As early as before the Galen era, people have realized that blood has a special importance to the human body. Even in the most primitive society, blood has been endowed with special qualities. Today we are still talking about blood debt and blood oath. We often say, "Radish doesn't bleed." Enemies can be said to be "blood feuds". Cruel competition is described as "cold-blooded struggle". In some societies, blood is used to witness marriage and business contracts, and some ancient tribes believe that drinking blood will gain courage and youth. There has always been a legend of vampires in popular culture, saying that vampires rely on other people's blood to ensure their immortality. This story can still be found in books and movies today. Today, many people who know little still believe that blood transfusion can transfer the personal qualities of blood donors to recipients.

Both Hippocrates and Aristotle know that the movement of blood in the human body is very important to the process of life.

Aristotle's research concluded that the heart is the central organ of the human body. According to Aristotle, this is where wisdom lies. The heart also controls the flow of blood throughout the body and provides heat to animals through blood.

Through extensive collection of ancient knowledge about blood and his own experiments, Galen got different and more detailed conclusions. He believes that the human body is physiologically dominated by three different organs, body fluids and gas fields. These three systems are located in the liver, heart and brain respectively.

According to Galen's theory, all blood comes from the liver. After ingesting food, the human body "cooks" or "cooks" in the stomach, and then becomes a liquid substance called chyle. Chyloid moves to the liver, where it is transformed into blood and filled with the "natural spirit" that dominates nutrition. The liver is the starting point and source of all veins. Venous network is like an irrigation system in the body, which provides blood for the whole body. It is dark red, bearing its nutrients and "natural aura". Every part of the body attracts the blood it needs, and the blood flows through fluctuations.

Galen believes that blood reaches the right side of the heart through veins, and some blood turns from the right side to the left side through invisible micropores on the diaphragm (the boundary between the two chambers). On the right side of the heart, blood is mixed with air inhaled from the lungs, so it is full of "essence", and essence dominates emotions, so blood becomes brighter and is transported to other parts of the body through the arterial system.

Although Galen won a reputation as one of the second Wiki big doctor, his authority convinced him that even if he was wrong-so was his view on the use and diversion of blood in the human body. Part of arterial blood enters the brain, where it produces "animal spirit" and is transferred to the whole body through the nervous system. Galen thinks that the nervous system is a network composed of hollow pipes. "Animal aura" dominates sensation and movement.

Later, in Galen's view, the basic function of blood is to divert important "life gas field", which itself makes blood move. The role of the lungs is to cool and ventilate the naturally hot heart-the heart is hot because it is the "soul". He also believes that the primary task of the heart is to prepare the "life gas field".

Like most of Galen's theories, the whole system, including various mysterious injection methods of "aura", is very attractive to many Christians because of its consistency with theological thinking and its exquisite internal coordination. But in the16th century, it began to be full of loopholes. In other words, it is difficult for some anatomists to find some very important pores. They are looking for micropores or channels in the diaphragm between two chambers of the heart.

The controversial and outspoken Spanish doctor Servit (about1511-1553) first concluded that the heart has no channel. His research on Galen and other anatomists, coupled with his own direct observation, led him to form another theory about the movement of blood in the body. Servit's reason is that if the channel does not exist, so much blood can't flow from the right side to the left side of the heart. He noticed that the pulmonary artery was quite thick and the blood flow from the heart to the lungs was very strong. He thinks this is because the blood sent to the lungs exceeds the amount needed for nutrition. He argued that blood must reach the lungs to breathe, and it will change color when it passes through the lungs. Later it returned through the pulmonary vein. In fact, he thought, it didn't go through the diaphragm. Servit is not a famous anatomist, but a doctor, but his thought of "small circulation" may encourage more people to challenge the intellectual and philosophical shackles imposed by Galen on physiology.

Unfortunately, religious conflicts broke out one after another at that time. As a theologian, Servit dared to be as outspoken as a doctor. His heretical religious views made him an opponent not only of Catholics, but also of Protestants. Not everyone will easily accept other people's accusations, but he is obviously too risky, and both the Catholic Church and Protestants angrily demand his immediate execution. He managed to escape from the Catholic inquisition, but was caught by Protestants in Geneva. There, he refused the "forgiveness" sentenced to hanging earlier, was tied with chains, tied to a stump and burned alive.

However, the challenge to Galen never ended. Another more famous anatomist was also troubled by his failure to find a tiny channel so important to Galen's theory. 1555, Vesaliua uz wrote: "The diaphragm is as thick and dense as the rest of the heart. Therefore, I can't see that even the smallest particle can pass through it and transfer from the right ventricle to the left ventricle. " At that time, Vesaliua uz was still a Galen when dealing with physiological problems. He assumed that air holes must exist, but they were too small to be found.

A confused contemporary of Vesaliua wrote, "Only God knows the movement of the heart."

There is a student named Rialdo Colombo in Vesaliua (15 16- 1559). After Visarius, he became a professor of surgery and anatomy at the University of Padua. He is one of the fiercest opponents of human body structure. He once wrote a medical paper entitled "Deanatomy", which was published by his children in 1559. Although it is criticized as a rough imitation of human body structure (but there are no illustrations), it does contain Columbus' theory about human blood movement. Columbus read Servit's book. He may have borrowed from Servit the argument that blood flows from the right side of the heart to the left side through the lungs, but he wrote more clearly that he was the first famous anatomist to publish this so-called small circulation thought. However, this work did not really touch the foundation of Galen's intricate cardiovascular system. Colombo's reputation is not attractive enough, and his evidence is not enough to convince most people. The solution of heart and blood problems, as well as Karen's real physiological revolution, will be solved by another talented and conscientious British doctor in 70 years.

Just like Darwin, another great scientist, we will meet Darwin in another part of this book. Harvey is an unconscious revolutionary. Harvey respects Galen and Aristotle and is a calm, elegant and conservative person. However, Harvey developed the theory of blood circulation and gave detailed evidence, which made Galen medicine suffer the most severe blow.