Book II 8SVPHILIS — ) 149

Since contagious diseases have their own special analogies
(selective properties) and their special principles, as I have al—
ready said, must be analogous with such things as receive the
infection, it is clear that the principles of this contagion were
analogous with thick, foul phlegm. For, if we consider the
pustules which appeared in this malady, the gummata, and the
pains in the muscles,*5 we shall see everywhere only mucus and
foulness, and finally viscous, mucilaginous, thick phlegm.  From
this we must conclude that the germs also, on which every con—
tagion per se depends, were, in their own fashion, of this same
character; and that the air also, in which was the source of the
disease, had contraeted a disposition of that kind; that the
germs in it were also viscous and analogous with a precisely
similar phlegm, and had power to produce in their turn, in it,
other germs of the same kind as were the original germs. And
since this contagion erodes and eats its way out, its germs must
be sharp, though they were enclosed and buried deep in much
viscosity. We must therefore suppose that this infection pos—
sessed principles of this kind, and that there had stolen into
the air a certain foul putrefaction which later proved to be
analogous with the thick, foul phlegm in our bodies.  But how,
and from what causes, there was produced in the air a disposi—
tion of that kind is indeed hard to know for certain.  But if it
be possible to make a rational conjecture, it will surely be the
following: Whatever may be the cause and principle that
produced this contagion, it must be one of those that seldom
happen; seeing that that disposition of the air which gave birth
to this contagion, so seldom seen, is among those which seldom
happen. Now since, as I have said above, our world below
can be greatly changed by what lies above us, I mean the sky
and the heavenly bodies, and is affected by them in various
ways, there seems to be no other possible factor which could
have so contaminated the air over so many countries and over
so great a space, except the constitutions of the sky and the
heavenly bodies, and these constitutions must have been such
as seldom occur, but when they do occur can produce great
effects. As I have shown above, the heavenly bodies can bring
into play on this earth great and portentous phenomena at
that time when several of them are in conjunction.  And in
faect we have seen in our time such a reunion and conjunection
of the heavenly bodies, namely the three of highest rank, Saturn,