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Originally appearing in Volume V21, Page 896 of the 1911 Encyclopedia Britannica.
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POISON. An exact definition of the word "poison" (derived through Fr. from Lat. polio, potionem, a drink; i.e. a deadly draught) is by no means easy. There is no legal definition of what constitutes a poison, and the definitions usually proposed are apt to include either too much or too little. Generally, a poison may he defined to be a substance having an inherent deleterious property, rendering it capable of destroying life by whatever avenue it is taken into the system; or it is a substance which when introduced into the system, or applied externally, injures health or destroys life irrespective of mechanical means or direct thermal changes. In popular language a poison is a substance capable of destroying life when taken in small quantity; but a substance which destroys life by mechanical means as, e.g. powdered glass, is not, strictly speaking, a poison. The subject of toxicology forms one of the most important branches of medical jurisprudence (q.v.). The medical jurist should be familiar with the nature and actions of poisons, the symptoms which they produce, the circumstances which modify their working, the pathological results of their action, and the methods of combating these. Action of Poisons.—Poisons may exert a twofold action. This may be either local, or remote, or both local and remote. The local action of a poison is usually one of corrosion, inflammation, or a direct effect upon the sensory or motor nerves. The remote actions of poisons are usually of a specific character, though some writers group the remote effects of poisons under two heads, and speak of the common and the specific remote effects of a poison. The local action of a poison of the corrosive class is usually so well marked and obvious that the fact of the administration of a poison of this class is generally unmistakable. The same may be said, in a less degree, of the irritant poisons, especially the mineral irritants; but here the symptoms some-times so closely simulate those of natural disease as to render the recognition of the administration of poison a matter of difficulty. Hence an accurate acquaintance with the remote specific effects of the various poisons is indispensable to the medical jurist. The class of poisons which has been administered or taken will thus be suggested to his mind by the observation of the symptoms; and not unfrequently the specific poison taken will be suspected. It is almost universally admitted that absorption of a poison is necessary for the production of its specific remote effects, and the old notion that a poison may kill, by its action through the nervous system, without absorption, is abandoned. Modifying Circumstances.—The ordinary action of a poison may be greatly modified by the largeness of the dose, by the state of aggregation, admixture, or of chemical combination of the poison, by the part or membrane to which it is applied, and by the condition of the patient. Thus, for example, opium may be a medicine or a poison, according to the dose in which it is given; and a dose of the drug which may be beneficial to an adult in certain states of the system may be fatal to a child, or to an adult when suffering from some forms of disease. All barium salts, again, are poisonous, except the quite insoluble sulphate. The simple cyanides, and many double cyanides, are highly poisonous; but yellow prussiate of potash, which is a double cyanide of iron and potassium, is almost without action upon the system. The part or tissue to which a poison is appliedgreatly affects the activity of a poison, owing to the varying rapidity with which absorption takes place through the cutaneous, mucous and serous surfaces, and by the other tissues of the body. Curare, an arrow poison, may be swallowed in considerable quantity without appreciable result, whilst a minute quantity of the same substance introduced into a wound is speedily fatal. Idiosyncrasy has an important bearing in toxicology. Pork, mutton, certain kinds of fish, more especially shell-fish so-called, and mushrooms have each produced all the symptoms of violent irritant poisoning, whilst other persons who have partaken of the same food at the same time have experienced no ill effects. Some persons are stated, on good authority, to be capable of taking with impunity such poisons as opium, corrosive sublimate, or arsenic, in enormous doses—and this irrespective of habit, which is known to have such an influence in modifying the effects of some poisons, notably the narcotics. A tolerance of poisons is sometimes engendered by disease, so that a poison may fail to produce its customary effect. Thus, opium is tolerated in large quantities in tetanus and in delirium tremens; and mercurial compounds may in some febrile affections fail to produce the usual constitutional effects of the metal. On the other hand, diseases which impede the elimination