The commercial dried leaves of Nicotiana Tabacum (nat. ord. Solanaceae).

Habitat

Tropical America; cultivated.

Characters

Up to 50 cm. long, oval or ovate-lanceolate, acute, entire, brown, friable, glandular-hairy, of a heavy, peculiar odor, and a nauseous, bitter, and acrid taste.

Composition

The chief constituent is - (1) Nicotine, C10H14N2(0.7 to 5, sometimes 11 per cent.). A colorless, volatile, oily alkaloid, smelling and tasting like Tobacco leaves, darkening with age.

Solubility

Soluble in water, more so in Alcohol and Ether. Turkish Tobacco contains hardly any. (2) Nicotianine. (3) Salts and flavoring agents.

Nicotine is decomposed by heat, consequently Tobacco smoke contains none (Binz), but consists of small quantities of various Pyridine compounds, as Pyridine C5H5N, Picoline C6H7N, Lutidine C7H9N, Collidine C8H11N, Parvoline C9H13N, Coridine C10H15N, Rubidine C11H17N, and small amounts of Hydrocyanic and Acetic Acids, Creosote, Sulphur, and Carbon compounds.

Action Of Tobacco

Tobacco leaves, when taken internally, act entirely by virtue of their nicotine, which is one of the most powerful and rapid poisons known.

External

Nicotine is an antiseptic.

Internal

Gastro-intestinal tract. - Nicotine in even minute doses (1/7 gr. .009 gm.) promptly produces greatly increased salivary flow, burning pain in the mouth, oesophagus and stomach, horrible nausea, quickly succeeded - owing to its action on the gastro-intestinal muscle - by vomiting and free purging. The marked characteristic of this gastro-intestinal irritation is the extreme collapse which accompanies it. Thus there is a rapid, very feeble pulse, intense muscular weakness, labored respiration, partial loss of consciousness, occasional convulsions, icy extremities, and profound general collapse. A dose of nicotine has been known to kill in three minutes, but in both man and animals a certain tolerance may be acquired.

Circulation. - Nicotine disintegrates the red blood-corpuscles of freshly-drawn blood, but has not this effect upon living blood, although the spectrum of haemoglobin is altered, so that the corpuscles must be in some way affected. The action on the heart is obscure; the muscle itself is unaffected, but the rapid-running, feeble pulse shows that some part of the cardiac apparatus is powerfully influenced. The blood-pressure falls rapidly; this is not entirely due to the action of nicotine on the heart, but is in part due to its peripheral action on the vessels.

Respiration. - This is at first accelerated and deepened; ultimately it is paralyzed from depression of the centre. Death is partly due to asphyxia.

Nervous system. - The higher faculties are depressed by large doses of nicotine, for those poisoned by it become comatose within even a minute or two of taking a large dose. The convulsions occasionally observed in man, and always in the frog, are due to spinal stimulation. All observers are agreed that ultimately the function of the motor nerves is entirely abolished. This explains the intense muscular weakness. Probably the sensory nerves, and certainly the muscles, escape.

Eye. - A toxic dose taken internally, or the local application of nicotine to the eye, contracts the pupil of man and most animals. This will occur in excised eyes, and is therefore a local effect. With some animals nicotine is a mydriatic. We know nothing of the details of its action.

Secretion. - Nicotine first stimulates but ultimately paralyzes the secretory structures of the salivary, sweat and lachrymal glands.

Elimination. - Nicotine is eliminated partly by the lungs, but chiefly in the urine, the secretion of which it increases.

Therapeutics Of Tobacco

Tobacco is never used therapeutically. In non-smokers it is useful to relieve the symptom asthma. Formerly it was employed in the form of an enema of leaves to relax muscular spasm, so as to facilitate the reduction of dislocations. This enema was also sometimes given as a purgative. Pyridine which is found in tobacco, but commercially is obtained from other sources, when administered by inhalation will frequently relieve the paroxysms of asthma. For this purpose a fluid drachm; 4. c.c, is necessary, placed in a dish, so that it may slowly evaporate. Its persistent and abominable odor is a great obstacle to its use.

Tobacco smoking, in those who are unaccustomed to it, produces, to a greater or less degree, the symptoms of gastro-intestinal irritation and collapse just mentioned. Even in those who are used to it the smoke may produce catarrh of the pharynx. Some persons find smoking after breakfast assists the daily action of the bowels. With many people it has an obscure effect, especially among those who lead sedentary lives, in stimulating the brain and producing a peaceable, calm state of mind. Overindulgence in it may lead to loss of appetite, irregularity of the heart, chronic laryngeal and pharyngeal catarrh, and retrobulbar neuritis of the optic nerve. The effect of this is that the sufferer complains that objects look misty, he has a central scotoma, sometimes complete, often only for red and green, and finally atrophy of his optic nerve.

Toxicology

Symptoms

The symptoms are those which we should expect from its physiological action.

Treatment

Tannic acid followed by emetics (see p. 139). Strychnine is the true physiological antidote. Alcohol and ammonia stimulate the heart. The recumbent position must be maintained. Artificial respiration may be necessary.

B. The following depresses the motor end-plates.