Ibn al-Nafis: The Muslim Doctor Who Discovered Blood Circulation 300 Years Before Harvey

In medical textbooks across the world, William Harvey (1628 CE) is credited with discovering blood circulation. But Harvey himself was building on anatomical knowledge that a 13th century Syrian Muslim physician had already correctly described — 300 years earlier.

Ala al-Din Abu al-Hasan Ali ibn Abi Hazm al-Qarshi al-Dimashqi — universally known as Ibn al-Nafis (1213–1288 CE) — correctly described pulmonary (lung) blood circulation in his 1242 CE commentary on Ibn Sina's Canon of Medicine. He also proposed the existence of coronary circulation — the blood supply to the heart muscle itself.

Both of these discoveries were ignored by European science for three centuries. When they were finally rediscovered in the 16th century (via a partial Latin translation), Harvey completed the work — but the credit has historically gone almost entirely to Harvey.

1. The Error Ibn al-Nafis Corrected: Galen's 1,000-Year Mistake

For over 1,000 years, the dominant anatomical theory — established by Galen (129–216 CE) — held that:

1. Blood was produced in the liver from food
2. Blood traveled through the right side of the heart
3. Some blood crossed through invisible pores in the septum (the wall between heart chambers) to the left side
4. The lungs merely cooled the heart — they had no circulatory role

This was fundamentally wrong on every point. There are no pores in the cardiac septum. Blood does not originate in the liver. The lungs are not a cooling system.

No one — Greek, Arab, Persian, or European — had challenged this model successfully for 1,000 years. Until Ibn al-Nafis.

Ibn al-Nafis proved that blood travels from the right ventricle through the pulmonary artery to the lungs for aeration before entering the left ventricle.

2. Ibn al-Nafis's Revolutionary Discovery (1242 CE)

In his Sharh Tashrih al-Qanun (Commentary on the Anatomy of the Canon of Medicine), Ibn al-Nafis wrote:

"The right cavity of the heart is connected to the left cavity. But there are no visible pores between them, as Galen thought, nor any invisible pores which would allow blood to pass through... The blood from the right chamber of the heart must flow through the pulmonary artery to the lungs, spread through its substance, be mingled with air, pass through the pulmonary veins to reach the left chamber of the heart, and there form the vital spirit."

This is an exact, correct description of pulmonary circulation — the path blood takes from the right heart → lungs (oxygenation) → left heart → body.

        IBN AL-NAFIS'S PULMONARY CIRCULATION MODEL (1242 CE)
        
   Right Heart Ventricle
          │
          ▼ (Pulmonary Artery)
   LUNGS — blood spreads through lung substance
          │ "mingled with air" (oxygenation)
          ▼ (Pulmonary Vein)
   Left Heart Ventricle
          │
          ▼
   BODY (systemic circulation)
   
   Ibn al-Nafis's model: CORRECT ✅
   Galen's model (interventricular pores): WRONG ❌

This was proven correct by modern physiology. There are definitively no pores in the cardiac septum. Blood circulates exactly as Ibn al-Nafis described.

3. The Method: Reason Over Authority

Ibn al-Nafis explicitly describes his methodology for reaching this conclusion:

"Having verified these matters by reason and examination, and having found that Galen and Ibn Sina are in error, I have been led to suspect their anatomy. Therefore I investigated this more carefully, and I found that blood from the right ventricle passes through the pulmonary artery to the lungs..."

"Verified by reason and examination" — He performed anatomical dissection to check the septum for pores and found none. He then reasoned from this negative finding to the correct model.

This is exactly the methodology Ibn al-Haytham used in optics — observation overriding authority, experiment over received tradition.

4. Coronary Circulation: Another Discovery Ahead of Its Time

Ibn al-Nafis also described the coronary arteries — the blood vessels that supply the heart muscle itself — with a functional insight:

"The heart is nourished by the blood that penetrates its walls through the vessels that are distributed throughout the body of the heart."

He correctly identified that the heart does not absorb nutrients from the blood inside its chambers but is instead supplied by its own dedicated circulatory system (the coronary arteries). Coronary artery disease — the leading cause of heart attack death globally — occurs precisely in this system Ibn al-Nafis described in 1242 CE.

5. Why Was This Discovery Lost for 300 Years?

Ibn al-Nafis wrote in Arabic. His Sharh Tashrih al-Qanun was not translated into Latin until the Venetian physician Andrea Alpago partially translated sections in the early 16th century.

Michael Servetus (1553 CE) and Realdo Colombo (1559 CE) — European physicians who "rediscovered" pulmonary circulation — had access to Alpago's translations. The historical debate about whether they knew of Ibn al-Nafis's work continues in medical history scholarship.

William Harvey's 1628 publication De Motu Cordis completed the description of full systemic circulation — but pulmonary circulation, which Harvey confirmed, had already been correctly described by Ibn al-Nafis 386 years earlier.

6. Ibn al-Nafis's Other Contributions

Ibn al-Nafis was not only a cardiologist. His medical work spanned multiple disciplines:

He served as Chief Physician of the Al-Mansuri Hospital in Cairo — the same bimaristan discussed in our earlier article — where he could apply his discoveries clinically.

7. Islamic Faith as the Foundation of Discovery

Ibn al-Nafis's willingness to challenge Galen — accepted for 1,000 years as infallible authority — reflects the Islamic tradition that no human authority can override empirical reality. The Quran repeatedly commands direct observation:

"Do they not look at the camels — how they are created?"
(Surah Al-Ghashiyah 88:17)

For Ibn al-Nafis, looking at the heart — and refusing to "see" pores that were not there because Galen said they should be — was an act of intellectual and religious integrity. Truth, even when it contradicts authority, must be followed.

Conclusion: The Heart's First Cartographer

Ibn al-Nafis drew the first correct map of how blood moves through the lung — the fundamental circuit that keeps every human being alive. He did it with a scalpel, a critical mind, and a deep commitment to the Islamic principle that knowledge (ilm) must be grounded in reality, not inherited error.

William Harvey completed a journey that Ibn al-Nafis began. The full story of blood circulation's discovery is an Islamic story first — and it is only justice that it be told correctly.

"Seek knowledge, even unto China."
— Prophet Muhammad ﷺ

Ibn al-Nafis sought it in the human heart. And he found the truth.