Chapter III: Section III

_Of the primary Seat of a Pestilence; where,
by the Way, is considered the Nature of
the Spirits, and their Infection in an
humane Body from Poison._

IN Order to put an End to the Controversies about the Seat of a Pestilence, which have from Antiquity even to this Day been warmly maintained, many Authors putting the Heart for the Principle of Life and Death, some the Brain, and others the Stomach, Lungs, or Liver: It will be necessary here to discover the immediate Residence of the pestilential _Seminium_. Since therefore the above-mentioned _Aura_, according to Hypothesis, is very subtile and spirituous, for that Reason there must necessarily be some conformable Property in the Matter which is fit to receive it; as therefore there is not in the whole humane Machine any Subject more apposite, and capable of its Union, than the animal Spirits, we must fix its Residence there. But because I am sensible what Objections this Opinion lies open to, with some Persons, who may not conceive how an immediate Infection of the Spirits is communicable to the Viscera, and all Parts of the Body, it will be necessary to go thro’ this Matter in a very particular Manner, by enquiring;

_FIRST_, What are the Spirits concerning which we are here speaking?

_SECONDLY_, What is that Disposition of Spirits which makes them fit to receive the pestilential Impression? And,

_THIRDLY_, After what Manner the vitiated Spirits can affect the whole Body with Disorders?

TO this Purpose we must know, that the Spirits are the most thin and subtile Particles of the Aliment and other Juices, raised to the utmost Perfection and Volatility by the innate Heat, and the nitro-aerial Spirit, to serve in the Operations of the Mind, and all the Purposes of the animal OEconomy.

THE Matter whence the Spirits are generated is the Chyle, and their Restauration, Confirmation, and Vigour, from the Recruits of Food, as is their Languor, Prostration, and utter Extinction from the Want of it; so that howsoever they were first generated in the original, they owe their Conservation and Vitality to the Nourishment continually brought in; and although in a State of perfect Health _they_ are never changed by _that_, yet they continually act upon that after various Ways, bringing it from a crude, recrementicious State, into a noble Juice, or rich spiritual Balsam, retaining its ideal Character: And hence it comes about, that although there is a daily Waste of Spirits, there is no Want, because Nature is continually, while Things are in Health, making more; insomuch that after a due Constitution of Spirits is obtained, they of themselves are the main Efficients in making more, as one Light is kindled by another, and as the Blood it self is the chief Instrument in Sanguification, or making more Blood.

IT is a Matter indeed of much more Difficulty to determine, how Particles from a gross Origin, should be raised to so great Volatility and Fineness; but this is very certain, that when they are elaborated in the most perfect Manner, they exceed even the Light and Activity of the Sun-Beams; and the brighter and more active they are, the better do they perform their Offices in the OEconomy, as from their Efficiency is procured a State of Health and Vigour both in Body and Mind.

IT is of no great Moment to enquire, what Quantity of Spirit is necessary for the Conservation and Support of an humane Body, so that we do but know they partake of the Source from whence they are generated, insomuch that they are more or less perfect, according to the greater or lesser Degree of Purity in their productive Juices.

BUT I must here acknowledge my self diffident in that Opinion of the Spirits being prepared of a different Nature for particular Parts, for according to the Influences of the Mind, and the Contiguity, Rectitude, or Consent of the Vessels, they are by a voluntary Act determined the same into this or that Limb or Part: Which is manifest enough in the Prick of a Needle, or a venomous Bite, from the great Affluence of Spirits to that Part; I have therefore no Notion of a continued Emanation of Spirits, but that on such Occasions they are called, by the Sensation upon the affected Part, from the nervous Origin where they are elaborated.

_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.

AND Lastly, to conclude this Doctrine concerning the Spirits Infection, this irrefragable Argument may be produced from the Intention of Cure; for I have experienced by more than a thousand Instances, that the more cardiack and alexipharmick Medicines are subtile and spirituous, the more certainly do they encounter the pestilential Poison with Success; whereas, on the contrary, those Medicines which are coarser and slower of Exertion, do little or no Good. But this we refer to the curative Part hereafter in another Section.