448 H. J. CONN 



of whey added to the milk from 0. 1 cc. up to Ice. and bj' record- 

 ing the time necessary for coagulation, it is possible to make com- 

 parisons between different cultures on a quantitative basis. 



The advantages of this method are as follows: the unheated 

 milk curdles readily and forms a typical firm rennet curd; the 

 peptonizing enzymes act more slowly and do not in any way 

 obscure the curdUng action of the rennet; the period of observa- 

 tion is so short that neither the bacteria present in the milk nor 

 those added in the cultures have time to act on the milk them- 

 selves and the amount of whey added is too small to precipitate 

 the casein by the action of any acid it might contain, hence the 

 reaction occurring is due to the action of enzymes alone. By 

 the use of this method it has been found possible to obtain typi- 

 cal rennet curds from certain organisms ordinarily producing 

 both acid and rennet and from others ordinarily digesting the 

 milk so rapidly that no true curd could be observed. By the 

 usual method the production of rennet by these organisms was 

 suspected but could not be actually demonstrated. 



This technic is offered as an addition to the methods of pure 

 culture study in use in connection with the society's descriptive 

 chart. 



