this new way of conceptualizing the body. The vivisection method enabled Colombo to study the operation of the voice, the motion of the lungs, the heart and the motion of the arteries, the dilation and contraction of the brain, variations of the pulse and other functions. With the centrality of vivisection, the three ‘rivers’ was also emphasized in Colombo’s book, specifically Book XI. “There are three fountain-heads, the liver, heart, and brain, from which are distributed throughout the body the three rivers of the natural blood, the vital blood and the animal spirits respectively. The view of the three rivers does not come from any known ancient source.” Although there were many important organs like the liver in the abdomen area and the heart, for Columbo, the supreme organ was the brain. Colombo described the organs in the form of hierarchy and because the brain was said to be the most noble of organ, it was ‘King of the principal members’ of the body. The supremacy of the brain was directly related to his view of the three rivers. “What is generated in the brain and distributed through the nerves, is what differentiates the live body from the dead one.” Among other reasons, the most important one for the brain being King of all organs, is the fact that the brain is the source of sense and motion. Contributions to anatomy Colombo made several important advances in anatomy, including the discovery of the pulmonary circuit which paved the way for William Harvey's discovery of circulation years later. In the Galenic tradition, blood passed between the ventricles of the heart through micropores in the heart's septum and venous blood became arterial blood in the left ventricle of the heart where air was supplied by the pulmonary vein. During vivisections of dogs and other animals, Colombo repeatedly found only blood, and no air, in the pulmonary vein. In his model, venous blood travelled from the heart to the lungs where it was mixed with air and then returned to the heart. The permeability of the septum was questioned by Michael Servetus in Christianismi Restitutio in 1553 and by Ibn al-Nafis in the 13th century and both proposed that the blood was pushed from the right ventricle to the left via the lungs, however, both of these accounts were largely forgotten. Colombo was the first to propose the pulmonary circuit in an intellectual