122 



BIOLOGIC BASIS OF SEX 



TABLE 2.3 



Effects of hormones on derivatives of the urogenital sinus and the 

 external genitalia in mammalian embryos 



ACTION OF MALE HORMONE ON FEMALES 



ACTION OF FEMALE HORMONE ON MALES 



» r/7/5 effect appears only with large dosages 



corresponds to the altered sex of the gonad. 

 Castration of mature males results in retro- 

 gression of the glands and after early castra- 

 tion the cloaca remains sexually undifferen- 

 tiated in both sexes (de Beaumont, 1933). 

 However, testis tissue grafted into castrates 

 (de Beaumont) , or treatment with male 

 hormone {e.g., Burns, 1939c), readily in- 

 duces development of male cloacal glands in 

 individuals of either sex (for a review see 

 Humphrey, 1942). 



In the development of mammalian em- 

 l)ryos the urinogenital sinus is separated at 

 an early stage from the cloacal region of the 

 hind-gut by formation of the perineal sep- 

 tum. In its primitive condition the sinus is 

 a short canal, extending from the neck of 

 the bladder to the exterior, with a meatus 

 at the base of the genital tubercle. The 

 paired gonaducts open into it near the neck 

 of the bladder (Fig. 2.22). Sexual differenti- 

 ation in females chiefly involves anatomic 

 and histologic changes associated with de- 

 velopment of the vagina, to which the urino- 

 genital sinus makes an important contribu- 

 tion; at the same time the male sex ducts 

 regress and largely disappear (Fig. 2.22B). 

 In placental mammals fusion of the poste- 

 rior ends of the Miillerian ducts as they ap- 

 proach the urinogenital sinus gives rise to 

 the unpaired, median vagina, but in marsu- 



pials the ducts remain separate and paired 

 lateral vaginal canals are formed (Fig. 

 2.22B). In male embryos the main features 

 of sinus differentiation are the involution of 

 the ]\Iiillerian ducts with absence of vaginal 

 development, and the differentiation of elab- 

 orate prostatic glands. Sex hormones show a 

 high degree of specificity in their effects on 

 the sinus structures, inducing development 

 of typically male or female forms. Results 

 are available for a number of species be- 

 longing to several orders of mammals,^'' and 

 are in agreement except for minor details 

 (for some representative species see Table 

 2.3). 



The histologic aspects of the differentia- 

 tion of the sinus are well illustrated in young 

 opossums. The effects of male hormone 

 (testosterone propionate) in male and fe- 

 male pouch young are compared in Figure 

 2.29. The effect of the hormone in males is 



^\See Greene (1942) for the rat: Raynaud 

 (1942), Turner (1940) for the mouse; Jost (i947a) 

 for the rabbit; Godet (1950) for the mole; Wells 

 and van Wagenen (1954) for the monkey; Burns 

 (1939a, b) and Moore (1941) for the opossum. 

 Simimaries for these and other species are to be 

 found in Colloques Intcrnationaux : La Differencia- 

 lion Sexuelle choz les Vertebre.*, Masson et Cie., 

 Paris, 1951. As an exception, the effects in the 

 hamster are rather slight (Bruner and Witschi, 

 1946; White, 1949). 



