On the Influence of Ozone on the Vitality of some Bacteria. 59 



test the action of ozone on bacteria, apart from an important disturbing- 

 factor. The bacteria were submitted to the action of ozone in the 

 presence of a large amount of dead organic matter, and it was quite 

 conceivable that such an amount of the ozone might have been decom- 

 posed in the oxidation of the dead organic matter that but little had 

 been left to exert any action on the living bacteria.* 



Experiment II. — In this experiment we endeavoured to test the action 

 of ozone on the bacteria in the absence — so far as we could ensure the 

 condition — of dead organic matter. The same culture tubes were used, 

 but instead of inoculating agar or gelatin nutrient surfaces we inoculated 

 small blocks of plaster of Paris from stock cultures of the various 

 bacteria tested. These plaster of Paris blocks when inoculated were 

 placed in the culture tubes, and the inlet and outlet tubes were plugged 

 with fine Italian asbestos fibre instead of with cotton wool. And instead 

 of passing the same current of ozone over a series of tubes in succession, 

 we connected each tube separately with a main feeding pipe with 

 lateral branches, the respective tubes being held in contact by pieces 

 of india-rubber tubing. Thus each culture tube had a fresh supply 

 of ozone. Ozone was generated as before, and passed over blocks 

 inoculated from stock cultures of the following : — ■ 



1. Staphylococcus pyogenes aureus. 7. Bacillus typhosus. 



2. Streptococcus pyogenes. 8. Bacillus coli communis. 



3. Micrococcus melitensis. 9. Bacillus pyocyaneus. 



4. Bacillus mallei. 10. Bacillus pneumonia' 

 b. Bacillus diphtheria'. (Friedlander). 



6. Bacillus anthracis 11. Bacillus prodigiosus. 



(from sporing culture). 12. Saccharomyces albicans. 



Duplicate tubes were inoculated with each organism, and a con- 

 tinuous current of air was pumped over the ozoniser, which was 

 enclosed within a glass cylinder connected with the main feeding 

 tube, and then through the culture tubes for a period of thirty minutes. 

 The actual amount of ozone used was not estimated, but iodide of potas- 

 sium and starch paper held over the outlet tubes gave a positive reaction 

 within sixty seconds of the commencement of the experiment. The 

 small plaster of Paris blocks were then shaken up in tubes containing 

 3 c.c. of nutrient broth, from the broth tubes loopfuls were transferred 

 to other media, and the growth obtained after incubation compared with 

 the growth on control tubes. 



The results obtained on incubating the sub-cultures made it evident 

 that none of the bacteria had been affected by the ozone in such a way 

 as to impair either their capability of growth, or, in the case of the two 



* We are indebted to Mr. Bridge, chemist, of Bournemouth, for assistance in 

 the working of the ozonising apparatus used in carrying out this experiment. 



