Siamese twin

n.
Either of a pair of identical twins born with their bodies joined at some point, a result of the incomplete division of the ovum from which the twins developed.

[After Chang and Eng Bunker (1811-1874), joined Chinese twins born in Siam (Thailand).]

Conjoined twins result when there is incomplete cleavage and separation of monozygotic (single egg) twins. The twins may be joined at the head end (craniopagus) or tail end (ischiopagus and pyopagus), but the majority who survive are joined ventrally with varying degrees of coalescence (thoracopagus and omphalopagus). They may share heart, blood vessels, liver, and gut. Successful surgical separation will depend upon the degree of coalescence of major organs.

Throughout recorded history there are many references to surviving conjoined twins. One of the earliest reports concern Mary and Eliza Chalkhurst, born at Biddenden, Kent, England in the year 1100. They died in 1134 within six hours of each other. They bequeathed 20 acres of land to the church wardens from which a yearly income was used to provide, for the poor, cakes with the imprint of their effigies ‘in their habit as they lived’ together with bread and cheese. For many years this ceremony took place on Easter Monday at their birthplace. As late as 1874 an observer noted that the Biddenden Maids cakes are ‘simple flour and water, are four inches long by two inches wide and are much sought after’. They bear the date 1100 and also their age at death.

'The Biddenden Maid biscuits' — reproduction of an imprinted cake. From Ballantyne, J. W. (1904), Manual of antenatal pathology and hygiene. Wm. Green, Edinburgh


The most notable were the Siamese twins, Eng and Chang, who were born in Siam in 1811, the fourth pregnancy of a Chinese father and a half-Siamese/Chinese mother. They were joined at the chest and upper abdomen. They were ‘discovered’ in 1829 by a Scottish trader, Andrew Hunter who realized their commercial potential and took them to England in 1830, where he exhibited them as ‘The Siamese Double Boys’ for five years. Chang, Eng, and Hunter then embarked on a tour of America, where Phineas T. Barnum ‘acquired’ them in 1835 as exhibits in ‘The Greatest Show on Earth’. By 1840 they had earned enough money to retire and became gentlemen farmers in North Carolina. In 1844 they married Addie and Sally Yates, daughters of a nearby farmer, and during the next 20 years had 21 children between them, 10 to Addie, who was married to Chang, and 11 to Sally.

With the advent of the Civil War in 1861 Chang and Eng were forced to move north with their families, and in New York they rejoined Barnum and recouped their lost fortunes. During their travels on show they were seen by many famous surgeons, who considered their separation. Sir James Young Simpson, Professor of Medicine and Midwifery in the University of Edinburgh, gives full details of his examination of them in the British Medical Journal of February 13, 1869.

Whilst on a voyage from Liverpool to New York in 1872, Chang had a paralytic stroke and was partially dragged about by Eng for some months thereafter. Fortunately they had by this time amassed sufficient money to return to the South and rebuild their mansions. At the age of 63, Chang, who was the more argumentative and aggressive of the brothers, and who drank to excess, developed a chest infection. It had been the custom for many years for the families to spend two weeks in alternate mansions. Chang's ‘bronchitis’ developed on Monday 12 January, 1874, and in spite of being unwell he moved to Eng's house on the Thursday of that week. He died on the Saturday morning whilst sleeping on a couch in front of the fire. Eng wakened and discovered his dead brother but died a little more than two hours later. Postmortem examinations showed that they shared muscle and liver tissue, and they were buried, still joined, in a single grave in North Carolina.

— Jim Nielson, Forrester Cockburn

Identical (monozygotic) twins joined together at birth. The connection may be slight or extensive. It involves skin and usually muscles or cartilage of a limited region, such as the head, chest, hip or buttock. The twins may share a single organ, such as an intestine, or occasionally may have parts of the spine in common. A rare congenital malformation in animals. Called also conjoined twins.

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