factors: (1) The development of the
cells and fibers of which it is composed, and (2) its general tone of
health and vigor. The actual number of cells in the nervous system
increases but little if at all after birth. Indeed, it is doubtful
whether Edison's brain and nervous system has a greater number of cells
in it than yours or mine. The difference between the brain of a genius
and that of an ordinary man is not in the _number_ of cells which it
contains, but rather in the development of the cells and fibers which
are present, potentially, at least, in every nervous system. The
histologist tells us that in the nervous system of every child there are
tens of thousands of cells which are so immature and undeveloped that
they are useless; indeed, this is the case to some degree in every adult
person's nervous system as well. Thus each individual has inherent in
his nervous system potentialities of which he has never taken advantage,
the utilizing of which may make him a genius and the neglecting of which
will certainly leave him on the plane of mediocrity. The first problem
in education, then, is to take the unripe and inefficient nervous system
and so develop it in connection with the growing mind that the
possibilities which nature has stored in it shall become actualities.

UNDEVELOPED CELLS.--Professor Donaldson tells us on this point that: "At
birth, and for a long time after, many [nervous] systems contain cell
elements which are more or less immature, not forming a functional part
of the tissue, and yet under some conditions capable of further
development.... For the cells which are continually appearing in the
developing cortex no other source is known than the nuclei or granules
found there in its earliest stages. These elements are metamorphosed
neuroblasts--that is, elementary cells out of which the nervous matter
is developed--which have shrunken to a volume less than that which they
had at first, and which remain small until, in the subsequent process of
enlargement necessary for their full development, they expand into
well-marked cells. Elements intermediate between these granules and the
fully developed cells are always found, even in mature brains, and
therefore it is inferred that the latter are derived from the former.
The appearances there also lead to the conclusion that many elements
which might possibly develop in any given case are far beyond the number
that actually does so.... The possible number