The stethoscope is an instrument for listening to sounds inside the human body for diagnostic purposes. Until the stethoscope was invented, clinical examination of patients was largely limited to external observations.

Medical knowledge about the inside of a patient's body took its first important step forward when Leopold Auenbrugger (1722-1809), a Viennese doctor, developed a technique he called percussion. Auenbrugger tapped on his patient's chest and then analyzed the different sounds to tell what conditions existed inside the chest. He published his findings in a 1761 pamphlet, which was ignored by the medical profession.

In the early 180Os, Jean Nicholas Covisart (1755-1821), Napoleon Bonaparte's personal physician, espoused Auenbrugger's percussion technique and translated the doctor's pamphlet into French. Covisart encouraged one of his students, Rene Theophile Laennec (1781-1826), to study acoustic diagnosis.

Laennec invented the stethoscope in 1816 during an examination of a young woman with a heart affliction. Due to both the patient's stoutness and prevailing standards of modesty, Laennec was unable to put his ear to the woman's chest. In a burst of inspiration, Laennec rolled a sheaf of paper tightly into a tube, placed one end of the tube over the patient's heart, and listened from the other end. The doctor later wrote, "I was both surprised and gratified at being able to hear the beating of the heart with much greater clarity and distinctness than I had ever done before by direct application of my ear."

Later, Laennec developed a wooden stethoscope. When his book describing his instrument and the diagnoses to be made with it appeared in 1819, the publisher gave a stethoscope to each purchaser of the book.

As the stethoscope came into standard use, promoted especially by the Austrian doctor Joseph Skoda (1805-1881), some modifications were made. Pliable tubing was introduced in 1850, the American doctor George P. Cammann developed a binaural stethoscope in 1852, and the electronic stethoscope appeared in 1980. Although advanced diagnostic tools such as CAT scans have reduced the importance of the stethoscope, it remains a valuable and widely used instrument.