Harvesting cinchona bark. Historical illustration showing men harvesting cinchona bark from cinchona trees (Cinchona sp.) The bark of these trees contains high levels of quinine, a strong anti- malarial drug. Cinchona bark was the first source of this drug. During harvesting, the outer bark is removed, exposing the inner bark. After being cleaned, the inner bark is stripped from the tree with a knife (lower left), stacked (bottom left corner) and dried in the sun. The cinchona tree is native to South America. From The Family Physician, published by Cassell and Co., London, England.