676° 
other as the volume of the nerve cell to that of its nerve fiber. 
This is of great significance in the mechanism of the neurone. 
Through the found proportionality of the volume of the plasm 
with P's it now becomes clear that in animal species of the same form, 
but of different sizes, the area of the cross section of the axis cylinder 
(and also of the nerve fiber) is in a relation of uniformity with the 
plasm of the nerve cell from which it proceeds. Hence this area 
varies as the 2/3 power of the plasm-volume, ie. by P% or Po, 
The volumes of homologous nerve fibers of animal species having 
the same shape, the lengths of which are proportional as P*%h or 
P33, must therefore vary proportionally as Ph or P055, And as 
the ganglion cel! constitutes only a very small part of the volume 
of the neurone (in the above described motor neurone of the finger 
muscles of man, e.g., the nerve fiber has 870 times larger volume 
than the ganglion cell), we may also say that the volume of the 
neurone, hence also the complex of neurones, which we call the 
brain, varies by the power %/ or 0.55 of the body weight.) 
Thus the rational character of this apparently incomprehensible 
power is clearly shown. 
At the same time, the mechanism of the neurone becomes more 
distinct. 
Also for species of different shape, as Man and the Mouse, we saw 
the volame of homologous, also analogous ganglion cells (functioning 
in the same way) vary proportionally as P°2* or Phs, and we may, 
therefore, assume that the volume of the plasm of these cells varies 
proportionally as P0 or P's, hence as the mean linear dimension 
(for uniform species, as every homologous linear dimension) of the 
body. The proportionality with the mean linear dimension of the 
body is, indeed, a necessary condition for the cooperation of ail the 
neurones in the nervous system, the nerve fibers of which inter se 
differ greatly in length. Consequently the relations of the elements 
of the neurocyte must be valid both for species of different shape 
and for species having the same shape. 
The existence of these fixed relations of volume of the 
1) The degree of accuracy of the data does not allow us to ascertain whether 
the volume of the neurone or only that of the nerve fiber varies proportionally 
as the square of the volume of the ganglion cell. Hence it may very well be that 
the ganglion cell, which besides being the station, is also the road for the impul- 
sions, at least as regards its plasm, must also be included in the proportional 
section of the nerve fiber. Then the volume of the neurone is at least almost 
exactly proportional as P or PS, 
ti 
