There is another peculiar feature in the walk of the chimpanzee. The arms and legs do not alternate in motion with the same degree of regularity that they do in man or quadrupeds. This ape uses his arms more like crutches. They are moved forward, not quite, but almost at the same instant, and the motion of the legs is not at equal intervals. To be more explicit: the hands are placed almost opposite each other; the right foot is advanced about three times its length; the left foot is then placed about one length in front of the right; the arms are again moved; the right foot is again advanced about three lengths forward of the left; and the left again brought about one length in front of that. The same animal does not always use the same foot to make the long stride. It will be seen by this that each foot moves through the same space, and that, in a line, the tracks of either foot are the same distance apart; but the distance from the track of the right foot to that of the left is about three times as great as the distance from the track of the left foot to that of the right. Or the reverse may be the case. The distance from the track of either foot to the succeeding track of the other is never the same between the right and left tracks, except where the animal is walking at great leisure. There is, perhaps, no animal more awkward than the chimpanzee, when he attempts to run. He sometimes swings his body with such force between his arms as to lose his balance and fall backward on the ground. Sometimes when he rights himself again, he is half his length backward of his starting point. The chimpanzee is doubtless a better climber than the gorilla. He finds much of his food in trees; but he is not, in the proper sense of the term, arboreal. To be arboreal, the animal must be able to sleep in a tree or on a perch. The chimpanzee cannot do so. He sleeps the same as a human being does. He lies down on his back or side, and frequently uses his arms for a pillow. I do not believe it possible for him to sleep on a perch. He may sometimes doze in that way, but the grasp of his foot is only brought into use when he is conscious. I have often known Moses to climb down from the trees and lie upon the ground to take a nap. I never saw him so much as doze in any other position.