vni FROM THE ALIMENTARY CANAL TO THE HEART 103 



the body, and are further changed in absorption, so that 

 they can be used to nourish the cells and to give us 

 strength. The proteids are now albumins, the carbo- 

 hydrates are a kind of sugar, the fats and oils are 

 human fat, and the water and salt are unchanged. 

 The plasma of the blood is about ninety per cent water, 

 and dissolved in it are all of these foods. 



82. The Large Intestine. We have learned that 

 the food reaches its largest bulk in the small intestine 

 because the quantity absorbed up to this point is less 

 than that of the digestive fluids added. The rapid 

 absorption of all kinds of foods from the small intes- 

 tine, and of water and salt from the large intestine, 

 diminishes the contents very much. Toward the end of 

 the colon the contents become quite solid in consist- 

 ency, and take on a darker color. 



Many kinds of bacteria are found in both the small 

 and large intestines. They live here and decompose 

 many of the undigested food materials. But they do 

 no harm if the large intestine is emptied every day. 

 In this way many useless substances taken with the 

 foods and some waste products formed within the body 

 are removed. 



SUMMARY OF THE MAIN POINTS 



1. Absorption means the transfer of foods from the alimen- 

 tary canal into the blood. 



2. Foods get through the mucous membrane by soaking 

 through, by osmosis, and by the action of the living cells. 



, 3. From the mouth and the oesophagus there are absorbed 

 some water and salt, and sometimes small amounts of sugar. 



