Cause must be either in the Air , or Atmosphere , because we have no constant and immediate Commerce with any other Mediums .
Some great Physicians observing this, and that depriv'd by whatsoever means of Communication with the external Air, we became instantly extinct, have imagin'd, that in the Act of Inspiration certain purer parts of the Air, mixed with the Blood in the Lungs, and was convey'd with it to the Heart, where it nourish'd a sort of Vital Flame, which was the Cause of this reciprocal Æstus of the Heart. Others not quite so gross, rejecting an Actual Flame, have fancied, that these fine Parts of Air mixing with the Blood in the Ventricles of the Heart, produc'd an Effervescence which dilated it. But these Fancies have been long
since exploded and condemn'd upon ample Conviction; and 'tis a Point yet undetermin'd, whether any Air does mix with the Blood at all in the Lungs, or not.
But supposing, that some Air may insinuate it