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shew, How exactly these two are calculated for its Motion, and how well adapted to distribute the Bloud into the parts of the whole Body.
In the First Chapter then, he considers the Diversity of the Situation of the Heart in different Animals, and the Reason thereof; proceeding to discourse of the Pericardium and its Use, together with the Origin and Use of the Serum therein; and why in Man onely that Case of the Heart grows to the Midriff, and what makes it to do so; as also, why the Cone in an Humane Heart bends much more to the Left side, than in Brutes: Then shewing, that Arteries have their rise from the Heart, but Veins terminate in it, and how and by what Vessels the Heart is nourisht by the Alimentary Juyce: treating also of the Vessels of the Heart, its Nerves, and the various Influx of the Animal Spirits through the Nerves into the Heart, according to the various shapes of Animals, together with the Cause thereof: Proving further, that the substance of the Heart is perfectly Muscular, and in perfection surpassing all other Muscles of the Body (where he expatiates into un-common Observations concerning Muscles in general;) then descending to a Minute Explication or the parts of the Heart, and there particularly shewing the Mechanical Contrivance of the Heart for its Systole and Diastole, together with an accurate description of the Foramen Ovale, and its Use in the Fœtus, the Clausure of the same in Animals born.
In the Second Chapter he treats of the Motion and Office of the Heart; Where, as he admits not of any Ferment or Eouilition of the Bloud in the Heart (which he affirms would be an Obstacle to its Systole, as 'tis needless to the Diastole,) so he assents, that the Motion of the Heart depends not from such an Eoullition (which he proves by Exoerimf nts, and vindicates from Objections;) but that the genuine and immediate Instruments of the Heart's Motion are its Fibres, Nerves, and Spirits flowing through them, the action of the Heart being altogether conform to that oi other Muscles: Where he takes occasion to make it out, that the Motion of Muscles is not caus'd by their being inflated, nor by any Explosion of the Spirits passing through them, out after the manner, as two men taking one another by their hands, draw them-
