remarkable cartilaginous organ the seat of the voice ; the
upper part of the trachea specially modified. It is com-
posed of several pieces of cartilage, which are united
together in some places by synovial, in others by fibrous
articulations. Elastic expanded ligaments in some situa-
tions strengthen the connection. The larger cartilages are
five in number ; thyroid, cricoid, two arytenoids, and epi-
glottis. The Thyroid is the largest, and consists of a body
and two wings. The body is supero -anteriorly placed, and
is the thickest portion of the cartilage. It has two surfaces,
anterior and posterior, and four margins, superior, inferior,
and two lateral. To the internal surface the epiglottis is
attached by elastic tissue, the external surface is in contact
with the sterno-thyro-hyoidei muscles. To the superior mar-
gin is attached the thyro-hyoid ligament, to the inferior mar-
gin the crico -thyroid ligament, and the aloi or ivings arise from,
the two lateral margins. The aloi are firm flat portions of the
cartilage which exhibit a tendency to undergo ossification ;
each of them manifests the form of an oblique-angled paraL
lellogram, the anterior acute angle of which blends with the
body of the cartilage ; the postero-inferior acute angle is
rather elongated, and presents a synovial surface for articu-
lation with the antero-inferior synovial facet of the cricoid
cartilage. The postero-superior oblique angle presents a
flexible cartilaginous prolongation, superior cornu of the
posterior margin, the free extremity of which is united by
fibro-cartilaginous tissue to the posterior extremity of the
heel process of os hyoides. The antero-inferior oblique angle
forms the point of junction of the anterior and inferior
margins, to both of which is attached the crico-thyroid
ligament. The superior margins of the two alse are con-
nected together by the superior extremity of the body and
from the whole ridge thus formed the thyro-hyoid ligament

174 OUTLINES OF EqUlXE AK ATOMY.

runs to the posterior crescentic margin of the hjoid bone.
This ligament fills the space between the superior cornu of
the cartilage and the alse, with the exception of the angle,
where it is deficient, and thns a foramen is formed through
wJiich the terminal ])ortion of the siijperior laryngeal branch of
the imeumogastric runs to supply the mucous membrane of
the larynx with exquisite sensibility. The external surface of
the thyroid alse is in contact with the thyro-hyoideus supe-
riorly ; thyro-pharyngeus supero-posteriorly ; crico-thyroi-
deus inferiorly ; between these the short portion of sterno-
thyro-hyoideus is attached. From the superior cornu the
posterior part of hyo-thyro-pharyngeus runs upwards. The
internal surface is superiorly covered by mucous membrane,
inferiorly by thyro-arytenoidei posticus and anticus (and is
in contact with crico-ary tenoideus lateralis) . The Epiglottis
has aptly been likened to a sage leaf, the base of which
is attached by elastic tissue to the internal surface of the
body of the thyroid, the apex is invested closely by mucous
membrane, and is free. It consists of yellow elastic car-
tilage, and the mucous membrane covering it presents
very large mucous gh.nds. To the anterior surface mucous
membrane proceeds from the base of the tongue, and by
removal of this centrally we shall expose

Syo-eijiglottideus running from the posterior part of the
body of OS hyoides, directly backwards to the anterior sur-
face of the epiglottis. The base of the epiglottis on either
side is continued by a prolongation which runs in a back-
ward direction, connected by cartilaginous nodules (called
the cuneiform cartilages) to the arytenoid cartilages. The
posterior surface of the epiglottis is covered by mucous
membrane, and during the act of deglutition is brought
down over the glottal opening or entrance to the larynx.

The cricoid cartilage, as its name indicates, is extremely
like a finger-ring. Its smallest part is anteriorly situated,
and from this it increases in size irregularly in a posterior
direction. The posterior part forms a flat hexagonal sur-
face, with a central ridge and four synovial articulatory
facets, two at the antero-inferior angles for articulation
mth the posterior acute angles of the thyroid alse, two at
the postero-superior angles for articulation with the ary-
tenoid cartilages. On either side of the central ridge is
attached a crico-arytenoideus posticus, while crico-aryte-
Tioideus lateralis originates from the posterior j^art of the

THE NECK. 175

superior margin of tlie smaller portion of the cartilage.
The whole interior margin affords attachment to the crico-
trachealis ligament, the anterior part of the superior
margin to the crico-thyroid ligament. The lateral parts of
the external surface to the crico-thyroid muscles. The
internal surface is lined by mucous membrane.

The arytenoid cartilages, two in number, articulate
inferiorly by synovial joints with the cricoid cartilage. The
articulatory part is shaped like a prism, the inner angle of
which is elongated in a posterior direction towards its
fellow; the outer angle in an anterior direction towards
the epiglottis, with which it is indirectly connected by the
above-mentioned cartilaginous nodules. The superior ex-
tremity of the prismatic portion is expanded, and sends a
peculiar thin process in an anterior direction to be united
by mucous membrane to the epiglottis. Thus the external
surface presents two triangular spaces, into the posterior of
which arytenoideus is attached (running from one cartilage
to the other), into the anterior the thyro-arytenoidei j^os-
ticus and anticus, while crico-arytenoidei lateralis and pos-
ticus are attached to the prominent ridge between the two.
The superior margins of the arytenoid cartilages are con-
nected by continuity of their investing mucous membrane.

From the internal surface of the arytenoid cartilages to
the inner surface of the thyroid cartilage and of the crico-
thyroid ligament run bands of yellow elastic tissue termed
the vocal cords, by the tension of which the sound of the
voice is modulated. They are covered on their internal
surface by the laryngeal mucous membrane, and externally
are in contact with the thyro-arytenoidei muscles ; the tri-
angular space between them is the rima glottidis. In our
description of the cartilages we have incidentally noticed
the different layers of yellow elastic tissue which, while
they serve to connect the different portions of cartilage
together, also by their elasticity cause them to return to
their normal position after allowing them to accommodate
themselves to the movements of the neighbouring parts.
The crico-thyroid, crico-trachealis, crico- arytenoid, and
thyro-hyoid ligaments therefore require no further descrip-
tion. The mucous membrane of the postero-inferior part
of the pharynx, after being reflected over the margin of the
arytenoid and epiglottic cartilages before investing the
vocal cords on either side, presents a diverticulum, the

176 OUTLINES OF EQUINE ANATOMY.

ventricles of the larynx, which are suj)posed to give
resonance to the voice ; they j^ass down between the thyro-
arytenoidei anticus and posticus, and in the upper part of
each in the ass we see a small opening leading into a
secondary cavity. After passing over the cordse vocales
the mucous membrane lines the inner surface of the cricoid
cartilage, and is continued downwards into the trachea.

Thyro-hyoideus arises from the external surface of the
wing of the thyroid, and runs to be attached to the heel
process of os hyoides ; its internal surface is in contact
with the thyro-hyoid ligament.

Crico-thyroideus runs from the external surface of the
lateral part of the cricoid to the posterior part of the inferior
border of the wing of the thyroid.

Crico-arytenoidens posticus arises from the superior
surface of the posterior hexagonal part of the cricoid, and
its fibres converge to become inserted into the central
ridge on the external surface of the arytenoid, in common
with

Crico-arytenoideus lateralis, which arises from the
superior margin of the cricoid at the lateral part. Ary-
tenoidens runs from the external surface of one arytenoid
to that of the other, consisting really of two muscles
blending along the central line.

Thyro-arytenoidei posticus and anticus (generally con-
sidered as one muscle) are separated by the inflection of
mucous membrane, which forms the ventricle of the larynx.
They arise from the internal surface of the thyroid, and
run to the anterior part of the external surface of the
arytenoid.

The trachea is a large tube through which air passes in its
l^assage from the larynx into the lungs and vice versa. It is
composed of a series of cartilaginous rings, fifty to sixty in
number, which are embedded in and connected together by a
quantity of yellow elastic tissue. These rings are thickest in-
feriorly,and superiorly are deficient, being terminated by two
thin expanded extremities which overlap each other, and are
connected together by loose areolar tissue. Anteriorly the
trachea commences by being connected to the inferior mar-
gin of the cricoid cartilage by the crico-trachealis ligament y
which allows considerable motion between the two. Pos-
teriorly after crossing the base of the heart in the thorax^
where it is situated between the large arteries at their com-

THE NECK. 177

mencement and tlie large veins at their termination, it ter-
minates, forming the two bronchi, round cartilago- elastic
tubes running to the lungs. Its last cartilaginous ring is
different from the rest, since it forms a species of sac from
either side of which a bronchus passes, the right opening
being the largest. The trachea therefore passes down
the neck slightly inclined to the right side ; superiorly it
is in contact with the longi colli muscles, laterally with
the carotid arteries, the pneumogastric, recurrent, and
sympathetic nerves, and on the left side with the oesophagus.
The jugular veins are in contact with its lateral part
superiorly and inferiorly, but at the centre are separated
by the subscapulo-hyoidei muscles. Sterno-maxillaris and
sterno-thyro-hyoideus respectively, by blending with their
fellows, help to support it. In passing between the first
ribs it is superiorly placed to the commencement portion
of the anterior vena cava, and to the termination of the
arteriae innominatse, and here the oesophagus passes over
it to gain the right side. At its extreme upper -psivt the
oesophagus is superiorly placed, and the thyroid bodies on
either side generally connected by a central portion which
runs round its inferior face. On the inner surface of the
trachea, running from one side to the other at its superior
3)art, is a continuous layer of transverse unstriated mus-
cular fibres termed trachealis transversus ; the outer surface
of this muscle is connected to the cartilages by extremely
loose areolar tissue, while its inner surface is covered by the
mucous membrane which lines the trachea, and which
presents ciliated columnar epithelium. The pneumo-
gastric nerve, after emerging from the cranium through
foramen lacerum basis cranii, and sending numerous fibres
to the neighbouring nerves and ganglia, gives off the
superior laryngeal nerve ; it then runs down the neck in a
sheath with the carotid artery and the recurrent, and sym-
pathetic nerves. The recurrent is the inferior laryngeal
nerve, and supplies all the intrinsic muscles of the larynx
ivith motor poiuer except crico-thyroideus, ivhich receives a
branch from the superior laryngeal. The left recurrent
nerve is involved in the disease termed " roaring," whence
jjaralysis and fatty degeneration of the muscles supplied
by it ensues especially of the crico- and thyro-arytenoidei
muscles. The superior-laryngeal nerve is compound at
its origin ; on arriving at the larynx it supplies some of

1^

178 OUTLINES OF EQUINE ANATOMY.

the pharyngeal muscles, and thyro-hoideus and crico-thy-
roideus, and then becoming purely sensory pierces the fora-
men beween the thyroid cornu and the wing of the thyroid,,
and supplies the lining mucous membrane. The carotid
artery in passing wp the neck along the lateral part of the
trachea gives branches to the oesophagus and other neigh-
bouring structures, but the only constant branch is one
which runs to the thyroid body, and which also sends off
a large branch, the laryngeal, to the larynx. Along the
under surface of the vertebrae runs Longus colli, which
anteriorly extends to the tubercle or inferior spinous pro-
cess of the atlas, and runs as far back as the sixth dorsal ver-
tebra, becoming attached to the under surface of the
bodies and transverse processes, and inferior spinous pro-
cesses (except sixth cervical) of all the intervening
vertebrae. It lies in contact with its fellow internally, and
its thoracic portion is covered by pleura and forms a some-
what remarkable prominent cylindrical muscular mass. On
its external surface posteriorly just in front of the first
rib we see the vertebral artery and vein in their course
between the canal through the sixth cervical transverse
process and the entrance to the thorax. With them runs
a nerve formed by union of a branch from each cervical
nerve, through the middle, to the inferior cervical ganglion
— both of which ganglia are situated between the two first
ribs. These structures are hid from view by

Scalenius, a muscle composed of two distinct heads, the
superior or shorter arises from the transverse j^rocess of
the seventh cervical vertebra and runs to the anterior
margin of the inferior extremity of the su23erior third
of the first rib ; the longer or inferior arises from the
transverse processes of the fourth, fifth, and sixth
cervical vertebrae, and its fibres converge to become in-
serted into the superior part of the inferior third of the
external surface of the first rib. Between the two heads the
axillary ^plexus of nerves ]jasses, heloio the inferior head, the
axillary artery and vein, the latter heincj inferiorly sitimted.
On removal of this muscle we see the origin of the axil-
lary plexus from the sixth, seventh, and eighth cervical,
and first dorsal, and sympathetic nerves, and the phrenic,
running in a direction backwards, having originated by
fibres from the fourth, fifth, and sixth cervical. At the
janterior part of the neck longus colli is covered by the

THE NECK. 179

Rectus capitis anticus major, wliicli arises from tlie
transverse processes of the third, fourth, and fifth cervical
vertebr£e, and becomes inserted into the under part of the
posterior extremity of the body of the s23henoid bone.
Just behind this

Rectus capitis anticus minor is inserted into the antero-
inferior part of the basilar process of the occiput, running
from the under surface of the body of the atlas, and
becoming attached to the atloido-occipital capsular liga-
ment in its course. The inferior surface of these muscles
is covered by the mucous membrane of the guttural pouch,
and is in contact with numerous large nerves, the internal
carotid artery, and the superior cervical ganglion, a grey
nodular body, from which the gangliated cord of the
sympathetic commences its cervical portion.

The supero-posterior part of the neck is supplied with
blood by the posterior cervical artery. It commences from
the antero-suj)erior part of the arteria innominata, on the
left side separately, on the right side by a root common also
to the anterior dorsal artery. It passes upwards through the
first intercostal space, giving off the first intercostal artery.
It then passes forwards and upwards over cervico-dorsalis,
and subsequently runs between ligamentum nuchse and
complexus major to anastomose with the artery of the
poll.

The infero-j^osterior part is supplied by the inferior
cervical artery, which shortly after its origin from the
arteria innominata passes forwards, and breaks up in sup-
plying the muscles in this neighbourhood — panniculus
carnosus, pectorales transversus and anticus, sterno-maxil-
laris, &c. Three sets^of intrinsic muscles of the neck require
to be noticed :

Intertransversalis colli passes from the transverse pro-
cess of one vertebra to that of the vertebra next in order
to it.

Spinalis colli runs from the oblique process of one bone
to the transverse process of the vertebra second in order
behind it.

Semispinalis colli from the superior spinous process of
one vertebra, passing over two bones, gains the oblique
process of the third in order.

We have now arrived at the cervical portion of the spinal
column ; by sawing through the laminse of the vertebrse on

180 OUTLINES OF EQUINE ANATOMY.

•eitlier side we may expose tlie spinal cord, in situ, covered
"by its membranes. The dura mater of the cord differs
from that of the brain in that it does not form the peri-
osteum lining the bony cavity in which it is placed. It is
continuous anteriorly with the corresponding membrane
of the brain, in passing to the margin of foramen mag-
num of the occiput. Posteriorly it forms the fihim ter-
w^inale in becoming attached to the posterior extremity
of the bony canal. On either side it is closely attached to
the intervertebral foramina, and is reflected across these
openings to close them, so that here it is thick, and pre-
sents two rows of foramina, through which the collections of
nei-ve-fibres pass. The pia mater is directly continuous
with that of the brain and closely invests the cord. It in
structure closely resembles that of the brain, and laterally
is connected to the dura mater by the ligamentum denti-
«culatum. This is a band of white fibrous tissue extending
along the lateral part of the cord, attached to the external
surface of the pia mater, between the superior and inferior
roots of the nerves. It sends processes outwards opposite
the bodies of the vertebrae, which become attached to the
inner surface of the dura mater. The arachnoid mem-
l)rane is continuous with the cranial arachnoid, lines the
dura mater, covers the pia mater loosely so as to j)roduce
.a suharaclmoid space, and invests the processes of liga-
iQientum denticulatum, and those portions of the nerves
■which pass through the arachnoid space.

The Spinal cord consists of a number of nerve-centres
united together by white fibrous nerve cords, which render
it a continuous and extremely elongated mass extending
irom the brain anteriorly, through the spinal column as far
rfxs ahout opposite the second sacral hone. It varies in size in
'different parts, and this variation is due to the number of
aierves it must give off. Thus those parts which supply
merves to the fore and hind extremities are very large. It
is moderate in size in the central part of the cervical region,
Ibut in the posterior cervical and anterior dorsal vertebrae
it grows larger, and from this decreases in size until the
lumbar region, where it becomes large in giving off nerves
-to the hind limb. As a rule the nerves pass straight out-
wards to the intervertebral foramina, but in the sacral region
Ihey run obliquely backwards, and the superior fibres unite
with the inferior and again separate, forming the superior

THE NECK. 181

branches wHcli pass tlirough tlie supersacral, tlie inferior
through the subsacral foramina. In all other regions this
union and subsequent separation occurs after the nerves
have pierced the dura mater in passing through the inter-
vertebral foramina. This arrangement of the nerve-fibres
in an oblique direction in the sacral region forms the caudco
equina. The spinal cord consists of two hemispheres j^laced
side by side, separated superiorly by the superior longitu-
dinal fissure, inferiorly by the inferior longitudinal fissure^
the latter is shallower and broader than the former. They
are separated by a transverse band connecting the hemi«
spheres, termed the commissure, which consists of grey
matter Avith white substance on each surface, of which only
the superior layer is thick enough to be visible to the naked
eye. A transverse section of the cord shows that centrally
it presents grey matter arranged like inverted commas in
the hemispheres, connected by the grey commissure the
convex surface of one to that of the other. Thus the grey-
matter presents two cornua in each hemisphere. The superior
is the longest and narrowest, and runs upwards and out-
wards, reaching the surface of the cord. The inferior is
rounded and separated from the surface by a layer of white
matter. From the superolateral part of the cord to which
the superior cornu approaches the superior nerve -fibres
arise from the whole length of the cord, while from the
infero-lateral part nearest the inferior cornu the inferior
fibres arise. The superior or sensory fibres are divided into
sets which converge towards the intervertebral foramina.
They pass through the superior openings in the dura mater,
have a ganglion in connection with them, and are micro-
scopically indistinguishable from the inferior or motor fibres-^
which run from the cord through the inferior row of open-
ings in the dura mater to subsequently unite with the supe-
rior fibres forming the spinal nerves. By this arrangernent
of the nerve-fibres each hemisphere of the cord is divided
into a superior, a middle and an inferior column. The
spinal nerves at the commencement send fibres or receive
fibres from the nearest sympathetic ganglion. In most
regions the ganglia of the sympathetic cord are close
against the intervertebral foramina, but in the neck the
fibres from each nerve unite to form a branch running witb
the vertebral artery through the foramina in the transverse
processes of the vertebrae to terminate at the inferior cer*

182 OUTLINES OF EQUIN'E ANATOMY.

Tical ganglion. The cervical nerves are eight in number.
The first or suboccipital emerges through the foramen in
the pedicle of the atlas, through which the vertebral artery
gains the spinal canal. It sends fibres to the auricular
nerves and to the superior cervical ganglion (situated under-
neath the ala of the atlas) . The second nerve emerges through
the foramen in the anterior part of the pedicle of the den-
tata. The third, fourth, and fifth nerves send fibres to form
the phrenic nerve, while fibres from the sixth, seventh, and
eighth, first dorsal, and sympathetic form the axillary plexus.
Each of these nerves after passing through its foramen
sends oif a superior branch to the structures above the ver-
tebrae, an inferior to those below. On the lateral part of
the cord as far down as the fifth cervical vertebra may be
seen the spinal accessory nerve which j^asses upwards, be-
tween the superior and the inferior roots of the nerves,
receiving fibres along its whole course from the cord as far
up as the medulla oblongata.

After removing the cord and its membranes we may ex-
amine the superior vertebral ligament, which extends along
the upper surfaces of the vertebrae throughout the whole
canal. It becomes widened in becoming attached to each
intervertebral cartilage and is attached to the roughened
line on the centres of the upper part of the bodies of the
vertebrae, having on either side a venous sinus extending
along the whole length of the canal, sending a transverse
communicating branch under this ligament opposite the
centre of the body of each vertebra — also sending branches
outwards through each intervertebral foramen. These
sinuses anteriorly through the medium of the posterior
petrosal sinuses are connected to the cavernous sinus.

THE BACK. 183

PART yi.— SPECIAL ANATOMY.
The Back.

By dissecting the skin from the lateral thoracic incision
to the middle line of the back the panniculus is first ex-
posed, and then the manner in which, by uniting with the
combined ajDoneurotic exjDansions of latissimus dorsi, the
two small serrati (or superficialis costarum), and the dorsal
trapezius, it forms the lumbar faschia, which extends along
the whole length of the back, from the shoulders to the
quarters, where it blends with the gluteal investing layer.
It is attached to the superior spinous ligament and extends
about six inches on either side of the sj^ine.

Having divided panniculus and thrown it back, leaving
it attached to the lumbar faschia, we expose latissimus
dorsi, running from about the centre of the mass of muscle
forming the shoulder. Its muscular portion terminates
about opposite the eighth rib, where it blends with the
lumbar faschia. Superiorly situated to this is trapezius, a
triangular muscle, the apex of which is fixed to the tubercle
on the spine of the scapula, its base to the superspinous
ligament blending with the lumbar faschia posteriorly, an-
teriorly covered by levator humeri, and with it attached to
the cordiform upper portion of ligamentum nuchse. Its
tendinous portion extends from its apex to its base at the
withers, thus dividing the muscular portion into two
parts.

The posterior small serratus is exposed to view by re-
moval of panniculus. It presents a serrated margin infe-
riorly, its fibres runnmg in an upward direction from the
posterior margins of the seven posterior ribs to the lumbar
faschia.

Below this we see the external intercostals running in a
downward and backward direction from the posterior
.margin of one rib to the anterior margin of the next. Still

184 OUTLINES OF EQUINE ANATOMY.

lower, attaclied to tlie inferior extremity of the external
surface of the ribs, is the serrated margin of obliquus ab-
dominns externus. Having cut through and dissected
back latissimus dorsi and trapezius, the operator must
show the posterior attachment of rhomboideus muscle,
which arises from the cordiform portion of the ligamentum
nuchse to within six inches of the occiput, and from the
continuation of it as far back as the sixth dorsal superior
spinous process, from which points it runs to become in-
serted into the venter surface of the cartilage of elongation
of the scapula, and to that bone above serratus magnus.
Now rhomboideus may be cut through, and the fore limb
(if not by this time separated) may be drawn downwards,
and serratus magnus traced to its inferior attachments.
We now see the small anterior serratus muscle running
from the anterior border of the ribs from the sixth to
twelfth become attached by tendinous expansion superiorly
to the superior spinous processes of the dorsal vertebrae
from the second to the thirteenth. By dividing the dorsal
and lumbar faschia and turning the serrati downwards
upon their inferior attachments we expose

Transversalis eostarum, a thin, complex muscle, about
two inches broad, anteriorly attached to the transversa
process of the last cervical vertebra, in common with lon-
gissimus dorsi, and by small tendons attached to small
roughened surfaces on the posterior margin of all the ribs-
(in the first at the tubercle). By muscular attachments it
is connected to the anterior margin of the ribs as high up
as their tubercles. Posteriorly it becomes attached to the
transverse processes of the anterior lumbar vertebrae. Its
internal surface rests on the external intercostals, while its
superior margin is in direct contact, and almost blends
with

Longissimus dorsi. This is, posteriorly,, an immense
fleshy mass situated at the posterior part of the back and
on the upper surface of the lumbar vertebrae ; it is the
largest muscle in the horse's body, and is attached to thet
crista of the ilium, extending from the antero-inferior
to the supero-posterior spinous j^i'ocess, and occupying a
slight portion of its venter surface, whereby it become??
attached to the sacro-iliac ligament and the transverse
oblique and superior spinous process of the first and second-
sacral bones, and extends backwards into the triangular

THE BACK. 1-8^

space on tlie supero-Lateral part of tlie sacrum, where it is
attached to the sacral and to the ilio-sacral ligaments. It
is attached to the transverse, oblique, and superior spinous
processes of all the lumbar and of the posterior dorsal ver-
tebrae, to the posterior part of the heads of all the ribs, and
to the transverse processes of the twelve anterior dorsal
vertebrse, and the last cervical in common with transversalis
costarum. At its anterior part it is separated by cervico-
dorsalis from complexus major ; at the posterior part of the
withers it comes in contact with

Spinalis dorsi, which receives from it a large and strong-
tendon. It is attached posteriorly to the summits of the
twelve anterior superior spinous processes of the dorsal
vertebrge and to the posterior margins of the superior
spinous processes of the six anterior of these bones.
Anteriorly with ligamentum nuchse, it becomes attached to
the superior spinous processes of the three posterior cer--
vical vertebrse. This muscle internally lies in contact with
its fellow of the opposite side, for the ligamentum nuchse
is here deficient.

The posterior cervical artery, after passing between the
first and second ribs, and giving off the first intercostal
branch, runs over spinalis dorsi to reach the external sur-
face of ligamentum nuchse, along which it runs up the
neck parallel to the vertebral column. It arises on the
right side by a root common to it, and the dorsal artery,
from the right arteria innominata, round the common root,
the recurrent or inferior laryngeal branch of the right pneu-
mogastric nerve winds from without inwards and then runs
up the neck; on the left side these two arteries arise
separately, for the left recurrent nerve passes round the
aorta. The dorsal artery gives off a branch which runs-
underneath the heads of the ribs to meet the sixth inter-
costal artery, the first given off by the posterior aorta.
From this arch run the third, fourth, and fifth intercostals ;
the second intercostal is the next branch given off by the
dorsal, which subsequently passes over cervico- dorsalis
towards the withers. By removal of longissimus dorsi and
transversalis costarum we show a series of muscles running-
obliquely downwards and backwards from the superior
spinous processes to the oblique processes of the vertebrse,
and on examination we find this arrangement obtains in;'^
the cervical lumbar and dorsal regions constituting the

186 OUTLINES OF EQUINE ANATOMY.

Semispinales colli, dor si, et lumborum, wliicli com-
mences at the superior spinous process of the dentata and
extends to the sacrum. It is composed of a chain of muscu-
lar fasciculi, which run obliquely downwards and bachwards
from the superior spinous processes of the vertebrae to the
oblique processes of the vertebrae posteriorly placed to these,
sometimes passing over two or three prior to insertion. A
somewhat similar muscle is

Intertransversales colli, dorsi, et lumborum, which is
composed of a series of fasciculi, which in the neck are
situated between the transverse processes of the vertebrae,
in the back are blended with levatores costarum, and in the
loins are found between the transverse processes.

Levatores costarum are a series of small triangular
muscles arising from the transverse processes of the dorsal
vertebrae, and running to the anterior border and external
surface of the ribs as high up as their necks ; superiorly
they blend with intertransversales dorsi, and they are
merely the superior parts of the

Intercostales externi, which consist of muscular and ten-
dinous fibre intermixed, which run obliquely downwards
and backwards from the posterior margin of one rib to the
anterior margin of the rib immediately posterior to it.
They extend no lower than the inferior extremities of the
ribs, for between the cartilages the

Intercostales interni fill the intervening spaces with
fibres running obhquely downwards and forwards. Those
portions of these muscles situated between the sterno-
costal cartilages (which are attached inf eriorly to the lateral
parts of the sternum) are termed sterno-costales externi.
From this point upwards we see the internal intercostals
situated internally to the external intercostals, the artery,
vein, and nen^e being, during a considerable part of their
course, between the two muscular layers thus formed. The
pleura costalis covers the inner surface of the internal
intercostals.

The source of the intercostal arteries has been already in-
dicated. From their origin they run over the lateral part
of the bodies of the dorsal vertebrae, giving off medullary
tranches to these bones ; of those intercostals which arise
from the posterior aorta the right are somewhat the longest,
and before reaching the intercostal spaces pass above the
thoracic duct and vena azygos. In passing the interver-

THE BACK.

18T

tebral foramen, the artery gives off a branch which imsses
inwards to siipijly the sjmial cord and its membranes. It
next sends a large branch to the muscles of the baclc, and on
£rst gaining the intercostal space is at the anterior margin
of the rib behind, but soon gains the posterior margin of
the rib in front, along which it passes protected by the bony
groove, and by the intercostal muscles, between which it is
placed. It sends ramuscules to the ])leura, muscles, ribs,
and skin in the neighbourhood, and the anterior intercostals
help to supxDly serratus magnus ; they are therefore the
largest. At the inferior part of the intercostal spaces
these vessels anastomose with the internal thoracic artery
anteriorly, posteriorly with that branch which it sends
along the inferior extremities of the false ribs. Thus the
posterior intercostals indirectly supply the abdominal mus-
cles and anastomose with the lumbars, circumflex ^ of the
ilium, epigastric, and abdominal branch of the internal
thoracic.

The intercostal veins, after accompanying the arteries
as far as the thorax, for the most part empty themselves
into the

Vena azygos, a vessel which arises under the loins and
passes with the thoracic duct and posterior aorta through
the hiatus aorticus (a foramen of the diaphragm) into the
thorax, where they pass in the superior part of the medias-
tinum underneath the bodies of the dorsal vertebrae, vena
azygos being on the right, posterior aorta on the left, and
the thoracic duct centrally placed. This vein passes to the
anterior vena cava, with one of the branches of which it
communicates by means of a subcostal branch, into which
the third, fourth, and fifth intercostal veins pass, thus
completing the analogy of the arrangement of the arteries
and the veins of this region, for the second intercostal and
subcostal veins pass to the dorsal vein, the first intercostal
to the posterior cervical. The blood from the intercostal
veins therefore passes to the anterior vena cava. The in-
tercostal nerves are derived from the dorsal intervertebral
nerves, each of which on emerging from the intervebral
foramen, after sending fibres to and receiving fibres from the
gangliated cord of the sympathetic, sends superior branches
to longissimus dorsi and the other structures on the back,
while its inferior branch runs between the ribs. Those
most posteriorly situated are continued from the inferior

3 88 OUTLINES OP EqUINE ANATOMY.

extremities of the intercostal spaces over the external
surface of transversalis abdominis, forming remarkable
parallel white cords (falsely termed abdominal ribs). The
most ]3osterior of these are derived from the lumbar
nerves which resemble the dorsal, but, of course, do not
possess intercostal branches.

The THORAX must now be opened, which may be done
by cutting through the superior and inferior extremities of
the ribs from the second to about the twelfth by means of
a saw, and removing the separated portion of the wall of the
chest by cutting through the first and twelfth intercostal
muscles. The pleura or serous lining membrane of the
chest is thus exposed, and since it is very transparent we
can see the structures it covers very plainly through it.
The thorax is the anterior cavity of the trunk. It is
pyramidal in form, its apex being anteriorly placed, its
base cut off obliquely from below upwards posteriorly.
Superiorly it is bounded by the under surfaces of the^
bodies of the dorsal vertebrae, which centrally form a
prominent ridge, which anteriorly from the sixth vertebra
is bounded on either side by a prominent fleshy mass, the-
thoracic ])ortion of longus colli. On either side the roof of
the thorax is formed by the arch of the ribs, while the
straighter portion of them passes downwards to articulate
with the sternum through the medium of the costal carti-
lages, thus with the aid of the intercostal muscles form-
ing the sides of the thorax. Its floor is about one half-
the length of the roof, and is formed of the sternum with
its cartilages. Its apex is the space between the two first
ribs, through which important structures pass, i. e. longus
colli muscles (2), common carotid, axillary (2), vertebral
(2), inferior cervical (2), external pectoral (2), arteries with
the corresponding veins (jugular vein corresponds to
carotid artery), trachea, oesojDhagus, pneumogastric, recur-
rent, phrenic, gangliated cord of sympathetic nerves.

The base of the thorax is formed by the anterior, coru
vex, surface of the diaphragm, the thin expanded muscle
which separates this cavity from the abdomen. The

DIAPHRAGM presents centrally a heart-shaped tendi-
nous portion, the fibres of which are much interlaced, and
which, on the right side by separation of its fibres, forms
the foramen dextrum, by passing through which the
posterior vena cava gains the cavity of the chest, during

THE BACK. 189

its passage receiving blood from the flat plirenic or dia-
phragmatic venous sinuses. From the outer margin of
this tendinous portion muscular fibres radiate towards the
inner surfaces of the inferior extremities of the twelve
posterior ribs, or of their cartilages, where thej become
inserted in forming digitations with transversalis abdo-
minis, and towards the upper surface of the ensiform
cartilage. The indentation in the upper part of the tendon
is filled bj three muscular masses, two of which arise from
the left, the third from the right side of the tendon. Between
the right muscular mass and the central one is foramen
sinistrum, through which the oesophagus and the pneumo-
gastric nerves pass in their course from the thorax into the
abdomen; subsequently these two masses combine and
form a tendon, the right crus, which becomes attached to
the inferior vertebral ligament as far back as the fifth
lumbar vertebra; the third mass terminates in a much
shorter tendon is termed the left crus of the diaphragm,
and becomes inserted into the inferior vertebral ligament
below the body of the first lumbar vertebra. Between the
right and left crura is situated hiatus aorticus, which
admits the passage of the thoracic duct, posterior aorta, and
vena azygos, while passing through this opening the pos-
terior aorta gives off the phrenic artery which supplies the
crura of the muscle. That portion of the diaphragm ex-
tending from the spine to the internal surface of the last
rib passes over the anterior part of the inferior surface
of the psoas muscles, and above it also we see the gan-
gliated cord of the sympathetic and the greater and lesser
splanchnic nerves passing on either side.

The chest is lined, and the viscera it contains covered
by the pleura, a serous membrane arranged in such a
manner as to form two sacs, one on each side of the
cavity, which lie together along the middle line so as to
form a septum extending in an antero-posterior direction,
consisting of two adjacent layers of pleura in some parts
in close apposition, in others separated by the interposi-
tion of important structures, but postero-inferiorly pre-
senting numerous perforations, whereby one pleural sac
is brought into communication with the other. This is
the mediastinum, and extends from the internal surface
of the two first ribs to the central line of the diaphragm.
■Centrally it contains the heart, being reflected to form

190 OUTLINES OF EQUINE ANATOMY.

tlie external serous layer of tlie pericardium. This is tlie
'middle onediastinum, while those portions anteriorly and
posteriorly placed to the heart are the anterior and pos-
terior mediastina. The anterior mediastinum, therefore,
contains the following structures ; anterior aorta and two
arterise innominatse with the commencement portion of the
branches given off by them ; the anterior vena cava with
the terminating portions of some of its component veins ;
part of the trachea and oesophagus, pneumogastric, phrenic,
recurrent, and sympathetic nerves and thoracic duct, and
superiorly the terminating portion of longi colli (right and
left) ; interiorly, the thymus gland or its remains. The
middle mediaslinum is mainly occupied by the heart en-
closed in the pericardium, and superiorly may be dis-
tinguished the large vessels which it receives or gives off
(including vena azygos, which it receives indirectly), and
which serve to attach it to the under surface of the spine.
Also we here see the oesophagus situated on the right side
of the base of the heart ; the trachea terminating in
bifurcating to form the right and left bronchi, and the
thoracic duct winding from the right to the left side towards
its termination. From the supero-lateral parts of this
mediastinum also we find the visceral pleura projecting, to
surround the right and left lungs. Through this medias-
tinum also the two pneumogastrics, the left recurrent and
the two phrenic nerves, run. The posterior mediastinu^l
is much longer suj)eriorly than inferiorly, and is j^erforated
inferiorly. At its superior part are three vessels which,
after passing through or while going to hiatus aorticus,
course along the under surface of the spine. On the
right side vena azygos, on the left the posterior aorta ;
centrally the thoracic duct which seems to be simply a
space between the two, so thin and uncoloured are its
walls. Lower down the oesophagus accompanied by the
two pneumogastric nerves courses through this medias-
tinum towards the foramen sinistrum, with it also runs the
left lohrenic nerve. The right 2?lirenic nerve with posterior
vena cava passes through a sj^ecial fold of pleura situated
between two lobes of the right lung.

We have now examined the pleura and have seen that
it is divided into a parietal and a visceral portion ; the
former consists of the costal and phrenic, the latter of the
pulmonary and raediastinal portions. In health these parts

THE BACK. 191

lie in contact with one another, the pleural sac being prac-
tically obliterated, only producing sufficient serous fluid to
obviate any friction which might be caused b}^ the move-
ments of the parts. Thus any enlargement of the thorax
causes distension of the lungs, for air rushes in through the
trachea to fill up the extra space. In disease frequently
large quantities of fluid collect here, and membranes are
formed which, by causing union of the parietal to the
visceral portion of the pleura, lead to obliteration of the
sac, placing the animal in a condition analagous to that
normally obtaining in birds, which class of animals is
characterised by absence of pleura. Where the parietal
comes into connection with the visceral pleura the bronchi
and pulmonary arteries enter the lung, and the pulmonary
vems emerge from it. This is termed the root of the lung".
(The root of the left side is attached to the base of the
heart.)

The trachea breaks up into two bronchi. The right is the
largest, and passes to the right, being crossed by the oeso-
phagus. It is larger than the left, and breaks up into three
parts on joining the right lung ; for this lung is larger
than the left, which is deficient centrally to allow room
for the movement of the apex of the heart in a direction
upwards and to the left. And it has also three lobes, while the
left has hut two. Between its middle and posterior lobes is
situated the pleural fold for the posterior vena cava and
right phrenic nerve.

