THE NERVOUS CYTOLOGY OF PERIPLANETA ORIENTALIS. 349 



gave the appearance of being stretched. There was upon it, evenly distributed, 

 the deeply staining granules and masses. There was no perinuclear condensation 

 and no peripheral laceration of the reticulum, except from stretching. The appear- 

 ance of the individual cells was very much like those fixed in formalin vapor, except 

 for the differences just enumerated, and some of them, in which less stretching had 

 occurred, were almost identical in appearance, except for the nuclear reticulum. 



XII. CELLS FIXED IN DIFFUSED ALCOHOL. 



i. Technique. — By the use of a simple diffusion-bottle the ganglia were placed 

 in water to which alcohol was gradually added till a concentration of between 

 80% and 90% was reached at the end of three or four hours. The subsequent 

 treatment was the same as in the preceding method. 



2. Observations. — The results (PI. XXVII, Figs. 35-37) were similar in the 

 main to those of formalin vapor and graded formalin. The cell-spaces were not much 

 distorted, but moderate shrinkage of the cells prevented them from filling their spaces, 

 and caused some of their margins to present the same appearance as after graded 

 formalin. The nuclei exhibited a reticulum as after graded formalin. Its membrane 

 was distinctly indented and shrunken. This shrinkage was evident also in the wrink- 

 ling and kinking of the individual strands of the cytoreticulum and the narrowing of 

 each interstice, a change which was present to about the same extent in all parts of 

 the cell-body. The strands and nodes of the reticulum presented the same deeply 

 staining substance as with the formalin methods, but it occurred in somewhat dif- 

 ferent form, there being fewer granules and more irregular masses along the fibrils. 

 There was no perinuclear condensation and no centripetal arrangement or lacera- 

 tion of the reticulum, except for the marginal shrinkage above described. 



Some experiments were next undertaken in the hope of throwing additional 

 light on the nature of the substance which exhibited such a strong affinity for 

 methylen blue and appeared in granules and masses upon the cytoreticulum in all 

 specimens of the fixed cell. Held ('97, p. 204) has stated that the chromophilic 

 plaques of the nerve-cells in higher vertebrates do not exist as such during life, but 

 are formed by the post-mortem precipitation of certain bodies contained in the cell 

 lymph, that this precipitation is due to the post-mortem change in the chemical reac- 

 tion of the tissues from alkaline to acid, and that by immersing such cells in alkaline 

 solutions these plaques can be dissolved out. On this suggestion two experiments 

 were performed. 



