appendix, small, worm-shaped blind tube, about 3 in. (7.6 cm) long and 1/4 in. to 1 in. (.64–2.54 cm) thick, projecting from the cecum (part of the large intestine) on the right side of the lower abdominal cavity. The structure, also called the vermiform appendix, has no function in people and is considered a vestigial remnant of some previous organ or structure, having a digestive function, that became unnecessary to people in their evolutionary progress (see digestive system). Infection of accumulated and hardened waste matter in the appendix may give rise to appendicitis, the symptoms of which are severe pain in the abdomen, nausea, vomiting, fever, abdominal tenderness, and muscle spasm. A blood count usually shows a rise in the number of white corpuscles. Appendicitis may occur at any age, although it is more prevalent in persons under 40 years of age. The danger in appendicitis is that the appendix can rupture, either spontaneously or because the patient has injudiciously been given laxatives or an enema, and that the infection can spread to the peritoneum (see peritonitis). Surgery is indicated in appendicitis, preceded and followed by antibiotic therapy.