Chapter 35

_Symptoms._--The symptoms vary according to the severity of the attack. In some cases there is marked fever, and in some slighter cases it may be almost altogether wanting, but there is always a lack of vigor and energy, bespeaking general disorder. The local symptoms are in the main those of internal ophthalmia, in many cases with an increased hardness of the eyeball from effusion into its cavity. The contracted pupil does not expand much in darkness, nor even under the action of belladonna. Opacity advances from the margin, over a part or whole of the cornea, but so long as it is transparent there may be seen the turbid, aqueous humor with or without flocculi, the dingy iris robbed of its clear, black aspect, the slightly clouded lens, and a greenish-yellow reflection from the depth of the eye. From the fifth to the seventh day the flocculi precipitate in the lower part of the chamber, exposing more clearly the iris and lens, and absorption commences, so that the eye may be cleared up in ten or fifteen days.

The characteristic of the disease is, however, its recurrence again and again in the same eye until blindness results. The attacks may follow one another after intervals of a month, more or less, but they show no relation to any particular phase of the moon, as might be inferred from the familiar name, but are determined rather by the weather, the health, the feed, or by some periodicity of the system. From five to seven attacks usually result in blindness, and then the second eye is liable to be attacked until it also is ruined.

In the intervals between the attacks some remaining symptoms betray the condition, and they become more marked after each successive access of disease. Even after the first attack there is a bluish ring around the margin of the transparent cornea. The eye seems smaller than the other, at first because it is retracted in its socket, and often after several attacks because of actual shrinkage (atrophy). The upper eyelid, in place of presenting a uniform, continuous arch, has, about one-third from its inner angle, an abrupt bend, caused by the contraction of the levator muscle. The front of the iris has exchanged some of its dark, clear brilliancy for a lusterless yellow, and the depth of the eye presents more or less of the greenish-yellow shade. The pupil remains a little contracted, except in advanced and aggravated cases, when, with opaque lens, it is widely dilated. If, as is common, one eye only has suffered, the contrast in these respects with the sound eye is all the more characteristic. Another feature is the erect, attentive carriage of the ear, to compensate to some extent for the waning vision.

The attacks vary greatly in severity in different cases, but the recurrence is characteristic, and all alike lead to cataract and intraocular effusion, with pressure on the retina and abolition of sight.

_Prevention._--The prevention of this disease is the great object to be aimed at, and this demands the most careful breeding, feeding, housing, and general management, as indicated under "Causes." Much can also be done by migration to a high, dry location, but for this and malarious affections the improvement of the land by drainage and good cultivation should be the final aim.

_Treatment_ is not satisfactory, but is largely the same as for common internal ophthalmia. Some cases, like rheumatism, are benefited by 1-scruple doses of powdered colchicum and 2-dram doses of salicylate of soda twice a day. In other cases, with marked hardness of the globe of the eye from intraocular effusion, aseptic puncture of the eye, or even the excision of a portion of the iris, has helped. During recovery a course of tonics (2 drams oxid of iron, 10 grains nux vomica, and 1 ounce sulphate of soda daily) is desirable to invigorate the system and help to ward off another attack. The vulgar resort to knocking out the wolf teeth and cutting out the haw can only be condemned. The temporary recovery would take place in one or two weeks, though no such thing had been done, and the breaking of a small tooth, leaving its fang in the jaw, only increases the irritation.

CATARACT.

The common result of internal ophthalmia, as of the recurrent type, may be recognized as described under the first of these diseases. Its offensive appearance may be obviated by extraction or depression of the lens, but as the rays of light would no longer be properly refracted, perfect vision would not be restored, and the animal would be liable to prove an inveterate shyer. If perfect blindness continued by reason of pressure on the nerve of sight, no shying would result.

PALSY OF THE NERVE OF SIGHT, OR AMAUROSIS.

_Causes._--The causes of this affection are tumors or other disease of the brain implicating the roots of the optic nerve, injury to the nerve between the brain and eye, and inflammation of the optic nerve within the eye (retina), or undue pressure on the same from dropsical or inflammatory effusion. It may also occur from overloaded stomach, from a profuse bleeding, and even from the pressure of the gravid womb in gestation.

_Symptoms._--The symptoms are wide dilatation of the pupils, so as to expose fully the interior of the globe, the expansion remaining the same in light and darkness. Ordinary eyes when brought to the light have the pupils suddenly contract and then dilate and contract alternately until they adapt themselves to the light. The horse does not swerve when a feint to strike is made unless the hand causes a current of air. The ears are held erect, turn quickly toward any noise, and the horse steps high to avoid stumbling over objects which it can not see.

