128 DIGESTION 



alkali is important in aiding the emulsification of fats. 

 It varies in quantity in different regions of the intestine, 

 being scarce in the upper part and very plentiful in the 

 lower or ileac region. Its specific action is due mainly to 

 the presence of two kinds of enzymes. One, similar to 

 amylopsin, aids in converting the starches to sugar. The 

 other (invertase) converts cane sugar and other forms of 

 sugar to grape sugar so that all sugars and starches are 

 finally absorbed as grape sugar. 



SUMMAEY. 



1. The food enters the intestine as an acid mixture called 

 chyme. 



2. It is mixed in the intestine with three juices, bile, pan- 

 creatic juice, and intestinal juice. 



3. The three juices transform the acid chyme into an alkaline 

 mixture called chyle. 



4. In this alkaline medium the various enzymes of the three 

 juices transform proteids and albuminoids to peptone; fats to 

 soap and emulsions; starches and sugars, to grape sugar. 



5. The action of the enzymes is aided by the mechanical action 

 of the muscle walls. 



6. The resulting mixture is then ready for absorption. 



Digestion op the Large Intestine. 



That part of the alimentary tract included under the 

 name of the large intestine is subdivided, like the small 

 intestine, into regions. These regions are termed the 

 ccecum, the colon, the sigmoid flexure, and the rectum. 



The csecum is the name applied to the saclike pouch 

 into which the small intestine opens at the top by an 

 orifice, guarded by a valve called the ileocolic valve. At 



