much distress'd as t'other; for they are forc'd to beg the Question twice, which, even when granted, will not answer their Ends. First, they suppose, that an intimate mixture or confusion of Air with the Blood , is necessary for the support of Animal Life, a Postulatum , which perhaps the former part of this Discourse may have render'd unnecessary; and next, that the Fœtus is supply'd with Air from, and its Blood mix'd with it in the Placenta .
But here again they fetch a Compass without necessity or proof. For if a mixture of Air were necessary to a Fœtus, why should it be separated from the Mother's Blood, and not rather both communicated together, since it is so much more easie and commodious? But neither does the Placenta seem to be instructed and provided for the separation of Air, but of a much grosser Fluid, destin'd to some other use, which Autopsie confirms: Yet, were both these Opinions
true, they are however defective, and the Circular Motion of the Blood unprovided for.
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