It is not easy to specify the period after which a poison that has excited vomiting need not be looked for in the stomach. It must vary with a variety of circumstances whose combined effect it is almost impossible to appreciate, such as the solubility and state of division of the poison, the frequency of vomiting, the substances taken as remedies, and the like. When the poison is in solution and the patient vomits much, an analysis may be expected to prove frequently abortive, even though the individual survives but a few hours, as in Mr. Hewson’s case already noticed. In other circumstances, however, as various facts quoted above will show, poisons may frequently be found after two days incessant vomiting; and on the whole it may be stated, that the recent improvements in analysis render the period much longer than it has generally been, and would naturally be imagined. Metzger has related the case of a woman poisoned with arsenic mixed with currants, in whose body, after eight days of frequent vomiting, he found ten or twelve currants, which gave out an odour of garlic when burnt;[[93]] but here the dose, if there was really arsenic, must have been repeated recently before death, for it is not possible to conceive how currants could remain in the stomach so long, whatever may be thought of the possibility of arsenic remaining. It is farther proper to add, that Professor Henke of Erlangen, one of the highest living authorities in Germany, once found grains of arsenic in the gullet, although he found none in any other part of the body, of a person who survived the taking of the poison four days.[[94]] Allowing to this fact all the weight derived from the high name of its author, I must nevertheless express great doubt whether the arsenic was not repeated more recently before death.
2. The poison may have disappeared, because it has been all absorbed. It has several times happened that in the bodies of those poisoned with laudanum, or even with solid opium, none of the drug could be detected after death. Sometimes indeed it is found, even though the individual survived the taking of the poison many hours. Thus a case related by Meyer of Berlin, in which the person lived ten hours after taking the saffron-tincture of opium; and nevertheless it was detected in the stomach by a mixed smell of saffron and opium.[[95]] But more commonly it all disappears, unless the dose has been very large. In a case of poisoning with laudanum, which I examined here along with Sir W. Newbigging in 1823, none could be detected, although strong moral circumstances left no doubt that laudanum had been swallowed seven or eight hours before death. An instance of the same kind has been minutely related by Pyl. It was that of an infant who was poisoned with a mixture of opium and hyoscyamus, and in whose stomach and intestines none could be detected by the smell.[[96]] Similar observations have been often made on animals; and several additional cases of the same purport, occurring in man, will be related under the head of opium.
It might be of use to quote some of the numerous errors committed by medical witnesses, in consequence of having overlooked the effect of absorption in removing poisons beyond the reach of chemical analysis. But not to be too prolix, I shall be content with mentioning a single very distinct case in point, which happened at a Coroner’s Inquest in London, in 1823. A young man one evening called his fellow-lodger to his bedside; assured him he had taken laudanum, and should be dead by the morrow; and desired him to carry his last farewell to his mother and his mistress. His companion thought he was shamming; but next morning the unfortunate youth was found in the agonies of death. The moral evidence was not very satisfactory; but that is of little consequence to my present object. The point in the case I would particularly refer to is the declaration of the medical inspector, that laudanum could not have been taken, because he did not find any by the smell or by chemical analysis in the contents of the stomach.[[97]]
