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of target cells (neurons), whereas older embryonic cells
could not. Herein lies the natural division of my work
into the two following chapters according to the results
obtained: separation of day 7-8 cells (Chapter II) and
separation of day 12-13 cells (Chapter III). Although these
results precluded my ability to obtain purified populations
of immature glia as I originally had hoped for, many unique
and interesting experimental phenomena occured in the
purified cultures. These have led to a better (or more
confused, depending upon the point of view) understanding
of the potentials and restrictions of embryonic cells when
their development is perturbed in a controlled fashion.