Erasistratus

Greek physician

• Born: c. 304 b.c.e.
• Birthplace: Iulis, Island of Ceos (now Keos, Greece)
• Died: c. 250 b.c.e.
• Place of death: Unknown

Erasistratus made numerous physiological and anatomical discoveries, perhaps using an exceptional combination of human and animal dissection (and possibly vivisection) to explore the structure and workings of the human body.

Early Life

Already during his childhood on the rocky, forested Aegean island Ceos (now Keos), Erasistratus (er-ah-SIHS-trah-tuhs) was no stranger to medicine. His father, Cleombrotus, was a physician, as was his mother’s brother Medius (or Medias). His brother, Cleophantus, joined this family tradition as well. Erasistratus apparently left Iulis for apprenticeships, perhaps with the doctor Metrodorus (whom one ancient source identifies as the third husband of Aristotle’s daughter Pythias) and Metrodorus’s teacher Chrysippus of Cnidus, whom Erasistratus regarded as his main mentor. He may also have attended lectures by Theophrastus, Aristotle’s successor as leader of the Peripatetic school of philosophy in Athens, and come under the philosophical influence of Theophrastus’s successor, Strato of Lampsacus, but this remains a matter of dispute.

Where Erasistratus subsequently practiced and conducted his research has become a controversial issue, but the ancient evidence suggests that he was at the court of the Seleucid rulers in Syrian Antioch (founded on the Orontes River in 300 b.c.e.) for at least some time in the late 290’s. Several ancient sources report that Erasistratus cured a mysteriously ill, suicidal Antiochus (the future King Antiochus I Soter) in Antioch. Through imaginative observation of the patient’s face, demeanor, heart, and pulse, it is said, the physician correctly diagnosed that young Antiochus was in love with his stepmother Stratonice. Erasistratus subtly persuaded Antiochus’s father, King Seleucus I Nicator, to give up Stratonice in order to save his son; the king promptly arranged the marriage of his wife and son.

Whether Erasistratus also practiced in Alexandria, as many modern historians have assumed, is less certain. No ancient evidence explicitly confirms his presence in Alexandria, but there is suggestive indirect evidence that he may have worked in Alexandria for at least some time during the lifetime of Herophilus.

Life’s Work

Erasistratus’s ingenuity as a physiologist overshadows his anatomical discoveries, but the two are closely linked. By dissecting animals—and possibly, like his brilliant contemporary Herophilus, by dissecting and vivisecting humans, as one ancient source claims—Erasistratus made major anatomical and physiological discoveries. Among his achievements, two, in particular, won high praise from later authors. First, he described the heart valves (more accurately than did Herophilus), noting the irreversibility of the flow through the valves and detailing the heart’s pumping action. Second, his account of the brain includes descriptions of its four ventricles, the convolutions of the cerebrum and the cerebellum (which he linked to humans’ superior intelligence), and the origin of the nervous system in the brain (or, as Erasistratus originally believed, in the dura mater, the outermost and toughest of the three membranes covering the brain and the spinal cord).

Three strikingly consistent features of Erasistratus’s physiology are his use of mechanical principles rather than Aristotelian innate powers or invisible “faculties” to explain processes in the body, his willingness to verify hypotheses by means of experiments, and a teleological perspective (which he shared with Aristotle and others). In his version of the vascular system, the veins contain only blood, whereas the arteries transport only pneuma, a warm, moist, airlike substance ultimately derived from the atmosphere by respiration. From the lungs the “veinlike artery”—that is, the pulmonary vein—carries pneuma to the left ventricle of the heart, where it is refined into “vital” (life-giving) pneuma before being pumped into the arteries. If, however, the arteries contain only an airlike substance, how did Erasistratus account for the fact that blood flows from a punctured artery? Resorting to one of his favorite mechanical principles, he argued that when the artery is cut, its pneuma escapes, creating an empty space into which blood instantly rushes from the adjacent veins (veins being connected to the arteries throughout by means of synanastomōseis, or capillarylike communications). The underlying mechanical principle—“following toward what is being emptied,” later called horror vacui —is that if matter is removed from a contained space, other matter will inevitably enter to take its place, because a natural massed void or vacuum is impossible. It is, therefore, blood from the veins, not from the artery, that escapes when a lesion of an artery occurs.

Erasistratus’s similarly mechanical explanation of the pulse is closer to the truth than his view of the content of the arteries. Whereas Herophilus believed that a “faculty,” flowing from the heart to the arterial coats, draws or pulls a mixture of blood and pneuma from the heart into the arteries when they dilate, Erasistratus recognized that the heart functions as a pump: Every time the heart contracts, according to his account, its left ventricle pushes pneuma through a one-way valve into the aorta and the whole arterial network, causing the arteries to dilate. Because the left cardiac ventricle is empty after contraction, pneuma from the lung rushes into it again as it dilates, in accordance with the horror vacui principle, and thus the cycle continues, the systole of the heart always being simultaneous with the diastole of the arteries. Once in the arteries, the pneuma cannot return to or through the heart because of the one-way valves. After circulating through the arteries and providing the body with air, the pneuma apparently passes out of the body through the pores, making room for the fresh pneuma constantly being pumped into the arteries.

