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U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ANIMAL INDUSTRY.
A. D. MELVIN, CHIEF OF BUREAU.
* * * * *
SPECIAL REPORT
ON
DISEASES OF THE HORSE.
BY
Drs. PEARSON, MICHENER, LAW, HARBAUGH, TRUMBOWER, LIAUTARD, HOLCOMBE,
HUIDEKOPER, MOHLER, EICHHORN, HALL, AND ADAMS.
* * * * *
REVISED EDITION, 1916.
[Illustration]
WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1916.
DEPARTMENT OF AGRICULTURE,
_Washington, March 30, 1916._
* * * * *
Transcriber's note: The italic markup for single italized letters are
deleted for easier reading. Minor typos have been corrected and footnotes
moved to the end of the sections.
* * * * *
This edition of the Special Report on Diseases of the Horse has been
prepared in compliance with House Concurrent Resolution No. 13, passed
February 3, 1916, as follows:
_Resolved by the House of Representatives (the Senate
concurring)_, That there be printed and bound in cloth one
hundred thousand copies of the Special Report on the Diseases
of the Horse, the same to be first revised and brought to date,
under the supervision of the Secretary of Agriculture; seventy
thousand copies for the use of the House of Representatives and
thirty thousand for use of the Senate.
Since the original edition issued by the Department in 1890 several
editions have been printed by order of Congress. The work was reprinted
in 1896, and revised and reprinted in 1903, 1908, and 1911. In
accordance with the foregoing resolution it again has been revised so as
to embody the latest practical development of knowledge of the subject.
D. F. HOUSTON,
_Secretary._
CONTENTS.
Page.
The examination of a sick horse. By Leonard Pearson 7
Fundamental principles of disease. By Rush Shippen Huidekoper 27
Methods of administering medicines. By Ch. B. Michener 44
Diseases of the digestive organs. By Ch. B. Michener 49
Diseases of the respiratory organs. By W. H. Harbaugh 95
Diseases of the urinary organs. By James Law 134
Diseases of the generative organs. By James Law 164
Diseases of the nervous system. By M. R. Trumbower 210
Diseases of the heart, blood vessels, and lymphatics.
By M. R. Trumbower 247
Diseases of the eye. By James Law 274
Lameness. By A. Liautard 298
Diseases of the fetlock, ankle, and foot. By A. A. Holcombe 395
Diseases of the skin. By James Law 458
Wounds and their treatment. By Ch. B. Michener 484
Infectious diseases. By Rush Shippen Huidekoper 507
Shoeing. By John W. Adams 583
Index 607
ILLUSTRATIONS.
PLATES.
Page.
PLATE
I. Inflammation 32
II. Inflammation 32
III. Digestive apparatus 48
IV. Age of horses as indicated by teeth 58
V. Intestinal worms 92
VI. Bots 92
VII. Position of the left lung 112
VIII. Longitudinal section through kidney 136
IX. Microscopic anatomy of kidney 136
X. Microscopic anatomy of kidney 136
XI. Calculi and instrument for removal 152
XII. Normal presentation 192
XIII. Some factors in difficult labor 192
XIV. Instruments used in difficult labor 192
XV. Abnormal presentations 200
XVI. Abnormal presentations 200
XVII. Abnormal presentations 200
XVIII. Abnormal presentations 200
XIX. The nervous system 216
XX. Interior of chest, showing position of heart and diaphragm 248
XXI. Circulatory apparatus 248
XXII. Diagrammatic vertical section through horse's eye 277
XXIII. Skeleton of horse 304
XXIV. Superficial layer of muscles 304
XXV. Splint 312
XXVI. Ringbone 312
XXVII. Various types of spavin 312
XXVIII. Bone spavin 312
XXIX. Bone spavin 312
XXX. Dislocation of shoulder and elbow, Bourgelat's apparatus 360
XXXI. The sling in use 360
XXXII. Anatomy of foot 400
XXXIII. Anatomy of foot 400
XXXIV. Anatomy and diseases of foot 400
XXXV. Sound and contracted feet 400
XXXVI. Quarter crack and remedies 432
XXXVII. Foundered feet 432
XXXVIII. The skin and its diseases 458
XXXIX. Mites that infest the horse 480
XL. Glanders 544
XLI. Glanders 544
XLII. Glanders 544
TEXT FIGURES.
Page.
FIG.
1. Ground surface of a right fore hoof of the
"regular" form 590
2. Pair of fore feet of regular form in regular standing position 591
3. Pair of fore feet of base-wide form in toe-wide standing
position 591
4. Pair of fore feet of base-narrow form in toe-narrow standing
position 592
5. Side view of an acute-angled fore foot, of a regular fore
foot, and of a stumpy fore foot 592
6. Side view of foot with the foot-axis broken backward as a
result of too long a toe 595
7. Left fore hoof of a regular form, shod with a plain fullered
shoe 599
8. Side view of hoof and fullered shoe 599
9. An acute-angled left fore hoof shod with a bar shoe 601
10. A fairly formed right fore ice shoe for a roadster 601
11. Left fore hoof of regular form shod with a rubber pad and
"three-quarter" shoe 602
12. A narrow right fore hoof of the base-wide standing position
shod with a plain "dropped crease" shoe 602
13. Hoof surface of a right hind shoe to prevent interfering 603
14. Ground surface of shoe shown in fig. 13 603
15. Side view of a fore hoof shod so as to quicken the "breaking
over" in a "forger" 604
16. Side view of a short-toed hind hoof of a forger 604
17. A toe-weight shoe to increase the length of stride of fore
feet 605
18. Most common form of punched heel-weight shoe to induce high
action in fore feet 605
SPECIAL REPORT ON DISEASES OF THE HORSE.
