358 INTERNAL SECRETION 



There is a striking difference, in the two sexes, in the structure 

 of the excretory ducts from the genital glands and in the external 

 genitals, as well as in those organs which are calfed the secondary 

 genital organs. 



The study of embryology shows that the primitive beginning 

 of these apparatuses is, in both sexes, common and indifferent. 

 In addition to the primitive genital trace, it comprises the Wolffian 

 body or primordial kidney, the Wolffian duct or primordial 

 ureter, and Miiller's duct. The latter runs along the lateral side 

 of the Wolffian duct and has a common opening with the latter 

 into the sinus urogenitalis. At the end of the third month of 

 embryonal life, this primitive beginning becomes differentiated in 

 accordance with the characteristics of one or the other sex, and 

 develops to form either the male or the female sexual apparatus. 

 But whichever the sex of the individual, portions of the charac- 

 teristics of the other sex remain as rudimentary organs. 



If a testis develops from the primitive genital trace, an 

 epididymis is formed from the head portion of the Wolffian body ; 

 the caudal portion forms blind ducts which eventually become 

 the paradidymis and aberrant ducts ; and the Wolffian duct be- 

 comes the vas deferens. Mu'ller's duct disappears, but the caudal 

 and cranial portions remain to form the hydatid of Morgagni and 

 the sinus pocularis (uterus masculinus). 



Where the primitive genital trace develops to form an ovary, 

 Miiller's ducts form the Fallopian tubes, uterus and vagina. That 

 portion of the Wolffian body which is in communication with the 

 ovarian tract shrivels up to form the parovarium (epoophoron), 

 which corresponds to the male epididymis. Vestiges of the caudal 

 portion of the Wolffian body persist as the paroophoron, situated 

 in the ligamentum latum, and occasionally also as structures cor- 

 responding to the ductuli aberrantes. The cranial portion of the 

 Wolffian duct forms a portion of the epoophoron with the appen- 

 dix vesicularis, while the remnants of the caudal portion form 

 the so-called ducts of Gaertner. 



This brief sketch of the developmental history of the sexual 

 apparatuses shows that the primordial beginning of the secondary 

 genital organs is independent of that of the generative glands. 

 The secondary genital organs have a bisexual origin and, in 

 the adult animal, these show a certain degree of hermaphroditism. 

 This bisexual origin leads occasionally to the development of 

 both sets of genital ducts and external genitals, thus producing 

 instances of pseudo-hermaphroditism. Pseudo-hermaphrodites 

 are individuals in whom the genital glands are unisexual, while 

 the rest of -the genital apparatus is, either wholly or in part, 

 bisexual. 



As a general rule, the development of the excretory ducts 

 proceeds in accordance with the sexual character of the genital 

 glands, though malformations have been observed which seem 



