20 Alfred Jost 



be stimulated to glandular activity as in the adult, even by- 

 large doses of testosterone. 



The urogenital sinus provides another interesting example. 

 This part is identical in young male and female embryos. 

 Prostatic buds appear in the male if the testis has acted on the 

 undifferentiated tissue for a sufficient period of time. Early 

 castration, on day nineteen, completely prevents the forma- 

 tion of the buds; castration performed one or two days later 

 permits the development of two straight unbranched buds; 

 castrating two days later still, on day twenty-three, when only 

 mere anlage have appeared, does not stop prostatic growth. 

 The buds continue to differentiate, although generally in a 

 somewhat reduced manner in comparison with control animals. 



During the short period of time involved, the testis has 

 completely changed the properties of a special part of the 

 urogenital sinus, which has become the prostatic region. It 

 would be of great importance to know what happened in 

 these cells, what kind of change they underwent. 



After day twenty-four the male rabbit foetus is definitely 

 marked as a male ; the sexual structures have passed a turning- 

 point after which removal of the testis does not inhibit further 

 differentiation. Even if the testicular function of the normal 

 male were reduced at late stages of pregnancy, the sexual 

 organogenesis would be normal: something similar seems to 

 happen in the human foetus, in which the testicular intestitial 

 cells are very large and rich in cytoplasm from the stage of 

 3 cm. to a stage of about 15 cm., after which they almost 

 disappear (Gillman, 1948); masculine organogenesis was 

 already complete. 



The age factor in pituitary function 



Research into hypophyseal function in the rabbit foetus 

 was initiated in 1947, in order to verify whether the pituitary 

 gland controls testicular activity. The foetuses were deprived 

 of their hypophyses by the decapitation method, the value of 

 which has already been discussed (Jost, 1951). 



