People always wanted to look inside the human body and understand what was going on there. Doctors of the past have come up with a method of auscultation, or, in simple words, listening to the heart. At first they simply put their ear to the patient's chest, but then they invented special devices that allowed them to hear the heart much better. First came a stethoscope. It looked like an ordinary funnel. But then a membrane was added to this funnel, and the stethoscope became a phonendoscope - a tool that no doctor can now do without.