CHAPTER IX. 



BACTERIOLOGICAL ANALYSIS OF MILK. 



THE recognition of the importance of bacteria as affecting 

 the wholesomeness of milk and as modifying dairy products, 

 has led to the attempt to determine by laboratory analysis 

 the nature of the bacteria in the milk, in order to gain some 

 idea as to its wholesomeness and its fitness for use. Can a 

 bacteriological analysis of milk be made which will enable 

 us to determine whether the milk is in proper condition for 

 use? 



The analysis of drinking water has served as an example, 

 since here a bacteriological analysis has proved extremely 

 useful as an assistance in the determination of its healthful- 

 ness. The study of the bacteria of water has reached con- 

 siderable perfection, and it has been quite natural that the 

 methods used there should be transferred directly to the 

 study of milk. The bacteriological analysis of water has, in 

 past years, consisted chiefly in a quantitative determination 

 of the number of bacteria in each cubic centimeter, and then 

 the drawing of a conclusion as to the suspicious nature of the 

 water from the number of bacteria that are present. In 

 recent years more attention has been paid to a differen- 

 tiation of the species of bacteria in water, but most of the 

 bacteriological analysis is simply quantitative. As a result, 

 the bacteriological analysis of milk has been of a similar 

 character, and nearly all of the work that has been done 

 hitherto has been confined to the study of the number of bac- 

 teria per cubic centimeter, with only here and there an 

 attempt to determine the kinds of bacteria. We may, there- 

 fore, notice first the methods of quantitative analysis of milk 

 bacteria. 



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