The founding concepts of circulation of the allopathic science of medicine originate in the doctrines conveyed by the giant personality of his time, the great Aristotle. That does not mean there was no comprehension of circulation prior to Aristotle but it is not relevant to the changes we seek following the new findings as reported in my work.

I am sure Aristotle himself looked over his shoulders at the teaching of his elders. His father was a physician to the king of Macedonia and therefore was exposed to the teachings of biology, physiology, and anatomy very early in his life. He later became a student of Plato.

Aristotle, according to his observation in a chick embryo, established the heart as the first organ to be formed in the body. He described it as a three-chambered organ and as the center of vitality in the body. Somehow all these authors were convinced that the warmth of the body was generated by the heart, and when heart stops, the body cools down and the person dies. They hypothesized that the heart circulates pneuma (air) and vital spirit through the arteries to the rest of the body. They also postulated that the human body needs nourishment to live. This postulation was a great step forward since until that time it was thought that nourishment was derived from the divine causation rather than the absorption of food into the intestines. It was the first time ever described that nourishment is derived from the intestines and goes to the liver where blood is manufactured and the origin of veins from the liver carry nourishment and humor or temperaments to the rest of the body. Maintaining the balance of these four temperaments is the secret of good health. Originally, Aristotle named all vessels as veins. Later, Praxagoras was the first to name arteries and veins separately. The understanding of the time was that arteries begin in the heart and carry pneuma and vital spirit to the rest of the body, but they did not give credit to the flow of blood in the arteries. They considered the spirit of life as the vital force, and pneuma flowed in the arteries and was diffused to the tissues. They believed that the liver played the central role and blood flowed from there centrifugally with the vena cava ascending up from the liver and taking blood to the heart, brain, and lungs. Then the vena cava descending downward takes blood to the rest of the body tissues. The atrium was not considered to be a separate chamber and part of the heart. They believed the vena cava carried blood to the brain, heart, and lungs at the junction of the ventricles, which expanded to a pouch and served as a collection and delivery area of the blood to the ventricles. Hence the atria were described as an extension and part of the vena cava and pulmonary veins rather than a separate chamber of the heart. To further support their thinking, observation of the atrial wall with the naked eye resembled the vena cava rather than the ventricles with the exception of a small non-functioning appendage, which they named the auricle as it appeared to be an extension and remnant of the ventricle. Therefore, all explanations and teachings of the heart were based on two ventricles. This teaching influenced Sir William Harvey as well and was grounded in a genuine reason. The syllabus of the medical school in Padua consisted of subjects of anatomy, philosophy, and physiology written by Aristotle and Galen. Harvey fostered those teachings and his experiments of the heart were mainly concentrated on the ventricles.

The above teaching about the atrium continues to the present time and the atrium was never given a functional importance. Modern anatomists definitely described the atria as two separate chambers of the heart and not as an extension of the vena cava. That is the only progress that has been made at the anatomical level. At present, the heart is described as a four-chambered organ.

The anatomical structure of the heart was defined by Aristotle and the rest of the stalwarts who followed him continued his teachings. Aristotle defined the heart as hard flesh not easily injured and composed of hard and tense muscular fibers. That definition surpassed all the others. Definitely only two chambers of the heart, the right and left ventricles, corresponded to that description of the heart with the exception of the auricle of the atrium, which appears to be an appendage of the ventricle. The remainder of the atrium did not even come close to it and was never considered to be a functional part of the heart. Sir William Harvey did not devote any importance to the atrial chambers in his theory of the explanation of the motion of blood in the body. He concentrated his efforts solely on the ventricular chambers. He thought of the atria as a storage house for blood. Up to the end of Galen's era, all anatomists believed that the arteries and veins were end vessels and diffused into the tissues.

Vital spirits flowing to the end arteries are continuously dissipated into the tissues. We can generalize the theory of the circulation during the pre-Galenic era as explained in the diagram (Figure 1.1). Nourishment is taken from the intestine via the portal vein to the liver and it transforms this nourishment into blood and distributes it to various parts of the body through the hepatic vein and into the vena cava. The ascending portion of the vena cava supplies the heart, brain, and lungs. The descending portion of the vena cava supplies the rest of the body. The left ventricle and arteries are thought to be devoid of blood. It distributes the pneuma and life spirit to the rest of the body. Both the arteries and veins are thought to be end vessels and diffuse into the tissues. These were the concepts and teachings of circulation at the time. Based upon this, various ailments were treated (Figure 1.1).

