INTERNAL SECRETION OF OVARY 249 



Mingazzini in reptiles, and by Giacomini in birds, amphibians 

 and fishes. The condition also seems to vary in the different 

 species of fishes (Wallace), some presenting hypertrophy of the 

 foUicular epithelium and others not. Van der Stricht made 

 observations on the bat and concluded that here the corpus 

 luteum is of a mixed origin. Bell (1920) holds that the corpus 

 luteum is formed entirely of cells of the theca interna. On the 

 contrary Fraenkel (1914, p. 20) defends the view that the 

 corpus luteum is formed only by cells of the membrana 

 granulosa, in accordance with Sobotta for the rabbit and 

 mouse, with Franz Cohn for the rabbit, and with Rob. Meyer 

 and others for man. Marshall (1901 and 1903, quoted from 

 Marshall, 1905) has demonstrated this for the sheep, and 

 Zietschmann (1921) for the cow. As regards birds, amphibians, 

 reptiles and fishes, Fraenkel declares that no corpus luteum 

 exists in these species at all, and that even in the monotremes 

 and marsupials the corpus luteum is only rudimentary. 

 According to Hill and O'Donoghue the corpus luteum is present 

 in the monotremes, and certainly in the marsupials. 



The contradictory statements of the above-mentioned 

 authors as to this question are evidently caused by the fact 

 that there is in reality no sharp line of demarcation between 

 the atretic follicle and the corpus luteum, just as there is no 

 sharp distinction to be drawn between the atretic follicle and 

 the interstitial tissue. Aschner insists that there is something 

 approaching an identity between the atretic follicle and the 

 corpus luteum in lower vertebrates. The former is often spoken 

 of as the so-called "corpus luteum atreticum" in some mam- 

 mals, i.e., in the case of atretic follicles closely resembling real 

 corpora lutea. Even Fraenkel admits that sometimes the 

 atretic follicle is formed by cells both of the membrana granu- 

 losa and theca interna intermingled with each other, although 

 in general, according to him, only the cells of the theca interna 

 form the atretic folHcle. Various authors (Volker, Winiwarter 

 Sainmont and recently Gerlinger, 1923 a) have called atten- 

 tion to the so-called "partial" corpus luteum, being a follicle 

 which has not ruptured, but is undergoing atresia and producing 

 lutein cells derived from the granulosa only in a Hmited zone 

 of the wall. 



Many authors have insisted on the great resemblance be- 

 tween the cells of the atretic foUicle (the theca-lutein cells 



