It has been known from ancient times that listening to a patient's heart and lungs is an important diagnostic tool for a physician. However, the first use of the stethoscope is credited to the French doctor Rene Laennec in 1816. As the legend goes, Dr. Laennec was unwilling to put his ear to the chest of a young female patient and instead rolled up a paper tube to listen through, and found that he could hear the chest sounds more clearly. The paper tube soon gave way to tubes of wood, metal, and/or ivory or bone. These are referred to as monaural stethoscopes, since the user listens to them with only a single ear. Monaural stethoscopes with flexible silk tubes instead of hard, straight tubes were a later invention.
Binaural, or two-ear, stethoscopes were actually invented in 1829, only a few years after Laennec's invention, but proved slow to catch on. Nathan Marsh of Cincinnati was the first to sell a binaural stethoscope, in 1851, but without much success. In New York, Dr. George Cammann had more success with a binaural stethoscope of his own design. Dr. Cammann's model was widely manufactured and promoted by leading instrument maker George Tiemann, and by the early 20th century binaural stethoscopes had become the standard.
The next evolution in stethoscope design was the replacement of the old-fashioned bell-shaped chestpiece with a diaphragm chestpiece. The diaphragm, first introduced in the early 20th century, picked up sounds more clearly and made it easier for the doctor to distinguish between heart and lung sounds. By the 1940s, the standard stethoscope had achieved the form still used today, with lightweight, spring-closed earpieces, a rubber tube, and a small chestpiece. In 1961, cardiologist Dr. David Littman designed a two-sided chestpiece with a bell on one side and a diaphragm on the other, and most modern stethoscopes are still based on Dr. Littmann's design.