Edward Stone (natural philosopher) piece of bark from a willow tree and was struck by its extremely bitter taste. Knowing that the bark of the Peruvian cinchona tree − from which quinine (used in the treatment of malarial fevers) is derived − has a similarly bitter taste, he surmised that the willow might also have therapeutic properties. Stone's interest in willows was due to the ancient "doctrine of signatures" – whereby the cause of a disease offers a clue to its treatment. According to Stone: "As this tree delights in a moist or wet soil, where agues chiefly abound, the general maxim that many
Jesuit's bark of the long list of brochures defending its use and the only independent article on this bark which has been issued by a Jesuit. The two Genoese, Girolamo Bardi, a priest, and Sebastiano Baldo, a physician, who were among the pioneer advocates of the plant, were intimate with the cardinal, and Baldo prefixed to his principal work a letter from de Lugo, dated 1659, on cinchona, which shows that the cardinal even when seventy-seven years old was still active in its behalf. Circumstances created a suitable opportunity for disseminating the bark from Rome throughout Europe by means of the Jesuits.