52 



LAWRENCE T. FAIRHALL AND PAUL M. BATES 



The source of ultra violet light was an R.U.V. straight tube 

 quartz mercury vapor lamp operating at 175 volts and 3.8 

 amperes when at its maximum. This lamp furnished a very- 

 constant source of ultra violet radiation, having once attained 

 its maximum brilliancy. The straight tube lamp is especially 

 advantageous in securing uniformity of exposure, since the rays 

 are distributed throughout its length rather than concentrated 

 at one point. 



TABLE 1 



Exposure at 5 cm. distance 



Plate 



Glucose agar tube 



B. Coli 



B. subtilis 



2 colonies 

 2 colonies 

 No growth 

 No growth 

 No growth 

 No growth 



The samples of inoculated oil were prepared by grinding up 

 the dried bacteria or mold spores with oil, so as to form an even 

 emulsion and then filtering through coarse filter paper in order to 

 free the oil from the larger particles. Control experiments made 

 with this inoculated oil by plating it on agar always yielded a 

 large number of colonies. In order to test the effect of the ultra 

 violet rays on this inoculated oil, portions of it were exposed in 

 open dishes at a fixed distance from the lamp and for varying 

 lengths of time. The preliminary results thus obtained are 

 shown in table 1. 



