. It is more liable to take place when
trotting, running, or jumping than when at a slower pace. A stone wedged
in the shoe and pressing on the frog or between the sides of the frog
and the shoe, if it remains for a time, produces the same results. A cut
through the horny frog with some sharp instrument or a punctured wound
by a blunt-pointed instrument may also cause suppuration and gangrene of
the plantar cushion. Broad, flat feet with low heels and a fleshy frog
are most liable to these injuries.

_Symptoms._--Lameness, severe in proportion to the extent of the bruise
and the consequent suppuration, is always an early symptom. When the
animal moves, the toe only is placed to the ground or the foot is
carried and the patient hobbles along on three legs. When he is at rest,
the foot is set forward with the toe on the ground and the leg flexed at
the fetlock joint. As soon as the pus finds its way to the surface the
lameness improves. If the frog is examined early the injured spot may
usually be found; later, if no opening exists, the pus may be discovered
working its way toward the heels. The horn is loosened from the deeper
tissues, and, if pared through, a thin, yellow, watery and offensive pus
escapes. In other cases a ragged opening is found in the frog, leading
down to a mass of dead, sloughing tissues, which are pale green in color
if gangrene of the plantar cushion has set in. In rare cases the coffin
bone may be involved in the injury and a small portion of it may become
carious.

_Treatment._--If the injury is seen at once, the foot should be placed
in a bath of cold water to prevent suppuration. If suppuration has
already set in, the horn of the frog, and of the bars and branches of
the sole, if necessary, is to be pared thin so that all possible
pressure may be removed, and the foot poulticed. When the pus has
loosened the horn, all the detached portions are to be cut away. If the
pus is discharging from an opening near the hair, the whole frog, or
one-half of it, will generally be found separated from the plantar
cushion, and is to be removed with the knife. After a few days the
gangrenous portion of the cushion will slough off from the effects of
the poultice; under rare circumstances only should the dead parts be
removed by surgical interference. When the slough is all detached, the
remaining wound is to be treated with simple stimulating dressings, such
as tincture of aloes or turpentine, oakum balls, a