Galen

Galen (Galenus) was a Greek physician, researcher and writer born in Pergamum (now Bergama, Turkey) in the second century CE. He spent much of his career in Rome, treating wealthy patients including emperors. His writings addressed human anatomy, bodily functions, medicines, and logic (the philosophy of reasoning).

Galen built his medical theory on the concept of 'humours' (dheecaan) inherited from the Hippocratic tradition: blood, phlegm, black bile and yellow bile. As he explained it, health depended on the balance of these humours, and disease arose when that balance was disrupted. This framework underpinned treatments including bloodletting, dietary regulation and compound medicines.

Anatomical Research

Galen conducted systematic dissections of animals—chiefly monkeys and pigs—because human dissection was forbidden in Rome at that time. Working from these experiments, he demonstrated that arteries carry blood (not air as previously thought) and that the spinal cord controls movement of the limbs below it. He also investigated the role of the kidneys in urine production. However, he applied his animal findings directly to human anatomy without qualification, an error that persisted for centuries.

Theory of Bodily Functions

Galen explained that food is transformed into blood in the liver, then distributed through the vessels, and utilized by the organs. He described different types of 'spirits' (pneuma) operating in the liver, heart and brain. His model of blood circulation was not a closed system; not until the 17th century did William Harvey demonstrate the true circulation of blood, which fundamentally revised much of Galenic theory.

Long-term Influence

Galen's writings were numerous and were translated into Syriac and Arabic during the medieval period. Scholars including Hunayn ibn Ishaq translated substantial portions, and Ibn Sina and others built upon them. In Europe, his texts were foundational to medical education in universities until the 16th century. Andreas Vesalius (1543) demonstrated through human dissection some of Galen's errors, initiating a divergence between Galenic tradition and modern anatomical science.