432 DISEASES OF THE HORSE. 
When thrush is present as a complication, its cure must be sought 
by measures directed under that heading. If sidebones, ringbones, 
navicular disease, contracted tendons, or other diseases have been the 
cause of contracted heels, treatment will be useless until the cause is 
removed. 
SAND CRACKS. 
A sand crank is a fissure in the horn of the wall of the foot. These 
fissures aré quite narrow, and, as a general rule, they follow the di- 
rection of the horny fibers. They may occur on any part of the wall, 
but ordinarily are only seen directly in front, when they are called 
toe cracks; or on the lateral parts of the walls, when they are known 
as quarter cracks. (Plate XXXVI.) 
Toe cracks are most common in the hind feet, while quarter cracks 
nearly always affect the fore feet. The inside quarter is more liable 
to the injury than the outside, for the reason that this quarter is not 
only the thinner, but during locomotion receives a greater part of the 
weight of the body. A sand crack may be superficial, involving only 
the outer parts of the wall, or it may be deep, involving the whole 
thickness of the wall and the soft tissues beneath. 
The toe crack is most likely to be complete—that is, extending from 
the coronary band to the sole—while the quarter crack is nearly al- 
ways 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, in- 
flammation of the lamin, suppuration, gangrene of the lateral car- 
tilage 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 predispos- 
ing 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 moun- 
tainous countries. Animals used to running at pasture when trans- 
ferred 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 sup- 
purative corns, must be included as occasional predisposing causes 
of sand cracks. 
