1334 



THE UEO-GENITAL SYSTEM. 



secondarily with the ductuli efferentes which are derived from the tubules of the meso- 

 nephros, and thus the mesonephric or Wolffian duct becomes the passage for the secretion 

 of the testis. 



In the female large epithelial cells are found in the stroma of the developing ovary, 

 beneath the germinal epithelium, as early as the thirty-third day. These primitive ova 

 are much more numerous than the primitive sperm cells of the male, and form a very 

 characteristic feature of the developing ovary. At first they lie isolated, but later about 

 the fifth week they become surrounded by other smaller cells having a like origin from 



the germinal epithelium. Each primitive 

 ovum surrounded by its cells becomes a 

 primitive follicle, the further development 

 of which has already been described (p. 

 1318). During the later stages the epi- 

 thelium has the appearance of growing 

 down into the stroma in the form of long 

 branching cellular processes which break up 

 into little nests of cells to form the future 

 follicles (p. 1318). The proliferation of cells 

 from the surface epithelium goes on until 

 the seventh month, but it is extremely 

 doubtful if any new ova arise in the later 

 months of gestation or after birth. 



THE 



FIG. 1045. THE URINO-GENITAL PASSAGES AT 

 INDIFFERENT STAGE OF DEVELOPMENT. 



Ureter, green solid outline. Wolffiau duct, green dotted 

 outline. The origin of the vesicula seminalis is 

 indicated. Miillerian ducts, orange. Rectum, 

 bladder, and urino-genital canal, red. 



THE GENERATIVE DUCTS. 

 Generative Ducts. As has been 



already stated, the male ducts arise from 



the Wolffian, and the female from the Mullerian ducts of the embryo. Both sexes at 

 first possess well-developed Wolffian and Mullerian ducts, which are arranged in a very 

 definite manner. The Wolffian ducts, communicating directly with the tubules of the 

 mesonephros, lie at first parallel to, and at 

 a considerable distance from, one another. 

 As they pass towards the caudal end 

 of the embryo they approach one another, 

 and each becomes enclosed in a fold of 

 peritoneum called the plica urogenitalis. 

 More caudally the ducts become closely 

 approximated to each other, are embedded 

 in a cord-like mass of connective tissue, 

 to which the term genital cord is applied. 

 They finally open into the anterior sub- 

 division of the cloaca (Fig. 1042). 



The Mullerian ducts, opening freely into 

 the body cavity at their cephalic ends, lie 

 to the lateral side of the Wolffian ducts. As 

 they are traced caudally they cross the 

 Wolffian ducts and enter the genital cord, 

 within which they unite and form a canal, 

 which occupies the median plane, and opens 

 into the anterior subdivision of the cloaca, 

 between the Wolffian ducts (Fig. 1042). 

 The manner in which the ureters become 

 separated from the Wolffian ducts has 

 already been described. 



Ducts in the Male. The seminiferous 

 tubules of the testis become connected 

 with the Wolffian duct through a fusion of 

 certain tubules of the mesonephros with the 



rete testis. The connexion is definitely established in the third month. The number o: 

 tubules taking part varies considerably, but corresponds to the number of ductul: 

 efferentes found in the adult. The connecting tubules becoming much convoluted, jusi 

 as they join the Wolffian duct, form the lobuli of the epididymis. The canal of th< 

 epididymis is directly formed from the cephalic part of the Wolffian duct, and the ductui 



FIG. 1046. THE URINO-GENITAL PASSAGES IN 

 THE MALE. 



Ductus deferens, dotted green outline. Ureter, solic 

 green outline. Utriculus prostaticus, orange. 

 Bladder and pelvic part of urethra, red. 

 portion of urethra, black. 



Penilt 





