THE ABSORPTION OF FOODS 12) 



SUMMARY OF DIGESTION AND ABSORPTION 



his finishes the story of the entrance of food into the body. 



brain begins the history by selecting the food through the 

 sense of taste; heat cooks and prepares it; the teeth grind it 

 into fine pulp which, by means of the tongue, is thoroughly 

 mixed with water and saliva. Then begins a series of chemi- 

 cal changes as the food is passed through that chemical lab- 

 oratory, the alimentary canal. It is taken into this labora- 

 tory as more or less solid material containing proteids, starches, 

 fats and other substances, but by the chemical action of the 

 ferments produced by the glands, these ingredients are soft- 

 ened and completely transformed until they are almost wholly 

 dissolved into a syrupy white mass, which does not bear the 

 slightest resemblance to the original food in appearance, and 

 very little in chemical nature. As the food is forced along, 

 the villi with which the intestine is lined begin to pick out of 

 the mass the useful parts, leaving the rest in the canal to be 

 ejected later as worthless. The sugars and proteids are handed 

 over to the blood vessels which take them to the liver where 

 a part of the sugars is temporarily stored. The fats are passed 

 to the lacteals which likewise carry them to the blood, but by 

 a different track, a side track as it were, which switches them 

 around the liver. Finally all the nutriment gets into the 

 blood by which it is carried around the body to any part 

 that needs it. Digestion and absorption are thus finished 

 and we may turn our attention to the next process 

 circulation. 



