48 Dr John Davy on Oxide of Arsenic. 
the Beck, I found the indications of arsenic in the one, of 
about the same degree of distinctness as in the other. 
As regards the question proposed,—Is arsenic in very 
small quantity, long continued in use, injurious to man?—do 
not the results described and the experience related justify 
an answer in the negative? To me they seem to warrant 
this conclusion, and also the conclusion equally, that no 
appreciable good effect is produced in the instance of man, 
or in that of the other animals mentioned, by its long-con- 
tinued use ; and in confirmation of this I may state, that one 
of the inhabitants of the village, a blacksmith, who on 
taking up his abode there some years ago, was subject to 
attacks of asthma, assured me that his complaint had from 
year to year been becoming worse rather than better, 
In a recent number of the Journal de Médecine et Chi- 
rurgie Pratiques,* there is a notice of a thermal spring (its 
temperature that of 106° Fahr.) in the regency of Tunis, 
called Bon-Chater, the water of which, from the analysis 
made of it by M. Guyon, contains a large proportion of 
arsenic in the state of arseniate of potash and of soda, larger 
indeed than any other yet known, being as much as four 
grains to the gallon; and yet we are assured, that it was 
used not only by the natives with impunity, but also by M. 
Guyon and his party. 
If, then, not noxious, used as above described, is there not 
another inference to be drawn,—viz., that arsenic, especially 
in combination with either of the alkalies, is not one of those 
substances which accumulate in the system; is, on the con- 
trary, as commonlyadmitted, one of those which are got rid of 
by excretion,—its elimination varying, probably, in different 
persons and in different animals as to rate, and varying, it 
may be, proportionally in the measure of its tolerance ? 
Analogy seems to favour this view. The tolerance of cer- 
tain substances taken in slowly increasing doses is very 
remarkable. I was assured by the medical man under 
whose care “ The Opium-Eater,” the late Mr De Quincey 
placed himself, that at the height of his indulgence he took 
half a pint of laudanum daily. The same practitioner as- 
sured me that another patient of his, a lady whom I knew, 
* Tom. xxxii. 369. 