_Treatment_ is only useful when the disease is symptomatic of some removable cause, like congested brain, overloaded stomach, or gravid womb. When recovery does not follow the termination of these conditions, apply a blister behind the ear and give one-half dram doses of nux vomica daily.

TUMORS OF THE EYEBALL.

A variety of tumors attack the eyeball--dermoid, papillary, fatty, cystic, and melanotic--but perhaps the most frequent in the horse is encephaloid cancer. This may grow in or on the globe, the haw, the eyelid, or the bones of the orbit, and can be remedied, if at all, only by early and thorough excision. It may be distinguished from the less dangerous tumors by its softness, friability, and great vascularity, bleeding on the slightest touch, as well as by its anatomical structure.

STAPHYLOMA.

This consists in a bulging forward of the cornea at a given point by the sacculate yielding and distention of its coats, and it may be either transparent or opaque and vascular. In the last form the iris has become adherent to the back of the cornea, and the whole structure is filled with blood vessels. In the first form the bulging cornea is attenuated; in the last it may be thickened. The best treatment is by excision of a portion of the rise so as to relieve the intraocular pressure.

PARASITES IN THE EYE.

Acari in the eye have been incidentally alluded to under inflammation of the lids.

_Filaria palpebralis_ is a white worm, one-half to 1 inch long, which inhabits the lacrimal duct and the underside of the eyelids and haw in the horse, producing a verminous conjunctivitis. The first step in treatment in such cases is to remove the worm with forceps, then treat as for external inflammation.

_Setaria equina_ is a delicate, white, silvery-looking worm, which I have repeatedly found 2 inches in length (a length as great as 5 inches has been reported). It invades the aqueous humor, where its constant active movements make it an object of great interest, and it is frequently exhibited as a "snake in the eye."[1] When present in the eye it causes inflammation and has to be removed through an incision made with the lancet in the upper border of the cornea close to the sclerotic, the point of the instrument being directed slightly forward to avoid injury to the iris. Then cold water or astringent antiseptic lotions should be applied.

_Filaria conjunctivæ_, resembling _Setaria equina_ very much in size and general appearance, is another roundworm which has been found in the eye of the horse.

The echinococcus, the cystic or larval stage of the echinococcus tapeworm of the dog, has been found in the eye of the horse, and a cysticercus is also reported.

FOOTNOTES:

[1] This worm is normally a parasite of the peritoneal cavity, and is probably transmitted from one horse to another by some biting insect which becomes infected by embryos in the blood.--M. C. HALL.

LAMENESS: ITS CAUSES AND TREATMENT.

BY A. LIAUTARD, M. D., V. M.,

_Formerly principal of the American Veterinary College, New York._

[Revised by John R. Mohler, A. M., V. M. D.]

It is as living, organized, locomotive machines that the horse, camel, ox, and their burden-bearing companions are of practical value to man. Hence the consideration of their usefulness and consequent value to their human masters ultimately and naturally resolves itself into an inquiry concerning the condition of that special portion of their organism which controls their function of locomotion. This is especially true in regard to the members of the equine family, the most numerous and valuable of all the beasts of burden, and it naturally follows that with the horse for a subject of discussion the special topic and leading theme of inquiry, by an easy lapse, will become an inquest into the condition and efficiency of his power for usefulness as a carrier or traveler. There is a great deal of abstract interest in the study of that endowment of the animal economy which enables its possessor to change his place at will and convey himself whithersoever his needs or his moods may incline him; how much greater, however, the interest that attaches to the subject when it becomes a practical and economic question and includes within its purview the various related topics which belong to the domains of physiology, pathology, therapeutics, and the entire round of scientific investigation into which it is finally merged as a subject for medical and surgical consideration--in a word, of actual disease and its treatment. It is not surprising that the intricate and complicated apparatus of locomotion, with its symmetry and harmony of movement and the perfection and beauty of its details and adjuncts, by students of creative design and attentive observers or nature and her marvelous contrivances and adaptations, should be admiringly denominated a living machine.

Of all the animal tribe the horse, in a state of domesticity, is the largest sharer with his master in his liability to the accidents and dangers which are among the incidents of civilized life. From his exposure to the missiles of war on the battlefield to his chance of picking up a nail from the city pavement there is no hour when he is not in danger of incurring injuries which for their repair may demand the best skill of the veterinary practitioner. This is true not alone of casualties which belong to the class of external and traumatic cases, but includes as well those of a kind perhaps more numerous, which may result in lesions of internal parts, frequently the most serious and obscure of all in their nature and effects.

