which account gives me no Satisfaction: Because the Systole being the proper, and (as himself confesses) the only motion of the Heart, a State of Contraction seems to be the natural State, and consequently without External Violence, it shou'd have no Diastole at all.
This will appear more plain, if we consider the Circumstances of it, and its Motion, as a Muscle, with respect to other Muscles. That Contraction is the proper Action, and State of all Muscles, is evident from Experience of Fact, as well as Reason. For, if any Muscle be freed from the power of its Antagonist, it is immediately contracted, and is not by any Action of the Will, or Spirits, to be reduced to a State of Dilatation. Thus, if the Musculi Flexores of any Joint be divided, the Extensores of that Joint being by that means free'd from the contrary Action of their Antagonists, that Joint is immediately extended without any consent of the Will, and in that State it remains; and so Vice versa, if the Extensores be divided. From whence it is plain, that the Muscles have no restitutive Motion, but what they derive from the Action of their Antagonists, by which they are balanc'd. Thus likewise the Sphincters of the Gula, Anus and Vesica, having no proper Antagonists, are always in a State of Contraction, and suffer nothing to pass
them, but what is forced through them by the contrary Action of some stronger Muscles, which, though not properly to be call'd Antagonists, yet on all necessary Occasions perform the Office of such.
That the Heart is a Muscle, furnish'd and instructed for Motion like other Muscles, is (in my Opinion at least) demonstrated beyond Contradiction by Dr. Lower and others. And, as it is a Solitary Muscle without any proper Antagonist, and not directly under the power of the Will, nor exercising Voluntary Motion, it approaches nearest to the Sphincter kind, which only has these Conditions in common with