32 CHARLES F. W. MC CLURE, 



sections prepared by other methods, the results obtained by progress- 

 ively staining freshly isolated cells in raethylen blue solutions, will 

 first be considered. The manner in which these solutions were pre- 

 pared has been described on a preceding page. 



One interesting result obtained by the use of this method, is that 

 ganglion cells (Limax), which have remained for some time in a weak 

 solution, or for a shorter time in a strong solution of methylen blue, 

 show a marked difference in the manner in which their cell bodies 

 and axis-cylinder processes are stained. 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. 



These results seem to accord with those of Dogiel (7), who 

 studied the structure of the nerve cells in the retina of the owl, as 

 progressively brought out by methylen blue solutions. I call the 

 reader's attention to his figures on tab. 20, especially 1 D, 2 E and 3, 

 in which the same difference is most pronounced. These figures re- 

 present different "Periods" of a progressive staining process, each 

 "Period" being characterized by the appearance in the cell of certain 

 structures which become stained by the methylen blue. 



The "First Period" is called the "Granular Period", as in it, 

 only the chromophilous granules (Körnchen and Körner) make their 

 appearance in the cell body. In the "Second Period", in addition to 

 the so-called "clumps of granules" (Schollen), which are collections 

 of smaller granules, the fibrils make their appearance in the cell 

 body and its processes. The "Third Period" is characterized by the 

 staining of the ground substance, which finally becomes as deeply 

 stained as the chromophilous granules, and thus prevents any details 

 of structure from being seen in the cell body. The contrast, however, 

 between the color of the cell body and the axis- cylinder process re- 

 mains unchanged (see Dogiel's fig. 3 mentioned above). 



Such, in general, are the main results obtained for the retinal 

 cells of the owl, in which Dogiel conclusively shows, that the dark 

 coloration of the cell body is chiefly due to the presence therein, of 

 chromophilous granules ("chromophile Substanz") which possess a 

 great affinity for methylen blue; while those parts of the cell which 

 are lacking in granules, remain practically unstained or are only 

 slightly stained. 



The question now arises, whether the cause which produces this 

 difference in the staining capacity of these two regions of the ganglion 



