356 MICRO-ORaANISMS IN WATER 



bacilli (see Eoux's experiments), the following experi- 

 ments were made : — ^A flask of bouillon infected with 

 typhoid was insolated during twenty-two hours, at the 

 end of which time the liquid was quite clear ; by 

 means of a sterilised pipette about 1 c.c. of this bouillon 

 was transferred to another flask of sterile bouillon, 

 which had not been insolated, and was placed in the 

 incubator at 37° C. No growths made their appearance^ 

 showing that the typhoid bacillus had really been de- 

 stroyed. The original flask of insolated bouillon in- 

 fected with typhoid bacilli, which had remained quite 

 clear, was re-inoculated with fresh typhoid bacilli and 

 placed in the incubator at 37° 0. Turbidity quickly 

 followed^ showing that the insolated bouillon had not. 

 undergone any change rendering it incapable of sup- 

 porting the typhoid bacilli. 



It will be remembered that in Eoux's experiments 

 it was found that the bacilli of anthrax could flourish 

 perfectly in previously insolated bouillon, whilst the 

 spores were unable to germinate except in bouillon in- 

 solated in the absence of air ; hence, as Janowski's re- 

 searches in this direction only extend to bacilli, we have 

 really only a confirmation of the previous experiments 

 made by Koux on anthrax bacilli. 



Careful experiments showed that from four to ten 

 hours' insolation suflSced to destroy the typhoid bacilli. 

 Numerous investigations were also made to ascertain 

 which were the rays of the spectrum which exercised 

 this bactericidal efiect ; but as Janowski did not decom- 

 pose the white light of the sun with a prism, but only 

 separated out the rays by means of coloured solutions, 

 his experiments in this direction are less precise than 

 those of Geisler, to be mentioned below ; he is, however, 

 led to attribute the bactericidal action of light to the 

 chemical rays of the spectrum, inasmuch as the sun- 



