68 DISEASES OE THE HORSE'S EOOT 



accommodating as it does the frog-stay, preventing the 

 tendency to backward movement becoming excessive, and 

 directing the change of form to the sides. Where the 

 greatest pressure is transmitted, then, is to the inner 

 aspects of the flexible lateral cartilages. The coronary 

 cushion being continuous with the plantar, the backward 

 and outward movements of the latter will tend to pull upon 

 and tighten the former, especially in front. This will 

 account for the contraction noted by Lungwitz in the 

 anterior half of the coronary edge of the hoof. 



Remove the body weight, and naturally the elastic nature 

 of the lateral cartilages and the coronary and plantar cush- 

 ions, with, in a less degree, that of the hoof, cause things 

 to assume their normal position. 



Repeat the weighting of the hoof, in this second case 

 without frog-hressnre, and we shall see at once that we have 

 done away with one of the greatest factors in determining 

 the outward and backward movements of the plantar 

 cushion — namely, the pressure from below on its wedge- 

 shaped mass. The movement of the plantar cushion will 

 now be downwards as well as backwards ; and, seeing that 

 it is attached to the inner aspect of each lateral cartilage, 

 we shall expect these latter, by the downward movement of 

 the plantar cushion, to be drawn inwards. This Lungwitz 

 has shown to occur. 



The chief function of the lateral cartilages, therefore, is 

 to receive the concussion engendered by locomotion, which 

 concussion is directed backwards and outwards by the pad- 

 like plantar cushion. 



In addition to this, the lateral cartilages, together with 

 the plantar and coronary cushions, play the part of a valve 

 to the zvliole of the veins of the foot. 



It is in this way : We have only to refer to the chapter 

 on anatomy to see that the whole of the foot is covered 

 with a tissue of extreme vascularity. Thus we find papillae 

 over the coronary cushion ; enlarged and modified papillae 

 — the sensitive laminae — covering the anterior face of the 

 os pedis ; and a numberless papillae again covering the sole. 



