CHANGES IN THE OVARY 119 



food supply, undergo ovogenesis than of the peripheral ones. The 

 rest of the cells, which are not able, for one cause or another, to 

 undergo these changes, appear to remain quiescent for a while, until 

 finally they regress, and pass into a condition of subserviency to the 

 needs of those which have become ova. Both follicle-cells and- 

 interstitial cells are, however, still potential ova. They have passed 

 through the initial stages, and only need enlargement and nuclear 

 transformations in order to become ova should the appropriate 

 stimulus be given [as will be described below, p. 155]. This chance 

 is not given to the follicle-cells. As soon as the follicles begin to 

 grow they multiply rapidly, and probably provide, by their [partial] 

 disintegration, the follicular secretion upon which the ovum feeds 

 and grows." ^ 



The description given above of the origin of the follicle and 

 interstitial cells applies especially- to the rabbit. Miss Lane-Claypon 

 has also investigated their developmental history in the rat,^ and 

 expresses belief that in this animal also they are derived from the 

 germinal epithelium by a similar process of differentiation. Both 

 follicular epithelial cells and interstitial cells are stated to pass 

 through identically the same stages^ but the latter are said to remain 

 grouped together in the spaces between the follicles instead of 

 arranging themselves around the diplotenic nuclei of the develop- 

 ing ova. 



Thus it appears that the ova, the follicular epithelial cells, and 

 most probably also the interstitial cells, are all derived from the 

 germinal epithelium by processes involving changes in the nuclear 

 chromatin ; but that, whereas these changes are similar in the case 

 of the follicle and interstitial cells, tfiose undergone by the developing 

 ova are more extensive and show a greater complexity. 



The significance of the common origin of these different ovarian 

 elements will be more apparent when we consider the views which 

 are held regarding the further development and the probable functional . 

 importance of these cells. 



It should be mentioned, however, that Allen ^ and Sainmont,* 

 working on the organogenesis of the ovary in the rabbit and the cat 

 respectively, have come to the conclusion that the ovarian interstitial 



1 Lane-Claypon, loc. cit. 



- Lane-Claypon, "On Ovogenesis and the Formation of the Interstitial 

 Cells of the Ovary," Jowr. Obstet. and Oynoec, vol. xi., 1907. 



^ Allen, "The Embryonic Development of the Ovary and Testis of the 

 Mammals," Amer. Jow. of Anat., vol. iii., 1904. Allen describes the inter- 

 stitial cells in a three-months-old rabbit as being derived from certain cells in 

 the thecse internae of degenerate follicles. The cells are said to lose their 

 walls, become irregular in shape, and undergo a rapid process of amitotic 

 division, after whion they become transformed into typical interstitial cells. 



* Sainmont, " Eecherches relatives a I'organogenfese du Testicule et I'Ovaire 

 chez le Chat," Arch, de Biol., vol. xxii., 1905. 



