MITOCHONDRIA IN VERTEBRATE NERVE CELLS 15 



mixture gives similar results. When sublimate acetic, picro- 

 sulphuric or Carney's fluid are used, in place of the acetic osmic 

 bichromate mixture of Bensley, the Nissl substance occurs in 

 the form of discrete, well formed masses in both types of cells. 

 This is shown in figure 11, drawn from a spinal ganglion cell of 

 a guinea-pig fixed in Carnoy's 6:3:1 fluid and stained with anilin 

 fuchsin methyl green (compare figs. 10 and 11). Attempts to 

 devise a fixative which would give a uniform Nissl substance in 

 the large cells failed. The diffuse Nissl substance in the small 

 cells stams with variable intensity with basic dyes (methyl green, 

 fig. 13, a and b). 



All my attempts to see formed Nissl bodies in unstained cells 

 were unavailing. The least toxic methylene blues (methylene 

 blue medicinale and the new methylene blues GB, N, NSS, 

 NSSF, NX, R, and RER), applied to spinal ganghon cells of 

 the frog (chosen because with a cold-blooded animal the warm 

 stage may be dispensed with), give first a diffuse coloration of 

 the cytoplasm followed by the appearance of irregular masses 

 of stained material, which look something like the Nissl bodies 

 of fixed tissues. I was unable to determine whether these blue 

 stained bodies represent pre-existent structures in the cytoplasm 

 which are invisible in the unstained cells by virtue of their low 

 refractive index. 



Pigment was seen only in the spinal ganglion cells of Necturus 

 and Rana. It has a bright orange color in Necturus and occurs 

 in a variety of forms. Sometimes as highly colored masses 

 (0.5-1^4 measured in fresh, unstained cells) which tend to fuse 

 together in a conglomerate way (1-6m). It may occur as spher- 

 ules of variable size (0.5-10^) and intensity of coloration; sickle- 

 shaped bodies (4.5^ long by 0.5/x wide), threads of variable 

 length and diffuse masses may also be made out. It varies in 

 amount in different cells of the same animal and in different 

 animals. The pigment in Rana is bright orange in color. It 

 occurs in the shape of globules and angular masses of consider- 

 able range in size (0.5-1.5^) either distributed evenly through- 

 out the cell or else gathered together in clumps. It is absent 



