Chapter IV: Part 4

_Causes._ 1st. =Compression of the jugular veins= by a too tight collar is the cause of one of the simplest forms of vertigo and is observed, in growing or fattening animals in which the neck has become gradually too large for the collar. The supply of a larger and well fitting collar will soon confirm the diagnosis by a complete and permanent removal of the trouble. In other cases the veins may be compressed by undue flexion of the head, the chin being drawn toward the breast, or by a throat latch buckled too tightly. The substitution of an overdraw check rein, or a loose throat latch will show the true source of the trouble.

2nd. =Disease of the valves= _of the heart_ or their insufficiency from cardiac dilatation is a common cause of vertigo, and may be recognized by auscultation and by the general symptoms of chronic heart disease.

3d. =Disease of the lungs= interfering with the flow of blood through the right heart and more distantly with the return of blood from the brain. It further effects the brain functions through the circulation of a highly carbonized blood, which fails to maintain the normal functions of the ganglia.

4th. =Disease of the blood vessels=, it may be by emboli washed on from clots in the pulmonary veins or the left heart and arrested in the vessels of the brain; it may be by aneurism of the anterior aorta as reported of a horse (Lustig); it may be by phlebitis and thrombosis of the jugulars; it may be by adjacent tumors pressing on the vessels.

5th. =Gastric Vertigo=, =Abdominal Vertigo=, is a complication of gastric or hepatic disorder with giddiness and unsteady movement. The abdominal disorder may be at once a cause and result of the vertigo and it is not always easy to decide which predominates. The unsteady movements in certain cases of overloaded stomach, in the horse are illustrations of purely abdominal vertigo, while on the other hand in vomiting animals nausea, retching, emesis, and other gastric disorders promptly attend on the primary cerebral disorder. There is also a special tendency to vertigo in the fat, idle, gorged horse and in those with torpor or other disorder of the liver occurring in pampered horses in spring and early summer.

6th. =Optic vertigo= is a reflex disorder, determined in the excitable nerve centres by the visual influence. Thus it has been seen in horses and sheep from the intense glare of the sun’s rays, reflected from a lake or river or from white snow or ice, or even from the glistening inner surface of the blinds. The effect is intensified if the animal has just emerged from a dark stable or a darker mine. The overdraw check may be a factor by reason of its turning the eyes upward and exposing them continuously to the full glare of the sun. The sense of motion conveyed through the eyes contributes to bring on giddiness and a sense of swimming. In man this is notorious, the sense of nausea and vertigo being precipitated by looking at the nearby, moving objects in cabin or on deck, while it may be retarded by directing the eyes to steady distant objects. As dogs, horses and other animals suffer from seasickness, and even railroad sickness, this attendant factor may be logically accepted. The mere limitation of the field of vision, by the use of blinds, and the disappearance in rapid succession of near objects behind this narrow screen probably has an influence similar to the visible motions in the ship between decks, in cases in which these portions of the harness are manifest factors.

7th. =Aural Vertigo= is determined by irritations of different kinds affecting the external, middle or internal ear. Experimental sections show that this is especially due to injuries of the semicircular canals. If the _horizontal canal_ is divided there are pendulum-like movements of the head alternately to the right and left, also lateral rolling of the eyes. If the _posterior canal_ is cut there is a vertical movement, or nodding of the head and vertical rolling of the eyes. If the _superior vertical canals_ are injured there are pendulum-like vertical movements of the head and the animal tends to fall forward. Injury to the _anterior canal_ causes diagonal rolling of the eyeball. In destruction of _all the canals_ various pendulum-like movements are performed, and standing often becomes impossible. Stimulation of one auditory nerve is followed by rotation of the eye and rotation of the body on its axis toward the injured side. The passage of a galvanic current through the head _between the mastoid processes_, or _from one external auditory meatus to the other_, causes rolling of the eyeballs. _Injection of water violently into a rabbit’s ear_, or of _iced water_ or of a _rhigolene_ jet, causes rolling of the eyes, and rotation of the body toward the side operated on. Dr. Weir Mitchell had a similar experience in his own person. If the injections are repeated a permanent vertiginous condition is induced, and the rabbit or Guinea pig, which has been kept in darkness for a few hours and is then suddenly exposed to sunlight, is unstable on its limbs for a few seconds. Lucæ found that with perforation of the membrana tympani, an _ear air douche_, at 0.1 atmospheres caused abduction of the eyeball, dyplopia, giddiness, sense of darkness, and disturbed respiration. Vulpain found that a 25 per cent. solution of _chloral hydrate dropped into the ear_ of a rabbit caused vertiginous movements. McVey records the case of a music teacher who had intense vertigo induced by the _low bass notes_ of a piano. Crum Brown noticed that if a person with bandaged eyes, is rotated for some time as on a potter’s wheel, he can at first estimate the degree of rotation, but after a time he fails to do so, and the rotation may be stopped, without checking his sense of whirling. The familiar method of subduing an intractable or vicious horse by _running_ him rapidly around _in a very narrow circular course_, or by tying head and tail together and letting him circle around until he staggers or falls, is another manifest example of this aural vertigo. Rabbits and dogs suffering from _acariasis of the external ear_ move around in a circle, or even turn somersaults tending toward the affected side. Trasbot has found larvæ of insects (simulium cinereum?) in the ears of vertiginous horses, which he successfully treated with injection of chloroform. Even hard pellets of wax pressing on the tympanic membrane have been found to give rise to vertigo.

