THE MICROTOMIST'S VADE-MECUlI

CHAPTER XXII.
COAGULATION IMBEDDING-MASSES.                      f 0
is  si
247. Egg Emulsion (Calberla's formula').-The white of        to
several eggs is separated from    the yolk, the chalaze are     t es
removed, and the white is cut up with a pair of scissors.
Fifteen parts of the white are then mixed with 1 part of a
10 per cent. solution of sodic carbonate (10 parts of calcined  adi
soda to 100 of water) and briskly shaken. To the solution
of albuminate of soda thus obtained the yolks of the eggs are    itea
now added and the whole is well shaken up. The mass is
then poured into a deep vessel, allowed to settle for a short
time, the foam and floating fragments of vitelline membrane
are skimmed off with a strip of paper, and any larger pieces     h;
removed with forceps. The mass is then ready for use.             il
The objects to be imbedded are soaked in water for from three
to ten minutes, in order to free them from the liquid in which
they have been preserved. They are then soaked for from five
to ten minutes in a portion of the egg mass placed in a shallow
vessel (very delicate objects are soaked in common white of
egg instead of egg mass). They are then fastened (with           a
needles or otherwise) to the freshly-cut surface of a piece of
egg mass that has previously been hardened by the process
described below, and are then hardened by the same process.
(If the objects are very small, the freshly-cut surface of       boo
hardened mass on which they are to be fixed is covered with      hour
a few drops of the emulsion, and the objects are arranged        ohit
in this when it is nearly dry, which happens in five minutes',
1 ' Morph. Jahrb.,' Bd. ii, 3tes Heft (1876), p. 445.  ce

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