( 442 ) 



Ai2_ bBR 



(5) 



As a rule, however, lliis forniiila may not he applied in the 

 case of psychical processes, because the above-slated conditions have 

 not been fulfilled. It is impossible to suppose the case of a peripheral 

 stimulus hitting oidy one single peri[>heral neuron, or of one single 

 gronj) of neurones being exposed uniformly and with equal force to 

 that stimulus. 



Let us see, what happens when a sense-organ in the living human 

 organism is subjected to a stimulus. For instance we may consider 

 the action of pressure on the skin. 



Suppose the compressing object to be in contact with a limited 

 surface of the skin al tiie moment the pressure commences. We 



may take it for granted that all end- 

 ■<<yy>i I- organs situated within the limited skin- 



"I surface in direct contact with the com- 

 ]tressing ol)ject, undergo an equal and 

 uniform i)ressure, and that in the case 

 of this i)ressure being increased, its action 

 will remain uniform. To the neurones con- 

 nected with the nerve terminations ^7, rtf,a,rz, 

 our deduced law (5) may be therefore 

 applied. As soon as the ])ressure increases 

 the skin-surface will undergo a change 

 of shape and be compressed (see fig. 1). 

 This implies that nerve-endings b, h, situ- 

 ated outside of the originally conqu-essed 

 surface, will also enter into an excitatory 

 state. If this deformation be a sliulit one, 

 only the nearest end-organs h, h will be 

 conq)ressed. By increased })ressure the nu)re distantly situated ones 

 c, c, d, d etc. will also be stimulated. To all these end-organs, 

 situated outside of the originally compressed surface, impulses are 

 given, which are conilucted to the central nervous system. From all 

 the combined impressions finally results the sensation by which our 

 judgment is decided. 



The neurones connected with J), h c, c d, d etc. will likewise obey 

 the law of stimulation and effect. The intensity of stimulus however 

 is different for all these neurones, and also different from that for the 

 neurones a, a, a. Therefore, whilst for the neurones aad, the expression 



dR ,f^>'^ 



p = — = A' 



E R 



o o o ^ c, cr. 



■ > i o o 

 cl c V» ; Sl. i \f3 • c ! t\ 





Fis. 1. 



