282 Means of detecting Arsenic in the Animal Body, &c. 
periments of a single individual, but drawn from numerous care 
ful researches, made by skillful chemists. What is still more 
convincing on this point, is, that even in some few cases, where 
an animal has been poisoned by arsenic, its liver will not indi- 
cate its presence. . , 
To sum up the answer to this question in a few words—the 
bones do contain arsenic. No positive evidence has as yet bee 
given to lead us to believe that the muscles contain the smallest 
quantity of arsenic. We have the most positive evidence that 
the organs do not contain the least trace of arsenic. 
Is not Marsh’s apparatus subject to set “ees serious objec- 
tions ? Pan = he 
This valuable instrument I think was discussed a year or two 
since, by Dr. Mitchell, of Philadelphia, but as I have never seen 
his article on the subject, I hope, that if this should meet his eye, 
he will excuse such parts of it as may be a repetition of what he 
then stated. Most that is about to be mentioned concerning this 
apparatus, belongs to the investigation of those more intimately 
connected with the subject than myself. 
Marsh’s apparatus, modified from its original and rather com- 
plex form, consists of a four or eight ounce phial, with a peor 
ted cork and glass tube, bent at right angles, or straight, (the for- 
mer is considered preferable, though in both instances the ex- 
tremity must be drawn out to a capillary opening, ) and furnished 
with a porcelain plate or saucer, and the materials for generating 
hydrogen—zinc, sulphuric acid and water. These three last su 
stances in effect constitute the instrument. ‘The first question to 
be decided is, whether any of them are subject to an impurity 
that might create an error. 
- As regards the zinc, that there are some instances of the zine 
of commerce containing a small quantity of arsenic, is not to be 
denied ; and that this will give rise to an impure hydrogen; 
when-acted upon by pure sulphuric acid and water. — But then, 
again, there is nothing more easy than to procure zine of com: 
merce which will generate hydrogen perfectly free from arsenl¢s 
notwithstanding there are some who say that purified zinc 1s 0 
free from this metal ; but it is evident that they must be mistaken; 
as any one may see by making the experiment, which, a5 ot 
very simple one, it would be well to perform; and I feel confi- 
dent in saying that little or no difficulty will be found in procur 
