700 



Journal of Agricultural Research 



Vol. 62, no. 9 



An ocular micrometer disk, such as is used for counting bacteria in 

 milk, was used in counting spores in the fields of the stamed smears 

 The area of the circle etched on this disk was found to be O.OOUUbUb^ 

 cm^ when used in a biaocular microscope with 15 X paired eyepieces 

 anda 1.8-mm oil-immersion objective. Therefore, the factor it became 



16,441.96. ^ , , ,. . 



The spores in 30 fields from each of the duphcate smears were 

 counted, making a total of 60 fields (AT) for each honey-spore sample. 

 The fields were counted at random from various parts of the smear. 

 From these counts the actual mean number of spores per field re- 

 covered in 60 fields for each honey-spore sample was determined 



Substituting the values for K and N and 0.02 (1/50) for D, the 

 spore dilution in the foregoing formula gives 



Number of spores per cubic centimeter 



_ 16,442X60XX100X0.02 _g^ ^^^^ 



COMPUTATION OF THEORETICAL MEAN NUMBER OP SPORES PER FIELD 



The theoretical mean numbers of spores per field that should be 

 recovered from each of five honey-spore samples used, under ideal 

 conditions where there is no loss of spores during the process, were 

 calculated by the foregoing formula, which for this purpose may be 

 stated as follows: 



X-- 



Number of spores per cubic centimeter 

 32,884 



X now designates the theoretical mean number of spores per field. 

 In table 2 these values are given in comparison with the corresponding 

 actual mean number of spores per field for each honey-spore sample. 



Table 2. — Relation between the actual and the theoretical mean numbers of spores of 

 Bacillus larvae per field recovered from five samples of honey containing known 

 numbers of spores per cubic centimeter 



Spores per cubic centimeter in sample (number) 



Mean spores per field 



Theoretical 



Actual 



Standard 

 deviation 



Ratio of 

 actual mean 

 to theoret- 

 ical mean 



1,000,000. 

 800,000.. 

 500,000-. 

 300,000.. 

 50,000... 



Number 



30. 4100 



24. 3279 



16. 2050 



9.1230 



1.6205 



Number 



27. lOOOiO. 3554 



21. 3167± . 2751 



13.2167± .2011 



7. 9500it . 1708 



1. 2833± . 0747 



Number 

 4. 0812 

 3. 1596 

 2.3100 

 1.9615 

 .8582 



Percent 

 89.12 

 87.62 

 86.92 

 87.14 

 84.40 



RESULTS OBTAINED BY USE OF THE METHOD 



By the method used, the actual mean number of spores per field 

 obtained by counting 60 fields from each honey-spore sample differed 

 from the calculated theoretical mean number of spores per field by 

 10.88 percent for the honey containing 1,000,000 spores per cubic 

 centimeter to 15.60 percent for the honey containing 50,000 spores per 



