History of Physiology: Antiquity & Renaissance PDF

**Glimpses of the History of Physiology -- from Antiquity to Renaissance** Prof. Dr. Cristian Bârsu Attention This course support is intended exclusively for students from the Faculty of Medicine of the \"Iuliu Haţieganu\" University of Medicine and Pharmacy. That is why the course support should...

**Glimpses of the History of Physiology -- from Antiquity to Renaissance** Prof. Dr. Cristian Bârsu Attention This course support is intended exclusively for students from the Faculty of Medicine of the \"Iuliu Haţieganu\" University of Medicine and Pharmacy. That is why the course support should not be broadcast by any means outside the academic community of the "Iuliu Haţieganu" U. M. F. The term "physiology" was coined by Jean François Fernel (1497-1558), in the Renaissance. This name comes from the Greek words *physis* -- meaning nature -- and *logos* -- meaning science. Starting with the 16^th^ century, especially due to Andreas Vesal (1514-1564) until the mid-18^th^ century, the preoccupation of many physicians for the study of anatomy implied their interest in discovering the functions of different organs. In the 18^th^ century, Albrecht von Haller (1708-1777) described physiology as ‟anatomy in motion", to explain the functions of various organs and systems. Since the beginning of the 19^th^ century, physiology has developed by making its own methods of study and reaching important discoveries. Thus, it has become an independent science. This did not mean his isolation from other medical and biological fields. On the contrary, advances in histology, biochemistry, pharmacology etc. favoured the rapid evolution of physiology. **Precursors of physiology in antiquity** The first notions about the functions of the organs were recorded in Antiquity. It should be noted that in prehistory there was a limited interest in knowing the morphology of the human body, absolutely insufficient to research some simple functions of the organs. In **Mesopotamia** The decipherment of the cuneiform writings led to know many aspects of the medical knowledge of Mesopotamia. Mesopotamian priests-physicians focused their attention to establish the prognosis. For this purpose they examined mainly the liver[^1^](#fn1){#fnref1.footnote-ref}. This organ was considerated responsitive of the most important vital processes of the human body. This conception suggests the existence of rudimentary notions of physiology. For example, in this organ took place the formation and the storage of the blood. Saliva was considered to carry the ‟breath of life" and to hold a creative force. No attention was paid to the functions of the brain. In **ancient Egypt** Ancient Egypt medicine was deeply impregnated with philosophy. Some notions have been recorded in the "Ebers papyrus". They are relevant for the level of the antic physiological notions. Respiration was considered the fundamental function of life. From this point of view, the following description is interesting: ‟air enters through the nose, passes in the heart and lungs, which distributes it throughout the body"[^2^](#fn2){#fnref2.footnote-ref}. The heart was known to pulsate. The places for palpation the pulse were knew, although it was not counted. The liver was thought to be the reservoir of blood. In **ancient India** Physiological conceptions in ancient India were established on the basis of the interrelationship between human body and nature, as mentioned in the famous Vedic writings. It was considered that the five elements of the universe: earth, water, fire, wind and space were correlated with the following components of the human being: solid (consistent) structures, phlegm, bile, breath and cavities of the body. In "Ajurveda" ("The Science of longevity") it was stated that the breath (‟prana" - the vital agent) corresponded to the wind; phlegm had the same role as water in nature etc. "Prana" contained the following breaths: \- mouth murmur, which was an agent of respiration and swallowing; \- breath of speech; \- breath that produced heating of the body and that ‟cooked" the food (digests it); \- breath pushing the excrement down; \- breath that passed through the body and limbs and ensured the movement. In **ancient China** Doctor Shun-Yu (from the ancient China) established a correlation between the five viscera: heart, lungs, kidneys, liver, spleen with five colours, five organs five planets, five elements and five tastes. He did the following correspondences: \- spleen -- planet Saturn -- earth -- yellow colour -- sweet taste; \- liver -- planet Jupiter -- wood -- green colour -- salty taste; \- heart -- planet March -- fire -- red colour -- bitter taste; \- lung -- planet Venus -- metal -- white colour -- sour taste; \- kidney -- planet Mercury -- water -- black colour -- salty taste. In Nei Ţing's writings (dating also from Antiquity) are mentioned the following physiological aspects: \- the heart patronizes the functions of the blood, directs the circulation of vital energy and provides heat \- the liver is the reservoir of blood and the seat of the soul \- the lungs have a role in breathing. In **ancient Greece** In antiquity, Hellenistic