1906.] 



Action on Bacteria of Electrical Discharges. 



83 



been exposed to the action of the peroxide the formation of pigment was 

 obvious from the first appearance of growth, in the cultures from bacilli which 

 had been immersed in the solution the formation of pigment was not apparent 

 until the third or fourth day of incubation. This effect was repeatedly noticed 

 in experiments with this organism, and also with the other chromogenie 

 organism tested, B. pyocyaneus. 



Experiments in an Atmosphere of Pure Carbon Dioxide. 



We next tested the action of the discharges when sprayed on to bacterial 

 emulsions through an atmosphere of pure carbon dioxide, the gas having been 

 prepared by the action of hydrochloric acid on marble and purified by passage 

 through a solution of nitrate of silver. 



Experiments which have been recorded by Dr. Charles Slater* showed that 

 it was improbable that under the time conditions of our experiments carbon 

 dioxide itself would have any action on the bacteria ; but we first tested the 

 action of the gas by passing it rapidly through bacterial emulsions for 

 periods of 60 minutes, and found that no degree of germicidal action was 

 manifested. 



The results of a few experiments in which the discharge was sprayed on to 

 the bacterial emulsion through an atmosphere of carbon dioxide are given in 

 Table VIII. 



Table VIII. 



Species. 



B. typhosus . 



B. pyocyaneus 

 B. prodigiosus 



Current at 100 volts 



supplied to motor 

 driving the alternator. 



Duration of exposure 

 to the discharge. 



amperes. 



mins. 

 15 

 30 

 45 

 60 

 60 

 60 

 60 

 15 

 30 

 60 

 60 



Result. 



+ 

 



Scanty growth. 

 

 

 

 

 + 

 + 

 

 



When the discharge is sprayed on to the bacterial emulsion through an 

 atmosphere of carbon dioxide, distinct germicidal effects are obtained in some 

 experiments ; but, as was the case when the discharge occurred in an 

 atmosphere of hydrogen, we found that peroxide of hydrogen was taken up in 



* ' Journal of Pathology and Bacteriology,' vol. 1, p. 468 1893. 



