25 
After a darkening of 20 min. the response to 1400 M.C.S. has already 
much approached the response of cells adapted to the dark, which 
has been added for comparison in the 6% curve of fig. 3. 
TABLE III. Response to 1400 M.C.S. of cells, adapted to 64 M.C. at different 
points of time after the darkening. 
ui a5 2) maximum minimum 
Bie to Poe ee S a3 
zoë SES, in perc. 
So's wees after = ofthegrowth after in perc. 
* Sess in dark 
— -_= 
6/2 min. 5/o—T'/2 Ts Oe min. 102 114/2—13'/2 Mm. 98 
sd 6 —8 1 25101.G, 110 eee ee 86 
ie 5 —7 ea. 133 ee) a 78's 
BOS 4¥e—642- [5e ,, 148 Cee ee 73 
2 hours Bt TO ,, 152 17 een 85 
(full | 
adaptation) 
In the experiments of Tables Il and III the process of the dark- 
adaptation — increase of sensitiveness — has to some extent 
been graphically represented by the percentages of the maxima of 
growth attained. Yet the quantitative proportion of the sensitiveness 
at different points of time of the adaptation-process has not been 
expressed in them, but the increase of the reaction-energy, being 
the result of that increased sensitiveness. But it is more important 
to express quantitatively the increase of the sensitiveness itself, and 
for that it is necessary to determine the quantities of light, causing 
an equal effect at different points of time of the adaptation-process, 
in order to make the sensitiveness inversely proportional. For this 
we prefer to choose the minimum effect, which is still perceptible 
to us, ie. the limit or minimum-quantity, by which the light-growth- 
response occurs or with the classical term, the thresholds of stimulation. 
Since it seems quite evident, that the effect of the light-energy 
in the cell with increasing stimuli gradually appears as response 
of growth and increases, we should be with this stimulus-process 
— and probably a great many others — careful with the tendency, 
lying in the word threshold. For convenience’ sake we shall use 
the word here with that reserve. 
Experiments B. In order to draw a comparison with the sensi- 
tiveness of the cell still completely adapted to 64 M.C., the threshold 
of stimulation was determined in cells being in 64 M.C. 
When an additional 2000 M.C.S. was applied, no trace of a response 
