I 



Phenomena of neiirobiotnxis in the optic system 289 



noniena of neurobiotaxis and that this selectivity ¡s based on simultanei- 

 ty of function, i. e. on correlation 1. 



This capital law of psychology consequently proves to have a forma- 

 tive signiñcance and to be also the capital law of neurobiotaxis. 



After finding this law in the behaviour of the dendrites and cell-bodies, 

 it seemed interesting to know if it is also determining for the growth 

 and ñnal arrangements of the effectoíy parts of the neurone— the axon 

 which apparently grows out in a direction opposite to the dendritie 

 growth (fig. 20); thus not stimulo-petaly but stimulofugally on better; 

 stinitdo-concurrent . 



That indeed the development of the axon results from the stimulus, 

 was proved in this institute by Bok (fig. 21) who in a very interesting 



1 This is clearly proved by the following observations and deductions: Tn 

 lower water living animáis taste is a very important agent as an organ of sense 

 for the gills, taste evidently being a judge not of food alone, but also of respiration- 

 water. 



ín sonie bony-ñshes the taste-Duds are enormouslv developed (Hei-rick). So 

 in siluroid-fishes they not only cover the mouth and the gill-arches, but also the 

 head and the whole body, including the tail. In such animáis we find a consider- 

 able enlargement of the primary and secundary taste-tracts in the oblongata. 

 This increase of the secundary taste-tracts causes a ventral shifting of the motor 

 nuclei of the jaws and the gills towards those tracts. 



The nuclei of the eye-muscies however are not in the least influenced bv these 

 enlarged taste-systems. On the contrary if the fase, longitudinalis posterior — a 

 path of optic and vestibular reflexes — increases, as occurs in sharks, the position 

 of the eye-muscle-nuclei is influenced by it, but that of the gill-muscle- nuclei not 

 in the least. In other terms in the shifting of cells, there appears to be a verv 

 particular selection. By comparative anatomical investigations, we find this se- 

 lection to be caused by the fact that outgrowth and shiftings only occur between 

 stimulatively (or functionally; correlated elements. 



The correlative relation between eye-muscles and light-stimuli in one case and 

 the relation of the gill-arches and taste in the other, or generally expressed, the 

 relation of stimull in the periphery of the body determines and precedes the cen- 

 tral fibre-relation. 



Synchronic stimuli acting on or in particular parts of the animáis body, will 

 excite in the central nervous system an organic relation. After all, this is not a 

 surprising postúlate, since psychology taught us centuries ago that correlated (si- 

 multaneous) stimuli act an important part in education and instruction, learning 

 being nearly entirely based on association. The same is evidently the case with 

 the fiberconnections. 



Homenaje a Oajal • i<í 



