Ankles

Aquarius takes the ankles and the calves, and in most versions the circulation of the blood. The circulatory assignment is worth pausing on, because it postdates the anatomy: William Harvey demonstrated the circulation of the blood in De Motu Cordis in 1628, and astrological texts written before that date cannot have meant by circulation what later texts mean. The tradition absorbed the discovery and attached it to the sign whose classical ruler is Saturn and whose modern ruler is Uranus, itself an eighteenth-century addition. The layer is therefore modern, and the example is a useful one: astrological correspondence systems are not fixed, they take in new material as it becomes available, and dating a particular correspondence is often possible if one asks when the thing it refers to became known.

Uranus itself was not always going to bear that name: William Herschel, who discovered the planet in 1781, proposed calling it Georgium Sidus, George's Star, after King George III, and it was only decided by international astronomical convention across the following decades, settling by around the middle of the nineteenth century, that it should instead take a name from Greek mythology to match the other planets. The assignment of this comparatively young planet to Aquarius, and by extension to the ankles in the modern layer of the melothesia, is accordingly a nineteenth-century addition to a scheme whose other correspondences are many centuries older.

Sources AstronomicaMarcus Manilius with William Harvey's Natural PhilosophyRoger French, Discoverers of the Universe: William and Caroline HerschelMichael Hoskin

Aquarius takes the ankles and the calves by position, and in most modern versions the circulation of the blood as well. That last item is the clearest datable retrofit in the whole scheme, and it makes a useful test of any source that presents melothesia as an ancient and unchanging inheritance.

The circulation of the blood was demonstrated by William Harvey in De Motu Cordis, published in 1628. Before that the prevailing account, from Galen, had blood produced in the liver and consumed at the periphery, with no circuit at all. A first century writer such as Manilius could not have assigned the circulation to any sign, because the circulation was not a thing anyone thought existed.

So the entry arrives after 1628, and in practice much later, in the popularising astrological literature of the nineteenth and twentieth centuries which redistributed the body according to physiology as it was then understood. The same period gave Gemini the nervous system and Cancer the lymphatics.

None of this makes the modern lists worse than the old ones. It makes them modern, and it shows a supposedly fixed correspondence tracking the medical knowledge of whoever was writing it down. The atlas records the assignment and its date, and makes no claim about the circulatory system.

Sources AstronomicaMarcus Manilius with William Harvey's Natural PhilosophyRoger French, Ancient MedicineVivian Nutton