The horse is too important a factor in the practical details of human life and fills too large a place in the business and pleasure of the world to justify any indifference to his needs and physical comfort or neglect in respect to the preservation of his peculiar powers for usefulness. In entering somewhat largely, therefore, upon a review of the subject, and treating in detail of the causes, the symptoms, the progress, the treatment, the results, and the consequences of lameness in the horse, we are performing a duty which needs no word of apology or justification. The subject explains and justifies itself, and is its own vindication and illustration, if any are needed.

The function of locomotion is performed by the action of two principal systems of organs, known in anatomical and physiological terminology as passive and active, the muscles performing the active and the bones the passive portion of the movement. The necessary connection between the cooperating parts of the organism is effected by means of a vital contact by which the muscle is attached to the bone at certain determinate points on the surface of the latter. These points of attachment appear sometimes as an eminence, sometimes as a depression, sometimes a border or an angle, or again as a mere roughness, but each perfectly fulfilling its purpose, while the necessary motion is provided for by the formation of the ends of the long bones into the requisite articulations, joints, or hinges. Every motion is the product of the contraction of one or more of the muscles, which, as it acts upon the bony levers, gives rise to a movement of extension or flexion, abduction or adduction, rotation or circumduction. The movement of abduction is that which passes from and that of adduction that which passes toward the median line, or the center of the body. The movements of flexion and extension are too well understood to need defining. It is the combination and rapid alterations of these movements which produce the different postures and various gaits of the animal, and it is their interruption and derangement, from whatever causes, which constitute the pathological condition known as lameness.

A concise examination of the general anatomy of these organs, however, must precede the consideration of the pathological questions pertaining to the subject. A statement, such as we have just given, containing only the briefest hint of matters which, though not necessarily in their ultimate scientific minutiæ, must be clearly comprehended in order to acquire a symmetrical and satisfactory view of the theme as a practical collation of facts to be remembered, analyzed, applied, and utilized.

It was the great Bacon who wrote: "The human body may be compared, from its complex and delicate organization, to a musical instrument of the most perfect construction, but exceedingly liable to derangement." In its degree the remark is equally applicable to the equine body, and if we would keep it in tune and profit by its harmonious action we must at least acquaint ourselves with the relations of its parts and the mode of their cooperation.

ANATOMY.

The bones, then, are the hard organs which in their connection and totality constitute the skeleton of an animal (see Plate XXIII). They are of various forms, three of which--the long, the flat, and the small--are recognized in the extremities. These are more or less regular in their form, but present upon their surfaces a variety of aspects, exhibiting in turn, according to the requirement of each case, a roughened or smooth surface, variously marked with grooves, crests, eminences, and depressions, for the necessary muscular attachments, and, as before mentioned, are connected by articulations and joints, of which some are immovable and others movable.

The substance of the bone is composed of a mass of combined earthy and animal matter surrounded by a fine, fibrous enveloping membrane (the periosteum) which is intimately adherent to the external surface of the bone, and is, in fact, the secreting membrane of the bony structure. The bony tissue proper is of two consistencies, the external portion being hard and "compact," and called by the latter term, while the internal, known as the "spongy" or "areolar tissue," corresponds to the descriptive terms. Those of the bones that possess this latter consistency contain also, in their spongy portion, the medullary substance known as marrow, which is deposited in large quantities in the interior of the long bones, and especially where a central cavity exists, called, for that reason, the medullary cavity. The nourishment of the bones is effected by means of what is known as the nutrient foramen, an opening established for the passage of the blood vessels which convey the nourishment necessary to the interior of the organ. Concerning the nourishment of the skeleton, there are other minutiæ, such as the venous arrangement and the classification of their arterial vessels into several orders, which, though of interest as an abstract study, are not of sufficient practical value to refer to here.

The active organs of locomotion, the muscles (see Plate XXIII), speaking generally, form the fleshy covering of the external part of the skeleton and surround the bones of the extremities. They vary greatly in shape and size, being flat, triangular, long, short, or broad, and are variously and capriciously named, some from their shape, some from their situation, others from their use; and thus we have abductors and adductors--the pyramidal, orbicular, the digastricus, the vastus, and so on. Those which are under the control of the will, known as the voluntary muscles, appear in the form of fleshy structures, red in color, and with fibers of various degrees of fineness, and are composed of fasciculi, or bundles of fibers, united by connective or cellular tissue, each fasciculus being composed of smaller ones but united in a similar manner to compose the larger formations, each of which is enveloped by a structure of similar nature known as the sarcolemma. Many of the muscles are united to the bones by the direct contact of their fleshy fibers, but in other instances the body of the muscle is more or less gradually transformed into a cordy or membranous structure known as the tendon or sinew, and the attachment is made by the very short fibrous threads through the medium of a long tendinous band, which, passing from a single one to several others of the bones, effects its object at a point far distant from its original attachment. In thus carrying its action from one bone to another, or from one region of a limb to another, these tendons must necessarily have smooth surfaces over which to glide, either upon the bones themselves or formed at their articulations, and this need is supplied by the secretion of the synovial fluid, a yellowish, unctuous substance, furnished by a peculiar tendinous synovial sac designed for the purpose.

