Nature formed the synovial cavity of the joint as a distinct and separate part. It is usual for teachers to promulgate a maxim that Nature is all-wise. Man, however, it appears, can violently disarrange her provisions; yet, by his fellow-men, he is accounted to have done no wrong who destroys the harmony of Nature. Thorough-pin is not, in popular estimation, essentially unsoundness. A horse thus disfigured is believed, nay, professionally pronounced to be, perfect, although two distinct parts are battered into one. If two are beneficial, why was one only created? The horse may not be lame; but, granting Nature to be all-wise, must not the uses for which the limb was designed be injured? The question is not, whether an animal trots sound; but it is, whether it really is sound. What sane man would assert such to be the case, where the anatomical structures have been disorganized?
CAPPED KNEE.
Capped knee, in the fore limb, answers to bog spavin in the hind leg; the diseases are alike in most respects. Both affect the principal articulation of a complicated joint; both may be provoked by the like causes; but the fore leg, being less exposed to shocks than the hinder member, must have been much abused before it could become thus deformed.
THE SYNOVIAL MEMBRANE OF THE KNEE-JOINT ENLARGED.
Blows, also, are common originators of capped knee. This disorder is likewise peculiar for a course it takes. The fluid within the swollen joint is, upon excitement, secreted in such quantity as to tighten the enlargement. Ultimately it lames the horse, and at length bulges out, or points, after the manner of an abscess. If let alone, it would burst. Much of the surrounding parts would have to be absorbed or would be effectually destroyed before such a termination could ensue. The life would be endangered, or a lasting blemish would be left behind. To prevent this, the surgeon draws the skin to one side, and, holding the point of his lancet upward, opens the capped knee upon its lower surface. A quantity of synovia, more or less in a turbid state, escapes, and an open joint remains. For the treatment of this contingency, the reader must turn to "Open Joint." (Injuries.)
Capped knee is, by certain persons, viewed as a trivial accident. Generally, however, it is regarded in a more serious light, because it is more conspicuous than bog spavin. We also should object to it, because, while liable to the same changes as wind-galls, etc., it is also likely to expose the horse to an open joint. It is, like wind-galls and bog spavin, to be reduced by pressure, though sometimes pressure will call up aggravated symptoms. Rest is the best treatment; during the rest pressure may be safely applied. Pressure does not answer, however, while the limb is exposed to the irritation of work. The horse must be thrown up during treatment, and gently used after the animal has been patched up or "cured."
CAPPED HOCK.
When an injury is formed near an important part, Nature is so conservative of her creature's welfare that she always has some means ready to preserve the utility of the structure. Thus when, from external violence, the hock becomes capped, or a swelling like to that represented in the following engraving ensues, to prevent the joint being thrown out of use Nature allows the skin to enlarge. The cap of a hock, originally, was a bursa. A bursa is a little bladder or round sac, formed of the finest possible membrane, and filled with a fluid similar to joint oil. Its use is to facilitate motion; hence it eases the tightened skin over the points of the bony hock. But when it becomes deranged and swollen, the skin, which was dense, hard, and solid, stretches so as to cover the increase of bulk.