Take the tonsils. We are all familiar with them, but how many of us know quite what they do? In fact, nobody knows quite what they do. They are the two fleshy hummocks that stand sentinel on either side of the throat at the back. (Confusingly, in the nineteenth century they were often called amygdalae, even though that name was already applied to structures in the brain.) Adenoids are similar but lurk out of sight within the nasal cavity.
