Hind presentation with leg bent at hock.—In this form the quarters of the foal with the hind legs bent up beneath them present, but can not advance through the pelvis by reason of their bulk. (Plate XV, fig. 3.) The oiled hand introduced can recognize the outline of the buttocks, with the tail and anus in the center and the sharp points of the hocks beneath. First pass a rope around each limb at the hock, then with hand or repeller push the buttocks backward and upward, until the feet can be brought up into the passages. To this the great length of the shank and pastern in the foal is a serious obstacle, and in all cases the foot should be protected in the palm of the hand while being brought up over the brim of the pelvis; otherwise the womb may be torn. When the pains are too violent and constant to allow effective manipulation, some respite may be obtained by the use of chloroform or morphin and by turning the mare on her back, but too often the operator fails and the foal must be sacrificed. Two courses are still open: First, to cut through the cords behind and above the hock and extend the upper part of the limb, leaving the hock bent, and extract in this way, and, second, to amputate the hind limbs at the hip joint and remove them separately, after which the body may be extracted.
Hind presentation with legs bent forward from hip.—This is merely an aggravated form of the presentation last described. (Plate XVII, fig. 1.) If the mare is roomy, a rope may be passed around each thigh and the body pushed upward and forward, so as to bring the hocks and heels upward. If this can be accomplished, nooses are placed on the limb further and further down until the fetlock is reached and brought into position. If failure is met with, then amputation at the hips is the last resort.
Hind presentations with back turned sideways or downward.—These are the counterparts of similar anterior presentations and are to be managed in the same way.
Presentation of the back.—This is rare, yet not unknown, the foal being bent upon itself with the back, recognizable by its sharp row of spines, presented at the entrance of the pelvis and the head and all four feet turned back into the womb. (Plate XVI, fig. 1.) The body of the fetus may be extended across the opening transversely, so that the head corresponds to one side (right or left), or it may be vertical, with the head above or below.
In any such position the object should be to push the body of the fetus forward and upward or to one side, as may best promise to bring up the fore or hind extremities, and bring the latter into the passage so as to constitute a normal anterior or posterior presentation. This turning of the fetus may be favored by a given position of the mother, by the free use of oil or lard on the surface of the fetus, and by the use of a propeller.
Presentation of breast and abdomen.—This is the reverse of the back presentation, the foal being extended across in front of the pelvic opening, but with the belly turned toward the passages and with all four feet engaged in the passage. (Plate XVI, fig. 2.) The most promising course is to secure the hind feet with nooses and then push the fore feet forward into the womb. As soon as the fore feet are pushed forward clear of the brim of the pelvis, traction is made on the hind feet so as to bring the thighs into the passage and prevent the reentrance of the fore limbs. If it proves difficult to push the fore limbs back, a noose may be passed around the fetlock of each and the cord drawn through the eye of a rope carrier, by means of which the members may be easily pushed back.
Embryotomy consists in the dissection of the fetus, so as to reduce its bulk and allow of its exit through the pelvis. The indications for its adoption have been furnished in the foregoing pages. The operation will vary in different cases according to the necessity for the removal of one or more parts in order to secure the requisite reduction in size. Thus it may be needful to remove head and neck, one fore limb or both, one hind limb or both, to remove different parts of the trunk, or to remove superfluous (monstrous) parts. Some of the simplest operations in embryotomy (incision of the head in hydrocephalus, incision of the belly in dropsy) have already been described. It remains to notice the more difficult procedures which can be best undertaken by the skilled anatomist.
Amputation of the head.—This is easy when both fore limbs are turned back and the head alone has made its exit in part. It is more difficult when the head is still retained in the passages or womb, as in double-headed monsters. The head is secured by a hook in the lower jaw, or in the orbit, or by a halter, and the skin is divided circularly around the lower part of the face or at the front of the ears, according to the amount of head protruding. Then an incision is made backward along the line of the throat, and the skin dissected from the neck as far back as possible. Then the muscles and other soft parts of the neck are cut across, and the bodies of two vertebra (neck bones) are severed by cutting completely across the cartilage of the joint. The bulging of the ends of the bones will serve to indicate the seat of the joint. The head and detached portion of the neck may now be removed by steady pulling. If there is still an obstacle, the knife may be again used to sever any obstinate connections. In the case of a double-headed monster, the whole of the second neck must be removed with the head. When the head has been detached, a rope should be passed through the eyeholes, or through an artificial opening in the skin, and tied firmly around the skin, to be employed as a means of traction when the missing limbs or the second head have been brought up into position.
