CHAPTER IV
THE DIFFERENTIAE AND ACCIDENTS OF PESTILENT FEVERS

Of pestilent fevers, some reach us from. outside, others arise
originally in us; some are always fatal, others are fatal to the
majority, others again are only frequently fatal. Their analogy
(selective property) is varied and surprising. For some are
especially analogous with the blood,^3 others with the bile, while
some are analogous with certain humors, others again are analo—
gous with all the humors indiscriminately, others with the spirits
alone, or with them especially. Some are quickly fata!, others
kill more slowly.

Of external origin are those fevers whose germs have been
first conceived in the air or the earth etc. and these things must
have been previously corrupted, if the term contagion is to be
used correctly. I say germs, not simple vapors, for, as I have
said above, there is a great difference between germs and vapors.
In our bodies, originally, arise those fevers which along with
others have their origin in general causes such as plethora&
obstructions and a malignant condition of the humors.  But in
this case the putrefaction is both foul and confined, and of
such a kind that germs of pernicious contagion are produced in
it. 'There is no reason why such a contagion should not often
be produced first in some individual, and presently be trans—
mitted from that person to others. But all contagions that
have analogy with the spirits and spiritua!l factors are fatal,
especially those that reach us from without and are drawn in
by the breath.  'Those that are analogous with the keen humors
are fatal to most of the infected, especially if they are carried
into the body from without; those that are related to the denser
humors are fatal in many cases. How and for what reasons
their analogies are so various I have stated above in a general
way, and I shall therefore not repeat myself now.

Let me now speak of their accidents, (incidental charaeter—
isties) in so far as we know their indications and have experience
of these fevers. First and foremost, these fevers are per se

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