Smallwood and Rogers, MoUuscan Nerve Cells. 63 



Distribution. — ^These deeply staining granules were found by Rhode ('04a) 

 in both vertebrates and invertebrates to occupy a zone of the cytoplasm surround- 

 ing the nucleus but not extending out to the cell wall. A rather broad zone (the 

 spongioplasm) at the periphery of the cell is free from these bodies, so that the 

 ganglion cell resembles the Amoeba in that it has a light ectoplasm and a dark 

 entoplasm. Only the finely granular hyaloplasm enters into the axis cylinder. 



McClure ('97) found the granules to be arranged chiefly in rows, but at certain 

 points in the cell body they appeared to be collected into spindle-shaped groups, 

 having their long axes parallel to the periphery of the cell (see Fig. Ii). A state- 

 ment of McClure's is of particular interest: "The cell bodies stain a deep 

 blue, while the axis cylinder processes are only partially affected by the stain, and 

 thus appear light in color. The cause which produces this difference is funda- 

 mentally the same in both cases: namely that the intense staining capacity of the 

 cell body, and the lack of the same for the axis cylinder process in Limax are due 

 respectively to the presence and absence of the chromophilous granules. The 

 Flemming-iron-hasmotoxylin preparations are especially interesting for the reason 

 that they show with great clearness, not only the same chromophilous granules 

 but also certain spindle shaped structures in the cell body, which in all probability 

 are collections of some small chromophilous granules. The above results concern- 

 ing the presence of chromophilous granules in the nerve cells of Gasteropods 

 point toward the acceptance of the view that this chromophilous substance is 

 homologous with that found in the nerve cells of vertebrates (NissL bodies)." 



Pflucke ('95) found that in the crab the chromophile granules of the nerve 

 cells are arranged in rows, and in the nerve processes they were few in number. 

 The granules were especially numerous about the nucleus, being regularly dis- 

 tributed. Under high magnification they were found to be spindle-shaped and to 

 be arranged in parallel concentric rows. 



Floyd ('03) finds the granules disposed in areolar fashion in the cell, deposited 

 upon the cyto-reticulum. 



Physical constitution. — Among vertebrates the NisSL bodies have been found 

 by Flemming, von Lenhossek, Marinesco, van Gehuchten, Held, Cajal, 

 Pflucke, Ewing, Carrier and others to have a granular structure— to be in 

 reality aggregations of minute particles of deeply staining substance. Floyd and 

 McClure have presented evidence of the same structure for the NissL bodies of 

 the invertebrates. 



Resistance to degenerative change. — The work of Ewing ('98) upon cadaveric 

 changes taking place in the ganglion cells of brains and cords of rabbits which were 

 allowed to decompose in the air from 48 to 72 hours may give evidence as to the 

 function of the NissL granules. During the first twenty-four hours there was 

 noticed a granular disentegration of the chromatic substance. This disintegration 

 was evidently due to the separation from each other of the granules which made 

 up the NissL bodies. As the degenerative changes proceeded, the granular dis- 

 integration became more and more marked. During this time the individual 

 granules retained all of their natural capacity for stains. Later when putrefaction 

 changes were set up in the cells the Nissl granules exhibited a remarkable resistance 

 to the action of the bacteria and still retained distinct outlines even when the cells 

 were becoming filled with vacuoles or when the cell consisted merely of a nucleus 

 v/ith a narrow fringe of granules (see Figs. 12-13). 



