226 INTERNAL SECRETIONS 



The atresia and fatty transformation of the folHcles begin in 

 the human ovary in the fifth month of intrauterine hfe. 

 According to Winiwarter {1908), interstitial cells are present 

 in the human ovary long before. But typical interstitial cells 

 are derived also from the connective tissue cells of the stroma. 

 There is no cytological difference between the interstitial cells 

 originating from the stroma and those originating from follicular 

 atresia. Once follicular atresia begins, formation of interstitial 

 cells from cells of the stroma ceases, indeed, to play a 

 quantitatively important role. 



Observers differ as to the extension of follicular atresia 

 and of the interstitial tissue during childhood, but all agree 

 that an increase of the interstitial cells takes place in man 

 during gravidity. A very great number of follicles undergo 

 atresia in the second half of gravidity. An enormous quantity 

 of interstitial cells is, so to speak, poured out into the ovarian 

 stroma. According to Seitz (1906, p. 263), these cells assume 

 the character of lutein cells; they increase in size and become 

 epithehoid, so that their appearance is very like that of the 

 cells of the corpus luteum. Seitz called these cells "theca- 

 lutein-cells." This transformation of cells of the theca interna 

 into theca-lutein-cells becomes all the more intensified, the 

 further gravidity has proceeded. As Seitz points out, all the 

 larger follicles present undergo atresia during gravidity; as the 

 cells of the theca interna increase also in number, a great 

 quantity of new theca-lutein-cells full of fatty and lutein 

 inclusions arise by follicular atresia during the second half of 

 gravidity. Like Seitz, other authors hold that the epithelioid 

 cells of the ovarian stroma containing fat and lutein are derived 

 from the cells of the theca interna. In the fifth section of this 

 chapter we shall learn the physiological bearing of such a 

 transformation of the cells of the theca interna into cells some- 

 what similar to those of the corpus luteum. 



It is, indeed, not impossible that cells of epithehal origin also 

 take part in the formation of the interstitial tissue. The 

 membrana granulosa of the follicle undergoing atresia is 

 possibly such a source of the epithelioid cells of the interstitial 

 tissue. Ra^mussen (19 18) finds it probable that in the wood- 

 chuck new interstitial cells can originate from the germinal 

 epithelium. A similar view is held by Ochoterena and Ramirez 

 (1920) as a result of observations on the rat and on the rabbit. 



