82 THE STORY OF GERM LIFE. 



cream resulting therefrom, these differences in 

 the flavour of the butter are also in part depend- 

 ent upon the different species of bacteria which 

 are present in the ripening of cream at different 

 seasons. The species of bacteria in June cream 

 are different from those that are commonly pres- 

 ent in January cream, and this is certainly a fac- 

 tor in determining the difference between winter 

 and summer butter. 



USE OF ARTIFICIAL BACTERIA CULTURES FOR 

 CREAM RIPENING. 



Bacteriologists have been for some time en- 

 deavouring to aid butter makers in this direction 

 by furnishing them with the bacteria needful for 

 the best results in cream ripening. The method 

 of doing this is extremely simple in principle, but 

 proves to be somewhat difficult in practice. It is 

 only necessary to obtain the species of bacteria 

 that produce the highest results, and then to fur- 

 nish these in pure culture and in large quantity 

 to the butter makers, to enable them to inocu- 

 late their cream with the species of bacteria 

 which will produce the results that they desire. 

 For this purpose bacteriologists have been for 

 several years searching for the proper species of 

 bacteria to produce the best results, and there 

 have been put upon the market for sale several 

 distinct " pure cultures " for this purpose. These 

 have been obtained by different bacteriologists 

 and dairymen in the northern European countries 

 and also in the United States. These pure cul- 

 tures are furnished to the dairymen in various 

 forms, but they always consist of great quanti- 

 ties of certain kinds of bacteria which experience 



