Herophilus and Erasistratus: Discoverers of the Nerves

Herophilus of Chalcedon and Erasistratus must have had nerves of steel when they made these discoveries. To arrive at their findings, they did not shy away from dissecting living humans. At least, that is what the Roman encyclopedist Aulus Cornelius Celsus, who lived a good 200 years after the two Greeks, claimed. According to Celsus, the unfortunate subjects of their studies were prisoners who were “handed over to them from the prisons and whom they examined while they were still breathing.” At that time, brain dissections on humans were only possible without restriction and in unlimited numbers in Egypt. This was because medicine was particularly promoted there, and vivisection, which was taboo elsewhere, was considered the only way to gain knowledge. Of course, one needed good contacts with the powerful. However, Herophilos had these contacts.

Herophilus was born around 330 BC in a district of what is now Istanbul. He later studied medicine on the Greek island of Kos. As a practicing physician, now in Alexandria, Egypt, Herophilus was far ahead of his time in terms of diagnostics. When visiting patients, he always carried a portable water clock with him, so he did not have to compare the patient's pulse with his own, as other doctors did. He simply reached for the water clock, measured the exact time, and then calculated the heart rate. But his own heart beat less for medicine than for research.

Far less is known about the life of Erasistratos. He was probably born around 305 BC in Iulis on the Aegean island of Keos – now known as Kea. He devoted himself to studying medicine in Athens. Eventually, probably at an advanced age, he settled in Alexandria. Together with Herophilus, he founded a school of anatomy there.

For their anatomical studies, the two needed human bodies as objects of dissection – preferably still alive. The rulers of Alexandria saw nothing wrong with this and supported Herophilus and Erasistratos in their research. And the fact that the two early anatomists actually used living humans for their studies, as Celsus claims, is suggested by at least some of their findings. Herophilus was the first to correctly describe the pulmonary veins and arteries. However, he could only achieve this scientific coup if, among other things, he knew the direction of blood flow – and for that, the blood had to still be flowing.

Herophilus and Erasistratos were also the first to distinguish between motor and sensory nerves. The easiest way to determine whether a nerve is sensory or motor is by examining functional failures – and for this, too, the object of study must still be alive. In addition, the two anatomists were probably the first to discover the motor and sensory nerves, as motor functions had previously been attributed to the arteries. And with regard to sensory nerves, the philosopher ▸ Alcmaeon had already established that there were connections between the eyes and the brain. But it was probably Herophilus who first described these connections as “nerves of sensation.”

The list of achievements by the research duo goes on: Herophilus and Erasistratos were the first to describe the cerebrum and cerebellum, the meninges, and the ventricles in great detail. And they attributed the degree of intelligence of a living being to the number of convolutions in the cerebrum. The merits of Herophilus and Erasistratus as the most important descriptive anatomists of antiquity, alongside ▸ Galen, are undisputed. However, the price paid for this by their subjects was extreme.