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 climate that could expand on his theory. In addition to the pulmonary circuit, Colombo also discovered that the main action of the heart was contraction, rather than dilation, as had previously been thought. Both of these discoveries were later confirmed by William Harvey. In addition, Colombo is credited with coining the term "
placenta" and in his work describes the placenta as a place where pure and perfect blood is stored for the baby before birth. He believes Galen misinterpreted the placenta when it comes to humans and challenges Galen’s views on the placenta because Galen only performed dissections on animals. Colombo argues that performing vivisections helps one to understand how the system works as a whole. At the time, his work in this anatomical area was revolutionary and provided the basis for the understanding of the placenta and other anatomical structures we have today. These detailed descriptions and critiques are in his book
De Re Anatomica Libri XV. Much cited is Columbo's naming and description of the clitoris as "Amor Veneris, vel Dulcedo Appelletur." He stated, "It should be called the love or sweetness of Venus." While Colombo was not the first to discover the clitoris, he is one of the first to propose its role in female sexual pleasure. This finding caused quite a stir amongst the general public as it was already thought that females had anatomy corresponding to their male counterparts; the addition of a bodily structure could cause women to be viewed as hermaphrodites. == Written works ==