248 Proceedings of Royal Society of Edinhurgli. [march 19 , 
tartaric acid (these are probably the best solvents), the latter only 
in perfectly fresh solutions ; but, in so rendering the bichloride of 
mercury soluble, we greatly increase the risks of poisoning by 
absorption into the system, so that in increasing the antiseptic powers 
of the lotion we also increase its poisonous properties. In obstetrical 
practice, and in wounds extending over a large area, such a factor 
cannot be left out of account. 
Here the biniodide possesses advantages over the bichloride 
which cannot be lightly esteemed. It is considerably less poisonous. 
Cash has pointed o\i\, {Local Government Board Rejport, Supplement^ 
1885, p. 186) that guinea pigs are much more tolerant of it than of 
the bichloride ; and pharmacologists are agreed that the poisonous 
dose is probably at least double that of the bichloride. 
The bichloride dissolved in tartaric acid is probably more 
dangerous, because of the extreme difficulty of rendering it again 
insoluble. If taken internally, none of the ordinary antidotes for 
the bichloride could be got to take effect. I venture to suggest the 
following as reasons why surgeons and obstetricians are gradually 
coming to see that they have in the biniodide of mercury a safer 
and more reliable antiseptic than the bichloride : — 
1. It is not so poisonous, hence the risks of poisoning by absorp- 
tion are not so great. 
2. It does not form an albuminate, consequently the whole of the 
salt is available as an antiseptic. 
3. It may be used with either acids (especially vegetable acids) 
or alkalies, neither of which appear to interfere immediately 
with its antiseptic properties. 
4. It is not necessary that the solution should be made with 
distilled water; all that is necessary is a slight excess of 
iodide of potassium. 
5. The mercury from this solution is not deposited on the surface 
of the skin or on instruments, or the deposit is exceedingly 
slight, so slight indeed that it will not injure the most 
delicate instrument. 
6. The exact strength of the solution is always known, as its 
properties remain constant. 
As a preservative fluid for pathological and other specimens, it is 
