' LECTUKE VI. 135 



vertebree^ to whicli is attaclied the ligamentum nuchce inserted 

 in the occiput. A well-proportioned skull will be in equilihrio 

 when supported on the two articular surfaces at the base near 

 the occipital foramen ; if the jaws project forwards^ as in the 

 prognathous negroes^ the occiput becomes elongated in order 

 to establish the equilibrium. Not so in the mammaha. In 

 the natural position of most of these, the axis of the vertebral 

 column runs parallel with the horizontal plane of the pelvis ; 

 whilst in man it forms with it nearly a right angle. The axis 

 of the head, again, forms in mammals a right or an obtuse 

 angle with the axis of the vertebral column ; its direction is 

 perpendicular, and the long jaws form the ai'm of a lever which 

 draws the head still more downwards and forwards. The elastic 

 ligamentum nuch^ is then developed as a counterpoise ; and 

 even in the most anthropoid apes, the orang and chimpanzee, but 

 especially in the formidable gorilla, we find the cervical spines 

 prominent, and provided with powerful muscles and ligaments. 

 With all this, the position of the occipital foramen itself is 

 closely connected, as we shall see in the comparative structure 

 of the skull. 



The relations of the thorax and pelvis may also be explained 

 by the erect posture. The transverse diameter of the human 

 chest is greater than the antero-posterior, the reverse of the 

 proportion in mammals. The chest of man is flattened in front 

 and behind, and arched on the sides ; that of the mammal is 

 laterally compressed, with a cuneiform inclination towards the 

 sternum and the backbone. The arms and hands of man hang 

 down by the sides freely, and are thus unconfi.ned in their 

 movements, and adapted to the manifold purposes which their 

 not being used to aid the support of the body, enables them 

 to subserve. For in all mammals, in which the hand is not 

 transformed into an instrument for flying or into a fin, the an- 

 terior limb always serves as a support in locomotion. This is 

 the case even in the most anthropoid apes. 



In the ape the anterior hand as well as the posterior is used 

 for climbing ; and when the animal moves on the ground, it 

 supports itself on the closed fist, when, from the length of the 

 arms, it assumes a more or less half erect position. But every- 



