AND this Aptitude, or Propensity of the Spirits to receive a pestilential Taint, is manifest from their fiery, or rather saline Nature, for on Account of that Subtilty which they acquire thereby, do they more naturally attract the contagious _Aura_, than Bodies more gross and heavy: For as these Spirits, as before observed, are nitrous, and inflammable, by their Similitude to a pestilential _Aura_, they not only are fitted to receive, but even attract it, and provoke it into Union; as the Snuff of a Candle just blown out, if it is not too far off, will by an Affinity of Qualities be soon rekindled by another lighted one at some Distance; and how much soever the poisonous Qualities of the pestilential _Effluvia_ may be destructive of the animal Spirits, yet there is nothing more certain, than that their Taint is very easily impressed upon them. AFTER the pestilential Poison is thus received by the Spirits, it is impossible to express the fatal Consequences, and the cruel Havock that is made in the whole OEconomy; for the same Instruments which before were aery, lucid, and like the Rays of the Sun, immediately become vapid, dark, and useless, neither able to invigorate the Constitution, nor defend it against the Contagion. _THIRDLY_, Having briefly passed over these Matters, it remains that we shew by what Steps the humane Frame comes to be disordered by this pestilential Invasion; and in Order to this, I know not a more fatal Circumstance in Nature than to have the very Guards and tutelary Preservers of Life, turn, as it were, Deserters and Betrayers. For there is nothing more manifest, than that the whole Compage, and its several Parts, run into Decay as soon as the pestilential Taint takes Place; for immediately upon the first Seizure, the whole Effort of Nature, as at _Rome_ when _Hannibal_ was at their Gates, is recollected against the Enemy, as sensible that all is at Stake, but being unequal to the Conflict, they retreat, and are taken Prisoners, leaving the whole Body defenceless. Hence the Infection runs through all the Blood, whereby the Heart and Lungs are principal Sufferers. Hence such a Corruption of the nutritive Fluids, that the whole nervous System is disturbed, the burning Heat of the _Pancreas_ produces the most extream Sickness, and hence follows such a Depravation of the whole Machine, that all the vital Faculties cease to act, and Death closes the fatal Scene. BUT I do not at all see how such a noble Part as the Heart, should be first affected by any particular specifick Quality in the Poison of a Plague, to affect that more than any other; as if it was so frightful, as some would have it, to attack the Principles of Life at once; for the Heart seems at first to be affected chiefly from the Multiplicity of Vessels, and the great Crowd of Circulation that Way, giving Opportunity for the Venom sooner to arrive thither; concerning which we shall have Occasion to say more under that Head of Symptoms.