What discovery did Claudius Galen make that is still important today?

Claudius Galen, a prominent Greek physician in the Roman Empire, made significant contributions to anatomy and medicine, one of which was his discovery of the importance of the pulse in diagnosing health. He was among the first to systematically study the circulatory system and the relationship between the heart and blood flow. His work laid the foundation for understanding bodily functions and influenced medical education for centuries. Galen's emphasis on observation and experimentation continues to underpin modern medical practices today.