MEDICO-LEGAL CONTRIBUTIONS ON ARSENIC. 173 
If this examination shows the vessels and chemicals to be 
pure or free from poison, the analyst may at once proceed to 
the examination of the suspected material ; and if otherwise, 
he will detect the impure materials, and can replace them. 
Only after this procedure can the real examination be properly 
undertaken ; the results will then be entitled to confidence, 
and all doubt will be removed from the mind of the examiner 
regarding the source of the poison, in case any is found; it 
wdll, besides, free him from many embarrassing questions 
when in the witness-box, which otherwise might seriously 
affect him. 
It may be stated here that it was probably in consequence 
of arsenic occurring in the reagents employed in the investi- 
gations,and the omission of their preliminary examination, that 
led to Orfila^s erroneous assertion that arsenic is a normal con¬ 
stituent of the human body. Because of this omission in the 
case of Mrs. Wooler (Durham, England,Winter Assizes, 1855), 
doubt was thrown on the scientific evidence by reason of the 
useof chlorhydric acid containing arsenic, thediscovery of which 
impurity was not made until after the analysis was completed. 
In every case investigated by me a preliminary examina¬ 
tion has been made in the way just mentioned. It is true 
that but a few poisons, of w’hich the chief is arsenic, are 
likely to occur in the materials employed in analysis; occa¬ 
sionally, how^ever, others are present, and as a general rule, 
therefore, it is advisable to make a preliminary examination. 
5. Separate Examination of each Part .—It is always desirable 
that each part be separately examined—as, for instance, the 
stomach, the contents of the stomach, the small intestines, 
the large intestines, the liver, &c.—for often, by proceeding 
thus, important information may be obtained. It is best 
also to consume in the first examination but a part of the 
material (after the whole has been finely divided and intimately 
mixed)—two thirds, for example—so that, in case of accident, 
an examination may still be made; and to this there is 
usually no objection, since in almost all cases, if the poison 
can be detected in the whole, it can be in the part mentioned, 
and in sufficient quantity not only to identify it, but to make 
the greater number of the confirmatory tests. 
[To he continued.) 
