ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
533 
example, we may use a thinner collodion and arrange a large number 
of insect embryos or small worms in a compact bundle like a package of 
cigarettes, and cut them all at once. 
New Machine for Cutting Thin Sections of Rocks and Minerals.* 
— This machine was constructed for the petrographical laboratory of 
the John Hopkins University in Baltimore, by the Donaldson Macrae 
Electric Company. Its most interesting feature is that it is driven by 
an electro-motor. 
C4) Staining and Injecting. 
Modification of Golgi’s Method for Study of Human Brain.f — 
Dr. W. Lloyd Andriezen states that he obtains good results with the 
following method : — Slices of brain 2 to 4 mm. in diameter were suspended 
in 95 ccm. of 2 per cent, bichromate of potash ; after 10 to 15 minutes 
5 ccm. of 1 per cent, osmic acid was added, and the whole left in 
the dark for a day; the specimen was then suspended for 2 days in 
90 ccm. of 2*5 per cent, bichromate and 10 ccm. of 1 per cent, osmic; 
and was finally changed into Golgi’s mixture of 80 ccm. 3 per cent, 
bichromate and 20 ccm. of 1 per cent, osmic. It is well to have two 
specimens, hardened 3J and 4J days respectively. After this rinse in 
distilled water, plunge into 3/4 per cent, silver nitrate solution for 5 to 
15 minutes in the dark, change into 100 ccm. of silver nitrate to which 
one drop of formic acid has been added ; place in incubator in the dark 
at a temperature of 25° to 27°, change silver solution for fresh after a 
day ; after three or four days rinse in methylated spirit and fix in wax, 
cut under spirit, pick out best sections, and place in a large quantity 
of distilled water till nearly freed from spirit (about 5 minutes) ; then 
place sections in 3/4 per cent, silver nitrate for 1/2 to 1 hour; dehy- 
drate in spirit, and then in xylol-piridine, equal parts, clear twice in 
xylol, and mount in xylol-dammar, hastening drying by placing the 
slides in an incubator at 37° to 40° for a day or rather more. 
Successful preparations will show the nerve-cells and their processes 
down to their finest ramifications and endings, and all the cell-elements 
will be sharply differentiated from one another and from the clear 
ground substance. The method is applicable to adult human brains 
(which Golgi’s methods are not), provided post-mortem changes are not 
> too advanced, or the tissue disintegrated or softened. 
Two new Staining-reagents for Meristems.J — In the place of the 
anilin-brown and ferric tannate hitherto employed, M. A. Lemaire 
recommends, for staining the walls of cells in process of division, the 
use of two staining reagents, known in Germany as “ Schwarzbraun ” 
and “ Kernschwarz,” the composition of which is not given. To the 
walls of cells deprived of their protoplasmic contents the former gives 
a brown colour which is not destroyed by absolute alcohol, xylol, or 
Canada balsam. The latter reagent stains the nucleus black, the rest of 
the protoplasm being nearly unaffected unless the solution is very strong. 
The sections must first be treated with hypochlorite and potassa, and 
the latter removed by water slightly acidulated by acetic acid. 
* Amer. Journ. Sci., iii. 45 (1893) p. 102. See Zeitschr. f. Instrumentenk., xiv. 
(1894) pp. 184-5. f Brit. Med. Journ., No. 1739 (1894) p. 309. 
X Bull. Soc. Bot. France, xli. (1894) pp. 88-90. 
1894 2 o 
