THE MICROTOMIST S VADE-MECUM

storax). In the drug trade it is known as " strained gum
styrax." Van Heurck,' who first suggested this medium,
recommended styrax from Liquidambar styraciflor and
liquidambar from L. orientalis. " Liquidambar is preferable
as being very pale yellow instead of a brownish yellow, but
it does not appear to be obtainable from European drug-
gists." It is officinal in America. Van Heurck's styrax was
supplied by Gebe and Co., of Dresden.
358. Monobromide of Naphthalin.2-This liquid is colour-
less and oleaginous, with the odour of naphthalin. It is solu-
ble in alcohol and ether and has a density of 1555, with a
refractive index of 1-658, giving therefore as the " index of
visibility" 22 as against 11 for Canada balsam. It is not
volatile.
It was found by Abbe and Van Heurek that this medium
gave good results with diatoms. Max Flesch3 experimented
with it for histological preparations, and found that though
in many cases the results did not bear out his expectations,
vet there is probability that some objects will be better shown
in it than in other media. When first mounted, preparations
are very sharply defined, and it appears certain that they
give better images than Canada balsam or glycerin prepara-
tions. After the lapse of a year and a half the preparations
are found to be well preserved, but are no longer superior to
Canada balsam preparations.
Tissues must be very carefully dehydrated before mounting
as the least trace of moisture causes turbidity; they may either
be brought direct from absolute alcohol into the medium or
be first cleared with turpentine (clove oil and kreasote do not
answer so well). The mounts may be luted with wax fol-
lowed by shellac-varnish, or with thickened " Venetian turpen-
I ' Bull. Soc. BeIg. Mic.,' ix (1883), pp. 134-6. 'Journ. Roy. Mic. Soc.'
(N.S.), iii (1883), p. 741.
2 'Journ. Roy. Mic. Soc.,' iii (1880), p. 1043.
S'Zool. Anz.,' v (1882), p. 555.

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