284 MUSCLES 



Let us examine this analogy more closely to see 

 how this explanation of the production of contraction 

 and expansion in a muscle cell fits in with known condi- 

 tions for muscular activity. 



In the engine, if the supply of fuel becomes lessened, 

 the amount oxidized is necessarily less and the power 

 to do work becomes diminished. Likewise, in the muscle, 

 any interference with the food supply must decrease the 

 amount of fuel and lessen the working power of the mus- 

 cles. It is essential, therefore, that the muscles be pro- 

 vided with a good supply of blood, and that this blood 

 contain the proper kind of food for fuel. It is for this 

 reason that athletes and others who use their muscles 

 extensively are limited to a diet rich in the foods required 

 for muscle building and combustion. Meats, coarse breads, 

 eggs, vegetables, fruits, supply aU the important carbo- 

 hydrates and proteids. Fats and pastries are usually 

 excluded, not because they do not contain energy pro- 

 ducing material but because they are difficult to digest. 



Tobacco and alcohol also tend to diminish the irrita- 

 bility of the cells, and should be excluded from the diet. 

 "Wliat is good for the athlete is evidently well suited for 

 the gi-owing boy and girl, and, in general, the food of all 

 people should contain the materials suited to the upbuild- 

 ing of muscle cells and, at the same time, fitted to provide 

 the fuel necessary for their action. 



Again, if the fire of the engine is not supplied with a 

 good draught, that is, a constant supply of oxygen, the 

 production of heat must necessarily stop. So, in the 

 body, the muscles must be supplied constantly, not only 

 with food-laden blood, but also with oxygen-laden blood. 

 This means that the lungs, from which this supply is 



