104 EFFECT OF OTHER AGENTS ON BACTERIA 



an electric current through a sodium chlorid solution brings about 

 an extremely complex change, as indicated in the folio wing equations: 



2NaCl = 2Na + C1 2 



2Na + 2HOH = 2NaOH + H 2 



4C1 + 2HOH = 4HC1 + O 2 



2NaOH + 2C1 = NaCIO + NaCl + H 2 O 



SNaCIO = NaClOs + 2NaCl 



Many of the products so formed, if in sufficient concentration, are 

 good germicides and would be, therefore, the agents causing death 

 instead of the electricity doing it. Moreover, the passing of an 

 alternate current through a medium may heat it sufficiently to kill 

 many bacteria. When the solution is properly cooled the action 

 of the current is practically zero. 



Zeit, who has made a very careful study of the effect of electricity 

 upon bacteria, summarizes his findings as follows : 



"1. A continuous current of 260 to 320 milliamperes passed 

 through bouillon cultures kills bacteria of low thermal death points 

 in ten minutes by the production of heat 98.5 C. The anti- 

 septics produced by electrolysis during this time are not sufficient 

 to prevent growth of even non-spore-bearing bacteria. The effect 

 is a purely physical one. 



"2. A continuous current of 48 milliamperes passed through 

 bouillon cultures for from two to three hours does not kill even 

 non-resistant forms of bacteria. The temperature produced by such 

 a current does not rise above 37 C. and the electrolytic products 

 are antiseptic but not germicidal. 



"3. A continuous current of 100 milliamperes passed through 

 bouillon cultures for seventy-five minutes kills all non-resistant 

 forms of bacteria even if the temperature is artificially kept below 

 37 C. The effect is due to the formation of germicidal electrolytic 

 products in the culture. Anthrax spores are killed in two hours. 

 Subtilis spores were still alive after the current was passed for three 

 hours. 



"4. A continuous current passed through bouillon cultures of 

 bacteria produces a strong acid reaction at the positive pole, due 

 to the liberation of chlorin which combines with oxygen to form 

 hypochlorous acid. The strongly alkaline reaction of the bouillon 

 culture at the negative pole is due to the formation of sodium 

 hydroxid and the liberation of hydrogen in gas bubbles. With a 

 current of 100 milliamperes for two hours it required 8.82 mg. of 

 sulphuric acid to neutralize 1 c.c. of the culture fluid at the negative 

 pole, and all the most resistant forms of bacteria were destroyed 

 at the positive pole, including anthrax and subtilis spores. At the 

 negative pole anthrax spores were killed also, but subtilis spores 

 remained alive for four hours. 



