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 is 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 

 fiat 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 is 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- 



