The Four Humours was a theory in medieval medicine that suggested health depended on the balance of four bodily fluids: blood, phlegm, yellow bile, and black bile. Each humour was associated with specific qualities and parts of the body. This belief was based on ancient Greek ideas, especially those of Hippocrates, and was widely accepted during the Middle Ages.

Source A: Excerpt from Hippocrates' writings

'Health is maintained when the four humours are in proper balance; disease occurs when there is an imbalance.' Provenance: Ancient Greek medical texts, 4th century BCE.

Medieval practitioners used various methods to treat imbalances, including bloodletting, purging, and special diets. These methods aimed to restore the balance of humours and cure illnesses.

Source B: Medieval medical manual

'When the blood is too hot and thick, bleed the patient to remove excess; when phlegm dominates, purge the excess to restore harmony.' Provenance: A medieval medical textbook, 14th century.

By the 17th century, advances in science and anatomy led to the decline of the Four Humours theory. Physicians began to understand the body in new ways, focusing on germs, blood circulation, and organs.

Source C: Excerpt from a Renaissance medical text

'The humours no longer explain the mysteries of health; new discoveries reveal the importance of anatomy and the circulatory system.' Provenance: Renaissance medical writings, 16th century.