42 Biology of Bacteria 



a recent careful study of this subject Weinzirl * found that 

 when bacteria were placed upon glass or paper, and exposed 

 to the direct rays of the sun, without any covering, most 

 spore-bearing bacteria, including B. tuberculosis, B. diph- 

 theriae, B. typhosis, S. cholerae-asiaticae, B. coli, B. pro- 

 digiosus, and others are killed in from two to ten minutes. 

 Certain colors are distinctly inhibitory to the growth, blue 

 being especially prejudicial. 



Certain chromogenic bacteria produce colors only when 

 exposed to the ordinary light of the room. Bacillus mycoides 

 roseus produces its red pigment only in the dark. The 

 virulence of many pathogenic bacteria is gradually attenuated 

 if they are kept in the light. 



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

 tricity passed through cultures of bacteria have been found 

 to kill the organisms and change the reaction of the culture 

 medium; rapidly reversed currents of high intensity to 

 destroy the pathogenesis 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 

 recently made by Zeit,f 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 minutes 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 germi- 

 cidal. 



3. A continuous current of 100 milliamperes passed 

 through bouillon cultures for seventy-five minutes kills all 



* " Jour. Infectious Diseases," vol. iv., 1907, Supplement, No. 3, 

 p. 128. 



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