Amputation of the hind limb.—This may be required when there are extra hind limbs or when the hind limbs are bent forward at hock or hip joint. In the former condition the procedure resembles that for removal of a fore limb, but requires more anatomical knowledge. Having noosed the pastern, a circular incision is made through the skin around the fetlock, and a longitudinal one from that up to the groin, and the skin is dissected from the limb as high up as can be reached, over the croup, if possible. Then cut through the muscles around the hip joint, and, if possible, the two interarticular ligaments of the joint (pubofemoral and round), and extract the limb by strong dragging.
Amputation of the fore limbs.—This may usually be begun on the fetlock of the limb projecting from the vulva. An embryotomy knife is desirable. This knife consists of a blade with a sharp, slightly hooked point, and one or two rings in the back of the blade large enough to fit on the middle finger, while the blade is protected in the palm of the hand. (See Plate XIII, fig. 4.) Another form has the blade inserted in a mortise in the handle, from which it is pushed out by a movable button when wanted. First place a noose around the fetlock of the limb to be amputated, cut the skin circularly entirely around the fetlock, then make an incision on the inner side of the limb from the fetlock up to the breastbone. Next dissect the skin from the limb, from the fetlock up to the breastbone on the inner side, and as far up on the shoulder blade as possible on the outer side. Finally, cut through the muscles attaching the limb to the breastbone, and employ strong traction on the limb, so as to drag out the whole limb, shoulder blade included. The muscles around the upper part of the shoulder blade are easily torn through and need not be cut, even if that were possible. In no case should the fore limb be removed unless the shoulder blade is taken with it, as that furnishes the greatest obstruction to delivery, above all when it is no longer advanced by the extension of the fore limb, but is pressed back so as to increase the already thickest posterior portion of the chest. The preservation of the skin from the whole limb is advantageous in various ways; it is easier to cut it circularly at the fetlock than at the shoulder; it covers the hand and knife in making the needful incisions, thus acting as a protection to the womb; and it affords a means of traction on the body after the limb has been removed. In dissecting the skin from the limb the knife is not needful at all points; much of it may be stripped off with the fingers or knuckles, or by a blunt, iron spud, pushed up inside the hide, which is meanwhile held tense to render the spud effective.
In case the limb is bent forward at the hock, a rope is passed round that and pulled so as to bring the point of the hock between the lips of the vulva. The hamstring and the lateral ligaments of the hock are now cut through, and the limbs extended by a rope tied round the lower end of the long bone above (tibia). In case it is still needful to remove the upper part of the limb, the further procedure is the same as described in the last paragraph.
In case the limb is turned forward from the hip, and the fetus so wedged into the passage that turning is impossible, the case is very difficult. I have repeatedly succeeded by cutting in on the hip joint and disarticulating it, then dissecting the muscles back from the upper end of the thigh bone. A noose was placed around the neck of the bone and pulled on forcibly, while any unduly resisting structures were cut with the knife.
Cartwright recommends to make free incisions round the hip joints and tear through the muscles when they can not be cut; then with cords round the pelvic bones, and hooks inserted in the openings in the floor of the pelvis to drag out the pelvic bones; then put cords around the heads of the thigh bones and extract them; then remove the intestines; finally, by means of the loose, detached skin, draw out the body with the remainder of the hind limbs bent forward beneath it.
Reuff cuts his way into the pelvis of the foal, and with a knife separates the pelvic bones from the loins, then skinning the quarter draws out these pelvic bones by means of ropes and hooks, and along with them the hind limbs.
The hind limbs having been removed by one or the other of these procedures, the loose skin detached from the pelvis is used as a means of traction and delivery is effected. In case of a monstrosity with extra hind limbs, it may be possible to bring these up into the passage and utilize them for traction.
Removal of the abdominal viscera.—In case the belly is unduly large, from decomposition, tumors, or otherwise, it may be needful to lay it open with the knife and cut or tear out the contents.
Removal of the thoracic viscera.—To diminish the bulk of the chest it has been found advisable to cut out the breastbone, remove the heart and lungs, and allow the ribs to collapse with the lower free ends overlapping each other.
