The human anatomy references used by doctors through the year A.D. 1500 were actually based mostly on animal studies, more myth and error than truth.
Andreas Vesalius was the first to insist on dissections, on exact physiological experiment and direct observation, scientific methods, to create his anatomy guides. His were the first reliable, accurate books on the structure and workings of the human body.
Versalius’s work demolished the long-held reliance on the 1,500-year-old anatomical work by the early Greek, Galen, and marked a permanent turning point for medicine. For the first time, actual anatomical fact replaced conjecture as the basis for medical profession.
Andreas Vesalius was born in Brussels in 1515. His father, a doctor in the royal court, had collected an exceptional medical library. Young Vesalius poured over each volume and showed immense curiosity about the functioning of living things. He often caught and dissected small animals and insects.
At age 18 Vesalius traveled to Paris to study medicine. Physical dissection of animal or human bodies was not a common part of accepted medical study. If a dissection had to be performed, professors lectured while a barber did the actual cutting. Anatomy was taught from the drawings and translated texts of Galen, a Greek doctor whose texts were written in 50 B.C.
Vesalius was quickly recognized as brilliant but arrogant and argumentative. During the second dissection he attended, Vesalius snatched the knife from the barber and demonstrated both his skill at dissection and his knowledge of anatomy, to the amazement of all in attendance.
As a medical student, Vesalius became a ringleader, luring his fellow students to raid the boneyards of Paris for skeletons to study and graveyards for bodies to dissect. Vesalius regularly braved vicious guard dogs and the gruesome stench of Paris’s mound of Monfaucon (where the bodies of executed criminals were dumped) just to get his hands on freshly killed bodies to study.
In 1537 Vesalius graduated and moved to the University of Padua (Italy), where he began a long series of lectures, each centered on actual dissections and tissue experiments. Students and other professors flocked to his classes, fascinated by his skill and by the new reality he uncovered, muscles, arteries, nerves, veins, and even thin structures of the human brain.
This series culminated in January 1540, with a lecture he presented to a packed theater in Bologna, Italy. Like all other medical students, Versalius had been trained to believe in Galen’s work. However, Vesalius had long been troubled because so many of his dissections revealed actual structures that differed from Galen’s descriptions.
In this lecture, for the first time in public, Vesalius revealed his evidence to discredit Galen and to show that Galen’s descriptions of curved human thighbones, heart chambers, segmented breast bones, etc., better matched the anatomy of apes than humans. In his lecture, Vesalius detailed more than 200 discrepancies between actual human anatomy and Galen’s descriptions. Time after time, Vesalius showed that what every doctor and surgeon in Europe relied on fit better with apes, dogs, and sheep than the human body. Galen, and every medical text based on his work, were wrong.
Vesalius stunned the local medical community with this lecture. Then he secluded himself for three years preparing his detailed anatomy book. He used master artists to draw what he dissected, blood vessels, nerves, bones, organs, muscles, tendons, and brain.
Vesalius completed and published his magnificent anatomy book in 1543. When medical professors (who had taught and believed in Galen their entire lives) received Vesalius’s book with skepticism and doubt, Vesalius flew into a rage and burned all of his notes and studies in a great bonfire, swearing that he would never again cut into human tissue.
Luckily for us, his published book survived and became the standard anatomy text for over 300 years.
The average human brain weighs three pounds and contains 100 billion brain cells that connect with each other through 500 trillion dendrites. No wonder it was hard for Vesalius to see individual neurons.