124 THE PHYSIOLOGY OF REPRODUCTION 



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, those 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 1 and Sainmont, 2 

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

 cat respectively, have come to the conclusion that the ovarian 

 interstitial cells have a connective tissue origin, but these in- 

 vestigators do not appear to have traced the successive stages of 

 cellular development with the same completeness as Miss Lane- 

 Claypon. Sainmont is of opinion that they have a trophic 

 function, a suggestion which was first made by Pfliiger. 3 



There would seem to be no doubt that the developing ova 

 in the immature ovary subsist and grow at the expense of the 

 surrounding tissue. Thus protoplasmic masses, formed by the 

 aggregation of very young ova, have been described by Balfour, 4 

 who made the suggestion that one ovum may develop at the 

 cost of the others. These aggregations of ova were noticed in 

 the ovary of the foetal rabbit at about the sixteenth day of 

 pregnancy. A day or two previously the ova were observed 

 to be separate. Miss Lane-Claypon, who confirms the observa- 

 tion, is of opinion that Balfour's suggestion was right, and that 

 the ova which disappear serve ultimately as food-stuff for the 



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

 Mammals," Amer. Jour, 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, afier which they become transformed into typical interstitial cells. 



* Sainmont, Recherches relatives k 1'organogencse du Testicule et 1'Ovaire 

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



3 Pfliiger, Ueber die Eicrstiklce der Sauyethiere und des Menschen, Leipzig, 

 18G3. 



4 Balfour, loc. cit. 



