Contamination of Milk. 39 



teat, although this factor can be controlled to a less de- 

 gree than any of the others. The actual loss occasioned 

 in doing this is very slight, as the first part of the milk- 

 ing is very poor in butter fat. 



Dust in the air of the barn is a minor factor, yet this 

 can be materially reduced by exercising care relative to 

 feeding dry fodder, or bedding the animals just previous 

 to, or during the milking. 



The number of germs derived from the animal itself 

 and the milker can be largely decreased by keeping the 

 animal thoroughly clean, and having the milker milk with 

 clean hands. 



The effect of contamination arising from imperfectly 

 cleaned milk vessels can be practically excluded by ster- 

 ilizing all such utensils in steam, or even in scalding 

 water for a short time. 



To determine what reduction could be accomplished by 

 drawing and handling the milk under as clean conditions 

 as possible, the following experiment was carried out: 

 The udder was thoroughly carded, and then moistened; 

 the milk received in steamed pails, the fore milk being 

 rejected. 



The milk from a cow treated in this way contained 330 

 bacteria per cc., while that of a mixed herd taken under 

 usual conditions was 15,500 bacteria for same volume. 

 This carefully handled milk kept over twenty hours 

 longer at room temperatures than the ordinary product. 

 Backhaus estimates that the germ life in milk can be 

 easily reduced to Wire of its original number by using 

 care in milking. Methods of this sort must be instituted 

 in those dairies that are furnishing the highest grade of 

 product. Where such methods are in vogue, bacteria 

 are excluded for the most part and pasteurization be- 

 comes unnecessary. Such milks are frequently known as 