Erasistratus tried to prove experimentally that it is the heart, functioning as a pump, that causes pulsation, rather than some invisible “pulling” faculty in the arterial coat. After exposing an artery in a living subject, he tied a ligature around the artery. Below the ligature he made a lengthwise incision in the artery, into which he inserted a tube or hollow reed. The incised section of the artery was then ligated, with linen thread wound all around the tube and the surrounding tissue. When the ligature above the tube was undone, Erasistratus claimed, the pulse could be observed below the tube as well as above it, proving that the content of the arteries, pumped in by the heart, causes the pulse. The pulse could not, then, be attributed to a faculty in the incised, ligated, and hence “interrupted” coats of the arteries. (Galen, who reports this experiment, claims that he repeated it with opposite results.)

The central blood-making organ of the body, according to Erasistratus, is not the heart but the liver, where digested food finally is converted into blood. From the liver blood is carried as nourishment for the entire body through the veins. The largest vein in the body, the vena cava, carries blood into the right side of the heart through the tricuspid valve to nourish the heart. From the heart blood flows to the lungs through the pulmonary valve and pulmonary artery, or, as Erasistratus called it, the “arterial vein.” The liver, however, cannot in and of itself account for the flow of the blood, since it has no pushing or pulling motion of its own. It is possibly for this reason that Erasistratus described the heart as the archē (origin, principle, or rule) not only of the arteries but also of the veins, despite his regarding the liver as the central blood factory. “The heart itself,” Galen reports Erasistratus saying, after each contraction “expands like a blacksmith’s bellows and draws in matter, filling itself up by its dilation.” The horror vacui principle thus renders the heart responsible for the movement of blood into and from the heart and consequently, it would seem, for the motion of all blood through the veins, just as it is for the movement of pneuma through all the arteries (although blood is also absorbed into tissues throughout the body, thus creating space for fresh blood in the veins).

The nervous system, muscular activity, respiration, appetite, digestion, and the vascular system are all united by Erasistratus in a brilliantly coherent and comprehensive physiological model. External air moves into the lungs through the windpipe and bronchial ducts when the thorax expands. While the air (pneuma) is in the lungs, the left ventricle of the heart draws some pneuma into itself by its own expansion or diastole, contributing to the cycle described above. Excess air, having absorbed some of the superfluous body heat produced by the heart, is then exhaled by the lungs as the thorax contracts, after which the thorax expands once again, drawing in fresh air. The breathing cycle of the lungs thus both cools the body and provides the arteries with the pneuma they need for the body’s life and health, whereas appetite and digestion—both of which are similarly explained in terms of the horror vacui principle—along with the liver, provide the veins with the food-derived nourishment that the body needs.

The nerves, like the arteries, carry pneuma that is ultimately derived from respiration, but it is a more highly refined version of air. Some of the vital pneuma produced in the left ventricle of the heart is carried by the arterial system to the brain, where it is refined into “psychic” pneuma, which in turn is distributed to the body through the nerves emanating from the brain. Not unlike Herophilus, Erasistratus distinguished between sensory and motor nerves; in his system, it is presumably by means of psychic pneuma that data and impulses are transmitted through the nerves to and from the brain.

Voluntary motion takes place through the muscles, which—like the nerves and perhaps all organic structures in the body—consist of triple-braided strands of veins, arteries, and nerves. Pneuma carried to the muscles by the arteries or nerves endows them with the ability to contract or relax—that is, to increase their width while simultaneously reducing their length, or vice versa, the speed of the muscular motions standing in direct relation to the amount of pneuma in the muscle at a given time.

Erasistratus’s efforts in pathology were marked by some innovation as well. He emphasized three related causes of disease that, though not entirely inconsistent with humoral and other earlier theories, introduce some new perspectives. Plethora or hyperemia is a condition marked by excessive blood-nutriment in the veins, which can cause swollen limbs, diseases of the liver and stomach, epilepsy, spleen and kidney ailments, fever, inflammation, blockage of the arteries, and mental disorders (in part because excessive blood in the veins can spill over into the arteries through the synanastomōseis between veins and arteries, thus impeding the flow of vital pneuma). Second, disease can result from other disturbances of the arterial flow of pneuma, such as when blood enters a punctured artery (horror vacui) and some of it remains trapped in the artery after the wound has healed. Third, digestive dysfunctions cause the presence of sticky, bad moistures in the body that give rise to ailments such as apoplexy and paralysis. In Erasistratus’s system, all bodily malfunctions, like all functions, must be understood in terms of the actions and interactions of matter, whose ultimate constituents are solid, possibly atomlike particles. Numerous diseases, their symptoms, and their causes were described by Erasistratus; his works, which are all lost, addressed subjects such as dropsy, diseases of the abdominal cavity, and fevers.

