nd menstruation cease, which, unless brought about
earlier by disease, usually occurs about the forty-fifth year of her
age.

FECUNDATION.

Since in the beginning God created male and female, and said unto them,
"Be fruitful, and multiply, and replenish the earth," it is evident that
what was originated by creation must be continued by procreation. The
process of generation the reader will find described on pages 12 and 13.
Then commences a wonderful series of transforming operations,
rudimentary changes preliminary to the formation of tissues, structures
and functions, which finally qualify the organism for independent
existence. The ovum, when expelled from the ovary, enters the
fimbriated, or fringe-like extremity of the Fallopian tube, to commence
at once its descent to the uterus. The process of passing through this
minute tube varies in different animals. In birds and reptiles, the bulk
of the expelled ova is so great as to completely fill up the tube, and
it is assisted in its downward course, partly by its own weight and
partly by the peristaltic action of the muscular coat of the canal. In
the human subject, however, the ova are so minute that nature has
supplied a special agent for their direct transmission; otherwise they
might be retained, and not reach their destination. Accordingly, the
fimbriated, trumpet-shaped extremity of the Fallopian tubes, which is
nearest to the ovaries, and, consequently from the ovary first receives
the ovum when expelled; is provided with a series of small hairs, termed
_cilia_, forming the lining or basement membrane of the tubes, and, the
movements of these cilia being towards the uterus, transmit, by their
vibrating motion, the ovum from the ovary, through the Fallopian tubes,
to the uterus.

The mature ovum, however, is not by itself capable of being converted
into the embryo. It requires fecundation by the spermatic fluid of the
male, and this may take place immediately on the expulsion of the ovum
from the ovary, or during its passage through the Fallopian tube, or,
according to Bischoff, Coste, and others, in the cavity of the uterus,
or even upon the surface of the ovary. Should impregnation, however,
fail, the ovum gradually loses its vitality, and is eventually expelled
by the uterine secretions. It occasionally happens that the descent of
the impregnated ovum is arrested, and the formation of the embryo
commences in the ovary. This is termed _ovarian pregnancy_