An ancient medical system devised in Mesopotamia, in modern-day Iraq, where a patient would be diagnosed by a physician, not by inspecting that patient, but the livers of some sacrificed animals. The liver was believed at this time to be the source of our blood, which meant it was the source of life itself. Following this logic, people therefore believed that the will of the gods could be divined by inspecting the livers of sacrificed sheep. Each section of the liver was believed to correspond to a particular deity, and clay models of sheep's livers have been found dating back as far as 2050 B.C.
Patient: "Doctor, what's wrong with me!?"
Mesopotamian physician: "Hmm, by the laws of hepatomancy, allow me to inspect my sheep's liver, so we may gather a proper diagnosis."