Medical Astrology: Science, Art, and Influence in early-modern Europe
General Medicine, Precisely Timed
Explore: General Medicine by the Moon and Sun| Eclipses and the Lunar Nodes: A Brief, Astronomical Excursus | Diagnostic Diagrams: Assessing Lunar Influence
General Medicine by the Moon and Sun
Detail of the "Shadow of the Earth" volvelle from the Astronomicum Caesareum (1540). Click the image for more information.
To practice medical astrology was to observe a careful schedule. To determine this schedule, physicians drew on any number of different astrological methods, which historians often divide into two occupational camps: natural and judicial astrology.* For the historian, this distinction is useful. It sheds light on the many meanings and histories conveyed by the word “astrology,” and disentangles widely accepted practices from contested ones. In this divided construct, natural astrology is framed as universally embraced, while judicial astrology is described as controversial. This disparity is framed as a matter of means and method: the former is said to stress observable planetary influences—e.g., light, heat, etc.—to make predictions about weather, health, and husbandry, among other topics, while the latter is said to favor horoscopic interpretation over direct observation. Although a useful construct for the historian, this division is somewhat misleading for the imagery in this survey, which illustrates the influence of both methods. Better suited for this imagery is an artificial distinction between popular and pointed prognostication, or between Generalist and Specialist Medicine. The imagery on this page and the next reflects this idea of General medical astrology. It paints a picture of a practice primarily centered on the movements of the Moon and the Sun, such that preventative and curative treatments typically followed a monthly or seasonal schedule. Physicians, barber surgeons, and others practicing this lunar- and solar-based physic* generally determined schedules for treatment without drawing individual horoscopes: i.e., a visual diagram showing the positions of the planets at a particular time. Following guidelines laid out in Ptolemy’s Tetrabiblos, the lunar- and solar-focused physician instead stressed a few particular data points: (1) the time of year; (2) the location of the Moon in the Zodiac; (3) the lunar phases; and (4) the planetary hours. The Zodiac Man was central to the imagery of this practice, as were calendrical diagrams of the Moon and its many phases. Particular attention was also paid to eclipses—to their time, location, and duration—though, their calculation was generally the purview not of astrologer-physicians but of astronomer-astrologers like Johannes Müller von Königsberg (1436–1476), otherwise known as Johannes Regiomontanus.
* The term physic refers to the art or science of medical healing, as well as to the curative substances or remedies used to treat disease—especially purgative treatments, e.g., laxatives, emetics, bloodletting, etc
Click on any of the images below for more information.
Eclipses and the Lunar Nodes: A Brief, Astronomical Excursus
The images above underscore astrology's interdisciplinarity. Note, for example, the first two images in the gallery. These are pages from the first edition of Johannes Regiomontanus’s Calendarium from 1474, which provided projections of eclipses, as well as new and full moons for the years 1474–1530. In July 1471, Regiomontanus wrote of his intention to make important scientific works available in print, and this is precisely what his Nuremberg press achieved during the few short years of its operation (ca.1471 to 1475). His calendars and massive 896-page ephemerides, replete with daily planetary positions, set a new standard for both the calculation and visual communication of celestial information, particularly eclipses. Pages, like the ones above, not only predicted the time of eclipses accurately to within 7 minutes but also rendered the extent and character of each event comprehensible at a single glance, thanks to carefully hand-colored diagrams. These highly sought-after publications were a boon, in particular, for bloodletting procedures. Precise knowledge of eclipses provided physicians with powerful information with which to treat patients, since performing procedures near the time of an eclipse was considered particularly perilous.
Of equal interdisciplinary import were the eclipse illustrations by Michael Ostendorfer (1490–1559) from Peter Apian’s Astronomicum Caesareum (1540)—displayed in the galleries both above and below. Apian’s landmark, folio-format text features no fewer than five volvelles with which to calculate eclipses. Following in the footsteps of Regiomontanus, Apian’s devotion to eclipses and their visualization was significant not only for the practice of physic but also, writes historian Anthony Grafton, for historical scholarship and its practices. One of the innovations of the Astronomicum Caesareum is Apian’s advocacy for the marriage of history, astronomy, and philology by means of eclipses. Apian’s wager: use the eclipses mentioned in ancient and medieval texts to rectify chronological inaccuracies and determine historical dates—both past and future—with absolute precision. Although Apian bungled his own wager, the German astronomer Paulus Crusius (1525–1572) followed by the Dutch historian Joseph Scaliger (1540–1609) later confirmed his idea, proving that eclipses could be used to resolve ambiguities in the historical record, since they were precisely calculable events.
A key calculation in Apian’s proposition was the Lunar Nodes. Briefly defined, the Lunar Nodes are the two precisely calculable yet changeable points at which the Moon crosses the ecliptic twice a year. The ecliptic is so-called because solar and lunar eclipses can only happen when the Moon crosses this plane. During eclipses, then, the Moon is to be found at the ecliptic; but, at other times, the Moon is either slightly below the ecliptic or above it. The North Node [☊] marks the Moon's ascension from below to above, while the South Node [☋] indicates the opposite, marking the Moon's descending passage from above to below. However, the position of each node changes with each lunar crossing over the course of a 19-year period known as the Metonic Cycle.** The Moon eventually returns to these points over the course of its next cycle.
