ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
603 
use of the method of Vom Rath, in which the tissue is fixed in a solution 
of osmic, acetic, and picric acids, and platinic chloride, and afterwards 
reduced in crude pyroligneous acid. It is stated that this method 
presents the double advantage of being unfailing in its results, and of 
yielding preparations which are remarkably clear and trustworthy. The 
author has improved his depigmenting fluid (0 • 1 per cent, aqueous 
solution of potassic hydrate) by using as a fixative for the sections a 
mixture of the fixatives of Schallibaum and Mayer. When small drops 
of each of these fluids are thoroughly mixed on a slide a whitish sticky 
paste results, which, even in extremely small amounts, resists the 
loosening action of both potash and absolute alcohol. The number of 
retinal elements was determined by counting the corneal facets. The 
author describes in detail the method by which he effected it. In justi- 
fication of its use he points out that the difference between the estimated 
and the actual number did not differ by as much as 1 per cent. 
Fixing and Staining Nervous Tissue to Demonstrate Changes in 
the Cells.* — Dr. G. Mann uses the following fluid for fixing nervous 
tissue : — Saturated solution of HgCl 2 in 3/4 per cent. Nad, 100 ccm. ; 
picric acid, 1 gr. ; tannin, 1 gr. ; or simply a saturated solution of Hgd 2 
in 3/4 per cent. NaCl 2 . 
Various stains w^ere used, and the following procedure is given in 
detail when methyl-blue is used. The ganglia were fixed in HgCl 2 
and imbedded in paraffin. The sections were stuck to the slide by the 
author’s albumen method, and after removal of the paraffin immersed in 
the following solution : — 1 per cent, methyl-blue (water-soluble) 35 ccm., 
1 per cent, eosin (water-soluble) 45 ccm., H 2 0 100 ccm. (1) Stain for 
24 hours. (2) Remove superfluous stain with w r ater. (3) Dehydrate in 
absolute alcohol. (4) Place slide in glass vessel containing absolute 
alcohol 30 ccm. and 1 per cent. NaHO 4 drops, and leave until the 
dark-blue section has become reddish (1-5 minutes). (5) Wash out all 
traces of soda with absolute alcohol. (6) Immerse sections in tap-water, 
and when the bluish-red clouds are no longer given off, transfer to water 
acidulated with 2-3 drops of acetic acid for 3 minutes. (7) Dehydrate 
with absolute alcohol and mount in turpentine balsam. If the sections 
be still too blue, the process must be repeated. 
Methylen-blue Staining Granules of Pneumonia and Anthrax, t — 
Dr. N. Pane describes certain granules occurring in cells taken from the 
blood, spleen, and bone-marrow of rabbits infected with pneumonia and 
anthrax. These granules stain well with aqueous methylen-blue solution 
(1 : 800), and are usually of a decided blue or of a slightly different tone 
from the rest of the preparation (metachromatism). Similar prepara- 
tions taken from healthy animals do not exhibit these granules. 
After pointing out that these granules resemble those of “ Mast- 
zellen,” the author negatives their identity by showing that the two sets 
of granules differ in their receptivity for methylen-blue and dahlia, and 
in their resistance to a temperature of 70°-75°. Preparations made 
from spleen-pulp indicated that the “ methylen-blue ” granules had a 
* Journ. Anat. and Physiol., xxix. (1894) pp. 100-7. 
f Centralbl. f. Bakteriol. u. Parasitenk., l te Abt., xvii. (1895) pp. 789-94 (3 colrd. 
figs.). 
