CHAPTER II 



THE MUSCLES, WHICH ARE THE MOTOR ENGINES OF THE 

 HUMAN BODY, COMPARED TO THE ENGINE OF A MOTOR 

 CYCLE. THE ENGINES WHICH MOVE THE LEGS IN 

 WALKING 



When I tell you that I am going to compare the human 

 body to a motor cycle you must think I have gone crazy 

 in putting side by side things which everybody can see to 

 be very different. At least, you will permit me to try 

 and show you how the comparison answers. Let us 

 suppose, then, that it is a fine day in summer, and that 

 you, mounted on a motor bicycle and I on my two legs, 

 have reached a point on a dusty country road where there 

 is a steep ascent straight in front of us for a stretch of 

 miles. We start to climb the hill. Your body is carried 

 to the top in a few minutes by the motor cycle. At a 

 slower pace and on foot I also toil to the to_p of the hill. 

 There is no doubt as to how your body was carried up. 

 All the time the throbbing engine of your bicycle was 

 hard at work. The engine of the bicycle was the active 

 agent which carried your body up the long, steep hill. 

 Nor is there any doubt about the active agents which 

 carried my body up as I strode after you on foot. All 

 the time certain living structures in my body were actively 

 performing mechanical work, moving my limbs and 

 carrying my body up the hill — doing just the same kind 

 and amount of work as was performed by your bicycle 

 engine. The mere fact that we have given to the active 

 or motor engines of the human body the name of muscles 

 will not blind us to their true nature ; they are the 



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