The explanation of cases of aural vertigo, has been sought in the physiological action of the endolymph and perilymph on the end filaments of the nerve in the membranous labyrinth, the turning of the head from one side to the other having the effect of changing the pressure in different parts and establishing currents by which the change of position is recognized; on the other hand any injury to the canals, by disturbing the pressure of the perilymph and interfering with the relative position of the canals, and the direction and force of the currents of the endolymph and perilymph, destroys all proper sense of balance. The rotation of the subject as on a wheel or in turning in a narrow circle, is held to cause circular currents in and around the membranous labyrinth which temporarily destroy all sense of equilibrium. Seasickness and railroad sickness are doubtless in part due to the swaying motions causing disturbance in the canals. The intimate relation between the root of the auditory nerve and that of the vagus in the medulla, may serve to explain the mutual interdependence of derangement of the stomach and liver on the one hand and the occurrence of vertigo on the other. Again the relation of vertigo to visual troubles, both as to cause and effect, has been attributed to the close relations of the ganglia presiding over the 3d, 4th, 5th and 6th nerves and those of the nerve of hearing.

There is a degree of deafness in nearly all cases of aural vertigo, a circumstance which may be utilized in the diagnosis of such cases, the presence of disease of the guttural pouch, or Eustachian tube, and evidence of deafness on one side rather than the other, may be taken as corroborative evidence of the affection. On the other hand James shows that the stone deaf are much less subject to both seasickness and vertigo than those that hear. The disorder that leads to vertigo implies a retention of a measure of the normal function of the internal ear, and therefore of hearing, whereas the disease that has caused complete destruction of the internal ear and consequent loss of hearing has equally destroyed the function of the labyrinth in maintaining a sense of balance, and has obviated the aural sensations of equilibrium and loss of balance.

8th. =Cerebral Vertigo= may be associated with derangement of the circulation, or disease in the brain or its meninges. Anæmias and congestions resulting from disease or impaired function of heart, lungs, arteries or veins have been already noticed. It remains to note the presence of cholesteatomata and other tumors, and of parasites (cysticercus cellulosa in pig; cœnurus cerebralis in sheep) in the encephalon, and of injuries from concussion, degeneration and softening of the brain substance.

9th. =Nasal Vertigo= has been noted by Cadeac in connection with irritation in the nose and especially by the larva of œstrus ovis (sheep), and the linguatula (dog, horse). In certain of the cases manifested by jerking of the head and diverging to one side, the recovery after section of the pes anserina indicates a nasal origin.

10th. =Vertigo from Narcotics= (alcohol, lolium temulentum, belladonna, solanum, various essential oils, carbon monoxide, etc.), have been already referred to.

11th. There remains to be noted cases in which no narcotic poison, no mechanical disturbance of the circulation, no visual, aural nor nasal trouble, no gastric nor hepatic disorder, and not even a distant nervous lesion can be found; the disease may in such cases be ranked for the present as =essential vertigo=.

_Symptoms._ As usually seen in the horse, vertigo often attacks the nervous, irritable animal in which the slightest occasion of irritation or disturbance causes intense suffering and quick response. This is often aggravated by the plethoric condition of the animal, kept on a liberal ration of grain and having little exercise. In some forms of the affection, however, and especially the gastric and hepatic, the subject is dull, carries the head low, and lacks vivacity and energy.

In the first form (the most common in the horse) the animal which has been full of life and vigor, slackens his pace and the tension on the reins, or stops suddenly, shakes the head, vertically or horizontally, or jerks it to one side, trembles, staggers, props his legs outward for more stable support, presses against the pole, or the other horse, or a wall, leans on the breeching or hangs on the breast strap, plunges forward, or to one side, or rears up and even falls backward, and comes to the ground. Profuse perspiration ensues, the eyes roll, the face is pinched and drawn, the prostrate animal may struggle in a helpless way, and, if the harness is loosened, he may get up in a few seconds and slowly recover. Often, however, he remains for an hour or more, nervous, sensitive, bedewed with sweat, trembling and with anxious expression. Such are the more common manifestations of what is familiarly known as blind staggers. The symptoms will vary however, with the cause.

In =gastric= or =hepatic= cases there may be more particularly dullness and lack of energy, low carriage of the head, unsteadiness of gait, lack of lustre in the eye, pupils dilated, semi-closed eyelids, pendent lips, a tendency to lean on the stall or hang on the harness, and though the animal may stagger and fall, there is not the abrupt transition from life and energy to the active excitement and uncontrollable movements. The same remarks apply in a measure to narcotic vertigo.

With =optic vertigo=, the attendant conditions will help to a diagnosis. The animal has come from darkness to full sunshine; there is the white, icy or snowy reflection everywhere which the animal was facing when attacked, or the glistening lake or river, the overdraw check rein, or the blind with perhaps a shining inner surface. The pupil is closed, and the eye is rolled back or oscillates in one direction or another. The symptoms are checked by covering the eyes or removing the subject into a dark building or even into the shade of a tree or shed.

With =aural vertigo= there may be similar rolling of the eyes, without the pupillary closure, the ear may be drawn down or back, and the shaking or jerking of the head is likely to be a marked feature. If there is more motion of one ear than the other, if the head is jerked to the one side, if there is a measure of deafness in the one ear (to be ascertained rather in the intervals between attacks), if there is disease of the pharynx, the Eustachian tube or pouch, or swelling about the root of the ear, if there is wax, scurf, or acarus in the ear, if the animal rubs it frequently, aural vertigo may be suspected.

=Nasal vertigo.= Those forms in which the head is jerked horizontally, vertically, or diagonally, the animal pressing against its mate or the pole, or outward in the harness, and getting out of its track, even if it should stop short of falling, and which appear only during work, or are aggravated by exertion, have been attributed to lesions of the ear (Fleming), but in some cases they can be warded off by wearing a net over the nostril, and can be entirely stopped by complete transverse section of the pes anserina, so that in a certain number at least they must be accounted nasal. These are not usually attended by sneezing. The simple expedient of driving with a rather close net over the nostril may enable one to diagnose many of the purely nasal forms.

=Plethoric vertigo= may be suspected when the attack comes on in spring, in a fleshy or fat horse, overfed and little exercised, when there is dark red congestion of the nasal mucosa and conjunctiva, and a subsidence with rest.

