DETECTION OF ARSENIC. 119 



tate or sublimate is generally sufficient to establish the identity 

 of any chemical body. But when human life itself may de- 

 pend upon the colour, specific gravity, and other properties of 

 a precipitate or sublimate, whose weight is scarcely appreciable 

 by a delicate balance, it becomes an object of vast importance 

 to be enabled to decide without the shadow of a doubt, on the 

 identity of our results with the character of those compounds, 

 which are produced when we apply our reagents to solutions 

 containing certain known elements. Hence every possible 

 care has been taken by toxicologists in describing those phe- 

 nomena, which are most, nay, infallibly characteristic of the 

 presence of arsenic, and they have not less carefully noted 

 down the false lights by which our steps may be led astray, 

 and our conclusions rendered incorrect by deductions from 

 false facts. 



Premising then, that the experimenter who is engaged in a 

 medico-legal investigation where poisoning by arsenic is sus- 

 pected, should come to his task entirely unprejudiced, and with 

 a calm, philosophic determination to note and observe facts as 

 they occur and draw inferences fully warranted by the facts as 

 observed, I proceed to arrange the tests by which his experi- 

 ments will be performed, and to detail his manner of using 

 them, describing at the same time the results which they pro- 

 duce, and noticing the fallacies to which they may give rise. 

 This caution of preserving an unbiassed mind, may perhaps 

 excite a smile from those whose philosophic pursuits qualify 

 their minds for the investigation of truth alone, but the remark 

 is induced from having met with a recorded case, where cer- 

 tain physicians in a country village having conceived that a 

 brother practitioner had treated a patient incorrectly, took up 

 the idea that the man had been poisoned by arsenic, and esta- 

 blished, as they thought, the certainty of its presence by a post 

 mortem examination and chemical investigation of the stomach 

 and contents, to the satisfaction of a coroner's jury ; while, 

 subsequently, a review of their analysis, by the medical gen- 

 tlemen accused of malpractice, fairly demonstrated that the 

 patient had died of ordinary inflammation of the bowels, and 

 that a large dose of something which had been given him, and 

 which the inquisitors thought or had heard was arsenic, was 

 an ounce of sulphate of soda, which his physician had pre- 



