This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Tobacco consists of the leaves of Nicotiana Tabacum, a well-known, annual plant, indigenous in tropical America, and cultivated in most civilized countries, but nowhere so extensively as in the United States. All parts of the plant have medicinal properties; but the leaves only are officinal. These are cut in August, dried under cover, and then tied in bundles, in Which condition they come into the market. By drying, they acquire an odour not before possessed, and are probably somewhat modified in other respects.
Dried tobacco leaves are yellowish-brown, of a peculiar strong narcotic odour, and a bitter, acrid, nauseating taste. They impart their virtues to water and alcohol. These virtues are destroyed or dissipated by long boiling; so that the extract is nearly inert.
There are two active principles in tobacco, nicotia and nicotianin, the former an organic volatile alkali, the latter a concrete volatile oil. it is the nicotia upon which the powers of the medicine mainly depend.
Nicotia was discovered by Vauquelin; but was first obtained quite pure by MM. Henry and Boutron. it exists in the leaves combined with an excess of some organic acid, and becomes fixed by this combination. in the process for procuring it employed by the chemists last mentioned, the native salt, as it exists in the leaves, is decomposed by means of soda, and the nicotia then separated by distillation. As the alkaloid comes over, it is received in sulphuric acid diluted with water, from which it is again separated, in a purer form, by the addition of soda, and another distillation. As thus obtained, it is still mixed with water and ammonia, the latter of which is separated along with it from the leaves. From these impurities it may be freed by placing it under the receiver of an air-pump, and exhausting the air.
It is a colourless or nearly colourless liquid, somewhat heavier than water; having little smell when cold, but of a strong peculiar odour and very irritant to the nostrils when heated; of an exceedingly acrid taste; entirely volatilizable; inflammable; soluble in water, alcohol, ether, and the fixed and volatile oils; of a strongly alkaline reaction, and capable of forming salts with the acids, most of which are crystallizable, and have the acrid taste of their base. When fuming muriatic acid is brought near it, white vapours are produced as with ammonia. it imparts a greasy stain to paper, which disappears upon the application of heat. it contains no oxygen, but an unusually large proportion of nitrogen; consisting of 2 equivalents of nitrogen, 20 of carbon, and 14 of hydrogen. Tobacco contains from two to about eight per cent. of it according to the quality. Nicotia is a powerful poison, and has been used effectually both for murder and suicide. Two or three drops of it will destroy life; and its effects in a large dose are very speedy. in a case which occurred a few years since in London, death is supposed to have taken place in from three to five minutes. (Guy's Hospital Reports, 1858, p. 352.) After death the blood has been found dark and liquid, and the lungs, liver, and stomach strongly congested.
Nicotianin is procured by distilling the leaves with water. it concretes upon the surface of the water distilled, in the form of a fatty matter. it is volatile, with the odour of tobacco smoke, and somewhat bitter. One grain of it occasions giddiness and nausea when swallowed; but the proportion contained in tobacco is too small to contribute materially to the effects of that medicine. The probability is, that it is developed in the drying of the leaves, and that it is the odorous principle of the drug.
Tobacco yields by destructive distillation an empyreumatic oil, which may be obtained colourless by rectification, but becomes brown by time, and, as usually found in the shops, is dark-brown or almost black, and of a thickish consistence. it has an acrid taste, and precisely the odour of old tobacco pipes. Two drops of it killed a dog. it is, therefore, very poisonous; but, according to the experiments of Brodie, it acts in a manner quite different from tobacco, and must consequently contain an energetic principle not pre-existing in the plant. it is said to contain nicotia.
Tobacco is locally excitant. Applied to the mucous membranes, or the denuded cutis, it produces more or less irritation. Thus, in the nostrils it occasions sneezing and increase of secretion, in the mouth an acrid taste, and copious flow of saliva, in the throat a peculiar sensation of acrimony and heat, in the stomach a feeling of warmth, and afterwards nausea and vomiting, and in the rectum often purging. its general action is that of a powerful sedative to the nervous system, and through that to the circulation. it often also operates as a diuretic. The effects produced by it upon the system are of the same character, to whatever surface it may be applied.
When so employed as to act moderately on the system, without nauseating, it produces an agreeable tranquillizing effect, with feelings of delicious languor and repose, which have rendered it a favourite article of luxury in all parts of the world. With this general nervous quietude, there is a slight peculiar impression on the brain, for which there is no adequate name, and which only they who have felt it can appreciate. Notwithstanding, however, this feeling of calmness and repose, there is in general no tendency to drowsiness; but, on the contrary, a disposition rather to wakefulness; and persons accustomed to the use of the drug, often resort to it as a means of overcoming heaviness, and facilitating the performance of intellectual tasks, requiring concentration of thought. From this effect, tobacco has been considered by some as stimulant to the brain. I am disposed to look upon the effect as the result of a slight sedative operation, which, quieting all the little nervous uneasinesses and consequent distractions to which most persons are liable, enables them to fix their attention upon the subject before them. it is quite different from the exhilaration and temporary invigoration of opium and alcohol; and, when augmented in degree, diverges still more from the effects of those cerebral stimulants, and is indeed in direct opposition to them. Hence, opium and alcohol are among the best counter-agents to the excessive influence of tobacco; which could not happen, if the latter were also stimulating to the brain.*