DISEASES OF THE HIND LIMB
FRACTURE OF THE ILEUM, "Hipped."--Fracture of the angle and neck of the
ileum may be classed among the common fractures in horses and cattle.
Fractures involving other parts of the pelvic bones are less common. Such
fractures are due to accidental causes, as striking the point of the haunch
on the door frame when hurrying through a narrow doorway and falling on
frozen ground.
Fractures of the _external angle_ of the ileum or point of haunch are
usually followed by displacement of the fractured portion. The same is true
of fractures of the _neck of the ileum_. The result is a deformity of the
quarter.
In making an _examination_ of these parts the examiner should see that the
horse is standing squarely on its feet, and then compare the conformation
of the two quarters. Fractures of either the external angle or the neck of
the ileum cause the quarter to appear narrow and low. A close examination
may enable the examiner to differentiate between the two fractures.
Fractures of the neck of the ileum can be recognized by manipulating the
part through the walls of the rectum or vagina.
The degree of lameness may vary. In some cases there may be no lameness
when the animal walks, but a slight degree of lameness may be noticed when
it trots. For several weeks after the injury the horse may be unable to use
the limb, but it may eventually make nearly a complete recovery.
Atrophy of the muscles of the hip or quarter (Fig. 44) should not be
mistaken for fractures of the ileum. This condition involves the heavy
gluteal muscles and may occur as a complication of azoturia, or a lameness
of the hind limb that is usually due to a spavin.
It is very seldom necessary to give fractures of the ileum any special
care. If the animal is very lame, it should be given a narrow stall, and
placed in a sling until it can support its weight on the limb. The same
treatment is indicated in cattle. It is not advisable to breed a mare that
has had the ileum fractured. The bony enlargement that results from the
union of the broken ends of the bone may interfere with the passage of the
foetus through the pelvic cavity and cause difficult parturition.
[Illustration: FIG. 44.--Atrophy of the muscles of the quarter.]
LUXATION OF THE PATELLA, "Stifle Out."--This is a common accident in horses
and mules. Young, immature animals are more prone to displacement of the
patella than when mature. The displacement is usually upward or outward.
Outward displacement is comparatively rare.
_The causes_ of "stifle out" may be described as follows: The patella or
knee-cap rests on a pulley-like articular surface belonging to the inferior
extremity of the thigh-bone. The external lip of this articular surface is
smaller than the internal lip. The patella is held in place from above by
the heavy muscles of the anterior region of the thigh, and from below, by
straight ligaments that attach it to the leg-bone. If the retaining
structures mentioned become relaxed, the patella may, when the limb is
extended, become so displaced as to rest on the superior portion of the
external lip. Laxness of the muscles and ligaments in young animals is a
predisposing factor. Hard work that tires the muscles and causes them to
become relaxed, strains, unusual movements, as kicking in the stable and
slipping, may cause this accident. Congenital displacement results from
imperfect development of the external lip of the trochlea. Such a deformity
subjects the animal to frequent luxations.
_The symptoms may vary_. The displacement may be first noticed when the
horse is backed out of the stall or turned quickly. A slight "hitch" in the
movement of the limb is noted, that is followed by more noticeable flexion
of the hock than normal. In case the luxation is more permanent, the horse
stands quietly with the affected leg held stiffly and extended backward.
When made to move forward, it hops on the well leg and carries the affected
one, or drags it on the toe. If both limbs are affected, the animal is
unable to move. The inability to move the limb is due to the patella
resting on the external lip of the pulley surface, and a locking of the
stifle- and hock-joint.
This accident is annoying, and in case the horse is subject to it should be
considered an unsoundness.
The following _treatment_ may be recommended: The luxation may be reduced
in the large majority of cases by backing or turning the animal. If this
does not reduce the displacement, a collar should be placed on the animal,
and a hobble strap fastened to the pastern of the involved limb. One end of
a long rope is tied to the collar, passed backward between the front limbs,
through a ring in the hobble and back over the outside of the shoulder and
under the collar. While an attendant pulls the limb a little forward with
the rope, the operator takes hold of the foot and attempts to flex the
limb, at the same time pushing inward on the patella. After reducing the
luxation it is advisable to tie the rope to the collar, so that the limb is
carried forward. This prevents the animal from throwing weight on the foot.
It may be advisable to tie the animal so that it can not lie down, if the
foot is to be left hobbled for a few days. A fly blister should be applied
to the front and outside of the stifle and the application repeated in two
or three weeks.
STRING-HALT.--This term is applied to a peculiar involuntary movement of
one or both hind limbs that is characterized by a sudden, purposeless
flexion of the hock-joint (Fig. 45). Horses that are slightly affected may
show this movement of the hind limbs when first exercised. Other horses may
be "string-halted" when backed, turned, walked, or trotted, and fail to
drive out of it. The cause of true "string-halt" is not known.
_The treatment recommended is surgical._ This consists in cutting the
tendon of the peroneus muscle. The seat of the operation is a little below
the hock and on the external face of the cannon.
[Illustration: FIG. 45.--String-halt.]
SPAVIN.--A spavin is a chronic inflammation of the articular faces of the
hock bones, ligaments and synovial membranes. The inflammation may result
in the formation of a bony enlargement on the inner surface of the region,
and a union between the small bones forming the lower portion of the hock,
and the upper extremities of cannon and lower hock bones (Figs. 46 and 47).
[Illustration: FIG. 46.--A large bone spavin.]
The _predisposing causes_ are of the greatest importance. A spavin is one
of the unsoundnesses of horses that may be transmitted to the offspring.
Young colts that have heavy bodies and are fed a fattening ration are
predisposed to it. Crooked hind limbs, small hocks and quarters that are
heavily muscled are predisposing factors. The _external causes_ are strains
caused by slipping, turning quickly, rearing, pulling heavy loads and
kicks. Horses three or four years of age if given work that favors hock
strain, such as excavating cellars, may develop a spavin.
[Illustration: FIG. 47.--Normal cannon bone and cannon bone showing bony
enlargement and lower hock bones united to superior extremity; this occurs
in bone spavin.]
_The symptoms_ or lameness are more characteristic than in most diseases of
the limb. At the very beginning of the inflammation, and sometimes for
several months afterward, the lameness is intermittent and disappears with
exercise. After a time it is permanent. It is characterized by a stiffness
of the hock. The extension of the hock is incomplete, the step is short and
quick, the animal "goes on its toe" and the wall or shoe at the toe shows
considerable wear. Because of the stiffness in the hock the animal raises
the quarter when the limb is carried forward. Turning toward the well side
may increase the lameness. The _spavin test_ may be of value in diagnosing
lameness. This consists in picking up the foot and holding the hock in a
flexed position for a few minutes. The foot is then dropped to the ground
and the animal moved off at a brisk trot. If the lameness is more marked,
it indicates that the seat is in the region of the hock. This test is of
greatest value in young animals. The bony enlargement can usually be seen
best if the examiner stands in front and to one side of the animal. The
hock should be observed from directly behind as well. The hocks of both
limbs should be compared, and the general conformations of the other joints
as well. This may prevent the examiner from mistaking rough hocks for
spavin enlargements or "a pair" of spavins for rough hocks. A bony
enlargement does not always accompany the lameness, and a spavin may be
present without the horse going noticeably lame.
[Illustration: FIG. 48.--Bog spavins.]
_The prognosis_ is always uncertain and should be guided somewhat by the
conformation of the limb, character of the work required of the animal,
position of the bony enlargement and the degree of lameness. The size of
the enlargement is changed very little by the treatment. Veterinarians
report recoveries in from fifty to sixty per cent of the cases treated.
_The object of the treatment_ is to destroy the inflammation and bring
about a union between the bones. The treatment recommended is
counterirritation and rest. The most satisfactory method of
counterirritation is firing followed by blistering. Following this
treatment, the horse should be placed in a stall and given no exercise for
a period of five or six weeks. It is sometimes advisable to repeat the
counterirritation if the results of the first firing are unsatisfactory.
BOG SPAVIN.--Bog spavin is an extensive distention of the capular ligament
of the hock-joint by synovia (Fig. 48). It is generally due to chronic
inflammation of the synovial membrane. This blemish or unsoundness is most
common in young horses. Thorough pin (Fig. 49) involves the sheath of the
large tendon only. (Compare Figs. 48 and 49.)
[Illustration: FIG. 49.--Thorough pin. Note the relation of the enlargement
to the tendon, and the freedom of the hocks from bog spavin.]
Certain conformations of the hock favor the development of bog spavin. This
is especially true of upright and "fleshy" hocks. Hard work may cause the
hocks to "fill" when followed by a brief period of rest. The common cause
is a sprain due to slipping and pulling heavy loads.
The _following symptoms_ may be noted: Lameness is not a common symptom of
bog spavin. If there is inflammation present or the articulation is
injured, lameness occurs. The soft swelling that characterizes the bog
spavin is most prominent toward the inside and front of the region. In the
upper portion or hollow of the hock, and on the inside and outside, there
may be a second enlargement. Smaller enlargements may be present in other
regions. All of the swellings feel soft, and pressure on any one of them
moves the fluid present in the others.
_The treatment_ is directed at the removal of the lameness. Acute
inflammation resulting from spavin may be relieved by cold applications and
rest. Chronic lameness should be given the same treatment as recommended
for bone spavin. The enlargement can be successfully removed in growing
colts by the repeated application of mild blisters. It may be necessary to
continue the treatment for several months. The removal of the enlargement
in adult horses by an operation is recommended. The _greatest caution_ is
required in performing this operation.
CAPPED HOCK.--All swellings on the point of the hock are termed "capped
hock." The swellings may be due to an injury to the skin and the
subcutaneous tissue, or more important structures may be involved, as the
subcutaneous bursa, the tendon, or the synovial bursa or sack.
Capped hock is _caused_ by the animal kicking in the stall or in harness,
shipping in freight cars and lack of bedding in the stall. Unless the
deeper structures are bruised and inflamed the animal shows no lameness.
_The character_ of the enlargement varies. When the injury is superficial,
the swelling feels firm, or pits on pressure. Later it may become more firm
and feel like a loose, thickened, fibrous cap for the hock. Soft,
fluctuating swellings are due to an inflammation of the bursa. Recent
injuries feel hot.
_The preventive treatment_ consists in hobbling the hind limbs of a horse
that kicks in the stable. This is usually necessary only at night. It may
be advisable to pad certain parts of the stall. Horses that are transported
in cars should be protected against injuries during transit by the use of
proper care and such arrangement of the animals in the car as may expose
them to the least injury. Recent injuries should be treated by the
application of cold and rest.
After the inflammation has subsided tincture of iodine or blisters may be
applied. The treatment of bursal enlargements is surgical. This consists in
opening the bursa, destroying the lining membrane of the cavity and
treating the part daily until healed. The operation must be performed
carefully, as there is danger of infection with irritating organisms. The
animal should be given complete rest until the part is healed. Tincture of
iodine may be applied to the enlargement that may remain after healing has
occurred. This should be continued daily until the skin becomes noticeably
irritated. The treatment may be repeated, if necessary, after an interval
of two weeks.
[Illustration: FIG. 50.--Curbs.]
CURB.--This term is applied to all swellings on the posterior border of the
hock (Fig. 50). Thickenings or enlargements in this region may involve a
variety of structures. Thickening of the skin, tendons and sheath may
occur. The large ligament that extends from the posterior border of the
bone that forms the summit of the hock to the external splint bone, and
acts as a stay for the point of the hock, is the structure usually involved
in curb.
Faulty conformation is a _predisposing cause_. A narrow base weakens the
hock at this point, and the extreme length of the bone that forms its
summit gives the powerful muscles attached to it greater leverage than in a
well-conformed hock. This results in strain to the ligament at the
posterior portion of the region.
_The exciting causes_ are strains resulting from jumping, slipping,
rearing, heavy pulling and bruising of the part.
_In examining the hock_ for curb it is necessary to stand to the side and
note the profile of the posterior border. Excessive development of the head
of the external splint bone should not be mistaken for curb. As viewed from
the side, the posterior border of the hock should appear straight.
The curb appears as a swelling on this straight line. It varies in size. A
recent curb is usually hot and firm, or may feel soft if enlargement is
formed by fluid, hard if formed by bone. Lameness seldom occurs, but if
present, resembles spavin lameness.
