LAMENESS, FROM VARIOUS CAUSES. 363 



tain conditions, to have the heels of his fore hoofs becoming con- 

 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 horsea 

 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 bon€, 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 to 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 feei^ 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 lameness happens to 

 arise from it without being discovered. The crack first takes place 

 [lirough the superior or coronary border of the hoof, tiiat being 

 composed of newly-formed horn, and, consequently, tliin and 

 d-agile. Quickly it extends downward, through the thickest part 

 of the wall, stopping, as it does in some instances, at least for a 

 time, half way down, and afterward reaching nearly or (^uite to 

 the bottom. 



Sand-crack is either penetrant or non-penetrant. It is iwually 

 rienetraut, by whie^A we mean the crack extends completely through 

 28 



