DEVELOPMENT OF THE OVARY AND TESTICLE. 889 



the vasa aberrantia (a) of the testicle (Kobelt). The hydatid of Morgagni (h), at the head of 

 the epididymis, according to Luschka and others, is a part of the epididymis Fleischl regards 

 it as the rudiment of the male ovary. The organ of the Giraldes is part of the Wolffian body. 

 The Wolffian duct itself becomes the vas deferens (V) from which the vesiculse seminales are 

 developed. The two Wolffian and two Miillerian ducts, as they enter the pelvis, unite to form 

 a common cord the genital cord. 



In the female, the tubes of the Wolffian bodies disappear, all except a few tubules, lined with 

 ciliated epithelium, constituting the parovarium, or organ of Rosenmuller (fig. 646), and a part 

 analogous to the organ of Giraldes in the broad ligament of the uterus ( Waldeyer) (fig. 682, 

 P). The same is the case with the Wolffian ducts. In some animals (ruminants, pig, cat, and 

 fox) they remain permanently as the ducts of Gaertner. 



The Miillerian duct is frayed out at its upper end to form the fimbriae of the Fallopian tube, 

 and it is often provided with a hydatid (A 1 ). That part of the uro-genital sinus into which the 

 four ducts open grows above into a hollow sphere, which forms the vagina (Eathke). Accord- 

 ing to Thiersch and Leuckart, however, the two Miillerian ducts unite at their lower ends to 

 form the united uterus (U) and vagina, while their free upper ends form the Fallopian tubes (T). 

 The Miillerian ducts at first open into the posterior part of the urinary bladder below the 

 ureters (uro-genital sinus, S), while ultimately this part of the bladder becomes so elongated 

 posteriorly that the vagina (the united Miillerian ducts) and the urethra are united below and 

 deeply within the vestibule of the vagina. At the 3rd to the 4th month, the uterus and 

 vagina are not separate from each other, but at the 5th to the 6th month the uterus is defined 

 from the vagina. 



The testicles lie originally in the lumbar region of the abdominal cavity (fig. 684, V, t), and 

 are carried by a fold of the peritoneum the mesorchium (ra). From the hilum of the testicle 

 a cord, the gubernaculum testis, runs through the inguinal canal into the base of the scrotum. 

 At the same time a septum-like process is developed independently from the peritoneum to the 

 base of the scrotum (pv). The testicle passes through the inguinal canal into the scrotum, but 

 the mechanism and the cause of the descent are not accurately ascertained. [Descent of testis, 

 446.j 



The ovaries also descend somewhat. The round ligament of the uterus corresponds to the 

 gubernaculum testis. A process of the peritoneum passes in the female into the inguinal canal 

 as Nuck's canal. It is rare to find the ovaries descending into the labia majora. 



[The origin of the urinary and generative organs is undoubtedly associated with the develop- 

 ment of the Wolffian bodies. The researches of Semper and Balfour on elasmobranch fishes 

 show that the process is a very complex one. There is a mass of cells on each side of the verte- 

 bral column, which is divided into three parts, the first called the pronephros, or head-kidney 

 of Balfour and Sedgwick, the middle one, the mesonephros or Wolffian body, and the posterior 

 one or metanephros, which is formed after the other two, gives origin to the permanent kidney 

 in the amniota. The Miillerian duct is connected with the pronephros, the Wolffian duct with 

 the mesonephros, and the ureter with the metanephros.] 



[The following table, modified from Quain, shows the destiny of these structures : 



Mullerian Ducts (Ducts of the Pronephros). 

 Female. Male. 



Fallopian tubes. Hydatid of Morgagni. 



Hydatid. Male uterus. 



Uterus and vagina. 



Wolffian Bodies (Mesonephros). 

 Parovarium. Vasa efferentia, Coni vasculosi. 



Paroophoron. Organ of Giraldes, Vasa aberrantia. 



Round ligament of the uterus. Gubernaculum testis. 



Wolffian Ducts. 

 Chief tube of parovarium. Convoluted tube of epididymis. 



Ducts of Gaertner. Vas deferens and vesiculse seminales. 



Metanephros. 

 Kidney. Ureter.] 



The external genitals are at first not distinguishable in the two sexes (fig. 684, I). At the 

 4th week, there is merely an orifice at the posterior extremity of the trunk, representing both the 

 anus and the opening of the urachus, and forming a cloaca (fig. 682, 4, K). In front of this an 

 elevation the genital eminence appears about the 6th week, and on each side of the orifice a 

 large cutaneous elevation (II, w). At the end of the 2nd month, there is a groove on the under 

 surface of the genital eminence, leading back to the cloaca, and with distinct walls bounding it 

 (II, r). At the middle of the 3rd month, the cloacal opening is divided by the growth of the 



