(410) 
Whilst in the case of the passage from the secondary motor 
neuron to the primary neuron we have to consider only the 
passage from one single neuron to another single neuron, (this 
latter however receiving probably also stimuli from other secondary 
neura: commissural cells, cerebellar and sensible neura etc.) we 
know for certain that in the case of the sensible neura every 
peripherie sensible neuron is related to numerous secondary neura. 
An elementary stimulus, applied to one single sensible neuron of 
the first order, will therefore needs rouse to action several secondary 
neura Furtheron we shall have occasion of referring again to this 
fact. 
Meanwhile we may state with absolute certainty that no sensation 
is possible after a peripherical stimulus, unless at least three suc- 
cessive neura have been roused to action, and also that, if we 
desire a sensation explaining the cause of the stimulation, — in 
other words an associative sensation — at the very least four suc- 
cessive neura must be in function, but most probably a great 
many more. 
First of all we will examine what becomes of our law in the 
case of a stimulus being transmitted to several excitable organs, in 
such a manner that the effect of the stimulus on the most peri- 
pherie neuron is supposed to form the stimulus for the following 
neuron. We take thus for granted here that the effect of the original 
stimulus e.g. the potential wave extending itself along the peripheral 
neuron forms the adequate stimulus for the next neuron. 
Very strong arguments may be forwarded in favour of this view, 
whilst a combating of it, as took place only very recently on the 
physiological congres at Turin, does not imply the whole of the 
conclusion from the there alleged experiments. For the moment | 
think our view may safely be considered as an orthodox one. 
The stimulus Z, applied to a peripheric neuron, operates an 
effect that, as has been proved elsewhere, may be represented by: 
—B,(R—C)) 
E, = A,i1—« orale lle sk NRN 
This formula may also be written in a slightly altered form: 
—b R 
E, — are € . e 7 . . . . . (2). 
wherein: 
di == b= GB; en ¢; = —T 
1 
