tgoo-i.] The Ripening of Cheese. 107 



this single microbe was Bacillus x ; when it was absent, it was replaced 

 b)' other bacteria belonging to the same class of lactic acid ferments 



Adametz had also found in predominating numbers a germ very 

 like Bacillus x, and which also behaved as a true lactic ferment. 



It did not appear probable that these germs alone produced all the 

 phases of ripening without the co-operation of other bacteria. 



Lloyd, who was appointed by the Council of the Bath and West of 

 England Society to make investigations upon Cheddar cheese making, 

 did much work on this subject ; and, although no numerical data are 

 given, he stated after making over 100 separate cultivations that, " In 

 the manufacture of Cheddar cheese, one and only one organism plays an 

 important part up to the time the curd is put into the vat, and that 

 organism is Bacillus acidi lactici. Further, when the cheese was ripe, 

 this bacillus was most abundant, and that the ripening during the first 

 few months depended mainly on B. acidi lactici, supplemented as the 

 cheese grew older by the growth and action of B. aniylobacter!' 



De Freudenreich in 1895 followed up his first work by a very 

 extensive contribution to the subject. He analysed bacteriologically 

 five Emmenthaler cheese made at the Rutti Dairy School. By means 

 of special methods, such as the use of milk serum gelatine, milk agar, 

 anaerobic culture methods, and partially sterilized cheese emulsions, he 

 endeavoured to give the best opportunities for the liquefying species to 

 grow, especially Duclaux's Tyrothrix forms. The latter were, however, 

 found only a few times. The principal liquefiers present were bacilli 

 belonging to the s?ibtilis and niesentericus groups. These researches 

 corroborated his former work. 



The lactic acid species, abundant from the start, increased greatl)' 

 during the ripening process, whilst the liquefying germs were few in 

 number and decreased rapidly. 



The most complete numerical data given of a single cheese were as 

 follows : 



Age in Days. Number of Bacteria per Gramme. 



Fresh Cheese 1 750,000 



9 1 5,000,000 



33 20 — 30,000,000 



42 40,000,000 



65 20,000,000 



Forms resembling Tyrothrix were found only four times out of 

 sixteen analvses. 



