definition needed!

[Kaaren Linton <Kaaren.Linton@M.K12.UT.US>]

Help!  A student has just come in needing the definition of periactus.  I
have checked Webster's Unabridged Dictionary and World Book Unabridged
Dictionary with no luck.  We know that it is something Greek -- comes
from Socrates, in Plato _Republic 518B-D  "...together with the entire
soul, like the scene-shifting periactus in the theatre..."

TIA

Kaaren Linton                       kaaren.linton@m.k12.ut.us