Читать книгу Treatise on Poisons - Robert Sir Christison - Страница 12

Evidence from experiments on animals with articles supposed to contain poison is more equivocal than was once imagined. But it may be doubted whether some medical jurists have not overstepped the proper limits, when they hold it to constitute little or no proof at all.

Evidence from express experiments should rarely form part of a regular medical inquiry into a charge of poisoning. For in the first place, to make sure of performing an experiment well requires more experimental skill than the generality of practitioners can be expected to possess; then, as will seen in the sequel, evidence procured from this source can very rarely be more than presumptive; and lastly, if the quantity of poison in the suspected substance is great enough to affect one of the perfect animals, it may generally be recognized to a certainty by its physical or chemical properties.

For these reasons it is not likely, that, in an inquiry undertaken by a skilful toxicologist, he will put himself in the way of delivering an opinion on the force of such evidence. But it is nevertheless necessary for me to consider it in detail, because he may have to give his opinion regarding experiments made inconsiderately by others, or accidents caused by domestic animals eating the remains of substances suspected to be poisoned.

The matter subjected to trial may be either suspected food, drink, or medicine; or it may be the stuff vomited during life, or found in the stomach after death; or it may be the flesh of poisoned animals.

1. The evidence derived from the effects of suspected food, drink, or medicine is better than that drawn from the effects of the vomited matter or contents of the stomach. But an important objection has been made to both, namely, that what is poison to man is not always poison to the lower animals, and that, on the other hand, some of the lower animals are poisoned by substances not hurtful to man.

A good deal of obscurity still hangs over the relative effects of poisons on man and the lower animals. There are two species, however, whose mode of life in respect to food closely resembles our own, and which, according to innumerable experiments by Orfila, are affected by almost all poisons exactly in the same way as ourselves, namely, the cat and dog, but particularly the latter.

In general poisons act less violently on these animals; thus two drachms of opium are required to kill a middle-sized dog,^[105] while twenty grains have killed a man, and undoubtedly less would be sufficient. It appears that one poison, alcohol, acts more powerfully on them than on man. There are also some poisons, such as opium, which, although deleterious to them as well as to man, nevertheless produce in general different symptoms. Yet the differences alluded to are probably not greater than exist between man and man in regard to the same substances; and therefore it may be assumed, that, on the whole, the effects of poisons on man differ little from those produced on the dog and cat.

The present objection is generally and perhaps justly considered a stronger one, when it is applied to other species of animals. But it must be confessed after all, that our knowledge of the diversities in the action of poisons on different animals is exceedingly vague, and founded on inaccurate research; and there is much reason to suspect, that, if the subject is studied more deeply, the greater number of the alleged diversities will prove rather apparent than real. Both reasoning and experiment, indeed, render it probable, that some orders, even of the perfect animals, such as the Ruminantia, are much less sensible than man to many poisons, and especially to poisons of the vegetable kingdom. But so far as maybe inferred from the only accurate inquires on the subject, their effects differ in degree more than in kind. Some exceptions will without doubt be found to this statement. For example, oxalic acid, besides inflaming the stomach, causes violent convulsions in animals, but in man it for the most part excites merely excessive prostration; and opium most generally excites in man pure sopor, in animals convulsions also. Other exceptions, too, exist by reason of functional peculiarities in certain animals. Thus irritant poisons do not cause vomiting in rabbits or horses, because these animals cannot vomit; neither do they appear to cause much pain to rabbits, because rabbits have not the power of expressing pain with energy. But exceptions like these, and particularly such as are unconnected with functional peculiarities, will probably prove fewer in number, and less striking than is currently imagined. For it is, on the other hand, well ascertained, that many, indeed most of the active poisons whose effects have been examined by a connected train of experiments, produce nearly the same effects on all animals whatever from the highest to the lowest in the scale of perfection. It has been fully proved, that arsenic, copper, mercury, the mineral acids, opium, strychnia, conia, white hellebore, hydrocyanic acid, cyanogen gas, sulphuretted hydrogen, and many others, produce nearly the same effects on man, quadrupeds, birds, amphibious animals, and even on fishes and insects.^[106]

