A curious mistake, almost universally made, is that of supposing that the oily juice which forms in a pipe or at the end of a cigar is “nicotine,” the chief nerve-poison of tobacco. As a matter of fact, this juice, though it contains injurious substances, contains little or no “nicotine.” Nicotine is a colourless volatile liquid, which is vapourised and carried along with the smoke; it is not deposited in the pipe or cigar-end except in very small quantity. It is the chief agent by which tobacco acts on the nervous system, and through that on the heart--the agent whose effects are sought and enjoyed by the lover of tobacco. A single drop of pure nicotine will kill a dog. Nicotine has no aroma, and has nothing to do with the flavour of tobacco, which is due to very minute quantities of special volatile bodies similar to those which give a scent to hay. Most people are acquainted with the three ways of “taking tobacco”--that of taking its smoke into the mouth, and more or less into the lungs, that of chewing the prepared leaf, and that of snuffing up the powdered leaf into the nose, whence it ultimately passes to the stomach. A fourth modification of the snuffing and chewing methods exists in what is called the “snuff stick.” According to the novelist, Mrs. Hodgson Burnett, the country women in Kentucky use a short stick, like a brush, which they dip into a paperfull of snuff; they then rub the powder on to the gums. Snuff-taking has almost disappeared in “polite society” in this country within the past twenty years, but snuffing and chewing are still largely practised by those whose occupation renders it impossible or dangerous for them to carry a lighted pipe or cigar--such as sailors and fishermen and workers in many kinds of factories and engine-rooms.