184 COMPENDIUM OF THE VETERINARY ART. 



when the arteries have been injected with 

 coloured sise. Hence we are enabled to ac- 

 count for thrushes, and that rottenness of the 

 frog which generally accompanies this dis- 

 ease; for when th^^ sensible frog is compressed 

 and inflamed by a contraction of the heels, it 

 becomes incapable of performing its principal 

 function, that is, the secretion of horn ; and 

 the blood which should have been applied to 

 this purpose is chiefly expended in forming 

 that offensive matter discharoed in thrushes. 

 From this we may learn also the cause of that 

 unnatural thinness in the soles of horses that 

 have pumice or flat feet. When the crust 

 gives way to the pressure of the horse's 

 weio'ht, allowino- the internal foot to bear so 

 upon the sole as to render it either flat or 

 convex, the extraordinary pressure which the 

 sensible sole receives inflames it, and impedes 

 in a greater or less degree the secretion of 

 horm 



The sensible sole lies immediately under 

 the horny sole, by which it is defended from 

 blows or pressure. When the horny sole 

 loses its concave form, and becomes thin, and 

 incapable of performing its function, if flat, 

 shoes were applied, or if the sole were suf- 



