DIGESTION IN THE SMALL INTESTINE. 393 



globin being thus liberated and then decomposed into bilirubin, the iron 

 escaping in the form of a phosphate in the bile. As regards the origin 

 of bile a"cids little is known, though they are probably derived from the 

 breaking clown of albuminoids. 



The action of the nervous system in modifying the secretion of the 

 bile is almost entirely unknown. No nerve has been found whose stim- 

 ulation leads to an increased flow of bile, or causes its arrest when 

 actively flowing. The splanchnic nerve has been noticed, when stimu- 

 lated, to cause an increase in the flow of bile from biliary fistulas, but this 

 action is evidently due to the production of contraction of the biliary 

 ducts. 



3. The Physiological Action of the Bile. — The bile enters the intes- 

 tine, in most animals, associated with the pancreatic juice, as seen in the 

 horse, goat, and dromedary, while in the ox and rabbit the bile-duct is 

 separated for a considerable distance from the opening of the pancreatic 

 duct. The fact that it enters the intestine simultaneously with the pan- 

 creatic juice, or even before it, shows that in its physiological action it 

 must be associated with the latter. Its action on the food-stuffs is of 

 but slight importance. On proteids it produces no distinct action what- 

 ever, and, in fact, would seem to interfere with the digestion of proteids 

 as commenced in the stomach. Thus, when bile, or a solution of tauro- 

 cholic acid, is added to the products of gastric digestion, a copious 

 precipitate takes place, which consists of coagulable albumen, syntonin, 

 and pepsin, — the latter being indicated by the fact that when this precip- 

 itate is filtered off and the supernatant liquid acidified it has no peptic 

 power. This precipitate is, however, redissolved in an excess of bile 

 or a solution of bile salts, and its object would appear to be, by precipi- 

 tating the parapeptone to delay its passage through the intestine and so 

 give the pancreatic juice time to act, while, at the same time, by precipi- 

 tating the pepsin the pancreatic ferments are protected from the solvent 

 action of the gastric juice. For we find that during active digestion, 

 as a rule, the contents of the small intestine are strongly acid in the 

 greater portion of its upper extremity, and were the pepsin not precipi-. 

 tatecl the pancreatic ferments would be digested and therefore destroyed 

 through the action of the gastric juice. The re-solution of the precipi- 

 tate produced bj r bile in the products of gastric digestion is due to an 

 excess of taurocholic acid. In most animals (ox, sheep, and horse), the 

 bile lias been found to contain a ferment, present in small amount, which 

 is capable of converting starch into sugar. A similar action is also pro- 

 duced on glycogen. This action is, however, secondary, and of but little 

 importance in the digestion of carbohydrates, other than that the bile 

 assists the amylolytic action of the pancreas. In the dog's and pig's 

 bile no cliastatic ferment is present. 



