§ 334. Physiological Action.—Nicotine is absorbed into the blood and excreted unchanged, in part by the kidneys and in part by the saliva (Dragendorff). According to the researches of Rosenthal and Krocker,[361] nicotine acts energetically on the brain, at first exciting it, and then lessening its activity; the spinal marrow is similarly affected. The convulsions appear to have a cerebral origin; paralysis of the peripheral nerves follows later than that of the nerve centres, whilst muscular irritability is unaffected. The convulsions are not influenced by artificial respiration, and are therefore to be considered as due to the direct influence of the alkaloid on the nervous system. Nicotine has a striking influence on the respiration, first quickening, then slowing, and lastly arresting the respiratory movements: section of the vagus is without influence on this action. The cause of death is evidently due to the rapid benumbing and paralysis of the respiratory centre. Death never follows from heart-paralysis, although nicotine powerfully influences the heart’s action, small doses exciting the terminations of the vagus in the heart, and causing a slowing of the beats. Large doses paralyse both the controlling and exciting nerve-centres of the heart; the heart then beats fast, irregularly, and weakly. The blood-vessels are first narrowed, then dilated, and, as a consequence, the blood-pressure first rises, then falls. Nicotine has a special action on the intestines. As O. Nasse[362] has shown, there is a strong contraction of the whole tract, especially of the small intestine, the lumen of which may be, through a continuous tetanus, rendered very small. This is ascribed to the peripheral excitation of the intestinal nerves and the ganglia. The uterus is also excited to strong contraction by nicotine; the secretions of the bile and saliva are increased.
[361] Ueber die Wirkung des Nicotines auf den thierischen Organismus, Berlin, 1868.
[362] Beiträge zur Physiologie der Darmbewegung, Leipsic, 1866.
§ 335. Fatal Dose.—The fatal dose for dogs is from 1⁄2 to 2 drops; for rabbits, a quarter of a drop; for an adult not accustomed to tobacco the lethal dose is probably 6 mgrms.
§ 336. Post-mortem Appearances.—There seem to be no appearances so distinctive as to be justly ascribed to nicotine or tobacco-poisoning and no other.
A more or less fluid condition of the blood, and, generally, the signs of death by the lungs, are those most frequently found. In tobacco-poisoning, when the leaves themselves have been swallowed, there may be some inflammatory redness of the stomach and intestine.
§ 337. Separation of Nicotine from Organic Matters, &c.—The process for the isolation of nicotine is precisely that used for coniine (see [p. 269]). It appears that it is unaltered by putrefaction, and may be separated and recognised by appropriate means a long time after death. Orfila detected it in an animal two or three months after death; Melsens discovered the alkaloid unmistakably in the tongues of two dogs, which had been buried in a vessel filled with earth for seven years; and it has been found, by several experiments, in animals buried for shorter periods. Nicotine should always be looked for in the tongue and mucous membrane of the mouth, as well as in the usual viscera. The case may be much complicated if the person supposed to be poisoned should have been a smoker; for the defence would naturally be that there had been either excessive smoking or chewing, or even swallowing accidentally a quid of tobacco.[363] A ptomaine has been discovered similar to nicotine. Wolckenhaar separated also an alkaloid not unlike nicotine from the corpse of a woman addicted to intemperate habits; but this base was not poisonous, nor did it give any crystals when an ethereal solution was added to an ether solution of iodine. It will be well always to support the chemical evidence by tests on animal life, since the intensely poisonous action of nicotine seems not to be shared by the nicotine-like ptomaines.