In 1541, while in Bologna, Vesalius uncovered the fact that all of Galen's research had been based only on animal anatomy since dissection of humans had been banned in ancient Rome.
Previously Vesalius' topics had been taught primarily from reading classic texts, mainly Galen, followed by an animal dissection by a barber-surgeon whose work was directed by the lecturer.
In 1543, Vesalius asked philologist Johannes Oporinus to help him publish the seven-volume De humani corporis fabrica (On the fabric of the human body), a groundbreaking work of human anatomy.
Vesalius was only 30 years old when the first edition of Fabrica was published.
Over the next 12 years, Vesalius traveled with the court, treating injuries from battle or tournaments, performing surgeries and postmortems, and writing letters addressing specific medical questions.
Vesalius, on the other hand, carried out dissection as the primary teaching tool, handling the work himself while his students clustered around the table.
Born in Brussels, Vesalius studied at the University of Paris and received his medical degree at the University of Padua, where he became a lecturer on surgery.
After the abdication of Charles, Vesalius continued at court in great favor with Charles' son Philip II, who rewarded him with a pension for life and by being made a count palatine.
Until Vesalius pointed this out, it had gone unnoticed and had long been the basis of studying human anatomy.
In 1539, a Paduan judge became interested in Vesalius' work and made bodies of executed criminals available to him for dissection.
Vesalius' pamphlet supported Galen's view, and supported his arguments through anatomical diagrams.
In 1538, Vesalius also published a letter on bloodletting, which was a popular treatment for almost any illness.
In 1543, Vesalius conducted a public dissection of the body of Jakob Karrer von Gebweiler, a notorious felon from the city of Basel, Switzerland.
Vesalius challenged the prevailing idols of his era: Galen and Aristotle, often at grave risk to his reputation and professional career.