Siddha medicine is a form of traditional medicine originating in southern India. It is one of the oldest systems of medicine in India. In rural India, siddhars have learned methods traditionally through master-disciple relationships to become local "healers". Siddhars are among an estimated 400,000 traditional healers practicing medicine in India, comprising some 57% of rural medical care. Siddha practitioners believe that five basic elements – earth, water, fire, air, sky – are in food, "humours" of the human body, and herbal, animal or inorganic chemical compounds, such as sulfur and mercury, used as therapies for treating diseases.