MICRO-ORGANISMS AND ENZYMS 299 



except that one of its most distinctive characteris- 

 tics is its abihty to form, among other products, 

 ammonia, and that, therefore, galactase plays a 

 principal role in cheese-ripening. Their galactase 

 work has been confirmed to the extent that there is 

 in milk some enzym that causes more or less de- 

 composition of milk-casein and of cheese paracasein 

 in the presence of chloroform or ether. In work 

 done at the New York experiment station, the ability 

 of galactase to form ammonia was not confirmed 

 either in case of milk or cheese. Cheese kept in an 

 atmosphere of chloroform produced no ammonia or, 

 at most, only slight traces even at the end of 15 

 to 24 months. Samples of the cheese were sent to 

 the Wisconsin experiment station, and the absence of 

 ammonia was there confirmed. The view previously 

 held to the efifect that galactase was able to account 

 for most of the changes in cheese-ripening was then 

 modified. 



RENNET-ENZYMS 



Rennet-extract contains one or two unorganized 

 ferments or enzyms. There has long been a differ- 

 ence of opinion as to whether there is in rennet-extract 

 one enzym which acts in two different ways or two 

 different enzyms„ each with its own characteristic 

 action. So far as the essential facts are concerned, 

 rennet-extracts possess the power of effecting two 

 distinct kinds of changes : ( i ) coagulation of milk- 

 casein and (2) dissolving or digesting the milk-casein 

 coagulum. Those who regard these two actions as 

 due to two different enzyms contained in rennet call 

 the coagulating enzym rennin or chymosin, and the 



