changes are those depending upon the amount of haemorrhage and the
accompanying inflammatory phenomena occasioned by the injury.

Thus, with the haemorrhage we get ecchymosis, and consequent red staining
of the surrounding structures. As is the case with extravasations of blood
elsewhere, the haemoglobin of the escaped corpuscles later undergoes a
series of changes, giving rise to a succession of brown, blue, greenish and
yellowish coloration.

With the inflammation thereby set up we get swelling of the surrounding
bloodvessels, pain from the compression of the swollen structures within
the non-yielding hoof, and moistness as a result of the inflammatory
exudate.

In a severe case the inflammation is complicated by the presence of pus.

_Classification_.--Putting on one side the classification of Lafosse
_(natural_ and _accidental_), as perhaps wanting in correctness, seeing
that all are accidental, and disregarding the suggested divisions of Zundel
_(corn_ of the _sole_ and _corn_ of the _wall_) as serving no practical
use, we believe, with Girard, that it is better to classify corns according
to the changes just described.

Following his system, we shall recognise three forms: (1) _Dry_, (2)
_moist_, (3) _suppurating_.

The _dry_ corn is one in which the injury has fortunately been unattended
with excessive inflammatory changes, and where nothing but the coloration
imparted to the horn by the extravasated blood remains to indicate what has
happened.

The _moist_ corn is that in which a great amount of inflammatory exudate is
the most prominent symptom. It indicates an injury of comparatively recent
infliction.

The _suppurating_ corn, as the name indicates, is a corn in which the
inflammatory changes are complicated by the presence of pus.

_Causes_.--The causes of corns we may consider under two headings--namely,
_predisposing_ and _exciting_.

_Predisposing Causes_.--By the heading of this chapter we have already
intimated that corns are due to faulty conformation of the foot. It is,
therefore, merely a description of such shapes of foot as favour their
formation that will need mention here.

The wide, flat foot, with low heels, may be first considered. Here the
posterior portions of the sole, those portions between the wall and the
bars, fall very largely in the same plane as the wearing surface of the
bars and the wall. As a consequence, these portions of the sole are more
prone to receive injury fro