And the History of the most terrible of all the Plagues, that ever were in these Parts of the World, which was that in the Year 1349, gives a manifest Proof from whence all _Europe_ may trace the Origine of these Evils, viz. from _Asia_: for [8]This taking its Rise in _China_ in the Year 1346, advanced through the East _Indies_ to _Syria_, _Turkey_, _Ægypt_, _Greece_, _Africa_, &c. In 1347 some Ships from the _Levant_ carried it to _Sicily_, _Pisa_, _Genoa_, &c. In 1348 it got into _Savoy_, _Provence_, _Dauphiny_, _Catalonia_, _Castile_, &c. In 1349 it seized _England_, _Scotland_, _Ireland_, and _Flanders_; and in the next place _Germany_, _Hungary_, and _Denmark_; and in all these Countries made most incredible Havock. But to return to the Consideration of the Air, which we left in a putrid State: It is to be observed, that Putrefaction is a kind of Fermentation, and that all Bodies in a Ferment emit a volatile active Spirit, of Power to agitate, and put into intestine Motions, that is, to change the Nature of other Fluids into which it insinuates it self. It were easy to shew from the best _Theory_ of Fevers[9], how the Alterations made in the _Blood_ this Way will favour _Pestilential_ Diseases, by rendring the Body obnoxious to them: But the Digression would be too great. THIS is one step towards _Contagion_. The next, as it seems to me, proceeds after this Manner. The Blood in all _Malignant Fevers_, especially _Pestilential_ ones, at the latter End of the Disease, does like Fermenting Liquors throw off a great Quantity of active Particles upon the several _Glands_ of the Body, particularly upon those of the Mouth and Skin, from which the Secretions are naturally the most constant and large. These, in _Pestilential_ Cases, although the Air be in a right State, will generally infect those, who are very near to the sick Person; otherwise are soon dispersed and lost: But when in an evil Disposition of _This_ they meet with the subtle Parts, its Corruption has generated, by uniting with them they become much more active and powerful, and likewise more durable and lasting, so as to form an _Infectious Matter_ capable of conveying the Mischief to a great Distance from the diseased Body, out of which it was produced. They who know what strange Attractions and Combinations are made by volatile Spirits will understand this Reasoning; especially if they consider, how easily all kinds of _Effluvia_ are diffused in a warm Air, such as we have described an Infectious one to be; and further, of how penetrating a Force the finest Parts of Animal Juices are; of which the strange Stench of a mortified Limb, upon a Body yet living, will convince any one.