(346) 
In direct consequence of the initial condition, i. e. that Z being 
= 0, £ too must be = 0, it follows that EZ, = A, therefore (6) becomes 
ESA See 82). Shee A 
For practical use we ought still to add a restriction to this expres- 
sion. We know that a stimulus operates an effect only then, 
when its intensity has risen above a certain initial value, the so-called 
threshold-value, ,Schwellenwerth’’. Therefore we are not allowed to 
count the full value £, but only the remainder obtained by substrac- 
ting the threshold-value; the latter being expressed by C, our formula 
finally then will be found to stand thus : 
E=Aj}l—e—-24@—O} for RC : eee 
In this way we have established a formula, expressing a relation 
between magnitude of stimulus and effect, based on a few supposi- 
tions initially taken for granted. These premises were: 
1°. that the increment of stimulus being very small, the increment 
of effect was proportionate to it, 
2°. that the quantity of transformed substance in a very small 
particle of time was proportionate to the extant quantity of transfor- 
mable substance (Law of mass-action). 
30, that the effect was proportionate to the quantity of transformed 
substance. 
For the present I do not intend testing the appropriateness of 
these premises. If the suppositions are inexact, then the law too shali 
prove infallibly inexact. If on the other hand the law is proved to 
be in accordance with the results of experiment, this sole fact will be 
sufficient proof for the probability of our premises. Undoubtedly 
however we will have even then to examine more closely the signi- 
ficance of the premises, from which we started. 
What now is the real meaning of the formula (8). In the first. 
place I wish to lay some stress on its analogy with several well- 
known physical laws. | 
For the charging of a condensator through a non-inductive resistance 
we possess a similar formula, wherein however the quantity of elec- 
tricity extant is substituted for Z, and the time t for the stimulus 
R—C,. For the monomolecular reactions too we find a similar expres- 
sion, indicating the quantity of substance transformed after a definite 