_The preventive treatment_ consists in selecting for breeding, animals that
have strong, straight hocks, and using the necessary care in handling and
working horses. It is not uncommon for young horses at the time they are
broken to harness to develop a curb. This may be prevented to a large
degree by careful handling. At the beginning of the inflammation the
application of cold and hand rubbing is indicated. After the inflammation
has subsided tincture of iodine or blisters should be applied. Rest is a
necessary part of the treatment early in the inflammation. If the lameness
does not respond to the above treatment, it should be treated the same as
for bone spavin.
QUESTIONS
1. Describe the different fractures of the ileum and give treatment.
2. Describe string-halt lameness and give treatment.
3. What is bone spavin? Describe spavin lameness.
4. Give the causes and treatment of bog spavin.
5. Give the causes and treatment of capped hock.
6. Give the causes and treatment of curb.
PART III.--THE TEETH
CHAPTER XIX
DETERMINING THE AGE OF ANIMALS
[Illustration: FIG. 51.--Head of young horse with bone cut away, and
showing position and size of teeth.]
GENERAL DISCUSSION.--The teeth are the passive organs of digestion. They
are hard organs, implanted in the superior and inferior jaws in the form of
a long and narrow arch that is open posteriorly. The free portions of the
teeth project into the mouth, and present sharp or roughened table surfaces
for the crushing and tearing of food. In solipeds and ruminants the arch is
interrupted on each side by the inter-dental space or bars (Fig. 51). The
teeth that form the middle and anterior portion of the arch are termed
incisors (Fig. 52). Posterior to the incisors are the canines or tusks, and
forming the arms of the arch are the molar teeth. Animals have two sets of
teeth, temporary and permanent. The following table gives the number of the
different kinds of temporary and permanent teeth.
Temporary Teeth Permanent Teeth
Incisors Canines Molars Incisors Canines Molars
Solipeds 12 12 12 4 24
Ox 8 12 8 0 24
Sheep 8 12 8 0 24
Hog 12 12 12 4 24
The tusks or canine teeth are not always present in the female. Ruminants
do not have upper incisor teeth. The temporary teeth are erupted either
before or within a few days to a few months after birth. The eruption of
the permanent teeth and the replacement of the temporary teeth occur at
different periods up to the age of four and one-half years (Fig. 53). It is
well to keep the following table of dentition in mind when examining the
mouths of animals for the purpose of determining their age.[1]
Horses Cattle Hogs
Teeth Temporary Permanent Temporary Permanent Temporary Permanent
Incisors: yrs. mos. yrs. mos. mos.
Centrals At birth 2 6 At birth 1 8 At birth, 12
or 3-4
weeks
First 4-6 wks. 3 6 At birth 2 9 8-12 wks. 18
laterals
Second 5-12 days 3 6
laterals
Corners 6-9 mos. 4 6 12-18 days 4 6 At birth 9
Molars:
First At birth 2 6 At birth 2 6 7 weeks 5
Second At birth 2 6 At birth 1 6 8-28 days 14
Third At birth 3 6 At birth 3 8-28 days 13
Fourth 10-12 1 6 13
Fifth 2 2 5
Sixth 4-5 2 6 9
Seventh 18
Canines or 4-5 9
tusks
IN DETERMINING THE AGE of the different domestic animals by the development
and appearance of the teeth, most of the attention is given to the lower
incisor teeth. Up to the fifth year, the age of the horse or ox can be
easily determined by the eruption and replacement of the incisors.
At _one year_ of age the colt has a fully developed set of temporary
incisors. The ruminant's incisors at this age all show wear.
_The two-year-old colt_ shows a well-worn set of incisor teeth, and the
ruminant at this age has replaced the nippers or centrals.
_The third_, _fourth_ and _fifth years_ are indicated by the replacement of
the temporary nippers, dividers and corners in the horse, and the first and
second dividers and corner teeth in ruminants.
[Illustration: FIG. 52.--Longitudinal section of incisor tooth: cup;
cement; enamel; ivory; and pulp cavity.]
In the horse the permanent nippers are full grown and in wear at _three
years_ of age; the permanent dividers are full grown and in wear at _four
years_ of age; and the permanent corners are full grown and in wear at
_five years_ of age. The table surfaces of the incisor teeth of a
five-year-old horse show different degrees of wear. At this period in the
animal's age, the nippers have been in wear two years, the dividers one
year, and the corners are beginning to show wear. In ruminants, all of the
chisel-shaped table surfaces of the incisors show considerable wear when
the animal is five years old.
After the animal has a full set of permanent teeth, we judge the age by the
degree of wear or the appearance of the table surfaces of the incisors,
their shape, the angle with which they meet and the general appearance of
the head.
[Illustration: FIG. 53.--Cross-section of head of young horse showing
replacement of molar tooth.]
There are several different factors that may cause the wear on the teeth,
and the appearance of their table surfaces to vary in the different
individuals. The two factors that are of the most importance are the
quality of the teeth and the character of feed. Soft teeth wear more
quickly than hard teeth, and the teeth of horses that feed over closely
cropped and sandy pastures wear rapidly because of the dirt and grit
present on the short grass. This variation in the wear is of little
importance to the person who must judge the age of a horse that he expects
to purchase by the condition of the teeth. In reality, a horse is just as
old as the wear on the teeth and his general appearance indicate. In order
to stand severe work the animal must be able to masticate the feed, and
prepare it for digestion in the stomach and intestines. The degree of wear
on the molar teeth may be indicated by the wear on the incisors. The
general condition of the horse and his ability to stand hard work depend
very largely on the condition of the table surfaces of the molars.
It is very difficult to judge the age of horses that have deformed mouths
or that are in the habit of crib-biting, because of the irregularity in the
wear of the incisors.
When examining the teeth for the purpose of determining the horse's age,
the shape of the incisors, the angle with which they meet and the
appearance of their table surfaces should be observed. The teeth of young
horses show more or less yellowish cement. At about seven years of age the
anterior faces of the teeth are usually white, later a yellowish color. The
teeth of middle-aged horses may be long, and in aged animals, narrow and
short. The incisors meet at a more acute angle in old than young horses.
_The free portion of the incisor_ tooth is flattened from before to behind.
At the level of the gums its two diameters are about the same, but the
portion of the tooth imbedded in the jaw bone is flattened from side to
side. As the tooth becomes worn off, the length of the free portion is
maintained by a pushing out of the tooth, and a corresponding shortening of
the portion that is fixed or imbedded in the jaw.
_The table surface of the unworn incisor_ tooth is covered with enamel, and
in the middle portion the enamel forms a deep cup. After the tooth has
become worn the margin of the table portion is then limited by a ring of
enamel. This is termed the encircling enamel ring. The central portion of
the table shows a second ring, the central enamel ring, that limits the cup
margin (Fig. 54).
[Illustration: FIG. 54.--Transverse section of incisor tooth: peripheral
cement; peripheral enamel; ivory; central enamel; and central cement.]
_As the table surface_ represents a cross section of the tooth, its
appearance and shape will then depend on the portion of the tooth that it
represents. From year to year, there is a gradual shortening in the lateral
diameter, and an apparent increase in the diameter from before to behind.
These changes in shape are from a long, narrow table surface to an oval,
from oval to circular and from circular to triangular (Fig. 55). As the
original free portion of the tooth wears off, the cup becomes shallow and
smaller until the remnant is represented by a mere dot of enamel that
finally disappears from the posterior portion of the table. After the cup
has moved from the central portion of the crown and occupies a more
posterior position, the dental star, which represents a cross section of
the pulp cavity, puts in its appearance. It first takes the form of a brown
or dark streak, and later a circular dark spot which gradually increases in
size with the wear on the tooth and the age of the animal.
[Illustration: FIG. 55.--Table surfaces of nippers at different ages: four
years; six years; nine years, and fifteen years of age.]
The following changes in the shape and appearance of the incisor teeth of
the average horse occur in the different years. Unless otherwise mentioned,
the statements made regarding the appearance and wear on the table surfaces
apply to the lower incisor teeth.
SIX YEARS.--The table surfaces form the most accurate guide. The cups of
the nippers tend to an oval form. The corner teeth have been in wear one
year at this time. The cup is deep and the posterior margin may show little
wear. It is not uncommon to meet with corners that possess irregularly
developed tables, and have cups with posterior margins that are thin and do
not come into wear until later. For this reason, it is not best to depend
on the appearance of the corner teeth alone.
SEVEN YEARS.--The teeth are usually whiter than the previous year. The
profile of the upper corner teeth shows a notch in the posterior portion of
the table surface. This is due to the superior corners overhanging the
inferior corner teeth posteriorly, resulting in this portion not wearing
away. This notch is sometimes slightly in evidence the previous year. The
cups in the corners are smaller and the worn surface larger than at six.
The nippers show oval table surfaces and the dividers are beginning to take
on this shape. The shifting of the cups toward the posterior portion of the
tables of the nippers and dividers is noticeable.
EIGHT YEARS.--As viewed from the side, the profile of the teeth shows a
very noticeable increase in the obliquity with which they meet. The
posterior borders of the corners show considerable wear. The notch in the
superior corners is still present, but as the teeth come more nearly in
apposition it may begin to disappear. All of the inferior tables are level.
The nippers and dividers are oval in shape, and the cups have become
decidedly narrow. The nippers show a well-defined dark streak just in front
of the cups. This is the beginning of the dental star.
NINE YEARS.--The appearance of the table surface is more characteristic at
this time than the previous year. The cups are less prominent and the
plainness or smoothness of the inferior table is more noticeable. The
nippers are round, the cups triangular and the dark streak narrower and
more distinct than the previous year. The dividers are becoming round and
the corner teeth are oval.
TEN YEARS.--The teeth are more oblique than in the eight-year-old and
nine-year-old mouth. The table surfaces of the inferior nippers are
decidedly rounded, the cups are small, triangular and situated well toward
the posterior borders. The dark brown streak or dental star is situated in
the central portion of the nippers and dividers. The tables of the dividers
are round.
ELEVEN YEARS.--The tables of the corner teeth are rounded. The dark streak
or dental star is present in all of the teeth, and the remnants of the cups
appear as small rings or spots of enamel near to the posterior borders of
the tables. The notch in the superior corners may reappear at this time.
TWELVE YEARS.--The profile of the teeth when viewed from the side is quite
oblique. The table surfaces of all the incisors are round. But a trace of
the cup remains in the inferior incisors. The head of the animal is
beginning to show age. The inferior border of the jaw bone appears
narrower, or sharper than in the young horse.
THIRTEEN YEARS.--All of the specks of enamel or the remnants of the cups
are gone from the lower incisors. A larger notch may be present in the
upper corner teeth than at twelve. The tables of the inferior nippers are
becoming triangular and show a small, dark spot or dental star.
FOURTEEN YEARS.--The tables of the inferior nippers are triangular, and the
dental star appears as a dark round spot in both the nippers and dividers.
FIFTEEN YEARS.--The angle with which the teeth meet is greater than at
twelve, the teeth are smaller and dental stars are represented by dark
round spots in all of the inferior incisors. The tables of the nippers and
dividers are triangular.
SEVENTEEN YEARS.--All of the tables of the lower incisor teeth are
triangular. The teeth are narrower and smaller than at fifteen. The profile
of the incisors, viewed from the side, is quite angular. The dental stars
are prominent.
NINETEEN YEARS.--All of the signs of the seventeen-year-old mouth are more
prominent. The cups have usually disappeared from the upper incisors.
[Footnote 1: This table is from dentition tables given in "Age of the
Domestic Animals," by Huidekoper.]
QUESTIONS
1. Name the different kinds of teeth; state the arrangement and number.
2. How is the age of an animal determined?
3. Give the time of replacement of the temporary incisor teeth.
4. How is the age of the animal determined between the fifth and ninth
years?
5. What changes in the appearance of the table surfaces occur between ten
and fifteen years of age?
CHAPTER XX
IRREGULARITIES OF THE TEETH
Parrot-mouth, Lantern-jaw and Scissor-mouth.--The common deformities of the
jaw and teeth are the overshot or parrot-mouth, the undershot or
lantern-jaw, and the scissor-mouth. These different deformities result in
unequal wear on the table surfaces of the incisors and molars. In both the
overshot and undershot jaws, the incisor teeth become abnormally long. In
the _parrot-mouth_, the wear occurs on the posterior face of the superior
and the anterior face of the inferior incisors, the teeth becoming worn to
rather a sharp edge, depending on the degree of the deformity. In the
_lantern-jaw_, the wear occurs on the posterior face of the lower and the
anterior face of the superior row of incisors, the teeth taking on somewhat
the same shape as the parrot-mouth. The greater the deformity and the older
the horse becomes, the more difficult it is for the animal to feed or
graze on pasture.
