200 TIeport of the Chemical Department oe the 



rennet-extract contained any proteolytic bacterial enzymes, as 

 compared with the fresh extract. 



(2) If we compare the results secured by the use of the purest 

 commercial pepsin with those given by the rennet-extracts, we 

 find that, in the presence of acid, there are formed soIuidIc 

 nitrogen compounds quite close in amount to those formed by 

 rennet-extract. The amount of soluble nitrogen compounds 

 formed in neutral solution was fairly stationary during the 9 

 months, while, in the case of the rennet-extracts, there was a 

 slow increase. The amount of amido compounds was surpris- 

 ingly uniform in the case of the pepsin and the rennet-extracts, 

 in both neutral and acid reaction. These results suggest that the 

 pepsin was able to account for all the changes observed in the 

 case of the rennet-extracts in the presence of acid. If there had 

 been proteolytic enzymes of bacterial origin in the rennet- 

 extracts, we should have expected a larger amount of digestion 

 of milk-casein, and particularly in the class of amido compounds. 



(3) In the case of the rennet-extracts in neutral solution, we 

 notice that there was a small, but noticeable increase of water- 

 soluble nitrogen compounds not observed in the case of pure 

 pepsin. This increase was confined mostly to the caseoses and 

 peptones. This increase may be due to the presence of some 

 proteolytic enzyme, able to act in neutral solution, present in the 

 rennet-extracts besides the rennet-enzyme proper. Granting 

 that there is regularly present such an extra enzyme in rennet- 

 extract, it could have very little to da with cheese-ripening, since 

 in our experiments with milk we had much larger proportions 

 of rennet-extract than are used in cheese-making. We added 

 to the milk about 14 times as much rennet-extract as we com- 

 monly use in cheese-making; and this amount remained in' the 

 milk all the time, while in cheese-making some of the rennet- 

 ferment passes into- the whey. 



(4) The increased activity of rennet-extract as well as of pepsin 

 in the presence of acid is very marked. 



experiments in the use of commercial pepsin in cheese- 

 ripening. 

 In experiments 55, 56 and 57, the cheeses were made without 



