THE OVARIES 27 



In the human ovary he could find no trace of an ' inter- The inter- 



.... , , , , stitial cells of 



Stltial gland . the ovary. 



All histologists are familiar with the structure of the 

 human ovary (fig. 10), and the obvious scarcity of secretory 

 cells, apart from those connected with the follicles. But 

 if we examine the ovary of an adult rabbit and of certain 

 other rodents, we see a most remarkable structure : nearly 

 the whole of the organ is composed of a mass of cells which 

 are epithelioid in character ; and equally striking is the 

 appearance of the corpora lutea, the cells of which can 

 only be distinguished, if at all, from the cells of the stroma 

 by their larger size ; while the Graafian follicles are 

 crowded round the periphery of the ovary as though 

 pushed outwards (fig. 11). 



What does this extraordinary appearance in rodents 

 indicate ? From very close observation of the corpora 

 lutea in all the stages of development I have come to 

 the conclusion that either they do not all undergo 

 involution in this order as in the higher mammals, but 

 that many of them ultimately form the so-called inter- 

 stitial stroma-cells, or that the lutein cells are developed 

 from interstitial stroma-cells which have already become 

 specialized. 



If, however, we examine the ovary of a rabbit a few 

 weeks old we find that it is composed entirely of pri- 

 mordial ova and a few follicles, scattered evenly through- 

 out the organ, and that these are separated by bundles 

 of connective tissue. There is an almost entire absence 

 of definite interstitial cells (fig. 12). The absence of these 

 cells in the very young rabbit also indicates the likeli- 

 hood of their origin from the same source as if not 

 actually from those of the corpora lutea in the adult, 

 although it is probable that in the human ovary and in 

 the ovaries of animals which contain very few inter- 

 stitial cells these cells arise entirely from specialized 

 stroma-cells. 



In approaching the question of the function, or 

 functions, of the interstitial cells of the ovary we are 

 arrested by the uncertainty of our knowledge concerning 



