How did vesalius and narvey disprove many of galens theories?

Andreas Vesalius and William Harvey significantly advanced the understanding of human anatomy and physiology, challenging Galen's long-held theories. Vesalius conducted meticulous dissections and detailed observations, revealing that many of Galen's anatomical descriptions were based on animal studies rather than human anatomy. Harvey, through his experiments, demonstrated the circulation of blood, disproving Galen's ideas about blood movement and the role of the liver. Together, their empirical approaches laid the foundation for modern anatomy and physiology, emphasizing observation over tradition.