Eugen Steinach researched sex hormones and their effects on mammals in the late nineteenth and early twentieth centuries in Europe. He experimented on rats by removing their testicles and implanting them elsewhere in their bodies, and he found that the testes interstitial cells produce male sex hormones. He developed the Steinach Rejuvenation Procedure, which he claimed could rejuvenate men by increasing their production of sex hormones. Steinach’s work on female sex hormones and on ovarian extracts led to the development of the first standardized injectable estrogen. Steinach’s research on reproductive hormones helped researchers explain the roles of sex hormones and develop hormone drugs.

Mary Ware Dennett, an activist in the US for birth control and sex education in the early twentieth century, wrote an educational pamphlet in 1915 called “The Sex Side of Life, and it was published in 1919. The pamphlet defined the functions of the sex organs, emphasized the role of love and pleasure in sex, and described other sexual processes of the body not usually discussed openly. In the early twentieth century in the US, individuals did not have wide access to sex education due to the limitations enforced by the Comstock Act, which prohibited the distribution and discussion of topics that were considered obscene. In 1929, the US tried Dennett for mailing her pamphlet as a violation of the Comstock Act, sending obscene material through the United States Postal Service. Dennett’s pamphlet, Tthe “Sex Side of Life,” and her subsequent trial, United States v. Dennett, contributed to a national discussion about sex education and human reproduction and led to the revision of reproduction- related obscenity laws.