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sheath has undoubtedly not the entirely passive significance of the 
insulator in the electric cable (just as the axone cannot be compared 
to the wire), it nevertheless certainly does not take part directly in 
the transmission of the process of stimulation. The axone, certainly, 
is directly involved in this transmission. 
With the varying size of the animal species the volume of the 
axone always varies proportionally to half the square of the volume 
of the ganglion cell. The length 7 and the area of the cross section 
q of the axone (like that of the nerve fiber) indeed vary (as was 
discussed above with regard to the nerve fiber *)) in inverse ratio 
to each other, so that their product /q remains the same. Hence 
the product /q varies proportionally as 4 C?. 
Let us consider in this connection the propagation of the process 
of stimulation in the nerve fiber. 
On discharge of the ganglion cell (we shall confine ourselves to 
the efferent neurone; what follows holds inversely for the afferent 
neurone) potential energy of some form must certainly be consumed 
to supply motive energy in the nerve fiber. Let us suppose this to 
be performed by a layer of anions (or other material particles) 
placed in the cross sectional plane of the axone. It leaves the 
ganglion cell with a velocity v, travels the whole path to the other 
end of the axone, and assumes there a state of rest. This layer, 
whose mass is proportional to g, must have possessed a potential 
energy in the ganglion cell proportional to /q, and obtained a kinetic 
energy, equal to this, proportional to } qv’. 
We also found /g proportional to 4 C?, from which follows that 
Y 
v is proportional to an As for animal species having the same form 
q is proportional as P°22 or P*hs and C as Poi or Phs, we find 
v proportional as P16 or Ps. This is the same ratio in which the 
nucleus volume increases with increasing body weight. The velocity 
of the metabolism of the cytoplasm and the velocity of the process 
of dissimilation im the axone varies proportionally with the increase 
of the nucleus volume; we must therefore consider the movement in 
question as having begun in the cytoplasm with a velocity which 
1) Comp. my communication “On the Relation between the Quantities of the 
Brain, the Neurone and its Parts, and the Size of the Body. These Proceedings 
Vol. XX, p. 1828—1337. The areas of the cross sections of analogous nerve 
fibers of Man and the Mouse referred to above, are based on direct measurements 
of the diameters of the axones by Irvine Harpesty. 1 assumed double the cross- 
seclional areas of the axones for the nerve fibers, in virtue of researches by 
Donatpson and Hoke and others. 
