a developmental defect in which a double fetus (twins) is fused in the region of the sternum or its sword-shaped appendage (the xiphoid process; hence the name). An example of xiphopagus were Chang and Eng Bunker (”Siamese twins”), who lived for 63 years (1811-74) in good health, were married, and had normal, healthy children. Modern medical science eliminates xiphopagus through surgery.