Concerning the First.
[ 3] Respiration [〈 in non-Latin alphabet 〉] is an Action of the Breast and Lungs consisting of two contrary motions alternately successive, or of two parts,* viz. (1) Inspiration [〈 in non-Latin alphabet 〉] in which the am∣bient aer is impelled into the Lungs and chest, at that time dilated: (2) Exspiration [〈 in non-Latin alphabet 〉] wherein the same aer is again expelled out of the Lungs and Chest, those parts spontaneously contracting or compressing themselves.
Concerning the Inspiration, the grand Question is, Whether the Breast and Lungs are di∣lated, because they are filled and distended with the aer; as a bladder is distended by aer blown into it: or, Whether they receive in the aer, because they are dilated; as a pair of Bellowes is filled with aer, only because it is dilated or opened by external force?
[ 4] To solve this difficulty, in a word, we say, the Breast is first dilated,* before it can be filled with aer, and that Dilatation or heaving up of the brest is the cause of the airs rushing in at the mouth and nostrills, down the Aspera Ar∣teria, or wind-pipe, into the Lungs. For, since there is no vacuity (at least no Coacervate one) in the world, no body can be moved out of its place, but the next body must give way, and the next to that likewise give back, till such a Page 131 part of space as is adequate to the dimensions of the body first moved, be made to receive it, and the space which it abandoned, be again fully possessed by another body succeeding into it: we say, since this is necessary, it is ma∣nifest, that the aer next incumbent on, or con∣tiguous unto, the Breast and Abdomen being urged and impelled by the breast, while that is dilated or expanded, is forced to give back, and press the aer next to it, which likewise drives back the next aer, untill at length the compressed aer wanting room to retreat into, and endeavouring to avoid further compressi∣on, (its own Elater ingaging it thereto) rush∣eth into the breast and there possesseth that room or part of space, which was left by the breast, when it began its motion. So that so much aer is impelled into the breast, as is dri∣ven out of its place by the superfice or out∣side of the breast, during its expansion or di∣latation.
As for the Attraction of Aer into the Lungs, ad fugam vacui; it is a meer dream; as well because all motion is by Impulsion, as because Nature doth not abhor vacuity primario or ex se,* but only ex Accidente, or in respect of the confluxibility of the insensible particles of Fluid bodyes, as we have elsewhere amply demonstrated.
And if there were any Cause to be found, that might blow the aer into the breast, as it is blown into a bladder, so as to distend it; or at least, if the aer could be conceived to enter Page 132 into the breast spontaneously, or of its own ac∣cord, without impulsion, so as to force, or heave up the same: then indeed, would the Compa∣rison betwixt the dilatation of the breast, and that of a Bladder, by wind blown violently into it, hold good, and we should not need to seek further. But, there being no such insuffla∣ting cause assignable; and it being ridiculous to imagine the aer should spontaneously move it self, so as to flow uncompelled into the cavity of the Chest (as is manifest not on∣ly in dead men, into whose breasts, though their mouths and nostrils are wide open, the aer doth not croud it self: but also in living men, when they at their pleasure keep their breasts compressed, or hold their breath, as the vulgar phrase is), it seemes much more reaso∣nable to explain the reason of Inspiration, by that other similitude of the flux of aer into a pair of Bellows; there being no other diffe∣rence betwixt the repletion of the Chest, and the repletion of a pair of Bellows, with aer, but only this; that the Bellowes are opened by an externall force, and the Chest is dilated by an internal.
[ 5] And as for the Exspiration, that is evidently from the compression of the breast and Lungs,* which is the naturall motion of Restitution For, the Dilatation being an action, whereby the parts of the Chest are distended into a position more large, than is natural to them; the Contraction seemes to be nothing else, but a certain falling down or relaxation of the Page 133 parts distended, whereby they spontaneously return to their natural position, and such as they hold in a dead body; and this not onely in the Lungs, but also in the Diaphragme, which in dead bodyes is not extended down∣ward to the stomach and guts (as in inspira∣tion) but riseth upward toward the Lungs and Heart. But if it be here demanded, whether Inspiration, or Exspiration be first; we answer that it is necessary that the aer should be first inspired, before it can be exspired; and eve∣ry ANIMAL dyes Exspirando, in Exspirati∣on.
