LOCOMOTION ON SOLIDS. STANDING. 173 



balanced on the neck by the complex!, splenii, sterno-mastoidei, and 

 other deeper muscles. At the knee-joint, the crucial ligaments are 

 stretched, as the thigh assumes the vertical position over the legs ; 

 they thus retain those bones in apposition, like a rigid pillar, with little 

 or no muscular effort. The ligamentum teres, and the external ac- 

 cessory, or ilio-femoral, ligament in front of the hip-joint (see Fig. 1), 

 perform the same office there. The elastic ligaments connecting the 

 arches of the vertebrae behind, economize, as already mentioned, the 

 muscular power of the erector muscles of the spine. The muscles at 

 the back of the neck, are instinctively relieved by a slight inclination 

 of the head backwards, so as to bring the centre of gravity over the 

 basis of support in the vertebral column. 



In thus standing erect on both legs, the weight of the body is trans- 

 mitted perpendicularly through the vertebral column ; thence, laterally 

 and obliquely, through the sacrum, to the hip-bones ; and thence, 

 through the lower limbs, to the ground. In this position, the centre 

 of gravity is placed perpendicularly over the middle of the basis of 

 support, which corresponds with the surface of the ground covered by 

 the feet, and with that forming the interval between them ; a line let 

 fall from it passes midway between the inner ankles. The natural 

 slight eversion of the feet, materially increases the mechanical base of 

 support, over which it is easy to maintain the weight of the body. In 

 standing at ease, one leg bears nearly all the weight of the body, whilst 

 the other is simply planted, at a little distance forwards, upon the 

 ground; the trunk inclines over the limb which bears the weight, and 

 a line let fall from the centre of gravity, now passes through the mid- 

 dle of the ankle-joint of that foot; the limb being stiffly extended, the 

 ligaments of the knee and hip-joints are so stretched on that side, as 

 to save muscular power. On the opposite side, the pelvis is lowered, 

 the thigh is bent a little upon it, and the leg a little on the thigh ; so 

 that the muscles of that leg also thus obtain some rest. In standing 

 entirely on one leg, a line from the centre of gravity passes through 

 that limb to the ground ; and, unlike the position just mentioned, this 

 attitude demands considerable muscular effort, especially to keep the 

 leg and thigh erect upon the ankle and knee, and to balance the pelvis, 

 which inclines over to the same side, upon the head of the thigh-bone. 

 Standing on one leg soon becomes very fatiguing, not only because 

 the limb has to bear double the usual weight, but because the base of 

 support is so reduced, that more energetic muscular action is needed, 

 in order to keep the centre of gravity in the proper position over it. 

 It has been computed and it is quoted as an example of the dispro- 

 portion already mentioned as prevailing between the muscular power 

 expended, and the useful work accomplished that, in raising the heel, 

 and standing on tip-toe on one foot, the muscles of the calf must de- 

 velop 80 times more force than would directly counterpoise the weight 

 of the body ; so that, if the latter be taken at 150 Ibs., the muscles of 

 the calf must exert an effort equal to 12,000 Ibs. In the act of walk- 

 ing, as we shall see, the body is partly, and in the act of running, 

 mtirely, supported in this way during a certain part of every step. 

 The act of walking is accomplished by means of alternate unsym- 



