Part 42

Pathology.--In congestion of the brain the cerebral vessels are loaded with blood, the venous sinuses distended to an extreme degree, and the pressure exerted upon the brain constitutes actual compression, giving rise to the symptoms just mentioned. On post-mortem examinations this engorgement is found universal throughout the brain and its membranes, which serves to distinguish it from inflammations of these structures, in which the engorgements are confined more or less to circumscribed portions. A prolonged congestion may, however, lead to active inflammation, and in that case we find serous and plastic exudations in the cavities of the brain. In addition to the intensely engorged condition of the vessels we find the gray matter of the brain redder than natural. In cases in which several attacks have occurred the blood vessels are often found permanently dilated.

Treatment.--The animal should be taken out of harness at once, with prompt removal of all mechanical obstructions to the circulation. If it is caused by venous obstruction by too tight a collar, the loosening of the collar will give immediate relief. The horse should be bled freely from the jugular vein. If due to tumors or abscesses, a surgical operation becomes necessary to afford relief. To revive the animal if it becomes partially or totally unconscious, cold water should be dashed on the head. Give a purge of Glauber's salt. If the limbs are cold, tincture of capsicum or strong mustard water should be applied to them. If symptoms of paralysis remain after two or three days, an active cathartic and iodid of potassium will be indicated, to be given as prescribed for inflammation of the brain. In confirmed cases, treatment is not advisable, as there is considerable danger to the owner should an attack occur in a crowded street.

Prevention.--Well-adjusted collar, with strap running from the collar to the girth, to hold down the collar when pulling upgrade; regular feed and exercise, without allowing the animal to become excessively plethoric; moderate checking, allowing a free-and-easy movement of the head; well-ventilated stabling, proper cleanliness, pure water, etc.

SUNSTROKE, HEAT STROKE, OR HEAT EXHAUSTION.

The term sunstroke is applied to affections occasioned not exclusively by exposure to the sun's rays, as the word signifies, but by the action of great heat combined generally with humid atmosphere. Exhaustion produced by long-continued heat is often the essential factor, and is called heat exhaustion. Horses on the race track undergoing protracted and severe work in hot weather often succumb to heat exhaustion. Draft horses which do not receive proper care in watering, feeding, and rest in shady places and are exposed for many hours to the direct rays of the sun suffer very frequently from sunstroke.

Symptoms.--Sunstroke is manifested suddenly. The animal stops, drops his head, begins to stagger, and soon falls to the ground unconscious. The breathing is marked with great stertor, the pulse is very slow and irregular, cold sweats break out in patches on the surface of the body, and the animal often dies without having recovered consciousness.

The temperature becomes very high, reaching 105 deg. to 109 deg. F.

In heat exhaustion the animal usually requires urging for some time prior to the appearance of any other symptoms, generally perspiration is checked, and then the horse becomes weak in its gait, the breathing hurried or panting, eyes watery or bloodshot, nostrils dilated and highly reddened, assuming a dark, purple color; the pulse is rapid and weak, the heart bounding, followed by unconsciousness and death. If recovery takes place, convalescence extends over a long period of time, during which incoordination of movement may persist.

Pathology.--Sunstroke, virtually active congestion of the brain, often accompanied with effusion and blood extravasation, characterizes this condition, with often rapid and fatal lowering of all the vital functions. In many instances the death may be due to the complete stagnation in the circulation of the brain, inducing anemia, or want of nourishment of that organ. In other cases it may be directly due to the excessive compression of the nerve matter controlling the heart's action, and cause paralysis of that organ. There are also changes in the composition of the blood.

Treatment.--The animal should be placed in shaded surroundings. Under no circumstances is blood-letting permissible in sunstroke. Ice or very cold water should be applied to the head and along the spine, and half an ounce of carbonate of ammonia or 6 ounces of whisky should be given in 1 pint of water. Cold water may be used as an enema and should also be showered upon the body of the horse from the hose or otherwise. This should be continued until the temperature is down to 103 deg. F. Brisk friction of the limbs and the application of spirits of camphor often yields good results. The administration of the stimulants should be repeated in one hour if the pulse has not become stronger and slower. In either case, when reaction has occurred, preparations of iron and general tonics may be given during convalescence: Sulphate of iron, 1 dram; gentian, 3 drams; red cinchona bark, 2 drams; mix and give in feed morning and evening.

Prevention.--In very hot weather horses should have wet sponges or light sunshades on the head when at work, or the head may be sponged with cold water as many times a day as possible. Proper attention should be given to feeding and watering, never in excess. During the warm months all stables should be cool and well ventilated, and if an animal is debilitated from exhaustive work or disease it should receive such treatment as will tend to build up the system. Horses should be permitted to drink as much water as they want while they are at work during hot weather.

An animal which has been affected with sunstroke is very liable to have subsequent attacks when exposed to the necessary exciting causes.

APOPLEXY OR CEREBRAL HEMORRHAGE.

Apoplexy is often confounded with cerebral congestion, but true apoplexy always consists in rupture of cerebral blood vessels, with blood extravasation and formation of blood clot.

