BookIII OF THE INFECTED SUBSTANCE 201

especially useful, not only because they are drying, but also
because by their peculiar stickiness they give the substance
more consistency. 'The dissolution may also be checked by
the admixture of certain powders which are themselves not
subject to putrefaection; when triturated as finely as possible
and inserted between the parts of the substance, they not only
by their very interposition hinder the activity of the substance
that is undergoing change, but also they hold the substance
together by a sort of binding which prevents it from being dis—
solved; in the same way as when one mixes sand with lime, which
binds it and gives it tenacity, or when flour is mixed with water.
For the tiny, moist particles penetrate into the finest pores, so
called, of the dry parts of the substance and cannot be separated
from them on account of the vacuum; and this above all con—
tributes to the strength of the combination, since nothing else
can make its way in.

Therefore you must not overlook or underrate the action of
these very small particles thus interspersed.  Who could imagine
that the presence of a little rennet in a large quantity of milk, or
the fine dust of the feathery flower of the artichoke, would coagu—
late the whole of the milk? Who would believe that when you
have a large copper kettle of boiling sugar,' so hot that it is on
the point of boiling over, you have only to throvw in a tiny piece
of butter, and it stops boiling and ceases to separate, so that
the boiling over and all the swelling ceases? And, as regards
putrefaction, we all know, do we not, how wine is preserved in
large caseks by the addition of a little alum, without which it
would very quickly putrefy? So we need not be surprised if,
by the interposition of certain powders, the putrefactions that
arise in our bodies can be checked. 'These, then, are the reme—
dies suitable for the substance when it is already imperilled.

In dealing with the substance that has already been corrupted
and cannot be restored to normal, there is only one thing to
aim at in treating it, namely to remove it from the body. 'This
is done either by drugs, when the substance is within the body,
or by incisions or dissolvents when it is external. For these
conditions, special prescriptions must be prepared by the doctor,
I do not mean those which restore to normal, but those which
make evacuation easier. Of all these I shall speak in more
detail when I discuss the particular diseases, since I am now
running through the more general methods.