The astrological iconography associated with the Lunar Nodes helps to simplify this otherwise confusing topic. The North Node is called "The Dragon's Head" while the South Node is known as "The Dragon's Tail." Why Dragons? One explanation is philological: the "head of the dragon" and "tail of the dragon" are terminological holdovers from medieval Arabic astronomy, and likely derive from twelfth-century Latin translations. Another explanation is astronomical: it stems from Athanasius Kircher's Ars magna lvcis et vmbrae (1646), specifically from the image above. This ingenious image is an eclipse calendar. It records both actual and projected dates for the solar and lunar eclipses during the years 1645–1650. A quick glance at NASA's eclipse tables confirms this information: there was a partial lunar eclipse on 10 February 1645 (Saros 108) followed by a hybrid solar eclipse on 21 August 1645 (Saros 139), and so on; though, some of Kircher's predictions are more precise than others. Still, this image is remarkable because it delineates a possible astronomical explanation for the dragon. The gnomonic grid at center represents the ecliptic and Zodiac belt, which the Moon crosses twice a year. The dragon, winding its way through this grid, evokes the Moon's varying passage through the ecliptic. It shows how the Moon's crossing points, when plotted and linked over time, chart a sinuous, serpentine course through the ecliptic. Hence, the astrological association between the Lunar Nodes and the Dragon; or rather, one possible explanation for this association.
The takeaway from this excursus: Eclipses were tremendously significant for all the astrologically interrelated disciplines at this time—medicine included. For this reason, much ceremony is devoted to their calculation, as the images and the video below further demonstrate.
**The term "Metonic Cycle" refers to a relationship between the cycles of the Moon and the cycles of the Sun. Named for the 5th century BCE Greek astronomer Meton of Athens, it describes a period of 19 years—or 235 lunar months— after which the new moon recurs on the same day of the year.
Lunar Phases Volvelle. Astronomicum Caesareum (1540). Click the image for more information.
Lunar Node Volvelle. Astronomicum Caesareum (1540). Click the image for more information
Title Page: Detail. Astronomicum Caesareum (1540). Click the image for more information.
Diagnostic Diagrams: Assessing Lunar Influence
These lunar-themed roundels from MS 26 (1553) are the ornamental offspring of the circular eclipse calendars that are typically found in late-medieval folding almanacs. Each medallion shows a Zodiac figure surrounded by English text that reads: "Luna being in Aries," "Luna being in Taurus," and so on. These framed medallions appear in a section of MS 26 entitled "The Infirmities, Members & Faces of Signs." This section modifies the manuscript's earlier assessments of the Planets and Signs by connecting certain Planet-Sign combinations to new parts of the body. For example, we learn earlier in the manuscript that the Moon governs the brains and Aries the head. At this point, however, we learn that when the Moon is in Aries it instead governs the knees [Luna hath ye knees]. The roundels thus transform an earlier, calendrical type into a visual heuristic, or mental shortcut, for deciphering the combined Planet-Sign influence on the body.
Works Cited on this Page
Barnes, Robin Bruce. Astrology and Reformation. Oxford; New York: Oxford University Press, 2016.
Bryan, Elizabeth J. “Astronomy Translated: Caput Draconis and the Pendragon Star in Geoffrey of Monmouth, Wace, and Lazamon.” Arthuriana 26, No. 1 (2016): 141–163.
Carey, Hilary M. “What is the Folded Almanac? The Form and Function of a Key Manuscript Source for Astro-medical Practice in Later Medieval England.” Social History of Medicine 16, No. 3 (2003): 481–509.
Grafton, Anthony. “Petrus Apianus Draws up a Calendar.” Journal for the History of Astronomy 42, No. 1 (2011): 55–72.
Grafton, Anthony. “Some Uses of Eclipses in Early Modern Chronology.” Journal of the History of Ideas 64, No. 2 (April 2003): 213–229.
Jensen, Phebe. Astrology, Almanacs, and the Early Modern English Calendar. London; New York: Routledge, 2021.
Rutkin, Darrel H. Sapientia Astrologica: Astrology, Magic, and Natural Knowledge, ca. 1250–1800. Archimedes 55: New Studies in the History and Philosophy of Science and Technology. Cham, Switzerland: Springer, 2019.
Rutkin, Darrel H. “Understanding the History of Astrology (and Magic) Accurately: Methodological Reflections on Terminology and Anachronism.” Philosophical Readings 7, No. 1 (2015): 42–54.
Schmidt, Suzanne Kathleen Karr. Interactive and Sculptural Printmaking in the Renaissance. Leiden; Boston: Brill, 2018.
Shank, Michael H. “The Geometrical Diagrams in Regiomontanus’s Edition of His Own Disputationes (c.1475): Background, Production, and Diffusion.” Journal for the History of Astronomy 43, No. 1 (2012): 27–55.
Steele, John M. and F. Richard Stephenson. “Eclipse Observations Made by Regiomontanus and Walther.” Journal for the History of Astronomy 29, No. 4 (1998): 331–344.
Wallis, Faith. “Medicine in Medieval Calendar Manuscripts.” In Manuscript Sources of Medieval Medicine: A Book of Essays. Edited by Margaret R. Schleissner. 1995.
* For more on this terminological distinction, including arguments against it, see in particular:
Campion, Nicolas. A History of Western Astrology, Volume II: The Medieval and Modern Worlds (London; New York: Continuum, 2009), xii, 13–14, 33–34.
Cooper, Glen. “Galen and Astrology: A Mésalliance?” Early Science and Medicine 16, No. 2 (2011): 123–24.
Jensen, Phebe. “1.1 Astrology,” in Astrology, Almanacs, and the Early Modern English Calendar (London; New York: Routledge, 2021), 7, 17–33.
Rutkin, Darrel H. Sapientia Astrologica: Astrology, Magic, and Natural Knowledge, ca. 1250–1800. Archimedes 55: New Studies in the History and Philosophy of Science and Technology. Cham, Switzerland: Springer, 2019.
Rutkin, Darrel H. “Understanding the History of Astrology (and Magic) Accurately: Methodological Reflections on Terminology and Anachronism.” Philosophical Readings 7, No. 1 (2015): 44.