The bronchi are composed of complete cartilaginous
rings ; they divide and subdivide in the substance of the
lung, and the cartilaginous rings become thinner and divided
into several small portions until at last they disappear ; so
in the smaller bronchial tubes the walls are membranous.
Between the cartilaginous rings and the mucous membrane
are situated unstriated muscular fibres, extending in a cir-
cular manner comi^letely round the tubes. The mucous
membrane itself at first, like that of the trachea with which
it is directly continuous, presents columnar ciliated ej^i-
thelium ; but in the smallest bronchi the cells assume the
tessellated character and lose their ciliae, so that here it
resembles serous membrane. These minute bronchial tubes
terminate in the air-cells or infundibula, elongated spaces
with saculated ivalls (air-sacs), on the external surface of
which the pulmonary capillaries are distributed in so close

192 OUTLINES OF EQUINE ANATOMY.

a network that the meshes are not so large as the vessels
themselves ; and to bring about more complete aeration of
the blood, in consequence of the close connection of the
air-cells, each layer of capillaries is in apposition on both sur-
faces with the thin wall of an air-cell, which has here become
but little more than a layer of basement membrane covered
by simple tessellated epithelium. Thus the air and the
blood do not come into direct contact, but interchange of
gases takes place by the process of osmosis through the
layers of epithelial cells of the air- sacs and of the capillaries
and their respective basement membranes. Two arteries
pass to the lungs ; of these the bronchial, derived by a
root which it shares with the oesophageal, from the posterior
aorta or from the sixth intercostal artery, is the nutrient
vessel of the organ ; while the pulmonary artery is the func-
tional vessel, which brings that • blood which requires aera-
tion (and which will be shortly noticed) . The blood obtained
•through these two vessels seems to become mixed in the
capillaries, and returns either by the pulmonary veins into
the heart, or by the bronchial veins into vena azygos, and
so indirectly into the anterior vena cava. The lym])liatics
of the lungs are numerous and converge towards certain
bronchial lymphatic glands, which may be found as grey
nodular bodies at the root of the lungs. The nerves are
the pneumogastric and the sympathetic, which intermix
their fibres intimately in forming the bronchial plexus at
the root of the lung. All these structures are united
together by areolar tissue, to which the term jpare7ichyma
is applied; but this term is very indefinite, sometimes
being used to indicate the whole lung-tissue as opposed to
the pleura, its use therefore should be discontinued. If
we now remove the exposed lung by cutting through its
root we shall see the HEART, in situ. It is enclosed in a
dense membrane, the pericardium, and presents a base and
an apex ; and to its base, which is superiorly placed, vessels
from above, from behind, and from before, are attached,
and serve to sling it in position. The pericardium consists
-essentially of a membrane composed of white fibrous tissue,
fibrous pericardium, which extends from these vessels at
the base of the heart, in a downward direction, to become
attached to the upper surface of the ensiform cartilage
and posterior part of the sternum. It is covered externally
by the layers of pleura forming the middle mediastinum,

THE BACK. 193

wMch here separate to accommodate the central organ of
circulation. Internally it presents a smooth surface, for it
is lined by a serous membrane, serous pericardium, which
becomes reflected from the base of the heart in a downward
direction over that organ, which it invests as far as the
apex, and thus forms a closed sac, pericardial sac, which
sometimes contains a little serous fluid, and allows the
frictionless play of the heart on the inner surface of the
fibrous pericardium, whose function is to restrain its
excessive action.

If we have opened the chest on the right side we shall
now be able to see the large veins which bring the blood
from the various parts of the system to the right or pulmo-
nary division of the heart.

Anterior vena cava commences at the junction of the
jugulars between the two first ribs, and runs directly back-
wards to open into the supero-anterior part of the right
side of the heart. It receives branches corresponding to
the arteries given off by the arteriae innominatae, — axillary,
vertebral, dorsal, internal thoracic, and several others,
including

Vena azygos, a vein which commencing underneath the
loins from the most anteriorly placed lumbar veins, runs
in a forward direction underneath the spine with posterior
aorta and the thoracic duct (being situated most to the
right side). About oioposite the sixth dorsal vertebra it
dips downwards to open into the anterior vena cava just at
its termination, and during its course receives the thirteen
posterior intercostal veins and the subcostal branch from
the dorsal ; just before its termination it receives the bron-
chial veins. In consequence of its situation the left inter-
costal veins are longer than the right, but we have observed
an accessory vena azygos on the left side of the spine of the
ass. The anterior vena cava at its termination for about
three inches presents red muscular fibres, so that it seems
to be a continuation of the wall of the auricle ; thus, in
the heart removed from the body, it may be distinguished
from the

Posterior vena cava, which, on emerging into the thorax
through foramen dextrum enclosed in a special double fold
of pleura (with the right phrenic nerve), runs direct to the
postero-superior part of the right side of the heart, receiving
no vessels in its course. The large arteries may be seen

13

194 OUTLINES OF EQUINE ANATOMY.

best by laving open tbe left side of the thorax. From the
base of the heart, between the two ventricles the aorta
passes upwards for about two inches. It is a large vessel
with stout elastic walls, and gives off the coronary arteries
to the substance of the heart in a manner which will be
hereafter described. It terminates superiorly in the anterior
and posterior aortge. The terminal portion of the trachea
lies in contact with its right side, while on the left is the
pulmonaiy artery and also the left pneumogastric, which on
passing gives off its recurrent branch, coursing from without
inwards around the posterior margin of the aorta, and
running forwards and up the neck to supply all the mus-
cles of the larynx with the exception of the crico-thyroideus.
In consequence of this arrangement many authorities con-
sider that pressure upon this nerve durmg the heart's
action, by producing atrophy of the muscles it supplies,
causes that defect in respiration termed " roaring."

The anterior aorta, after coursing for a short distance
through the anterior mediastinum, situated below and
slightly to the left of the oesophagus and trachea, terminates
in forming the two arterise innominatse, the right of which is
much the largest. The right arteria innominata runs in
a forward direction as far as the first rib. The first branch
it gives off superiorly is the common root of the anterior
dorsal and lyosterior cervical arteries (which have been already
noticed) ; around this from without inwards the recurrent
branch of the right pneumogastric winds prior to passing
uj) the neck. These vessels arise se23arately on the left side,
for, as just noticed, the recurrent branch of that side winds
round the aorta. From its anterior part the right arteria
innominata gives off the vertebral, inferior cervical, axillary,
and common carotid arteries. The left arteria innominata
gives off corresponding branches with the exception of the
common carotid, and from the inferior part of each vessel is
given off an internal thoracic artery, which runs along the
floor of the thorax at the lateral j^art of the superior sur-
face of the sternum. It gives off branches outwards to
anastomose with the external pectoral and intercostal
branches, and opposite the ensiform cartilage divides, one
of its branches running along the floor of the abdomen to
anastomose with the epigastric artery ; the other along the
inferior margins of the false ribs, anastomoses with the
terminal extremities of the posterior intercostal arteries,

THE BACK. 195

and sends brandies backwards to supply tlie abdominal
muscles. The common carotid is situated below the trachea
in the anterior -psivt of the thorax, between the two first
ribs. It arises from the right arteria innominata, and ter-
minates in bifurcating to form the right and left carotid
arteries.

The thoracic duct after passing through hiatus aorticus
runs forwards situated between vena azygos on the right
and posterior aorta on the left. Opposite, about the sixth
dorsal vertebra, it swerves to the left side and passes towards
the anterior opening of the thorax to terminate in the left
jugular or the left axillary vein. Its walls are very thin, so
that its course is demonstrable but with difficulty. Almost
in apposition with the inner surface of the first rib we may
find the inferior cervical ganglion, to which the sympa-
thetic cord running down the neck passes, after presenting
a little below and in front a small nodular enlargement, the
middle cervical ganglion. The inferior cervical ganglion
also receives a band of nerve-fibres coming from the fora-
mina in the transverse processes of the cervical vertebrse,
made uj) of fibres derived from the cervical nerves while
emerging through the intervertebral gaps in the neck.
From this ganglion backwards extends the gangliated cord,
running first against the lateral part of the longus colli
muscle, then at the suj)ero-lateral part of the thorax against
the heads of the ribs, having a ganglion opposite each
vertebra and being visible through the pleura costalis, by
which only it is covered. Each ganglion receives fibres
through the nearest intervertebral gap from the spinal cord,
and sends fibres to the neighbouring intercostal nerves
From the thirteen or fourteen posterior ganglia fibres
are given off which combine to form the greater splanchnic
nerve, with difficulty separable from the gangliated cord as
it runs backwards, and passes above the diaphragm with
the psoas muscles to reach the semilunar ganglion in the
antero-superior part of the abdomen, some of its fibres run-
ning directly to the kidney. The lesser splanchnic nerve
arises from the two or three posterior dorsal ganglia, and
accompanies the greater nerve, terminating in a similar
manner. The inferior ganglion gives off fibres which run
downwards to assist the pneumogastric in forming the car-
diac i^lexus at the base of the heart, and the i^ulmonary at the
root of the lungs. These plexuses have communication with

196 OUTLINES OF EQUINE ANATOMY.

the phrenic nerve, whicli arises in the neck from branches
of the third, fourth, and fifth cervical nerves, commnni-
cating with the axillary plexus, and runs backwards over
the base of the heart to the diaphragm, that of the left side
passing through the posterior mediastinum, the right
phrenic nerve accompanying the posterior vena cava in its
special fold of pleura.

We can now, by division of the above-described vessels,
remove the heart from the thorax. We find that it is a
hollow muscular organ, cone-shaped, with its base upwards,
having its apex directed downwards and backwards. It is
covered by the visceral layer of the serous pericardium,
which gives it a glistening appearance, and through which
may be seen the furrows on the surface which mark its
division into several cavities. Of these we see one running
downwards on each side, ventricular furrow, one^running
horizontally around the base of the heart, auriculo-ven-
tricular furrow. These contain the vessels of the organ
with nerves embedded in a quantity of fat. The two
ventricular furrows do not reach the apex of the organ,
but meet on the right side a little above that point.

The heart is divided into two sides ; 7igM or imlmonary
heart, left or systemic heart. In the foetus these sides com-
municate by the foramen ovale, which pierces the auricular
septum, being partially closed by a valvular arrangement
of the lining membrane of the heart ; but in the adult,
under normal conditions, this becomes impervious, being
still recognisable on the right side of the septum as a light
circular spot, fossa ovalis, surrounded by a prominent elastic
ring, annulus ovalis. Thus, after birth in mammalia, the
two sides are distinct ; each side consists of two cavities —
an auricle superiorly, a ventricle inferiorly. The heart is
lined by serous membrane, endocardium, which is con-
tinuous with the serous membrane lining the large vessels,
which run to or from its cavities. On the left side, espe-
cially in the auricle, we find a layer of yellow elastic tissue
between the muscular structure and endocardium. The
hasement structure of the heart is situated at the point of
junction of the four cavities. Here we find a firm, irregular-
shaped piece of fibro-cartilaginous substance, which in the
ox is always, in the horse occasionally, ossified ; from this
run three yellow elastic rings ; one to the right side, cir-
cumscribing the right auriculo -ventricular opening ; another

THE BACK. 197

backwards and slightly to the left, surrounding the left
auriculo-ventricular opening ; the third to the left slightly
forwards, from which superiorly the elastic layer of the
aorta commences ; while outwardly it is continued to form
a ring for the commencement of the pulmonary artery
(this bemg the weakest of them all). To these rings is
attached the muscular structure of the heart, consisting of
fibres all arranged in a more or less oblique manner. Each
cavity possesses fibres peculiar to itself, while the two
auricles are connected together by common fibres, and the
two ventricles also by common fibres, the auricles thus
being separable from the ventricles without division of
muscular fibre. Thus the auricles first contract together
(synchronously), then the ventricles contract simultaneously.
The muscular walls of the heart are smooth externally,
but present ^prominences and depressions internally. The
right auricle is situated at the supero -anterior part of the
heart. It has thin walls, which collapse when the cavity is
empty, and is divided into two parts, sinus and apiJendix.
It is termed auricle from the likeness of the corresponding
part in the human subject to a dog's ear ; in the horse the
appendix portion assumes this figure, and is inclined to
the left side, where it terminates in a point. The inner
surface of this part presents prominences of muscular sub-
stance arranged in a reticulated manner, musculi i^ectinati,
separated by dej^ressions, foramina Thehesii, into the latter
small blood-vessels are supposed to open. The sinus portion
presents five openings. At its supero-anterior part it
receives the anterior vena cava, with which vessel its
muscular walls are structurally continuous. At its supero-
posterior part the posterior vena cava, below which is the
double opening of the cardiac or coronary veins. The walls
of the sinus present but few muscular prominences ; a broad
ridge separates the opening of the anterior from that of the
posterior vena cava, this is tuherculum Loweri ; below it may
be seen the remains of the foramen ovale (fossa ovalis and
annulus ovalis). In the human subject the anterior margin
of this opening presents the crescent-shaped Eustachian
valve ; we have not seen it in the ass. Between the coro-
nary opening and the termination of posterior vena cava is
a thin double layer of endocardium, with a small quantity
of muscular structure intervening, the valve of Thehesius.
The inferior part of the auricle presents the right auriculo-

198 OUTLINES OP EQUINE ANATOMY.

ventricular opening, consisting of a smTonnding fibrous
ring, from whicli hang three flaps, composed of double
layers of endocardmm (the serous membrane lining the
heart, which resembles the internal coat of blood-vessels),
which serve to regulate the passage of the blood from one
cavity to the other. They are triangular in shape, having
their outer boundary attached to the circular fibrous ring,
with its terminating angles confluent with the other two
sides which form the free margin to which powerful fibrous
cords (cliordce tendinece) are attached. These chordae ten-
dinese nin to large projections from the inner surface of
the muscular wall of the ventricle, which receive the
special name musculi loapillares ; they are three in number,
one projecting from the outer wall, two from the septum
ventriculorum. From one musculus papillaris chordae ten-
dinese run to each of the three flaps of the tricuspid valve.
The wall of the right ventricle is thicker than that of
the auricle, and presents on its internal surface three
forms of muscular prominences (carnese columnae). The
mnsculi impillares, having one end free, constitute the
first set; the moderator lands run from one side of the
cavity to the other, often consist simply of yellow elastic
tissue covered by serous membrane, they form the second ;
while the third or true carnece columnce are attached by
both ends and by one margin, thus resembling the musculi
pectinati of the auricle. The right ventricle does not
extend to the apex of the heart, which is wholly formed by
the left, but superiorly it forms a funnel-shaped cavity
(termed conus arteriosus), behind the posterior flap of the
tricuspid valve, from the upper extremity of which the
pulmonary artery commences. The communication of the
ventricle with this vessel is guarded by three crescentic
flaps which constitute the semilunar pidmonary valves. They
have a free and an attached margin. The free margin
centrally presents a point on which we sometimes see a
small nodule {corpusculum arantii), which serves to ensure
complete closure of the opening by the valves. The
attached margin is continuous with the pulmonary fibrous
ring and its extremities meet the other flaps. The
pulmonary artery runs backwards and in passing under
the posterior aorta is connected to it by an imi)ervious cord,
the remains of the ductus arteriosus of the foetus. After this
it bifurcates, its larger division passing to the right lung,

THE BACK. 199

its smaller to tlie left. On examining tlie inner surface of
this vessel three saccular dilatations (sinus Valsalvce) of its
walls may be noticed behind the valves, serving to accom-
modate them during the rush of blood from the ventricle,
and to allow blood to collect behind the flaps in sufficient
quantity when this rush ceases to throw the valves into
position and thus prevent regurgitation of blood. The
pulmonary arteries divide and subdivide in the lungs,
and finally terminate in capillaries in which the blood is
oxygenated, and from which it is carried by the pulmonary
veins to the left auricle of the heart. The pulmonary
veins unite and reunite until by (generally) four openings
they pour their contents into the heart ; they never leave
the lung substance, for it is here also attached to the heart
substance. These veins have no valves. The left auricle
very much resembles the right, from which, however, it
differs in the greater amount of yellow elastic tissue lining
it, and in presenting more marked musculi pectinati and
foramina Thebesii,but no fossa ovalis,annulus ovalis, tuber-
crum Loweri, or Thebesian valve. Its auriculo -ventricular
opening too is guarded by a stout valve consisting of but
two flaps, the hicuspid or mitral valve. It leads into the
left ventricle, similar in structure and figure to the right
ventricle, but with only two musculi papillares, both of
which are attached to the outer wall of the cavity. Its
moderator bands generally contain muscular fibres, and its
walls consist of very thick muscular substance. This com-
partment, however, at the extreme inferior part, where it
alone forms the apex of the heart, consists of little more
than a double layer of serous membrane, the endo-
cardium lying in contact with the pericardium. The thick-
ness of the muscular wall is related to the force required
in driving the blood through the system when the elasticity
of the coats of many large and strong vessels has to be
temporarily counteracted. The blood from this cavity
passes in an upward direction into the aorta, which is
situated on the right side of the pulmonary artery, to
which one of its primary divisions (posterior aorta) is
connected by an elastic ligament. The opening into this
vessel, like that of the pulmonary artery, presents semi-
lunar valves, but they are larger, stronger, and present
more marked corpora arantii ; while the sinus Valsalvse
into which they fit are deeper than those of the pulmonary

200 OUTLINES or EQUINE ANATOMY.

artery, so that tlie vessel is largest and its walls thinnest
and most liable to rupture here. From the posterior and
also from the internal sinus Valsalvse a coronary artery
arises, going to supply the substance of the heart. The left
coronary artery, the shortest, runs directly down the left
ventricular furrow, and its terminal branches anastomose
with those of the right at the point of union of the two
ventricular furrows. It gives off a branch in a posterior
direction which passes in the posterior auriculo -ventricular
furrow to the vessel of the right side. The right coronary
artery, after winding through the anterior auriculo -ventri-
cular furrow, meets the posterior branch of the left artery
and then runs down the right ventricular furrow to meet
the left artery at the inferior extremity. The blood from
the heart is returned by the coronary or cardiac veins,
of which the left is the longest ; they terminate almost
by a common opening in the right auricle as already
described.

The heart is supplied with nerve power from three
sources : By the ^neumogastric and gangliated cord of the
symjMtlietic through the medium of the cardiac plexus, and
by small symjKitlietic ganglia emhedded in its substance. The
latter endow it with its regularity of contraction (rhythmic
action), the pneumogastric serves to restrain, the glan-
gliated cord of the sympathetic to stimulate its action.

The muscular fibres of the heart are involuntary ; they
nevertheless present slight striation and a modena red
colour, similar to that of voluntary muscle. They differ
from the latter, however, in the imperfection of their
striation, in the absence of a sarcolemmatous sheath, and
in frequent anastomosis of the constituent fibrillse.

In the infero-anterior part of the thorax, at the lower
part of the anterior mediastinum, especially developed in
the foetus, in whom it extends a short way up the neck, is
the thymus gland, a body resembling a salivary gland in
appearance, and pouring the product of its lobules into a
central cavity, from which, as there is no duct, it seems to
be reabsorbed. It is a vascular gland, and is the true
" sweetbread."

THE POKE EXTREMITY. 201

. PAUT VII.— SPECIAL ANATOMY.

The Fore Extremity.

The skin having been dissected back from the withers
(a work rendered easy by the primary incisions on either
side) down to a little below the elbow- joint, the panniculus
is shown extending over the limb on the outside as far as
this joint, becoming indirectly attached to the spine of
the scapula, the point of the shoulder, the humeral ridge,
&c. Anteriorly it is somewhat intimately connected with
levator humeri, posteriorly it covers the muscles of the
shoulder, and dorsal trapezius, and extends on to the lateral
part of the thorax. From the lateral parts of the thorax
some fibres of panniculus run forwards to the internal
surface of the shoulder. The panniculus having been re-
moved, levator humeri must be traced in its attachments,
to the spine of the scapula (blending with trapezius), the
external ridge of the humerus, with the fibrous band run-
ning downwards from it, and the antero- inferior part of the
humerus. The latter attachment being also that of pec-
toralis transversus, which will be found running from the
under surface of the sternum to this attachment, and by
a broader part (almost separated from the former) to the
faschia covering the inner surface of the arm. By divi-
sion of levator humeri along the anterior margin of the
scapula, pectoralis anticus is exposed ; it is a triangular
elongated muscle arising from the lateral part of the cari-
niform cartilage and from the external surface of the an-
terior sterno-costal cartilages and muscles, and running
along the front of the shoulder, passing over pectoralis
magnus and growing thinner superiorly to blend with the
faschia covering antea spinatus and to reach the spine of
the scapula. Between this muscle and those of the neck
is situated a quantity of loose cellular tissue in which
much fat and the prescapular lymphatic glands are situ-
ated. The subscapulo-hyoideus muscle runs on the inner

20.-^ OUTLINES OF EQUINE ANATOMY.

side of pectoralis anticus, forming a broad muscular layer
attached to the tendinous aponeurosis of subscapularis ;
in proceeding up the neck about the middle third this
muscle becomes intimately connected with the internal
surface of levator humeri, so that these muscles are not
easily separable; it subsequently passes between the jugular
vein and the carotid artery to its insertion into the hyoid
bone.

The muscles connecting the fore limb to the various
neighbouring parts must now be divided (reference
should be made to the several regions under the heads of
which their attachments are described), and the external
scapular miiscles exposed, these are —

Antea spinatus, running from the anterior dorsal fossa
of the scapula, by a rounded prominent border clothing
the major portion of the anterior costa of that bone and
becoming attached to a ligament, which runs from here to
the coracoid process, between which and the bone pass the
dorsal scapular vessels and nerves. Inf eriorly it bifurcates
and with pectoralis magnus becomes inserted into the ex-
ternal and internal tubercles on the anterior part of the
humerus ; the surface between the two heads is lined by a
tendinous theca or sheath, which is reflected on the middle
tubercle of the bone to facilitate the gliding of the carti-
laginous superior extremity of

Flexor brachii or coraco-radialis, which having arisen
by a strong tendon from the coracoid process of the scapula,
after passing through this sheath, where its tendon is in-
dented to fit upon the middle tubercle, runs down the front
of the humerus inclined to the inner side, forming a pro-
minent muscular cord which sends a strong band of white
fibrous tissue downwards to extensor metacarpi magnus,
and becomes inserted into the roughened spot previously
noticed as situated at the supero-internal part of the an-
terior surface of the radius and into the capsular ligament
of the elbow-joint; at the antero-superior part of its tendon
we see some muscular fibres.

Postea spinatus is to be found in the posterior fossa
of the dorsum of the scapula, which it occupies for
its superior two thirds ; separating below it forms two ten-
dons, one of which is attached to the fourth or external
tubercle of the head of the humerus, while the other plays
over this, from which it is separated by a synovial bursa,

THE TORE EXTREMITY. 203

and becomes inserted into the upper part of tlie ridge
running down from the external tubercle. The inner sur-
face of the first head is attached to the capsular ligament
of the shoulder- joint.

Teres externus arises from faschia which covers postea
spinatus and extends as far forwards as the spine of the
scapula, also from the superior part of the posterior costa
of the scapula. It is at first composed of two layers, but
these combine inferiorly to become inserted into the lower
part of the humeral ridge. Between this tendon and the
lower tendon of postea spinatus the

Scapulo-humeralis externus is inserted, after passing
over the capsular ligament of the shoulder-joint and becom-
ing attached to it, and arising from a roughened ridge at
the postero-external part of the neck of the scapula at the
lower part of the fossa postea spinatus in front of caput
magnum, extending to a slight extent around its inferior
extremity to its posterior surface. By removing the superior
attachment of this muscle, we generally expose a branch
from the posterior scapular artery passing through the
medullary foramen of the scapula.

Underneath the above-named muscles to the posterior
surface of the humeral ridge the

Caput medium of the triceps extensor brachii is attached.
The triceps is that large mass of muscle which fills up the
triangular space between the scapula and the humerus ;
as its name indicates, it consists of three parts or heads,
named according to their respective sizes. Caput magnum
is attached superiorly along the major portion of the pos-
terior costa of the scapula, not extending, however, to
the extreme inferior part. It is attached to the cap-
sular ligament of the shoulder- joint and covers scapulo-
humeralis posticus, and at the extreme inferior part becomes
large and thick, and internally to its superior attachment
presents a groove in which rests the teres major vel in-
ternus ; between the two muscles is the posterior scapular
artery with its accompanying vein and nerve. It is a branch
of the axillary artery and runs upwards, sending branches
to the muscles, between which it runs to subscapularis.
The fibres of this head converge, and run towards the point
of the ulna, into which they become inserted through the
medium of a short stout tendon which passes over a bursa
prior to insertion. Caput medium runs from the posterior

204 OUTLINES OF EQUINE ANATOMY.

part of the humeral ridge to be attached by a wide inser-
tion to the tendon of the caput magnum and to the outer
surface of the olecranon. Caput parvum arises from the
upper part of the internal ridge which bounds the ole-
cranian fossa of the humerus and passes to the point of the
ulna and to the internal surface of its olecranian process.
The internal surface of this head is in contact with the
humeral vessels and nerves derived from the axillary
plexus; also above with the humeral attachments of

Teres interims, which arises from the superior part of
the posterior costa of the scapula, is externally in contact
with caput magnum as above described, and inferiorly
terminates by a tendon common also to latissimus dorsi, at
a roughened spot on the internal surface of the middle
third of the humerus ; over this tendon the humeral artery
and vein and several important branches of the axillary
plexus of nerves pass. It will be seen that this muscle
exactly corresponds in its course to the teres externus on
the outside of the limb. To the latissimus dorsi over its in-
ferior extremity runs the external thoracic branch of artery.

On looking at the external surface of the shoulder, we
see that the venter surface of the scapula is covered over
its inferior two thirds by

Subseapularis, which is covered by faschia, from which
subscapulo-hyoideus arises. Superiorly it presents a margin
of attachment divided into three projections, whereby it
leaves two triangular spaces for insertion of serratus
magnus. Inferiorly it becomes more narrow, and finally
for the most part tendinous, and inserted into the tubercle
situated on the inner surface of the head of the humerus.
The anterior margin of this muscle is in contact with
antea spinatus, which here presents a rounded surface apt
to be mistaken for another muscle until the limb is turned
over ; between these two muscles, above the coracoid pro-
cess, the anterior scapular artery (a branch of the axillary)
passes with its accompanying vein and nerve.

Attached to the process on the internal surface of the
coracoid process is the tendon of

Coraco-humeralis, which, emerging from between the two
muscles, passes over the insertion of subscapularis, over
which it plays through the medium of a bursa, then breaks
up into two muscular portions which go to be attached, the
superior one to the internal surface of the superior third of

THE FORE EXTREMITY. 205

the liumerus, the inferior to the superior part of the inferior
third of the anterior surface of that bone. Between these
two heads runs a branch of the humeral artery (with its
vein and nerve) to supply flexor brachii. The axillary
nerves and vessels will be found in contact with the upper
part of this muscle.

Scapulo- ulnar is runs from the posterior angle of the
scapula with caput magnum, and covering the internal
surface of the posterior part of the triceps, expands below
to become inserted into the inner surface of the olecranon
and the faschia covering the internal surface of the arm,
foi-ming an aponeurotic expansion which extends upwards
to blend with its superior attachment.

By removal of triceps we expose two muscles, both of
which are attached to the capsular ligaments of the joints
with which they respectively are in contact.

Scapulo-humeralis posticus consists of a few fleshy fas-
ciculi, which run from immediately behind the glenoid
cavity of the scapula, emerging from within the attachment
of caput magnum, and after passing over and becoming
attached to the capsular ligament of the shoulder- joint,
dip between the fibres of humeralis externus to become
inserted to the extreme postero- superior part of the hu-
merus immediately below the articular cartilage of the head.

Anconeus arises from the superior part of the ridges
which bound the olecranian fossa of the humerus (espe-
cially from the outer), becomes attached to the capsular
ligament of the elbow-joint, which extends around the
articular part of the fossa, and becomes inserted into the
antero- superior, inclined to the outer part of the olecranon.

Humeralis externus arises from the posterior part of
the humerus immediately beneath its head, where it covers
scapulo-humeralis posticus, and from the back of the bone
as far down as the supra - condyloid ridges. It winds
around the external surface of the bone in a spiral fossa
bounded by ridges (with the spiral nerve), passes beneath
the band of white fibrous tissue, mixed with yellow elastic,
which runs from the inferior extremity of the humeral
ridge to the external ridge of the inferior extremity of the
humerus, passes between flexor brachii and extensor meta-
carpi magnus beneath the tendinous band connecting
these two muscles, and having become attached to the
anterior part of the capsular ligament of the elbow-joint,

206 OUTLINES OF EQUINE ANATOMY.

forms a flat tendon whicli passes nnderneatli tlie inferior
portion of tlie internal lateral ligament, where it is lubri-
cated with synovia, and becomes inserted into the internal
surface of the head of the radius and into the inner
sharpened border of the ulna.

Muscles attached to the capsular ligament of the sca-
pulo -humeral joint :

Antea spinatus, postea spinatus, subscapularis, scapulo-
humerales externus and posticus, and caput magnum.
Flexor brachii is separated from it by a quantity of fat
and its bursa, coraco-humeralis by the subscapularis ten-
don and a bursa.

The axillary artery must now be viewed as a whole.
It commences from the anterior part of arteria innominata
within the chest, and takes a turn around the anterior
margin of the first rib below the inferior head of scalenus
at its posterior attachment. It thus gains the external
part of the thorax and the internal surface of the limb,
so that on raising the limb after division of the pectoral
muscles we see this vessel with its corresponding vein, and
the axillary plexus of nerves, with the axillary lymphatic
glands embedded in loose cellular tissue, in the neighbour-
hood of the shoulder- joint. It gives off arteria dorsalis
scapulse (or anterior scapular artery), posterior scapular
(or subscapular), external thoracic, and humeral arteries,
the course of which we have already noticed; also the
humeral thoracic which runs to supply pectoralis magnus
and antea spinatus at the point of the shoulder. The
humeral artery in its course along the internal surface of
the humerus gives off a hrcmch anteriorly, which passes
hehveen the tivo heads of coraco-humeralis to flexor hrachii,
a large branch hackivards to tricejos extensor hrachii,^ and a
branch inwards opposite the superior part of the inferior
third of the bone, which pierces its substance by imssing
through the medullary foramen. The artery then passes to
the anterior margin of the bone and breaks up into the
ulnar, spiral, and radial arteries. The ulnar runs back-
wards, and very soon breaks up to form a number of
smaller vessels, which all run to structures near the ole-
cranon. The spiral passes over the front of the elbow-
joint, and runs down the anterior surface of the radius
in company with a vein and nerve. The radial, after
passing over the internal surface of the elbow -joint, dips

THE PORE EXTREMITY. 207

underneatli flexor metacarpi internus, on the inner sur-
face of which it runs, in company with an artery, vein,
and nerve, as far as the knee, sending out branches to the
flexors in its course, even to fleccor metacarpi externus ; the
hranch to this muscle runs through the arch in the u7iion of
the ulna to the radius^ and in the passage gives off the medul-
lary artery of the radius.

The axillary plexus of nerves is formed by the union of
nerve -fibres from the three posterior cervical and the first
dorsal intervertebral nerves, which also receive a branch
from the sympathetic system. Emerging between the long
and short heads of scalenus, the plexus is thus separated
in winding around the first rib from the artery and vein by
the lower head of that muscle. From this point collections
of fibres pass in company with the corresponding arteries,
thus we find the dorsalis scapulce, humeral thoracic, external
thoracic, and subscapular nerves, which differ only in arrange-
ment from the arteries in that their fibres separate before ar-
riving at the parts which they supply, and become thus more
diffused over its surface. lu addition to these the axillary
plexus gives off the ulnar, spiral and radial nerves, for we find
no recognised humeral nerve. The radial runs with the artery
of the same name, and below the knee forms the internal
metacarpal nerve ; it gives off a branch which runs forwards
with the spiral artery to the front of the elbow -joint,
where it meets the true spiral nerve, which ran in a back-
ward direction, behind the humerus, piercing the fleshy
mass of the shoulder by passing between caput parvuni
and caput magnum to gain the inferior margin of hume-
ralis externus, with which it winds round the external
surface of the bone, gains the anterior surface of the joint,
and meets the artery, with which it runs to the extensor
muscles and the skin covering the front of the limb. The
ulnar nerve, from the point of the ulna, sends a loiig hranch
down behind the limb underneath ulnaris accessorius, which
below the knee becomes the external metacarpal nerve.

Two important veins are to be found in the region of
the shoulder. The humeral vein receives blood from the
radial and ulnar veins, and also from a branch which runs
to it from just in front of the termination inferiorly of
flexor brachii. It then runs up the limb posteriorly
placed to the artery and terminates in the axillary vein,
which in most respects resembles the artery and opens into

208 OUTLINES OF EQUINE ANATOMY.

tlie anterior vena cava. Along tlie internal surface of the
fore limb, in the living animal, we may see a large vein
running upwards along the subcutaneous portion of the
radius. This is the superficial brachial, cephalic, or
plat vein, from which blood is sometimes extracted by the
process of venesection ; at the insertion of flexor brachii
it sends a branch internally to that muscle to join the
humeral vein as above mentioned, but the main portion
runs along the groove between this muscle and extensor
metacarpi magnus, and proceeding upwards empties its
contents into the jugular vein ; opposite the front of the
elbow-joint this vessel receives the spiral vein. Now the
skin may be removed from the internal surface of the arm ;
this may be done by an incision along the central line from
the elbow- joint to the lower part of the knee, through the
circular horny process or chestnut found opposite the
inferior part of the superior third of the radius, and dis-
secting the skin backwards and forwards. It will be
advisable also to remove the integuments from the outer
surface of the limb as low as the knee, if sufficient time is
available for examination of both aspects of the arm (other-
wise the white fibrous tissue of the outside will become
dry and hard by exposure to the air). Thus the aponeu-
rotic expansion of pectoralis transversus and panniculus is
exposed, it inferiorly gradually blends with the ordinary
subcutaneous areolar tissue. By division of it we bring to
view the faschia of the arm, a dense layer of white fibrous
tissue running round the back of the limb from the outer
sharpened border of the ulna to the inner surface of the
radius, supero -internally it terminates by blending with the
internal lateral ligament of the elbow-joint, and by becoming
attached to the point of the ulna, between these two attach-
ments it receives the insertion of scapulo-ulnaris. Inferiorly
it blends with the annular ligament of the knee, which is
nothing more than a thickening of this faschia in conse-
quence of the addition to its substance of fibres, some of
which run from the inner surface of the radius just above
the knee to trapezium, others from the inner surface of the
knee obliquely upwards and outwards. From the internal
surface of the annular ligament of the knee thick fibrous
bands pass to enclose the tendons situated at the back of
the knee-joint. The first muscle posteriorly situated to the
radius is —

THE TORE EXTREMITY. 209^

Flexor metacarpi internus. It arises from tlie internal
surface of the inferior extremity of the humerus, where it
is attached to a slightly prominent ridge, j^asses over the
caj)sular ligament of the elbow- joint, to which it is firmly
attached, and runs downwards along the internal margin of
the posterior surface of the radius covering the radial artery y
vein, and nerve. It then runs through a synovial sheath
behind the knee, and becomes inserted into the head of the
inner small metacarpal bone. This sheath is strengthened ex-
ternally by a fibrous band reflected from the internal surface
of the annular ligament, which superiorly blends with the
stipe7'ior siisiDensory ligament, a dense white fibrous tissue
band running from the posterior part of the inferior ex-
tremity of the radius to the perforans and the perforatus
tendons. This septum is broad superiorly, but inferiorly
grows narrow, and separates the tendon of flexor metacarpi
internus from those of the perforatus and the perforans.
Opposite the superior part of this reflection a small branch
runs from the radial artery to become superficially placed
on the inner surface of the limb, the small metacarpal,
which anastomoses with the recurrent branch of the large
metacarj^al, and gives off the medullary artery of the large
metacarpal bone. The annular ligament of the knee
terminates below in a definite band of white fibrous tissue
at the inferior part of the middle third of the internal
surface of the inner small metacarpal bone ; between this
bandand the remainder of the ligament the inyier metacarpal
vein passes to gain the cutaneous surface of the limb, and
from it the superficial radial vein arises, which passes
upwards to the superficial brachial vein.

Flexor metacarpi medius is situated posteriorly to flexor
metacarpi internus. It is broad superiorly, where we see
some of its tendinous fibres running transversely from the
point of the ulna to get a firm insertion into the capsular
ligament of the elbow-joint, and into the inferior part of
the ridge running upwards from the inner condyle of the
humerus. Under this part run the ulnar artery, vein, and
nerve. The ulnar nerve proceeds down the back of ih&
limb at first underneath ulnaris accessorius, and then about
opposite the inferior part of the middle third of the radius
passes under the tendon of that muscle to gain the inner
surface of flexor metacarpi externus. The postero-superior
part of flexor metacarpi medius blends with ulnaris acces-

14

210 OUTLINES OF EQUINE ANATOMY.

sorius, becoming attaclied firmly to tlie posterior surface of
the superior extremity of the olecranon ; inferiorly it blends
with the faschia of the arm and with flexor metacarpi
internus, the tendinous band so formed becoming firmly
attached to the superior margin of trapezium, and to the
annular ligament of the knee.

