BACTERIOLOGY OF MILK 



615 



lactic-acid-forming organisms are killed, and if the treated 

 milk be kept, the residuum of resistant putrefactive, etc., 

 bacteria multiply enormously, without obvious change in 

 the milk and " returned " milk can be utilised again and 

 again. Pasteurised milk should be rapidly cooled and be 

 consumed within twenty-four hours of treatment. Behring 

 has advocated the addition of formaldehyde to all milk 

 used for the feeding of children. Another method for 

 sterilising milk is the Budde process, 1 in which the milk, 

 after the addition of hydrogen peroxide, is heated for 

 three hours to 52-53 C. All non-sporing organisms are 

 destroyed, and the added hydrogen peroxide is decomposed 

 into H 9 and 0. 



All milk should be distributed in closed bottles, and 

 pasteurised milk should be consumed within thirty-six 

 hours of treatment. 



The thermal death -point of pathogenic organisms in milk is 

 as follows : 2 



The thermal death-point of tubercle bacillus, especially in milk 

 has been the subject of some controversy (see also p. 309). De Man 

 found that an exposure of fifteen minutes at 65 C. was necessary 

 l> destroy the infective properties of tuberculous milk. Bang, of 

 Copenhagen, considers that pasteurisation cannot always be relied 

 upon, and recommends that milk should be heated to 85 C. The 

 writer found that the vitality of the ordinary non-virulent laboratory 

 cultures was destroyed by a temperature of 60 C. acting for ten 



1 Hewlett, Lancet, 1906, vol. i, January 27. 



2 Rosenau, Hygienic Lab., Washington, Bull. 42, 1908. 



