839 
only when attached through adsorption to the surfaces of the cells, 
and not when they are located at various distances from the cells. 
An improved adsorption, by which a larger number of a certain 
group of ions attaches itself to the cells in a circulating fluid of 
a given composition, improves the result elicited by these ions. 
There is a simple means to detect sensibilizers for radioactivity. 
One has only to start from radio-active antagonism ’). 
We, therefore, preferred to experiment on the heart of a cold- 
blooded animal, because the cells of this organ, the seat of automa- 
tie movement, are washed directly by the circulating fluid. 
The heart of an eel or a frog beats only when, given the further 
necessary conditions, a radio-active component is present in the 
circulating fluid in the proper dosage. It does not matter whether 
the element under consideration is an «-rayer or a B-rayer (our 
normal g-rayer is potassium). When applying the «- and the 3-rayer 
simultaneously, the quanta may be counterbalanced so as to inhibit 
each other’s effect completely. At such a moment there is a standstill. 
A slight balance on the one side or the other will restore automaticity, 
The dosage of «- and g-rayers in the circulating fluid must be 
much smaller in summer than in winter. When taken alone, 5 mgr 
of potassium chloride or 0,1 mgr of uranylnitrate per litre circulating 
fluid is in summer sufficient to maintain the automaticity of sensitive 
hearts. In winter at least 20 mgr of potassiumchloride or 10 mgr of 
uranylnitrate per litre is needed. Accordingly the summer-, and the 
winter-equilibria differ very much. In summer a combination of 20 
to 30 mgr of potassiumchloride and 0,1 mgr of uranylnitrate (per 
litre) may arrest the hearts action; in winter this result can be 
achieved only by 40 mgr of potassiumchloride and 10 mgr of uranyl- 
nitrate. 
After having secured an equilibrium, no matter in what season, a 
number of substances will give a shifting, which again restores 
automaticity. Among the anorganie components it is especially the 
caleium-ion to which we must ascribe a great influence; among the 
organic substances | found a number of substances having in common 
the property of considerable surface-activity (as observed for the 
boundary layer air-water). 
Shiftings may be observed on either side. When on the a-side, 
so that a uranium-beat ensues, fresh potassium has to be added to 
obtain a standstill again. When the shiftings are on the g-side, 
uranium must be added to produce the same effect. 
1) Kon. Akad. v. Wetensch. 27 April 1917. © 
