appendix (anatomy)

Short, blind-ended tube attached to the caecum. It has no known function in humans, but in herbivores it may be large, containing millions of bacteria that secrete enzymes to digest grass (as no vertebrate can secrete enzymes that will digest cellulose, the main constituent of plant cell walls).

The appendix secretes antibodies into the gut and so plays a role in the body's immune system, though it is not a vital one, as patients survive perfectly well following removal of the appendix. (See appendicitis.)