SUNSHINE AND LIFE 69 



Geisler's work in St. Petersburg is especially in- 

 structive in this respect, for by decomposing with 

 a prism the sun's light, as well as that emitted by 

 a i,ooo-candle-power electric lamp into their con- 

 stituent rays, he was able to compare the different 

 effects produced by the separate individual rays of 

 both these sources of light. 



The organism selected was the typhoid bacillus, 

 and it was found that its growth was retarded in 

 all parts of the two spectra excepting in the red, 

 and that the intensity of the retardation was in- 

 creased in passing from the red towards the ultra- 

 violet end of the spectrum, where it was most 

 pronounced of all. 



But whereas from two to three hours of sun- 

 shine were sufficient to produce a most markedly 

 deleterious effect upon the typhoid bacillus, a 

 similar result was only obtained by six hours' 

 exposure to the electric light. 



Dr. Kirstein, of the University of Giessen, in 

 the course of some experiments he made to ascer- 

 tain how long different varieties of bacteria can 

 exist when they obtain access to the air in the 

 form of fine spray, and subsequently, as happens 

 under ordinary circumstances, get dried up, noted 

 also the effect upon their vitality of exposure in 

 daylight and darkness respectively. For this 

 purpose the apparatus in which the experiments 



