of an increased quantity of blood in the vessels and an exudation of
its fluid into the tissues surrounding them, but in passive congestion
we have a dark, thick blood which has lost its oxygen, instead of the
rich, combustible blood rich in oxygen which is found in active
congestion.
The termination of congestion is by resolution or inflammation. In the
first case, the choked-up blood vessels find an outlet for the excessive
quantity of blood and are relieved; the transuded serum or fluid of the
blood is reabsorbed, and the part returns almost to its normal
condition, with, however, a tendency to weakness predisposing to future
trouble of the same kind. In the other case further alterations take
place, and we have inflammation.
INFLAMMATION.
(Plates I and II.)
Inflammation is a hypernutrition of a tissue. It is described by Dr.
Agnew, the surgeon, as "a double-edged sword, cutting either way for
good or for evil." The increased nutrition may be moderate and cause a
growth of new tissue, a simple increase of quantity at first; or it may
produce a new growth differing in quality; or it may be so great that,
like luxuriant, overgrown weeds, the elements die from their very haste
of growth, and we have immediate destruction of the part. According to
the rapidity and intensity of the process of structural changes which
takes place in an inflamed tissue, inflammation is described as acute or
chronic, with a vast number of intermediate forms. When the phenomena
are marked it is termed sthenic; when less distinct, as the result of a
broken-down and feeble constitution in the animal, it is called
asthenic. Certain inflammations are specific, as in strangles, the
horsepox, glanders, etc., where a characteristic or specific cause or
condition is added to the origin, character of phenomena, or alterations
which result from an ordinary inflammation. An inflammation may be
circumscribed or limited, as in the abscess on the neck caused by the
pressure of a collar, in pneumonia, in glanders, in the small tumors of
a splint or a jack; or it may be diffuse, as in severe fistulas of the
withers, in an extensive lung fever, in the legs in a case of grease, or
in the spavins which affect horses with poorly nourished bones. The
causes of inflammation are practically the same as those of congestion,
which is the initial step of all inflammation.
The temperament of a horse predisposes the animal to inflammation of
certain organs. A full-blooded animal, whose veins show on the surface
of the body, and which has a strong, bounding heart pumping large
quantities of blood into the vascular organs like the lungs, the
intestines, and the laminae of the feet, is more liable to have
pneumonia, congestive colics, and founder, than lymphatic, cold-blooded
animals which have pleurisies, inflammation of the bones, spavins,
ringbones, inflammation of the glands of the less vascular skin of the
extremities, greasy heels, thrush, etc.
[Illustration: PLATE I.
INFLAMMATION.
1--_Uninflamed wing of the bat._
2--_Inflamed wing of the bat._]
[Illustration: PLATE II.
INFLAMMATION.
1--_Non-inflamed mesentery of the frog, 400 diameters, reduced 1/2: a,
a, Venule with red and white corpuscles; b, b, Gelatinous nerve fibre;
c, Capillary; d, d, Dark-bordered nerve fibre; e, e, Connective tissue
with connective tissue corpuscles and leucocytes scattered sparsely
through it._
2--_Inflamed mesentery of the frog, 400 diameters, reduced 1/2: a, a,
Venule filled with red and white corpuscles, the red in the centre and
the white crowding along the walls; c, c, Capillary, distended with red
and white corpuscles, number of the white much decreased; d, d,
Connective tissue between venule and capillary filled with migrated
leucocytes; e, e, Connective tissue with less infiltration; f,
Dark-bordered nerve fibre; g, Number of nuclei, in sheaths increased._]
Young horses have inflammation of the membranes lining the air passages
and digestive tract, while older animals are more subject to troubles in
the closed serous sacs and in the bones.
The work to which a horse is put (saddle or harness, speed or draft)
will influence the predisposition of an animal to inflammatory diseases.
