what did william harvey discover
Thus, Colomboâs system is a hybrid between closed (pulmonary) and open (systemic). (D) Harvey discovered that blood circulates not only in the lung, but also around the whole body. An important clue was the presence of valves in the veins (two of them are shown in white). The liver is no longer the source of veins. Rather, the system is driven by the mechanics of the heart (now shown in black).