Percussor and pleximeter, 19th century.

Leopold Auenbrugger (1722-1809) discovered the diagnostic value of percussion in Vienna in 1781, tapping the chest or another body part and listening to the resonant quality of the sounds. When a healthy patient's chest is tapped it produces a hollow sound, but fluid congestion or certain diseases alter the sound to a dull, flat thud. The pleximeter (bottom) was held on the skin, and tapped with the hammer (percussor), such as this example which has a wooden handle and a rubber tipped metal head. It was believed that this gave clearer sounds than just using the fingers. The pleximeter shown has an ivory plate bearing a measuring scale.