It is unnecessary to enter more into detail as to the anatomy of the foot. Within the sensitive layer just noticed are the bones, and attached to them the tendons which move the limb in progression. There are two structures, however, which must be mentioned. The chief bone of the foot - the coffin-bone - which gives the general form to the hoof, does not extend throughout its whole interior. It forms the basis of the front and sides of the hoof, but towards the heels is replaced on each side by plates of gristle or cartilage (fig. 628). This elastic material can be felt at the inner and outer sides of the coronet through the skin of the living horse. When diseased and converted into bone it forms the so-called side-bones, which sometimes cause lameness, and always destroy the natural elasticity of the foot. These cartilages, replacing bone at the back parts of the foot, give resiliency to the hoof, and so prevent concussion.
Fig. 628. - Lateral Cartilages, etc, of the Foot.