CONTROL OF THE PUBLIC MILK SUPPLY 389 



formly with the date of delivery to the consumer. Raw milk should not be dated 

 with the date of production while pasteurized milk is dated with the date of 

 pasteurization, since this places certified milk at a disadvantage by making it 

 possible for pasteurized milk of a lower grade to carry a later date. The stamp- 

 ing on the label of the day of the week is sufficient for dating. 



BACTERIA 



The subject of bacteria in milk received more attention than any other matter 

 brought before the commission. The commission recognizes that bacteria in 

 milk in the majority of instances indicate dirt, or lack of refrigeration, or age, 

 while in the minority of instances the bacteria of disease may be present. The 

 routine laboratory methods for examining milk have as their purpose only the 

 control over dirt, refrigeration, and age, and it is a rare thing for a laboratory to 

 undertake the examination of milk for the bacteria of disease because of the ex- 

 treme difficulties in detecting them. The more efficacious method of protecting 

 milk from infection by the bacteria of human contagion is by medical, veterinary, 

 and sanitary inspection, and by pasteurization. Milk with a high bacteria count 

 is not necessarily harmful, but when used as a food, particularly for children, is 

 a hazard too great to be .warranted. Milk with a high bacteria count, therefore, 

 should be condemned. Milks with small numbers of bacteria are presumed to 

 be wholesome, unless there is reasonable ground for suspecting that they have 

 been exposed to contagion. 



BACTERIAL STANDARDS 



The commission recognizes the difficulty in interpreting bacteria counts. At 

 times misleading conclusions have been drawn from such counts. In establishing 

 the bacterial standards for a city it is always necessary to take into consideration the 

 necessary age of the milk and in lesser measure the distance hauled and methods 

 employed in its hauling. It will always be possible for a community which 

 consumes milk produced on its own premises, or within 12 hr. of its production, 

 to insist upon and maintain a lower bacterial standard than can one where the 

 milk is hauled many miles into town in a wagon, to be consumed within 24 hr. 

 after it is produced. In like manner this second type of city can always maintain 

 a lower bacterial standard than a city where the general milk supply is hauled by 

 railroad long distances and is several days old when consumed. In drawing con- 

 clusions as to the relative efficacy of milk control in cities comparisons must be 

 made between cities of the same class. 



The commission deems it of the utmost importance that some standard 

 method should be adopted for estimating and comparing the bacterial character 

 of mliks, since by this means only is it possible to grade and classify milks and to 

 enforce bacterial standards. There is much diversity of opinion as to the best 

 method of valuing bacteria counts. The average of a series gives results which 

 are misleading about as frequently as otherwise. In the average a single high 

 figure may unduly overbalance a large number of exceedingly low counts. There 

 are objections to the use of the " median" or middle number when the counts are 

 arranged in order of size, for the reason that the middle figure does not distinguish 

 between two groups in one of which there may be some very high counts above 

 the median and in the other of which there are none. The method of dividing 



