Menstruation
Menstruation occurs at the end of a placental mammal's menstrual cycle. There are two types of menstruation:
- Overt menstruation, occuring in humans and great apes, in which the lining of the uterus is shed and expelled from the body to prepare the uterus for a fertilized ovum[1];
- Covert menstruation, occuring in all other placental mammals, in which the endometrium is reabsorbed.
Menstruation and the Bible
Under Old Testament law, a woman was to be put apart during menstruation:
And if a woman have an issue, [and] her issue in her flesh be blood, she shall be put apart seven days: and whosoever toucheth her shall be unclean until the even. And every thing that she lieth upon in her separation shall be unclean: every thing also that she sitteth upon shall be unclean. And whosoever toucheth her bed shall wash his clothes, and bathe [himself] in water, and be unclean until the even. And whosoever toucheth any thing that she sat upon shall wash his clothes, and bathe [himself] in water, and be unclean until the even. And if it [be] on [her] bed, or on any thing whereon she sitteth, when he toucheth it, he shall be unclean until the even. And if any man lie with her at all, and her flowers be upon him, he shall be unclean seven days; and all the bed whereon he lieth shall be unclean. Leviticus 15:19-24 (KJV)