72 



The same cause as in the arm, viz. a continuance of a large 

 proportion of fleshy fibres to the lower end of the muscles, co- 

 extensive with the thigh, gives a great circumference to that 

 segment of the limb above the knee-joint, and a more uniform size to 

 it than in man. The relative shortness of the thigh, its bone being 

 only eight-ninths the length of the humerus (in man the humerus 

 averages five-sixths the length of the femur), adds to the appearance 

 of its superior relative thickness. Absolutely the thigh is not of 

 greater circumference at its middle than is the same part in man. 



The chief difference in the leg, after its relative shortness, is the 

 absence of a ' calf,' due to the non-existence of the partial accumu- 

 lation of carneous fibres in the gastrocnemii muscles, causing that 

 prominence in the type-races of mankind. In the gorilla the 

 tendo-achillis not only continues to receive the 'penniform' fibres 

 to the heel, but the fleshy parts of the muscles of the foot receive 

 accessions of fibres at the lower third of the leg, to which the 

 greater thickness of that part is due, the proportions in this 

 respect being the reverse of those in man. The leg expands at 

 once into the foot, which has a peculiar and characteristic form, 

 owing to the modifications favouring bipedal motion being super- 

 induced upon an essentially prehensile, quadrumanous type. The 

 heel makes a more decided backward projection than in the chim- 

 panzee; the heel-bone is relatively thicker, deeper, more expanded 

 vertically at its hind end, besides being fully as long as in the 

 chimpanzee. This bone, so characteristic of anthropoid affinities, 

 is shaped and proportioned more like the human calcaneum than 

 in any other ape. The malleoli do not make such well-marked 

 projections as in man; they are marked more by the thickness of 

 the fleshy and tendinous parts of the muscles that pass near them, 

 on their way to be inserted into parts of the foot. Although the 

 foot be articulated to the leg with a slight inversion of the sole, it 

 is more nearly plantigrade than in the chimpanzee or any other 

 ape. The hallux (great toe, thumb of the foot), though not rela- 

 tively longer than in the chimpanzee, is stronger; the bones are 

 thicker in proportion ,to their length, especially the last phalanx, 

 which in shape and breadth much resembles that in the human 

 foot. The hallux in its natural position diverges from the other 

 toes at an angle of 60 deg. from the axis of the foot; its base is 

 large, swelling into a kind of ball below, upon which the thick 

 callous epiderm of the sole is continued. The transverse indents 

 and wrinkles show the frequency and freedom of the flexile move- 



