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
subordinate causes. By these, according to his opinion, the
quality of the air, and of the other elements, was so altered that
they set poisonous fluids in motion towards the inward parts of
the body, in the same manner as the magnet attracts iron; whence
there arose in the commencement fever and the spitting of blood;
afterwards, however, a deposition in the form on glandular
swellings and inflammatory boils. Herein the notion of an
epidemic constitution was set forth clearly, and conformably to
the spirit of the age. Of contagion, Guy de Chauliac was