[Contribution of experimental intersexuality in chickens to the problem of gonadal differentiation and its abnormalities in amniotic vertebrates].

The grafting of embryonic testes to chick embryos realizes an experimental model which is near the spontaneous situation of the cattle "free-martin". It allows to obtain a masculinization of female host embryos developing in some cases up to a total and definitive reversal of sex differentiation. Indeed, it is possible, by this way to obtain testes induced under the influence of substance(s) secreted by the grafts which determine epigenetically a sexual phenotype opposite to the genotype of the host embryos. The analysis of such testis morphogenesis shows that it results from an inhibitory mechanism. Some experimental data strongly suggest to ascribe it to the anti-Mullerian hormone secreted by the graft. The ovotestes and testes observed in adult treated animals present various degrees of development, especially at the level of seminiferous tubules in which the spermatogenesis, when present, may be completed until spermatozoa. Some gonadal abnormalities interesting genetically female human beings, like a majority of the hermaphrodites, or certain XX men, are discussed at the light of these experimental data.