THE EXAMINATION OF A SICK HORSE.
By Leonard Pearson, B. S., V. M. D.
In the examination of a sick horse it is important to have a method or
system. If a definite plan of examination is followed one may feel
reasonably sure, when the examination is finished, that no important
point has been overlooked and that the examiner is in a position to
arrive at an opinion that is as accurate as is possible for him. Of
course, an experienced eye can see, and a trained hand can feel, slight
alterations or variations from the normal that are not perceptible to
the unskilled observer. A thorough knowledge of the conditions that
exist in health is of the highest importance, because it is only by a
knowledge of what is right that one can surely detect a wrong condition.
A knowledge of anatomy, or of the structure of the body, and of
physiology, or the functions and activities of the body, lie at the
bottom of accuracy of diagnosis. It is important to remember that
animals of different races or families deport themselves differently
under the influence of the same disease or pathological process. The
sensitive and highly organized thoroughbred resists cerebral depression
more than does the lymphatic draft horse. Hence a degree of fever that
does not produce marked dullness in a thoroughbred may cause the most
abject dejection in a coarsely bred, heavy draft horse. This and similar
facts are of vast importance in the diagnosis of disease and in the
recognition of its significance.
The order of examination, as given hereafter, is one that has proved to
be comparatively easy of application and sufficiently thorough for the
purpose of the readers of this work, and is recommended by several
writers.
HISTORY.
It is important to know, first of all, something of the origin and
development of the disease; therefore the cause should be looked for.
The cause of a disease is important, not only in connection with
diagnosis, but also in connection with treatment. The character of feed
that the horse has had, the use to which he has been put, and the kind
of care he has received should all be closely inquired into. It may be
found by this investigation that the horse has been fed on damaged feed,
such as brewers' grains or moldy silage, and this may be sufficient to
explain the profound depression and weakness that are characteristic of
forage poisoning. If it is learned that the horse has been kept in the
stable without exercise for several days and upon full rations, and that
he became suddenly lame in his back and hind legs, and finally fell to
the ground from what appeared to be partial paralysis, this knowledge,
taken in connection with a few evident symptoms, will be enough to
establish a diagnosis of azoturia (excess of nitrogen in the urine). If
it is learned that the horse has been recently shipped in the cars or
has been through a dealer's stable, we have knowledge of significance in
connection with the causation of a possible febrile disease, which is,
under these conditions, likely to prove to be influenza, or edematous
pneumonia.
It is also important to know whether the particular horse under
examination is the only one in the stable, or on the premises, that is
similarly afflicted. If it is found that several horses are afflicted
much in the same way, we have evidence of a common cause of disease
which may prove to be of an infectious nature.
Another item of importance in connection with the history of the case
relates to the treatment that the horse may have had before he is
examined. It sometimes happens that medicine given in excessive
quantities produces symptoms resembling those of disease, so it is
important that the examiner be fully informed as to the medication that
has been employed.
ATTITUDE AND GENERAL CONDITION.
Before beginning the special examination, attention should be paid to
the attitude and general condition of the animal. Sometimes horses
assume positions that are characteristic of a certain disease. For
example, in tetanus (lockjaw) the muscles of the face, neck, and
shoulders are stiff and rigid, as well as the muscles of the jaw. This
condition produces a peculiar attitude, that once seen is subsequently
recognized as rather characteristic of the disease. A horse with tetanus
stands with his muscles tense and his legs in a somewhat bracing
position, as though he were gathered to repel a shock. The neck is stiff
and hard, the head is slightly extended upon it, and the face is drawn,
and the nostrils are dilated. The tail is usually held up a little, and
when pressed down against the thighs it springs back to its previous
position. In inflammation of the throat, as in pharyngolaryngitis, the
head is extended upon the neck and the angle between the jaw and the
lower border of the neck is opened as far as possible to relieve the
pressure that otherwise would fall upon the throat. In dumminess, or
immobility, the hanging position of the head and the stupid expression
are rather characteristic. In pleurisy, peritonitis, and some other
painful diseases of the internal organs, the rigid position of the body
denotes an effort of the animal to avoid pressure upon and to protect
the inflamed sensitive region.
