( 286 ) 



10 minutes to 70° C, another part for half an hour left in contact 

 with 0.01% Na HO and then neutralized again. Now the result was : 



After heating I After action of alkali 

 2 cc. enzym with water 4- 8 cc. milk ! curdling in 2 1 /» min. ! no curdling 

 2 „ „ » extract + 8 „ „ | no curdling t curdling in 1 1 min. 



Gewin also examined two rennet-preparations of commerce, one 

 Dutch of van Hasselt and one Danish of Hansen. Both showed the 

 qualities of Bang's chymosin. But when, by dialysis and precipitation 

 with acetic acid, the enzym had been isolated and at least for the 

 greater part been freed from impurities, they had become much more 

 susceptible to alkali and much less so to heating. 



That the enzym is destroyed not only by alkaline, but gradually 

 also by neutral reaction has been made clear by Pawlow and 

 corroborated by Gewin in numerous experiments. From this Gewin 

 explains the difference found by Bang between chymosin and para- 

 chymosin, the solution being diluted. What Bang calls chymosin is 

 the enzym mixed with substances protecting it from alkali. When 

 those substances are present, it may be assumed that the enzym is 

 better proof against the dilution with water, by which the number 

 of hydroxyl- and metal-ions increases. A solution of purified enzym 

 (parachymosin), possessing the same curdling power as a not purified 

 solution of calf-enzym (chymosin), shows, when diluted, sooner a 

 decrease in action, and consequently must, also sooner, show the 

 promoting influence of the addition of chlorcalcium. 



So there is no reason for assuming different rennet-enzymes in 

 different kinds of animals. The difference does not lie in the enzym 

 but in other substances originating from the mucous membrane of the 

 stomach. If it is necessary to give a separate name to the enzym of 

 the gastric juice that can curdle milk, it is sufficient to use the word 

 chymosin for it. 



But is even this necessary? Should it be assumed that chymosin 

 is different from pepsin? 



To the solution of this question Gewin has devoted the second 

 part of his investigation. It was tried in vain to divide the enzym 

 into a proteolytic and a curdling part. It is a well-known fact that 

 proteins, undissolved and at a temperature of 15° C. put into a 

 pepsin-solution, take up and keep back this enzym, so that it is not 

 to be separated from it by washing it out. Coagulated and minced hen's 

 albumen was put in a solution of purified pepsin in 0.2 °/ HC1. 

 Now, if chymosin were a different matter from pepsin, only the last 

 mentioned would perhaps be extracted from the solution by the 

 albumen. It appeared, however, that the liquid filtered from the 



