II

50            THE MICROTOMIST S VADE-MECUM
be very alkaline, the colouring will be too intense, and much     W
of the soft tissue or imperfectly-formed material around the
germinal matter is destroyed by the action of the alkali. If,
on the other hand, the reaction of the solution be neutral, the   :
uniform staining of tissue and germinal matter may result.
When the vessels are injected with the Prussian-blue fluid,
the carmine fluid requires to be sufficiently alkaline, to
neutralise the free acid present. The permeating power of
the solution is easily increased by the addition of a little     IJul
more water and alcohol. In some cases the fluid must be ji&ihe
diluted with water, alcohol, or glycerin; and the observer        oid
must not hastily condemn the process, or conclude, as some        hait O
have, that a particular form of germinal matter is not to be      kis
coloured, till he has given the plan a fair trial, and tried a     i.
few experiments."
The present writer, who has tried this fluid by using it
daily for more than a year, feels constrained to disagree with
Prof. Ranvier, who teaches that it " presents no real advan-       Diss
tages, whilst it has the disadvantage of a tendency to diffusion
of the colouring." He may be right in the latter remark;
but it is self-evident that the excellent preservative solution    Ibr
afforded by this mixture of weak glycerin and alcohol, is a       Esfe
very " real advantage " both as regards the preservation of       1e
the tissues immersed in it, and the stability of the liquid       b,
itself. The diffuseness of the colouration may always be a
counteracted by washing in weak 1C11.
51. Ammonia-carmine (Beale's second formula').
Carmine .             .             . 15 grains.
Liq. Amm. fortissmus     .    .     .   - drachm.           I
Price's glycerin    .    .    .     .   2 ounces.
Alcohol .     .     .    .    .     .   6 drachms.
This fluid is specially designed for the purpose of staining     11
by means of injection. Inject, and leave the preparation           to
twenty-four hours.     Then inject a little pure glycerin, to
'How to Work, &c.,' p. 304.


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