Syn. White Arsenic. White Oxide of Arsenic.

Effects. For a general account of arsenic, including arsenious acid, see pages 318 and 335 of the present volume. As an escharotic, it is somewhat peculiar in its properties and applications. When applied to a living tissue, so far diluted as not to prove caustic, arsenious acid is powerfully irritant, exciting sometimes intense and diffusive inflammation. in a more concentrated state, it is an energetic escharotic, but usually causes intense pain before destroying the life of the part, and gives rise to much inflammation in the contiguous living tissue. When the cuticle remains, it exercises comparatively little caustic influence. Moreover, if applied at the same time to diseased and healthy structure, it is said to act preferably as an escharotic upon the former, which it is asserted sometimes to destroy, while it merely inflames the latter. Another interesting fact, in relation to its local effect, is that it is strongly antiseptic, preserving animal structure, immersed in its solution, unchanged in appearance for years.

From all these facts, it may be fairly inferred that arsenious acid acts dynamically as a caustic, and not by chemical combination with the tissues. Through its intense irritant action, it probably produces a degree of excitement in the part beyond its capacity to support. Upon this principle may be explained its preferable escharotic action upon the diseased tissue, which has less vital power of resistance than the healthy. Hence, too, the violent pain which precedes the death of the part. Were it through a chemical influence that it acted, the cuticle should not afford the impediment it seems to do; and normal structure would yield as readily as the morbid. it appears to me, also, that dead organic matter should exhibit stronger evidence than it does of a decomposing action on the part of the acid.

Another consideration of great importance, in regard to the use of arsenious acid externally, is that it is capable of exercising its constitutional influence by absorption from without. Numerous cases of fatal poisoning by this substance, externally applied, have been placed on record. This fact renders extreme caution necessary in its use. At one time, it was supposed that the danger was in proportion to the quantity applied, and that the main caution demanded was not to employ it too largely. But a certain amount is necessary for any extensive caustic effect, and that quantity, if absorbed, would be sufficient to prove fatal. Danger is, therefore, necessarily incurred by its external use as an escharotic. it is true that it has been employed, with perfect impunity, in a vast number of cases; and, with those who believe that it is capable of doing much good, the circumstance of these comparatively rare cases of death would not operate to its exclusion, were there no other remedy capable of the same therapeutic effect. it becomes, therefore, important to decide which is the mode of application least liable to the poisonous result. At present, the weight of testimony, as well, I think, as of reason, is in favour of the opinion, that it is least dangerous when freely used, so as to produce the death of the part quickly and effectually. Dead structure does not absorb. if a part, therefore, is destroyed by the arsenic, it not only takes up none of the poison itself, but serves, in some degree, as a barrier between it and the living and absorbing tissue. The practical conclusion is, that, when arsenious acid is employed as an escharotic, it should be applied freely; and, when as a mere stimulant or alterative to the part, that the quantity used within a given time should not be sufficient, if the whole of it were taken into the system, to produce fatal effects.

Another important point, ascertained by observation, is that a freshly cut and bleeding part absorbs the arsenical preparation much more rapidly than the surface of an ulcer; and, consequently, it should never be applied to a recent wound.

Medical Uses

The ancients were acquainted with the escharotic property of the arsenical preparations, and used the sulphuret for a depilatory. it was formerly also employed considerably, as an external remedy, in cutaneous diseases, and not without benefit. But its hazardous character has tended to limit its use, in recent times, to more serious affections.

Cancerous, and other malignant ulcerous complaints, are those in which arsenic has been most used, and has the highest claims to consideration. Most of the nostrums which have, at different times, obtained greater or less repute in the treatment of these complaints, have been found to contain arsenic as their chief ingredient; the others serving merely to dilute or conceal it. it is impossible entirely to refuse credence to the many statements of regular, as well as irregular practitioners, to the effect, that arsenious acid often greatly ameliorates these ulcers and tumours, and sometimes completely eradicates them. it is said, as before stated, to destroy preferably the substance of the tumour. An eschar forms, which, after two, three, or four weeks, separates, leaving a surface sometimes healed, or in a fair way to heal, and frequently very much improved. it is certain that many of the tumours thus permanently removed, and ulcers healed, were not really carcinomatous; but some possibly were, and there is no doubt that many real cancerous affections have been ameliorated. Admitting all this, however, it is a serious question, whether all the good that has been achieved, in relation to cancer, might not be better obtained by the knife, and with greater safety. Surgeons had generally come to this conclusion, before the use of anaesthetic inhalations in surgical operations; and, since that time, the conclusion has been strengthened; as the knife has been deprived, in great measure, of those terrors which weighed so greatly in the decision between it and the use of caustic. Whenever it is proper that a tumour should be removed, the knife is not only a more certain, but a less painful, and in all respects less disagreeable means of extirpation than escharotics.

But there are destructive ulcerous affections, which the surgeon would not venture to attack with the knife; and there are stages of cancer, in which few would think of employing it. Here there is ground, at least debatable, for the use of arsenious acid; and, whether that agent be employed or not, must be determined by the individual judgment of the practitioner, after examining the different sides of the question. I am inclined to think that we should do wrong, to throw away entirely a remedy which is capable, if not of saving life, certainly of protracting and rendering it more comfortable. The practitioner should bear in mind the practical rule above given, as deduced from general observation, that the acid should either be used freely, so as quickly to cauterize, or in very small quantities, as a stimulant, insufficient if absorbed to destroy life. in the latter method, it may be applied without hesitation to obstinate, destructive, and malignant ulcers, whenever it is found capable of alleviating them; in the former, it should be restricted to cases which would in all probability prove fatal without it. Happily, the introduction of chloride of zinc into use, as a caustic, is likely in great measure to supersede arsenic, which it resembles, without being dangerous.

In ulcerous lupus, arsenious acid was used advantageously by Dupuy-tren, diluted with twenty times its weight of calomel, and either dusted on the ulcerated surface, or applied in the form of paste made with mucilage. He removed the application at the end of two or three days, and renewed it five or six times when necessary.

Mr. Luke, Surgeon of the London Hospital, considers a mixture of two grains of arsenious acid and an ounce of spermaceti ointment, as almost a specific in onychia maligna. (Pereira, Mat. Med., 3d ed., p. 666.) Under corrosive sublimate, I shall have to speak of another remedy equally certain.

It is customary to dilute arsenious acid with sulphur. For use as a stimulant or alterative, one grain of the acid may be mixed with a drachm of sulphur, and then incorporated with seven drachms of simple ointment; and the strength might well be doubled, or even quadrupled, when the extent of surface to be covered is small. Sir Astley Cooper employed, with a view to the caustic effect, an ointment consisting of a drachm of arsenious acid, a drachm of sulphur, and an ounce of spermaceti cerate, to be removed at the end of twenty-four hours. The arsenical powder of Frere Cosme and Rousselot, which is recognized by the French Codex, consists of one part of arsenious acid, two of dragon's blood, and two of porphyrized cinnabar, and is to be applied in the form of a paste made with the saliva, or with mucilage. Particular formulas, however, are of little importance. One part of the acid may be incorporated with from four to eight or nine parts of inert material, either in the form of an ointment, or of a paste made with mucilage. it might be well to add a little of one of the salts of morphia to allay pain.