Poison is commonly defined to be a substance which, when administered in small quantity, is capable of acting deleteriously on the body; but this definition is obviously too restricted, for it would exclude numerous substances which are only poisonous when administered in large doses, as the salts of lead, antimony, &c.; hence the quantity required to kill must not enter into the definition. A good practical definition of a poison is 'any substance or matter which, when introduced into the body in any way, can destroy life by its own inherent qualities without acting mechanically.' This definition includes poisonous solids, liquids, and gases of definite chemical composition—the products of decomposition or of bacterial organisms, and the virus of contagious diseases. The last mentioned produce the symptoms of the various infectious and contagious diseases, and are not included in treatises on poisons. The others are classified sometimes according to their source, as mineral, vegetable, and animal; or more conveniently according to their action, as Irritants, Narcotics, and Narcotico-irritants.
The Irritants, when taken in ordinary doses, speedily occasion intense vomiting and purging and severe abdominal pain. They act chiefly on the stomach and intestines, which they irritate, inflame, and frequently corrode, and may thus occasion ulceration, perforation, or gangrene. Amongst those which possess corrosive properties are the strong mineral acids, caustic alkalis, corrosive sublimate, &c.; whilst among the pure irritants which exert no destructive chemical action on the tissues with which they come in contact may be mentioned cantharides. The Narcotics act specially on the brain and spinal cord. Amongst their most common symptoms are giddiness, headache, obscurity of sight or double vision, stupor, loss of power of the voluntary muscles, convulsions, and, finally, complete coma. These poisons have no acrid, burning taste, nor do they usually give rise to vomiting or diarrhoea, and, excepting a slight fullness of the cerebral vessels, they leave no well-marked post-mortem appearance. They are few in number, and none of them belong to the mineral kingdom. The Narcotico-irritants have, as their name implies, a mixed action. At varying periods after they have been swallowed they give rise to vomiting and purging, like irritants, and sooner or later produce stupor, coma, paralysis, and convulsions, owing to their effect on the brain and spinal marrow. As familiar examples we may point to monkhood, tobacco, and poisonous mushroom rooms. Sometimes the more violent of the poisons here classed as irritants are made into a separate group—Corrosives; the narcotics are put under the head Neurotics; and the gaseous poisons are treated as a separate class.
Under the head of Irritant Poisons may be included (1) Mineral Acids, as sulphuric, nitric, and hydrochloric acids; vegetable acids, and some of their salts, as oxalic acid, binoxalate of potash, and tartaric acid (in doses of half an ounce or more); the alkalies, as pearl-ash (carbonate of potash), soap lees (carbonate of soda), ammonia and its sesquicarbonate in strong solution; and metallic compounds, as white arsenic (arsenious acid), yellow arsenic (orpiment), corrosive sublimate, pernitrate and other salts of mercury, acetate of lead (sugar of lead) in doses of an ounce and upwards, sulphate of copper (blue vitriol), subacetate of copper (verdigris), arsenite of copper (commonly known as Scheele's green or emerald green, which has been employed under the name of extract of spinach for colouring confectionery), tartarated antimony, chloride of antimony (butter of antimony), chloride of zinc (Sir W. Burnett's Fluid), nitrate of silver (lunar caustic), sulphate of iron (copperas or green vitriol), and bichromate of potash; (2) Vegetable Substances—viz. colocynth and gamboge in large doses, savin, croton-oil, elaterium, &c.; and (3) Animal Substances, such as cantharides, to which must be added the occasional cases in which sausages, and certain fish and molluscs, usually quite innocuous, act as irritant poisons. The Narcotic Poisons include opium, hydrocyanic (or prussic) acid, cyanide of potassium, henbane, alcohol, ether, chloral, and chloroform. The Narcotico-irritant Poisons include nux vomica, meadow saffron (Colchicum), white hellebore, foxglove, common hemlock, water hemlock (Cicuta virosa), hemlock water-dropwort (Enanthe crocata), fool's parsley, thorn-apple, monkhood or aconite, deadly nightshade, tobacco, Indian tobacco (Lobelia inflata), the bark and seeds of the common laburnum, the berries and leaves of the yew-tree, and certain kinds of fungi.
