DESTRUCTION OF TYPHOID AND COLON BACILLUS. 455 



The insolated bonilloii was tlieu kept in dift'use dayliglit for forty 

 days and again inoculated with the typhoid bacilhis. Within twenty- 

 four hours the tubes of bouillon became turbid and plates made from 

 them showed innumerable colonies. 



It is difficult to account for the eftect of insolation on culture media. 

 Roux in his experiments on anthrax found that insolation of bouillon 

 for two or three hours rendered it unsuitable for germination of the 

 spores, but if the bacilli were introduced they would thrive. He attrib- 

 utes this alteration to some chemical change which the culture media 

 undergo during the insolation. lie found also that if the insolated 

 media were kept in the dark or in diffuse daylight for a time, the orig- 

 inal nutritive qualities were restored and germination of spores would 

 rake place. Geisler and Janowski observed the bactericidal properties 

 of insolated media, but the latter could lind no chemical alteration in 

 such media. 



Percy Frankland in his chapter on action of light on micro-organisms^ 

 concludes from the results obtained by many investigators "that the 

 effect is due to a process of oxidation jtossibly brought about through 

 the agency of ozone or peroxide of hydrogen, or both; that all appar- 

 ently direct low temperature oxidations require the presence of water. 

 And inasnuTch as the bactericidal action of light is unquestionably a 

 case of low temperature oxidation, there is the strongest presumptive 

 evidence, as well as weighty experimental evidence, that moisture, 

 which practically means the possibility of the presence of peroxide of 

 hydrogen, or of some similar material, is essential for its manifesta- 

 tion."^ Westbrook^ found that old broth cultures of the tetanus bacil- 

 lus iu an atmosphere of hydrogen were not in the least affected by 

 exposure to sunlight, either in regard to their virulence or their raj^id- 

 ity of growth on reinoculation. 



When the same culture was sealed up iu the presence of air the 

 micro-organisms were not only killed, but the material was completely 

 harndess when inoculated into white mice. It was however, possible 

 to obtain vigorous and virulent growths from cultures which had been 

 made quite innocuous by the action of the sun. Oxygen was used up 

 in the process. Under ordinary circumstances one might be tempted 

 to explain the effect of sunlight in destroying bacteria by the drying of 

 the organisms exposed to it. especially in the case of those bacteria 

 which do not form spores, but our experiments show that desiccation 



'Micro-organisms in water, page 890. 



^Gelatin, to which were added different amounts of the peroxide of hydrogen, was 

 inoculated with the bacillus typhi abdominalis and poured into plates. Those 

 plates iu which more than one part of the peroxide to 5,000 of gelatin was used 

 were sterile. 



■' Sonic of t!ie effects of sunlight on tetanus cultures, Jour, of Pathol, and Bacteriol., 

 Ill, Nov., 18u4, page 71. 



