Winslow gives an interesting report of the dissection of this monster, and mentions that he had seen an Italian child of eight who had a small head proceeding from under the cartilage of the third left rib.
Sensibility was common, pinching the ear of the parasitic head causing the child with the perfect head to cry.

Each of the two heads received baptism, one being named John and the other Matthew.

A curious question arose in the instance of the girl, as to whether the extreme unction should be administered to the acephalous fetus as well as to the child.
In 1742, during the Ambassadorship of the Marquis de l'Hopital at Naples, he saw in that city an aged man, well conformed, with the exception that, like the little girl of Winslow, he had the inferior extremities of a male child growing from his epigastric region.

Haller and Meckel have also observed cases like this.

Bordat described before the Royal Institute of France, August, 1826, a Chinaman, twenty-one years of age, who had an acephalous fetus attached to the surface of his breast (possibly "A-ke").
Dickinson describes a wonderful child five years old, who, by an extraordinary freak of nature, was an amalgamation of two children.
From the body of an otherwise perfectly formed child was a supernumerary head protruding from a broad base attached to the lower lumbar and sacral region.