When the Department of Neurosurgery and the Department of Biomedical Engineering began converting the old operating suite in the Carnegie Building into a joint laboratory, they decided to leave one historic element intact.

A six-point compass, which bears only fragments of its original yellow paint, remains on a section of floor. It was used by legendary Johns Hopkins neurosurgeon Walter Dandy (1886–1946) to orient patients on whom he was practicing ventriculography and pneumoencephalography. His pioneering procedures made brain tumors visible for the first time on X-rays by injecting air into the brain’s ventricles.

The floor compass helped Dandy “align the patient’s head for the X-ray—and revolutionized medicine,” says Henry Brem, director of the Department of Neurosurgery. Renovation plans call for a plaque to explain the preserved artifact and its role in neurosurgical history.