THE MICROTOMIST' S VADE-MECITM

,swelling of the nuclei; but used with picric-acid specimens it   2
gives true appearances.
Gell-diviion.-For the special study of the phenomena of        1
cell-division, the best object is the above-mentioned gill-plates note
of the larva of salamandra. Picric acid in saturated solution 4
is the best reagent for preserving the karyokinetic figures. 1
(Care must be taken not to let the preparations be invaded buti1
by mould.)    Stain, if required, with hmmatoxylin (in weak      osers
solution) or carmine. Chromic acid and chloride of gold may      iubli
also be used.                                                    ithi
485. Fixing Agents for Study of Cell-anatomy (Flemming's R.
methods 1).-Pieric and    chromic acid    (to be followed by     Ril
hmmatoxylin- or anilin-staining) are to be preferred to alcohol All
and other agents for the study of the cells of Vertebrates. actto
Shrinking and distortion of the nuclear figures (and, with       more
picric acid, swellings of them) are to be expected, but other    In
agents have the same defect to a much greater degree; alcohol Ilft)
especially causes entanglement of the filaments. Acetic acid those
does the same, and causes swelling besides.
"Those who seek to study cell-division by means of bichromate rafe
of potash or other chromic salts are hopelessly in the wrong     street
road."2  And this, because of the injurious action of the        ash
bicbromate, not on the body of the cell, which it preserves thtt
well, but on the karyokinetic figures. Osmium       is useless, Caica
because it does not sufficiently stain the nuclear figures,       Ch
and prevents them    from  staining well with other reagents. from
In the case of epithelium, thin sections should be made          t en
through tissues hardened in chromic or picric acid, stained       Pi(
with humatoxylin or anilin, and cleared. This is better than     Acetic
to attempt to isolate the cells.    Picric-acid solutions must    Alt
never be weak.                                                   forth
For staining he recommends:                                    then
1. Bismarck brown (Mayzel's formula, No. 155).                 itia
1 'Arch. Mik. Anat.,' xviii (1880), p. 250.        Mik
2 L. c., p. 352.

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