308 DISEASES OF THE HORSE’S FOOT 
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 ex- 
citing cause of canker is therefore still an open question, 
and a matter for research. We may, however, sum the 
matter up by briefly discussing the causes, so far as clinical 
observation teaches us. This we shall do under two head- 
ings—namely, Predisposing and Exciting. 
Predisposiny Causes.—Starting with the assumption that 
the disease is due to local infection, we may relate as pre- 
disposing causes anything having a prejudicial effect upon 
the horn, disintegrating it, and so laying the tissues beneath 
open to attack. The most prominent in this connection is 
certainly a continued dampness of the material on which 
the animal has to stand. Particularly is this the case 
when the material is also excessively foul and dirty, con- 
taminated with the animal discharges, and presumably 
swarming with the lower forms of animal and plant life. 
We shall therefore find bad cases of canker in stables 
