We have all heard of Boccaccio's _Decameron_--only naughty people have _read it_--and how it was written when the plague was raging at Florence, the great plague that carried off Petrarch's Laura, and those other thousands of whom the world knew nothing then and knows nothing now. Some, too, have heard that the plague swept over Europe--desolating, devastating--the spectre with the swinging scythe mowing down broad swathes of men. Some, when they hear of it, picture to themselves Pope Clement VI. at Avignon, sitting in that vast palace that overlooks the Rhone, the stench of corpses mastered for him by the fragrant smoke of aromatic logs burning in huge pyres round about him night and day. Some have heard of Giovanne Villani, the historian of Florence, who wrote feebly about that same pestilence in his native city, and who doubtless would have written more, and more plainly and more strongly, but that in the midst of his writing Azrael touched him too, and his pen fell from his hand. [Footnote: Muratori, "Rerum Italicarum Scriptores," vol. xiii. pp, 1-771.] Some few, again, have a faint recollection of that Emperor of the West, John Cantacuzene, who ruled at Constantinople when the plague was, and who wrote about it. [Footnote: His four books of Histories are to be found in the "Corpus Scriptorum Historiae Byzantinae."] Didn't he? Nay! Hadn't he a son, Andronicus, who died of it? How did it come to pass that Gibbon did not so much as allude to it? Some, peradventure, think of Rome and of Rienzi, and how it was about that time that he was potent, or was he in hiding there among the Fraticelli? And isn't there something too about the plague visiting Greenland, and putting back the clock that was moving on steadily, but which suddenly stopped? How vague we are! * * * * * * * What was this plague? How did it strike men down? "It showed itself," says Boccaccio, "in a sad and wonderful manner; and _different from what it had been in the East_, where bleeding from the nose is the fatal prognostic, here [at Florence] there appeared certain tumours in the groin or under the armpits, some as big as an apple, others as big as an egg; and afterwards purple spots in most parts of the body: in some cases large and but few in number, in others less and more numerous, both kinds the usual messengers of death... They generally died," he adds, "the third day from the first appearance of the symptoms, without a fever or other bad circumstance attending." "It took men generally in the head and stomach, appearing first in the groin," says Villani, "or under the armpits, by little knobs or swellings called kernels, boils, blains, blisters, pimples, or plague-sores; being generally attended with devouring fever, with occasional spitting and vomiting of blood, whence, for the most part, they died presently or in half a day, or within a day or two at the most."