20 E. V. COWDRY 



I have failed to observe Nissl bodies in unstained spinal gan- 

 glion cells teased out in isotonic media, and the vital dyes which 

 I have used (Methylene blue medicinale (M. L. B.) and New 

 Methylene blue GB, N, NSS, NSSF, NX, R and RRR) give 

 first a diffuse staining of the ground substance followed by the 

 appearance of typically blue stained Nissl bodies, which look 

 very much like coagula. I would be inclined to interpret the 

 gradations which I have observed in fixed preparations between 

 the diffuse Nissl substance in the small spinal ganglion cells of 

 the guinea-pig and the well formed Nissl bodies in the large 

 ones (fig. 10, a, b, c and d) as due to a difference in the coagula- 

 bility of a Nissl substance originally present in the diffuse state 

 in all. The fact that by the use of other fixatives, which are 

 perhaps more energetic coagulants or precipitants, formed Nissl 

 bodies may also be seen in the small cells (fig. 11, a) supports 

 this view. 



On this supposition the fact that the Nissl bodies are larger 

 in the peripheral cytoplasm would easily be explained because 

 the action of the fixative is more powerful there. The'chromo- 

 phile cells' (Barker '99, p. 123) may be interpreted as cells in 

 which the coagulability of the diffuse Nissl substance is reduced. 

 I do not desire to draw a sharp line of demarcation between the 

 terms 'coagulation' and 'precipitation.' Researches on a differ- 

 entiation between functional groups of nerve cells, on the basis 

 of the appearance of their Nissl bodies as seen in fixed prepara- 

 tions (Malone '10, etc.) stand as genuine contributions, even 

 though they be interpreted on a hypothetical difference in coag- 

 ulability due to a quantitative or a qualitative change in the 

 Nissl substance or both. For if the diffuse Nissl substance is 

 present in different concentration in certain types of cells, the 

 coagula resulting from similar fixation may be different. Or it 

 may be that the Nissl substance actually differs in kind. The 

 great mass of work which has been done on nerve cell physi- 

 ology, with the Nissl bodies as indicators (DoUey '13, etc.), is 

 best interpreted on the first supposition, of a quantitative change; 

 for here, coincident with the reduction in the Nissl substance in 

 fatigue, the Nissl bodies become smaller and present a more dif- 