In the _vertigo_ of brain lesions, the acute forms are attended by fever and marked signs of delirium or disordered nervous functions, while in the chronic forms there may be permanent hyperæsthesia or anæsthesia, general or with rather diffuse limits, and the vertiginous attacks repeat themselves frequently irrespective of weather, though they may be precipitated by faults of feeding, indigestion, severe exertion, or some of the other exciting causes above mentioned.

These cases are to be distinguished from epilepsy by the absence of any spasmodic contraction, aside from the jerking of the head and rolling of the eyes, and by the fact that consciousness is retained throughout. During the attack the animal may fail to respond to irritation of the nasal mucosa, but this appears to be due to the fact that his whole attention is engaged with a more serious trouble.

The duration of an attack is from one to two, or exceptionally five minutes. The form which is represented by jerking of the head and deviation from the direct line of motion may continue so long as exercise is kept up.

In the =nasal vertigo= of sheep and dogs, due to parasites, sneezing, and congestion of the mucosa are to be looked for.

In the =cerebral parasitic vertigo= of sheep and pigs, the symptoms vary according to the seat of the parasite. These may be blindness, turning in a circle, moving straight ahead regardless of obstacles, jerking upward of the head with nose protruded, hemiplegia, hemianæsthesia, cross hemiplegia, cross hemianæsthesia, and any one of the many forms of paralysis, or exaggerated nervous action. The animal usually turns to the side on which the parasite lies and is paralyzed on the opposite side of the trunk. A peculiarity of these cases is that while the symptoms are continuous, yet there are periodic aggravations which bear no relation to feeding, exertion or excitement, but depend on the protrusion at intervals of the heads of the parasites into the brain substance. If there are several parasites in the brain and they do this at different times the symptoms are liable to vary according to their seat, and the special organ which is irritated. This variability of symptoms is suggestive of parasitism.

While turning around in a circle has been already noticed there remains, in certain cerebral forms, the peculiar phenomenon of the animal rotating rapidly on its longitudinal axis. The patient falls on its side and rolls over and over. Among the brain lesions with which it has been experimentally identified are injuries to the _middle peduncles of the cerebellum_, or of the _superoexternal portion of the cerebral peduncles_, or of the _posterior part of the encephalon_, or of different parts of the hemispheres.

Cases of vertigo that occur without any appreciable lesion have been named _essential vertigo._ Guibert has attributed some cases to irritation of the lower part of the limbs by contact with the litter but this could only occur in an animal in which the nervous system was in a morbidly excitable condition.

_Treatment._ The prophylactics and therapeutics of vertigo will vary with the cause. The diagnosis of the cause is therefore the most important step. In pampered, overfed, idle horses a reduced ration and daily exercise or work will often suffice. It is usually desirable, however, to remove intestinal irritants and deplete the vascular system by an active purgative. If the attacks appear only in Spring this care should be especially given at such seasons. A tight or badly fitting collar should be corrected, also a position of the breast strap which causes it to press on the jugular veins. A short bearing rein causing undue flexion of the head must be lengthened or abandoned. A too dark stable should be avoided, also the sudden exposure to white, dusty roads and, still more so, to the glare of snow, ice, or water. A short, overdraw check rein, turning the eyes up directly into the sun’s rays, or blinds with a glistening inner surface may require correction. It may be better to abandon blinds altogether, or to cover the eyes by a piece of leather, 2 to 4 inches wide, extending across the forehead from one eye to the other; or a sunshade attached to the headstall may be worn so as to protect the eyes. Horses which become seasick or carsick may sometimes be helped by covering the eyes. Other indications would be to treat any existing trouble which interferes with a normal circulation in the brain (pulmonary congestion, aneurisms, tumors pressing on carotids or jugulars, phlebitis, etc.), and such as affect the ear (disease of the pharynx, guttural pouches, adjacent glands, petrous temporal bone, membrana tympani, external ear). Indurated wax, insects or insect larvæ may be removed by careful irrigation with warm water, and perhaps by chloroform. Nasal parasites must be washed out or destroyed by benzine, and any hyperæsthesia of the nasal mucosa may be met by covering the nostril with a net, or radically by cutting the facial branch of the 5th nerve as it emerges from the infra-orbital foramen.

When attacked the horse should be at once stopped and put under the shadow of a roof or tree, or in their absence a blanket or lap robe may be used to cover his eyes. If there is danger of falling remove the harness, and secure a soft piece of ground, free from stones or other hard bodies. Cold water applied to the head will sometimes check. A common practice is to bleed from the palate, and in plethoric cases especially, and in such as are dependent on congestion, tumors or other lesion of the brain it is to be commended. The action will be rendered more prompt and effective if the blood is taken from the jugular. A laxative diet, and carefully regulated work are desirable to obviate the tendency to the affection, and this may often be accomplished by a run at pasture. Otherwise daily small doses of Glauber salts in the feed may suffice. Bromides may be used to calm nervous excitement.

In cases of =gastric vertigo= an active cathartic, followed by smaller laxative doses or a laxative diet and a course of bitters may prove useful. Such cases should never be worked on a full stomach but should be left at rest for at least an hour after a meal.

In =aural vertigo= special attention must be given to the throat, and external ear. Bromides may often be useful, and sometimes benefit may be derived from an occasional blister or light firing back of the ear.

In =cœnurus cerebralis= in sheep the only resort is to trephine and remove the parasite.

CONCUSSION OF THE BRAIN.

Definition. Causes: leaps, trips, falls, blows. Symptoms: fall,
insensibility, flaccidity, suspended respiration, tumors, vomiting,
recovery, signs of cerebral congestion. Pathology: anæmia followed by
congestion. Diagnosis: from fracture, epilepsy. Treatment: quiet,
rubbing of limbs, ammonia, cold to head, or heat; for congestion,
bromides, depletion, ice pack, derivatives.

_Definition._ Concussion is the condition produced by mechanical jar or shock of the cerebral mass, and manifested by modification of the brain functions of any grade from a simple dazed condition to that of complete unconsciousness.

