Herophilus, Galen and the “valve” of pneuma
Around the fourth to third centuries BCE, Herophilus was among the first anatomists in Alexandria to dissect the human body systematically. Most of what he wrote has been lost, so much of the pineal gland story has to reach us indirectly through Galen, who lived several centuries later and preserved Herophilus’s ideas in his own anatomical works.
According to Galen, Herophilus believed this small structure helped regulate the flow of pneuma between the brain’s ventricles, almost like a mechanism that could open and close. In Greek medicine of the time, pneuma was a physiological concept used to explain life, sensation, movement and bodily activity; it was very different from the way terms like “spiritual energy” are often used in New Age language today.
To modern ears, the idea of the pineal gland regulating pneuma sounds strange. But at a time when neuroanatomy had barely begun to take shape, people were looking at hollow spaces inside the brain, watching fluids move through the body, and trying to make sense of an enormously complicated biological machine with the concepts available to them. Suspecting that a small structure beside the ventricles might work as some kind of valve was not a completely random guess.
Galen did not buy the theory.
He described the pineal gland in some detail, called it kônarion because of its resemblance to a pine cone seed, and rejected the idea that it could open and close the flow of pneuma. His objections came from anatomy itself: the gland’s position did not fit the role of a valve between the ventricles, and it also lacked any obvious mechanism that would allow it to move in that way. Galen instead associated it more closely with the deep vascular structures around it than with any kind of gate controlling the brain.
Even in antiquity, the pineal gland had already been given a large role in explaining how the brain worked, only to have that role challenged by someone else using anatomical observation.
That back-and-forth between speculation and criticism would return many times in the gland’s history. Each period brought its own vocabulary and assumptions to the same small organ, while later generations kept revising, discarding or adding new meanings to what came before.
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