5N 



Dr. A. Ransome and Mr. A. G. R. Foulerton. 



surface, and allowed the ozonised air to escape after passing over the 

 bacteria. The culture tubes were closed at the upper end by a piece 

 of cork through which passed a short length of the OT5 cm. tubing, 

 which formed the inlet for the ozonised air. 



The inlet and outlet tubes were loosely plugged with cotton wool, 

 and by means of them and short lengths of india-rubber tubing the 

 culture tubes could be connected up in series, and sterile ozonised air 

 drawn over the inoculated surfaces. 



Such culture tubes were inoculated with the following bacteria : — 



Glycerin-agar tubes (Nos. 1 to 6) with Bacillus tuberculosis. 



„ „ (Nos. 7 and 8) „ Bacillus mallei. 



Nutrient-agar (Nos. 9 and 10) „ Bacillus diphtheria'. 



„ „ (Xos. 11 „ 12),, Bacillus anthracis (sporing). 



Nutrient-gelatin ,, (Nos. 13 ,, 14),, Bacillus typhosus. 



,, ,, (Nos. 15 „ 16) „ Micrococcus melitcnsis. 



,, „ (Nos. 17 „ 18) „ Micrococcus candicans. 



The tubes were then arranged in two series, those numbered 1 to 12 

 being connected up in one series and those numbered 13 to 18 in 

 another. The two series of tubes were then placed in a room of about 

 900 cubic feet capacity and ozone was generated in the air of the room 

 by means of four small " ozonisers," a 3-inch spark Ruhmkorff coil and 

 an accumulator battery being used. The " ozonisers " were kept 

 working for four hours, during the whole of which time ozonised air 

 was slowly aspirated through the tubes. At the end of four hours the 

 arrangement of the tubes was altered ; a fresh series, including those 

 numbered 3 to 12 and 15 to 18, being connected up, and pure oxygen 

 charged with ozone was forced through the tubes for a period of thirty 

 minutes. During this half -hour ozonised air was still being drawn through 

 tubes 13 and 14. The culture tubes were then incubated, Nos. 1 to 12 

 at 37° C, and Nos. 13 to 18 at 22° C, the respective control tubes 

 being incubated with them. The result of the experiment was that in 

 the case of two out of the seven species tested, there seemed to have 

 been some slight retardation of growth as the result of the exposure to 

 the ozone ; that is to say, in the case of one or both of the duplicate 

 tubes containing Bacillus mallei and Bacillus diphtheria^ the growth of 

 the experimental cultures seemed at first to be rather slower than 

 it was in the corresponding control tubes. But at the end of eight 

 days' incubation all difference between the experimental and control 

 tubes had disappeared, and growth was equal in both sets ; and in 

 further experiments this effect was not obvious. In the case of the 

 other five species not the slightest effect could be observed as the result 

 of the exposure. This experiment was carried out under conditions 

 which, although they might approximate to those which would prevail 

 in the actual use of ozone as an aerial disinfectant, were not adapted to 



