Mercury in Medical Astrology

Mercury was the planet of speech and thought in Ptolemy and of the tongue, the brain and the hands in Lilly and Culpeper, and it was the one classical planet whose humoral nature the texts refused to fix. Ptolemy wrote that it dried or moistened according to the planet it joined, and Lilly repeated the rule that Mercury took on the nature of its company. Its place in a sickness question was the same as any planet’s, read from the house it occupied and the parts assigned to it, and it had a special tie to the 1st house, where Lilly said it rejoiced. Two things set it apart in practice: it stood within a sign of the Sun at all times, so it was combust more often than any other body in the chart, and it ran retrograde for about a fifth of its days. Both were debilities in Lilly’s table, and this page says what the texts held them to signify, never what they do to anyone.

Lilly’s table of essential dignities gave Mercury two houses, Gemini and Virgo, and set its exaltation in Virgo as well, the only case in the table where a planet’s house and its exaltation were the same sign. Its detriment fell in Sagittarius and Pisces, its fall in Pisces, and its triplicity was the airy signs by night. Mercury had terms and faces of its own, as the five planets did, and a Mercury with none of these in its place was peregrine, a debility Lilly scored as heavily as detriment.

The retrograde share in the stays table is 19.17% of days, the largest of the three planets that stay close to the Sun. Lilly listed retrograde motion among the debilities and read a retrograde significator in a question as a matter that returned, undid itself or went otherwise than it seemed. In the chapter on sickness that reading was applied to the course of the disease rather than to the person, as a sign the texts took to mean the matter would not go straight. A planet turning direct was read the other way, and Lilly gave weight to the exact day of the station.

Combustion applied to Mercury more than to any other planet, because Mercury never stands farther from the Sun than about a sign’s width and passes it twice in every loop. Lilly counted a planet combust within a fixed distance of the Sun in the same sign, under the beams at a wider one, and cazimi at the Sun’s very center, which he scored as a strong fortitude. The tradition read a combust Mercury as a significator whose voice was drowned out by the Sun’s light. Because the two met so often, astrologers of Lilly’s time counted Mercury’s combustion as a routine entry in the score rather than as a mark of anything unusual.

The stays table for Mercury is the most irregular of the four fastest movers in this series, and the irregularity is the loops. Over 1900 to 2050 the sample counts 2,236 sign entries, more than the Sun’s twelve a year, because a retrograde Mercury that retreats across a cusp and then crosses it again forward is counted at each crossing. The mean stay of 24.7 days is shorter than a solar month for the same reason: some entries are brief visits that end when the planet turns.

At the other extreme the longest stay is 70 days, in Cancer, which is what a retrograde loop made entirely inside one sign looks like in a table of days. Mercury entered the sign, slowed, stationed, ran backward without leaving, stationed again and finally crossed out, and the sign kept it for more than two solar months. The signs that catch a whole loop vary from year to year, so the table spreads such long stays across the zodiac rather than piling them on one sign.

The spread by sign is wider than the Sun’s or the Moon’s. Mercury spends 9.08% of its days in Sagittarius and 7.55% in Gemini, two signs opposite each other across the zodiac. The reason lies in the shape of Mercury’s orbit, the most elongated of the classical seven, and in where its loops tend to fall against the Sun’s yearly round; the unevenness is in the ephemeris, not in any doctrine of the texts. No example chart appears on this page, since neither of the site’s two specimen charts has Mercury in the 6th or on an angle, and the tables themselves stand as the specimen.

The table beneath this section gives the three sources in their own words. Ptolemy’s row runs to speech and thought as faculties and then to the tongue, the bile and the buttocks. Lilly’s begins with the brain and the tongue and adds the hands and the imagination. Culpeper’s matches Lilly’s for the brain, the tongue and the hands, and finishes with the nerves in place of the imagination. The tongue is therefore the one organ in every column, and speech, the tongue’s work, is the faculty Ptolemy led with.