physiology was influenced by philosophy. The insufficiency of anatomical knowledge determined that rudimentary notions of physiology. The first thinkers of Miletus, who tried to decipher some phenomena of life, were called ‟physicists" or ‟physiologists". According to their way of thinking, they can be grouped in the following way: \- Thales of Miletus (7^th^-6^th^ centuries BC), Anaximenes (c. 560-c. 480 BC) and Heraclitus (540-480 BC) considered that the elements in nature are transformed into other elements; for example, the result ot water's condensation is represented by solid bodies, and its evaporation gave rise to a special air, which produce fire; \- Pythagoras of Samos (c. 580-500 BC) and his followers (called ‟Pythagoreans") hypothesized that matter was a conglomeration of elements spread in an empty field, which contained air (‟pneuma"); for these philosophers, the composition of bodies corresponded to numerical combinations; \- Anaximander of Miletus (c. 610-c. 547 BC) and Anaxagoras of Clazomene (c. 500-c. 428 BC) considered that the primordial principle, as well as the material cause of things, is the ‟apeiron". This term[^3^](#fn3){#fnref3.footnote-ref} encompasses two notions: the infinite[^4^](#fn4){#fnref4.footnote-ref} and the indefinite. It contains all elements of all bodies. At that time, it was known that air enters and circulates in the body. In the ancient conception, life was due to the existence of the ‟vital breath", named ‟pneuma". It was also known that disrupting moods - such as blood and secretion of organs - caused health problems. Alcmaeon of Crotona (5^th^ century BC) named this imbalance ‟[dyscrasia]". Until Hippocrates, the attention was given only to the following secretions: the bile and the phlegm. Polybius (Hippocrates\' son-in-law) divided the term bile into yellow bile and black bile. Until Galen (c. 131-200 AD.), the most representative physicians who were concerned with deciphering the body's functionality were: \- Hippocrates \- Aristotle \- Herophilus and \- Erasistrate. **Hippocrates of Cos** (c. 460-c. 377) and his disciples described four humors of the body: \- blood, characterized by heat and associated with humidity; it was considered to come from food and has a flow of ebb and flow; \- phlegm - considered to be the secretion of the brain - was also called pituitary; it was cold damp and antagonistic to other humors; \- yellow bile corresponded to heat and dryness; it was formed by the liver; \- black bile was perceived to be the secretion of spleen; it was called ‟melancholy". The term came from: *melanos* -- which means black -- and *cholia* -- which means secretion. In reality, black bile was the venous blood of the spleen. Black bile had the attributes of cold and dryness. Hippocrates had a naturist and vitalist doctrine. The "vital breath" was considered to be the cause of life. It was distributed as an "internal heat" in the body through the vessels. The body and pneuma were also considered to be deeply united. Regarding the circulation of blood, the Hippocratic writings mentioned the existence of veins, which started from the head and were distributed to the whole body, up to the toes. In fact, Hippocrates called veins what later were called arteries[^5^](#fn5){#fnref5.footnote-ref}. In some texts from the collection of Hippocratic writings -- called the "Corpus Hippocraticum" -- were included several writings of physicians who were not disciples of Hippocrates. In this collection was made the distinction between arteries and veins, based on their content (but this content was misinterpreted: air being considered to be in the arteries and blood in the veins). It was believed that the heart narrows or relaxes the veins (later, these elements were integrated into what is called vasomotricity). The roles of the brain were to receive and to distribute the humours. The brain was considered a gland from moist areas of the body. Aristotle (384-322 BC) collected most of the knowledge of his time in his works. So: 1\. he admitted the existence of the vital spirit as an immaterial and immortal principle, which governs vital phenomena 2\. he considered that all things are based on 5 elements: water, air, fire, earth and the ‟celestial" 3\. he demonstrated that the raw material was characterized by four fundamental principles: drought, humidity, heat and cold; their pairwise correlation could only be done in four ways: fire and air; air and water; water and land; earth and fire 4\. he considered the heart to be the most important organ: the pulse was the result of an uninterrupted heartbeat 5\. he demonstrated that there were changes in the pulse according to the different states of the body and mind: fear, hope, agony 6\. he described the pulmonary artery and aorta as large vessels that carry blood to organs. According to his conception, the arteries did not contain fluid but air 7\. he considered the brain to be a cold organ: the brain in men was larger than in women and much larger than in animals 8\. he showed that the spinal cord is located in a bone canal formed by vertebrae; the spine being the source of all the bones 9\. he attributed the role of ventilation to