The hoof, therefore, being the external covering to the foot of the horse, and not being liable to the same action as organic secretions, serves to confine pus or matter when generated within its substance. Pus could work through the largest organized body; but it cannot escape through the thinnest layer of horn. Now, most of the other substances which enter into the composition of the horse's foot are such as slowly decay; but those parts which slowly decay being without sensation during health, occasion the most extreme agony when diseased.
The cause of quittor always is confined pus or matter, which, in its effort to escape, absorbs and forms sinuses in various directions within the sensitive substances of the hoof. In the hind feet of cart-horses quittor generally commences at the coronet; the coronet is wounded or bruised by the large calkins or pieces of iron turned up at the back of the hind shoes, which are universally worn by animals of heavy draught. Any one who has punctured or cut the coronet of a dead horse knows this structure is as difficult to penetrate and as hard to divide as cartilage itself; the consequence of an injury to such a part is, the bruise produces death of some deep-seated portion of the compact coronet. Nature, after her own fashion, proceeds to cast off that which is without vitality, or, in other words, she divides the dead from the living tissues by a line of suppuration; but the matter thus located cannot readily escape through the harsh material of the horse's coronet. It is confined and becomes corrupt, while the constant motion of the foot and the higher organization of the secreting membrane of the horn inclines the pus to take a downward direction. However, it is more difficult for pus to pierce the horny sole than to penetrate the coronet; so the effort is renewed above; numerous pipes or sinuses are thus formed upon the sensitive laminæ; the fleshy sole is often under-run, and this mischief goes on until the coronet, which becomes of enormous size, at last yields to the increasing evil.
Another cause is pricking the sensitive part of the foot with a nail during shoeing; the wound generates pus, the pus cannot penetrate the horn, and the motion of the coffin-bone causes it to absorb upward, until after some time it breaks forth at the coronet.
DIAGRAM.
Which supposed the outward covering of the
coronet and the horny wall of the hoof
removed, to expose the ravages of quittor,
when commencing in the coronet of a heavy
horse.
DIAGRAM.
The covering of the coronet and horny crust
supposed to be absent, and exposing the
manner in which any suppurating injury
to the sole of the foot ultimately causes a
wound above the hoof.
Another cause is corn; the horse's corn is nothing more than a bruise; the bruise, in some instances, is severe, and takes on the suppurative action. The pus, as before, is confined, and by the motion of the coffin-bone it is propelled upward till it breaks forth at the coronet, which, as before, enlarges to deformity; in short, any injury done to the sole of the foot or to the coronet above it may produce quittor.