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ELEMENTS OF MATERIA MEDICA.

cises a specific influence over the nervous system ; at least I infer this,partly from the effects observed by Orfila when it was injected into theveins of animals, and partly from its occasionally curative powers inaffections of his system, as epilepsy and chorea.

The blueness, or slate colour, or bronze hue of the skin just alluded to,has been produced in several patients who have continued the use of thenitrate during some months or years (Medico-Chirurg. Trans, vii. andix.)In some of the cases the patients have been cured of the epilepsy forwhich they took the medicine ; in others the remedy has failed (Rayer,Treatise on Skin Diseases, by Willis, 961). In one instance which fellunder my notice, the patient, a highly respectable gentleman, residing inLondon , was obliged to give up business in consequence of the discolora-tion ; for when he went into the street, the boys gathered around him,crying out “ there goes the blue man.” In this instance no perceptiblediminution of the colour had occurred for several years, but in some casesit fades in intensity. The corion is the essential seat of it. Dr. Baddeley( Med.-Chir. Trans, ix. 238) found that blisters rose white,—a proof that inhis patient the colouring matter was below the epidermis. But in someinstances the cuticle and corpus mucosum of the face and hands participatein the tint. In one instance the mucous membrane of the stomach andintestines was similarly tinted. A case is mentioned by Wedemcyer(Lond. Med. Gaz. iii. 650) of an epileptic who was cured by nitrate ofsilver, but eventually died of diseased liver and dropsy: all the internalviscera were more or less blue, and Mr. Brande obtained metallic silverfrom the plexus choroides and pancreas. The discoloration of the skinis usually regarded as permanent and incurable ; but I have beeninformed that in one instance washes of dilute nitric acid diminished it.If this observation be correct, I woidd suggest the exhibition of nitricacid internally, as well as its external use. Dr. A. T. Thomson ( Elem. ofMat. Med. i. 715) suggests that if nitric acid were conjoined with nitrateof silver, the discoloration might be prevented ; and the suggestion cer-tainly deserves attention. But I would observe, that if the acid shouldprove efficacious, his hypothesis, that the colour depends on blackenedchloride of silver, will be disproved ; for nitric acid can neither preventthe action of the compounds of chlorine on the salts of silver, nor can itdissolve the white chloride or the black subchloride.

Uses. —Nitrate of silver has been employed internally in a very fewcases only ; and of these the principal and most important are epilepsy,chorea, and angina pectoris. Its liability to discolour the skin is a greatdrawback to its use; indeed, I conceive that a medical man is notjustified in risking the production of this eflect without previously inform-ing his patient of the possible result.

In epilepsy it has occasionally, perhaps more frequently than any otherremedy, proved successful. Dr. Sims (Mem. of the Med. Soc. of Lond.iv. 379), Drs. Baillie, R. Harrison, Roget , and J. Johnson (Treat, onNerv. Dis. by J. Cooke, M.D. ii. Pt. 2, 147), have all borne testimony toits beneficial effects. Its methodus medendi is inexplicable. This, indeed,is to be expected, when it is considered that the pathology and causes ofepilepsy are so little known, and that, as Dr. Sims has justly observed,every thing concerning this disease is involved in the greatest doubt andobscurity, if we except the descriptions of a single fit, and that it returnsat uncertain intervals. In this state of ignorance, and with the already-