The Greatest Benefit to Mankind. Roy Porter

to reasoning. For him, anatomy proved the truth of Plato’s tripartite soul, with its seats in the brain, heart and liver; and Aristotelian physics with its elements and qualities explained the body system.

      Philosophy should promote medicine, Galen taught, though the physician must master philosophy – logic (the discipline of thinking), physics (the science of nature), and ethics (the science of action). Philosophy and medicine were thus counterparts: the best doctor was also a philosopher, while the unphilosophical healer (the Empiric) was like an architect without a plan. A good physician would practise for the love of mankind, while accepting his due rewards in fame and fortune.

      The patient’s trust was essential in the healing process. It could be won by a punctilious bedside manner, by meticulous explanation, and by mastery of prognosis, an art demanding experience, observation and logic. Galen brought psychosomatic conditions to light, including uneasiness amongst defendants in court cases or those whose pulses raced through guilty passions.

      Galen prided himself on being more than a fine clinician; he was a medical scientist. He performed dissections, mainly of apes, sheep, pigs and goats and even of an elephant’s heart, but not of humans. He knew much skeletal anatomy, but, dissection being out of the question, little internal human anatomy. Two mistakes were particularly critical for the future. Dissections of calves revealed a network of nerves and vessels, the rete mirabile at the base of the brain, earlier found by Herophilus, which he assumed also existed in humans. This, he said, was the site where the vital spirits in the arteries turned into animal spirits. He also misleadingly described the liver (which he believed to be the source of the veins) as grasping the stomach with its lobes as if by fingers, an image derived from dissection of pigs or apes. Forced to apply animal findings to humans, his human womb also had cotyledons like a dog’s. Such mistakes aside, his explanations of anatomical phenomena in terms of the teleology of a divinely ordered universe were internally coherent and provided a rational basis for further investigation.

      Gross anatomy and experiments offered paths to understanding, but Galen did not restrict himself to sensory perceptions. By combining his observations with Platonic speculations about the macrocosm at large, he formulated models of concealed bodily structures. Each part functioned only when its basic elements were properly adapted, and any change would result in functional failure or disease. The unknown was thereby explained in terms of a structural/functional physiology. His systematizing zeal was both a boon and a bane.

      Galen presented his work as ‘perfecting’ Hippocrates’ legacy, and this gives his oeuvre a remarkable unity, fusing the clinical and the theoretical. Take his writings on fever: fever might result from either an excess of yellow bile, black bile or phlegm (a condition he called cacochymia), or from an excess of blood (plethora). Surplus humours might accumulate in some bodily part where they would cause putrefaction and excessive heat or fever. To remove such superfluities and restore humoral balance, he advocated energetic blood-letting. The physician should let blood from a patient not only when he was ill but prophylactically, whenever a fever was on the cards. Indications were given of when and how much blood to draw, depending on the patient’s age and constitution, the season of the year, the weather and the place. Instead of the earlier Hippocratic treatment of fevers by starvation, Galen urged venesection (letting blood from the veins) to cool the body.

      He justified blood-letting in terms of his elaborate pulse lore. Written in the early 170s, his sixteen books on the pulse were divided into four treatises, each four books long. The first, On the Differences between Pulses, displayed his learning, logic and linguistic skills. In the next four books On the Diagnosis of Pulses, he explained how to take the pulse and interpret it, raising key questions. How was it possible to tell whether a pulse was ‘full’, ‘rapid’ or ‘rhythmical’? Such questions he resolved partly from experience and partly by reference to earlier authorities.

      On the Causes of Pulsation addressed anatomy. Although Galen was convinced, pace Erasistratus, that arteries contained blood from the heart, his idea of pulsation was quite different from ours. The heart and the artery contracted simultaneously and arterial expansion and contraction were separate, active movements. In contraction, superfluities were expelled; in expansion, atmospheric air was taken in to cool things down and, by mixing with blood in the heart, to generate vital spirits (pneuma). It was this vital spirit which was mainly responsible for creating the pulsative power within the coats of the artery.

      Blood, Galen taught, was made in the liver, incorporating ingested foods in the form of chyle; it then moved to the extremities carrying natural spirits which supported the vegetative functions of growth and nutrition. This dark venous blood, passing from the liver to the right ventricle of the heart, divided into two streams. One passed to the lungs via the pulmonary artery; the other crossed the heart through ‘interseptal pores’ into the left ventricle, where it mixed with pneuma (air), became heated, moved thence from the left ventricle to the aorta, and finally to the periphery. His belief that the veins originated in the blood-making liver, carrying nutrition to the parts whenever needed, while the arteries originated in the heart, was one of the errors in his model of the circulatory system which, after dominating medicine for well over a millennium, was challenged by Renaissance anatomy.

      From a clinical standpoint, Galen was principally concerned to teach the doctor to read the various pulse phenomena. This he provided in the final part, On Prognosis from the Pulse, where he adopted a double strategy. The first two books described the complaints a specific pulse type might betray: for example, the ‘double-hammer pulse’ was a frequent sign of heart weakness. The last books detailed the sort of pulse found in specific disorders: for example, in hectic fevers the pulse increased in frequency and rapidity.

      Whatever the disorder – even blood loss – Galen judged bleeding proper. All depended on knowing where and when to do it, and how much blood to take. For severe conditions he recommended phlebotomy twice a day; the first should be stopped before the patient fainted, but the second time the physician could bleed as far as unconsciousness. Convinced that nature prevented disease by discharging excess blood, he pointed out that menstruation spared women many diseases – gout, epilepsy, apoplexy – to which males were prone. The quantities of blood he removed were large, and would often, to our thinking, have been harmful. His teachings on plethora and venesection remained influential until the nineteenth century.

      Galen took clinical Hippocratic medicine and set it within a wider anatomo-physiological framework. In broad terms this built on the Platonic doctrine of a threefold division of the soul, which distinguished vital functions into processes governed by vegetative, animal, and rational ‘souls’ or ‘spirits’. Animal life was possible only because of the existence of pneuma. Within the human body, pneuma (air), the life breath of the cosmos, was modified by the three principal organs, the liver, heart and brain, and distributed by three types of vessels: veins, arteries and nerves. Pneuma, modified by the liver, became the nutritive soul or natural spirits which supported the vegetative functions of growth and nutrition; this nutritive soul was distributed by the veins. The heart and arteries were responsible for the maintenance and distribution of innate heat and pneuma or vital spirits to vivify the parts of the body. The third alteration, occurring in the brain, ennobled vital spirits into animal spirits, distributed through the nerves (which Galen thought of as empty ducts) to sustain sensation and movement.

      For Galen, anatomy, logic and experience fitted together. Not least because he had an explanation for everything, Galenic medicine proved monumental, as he intended it should:

      I have done as much for medicine as Trajan did for the Roman Empire when he built bridges and roads through Italy. It is I, and I alone, who have revealed the true path of medicine. It must be admitted that Hippocrates already staked out this path … he prepared the way, but I have made it passable.

      MEDICINE IN THE AGE OF GALEN

      Personal in Greece, medicine remained personal in Rome. No medical degrees were conferred or qualifications required. In the absence of colleges and universities, the private, face-to-face nature of medical instruction encouraged fluidity and diversity; students attached themselves to an individual teacher, sitting at his feet and accompanying