Claudius Galen was a second century physiologist, philosopher, and writer who is often considered the most important contributor to medicine following Hippocrates.  Even though Galen is fairly well known, his fame does not compare to that of Hippocrates, so Galen's reputation and work are often underscored by Hippocrates' notoriety.  While Galen's name is mentioned in most sources about ancient medicine, usually only a small portion of the piece is dedicated to his accomplishments; this coverage often does not do him justice.  Of the sources specifically written about Galen, most are fairly old and tend to focus a lot on Galen's philosophies and how his ideas measure up to the different schools of thought that existed in his time rather than on his medical acclaim.  Newer and sometimes less complete sources on Galen often neglect to discuss extensively the philosophical aspect of Galen's works.  Nevertheless, both medical pursuits and philosophy were major aspects that shaped Galen's life, work, and results.  Therefore, this examination of Galen will aim to illustrate how medical, philosophical, and other influences affected Galen's work and shaped his reputation in the history of medicine.

        The influence of ancient medicine is still present in modern medicine.  Even today, despite technological, methodological, and experimental advances in medicine, many of the basic foundations in medical teachings date back to ancient times.  Hippocrates and Galen are two of the earliest and most frequently cited influences on the development of medicine.  While Hippocrates is known mostly for his contributions to patients' rights and the moral and professional obligations of physicians, Galen is still respected for his contributions to anatomy, physiology, and pharmacology and for his incorporation of philosophy, logic, and experiment with medicine.  Galen's impact on medicine was particularly profound because of his extensive and meticulous research and his relentless search for the truth.

Before Galen's Time

         For hundreds of years before Galen's time, debates existed among physicians about which philosophy of medicine was most proper.  By Galen's time, the Empiricists and the Rationalists were two of the major schools of philosophy influencing medicine and science.  Empiricists believed that a competent doctor gained knowledge by experience not by creating or following medical theories.  Others who believed that theories were necessary to supplement pure experience for adequate treatment of patients became known as Rationalists (Galen, 1985 xxii).  In the fourth and fifth centuries BCE, both Aristotle and Plato rejected the idea that science could be adequately understood and practiced by experience alone and instead preferred the use of reason to provide medical knowledge.  At this time, scholarly doctors who were extensively trained in their field studied and formulated rational theories about the human body and disease states, whereas practitioners who had gained knowledge through experience were often able to practice medicine as doctors without extensive training (Galen, 1985 xxiv-xxv).  Because trained doctors used theoretical understanding to distinguish themselves from other less qualified practitioners, the tendency of Aristotle, Plato, and other scholarly physicians to rely on medical theory over pure experience was understandable.  However, Empiricists argued that theoretical assumptions were unreliable and unverifiable, and that their method of using observable and quantifiable data to develop methods of treatment for similar classes of diseases was superior to Rationalist methods (Galen, 1985 xxv).

    Around the same time that the debate between the Rationalists and Empiricists was going on, Hippocrates, a very influential physician, produced many writings stressing the importance of examining symptoms, finding natural causes, using rational cures, and keeping records of the course of diseases (BBC [b]).  Because a religious prohibition on human dissection restricted Hippocrates and his followers' understanding of the body, they relied mostly on observable changes in the characteristics of their patients (Fishbein 9-11; Wischik).  Hippocrates' concentration on observable characteristics of disease influenced medicine beyond his own lifetime and into modern times.  Another influence that had developed around 500 BCE was the belief in Asclepius, the god of healing, who was thought to produce supernatural causes and cures for diseases.  Many people believed in both natural and supernatural causes of disease because of these two major influences (BBC [b]).  Therefore, in addition to the influences of the Rationalists and Empiricists, the belief in Asclepius and importance placed on Hippocratic teachings all helped to shape the state of medicine that Galen faced in his time around the second century AD.  Physicians were still divided by their various approaches to medicine; however, Galen took a unique approach by incorporating both Rationalist and Empiricist ideas with a respect for his predecessors and for the supernatural role in disease and healing.

Background and Training

        Galen was born around 129 AD in Pergamum, Asia Minor and belonged to a prestigious family headed by his father, Nicon, an architect (Galen, 1985 xii).  Pergamum was a wealthy city, famous as a center of learning and for its temple of Asclepius, a god of healing (Galen, 1985 xii).  While Nicon intended for Galen to study philosophy or politics, Asclepius supposedly came to Nicon in a dream and told him to allow Galen to study medicine (Pearcy).  Starting at the age of sixteen or seventeen, Galen studied medicine as he traveled to Smyrna, Corinth, and Alexandria in order to achieve a more vast and extensive knowledge of medicine (Pearcy; Galen, 1985 xii).  During this time he also studied philosophy from at least four different schools of thought in order to learn many different viewpoints so he could make up his mind about which was correct (Fishbein 22-23; Galen, 1985 xii).  Because he found both strengths and faults with many philosophies, he avoided using one method of thought exclusively.  Galen's accumulation of knowledge in many fields and his tendency to make conclusions based on facts and truth throughout his life contributed to his success and reputation.

