Book II THE PLAGUE 115

tain similar affections and dispositions from which a pestilent
fever is presently produced, first in our bodies and is transmitted
from one person to another. Again, some of these fevers are
produced originally in us, not by means of a taint in the air,
but from a taint in other things such as food, and generally
speaking, from the tainted condition of such things as are wont
to cause pernicious putrefactions.

Since this contagion is susceptible (invades) so very quickly,
we must conclude that the germs of these fevers are very keen
and very volatile, and further that they have a special analogy
(selective affinity) either with the spirits and spiritual factors
or with the bilious humors. Hence some are fatal in a few
hours, I mean those which are analogous with the spirits and
spiritual factors and work not only by a material but also by a
spiritual antipathy. Others kill more slowly, though they are
still fatal in all or most eases. 'Those which work by both
kinds of antipathy against the spirits and the heart, and depend
mainly on the air, and are inhaled with the breath are always
fatal; while those which have their seat in the bilious humors, or
in blood which is burned or even pure, are fatal in most cases;
and for this reason insomnia is more frequent in this sort of
fever than in others; whereas those which arise in the blood,
especially if there is abundant pituita, induce sleep alternating
with insomnia. For the rest, these fevers also have a mild
aspect, though the malady is very serious. 'The cause of this
is the same as in other fevers, namely that the putrefaction is
deep—seated and foul, hence its acuteness is not clearly percep—
tible, partly because it is blunted by the great amount of mois—
ture that evaporates, (a proof of which is that the germs are vis—
eous and leave fomes behind), partly because the senses them—
selves are dulled.  But if some of these fevers are aecompanied
by very high temperature in the initial stage, that is due to the
fact that the putrefaction is not yet deep—seated, for that kind
of fever begins originally in our bodies and behaves like other
fevers which are not contagious, but are for the most part bilious.
Soon, however, deep—seated putrefaction is produced, and now
the fever begins to appear both contagious and less violent.

For the reason that has been stated for other fevers, the pulse
is observed to be small and slow, I mean that nature does not
venture to expand the veins, lest she should open a way in for
the poison. 'The fact that the urine in some cases looks like