_Causes._ The most familiar cause is the stroke of the butcher’s pole axe, producing sudden and absolute insensibility. A horse in leaping, trips and falls on his head or running against a wall sustains a concussion, which leaves him for some seconds without any signs of life. The same will happen to other animals, but above all to rams which in their combats, back for a number of yards and running together meet with a shock from the effect of which even their thick skulls cannot save them. Other blows upon the head operate to the same end.

_Symptoms._ Concussion is manifested by different grades of symptoms. At first there is usually a fall with complete insensibility. The animal lies flaccid, utterly insensible to external irritation and there is suspension of respiration. The heart continues to beat and a frequent weak pulse may be often detected. In slight cases, breathing may be reestablished at the end of a minute or two, with muscular tremors and movements of the limbs; then the animal rises, shakes his head, neighs, and walks at first unsteadily and afterward with greater and greater firmness. In vomiting animals, emesis occurs.

In some cases this may be followed, after an hour or two, by signs of congestion, heat of the head, redness of the eyes, irritability, or dullness and stupor and perhaps muscular twitching. This may improve or it may terminate in death preceded by spasms, general convulsions, rolling of the eye balls, and stupor or coma with general muscular relaxation.

The primary condition is usually an anæmia of the cerebral matter as seen in the brain of the animal suddenly killed by the blow of a hammer. The return of consciousness or semi-consciousness is connected with the resumed freedom of the cerebral circulation. The later convulsions, stupor or coma, usually imply active congestion or the effusion of blood on the brain surface, or in its substance.

_Diagnosis_ from fracture must be made mainly by manipulation of the bone in the seat of the blow, and by the absence of the increasing stupor and coma which attend on pressure from a gradually increasing blood clot. From epilepsy it is to be distinguished by the evidence of mechanical injury, by the absence of spasms at the first, by the suspension of breathing and the absence of froth about the lips.

_Treatment._ Keep the patient still and prostrate until there are signs of returning respiration and free cerebral circulation. This may be hastened, however, by active rubbing of the limbs and body, by giving guarded inhalations of ammonia, or even by friction of the skin with ammonia and oil. Sometimes reaction is favored by dashing cold water on the head, while in other cases hot water to the poll will prove more effective, or the two may be used alternately with good results.

If, after partial recovery, there is marked restlessness, or irritability it may be met with bromides. If secondary unconsciousness supervenes effusion of serum or blood is to be feared, or extreme congestion, and blood may be drawn from the jugular or by cups from the cranium, and ice bags or cold water may be applied to the head. Hot foot baths or mustard embrocations applied to the limbs, and even derivation toward the bowels may be used. The indications for treatment come to be for meningo-encephalitis.

LIGHTNING STROKE. ELECTRIC SHOCK.

Fatal. Non-fatal. Herbivora at pasture under tree. Symptoms: dazed for
a few minutes, unconscious for hours, permanent paresis or paralysis.
Lesions: lines of burned hair, skin or muscles, rigor mortis slight,
decomposition rapid, bluish black venous and capillary congestion,
extravasations, blood fluid. Diagnosis. Treatment: ammonia, ether,
alcohol, caffein, nerve stimulants.

While a stroke of lightning is usually fatal, yet in certain cases, the victim is but temporarily stunned and recovers with more or less remaining paralysis. The subject has also great importance in connection with the claim of the owner against a company which may have insured his stock against lightning.

Any animal may be struck, but the herbivora which are turned out to pasture are especially liable to such injuries, because they seek shelter under trees, which operate as lightning rods.

_Symptoms._ In slight cases of shock whether by lightning or the current of a hanging live electric wire, the subject may be simply dazed and may or may not fall to the ground, and recover itself in a very few minutes. In other cases there is a more violent shock which prostrates the animal to the earth, where it may lie unconscious for some hours and yet quickly and completely recover. In still other cases after such prostration recovery is incomplete and the animal remains affected with paresis or paralysis of one or more, commonly of both hind, or all four limbs. In the more violent shocks death is instantaneous.

Often the impact and course of the current are marked by visible lesions. Sometimes the skin is wounded exposing a bluish black tissue beneath. More commonly there is an area of burnt hair, or straight, radiating or angular lines of raised and frizzled hair marking the course of the current. In a horse killed by an electric light wire in Ithaca recently the current had burned to a depth of several inches in the muscles of the shoulder which rested on the wire.

_Lesions_ are often rather indefinite. There may be no appreciable change in the nervous system. Rigor mortis is slight; it passes off rapidly and decomposition sets in early. The venous system and capillaries are usually filled with liquid blood of a dark bluish black color, and at intervals are points, spots and patches of blood extravasation. The uniformly liquid state of the blood is one of the most marked phenomena of death from electricity. The dark blue congestion of the radical veins is also very pathognomonic, the part struck or traversed by the main current, being the seat of the most elaborate arborescent network. This arborescent appearance of the dark colored veins, and the petechiæ are often marked in the internal organs (brain, kidneys, liver, lungs).

_Diagnosis._ The environment of the animal will often clear the diagnosis. The patient is found helpless, or dead under a tree, by a pole, or under a hanging wire, and if a tree there are evidences of the electric shock in scattered leaves and branches, stripping off of the bark, or perhaps rending of the tree in pieces. In case of wires attached to or passing near such a tree, the supporting poles show similar splitting and rending. Add to these the fluidity of blood in the carcase, the thickly ramifying network of the minute dark bluish, red veins, the petechiæ and the comparative absence of cadaveric rigidity, and we have a picture very significant of lightning stroke.

_Treatment_ in such cases is according to the condition. The primary unconsciousness is met by inhalations of ammonia or ether, or the injection of brandy or alcohol subcutem. Caffein, atropine or hyoscyamin may be used as substitutes. If consciousness returns recovery is usually rapid and complete. Should paresis or paralysis remain it must be treated like any ordinary case of these affections.

INTRACRANIAL HÆMORRHAGE AND THROMBOSIS. APOPLEXY. SOFTENING OF THE
BRAIN.

