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had incorporated with it; that it was Red, was due to the Tinging Powe,'of the Air. To expect that this Change sliould be made in the Heart byany Local Ferment, or Flamma Vitalis is fruitless ; because we find it per-form’d before its arrival there ; the Structure of the Heart denotingthat Engine tobe principally made for Projecting th e Blood, in order to aCirculatio» through thole various Arteries, or Pipes, which are branchedfrom the Heart. Let us therefore examine the Structure of the Lttngs, andwe shall soon diseover it to be a Pneumatick Engine made principally for ta-king in Air, and that in great Quantiries. It’s true, wemay call the Lungsa Contexture of Veins,Arteries, Nerves, Lympha-dt<£h, &'c. and that the se dovery much malte up the Parenchyma (as forne do use the word) of the Lungs ;but yet we fhaU find the great bullt of the Lungs to be Veficular : It seems tome tobe aContinuation of the Ajhera Arterta, or Wind-pipe, divided andsubdivided into many Branches, and tbese stili spun out into lesler and lesterPipes, all of them Hollow ; the fartherthey Run the Thinner their Sides dogrow, which upon the Infyiration of the Air do Swellup and grow Round,and upon Expiration do fall something Flaccid, and abate something of thatFigure, as the Microscope does plainly represent.

It is therefore more than probable, that the Air should insinuate it selfinto this Machine which is so truly adapted to reccive it, and that in greatQuantity ; for in each Infyiration the Lungs are stretch’d at that rate, as totake up double the Room they do in the State of Expiration, or in theirCompressed State ; and even in this State the Air-Bladders are not fully Eva-cuated, but contain Air for good purposes. Nor can it be pretended, thatany Augmentation is due to the Expanfion of the Blood-Vejjels, or any otherwhich do not Swell beyond their usoal Tension in each Inß>iration. TheSanguiferous-VeJJels are divaricared through all Ee Lobes of the Lungs, and dogive a very dose attendance ro each Vesicula (for there is not the lea st Veficulabut has a Capillary Veste! which intimately infumates into it) in order toreceive forne considerable Benefit from it; and this appears to the Eye ; forin an Instant adarkand foul Blood is Changed into a Bright Florid Red Co-lour. Nor is the Air thus Infus’d into the Lungs for a bare Colour, and ofno farther conside ration : But Iamapt tobelievethe great Ferment ations ofthe Blood the Causc of the Motions and Actions of the Muscles ; the AnimalSpirits thcmfelvcs, the great Spring of Motions, deriving their Energy andPowers, if not Nature, from hence. But Corollary. i. That the Air is fui!of Volatile Salts, none will deny; but that these Salts must bear the Nameof Nitrous Salts, is called in Question by this, and forne other Experi-ments I have made. Nitrous Salts seem to me not to have any property ofVolatile Salt, Nitre is a Salt of so Fix’d a Nature, that it will continuemelted in a very strong Fire, with searce any Evaporat ion; but if you putinto it Charcoal or Brimstone, or give it an Accension, by another Enchetre-fis you may obtain a great Quantity of as Fix’d a Salt as anv Concrete what-ever affords; so that to me Gold seems not of a more Fix’d Nature.

Corol. II. A Standard of Volatile Salts should be settled, at present 1 canthink of none better than Water: That Salt which in Distillation is more

Fix’d