THE

HEART

AND ITS

Anatomical Constitution

THE ANATOMY OF LEONARDO DA VINCI

THE ORGANS OF RESPIRATION AND THE HEART

Observations on the Movement of the Air

The windpipe original: "aspre arteria" or trachea does not change its position during the act of breathing, but rather it is the lung that expands and contracts against the ribs of the chest. Note how the ribs must expand to allow for the fullness of the breath.

It is observed that the heart is a muscle of great strength, much more powerful than the other muscles. The heat of the heart is generated by the rapid motion of the blood. I have found that the heart is not the source of the nerves, as many have previously claimed, but rather it is a vessel made of dense muscle, nourished by arteries and veins like other muscles.

On the Valves of the Heart

Part of the Heart	Function	Observation
Right Ventricle	Receives blood from the liver	Thick-walled and robust
Left Ventricle	Contains the vital spirit Leonardo refers here to the oxygenated blood, which ancient medicine termed "vital spirits."	Thinner than the right
The Valves	To prevent the reflux of blood	They close with marvelous precision

The percussion of the blood against the walls of the heart creates a sound that can be felt. This is the pulse of life itself. When the heart contracts, it expels the blood into the large artery The aorta, and this movement is what gives life to the entire body.

Compare this to the flow of water in a riverbed.

One must consider how the diaphragm The muscular partition separating the chest from the abdomen...