THE SANITARY FACTORS 93 



contamination and from later development of the con- 

 taminating bacteria. The total count does not, how- 

 ever, give any information as to the kind of bacteria 

 present. Pathogenic organisms are not detected. Nor 

 is it possible, by this test alone, to determine how far 

 the count is due to contamination and how far to mul- 

 tiplication of the bacteria through insufficient refrigera- 

 tion. The count depends, as a rule, far more on such 

 multiplication than on the initial contamination. Pas- 

 teurization, moreover, destroys the value of the total 

 count as an indicator of the previous state of the milk. 

 The question may be asked, what means we have of 

 determining the presence of contaminating matter or 

 of disease germs in milk. The routine detection of 

 specific disease germs in milk is impracticable because 

 of difficulties of bacteriological technique, and their 

 presence, even if detected, would not be known until 

 after the milk had been distributed and consumed. 

 The estimation of dirt or filth contamination is, how- 

 ever, feasible. The tests for this purpose will be dis- 

 cussed in the following section. 



Notwithstanding what has just been said, the total 

 count, taken as a general index of contamination plus 



individual bacteria and . . . are probably always lower than they 

 should be because of the fact that not all bacteria will grow on nutrient 

 agar at the incubation temperature used." While this qualification is 

 well recognized by bacteriologists, there is danger of its being neglected 

 even by them. Microscopical studies are cited by Mr. Breed to indicate 

 that the actual numbers of (living?) bacteria in market milk are from 

 one and a half to twenty-five or more times the number of colonies 

 developing, depending on the kinds present. Until, however, some 

 other form of statement is adopted, the number of " bacteria per c.c.," 

 i. e., of plate colonies, remains the practical basis of comparison of the 

 general bacterial character of different samples of milk. 



