769 



foi' potassium cliloride from 20 to 50 mgr. p. Liter 



,, rubidium chloride from 30 to 70 ,, ,, ,, 



„ a uranium salt from 0,6 to 5 ,, ,, ,, 



„ thorium nitrate from 2 to 10 ,, ,. „ 



Fixing the typical winter-doses for the four salts at 100, 150, 

 25 and 50 mgrms per Liter, an appropriate correspondiug summer 

 dosis will be 50, 70, 1 — 5, and 1 — 10. In summer, however, the 

 individual differences are larger and the hearts are more sensitive 

 to the toxic effect of too massive a dosis and to the absence of the 

 radio-active element when the dosis is small, so that the proper 

 concentration for each salt is more difficult to find. 



Approximate Metaldosis. 

 (mgrms) 



It seems to me that for the Rana esculenta a somewhat smaller 

 quantum of radio-active element will generally suffice than foi' the 

 Rana temporaria, but on the other hand its toxic dosis is also 

 smaller. What factors determine the quantity for every type of 

 animal we have not yet been able to decide. My impression is that 

 the temperature, provided it be maintained, the exposure to the sun 

 on the preceding days and the nutritive condition are of some 

 influence here. Dr. S. dé Bokr will discuss the summerdosage in 

 detail in a special article in the "Archives Néerlandaises". 



In an earlier volume of these Proceedings (Vol. XIX p. 1043) we 



