After this we may naturally conclude, that where the Rooms, or Houses are small, there ought to be frequent Admissions of the External Air, but especially where those Rooms or Houses are too much crouded with People; and if it is supposed that the External Air is Infectious, the burning of _Aromaticks_, _Gums_, or _Herbs_, upon the letting in of fresh Air, is necessary. From the foregoing Observations we may learn, that all Pestilential Distempers, whether in Animals or Plants, are occasion'd by poisonous Insects convey'd from Place to Place by the Air, and that by uncleanly Living and poor Diet, Humane and other Bodies are disposed to receive such _Insects_ into the Stomach and most noble Parts; while, on the other Hand, such Bodies as are in full Strength, and are well guarded with Aromaticks, would resist and drive them away, but chiefly how necessary it is to allow the Body a Freedom of Air, and how to correct it if it is Infected. And I shall conclude with some Memorandums taken from the Papers of a learned Gentleman, who in the time of the late Plague in _London_ was curious enough to make his Remarks upon the Signs of that Distemper, and the Method of its Cure. He tells, the Plague proceeds first from a corrupted and unwholsome Air. The Second, is putrified Humours, hot Blood, caused by breathing in such corrupt Air; and if the Diet before were perverse, it fills the Body with superfluous Humours. Concerning the common Fear of Infection, which makes many rich Men, which might and ought to maintain poor visited People; and some Physicians likewise, whose Duty it is to administer Physick to them, flee away, so that in time of great Infection we hear more cry out for want of Bread and necessary means, than for anguish of the Disease. Hence also came that inhumane Custom of shutting up of Houses that are visited with Pestilence, dejecting their Spirits, and consequently making way for the Disease, and taking Men from their Labour, which is a digester of Humours, and a preserver of Health; and if the Disease be Infectious (as in their Opinion it is) it is plain Murder, to shut Men up in an infected and destroying Air. But all Mens Bodies are not full of Humours; if they were, all would be infected. After this I find the following Directions to prevent Infection. _First_, To avoid the Fear of it, and support the Spirits in the next place. _Secondly_, To keep the Body soluble, and to use the juice of _Lemons_ often. _Thirdly_, he recommends a Diet of quick Digestion, and to eat and drink moderately: He prescribes likewise the Smell of Aromaticks, such as _Camphire_, _Styrax_, _Calamites_, Wood of _Aloes_, &c. and to be taken inwardly, _Mithridate_, _Anjelica_, and _Petasetis_-Roots; and, in an express Manner, he recommends Cleanliness, and the Choice of a clear Air.