1048 
menced under the influence of an excess of uranium. The continuous 
line marks the results of a series of experiments with fluids containing 
besides the antagonistic. salts, the sodium chloride and the buffer 
also 200 mgrms of calcium chloride per litre. Under it is seen a 
dotted line, illustrating the same for circulating fluids containing only 
100 mgrms of calcium chloride. 
Also the antagonism of uranium for radium-radiation (through 
a thin micawall) respectively, mesothorium-radiation (through a thin 
glass wall) is easy of determination. From the balance-point of the 
antagonists potassinm-uranium the heart may, through exposure to 
radiation, resume its normal beats in a wonderfully short time, in a few 
minutes. When adding some uranyl-nitrate a standstill will ensue 
from which the heart will recover again on exposure to radiation ». 
In the condition of equilibrium the radiation is evidently on the 
side of the potassium, opposed to the uranium. 
It is especially the last experiments, which we made repeatedly, 
that show distinctly that nothing but the radioactivity of the uranium 
counterpoises the influence of the radiation (through a mica- or a 
glass-wall). If so the potassium-uranium antagonism must be entirely 
ascribed to these canses. 
Obviously we feel inclined to deduce from the detected antago- 
nism an index for the biological radioactivity of potassium and to 
place it alongside of the photochemic respectively the electric; but 
as yet an impediment is met with in the complicate influence 
(counteracting) of the calcium, which (in Fig. 3) originated two 
curves of a similar character, one for the simultaneous addition 
of 100 and another for that of 200 mgrms of calcium chloride 
per litre. 
1) A prolonged exposure brings about another standstill which will be followed 
by pulsation after the addition of uranium, not after that of potassium. Gradually, 
however, a condition manifests itself whose nature | have not been able to make 
out, and which I will provisionally term the secondary condition of radio-activity. 
Its peculiar feature is that the heart will beat only with a RrnGer-solution con- 
taining neither potassium nor uranium. When criticizing these experiments due 
regard should be paid to the presence of the minuie amounts of uranium X in 
addition to the uranium. 
