History of Medicine : The Stethoscope

In the early 1800s, doctors began to listen to patients' chests to diagnose diseases of the heart and lungs. At first, the physician put his ear to the patient's chest. One day when examining a young lady under the watchful eye of her family, René Laënnec was embarrassed to place his head right next to her breast. Instead, he listened through a rolled up a piece of paper, and found he could hear much more clearly than without it--thus the stethoscope was invented.

Laënnec, A l'Hopital Necker, Ausculte Un Phtisique (Laënnec, at the Hopital Necker, Examining a Consumptive Patient by Auscultation)
Théobald Chartran (1849­-1907)


Source:
http://en.wikipedia.org/wiki/Ren%C3%A9_Laennec