Hand and Foot in Man and Apes. 159 



this reason the diiving-wheel.s of all heavy traction-engines 

 are provided witli sloping or chevron lines. 



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

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

 ape's hand M^as 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 

 anthropoids with that of man, and shown how tho 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 the 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 (PI. 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 widtii 

 of the sole, exclusive of the great toe, is 2*6 cm. The 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 tiie other digits, but becomes free just 

 beyond the mid-point of the sole. Behind 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, oj)pose 

 the great toe. The web of the four outer toes reaches about 

 halfway down the proximal phalanges and prevents any great 

 separation of these digits. 



The following are tlie 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 hallux, while 

 the larger bears the lour outer toes. This dividing crease 

 and clctt are caused by the opposability of the hallux. 



2. From the preceding crease near its commencement, 

 another smaller crease pusses outwards and forwards in front 



