Hand and Foot in Man and Apes. 159 



this reason the driving-wheels of all heavy traction-engines 

 are provided with sloping or chevron lines. 



Professor Goodsir [i] many years ago pointed out that the 

 hand of man was the only perfect hand, and that while the 

 ape's hand was fitted to grasp a cylinder such as the branch 

 of a tree, it was much less able than the human hand to grasp 

 a sphere. Hepburn [2] has compared the hands of the four 

 antiiropoids w-ith that of man, and shown how the develop- 

 ment in the latter of the muscles of thenar and hypothenar 

 eminences has modified the position of the creases. In the 

 gibbon the fingers are capable of flexion and adduction to 

 the middle line, but have little tendency to oppose tiie thumb ; 

 the transverse and longitudinal creases are therefore met 

 with. In man opposition of the thumb to the fingers is one 

 of the most prominent characteristics of the hand, and the 

 creases in consequence are oblique. 



The Foot. 



The foot (PL V. fig. 1, B), from the point of the heel to the 

 end of the middle toe, measures 14 cm. in length, of which two 

 thirds belong to the sole and one third to the toes. The width 

 of the sole, exclusive of the great toe, is 2*6 cm. Tlie hallux 

 reaches to the level of the proximal interphalangeal joint of 

 the second toe. Unlike the foot of man, the hallux is not 

 bound up parallel to the other digits, but becomes free just 

 beyond the mid-point of the sole. Beiiind this point it is 

 marked off from the rest of the foot by a deep crease. The 

 hallux is a much more powerful digit than the poUex. All 

 the toes have a tendency to point outwards, being set at an 

 angle to the plane of the long axis of the sole. In conse- 

 quence of this angle the four outer digits, on flexion, oppose 

 the great toe. The w^eb of the four outer toes reaches about 

 halfway down the proximal phalanges and prevents any groat 

 separation of these digits. 



I'he following are the chief skin-creases found in the sole : — 



1. On looking at the sole it is seen to be divided into two 

 unequal parts by a longitudinal crease which starts on the 

 inner side of the heel and, passing forwards, gradually deepens 

 into a cleft which divides the great toe from the rest of the 

 sole. The smaller of these portions carries the huUux, while 

 the larger bears the four outer toes. This dividing crease 

 and cleft are caused by the opposability of the hallux. 



2. From the preceding crease near its commencement, 

 another smaller crease jjasses outwards and forwards in front 