Accordingly there are cases, in which the evidence from experiments on animals with suspected articles of food is unequivocal. For example;—a sexton and his wife, who had got a bad name in their village in consequence of informing against the bailiff for smuggling, and who were on that account shunned by all the neighbours, accused the bailiff and his wife of having tried to poison them by mixing poison with their bread. Immediately after eating they were attacked, they said, with sickness, griping, swelling, and dizziness; and they added, that a cat was seized with convulsions after eating a part of it, had sprung away, and never returned. A large portion of the loaf was therefore sent to the Medical Inspector of the district; who reported, that it seemed exactly similar to another unsuspected loaf;—that, although he was not able to detect any poison, it might after all contain one,—vegetable poison particularly;—but that he could hardly believe it did, for he fed a dog, a cat, and a fowl several days with it, and they not only did not suffer any harm, but even appeared very fond of it.^[107] In this case it was clear that poisoning was out of the question. On the other hand, the effects of some poisons on man may be developed so characteristically in animals as to supply pointed evidence. Thus, in the case of Mary Bateman, an infamous fortune-teller and charm-worker, who after cheating a poor family for a series of years, at last tried to avoid detection by poisoning them, it was justly accounted good evidence, that a portion of the pudding and the honey, supposed to have been poisoned, caused violent vomiting in a cat, killed three fowls, and proved fatal to a dog in four days, under symptoms of irritation of the stomach such as were observed in the people who died.^[108]

It has been farther objected to experiments on animals with suspected articles of food, drink, or medicine, that it is difficult to administer poison to them in a state of concentration, and to prevent it from being discharged by vomiting. This objection, however, may be obviated by performing the experiment in the way recommended by Professor Orfila. A small opening is made into the gullet, previously detached from its surrounding connexions, the liquid part is introduced by a funnel thrust into the opening, and the solid portion previously made into little pellets is then squeezed down. Lastly, the gullet is tied under the aperture. The immediate effect of the operation is merely an appearance of languor; and no very serious symptom is observable till four or five days at soonest after the tying of the gullet. Hence if signs of poisoning commence within twenty-four hours, they are independent of the injury done by the operation.^[109] This process requires some adroitness to execute it well. It cannot be tried successfully but by a practised operator, who, for reasons already given, would hardly ever try experiments of the kind with suspected articles. Mention is here made of it, therefore, chiefly because it is the best mode of experimenting in those cases in which it is necessary, as will presently be seen, to determine disputed points in the physiology of poisons.

I may here shortly notice a method which has been lately proposed for detecting poisons that enter the blood, and which is founded on their effects on animals. M. Vernière suggests that advantage may be taken of the extreme sensibility of the medicinal leech to procure at least presumptive evidence, when no evidence can be procured in any other manner. He has related some experiments to prove that the leech, when placed in the blood of dogs killed by nux-vomica, is affected even when the quantity of the poison is exceedingly small.^[110] It is extremely doubtful whether any importance can be attached to this criterion, as every one knows that the leech is apt to suffer from a variety of obscure causes, and among the rest from some diseased states of the body.

2. In the case of the vomited matter or contents of the stomach there are other and weightier objections to experiments on animals.—In the first place, the poison which has caused death may have been either in part or wholly vomited before-hand, or absorbed, or transmitted into the intestines, or decomposed by the process of digestion. Secondly, though abounding in the matter vomited or which remains in the stomach, it may be so much diluted, as not to have any effect on an animal. And, thirdly, the animal fluids secreted during disease are believed to act occasionally as poisons.

The first two objections are so plainly conclusive as scarcely to require any illustration. It may be well, however, to mention as a pointed practical lesson, that Professor Orfila once detected a considerable quantity of arsenic in the contents of the stomach, where a prior investigation had shown that the same article produced no effect on two animals, and where the reporters from this and other circumstances declared, that in their opinion death was not owing to poison.^[111]

