THE MICROTOMIST'S VADE-MECUM

CHAPTER XLVII.
PROTISTA.
637. Osmic Acid for Infusoria, &c. (Pelletan's formule I).-
Drop a little 1 per cent. osmic-acid solution on the organisms
and expose to a current of air, which carries off the vapours
of osmium and evaporates the water. Mount in 1 per cent.
carbolic-acid solution. If it be desired to stain, use a 1 to
400 or 500 solution of gold chloride, placing the preparations
in the light and washing with distilled water. Overstained
preparations may be treated with very dilute formic acid, or
may be mounted in glycerin.
638. Infusoria (Certes' methods 2).-Fix with osmic acid of
2 per cent. (In the case of very contractile Infusoria, place a
drop of the solution on the cover-glass, and place it on the
drop of water that contains them. But generally speaking
it is best to employ only the vapour of the solution, exposing
the organisms to its action for not more than from ten to
thirty minutes.)
The objects having been covered, the excess of liquid is
removed by means of blotting paper, and the following stain
is allowed to flow in:
Glycerin.     .     .    .    .     .    1 part.
Water    .     .    .    .    .     .    1
Piero-carmine.           .    .     .    1
1 'Journ. Roy. Mic. Soc.,' i (1878), p. 189. ('Journ. de Micrographie.')
2 Comptes rendus,' 1879, p. 433 (1r sem.).

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