Flexores pedis perforansand perforatus. — Attached to the
infero- posterior part of the ridge running upwards from
the inner condyle of the humeiiis and to the capsular liga-
ment of the elbow-joint, are numerous muscular fasciculi,
comprised mainly of four masses which run down the pos-
terior surface of the radius and inferiorly combine, three
of them forming the perforans tendon, the other the per-
foratus ; the first is triangular in shape, being concave on
its posterior surface for the reception of the second. To
the inner margin of each tendon runs a part of the supe-
rior suspensory ligament, that to perforatus being the
widest and strongest. Here the tendons of radialis and
nlnaris accessorius blend with that of perforans. The
tendons of perforans and perforatus with the metacarpal
artery, vein, and nerves run together in a synovial sheath,
separated from that of flexor metacarpi internus by a fibrous
layer from the annular ligament. This sheath superiorly
is bounded by the superior suspensory ligament, extends
downwards for about four inches, terminating inferiorly
opposite the heads of the small metacarpal bones, where it
is bounded by the subcarpal ligament, a diffused layer of
ligamentous fibres which arises from the inferior part of
the annular ligament, where it immediately invests the pos-
terior surface of the small bones of the knee, and runs
mainly to the perforans tendon, though a few of its fibres
run on either side of that tendon to perforatus. Perforans
is said to form a sheath for perforatus at the back of the
knee, this is hardly correct ; it forms the anterior part of
an imperfect sheath which is laterally composed of superior
suspensory ligament, and another layer of the annular
ligament of the knee, but between the two tendons is a
synovial sheath, which on the outer side communicates with
the former sheath, but does not extend so far inferiorly

(by one and a haK inches), though superiorly it extends as
far up as the superior part of the inferior third of the
radius. We must temporarily defer the examination of the
xemaining portion of these tendons.

THE POKE EXTREMITY. 211

Radialis accessorius arises from the posterior surface of
the middle third of the humerus inclined to its outer side ;
its fibres become inserted into the perforans tendon, in
blending with the superior suspensory ligament above and
"behind the knee.

Ulnaris accessorius runs to the same insertion, after
arising from the posterior part of the olecranon in common
with flexor metacarpi medius. Its muscular portion covers
the ulnar nerve and is covered by the faschia of the arm.

On examination of the external surface of the arm we
find that the faschia of the arm blends anteriorly with the
fibrous band of extensor metacarpi magnus, which runs
from flexor brachii. Supero-externally its fibres converge
to form a white tendinous band (which contains some yel-
low elastic fibres, and to which levator humeri and pectoralis
transversus are attached). This, superiorly, is firmly at-
tached to the inferior extremity of the ridge running down-
wards from the external tubercle of the humerus, passes
over and binds down humeralis externus in its course over
the external surface of the humerus, and posteriorly runs
to become attached to the ridge passing upwards from the
■external condyle of the humerus, inferiorly it blends with
•caput medium.

Extensor metacarpi magnus at its superior attachment
to the ridge running upwards from the external condyle of
the humerus, blends with extensor pedis. It is also at-
tached by a strong tendon to the anterior part of the cap-
sular ligament of the elbow- joint, thus separating humerali*
•externus from that ligament. Between the upper part of
this muscle and humeralis externus runs the spiral nerve,
which after meeting the spiral artery and vein and their
small accompanying nerve at the front of the joint proceeds
with them down the front of the limb under the muscles.
At the upper part of the front of the knee its tendon is in
contact with extensor metacarpi obliquus, which passes over
it in its course from without inwards and downwards, and
is separated from it by a bursa. Passing then through the
central one of the three grooves at the anterior part of the
inferior extremity of the radius, and through a special
channel in the annular ligament of the knee, where it is
lubricated with synovia, the tendon of this muscle becomes
inserted into the j)rominence on the antero-superior part of
the large metacarpal bone, slightly inclined to the inner side.

212 OUTLINES or EQUINE ANATOMY.

Extensor metacarpi obliqiuis arises from the outer part
of tlie middle third of the radius "between extensor'
suffraginis and extensor j)edis. Its muscular fibres in
running under the tendon of extensor pedis converge, and
they form a tendon which runs over extensor metacarpi
magnus (from wdiich it is separated by a bursa), passes
through the oblique groove on the inner surface of the in-
ferior extremity of the radius, through a channel in the
annular ligament of the knee, lubricated by synovia, ta
become inserted into the head of the inner small meta-
carpal bone through the medium of the inner lateral
ligament of the knee.

Extensor pedis has a penniform arrangement. Supe-
riorly it blends with extensor metacarjn magnus in becoming'
attached to the external condyle of the humerus, and its-
fibres are attached to the inner lateral and capsular liga-
ments of the elbow-joint, and to the outer part of the
radius as far down as the inferior part of the superior
third. A remarkable round band of its muscular fibres
runs underneath extensor suffraginis to the foramen
between the ulna and the radius, where it becomes
attached in contact with the branches of the radial vessels
which pass through the foramen. While passing over ex-
tensor metacarpi obliquus the muscle becomes tendinous
and passes through the antero-external groove at the
antero- inferior part of the radius and the annular ligament
in a special channel, lubricated with synovia. Beloio the
Tcnee it sends a hranch to assist in foroning Ugamenium ex--
tensorum. Between the upper part of this muscle and
extensor metacarpi magnus is a slight inflection of the
faschia of the arm, but a much thicker fold separates it from

Extensor suiFraginis, and forms a sheath in which
this muscle plays, and whereby from the elbow to the knee
it is firmly fixed to the lateral part of the radius. It-
arises superiorly through the medium of the external'
lateral ligament from the outer condyle of the humerus,
at first forms a bridge over the erratic portion of extensor
pedis and then becomes fixed to the radius as above
mentioned. It passes through the external groove on
the antero-inferior part of the radius, and through the
annular ligament, from which it receives a fibrous cord
opposite the head of the small metacarpal bone, and
below the knee becomes rather expanded on the external'

THE FORE EXTREMITY. 213

■surface of tlie large metacarpal boue, receives a portion of
tendon from extensor pedis, and is liere termed liga-
jnentuni extensorum. After passing over tlie capsular
ligament of the fetlock -joint to which it is attached, it
becomes inserted into the supero-anterior and external part
of OS suffraginis.

Flexor metacarpi externus, superiorly, is attached to the
-extreme posterior part of the ridge running from the ex-
ternal condyle of the humerus and to the capsular ligament
of the elbow-joint (being the only flexor of the forearm
which arises from the outer surface of the limb) ; it runs
downwards and inferiorly blends with the fibrous sheath
of extensor os suffraginis (which is here part of the
annular ligament of the knee), becoming inserted into the
superior margin of the trapezium, while it sends a small
round tendon through the groove running obliquely down-
wards and forwards on the external surface of this bone
^which is lubricated with synovia), and passes to the head
of the outer splint bone.

Remove the skin from the remainder of the limb as
far as the hoof, clean the tendons and ligaments thus ex-
posed by careful removal of the areolar tissue anteriorly ;
the tendon of extensor os suffraginis will be found arranged
as above indicated ; that of extensor pedis, after playing
over a large bursa at the antero-inferior part of the large
metacarpal bone, grows wider in becoming attached to the
front of the capsular ligament of the fetlock, receives on
each side a strong band running from the inferior extremity
of the superior sesamoideal ligament obliquely over the
lateral parts of the pastern bone, and becomes inserted into
a somewhat heart-shaped prominence on the anterior sur-
face of the coronal process of os pedis. It is firmly fixed
to the anterior surfaces of ossa coronse and suffraginis, and
of the capsular ligaments of the pastern and cofiin joints
by dense white fibrous tissue, and in the same way is united
on both sides of its extreme inferior part to the lateral
.cartilages.

From the inferior margin of trapezium a portion of the
annular ligament runs to the supero-lateral part of the
•small external metacarpal bone ; it serves to protect the
jierves and blood-vessels of this neighbourhood.

The radial artery breaks up into two vessels just at the
.superior suspensory ligament, the smaller, small metacarpal

214 OUTLINES OF EQUINE ANATOMY.

artery, passes over the annular ligament of the knee and
subsequently becomes internally placed to the inner splint
bone. At about the inferior part of the superior third of
the posterior surface of the large metacarpal bone it gives
off the medullary artery of that hone, and about at the bifur-
cation of the superior sesamoideal ligament it anastomoses
vfith a small recurrent hranch of the large metacarpal
artery, which we last noticed as being enclosed with the
nerves in the synovial sheath of the flexor tendons at the
back of the knee. It (the large metacarpal) passes doAvn
the back of the leg in contact with the inner margin of
these tendons, and subsequently between them and the su-
perior sesamoideal ligament, where it gives off the recurrent
branch, and then bifurcates to form the plantar arteries.
If we trace out one of these arteries we shall find that it
passes on to the lateral part of the fetlock, where it is sub-
cutaneous and where the corresponding vein is in front, the
nerve behind it. It gives off a large branch forwards, ramify-
ing in front of os suffraginis, and small unnamed branches
hacJctvards to the heel, and then runs directly to the internal
surface of the lateral cartilage. Just at the lateral part of the
cofiin- joint it gives two branches forwards and one back-
wards. The two running forwards anastomose with their fel-
lows from the opposite side at the front of the coronet, one
externally situated to the extensor pedis tendon being the
superficial coronoj^'y and sending on either side of the
tendon a branch inwards to the other, which being inter-
nally placed to the tendon is termed the deep-seated coro-
nary artery. The posterior hranch goes to the frog and
bifurcates, one of its branches running to the bulb, one to
the apex of that organ, each of them anastomoses with its
fellow. The plantars give off the lateral laminal arteries,
while running over the internal surface of the lateral car-
tilages, and these pass outwards through the foramen in
the wing of the os pedis (or between os jDedis and the
cartilage), running forwards in a groove to anastomose at
the front of the bone with each other, and giving branches
superiorly to the coronary arteries, inferiorly to the circum-
flex artery of the toe, and inwards to the arterial circle
formed in the substance of os pedis by the anastomosis of
the two plantars, which, after jmssing through grooves on
the under surface of os pedis between the inferior broad
ligament of the navicular bone and the perforans tendon,

THE FORE EXTREMITY. 215

enter the bone througli the foramina on its plantar
surface. Branches running downwards through the sub-
stance of the bone from this circulus arteriosus of the
foot pass out of the large foramina at the outer margin of
the plantar surface of os pedis, where they form a continu-
ous arterial circle, the circumflex artery of the toe, which
receives branches superiorly from the lateral laminal arte-
ries, which sometimes mainly form it ; and on the plantar
surface some large arteries (solar) radiate to it from the
artery of the apex of the frog. It will be thus seen that
the arteries form an intricate plexus, not only in the sensi-
tive structures, but also in the bones of the foot ; the veins
are more numerous, they form an intraosseous plexus, the
vessels of which mainly converge to a trunk corresponding
to the plantar arteiy inside the lateral cartilage ; and also a
superficial plexus composed of vessels with but small meshes,
which are found in the whole of the vascular investing and
secreting layer of the foot, they converge towards certain
larger veins which are on the external surface of the lateral
cartilages and form a vein which unites above the cartilage
with the intraosseous vein to form the plantar which runs
upwards (receiving branches), with and in front of the artery
to unite with its fellow above the fetlock. From this junction
four or five vessels inin upwards, bemg the satellites of the
large and small metacarpal arteries, and form the radial and
superficial brachial veins respectively; since the smaller veins
of the foot have no valves, they can be injected from the
plantar.

After passing with the flexor tendons through the annu-
lar ligament of the knee, the metacarpal nei*ves accompany
the tendons as far as opposite the superior part of the
inferior third of the large metacarpal bone. The external
metacarpal nerve is derived from the ulnar, the internal
metacarpal nerve from the radial. The internal gives olf
fibres which form a trunk extending obliquely downwards
and outwards between the skin and the flexor tendons to
the external metacarpal nerve. At the side of the fetlock
each nerve divides into three parts ; one runs over the front
of OS suffraginis ; it is separated by the plantar vein from
the middle branch which runs to the coronet, and is
separated by the plantar artery from the posterior plantar
nerve which supplies the major portion of the foot witfe
nerve force.

:216 OUTLINES OF EQUINE ANATOJIY.

PART VIII.— SPECIAL ANATOMY.

The Abdomen.

The operator commences by dissecting tbe skin down-
wards from tlie middle tlioracic incision towards the middle
line of tbe abdomen. Thus he exposes the panniculus, ex-
tending over the lateral part of the belly from the external
surface of the shoulder. Infero-anteriorly is situated ])ec-
toralis magnus, which is superiorly slightly covered by
panniculus ; it is about five inches wide, and covers about
one third of the length of the under surface of the belly.
Posteriorly the panniculus divides into two layers, one of
which covers the outer surface of the quarter, the other
runs to the inner surface and, as these two layers are in-
timately connected, a somewhat tense sheath is formed,
which is superiorly attached to the antero -inferior spinous
process of the ilium, inferiorly around the patella. It blends
posteriorly with the faschia of the quarter. It is the por-
tion of panniculus extending to this sheath in the ox, which,
covered by skin, foiins that thin fold termed by butchers
" the flank." Below this is the superficial abdominal
faschia, a smooth yellow layer formed of elastic tissue which
is immediately subcutaneous. It is widely spread over the
aponeurotic expansions of the abdominal muscles as far
forwards as the ensiform cartilage, backwards as the sym-
physis pubis. Thick towards the linea alba, gradually
grows thinner on approaching the muscular portion of
obliquus abdominis externus, and at the postero-inferior
part sends a process which, in the male, combines with that
-of the opposite side, forming the suspensory ligament of the
^eniSfi-a. thefemale the elastic divestment which covers themam-
mary gland, and which sends trabeculae inwards to separate
its lobes. Internally this layer is attached to the external
oblique abdominal muscle, externally it affords attachment
to pectoralis magnus anteriorly, posteriorly it becomes
inflected to the internal surface of the thigh*

THE ABDOMEN. ^17

Tlie fore limb should now he elevated by means of an
iron fork, and tlie pectoral muscles dissected. Pectoralis
transversus is superficially situated, it blends witli its
fellow at tlie under part of the cariniform cartilage, and
anterior part of the sternum, being connected to these firmly
•at its anterior part by areolar tissue ; x^osteriorly, as far
as the lower extremity of the fifth rib, so that it has
free play over this surface ; from this its fibres run to
the inner side of the fore limb, and with levator humeri
become attached to the fibrous band running from the
inferior extremities of the humeral ridge to the infero-ex-
ternal part of the humerus.

Anteriorly to the firm attachment of pectoralis trans-
versus is the originating point of sterno-maxillaris, above
which sterno-thyrO'hyoideus is attached to the cariniform
cartilage. Higher up pectoralis anticus is attached to the
lateral part of the sternum, extending as far back as about
the fourth sternal bone, and being slightly united to the
corresponding sterno-costal cartilages ; it runs upwards
to the antero-superior part of the scapula.

Pectoralis mag^nus runs from the post ero -lateral part of
the sternum, and from the under surface of the ensiform
cartilage and from the anterior part of faschia superficialis
abdominis to the external and internal tubercles upon the
anterior part of the head of the humerus, where it is at-
tached with antea spinatus, and between which attachments
runs the superior cartilaginous tendon of flexor bracliii.

By section of the pectoral muscles a quantity of loose
areolar tissue is shown, into the inferior part of which
subscapulo-hyoideus seems to be attached, gaining ap-
parently a very unsubstantial origin. The axillary artery
may now be seen running to the internal surface of the
shoulder- joint, while the axillary plexus of nerves is seen
sending off numerous trunks. The axillary artery after
being given off by the arteria innominata, winds round a
smooth surface on the anterior border of the first rib below
the inferior attachment of the scalenus muscle ; on gain-
ing the internal surface of the shoulder- joint it breaks up,
sending the humeral thoracic branch anteriorly to pector-
alis magnus and antea spinatus at their insertion ; the
anterior scapular between subscapularis and antea spina-
tus to the anterior dorsal fossa of the scapula ; the pos-
terior scapular or subscapular artery, which passes under

218 OUTLINES OF EQUINE ANATOMY.

teres internus, and runs between this muscle and tlie caput
magnum of triceps extensor brachii, to the posterior angle
of the scapula ; and the external thoracic artery, which
runs backwards to the lateral j^art of the thorax, under
latissimus dorsi. Inferiorly the humeral artery runs from
the axillary artery towards the elbow-joint, sending off
several constant branches, and finally breaking up into the
tdnar, spiral, and radial branches : the ulnar runs to break
up about the point of the ulna, sending an important
branch down the limb beneath ulnaris accessorius ; the
spiral twists round the front of the humerus ; the radial
runs along the internal surface of the limb.

I have thus particularised these arteries, since with each
of these runs a nerve from the axillary plexus, which,
being formed by branches from the sixth, seventh, and
eighth cervical nerves, and the first dorsal (with a sym-
pathetic branch), passes between the long and short heads
of scalenus, and breaks up into the humeral thoracic, ex-
ternal thoracic, anterior and ^posterior scajoular, tdnar, spiral^
and radial nerves.

By division of the pectorals we have exposed the lateralis
sterni, running in a downward and backward direction
from the posterior border of the lower third of the first
rib, to be attached below the inferior extremity of the fourth
sterno-costal cartilage to the lateral part of the sternum.
This muscle being removed, we have the intercostales
interni as continued between the sterno-costal cartilages
exposed to view; they run in a downward and forward
direction, obliquely from the anterior border of one carti-
lage to the posterior border of the one immediately in
front of it. Posteriorly they are covered by the anterior
extremity of rectus abdominis, which is anteriorly attached
to the external surface of the three or four posterior sternal
cartilages of the true ribs.

Having examined these structures, we remove the
aponeurotic layer covering serratus magnus, and thus
expose its inferior attachments. It will be found to arise
from the transverse processes of the five posterior cervical
vertebrae, and from the external surface of the eight true
ribs, having four digitations posteriorly with obliquus
abdominis externus ; from these points its fibres, forming
a large fleshy slab of muscle, converge towards the superior
margin of the venter surface of the scapula, into which they

THE ABDOMEN. 219

become inserted between the attachments of rbomboideus.
and subscapularis, some of the fibres running to the ex-
ternal surface of the cartilage of elongation at its posterior
part. This, with the corresponding muscle of the opposite
side, forms a slingby which the body is anteriorly supported.

The following are the muscles by which the fore extremity
is connected to the trunk : — panniculus carnosus, levator
humeri, rhomboideus, trapezius, latissimus dorsi, pectorales
magnus, anticus, and transversus, subscapulo-hyoideus, and
serratus magnus.

The f aschia superficialis abdominis must be now removed
with care, for on the proper removal of this depends the
successful demonstration of the aponeuroses of the abdo-
minal muscles. If it has become too dry for removal, it is
better to raise it with the tendon of obliquus abdominis
externus, the fibres of which run downwards and backwards
towards the linea alba. This is a thick elastic band, formed
by the general union of the abdominal muscles at the
middle line of the abdomen, extending from the ensiform
cartilage to the symphysis pubis, before arriving at which
it becomes broader and receives fibres from the several
tendons of the abdominal muscles, and a distinct band
of tendinous fibres from the antero-inferior spinous pro-
cess of the ilium, Poupart's ligament or the crural arch.
Into this ligament (which is really but a portion of obli-
quus abdominis externus), the posterior fibres of the
external oblique are inserted, and between these and those
inserted into the linea alba is the external abdominal ring",
through which passes the spermatic cord, covered by the
cremaster muscle. It runs upwards from the external ring
posteriorly towards the antero-inferior spinous process of
the ilium, the cremaster becoming lost in the lumbar
faschia ; the remainder of the cord resting on obliquus
abdominis internus, at length passes between its fibres
and gains the abdominal cavity at the internal abdo-
minal ring, the space between the two rings being the
inguinal canal. This is the passage between the external
oblique and the internal oblique muscles ; it terminates^
superiorly at the internal abdominal ring, which is formed
by the passage of the prolongation of the peritoneum from
the floor of the abdomen to line the scrotum, forming the
tunica vaginalis scroti; this passes between fibres of the
internal oblique muscle. Situated at about the anterion

220 OUTLINES OF EQUINE ANATOMY.

part of tlie posterior third of tlie linea alba is the umbi-
licus ; this is a slight puckering of the layers forming the
iloor of the abdomen to close ujd an opening which, in the
foetus, admitted the passage of the umbilical arteries and
the urachus to the foetal membranes, and the umbilical
veins from them ; it becomes impervious in extra-uterine life,
being no longer needed.

Obliquus abdominis externus is attached to the external
surface of the fourteen posterior ribs almost as low down
as their cartilages, having anteriorly four fleshy digitations
with serratus magnus. From these points its fibres run
•obliquely downwards and backwards to the under surface
of the ensiform cartilage, the linea alba, symphysis pubis,
antero-inferior spinous process of the ilium and lumbar
faschia. Some of the fibres are arranged to form Poupart's
ligament (vide supra) into which others are inserted, while
some run to become attached by aponeurosis to the internal
. surface of the hind limb. Removing this muscle we expose
some thin tendinous fibres running obliquely downwards
and forwards ; these belong to

Obliquus abdominis internus, which seems to be composed
of fibres radiating from the antero-inferior spinous process
of the ilium and the lumbar faschia and the transverse
processes of the three anterior lumbar vertebrae. The most
superior of these run to the last rib, and being slightly
separated from the rest are sometimes considered as a dis-
tinct muscle and termed retractor costae ; a few run to the
internal surface of the posterior cartilages of the false ribs,
most of them running to the linea alba along its whole
length, the posterior ones separating to form the internal
abdominal ring and the inner wall of the inguinal canal.

Extending for a considerable distance on either side of
the linea alba, forming the under part of the wall of the
belly, we see a muscle wide centrally and growing narrow
■anteriorly to become attached to the under surface of the
■ ensiform cartilage and to the external surface of the four
posterior sterno-costal cartilages of the true ribs. Poste-
riorly it grows narrow to become attached to the thick tendon
running to the anterior part of symphysis pubis ; its inner
margin is attached along the whole length of linea alba,
and it presents many transverse tendinous markings,
by which it is considerably strengthened ; this is rectus
.abdominis, its internal surface lies in contact with a few

THE ABDOMEN. 221

scattered tendinous fibres apparently belonging to the
internal oblique muscle. Having removed these we see'^
trausversalis abdominis, on the external surface of which
certain nerves rendered consinciious by their tvhiteness run-
directly from the intervertebral lumhar and posterior doi^sal
nerves, in a direction similar to the fibres of this muscle,
which run perpendicularly to the linea alba. On the ex-
ternal surface of this muscle we also see the arteries which
supply the abdominal walls with blood and their accom-
panying veins. Superiorly lumbar branches, derived directly
from the posterior aorta, and the circumflex artery of the
ilium, which arises from the external iliac artery, runs
directly to the antero-iuferior spinous process, and then,
breaks up in supplying the abdominal muscles. Posteriorly
the epigastric is given off by arteria profunda femoris
below symphysis pubis, and passing over the internal sur-
face of the femoral artery and of the inguinal canal, runs-
forwards under rectus abdominis ; it sends off the external
fudic artery to the sheath in the male, the mammary
gland in the female ; in the male also the external pudic
artery gives off the anterior dorsal artery of the ;penis, one
branch of which runs forwards along the superior part of
the organ as far as the glans, the other backwards to anas-
tomose with the posterior dorsal artery from the internal
pudic.

The internal thoracic artery at the ensiform cartilage
divides, sending one branch, the anterior abdominal, along
the floor of the abdomen, the other upwards along the infe-
rior extremities of the ribs, where it anastomoses with the
intercostals, and sends twigs to the abdominal walls :
all these arteries anastomose by their terminal twigs one
with the other.

Transversalis abdominis arises from the internal sur-
face of the twelve posterior ribs, of their cartilages, and
by faschial expansion from the transverse processes of the
lumbar vertebrae, its fibres run to be inserted perpendicu-
larly into the upper surface of the ensiform cartilage and
the linea alba. Anteriorly inside the ribs its attachments
digitate with those of the diaphragm. Posteriorly its
fibres grow gradually more and more sparse, none being
found at the internal abdominal ring. By removing this
muscle we expose the peritoneum or serous lining mem-
brane of the abdomen covered in places by white fibres

222 OUTLINES OF EQUINE ANATOMY.

Avhicli serve to strengthen it. It is transparent and
through it we see the caecum and colon, with their longitu-
dinal muscular bands and resulting puckerings.

The abdominal cavity is bounded anteriorly by the
diaphragm, inferiorly and laterally by the abdominal
muscles, superiorly by the ]3S08e muscles attached under-
neath the lumbar vertebrae, posteriorly by the pelvis with
its viscera. Its anterior surface is concave, in consequence
of the concavity of the diaphragm against which the liver
rests on the right side, the stomach and the spleen mainly
on the left.

On laying open the cavity from below at the linea
alba we expose the various viscera all covered by peri-
toneum, so that none of them can be touched except
after removal of their investing serous layer : it likewise
forms several double reflections around the viscera, which
serve to support the organs and which receive special
names. After covering the floor and the sides of the
belly it runs upwards posteriorly to be reflected to form
the ligaments of the bladder ; from the floor of the belly
along the central line a double fold runs to the fundus or
anterior portion of the bladder, being the susj^ensory liga-
ment. From the sides hroad ligaments run horizontally
to the fundus, and on the free margin of each between
the folds of peritoneum, is situated the round ligament
of the bladder, which in the foetus is the umbilical artery ;
it arises from the artery of the bulb, and in the adult
becomes impervious. The broad ligaments separate to
enclose the bladder, and the layer forming the ui)per surface
of these ligaments and covering the upper surface of the
bladder is posteriorly inflected upwards on to the under
surface of the commencement portion of the rectum and
the single colon, on either side of which the membrane
becomes firmly attached, superiorly forming by the union
of the two layers the meso-rectum, by which this portion
of the intestine is supported against the spine, and which
extends almost as far forwards as the stomach. On ar-
riving at the lumbar region it gives off a pouch on the
right side in which are enclosed the double colon and the
caecum and which forms the meso-colon, and the meso-
caecum, and another on the left in which the small intes-
tines lie, which is termed the mesentery ; from this pos-
teriorly a smaller fold extends on the right side around

THE ABDOMEN. 223

tlie duodenum whicli it connects to tlie porta of the liver,
and from the anterior extremity of the bowel is continued
one layer over the ant ero -inferior surface of the stomach.
After tracing the peritoneum thus far from behind we
may commence to examine it anteriorly. Passing forwards
from the umbilicus on the floor of the abdomen it forms
centrally a longitudinal fold which runs from behind
forwards, extending farther back in young subjects than
in old ; this is one of the ligaments of the liver, falciform
or suspensory ligament. It runs on to the posterior surface
of the diaphragm and extends as far as foramen dextrum ;
on its free margin, enclosed between the two layers, is an im-
pervious fibrous cord, round ligament, which is the dege-
nerated umbilical vein of the foetus by which the blood is
carried from the umbilicus to the liver. It is this liga-
ment which is sometimes inquired after as being " the
only ligament of the liver not formed by peritoneum."
The layers of serous membrane forming the falciform
ligament separate superiorly and in surrounding the j)os-
terior vena cava in its course from the liver to the foramen
dextrum form the coronary ligament. The peritoneum
then forms the right lateral ligament, running from the
superior margin of the right lobe of the liver ; this liga-
ment is broad and wide, and on its posterior surface we
may see a small special ligament passing to the lohuhis
Spigelii; its posterior layer is reflected from the roof of
the abdominal cavity at the right kidney. A correspond-
ing ligament, but longer and narrower, runs from the pos-
terior surface of the left side of the diaphragm to the left
extremity of the superior margin of the liver, which is the
left lateral ligament. After investing the liver the serous
membrane forms the gastric liejmtic omentum which runs
from the transverse fissure of the liver to the lesser cur-
vature of the stomach and to the attachment of the duo-
denum to the spine ; between its layers run the hepatic and
pancreatic ducts. The stomach will be found to be enclosed
in a sac, which, in consequence of the fatty matter between
its layers arranged around its vessels, is apparently reti-
culated. This is the omentum major or gastro-colic omentum
{caul), which forms a peculiar cavity connected with the
general peritoneal cavity by a channel, foramen of Winslow,
which is situated below the spine against the coeliac axis.
The reflections of peritoneum from the stomach to the

224 OUTLINES OF EQUINE ANATOMY.

neighbouring viscera are termed omenta : we have noticed
the gastro-hepatic, and gastro- colic omenta ; from the left
extremity of the greater curvature the (jastro-spleniG
omentum passes to the spleen, which is suspended between
its two folds ; and to the extreme left part of the greater'
curvature the cjastric-plirenic omentum is reflected from the
diaphragm, it terminates in forming the cardiac ligament
surrounding the terminating portion of the oesophagus.

In the male at the internal abdominal rings on either
side at the posterior part of the cavity the peritoneum is
reflected through the inguinal canal into the scrotum,
forming tunica vaginalis scroti, which by a serous frsenum
is connected with tunica vaginalis testis, a reflection from
the roof of the cavity. There is also a slight fold connecting^
the tvjo terminal portions of the vasa defer entia together, between
tuhich lies the third vesicula seminalis. In the female from
the u]3per surface of the bladder it passes to the anterior
portion of the vagina and invests the uterus, from the
horns of which it passes to the roof of the cavity, forming-
the hroad ligaments, which anteriorly contain the ovaries
and fallopian tubes, and which have the round ligaments of
the uterus and those of the ovary between their double layers.
Between the two horns the serous membrane is reflected
backwards over the upper surface of the body of the uterus
to the vagina, from which it passes upwards to the under
surface of the anterior part of the rectum.

By incision through the terminal portion of the oesophagus,
through the rectum, and through their serous connections
to the neighbouring organs, especially up against the spine,
the intestines and stomach may be removed from the abdom-
inal cavity. In the process we expose the pancreas, a body
resembling a salivary gland in structure, appearance, and al-
most in function. It assumes the form of a number of greyish
white lobuli placed around the anterior mesenteric artery,
moulded in between the various structures in this neigh-
bourhood. It is mainly attached to the double colon, from
which it rec[uires careful separation, and will be found for
the most part on the right side of the spine, which portion
is termed its head, and around which the duodenum curves
in its upward course. Its various lobules give off ducts
which unite and reunite to form finally the pancreatic
duct, which passes into the gastro-hepatic omentum, where
it unites with the biliary (or hepatic) duct and terminates at

THE ABDOMEN. 225

the duodenum. It is supplied with blood from the coeliac
and anterior mesenteric arteries ; its blood passes into vena
portse.

The liver is another important accessory gland of diges-
tion. It is that chocolate coloured body found in the
anterior part of the abdomen inclined to the right side
lying in contact with the diaphragm anteriorly, while
the duodenum courses from below upwards over its posterior
surface. It is thickest in the centre, and grows gradually
thinner towards its outer circumferent margin. It is
divided by deep fissures into lobes, of which there are
three principal and several accessory. The right lobe is
the largest, and is connected to the left by the middle. Its
anterior surface is smooth, invested by peritoneum ; its
superior margin presents a depression, fossa renalis, on
which the right kidney rests; from this part the right
lateral ligament runs, and superficially through the supero-
anterior part of the right lobe, the posterior vena cava
passes from the right side of the spine to foramen dex-
trum. The posteror surface of the right lobe presents
superiorly a peculiar triangular accessory lobe, the lohus
Spigelii vel caudatus. The external and inferior margins
are free while the inner is in connection with the middle
lobe, which anteriorly receives the falciform and round
ligaments. Posteriorly, it presents the porta or transverse
fissure, which extends to the right and left lobes, and to which
the arteries resulting from division of the hepatic branch of
the coeliac axis pass, and also the vena portse and gastro-
hepatic omentum, between the folds of which the nerves
and lymphatics run, and also the hepatic duct, which meets
the pancreatic duct, and the vessel thus formed opens into
the duodenum. (There is no gall-bladder in the horse,
hence no cystic duct, as in other animals.) The inferior
margin of the middle lobe is divided by numerous iissures
into several almost equal parts, between two of which the
round ligament passes in terminating. This is the lohus
scissatus. The left margin of the middle lobe blends with
the right of the left lobe, to the superior margin of which
the left lateral ligament is attached. Its other margins are
regular, and its surfaces smooth. On carefully examining
the surface of the liver we may see that it is _ mapped out
into minute polygonal divisions or lohuli, which are found
to be shaped like an ivy leaf and consists of a number of

226 OUTLINES OF EQUINE ANATOMY.

hexagonal epithelial "bile cells" recognizable by tlieir yellow
colour, due to granular contents. These acini or lobules
are embedded in the sj^ecial stroma of the gland, Glisson's
capsule, which has a thin layer investing the surface of the
organ and becomes well marked at the transverse fissure.
The circulation through the liver is complex. Vena
portse receives the blood from the anterior and posterior
mesenteric, pancreatic, splenic, and (lastly) gastric veins ; it
passes through a ring formed by the pancreas and direct
to the porta of the liver, during its whole course inferiorly
placed to the posterior vena cava. It enters the left ex-
tremity of the transverse fissure and sends a branch to each
lobe,which breaks up into vaginal hranclies iowiidi in Glisson's
capsule, which divide and subdivide, at length forming the
interlobular veins, which ramify on the surface of the lobule
sending branches inwards ; these radiate towards the centre
of the lobule, where they terminate in the intralobular vein,
which at the base of the lobule opens into a sublobular
vein, in relation to which the acinus is placed as a sessile
leaf is to a branch. By union and reunion the sublobular
veins at length form the hepatic veins, which terminate by
numerous orifices at the posterior vena cava, as may be
exposed by slitting up in its interhepatic portion. The
hepatic artery is a branch of the coeliac axis ; gives off a
branch to the duodenum, which gives off the right gastric
artery, and terminates by breaking up before arriving at
the porta. Its mode of termination with regard to the hepa-
tic and portal veins is not yet known, its subdivisions
have been traced into the substance of the lobuli. The
liver is supplied with nerve force by the sympathetic and
pneumogastrics.

The abdominal portion of the alimentary tract consists
of the stomach and the major j)ortion of the intestinal
canal. It presents three coats, peritoneal, muscular, and
mucous. The peritoneal coat of the stomach is continued
on each side as the omenta ; that of the intestines has
been described. It is named differently in different parts.
Thus the duodenum is supported by a continuation of the
gastro-hepatic omentum, the remainder of the small in-
testines by the mesentery, and the several j)arts of the large
intestine by the mesocsecum, mesocolon, and mesorectum
respectively. The mesentery is arranged in a spiral manner
around the anterior mesenteric artery. In its free margin, be-

THE ABDOMEN. 227

tween its folds lie the jejunum and tlie ileum. At first sliort,
it gradually increases in length until it gains its maximum,
when it again grows short. Between its folds are arteries,
veins, lacteals (or lymphatics), and nerves. The arteries are
mesenteric hranclies, from thirteen to eighteen in number,
which pass from a common centre and radiate, being con-
nected, forming arches at the attached border of the small
intestine, from which smaller vessels are given off, which
pass to break up in supplying the coats of the bowel. The
veins, arranged in like manner, terminate in forming the
anterior and posterior mesenteric veins, which form the
commencement portion of the vena portse. The nerves are
some of those branches of the sympathatic which, in radi-
ating from the semilunar ganglion, form the solar plexus.
The lacteals are lymphatic vessels, which being filled with
an opaque milky fluid, chyle, the product of digestion, re-
ceive a name distinct from from those in other parts of the
body. Passing from the intestinal villi, these minute vessels
proceed upwards towards the spine and near the anterior
mesenteric artery pass through the mesenteric glands, num-
erous greyish nodular bodies, by which the lacteal fluid is
rendered cellular and coagulable ; they differ in no point in
structure from other lymph-glands of the body. The ter-
mination of the lacteals is in the receptaculum chyli, a
dilated vessel which receives lymph from the hinder parts
of the body and the chyle, and from the anterior part of
which the thoracic duct runs forwards and serves to convey
the fluid into the venous circulation. This cavity has very
thin transparent walls, and is situated between the anterior
mesenteric artery and the coeliac axis, in which situation also
we may find the semilunar ganglion, the largest ganglion
in the body, to which the splanchnic and part of the pneumo-
gastric nerves pass, and from which plexus run with the
branches of the coeliac axis, anterior and posterior mesen-
teric, and renal arteries receiving their names after the ar-
teries they surround. Those in the mesentery form the
solar plexus. Branches run backwards to the hypogastric
plexus.

The peritoneal coat of the double colon is reflected from
the under surface of the loins and covers at once both the
diverging and returning portions, so that they are con-
tained in a common serous covering terminating in a blind
extremity at the sigmoid flexure. That portion between

228 OUTLINES OF EQUINE ANATOMY.

the two divisions of the intestine, wHcli is most marked at
the sigmoid flexure, is termed the mesocolon. It presents
the figure of a racket bat, the broad portion of which is at
the sigmoid flexure. The diverging portion of the double
colon is also attached to the caecum by a double fold of
peritoneum, the mesocsecum, while the single colon floats
atvthe free margin of a double peritoneal fold, which, after
being continued for a slight distance posteriorly around the
anterior ^^art of the rectum (the mesorectum), is reflected la-
terally on to the walls of the abdomen in forming the anterior
boundary of the pelvis. In the large, as in the small intes-
tine, we find the arteries forming loops between the peritoneal
supporting layers from which branches run to the attached
margin of the intestine, where they break up in supplying
mainly the muscular and the mucous coats. The csBcum is
supplied by two branches of the anterior mesenteric artery.
They run towards its apex and anastomose just before reach-
ing it ; they send off numerous branches. The double colon
is supplied by two branches from the anterior mesenteric,
which run along the attached margins of the diverging a,nd
returning portions respectively, and anastomose on con-
verging at the sigmoid flexure. A branch from the anterior
mesenteric also passes to the anterior part of the single
colon, and posteriorly joins the first branch of the pos-
terior mesenteric, which breaks up in the mesorectum,
forming arched vessels which supply the single colon and the
anterior part of the rectimi, anastomosing posteriorly with
the hsemorrhoidal branches of the lateral sacral, by which,
in conjunction with branches of thp, artery of the bulb, the
posterior part of the rectum and the anus are supplied.
The veins of the large intestine converge to form the an-
terior and posterior mesenteric veins, which form the
commencement of vena portae, up against the anterior
mesenteric artery. The 7ierve siipijly of the large intestine
is conveyed by branches from the semilunar and posterior
meseiiteric ganglia. The latter is found in contact with
the artery of the same name, and sends fibres in a back-
ward direction, which combine to form an intricate arrange-
ment of nerve-fibres of the walls of the rectum in the pelvis,
to which the name hypogastric ])lexus is given. Numerous
lymphatic or lacteal glands may be seen in apposition with
the attached portions of the large intestine along its whole
length, but ^predominating in the anterior part. The vessels

THE ABDOMEN. 229

from thence pass towards the spine to empty themselves into
the receptaculum chyli.

