o+2 
Thirteen times the same result was obtained, namely just as with 
uranium, the heart was restored at once to its normal condition. 
The contractions were at once normal as to extent and frequency ; 
the electrocardiogram also was quite normal again. There was no 
change of tonicity in this process. 
Now we wanted to note again the behaviour of the heart when, 
after the cireulation of the thorium-containing fluid, the common 
RinGeR’s mixture was again allowed to run through it. [t appeared 
that in this case a standstill ensued immediately, from which the 
heart recovered only when fed with (R—K) or with thorium-con- 
taining (R—K). The same phenomenon had previously been observed 
with uranium. For the present I take it that the accumulative effects 
of potassium and thorium or uranium are responsible for this standstill. 
We now had to consider the possibility that activity was conferred 
on the thorium either through contamination with potassium or 
rubidium, or through its transformation products. To solve these 
problems the thorium was purified in the following way : 
With strong ammonia the thorium was thrown out of a strong 
solution of thoriumnitrate, which yielded a precipitate of thorium- 
oxid. Any contamination of potassium or rubidium present in the 
thorium will remain in solution, a few traces excepted. These traces 
precipitated along with the thorium, cannot provoke the action, as 
it has been shown in our previous publication that the addition of 
5 mgrms of potassium chloride per litre of (R—K) is insufficient *). 
This precipitate was filtered off and subsequently washed three times. 
Now it was necessary to convert the thoriumoxide again into a 
soluble compound. It was, therefore, taken up with some water, and, 
while it was being warmed, dilute nitric acid was added cautiously, 
the reaction of the fluid being continually noted by means of small 
strips of litmus-paper. With a neutral reaction only an inappreciable 
quantity of the thorium-precipitate was dissolved. The reaction was, 
therefore, acidified by the addition of some more nitric acid, with 
the satisfactory result that a large part of the thoriumoxide was 
dissolved. A quantity of 2 e.c. of this fluid was now measured off, 
evaporated to dryness and heated till the thoriumnitrate was converted 
'\ Bottwoop’s *) experiment proved that when thorium is extracted with ammo- 
nia as a thoriumoxide residue, only radiothorium is thrown out of solution with it **). 
The mesothorium 1 and 2 and the thorium X remain in solution. The thorium 
is consequently freed from its principal transformation products, with the exception 
of the radiothorium. 
*) Ruruerrorp in E. Marx. Hdb der Radiologie Vol. Il, p. 491. 
**) RUTHERFORD 1. C. p. 459. 