Causes.--Two causes are involved in the production of apoplexy, the predisposing and the exciting. The predisposing cause is degeneration, or disease which weakens the blood vessel; the exciting cause is any one which tends to induce cerebral congestion.

Symptoms.--Apoplexy is characterized by a sudden loss of sensation and motion, profound coma, and stertorous, difficult breathing. The action of the heart is little disturbed at first, but soon becomes slower, then quicker and feebler, and after a little time ceases. If the rupture is one of a small artery and the extravasation limited, sudden paralysis of some part of the body is the result. The extent and location of the paralysis depend upon the location within the brain which is functionally deranged by the pressure of the extravasated blood; hence these conditions are very variable.

In the absence of any premonitory symptoms or an increase of temperature in the early stage of the attack, we may be reasonably certain in making the distinction between this disease and congestion of the brain, or sunstroke.

Pathology.--In apoplexy there is generally found an atheromatous condition of the cerebral vessels, with weakening and degeneration of their walls. When a large artery has been ruptured it is usually followed by immediate death, and large rents may be found in the cerebrum, with great destruction of brain tissue, induced by the forcible pressure of the liberated blood. In small extravasations producing local paralysis without marked general disturbance the animal may recover after a time; in such cases gradual absorption of the clot takes place. In large clots atrophy of the brain substances may follow, or softening and abscess from want of nutrition may result, and render the animal worthless, ultimately resulting in death.

Treatment.--Place the animal in a quiet, cool place and avoid all stimulating feed. Administer, in the drinking water or feed, 2 drams of the iodid of potassium twice a day for several weeks if necessary. Medical interference with sedatives or stimulants is more liable to be harmful than of benefit, and blood-letting in an apoplectic fit is extremely hazardous. From the fact that cerebral apoplexy is due to diseased or weakened blood vessels, the animal remains subject to subsequent attacks. For this reason treatment is very unsatisfactory.

COMPRESSION OF THE BRAIN.

Causes.--In injuries from direct violence a piece of broken bone may press upon the brain, and, according to its size, the brain is robbed of its normal space within the cranium. It may also be due to an extravasation of blood or to exudation in the subdural or arachnoid spaces. Death from active cerebral congestion results through compression. The occurrence may sometimes be traced to the direct cause, which will give assurance for the correct diagnosis.

Symptoms.--Impairment of all the special senses and localized paralysis. All the symptoms of lessened functional activity of the brain are manifested to some degree. The paralysis remains to be our guide for the location of the cause, for it will be found that the paralysis occurs on the opposite side of the body from the location of the injury, and the parts suffering paralysis will denote, to an expert veterinarian or physician, the part of the brain which is suffering compression.

Treatment.--Trephining, by a skillful operator, for the removal of the cause when due to depressed bone or the presence of foreign bodies. When the symptoms of compression follow other acute diseases of the brain, apoplectic fits, etc., the treatment must be such as the exigencies of the case demands.

CONCUSSION OF THE BRAIN.

This is generally caused by falling over backward and striking the poll, or perhaps falling forward on the nose, by a blow on the head, etc. Train accidents during shipping often cause concussion of the brain.

Symptoms.--Concussion of the brain is characterized by giddiness, stupor, insensibility, or loss of muscular power, succeeding immediately upon a blow or severe injury involving the cranium. The animal may rally quickly or not for hours; death may occur on the spot or after a few days. When there is only slight concussion or stunning, the animal soon recovers from the shock. When more severe, insensibility may be complete and continue for a considerable time; the animal lies as if in a deep sleep; the pupils are insensible to light; the pulse fluttering or feeble; the surface of the body cold, muscles relaxed, and the breathing scarcely perceptible. After a variable interval partial recovery may take place, which is marked by paralysis of some parts of the body, often of a limb, the lips, ear, etc. Convalescence is usually tedious, and frequently permanent impairment of some organs remains.

Pathology.--Concussion produces laceration of the brain, or at least a jarring of the nervous elements, which, if not sufficiently severe to produce sudden death, may lead to softening or inflammation, with their respective symptoms of functional derangement.

Treatment.--The first object in treatment will be to establish reaction or to arouse the feeble and weakening heart. This can often be accomplished by dashing cold water on the head and body of the animal; frequent injections of weak ammonia water, ginger tea, or oil and turpentine should be given per rectum. In the majority of cases this will soon bring the horse to a state of consciousness. In more severe cases mustard poultices should be applied along the spine and above the fetlocks. As soon as the animal gains partial consciousness stimulants, in the form of whisky or capsicum tea, should be given. Owing to severity of the structural injury to the brain or the possible rupture of blood vessels and blood extravasation, the reaction may often be followed by encephalitis or cerebritis, and will then have to be treated accordingly. For this reason the stimulants should not be administered too freely, and they must be abandoned as soon as reaction is established. There is no need for further treatment unless complications develop as a secondary result. Bleeding, which is so often practiced, proves almost invariably fatal in this form of brain affection. We should also remember that it is never safe to drench a horse with large quantities of medicine when he is unconscious, for he is very liable to draw the medicine into the lungs in inspiration.