The cases in which there are antidotes qualified to neutralise chemically the action of the poison are few in number. For the mineral acids chalk or magnesia in water must be used, with the view of neutralising them, after which milk should be given freely. The alkalies and their carbonates must be neutralised by vinegar and water, or lemon-juice mixed with water, after which milk should be given. For oxalic acid the antidote is chalk or magnesia in water, by which an insoluble oxalate of lime or magnesia is formed. For arsenic the hydrated peroxide of iron has been regarded as an antidote, but its efficacy is doubtful. Vomiting should be excited by the administration of a scruple of sulphate of zinc in warm water, and, after the stomach has been well cleared out, demulcent fluids, such as flour and water or milk, should be given. Corrosive sublimate combines with albumen (white of egg), and forms an insoluble inert mass; nitrate of silver is neutralised by chloride of sodium (common salt) dissolved in water; tartarated antimony is to a great degree rendered inert by the administration of decoction of bark or gall-nuts; and acetate of lead is rendered inert by the administration of sulphate of magnesia, which converts it into an insoluble sulphate of lead. In all cases of suspected poisoning, in which the nature of the poison is not known, the safest course is at once to produce vomiting by sulphate of zinc, or in its absence by a dessert-spoonful of flour of mustard suspended in tepid water, and to continue the vomiting till all the contents of the stomach are discharged, after which milk should be given freely.
Most of the known gases have a poisonous action when inhaled into the lungs; in these cases death may be due simply to suffocation or to a specific action of the gas. Carbonic Acid (q.v.), although seldom employed as an instrument of murder, is a frequent cause of accidental death, and in France is a common means of self-destruction. It is established by numerous experiments that air containing more than one-tenth of its volume of carbonic acid will, if inhaled, destroy life in man and the higher animals; when diluted with two or more volumes of air it can be breathed, and produces symptoms of vertigo and somnolency, and so great a loss of muscular power that the individual, if in an erect or sitting position, falls as if struck to the ground. The respiration, which at first is difficult and stertorous, becomes suspended. The action of the heart is at first violent, but soon ceases, sensibility is lost, and the person now falls into a comatose or death-like state. Those who have been resuscitated usually feel pain in the head and general soreness of the body for some days, and in a few severe cases paralysis of the muscles of the face has remained. The patient must, of course, be at once removed from the poisonous atmosphere, after which artificial respiration should be had recourse to. If the skin is warm cold water may be poured on the head and spine; while if the surface be cold a warm bath should be employed. When respiration is re-established venesection will often relieve the congestion of the vessels of the brain. The inhalation of oxygen gas is said to have been of service in these cases. Carbonic oxide is also an active poison, and is present in coal-gas and in charcoal fumes. Both carbonic acid and carbonic oxide act as powerful narcotics. The fatal power of ordinary coal-gas as an asphyxiant and irritant is probably due to the carbonic oxide present; the post-mortem appearances are very similar in cases of poisoning by coal-gas and by carbonic oxide. Sulphuretted hydrogen, which occurs abundantly in foul drains, sewers, cesspools, &c., is a gaseous poison whose effects are often noticed. Nothing certain is known of the smallest proportion of this gas required to destroy human life; but air containing only th of its volume of this gas will destroy a dog; and when the gas exists in the proportion of th it will kill a horse. During the construction of the Thames Tunnel the men engaged in the work suffered severely from the presence of this gas, which was probably derived from the action of the water on the iron pyrites in the clay, and which issued in sudden bursts from the walls. By respiring this atmosphere the strongest and most robust men were in the course of a few months reduced to an extreme state of exhaustion, and several died. The symptoms with which they were first affected were giddiness, sickness, and general debility; they became emaciated, and fell into a state of low fever accompanied by delirium. In this case the dilution was extreme; when the gas is breathed in a more concentrated form the person speedily falls, apparently lifeless. It appears to act as a narcotic poison when concentrated, but like a narcotico-irritant when much diluted with air. The action of the vapour of sulphide of ammonium, which is also commonly present in cesspools, &c., is probably much the same as that of sulphuretted hydrogen. Many of the gases which are only found as products of the laboratory are in the highest degree poisonous, as arseniuretted hydrogen; but as few persons run the risk of inspiring them it is unnecessary to enter into details.
