There are several species of aconite, all of which are poisonous. The _monkshood_ is a well known plant, met with in our gardens, and when swallowed in any quantity will produce the symptoms, characteristic of vegetable poisons. All the parts of aconite, in the fresh state, when chewed, produce a sense of heat, and shortly afterwards a sensation of numbness in the lips and gums, which does not subside for several hours. In ancient authors, we frequently meet with _aconite_ as a poison, but it has been fairly questioned whether any particular plant was designated by the term[412]; like that of _cicuta_, it seems to have been a word expressive of poisons generally. The most powerful form in which this vegetable poison exists is in that of extract, or inspissated juice[413], and, if prepared according to the improved process of _Mr. Barry_,[414] it will prove highly dangerous in small doses. _M. Orfila_ relates several fatal accidents from the ingestion of this plant; his experiments have also shewn that it will produce its effects by an external application. We agree, however, with _Mr. Brodie_ in considering that it acts, without being absorbed, on the brain, through the medium of the nerves; and we have accordingly placed it in the first division of our classification. The plants already enumerated are sufficient to illustrate the symptoms and physiological action of the acrid poisons of the vegetable kingdom. We shall, therefore, conclude the history of this class with some account of the _nitrate of potass_, which has been ranked both by _Fodéré_ and _Orfila_ under this division of their classification. NITRE. _Nitrate of Potass._ The sensible qualities of this salt are too well known to require any description. It generally occurs crystallized in six-sided prisms, terminated by dihedral summits. It is composed of one proportional of nitric acid, and one proportional of potass. It dissolves in seven parts of water at 60°, and in its own weight at 212° _Fah._ Its solution is attended with a great reduction of temperature. It is permanent in the air, melts when exposed to a moderate heat; and, when cast into moulds, constitutes what is known in commerce by the name of _sal prunelle_. When mixed with inflammable matter it undergoes, in a strong heat, a rapid species of combustion, which, in chemical language, is termed _deflagration_. Concentrated sulphuric acid, when poured upon this salt in powder, decomposes it at the ordinary temperature, and disengages vapours of nitric acid, which are white, and not very abundant. _Symptoms of poisoning by Nitre._ This salt, when taken in a large dose, acts violently on the stomach and bowels, and occasions syncope and death. There are several cases recorded of its having been taken by mistake for _Glauber’s salt_.