144 THE PHYSIOLOGY OF REPRODUCTION 



further studied by Cohn, 1 while the same process in the marmot has 

 formed the subject of an investigation by Yolker. 2 Both authors 

 agree in supporting Bischoff. Yolker finds that the theca externa 

 takes a share in the connective tissue ingrowth, while the theca 

 interna does not become exhausted in the process. 



Jankowski, 3 however, has arrived at totally different conclusions, 

 and adopts the view that the luteal cells are modified connective 

 tissue cells. The material employed in this research appears to 

 have consisted of a miscellaneous collection of sows' and guinea-pigs' 

 ovaries obtained without any attempt at systematic investigation, so 

 that the ages of the corpora lutea were unknown. Jankowski bases 

 his opinion largely on the appearance of cells resembling luteal cells 

 in the theca interna of the undischarged follicle. It would seem 

 possible that these were interstitial cells, and so probably potentially 

 equivalent to follicle-cells (as supposed on independent grounds by 

 van der Stricht and Miss Lane-Claypon). More recently Corner 4 

 has come to the conclusion that in the sow the corpus luteum is 

 formed from both epithelium and theca interna. 



Sobotta 5 and Loeb 6 have investigated the formation of the 

 corpus luteum in the guinea-pig, and find, contrary to Jankowski, 

 that it is substantially the same as in the mouse, the rabbit, and 

 the sheep. According to Robinson 7 the luteal cells are formed from 

 the follicular epithelial cells in the ferret. 



The results of those investigators who agree in adopting Bischoffs 



1 Cohn, "Zur Histologie und Histogenesis des Corpus Luteum und des 

 Interstitiellen Ovarialgewebes," Arch. f. Mikr. Anat., vol. Ixii., 1903. Schafer, 

 however, states that in the rabbit the epithelial cells are entirely extruded at 

 ovulation, the cavity becoming filled largely with blood-clot prior to ingrowth 

 from the connective tissue wall (Essentials of Histology, llth Edition, London, 

 1920). The present writer has reinvestigated the question and finds that the 

 epithelium is retained. The confusion may have arisen through mistaking 

 atrophic follicles for discharged ones (see p. 150). 



8 Volker, "Uber die Histogenese Corporis Lutei bei den Ziesel (Spermo- 

 philus citillus)" Bull. Internat. A cad. Science (Medicine), Prague, 1904. 



3 Jankowski, " Beitrag zur Entstehung des Corpus Luteum der Saugethiere," 

 Arch. f. Mikr. Anat., vol. xliv., 1904. Williams (Obstetrics, New York, 1904) 

 takes up the same position as Jankowski, partly on the ground that " the 

 rnembrana granulosa presents extensive degenerative changes, and is usually 

 cast off in great part at the time of rupture," and partly because certain cells 

 of the theca interna come to resemble luteal cells prior to ovulation. The 

 former statement is far from proved, and the latter cannot be regarded a 

 conclusive (see text). Cf. also Seitz, "Die Follikelatresie," Arch. f. Gyncik., 

 vol. Ixxvii., 1906. 



4 Corner, "On the Origin of the Corpus Luteum of the Sow," Amer. Jour. 

 Anat., vol. xxvi., 1919. 



5 Sobotta, " Uber die Bildung des Corpus Luteum beim Meerschweinchen," 

 Anat. Hefte, vol. xxxii., 1906. 



6 Loeb (L.), " Uber die Entwicklung des Corpus Luteum beim Meer- 

 schweinchen," Anat. Am., vol. xxviii., 1906. 



7 Robinson, " The Formation, Rupture, and Closure of Ovarian Follicles in 

 Ferrets," Trans. Roy. Hoc. Edin., vol. lii., 1918. 



