This device uses a bell jar to represent the thoracic cavity, a rubber dam as the diaphragm, a Y-shaped tube as the trachea and bronchial tubes, and two balloons as lungs. Manipulation of the diaphragm causes the balloons to inflate and deflate. Lightweight, break-resistant plastic bell jar may be handled safely by the entire class. Overall dimensions, 7-5/8 in. high, 8 in. dia.