meness without actual pinching of the structures implicated.

The severity of the lameness will vary with the rapidity of the gait, and
with the character of the road upon which the animal is made to travel. For
instance, many animals in which the lameness is imperceptible at a walk
become 'dead' lame at a fast trot. It is sufficiently explained when
one remembers the greater movements of expansion and contraction of the
posterior parts of the wall brought about by the increase in the rate of
progression. The same animal, too, will go distinctly more lame upon a hard
than upon a soft surface.

In like manner the lameness from toe-crack also varies in degree with the
rate of progression and the character of the travelling, though not to
such a noticeable extent as in the lameness from quarter-crack. A greater
variation may in this case be brought about by moving the animal on
ascending and descending ground. Descending an incline, with a more than
ordinary share of the body-weight thus thrown upon the heels, the lameness
is most marked. The reason would appear to be that the greater expansion
of the wall of the heels thus brought about leads to a proportionate
contraction of the wall at the toe, especially at the edges of the crack,
thus causing undue pressure upon the exact spot of the wound in the
sensitive structures. Ascending--the weight in this case transferred from
the posterior to the anterior portion of the foot--the expansion of
the heels becomes a contraction, with a corresponding lessening of the
contraction at the toe and a distinct decrease in the lameness.

In the case of a deep but recent crack there is always more or less
haemorrhage. This favours risk of infection of the lesion with pus-forming
organisms, and so leads to a more or less pronounced lameness, a degree of
swelling, heat and tenderness in the coronet above, and a certain amount of
surgical fever.

The acute symptoms subdued, but the fissure still remaining, gives us the
crack we have classified as 'old.' This may in every case be distinguished
from a more recent lesion by the amount of thickening of the overhanging
coronet, and the presence of an increased quantity of sub-coronary horn in
the region immediately about the crack. The previous inflammatory changes
in the adjoining sensitive structures have here led to an increased
secretion of horn, and a greater or less deposition of inflammatory
connective tissue in the wounded coronary cus