282 Cc. U. ARIENS KAPPERS 
of Loeb and Budgett that the kathodie tropism, following the 
law of irritation, is chiefly dependent on intra-cellular proto- 
plasmatic conditions and that the extra-cellular medium. does 
not act such a part here as it does in anodal extensions. 
Indeed, it seems more probable that the later outgrowth of 
the dendrites as well as their secondary contraction, including 
the shifting of the cell body is a process different in principle 
from the anodal outgrowth of the axis-cylinder, a process for 
which a greater functional completeness of the neurone is neces- 
sary, and that we may only say that the character of the chemical 
constitution of the dendrite is not such that it would interfere 
with it by a disturbing anodal process. 
There are still three questions that may be mentioned in this 
discussion. 
MONOAXONISM AND POLYDENDRITISM 
The first question is why only one axis-cylinder leaves the 
cell, one which becomes complicated only by collaterals which 
proceed perpendicularly from it during its course, while from the 
cell-body, a large number of dendrites may and generally do 
grow out to several centers of stimulation (monoaxonism and 
polydendritism). 
To explain the monoaxonism we may first consider what 
would happen if two kathodie currents traversed the young 
neuroblast at the same time. In a purely polar tropism, as 
galvano-tropism preéminently is, it is a familiar feature that the 
object under the influence of the current places itself so that the 
influence is equally great on both sides of the object. Only 
then does the state of equilibrium begin. 
J. Loeb“ in particular has shown this repeatedly, for example 
in his 7th Lecture, in which he speaks of radiating energy and 
heliotropism, and points out that the orientation of a simple 
object will continue until all its parts lie at the same angle with 
reference to the influence. 
40 J, Loeb. Vorlesungen iiber die Dynamic der Lebenserscheinungen. Leip- 
zig, Joh. Ambr. Barth, 1906, p. 171. 
