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Microbes and You 



the colonies on agar plates. The guide squares are clearly visible 

 through the agar in the dish, and by counting colonies in an orderly 

 sequence, square by square and line by line, no colonies should be 

 counted twice nor should any colonies be missed in the operation. 



Fig. 29. Quebec colony counter in use. (Courtesy of the Americdn 

 Optical Company, Instrument Division, Buffalo, New York.) 



There is no doubt that these chambers improve the accuracy of the 

 counting procedure. 



It should be emphasized that not all bacteria that are alive in a 

 tested material such as milk or water will develop into colonies in 

 the standard plating technic. There is no universal medium which 

 will allow every species of organism to develop under one set of 

 growth conditions. Temperature requirements, nutritional needs. 



