Not all of Hippocrates’ ideas were accurate.
Hippocrates believed that illness occurred when body fluids were out of balance.
These fluids were called humors and included blood, phlegm, yellow bile, and black bile.
The humors occurred when the four main elements of Greek thought: fire, air, earth, and water, mixed with dryness, dampness, heat, and cold.
So, overheating the brain with too much bile resulted in fear and the face would flush.
Anxiety would result if the brain was overcooled with too much phlegm.
This theory led to the practice of bloodletting, where blood was drained from the body of a sick person so that disease would flow out with the blood.
Hippocrates correctly made the connection between the brain and emotions, but the idea of humors was disproved centuries later when human anatomy was studied more closely.