242 HISTORY OF THE HUMAN BODY 



been but slight, simply because there has been no need of such 

 a modification. 



To review the complete homology of the muscles of the 

 hand and foot would prove too long a task for the present 

 work, but a large part of the correspondence may be presented 

 in the form of a diagram (Fig. 64), which gives all the muscles 

 of the flexor surface, excepting the lumbricales and the intcr- 

 ossei. In both there is seen a double system of flexor tendons, 

 perforantes and perforati; the first digit has the perforans 

 alone, in both hand and foot, and in the foot a perforatus is 

 wanting in digit V, possibly a regressive change. In the 

 anterior limbs both of these systems are long muscles, their 

 bellies lying along the forearm, while in the foot the belly be- 

 longing to the three perforated tendons of digits II to IV 

 is a short one, confined to the foot region. The two outer 

 digits are richly supplied with individual muscles, in which 

 there is a remarkable correspondence between hand and foot, 

 and that too in spite of the loss of independent action in the 

 case of the little toe. This fact of the rich supply of muscles 

 to the marginal digits, I and V, is made much of by supporters 

 of the theory of the pra-pollex and post-minimus, theoretical 

 digits that may have once existed at either end of the present 

 series of five. The muscles in question are interpreted as the 

 musculature of these extra digits, remaining after the loss of 

 the skeletal parts to which they were originally attached. It is 

 noteworthy also that the opponens hallucis is absent in man 

 and has to be supplied in the diagram from the orang and other 

 apes in which it is present, and that a similar loss or, at least, 

 lack of individuality, is observable in the appearance of the 

 little toe, two further regressive characters suggestive of a 

 slight simplification through reduction. 



The subject of the homology of the limbs cannot be complete 

 without reference to the various methods of comparison which 

 have been proposed by numerous investigators, and which 

 depart more or less radically from the one given here. Thus 

 the torsion to which the limbs have been plainly subjected ap- 

 pears to many a hindrance to a direct comparison of similar 



