As outlined by Charis Roussos in the fascinating prologue to this two-part monograph, even when the term thorax first entered the Greek language it had a meaning of protection. At that time, it referred to a wall-like protective device around the body, a city, or a fortress. Thus, in Homer's accounts of the war between the Greeks and the Trojans, a thorax was a leather or copper cover over a soldier's chest.
By the fifth century, in concert with progress in the arts and sciences, the term thorax had undergone a gradual transformation of its meaning. Aristophanes used it to mean the anatomic chest wall of a warrior, rather than his protective breastplate. Plato, reflecting growing medical interest in internal organs, talked of the "cavity of the thorax," but included organs both above and below the diaphragm. Aristotle began to differentiate the thorax from the abdomen, and Galen stated that