The man who listened to the heart.

When you go to your doctor, he or she uses a stethoscope (STETH-uh-skope) to listen to the messages sent by your body. Your doctor can hear the ticktock of your heartbeat or check your lungs for possible congestion.

There was a time when a doctor could only listen to these important sounds by putting his ear to a patient's back or chest. This did not work very well because there was nothing to amplify the sound.

The idea for the stethoscope came to a young French physician, Rene Laennec, when he had stopped to watch two children at play. The children held a wooden stick. One child scratched his end of the stick, while the other child held the opposite end to his ear and listened as the small sound traveled along. This gave Laennec an idea. He rolled a small piece of paper into a tube. He then placed one end over the heart of a young woman patient, and the other end to his ear.

Later he wrote, "I was surprised and pleased to find that I could perceive the heart's action in a manner much more clear and distinct than I had ever been able to do."

The modern stethoscope is designed with much more knowledge about the transmission of sound. There is now a fitted ear piece and tubing of a special length between patient and doctor. Special heads pick up both high- and low-pitched sounds. An experienced doctor can listen to all the body's sounds and interpret their meaning. Thanks to the stethoscope, he or she can hear all your body's special messages.