In 1761 Cotugno gave the first reliable account of ventricular and subarachnoid fluid.¹ Until Cotugno, anatomists had found empty spaces around the brain and cord and thought that in life they were filled by vapour. Willis said the ventricles were empty spaces, or served the “vile duty of a sewer. In the dead they may be filled with water…if the serous fluid in the blood is too abundant.”² Albrecht von Haller’s famous textbook³ (at the same time as Cotugno’s studies) describes:

“As in the pericardium…a thin humour constantly exhales from the arteries into the ventricles of the brain and is constantly drawn back through the veins…so often the collected moisture turns into water and even distends the ventricles…A great abundance of water has been found in the ventricles of apoplectics, the soporose, convulsives, paralytics, and victims of epidemic fevers; hydrocephalus even more.”

Cotugno studied 20 adult male bodies. He established the free …