even craving, and only a light pain in
their heads, have sent for physicians to know what ailed them, and have
been found, to their great surprise, at the brink of death: the tokens
upon them, or the plague grown up to an incurable height.

It was very sad to reflect how such a person as this last mentioned
above had been a walking destroyer perhaps for a week or a fortnight
before that; how he had ruined those that he would have hazarded his
life to save, and had been breathing death upon them, even perhaps
in his tender kissing and embracings of his own children. Yet thus
certainly it was, and often has been, and I could give many particular
cases where it has been so. If then the blow is thus insensibly
striking--if the arrow flies thus unseen, and cannot be discovered--to
what purpose are all the schemes for shutting up or removing the sick
people? Those schemes cannot take place but upon those that appear to be
sick, or to be infected; whereas there are among them at the same time
thousands of people who seem to be well, but are all that while carrying
death with them into all companies which they come into.

This frequently puzzled our physicians, and especially the apothecaries
and surgeons, who knew not how to discover the sick from the sound; they
all allowed that it was really so, that many people had the plague in
their very blood, and preying upon their spirits, and were in themselves
but walking putrefied carcases whose breath was infectious and their
sweat poison, and yet were as well to look on as other people, and even
knew it not themselves; I say, they all allowed that it was really true
in fact, but they knew not how to propose a discovery.

My friend Dr Heath was of opinion that it might be known by the smell of
their breath; but then, as he said, who durst smell to that breath
for his information? since, to know it, he must draw the stench of the
plague up into his own brain, in order to distinguish the smell! I have
heard it was the opinion of others that it might be distinguished by the
party's breathing upon a piece of glass, where, the breath condensing,
there might living creatures be seen by a microscope, of strange,
monstrous, and frightful shapes, such as dragons, snakes, serpents, and
devils, horrible to behold. But this I very much question the truth
of, and we had no microscopes at that time, as I remember, to make the
experiment with.

It was the opinion also of another learned man,