As in congestion, the functional activity of a part is an important
factor in localizing this form of disease. Given a group of horses
exposed to the same draft of cold air or other exciting cause of
inflammation, the one which has just been eating will be attacked with
an inflammation of the bowels; the one that has just been working so as
to increase its respiration will have an inflammation of the throat,
bronchi, or lungs; the one that has just been using its feet excessively
will have a founder or inflammation of the laminae of the feet.
The direct cause of inflammation is usually an irritant of some form.
This may be a pathogenic organism--a disease germ--or it may be
mechanical or chemical, external or internal. Cuts, bruises, injuries of
any kind, parasites, acids, blisters, heat, cold, secretions, such as an
excess of tears over the cheek or urine on the legs, all cause
inflammation by direct injury to the part. Strains or wrenches of
joints, ligaments, and tendons cause trouble by laceration of the
tissue.
Inflammations of the internal organs are caused by irritants as above,
and by sudden cooling of the surface of the animal, which drives the
blood to that organ which at the moment is most actively supplied with
blood. This is called repercussion. A horse which has been worked at
speed and is breathing rapidly is liable to have pneumonia if suddenly
chilled, while an animal which has just been fed is more liable to have
a congestive colic if exposed to the same influence, the blood in this
case being driven from the exterior to the intestines, while in the
former it was driven to the lungs.
_Symptoms._--The symptoms of inflammation are, as in congestion, change
of color, due to an increased supply of blood; swelling, from the same
cause, with the addition of an effusion into the surrounding tissues;
heat, owing to the increased combustion in the part; pain, due to
pressure on the nerves, and altered function. This latter may be
augmented or diminished, or first one and then the other. In addition to
the local symptoms, inflammation always produces more or less
constitutional disturbance or fever. A splint or small spavin will cause
so little fever that it is not appreciable, while a severe spavin, an
inflamed joint, or a pneumonia may give rise to a marked fever.
The alterations in an inflamed tissue are first those of congestion,
distention of the blood vessels, and exudation of the fluid of the blood
into the surrounding fibers, with, however, a more nearly complete
stagnation of the blood; fibrin, or lymph, a plastic substance, is
thrown out as well, and the cells, which we have seen to be living
organisms in themselves, no longer carried in the current of the blood,
migrate from the vessels and, finding proper nutriment, proliferate or
multiply with greater or lesser rapidity. The cells which lie dormant in
the meshes of the surrounding fibers are awakened into activity by the
nutritious lymph which surrounds them, and they also multiply.
Whether the cell in an inflamed part is the white ameboid cell of the
blood or the fixed connective tissue embedded in the fibers, it
multiplies in the same way. The nucleus in the center is divided into
two, and then each again into two, ad infinitum. If the process is slow,
each new cell may assimilate nourishment and become, like its ancestor,
an aid in the formation of new tissues; if, however, the changing takes
place rapidly, the brood of young cells have not time to grow or use up
the surrounding nourishment, and, but half developed, they die, and we
then have destruction of tissue, and pus or matter is formed, a material
made up of the imperfect dead elements and the broken-down tissue.
Between the two there is an intermediate form, where we have imperfectly
formed tissues, as in "proud flesh," large, soft splints; fungous
growths, greasy heels, and thrush.
Whether the inflamed tissue is one like the skin, lungs, or intestines,
very loose in their texture, or a tendon or bone, dense in structure,
and comparatively poor in blood vessels, the principle of the process is
the same. The effects, however, and the appearance may be widely
different. After a cut on the face or an exudation into the lungs, the
loose tissues and multiple vessels allow the proliferating cells to
obtain rich nourishment; absorption can take place readily, and the part
regains its normal condition entirely, while a bruise at the heel or at
the withers finds a dense, inextensible tissue where the multiplying
elements and exuded fluids choke up all communication, and the parts die
(necrose) from want of blood and cause a serious quittor, or fistula.
This effect of structure of a part on the same process shows the
importance of a perfect knowledge in the study of a local trouble, and
the indispensable part which such knowledge plays in judging of the
gravity of an inflammatory disease, and in formulating a prognosis or
opinion of the final termination of it. It is this which allows the
veterinarian, through his knowledge of the intimate structure of a part
and the relations of its elements, to judge of the severity of a
disease, and to prescribe different modes of treatment in two animals
for troubles which, to the less experienced observer, appear to be
absolutely identical.
