Ibn al-Nafis (1210-1288) was an Arab physician who contributed much to the advancement of medical knowledge and science in the 13th century. He was involved in jurisprudence, politics, and anatomical studies as well. Although a prominent ophthalmologist by training, today he is most recognized for his discovery of the lesser or pulmonary circulation. His was the first work to contradict the accepted teachings of Galen, which had existed since the 2nd century AD. His description included the observation that the wall of the septum is not porous either grossly or macroscopically as was believed by earlier scholars. Therefore, blood from the venous circulation had to be directed through the pulmonary artery ("venous artery") through the lungs to be "mixed with air" and drained back to the left side of the heart through the pulmonary vein ("arterial vein"). This discovery would lead to a change in the historical observations that the pulmonary circulation was discovered by European scientists in the 16th century and lead many to wonder if these scientists had access to Ibn al-Nafis' translated works. Ibn al-Nafis was devout to his work and to his religion, contributing much to the body of knowledge in anatomy and medicine as well as being a prominent and exceptional physician.