BEHAVIOUR OF BACTERIA IN MILK 55 



Fresh Byre Milk incubated for %4 hours at 15 C. 



Fresh Byre Milk incubated for %^ hours at 80-81 C. 



Milk is a complex fluid bacterially, and the presence of 

 other kinds of bacteria might be expected to influence materially 

 the multiplication of B. coli. The results on the whole show 

 less variation than might have been anticipated. At 15 C. 

 the increase was usually 100 fold, occasionally 1000 fold, and 

 practically never greater than this. At 20 21 C. the increase 

 was usually 10,000 fold, but was less when the initial number 

 of B. coli was very great. 



These experiments show that temperature is a more im- 

 portant factor than initial number in determining the final 

 number of B. coli, but that both are very important. From a 

 few experiments made, but not recorded here, it would seem 

 that time is less important than temperature. 



From the point of view of standards for vended milk the 

 results of the incubation at 15 C. of samples of milk with 

 initial B. coli content of not over 1 per c.c. are of greatest 

 interest. As the tables show, the increase was variable, but 

 was very rarely over 1000 fold, and was usually much less. 



