SUSCEPTIBILITY OF CELLS TO RADIUM RADIATION-. 175 



the rays quickly raises the permeability above the limit and the 

 cell dies. But if it is low, the lethal point is reached only after a 

 prolonged exposure. 



A similar phenomenon is observed in eggs exposed during dif- 

 ferent ph.i-t - "f mitosis. At the metaphase their permeability, 

 as shown by I. yon iv and others, is notably greater than at any 

 other period : so also is their susceptibility . Ihaveshown 12 'hat 

 an amount .f radiation \vhich will induce a quickened cell di\ i-ion 

 in sea urchin when applied just before or after the meta- 



pha-e. ha- .i n 'tarding effect when applied at that period. That 

 i-. the ( i -11- are mop- -<-n-itive then than they are during the pn>- 

 pha-e or tclopha-e of mitosis. 



The -.tine re-uh- are obtained when other cytolytic agent- are 

 1 in pi. n e . .1 radium radiations. Lillie ( 14) finds that if freshly 

 li/eil sea urchin e^g-, which arc highly impermeable, 

 t re. ited uith hypotonic sea water they resist its cytolytic action 

 fur thirty minutes. But if they are placed in thi- -olution when 

 the clea\agi- furrow appears, they rapidly undergo rytoly-i-. 



It appears possible therefore that the susceptibility of cell- 

 may be rai-ed by the simple expedient of increasing their per- 

 bility by heat or by some other means. Thi- ha- been done 

 l>v Rhodenburg and Prime (7) in the experiments already citrd. 

 ll'.u far thi- method can be used in the treatment of abnormal 

 ti ue growths remains to be demonstrated. 



The fact that agents which differ so widely as do radium radia- 

 tion- and h\ po tonic sea water produce the -ana- effects under 

 -imilar i > IK lit ions suggests that the action of the-e rays, and al-o 

 other t \pe-of radiant energy, such as* ultra-violel light and alpha 



3, i- not peculiar to themselves. Indeed il may be -aid that 

 any of tin- rays which are absorbed at the surface of ihe <vll will 

 cause changes differing in no way from tho-e prodixvd by a great 

 variety of chemical cytolytic agents. 



The mori- penetrating beta ra\ -. tin- gamma, and X-ray- 

 appe.:r to be so -lightly absorbed at the -urf.n e oi , dl- \vhich are 

 freel\- iApo-i'd to them that they can produce little or no eff< 

 Ki. haul- i - ic-ti-d the permeabilit \ of \ariou- eggs and of Arcni- 

 cola lar\a- after an exposure to X-rays and found no evidence of 

 any increa-e. I h,i\e-hown that the rapid beta and the gamma 

 ray- of radium do not act on the surface layer of r<irtiia-< ini. 



