1. A MASK COMPRISING A HOLLOW HEADPIECE HAVING AN OPEN BASE TO ADMIT THE HEAD OF A WEARER, MEANS EXTENDING DOWNWARDLY FROM THE HEADPIECE TO ENGAGE THE CHEST OF THE WEARER TO MAINTAIN THE HEADPIECE POSITION, A JAWPIECE PROJECTING FORWARDLY FROM THE BASE AND PIVOTED THERETO, A CHIN SADDLE EXTENDING ACROSS SAID OPEN BASE AND ATTACHED TO THE JAWPIECE, THE SADDLE BEING POSITIONED TO ENGAGE THE WEARER''S CHIN, AND MEANS RESILIENTLY CONNECTING SAID JAWPIECE TO SAID HEADPIECE WHEREBY THE JAWPIECE MAY BE CAUSED TO OSCILLATE BY THE WEARER''S JAW MOVEMENT.