In 1816 the French physician René Laënnec was convinced that if he could listen carefully to the sounds made by his patients’ lungs and hearts, he would hear many clues to their conditions. But he found it difficult to isolate the swish of the lungs or the lub-dub of the beating heart. Many of his patients were so fat that the sounds coming from their chests were lost.
One day Dr. Laënnec was watching children play on a pile of timber. He saw one boy put his ear to the end of a long beam while another tapped on the opposite end. The sound traveled along the wood. At once Laënnec saw the answer to his problem. He hurried back to his hospital, took a paper-covered book, and rolled it tightly into a tube. To everyone’s astonishment, he then put one end of the tube to a patient’s chest and applied his ear to the other. As he expected, he heard the heart sounds clearly. Then he made little wooden “listening trumpets” on a lathe, and the stethoscope was invented.