"Menstruation is just blood and tissue you ended up not using"

"the kind of bias that produces a doctor who can believe that menstrual toxins exist, and launch a field of study on them based on some wilted flowers (if the story really did happen the way he tells it), did not come from one man alone. The cultural conditioning that has produced the idea that women are dirty, particularly during menses, is quite old. The Old Testament of the Bible claims that women are unclean when they menstruate, and menstrual huts exist in some cultures to separate out menstruating women from the rest of their group... 

De Secretis Mulierum went through at least eighty editions over several centuries (Rodnite Lemay 1992). While it was not a strictly medical text, it is clear that it was both popular and influential. Do doctors refer to De Secretis Mulierum today? Of course not. But this book, to me, represents a broader cultural understanding that menstruation is dirty, that women are powerful, mysterious, dangerous, and sub-human... 

Soon, people were injecting menstrual blood into rodents, and those rodents were dying (Pickles 1979). Others were growing plants in venous blood from menstruating women to determine phytotoxicity; the sooner the plants died, the higher the quantity of menotoxin assumed in the sample.

What’s worse, the presence of the menotoxin in the female body began to expand beyond menstruation. Any woman who was post-menarcheal and pre-menopausal could be found to have the menotoxin in her system. She could not escape it: some reported that the menotoxin could be found in a woman’s menstrual blood, but also venous blood, sweat, and breastmilk. One case study reports that a mother gave her child asthma because she was menotoxic during pregnancy (Perlstein and Matheson 1936), and several contended that colic was caused by menotoxin in breastmilk (Ashley-Montagu 1940; Perlstein and Matheson 1936)."

https://blogs.scientificamerican.com/context-and-variation/menstruation-blood-and-tissue/

FB: The history of some male scientists' weird theories about menstruation "And this is where I bring it back to my first two points about bias, that science can be biased by the cultural conditioning of those who perform it, and those who tell it. The people who studied the menotoxin really, really wanted to believe in it, to the point that they would ignore negative results and overstate the power of their anecdotes and case studies. The study of the menotoxin spans at least sixty years, maybe ninety depending on which references you consider legitimate, debated in Lancet letters to the editor, and published in several medical journals."