GERM-CELL ORIGIN 



119 



PROLI FE RAT IN G 

 GERMINAL EPITHELIUM 



GERM CELLS WITH 

 FORMING FOLL ICLES 



pflUger's cord 

 Fig. 63 



Fig. 64 



Fig. 63. Cells proliferating inward from germinal epithelium of the ovary of a one- 

 day-old rat. Observe cords of cell.s (Pfliiger's cords) projecting into the ovarian substance. 

 Within these cords of cells are young oogonia. (After Vincent and Dornfeld, '48.) 



Fig. 64. Cellular condition near the surface of the ovary of a young female opossum. 

 This section of the ovary is near the hilar regions, i.e., near the mesovarium. Observe 

 young oocytes and forming Graafian follicles. Primitive germ cells may be seen near the 

 germinal epithelium. 



germinal epithelium has been espoused by various authors. (See Moore and 

 Wang, '47; and Pincus, '36, Chap. II.) More recent papers have presented 

 views which are somewhat conflicting. Vincent and Dornfeld, '48 (fig. 63) 

 concluded that there is a proliferation of germ cells from the germinal epi- 

 thelium of the young rat ovary, while Jones ('49), using carbon granules as 

 a vital-marking technic, found no evidence of the production of ova from 

 the germinal epithelium in rat ovaries from 23 days until puberty. In the 

 adult rat, she concedes that a segregation of a moderate number of oogonia 

 from the germinal epithelium is possible. 



Aside from the above studies of carefully-made, histological preparations 

 relative to the time and place of origin of the primordial and definitive germ 

 cells, many experimental attacks have been made upon the problem. Using 

 an x-ray-sterilization approach, Parkes ('27); Brambell, Parkes and Fielding 

 ('27, a and b), found that the oogonia and oocytes of x-rayed ovaries of 

 the mouse were destroyed. In these cases new germ cells were not produced 

 from the germinal epithelium. Brambell ('30) believed that the destruction 

 of the primitive oogonia was responsible for the lack of oogenesis in these 

 x-rayed ovaries. However, this evidence is not conclusive, for one does not 



