84 THE STORY OF GERM LIFE. 



ed culture alone. This method proves to be suc- 

 cessful, and in the butter-making countries in 

 Europe it is becoming rapidly adopted. 



In this country, however, this process has 

 not as yet become very popular, inasmuch as the 

 heating of the cream is a matter of considerable 

 expense and trouble, and our butter makers have 

 not been very ready to adopt it. For this reason, 

 and also for the purpose of familiarizing butter 

 makers with the use of pure cultures, it has been 

 attempted to produce somewhat similar though 

 less uniform results by the use of pure cultures 

 in cream without previous healing. In the use 

 of pure cultures in this way, the butter maker is 

 directed to add to his cream a large amount of 

 a prepared culture of certain species of bacteria, 

 upon the principle that the addition of such a 

 large number of bacteria to the cream, even 

 though the cream is already inoculated with 

 certain bacteria, will produce a ripening of the 

 cream chiefly influenced by the artificially added 

 culture. The culture thus added, being present 

 in very much greater quantity than the other 

 " wild " species, will have a much greater effect 

 than any of them. This method, of course, can- 

 not insure uniformity. While it may work satis- 

 factorily in many cases, it is very evident that in 

 others, when the cream is already filled with a 

 large number of malign species of bacteria, such 

 an artificial culture would not produce the desired 

 results. This appears to be not only the theo- 

 retical but the actual experience. The addition 

 of such pure cultures in many cases produces 

 favourable results, but it does not always do so, 

 and the result is not uniform. While the use of 

 pure cultures in this way is an advantage over 



