On the Influence of Ozone on the Vitality of some Bacteria. 57 



of the ozone, gave rise to a free growth of bacteria, when incubated 

 in the same medium. Sonntag and Ohlmiiller's experiments, on the 

 other hand, seemed to show that ozone in the dry state had little or 

 no action on bacteria, but was capable of destroying them when passed 

 through water containing them. Thus B. anfJiracis, suspended in 

 distilled water, was destroyed after air containing 9'6 millegrammes 

 of ozone per litre had been passed through the mixture for ten 

 minutes. A sporing culture of the same bacillus was killed by pass- 

 ing air containing 15*2 milligrammes of ozone per litre through the 

 water for ten minutes. If, however, organic matter, such as blood 

 serum, were added to the water the results were different; and it 

 seemed that under these latter conditions the most part of the ozone 

 was expended in oxidation of the dead organic matter present, whilst 

 the bacteria were little if at all affected. 



Our experiments were planned with the view of ascertaining whether 

 ozone applied in large quantities, either in a mixture with atmospheric 

 air or with pure oxygen, has in reality a destructive influence on 

 bacterial life, and especially whether it has any such influence under 

 conditions which would enable it to be used for practical purposes of 

 disinfection. 



The experiments have included the testing of the action of ozone, 

 (1) on the vitality of certain pathogenic and saprophytic bacteria, 

 iind (2) on the virulence of one pathogenic species. For the purposes 

 of the latter test, we decided to test the action of the gas on B. tuber- 

 culosis, an organism which is known to be readily affected by the 

 direct action of ordinary chemical agents, and one which numerous 

 experiments would lead us to believe is very susceptible to the action 

 of direct sunlight (Koch,* Ransome and Delepine,f and Jousset).| 



Experiment I. — In our first experiment, culture tubes with " sloped " 

 surface of nutrient agar or gelatin were inoculated with various 

 bacteria; a mixture of atmospheric air and ozone was passed con- 

 tinuously over the inoculated surface for a period of at least four 

 hours, commencing twenty-four hours after the tubes were inoculated. 

 The tubes were then incubated at appropriate temperatures, and the 

 result compared with that obtained in control tubes which had been 

 inoculated from the same stock cultures at the same time. 



In detail the following was the procedure carried out : — The culture 

 tubes were of the ordinary 15x2 cm. size, into the sides of which short 

 pieces of 0*75 cm. calibre glass tubing had been blown in such a way 

 that they opened into the lumen of the culture tubes about 3 cm. from 

 the bottom and just above the lower level of the sloped nutrient 



* 1 Uebei* bacteriologische Forsclrang.' Introductory Address, Tenth Inter- 

 national Medical Congress, August 4, 1890. 

 f ' Eoy. Soc. Proc.,' vol. 56. 



% ' Comptes Rendus de la Societe de Biologie,' 1900, Tome 52, p. 884. 



F 2 