In point of Law, the use of poison to kill or injure a human being or certain animals renders the poisoner amenable to the criminal courts. With regard to the sale of poisons, the legislature found it necessary to put some restrictions on one description—viz. arsenic—in order to prevent persons obtaining it with facility, and in such a manner as to avoid detection. The 14 and 15 Vict. chap. 13, requires every person who sells arsenic to enter in his books the date and quantity and purpose of its use, and later acts apply this rule to other poisons. It is not to be sold to one who is unknown to the vendor unless in presence of a witness who is known, and whose place of abode is recorded in the book. The arsenic must also be mixed with soot or indigo, in the proportion of oz. of soot or indigo to the lb. All the boxes, bottles, &c. must be labelled 'Poison.' Those who offend as to arsenic incur a penalty of £20; but in ordinary prescriptions poisons may be used in the ordinary way by duly qualified medical practitioners. As to the restriction on the sale of other poisons, see CHEMISTS AND DRUGGISTS. The offences committed by those who administer poisons to mankind are as follow: Whoever causes death by poison commits murder, for the means are immaterial if the death was caused by such means with a felonious intent. Where death is not caused, nevertheless whoever administers poison, or causes it to be administered to any person, with intent to commit murder is guilty of felony, and is liable to penal servitude for life, or for not less than three years. Moreover, whoever attempts to administer poison, or other destructive thing, to any person with intent to commit murder is guilty of felony, and is punishable in the same way. These offences are committed whether the poison administered or attempted to be administered, does injury or not; and it is a sufficient committing of the offence if the poison is put in such a place that a party was likely, and was intended to take it. Moreover, even though murder was not intended, but merely an intent to endanger life or inflict grievous bodily harm, still the offence is felony, and is punishable by penal servitude varying from three to ten years. There is also a similar punishment for the attempt to administer any stupefying drug. Not only is it a crime to administer or attempt to administer poison to human beings, but if cattle are maliciously killed by poison the offence is felony, punishable by penal servitude of from three to fourteen years. So to kill by poison any dog, bird, beast, or other animal, ordinarily kept in a state of confinement, is an offence punishable by justices of the peace with imprisonment for six months, or a fine of £20 over and above the injury done. If any person lay poison on lands to kill game he incurs a penalty of £10. Moreover, by the Act 26 and 27 Vict. chap. 113, extending to the United Kingdom, whoever sells or offers to sell poisoned grain, seed, or meal incurs a penalty of £10. Whoever sows, lays, or puts on ground such poisoned grain incurs a like penalty. The use of poisoned flesh is also prohibited. But the sale or use of any solution, material, or ingredient for dressing, protecting, or preparing any grain or seed for agricultural use only, if used bonâ fide, is not interfered with.
SECRET POISONING is a mode of taking away life by poisons so slow in their operation that the gradual sinking of the victims under their influence closely resembled the effects of disease or the ordinary decay of nature. It has been practised in all ages, and several undoubted and numerous supposed instances of it are mentioned by Greek and Roman writers. The prevailing ignorance of pathology and chemistry enabled crimes to be carried out with impunity with poisons which would be readily detected at the present day; and for similar reasons many deaths were ascribed to poison that were doubtless due to natural causes. It is impossible to attach much credence to stories such as that Henry VI. was killed by a pair of poisoned gloves, or that victims were simply got rid of by inducing them to smell a poisoned rose. And it is wholly incredible that in pre-scientific days treacherous friends and hidden enemies had access to secret and mysterious methods of poisoning beyond the power of detection that are happily denied to scientific investigators in days when we are acquainted with ten times as many and ten times as subtle poisons. In secret poisoning various preparations of arsenic seem once to have been most frequently used. In the 17th century this atrocious practice became of specially frequent occurrence; and from this time it rapidly increased, spread over western Europe like an epidemic, and became gradually a regular branch of education among those who professed a knowledge of chemistry, magic, or astrology. These persons regarded the knowledge of the mode of preparing secret poisons as of the highest importance, and many of them realised large sums by the sale of their preparations, and occasionally of the secret of their composition. It was in Italy and France that this art was chiefly practised and brought to the highest perfection; but it seems also to have prevailed in England to a considerable extent, for in 1531 the poisoning of seventeen persons, two of whom died, by the Bishop of Rochester's cook led to the passing of an act which declared the employment of secret poisons to be high-treason, and sentenced those who were found guilty of it to be boiled to death. This act was repealed in 1547.
