56 Studies on the Neuroglia 



and when a section is not completely differentiated. In well-differen- 

 tiated sections and more easily in longitudinal sections, it may usually 

 be made out very clearly that the neuroglia fibers pass over or under 

 or in close proximity to such cells and are not interrupted by them. 



Cat. — The neuroglia of the spinal cord of the cat presents essentially 

 the same appearances as those described for the dog. Nearly all of 

 the neuroglia cell nuclei are of the vesicular variety with very little 

 chromatin. In many of the cells, very little protoplasm can be made 

 out, the nuclei appearing as free nuclei. In others, the protoplasm, 

 staining a brownish red color, is readily made out, such cells often ap- 

 pearing distinctly branched, with three, four or five protoplasmic 

 branches, varying in thickness and length and recognized between the 

 cross-cut nerve fibers. The neuroglia fibers of the spinal cord of the 

 cat are somewhat coarser than those found in the dog. They are 

 clearly differentiated and may be traced over or under or around the 

 neuroglia cell nuclei or neuroglia cells. The statements made con- 

 cerning the relation of the neuroglia cells and nuclei and neuroglia 

 fibers, as seen in the dog, are equally applicable for the cat and need, 

 therefore, no further repetition. 



Rabhit. — The neurogliar tissue of the spinal cord of the rabbit is 

 not so easily stained differentially as that of the dog and cat. This is 

 due to the fact that the protoplasm of many of the neuroglia cells shows 

 a greater affinity for the toluidin blue than seems to be the case in the 

 dog and cat and, as a consequence, one often finds neuroglia cells with 

 protoplasm and nucleus staining a purplish color, sometimes of a lighter 

 and sometimes of a darker shade. A longer differentiation in the creo- 

 sote bleaches not only such cells but also to some extent the neuroglia 

 fibers. The right degree of differentiation is therefore somewhat diffi- 

 cult to obtain. The majority of the nuclei of the neuroglia cells are of 

 the vesicular type, varying greatly in size and shape and in the char- 

 acter and amount of chromatin contained. This may be present in the 

 form of numerous fine granules or as one or several larger granules. 

 Small nuclei, staining deeply, are found, but are not numerous. Many 

 of the nuclei appear as free nuclei and show no or very little protoplasm 

 surrounding them. The large vesicular nuclei, with one or several 

 granules, are generally found in masses of protoplasm which are readily 

 made out. Such cells are usually branched and when stained are pur- 

 plish-blue in color; the protoplasmic branches can be very readily traced 

 between the nerve fibers. The neuroglia fibers of the rabbit are rela- 

 tively fine and stain a deep blue color and, in the great majority of 

 cases, it can be readily seen that the fibers are independent of the nu- 



