Section of the Uterus, with the Ovum and appendages, at about one month of gestation.--_a. a. a._ The substance of the walls of the Womb.--_b. b._ The Embryo.--_c._ The different vessels by which it is connected with the Placenta.--_d. d._ The Placenta.--_e._ The Vitellus.--_f. f. f._ The Membrane lining the Uterus, called the Decidua; it is seen to be bent double, or reflected, the Embryo being on the outside of it.--_g. g._ The Chorion, or Middle Membrane, which is studded over with villosities, or small blood vessels.--_h. h._ The Amnion, or inner membrane, which contains the fluid called the liquor amnii, in which the Embryo floats.--_i. i._ The blood vessels which connect the Placenta with the Womb.--_j._ Is a plug of Mucus, by which the mouth of the Womb is now blocked up.--_k. k._ The ends of the Fallopian Tubes, which are cut off; these are also blocked up with mucus, the same as the Os Tincæ.--_l._ The Os Tincæ, or mouth of the Womb.--_m._ The Vagina. [Illustration: Plate XII. Section of the Uterus, with the Ovum and appendages, at about one month of gestation.] FŒTAL NUTRITION. The manner in which the new being derives its nutriment, or the material by which it grows, is, in a great measure, unknown to us, though we certainly obtain some little information about it by a study of the apparatus employed in the process. For the first fifteen or twenty days the substance called the _Vitellus_, (_e._ Plate XII.) which is analagous to the yelk of the ordinary egg, appears to supply most, if not all of the material that is required in the formation of the new being; and indeed this substance does not totally disappear till after the third month, though we cannot suppose it to be the sole source of nutriment then. It is also supposed, by some, that the amniotic liquor, in which the fœtus floats, may afford some nutriment, either by being swallowed, or by being absorbed through the skin. It is certain that this fluid is nutritive, and there is nothing impossible in its absorption, though it is not very likely to occur to a sufficient extent. The idea that it can be swallowed however, is erroneous, because the mouth of the Fœtus is firmly closed while in the Womb; and besides, children have been born alive without _mouths_, and even without _heads_, and of course they could not have swallowed anything. It is now generally conceded by physiologists that the material required by the Fœtus, for its nutrition, is obtained from the blood of the mother, through the medium of the Placenta, and the vessels in the Umbilical cord. It is, however, a matter of dispute whether the maternal blood is sent directly, in its ordinary state, into the body of the child, or whether it first undergoes a preparatory process, which most modern authors suppose it does.