Vesalius was instrumental in revolutionizing anatomical knowledge through his meticulous dissections and detailed illustrations. He published "De Humani Corporis Fabrica" (On the Fabric of the Human Body) in 1543, which challenged the prevailing Galenic theories and provided a more accurate understanding of human anatomy.
However, Vesalius's work focused on the structure of the heart and vessels, not their function. While he described the intricate network of blood vessels, he didn't understand the mechanism of how blood moved through the body. He still adhered to the Galenic idea of the heart being the center of the body where blood was produced and consumed.
It was Harvey who, through careful experimentation and observation, established the concept of blood circulation. He demonstrated that the blood circulated in a continuous loop, pumped by the heart and flowing through arteries, veins, and capillaries.
Therefore, while Vesalius's anatomical work laid the foundation for understanding the circulatory system, it was William Harvey's groundbreaking discoveries that finally revealed the true nature of blood circulation.