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
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