assuming, therefore, that nicotianin, from its feebler action and small amount, is not a very efficient principle in producing the narcotic effects of tobacco, and that the empyreumatic oil consists only of fatty matters holding the alkali in solution, we are forced to believe that the only constituent worthy of much attention, as the very soul and essence of the plant, is the organic base, nicotin, or nicotia. it is probable that the tobacco-chewer, by putting fifty grains of the solace, honey-dew, or cavendish into his mouth for the purpose of mastication, introduces at the same time from one to four grains of nicotin with it, according to the quality of the tobacco he uses. it is _not_ probable that anything like this amount is absorbed into the system. nature protects itself by salivation. it is possible, that, in smoking one hundred grains of tobacco, there _may_ be drawn into the mouth two grains or more of the same poison; for, as nicotin volatilizes at a temperature below that of burning tobacco, it is constantly present in the smoke. it is not probable that here, again, so much is absorbed. but we will return to this question of the relative effects of chewing, cigar- and pipe-smoking, and snuff-taking, presently. for we suppose that the anxious mother, if she has followed us so far, is by this time in considerable alarm at this wholesale poisoning. poisons are to be judged by their effects; for this is the only means we have of knowing them to be such. and if a poison is in common use, we must embrace all the results of such use in a perfect generalization before we can decide impartially. we do not hesitate to eat peaches, though we know they owe much of their peculiar flavor to prussic acid. it is but fair to apply an equally large generalization to tobacco. chemistry can concentrate the sapid and odorous elements of the peach and the bitter almond into a transparent fluid, of which the smell shall be vertiginous and the taste death. but chemistry is often misunderstood, in two ways: in the one case, by the incredulity of total ignorance; in the other, by the overcredulity of imperfect knowledge. that poor woman who murdered her husband by arsenic not long since was an instance of the first. she laughed to scorn the idea that the chemists could discover anything in the ejected contents of the stomach of her victim, which she voluntarily left in their way. she could not conceive that the scattered crystals of the fatal powder might be gathered into a metallic mirror, the first glance at which would reflect her guilt. they who gape, horror-struck, at the endless revelations of chemistry, without giving reason time to act, err in the second manner. led away by the brilliant hues and wonderful transformations of the laboratory, they forget the size of the world outside, in which these changes are enacted, and the quiet way in which nature works. the breath of chlorine is deadly, but we daily eat it in safety, wrapped in its poison-proof envelope of sodium, as common salt. carbonic acid is among the gases most hostile to man, but he drinks it in soda-water or champagne with impunity. so we cannot explain how a poison will act, if introduced into the body in the diluted form in which nature offers it, and there subjected to the complicated chemico-vital processes which constitute life. in the alembic of the chemist we may learn analysis, and from it infer, but not imitate, save in a few instances, the synthesis of nature. changes in the arrangement of atoms, without one particle altered that we can discover, may make all the difference between starch and sugar. by an obscure change, which we call fermentation, these may become alcohol, the great stimulant of the world. by subtracting one atom of water from its elements we change this to ether, the new-found _lethe_ of pain. as from the inexhaustible bottle of the magician, the chemist can furnish us from the same two elements air or aquafortis. we may be pardoned these familiar examples to prove that we must not judge of things by their palpable qualities, when concentrated or in the gross. that fiery demon, nitric acid, is hid, harmless in its imperceptible subdivision, in the dew on every flower. from all this we conclude that the evil effects of tobacco are to be determined by their proved _physiological_ effects; and also that we must aid our decision by a survey of its general asserted effects. in treating of these effects, we shall speak, first, of what is known; second, of what its opponents assert; and, third, of what we claim as the results of its use. what is absolutely known is very little. we see occasional instances of declining health; we learn that the sufferers smoke or chew, and we are very apt to ascribe all their maladies to tobacco. so far as we are aware, the most notorious organic lesion which has been supposed due to this practice is a peculiar form of cancer of the lip, where the pipe, and particularly the clay pipe, has pressed upon the part. but more ample statistics have disproved this theory. we have as yet become acquainted with no satisfactory series of experiments upon tobacco analogous to those which have been made of some articles of food. the opponents of tobacco, upon whom we consider the burden of proof to rest, in the absence of any marked ill effects palpable in so large a consumption of the herb, are thus reduced to generalities. tobacco is said to produce derangement of the digestion, and of the regular, steady action of the nervous system. these effects must be in a measure connected; but one distinct effect of tobacco is claimed, upon the secretions of the mouth, with which it comes into direct contact. it is said to cause a waste and a deterioration of the saliva. let us examine this first. the waste of saliva in young smokers and in immoderate chewers we admit. the amount secreted by a healthy man has been variously estimated at from one and a half to three pounds _per diem_. and it certainly seems as if the whole of this was to be found upon the vile floors of cars, hotels, and steamboats. the quantity secreted varies much with circumstances; but experiments prove the _quality_ to be not affected by the amount. to show how the deterioration of this fluid may affect digestion, we must inquire into its normal physiological constitution and uses. its uses are of two kinds: to moisten the food, and to convert starch into sugar. the larger glands fulfil the former; the smaller, mostly, the latter office. almost any substance held in the mouth provokes the flow of saliva by mechanical irritation. mental causes influence it; for the thought of food will make the mouth water, as well as its presence within the lips