Between 400 and 1200 AD, Arab traders introduced opium to China, and to India by 700. The physician Muhammad ibn Zakariya al-Razi of Persian origin ("Rhazes", 845–930 AD) maintained a laboratory and school in Baghdad, and was a student and critic of Galen; he made use of opium in anesthesia and recommended its use for the treatment of melancholy in "Fi ma-la-yahdara al-tabib", "In the Absence of a Physician", a home medical manual directed toward ordinary citizens for self-treatment if a doctor was not available.