Hektoen International

A Journal of Medical Humanities

Gerard Blasius (1627–1682)

Engraving of Gerard Blasius
Gerardus Leonardus Blasius (1625–1695), physician and professor in medicine. Anonymous c. 1660. Stadsarchief Amsterdam.

Gerard Blaes (Blasius) was a Dutch physician and anatomist, famous for his work on the spinal cord and for one of his students discovering the parotid (Stensen’s) duct. As a young man he had lived and studied in Copenhagen, where his father was architect to the king of Denmark. When his father died, his family returned to the Netherlands. There he studied medicine and graduated around 1655 with a thesis on nephritis. Like many learned physicians of his time, he also had an interest in botany, chemistry, and embryology.

In 1660 he became the first professor of medicine in Amsterdam, but, not being a surgeon, was not allowed to dissect in the now often famously painted Theater Anatomicum. Working with his students in his own home, he dissected corpses of patients from the hospital and also monkeys and hedgehogs, calves, horses, sheep, tortoises, herons, and snakes. Through his medical practice he amassed a large fortune, and he wrote dozens of books.

A controversy ensued in 1661 around the discovery of the parotid duct. This had been first noted by one of his former Danish students, Niels Stensen. He had first been received into Blasius’ house and allowed to dissect whatever he decided to buy. Purchasing a sheep’s head, he discovered in it a canal that he thought had never been described before. As this was dismissed by Blasius as a poorly performed dissection, he repeated his dissection with the head of a dog and found the same structure. As such discoveries were quite important in these heady days of anatomy, Blasius then claimed he had made the discovery himself, leading to an acrimonious dispute. But to this very day, the duct leading from the parotid gland to the mouth is referred to as Stensen’s duct.

Blasius’ most important contribution to anatomy was his work on the spinal cord, previously only sketchily described by some of his illustrious predecessors. In his Anatome medullae spinalis, et nervorum inde provenientium, published in 1666, he described his dissections of 119 animals published in seventy-eight illustrations. He differentiated the gray from the white matter of the spinal cord and was the first to illustrate the H-shape of the gray matter in a horizontal section. He also described the spinal nerve roots, the cerebellum, the spinal dura, the vertebral artery and several other blood vessels and structures. In 1674 he reported the first case of non-malignant stricture of the esophagus in the absence of trauma, syphilis, or tuberculosis. He is considered to have been one the most important anatomists of the seventeenth century and, through his work on both humans and animals, one of the founders of comparative anatomy.


  1. Bahşii I, Adanır SA. Life of Gerard Blasius, and His Description of the Spinal Cord. Lokman Hekim Dergisi 2019;9(1):30-6.
  2. Markatos K, Laios K, Korres D et al. Gerard Blaes (Blasius) (1627–1682): The Dutch Physician and Chemist, His Work and Description of the Spinal Cord. World Neurosurgery Aug 2017;104:148-51.

GEORGE DUNEA, MD, Editor-in-Chief

Winter 2020



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