( 476 ) 
In the psychophysical law of Wrper-FECHNER we find for the 
absolute and relative differential threshold-value: 
AR 
AF =-eonst. XR. vand == CONE. wt ee (A 
ie. the relative threshold-value is constant. 
Almost all experiments concerning the question of the correctness 
of the Weper-Frcuner law, have tended to prove this last condition. 
The results obtained by them are well-known. Neither FecHNer, 
nor HerLMHOLTZ, nor Kéyic, nor BRODHUN, nor MüLLER—LYER, 
nor the English, American and French investigators have been able 
to afford definite proofs for the absolute constancy of the differential 
threshold-value. 
Most of them have been led by their experiments to the conclu- 
sion that over a definite area the relative threshold-value was smallest, 
and that it became greater as well above as below that area. This 
is beautifully demonstrated by the experiments of STANLEY HALL, 
Yuzera Morora, AUBERT, HELMHOLTZ, Kénig—Bropuun and many 
others, who all found an ,optimum” in the curve of intensity above 
and below which the relative threshold-values rose. 
Considering now our formula (16) for the relative threshold-value, 
deduced from our law for the relation between stimulus and effect, 
we find: 
AR en 
RK k 
This formula may again be represented by a curve. In what 
manner will that curve progress? To know this we ask in the first 
place whether there is a maximum ora minimum. This last is proved 
to be the case. There is a minimum for: 
R= 
llen 
If however we compare the curve represented by (14) with curves 
that may be obtained from the results of the above mentioned expe- 
riments, then it becomes clear that only for the sense of weight a 
somewhat sufficient acccordance is obtained. 
By the experiment of Kénic and Bropuun is shown clearly, that 
