would prefs the Fluids even up to our Mouths, &c. as the additional Preffure of Water does when one goes down to any confiderable Depth. Whereas on the contrary, we fee fomething within can diftend our Bellies to a great Degree, notwithstanding the Refiftance of the Pref fure of the Air, and that of the Muscles of the Belly, nay even against an additional Preffure of several Fathoms of Water. And if the Mouth and Nose be ftopped, so that the Steam cannot iffue out at the Lungs, notwithstanding the Emiffion of the Steam at the Pores, and the Preffure of the Atmosphere, the Parts will all extend, and foon put an End to Circulation and Motion. When the steam is very grofs, fo that it goes off flowly, the Pulle moves flowly; and the more 'tis pent in, the more the Guts will extend.

When the Preffure of the outward Air is taken off an Animal in the Air-Pump, Steam diftends, and would burst the Body, if the Pores did not vent it. But if the Blood were circulated by the Force of the Heart, it would have no fuch Effect: For if the Heart pumped the Blood with never so great Force, the Arteries must ftill be full, and it could pump the Blood

into

into them no fafter than the Veins fupplied it, and the inward Parts, where the Force was greateft, would be moft extended. I believe, if an Animal had the Pref fure of the Air taken off its Body, and had Liberty to draw Air into the Lungs, and refpire it, (if Respiration could be performed when the Air is kept off the Outfide,) the Steam would go a great way towards bursting the Blood-Veffels. And I prefume, moft of the Blood in a Creature killed in an Air-Pump, by taking out the Air, would be found in the outward Parts, and I fhould be glad to fee how it would, whilft alive, and the Air was taken off, bleed at a Vein, and how at an Artery, and how when more than the ordinary Air is pumped in. And if the Preffure of the Air were kept off the lower Belly, I fhould be glad to fee how the Lungs would refpire: For I think, when the Steam within prevails, it forces a great Part of the Blood into the outward Parts, and diftends those Veffels, and when the Preffure of the Air or Cold prevails, they force a greater Share of the Blood into the inward Parts. And as the Lungs are fo contrived, that they cannot emit, or vent the Steam, without Air, when the air is kept off, or hindered from

entering

entering at the Nofe or Mouth, for want of Discharge, the Steam prevails, diftends the Parts, &c. fo if the Air were kept off the Outfide of the Body, and admitted into the Lungs, and extended the Bladders, and admitted as much Steam as its Intervals could receive, * and if the Mufcles of the Lungs, and the Elafticity of the Air filled with Steam, could fuccef fively refpire it, I believe the Steam would force moft of the Blood into the Veins, and fill the Arteries with Steam, and the Blood* would not return out of the Veins to the Heart, for want of the Preffure of the Air: For the Blood moves equally in the Veins, and is not governed by the Pulfes of the Heart, neither in its Paffage, nor when a Vein is opened.

Abundance of Obfervations and Proofs might be made about Circulation, Refpiration, &c. If a Man were put into a large Veffel made clofe of Lead or Brass, with an Air-Pump fixed in it to draw out, or Pump in the Air, fo long as he could endure it, and by fixing a Pipe thro' the Side, to keep close in his Mouth, to draw

in,

*Or thus, If in this Condition Refpiration could be carried on, I believe the Steam would force most of the Blood into the Veins, and leave the Arteries empty; and the Blood, &c.

in, and refpire the Air. And perhaps many Diseases might be cured by strengthening or weakening the Preffure of the Air, which environ'd his Body.

In Proportion to the Increase of the Quantity of Steam emitted from the Stomach and Guts, whether by too great a Ferment of the Juices there, as in a Fever, or by too much fpirituous Liquor, or violent Exercise, the Blood moves quicker, and all the Vents, as the Lungs, Pores, &c. emit greater Quantities of that Steam; especially in violent Action, the Lungs quicken their Motion, in Proportion to the Motion of the Heart, and flacken as that Steam abates or waftes; and in Proportion to the Degree of Expanfion, or Quantity of the Steam, the Lungs are expanded more or lefs, and admit greater or leffer Quantities of Air at once; and also admit it oftener, or feldomer, or quicker, or flower. And though you can admit and discharge it quicker and flower voluntarily, yet if you do it quicker, and do not at the fame time ufe Action to make the Steam rife, your Strength will foon be spent, fo that you cannot continue it. Outward Cold fhuts the Pores, and by preferving, encreases the Force of the Steam. But if the outward Cold thicken VOL. X.

P

E

the

the Juices in the Pores and capillary Vef fels too much, and fhut them fo clofe, that the Steam cannot get out of the out

ward Parts, they will turn red and swell. See p. 34. And the Coolness of the Air contributes fomething towards the condenfing the Steam in the Lungs, or admits a greater Quantity of Heat into its Vacancy, for otherwife hot Air might bring off as much Moisture as cool Air. Nay, when the Ferment is very violent, the Steam drives too crafs Matter into the Blood, and almoft all the liquid Part out of the Blood-Veffels, and leaves little, but that crafs Matter there, and the grumous Part of the Blood, which cannot perfpire nor fecrete, and a great Part of that almoft as tough as Turpentine; fo that it cannot pass the capillary Veffels, but caufes Pain, Swelling, &c. and when the Steam is too weak, it will carry too little, and not make the Blood move faft enough. And though we have Power to stop the Motion of the Lungs for a fhort Time, and by keeping the Air in them for that Time, become ftronger, or to use them for Speech, &c. yet I think the Motion of both the Lungs and the Heart are involuntary, and forced by the continual Succeffion of the Steam. And I think,

if