Tobacco, the leaves of several species of the solanaceous genus Nicotiana, prepared for use as a narcotic, either by smoking, chewing, or inhaling (as snuff). It is the most widely used of narcotics, its employment in all three ways being made known to Europe by Columbus and the Spaniards between 1492 and 1502. The plant was brought from Mexico to Spain in 1558, and Jean Nicot, French ambassador to Portugal, having sent seeds to Catherine de Medici, the plant has been given his name. Smoking in Europe was mainly the result of English example after Drake's return from Virginia in 1586, and spread rapidly, in spite of James I.'s Counterblaste of Papal bulls, of sultans' sentences to death, and of the Russian knout. Most tobacco, and that of the best quality, is the product of N. Tabacum, the Virginian tobacco, a coarse-growing, viscid, unbranched annual, six feet or more high, with scattered simple leaves, sometimes two feet long, the upper ones amplexicaul or decurrent, and a panicle of pink flowers with long corolla~tubes, It is the source of Virginian, Cuban, Manilla, Latakia, and Turkish tobacco. N. rustica, or Green tobacco, a smaller, much-branched plant, with a shorter, greenish corolla, originally a native of Brazil, is cultivated in the East Indies: a white-flowered species, N. repanda is, said to furnish some of the finest Havannah cigars; and N. persica, the tobacco of Shiraz. Tobacco does best with a mean annual temperature not less than 40° F., no early autumnal frosts, and a low rainfall: it is an exhausting crop, requiring abundant manure rich in potassium-nitrate. In Europe it is sown in hotbeds in March, transplanted in May, and harvested in September. Each plant should have from 8 to 12 large leaves. These are gathered when beginning to droop; allowed to wilt, or sweated for three or four days; "cured" either slowly by currents of dry air, or quickly by artificial heat rising in four or five days to 170° F.; rendered soft by the admission of damp air; stacked and allowed to ferment for from three to five weeks. Tobacco leaves contain 18 to 22 per cent. of ash, principally calcium carbonate, and potassium salts, besides salts of ammonia and nitrates. They have also 25 per cent. of albuminoids; 10 to 14 per cent. of malic and citric acids; 7 or 8 per cent. of cellulose; from 4 to 6 per cent. of resin and fat; about 5 per cent. of pectic acid, and 1 or 2 per cent. of oxalic; acetic acid, increasing during fermentation and reaching 3 per cent. In snuff; from 1.5 to 9 per cent. of the. acridly poisonous, colourless, liquid, volatile alkaloid nicotine (C10H14N2); and a solid camphor like substance, nicotianine. The nicotine increases in the leaves with age, and is mainly destroyed when the tobacco is burnt, though it also occurs in the remaining oil. The proportion of nicotine determines the strength, but not the flavour, of the tobacco. In snuff the malic and citric acids are largely destroyed, and free ammonia is present, giving the snuff its alkaline pungency. Many habitual smokers find that tobacco relieves bodily or mental fatigue: strong tobacco may undoubtedly produce the disease of the eyes known as amblyopia; and the excessive use of tobacco, especially by the young, seems to affect both the digestion and the nervous system injuriously, inducing more particularly affections of the heart. Most countries have made the cultivation and importation of tobacco a source of revenue. Though it cannot be relied upon as a crop in our climate, its cultivation is chiefly prevented by fiscal prohibitions. During the ten years ending 1881 tobacco was grown on 600,000 to 700,000 acres in the United States, the average annual production being 472,000,000 lbs., the value of which ranged from 40,000,000 to 45,000,000 dollars. During the decade nearly 1,900,000,000 lbs. were manufactured for home use, and over 2,500,000,000 lbs, were exported. In 1890 the crop was valued at £9,OOO,OOO sterling, and the exports at over £5,000,000. England in that year retained for home consumption 56,000,000 lbs. of unmanufactured and over 2,000,000 lbs. of manufactured tobacco, a consumption of about 1-3/4 lb. per head of the population.