Counsel Against the Plague

pigs
cat
dog

...times [it] has been transmitted from humans to pigs. It may perhaps be because of some similarity—I do not say of spirits, but of complexion. Twice in these days, a cat and a dog have carried the disease from house to house, and said animals are not sick. And do not marvel that sometimes the beast or human catches said vapor and is not harmed by it, and yet harms others, because a red-hot iron inflames and consumes tow and straw, and is not consumed itself. This proceeds from the disposition of the receiving subject, in which consists the greater part of the effect, according to Aristotle, Galen, and Avicenna. In such a way that in these days in our village, a child of two years stayed all day long close to one diseased, aged seven, and many times ate morsels that he had chewed; it did not catch on him, but it did on others who stood further away. Do not trust, therefore, in saying, "I am perhaps not disposed to receive it." Keep in mind this physical rule:

and very disposed
by small cause
are harmed.

that when the matter is very disposed, the acting cause, however weak it may be, operates quickly. Thus, the spark ignites the tow and the sulfur; and conversely, the most potent cause operates in the matter even if it does not appear disposed.

and not disposed
by most potent
cause are harmed.

And although the match catches fire more quickly than the wood, and dry wood [catches more quickly] than—