CHAPTER III 



HOW THE BACKBONE IS BALANCED AS WE SIT, STAND, OR 

 WALK, AND SOME POINTS OF DIFFERENCE BETWEEN 

 THE MOTOR CYCLE AND HUMAN BODY 



In the last chapter we have been speaking of the engines 

 which move the legs in walking ; we should make a great 

 mistake, however, if we thought that only the muscles 

 of the lower limbs were at work when we walk. There 

 is one other and very important part of the body which 

 has at the same time to be kept upright and balanced, 

 and that is the backbone or spine. If we have had 

 to walk a long way, especially if the day has been close 

 and hot and the road hard and dusty, we are glad to sit 

 down, for that rests the tired muscles of our legs and 

 thighs and gives them time to regain strength. But it 

 is not enough merely to sit down ; to feel really com- 

 fortable we must bend forwards and rest our bodies against 

 our knees, or recline backwards against a fence or tree 

 trunk ; or if very tired we throw ourselves down on the 

 sward, and that position brings a feeling of relief. Clearly 

 then when we walk more muscles than those of the limbs 

 become worn out ; those of the back also become tired 

 and need a rest. 



It is not only when we stand or walk that the muscles 

 of the back have to be set to work. Every boy and girl 

 knows how tiring it is to sit bolt upright in school ; 

 presently comes the wish to lean backwards against some- 

 thing, or to bend forwards over the desk and rest the head 

 on a hand, or to twist the body round a little ; all of 

 these plans seem to bring us greater ease. We want to 



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