        At the age of 28, Galen was appointed as the physician to the gladiators.  This was a prestigious position that provided him with plenty of opportunities to practice surgery techniques.  These skills were useful when he conducted numerous dissections in his later years (Fishbein 22; BBC [a]).  Several years later, Galen was summoned to be the physician to the emperors Marcus Aurelius and Commodus (Fishbein 23).  These prestigious positions helped Galen to become a part of Rome's intellectual life and contributed to his opportunities to learn and study in the most conducive environment (Pearcy).  Because Rome was a thriving academic center during Galen's lifetime, it was a prime location for him to conduct his experiments.  Galen's career, research, and teachings thrived in Rome, so he remained there until his death around 200 AD (Galen, 1985 xiii).  While Galen's fortunate background and prestigious appointments early in his career helped to strengthen his likelihood for success, the importance of his extensive and exhaustive research and writing on a plethora of topics cannot be discounted.

Beyond Medicine

    Philosophy and linguistics were major components of Galen's work and served as important tools in his medical career.  In fact, the majority of his more than 300 writings were on the subjects of philosophy, medicine, and philology, which shows that Galen was very dedicated to multiple studies (Pearcy; Nutton 1998; Galen, 1985 xiii).  Galen believed that philosophical knowledge was essential to all educated persons, especially physicians.  To Galen, philosophical knowledge included an understanding of logic, ethics, and physics (Pearcy; Weisstein; Virginia; Galen, 1985 xv-xvi).  Unlike most of his predecessors and contemporaries, Galen avoided joining any school of thought in medicine or philosophy, because he believed that the his loyalty to " 'the constant endeavor to find out what is true and to discern what is true and false in the claims made by others' " was more important than proclaiming loyalty to any one group of philosophers or physicians (Temkin 36; Fishbein 26).  This lack of loyalty allowed him to develop his own thoughts and ideas while respecting his predecessors and criticizing his contemporaries.  However, because he was not affiliated with any particular group, Galen frequently criticized his contemporaries, leaving him with the reputation of being self-admiring and argumentative (Pearcy).  Although Galen was often criticized for being arrogant because of the rigidity of his beliefs, his disregard of more common political and professional associations helped to make his perspectives unique and relatively unbiased.

        Another characteristic of Galen central to his methods and perspectives was his relentless search for truth.  Galen used meticulous dissections and sensory observations to confirm or disprove his new ideas and others' previous claims.  He believed that logic was important for demonstrating truths, but warned that it should be used carefully when trying to confirm hypotheses, because it could pervert one's conclusions (Temkin 12, 22).  Galen believed that both reason and observation served the dual purpose of helping to arrive at truths while helping to confirm truths once they were established (Galen, 1985 xxxii).  The best method of discovery according to Galen's way of thinking was to assimilate the functions of reason with the clues obtained by the senses.  Assertions by Galen himself about the importance of distinguishing fact from speculation confirm the impression of Galen as a "fanatical lover of truth who wages an unceasing battle against ignoramuses and scientific opponents" (Temkin 53).  Galen believed that his methods of ensuring accurate research results was superior to other systems, so he did not accept any way besides his own as adequate.  Nonetheless, Galen's firmly established criteria for evaluating the nature and quality of theories provided a high standard to which he held himself and others and ultimately contributed to his success.

Although Galen used some of the ideas of his predecessors, he did not hesitate to deviate from accepted theories when appropriate.  Galen believed that the authority of ancients was limited to the validity of their claims, and that, while their theories need not necessarily be replaced, they usually required clarification and progression.  His tendency to reexamine ancient science and to incorporate modified theories with his own ideas reflected his belief that progress is a cumulative process subject and knowledge is subject to verification (Temkin 31-3).  For example, Galen found it necessary to reexamine Hippocrates' work in order to uncover previously misinterpreted science (Pearcy).  He thought more accurate science was buried beneath centuries of inaccurate interpretations.  Galen adopted Aristotle's theory of the four humors, which stated that the body is composed of a balance between the four elements present on earth- fire, earth, water, and air- which were manifested in the body as yellow bile, black bile, water, and phlegm, respectively.  Further, Galen agreed with the Aristotelian notion of experiment, and he also believed in Aristotle's idea of the functional form of natural bodies, meaning that all bodies arising from nature are suited structurally for their function (Temkin 73).  Nevertheless, he branched out with his own theories regarding ideas like the residing place of the soul and the functions of major organs such as the heart, brain, and liver.  He elaborated on many old conceptions such as when he expanded the humors theory by asserting that a person's temperament could be distinguished by feeling the palm of the hand (Fishbein 25; Temkin 19, 73).  Thus, Galen's work resulted from the foundations of Plato, Aristotle, and Hippocrates and provided a comprehensive summary of medicine until his time, but also further expanded science through his own experiments (Nutton 1998; Virginia; Pearcy).

