1906.] Action on Bacteria of Electrical Discharges. 77 



of pure hydrogen, for in this case ifc appeared as if this substance were the 

 active germicidal agent in certain cases which will be referred to in detail 

 further on. 



VIII. — Results of Experiments in which the Electrical Discharge was 

 Sprayed Through an Atmosphere op Various Pure Gases on to 

 Bacteria Suspended in Water. 



The remaining experiments which we have to describe were carried out by 

 spraying the electrical discharge on to the bacterial emulsion through an 

 atmosphere of one or other of the following pure gases : — Hydrogen, carbon 

 dioxide, carbon monoxide, and nitrogen. The object of these experiments 

 was, by discharging the current under conditions such that electrolytic 

 changes were likely to be reduced to a minimum, to observe the action of the 

 discharge and current on the bacteria without the concomitant germicidal 

 action of the nitrous and nitric acids which are formed under the ordinary 

 conditions when the discharges are used in medical practice. In some 

 instances we succeeded in our object, inasmuch as we found that when 

 electrolytic changes were inappreciable, or nearly so, we were able to expose 

 the bacteria to the action of the discharge for periods of 30 and 

 60 minutes without affecting their subsequent growth in any way. But 

 in many other experiments we found that, even when the discharge occurred 

 in an atmosphere of a pure gas, electrolytic changes resulted after a time, in 

 most cases probably depending upon the rising of water vapour in the tube 

 from the emulsion with the formation of peroxide of hydrogen and possibly 

 other germicidal substances. 



Experiments in an Atmosphere of Pure Hydrogen. 

 The hydrogen used in our experiments was prepared by the action of 

 diluted pure sulphuric acid on pure zinc, the gas being passed successively 

 through solutions of potassium hydroxide, potassium permanganate, and 

 silver nitrate. 



The gas thus prepared had no appreciable action on bacteria under 

 the time conditions of our experiments ; it was passed continuously for 

 90 minutes through bacterial emulsions such as those used in our subsequent 

 experiments, and sub-cultures made from the emulsion after the passage 

 showed that the gas had no injurious action. 



A few preliminary experiments were carried out with emulsions of 

 B. pyocyaneus and B. prodigiosus, the current being discharged from a brush 

 of twisted platinum wire suspended in an atmosphere of hydrogen 2*5 cm. 

 above the emulsion. The results are given in Table V : — 



