At this point I wish to draw attention to one important fact. The tendons of the foot, which open and close the digits, are imbedded in the palm in a deep layer of coarse, gristly matter, which forms a pad, as it were, under the soles of the foot and prevents it from bending. Therefore it is not possible for a gorilla to sleep on a perch. In this respect he resembles man more than the chimpanzee does, but it is quite certain that neither of them has the true arboreal habit. The gorilla is an expert climber, but he cannot sleep in a tree. In the hand the tendons which close the fingers are the same length as the line of the bones, and this permits him to open the fingers to a straight line, which the chimpanzee cannot do. One other important point I desire to mention. The muscles in the leg of the gorilla will not permit the animal to stand or walk erect. The large muscle at the back of the leg is shorter than the line of the bones of the leg above and below the knee. When this muscle is brought to a tension, those bones form an angle of from 130° to 160°, or thereabouts. So long as the sum of two sides of a triangle is greater than the other side, a gorilla can never bring his leg into a straight line. In the infant state, while the muscles are elastic and the bones less rigid, the leg can be forced nearly straight. The habit of hanging by the arms and walking with them in a straight line develops the corresponding muscle in those members so that the bones can be brought in line and the limbs straightened. The gorilla can stand upon his feet alone and walk a few steps in that position; but his motion is very awkward; his knees turn outward, forming an angle of 40° or 50° on either side of the mesial plane. He never attempts to walk in this position except at perfect leisure, and then he holds on to something with his hands. [Illustration: YOUNG GORILLA WALKING (From a Drawing.)]