STRONn, Rri'irzv of tlic GoI[^j MctJiod. 125 



consider it fitting to add that the best and finest reactions in the 

 nerve fibers and the interstitial difTuse network was observed 

 by me in pieces (from the spinal cord of the new-born kitten) 

 which had lain a long time (in part over two years) in a one per 

 cent, solution of sublimate after a long preceding sojourn in a 

 bichromate solution (first, Miiller's fluid, then, pure bichromate 

 to 3^). Since they were pieces which had lain in the labora- 

 tory in this way ready for examination but had not been used, I 

 can, naturally, not tell what influence the long sojourn in the 

 sublimate may have exerted. 



" The modification introduced by me, to which I must at- 

 tribute a certain value for the clear demonstration of fine details 

 and to which I call the attention of the observer, consists simply 

 in a slight addition, viz., the blackening of the glistening white 

 stain which the nerve elements receive by means of the mercury 

 impregnation. 



" As is known, the elements treated with sublimate appear 

 black in transmitted light on account of the opacity caused by 

 the reaction but in reflected light they appear white. This dif- 

 ference may be easily observed by turning off the mirror of the 

 microscope. 



" This kind of appearance is satisfactory for observation 

 with low or medium magnification, where less fine details are 

 concerned, but it is otherwise with the finer details where 

 stronger magnification is required. In this case the metallic 

 luster of the fine parts, e. g. the finest divisions of the nerve 

 fibers, evidently affects the observation unfavorably by giving 

 the pictures a certain indistinctness. The black stain which re- 

 places the white-metallic brings out better the outlines of the 

 fibers and so increases the demonstrative value of the pre- 

 paration. 



" Inasmuch as the impregnation consists of metallic mer- 

 cury, the transformation of the metallic white into deep black 

 can be accomplished, according to the teaching of elementary 

 chemistry, by means of a number of reagents. There can serve 

 for this purpose : the sulphite and hyposulphite (particularly 

 sodium sulphite and hyposulphite in 5 % solution), the sulphide 



