THE MICROTOMIST' S VADE-MECUM

55. Ammonia-carmine (Betz's formulat).
Commercial carmine is rubbed up with a little water in a
mortar until a thick syrupy mass is obtained; on to this,
ammonia is poured, with continual stirring. The solution is
diluted with a large quantity of water and filtered. The
filtered solution is exposed to the sun in an uncorked vessel,
which must be of green glass, until a dirty-red, flocculent
precipitate appears; it is then filtered. The filtrate is again
left to stand in the same conditions as before, and when the         r::
precipitate reappears, it is again filtered, and the filtrate
again exposed. Generally no third precipitate appears; if it 9
does, filter again. In either case, the preparation is now         dutin
finished, and the solution is to be preserved for use in a
corked vessel.    It will keep for months.       It sometimes      w'
happens that the solution whilst exposed to the sun acquires        i4
a bad smell, and becomes covered with a white flocculent (DO1t
membrane. This does not hinder the preparation, but, on the        tEsOt'
contrary, furthers it. itsets
Half an hour, or at most an hour, suffices to stain sections.    offtv
The first elements that stain are the granular mass of the          D
grey matter, then nerve-cells, epithelium, and lastly, other       in
structures. A nuclear stain. Permanent.                             1laed
' 'Arch. Mik. Anat.,' ix (1873), p. 112.
to
saO
stlid
ttOts

52


F-