From Boing Boing, check out this site about the history of conjoined twins. It’s called “From ‘Monsters’ to Modern Medical Miracles,” and is packed with images and information dating back to the 15th Century. I especially recommend the gallery of images, most of which is old medical drawings. They are beautiful and frightening and sad.
Buried in the bibliography is a reference to an 1869 book called History and Medical Description of the Two-Headed Girl. Hmm.