The horse may be down in the stall and unable to rise. This condition
may result from paraplegia (paralysis), from azoturia, from forage
poisoning, from tetanus, or from painful conditions of the bones or
feet, such as osteoporosis or founder. Lying down at unusual times or in
unusual positions may indicate disease. The first symptom of colic may
be a desire on the part of the horse to lie down at an unusual or
inappropriate time or place. Sometimes disinclination to lie down is an
indication of disease. When there is difficulty in breathing, the horse
knows that he can manage himself better upon his feet than upon his
breast or his side. It happens, therefore, that in nearly all serious
diseases of the respiratory tract he stands persistently, day and night,
until recovery has commenced and breathing is easier, or until the
animal falls from sheer exhaustion. If there is stiffness and soreness
of the muscles, as in rheumatism, inflammation of the muscles from
overwork, or of the bones in osteoporosis, or of the feet in founder, or
if the muscles are stiff and beyond control of the animal, as in
tetanus, a standing position is maintained, because the horse seems to
realize that when he lies down he will be unable to rise.
Abnormal attitudes are assumed in painful diseases of the digestive
organs (colic). A horse with colic may sit upon his haunches, like a
dog, or may stand upon his hind feet and rest upon his knees in front,
or he may endeavor to balance himself upon his back, with all four feet
in the air. These positions are assumed because they give relief from
pain by lessening pressure or tension upon the sensitive structures.
Under the general condition of the animal it is necessary to observe the
condition or state of nutrition, the conformation, so far as it may
indicate the constitution, and the temperament. By observing the
condition of nutrition one may be able to determine to a certain extent
the effect that the disease has already had upon the animal and to
estimate the amount of strength that remains and that will be available
for the repair of the diseased tissues. A good condition of nutrition is
shown by the rotundity of the body, the pliability and softness of the
skin, and the tone of the hair. If the subcutaneous fat has disappeared
and the muscles are wasted, allowing the bony prominences to stand out;
if the skin is tight and inelastic and the coat dry and harsh, we have
evidence of a low state of nutrition. This may have resulted from a
severe and long-continued disease or from lack of proper feed and care.
When an animal is emaciated--that is, becomes thin--there is first a
loss of fat and later the muscles shrink. By observing the amount of
shrinkage in the muscles one has some indication as to the duration of
the unfavorable conditions under which the animal has lived.
By constitution we understand the innate ability of the animal to
withstand disease or unfavorable conditions of life. The constitution
depends largely upon the conformation. The type of construction that
usually accompanies the best constitution is deep, broad chest, allowing
plenty of room for the lungs and heart, indicating that these vital
organs are well developed; capacious abdomen, allowing sufficient space
for well-developed organs of digestion; the loins should be short--that
is, the space should be short between the last rib and the point of the
hip; the head and neck should be well molded, without superfluous or
useless tissue; this gives a clear-cut throat. The ears, eyes, and face
should have an expression of alertness and good breeding. The muscular
development should be good; the shoulders, forearms, croup, and thighs
must have the appearance of strength. The withers are sharp, which means
that they are not loaded with useless, superfluous tissue; the legs are
straight and their axes are parallel; the knees and hocks are low, which
means that the forearms and thighs are long and the cannons relatively
short. The cannons are broad from in front to behind and relatively thin
from side to side. This means that the bony and tendinous structures of
the legs are well developed and well placed. The hoofs are compact,
tense, firm structures, and their soles are concave and frogs large.
Such a horse is likely to have a good constitution and to be able to
resist hard work, fatigue, and disease to a maximum degree. On the other
hand, a poor constitution is indicated by a shallow, narrow chest, small
bones, long loins, coarse neck and head, with thick throat, small, bony,
and muscular development, short thighs and forearms, small joints, long,
round cannons, and hoofs of open texture with flat soles.
The temperament is indicated by the manner in which the horse responds
to external stimuli. When the horse is spoken to, or when he sees or
feels anything that stimulates or gives alarm, if he responds actively,
quickly, and intelligently, he is said to be of lively, or nervous,
temperament. On the other hand, if he responds in a slow, sluggish
manner, he is said to have a sluggish, or lymphatic, temperament. The
temperament is indicated by the gait, by the expression of the face, and
by the carriage of the head and ears. The nature of the temperament
should be taken into consideration in an endeavor to ascertain the
severity of a given case of illness, because the general expression of
an animal in disease as well as in health depends to a large extent on
the temperament.
THE SKIN AND THE VISIBLE MUCOUS MEMBRANES.
The condition of the skin is a fair index to the condition of the
animal. The effect of disease and emaciation upon the pliability of the
skin have been referred to above. There is no part of the body that
loses its elasticity and tone as a result of disease sooner than the
skin. The practical herdsman or flockmaster can gain a great deal of
information as to the condition, of an animal merely by grasping the
coat and looking at and feeling the skin. Similarly, the condition of
the animal is shown to a certain extent by the appearance of the mucous
membranes. For example, when the horse is anemic as a result of disease
or of inappropriate feed the mucous membranes become pale. This change
in the mucous membranes can be seen most readily in the lining of the
eyelids and in the lining of the nostril. For convenience of examination
the eyelids can readily be everted. Paleness means weak circulation or
poor blood. Increased redness occurs physiologically in painful
conditions, excitement, and following severe exertion. Under such
conditions the increase of circulation is transitory. In fevers there is
an increased redness in the mucous membrane, and this continues so long
as the fever lasts. In some diseases red spots or streaks form in the
mucous membrane. This usually indicates an infectious disease of
considerable severity, and occurs in blood poisoning, purpura
hemorrhagica, hemorrhagic septicemia, and in urticaria. When the liver
is deranged and does not operate, or when the red-blood corpuscles are
broken down, as in serious cases of influenza, there is a yellowish
discoloration of the mucous membrane. The mucous membranes become bluish
or blue when the blood is imperfectly oxidized and contains an excess of
carbon dioxid. This condition exists in any serious disease of the
respiratory tract, as pneumonia, and in heart failure.
