232 AGRICULTURAL BACTERIOLOGY 



while Chicago requires that the milk on arrival in the city 

 shall contain not more than 1,000,000 per cubic centimeter 

 from May first to September thirtieth, and not more than 

 500,000 between October 1 and April 30. The sale of milk 

 containing; more than 3,000,000 bacteria per cubic centi- 

 meter is prohibited. 



It has been urged that bacterial standards are not of 

 value since the healthfulness of milk depends on the kind 

 of bacteria present rather than on the number. It is well 

 recognized that milk containing millions of acid-forming 

 organisms, buttermilk, is a healthful food, while that con- 

 taining many less bacteria may harbor some disease-produc- 

 ing organisms. It has been urged that a qualitative stand- 

 ard should supplant the quantitative. The consumer de- 

 sires milk that has been produced under clean conditions 

 and which has good keeping qualities. The harmless forms 

 of bacteria exert the greatest influence on the keeping qual- 

 ity. Experience has shown that the quantitative examina- 

 tion of the milk supply as it comes from the farm is the 

 most feasible method of determining, in the laboratory, 

 whether the farmer has obeyed the rules with reference to 

 cleanliness and cooling of the milk. The bacteriological ex- 

 amination also gives an indication as to whether the large 

 number of bacteria is due to gross contamination of the 

 milk with mud and manure, or actual growth of bacteria, as 

 in old milk. In the latter case the ordinary acid-forming 

 bacteria will usually predominate in the milk, while in the 

 former the number of kinds of bacteria and the proportion 

 between the kinds will be changed. It is, of course, evi- 

 dent that the quantitative standards should be applied 

 with judgment. 



It is also claimed that the delay in securing the results 

 in the quantitative examination of milk is an objection to 

 the bacterial standard, since the milk is consumed before 



