62 Biology of Micro-organisms 



with reference to light. Non-pathogenic water protozoa 

 love the light and die in the dark. 



Electricity, X-rays, etc. Powerful currents of electricity 

 passed through cultures have been found to kill the organ- 

 isms and change the reaction of the culture-medium; rapidly 

 reversed currents of high intensity, to destroy the patho- 

 genesis of the bacteria and transform their toxic products 

 into neutralizing bodies (antitoxin?). Attention has been 

 called to this subject by Smirnow, d'Arsonval and Charin, 

 Bolton and Pease, Bonome and Viola, and others. 



An interesting contribution upon the " Effect of Direct, 

 Alternating, Tesla Currents and X-rays on Bacteria " was 

 made by Zeit,* whose conclusions are as follows: 



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

 bouillon cultures kills bacteria of low thermal death-points in ten min- 

 utes by the production of heat (98.5 C.). The antiseptics produced 

 by electrolysis during this time are not sufficient to prevent the 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 bac- 

 teria produces a strongly 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 libera- 

 tion of hydrogen in gas bubbles. With a current of 100 milliamperes 

 for two hours it required 8.82 milligrams of H 2 SO4 to neutralize i 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. 



5. The continuous current alone, by means of Du Bois-Reymond's 

 method of non-polarizing electrodes, and exclusion of chemic effects by 

 ions in Kruger's sense, is neither bactericidal nor antiseptic. The 

 apparent antiseptic effect on suspension of bacteria is due to electric 

 osmosis. The continuous electric current has no bactericidal nor anti- 

 septic properties, but can destroy bacteria only by its physical effects 

 (heat) or chemic effects (the production of bactericidal substances by 

 electrolysis). 



6. A magnetic field, either within a helix of wire or between the 

 poles of a powerful electromagnet, has no antiseptic or bactericidal 

 effects whatever. 



* "Jour Amer. Med. Assoc.," Nov. 30, 1901. 



