Terming this sexual deviation undinism,[2] it is one of several topics covered in the seventh and final volume of his studies in the psychology of sex.
Volume seven was originally published in the United States due to the stigma surrounding transgenderism, homosexuality, and other sexual deviations in England at the time.
[5] Many of the laws and regulations pertaining to sexual deviations in England in the early 1900s were focused on homosexuality among men, viewing it as a mental illness that should be cured.
[7] This was supported by the fact that all the introduced case studies were purely heterosexual men, who simply felt the urge to express themselves as a female primarily through cross dressing.
[14] All seven volumes of Studies in the Psychology of Sex were widely accepted in the scientific community,[15] even with the progressive perspectives in which it portrayed human sexuality and perversions.
Despite this, the book was not published in England until the middle of the 20th century, as it was strongly believed that putting Ellis' ideas into the public would increase the rates of individuals with sexual perversions.
[1] A few years prior to Ellis' publication of the first volume in his series, Krafft-Ebbing, an Austrian professor of psychiatry, also took an interest in the sexual impulses of transgender individuals.
Magnus Hirschfeld, a German sexologist, began to similarly explore the sexual impulses and behaviours of transgender individuals, and eventually gender reassignment surgery.
[18] Although Ellis' book was not published everywhere until years after its initial release in the United States, it opened the door to a more accepting view on transgenderism and other sexual perversions, and for the first time disconnected these concepts from mental illness.
[18] The first official gender reassignment procedure was performed in 1931 – 3 years after the publication of Ellis' last volume – on Lili Elbe, a Danish transgender woman living in (Germany).