The temperature of the skin varies with the temperature of the body. If
there is fever the temperature of the skin is likely to be increased.
Sometimes, however, as a result of poor circulation and irregular
distribution of the blood, the body may be warmer than normal, while the
extremities (the legs and ears) may be cold. Where the general surface
of the body becomes cold it is evident that the small blood vessels in
the skin have contracted and are keeping the blood away, as during a
chill, or that the heart is weak and is unable to pump the blood to the
surface, and that the animal is on the verge of collapse.
The skin is moist, to a certain degree, at all times in a healthy horse.
This moisture is not in the form of a perceptible sweat, but it is
enough to keep the skin pliable and to cause the hair to have a soft,
healthy feel. In some chronic diseased conditions and in fever, the skin
becomes dry. In this case the hair has a harsh feel that is quite
different from the condition observed in health, and from the fact of
its being so dry the individual hairs do not adhere to one another, they
stand apart, and the animal has what is known as "a staring coat." When,
during a fever, sweating occurs, it is usually an indication that the
crisis is passed. Sometimes sweating is an indication of pain. A horse
with tetanus or azoturia sweats profusely. Horses sweat freely when
there is a serious impediment to respiration; they sweat under
excitement, and, of course, from the well-known physiological causes of
heat and work. Local sweating, or sweating of a restricted area of the
body, denotes some kind of nerve interference.
Swellings of the skin usually come from wounds or other external causes
and have no special connection with the diagnosis of internal diseases.
There are, however, a number of conditions in which the swelling of the
skin is a symptom of a derangement of some other part of the body. For
example, there is the well-known "stocking," or swelling of the legs
about the fetlock joints, in influenza. There is the soft swelling of
the hind legs that occurs so often in draft horses when standing still
and that comes from previous inflammation (lymphangitis) or from
insufficient heart power. Dropsy, or edema of the skin, may occur
beneath the chest or abdomen from heart insufficiency or from chronic
collection of fluid in the chest or abdomen (hydrothorax, ascites, or
anemia). In anasarca or purpura hemorrhagica large soft swellings appear
on any part of the skin, but usually on the legs, side of the body, and
about the head.
Gas collects under the skin in some instances. This comes from a local
inoculation with an organism which produces a fermentation beneath the
skin and causes the liberation of gas which inflates the skin, or the
gas may be air that enters through a wound penetrating some
air-containing organ, as the lungs. The condition here described is
known as emphysema. Emphysema may follow the fracture of a rib when the
end of a bone is forced inward and caused to penetrate the lung, or it
may occur when, as a result of an ulcerating process, an organ
containing air is perforated. This accident is more common in cattle
than it is in horses. Emphysema is recognized by the fact that the
swelling that it causes is not hot or sensitive on pressure. It emits a
peculiar crackling sound when it is stroked or pressed upon.
Wounds of the skin may be of importance in the diagnosis of internal
disease. Wounds over the bony prominence, as the point of the hip, the
point of the shoulder, and the greatest convexity of the ribs, occur
when a horse is unable to stand for a long time and, through continually
lying upon his side, has shut off the circulation to the portion of the
skin that covers parts of the body that carry the greatest weight, and
in this way has caused them to mortify. Little, round, soft, doughlike
swellings occur on the skin and may be scattered freely over the surface
of the body when the horse is afflicted with urticaria. Similar
eruptions, but distributed less generally, about the size of a silver
dollar, may occur as a symptom of dourine, or colt distemper. Hard
lumps, from which radiate welt-like swellings of the lymphatics, occur
in glanders, and blisterlike eruptions occur around the mouth and
pasterns in horsepox.
THE ORGANS OF CIRCULATION.
The first item in this portion of the examination consists in taking the
pulse. The pulse may be counted and its character may be determined at
any point where a large artery occupies a situation close to the skin
and above a hard tissue, such as a bone, cartilage, or tendon. The most
convenient place for taking the pulse of the horse is at the jaw. The
external maxillary artery runs from between the jaws, around the lower
border of the jawbone, and up on the outside of the jawbone to the face.
It is located immediately in front of the heavy muscles of the cheek.
Its throb can be felt most distinctly just before it turns around the
lower border of the jawbone. The balls of the first and second or of the
second and third fingers should be pressed lightly on the skin over this
artery when its pulsations are to be studied.
The normal pulse of the healthy horse varies in frequency as follows:
Stallion 28 to 32 beats per minute.
Gelding 33 to 38 beats per minute.
Mare 34 to 40 beats per minute.
Foal 2 to 3 years old 40 to 50 beats per minute.
Foal 6 to 12 months old 45 to 60 beats per minute.
Foal 2 to 4 weeks old 70 to 90 beats per minute.
