DAIRY MEETING. 145 



DIRT AND ITS RELATION TO BACTERIA IN MILK. 



H. D. Evans, Director, State Laboratory of Hygiene. 



Alilk, as one of the earliest and most used of our foods, was 

 one of the earHest to be adulterated. That adulteration has 

 continued down to the present day. Laws relating to the adul- 

 teration of milk antedate all other of our food laws; yet it is a 

 striking fact that the form of adulteration which has the great- 

 est effect on the health of the users of milk, has but recently 

 come into its deserved prominence. A substance may be said to 

 be adulterated either when there has been abstracted from it 

 some natural constituent, either wholly or in part ; or when 

 there has been added tp it some foreign substance, irrespective 

 of its nature. 



Thus we have, for years, recognized milk as being adulterated 

 when it has been skimmed, or watered, or colored, or thickened, 

 or preserved, or when any combinations of these forms of sin- 

 gle adulteration have been practiced ; but we have, until recently, 

 failed to recognize a form of adulteration of the second class, 

 that is more far-reaching in its effects on health than all of the 

 other forms combined. I refer to the bacterial adulteration of 

 milk through the carrying agency of dirt. 



If a food is adulterated when any foreign substance is added 

 to it, — and this is a definition recognized by all of our state 

 laws — ^then the presence of dirt in a milk constitutes an adulter- 

 ation, just as much as does added water, or a preservative, or 

 a coloring agent. This fact has been recognized by the courts 

 of at least one state within the last year. The same statement 

 will apply to the presence of bacteria in milk, but, owing to the 

 fact that it is a practical impossibility to exclude all bacteria 

 from milk, it is best to consider the two forms- of adulteration 

 of milk, by dirt and by bacteria, in their relation to each other. 



In my paper before this Association last year I took up in 

 considerable detail the general subject of bacteria, and so shall 



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