— 77 — 
— or, also, fixing in Lang's fluid (corrosive sublimate 12 Vo sea- 
water, or in an aqueous solution of chloride of sodium 6 7o acetic 
acid 6 ^/o, alum 0.5 ^'0) then washing out, hardening a little in 
alcohol gradatim and staining with Heidenhains hæmatoxylin 
as above. 
Ali these metliods can be safely recommended for trials; every- 
one of them will, I think, for certain purposes afford results which 
certainly are obtained by none of the metiiods employed before. 
My list of methods is however not yet finished. For some 
purposes even the above mentioned ones were not sufficient, e. g. 
in MoUusca, where it was extremely difficult to arrive at any clear 
idea of the most minute structure of the nerves and Leydigs »Punkt- 
substanz«. The foUowing method gave, however, excellent results. 
The pieces for examination, cut as small as possible, were 
treated with osmic acid (i %) for 48 hours, then washed in run- 
ning water, and cut at once by the hand or in the microtome or they 
may first be hardened in alcohol and then cut. The sections, transverse 
and longitudinal, were stained in Delafields hæmatoxylin (diluted), 
and decoloured in water containing a little acetic acid. The sections 
were examined in glycerine or canada balsam. In this way, very 
distinct preparations of the fibrillar substance are obtained; the sub- 
stance obtaining a distinct blackish staining. 
Finally, I shall now mention a method whose importance for 
our future knowledge of the nervous system can scarcely be over- 
estimated, as it affords really quite marvellous preparations and far 
surpasses every method hitherto known. 
This is the black chromo-silver metJwd of Prof GOLGI (at Pavia). 
By modifications of this method I have obtained exellent preparations, 
even from the spinal nerve-cord of Fishes, in which nobody before 
has succeeded. Dr. FUSARI, assistent at the histological laboratory 
in Pavia, told me that he had worked for more than a year with 
the nervous system of fishes without getting any staining by this 
method in the spinal nerve-cord. In the brain, however, the method 
gave excellent results, which indeed Dr. FuSARls preparations also 
richly prove. This gentleman is, so far as I know, the only one 
who, besides myself, has successfully up to this time employed the 
method for fishes. I am largely indebted to him for the communi- 
cation of his experiences obtained in a lengthened use of the method. 
Besides on fishes and other vertebrates, I have also tried the 
method on several invertebrates, not yet, however, with so much 
