THE MICROTOMIST' S VADE-MECUM

in claiming for the method that it is likely to be of much use
in certain special researches. I recommend the reader to
carefully study the article, which does not well bear
abstracting.
The proportions of the oil-mixture may be varied within
certain limits if desired. Those quoted are, however, recom-
mended as having given the best results. If it happen that
too large portions of tissue have been taken, so that the mix-
ture becomes cloudy, a little ether may be added to restore
the balance, but care must be taken not to add so much
ether as seriously to change the proportional composition of
the mixture.
466. Eau de Javelle (Hypochlorite of Potassium) (Noll's
method ').-Noll remarks that the usual method of preparing
the skeleton of siliceous sponges and similar structures by
corroding away the soft parts by means of caustic potash
has many disadvantages, of which a principal one is that the
spicula are not preserved in their normal positions. He
therefore proceeds as follows: A piece of sponge is brought
on to a slide and treated with a few drops of eau de Javelle,
in which it remains until all soft parts are dissolved. (With
thin pieces this happens in twenty to thirty minutes.) The
preparation is then cautiously treated with acetic acid, which
removes all precipitates that may have formed, and treated
with successive alcohols and oil of cloves, and finally mounted
in balsam.
The same process is applicable to calcareous structures.
Eau de Javelle may also be used for clearing plant sections.
After treatment for a quarter of an hour, everything is re-
moved from such sections except the mere cell-walls ; the sec-
tions are then washed with acetic acid and mounted in gly-
cerin-jelly or Meyer's fluid (glycerin 1 part, water 2 parts, to
10 volumes of which mixture are added 1 volume of salicylic

I ' Zool. Anzeig.,' 122 (1882), p. 528.

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