LEONARDO DA VINCI

ANATOMICAL STUDIES

THE THORAX AND THE ABDOMEN

The Mechanism of the Heart and Lungs

The heart is a muscle of great strength, much more powerful than the other muscles. Leonardo was among the first to correctly identify the heart as a muscle rather than a heat-generating organ. I ask whether the heart, at its death, changes its capacity or not; and if it is found to be of greater capacity or less than when it was alive.

The movement of the lungs

The lungs are always full of air, even when they have expelled it. This refers to "residual volume," the air that remains in the lungs after a forceful exhale to prevent the collapse of the air sacs. When the lung is expanded, it touches the ribs; and when it is contracted, it is separated from them.

Note: examine the valves of the heart in a dead ox.

The spirit original: "spirito" - in this context, Leonardo refers to the vital force or pressurized air believed to move through the body. passes from the heart to the lungs through the artery-like vein original: "vena arteriale" - the pulmonary artery., and it is not possible for it to return, because the valves are so arranged that they close when the spirit tries to go back.

The diaphragm is a thick, muscular membrane that separates the vital organs The heart and lungs from the natural organs The digestive system.

When the diaphragm contracts, it flattens and allows the lungs to fill with air. This is the cause of breathing.

The nerves of the neck? descend to the diaphragm and control its movement. If these nerves are severed, the breathing stops immediately and the man dies. Leonardo is likely referring to the phrenic nerve.