In all horses, the two rows of molar teeth are wider apart in the superior
than in the inferior jaw. This results in the external border of the tables
of the superior row of molars becoming longer, or projecting further
downward than the internal border. The wear on the table surfaces of the
inferior row of molars is just the opposite of the superior row. In the
_scissor-mouth_ the wear takes place largely on the internal face of the
superior and the external face of the inferior row of molars. The teeth
become worn to more or less of a blunt cutting edge, and after a time the
molars come together somewhat like the jaws of a pair of scissors. A horse
with a badly deformed scissor-mouth is unable to grind the feed, and unless
given special care, suffers severely from innutrition.
_The treatment_ of deformed mouths consists in removing the irregular or
unworn portion of the teeth by means of the tooth float and cutters. This
attention should be given early before the free portion of the tooth has
become excessively long and irregular. This should be followed by dressing
the teeth every six or twelve months.
SHARP LATERAL BORDERS ON THE MOLAR TEETH.--This is a very common condition
in horses. The external border of the superior and the internal border of
the inferior row of molars wear away slowly, and sometimes become quite
sharp. This is objectionable because the sharp points lacerate the mucous
membrane of the cheek and tongue, and the mastication of the feed is
seriously interfered with.
This condition is _caused_ by an excessive difference in the width of the
jaws, unusually prominent ridges of enamel on the external face of the
superior molars, and any conditions that may limit the movements of the
jaw.
The following _symptoms_ may be noted. The animal has difficulty in
masticating the feed because of injury to the cheeks or tongue by the sharp
points of enamel. This condition may be indicated by holding the head to
one side. Salivation is usually present. Acute indigestion and innutrition
may occur.
By examining the teeth, their condition can be determined. The sharp
borders may be removed by dressing or floating the teeth. It is advisable
in the majority of horses to float the teeth at least once in every twelve
months.
IRREGULARITIES IN THE TABLE SURFACE OF THE MOLAR TEETH.--Horses eight years
of age or older frequently have irregular molars (Fig. 56). This is due
very largely to the difference in the quality of the teeth. The harder
molars do not wear off as rapidly as the softer ones. This results in the
table surfaces of the rows of molars becoming wavy or step-like in outline.
Sometimes the first or sixth molar overhangs or projects beyond the
corresponding tooth of the opposite jaw. When this occurs, the over-hanging
portion may become long and sharp. A molar tooth becomes excessively long
if the opposite one is decayed or removed.
_The symptoms_ are very much the same as when the borders of the molars
are sharp.
[Illustration: FIG. 56.--Teeth showing uneven wear occurring in
old horses.]
_The treatment_ consists in levelling the tables as frequently as necessary
by cutting off the longer projections, and removing the sharp edges with a
tooth float.
SMOOTH MOUTH.--In old age the tables of the molar teeth may become so
smooth that the horse cannot grind or masticate the feed. When all of the
molars are in this condition, a rubbing sound may be noted when the animal
is masticating hay. After attempting to chew the hay, it may be dropped
from the mouth. Innutrition always occurs.
_The treatment_ consists in feeding chops and soft feeds.
DENTAL DISEASES.--Inflammation of the alveolar periosteum is a common
dental disease in domestic animals. This is an inflammation of the alveolar
dental membrane that fixes the tooth in the tooth cavity.
Injuries to the gums and cracks or fissures in the tooth are the _common
causes_. Caries or tooth decay is not uncommon. The predisposing factor is
a poor quality of enamel and dentine. The process of decay is assisted by
microorganisms.
The _early symptoms_ may escape notice. Slobbering, masticating on one
side, holding the head to one side, retained masses of food in the mouth
and a disagreeable odor frequently occur. Caries may be indicated at first
by a dark spot on the table of the tooth, later by a cavity. In horses,
inflammation of the alveolar membrane results in a bony enlargement on the
side of the face if the superior molar is involved. A swelling of the jaw
and fistula may result if a lower molar is involved (Fig. 57).
[Illustration: FIG. 57.--Fistula of jaw. This condition was the result of
neglected treatment of decayed teeth.]
_The treatment_ consists in the prompt removal of the tooth. This is more
difficult in young animals than it is in the middle-aged or old. Unless the
tooth is already loosened it may be necessary to remove it by trephining.
QUESTIONS
1. Describe the appearance of the teeth in an overshot or undershot jaw.
2. Describe the appearance of sharp molar teeth; a scissor-mouth.
3. What are the causes of decayed teeth?
PART IV.--SURGICAL DISEASES
CHAPTER XXI
INFLAMMATION AND WOUNDS
Inflammation is a pathological condition of a tissue, characterized by
altered function, disturbance of circulation, and destructive and
constructive changes in the irritated part. Heat, redness, swelling, pain
and disturbed function are the symptoms which characterize inflammation.
_The changes in the circulation_ occurring in inflammation are as follows:
(1) An increase in the rate of the blood-flow through the blood-vessels of
the part and their dilation; (2) diminished velocity followed by the
blood-flow becoming entirely suspended; (3) following the retardation or
suspension of the blood stream, white blood-corpuscles accumulate along the
walls of the small veins and capillaries; (4) white and red
blood-corpuscles migrate from the vessels into the neighboring tissue, and
blood-serum transudes through the walls of the vessels, forming the
inflammatory swellings. The red blood-cells do not escape from the
blood-vessels in any numbers unless the walls of the blood-vessels become
injured or badly diseased.
_The causes of inflammation_ may be grouped under the following heads:
mechanical, chemical, thermic and infectious. The _mechanical_ or
_traumatic causes_ commonly produce inflammation in domestic animals. These
are kicks, strains of tendons, ligaments or muscles and wounds.
Inflammation originating from injuries very frequently changes to an
infectious form, through the infection of the part by bacteria. Bruised
tissue may become infected with pus-producing organisms, and an abscess or
local swelling form. All accidental wounds in domestic animals become more
or less infected by irritating microorganisms.
The following _symptoms_ occur in local inflammation. Increased heat in the
part is an important symptom. It is due to the increased blood-flow to the
part. Because of the pigmented, hairy skin of domestic animals, redness is
of little value in locating superficial inflammation. Swelling is a
valuable local symptom. It is produced by the inflammatory exudates. Pain
results from the pressure on the sensory nerves by the inflammatory
swelling. For example, the laminae of the foot are imprisoned between the
horny wall and the pedal bone. This structure is well supplied with sensory
nerves, and when it becomes inflamed and swollen, the tissues are subject
to severe pressure and the pain is severe. Inflammation of a tendon results
in lameness; of the udder, in suspension of milk secretions; and of the
stomach by interference with digestion of the feed. Such symptoms may be
grouped under the head of disturbed functions.
_The character of an inflammation_ is largely modified by the nature of the
tissue in which it occurs. A serous inflammation is characterized by
serous, watery exudates. This form occurs in the serous membranes, mucous
membranes and skin. Blisters on the skin and inflammation of bursae (capped
hock and shoe boil) are examples of this type. Sero-fibrinous
inflammations, such as occur in pleurisy and peritonitis, are common.
Chronic inflammation commonly results in new formations of tissue, and it
is named according to the character of the new tissue formed, as ossifying,
adhesive, and fibrous inflammation. Pus-forming bacteria produce
suppurative inflammation. Such diseases as tuberculosis, glanders and
hog-cholera are specific inflammations. Specific infectious diseases may be
classed as generalized inflammation, as they usually involve the entire
body.
Inflammation terminates in resolution when the serum is reabsorbed by the
blood-vessels and lymphatics, the living blood-cells find their way back
into the circulation and the dead cells disintegrate and are taken up by
the vessels. The time required for the tissues to return to the normal
varies from a few hours to several weeks. An acute inflammation may end in
the chronic form. This may then terminate in new formations, such as
adhesions, fibrous thickenings and bony enlargements. Severe inflammation,
especially if localized and superficial, may result in death of the part or
gangrene.
The following _treatment_ is recommended: The cause of the irritation to
the tissue must be removed. It is very essential that the part be rested.
The necessary rest may be obtained in different ways. Inflamed tendons,
ligaments, and muscles may be rested by placing the animal in a sling,
standing it in a stall, or fixing the part with bandages. Rest of the
stomach or intestinal tract may be obtained by feeding a light diet, or
withholding all feed. Comfortable quarters, special care and dieting the
animal are important factors in the treatment of inflammation.
The agents used in the treatment of superficial and localized inflammation
are _heat, cold, massage_ and _counterirritation_. _Heat_ is indicated in
all inflammations, excepting when of bacterial origin. It stimulates the
circulation and reabsorption of the inflammatory exudates, and by relaxing
the tissues helps greatly in relieving pain. _Cold_ is more effective in
the highly acute and septic (suppurative) inflammation. Its action consists
principally in the contraction of the dilated blood-vessels. Continuous
irrigation of the part with cold water is the most satisfactory method of
applying cold. _Massage_ is a very important method of treating superficial
inflammation. Mild, stimulating liniments are usually used in connection
with hand-rubbing or friction. Chronic inflammation is usually treated with
_counterirritants._ Blistering and firing are the most important methods
of treatment. Such counterirritation makes possible the absorption of the
inflammatory exudates by changing the chronic inflammation to the acute
form.
WOUNDS.--A wound, in the restricted sense that the term is commonly used,
includes only such injuries that are accompanied by breaks or divisions of
the skin and mucous membrane. It is usually an open, hemorrhagic injury.
If the tissues are severed by a sharp instrument and the edges of the wound
are smooth, it is classed as an _incised_ or _clean-cut wound_. This class
is not commonly met with in domestic animals outside of operative wounds.
When the tissues are torn irregularly, the injury is classed as a
_lacerated wound_. A barb-wire cut is the best example of this class.
A _contused wound_ is an injury caused by a blunt object. Such injuries may
be divided into superficial and deep. Superficial-contused wounds may be an
abrasion to the skin or mucous surface. Deep-contused wounds may be
followed by loss of tissue or sloughing, and may present irregular, swollen
margins. Such injuries are commonly caused by kicks.
_Punctured wounds_ are many times deeper than the width of the opening or
break in the skin or mucous membrane. This class is produced by sharp
objects, such as nails, splinters of wood, and forks.
Sometimes, wounds are given special names, as gun-shot, poisoned, and open
joint, depending on the nature of the cause and region involved.
Bleeding or hemorrhage is the most constant symptom. The degree of
hemorrhage depends on the kind, number and size of the blood-vessels
severed. In arterial hemorrhage, the blood is bright red and spurts from
the mouth of the cut vessel. In venous hemorrhage, the blood is darker and
flows in a continuous stream. In abrasions and superficial wounds capillary
hemorrhage occurs. Death may follow severe hemorrhage. Weak pulse,
general weakness, vertigo, loss of consciousness and death may result if
one-third of the total quantity of blood is lost. Unthriftiness and general
debility may follow the loss of a less quantity of blood.
The following _symptoms_ may be noted in the different kinds of wounds: The
sensitiveness to the pain resulting from accidental or operative wounds
varies in the different individuals and species, and in the kind of tissue
injured. Injuries to the foot, periosteum, skin and mucous membrane are
more painful than are injuries to cartilages and tendons. The appearance of
the wound varies in the different regions and the different tissues.
If the tissues are badly torn or bruised, swelling and sloughing may occur.
If the wound is transverse to the muscular fibres, it gaps more than when
parallel to the muscle. When infected by irritating organisms, open and
punctured wounds (Fig. 58) become badly swollen, discharge pus freely and
heal slowly with excessive granulations. Wounds involving tendons, bursae
and closed articulations become swollen and discharge synovia. Wounds
involving muscles, tendons and bursae usually cause lameness, and when
involving a special organ, interfere with, or destroy, its function.
Extensive or serious wounds may be followed by loss of appetite. An
abnormal body temperature and other symptoms characteristic of the
different forms of blood poisoning may follow infection of the injured
tissues by certain germs.
[Illustration: FIG. 58.--A large hock caused by a punctured wound of the
joint.]
