In the early days of Rome, it was still the Greek doctors who made medicine progress in the works, in teaching and in professional practice. But flipping through the texts that have come down to us, it is not possible to find anything new about cardiological knowledge. Not even in the De Medicina of Celsus (1st century AD), which today is considered the only treaty of medicine written in the language of the Romans, there are references to the structure, function and diseases of the cardiovascular system. The treaty contains only a brief chapter on cardiac disorders (De Cardiacis), but it does not contain a single word that really refers to the heart.

Celsus only speaks of the swoon and syncope that originate from weakness of the stomach. In this context, for example, the word praecordia did not have a precise meaning at the time, but was used indifferently for the parts of the body located above and below the diaphragm.

These problems were then addressed in the second century after Christ by Galen (138-201), who systematized the ancient medicine and was the greatest physician of antiquity, after Hippocrates. With few exceptions, every expression of European medical knowledge until the Renaissance was brought back to Galen. In his anatomical studies, Galen was not content to describe the parts observed but he rebuilt their functions. In his unitary vision of the human body, he did not want to separate the concept of structure from that of function. He carried forward the conviction that the necessity of the dissection had to be put before the needs of the pathology, for a precise observation. Observations and concepts of physiology are found scattered throughout all the works of Galen, he always affirmed the need to bring his reasoning back to the biological foundations of medicine. The work entirely dedicated to physiology is the De usu partium corporis humani. Unfortunately, the field of physiology of Galen which more than any other was built on erroneous observations and deductions is that of the cardiovascular system.

To give a convincing explanation of the movement of blood in the vessels, Galen elaborated a pattern of life processes, structured in part on biological truths and partly on inconsistent conjectures. This physiological system, handed down through the Middle Ages, dominated unchallenged until the beginning of modern times. He imagined that the human body was dominated by 3 organs: liver, heart and brain. This three organs are the seat and the centers of diffusion of the “pneuma” (that is, the essence of life in his theory), which feeds the 4 elements of which the body is composed (blood, phlegm, yellow bile and black bile).

For Galeno, the pneuma has 3 forms:

1) The natural spirit, based in the liver that presides over the formation of blood and the functions of nutrition

2) The vital spirit, based in the heart, which regulates the course of the blood and the heat of the body

3) The animal spirit, which resides in the brain, directs the high functions of sensitivity and movement.

This is how, according to Galen, the physiological process takes place: the blood has its main station in the liver. In this organ the nutrients come from the intestine. Along the ramification of the venous vessels which originates and radiates from the liver, the blood – animated by the vital spirit – spreads throughout the body.

Human physiology according to Galen

The distribution spreads with a wave movement of flow and reflux. In this way, the sprayed organs absorb the blood they need and send back that which exceeds to the other organs. With this activity the function of the liver and of the venous system does not end. One of the venous branches that radiate from the liver (our vena cava) reaches the right side of the heart and here blood plays two essential functions to life:

1)    Most of the blood stops in the right ventricle to be purified: for this, part of the blood flows back into the lungs at each cardiac systole, to expel with the respiration and discharge into the atmosphere its impurities. Thus purified, it returns to the veins.

2)    A small part of venous blood passes from the right ventricle to the left, through invisible pores of the intraventricular septum. Here, under the influence of the innate heat of the heart, with the air that comes from the lung with each inhalation, the blood processes that higher form of spirit, which is the vital spirit, and distributes it throughout the body, through arterial branching.

The heart is therefore, according to Galen, the center of innate heat and is similar to a small furnace in which the intensity of the fire is changeable. The air of lung respiration fuels the heat and keeps it in proper combustion, expiration instead has an attenuating effect. If the air gets in excess, the combustion increases and the normal heat becomes fever; if instead the air is poor, the fire is attenuated and, stops entering, goes off and life ends. According to these ancient imaginative hypotheses, the vivification of the blood is not carried out in the lung with the respiratory exchanges, but in the heart through the mixing of the blood, through the imaginary invisible pores of the interventricular septum.

Besides these, there is a third fundamental activity in the physiological system of Galen: some of the arterial branches that start from the heart with the blood rich in vital spirit reach the brain, dividing into a very thin net where the animal spirit born, ethereal substance that it spreads throughout the body through the nerves (considered by Galen as empty channels) and presides over the delicate psychic and nervous functions. This is undoubtedly an important contribution to the development of physiological thought, since Galen thus returned to the brain its true nature as the central organ of the nervous system, already foreseen by Alcmeone and then denied by Aristotle (the Aristotelian conception has always been based on the idea that the heart was home to feelings, emotions and intelligence).

Another contribution of Galen was the correction of the mistake made by the Alexandrian school scholars, who believed that only the right heart and the venous system were full of blood, while the left heart and the arteries would be empty and bloodless, given that their task was to bring the vital spirit to the various parts of the body. Galen proved that it was enough to puncture any artery or the left heart to see blood come out, which, unlike that of the veins, was vaporous and tenuous (his words), resulting from the mixing of the blood with the air drawn from the lung. The center of the arteries, for Galen, was the left heart, which in the systole sent blood enriched with vital spirit to revive the organs. The vein center was the liver, from which the nutritive blood is pushed to all parts of the body for an attractive and selective action of the organs.

These precious contributions are however obscured by two crucial errors inherent in the Galen system: the porosity of the septum and the systolic reflux. This indicates that Galen was very far from the dynamic concept of circulatory function. He believed that the venous and arterial system were two closed systems independent of each other, he had not thought about the existence of the small and the great circulation through which blood, with a circulatory movement, starts from the heart and returns to the heart. In fact, Galen in his treatises never used either the concept or the word circulation: it appeared for the first time in the writings of Cesalpino (XVI century).

In the following centuries Galen’s greatest virtue, that of being an example and guide in the path of observation and experimentation, could have given a valid impulse of progress to science. But this did not happen, partly because of the double soul of Galen’s method: on the one hand, in his study program he rigorously followed biological research, on the other he always wanted to give an explanation to the facts he observed. When the observation was not enough to solve the problem, it took refuge in abstract hypotheses and in philosophical speculations. If Galen’s life had been a few centuries long, Galen would probably have corrected his mistakes, but the characteristics of the galenic construction were a serious impediment to the development of medicine until modern times.

For centuries the ipse dixit of Galen dominated the mind of scholars who, even when they began to dissect corpses and observe the human body more closely, did not dare to totally contradict his doctrine. The errors that emerged from anatomical observation were then attributed to the copyists or to the fact that the structure of man had changed over time. The first to contradict Galen through anatomical observation was Mondino de’ Luzzi, who in 1270 founded the chair of anatomy at the University of Bologna.