(6553 
for the sense of sight by Auperr and lately by means of radioscopie 
experiments by BECLERE. One glance at the curves of AUBERT will 
show us, that in ali probability these curves may be expressed with 
very sufficient accuracy by the term of restoration in our formula (4). 
Formula (15) offered us a complete image of the course of the 
magnitude of effect. For very feeble stimuli this formula can be 
greatly simplified. We know that for minimum-stimuli magni- 
tude of stimulus and effect are nearly proportional, consequently we 
may, without committing a mathematical error, apply the time-factor 
to the stimulus instead of applying it to the effect. Moreover with 
such small stimuli the dissimilation may safely be neglected. We 
may then write for the effect: 
PS pt B(l—e")] pl . 4. a « (21) 
Where subminimum-stimuli are concerned, if t=0,ApR< pC. 
Through the influence of B(1—e—*), after a sufficient time having 
elapsed, the formula will be transformed to: 
Re RCM BRO A A wah ego) 
in which it is possible that p(A+ B)R>pC. In other words: 
circumstances may occur, rendering it possible that subminimum- 
stimuli still cause an effect, if only the duration of their time of 
action be long enough. The truth of this fact is known so well, 
that it would be useless to give instances here. 
Now we are enabled also to explain the initial deviation from 
our law, mentioned in the three former communications. WALLER 
demonstrated in his essay that, concerning the sense of sight, the 
graphical representation of the relation between stimulus and effect 
resembled somewhat the shape of an S, stretched longitudinally. 
This lower curve, placed convex to the z-axis, is perfectly explain- 
able by the fact, that we were dealing with time-stimuli, causing 
the subminimum stimuli still to operate an effect. 
I think I may refrain here from an alteration in a formula 
expressing this curve. This much only I wish to indicate: that 
this might be possible e.g. by substituting for the constant c in 
our stimulation-law an exponential function of Rs; the latter then 
would stand thus: 
(. —6R 
{ — BR—«'1—« ) | . 
ee ALY it 
I give this formula here because it may be maintained on purely 
physical grounds, because at the same time by means of it we may 
get indeed some conception about the nature of the constant c, about 
the threshold-value; and this conception shows us the threshold- 
Fae as) 
