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 (Pl. 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 (Pl. 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 fleshy 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 (Pl. XLVII. fig. 5): the whole sole is bare (ib. fig. 4). 
The hallux (great toe, thumb of the foot, Pl. XLVI. figs. 4 & 57), 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 sailors 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. pl. t. * Ib. p. 14: compare pl. 3 with pl. 7. * Ib. p. 22. pl. 11. 
