Contamination of Milk. 



25 



30. Milk, germ-free in udder. Under ordinary con- 

 ditions, when examined in the proper manner, milk 

 always reveals bacterial life. This germ content, how- 

 ever, is due to infection from without, for in the udder of 

 a healthy animal, as secreted, the milk like the other 

 secretions and tissues of the body is normally sterile. 



31. Contamination of milk. In withdrawing the 

 milk from the udder, it invariably comes in contact with 

 germ life. The same is true after it is milked. From 

 the time of milking, until it is consumed in one form or 

 another, it is continually subject to contamination from 

 exterior sources. In the main, germ life gains access 

 while the milk is on the farm, but even in the factory 



FIG. 5. Microscopic appearance of milk showing relative size of fat globules 

 and bacteria. Group of bacteria on left are lactic acid organisms. 



the opportunities for infection are present in greater or 

 lesser degree. Those forms that gain an early entrance 

 generally predominate in the milk, as their early intro- 

 duction enables them to develop for a longer period of 

 time. 