The pulse is accelerated by the digestion of rich food, by hot weather,
exercise, excitement, and alarm. It is slightly more rapid in the
evening than it is in the morning. Well-bred horses have a slightly more
rapid pulse than sluggish, cold-blooded horses. The pulse should be
regular; that is, the separate beats should follow each other after
intervals of equal length, and the beats should be of equal fullness, or
volume.
In disease, the pulse may become slower or more rapid than in health.
Slowing of the pulse may be caused by old age, great exhaustion, or
excessive cold. It may be due to depression of the central nervous
system, as in dumminess, or be the result of the administration of
drugs, such as digitalis or strophantus. A rapid pulse is almost always
found in fever, and the more severe the infection and the weaker the
heart the more rapid is the pulse. Under these conditions, the beats may
rise to 80, 90, or even 120 per minute. When the pulse is above 100 per
minute the outlook for recovery is not promising, and especially if this
symptom accompanies high temperature or occurs late in an infectious
disease. In nearly all of the diseases of the heart and in anemia the
pulse becomes rapid.
The pulse is irregular in diseases of the heart, and especially where
the valves are affected. The irregularity may consist in varying
intervals between the beats or the dropping of one or more beats at
regular or irregular intervals. The latter condition sometimes occurs in
chronic diseases of the brain. The pulse is said to be weak, or soft,
when the beats are indistinct, because little blood is forced through
the artery by each contraction of the heart. This condition occurs when
there is a constriction of the vessels leading from the heart and it
occurs in certain infectious and febrile diseases, and is an indication
of heart weakness.
In examining the heart itself it is necessary to recall that it lies in
the anterior portion of the chest slightly to the left of the median
line and that it extends from the third to the sixth rib. It extends
almost to the breastbone, and a little more than half of the distance
between the breastbone and the backbone. In contracting, it rotates
slightly on its axis, so that the point of the heart, which lies below,
is pressed against the left chest wall at a place immediately above the
point of the elbow. The heart has in it four chambers--two in the left
and two in the right side. The upper chamber of the left side (left
auricle) receives the blood as it comes from the lungs, passes it to the
lower chamber of the left side (left ventricle), and from here it is
sent with great force (for this chamber has very strong, thick walls)
through the aorta and its branches (the arteries) to all parts of the
body. The blood returns through the veins to the upper chamber of the
right side (right auricle), passes then to the lower chamber of the
right side (right ventricle), and from this chamber is forced into the
lungs to be oxidized. The openings between the chambers of each side and
into the aorta are guarded by valves.
If the horse is not too fat, one may feel the impact of the apex of the
heart against the chest wall with each contraction of the heart by
placing the hand on the left side back of the fifth rib and above the
point of the elbow. The thinner and the better bred the horse is the
more distinctly this impact is felt. If the animal is excited, or if he
has just been exercised, the impact is stronger than when the horse is
at rest. If the horse is weak, the impact is reduced in force.
The examination of the heart with the ear is an important matter in this
connection. Certain sounds are produced by each contraction of the
normal heart. It is customary to divide these into two, and to call them
the first and second sounds. These two sounds are heard during each
pulsation, and any deviation of the normal indicates some alteration in
the structure or the functions of the heart. In making this examination,
one may apply the left ear over the heavy muscles of the shoulder back
of the shoulder joint, and just above the point of the elbow, or, if the
sounds are not heard distinctly, the left fore leg may be drawn forward
by an assistant and the right ear placed against the lower portion of
the chest wall that is exposed in this manner.
The first sound of the heart occurs while the heart muscle is
contracting and while the blood is being forced from the heart and the
valves are rendered taut to prevent the return of the blood from the
lower to the upper chambers. The second sound follows quickly after the
first and occurs during rebound of blood in the arteries, causing
pressure in the aorta and tensions of the valves guarding its opening
into the left ventricle. The first sound is of a high pitch and is
longer and more distinct than the second. Under the influence of disease
these sounds may be altered in various ways. It is not profitable, in a
work such as this, to describe the details of these alterations. Those
who are interested will find this subject fully discussed in the
veterinary textbooks.
TEMPERATURE.
The temperature of the horse is determined roughly by placing the
fingers in the mouth or between the thighs or by allowing the horse to
exhale against the cheek or back of the hand. In accurate examination,
however, these means of determining temperature are not relied upon, but
recourse is had to the use of the thermometer. The thermometer used for
taking the temperature of a horse is a self-registering clinical
thermometer, similar to that used by physicians, but larger, being from
5 to 6 inches long. The temperature of the animal is measured in the
rectum.
The normal temperature of the horse varies somewhat under different
conditions. It is higher in the young animal than in the old, and is
higher in hot weather than in cold. The weather and exercise decidedly
influence the temperature physiologically. The normal temperature varies
from 99.5 deg. to 101 deg. F. If the temperature rises to 102.5 deg. the horse is
said to have a low fever; if the temperature reaches 104 deg. the fever is
moderate; if it reaches 106 deg. it is high, and above this point it is
regarded as very high. In some diseases, such as tetanus or sunstroke,
the temperature goes as high as 108 deg. or 110 deg.. In the ordinary infectious
diseases it does not often exceed 106 deg.. A temperature of 107.5 deg. and
above is very dangerous and must be reduced promptly if the horse is to
be saved.
