THE MICROTOMIST'S VADE-MECUM

cent. alcohol, and to stain very slowly (twenty-four hours).
Wash out with HCI in alcohol as in the case of borax-
carmine alone. Nuclei should appear pure carmine-red,
protoplasm orange, formed tissues generally very pale yellow.
For Appendicularia I find this stain gives better results than
any other. And I found the same with Sagittc.
Prof. Fol informs me that he obtains a similar stain by
washing out borax-carmine objects with HC1-alcohol in which
a little picric acid is dissolved. The HC1 is taken weaker in
this case.
174a. Borax-Carmine and Indigo-Carmine (Merkel's me-
thoc).-The following is from a paper read by Golding-Bird
before the " Medical Microscopical Society" in April, 1877
describing the method originated by F. Merkel in Germany
in 1874, and from another account, i.e. xviii, p. 242.
(A) Take half a drachm of carmine, two drachms of borax,
and four ounces of water. Rub up in a mortar, allow the
fluid to stand some time, decant, filter, and keep in a
stoppered bottle.
(B) Take two drachms indigo-carmine, two drachns borax,
and four ounces water. Mix, decant, filter, and preserve, as
before.
Before using, mix A and B in equal proportions.
The objects to be stained must be thin; all traces of
chromic acid or chromates must have been carefully washed
out from them; and they must be soaked in alcohol before
staining. Stain for fifteen or twenty minutes. Wash out
with saturated aqueous solution of oxalic acid, for a rather
shorter time; wash the acid out with water, and mount as
desired.
The oxalic acid is necessary for fixing the indigo-carmine,
which being very soluble in water would otherwise be washed
out. Unfortunately, it precipitates carmine, so that successful
preparations are not easily obtained; the carmine being
1 ' M. M. J.,' xvii (1877), p. 317.

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