In the last or mildest form the inability of voluntary control of the limbs becomes but slightly marked, the power of swallowing never entirely lost, and the animal has no fever, pain, or unconscious movements. Generally the animal will begin to improve about the fourth day and recovers.

In a few cases the spinal symptoms, manifested by paraplegia, may be the most prominent symptoms; in others they may be altogether absent and the main symptoms may be difficulty in mastication and swallowing; rarely it may affect one limb only. In all cases in which coma remains absent for six or seven days the animal is likely to recover. When changes toward recovery take place, the symptoms usually leave in the reverse order to that in which they developed, but local paralysis may remain for some time, rarely persistent.

On post-mortem the number of lesions observable to the naked eye is in marked contrast to the severity of the symptoms noted. The pharynx and larynx are inflamed in many cases, and sometimes coated with a yellowish-white glutinous deposit, extending at times over the tongue and occasionally a little way down the trachea. The lungs are normal, except from complications following drenching or rec.u.mbence for a long period. The heart is usually normal in appearance, except an occasional cl.u.s.ter of hemorrhagic points on the outer surface, while the blood is dark and firmly coagulated. The lining of the stomach indicates a subacute gastritis, while occasionally an erosion is noted. An edema is observed in the submucosa of such cases. The first few inches of the small intestines likewise may show slight inflammation in certain cases, while in others it is quite severe; otherwise the digestive tract appears normal, excluding the presence of varying numbers of bots, _Strongylus vulgatus_, and a few other nematodes. The liver is congested and swollen in some cases, while it appears normal in others. The spleen is, as a rule, normal, and at times the kidneys are slightly congested.

The bladder is often distended with dark-colored urine, and occasionally a marked cyst.i.tis has been observed. The adipose tissue throughout the carca.s.s may show a p.r.o.nounced icteric appearance in certain cases. On removing the bones of the skull the brain appears to be normal macroscopically in a few instances, but in most cases the veins and capillaries of the meninges of the cerebrum, cerebellum, and occasionally the medulla is distinctly dilated and engorged, and in a few cases there are p.r.o.nounced lesions of a leptomeningitis. An excessive quant.i.ty of cerebrospinal fluid is present in most of the cases. On the floor of the lateral ventricles of several brains there was noted a slight softening caused by hemorrhages into the brain substance. There is always an abundance of fluid in the subarachnoid s.p.a.ces, ventricles, and at the base of the brain, usually of the color of diabetic urine, and containing a limited number of flocculi, but in a few cases it was slightly blood tinged. The spinal cord was not found involved in the few cases examined.

_Treatment._--One attack of the disease does not confer immunity. Horses have been observed which have recovered from two attacks, and still others that recovered from the first but died as a result of the second attack.

Inasmuch as a natural immunity does not appear after an attack of cerebrospinal meningitis, it might be antic.i.p.ated that serum of recovered cases would possess neither curative nor prophylactic qualities. Nevertheless, experiments have been made along these lines with serum from recovered cases, but without any positive results.

Similar investigations have been conducted by others in Europe with precisely the same results. With the tendency of the disease to produce pathological lesions in the central nervous system, it seems scarcely imaginable that a medicinal remedy will be found to heal these foci, and even when recovery takes place considerable disturbance in the functions, as blindness, partial paralysis, dumbness, etc., is liable to remain. Indeed, when the disease once becomes established in an animal, drugs seem to lose their physiological action. Therefore, with all the previously mentioned facts before us, it is evident that the first principle in the treatment of this disease is prevention, which consists in the exercise of proper care in feeding only clean, well-cured forage and grain and pure water. These measures when faithfully carried out check the development of additional cases of the disease upon the affected premises.

While medicinal treatment has proved unsatisfactory in most cases, nevertheless the first indication is to clean out the digestive tract thoroughly, and to accomplish this prompt measures must be used early in the disease. Active and concentrated remedies should be given, preferably subcutaneously or intravenously, owing to the great difficulty in swallowing, even in the early stage. Arecolin in one-half grain doses, subcutaneously, has given as much satisfaction as any other drug. After purging the animal the treatment is mostly symptomatic.

