DIGESTION OF FOOD IN THE MOUTH 53 



As a general rule it is best to cook each kind of food separately. 

 Each substance can then be cooked in its own peculiar manner. In 

 roasting and broiling, the fat drips away. The outside of the meat, 

 subjected to a high degree of heat, becomes hard, imprisoning the 

 juices within. The inner part of the meat is protected from the heat 

 and is cooked at a lower temperature 

 than the outside. So its juices remain 

 in a more natural state. 



When food made from vegetables or 

 grain is baked, a crust forms upon the 

 outside. This consists of hardened albu- 

 min mixed with starch, which is partly 

 changed by the heat to a kind of sugar. 

 If the crust is not too much cooked and 

 dried it is palatable and easily digested. 



67. The alimentary canal. 

 Food is taken into the body and 

 digested by means of a tube lead- 

 ing through the body. Beginning 

 at the upper end, the parts of this 

 tube, which is called the alimen- 

 tary canal, are the mouth, phar- 

 ynx, esophagus, stomach, and 

 intestine. 



68. The mouth. The food is 

 held in the mouth for a few sec- 

 onds while it is mixed with the 

 watery fluid called the saliva, and 

 ground fine by the teeth. This 



grinding is mastication, and the mixture with saliva is in- 

 salivation. In these two processes, the teeth, tongue, 

 cheeks, lips, and salivary organs all take part. The 

 roof of the mouth is formed by the bony palate in front, 

 and the soft movable palate behind. It is bounded on 

 the sides and in front by the teeth, cheeks, and lips. 



