348 



On the Nature of the Toxic Action of Electric Discharge upon 



Bacillus coli communis. 

 By J. H. Priestley and E. C. Knight. 



(Communicated by J. Bretland Farmer, F.B.S. Received February 13, — Bead 



April 10, 1913.) 



Introduction. 



In a recent paper, Thornton* has drawn attention to some results he had 

 obtained in experiments upon the bactericidal action of electric discharge. 

 Plates of agar were infected with bacteria of various species, and subjected, 

 under different conditions, to the discharge from an electrified point. The 

 plates of agar were subsequently incubated and observations taken of the 

 development of colonies from the surviving bacteria. From experiments 

 upon these lines he concluded that the ionised air, i.e. the small current 

 (the whole of the current passing from the point was about 4 micro-amperes) 

 produced by his discharge methods, proved fatal after longer or shorter 

 periods to all the species of bacteria subjected to it. 



This conclusion is of considerable interest, suggesting, as it does, the 

 possibility of electrical treatment of tissue attacked by pathological bacteria, 

 with a view to retarding bacterial action. Our attention was attracted to 

 this paper by the fact that its conclusions seem at variance with some 

 conclusions previously arrived at by one of us in conjunction with 

 Miss E. M. Lee, in an investigation carried out at the University of Bristol, 

 of which only a brief preliminary note has so far been published,f pending 

 the further experiments which Miss Lee hopes to be able to carry out. 



In this research cultures of the sour-milk bacillus, B. Bulgarians, were 

 subjected to small electric currents, and observations were made to determine 

 the effect of such treatment upon their vitality. Contrary to Thornton's 

 experience it was found that current densities below about 58 micro-amperes 

 per square centimetre served to increase both the fermentation power of 

 the bacteria as determined by electrical conductivity, and also the rate of 

 growth as determined by countings. The fact that the current density 

 required to produce any inhibitory effects in these experiments had to be 

 greater than about 60 micro-amperes per square centimetre may have been 

 due to the fact that in these cases the electric current was derived from 



* "Influence of Ionised Air on Bacteria," ' Koy. Soc. Proc.,' 1911, B, vol. 84, p. 280. 

 + " The Influence of Electricity on Micro-organisms," J. H. Priestley and E. M. Lee, 

 'Brit. Assoc. Eeport,' 1911, p. 603. 



