In the past, the appendix (see figure) was largely thought to be useless.
Appendicitis, a life-threatening condition, would call for removal of the appendix. In 2007, Randal et al. at Duke University conducted research into the vermiform appendix. The researchers observed that when the body was under attack by pathogens, the appendix would release probiotic bacteria that would perfectly counter the specific type of invaders. The appendix does this by releasing them into the cecum when the body is infected.