278 MILK 



stream." Barthel, on the other hand, found that the micro- 

 organisms which he observed in the udder of a freshly slaughtered 

 cow were the same as those existing in the air of the stable. This 

 work has been referred to before. 



The unsuitability of the interior of the udder for bacterial 

 growth is further proved by the fact that cultures introduced into 

 the udder gradually disappear unless injected in large quantity, 

 in which case an inflammation usually results. The udder flora 

 apparently cannot be deliberately altered by experiment, but re- 

 mains characteristic. But a relatively small number of micro- 

 organisms are able to thrive there. 



^ Contamination During Milking Operations 



We have seen that milk when drawn from the udder contains 

 some germ life, but the number of micro-organisms in such milk 

 is relatively small. When the calf sucks the milk this number of 

 germs is not greatly increased, the only possible source of increased 

 germ content being the dirt which adheres to the teats. The 

 milk which is drawn by human hands and which is destined for 

 human consumption is subjected to a variety of operations, and 

 at each step a new source of contamination exists. During the 

 milking process micro-organisms may enter the milk from 1, dirt 

 dropping from the outside of the udder and the coat of the animal; 

 2, from dust in the air, and 3, from the hands and clothes of the 

 milker. 



1. Dirt from the Outside of the Udder and the Coat of the 

 Animal. — The dirt which may drop into the milk from the coat of 

 the animal is chiefly cow manure, although particles of fodder and 

 bedding, hairs, chips of wood, soil particles, and other foreign 

 material are occasionally found in milk. Very ordinary cleanli- 

 ness can protect the milk from gross substances, but the fine dust 

 which is shaken from the animal at every move, by switching the 

 tail, or by the movement of the udder during the milking process, 

 is not so readily kept out of the milk. Solid material falling into 

 the milk breaks up and the bacteria are distributed throughout 

 the bulk of the milk. It is a strange testimony of ignorance that 

 a farmer pays more attention to the cleanliness of his horses than 

 to that of cows, although horses are used for work only, while 

 cows produce the most valuable food product for man and upon 

 which the very lives of many babies depend. 



The dirt which mixes with the milk is a carrier of micro-organ- 

 isms and it might be supposed that there is a definite relation be- 

 tween the amount of dirt and the germ content of milk. This, 

 however, is only approximately true. It is, of course, not an easy 



