Part 15

Special nervous tonics are next demanded. No agent has a better reputation than arsenious acid. Ten drops of a 1 per cent. solution of arsenite of soda may be given daily to the dog or one ounce to the horse. If gastric irritation forbids the use of this agent, sulphate of zinc may be given in 1 to 3 grain doses twice a day to the dog. In other cases strychine ¹⁄₈₀ to ¹⁄₆₀ of a grain may be given in the same manner.

Nerve sedatives often have a good effect in calming the nervous irritability and in this way belladonna, conium, cannabis Indica, chloral, chloroform, acetanilid, trional, etc., have been employed.

In the same line are ice bags or ether spray applied to the spine for ten minutes at a time, and douche baths of cold water, the animal being afterward rubbed dry. This last partakes of the nature of a stimulant and may be classed with gentle exercise which at once distracts the patients’ attention from the nervous infirmity, trains him to control the muscles, gives normal exercise and tone to the enfeebled organs and improves the general health.

CONVULSIVE TWITCHING OF THE FACE.

Nature of phenomenon, arhythmic, hyperexcitability of nerve centres or skin. Nerve section. Head jerking: =horse=, hard bit, severe check, internal pain, exertion, hypersensitiveness. Treatment: nerve section. Tongue lolling, etc. Flapping of lower lip. Nasal rhythmic movements. Weaving, from impatience, rhythmic. Rocking on hind limbs. Resting foot on coronet. Pawing. Treatment: eliminate irritation, nerve tonics, sedatives, hygienic measures.

This has been observed especially in the dog and may be easily confounded with chorea. The muscles on one side of the face, are twitched at more or less regular intervals, or in other cases there are sudden opening and closing of the lower jaw. The affection has not been satisfactorily connected with any special brain lesion, though as in chorea proper and epilepsy, we must invoke a special disorder or hyperexcitability of the nerve centres presiding over the affected muscles. The clonic spasm may in some cases be due only to a motor impulse from such excited nerve centre, while in others it may be traced backward along the afferent nerves to an oversensitive part of the skin or other organ. In these last purely reflex forms of the trouble it may be possible to correct it by section of the sensory nerves involved.

Convulsive Movements of the Head.

Convulsive movements of the head as a whole constitute a frequent form of chorea in the dog. It is especially common in horses and shows itself in different forms. A horse with a tender mouth, or which has been used with a hard bit, or with a heavy hand on the reins, or which has been driven with a check rein so short as to be unsuited to its conformation, is liable to indulge in annoying elevation and depression of the head when under the saddle or in harness. The same phenomenon may be shown in connection with violent internal pains, as in strangulated hernia, intussusception, or twisting of the bowels. The habit once formed is not easily corrected, so that careful treatment with the view of prevention is especially to be given.

Another more objectionable, dangerous, and less voluntary motion is the sudden jerking of the head upward, or to one side when excited under the saddle or in harness. The disorderly movements are not, as a rule, seen while the animal is at rest, but seem to be produced under the stimulus of exertion. They appear to be quite involuntary, and suggest the dread caused by the settling or buzzing of an insect about the nose or ears, but occur in the depth of winter in the absence of insect life, as well as in midsummer. The suddenness and involuntary nature of the movement is suggestive of epilepsy, but there is no indication of attendant unconsciousness. From choreic movements it is apparently distinguished, by its presence only when ridden or driven. It is unquestionably associated with hypersensitiveness of the nerve centres, and yet in many cases it appears to be a reflex originating in a specially tender or sensitive part of the skin or mucous membrane. In more than one instance in this college clinic the trouble was corrected by the section of both facial branches of the 5^{th} cranial nerves as they emerged from the infra-orbital foramina.

Abnormal Movements of the Tongue.

Some horses double the tongue downward, others upward of the bit; others protrude the tongue and give it a sinuous, serpentine motion which causes alternate protrusion and retraction.

Flapping of the Lower Lip.

This habit of rapid opening and closing of the lower lip so as to produce a disagreeable flapping noise by striking it against the upper, is seen in many horses and proves a most objectionable trait in harness or saddle animals.

Rhythmical Movements of the Nose.

Certain horses apply the protractile end of the nose against the lower lip and spend hours in succession in moving it rhythmically forward and backward, or from side to side.

Weaving. Movement like a Bear in a Cage.

This consists in a lateral rocking of the head and neck, and sometimes of the chest as well with alternate stepping on the right and left fore feet. It has been supposed to represent the movement of the weaver in working a hand loom, or still better the movement of a caged wild beast in constant turning toward the right and left of the front of his cage. The motions are as regular as a pendulum, and involve the contraction of corresponding groups of muscles on the two sides of the body.

