There is rather an interesting arrangement in the old Gorillas, which is not found in the young or in man, and which appears to have to do with the power of this muscle and its prolonged action. The muscle is well supplied with blood, and the nerve which endows it with energy is particularly well prevented from being compressed during the movements of the muscles amongst which it runs, any compression being very injurious. The upper edge of the blade-bone is notched, and a dense tissue or ligament stretches from one point of the notch to the opposite one, enclosing a small open space; now the nerve runs through this space, and is protected by the hard tissues of bone and ligament from the contraction of the soft muscles. In the old Gorilla a further protection is found in the presence of a little projection of bone in this space, which acts as a greater preventer of pressure. After passing through this space the nerve enters the very substance of the muscle, and is distributed to its fibrils. The upper arm reaches down from the shoulder to the hips in the Gorilla, and its bone (_os humerus_, from the Latin) is strongly marked on its surface by roughnesses and ridges, to which the great muscles are attached. In man the shape of the upper arm varies with the strength of the individual, but in the strongest man and in the most beautifully-shaped woman it has a swelling on the front, and tapers more or less towards the elbow. This is caused by the two-headed or biceps muscle, and by other muscles ending in tendons. But the Gorilla has a very shapeless upper arm; it is, as it were, fat and round throughout, and very large above the elbow, and this is because of the size of the bone within, and on account of the muscles not tapering as they do in man, but being well developed right down to their ends. Hence, elegance of shape is sacrificed to extra muscular strength and size of bone.