The stomach, somewhat small in the horse as compared
with other animals, is found mainly in the left hypochondriac
region of the abdomen. It however extends into the epi-
gastric, and sometimes into the right hypochondrium under
extreme distension. It is likened to the bag of a bagpipe,
and from this it may be seen that it is a somewhat elon-
gated body, curved upon itself, having two extremities.
To one of these extremities, that placed on the left side
and most superiorly, in contact with the posterior surface
of the diaphragm, the oesophagus passes after emerging
through foramen sinistrum. It is surrounded by a fold
of peritoneum, which is designated the cardiac ligament,
which posteriorly ex^^ands over the stomach, while to the
left it forms an omentum which serves to connect the
stomach to the diajphragm, and is termed the gastro-
phrenic oinentum. This extremity of the stomach is termed
the left or cardiac, while from' the right or pyloric ex-
tremity the small intestine commences. That margin of
the organ situated between these two extremities, and
which is most superiorly placed, passing in an oblique
direction from left to right and from above downwards,
is termed the lesser curvature, and from it the gastro-
hepatic omentum runs to the porta of the liver, and on
the right side extends to the spine, having the duodenum
between its layers at the free margin, to which the duct
formed by combination of the excretory vessels of the
pancreas and liver runs, almost directly from the liver to
the bowel, into which it opens about four inches from the
pylorus, on the free margin, having wound round the
intestine for that purpose. The two extremities of the
stomach being attached to the upper wall of the abdomen,
the greater curvature of the stomach is situated below
and behind the lesser in such a manner that the organ
being obliquely placed from above downwards from left
to right, as well as from before to behind, presents a j^os-
tero -superior and an antero -inferior surface, both of which
are covered by layers of peritoneum, which at the greater cur-
vature form omenta. Thus, to the left extremity is attached
the spleen by the gastro- splenic omentum, while to the
greater part of the greater curvature the gastro-colic omen-
tum is attached, and, by running in a backward direction,

280 OUTLINES OF EQUINE ANATOMY.

and then again forwards, and forming a covering for part
of the double colon, produces a peculiar cavity of serous
membrane, connected to the main cavity by a channel up
against the anterior mesenteric artery, which has received
the name of foramen of Winslow. In the gastro-colic or
or omentum major, we sometimes find much fat. By
butchers it is termed the " caul.''

The stomach of the horse presents a rounded cul-de-sac
at its left extremity, more marked than in most other
animals. It has a muscular and a mucous coat in addition
to the peritoneal already described. The muscular coat,
centrally placed between the serous and mucous layers,
presents three lasers of fibres : longitudinal, most marked
along the lesser curvature, continuous with those of the
oesophagus and duodenum at their extremities ; oblique,
which predominate at the left extremity ; and circular, con-
tinuous with those of the oesophagus and duodenum, ex-
tending over the whole surface of the viscus, and which
centrally by their contraction seem sometimes to practically
divide it into two compartments.

The mucous layer is divided into two parts, cuticular
and villous. These two portions present a sharp line of de-
marcation, which is sigmoid. The former occupies about the
left third of the inner surface of the stomach, and is ana-
logous with the mucous membrane of the three first com-
partments of the stomach of the ruminant, for it is directly
continuous with that of the oesophagus, being whiter and
more firm than that forming the villous portion, which is
reddish in colour, slimy in nature, and occupies the left
two thirds of the stomach, being continuous through the
pyloric opening with that of the duodenum. Upon exa-
mination under the microcsope we may distinguish in this
portion glandular follicles or peptic glands, the deeper
portions of which are lined by spheroidal epithelium, and
which secrete the gastric juice, in addition to those mucous
follicles lined by tessellated epithelium, which secrete
mucus, and are apparent also in the cuticular portion.
To the cuticular portion we sometimes find bots (oestrus
equi) adhering, rarely to the villous. The left extremity
of the stomach comes in apposition with the pancreas, dia-
phragm, left kidney, and left pre-renal capsule. All the
branches of the coeliac axis supply this organ ivith blood.
The gastric (centrally situated) runs direct to the centre

THE ABDOMEN. 231

of the lesser curvature, where it breaks up in forming the
superior and inferior gastric artefi'ies, which run to the sur-
faces of the same name. The splenic, inclining to the left,
passes between the layers of the gastro-splenic omentum,
sending branches outwards to the spleen, inwards to the
stomach, and, after gaining the apex of the spleen, it con-
tinues along the greater curvature as the left gastric artery.
The hepatic, running to the right side to gain the porta of
the liver, sends a branch to the duodenum, which, on gain-
ing the intestine, sends a branch backwards to anastomose
with the first mesenteric branch of the anterior mesen-
teric trunk, and one forwards to be continued beyond
the pylorus, over the right extremity of the greater cur-
vature, forming the rigid gastric artery. All these vessels
give off branches freely, which anastomose, and from which
the blood is returned by the gastric vein, which is the last
to gain vena portse before it enters the liver. The nerves
of the stomach are derived from the splanchnic and solar
nerves ; while the left pneumogastric mainly expends
itself on the upper surface, the right runs to the inferior,
but both these nerves are intimately connected with the
semilunar ganglion. For convenience of reference the
cavity of the belly is by anatomists artificially divided
into nine parts. From either side of the ensiform car-
tilage in a direct line backwards to the brim of the pelvis,
and from the ant ero -inferior spinous process of one ilium
to the other, and from the posterior margin of the last rib
to that of the other, lines are drawn, and in this way the
cavity is found to present anteriorly the epigastric portion,
with the right and left hypochondriacs on either side ;
centrally, the umbilical portion, with the right and left
lumhars ; posteriorly, the hypogastric and the right and left
iliacs.

The intestines present three coats — serous, muscular, and
mucous. The serous coat has already been noticed as
part of the visceral peritoneum. It is the most external of
the coats, and extends from the stomach to the anterior
part of the rectum, thus leaving the posterior part of that
bowel with only two coats. It is also deficient where two
portions of intestine lie in close apposition permanently,
or where organs, as the pancreas, come into intimate con-
tact with the intestinal walls. The muscular coat consists
of two orders of fibres of the white, unstriated, or involun-

23-2 OUTLINES OF EQUINE ANATOMY.

tary class. The internal or circular, wliicli run round the
intestinal tube, are found in all parts evenly diffused over
the surface of the intestine, being anteriorly in direct con-
nection with the circular fibres of the stomach at the
pylorus. Posteriorly collected into a mass, which forms
the internal portion of the sphincter ani. The external w
loncjitucli7ial order of fih'es is evenly diffused over the surface
of the small intestine and of the rectum, while in the csecum
and colon these fibres are collected into thick bands, which
run longitudinally to the course of the bowel, and are more
or less numerous in different parts. Being shorter than
the bowel itself, and at the same time intimately attached
to its walls, they serve to " pucker" up its surface into a
number of cavities, which give it a peculiar appearance,
whilst by division of the bands it may be reduced to a tube
of uniform diameter and of much greater length. On ex-
posing the bowels of an animal shortly after death we may
observe the vermic2ilar or ^yeristaltic action of the intestines,
that slow consecutive contraction of their fibres commencing
anteriorly and extending backwards, whereby the ingesta
is slowly propelled from the pylorus to the anus. The
mucous coat of the bowels is of a reddish-grey colour and
slimy nature, extends from the pylorus (where it is con-
tinuous with the villous portion of the gastric mucous
membrane) to the anus, where it gradually blends with the
common integument. It consists of corium and basement
membrane, on the free surface of which is columnar epi-
thelium, and throughout presents depressions of this
mucous membrane termed follicles of Lieberhnhn, which
secrete mucus, and prominences of the same, villi orpapillce,
from the centre of which a lacteal commences, either by a
plexus, loop, or a blind pouch, for these are the portions of
the intestine from which the lacteals arise, and, though
most numerous in the small intestine, they may be found
also in the large. Throughout the intestinal tract also we
find embedded in the mucous membrane small bodies
called solitary gkmds, which consist apparently of a number
of cells bound together by somewhat dense areolar tissue,
and having blood-vessels runniog through them. They
present no ducts, and hence are considered to be analogous
in nature and function with the Malpighian corpuscles of
the spleen, though some aiithorities assert that by bursting
they discharge their contents into the intestine, and thus

THE ABDOMEN. 233

give tlie faeces its peculiar odour. The intestines of tlie
horse are about ninety feet in length, and as the posterior
eighteen feet are much larger in calibre than the rest, it is
divided into the large and the small intestine. The small intes-
tine commences from the pyloric extremity of the stomach,
and just after its commencement becomes very large. It
is here termed the duodenum, and takes an upward direc-
tion over the posterior concave surface of the liver, to the
porta of which it is attached by a continuation of the
gastro-hepatic omentum, between the two layers of which
the duct common to the liver and the pancreas runs to the
attached margin, and then, after passing beneath the peri-
toneal coat, opens on the free margin through a perforated
papilla into the intestinal canal, about four inches from
the pylorus. Passing in an upward direction, the duo-
denum takes a curve around the head or right extremity
of the pancreas (termed its horse-shoe curve), and then,
passing underneath the spine behind the anterior mesen-
teric artery, terminates. The rest of the small intestine
occupies no regular position in the abdomen, for, being
attached in the free margin of the mesentery, it hangs
loose, but terminates in the right lumbar region, where it
opens into the large intestine, the muscular coat being here
doubled in such a manner as to form the ileo-csecal valve,
which prevents food from passing from the large into the
small intestines under ordinary circumstances. The ante-
rior two fifths of this portion of the small intestine is
termed the jejumtm, and the posterior three fifths the
iletmi. This division is purely artificial, and anatomists
now prefer to describe the fixed or duodenal, and the free
portions of the small intestine. The mucous coat of the
duodenum presents, in addition to papillae, follicles of
Lieberklihn, and solitary glands (extremely rare here),
certain small racemose glands, in every respect resembling
salivary glands, even, it is supposed, in the nature of their
secretion, of which, however, nothing definite is known,
these are named Brunner's glands, after their discoverer.
On the free margin of the ileum and of the posterior part
of the jejunum may be seen elongated patches, apparently
of pigmentary matter. These are Peyer's patches, and
when examined microscopically are found to be aggrega-
tions of solitary glands surrounded by a row of fol-
licles of Lieberklihn termed the corona tubulorum, while

234 OUTLINES OF EQUINE ANATOMY.

villi may be seen covering tlie space enclosed by the
corona.

The large intestine consists of three portions : ccemim,
colon, and rectum. The ileum terminates at a peculiarly
arched portion of intestine, the ccecuni caput coli, at its
lesser curvature, anteriorly is the commencement of the
double colon. The caecum, a plicated portion of in-
testine, presents a base situated in the right lumbar and
right iliac regions, from which it extends in a direction
forwards and to the left, through the umbilical region along
the floor of the abdomen, to terminate in the apex in the
left hypochondriac region. Its plicae are due to the collec-
tion of its longitudinal muscular fibres into three bands at
the apex, while subsequently a fourth appears. This
viscus is capable of containing about four gallons of fluid,
and is supposed to be the destination of the huge draughts
of water sometimes consumed by horses, which rushes
directly through the stomach hither ; and since it is apt to
carry with it any undigested matters, we learn from this
the rule found valuable in practice — "to water before
feeding."

The colon is divided into two portions — double and
single; for after proceeding a certain distance the bowel
bends backwards and returns on the same course, becoming
attached to the diverging portion by the meso-colon, and
in some parts closely in contact with it. The posterior
part of the colon, however, runs a single course, being
situated at the free margin of the mesorectum, and like
the free portion of the small intestine having no regular
situation. It takes the following course : — Commencing at
the right lumbar region with two muscular bands, it runs
in a forward direction from the caecum caput coli into the
right hypochondriac region, where it obtains a third, and
subsequently a fourth longitudinal band ; passing over to
the left, above the ensiform cartilage, it gains the left
hypochondrium, and, in running from this backwards,
grows gradually smaller in calibre as it passes through the
left lumbar into the left iliac region. Its bands also
decrease in number, so that when it makes its sigmoid
flexure in the left iliac region it has but one, and that is
on the attached margin. The bowel is here very small,
though not so small as at its commencement, and in pass-
ing forwards through the left lumbar and left hypochon-

THE ABDOMEN. 235

driac regions, superiorly placed to the diverging portion, it
increases in size and the number of its bands until it again
reaches the epigastric region, when it inclines backwards,
it attains its maximum calibre, and has three muscular
bands. After passing into the umbilical region it termi-
nates in the single colon, which has two muscular bands,
hangs freely in the free margin of the mesorectum, being
about three^ feet in length, until at the central line poste-
riorly it terminates in forming the rectum, which runs
directly from the posterior part of the hypogastric region
to the anus. Its muscular wall is very thick with the
fibres well marked; superiorly it is in contact with the
under surface of the sacrum and the structures about it ;
while its inferior surface, in the male, rests upon the upper
surface of the bladder, prostate, &c., and in the female
upon the vagina. In contact with its walls laterally is the
hypogastric plexus. Its muscular coat terminates poste-
riorly in forming the inner portion of sphincter ani, of
which the external portion is formed of dark-red fibres,
supplied with nerve-force hy the posterior part of the spinal
cord. To this muscle superiorly is attached levator ani,
running from the under part of the anterior coccygeal
bones. Laterally, retractor ani, from the inner surface of
the sacro-sciatic ligament, as far forward as the ileum ;
inferiorly, depressor ani, which, in the female, blends with
sphincter vaginae ; in the male with retractor penis. The
mucous membrane of the rectum is continuous posteriorly
with the thin, hairless skin, which is around the anus
" like the mouth of a draw-purse," and which has many
sebaceous glands. Some fat also enters into the formation
of the anus. The glands and villi of the mucous mem-
brane gradually decrease in number from the csecum to
the anus.

The spleen is a peculiar sickle-shaped organ, attached to
the left extremity of the greater curvature of the stomach
by the gastro-splenic omentum. Of a bluish colour, and
about three pounds in weight ; it presents a base and an
apex^ a greater and a lesser curvature, and two surfaces. The
hase is attached up against the left kidney, and prerenal
capsule, and from this the organ extends in a downward and
backward direction and towards the right side, gradually de-
creasing in size. The lesser curvature, hilum, is that situated
nearest the stomach along which the vessels of the organ

236 OUTLINES OP EQUINE ANATOMY.

run ; from this tlie organ decreases in thickness towards
the greater or free curvature, around which the serous
membrane is reflected joining the layers on the surfaces ;
the curvatures meet at the apex. The special ca29s^^Ze oftlie
spleen consists mainly of yellow elastic tissue, whereby it is
endowed with great capacity of distension, for it is an
erectile organ. From this outer covering trabecules or
septa project inwards in all directions, thus dividing the
organ into spaces which contain a peculiar reddish matter,
spleen pulp, ai^tly compared to raspberry jam. On ex-
amination under the microscope this is found to consist
essentially of large cells, each containing one or more red
cells, in a more or less advanced state of disintegration,
for it is supposed that the spleen is the organ whereby
excess of red corpuscles in the blood is prevented. The
spaces between the trabeculse also contain vessels. The
arteries, derived from the splenic branch of the coeliac axis,
terminate in venous sinues, and are also remarkable for pre-
senting at various intervals, embedded in their fibro-areolar
coat, small bodies analogous in structure to the solitary
glands of the intestines. These are Malpighian corpuscles,
the use of which is not known, and which consist of aggre-
gations of cells embedded in a fibrous stroma. The veiiis of
the spleen commence from the venous sinuses, they have
few if any valves, and pour their contents into the vena
portse. The nerves of the spleen are derived from the
semilunar ganglion. The prerenal capsule is another organ
the use of which is undetermined. There is one on either
side of the body, situated between the kidney and the
spine, and presenting two surfaces. It derives its blood
by a special arterial branch, either from the posterior aorta
or from the renal arteiy. When cut into it presents an ex-
ternal dark, or cortical portion, the use of which is unknown ;
and a central lighter medullary part, supposed to be a nerve
centre. It is included among the ill-understood ductless
or vascular class of glands.

Having removed the alimentary viscera from the belly
we are enabled to examine the structures situated in the
upper part of the cavity. On the central line we see im-
portant vessels and nerves. The posterior aorta, after
passing through hiatus aorticus of the diaphragm in
company with the thoracic duct and vena azygos, runs
backwards, inclined to the left side of the spine. In its

THE ABDOMEN. 287

course it gives off important vessels. Coeliac axis, a single
trunk, is but a short vessel, for it soon breaks up into
three branches, gastric, splenic, and hepatic. The gastric
runs direct from its commencement to the central part of
the lesser cui-vature of the stomach, where it breaks up in
forming the superior and inferior gastric arteries. The
splenic inclining to the left side and gaining the base of
the' spleen runs along its lesser curvature between the two
folds of peritoneum which constitute gastro-splenic omen-
tum. During its course it gives off large branches to the
spleen, smaller branches to the stomach, and at the apex
of the spleen is continued along the greater curvature of
the stomach as the left gastric artery. The hepatic artery,
which inclines to the right side, has already been de-
scribed.

Anterior mesenteric artery (in the ass extremely liable to
aneurism from the presence of parasites of the nematode
class — strongylus armatus) arises from the under part of
the posterior aorta. It gives off a few branches to the
pancreas which completely surrounds it. And then the
branches : mesenteric, thirteen to eighteen in number,
which radiate through the mesentery to the small intestine ;
the first anatomoses with the duodenal branch of the
hepatic, the last with the ccecal branch, which in its turn
communicates with the tranches to the double colon, and
they with that to the single colon, which joins the first
branch of the posterior mesenteric artery, a vessel
supplying the single colon and rectum in a manner already
described ; it arises from the under surface of the posterior
aorta just prior to its termination.

Renal arteries arise from the lateral part of the posterior
aorta just behind the anterior mesenteric trunk. They are
large vessels, given off at right angles. They are also
termed the emulgent arteries, and before arriving at
the kidneys break up, sometimes sending a branch to the
prerenal capsule (which sometimes arises from the posterior
aorta). Most of their branches enter the kidney at a
particular notch, in its substance termed the hilum, some
run to other parts of the organ. The inclination of the
posterior aorta to the left side of the spine renders the
right renal artery the longest, for it has to pass under the
posterior vena cava. It is also given off more anteriorly than
the left.

238 OUTLINES OF EQUINE ANATOMY.

The spermatic artery is given off from the posterior
aorta, between the commencement of the renal and the pos-
terior mesenteric vessels. It is remarkable for its length
in proportion to its size, and for the convoluted manner in
which it runs through the spermatic cord. It runs in a
downward and backward direction to the internal ab-
dominal ring, where it gains the spermatic cord, in the
anterior part of which it passes much curled upon itself. On
getting near the testicle it sends off small long branches
to the commencement portion of the vas deferens, and on
gaining the antero-superior part of the organ divides into
two parts, one of which runs in a backward direction, the
other downwards until it gams the inferior margin, when
it also curves backwards. Both of these divisions send
branches into the substance of the organ which help to
form the tunica vasculosa. Sometimes the artery of the
cord is given of£ from the posterior aorta (often from the
external iliac). It runs to the posterior part of the cord,
supplying the cremaster and vas deferens. These vessels
are arranged as above described in the male, but in the
female the ovarian artery takes the place of the spermatic,
being much shorter and smaller in every respect. These
conditions, however, are reversed in the uterine artery,
which much exceeds its analogue the artery of the cord in
size, especially during pregnancy. It runs downwards and
backwards towards the pelvis between the two folds of
peritoneum which constitute the broad ligaments of the
uterus.

From its upper surface the abdominal portion of the
posterior aorta gives off the lumbar arteries, which passing
upwards, give branches to the psoae muscles, others to
the muscles on the loins, the medullary arteries to the
lumbar vertebrae, and the arteries to the lumbar por-
tion of the spinal cord. Then the posterior aorta gives
off the external iliac arteries in an outward direction,
whereby it is much reduced in calibre, and under the
second sacral bone it terminates in forming the internal
iliacs, and sometimes the middle sacral, the former
running downwards and outwards, the latter directly back-
wards. On the right side of the posterior aorta runs the
posterior vena cava ; it commences beneath the anterior
part of the under surface of the sacrum, resulting from the
convergence of the common iliac veins, and in passing

THE ABDOMEN. 239

forwards, receives sorae veins corresponding to arteries
given off by its companion YQS,s,Q\,spermaticvein, posterior luni'
har veins (anterior Imnhar veins combine to form vena azygos)
and renal veins. Of the renal veins, the left is the longest,
but the right anteriorly placed, and shortly after receiving
this vessel the post vena cava passes through its sjDecial
channel in the upper part of the right lobe of the liver.
While passing through this it presents the oj^enings, num-
erous and varying in size, of the hepatic veins, and on
emerging, is surrounded by the coronary ligament in its
short course to foramen dextrum, where it receives the
plirenic venous sinuses, and then runs straight through the
chest, enveloped in a special fold of pleura to the base of the
heart.

On removing the peritoneum from the lateral parts
of the upper surface of the abdomen, we find that it
simply covers the under surface of the kidneys, from
which it is separated by a quantity of fat, unusually
firm in consequence of the predominance of stearin in
its composition. This is vulgarly named "suet," and
by some anatomists has been termed the tunica adiposa
renalis.

The kidneys are the organs which serve to separate urine
from the blood. They are two purple-coloured organs
situated up against the crura of the diaphragm. The
right is most anteriorly placed, and differs from its fellow
in being heart-shaped, and resting against the diaphragm,
and in a special depression on the upper part of the right
lobe of the liver termed the fossa re7ialis. The left kidney
is elongated from behind forwards, being shaped like a
"kidney-bean." It receives the shortest artery and the
longest vein, and lies in contact with the base of the sj^leen
and with the left extremity of the stomach. Both kidneys
have a prerenal capsule in contact with the anterior part
of their inner border which presents a notch or hilum, to
which most of the branches of the renal arteries pass, and
from which those of the renal vein together with the ureter
commence. The anterior part of the kidney is slightly the
largest, the outer margin convex, the inner straight, while
the under surface is flatter than the upper. The organ is
supported by a special stroma {renal capsule) which is con-
siderably more abundant in the substance of the organ,
investing its vessels, and connecting together its com-

240 OUTLINES OF EQUINE ANATOMY.

ponent structures. A horizontal incision displays centrally
a cavity lined with mucous membrane, pelvis. Externally a
reddish-mottled smooth surface, cor?fzcaZjJorh'o%, andbetween
the two, the medullary ijortion, which is apparent to the
naked eye as consisting of tubular fibres, radiating from
the central cavity to the cortical portion. By microscopic
examination we may find that these tubes, hibuli uriniferi^
are continued into the cortical portion, when they be-
come much convoluted, forming the tuhidi contorti, and
finally terminate in blind dilated extremities, Malijigliian
capsules.

The branches of the renal arteries after division and
subdivision by traversing the medullary part, and breaking
up in their course gain the cortical portion, where as small
afferent vessels they run to the Malpighian corpuscles of
which they push the mucous membrane before them, caus-
ing it to bulge towards the commencement of the tubulus
uriniferus, for they exert their pressure at a point opposite
to this. On entering the depression of the wall of the cor-
puscles thus produced, the vessel breaks up into smaller
branches,which divide and reunite producing the glomerulus
or Malpighian tuft, from which arises the efferent vessel,
which emerges from the depression at the point where the
afferent vessel enters, and then runs to the wall of the
contorted portion of the uriniferous tube, around tvJiich it
forms a plexus of capillaries, from which veins arise, and
after passing through the medullary portion of the kidney
by union and reunion, combine to form the renal vein.
The tubuli uriniferi in the medullary portion, in their
course from the cortical portion to the pelvis, unite two
by two (dichotomously),and as this occurs frecjuently, the
whole of the tubes opening by one perforation into the
pelvis may be represented by a pyramid, the base of which
is at the cortical portion, the apex at the pelvis, and in the
foetal colt the kidney is lobulated, divided into the ''pyra-
mids of MaljngJii," while the same condition obtains per-
manently in the ox. The pelvis of the kidney of the horse
is a fan-shaped cavity lined by spheroidal epithelium, and
around its convex border a ridge extends on to which the
uriniferous tubes open. This ridge terminates laterally in
cavities termed calyces of the pelvis, while at the hilum the
pelvis is continuous with the ureter. This is a musculo-
membranous canal extending along the roof of the abdo-

THE AB'JOMEN. 241

men, downwards, outwards, and backwards to the pelvis,
where it terminates at the supero-posterior part of the
bladder. It first passes through the muscular coat of that
organ, and after running for a short distance between
this and the mucous coat, penetrates the latter, and thus
distension of the bladder serves more securely to prevent
reflux of urine upon the kidneys. It presents a muscular
coat, with an external layer of longitudinal, and an internal
layer of circular fibres, and is lined with mucous memhrane
which presents epithelial cells of the spheroidal character.
The ureters run between the two layers of the broad liga-
ments of the bladder, and hence are by some anatomists
described as having an external serous coat. The bladder
is situated in the lower part of the pelvis, and is a pyri-
form organ, rounded anteriorly, terminating posteriorly in
becoming constricted to form the nech. The anterior por-
tion is the fundus, and the portion between the fundus
and the neck is the hody. Superiorly it is in contact in
the female with the vagina and the uterus, with the rec-
tum in the male ; while on either side from before back-
wards run a vesicula seminalis and a vas deferens. The
under surface rests upon the upper concave surface of the
j)ubic portion of the ossa innominata. The fundus presents
a remarkable puckering, the result of the change which
the bladder undergoes after birth, whereby it gradually
decreases in proportionate size, and tends to retract from
the umbilicus into the pelvis, from which it extends into
the abdomen in a degree varying with its plenitude. To
the fundus run the round ligaments of the bladder, which
diverge at an acute angle and run forwards and outwards,
enclosed in the double folds of peritoneum forming the
hroad ligaments, towards the umbilicus. The fundus also
receives a coating of peritoneum which forms a small cap for
it, extending farthest backwards superiorly and presents
double folds runnmg in various directions ; thus longitu-
dinally forwards the falciform or suspensory ligame7it yvlus to
the umbilicus. Laterally, the broad Ugamerits (with the
round ligaments in their free margins) to the walls of the
cavity, and superiorly a longitudinal fold, vesico-rtctal fold
in the male, vesico -vaginal in the female. The vesico-rectal
fold is bounded laterally by the vasa deferentia, and encloses
the third vesicula seminalis between its layers. The ureters
pass to the supero-posterior part of the bladder, and open

IG

2i2 OUTLINES OF EQUINE ANATOMY.

into it in the peculiar manner already described. Tlie
organ presents tiuo coats — muscular arid mucous. When it
is distended, the mucons coat may he seen between the mus-
cular fibres, which seem to be irregiilarly arranged, but they
present a species of oblique arrangement on closer inspec-
tion, forming what is termed detrusor urinw, while towards
the neck of the bladder they tend to assume the circular
form, producing the sphincter vesicce. The mucous coat
lines the bladder throughout, and is continuous with that
of the ureters, and with that of the urethra ; it presents-
thick and viscid epithelium, which serves to protect the
organ from the irritant action of the urine, and much of
which is expelled with that fluid.

The urethra is a membranous elongated passage, com-
mencing at the neck of the bladder and running in a
backward direction as far as the ischial arch, around which
it winds, and then runs in a forward direction forming the
central part of the penis, to between the symphysis pubis
and the umbilicus. It consists of a mucous membrane,
which extends throughout, and in some parts presents large
mucous crijpts or lacunoe, which also communicates with
that hning the bladder, ejaculatory ducts, prostatic, and
Cowper's ducts, and with the lining layer of the prepuce.
It is divided into three ^ovtiows,, prostatic, membranous, and
spongy. The prostatic portion is the shortest, and is sur-
rounded by the prostate gland. It commences at the neck
of the bladder and passes to the membranous portion.
Its mucous membrane presents at its upper part two pecu-
liar prominences perforated by two foramina, the openings
of the ejaculatory ducts formed by union of the vasa
deferentia and of the ducts from the vesiculae seminales.
This prominence is the veru montanum or caput cjallina-
ginis. On either side also may be seen a row of small
papillae, on to which open the prostatic ducts. The mem-
branous portion extends from the prostatic as far back-
wards as the ischial arch, and on its postero-lateral parts
are two rounded bodies about the size of a walnut. These
are Coivpers glands, and like this jDortion of the canal
they are invested by a portion of muscle, Wilson's muscle,
the fibres of which run transversely above the canal from
one side to the other. Like the prostatic their ducts oj)en
upon numerous small papillse arranged in rows, one on
each side of this portion of the urethral canal. The

THE ABDOMEN. 243

spongy portion is completely invested by tlie corpus spon-
giosum of the penis, and anteriorly dilates, forming the
widest joortion or fossa navicularis, prior to terminating in
its narrowest ]jortion, meatus urinarius extermis. A catheter
which will pass through here will pass along any portion
of the canal, unless obstructed by foreign matter.

The prostate gland is a body which embraces superiorly
and laterally the neck of the bladder. It is divided into
two lateral, and a connecting isthmus or middle lohe. This
gland is racemose in its nature, and pours its secretion
through the above described openings into the urethra.
Cowper's glands are two in number, and are covered by
Wilson's muscle ; they resemble the prostate in structure.
The function of these glands is but little known. Their
secretion, by mixing with the semen, is considered to in-
crease its efficacy. The prostate gland hides from view
the terminal portion of the vas deferens, and of the duct
of vesicula seminalis and the ejaculatory duct.

The penis is a dense elongated organ extending from
the posterior part of the ischium in a forward direction
under the symphysis of the ossa innominata. It is mainly
composed of the corpus cavernosum. This is situated
at the superior part, and presents a supero-lateral surface,
rounded and covered by a plexus of veins, an inferior sur-
face concave forming a groove through whrch the urethra
(spongy) runs, surrounded by corpus spongiosum. Ante-
riorly it presents two sharp points, which are concealed by
the glans penis; posteriorly, by bifurcation, it produces
the crura, dense, yellowish, fibrous bands running to be-
come attached to the tuberosities of the ischium, which are
surrounded by the erectores penis muscles, arising from
the tuberosities of the ischium and becoming inserted into
the root of the penis. On transverse section this organ
will be found to present a tendency to division into two
parts. It has externally a thick layer of yellow elastic
tissue, from which trabeculae and bands are sent inwards,
which, by their union and reunion, produce spaces, which
are occupied by venous sinuses. The most remarkable of
these septa projects from the central line at the superior
part. It consists of a number of bands running down-
wards, resembling in arrangements the teeth of a comb,
septum pectiniforme.

The penis anteriorly receives blood from the external

244 OUTLINES OF EQUINE ANATOMY.

puclic artery, whicli sends a brancli backwards along the
upper surface of the organ to meet the anterior hranch of
the internal pudic, which also gives off a branch backwards
to gain the artery of the bulb. Immediately investing
the surface of the urethra, situated in the inferior groove
of corpus cavernosum, is corpus spongiosum, a thin layer
consisting of erectile tissue analogous to that found in
the hard palate serving to connect the mucous membrane
to the bony palate. Thus it consists of a network of
elastic tissue, through which blood-vessels ramify, and
which sometimes presents venous sinuses. Posteriorly,
against the crura, it forms a small dilatation termed the
bulb, which is covered by erectores penis. Posteriorly
it forms a large prominent portion, glans penis, which,
under erection, assumes the shape of the extremity of a
trumpet. It completely covers the anterior portion of the
corpus cavernosum, and around its outer circumferent
margin is a row of glands, corona glanclis, which secrete a
sebaceous material. It is covered by a highly sensitive
mucous layer, and at its centre, inclined to the lower part,
presents a deep depression, into which the anterior extre-
mity of the urethral canal projects, and which secretes a
strong-smelling greyish matter, termed smegma preputii.
Prom one infero-lateral part of the corpus cavernosum to
the other, transverse, dark- coloured muscular fibres run
underneath the urethra and corpus spongiosum, forming
the accelerator urinae muscle, which runs from the glans
penis as far back as the erectors. Along its under surface
may be seen two bands, apparently of white fibrous tissue,
which may be traced as far as the lateral part of sphincter
ani. These are the retractores penis, composed of invo-
luntary muscular fibres.

The penis as above described is inferiorly covered by
skin which communicates laterally with that covering the
thighs, superiorly with that ^^ortion extending towards the
anus over the sj)ace termed the perineum, and anteriorly
it spreads outwards and joins the posterior part of the
cuticular layer of the scrotum, and in front of this the outer
layer of the prepuce. The prepuce or foreskin is a circular
inversion of the skin inward to form mucous membrane.
Anteriorly it is continued forwards to form a raphe in the
neighbourhood of the umbilicus. The skin in this region
is very thin, and in most horses almost hairless. The

THE ABDOMEN. 245

mucous membrane lining tlie prej)uce is darkened bj pig-
ment, and presents many glands, cjlandulce odoriferce, which
secrete a peculiar unctuous lubricating matter. It is con-
tinuous with that of the glans penis. Between it and the
skin is a layer of yellow elastic tissue, reflected from the
faschia superficialis abdominis, which, forming a sling be-
neath the anterior part of the penis, is termed the suspensory
ligament. From the central part of the under surface of
symphysis pubis a fibrous ligament extends, composed
of two diverging portions, one of which runs to either
side of corpus cayernosum ; this is the triangular ligament
of the penis, between its two parts runs a vein. This organ
serves to direct into the vagina of the female the semen or
tnale fecundating fl.uid. Semen is produced by certain organs,
testes or testicles, which are suspended from the upper part
of the abdominal cavity in certain special cavities, vaginal
cavities, situated at the posterior lateral and inferior part
of the belly. These cavities are covered by layers con-
tinuous with those of the floor of the abdomen which form
the

Scrotum, or "jji^r^e," situated just behind the sheath, which
presents externally a layer of thin skin, along the central
line of which running from before backwards is an irregu-
lar ridge or raphe. This covers the dartos muscle, com-
posed of unstriated muscular fibres, continuous with faschia
superficialis abdominis, which throws across the cavity a
septum (septum scroti), whereby the right scrotal cavity
is separated from the left. It is contraction of this
which causes corrugation of the scrotum under the in-
fluence of cold, by means of the inter collumnar faschia
(derived from obliquus abdominis externus), its inner sur-
face is attached to the cremasteric faschia.

The cremaster muscle is but a portion of the internal
oblique of the abdomen. Arising from the psoas faschia,
or from the antero-inferior spinous process of the ilium, it
passf s through the inguinal canal and the external abdo-
minal ring, externally situated to the spermatic cord, and
on approaching the scrotum its fibres form a species of
sling serving to support the testis. To this portion the
name cremasteric faschia is applied, and its internal surface
is connected by the infundihuliform faschia (occasionally
connected with transversalis abdominis) to the external
surface of tunica vaginalis scroti or propria, a continuation

21-6 OUTLI>ES OF EQUINE ANATOMY.

of tlie serous membrane covering the floor of tlie belly
through the inguinal canal. The external surface of this
membrane is sroooth, covered with tessellated epithelium,
which secretes a serous fluid to enable the surface of tunica
vaginalis testis or reflexa to glide on it freely. These two
serous layers are posteriorly connected by d^frcenimi, which
extends up as far as the loins whence the testes originally
descended. In the fcetal colt, as in adult birds, the testis
occupies a position against the kidney. To its under part
is attached a white fibrous cord, gubernaculum testis, sur-
rounded by serous membranes, running to the internal
abdominal ring. In the process of development this guides
the testis towards the inguinal canal, and then becoming
everted in passing into the scrotum, its serous covering
becomes the tunica vaginalis scroti. The testis may
generally be found in the scrotum at birth ; it subse-
quently, at a period varying according to the breed and
treatment of the colt, passes again into the inguinal canal,
where it remains for some time, sometimes permanently,
and again descends into the scrotum. Sometimes, how-
ever, it is drawn up into the abdomen, and on account of
increase of its size is unable again to descend. If this
occurs to but one testis, the animal is termed a monorcJiid or
rig, and if the other testis has been removed by castration,
he will be lustful, but an uncertain stock-getter.

The immediate coats of the testis are a serous layer,
tunica vaginalis testis and tunica alhuginea. The latter is a
dense fibrous mass, forming the stroma of the organ, send-
ing fibres and septa inwards from an outer layer, to support
and separate the different lobules of the gland, and to in-
vest its larger vessels. It predominates at the upper part
of the organ, where it is termed mediastinum testis. The
testis consists of a number of long tubules curled uj)on
themselves, forming the lohuli testis. Each lobule is iso-
lated from its fellows, receives a vascular coating (by some
anatomists termed tunica vasculosa), and terminates Supe-
riorly in a vas rectum. The vasa recta unite and form a
plexus in the substance of mediastinum testis, at the
anterior part of which they converge to form the vasa
effereiitia, which emerge from the testis proper, and, be-
coming very convoluted, (coni vasculosi), form the j^os^mor
globus of the ejndidymis.

