HORMONES IN DIFFERENTIATION OF SEX 



125 





Fig. 2.31. The effects of a stronger dosage of estradiol dipropionate on the urinogenital 

 sinus at a much earher stage. A. Young male treated from birth to an age of about 12 days, 

 for comparison with the normal male sinus (inset, B) of the same age. Compare the charac- 

 ter of the sinus epithelium with that in the older specimen shown in Figure 2.30C This 

 condition of the sinus epithelium is induced at an age which precedes by se^■eral days the 

 normal appearance of the prostatic buds, which never develop. 



(Table 2.2; Jost, 1947b; Raynaud and Fril- 

 ley, 1947; Wells, 1950). In castrate males 

 prostatic differentiation is prevented and 

 development of a vagina (correlated with 

 persistence of the Miillerian ducts in male 

 castrates) results in a sinus of female type 

 (Fig. 2.27 A). Male and female castrates are 

 morphologically very similar, and both 

 closely resemble the normal female. Again it 

 is clear that the embryonic testis is the es- 

 sential factor in male development, whereas 

 the female pattern is independent of hor- 

 monal conditioning and also of sex consti- 

 tution, since in the absence of the gonads it 

 develops spontaneously in castrates of either 

 sex. 



The factor of time is again of paramount 

 importance and sharply limits the effective- 

 ness of castration. This holds for the devel- 

 opment of other accessory structures (Table 

 2.2) but is particularly clear in the case of 

 the prostate which will serve to illustrate. 

 In male rabbit embryos castrated on or after 

 the £3rd day of gestation there is only a 



slight effect on prostatic development, which 

 continues in a practically normal manner; 

 but if the operation is performed a day ear- 

 lier there is a distinct reduction in size. In 

 fetuses castrated from the 20th to the 21st 

 day only small ventral buds are found which 

 are already formed at the time of operation, 

 and after castration earlier than 20 days 

 prostatic buds are absent altogether (Fig. 

 2.27; Jost, 1947b, c). The period from 20 to 

 21 days, then, is critical for the appearance 

 of the prostatic buds and their further differ- 

 entiation for which the embryonic testis is 

 essential. However, absence of the testis is 

 fully compensated for by male hormone ; in 

 castrates receiving androgen the develop- 

 ment of all male parts proceeds normally. 

 A similar result has been obtained in the 

 fetal rat (Wells, Cavanaugh and Maxwell, 

 1954). Late castration has little effect, but 

 castration on day 18 results only in buds 

 which do not undergo branching. Earlier cas- 

 tration has not proved feasible in this spe- 

 cies. 



