Ibn al-Nafis: The Secret of Blood Circulation

Shariq Ali
Valueversity

In a small study chamber of a madrasa in Damascus, a young physician was deeply absorbed in reading an ancient medical text. The book belonged to the great Greek physician Galen, whose ideas had been regarded as the final truth in medicine for centuries. Yet the young physician’s forehead was marked with lines of doubt.
He thought to himself:
“It cannot be possible that blood passes directly from one side of the heart to the other. If that were so, why would the heart have separate chambers? There must be some pathway in between.”

This young physician was Ibn al-Nafis, a scholar who would eventually challenge a centuries-old misconception about the human body.

Ibn al-Nafis was born in Damascus in 1213. He studied medicine at the famous medical institution Bimaristan al-Nuri. Later he moved to Egypt, where he worked as a physician and teacher at the great Al-Mansuri Hospital in Cairo. It was during this period that he began his deep investigations into the human body.

According to the prevailing medical theory of the time, blood moved directly from the right side of the heart to the left side through invisible pores. Ibn al-Nafis rejected this idea and proposed a new explanation.
He wrote that blood first travels from the right side of the heart to the lungs, where it interacts with air and becomes purified. It then returns from the lungs to the left side of the heart. Today we call this crucial part of blood circulation pulmonary circulation.

This idea was astonishing for its time because it challenged the authority of Galen, whose teachings had dominated medicine for over a thousand years.

Interestingly, in Europe a similar concept gained widespread recognition nearly three hundred years later, after the work of William Harvey.

Ibn al-Nafis was not only a physician but also a thinker and prolific writer. He authored numerous works on medicine, philosophy, and science. Yet his greatest legacy remains his discovery of a new and vital pathway of blood within the human body.

Sometimes in the history of knowledge, a single critical question in the mind of a scholar can overturn beliefs that have stood for centuries.
Ibn al-Nafis’s question was one such moment.