384 
It is a moot point as yet whether this action of radiation is direct 
or indirect. 
It may be, namely, that the radiations first liberate the potassium 
from the potassium-dépôts*), which are present in the cardiac muscle 
and that only then this liberated potassium, diffusing to the circulating 
fluid, causes the function to revive. 
This possibility could not be ignored a priori, it being a fact that 
during the radiation rather considerable quanta of potassium may 
quit the blood-cells and perhaps the heart-cells’). 
One of these days I was in a position to carry out an experimentum 
crucis. 
There is namely antagonism between «- and g-rayers. When applied 
coincidently with the same activity, they counter-balance each other’s 
action completely. 
This antagonism also obtains with external polonium-radiation 
(a-rayer) and internal appliance of potassium (g-rayers). This became 
evident when a frog’s heart, which had been brought to a standstill 
by removing the potassium from the circulating fluid, and had 
recovered its beats again through polonium, ceased beating again 
after being given a physiological dosis of potassium, whereas it 
resumed its pulsations both by removal of polonium and by that of 
potassium. 
When the polonium was removed, the potassium gradually regained 
its influence; when the potassium was removed, only the after-effect 
of the a-radiation remained. 
From the existence of the antagonism polonium-potasstum we must 
conclude that in this case there is a direct action of radiation. 
For, if the liberation of potassium-atoms (supposing it to occur) 
1) In the cells of the cardiac muscle there is a rich store of potassium. It is 
strange that this permanent substance is of itself not competent to keep up the 
function. This inactivity cannot be due to incapacity of the radiation of the 
potassium-dépôt to reach as far as the seat of automaticity. To W. E. RINGER 
and to myself the radiation seemed to be too penetrating for it. Nothing less than 
a tissue sheet of 1 m.m. thickness is capable of lessening by half the high pene- 
trating power of potassium. I have therefore been obliged to relinquish my 
original hypothesis. | am now inclined to look for the explanation in the 
coincident presence of iron. The cells of the cardiac muscle contain iron atoms 
where also the potassium-atoms are located. Consequently the miniature magnetic 
fields surrounding the iron atoms, will dislodge the g-particles of the potassium. 
It may, therefore, be considered whether perhaps this circumstance constitutes 
an obstacle for outward radiation. 
Biologically, various explanations are given, starting from the inactivity of 
continuous causes and the stimulation of temporary ones. 
2) Researches not published yet. They will be recorded elsewhere. 