the lungs because it attracts air when breathing 10\. he considered that digestion was done by processing food under the influence of heat 11\. he stated that the role of the kidneys is to form urine, which collects in a reservoir (i.e. in the bladder) 12\. he described the diaphragm as a ‟transverse septum", which he named ‟praecordia" because it separated the heart and lungs from the abdominal organs by placing a barrier between the sensitive and vegetative soul. 13\. he supported the importance of the periosteum in bone formation 14\. he argued that in the blood are two parts: one watery, the other fibrinous. he admitted the existence of the vital spirit as an immaterial and immortal principle, which governs vital phenomena 2\. he considered that all things are based on 5 elements: water, air, fire, earth and the ‟celestial" 3\. he demonstrated that the raw material was characterized by four fundamental principles: drought, humidity, heat and cold; their pairwise correlation could only be done in four ways: fire and air; air and water; water and land; earth and fire 4\. he considered the heart to be the most important organ: the pulse was the result of an uninterrupted heartbeat 5\. he demonstrated that there were changes in the pulse according to the different states of the body and mind: fear, hope, agony 6\. he described the pulmonary artery and aorta as large vessels that carry blood to organs. According to his conception, the arteries did not contain fluid but air 7\. he considered the brain to be a cold organ: the brain in men was larger than in women and much larger than in animals 8\. he showed that the spinal cord is located in a bone canal formed by vertebrae; the spine being the source of all the bones 9\. he attributed the role of ventilation to the lungs because it attracts air when breathing 10\. he considered that digestion was done by processing food under the influence of heat 11\. he stated that the role of the kidneys is to form urine, which collects in a reservoir (i.e. in the bladder) 12\. he described the diaphragm as a ‟transverse septum", which he named ‟praecordia" because it separated the heart and lungs from the abdominal organs by placing a barrier between the sensitive and vegetative soul. 13\. he supported the importance of the periosteum in bone formation 14\. he argued that in the blood are two parts: one watery, the other fibrinous. Erasistratus of Cos (c. 340-257 B.C.) was famous especially for his studies in physiology. He was considered one of the founders of physiology, as a science. For him, the pneuma played the most important role. He recognized two types of pneuma: - ‟vital" - located in the left ventricle of the heart - ‟psychic" - located in the ventricles of the brain. Regarding the deciphering of the blood circulation, Erasistratus brought remarkable elements, which remained valid for 18 centuries, until Harvey's descriptions. Thus, Erasistratus correctly showed that: 1\. the heart is the motor of arterial and venous circulation 2\. the pulmonary veins go from the lungs to the heart; they look like arteries 3\. the blood from the liver reaches the heart through the vena cava 4\. the blood from the right ventricle is sent to the lungs at each systole of the heart 5\. the heart absorbs blood from the vena cava at each diastole 6\. the aorta originates in the left ventricle 7\. the sigmoid valves of the pulmonary artery and aorta prevent blood from flowing back to the heart during diastole 8\. the arteries and veins are connected to each other. 9\. Erasistratus used this idea to explain why in the section of the arteries blood and not air flowed from the arteries 10\. the role of the epiglottis is to close the larynx during swallowing 11\. the digestion takes place in the stomach; food is crushed due to peristaltic movements of gastric muscle fibers, which have been correctly described by Erasistratus. Erasistratus'positive contribution to physiology was diminished by his misconceptions: a\. the arteries contain only air - a belief due to his observations on corpses b\. the blood is produced by the liver; the lack of differentiation of the heart atria, which he unified with the two pulmonary vessels; he did not recognize the atria as belonging to the heart; Erasistratus described the tricuspid valve as belonging to the vena cava and the bicuspid valve as belonging to the pulmonary veins d\. the pulmonary veins open directly into the left ventricle e\. the left ventricle contains fresh air from the lungs f\. the air from the left ventricle is sent through the aorta and arteries throughout the body during each systole of the heart g\. at each diastole, the heart absorbs air from the pulmonary veins h\. the vena cava opens directly into the right ventricle. Precursors of physiology in the **ancient Roman period** The famous Greek physician Galen (129-201 AD) made many and important contributions to the development of physiology. His achievements in the field of the [central and peripheral nervous system] are as follows: 1\. he made the beginning of experiments in the study of brain and peripheral nervous function 2\. he argued that some nerves originate from the brain and others from the spinal cord and not from the heart (as it was believed before him); to prove his claims, he made numerous cuts to different levels of the pig\'s spinal cord. Thus, he has publicly demonstrated that longitudinal cuts in the right or left half of the spinal cord do not produce major changes, while transverse cuts cause paralysis of various organs. 