TYPES OF BACTERIA COMMONLY FOUND IN MILK 291 



Ayers and Johnson also studied the rate of destruction of different 

 groups of organisms acid-forming, peptonising, inert, and alkali- 

 forming and showed that the effect produced upon these by heat 

 differs very considerably. 



The nature of the organisms surviving pasteurisation is shown 

 in Plate V, the total numbers of bacteria at different times in the 

 same experiment being given in the table on p. 292. 



A 54.4 C. C/30 



fSfe 



X 



Figure showing the Bacterial Reduction during 

 Pasteurisation for Three Hours at 54*4 C. 

 (130 F.), 57'2 C. (135 F.), and 60 C. 

 (140 F.). 



The figure shows that the acid-forming organisms survive in 

 greater number than any of the other types. The same result 

 was obtained in a large number of experiments to which it is 

 impossible to refer here. 



The authors remark that the change in the group percentages 

 which is shown between three and a half and four hours is un- 

 doubtedly due to experimental error. 



u 2 



