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 been 

 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 apfai^atus subject to many and serious objec- 

 tions ? 



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 perfora- 

 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 sub- 

 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 zinc 

 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 zinc of com- 

 merce which will generate hydrogen perfectly free from arsenic, 

 notwithstanding there are some who say that purified zinc is not 

 free from this metal ; but it is evident that they must be mistaken, 

 as any one may see by making the experiment, which, as it is a 

 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- 