Significance

In his Hoi katholou logoi (general principles) and other lost works, Erasistratus succeeded in accounting for practically all bodily functions within a single explanatory model whose economy, coherence, and scope are unmatched in antiquity except perhaps by those of Aristotle and Galen. Especially striking is his amalgam of mechanical principles and teleology. The latter is expressed in his Platonic-Aristotelian view of nature as a supreme artisan, whose providential care for living beings is revealed in the perfection and beautiful purposiveness of every part of the human body. Erasistratus’s anatomical discoveries were, however, not as numerous as those of Herophilus, and there are some weak links in his system, such as his reproductive theory.

Bold in his theories, Erasistratus advocated restraint in practice. He assigned higher priority to preventive hygiene, on which he wrote a treatise, than to therapeutics, which, along with the study of symptoms, he regarded as a merely “stochastic,” or conjectural, venture (in contrast to etiology and physiology). Proper treatment of patients requires the clear identification of the causes, both proximate and ultimate, of their diseases, as well as an individualized, mild therapy. Opposed to drastic cures, he also rejected the tradition of therapeutic bloodletting in all but a few cases, thereby provoking the notorious ire of Galen, who wrote an entire treatise against Erasistratus’s views on bloodletting (and another against the Erasistrateans of Galen’s own time, who were defending their patriarch). Instead of bloodletting, Erasistratus advocated drawing off morbid substances through fasting, vomiting, and inducing perspiration as well as through urine, plasters, poultices, steam baths, fomentations, fairly conventional dietary prescriptions, and exercise.

For all of their theoretical differences, Erasistratus and Herophilus shared this combination of theoretical audacity and clinical restraint, exceptional scientific originality and pragmatic conservatism. To a greater degree than in the case of Herophilus, Erasistratus’s views—as transmitted through fragments and secondhand reports, since none of his works is extant—were met with the polemics of Galen. Even a hostile Galen could not refrain from repeatedly acknowledging Erasistratus’s significant stature in the history of medicine. Galen also recognized his enemy’s scientific honesty: Even in old age, he reports, Erasistratus stood ready to correct his errors in the light of fresh observations. In his search for a better understanding of the human body, the great theorist did not allow the systematic coherence of his theories to stand in the way of his own scientific progress.

Bibliography

Galen. Galen on Bloodletting. Translated by Peter Brain. New York: Cambridge University Press, 1986. Includes translations of Galen’s works against Erasistratus and the Erasistrateans, with extensive annotations.

Galen. On Respiration and the Arteries. Edited by David J. Furley and J. S. Wilkie. Princeton, N.J.: Princeton University Press, 1984. Pages 26 to 37 offer an excellent introduction to Erasistratus’s views on respiration, the heart, and the arteries. The volume also includes an annotated translation of three Galenic works that are important sources for Erasistratus’s physiology.

Galen. Three Treatises on the Nature of Science. Translated by Michael Frede and Richard Walzer. Indianapolis, Ind.: Hackett Publishing, 1985. A useful source for aspects of Erasistratus’s theory of scientific method and his epistemology.

Harris, C. R. S. The Heart and the Vascular System in Ancient Greek Medicine. Oxford, England: Clarendon Press, 1973. Chapter 4 presents the most extensive analysis available of Erasistratus’s description of the vascular system, with some attention to his theories of respiration and the nerves.

Jackson, Michael, and Amy Norrington. “An A to Z of Medical History: Part 1.” Student British Medical Journal 10 (September, 2002): 317. This exploration of the history of medicine covers Erasistratus and his dissection techniques.

Lloyd, G. E. R. “A Note on Erasistratus of Ceos.” Journal of Hellenic Studies 95 (1975): 172-175. Argues against Fraser (see above) that Erasistratus performed human dissection, was an outstanding anatomist, and worked for at least some time in Alexandria.

Lloyd, G. E. R. Science, Folklore, and Ideology. Indianapolis: Hackett, 1999. Excellent observations throughout, especially on the standardization of anatomical terminology.

Pope, Maurice. “Shakespeare’s Medical Imagination.” Shakespeare Survey 38 (1985): 175-186. Traces the influence of Erasistratus’s physiology on Renaissance poetry.

Smith, W. D. “Erasistratus’s Dietetic Medicine.” Bulletin of the History of Medicine 56 (1982): 398-409. Argues that attention to Erasistratus’s own words, in the literal fragments preserved by Galen and others, reveals a less revolutionary, less contentious, and more conventional Erasistratus than the one suggested by Galen’s polemics. Shows that his dietetics was a conservative development of an earlier tradition.

Von Staden, Heinrich. “Experiment and Experience in Hellenistic Medicine.” Bulletin of the Institute of Classical Studies 22 (1975): 178-199. Relates the growth and decline of experimentation in Erasistratus’s century to changing theories of scientific method; includes a close analysis of some of Erasistratus’s experiments.