An occasional out-pouching of the small intestine is universally referred to as a Meckel's diverticulum, after Johann Friedrich Meckel (1781-1833), sometimes called Meckel "the younger." However, the diverticulum was not first described by that distinguished Prussian anatomist. One hundred years before, in 1701, Frederick Ruysch of Leyden published an excellent illustration (Fig 1) of this malformation.1The presence of the diverticulum before birth was also recognized before the time of Meckel, and its origin from the vitelline duct was undoubtedly also previously known. It was to Johann Friedrich Meckel,2however, that we owe the theory of the origin of the pouch in question, ie, from the omphalomesenteric duct. We are also indebted to him for first calling attention to its importance as the cause of serious disease. Frederick Ruysch (1630-1731) had his MD, FRS from Leyden. He was Professor of Anatomy and Botany at Amsterdam and a pioneer