124 



BIOLOGIC BASIS OF SEX 



out attempting to allow for the constitu- 

 tional sex factor mentioned above, this 

 amount of androgen would appear to be 

 roughly equivalent to the hormonal activity 

 of the embryonic testes at this period. 



Female hormone has opposite effects on 

 the urinogenital sinus and its derivatives in 

 young opossums. Estradiol dipropionate 

 completely suppresses prostatic differentia- 

 tion in males and transforms the sinus epi- 

 thelium into a stratified squamous epithe- 

 lium of vaginal type (Fig. 2.30) ; in fact the 

 histologic picture is one of intense prolifera- 

 tion and cornification like that of the adult 

 vagina at estrus. Moreover, a single dose of 

 estrogen administered during the 15th day 

 of pouch life, shortly before the prostatic 

 buds would normally appear, results in com- 

 plete suppression of the prostate, an effect 

 which is also permanent (Burns, 1942a, b, c) . 

 Thus, there is a relatively short period dur- 

 ing which induction and continued develop- 

 ment of ])rostatic glands in females, or their 



permanent suppression in males, is wholly 

 conditioned by the presence of the appropri- 

 ate hormone. Quantitatively as well as qual- 

 itatively the reactivity of the embryonic 

 sinus epithelium to estradiol is remarkable. 

 Again a sex difference, as measured by 

 growth and proliferation is seen, this time in 

 favor of the female. Transformation to a 

 typical vaginal epithelium in the estrous 

 phase can be induced in very young male 

 embryos, long before the time of appearance 

 of prostatic buds (Fig. 2.31; Burns, 1942c). 

 It is hardly surprising that an epithelium of 

 this type permanently loses all capacity to 

 produce prostatic tissue. 



The effects of castration on the develop- 

 ment of the urinogenital sinus and its de- 

 rivatives in mammalian embryos follow the 

 pattern previously described for the sex 

 ducts. The male form of sinus is incapable 

 of developing in the absence of the testes, 

 whereas morphogenesis of the female form 

 is not significantly affected by castration 





B 



Fig. 2.30. The effects of estradiol dipropionate on the development of the urinogenital sinus 

 and prostate in young opossums. A. The normal sinus of a young male aged 30 days, showing 

 the condition of the prostatic buds, for comparison with a normal female of the same age (fi). 

 Note the bilobed form of the sinus canal in the male as compared with the typical pentangu- 

 lar form in the female. C. The effect of the female hormone in a male littermate of the 

 same age, treated from the time of birth. Complete suppression of the prostatic glands has 

 occurred, the form of the sinus canal is typically female, and the sinus epithelium has been 

 transformed into a thick stratified squamous epithelium, like that of the adult vagina, in a 

 state of pronounced keratinization and desquamation. The effect of an identical dose in a 

 female subject is similar but much more intense. 