THE ORGANS OF RESPIRATION.
In examining this system of organs and their functions it is customary
to begin by noting the frequency of the respiratory movements. This
point can be determined by observing the motions of the nostrils or of
the flanks; on a cold day one can see the condensation of the moisture
of the warm air as it comes from the lungs. The normal rate of
respiration for a healthy horse at rest is from 8 to 16 per minute. The
rate is faster in young animals than in old, and is increased by work,
hot weather, overfilling of the stomach, pregnancy, lying upon the side,
etc. Acceleration of the respiratory rate where no physiological cause
operates is due to a variety of conditions. Among these is fever;
restricted area of active lung tissue, from filling of portions of the
lungs with inflammatory exudate, as in pneumonia; compression of the
lungs or loss of elasticity; pain in the muscles controlling the
respiratory movements; excess of carbon dioxid in the blood; and
constriction of the air passages leading to the lungs.
Difficult or labored respiration is known as dyspnea. It occurs when it
is difficult, for any reason, for the animal to obtain the amount of
oxygen that it requires. This may be due to filling of the lungs, as in
pneumonia; to painful movements of the chest, as in rheumatism or
pleurisy; to tumors of the nose and paralysis of the throat, swellings
of the throat, foreign bodies, or weakness of the respiratory passages,
fluid in the chest cavity, adhesions between the lungs and chest walls,
loss of elasticity of the lungs, etc. Where the difficulty is great the
accessory muscles of respiration are brought into play. In great dyspnea
the horse stands with his front feet apart, with his neck straight out,
and his head extended upon his neck. The nostrils are widely dilated,
the face has an anxious expression, the eyeballs protrude, the
up-and-down motion of the larynx is aggravated, the amplitude of the
movement of the chest walls increased, and the flanks heave.
The expired air is of about the temperature of the body. It contains
considerable moisture, and it should come with equal force from each
nostril and should not have an unpleasant odor. If the stream of air
from one nostril is stronger than from the other, there is an indication
of an obstruction in a nasal chamber. If the air possesses a bad odor,
it is usually an indication of putrefaction of a tissue or secretion in
some part of the respiratory tract. A bad odor is found where there is
necrosis of the bone in the nasal passages or in chronic catarrh. An
ulcerating tumor of the nose or throat may cause the breath to have an
offensive odor. The most offensive breath occurs where there is
necrosis, or gangrene, of the lungs.
In some diseases there is a discharge from the nose. In order to
determine the significance of the discharge it should be examined
closely. One should ascertain whether it comes from one or both
nostrils. If but from one nostril, it probably originates in the head.
The color should be noted. A thin, watery discharge may be composed of
serum, and it occurs in the earlier stages of coryza, or nasal catarrh.
An opalescent, slightly tinted discharge is composed of mucus and
indicates a little more severe irritation. If the discharge is sticky
and puslike, a deeper difficulty or more advanced irritation is
indicated. If the discharge contains flakes and clumps of more or less
dried, agglutinated particles, it is probable that it originates within
a cavity of the head, as the sinuses or guttural pouches. The discharge
of glanders is of a peculiar sticky nature and adheres tenaciously to
the wings of the nostrils. The discharge of pneumonia is of a somewhat
red or reddish brown color and, on this account has been described as a
prune-juice discharge. The discharge may contain blood. If the blood
appears as clots or as streaks in the discharge, it probably originates
at some point in the upper part of the respiratory tract. If the blood
is in the form of a fine froth, it comes from the lungs.
In examining the interior of the nasal passage one should remember that
the normal color of the mucous membrane is a rosy pink and that its
surface is smooth. If ulcers, nodules, swellings, or tumors are found,
these indicate disease. The ulcer that is characteristic of glanders is
described fully in connection with the discussion of that disease.
Between the lower jaws there are several clusters of lymphatic glands.
These glands are so small and so soft that it is difficult to find them
by feeling through the skin, but when a suppurative disease exists in
the upper part of the respiratory tract these glands become swollen and
easy to feel. They may become soft and break down and discharge as
abscesses; this is seen constantly in strangles. On the other hand, they
may become indurated and hard from the proliferation of connective
tissue and attach themselves to the jawbone, to the tongue, or to the
skin. This is seen in chronic glanders. If the glands are swollen and
tender to pressure, it indicates that the disease causing the
enlargement is acute; if they are hard and insensitive, the disease
causing the enlargement is chronic.
The manner in which the horse coughs is of importance in diagnosis. The
cough is a forced expiration, following immediately upon a forcible
separation of the vocal cords. The purpose of the cough is to remove
some irritant substance from the respiratory passages, and it occurs
when irritant gases, such as smoke, ammonia, sulphur vapor, or dust,
have been inhaled. It occurs from inhalation of cold air if the
respiratory passages are sensitive from disease. In laryngitis,
bronchitis, and pneumonia, cough is very easily excited and occurs
merely from accumulation of mucus and inflammatory product upon the
irritated respiratory mucous membrane. If one wishes to determine the
character of the cough, it can easily be excited by pressing upon the
larynx with the thumb and finger. The larynx should be pressed from side
to side and the pressure removed the moment the horse commences to
cough. A painful cough occurs in pleurisy, also in laryngitis,
bronchitis, and bronchial pneumonia. Pain is shown by the effort the
animal exerts to repress the cough. The cough is not painful, as a rule,
in the chronic diseases of the respiratory tract. The force of the cough
is considerable when it is not especially painful and when the lungs are
not seriously involved. When the lungs are so diseased that they can not
be filled with a large volume of air, and in heaves, the cough is weak,
as it is also in weak, debilitated animals. If mucus or pus is coughed
out, or if the cough is accompanied by a gurgling sound, it is said to
be moist; it is dry when these characteristics are not present--that is,
when the air in passing out passes over surface not loaded with
secretion.