_Termination of inflammation._--Like congestion, inflammation may
terminate by resolution. In this case the exuded lymph undergoes
chemical change, and the products are absorbed and carried off by the
blood vessels and lymphatics, to be thrown out of the body by the
kidneys, liver, the glands of the skin, and the other excretory organs.
The cells, which have wandered into the neighboring tissues from the
blood vessels, gradually disappear or become transformed into fixed
cells. Those which are the result of the tissue cells, wakened into
active life, follow the same course. The vessels themselves contract,
and, having resumed their normal caliber, the part apparently reassumes
its normal condition; but it is always weakened, and a new inflammation
is more liable to reappear in a previously inflamed part than in a sound
one. The alternate termination is necrosis, or mortification. If the
necrosis, or death of a part, is gradual, by small stages, each cell
losing its vitality after the other in more or less rapid succession, it
takes the name of ulceration. If it occurs in a considerable part at
once, it is called gangrene. If this death of the tissues occurs deep in
the organism, and the destroyed elements and proliferated and dead cells
are inclosed in a cavity, the result of the process is called an
abscess. When it occurs on a surface, it is an ulcer, and an abscess by
breaking on the exterior becomes then also an ulcer. Proliferating and
dying cells, and the fluid which exudes from an ulcerating surface and
the debris of broken-down tissue is known as pus, and the process by
which this is formed is known as suppuration. A mass of dead tissue in a
soft part is termed a slough, while the same in bone is called a
sequestrum. Such changes are especially liable to occur when the part
becomes infected with microorganisms that have the property of
destroying tissue and thus causing the production of pus. These are
known as pyogenic microorganisms. There are also bacilli that are
capable of multiplying in tissues and so irritating them as to cause
them to die (necrose) without forming pus.
_Treatment of inflammation._--The study of the causes and pathological
alterations of inflammation has shown the process to be one of
hypernutrition, attended by excessive blood supply, so this study will
indicate the primary factor to be employed in the treatment of it. Any
agent which will reduce the blood supply and prevent the excessive
nutrition of the elements of the part will serve as a remedy. The means
employed may be used locally to the part, or they may be constitutional
remedies, which act indirectly.
_Local treatment._--Removal of the cause will frequently allow the part
to heal at once. Among causes of inflammation may be mentioned a stone
in the frog, causing a traumatic thrush; a badly fitting harness or
saddle, causing ulcers of the skin; decomposing manure and urine in a
stable, which, by their vapors, irritate the air tubes and lungs and
cause a cough.
Motion stimulates the action of the blood, and thus feeds an inflamed
tissue. This is alike applicable to a diseased point irritated by
movement to an inflamed pair of lungs surcharged with blood by the use
demanded of them in a working animal, or to an inflamed eye exposed to
light, or an inflamed stomach and intestines still further fatigued by
feed. Rest, absolute quiet, a dark stable, and small quantities of
easily digested feed will often cure serious inflammatory troubles
without further treatment.
The application of ice bags or cold water by bandages, douching with a
hose, or irrigation with dripping water, contracts the blood vessels,
acts as a sedative to the nerves, and lessens the vitality of a part; it
consequently prevents the tissue change which inflammation produces.
Either dry or moist heat acts as a derivative. It quickens the
circulation and renders the chemical changes more active in the
surrounding parts; it softens the tissues and attracts the current of
blood from the inflamed organ; it also promotes the absorption of the
effusion and hastens the elimination of the waste products in the part.
Heat may be applied by hand rubbing or active friction and the
application of warm coverings (bandages) or by cloths wrung out of warm
water; or steaming with warm, moist vapor, medicated or not, will answer
the same purpose. The latter is especially applicable to inflammatory
troubles in the air passages.
