120 THE MECHANICAL FUNCTIONS OF THE FOOT. 



Martinak measured the living hoof by means of callipers, 

 and found well marked dilatation at the bulbs and heels of the 

 hoof when loaded. His experiments on the living hoof, in 

 which he used a bar shoe, also seemed to contradict Lechner's 

 rotation theory. 



Steglich, along with Schenkel, made experiments on dead 

 hoofs. They concluded that : — 



" The weight of the body produces lateral dilatation of the 

 hoof, greatest at the coronary border and least at the bearing 

 surface of the horny capsule. Dilatation both of the coronary 

 and bearing surfaces is best marked in the region of the heels. 

 Towards the quarters it becomes less, and where the quarters 

 abut on the toe it entirely disappears. The cause of dilatation 

 at the coronary margin is the thrusting downwards and inwards 

 of the broader parts of the os coronas between the lateral 

 cartilages at the moment of greatest extension (greatest weight). 

 Dilatation at the bearing surface is produced by lateral dis- 

 placement of the plantar cushion and horny frog under the 

 pressure of the body-weight. The simultaneous descent of 

 the horny sole permits of expansion of the bearing surface 

 of the foot." 



Schwentzky measured twenty-two living hoofs, and, except in 

 the case of four abnormal hoofs, found that, when the animals were 

 standing at rest, the amount of dilatation at the bearing margin 

 was from 1 to 2 millimetres ; the average 1*45 millimetre. 



Peters has taken a prominent part in the study of the 

 expansion of the foot. He advanced what was termed the 

 " depression theory," and placed .particular stress on the 

 possibility of elongation of the laminal sheath of the wall and 

 on the direction of its fibres, by which alone descent of the 

 pedal bone becomes possible, and in the further study of which 

 the explanation of all the phenomena of the movements of the 

 foot is to be found. His experiments led him to the conclusion 

 that the pedal bone, which is fastened to the wall, enjoys a 

 certain degree of mobility, owing to the possibility of elongation 

 of the laminal sheath and to the elasticity of the coronary 

 border of the hoof ; that movement occurs around the toe of 

 the OS pedis as around a fixed point, and, therefore, that the 

 navicular bone, being, as it were, an appendix of the os pedis, 

 must take part in these movements. Tlie depression or elastic 



