The tongue is a muscular organ attached to the back of the bottom of the mouth. It contains all the taste buds found in the body, allowing a person to have a sense of taste. It also plays a major role in speech.
Most people have fine control of the muscles of the tongue, allowing them to move it through a wide range of positions and shapes. Not being able to move the tongue properly is a sign of many neurological disorders. In Half-Wit, Eric Foreman runs through a series of tests with a patient to show control over the tongue that shows normal neurological function.
In No Reason, House deals with a patient who has a severely swollen tongue.