QUANTITATIVE STANDARD OF MILK BACTERIA. 265 



from the possibility of secondary contamination with path- 

 ogenic bacteria. Hence it will follow that milk which by 

 quantitative analysis shows a small number of bacteria, and, 

 therefore, indicates conditions of care on the part of the milk 

 producer, is likely to have been protected from secondary 

 contamination. On the other hand, the presence of large 

 numbers of bacteria suggests carelessness in the production 

 and the handling of the milk, thus giving a greater opportu- 

 nity for the introduction of mischievous bacteria. Hence it is 

 that, while the presence of large numbers of bacteria does not 

 necessarily render the milk unwholesome, it does render us 

 suspicious of the conditions to which it has been subjected. 



It is probably impossible to fix upon any standard as to 

 the number of bacteria which wholesome milk may contain. 

 Should we condemn milk when it has 10,000 per c.c. or 30,000 

 or 100,000, or 1,000,000 bacteria? To fix a standard is diffi- 

 cult, because the number is so dependent upon the tempera- 

 ture and the season of the year. It might be possible to set 

 a standard which could be enforced easily in the winter, but 

 such a standard would be quite impracticable for summer 

 weather. The number of bacteria is sure to increase in 

 the warm weather, and no standard which can be adopted for 

 winter would be practicable for the warmer seasons. On 

 the other hand, if a number should be adopted which would 

 be practicable for warm weather it would be so high as to 

 be of no use in winter weather. In some cities the attempt 

 has been made to establish such a standard for certain grades 

 of milk. Special dairies, referred to in the previous pages, 

 set a bacteriological standard and guarantee to furnish milk 

 to the consumer which contains no more than a certain num- 

 ber of bacteria. Sometimes this number has been fixed at 

 ten thousand, in other cases at thirty thousand. This is prac- 

 ticable for small dairies where the dealer wishes to furnish a 

 special product at a special price, and where the dairy is 

 within a short distance of the consumer. A bacteriological 



