NOW it is not improbable that the _Animal Spirits_ are a thin Liquor, separated in the Brain, and from thence derived into the Nerves, of such a Nature that it admits, and has incorporated with it, a great Quantity of this _elastic Fluid_: which makes it a vital Substance of great Energy. And a Liquor of this kind must be very susceptible of Alterations from other active Bodies of a different Nature from it, if they approach to and are mixed with it: as we see some _Chemical Spirits_ upon their being put together, fall into a Fermentation, and make a Composition of a quite different kind.
IF therefore we allow the _Effluvia_ or _Exhalations_ from a corrupted Mass of Humours in a Body that has the _Plague_ to be volatile and firey Particles, carrying with them the Qualities, of those fermenting Juices from which they proceed; it will not be hard to conceive how these may, when received into the _nervous Fluid_ of a sound Person, excite in it such intestine Motions as may make it to partake of their own Properties, and become more unfit for the Purposes of the animal Oeconomy. But of this more in another Place.
THIS is one means by which the _Plague_, when once bred, is spread and increased: but the second of the forementioned Causes, namely, _Goods from infected Places_, extends the Mischief much wider. By the preceding Cause, the _Plague_ may be spread from _Person_ to _Person_, from _House_ to _House_, or perhaps from _Town_ to _Town_, tho' not to any great Distance; but this carries it into the remotest Regions. From hence the trading Parts of _Europe_ have their principal Apprehensions, and universally have recourse to _Quarantaines_ for their Security. The Universality of which Practice is a strong Argument, that _Merchandize_ will communicate _Infection_: for one cannot imagine, that so many Countries should agree in such a Custom without the most weighty Reasons. But besides, there is not wanting express Proof of this, from particular Examples, where this Injury has been done by several sorts of Goods carried from infected Places to others. Some of these I shall hereafter be obliged to mention; at present I shall confine my self to three Instances only. The _first_ shall be of the Entrance of the _Plague_ into _Rome_ in the Year 1656, which we are assured was conveyed thither from _Naples_ by Clothes and other Wares from that Place, brought first to Port _Neptuno_, and carried from thence to the Neighbouring Castle of St. _Lawrence_: which after having been kept some time there, were conveyed into _Rome_[51]. The _second_ Instance I shall take is from the Account given us of the Entrance of the Plague into _Marseilles_[52]; which being drawn up with great Exactness, may be the more rely'd on. It appears indisputably by this Account, that the Mischief was brought thither by Goods from the _Levant_. For the first, who had the Distemper, was one of the _Crew_ of the _Ship_, which brought those _Goods_: the next were those, who attended upon the same _Goods_, while they were under _Quarantaine_; and soon after the _Surgeon_, whom the Magistrates of _Marseilles_ appointed to examine the Bodies of those, who died.