106 



BIOLOGIC BASIS OF SEX 



are just in process of separation from the 

 overlying germinal epithelimii. The germi- 

 nal epitheliimi, however, is still present as a 

 layer of low, columnar cells and at this stage 

 represents, potentially, the female compo- 

 nent of the young testis. Normally the ger- 

 minal epithelium does not survive long after 

 birth. In the course of the first day of post- 

 natal life irreversible changes occur which 

 lead to its rapid involution. It is the pres- 

 ence at stage 34 of a viable germinal epi- 

 thelium which makes possible the subse- 

 quent conversion of the testis into an ovary, 

 since it is this layer which must produce 

 the cortical zone of the transformed gonad 

 by the proliferation of secondary sex cords. 

 In so doing it plays precisely the same role 

 as the corresi)onding layer in the develop- 

 ment of the ovary. 



Treatment with estradiol dipropionate has 

 been carried out over varying periods up to 

 an age of 30 days postpartum or somewhat 

 longer, after which survival becomes diffi- 

 cult (Burns, 1939b). At the present time 

 46 male fetuses have been studied histologi- 



cally, comprising all the surviving males of 

 13 litters. Without exception, every speci- 

 men shows histologic modifications of the 

 type described below, the stage of transfor- 

 mation attained varying only with the 

 length of treatment. The process of trans- 

 formation consists at first of a gradual in- 

 hibition and suppression of testicular differ- 

 entiation, accompanied by persistence of the 

 germinal epithelium. At the same time the 

 differentiation of the interstitial tissue is 

 severely repressed (compare A and B, Fig. 

 2.17). Atrophy of the interstitial tissue has 

 also been described by Raynaud (1950) in 

 the testes of mouse embryos treated with 

 estrogen. After an interval (which varies in 

 different experimental litters and is appar- 

 ently influenced by dosage) the germinal 

 e})it helium again becomes active, producing 

 secondary sex cords which form a cortical 

 zone of varying thickness depending on the 

 length of treatment (Fig. 2.181. 



The first essential in obtaining transfor- 

 mation of the testis is the timing of the first 

 treatment, which must not be later than 





Fig. 2.17. The effects of female hormone on differentiation of the testis in young opossums. 

 A. Normal testis about 10 days after birth. Note tlie thin, .serous character of the epithehum 

 covering the testis (originally the germinal epithelium), the presence of a distinct tunica 

 albuginea, the prominent testis cords (prospective tubules), and the richly developed inter- 

 stitium. B. Testis (at somewhat higher magnification) of a young male aged 14 days, modi- 

 fied by the action of the female hormone estradiol dipropionate. Note the greatly reduced 

 condition of the testis cords and interstitial tissue, the thick, spongy character of the tunica 

 albuginea, and especially the survival of the germinal epithelium long after the stage at 

 which it normally undergoes involution. 



