The influence of the position of the moon in determining the proper seasons for surgical operations, and for the administration of medicines, may be best illustrated by a few extracts from ancient almanacs. An antique illustrated manuscript almanac for the year 1386 contains the following advice to physicians: In a new mone sal not be layting of blode, for yan are mennys bodyes voyed of blode and humos, and yan by layting of blode sal yay more be anoyded. And again:— It es to know generally, yt ye tyme electe to gyve a medcyn in es whan ye mone and ye Lord ascendyng ar free from all ille and not let by it, … and it es hyely to be ware to a medcyn whyles ye mone es in an ill aspect, wt Satne or Mars. An almanac for the year 1568, published by John Securis, London, contains a list of days in that year favorable or otherwise for the preservation of man’s health. The second day of January was therein declared to be wholly propitious. The twelfth was unfavorable, owing to the furious aspect of Mars to the Sun, which was not, however, likely to cause bodily sickness, but rather to incline the hearts of some people to imagine evil of their rulers. The fifteenth of April was especially to be dreaded. On that day, says the writer, “God keep us from the fury of Mars.” In June evil passions were to stir men’s hearts, anger, hatred, and strife; for in that month were no less than six quartile aspects of the planets, one to another. Many propitious days are also mentioned, and in conclusion _all_ days are declared to be favorable to a good man. “A New Almanacke and Prognostication for the Yeare of our Lord God 1569” (London) says that surgical operations must be performed only when “the Moone or Lorde of the firste house” is in the zodiacal sign governing the particular member or organ which is to be operated upon. And in an English almanac for the year 1571 we find the following passage:— No part of man’s body ought to be touched with the Chirurgicall instruments, or cauterie actuall or potencial, when the Sunne or Moone, or the Lord of the Ascendent, is in the same signe that ruleth that part of man’s body. Also _Gemini_, _Leo_, the last halfe of _Libra_, and the first 12 degrees of _Scorpio_: with _Taurus_, _Virgo_, and _Capricorne_, are not good for the letting of bloud. Two days before the change of the Moone, and a day after, is yll to let bloud.… If the same be for the Pestilence, the Phrensie, the Pluresie, the Squincie, or for a Continuall headach, proceeding of choler or bloud; or for any burning Ague, or extreme paine of partes, a man may not so carefully stay for a chosen day by the _Almanack_: for that in the meane tyme the pacient perhaps may dye. For which cause let the skilfull Chirurgeon open a veine, unless he finde the pacient verie weake, or that the Moone be in the Same Syne that governeth that part of man’s body.