SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 95 



RESULTS 



Decolorized cells appeared in the green plates where the wave 

 lengths of ultraviolet proved to be lethal or radiotoxic. (See pi. i.) 

 The times of first appearance, i. c, the periods elapsing between 

 irradiation and visibility of the colorless regions, are tabulated for 



PROPORTIONALITY OF RADIOTOXICITY TO THE PRODUCT OF THE 

 INTENSITY AND THE EXPOSURE TIME 



In a previous paper (Meier, 1934) the assumption was made that 

 the radiotoxic effect is proportional to the product of the intensity 

 of irradiation and the duration of irradiation. In other words, a 3- 

 minute exposure to x intensity should produce a given radiotoxic 

 effect in the same reaction time as a i -minute exposure to 3 x in- 

 tensity ; or again expressed differently, the reaction time is inversely 

 proportional to the lethal dose, which is the product of the exposure 

 time by the intensity. 



