386 



INTERNAL SECRETIONS 



A similar observation was made by Keller (1920) on the 

 goat. In triplets two foetuses were male, whereas the third 

 revealed external female genital organs, but the uterus was 

 underdeveloped. The Wolffian ducts were developed like 

 those in the sterile freemartin. The gonads externally 

 resembled testicles, but were to be found in the normal position 

 of the ovaries. Microscopically seminal tubules like those in 

 a retained testicle were found; but genital cords like those of 

 the ovary were present, and the stroma resembled that of an 

 ovary. The examination of the membranes and of the blood 



Fig. 131. — Twins in sheep, x 2/9. Both females. Fusion of chorionic 

 vesicles, but no anastomosis of blood vessels from the two sides. — From 

 Lillie. 



vessels showed that there was a great anastomosis between 

 the chorions. 



The authors concluded from these observations that the 

 abnormality of the female foetus in opposite-sexed twins is 

 caused by the fact that, owing to the direct communication 

 between both foetuses, the female one undergoes masculiniza- 

 tion under the influence of a male sexual hormone entering the 

 blood of the female. The authors consider the condition to be 

 similar to that of the animals employed in Steinach's experi- 

 ments on masculinization and feminization. But in the case 

 of the freemartin there is presumed to be a masculinization of an 

 embryonic soma, which had begun its sexual differentiation 



