Sibson type combined percusor and pleximeter, c 1860.
© Science Museum / Science & Society Picture Library
Leopold Auenbrugger (1722-1809) discovered the diagnostic value of percusion 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 was held on the skin, and tapped with the hammer (percusor). It was believed that this gave clearer sounds than just using the fingers. This example is made of ivory, bras and steel.