THE INFLUENCE OF THE BILE ON DIGESTION 115 



proteid metabolism goes on in other tissues, there are produced, 

 in those tissues materials (ammonia compounds) which, when 

 carried to the liver, are converted by it into urea. Further notice 

 will be given to this phase of the subject under Nutrition. 



The liver cells produce urea; it enters the blood, is carried to 

 the kidneys and eliminated by those organs. In the mechanism 

 of its production and discharge from the liver, it thus corresponds 

 to the internal secretions, though urea is distinctly an excretion. 



It must not be supposed, however, that the liver is the only 

 organ producing urea. There are other organs which certainly 

 produce it, while there are those who maintain that it is produced 

 directly wherever proteid metabolism is in progress. 



The Influence of the Bile on Digestion 



The bile is not, properly speaking, a digestive fluid, for it 

 contains no enzyme capable of effecting digestive changes in 

 any of the foods; but it so materially affects the action of some 

 of the other fluids that it cannot be overlooked in a discussion 

 of intestinal digestion. 



So far as the bile acids, glycocholic and taurocholic (com- 

 bined to form salts of sodium) are concerned, the fluid is a se- 

 cretion, and it is these which are mainly concerned in the diges- 

 tive process. The production of bile is continuous, but the 

 gall bladder acts as a reservoir in which a part at least of the 

 secretion is stored in the intervals of digestion, to be discharged 

 in greater abundance when chyme enters the duodenum. While 

 the action of bile in most of the digestive functions to be men- 

 tioned is obscure, it is known to have at least these uses: 



1. It promotes intestinal peristalsis. 



2. It has an inhibitory effect on putrefaction in the intestinal 

 tract. By this it is not to be understood that the bile is directly 

 antiseptic, for it undergoes putrefaction very readily itself, but 

 only that in some way its withdrawal from the substances passing 



