150 



THE HUMAN BODY. 



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in the articulation between the sacrum and the last lumbar 

 vertebra, and the perpendicular drawn from it will reach the 

 ground between the two feet, within the basis of support af- 

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

 posture is not very stable, and in standing we commonly 

 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 swaying back and 

 forward will be compatible with safety ; and 

 the greater the lateral distance separating 

 them the greater will be the lateral sway 

 which is possible without falling. Conse- 

 quently 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- 

 I J*H 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 almost balanced on the top of 

 the vertebra] column, so that but little 

 muscular effort is needed to keep it up- 

 right. In the same w r ay the trunk is almost 

 balanced on the hip joints, but not quite> 

 its centre of gravity falling rather behind 

 them; so that just as some muscular effort 

 is needed to keep the head from falling 

 forwards, some is needed to keep the trunk 

 from toppling backwards at the hips. In 

 a similar manner other muscles are called 



illto P la J at otner J oints : as between the 

 lines) which pass before vertebral column and the pelvis, and at 



and behind the joints r 



and by their balanced the knees and ankles i and thus a certain 



activity keep the joints . _ ,, 



rigid and the body erect, rigidity, due to muscular effort, extends all 

 along the erect Body : which, on account of the flexibility of its 

 joints, could not otherwise be balanced on its feet, as a 

 statue can. Beginning (Fig. 68) at the ankle-joint, we find 

 it kept stiff in standing by the combined and balanced con- 

 traction of the muscles passing from the heel to the thigh, 

 and from the dorsum of the foot to the shin-bone (tibia). 



il I J 



FIG. 68. Diagram ii- 



