ORGANS AND PROCESSES OF DIGESTION 157 



of dissolving it under certain conditions). 2. To be con- 

 verted by the sodium carbonate into a form of soap which 

 is soluble in water. 



The emulsification of fat is known to occur in the small intestine. 

 By this process the fat is separated into minute particles which are sus- 

 pended in water, but not changed chemically, the mixture being known 

 as an emulsion. While this is believed by some to be an actual process 

 of digestion, the advocates of the solution theory claim that it is a pro- 

 cess accompanying and aiding the conversion of fat into fatty acid and 

 glycerine. 1 



The Intestinal Juice is a clear liquid with an alkaline 

 reaction, containing water, mineral salts, and certain proteid 

 substances that may act as enzymes. It assists in bring- 

 ing about an alkaline condition in the small intestine and 

 aids in the reduction of cane sugar and maltose to the sim- 

 ple sugars, dextrose and levulose. Since it is difficult to 

 obtain this liquid in sufficient quantities for experimenting, 

 its uses have not been fully determined. Recent investi- 

 gators, however, assign to it an important place in the 

 work of digestion. 



Work of the Small Intestine. The small intestine is 

 the most important division of the alimentary canal. It 

 serves as a receptacle for holding the food while it is being 

 acted upon ; it secretes the intestinal juice and mixes the 

 food with the digestive fluids ; it propels the food toward 

 the large intestine; and, in addition to all this, serves ^s 

 an organ of absorption. 



Digestion is practically finished in the small intestine, 

 and a large portion of the reduced food is here absorbed. 

 There is always present, however, a variable amount of 

 material that is not digested. This, together with a con- 

 siderable volume of liquid, is passed into 



1 Fischer, Physiology of Alimentation. 



