444 DESTRUCTION OF PEPSIN IN SMALL INTESTINE. [BOOK II. 



This neutralisation of free acids would of itself bring peptic digestion 

 to a standstill, even in the absence of other factors. 



We have already pointed out (see page 352) that one principal 

 result of the admixture of the acid chyme with the bile is the pre- 

 cipitation of the pepsin of the gastric juice, the digestive activity of 

 which is ipso facto abolished (Pappenheim, Briicke). It appears that, 

 once rendered inactive by admixture with bile, pepsin cannot regain 

 its activity. The fact that digestion may in the stomach go on in the 

 presence of some bile is in no sense in contradiction with the state- 

 ment as to what must take place in the intestine. In the stomach a 

 continual secretion of pepsin can occur, to replace that which has 

 been rendered inactive, e.g. by the bile which may have penetrated 

 into the stomach. 



But, in addition to its more or less complete precipitation by the 

 bile, the pepsin which has entered the duodenum finds itself sub- 

 jected to the action of the NaaCOg of the pancreatic juice. As 

 Kuhne 1 first pointed out, and as Langley 2 subsequently confirmed, 

 pepsin is destroyed by digestion with weak alkaline solutions. The 

 latter observer shewed that solutions of sodium carbonate, at the 

 temperature of the mammalian body, exerted a powerfully destruc- 

 tive influence on pepsin. 



It is impossible to estimate exactly the relative part played by 

 the bile on the one hand, and the sodium carbonate on the other, in 

 putting the pepsin hors de combat, but we may surmise that it is 

 upon the bile that the burden of the work chiefly falls. Whilst the 

 action which it exerts on the mixture of pepsin, albumoses and free 

 acid is a well-nigh instantaneous one, that of the sodium carbonate 

 is a gradual one, time being one of the important elements influencing 

 the result. 



The paramount importance of this destruction of pepsin is apparent 

 when we reflect that pepsin, in the presence of free acids, exerts a 

 rapid destructive influence on trypsin. 



Corvisart 3 had stated that pepsin and trypsin exert a mutually de- 

 structive influence on one another. Kuhne, whilst emphasising strongly 

 the power of pepsin in acid solution to destroy trypsin, spoke of the 

 indestructibility of pepsin by pancreatic digestion 4 . Langley 5 , however, 



1 W. Kuhne, 'Ueber das Verhalten verschiedener organisirter und sog. ungeformter 

 Fermente.' Separat-Abdruck aus den Verhandlungen des Heidelberg, naturhist. med. 

 Vereins. Sitzung am 4. Feb. 1876. 



2 J. N. Langley, ' On the Destruction of Ferments in the Alimentary Canal,' Journ. 

 of Physiology, Vol. in. (188082), pp. 246268. 



3 L. Corvisart, 'Mais c'est une chose remarquable que si les deux ferments digestifs 

 se rencontrent a 1'^tat pur, les deux digestions cessent de s'exercer aussi librement; 

 loin que le produit digerl soit doub!6 par cette reunion, au contraire il peut se require 

 a rien, car dans cette circonstance non physiologique, la pepsine et la pancreatine 

 s'entre-de'truisent. ' Sur une fonction pen connue du Pancreas &c. Paris, Victor 

 Masson, 185758. See p. 116. 



4 W. Kuhne, 'Die Unzerstorbarkeit des Pepsins bei der pankreatischen Verdauung,' 

 op. cit., p. 5. 



5 J. N. Langley, op. cit. 