In the examination of the chest we resort to percussion and
auscultation. When a cask or other structure containing air is tapped
upon, or percussed, a hollow sound is given forth. If the cask contains
fluid, the sound is of a dull and of quite a different character.
Similarly, the amount of air contained in the lungs can be estimated by
tapping upon, or percussing, the walls of the chest. Percussion is
practiced with the fingers alone or with the aid of a special percussion
hammer and an object to strike upon known as a pleximeter. If the
fingers are used, the middle finger of the left hand should be pressed
firmly against the side of the horse and should be struck with the ends
of the fingers of the right hand bent at a right angle so as to form a
hammer. The percussion hammer sold by instrument makers is made of
rubber or has a rubber tip, so that when the pleximeter, which is placed
against the side, is struck the impact will not be accompanied by a
noise. After experience in this method of examination one can determine
with a considerable degree of accuracy whether the lung contains a
normal amount of air or not. If, as in pneumonia, air has been displaced
by inflammatory product occupying the air space, or if fluid collects in
the lower part of the chest, the percussion sound becomes dull. If, as
in emphysema, or in pneumothorax, there is an excess of air in the
chest cavity, the percussion sound becomes abnormally loud and clear.
Auscultation consists in the examination of the lungs with the ear
applied closely to the chest wall. As the air goes in and out of the
lungs a certain soft sound is made which can be heard distinctly,
especially upon inspiration. This sound is intensified by anything that
accelerates the rate of respiration, such as exercise. This soft,
rustling sound is known as vesicular murmur, and wherever it is heard it
signifies that the lung contains air and is functionally active. The
vesicular murmur is weakened when there is an inflammatory infiltration
of the lung tissue or when the lungs are compressed by fluid in the
chest cavity. The vesicular murmur disappears when air is excluded by
the accumulation, of inflammatory product, as in pneumonia, and when the
lungs are compressed by fluid in the chest cavity. The vesicular murmur
becomes rough and harsh in the early stages of inflammation of the
lungs, and this is often the first sign of the beginning of pneumonia.
By applying the ear over the lower part of the windpipe in front of the
breastbone a somewhat harsh, blowing sound may be heard. This is known
as the bronchial murmur and is heard in normal conditions near the lower
part of the trachea and to a limited extent in the anterior portions of
the lungs after sharp exercise. When the bronchial murmur is heard over
other portions of the lungs, it may signify that the lungs are more or
less solidified by disease and the blowing bronchial murmur is
transmitted through this solid lung to the ear from a distant part of
the chest. The bronchial murmur in an abnormal place signifies that
there exists pneumonia or that the lungs are compressed by fluid in the
chest cavity.
Additional sounds are heard in the lungs in some diseased conditions.
For example, when fluid collects in the air passages and the air is
forced through it or is caused to pass through tubes containing
secretions or pus. Such sounds are of a gurgling or bubbling nature and
are known as mucous rales. Mucous rales are spoken of as being large or
small as they are distinct or indistinct, depending upon the quantity of
fluid that is present and the size of the tube in which this sound is
produced. Mucous rales occur in pneumonia after the solidified parts
begin to break down at the end of the disease. They occur in bronchitis
and in tuberculosis, where there is an excess of secretion.
Sometimes a shrill sound is heard, like the note of a whistle, fife, or
flute. This is due to a dry constriction of the bronchial tubes and it
is heard in chronic bronchitis and in tuberculosis.
A friction sound is heard in pleurisy. This is due to the rubbing
together of roughened surfaces, and the sound produced is similar to a
dry rubbing sound that is caused by rubbing the hands together or by
rubbing upon each other two dry, rough pieces of leather.
THE EXAMINATION OF THE DIGESTIVE TRACT.
The first point in connection with the examination of the organs of
digestion is the appetite and the manner of taking food and drink. A
healthy animal has a good appetite. Loss of appetite does not point to a
special diseased condition, but comes from a variety of causes. Some of
these causes, indeed, may be looked upon as being physiological.
Excitement, strange surroundings, fatigue, and hot weather may all cause
loss of appetite. Where there is cerebral depression, fever, profound
weakness, disorder of the stomach, or mechanical difficulty in chewing
or swallowing, the appetite is diminished or destroyed. Sometimes there
is an appetite or desire to eat abnormal things, such as dirty bedding,
roots of grass, soil, etc. This desire usually comes from a chronic
disturbance of nutrition.
