206 PHYSIOLOGY CHAP. 



of the corpora lutea in rabbits causes lasting nutritive disturbances 

 of the uterus, shown by retrogressive metamorphosis similar to 

 that which is observed after bilateral ovariotomy. 



As, however, the uterus is nourished and develops during the 

 time of active growth, that is, the period which precedes ovulation 

 and menstruation, it is necessary to admit that not only the lutein 

 cells, but the whole of the epithelia entering into the constitution 

 of the ovarian parenchyma, are the seat of an internal secretion 

 which not only regulates the nutrition of the uterus, but in- 

 fluences that of the whole organism. Perhaps this continuous 

 internal secretion of the ovarian parenchyma increases periodically, 

 or acquires a different specific nature coincidently with the bursting 

 of the follicle and the development of the lutein epithelium. 



This interesting subject of the continuous and periodic internal 

 secretion of the ovary deserves to be placed in greater prominence, 

 determining, as it possibly does, the different functional value to 

 be attached, from the point of view of the endocrine function, to 

 the different epithelial elements of the ovarian parenchyma. 



So far we have made acquaintance with the germinal epithelium 

 which invests the surface of the ovary, with the cells of the tubes 

 or cords which sink from the surface to form the primary oophorous 

 follicles, from which are developed the mature or Graafian follicles ; 

 lastly, the special lutein cells which are developed after the burst- 

 ing of the follicles and constitute the essential elements of the 

 corpora lutea. But we have not had an opportunity of making 

 any reference to the so-called interstitial cells which are scattered 

 in fair numbers in the supporting connective tissue stroma of the 

 female genital glands ; these cells are in all respects similar to 

 the interstitial cells of the testicle, of which we have spoken in 

 the preceding Chapter (v. para. VII.). Concerning these structures, 

 their origin and their function, a rich literature has been formed 

 recently. 



They are large polyhedral cells, with a protoplasm rich in fat 

 granules, and morphologically identical with the corresponding 

 cells of the testicle. It is agreed also that they are identical with 

 the cells which compose the theca interna of the follicles ; many 

 observers maintain that they are of a connective tissue nature, 

 but many others judge them to be of an epithelial character. 



According to Pliiger and others they have a functional value 

 essentially trophic in respect to the development of the ova; 

 others, on the other hand, see in them the principal anatomical 

 substratum of the internal secretion of the ovary. Their re- 

 semblance in morphological and chemical characters to the lutein 

 cells, from which they differ only in their smaller size, have 

 induced some to consider them as elements of the same kind. 

 From the comparative histological researches carried out by Cesa- 

 Bianchi (1907) there would appear to be an inverse development 



