SECONDARY SEXUAL CHARACTERS. 47 



on the mammary gland, If this guinea pig should represent an 

 analogue to the freemartin in cattle, we would have to assume 

 that the male characteristics of the gonad were produced in an 

 original female through the influence of the testicular substance 

 of the male brother. While such an origin has been made pos- 

 sible through the findings of Lillie, the essential point is that, 

 whatever the origin of this condition, we have every reason to 

 consider the gonad which we described as male. 



It is the complete examination of the gonads in serial sections 

 which makes it possible for us to exclude the presence of ovarian 

 structures in this animal and to prove the similarity of the organs 

 with the testicles found under certain experimental and natural 

 pathological conditions. There is no reason for assuming that 

 the gonads in our case represented really ovarian tissue. We 

 have examined many hundred of ovaries of guinea pigs of various 

 ages and have never been able to detect in the ovaries of guinea 

 pigs structures resembling the interstitial gland of the testicle, 

 while on the other hand such structures are strongly developed 

 in testicles which have been retained in the abdominal cavity. 



The findings of Lillie and Chapin suggest very strongly, and 

 I take this also to be the interpretation of Lillie, that even in the 

 freemartin the gonad which originally was destined to become 

 female, assumes at least in part true male characters. If this 

 were not so, it would be difficult to explain why seminal vesicles 

 could develop in a freemartin. We should expect that the auto- 

 genous ovarian substances would prevent the heterogenous 

 testicular substances from exerting such an influence on the 

 secondary sexual organs of the female twin. 



We found in our case a marked development of sexual instinct 

 associated with the absence of generative cells and with a very 

 marked development of the interstitial tissue. Now, as we have 

 pointed out in previous papers, it is improbable that in the guinea 

 pig the interstitial gland is responsible for the manifestation of 

 sexual desire in the female. 1 



1 Loeb, Leo, Zentralblatt f. Physiologic, 1911, XXV., No. 9, and Loeb, Leo, 

 " The Relation of the Ovary to the Uterus and Mammary Gland from the Experi- 

 mental Aspect," Surgery, Gynecology and Obstetrics, 1917, XXV., p. 300. (A review 

 of the literature concerning this and other aspects of the mechanism of the sexual 

 cycle.) In accordance with the most widely accepted view we assumed in our 