The last objection is a very important one; but there is reason for suspecting that it has been a good deal exaggerated by medical jurists.—Animal fluids are certainly poisonous when putrid. The repeated and fatal experience of anatomists, together with the precise experiments of M. Gaspard and M. Magendie,^[112] leave no doubt that putrid animal fluids, when introduced into an external wound, cause spreading inflammation of the cellular tissue; and although Magendie says he has found such fluids harmless when introduced into the stomach of dogs,^[113] it is probable, from their effects on man, that they will act as irritants on animals not habituated to their use. I believe, too, that independently of putrefaction, vomited matter or the contents of the stomach may be apt to make dogs vomit on account of their nauseous taste; and perhaps we may infer, that they will also cause some of the other symptoms of poisoning with the irritants, particularly if not vomited soon after being administered.—As to the influence of disease in rendering the contents of the stomach deleterious, it is to be observed that the effects just mentioned are probably owing to the influence of disease on the secretions, but that beyond this we know very little of the subject. In authors I have hitherto found only one fact to prove that disease can render the contents of the stomach decidedly poisonous; and on the negative side of the question there exists no facts at all. Morgagni describes the case of a child who died of tertian ague, amidst convulsions, and in whose stomach a greenish bile was found, which proved so deleterious, that a little of it given with bread to a cock caused convulsions and death in a few minutes, and a scalpel stained with it, when thrust into the flesh of two pigeons, killed them in the same manner.^[114] It is not easy to say what to think of this experiment; which, if admitted to the full extent of the conclusions deducible from it, would lead to the admission, that disease may impart to the secretions the properties of the most active narcotics. Farther researches are certainly required before this admission can be made unreservedly.

On the whole, it appears that in the present state of our knowledge, experiments or accidental observations on the effects of the contents of the stomach, or of vomited matter, on animals are equivocal in their import. At the same time it may be observed, as with regard to articles of food, drink, or medicine, that the effects of some poisons on man may be developed so characteristically on animals by the contents of the stomach, as to supply very pointed evidence indeed. Of the force of this statement the following example is a striking illustration. In the case of a girl, who was proved to have died of accidental poisoning with laudanum, the inspector evaporated the contents of the stomach to dryness, made an alcoholic extract from the residue, and giving this to several dogs, chickens, and frogs, found that they were all made lethargic by it, some of them oftener than once, and that a few died comatose.^[115] Facts such as these, agreeing so pointedly with the known effects of the poison suspected, appear to me to yield evidence almost unimpeachable.

3. The effects of the flesh of poisoned animals, eaten by other animals, constitute the least conclusive of all the varieties of the present branch of evidence. For the flesh of animals that have died of poisoning is not always deleterious; while on the other hand flesh is sometimes rendered so by natural causes, as will be seen in the Chapter on Diseased and Decayed Animal Matter.

This subject stands much in need of careful and methodic investigation. And it is of more practical importance than might be imagined at first sight. For the question has actually occurred in a legal inquiry in this country,—Whether poisoning in the human subject may be caused by the flesh of a poisoned animal?

In regard to some poisons it is well established, that animals killed by them may be eaten with impunity, such as game killed with the wourali poison, or fish by cocculis-indicus. This seems the general rule. But it is not clear that all poisons are similarly circumstanced.

The only systematic researches hitherto undertaken on this question are some recently made at Lucca by Professor Gianelli; of which however I have only seen an abstract. He found that the blood, urine, and lungs of animals poisoned with arsenic acted as a poison on small birds, such as sparrows, whether the parts were taken from the body while the animal was alive, or after death; but that alcohol, cherry-laurel water, corrosive sublimate, sulphate of copper, tartar-emetic, acetate of lead, nitrate of silver, trisnitrate of bismuth, chloride of tin, sulphate of zinc, laudanum, acetate of morphia, strychnia, and cantharides, had no such effect.^[116] Orfila has since shown some reason for doubting the conclusiveness of Gianelli’s investigations; and on repeating them, obtained such results as render it doubtful whether any reliance can be put upon experiments made upon small birds.^[117] Guérard however has ascertained, that dogs, fed on the flesh and entrails of sheep which had taken arsenic, were attacked with vomiting and purging, became reduced in flesh, and at length would not eat what was put before them; but none of them perished, or seem to have been seriously ill. Arsenic was detected in their urine.^[118]

