218 PHYSIOLOGY CHAP. 



pepsin digestion, even before the acidity of the chyme had been 

 neutralised. But when the alkaline pancreatic juice and the 

 free alkali of the bile have neutralised the mixture and rendered 

 it faintly alkaline, the syntonin and propeptones thrown out dis- 

 solve again, and the pancreatic ferment once more acts energetic- 

 ally in the alkaline medium. 



Bile therefore aids the pancreatic juice in its digestive function, 

 by checking peptic digestion in an acid medium, and promoting 

 pancreatic digestion in an alkaline or neutral medium. 



From the work of Maly and Emich, it would seem that special 

 importance attaches to the taurocholic (not glycocholic) acid, 

 liberated by the action of the hydrochloric acid of the chyme. It 

 has the property of throwing out the albumin and the gelatin, on 

 which the pepsin also comes down in the precipitate, while neither 

 the albumin-peptone nor the gelatin-peptone is precipitated. In 

 consequence of this action of the taurocholic acid, the peptone 

 must therefore be separated in the duodenum from the proteins 

 that are little or not at all modified by the gastric juice ; the 

 peptone can at once be absorbed, the proteins, on the contrary, 

 must remain in the duodenum and be acted on by the pancreatic 

 juice. But, as we showed in the last chapter, the chyme which 

 passes from the stomach to the duodenum normally contains 

 either no peptones or hardly a trace of them; this process of 

 separation of peptone from the still incompletely digested proteins 

 is therefore of little importance. 



That bile inhibits the enzymic action of pepsin, and thus 

 reduces or entirely suppresses the digestive function of the gastric 

 juice, is an undoubted fact which was confirmed by the work of 

 Bruno (1899), carried out by methods that leave nothing to be 

 desired in their accuracy. It is, however, very difficult to deter- 

 mine by what process this phenomenon comes to pass. To the 

 hypothesis that bile effects the destruction of pepsin, we may 

 oppose the fact that Hammarsten succeeded in isolating a pepsin 

 from gastric juice that had lost its digestive power by admixture 

 with bile, which on the addition of hydrochloric acid recovered 

 its digestive efficacy. It is possible that bile modifies proteins by 

 entering into combination with them, as Hammarsten thinks, and 

 thus rendering them indigestible by gastric juice; it is also 

 possible that it modifies the enzymic property of pepsin without 

 destroying it. 



Bruno also points out that the bile which flows into the 

 intestine during the first hour of digestion exerts, caeteris paribus, 

 owing to its greater density, a more pronounced depressing action 

 on the gastric juice than the bile poured out in the succeeding 

 period. This still further emphasises the physiological function 

 of the bile, in destroying the enzymic action of the gastric juice in 

 favour of that of the pancreatic. 



