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 or cervix. The uterus is a very remarkable organ, with a muscular structure that is capable of immense enlargement. In pregnancy, it distends from ten to fifteen times its normal length and many times its normal breadth.

There is an abundant supply of blood vessels to the uterus, which is not merely for nutrition, but to provide for the demands of menstruation and pregnancy. The internal mucous lining of the uterus is smooth and pink in color, except during menstruation, when it is red, and swollen to double its normal thickness.

The Vagina. The vagina (Latin, meaning a sheath) is the tube or canal which serves as an outlet from the uterus to the vulva, or external parts. It is a distensible and curved, a muscular tube which helps to support the uterus, as well as serving as its outlet. It is about three and a half inches long, and is often called the "birth canal," because the baby must pass through it on its way from the womb in the process of birth.

The upper end of the vagina is more spacious, where it surrounds the uterus, than at its external opening. The latter portion is somewhat contracted, and in the virgin is partly closed by a fold of membrane called the hymen, or "maidenhead," which extends forward from the posterior wall to the opening.

This thin membrane is usually ruptured at the time of the first sexual intercourse; consequently its presence has been considered by many, especially in the past, as an infallible sign of virginity. It is now generally recognized, however, that no definite interpretation can be placed upon the presence or absence of the hymen. It may be ruptured in early childhood by injury, surgically removed as an hygienic expedient, or otherwise eliminated. On the other hand, even after sexual experience, it may be stretched instead of ruptured,