BACTERIOLOGY OF MILK IN ITS RELATION TO DISEASE 467 



As we have seen, the milk in New York City is found on bacterio- 

 logical examination to contain, as a rule, excessive numbers of bacteria. 

 During the coldest weather the milk in the shops averages over 300,000 

 bacteria per cubic centimetre, during cool weather about 1,000,000, 

 and during hot weather about 5,000,000. The milk in other large 

 cities is, from all accounts, in about the same condition. 



The above statement holds for milk sold at the ordinary shops, and 

 not that of the best of the special dairies, where, as previously stated, 

 the milk contains only from 10,000 to 30,000 bacteria, according to the 

 season of the year. 



The question might be raised, Are even these enormous numbers 

 of bacteria in milk during hot weather actually harmful? 



Our knowledge is probably as yet insufficient to state just how many 

 bacteria must accumulate to make them noticeably dangerous in milk. 

 Some varieties are undoubtedly more harmful than others and we 

 have no way of restricting the kinds that will fall into milk, except by 

 enforcing cleanliness. We have also to consider that milk is not entirely 

 used for some twelve hours after being purchased, and that during 

 all this time bacteria are rapidly multiplying, especially where, as 

 among the poor, no provision for cooling it is made. Slight changes 

 in the milk which to one child would be harmless, would in another 

 produce disturbances which might lead to serious disease. A safe 

 conclusion is that no more bacterial contamination should be allowed 

 than it is practicable to avoid. Any intelligent farmer can use sufficient 

 cleanliness and apply sufficient cold, with almost no increase in expense, 

 to supply milk twenty-four to thirty-six hours old which will not con- 

 tain in each cubic centimetre over 50,000 to 100,000 bacteria, and no 

 milk containing more bacteria should be sold. 



The most deleterious changes which occur in milk during its trans- 

 portation are now known not to be due to skimming off the cream, or 

 to the addition of water, but to the changes produced in the milk 

 by multiplication of bacteria. During this multiplication, acids and 

 distinctly poisonous bacterial products are added to the milk, to such 

 an extent that much of it has become distinctly deleterious to infants 

 and invalids. It is the duty of health authorities to prevent the sale 

 of milk rendered unfit for use through excessive numbers of bacteria 

 and their products. 



The culture tests to determine the number of bacteria present in 

 any sample of milk require at least forty-eight hours ; so that the sale 

 of milk found impure cannot be prevented. It will, however, be the 

 purpose of the authorities gradually to force the farmers and the middle- 

 men to use cleanliness, cold, and dispatch in the handling of their milk, 

 rather than to prevent the use of the small amount tested on any one day. 



If the milk on the train or at the dealer's were found to contain exces- 

 sive numbers of bacteria, the farmers would be cautioned and instructed 

 to carry out the simple necessary rules, which would be furnished. 



Transmission of Contagious Diseases through Milk. No farmer or 

 dairyman should allow anyone who has a contagious disease, or who 



