In 1616, an English physician proposed a revolutionary theory and explained blood circulatory system instrumental in the success of the several surgeries and procedures and triggering the advancement of the medical field: How William Harvey's efforts saved several lives?

In 1616, William Harvey proposed a theory that explained how blood circulates through the body. Harvey was an English physician who studied medicine at Cambridge and the University of Padua. His work was based on observation, dissection and experiments rather than only on the writings of earlier authorities. He concluded that blood moves from the heart through the arteries and returns through the veins. He later published his findings in 1628. His work challenged ideas linked to Galen and changed the study of anatomy and physiology. It also helped establish observation and experimentation as methods for studying the human body.

In 1616, William Harvey proposed a theory that explained blood circulation

William Harvey did not invent a machine or physical device. His contribution was a medical discovery about the movement of blood. Harvey showed that blood circulates continuously through the body. He argued that the heart acts as the organ that moves blood through the arteries and veins.

His theory differed from the medical ideas that had been accepted for centuries. Earlier teachings, based in part on Galen, described separate systems for different types of blood. Blood was also thought to be produced and then consumed by the body.


Harvey used observation and experiments to question these ideas. His work eventually became one of the developments associated with the Scientific Revolution.

Who was William Harvey?

William Harvey was born on April 1, 1578, in Folkestone, Kent, England. He was the first of nine children of Thomas Harvey and Joan Halke. His family had moved from farming into commerce. Five of his brothers became international merchants. Harvey received his early education at home before entering the King’s School in Canterbury at age 10.

At 16, he received a Matthew Parker scholarship to Gonville and Caius College at Cambridge. He studied arts and medicine there from 1593 to 1599. Harvey then travelled to Italy and entered the University of Padua in December 1599. Padua was known for experimental research and anatomical study.

There, Harvey studied comparative anatomy, embryology and experimental physiology. His teacher Hieronymus Fabricius had studied the valves inside veins. Fabricius's work became important to Harvey's later investigation of blood movement. Harvey received his medical doctorate from Padua on April 25, 1602. He then returned to England and began working as a physician.

His medical career in England

Harvey became a candidate for the College of Physicians in 1604 and was elected a fellow in 1607. He married Elizabeth Browne, the daughter of physician Launcelot Browne. The couple did not have children. In 1609, Harvey became physician at Saint Bartholomew’s Hospital in London. He treated patients at the charity hospital and also worked with the College of Physicians.

In 1615, he became Lumleian lecturer in anatomy and surgery. This position gave him an opportunity to present his studies of the human body. On April 17, 1616, Harvey announced his belief that blood travelled through the arteries to the body and returned to the heart through the veins.

How did Harvey reach his conclusion?

Harvey's theory came from years of observation and experimentation. He studied the volume of blood moving through the body. He examined the movement of the heart and the way its muscles contracted. He also examined the valves in veins.

These valves allowed blood to move in one direction and restricted movement in the opposite direction. Harvey reasoned that the amount of blood moving through the arteries could not be explained by the belief that the body simply produced and consumed blood.

He argued that the blood leaving the heart through the arteries had to return through the veins. Otherwise, the arteries would contain too much blood while the veins would become empty. His dissections and observations of living and dead animals supported his conclusion.

The heart as the source of movement

Harvey also studied the heartbeat. Before his work, some medical thinkers believed that the active movement of the heart drew blood into the heart.

Harvey observed the heart in animals, including animals whose heartbeats were slower. He concluded that the heart contracts during its active phase and becomes smaller inside as it pushes blood out.

He therefore understood the heart as the organ responsible for forcing blood into the arteries. He also linked the pulse to the movement of blood through the arteries. When blood flow was restricted, he observed that the pulse decreased.

The amount of blood became part of his argument

Harvey also used estimates to support his theory. He calculated the approximate volume of the heart's ventricles, the amount of blood expelled with each contraction and the number of heartbeats.

Even using conservative estimates, he found that the heart moved more blood than could have been produced and consumed by the body under the existing explanation.

His calculations suggested that the heart pumped about 0.5 to 1 litre of blood each minute. Modern figures are about 4 litres per minute at rest and about 25 litres per minute during exercise.

The human body contains about 5 litres of blood. Harvey's calculation therefore provided another reason to conclude that blood had to circulate rather than be continually produced and consumed.

Why did Harvey's theory face opposition?