Intestinal disinfectants, particularly calomel, salol, and salicylic acid, have been recommended, and mild, antiseptic mouth washes are advisable. Antipyretics are of doubtful value, as better results are obtained, if the temperature is high, by copious cold-water injections.

An ice pack applied to the head is beneficial in case of marked psychic disturbance. One-ounce doses of chloral hydrate per r.e.c.t.u.m should be given if the patient is violent or if muscular spasms are severe. If the temperature becomes subnormal, the animal should be warmly blanketed, and if much weakness is shown this should be combated with stimulants, such as strychnin, camphor, alcohol, atropin, or aromatic spirits of ammonia. Early in the disease urotropin (hexamethylenamin) in doses of 25 grains, dissolved in water and given by the mouth every two hours, appeared to have been responsible for the recovery of some cases of the malady. During convalescence tonic treatment is indicated.

_Hygienic measures needful._--Whenever this disease appears in a stable all the animals should be removed as soon as possible. They should be provided with clean, well-ventilated, and well-drained stables, and each animal should receive a laxative and be fed feed and given water from a new, clean source. The abandoned stable should be thoroughly cleansed from all waste matters, receive a coat of whitewash containing 4 ounces of carbolic acid to the gallon of water and should have time to dry thoroughly before the horses are replaced. A complete change of feed is of the very greatest importance on account of the belief that the cause resides in diseased grain, hay, and gra.s.s.

TETa.n.u.s, OR LOCKJAW.

This disease is characterized by spasms affecting the muscles of the face, neck, body, and limbs and of all muscles supplied by the cerebrospinal nerves. The spasms or muscular contractions are rigid and persistent, yet mixed with occasional more intense contractions of convulsive violence.

_Causes._--This disease is caused by a bacillus that is often found in the soil, in manure, and in dust. This germ forms spores at the end of the organism and grows only in the absence of oxygen. It produces a powerful nerve poison, which causes the symptoms of teta.n.u.s. The germ itself multiplies at the point where it is introduced, but its poison is absorbed and is carried by the blood to all parts of the body, and thus the nervous system is poisoned. Deep wounds infected by this germ are more dangerous than superficial wounds, because in them the germ is more remote from the oxygen of the air. Hence, nail p.r.i.c.ks, etc., are especially dangerous. In the majority of instances the cause of teta.n.u.s can be traced to wounds, especially p.r.i.c.ks and wounds of the feet or of tendinous structures. It sometimes follows castration, docking, the introduction of setons, inclusion of a nerve in a ligature, etc. It may come on a long time after the wound is healed--three or four months.

Horses with a nervous, excitable disposition are more predisposed than those of a more sluggish nature. Stallions are more subject to develop teta.n.u.s as the result of wounds than geldings, and geldings more than mares.

_Symptoms._--The attacks may be acute or subacute. In an acute attack the animal usually dies within four days. The first symptoms which attract the attention of the owner is difficulty in chewing and swallowing, an extension of the head and protrusion over the inner part of the eye of the membrana nict.i.tans, or haw. An examination of the mouth will reveal an inability to open the jaws to their full extent, and the endeavor to do so will produce great nervous excitability and increased spasm of the muscles of the jaw and neck. The muscles of the neck and along the spine become rigid and the legs are moved in a stiff manner. The slightest noise or disturbance throws the animal into increased spasm of all the affected muscles. The tail is usually elevated and held immovable; the bowels become constipated early in the attack. The temperature and pulse are not much changed. These symptoms in the acute type become rapidly aggravated until all the muscles are rigid--in a state of tonic spasm--with a continuous tremor running through them; a cold perspiration breaks out on the body; the breathing becomes painful from the spasm of the muscles used in respiration; the jaws are completely set, eyeb.a.l.l.s retracted, lips drawn tightly over the teeth, nostrils dilated, and the animal presents a picture of the most extreme agony until death relieves him. The pulse, which at first was not much affected, will become quick and hard, or small and thready when the spasm affects the muscles of the heart. In the subacute cases the jaws may never become entirely locked; the nervous excitability and rigidity of the muscles are not so great. There is, however, always some stiffness of the neck or spine manifest in turning; the haw is turned over the eyeball when the nose is elevated. It is not uncommon for owners to continue such animals at their work for several days after the first symptoms have been observed. All the symptoms may gradually increase in severity for a period of ten days, and then gradually diminish under judicious treatment, or they may reach the stage wherein all the characteristics of acute teta.n.u.s become developed. In some cases, however, we find the muscular cramps almost solely confined to the head or face, perhaps involving those of the neck. In such cases we have complete trismus (lockjaw), and all the head symptoms are acutely developed. On the contrary, we may find the head almost exempt in some cases, and have the body and limbs perfectly rigid and incapable of movement without falling.

