It is therefore evident that before narcotic poisons can exert a general influence they must be carried into the circulation. Duprey and Brachet, two French physiologists, have sought to prove that animals cannot be destroyed by narcotic poisons, introduced in the stomach, if the _nervus vagus_ has been divided on both sides; at least, that they do not die so soon. However, Wernscheidt, in thirty experiments on mammalia, could not perceive this difference, provided the animals were of the same size and species. Prussic acid exerts its influence so rapidly that it cannot be supposed to have been thrown into the circulation. The spirituous solution of the extract of nux vomica introduced in the mouth of a rabbit, produces immediate death, whereas when applied to any nerve distant from the brain it produces no general symptoms. This rapid effect of prussic acid is supposed to arise from its great volatility and powers of expansion, by which it is diffused more quickly through the circulation than the blood. According to Schrader one drop of this substance introduced in the bill of a bird killed it in four or five minutes. Hydrocyanic acid gas mixed with atmospheric air has when inhaled destroyed dogs, cats, rabbits, and various birds, in from two to ten seconds. Magendie found that the introduction of one drop of the acid in the jugular vein caused instantaneous death; a glass tube dipped in this perilous substance applied to the tongue of a dog, produced a similar effect, which was also the result when applied to the eye. It is not generally known that tobacco and its preparations are deadly poisons, one drop of oil of tobacco introduced in the mouth of a dog produced violent convulsions with hurried breathing; a quarter of an hour after, the unfortunate animal seemed to be recovered, when the introduction of another drop killed it in two minutes. M'Cartney and Orfila obtained similar results, though no such effects were produced when it was applied to a nerve or the surface of the brain. The French poet Santeuil died from having drank wine in a glass containing some snuff. In all cases of death produced by this substance the lungs are found dense and livid. It is not only in the upas that the Indians seek the means of poisoning their missiles. In America they employ the _Ticronas_ a juice extracted from various plants, and the preparation of which, transmitted from one generation to another is considered a valuable secret. La Condamine asserts that its mere odour is sufficient to destroy the criminals doomed to smell it, but Fontana has found by many experiments that this assertion was made upon report, which travellers too frequently rely upon to save themselves the trouble of investigation. Arrows saturated with this poison, become more active after having been dipped in hot water.