et be in no danger of Greasing. Now, pray, what were these offending
Humours doing before the Bruises given by the Stick?'

At the present day it is safe to assert that neither the ulcerative, the
cancerous, nor the constitutional theory is believed in widely, and, among
the mass of contrary opinions as to the cause of this disease, we may find
that even quite early many of the older writers had discarded them.

Quoting from Zundel, we may say that Dupuy in 1827 considered canker as
a hypertrophy of the fibres of the hoof, admitting at the same time that
these fibres were softened by an altered secretion; while Mercier in 1841
stated that canker was nothing more than a chronic inflammation of the
reticular tissue of the foot, characterized by diseased secretions of this
apparatus.

Saving that they make no mention of a likely specific cause, these last two
statements express all that we believe to-day. As early as 1851, however,
the existence of a specific cause was hinted at by Blaine in his
'Veterinary Art.' We find him here describing canker as a _fungoid_
excrescence, exuding a thin and offensive discharge, which _inoculates_ the
soft parts within its reach, particularly the sensitive frog and sole, and
destroys their connections with the horny covering.

The use of the word 'fungoid,' and particularly that of 'inoculate,' is
suggestive enough, and is evidence sufficient that either Blaine or his
editor recognised, simply through clinical observation, the working of a
special cause.

Four years later, Bouley is found holding the opinion that canker was
closely allied to tetter, thus recognising for it a local specific cause.
The same observer also pointed out that the secretion of the keratogenous
membrane instead of being suspended was greatly increased, taking care to
explain, as did Dupuy, that the products of the secretion were perverted
and had lost their normal ability to become transformed into compact horn.

In 1864 this slowly growing recognition of a specific cause received
further impetus from the statements of Megnier. This observer claimed to
have discovered in the cankerous secretions the existence of a vegetable
parasite (namely, a cryptogam, as in favus), which he termed the
keraphyton, or parasitic plant of the horn.

Modern research, though failing to substitute anything more definite, has
not confirmed this. The exact and exciting cause of canker is therefore
still an open question, and a ma