Range of Action of Digestive Ferments. 163 



not only to neutralise the soda, but to leave an excess equal 

 to 1 part in 500 of the mixture. To this was then added 

 coagulated white of egg in thin slices, and the whole kej)t 

 for 3 hours at 100° F. At the end of that time the albumen 

 was not appreciably altered ; while similar slices, treated in 

 the same way with fresh pepsin and hydrochloric acid, 

 ] in 500, were found, at the end of 3 hours, to be completely 

 dissolved. The quality of the pepsin being thus shown to 

 be good, it follows that the treatment to which it had been 

 subjected had had a destructive influence on it. Whether 

 this was owing chiefly to the action of the bicarbonate of 

 soda, or to that of the zymine, remains, of course, undeter- 

 mined, though the probability is that the latter supposition 

 is the correct one. 



As this question did not enter into the scope of the 

 original inquiry, though it is of great interest, it had to be 

 left, the investigation having proved sufficiently laborious. 



The general conclusions are : — 



I. That the pancreatic ferments are not merely temporarily 

 inhibited in their digestive action by small quantities of 

 hydrochloric acid, but are permanently injured, when the 

 strength of the acid reaches the proportion of 1 to 1 000, or 

 even 1 to 5000, for 2 hours. 



II. That pepsin does not seem to have any power, in 

 association with the acid, in bringing about or even hastening 

 this destructive action. 



III. That, on the contrary, the trypsin of the pancreatic 

 secretion seems to bring about the destruction of pepsin in 

 sHghtly alkaline solutions. 



I have to acknowledge my great obligations to Mi-. 

 Frederick Dunn, public analyst, for assistance in the way 

 of carrying out the practical details of the experiments. 

 Without that assistance, indeed, I fear that the inquiry 

 would scarcely have been carried out at all. 



M 2 



