page_title: Conjoined twins
section_title: Born 19th century and earlier
hierarchical_section_title: Conjoined twins / Notable people / Born 19th century and earlier
caption_attribution_description: Chang &amp; Eng Bunker (1835 or 1836) - public domain "The image featured above is an original watercolor on ivory depicting the twins, and it was painted by an unidentified French or Dutch artist in Paris between December, 1835 and March, 1836. It is currently in the holdings of the North Carolina Collection Gallery." http://www.lib.unc.edu/ncc/gallery/twins.html 01:14, 13 November 2004 CatherineMunro 333x461 (36,998 bytes) (Chang &amp; Eng Bunker (1835) - public domain)
context_page_description: Conjoined twins, also known as Siamese twins, are identical twins joined in utero. A very rare phenomenon, the occurrence is estimated to range from 1 in 49,000 births to 1 in 189,000 births, with a somewhat higher incidence in Southwest Asia and Africa. Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1.
  Two contradicting theories exist to explain the origins of conjoined twins. The more generally accepted theory is fission, in which the fertilized egg splits partially. The other theory, no longer believed to be the basis of conjoined twinning, is fusion, in which a fertilized egg completely separates, but stem cells find similar stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac, although these characteristics are not exclusive to conjoined twins, as there are some monozygotic but non-conjoined twins who also share these structures in utero.
  Chang and Eng Bunker, Thai brothers born in Siam, now Thailand, traveled widely for many years and were labeled as The Siamese Twins.
context_section_description: Mary and Eliza Chulkhurst, alleged names of the Biddenden Maids (per tradition, born in the 12th century) of Kent, England. They are the earliest set of conjoined twins whose names are (purportedly) known.
  Lazarus and Joannes Baptista Colloredo (1617–1646?) autosite-and-parasite pair
  Helen and Judith of Szony (Hungary, 1701–1723) pygopagus
  Chang and Eng Bunker (1811–1874), from Thailand (formerly Siam), joined by the areas around their xiphoid cartilages, but over time, the join stretched; the expression Siamese twins is derived from their case
  Millie and Christine McCoy (July 11, 1851 – October 8, 1912) American conjoined twins who went by the stage names "The Two-Headed Nightingale" and "The Eighth Wonder of the World." (oblique pygopagus)
  Giacomo and Giovanni Battista Tocci (1875?–1912?) (dicephalus tetrabrachius dipus)
caption: Chang and Eng Bunker, watercolor on ivory, 1835 or 1836
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