592 ON DETECTING THE 
with a solution of arsenic; the least that is re- 
quired is, that several of the tests should in the 
results of their action corroborate each other in 
the most full and satisfactory manner, unless by _ 
the action of one of them alone a precipitate is 
obtained which can be collected, and which is so 
free from the objectionable part of the matter from 
which it has been caused to deposit, that it can be 
decomposed, and the arsenic contained in it be 
reduced to, and exhibited in, the metallic state ; 
or, its quantity being sufficient, it be capable of 
being caused to undergo those changes, whereby 
such a solution may be formed from it as will 
completely give all the appearances which are 
expected from a pure solution of arsenious acid, 
by the application of those tests which gave 
unsatisfactory results when applied directly to the 
fluid contents of the stomach: and it is far from 
being extravagant to suppose that in cases of 
poisoning by arsenic it may happen, or that it not 
seldom does happen, that the alimentary canal of 
the individual to whom the arsenic was adminis- 
tered, has become evacuated to such a degree 
before the occurrence of death, that, on post 
mortem examination, the quantity of matter found 
whereupon to operate, is at most not greater than 
to allow of the exhibition, to the most skilful 
