Laboratory Outline for General Bacteriology 



Counting Bacteria and Molds on Air Plates 



It has been shown that the bacteria from ten liters of air will 

 fall on one hundred square centimeters in five minutes. From 

 this is derived the formula 



10 x no. bact. or molds on plate 

 area of plate 



no. bact. or 

 =molds per liter 

 of air. 



In counting a plate place it on the glass plate ruled in squares. 

 Remove the cover of the dish. Use the lens holding it near the 

 eye. Bring the plate near enough to focus clearly. . Beginning at 

 the upper part of the plate follow along the lines working back and 

 forth until the whole plate is counted. 



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