Ever wonder why people put leeches on their skin in the Middle Ages?

Medieval bloodletting was all about healing via balancing the four bodily humors: blood, phlegm, yellow bile, and black bile.

This is everything you need to know about medieval bloodletting and the four humors. 🧵 Galen, Aristotle and Avicenna were great contributors to the corpus of the medieval understanding of humoral theory.

The concept of humors originated in ancient Greek medicine, as they were even mentioned by Hippocratic treatises, and were defined as “specific bodily fluids essential to the physiological functioning of the organism”.

A book called De Natura Hominis (“On the Nature of Man”) by the 4th-century Christian philosopher Nemesius was what presented the standard set of four humors.