Dissection of the trunk.—In case it becomes necessary to remove other portions of the trunk, we should follow the general rule of preserving the skin so that all manipulations can be made inside this as a protector, that it may remain available as a means of exercising traction on the remaining part of the body, and as a covering to protect the vaginal walls against injuries from bones while such part is passing.
This is rare in the mare, but not unknown, in connection with a failure of the womb to contract on itself after parturition, or with eversion of the womb (casting the withers), and congestion or laceration. If the blood accumulates in the flaccid womb, the condition may be suspected only by reason of the rapidly advancing weakness, swaying, unsteady gait, hanging head, paleness of the eyes and other mucous membranes, and weak, small, failing pulse. The hand introduced into the womb detects the presence of the blood partly clotted. If the blood escapes by the vulva, the condition is evident.
Treatment consists in evacuating the womb of its blood clots, giving a large dose of powdered ergot of rye, and in the application of cold water or ice to the loins and external generative organs. Besides this, a sponge impregnated with a strong solution of alum, or, still better, with tincture of muriate of iron, may be introduced into the womb and squeezed so as to bring the liquid in contact with the walls generally.
If the womb fails to contract after difficult parturition, the after-pains will sometimes lead to the fundus passing into the body of the organ and passing through that and the vagina until the whole inverted organ appears externally and hangs down on the thighs. The result is rapid engorgement and swelling of the organ, impaction of the rectum with feces, and distention of the bladder with urine, all of which conditions seriously interfere with the return of the mass. In returning the womb the standing is preferable to the recumbent position, as the abdomen is more pendent and there is less obstruction to the return. It may, however, be necessary to put hobbles on the hind limbs to prevent the mare from kicking. A clean sheet should be held beneath the womb, and all filth, straw, and foreign bodies washed from its surface. Then with a broad, elastic (india-rubber) band, or in default of that a long strip of calico 4 or 5 inches wide, wind the womb as tightly as possible, beginning at its most dependent part (the extremity of the horn). This serves two good ends. It squeezes out into the general circulation the enormous mass of blood which engorged and enlarged the organ, and it furnishes a strong protective covering for the now delicate, friable organ, through which it may be safely manipulated without danger of laceration. The next step may be the pressure on the general mass while those portions next the vulva are gradually pushed in with the hands; or the extreme lowest point (the end of the horn) may be turned within itself and pushed forward into the vagina by the closed fist, the return being assisted by manipulations by the other hand, and even by those of assistants. By either mode the manipulations may be made with almost perfect safety so long as the organ is closely wrapped in the bandage. Once a portion has been introduced into the vagina the rest will usually follow with increasing ease, and the operation should be completed with the hand and arm extended the full length within the womb and moved from point to point so as to straighten out all parts of the organ and insure that no portion still remain inverted within another portion. Should any such partial inversion be left it will give rise to straining, under the force of which it will gradually increase until the whole mass will be protruded as before. The next step is to apply a truss as an effectual mechanical barrier to further escape of the womb through the vulva. The simplest is made with two 1-inch ropes, each about 18 feet long, each doubled and interwoven at the bend, as seen in Plate XIV, figure 4. The ring formed by the interlacing of the two ropes is adjusted around the vulva, the two ends of the one rope are carried up on the right and left of the tail and along the spine, being wound around each other in their course, and are finally tied to the upper part of the collar encircling the neck. The remaining two ends, belonging to the other rope, are carried downward and forward between the thighs and thence forward and upward on the sides of the belly and chest to be attached to the right and left sides of the collar. These ropes are drawn tightly enough to keep closely applied to the opening without chafing, and will fit still more securely when the mare raises her back to strain. It is desirable to tie the mare short so that she may be unable to lie down for a day or two, and she should be kept in a stall with the hind parts higher than the fore. Violent straining may be checked by full doses of opium (one-half dram), and any costiveness or diarrhea should be obviated by a suitable laxative or binding diet.
In some mares the contractions are too violent to allow of the return of the womb, and full doses of opium one-half dram, laudanum 2 ounces, or chloral hydrate 1 ounce, may be demanded, or the mare must be rendered insensible by ether or chloroform.
