HORMONES IN DIFFERENTIATION OF SEX 



115 



B 



D 



Fig. 2.24. Diagrammatic representation of the effects of relatively large doses of testos- 

 terone propionate, administered from birth to an age of 50 days, on the development of the 

 sex ducts in young opossums. A. Sex ducts as they appear in a normal male at 50 days; the 

 vas deferens (Wolffian duct), epididymal tubules and remnants of mesonephric tubules are 

 shown in black; the atrophic Miillerian duct is unshaded and the testis stippled. B. The ef- 

 fects of the male hormone on the male duct system appear throughout; however, large 

 dosages also induce a paradoxical growth and development of the uterine and tubal regions 

 of the Miillerian duct, but the vaginal segment is absent as in the normal male. C. The sex 

 ducts as they appear in a normal female at 50 days — breakdown and disappearance of the 

 Wolffian duct and associated structures, regional development of the Miillerian duct into 

 tubal, uterine, and vaginal segments. The contribution of the urinogenital sinus to the 

 vaginal canal is indicated in stipple. D. The effects of the male hormone in a female subject : 

 note the preservation and great hypertrophy of the male duct system which is not, however, 

 as large or as well differentiated as in the treated male; note also the striking paradoxical 

 effect of a large dosage of androgen on the female genital tract which, at the same dosage 

 level, is far greater than in the treated male (B). These paradoxical effects of androgen on 

 the Miillerian duct dorivativos disappear entirely at lower dosages. 



carried out in a number of species of birds 

 and mammals. ^'^ 



Early castration of avian cml)ryos is fol- 

 lowed by persistence and development of 

 Miillerian ducts in both sexes (the chick 

 and the duck, Wolff and Wolff, 1951; Huij- 

 bers, 1951). After total castration in males 

 both ducts persist and develop, but partial 

 castration results in regression as usual. In 

 females, in which the right duct normally 

 regresses, both ducts persist and are well 

 developed. ^^ Thus, in the absence of the gon- 

 ads the Miillerian ducts follow the same 

 pattern of development regardless of sex 

 (Fig. 2.25). It is clear that the testes are 



'Mu the rabbit (Jost, 1947b); the mouse (Ray- 

 naud and Frilley, 1947) and the rat (Wells, 1946, 

 1950); in the chick and the duck embryo (Wolff, 

 1950; Wolff and Wolff, 1951; and Huijbers, 1951). 



" In birds involution of the right Miillerian duct 

 of the female is normally conditioned in some 

 manner by the ovaries, and it has been shown fur- 

 ther that the presence of either ovary is sufficient 

 (Wolff and Wolff, 1951). The exact nature of the 

 inhibitory factor in this interesting case is not 

 known. 



necessary for normal inhibition of the ducts 

 in male embryos, and it was pointed out 

 earlier that a graft of the embryonic testis 

 has the same effect in females (Wolff, 1946). 

 The ovaries, on the contrary, have no posi- 

 tive role in the development of the Miille- 

 rian ducts, but actually inhibit the right 

 duct; in their absence both ducts develop 

 without hormonal conditioning. 



Among mammalian embryos the case of 

 the rabbit is best known (Jost, 1947b). Cas- 

 tration of the female again has no important 

 consequences; the Miillerian ducts continue 

 to develop and shortly before birth are only 

 slightly smaller than in normal females. In 

 male castrates, on the other hand, the situa- 

 tion is very different; if the operation is 

 performed early enough the Miillerian ducts, 

 instead of regressing, persist and develop, 

 becoming practically indistinguishable from 

 those of castrate females (Table 2.2, Fig. 

 2.26). Thus, as in birds, castrates of either 

 sex follow identical patterns of development. 



Nevertheless, if castration is delayed be- 



