ii8 Journal of Comparative Neurology. 



of tissue to be examined are useless after a few days. Here the 

 fresh pieces (with or without injection) are laid in the bichro- 

 mate solution and remain, so to speak, in the hand of the inves- 

 tigator. They can either immediately or later be tried i. e. 

 during a period of from 3 or 4 to 25 or 30 days after the immer- 

 sion. If one during this whole period transfers at intervals of 

 2 to 3 or 4 days some pieces into the osmium-bichromate solu- 

 tion, he thus possesses many secondary series of pieces which 

 are brought singly (i or 2 at a time) into the nitrate solution. 

 These, from the third or fourth to the eighth or tenth day of 

 their sojourn in the mixture, yield with certainty, when brought 

 into the silver, preparations with all the consecutive gradations 

 and combinations described in the original method and also 

 possessing surprising fineness. 



''Aftcr-treatvicnt. Preservation of the pieces in the silver 

 solution ; pure alcohol for 2 or 3 days, till one has time to un- 

 dertake the examination; repeated washing out of the sec- 

 tions with absolute alcohol ; cresote, turpentine, damar, mount- 

 ing without cover glass. 



"This is the method which I at present prefer for the 

 demonstration of the finest details in the structure of the central 

 nervous system. The particular grounds for this preference are 

 the following: (i) Certainty of obtaining the reaction in many 

 gradations, if one makes use of a certain number of pieces. 

 (2) The considerable length of time during which one can 

 obtain the reaction — while one can also attain it in a few days. 

 This renders an accurate investigation much easier. (3) The 

 pieces are much more conveniently treated. (4) Finally, one 

 obtains at the same time with the gentle gradation of the results 

 also a greater fineness of the same, especially regarding the be- 

 havior of the functional processes of the ganglion cells. 



"3. Mctliod of the consecutive actions of the bichromate 

 of potassium and of bichloride of mercury. This can likewise 

 yield valuable results whose value is nut diminished because 

 they in many respects conform to those obtained by the silver 

 nitrate. Indeed, the particular purposes it can fulfil and its 

 peculiar advantages are in and for themselves so important that 



