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.