1040 General Notes. 
and that only the chemically pure article will give the results obtained 
by Ehrlich, 
Instead of a saturated solution, Dr. Joseph recommends the 
strength originally employed by Ehrlich,—one-quarter gram color in 
100 grams of the physiological salt solution. ee 
The best stain was reached about six hours after injection in 
the body-cavity. 
Biedermann’ has employed nearly the same method for Crustacea 
and insects. 
CENTRAL TERMINATION OF THE OPTIC NERVE IN VERTE- 
BRATES.’—For tracing the course of nerve-fibres, the following 
method has been employed with great success by Prof. Bellonci. — 
1. The brain, or a part of it containing the nervus opticus, is 
placed in osmic acid (4 to 1 per cent.) for fourteen to twenty 
ours, 
2. Sections are then made with free hand in aleohol of 70 per 
cent. ; the sections are washed in distilled water a few minutes, and 
then placed in 80 per cent. alcohol three or four hours. 
3. The sections are again placed in distilled water, and then 
transferred to the object-slide, and covered with a cover-slip. 
4, A few drops of ammonia are then allowed to mix with the 
water under the cover-slip. This reagent makes the brain trans- 
parent as glass, with exception of the nerve-fibres, which remain 
black, and which are brought out with such distinctness that their 
course is easily followed. : 
The sections are of course thick, but this is an advantage in 
tracing the winding course of the fibres. ‘ 
Sections cut in celloidin with the microtome can be treated in 
same manner, but the action of the ammonia is much slower, 
requiring several days. 
DoUBLE-STAINING OF THE CENTRAL Nervous SysTEM.’— 
. Of the various fluids used for hardening, a 3 to 4 per a 
solution of bichromate of potassium gives the best results. P 
object must be in a fresh condition when placed in the fluid, an 
the fluid must be changed often during the process of hanes: 
2. The sections are best when made, without imbedding in cet- 
loidin, from pieces fastened to cork with gum and then placed in 
alcohol long enough to harden the gum.‘ 
1 Sitzb. d. Kaiz. Akad. d. Wissensch., Vol. xevi., 3 Abth. 1887. bel 
* Josef Bel/onci. Weber die centrale Endigung des Nervus opticus 
den Vertebraten, 
Zeitschr. f. wiss. Zoologie, xlvii., I., p. 4, September, 1888. we 
= Hermann Sahli. Ueber eine neue Doppelfärbung des cen 
ervensystems. Zeitsch. f. wiss. Mikroskopie, ii., i Spey ‘But the 
reparations left several days in alcohol can sti 
sections should be laid in the bichromate of potassium for an hour, and 
