Hektoen International

A Journal of Medical Humanities

The two Sylvius anatomists

Buried deep in the cobwebs of medical history lies the persisting misconception that a single person called Sylvius made important advances in the discipline of anatomy. But in fact, there were two persons remembered by that name. There was Jacobus, whose name is most commonly linked to the Aqueduct of Sylvius, and there was Franciscus, who is generally associated with the Sylvian Fissure.1 To this very day the men are frequently confused with one another, as well as having their names linked to anatomical structures already described earlier by others. Other obscure anatomical structures also bear the name of Sylvius.1

Jacobus Sylvius (1478–1555)1,2

Portrait etching of Jacobus Sylvius (Jacques Dubois), a man in a large hat facing right
Jacobus Sylvius (Jacques Dubois). Via Wikimedia.

Remembered by the Latinized name Jacobus, this Sylvius has his name linked to the aqueduct or narrow conduit that connects the third and fourth ventricles of the brain and was already described by Galen in the second century AD. By what one could call a reversal of fortune, the valve in the inferior vena cava that Jacobus Sylvius described is called the Eustachian valve.

Jacobus Sylvius was born near Amiens in France, and his original name was Jacques Dubois. After studying the classics and mathematics, he switched to medicine, obtained his medical degree from the University of Montpellier, and became a physician and anatomy instructor in Paris, later a professor at the University of Paris. He was the first in France to teach anatomy by dissecting human cadavers and is credited for using names we still use today, instead of numbers, to designate muscles and blood vessels, such as the biceps, triceps, jugular, phrenic, axillary, renal, mesenteric, femoral, and popliteal.

Though progressive in these respects, Jacobus Sylvius clung to many of the antiquated concepts promulgated by the Greek physician Galen, whose writings he idolized and which brought him into conflict with his younger pupils. He became embroiled in an argument with his former pupil, Andreas Vesalius, and carried the dispute so far as to later write to his employer, the Holy Roman Emperor Charles V, asking him to punish severely “this worst example of ignorance, ingratitude, arrogance, and impiety, to suppress him so that he may not poison the rest of Europe with his pestilential breath.”

Jacobus Sylvius was regarded as the foremost anatomist of his time. He was an effective teacher but was not liked. He was stingy, intolerant, and vindictive, feeding his servants only bread and water, and refusing to keep a fire going during the notoriously cold Parisian winters. In his later years his students ridiculed him, and he tends to have become forgotten largely because of his personality.

Franciscus Sylvius (1614–1672)3

Portrait etching of Franciscus Sylvius (Franz de le Boë), a man with curly hair under a small cap
Franciscus Sylvius (Franz de le Boë). Rijksmuseum. Via Wikimedia.

This was the nice Sylvius, Franciscus. Born in Hanau, Germany, as Franz de le Boë almost 150 years after his namesake Jacobus, he came from a Du Bois Protestant family that originally lived in Cambrai and left France for religious reasons.3 He studied in various universities in Europe, and after briefly practicing medicine in his hometown of Hanau, moved to the Netherlands in 1639 and became lecturer in anatomy in Leiden. After 1641 he had a successful practice in Amsterdam. He returned to Leiden in 1658 as a professor of anatomy, working for an unusually high annual salary of 1,800 guilders, twice the going rate at the time. But he was popular with students, whom he attracted from all over Europe, and was one of the first doctors to have them accompany him on ward rounds and to teach by the Socratic method of questions and answers.3 He promoted the study of anatomy by dissection, described the dural venous sinuses, and was an enthusiastic supporter of William Harvey’s (1604–1649) new theory of the circulation of the blood, using dogs to demonstrate its validity.1

Franciscus Sylvius founded a school of thought known as “iatrochemistry,” which proposed that all physical events in the body, including diseases, were based on chemical reactions, such as between acids and bases, and he developed theories to explain how this came about. He arranged for the construction of one the first university chemistry laboratories and recognized scrofula as a form of skin tuberculosis. His interest in chemistry resulted in his playing a part in the history of gin in that by mixing juniper berries, herbs, and alcohol he created a medicine for heartburn, digestive problems, and disorders of the kidney and liver. This was marketed as “genever,” a name derived from the Dutch name for juniper and later changed in England to “gin,” becoming exceedingly popular there, cheaper than beer, and consumed in huge amounts during the “gin craze.”

After Franciscus Sylvius died, one of his students, Bartholinus, credited him in 1641 with having described the lateral fissure or sulcus separating the frontal and parietal lobes of the brain from the inferiorly located temporal lobe of the brain. This is still named the Sylvian fissure, though described earlier by Fabricius d’Acquapendente, by Berengerius Carpensis in 1521, and probably by Erasistratus and Herophilus in antiquity.1


Both anatomists remembered by posterity as Sylvius were distinguished professors who made significant contributions to anatomy. But they also illustrate the hazards of using eponymous names, especially in anatomy, and of attributing discoveries and new advances to the wrong person.


  1. Barclay Bakkum. A historical lesson from Franciscus Sylvius and Jacobus Sylvius. J Chiropr Humanit 2011 Dec;18(1):94-98.
  2. Jacobus Sylvius (Jacques Dubois) 1478-1553—Preceptor of Vesalius. Editorial. JAMA 1966;195(13):1147.
  3. JMS Pearce. The fissure of Sylvius (1614–72). J Neurol Neurosurg Psychiatry 2000;69(4):463.
  4. Efrain Miranda. Jacobus Sylvius. Medical Terminology Daily. April 21, 2014. https://clinicalanatomy.com/mtd/589-jacobus-sylvius.

GEORGE DUNEA, MD, Editor-in-Chief

Winter 2023



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