THE MICROTOMIST' S VADE-MECUM

the penetration of staining fluids. Besides this, it often gives      r
rise to a coagulation of the perivisceral fluids that glues the
viscera together in a most undesirable manner.   Therefore, if      1e
alcohol is used, acidulated alcohol is generally taken (see g
FIXING AGENTS). But the fluid most used is Kleinenberg's
picro-sulphuric acid (see FIXING AGENTS). The great advan          a
tages of this fluid are that it kills quickly, that it removes the T
sea-salts from the tissues, and that it allows of good staining    V11401
subsequently. For special cases picro-nitric or picro-hydro-        te 01
chloric acid is used instead (see FIXING AGENTS). Osmic acid        1 els
is used, but only for very permeable tissues (on account of its    ardl
very feeble penetrating power), and in cases in which it is         tIa
not important that a subsequent nuclear stain should be ie
easily attainable (see FIXING AGENTS). Chromic acid is also
avoided as much as possible on account of its hindrance to          U1ti
staining (see FIXING AGENTS). Combined with platinum chlo-          Lnt
ride however, in the mixture known as Merkel's fluid, it is said to  clming
allow of good staining, and is found useful in some special isdeve
cases (see FIXING AGENTS), Corrosive sublimate is found very        N
convenient, and is the fluid most used, excepting picro-sul- 410Y
phuric acid (see FIXING AGENTS).
Washing out is done with successive alcohols, water being         ceit
used only in the case of corrosive sublimate, osmic acid, or        intj
the chromic mixtures. Staining is done in almost all cases          word
with alcoholic staining media, and these are made to contain        ptrat
if possible about 70 to 80 per cent. alcohol (not more, because      It i
it is found that fluids containing much more than that pro- rther
portion of alcohol stain more diffusely than solutions weaker kee,
in alcohol). The stains most used are Grenacher's borax-
carmine, Mayer's modification of Grenacher's alcoholic carmine,      stabi6
Kleinenberg's humatoxylin, and Mayer's cochineal (for all           4U
these see STAINING AGENTS). Anilin stains are only used             intI
in special cases, viz. as nuclear stains by the Hermann-             di6h
Bittcher process (see STAINING AGENTS, ANILIN STAINS).              18
Aqueous stains are more seldom used, but alum-carmine
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