MICRO-ORGANISMS IN MILK 



295 



3. Contamination from the Hands and Clothes of the Milker. 



— The milker may become a source of bacterial contamination of 

 milk, and this factor is one of considerable importance. Cleanly 

 personal habits (Fig. 101) will aid in keeping the germ content 

 low, while filthy habits serve to increase it. Russell has shown 

 that by careful milking the milk may contain 120 to 300 bacteria 

 per cubic centimeter, against 7680 to 15,000 by ordinary milk- 

 ing. Esten and Mason found that after a milker had washed his 

 hands in a quart of sterile water 45,000,000 bacteria had been re- 

 moved from the hands. After the milker had washed his hands 

 with soap and warm water but 900,000 could be removed with 

 sterile water — a reduction of 98 per cent. This experiment shows 

 that a large number of bacteria may drop into the milk from dirty 



Fig. 101. — Clean milkers in clean suits. 



hands. It is obvious that dust-laden clothing of the milker may 

 also add a contribution of germ life to the milk. 



That the bacterial content of milk may vary when different 

 milkers milk the same cow has been clearly shown by Stocking. 

 By comparing the germ content of milk drawn by regular men with 

 that of milk drawn by students who had received college training 

 in cleanly milking, it was found that the milk drawn by regular 

 men contained an average of 2846 bacteria per cubic centimeter, 

 against 914 in the milk drawn by students. These results were 

 substantiated by another series of tests with 19 lots of milk. 

 While the milk drawn by regular men averaged 17,105 bacteria 

 per cubic centimeter, the milk drawn by students contained 2455. 



The reduction of germ content by milkers trained in habits of 

 cleanHness is not the only reason why attention should be given 



