198 HUMAN PHYSIOLOGY CHAP. 



137. Food of Muscles. Muscle cells become worn 

 out by use. To keep them in good working order it is 

 necessary to supply them with an abundance of nutri- 

 tious food and oxygen. The proteids, you remember, are 

 the building foods and are necessary to repair the cells 

 after every contraction. The blood should always con- 

 tain a sufficient amount of this class of food stuffs. A 

 person who does much muscular work must eat meats, 

 cheese, eggs, or other articles containing proteids. The 

 heat and energy used by a working muscle can be 

 obtained more easily from carbohydrates and fats than 

 from proteids. There should be an adequate supply of 

 these foods in order that the muscles may do their work 

 with the greatest ease and economy. Water and salt 

 are essential to the health and proper activity of muscle 

 cells. 



A sufficient amount of pure fresh air to oxidize the 

 different foods in the muscles is of the utmost impor- 

 tance. If there is a lack of oxygen, the foods cannot 

 easily be burned, and consequently there is a lack of 

 heat and energy for the muscles to work properly, al- 

 though there may be an abundance of food. The foods 

 are at best only partially oxidized and so do not furnish 

 as much heat as they should. And besides that, the 

 wastes formed under such conditions are very poisonous, 

 and difficult to remove from the blood. 



The blood should contain all the different food stuffs 

 in the right proportions, and an adequate supply of 

 oxygen. The activity of the muscles depends upon the 

 foods we eat and the air we breathe. 