Local bleeding frequently affords immediate relief by carrying off the
excessive blood and draining the effusion which has already occurred. It
affords direct mechanical relief, and, by a stimulation of the part,
promotes the chemical changes necessary for bringing the diseased
tissues to a healthy condition. Local blood-letting can be done by
scarifying, or making small punctures into the inflamed part, as in the
eyelid of an inflamed eye, or into the sheath of the penis, or into the
skin of the latter organ when congested, or the leg when acutely
swelled.
Counterirritants are used for deep inflammations. They act by bringing
the blood to the surface and consequently lessening the blood pressure
within. The derivation of the blood to the exterior diminishes the
amount in the internal organs and is often very rapid in its action in
relieving a congested lung or liver. The most common counterirritant is
mustard flour. It is applied as a soft paste mixed with warm water to
the under surface of the belly and to the sides, where the skin is
comparatively soft and vascular. Colds in the throat or inflammations at
any point demand the treatment applied in the same manner to the belly
and sides and not to the throat or on the legs, as so often used.
Blisters, iodin, and many other irritants are used in a similar way.
_Constitutional treatment_ in inflammation is designed to reduce the
current of blood, which is the fuel for the inflammation in the diseased
part, to quiet the patient, and to combat the fever or general effects
of the trouble in the system, and to favor the neutralization or
elimination of the products of the inflammation.
Reduction of blood is obtained in various ways. The diminution of the
quantity of the blood lessens the amount of pressure on the vessels,
and, as a sequel, the volume of it which is carried to the point of
inflammation; it diminishes the body temperature or fever; it numbs the
nervous system, which plays an important part as a conductor of
irritation in diseases.
Blood-letting is the most rapid means, and frequently acts like a charm
in relieving a commencing inflammatory trouble. One must remember,
however, that the strength of the body and repair depend on the blood;
hence blood-letting should be practiced only in full-blooded,
well-nourished animals and in the early stages of the disease.
Cathartics act by drawing off a large quantity of fluid from the blood
through the intestines, and have the advantage over the last remedy of
removing only the watery and not the formed elements from the
circulation. The blood cells remain, leaving the blood as rich as it was
before. Again, the glands of the intestines are stimulated to excrete
much waste matter and other deleterious material which may be acting as
a poison in the blood.
Diuretics operate through the kidneys in the same way.
Diaphoretics aid depletion of the blood by pouring water in the form of
sweat from the surface of the skin and stimulating the discharge of
waste material out of its glands, which has the same effect on the blood
pressure.
Antipyretics are remedies to reduce the temperature. This may be
accomplished by depressing the center in the brain that controls heat
production. Some coal-tar products are very effective in this way, but
they have the disadvantage of depressing the heart, which should always
be kept as strong as possible. If they are used it must be with
knowledge of this fact, and it is well to give heart tonics or
stimulants with them. The temperature of the body may be lowered by cold
packs or by showering with cold water. This is a most useful procedure
in many diseases.
Depressants are drugs which act on the heart. They slow or weaken the
action of this organ and reduce the quantity and force of the current of
the blood which is carried to the point of local disease; they lessen
the vitality of the animal, and for this reason are now used much less
than formerly.
Anodynes quiet the nervous system. Pain in the horse, as in the man, is
one of the important factors in the production of fever, and the dulling
of the former often prevents, or at least reduces, the latter. Anodynes
produce sleep, so as to rest the patient and allow recuperation for the
succeeding struggle of the vitality of the animal against the exhausting
drain of the disease.
The diet of an animal suffering from acute inflammation is a factor of
the greatest importance. An overloaded circulation can be starved to a
reduced quantity and to a less rich quality of blood by reducing the
quantity of feed given to the patient. Feeds of easy digestion do not
tire the already fatigued organs of an animal with a torpid digestive
system. Nourishment will be taken by a suffering brute in the form of
slops and cooling drinks when it would be totally refused if offered in
its ordinary form, as hard oats or dry hay, requiring the labor of
grinding between the teeth and swallowing by the weakened muscles of the
jaws and throat.
