272 CITY MILK SUPPLY 



artificial means to make its acquired impurities harmless. . As man heats 

 other foods, it is natural that he should milk. Rosenau has pointed out 

 that milk is the only nitrogenous food that man eats raw. In fact, in 

 many countries it is customary to cook milk but in the United States 

 it was not, so that this new product, heated milk, was viewed with 

 suspicion and had to make its way slowly. 



Pasteurizing Milk and Dirty Dairying. Another objection that was 

 raised to pasteurization was that it would militate against sanitary dairy- 

 ing. It was known that much of the milk came into the cities from very 

 dirty dairies and it was felt that pasteurization would tend to perpetuate 

 their existence by making the milk from them more readily marketable, 

 for in the raw state it might be expected to spoil quickly on account of 

 the heavy contamination that it had received, whereas by pasteurization 

 this might be delayed till the contractor could place it in the home of the 

 consumer. It was felt, too, that pasteurization would encourage the use 

 of unclean methods by the producer for, knowing that the milk was to 

 be pasteurized, he would feel that the effects of his carelessness would 

 be obliterated. 



Spore-bearing Organisms Survive Pasteurization. The experiments 

 of Fltigge in 1894 greatly influenced many adversely toward pasteurized 

 milk. He heated milk to near the boiling point till few if any other 

 bacteria than spore formers survived and then by employing suitable 

 methods isolated 12 cultures of bacteria that when grown in milk at 

 98F. for 2 days, peptonized it. Of these 12 cultures, three when so 

 grown in milk, proved poisonous when fed to dogs; the others did not. 

 From this work, which nowadays would not be considered extensive 

 enough to be conclusive, the inference was widely drawn that noxious 

 spore-forming bacteria survived pasteurization and it was believed that 

 they were particularly dangerous in that they rotted the milk without 

 making its putrid condition apparent to the consumer. In criticism of 

 Fliigge's results it has been said that he grew the organisms at tempera- 

 tures which assured a maximum of toxin production and that according 

 to his own account his cultures were in a stinking condition when fed to 

 the dogs. Careful experimentation has demonstrated that at the tem- 

 peratures now employed in this country in pasteurization, enough lactic 

 acid bacteria survive to overgrow any peptonizing forms that may be 

 present and so to prevent putrefaction taking place. 



In an investigation covering 18 months extending from the spring of 

 1913 to the fall of 1914, Ford and Pryor studied the market milk of Balti- 

 more and Washington in an attempt to repeat Fliigge's experiments. 

 Fliigge held that milk heated to various temperatures shows after incu- 

 bation, at 71.6F. or at 98.6F.- two sorts of decomposition the one being 

 explosive and due to gas-producing anaerobes and the other consisting 

 of a slow liquefaction of the proteins of the milk, due to peptonizing 



