THE PELVIS

The internal sex organs are situated in the lower part of the
abdominal cavity, the part that is called the _pelvis_, or pelvic
cavity. The meaning of the word pelvis in Latin is basin. The pelvis,
also referred to as the pelvic girdle or pelvic arch, forms a bony
basin, and is composed of three powerful bones: the sacrum, consisting
of five vertebrae fused together and constituting the solid part of the
spine, or vertebral column, in the back, and the two hipbones, one on
each side. The two hipbones meet in front, forming the _pubic arch_.

The hipbones are called in Latin the ossa innominata (nameless bones)
and each hipbone is composed of three bones: the ilium, the ischium,
and the os pubis. The thighs are attached to the hipbones, and to the
hipbones are also attached the large _gluteal_ muscles, which form the
buttocks, or the "seat."

The pelvis of the female differs considerably from the pelvis of the
male. The female pelvis is shallower and wider, less massive, the
margins of the bones are more widely separated, thus giving greater
prominence to the hips; the sacrum is shorter and less curved, and the
pubic arch is wider and more rounded. All this is necessary in order
to permit the child's head to pass through. If the female pelvis were
exactly like the male pelvis, a full-term living child could never
pass through it. The two illustrations show the differences between
the male and female pelvis very clearly.

Note particularly the differences in the pubic arches: in the male
pelvis it is really more of an angle than an arch. Also note how much
longer and more solid the sacrum (with its attached bone, called the
coccyx[2]) is in the male pelvis. The differences in the pelves (the
plural of pelvis is pelves) of the male and female become fully marked
at puberty, but they are present as early as the fourth month of
intra-uterine life.

FOOTNOTES:

[1] Mucous membrane--briefly a membrane which secretes mucus or some
other fluid.

[2] The coccyx consists of three rudimentary vertebrae; it is the
vestige of an organ which we once possessed in common with many other
animals, namely--a tail.

CHAPTER THREE

THE PHYSIOLOGY OF THE FEMALE SEX ORGANS

Function of the Ovaries--Internal Secretion of the
Ovaries--Function of the Internal Secretion--Number of Ova in the
Ovaries--The Graafian Follicles--Ovulation--Corpora
Lutea--Function of the Fallopian Tubes--Function of the
Vagin