Percussion

Percussion is a technique used by physicians in examining the thorax and the abdomen to look for abnormalities. It is performed by the physian placing one middle finger on the structure to be examined and striking it with the other finger to listen to the resulting sound. Solid structures should have a dull sound, while air filled structures should have a resonant sound. 
The technique was developed by Dr. Leopold Auenbrugger in the 18th century when he noticed wine and liquor merchants could tell how full a barrel was just by striking it. He realized the technique could be applied to any solid or hollow structure. 
Basic percussion sounds can easily be learned and remembered by striking one's own body:
*Tympanic, by striking one's own abdomen
*Hyperresonant, by striking air filled cheeks
*Normal resonance, by striking the chest
*Dull, by striking an organ such as the liver
If percussion induces pain, this can indicate a serious underlying disease. 
House's skills with percussion are unparalleled. In The Right Stuff, he uses percussion and a stethoscope to realize that Greta Cooper has masses in her chest. In Twenty Vicodin, he uses his ear alone to find an acoustic shadow in Nick's chest.
Medical percussion at Wikipedia
Category:Medical procedures