Kinds in Butter 413 



Oidium lactis and other molds, and various yeasts. 

 In stored butter, the lactic-acid species decrease rapidly, 

 while Bacillus fluorescens liquefaciens may increase for 

 a time. Oidium lactis is always prominent, but is finally 

 suppressed by another common butter mold, Clados- 

 porium butyri. Certain yeasts also persist in stored 

 butter, and become so prominent at times as to constitute 

 nearly the entire flora. There is still a difference of opin- 

 ion as to the part played by these various organisms in 

 the development of rancidity in butter. It has been 

 found that samples of butter prepared under aseptic 

 conditions become rancid when inoculated with a culture 

 of Bacillus fluorescens liquefaciens, or of Bacterium prodigi- 

 osum. On the other hand, the mold, Oidium lactis, while 

 capable of developing strong acidity in butter and of 

 decomposing the butter-fats, does not cause rancidity 

 when present alone. Neither does Cladosporium butyri; 

 yet, when the two are growing together, rancidity is 

 produced. We note thus associative action in the pro- 

 duction of rancidity by two prominent butter molds, and, 

 in general, it may be said that bacteria, molds and 

 yeasts contribute to the development of rancidity and 

 to other changes that occur in butter. 



Disease bacteria in butter. — The spread of infectious 

 diseases by means of butter has been made the subject 

 of considerable discussion. The wide prevalence of 

 bovine tuberculosis, and the frequent presence of tuber- 

 cle bacilli in milk, are the cause of the presence of the 

 bacilli of tuberculosis in butter. An examination of 

 forty samples of market butter in Posen revealed the 

 presence of tubercle bacilli in 22 per cent of these sam- 



