THE EXTERNAL FORM OF ANTHROPOID APES. 19 



than, sometimes of the same length as, the first, and 

 the fourth is decidedly shorter. The back of the wrist 

 is covered with deep oblique folds. A network of 

 wrinkles, oblique or curved, also covers the skin on 

 the back of the fingers, on which there are 

 callosities up to the first joint. The gorilla closes 

 the fingers when going' on all fours, and turns the 

 back of the hand on the ground, thus producing 

 this thickening of the upper skin on the joints. 

 Callosities of the same nature, although not so ex- 

 tensive, are not rare on the second finger-joints. 

 The palm of the hand is covered with a hard, horny 

 skin, generally beset with warts, especially at the 

 roots of the fingers. lu spite of the blackness of 

 the skin which covers them, these characteristics are 

 still apparent. 



The fingers are united by a strong web, remind- 

 ing us of the membrane found on the otter and other 

 web-footed animals, and reaching nearly to the first 

 finger-joint. A thick coat of hair extends to the 

 root of the fingers, although on the backs of the 

 fingers there are only a few isolated hairs. 



The trunk of the body of a gorilla, seen from 

 behind, somewhat resembles a trapezium in form, of 

 which the longer of the two parallel sides extends 

 between the shoulders, and the shorter between the 

 two halves of the pelvis. The longitudinal sides, 

 which are not parallel, correspond to the sides of the 

 back. The arrangement of all the lower part of the 

 trunk, on which the bones of the pelvis stand out 

 prominently in an oblique direction, somewhat re- 

 sembles a four-sided pyramid with its apex reversed. 



