ditional weight is imposed upon it. Fracture results.

Take, again, the vice of contracted heels. Here, in the first place, we
have a variety of causes tending to bring about the contraction. With the
contraction, and its consequent pressure upon the sensitive structures
in the region of the quarters and the frog, has arisen a low type of
inflammation. The horn of the part has become dry and brittle. The exciting
cause of its fracture is found in an excessive day's work upon a hard, dry
road, with, perhaps, a suddenly-imposed improper distribution of weight,
due to treading upon a loose stone, or a succession of such evil transfers
of weight due to travelling upon a road that is rough in its whole extent.

In their turn, too, such defects of the feet as we have mentioned in the
last chapter--as, for example, the foot with the pumiced horn, the foot
with abnormally upright heels, or that which is upright on one side only,
or crooked--each offers a condition which is predisposing to the formation
of a sand-crack. In each case it wants but the uneven distribution of
the body-weight, which, as a matter of fact, some of these conditions
themselves give, to bring about a fracture.

Apart from the predisposition conferred by conformation, must be remembered
the simpler predisposing causes leading to brittleness of the hoof. We
refer to the after-effects of poulticing, the moving from pasture to
stable, the emigration from a damp to a dry climate, or the alternate
changes from damp to dry in a temperate region. Each may have a
deteriorating influence upon the horn, rendering it liable to the condition
we are describing. Excessive dampness alone, especially when the animal is
called upon to labour at the drawing of heavy loads upon a rough road, is
not infrequently a cause. In this case the wet, together with the constant
friction of the sharp materials of which the road is made, serves to
destroy the varnish-like periople. The wet gains access to the inner
structures of the wall, the agglutination of the horn fibres is weakened,
and fissures begin to appear.

Other causes of sand-crack are purely accidental. An animal at fast work
over-reaches. The secretion of horn at the injured coronet is interfered
with, a diminished supply at an isolated spot being the result. From this
point grows down a fissure in the wall.

An injury of the same character may also be sustained in various other
ways--treads from other animals when wor