of a poison may intensify its effects. The evidence that a poison has been administered is based upon the symptoms produced, on the appearances met with in the body after death, on the analysis of articles of food and drink, of excreta and ejecta, and of the organs of the body after death, and on physiological experiments made with substances extracted from the same articles. These physiological experiments are usually made upon animals, but in some cases, as for instance when aconite has to be searched for, the physiological experiments must be made also upon the human subject. The evidence obtained from one or more of these sources, as compared with the properties or effects of varicus known poisons, will enable the medical jurist to form an opinion as to the administration or non-administration of a poison. The symptoms exhibited by the patient during life rarely fail to afford some clue to the poison taken. Persons may, however, be found dead of whose history nothing can be learned. Here post mortem appearances, chemical analysis, and, it may be, physiological experiments; are all-important for the elucidation of the nature of the case. Poisoning may be acute or chronic. The general conditions which should arouse a suspicion of acute poisoning are the sudden onset of serious and increasingly alarming symptoms in a person previously in good health, especially if there be pain in the region of the stomach, or, where there is complete prostration of the vital powers, a cadaveric aspect, and speedy death. In all such cases the aid of the analytical chemist must be called in either to confirm well-founded or to rebut ill-founded' suspicions. The mode of treatment to be adopted in the case of poisoned persons varies greatly according to the nature of the poison. The first indication, when the poison has been swallowed, is to evacuate the stomach; and this may usually be done by means of the stomach-pump when the poison is not of the corrosive class; or the stomach may be gently washed out by means of a funnel and flexible siphon-tube. In many cases emetics are valuable. Antidotes and counter-poisons may then be given. The former are such substances as chalk to neutralize the mineral acids and oxalic acid; the latter have a physiological counter-action, and are such as atropine, which is a counter-poison to morphia. These may usually be administered most effectively by hypodermic injection. The stomach may to a certain degree be protected from the injurious effects of irritants by the administration of mucilaginous drinks; alka:oids may be rendered sparingly soluble by means of astringent substances containing tannin; and pain may be relieved by means of opium, unless contra-indicated by the nature of the poison. The effects of the convulsant poisons, such as strychnine, may be combated by means of the inhalation of chloroform. The classification of poisons is a matter of difficulty. Various attempts have been made to classify them scientifically, but with no signal success; and perhaps the best system is that which groups the various poisons according to the more obvious symptoms which they produce. Our knowledge of the more intimate action of poisons is still too imperfect to admit of any useful classification according to the manner in which they specifically affect the vital organs. Poisons may in the manner indicated be classified as (I) Corrosives, (2) Irritants, (3) Neurotics, and (4) Gaseous Poisons. 1. Corrosives. The typical member of this class is corrosive sublimate, the soluble chloride of mercury. In it are included also the concentrated mineral acids (sulphuric, nitric and hydrochloric) ; oxalic acid; the alkalies (potash, soda, and ammonia) and their carbonates; acid, alkaline, and corrosive salts of the metals (such as bisulphate of potash, alum, butter of antimony and nitrate of silver) ; also carbolic acid. The symptoms produced by the mineral acids and the alkalies are almost altogether referable to local action; but some corrosive poisons, such as carbolic acid, produce, besides a local action, remote and specific constitutional effects. The symptoms of corrosive poisoning are marked and unmistakable, except in infants. Immediately on swallowing the corrosive substance, an acid, caustic or metallic burning sensation is experienced in the mouth, fauces, gullet and region of the stomach, and this speedily extends over the whole belly; as a rule vomiting speedily follows. In the case of the mineral acids, and in oxalic acid poisoning, the vomit is so acid that if it falls upon a marble or concrete floor effervescence ensues. No relief follows the evacuation of the stomach. The ejected matters contain blood, and even fragments of the corroded walls of the alimentary canal. The belly becomes distended with as and horribly tender. High fever prevails. The mouth is found to be corroded. Death usually ensues within a few hours; or, if the patient survives, he or she may perish miserably, months after the poison was taken, through starvation consequent upon the gradual contraction of the gullet, brought about by its corrosion and subsequent healing. The treatment of corrosive poisoning consists in very gently emptying and washing out the stomach by means of a soft siphon-tube. The stomach-pump cannot be used with safety in con-sequence of the weakening of the walls of the stomach by corrosion. Demulcents and opiates may be subsequently administered. After death from corrosive poisoning the walls of the stomach are found corroded and even perforated. I. Corrosive Sublimate.