and
follows the direction of the horny fibers; but the trouble can only be
positively diagnosed by paring away the outside layers of horn until the
fissure is exposed. In toe cracks the walls of the fissure are in close
apposition when the foot receives the weight of the body, but when the
foot is raised from the ground the fissure opens. In quarter crack the
opposition is true; the fissure closes when the weight is removed from
the foot. As a rule, sand cracks begin at the coronary band, and as they
become older they not only extend downward, but they also grow deeper.
In old cases, particularly in toe cracks, the horn on the borders of the
fissure loses its vitality and scales off, sometimes through the greater
part of its thickness, leaving behind a rough and irregular channel
extending from the coronet to the end of the toe.

In many cases of quarter crack, and in some cases of toe crack as well,
if the edges remain close together, with but little motion, the fissure
is dry; but in other cases a thin, offensive discharge issues from the
crack and the ulcerated soft tissues, or a funguslike growth protrudes
from the narrow opening.

When the cracks are deep and the motion of their edges considerable, so
that the soft tissues are bruised and pinched with every movement, a
constant inflammation of the parts is maintained and the lameness is
severe.

Ordinarily the lameness of sand crack is slight when the patient walks,
but it is greatly aggravated when he is made to trot, and the harder the
road the worse he limps. Furthermore, the lameness is greater going
downhill than up, for the reason that these conditions are favorable to
an increased motion in the edges of the fissure. Lastly, more or less
hemorrhage accompanies the inception of a sand crack when the whole
thickness of the wall is involved. Subsequent hemorrhages may also take
place from fast work, jumping, or a misstep.

_Treatment._--So far as preventive measures are concerned, but little
can be done. The suppleness of the horn is to be maintained by the use
of ointments, damp floor, bedding, etc. The shoe is to be proportioned
to the weight and work of the animal; the nails holding it in place are
to be of proper size and not driven too near the heels; sufficient calks
and toe pieces must be added to the shoes of horses working on slippery
roads; also, the evils of jumping, fast driving, etc., are to be
avoided.

When a fissure has made its appearance