THE CHIMPANZEE AND ORANG UTAN. 353 
cility of climbing and grasping, render the entire frame in a proportionate degree de- 
pendent on the upper extremities for support and progression. But while the Chim- 
panzee thus adheres to the Quadrumanous character, and especially in the curtailed 
proportions and detached opposable condition of the hallue, it must be admitted to ap- 
proach the Bimanous type in the length and strength of the hinder thumb more closely 
than any of the lower Quadrumana. 
The agile and powerful locomotive actions of the Chimpanzee require a proportionally 
ample development of the respiratory system, and the size and expansion of the thorax 
is accordingly a prominent character in its skeleton. The transverse exceeds the an- 
tero-posterior diameter of this cavity, but not to the same extent as in Man. The ribs 
are thirteen in number on each side, seven true and six false. The last two pairs are 
proportionally longer than in Man; and the end of the last rib is not pointed, but trun- 
cated for the attachment of a cartilage, which does not, however, join the cartilage of 
the rib above. The sternum is flattened from before backwards, but is not so broad as 
in the Orang: in the adult specimen not only does the harmonia between its body and 
the manubrium remain, but those of the four single pieces of which the body is itself 
composed are still visible. 
The clavicle is long and strong, so that the shoulders are kept wide apart : it is not 
straight as in the Orang, but exhibits the same sigmoid curve as in Man, though in rather 
aless degree. The scapula, on the other hand, recedes further from the human type in 
the Chimpanzee than in the Orang, being narrower in proportion to its length, and 
having the spine running more in the direction of the axis of the trunk, and situated 
more towards the middle of the scapula, and more perpendicular to its plane. The 
acromion process is longer and narrower than in Man. The humerus very closely re- 
sembles that of the human subject, but is proportionally longer and stronger ; and the 
peculiar twist is more marked, and occurs lower down the bone. The distal articu- 
lating surface is formed so as to allow of the same advantageous variety and freedom 
of motion to the bones of the fore arm as in Man. 
As the segments of each limb recede from the trunk they become subject to more 
extensive and varied modifications. This is more especially exemplified in the lower 
extremities of the Chimpanzee; and the bones of the upper extremity follow the same 
law. ‘The disproportionate length which the humerus already presents becomes greater 
in the bones of the fore arm; and those of the hand recede still further from the Bi- 
manous type. Both the radius and ulna are more curved than in Man, and the inter- 
osseous space is, in cousequence of the direction of their curves, much wider. 
The carpal bones have the same number and relative position as in the human sub- 
ject; but the trapezium and trapezoides are proportionally smaller, while the os prsi- 
forme is of larger dimensions, being nearly equal to the os magnum. 
The small size of the trapezium evidently relates to the shortness of the thumb, 
which it supports, and which does not quite equal the metacarpal bone of the first 
