DE HISTORIA NATURAL 231
in the central nervous system, after nerve cells. They must
therefore perform a function of considerable importance and one
•which accounts for their presence, particularly among the myelin
sheaths of the white mat
ter.
In the grey matter
oligodendroglia cells are
found, though fewer in
number. Here they are
satellites for nerve cells,
appearing most frequently
about the neurones of me
dium size. It is a matter
of frequent observation
that satellite nuclei are
very rare about the large
pyramidal cells of the mo
tor area (Betz cells), also
about the cells of Purkinje
and the largest cells of
the p o n s and medulla.
T h o u g h oligodendroglia
cells are not found applied
to these neurone bodies,
yet in the bulb at least
they are to be found about
the origin of neuronal ex
pansions of s o m e large
cells which have no satel
lites proper to the cell
body.
Oligodendroglia of the
grey matter seems to be
smaller than in the white
matter. Its expansions
as seen by the most suc Fig. 5.—Oligodendroglia satellites about neu
cessful impregnations are rones from the cerebral cortex.
smaller than those of the
"interfascicular glia". The cells are applied to the convexity of
the neurone body (fig. 5), but a narrow intervening zone can often