( 469 ) 
Physiology. — Dr. C. WINKLER presents in the name of Prof. 
J. K. A. WeRTHEIM SALOMONSON an essay, entitled: “4 new 
law concerning the relation of stimulus and effect.” (UI). 
In our two former essays we have demonstrated the relation, 
existing between magnitude of stimulus and effect. We proceeded 
to test the law, by which this relation is expressed, to the results 
obtained experimentally by some physiologists, and found this law 
prevailing for all direct and indirect stimulation of the muscles, for 
galvanic as well as for faradic stimulation, for stimulation with 
ascending or descending make or break shocks. The law was 
further proved to prevail too for the electrical stimulation of nerve- 
fibres. Lastly we found the facts, kown to us about the relation 
between stimulus and effect for the eye, to be in accordance with 
our law, for all stimulation either by light or by electricity. 
Our present essay intends to examine if our law may be applied 
to sense-perception; in how much therefore it might be called a 
psychophysical law (in the biological sense of course). At the same 
time we will try to investigate its connection with the well known 
psychophysical law of WEBER-FECHNER. 
Whilst for the nerve-muscle preparations the relations are very 
transparent — there we have only one conducting organ: the nerve 
fibre, and one organ receiving and transforming the stimulus: the 
muscle — in the case of the senses the relation is infinitely more 
complicated. 
Here in the first place there does exist a peripherical organ, 
receiving the stimulus, e.g. the retina-elements, the Cortian organ, 
the tactile corpuscles etc. These are directly connected to the primary 
sensible neuron or form part of it. From this primary neuron 
a stimulus is transferred to a secondary neuron ending in the 
thalamus opticus; thence the stimulus passes on to a third sensible 
neuron, its endarborisation being placed in the cortex cerebri. To 
reach the sensible cortical centrum therefore a stimulus must pass 
at least three neura. And even after this having happened, we 
know to a certainty that only a first step has been taken 
towards the bringing about of a “sensation”. We have only suc- 
ceeded in raising the general impression of light, touch, hearing or 
smell, without a single indication as to the nature of that sensation. 
This is achieved oniy when still higher neura — associative 
neura — have been brought into action and when the stimulus has 
been conducted from the projection-systems to the associationpaths. 
31 
Proceedings Royal Acad, Amsterdam, Vol. IV. 
