1/2 PRACTICAL DAIRY BACTERIOLOGY 



So far as concerns the likelihood of milk being the cause of 

 the diarrheal troubles, the matter stands differently. These ap- 

 pear to be associated with the development of bacteria in the 

 milk, and any of the dairy methods already pointed out, which 

 reduce the multiplication of bacteria, and which bring about a 

 condition where the milk on sale in our markets shall contain 

 a comparatively small number, will probably tend to reduce 

 these dangers. 



CLEAN MILK 



The desirability of having clean milk needs no emphasis, but 

 the methods by which this can be accomplished, and the methods 

 by which it can be determined whether milk is clean, are not so 

 simple. How is it possible to study miscellaneous samples of 

 market milk and determine whether each was produced under 

 conditions of proper cleanliness and with proper care? This 

 question in one form or another has been asked over and over 

 again ; but up to the present time it has received no satisfactory 

 answer. The method of determining this by actually estimating 

 the amount of dirt in the milk, as indicated on page 297, is 

 quite impractical. The accuracy of the dirt determination is so 

 uncertain and the results in the hands of the different people 

 show so much variance, that it has hardly been seriously sug- 

 gested that the determination of the dirt in milk shall form a 

 part of the municipal inspection. While such determination is 

 of value, it is as yet impractical for the purpose of controlling 

 or testing the public milk supply. 



A method that has been gradually coming into adoption for 

 this purpose is the determining of the number of bacteria in 

 the milk. It is fairly easy to determine, with moderate accuracy, 

 the number of bacteria, and if we assume that the value of the 

 milk is in proportion to the smallness of the number of bacteria, 

 it is fairly easy to reach conclusions as to its wholesomeness. 

 Recognizing, as we have done, that bacteria-free milk is impos- 