The rapidity with which wounds heal depends upon the kind of tissue injured
and the amount to be replaced, the degree of motion in the part, the kind
and degree of infection and irritation and the general condition of the
animal. In general, skin and muscles heal rapidly, tendons slowly,
cartilages unsatisfactorily and nerve tissue very slowly. Healing is
greatly interfered with by movement of the part (Fig. 59). The more nearly
the part can be fixed or rested, the more quickly and satisfactorily does
healing occur. Irritation by biting, nibbling, licking, bandaging, wrong
methods of treatment and filth retard healing and may result in serious
wound complications. An animal in poor physical condition, or one kept
under unfavorable conditions for healing, cannot recover from the injury
rapidly or satisfactorily.
[Illustration: FIG. 59.--A large inflammatory growth following an injury to
the front of the hock.]
WOUND HEALING.--The following forms of healing commonly occur in wounds:
First and second intention; under a scab, and by abnormal granulation.
_Healing by first intention_ occurs when the wound is clean cut and there
is very little destruction of tissue, and when there is no suppuration or
pus formation. The blood and wound secretions cause the edges of the wound
to adhere. After a few days or a week the union becomes firm. Very little
scar tissue is necessary in this form of healing.
_Healing by second intention_ is characterized by pus formation and
granulation tissue. After the first day, the surface of the wound may be
more or less covered by red, granular-like tissue. Later this granular
appearance is modified by an accumulation of creamy pus and swelling of the
part, and finally scab formation and contraction of the new scar tissue.
Abrasions and superficial wounds usually _heal under a scab_. The scab is
formed by the blood and wound secretions. This protects the surface of the
wound until finally the destroyed tissue is replaced by the granulations,
and the skin surface is restored.
_Abnormal granulation_ is not an uncommon form of healing in domestic
animals. Mechanical and bacterial irritation causes the injured tissue to
become swollen and inflamed. In such a wound, excessive and rapid
granulation occurs, the new tissue piling up over the cut surfaces and
appearing red and uneven. This is termed excessive granulation or "proud
flesh." This tissue may refuse to "heal over," or the scar may be large,
prominent and painful. Abnormal tissue (horny or tumor-like) may sometimes
form.
WOUND TREATMENT.--Wounds in domestic animals are frequently allowed to heal
without special care or treatment. This is unfortunate. The careful and
intelligent treatment of wounds would greatly decrease the loss resulting
from this class of injuries. The method of treatment varies in the
different kinds of wounds.
_The first step_ in the treatment is to _check the haemorrhage_. Heat,
ligation, pressure and torsion are the different methods recommended.
Bathing the wound with hot water (115\260-120\260 F.) is a satisfactory
method of controlling haemorrhage from small blood-vessels. Ligation and
torsion of the cut end of large blood-vessels should be practised.
Pressure over the surface of the wound is the most convenient method of
Controlling haemorrhage in most cases. Whenever possible, the part should
be bandaged heavily with clean cheese cloth or muslin. Before applying
the bandage, it is advisable to cover the wound with a piece of sterile
absorbent cotton that is well dusted with boric acid. Hemorrhage from
wounds that cannot be bandaged may be temporarily stopped by pressure
with the hand, or, better, by packing the wound with absorbent cotton
and holding this in place with sutures. This should be left in place for
a period of twelve or thirty-six hours, depending on the extent of the
haemorrhage and character of the wound.
The next step is the _preparation of the wound for healing._ The injured
tissues should be carefully examined for foreign bodies such as hair, dirt,
gravel, slivers of wood and nails. The hair along the margins of the wound
should be trimmed, and all tissue that is so torn and detached as to
interfere with healing cut away. Drainage for the wound secretions and pus
should be provided. The advisability of suturing the wound depends on its
character and location. A contused-lacerated wound should not be closed
with sutures unless it is clean and shows no evidence of sloughing. A badly
infected wound should be left open unless satisfactory drainage for the pus
and wound secretions can be provided. Wounds across the muscle and in parts
that are quite movable should not be sutured.
_The after-treatment_ consists in keeping the animal quiet, if the wound is
in a part that is quite movable, and preventing it from biting, licking or
nibbling the injury. Wounds in the region of the foot become irritated with
dirt and by rubbing against weeds and grass. This makes it advisable to
keep the animal in a clean stall until healing is well advanced. Local
treatment consists in keeping the wound clean by washing the part daily, or
twice daily, with a one per cent water solution of a cresol disinfectant.
Liquor cresolis compositus may be used. It is sometimes advisable to
protect the granulating surface against irritation by dusting it over with
a non-irritating antiseptic powder, or applying a mixture of carbolic acid
one part and glycerine twelve parts. After the wound shows healthy
granulations longer intervals should lapse between treatments.
In poorly cared for, and badly infected wounds, the part may become badly
swollen, the granulations pile up and the wound refuse to "heal over." It
may be advisable in such cases to cut away the excessive granulations and
stop the haemorrhage by cauterization with a red-hot iron, or by
compression. Unhealthy granulations may be kept down by applying caustic
occasionally.
ABSCESS.--This is an accumulation of pus in the tissues. It may be due to a
severe bruise or contusion that is followed by the infection of the part
with some of the pus-producing bacteria. Abscesses occur in certain
infectious diseases. In strangles, the disease-producing organism may be
carried to different regions of the body by the circulatory vessels. This
may result in a number of abscesses forming in the different body tissues.
The following _forms of abscess_ are recognized: hot and cold, superficial
and deep, simple and multiple. The hot is the acute, and the cold the
chronic abscess. The terms superficial and deep allude to the relative
position of the abscess, and simple and multiple to the number present.
An abscess may first appear as a hot, painful swelling. If superficial, the
skin feels tense and the contents fluctuate when pressed on. Later the
fever subsides and no pain may occur when the abscess is pressed upon. Deep
abscess may not fluctuate.
_The treatment_ consists in converting the abscess into an open wound
whenever possible. The incision should extend to the lowest part of the
wall, so as to insure complete drainage. A cold abscess in the shoulder
region may become lined by a layer of tissue that retards healing. In order
to hasten the healing process, it may be necessary to remove this. Until
granulation is well advanced, the abscess cavity should be irrigated daily
with a one per cent water solution of liquor cresolis compositus, or a one
to two thousand water solution of corrosive sublimate. The surface of the
skin in the region of the abscess should be kept clean.
[Illustration: FIG. 60.--Fistula of the withers, showing the effect of
using caustics carelessly.]
FISTULOUS WITHERS AND POLL EVIL.--These terms are applied to swellings,
blood tumors, abscesses and pus fistulae that may be present in the region
of the poll and withers (Fig. 60). Pus fistula is the characteristic lesion
present, and it is the result of a suppurative inflammation of the tissues
in the region. The abscess cavity or cavities are usually deep, and may
involve the ligaments and vertebrae.
Bruises or contusions are the most _common causes_. The prominence of these
regions predisposes them to injury in the stable, or when rolling on rough
or stony ground. Bites and bruises to the withers resulting from other
horses taking hold of the region with the teeth, or striking the part
against a hard surface, are frequent causes.
_The treatment_ is both preventive and surgical. All possible causes should
be investigated. This is of special importance on premises where several
horses develop fistulous withers and poll evil. If the cause then becomes
known, it should be removed.
_The surgical treatment_ consists in opening up the different abscess
cavities, providing complete drainage for the pus and destroying the tissue
that lines the walls of the cavities. Horses that are prone to rub the
region should be prevented from doing this, as such irritation retards
healing. Autogenous bacterins should be used in addition to the surgical
treatment. A pus fistula should heal from the bottom, and if the opening
becomes closed, drainage should be re-established. The daily treatment is
the same as recommended for abscesses. Excessive cutting and destruction of
the tissues with caustic preparations result in scarring and deformity of
the part. Such radical lines of treatment should be discouraged. We should
not delay the surgical treatment of abscesses in the regions of the poll
and withers.
QUESTIONS
1. Name and describe the different forms of inflammation.
2. Give the causes and treatment of inflammation.
3. Name and describe the different methods by which wounds heal.
4. Describe the treatment of wounds.
5. What are the causes of an abscess? Give the treatment.
6. What are the causes of fistula and poll evil? Give the treatment.
CHAPTER XXII
FRACTURES AND HARNESS INJURIES
FRACTURES.--Broken bones or fractures are not uncommon in domestic animals.
In the horse, the bones of the leg, forearm, foot, and spine are the most
commonly broken. In the dog the largest percentage of fractures occurs in
the superior regions of the limbs.
Fractures may be classified as _simple_ and _compound, complete_ and
_incomplete, comminuted_ or _splinter_. In the simple fracture the skin
over the region escapes injury, but in the compound fracture the skin is
broken and the ends of the broken bone may protrude through it. The terms
complete and incomplete are used in describing fractures in which the ends
of the bones are not attached to each other, or partially so. In the
comminuted fracture the bone is broken into a number of pieces. There are a
number of other terms that may be used in designating the different kinds
of fractures, such as double, when both bones in the region are broken, and
oblique, transverse and longitudinal, depending on the direction of the
break.
_The causes_ of fractures may be divided into external or mechanical, and
internal. Fractures may result from kicks, blows, muscular strain and
contusions. Abnormal fragility due to disease, extreme youth and old age
are the internal predisposing factors.
_The symptoms_ are crepitation, abnormal movement and deformity of the
part. Abnormal movement of the part and inability to support weight occur
in fractures of the bones of the limbs. Crepitation or a grinding, rubbing
sound due to the movement of the ends of the broken bones on one another
occurs when the part is moved or manipulated with the hands. Pain, swelling
and injury to the skin are other local symptoms. The new tissue or bone
callus is formed by the bone-forming cells in the deeper layer of the
periosteum and bone-marrow.
_The prognosis is unfavorable._ The larger percentage of fractures in
domestic animals are incurable, or make an unsatisfactory recovery. This is
due to careless treatment, the character of the fracture and the inability
to fix the ends of the broken bone. Fractures in young and small animals
usually heal quickly. Individuals that are healthy and vigorous usually
make a speedy recovery. Fractures heal very slowly in the aged. Compound
and comminuted fractures are impossible to treat in the larger percentage
of cases.
_The treatment_ consists in fixing the broken bone or bones in a normal
position by means of bandages and splints. If this is not practised, the
surrounding tissues become injured by the broken ends of the bone, and the
fracture may become so complicated as to render treatment useless. Motion
retards or prevents the repair of the break.
However, fractures of the ribs, pelvic bones and sometimes long bones that
are well covered by heavy muscles heal naturally or in the absence of any
means of retention.
_Bandaging_.--The attendant must use good judgment in devising means of
fixing the broken bone, and in holding it in its natural position. Whenever
possible, a plaster bandage should be used. This must not be made too
heavy, and it is very necessary to adjust it properly, so that it will stay
in place and not become too tight or too loose. When applied to the limb,
the bandage should extend as far down as the hoof, and some distance above
the break. This is necessary in order to keep it from slipping down and
becoming too loose. A soft bandage should be applied first in order to
equalize the pressure from the plaster cast and protect the skin. Wooden
splints are not very satisfactory agents for the treatment of fractures.
Thick leather that has been made soft by soaking in warm water and then
shaping it to the part makes a more satisfactory splint. In all cases a
soft bandage should be applied under the splint. The adjustment of the
plaster bandage or splint should be noticed daily, and whenever necessary
it should be removed and readjusted. Injuries to the skin must be carefully
cleaned, disinfected and bandaged before applying the plaster bandage. If
evidence of wound infection occurs later, the bandage must be removed and
the wound treated. Large animals suffering with a fracture of any of the
bones of the limb should be placed in slings. Incomplete fracture should
receive the same treatment as simple fracture. If this is practised, the
danger of its becoming complete is avoided.
[Illustration: FIG. 61.--Shoulder abscess caused by loose-fitting harness.]
HARNESS INJURIES.--This class of injuries is common in horses that are
given steady, hard work, or that are not accustomed to work. Young horses,
when first put to hard work, are especially prone to injuries from the
collar. A large proportion of these injuries are due to an ill-fitting
harness or saddle.
When the harness is not adjusted or fitted properly, there is severe
pressure on certain parts. This is the common cause of shoulder abscesses
(Fig. 61), sore necks and sit-fasts. Rough, uneven surfaces on the faces of
the collar and saddle are the common causes of galling. The character of
the work is an important factor. Work that requires the animal to support
weight on the top surface of the neck is productive of sore neck. Heavy
work over rough, uneven ground frequently causes shoulder abscesses and
strained muscles.
