Sternomancy, from the Greek sternon (chest) is a divination

Divination

Divination is the attempt to gain insight into a question or situation by way of an occultic standardized process or ritual...

 practice involving reading the markings or bumps on the chest or breast bone (or the area "from the breast to the belly", according to some sources). Sternomancy may have been commonly practiced on victims of sacrifice. Sternomancy may also include speaking through the chest (believed to be an early form of Ventriloquism

Ventriloquism

Ventriloquism, or ventriloquy, is an act of stagecraft in which a person manipulates his or her voice so that it appears that the voice is coming from elsewhere, usually a puppeteered "dummy"...

).

The size and shape of the sternum bone are taken into consideration, as well as the way in which the bone burns when placed into a fire. The old holiday custom of the breaking of a chicken's or turkey's wishbone by two persons is actually a remnant of this type of divination.

Sternomancy is related to phrenology

Phrenology

Phrenology is a pseudoscience primarily focused on measurements of the human skull, based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules...

 (head-reading), Palmistry (chiromancy) and scapulomancy (divination by observing animal shoulder-blades).