—Here all the signs and symptoms of corrosive poisoning are produced in their severest form. A grain or two of this poison may prove fatal. Fortunately there is an efficient antidote in white of egg, the albumen of which, if administered at once, renders the salt insoluble. The eggs should be divested of their yolks, beaten up with water, and given promptly, repeatedly, and abundantly, followed by emetics. Poisoning by corrosive sublimate may be followed by the specific toxic effects of mercury, such as salivation and tremor. Workers in mercury, such as water-gilders, looking-glass makers, and the makers of barometers and thermometers, are apt to suffer from a peculiar form of shaking palsy, known as " the trembles," or mercurial tremor. This disease affects most frequently those who are exposed to mercurial fumes. The victim is affected with tremors when an endeavour is made to exert the muscles, so that he is unable, for instance, to convey a glass of water to the lips steadily, and when he walks he breaks into a dancing trot. The treatment consists in removal from the mercurial atmosphere, baths, fresh air, and the administration of iron and other tonics. 2. Mineral Acids.—These are oil of vitriol or sulphuric acid, aqua fortis or nitric acid, and spirit of salt or hydrochloric (muriatic) acid. These, when taken in a concentrated form, produce well-marked symptoms of corrosion. When they are diluted, the symptoms are those of an irritant poison. Nitric acid stains the mouth and skin of a yellow colour. The treatment consists in the administration of the alkalies or other carbonates, chalk, whiting, or even uncoloured plaster scraped off the walls or ceiling, with the view of neutralizing the acid. 3. Oxalic acid is a vegetable acid. When taken in the state of concentrated solution it acts as a corrosive, but when diluted as an irritant. But it also exerts a specific effect, killing the patient by cardiac syncope not unfrequently within a few minutes. When a person after taking a crystalline substance, tasting strongly acid, dies within 15 or 30 minutes, after the manifestation of great weakness, small pulse and failure of the heart's power, poisoning by oxalic acid is almost certain. The treatment consists in promptly administering an emetic, followed by chalk, whiting, or any sub-stance containing carbonate of calcium. The alkaline carbonates are valueless, for the alkaline oxalates are almost as poisonous as oxalic acid itself. 4. The Alkalis.—Caustic potash and caustic soda produce symptoms resembling those of the mineral acids, except that purging is a usual accompaniment. 5. Carbolic acid.when taken in the form of a concentrated liquid acts as a corrosive, causing whitening and shrinking of all the animal membranes with which it comes in contact. The patient, however, becomes speedily comatose, the poison acting profoundly upon the great nervous centres. A curious phenomenon—black or dark green urine—is commonly observed after the administration of this poison. Saccharated lime-water, diluted and drunk freely, and a solution of sulphate of soda are perhaps the most useful remedies. 2. Irritant Poisons. Irritant poisons are of two classes—metallic irritants and vegetable and animal irritants, these latter being for convenience grouped together. Perhaps none of the irritants act purely as such, the irritant symptoms being usually accompanied by well-marked effects upon the nervous system. An irritant is a substance which causes inflammation of the part to which it is applied—usually the alimentary canal. Arsenic is by far the most important of the metallic irritants. Other irritants are the moderately diluted acids, many metallic salts, such as those of antimony, lead, copper, zinc and chromium. Elaterium, gamboge, aloes, colocynth and croton•oil are good examples of vegetable irritants; and cantharider of animal irritants. Animal and vegetable food when decomposed, or infested with certain organisms known as bacteria, may produce violent irritant symptoms. The symptoms produced by irritant poisons are usually more slow in their development than where a corrosive has been administered. Usually, after an interval, greater or less according to the specific nature of the irritant swallowed, a burning pain is felt in the mouth, throat and gullet, with a sense of constriction of the parts, and followed by burning pain in the region of the stomach. This is increased, and not alleviated, by pressure, a mark which serves to distinguish the attack from one of ordinary colic. Nausea, vomiting and thirst