The aortic valve

Recto: notes on the valves of the heart and the flow of blood within it, with illustrative drawings; a drawing of a mould for the making of a glass model of the pulmonary or aortic valves. Leonardo’s analysis of the heart was the most brilliant of his many scientific investigations. Working with the hearts of oxen, he studied the arrangement of the vessels and the action of the valves in a series of densely annotated sheets. Here Leonardo records a remarkable experiment in which he utilized his technical knowledge as a sculptor to understand the flow of blood through the valves. He poured molten wax into the cavities around the aortic valve, and from the wax cast he made ‘a mould of gypsum for blowing thin glass inside’ – seen in cross-section at top right. Leonardo then pumped water mixed with grass seeds through his glass model, observing turbulent vortices in the widening (sinus) beyond the valve (drawn schematically at centre right), and correctly concluded that these vortices help to close the valve when blood flow ceases after each beat of the heart. Text adapted from Leonardo da Vinci: A life in drawing, London, 2018