343 
into thoriumoxide. By determining the weight of the residue we were 
in a position to caleulate the amount of thoriumnitrate in 2 c.c. of 
the fluids. Thus we were enabled to add so much of the fluid to 
(R—K) that it contained precisely 50 mgrms of thoriumnitrate per litre. 
As an addition to RiNGER’s mixture of a large quantity of the 
fluid, strongly acidified with nitric acid, would alter the reaction, 
which should of all things be carefully avoided’), it was essential 
to concentrate the fluid as much as possible. When 2 c.c. of the 
fluid produced a residue of about 25 mgrms of thoriumoxide, the 
fluid was in a suitable condition to supply the thoriumnitrate for the 
thorium-containing (R—K). A special investigation, in which rosolic 
acid was used as an indicator, taught me that the thoriumnitrate- 
solution should be added to (R—K) to such an amount, that the 
reaction of this liquid was not altered perceptibly. 
The behaviour of the thoriumnitrate solution, treated in this manner, 
was similar to that of the thoriumeompound that bad not been 
purified in the process of precipitation with ammonia. 
It appears then ‘that there is no question about contaminations 
with potassium or rubidium, and moreover that the transformation 
products, radiothorium excepted, cannot induce the action. It may 
be, therefore, that the radiothorium is the active constituent. 
We have already communicated at the beginning of this paper 
that, if 100 mgrms of thoriumnitrate is added to (R.—K.) the fluid 
has a toxie influence upon the heart, through which it is allowed 
to pass. We now considered it essential to discover whether the 
toxic action could be arrested by increasing the amount of calcium. 
Consequently 200 mgrms of calciumehloride were added to the 100 
merms of thoriumnitrate-containing potassium-free fluid. When a 
stream of this fluid passed through the heart, the cardiac action was 
normal, as was the case with the smaller antagonizing dose. 
Thus, if the quotient 
‘ 
Th (NO,), : CaCl, 
is #, the limit of toxicity for thoriumnitrate is passed. Ah addition 
to the (R—K) of 150 mgrms of thoriumnitrate brings the above 
qnotient up to 7. Another addition of 400 mgrms of calciumchloride 
is still required to bring about a normal action of the heart. 
Only thus far can the antagonism be watched experimentally. 
When 200 mgrms of thoriumnitrate is added to the fluid a precipitate 
1) Mines. Journal of the Marine biological Association, Vol. LX, No, 2, 1911. 
