Notes and Drawings on the Thorax and Abdomen

The valve of the left ventricle the lower chamber of the heart is three in number?, which have a circular? base? around the circumference? of the aorta the main artery of the body, and their tips join together in the center? of said aorta. These close by the backflow? original: "refresso" of the blood, which, after it is pushed? from the ventricle into the artery, would—by its own weight—tend to return into the ventricle. But the percussion? the physical impact or pressure that it makes between these three valves forces them to join? together and shut the way against the aforementioned blood.

Text adjacent to the diagram on the left
Here one sees how the percussion? of the blood opens and closes the valves with its circular? motion? Leonardo correctly intuited the vortex-like movement of blood in the heart. It is also seen how the blood? divides? into three parts to go and fill? the three sinuses? the pockets behind the valve leaflets of the aforementioned valves.

The letter 'A' identifies the main cross-section of the aortic valve assembly in the diagram.

Text block below the diagram
Each of these three valves has in itself a dual? office? function or duty: one is to yield? to the furious? push of the blood exiting the ventricle, the other is to resist? the weight? of the same blood when it would turn? backward?. It is seen by experience? Leonardo's term for empirical observation or experiment that if such valves were? not of such form? and substance?, the heart could not send? the blood through the arteries with that fury? which is necessary? to nourish? the remote? limbs?.