The Origin of Bacteria in Milk. 31 



A perfect condition of the milk is not merely de- 

 pendent on the cleanliness while drawing it, but also 

 on the carefulness with which milk is kept after milk- 

 ing. It is easily understood that unclean vessels and 

 utensils are. able to infect clean milk with bacteria, 

 and that an infection with these will unavoidably 

 follow if milk is left standing, for any considerable 

 time, in the air of the stable impregnated with bac- 

 teria. The greatest influence on the number of bac- 

 teria is, however, exercised by the temperature to 

 which milk is exposed after milking, as the vitality of 

 bacteria is greatest at bloodheat and somewhat above 

 that. 



The number of germs will, according to Weig- 

 mann, multiply : 



We see from the above that not even the tempera- 

 ture of the cellar is able to prevent these germs from 

 propagating, although for the first few hours they are 

 considerably restrained from so doing. The preser- 

 vation on ice has a far better result— a number of 

 observations made were unable to detect any increase 

 worth recording. 



It is sufficiently clear from these numbers that 



