426 APPLIED BACTERIOLOGY 



temperature of 68° C, but must be maintained at this 

 temperature for twenty minutes. Bitter has invented an 

 apparatus for efficient pasteurisation, in which the milk is 

 kept at a temperature of from 70° to 72° C, for thirty 

 minutes, after which it is rapidly cooled. 



A very simple apparatus is sufficient for household use, 

 the essential parts being : an easily cleansed bottle with a 

 cotton-wool plug, to contain the milk ; a metal vessel pio- 

 vided with a wire stand at the bottom to support the bottle; 

 and a thermometer, the stem of which passes through the 

 lid of the outer vessel so that the temperature can be 

 ascertained without the cover being removed. The 

 temperature of the water should be slowly raised to 

 70° C, after which the vessel should be taken off the 

 fire, and should be kept for thirty minutes under a thick 

 cosy. At the end of this period the bottle should be 

 taken out of the water, and put in a cool place so that 

 the temperature of the milk may be lowered as rapidly as 

 possible. 



By this method of procedure as much as 99'9 per cent, 

 of the organisms in the milk may be destroyed. 



A very important point in connection with the pas- 

 teurisation of milk is to determine if this process is as 

 effectual in destroying pathogenic organisms as the sterilisa- 

 tion process. 



Forster, from his own and other investigations conducted 

 in his laboratory, states that milk kept for half an hour at 

 66° C. is freed from the organism of tubercle, typhoid, 

 cholera, etc. Fliigge, from his own researches and those of 

 others in his laboratory, states that half an hour at 70° C. is 

 necessary. As regards the bacillus of diphtheria, Loffler 

 states that half an hour at 60° C. is sufficient to destroy it. 

 The results of these experiments have been confirmed by 

 other workers; and it may safely be accepted that milk 



