248 INTERNAL SECRETIONS 



trophy under experimental conditions, and cause an hormonic 

 effect, as normally observed only in gravidity. In view of these 

 results two new questions arise: are there, first, genetical and, 

 secondly, physiological relations between the cells of atretic 

 folHcles or the interstitial cells on the one hand, and the corpus 

 luteum, which characterizes the ovary during gravidity, on 

 the other? 



(a) Histogenesis of the corpus luteum. 



The origin of the cells of the corpus luteum graviditatis 

 (Fig. Ill, see also Fig. 98) has been a matter of much dis- 

 cussion. According to most authorities these cells are derived 

 only from the membrana granulosa; others are of the opinion 

 that cells of the theca interna also give rise to cells of the corpus 

 luteum. The first theory implies that the cells of the corpus 

 luteum are of epithehal origin only, whereas, according to the 

 second, cells originating from connective tissue can also become 

 luteal cells. 



Great importance has been attributed to this question by 

 various authors. If the corpus luteum is formed only from 

 cells of the membrana granulosa, and if the cells of the inter- 

 stitial tissue (to which atretic follicles belong) originate only 

 from the theca interna or from stroma cells, the two formations 

 are genetically different. But, on the other hand, if the cells 

 of the corpus luteum are of a mixed origin, the whole apparatus 

 of epithelioid cells of the ovary might be regarded as genetically 

 one. It seems clear that this conclusion might supply evidence 

 of a functional similarity between the two parts of the ovary. 

 I myself have no experience of this field of enquiry, and it is 

 for the histologist to settle the question as to the origin of the 

 cells of the corpus luteum. Comparative observations on 

 different species play a great role in these discussions. Most 

 observers agree that in lower vertebrates, as in fishes, am- 

 phibians and reptiles, the corpus luteum, when present, is 

 built up out of the epithelial cells of the granulosa (Marshall, 

 1905). On the contrary, Aschner (1914 a, 1918) pointed out that 

 in some species the ovum is surrounded only by a simple layer 

 of cells belonging to the granulosa, and that cells of the theca 

 take an important part in the building up of the corpus luteum. 

 But this is not true for all lower vertebrates, an hypertrophy 

 of the cells of the granulosa having been observed by 