The testicle, thus constituted, is a rounded body, clon-

THE ABDOxMEN, 247

gated from before backwards, slightly flattened from side
to side. It is firm to the touch, but on laying it open we
find that it consists of a quantity of soft greyish matter.
From its antero- superior part the epididymis commences
and extends from before backwards, consisting of an ante-
rior and a posterior glohus^ and a hody. The anterior ^ or
^mailer globus consists of the contorted vasa efferentia ;
they, however, unite and reunite, becoming larger in
calibre, until they form but one tube, which, by its extreme
convolution, forms the hody and the ]josterior or major
globus, from which, as the vas deferens, it passes up the
posterior part of the spermatic cord towards the pelvis,
where it becomes dilated on the superolateral part of the
bladder, and, after passing beneath the prostate, opens into
the urethra near its commencement.

The epididymis is connected to the testis by a double
fold of visceral vaginal serous membrane, which is con-
tinued upwards to the internal abdominal ring surrounding
the spermatic cord. In the anterior part of the cord runs
the extremely convoluted spermatic artery with the plexus
of spermatic vems or cmyus pamjnniforme ; in the poste-
rior part the vas deferens with the artery of the cord. The
walls of the sperni-bearing vessels or tuhuli seminiferi increase
in complexity from their commencement to the termination
of the vas deferens in the urethra. At first they consist of
but basement membrane and epithelial cells, in which
latter may be seen round bodies, which in their course to
the vas deferens gradually acquire tails, and at length
become free as spermatozoa, small, actively moving bodies,
propelled by the vibration of an elongated cilium, running
from the posterior part of the cell, giving it a " tadpole-
like" appearance. The muscular walls of the vas deferens
^re thick, giving it its distmctively firm feel in its course
through the spermatic cord.

The testis derives its nerves from the hypogastric
plexus.

Vesiculae seminales are pyriform sacs, resting upon the
supero-posterior part of the bladder, in such a manner
-as to conceal the terminations of the ureters. They have
but very thin walls, and each terminates anteriorly in a
blind pouch, posteriorly in the duct which unites with
vas deferens to form the ejaculatory duct, which runs
to a special opening on the veru montanunu It pre-

:2tt8 OUTLINES OF EQUINE AXATOilY.

sents a small amount of m.uscular structure in some parts
of its walls, and is lined with mucous membrane. There
is no doubt but that it secretes a special fluid to be added
to the semen. It also may, to a certain extent, serve as a
receptacle for retention of the semen until it is required
for use.

The generative organs of the male produce the sperm-
cell, those of the female the germ-cell or ovum, and without
contact of these two cells reproduction cannot occur. The
ovum is produced in a special organ, one of which is
situated on either side of the spine in the lumbar region.
These are the ovaries or female testes. They are smaller
than the testes of the male and more rounded, and their
external surface is generally lobulated in consequence of
projection of certain vesicles which the organ contains. It
is invested by peritoneum, being situated at the anterior
part of the broad ligament of the uterus, and presents a
white fibrous stroma, tunica alhugmea, embedded in which
are certain vesicular bodies lined with tessellated epithe-
lium, and containing a quantity of albuminous fluid, in
which floats the ovum. These cysts receive the name
Graafian vesicles, and their lining membrane, which is
thickest at that part with which the ovum lies in contact,
is the memhrana granulosa. The ovum is a cell consisting
of a ceZ?-i6-a?/, zona pelliicida, and cell contents; the latter
consists of a nucleus or germinal vesicle, and a nucleolus
or germinal spot, floating in an albuminous fluid.

The Graafian vesicles are sraallest at the centre of the
organ, and gradually increase in size on extending towards
the outer surface. By pressure they cause absorption of
the stroma, and thus at length bulge against the peritoneal
coat of the organ. Finally they rupture, thus discharging
their contents into the Fallopian tube. This occurs when
the animal is in "heat," as it is commonly termed, and
thus the ova commence their process of development into
the foetus. After rupture the Graafian vesicles become
filled with a mixture of blood and lymph, Vv'hich undergoes
contraction and organization until a stellate cicatrix, corpus
luteum, is produced, which is much more persistent when
its ovum has been impregnated than when it has under-
gone no further stage of development. These bodies
form our main guide in post-mortem decision, as to
whether an animal has ever been pregnant or not.

THE ABDOMEN. 249

Attached to the ovary is the Fallopian tube, a trumpet-
shaped organ, the anterior extremity of which presents a
very irregular margin, which is much jagged, and is
termed the jimhriated extremity or morsus diaholi. It is one
of the divisions of this extremity which connects it to the
ovary. It is perforated by a canal, which posteriorly gains
the- cavity of the uterus at a very small extremity in the
extreme anterior part of the horn of that organ. Ante-
riorly it dilates, opening into a peculiar serous sac of which
the ovary forms one boundary and which communicates on
one side freely with the main peritoneal cavity. The
ciliated epithelium with which it is lined is here replaced by
tessellated epithelium. This is considered remarkable as an
instance of a mucous membrane being directly continuous
with a serous membrane, but the histological distinction
between the two is insignificant. During sexual excite-
ment the fimbriated extremity is supposed to grasp the
ovary, approximating its anterior opening to the rupturing
Graafian vesicle. The tubes are convoluted, and present
muscular fibres of the unstriated class in their walls.

The uterus is a large organ which occupies the anterior
part of the pelvis and the posterior part of the abdomen.
Its position, however, varies with its j^regnant or unim-
pregnated condition. Anteriorly it is bifid, presenting
two rounded sacs, the cornua or liorns. These meet at
an acute angle in the mare ; thus the equine uterus pre-
sents no fundus or space between the cornua. They open
into the body, which extends backwards to terminate in-
the nech, the portion running for a short distance into the
vagina to terminate at the os uterinum externum. The
oj^ening leading from the cavity of the body of the organ
to the passage of the neck is os uterinum internum. The
uterus is completely enveloped by peritoneum, being en-
closed in a double fold of that membrane, which on either
side extends to the supero -lateral parts of the abdomen,
forming the hroad ligaments of the uterus, on the free mar-
gin of which are the ovary, fallopian tube, and uterine
horn. Between the two layers of this ligament the round
ligament of the ovary runs from that organ to the extre-
mity of the horn of the uterus, from which point another
white fibrous (or muscular band) runs towards the internal
abdominal ring, where it becomes lost, the round liga-
ment of the uterus. The ovarian artery, after bemg

250 OUTLINES OF EQUINE ANATOMY.

given off by the posterior aorta, runs tlirougli tlie broad
ligament to the ovary, wliere it breaks up, forming, accord-
ing to some anatomists, a tunica vasculosa surrounding the
organ. It corresponds to the spermatic artery of the male,
than which it is much smaller. Through this ligament,
the vessel corresponding to the artery of the cord in the
male, the uterine artery takes a convoluted course down-
wards and backwards. It is much larger than the artery
of the cord, and increases very considerably in size during
pregnancy. The muscular coat of the uterus presents two
layers of fibres ; longitudinal externally, circular internally
(it also has oblique fibres) . These are of the unstriated order,
but during pregnancy become developed into fibres with faint
traces of striae. The mucous membrane is of a reddish colour,
and collected into rugae in the unimpregnated uterus. It
becomes highly vascular, and its epithelium much increased
in quantity during pregnancy ; for the blood of the foetus
passes to the chorion, a membrane lying in intimate con-
tact with the vascular part of the mucous membrane of
the dam, and in which the ^^rocess of aeration of the blood
ensues. (The excess of epithelium after parturition is
thrown off as the membrana decidua.) In some parts,
especially up against the fallopian tubes, the epithelium
is ciliated, serving to waft the spermatozooa upwards.
Around the neck of the organ the mucous glands increase
in complexity, and secrete a more viscid matter ; they are
the glandulce of Nahoth. The muscular coat in the cervix
uteri is very thick, thereby causing puckering of the
mucous membrane longitudinally in this part ; laterally
it comes in contact with the muscular coat of the vagina,
and posteriorly, covered by the mucous membrane, pro-
jects in a remarkable manner into the vaginal cavity "like
the tap of a beer barrel," thus forming the cauliflower
excrescence {fleur ^panouie of the French anatomists) , which
projects more inferiorly than superiorly.

The vagina is the cavity placed immediately posterior
to the uterus extending to the vulva, from which it is
separated by the hymen. It is largest centrally, becoming
anteriorly constricted in surrounding os uteri, and running
to join the cervix ; posteriorly smaller in joining the vulva ;
superiorly it is in contact with the rectum ; inferiorly with
the bladder. Its anterior part is covered with peritoneum,
which laterallv blends with the broad ligaments of the

THE ABDOMEN. 251

uterus, and sends off longitudinal folds; superiorly the
vagino -rectal, inferiorly the vagino-vesical, folds to tlie
rectum and bladder respectively. It presents also a mus-
cular coat with longitudinal and circular fibres ; in contact
with this lies a quantity of erectile tissue, analogous to that
forming the corpus spongiosum of the penis. It is lined
by' mucous membrane, with stratified squamous epithe-
lium, and which anteriorly becomes puckered up to join
that of the nect of the uterus ; posteriorly forms a re-
markable double fold, hymen, almost, but seldom com-
pletely, separating the vaginal cavity from that of the
vulva. Generally lunate in the virgin, it is lacerated in
the first act of coition by the penis of the stallion, and
subsequently appears as an irregular fringe extending
round the vagino-vulval opening, carunculsB myrtiformes.

The vulva leads from the vagina to the external genera-
tive opening, and presents coats similar to those of the
vagina, with a much greater quantity of erectile tissue
(bulb of vulva). Posteriorly the muscular coat becomes
redder in colour, with its fibres striated and arranged in
a circular manner around the external opening, forming
the sphincter vaginsB (more correctly sphincter vulvse).
The floor of the vulva, just behind the hymen, about four
inches from the lower j)art of the external opening, pre-
sents the meatus urinarius externus, much larger than
that of the male, being the opening from a larger canal ;
between this and the hymen anteriorly is a valvular flap
of mucous membrane.

The external generative opening is an elliptical fissure
extending from above downwards. It terminates above in
an acute angle, superior commissure, situated about two
inches below the anus, the intermediate space being peri-
neum. Below, it is more rounded, forming the inferior
commissure. The opening is bounded laterally by the
labia, elongated prominences consisting of the sphincter
vulvae, fat, and vascular structure covered externally by
thin, hairless skin, which externally is continuous with the
mucous membrane of the vulva, the latter becoming folded
longitudinally to form the labia minora or nymphse. At
the inferior commissure is a triangular space, which may
be exposed by sej^aration of the labia, fossa navicularis,
on which projects the clitoris, a small organ analogous to
the penis of the male, and the seat of the pleasure expe-

252 OUTLINES OF EQUINE ANATOMI.

rienced during sexual intercourse. It is surrounded "by
a mucous fold, prseputiiim clitoridis, whicli covers its free
extremity, and centrally presents a depression leading into
a blind sac, wliicli generally contains an odorous oily
matter. This organ is fixed by two crura to the ischial
arch, has two erectores clitoridis running to its substance
from the same part, a,nd presents a corpus cavernosum, a
corpus spongiosum, and a cjlans.

The young animal at birth being incapable of supplying
itself with nutriment, and even incapable of digesting or-
dinary alimentary matters, is for a time supplied with
milk produced by the mammary gland of the dam. This
function the mare shares in common xvWh all the females
of the higher order of vertebrated animals, mammalia.
Situated between the thighs are two prominences, from the
under part of which small finger-like portions project,
having at their extremity three or four small openings.
These are the teats, and they are covered by a continuation
of the delicate skin investing the mammary glands. They
are longest in the animal which has " given suck." The
faschia superficialis abdominis, at the postero-inferior part
of the abdomen of the mare, is reflected downwards to
invest the mammary gland. It sends in septa between
the different lobes, for this is a racemose gland, presenting
a structure similar to that of the salivary glands. Its
primary secreting saccules, lined by spheroidal epithelium,
open mto the primary ducts, which unite and reunite with
those from other j^arts of the gland, until at length they
terminate in a dilated cavity at the base of the teat, galac-
tophorous sinus. This is divided into parts corresponding
in number, and leading by ducts to the openings on the
teats. The teats contain yellow elastic tissue, but no mus-
cular fibre, for the milk is withdrawn by the suction action of
the young animal. Around the openings the skin becomes
continuous with the mucous membrane of the glands.

Milk consists of water with an albumenoid matter,
casein (cheese), and salts, in solution. Floating in it are
numerous fat- globules, which form the cream. The first milk
produced after foaling contains a number of the epithelial
cells of the gland in a state of fatty change, a number
of fat-globules being connected together by the tough
w^all of the cell, forming the peculiar colostrum-corpuscles,
for this milk is termed colostrum (or beastlings). It has a

THE ABDOMEN. 253

laxative effect, and serves to remove from tlie alimentary
canal of the newly born animal the meconium or inspissated
biliary matter which has accumulated in the intestines
while the animal was in the uterus, in consequence of the
large supply of blood received by the liver during that
period. Where this precaution is neglected, the meconium
sometimes collects in large quantities of pellets, like sheep
dung in the rectum, causing obstinate constipation.

The dissector may be fortunate enough to obtain a preg-
^nant animal for dissection ; he will then be enabled to
study the FCETAL APPENDAGES. By cutting through
the walls of the uterus, he will expose the chorion lying
in immediate contact with the uterine mucous membrane
over its whole surface. It consists of an intricate network
of blood-vessels arranged in a ^^lexiform manner to come
in apposition with the vascular layer of the uterine mucous
membrane. While in these vessels, being separated from
the blood of the dam only by layers of epithelial cells and
of basement membrane, the blood of the foetus is enabled
to exchange carbonic anhydride for oxygen, sufficient in
quantity to support his torpid life, for he moves but little,
and his temperature is maintained by that of his dam in
whose body he lies ; thus two of the demands for oxygen
in the blood which obtain after birth are absent in the
foetus, and his life consists more in active addition to
existing structures, growth, than in disintegration of tissue
with substitution of fresh matter, such as obtains in the
adult. Blood from the internal iliac branch of the posterior
aorta of the foetus passes through the umbilical arteries.
These vessels, which in the adult become impervious, de-
generating into the round ligaments of the Madder, after
becoming attached to their respective sides of the bladder
gain the umbilical opening ; here they unite and form one
vessel, which runs outside the body of the foetus to the
chorion through the umbilical cord. The veins of the
chorion unite and reunite to at last form two vessels which
pass along the umbilical cord, and on gaining the umbili-
cus unite to form the umbilical vein, which runs in a-
forward direction along the floor of the belly between the
peritoneal folds, forming the falciform ligament of the liver
to which organ it runs without (in the colt) having any direct
communication with the posterior vena cava through the
ductus venosus as found in many other animals. It passes

254 OUTLINES OP EQUINE ANxiTOMY.

between two of tlie divisions of lobulus scissatus, where it
breaks np, and its blood, after ramifying througli the liver
(which is very large in the foetus), as in the adult, gains
the posterior vena cava through the hepatic veins. It
thus passes to the heart, and the major portion of it
through the foramen ovale in the septum auricularum
into the left auricle, where it meets with blood from the
lungs, and with it through the left ventricle passes into the
aorta, and from that into the anterior aorta, for the pos-
terior aorta is mainly occupied by another current. The
blood which gained the right auricle from the anterior vena
cava, though a small amount of it passes through foramen
ovale, for the most part having traversed the right ven-
tricle, gains the pulmonary artery, from which some passes
to the lungs, but a considerable portion through the ductus
arteriosus, a vessel connecting the pulmonary artery to the
posterior aorta. Through the posterior aorta some passes
to the body of the foetus and some through the uterine
arteries to be reoxygenated in the chorion. Foramen ovale
is an opening through septum auricularum just in front of
the termination of the posterior vena cava ; it is guarded
by a valve formed of a double fold of endocardium. After
birth it becomes obliterated on the left side, traces of it
remaining on the right side, forming the fossa ovalis sur-
rounded by a prominent yellow ring, annulus ovalis.

Immediately, but loosely, surrounding the foetus in utero
is the amnion. This is a thin membrane which presents
some extremely convoluted vessels, ramifying over its
surface, and serves to secrete a fluid in which the foetus
floats (liq[UOr aninii) . It is contmuous with the skin of
the foetus at the umbilicus, becoming reflected over that
portion of the umbilical cord nearest to this opening, and
which is therefore termed the amniotic portion. Floating
about in the liquor amnii generally are one or more
brownish masses of soft substance. These are the hippo -
manes, and are supposed to be composed of nutritious
matter. Sometimes they are attached to the inner sur-
face of the amnion. In this country they are generally
termed ''false tongues,'' from their peculiar shape.

Investing the amnion, and lining the chorion, is a serous
membrane, the allantois. Its parietal or cJiorial fortiori is
continuous with its visceral or amniotic portion by a portion
reflected over that part of the umbilical cord which ex-

THE ABDOJIEN. 255

tends from tlie amnion to tlie chorion. The amnion
presents the characters of all other serous membranes, but
it contains the urine of tke foetus, since the allantoid sac
is brought into communication with the bladder of the
foetus (from which it was originally derived) by the
urachus, a tube running through the amniotic part of the
umbilical cord. The foetus in utero, therefore, is surrounded
by his own urine. The umbilical cord, therefore, is
divided into two parts : The allantoid portio7i consists simply
of two umbilical veins, and an umbilical artery surrounded
by the allantois. The amniotic portion, in addition, contains
the urachus, and those vessels which belong to the amnion.
In both parts the vessels receive coatings of embryonic cells^
and in the amniotic portion the vessels are arranged spirally,
giving this part a rope-like appearance. Finally, we
may notice that the bladder of the foetus is larger in propor-
tion than that of the adult, extending to the umbilicus, where
it terminates in the urachus. That the so-called vascular
glands are largest in the foetus (in proportion) ; that the
kidneys are lobulated; the testes in the lumbar region in the
colt ; and the lungs, dark red solid organs, for they have
not yet been filled with air. When the labour-pains of
the dam occur the chorion is ruptured, and the amnion
with its serous layer is the first to protrude through the
external opening, being vulgarly termed the " water bag J'
On rupture of this the foetus is expelled, and sometimes in
falling ruptures the umbilical cord. The membranes
follow at variable periods. On first feeling the chill ex-
ternal air the young animal gasps, and so draws air
through the trachea, it permeates the air-vessels, and for
the rest of his life the animal is an air-breather. Those
communications between the several portions of the vascular
arrangement of the foetus, which are not required after
birth speedily become impervious ; if they are persistent
they cause disease.

We may examine the attachments of some muscles
underneath the loins.

Psoas magnus arises as far forward as the inner surface
of the last two ribs; it is attached to the transverse
processes of the lumbar vertebrae, and its fibres interiorly
join with iliacus in becoming inserted into trochanter minor
internus. Arteria profunda femoris runs across the in-
ferior tendon.

256 OUTLINES OP EQUi>,'E ANATOMY.

Psoas parvus is longer and thinner tlian psoas magnns.
Its fibres from the lateral part of the bodies of the last
three dorsal and the anterior liJinbar vertebrae converge
to form a tendon, which becomes inserted into the brim of
the pelvis midway between the antero -inferior spinous
process of the ilium and the acetabulum.

Quadratus lumborum is attached to the last rib, and to
the transverse process of all the lumbar vertebrae running
to the venter ilii near the crista.

Intertransversales lumborum are situated between the
transverse processes of the lumbar vertebraa.

The psoas faschia covers the under surface of the psose
muscles. It affords attachment to transversalis abdominis
and obliquus abdominis internus, and from it in some sub'
jects arise sartorius and cremaster muscle.

THE HIND EXTIIE5IITY. 257

PART IX.— SPECIAL ANATOMY.
The Hind Extremity.

From an incision wliicli the operator fii'st makes along
the central line of the quarters he dissects the skin back
over the external surface of the quarter, and posteriorly as
far as the incision originally made along the central and
inferior line of the body towards the root of the tail.
By so doing he exposes a wide-sj^read and rather thick
layer of substance of an elastic fibro-adipose material,
which covers the muscles of the quarter, and anteriorly
blends with the lumbar faschia, while superiorly, in blend-
ing with its corresponding layer from the opposite side, it
becomes firmly attached to the superior vertebral ligament
in the sacral region. This faschia of the quarter inferiorly
is imperceptibly blended with the faschia lata or the faschia
covering the thigh, and on removing it we find that gluteus
maximus and gluteus externus are attached to it to a con-
siderable extent, whence care is required in the process
to avoid injuring the appearance of the subject. By its
removal we expose the

Gluteus externus, a Y-shaped muscle, that is to say,
one with two points of origin, which converge to a common
centre of insertion. The anterior part we shall find arises
in common with tensor vaginae femoris from the inferior
part of the antero -inferior spinous process of the ilium,
while the posterior is attached to the spines and transverse
processes of the second and third sacral bones. The mus-
cular fibres of both these parts are more or less attached to
the under surface of the gluteal faschia, and blend opposite
the anterior tubercle of trochanter major, where they be-
come, for the most part, tendinous, and from this they run
to the trochanter minor externus, where they are firmly
inserted. Over the anterior tubercle this tendon plays freely

17

258 OUTLINES OF EQUINE ANATOMY.

through the medium of a synovial bursa. Almost as far
as the inferior part of the anterior extremity of this muscle

Tensor vaginae femoris blends with its anterior part to
a considerable extent. It arises from the inferior part of
the antero-inferior spinous process of the ilium, and in-
feriorly forms an aponeurotic expansion, which blends with
the faschia lata, and which slightly extends over the in-
ternal surface of the muscles in front of the femur. It
becomes firmly attached to the external surface of the pa-
tella. By dividing and dissecting back these muscles we
expose

Gluteus maximus, a large bulky mass of muscular sub-
stance, clothing the dorsum of the ilium. It arises from
the tendinous structure of the longissimus dorsi by a pro--
jecting process, which grows narrower and thinner until it
terminates opposite the last rib ; from the antero-inferior
and supero-posterior spinous processes and dorsum surface
of the ilium as far down as the neck ; also from the ante-
rior part of the sacro-sciatic ligament. Inferiorly it is in-
serted by two heads; one runs to the anterior tubercle of
trochanter major of the femur, it constitutes a broad
tendon, which first passes over the superior smooth surface,
from which it is separated by a bursa, and then becomes
attached to a roughened ridge ; the other contains mus-
cular fibres, and after becoming- inserted into the prominent
posterior tubercle of this eminence, sends muscular fibres
to the ridge running from it to trochanter minor externus.
By careful division of this muscle inferiorly we may expose
gluteus internus, which arises from the external surface of
the neck of the ilium, and runs to the roughened internal
surface of trochanter major ; it crosses, and is attached to
the capsular ligament of the hip-joint, and on the dry
bones its superior point of attachment is marked by a
transverse irregular ridge.

Triceps abductor femoris arises from the superior
spinous ligament of the middle sacral bones, and from the
sheath of faschia which invests the coccygeal muscles of
the lateral part of the sacrum, blending with biceps ro-
tator tibialis, from the sacral transverse process, and from
the sacro-sciatic ligament ; it receives a bulky mass from
the tuberosity of the ischium, and after sending a some-
what irregular fibrous band to the posterior surface of the
femur, midway between the two small trochanters (with

THE HIND EXTREMITY. 259

ischio-femoralis), divides into three portions. The siqw-
rior runs to the outer surface of the patella, the middle to
the outer surface of the tibia and the outer straight liga-
ment of the patella, blending with the faschia lata, the
■inferior is said to blend with gastrocnemius externus, biit
careful examination shows that it joins the white fibrous
tissue layer, which arises from a ridge in common with
that muscle, and with this runs to form that firm tendinous
band into which plantaris passes, and which extends to the
point of the hock.

Biceps rotator tibialis arises from the superspinous liga-
ment and the transverse process at the posterior part of the
sacrum, like the other muscles of the region, somewhat in-
definitely. It forms a considerable portion of the fleshy mass
of the quarter, and in its course down the limb receives a
branch of equal size from the tuberosity of the ischium.
Through thus reinforced, it forms a somewhat small tendon,
wliich winds round the smooth internal surface of the tibia,
where it is lubricated by synovia to reach the sharp ridge
on the antero-superior part of that bone. From this tendon
also a white fibrous band runs to the hock. This muscle is
also termed semi-tendinosus. Posteriorly it is in contact
with semi-memhranosus or

IscMo -tibialis, the muscle which forms the prominence
at the posterior part of the quarter. This muscle arises
mainly from the tuberosity of the ischium, but superiorly
sends a thin band in an upward direction to be attached to
the sacro-ischiatic ligament and to the posterior sacral and
the anterior coccygeal bones. Inferiorly it passes to the
internal surface of the inferior extremity of the femur
and of the head of the tibia, and the lateral ligament which
connects them. It also sends a band of white fibrou-^
tissue to unite with that of biceps rotator tibialis and
run to the point of the hock. By removal of the three
last-mentioned muscles we expose superiorly, up at the
lateral part of the spine, the coccygeal muscles enveloped
in a white fibrous tissue sheath. Below this the sacro-
sciatic and the sacro-ischiatic ligaments, on the external
surface of which are to be seen the gluteal and sacro-
sciatic nerves, and the gluteal arterial branches which
emerge from the jDelvis through foramina in the liga-
ment. At the infero-posterior part we see certain muscles
winding round the neck of the ischium to become inserted

260 OUTLINES OF EQUINE ANATOMY.

into the troclianteric fossa. Having examined tliese
muscles on the outer surface of the limb, we will now ex-
amine those which form the rounded fleshy mass on the
inside of the thighs. On removal of the skin from the
central line we expose gracilis, occupying the posterior
part of this region, sartorius centrally, vastus internus an-
teriorly placed. Between gracilis and sartorius pass a
large branch of the crural nerve and the vena saphena, to
gain the femoral space. They run from the hock over the
inner surface of the tibia and the thigh immediately
beneath the skin.

Gracilis, supero-posteriorly, intercrosses its tendinous
fibres with those of its fellow, and supero- anteriorly blends
with the .tendon common to the abdominal muscles ; it is
thus indirectly attached superiorly along the whole length
of the pelvic symphysis. We have to cut through the ten-
dinous structures at the point of junction of the two limbs
for more than an inch before we reach the bone. Inf eriorly
this muscle forms an expanded tendon, which sends off a
band passing to the white fibrous tissue band running
to the hock, but mainly becomes inserted into the inner
straight ligament of the patella, into the inner part of the
head of the tibia, and into the faschia clothing the inside
of the thigh, blending anteriorly with

Sartorius, a thin long ribbon-like muscle, which arises
from the under surface of the psoas faschia, and from the
antero -inferior spinous process of the ilium through the
medium of iliacus, and is inserted by blending inferiorly
with gracilis. It covers that portion of the crural nerve
which intervenes between the brim of the pelvis and the
femoral space.

The femoral space is an elongated space situated in this
region, through which pass the femoral artery and vein,
and crural nerve ; and which also contains the inguinal
lymphatic glands and some fat. It is bounded : anteriorly,
by sartorius ; posteriorly, by pectineus, and biceps adductor
f emoris inferiorly ; externally by vastus internus ; inter-
nally, by gracilis.

On removing the layer of muscles formed by gracilis
and sartorius we expose supero-anteriorly vastus internus
and rectus femoris ; posteriorly ischio-tibialis and biceps
rotator tibialis ; centrally pectineus and biceps adductor
femoris, between which run an artery, vein, and nerve.

THE HIND EXTREMITY. 261

A thick band of white fibrous tissue fills up the trian-
gular space, which is bounded by the brim of the pelvis on
either side from the pectineau tubercle to the symphysis.
Around this the pectineiis winds in a direction backwards
to its insertion into a roughened line on the inner surface
of the femur, commencing at the inferior extremity of the
trochanter minor internus. To the under surface of the
above-mentioned ligament is attached the common tendon
of the abdominal muscles, and from each of its lateral
parts a round tendinous cord runs to pass above the trans-
verse ligament of the hip- joint, and becomes inserted into
the head of the femur ; it is the puhio-femoral ligament.
Posteriorly placed to this is a large vein which runs from
one external iliac vein in a transverse direction to the other,
and which receives on either side in the male a branch from
the penis, in the female from the mammary gland ; by
this vein (the transverse branch) pectineus is separated
from the small head of

Biceps adductor femoris, which arises from the under
surface of symphysis pubis. The large head of this muscle
arises from the under surface of symphysis ischii ; opposite
trochanter minor internus, the two combine to form
a single fleshy mass, the muscle then rediyides ; the
smoiler head becomes inserted into the posterior part
of the middle and inferior thirds of the femur just
below the inner small trochanter ; the large extends
obliquely over the posterior surface of the femur as far
down as the outer condyle ; the femoral artery and vein
pass between its fibres, thus apparently dividing it into
two heads, the lower of which blends with the inser-
tion of ischio-tibialis, thus becoming attached to " the in-
ternal surface of the inferior extremity of the femur, and
of the head of the tibia and the lateral ligament which
connects them."

On removal of these muscles we expose the insertion
common to iliacus and psoas magnus into trochanter minor
internus.

Iliacus arises from the venter surface of the ilium, ex-
tending as far downwards as the pectineau tubercle, as far
back as the transverse process of the first sacral bone to
which it is attached. It is in contact v/ith the inner surface
of the capsular ligament of the hip-joint, to which it is
attached, and blends with psoas magnus to become in-

262 OUTLINES OF EQUINE ANATOMY.

serted as above mentioned into tlie inner small trochanter.
Externally it is ir^ contact with the origin of

Hectus femoris. This muscle combines mth the two
vasti to form that large fleshy mass which clothes the front
of the femur, by some anatomists described as a single
muscle under the term triceps extensor cruralis, since,
being inserted l>elow mto the upper surface of the patella,
they serve through the medium of its three straight liga-
ments to extend the tibia on the femur. Rectus femoris
arises by two fiat tendinous bands from the external and
internal surfaces of the neck of the ilium ; between these is
a bursa with a mass of fat. It passes over ilio-femoralis
at its attachment to the capsular ligament of the hip-joint,
and opposite, about the centre of the femur, blends with
the vasti.

Vastus externiis arises from the antero-extemal part of
the femur, extending as high up as trochanter major, oppo-
site the middle third of the femur it blends with

Vastus interims, which is attached to theantero-intemal
part of the superior two thirds of the femur. Between it
and vastus externus superiorly is the inferior attachment of

Ilio-femoralis, a small muscular band attached supe-
riorly to the front of the neck of the ilium, below the heads
of rectus femoris-, passing over and becoming attached to
the capsular ligament of the hip- joint, which it prevents
from injury during movements, and becoming inserted
for aboat two inches and a half along the upper part of the
central line of the front of the femur. It thus corresponds
exactly to scapulo-humeralis posticus of the foi^ limb.

In the attachments of the " triceps cruralis" to the patella
are distinguishable several synovial bursse, and between
rectus femoris and vastus internus run the main branch
of the crural nerve, and the inguinal artery and vein.
These parts just described are supplied with blood by the
external iliac artery, which arises from the posterior
aorta, where it passes on to the underneath surface of the
sacrum, about two inches before it breaks up to form the
internal iliac arteries. Just at its origin it gives off the
circumflex artery of the ilium, which runs forwards and
downwards to the antero-inferior spinous process of the
ilium, supi^lying in its course iliacus and proceeding on
inio the flank, where its terminal ramifications anastomose
with those of the lumbar, intercostal, internal thoracis-.

THE HIND EXTREMITY. 203

and epigastric arteries. The artery of the cord (of the
male) generally arises from the external iliac near its
commencement, and runs to the internal abdominal ring,
where it commences to -supply the structures of the
posterior part of the spermatic cord ; in the female this
artery is termed the uterine, it is very large and runs
directly backwards to supply the uterus, being much
enlarged in pregnant animals. The main trunk of
the external iliac continues along the brim of the pelvis
and about one and a half inches below the pectinean
tubercle it breaks up, forming the arteria profunda femoris
and the femoral artery. Arteria profunda femoris passes
in a direction backwards, but gives ofl' the epigastric artery,
which runs forwards. It then passes between pectineus
and the terminal portion of psoas magnus and iliacus
above trochanter minor internus, then externally to ischio-
femoralis, and so gains triceps abductor femoris, which it
mainly supplies. It sends a long branch downwards with
the sacro-sciatic nerve to supply biceps rotator tibialis and
ischio-tibialis. The epigastric artery arises from arteria
profunda femoris about half an inch from its origin,
courses its way forwards over the inner surface of the
femoral artery and thus gains the muscles of the flank,
where its terminal ramifications blend with those of the
numerous arteries supplying this region, while one of its
branches, the external pudic, passes downwards, and after
passing through the external abdominal ring, in the female
supplies the mammary gland with blood, in the male the
penis, breaking up to form the anterior dorsal artery of the
penis, which runs forwards towards the glans, and the
posterior dorsal artery of the penis, which runs backwards
to anastomose with the branches of the internal pudic
branch of the obturator arter}^

The femoral artery from the neck of the ilium passes
downwards over the internal surface of the insertion of
iliacus, and here gives off the inguinal branch, which dips
with the crural nerve between rectus femoris and vastus
internus. It then passes over the inner surface of the
femur, through the femoral space, giving off muscular
branches forwards and backwards and the medullary artery
of the femur, the largest medullary artery in the body. It
courses its way between the insertions of pectineus and the
short head of biceps adductor femoris on the one side, and

264* OUTLINES OF EQUINE ANATOMY.

the internal surface of vastus internus on the other, then
dips between the two portions of the large head of biceps
adductor. Thus it gains the posterior part of the femur,
and after giving off a large branch running directly hade-
wards, passes between the internal head of gastrocnemius
externus and gastrocnemius inter nus.

After giving off the external iliac arteries, the posterior
aorta becomes very small in calibre, and after running
about two inches on the under surface of the sacrum,
breaks up to form two internal iliac arteries, between
which is sometimes seen the middle sacral artery. The
internal iliacs diverge, running in a downward, outward,
and backward direction, giving off the artery of the hulb,
and termina^te by breaking up into the obturator, gluteal,
and lateral sacral trunls. The artery of the bulb, almost
at its origin gives off the umbilical artery, which, pervious
in the foetus, in the adult degenerates into an impervious
fibrous cord, w^hich runs to the central part of the fundus
of the bladder between the two folds of the broad liga-
ment of that organ. It is termed the round ligamerit of
the bladder, and in the foetus serves to carry blood to the
chorion for revivification. After giving off this vessel the
artery of the bulb passes along the side of the pelvis, gives
off a large branch to supply the bladder and prostate gland,
and terminates in the bulb of the penis ; in the female in
the erectile walls of the vagina. It gives off perineal
branches, which supply the posterior part of the rectum
and the anus, anastomosing with branches from the lateral
sacral and internal puclic arteries.

The obturator runs from its origin directly over the
venter surface of the ilium to the anterior and external part
of the obturator foramen, after passing through which it
breaks up into three very indefinite branches : pmbic runs
forwards, ischiatic downwards, and the internal pudic to
the bulb of the penis, breaking up in the erector penis
muscle, and anastomosing anteriorly with the posterior
dorsal artery of the penis, given off by the external pudic
branch of the epigastric, posteriorly with the artery of
the bulb. While pa'ssing over the surface of the ilium, the
obturator gives off a branch which passes over the brim of
the pelvis just above the origin of rectus femoris, and
passes mainly between that muscle and vastus externus ; it
is the arteria innominata.

THE HIND EXTREMITY. 265

The gluteal artery, immediately after its origin, passes
through the foramen situated between the posterior margin
of the ilium and the anterior margin of the sacro- sciatic
ligament. It then breaks up, sending large branches to
the gluteal muscles, and among others a remarkable one
running along the lateral margin of the sacrum between
two folds of the ligament. Thus the muscles on the quarter
are supplied with blood.

The lateral sacral artery passes from the terminal por-
tion of the internal iliac in a backward direction along the
outer margin of the under surface of the sacrum ; thus the
artery tends to approach its fellow. It terminates poste-
riorly in giving origin to vessels running to the tail {lateral
coccygeal arteries). Superiorly it gives off small hrancJies
to the spinal cord, which pass through the subsacral fora-
mina and medullary arteries to the sacral hones. Inferiorly
it gives off hcemorrhoidal branches to the rectum, w^hich
anteriorly anastomose with the terminal branches of the
posterior mesenteric, posteriorly with the artery of the bulb
and its branches.

The middle sacral when present runs along the central
line of the under surface of the sacrum, and terminates in
giving rise to the middle or hiferior coccygeal artery.

The femoral vein exactly corresponds to the femoral
artery ; just above the trochanter minor internus it receives
the vena saphena (which we have already seen coursing
along the inner surface of the limb from the hock, subcu-
taneously placed). Also in front of symphysis pubis it
receives the transverse branch already noticed. It termi-
nates superiorly in forming the external iliac vein, which
unites with the internal iliac vein (which brings blood
from the parts supplied by the artery of the same name)
to form the common iliac vein, a vessel of about three
inches in length, which combines with its fellow under the
last lumbar vertebra, above the posterior aorta, to form
the commencement of posterior vena cava. This vessel
receives the circumflex vein of the ilium ; it is to be found
between the external and internal iliac arteries. The pos-
terior extremity is supplied by four large nerves in addi-
tion to small sacral branches and the sympathetic system ;
these are the crural, gluteal, sciatic, and obturator.

