What is an appendix?  I had never heard of an appendix attack, except when I was in Louvain, when one of the American theology students there had an attack and died.  I knew it was serious.  Otherwise, an appendix was always something that you added on at the end of some work to explain some obscure points.  Thus, an appendix in the body, meant something not that useful, although it could cause death.  I learned that the appendix is a finger-like, blind-ended tube connected to the cecum, a pouch-like structure of the large intestine, located at the junction of the small and the large intestines. The term “vermiform appendix” comes from Latin and means “worm-shaped.”  Thus, the human body appendix was once considered a useless human organ.  This human appendix averages 3.5 inches in length and a quarter inch in diameter.  The longest appendix ever removed was about 10 inches long.  The appendix is usually located in the lower right quadrant of the abdomen, near the right hip bone that separates the large intestine from the small intestine.  The notion that the appendix was useless was widely held.  However, this has changed since the early 2000s.  Research suggests that the appendix may serve as an important purpose as a reservoir for beneficial gut bacteria, so that the human appendix is a “safe house” for beneficial bacteria in the recovery from diarrhea.  This appendix serves as a haven for useful bacteria when illness flushes the bacteria from the rest of the intestines.  The immune system supports the growth of beneficial intestinal bacteria, in combination with many well-known features of the appendix, including its location just below the normal one-way flow of food and germs in the large intestine, and its association with copious amounts of immune tissue.  Individuals without an appendix were four times as likely to have a recurrence of Clostridium difficile colitis.  This reservoir of bacteria serves to repopulate the gut flora in the digestive system following a bout of dysentery or cholera or to boost it following a milder gastrointestinal illness.  The appendix has been identified as an important component of the immune functions.  This structure helps in the proper movement and removal of waste matter in the digestive system, contains lymphatic vessels that regulate pathogens, and lastly might even produce early defenses that prevent deadly diseases.  Thus, the appendix has major immune benefits and is not as useless as many people thought before 2000.  What do you know about a human appendix?