394 ABSORPTION 



ileocecal valve. This amount, less the loss in the feces, is absorbed in the 

 large intestine. 



Absorption of Carbohydrates by the Intestines. Carbohydrates 

 are broken down to dextrose, levulose, etc., and are absorbed as such. Even 

 the soluble cane-sugar is split by the invertase of the intestine into the mono- 

 saccharides, dextrose and levulose. Starch is the source of most of the 500 

 grams of dextrose absorbed in an average diet per day. During the absorp- 

 tion of a carbohydrate meal the percentage of dextrose in the blood of the 

 portal vein is increased over the normal, which is o . i to 1.5 per cent. This 

 excess of dextrose passes through the liver and is temporarily stored in the 



FIG. 284. Section of the Villus of a Rat Killed during Fat Absorption, ep, Epithelium; 

 str, striated border; c, lymph cells; c', lymph cells in the epithelium; /, central lacteal con- 

 taining disintegrating lymph corpuscles. (E. A. Schafer.) 



liver cells as glycogen. In the case of a fistula in the receptaculum chyii, 

 the chyle contained less than a half per cent, of the total dextrose absorbed. 



Experiments on the rate of absorption of the different sugars seem to 

 indicate that their absorption does not follow known physical laws and that 

 we must assume an unknown chemical factor in the living protoplasm. 



Dextroses are absorbed readily by the large intestine. 



Fermentation processes from bacterial growth produce certain acids from 

 the carbohydrates, chiefly in the large intestine. These are readily absorbed. 



Absorption of Fats by the Intestines. Fats reach the absorbing 

 epithelium in two forms, as soluble glycerol and soaps and as finely emulsi- 

 fied fats. The first two are taken up by the epithelium readily enough, 

 but in the last the process of absorption is not so clear. It is comparatively 