Methods and Achievements

       Anatomy was very important to Galen.  He believed that "the working body is not understandable without knowledge of its structure" (Temkin 13).  Galen did not dissect humans because of the negative social and religious stigmas associated with experimentation on the human body, but he performed dissections and vivisection experiments on many animals including apes, goats, dogs, and pigs (Fishbein 25; BBC [a]).  Because he could only study animals, some of Galen's anatomical assertions were inaccurate with respect to the humans (Wischik).  While studying animals led to some errors in his work, many more accurate observations and key ideas were uncovered through his thorough and intensive anatomical explorations.  Galen shared his knowledge of anatomy with others by carefully recording his observations and techniques so as to help " 'all seriously interested in anatomy' " while ensuring that it was written " 'as clearly as possible for those who have never seen the operations' " (Temkin 12).  Thus, although Galen's writing is very detailed and uses medical terminology, his writings were clear enough to be understood by anyone with minimal medical knowledge.  Galen's reliance on anatomy and experiment showed his belief in the value of observation in medicine.  He argued that diseases were manifestations of impaired anatomical functioning, so in order to diagnose and to treat disease, a fundamental understanding of the human structure was critical (Temkin 13).  In other words, physicians could not possibly understand a disease and its effects on the body unless they understood the layout and functioning of a normal human body.  Galen's methodology included reliance on experimental and observational results in conjunction with logic and reasoning to help elucidate concepts; his methods, in turn, became popular methods of study and research in medicine.

        Galen's experiments and the texts which describe them were very meticulous and detailed.  The care and persistence that he must have possessed surely contributed to his vast array of accomplishments.  Dedication and patience were required from Galen in order to produce the extensive volumes of writing that he did, especially when considering that he wrote each word by hand with a stylus on papyrus, without the help of a stenographer, for the sake of learning and science alone (Fishbein 26).  One of Galen's major advances was his work on the movement of blood in the body.  While he never explained how the blood circulated, he made many important discoveries regarding the movement of blood in the body, including the differences between veins and arteries and the anatomy of the heart and its associated vasculature (Weisstein; Nutton 1998; BBC [a]; Fishbein 25).  He incorrectly believed that food from the stomach was digested and taken to the liver, where it was transformed into blood (Temkin 155).  From there, Galen explained "the veins which nourish the whole body all have their origin from the vena cava...the vena cava has two subdivisions of which one makes its way ascending upwards, and the other descends downwards" (Galen, 1962 169-70).  Galen described with great detail how the veins and arteries running throughout the body nourish it with blood, but he never quite formed the link to connect the beating of the heart with the pattern of blood flow through the body.  Instead, he thought that the heart provided the vital heat of the body (Temkin 154).  The detail with which he studied the heart and blood vessels contributed to his progress with the cardiovascular system and contributed a vast amount of knowledge to medicine's understanding of this crucial process.

        Galen's precise descriptions and studies of neurological functions and anatomy also led to major breakthroughs.  Galen used dissection to explore the anatomy of the brain and spinal cord, including the spinal nerves (Galen, 1962; Nutton 1998; Fishbein 25).  Not only did he explore anatomy, but he also demonstrated the functions of nerves.  For example, Galen tied off laryngeal nerves to demonstrate their function with the voice and to relate their function to the brain (Nutton 1998).  He also showed that severing nerves at different locations along the spinal cord produced varying levels of paralysis (Temkin 14; Fishbein 25; BBC [a]).  These experiments and anatomical examinations led to the discovery of seven of the ten pairs of cranial nerves and the identification of many spinal nerves (Nutton 1998; Galen, 1962).  Galen's use of experiments to prove his theories rather than being satisfied with speculation was unique and significant to his success.  Considering that Galen had absolutely no technology to assist him and could only use his eyes and very basic instruments to carry out dissections and experiments, it is amazing that he was able to ascertain such vast amounts of knowledge about human function.

        Galen also explored many other aspects of the human body, including the eyes, tongue, larynx, fetal development, and reproductive organs (Galen, 1962).  In addition, his experiments with the kidneys showed that they were functionally related to the bladder (Nutton 1998).  Ultimately, Galen's ideas about the body were explained by his belief in three bodily systems.  The three systems consisted of the brain and nerves, the heart and arteries, and the liver and veins.  The systems were each represented by a form of pneuma, an air like substance that was considered to be essential to all life.  The pneuma physicon, or animal spirit, was present in the brain, the organ that was correctly predicted to be responsible for sensation and thought.  Pneuma zoticon, or vital spirit, was in the heart, and represented life energy.  The third system, consisting of the liver and veins, was involved with nutrition and growth and embodied the pneuma physicon, or natural spirit (Virginia; Nutton 1998; Weisstein).  Galen divided the body into these systems according to his understanding of vital human functions and how they interacted based on his exploration of many bodily functions and structures.  The systems and their corresponding pneuma contributed to his theory about the existence of the soul, a notion that eventually gained him both criticism and acclaim.

