During the Dark Ages following the fall of the Roman Empire, the Arabic world was instrumental in fostering the development of the sciences, including medicine. The quest for original manuscripts and their translation into Arabic reached its climax in the House of Wisdom in Baghdad, and the dissemination of the compiled texts was facilitated by the introduction of paper from the East. Foremost among the Arabic physicians were Rhazes, Avicenna, Haly Abbas and Albucasis, who lived during the period 950-1050 AD. Their writings not only followed Hippocrates and Galen, but also greatly extended the analytical approach of these earlier writers. The urine was studied and the function and diseases of the kidneys described. Despite the fact that experimentation on the human body was prohibited by religion, some anatomic dissection and observation seems to have been undertaken, and the pulmonary circulation was described by Ibn Nafis. Anatomic illustrations began to appear in Arabic texts, though they did not have the detail and artistic merit of those ofVesalius.