THE RELATION OF MICROORGANISMS TO MILK 



375 



Water Supply. — Sometimes the water used for washing the dairy- 

 utensils is a serious source of contamination. Serious epidemics of 

 disease have been traced to this source where the utensils were washed 

 with water contaminated by typhoid or other disease organisms 

 and were not sufficiently sterilized to kUl those remaining in the uten- 

 sils. Such dairy troubles as ropy milk and gassy milk may be caused: 

 by the water used for washing purposes. 



Fig. 129.— Colonies developed from a bit of dust found in cow stable. Agar plate 



culture. (Original.) 



Methods or Preventing Contamination of Milk 



Individual Cows. — Normally the number of microorganisms 

 found in the udder is not sufficient to be a serious source of contami- 

 nation for market milk. There are, however, certain cows which 

 have a much higher germ content than others, and where a very low 



