Some science behind the scenes
Menstruation is the periodic discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. This cyclic discharge begins with the onset of menarche at or before sexual maturity and stops at or near menopause (the end of a woman's fertility). So much for the normal scientific definition.
Menstruation within the Mysteries is associated with the symbol of the pomegranate and the pomegranate seed is symbolic of the belief that women – even if they had been united with their Higher spirit and become 'gods' were forced to become separate again from the Higher spirit during menstruation.
The Greeks, for example, believed that when a woman menstruates she is no longer in touch with her Higher spirit, her power is temporarily taken away. Menstruation is the shedding of the uterine lining, but it is from this belief of loss of energy that we get all the menstruation-related traditions in religions.
There may be bans on certain actions during menstruation (such as intercourse in some movements of Judaism and Islam), or rituals to be performed at the end of each menses (such as the mikvah in Judaism and the ghusl in Islam). Some traditional societies sequester females in residences, "menstrual huts", that are reserved for that exclusive purpose until the end of their menstrual period. In Hinduism, it is also frowned upon to go to a temple and do pooja (prayer) or do pooja at religious events if you are a woman who is menstruating.
So this is a widespread belief in ancient cultures. That a menstruating woman temporarily loses the powers she has gained through merging with her Higher spirit – the goddess becomes mortal!
The following is not very satisfactory scientifically, in fact it is about as scientific as the beliefs above, but it provides another slant on the subject, which adds interest to the belief.
The Jacques Romano story – Dr Berthold Eric Schwartz
Professor Otto Rahn of Cornell University noted how some menstruating women had a "harmful emanation" that could produce changes in yeasts and bacteria. He speculated about a "menotoxin" which he related to oxycholesterol, and he wondered if this 'menotoxin" could account for such practical commercial problems as the wilting of flowers used for French perfume factories, ruining mushroom beds, making bread dough that would not rise normally, and packing pickles and sauerkraut that would not keep. He also quoted documented instances of adverse effects of such an emanation in the dairy industry, where poor cultures were obtained, and in the making of improperly fermented wine.
Oxycholesterol does exist, is a form of oxidized cholesterol implicated in atherosclerosis. I could not find any papers on PubMed that supported Professor Rahn's assertion that women cause endless problems in the wine and dairy industry, but it might be fun to do a study!!
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