I lo Journal of Comparative Neurology. 



seen so that neither its course, direction nor its few or numerous 

 branches can be perceived. With the gradual progress of the 

 reaction the nerve cells are displayed more clearly and the finest 

 subdivisions of their protoplasmic as well as their nervous pro- 

 cesses appear. 



"3. Cells of tJie ;:r:iyoglia. An interesting reaction oc- 

 curs in the cells of the neuroglia ; it may be said that it takes 

 place in pieces suitably hardened in bichromate from the begin- 

 ning of the phase to the end. In fact at both the time when 

 the fibers predominate and when the cells predominate individ- 

 ual neuroglia cells or groups of them are to be seen showing the 

 characteristic reaction of the silver nitrate (coffee-brown or yel- 

 lowish). Besides, with this species of element the reaction only 

 becomes fine and diffused in a somewhat advanced period of 

 hardening so that their typical form and relations are plain. 

 The reaction in neuroglia cells takes place for a long time be- 

 yond the time favorable for staining nerve cells. 



The finest reaction for the nerve cells, especially for the 

 nervous processes, occurs at a somewhat advanced stage 

 of hardening, namely when, with the advance of the re- 

 action among neuroglia cells, it is limited among the gan- 

 glion cells. It is precisely among isolated blackened cells 

 that the stain of the individual functional (axis-cylinder) 

 processes is finest ; one can observe the smallest details of 

 their course and branching. I must again recall that the reac- 

 tion must be produced in a series of pieces which have consecu- 

 tively received suitable treatment in order to learn to know all 

 its phases. 



"After we have so circumstantially laid down the funda- 

 mental rules of procedure, it would be superfluous to go into 

 particulars about the differences obtaining between the different 

 provinces of the central nervous system (the cortex cerebri, the 

 so-called ganglia of the base, the cerebellum, the spinal cord). 

 I only remark here that, under similar conditions, pieces from 

 the cortex reach in bichromate the suitable state of hardening 

 somewhat sooner that than those from the cerebellar laminae, 

 that the latter reach it a little later than pieces of the spinal cord 



