Herophilos and Erasistratos: Advances in Anatomy
In the fourth century BCE, the locus of medical thought and practice was not Cos, the island home of Hippocrates. Instead, it was the great center of Greek learning at Alexandria, founded in 331 BCE by Alexander the Great and governed by a dynasty stemming from his general Ptolemy. The Ptolemaic rulers gave lavish financial support to the library and museum at Alexandria, which consequently attracted researchers in all fields. Medical research in the Alexandrian museum became world renowned. Two of its most influential investigators were Herophilos of Chalcedon (fl. circa 280 BCE) and Erasistratos of Iulis (fl. 250 BCE). Most of our knowledge of their work is derived from later commentators in the Roman period, such as Celsus and Galen.
Herophilos is remembered primarily for his contributions to the study of human anatomy, on which he composed several treatises, including On Dissections. We know he made a careful study of the brain which, against the view of Aristotle, he recognized as the center of of the nervous system. A number of the terms he coined passed into anatomical vocabulary, either directly or via their Latin translations.
In dissecting the brain, Herophilos applied the epithet chorioeides, “like the chorion,”to the meninges, because he thought of them as like two membranes, chorion and amnion, which envelop the fetus in the womb. His line of thought survives in the Latin expressions which we still use. In his account of the blood vessels of the brain, Herophilos identified the confluence of the sinuses, which he called the “wine press”(lenos) and which anatomists after him called the tocular Herophili.
He dissected the eye and distinguished its principal membranes; he likened one of these membranes to a retiform, a Greek word meaning “net-like.” We still call this membrane the retina. Another term he successfully coined is duodenum, the Latin translation of the Greek dodekadaktylon, (“twelve fingers long”), supposedly representing the average length of this portion of the human intestine.
Herophilos’s most important contribution to clinical medicine was his theory of the diagnostic value of the pulse. Although the pulse is referred to occasionally by earlier writers (for example by Aristotle in his Inquiry Concerning Animals, 521a5f), it was Herophilos’s teacher, Praxagoras, who first restricted the pulse to a distinct group of vessels and held that it could be used as an indicator of disease.
Herophilos corrected his master’s teaching on several points. He maintained that the pulse is not an innate faculty of the arteries, but one they derive from the heart. He also distinguished the pulse not merely quantitatively, but also qualitatively, from palpitations, tremors and spasms, which are muscular in origin.
Herophilos elaborated a far-reaching doctrine of the pulse. The essential phenomenon in the pulse, according to Herophilos, is rhythm, as in music. To understand the pulse, then, we must study the theory of music. Herophilos was chiefly guided by the musical theories of Aristoxenus of Tarentum, a Peripatetic philosopher and a musician, a pupil of Aristotle. Following this route, the doctrine of the pulse became so complicated that no one but a skilled musician could possibly understand it.
When we reflect that Herophilos had no accurate means of timing the pulse-rate, his attempt to develop a systemic theory of pulse is astonishing. As Galen (K IX 464) reports: “as the musicians establish their rhythms according to certain definite arrangements of time-periods, comparing arsis and thesis with one another, i.e. the upward and downward beat, so Herophilos supposed that the dilation of the artery corresponds to arsis and its contraction to thesis.”
This idea borrows elements of Pythagoreanism, a sect of philosophy which held that numbers rule the universe. Thus, the stars move through the firmament at fixed distances, and their harmony corresponds to the tonal intervals on a music scale. The human body is also arranged according to musico-mathematical rules. Herophilos attempted to discover these rules, to reduce the rhythm of the pulse to mathematically expressible relations analogous to musical theory. Although this project was doomed to failure, Herophilos’s insistence on the importance of the pulse in diagnosis was of lasting value.
Erasistratos, Herophilos’s rival at Alexandria, made remarkable progress in anatomy, describing the brain even more accurately than Herophilos. He distinguished the cerebrum from the cerebellum, and determined that the brain was the origin for all nerves. He distinguished sensory from motor nerves and was the first to dispel the notion that nerves are hollow and filled with pneuma (air). Instead, he averred that they are solid, consisting of spinal marrow. In his account of the heart and its function, he distinguished between pulmonary and systemic circulation.
Antiochus, son of Seleucus I Nicator, King of Syria, was dangerously ill, and, when other physicians failed to help him, Erasistratos was called in. While he was examining the patient, Stratonice, one of the elderly king’s wives and a young woman, entered the room. From the quickening of the sick man’s pulse and from the flush which spread over his cheeks, the doctor recognized that the illness was mental rather than physical—that a passion for his inaccessible stepmother was at the root of the problem.
Dissection and Vivisection
In Alexandria the dissection of corpses was a regular practice, whereas before the fourth century BCE it had been condemned and outlawed on religious principle. Celsus had also publicized a rumor that the anatomists used living people, most likely condemned criminals, in vivisection.
We can credit the philosophical teachings of Aristotle for changing the minds of learned men regarding dissections. First, Plato had taught that the soul was an independent and immortal being, which carried the body as a mere envelope and instrument to be discarded at death. Aristotle declared that the soul constituted a higher value than the whole organism, implying that after death nothing remained but a physical frame, without feelings or rights. Therefore, one could justly claim a dead body for dissection and anatomical study.