The zodiac man: the Moon in medieval astrological medicine

In the calendars and books of hours of the late Middle Ages a curious figure often appears: a naked man whose body is covered by the signs of the zodiac, with Aries on his head and Pisces at his feet. This is the so-called zodiac man, or homo signorum, the illustration of an ancient doctrine called melothesia, which assigned each part of the body to a sign. In this tradition the Moon, with her monthly passage through the signs, played a leading role.

An ancient doctrine

The idea of a correspondence between the zodiac and the human body was already set out in the first century AD by the Latin poet Manilius in his Astronomica, and it appears in many Greek astrological texts. The most common scheme runs from top to bottom: Aries rules the head, Taurus the neck, Gemini the shoulders and arms, Cancer the chest, and so on down to Pisces, lord of the feet. It was a way of mirroring in the human microcosm the order of the celestial macrocosm.

Medieval medicine, based on the theory of humours of Hippocratic and Galenic tradition, adopted these correspondences in the universities of Bologna, Padua, Paris and Montpellier, where astrology was also taught as an auxiliary discipline. The learned physician was expected to know the position of the Moon and the critical days of illnesses, a doctrine of Hippocratic origin that Galen, in the second century, had related to the lunar cycle.

Iron and the Moon

The most famous rule tied to the zodiac man concerned bloodletting, the practice of drawing blood that for centuries was among the most common in European medicine. According to tradition, one was not to cut a part of the body while the Moon was passing through the sign that governed it. The rule is stated in one of the aphorisms of the Centiloquium, the collection attributed to Ptolemy but of later date, and it is repeated in countless medieval and Renaissance calendars.

For this reason lunaries and almanacs recorded, day by day, the sign occupied by the Moon, often beside a small figure of the zodiac man with lines linking each sign to the corresponding part. The barber-surgeons who performed bloodletting consulted tables of this kind. This knowledge has been entirely superseded by scientific medicine, but it explains the constant presence of the Moon in the medical culture of those centuries.

Famous images

One of the best-known depictions of the zodiac man is found in the Très Riches Heures of the Duke of Berry, the book of hours illuminated by the Limbourg brothers in the early fifteenth century and now kept at the Musée Condé in Chantilly. The page shows a double human figure, seen from the front and from the back, set within a mandorla bearing the zodiac signs. Similar but simpler images spread through the woodcuts of printed almanacs in the fifteenth and sixteenth centuries.

In many manuscripts the figure comes with tables of lunar days, indicating which moments of the month were thought suitable or unsuitable for treatments, journeys or work. These collections, called lunaria, blend learned astrology with beliefs of more popular origin, and they show how the Moon was the meeting point between university learning and the daily life of peasants, craftsmen and merchants.

The zodiac man is today a familiar image to historians of art and medicine, and it remains a precious witness to how people of the past imagined the human body immersed in the rhythms of the cosmos. The Moon, which each month travels over the whole figure from head to foot, was its most evident measure, together with the slow yearly course of the Sun.