TOXICOLOGY (from Gk. ro,Fau5c, toxikon, poison. nem sg. of To,;iseic, toxikos, relating to the bow, from 76.=ov, toson, bow, so called be cause first used to poison arrow-points + -login, account, from i.e)eir, leqein, to say). The branch of medical science which treats of the nature of poisons, of their morbific effects on the animal system, of their detection in the organs or tissues of the body. of their antidotes, of the treatment of poisoning, and, finally. of the legal questions connected with poisoning. A poison may be defined as any substance which when applied to the,body or introduced into the system, in whatever manner, produces death or serious bodily harm. Poisons may enter the body in various ways. The mouth is the usual channel. Poisons may be absorbed by the skin in amounts sufficient to cause death or severe toxic symptoms, as in the case of lotions or salves containing opium. corrosive sublimate, arsenic, carbolic acid, etc. Gaseous or volatile poisons may enter the lungs through the inspired air, e.g. illuminating gas, carbon monoxide, or chlorine. Poisons may gain access to the circulation through ulcerated surfaces or wounds; by direct injection into the tissues, as by hypodermic in jection, poisoned arrows, or snake-bites; or they may be introduced by way of the mucous mem brane of the rectum, vagina, urethra, nose, or eye.
Most medicinal agents are poisonous if taken in sufficient quantity, and this quantity varies with the individual, the state of bodily health, fullness or emptiness of the stomach, habit, and other circumstances. The influence of habit is shown by opium habitu6s who take enormous doses of the drug without immediate evil effects. A special susceptibility to certain substances is noted in some individuals. This is called idiosyncrasy. Thus, five grains of quinine have nearly killed certain persons, or produced un pleasant symptoms, as blindness or deafness. in others. Races and individuals, on the other hand, may possess or attain a high degree of im munity to particular poisons; e.g. the Oriental is much less susceptible to opium than the Euro pean, and the latter bears alcohol better than savage races. In certain diseases there is a diminished susceptibility to the action of particu lar poisons, while in others there is increased sensibility. Thus in tetanus (q.v.), hydrophobia, mania, or delirium tremens, (loses of various sedatives may be given with benefit which would in health prove fatal: on the other hand, when there is a predisposition to apoplexy an ordinary dose of opium may eause death. Some poisons
are harmless when taken into the stomach. but violently toxic when injected beneath the skin.
Poisons may be classified according to their chemical properties or their physiological action. The latter is the usual and most satisfactory basis, and depends upon the effects of poisons upon the system when it is in a healthy con dition. According to the physiological classifica tion poisons are divided into two great groups, viz. (1) the irritants and (2) the neurotics. An irritant poison is one which when swallowed produces an irritant effect upon the mucous membrane of the alimentary canal, resulting in nausea, vomiting. purging, pain in the abdomen, cramps in the stomach and other parts of the body. This group is subdivided into (a) corro sires, whose action is chiefly local, and (b) the true irritants, whose local effects may he slight, but which produce their characteristic effect after absorption. Many drugs act in both ways; for example. oxalic acid and carbolic acid. A neurotic poison is one which acts chiefly on the nervous system, producing drowsiness (nar cotic), giddiness. headache, delirium (deliri ant), stupor, coma, convulsions (tetanic), or paralysis.
Before proceeding to a systematic considera tion of poisons a few principles of the general treatment of poisoning may be given. The indi cations are ( 1) to neutralize and render harm less the poison by the administration of the proper antidote (q.v.) ; (2) to remove the poistm from the body by inducing vomiting or washing out the stomach; (3) to combat the effects of the poison already absorbed, by giving drugs which are physiologically antagonistic to the one absorbed, and supporting life until the body rids itself of the poisonous substance through the natural excretory channels. Antidotes affect a poison either mechanically o• chemically, or both, so as to remove it from the body or alter its character before absorption and thereby prevent its toxic action upon the organism. Alechanieal antidotes include the use of the stomach tube or pump, the employment of emetics, cathartics, stimulants, injections, ligations, etc. The true or chemical antidotes include albumen, milk, charcoal, soap, starch, oils, tannin, turpentine, acids, alkalies, potassium, permanganate, sodium, chloride, iodine, iron, etc.