174 THE STRUCTURE OF THE HORSE. 



That would be obviously impossible with such a re- 

 duction of the bony elements. The difference (far 

 less marked in the upper part of the arm) is espe- 

 cially pronounced in the last segment or manus, or 

 hand proper, where the fifteen intrinsic muscles of 

 the human hand are represented by only five * in the 

 horse. Four of these — the two inter ossei and the two 

 lumbricales — are in a very greatly reduced condition ; 

 and the fifth, the short flexor (represented in the hu- 

 man foot by the muscle called the " first plantar in- 

 terosseous n )j is a remarkable instance of a structure 

 not becoming rudimentary and useless, but, while re- 

 taining its size, position, and connections, being di- 

 verted from its original purpose and completely 

 changing not only its function, but its structure. It 

 is termed in veterinary anatomy "the suspensory 

 ligament of the fetlock," and appears as a very strong 

 band or cord of non-elastic fibrous tissue, lying close 

 to the back of the large metapodial bone, attached 

 above to the posterior surface of the upper extremity 

 of this bone, and at its lower end dividing into two 

 portions, which, diverging from each other, embrace 

 the metatarso-phalangeal or fetlock joint, and are 

 inserted partly into the sesamoid bones and partly 

 into the extensor tendon on the dorsal aspect of the 



* This is the number according to the usual statements, 

 but recent careful dissections have shown traces of others. 



