THE NERVOUS CYTOLOGY OF PERIPLANETA ORIENTALIS. 343 



sections, however, only the outer part of the pith of the fibre was so shrunken and 

 the central portion showed a fine reticulum, with enlargements at the nodal points. 

 In longitudinal sections (Fig. 8, 10) most of the fibres presented appearances corre- 

 sponding to the first condition described above, but the best specimens exhibited 

 a number of granules elongated in the direction of the fibre, and an indistinct 

 appearance of longitudinal striation, the striae often starting from the granules. 



III. CELLS FIXED IN PICROFORMALIN. 



1. Technique. The ganglia, obtained in the manner already described, were 

 placed in picroformalin * for twenty minutes. The subsequent treatment was the 

 same as that described for vom Rath preparations except for the addition of staining. 

 The sections were overstained in Nissl's methylen blue f or Unna's polychrome, and 

 then decolorized to the proper point in passing through the alcohols. A number 

 were counterstained in alcoholic eosin as well. 



2. Observations The cell-spaces again appeared somewhat shrunken in out- 

 line. The nuclear membrane was distinct, and its outline regularly plump and even. 

 It varied somewhat in thickness, due to slight nodular enlargements, and in some 

 cases was apparently deficient in part, the cytoplasm passing over into the nucleus 

 without its interposition (PI. XXV, Fig. 13). The nucleus was occupied by a more 

 or less incomplete network of fine fibrils with considerable nodal enlargements, and 

 by some irregular masses of amorphous matter. It regularly contained one or two 

 deeply staining nucleoli. The nucleus, as a whole, stained very much more faintly 

 than the adjoining cytoplasm. The cell-body, while still divisible into an inner granu- 

 lar and an outer fibrillar zone, exhibited far more detail of structure than after fixa- 

 tion with vom Rath's fluid. The inner granular zone took an intense blue stain. 

 The granules varied only moderately in size, but markedly in quantity (Figs. 11-13). 

 When very numerous they formed a blue granular mass of areolar structure, but when 

 less copious they were seen to be definitely arranged along the strands of a fine net- 

 work (Figs. 12, 13). This difference was not an artifact of staining, as cells lying next 

 each other in the same section exhibited it quite as markedly as any others (Fig. 13). 

 The granular zone was regularly most dense next the nucleus, fading towards the outer 

 margin. Sometimes it varied in density in different parts of the cell, and in one or 

 two instances a double granular zone was observed (Fig. 12). The outer fibrillar 

 zone, which took a red stain when eosin was used, was larger in proportion and more 



* Picroformalin: Sat. aq. sol. picric acid, 50 pts. ; 5% or 8% aq. sol. formalin, 50 pts. 



j 1 Nissl's methylen blue: Methylen blue, 3.75 pts.; castile soap, 1.75 pts.; distilled water, 1000 pts. 



