190 DISEASES OF THE FEET. 



of hay or grass, combined with exercise, would remove under 

 healthy conditions. 



I am convinced that laminitis very rarely ocours from only one 

 cause, except in foaling cases. 



"Attentive observation of facts demonstrates that laminitis 

 attacks equally all horses, whatever may be the shape of 

 their hoofs " [Peuch and Toussaint). At the same time we must 

 not forget that the more upright the foot, whether caused by 

 shoeing, allowing the heels to grow too long, or by conformation, 

 the more liable will it be to suffer from laminitis induced by con- 

 cussion, and by long-continued standing; for the more the weight 

 is brought forward, the greater will be the strain on the secreting 

 membrane of the hoof. An upright form of pastern will act in the 

 same way. 



As the fore feet are far more exposed to the effects of concussion 

 than the hind, and as they are not so frequently moved when the 

 horse is standing, we generally find that one or both of these feet 

 are alone implicated in an attack of laminitis, whether the disease 

 proceeds from congestion or from injury. 



NATURE OF THE DISEASE.— The whole body of the horse 

 (like that of a man) is covered by a membrane which acts as a 

 filter for the removal, from the body, of watery fluid and waste 

 products contained in it. Thus, in the lungs, it gives off water and 

 carbonic acid ; and on the surface of the body, principally water in 

 the form of perspiration. The kidneys, which are a peculiarly 

 modified portion of this covering, discharge urine. Besides its 

 office as a filter, it has the power, to a certain extent, of altering 

 the composition of the waste material which passes through it, 

 chiefly as a protective layer, in the form of epithelium (p. 154) 

 which assumes special characters according to its position. Thus, 

 the true skin excretes scarf-skin (p. 154) and hair; and the mem- 

 brane which covers the sensitive parts of the foot, secretes horn. 

 At the coronet, the horn-producing membrane excretes the wall of 

 the hoof ; on the outer surface of the pedal bone (Fig. 70, p. 209) it 

 excretes soft homy cells which bind it (the sensitive lamince) to the 

 wall ; and underneath the foot it excretes the sole and frog. 



The growth of this protective covering (epidermis) is dependent 

 on the amount of serum (watery portion of the blood) which ac- 

 cumulates inside the secreting membrane. Hence, the slower the 

 superficial circulation, the thicker will be the protective covering. 

 Thus, the colder the climate, the more developed are the hair, 

 hoofs, and horns of animals which live in it. A blister and pres- 

 sure (as in the case of corns from tight boots) increase epidermal 

 growth in a similar manner. Comparative stagnation of blood 



