short, and without any Arguments to support them, that by exposing them naked, they seem rather to discourse of it transiently, as Men oblig'd by the Nature of their Subjects to say something of it, than solicitous to give any full or satisfactory Account; and therefore I shall proceed no farther upon them here.
But though the Hypothesis of Borellus may, in this Case, be found precarious or insufficient
(a Misfortune that has befallen him in divers other Particulars) his Theory holds still good. At least it ought to be allow'd, in justice to his great Abilities and Exactness, till some Body convicts him of some material Error in his Calculations, which has not as yet been done by any Body, that I know of.
Supposing then the force of the Heart, and of the Muscular Coat of the Arteries, as likewise of the resistance, which they must overcome, to be computed with any degree of accuracy, there remains yet such a prodigious disproportion to be accounted for, as requires some more powerful Agent, than any yet assign'd, to make up the deficiency.
What assistance the Heart receives from the action of the Thorax towards the facilitating its Contraction, without which assistance there cou'd have been no Systole, has been already shewn. But neither the Intercostal Muscles, or Diaphragm, which are so instrumental in that part of its action, can contribute any thing to the Diastole; because they serve only to enlarge the Cavity of the Thorax, and thereby to open a passage to the Blood from the Heart, and promote its Constriction.
Whatever therefore the force is, that dilates the Heart, and is the cause of the Diastole , it must be equal to that of the Heart, the Intercostal Muscles and Diaphragm ; to all which it acts as an Antagonist. I take no notice of the Serratus Major Anticus , and other Muscles; which have an obscure share in the Elevation of the Costæ , because as much may reasonably be deducted