3\. he demonstrated the existence of sudden death by cutting the spinal cord above the first cervical vertebra or between the first and second cervical vertebra 4\. it provided evidence for the role of intercostals muscles in respiration 5\. he discovered the intercostals nerves that coordinate the intercostals muscles and where each nerve emerges 6\. it demonstrated the role of the nervous system in breathing and motility 7\. he offered evidence on the difference between compression and sectioning of cerebral substance in monkeys. Galen's conception of [blood circulation] has the following correct elements: a\. the heart produces the movement of blood b\. the pulsation of the arteries is due to the contractile property of a structure that exists in the arterial wall; through this observation, [Galen can be considered as a precursor of histological discoveries made intuitively ] c\. there is also blood in the arteries d\. Venous blood is dense in appearance and dark in color, while arterial blood is red. Galen made a great mistake in considering that the blood from the right ventricle passes directly into the left ventricle of the heart, through the interventricular wall. Regarding [breathing], Galen pointed out that air does not enter the heart directly (as it was believed at the time), but enters the lungs by inspiration and leaves the lungs by expiration. Through many experiments, he has shown that the chest relaxes on inspiration and retracts on expiration. Galen described [the path of an ingested odorous substance], from the moment of ingestion until its smell is felt in the exhaled air: from the mouth it passes into the pharynx, the esophagus, the stomach, the large intestine, then in the ‟mesaric" veins, in the veins of the liver, from here in the vena cava, in the heart, then in the lung. Thus, he made a fairly correct description of the digestive tract and the passage of the product into the bloodstream. Galien issued [the theory of the three types of pneuma]: psychic, vital, and natural. Like Hippocrates, [Galen adhered to the doctrine of the four moods]. Galen also [developed the theory of human behavior based on the preponderance of a mood]: \- the predominance of blood determines the blood temperament \- when the proportion of black bile increased, melancholy appeared \- excess phlegm produces phlegmatic temperament \- the predominance of yellow bile externalizes by an angry temperament. Significant is the fact that [temperament names have remained in contemporary vocabulary]. However, the positive aspects of Galen's contribution to physiology were associated with erroneous conclusions, due to the fact that he did not have a correct basis for human anatomy. For example: \- the involvement of the uterus in nutrition \- the formation of blood in the liver \- the production of black bile by the spleen. Precursors of physiology during **the Renaissance** In the field of medicine, the 15^th^ century (early Renaissance) was marked by the remarkable progress of anatomy. In the next century (the 16^th^ century) having a sufficiently broad base of anatomical knowledge, the physiology developed and became an independent science. The name physiology was coined by Fernel[^6^](#fn6){#fnref6.footnote-ref}, who considered that the purpose of the new science was to know ‟the nature of the healthy man, of all his forces and all his functions"[^7^](#fn7){#fnref7.footnote-ref}. Fernel studied physiology on an anatomical and psychological basis, but his conception was limited and tributary to ancient theories, because he did not perform experiments. For Fernel, the soul was the fundamental principle and cause for all existential functions that ensured life. The anatomist and philosopher Alessandro Achilini (1463 - 1512) conducted research on the physiology of hearing. Paracelsus (ca. 1493-1541) was the most representative of the chemists who studied medicine. The contribution in physiology refers to: - elaboration of the conception about the functioning of the organism based on chemical processes; - highlighting the presence of sodium chloride and sulfur in the components of the organs. In the middle of the 16th century, a new stage in physiology began, when Servetus, Colombo and Cesalpino conducted separate investigations into small circulation. Miguel Servet (c. 1509-1553) described in 1553 the pulmonary circulation. This was part of his theological work Restitutio Christianismi. Napkin stated that: \- the blood in the two ventricles does not communicate directly through the interventricular wall, but leaves the right half of the heart through the pulmonary artery and reaches the lung \- in this organ the ‟black" blood (ie venous) turns into ‟red" blood (which means oxygenated); then through the pulmonary vein and reaches the left side of the heart. Mateo Realdo Colombo (1516-1559) detailed