What did Claudius Galen discover?

Answer 1

Galen was and is considered the authority on ancient medicine. He wrote a book on it that has come down to us pretty much intact. However his greatest discovery was with nerve experiments, which proved that the brain controls the movements of the body by means of the cranial nervous system. This theory is still believed today.

Answer 2

He concluded that differences in human moods come as a consequence of imbalances in one of the four bodily fluids: blood, yellow bile, black bile, and phlegm.