Irving Hardesty — 97 
the medullary sheath, might be taken for such. At first it was thought 
they were artefacts or nuclei injured by the knife but a close study of 
their occurrence and appearance lends more to the idea that they are 
constant structures. They always occur in the midst of a network of 
neuroglia fibers. 
For purposes of comparison and in order to test how far the special 
technique of the neuroglia method affects the shape, size and structure 
of the neurogla nuclei, sections of the elephant’s cord were examined 
after preparation by other methods. Without previous treatment, 
other than the action of the formalin in fixation, the tissue was imbed- 
ded in celloidin and sectioned. Some of these sections were stained 
with Ehrlich’s hematoxylin and counterstained with congo red, others 
with erythrosin and toluidin blue. In these sections all of the above 
types of neuroglia cells and nuclei may be identified by careful examina- 
tion under the oil immersion. The nuclei are not only the same as to 
size and structure, but stain in much the same way as by the toluidin 
blue in the special neuroglia stain. The large (Deiters’) cell with cyto- 
plasm sufficient to fill the inter-axone area and sending processes be- 
tween the adjacent nerve fibers is readily found. This is the identical 
neuroglia cell often pictured in the older text-books and is no doubt 
one of those described later by Ranvier.” I consider it as corresponding 
to types 1 and 2 described above, the differences in the appearance of 
the cytoplasm and the lack of differentiated neuroglia fibers being due 
to differences in the method of treatment. Also, in these sections cells 
with but a small amount of cytoplasm about the nucleus are of frequent 
occurrence. However, owing to the diffuse manner in which the 
counterstains act, a small quantity of cytoplasm is not so easily dis- 
tinguished as after the Benda neuroglia stain. The majority of the 
nuclei are as evidently “free” as in the Benda preparations. As to be 
expected, neither of the ordinary methods mentioned give any distine- 
tion between pia mater and neuroglia, but though undifferentiated, the 
neuroglia fibers may be distinguished after one is familiar with their 
size and distribution when stained by the special methods. 
I have classified the neuroglia cells and neuroglia nuclei in the above 
order because a study of them in the spinal cord has suggested that in 
this sequence they may illustrate some of the phases in the develop- 
ment of the neuroglia fibers. The phases suggested may be presented 
as follows: 
1. “ Neuroglia cell” is a misnomer if the term is considered as ex- 
Ranvier. De la Névroglia. Arch. de Physiologie, 1883. 
