Homosexuality, or inversion, is defined by medical discourses since the middle of the XIXth century, as a condition which radically marks individuals so labelled. Through those discourses, a figure, a character, is built. It is no longer precise sexual acts which are at stake, but the totality of the person, who has salient features, biological, psychological as well as behavioral. Those salient features are built on gender mixing, even on sexual characteristics mixing. The inverts, in such a definition, stress the bipolarity of sexes because they embody an intermediate state, the 'third sex'. But this conceptualisation implies also a reinforcement of the two poles of categorisation. Homosexuals do not follow 'the natural law' which defines men and women. Third part excluded from bicategorisation, indifferentiate freaks, those characters are analysers for social definitions of sexes, genders and their evolution.