MACERATIONS AND CORROSIONS

The student will do well not to neglect this simple method,
which is one that it is most important to be acquainted
with.
447. Iodised Serum.-Iodised serum was first recommended
by Max Schultze ('Virchow's Archiv,' xxx, 1864, p. 263). I
,take the following instructions concerning it from Ranvier
(' Traith,' p. 76).
The only serum that gives really good results is the amniotic
iliquid of mammals. A gravid uterus of a sheep or cow
thaving been obtained (in large slaughter-houses such can be
,obtained without difficulty), an incision is made through the
wall of the uterus and the foetal membranes. A jet of serum
issues from the incision, and is caught in a flask prepared for
the purpose. Flakes of iodine are then added, and the flask
is frequently agitated for some days. Two points should be
noted. A perfectly fresh amnios must be taken; for the
merest incipience of putrefaction will spoil the preparation.
The flask should have a wide bottom, so that the serum may
form only a shallow layer in it; otherwise the upper layers
will not be sufficiently exposed to the action of the iodine.
Another method is as follows:-Serum is mixed with a
'large proportion of tincture of iodine; the precipitate of
iodine that forms is removed by filtration, and there remains
a strong solution of iodine in serum. This should be kept in
stock, and a little of it added every two or three days to the
serum that is intended for use.
Ranvier explains that at the outset serum dissolves very
little iodine; but if an excess of iodine be kept constantly
present in the solution, it will be found that after two or
three weeks iodides are formed, and allow fresh quantities of
iodine to dissolve; so that after one or two months a very
strongly iodised serum is obtained. It should be dark brown.
Such a solution is the most fitting for the purpose of iodising
fresh serum in the manner directed above, and for making
the different strengths of iodised serum that are required for

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