Melothesia was not a diagram to be contemplated. It was operational, and the operation was a prohibition: do not cut, cauterise or bleed a member while the Moon stands in the sign that governs it. The rule appears in regimen literature across medieval Europe, it was taught in university medical faculties alongside the rest of astrological medicine, and it governed the practice of the barber surgeons who actually held the knife.
For the neck and throat, the sign is Taurus, and the prohibition bore on a real and frequent procedure. Bleeding from the jugular was standard for complaints of the head and throat, so a barber surgeon working from an almanac would defer it while the Moon passed through Taurus, roughly two and a half days in every month.
The instrument that carried the rule to the practitioner was the folding almanac, a set of parchment leaves worn at the belt, several English examples of which survive from the fourteenth and fifteenth centuries. Later the printed almanac took over, with the zodiac man on an early page, and the figure persisted in popular almanacs long after the medicine around it had gone.
The atlas records the doctrine as historical practice. It is not a description of how the body works and it is certainly not advice about any procedure.