laity, and not until comparatively recent times have its origin,
structure, and use been satisfactorily explained. Its meaning
profoundly interested primitive men and stimulated their imagination
scarcely less than the mystery of conception. Some uncivilized tribes
believed that the after-birth was animated like the child;
consequently they spoke of it as "the other half," and often saved it
to give to the child in case of sickness. But generally the after-
birth was buried with religious ceremony, and was occasionally
unearthed later to discover whether the woman would have other
children; the prophecy was made according to the manner of
disintegration or some other equally absurd circumstance.

The after-birth consists of a round, fleshy cake, the placenta, to
which two very essential structures are attached. One of these,
running from one surface of the cake, is a rope-like appendage, the
umbilical cord, which links the placenta with the fetus. The other,
attached to the circular edge of the cake, is a thin veil of tissue,
in some part of which a rent will be found. Now, if we lift the
margin of the rent, we shall see that the veil and the cake together
form a sac which we are holding by the opening. This aperture through
which the fetus passed, and it was really made for that purpose, was
formerly placed over the mouth of the womb; the sac itself, distended
by the fetus and the amniotic fluid, was fastened everywhere to the
inner surface of the womb.

It is plain that we have now in our hands the fetal sac, the
development of which we have already traced from the beginning. The
wall of the sac, it will be recalled, was originally of the same
formation throughout; but when the ovum became imbedded in the womb,
that part of its capsule which remained in permanent contact with the