78 BIOLOGY AND TECHNIQUE 



that anthrax spores are more quickly destroyed by direct sunlight 

 than are the vegetative cells. These findings require further 

 confirmation. 



It has been shown by various authors that the influence of sun- 

 light is not to be attributed in any way to temperature, nor always 

 to a direct action of the light upon the bacteria, but depends largely 

 upon photochemical changes produced by the light rays in the 

 media. . Richardson 8 and Dieudonne 9 conclude that under ordinary 

 aerobic conditions in fluid environment peroxide of hydrogen is 

 formed under the influence of light. Novy and Freer 10 believe that 

 the bactericidal effects in fluids noticed as a result of exposure to 

 light are too strong to be explained by the formation of small 

 quantities of peroxide of hydrogen, and attribute this action to 

 organic peroxides formed under the described conditions, such as 

 the peroxides of diacetyl, benzoylacetyl, and others. These views 

 are somewhat strengthened by the fact that exclusion of oxygen 

 from media markedly diminishes the bactericidal power of light. 11 

 That the photochemical changes alone, however, do not explain this 

 action follows from the fact that dried bacteria, not surrounded by 

 media, are subject to a similar action. 12 



In analyzing sunlight in regard to its bactericidal power, it has 

 been found by various observers that the most powerful action is 

 exerted by the ultraviolet spectral rays, whereas the yellow, red, 

 and ultra-red rays are practically innocuous. 13 



It is of importance to note that sunlight has been found also 

 to have a strong attenuating influence 14 upon some bacterial poisons, 

 as shown by the experiments of Ferri and Celli upon tetanus toxin. 



Electric light exerts a distinct bactericidal action when applied 

 in strengths of 800 to 900 candle power for seven or eight hours. 15 



Rontgen or X-rays are said by Zeit, 18 Blaise and Sambae, 17 and 



* Richardson, Jour. Chem. Soc., i, 1893, Kef. Deut. chem. Gesells., xxvi. 



9 Dieudonne, loc. cit. 



10 Novy and Freer, 3d Ann. Meeting Assn. Amer. Bacteriologists, Chicago, 1901. 

 "Eoux, Ann. Inst. Past., ix, 1887. 



12 Dieudonne, loc. cit. 



13 Ward, Proc. Eoyal Soc., 52, 1893. 



14 Ferri and Celli, Cent, f . Bakt., I, xii, 1892. 



15 Dieudonne, loc. cit. 



18 Zeit, Jour. Amer. Med. Assn., xxxvii, 1901. 



17 Blaise and Sambae, Compt. rend, de la soc. de biol., 1896. 



