percussion, in medicine, diagnostic procedure that entails striking the body directly or indirectly with short, sharp taps of a finger or, rarely, a hammer. The procedure was first described in 1761 by the Austrian physician Leopold Auenbrugger von Auenbrugg. Although generally ignored by his contemporaries, it is now routinely employed. The sounds produced by the procedure are helpful in determining the size and position of various internal organs, in revealing the presence of fluid or air in the chest, and in aiding in the diagnosis of certain lung disorders.