124 DEVELOPMENT OF THE OVARY. 



certain length, the amount of this upward extension of the fused ducts varying in 

 different animals. 



The united part of the Mullerian ducts afterwards forms the foundation of the 

 vagina and uterus in the female, and the prostatic vesicle, or uterus masculinus in 



Fig. 150. TRANSVERSE SECTIONS OF THE 



GENITAL CORD IN A FEMALE CALF EM- 

 BRYO. MAGNIFIED FOURTEEN DIAMETERS. 

 (Kblliker. ) 



1, near the upper end ; 2 and 3, near the 

 middle ; 4, at the lower end ; a, anterior, 

 p, posterior aspect ; m, Mullerian ducts 

 united or separate ; w t Wolffion ducts. 



the male ; the upper or fore part of 

 the Mullerian duct disappears in 

 the male, in the female it forms the 

 oviduct (.Fallopian tube). 



The hydatids of Morgagni are 

 remnant of part of the Mullerian 



v J 



believed to represent in the 

 duct. 



the 



In the human embryo of the third month the uterus is bifid, and it is by the upward ex- 

 tension of the median fusion that the triangular body of the uterus is produced. The bifid 

 condition corresponds with the bicorned uterus of many animals, and the process of fusion 

 above described explains the occasional malformation of a partial or complete division of the 

 uterus and vagina into two passages. Up to the fifth month there is no distinction between 

 vagina and uterus. Then the os uteri begins to be seen, and the cervix uteri subsequently 

 becomes manifest as a part, which is at first thicker and larger than the rest of the organ. 



In some animals the prostatic vesicle of the male is prolonged into cornua and tubes like 

 the uterus of the female. 



The germinal epithelium. This name was given by Waldeyer to the thick- 

 ened epithelium lying along the inner side of the Wolfnan projection (fig. 143, a). 

 The cells become at first columnar, and then two, three, or even several layers thick, 

 while at the same time the mesoblast below them becomes increased in amount, and 

 thus a marked projection is produced, which in some vertebrates forms a distinct 

 ridge the genital ridge. Amongst the cells of the germinal epithelium, some are 

 seen which are larger and more spherical than the others, these are the primordial 

 ova (fig. 143, 0), and occur in both sexes ; in fact, up to a certain point, the differ- 

 ence of sex of the embryo is not apparent. 



Development of the ovary. In the female sex the germinal epithelium: soon 

 becomes much thickened, and begins to grow down into the mesoblastic stroma in the 

 form of columns of epithelium cells, which enclose amongst them some of the prim- 

 ordial ova. 1 These columns constitute the egg-tubes of Pfliiger (fig. 152). They 

 are separated from one another by mesoblast, which grows towards and into the 

 germinal epithelium simultaneously with the down-growth of the egg-tubes, and 

 there is thus produced a complete interlocking of strands of connective and epithelial 

 tissue, which together constitute the ovary. The egg-tubes next become broken up 

 into rounded groups or " nests " of germinal epithelial calls, each of which may 

 enclose one or more primordial ova. The primordial ova eventually develope into 

 ordinary ova, two or more frequently fusing together to form a single ovum (Balfour), 

 while from the remaining cells in the "nest " the epithelium of the Graafian follicle 

 is eventually produced. In many of the cell nests, primordial ova cannot at first be 



1 Mihalkovics states that the cells which are to form the follicular epithelium first sink into the 

 stroma r and that afterwards the primordial ova follow them, and become enclosed by them. 



