Having now done with the ancient authorities, we shall only give further the declaration of the celebrated Boccacio regarding the plague of Florence: “E fu questa pestilenza di maggior forza, percio che essa dagl’ infermi di quella per lo communicare insieme s’avventava a’ sani non altramenti che faccia il fuoco alle cose secche o unte, quando molto gli sono avvicinate.” (Decameron, Introduzione.) The result of our investigations into the opinions of the ancients on this subject leads us to the conclusion, that all, or at least the most intelligent of the medical authorities, held that the plague is communicated, not by any specific virus, but in consequence of the atmosphere around the sick being contaminated with putrid effluvia. Hence, they maintained that mild fevers (συνηθεῖς) which show no tendency to putrescency are not communicable from one person to another. See Alexander Aphrodisiensis, (_l. c._) Fracastorius, in like manner, considered putrefaction as the source of all contagion. (De Contag. i); and nearly the same opinion was maintained by the learned Fernel, Franciscus de Pedemont, Ingrassius, Ficinus, and others. (See Prælect. Mar. 77.) Although Galen several times speaks of a poison being formed in the human body, he means that the animal fluids are so altered as to become deleterious, and does not hold that there is any specific virus transmitted from one person to another. (De Loc. Affect. v, 7, vi, 5; Epidem. iii.) We may take this opportunity of stating that, after a pretty extensive investigation into the histories of pestilential epidemics, we have come to the conclusion that the plague has almost invariably assumed one or other of the following phases: 1st. That of cholera and dysentery. The plague described by Thucydides, and that of Ingrassias, and many other pestilential epidemics described in ancient and modern times, including the Asiatic cholera of the present age, belong to this class. 2d. That of profuse; and, as they have been termed, syncoptic sweats. The celebrated epidemic of the fifteenth century, now so admirably illustrated by M. Hecker, is the best marked instance which we possess of this form of the disease. M. Hecker, indeed, supposes that the Cardiac disease of the ancients was of a similar nature to the sweating sickness. But it strikes us (although we must admit that we have not had time to consider this point maturely), that the syncoptic fever or cardiac disease of the ancients, was not of a pestilential nature. 3d. The other form is the Glandular plague, which many late authorities would consider as the only form of the disease; but as we think erroneously, since the other types are often mixed up with this in the same epidemic. Thus in the plague of Aleppo, during the years 1760, 1761, and 1762, although the ordinary form of the disease was the glandular, a considerable proportion of the cases assumed the first form which we have noticed. And in the plague of