This Old Babylonian tablet in the shape of a sheep’s liver is divided into sections that are annotated for the use of a diviner. The anatomically detailed model—more accurate than later, medieval European ones—was probably used to teach apprentices how to read the entrails of certain specially slaughtered animals. So important was divination that such omens were taken before the king traveled or his armies went to war.

Mesopotamia- The Mighty Kings, Alexandria, Virginia- Time-Life Books, 1995, p. 17.

See also-

Before Tea Leaves- Divination in Ancient Babylonia, William W. Hallo, BAR 31-02, Mar-Apr 2005.