Il6 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



substances passing through the alimentary canal allows their 

 more ready disintegration. 



3. It aids in the emulsification of fats. 



4. It promotes the absorption of fats. Recently the state- 

 ment that the bile promotes all kinds of absorption has appar- 

 ently been successfully disproved, but it seems certain that 

 "the bile acids enable the bile to hold in solution a consider- 

 able quantity of fatty acids, and possibly this fact explains 

 its connection with fat absorption." (American Text-Book.) 



The Secretion of the Intestines. 



The intestinal secretion, or succus entericus, is a product 

 of the crypts of Lieberkuhn and Brunner's glands. It is 

 scanty, of a yellow color and an alkaline reaction. Opinions 

 vary as to what foods are affected by this fluid, but since the 

 more recent experiments have overcome some difficulties in 

 obtaining specimens, the conclusions based upon them seem 

 most reliable. It is said to have no effect on proteids or 

 fats. It contains an amylolitic enzyme, which aids the pan- 

 creatic juice in converting starch into maltose. It also has 

 an enzyme, invertase, which converts cane sugar 'into dex- 

 trose and levulose, as well as an allied enzyme, maltose, 

 which converts maltose into dextrose. The carbohydrates 

 are absorbed as dextrose, with the probable exception of 

 lactose. It is mainly cane sugar, maltose (from starch) 

 and lactose that are in the alimentary tract and require to be 

 thus changed to dextrose. 



It is not out of place to say that ptyalin produces maltose 

 and a little dextrose, and that the pancreatic juice and succus 

 entericus produce maltose and considerable dextrose. The 

 maltose is converted into dextrose during the process of 

 absorption. It is, therefore, customary to say that the carbo- 

 hydrates are absorbed only as dextrose. 



Movements of the Small Intestine. The effect of intesti- 

 nal movements is to force the contents onward through the 



