THE MICROTOMIST'S VADE-MECUM

having been soaked out by water the tissues are prepared for
freezing in the following manner, which it is important to
observe, otherwise it will be found that the crystals of ice so
break up the delicate nervous tissue as to render it totally
useless for minute examination. The tissues are to be well
soaked in syrup. The sugar somewhat retards the freezing,
and besides, seems to alter the manner of cry stallisation, so
that instead of the ice being spicular in form it becomes
granular and does no injury to the parts.
The syrup requires to be of a particular strength, viz.
double refined sugar, 2 ounces; water, 1 fluid ounce.
Wash the superfluous syrup from the surface, and put into
the ordinary mucilage for an hour or so before cutting.
Imbed in the freezing microtome with mucilage in the usual
way. Float the sections into water.
245. Gum and Syrup Congelation Mass (Cole's formula').
-Gum mucilage (B. P.) 5 parts; syrup, 3 parts. (For brain
and spinal cord, retine, and all tissues liable to come in pieces
put 4 parts of syrup to 5 of gum). Add 5 grains of pure
carbolic acid to each ounce of the medium.
(Gum mucilage (B. P.) is made by dissolving 4 ounces of
picked gum acacia in 6 ounces of water.)
The syrup is made by dissolving 1 pound of loaf sugar in 1
pint of water and boiling.
This medium is employed for soaking tissues previous to
freezing. They may remain in it for " any length of time;
all the year round " if desired.
The freezing is conducted as follows: the gum and syrup
is removed from the outside of the object by means of a cloth;
the spray is set going and a little gum mucilage painted on
the freezing-plate; the object is placed on this and surrounded
with gum mucilage; it is thus saturated with gum and syrup,
but surrounded when being frozen with mucilage only. This
1 ' Methods of Microscopical Research,' 1884, p. xxxix. ' Journ. Roy.
Mic. Soc.' (N.S.), iv (1884), p. 318.

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