THE MICROTOMIST' S VADE-MECUM

melted on to the slide as before), and the mount is completed
by means of xylol balsam.
Both the moistening with alcohol, and the heating, are
necessary for the attachment of the sections to the slide; the
effect is not obtainable by means of one of these manceuvres
alone.
269. Gutta-percha Section-fixing Process (Frenzel's first
method'). -Dissolve gutta percha in chloroform + benzin,
allow the solution to settle, and filter until clear and almost
colourless. (The filtrate should be allowed to stand two or
three weeks, be frequently well shaken, and any precipitate
that may form at the end of that time be removed by
filtration. An excellent 1 per cent. gutta-percha solution
may be obtained from Ferd. Beyrick, Berlin, N. Linienstrasse,
114.) The solution should not be too thin; it should flow but
slowly on the slide.
The slides are prepared by brushing with the solution, and
allowing to dry.
Paraffin sections are arranged on the prepared surface, and
smoothed out, if necessary, by treating them with abso-
lute alcohol. They are then exposed for five or ten minutes
(or even a few seconds) to a temperature of 35' to 50' C. (in
no case higher than 550). This makes the gutta-percha film
sticky and fastens the sections. Allow the slide to cool.
When cool, pour over the sections ample quantities of
naphtha, allowing the naphtha to flow away quickly, until the
sections appear almost dry. You can now remove the naphtha
with absolute alcohol, and pass through successive alcohols
for the purpose of staining; or you can mount direct in
balsam. Or, in the case of very small sections, you can take
a further precaution. Allow the naphtha almost to evaporate,
pour a few drops of gutta-percha solution over the sections,
and allow the gutta percha to dry before bringing them into
alcohol. Staining succeeds perfectly in this case, as the
' IZool. Anz.,' No. 130 (vol. vi, 1833), p. 51, anl No. 145, p. 423.

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