moderate deformity of the hoof occurring after laminitis). In the badly
laminitic hoof, however, this deformity is largely increased, until in some
cases the shapeless mass can hardly be likened to a foot at all (see Fig.
122).

The inferior or solar surface of the foot also offers certain changes for
our consideration. The first thing that strikes one is the convexity of the
sole. This, as we have already pointed out, is due to descent of the os
pedis, and the highest point of the convex portion is that immediately in
front of the apex of the frog. Here the horn is sometimes found to be quite
yielding to the finger, is excessively thin, and is more or less granular
and inclined to break up under manipulation. As a consequence, any rough
use of the drawing-knife, or an accidental wounding with sharp flints or
stones, leads to exposure of the sensitive structures and local gangrene.

With the horn of the sole thus deteriorated by reason of excessive and
continued pressure upon the parts secreting it, it is not surprising to
find that, in many cases, actual penetration of it with the os pedis
occurs. It is the anterior portion of the inferior margin of the bone that
makes its appearance, and shows itself as a small semicircular white or
dark gray line on the sole.

[Illustration: FIG. 123.--SOLAR ASPECT OF FOOT WITH CHRONIC LAMINITIS,
SHOWING ITS ABNORMAL OVAL SHAPE FROM BEFORE BACKWARDS, AND THE EXCESS OF
HORN GROWING FROM THE WHITE LINE IN THE REGION OF THE TOE.]

Exposure of the bone is soon followed by its necrosis, in which case the
wound takes on an ulcerating character. From it there is a discharge of
pus, black in colour and offensive in smell, and, protruding from the
opening, are excessive granulations of the remains of the sensitive sole.

The 'white line,' so apparent when a normal foot is cleaned with the knife,
can no longer be sharply distinguished from the surrounding horn, while in
some cases the horn composing it takes on an abnormal growth at the toe
(see Fig. 123). This adds still further to the abnormal lengthening of the
antero-posterior diameter of the foot already mentioned.

In other cases horn in this position is altogether wanting, and in its
place is a well-defined cavity, into which the blade of a knife can be
readily passed. This cavity is bounded in front by the original wall of the
hoof, and is here lined by a degenerated and hypertrophied growth of the
horny laminae. Posteriorly the c