Galen of Pergamon was a Greek physician whose ideas dominated medical thinking in Europe for over 1,000 years. His theories about the body, health, and disease heavily influenced medieval medicine.

Key events in Galen's influence:

• 129 AD: Galen is born in Pergamon (modern-day Turkey).
• 150 AD: Galen begins practicing medicine in Rome.
• Late 2nd century: Galen writes many influential works on anatomy, physiology, and medicine.
• 4th century: Galen's texts are translated into Latin and become the foundation of medical education.
• Medieval Period: Galen's ideas are accepted as scientific truths, shaping medical practice.
• 14th-15th centuries: Galen's theories are challenged by new ideas during the Renaissance.

Galen's key ideas:

• The theory of the four humours: blood, phlegm, black bile, and yellow bile.
• The belief that the body was made up of three parts—brain, heart, and liver.
• The importance of balancing the humours to maintain health.

Source: Excerpts from Galen's writings and medieval medical texts.