Dr John Davy on Oxide of Arsenic. 49 
took daily two drams of solid opium, but not without injury 
to her fine mental faculties, I may mention another in- 
stance, and one more extraordinary, which came to my 
knowledge at Constantinople, of a Turk who took daily, and 
for fifteen years, two drams of solid opium, with half that 
quantity of corrosive sublimate. My informant knew the 
man well,—he was a porter at the arsenal (of which my 
friend was an official), and though in shattered health, was 
capable of his easy duties. I obtained a specimen of what 
was used as corrosive sublimate, and, testing it, found it to 
be this compound, of ordinary purity. The main motive for 
its use, he said was, that it improved—increased, the effects 
of the opium. This instance, according to the apothecaries 
in Pera, is not a solitary one of its kind; their experience 
having taught them that the opium-eater has recourse to 
it when the narcotic has ceased to have its original effect. 
The tolerance of certain substances, in connection with 
their elimination, has not, I am disposed to think, had all 
the attention which it deserves. Why is it that individuals 
living under the same circumstances, using the same kind 
of diet and the same drinks, are some of them subject to 
gout, whilst others are free from it? Is it not because the 
latter possess in their organisation a greater power of elimi- 
nating the causa mali—lithic acid? Why is it that nitrate 
of silver long used, in some persons (the very few) becomes 
—that is the metal—lodged in the cutis vera, occasioning 
there its peculiar discolouring effect, whilst in the majo- 
rity, after long use, no effect of the kind is witnessed ? Is 
not the rationale of the difference the same ? 
We have had it confirmed that the water of Whitbeck 
is, in the solitary instance of the duck, injurious; ultimately 
it would appear to be fatal. This may be owing, it may be 
conjectured, to the duck seeking its food so much more in 
water, and to a delicacy, an idiosyncrasy rendering it pecu- 
 liarly susceptible of the effect of arsenic ; a peculiarity itself 
which may be connected with a feeble eliminating power, 
especially of the kidneys, its urine, like that of birds in 
general, approaching to a solid. 
A somewhat similar instance of great susceptibility of 
the effects of arsenic occurs, I believe, in the charr, one of the 
NEW SERIES,—VOL. XVIII. NO, I.—JULY 1863. G 