in 1559 the pulmonary circulation as follows: \- the blood reaches the lungs through the ‟arterial vein" (ie the pulmonary artery) \- in this organ the blood is aerated \- it is further sent to the ‟venous artery" (hence the pulmonary vein) from where it reaches the left ventricle of the heart \- there is no passage of blood from one ventricle to another. He made some accurate observations about heart contractions. Colombo also had some misinterpretations: \- the veins bring nutritious blood to the organs \- the liver is a reservoir of blood. Andrea Cesalpino (1519-1603) contributed to the development of circulation physiology by: \- making a brief description of the pulmonary circulation and intuiting the existence of the great circulation (in 1569); thus the blood comes through the vena cava into the right ventricle of the heart. From here it reaches the lung through the ‟arterial vein". At this level it enters the anastomoses with the ‟venous artery"; in this way it reaches the left ventricle, from where it enters the aorta. The movement of blood through the heart and lungs is perpetual. He used the term ‟circulation" in 1589 \- highlighting the mixture of blood and air in the lungs, probably in the sense defined later as oxygenation of the blood \- recognition of the structural difference between the walls of the veins and arteries - description of the communications between the portal vein and the vena cava \- highlighting the fact that the vena cava is thicker near the heart than its portion in the vicinity of the liver; therefore he concluded that the origin of this vein was not in the liver \- mentioning the relationship between heart contraction and artery dilation \- observing the role of ‟membranes" (hence the valves) from the origin of large vessels, which prevent blood backflow. In Cesalpino's conception, all the functions of the organs and the psyche were coordinated by the soul. It was unique, indivisible and located in the heart. The soul exercised its authority through the heat, which spread to all parts of the body through the blood. So the most important organ of man was the heart and not the liver, as it was considered until his time. His studies of circulation were published six decades before Harvey's work. Leonardo Botallo (1519-1587) deciphered partially the blood circulation in the fetal period. He described the oval foramen in the interventricular septum. He also described the arterial duct. These formations received later their name in his honour. Girolamo Fabrizio d'Acquapendente (1533-1619) described the vein valves (1574). He mentioned the risk of rupture of the venous valves of the lower limbs in case of large accumulations of blood at this level. Another direction of his research was the physiology of movement. He studied the muscles of the extremities while walking, jumping, etc. Regarding the physiology of vision, he described, for the first time, the movement of the pupil. He contributed to the knowledge of the mechanism of respiration and the mode of action of the laryngeal muscles in phonation (1558). In the field of auditory physiology, research was conducted by Bartholomeo Eustachio (1520 - 1574) and Gabriel Faloppio (1523 - 1562). ::: {.section.footnotes} ------------------------------------------------------------------------ 1. ::: {#fn1}. See the course on the history of anatomy, written by Professor Cristian Bârsu.[↩](#fnref1){.footnote-back} ::: 2. ::: {#fn2}. Bârsu C. Istoria fiziologiei, biochimiei şi biofizicii (History of Physiology, Biochemistry and Biophysics), first vol., U.T. Press, Cluj-Napoca, 2007, 3.[↩](#fnref2){.footnote-back} ::: 3. ::: {#fn3}. It is very difficult to translate this term.[↩](#fnref3){.footnote-back} ::: 4. ::: {#fn4}. In the conception of these philosophers, the infinity of the substance was present since the origin of phenomena.[↩](#fnref4){.footnote-back} ::: 5. ::: {#fn5}. This fact explains why many researchers considered that Hippocrates confused the two types of vessels.[↩](#fnref5){.footnote-back} ::: 6. ::: {#fn6}. Jean François Fernel (c. 1497-1558) was a famous French physician, astronomer and mathematician. He was the first physician of King Henry II. Fernel is the author of Universa medicina (13 books), where he methodically categorized medical knowledge. Seven books dealt with physiology, describing the different parts of the body and their uses, the various elements and temperaments, the spirits and inner warmth, the functions and moods, as well as the generation. Three books dealt with pathology; Fernel describes diseases, their causes, signs and symptoms, pulse and urine. Seven books dealt with therapeutics, describing cases of healing, bleeding, purgatives, use, and action of medications. His book on psychology is the first treatise in this field since Galen (more than 13 centuries). Fernel, as a forerunner, therefore opposes the new medicine of Michel Servet, Paracelse and Andrée Vésale, while reforming the classic Galien -...... [↩](#fnref6){.footnote-back} ::: 7. ::: {#fn7}. Bârsu Cristian, History of physiology, biochemistry and biophysics, vol. 1, U.T. PRESS, Cluj-Napoca, 2007, p. 24.[↩](#fnref7){.footnote-back} ::: :::