Definition. Causes: Nature: intracranial rupture, with pressure,
serous effusion, excessive congestion, experimental cases, anæmia from
pressure, comparative immunity of horse, heart disease, Bright’s
disease, atheroma, degeneration, emboli, age, blood tension, severe
exertion, excitement, concussion, insolation, venous obstruction,
toxins, neoplasms. Lesions: blood clots, small and multiple, large and
solitary, brain absorption, cavities, cysts. Symptoms: dullness,
swaying, trembling, elevation of head, turning in circle, sudden fall,
spasms, unequal dilated or contracted pupils, eyes turned to affected
side, congested or anæmic mucosæ, stertor, puffing cheeks except in
solipeds, pulse slow, soft, full, vomiting, stupor, coma,
unconsciousness, paralysis, monoplegia, hemiplegia, sequelæ.
Diagnosis: sudden unconsciousness, with little spasm, but paralysis,
history, sign of trauma, deep coma, eyes turned to one side, pupils
unequal, stertor, slow breathing and pulse; from uræmia, pulmonary
apoplexy, œdema or anthrax. Treatment: bleeding, ice pack, snow, cold
water, rest, derivatives to limbs, later purge, bromides, potassium
iodide, tonics, open air life.

_Definition._ Cerebral apoplexy has been defined as a sudden loss of sensation and voluntary motion, from pressure originating within the cranium and followed by paralysis, often unilateral. The definition is somewhat insufficient as regards the early symptoms as the same conditions attend on convulsions and epilepsy (haut mal), and it is only by excluding these by their characteristic features of sudden seizure with clonic spasms and their intermittent and paroxysmal habit that we reach an easy and satisfactory distinction. Later the paralysis tends to identify the apoplectic attack.

_Causes and Nature._ The immediate cause and essential lesion of apoplexy has been generally held to be the rupture of an intracranial artery and the formation of a considerable blood clot which presses upon (and abolishes the functions of) the brain. There are cases, however, in which the characteristic symptoms are present, and yet a complete recovery ensues at an early date, too early to allow for the absorption of a considerable clot. Moreover, in fatal cases perhaps no blood clot is to be found, but in place a serous effusion, or an internal congestion which exercised the fatal pressure on the brain. So far, therefore, as clinical phenomena are concerned, we must allow that apoplexy may arise from any sudden pressure on the brain substance. Pagenstecher produced the symptoms of the disease by injecting, at a regulated pressure, melted wax and tallow between the skull and dura mater in the dog. In the moderate cases there were drowsiness, psychic depression and general muscular weakness. In the more severe ones there were added sleep and unilateral paralysis. In the more extreme cases death followed in a few hours after coma set in, though in some of these a partial recovery ensued if the waxy mass was scooped out before the fatal symptoms appeared. Cases ended fatally only when the injection pressure equalled that of the blood, and convulsions occurred only when the pressure was unsteady. The temperature fell as it does in apoplexy in man, at the outset, but it continued falling to the fatal issue contrary to what takes place in man.

Duret injected water into the cranium of animals so as to produce great tension of the occipito-atloid membrane causing thereby arrest of the respiration and slowing of the heart’s action. On tearing the membrane so as to allow escape of the water, respiration began anew and consciousness was gradually restored.

Edes sustains the view that apoplexy is directly due to anæmia of a lesser or greater portion of the brain substance, and that this need not be in any one particular seat nor of any definite extent. This anæmia is usually induced by pressure and may be caused by effused blood, or serum, or by the extreme congestion due to narcotic poisons, or other cause. Embolism of a cerebral vessel, however, by cutting off the blood from the part of the brain which it supplies may give rise to the apoplectic phenomena.

Friedberger and Fröhner found apoplexy quite frequent in sheep, ox. and dog, and rare in the horse, although more subject to the violent exertion which they put in the front of all causes. It is probable that the sluggish, pampered life of the first three animals, and the tendency to fatty degenerations and heart disease introduces a special predisposition as it does in man, while the horse, inured to an open air life and a vigorous muscular condition, is comparatively immune. Bright’s disease is a common cause in the human subject, with its resulting cardiac hypertrophy. The degenerations attendant on these conditions and especially fatty change (atheroma) in the walls of the cerebral arteries, pave the way for their rupture and for blood effusion. Emboli also carried from the diseased heart not only cut off the blood from the parts supplied by the plugged arteries, but increase the blood tension on the cardiac side of the obstruction and endanger rupture at any weak part. Thus they may cause apoplexy from anæmia without rupture or apoplexy from the pressure of effused blood.

=Age= which is such a notorious factor in man is not without its influence in the lower animals. It is in the old that we mostly see disease of kidneys and heart and the degenerations of the tissues, including the brain and its vessels; in these, therefore, rupture and extravasation are the most frequent.

The other causes are mostly connected with increased blood tension with or without a debility of the vascular walls. Violent exertions as in racing, coursing, dragging heavy loads up hill or on heavy ground, severe excitement, cerebral concussion, insolation, and intense congestion of the brain substance have all been recognized as causative factors. The compression of the jugulars by a small collar, the violent straining attendant on parturition, or constipation, and even the retrocession of blood from the surface when exposed to extreme cold, may contribute to the final rupture.

In infectious diseases in which the toxic products tend to produce profound modifications in the blood and tissues, extravasations are met with in the brain as in other organs. Thus they are seen in anthrax, Texas fever, petechial fever, etc.

Then the formation of =neoplasms= in the brain may be the occasion of the rupture of the vascular walls and apoplexy. =Hæmatoma= of the dura in the dog (Friedberger and Fröhner), =cholesteatomata= in the horse, and =carcinoma= may be apparent causes.

The effect of =mechanical injury= must be admitted, as blows on the head, injuries from an ox yoke, and concussions during the battles of rams and bulls.

