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 unyielding horn below. 
Feet with high and contracted heels are also predisposed 
to corn. The contraction in this case interferes with 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 the contracted foot, 
too, the nutrition of the vessels supplying the secretory 
apparatus of the horn is largely interfered with. 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 
