Hence the extra digit is attached to the normal digit, the extra head to the one neck, the extra tail to the croup, extra teeth to the existing teeth, and even two similarly formed bodies are attached by some point common to both, as the navels, breastbones, backs, etc.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
In each of them a triple row of bronze chains fastened to the navels of the Pataec gods extended in parallel lines from one end to the other; the crowd was massed against the houses, and servants, belonging to the Ancients, walked in the middle brandishing thongs.
"Salammbo"
Gustave Flaubert
A colonist in describing the practice wrote that "they have many professed phisitions, who with their charmes and rattels, with an infernall rowt of words and actions, will seeme to sucke their inwarde griefe from their navels or their grieved places."
"Medicine in Virginia, 1607-1699"
Thomas P. Hughes