840 
The shifting does not at all prove that the substance, by which 
it is generated, is a sensibilizer; it only renders this probable. To 
ascertain this we have to find out the maximum-, and minimum- 
doses, between which the automaticity of the organ can be main- 
tained; the potassium limits are the most important. In summer 
these extremes vary with the individuality of the animal, and range 
from 5 to 20 and from 10 to 300 mgr. of potassium chloride per 
Litre, a low threshold corresponding with a low upper-limit, ete. ; 
in winter the extremes are more constant; 20—30 and 600—800 
mgr. potassium chloride per litre. Similar observations were made 
for the other radio-active elements, but I pass them over in silence, 
since these elements do not occur in the animal organism. The 
same holds good for the majority of the sensibilizers found by us. 
An exception is afforded by cholin and adrenalin, both hormones 
occurring in every organism. Their sensibilizing power for BECQUEREL 
rays is very strong, even when the dosis of cholin is one mgr. per 
litre of circulating fluid and of adrenalin 0,001 mgr. *) 
In the presence of one of these hormones the potassium-dosis that 
keeps up the heart’s action, may be reduced to half the normal 
dosis, nay, to less even. In summer, therefore, these dosages are 
extremely small, even '/, mgr. of KCl per litre. Then the greatest 
purity of chemicals is of the utmost importance. 
However, there is a difference: Cholin shifts a potassium-uranium 
equilibrium towards the potassium-side, adrenalin towards the ura- 
nium-side. Whether this difference will also manifest itself in normal 
life is still an open guestion. For aught we know, there is nowhere 
in the organism an a-rayer, unless it be the trace of rest-activity left 
behind by emanation, when it is inspired and expired in minimal 
quanta as an indifferent gas together with the atmospheric air. 
Potassium, cholin, adrenalin are normal constituents of the organ- 
ism. Accordingly, the study of their mutual relations is a true 
physiological study. | 
The bio-radio-activity of potassium has no temperature-coëfficient. 
Both the velocity of effect and the dosage remain the same with 
der lor ne 
The small differences lie within the latitude of the experimental 
errors. In this respect physiological radio-activity is analogous to 
photo -hemical actions, whose temperature-coefficient is likewise 
h W. LieBrecHT used for the same purpose but in another connection 0,05 
mgr. per litre. (Arch. int. de Physol. T. 15, p. 357). 
2) Summer- and winterdosage do not differ on account of the difference of 
temperature. We mention the difference in hormones as a possible cause. 
