137 



of the horse, induced mainly by external causes, the principal 

 of which is undue pressure exerted by its horny investment, 

 there exists a predisposing cause to visceral irritation, both 

 thoracic and abdominal, and thence to the skin, — or the order 

 of causation may commence with the skin or either of the 

 visceral structures, and end in the feet through the medium of 

 the excito-motory or the sympathetic system of nerves, or, per- 

 haps, both conjoined ; and that thus, those mysterious inter- 

 transmutations of disease, termed metastasis, may in some 

 rational manner be accounted for. 



THE FACTS OF PATHOLOGY 



indicate an intimate connection between the external skin and 

 the internal mucous membranes. Cold in the former produces 

 functional derangement in the latter, and vice versa. Func- 

 tional derangements of the latter will produce manifestations of 

 disorder in the former. The removal of the cause or causes 

 in one, will induce a cessation of the effects in the other. 



Let it also be remembered that the foot is made up of the 

 same materials as enter into the composition of the skin and 

 we shall have no difficulty in conceiving of the sensitive struc- 

 tures of the foot, — its secreting papillae, and its whole nervous 

 organization, as involved in the general mutual sympathy 

 that exists between the external skin and all internal mucous 

 membranes. 



CONCURRENT OR PREDISPOSING CAUSES. 



Moreover, the legs, and especially the feet of horses, being 



the furthest situated from the nerve and circulating centers — 



those parts, and particularly the feet — are more exposed and 



liable to the effects of a cold and humid atmosphere than other 



parts nearer the centers of circulation and of nerve force. 



Add to these considerations the fact that the iron appendage 



to the horse's foot is a rapid conductor of heat, and that in 



very numerous instances horses have to stand upon a cold, 



k 



