STANDING, WALKING, AND RUNNING 



291 



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tebra, and if the body were rigid it would remain erect 

 as long as the line from the center of gravity fell within 

 the area of the feet. As the feet were spread apart and 

 the base support correspondingly increased, 

 the more difficult it would be to upset the 

 body. If, then, we had a rigid structure the 

 only precaution necessary to secure erect 

 position would be to fulfil this law of 

 physics. But in our body there are many 

 joints, and the tendency of the whole system 

 is to .bend and pitch the body forward. To 

 remedy this it is necessary for the muscles 

 that control the movements of the bones to 

 be so fixed as to keep these joints rigid. 

 This is accomplished bj' opposing the various 

 flexor and extensor muscles so as to hold the 

 bones of the legs and body in an upright 

 position and prevent movement about the 

 joints. To do this requires complete nerve 

 control, and this control is only acquired 

 by much practice as is evidenced by the 

 difficulty which children experience in their 

 first attempts to stand upright. The reel- 

 ing of the drunken man is another evidence 

 that the erect position is the result of FiG.i25-Arrange- 

 nervous control since, in such case, the "/"tiie°LusXs 

 alcohol has disturbed the nerve centers ■wi^'i^ah. keep the 



body erect. 



only. 



Some one has described walking as the act of falling 

 down and recovering oneself repeated at regular intervals. 

 This is an apt description, for as the flexors bend the leg 

 muscle, the body falls forward upon the other foot as a 



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