66 W. M. BALDWIN. 



a loss of color reaction of solutions from prolonged exposure to 

 the rays. Very careful histological examination under high- 

 power magnification has failed up to the present to detect a 

 change in the color of the absorbed stain after raying, or to give 

 evidence of a redistribution of the stain in the cytoplasm. 

 Moreover, a series of experiments in which normal paramoecia 

 were stained by trypanblau solution which had previously been 

 rayed for periods varying from five to thirty minutes, failed to 

 demonstrate either an injurious effect of the rayed stain upon the 

 organisms or an increased rapidity of absorption by the organ- 

 isms of that stain. The cause for the increased susceptibility 

 of the organisms to X-ray energy is to be found apparently 

 in some factor which is operative only when X-rays act on the 

 cells in the presence of the stain. 



