DIGESTION 257 



cases in which bile is prevented from escaping into 

 the bowel is due to the unabsorbed fat favouring putre- 

 faction. 



The frequency with which biliary obstruction is asso- 

 ciated with constipation has led to the belief that bile 

 acts as a stimulant to peristalsis, but of this there is as 

 yet no experimental proof. 



The stimuli to the discharge of bile into the 

 intestine are apparently the same as those of pancreatic 

 secretion acids and fats. Proteins also call out an 

 increased secretion of bile, probably because they lead 

 to a large production of acid in the stomach. Starches 

 have very little influence ; hence it may be that restric- 

 tion of starchy foods and an increase of the amount 

 of meat in the diet are useful in cases of ' biliousness ' 

 in which bile production is believed to be defective. 



Intestinal Digestion. 



The importance of the succus entericus as a digestive 

 agent has been greatly enhanced in recent years since it 

 became known that by means of enterokinase it ' activates ' 

 trypsinogen, and since the discovery in it of the ferment 

 * erepsin,' which, though not able to attack proteins 

 (except, apparently, casein), has the power of splitting up 

 proteoses and peptones with the formation of amines and 

 diamines. It is believed that this part of its action 

 is not exerted in the lumen of the intestine, but in the 

 actual cells of the villi, and its importance in the picking 

 to pieces of the protein molecules of the food and their 

 reconstitution into body proteins has already been 



referred to (p. 30). 



17 



