580 APPENDIX 
LL NAA 
~ BB 
apes 
tA 
wes or 
. yo ash 
crane ach 
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i 
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ers 
am 
Frost’s Plate Counter. 
Each of the larger squares represents an area of 1 sq. cm. 4 
number of square centimeters in the circles bounded by the respective lines. Each sector is one- 
tenth the area of its circle. ; oo , , 
Department of Bacteriology, University of Illinois. 
The figures 60 and 40 indicate the 
