king in pairs, accidental wounding
with the stable-fork, blows of any kind, or a self-inflicted tread with the
calkin 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 attributable to the force exerted in starting a heavy load.

Unskilful shoeing also plays a part in the causation of sand-crack. Removal
of the periople by excessive rasping of the wall is most certainly a
predisposing cause. Cracks, or their starting-points, may also be caused by
using too wide a shoe, or by the use of nails too large in the shank. Also,
they may arise from unskilful fitting of the toe-clip, especially in the
hind-foot of a heavy animal. It must be admitted, however, that the part
shoeing plays in the causation of sand-crack is not a large one; far more
depends upon the state of the horn and the animal's conformation 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 met with, and then it is always in connection with some
exceptionally deteriorated quality of the horn, as in the case 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.

_Symptoms_.--In every case the fissure, or evidence of its commencement,
is a diagnostic symptom. It is well to remember, however, that this may
be easily overlooked, especially when the crack is one commencing at the
coronary margin. The reason is this: Sand-cracks in this position often
commence in the wall proper, and not in the periople. They may, in fact, be
first observed as a fine separation of the horn fibres immediately
beneath the perioplic covering. A crack of this description may even show
haemorrhage, and have been in existence for some time, without the periople
itself showing any lesion whatever. Thus, unless lameness is present, or a
more than specially keen search is dire