This may occur from the feet of the foal during parturition, or from ill-directed efforts to assist, but it is especially liable to take place in the everted, congested, and friable organ. The resultant dangers are bleeding from the wound, escape of the bowels through the opening and their fatal injury by the mare's feet or otherwise, and peritonitis from the extension of inflammation from the wound and from the poisonous action of the septic liquids of the womb escaping into the abdominal cavity. The first object is to close the wound, but unless in eversion of the womb this is practically impossible. In the last-named condition the wound must be carefully and accurately sewed up before the womb is returned. After its return, the womb must be injected daily with an antiseptic solution (borax, one-half ounce, or carbolic acid, 3 drams to a quart of tepid water). If inflammation threatens, the abdomen may be bathed continuously with hot water by means of a heavy woolen rag, and large doses of opium (one-half dram) may be given twice or thrice daily.
These are attended with dangers similar to those belonging to rupture of the womb, and in addition by the risk of protrusion of the bladder, which appears through the lips of the vulva as a red, pyriform mass. Sometimes such lacerations extend downward into the bladder, and in others upward into the terminal gut (rectum). In still other cases the anus is torn so that it forms one common orifice with the vulva.
Too often such cases prove fatal, or at least a recovery is not attained, and urine or feces or both escape freely into the vagina. The simple laceration of the anus is easily sewed up, but the ends of the muscular fibers do not reunite and the control over the lower bowel is never fully reacquired. The successful stitching up of the wound communicating with the bladder or the rectum requires unusual skill and care, and though I have succeeded in a case of the latter kind, I can not advise the attempt by unprofessional persons.
(See "Effusion of blood in the vaginal walls," p. 190.)
This sometimes follows on inflammation of the womb, as it frequently does on disorder of the stomach. Its symptoms agree with those of the common form of founder, and treatment need not differ.
These may result from injuries sustained by the womb during or after parturition, from exposure to cold or wet, or from the irritant infective action of putrid products within the womb. Under the inflammation the womb remains dilated and flaccid, and decomposition of its secretions almost always occurs, so that the inflammation tends to assume a putrid character and general septic infection is likely to occur.
Symptoms.—The symptoms are ushered in by shivering, staring coat, small, rapid pulse, elevated temperature, accelerated breathing, loss of appetite, with arched back, stiff movement of the body, looking back at the flanks, and uneasy motions of the hind limbs, discharge from the vulva of a liquid at first watery, reddish, or yellowish, and later it may be whitish or glairy, and fetid or not in different cases. Tenderness of the abdomen shown on pressure is especially characteristic of cases affecting the peritoneum or lining of the belly, and is more marked lower down. If the animal survives, the inflammation tends to become chronic and attended by a whitish mucopurulent discharge. If, on the contrary, it proves fatal, death is preceded by extreme prostration and weakness from the general septic poisoning.
Treatment.—In treatment the first thing to be sought is the removal of all offensive and irritant matters from the womb through a caoutchouc tube introduced into the womb, and into which a funnel is fitted. Warm water should be passed until it comes away clear. To insure that all the womb has been washed out, the oiled hand may be introduced to carry the end of the tube into the two horns successively. When the offensive contents have been thus removed, the womb should be injected with a quart of water holding in solution 1 dram permanganate of potash, or, in the absence of the latter, 2 teaspoonfuls of carbolic acid, twice daily. Fomentation of the abdomen, or the application of a warm flaxseed poultice, may greatly relieve. Acetanilid, in doses of half an ounce, twice or thrice a day, or sulphate of quinia in doses of one-third ounce, may be employed to reduce the fever. If the great prostration indicates septic poisoning, large doses (one-half ounce) bisulphite of soda, or salicylate of soda, or sulphate of quinin may be resorted to.
This is a white, glutinous, chronic discharge, the result of a continued, subacute inflammation of the mucous membrane of the womb. Like the discharge of acute inflammation, it contains many forms of bacteria, by some of which it is manifestly inoculable on the penis of the stallion, producing ulcers and a specific, gonorrheal discharge.
Treatment may consist in the internal use of tonics (sulphate of iron, 3 drams, daily) and the washing out of the womb, as described under the last heading, followed by an astringent antiseptic injection (carbolic acid, 2 teaspoonfuls; tannic acid, 1/2 dram; water, 1 quart). This may be given two or three times a day.
