The lower cavity: the origins and history of an anatomical idea.

This paper examines the history of the 'lower cavity' of the gastrointestinal tract, a distinctive anatomical feature in Greco-Roman medicine that described a second stomach-like organ in the large intestine. It traces how a bipartite model of the digestive system emerged in fourth-century bce Greek medical and philosophical thought and persisted in the works of influential figures such as Galen, Vesalius, and Glisson, despite shifts in terminology, anatomical observations, and physiological theories. The study demonstrates that this understanding arose primarily from three complementary factors: a specific terminology that paired the stomach with a lower cavity, systematic animal dissections that revealed pronounced caeca in certain species, and emerging physiological theories that required separate bodily receptacles for digested food and residues. Through this case study, the paper illuminates how premodern anatomical knowledge was articulated by a constant negotiation between animal bodies, human bodies, and past textual authorities, facilitating the surprising longevity of ideas like the 'lower cavity' in the gastrointestinal tract.