Stomach

Virgo takes the abdomen, the intestines and the process of digestion and assimilation, which is the same idea of sorting and separating that the sign carries generally, applied to the body. Medieval and early modern medicine, working within humoral theory inherited from Hippocrates and Galen, understood digestion as a series of concoctions in which the useful was separated from the superfluous, so the sign's general character and the region's function were held to correspond closely. Virgo being mutable, earthy and Mercurial, the texts read the region for complaints held to arise from anxiety and from irregularity as much as from diet, a connection modern medicine also makes, though for entirely different reasons and with an actual mechanism.

Galen's physiology, which medieval medicine inherited alongside its astrology, described digestion as proceeding through three successive concoctions, the first in the stomach, turning food into chyle, the second in the liver, turning chyle into blood, and the third in the tissues themselves, turning blood into flesh; Virgo's rulership of the first of these gave the sign a foundational role in the larger digestive process even though later concoctions were assigned, in the planetary scheme recorded separately under Organs, to different rulers entirely. The overlap and disagreement between the zodiacal and planetary body schemes recorded across this family of articles is therefore not confined to a single case, but recurs wherever Galenic physiology's own multi-stage processes met a single-organ zodiacal assignment.

Sources AstronomicaMarcus Manilius with Ancient MedicineVivian Nutton

The abdomen and the digestive process go to Virgo, and the stomach itself is claimed by both Virgo and Cancer depending on which authority is being followed. That disagreement is not a discrepancy introduced here. It is in the sources, and tracing it shows how the scheme was actually transmitted.

The earliest full statement of the head to foot order in Latin is in Manilius, whose Astronomica was written in the first century, and his sequence is the one most later writers follow. But the scheme circulated for fifteen hundred years through commentary, translation, medical compendia, almanacs and finally print, and at every stage the boundaries between one sign's territory and the next were redrawn slightly, because the body does not have twelve natural divisions and the signs had to be fitted to it somehow.

The contested cases cluster where a boundary falls in soft territory or where a planetary rulership pulls against the positional order. The stomach sits between Cancer's chest and Virgo's abdomen. The kidneys are positionally Libra's and planetarily Venus's. The liver is positionally Sagittarius's and planetarily Jupiter's.

The atlas records the competing assignments where they exist and marks them as contested rather than silently picking the version a given source happens to give.