38 



EFFECTS OF /3-RAYS OF DIFFERENT VELOCITIES 



number of rays struck the edges of the slit and were "reflected" in 

 all directions so that all the beams were contaminated by a consider- 

 able number of rays of velocity considerably greater or smaller than 

 the modal velocity of the beam. The only way the contribution 

 of these scattered rays to each beam could be accounted for was a 

 direct physical measurement made with the same apparatus as was 

 used for the physiological experiments. 



0) 



c 



■XJ 



J 



S 10 



InTensiTif of radiation 



so 



Fig. 3. Curve used to determine the relative intensity of the physiologically 

 effective radiation from its effect on the membrane of Nereis eggs. The points 

 are experimental results obtained with known intensities of heterogeneous radia- 

 tion. The line is the curve used in calibrating the experimental results with 

 homogeneous beams. Intensities measured in millicurie centimeters along the 

 abscissa. Membrane volumes measured in 100,000 cubic microns along the or- 

 dinate. Experiment of August 29, 1918. 



