Physicians have been listening to their patients' chests since, at least, 1500 B.C. But it was not until the early 19th century when a French doctor named René Théophile Hyacinthe Laënnec (1781–1826) systematically investigated the clinical meanings of both breath and heart sounds.

Laënnec considered the time-honored method placing one's ear directly on a patient's chest to be both useless and distasteful. He complained about the inability to hear muffled sounds within the chests of obese people as well as his patients' hygiene, many who were unwashed and lice-ridden.

Instead, he preferred to auscultate (from the Latin auscultare, "to listen") using a hollow tube he named the stethoscope. Laënnec coined this odd name using the Greek roots stethos, or chest, and skopein, to look at or to observe.

Historians have been arguing over the precise events leading to Laënnec's creation for nearly two centuries.

According to the most charming version, one fall day in 1816, Laënnec was running late to examine a young woman stricken with heart disease. He took a shortcut through the Louvre's courtyard where a group of children were playing atop a pile of old timber. A pair of youngsters toying with a long, narrow wooden beam especially entranced Laënnec. One child held the beam to his ear while the other tapped nails against the opposite end; both boys had a jolly good time transmitting sound.

Upon entering his patient's room later that afternoon, Laënnec asked for a quire of paper and rolled it into a cylinder. Placing it against the her chest, he was amazed to find how well he could "perceive the action of the heart in a manner much more clear and distinct than [he had] ever been able to do by the immediate application of the ear."

Whether or not these events actually occurred, Laënnec would later record that his invention was inspired by the fact that sound is "conveyed through certain solid bodies, as when we hear the scratch of a pin at one end of a piece of wood, on applying our ear to the other."

For the next three years, Laënnec experimented with a series of hollow tubes that he fashioned out of cedar or ebony, arriving at a model approximately one foot in length and 1.5 inches in diameter, with a 1/4-inch central channel.

Able to accurately diagnose a number of lung and heart diseases, he announced his findings to the world in his 1819 book, De l'Auscultation Médiate. Initially, it caused hardly a ripple in the medical world--even at the bargain price of 13 francs, with a stethoscope thrown in for an extra 3 francs. But by the late 1820s, Laënnec's text had been reprinted and translated into several other languages, which led to universal acceptance of Laënnec’s tube. With each passing decade, advances in acoustics and audiology have changed the shape and look of the stethoscope. But it still remains one of the iconic symbols of medicine.

The great irony of the stethoscope, of course, is how it separates the doctor's ear, and head, from the patient’s body. Modern medicine’s arsenal of noninvasive imaging techniques affords even more stunning glimpses into the human body. But with that technology, the distance between doctor and patient has grown exponentially. Perhaps, then, we doctors need to hang onto our stethoscopes as a gentle reminder of how separation can alter the enduring task of physicians: listening to our patients.