MICRO-ORGANISMS AND ENZYMS 



carbon dioxid. In freshly drawn milk, the proportion 

 of casein coagulated decreases until the temperature of 

 the surrounding air is reached, when it becomes sta- 

 tionary, until the formation of lactic acid causes in- 

 crease in activity of rennet-enzym. When fresh milk 

 fails to coagulate with rennet-extract, it is probably 

 slightly alkaline or contains no soluble calcium salts ; 

 that is, it is abnormal. 



(n) Different milks behave differently toward 

 rennet-enzym. This is true not only of milk. from dif- 

 ferent cows, but also of milk from the same cow at 

 different times. The following results of work done 

 at the New York experiment station illustrate this 

 statement : 



1 Close of lactation period. 2 Fresh in milk. 



These results show that in the individual milkings 

 of these 17 cows the time of rennet coagulation of 

 fresh milk varied from 40 seconds to 50 minutes. In 



