DIRTY MILK 81 



Heated milk appears to have more cells than the raw milk 

 for reasons that are not at all clear. 



The cells in the milk are not in themselves harmful. 

 They may indicate inflammation either through their char- 

 acter, their excess of numbers, or association with harmful 

 micro-organisms, especially the streptococci. 



The germicidal property of milk 



The so-called germicidal property of milk has been much 

 misunderstood. Judged by the number of colonies that 

 develop upon agar plates the bacteria at first diminish, 

 then increase in number. This apparent diminution occurs 

 only in raw milk during the first eight or twelve hours after 

 it is drawn. Although the bacteria seemingly decrease in 

 numbers, they never entirely disappear. After the initial 

 decrease there is a continuous and rapid increase until the 

 milk contains almost infinite numbers in each cubic centi- 

 metre. 



This power of milk to restrain the development of bac- 

 teria lasts from six to twenty-four hours, depending upon 

 the temperature at which the milk is kept. If the milk is 

 kept warm, say at body heat, the decrease is pronounced 

 within eight or ten hours. After this the milk entirely loses 

 its restraining action. If, on the other hand, the milk is 

 kept cold, say at 15° C, the decrease in the number of 

 bacteria is less marked, but the action is more prolonged, 

 sometimes lasting twenty-four hours. 



No actual decrease in the number of bacteria really 

 takes place. The decrease is apparent rather than real, 

 and is due in large part to the fact that the bacteria in the 

 fresh milk agglutinate into clusters. Each group then 

 grows as one colony upon agar plates. This may be proven 

 by the fact that these clusters may be shaken asunder and 

 separate colonies obtained from each individual organism. 

 The germicidal action is, therefore, not a true power to de- 

 stroy bacteria at all, but there is a definite though tempor- 



