The Physical Basis of Mind: Being the Second Series of Problems of Life and Mind.Lewes, George Henry
Philosophy
The Physical Basis of Mind: Being the Second Series of Problems of Life and Mind.
Lewes, George Henry
Mind and body; Psychophysiology
136. From another point of view we must reject the hypothesis. Not
only does the evidence which points to the essential continuity in
structure of nerve cell and fibre discredit the notion of their
physiological diversity, but it is further supported by the fact
that although the whole nervous system is structurally continuous,
an immense mass of nerve-fibres have no _immediate_ connection with
ganglionic cells:--neither springing from nor terminating in such
cells, their activity cannot be assigned to them. To many readers this
statement will be startling. They have been so accustomed to hear
that every fibre begins or terminates in a cell, that a doubt thrown
on it will sound paradoxical. But there is an equivoque here which
must be got rid of. When it is said that every fibre has its “origin”
in a cell, this may be true if origin mean its _point of departure
in evolution_, for “cells” are the early forms of all organites;
but although every organite is at first a cell, and in this sense a
nerve-fibre must be said to originate in a cell, we must guard against
the equivoque which arises from calling the highly differentiated
organite, usually designated ganglionic cell, by the same name as
its starting-point. On this ground I suggest the term neuroblast, in
lieu of nerve-cell, for the earlier stages in the evolution of cell
and fibre. Both Embryology and Anatomy seem to show that cell and
fibre are organites differentiated from identical neuroblasts, with a
somewhat varying history, so that in their final stages the cell and
fibre have conspicuous differences in form with an underlying identity;
just as a male and female organism starting from identical ova, and
having essential characters in common, are yet in other characters
conspicuously unlike. The multipolar cell is not necessarily the origin
of a nerve-fibre, although it is probable that some short fibres
have their origin in the prolongations of cells. Although the latter
point has not, I think, been satisfactorily established, except in the
invertebrata, I see no reason whatever to doubt its probability; what
seems the least reconcilable with the evidence is the notion that all
fibres arise as prolongations from ganglionic cells, instead of arising
independently as differentiations from neuroblasts. The reader will
observe that my objection to the current view is purely anatomical; for
the current view would suit my physiological interpretations equally
well, and would be equally irreconcilable with the hypothesis of the
cell as the source of Neurility, so long as the identity of structure
in the axis cylinder and cell contents is undisputed.
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