R: The heart, bronchi and bronchial vessels

This is a view of the heart and the bronchi and bronchial vessels of the lungs. In the extensive notes Leonardo describes the ‘most minute’ branching of the bronchi, accompanied by veins and arteries ‘in continuous contact right to the ends.’ He refutes the traditional belief that air passes from the lungs directly into the heart, though he had no knowledge of gaseous exchange between the respirated air and the blood.

Leonardo’s last known anatomical campaign, an analysis of the heart, was perhaps the most brilliant of his many scientific investigations. After 1511 he had little or no access to human material, and his dissections were therefore of an ox’s heart, focussing on the arrangement of the vessels and the action of the valves.