1912.] The Electrical Conductivity of Bacteria. 341 



A thermometer was afterwards inserted, and could be readily removed to 

 take samples with a pipette. It was found necessary, on account of the 

 heat produced by the passage of the current, to pack the outer crucible in 

 ice, or, when the stronger currents were used, in a freezing mixture. The 

 temperature was never allowed to rise above 65° C. in one set of trials or 

 55° C. in another. Working at the lower current densities it was possible 

 to prevent the temperature exceeding the above limits for the whole time 

 of exposure, without stopping the current; but with the higher currents 

 this could not be done, and the time at - 3 ampere per square centimetre, 

 for example, of three to four minutes, was made up of half-minute runs 

 with the same time for cooling. About 70 exposures were made, of which 

 55 are given for the 65° C. limit. Cultures were taken as sterile when they 

 showed no growth after 24 hours' incubation at 37° C. 



05 IO 15 -20 -25 -30 



The results given previously of prolonged exposure to alternating 

 currents at current densities of the same order as the above prove that 

 sterilisation obtained by a few minutes' exposure, accompanied by rapid 

 changes of temperature, must be regarded as thermal rather than electrical 



