346 MICRO-ORGANISMS IN WATER 



with spores, bacilli were introduced (a drop of blood 

 from an animal dead of anthrax, for example), the 

 latter developed freely, thus showing that by the 

 exposure to light the bouillon had been only so 

 far modified as to prevent the germination of the 

 spores, but not so as to inhibit the multiplication of the 

 bacilli. 



These results afford an explanation of the fact 

 observed by Arloing, which he attributed to the 

 greater powers of resistance in the presence of light 

 possessed by the bacilli over the spores of anthrax. 

 Eoux's experiments show that this depended upon 

 the bacilli being capable of growing in the modified 

 insolated bouillon, whilst the spores were unable to 

 do so. 



That the presence or absence of air during insola- 

 tion has an important effect upon the vital activity of 

 the spores of anthrax has been shown very conclu- 

 sively in the preceding experiments. Eoux further de- 

 monstrated this by showing that if sterile bouillon 

 was placed in vacuous tubes or in an atmosphere of 

 carbonic-acid gas and was then insolated for several 

 hours, on being subsequently inoculated with anthrax 

 spores, the latter were able to germinate. On the other 

 hand, if the same bouillon was subsequently insolated 

 in the presence of air, the spores were unable to ger- 

 minate when introduced into it. Eoux also found that 

 when culture media, which through previous insolation 

 in the presence of air had been rendered unsuitable 

 for the germination of spores, were subsequently kept 

 for a certain time in the dark or in diffused light their 

 original nutritive qualities were restored. 



These exceedingly interesting and important experi- 

 ments of Eoux, by showing that the greater insus- 

 ceptibility towards light of the bacillar than the spore 



