In 1790, while translating A Treatise on Materia Medica by Dr. William Cullen, Hahnemann came across a passage about Peruvian bark, or cinchona, which was to change his life as well as the lives of many people throughout the world. In his book, Cullen stated that quinine, which is a substance purified from the bark of the cinchona tree, was a good treatment for malaria because of its astringent qualities. This made no sense to Hahnemann who, as a chemist, was aware that there were other much more powerful astringents which had no effect on malaria whatsoever. He decided to investigate further. For several days he dosed himself with quinine and recorded his reactions in great detail. To his astonishment, he began to develop the symptoms of malaria one after another, despite the fact that he did not actually have the disease. The symptoms recurred every time he took a dose of quinine, and lasted for several hours. If he did not take any quinine, he had no symptoms. Was this, he wondered, why malaria was also cured by quinine? To test out his theory, he repeated the doses of quinine, which he called “provings”, on people he knew well, again noting the reactions in great detail. He then went on to repeat the process with other substances that were in use as medicines, such as arsenic and belladonna. These provings were carried out under strict conditions and the provers were not allowed to eat or drink anything that might confuse the results, such as alcohol, tea and coffee, and salty or spicy foods.