Where Lilly and Culpeper agreed and Ptolemy did not is the brain and the hands. Ptolemy had placed the brain under the Sun, and the hands belong in the sign list rather than the planet list in his scheme, under the Twins. The English authors drew the two lists together, and since Mercury ruled Gemini the hands moved from the sign to its lord. Ptolemy’s bile and buttocks have no counterpart in the later rows; Culpeper’s nerves have none in the earlier, and reflect the anatomy of his own century rather than Ptolemy’s.

The nature column reads changeable (no vote), which is the site’s way of recording Ptolemy’s rule that Mercury had no fixed quality of its own; the temperament calculator accordingly gives a Mercury in the 1st house no vote. The two signs in the rules column, Gemini and Virgo, were listed on the Zodiac Man at the arms and hands and at the belly and bowels, so one of Mercury’s signs matched its planet list and the other did not. The planets and the body guide sets this row against the other six.

Lilly’s chapter on the houses gave each planet a house in which it rejoiced, and Mercury’s was the 1st. A Mercury in the 1st house was therefore in its joy, an accidental fortitude in his table, and in a nativity it stood in the house of the native’s body and mind. Lilly’s chapter on Mercury, like his other planet chapters, described the person it signified when it ruled the Ascendant or stood in the 1st, by stature, coloring and manner, as portraiture and not as medicine. Ptolemy read the mind from Mercury and the Moon together, in the chapter that follows his chapter on the body.

The 6th house had a different tie to Mercury. In the order of consignificators that Lilly set out, each house took a planet in the Chaldean sequence beginning with Saturn in the 1st, and the 6th fell to Mercury; its consignificator among the signs was Virgo, Mercury’s own sign and exaltation. Mars rejoiced in the 6th, not Mercury, but Mercury was the planet Lilly named as the house’s natural partner. A Mercury inside the 6th was then read as one of the significators of the disease, by its state and by the parts in the table above, with the tongue, the brain and the hands as the regions the texts attached to it.

Culpeper’s decumbiture method read the same house with the same significators, and his chapter on the planets listed Mercury’s diseases under the parts above. Because Mercury had no humor of its own, both authors judged the quality of what it signified by the planet it was joined to or aspected by, hot with Mars, cold with Saturn, and so on. The 6th house guide sets out the house, its ruler and what the 1st, 8th and 12th added to the reading.

Mercury travels with the Sun, so it stands in the Placidus 6th house in the hours around dusk: a little before sunset when it trails the Sun through the zodiac, a little after when it leads. The sample finds it there 2.02 hours a day at forty degrees north, which is 8.43% of charts, with 8.35% at the equator and 8.47% at sixty degrees north. The Whole Sign count at forty degrees north is 8.35%, which differs from the Placidus count by less than the sampling step could resolve.

Every figure in the table sits near one twelfth, and the slight rise with latitude is small enough to be the sample rather than the sky. What the table does establish is that Mercury in the 6th is an ordinary placement, one chart in about twelve, under either house system. For a chart near the cusp the two systems can disagree, and the methodology page states the house system and the stepping the sample used.

Since Mercury took its quality from its company, Lilly’s first move after noting its sign and house was to find that company: the planet it was conjoined to, the planets casting a sextile, square, trine or opposition to it, and the lord of the sign it stood in. A Mercury joined to Saturn was read cold and dry, to Mars hot and dry, and the parts and diseases it signified were colored accordingly. Its distance from the Sun came next, since combustion or cazimi changed its score, and then its motion, direct, retrograde or stationary.

Of the other pages in this series, Venus is the closest companion, as the other planet bound to the Sun’s neighborhood with a retrograde loop of its own; the Sun page explains the combustion rule from the Sun’s side. The sign pages for the 6th house include both of Mercury’s signs, Gemini and Virgo, among the twelve cusps. The planets and the body guide reads the seven rows of the parts table together, and the Zodiac Man guide explains the sign list that gave Gemini the hands.