86 The Neuroglia of the Spinal Cord of the Elephant 
Embryologically, all neuroglia is generally considered as derived from 
ectodermal cells. 
5. The neuroglia nuclei have been variously classified according to 
both their shape and size, but they may be sufficiently described under 
the two divisions originally made by Weigert: 
a. Large. Sometimes attain a diameter of 16 yw Usually spherical 
or oval in shape but may vary. Very vesicular. Granular chromatin 
usually accumulated in one or two larger masses (nucleoli) surrounded 
by smaller granules. 
b. Small. Diameter 4 y or even less. Various shapes but usually 
spherical. Compact chromatin a deeply staining almost homogeneous 
mass. 
There are to be found all transition forms between the two varieties. 
I have arranged what seem to me the principal findings of the litera- 
ture under the above five heads because such observations as I have 
been able to make on the neuroglia of the spinal cord of the elephant 
and collaterally of that of man seem to fall under one or the other of 
these heads. 
After a brief general description of the neurogha of the elephant I 
shall confine myself to one or two less generally emphasized points sug- 
gested by a study of the preparations, and the figures given are intended 
to illustrate features less usually described. To avoid slight confusion, 
the description will better be based upon appearances resulting from 
the application of the Benda method alone. 
The neurogla of the spinal cord of the elephant as seen in both 
transverse and longitudinal sections may be described as follows: The 
neuroglia fibers stain a deep bright blue, whereas cytoplasm, of the 
neuroglia cells, when present, takes a pale brick color with rarely a 
slight tinge of blue. The cytoplasm is distinctly granular, while the 
neuroglia fibers have a smooth, even contour and each a practically 
constant thickness. Thus the fibers differ both physically, and in their 
chemical reaction to the stains, from the cytoplasm of the cell-bodies, 
and so agree with one of the general statements made by Weigert for 
human neuroglia and confirmed by subsequent investigators of neuroglia 
both human and comparative. The neuroglia fibers in the elephant are 
in general somewhat larger than in the human specimens I have exam- 
ined and, judging from the descriptions found in the literature, they are 
larger than those found in other animals. On the whole, they do not 
vary greatly in size. Very few seem under 0.5 in thickness and the 
average is somewhat over that figure. Occasionally what seems an ex- 
ceptionally large fiber is noticed. On measurement these often acquire 
