It has been hiding in plain sight for the past 500 years, and now two Johns Hopkins professors believe they have found it: one of Michelangelo’s rare anatomical drawings in a panel high on the ceiling of the Sistine Chapel.

Michelangelo was a conscientious student of human anatomy and enthusiastically dissected corpses throughout his life, but few of his anatomical drawings survive. This one, a depiction of the human brain and brain stem, appears to be drawn on the neck of God, but not all art historians can see it there.

This is not the first picture of a human organ someone has found, or at least imagined, in Michelangelo’s Sistine frescoes. In 1990, in an article in the Journal of the American Medical Association, a physician described what he saw as a rendering of the human brain in the Creation of Adam, the panel showing God touching Adam’s finger. And one physician, a professor of medicine at Baylor University, published an article in a medical journal in 2000 suggesting that Michelangelo had included a drawing of a kidney in another ceiling panel. The author was, perhaps not coincidentally, a kidney specialist.

The latest find, described in a study in the May issue of the journal Neurosurgery, appears directly above the altar in “The Separation of Light From Darkness,” another panel from the series of nine depicting scenes from the Book of Genesis.