1886. } Microscopy. 89 
the slide inverted over a capsule containing go p. C. alcohol to 
which a few drops of strong nitric acid have been added. Copious 
fumes are given off, and the pigment dissolves. The action can 
be arrested at any moment by washing with neutral alcohol. 
4. The sections are next stained with hematoxylin or with any 
other solution. The best results were obtained with hematoxylin 
made after Mitchell’s' formula. 
For teasing the best solution is chloral hydrate. The prepara- 
tion is left in a 5 p. c. solution for twenty-four hours, and then 
teased with needles and mounted in glycerine. 
GRENACHER’S METHODS OF PREPARING THE ARTHROPOD EYE.’ 
Hardening Fluids —Chromic acid and its salts produce a coarse 
granulation, and on this account must be considered objection- 
able. Oxalic acid, in aqueous or alcoholic solution, as recom- 
mended by M. Schultze and Steinlin, gives good results in some 
cases, bad in others. Picric acid gives wholly unsatisfactory 
preparations, while picro-sulphuric acid works well in many 
cases. The latter fluid, cannot, however, be used with most 
of the Crustacea, as here the integument contains calca- 
reous salts which react with the acid to produce crystals of 
gypsum and carbonic acid, both of which work injury to the soft 
tissues. Merkel’s chrom-platinum solution gives excellent results 
with some simple eyes (e. g. Phalangium and Acilius larvz), but is 
unsatisfactory in the case of spiders and with compound eyes. 
smic acid, so highly recommended by M. Schultze, while it has 
some valuable qualities, is, on the whole, not very serviceable. It 
preserves, to a certain extent, the character of the fresh tissues, - 
but it renders the pigment less easily soluble, lessens important 
differences in refrangibility (e. g. between the rhabdomeres and 
the protoplasm of the cells), and besides leaves the preparation 
brittle, so that good sections are not easily obtained. 
he most serviceable hardening fluid for the compound eye is 
alcohol (70 p. c.—90 p. c.). The hyaline rhabdomeres generally re- 
main clear and transparent, but lose their color and often a part of 
their refrangibility. 
Bleaching—The pigment is dissolved very rapidly by caustic 
potash, but this agent destroys almost equally rapidly other parts, 
even to the chitinous parts. The strength first recommended by 
Moleschott, 30-35 p. c., allows time for examination in detail. 
e best means of bleaching is found in nitric acid, first recom- 
mended for this purpose by Gottsche, Gottsche used the full — 
strength, M. Schultze, 25 p. c.; Grenacher employed 20-25 p. C» — 
adding a drop to the sections lying in dilute glycerine, under the © 
Cover-glass. The demonstration of nuclei by means of the ordi- 
„The Science Monthly, March, 188 
4. 
= organ der Arthropoden,” p. 22-25, 1879. 
* Mil. Arch, 1852, p. 486. p> é P 5 
