THE SANITARY FACTORS 97 



ease of making the smears at the dairy or shipping station, 

 subsequently sending them to the laboratory for microscopic 

 examination, renders the method especially applicable at the 

 dairy end of the line. 20 



III. CONTAMINATION TESTS 



We have already referred to the value of being able 

 to determine the presence of dirt and filth, particularly 

 manural pollution, in milk. Concerning the present 

 status of tests for such contamination we cannot do 

 better than to quote at some length from a paper of 

 Dr. John Weinzirl: 



This problem [of eliminating dirt from milk] resolves 

 itself into two distinct phases: first, the problem of finding 

 the most suitable method of detecting dirt in milk; secondly, 

 bringing the evidence home to the dairyman and making him 

 respond to the new demands. Let us first consider the 

 methods of detecting filth in milk. 



Three methods are in use more or less commonly, viz.: 

 (1) Determining the total number of bacteria present in 

 the milk, assuming this to be an index of its cleanliness, and 

 fixing a line beyond which the count may not go, otherwise 

 sale is forbidden. (2) Determining the number of B. coli 

 present and setting a similar standard. (3) Determining 

 visible dirt, and again making a standard for purity. To 

 these the writer now desires to add another, (4) Determining 

 B. sporogenes and creating a standard of purity. 



It is well known that the total count depends upon other 

 factors as well as upon dirt, for time and temperature may 

 cause a high count in an otherwise clean milk; doubtless 

 such milk should be barred from sale, but it does not reach 

 the real question, which is, the amount of dirt present in it. 

 Again, if the milk is pasteurized, the total count fails utterly 



