THE MICROTOMIST'S VADE-MECUM

solution to settle for a few days, filter, and dilute with one
half of water,                                                     Ilt
For Protozoa.-The organisms having been fixed with solu-
tion of Kleinenberg, and washed out with successive alcohols
up to absolute alcohol, are stained in the saffron solution; they
are then washed out with 80 per cent. alcohol, the washing
out being continued until the colouring matter is sufficiently '
removed from the protoplasm; as soon as this is seen to be the
case absolute alcohol followed by oil of cloves is substituted     t tu
for the 80 per cent. alcohol, and the preparations when
cleared are mounted in balsam.     A nuclear or protoplasmic      Dlh
stain, which Blanc prefers to picro-carmine because its action
is more rapid, and can be controlled more precisely by means
of washing out according as it is desired to stain the pro-
toplasm or the nuclei alone.                                      It sd
107. Orchella (Wedl's formula'). -French orchella extract,     Spa
from which the excess of ammonia has been removed by gentle        56
warming in a sand-bath, is poured into a mixture of absolute     Ptbli,
alcohol 20 c.c., acetic acid (concentrated, of 1070 sp. gr.) 5 c.c.,  elss
and water 40 c.c., until a saturated dark-red stain is obtained,  i
which must then be filtered once or twice. Sections are           knisi
washed with water, drained, and treated with the stain.           t
Mount in levulose. A protoplasmic stain, nuclei remaining
colourless. Connective-tissue cells stain deeply, the intercel-
lular substance less deeply. Epithelia, if horny or calcareous,  tabot
are not stained. The basic substance of bone and teeth take
the stain, and so do ganglion-cells and their processes.
108. Ink Process (Paul's method).- Stephens' "blue-black"
ink is the ink usually employed. It must be quite fresh.
Sections of spinal cord (chromic acid preparations) are stained
for a few minutes in a solution of 1 part of the ink to 5 or 10
I ' Arch. f. path. Anat.,' lxxiv, p. 143. ' Journ. Roy. Mic. Soc.,' ii,
1879. For an account of this substance vide Cooley's ' Cyclopaedia,' sub
voce ' Archil.'
2 Marsh's ' Section-cutting,' 2nd ed. (1882), p. 148.

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