Like all the other spinal nerves, those in the lumbar
region, on emerging from the spinal canal through the

2(jQ OUTLINES OF EQUINE ANATOMY.

intervertebral gaps, break up into superior and inferior
branches. The superior branches pass upwards to supply
longissimus dorsi and the other muscles in the lumbar
region of the back ; the inferior branches break up, sending
some fibres to the abdominal muscles running over trans-
versal! s abdominis ; others to the psoae muscles ; others
from the second, third, fourth, and fifth to form the crural
nerve, which passes along the brim of the pelvis, and
opposite symphysis pubis breaks up, its main portion run-
ning between rectus femoris and vastus internus to supply
the muscles clothing the front of the femur, a small, long
branch (saphenous nerve) passing downwards with vena
saphena subcutaneously as far as the hock. From the in-
ferior branches of the third and fourth lumbar nerves the
obturator nerve arises. It takes the same course as the
artery of the same name, and supplies the structures on
the external and internal surface of the obturator foramen
and ligament.

The sacral nerves differ from the other spinal nerves in
that they run in an oblique direction outwards and back-
wards from their origin, thus forming that arrangement
in the terminal portion of the spinal or vertebral canal
to which the name cauda equina has been given. They
also divide into superior and inferior branches prior to
leaving the canal. The superior branches pass in an upward
direction through the supersacral foramina to supply the
anterior portion of the coccygeal muscles and the upper
parts of the muscles of the quarter ; the inferior branches
run to supply the muscles of the quarter, fibres from the
first sacral, and the last lumbar nerves, combining to form
the gluteal nerve, which passes through the foramen at
the anterior part of the sacro-sciatic ligament between it
and the ilium, thus gaining the external surface of the
ligament, where it supplies the muscles of the cjuarter. The
inferior branches of the last lumbar, with the first three
sacral nerves, combine to form the

Sciatic nerve, the largest in the body, which, by passing
with the gluteal, gains the external surface of the sacro-
sciatic ligament, over which it runs on the inner surface
of triceps abductor femoris over the neck of the ischium,
between the cotyloid cavity and the tuberosity of the
ischium, and down as far as the superior extremity of the
gastrocnemii muscles. In its course behind the femur it

THE HIND EXTREMITY. 267

is accompanied by two roots of vena profunda femoris, and
a branch of arteria profunda femoris. Inferiorlj it breaks
up to form the anterior and iiosterior tibial, and popliteal
nerves. In its course down the limb it gives off fibres to
all the large muscles among which it runs. Bj removal of
the above-mentioned structures we are enabled to see

Ischio-femoralis, which arises from the under surface of
the neck of the ischium, and becomes inserted with the ten-
dinous band of triceps abductor femoris to the posterior
surface of the femur midway between the two small tro-
chanters ; it is triangular and fleshy ; also the four
muscles which become inserted into the fossa behind
trochanter major are thus exposed ; these are

Obturator externus, which arises from the under surface
of the obturator ligament and the margins of the obturator
foramen. It resembles a number of small muscles united
together.

Gemini vel iscMo-trochanterius, composed of two very
similar united portions, which arise from the under surface
of the neck of the ischium in front of ischio-femoralis.

Obturator internus, which arises within the pelvis from
the upper surface of the obturator ligament, is superiorly
covered by a reflection inwards of the sacro-sciatic liga-
ment and is also attached to the margins of the obturator
foramen. This muscle combines with

Pyriformis, arising from the posterior part of the venter
ilii, as high up as the transverse process of the first sacral
vertebra. The tendon common to the two gains exit from
the pelvis by passing between the sacro-sciatic ligament
and the neck of the ischium in winding round the bone,
where it is lubricated by synovia; it then blends with
obturator externus and gemini in passing to their common
insertion. The limb may now be removed from the trunk
by sawing through the middle of the femur transversely.
The gastrocnemii muscles may then be examined.
_ Gastrocnemius externus arises by two heads from the
ridges bounding the fossa on the postero-inferior part of
the femur inclined to the outer side, one from the inferior
third of the external surface, the other from the inferior
third of the posterior surface of that bone. The external
head is covered by a hroad aponeurotic hand, which runs
to form a sheath for gastrocnemius externus, after receiving
a band from the aponeurosis of gracilis. It then meets a

268 OUTLINES OF EQUINE ANATOMY.

funiculus running from gastrocnemius internus, and forms
a loop through which plantaris runs. This band, plan-
taris, and gastrocnemius externus, together become inserted
into the point of the hock, after playing over a bursa.
About opposite the superior j)art of the inferior third of
the tibia the tendon of gastrocnemius internus, which has
been hitherto placed in front of the externus, winds from
within oidivards around the externus tendon, on which it
plays through the medium of a synovial sheath,

Plantaris is a fleshy muscle, apparently too long for its
situation, running from the superior part of the fibula to
become inserted as above described into the superior part
of OS calcis. The aponeurosis of the lowest head of
triceps abductor femoris sends downwards a broad band of
white fibrous tissue ; some of the muscular fibres of biceps
rotator tibialis terminate in tendinous structure, which
blends with the above ; a little lower down this band
receives fibres from gastrocnemius internus. About an
inch and a half above the point of the hock it bifurcates,
one division running on to the inner, the other to the outer
surface of the point of os calcis, from Avhich they pass to
the dilated portion of the tendon of gastrocnemius in-
ternus, which forms the cap of the hock, which they serve
to prevent from dislocation, being assisted by some liga-
mentous fibres which run directly from the cap to the bone.
Gastrocnemius internus arises from the fossa at the
postero-external part of the femur, between the two heads
of the gastrocnemius externus. It passes over the posterior
part of the stifle joint, and after sending some tendinous
structure to the fibrous band running to the hock,
becomes tendinous, winds round the tendon of the external
gastrocnemius muscle from within outwards, and then,
widening, forms a cap for the point of os calcis, which is
retained in position in the above-mentioned manner by two
fibrous bands, and which plays over a large synovial bursa ;
continuing downwards it is termed the perforatus tendon,
and exactly corresponds to that of the fore extremity.

Popliteus is attached inf eriorly to a triangular roughened
surface, situated on the inner part of the postero-superior
region of the tibia ; its fleshy fibres converge, forming a
tendon which runs in an outward direction over the surface
of the capsular ligament of the stifle-joint within its external
lateral ligament (lubricated with synovia), to become

THE IIIXD EXTREMITY. 2G9

inserted into a groove between the outer condyle and outer
ridge of the femur.

Flexor pedis perforans also arises from the posterior
surface of the tibia, but is externally placed, being also
attached to the posterior margin of the fibula ; it becomes
tendinous above the hock, passes over the concave internal
surface of os calcis, where it is lubricated with synovia ;
opposite the superior third of the large metatarsal bone
receives the tendon of flexor pedis accessorius and the
subtarsal ligament, which is not so strong as the sub-
carpal. Below this it comports itself in a manner corre-
sponding to the similar tendon of the fore limb.

Flexor pedis accessorius arises from the posterior surface
of the tibia, between the attachments of popliteus and the
perforans ; it becomes tendinous oj^posite the inferior third,
and passes through a groove situated just behind the inner
malleolus of the tibia, where it is bound down by a con-
tinuation of the posterior annular ligament, and lubricated
with synovia, having a sheath which extends obliquely
downwards and backwards over the lateral part of the
hock. It terminates in becoming blended with perforans,
opposite the superior third of the large metatarsal bone.
On the external surface of the limb we see three muscles.

Peroneus arises from the outer surface of the fibula,
being continuous superiorly with the outer lateral ligament
of the stifle-joint. Its fibres converge in a bipenniform
manner to form a small tendon, which passes through the
groove found on the external malleolus of the tibia. It is
here lubricated by synovia, and, enclosed in a synovial
sheath, passes within the annular ligament in an oblique
direction forwards, joining extensor pedis tendon with
extensor pedis accessorius at the inferior part of the
superior third of the large metatarsal bone.

Flexor metatarsi arises by a round tendon common to
it and to extensor pedis from the depression between the
outer condyle and the outer ridge of the femur. This
tendon, after becoming attached to the capsular ligament,
passes in the groove between the spine of the tibia and the
head of the fibula, where it plays over a synovial bursa ;
it then gives off extensor pedis, and receives numerous
muscular fibres from their attachment in the external
channel of the tibia. The tendon, however, continues as a
white fibrous band to the front of the hock, where it breaks

270 OUTLINES OF EQUINE ANATOMY.

up to become inserted into several of the small bones of
that joint, while the tendons of the muscular portion pass
between its divisions, thus completing its inferior attach-
ment to all the small bones of the hock, directly or indi-
rectly, and to the upper part of the three metatarsal bones.
With one of these tendons the middle band of the anterior
annular ligament of the hock blends.

Extensor pedis, arising from the originating portion of
the tendinous part of flexor metatarsi, as above indicated,
passes down the front of the hock, and through its three
anterior annular ligaments, lubricated by synovia. After
receiving the tendons of peroneus and extensor pedis
accessorius opposite the inferior part of the superior third
of OS metatarsi magnum, it comports itself as does the
extensor pedis of the fore limb.

Extensor pedis accessorius arises from the front of
astragalus below its articular ridges, and joins extensor
pedis, which covers it from its origin, bein g slightly visible
between it and peroneus.

The terminal portion of the femoral artery passes
between the two heads of gastrocnemius externus, and
then between its internal head and the head of ga.strocne-
mius iuternus. It sends off a hrancJi ichich runs doiunwards
behveen the huo gastrocnemii, and then passes between the
condyles of the femur to break up behind the stifle-joint,
forming the anterior and the posterior tibial arteries.

The posterior tibial artery runs down the posterior sur-
face of the tibia, at first between popliteus and the bone,
subsequently between flexores pedis j)erforans and acces-
sorius. It becomes superficial at the supero -internal part
of the hock, and here makes its sigmoid flexure, by which,
in terminating, it anastomoses superiorly with the arterial
branch between the gastrocnemii, inferiorly with the recur-
rent branch of the metatarsal artery. It supplies the
muscles and skin at the posterior part of the tibia, and
the medullary artery of that bone at the inferior part of
its superior third.

The anterior tibial artery runs in a forward direction
from its origin, and passes between the tibia and the fibula,
and thus underneath jDeroneus to gain the front of the
limb, down which it passes underneath flexor metatarsi
and extensor pedis, which it supplies. At the front of the
hock it passes through an oblique groove at the outer

THE HIND EXTREMITY. 271

part of the superior extremity of the large metatarsal
bone, and thus gains the channel between this bone and
the extei'nal small metatarsal, in which it runs subcuta-
neously, so that the pulse may be taken here. It passes
between the inferior extremity of the small bone and the
large bone to gain the posterior part of the inferior third
of the latter, where, after giving off the recurrent branch,
it bifurcates in passing between the divisions of the supe-
rior sesamoideal ligament, forming plantar arteries ana-
logous in situation and distribution to those of the fore
limb. The recurrent branch passes up the back of the
OS metatarsi magnum, protected by the inner small meta-
tarsal bone, and at the inferior part of the superior third
gives off tlie medullary artery of the large metatarsal hone. It
terminates at the supero-internal part of the hock, by anas-
tomosing with the posterior tibial at its sigmoid flexure.

The superficial metatarsal vein runs on the inner sur-
face of the limb in the groove between the large and inner
small metatarsal bones. At the front of the hock it bifur-
cates ; one branch runs on to the internal surface of the
tibia, forming the commencement portion of the vena
saphena, the other, by uniting with a large branch running-
from between the bones of the hock, forms the anterior
tibial veins, generally two in number, one of them beings
enlarged, the varicose vein of the thigh, they pass with the
artery of the same name. The deep-seated metatarsal
veins divide superiorly ; one division forming the inter^
osseous branch, which passes between the bones of the hock
to assist in forming the anterior tibial, the other passincr
through the groove of the calcis to form the posterior
tibial veins, which accompany the arteries of the same
name up the back of the til3ia.

Just above the commencement of the gastrocnemii
muscles the sacro- sciatic nerve terminates in breaking
up to form the anterior and posterior tibial, and pojAiteal
nerves. The popliteal proceeds down the back of the
limb, and dips between popliteus and the flexors, which
it supplies with nerve force. The anterior tibial passes
over the external head of gastrocnemius externus and
peroneus to gain the muscles in front of the tibia It
thus presents a marked difference in its course as com-
pared with that of the artery and vein of the same
name. It is sometimes divided at its superficial part by

272 OUTLINES OF EQUINE ANATOMY.

the operation of neurotomy. To expose it, only skin,
fascliia, and aponeurosis of triceps abductor fenioris re-
quire to be divided. The posterior tibial nerve, dipping
between the internal head of gastrocnemius externus and
gastrocnemius internus, follows the course of its corre-
sponding artery over the back of the stifle-joint, and run-
ning down the posterior surface of the femur between the
gastrocnemius and perforans, just above the hock, divides
to form the external and internal metatarsal nerves, which,
after passing with the perforans tendon over tlie inner
surface of os calcis, separate and take a course, and give off
branches exactly as the metacarpal nerves do in the fore limb.

In the space just above the heads of the gastrocnemii
muscles lie the popliteal lymphatic glands. It will thus
be seen that the hind limb below the hock very closely
resembles the fore limb below the knee ; besides the differ-
ences between the pedal and the cannon bones of the fore
and hind limb, the hoofs differ, those of the hind limb being
smaller, more upright, and having their ground surface
much longer than broad, and more concave, with thicker
soles than those of the fore.

The coccygeal muscles I'equire a passing notice.

Levator coccygis arises from the lateral part of the
sacrum between the superior spinous and transverse pro-
cesses, blending anteriorly with longissimus dorsi. It
passes backwarcls, and its several fasciculi become attached
to the rudimentary transverse processes of the coccygeal
vertebrae. It is covered by a layer of faschia.

Curvator coccygis arises from the postero-lateral and
inferior part of the sacrum, and its fibres and fasciculi run
along the lateral part of the tail ; they are separated from
levator coccygis anteriorly by faschia.

Compressor coccygis is a broad square muscle, which
extends from the inner surface of the sacro- sciatic ligament
to the transverse processes of the two or three anterior
coccygeal bones.

Depressor coccygis is attached to the under surfaces of
the anterior coccygeal bones, its fibres pass downwards
towards the anus and become confounded with those of
levator ani.

The tail is supplied with blood by the lateral and middle
coccygeal arteries, with nerve force by coccygeal branches
from the posterior part of the spinal cord.

THE FOOT. 27o

PART X.— SPECIAL ANATOMY.

The Foot.

CoN^siDERED zoologically tlie foot of the horse compre-
hends all those structures placed below the inferior ex-
tremity of the tibia ; the point of os calcis corresponds to
the heel of the human subject. From the tarsus the
metatarsals run downwards ; their normal number in mam-
malia is five, in the horse, however, we find but three, for
the inner digit is absent and the two central ones coalesce.
The outer of the three in the fossil forms of the horse
present hoofs, and other structures found in the existing
forms only in connection with the double central digit. In
some cases even in the present day, however, we find a
rudimentary hoof produced below one of the metacarpal
or metatarsal splint bones, in rare cases ; generally these
bones terminate inferiorly in a slight bulbous enlargement.
It is, then, with the double central digit we have here to
deal ; its comj^osition of two similar parts is shown by its
symmetry, and by a depression well marked in some cases
at the antero- inferior part of the toe of os pedis. Again,
in all cases the frog is divided into two similar portions by
a deep fissure, the cleft, and often we see a projection on
the inner surface of the hoof opposite the depression in
the toe of os pedis just at the point of junction of the
wall and the sole of the hoof. That portion commonly
known as the foot, consists of a horny box with its con-
tents. The horny box corresponds to the nail of the toe
of the human subject with the thickened skin on the sole
of the foot, while the contents comprise certain bones with
their appendages covered by a layer of highly vascular
tissue, which corresponds to the true skin, and which pro-
duces the horn, which is analogous with the epidermis or
cuticle. The HOOF is separable from the other structures
by maceration by a continuation of this process it may be

18

274 OUTLINES OP EQUINE ANATOMY.

separated into minor parts, we generally see it as a horny
box presenting an opening above. It is composed of epi-
thelial cells, being (as before observed) merely epidermis
so modified as to form the substance commonly known as
horn. Horn consists of tubular processes similar to hairs
united by softer epithelial cells, the latter forming a matrix
for the fibres and, by fixing them firmly together giving the
horn its consistency. The horn of the hoof presents two
parts with different characters. The horny frog is much
softer in consistency and more elastic than the remainder
of the hoof, and resembles in nature and structure (as
pointed out by Professor Gamgee) the foot pad of the dog.
It owes its peculiarities to the delicacy of its horn fibres,
which are finer than those of most other parts of the hoof,
and which are produced by the delicate papillae of the sen-
sitive frog. The hoof consists of several parts agglutinated
together in the same manner though less firmly than the
individual fibres. These are the wall (with the bars), sole,
and frog. The frog and the sole are separable by mace-
ration, but the bars are mere reflections forward and
inwards of the wall, and therefore remain firmly fixed to
that part. The Wall is all that portion of the hoof which
is visible from before and from the sides when the foot
rests upon its plantar surface. It is artificially divided into
six parts, three on each side. The anterior or toe centrally
lies in connection with its fellow, externally is continuous
with the quarter or middle part at its anterior part, while
the posterior margin of the quarter is continuous with the
heel, from the posterior margin of which the bars run in a
direction forwards and inwards for about two inches, being
separated from the frog by the commissures, terminating
anteriorly in a point. In all jjarts the fibres of the hoof run
obliquely downwards and forvmrds. The toe and the pos-
terior margin of the heel have the same direction, the
latter being not half so high as the former in a well-foi-med
hoof ; their superior extremities are connected by a thin
ridge running obliquely downwards and backwards, their
inferior margin is horizontal. The internal surface of the
wall superiorly presents a concave surface extending
obliquely downwards and backwards about half an inch in
depth, growing broader posteriorly in becoming inflected
forwards to form the crust of the bars which blend with the
horny sole anteriorly. It presents a number of deep small

THE FOOT. 2T5

foramina, into whicli the papillae of tlie vascular coronary
secreting substance pass. The wall is divided into crust
and horny Jamince ; the horny laminae are leaf-like plates
projecting from the inner surface of the crust, taking a
direction corresponding to the fibres of the wall, commenc-
ing superiorly at the inferior margin of the above men-
tioned perforated surface. They are longest at the toe
and become insensibly merged in the wall at the anterior
extremity of the bars. Between each pair of these in the
fresh subject for the greater part of their length lies a sen-
sitive lamina, and the surfaces of the horny laminae present
foramina into which pass papillae from the sensitive coun-
terpart. The outer utargm of each lamina is continuous
with the crust, the inner is free. The superior extremity
terminates in a point in blending with the above described
concave surface, the inferior terminates on the ground sur-
face at the line of junction of the wall with the sole, at which
part the outer laminated edge of the sole fits between the
horny laminae as the sensitive laminae do in other parts ;
the extent of this junction depends upon the variable
thickness of the sole. The horny laminae are produced by
the sensitive laminae, and the crust by the coronary secret-
ing substance ; in consequence, therefore, of the constant
additions to its thickness the wall has a tendency to
greater bulk in its lower than in its upper part. That
portion of the wall situated at the extreme superior edge,
which is secreted by the line of vascular substance which
presents very minute papillae and seems to be the first stage
of change in the character of the skin, thus presents fibres
more delicate than those of the rest of the wall, correspond-
ing to those of the frog, extending for but a short distance
downwards, about half an inch. It is narrowest anteriorly
and becomes deepest at the heels in blending with the frog.
This is the coronary frog band of Bracy Clark (the original
specimen of this by Bracy Clark in the museum of the
Eoyal Veterinary College is much too thick anteriorly,
where a small portion of coarser substance has been left) .
The wall is thickest at the toe, it gradually decreases in
thickness towards the heels, and again increases slightly at
the extreme posterior part, where it is inflected forwards
to form the bars. In no part is the wall so thin as the
coronary frog band at the extreme superior part. The
angle the toe of the hoof should make with the ground has

276 OUTLINES OF EQUINE ANATOMY.

been stated as 50° in a good foot, but it is influenced loj
various causes, as breed, age, period since last shoeing, &c.
Low bred horses have a small angle, in better bred horses,
mules, and asses it is less acute. The obliquity decreases
towards the quarter and is reversed at the heels, where the
posterior line of the plantar surface is in front of the per-
pendicular let fall from the extreme posterior part of the
coronet. The obliquity is downwards and outwards at the
bars. The inner quarter is more upright than the outer, and
the wall on the inner side, taken as a whole, is thinner
and, therefore, more readily yields to superincumbent
weight.

The horny sole presents two surfaces and two margins,
which posteriorly form four projections. It is crescent
shaped, having its outer circuwf event margin attached to the
inner surface of the inferior margin of the wall. Its pos-
ter o-iiitemal part is fitted into the horny laminse of the
bars, and continuous with the crust of the bars, while the
central part of the posterior margin is occupied by the horny
frog, which forms a wedge-shaped projection into it ex-
tending to within about two inches of the toe. The inferior
surface is concave, varying in degree in different feet, but
it presents a general slant from the outer margin upwards
to the inner. It is covered by scales of horn, for it consists
of a number of short coarse fibres matted together, which,
after attaining a certain length, desquamate regularly.
The union of the sole with the wall is by projection of its
substance between the horny lamina, and union of the two
by connecting epithelial cells, forming a marked line of
junction, softer in consistency than the rest o-f the hoof
and more friable. It will be observed that the fibres of
the sole run like those of the crust, obliquely downwards
and forwards in all parts. The union with the anterior
extremity of the frog is simply by epithelial cells. The
upper surface of the sole is convex, an exact counterpart of
the lower, presenting foramina, into which the papillae of
the sensitive sole project, and which are most marked
centrally.

The Lorny frog is situated on the middle line of the
hoof at the posterior part. It is a wedge-shaped body,
having its base posteriorly, its apex anteriorly placed, ex-
tending to within two inches of the toe of the foot. It
presents two lateral margins, which anteriorly are attached

THE FOOT. 277

to tlie liornj sole, posteriorly to the horiij bars, and at the
posterior angles are continuous with the coronary frog band.
The posterior margin becomes very thin, blending with the
epidermis of the skin of the heels. The frog bulges oa the
ground surface of the foot, presenting anteriorly a rounded
angle or apex, and posteriorly, at the base, two rounded
prominences termed the bulbs, separated by the cleft, which
extends more than half the length of the frog in a forward
direction, being widest posteriorly, terminating in a point
anteriorly on the ground surface. The bulbs of the froo-

are separated from the bars by the commissures, deep fis-
sures readily noticeable. The u]3per surface of the frog is
the exact counterpart of the lower, presenting centrally a
peculiar high prominence, terminating superiorly in a
rounded point, which fits into the cleft of the fibrous frog
(covered by its vascular coat) . This is termed the frog-
stay or peak, and on either side of it lies a concavity,
widest posteriorly, by its elevated outer margin blending
with the bars and sole. The two concavities run together
anteriorly, terminating in a point. This surface presents
small foramina for the delicate papillae of the sensitive
frog, least marked on the most prominent portions. The
fibres of the frog run obliquely downwards and forwards.
The colour of the hoof, in general, depends upon that of
the sensitive structure by which it is 2)i'oduced ; thus, in
horses with white coronets it is generally white, but any
coloration of the coronet is marked by corresponding colour
of the hoof below this point, extending from above towards
the ground surface, varying in length in direct proportion
to the superficiality, or otherwise, of the pigmentary
deposit.

The hoof of the fore foot is marked by the roundness of
the plantar surface, broken posteriorly by the space for the
frog ; also by the obliquity of its walls, which are thickest
at the toe, and decrease in thickness towards the heels.
The distances from the centre of the toe to the extremity
of each heel should be equal, and also equal to the broadest
transverse diameter. The inner half of the sole is generally
smaller and narrower than the outer ; the inner quarter is
the most upright, and is thinner in the wall than the
outer.

The hind hoof is ovoid, having its long diameter from
behind forwards. It is wide at the posterior part of the

278 OUTLINES OF EQUINE ANATO:\IY.

quarters, while their anterior part is rather flat. The hoof
in general is more upright than the fore ; the thickest horn
is at the quarters, and the sole is very concave, the frog
being smaller and narrower. The heels also are longer
than those of the fore foot.

The sensitive structures of the foot are generally exposed
by heating the foot in a forge fire, removing the heated
horn from the outer margin of the plantar surface of the
foot by means of a drawing knife, as far down as the sen-
sitive structures, and wrenching the wall and sole thus
separated off by means of pincers, the foot having been
fixed in a vice. The frog will be removed with the sole.
Some art is required in the operation, slow traction being
preferable to sudden jerks. By this means we expose a
red and highly vascular structure, investing the digit from
the coronet downwards. Opposite the centre of the external
surface of the lateral cartilage, extending round the foot
anteriorly and posteriorly, is a line marking where the
skin commences to change its characters. The epidermis
at first becomes soft and light in colour, and then modified
to form the hoof, some hairs from the coronet being em-
bedded in the white cheesy upper rim of the hoof. The
ordinary skin terminates in a regular and well-marked
line, light in colour, covered with fine papillae, and
growing wider at the posterior part, becoming blended
with the bulbs of the sensitive frog. Below this, ex-
tending in a downward direction for about half an inch,
is the

Vascular layer of the coronary secreting substance. It
gradually decreases in size in a direction backwards, more
so on the inner than on the outer side, and at the posterior
part, against the bulbs of the frog, it terminates in an
acute point, being thickest just before this, in consequence
of its inflection forwards to join with the vascular sole,
towards which it runs, being here about two inches in
length, a quarter of an inch in width, separating the sensi-
tive laminae of the bars from the sensitive frog. It differs
slightly from the above description in the hind foot, in
accordance with the different shape of the hoof. The vas-
cular or sensitive coronary secreting substance is covered
with papillae, which are minute superiorly, but inferiorly
become very marked. In some cases a few may be seen
running from the upper part of the vascular laminae,

THE FOOT. 279

whicli are thin plates covering tlie remainder of the antero-
lateral surface of the basement structure of the foot, run-
ning from above downwards, at the anterior jmrt meeting
the ground surface at right angles, becoming oblique
laterally. This obliquity from behind forwards and
downwards increases towards the heels, the laminae also
becoming shorter in proportion. At the heels this layer
is reflected forwards, slightly inwards, for about one and a
half inches between the heel of the sole and the anterior
inflection of the vascular coronary secreting substance,
anteriorly and inferiorly blending with the sole, terminating
in an ill- defined point, for here we see a useful indication
of the nature of the lamince, the fact that they are linear
rows of papillae united together for a specific purpose being
here demonstrable. By careful examination we may see
secondary papillce extending horizontally into the inter-
spaces between the laminae from the surfaces of the layers.
These laminae are 500 to 600 in number ; they are smallest
superiorly, where they commence in blending with the coro-
nary secreting substance ; inferiorly they blend gradually
with the sensitive sole.

The sensitive sole covers the whole of the plantar sur-
face of OS pedis, with the exception of a small wedge-
shaped portion running forwards from the centre of the
posterior crescentic margin, which is occupied by the apex
of the sensitive frog. At the anterior jjart also, centrally,
we find in most feet a marked notch, so that the sensitive
sole is narrowest centrally, and from this gradually in-
creases in width to the anterior part of the laminae of the
bars, where it bifurcates ; the outer division terminating
in a point at the inflection of the laminae ; the inner divi-
sion blends with the termination of the coronary secreting
substance. The whole surface presents papillae, which
around the outer margin are small and continuous with
the inferior extremities of the sensitive laminae. They
gradually increase in size to the central line and then
again decrease, being absent at the line of junction of the
frog with the sole. The apex of the frog extends to within
an inch of the toe of the sole.

The sensitive frog covers the external surface of the
fibrous frog, and consequently presents two prominent
ridges running from behind forwards, obliquely inwards,
meeting at about the centre^ and continued on to form a

280 OUTLINES or EQUINE ANATOMY.

very acute angle at the apex. These are separated by the
cleft, and on either side laterally blend with the sensitive
sole. On the ridges are very marked papillae, which gra-
dually decrease in size in extending from the prominences
until they are absent at the line of junction with the sole.
There is a slight line caused by diminution in size of the
papillae, mapping out the boundary of the commissures. It
may be noticed that the papillae of the frog are smaller
than those of the sole and of the coronary secreting sub-
stance. The vascular horn-secreting layer in all parts
consists of loose areolar tissue, with very numerous vessels
ramifying through it. The vascular sole is connected to
iKe bone by loose areolar tissue, in which is situated a
plexus of veins, and the solar arteries running from the
artery of the frog outwards in a radiating manner to the
circumflex artery of the toe, which runs round the outer
circumferent margin of the plantar surface of os pedis.
The sensitive laminae are connected by denser areolar
tissue, which attaches them to the antero -lateral surface
of OS pedis, where they cover the lateral laminal arteries
and the branches they send upwards to the superficial
coronary artery, and downwards to the circumflex artery
of the toe. The sensitive layer of the coronary secreting
substance is firmly attached to a somewhat dense band of
substance (fibrous coronary band) which extends round
the coronet. This is deepest at the toe, where it is attached
to extensor pedis tendon at its insertion ; laterally it rests
on the centre of the lateral cartilage (external surface),
and posteriorly it terminates in blending with the fibrous
or fatty frog. This is an elastic substance, occupying the
centre of the posterior part of the foot. It consists of a
quantity of yellow elastic tissue arranged in fibres, which
interlace in all directions, but the largest of which take a
direction obliquely from above downwards and forwards.
In the meshes of these fibres is a quantity of substance
apparently of a fatty nature, whence this organ has
received the name of fatty frog. It is a wedge-shaped
body with two surfaces, a base and an apex. The S2iperior
surface lies in contact with the under surface of the ex-
panded perforans tendon, with the intervention of a thin
fibrous layer. It extends forwards on co the plantar sur-
face of OS pedis at the posterior crescentic margin at its
centre, where it forms a triangular projection. Its hase

THE rooT. 281

becomes blended posteriorly witli the corium of tbe skin
of the heels, and laterally receives the termination of the
coronary fibrous band. The apex extends to within about
one inch of the toe of the os pedis. The lateral parts
superiorly are separated from inner surface of the lateral
cartilage by means of a plexus of veins ; inferiorly are
firmly attached to the inflections of the cartilages, the
transition between the two structures being gradual. The
inferior surface presents a figure analogous to that of the
under surface of the horny frog, which is moulded upon
it with the intervention of the vascular frog. It therefore
presents two hulbs separated from each other by a cleft,
which form the base, and which converge anteriorly,
and are continued forward to terminate in a point, the
aj^ex.

We now come to the basement structure of the foot,
the several parts composing which we must now examine.
The bones in the foot are, os pedis, os navicular e, and the
inferior extremity of os coronce.

OS CORONA, though broader than long, and possessing
no medullary canal, is generally considered to be a long
round bone. It really consists but of two extremities. Its
superior extremity articulates with the inferior articulatory
surface of os suffraginis, and thus presents a smooth sur-
face coated with articular cartilage, consisting of two
shallow concavities, the inner of which is the largest.
These are separated by a slight prominence, extending in an
antero-posterior direction ; the articulatory surface taken
as a whole is concave from before backwards, and the
prominence terminates posteriorly in a projecting point.
The inferior extremity articulates with the os pedis and os
naviculare ; thus it presents a smooth surface which is broad
jDOsteriorly, and at the anterior part terminates in a point,
to which the coronal process of the os pedis is adapted.
The surface presents two prominences separated by a
shallow groove ; the inner division is slightly the largest.
The posterior surface of the bone superiorly presents a pro-
minence extending from the inner to the outer surface,
which superiorly is roughened for attachment of the long
inferior sesamoideal ligament, and below this presents a
smooth surface coated with articular cartilage, lubricated
with synovia, over which the flexor pedis perforans plays
immediately after passing between the two terminal divi-

282 OUTLINES OF EQUINE ANATOMY.

sions of perforatus, wliich become attaclied to tlie extre-
mities of this ridge inclined to the lateral surfaces of the
bone. Between this ridge and the inferior articulatory
surface the posterior part of the bone is unoccupied, merely
presenting foramina for the passage of vessels into the
bone. The lateral surfaces are exactly similar. Superiorly
they are roughened for attachment of the broad lateral
ligament of the pastern-joint. Inferiorly, inclined to the
anterior surface, is a peculiar depression, which, with its
fellow, seems as though the bone, when in a soft state, had
been compressed between the thumb and finger. To this
the lateral ligament of the pedal joint runs. The anterior
surface of this bone is occupied by the expanded inferior
part of extensor pedis tendon, which is attached somewhat
firmly by areolar tissue.

OS PEDIS is an irregular bone, and since it receives no
bony support from below is a floating bone. It is sym-
metrical, presenting two very similar halves, the inner of
which is the smallest. At the extreme antero- inferior part
may bo seen in many cases a notch, a trace of the division,
such as we see in ruminants, of this bone into two similar
parts. It presents three surfaces : supero-posterior, infero-
posterior, and antero-lateral. The supero-posterior surface
centrally is articulatory, presentmg a surface covered with
cartilage, divided primarily into two parts. The anterior
part is roughly heart-shaped, concave in an antero-posterior
direction, elongated and slightly convex from side to side.
Anteriorly it terminates in an obtuse point, extending in
an upward direction on the posterior surface of the coronal
process ; posteriorly it presents an oblique angled indenta-
tion, into which the posterior part fits. The sides of the
oblique angle meet the external convex margins of the
articulatory surface at an acute angle outwardly and pos-
teriorly. This surface centrally presents an antero-poste-
rior broad ridge with a shallow concavity on either side,
the inner being slightly the largest. It articulates ante-
riorly with OS coronse, and this portion is directly continuous
with that between its posterior margins, with which os
naviculare comes in apposition, and which is bounded pos-
teriorly by a line extending from one posterior angle of the
heart-shaped surface to the other. This surface of the
bone is completed by a roughened ridge on each side run-
ning at first outwards and then directly backwards for

THE FOOT. 283

about three eiglitlis of an inch, from the posterior angles
of the articulatory surfaces. The point where the ridges
bend backwards form posteriorly smooth grooves, through
which the plantar arteries run downwards in their course
between the inferior broad ligament of the navicular bone
and the perforaus tendon to the foramen on the infero-
posterior surface of os pedis.

The postero-inferior surface of the bone is mainly occu-
pied by the plantar surface, semilunar in form, bounded
by two margins, which meet posteriorly at acute angles.
Thus this surface is broadest centrally, and gradually
decreases in size posteriorly. It presents a slant from the
greater or outer to the lesser or inner curved margin, and
is perforated by foramina, which are most numerous at
the angles and at the outer circumferent margin ; and at
the line of junction of this with the antero-lateral surface
is a series of openings larger than the rest. Extending
backwards from the posterior margin is a roughened space,
bounded posteriorly by the articulatory surface for os
naviculare, which on either side extends slightly on to this
face of the bone. This roughened space is divided on
either side into two parts by a groove extending from
behind forwards, to terminate in a foramen. Through
this the terminal portion of the plantar artery runs, and
thus gains a canal extending through the substance of the
hone from one foramen to the other, in which it anasto-
moses with its fellow, completing the circulus anteriosus
of the foot. The walls of the grooves, as well as those
of the canal, are perforated by foramina, through which
branches pass outwards. The space between these grooves
and the navicular articulatory surface is roughened for
attachment of the inferior broad navicular ligament ; it
is perforated by articular foramina. That space between
the grooves and the posterior margin of the plantar sur-
face is about three eighths of an inch broad in the centre,
and is rough for attachment of the extensor pedis tendon.
The antero-lateral surface is largest centrally, and gra-
dually diminishes in size posteriorly. At its superior part
it presents a smoother portion of bone than the rest, of a
pyramidal shape, having its apex superiorly placed. This
is the coronal process ; around its superior part, at about
a quarter of an inch from its superior margin, runs a line
marking out the inferior attachment of extensor pedis,

284: OUTLINES OF EQUINE ANATOMY.

■wliicli tlius intervenes between the coronary secreting sub-
stance and the bone at this part. This surface is perforated
by numerous foramina, and presents small irregular plates
running from above, most marked near the inferior mar-
gin, where, also, at varying distances from each other, are
large foramina for the passage of the anterior branches of
the interosseous plantar artery, which assist to form the
circumflex artery of the toe. Supero-laterally is a deep
depression, smooth at its bottom for attachment of the
lateral ligament of the coffin-joint. Behind this is the
alct, running backwards for attachment of the lateral car-
tilage, which also seems to continue the bone from the pos-
terior margin of this surface, assisting to form a foramen
through which the lateral laminal branch of the plantar
artery runs, coursing its way through a groove in a forward
direction between the bone and the sensitive laminse ; at
the anterior extremity of the bone it enters its substance
through a large foramen. It sends off numerous branches,
especially one running straight downwards, for which
there is a special secondary groove, and which forms the
commencement of the circumflex artery of the toe. The
posterior margin of this surface presents superiorly the
ala, inferiorly the angles of the plantar surface ; between
these two is the lateral laminal groove. They are rough,
and are directly continuous with the lateral cartilage. In
consequence of its porous nature, and the close reticula-
tion of blood-vessels in its substance, os pedis seems to be
soft, but its structure in the dried bone will be found to
be remarkably hard.

