INTESTINAL DIGESTION. 163 



a great proportion of the fatty part passes out of the ali- 

 mentary canal unabsorbed. There is no doubt therefore 

 that the bile somehow aids in the absorption of fats. 



The Succus Entericus or Intestinal Juice consists of the 

 mixed secretions of the glands of Brunner and the crypts 

 of Lieberkiihn. It is very difficult to obtain it pure, and 

 hence its digestive action is but imperfectly known. 

 It is alkaline and so helps to overcome the acidity of the 

 chyme and allow the trypsin of the pancreas to act on pro- 

 teids, and seems capable itself of dissolving some kinds of 

 proteids and turning them into peptones. 



Intestinal Digestion. Having considered separately the 

 digestive actions of the different secretions poured into the 

 small intestine, we may now consider their combined ac- 

 tion. The acid chyme entering the duodenum from the 

 stomach is more than neutralized by the alkaline secretions 

 which it meets in the small intestine; it is made alkaline. 

 This alkalinity allows the pancreatic secretion to finish the 

 solution and transformation into peptone of proteids which 

 have escaped conversion in the stomach. The pancreatic 

 secretion also continues that conversion of insoluble starch 

 into soluble and absorbable grape sugar, which had com- 

 menced in the mouth but was checked in the stomach. 

 The bile and pancreatic secretion together emulsify the 

 fats, with which they are thoroughly mixed by the contrac- 

 tions of the muscular coat of the intestine; they get them 

 into a state of very fine division in the form of microscopic 

 droplets, which are taken up by the cells lining the intes- 

 tine. To a certain extent the fats are also saponified. The 



What does the snccus entericus consist of? Why is its digestive 

 action but little known? Point out some of its uses. 

 Describe the process of intestinal digestion. 