ensue, speedily followed by distension of the whole abdomen, which is exceedingly tender to the touch. Ordinarily the vomiting is followed by profuse diarrhoea. Should the poison not be speedily eliminated in the vomited and faecal matters, inflammatory fever sets in, followed by collapse; and death may ensue in a few hours. There is danger of confounding irritant poisoning with some forms of natural disease, such as gastritis and gastric ulcer, colic, peritonitis, cholera and rupture of the intestines. i. Arsenic is a specific irritant poison. Almost all the compounds of this metal are poisonous. The term " arsenic " is, however, most commonly applied, not to the metal itself, but to its lower oxide, arsenious oxide, which is also known as white arsenic. By whatever channel arsenic is introduced into the system, it invariably affects specifically the stomach and intestines, causing congestion or inflammation. The common sources of arsenical poisoning are the taking of white arsenic, which causes acute poisoning, and the inhalation of dust from arsenical wall-papers and textile fabrics, whereby a chronic form of poisoning is induced. The symptoms and treatment of arsenical poisoning are described under Arsenic (q.v.). Arsenic-eating, or the ability of some persons to take relatively large doses of arsenic habitually, is a well-established fact. The cause of this singular immunity from the ordinary results of arsenic is unknown. 2. Lead.—The salts of lead, more especially the acetate (sugar of lead), are irritant poisons of no very great activity; and, though occasionally death ensues, recovery is the rule. Chrome yellow, or lead chromate, is a powerful irritant poison. All chromates are, indeed, irritant poisons. (See LEAD POISONING.) 3. Copper.—The soluble salts of copper, such as blue vitriol (the sulphate) and verdigris (subcarbonate and subacetate), are emetic and irritant salts. Their emetic effects usually, but not invariably, secure their prompt rejection by the stomach. Occasionally fatal effects have resulted from their administration. Copper becomes accidentally mixed with articles of dietary in a variety of modes. It is also used for improving the colour of preserved fruits and vegetables. Its deleterious properties when thus used in minute quantities have been both asserted and denied. There is, however, a large body of evidence in favour of the at all events occasional poisonous effects of minute quantities of copper. 4. Zinc salts and barium salts, except the quite insoluble barium sulphate, are irritant poisons; and barium compounds act also upon the central nervous system. 5. Chromates, e.g. bichromate of potash, are violent irritants. Chrome yellow, or; lead chromate. has already been mentioned. 6. Phosphorus.—Of the two chief forms of the elements—the yellow or ordinary and the red or amorphous—the former only is poisonous. Rarely there is met with a chronic form of poisoning among workers in the material, arising from the inhalation of phosphorus vapours. Its special characteristic is a peculiar necrosis or death of the bony structure of the lower jaw. Acute phosphorus poisoning is more common. Phosphorus is used for tipping matches, and is also the basis of several vermin destroyers. (See PHOSPHORUS and MATCH.) 7. Vegetable Irritants.--These produce drastic purgative effects. Frequently the nature of the illness may be ascertained by the discovery of portions of the vegetable substance recognizable by the microscope—in the matters ejected by the patient. 8. Cantharides.—The administration of cantharides (q.v.) is followed by vomiting, purging, strangury, or even entire inability to pass the urine. In the ejecta portions of the shining elytra or wing-cases of the fly may often be recognized. There is often great excitement of the sexual proclivities. The active principle of the fly, cantharidin, may be extracted from suspected matters by means of chloroform, and the residue left after the evaporation of this blisters the lip or any tender mucous surface to which it is applied. Demulcent remedies, with opiate enemata and injections, afford the best relief by way of treatment. 3. Neurotics. t. Prussic or Hydrocyanic Acid.—Hydrocyanic acid is one of.the best known poisons, and a very deadly one. In the pure state it is said to kill with lightning-like rapidity. It is met with in commerce only in a dilute state. In Great Britain two kinds of acid. are commonly sold—the pharmacopoeial acid, containing 2 % of anhydrous prussic acid, and Scheele's acid, containing 4 to 5%. Less than a teaspoonful of the 2 % acid has caused death. Given in fatal doses, the symptons of prussic-acid poisoning set in with great rapidity; and, in consequence of the readiness with which the poison is absorbed from the stomach and diffused through the circulation, the onset of symptoms is reckoned by seconds rather than by minutes. Occasionally the victim may be able to perform a few voluntary actions before alarming symptoms are developed. There is first a very brief stage of difficult breathing, and slow