( 711 ) 
nature of the transformer is not changed in consequence of the 
stimulation. The elastic after-phenomena in muscles show most 
clearly, that also this law which we might call the law of the 
invariability of the transformer, holds only by approximation. Led 
by my own experiments I hope to demonstrate, that besides these 
small continuous variations the constant A can also show discon- 
tinuities. In consequence of these two laws of approximation involved 
in the summation, the interpolation formula of FEcHNER is only 
applicable for a limited interval, within which no discontinuities occur. 
The method used by Fecuner for the determination of the constant 
of integration which occurs in formula (III), is erroneous for physio- 
logical systems, as it is based on the existence of a threshold value, 
while the formula, in virtue of its deduction, premises an ideal 
reflex-apparatus. In accordance with its sense this formula of inter- 
polation has proved to be of general application in physiology. 
To confirm this I shall only refer to the investigations of 
Dewar and M’Kenoprick!), of WALLER ®*), of WINKLER and VAN 
WAYENBURG °), of LANGELAAN *) and so many others. Also botanists 
have found it applicable, as appears from the experiments of PFEFFER 5), 
Massart °), VAN RYSSELBERGHE “). 
The apparent uniformity of the natural phenomena to which this 
formula leads, is not founded on the nature of these phenomena, but 
is due to the character of interpolation formula of this form. 
Experimental psychology which has discovered this interpolation 
formula through the investigations of WEBER and FECHNER, sub- 
stituted the value of the sensation for / in formula (ILI). If we 
consider the physiological law as being given first and the conformity 
with the psychological law as not accidental, then we may say that 
experimental psychology extended the ele law of distribution also 
to that quantity, whose variation appears to our consciousness as a 
change in our sensation. 
Looked upon from this point of view, FECHNER has come in con- 
tradiction with his theory, which explained the logarithmical relation 
from the form of the distribution law. For the case that this psy- 
1) Trans. Roy. Soc. Edinb. 1876, vol. 27. p. 141. 
2) BRAIN, 1895, vol. 18. p. 200. 
3) Van WayensurG, Disserlatie. 1897. 
4) Archiv f. Physiol. 1901. p. 106. 
5) Prerrer, Unters. Bot. Inst. Tübingen, 1884, lter Bd. 3tes Heft, p. 395. 
6) Massart, Bull. Acad. roy. Belgique, 1888. 3me Série T. 16, p. 590. 
7) VAN RyssELBERGHE, Extrait Mém. couronnés. Acad, R. de Belgique, T. LVIII. 
47 
Proceedings Royal Acad. Amsterdam, Vol, IV, 
