Pyridine is found in nature as one of the principles of tobacco-juice, and is imitated in chemistry, and derived from chinolin. It is a volatile liquid with strong aromatic odor. It gives off, at ordinary temperatures, a vapor which is used medicinally, having a stimulant effect on the respirations and on the spinal cord. On the heart it has an influence resembling that of digitalis, increasing the strength of the systole.

Average dose,  v.- 0 3 Gm.