Discovering the Heart: A Timeline

For well over a thousand years, the best-known explanation of the heart came from Galen, a Greek physician born in Pergamon in AD 129 who later worked in Rome. He watched the beating hearts of injured gladiators and dissected animals. He taught that blood was made in the liver and used up by the body, and that some blood passed from the right side of the heart to the left through invisible pores in the septum. Both ideas turned out to be wrong, but they were taught for centuries.

In the 13th century, Ibn al-Nafis, a physician who worked in Cairo and died there in 1288, challenged Galen directly. In a commentary on the anatomy section of Ibn Sina's Canon of Medicine, he wrote that the septum is thick and solid, with no visible or invisible passage. Blood from the right side, he argued, must travel through the pulmonary artery to the lungs, mix with air there, and return to the left side of the heart. This is the earliest known description of the pulmonary circulation.

For a long time, European writers credited the idea to the Spanish physician Michael Servetus, who described it in the 1500s. Ibn al-Nafis had written it down roughly three centuries earlier.

In 1543 the anatomist Andreas Vesalius still repeated Galen's claim that blood soaks through the septum. In the second edition of his great anatomy book, in 1555, he changed his mind and wrote that he could not see how even the smallest amount of blood could pass through it. Other anatomists, such as Realdo Colombo, confirmed the lung circuit and noted that the heart's valves let blood go only one way.

The English physician William Harvey put the pieces together. In 1628 he published De Motu Cordis ('On the Motion of the Heart and Blood'), backed by experiments rather than old authority.

One of his strongest arguments was a simple sum. He estimated how much blood the heart pushes out with each beat and multiplied it by the number of beats. The answer was far more blood in a single day than the body could possibly make from food. So the blood could not be used up and replaced: it had to go round and round in a circuit. Harvey also showed, by pressing on the veins of a bound arm, that the valves in veins let blood flow only towards the heart.

Harvey could not see how blood got from the arteries to the veins; he had no microscope good enough. In 1661 the Italian scientist Marcello Malpighi studied a frog's lung under the microscope and saw tiny vessels joining the two: the capillaries. His observation confirmed Harvey's circuit.

In 1887 the physiologist Augustus Waller recorded the first human electrocardiogram, picking up the heart's weak electrical signals from the surface of the body. The Dutch physiologist Willem Einthoven, who had watched that recording, named the five main waves P, Q, R, S and T in 1895, and in 1903 published his string galvanometer, a far more sensitive recorder that became the forerunner of modern ECG machines. He received the Nobel Prize in Physiology or Medicine in 1924 for his work on the electrocardiogram.

On 3 December 1967, at Groote Schuur Hospital in Cape Town, South Africa, a team of about thirty led by surgeon Christiaan Barnard carried out the first human-to-human heart transplant. The patient, Louis Washkansky, was 53. The new heart worked, but he died of pneumonia 18 days later. The operation showed that a heart could be replaced, and it opened a new field of surgery.