150 THE PHYSIOLOGY OF REPRODUCTION 



matic investigation, so that the ages of the corpora lutea were 

 unknown. Jankowski bases his opinion largely on the appear- 

 ance 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). 



Sobotta, 1 however, and also Loeb, 2 have subsequently in- 

 vestigated the formation of the corpus luteum in the guinea-pig, 

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

 rabbit, and the sheep. 



The results of those investigators who agree in adopting 

 Bischoff s theory of the mode of formation of the corpus luteum 

 may be summarised as follows : The luteal cells represent the 

 epithelial cells of the undischarged Graafian follicle. These, 

 after rupture, undergo a great hypertrophy, which may be 

 accompanied in the earlier stages by mitotic division, but only 

 to a relatively slight extent (Ovis, Vesperugo, &c.). Meanwhile 

 the thickness of the wall of the discharged follicle is further 

 increased by an ingrowth of connective tissue, which eventually 

 forms an anastomosis of cells, generally fusiform in shape, be- 

 tween the hypertrophying follicular epithelial cells. This con- 

 nective tissue ingrowth is either derived from the theca interna 

 alone (Mus, Cavia, Tarsius, Tupaia, Sorex, Dasyurus, Vesperugo, 

 &c.), or it may arise from both the theca interna and the theca 

 externa (Lepus, Ovis, Spermophilus}. The theca interna may 

 become entirely spent in this process (Mus, Cavia, Tarsius, 

 Tupaia, Sorex, Ovis, Dasyurus), or certain strands of this layer 

 may still remain and line the outside edge of the follicle after 

 it has become transformed into a fully developed corpus luteum 

 (Lepus, Spermophilus, Vesperugo). In some animals the inter- 

 stitial cells of the theca interna may develop into luteal cells 

 in just the same manner as the follicular epithelial cells 

 (Vesperugo, &c.). The cavity of the discharged follicle becomes 

 filled in eventually by the further ingrowth of connective tissue, 

 which forms a central plug. 



1 Sobotta, " liber die Bildung des Corpus Luteum beim Meerschweinchen," 

 Anat. Hefte, vol. xxxii., 1906. 



2 Loeb (L.), " liber die Entwicklung des Corpus Luteum beim Meer- 

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



