TOBACCO AND THE TOBACCO HABIT. 671 



ing in uneven teeth. The genus Nicoiiana includes some fifty 

 other species, mostly natives of America, but some of Australia 

 and the islands of the Pacific Ocean. Of these, some fifteen or 

 twenty species are cultivated and give rise to different foreign 

 tobaccoes, the taste and properties of which are varied. A few 

 species, remarkable for the richness of their colors and their grace- 

 ful growth, are cultivated as ornamental plants in gardens. 



Tobacco leaves contain principles common to all vegetable 

 substances such as starch, cellulose, sugar, organic acids, and 

 salts principles soluble in ether, nitrogenous substances, and a 

 peculiar alkaloid to which the plant owes its special qualities, 

 called nicotine. This alkaloid, discovered by Posselt and Remann, 

 was isolated by Vauquelin in 1809. It is an oily liquid, trans- 

 parent and colorless, which becomes brown and thick in the air 

 by absorbing oxygen. Its acrid and virulent odor is like that of 

 tobacco ; it has a burning taste, and its vapor is so irritating that 

 breathing is painful in a room where a drop of it has fallen. It 

 is very hygrometric, and soluble in water, alcohol, and ether. It 

 combines directly with acids, with the evolution of heat. It is 

 found as a malate in the leaves. The different kinds of tobacco 

 do not contain the same quantities of it. The black, unctuous 

 tobacco of the Antilles, the pronounced savor, ready burning, 

 and white ash of which make it in demand among experienced 

 smokers, contains much more nicotine than the light, fragrant 

 tobacco of the Levant. The quantity of it increases with the 

 development of the plant, and varies according to the thickness 

 of the leaves. The thinner-leaved plants contain less of it. The 

 fermentation to which tobacco is subjected in manufacturing 

 volatilizes a part of the nicotine and substitutes ammonia for it. 

 Consequently, there is less nicotine in tobacco prepared for con- 

 sumption than there was in the dry leaves before the preparation. 

 Combustion destroys about three quarters of this. According to 

 M. Pabst, the smoke of five grammes of tobacco yields about 

 three milligrammes of nicotine ; but it contains a number of 

 other principles besides, the enumeration of which here would 

 not be interesting. Nicotine is the active principle of tobacco, as 

 atropine is of belladonna and morphine of opium ; but there are 

 other poisons among the substances united with it. The less 

 volatile ones condense during combustion, and produce a brownish 

 empyreumatic liquid, a kind of coal-tar of tobacco, a part of which 

 oozes through porous pipes, and the whole of which is retained in 

 the water of nargilehs. 



Among the volatile principles that pass into the smoke along 

 with nicotine are hydrocyanic acid and carbonic oxide. Dr. Gre- 

 hant has shown that a notable quantity of them is absorbed by 

 rapid smokers swallowing the smoke, and the gas passes into the 



