In his treatises on surgery, Paré also described “trepanes or round saws for cutting out a circular piece of bone with a sharp-pointed nail in the centre projecting beyond the teeth,” and another trepan with a transverse handle. The mechanical cogwheel trepan (above left) was invented by Matthia Narvatio in Antwerp in 1575. The cogwheel was connected to a second wheel which rotated a circular saw that cut through the bone. This instrument was used much in the same way as a modern hand drill - held in one hand and cranked with the other.Warning: Not for the faint of heart!
Neurophilosopher had a great post yesterday on the history of trepanation, the skull surgery that's been performed in one way or another since prehistoric times. The money quote: