INFLAMMATORY AFFECTIONS 309 
where the “sets” are irregular, or where no paving at all 
is attempted, where the drainage is defective, and where 
darkness and want of proper ventilation favours organismal 
growth. The fact that with modern drainage and a general 
hygienic improvement in stabling, canker has to a large 
extent died out, supports this contention. 
Again, as with thrush, anything removing the counter- 
pressure of the frog with the ground and throwing that 
organ out of play, may be looked upon as a predisposing 
cause. The atrophy of the frog thus occurring, the de- 
terioration in the quality of its horn and the fissures in its 
surface lay it specially open to infection. That one of the 
principal factors in the treatment of canker is a restoration 
of ground-pressure to the frog and the sole is sufficient 
proof of this. 
Further, it is well to note that, although playing no 
part in the actual causation, certain constitutional con- 
ditions may in some measure predispose the foot to attack. 
Clinical observation teaches us that animals of a lymphatic 
nature, with thick skins and an abundance of hair, with 
flat feet and thick, fleshy frogs, are far more liable to 
attack than are animals with reverse points. 
Exciting Causes.—Those who give this subject careful 
consideration cannot fail to arrive at the conclusion that 
canker is most certainly due to local infection with a 
specific poison, and that poison a germicidal one from the 
ground. The symptoms arising may be due to the action 
of a single germ, or to two or more germs acting in con- 
junction. As to whether the parasitic invasion is single or 
multiple we cannot feel certain, but that it 2s parasitic we 
feel absolutely assured. 
It is simply the light that bacteriological advance has 
made during the last two decades that enables us to make 
the statement with such feelings of assurance. We arrive 
at our conclusions by reasoning from analogy. Here we 
have a disease always exhibiting the same symptoms, more 
or less peculiar to one class of animal, always with a 
similar characteristic appearance and smell, always obsti- 
