Craniopagus twins the set of twins as being a unique malformation and a punishment from their mother’s mistake. Furthermore, in Ambroise Pare’s book, "On Monsters and Marvels", various types of "supernatural" twinning are illustrated and described as "monstrous and marvelous creatures that proceed from the judgment of God". This published history suggests that conjoined twins, and in specific craniopagus twins, were viewed as literal monsters during that era. Craniopagus twins Craniopagus twins are conjoined twins that are fused at the cranium. This condition occurs in about 10–20 babies in every million births in the United States. Among this small group, cephalic conjoining,
Tarzan and the Tarzan Twins it features Tarzan's first meeting with Doctor Karl von Harben, with whom he is already acquainted in "Empire". Because "Twins" is a children's book, however, it is customarily omitted from listings of the main Tarzan series. Thus "Tarzan, Lord of the Jungle" is generally considered the eleventh Tarzan book rather than "Twins". Two schoolboys, Dick and Doc, are cousins who resemble each other because their mothers are twins. As Dick is also related to Tarzan through his father, they become known as the Tarzan Twins. Invited to visit Tarzan's African estate, they become lost in the jungle and are imprisoned