This is comparatively rare in the mare, though in some cases the udder becomes painfully engorged before parturition, and a doughy swelling, pitting on pressure, extends forward on the lower surface of the abdomen. When this goes on to active inflammation, one or both of the glands becomes enlarged, hot, tense, and painful; the milk is dried up or replaced by a watery or reddish, serous fluid, which at times becomes fetid; the animal walks lame, loses appetite, and shows general disorder and fever. The condition may end in recovery, in abscess, induration, or gangrene, and, in some cases, may lay the foundation for a tumor of the gland.
Treatment.—The treatment is simple so long as there is only congestion. Active rubbing with lard or oil, or, better, camphorated oil, and the frequent drawing off of the milk, by the foal or with the hand, will usually bring about a rapid improvement. When active inflammation is present, fomentation with warm water may be kept up for an hour and followed by the application of the camphorated oil, to which has been added some carbonate of soda and extract of belladonna. A dose of laxative medicine (4 drams Barbados aloes) will be of service in reducing fever, and one-half ounce saltpeter daily will serve a similar end. In case the milk coagulates in the udder and can not be withdrawn, or when the liquid becomes fetid, a solution of 20 grains carbonate of soda and 10 drops carbolic acid dissolved in an ounce of water should be injected into the teat. In doing this it must be noted that the mare has three separate ducts opening on the summit of each teat and each must be carefully injected. To draw off the fetid product it may be needful to use a small milking tube, or spring teat dilator designed by the writer. (Plate XIV, figs. 2 and 3.) When pus forms and points externally and can not find a free escape by the teat, the spot where it fluctuates must be opened freely with the knife and the cavity injected daily with the carbolic-acid lotion. When the gland becomes hard and indolent, it may be rubbed daily with iodin ointment 1 part, vaseline 6 parts.
As the result of inflammation of the udder it may become the seat of an indurated diseased growth, which may go on growing and seriously interfere with the movement of the hind limbs. If such swellings do not give way in their early stages to treatment by iodin, the only resort is to cut them out with a knife. As the gland is often implicated and has to be removed, such mares can not in the future suckle their colts and therefore should not be bred.
By the act of sucking, especially in cold weather, the teats are subject to abrasions, cracks, and scabs, and as the result of such irritation, or independently, warts sometimes grow and prove troublesome. The warts should be clipped off with sharp scissors and their roots burned with a solid pencil of lunar caustic. This is best done before parturition to secure healing before suckling begins. For sore teats use an ointment of vaseline 1 ounce, balsam of tolu 5 grains, and sulphate of zinc 5 grains.
The nervous system may be regarded as consisting of two sets of organs, peripheral and central, the function of one being to establish a communication between the centers and the different parts of the body, and that of the other to generate nervous force. The whole may be arranged under two divisions: First, the cerebrospinal system; second, the sympathetic or ganglionic system. Each is possessed of its own central and peripheral organs.
In the first, the center is made up of two portions—one large and expanded (the brain) placed in the cranial cavity; the other elongated (spinal cord), continuous with the brain, and lodged in the canal of the vertebral column. The peripheral portion of this system consists of the cerebrospinal nerves, which leave the axis in symmetrical pairs and are distributed to the skin, the voluntary muscles, and the organs.
In the second, the central organ consists of a chain of ganglia, connected by nerve cords, which extends on each side of the spine from the head to the rump. The nerves of this system are distributed to the involuntary muscles, mucous membrane, viscera, and blood vessels.
The two systems have free intercommunication, ganglia being at the junctions.
Two substances, distinguishable by their color, namely, the white or medullary and the gray or cortical substance, enter into the formation of nervous matter. Both are soft, fragile, and easily injured, in consequence of which the principal nervous centers are well protected by bony coverings. The nervous substances present two distinct forms—nerve fibers and nerve cells. An aggregation of nerve cells constitutes a nerve ganglion.
The nerve fibers represent a conducting apparatus and serve to place the central nervous organs in connection with peripheral end organs. The nerve cells, however, besides transmitting impulses, act as physiological centers for automatic, or reflex, movements, and also for the sensory, perceptive, trophic, and secretory functions. A nerve consists of a bundle of tubular fibers, held together by a dense areolar tissue, and inclosed in a membranous sheath—the neurilemma. Nerve fibers possess no elasticity, but are very strong. Divided nerves do not retract.
Nerves are thrown into a state of excitement when stimulated, and are, therefore, said to possess excitable or irritable properties. The stimuli may be applied to, or may act upon, any part of the nerve. Nerves may be paralyzed by continuous pressure being applied. When the nerves divide into branches, there is never any splitting up of their ultimate fibers, nor yet is there ever any coalescing of them; they retain their individuality from their source to their termination.
