236 RADIOACTIVITY AND POTASSIUM 



both, into a less harmful one through a more rapid oxidation. Lind 

 has shown that penetrating rays can cause the formation of water 

 from and H and that H2O2 seems to be an intermediate product in 

 the reaction."* On the basis of these observations it is quite probable 

 that H2O2 is formed or that oxygen is activated in some other form 

 when penetrating rays go through the cells of the heart, and that the 

 rate of oxidation is increased in the cells of the heart. This might 

 explain Zwaardemaker's experiments on the restoration of the heart 

 beat by U, Th, and radium without compelling us to assume that KCl, 

 Rb, and even Cs act physiologically by radioactivity. 



CONCLUSIONS. 



1. The non-radioactive cesium ion can replace the potassium ion 

 almost quantitatively in solutions required for the development of the 

 egg of the sea urchin into swimming blastulae. 



2. Thorium chloride and uranium acetate cannot replace the potas- 

 sium chloride in the solutions required for the development of the egg. 



3. Thorium chloride and uranium acetate do not antagonize the 

 action of the potassium contained in sea water upon the development 

 of eggs. 



4 Lind, S. C, /. Am. Chem. Soc, 1919, xli, 551. 



