102 THE MICROSCOPE. July 



proves a matter of much more difficulty to isolate and 

 cultivate the proper species of bacteria for butter ripen- 

 ing than to produce pure yeasts. Still this has been 

 done by at least three of the experimenters above men- 

 tioned. Prof. Storcli, Prof. Weigmann and the author of 

 this article, have each succeeded in isolating from ripen- 

 ing cream species of bacteria which produce a high 

 quality of butter where used in laboratory experiments. 

 The introduction of these experiments into creameries 

 presents special difficulties and yet difficulties that are 

 being rapidly overcome. Already creameries in the vi- 

 cinity of the laboratories of the above mentioned exper- 

 imenters have been furnished with pure cultures of bac- 

 teria for the purpose of improving the butter product- 

 The success of the experiments has been marked in each 

 case. In Denmark it is getting to be more or less com- 

 mon to use an artificial ferment for cream ripening. 

 The same is true in certain regions of Germany. In this 

 country the work is more recent, but several creameries 

 have undertaken the use of pure bacteria cultures for 

 ripening cream and with universal success. Wherever 

 the artificial ferment has been used there has been found 

 an immediate and quite noticeable improvement in the 

 character of the butter, and creameries that have once 

 used this method are so pleased with it as to desire to 

 keep it up indefinitely, for they find not only a better 

 butter results, but a much greater uniformity in the 

 quality. 



An interesting fact in connection with these experi- 

 ments is that the species of bacteria used for this pur- 

 pose by the different experimenters do not appear to be 

 the same or to have any special relation to each other. 

 Cultures used in some places are those producing lactic 

 acid, souring the milk and cream rapidly, while in other 

 localities the cultures that produce good results do not 

 give rise to any considerable quantity of lactic acid and 



