IN CASES OF POISONING. 263 



stomach and intestines themselves. This is always 

 necessary before the arsenic can be detected with cer- 

 tainty. 



It is indispensably necessary that this operation 

 should be preceded by a most careful examination of 

 the reagents to be employed, in order to ascertain 

 whether they contain, as is not unfrequently the case, 

 a small quantity of arsenic. This is equally requisite 

 whether the reagents have been purchased or have 

 been prepared by the analyst himself. The distilled 

 sulphuric acid, the hydrochloric acid, and the zinc 

 must especially be examined. This is most conveni- 

 ently effected in Marsh's apparatus, which will be pre- 

 sently described, and which is invaluable as allowing 

 the reagents, which are employed in it, to be so readily 

 and surely tested. "Without such previous proof of 

 the absence of arsenic in the reagents, upon which the 

 chemist must lay great stress in his depositions, the 

 detection of arsenic in investigations of this descrip- 

 tion cannot be brought forward in evidence, since it 

 might have been derived from the reagents employed. 

 It should farther be observed and stated in evidence, 

 that the investigation was conducted with new utensils 

 and vessels which had not been used before ; and it is 

 advisable, moreover, to insure perfect satisfaction, that 

 it should not be carried out in an ordinary chemical 

 laboratory, or, at all events, that the laboratory should 

 be well cleared before the judicial inquiry is entered 

 upon. 



If arsenic should be found in an examination con- 

 ducted with all these precautions it is still necessary 

 to reflect that it might occur in the body quite acci- 

 dentally ; especially after the administration of certain 

 medicinal remedies, such as the antimonial compounds, 

 preparations of phosphorus, phosphoric, sulphuric, 

 and hydrochloric acids, which may contain arsenic 

 from carelessness in their preparation. Even the hy- 



