162 



THE STEUCTUKE OF THE HOESE 



behind, though with new relations and uses, sometimes 

 in a most reduced and almost, if not quite, functionless 

 condition, and sometimes even with completely changed 

 structure. 



From this point of view the muscles of the horse's 

 limbs form a most interesting study. It has been truly 

 said by Dr. G. B. Dobson, 1 that if no other evidence 

 were obtainable of his five-toed ancestors, the condition 

 of the muscles of the foot would sufficiently indicate 

 them. 



In the fore limb, where, the ulna is represented only 

 by the olecranon (projection of the elbow) and a greatly 

 attenuated upper part of the shaft, and the digits reduced 

 to one, most of the forearm muscles of the five-toed 

 mammals are represented, the proper extensor of the 

 fifth digit (extensor minimi digiti) even surviving, 

 although both its insertion and special function have 

 been completely altered. In the hind limb the two 

 flexors of the toes (flexor digitorum longus and flexor 

 hallucis longus) are both present, with well-developed 

 tendons united in the foot as in the great number of 

 five-toed mammals. 



It must not, however, be supposed from what has 

 just been said that anything like all of the numerous 

 muscles that are developed in the hand of man, with its 



1 ' On the Comparative Variability of Bones and Muscles,* &c. 

 Journal of Anatomy and Physiology, vol. xix. p. 16. 



