BACTERIA IN MILK AND ITS PRODUCTS. 



CHAPTER I. 



THE NATURE OF BACTERIA. 



THE last fifteen years have seen a very great change tak- 

 ing place in the methods of handling milk products. These 

 changes have affected not only the handling of milk dis- 

 tributed for public consumption, but also the manufacture of 

 butter, and they are rapidly producing improvements in the 

 manufacture of cheese. The modifications of dairy meth- 

 ods have been more rapid in the last twenty years than ever 

 before, and we may almost say that greater changes have 

 taken place within this short time than in the previous two 

 centuries. A variety of new conditions and new discoveries 

 have contributed to this end, but nothing has had a greater 

 influence than the knowledge which has developed concern- 

 ing the nature of bacteria and their relation to milk. Dairy 

 bacteriology has to a large extent revolutionized, modern 

 dairying. Sometimes the connection between modern 

 methods and bacteriological discoveries is very apparent ; 

 sometimes it is less apparent or only incidental, but there is 

 no one series of facts which has produced such a profound 

 effect upon dairy processes as those associated with bac- 

 teriology. 



WHAT ARE BACTERIA? 



Bacteria are microscopic, colorless plants which are ex- 

 tremely abundant in earth, air and water. The term bac- 

 teria is a comparatively recent one. In the early work of 

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