, and their development is a more complicated process; hence,
their young need greater protection, and, for this reason, the ova,
instead of being discharged from the body of the female after
fecundation, are retained.[3] As we have seen that a suitable
receptacle is sometimes provided outside of the body, so now a
receptacle is needed, and is provided in the interior of the body of
the female. This receptacle is called

[Footnote 3: Curious examples of internal development sometimes occur
in animals which usually deposit eggs. Snakes have been known to produce
both eggs and living young at the same time. At the annual meeting of
the American Society for the Advancement of Science, at Detroit, Mich.,
in August, 1875, we had the pleasure of examining a specimen, exhibited
by Prof. Wilder, of a chick which had undergone a considerable degree
of development within the ovary of the hen. It had a head, a rudimentary
brain, and internal viscera, but no feathers nor limbs. It was, in fact,
an egg hatched before it had been laid. The anomaly excited much
interest at that time and since among biologists.]

The Uterus.--This is a hollow, pear-shaped organ, located in the median
line, just behind the bladder, between it and the rectum. It is
supported in place by various ligaments and by the juxtaposition of
other organs. Its larger end is directed upward, and communicates upon
each side with a very narrow tube which is prolonged outward on either
side until it nearly touches the ovary of the same side. Its lower and
smaller end fills the internal extremity of the passage previously
described as the vagina. When an ovum is matured, it escapes from the
ovary into the narrow tube referred to, called the _Fallopian tube_,
and passes down into the cavity of the uterus. If fecundation does not
occur, it is expelled or absorbed after six to twelve or fourteen days.
If copulation occurs, however, zoosperms are brought into the cavity
of the uterus, and, coming in contact with the ovum, fecundate it. This
is _conception_. When the natural process is allowed to proceed,
development occurs.

Uterine Gestation.--This is the term applied to the process last
referred to. We shall not attempt to describe in detail this most
wonderful and intricate of all living processes; but will sketch only
the chief points, leaving the reader who would obtain a more complete
knowledge of the subject to consult any one of the numerous
physiological and obs