The only undoubted instance of this crime which appears prominently in English history is the murder of Sir Thomas Overbury (q.v.) by Viscount Rochester (the favourite minion of James I.) and his wife, the divorced Countess of Essex. Prince Henry was falsely supposed to have been poisoned by his father, James I. (1612); and James's own death was similarly ascribed to nefarious practices on the part of Buckingham, nay, even of Charles I. (Milton). Undoubtedly such was the popular impression at the time, for Dr Lamb, a conjuror and quack, who was believed to have furnished Buckingham with the poisons, was seized by the angry populace in Wood Street, Cheapside, London, and beaten and stoned to death. But it was in Italy that this mode of poisoning was most prevalent. There, judging from the writings of various authors, it seems to have been looked upon as a not unjustifiable proceeding to get rid of a rival or enemy by poison; and from the time of the Lombard invasion down to the 17th century Italian history teems with instances which sufficiently show that poison was both the favourite weapon of the oppressor and the protection or revenge of the oppressed. The Borgias (q.v.) are generally singled out and held up to the horror and detestation of mankind; but as far as their poisonings are concerned they merely employed this method of destroying their adversaries a little more frequently than their neighbours. To show the popular feeling on this subject we may instance the case mentioned in the Mémoires of Henry II., fifth Duke of Guise, of a soldier who was requested to rid the Duke of Gennaro Annese, one of his opponents in Naples. Assassination was the mode proposed to the soldier, but he shrank with horror from the suggestion, stating at the same time that he was quite willing to poison Annese. It was shortly after the date of this story (1648) that secret poisoning became so frequent; and the Catholic clergy, despite the rules of the confessional, felt themselves bound to acquaint Pope Alexander VII. with the extent of the practice. On investigation it was found that young widows were extraordinarily abundant in Rome, and that most of the unhappy marriages were speedily dissolved by the sickness and death of the husband; and further inquiries resulted in the discovery of a secret society of young matrons which met at the house of an old hag, by name Hieronyma Spara, a reputed witch and fortune-teller, who supplied those of them who wished to resent the infidelities of their husbands with a slow poison, clear, tasteless, and limpid, and of strength sufficient to destroy life in the course of a day, week, month, or number of months, as the purchaser preferred. The ladies of Rome had been long acquainted with the 'wonderful elixir' compounded by La Spara; but they kept the secret so well, and made such effectual use of their knowledge, that it was only after several years, during which a large number of unsuspected victims had perished, and even then through a cunning artifice of the police, that the whole proceedings were brought to light. La Spara and thirteen of her companions were hanged, a large number of the culprits were whipped half-naked through the streets of Rome, and some of the highest rank suffered fines and banishment. About half a century afterwards the discovery was made of a similar organisation at Naples, headed by an old woman of threescore and ten named Toffania, who manufactured a poison similar to that of La Spara, and sold it extensively in Naples under the name of acquetta, and even sent it to all parts of Italy under the name of 'Manna of St Nicola of Bari,' giving it the same name as the renowned miraculous oil of St Nicola to elude discovery. This poison, now best known as the 'Acqua Tofana' or 'Acqua di Perugia,' is said by Halmann to have been compounded of arsenical neutral salts; while Garelli states that it was crystallised arsenic dissolved in a large quantity of water; but both agree that it produced its effect almost imperceptibly by gradually weakening the appetite and respiratory organs. After having directly or indirectly caused the death of more than 600 persons, Toffania was at length seized, tried, and strangled in 1719. From this time the mania for secret poisoning gradually died away in Italy.
