Jesuits bark, also known as Peruvian bark or cinchona bark, is a natural medicine that has been used for centuries to treat fevers and other illnesses. The substance contains quinine, which is used to treat malaria. However, there are other words that can be used to refer to Jesuits bark. For instance, it is sometimes called calisaya bark, which refers to a specific species of the plant. It is also sometimes called Jesuit powder, as the Jesuits were known for distributing the bark to treat disease. Other synonyms for Jesuits bark include quina-quina, cinchona, and fever tree bark. Regardless of what it is called, Jesuits bark remains an important medicine that has saved countless lives over the years.