244 



NORMAL HISTOLOGY. 



stalked or sessile hydatid, in close relation with the epididymis, 

 and as the short diverticulum opening into the prostatic portion of 

 the urethra, the uterus masculinus or sinus pocularis, which is 

 therefore the homologue of the vagina and uterus. 



In the female the indifferent sexual gland early exhibits a grouping 

 of the mesothelial elements into cylindrical masses, the sexual cords, 

 which in the ovary, however, retain a closer connection with the ger- 

 minal mesothelium than do those of the testicle. Many groups of 

 epithelial elements are disposed vertically to the free surface of the 

 organ, and constitute the primary egg-tubes. In the ovary, as in 

 the testicle, the sexual cords contain the large sexual cells, the latter 

 being much more plentiful in the female than in the male gland. The 



ovarian stroma originates 

 later as a secondary ingrowth 

 of the surrounding mesoderm 

 between the groups of sexual 

 cells. The genetic relations 

 between the embryonal ele- 

 ments, particularly the large 

 cells, and the ova and the 

 follicular cells of the fully- 

 formed ovary, are still indefi- 

 nite. It may be assumed as 

 established, however, that 

 both these constituents of the 

 later organ are derived from 

 the cells constituting the sex- 

 ual cords, and, therefore, in- 

 directly from the ovarian 

 mesothelium or primitive 

 germinal epithelium. 

 Whether the large sexual cells are the direct ancestors of the ova 

 alone or contribute to the production of the follicular elements as 

 well is uncertain, but it seems probable that the later ova are the 

 immediate descendants especially of the large sexual cells. 



The passages providing for the escape of the product of the ovaries, 

 the ova, are derived from the Miillerian ducts, their anterior seg- 

 ments remaining distinct tubes, the oviducts, while their middle and 

 posterior divisions become fused and form respectively the uterus 

 and the vagina. The Wolffian body and its duct in the female 

 are represented by rudimentary structures, the parovarium and the 

 paroophoron. The horizontal head-tube of the former is the 

 persistent anterior segment of the Wolffian duct, while the shorter 

 vertical branches are the remains of the Wolffian tubules. The 



Section of ovary from very young kitten : a, ovarian 

 mesothelium or germinal epithelium, containing large 

 sexual cell (c) ; b, cylindrical epithelial masses consti- 

 tuting egg-tubes ; d, developing stroma. 



