ACTION OF SEX HORMONES IN FOETAL LIFE 407 



This is the youngest free-martin found ; its reproductive system 

 is ah-eady definitely of the sterile free-martin type. The gonads 

 are much smaller than in the normal female (cf. description by 

 Miss Chapin '17, p. 455). Miss Chapin's observations de- 

 scribed in the follo^^^ng paper demonstrate a complete absence 

 of cortical tissue in the ovary; the medullary component is 

 hypertrophied as compared with the normal, and an albuginea 

 is present. The ducts also show a sifting in the male direction 

 (Chapin, p. 459), the Miillerian duct being in process of degenera- 

 tion. Thus already at this stage the characters of the sterile 

 free-martin are definitely estabhshed, and it is proved that the 

 primary effect of the male sex hormones is to prevent the forma- 

 tion of the ingrowths that normally form the cortex of the ovary. 

 This is a matter of great significance, which is repeated in all the 

 other cases. 



History. Collected October 20, 1915. Maternal ovaries 

 absent. These twins were contained in a single chorion with 

 broad connection occupied by cotyledons between the two 

 halves. 



2. The next stage ( $" 12.5 cm., case 26) was used for histo- 

 logical work; it is described by Miss Chapin. No study of the 

 gross anatomy. 



.3. Case 17. d" 13.75 cm.; ^ 13.1 cm. in length; figure 14, 

 urinogenital system of ^. X 4. 



In this preparation the very minute size of the gonad strikes 

 the eye sX once; (compare fig. 6, normal female 10.2 cm. long, 

 and 9 normal female 17 cm. long). The Wolffian body has 

 entirely degenerated. Phallus typically female. About mid- 

 way between the gonad and the genital cord the inguina' fold 

 arching over the umbilical arteries unites the ducts (urinogenital 

 fold) to the lateral body-wall; this fold is the foundation for the 

 round ligament in the female and is the site of formation of the 

 gubernaculum in the male. The ducts are interpreted as Wolf- 

 fian ducts, though they appear to be united in the posterior 

 third of the genital cord; Miillerian ducts are not \dsible 

 macroscopically. 



History. Bovine twins cf and ^. Collected October 9, 

 1915. One maternal ovary missing ; the other had a single corpus 



