Although "ausculatory percussion" -- the evocation of sounds within the chest by finger-tapping -- had been introduced in the later 18th-century, it only became established once Corvisart had republished Auenbrugger's classic book in 1808. While Laennec was much indebted to Corvisart, his teacher, the stethoscope was his invention -- first in the form of a roll of paper, and then in the refined version, illustrated in his book, of a short wooden tube with a narrowing lumen for use at one ear. An instrument for "indirect ausculation" through amplification of the chest sounds, it has been called "the most important advance in physical diagnosis between Auenbrugger's introduction of percussion in 1761 and Roentgen's discovery of X-rays in 1895" [Heirs of Hippocrates]