action of the heart, with a tendency for the organ to stop in the state of dilatation. With widely-dilated pupils of the eye, the patient is then seized with violent irregular convulsive movements. The rhythm of the respiratory movements is disturbed, and the countenance becomes of a bluish cast. The patient now sinks to the ground with complete loss of muscular power; and the third or asphyxial stage is reached, in which there are slow gasping respirations, loss of pulse, and paralysis of motion. Death is frequently preceded by muscular spasms. The foudroyant character of the illness, and the speedy death of the patient, coupled with the peculiar odour of the acid in the breath and atmosphere around the body, seldom leave any doubt as to the nature of the case. The treatment consists in inhalation of fumes of strong ammonia, drinks of warm and cold water alternately, friction of the limbs, and artificial respiration. The subcutaneous injection of atropine, which acts as a cardiac stimulant, may prove serviceable. Other soluble cyanides, more especially cyanide of potassium, a salt largely used in photography and in the arts, are equally poisonous with hydrocyanic acid. (See PRUSSIC ACID.) 2. Opium.—In consequence of the extent to which opium, its preparations, and its active alkaloid morphia are used for the relief of pain, poisoning by opium is of frequent occurrence. It is largely used by suicides; and children, being very susceptible to its influence, frequently die from misadventure after administration of an over-dose of the drug. The ordinary preparations of opium are the drug itself, which is the inspissated juice of the oriental poppy, and the tincture, commonly known as laudanum. Opium contains a variety of more or less active principles, the chief of which is the alkaloid morphia, which is present in good opium to the extent of about to % in combination with meconic acid, which is physiologically inactive. Opium is largely used by Eastern nations for smoking, and there is great discrepancy of opinion as to the extent to which opium smoking is deleterious. The preponderance of opinion is in favour of the view that opium smoking is a demoralizing, degrading, and pernicious habit, and that its victims are sufferers both in body and mind from its use. (See OPIUM and MORPHINE.) 3. Strychnine and Strychnine-yielding Plants.—The alkaloids strychnine and brucine, as well as all the plants in which they are found, all act in the same manner, being highly poisonous, and causing death after spasms of a severe character. Many vermin killers contain strychnine as their active ingredient. Strychnine, and all substances containing that alkaloid, produce their effects within a very few minutes—usually within ten or fifteen minutes. The patient complains of stiffness about the neck, and his aspect exhibits terror. There is an impression of impending calamity or death. Very speedily the head is jerked back, the limbs extended, the back arched (opisthotonos), so that the body may rest on the head and heels only. In a few moments these symptoms pass off, and there is complete relaxation of the spasm. The spasmodic condition speedily returns, and is brought about by the slightest touch or movement of the patient. Accessions and remissions of the tetanic state ensue rapidly till the patient succumbs, usually within half an hour of the administration of the poison. The best treatment is to put, and keep, the patient under the influence of chloroform till time is given for the excretion of the alkaloid, having previously given a full dose of chloral hydrate. (See STRYCHNINE.) 4. Aconite Poisoning.—The ordinary blue rocket, wolf sbane or monkshood, Acontium Napellus, and an alkaloid extracted from it, aconitine, are perhaps the most deadly of known poisons. One-sixteenth of a grain of aconitine has proved fatal to a man. All the preparations of aconite produce a peculiar burning, tingling, and numbness of the parts to which they are applied. When given inlarge doses they produce violent vomiting, as a rule, more or less paralysis of motion and sensation, and great depression of the heart, usually ending in death from syncope. Intelligence remains unaffected till almost the last. The treatment consists in the hypodermic injection of digitalin, which is a counter-poison in its action upon the heart. The root of aconite has been eaten in mistake for that of horse-radish. 5. Belladonna.—The belladonna or deadly nightshade, Atropa Belladonna, contains an alkaloid, atropine, which is largely used by oculists to procure dilatation of the pupils of the eye. The bright scarlet berries of the plant have been eaten by children, who are attracted by their tempting appearance. Belladonna produces dilatation of the pupils, rapid pulse, hot dry flushed skin, with an eruption not unlike that of scarlatina, soreness of the throat, with difficulty of swallowing, intense thirst, and gay, mirthful delirium. The treatment consists in evacuation of the poison by means of the stomach-pump, and the hypodermic injection of morphia as a counter-poison. 