16 Comparative Neurology. (January, ; : 
COMPARATIVE NEUROLOGY. 
BY S. V. CLEVENGER, M.D. 
HAT can we say of the nervous system of Protozoa, but — 
that it exists in a diffuse undifferentiated state? If we 
speak of a nerve force it implies the existence of a nerve, and 
herein we have the mystery explained. I do not believe in a 
nerve force after the general acceptation of the term, as a sort of 
aura residing in and produced by nerve cells. Let us see how 
much a reconstructed view will account for the hitherto unac- 
countable. There are certain natural “forces” or vibrations of — 
matter, called sound, heat, light, electricity, etc. Expose albu- 
men to the influence of any or all of them and determinable 
motions are produced in its mass. Protoplasm has a definite 
molecular composition which never fails to be susceptible to 
these influences. The contractile phenomenon is not a whit more 
of a mystery than the beautiful laws of electrodynamics as de- 
duced by Ampére from the fundamental experiment of Cérsted: 
1. Two currents which are parallel, and in the same direction, at- 
tract one another. 1. Two currents parallel but in contrary direc- 
tions, repel one another. To demonstrate this, one current should 
be fixed and the other movable. In a few words the Amceba is 
the medium for the movable current while its pabulum is equiva- 
lent to the fixed current which attracts the animal. I do not 
mean to lay this down as actually the case, for the causes of 4 
Ameebic movements are multiplex, from which, as might be ex- 
pected, there would be multiplicity of changes in its sarcode. 
But this alone would indicate how sufficiently the laws of phys- 
ical forces may some day go to explain the protoplasmic motions. 
We see that all matter is mobile. The molecules of the Amoeba 
EES eee 
eit 
Sa Sa a af 
are not force proof, and these forces would, from the very homo- a 
geneity of the mass, pass in varying directions through the animal 
as governed by extrinsic causes. But as soon as differentiation be- 
gan, by even as simple a process as an induration of one part of the 4 
protoplasm, currents must be deflected from their former courses.  ~ 
Huxley considers Kleinenberg’s fibers of the Hydra as internun- 
cial, and hence the primary form of a nerve. In this case we have ~ 
a contractile muscle with a nerve differentiated from, and con- 
tinuous with the muscle. How has this come about ? 
Immediately upon the definite location of tissue which is more — 
