THE INFLUENCE OF THE BILE ON DIGESTION 115 



on in other tissues, there are produced in those tissues ma- 

 terials (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 me- 

 chanism 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 cer- 

 tainly produce it, while there are those who maintain that it 

 is produced directly wherever proteid metabolism is in pro- 

 gress. 



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 

 secretion, and it is these which are mainly concerned in the 

 digestive 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 dis- 

 charged in greater abundance when chyme enters the duo- 

 denum. While the action of bile in most of the digestive 

 functions to be mentioned 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 intesti- 

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

 directly antiseptic, for it undergoes putrefaction very read- 

 ily itself, but only that in some way its withdrawal from the 



