a constitutional taint is
supposed to exist, with swelling of the legs, grease, etc., a purgative,
followed by dram doses of sulphate of iron, repeated daily, may be
prescribed. In cases where the growth of horn seems too slow a
Spanish-fly blister applied to the heels is often followed by good
results. Feet in which the disease is readily induced may be protected
in the stable with a leather boot. If the thrush is but a sequel to
other disease, a permanent cure may not be possible.

CANKER.

Canker of the foot is due to the rapid reproduction of a vegetable
parasite. It not only destroys the sole and frog, but, by setting up a
chronic inflammation in the deeper tissues, prevents the growth of a
healthy horn by which the injury may be repaired. Heavy cart horses are
more often affected than those of any other class.

_Causes._--The essential element in the production of canker is the
parasite; consequently the disease may be called contagious. As in all
other diseases due to specific causes, however, the seeds of the
disorder must find a suitable soil in which to grow before they are
reproduced. It may be said, then, that the conditions which favor the
preparation of the tissues for a reception of the seeds of this disease
are simply predisposing causes.

The condition most favorable to the development of canker is
dampness--in fact, dampness seems indispensable to the existence and
growth of the parasite; the disease is rarely, if ever, seen in high,
dry districts, and is much more common in rainy than in dry seasons.
Filthy stables and muddy roads have been classed among the causes of
canker; but it is very doubtful whether these conditions can do more
than favor a preparation of the foot for the reception of the disease
germ.

All injuries to the feet, by exposing the soft tissues, may render the
animal susceptible to infection; but neither the injury nor the
irritation and inflammation of the tissues which follow are sufficient
to induce the disease.

For some unknown reason horses with lymphatic temperaments--thick skins,
flat feet, fleshy frogs, heavy hair, and particularly with white feet
and legs--are especially liable to canker.

_Symptoms._--Usually, canker is confined to one foot; but it may attack
two, three, or all of the feet at once; or, as is more commonly seen,
the disease attacks first one then another, until all may have been
successively affected. When the disease follows an injury which h