Page:Horse shoes and horse shoeing.djvu/664

 structures, perfect and suitable in every way to the requirements of limb and foot.

In the fore limb, which is chiefly concerned in sustaining weight, the crust or wall of the hoof is formed of fibres running continuously from above, where they are secreted, to below, where they are worn, and following the same direction as the wall itself. As we examine them from within to without—from the surface where they are in contact with the living tissues, we find that they are at first loose and soft in texture, and easily penetrated, while they can be readily dispossessed of their moisture, and then shrivel up into thin, brittle fragments. As we recede from this surface and approach the external fibres, we notice that, like the cells of the human epidermis, they grow more resisting and dense, are smaller, packed closer and more cohesively together, until near the outer face of the wall, when they become rapidly harder, stronger, and more whale-bone like, and though porous, yet appear destitute of moisture. In this respect they resemble the fibres of an ordinary cane, and further than this are, as in the cane, entirely covered with a delicate, translucent, varnish-like secretion, intended to prevent the too rapid evaporation of moisture from the fibres, and to guard against their shrinking and splitting. The bars are similarly formed, and are secreted, like the wall, from the large projecting, elastic mass, the coronary ring, that lies in a wide concavity around the upper and inner aspect of the crust, and has an important share in supporting the weight, and preventing the sole being unduly pressed upon by the bone resting upon it. The crust being always, in an unshod condition, exposed to wear, is