NEUROBIOTAXIS 267 
While, however, it was evident that the approach of the 
dendrites and nerve cells to a territory (fig. 3) took place towards 
the center of the stimulation (as a stimulopetal or centripetal 
tropism), that is, against the nervous current of stimulation pro- 
ceeding from this center, the problem became much more diffi- 
cult to explain how the connection between correlated centers 
was effected by the axis-cylinder, since it was obvious that the 
axis-cylinder does not grow towards the stimulation (stimulo- 
petal) to meet it, but moves in the same direction as the stimu- 
lus-irradiation (stimulo-fugal or centri-fugal). 
BOK’S RESEARCHES: THE STIMULOGENOUS FORMATION OF THE 
AXON 
That the axis-cylinder. really grows with the current and 
that the irradiation of this current plays an important part in 
its growth has been proved and very carefuliy examined in this 
Institute by S. T. Bok, who got highly important results. 
Bok” found that when an axis-cylinder or a bundle of amye- 
linated nerve-fibers grows out and passes nerve cells on its 
way, these nerve cells can be activated to send out an axis- 
cylinder of themselves in a region perpendicular to the activat- 
ing axon or bundle (fig. 4). 
This fact was found with the fasciculus longitudinalis posterior 
in such a form as left no doubt, since it appeared that the motor 
nuclei which undergo the influence of this bundle were only 
activated according to the degree in which the fasciculus longi- 
tudinalis posterior had grown out. So the axons of the tri- 
geminal" cells first grow out, then follow the axons of the faci- 
alis cells, then those of the glossopharyngeus and vagus. 
The same was seen in the activation of the oculomotorius, 
abducens and hypoglossus nuclei which are activated by another 
influence of the same character. . 
2 Bok. Die Entwicklung der Hirnnerven und ihrer Zentralen Bahnen. Dei 
Stimulogene Fibrillation. Folia Neurobiologica. Bd. 9, 1915. See also Bok, 
Stimulogeneous Fibrillation. The cause of the structure in the nervous system. 
Psych. en Neurologische Bladen, Amsterdam, 1915. 
13 Concerning the Trochlearis. See the first-named original. 
