Contamination of Milk. 33 



with clean water. By this treatment it is possible to 

 destroy practically all bacteria. For this reason most 

 city dairy companies and even some cheese-factories 

 and creameries wash the cans of their patrons. Where 

 steam is not available the utensils may be immersed in 

 boiling water. Some such treatment is especially 

 recommended to the milk producer supplying milk to 

 the city market. 



The milk producer who uses a milking machine 

 avoids one source of contamination only to meet an- 

 other unless care is taken in the handling of the ma- 

 chine. The rubber tubes used in connection with the 

 machine are very difficult to clean. They should be 

 well rinsed after use and at once placed in a 3 per cent 

 formaldehyde solution in such a way that the entire 

 tube will be filled with the solution. This will prevent 

 all growth of bacteria in the tubes. If some such treat- 

 ment is not given the tubes, the milk drawn by the ma- 

 chine will be found to contain more bacteria than that 

 drawn by hand. This is due to the k fact that it is im- 

 possible to remove all of the milk from the tubes by 

 rinsing them, and since it is also impossible to dry the 

 inside of the tubes, conditions are favorable for bac- 

 terial growth with the result that, when the tubes are 

 next used, the bacteria pass into the milk. The milking 

 machine is an aid in the production of clean milk only 

 when used in an intelligent and careful manner. 



Contamination from the air. In the barn air more or 

 less dust is to be found, coming from the feed, bedding, 

 and dried manure. The dust particles act as floats for 

 the bacteria, and when the dust settles into the milk 

 pail, the milk is contaminated with bacteria. The barn 

 air should contain the minimum of dust at milking 