The simplest and most common harness injuries are galling, sore shoulders
and sore neck. Harness galls first appear as flat, painful swellings. On
raising the collar from the skin the inflamed area appears dry and the
surrounding hair is wet with sweat. Later, the skin becomes hard and its
outer layer, and sometimes the deeper layer as well, slough, or is rubbed
off by friction of the harness. The surface then appears red and moist.
Fluctuating swellings due to small collections of blood and lymph sometimes
form. Sometimes, small areas on the face of the shoulder and that portion
of the back pressed on by the saddle become swollen, indurated and hard and
give the shoulder a rough appearance. Continuous irritation from the collar
may cause an inflammatory thickening of the subcutaneous tissue in the
shoulder region, and the skin appears loose and somewhat folded. This
uneven surface is productive of chronic collar galls.
_A sit-fast_ is characterized by a large swelling at the top of the neck,
followed by a deep sloughing of the tissues. A slightly swollen, wrinkled
condition of the skin over the top of the neck is sometimes present in
horses that resist the attendant, when he attempts to handle the part or
harness the animal. This form of sore neck is evidently very painful,
although little evidence of inflammation is present.
Strain of shoulder muscles and shoulder abscesses have been discussed under
their separate heads.
_The treatment is very largely preventive_. Too little attention is given
to the proper fitting of the harness and saddle. A well-fitted collar that
properly distributes the weight on the shoulder, and is neither too small
or too large at the top of the neck, is the best preventive for shoulder
and neck injuries. Old, ill-fitting, lumpy collars should not be used.
Neither should the same collar be used for different horses. Farmers should
avoid using sweat pads that are lumpy or soaked with sweat. If soft and
dry, such pads are useful in preventing galling. The surfaces of the collar
or saddle that come in contact with the skin should be kept smooth and
clean. In the spring of the year, it is advisable to bathe the shoulders of
work horses with cold water twice a day. Bathing the shoulders with the
following preparation is a useful preventive measure: lead acetate four
ounces, zinc sulfate three ounces and water one gallon. Smooth leather pads
for the top of the collar and saddle are useful preventive and curative
agents.
_Galls are lest treated by rest_. Ointments or "gall cures" are usually
applied. The following dry dressing dusted over the red, moist, abraded
surfaces is quite healing: tannic acid one ounce, boric acid four ounces,
and calomel two ounces. This may be dusted over the part two or three times
daily. Dry, abraded surfaces may be treated by applying a mixture of
glycerine four ounces, tannic acid one-half ounce and carbolic acid one
dram. In operating for the removal of fibrous enlargements, thickened skin
and abscesses on the front of the shoulder, it is advisable to make the
incision in the skin well to the side of the face of the shoulder in order
to avoid scarring the surface that comes in contact with the collar.
QUESTIONS
1. Name and describe the different kinds of fractures.
2. What are the symptoms of fracture?
3. Describe the treatment of fractures.
4. What are the causes of harness injuries?
5. Describe the treatment of the different harness injuries.
CHAPTER XXIII
COMMON SURGICAL OPERATIONS
DEHORNING CATTLE.--It is very often necessary to remove the horns of cattle
in order to prevent their injuring or worrying certain individuals in the
herd. This operation is of greatest economic importance in dairy and
feeding cattle. When first practised, the dehorning of mature cattle was
condemned by some persons who deemed it an inhuman and unnecessary
operation. It is surely a humane act to remove the horns of cattle that are
confined in small yards and pastures, and prevent them from painfully, or
seriously, injuring one another.
In most localities there are men who are well equipped to dehorn cattle,
and able to perform this operation for a very moderate fee. It is not
advisable to attempt to dehorn a number of adult cattle if the operator is
not well equipped for the work. Unless a well-constructed dehorning rack is
available for confining the animals, there is danger of injuring them and
it is very difficult to saw off the horn quickly and satisfactorily. This
increases the pain that the animal suffers, and horn stubs soon develop.
Good equipment, such as a chute, saw or clippers, is necessary. A dehorning
chute should be built of plank with a good frame well bolted together, with
stanchion and nose block for confining the head. Most operators prefer a
meat saw for cutting off the horns. It is preferable to dehorning shears,
as there is danger of fracturing the frontal bone when removing the horns
of mature cattle. The best form of dehorning shears have a wide V in the
cutting edge.
_The operation is very simple_. The horn should be cut off at a point from
one-quarter to one-half an inch below the hair line or skin. If this is not
practised, an irregular horn growth or stub of horn develops. It is usually
unnecessary to apply anything to the wound. If the animal does not strike
or rub the part, the clot that forms closes the blood-vessels and the
haemorrhage stops. In case of haemorrhage of a serious nature, a small
piece of absorbent cotton may be spread over the surface of the wound, and
pushed in to the opening in order to keep it in place. Pine tar may be
smeared over this dressing. Some operators prefer cauterizing the wound
with a red-hot iron for the purpose of preventing haemorrhage. During warm
weather, the wound should be washed daily with a two per cent water
solution of a coal tar disinfectant, until healing is well advanced. A very
necessary after-treatment is the washing of the part after two or three
days for the purpose of removing the dried blood.
The opening at the base of the horn communicates directly with the frontal
sinus, a large cavity situated between the two plates of the frontal bone.
Sometimes the bone is slivered, or the wound becomes infected and inflamed.
This may be due to a dirty dehorning saw, or getting dirt into the wound.
The inflammation may extend to the sinus and a heavy discharge from the
cavity occur. This complication may be prevented by placing the saw or
cutters in a disinfectant when not in use, and cleaning and disinfecting
the wound very carefully for a few days after the operation.
_The horn buttons of calves_ from a few days to one week of age can be
destroyed, and the growth of the horn prevented by applying caustic soda or
potash to them. The method of procedure is as follows: Clip away the hair
from around the base of the horn tissue and apply a little vaseline to the
skin near, but not close to, the base of the horn; moisten the horn button
and rub it two or three times with the end of the stick of caustic; do not
allow the calf to go out in the rain for a few days after applying the
caustic. The horns of calves a few weeks of age may be removed with a sharp
knife or calf dehorner.
CHOKING.--This is a common accident in cattle and horses. The object that
causes the choke may be lodged in the pharynx or oesophagus. Certain
individuals are more prone to choke while feeding than others. This is
because of their habit of eating greedily, and swallowing hastily without
properly mixing the bolus with the saliva. For this reason, choking occurs
when the animal is eating dry feed. Cattle frequently become choked on
pieces of such food as roots and apples that are too large to readily pass
down the oesophagus. Sharp objects taken in with the food sometimes become
lodged in the oesophagus or pharynx.
_The symptoms_ differ in complete and partial choke. In the latter, the
symptoms are not very characteristic. The animal may stop feeding, but
shows very little evidence of suffering pain. It may be able to swallow a
little water. On attempting to drink, a part of the water may be returned
through the nose, the same as in complete choke. Ineffectual efforts to
swallow, salivation, coughing, hurried respiration, and an anxious
expression of the face occur in complete choke. Bloating may complicate
this accident in ruminants. After partial choke has persisted for a day or
two, the animal appears dejected or distressed. Pressure on the trachea by
hard objects may cause difficult respiration.
Mechanical pneumonia sometimes occurs. This is due to the food and water
that the animal may attempt to swallow, being returned to the pharynx and
passed into the air passages and lungs.
_The treatment_ is as follows: Animals that have choked should not be given
access to feed of any kind. Any attempt to take food or drink water may
result in pneumonia. It may be necessary to drench the animal with a very
small quantity of water for the purpose of diagnosis. The most common form
of choke in horses is that due to accumulation of dry food in the
oesophagus. The administration of a drug that stimulates the secretion of
saliva is a very successful method of relieving this form of choke.
Pilocarpine is the drug commonly used. Cheap whips should not be introduced
into the oesophagus for the purpose of dislodging the foreign body. There
is always danger of the whip becoming broken off, and the broken part
lodging in the oesophagus. Neither should such rigid objects as a broom or
rake handle be introduced, because of the danger from serious injury to the
walls of the pharynx and oesophagus. The flexible probang, which is usually
made of spiral wire covered with leather, is a very useful instrument to
relieve choke when in the hands of an experienced operator. If the object
causing the choke is situated in the neck portion of the oesophagus, it may
sometimes be moved forward, or toward the stomach by pressure with the
fingers.
CASTRATION.--The castration of the male is a common operation in domestic
animals. The purpose of the operation is to render the animal more useful
for work or meat production.
_The age_ at which the operation is performed varies in the different
species. The colt is usually castrated when he is one year old, and the
calf, pig and lamb when a few weeks or a few months of age. It is not
advisable to castrate the young at weaning time. The operation and the
weaning together may temporarily check the growth of the animal. Colts that
are undeveloped and in poor flesh, or affected with colt distemper, should
be allowed to recover before they are operated on. In all animals, it is
advisable to wait until after they have recovered from disease and become
thrifty and strong.
The spring, early summer and fall are the most suitable seasons for
castrating the young. It may be practised during the hot or cold months of
the year with little danger from wound infection or other complications,
providing the necessary after-attention can be given.
_The preparation of the animal_ for the operation by withholding all feed
for about twelve hours is very advisable. If this is practised, the stomach
and intestines are not distended with feed, and the young are cleaner,
easier to handle and suffer less from castration. Clean quarters and
surroundings are very necessary to the success of the operation.
_The instruments required_ are sharp knives, preferably a heavy scalpel and
a probe-pointed bistoury, an emasculator for large and mature animals, and
surgeon's needles and suture material. Ropes and casting harness are
frequently used for confining and casting the large and mature animals. Two
clean pans or pails filled with a two per cent water solution of liquor
cresolis compositus, or an equally reliable disinfectant, should be
provided for cleaning the scrotum and neighboring parts and the
instruments. Pieces of absorbent cotton or oakum may be used in washing and
cleaning the scrotum. The instruments should be sterilized in boiling water
before using.
_If a number of pigs or lambs_ are to be castrated, it is best to confine
them in a small, clean, well-bedded pen. This enables the attendant to
catch them quickly and without unnecessary excitement or exercise. They
should be taken to an adjoining pen to be castrated. The scrotum should be
washed with the disinfectant, and the testicles pressed tightly against the
scrotal wall. An incision parallel with the middle line or raphe and a
little to one side is made through the skin and the coverings of the
testicle, and the testicle pressed out through the incision. The testicle
and cords are then pulled well out and the cord broken off with a quick
jerk and twist, or scraped off with a knife. The latter method is to be
preferred in large lambs if the operator does not have an emasculator. The
incision in the scrotum should be extended from its base to the lowest
part, in order to secure perfect drainage.
_Young calves_ may be castrated in the standing position or when cast and
held on the side. The method of operating is the same as recommended for
pigs and lambs.
_The castration of the colt_ may be performed in either the standing
position or when cast. The method of operating is the same as practised in
the smaller animals with the exception of cutting off the cord. The
emasculator is used here. This instrument crushes the stump of the cord and
prevents haemorrhage from the cut ends of the blood-vessels. Careful
aseptic precautions must be observed in operating on colts, as they are
very susceptible to wound infection and peritonitis.
The blood-vessels of the testicular cord are larger in the adult animals,
and the danger from haemorrhage is greater than in the young. For this
reason, it is advisable to use an emasculator in castrating all mature
animals.
Complications Following Castration.--The _haemorrhage_ from the wound and
stump of cord is usually unimportant in the young animals. Serious
haemorrhage from the vessels of the cord sometimes occur in the adult, and
a persistent haemorrhage results when a subcutaneous vein is cut in making
the incision in the scrotum. This complication is not usually serious, and
can be prevented and controlled by observing proper precautions in cutting
off the cord, or by picking up the cut ends of the vessel and ligating it.
Packing the scrotal sack with sterile gauze or absorbent cotton, and
closing the incision with sutures may be practised for the purpose of
stopping this form of haemorrhage. The packing should be removed in about
twelve hours.
_The infection of the wound_ always follows castration. If the incision is
small and the operation is followed by swelling of the neighboring tissues,
the clotted blood, wound secretions and pus become penned up in the scrotal
sack. Local blood poisoning or peritonitis follows. This is not an uncommon
complication. It can be prevented by aseptic precautions in operating, and
insuring good drainage by extending the incision to the lowest part of the
scrotal sac. The scrotal sac always contracts down and becomes more or less
swollen within a day or two following castration. We must keep this in mind
when enlarging the opening, and be sure and make it plenty large to permit
the escape of the infectious matter. In castrating sheep, all wool in the
region of the scrotal sac should be clipped off, as this interferes with
drainage from the wound.