_Lesions._ Blood extravasations may be found at any part of the brain: a. into the brain substance; b. into the ventricles; c. from the pia mater; d. into the arachnoid sac; e. between the skull and dura mater. It is especially common in connection with the ganglia adjoining the ventricles; the corpus striatum, optic thalamus, the corpora quadrigemini, the fornix. In other cases the crus cerebri, pons, medulla oblongata, corpus calosum. In other cases the convolutions of the cerebrum or cerebellum suffer. The amount of effusion may be limited to a few drops or it may cover an extensive area and cause considerable flattening of the brain substance.

When capillary hæmorrhages are present—the size of a millet seed or a pea—Friedberger and Fröhner have usually found them multiple, but when large enough to form distinct clots they are usually single and confined to one side. If a clot, involving the brain substance, is small, it merely separates the nervous fibres, but if larger, the cerebral tissue is broken down in the mass of clot, discolored, torn and softened. If the patient has survived the first attack the clot passes through the different stages of discoloration, brown, brownish yellow, yellow, and may become fibrous forming a distinct cicatrix, with loss of brain substance. In connection with the partial absorption of the effused blood, cavities may be filled with a serous fluid (apoplectic cysts), and these may show multiple loculi. The nerve fibres which lead to an old standing lesion are usually degenerated.

When effused into a ventricle, blood is less readily absorbed and tends to remain as a flattened discolored layer.

Extravasation between the dura mater and the cranium is probably always the result of direct mechanical violence.

_Symptoms._ Premonitory indications of apoplexy are less commonly recognized in the lower animals than in man, doubtless largely because of the impossibility of appreciating subjective symptoms. The first observed indications are usually dullness, some lack of coördination of movement, swaying, unsteady gait, trembling and a tendency to deviate to one side or to move in a circle. In the majority of cases, however, the first symptoms noticed are a complete loss of consciousness or nearly so, a sudden fall and often more or less convulsive movements of the limbs aggravated by any excitement. The eyes remain dilated, the pupils enlarged or sometimes contracted, and in case of unilateral effusion the axis of vision of both eyes is turned to the affected side, right or left. The pupil of one eye is likely to be more widely dilated than that of the other. Rolling of the eyeballs is not uncommon. Convulsions may occur, the head and hind limbs being drawn back forcibly as in oposthotonos, or the animal may lie flaccid and comatose from the first. The nasal, buccal and orbital mucous membranes are usually congested, deep red or livid, yet sometimes they are anæmic and pale (Shock). The breathing is usually characteristic, being deep, slow, labored, irregular and stertorous and accompanied by puffing out of the cheeks at each expiration (except in solipeds). Yet there are cases in which stertor is absent. The pulse is usually slow, full and soft, and, in the carotids, throbbing, but it may be weak and imperceptible. There may be complete unconsciousness, and again from the first, or nearly so, there may be a slight response to a stimulus, which cannot be referred altogether to reflex action. In vomiting animals, emesis may ensue. Stupor and coma are more or less marked, though liable to intermissions under any cause of irritation.

Along with the above symptoms the spasms and sequent paralysis, are significant. If confined to given muscles or groups of muscles (monoplegia) it usually implies pressure on some special cortical convolutions presiding over these muscles, and convulsions are to be expected. If there is hemiplegia it is suggestive of implication of the medulla or pons on the opposite side, or of a clot on the corpus striatum or extensively on one side of the cerebrum. A clot in the lateral ventricle tends to profound coma. So liable, however, is pressure to be extended from one side of the brain to the other, and irritation on the one side to rouse a corresponding condition on the opposite side, or in related ganglia, that deductions of this kind cannot always be implicitly relied on.

Though an animal should recover from an attack there is liable to remain some modification of the nervous functions, partial anæsthesia, circumscribed paresis, dullness, lack of energy, irritability, or muscular atrophy.

Cerebral embolism and thrombosis and their sequelæ, infarction and softening, give rise to corresponding symptoms, according to the seat of the lesion, and like lesions of the blood vessels predispose to subsequent attacks.

_Diagnosis_ is based largely on the appearance, usually sudden but sometimes slow, of a more or less profound unconsciousness, attended or followed by paralytic troubles. The history of the case may assist, any blow on the head, or sustained by falling, striking a wall or post, or wearing a yoke, is to be noted. Any extraordinary exertion or excitement must be considered. Any sign of injury about the head; the congestion of the cephalic mucous membranes in contrast with the pallor of _shock_; the onset of the attack without convulsions (or with them as in epilepsy); the deep coma indicating cerebral hæmorrhage or narcotic poisoning; the absence of the odor of alcohol, opium, or other narcotic from the breath; the turning of the eyes to one side and the inequality of the pupils on the two sides; the turning of the head to the same side as the eyes; the slow, labored, usually stertorous breathing; the slow, full, soft pulse; the occasionally rigid condition of the muscles and finally the paralysis, hemiplegic, and less frequently monoplegic or paraplegic, make up the diagnostic picture.

_Uræmia_ and _diabetic coma_ may be excluded by examination of the urine, _pulmonary apoplexy_ or _œdema_ by the predominance of respiratory troubles, and fulminant _anthrax_ by the examination of the blood and by the fact that this disease does not prevail in the locality.

_Treatment_ is very unsatisfactory in the lower animals, as the disease is very fatal, and unless recoveries are complete, they are not pecuniarily desirable. It is only in the slighter cases, therefore, that treatment can be recommended. At the very outset nothing is better than a full bleeding in a large stream from the jugular vein or temporal artery. Ice, snow, or cold water should meanwhile be applied to the cranial region. Absolute rest should be given, any harness that would impede circulation or respiration removed, and hot water or stimulating embrocations applied to the limbs.

When consciousness returns and the patient can swallow, an active purgative may be administered, or barium chloride or eserine may be given subcutem. Any recurring heat of the head may be met by renewal of cold applications, and the force of the circulation may be kept in check by small doses of bromides or aconite. In case of the formation of a clot, iodide of potassium and other alkaline agents may be resorted to. Quiet and the avoidance of all excitement together with a laxative non-stimulating diet must be secured throughout. A course of vegetable or mineral tonics and an occasional blister to the side of the neck may prove a useful sequel.

