organs of special sense. The foot has become "plantigrade" in connexion with the assumption of upright carriage. It has independently become plantigrade in the gibbons and the baboons. That is to say, we and they do not walk on the edge of the half-grasping foot as do the gorilla, chimpanzee, and orang, but more steadily and firmly on its flat sole (plantar surface), as do the bears and some other animals. At the same time man has lost very greatly (but not entirely) the power of grasping with his toes. The upright carriage enabled the early ancestors of man to survey, and so to judge the conditions of safety or danger at a distance from them, as well as to devote their hands to new and special uses. CHAPTER XXVII THE SKELETON OF APES AND OF MAN THE upright carriage of man has entailed remarkable changes in the proportions and shapes of parts of his body, as well as leading to special skill in the use of his hands. The vertebral column of man has not the single curve of a bow, as it has (practically) in the higher apes, but as he stands it curves (slightly, it is true, but definitely) forward at the neck, backward at the chest, forward at the loins, and backward again at the hips, an arrangement which appears to protect to some extent the brain from the transmission to it along the vertebral column of the shock caused by the sudden impact of the feet on the ground in jumping. The head is balanced on the top of this slightly elastic curvilinear column, the joint by which the skull rests on the vertebræ being placed beneath the brain-box and near the middle region of the skull. The ligaments which hold the skull in place are smaller than those in monkeys. In the higher apes the skull is not so balanced, but is held by very strong ligaments and muscles braced, as it were, on to the end of the forwardly sloping, nearly straight, backbone, from which it projects, and has further to be held in position by a great ligament attached to it and the dorsal processes of the neck vertebræ. As an adaptation to the upright carriage of man, the shape of his pelvic bones is that of a basin upon which his coiled mass of intestines can rest when he stands erect. The pelvic bones of the higher apes are flat, nearly parallel with the broad plane of the back, and give no such support; the viscera have to rest against the wall of the abdomen in the stooping position assumed by these animals in walking. The abdominal walls are consequently strong and thick, and the abdomen protrudes, as does that of a very young child. One result of man's upright carriage, showing that it is a recent acquirement and one to which he is not completely adapted, is the frequent occurrence in him of "hernia," or protrusion of the intestine through certain spaces in the deep fibrous wall of the abdomen. There would be no excessive pressure upon these spaces (near the groin), and therefore little danger of hernia, were it not for man's newly-acquired habit of erect gait.