Nerves which convey impressions to the centers are termed sensory, or centripetal, and those which transmit stimulus from the centers to organs of motion are termed motor, or centrifugal. The function of the nervous system may, therefore, be defined in the simplest terms, as follows: It is intended to associate the different parts of the body in such a manner that stimulus applied to one organ may excite or depress the activity of another.
The brain is that portion of the cerebrospinal axis within the cranium, which may be divided into four parts—the medulla oblongata, the cerebellum, the pons Varolii, and the cerebrum—and it is covered by three membranes, called the meninges. The outer of these membranes, the dura mater, is a thick, white, fibrous membrane which lines the cavity of the cranium, forming the internal periosteum of the bones; it is continuous with the spinal cord to the extremity of the canal. The second, the arachnoid, is a delicate serous membrane, and loosely envelops the brain and spinal cord; it forms two layers, having between them the arachnoid space which contains the cerebrospinal fluid, the use of which is to protect the spinal cord and brain from pressure. The third, or inner, the pia mater, is closely adherent to the entire surface of the brain, but is much thinner and more vascular than when it reaches the spinal cord, which it also envelops, and is continued to form the sheaths of the spinal nerves.
The medulla oblongata is the prolongation of the spinal cord, extending to the pons Varolii. This portion of the brain is very large in the horse: it is pyramidal in shape, the narrowest part joining the cord.
The pons Varolii is the transverse projection on the base of the brain, between the medulla oblongata and the peduncles of the cerebrum.
The cerebellum is lodged in the posterior part of the cranial cavity, immediately above the medulla oblongata; it is globular or elliptical in shape, the transverse diameter being greatest. The body of the cerebellum is composed of gray matter externally and of white matter in the center. The cerebellum has the function of co-ordinating movements; that is, of so associating them as to cause them to accomplish a definite purpose. Injuries to the cerebellum cause disturbances of the equilibrium but do not interfere with the will power or intelligence.
The cerebrum, or brain proper, occupies the anterior portion of the cranial cavity. It is ovoid in shape, with an irregular, flattened base, and consists of lateral halves or hemispheres. The greater part of the cerebrum is composed of white matter. The hemispheres of the cerebrum are usually said to be the seat of all psychical activities. Only when they are intact are the process of feeling, thinking, and willing possible. After they are destroyed the organism comes to be like a complicated machine, and its activity is only the expression of the internal and external stimuli which act upon it.
The spinal cord, or spinal marrow, is that part of the cerebrospinal system which is contained in the spinal canal of the backbone, and extends from the medulla oblongata to a short distance behind the loins. It is an irregularly cylindrical structure, divided into two lateral, symmetrical halves by fissures. The spinal cord terminates posteriorly in a pointed extremity, which is continued by a mass of nerve trunks—cauda equinæ. A transverse section of the cord reveals that it is composed of white matter externally and of gray matter internally. The spinal cord does not fill the whole spinal canal. The latter contains, besides, a large venous sinus, fatty matter, the membranes of the cord, and the cerebrospinal fluid.
The spinal nerves, forty-two or forty-three in number, arise each by two roots, a superior or sensory, and an inferior or motor. The nerves originating from the brain are twenty-four in number, and arranged in pairs, which are named first, second, third, etc., counting from before backward. They also receive special names, according to their functions or the parts to which they are distributed, viz:
Inflammation may attack these membranes singly, or any one of the anatomical divisions of the nerve matter, or it may invade the whole at once. Practical experience, however, teaches us that primary inflammation of the dura mater is of rare occurrence, except in direct mechanical injuries to the head or diseases of the bones of the cranium. Neither is the arachnoid often affected with acute inflammation, except as a secondary result. The pia mater is most commonly the seat of inflammation, acute and subacute, but from its intimate relation with the surface of the brain the latter very soon becomes involved in the morbid changes. Practically, we can not separate inflammation of the pia mater from that of the brain proper. Inflammation may, however, exist in the center of the great nerve masses—the cerebrum, cerebellum, pons Varolii, or medulla at the base of the brain—without involving the surface. When, therefore, inflammation invades the brain and its enveloping membranes it is properly called encephalitis; when the membranes alone are affected it is called meningitis, or the brain substance alone cerebritis. Since all the conditions merge into one another and can scarcely be recognized separately during the life of the animal, they may here be considered together.
