102 DIGESTION. LECT. V. 



contains a free acid, which should be lactic acid;* and that 

 it holds in solution a peculiar substance called pepsine, which 

 has been obtained in a sufficiently pure state. It is this 

 same substance which has been lately examined by Payen, 

 who termed it gasterase. The acidity of the gastric juice is 

 greater or less, according to the quality of the aliments ; in 

 an empty stomach, it is weaker: it augments by contact 

 with food, and it has its maximum when the elements are 

 composed of fibrine, albumen, &c. 



I here show you, in glasses, an infusion of pepsine to 

 which a few drops of hydrochloric acid have been added. 

 Into one of these small glasses has been put some coagu- 

 lated albumen ; into another some fibrine. The vessels thus 

 prepared have been placed for ten or twelve hours in an 

 atmosphere heated to 30 centig.[= 86 Fahr.,] and the 

 albumen and fibrine have already in a great measure disap- 

 peared ; there remain only some small fragments, which are 

 already transparent, on the edges, and which will shortly 

 entirely disappear. If I neutralize the acid, and then eva- 

 porate the solution, I can easily reproduce the albumen and 

 fibrine, which have not been changed in their nature, but 

 have merely dissolved by contact with the acid infusion of 

 pepsine. This substance acts, therefore, in the solution of 

 fibrine and albumen, as a body endowed with catalytic 

 properties, and their solution is effected by an action of 

 Contact. 



It is only in the stomach, or by certain glands situated in 

 the mucous membrane of this viscus, that the acid solution 

 of pepsine, or the gastric juice is separated. I have tried 

 the effect of placing pieces of the small or large intestine in 



* Liebig (Researches on the Chemistry of Food, p. 138.) infers from 

 Lehmann's experiments, that the gastric juice contains lactic acid, and is 

 similar to the juice of muscles. J. P. 



