BookIII OF THE INFECTED SUBSTANCE 205

are endowed with greater force than that due to material quali—
ties, as I have said above, and we must especially include in
this class Lemnian earth, Armenian bole, seordium, heptaphyllon,
the horn of the unicorn, and the gems prev10usly mentioned,
especially the emerald48, also theriace and mithridatum, and
any other that has been proved by experience. Causties must
be used only when the contagion is external and of a malignant
charaecter, and in the initial stage. For when the contagion is
internal, you cannot apply caustiecs without too great risk.
However, when it is external, you may apply them, and you
ought to, if the contagion be malignant; but benefit will be de—
rived only at the initial stage.  For if the contagion has already
taken root and insinuated itself within, you will do no good by
administering caustics externally. But you may sometimes
apply remedies akin to caustiecs, and then you must mix with
them certain fats to carry them further in.  But if the contagion
is external but not malignant, then again caustics should not
be employed; for then it is possible to relieve the disease by
other and milder means and by detergents only, as in scabies
and the like affections.  But I shall speak about these again in
discussing particular diseases, and say when and how they are
appropriate.

Hot and dry remedies you should use when the substance is
not very acute but rather cold; use dry and cold remedies when
the substance is warmer. But since, among these, many are
styptic (astringent) and of denser substance, I shall later on
consider how they should be administered and how not. NVou
will find decoctions helpful when the contagion is internal, for
instance in fevers. But you will employ powders when your
object is, above all, to resist the putrefaction by a means whose
effects are manifold. : I have said enough in regard to the general
method of treatment, and I shall now proceed to the particular
remedies for each disease, beginning with fevers.