Teta.n.u.s may possibly be confounded with spinal meningitis, but the character of the spasm-locked jaw, retraction of the eyeb.a.l.l.s, the difficulty in swallowing due to spasms of the muscles of the pharynx, and above all, the absence of paralysis, should serve to make the distinction.

_Prevention._--When a valuable horse has sustained a wound that it is feared may be followed by teta.n.u.s, it is well to administer a dose of teta.n.u.s ant.i.toxin. This is injected beneath the skin with a hypodermic syringe. A very high degree of protection may in this way be afforded.

This ant.i.toxin should be administered only by a competent veterinarian.

_Treatment._--The animal should be placed in a box stall without bedding, as far as possible from other horses. If in a country district, the animal should be put into an outbuilding or shed, where the noise of other animals will not reach it; if the place is moderately dark, it is all the better; in fly time it should be covered with a light sheet. The attendant must be very careful and quiet to prevent all unnecessary excitement and increase of spasm. Teta.n.u.s ant.i.toxin appears to be useful as a remedy in some cases, if given in very large quant.i.ties early in the disease; otherwise it is useless. Subcutaneous injections of carbolic acid in glycerin and water (carbolic acid 30 grains, glycerin and water each 1 ounce) appear to be useful in some cases. Injections should be given twice daily.

A cathartic, composed of Barbados aloes 6 to 8 drams, with which may be mixed 2 drams of the solid extract of belladonna, should be given at once. This is best given in a ball form; if, however, the animal is greatly excited by the attempt or can not swallow, the ball may be dissolved in 2 ounces of olive oil and thrown on the back of the tongue with a syringe. If the jaws are set, or nearly so, an attempt to administer medicine by the mouth should not be made. In such cases one-quarter of a grain of atropia, with 5 grains of sulphate of morphia, should be dissolved in 1 dram of pure water and injected under the skin.

This should be repeated sufficiently often to keep the animal continually under its effect. This will usually mitigate the severity of the spasmodic contraction of the affected muscles and lessen sensibility to pain. Good results may be obtained sometimes by the rectal injection of the fluid extract of belladonna and of cannabis indica, of each 1 dram, every four or six hours. This may be diluted with a quart of milk.

When the animal is unable to swallow liquids, oatmeal gruel and milk should be given by injection per r.e.c.t.u.m to sustain the strength of the animal. A pailful of cool water should be constantly before him, placed high enough for him to reach it without special effort; even if drinking is impossible, the laving of the mouth is refreshing. Excellent success frequently may be obtained by clothing the upper part of the head, the neck, and greater part of the body in woolen blankets kept saturated with very warm water. This treatment should be continued for six or eight hours at a time. It often relaxes the cramped muscles and gives them rest and the animal almost entire freedom from pain; but it should be used every day until the acute spasms have permanently subsided in order to be of any lasting benefit.

Recently subcutaneous injections of brain emulsion have been recommended. It is thought that the teta.n.u.s toxin will attach itself to the brain cells so injected and thus free the system of this poison.

When it is due to a wound, the wound should be thoroughly cleaned and disinfected with carbolic acid. If from a wound which has healed, an excision of the cicatrix may be beneficial. In all cases it is not uncommon to have a partial recovery followed by relapse when the animal becomes excited from any cause.

RABIES, HYDROPHOBIA, OR MADNESS.

This disease does not arise spontaneously among horses, but is the result of a bite from a rabid animal--generally a dog or cat. The development of the disease follows the bite in from three weeks to three months--very rarely in two weeks. (See also p. 559.)

