56 MILK AND THE PUBLIC HEALTH CHAP. 



Bacillus enteritidis sporogenes is another organism of im- 

 portance in estimating the purity of milk samples. The writer 

 incubated at 15 C. and at 21 C. 18 samples of milk in which 

 the number of the spores of this organism had been determined, 

 and found no evidence of any multiplication. 



The investigations of the writer were more particularly 

 directed to ascertaining the effects of time upon milk kept at 

 a temperature (15 C.) at which it would be likely to be 

 subjected under actual practical conditions. Other workers 

 have shown that if milk be kept at a low temperature, for 

 example 10 C., there will not be any marked increase in the 

 number of bacteria within a reasonable time. For example, 

 Houston kept 15 samples of milk at temperatures varying 

 from 6 to 11 C. for 24 hours, and roughly re-determined the 

 B. coli content. In 7 samples he found no change, in 6 an 

 increase, and in 2 a decrease. 



Stewart 1 kept 25 samples of byre milk at 10 C. for 10 

 and 20 hours. The temperature was reduced within one hour 

 of milking. Only comparatively slight increase took place in 

 the number of B. coli communis even after 20 hours. The 

 following table also shows the results of keeping 11 samples 

 at 40 F. (4-4 C.) for different periods : 



1 Report on the Bacteriological Examination of Milk Samples, 1909. 



[TABLE 