4. Gaseous Poisons. The effects of these are varied—some of them acting as irritants, while others have a specific effect, apparently in consequence of their forming chemical compounds with the red pigment of the blood, and thus destroying its capability of acting as a carrier of oxygen. i. Chlorine and bromine act as powerful irritants. They provoke spasm of the glottis when inhaled, and subsequently induce inflammation of the respiratory mucous membrane, which may prove speedily fatal. Inhalation of diluted ammonia vapour is the best remedy. 2. Hydrochloric or muriatic acid gas and hydrofluoric or fluoric acid gas are irritating and destructive to life. The former is more destructive to vegetable life than even chlorine. They are emitted in many processes of manufacture, and especially in the manufacture of carbonate of soda from common salt by Le Blanc's process, in the salt-glazing of earthenware, and in the manufacture of artificial manures. 3. Sulphurous Acid Gas.—The gas given off by burning sulphur is most suffocating and irritating. Its inhalation, even in a highly diluted state, may cause speedy death from spasmodic closure of the glottis. 4. Nitrous vapours, or gaseous oxides of nitrogen (except nitrous oxide), are given off from galvanic batteries excited by nitric acid; also in the process of etching on copper. They produce, when diluted, little immediate irritation, but are exceedingly dangerous, setting up extensive and fatal inflammation of the lungs. 5. Ammonia gas is highly irritant, but does not often prove fatal. 6. Carbon dioxide gas is heavier than atmospheric air, is totally irrespirable when pure, and is fatal when present in large quantities in respired air. It is given off from burning fuel, accumulates in pits and wells as choke-damp, and constitutes the deadly after-damp of coal-mines. It is also formed during alcoholic fermentation, and hence accumulates in partially filled vats in which fermented liquors are stored. When it is breathed in a concentrated state, death is almost instantaneous. Persons descending into wells foul with this gas sink down powerless, and are usually dead before they can be rembved from the vitiated atmosphere. In these cases there is true asphyxia; but carbonic acid is also a narcotic gas. Persons exposed to an atmosphere partially composed of this gas, but not long enough to produce fatal results, are affected with stertorous breathings, oppression, flushed face, prominent eyes, swollen tongue and feeble pulse. The proper treatment is removal from the foul atmosphere, alternate cold and tepid douches to the chest, friction of the limbs and trunk, and artificial respiration. When animation is restored the patient should be put to bed and kept quiet, but should be carefully watched in case of relapse. 7. Carbon monoxide gas is given off by burning charcoal and other forms of fuel, mixed with carbonic acid. The poisonous effects of charcoal fumes are perhaps due rather to the more poisonous carbonic oxide than to the less poisonous carbonic acid. An atmosphere containing less than i % of carbonic oxide would doubtless be fatal if breathed for many minutes. Carbonic oxide forms with haemoglobin, the red pigment of the blood, a bright scarlet compound. The compound is very stable, and the oxide cannot be displaced by atmospheric oxygen. Hence the blood after death from the inhalation of carbonic oxide is of a bright arterial hue, which it retains on exposure to air. 8. Coal-gas acts as an asphyxiant and narcotic. The appearances met with after death—more especially the fluid state of the blood—are similar to those observed after death from carbonic oxide gas, which is a constituent of coal-gas, and to which the chief effect of coal-gas may be due. 9. Sulphuretted hydrogen gas is highly poisonous by whatever channel it gains access to the body. In a concentrated form it produces almost instant death from asphyxia. Even in a diluted state it produces colic, nausea, vomiting and drowsiness. This may pass into insensibility with lividity and feeble respiration. The skin is cold and clammy, or bathed in perspiration. The red blood corpuscles are disintegrated. The treatment consists in removal from the contaminated atmosphere, friction to the surface of the body, warmth, and the administration of stimulants. The inhalation of chlorine gas has been recommended on chemical grounds; but it must be remembered that chlorine is itself poisonous. to. Anaesthetics.—Nitrous oxide, or laughing gas, and the gases or vapours of other anaesthetic substances, such as chloroform, may, if improperly administered, produce death by asphyxia, and perhaps otherwise. Obviously, as a rule, medical assistance is at hand. The treatment consists in artificial respiration, and the, use of galvanic current. I1. Vapours of Hydrocarbons.—The volatile vapours of the natural hydrocarbons known as benzoline, petroleum, &c., are poisonous when inhaled for lengthened periods. (T. S.*)
End of Article: POISON

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