Sagittarius takes the thighs and hips by the positional rule, and in a great many versions the liver as well. The liver has no business in the thigh, and the reason it is there is the second mapping pulling against the first.
Sagittarius is ruled by Jupiter, and Jupiter rules the liver in the planetary scheme of the organs, where the reasoning is Galenic: the liver was held to be the origin of the venous blood and the seat of the natural spirits, and Jupiter is the greater benefic, the planet of abundance and increase. Once the sign inherits its ruler's organ, the liver appears in Sagittarius's list, some distance from Sagittarius's region of the body.
This is worth watching because it happens repeatedly and it is the main source of the untidiness in the melothesia tables. Gemini acquires the lungs through Mercury. Libra acquires the kidneys through Venus, though there the two mappings happen to point the same way. Capricorn acquires the bones and the skin through Saturn.
A reader who knows to look for the planetary pull can usually tell, on meeting an odd entry in a melothesia list, whether it came from the head to foot order or from the ruling planet. The atlas records both mappings separately for that reason.
Sources AstronomicaMarcus Manilius with Ancient MedicineVivian Nutton