CEREBRAL HYPERÆMIA.
MENINGO—ENCEPHALIC CONGESTION.

Passive and active hyperæmia. Causes: _passive_: obstacles to return
of blood: anæmia: _active_: brain excitement, sun-stroke, violent
exertion, fear, abdominal tympany, ptomaines, narcotics, lead, darnel,
millet, leguminous seeds partly ripened, tumors, parasites. Symptoms:
_horse_: variable, vertigo, stupor, convulsions, apoplexy,
irritability, disorderly movements, strong, hard pulse, congested
mucosæ, heat of head, dulness, drowsiness, lethargy, coma, alternating
periods of violence, aggravated by what tends to increase vascularity
of brain, congested optic disc: _cattle_: parallel, with special heat
of horns: _dogs_: similar, with desire to move, or wander, or has
nausea, howls, snaps. Treatment: cold to head, derivation to limbs and
bowels, chloral, bromides, ergot, bleeding, darkness, coolness,
non-stimulating food.

Congestion of the encephalon is treated here as a pathological entity, though it cannot always be distinguished clinically from some forms of vertigo on the one hand and from the milder types of apoplexy or encephalitis on the other. It has been divided into _passive_ or _venous hyperæmia_ and _active_ or _arterial hyperæmia_.

_Passive hyperæmia_, as shown under vertigo and apoplexy is a common result of a tight collar, a tight strap used for cribbiting, a too short bearing rein, dilation or valvular disease of the right heart, or disease of the lungs, violent efforts in running, draught, etc. It tends to be associated with arterial anæmia on the principle that the closed cranial cavity can only admit a certain amount of blood and if an excess accumulates in the veins and capillaries, this must be compensated first by the movement backward to the spinal canal of the cerebro-spinal fluid, and second by the diminution of the blood in the cerebral arteries.

_Active hyperæmia_ may be brought about by any excitement which especially affects the brain. This has been already noted in connection with insolation (sun-stroke). It may result from severe exertion during hot weather, in a violently contested race, in drawing a heavy load up hill, or in harsh training. Violent exertion just after a meal is especially injurious. Also the excitement of travelling by rail, or that caused by proximity to locomotives, to discharges of firearms and to other causes of great fear; encreased blood tension in the cerebral vessels in connection with hypertrophy of the left ventricle, or obstruction in other vessels (of the limbs) so as to direct the force of the current into the carotids, the expulsion of blood from the splanchnic cavities by gastric or intestinal tympany, or overloading of the paunch, and irritation of the brain by ptomaines and toxins in certain infectious diseases (rabies, canine distemper, etc.). In the same way vegetable narcotics (opium, etc.) produce congestion. Among the most common causes of congestion are lead, poisoning by lolium temulentum, partially ripened lolium perenne, millet, Hungarian grass, and partially ripened seeds of the leguminosæ (chick vetch, vicia sativa.). Other causes are the presence of tumors (cholesteatoma) and parasites (cœnurus, cysticercus) in the brain.

_Symptoms._ Cerebral hyperæmia, like other brain disorders may give rise to a great variety of symptoms, according to the condition of the animal and the susceptibility of its nerve centres. Some cases have the characteristic seizures of vertigo, others the manifestations of heat stroke, and others, epileptic explosions or apoplectic symptoms. For these see under their respective headings. In other cases the symptoms are those of encephalo-meningitis but moderate in its type and often tending to a transient duration, or to prompt resolution and recovery.

=Horse.= There is manifest change of the nervous and intellectual conditions, which may show itself by irritability or restlessness, by pushing against the wall, by hanging back on the halter, by trembling, shaking the head, neighing, pawing and, in exceptional cases, by rearing, biting or kicking. The pulse is hard and full, the heart’s impulse strong, the beats in the carotids and temporal arteries being especially forcible, and the buccal, nasal and orbital mucosæ are strongly congested. Heat of the head is usually a marked feature. While usually very sensitive to touch, noise or light, the animal may be dull or drowsy, and in spite of its marked sensitiveness, it is then inert or lethargic and indisposed to any active exertion. Freidberger and Fröhner say that the habitual comatose condition alternates at intervals with periods of violent excitement during which the animal pushes or dashes against the wall, grinds the teeth, rears, paws, kicks, bites, etc., and then relapses into the state of coma. When the disease reaches this stage it may be questioned whether we are not dealing rather with acute encephalitis.

In active congestion the symptoms are always aggravated by whatever tends to increase the vascular tension in the brain. Active exertion, draught, the pendent position of the head, the recumbent position on the side with the head as low as the body or lower, aggravate all the phenomena and render the animal more helpless.

The following table slightly modified from Spitzka serves to point out the distinctions between anæmia and hyperæmia:

─────────────────┬─────────────────┬─────────────────┐
Symptoms. │ In Cerebral │ In Cerebral │
│ Anæmia. │ Hyperæmia. │
─────────────────┼─────────────────┼─────────────────┤
│ │ │
Pupils. │Usually dilated │Usually small or │
│ and mobile. │ medium. │
Respiration. │Often interrupted│Normal or nearly │
│ by a deep │ so. │
│ breath or sigh,│ │
│ even when at │ │
│ rest. │ │
Activity. │Lassitude. │Restless, but │
│ │ indisposed to │
│ │ exertion. │
Temperament. │Lethargic with │Irritable with │
│ exceptions. │ exceptions. │
Intelligence. │Senses impaired. │Impaired. │
Elevation of │Aggravates │No effect, or │
head. │ symptoms. │ improvement. │
Recumbent, │Amelioration. │Aggravation. │
dependent head.│ │ │
Straining. │Not necessarily │Aggravated. │
│ aggravated. │ │
─────────────────┴─────────────────┴─────────────────┘

=Cattle= show the same general congestion and heat of the head, ears and horns, congested mucosæ, fixed eyes, and pupils, indisposition to follow the herd, irritability, and dulness with often a disposition to lie down. This may go on to violent bellowing, pushing against the wall, grinding of the teeth, working of the jaws, rolling of the eyeballs, and violent dashing in different directions regardless of obstacles.

