THE MICROTOMIST'S VADE-MECUM

better stain is obtained by treating for twenty-four hours       int6
with osmic acid (of 0-1 per cent. in dilute glycerin) specimens d
that have been hardened in bichromate of potash.                 J WO
124. Osmic and Oxalic Acid (Brasicke's method ).-Osmic        1t .
acid, 1 per cent., one hour. Wash out the acid carefully, and     ,b0 U
put for twenty-four hours into cold saturated aqueous solu-     1le lI
tion of oxalic acid.                                             Wat (
Most kinds of tissue are stained by this treatment of various  5hey
hues of carmine, the nuclei being darker. The tissues are        II
well preserved. Care must be taken that the tissues do not      th@i
become blackened before removal from the osmic-acid bath,        $i4g
as in that case the oxalic acid is powerless to redden them.     other
(I have tried this stain and find it diffuse.)                  etht
125. Palladium    Chloride.-Weak solution of palladium         ii (18i
chloride (1-500, 1-800, 1-000) should be taken and allowed to Dhe
act on the tissues for several days. An irregular general .       X
stain, varying in the different tissues from yellow to inky 11.
black (medullated nerve) is obtained.
Not to be recommended as a stain, but admirable as a
hardening agent.
For the manner of preparing the solution and other details
see HARDENING AGENTS, No. 215.
126. Prussian Blue Impregnation (Leber's method2).-Treat       Re
the tissue for a few minutes with , per cent. solution of sul-
phate of protoxyde of iron, and then with 1 per cent. solution     S]
of red prussiate (ferricyanide) of potassium. Wash with           S6li
water.                                                            ht!
127. Perchloride of Iron Staining Process (the Hogyans'         di
method').-This method was first published, three years before     jt
the date quoted, in the ' Journal of the Quekett Club.'
The tissue (having first been fixed with - per cent. silver
'Science Gossip,' No. 175 (1879), p. 160. ' Journ. Roy. Mic. Soc.,' ii
(1879), p. 764.
2 Ranvier, 'Trait6.' p. 108.
3 'Journ. Roy. Mic. Soc.,' ii (1879), p. 358.

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