CHAPTER XXXI 

 HOW OUR BODIES DIGEST AND ABSORB FOOD 



The fires in our house heaters will not provide the 

 warmth we need if fuel is fed to them in wrong sizes or 

 amounts, or if clinkers and ashes are permitted to collect. 

 Our automobile motors will not run with crude oil fresh 

 from the wells. This oil must first be refined and modified 

 into energy-producing gasoline. 



Similarly the food we eat must be changed to a form 

 that will produce the energy we need. Fortunately our 

 human machine, the body, is equipped with wonderful 

 apparatus for this service. It takes our food fuel, trans- 

 forms it to a liquid, changes its nature and sends the 

 body-building and energy-producing elements through the 

 blood to points of need. Wastes, it eliminates. 



If we are healthy we let this apparatus labor along as 

 it will. It has, however, many parts which get out of order 

 if we misuse them, if we clog up the machinery, or if we 

 give it too much work to do. That is why, for our own 

 health and strength and comfort, we need to add to our 

 scientific knowledge an understanding of this apparatus 

 our digestive system. 



Digestion. Digestion is the process by which the food we eat 

 is so changed that the nutrient substances can be absorbed into the 

 blood. Digestion is accomplished by reducing the food to a liquid 

 and subjecting it to the action of chemical substances called 

 enzymes, or ferments, secreted, or given off, by glands in the body. 

 The nourishing parts of the food are then absorbed through the 

 lining membrane of the digestive organs into the blood, a process 

 called osmosis. 



The organs of digestion form a continuous tube known as 

 the alimentary canal. The most important parts of the alimentary 

 canal are the mouth, the pharynx, the esophagus, or gullet, the 

 stomach, the small intestine and the large intestine. The entire 

 canal is nearly thirty feet long. 



398 