Tonics and stimulants are remedies which are used to meet special
indications, as in the case of a feeble heart, and which enter into the
after treatment of inflammatory troubles as well as into the acute
stages of them. They brace up weakened and torpid glands; they stimulate
the secretion of the necessary fluids of the body, and hasten the
excretion of the waste material produced by the inflammatory process;
they regulate the action of a weakened heart; they promote healthy
vitality of diseased parts, and aid the chemical changes needed for
returning the altered tissues to their normal condition.
FEVERS.
Fever is a general condition of the animal body in which there is an
elevation of the animal body temperature, which may be only a degree or
two or may be 10 deg. F. The elevation of the body temperature, which
represents tissue change or combustion, is accompanied with an
acceleration of the heart's action, a quickening of the respiration, and
an aberration in the functional activity of the various organs of the
body. These organs may be stimulated to the performance of excessive
work, or they may be incapacitated from carrying out their allotted
tasks, or, in the course of a fever, the two conditions may both exist,
the one succeeding the other. Fever as a disease is usually preceded by
chills as an essential symptom.
Fevers are divided into essential fevers and symptomatic fevers. In
symptomatic fever some local disease, usually of an inflammatory
character, develops first, and the constitutional febrile phenomena are
the result of the primary point of combustion irritating the whole body,
either through the nervous system or directly by means of the waste
material which is carried into the circulation and through the blood
vessels, and is distributed to distal parts. Essential fevers are those
in which there is from the outset a general disturbance of the whole
economy. This may consist of an elementary alteration in the blood or a
general change in the constitution of the tissues. Fevers of the latter
class are usually due to some infecting agent and belong, therefore, to
the class of infectious diseases.
Essential fevers are subdivided into ephemeral fevers, which last but a
short time and terminate by critical phenomena; intermittent fevers, in
which there are alterations of exacerbations of the febrile symptoms and
remissions, in which the body returns to its normal condition or
sometimes to a depressed condition, in which the functions of life are
but badly performed; and continued fevers, which include contagious
diseases, such as glanders, influenza, etc., the septic diseases, such
as pyemia, septicemia, etc., and the eruptive fevers, such as variola,
etc.
Whether the cause of the fever has been an injury to the tissues, such
as a severe bruise, a broken bone, an inflamed lung, or excessive work,
which has surcharged the blood with the waste products of the combustion
of the tissues, which were destroyed to produce force, or the toxins of
influenza in the blood, or the presence of irritating material, either
in the form of living organisms or of their products, as in glanders or
tuberculosis--the general train of symptoms are much the same, varying
as the amount of the irritant differs in quantity, or when some special
quality in them has a specific action on one or another tissue.
There is in fever at first a relaxation of the small blood vessels,
which may have been preceded by a contraction of the same if there was a
chill, and as a consequence there is an acceleration of the current of
the blood. There is, then, an elevation of the peripheral temperature,
followed by a lowering of tension in the arteries and an acceleration in
the movement of the heart. These conditions may be produced by a primary
irritation of the nerve centers of the brain from the effects of heat,
as is seen in thermic fever, or sunstroke, or by the entrance into the
blood stream of disease-producing organisms or their chemical products,
as in anthrax, rinderpest, influenza, etc.
There are times when it is difficult to distinguish between the
existence of fever as a disease and a temporary feverish condition which
is the result of excessive work. Like the condition of congestion of the
lungs, which is normal up to a certain degree in the lungs of a race
horse after a severe race, and morbid when it produces more than
temporary phenomena or when it causes distinct lesions, the temperature
may rise from physiological causes as much as four degrees, so fever,
or, as it is better termed, a feverish condition, may follow any work or
other employment of energy in which excessive tissue change has taken
place; but if the consequences are ephemeral, and no recognizable lesion
is apparent, it is not considered morbid. This condition, however, may
predispose to severe organic disturbance and local inflammations which
will cause disease, as an animal in this condition is liable to take
cold and develop lung fever or a severe enteritis, if chilled or
otherwise exposed.