Attached to the upper margin of the alae of os pedis,
extending superiorly for about one and a half inches,
posteriorly for about one and a half inches behind the
posterior extremities of the alse, and extending farthest
forward at the superior part of their anterior margin,
are the lateral cartilag^es of the foot. These are pecu-
liar shaped portions of cartilage which present two sur-
faces, three margins. The external surface is convex,
extending at first upwards from the wing of os pedis with
an outward inclination, which is increased along its pos-
terior margin. Its anterior extremity becomes ultimately
blended with the dense fibrous tissue which, in this situa-
tion, seems to closely unite the lateral ligament of the
pedal-joint with the extensor pedis tendon at its inferior

THE FOOT. 285

extremity. Posteriorly tliis surface terminates in a point
at about one and a half inches from the ala of os pedis, for
here the cartilage is inflected in a forward direction, form-
ing that portion of the cartilage which, running along the
inner surface of the wing of os pedis, gradually terminates
in blending with the white fibrous tissue joining the ex-
panded perforans tendon. Inwardly it is continued as a,
firm but fine layer of fibrous tissue, which serves to separate
the fibrous frog from the tendon. The inferior margin of
the cartilage in becoming attached to the bone helps to
form the foramen through which the lateral laminal artery
passes, and posteriorly, on its under surface, presents a
triangular continuation of the plantar surface of the bone
which affords attachment to the sensitive bars.^ The m-
ternal surface, as a whole, is concave, and looks in a direc-
tion inwards and slightly upwards. Its inferior part is
formed by the upper surface of the inflections of the carti-
lages, which here are closely united to the fibrous frog^
many of the elastic fibres of which become attached to it.
This organ is separated from the main portion of _ thia
surface by a plexus of veins, which communicates with a
corresponding plexus on the external surface, not only by
branches proceeding ^through numerous foramina in the
cartilage, but also by junction of their resulting vessels
above the cartilage. The superior margin of the cartilage
is about its thinnest part ; the thickest is that just
behind os pedis. In contact with the plexus of vessels on
the external surface, centrally, hes the coronary secreting
substance, superiorly skin, interiorly the upper portions of
the lateral laminae, which are supplied by a special branch
detached from the lateral laminal artery running back-

wards.

OS NAVICTJLARE (SHUTTLE BONE) is a sesamoid

bone situated behind and slightly resting upon os pedis.
It is elongated from side to side, and presents two sur-
faces, two margins, and two extremities. The superior
margin looks upwards and backwards ; it is straight, and
presents some articular foramina. To it is attached the
superior broad navicular ligament, which runs obliquely
upwards and backwards to blend with \he perforans tQi\d.on,
and with the superior band of the stellate ligament. At its
posterior edge a continuation of the posterior smooth sur-
face of the bone is visible. Thi^ posterior surface is covered

286 OUTLINES OF EQUINE ANATOMY.

with fibro- cartilage, fonning the anterior boundary of the
navicular joint, and affording the perforans tendon a sur-
face to play over. Its superior margin is straight, its
inferior convex. It presents two level surfaces sloping
slightly towards the centre, and thus rendering more pro-
minent a ridge which here extends from above downwards
across the surface. The inferior margin of the bone is
convex, and posteriorly is rough, with numerous foramina,
affording attachment to the inferior broad ligament (run-
ning from this to the postero-inferior surface of os pedis) ;
anteriorly it presents a smooth articulatory surface, elon-
gated from side to side, which moves arthrodially on a
corresponding surface of os pedis, and is continuous by
a smooth rounded edge with the iqji^er or anterior surface
of the bone. This is covered with articular cartilage,
articulating with os coronae ; it has two elongated concave
surfaces, which centrally are separated by a broad con-
vexity. Its superior margin is straight, its inferior convex.
The surfaces and margins culminate in the two extremities,
which are angles, with a slight inclination in a posterior
direction. To them are attached the stellate navicular
ligaments, each of which, attached here by a single head,
divides into three parts, one of which runs to the inner
part of the wing of os pedis, blending with the inferior
broad ligament, another runs to inner surface of the lateral
cartilage, while the third, after uniting with the terminal
expansion of the perforans tendon, passes upwards and
divides, one part, after becoming attached to the inner
surface of the sujjerior part of the lateral cartilage being
continued on to blend with the lateral ligament of the
pastern- joint, while the other runs direct to the middle
of the lateral surface of os suffraginis, where it is
attached.

We have now examined the articulatory surfaces which
enter into the formation of the coffin and navicular joints.
The synovial membrane of the former covers the inner
surface of part of extensor pedis tendon and of the lateral
ligaments, and covers the anterior surface of both the broad
navicular ligaments. We have here a peculiar, but not
exceptional, union of a ginglymoid with an arthrodial
joint. The arrangement of the tendinous structure around
prevents the necessity for a capsular ligament. The syno-
vial membrane of the navicular joint (or more correctly

THE FOOT. 287

bursa), after covering tlie antero-superior part of the iiife-
rior jDortion of the tendon on reaching the superior broad
ligament above, is reflected over its posterior surface as
far as the bone, while from below it is reflected upwards
over the posterior surface of the inferior broad ligament
centrally, and laterally comes in contact with the stellate
ligament.

The blood-vessels and nerves of the foot have been already
noticed, but we may here repeat that each metacarpal or
metatarsal nerve just above the fetlock breaks up into
three divisions, which pass downwards over the lateral
surface of the joint, in company with the plantar vein and
artery. The anterior division runs forwards to suj^ply the
structures in front of the joint.

The middle division or anterior plantar nerve, crossing
the artery from behind forwards, runs to the coronet,
during the first part of its course situated behind the
artery and vein.

The posterior division or posterior plantar nerve is
situated behind the artery, and accompanies it to the pos-
terior part of the foot, sending off fibres to accompany
many of its branches ; this nerve is divided in the " Zo^y "
operation of neurotomy. The inferior extremity of the
metacarpal nerve before division is involved in the " high"
operation.

The flexor tendons must now be examined.

While passing through the sesamoid groove at the back
of the fetlock the perforatus tendon extends round the per-
forans, and thus forms a sheath for it, which is deficient
anteriorly, so that the theca between the tendons com-
municates with the sesamoid bursa. From the supero-
lateral angles of os suffraginis portions of white fibrous
tissue run to the posterior surface of the perforatus tendon,
which shortly after bifurcates one of its divisions runnino-
to each extremity of the posterior fibro-cartilaginous sur-
face of OS coronge. Between the divisions the perforans
tendon runs, playing over the fibro-cartilaginous surface ;
to its posterior surface run white fibrous tissue layers from
the infero-lateral parts of os suffraginis ; thus reinforced it
receives some white and yellow elastic fibres from the
superior margin of the navicular bone (superior broad
ligament) which run to its anterior surface. It then plays
over the inferior surface of os naviculare, through the

288 OUTLINES OF EQUINE ANATOMY.

medium of the navicular bursa, and becomes inserted by a
wide attachment to the posterior margin of the plantar
surface of os pedis. Its under surface is separated from
the fibrous frog by a white fibrous layer, which connects
the lateral cartilages at their inferior inflections.

nary (Right and Left) 200
rBBioR f Arteriaj Inno-
194 * I (right'SntTleft^

ARTERIAL TREE.

Posterior corvicnl— let intcrcoBtoI, 179 antl 1S5
Aoterior dorsal j 2nd intercostal, 1"'
186 Isubcostal— 3rd, 4

Vertebral 178

Carotid (common) f Bight I Ramus anastomoticus

Sy) 19'

i8 <Occipital 168
Posterior communicating 161
i & I Internal carotid 168 ■( Middle cerebral 161
78 I ^Anterior communicating 161
I Tbj-roidcal 178— Laryngeal 178
l^Eiternal carotid 168 f Submaxillary . . Lingual | Ranine

i. Ophthalm

bmaxillary .
117 and 169

I Branch to thymus gland 184

Anterior abdomimil 194
I^Superior branch 194

Sublingual 1
Submental or myeloid
Inferior labial 117
Anterior masseteric 11
Superior labial 117 —

Axillary j External thoracic
206 Humeral thoracic zuo

Anterior scapular (art. dorsalis scapula-) 206 .r. .,,.,.,

I Posterior scapular or subscapular 203 i Medulla:

LHumeral 206 |

1 I Branch to Hex
Medullary of I
I Muscular brar

^loQ

liar (sometimes) 123

Inferior maxillary

Deep temporal branches 125

Ocular I Supra-orbital 126

Ciliary 126

l_ Lateral

fMolar branches 125

branches to sup. meatus 126

--■-"' iddle meatus 126

iferior meatus 126

' . ralatine

I Molar branches 126
Canine branches 126
Incisor branches 126
tlnfra-orbilal branches 126

Branch t'
Superficial coronary i .
Deep-seated coronary J
Branch to frog I Branch

ARTERIAL T'REE—ouiiUiiu

b189
I supbiior branches 238
Lumbar { Inferior branches 238

Medullary of dorsal vertebra 180
Branch to spinal cord and its mem
Dorsal branches 187
1 Cutaneous, muscular, and pleural b

Medullary of lumbar verlebrs 238
i Branches to spinal cordaudit8membranes238

rGastric < Superior 237 "|

sis i 237 5 Inferior 237 }-~^

Splenic 237 . Left gastric 237- J "-^ ^

[Hepatic 226 f Branches to the liver 226 '

} Duodenal branch 226 r Eight giistric 2-.

f Pancreatic 237 i Intestinal 226

Duodenal 237
Mesenteric (15-18 in number) 237

237 t Branches i

I Branch t
)rL-renal capei
) kidney 237

237 fTwo branches to double colol

(.Branch to single colon 237
ich to single colon 237

237

Branches to spermatic cord 237
Branches to epididymis 237
Artery of cord (male) 263 , Sometimes from external iliac

: i Artery of tl

■ Middle coccygeal (sometimes) 26.5
fUmbilical {|:-f,'ES261
Vesical branches 2(U

1 and perineal branches 2Gi

1 Cutaacoua braucbee '270

the bladder 2(31

Auterioi- tibial

/Large meta
1 271

^ riantars 1
13 branches 271
: branches 271

|.r;

Obturator < Pubic 264
26-1 Ischiatic 264

[^ Internal pubic — Posterior dorsal artery of the penia 264
Gluteal 265 , ^^^

Lateral sacral 265 — Lateral (sometimes middle) coccygeal 265
C Circumflex artery of the ilium 262
( Arteria profunda ("Epigastr- ''"—^

of penis 2G3

rPost. abdominal branches 263
Externiil pudicf Anterior dorsal artery
(. - ■ — "

NEKVOUS SYSTEM.

Sympatlietic Bystem 13

ilhmuB h:jo uemispnfres

I Cnghtanikft)]

Ifactory bulb and sheath 160

Hcmiapheres lol
Superior tracts 181

aiuus opticus f" Corpora geniculal
157 < Tubercle 1="

Grey com.

fimbriate 1
Septum lucidum 1
[Corpus albicans 16

Crura f Anterior (processus ad
159 J. testes) 153

Middle (pons Varolii)
1.59
(.Posterior 160

Corpora py

Corpora pyramida- Inferior ditto

Ha inf. 160
Corp.

Corp.

On the superior Cervical superior 179 Card

Pharjnge«l 177
Pulmonary 192
Cardiac 2O0

Posterior mesenteric

Vertebral 195
Gangliated cord 19.5
Splflichnic greater 19-
„ leaser 195
CUiary 145
Inhibitory [?] (with

H^gas

Corpora quadrigemiaa < Testes lo8
'ineal body and its crura 158

Complex
isso-pharj'Dgeal f Glossal branch (f

9th, 139 I Pharyngeal

r Communicating branchea 177
eumogastric <

10th, 177 Superior laryngeal

lea 177
Pharyngeal 177

Portio molli8,8th, 164

Inferior laryngeal or recurrent 177
Branches to thoracic plexus 192
„ ganglia 192
CEsophageal (-Gastric branches
(sup. and inf.) tBraneh to solar ple3
Sensory fOphthal- T Palpebral

Pathetic or trochlear, 4
dbduccns, 6th, 145
Spinal accessory, 11th,
Lingual, 12th, 136

f opbthalti
Tympani.

Petrosal facial

Superior
lary 127

halniic ganglio
' Branch to molar

Pal a to- max i I
J. dental 1
Molar

r Branches to sup. cer-
vical ganglion
Auricular branches
Branches to neigh-
bouring nerves

[ Ac.

Istto 17lh or 18th
Muscular branches &c.
Branches to gangliated cord
Intercostal branches

Lumbar 265
Ist Muscular superior

Ganglionic
Abdominal

crural fibres
3rd 1 Similar to 2nd a

Ganglionic fibres
Gluteal fibres

Sciatic fibres

Muscular superior
„ inferior

Infra-orbital branch
Inferior f Facial branch 119
maxil- < Buccal branch
lary 124 Auricular branch 124

Gustatory branch 124 (special seuse)
[^ Inferior dental

i 5th muscular and phrenic branchea
i 8th muscular branchea and axillary
1 and communicating branches to

Subscapular
Humeral thoracic
External thoracic
Muscular branches

3rd Muscular super:
„ inferii
Coccygeal
Ganglionic

4lh— Coccygeal &c.

bmral

Ulnar — External metararpal r Plantar r

Radial— Internal mclaoarpan ' .,;»

^Popliteal 267

; Anterior tibial 267

1^ Posterior tibial 272

Ext. metatarsal 21

Int. metatarsal 27

INDEX.

PACK

PAGE

^Abdomen

. 216

Angle of inferior maxilla

. 41

— divisions of

. 231

— mouth .

. 120

— lining membrane of

. 222

— palpebral fissure

. 120

— muscles of

. 220

— rib .

. 58

— regions of

. 231

Ankle ....

. 92

■ — viscera of

. 224

Annular cartilage

. 122

Abdominal rings .

. 219

— ligaments

. 11

Absorbent glands, see Glands

Annulus ovalis

. 197

lymphatic.

Anthropotomy

. 1

Absorbents, see Lymphatics.

Antrum

. 142

Acetabulum .

. 82

Anus ....

. 235

Acini ....

. 226

Aorta ....

. 199

Afferent lymphatics

. 19

— anterior .

. 194

— vessel of kidney

. 240

— posterior

. 236

Age of subject for dissection

3

— valves of

. 199

— as shown by teeth .

. 131

Apophysis .

. 8

Air cells

. 191

Apparatus, lachrymal .

. 121

— sacs

. 192

Appendix

. 197

Alse of atlas

. 48

Aqueduct of Sylvius

. 158

— nostrils .

. 139

Aqueous humour

. 149

— thyroid cartilage

173

Arachnoid (cranial)

. 154

Albuginea testis, tunica

246

— fluid

. 155

Allantois

255

— (spinal) .

. 180

Allantoid sac

255

Arch, crural

. 219

Alveoli

34

— haemal .

. 42

Amnion

255

— fibular .

. 92

Amphiarthrosis .

100

— ischial .

. 85

Ampullae

163

— neural

. 42

Anastomosis (of arteries)

21

— palatine

. 38

Anatomy

1

— radio-ulnar

. 69

— comparative .

1

— vertebral

. 43

— descriptive

2

— zygomatic, 5ee Zygomatic ridge.

— general .

1

Arcus senilis

. 147

— pathological .

2

Arteries, general description

— philosophical .

2

of . . .

. 20

— transcendental

1

— injection of

. 2

39

290

INDEX.

PAGK

PAGE

Arteries, coats of

. 21

Arteries, iliac, internal

. 264

— descriptive anatomy of:

— infra-orbital, see Superior

— abdominal

. 221

dental.

— aorta

. 199

— inguinal .

. 263

— — anterior .

. 194

— innominate, right

. 194

— — posterior .

. 236

— — left .

. 194

— auricular

. 123

— — branch of obtu

i-ator. 264

— axillary

. 206

— intercostals

185, 186

— basilar .

. 161

— — first

. 179

— bronchial

. 192

— ischiatic .

. 264

— of bulb .

■ . 26i

— labial, superior

. 117

— carotid, common, 16

3,178,194

— lachrymal

. 145

— — external .

. 168

— laminal, lateral

. 214

— — internal .

. 168

— laryngeal

. 178

— centralis retinae

. 145

— lingual .

. 136

— cerebellal

. 161

— lumbar .

. 238

— cerebral .

. 161

— mammary

. 263

— cervical, inferior

. 179

— masseteric

. 117

■ — " — posterior .

179, 185

— maxilary, internal

. 125

— ciliary

. 145

— — inferior .

. 125

— circulus arteriosus p

edis . 214

— mesenteric

. 227

— circumflex, of ilium

. 262

— — anterior .

. 237

— toe . .

. 215

— — posterior .

. 237

— coccygeal

. 265

— metacarpal, small

. 213

— cceliac .

. 237

— — large

. 214

— csecal

. 237

— metatarsal, large

. 271

— colic

. 237

— — recurrent

. 271

— communicating

. 161

— nasal, lateral .

. 126

— of cord .

, 263

— obturator

. 264

— coronary, of heart

. 200

— occipital

. 168

— — foJt

. 214

— oesophageal

. 192

— corporis callosi

. 156

— ophthalmic

. 145

— dental, superior

. 126

— orbital .

. 145

— dorsal .

. 185

— ovarian .

. 238

— dorsalis scapulae

. 217

— palato-mixillary

. 126

— diaphragmatic, see ]

Phrenic.

— pectoral, external, se

eTho-

— duodenal of hepatic

. 226

racic.

— emnlgent

. 237

— phrenic .

. 189

— epigastric

. 263

— plantar .

. 214

— facial

. 117

— profunda femoris

. 263

— femoral .

, 263

— pubic

. 264

— of frog .

. 214

— pudic, external

. 263

— gastric, superior

. 231

— — internal .

. 264

— — inferior .

. 231

— pulmonary

. 198

— — right

. 231

— radial

. 206

— — left .

. 231

— ramus anastomoticu

3 . 168

— gluteal .

. 265

— ranine

. 136

— hepatic .

. 226

— recurrent

. 270

— humeral .

. 206

— renal

. 237

thoracic

. 206

— sacral, middle

. 265

— iliac, external

. 262

— — lateral .

. 265

INDEX.

291

PAGE
217

217
286
238
126
200
237
236
136
169
217

Arteries, scapular, anterior
206,

— — — posterior . 206,

— solar

— spermatic

— spheno-palatine

— spiral

— "splenic .

— of stomach

— sublingual
-7 submaxillary . . I17.

— subscapular .

— subzygomatic, see Tem-

poral.

— supra-orbital . . . 126

— temporal . . , igg

— — deep . . . 125

— thoracic, external . . 2IS

— — internal . . . 194
— ■ thyroid . . . .178

— tibial, anterior . . 270

— — posterior . . 270

— ■ulnar .... 206

— umbilical . . . 264
-- uterine . . 238, 263

— utero-ovarian, see Ovarian.

— vertebral . . . 173

— vesico-prostatic . . 264<
Arthrodial joint . . . 100
Arthrology .... 199
Articular cartilage . .17

— eminences ... 9

— laminae . . . .10
Articulation, see Joint.
Arytenoid cartilages . . 172
Ass ..... 3
Auditory canal, external . 123

— meatus, external . .123

— — internal . . .32
Auricle of heart, right . . 197

— left . . . .199
Auriculo- ventricular furrows 196

— — opening, right . 198

— — — left . . .199

— — valves . . .199
Axonoidal joints . . . 101
Azygos vena . . . 187

Bacillary layer
Back .
Barb .

148
183
132

Bars of hoof
Base of mouth

— brain

Ba'^ement membrane
" Beastlings "
Belly of muscle .
Bicuspid valve
Bile duct
Bladder, gall, absence of

— urinary .

— — foetal

— — ligaments
Blind spot .
Blood, circulation of.

— vessels .
Body of thyroid .
Bone, general anatomy

— cavities of

— composition of

— classes of

— tissue, kinds of

— eminences of .

— formation and grow

— Haversian canals

— — systems .

— lacunae of

— lamellas .

— medulla of

— periosteum of .

— processes of .

— organization of

— long, round

— flat

— short

— irregular

— astragalus

— atlas

— axis

— oaleis

— carpal

— coccygeal vertebras

— coronal .

— cranial .

— cuboid .

— cuneiform of carpus

— — magnum (tarsus)

— — medium

— — parvum

— ear

— ethmoid

— face

of

thof

FAOX

. 276
. 128
. 160
. 14
. 232
. 12
. 199
. 233
. 225
. 241
. 255
. 241
. 148

. 19
. 166

. 7
. 10
. 6
. 8
. 8
10
7

. 8
. 8
. 8
. 8
. 8
. 9
. 10
. 9
. 8
. 9
. 9
. 9
. 93
. 47
. 49
. 92
. 72
. 56
. 281
. 150

. m

. 73

. 94

. 95

. 96

. 164

. 29

. S3

292

INDEX.

Bone, femur

PAGE

. 85

Bone, sufFraginis .

— fibula

. 91

— tarsal

— foot

. 281

— temporal, petrous

— forearm .

. 68

— — squamous

— fore extremity

. 61

— tibia

— frontal .

. 27

— trapezium

— hind extremity

. 82

— trapezoid

— hock

. 92

— triquatral

— humerus

. 65

— turbinated, superior

— hyoid

. 133

— — inferior .

— ilium

. 82

— ulna

— incus

. 164

— unciform

— innominate

. 82

— vertebral, cervical

— ischium

. 84

— — coccygeal

— lachrymal

. 36

— — dorsal

— lunare .

. 72

— — false

— magnum

. . 75

— — lumbal .

— malar

. 38

— — sacral

■ — malleus .

. 165

— — true

■ — maxillary, anterior

. 33

— — typical .

— — inferior .

. 40

— vomer

— — superior .

. 34

— zygomatic

— metacarpal, large

. 77

Brain .

— — small

. 78

circle of Willis

— metatarsal, large

. 98

ventricles .

— — small inner

. 98

Bronchi

— — — outer

. 98

B runner's glands .

— nasal

. 33

Buccal salivary glands

— navicular

. 285

Bulb, olfactory .

— occipital

. 24

— penis

— palatine

. . 37

— vagina .

— parietal .

. 26

Bursa .

• — patella .

. 88

— pedal (fore) .

. 282

Caecum

— — (hind) .

. 98

— caput coli

— pelvic

. 82

Calamus scriptorius

— pisiform .

. 77

Calcaneo-cuboid ligame

lit

— pterygoid

. 38

Calyces of kidney

— pubic

. 85

Canals ....

— quadrate

. 101

CanaJ, alimentary, see ^

— • radius

. 68

mach, &c.

— ribs

. 56

— Haversian

— sacral

. 54

— auditory external .

— scaphoid

. 72

— of Fontana

— scapula .

. 61

— of Petit .

— sesamoid

80, 98

— inguinal .

— shuttle .

. 285

— spinal

— skull

. 24

Canaliculi .

— sphenoid

. 30

Cancellated structure .

— stapes

. 164

Canine teeth

— sternal .

. 60

Cauthi of eyelids .

Sto-

INDEX.

293

PAGE

PAGE

Capillaries .

. 26

Cauda equina

. 266

Capsular ligaments . . 100

Caudatus lobus .

. 225

Capsule, Glisson's

. 226

Caul .

. 230

— of lens .

. 149

Cavernosum, corpus

. 243

— pre-renal

. 236

Cavernous sinus .

. 154

— supra-renal, see Pre-renal 236

Cavities of bones .

9, 10

— renal

. 239

— heart.

. 196

Caput gallinaginis

. 242

— reserve .

. 130

Cardia of stomacli

. 229

Cavity, abdominal

. 230

Cardiac ligament .

. 224

— alveolar .

. 33

Cariniform cartila

ge . .60

— cranial ,

. 150

CarneaB columnse

. 198

— glenoid .

. 63

Carpus, bones

. 71

— pulp

. 132

— articulations

. 107

Cells, ethmoid

. 30

Cartilage

. 7

— hepatic .

. 226

General :

— mastoid .

. 164

— cellular .

. 8

— nerve

. 14

— elastic ,

. 7

Cementum .

. 129

— fibro-

. 7

Centralis retina arteria

. 145

— hyaline .

. 7

Centrum ovale major

. 156

— permanent

. 7

— — minor

. 156

— temporary

. 8

— vertebral

. 43

— true

. 7

— nerve

. 13

— articular .

.7

Cerebellum .

. 159

Particular :

Cerebro-spinal nervous

sys-

— annular .

122

tem

. 13

— arytenoid

*. 175

Cerebrum

. 155

— auricular

. 122

— crura of .

. 160

— cariniform

. 60

Ceruminous glands

. 123

— costal

. 58

Cervix vesicae, see Neck of

— cricoid .

. 174

bladder.

— elongation of scapula . 63

— uteri, see Neck of u'

erus.

— — ribs

. 58

Chambers of the eye

. 149

— — ensiform

. 60

— nasal

. 139

— epiglottis

. 174

Channels

. 10

— of foot (lateral) . . 284

Cheek .

. 118

— inter-articular

discs of

Chestnut

. 208

stifle-joint

. Ill

Chorda tympani .

. 124

— — temporo ■

maxillary

Chordae tendinese

. 198

joint

. 101

Chorion

. 253

— larynx .

. 173

Choroid

. 147

— nictitans

. 143

— plexus of lateral ventri-

— of nostrils

. 139

cles

. 155

— septum nasi

. 173

— — of third ventri(

jle . 155

— scutiform

. 122

Cilise .

. 16

— tarsal

. 120

Ciliary arteries

. 16

— thyroid .

. 173

— ligament

. 148

— of trachea

. 176

— processes

. 147

— xiphoid .

. 60

— zone

. 149

Curuncula lachry

malis . 121

Ciliated epithelium

. 16

Carunculse myrtif

ormes . 251

Cineritious brain mattei

r . 156

294

INDEX.

Circle of Willis .
Circulation, blood, foetal
— through liver .
Circulus arteriosus pedis

PAGE

161

253

. 226

, 214

Circumferential cartilage (hip) 111
Circumflex artery of the toe 215

Clitoris

. 251

Coats of stomach

. 230

Coccyx . ' .

. 56

Coccygeal vertebrae

. 56

Cochlea

. 163

Cceliac axis .

. 237

Colon, double

. 234

— single

. 235

Colostrum .

. 253

Colour of the hoof

. 276

Column, vertebral

. 42

ColumnsB carnese

. 198

Columns of spinal cord

. 181

Commissures of hoof .

. 274

— grey

. 157

— soft

. 157

— of spinal cord .

. 181

— anterior .

. 158

— posterior

. 158

Communicating arteries

. 161

— foramina, anterior .

. 158

— — posterior .

. 158

Compact tissue of bone

. 8

Compound glands

. 19

Conchial cartilage

. 122

Condyles

. 10

— of femur

. 88

— of humerus .

. 67

— of inferior maxilla .

. 40

— of occiput

24,25

Conjunctiva

. 121

Constrictors of the pharynx

. 138

Contorti tubuli .

. 240

Convolutions of the brain

. 155

Coracoid process .

. 61

Cord, artery of .

. 238

— sperm.atic

. 245

— spinal

. 180

— umbilical

. 255

Cord 03 vocales

. 175

— Willisii .

. 153

Corium

. 16

Cornea

. 46

Corneal cartilage .

. 139

Cornua of os hyoides, short

. 134

Cornua of os hyoides, long

— of spinal cord .

— of thyroid cartilage

— of ventricles (lateral)
Corona glandis

— tubulorum
Coronal suture
Coronary arteries .

— fibrous band .

— frog band

— secreting substance
Corpus albicans .

— callosum.

— cavernosum

— dentatum

— geniculatum .

— luteum . . •

— olivare .

— spongiosum
Corpora arantii .

— striatum .

— pyramidalia .

— restiformia

— nigra

— quadrigemina .
Corpuscles, Malpighian,

kidney .

— -^ spleen
Costse .

Costal cartilages .
Cotyloid cartilage

— cavity .
Cowper's glands .
Cranium
Cranial nerves
Cremasteric faschia
Crest .

— of occiput

— of ilium .
Cribriform plates of the

ethmoid
Cricoid cartilage .
Crista galli process
Crown of tooth .
Crucial ligament .
Crura cerebri

— cerebcUi .

— of corpus cavernosu

— of diaphragm .

— fornix

— of pineal body

INDEX.

295

PAGE

tAGE

Crura of splienoid bone

. 31

Dacts, nasal

. 143

Crural arch ...

. 219

— pancreatic

. 224

Crusta petrosa

. 129

— of Stenson

. 141

Crypts, mucous .

. 242

— thoracic .

. 195

Crystalliue lens .

. 148

— Wharton's

. 132

Curvatures of stomach

. 229

— ejaculatory

. 247

— spleen .

. 236

Ductus ad nasum .

. 143

Cuticle, see' Epidermis.

— arteriosus

. 198,254

Cuticular layer of" stomach . 230

— venosus .

. 253

Cutting the teeth

. 130

Ductless glands .

. 19

Cylinder, axis

. 14

Duodenum .

. 233

Dura mater of the bra

in . 153

Dark chamber

. 149

— — cord

. 180

Decidua membrana

. 250

Decussation, optic

. 160

Ear .

. 163

— of motor fibres

. 160

— external .

. 122

Dentata

. 49

— internal .

. 163

Dentition (table) .

. 131

— middle .

. 164

Dentine

. 129

— wax, see Cerumen.

Depressions on bones

, see

Ejaculatory ducts

. 247

Cavities.

Elastic tissue

. 7

Dermis

. 17

Elastica, cornea .

. 146

Descent of testis .

. 246

Elongation, cartilage,

of rib . 58

Destruction of subject

. 4

— — of scapula

. 62

Detrusor urinae .

. 242

Eminences of bones

. 9

Development of teeth .

. 130

Enamel

. 129

Diaphragm .

. 188

Encephalon .

. 162

Diapophysis .

. 8

Endocardium

. 196

Diarthrosis .

. 100

Endolymph

. 163

Digital impressions

. 10

Ensiform cartilage

. 60

Digastric muscles

. 12

Epidermis .

. 434

Digestive organs, see

Stomach,

Epididymis .

. 247

&c.

Epiglottis .

. 289

Dilators of the pharyn

X . 138

Epiphysis .

. 8

Diploe

9,150

Epithelium, ciliated

. 16

Disc, optic .

. 148

— columnar

. 16

Dissection of head

. 115

— spheroidal

. 16

— of neck .

. 166

— stratified

. 16

— of abdomen .

. 216

— tesselated

. 15

— of back .

. 183

Erectile tissue

. 236

— of fore extremity

. 201

Ethmoid bone

. 29

— of hind extremity

. 257

— cells

. 30

Division of the subject

. 4

— fosso3

. 151

Dorsal vertebrae .

. 50

— sinuses .

. 29, 142

Dorsum scapulae .

. 63

Eustachian tube .

. 137

- ilii . . .

. 83

Extremities, anterior,

see Fore

Drum of the ear, see

Tym-

limb.

panum.

— posterior, see Hin

1 limb.

Ducts, bile .

. 225

Eye

. 146

— of glands

. 19

— muscles of

. 144

— hepatic .

. 225

Eyeball

. 146

JiUt)

INDEX.

PAGE

PAGE

Eyelids

. 120

Fimbriated extremity .

. 249

Eyelid, third

. 143

Fissure . . ' .

. 10

Eyelashes

. 121

Fissures of spinal cord .

. 181

Excrescence, cauliflower

. 250

— cerebrum

. 155

External ear

122

— palpebral

. 121

Extremity, dissection of fore 201

— of Sylvius

. 161

— — of hind .

. 257

— of liver, transverse
Flat bones .

. 225
. 9

Face ....

. 24

Fixed joints

. 99

— bones of .

. 33

Fleur epanouie

. 250

Facial nerve

. 119

Flexure, sigmoid, of double

Falciform ligament of bladder 241

colon .

234

— — of liver .

. 22

Foal, peculiarities of .

255

Fallopian tube

. 249

Foetal appendages

253

False nostril

. 116

— circulation

253

— ribs

. 58

Follicular glands .

18

— tongues .

. 254

Follicles of Lieberklihn

232

— vertebrse

. 44

Fontaua, canal or

148

Falx cerebri .

. 153

Foot ....

273

Fang of tooth

. 128

— bones of .

281

Faschia or fascia .

. 11

— nerves of

287

— of arm .

. 210

— vessels of

280

— abdouiinalis superf.

. 216

— tendons of

287

— cremasteric • .

. 245

Foramen auditorium exter-

— intercolumnar

. 245

num

32

152

— lata

. 258

— — internum

32

,151

— lumbar .

. 183

— communicating anterior .

157

— psoas

. 256

— — posterior .

158

— of quarter

. 257

— condyloideum

25*,

151

Fasciculi of muscle

. 12

— dextrum.

188

Fat in orbit .

. 143

— incisorum

34

Fatty mane .

. 166

— infra-orbitale .

35

Fauces, isthmus of

. 137

— lacerum basis cranii

151

— pillars of

. 137

— — orbitale .

30,'

152

Feelers

. 120

— lachrymal

37

Female generative organs

. 273

— magnum occiputum

151

Femoral space

. 260

— — vertebral

49

Fenestra ovalis .

. 164

— maxillary, anterior

41

— rotunda .

. 164

— — posterior .

41

Fenestrated membrane

of

— medullary

9

Henle .

. 21

— menti

41

Fibres of Corti .

. 164

— of Monro

157

— nerve

. 14

— obturator

84

— muscle .

. 12

— optic

152

Fibrillar

. 12

— orbitale internum .

152

Fibro-cartilage

. 7

— ovale

196,

254

Fibrous coronary band

. 280

— palato-maxillary

38

Fibrous tissue

. 7

— pathetic .

152

Fibular arch

. 92

— rotundum

30,

152

Filiform papillse .

. 133

— siuistrum

189

Filum terminals .

. 180

— Soemering

148

INDEX.

297

Foramen, spheno-palatine

PAGE

. 37

Ganglion, Inferior

— styloid . . .32, 152

— lenticular

— subsacral

. 56

— middle .

— subsphenoidal

. 30

— Meckel's

— snpersacral

. 56

— ophthalmic

— sxipra-orbital .

. 28

— otic

— of Winslow .

. 223

— semilunar

Foramina .

. 10

— post-meseuteric

— articular

. 9

Ganglionic nervous system

— of cranium

. 151

Gaps, intervertebral

— intervertebral

. 43

Gastric glands

— Thebesii .

. 197

Gastro-hepatic omentum

Fore limb, articulations of

. 106

— jihrenic omentum .

— bones of

. 61

— splenic omentum

— dissection of .

. 201

— colic omentum

Foreskin

. 244

Generative organs, female

Fornix

. 381

— — male

Fossa ....

. 10

Geniculata, corpora

— antea spinatus

. 63

Genu of corpus callosum

— ethmoid

. 150

Ginglymoid joint

— intercondyloid (femur)

. 88

Glands

— navicularis, male .

. 243

— Brunner's

— — female .

. 251

— buccal .

— olfactory

. 30

— ceruminous .

— optic

. 29

— Cowper's

— ovalis

. 197

— ductless .

— postea spinatus

. 63

— gastric .

— renal

. 239

— labial .

— temporal

. 125

— lachrymal

— trochanteric .

. 86

— of large intestine .

Frsenum linguse .

. 133

— lymphatic

Frgena (synovial)

. 15

— — inguinal

Freely moveable joints

. 100

— — popliteal

Fringes, synovial

. 15

— — mesenteric

Frog-, liorny

. 276

— lymphatic axillary .

— sensitive

. 280

— — bronchial

— fibrous or fatty

. 280

— — prescapular

— stay

. 276

— — parotid .

Frontal sinus

. 142

— mammary

Fundus of bladder

. 241

— Meibomian

Fungiform papillae

. 133

— mucous, of stomach .

Furrows

. 10

— molar, see Buccal.

— of heart .

. 196

— • ofPacchioni

Galactophorous sinuses

. 252

— palatine .

G.ill duct, see Bile duct.

— pancreas

Ganglia

. 13

— parotid .

— of heart .

. 200

— peptic .

Gangliated cord .

. 195

— Pej'er's .

Ganglion, Arnold's, see Otic.

— prostate

— cervical, superior

. 178

— salivary .

— Gasserian

. 126

— sebaceous

%y«

INDEX.

PAGE

)

PAGE

Glands, of skin .

. 17

Heart, cavities of

; 197

— of small intestine .

. 232

— chordae tendincEe .

. 198

— solitary .

. 232

— columnas carnea3

. 198

— sublingual salivary .

. 133

— corpora arantii

. 199

— submaxillary salivary

. 167

— endocardium .

. 196

— sudoriparous .

. 17

— fibrous rings of

. 196

— thymus .

. 200

— foetal .

. 254

Glaus penis

. 241

— foramina Thebesii .

. 197

Glenoid cavity

. 10

— fossa ovalis .

. 197

Glisson's capsule .

. 226

— furrows .

. 196

Globe of the eye .

. 146

— lining membrane .

. 196

— epididymis

. 247

— muscular fibres of .

. 197

Glosso-pharyngeal nerve

. 139

— musculi papillares .

. 198

Glottal opening .

. 175

— — pectinati .

. 197

Glottidis, rima

175

— nerve supply .

. 200

Gomphosis .

99

— orifice, auriculo-ventricu

Graafian vesicles .

248

lar, right

. 197

Grey nerve-fibres

13

— — — left .

. 199

Gristle, see Cartilage.

— — pulmonary

. 198

Groove

10

— — aortic

. 199

— primitive dental

130

— sinus Valsalvae

199

Gubernaculum testis

246

— systemic.

. 196

Gullet, see CEsophagus.

— tuberculum Loweri .

. 197

Gums ....

128

— valves, auriculo-ventricu

Gustatory nerves

136

lar, right

197

Guttural pouches

137

— — — left .

199

Gyri ....

155

— — Eustachian

197

Gyrus fornicatus

155

— — mitral or bicuspid

199

— — pulmonary

196

Ha3mal arch . . 42

,150

— — semilunar aortic

199

— spine . . . .

43

— — — pulmonary

198

Hsemorrhoidal, see Rectal.

— — systemic .

196

Hair

17

— — Thebesii .

197

— follicles . . . .

17

— ventricle, right

198

— root . . . .

