CHANGES IN THE OVARY 



117 



Nagel, 1 and van Winiwarter, 2 have followed Waldeyer in suppos- 

 ing that the follicular epithelial cells (which form the innermost 

 layer of the wah 1 of the Graafian follicle) are derived like the ova 

 from the germinal epithelium. Schafer described appearances 

 indicating the possibility of the innermost layer of follicular 



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f 



i ^r^p <,. 





, 



-' 'ff-u 



K; fs . -^n r^v^ - " 

 P 



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FIG. 22. Cortex of pig embryo, showing germinal epithelium, Pfluger's 

 tubes with ova in various stages of development. (From Williams' 

 Obstetrics, Appleton & Co.) 



epithelium being derived from the ovum itself ; but, as he himself 

 pointed out, this view does not involve any morphological ab- 

 surdity if the ova and follicle-cells have a common origin. Balfour 

 described protoplasmic masses of embryonic ova in which the 

 cells appeared to be united together in such a way as to suggest 



1 Nagel, " Das menschliche Ei," Arch. f. Mikr. Anal., vol. xxxi., 1888. 



2 Van Winiwarter, " Recherches sur 1'Ovogenese," &c., Arch, de Biol,, 

 vol. xvii., 1901. 



