Note 224 — PHARMACOLOGIA. ON THE OPERATIONS OF MEDICINAL BODIES, AND ON THE CLASSIFICATIONS FOUNDED ON THEM. (continued 2)

It is a very curious fact, that the Oil of Tobacco should differ so essentially in its physiological action from the Infusion of that vegetable poison; the former we have stated, affects the brain only, the latter we now learn, when taken into the alimentary canal, suspends the action of the heart. This apparent anomaly at first led Mr. Brodie, as he has since informed me, to suspect the accuracy of his experiments: and I suggested to him, whether a probable explanation might not be derived from the late chemical researches into the composition of tobacco, which have shewn the existence of two active principles, viz. Nicotin, and an Essential Oil? Where an infusion is employed, we seem to obtain the influence of the former, and the effects are displayed upon the heart; but where the oil is applied, the Nicotin has been removed, and the brain is the organ principally affected—see Tabaci Folia.