Thomas Willis and circle of arteries

In 1664 the British scientist Thomas Willis (1621-1675) described in his treatise about a circle of arteries at the base of the brain that act as a traffic for the blood flowing to the head.

Willis landmark text, Cerebri Anatome, 1664, was reproduced many times and developed into a pocket-sized standard textbook for medical students.

The circle of Willis provides a potential diversion for collateral blood supply following the occlusion of one major cranial arteries feeding, into it.

Because of Willis’s thorough illustrations and explanation of this structure, it is known today as the circle of Willis.

Scientists had observed this circle as early as the 16th century, but it was Thomas Willis, Sedleian Professor of Natural Philosophy at Oxford, who first noted it importance in directing the flow of blood. He was aware of this feature and asked his friend Christopher Wren, the architect of Canterbury Cathedral, to illustrate the arterial circle which he did masterfully.

Wren had for the first time injected fluid into the vessels of an animal while being architect for King Charles II, for whom he built St. Paul’s Cathedral in London and 53 other churches.
Thomas Willis and circle of arteries

Human anatomy discovery by Andreas Vesalius

The human anatomy references used by doctors through the year AD 1500 were actually based mostly on animal studies, more myth and error than truth.

Andreas Vesalius (1514-1564) was the first to insist on dissections, on exact physiological experiment and direct observation.

Vesalius discovered many errors in Galen’s work and revealed his evidence to discredit Galen and to show that Galen’s description of curved human thighbones, heart chambers, segmented breast bones, etc, better matched the anatomy of apes than humans.

Vesalius dissected the cadavers himself. This contravened the usual procedure, on which the professor read from a Galenic text while the body was opened by a menial or prosector. Vesalius began to employ drawings to clarify the various structures of the body.

Vesalius detailed more than 200 discrepancies between actual human 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 human body.

Vesalius De Humani Corporis Fabrica was completed and published his magnificent anatomy book in 1542.

Ultimately the scientific study of anatomy became accepted as the avenue of increasing the knowledge of this discipline and the practice of medicine.

With the rise of modern science, the approach that Vesalius pioneered became the standard for medicine. Physicians followed him into the body dissecting it as a way of understanding how it worked.
Human anatomy discovery by Andreas Vesalius