Irving Hardesty 91 
The study of the neuroglia cells was made from both longitudinal 
and transverse sections. In general it may be said that the great ma- 
jority of nuclei are entirely free from cytoplasm or possess a very small 
amount. Of such as do possess cytoplasm, a comparison of appearances 
in the two planes indicates that the longest diameter is generally in the 
direction of the long axis of the spinal cord (Tig. 4, ¢c). Sometimes 
two, and rarely even three, nuclei may be found with a common cyto- 
plasm (Fig. 2). Krause” found glia cells with more than one nuclets 
in the apes, and Aguerre (loc. cit.) describes such for the half apes and 
for man. 
In all my preparations the neuroglia is better studied in the white 
substance than in the gray. 
The study of the neuroglia cells and the neuroglia nuclei with refer- 
ence to their relation to the neuroglia fibers, has suggested a series of 
changes which may probably indicate some of the steps in the develop- 
ment of the neuroglia fibers. The accompanying drawings are taken 
from fields especially chosen as suggestive of these changes. They are 
all camera drawings and Figures 2, 3 and 4 are on the same scale (oc. 
4, 1/12 oil immersion, Zeiss). The drawings represent the areas chosen 
except in case of one cell, noted in the explanation, which was drawn 
from an adjacent field. This cell merely substitutes another of 
the more common type and otherwise does not affect the normal appear- 
ance of the area represented. Neuroglia cells similar in appearance 
to those shown may all be found on the same slide, and therefore the 
various forms evident can hardly be due to variations in the applica- 
tion of the staining method. 
The cells and nuclei, as found in the spinal cord of the elephant, may 
be described together. To indicate the series of changes suggested, 
they may be taken up in the following order: 
1. Cells with a large amount of cytoplasm which is largely present in 
the form of extensive, branched processes. The cytoplasm is sufficient 
to fill the inter-axone space occupied by the cell—the processes being 
sent out between the adjacent nerve fibers, give the impression that 
the shape of the cell is the result of its position—it merely fitting into 
the space it occupies. For obvious reasons this shape is best observed 
in transverse sections. The cytoplasm is granular after the technique 
employed, and, by the Benda method, stains a brownish-red, with occa- 
sionally a tinge of blue. The nucleus is always of the large vesicular 
variety, i. e., with a diameter of from 10 # to 16 yw and with granular 
10 Krause, R. Untersuchungen iiber die Neuroglia des Affen. Abhandl. der Konig]. 
Akad. der Wissenschaften zu Berlin. Anhang, 1899. ; 
