No. 2.] THE HARD PARTS OF THE MAMMALIA. 153 
his hold by a curvature of the claws, which was in his ancestors 
voluntary, but which has now become fixed by modifications of 
the articulations themselves. This habit has resulted in a pro- 
gressive lengthening of the bones of both the leg and the foot, 
but especially of the leg, and most of the fore leg, which has 
prehensile uses not experienced by the hind leg, in serving the 
feeble intelligence 
of the animal. RC ea othe 
A similar case iF ih lane 
ot velon sation 
through _ suspen- 
sion is that of the 
fore les of the 
Quadrumana. This 
modification of 
structure is direct- 
ly as the habit of 
swinging by the 
fore leg, as in the 
Ateles of South 
America, and in 
the Simiidz of the 
Old World. Inthe 
genus Hylobates 
the habit of pro- 
gressing rapidly 
through the forest 
by swinging from 
they Horie legs, 
reaches a maxi- 
mum. The aban- Figure 4.—Tarsi of bats, much enlarged; from H, 
donment of this atten. 4. Rhinolophus capensis. B. Carollia brevicauda, 
habit by man has C. Chilonycteris sp. D. Rhynchomycteris sp. E. Ves- 
resulted in the pro- pertilio subulatus. F. Atalapha noveboracensis. Letter- 
ing: 4 tibia; f fibula; a. astragalus; ca. calcaneum; cal, 
calcar; cw, cuboid; x, navicular; 7, 2, 3, tarsalia. 
gressive — shorten- 
ing of the fore limb, 
both in comparison with the apes, and between the higher and 
lower races. 
In certain types the proportions of the tarsus have undergone 
modifications from the same cause, In the sloths, the astragalus 
