162 A REVIEW OF THE GOLGI METHOD. 



spots scattered here and there. After 4 or 5 days more one sees 

 the cell-forms gradually become more complete and numerous, 

 and the reaction thenceforward continues to extend and complete 

 itself. It even appears that further advantages are gained when 

 the sojourn in the sublimate solution is extended indefinitely, the 

 sublimate being changed as often as it becomes yellow through 

 the presence of bichromate. With brains which have been long 

 exposed to the action of the bichromate, — and such often yield 

 the most beautiful results, — the sublimate solution must be changed 

 during several months before this yellowing ceases. 



" The above constitutes a further difference from the manner 

 of action of the silver nitrate, inasmuch as in the latter the whole 

 action is completed in 24 to 48 hours, after which no further action 

 is exerted, although the pieces can be kept in it longer. 



" When the reaction has reached its maximum, the pieces 

 remain colourless, and have the appearance of fresh brain tissue 

 which has been slightly washed in water. 



" The pieces may remain in the sublimate solution as long as 

 one pleases, not only on account of the possibility of a further 

 extension of the reaction, but also because they thereby receive a 

 hardening better adapted for making fine sections. 



" As to the manner in which the reaction extends to the differ- 

 ent elements, I will merely remark that the reaction affects the 

 ganglion cells in pieces which have reached that degree of harden- 

 ing attained in the first month's immersion in bichromate, and the 

 reduction only extends itself gradually to the nerve fibres also. 

 The reaction displays itself to the fullest extent in the nerve fibres 

 almost exclusively in pieces which have lain a long time in bichro- 

 mate, and are very strongly hardened. I recall in this connection 

 the brains which have been kept very nearly a year in bichromate ; 

 they showed an almost universal very fine stain of the bundles of 

 nerve fibres, and of their finest subdivision. 



" Treatment and preservation of microscopical preparations. 

 The only special precaution required by preparations made by 

 means of the sublimate reaction before they are mounted in 

 glycerine or balsam is a careful washing in water. Without this 

 precaution a precipitate in the form of a black powder or needle- 

 shaped crystals is formed in the sections some days after mountmg, 



