After draining the fresh blood in the great vessels of the chest, Harvey
found himself face-to-face with the dead man’s heart and lungs. When an
anatomist encounters a heart, the most prominent artery that immediately
arises out of the topmost part of the heart is the pulmonary artery, the large
diameter vessel that transmits oxygen-poor blood from the right side of
the heart to the lungs [see picture in image section]. Harvey took a piece
of string, and wrapping it around the pulmonary artery, ligated it tightly,
preventing the flow of fluid. Carefully cutting open the right ventricle,
Harvey next inserted a metal tube into the heart chamber and tried
injecting water into it. With the pulmonary artery tied shut, there was no
way for the water to pass through it, and even more important, water did
not pass across the thick-walled septum that separates the right and left
ventricles. Opening the left ventricle, Harvey observed not a single drop of
fluid, and stated, “By my troth, there are no pores.”^7 Galen was wrong.
Releasing the ligature from around the pulmonary artery, Harvey again
injected water into the right ventricle, and within seconds, water poured
into the left ventricle. This blood-tinged fluid had obviously passed from
the right side of the heart, through the lung tissue, and then returned to the
heart in the pulmonary veins and into the left side of the heart. In an
instant, he knew that Colombo had been correct in asserting that the heart
pumped blood to the lungs, and that the blood returned back to the heart
vivified and scarlet.
William Harvey had convinced himself of the interrelationship of the
heart and lungs, but he remained confused about the action of the heart.
Should he continue to doubt Galen (true sacrilege among physicians), or
believe that the heart, like all organs, swells and draws blood to itself?
After dissecting the hanged man, Harvey returned again to his marine
fauna, some of which had translucent skin that allowed him to peer at their
tiny beating hearts. The germinating skepticism about a heart that flexes
open to siphon blood to itself was growing into an ironclad incredulity the
more he dissected small living things.
Harvey sliced open the chest cavity of a fish, and observed the
minuscule heart rapidly pulsating, even witnessing the flow across the
transparent aorta. Placing his finger on the heart, he could feel it
contracting, further convincing himself that the heart was more like a
muscle and unlike a bellows that opens to suck air (or blood) into itself.
Experimenting on an eel, Harvey carved open the fish’s chest and cut out