Havelock Ellis,
Studies in the Psychology of Sex…
“ Sexual inversion, as here understood, means sexual instinct turned by inborn constitutional abnormality toward persons of the same sex. It is thus a narrower term than homosexuality, which includes all sexual attractions between persons of the same sex, even when seemingly due to the accidental absence of the natural objects of sexual attraction, a phenomenon of wide occurrence among all human races and among most of the higher animals. It is only during recent years that sexual inversion has been recognized ”