_Symptoms._--The first manifestation of the development of this disease may be an increased excitability and viciousness; very slight noises or the approach of a person incites the animal to kick, strike, or bite at any near object. Very often the horse will bite his own limbs or sides, lacerating the flesh and tearing the skin. The eyes appear staring, bloodshot; the ears are on the alert to catch all sounds; the head is held erect. In some cases the animal will continually rub and bite the locality of the wound inflicted by the rabid animal. This symptom may precede all others. Generally the bowels become constipated and the animal makes frequent attempts at urination, which is painful, and the urine very dark colored. The furious symptoms appear in paroxysms; at other times the animal may eat and drink, although swallowing appears to become painful toward the latter stage of the disease, and may cause renewed paroxysms. The muscles of the limbs or back may be subject to intermittent spasms, or spasmodic tremors; finally, the hind limbs become paralyzed, breathing very difficult, and convulsions supervene, followed by death. The pulse and respirations are increased in frequency from the outset of the attack. Rabies may possibly be mistaken for teta.n.u.s. In the latter disease we find tonic spasms of the muscles of the jaws, or stiffness of the neck or back very early in the attack, and evidence of viciousness is absent.

_Treatment._--As soon as the true nature of the disease is ascertained the animal should be killed.

_Prevention._--When a horse is known to have been bitten by a rabid animal, immediate cauterization of the wound with a red-hot iron may possibly destroy the virus before absorption of it takes place.

PLUMBISM, OR LEAD POISONING.

This disease is not of frequent occurrence. It may be due to the habitual drinking of water which has been standing in leaden conductors or in old paint barrels, etc. It has been met with in enzootic form near smelting works, where, by the fumes arising from the works, lead in the form of oxid, carbonate, or sulphate was deposited on the gra.s.s and herbage which the horses ate.

_Symptoms._--Lead poisoning produces derangement of the functions of digestion and locomotion, or it may affect the lungs princ.i.p.ally. In whatever system of organs the lead is mostly deposited there we have the symptoms of nervous debility most manifest. If in the lungs, the breathing becomes difficult and the animal gets out of breath very quickly when compelled to run. Roaring, also, is very frequently a symptom of lead poisoning. When it affects the stomach, the animal gradually falls away in flesh, the hair becomes rough, the skin tight, and colicky symptoms develop. When the deposit is princ.i.p.ally in the muscles, partial or complete paralysis gradually develops. When large quant.i.ties of lead have been taken in and absorbed, symptoms resembling epilepsy may result, or coma and delirium develop and prove fatal. In lead poisoning there is seldom any increase in temperature. A blue line forms along the gums of the front teeth, and the breath a.s.sumes a peculiarly offensive odor. Lead can always be detected in the urine by chemical tests.

_Treatment._--The administration of 2-dram doses of iodid of pota.s.sium three times a day is indicated. This will form iodid of lead in the system, which is rapidly excreted by the kidneys. If much muscular weakness or paralysis is present, sulphate of iron in 1-dram doses and strychnia in 2-grain doses may be given twice a day. In all cases of suspected lead poisoning all utensils which have entered into the supply of feed or water should be examined for the presence of soluble lead. If it occurs near lead works, great care must be given to the supply of uncontaminated fodder, etc.

UREMIA.

Uremic poisoning may affect the brain in nephritis, acute alb.u.minuria, or when, from any cause, the functions of the kidneys become impaired or suppressed and urea (a natural product) is no longer eliminated from these organs, causing it to acc.u.mulate in the system and give rise to uremic poisoning.

Uremic poisoning is usually preceded by dropsy of the limbs or abdomen; a peculiar, fetid breath is often noticed; then drowsiness, attacks of diarrhea, and general debility ensue. Suddenly extreme stupor or coma develops; the surface of the body becomes cold; the pupils are insensible to light; the pulse slow and intermitting; the breathing labored, and death supervenes. The temperature throughout the disease is seldom increased, unless the disease becomes complicated with acute, inflammatory disease of the brain or respiratory organs, which often occur as a result of the urea in the circulation. Alb.u.men and tube casts may frequently be found in the urine. The disease almost invariably proves fatal.

Treatment must be directed to a removal of the cause.

