The student recognized two divisions of divination--the involuntary, dealing with the interpretation of signs forced upon our attention, such as the phenomena of the heavens, dreams, etc., and voluntary divination, the seeking of signs, more particularly through the inspection of sacrificial animals.

This method reached an extraordinary development among the Babylonians, and the cult spread to the Etruscans, Hebrews, and later to the Greeks and Romans.
Of all the organs inspected in a sacrificial animal the liver, from its size, position and richness in blood, impressed the early observers as the most important of the body.

Probably on account of the richness in blood it came to be regarded as the seat of life--indeed, the seat of the soul.

From this important position the liver was not dislodged for many centuries, and in the Galenic physiology it shared with the heart and the brain in the triple control of the natural, animal and vital spirits.

Many expressions in literature indicate how persistent was this belief.