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THis Learned Author, a worthy Member of the R. Society, in discoursing upon this no less difficult than important subjcect, observes this Method;
First, he lays for a ground, that there is and needs must be Motion in the Bloud. Secondly, he declares what kind of Motion and how various that is, shewing also, that all those motions are to be adscribed to the Vital Bloud, and to be preserved therein. Thirdly, he maketh it his business to prove (which is his main design, that those Motions are both continually produced, and maintained by the means of Respiration, premising something about the Nature and Properties of the Air, and the Fabrick and Motion of the Pneumatick parts.
This done, he sheweth the probability of his Hypothesis, as being intelligible and able to solve innumerable questions, and among them such, as have been esteemed almost insoluble. And first, he teaches, how Respiration maintains that Progressive Motion, which he also cals the Motion of Rivers; and then, how it preserveth the Motions of Fluidity, and Warmth, by the Airs subduing, comminuting, and diluting the Blood. Where he digresseth to give an Answer to those, that will not allow the Air to have any ingress into the Bloud; as also to explain the cause of Sanguification, adscribing it neither to the Heart nor the Liver, but principally to the Lungs in those that are borne; but in Fœtus's, to the maternal Bloud, and the Vmbilical vessels.
Next, he proceeds to explicate the many Problems of Respiration by the delivered Hypothesis: And chiefly why Respiration is so absolutely necessary to Life, viz because Life principally consists in the motion of the Bloud; which soon ceaseth, when Respiration is stopp'd. Upon which Question thus resolved, depends also the solution of divers others, to be found in this Book.
To all which he adds the reason of the Difference, there is, as to Respiration, between the Borne and Vn-borne; solving that knotty Hervean Problem, viz. Why a Fœtus, being divested of the Secondine, and having once breathed in the open Air, cannot live afterwards without it, but dyes presently? Which he imputes to the hindred Motion of the Bloud, entertained by Respiratlon.
But why, after that Respiration hath once begun, the Bloud will not, when there is need, return to its former passage through the Voramen Ovase; we refer to the Author himself for an Answer: as we also do for other considerable Solutions of many other difficulties occurring in this Learned Treatise.
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