AND AFFINITIES OF THE GORILLA. 249 



Gorilla must naturally and with more ease resort occasionally to station and progression 

 on the lower limbs than any other Ape'. 



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

 to the lower end of the muscles, coextensive 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 accumulation of carneous fibres in the upper 

 half of the gastrocnemii muscles, causing that prominence in the type-races of Man- 

 kind. 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 (PI. XLVII. figs. 4 & 5), 

 owing to the modifications favouring bipedal motion being superinduced upon an essen- 

 tially prehensile quadrumanous type. The heel makes a more decided backward pro- 

 jection (PI. XLVI. fig. 1) than in the Chimpanzee ; the heel-bone is relatively thicker, 

 deeper, more expanded vertically at its hind end, besides being fully as long, relatively 

 to the size of the animal, 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, but with differences far greater than those which any two genera of 

 Quadrumana present in serial comparison. The malleoli do not make such well-marked 

 projections as in Man ; they are marked more by the thickness of the fieshy and tendi- 

 nous 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 hairy 

 integument is continued along the dorsum of the foot to the clefts of the toes, and upon 

 the first phalanx of the hallux (PI. XLVII. fig. 5) : the whole sole is bare (ib. fig. 4). 



The hallux (great toe, thumb of the foot, PI. XLVII. figs. 4 & 5i), 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 more resembles 



attack, •' his walk is a waddle from side to side, his hind legs, which are very short, being evidently somewhat 

 inadequate to the proper support of the huge superincumbent body. He balances himself by swinging his arms, 

 somewhat as sailoi-s walk on shipboard." " My own observations led me to the concluson that the Gorilla 

 walks more often in the erect posture than the Chimpanzee ; and in this I agree with the conclusion of Prof. 

 Owen." (Du Chaillu, ' Explorations and Adventures in Equatorial Africa.') 



' Memoir, No. VII. p. 12. pi. 0. ' Ib. p. 14 : compare pi. 3 with pi. 7. ' lb. p. 22. pi. U. 



