164 DISEASES OF THE HORSE’S FOOT 
animal at fast work over-reaches. The secretiof2 of horn at 
the injured coronet is interfered with, a diminisled supply 
at an isolated spot being the result. From this point 
grows down a fissure in the wall. yi 
An injury of the same character may also be sulstained 
in various other ways—treads from other animals| when 
working in pairs, accidental wounding with the on 
blows of any kind, or a self-inflicted tread with the ¢alkin 
of an opposite foot—each with the same result. \ 
So far as causation is concerned, toe-crack stands in a 
class almost by itself. It is met with nearly always in a 
heavy animal in the hind-foot, and is directly attribu‘able Z 
to the force exerted in starting a heavy load. i z 
Unskilful shoeing also plays a part in the causation of, 
sand-crack. Removal of the periople by excessive raspin 
of the wall is most certainly a predisposing cause. Crac 
or their starting-points, may also be caused by using 
wide a shoe, or by the use of nails too large in the sh 
Also, they may arise from unskilful fitting of the toe-clij 
especially in the hind-foot of a heavy animal. It must 
depends upon the state of the horn and the animal’s co 
formation than upon the exciting cause. 
So far, our observations on the causes of sand-crack have 
referred to that form occurring in the wall. Sand-crack of 
the sole or frog we have already said is but seldom me 
with, and then it is always in connection with some ex 
ceptionally deteriorated quality of the horn, as in the casey 
of badly pumiced feet, or occurs as a result of direct injury. 
Extensive slit-like cuts in this region, when deep enough 
to lacerate the keratogenous membrane, are sometimes 
followed by the growth of a fissure in the horn, and what 
might almost be termed a permanent sand-crack results. 
Such cuts may be occasioned by sharp flints, broken glass, 
or other sharp objects picked up on the road, or may result 
from the animal treading on the toe-clip of a partially cast 
shoe. 
LEP yg 