Causes.—Exposure to extreme heat or cold, sudden and extreme changes of temperature, excessive continued cerebral excitement, too much nitrogenous feed, direct injuries to the brain, such as concussion, or from fracture of the cranium, overexertion, sometimes as sequelæ to influenza, pyemia, poisons having a direct influence upon the encephalic mass, extension of inflammation from neighboring structures, food poisoning, tumors, parasites, metastatic abscesses, etc.
Symptoms.—The diseases here grouped together are accompanied with a variety of symptoms, almost none of which, however, are associated so definitely with a special pathological process as to point unmistakably to a given lesion. Usually the first symptoms indicate mental excitement, and are followed by symptoms indicating depression. Acute encephalitis may be ushered in by an increased sensibility to noises, with more or less nervous excitability, contraction of the pupils of the eyes, and a quick, hard pulse. In very acute attacks these symptoms, however, are not always noted. This condition will soon be followed by muscular twitchings, convulsive or spasmodic movements, eyes wide open with shortness of sight. The animal becomes afraid to have his head handled. Convulsions and delirium will develop, with inability of muscular control, or stupor and coma may supervene. When the membranes are greatly implicated, convulsions and delirium with violence may be expected, but if the brain substances are principally affected stupor and coma will be the prominent symptoms. In the former condition the pulse will be quick and hard; in the latter, soft and depressed, with often a dilatation of the pupils, and deep, slow, stertorous breathing. The symptoms may follow one another in rapid succession, and the disease approach a fatal termination within 12 hours. In subacute attacks the symptoms are better defined, and the animal seldom dies before the third day. Within three or four days gradual improvement may become manifest, or cerebral softening with partial paralysis may occur. In all cases of encephalitis there is a marked rise in temperature from the very onset of the disease, with a tendency to increase until the most alarming symptoms develop, succeeded by a decrease when coma becomes manifest. The violence and character of the symptoms greatly depend upon the extent and location of the structures involved. Thus, in some cases there may be marked paralysis of certain muscles, while in others there may be spasmodic rigidity of muscles in a certain region. Very rarely the animal becomes extremely violent early in the attack, and by rearing up, striking with the fore feet, or falling over, may do himself great injury. Usually, however, the animal maintains the standing position, propping himself against the manger or wall, until he falls from inability of muscular control, or from unconsciousness. Occasionally, in his delirium, he may go through a series of automatic movements, such as trotting or walking, and, if loose in a stall, will move around persistently in a circle. Early and persistent constipation of the bowels is a marked symptom in nearly all acute affections of the brain; retention of the urine, also, is frequently observed.
Following these symptoms there are depression, loss of power and consciousness, lack of ability or desire to move, and usually fall of temperature. At this stage the horse stands with legs propped, the head hanging or resting on the manger, the eyes partly closed, and does not respond when spoken to or when struck with a whip.
Chronic encephalitis or meningitis may succeed the acute stage, or may be due to stable miasma, blood poison, narcotism, lead poisoning, etc. This form may not be characterized in its initial stages by excitability, quick and hard pulse, and high fever. The animal usually appears at first stupid; eats slowly; the pupil of the eye does not respond to light quickly; the animal often throws his head up or shakes it as if suffering sudden twinges of pain. He is slow and sluggish in his movements, or there may be partial paralysis of one limb, one side of the face, neck, or body. These symptoms, with some variations, may be present for several days and then subside, or the disease may pass into the acute stage and terminate fatally. Chronic encephalitis may effect an animal for ten days or two weeks without much variation in the symptoms before the crisis is reached. If improvement commences, the symptoms usually disappear in the reverse order to that in which they developed, with the exception of the paralytic effects, which remain intractable or permanent. Paralysis of certain sets of muscles is a very common result of chronic, subacute, and acute encephalitis, and is due to softening of the brain or to exudation into the cavities of the brain or arachnoid space.
Softening and abscess of the brain are terminations of cerebritis. It may also be due to an insufficient supply of blood as a result of diseased cerebral arteries and of apoplexy. The symptoms are drowsiness, vertigo, or attacks of giddiness, increased timidity, or fear of familiar objects, paralysis of one limb, hemiplegia, imperfect control of the limbs, and usually a weak, intermittent pulse. In some cases the symptoms are analogous to those of apoplexy. The character of the symptoms depends upon the seat of the softening or abscess within the brain.
