SECONDLY, It sometimes happens that the Spirits degenerate from their native Purity, as also at others that they prove abortive, in not arriving to their utmost Maturity, whereby they lie more open to foreign Impressions of Distemperature.
BUT when the juices, or common Promptuary from whence the Spirits are generated, is not uniform, genuine, and perfect in kind, it is impossible that Spirits should be made from it in any tolerable Perfection; for one may as well pretend to wash a Brick, or draw clear Water from a foul Spring, as expect pure and natural Spirits from a corrupt and vitiated Chyle; although even when the Chyle is in right Order, there may various Errors happen in the Generation of Spirits, as from too great an Heat agitating the Blood in a preternatural Manner, or from an imperfect or unequal Separation of Particles, or from too much Cold causing an Intermixture of Crudities; and again, although the Spirits
are duly elaborated, yet they may run into irregular Motions, and be the Occasion of many Disorders: But what is most to the Purpose, they may sometimes also receive a Taint from external Impressions.
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.
UPON the strong, presumptive Proofs therefore that the pestilential Poison chiefly resides in the Spirits, we cannot but much admire at the Weakness of those, who expect to detect its Nature and Cause from what they can find on the Dissection of morbid Bodies, and such like Circumstances: For a very noted Person, and one of exquisite Skill in Anatomy, although he himself at last fell in the general Calamity, affirmed, that the Seat of the last Pestilence was in the extream Angles of the Plexus Choroides, towards the Cerebellum, because he had found a small Vesicle there; others have observed the Lungs to have been marked with the Tokens of Infection; others report the Heart to have been tumefied, and burnt as it were, to a Coal; whereas it is plain, that these Parts are only so many Fields of Battle, where the Spirits and the Infection contend it with each other; Nor will any one, who rightly considers these Things, wonder, that such Marks of Devastation should every where be left by so cruel an Enemy.
THEREFORE, although it should be granted that the most obvious and open Tokens of a Pestilence are from a spiritual and an invisible Cause, and whose Effects may perhaps sometimes be laid open to Sight, yet I have no Intention to discourage anatomical Dissections as a needless Trouble, for by such Light, Medicine is recovered from the Reproach of Conjecture; but when Bodies are opened which have been destroyed by such subtile Agents as here spoke of, there is no Confidence to be given from thence to the Nature of the Disease; and those who have been most knowing in the Nature, Use, and Disorders of the Spirits, very well can direct how to recover those Disorders, and avoid future Inconveniencies by immediate Application thereunto.