=Dogs= show the same restlessness and excitability, congested head, eyes and nose, frequent movement from place to place, a desire to wander off, and it may be spasms. If there has been any gastric disturbance vomiting usually supervenes. As in the larger animals the disease may go on to more violent symptoms, and the animal howls, rushes in different directions, and may snap at imaginary objects, or at any one who interferes with him. His movements are liable to be unsteady, uncertain and swaying.

In all cases the ophthalmoscope reveals a congestion of the optic disc.

In the different animals too, acute cerebral hyperæmia tends to merge early into encephalitis with exudation and pressure, attended by stupor, coma, somnolence or profound lethargy.

_Treatment._ In slight cases of cerebral hyperæmia, it may be sufficient to apply cold to the head with a stimulating fomentation to the limbs, and an active purgative, with chloral or bromides. Ergot in full doses has often an excellent effect.

In the more acute types of the disease, bleeding is the first and most efficient measure. A full abstraction from the jugular will relieve the vascular tension and relieve the circulation on the brain. It has been counselled to avoid this when comatose symptoms have set in, and in some prostrate conditions a large and rapid abstraction of blood may fatally increase the prostration. In other cases, however, the less rapid abstraction will improve at once the intracranial circulation and nutrition, and solicit the reabsorption of the exudate which produces sopor and coma.

A purgative is one of the most efficient derivatives, the determination of an excess of blood to the bowels and of an abundant serous discharge into their interior acting as a valuable depletion, and abstraction of blood from the over-excited brain. At least a half more than the usual dose must be given, and may be supplemented by an injection of glycerine or a hypodermic exhibition of eserine. It is best to avoid too drastic or irritant purgatives as the cerebral congestion may be aggravated by the irritation, as it often is induced in severe indigestions. For the horse, aloes and podophyllin, or for ruminants, omnivora and carnivora castor oil may be resorted to.

The patient must be placed by himself in a dark, cool, well aired building, and when able to resume feeding must receive an easily digested, non-stimulating diet; for horses or cattle gruels, wheat bran mashes, pulped roots, or green food; for dogs and pigs, gruels, mush or milk.

Any sequent paralysis must be treated on general principles.

MENINGO—ENCEPHALITIS. STAGGERS.

Divisions. Causes: traumas, faulty diet, highly nitrogenous,
leguminous seeds, undergoing ripening, cotton seed, gluten meal,
forced feeding, buckwheat, ryegrass, lupins, cryptogams, trefoil,
equisetum, narcotics, microbian ferments, experiments with spoiled
food and epizootics in wet years, high temperature, violent exercise,
railroad travel, climatic change, complex causes, embolisms,
infections, lead, phosphorus, tumors, parasites. Symptoms: with
_meningitis_, fever, hyperæsthesia, active delirium and convulsions
predominate: with _encephalitis_, dullness, stupor, somnolence,
muscular weakness, anæsthesia, paralysis, coma; usually complex,
hyperthermia, periods of benumbing, followed by excitement; drowsy,
stupid, semi-closed eyelids, drooping lips, ears, and head, latter
resting on manger or wall, walks unsteadily, limbs out of plumb, hangs
on halter, won’t back, turns in circle, costive, indigestion,
tympanies, rumbling, abnormal (often slow) pulse and breathing,
congested optic disc; alternate with trembling, excitement, pawing,
rearing, plunging, pushing against the wall, trotting motions, etc.:
uncontrollable violence; severity and frequency of paroxysms indicate
gravity; recovery: sequelæ. Duration: death in 24 to 36 hours: or
weeks. Prognosis: one-quarter recover, with increased susceptibility;
nervous animals worst. Lesions: extravasation, congestion, exudates,
pus, thickened meninges; choroid plexus: brain matter gray or red,
puncta, infiltrated, softened, excess of leucocytes, red softening,
yellow softening, sclerosis, cicatrix, abscess. Diagnosis: from
rabies, cerebral congestion, immobility, influenza. _Cattle._
Symptoms: evidence of trauma, indigestion, lead poisoning, narcotism,
parasitism; dullness, stupor, somnolence, stertor, grinding teeth,
spasms, twitching, restless movements, blindness, violent actions,
bellowing, hebetude, palsy. Relation to causation. _Sheep_: Symptoms.
_Swine_: Symptoms. _Dog_: Symptoms. Diagnosis from rabies. Treatment:
quiet, darkness, coolness, restraint, ice or cold irrigation,
elimination, derivation, depletion, diuretics, potassium iodide,
antipyretics, laxative diet, cool water, evacuate abscess. _Cattle_,
similar, saline laxatives, for lead sulphuric acid, for cœnurus,
operation, for œstrus, benzine. _Dog_, parallel treatment, milk diet
or gruels, for linguatula, benzine.

The inflammatory affections in the cranial cavity have been divided primarily into the following:

1. _Meningitis._ Inflammation of the coverings of the brain, and

2. _Encephalitis_ (_Cerebritis_). Inflammation of the nervous
substance. These are further subdivided into:

_A._ _Pachymeningitis._ Inflammation of the dura Mater.

_B._ _Leptomeningitis._ Inflammation of the pia Mater.

_C._ _Purulent Meningitis._

_D._ _Serous Meningitis._

_E._ _Tubercular Meningitis._

_F._ _Traumatic Meningitis_, etc.

_G._ _Cerebro-Spinal or Infective Meningitis._

_H._ _Acute Meningitis._

_I._ _Chronic Meningitis._

_J._ _Polioencephalitis Corticalis._ Inflammation of the brain cortex.

_K._ _Polioencephalitis Superior._ Inflammation of convolutions around
the Sylvian fissure, palsy of the eyeball.

_L._ _Polioencephalitis Inferior._ Inflammation of the Medulla, bulbar
palsy.

_M._ _Interstitial Inflammation of the Brain._ Resulting often in
sclerosis.