ACTION OF LIGHT ON MICRO-ORGANISMS 341 



them not only remained alive, but acquired a more or 

 less pronounced degree of immunity. 



Nocard * objected to Arloing's conclusions as to the 

 greater susceptibility to light of the spores than the 

 bacilli of anthrax, by suggesting that during the expo- 

 sure of the spores they had developed into bacilli, and 

 that the light had acted on the latter, and not on the 

 spores, as maintained by Arloing. 



Straus, 2 in order to bring experimental evidence 

 to support this assertion of Nocard's, inoculated an- 

 thrax spores into sterilised distilled water, whilst, as a 

 control, a series of inoculations was also made into 

 sterile bouillon ; both sets of tubes were exposed to nine 

 hours' insolation. The result of these comparative 

 experiments was that all the spores in the bouillon 

 were found to be dead, whilst those immersed in dis- 

 tilled water yielded growths when inoculated into 

 sterile bouillon. Straus explains this difference by 

 observing that whereas in broth the spores were able 

 to germinate into bacilli in spite of the exposure to 

 light in the distilled water, w^hich does not afford a 

 suitable medium for the germination of the spores, they 

 remained, therefore, in the condition of spores, and 

 were thus able to withstand the action of light. 



Arloing 3 soon after published another memoir, con- 

 troverting Straus's conclusions. In this paper he refers 

 to experiments in which he distributed anthrax spores 

 in broth contained in vessels placed in contact with ice 



1 Eecueil de Medecine veterinaire, 1885. 



2 ' Charbon de 1'Homme et des Animaux,' Societe de Biologie, 1886, 

 p. 473. 



3 ' Les Spores du Bacillus Anthracis sont reellement tuees par la 

 Lumiere solaire,' Compt. rendus, 1 Mars, 1887, vol. civ. p. 701. See 

 also another paper published by Arloing in reply to Nocard : ' Influence de 

 la Lumiere blanche et de ses Rayons constituants sur le Developpement 

 et les Proprietes du Bacillus Anthracis,' Archives de Physiologic nornnile, 

 .et pathologique, 1886, vol. vii., No. 3, pp. 209-235. 



