The antidotes chiefly trusted to until recent times, such as vinegar, sugar, butter and other oily substances, lime-water, bitter decoctions, and the like, have now justly fallen into disuse. The liver of sulphur or sulphuret of potassium, which maintained its character for some time longer on account of its chemical action with oxide of arsenic in solution, is not more efficacious. The experiments of Renault on the counter-poisons for arsenic, confirmed by the subsequent researches of Orfila, have proved that the arsenical sulphuret formed by solutions of the liver of sulphur is scarcely less active than the oxide itself.[[813]]
It appears that fine impalpable powders, though inert as physiological agents, and destitute of any true chemical action with oxide of arsenic, may nevertheless prove useful in certain limited circumstances. Thus Mr. Hume of London and others have apparently found some advantage in the administration of large doses of magnesia.[[814]] If this substance be of any use at all, which is doubtful, it can act only by covering the arsenical particles with its fine insoluble powder, and so preventing them from coming in contact with the surface of the stomach; for in its state of magnesia it has no chemical action with oxide of arsenic. Another remedy of the same nature is charcoal powder, which was proposed in 1813 with much confidence by M. Bertrand.[[815]] That it has some efficacy when swallowed along with the poison seems to admit of no doubt; for the proposer of it himself swallowed five grains of arsenic in one dose along with charcoal in a state of emulsion, and sustained little inconvenience of any kind. In all probability it acts merely by enveloping the particles of arsenic. But it may possibly be also of service, if recently exposed to heat, by the superficial attraction it exerts over substances in solution; through means of which property it will remove many soluble substances from a fluid, and render them insoluble. Charcoal, however, has been proved to be destitute of all efficacy when not administered till after the arsenic is swallowed. The one must be given along with the other, otherwise it is useless.[[816]]
For some time past the formation of an insoluble arsenite has been aimed at by most experimentalists who have endeavoured to discover an antidote for arsenic. But in general the arsenites, though very insoluble in water, are sufficiently so in weak acids or in organic fluids, so that they are soluble enough in the juices of the stomach to enter the blood in such quantity as to prove fatal. The only exception now admitted to exist is the arsenite produced when a solution of oxide of arsenic is brought in contact with the hydrated sesquioxide of iron. The compound thus formed is held to be insoluble in the secretions of the stomach; and consequently the hydrated sesquioxide of iron is usually regarded as a true antidote.
The substance, the Ferrugo of the Edinburgh Pharmacopœia,—a compound which differs little from the older preparation, the rust of iron, when not deprived of its combined water,—was announced in 1834 by Drs. Bunsen and Berthold as an effectual remedy even when given some time after the arsenic is swallowed.[[817]] Their experiments were repeated with variable success. Similar results were obtained by MM. Soubeiran and Miquel, as well as MM. Orfila and Lesueur, in some experiments on dogs, and by M. Boullay on the horse.[[818]] The last experimentalist found that the effects of a dose adequate ta occasion death are almost entirely prevented in the horse by giving the oxide of iron either immediately after the poison, or within four hours. Results of the same nature were obtained in this country by Mr. Donald Mackenzie.[[819]] Others, however, such as Mr. Brett[[820]] and Mr. Orton,[[821]] have failed to observe any antidotal virtues, and even deny that the sesquioxide of iron can remove oxide of arsenic from a state of solution. But in 1840 the causes of these discrepant statements were explained by Dr. Douglas Maclagan,[[822]] who found, in corroboration of the remarks of Drs. Bunsen and Berthold, as well as various French authorities, that the oxide must be given in large quantity, and that the failures of some were owing to the quantity used having been too small. He ascertained, that, in order to remove one part of arsenic from a state of solution, twelve parts of oxide of iron in the moist state are necessary, and sixty parts if it be previously dried; that the arsenic so appropriated is with difficulty removed from the insoluble matter even by boiling; and that, as the discoverers of this antidote first stated, the preparation made by precipitating the sesquioxide of iron by means of ammonia, is a more active form than any other. As the oxide prepared in this way always contains ammonia, and the proportion necessary for removing the arsenic is far greater than what is required to constitute a simple arsenite of iron, it is reasonable to infer that the ammonia forms a part of the insoluble compound actually produced. At all events the action of the antidote would appear to be chemical, and not mechanical, as has been thought by many, and as was stated to be probable in the last edition of this work. In confirmation of these views, and as a fact worthy of farther investigation on its own account, it is worthy of notice, that, according to Dr. Duflos, the acetate of sesquioxide of iron answers equally well as an antidote with the sesquioxide itself. It precipitates both arsenious and arsenic acid from every state of solution, and always the more quickly the more the solution is diluted; and the co-existence of acetic acid is no obstacle to this action taking place.[[823]]—More recently Professor Orfila has called in question the absolute efficacy generally ascribed to the sesquioxide of iron. He alleges that the arsenical compound formed, though insoluble in water, is soluble to some extent in the gastric juices, and is consequently a poison to animals; that the sesquioxide is therefore only partial in its operation as a remedy; but yet that the influence of the animal fluids in the stomach in counteracting it may be overcome by giving it in excess, so that, as fast as the compound is dissolved, it is thrown down again.[[824]]
