he toe crack is most likely to be complete--that is, extending from the
coronary band to the sole--while the quarter crack is nearly always
incomplete, at least when of comparatively recent origin. Sand cracks
are most serious when they involve the coronary band in the injury. They
may be complicated at any time by hemorrhage, inflammation of the
laminae, suppuration, gangrene of the lateral cartilage and of the
extensor tendon, caries of the coffin bone, or the growth of a horny
tumor known as a keraphyllocele.

_Causes._--Relative dryness of the horn is the principal predisposing
cause of sand cracks. Excessive dryness is perhaps not a more prolific
cause of cracks in the horn than alternate changes from damp to dry. It
is even claimed that these injuries are more common in animals working
on wet roads than those working on roads that are rough and dry; at
least these injuries are not common in mountainous countries. Animals
used to running at pasture when transferred to stables with hard, dry
floors are more liable to quarter cracks than those accustomed to
stables. Small feet, with thick, hard hoofs, and feet which are
excessively large, are more susceptible to sand cracks than those of
better proportion. A predisposition to quarter cracks exists in
contracted feet, and in those where the toe turns out or the inside
quarter turns under.

Heavy shoes, large nails, and nails set too far back toward the heels,
together with such diseases as canker, quittor, grease, and suppurative
corns, must be included as occasional predisposing causes of sand
cracks.

[Illustration: PLATE XXXVI.

QUARTER-CRACK AND REMEDIES.]

[Illustration: PLATE XXXVII.

FOUNDERED FEET.]

Fast work on hard roads, jumping, and blows on the coronet, together
with calk wounds of the feet, are accidental causes of quarter cracks in
particular. Toe cracks are more likely to be caused by heavy pulling on
slippery roads and pavements or on steep hills.

_Symptoms._--The fissure in the horn is ofttimes the only evidence of
the disease; even this may be accidentally or purposely hidden from
casual view by mud, ointments, tar, wax, putty, gutta-percha, or by the
long hairs of the coronet.

Sand cracks sometimes commence on the internal face of the wall,
involving its whole thickness excepting a thin layer on the outer
surface. In these cases the existence of the injury may be suspected
from a slight depression, which begins near the coronary band