Those that contend for the conveyance of the _Nutricious_ Juice, through the _Umbilical_ Vein from the _Placenta_, are forc'd upon two Difficulties next to Absurdities. For first they are oblig'd to make this Vein, which, as all other Veins, seems dedicated to the Re-conveyance of Blood only, the proper and immediate Chanel, thro' which a very different Liquour is to be carried; and next, to give a Power of Attraction or Suction to it; because the _Nutricious_ Juice, which it is thus destin'd to carry, is both viscous and stagnant, and has neither force to drive, nor subtilty to penetrate, or insinuate it self into the Capillary Veins; and therefore must be drawn or suck'd as _Milk_ is from the _Breast_, to which the _Placenta_ and its _Nutricious_ Juice are by the Favourers of them expresly compar'd. But if this were the sole use of the _Placenta_, and _Umbilical Vessels_, why were the Umbilical _Arteries_ sent along with the Vein? Their business is not to bring any thing back to the _Fœtus_, nor can they contribute any thing to the benefit of the _Mother_; for the _Uterine_ Arteries bring all to the _Placenta_, the Umbilical Vein carries it to the _Fœtus_, and the _Uterine_ Veins convey back again the Surcharge of the _Mother_'s Blood; the Umbilical _Arteries_ only, have nothing to do, and are superfluous and impertinent, which is contrary to the constant Practice of Nature. Yet if _Autopsie_ did in the least countenance this Hypothesis, some Defence might still be made; but we find in the Umbilical _Vein_ of a _Fœtus_ nothing but _Florid_ Blood, such as in all probability it received immediately from the _Arteries_ of the _Mother_ without any mixture. And therefore I can't help concluding, that this Opinion engages its Favourers in some Absurdity, without Necessity and without Proof. They that from the _Placenta_ supply the Body of the _Fœtus_ with _Air_, are as 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.