60 A New Dairy Industry. 



tion of a tryptic enzyme. The lactic acid producing 

 species that make np the majority of individual 

 germs in the raw material were entirely destroyed by 

 the pasteurizing process. This class, as a rule, does 

 not form enclospores, consequently they are unable to 

 resist the heat employed in pasteurizing. 



In the normal milk it is to be noted that while the 

 majority of individual germs belong to the lactic 

 acid producing class, yet a larger number of species 

 producing little or no acid are to be found in milk. 

 These are, doubtless, the organisms derived from ex- 

 traneous sources. The}' are germs associated with 

 dirt and excreta, and gain access to the milk during 

 the milking. Baccillus mesentericus vulgatus, the 

 common potato baccillus, was frequently isolated 

 from the pasteurized as well as from the raw milk. 

 As these organisms that are thus associated with filth 

 of various kinds are able to persist in pasteurized 

 milk by virtue of their spores, it emphasizes the well- 

 known lesson that scrupulous cleanliness is an abso- 

 lute essential in dairies that pasteurize their milk for 

 direct consumption. Cleanliness in milking dimin- 

 ishes materially the amount of this class of bacteria 

 that gains access to the milk. The lactic acid bac- 

 teria, those that are essentially milk bacteria by pre- 

 diliction, are the forms that are habitually present in 

 the milk duct. These are the bacteria that cannot 

 well be kept out even by the greatest care. They 

 are, however, the forms that succumb most easily to 

 the pasteurizing process. 



