164 
many of the other diseases of the foot, of which we have already spoken, on 
the violent and continued concussion on the hard roads. The heavy weight 
of the animal, and the shoeing with high heels or calkins, are additional 
factors in the causation, High calkins deprive the foot of the uses which 
the frog serves as a buffer, and the concussion, received at every step by the 
heels, is thus directly transmitted to the cartilages, which suffer in 
consequence. The pressure on the heels is, moreover, greater than it would 
otherwise be, were high calkins dispensed with. Again, the sensitive frog is 
pressed downwards, by this practice of using high calkins, and the horny 
covering, being elevated from the ground, does not afford the support it 
otherwise would do. As in so many other diseases of man and animals | 
hereditary influence also, no doubt, predisposes very strongly to the 
contraction of this form of bony degeneration. The practical conclusion to 
be drawn from this fact is, that one should not breed from animals so 
affected. : 
The formation of a side-bone is often spread over a long period of time. 
When met with in aged cart-horses, whose progression is often thereby not 
much affected, they are not of any great moment. When, however, they are 
met with in the lighter breeds of horses, whether they cause lameness or 
not, and when they affect the gait of the cart horse, they are cof much more 
importance. Now, although side-bone constitutes unsoundness, it is not 
necessary, or even advisable, to condemn an animal as unsound, unless. the . 
progression be affected thereby. Side-bone is in most instances accompanied, 
uy 
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Pedal bone of the horse, showing the ossification of the lateral 
cartilages, A, A. 
