IX. ABSORPTION. 



In the processes of digestion, food is broken up and 

 transformed in various ways into soluble substances, 

 such as peptone, sugar, etc. This food, however, is still 

 in the aUmentary canal, and far removed from the cells 

 of the body which it is to repair and build up. In this 

 respect, then, the alimentary canal is like a big factory 

 whose whole action is centered in the preparation of food 

 products. A delivery system is necessary for factory 

 products to be made available for use, and, likewise, in 

 the body, a delivery system is necessary to distribute to 

 all parts of the body the food prepared by the alimentary 

 canal. In the bod}^ such a system is found in the blood 

 system, and it is evident that the first step necessary to 

 distribution of food is the transfer of the digested food 

 matter to the blood. In the business world such a trans- 

 fer of goods to a delivery system is called shipping. In 

 the body the processes which are concerned in transfer 

 of digested food to the blood are all included under the 

 name of absorption. The object of shipping and absorp- 

 tion is identical, namely, to get prepared products into 

 circulation. 



Relation of the blood vessels to the alimentary tract. — 



The transfer of food to the blood may take place in one 



of two ways. It may pass directly into the blood vessels 



which line the walls of the intestine and stomach, or it 



may enter another set of tubes called the lymphatics. 



These lymphatics are closed tubes hke the blood vessels, 



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