Fig. 67.—Gibbon—left hand.
Fig. 67 of a Hainan gibbon is very different on the palm from the other three apes for its ridges are nearly all longitudinal or slightly oblique, precisely as one would find this part if the palm were used very little for grasping boughs and much for discriminating globular objects procured for its repasts. The wonderful long digits of the gibbon form its main organ for supporting itself on branches and swinging its body rapidly from branch to branch, and the arched or nearly transverse ridges on the digits are placed just as the endless use of them for this purpose would be likely to follow from it. This example is a very clear one for showing, if it exist, the effect of use and habit on the disposition of the ridges.
Fig. 68.—Left foot of ring-tailed lemur.
Fig. 69.—Brown sapajou, right hand.
Fig. 68 shows the arrangement of papillary ridges in a lemur and 69 that of a brown sapajou.