The mystery of the appendix

Leonardo da Vinci's connections to the Guild of St. Luke the Painter allowed him to conduct autopsies on more than 30 cadavers between 1489 and 1513. He had a fascination with extracting parts of the body to draw them, often working by candlelight in a church.

His work was pioneering. He was credited with being the first to draw accurately the bones of the face and hands. Yet Leonardo's illustrations didn't unlock all the body's mysteries. Nearly 500 years after his death, we still puzzle over the functionality of the appendix, one of the organs he sketched.

That ambiguity may be over. According to a team of scientists at Duke University's Medical Center, the appendix, a 2- to 4-inch wormlike organ connected to the cecum, operates as a "safe house" for useful intestinal bacteria.

The intestines are layered with biofilm, a thin lining of microbes, mucous and bacteria. When someone contracts a disease such as cholera, amoebic dysentery or E. coli, the guts purge and the biofilm is flushed out. In their study, published in the Journal of Theoretical Biology, the Duke scientists contend that the appendix effectively reboots the body with good bacteria, which is necessary for digestion.

So, how do we survive without an appendix if itproduces bacteria we need?

Bill Parker, a surgery professor who co-wrote the study, said he believes people in modern, industrialized societies don't require the back-up bacteria the appendix provides because their intestines are replenished through bacteria they acquire from other people. (This would explain why, as modern medicine and health care developed, the appendix got the rap that it is superfluous.)

In less-developed regions of the world, the appendix is still needed to repopulate the gut with digestive helpers, the study contends. A working appendix is apparently more likely to be a healthy appendix. In the United States, 321,000 people were hospitalized with appendicitis in 2005. The incidence of appendicitis appears to be significantly lower in underdeveloped countries. (Granted, though, many of them don't keep thorough health records.)

This study won't save lives (or appendixes), but it does shed light on how the human body battled potentially deadly diseases before civilizations had good sanitation and health care. It also suggests the appendix still benefits humans in countries where diseases such as cholera and typhoid are still prevalent. That's something even Leonardo, with all his wisdom and talent, probably couldn't have fathomed.

Now, what about the tonsils?