Recto: four sections of the ventricles of the heart, with notes on the drawings; a diagram demonstrating the cardiac impulse, according to Galen's theory of ebb and flow. Verso: ten drawings of varying size of the heart, and details of semilunar valves; notes on the drawings. Mounted with RCIN 919074, the right side of this double sheet.

Leonardo’s last known anatomical campaign, his analysis of the heart, was perhaps the most brilliant of his many scientific investigations. A few years earlier he had satisfied himself that the heart (and not the liver) was the centre of the vascular system, and after 1511 he set about analysing the mechanics of the heart in a series of densely annotated sheets. Leonardo had little or no access to human material at this time, and his dissections were therefore of an ox’s heart.

The larger drawings on the verso of this double sheet show several views of the heart with the aorta and superior and inferior vena cava, which in the ox merge before they reach the atrium. The pulmonary trunk has been removed to reveal the open pulmonary valve, while the coronary arteries leave the base of the aorta and pass to either side of the pulmonary valve. At lower right are small diagrams of a three-cusped valve, both open and closed (labelled ‘apertaserrata’): Leonardo intuited that the valves were key to the functioning of the heart, and regarded them as a perfect example of mathematical necessity in the workings of nature. Despite his understanding of the valves, Leonardo never grasped the idea of circulation, instead adhering to the ancient theory of the flux and reflux of the blood between the two ventricles.

Text adapted from Leonardo da Vinci: A life in drawing, London, 2018