1163 
Distance between mesothorium and the Uranyl nitrate added to the primary 
heart (mm). | mixture (mgrms). 
8 2 (2) 
6 5,5 
5 | 7 
4 
3 
2 
8 
12 
20 
1,5 | 30 
1 | 40 
When representing the data of the table graphically we get a 
curved line reminding one of an exponential curve. I, therefore, 
plotted the distances along the axis of the abscissae and along the 
axis of the ordinates the logarithms of the mgrms of uranium salt 
present in the successive equilibria over and above the 10 mgrms 
that from the outset were present along with 40 mgrms of potassium 
chloride per litre of circulating fluid. The curve thus originating is 
represented in the graph by a firm line. 
As the figure points out the curve of the logarithms of the 
uranium dosage, counterbalancing the radiation, is approximately 
straight. A slight deviation is noticeable only for the greater distances. 
This result is not what could be expected: alpha-rays do not 
come into play here, as the restoring influence is exerted through 
an aluminium sereen of 0,2 mm and even a leaden screen of 0.1 
or 0.2 mm. Of the remaining beta-rays much is absorbed in the 
heart, as was shown when the heart was contained in the leaden 
roof of a small ionising-chamber. The gamma-rays passed almost 
unchecked. 
There are additional reasons for stating that the beta-rays in casu 
are biologically active. From the experiments just described it follows 
that the essential part is to a great extent absorbed by tbe air. 
Already at the distance of 9.5 mm the quantum liable to be com- 
pensated by uranium is spent. At 6 mm only an equivalent of an 
extra addition of 5 mgrms of uranyl nitrate per litre, is present: 
the very quantum transmitted through a 0,2 mm aluminium 
sereen placed at close distance *). 
1) A radium preparation of 3 mgrm. has a uranium equivalent through an alu- 
minium screen of 0,1 mm. In considering such values we should of course also 
