The finer Structure of the Nerve Cells of Invertebrates. 43 



•sections (Flemming or sub.-iron-alum-haematoxylin), fine connecting 

 fibrils between the granules of a row. These fine fibrils, which appear 

 as fine lines, stain darker than the ground-substance and lighter than 

 the chromophilous granules, and agree in every respect with the fibrils 

 of the axis-cylinder process (Figs. 11, 12 and 13). 



Pflücke (30) has described a somewhat similar arrangement of 

 fibrils and granules , as that last mentioned , for the nerve cells of 

 Astacus. That is, he finds a row-like arrangement of granules in these 

 cells with connecting fibrils between the granules. He also observed a 

 row-like arrangement of granules in the nerve cells of Helix, but was un- 

 able to find any connecting fibrils between them. He found, however, that 

 in each case these granules stained more deeply than the ground-substance. 



Pflücke's inability to find these connecting fibrils in Helix is 

 unquestionably due to the circumstance that the staining method used 

 by him was not the most desirable for bringing out fine fibrillar struc- 

 tures (Nissl's). 



In substantiation of this, I refer the reader to my own experience, 

 as related in the preceding pages, in connection with the staining of 

 axis-cylinder fibrils by the methylen blue-eosin stain. Here it was 

 seen that the fibrils were stained exclusively by the eosin. 



When methylen blue is used alone, without eosin, the fibrils are 

 stained very faintly. This circumstance, together with the fact that 

 the fibrils are extremely fine in Helix, probably accounts for Pflücke's 

 inability to identify these structures in the nerve cells of that species. 



Pflücke regards the granules in the nerve cells of Astacus, not 

 as isolated and independent structures, but rather as varicose thick- 

 enings of fibrils. If this statement is correct for the granules in the 

 nerve cells of Astacus, it must likewise be correct for those of Helix 

 and Avion. 



I am , however , unable to accept this view for either of these 

 cells, but regard the granules as isolated and independent structures, 

 which assume a row-like appearance by virtue of the fact, that lying 

 in a semi-fluid ground-substance, the granules will necessarily, when 

 currents are set up in the former, arrange themselves along or between 

 fibrils 1). 



1) I have carefully examined the structure of the nerve cells of 

 Astacus, and can say that the structure of these cells is fundamentally 

 the same as those of Helix and Arion. There is a slight difference, 

 however, as certain of the nerve cells of Astacus possess a "cylindre- 

 axe intracellulaire" (Binet), and their granules are larger, and their 



