THE HUMAN FRAME. 539 



The articular surfaces of the knee joint are 

 broader, and admit of greater extent of motion 

 m man than in quadrupeds : hence the leg can 

 be brought into the same line with the thigh, 

 and form with it a straight and firm column of 

 support to the trunk ; and the long neck of the 

 thigh bone allows of more complete rotation. 

 The widely spread basin of the pelvis effectually 

 sustains the weight of the digestive organs, and 

 they rest more particularly upon the broad ex- 

 pansion of the iliac bones : in quadrupeds, these 

 bones, having no such weight to support, are 

 much narrower. 



The base on which the whole body is sup- 

 ported in the erect position is constituted by the 

 toes, and by the heel, the bone of which projects 

 backwards at right angles to the leg. Between 

 these points the sole of the foot has a concavity 

 in two directions, the one longitudinal, the other 

 transverse, constituting a double arch. This 

 construction, besides conferring strength and 

 elasticity, provides room for the convenient pas- 

 sage of the tendons of the toes, which proceed 

 downwards from the larger muscles of the leg, 

 and also for the lodgement of smaller muscles 

 affixed to each individual joint, and for the pro- 

 tection of the various nerves and blood vessels 

 distributed to all these parts. The concavity of 

 the foot adapts it also to retain a firmer hold of 

 the inequalities of the ground on which we 



