sd 
Physiology. — “A new group of antagonizing atoms.” Il. By 
Mr. T. P. Frensrra, assistant at the Utrecht Laboratory for 
Physiology. (Communicated by Prof. Dr. H. ZWAARDEMAKER). 
(Communicated in the meeting of May 27, 1916.) 
In a previous paper') I have described experiments showing the 
property of uranium to serve as a sabstitute for potassium in RiNGeR’s 
mixture, also when it has been freed from its transformation products. 
Another element of another group of the periodical system of 
MENDELEJEFF, viz. thorium possesses the same property. 
However, with this element, the action may be provoked entirely 
or partially by one of the transformation products of thorium, viz. 
radiothorium, which bas properties similar to those of thorium, so 
that it is impossible to remove it from this element. 
My method in examining this element was that used in my ura- 
nium experiments, with this difference only that the mean tempe- 
rature in the present series was 18° C. | 
The new fluid was prepared from potassium-free RINGER’s mixture, 
denoted (as in our first paper) by (R—K). An average of 50 mgrms 
of thoriumnitrate was added per litre. A dose smaller than 40 mgrms 
per litre could on no account be used as it did not activate the fluid. 
The chances also were that by adding too much thoriumnitrate, the 
fluid would have a poisonous effect upon the heart; it will be seen 
below that when 100 mgrms was added per litre of (R— K) the 
circuiating fluid could not make the heart resume its pulsations. 
Another property of thorium had also to be taken into account, 
viz. thoriumnitrate will be precipitated, though slowly, as thorium- 
oxid in the slightly alkaline RiNGERr’s mixture. 
The fluids required for the experiment were prepared immediately 
before use, as we wanted all the thorium to be in solution. I also 
often observed that the fluid, after standing for about 24 hours, was 
inoperative ; a residue had then been thrown down upon tbe bottom 
of the flask. 
After the frog’s heart, subsequently to its being tied up, had been 
fed with the circulating common RiNGER’s mixture for fifteen minutes 
the latter was replaced by (R—K). This circulation was continued 
till a standstill of the heart ensued. 
The thorium-containing (R—K) was then administered, upon which 
the heart began to beat spontaneously and regularly, as at the 
beginning of the experiment. 
1) Proceedings of the Kon. Ac. v. Wetensch. Vol. XIX p. 99. 
