CALLOSITIES ON THE LIMBS. 



321 



plantigrade ancestors of the horse, we are met with the 

 difficulty that, in the horse, the fore chestnut is con- 

 siderably above the knee, and in the onager (Fig. 339), 

 it is nearer the elbow than the knee ; but Professor Ewart 

 has shown that it is close to the knee in the equine foetus, 

 and that its upward removal is effected^'^ by 'increased 



Photo bi] [M. H. H. 



Fig. 396. — Long chestnut on hind leg. 





Fig. 396A. — Posterior view of Kangaroo's hind leg, from toe to hock. 



growth of the lower part of the principal bone of the fore- 

 arm (radius). He considers that the fore chestnut corre- 

 sponds to the pad which is at the wrist (carpus) of the dog 

 and cat, and strengthens this theory by the fact that the 

 fore chestnut in an Iceland pony foal, at birth, closely 

 resembles in shape and structure this feline pad. 



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