ACTION OF LIGHT ON MICRO-ORG ANISM S 339 



concentrated by means of a lens their growth was 

 impeded. The blue and violet rays of this gas-light 

 were found to act prejudicially upon the development 

 of both the spores and bacilli, and also impeded the 

 sporulation of the latter. 



In subsequent experiments on anthrax Arloing l 

 substituted the light of the sun for that of the gas- 

 burner. Chicken-broth was again employed as the 

 culture material in which the bacilli and spores were 

 exposed, and as soon as the day's insolation was over 

 the tubes were placed in a refrigerator to prevent any 

 multiplication taking place in the interval. Finally, 

 when the period of insolation was completed, in order 

 to ascertain whether the anthrax was still alive or not, 

 the tubes were placed in an incubator and maintained 

 at a suitable temperature. Arloing found that insola- 

 tion for two hours, when the temperature registered 

 was between 35 and 39 C., was sufficient to entirely 

 destroy the spores of anthrax. If, however, the expo- 

 sure was less than two hours, from 1 to 1^ hour, the 

 development of the bacilli took place only after 16, 18, 

 30, 72, or even 96 hours, whilst in those tubes kept in 

 the dark incubator at as nearly as possible the same 

 temperature as those in the sunlight the bacilli de- 

 veloped already in from 8 to 1 2 hours. If tubes con- 

 taining spores were kept in the incubator for from 24 to 

 48 hours at a suitable temperature for the development 

 of the bacilli, and were then exposed to the light, when 

 they contained presumably no spores, it was found that 

 2 hours' insolation was not sufficient to destroy the 

 bacilli, but that from 26 to 30 hours were necessary, 

 even in the presence of a temperature of from 30 



1 ' Influence du Soleil sur la Vegetabilite de Spores du Bacillus An- 

 thracis,' Compt. rendus, 24 Aout, 1885, vol. ci. p. 511. Also see a further 

 note published in the same volume, 31 Aout, p. 535. 



