ACTION OF LIGHT ON MICRO-OKGANISMS 343 



and it will be seen later that as regards a layer of water, 

 even 1^ foot in depth, intervening between the source 

 of insolation and the object insolated, Buchner found 

 that it had no appreciable effect whatsoever, at any 

 rate in the case of the micro-organisms with which he 

 experimented, viz., typhoid and cholera, Bacillus Coli- 

 communis, Bacillus pyocyaneus, and Bacillus prodi- 



giosus. 



The extraordinary results obtained by Arloing, 

 pointing to the more refactory nature of the bacillar 

 than the spore forms of anthrax towards insolation, led 

 Eoux l to submit the whole question to an experimental 

 reinvestigation. The method adopted by Eoux was as 

 follows : 



A drop of blood containing anthrax bacilli was 

 inoculated into the aqueous humour obtained from the 

 eye of an ox. This was cultivated for ten days, and 

 finally all bacillar forms destroyed by an exposure of 

 the liquid for ten minutes to a temperature of 70 C. 

 One drop of this culture was then deposited on the 

 bottom of a sterilised test-tube, the mouth of which was 

 subsequently sealed up in the flame of the blow-pipe. 

 Fine capillary glass tubes were simultaneously com- 

 pletely filled with the same culture fluid and their ends 

 sealed in the flame. In the test-tubes, therefore, about 

 20 c.c. of air were present, whilst the capillary tubes 

 contained no air at all. These tubes were all exposed 

 during the same length of time to a July sun, the tem- 

 perature inside the tubes not exceeding 39 C., even on 

 the hottest days. At the end of the insolation one of 

 the test-tubes and one of the capillary tubes were 

 opened, and in the case of the former sterile bouillon was 

 added to the tube, whilst the whole contents of the 



1 ' De 1'Action de la Lumiere et de 1'Air,' Annales de Vlnstitut Pas- 

 teur, vol. i., 1887, p. 445. 



