THE SKELETON. 



without hands who have learned to write and paint with 

 their toes. 



Peculiarities of the Human Skeleton. These are largely 

 connected with the division of labor between the fore and 

 hind limbs referred to above, which is carried farther in man 

 than in any other creature. Even the highest apes frequently 

 use their fore limbs in locomotion and their hind limbs in 

 prehension, and we find accordingly that anatomically they 

 present less differentiation of hand and foot. The other more 

 important characteristics of the human skeleton are correlated 

 for the most part with the maintenance of the erect posture, 

 which is more complete and habitual in man than in the 

 animals most closely allied to him anatomically. These 

 peculiarities, however, only appear fully in the adult. In the 

 infant the head is proportionately larger, which gives the 

 centre of gravity of the Body a comparatively very high posi- 

 tion and renders the maintenance of the erect posture difficult 

 and insecure. The curves of the vertebral column are nearly 

 absent, and the posterior limbs are relatively very short. In 

 all these points the infant approaches more closely than the 

 iidult to the ape. The subsequent great relative length of the 

 posterior limbs, which grow disproportionately fast in child- 

 hood as compared with the anterior, makes progression on 

 them more rapid by giving a longer stride and at the same 

 time makes it almost impossible to go on "all fours" except 

 by crawling on the hands and knees. In other Primates this 

 disproportion between the anterior and posterior limbs does 

 not occur to nearly the same extent. 



In man the skull is nearly balanced on the top of the 

 vertebral column, the occipital condyles which articulate with 

 the atlas being about its middle (Fig. 30), so that but little 

 effort is needed to keep the head erect. In four-footed beasts, 

 on the contrary, the skull is carried on the front end of the 

 horizontal vertebral column and needs special ligaments to 

 sustain it. For instance, in the ox and sheep there is a great 

 elastic cord running from the cervical vertebrae to the back 

 of the skull and helping to hold up the head. Even in the 

 highest apes the skull does not balance on the top of the 

 spinal column; the face part is much heavier than the back ? 

 while in man the face parts are relatively smaller and the cra- 

 nium larger, so that the two nearly equipoise. To keep th,e 

 head erect and look things straight in the face, "like a man," 



