THE MICROTOMIST' S VADE-MECUM

different purposes. In general, for maceration purposes, a
serum of a pale brown colour should be employed.                  4
The manner of employing iodised serum for maceration is        vhon
as follows:-A    piece of tissue smaller than a pea must be
taken, and placed in 4 or 5 c.c. of weakly iodised serum in a    u
well-closed vessel. After one day's soaking the maceration is Rkit
generally sufficient, and the preparation may be completed by   toeus
teasing or pressing out, as indicated above ; if not, the soaking
must be continued, fresh iodine being added as often as the
serum becomes pale by the absorption of the iodine by the
tissues. By taking this precaution, the maceration may be
prolonged for several weeks.                                     tdo
It is obvious that these methods are intended to be applied  thoo
to the preparation of fresh tissues, the iodine playing the     oftheoco,
partof a fixing agent in regard to protoplasm, which it        a
slightly hardens.
448. Artificial lodised Serum (Frey's formula 1) :otih
Distilled water  .     .    .     .    135 grammes.           01
White of egg           .    .    .      15     ,,
Sodium chloride .      .    .    .       0-20  ,,
Mix, filter, and add-
Tincture of iodine     .    .    .       3     ,
There is formed a precipitate, which is removed by filtering    t
through flannel; and a little iodine is added to the filtrate.
Ranvier states that he has been unable to obtain good         ael
results by this method.                                          9er cnt
449. Alcohol.-Ranvier employs one-third alcohol (1 part       CR0Mino
of 360 alcohol to 2 parts of water). Epithelia will macerate    anatom
well in this in twenty-four hours. Ranvier finds that this       For A
mixture macerates more rapidly than iodised serum.                 or
Other strengths of alcohol may be used, either stronger r
(equal parts of alcohol and water) or weaker (1 alcohol, for      M
isolation of the nerve-fibres of the retina, for instance, Thin).
450. Sodium   Chloride and Alcohol (Moleschott and Piso
I ' Le Microscope,' p. 131. Ranvier, 'Traite,' p. 77.

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