_Exercise following castration_ is almost as essential as clean quarters.
Lack of exercise leads to _oedematous swelling_ in the region of the
scrotum, and the lips of the incision may become adhered if the animal is
at rest. Colts and all mature animals that are confined in close quarters
should be examined within forty-eight hours following the operation, and
the condition of the wound noted. If closed, the hands should be cleaned
and disinfected, and the adhesion broken down with the fingers. It is best
to exercise horses daily.
It is unsafe to expose castrated animals to cold, damp, chilly weather. The
shock and soreness resulting from the operation render the animal highly
susceptible to pleurisy and pneumonia. This is especially true of young
colts.
_Inguinal hernia_ or "_rupture_" may complicate the operation. This form of
hernia is quite frequently met with in pigs, and only occasionally in the
other animals. This complication is usually overcome by practising what is
commonly termed the covered operation. The pig is usually held or hung up
by the hind legs. A larger animal is placed on its back. The hernia is
reduced by manipulating the mass of intestines with the fingers, so that
they drop back into the abdominal cavity. The part is carefully cleaned and
disinfected and an incision made through the scrotal wall, and the thin
covering or serous sac in which the testicle is lodged is exposed. The
testicle with the cord and covering is drawn well out of the scrotum and
held by an attendant. The operator then passes a needle carrying a strong
silk thread through the cord and covering, below the point where he intends
severing it. The needle is removed and the cord and covering ligated at
this point. The cord is then cut off about one-half an inch from the
ligature, and the incision in the scrotum made plenty large in order to
insure drainage.
It is very essential to the success of this operation that the animal be
dieted for twelve or eighteen hours before attempting to operate. The
after-treatment consists in giving the animal separate quarters and feeding
a light diet.
_Enlarged or scirrhous cords_ follow infection of the wound, usually with
spores of a certain fungus (_Botryomyces_). This complication more often
follows castration of cattle and pigs than of colts. Wrong methods of
operating, such as leaving the stump of the cord too long and insufficient
drainage for the pus and wound secretions, are the factors that favor this
complication. Scirrhous cords or fibrous tumors should be dissected out and
removed before they have become large and begun breaking down.
CASTRATION OF RIDGELING OR CRYPTORCHID ANIMALS.--In the ridgeling animal
one or both of the testicles have not descended into the scrotal sac, and
are usually lodged in the inguinal canal or abdominal cavity. If the
testicle is lodged in the inguinal canal the animal is termed a "flanker."
In yearling colts the testicular cord is sometimes short, and the testicle
is situated high up in the scrotum and inguinal canal. In examining a
supposed cryptorchid colt, he should be twitched. This may cause the
testicle to descend into the scrotum.
The castration of a true cryptorchid requires a special operation. When
properly performed and the animal given special after-care, the operation
is not followed by any serious complications. An abnormally large, diseased
testicle is sometimes met with that cannot be removed in the usual way, and
which complicates and increases the difficulty of operating.
CAPONIZING.--The castration or caponizing of the male chicken is commonly
practised in certain localities. This operation changes the disposition of
the cockerel. He becomes more quiet and sluggish, never crows, the head is
small, the comb and wattles cease growing and the hackle and saddle
feathers become well developed. A capon always develops more uniformly and
is larger than the cockerel.
_The best time to caponize the cockerel_ is when he weighs between two or
three pounds. If older and heavier, the testicle becomes so large that it
is very difficult to remove, and the danger from tearing the spermatic
artery and a fatal haemorrhage resulting is greater.
There are several kinds of _caponizing instruments_. They may be purchased
in sets. Each set should contain an instrument for removing the testicle; a
knife for making the incision through the abdominal wall; a sharp hook for
tearing through the thin membrane; spring spreader for holding the lips of
the incision apart; a blunt probe for keeping the intestines out of the way
of the operator; and a pair of tweezers for removing clots of blood. The
different instruments for removing the testicles are a spoon-like scoop,
spoon forceps and cannula. The spoon-like scoop is preferred by most
operators.
_The cockerel_ is confined for the operation by passing a strong noose of
cord around both legs, and a second noose around the wings close to the
body, that have weights fastened to them. The cords pass through holes or
loops in a barrel or board that is used for an operating table. This holds
the cockerel firmly and prevents his struggling.
_The bird should be prepared_ for the operation by withholding all feed and
water for a period of twenty-four hours or longer, for the purpose of
emptying out the intestine. The operator must have a strong light, in order
to work quickly and safely. Direct sunlight or electric light should be
used.
The instruments should be placed in a two per cent water solution of
carbolic acid. A second vessel containing a two per cent water solution of
liquor cresolis compound for cleaning the skin is necessary. Absorbent
cotton should be used for washing the wound.
_The general method of operating_ is as follows: The incision is made
between the last two ribs and in front of the thigh. The feathers over this
region should be removed, and the skin pulled to one side before making the
incision. An incision about one and one-half inches in length is made
through the skin and muscles, and the spreader inserted. The sharp hook is
then inserted and the thin serous membrane over the intestine is torn
through. The testicles are situated in the superior portion of the
abdominal cavity or under the back. On pushing the intestines to one side,
both testicles, which are about the size of a bean and yellowish in color,
can be seen. The lower one should be removed first. After removing both
testicles, blood clots, feathers, or any foreign body that may have gotten
into the wound should be picked up with the tweezers before removing the
spreaders and allowing the wound to close. No special after-treatment is
required.
_The most common complication_ is rupture of the spermatic artery. This
occurs at the time the testicle is torn loose and may be due to careless
methods, or operating on cockerels that are too large. If all of the
testicle is not removed from the abdominal cavity, the bird is termed a
"slip." Sometimes air puffs form after the operation. These should be
punctured with a sharp knife.
OVARIOTOMY, "SPAYING."--The removal of the ovaries, or ovariotomy, is
practised for the purpose of rendering the female more useful for meat
production, prolonging the period of lactation, overcoming vicious habits
and preventing oestrum or heat. The operation is commonly performed in the
heifer and bitch, occasionally in the mare, and at present rarely in the
sow.
_Heifers_ are usually spayed between the ages of eight and twelve months;
the _bitch_ and _sow_ when a few months old, or before the periods of heat
have begun. The _mare_ is spayed when mature. It is possible to spay the
female at any age, but the ages mentioned are the most convenient. Pregnant
animals should not be operated on. The season of the year makes little
difference in the results, providing the animal can be kept under close
observation and given the necessary care and treatment. The spring of the
year, just before turning the herd on pasture, is the best season to spay
heifers.
_All animals should be prepared_ for the operation by withholding all feed
for at least twenty-four hours before they are operated on, and it may be
advisable to give them a physic. It is easier to operate when the
intestinal tract is comparatively empty, and the death rate is lower than
when the animal is not properly prepared for the operation.
_The method of operating_ is not the same in the different species. In
young heifers and sows, the flank operation is preferred, and in mares and
cows, the vaginal operation. The median line operation is practised in
bitches. A spaying emasculator, or ecraseur, are the special instruments
need for removing the ovaries.
The animal must be properly confined for the operation. Heifers are usually
held in the standing position by fastening the head securely, and crowding
the left side of the animal against a solid board partition, or side of a
chute. If the vaginal operation is performed, the mare or cow may be
confined in stocks. The bitch is usually anesthetized and placed on her
back on a table that is inclined, so that the hind parts are elevated.
Ovariotomy cannot be successfully performed by an untrained and
inexperienced operator. The necessary precautions against the infection of
the part must be observed, in order to promote the healing of the wound and
prevent peritonitis. The seat of the operation should be carefully cleaned
and disinfected.
_Following the operation_ the animal should be fed a spare diet for a few
days. This is a very necessary part of the care of the bitch. The general
condition of the animal should be noted daily until there is no further
danger from wound infection. Healing is usually completed in from seven to
twelve days. The sutures should then be removed, and if stitch abscesses
occur, the part should be washed with a disinfectant.
QUESTIONS
1. What is the purpose of dehorning cattle? Give different methods of
removing the horns.
2. Give the causes and treatment of choking.
3. What is the purpose of castration and ovariotomy?
4. At what age is it best to practise castration and ovariotomy?
5. In what way should an animal be prepared for castration? Give a
description of the method of castration in the different animals.
6. What special care should be given following castration?
7. What are some of the complications that may follow castration?
PART V.--PARASITIC DISEASES
CHAPTER XXIV
PARASITIC INSECTS AND MITES
Parasitic insects are common causes of skin diseases in domestic animals.
The diseased conditions of the skin, and the irritation that they may cause
the animal, depend on the life history and habits of the parasite. Species
that are unable to live independently of a host and are permanent parasites
are usually the most injurious to the animal. This is especially true of
parasites that are capable of puncturing the skin or burrowing into it.
Temporary parasites may cause fatal forms of disease. This is true of the
larva? of the sheep bot-fly, which develop in the sinuses of the head,
causing severe inflammation of these parts, nervous symptoms and death. The
character of the symptoms of a parasitic disease depends on the habits of
the parasite, and the tissue or organ, that it may attack.
The parasitic flies belong to the order _Diptera_, and the families
_Muscidae_ and _OEstridae_. Fleas belong to the sub-order _Pulicidae_. The
order _Hemiptera_ includes the lice, and the most important families are
_Pediculidae_ and _Ricinidae_. Mites and ticks belong to the order
_Acarina_. The most important parasites belonging to this order are the
_Sarcoptidae_ and _Ixodidae_.
OESTRIDAE.--The three common bot-flies are the _Gastrophilus equi_,
_Hypoderma lineata_ and _OEstrus ovis_. These flies are important because
of the parasitic habits of their larva. They inhabit the stomach and
intestines of horses (Fig. 62); the subcutaneous tissue and skin of cattle;
and the sinuses of the head and nasal cavities of sheep.
_The common bot-fly of the horse_ (_G. equi_) has a heavy, hairy body. Its
color is brown, with dark and yellowish spots. The female fly can be seen
during the warm weather, hovering around the horse, and darting toward the
animal for the purpose of depositing the egg. The color of the egg is
yellow, and it adheres firmly to the hair. It hatches in from two to four
weeks, and the larva reaches the mouth through the animal licking the part.
From the mouth, it passes to the stomach, where it attaches itself to the
gastric mucous membrane (Fig. 62). Here it remains until fully developed,
when it becomes detached and is passed out with the fasces. The third stage
is passed in the ground. This takes place in the spring and early summer
and lasts for several weeks, when it finally emerges a mature fly.
[Illustration: FIG. 62.--A piece of the wall of the horse's stomach showing
the bot-fly larvae attached.]
_The bot-fly of the ox_ (_H. lineata_) is dark in color and about the size
of a honey-bee. On warm days, the female may be seen depositing eggs on the
body of the animal, especially in the region of the heels. This seems to
greatly annoy the animal, and it is not uncommon for cattle to become
stampeded. The egg reaches the mouth through the animal licking the part.
The saliva dissolves the shell of the egg and the larva is freed. It then
migrates from the gullet, wanders about in the tissue until finally it may
reach a point beneath the skin of the back. Here the larva matures and
forms the well-known swelling or warble. In the spring of the year it works
out through the skin. The next stage is spent in the ground. The pupa state
lasts several weeks, when the mature fly issues forth.
_The bot-fly of sheep_ (_O. ovis_) resembles an overgrown house-fly. Its
general color is brown, and it is apparently lazy, flying about very
little. This bot-fly makes its appearance when the warm weather begins, and
deposits live larvae in the nostrils of sheep. This act is greatly feared
by the animals, as shown by their crowding together and holding the head
down. The larva works up the nasal cavities and reaches the sinuses of the
head, where it becomes attached to the lining mucous membrane. In the
spring, when fully developed, it passes out through the nasal cavities and
nostrils, drops to the ground, buries itself, and in from four to six weeks
develops into the mature fly.
SYMPTOMS OF BOT-FLY DISEASES.--The larvae of the bot-fly of the horse do
not cause characteristic symptoms of disease. Work horses that are groomed
daily are not hosts for a large number of "bots," but young and old horses
that are kept in a pasture or lot and seldom groomed may become unthrifty
and "pot bellied," or show symptoms of indigestion.
Cattle suffer much pain from the development of the larva of the _H.
lineata_. During the spring of the year, the pain resulting from the
presence of the larvae beneath the skin and the penetration of the skin is
manifested by excitement and running about. Besides the loss in milk and
beef production, there is a heavy yearly loss from the damage to hides.
