THE REASON WHY. 201 



' Whether therefore ye eat, or drink, or whatsoever ye do, do all to the glory of 

 God." CORINTH, x. 



CHAPTER XLI. 



*869. Why do we eat food? 



Because the atoms of which our bodies are composed are con- 

 tinually changing. Those atoms that have fulfilled the purposes 

 of nature are removed from the system, and, therefore, new matter 

 must be introduced to supply their place. 



870. Why do we eat animal and vegetable food ? 

 Because their substances are composed of oxygen,' hydrogen, 



carbon, and nitrogen the four chemical elements of w?iich the 

 human system is formed. They are, therefore, capable of nourish- 

 ing the body, after undergoing digestion. 



871. Why do ice masticate our food? 



Because mastication is the first process towards the digestion 

 of food. Before animal or vegetable substances can nourish us, 

 their condition must be entirely changed, their organic states must 

 be dissolved, and they must become simple matter, in a homoge- 

 neous mass, consisting of the four chemical elements necessary to 

 nutrition, and they must again be restored to an organic condition. 



872. Why does saliva enter the mouth when we are 

 eating ? 



Because, in addition to the mechanical grinding of the food by 

 the action of the teeth, it is necessary that it should undergo certain 

 chemical modifications to adapt it to our use. There are placed, 

 therefore, in various parts of the body, glands, which secrete 

 peculiar fluids, that have a chemical influence upon the food. 



The first of these glands are the salivary glands of the mouth, 

 which pour out a clear watery fluid upon the food we eat, and which 

 fluid has been found to possess a property which contributes to the 

 digestion of food. 



The moisture afforded by the salivary secretion is also necessary 

 to enable us to swallow the food. 



873. Why does the salivary juice enter the mouth just at 

 tke moment that ice are eating ? 



9* 



