ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
703 
and oxalic acid), 5 minutes, wash in water. (8) Second staining (e. g. in 
very dilute neutral carmine, 24 hours), rinse, dry. 
C. Freeing from water and preserving. (9) 70 per cent, alcohol 
with a trace of picric acid, 1 hour. (10) 95 per cent, alcohol, J hour, 
dry. (11) Plates on the sides of the section covered with filter paper 
moistened with carbol-xylol. 
Then follows a layer of canvas, then the second plate f>aper, and so 
on. Finally the plates are placed in (12) thin resin solution, then in 
(13) thick resin solution. (14) Transfer of the sections to glass slide. 
(15) Mounting. 
For the paraffin imbedding of large objects (brains) the author uses 
the following processes: — Immersion in 95 per cent, alcohol, then in 
carbol-xylol from 18 to 22 days, allow to evaporate, place in yellow 
vaselin, first on and then in the oven at 40° C., up to 8 days, until every 
trace of xylol has been removed ; place in a mixture of paraffin, which 
melts at 42°, and yellow vaselin (the proportions are 4:1, or 3 or 2 : 1 
according to the size of the plates), in oven at 40°, one to several days. 
The author has introduced modifications in his microtome, so as to 
make it suitable for celloidin objects. In the large model with double 
slide-way, the old knife-slide is replaced by a new one, in which the 
knife, by means of a special holder, can be displaced to right or left in a 
cross slide-way. 
(4) Staining- and Injecting. 
Formalin as a Mordant.* — Dr. A. P. Ohlmacher finds that formalin 
acts as a powerful mordant with anilin dyes. It may be used in 2-4 per 
cent, aqueous solution as a preliminary treatment before staining. The 
cover-glass film is treated for one minute with the solution, washed in 
water, and then stained in the cold. Or it may be used as a base in the 
same way as anilin, carbolic acid, &c., are ; e. g. formalin-fuchsin may 
be made by adding 1 grm. of fuchsin dissolved in 10 ccm. of absolute 
alcohol to 100 ccm. of a 4 per cent, aqueous solution of formalin. 
Formalin metbylen-blue, which affords a very effective stain, is made 
by dissolving 1 grm. of methylen-blue (methylen-blue Ehrlich) in 
100 ccm. of 4 per cent, formalin. 
A curious effect is obtained when safranin (O water-soluble, Griibler) 
is dissolved to saturation in 4 per cent, formalin. This results in a 
plasma stain, and when sections are previously coloured with the formalin 
methylen-blue solution a beautiful double stain results, the blue stain 
being nuclear. 
Staining Yolk-Nucleus of Lumbricus.t — Mr. G. N. Calkins arrived 
at his conclusions concerning the nature of the yolk-nucleus chiefly by 
micro-chemical reactions with differential staining. The combination 
stain of Heidenhain’s hasmatoxylin and orange makes the chromatin 
and the yolk-nucleus a blue-black, while the nucleus of the germinal 
vesicle and the cytoplasm are orange. The Biondi-Ehrlich mixture 
stains the young yolk-nucleus a bright green, while in the older eggs 
the disintegrated yolk-nucleus is stained a bright red. As the principal 
constituents of this mixture are methyl-green and acid fuchsin all doubt 
* Med. News, lxvi. (1895) pp. 184-5. 
t Trans. New York Acad. Sci., 1895, pp. 227 and 8. 
