Hamitton, Deviszon of Cells in Nervous System. 315 
the large number of small and large cells which cannot possibly 
be classed together as undifferentiated descendants of the germ- 
inal cells, and which from the period of birth up to and possi- 
bly beyond the fourth day, form the majority of the cells con- 
cerned in the growth of the nervous system. That these cells 
are originally the offspring of the ventricular germinal cells of 
His seems most probable; that they have migrated into the 
outer layer by amoeboid movements there is every evidence to 
show, for not only are they found in the white matter, but 
some of them in both gray and white are fixed in shapes which 
suggest that they have been through amoeboid changes. They 
are not, however, simply germinal cells which have migrated 
away from the ventricles, for they differ from the germinal cells 
in the character of their cytoplasm and in their size. The 
largest ventricular germinal cells measure in the cord 9 X I2 p, 
the dividing cells of the gray matter up to 12 X 18 w.' The 
outline of the germinal cell is difficult to make out, the cyto- 
plasm is clear, stains lightly ; the outlines of the large dividing 
cells is distinct and the cytoplasm—the outer zone, at least—is 
granular and stains deeply with protoplasmic stains. Certainly 
these cells are not simply the germinal cells which have mi- 
grated from the ventricles, and if they are the offspring of the 
germinal cells, they have undergone some change before divid- 
ing for a second time; they have become at least partially dif- 
ferentiated. This will be seen more clearly if the dividing cells 
shown in the drawings from different regions be compared, 
those from the endyma, from the nerve fiber tracts and from the 
gray matter of the cord and the gray matter of the brain. If 
these cells are compared, it will readily be seen that in every 
instance the dividing cell tends to resemble in morpho- 
logical character the resting cells in the region in which it 
is found. Inthe nerve fiber tracts the dividing cell is almost 
always small, narrow, with no apparent cell body—in other 
words it is like the neuroglia cell in these regions. Large divid- 
ing cells are rarely found in the fiber tracts, but in the cord 
1 These measurements were not taken from the multipolar cells. 
