Contamination of Milk. 47 



changes will be much increased as is shown in following 

 results obtained by Freudenreich. 1 



No. of bacteria per cc. in milk kept at different temperatures. 



77 F. 95 F. 



5 hrs. after milking < 10.000 30,000 



8 " " " 25,000 12,000,000 



12 u " " 46,000 35,283,000 



26 " " " 5,700,000 50,000,000 



PPOQEAY OF A SI/iQLE GERM 

 I/I 12 HOURS, I/I MILR ALLOWED 

 TO COOL /iATURALLY. 



-f,** I/S MILfT COOLED WITH 



''HUCA 



COLD WATER. 



Fro. 14. Effect of cooling milk on the growth of bacteria. 



If a can of milk is allowed to cool naturally, it will take 

 several hours before it reaches the temperature of the sur- 

 rounding air. During this time the organisms in the fore 

 milk are continuing their rapid growth, while those forms 

 which come from dust, and are presumably in a latent 

 state, awake from their lethargy under the influence of 

 these favorable surroundings. If bacteria once gain an 

 entrance and begin to germinate, a considerably lower 

 temperature is required to successfully check development 

 than to hold latent organisms, like spores, in a condition 

 where germination will not occur. 



To hasten this lowering of temperature artificial cooling 

 is a necessity. With good well water having a tempera- 



1 Freudenreich, Ann. de Microg., 1890, 2:115. 



