Four stage corss-section of the bronchus demonsrating the tissue changes occuring with asthma and chronic bronchitis. Four stages: normal bronchitis, hypersecretion of the mucous gland, swelling with lymphoid aggregations, and smooth-muscle spasm. The model includes cartlage, mucous glands and plug, spiraling smooth muscles, and the fibroelastic connective tissue and epithelial layers of the bronchus. All stages rotate on a hinge pin.