SUSCEPTIBILITY OF CELLS TO RADIUM RADIATIONS. 173 



left for only two hours in a small drop. But the radiated cells 

 display a marked shortening in the time required for destaining, 

 or, in other words, they show a considerable increase in permea- 

 bility, the change beginning very soon after the exposure to 

 radium commences. At the end of four hours the cells are still 

 alive but are for the most part motionless. If the exposure is 

 longer continued the cells die, showing the characteristic signs of 



cytolysis. 



The second figure ~ho\vs the result of a larger number of tests. 



hours of Radiation 



1234 



-glOO 



C 



S 95 



-o 



80 



o 



87S 



7 



Wl 



a> 

 P 



50 



c o 



unlrc 



Rolaiatc 



Cell' 



1 i \ i-rii.i'Ki-. . 



I li-- !! . t of i.i.li.iti..ii . 



Since they were made during the course of ni,m\- \\vt/k- the con- 

 trols varied somewh.it. although on any one day they weiv \r\ 

 uniform. The time required for destaining is here given in per- 

 centages of the control time which is reckoned as 100 per cent. 

 The curve clearly indicates that the normal semi-permeability of 



