GANGLION CELLS OF THE CRAYFISH 201 



and another was treated with vom Rath's picro-aceto-platino- 

 osmic fluid. 



In using the Nissl method, the ganglia were put for forty-eight 

 hours in 95% alcohol, then dehydrated, cleared in xylol, imbedded 

 in paraffin, cut in sections 10m. thick, and stained in toluidine 

 blue. In order to secure perfectly parallel treatment of the cells 

 in the staining, washing, and subsequent dehydration, serial 

 sections of the isolated ganglion of a normal individual and of an 

 individual operated upon were placed in alternate rows on the 

 same slide. Preparations were made in this way from materials 

 killed at intervals of from two to five days covering a period in 

 all of thirty-three days after the operation. 



The large nerve cells of the normal ganglia prepared by the 

 Nissl method presented a characteristic appearance (fig. 1). 

 Fibrillse in the axis cylinder were usually visible, though not all 

 the cells revealed them. That they were not always seen, is be- 

 lieved to be due to this method, which, as is well known, is not a 

 wholly satisfactory one for demonstrating fibrillse. The Nissl 

 ''flakes" were present, though somewhat less distinct than in the 

 ganglion cells of vertebrated animals. In some cases there ap- 

 peared, more or less distinctly, small centers, which stained deeply 

 and from which radiated irregularly threads of protoplasm. These 

 threads or strands connected with other similar centers or faded 

 out in the surrounding cytoplasm. These small centers or granules 

 with the network of radiating threads are confined almost wholly 

 to regions adjoining the axis-cylinder area. The nucleus exhi- 

 bited a full rounded form and possessed a reticular structure with 

 a very distinct and deeply stained nucleolus. Occasionally two 

 nucleoli were found in one nucleus. Sometimes a slight shrinking 

 of the cytoplasm next the nucleus was observed. 



With the state of the normal ganglion cells, are to be con- 

 trasted the conditions found in the corresponding ganglion cells 

 from a fifth ganglion (fig. 2) which had been nervously isolated 

 about twelve days, but otherwise had received identical treatment. 

 The cells from the isolated ganglia showed distinct alterations. 

 The nerve fibrillse in the axis-cylinder area had disappeared and 

 the Nissl flakes had become finely granular or had disappeared. 



