(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 quant.i.ty 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 const.i.tution 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 circ.u.mscribed 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 quant.i.ties 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.

[Ill.u.s.tration: PLATE I.

INFLAMMATION.

1--_Uninflamed wing of the bat._

2--_Inflamed wing of the bat._]

[Ill.u.s.tration: 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 spa.r.s.ely 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 pa.s.sages 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 const.i.tutional 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 a.s.similate 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 rea.s.sumes 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 ma.s.s 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 const.i.tutional 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 quant.i.ties 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 pa.s.sages.

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 p.e.n.i.s, 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.

_Const.i.tutional 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 quant.i.ty 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 quant.i.ty 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.

Diaph.o.r.etics 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 quant.i.ty 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 quant.i.ty and to a less rich quality of blood by reducing the quant.i.ty 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 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 const.i.tutional 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 const.i.tution of the tissues. Fevers of the latter cla.s.s are usually due to some infecting agent and belong, therefore, to the cla.s.s 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 quant.i.ty, 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.