within the protection of the bony pelvis or basin. This pelvis is,
compared with the male pelvis, broad and shallow, to provide for the
passage of the fully developed child at birth. The vagina is the
passage by which, during the birth process, the child reaches the outer
world, and it is also the sex organ by which, in the female, the union
of the male and female elements, of which we have spoken, takes place
in the sex act.

The male sex organs consist of the testicles, in which the sperm-cells
or spermatozoa are evolved, of a coiled duct leading there from, and of
the distinctive male sex organ, the penis. This last serves the double
purpose of providing an exit for the contents of the bladder and for
that emission of the spermatozoa which occurs in the sex act. There are
also certain glands situated in close relation to this duct which
provide a fluid which is emitted at the same time as the spermatozoa,
the whole being termed the seminal fluid. It is thus clear that in both
sexes there are essential reproductive organs, the ovaries in the one
case, the testicles in the other, providing respectively ova and
sperm-cells, and there are also organs for the purpose of securing the
union of these two elements, namely the vagina in the female and the
penis in the male. These two sets of organs form the primary sex
characteristics or actual sex organs.


_The Sex Act_


The special process which secures this union of the male and female
elements is termed copulation or coitus. It takes place in all
warm-blooded animals, as well as many others, but in man, with his