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success, as I think may, ultimately, probably be obtained. Still, I have 
also obtained staining here in several groups of invertebrates and, 
in further experiments, it may probably be possible to find a modi- 
fication of the method, by which it would succeed on a larger scale. 
In Homarus I have already obtained very good results; as com- 
municated a year ago ^) I have tried it on Ascidians, with some 
success. In Mollusca, I have also seen so many signs of a be- 
ginning reaction that I feel convinced that it is possible to obtain 
good staining, if only the most suitable modifications are employed. 
This perhaps a near future may enable us to succeed in. 
As I am still experimenting on this subject, I shall, for the 
present, only quite shortly communicate the method I at present 
employ for the spinal nerve-cord of Myxine ghitinosa. 
The nerve-cord is cut out of the living animal. It must not be 
isolated, hut must, necessarily, be tåken with the surrounding sheaths, 
muscles and corda spinalis if any reaction at all is to be obtained. 
It is, however, also necessary to take care that the surrounding 
mass is not too thick, because in that case the hardening agents 
will penetrate too slowly; the half thickness of the corda spinalis 
may, therefore, very well be removed. This done, it is desirable to cut 
the preparation into short pieces (one or a few centimetres long) or, if 
one wishes to keep it in longer pieces, then, to make, in these, deep 
incisions with a sharp knife at short intervals. This done, the pre- 
parations are laid in a solution of potassium bichromate (2 — 2.5 7o) 
for about an hour, then the solution is changed and made a little 
stronger (up to 3 7o or more). Here they remain for about 24 hours ; if 
there is plenty of solution it is not generally necessary to change it 
again. After 24 hours the preparations are put into a new solution con- 
sisting of 4 parts of 3 % solution of potassium-hichromate, and i part 
osmic acid (i 7o sol.) in this solution they remain for about three days 
(72 hours) ; if there is not sufficient solution, it is necessary to change 
it after i or 2 days. Sometimes I have also employed solutions with 
more osmic acid (i part osm. ac. [i 7o] 3 parts potass.-bichr. [3 Voj 
as recommended by GoLGi) sometimes also with less osmic acid (i part 
osm. ac. and up to 6 or 7 parts potass.-bichr.) The good results 
of these different solutions depend much upon the temperature 
maintained in the rooms where the preparations are kept. After 
three days, or about that time, (the duration must be tested by 
results) the preparations are directly treated with silver-nitrate. At 
1) Nansen 1. c. 1886. 
