INTESTINAL DIGESTION. 7'} 



is perhaps most strikingly demonstrated in the digestion and ab- 

 sorption of fat; for, in the absence of either secretion, large 

 amounts of unabsorbed fat appear in the faeces. Both juices 

 contain relatively large amounts of alkali, which neutralizes the 

 acidity of the chyme. In the pancreatic juice alone, for example, 

 there is a sufficient concentration of sodium carbonate to neu- 

 tralize the acid in an equal volume of gastric juice. The action 

 of pepsin disappears whenever the chyme becomes alkaline and 

 conditions thus become suitable for the activities of the pan- 

 creatic enzymes. Besides its neutralizing action, the bile causes 

 the chyme to assume a somewhat greater consistency, by pre- 

 cipitating incompletely peptonized protein, as well as pepsin. 

 The precipitate becomes redissolved when excess of bile has be- 

 come mixed with it, and the significance of the precipitation may 

 be that it causes a temporary delay in the movement of the chyme 

 along the duodenum, thus allowing it to become properly mixed 

 with pancreatic juice before it moves further along the intes- 

 tine. 



Composition, Properties and Functions of the Bile. 



Water 85.9 



Total Solids : 14.1 



of which : 



Bile Salts 9.14 



, Lecithin and Cholesterol 1.10 



^ Mucinoid Substance 



Pigment 



Inorganic Salts '. 0.78 



The bile is a greenish-yellow fluid of sticky consistency and 

 bitter taste. Its most interesting constituents are the bile salts, 

 which are complex organic substances, having an important func- 

 tion to perform in assisting the lipase and amylopsin of pan- 

 creatic juice in their digestive activities. Otherwise the bile con- 

 tains no digestive enzymes. The cholesterol is not a readily 

 soluble substance, so that it is apt to become precipitated in the 



1 2.98 



