THE GENERATIVE GLANDS 401 



Lutein cells may be derived from epithelium and from connective 

 tissue. The lutein cells of the corpus luteum are derived from 

 the epithelium of the membrana granulosa. The connective tissue 

 framework of the corpus luteum is formed, by means of invasion 

 by connective tissue buds, from the theca interna. There is, 

 however, no fundamental difference between the formation of 

 the corpus luteum of pregnancy and that of the corpus luteum of 

 menstruation. The compact corpus albicans is probably a pro- 

 duct of the involution of the corpus luteum. 



Atresia of the follicles is accompanied, both during and after 

 degeneration of the ovum and the epithelium, by proliferation of 

 the theca interna, which leads to the formation of a theca-lutein 

 layer. This layer is observed during pregnancy and in patho- 

 logical hypersemia of the genitals ; it is also observed under 

 normal conditions. The atretic follicle is entirely a connective- 

 tissue structure. 



Involution of the atretic follicle is accompanied by the de- 

 velopment of the theca-lutein cells into stroma cells, though in 

 some species this transformation is accomplished very gradually. 

 In such animals, the interstitial ovarian tissue is composed of 

 theca-lutein cells which have not, as yet, undergone degeneration. 

 The theca-lutein cell formation of the atretic follicles corresponds 

 in man to the interstitial ovarian tissue of certain animals. 



These investigations supply a complete morphological pic- 

 ture of the tissues of which the ovary is composed. We know 

 that, in addition to the Graafian follicles, the ovary contains two 

 other tissues, both of which, from the nature of their structure, 

 might possess an internal secretory function, but which in their 

 origin differ fundamentally from one another. These are : The 

 corpus luteum, which is derived from the epithelium ; and the 

 interstitial stroma cells, which have a connective-tissue origin. 

 That the interstitial stroma cells possess a secretory function is 

 suggested by the presence of fat granules and other secretory en- 

 closures, as well as by a certain resemblance, commented upon 

 by many (Mulon, Wallart), to the cells of the suprarenal cortex. 



Both tissues are present in a varying stage of development 

 in all mammals. The knowledge of this fact is of vital import- 

 ance to a right understanding of the ovarian secretory functions. 

 And of equal significance is a second fact, namely, that there are 

 no justifiable grounds for the distinction which has hitherto been 

 drawn between the true corpus luteum of pregnancy and the 

 so-called spurious corpus luteum of menstruation. As Ravano 

 also points out, there is no difference whatever either in form and 

 contents or in genesis, between the two structures ; both are true 

 corpora lutea, whether the ovum which proceeds from them is 

 fertilized or not. 



In the face of these facts, it is not possible to concur in the 

 theory which Bouin and Ancel have recently advanced (1909). 



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