Excerpts from Books and Wikipedia
"Unable to help one of his patients with a serious heart condition, he was suitably embarrassed when the patient obtained a herbal tea from a gypsy-woman and promptly recovered. Withering systematically tested each of the brew’s twenty-odd ingredients until he had isolated foxglove as the benefactor. The digitalis purpurea the plant produces increases the intensity of the heart muscle contractions while reducing the heart rate, and can also be used to treat dropsy. After extensive trials on animals and human patients, Withering published in 1785 An Account of the Foxglove and Some of its Medical Uses etc; With Practical Remarks on Dropsy and Other Diseases which advertised its curative properties to the world. It has been used ever since." [Blanning: Pursuit of Glory, p. 67]