uAMENESS, FROM VARIOUS CAUSES. 353 
tain conditions, to have the heels of his fore hoofs becoming von- 
tracted, and exhibiting quarter sand-cracks, Hot stables conduce 
to this, but, more still, hot climates. Hurtrel d’Arboval informs 
us that at the time the French army was in Egypt, their horses 
were continually having sand-cracks; and he adds that long 
voyages on board of ship are, on some occasions, attended with 
like results. 
The proximate cause of quarter sand-crack is, then, contraction. 
The horn, from dryness, or other cause, rendered cracky and 
fragile, breaks at the quarter of the wall, from being at that 
part bent across the edge of the ala of the coffin bone, during the 
curving in of the heel, the result of contraction ; and this oftenest 
happens to the inner quarter, from its being the thinner and 
weaker one, as well as from being the one which is the first and 
most disposed tu contract—not that sand-crack is the necessary 
consequence of contraction, but that contraction becomes a neces- 
sary precursor to sand-crack. If this were not the explanation 
of the case, sand-crack would be as likely to occur in any part of 
the wall as at the quarter, and on the outer as often as on the 
inner side of the wall. This likewise accounts for the compara- 
tive unfrequency of quarter sand-crack at the present day among 
our nag and cavalry horses, since that which has tended to dimin- 
ish the frequency of contraction has had the same effect in regard 
to the occurrence of sand-crack. Greater attention to shoeing, 
and increased care about the condition of the hoof itself, has, no 
doubt, had a very beneficial effect in the prevention both of con- 
traction and sand-crack. 
The origic of sand-crack is usually sudden, both in the fore 
and hind feet, though in the former case, from its situation in the 
mner quarter, a part not exposed to transient. view, it is possible 
for a crack to exist for some time, unless ]ameness happens to 
arise trom it without being discovered. The crack first takes place 
through the superior or coronary border of the hoof, that being 
composed of newly-formed horn, and, consequently, thin and 
fragile. Quickly it extends downward, through the thickest part 
of the wall, stopping, as it does in some instan:es, at least for a 
time, half way down, and afterward reaching nearly or quite te 
the bottom. 
Sand-crack is either penetrant or non-penetrant. It is usually 
venetrant, by whic! we mean the crack extends completely through 
22 
