390 THE AMERICAN MONTHLY [Dec 



ma when grown in milk or cream. This proved to be a 

 new species, for which he proposed the name Micrococcus 

 butyri-aromafaciens. 



It has always been the custom to allow cream to sour or 

 "ripen" before churning- it for butter, because after this 

 process the butter comes better and more quickly, is of 

 better texture and flavor, and keeps better than butter 

 made from sweet cream. Lord Lister and Pasteur, many 

 years ag^o, showed that the souring- of milk and cream is 

 due to minute micro-organisms. It remained for Profes- 

 sor Vilhelm Storch, of Copenhag-en, however, to introduce 

 the use of pure cultures of milk-souring- bacteria in butter 

 making-. Storch isolated three species that impart especi- 

 ally fine flavors to butter. 



A similar line of work was taken up by Professor Weig-- 

 mann, at Kiel, in Germany, and by Professor H. W, Conn, 

 of Wesleyan University, in the United States. 



Of the bacteria that have been described as producing a 

 beneficial effect in the ripening- of cream, Micrococcus 

 butyri-aromafaciens most nearly resembles Conn's Bacil- 

 lus No. 41 in its effects upon milk, but it differs in its mor- 

 phological and in many of its physiolog-ical characters. It 

 is a micrococcus growing- at 37 deg-rees and 20 deg-rees C. 

 It liquefies gelatin slowly, and does not g-row well on po- 

 tato. Recent cultures on g-elatin seem to show that the 

 or^-anism has lost to a considerable extent its power to 

 liquefy gelatin during- a year's cultivation. 



The culture of the micrococcus for use in creameries is 

 propagated in bouillon in Fernbach flasks (broad flasks so 

 constructed that a larg-e surface of liquid is presented to^ 

 the air). When ready for shipment, the culture is trans- 

 ferred to sterilized bottles under aseptic conditions and 

 hermetically sealed by means of sterilized corks and melted 

 paraffin. Put up in this way, the culture may be kept for 

 an indeiinite time without danger of infection by any other 

 organism, but in the sealed bottles the micrococcus loses 

 its vitality so rapidly that after eig-ht days it will no long-er 

 produce the best results. Experiments made on a com- 

 mercial scale show that cream ripened with the aid of 



