102 
containing R.-K. nor with the ordinary Rincer’s mixture adminis- 
tered after it. A prolonged circulation of uranium-containing R.-K. 
caused the heart to resume its normal beats after intervals about 
similar to those observed in the above experiment of arresting the 
heart’s action by means of R.-K. 
In three cases the heart, which after the ligature did not resume 
its beats with the ordinary Rincer’s mixture, acted regularly with 
uranium-contaming R.-K. 
In the first place we now tried to find out if this unexpected 
action of uranium nitrate might perhaps be due to contamination 
with potassium. If this were so the contamination could not possibly 
be more than 5 perc. as was borne out by our investigation *). 
However, as an addition of 10 mgrms of potassium chloride to R.-K. 
did not act favourably upon the heart, it appeared that an action 
of potassium was out of the question. 
In the second place we tried to ascertain whether the effect of 
uranium nitrate might be ascribed to uranium X, which is invariably 
present in chemically pure preparations of uranium-compounds. There- 
fore the uranylnitrate, which acts like uraniumnitrate, was freed 
from uranium X after Soppy and RusseLr’s method *). This uranium- 
X-free uranylnitrate then appeared to exert the action just as the 
uranylnitrate, which had not been purified after the same method. 
The antagonizing action of calcium chloride on the toxic effect of 
potassium chloride has been carefully observed by J. Lone *). 
As with regard to this subject, this investigator experimented upon 
Fundulus, he obtained quantitative results that could not be obtained 
in my experiments upon an organ very sensitive to osmotic pressure. 
In RiNGER’s mixture used by me the number of the molecules of the 
two salts potassium chloride and calcium chloride are in the ratio of 1:1. 
If in RiNcer’s mixture we substitute uranylnitrate for potassium 
chloride the ratio of the molecules is 
UO: (NG), CaCl let: 
If we add 50 erms instead of 25 grms of uranylnitrate per litre 
to R.-K. it induces a standstill in diastole. This then is the limit of 
the toxie action of a definite quantity of calcium salt. 
In other words a ratio of the molecules: 
1) | wish once more to express my thanks to Prof. ScHoorL for enabling me 
to ascertain this with the aid of a spectroscope of the Pharmaceutical Laboratory. 
2) Phil. Mag. Bd. XVIII, 6 Series, 1909, p. 623. 
3) Bioch Zeitschr. Bd. 32, S. 308. 