The importance of the inquiry, which the preceding experiments are intended to elucidate, will appear from the following singular case, for the particulars of which I am indebted to the kindness of Mr. Jamieson of Aberdeen, who was employed by the authorities to investigate it. An elderly woman, who kept fowls which occasionally trespassed on a neighbour’s fields, one morning observed four of them very sickly; and in the course of the day they became so ill that she killed them. She cleaned and prepared two of them for cooking, buried another, and gave away the fourth to a beggar, who was afterwards lost sight of. Next day soup made with the half of one of the fowls was given to a little girl, who suffered severely from sickness and vomiting, and also to a cat, which was similarly affected for the whole evening. On the day afterwards the woman herself and a female lodger, took broth made with what remained of the fowls, and also ate the gizzards; but the remainder was thrown with the offal upon the dunghill. In the course of five or six hours both women were attacked with severe illness. One had sickness, vomiting and great coldness; but after encouraging the vomiting with hot water and then taking some spirits, she got better in the night-time, and next morning was pretty well. The other, who was the owner of the fowls, was seized somewhat later than her friend with great thirst and shivering, and next day with pains in the stomach, severe sickness, and fruitless efforts to vomit. On the sixth day, when a medical man first saw her, she had great pain throughout the abdomen, much thirst, difficult breathing, a red, dry tongue, and a very frequent, small pulse. Next day the pain and difficult breathing became worse; and in the evening, after an attack of sneezing, she became gradually insensible and motionless, in which state she remained till the tenth day, when she expired. The stomach and intestines did not present any distinct morbid appearance; but the vessels of the brain were turgid, there were about two ounces of serosity in the lateral ventricles, both corpora striata were softened anteriorly, and a clot of blood as big as an almond was contained in the right anterior lobe of the brain.—A judicial investigation being ordered, it was ascertained that the fowl which the woman buried as well as the remains of the other fowls which were thrown upon the dunghill, had been carried off. But on searching the dunghill more carefully afterwards, the contents of one of the crops, which had been taken out and examined by the lodger, were discovered in the rubbish; and in the mass Mr. Jamieson detected a considerable quantity of arsenic.

This incident happened in 1836. More lately the same gentleman met with another extraordinary attempt of the same kind. A farmer, about to be married, gave directions for killing in the evening some fowls which were to be sent to the house of his bride where the ceremony was to take place. The killing of them however was accidentally delayed; and next morning, on the hen-house door being opened, the fowls ran furiously to the well, drank water incessantly, and died in an hour. On examining the bodies, Mr. Jamieson found arsenic in large quantity in their crops and gizzards.

On each of these occasions a particular individual came under suspicion; but the evidence against them was too slight to justify the authorities in bringing a formal charge; and consequently the proceedings did not go farther. In the former instance the evidence in favour of the flesh of poisoned animals being sometimes poisonous is strong; and the history of the woman’s case, although death seems to have been caused directly by apoplexy, renders it probable that even dangerous results might accrue.

The preceding remarks will enable the medical witness to know under what circumstances accidental observations or intentional experiments on animals furnish satisfactory proof.

Before quitting the subject, however, I have to add, that there is another purpose, besides procuring direct evidence, to which experiments with animals may be applied with great propriety;—namely, the settling disputed questions regarding the physiological and pathological properties of a particular poison. The science of toxicology is not yet by any means so perfect, but in particular cases topics may arise, which have not hitherto been investigated, and which it may be necessary to determine by experiment. Experiments on animals instituted for such purposes by a skilful toxicologist are not liable to any important objection. On the trial of Charles Angus at Liverpool in 1808, for procuring abortion and murder by poison, a trial of great interest, which will be referred to more particularly afterwards, it appeared from the evidence of the crown witnesses, that the poison suspected, corrosive sublimate, could not be discovered in the stomach by certain methods of analysis; and that, although corrosive sublimate is a powerful irritant, the villous coat of the stomach was not inflamed. But then it was proved by experiments made by one of their number, Dr. Bostock, that animals might be killed with corrosive sublimate without the stomach being inflamed, and without the poison being discoverable after death by the tests he used in the case.^[119] An attempt was made on the side of the prisoner to throw out this line of evidence as incompetent, on the ground of the discrepant effects of poisons on man and on the lower animals. But it was admitted by the judge, on the plea that it was only to illustrate a general physiological fact, and not to infer proof of poisoning. The importance of experiments on animals to settle incidental physiological questions has lately been again acknowledged in a very pointed manner in an English court of law: for a set of experiments, to settle the question of the rapidity with which hydrocyanic acid acts, was instituted before the trial by the medical witnesses, at the request of the judge who was to try the case.^[120]