3. Poisons may not be found, because the excess has been decomposed.
Vegetable and animal poisons may be altogether destroyed by the process of digestion. This observation will explain why sometimes no poison could be found in cases of poisoning with crude opium or other vegetable solids. A French physician, M. Desruelles, has related the case of a soldier, who died six hours and a half after swallowing two drachms of solid opium, and in whose stomach nothing was found but a yellowish fluid, quite destitute of the smell of the drug.[[98]]
Some mineral poisons, such as corrosive sublimate, lunar caustic, and hydrochlorate of tin, are also decomposed in the stomach. But they are not removed beyond the reach of chemical analysis. The decomposition is the result of a chemical, not of a vital process; and the basis of the poison may be found in the solid contents of the stomach under some other compound form. Other poisons again may be apt to elude detection by altering their form, by combining with other substances, without themselves undergoing decomposition. Thus it appears from a case related by Mertzdorff of Berlin, that, in poisoning with sulphuric acid, after the greater part of the poison is discharged by vomiting, the remainder may escape discovery by being neutralized: For, although he could not find any free acid in the contents of the stomach, he discovered 4½ grains in union with ammonia by precipitation with muriate of baryta.[[99]]
It may be also right to mention another kind of decomposition which may render it impossible to detect a poison that has been really swallowed—namely, that arising from decay of the body. In several recent cases bodies have been disinterred and examined for poison months or even years after death. In these and similar cases it would be unreasonable to expect always to find the poison, even though it existed in the stomach immediately after death. Some poisons, such as oxalic acid, might be dissolved and then exude; others, such as the vegetable narcotics, will undergo putrefaction; and others, such as prussic acid, are partly volatilized, partly decomposed, so as to be undistinguishable in the course of a few days only. The mineral poisons, those at least which are solid, are not liable to be so dissipated or destroyed. Some authors, indeed, have said that arsenic may disappear in consequence of its uniting with hydrogen disengaged during the progress of putrefaction, and so escaping in the form of arseniuretted-hydrogen gas; and they have endeavoured to account in this way for the non-discovery of it in the bodies of the people who had been killed by arsenic, and disinterred for examination many months afterwards.[[100]] But the supposition is by no means probable: at least arsenic has been detected in the body fourteen months, nay, even seven years, after interment. For farther details, on this curious topic, the reader may turn to the article Arsenic.
On the whole, the result of the most recent researches is that the effect of the spontaneous decay of dead animal matter in involving poisons in the general decomposition appears to be much less considerable than might be anticipated. For this most important medico-legal fact, the toxicologist is indebted to the experimental inquiries of MM. Orfila and Lesueur.[[101]] The poisons tried by them were—sulphuric and nitric acids, arsenic, corrosive sublimate, tartar-emetic, sugar of lead, protomuriate of tin, blue vitriol, verdigris, lunar caustic, muriate of gold, acetate of morphia, muriate of brucia, acetate of strychnia, hydrocyanic acid, opium, and cantharides. They found that after a time the acids become neutralized by the ammonia disengaged during the decay of animal matter;—that by the action of the animal matter the salts of mercury, antimony, copper, tin, gold, silver, and likewise the salts of the vegetable alkaloids, undergo chemical decomposition, in consequence of which the bases become less soluble in water, or altogether insoluble;—that acids may be detected after several years’ interment, not always, however, in the free state;—that the bases of the decomposed metallic salts may also be found after interment for several years;—that arsenic, opium, and cantharides undergo little change after a long interval of time, and are scarcely more difficult to discover in decayed, than in recent animal mixtures;—but that hydrocyanic acid disappears very soon, so as to be undistinguishable in the course of a few days.
4. Lastly, the poison which has been absorbed into the system, and may consequently be detected in certain circumstances in the textures of the body at a distance from the alimentary canal, may also be removed beyond the reach of analysis, by being gradually discharged along with the excretions. It has been fully proved in recent times, that in poisoning with arsenic the poison may be found in ordinary cases, for some days after being swallowed, in the liver especially, but also in the other textures, in the blood, and in the urine; but that if a flow of urine be established and kept up, in nine or ten days, and sometimes much sooner, it can no longer be discovered anywhere by the nicest analysis.[[102]]
Is the discovery of poison in the body or the evacuations essential to establish a charge of poisoning? It was mentioned at the commencement of the present section, that the chemical evidence is generally, and correctly, considered the most decisive of all the branches of proof in cases of poisoning. But some toxicologists have even gone so far as to maintain that without chemical evidence, or rather, in more general terms, without the discovery of poison either in the body itself or in the evacuations,—no charge of poisoning ought to be held as proved. This, however, is a doctrine to which I cannot assent. In the preceding observations on the evidence of general poisoning it has been several times alluded to as unsound; and repeated opportunities of establishing exceptions will occur in the course of this work, under the head of individual poisons. At present it may be well to illustrate its unsoundness in reference to those charges of poisoning, where no particular poison is pointed at by the medical evidence, but where a whole class of poisons must be kept more or less in view. Even here I apprehend there may be sufficient evidence in the symptoms and morbid appearances, without any chemical facts,—to render poisoning so highly probable, that in conjunction with strong moral evidence, no sensible man can entertain any doubt on the subject. Several illustrations might be here given; and some will be found scattered throughout the work. In the present place a few instances will be mentioned which cannot be conveniently arranged any where else, and which are well worthy of notice, as being striking examples of the decision of questions of poisoning without chemical evidence.