, a method which answers in common
plagues, but which here afforded no complete security, because such was
the fury of the disease when it was at its height, that the atmosphere of
whole cities was penetrated by the infection.

Of the astral influence which was considered to have originated the
"Great Mortality," physicians and learned men were as completely
convinced as of the fact of its reality. A grand conjunction of the
three superior planets, Saturn, Jupiter, and Mars, in the sign of
Aquarius, which took place, according to Guy de Chauliac, on the 24th of
March, 1345, was generally received as its principal cause. In fixing
the day, this physician, who was deeply versed in astrology, did not
agree with others; whereupon there arose various disputations, of weight
in that age, but of none in ours. People, however, agree in this--that
conjunctions of the planets infallibly prognosticated great events; great
revolutions of kingdoms, new prophets, destructive plagues, and other
occurrences which bring distress and horror on mankind. No medical
author of the fourteenth and fifteenth centuries omits an opportunity of
representing them as among the general prognostics of great plagues; nor
can we, for our part, regard the astrology of the Middle Ages as a mere
offspring of superstition. It has not only, in common with all ideas
which inspire and guide mankind, a high historical importance, entirely
independent of its error or truth--for the influence of both is equally
powerful--but there are also contained in it, as in alchemy, grand
thoughts of antiquity, of which modern natural philosophy is so little
ashamed that she claims them as her property. Foremost among these is
the idea of general life which diffuses itself throughout the whole
universe, expressed by the greatest Greek sages, and transmitted to the
Middle Ages, through the new Platonic natural philosophy. To this
impression of an universal organism, the assumption of a reciprocal
influence of terrestrial bodies could not be foreign, nor did this cease
to correspond with a higher view of nature, until astrologers overstepped
the limits of human knowledge with frivolous and mystical calculations.

Guy de Chauliac considers the influence of the conjunction, which was
held to be all-potent, as the chief general cause of the Black Plague;
and the diseased state of bodies, the corruption of the fluids, debility,
obstruction, and so forth, as the especial sub