FLEXURES OF THE PALM AND SOLE 



175 



flexures are distinguished by absence of movement, and the condi- 

 tions for fixing down the deeper layers of the skin to tbe bones 

 beneath are clearly present. That these are not indifferent struc- 

 tures is evident from what Macalister says, and though they be 

 small or even trivial may be held to have acquired at some time or 

 other selective value. Their early stages would necessarily be 

 too tentative, varied and slight to acquire such value. 



Fig. 78. — Foot of gibbon. 



Fig. 79. — Hand of chimpanzee. 



Fig. 72 is a sketch of the hand and foot of a squirrel (Sciurus) 

 and the numbers 1, 2, 3, 4, 5 and 6 are placed conspicuously 

 on the walking pads in accordance with the teaching of Dr. and 

 Mrs. Wilder Harris as to the six palmar and plantar walking-pads, 

 of which the typical palm and sole is constructed. The thick, black 

 lines indicate the flexures formed round the pads by the exercise 

 of the functions of the hand and foot. 