17

— — left

199

— stem . . . .

17

Heart's lymph

23

— bulb . . . .

17

Hemispheres of brain .

155

Hamular process of ulna

71

— cord . . . .

181

Harmonia . . . .

99

Hepatic cells

226

Haversian canals .

8

— duct . . . .

225

— systems . . . .

8

Hiatus . . . .

10

Haw, see Cartilago nictitans.

— aorticus . . . .

188

Head, dissection of

115

— sphenoideal or orbital

152

— bones of .

24

Hilum of kidney .

239

Heads

10

— spleen . . . .

236

Heart

192

Hind limbs . . . .

257

— annulus ovalis

197

— joints of .

111

— arteries of . . .

194

Hip-joint . . . .

10

— auricles of riglit

197

Hippocampus

157

— — left . . . .

199

Hippotomy . . . .

1

— — appendices

199

Histology . . . .

1

IND'EX.

299

Hock-bones .

PAGE

. 92

PAGE

Intestines, large, sigmoid

— joint

. 113

flexure

. 234

Hoof .

. 273

— — mucous membrane of 230

— hind

. 278

— — muscular coat of . 232

— commissures .

. 274

— — rectum .

. 235

— coronary frog-band

. 275

— — serous coat of

. 231

— frog of .

. 277

— small, duodenum

. 233

^- frog- stay of .

. 277

— — glands of

. 232

— heels of .

. 274

— — ileum

. 233

— horn of .

. 274

— — jejunum .

. 233

— laminae of

. 275

— — mucous membrane of 232

— quarters of

. 274

— — muscular coat of . 232

— sole of .

. 276

— — serous coat of

. 231

— - toe of .

. 274

Intralobular veins

. 226

— wall of .

. 274

Involuntary muscle

. 11

Horn .

. 271

Iris .

. 148

— secreting layer

. 80

Irregular bones .

. 9

Horsehair .

. 18

Ischial arch .

. 85

Humour, aqueous

. 149

Ischium

. 84

— third

. 149

Isthmus of the fauces

. 158

— vitreous .

. 149

Iter a tertio ad quartum ven-

Hymen

. 251

triculum

. 158

Hypochondriac regions

. 231

Iter e cerebello ad testis . 158

Hj-pogastric plexus

. 227

— region .

. 231

Jacobi, tunica

. 148

Hypoglossal nerve

. 136

Jacobson's canal .

. 141

Jaw, lower .

. 24

Heo-csecal valve .

. 233

— upper

. 24

Heum .

. 233

Jejunum

. 233

Iliac artery, external .

. 238

Joints, amphiarthrotic

. 100

— — internal .

. 238

— arthrodial

. 100

Ilium .

. 82

— atlaxoid

. 102

Imprint

. 10

— atloido-occipital

. 102

Incisions (primary, th

rough

— axonoides

. 101

skin) .

. 4

— carpal .

. 107

Incisors

. 129

— carpo-metacarpal

. 107

Incisive opening .

. 34

— coflin

. 109

Incus . . . .

. 164

— costal

. 105

Inferior maxillary sinus

. 142

— diarthrodial .

. 100

Infundibulum

. 161

— elbow

. 106

Inf undibuli .

. 129

— fetlock .

. 108

Inguinal canal

. 219

— fixed .

. 99

Injection of vessels

. 2

— of fore extremity

. 106

Inosculation

. 21

— ginglymus

. 100

Instruments

. 2

— harmonia

. 99

Interlobular veins

. 226

— of hind extremity .

. Ill

Intestines .

. 231

— hip

. Ill

— large

. 234

— hock

. 113

— — cfficum .

. 234

— hyoid

. 134

— — colon, double .

. 234

— knee

. 107

— — — single

. 235

— moveable

. 99

300

INDEX.

PAGE

Joints, partially inoveaLIe . 100

— pastern . . . .109

— pedal . . . .109

— radio -carpal . . . 107

— — ulnar . , .106

— shoulder . . . 106

— schindylesis .

— stifle . . . .111

— sutural . . . .99

— synarthrodial . . .99

— tarsal .... 113

— tarso-metatarsal . .113

— vertebral . . . 103

Kidney

. 239

— adipose tunic of

. 239

— calyces .

. 240

— capsule .

. 239

— corpuscles of Malpighi

. 240

— cortical substance .

. 240

— hilum

. 239

— left

. 239

— medullar)? substance

. 240

— pelvis of .

. 240

— pyramids of Malpighi

. 240

— right

. 239

Knee ....

. 71

— joint

. 107

Labia, see Lips.

— majora .

— minora .
Labyrinth .
Lachrymal canals

— foramen .

— gland

— puncta .

— sac

— tubercle .
Lacuna?

— of urethra
Lacteals

Lambdoidal suture
Lamina ci'ibrosa

— spiralis .
Laminae of bone

— vertebra

— horny

■ — sensitive
Larynx

. 251
. 251
. 163
. 143
. 37
. 143
. 143
. 143
. 36
. 8
. 241
23, 227
. 102
. 146
. 164
. 8
. 42
. 275
. 279
. 173

PACK

Laryns, cartilages of

. 174

— — arytenoid

. 175

— — cricoid

. 174

— — epiglottis

. 174

— — thyroid .

. 173

— ligaments

. 175

— mucous membrane of 176

— muscles of

. 176

— nerves of

. 177

— ventricles of

. 176

— vocal cords of

. 175

Lateral cartilage of foot . 284

Leg, see Limb.

Lens, crystalline .

. 149

— capsule of

. 149

Lenticular ganglion

. 145

Lieberkiihn's follicles

. 232

Ligaments .

. 119

— annular .

. 11

— of bladder

. 222

— calcaneo-cuboid

. 114

— capsular .

. 11

— cardiac .

. 219

— of bladder

. 241

— ciliary .

. 148

— coraco-scapular

. 62

— cotyloid .

. Ill

— crico-trachealis

. 176

— — thyroid .

. 173

— crucial, of stifle

. 112

— denticulatum .

. ISO

— extensor um

. 212

— interspinous .

. 104

— of liver .

. 233

— nuchse

. 104

— obturator

. Ill

— odontoid

. 103

— of patella

. 112

— of the pelvis .

. 109

— Poupart's

. 219

— pubis femoral

. Ill

— sacral

. 104

— stellate .

. 105

— — of navicular

. 286

— — of rib

. 105

— subcarpal

. 210

— superior sesamoidea

I . 208

— supra-spiuous

. 104

— suspensory, superior

. 210

— — penis

. 216,245

— tarsi

. 120

INDEX.

301

Ligaments, triangular penis

PAGE
. 8i

PAGE

Malpighian corpuscles of

Limb, see Extremities.

spleen .

. 236

— bones of fore .

. 61

— pyramids

. 240

— — hind

. 82

Mammary glands

. 252

— articulations of fore

. 106

— ducts of

. 252

— — hind

. Ill

— sinuses of

. 252

Linea alba .

. 228

Marrow

. 8

Lips ....

. 119

Mastoid cells

32, 164

Liquor Morgagni .

. 150

— lobule

. 161

Liver, cells of

. 226

Maxillary sinuses

. 142

— circulation through

. 226

Meatus, auditory, external . 123

— excretory apparatus of

. 224

— — internal

. 243

— Glisson's capsule of

. 226

— of nasal chambers

. 141

— ligaments of .

. 223

Mediastina .

. 189

— lobes of .

. 225

Mediastinum testis

. 286

— lobulus caudatus

. 225

Medulla spinalis, see Spinal

— — scissatus .

. 225

cord.

— — vessels of

. 226

— oblongata

. 159

Lobes of cerebrum

. 161

— ossium, see Marrow

— cerebellum

. 159

Medullary canal .

. 8

— liver

. 225

— foramen .

. 9

— lungs

. 191

— matter of brain

. 156

Lobule, mastoid .

. 161

— • — kidney

. 240

Lobules of liver .

. 225

— sheath .

. 14

— testis

. 246

Meibomian glands

. 120

Lobulus caudatus

. 225

Membrana decidua

. 250

— scissatus

. 225

— fusca

. 147

Locus perforatus anticus

. 161

— nictitans

. 142

— — posticus .

. 161

— pupillaris

. 149

Longitudinal sinus

. 153

— tympani

. 164

Long round bones

. 8

Membrane of Demeurs

. 149

Linear bone

. 72

— of Descemet .

. 149

Lungs, air-cells of

. 191

— hyaloid .

. 149

— lobes of .

. 191

— simple

. 14

— roots of .

. 191

— compound

. 15

— vessels, pulmonary .

. 196

— mucous

. 16

— — bronchial

. 192

— serous

. 15

Lutea, macula

. 148

— Schueiderian .

. 286

Lymph hearts

. 23

— synovial

. 15

— spaces

. 23

— tentorial

, 153

Lymphatics

. 22

— winking

. 143

— glands, see Glands.

Membranes of brain

. 153

— afferent .

. 23

— fcetus

. 253

— efferent .

. 23

— spinal cord

. 180

Membranous labyrinth

. 163

Macula lutea

. 148

— semicircular canals

. 163

Male generative organs

. 243

— urethra .

. 242

Malleolus

. 91

Meninges, see Membrar

es.

Malleus

. 165

Mesentery .

. 226

Malpighian corpuscles of kid

-

Meso-csecum

. 222

ney

. 240

— colon

. 222

3oa

INDEX.

PAGE

PAGE

Meso-csecum, rectum

222

Muscles, buccinator .

118

Milk .

'. 252

—

caninus ....

118

— teeth

. 129

—

caput magnum

203

Mitral valve

. 199

—

— medium .

203

Moderator bands

. 198

—

— parvum ,

204

Modiolus

. 163

—

cervical trapezius .

183

Molar teeth .

. 130

—

complexus major

171

Mou orchid .

. 246

—

— minor

171

Monro's foramen .

. 157

—

compressor coccygis

272

Morgagni, liquor .

. 150

—

constrictors of pharynx .

138

Motor nerve-roots

. 181

—

coraco-humeralis

204

Motores oculorum

. 145

—

— radialis .

202

Motorial plates

. 14

—

cornealis transversus

140

Mouth c . . .

. 127

—

costarum superticialis

104

Moveable joints .

. 100

—

— transversalis .

104

Mucous membrane

. 16

—

— levatores

186

— of intestines .

. 232

—

crico-arytennideus posticus 176

— lachrymal apparatus

. 121

—

— lateralis

176

— larynx

. 175

—

— pharyngeus

138

— mouth .

. 133

—

— thyroideus

176

— nose

. 141

—

curvator coccygis .

272

— oesophagus

. 172

—

depressor ani .

235

— palate

. 138

—

— coccygis

272

— pharynx .

. 138

—

— labii superioris

119

— stomach .

. 229

— oculi

144

— tongue .

. 133

—

detrusor urinse . 13C

,242

— trachea .

. 178

—

diaphragm

188

— tympanum

. 165

—

digastricus

135

— ureters .

. 240

—

dilator naris anterior

140

— urinary bladder

. 241

—

— — inferior .

119

— uterus

. 250

—

— — superior .

116

— vagina .

. 251

—

of external ear, extrinsic

123

— vvilva

. 251

—

— intrinsic .

122

Muscles

. 11

—

of internal ear

165

— voluntary

. 12

—

erector coccygis, see Le-

— involuntary

. 12

vator.

— varieties of

. 12

— -

extensor metacarpi maguus

— abdominal

. 219

211

— abductor oculi

. 144

_

— — obliquus

211

— — of ear

. 144

__

— pedis

212

— accelerator urinse .

. 244

—

— — (hind)

260

— adductor oculi

. 144

—

— suffraginis

212

— — auris

. 123

—

flexor brachii .

202

— anconeus

. 205

—

— metacarpi externus .

213

— of anus .

. 335

—

— — medius

209

— antea splnatus

. 202

—

— — internus .

209

— attolentes aurum

. 126

—

— metatarsi

269

— attrahentes aurum

. 120

—

— pedis accessorius

269

— auricular

. 126

—

— — perf(jrans 210,

269

— biceps adductor fern

oris . 261

—

— — — hind .

269

— — rotator tibialis

. 259

—

— — perforatus

210

INDEX.

303

PAGE

Muscles gastrocnemius exter-

nus . . . . 267

— — iuternus . . . 268

— gemini .... 267

— genio-liyoideus . . 134

— — liyoglossus . . 134

— gluteus externus . .257
■^— — interims . . . 258

— — maximus . . 258

— — medius, see Maximus 258

— gracilis .... 260

— liumeralis externus . 205

— h,yo-epiglottideus . .174

— hyoglossus brevis . . 134

— — lougus . . . 135

— — parvus . . . 185

— hyo-pharyngeus . . 138

— hyo-thyro-pbaryngeus . 138

— hyoideus magnus . .135

— — parvus . . . 135

— — trans versus . .134

— iliacus . . . .261

— ilio-femoralis . . . 262

— inferior oblique, of eye . 144

— intercostal! s externus . 186

— — internus . . 186, 218

— intertransversalis colli . 179

— — dorsi . . .186

— iscbio-femoralis . . 267

— — tibialis . . .259

— — trocbanterius . . 267

— of larynx . . . 176

— lateralis sterni . . 218

— latissimus dorsi . . 183

— levator ani . . . 235

— — coccygis . . . 272

— — costse . . . 186

— — bumeri . . 169, 201

— — labii superioris alseque
nasi .... 115

— — palpebrae superioris
externus . . . 120

— — — — internus . 143

— — oculi . . . 144

— longissimus dorsi . . 184

— longus colli . . . 178

— lambrici . . . .109

— masseter externus . . 116

— — internus . . . 123

— moutb, wbicb close . 125

— mylo-byoideus . . 123

Muscles, nasalis longus labii

superioris . . . 116

— obliquus abdominis exter-

nus .... 220

— — — internus . . 220

— — capitis auticus . . 170

— — — inferior . . 170

— — — superior . . 170

— obturator externus . 267

— — internus . . . 267

— orbicularis oris . . 120

— — palpebrarum . . 120

— palato-pharyngeus . . 137

— panniculus . 115, 166, 216

— parotides auricularis . 166

— pectineus

— pectoralis anticus .

— — magnus .

— — transversus

— peroneus

— of pharynx

— plantaris

— popliteus

— postea spinatus

— psoas magnus .

— — parvus

— peterygoideus .

— pyriformis

— radialis accessorius .

— rectus abdominis

261
217
217

217
269
138
268
268
202
255
256
124
267
210
220

— — capitis anticus major 179

— — — — minor . 179

— — — posticus major . 171

— — — — minor . 171

— — feraoris . . . 262

— retractor ani . . . 235

— — anguli oris . . 115

— — costse . . . 220
— - — labii, inferioris . 116

— — — superioris . 116

— — lingualis . . . 134

— — penis . . . 244

— retrahentes aurum , . 166

— rbomboideus . . . 183

— sartorius . . . 260

— scalenus . . . 178

— scapulo - bumeralis exter-

nus .... 203

— — — posticus . . 205

— • — -ulnaris . . . 205

— scuto-^uricularis externus 122

45Ui

INDEX.

PAGE

PAGE

Muscles, scuto-auriculai

'is in-

Myeloplaxes

. 8

ternus .

. 122

Myolemma, see Sarcoid

mma.

— semimembranosus .

. 259

Muzzle.

. 24

— semispiualis dorsi, &.

c. . 186

— semitendinosus

. 259

Naboth's glands .

. 250

— serratus magnus

. 218

Nares, anterior .

. 139

— — parvus anterior

. 184

— posterior

. 138

— — — posterior .

. 183

Nasal cartilages .

. 139

— sphincter ani .

. 235

— chambers

. 139

— — vesicse

. 242

— fossae or cavities

. 139

— spinalis dorsi .

. 185

— mucous membrane

. 145

' — — colli, &c. .

. 179

— nerve

. 145

— splenius .

. 170

— openings

. 139

— sterno-maxillaris .

. 167

— peak

. 33

— — -thyro-hyoideus

. 167

Nates .

. 158

— stapedius

. 165

Navicular fossa .

. 243

— stylo-maxillaris

. 168

— — female

. 257

— — -pliaryngeus .

. 139

Neck, dissection of

. 166

— — -hyoideus

. 136

— of tooth .

. 128

— subscapularis .

. 204

Nerve .

. 13

— subscapulo-hyoideus

217, 200

— cells

. 14

— superior oblique, of e

ye . 144

— fibres .

. 14

— — of tail .

. 272

— tissues .

. 13

— temporalis

. 124

Nerve, abduceus .

. 145

— tensor palati .

. 137

— auditory.

. 164

— — tympani .

. 165

— auricular

. 182

— — vagina3 femoris

. 258

— axillary plexus

. 207

— teres externus v. mir

lor . 203

— brachial, see Axillai

y-

internus v. major

. 204

— bronchial plexus

. 192

— thyro-arytenoideus

mti-

— buccal (of fifth) .

. 119

cas

. 176

— cardiac .

. 195

— — — posticus .

. 176

— cervical .

. 182

— — -hyoideus.

. 176

— chorda tympani

. 124

— pharyngeus .

. 138

— coccygeal

. 272

— of tongue

. 134

— crural

. 266

• — trachelo-mastoideus

. 170

— dental, superior

. 127

— trachealis transversu

5 . 177

— diaphragmatic, see F

hrenic.

— transversalis abdomir

lis . 221

— eighth cranial.

. 164

— — costarum

. 184

— eleventh cranial

. 163

— trapezius

. 183

— facial . . lis

, 126, 148

— triceps abductor feme

)ris . 258

— fifth cranial .

. 127

— — extensor brachii

. 203

— first cranial .

. 148

— — — cruralis .

. 262

— fourth cranial .

. 145

— ulnaris accessorius .

. 210

— glosso-pharyugeal .

. 139

— vastus externus

. 262

— gluteal .

. 266

— — internus .

. 262

— gustatory

. 124

— Wilson's

. 242

— hypoglossal

. 136

— zygomaticus .

. 115

— intercostal

. 404

Musculi pectinati

. 197

— laryngeal, superior .

. 177

— papillares

. 198

— — inferior .

. 177

Musculus ciliaris v. Ugar

aent 148

— lingual .

. 136

IXDEX.

305

PAGE

Nerve, lumbar . . .265

— maxillary, superior . .127

— — inferior . . . 124

— metacarpals . . . 287

— metatarsals . . . 272

— motores oculorum . . 145

— Basal, lateral . . . 145

— jimth . . . .139
-- obturator . . . 266

— olfactory . . . 141

— Oi^bthalmic, of fifth . . 145

— optic .... 148

— palato-maxillary . . 127

— pathetic .... 145

— phrenic .... 178

— plantar .... 287

— pueumogastric . . 177

— popliteal .... 271

— portio dura . . . 164

— portio mollis . . . 164

— radial .... 207

— recurrent . . . 177

— sacral .... 268

— scapular .... 207

— sciatic .... 266

— seventh .... 164

— sixth .... 145

— spinal accessory . . 182

— spiral .... 207

— splanchnic . . . 195

— subscapular . . . 207

— suboccipital . . . 182

— supra-orbital . . . 145

— sympathetic . . . 195

— third cranial . . . 145

— tibial, anterior . .271

— — posterior . . . 272

— twelfth . . . .136

— ulnar .... 207

— vertebral . . .195

— vestibular . . .164

— vidian .... 127
Nervosa, tunica . . . 148
Nervus vagus, see Pneumogastric.
Neural arch . . . 150
Neurilemma . . .14
Nipples, see Teat.
Non-articulatery eminences . 9
Non-ciliated epithelium . 16
Nostril, fiilse . . . 124
Notch . . . . .10

PAGE

Xotch, intervertebral, jee Gap 143

— isciiiatic .... 110
Nuckse, ligamentum . . 104

Oblique muscles of abdomen 220

— — eye . . . . 144

— flexor of metacarpus . 211
Oblongata, medulla . . 159
Obturator foramen . . 84
Occiput . . . .24
Occipital sinuses . . . 154
Odontoid ligaments . . 103

— process . . . .49
Odoriferous glands . . 244
(Esophagus .... 172
Olecranon . . . .71
01f;ictory bulb . . .160

— ibssa . . . .30

— nerve .... 160

— sinuses . . . ,150
Olivary bodies . . .159
Omenta, gastric . . . 223
Openings, pupillary . . 148
Ophthalmic ganglion . . 145
Optic decussation . . 160

— disc . . . .48

— fossa . . . ,29

— thalamus . . . 157
Ora serrata . . . .147
Orbiculare, os . . . 164
Orbital process of os frontis . 27

.1
Os, see Bone.

— planum .

— uterinum externum

— — internum
Ossicula auditus .
Ossific tentorium
Ossification .

— centres of
Osteology, descriptive
Otic ganglion
Otoconites .
Otolithes .
Ovale, foramen
Ovaries

— Graafian vesicles of

— ligaments of .

— tunica albuginea of

— structure

— artery of

20

124

248
249
164

26
7
7

24
1^5
163
163
254
248
248
249
248
248
238

306

INDEX.

PAGE

PAGE

Ovum .

. 248

Peptic glands

. 230

Perforated spaces of brain . 161

Paceliioni, glands of

. 154

Pericardium, fibrous

. 192

Palate, hard

. 128

— serous

. 193

— soft

. 128

Pericardial sac

. 193

Palatine arch

. 38

Perichondrium .

. 105

— canal

. 36

Perilymph .

. 163

Palpebral fissure .

. 121

Perineum

. 244

Pampiniforme, corpus

. 246

Peri-orbitale

. 143

Pancreas

. 224

Periosteum .

. 9

Pancreatic duct .

224

Peristaltic action of bowels . 232

Pauniculus carnosus

183, 216

Peritoneum

. 222

Papillaj

. 16

Permanent cartilaue

. 7

— dental .

. 130

— teeth

. 128

— hair-follicles .

. 17

Pes anserinus

. 127

— skin

. 17

Petit's canal

. 147

— tongue .

. 133

Peyer's patches .

. 233

— of bowels, see Villi

. 232

Pharynx

. 138

Papillary layer of skin

. 17

Pia mater of brain

. 155

— stage of tooth de^

i^elop-

— — spinal cord

. 180

ment .

. 130

Pigmentary layer of choroid 147

Par magnum, see l!

^erve.

Pillars of the fauces

. 137

pneumogastric.

— — tongue .

. 132

Parietal ridges .

. 26

Pincers

. . 129

Parotid gland

. 167

Pineal body .

. 158

— duct

. 168

Pituitary body

. 154

Pars trigemini

. 126

— membrane

. 140

Partially moveable join

ts . 100

Planum, os .

. 28

Patches, Peyer's .

. 233

Plates, cribriform

. 30

Patella, straight ligame

nts of 112

Pleura

. 189

Pathetic nerve

. 145

Plexus

. 14

Pectinean tubercle

. 85

— axillary .

. 218

Pectiniforme, septum .

. 243

— choroides, lateral ventricle 155

Pedicles

. 42

— — fourth ventricle . 155

Pellucid zone

. 248

— — hypogastric

. 227

Pelvis, ligaments of .

. 109

— — solar

. 227

— of kidney

. 240

Pneumogastric nerve

. 177

Pendulous portion of

soft

Polar nerve- cells .

. 14

palate .

. 138

Pons Varolii

. 159

Penis . . . .

. 243

Porta of liver

. 225

— bulb of . . .

. 244

Portse vena .

. 226

— corona glandis of' .

. 244'

Portio dura .

. 164

— corpus cavernosum (

)f . 243

— mollis

. 164

— — spongiosum of .

. 244

Porus opticus

. 146

— crura of

. 243

Pouches, guttural

. 137

— glansof

. 244

Poupart's hgament

. 219

— ligaments of .

. 245

Prteputium clitoridis

. 252

— meatus urinarius of

. 243

— penis

. 244

— muscles of

. 244

Premolar teeth .

. 132

— septum pectiniforme

of . 243

Prerenal capsule .

. 236

Penniform muscle

. 12

Preservation of subject

. 4

INDEX.

307

PAGE

PAGE

Primitive dental groove

. 130

Ramus anastomoticus .

. 168

Process

. 10

— of inferior maxilla .

. 41

auditory, external .

. 32

Raphe corporis callosi .

. 156

— basilar, of occiput .

. 25

— scroti

. 244

— coracoid, of inferior

Receptaculum chyli

227

maxilla ...

40

Recti muscles of eye .

.' 144

— — scapula .

61

Recto-vesical folds

. 241

■^— crista galli

29

Rectum

. 235

— haraular, of ulna

77

Rectus abdominis

. 220

— liyoid

32

Red muscular fibre

. 12

— mastoid, petrous tempora

32

Renal capsule

. 239

— — squamous temporal

31

Reproductive organs, see

— oblique .

43

Generative organs.

— odontoid, of axis

49

Restiform bodies .

. 160

— olecranon, of ulna .

71

Rete mirabile

. 20

— palatine, of palatine bone

37

— mucosum

. 17

' — — of anterior maxilla .

34

Reticulated layer of skin

. 17

— — of superior maxilla .

36

Retina

. 148

— styloid occiput

25

Retractor ani

. 235

— — petrous temporal

32

— costal

. 220

— spinous, anterior inferior.

— penis

. 244

of ilium

82

Ribs

. 56

— — superior posterior of

— false ...

. 59

ilium ....

83

— first

. 59

— — inferior .

43

— floating .

. 58

— — superior .

42

— last

. 60

— transverse

43

— true

- 58

— vermiform

159

Ridge

. 10

'• — zygomatic . . .

31

— alveolar .

- 42

Processes, ciliary .

147

— mastoid .

. 25

Prostate gland

243

Rima glottidis

. 176

Prostatic portion of the

Ring, abdominal, external

. 219

urethra

242

— — internal .

. 219

Pterygoid ligament

'^38

— vertebral

. 43

Pubio-femoral ligament 111,

261

Root of the lung .

. 191

Pulp of tooth

129

Rotatorial joint .

. 101

Puncta lachrymalia . 121

143

Round ligament of bladder

222

— vasculosa

156

— — liver

. 223

Pupil of the eye .

148

— — ovary

. 224

Pupillary opening

148

— — uterus

. 224

Pylorus ....

229

Ruyschiana tunica

. 147

Pyramids of medulla oblon-

gata ....

160

Saccular stage of tootl

I

— kidney ....

240

development

130

Quadrigemina, corpus .

158

Saccules
Sacs, air

163
191

Racemose glands .

19

Saggital suture .

102

Hadialis accessorius

210

Salivary glands .

118

Radio-carpal joint

107

. Sarcolemma

20

— -ulnar arch

69

Sarcous elements .

12

— — articulation

106

Satellites .

12

308

INDEX.

PAGE

PAGE

Scabrous pits of occiput . 26

Solar plexus

227

Scalae of cochlea .

. 163

Sole, horny ....

276

Schiudyjesis

. 99

— sensitive

279

Schneiderian membran

e . 141

Space, femoral

260

Scissatus, lobus .

. 225

Spermatic cord .

247

Sclerotic

. 146

Sphenoideal sinus

142

Scrotum

. 245

Spheroidal epithelium .

16

Scutiform cartilages

122

Sphincter ani

235

Sebaceous glands .

! 18

— vesical ....

242

Sella turcica

. 30

Spigelii, lobus

225

Semicircular canals

. 163

Spinal cord ....

180

Semilunar cartilages of

stifle 111

— column ....

42

— ganglion

. 227

Spines, see Processes, spinous.

Seminal clucts

. 241

Splanchnic nerves

195

— vesicles .

. 241

Spleen ....

235

Seminiferous tubes

. 241

— arteries ....

236

Sensitive frog of foot

. 280

— capsule ....

236

— sole —

. 279

— curvatures

236

— structures —

. 278

— hilum ....

236

Sensory roots of nerves

. 181

■ — internal structure .

236

— nerve fibres

. 13

— pulp ....

236

Septum lucidum .

. 156

Splint bones

79

— nasi

. 139

— — hind

98

— pectiniforme .

. 243

Spongiosum, corpus

244

— scroti

. 245

Spongy urethra .

243

Serous membrane

. 15

Squamous epithelium, see

Sheaths of tendons

. 15

Tesselated.

Sheath, medullary

. 14

— suture ....

99

Short bones

. 9

Stages of tooth development

130

Shoulder-joint

. 105

Stapes ....

164

Simple glands

. 18

Stenson's duct

141

Sinus

. 10

Steruo-costal cartilages

58

— of auricle

. 197

Stifle-joint ....

111

— of dura mater

. 153

Stomach ....

229

— olfactory

. 150

Straight patellar ligaments .

112

— Valsalvae, aortic

. 199

Stratified epithelium .

16

— — pulmonary

. 19?)

Strire

12

Sinuses of head .

. 142

Striated muscular fibre

11

— venous .

. 22

Subarachnoid fluid

155

Skeleton, artificial

. 7

— space (of cord)

180

— natural

. 7

— — (of brain)

155

Skin, dermis

. 17

Subcarpal ligament

210

— epidermis

. 17

Subcutaneous areolar tissue .

17

— glands of

. 17

Subject, choice of a .

3

— papillated layer of

. 17

Substantia perforata .

160

— rete mucosum

. 17

Sudoriparous glands

18

— incisors through th

3 . 4

Suet

239

Skull, bones of .

. 24

Sulci

155

Slit of the external ear

. 123

Superficial abdominal faschia 216

Small intestines .

. 233

Superior maxillary sinus

142

Smegma praeputii.

. 244

Supports for parts of subject

6

INDEX.

PAGE

Supra-renal bodies, see

Pre-

Tentorium, ossific

renal bodies.

Teres ligament

Suspensory ligament, bladder 223

Testes cerebri

— — liver

. 223

— (testicles)

— — penis

. 216

— coni vasculosi .

Suture

. 99

— coverings of .

Sutures of skull .

. 102

— descent of

Sylvius, fissure of

. 161

— epididymis

— aqueduct of .

. 158

— globus anterior

Sympathetic gangliated cord 196

— • — posterior .

— ■ nervous system

. 13

— gubernaculum

Symphysis maxillse inferioris 141

— lobuli

— ischii

. 84

— • mediastinum .

— pubis

. 85

— tunica albuginea .

Synarthrosis

. 99

— — vaginalis propria

Synovial fringes .

. 15

— — — reflexa

— membranes

. 15

— — vasculosa.

— joints

. 100

— vas deferens .
Thalami optici

Taenia semicircularis

. 157

Thebesius, foramina of .

Tail .

. 272

— valve of .

Tapetum lucidum

. 149

Thecal.

Tarsal cartilages .

. 120

Thorax

Tarsus

. 92

Thymus gland

Teeth .

. 128

Thyroid body

— canine .

. 129

— cartilage

— cavities of reserve of . 130

Tissue, yellow elastic .

— cementum

. 129

— white fibrous .

— compound

. 129

Tongue

— crown of

. 128

— bone of .

— crusta petrosa of

. 129

— fr^num .

— dentine of

, 129

— mucous membrane of

— development of

. 130

— muscles of, extrinsic

— enamel of

. 129

— — intrinsic .

— incisor .

. 129

— nerves of

— infundibulum of

. 12

— papillae of

— milk

. 129

— — circumvallate .

— molar

. 131

— — filiform .

— primitive dental groove . 130

— — fungiform

— pulp, dental .

. 129

Torcular Herophili

— table of development of . 121

Trabecule of corpus caver

— temporary

. 128

nosum .

— — eruptive stage

. 130

— of spleen

— — follicular stage

. 130

Trachea . . .176

— — papillary stage

. 130

Tract, optic .

— — saccular stage

. 130

Transverse fissure of brain

— — shedding of

. 130

— — liver

— wolf's .

. 132

Tricuspid valve .

Tendons

. 12

Trochanter major .

Tensor tympani .

. 165

— minor, external

Tentorium, membranou

s . 153

— — internal .

309

310

INCEX.

PAGK

PAGE

Trochanteric fossa

. 86

Uterus, epithelium of .

. 250

Tube, Eustachian

. 138

— fundus of

. 249

Tuber ciuereum .

. 161

— ligaments of .

. 249

Tubercle of atlas .

. 47

— mucous membrane of

. 250

— lachrymal

. 36

— OS or mouth of

. 249

— of rib

. 57

Utriculus

. 163

— pectineal!

. 85

Uvea ....

. 147

— superior maxillae

. 35

Tuberculum Loweri

. 197

Vagina

. 250

Tuberosity .

. 10

Vaginal cavities .

. 249

— of ischium

. 85

— portal veins .

. 226

Tubes, Fallopian .

. 249

— tunics

. 224

— uviniferous

. 240

Vagino-rectal fold

. 251

— contorted

. 246

— vesical fold

. 251

— seminiferous .

. 246

Valsalva, sinus of

. 199

Tunica adiposa renalis .

. 239

Valve, bicuspid .

. 199

— albuginea testis

. 246

— Eustachian

. 197

— Jacobi .

. 148

— ileo-caecal

. 233

— nervosa .

. 148

— mitral .

. 199

• — "Ruyschiana

. 147

— semilunar aortic

. 199

— vaginalia scroti

. 224

— — pulmonary

. 198

— — testis

. 224

— of Thebesius .

. 197

■ — vasculosa retinae

. 148

— tricuspid

. 198

— — testis

. 246

— of veins .

. 22

Turbinated bones .

. 33

— of Vieussens .

. 158

Tushes . . .

29, 132

Varolii, pons

. 159

Tympanic cavity .

. 164

Vas deferens

. 247

— — ossicula of

. 164

Vasa afferentia

. 23

— efPerentia

. 23

Umbilical artery .

. 253

— recta

. 246

— cord

. 253

— vasorum

. 20

— region of abdomen

. 231

Vascular coronary secretin

g

— vein

. 253

substance

. 278

TJnstriated muscular fil

)re . 11

— laminae .

. 279

Urachus

. 255

Vasculosa, tunica

. 148

Ureters

. 240

Vegetative nervous system

. 13

Urethra (male)

. 242

Veins ....

. 21

— fossa navicularis

. 243

— valves of

. 21

— lacunse of

242

— axillary

. 207

— mucous membrane <

if ! 242

— azygos

. 193

— membranous .

. 242

— brachial, superficial

. 207

— prostatic

. 242

— bronchial

. 192

— spongy .

. 243

— cardiac .

. 200

Urinary bladder .

. 241

— cava anterior .

. 193

Uriniferous tubes

. 240

— — posterior . . 193, 238

Uterus

. 249

— cephalic

. 207

— artery of

. 238

— corouary

. 200

— body of .

. 249

— circumflex, of ilium

. 265

— cavity or

. 249

— diaphragmatic, see Phrenic.

cervix of

. 249

— femoral .

. 265

— cornua of

. 249

— of foot .

. 215

INDEX.

311

Veins, hepatic

— humeral

— iliac, common

— — external

— — internal

— intercostal

— interlobular
— • intralobular

— jugular .

— lingual .

— lumbar .

— mesenteric, anterior

— posterior

— metacarpal

— metatarsal

— phrenic .

— plat

— portal

— pulmonary

— renal

— saphenous

— spermatic

— spiral

— splenic .

— sublobular

— tibial

— vaginal, portal

— varicose, of face
Velum pendulum palati
Vena cava, anterior

— — posterior

— portas .
Venffi Galeni

— vorticosEB
Venous sinuses
Venter scapulae .

— ilii

Ventricles of larynx
Ventricle, fifth

— fourth

— lateral .

— left (heart) .

— right —

— third
Vertebrse, cervical

— coccygeal

— dorsal

— false

193

PAGE

226
207
265
265
265
187
226
226
172
136
239
228
228
215
271
239
207
226
198
239
60
239
207
236
226
271
226
118
138
193
,238
226
153
147
22
63
84
176
156
158
156
199
198
158
46
56
50
44

PAGB

. 52

. 54
. 43
. 42
. 42
. 103
. 103
n.
. 242

Vertebra?, lumbar

— sacral

— true

— typical .
Vertebral segments

— articulations .

— ligaments

— column, see Spinal colum
Vena montanum .
Vesica urinaria, see Bladder.
Vesi(;les, germinal . . 248

— Graafian . . . .248

— seminal .... 247
Vestibule . . . .162
Vidian nerve . . . 127
Vieussens, valve of . . 158
Villi of bowels . . .232
Villous layer of stomach . 230
Vitreous humour . . 149

— tables . . . .150
Vocal cords .... 175
Voluntary muscle . . 125
Vomer . . . .39
Vulva 251

— commissures of . . 251

— erectile tissue of . . 251

— fossa navicularis of . 251

— labia of . . . .251

— mucous membrane of . 251

Wall of hoof . . . 274

"Water bag" . . • 255

Wharton's duct . . .132

White muscular fibre . . 11

— nerve fibres . . .14

— substance of Schivann . 14
Wilson's muscle . . . 242
Winslow's foramen . 223, 230
Womb, see Uterus.

Wrist, see Carpus.

Xiphoid cartilage . . 60'

Zima, zonula of . . . 144

Zona pellucida . . . 248

Zonula cilaris {v Zinnii) . 149

Zygoma . . . .31

Zygomatic ridge . . .35

— bone . . . .38

ERRATA.

Page 20. — Line 42, /or circular read circulus.

34. — „ ^,for incisorium read incisorum.

41. — „ 12, for carinus read caninu?.

59. — Lines 41 and 44, /or scalenius read scalenus.

76. — Line 33,/or unciform read unciforme.

80. — „ 38, /or sessamoid read sesamoid.
108. — „ 21, /or suffraginis, read coronse.
129. — „ 12,/or infundibuli read infundibula.
178. — „ 2^, for scalenius read scalenus.

PEIKTED EY J. E. ADLAltD, BAlil llOLUiltW CLOSJt.

iJi

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