366 A Manual of Veterinary Physiology. 



keep them in connection with the horny ones, without 

 which provision a drag on the dovetail arrangement would 

 occur. The fact of the lateral cartilages affording attach- 

 ment to about half of the sensitive laminae has been pre- 

 viously mentioned. As the posterior wall contracts the 

 lateral cartilages are carried inwards. 



At the heels the wall is turned in to form the bars, which 

 run some distance under the foot towards the apex of the 

 frog. The bars are part of the wall, and their function is 

 the same, viz., to support weight, for which purpose they 

 have the usual dove-tailed sensitive and insensitive lamina). 



The elastic movement of the foot must now occupy our 

 attention. The mechanism which brings this about has 

 already been touched on ; it only remains for us to briefly 

 describe the changes in shape which the foot undergoes as 

 the result of the body- weight. 



When the weight comes on to the foot, it is received by 

 the posterior part of the foot, viz., the posterior wall, bars, 

 frog, and through this the plantar cushion. The elastic 

 posterior wall is pressed outwards by the compressed india- 

 rubber-like frog, and it expands from the coronet to the 

 ground surface for about 7> L- of an inch; sometimes the 

 expansion at the coronet is not so marked as it is at the 

 ground surface, but in the majority of feet it exists. At 

 the moment of expansion the bulbs of the heel of the foot 

 at the coronary edge sink under the body weight, and come 

 nearer the ground ; and as a result of this, the anterior 

 coronary edge, that corresponding with the toe of the wall, 

 retracts, and the pedal bone slightly descends through its 

 elastic connection with the sensitive lamina 1 , and presses 

 the sole down with it. Under these conditions the blood 

 pressure in the veins of the foot rises, and the vessels are 

 emptied. When the weight is removed from the foot the 

 bloodvessels till, the frog retracts, the posterior walls con- 

 tract and become narrower from side to side, and the bulbs 

 of the heel rise; at the same time the anterior edge of the 

 coronet goes forward, and the pedal bone and sole ascend. 



Lungwitz lays stress upon the tense condition of the 



