POISON 639 POISON, any substance which, introduced in I small quantities into the animal economy, seri- ously disturbs or destroys the vital functions. Under this head are obviously included a vast number of bodies belonging to the mineral, [ vegetable, and animal kingdoms, some solid, j others fluid, and others gaseous, and deleteri- cms vapors and miasmata imperceptible to the senses. The science which treats of these is designated toxicology. Until of late years the true nature and effects of poisons were little understood, although poisonous mixtures were much used among the ancient Greeks and Romans. What these preparations were we cannot in all cases ascertain, but some of them can be identified with a considerable degree of probability. (See HEMLOCK.) Among the mul- titude of substances that rank as poisons are many, some possessing the most active quali- ties, which are also useful drugs, and which, administered in suitable quantities, are recog- nized among medicines in universal employ- ment and of the most beneficial character. The difference between a medicine and a poi- son is frequently a mere question of dose, and the line which divides them is sometimes nar- row. Certain poisons manifest their activity chiefly by their effect upon the alimentary canal, and are styled irritants, although they sometimes have also an action upon the con- stitution of the blood and secondarily upon the solid tissues. Such are the caustic alkalies, mineral acids, oxalic acid, arsenic, corrosive sublimate, to a certain extent tartar emetic, phosphorus, and many vegetables acting as drastic cathartics, such as scammony, croton oil, gamboge, and various other plants of the order euphorliacece. Some vegetables when handled, or even by their emanations, give rise to cutaneous eruptions. The manchineel of the West Indies (hippomane mancinella) and our native rhus toxicodendron and rhus vene- nata, or poison ivy, and poison dogwood, are of this class. The latter are supposed to owe their poisonous properties to the volatile toxi- codendric acid. The number of vegetables act- ing as poisons upon the nervous system, and secondarily upon the heart and other organs, is enormous. They are often called narcotic or narcotico-acrid, although their action is by no means always narcotic or stupefying. Such are opium, belladonna, henbane, savin, tansy, coninm, tobacco, lobelia, digitalis, aconite, ye- ratrum, Calabar bean, woorara, mix vomica (containing strychnia), and many others less known. To these may be added alcohol, chloroform, and chloral hydrate. Some vola- tile poisons appear to act chiefly upon the blood; such are carbonic oxide, illuminating and sewer gas, nitrous oxide, nitre-benzole, and hydrocyanic acid. But the line between this class and the preceding cannot be drawn with accuracy. The action of the poisons of venomous reptiles and insects is less easily understood, from the small quantities usually secreted at a time and obvious difficulties in. obtaining it. These poisons are rapidly ab- sorbed from the skin or subcutaneous tissues, but are much less noxious when taken by the mouth, provided no abrasion exists. The same is true of the woorara, curare, or ticunas, the South American arrow poison. The virus or contagions of many diseases, in some instances almost demonstrable, as in smallpox or syphilis, at others hypothetical, as in typhoid, yellow fever, diphtheria, &c., may be with some pro- priety classed among poisons, and their actions are seen in the symptoms of the special disease developed. Chronic poisoning may take place from the gradual introduction of small quanti- ties of various deleterious substances. Notable examples are lead poisoning, occurring in lead workers, type founders, painters, and persons using water standing in lead pipes, or liquor contaminated therewith ; mercurial poisoning in dry gilders and manufacturers of looking glasses, and from the medicinal use of the drug ; arsenical, from green paper hangings, clothing, &c. Chronic poisoning by tartrate of antimony has probably often taken place for criminal purposes. A considerable degree of tolerance may however be observed with certain drugs. Opium may be taken, by per- sons accustomed to it, in doses enormously larger than would be fatal to a person not habituated to its use. Certain persons in Styria and elsewhere are able to use poisonous doses of arsenic not only with impunity, but, as they allege, with benefit. Stille's " Medical Jurisprudence " speaks of a case, on the au- thority of Dr. Hartshorne, where a man was in the habit of taking five grains of corro- sive sublimate every day. The number of substances from which accidental or criminal poisoning frequently takes place is smaller than might be supposed from the above state- ments. In France, during 12 years from 1851 to 1862, 26 substances only were employed, and of these the most common were arsenic, phosphorus, sulphate of copper, verdigris, sul- phuric acid, and cantharides. In New York in 1872 deaths by accident and suicide took place from opium and its preparations in 20 cases; Paris green (arsenite of copper) in 24 (all suicides) ; arsenic, 2 ; carbolic acid, 2 ; hy- drate of chloral, 2 ; sulphuric acid, oxalic acid, phosphorus, rat poison (probably phosphorus), colchicum, prussic acid, chloroform, ether, yel- low wash, wine, each 1 ; chronic from lead, 5. In medico-legal cases evidence of poisoning depends on the symptoms and on the discovery of a poison. Symptoms alone can seldom if ever prove conclusively the action of a poi- son, but organic chemistry has made such pro- gress in recent years that criminal poison- ing is much less easily concealed than for- merly, and the alkaloid or other active prin- ciple which caused death can often be actu- ally exhibited in court. Many alkaloids, how- ever, are fatal in such exceedingly small doses that their separation is a work of very great delicacy, and may even be impossible. In