The cases of the successful employment of this antidote in the human subject, which have appeared in the periodical press during the last eight years, are so numerous, that its utility can scarcely be called in question, whatsoever may be its precise mode of action. The hydrated sesquioxide of iron ought therefore to be kept in readiness in every druggist’s establishment; for it cannot be prepared when wanted without great loss of time. The quickest way to make it is to dissolve the common anhydrous sesquioxide, formerly miscalled carbonate of iron, in diluted sulphuric acid aided with a gentle heat; to decompose the hot solution with an excess of strong ammonia; to filter off the fluid by means of a cloth filter and wash the precipitate well with warm water; and then to let it drain thoroughly and to squeeze out more of the water by expression. It should be kept in this state, and not allowed to dry.
In regard to all antidotes for arsenic, it must be observed, that they can seldom be otherwise employed than in unfavourable circumstances. If, as most generally happens, the poison has been taken some time before medical aid is obtained, its powder is diffused over the surface of the stomach, adheres with tenacity to the villous coat, and excites the secretion of tough mucus, through which it is with difficulty reached by any antidote possessing a chemical action with it. In all cases, therefore, it is advisable to promote vomiting occasionally, if not already full and free, so as to aid the stomach in clearing itself of the secreted mucus.
If the existence of a chemical antidote for arsenic be doubtful, much less is there any one known of that rarer denomination which operates by exciting in the system an action contrary to that established by the poison.
A good deal, however, may be done by general medical treatment to improve the chance of recovery. If vomiting should be delayed, as often happens, for half an hour or more, advantage ought to be taken of the opportunity to administer an emetic of the sulphate of zinc, with the view of withdrawing the powder in mass before it is diffused over the stomach; and for the same purpose milk should be drunk both before and after vomiting has begun, as it appears to be the best substance for enveloping the powder, and so procuring its discharge. The patient should never be allowed to exhaust his strength in retching without a little milk or other fluid in his stomach to act on. At the same time, there is probably some justice in the opinion expressed by a late writer on this subject, that large draughts of diluents are injurious; and that, unless the stomach is allowed to contract fully and frequently on itself, it cannot discharge from its surface the mucous secretion, in which the powder of arsenic is in general closely enveloped.[[825]] The stomach-pump, although it has been applied to cases of poisoning with arsenic, does not possess any advantage whatever over emetics or the natural efforts of nature, and is less effectual in expelling the mucus which envelopes the poison. Even emetics are unnecessary, when full vomiting is caused by the poison itself. If milk in sufficient quantity cannot be procured, strong farinaceous decoctions will probably prove useful.
Supposing the poison to have been removed from the stomach, or that the patient has been put on the course which appears best fitted to accomplish that end,—two objects remain to be accomplished, namely, to allay the inflammation of the alimentary canal, and to support the system under that extraordinary depression which it undergoes in the generality of cases. Were it not for the latter of these objects, the treatment would be both obvious and frequently successful. But it is highly probable that the active remedies, to which the physician trusts in internal inflammations generally, and which are urgently called for by the inflammation caused by arsenic, cannot be enforced with the requisite vigour, on account of the remote depressing effects also produced by this poison on the body.
Nevertheless, it is certain that in a few even very aggravated cases the purest and most vigorous antiphlogistic treatment has been resorted to with success. Dr. Roget’s patient, whose case was formerly referred to for another purpose, seems to have been saved by venesection; and at all events, the amelioration effected was unequivocal. In the Medical Repository there is another good example of the beneficial effects of blood-letting carried even to a greater extent than in Roget’s case;[[826]] and in the Medical and Physical Journal[[827]] a third instance will be found, which after the first twenty-four hours assumed the form of pure gastritis, and was treated as such with success. Blood-letting ought not to be practised till the poison is nearly all discharged from the stomach, because it promotes absorption by causing emptiness of the blood-vessels.