CHAPTER VIII
THE ANALOG* OF CONTAGIONS

Contagions have manifold and very surprising analogies
(selective properties). For instance, there is a certain pest
which attacks trees and crops, but harms no sort of animal;
again, there is a pest which attacks certain animals but spares
trees and crops. In the animal world, one pest will attack
man, another cattle, another horses, and so on; moreover, with—
in the human species, & contagion that affects children and
the young, does not harm old men, or vice versa; & contagion
which attacks men does not always attack women. Some
pests work promiscuously, so that some persons are infected,
others not; some persons can associate with the plague—stricken
and take no hurt,?' others cannot. 'The organs of the body
also have their own analogy (affinity), for ophthalmia harms
no organ save the eyes, while phthisis does not affect the eyes,
though they are so delicate, but does affect the lungs.?? Alo—
pecia and achores?3 attack the head only. It is true of the
humors also, that one sort of contagion affects one humor, but
not another, or again, another sort of contagion may affect all
the humors. Some contagions are especially fatal to the spirits.
All these phenomena are remarkable, but they resemble many
others which I discussed exhaustively in my treatise 'On Sym—
pathy!, where I investigated common causes which are to be
referred to the nature of the agent, or of the material, or again,
to the mode of application; that is the reason why all things
do not act on all things, but only certain ones on certain others,
and then they are called analogous.?^* But of particular /and
special analogies I do not intend to speak, and it would be
rash to discuss them.?5 For the present, if we cannot investi—
gate the special and immediate causes, at least let us try to
learn what are the intermediary causes, and so strive to ar—
rive at the proximate causes, so far as we may in view of the
material available.

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