On tHe THEORY OF GALVANOTROPISM 447 
entirely, with a stimulation of peripheral elements. That 
these elements are not excited by a current passing longi- 
tudinally may depend upon a fact which Maxwell and I 
discussed more fully in our paper, “Zur Theorie des Gal- 
vanotropismus,”’ namely, the orientation of the elements. 
5. In the experiments just described, especially in those 
in which the central nervous system is traversed by a longi- 
tudinal current, the central nervous system behaves like a 
homogeneous whole, one side of which is entirely in anelec- 
trotonus, the other in catelectrotonus. This result differs 
from those obtained by Maxwell and myself in Crustaceans. 
In these it seemed as if the phenomena observed could be 
explained in a satisfactory way under the assumption that 
the central nervous system does not go into electrotonus as a 
homogeneous whole, but that the individual elements (seg- 
ments?) are each composed of a catelectrotonic and an 
anelectrotonic portion, and that the effect of the current 
as a whole is made up of the effects of the current upon 
the individual elements (segments?). Must we now do away 
with this assumption, which is most probable in the case of 
the galvanotropism of Crustaceans, because in another class 
of phenomena, namely, the excitation of the glands in a differ- 
ent class of animals (salamanders), we find a different be- 
havior of the central nervous system? I think not. I 
have often convinced myself of the fact that even closely 
related animals, even different varieties of the same species, 
may behave absolutely differently heliotropically, geotropi- 
cally, and stereotropically; not to speak at all of our experi- 
ence concerning the artificial reversal of tropisms. I also 
consider it entirely possible or probable that in one class of 
animals the central nervous system may behave as a homo- 
geneous whole toward the current, while in another class it 
may behave as though composed of a series of individual 
1 Pfltigers Archiv, Vol. LXIII (1896), p. 121. 
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