Before  publication of Withering's book digitalis was a widely used folk remedy, occasionally mentioned in the literature. Withering established the correct dosages, and the action of digitalis in edema and on the heart became generally recognized. Withering did not know of the distinction between renal and cardiac edema. Digital facsimile from the Internet Archive at this link The copy reproduced does not appear to contain the engraving of the purple foxglove.