Firstly describe the pulmonary circulation, coronary circulation, and capillary circulation with true anatomy of the heart which form the basis of the circulatory system. He wrote: “The lungs are composed of parts, one of which is the bronchi, the second the branches of the arteria venosa and the third the branches of the vena arteriosa, all of them connected by loose porous flesh. The blood from the right chamber of the heart must enter the left chamber, but there is no direct pathway between them.
The thick septum of the heart is not perforated and does not have visible openings as some people thought or invisible pores as Galen thought. The blood from the right chamber must flow through the vena arteriosa (pulmonary artery) to the lungs, spread through its substance, be mingled with air, pass through the arteria venosa (pulmonary vein) to reach the left chamber of the heart Arteries and the heart do not expand and contract at the same time, but rather the one contracts while the other expands” and vice versa.
He also recognized that the purpose of the pulse is to help disperse the blood from the heart to the rest of the body. He completely rejected the Galenic theory of pulsation after his discovery of the pulmonary circulation. Furthermore, he developed his own Nevisian theory of pulsation after discovering that pulsation is a result of both natural and forced motions, and that the “Forced motion must be the contraction of the arteries caused by the expansion of the heart, and the natural motion must be the expansion of the arteries.
The primary purpose of the expansion and contraction of the heart is to absorb the cool air and expel the wastes of the spirit and the warm air; however, the ventricle of the heart is wide. Moreover, when it expands it is not possible for it to absorb air until it is full, for that would then ruin the temperament of the spirit, its substance and texture, as well as the temperament of the heart. Thus, the heart is necessarily forced to complete its fill by absorbing the spirit