They seem, in some cases, to begin in impatience in waiting for the feed, while other horses in the same row are being attended to first, but when the habit has been formed it may be continued most of the time in the intervals between feeds as well. Nervous horses and those that are hearty feeders are the most subject to this infirmity.

Disorderly Movements of the Limbs.

Some horses have a habit of continuously raising one hind limb, others raise the right and left alternately, rocking the hind quarters from side to side, others stand with the heel of one hind foot resting on the front of the coronet of the other, while still others paw continuously with the fore feet while standing in the stall.

Treatment. These various conditions even when begun as an expression of impatience, soon become fixed habits, that prove in the end virtually uncontrollable by an animal, which has no strong will and no consciousness of anything to be gained by resisting the impulse. They become virtual psychoses. In cases in which the habit can be traced to a peripheral irritation, the cutting off of this by complete section of the afferent nerves leading to the irritable nerve centre will sometimes succeed in effecting a cure. In other cases in which the source of the disorder is probably largely central in the cerebral ganglia, nerve tonics, and sedatives, and generally corroborative treatment are the most obvious means of palliation. Such measures are, however, rarely successful. Nourishing food and invigorating outdoor exercise are useful auxiliaries.

VERTIGO. MEGRIMS. BLIND STAGGERS.

Disadvantage of lack of subjective symptoms. Causes, varied, narcotics, overloaded stomach, cerebral anæmia or hyperæmia, degenerations, parasites, tumors, jugular obstruction, valvular heart disease, disease of internal ear, plethora. Susceptible animals, horse, ox, dog, pig, sheep. Direct causes: tight collar, or throat latch, flexion of head, heart disease, pulmonary disease, embolisms, gastric distension, hepatic disorder, optic vertigo, aural vertigo, injections into ear, rhigolene, chloral, acariasis, seasickness, railroad sickness, cholesteatoma, cœnurus, concussion, degeneration, softening, œstrus, linguatula, narcotics, essential oils: essential vertigo. Symptoms: in irritable animal, highly fed, and without exercise, crowds pole, his mate or a wall, shakes or jerks head, staggers, trembles, rears, plunges, falls, struggles, sweats, rolls eyes, recovers. In gastric or hepatic cases, dullness, pendent head, swaying gait, dull eye, dilated pupil, pendent lids and lips, leans on adjacent object, staggers, falls. In optic cases are obvious cause in transition to light, etc., and palliation by covering the eyes. In aural cases, rolling eyes, constrained position of ear, deafness, pharyngeal or Eustachian trouble, wax or acari in ear, tender or itchy ear. Plethoric cases in spring, in overfed, etc. Brain lesions may have fever and disordered innervation, but retained consciousness, and no marked spasm. Duration. Sheep: parasitic vertigo. Turning. Rotation. Treatment: according to cause: restrict ration, give exercise, purgative, adjust collar, breast strap, check, avoid sudden transitions of light, overdraw check, blinds, treat nasal, pharyngeal, ocular or aural trouble; during attack, stop in shade, cold to head, deplete, bleed, purge, shady pasture or light work, bromides, blisters, etc.

In dealing with vertigo or giddiness in animals we are confronted by the impossibility of realizing the subjective feelings of the animal, as we can so easily ascertain by interrogation in the case of man, and thus our conclusions are largely inferences drawn from certain unsteady, reckless or uncontrollable movements, or from an apparent inability to maintain a stable equilibrium. The condition is rather a symptom of a variety of morbid conditions, functional and structural, than a disease sui generis. It may be due to alcoholic or other narcotic intoxication, to overloaded or otherwise deranged stomach, to shock, to a stroke of lightning, to disturbances—anæmic or hyperæmic—in the circulation in the encephalon, to degenerations, parasites or tumors in the brain, to compression of the jugular veins, to valvular or other disease of the heart, to disease of the internal ear, to the plethora of spring or early summer, to the qualms of sea sickness, to insolation.

The purely toxic cases are more clearly defined and temporary so that they may be eliminated from consideration at present, yet their possible occurrence must always be borne in mind by the practitioner especially when called to pronounce upon cases of vertigo in connection with veterinary legal questions. The cases that are due to a persistent neurosis, or to circulatory troubles may well be placed in a list by themselves, yet in their legal relations it is highly important that the practitioner should as far as possible discriminate among these as well.

Susceptible Animals. Vertigo undoubtedly exists among all domestic animals. The symptoms by which it is recognized have been noted especially in the horse and much less frequently in ox, dog, pig and sheep.

Among horses it especially attacks the mature or aged, and family harness horses, pampered and irregularly exercised; (saddle horses rarely suffer); it is more likely to appear for the first time in spring though when established it happens at all seasons; it may come on when a horse is driven in blinders and fail to appear in the absence of these.

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.