Thirst is diminished in a good many mild diseases unaccompanied by
distinct fever. It is seen where there is great exhaustion or depression
or profound brain disturbance. Thirst is increased after profuse
sweating, in diabetes, diarrhea, in fever, at the crises of infectious
diseases, and when the mouth is dry and hot.
Some diseases of the mouth or throat make it difficult for the horse to
chew or swallow his feed. Where difficulty in this respect is
experienced, the following named conditions should be borne in mind and
carefully looked for: Diseases of the teeth, consisting in decay,
fracture, abscess formation, or overgrowth; inflammatory conditions, or
wounds or tumors of the tongue, cheeks, or lips; paralysis of the
muscles of chewing or swallowing; foreign bodies in upper part of the
mouth between the molar teeth; inflammation of throat. Difficulty in
swallowing is sometimes shown by the symptom known as "quidding."
Quidding consists in dropping from the mouth well-chewed and insalivated
boluses of feed. A mouthful of hay, for example, after being ground and
masticated, is carried to the back part of the mouth. The horse then
finds that from tenderness of the throat, or from some other cause,
swallowing is difficult or painful, and the bolus is then dropped from
the mouth. Another quantity of hay is similarly prepared, only to be
dropped in turn. Sometimes quidding is due to a painful tooth, the bolus
being dropped from the mouth when the tooth is struck and during the
pang that follows. Quidding may be practiced so persistently that a
considerable pile of boluses of feed accumulate in the manger or on the
floor of the stall. In pharyngitis one of the symptoms is a return
through the nose of fluid that the horse attempts to swallow.
In some brain diseases, and particularly in chronic internal
hydrocephalus, the horse has a most peculiar manner of swallowing and of
taking feed. A similar condition is seen in hyperemia of the brain. In
eating the horse will sink his muzzle into the grain in the feed box
and eat for a while without raising the head. Long pauses are made while
the feed is in the mouth. Sometimes the horse will eat very rapidly for
a little while and then slowly; the jaws may be brought together so
forcibly that the teeth gnash. In eating hay the horse will stop at
times with hay protruding from the mouth and stand stupidly, as though
he has forgotten what he was about.
In examining the mouth one should first look for swellings or for
evidence of abnormal conditions upon the exterior; that is, the front
and sides of the face, the jaws, and about the muzzle. By this means
wounds, fractures, tumors, abscesses, and disease accompanied by
eruptions about the muzzle may be detected. The interior of the mouth is
examined by holding the head up and inserting the fingers through the
interdental space in such a way as to cause the mouth to open. The
mucous membrane should be clean and of a light-pink color, excepting on
the back of the tongue, where the color is a yellowish gray. As
abnormalities of this region, the chief are diffuse inflammation,
characterized by redness and catarrhal discharge; local inflammation, as
from eruptions, ulcers, or wounds; necrosis of the lower jawbone in
front of the first back tooth; and swellings. Foreign bodies are
sometimes found embedded in the mucous membrane lining of the mouth or
lodged between the teeth.
The examination of the pharynx and of the esophagus is made chiefly by
pressing upon the skin covering these organs in the region of the throat
and along the left side of the neck in the jugular gutter. Sometimes,
when a more careful examination is necessary, an esophageal tube or
probang is passed through the nose or mouth down the esophagus to the
stomach.
Vomiting is an act consisting in the expulsion of all or part of the
contents of the stomach through the mouth or nose. This act is more
difficult for the horse than for most of the other domestic animals,
because the stomach of the horse is small and does not lie on the floor
of the abdominal cavity, so that the abdominal walls in contracting do
not bring pressure to bear upon it so directly and forcibly, as is the
case in many other animals. Beside this, there is a loose fold of mucous
membrane at the point where the esophagus enters the stomach, and this
forms a sort of valve which does not interfere with the passage of food
into the stomach, but does interfere with the exit of food through the
esophageal opening. Still, vomiting is a symptom that is occasionally
seen in the horse. It occurs when the stomach is very much distended
with food or with gas. Distention stretches the mucous membrane and
eradicates the valvular fold referred to, and also makes it possible for
more pressure to be exerted upon the stomach through the contraction of
the abdominal muscles. Since the distention to permit vomiting must be
extreme, it not infrequently happens that it leads to rupture of the
stomach walls. This has caused the impression in the minds of some that
vomiting can not occur in the horse without rupture of the stomach, but
this is incorrect, since many horses vomit and afterwards become
entirely sound. After rupture of the stomach has occurred vomiting is
impossible.
In examination of the abdomen one should remember that its size depends
largely upon the breed, sex, and conformation of the animal, and also
upon the manner in which the animal has been fed and the use to which it
has been put. A pendulous abdomen may be the result of an abdominal
tumor or of an accumulation of fluid in the abdominal cavity; or, on the
other hand, it may merely be an indication of pregnancy, or of the fact
that the horse has been fed for a long time on bulky and innutritious
food. Pendulous abdomen occurring in a work horse kept on a concentrated
diet is an abnormal condition. The abdomen may increase suddenly in
volume from accumulation of gas in tympanic colic. The abdomen becomes
small and the horse is said to be "tucked up" from long-continued poor
appetite, as in diseases of the digestive tract and in fever. This
condition also occurs in tetanus from the contraction of the abdominal
walls and in diarrhea from emptiness.