By the way of _Transfusion_, this great Phænomenon is naturally accounted for, and the Ends, for which the other two Hypotheses were devis'd, might both be answer'd with more ease. For the _Hysterick_ Arteries transmitting their Blood immediately to the _Umbilical_ Vein, may very easily transmit such _Nutricious_ Juices or _Aerìal_ Particles, as are contain'd in the Blood, along with it, without depositing them by the way. By this means so much of the Impulse of the Mother's Blood is preserv'd, as suffices to maintain that languid Circulation which a _Fœtus_ enjoys. For the Blood being driven through the _Arteries_ of the _Uterus_ into the _Umbilical Vein_, is convey'd directly to the _Sinus_ of the _Porta_, and thence by a short and direct Passage through the _Cava_ to the Heart; where passing through the _Foramen Ovale_ to the _Left_ Ventricle, and through the _Canalis Arteriosus_ from the _Right_ and _Pulmonary_ Artery, it is all deliver'd without coming at the _Lungs_ to the _Aorta_, and from thence again by the _Umbilical Arteries_ to the _Veins_ of the _Uterus_, making a sort of _Epicycle_ to the main Circulation in the Mother. As this Opinion is Favour'd by the Structure and Disposition of the Blood-Vessels on both Parts, so there is nothing in it difficult to be conceiv'd, or repugnant to Experience. Late Discoveries have made it appear, that the Arteries and Veins are continu'd Tubes, and that the latter contain nothing but what they receive from the former, and no Reason appears why we shou'd think this Method to be varied in the _Placenta_. On the other hand, if the Arteries of the _Uterus_ were continued to the Veins of the _same_ part, and those of the _Fœtus_ in like manner, without communicating with each other, their Confluence in the _Placenta_ seems to be altogether impertinent, and of no use, and the _Umbilical_ Arteries and Vein fram'd for no other Service or Purpose, than to give the Blood room for an idle Sally. Thus the Reasonableness of this old Opinion may be vindicated, but the Certainty of it rests upon stronger Proof. Mr. _Cowper_, to whose happy Industry we owe the Confirmation of many ancient Discoveries, and the Benefit of some new ones, has the Honour to re-establish this old, but long exploded Truth. For by pouring _Mercury_ into a Branch of the _Uterine Arterie_ of a _Cow_, that went into one of the _Cotyledones_ of the _Uterus_, he fill'd those Branches of the _Umbilical_ Veins, which went from that _Cotyledon_ to the _Navel_ of the _Fœtus_; which, with a part of the _Uterus_, he keeps prepared by him.