THE CHIMPANZEES AND ORANGS. 11 
sion at the middle in the Gorilla (fig. 18). The unciforme in the Gorilla (Pl. 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 (ib. 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 (Pl. X. fig. 1,1). The metacarpal does not exceed 
in length that of the same bone in the European male (ib. fig. 2,1). It is articulated 
with its fore and back parts more nearly on the same plane with those of the other me- 
tacarpals, 7. 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 boneis 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- 
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