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Some substances would seem to direct their powers to various parts of the alimentary canal; and the appearance so produced might be mistaken for the effects of the local action of the poison, had they not been clearly proved by experiment to have arisen from an application addressed through the medium of the circulation; thus is inflammation of the primæ viæ induced by the contact of Arsenic with an external surface of the body!

The Third Class of my arrangement includes those poisons which enter the circulation, and, through that medium, expend their influence upon the spinal marrow, without directly involving the functions of the brain. M. Majendie, in the year 1809, submitted to the first class of the French Institute a series of experiments which had conducted him to the extraordinary result above stated. He found that an entire class of vegetables (the bitter Strychnus) possesses this singular property.

The Fourth Class comprehends all those substances which destroy life by a local action upon the alimentary canal, not by any impression upon their nerves, but by simply inducing a fatal lesion in the membranes.