Treatment Methods and Theories

        The foundation of all of Galen's treatment methods was his belief that disease resulted from an internal imbalance of the four humors: air (blood), fire (yellow bile), earth (black bile), and water (phlegm).  Unlike Hippocrates, who believed that disease resulted from a humoral imbalance throughout the body, Galen believed that a disease-causing imbalance could be located within an organ (Nutton 1998).  Because the disease was considered to be afflicting primarily one organ or region in the body, treatments devised by Galen were able to be more precise.  Disease treatment was basically analogous to the Hippocratic method of treating with contraries; that is, by providing or removing opposing humors to correct the imbalance with which the patient was suffering (Temkin 18; BBC [a]).  While treatment by contraries seems simplistic according to modern views, current research supporting the role of neurotransmitter levels in moods and some mental and physical diseases shows that perhaps Galen had a better understanding of the body and disease than was initially believed (Wischik).  The use of opposites to treat diseases was undertaken by pharmacological agents or other "balancing" procedures, like bloodletting or purging.

    Drugs developed by Galen were made from herbs that he collected from all over the world (Fishbein 26).  The drugs were classified by their properties- heating, cooling, drying, or moistening- and were applied so as to counteract whatever humor disproportion existed.  Galen improved the use of drugs by establishing different degrees of potency to treat varying levels of dysfunction (Temkin 20, 112).  This was critical because now patients' afflictions were being treated more specifically and uniquely based on their particular symptoms and levels of distress.  Proper medicinal dosing is still a crucial aspect of modern medicine that was started by Galen nearly two thousand years ago.

        While most of the drugs and other methods of treatment popularized by Galen were used up until the seventeenth century, virtually none of these treatments were employed in more modern times.  One exception, however, was the practice of monitoring the pulse.  Galen was the first physician to use the pulse as an indicator of illness when compared to the normal pulse.  Galen used pulse observations to diagnose diseases and symptoms such as fevers (Temkin 165; BBC [a]).  Although the pulse measurement was one of the only treatments methods of Galen's that survived, Galen also furthered medical methods by starting the trend toward determining potency and doses of medicines, which is still fundamental in medicine of today.

Beyond Galen's Lifetime

        Galen achieved notoriety during his lifetime, and his ideas and writings lived on for about 1400 years after his death.  His texts were kept alive primarily by the Arabs until they were retranslated in Europe in the Middle Ages (Nutton 1998; Nutton 2000).  One of the crucial causes of this endurance was that Galen's concepts coincided, for the most part, with Christian beliefs.  Of great importance was Galen's assertion that human organs were suited for their function; this notion fit in with the Christians' "belief in a system ordained by nature" (BBC [a]).  In addition, although Galen was not Christian, his writings expressed his belief in one god and in the body as an instrument of the soul (Virginia).  Galen argued that three aspects of the soul existed, each coinciding with the functions of one of the three systems.  Because Galen's ideas were based on monotheistic beliefs that included the existence of a soul, his ideas concurred with Christians' system of beliefs.  Further, because Galen neglected to discuss the soul beyond its existence, it was subject to individual interpretation (Temkin 44, 171).  This vagueness regarding particulars about the mortality and nature of the soul sometimes helped his ideas to be accepted, but also made him and the physicians who followed his methods subject to criticism and to accusations that they were atheists (Temkin 169-71).

        Regardless of the religious approval or disapproval of Galen, his theories and writings remained prominent until the Renaissance.  During this time, Galen's works were reexamined and studied.  In particular, physicians found a new respect for Galen's emphasis on the identification and curing of illnesses and on detailed investigations of the body.  The importance he placed on anatomy and verification of science led his followers to create a surge in inquiries about bodily structure and function.  Ironically, Galen's own encouragement of experiment ultimately led to the overthrow of most of his ideas as Renaissance physicians found the flaws in Galen's work and developed new theories and medical techniques to replace or revise the older ones (BBC [a]; Nutton 1998; Nutton 2000).  Despite new developments and understanding of the body, Galenic practices and remedies lived on for some time because, even though the concepts behind the treatments had been proven wrong or partially inaccurate, the physicians still believed that Galen's methods were effective (Temkin 165).  And while Galen's practices, too, were eventually overturned and replaced with more modern therapies, Galen's influence on medicine was still crucial to modern medical science.  The progress Galen made in his lifetime was astonishing, especially because he managed to influence medicine and philosophy simultaneously in dramatic ways.

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