364 Contributions to the 



deed below the hip, possess little separate motion, the 

 entire limb swinging nearly as a whole. 



The tendons of the deep common flexor of the fingers, 

 [Flexor profundus digitorum) were so short as not to per- 

 mit the simultaneous extension of both hand and fingers ; 

 the latter could be straightened only when the former was 

 at right angles with the forearm, and when I bent the 

 hand back into a straight line the fingers closed tightly 

 upon mine. The advantage of this to a climbing animal 

 is at once apparent ; the hand having been placed upon a 

 branch, the mere weight of the body would cause the fin- 

 gers to close upon it like hooks without muscular exertion, 

 and they would retain their grasp till the strain was relieved 

 by means of the other limb. How else can we explain the 

 power which some Orangs have been said to possess, of 

 swinging upon a rope by the hands alone, for an hour at 

 a time ? It also readily accounts for the Anthropoids not 

 being able to apply their palms to the ground when on all 

 fours, but being obliged to rest on the knuckles. I have 

 never seen any direct reference to this structure, but it has 

 always been remarked that the digits of both hands and 

 feet of the Anthropoids are generally flexed, giving them a 

 hook-like appearance. By a similar structure, though not 

 nearly so marked, the human hand may be bent backward 

 a little farther when the fingers are flexed than when they 

 are straight ; and, the reverse of what exists in the Chim- 

 panzee, owing to the shortness of the extensor tendons, 

 man's hand and fingers cannot be flexed far together, but 

 by bending forward the closed fist the fingers are gradually 

 forced open. 



In general, the muscles lying upon the forearm difler 

 from our own in being less distinct from each other, and in 

 remaining fleshy often to the wrist, allowing more exten- 

 sive movements, but detracting much from the elegance 

 and pliability of the limb. 



Extensor communis digitorum. May be separated into 



