402 Proceedings of the Royal Society of Edinburgh. [Sess. 
The positive poles of copper, lead, and zinc cause precipitation, the 
firmest precipitate being that due to zinc. 
With an anode of iron a few bubbles of gas are given off, but no pre- 
cipitate is formed. 
It is evident, then, that surgeons, by using silver or platinum as the 
active pole, have been unconsciously courting the very danger of gas bubbles 
which they were endeavouring to avoid. We may draw the conclusion 
that this danger is nothing but a bogey. There is also no advantage in 
using iron electrodes, pace Dr Stevenson, for no coagulating effect is pro- 
duced, probably because the protosalts only are produced. Of the heavy 
metals Pb, Cu, Zn, which produce a precipitate, the latter is to be preferred 
both because its salts, if absorbed, are less toxic, and also because it forms 
the largest and firmest precipitate, and that without any gas at all being 
given off. In an experiment using zinc electrodes the current strength was 
maintained at 300 m.a. for ten minutes, equivalent to 50 m.a. for one hour, 
which is about the dose usually given by the Moore- Corradi method ; during 
that time the zinc electrode lost 5 centigrammes in weight and a precipitate 
weighing 5*35 grammes was formed. This precipitate has been kindly 
examined for me by Dr Drinkwater and by Miss Isabel Mitchell, and they 
find that it consists chiefly of a loose compound of albumen and zinc, an 
albuminate of zinc. By using a coil of zinc wire a firm precipitate binding 
together the wire spirals is formed. It is difficult to say whether such a 
precipitate in an aneurysm would, through the deposition of fibrin upon it, 
lead to the coagulation of the blood and to subsequent organisation of the 
clot, or whether it would be gradually washed away by the blood stream, 
or split up by hydrolysis into bodies of smaller molecular weight. The 
authorities whom I have consulted think that the precipitate would favour 
the coagulation of the blood. The clinical experience of surgeons and post- 
mortem examinations would help to settle this question. I venture in 
conclusion to suggest that surgeons should introduce zinc wire into an 
aneurysm which they may wish to treat electrolytically rather than the wire 
recommended by Dr Stewart or other clinical authorities who have not 
tested the coagulating effects of these metals experimentally in the physical 
laboratory ; for my experiments, which confirm those of Leduc, convince me 
that the passage of an electric current through an aneurysm in the orthodox 
Stewart-Moore-Corradi method in no way aids in bringing about the 
coagulation of the blood. Whatever coagulation is produced is due only to 
the introduction of the foreign body. 
(. Issued separately July 23, 1908.) 
