THE CHIMPANZEES AND ORANGS. H 



sion at the middle in the Gorilla (fig. 18). The unciforme in the Gorilla (PI. II. fig. 21) 

 is larger and broader on its dorsal surface, it has a greater extent of non-articular surface 

 on its ulnar and inner side (b, d) , beyond the surface {d) which articulates with the os 

 cuneiforme, than in Man {ih. fig. 22) : the surface (c) for the os magnum is placed at a 

 less acute angle with that for the cuneiforme, than in Man. The articular surfaces for 

 the fourth and fifth metacarpal are larger from behind forward, and somewhat deeper 

 than in Man. The chief difference is in the greater relative strength and length of the 

 process [d) for the insertion, through the medium of the annular ligament, of the tendon 

 of the flexor carpi ulnaris, which is prolonged to the base of the metacarpal bone of the 

 fifth finger : the lever of this powerful flexor is thereby increased and made more powerful 

 than in Man, in whom the process (fig. 22, d), by its more curved disposition, is called 

 ' unciform,' and suggested the name to the entire bone. 



The sum of the differences in the several carpal bones of the Gorilla, as compared 

 with those of the human skeleton, consists in giving greater proportional breadth, as 

 compared with the length, to the carpal segment in the great Ape. 



The most marked distinction in the framework of the pectoral limb is met with 

 in the bones of the thumb of the Gorilla (PI. X. fig. 1 , i). The metacarpal does not exceed 

 in length that of the same bone in the European male {ih. fig. 2, i). It is articulated 

 with its fore and back parts more nearly on the same plane with those of the other me- 

 tacarpals, i. e. with its inner or radial border turned less forwards, than in Man. Its base 

 shows a deeper concavity from before backward, chiefly due to the greater and more 

 pointed production of the palmar boundary, whereby the bone is more securely articulated 

 with the trapezium, with less extent and freedom in its movements, than in Man. 

 The shaft is relatively stronger than in Man, chiefly by the ridge-like production of its 

 outer border. The first phalanx is shorter than in Man, and is more flattened from 

 before backwards ; the second is shorter and much more slender beyond the articulation. 

 In Man the length of the three bones of the thumb nearly equals one-third the length 

 of the humerus : in the Gorilla it is little more than a fifth of that length. The meta- 

 carpal of the index digit in the Gorilla is twice the length of that of the pollex : in 

 Man it is little more than one-fourth larger : like the succeeding metacarpals, it is of 

 great strength in the Gorilla, and presents a greater relative expansion of the distal end. 

 The tuberosity on the palmar side near the proximal articulation, for the insertion of 

 the flexor carpi radialis, is more developed ; the dorsal side of the bone is flatter. In the 

 metacarpals of the third, fourth, and fifth digits the transverse rough ridge at the back 

 part of the base of the convex condyle is singularly developed. At the palmar aspect, 

 where the interossei diverge near the distal condyle, there is a tuberosity which is most 

 prominent in the metacarpal of the index ; a strong ridge is continued from it to the 

 condyle in the third and fourth metacarpals : it is wanting on the dorsal side in the 

 fifth. The distal expansion is most strongly marked in the third and fourth meta- 

 carpals, in which the articular surface begins with a slight concavity on the dorsal side 

 in the Gorilla. The proximal phalanges are chiefly peculiar for the thick and pro- 



