THE UTILIZATION OF FOOD IN ANIMALS 339 



food has passed a short way down the intestine, nearly all the 

 food which can be digested has been converted into soluble 

 substances; these pass with water through the wall of the 

 alimentary canal into the blood and are carried to all the 

 cells of the body. Small residues of food, consisting largely 

 of the fibers of food which cannot be digested and of residues 

 from the digestive juices, are swept along into the large in- 

 testine and finally voided as waste. 



345. Motions of the alimentary canal. The act of swallowing 

 is voluntary, but when food is once swallowed, it is passed 

 along by a process that is largely automatic. The chief stimuli 

 are the food itself and the secreted juices. Pleasant antici- 

 pation of food has a favorable effect on the whole process ; 

 extreme fatigue or emotion such as anger, fear, or worry 

 may entirely stop the digestion of food and its motion along 

 the alimentary canal. 



346. Proper care of the alimentary canal. Since the alimen- 

 tary canal is really a factory in which food is prepared for 

 the use of the cells, it is very necessary that we should give 

 it good care. Our first responsibility is to take good care 

 of the teeth. We need them all the flattened front teeth 

 (incisors) for cutting, the pointed canines for tearing, and 

 the bicuspids and molars for grinding. The dentist is a good 

 friend. Furthermore, we should use our teeth for the purpose 

 for which they were intended. If food is swallowed unchewed 

 the digestive juices can act upon it only slowly, the food 

 remains longer than it should in the alimentary canal, and 

 after a while the person may develop chronic indigestion. 



It is important to eat at regular hours and not to be con- 

 tinually eating between meals. The alimentary canal needs 

 to have a rest between meals just as much as the brain needs 

 to have a rest every night. 



We should be sure that the lower end of the alimentary 

 canal is cleaned out every day. The best ways to do this 

 are to drink much water every day j to eat some food at every 