The parasitic life of the bot-fly of sheep results in a severe catarrhal
inflammation of the mucous membrane lining the sinuses of the head, and a
discharge of a heavy, pus-like material from the nostrils. The irritation
produced by the larvae may be so serious at times as to result in nervous
symptoms and death.
TREATMENT OF BOT-FLY DISEASES.--The treatment of the different bot-fly
diseases is largely preventive. This consists in either the destruction of
the eggs or the larvae.
The different methods of destroying the eggs of the bot-fly of the horse
are clipping the hair from the part, scraping off the eggs with a sharp
knife, or destroying them by washing the part infested with eggs with a two
or three per cent water solution of carbolic acid. This should be practised
every two weeks during the period when the female deposits the eggs.
Housing the cattle, or applying water solutions of certain preparations to
the skin that may keep the female from depositing eggs, may be practised
for the prevention of the ox-warble. The most practical method of ridding
cattle of this pest is to destroy the larvae. This can be done by examining
each animal and locating the swelling or warble and injecting a few drops
of kerosene into the opening in the skin. A better method is to enlarge the
opening in the skin with a sharp knife, squeeze out the grub and destroy
it. This should be practised in late winter and early spring.
The application of pine tar to the nostrils of sheep is the most practical
method of preventing "grub in the head." This should be practised every few
days during the summer months. A very good preventive measure is plenty of
shade for the flock. Valuable animals may be treated by trephining into the
head sinus and removing the "grub."
LICE.--The sucking lice belong to the genus _Hoematopinus_, and the biting
lice of mammals belong to the genus _Trichodectes_. Different species of
sucking and biting lice occur on the different species of farm animals.
Poultry act as hosts for many different species of biting lice belonging to
the following genuses: _Lipiurus, Goniodes, Goniocotes_ and _Menopon_.
_The common sucking lice_ occurring on animals are the large-headed horse
louse, _H. macrocephalus_; the long-nosed ox louse, _H. tenuirostris_; the
large-bellied ox louse, _H. curysternus_; the _H. stenopses_ of sheep; _H.
suis_ of swine; and the _H. piliferus_ of the dog.
The _common biting lice_ (Fig. 63) that are found on domestic animals are
the _T. pilosus_ and _T. pubescens_ of solipeds, _T. scalaris_ of the ox,
_T. spoerocephalus_ of sheep and goats, _T. latus_ and _T. subrostratus_ of
the dog and cat. _Menopon palidum, Lipiurus variabilis_ and _Gonoides
dissimilis_ are the common lice found on poultry.
[Illustration: FIG. 63.--Biting louse.]
SYMPTOMS OF LICE.--The symptoms of lousiness depend on the variety of lice
present, the degree to which the animal is infested with them, its physical
condition and the care that it receives. Lice multiply more rapidly and
cause greater loss during the winter months than they do in the summer,
when the animals are not housed and the opportunity for infection from the
surroundings is not so great. The sucking louse (Fig. 64) is the most
injurious and irritating. The irritation and loss of blood that the animal
may suffer when badly infested by this parasite may result in marked
unthriftiness. Young and old animals that are not well cared for suffer
most. The biting louse may bite through the superficial layer of the skin,
and cause the animal to bite and rub the part. This irritation to the skin
prevents the animal from becoming rested, and after a time seriously
interferes with its thriftiness.
_Horses and mules_ show a staring, dirty, rough coat. The mane and tail may
become broken and matted. The animal rubs against the stall, fences and
trees, and bites the skin in its efforts to relieve the irritation. On
examining the coat, nits are found adhering to the hair (Fig. 65). We
should examine the parts of the skin covered by the long hair for the
sucking lice; and the withers, abdomen and limbs for the biting lice.
[Illustration: FIG. 64.--Sucking louse (much enlarged).]
[Illustration: FIG. 65.--Nits attached to hair (much enlarged).]
_The symptoms of lousiness in cattle_ are about the same as occur in
horses. Licking and rubbing the skin are prominent symptoms in cattle, and
the coat becomes dirty and rough. The licked part is matted and curled. The
lice may be discovered by parting the hair along the back and rump.
_The biting louse of sheep_ causes the fleece to become matted and tufts of
wool are pulled out. This is brought about by the sheep rubbing and
nibbling the fleece, and the lice cutting through the wool. The loss due to
the damage to the fleece is usually greater than that resulting from
unthriftiness.
_The hog-louse_ is the largest specie known. As well as the largest, it is
the most common of all lice found on domestic animals. The favorite points
of attack are the under surface of the body, the neck and the inside of the
thighs. The irritation and itching are severe, and the hog rubs and
scratches the skin. Young hogs suffer most from this parasite, and their
thriftiness is greatly interfered with.
The long-haired breeds of _dogs_ suffer more from lice than the
short-haired breeds. The almost constant scratching and biting of the skin
result in its becoming badly irritated and scabby. The symptoms differ
little from irritation to the skin caused by fleas, but the presence of
biting or sucking lice enables the person making the examination to
determine the cause of the irritation.
Lice are the most common parasites of _poultry_. It is uncommon to meet
with a flock of fowls that are not hosts for one or more of the many
different varieties of bird lice. Restlessness, picking, scratching,
flapping the wings, abandoning the nest and loss of condition are common
symptoms. Young birds suffer most from lice. This is especially true of
young chickens, death frequently resulting. Old fowls may show little
inconvenience unless badly infested. The finding of the lice with the head
imbedded in the skin or on the feathers enables the person making the
examination to positively diagnose the case. The head, back, region of the
vent and beneath the wings are the parts that should be carefully examined
for lice.
TREATMENT OF LOUSINESS.--The preventive treatment is very important. This
consists in carefully examining all animals or birds that have been
purchased recently, and if found to harbor lice, excluding them from the
herd or flock until after they have been properly treated.
It is impossible to rid animals of lice if the quarters are thoroughly
cleaned and disinfected. This is necessary in order to destroy lice that
have become scattered about by the lousy animals, and prevent the
reinfection of the treated animals. The best method to use in cleaning the
quarters is to remove all litter and manure from the stable or houses and
their immediate surroundings. It should be burned, or hauled to a field or
lot where other animals cannot come in contact with it for a few months.
The walls, floors and partitions should be sprayed with a three per cent
water solution of liquor cresolis compositus. Lime may be scattered about
the buildings, yards and runs. The most satisfactory method of destroying
lice on the bodies of animals is by washing or dipping in a water solution
or mixture of some reliable disinfectant or oil.
_Running hogs through a dipping tank_ that contains a one or two per cent
water solution of liquor cresolis compositus, or a coal tar disinfectant,
or that has from three-fourths to one and one-half inches of oil on top of
the water, is the most satisfactory method of destroying the hog louse.
Because of the thinness of the hog's coat and the danger from irritating
the skin when strong solutions of a disinfectant are used, most swine
breeders prefer crude oil as a remedy for lousiness in hogs. Crude oil may
be applied to the bodies of hogs with a swab. If this method is practised
instead of dipping, it is advisable to crowd the hogs into a small pen, and
apply the oil in front and between the thighs and back of the arms. This
may be practised during the cold weather when it is impossible to dip the
animals.
_Horses_ may be washed with a one or two per cent water solution of liquor
cresolis compositus, or a coal tar disinfectant. If the weather is cold, it
is advisable to pick a sunny day, and blanket the animal after rubbing it
as dry as possible in order to prevent chilling and catching cold.
_Cattle_ may be treated in the same manner as horses. Mercurial ointment
rubbed in small amounts on the skin back of the horns and ears, where the
animal cannot lick it, is a common remedy. The absorption of a small amount
of this drug does the animal no harm, but a larger quantity may salivate
it.
_Sheep_ are treated by dipping in a water solution of a reliable coal tar
disinfectant. This should not be practised during cold weather, as the
fleece does not dry out. Insect powder may be dusted into the fleece when
it is impossible to dip the animal.
A very satisfactory treatment for lousiness in _dogs_ and _cats_ is to wash
them with carbolized soap. We should wait a few minutes before rinsing off
the soapy lather and drying the coat.
A number of different remedies are used for the treatment of lousiness in
_poultry_. Dust baths and insect powder are recommended. Ointments are
commonly used. One part sulfur and four parts vaseline, or lard, may be
made into an ointment and applied to the head, neck, under the wings and
around the vent. Mercurial ointment may be applied to the margin of the
vent. Neither of them should be used for destroying lice on young chicks.
Mercurial ointment should be used very carefully because of its poisonous
effect. Lard may be used for destroying lice on young chicks. Crude
petroleum may be sprayed among the feathers by a hand-sprayer, while the
fowls are suspended by the feet.
[Illustration: FIG. 66--Sheep-tick.]
None of the disinfectants and oils recommended for dipping and washing
lousy animals destroy the nits. This makes it necessary to re-treat the
animal in from eight to ten days after the first treatment.
THE SHEEP-TICK.--This is not a true tick. It resembles a fly more than it
does a tick, and its right name is _Melophagus ovinus_ (Fig. 66). Louse-fly
is a better name for this parasite than tick, as its entire life is spent
on the body of a sheep. The general color of the body is brown. The legs
are stout, covered with hair and armed with hooks at their extremities. The
mouth parts consist of a tubular, toothed proboscis with which the parasite
punctures the skin and sucks the blood. Within a few hours after birth, the
larvae develop into pupae, which are hard, dark brown in color and firmly
glued to the wool. The young louse-fly emerges from the pupa in from three
to four weeks.
The sheep-tick is a very common external parasite. The adult parasites and
the pupae are large and easily found. When badly infested with ticks, a
sheep will rub, dig and scratch the skin and fleece. This results in pieces
of wool becoming pulled out and the fleece appears ragged. After clipping
the ticks migrate from the ewes to the lambs, which may become unthrifty
and weak.
_The treatment_ consists in dipping the flock in a one or two per cent
water solution of a coal-tar dip. Dips containing arsenic are most
effective in ridding sheep of ticks.
[Illustration: FIG. 67.--Sheep scab mite, ventral view. (From Farmers'
Bulletin No. 159, United States Department of Agriculture.)]
SCABIES.--This parasitic disease is one of the oldest and most prevalent
diseases of the skin. It is commonly known as scab or mange. The animals
most commonly affected are sheep, horses and cattle.
_The disease is caused_ by _small mites_ or _acari_ that are naturally
divided into the _Sarcoptes_, which burrow under the epidermis, forming
galleries; the _Psoroptes_, which live on the surface of the skin where
they are sheltered by scabs and scurf; and the _Symbiotes_, which also live
on the surface of the skin, but prefer the regions of the hind feet and
legs.
Acari multiply rapidly and live their entire life on the body of the host.
A new generation is produced in about fifteen days. Gerlach has estimated
the natural increase in three months at 1,000,000 females and 500,000
males. Scab and mange are exceedingly contagious diseases.
[Illustration: FIG. 68.--Sheep scab.]
_Common sheep scab_ is caused by that specie of mites known as the
_Psoroptes communis var. ovis_ (Fig. 67). Any part of the body may become
affected. The bites of the mites greatly irritate the skin, and the animal
scratches, bites and rubs the part in its effort to relieve the intense
itching. The skin becomes inflamed and scabby, the wool is pulled and
rubbed out, and the fleece becomes ragged (Fig. 68). By pulling wool out of
the newly infested area, or collecting skin scrapings and placing this
material on black paper in a sunny, warm place, the mites may be seen
crawling over the paper. This method of diagnosis should be resorted to in
all suspicious cases of skin disease, and before the disease has developed
to any great extent.
The mite that most commonly causes _mange in cattle_ is the _Psoroptes
communis var. bovis_. It may invade the skin in the different regions of
the body, but it is in the regions of the tail and thighs that the first
evidence of the mange is noticed. The animal rubs, scratches, and licks the
part. The itching is intense. The hair over the part is lost and the skin
appears inflamed, thickened, moist, or covered with white crusts. Cracks
and sores may form in the skin. The examination of scrapings from the
inflamed skin should be practised in order to confirm the diagnosis.
_Mange in horses_ may be caused by either psoroptic or sarcoptic mites.
_Psoroptes communis var. equi_ seems to be the more common parasite. The
itching is intense. The inflamed areas are small at first and scattered
over the regions of the rump, back and neck (Fig. 69). After a time the
small areas come together and form large patches, and further spreading of
the inflammation results from grooming, scratching and biting the skin.
