150 



THE HUMAN BODY. 



ground between the two feet, within the basis of support 

 afforded by them. With the feet close together, however, 

 the posture is not very stable, and in standing we com- 

 monly make it more so by slightly separating them so as to 

 increase the base. The more one foot 

 is in front of the other the more sway- 

 ing back and forward will be compati- 

 ble with safety, and the greater the 

 lateral distance separating them, the 

 greater the lateral sway which is possi- 

 ble without falling. Consequently we 

 see that a man about to make great 

 movements with the upper part of his 

 \ /^\ Body, as in fencing or boxing, or a sol- 



dier preparing for the bayonet exercise, 

 always commences by thrusting one 

 foot forwards obliquely, so as to increase 

 his basis of support in both directions. 

 The ease with which we can stand is 

 largely dependent upon the way in 

 || which the head is nearly balanced on 



the top of the vertebral column, so that 

 but little muscular effort is needed to 

 keep it upright. In the same way the 

 trunk is almost balanced on the hip- 

 ll|[| joints: but not quite, its centre of grav- 



ity falling rather behind them; so that 

 just as some muscular effort is needed 

 to keep the head from falling forwards, 

 FIG. 6i. Diagram ii- some is needed to keep the trunk from 

 c* m b?!S toppling backwards at the hips. In a 



the 



similar manner other muscles are called 

 klip 1 " thfjXs into pky at otner joints: as between the 

 rigid and the Body erect. ver tebral column and the pelvis, and at 

 the knees and ankles; and thus a certain rigidity, due to 

 muscular effort, extends all along the erect Body: which 

 on account of the flexibility of its joints could not other- 

 wise be balanced on its feet as a statue can. Beginning 

 (Fig. 61) at the ankle-joint, we find it kept stiff in standing 



