Irving Hardesty - 99 
begin to take the characteristic stain. In a cell with considerable endo- 
plasm, neuroglia fibers are never found except in the more remote por- 
tions of its processes (see Fig. 2). The processes, it must be remem- 
bered, are continuous with those of neighboring cells which usually pos- 
sess less endoplasm, for in the adult material, the great majority of 
the nuclei possess either a very small amount of endoplasm or none at 
all. 
3. The endoplasm continues to disappear or rather to be converted 
into exoplasm, and neuroglia fibers appear nearer and nearer the nu- 
cleus. This gradual conversion of endoplasm into exoplasm results in 
the well-known isolated masses of nucleated granular protoplasm which 
are usually described as neuroglia cells. Depending upon the extent to 
which transformation has taken place, these masses may be stellate, the 
processes pointing toward the spaces between the neighboring nerve 
fibers (Fig. 3, c), or fusiform (Fig. 2, ¢), or the nucleus may retain but 
a granular halo of endoplasm about it (Figs. 3 and 4, d). Remembering 
that the conversion of endoplasm into exoplasm takes place from all 
directions, the mass becoming surrounded by exoplasm, one expects to 
find neuroglia fibers passing both above and below a “cell” in this 
phase. Often, however, neuroglia fibers seem to actually pass through 
the endoplasm and sometimes even to terminate in it. 
4. Continued transformation of the endoplasm results in its com- 
plete disappearance giving the often described free nuclei with neu- 
roglia fibers passing over and about them in all directions and forming 
the characteristic loose feltwork among the nerve fibers. Since the 
neuroglia fibers are formed out of a common syncytium rather than 
from individual cells, the fact that a single fiber may be traced through 
the domain of several “ neuroglia cells” is nothing more than is to be 
expected. 
The question whether the fibers are intercellular or intracellular in 
origin has been often discussed. It is seen at once that they can he 
considered intercellular only when one looks upon the free nuclei or 
nuclei with a small quantity of endoplasm about them, as neuroglia 
cells. Otherwise they are intracellular, or better, intrasyncytial in both 
origin and position. 
The nerve fibers of the spinal cord do not occupy the whole of the 
Randschleier. There is always left a thin marginal veil about the 
periphery immediately underlying the pia mater. This zone or cortex 
of the cord, varies in thickness for different animals. In this the neu- 
roglia fibers develop undispersed by the nerve fibers and the result is 
a thicker feltwork of fibers, which in the elephant and human spinal 
