SOUND BODIES 



muscle can contract only when an impulse from the 

 nervous system tells it to contract. The impulse 

 which the muscle cell sends back stimulates the brain 

 cell to perform its function. If either cell is injured, 

 the other degenerates. 



That is to say, the injury or destruction of a muscle 

 of any individual's body let us say the amputation of 

 an arm brings about an actual degeneration of cells 

 within the brain of that individual. His central ner- 

 vous system is crippled as well as his muscular system, 

 and this not merely in an imaginary way, but actually 

 and demonstrably. One might even go a step further, 

 still keeping within the bounds of truth, and say that, 

 indirectly, every other organ of the body also suffers 

 to some extent, since it is not merely brain cell and 

 muscle cell that are linked in mutual dependence, but, 

 directly or indirectly, every pair of cells in the entire 

 body. 



Now since a less degree of injury than actual de- 

 struction will necessarily result in proportionate recipro- 

 cal weakening, it follows that the health of the brain and 

 of every other organ is in some measure linked with and 

 dependent upon the health of the muscular system. The 

 person who desires physical health can therefore do no 

 better than to seek the aid of his muscles in securing 

 it. And in doing this he need, in fact, can, do noth- 

 ing more than permit his muscles to secure exercise 

 through performance of their natural function of 

 contraction. 



But the power of the muscles as health-preservers ex- 

 tends beyond mere physical well-being. We have seen 



[43] 



