635 
the heart resume its beats after it had been brought to a standstill 
by the potassium-free Rineur’s mixture. About 15 minutes after the 
radium-circulation has commenced maximal contractions occur at 
irregular intervals at first, but presently they become as rhythmic 
as previously in the same heart. If the radium-RinGer’s mixture is 
replaced by potassinm-free Riycer’s mixture the radium-pulsations 
persist another hour or so. Finally the heart stops beating again. 
By applying radium-containing fluid again the beats recommence 
deliberately within a few (8-10) minutes. On the other hand, when 
administering normal Rincer’s mixture a radium-heart’s action is 
arrested abruptly, from which it recovers only after an hour. These 
results are quite in accordance with those previously obtained with 
uranium and thorium and which were then considered to be due 
to the accumulative effect of the hardly diffusible ion and the rapidly 
incoming potassium-ion. The question of antagonism, being theore- 
tically a matter of great moment, is kept back for a later paper. 
Thanks to Prof. ScHoort’s kindness we were also now in a position 
to determine any accidental amount of potassium both in the radiam- 
fluid and in the reagents. In all cases a Litre of potassium-free, resp. 
radium-containing circulating fluid contained less than 2.5 mgrms of 
potassium, an amount which, of itself, is incapable of maintaining the 
heart-beats, as has been shown in frequently repeated experiments. 
In three experiments the emanation was removed from tbe radium 
solution used for the preparation of the circulating fluid (first by 
boiling, then by neutralising) *). In these cases also we succeeded in 
making the heart resume its beats; with a well-measured dose this 
was even effected perfectly in the normal space of time. 
It is evident, therefore, that Potassium, Rubidium, Uranium, 
Thorium, and Radium ean replace each other, as far as the heart 
is concerned, in the Rineger-circulating fluid, provided that doses are 
taken in proportion to their total radio-activity. With all of them 
the recovery of the cardiac action as well as its toxie inhibition 
vecur in the same way. The most normal doses are : (See page 635). 
I beg leave for the present to merely make mention of the facts detected. 
lt goes without saying that they give ample scope for far-reaching 
speculations, but I wish to postpone them, as new experiments are 
being made, which, I feel confident, will throw more light upon 
these results. 
As observed above, potassium is the only radio-active element that 
plays a part in ordinary life. It is very likely, however, that an 
important rôle is played only by the free, mobile potassium, that 
1 Rurgerrorp in Marx’s Hdb. d. Radiologie Bnd 2 S. 422. 
