INTERSTITIAL CELLS OF MAMMALIAN OVARY 69 



clearer, with a well defined 'nucleolus.' No special cytological 

 study of nucleus or cytoplasm was made, hence the nature of 

 this nucleolus was not ascertained, whether true or false. 



The problem of the interstitial cell, on this side, therefore, 

 resolves itself into an examination of the conditions under which 

 this transformation occurs, and the part that the stroma plays 

 in the ever-continuous processes of growth within the ovary. 



That the stroma plays an important part in the development 

 of the ovary as a whole, in the transformations that take place 

 in the medulla of the developing ovary, and in the phenomena 

 of follicle development in the adult ovary, becomes quite evident 

 from the examination of such a series of ovaries as has been at 

 my disposal. The histological growth changes are so complex 

 however that their analysis and broad comprehension are ex- 

 ceedingly difficult. Stromal strands and lamellae penetrate the 

 primitive cortex, but any particular correlation with the egg 

 cords is not apparent. Oocytes that have either earlier or later 

 become separated by the breaking up of the egg cords, are sur- 

 rounded by a follicular epithelium, and there is usually recog- 

 nizable a concentric stromal investment. In the primary fol- 

 licles of the cortex in the adolescent and adult periods, the 

 follicular epithelial cells are so thin that careful examination is 

 necessary for their recognition. Such follicles possess no evident 

 theca. As soon, however, as the growth of the follicle begins, 

 and the follicular epithelium becomes cuboidal, columnar, and 

 then stratified in the well known method of growth of a Graafian 

 follicle, a concentric arrangement of the stroma is evident, be- 

 coming as growth proceeds, the theca of the Graafian follicle. 

 The so-called medullary cord of the fetal and post partum ovary 

 possesses a stromal sheath as a form of theca (figs. 11 and 12), 

 which becomes very evident in the larger masses. The concen- 

 tric arrangement of the stroma is found whether an ovum is 

 enclosed or not. Naked ova, lying free in the stroma are not 

 found save occasionally. Such ova are apparently always de- 

 generating or degenerated. The growth correlation which leads 

 to the formation of a definitive theca in the development of a 

 Graafian follicle, appears to be more directly between stroma and 



