348 BIOLOGICAL EFFECTS OF RADIATION 



as a sensitizer (77) . Huber (87) obtained similar results by 4 hr. exposure 

 to direct sunlight, toxicity being judged by either hemolytic power in 

 vitro or lethal effects on laboratory animals. Both papers show oxygen 

 to be necessary for this effect. Various other data pertinent to the 

 theory of photodynamic action are also given by Huber, 



It seems much more probable that the photoprocess involves oxida- 

 tion, as this work of Huber indicates, and as Roux and Yersin suggest 

 in the case of visible light, than that it is a reduction, as suggested by 

 Hertel (84) on the basis of experiments on this toxin and various enzymes 

 using light of X ::^ 2800 A. Hertel found 10 min. irradiation sufficient 

 to reduce the toxicity of diphtheria toxin to much less than 25 per cent. 

 This is much more rapid than inactivation by direct sunlight, but there 

 are no clues as to the relative energy flux in the two cases. 



Hartoch, Schiirmann, and Stiner (75) observed rapid destruction of 

 diphtheria toxin by ultra-violet light (Nogier-Triquet " Unterwasser- 

 brenner"), toxic, antigenic, and antitoxin binding powers being about 

 equally sensitive. 



Welch (162) tested the relative stability of the original bouillon and 

 the purified toxin prepared by Gross' method which eliminates most 

 of the nitrogen and leaves a clear, colorless toxin. This purified toxin is 

 much more quickly inactivated by the light of a carbon arc. The effect 

 is presumably due to screening by components of the bouillon other than 

 the toxin, as suggested by the author (cf. page 349 under Tetanus Toxin). 



Baroni and Jonesco-Mihaiesti (13) also observed inactivation of 

 diphtheria toxin by ultra-violet light. 



X-ray effects were studied by Gerhartz (70). Various conditions of 

 irradiation, using "soft" or "medium hard" tubes, were tried and 

 evidence of some destruction of toxin obtained, but the small number of 

 animals tested leaves the results far from quantitative, and Morgenroth 

 (120) criticizes the paper severely on this basis. Gerhartz's reply in the 

 same number of the same journal adds nothing new. Evidently an 

 effect of X-rays on diphtheria toxin is as yet not definitely proven. 



Fabre and Ostrovsky (52, 53), however, found detoxication when 

 they added 1 microgram of "radium" (Ra element or RaS04?) to each 

 milliliter of toxin and allowed the mixture to stand for 10 to 43 days. 

 Many desirable details are lacking in these papers, e.g., the description 

 seems to imply that the radium was ultimately injected into the test 

 animals, which seems improbable and undesirable. Their conclusions, 

 therefore, still leave some possible doubt as to any appreciable effect of 

 radiations of large quantum value on the properties of diphtheria toxin. 



Tetanus toxin was also very early found to keep less well in the light 

 than in the dark. Tizzoni and Cattani (158), in 1891, showed that in 

 bouillon cultures both bacteria and toxins had been destroyed by 4,^ 

 months in diffuse daylight, provided air (i.e., oxygen) was present. 



