"we must trephine at once"
by cm
Public DomainTrephining - Credit: Hieronymus Bosch

A trephine is a surgical instrument for cutting out discs of bone, generally from the skull.  It has a circular, saw-like blade.  Trephining, or trepanning, is the act of cutting a hole in the skull, often to relieve pressure or enable cranial surgery.


Public DomainTrephine - Credit: Chambers, 1908