Poisons are of several kinds: Animal, as snake-venoms and cantharides; Vegetable, as opium, strychnia, tobacco; Mineral, as arsenic and corrosive sublimate. But a more useful classification of them is according to their effects: as Depressants, Irritants, Neurotics, and Complex poisons.

Depressants are prussic (hydrocyanic) acid, tobacco, lobelia, hemlock, and aconite. It is true, the effects of these, and indeed of almost all poisons, have some complexity; but their chief effect is depression, sinking, prostration; which, from a certain dose, is fatal.

Irritants are strong acids, as sulphuric, nitric, hydrochloric, oxalic, citric, and tartaric acids; strong alkalies, as potassa, soda, and ammonia; phosphorus; corrosive sublimate; tartar emetic; salts of copper and of zinc; castor-oil seeds; colchicum; croton-oil; cantharides; and certain fishes and molluscs (some mussels, etc.).

Neurotic poisons either produce stupor, as do opium, chloroform, ether, chloral, hyoscyamus, and camphor (in excessive doses); or otherwise damage the nervous

system, with either delirium, convulsions, tremor, or paralysis, as strychnia (or nuxvomica), belladonna, stramonium, calabar bean, cocculus Indicus.

Complex (Irritant-Neurotic) poisons are such as arsenic, carbolic acid, creosote, digitalis, ergot, fungi (toadstools, etc.), hellebore, iodine, bromine, lead, etc.

Depressant poisons cause prostration, sinking: with paleness, coldness, feeble pulse, gasping breath, with or without nausea and vomiting; all the symptoms of collapse.

Irritant poisons produce burning and pain in the mouth, throat, stomach, and bowels; with nausea, vomiting, and purging; an artificial cholera-morbus.

Neurotic poisons have just been described as causing either stupor, delirium, convulsions, tremor, or paralysis. Complex poisons may combine several of either of these kinds of effects.

So far, we have been considering poisons as taken into the stomach by the mouth. It must be remembered, however, that they may also enter the system by being breathed into the lungs; injected under the skin; or even absorbed from the surface of the skin (especially with children; a tobacco leaf has been so fatally used); or inserted into the bowels, etc.

With these general remarks, we may now take up those poisons most likely to be met with, or heard or read about, alphabetically, for ease of reference by the reader.

Acids. As already said, strong acids are generally irritant poisons. Hydrocyanic or prussic acid is a powerful depressant. The antidotes for acids are alkalies and alkaline earths; as soda, limewater, chalk, mag nesia, and soap, etc. In like manner, acids of the milder sort, as vinegar, lemon-juice, etc., are antidotes for poisonous doses of strong alkalies or alkaline earths, as caustic potassa, soda, ammonia, or lime.