Scattered, elevated eruptions on the skin from which the hair has dropped
out are first noticed. These parts may show yellowish scabs. Later the skin
is thickened, smooth, wrinkled, cracked, or covered with sores. Scrapings
made from the inflamed areas of the skin may show the psoroptic mites.
_Mange in hogs_ is comparatively rare. It is caused by one of the sarcoptic
mites. The thin portions of the skin are usually first invaded. There are
violent itching and rubbing, and small, red elevations occur on the skin in
the region of the ears, eyelids or inner surface of the thighs, depending
on the part first invaded. The skin becomes greatly thickened and covered
with crusts and scabs. Pus formation and ulceration may occur.
TREATMENT OF SCAB AND MANGE.--A careful inspection of recently purchased
animals that pass through stockyards, or are shipped from sections where
scab and mange are common skin diseases, is an important preventive
measure. Infected animals should be completely isolated from the herd, and
kept apart from other animals until after they have been treated. Hogs that
are slightly infected should be quarantined and treated. If badly affected,
they should be killed, and the carcass disposed of by burning or burying.
[Illustration: FIG. 69.--A severe case of mange.]
_The different remedies used_ in the treatment of the disease may be
applied by dipping, hand dressing or washing, pouring, smearing and
spotting. The first method is the most satisfactory. The last method may be
used when a small area of the skin is involved, and during the cold
weather. Washing or dipping the animal with a two per cent water solution
of liquor cresolis compositus is an effective remedy for the psoroptic
forms of scab and mange. Tobacco, lime and sulfur, and arsenical dips are
recommended in the treatment of sheep and cattle. Ointments are recommended
for animals that are slightly affected with mange. Lime and sulfur dips are
recommended by the Bureau of Animal Industry. Small infected areas of the
skin may be treated by applying sulfur-iodide ointment. The following
ointment is commonly recommended: potassium sulfide ten parts, potassium
carbonate two parts, and lard three hundred parts.
Sheep cannot be safely dipped for scab during the cold weather. If
thickened and scabby, the skin should be scrubbed with the dip, or the
animal prepared for dipping or washing by first clipping the hair or wool
and scrubbing the skin with water and a good soap. In order to prevent
reinfection, it is necessary to remove the animal to new quarters, or
thoroughly clean and disinfect the old. It is necessary to wash or spray
the fences, floors, walls, brushes and curry-combs with a disinfecting
solution. Manure and other litter should be removed to a place where there
is no danger from its distributing the infection.
DISEASES OF POULTRY CAUSED BY MITES.--Mites or acarina that cause diseases
of poultry may live on the feathers, beneath the skin, and within the body
of the fowl.
_The small, red mite (Dermanyssus gallinae)_ remains on the surface of the
body only when feeding, and spends the rest of the time under collections
of filth and in cracks in the roosts and walls of the house. This parasite
causes the birds to become restless, emaciated and droopy.
_A very small mite (Sarcoptes mutans)_ is the cause of scaly leg. It lives
under the skin. The joints of the feet appear affected, and the foot and
leg become enlarged, roughened and scaly.
_Depluming scabies_ is caused by _Sarcoptes laevis var. gallinae_. This
mite causes the feathers to break off at the surface of the skin. Masses of
epidermic scales may form around the broken ends of the feathers. The
diagnosis can be confirmed by examining the skin lesions and finding the
mite.
_The air sac mite_ (_Cytodites nudus_) may cause sufficient irritation to
the mucous membrane lining the air sacs to seriously obstruct the air
passages with mucus, or produce death from exhaustion. A post-mortem
examination of a fowl that has died of this disease shows the mites on the
surface of the lining membrane of the air-sacs. They appear as a white or
yellow dust.
TREATMENT OF POULTRY DISEASES CAUSED BY MITES.--Diseases of poultry caused
by mites may be prevented by quarantining all recently purchased birds for
a period of from two to four weeks, and by keeping the poultry houses
clean. Birds that are found infested with parasites should be destroyed or
returned. In case the bird is valuable and suffering from external
parasites only, it should be given the necessary treatment.
_Red mites may be destroyed_ by thoroughly cleaning the poultry house, and
spraying the roosts, nests, walls and floor with a three per cent water
solution of liquor cresolis compositus. This should be repeated twice a
week for two weeks.
_Scaly-leg may be treated_ by applying a penetrating oil to the feet and
lower part of the leg. It is advisable to first remove the scales by
scrubbing the part with soap and warm water. Dipping the feet in a mixture
of kerosene one part and linseed oil two parts is recommended. This should
be repeated as often as necessary.
QUESTIONS
1. Describe the different bot-flies.
2. Give the life history of the bot-fly of the horse; of the ox; of sheep.
3. Give the symptoms of bot-fly diseases.
4. Give the symptoms of lousiness.
5. Give treatment for lousiness of different farm animals.
6. What is the damage from the sheep-tick? Give treatment.
7. Describe the injury from scabies and mange.
8. Give treatments for these diseases.
9. Mention the several poultry mites and tell how to treat them.
CHAPTER XXV
ANIMAL PARASITES
The common parasitic diseases of domestic animals are caused by the
following groups of worms: _Flukes_ or _trematoides_; _tapeworms_ or
_Cestoides_; _thorn-headed worms_ or _Acanthocephales_; and _round-worms_
or _Nematoids_. Flat worms, such as tapeworms and flukes, require secondary
hosts. The immature and mature forms of tapeworms are parasites of
vertebrate animals, but an invertebrate host is necessary for the
completion of the life cycle of the fluke. The hog is the only specie of
domestic animals that becomes a host for the thorn-headed worm. The
round-worm is a very common parasite. There are many species belonging to
this class.
[Illustration: FIG. 70.--Liver flukes.]
DISTOMA HEPATICUM (COMMON LIVER FLUKE).--Sheep are the most common hosts
for this parasite. It is present in the gall ducts and livers, and causes a
disease of the liver known as liver rot. The liver fluke is flat or
leaf-like and from thirteen to fifteen mm. long (Fig. 70). The head portion
is conical. It has an oval and ventral sucker, and the body is covered with
scaly spines. The eggs are oval and brownish in color.
_The life history_, in brief, is as follows: Each adult is capable of
producing an immense number of eggs which are carried down the bile ducts
with the bile to the intestine, and are passed off with the faeces. Under
favorable conditions for incubation, such as warm, moist surroundings, the
ova or eggs hatch and the _ciliated embryos_ become freed. The embryo next
penetrates into the body of certain snails and encysts. The _sporocyst_, as
it is now called, develops into a third generation known as _redia_ which
escape from the cyst. The _daughter redia_ or _cercaria_, as they are now
termed, leave the body of the snail and finally become encysted on the
stems of grass, cresses and weeds. When taken into the digestive tract of
the animal grazing over infested ground, the immature flukes are freed by
the digestive juices. They then pass from the intestine into the bile
ducts. The period of development varies from ten to twenty weeks; each
sporocyst may give rise to from five to eight _redia_ and each redia to
from twelve to twenty _cercaria_.
Fluke diseases occur among animals pastured on low, wet, undrained land.
Drying ponds and lakes are the homes of the fresh water snails, and in such
places there are plenty of hosts for the immature flukes. Wet seasons favor
the development of this parasite. Cattle and sheep that pasture on river
bottom land in certain sections of the southern portion of the United
States are frequently affected with fluke diseases.
_The symptoms of liver rot of sheep_ may be divided into two stages. The
first stage is marked by increase in weight and improved condition. In the
second stage of the disease, the animal shows a pale skin and mucous
membrane, dropsical swellings, loss of flesh and weakness. The character of
the symptoms of the disease depends on the age of the animals and the care
that they receive. Young, poorly cared for animals suffer severely from the
disease, and the death rate is usually heavy. The finding of fluke ova in
the faeces is conclusive evidence of the nature of the disease. It may be
advisable to kill one of the sick animals, and determine the nature of the
disease by a post-mortem examination.
[Illustration: FIG. 71.--Tapeworm larvae in liver (_Echinococcus
polymorphus_).]
[Illustration: FIG. 72.--Tapeworms.]
_The treatment is preventive_. Drainage water from a pasture infested with
snails harboring immature flukes is a source of infection, and should not
be used as a water supply for cattle and sheep. In sections where the
disease is prevalent, sheep should not be pastured on low, poorly-drained
land. Such land should be used for pasturing horses and cattle, but if
possible, it should be first drained and cultivated. Careful feeding and
good care may help the affected animals to recover.
[Illustration: FIG. 73.--Tapeworm larvae in the peritoneum (_Cysticercus
cellulosa_).]
TAPEWORMS OR CESTOIDES.--Tapeworms are formed by a chain of segments,
joined together at their ends, and are flat or ribbon-shaped (Fig. 71). The
head segment is small, and possesses either hooks or suckers. It is by
these that the worm attaches itself to the lining membrane of the
intestine. The anterior segments are smaller and less mature than the
posterior segments. Each segment is sexually complete, possessing both the
male and female organs, and when mature, one or more of them break off and
are passed out with the faeces. The mature or ripe segments are filled with
ova. On reaching the digestive tract of a proper host, usually with the
drinking water or fodder, the embryo is freed from the egg. The _armed
embryo_ uses its hooklets in boring its way through the wall of the
intestine. It then wanders through the tissues of its host until it finally
reaches a suitable place for development (Figs. 71 and 73). On coming to
rest, it develops into the larva or bladder-worm, which when eaten by a
proper host gives rise to the mature tapeworm.
The following tables give the most important tapeworms:
ADULT FORMS
Name Host Organ
Taenia expansa Sheep and ox Intestine
Taenia fimbriata Sheep Liver
Taenia denticulata Cattle Intestine
Taenia alba Cattle Intestine
Taenia perfoliata Solipeds Intestine
Taenia mamillana Solipeds Intestine
Taenia echinococcus Dog Intestine
LARVAL FORMS
Name Host
Cysticercus bovis Cattle
Cysticercus cellulosa Swine and man
Cysticercus tennicollis Cattle, sheep and swine
Coenurus cerebralis Cattle and sheep
Echinococcus polymorphus Cattle, sheep, swine and man
The adult tapeworms _Taeniae saginata_ and _soleum_, of which the
_Cysticerci bovis_ and _cellulosa_ are the larvae forms, occur in man. The
larvae are present in meat and pork, and this form of parasitism is termed
beef measles in cattle and pork measles in hogs. Man becomes host for these
two forms of tapeworms through eating measly pork or beef that is not
properly cooked.
The dog is the host for _Taeniae marginala_, _coenurus_ and _echinococcus_.
The larvae forms of these _taeniae_ are the _Cysticercus tennicollis_,
_Coenurus cerebralis_ and _Echinococcus polymorphus_. _C. tennicollis_ is a
parasite of the serous or lining membranes of the body cavities. It is not
of great economic importance. _C. cerebralis_ is a parasite of the brain of
sheep, and may cause a heavy death rate in flocks that are infested with
it. _E. polymorphus_ is a parasite of the liver, but it may occur in other
organs.
THE THORN-HEADED WORM OR ACANTHOCEPHALE.--This parasite requires a
secondary host. In this case a particular species of the May-beetle larva
or white grub that is commonly found about manure piles and in clover
pastures is the host. The hog eats a white grub that is host for the larval
form. The digestive juices free the larva, it then becomes attached to the
intestinal mucous membrane and develops into the adult thorn-headed worm
(Fig. 74). This parasite is characterized by a hooked proboscis or thorn at
its anterior extremity, and the absence of a distinct digestive tract. The
male is much smaller than the female. The eggs are passed out of the
intestine with the faeces.
[Illustration: FIG. 74.--Thorn-headed worms.]
THE ROUND-WORMS OR NEMATOIDS.--Round-worms are very common parasites of
domestic animals (Fig. 75). This group of worms is characterized by their
cylindrical form, the presence of a true digestive canal and the separation
into two sexes, male and female. The life history is more simple than in
the flat worms. Intermediate hosts are not required for the development of
the common forms. The eggs and embryos are deposited by the female in the
intestinal tract, air passages, or excretory ducts of the kidneys of the
host. Development may be completed here, or the eggs and embryos are passed
off with the body excretions. They may live for a short time outside the
animal body, or undergo certain development and again infest a host of the
same species from which they came, through the water, grass and fodder that
the animal may take into its digestive tract.
[Illustration: FIG. 75.--Large round-worm in intestine of hog.]
The following species of nematoids are common parasites of domestic
animals:
SOLIPEDS