engine, and then, having opened the valves, desert his post, and let the monster go thundering down the track to sure destruction. Certain persons are thrown into the stage of mental weakness by a single glass of liquor. How can they be excused when the fact of their peculiar liability lends additional force to the argument of abstemiousness, and they know that their only safety lies in total abstinence?--CARPENTER'S _Physiology._] 2. TOBACCO. The Constituents of Tobacco Smoke are numerous, but the prominent ones are carbonic-acid, carbonic-oxide, and ammonia gases; carbon, or soot; and nicotine. The proportion of these substances varies with different kinds of tobacco, the pipe used, and the rapidity of the combustion. Carbonic acid tends to produce sleepiness and headache. Carbonic oxide, in addition, causes a tremulous movement of the muscles, and so of the heart. Ammonia bites the tongue of the smoker, excites the salivary glands, and causes dryness of the mouth and throat. Nicotine is a powerful poison. The amount contained in one or two strong cigars, if thrown directly into the blood, would cause death. Nicotine itself is complex, yielding a volatile substance that gives the odor to the breath and clothing; and also a bitter extract which produces the sickening taste of an old pipe. In smoking, some of the nicotine is decomposed, forming pyridine, picoline, and other poisonous alkaloids. [Footnote: The analysis of tobacco as given by different authorities varies greatly. The one stated in the text suffices for the purposes of this chapter. Von Eulenberg names several other products of the combustion. One hundred pounds of the dry leaf may yield as high as seven pounds of nicotine. Havana tobacco contains about two per cent, and Virginia about six per cent.--See JOHNSTON & CHURCH'S _Chemistry of Common Life_, and MILLER'S _Organic Chemistry_.] PHYSIOLOGICAL EFFECTS.--The poison of tobacco, set free by the process either of chewing or smoking, when for the first time it is swept through the system by the blood, powerfully affects the body. Nausea is felt, and the stomach seeks to throw off the offending substance. The brain is inflamed, and headache follows. The motor nerves becoming irritated, giddiness ensues. Thus Nature earnestly protests against the formation of this habit. But, after repeated trials, the system adjusts itself to the new conditions. A "tolerance" of the poison is finally established, and smoking causes none of the former symptoms. Such powerful substances can not, however, be constantly inhaled without producing marked changes. The three great eliminating organs--the lungs, the skin, and the kidneys-- throw off a large part of the products, but much remains in the system. When the presence of the poison is constant, and especially when the smoking or chewing is excessive, the disturbance that at first is merely functional, must necessarily, in many cases at least, lead to a chronic derangement.