At the turn of the 20th century, there was growing confidence in the power of the medical sciences to finally understand human physiology and the patho-physiology of diseases. The source of this confidence was due in no small part to advances in the field of endocrinology: the study of hormones and the glands that produce them.
The term "hormone" was coined in 1905 by the British physiologist Ernest Starling, after the Greek word meaning "to incite to activity". In the early 20th century, a variety of chemicals were found to have "hormonal" effects in humans: they were produced in one tissue, entered the bloodstream and incited a specific effect on another distant and unrelated tissue. Insulin, thyroxine, testosterone and cortisone were discovered at this time and were found to have remarkable restorative properties when given to patients with a number of common diseases.
This enthusiasm for the therapeutic potential of "hormones" also extended to the area of human reproduction In the late 19th century, Professor Brown-Sequard, at the age of 72, injected himself with the extracts of guinea pig testicles and was astounded at their rejuvenating effects.
Between 1910 and 1930, the hormones estrogen and progesterone were found to play important roles in the physiology of female mammalian reproduction, and so by around 1940, it became apparent that in human females, fertility depended upon the complex interactions of a hierarchy of hormones which affected the ovaries first, and then the uterus. The ovaries were found to be the source of a "female factor" in human development (the ova or egg): complementary to and just as necessary for human reproduction as the"male factor". This picture -- which seems so clear today -- was in fact a dramatic insight, considering that even in the second half of the 19th century many scientists still believed that conception occurred when the male factor – a seed – was sown into the female womb– the soil. A woman’s contribution to conception was thought to be that off a passive receptacle offering a favorable environment for the germination of the seed.
The picture that now emerged meant that fertility in women was in the normal case orderly and cyclical, and therefore predictable. This new understanding of human reproduction seemed to lift the veil on an awesome event that, until then, had been shrouded in mystery. Science began to expose the mystery, to reveal the mechanics of how human beings came about, and made that event accessible and open to manipulation.
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