Illustrations in point of the agency of the synovial fluid in assisting the sliding movements of the tendons may be found under their various forms at the shoulder joint, at the upper part of the bone of the arm, at the posterior part of the knee joint, and also at the fetlocks, on their posterior part.

As the tendons, whether singly or in company with others, pass over these natural pulleys they are retained in place by strong, fibrous bands or sheaths, which are by no means exempt from danger of injury, as will be readily inferred from a consideration of their important special use as supports and reenforcements of the tendons themselves, with which they must necessarily share the stress of whatever force or strain is brought to bear upon both or either.

We have referred to that special formation of the external surface of a bone by which it is adapted to form a joint or articulation, either movable or fixed, and a concise examination of the formation and structure of the movable articulations will here be in place. These are formed generally by the extremities of the long bones, or may exist on the surfaces of the short ones. The points or regions where the contact occurs are denominated the articular surface, which assumes from this circumstance a considerable variety of aspect and form, being in one case comparatively flat and another elevated; or as forming a protruding head or knob, with a distinct convexity; and again presenting a corresponding depression or cavity, accurately adapted to complete, by their coaptation, the ball-and-socket joint. The articulation of the arm and shoulder is an example of the first kind, while that of the hip with the thigh bone is a perfect exhibition of the latter.

The structure whose office it is to retain the articulating surfaces in place is the ligament. This is usually a white, fibrous, inelastic tissue; sometimes, however, it is elastic in character and yellowish. In some instances it is funicular shaped or corded, serving to bind more firmly together the bones to which its extremities are attached; in others it consists of a broad membrane, wholly or partially surrounding the broad articulations, and calculated rather for the protection of the cavity from intrusion by the air than for other security. This latter form, known as capsular, is usually found in connection with joints which possess a free and extended movement. The capsular and funicular ligaments are sometimes associated, the capsular appearing as a membranous sac wholly or partially inclosing the joint, the funicular, here known as an interarticular ligament, occupying the interior, and thus securing the union of the several bones more firmly and effectively than would be possible for the capsular ligament unassisted.

The universal need which pertains to all mechanical contrivances of motion has not been forgotten while providing for the perfect working of the interesting piece of living machinery which performs the function of locomotion, as we are contemplating it, and nature has consequently provided for obviating the evils of attrition and friction and insuring the easy play and smooth movement of its parts by the establishment of the secretion of the synovia, the vital lubricant of which we have before spoken, as a yellow, oily, or rather glairy secretion, which performs the indispensable office of facilitating the play of the tendons over the joints and certain given points of the bones. This fluid is deposited in a containing sac, the lining (serous) membrane of which forms the secreting organ. This membrane is of an excessively sensitive nature, and while it lines the inner face of the ligaments, both capsular and fascicular, it is attached only upon the edges of the bones, without extending upon their length, or between the layers of cartilage which lie between the bones and their articular surfaces.

Our object in thus partially and concisely reviewing the structure and condition of the essential organs of locomotion has been rather to outline a sketch which may serve as a reference chart of the general features of the subject than to offer a minute description of the parts referred to. Other points of interest will receive proper attention as we proceed with the illustration of our subject and examine the matters which it most concerns us to bring under consideration. The foundation of facts which we have thus far prepared will be found sufficiently broad, we trust, to include whatever may be necessary to insure a ready comprehension of the essential matters which are to follow as our review is carried forward to completion. What we have said touching these elementary truths will probably be sufficient to facilitate a clear understanding of the requirements essential to the perfection and regularity which characterize the normal performance of the various movements that result in the accomplishment of the action of locomotion. So long as the bones, the muscles and their tendons, the joints with their cartilages, their ligaments, and their synovial structure, the nerves and the controlling influences which they exercise over all, with the blood vessels which distribute to every part, however minute, the vitalizing fluid which sustains the whole fabric in being and activity--so long as these various constituents and adjuncts of animal life preserve their normal exemption from disease, traumatism, and pathological change, the function of locomotion will continue to be performed with perfection and efficiency.