ARSENIOUS ACID.

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arsenic, or ought wc to refer it to a change effected by arsenic on thebody, daring life, causing “ a different disposition and affinity among theultimate elements of organized matter, and so altering the operation ofphysical laws in it ? ” The latter hypothesis, though advocated by Dr.Christison, appears to me untenable; for, in the first place, there is noevidence of any peculiar change of this kind during life ; secondly, thatthis does not take place appears probable, from the putrefactive processcommencing after death as usual; and it would appear that the peculiarinfluence of the arsenic does not commence, or at least is not evident,until this process has existed for some time, and when a garlic odour isevolved by the body. It is, indeed, true that the quantity of arsenicwhich has been detected in the body after death, is, as Dr. Christisonremarks, “ almost inappreciably small;” but it is probable that diequantity is much larger than chemists have yet been able to recognize ;and it is not at all unlikely that the arsenious acid may enter into newcombinations while within the dead body, and in this way become dif-fused, probably in a gaseous state: the garlic odour which is evolvedfavours this notion, as well as the statement made by some, that thequantity of arsenic in the body diminishes during the progress of themummifying process.

Moods Oderandi. —When we consider that arsenious acid operates asa poison to whatever part of the body it be applied, the nerves and mus-cular fibres excepted; that the quickness with which it acts is in pro-portion to the absorbing powers of the part, and that the most solubleare the most energetic preparations, we can have little difficulty inadmitting diat absorption into the blood-vessels is necessary to the actionof this potent agent. But the detection of arsenic in the solids andfluids of the body has hitherto not been effected in a satisfactory manner.Lassaigne (quoted by Wibmer, op. cit. i. 321) states, that he detected itin the infiltrated pleura of a horse ; and Fodere (quoted by Dr. Chris-tison) twice got indications of its presence in the urine: but Ilardeggand Schubartli, on the other hand, failed to recognize it, and thereforefurther evidence of its existence in the body is necessary, to enable us toplace confidence in the results of Lassaigne and Fodere. An acquaint-ance of Beissenhirz (quoted by Wibmer, op. cit. i. 318) obtained nearlythree grains of metallic arsenic from the stomach, caecum, lungs, liver,heart, and brain of a horse poisoned by six drachms of arsenious acid,taken at divided doses: but the extraction of this substance from thestomach and caecum is no evidence of its absorption.

Arsenious acid appears to exercise a specific influence over severalparts of the body, especially the alimentary canal, the heart, and thenervous system. That the alimentary canal is specifically affected isshown by the inflammation of the stomach, induced by the applicationof arsenic to wounds, and which, according to Sir B. Brodie {Phil.Trans, for 1812, 205), is more violent, and more immediate, than whenthis poison is taken into the stomach itself. That the heart is also spe-cifically acted on by arsenious acid is proved by the symptoms (theanxiety at the praicordia, the quick irregular pulse, &c.), and by the post-mortem appearances (red spots in the substance of this viscus), and bythe diminished susceptibility to the galvanic influence. The specificaffection of the nervous system is inferred from the symptoms: thus, theheadache, giddiness, wandering pains, impaired sensibility of the extre-