Harvey's conclusion contradicted established medical teachings. Galen had been an important authority in European medicine for centuries. Harvey's theory challenged ideas connected to Galen about the movement and purpose of blood.

The response to Harvey divided scholars. Some accepted the circulation theory, while others rejected it. Harvey continued to discuss and test his theory before publishing it.

The source material says that Harvey may have reached the discovery around 1618 or 1619, even though he announced his theory earlier and later published it. The delay helped him build an argument based on observations and experiments.

Publication of his circulation theory

Harvey published his main work in 1628. Its Latin title was Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus. It examined the movement of the heart and blood in animals.

The work explained that blood moved through one connected system of arteries and veins. The English version was published in 1653.

Harvey later published another work on circulation in 1649. It responded to criticism of his theory from French anatomist Jean Riolan. By the time Harvey died, his circulation theory had become established.

What was believed before Harvey?

Before Harvey, blood was generally understood through two separate systems. One system was believed to carry nutritive blood from the liver through the veins. Another was believed to carry vital blood through the arteries. The modern distinction between oxygenated and deoxygenated blood was not understood at that time.

The existence of capillaries was also unknown. Capillaries are the small vessels that connect arteries and veins. Their existence was confirmed later in the 17th century after the microscope had been invented. Harvey's theory therefore described circulation without having access to this later evidence.

How did his work influence medicine?

Harvey's work changed how physicians could study the body. He argued that anatomy should be studied through dissection and observation. He also believed that scientists should test claims themselves instead of accepting them because an earlier authority had made them.

His method involved collecting observations, recording them and testing explanations through experiments. He dissected animals and performed autopsies. He did much of this before the invention of the microscope.

This approach became part of the development of the scientific method. The source describes this method of observation and record-keeping as one of Harvey's major contributions to later scientific inquiry.

His work beyond blood circulation

Blood circulation was not Harvey's only area of study. He also investigated reproduction and embryology. He studied chickens to examine development inside eggs and deer to examine development inside the body.

His final major publication, Exercitationes de Generatione Animalium, appeared in 1651. It presented observations about the generation of animals and offered a view of foetal development as epigenetic.

Harvey also continued studying animals, insects and plants during his career. His work reflected an interest in understanding nature through direct observation.

Harvey as physician to the king

Harvey became physician to James I in 1618 and continued as physician to Charles I after Charles became king in 1625. He treated members of the royal household and had access to opportunities for animal observation.

In 1634, he examined women accused of witchcraft. His examination did not find unusual anatomical characteristics, and the women were cleared.

In 1636, Harvey travelled to Europe as part of a diplomatic mission to meet the Holy Roman emperor Ferdinand II. He also travelled with the king during the Scottish campaigns and the English Civil Wars. His association with the monarchy affected his professional life during the political conflict in England.

Loss of his research and final years

Harvey lost much of his written research when parliamentary troops ransacked his house in Whitehall in 1642. The lost material included notes about patients, postmortem examinations and animal dissections. He also lost work on the generation of insects. The source describes the loss of this research as one of the greatest setbacks of his life.

Harvey continued his scientific work after leaving public positions. He also helped establish a library for the College of Physicians. He died on June 3, 1657, in London. The source records his age as 79 and states that he died of a stroke.

Why William Harvey's discovery still matters?

William Harvey's work changed the understanding of the circulatory system. His main conclusion was that blood moves through the body in a continuous circuit. The heart pushes blood into the arteries, while the veins return blood to the heart.

This understanding created a basis for later study of the heart, blood vessels and circulation. His work also showed how observation, dissection, measurement and experimentation could challenge established medical ideas.

The discovery of circulation was therefore not only a change in medical knowledge. It was also part of a change in how scientists investigated questions about the natural world. The later development of knowledge about capillaries, oxygen and blood flow built on a framework that Harvey helped establish.

William Harvey's life

• William Harvey was born on April 1, 1578, in Folkestone, Kent.
• He studied at Cambridge and the University of Padua.
• He studied under Hieronymus Fabricius at Padua.
• He became Lumleian lecturer in 1615.
• He presented his circulation theory in 1616.
• He argued that blood travels through the arteries and returns through the veins.
• He studied venous valves as evidence for one-way blood movement.
• He used estimates of heart volume and heartbeats to support his argument.
• He published his main work on circulation in 1628.
• His theory challenged teachings associated with Galen.
• His research used observation, dissection and experimentation.
• He also contributed to embryology and the study of animal reproduction.
• He died in London on June 3, 1657.