THE MICROTOMIST' S VADE-MECUM

picro-carmine, or gentian violet. He recommends the follow-       0 enter iD
ing formula:                                                      of th
14. Chromo-aceto-osmic Acid Fixing Mixture (Flemming's          &(0
formula').                                                       stin to f
Chromic acid       0-25 per cent.                        tut the I
Osmic acid         0-1 per cent.    In water.
Glacial acetic acid 0-1 per cent.                          hai
The best results (as regards faithfulness of fixation) are
obtained with this mixture when it is allowed to act for only     per Centf
a short time (about half an hour).                                   de &
15. Chromo-acetic Acid Fixing Mixture (Flemming's for-            t
Chromic acid 0-2 to 0-25 per cent.
Acetic acid ca.     0-1 per cent. S In water.               -(S
Flemming finds this, followed by heematoxylin      staining,    ii it10
to be the best means for demonstrating the achromatic              Whet
figures. The preparations do not stain well with safranin or       lltdh
other anilins (p. 382).                                             1
16. Chromic Acid.-Chromic acid is employed in solution          fr
either in water or in alcohol.
The most usual strengths in which it is employed in
aqueous solution are from 0-1 to 1-0 per cent. for a period of
immersion of a few hours (structure of cells and ova). For          I
nerve-tissues weaker solutions are taken, 56th to 8th per
cent. for a few hours. Stronger solutions, such as 5 per            lie
cent., should only be allowed to act for a few seconds.             &EAny
The objects should be washed out with         water before       strog
passing into alcohol or staining fluids. Long washing in            &Y)
water is necessary to prepare them    for staining, except an      rote
anilin stain be used.                                               Re F1
Tissues that have been fixed in chromic acid may be              hi
stained in aqueous solutions if desired, as water does not           Aid
appear to have an injurious effect on them; the acid appears
'Zellsubstanz, Kern und Zel1theilung,' 1882, p. 381.
Ibid., p. 382.

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