184 DISEASES OF THE HORSE'S FOOT 



The low heels, too, favour a more than due proportion of 

 the body-weight being thrown on to the posterior parts of 

 the foot. Two evils, both inclining to the production of 

 corn, result from this. In the first place, the sensitive 

 structures of the posterior portions of the foot are subjected 

 to undue pressure from above ; secondly, the posterior half 

 of the foot, by reason of the extra weight thrown upon 

 it, is exposed also to greater effects of concussion than 

 normally it should meet. Added to this we find that the 

 abnormally flat condition of the sole has resulted in a great 

 loss of resiliency. With undue pressure above, and a loss 

 of resiliency and added effects of concussion below, the 

 sensitive structures included between the opposing pedal- 

 bone and the horny sole are bound to suffer more or less 

 bruising each time the foot comes to the ground, especially 

 if the animal is moved at a rapid pace. 



Writing here of the effects of pressure and concussion 

 affords a fitting occasion to mention the fact that corns 

 occurring in feet affected with side-bones are always worse 

 than in feet with normal elastic cartilages. The explana- 

 tion of this is simple, for there can be no doubt that the 

 loss of resiliency in the diseased cartilage is only another 

 aid to undue pressure and concussion. The sensitive 

 structures are pinched between unyielding bone above and 

 practically unyieldmg horn below. 



Feet with high and contracted heels are also predisposed 

 to corn. The contraction in this case interferes wdth the 

 downward movements of the os pedis during progression, 

 while in a state of rest there is a more or less constant 

 pressure upon the sensitive structures, due to the correct 

 downward displacement of the pedal-bone being opposed by 

 the amount of contraction present. In tiie contracted foot, 

 too, the nutrition of the vessels supplying the secretory 

 apparatus of the horn is largely interfered w'ith. The horn 

 loses its natural elasticity, fails to respond to the normal 

 movements of the parts within, and aids in the compression 

 and laceration of the sensitive structures. 



Weak feet, with horn too thin to withstand the expansive 



