Accordingly, a dissecting theater, the Theatrum Anatomicum was built for the guild of surgeons in the upper floor, in an octagonal room with a gallery running along the upper part of the wall. The surgeons dissected the corpses of criminals or others buried in unhallowed ground (witches, maybe?). Rembrandt made his sketches here for his painting The Anatomy Lesson of Professor Tulp (1628). In Latin and Dutch is a statement to the effect that the body parts of the criminal dead silently teach justice and medicine to the living (Michel Foucault might have said that legal and scientific principles were written on their very bodies). In Rembrandt's time the corpses were spirited (haha) up to the Theatrum Anatomicum by local bodysnatchers, but dissection was later legalized. The ceiling is painted blue with the coats of arms of the doctors or medical professors who taught there. Look for the Death's Head on one of them.
Today the upper floors of the Waag hold the Literacy Foundation and the Foundation for Old and New Media. The Theatrum Anatomicum is used for special events that are inexpensive (10 guilders) to attend, so one's chances of getting inside are good.