iv DIGESTION IN THE INTESTINE 219 



It is probably for this purpose that there is at the close of 

 gastric digestion (particularly if rich in proteins, and therefore 

 more stimulating to pepsin secretion) an abundant reflux of bile 

 from the duodenum into the stomach. This fact, observed by 

 Pawlow and his pupils, has been studied in detail by Boldiretij 

 who brings out its constancy and modifications. 



But the role of the bile is not confined to making possible 

 the digestive action of the pancreatic juice; it conspicuously 

 increases it, by promoting the enzymic activity of trypsin upon 

 proteins, of amylopsin upon starch and polysaccharides, of 

 steapsin upon fats. This is plain from the work of Martin, 

 Nencki, and others, and is confirmed and extended in the careful 

 experiments of Bruno, who compared the digestive power of a 

 mixture of pancreatic juice and bile in different proportions for 

 boiled protein, starch, and neutral fat. 



The following are the most important of Bruno's conclusions : 



(a) Bile added to pancreatic juice raises its proteolytic activity 

 by 1'6S times on an average, i.e. it increases the solvent action on 



t/ O ' A 



protein, as if the pancreatic juice contained T68 times more 

 trypsin. The maximum reinforcing action of bile is obtained 

 when the quantity added to the pancreatic juice is not large. 



(5) Bile added to pancreatic juice in the most favourable 

 proportions reinforces the amylolytic power of the latter to an 

 amount equal to increase of amylopsin by 2 - 43 times. But unlike 

 what has been stated for the action of bile upon trypsin, the 

 reinforcing action of bile on amylopsin increases in proportion as 

 the quantity of bile is greater. 



(c) Bile also reinforces the lipolytic power of the pancreatic 

 juice, due to steapsin ; this action on the fat-splitting enzyme is 

 indeed, the most marked. The bile excreted after a meal of milk 

 is the most active ; it increases the lipolytic action of the pancreatic 

 juice 20 times. Even boiled bile is capable of reinforcing the 

 action of the lipolytic enzyme (although to a less extent). 



These results justify the conclusion that the influence of bile 

 on pancreatic juice is precisely opposite to that which it exerts on 

 gastric juice. It is obvious that acquaintance with the action 

 of bile must throw not a little light on the work of digestion as 

 a whole, when it is accomplished under natural conditions in the 

 duodenum. 



Careful study of the effects of intestinal acliolia in dogs 

 operated on by a complete biliary fistula, confirms the coadjuvant 

 action of bile in the processes of intestinal digestion ; at the same 

 time it shows the capacity of the body to compensate itself com- 

 pletely for total absence of bile in the intestine. 



All the dogs operated on by Schwann with a complete biliary 

 fistula died shortly after; but Bidder and Schmidt discovered 

 that they could live a long while when fed more abundantly than 