Catharine de' Medici has been frequently charged with wholesale poisoning, and in 1558 four of the Scottish commissioners who had been present at Queen Mary's marriage to the Dauphin were poisoned, it was believed, at Dieppe. But it was about the middle of the 17th century that this horrible practice seems to have become most prevalent in France. Here, too, the agents were married women, and their husbands the victims; and, as in Italy, the extent to which the practice was carried was first made known by the clergy. The government, acting on the information thus obtained, seized and imprisoned in the Bastille two Italians named Exili and Glaser, who were suspected of having been the manufacturers and vendors of the poisons. Glaser died in prison; but Exili, becoming acquainted with another prisoner named St Croix, communicated to him his secret, which the latter made considerable use of after his release, compounding in particular the poison known as 'succession powder,' which subsequently became so celebrated. It was the same St Croix who played such a prominent part in the tragical history of the Marquise de Brinvilliers (q.v.). Penautier, the treasurer of the province of Languedoc, and the Cardinal de Bonzy were both pupils of St Croix, and managed, the one to pave the way for his own advancement, and the other to rid himself of his numerous creditors by the administration of poison; but the great influence of these men and the want of direct evidence barred all proceedings against them. Secret poisoning now became fashionable; the passions of jealousy, revenge, avarice, and even petty spite were all satisfied in the same way, and as a necessary consequence other offences decreased in proportion. The prisons teemed with suspected criminals, and the 'Chambre Ardente' was instituted for the special purpose of trying these offenders. In Paris this trade was chiefly in the hands of two women named Lavoisin and Lavogoreux, who combined with the ostensible occupation of midwife that of fortune-teller, and foretold to wives the decease of their husbands, to needy heirs that of their rich relatives, taking care at the same time to be instrumental in fulfilling their own predictions. Their houses were frequented by numbers of all classes, both from Paris and the provinces, among whom were the celebrated Marshal de Luxembourg (q.v.), the Duchess de Bouillon, and the Countess de Soissons; the two former of these, however, went merely from curiosity. Lavoisin and her confederate were at last discovered, tried, condemned, and burned alive in the Place de Grève, 22d February 1680; and from thirty to fifty of their accomplices were hanged in various cities of France. So common had this atrocious practice been that Madame de Sévigné, in one of her letters, expresses a fear lest the terms 'Frenchman' and 'poisoner' should become synonymous. For two years after the execution of the two Parisian poisoners the crime continued to be largely committed, being fostered by the impunity with which offenders of high rank were allowed to escape; and it was not till more than a hundred persons had died at the stake or on the gallows that the government succeeded in suppressing it. The mania for secret poisoning has not since been revived to the same extent, though isolated instances of its practice have occasionally been discovered, particularly in Hungary, where, within the last half of the 19th century, very extraordinary disclosures have at different times been made of the prevalence of this frightful crime among the peasant women. During the times of slavery the Obeah men among the negroes in the West Indies were credited with being expert poisoners. They used vegetable poisons obtained from plants, and there can be no doubt were often instrumental in getting rid of tyrannical or otherwise objectionable masters. In Britain famous poisoning trials have been those of W. Palmer (three victims, 1856), Madeleine Smith ('not proven,' 1857), E. W. Pritchard, M.D. (two victims, 1865), Mary Ann Cotton (sixteen victims, 1872), G. H. Lamson, M.D. (1882), P. Cross, M.D. (1887), and Mrs Maybrick (1889).
See the articles on ADULTERATION, ASPHYXIANTS, NARCOTICS, DISSECTION WOUNDS, LEAD-POISONING, PYEMIA, PROMAINES, SNAKES, VENOMOUS BITES, WOUNDS; the classification of diseases at DISEASE; for poisoned arrows, ARCHERY and CURARI; for the more important poisons and their treatment, ACONITE, ARSENIC, HYDROCYANIC ACID, STRYCHNINE, UPAS, &c.; for toxin and anti-toxic methods, and theories therein involved, GERM, BACTERIA, DIPHTHERIA, HYDROPHOBIA, TETANUS, TUBERCLE, &c.; the manuals of medical jurisprudence; and works on toxicology by Christison (1829), Taylor (1847; 2d ed. 1875), Reese (1874), Wormley (1867; 2d ed. 1875), A. Winter Blyth (1883; 2d ed. 1886), and J. D. Mann (1893).—For the Poison Ivy, see SUMACH.