Galen established his own doctrines on the subjects he taught. He mainly conducted dissections on apes and pigs. He revived the teachings and methods of treatment established by all the past Greek physicians and philosophers from the time of Hippocrates onward. His authority and influence were such that his theories of circulation lived unchallenged and unquestioned almost 1,300 years, at which time Sir William Harvey entered the scene.

Galen modified most of the old doctrines and gave a specific name and form to them and explained them in his own and very candid method. He demonstrated that the body is made of four definite humors which were not addressed until then, although the same concept since the time of Hippocrates had been practiced under various presumptions. Galen named them black bile, yellow bile, blood, and phlegm. A proper balance of these four humors in the human body is the hallmark of good health according to him. Based on that, he discussed “theory of Plenitude and Plethora.” During his time bloodletting as the main method of balancing of these humors became a very well-practiced treatment of many ailments and especially in the management of contagious diseases. He described various techniques of phlebotomy to various parts of the body to suit different ailments. He was the first to accept, in addition to pneuma and vital spirits that there is also blood in the arteries. He could not discard blood's obvious presence in the arteries and therefore he postulated a theory to describe the presence of blood in the left ventricle. The interventricular septum has pores through which some blood passes from the right ventricle to the left ventricle and flows to the arteries. However he did not give credit to it as the main content of the arteries. Galen still thought the pneuma comes from the lungs and the vital spirit from the heart. He might have derived this concept from his observation of the foramen oval in the mammalian fetal heart and might have thought that it continues to stay as invisible pores in the interventricular septum during the growth of the fetus.

It was Realdo Colombo (1516–1559), an Italian professor of anatomy and surgeon at the University of Padua, Rome, Italy, who established the pulmonary circulation, modulated by describing how venous blood of the right ventricle passes through the lung and reaches the left ventricle. According to Galen, the heart was the cauldron of the body. The heart warmed the blood and as it got warmer it ebbed out of the cauldron and overflowed into the vessels, like milk when boiled ebbs and flows out of the kettle, and was thus famously known as the ebb and flow theory of Galen (Figure 1.2). So Galen did not attribute any mechanical function to the heart. According to him, the liver was the main organ of circulation in the body. He believed that nutrition was absorbed from the intestines and was carried by the portal veins to the liver. It is in the liver where blood and other humors are manufactured continuously and distributed to the entire body through the veins. According to Galen both the veins and arteries are end vessels, and therefore blood dissipates into the tissues and is continuously produced and replaced by the liver. This is the same way pneuma and vital spirits dissipate into the tissues via the arteries.

Galen declared to the medical and literary world that the liver is the organ supporting circulation and the Arabic world, primarily embodied by the Persian, Egyptian, and Arabic worlds, attracted the attention of the poets and writers of that time. Later some of these beliefs were inherited by the Urdu language created by the “Mogul” emperors of India who were of Persian origin. That is how it came to be known among the Indian poets and writers as well.

According to the teachings of Galen, blood flowed away centrifugally in the veins to various parts of the body and was diffused into the tissues and never returned. The arteries and veins are thought to be end vessels and separate circulatory systems. An imbalance in the humors and the flow of blood was thought to be the main cause of many ailments, specifically the contagious and infectious components. Bloodletting was the common treatment of the time. A circulatory system powered by a pumping mechanism of the heart was never contemplated. During the next 1,500 years these theories and concepts went unchallenged and were upheld even after the deaths of Galen as well as that of Sir William Harvey. It is intriguing to me how generation after generation almost for the next 1,500 years were the blind followers of this system. Going through the historical events of first 1500 AC we can put out various theories that played a role that is not relevant and is a separate subject.

But suffice it to say here that this is a learning point that communicates that scientific reasoning is fragile and can be suppressed under political, theological, and cultural conditions. He died at the age of 80 in 210 AD. His studies were confined to that of living or dead animals. In keeping with the tradition of Aristotle's teachings, Galen believed in deductive logic to arrive at many conc...