escapes which, by permeating the horn in the
immediate neighborhood, stains it a dark color. If the injury is
continuously repeated, the horn becomes altered in character and the
soft tissues may suppurate or a horny tumor develop. Corns always appear
in the sole in the angle between the bar and the outside wall of the
hoof. In many cases the laminae of the bar, of the wall, or of both, are
involved at the same time.

Three kinds of corns are commonly recognized--the dry, the moist, and
the suppurative--a division based solely on the character of the
conditions which follow the primary injury.

The fore feet are almost exclusively the subjects of the disease, for
two reasons: First, because they support a greater part of the body;
secondly, because the heel of the fore foot during progression is first
placed upon the ground, whereby it receives much more concussion than
the heel of the hind foot, in which the toe first strikes the ground.

_Causes._--It may be said that all feet are exposed to corns, and that
even the best feet may suffer from them when conditions necessary to the
production of the peculiar injury are present. The heavier breeds of
horses generally used for heavy work on rough roads and streets seem to
be most liable to this trouble. Mules rarely have corns.

Among the causes and conditions which predispose to corns may be named
high heels, which change the natural relative position of the bones of
the foot and thereby increase the concussion to which these parts are
subject; contracted heels, which in part destroy the elasticity of the
foot, increase the pressure upon the soft tissues of the heel, and
render lacerations more easy; long feet, which by removing the frog and
heels too far from the ground deprive them of necessary moisture; this,
in turn, reduces the elastic properties of the horn and diminishes the
transverse diameter of the heels; weak feet, or those in which the horn
of the wall is too thin to resist the tendency to spread, whereby the
soft tissues are easily lacerated. Wide feet with low heels are always
accompanied with a flat sole whose posterior wings either rest upon the
ground or the shoe, and as a consequence are easily bruised; at the same
time the arch of the sole is so broad and flat that it can not support
the weight of the body, and in the displacement which happens when the
foot is rested upon the ground the soft tissues are liable to become
bruised or torn.

It is un