136 BACTERIOLOGY. 



stand why, in view of this indifference of the 

 producer, the consumer often prefers oleomar- 

 garine which, to say the least, is always appe- 

 tizingly prepared. 



In the ripening of cheeses, also, bacteria take 

 part. 1 Some kinds effect the natural ripening, 

 that is, the transformation of the casein and 

 the production of aromatic chemical compounds 

 which impart the individual flavor to different 

 cheeses, and some kinds bring about the vari- 

 ous " diseases " of cheese, the ripening in 

 wrong ways and the formation of poisons. The 

 studies upon cheese bacteria have been carried 

 forward especially by Freudenreich, Adametz, 

 and Beyerinck. If we except the use of the 

 " Edelpilz" a variety of the green pencil 

 mould (Penicillium), in ripening Roquefort 

 and Gorgonzola cheeses, then Persy n, with the 

 aid and direction of Hueppe, was the first to 

 put what was known in the matter to practical 

 use by the employment of pure cultures of 

 bacteria in the preparation of an Edam cheese 

 to which prizes have been repeatedly awarded. 



The rancidity of butter due to formation of 

 fatty acid depends, according to Duclaux and 

 Ritsert, upon the oxidation of the fat by at- 

 mospheric oxygen in the presence of light, and 



1 See also on this point, Babcock and Russell : " Unorganized 

 Ferments of Milk : a New Factor in the Ripening of Cheese." 

 Centralbl. f, Bakt., Abth. II., III., p. 615. 