ELECTRIC SHOCK.

Electric shock, from coming in contact with electric wires, is becoming a matter of rather frequent occurrence, and has a similar effect upon the animal system as a shock from lightning. Two degrees of electric or lightning shock may be observed, one producing temporary contraction of muscles and insensibility, from which recovery is possible, the other killing directly, by producing a condition of nervous and general insensibility. In shocks which are not immediately fatal the animal is usually insensible, the respiration slow, labored, or gasping, the pulse slow, feeble, and irregular, and the pupils dilated and not sensitive, or they may be contracted and sensitive. The temperature is lowered.

There may be a tendency to convulsions or spasms. The predominating symptoms are extreme cardiac and respiratory depression.

_Treatment._--Sulphate of atropia should be given hypodermically in one-quarter grain doses every hour or two hours until the heart beats are invigorated, the number and fullness of the respirations increased, and consciousness returns. Stimulating injections per r.e.c.t.u.m may also be useful in arousing the circulation; for this purpose whisky or ammonia water may be used.

DISEASES OF THE HEART, BLOOD VESSELS, AND LYMPHATICS.

By M. R. TRUMBOWER, V. S.

[Revised by Leonard Pearson, B. S., V. M. D.]

ANATOMY AND PHYSIOLOGY OF THE HEART AND BLOOD VESSELS.

(Pls. XX and XXI.)

The heart is a hollow, muscular organ, situated a little to the left of the center of the chest. Its impulse is felt on the left side on account of its location and from the rotary movement of the organ in action. It is cone-shaped, with the base upward; the apex points downward, backward, and to the left side. It extends from about the third to the sixth ribs, inclusive. The average weight is about 7 to 8 pounds. In horses used for speed the heart is relatively larger, according to the weight of the animal, than in horses used for slow work. It is suspended from the spine by the large blood vessels and held in position below by the attachment of the pericardium to the sternum. It is inclosed in a sac, the pericardium, which is composed of a dense fibrous membrane lined by a delicate serous membrane, which is reflected over the heart; the inner layer is firmly adherent to the heart, the outer to the fibrous sac, and there is an intervening s.p.a.ce, known as the pericardial s.p.a.ce, in which a small amount of serum--a thin translucent liquid--is present constantly.

The heart is divided by a shallow fissure into a right and left side; each of these is again subdivided by a transverse part.i.tion into two compartments which communicate. Thus there are four cardiac cavities--the superior, or upper, ones called the auricles; the inferior, or lower, ones the ventricles. These divisions are marked on the outside by grooves, which contain the cardiac blood vessels, and are generally filled with fat.

The right side of the heart may be called the venous side, the left the arterial side, named from the kind of blood which pa.s.ses through them.

The auricles are thin-walled cavities placed at the base, and are connected with the great veins--the venae cavae and pulmonary veins--through which they receive blood from all parts of the body. The auricles communicate with the ventricles each by a large aperture, the auriculo-ventricular orifice, which is furnished with a remarkable mechanism of valves, allowing the transmission of blood from the auricles into the ventricles, but preventing a reverse course. The ventricles are thick-walled cavities, forming the more ma.s.sive portion of the heart toward the apex. They are separated by a part.i.tion, and are connected with the great arteries--the pulmonary artery and the aorta--by which they send blood to all parts of the body. At the mouth of the aorta and at the mouth of the pulmonary artery is an arrangement of valves in each case which prevents the reflux of blood into the ventricles. The auriculo-ventricular valve in the left side is composed of two flaps, hence it is called the bicuspid valve; in the right side this valve has three flaps and is called the tricuspid valve. The flaps which form these valves are connected with a tendinous ring between the auricles and ventricles; and each flap of the auriculo-ventricular valves is supplied with tendinous cords, which are attached to the free margin and under-surface, so as to keep the valves tense when closed--a condition which is produced by the shortening of muscular pillars with which the cords are connected. The arterial openings, both on the right and on the left side, are provided with three-flapped semilunar-shaped valves, to prevent the regurgitation of blood when the ventricles contract. The veins emptying into the auricles are not capable of closure, but the posterior vena cava has an imperfect valve at its aperture.