Cerebral sclerosis sometimes follows inflammation in the structure of the brain affecting the connective tissues, which eventually become hypertrophied and press upon nerve cells and fibers, causing their ultimate disappearance, leaving the parts hard and indurated. This condition gives rise to a progressive paralysis and may extend along a certain bundle of fibers into the spinal cord. Complete paralysis almost invariably supervenes and causes death.
Lesions.—On making post-mortem examinations of horses which have died in the first stages of either of these diseases we find an excessive engorgement of the capillaries and small blood vessels, with correspondingly increased redness and changes in both the contents and the walls of the vessels. If death has occurred at a later period of the disease, it will be found that, in addition to the redness and engorgement, an exudation of the contents of the blood vessels into the tissues and upon the surfaces of the inflamed parts has supervened. If the case has been one of encephalitis, there will usually be found more or less watery fluid in the ventricles (natural cavities in the brain), in the subarachnoid space, and a serous exudation between the convolutions and interstitial spaces of the gray matter under the membranes of the brain. The quantity of fluid varies in different cases. Exudations of a membranous character may be present, and are found attached to the surfaces of the pia mater.
In meningitis, especially in chronic cases, in addition to the serous effusion, there are changes which may be regarded as characteristic in the formation of a delicate and highly vascular layer or layers of membrane or organized structure on the surface of the dura mater, and also indications of hemorrhages in connection with the membranous formations. Hematoma, or blood tumors, may be found embedded in this membrane. In some cases the hemorrhages are copious, causing paralysis or apoplexy, followed by speedy death. The meningitis may be suppurative. In this case a puslike exudate is found between the membranes covering the brain.
In cerebritis, or inflammation of the interior of the brain, there is a tendency to softening and suppuration and the formation of abscesses. In some cases the abscesses are small and numerous, surrounded with a softened condition of the brain matter, and sometimes we may find one large abscess. In cases of recent development the walls of the abscesses are fringed and ragged and have no lining membrane. In older or chronic cases the walls of the abscesses are generally lined with a strong membrane, often having the appearance of a sac or cyst, and the contents have a very offensive odor.
Treatment.—In all acute attacks of inflammation involving the membranes or cerebral masses, it is the pressure from the distended and engorged blood vessels and the rapid accumulation of inflammatory products that endangers the life of the animal in even the very early stage of the disease. The earlier the treatment is commenced to lessen the danger of fatal pressure from the engorged blood vessels, the less effusion and smaller number of inflammatory products we have to contend with later. The leading object, then, to be accomplished in the treatment of the first stage of encephalitis, meningitis, or cerebritis, and before a dangerous degree of effusion or exudation has taken place, is to relieve the engorgement of the blood vessels and thereby lessen the irritation or excitability of the affected structures. If the attempt to relieve the engorgement in the first stage has been only partially successful, and the second stage, with its inflammatory products and exudations, whether serous or plastic, has set in, then the main objects in further treatment are to keep up the strength of the animal and hasten the absorption of the exudative products as much as possible. To obtain these results, when the animal is found in the initial stage of the disease, if there is unnatural excitability or stupor with increase of temperature and quickened pulse, we should apply cold to the head in the form of cold water or ice. For this purpose cloths or bags may be used, and they should be renewed as often as necessary. If the disease is still in its early stages and the animal is strong, bleeding from the jugular vein may be beneficial. Good results are to be expected only during the stage of excitement, while there is a strong, full pulse and the mucous membranes of the head are red from a plentiful supply of blood. The finger should be kept on the pulse and the blood allowed to flow until there is distinct softening of the pulse. As soon as the animal recovers somewhat from the shock of the bleeding the following medicine should be made into a ball or dissolved in a pint of warm water and be given at one dose: Barbados aloes, 7 drams; calomel, 2 drams; powdered ginger, 1 dram; tincture of aconite, 20 drops.
The animal should be placed in a cool, dark place, as free from noise as possible. When the animal becomes thirsty half an ounce of bromid of potash may be dissolved in the drinking water every six hours. Injections of warm water into the rectum may facilitate the action of the purgative. Norwood's tincture of veratrum viride, in 20-drop doses, should be given every hour and 1 dram of solid extract of belladonna every four hours until the symptoms become modified and the pulse regular and full.