142 THE PHYSIOLOGY OF REPRODUCTION 



coition, or (in cases where coition did not or was not known to occur) 

 after oestrus was observed. The result of this investigation was to 

 confirm Bischoff s hypothesis in all essential particulars. The sheep, 

 however, was found to present some differences from the mouse (as 

 investigated by Sobotta) in regard to the origin of the connective 

 tissue network of the corpus luteum, this being discovered to 

 originate partly from the theca externa, and not merely from the 

 theca interna. It was found also that the cells of the follicular 

 epithelium continued to undergo mitotic division after the rupture 

 of the follicle, but not with the same frequency as previously. The 

 theca interna was stated to become entirely spent in the growth 

 of the connective tissue network. Four days after cestrus the 

 discharged follicle was found to have acquired all the characteristics 

 of the fully developed corpus luteum, the luteal cells, as seen in 

 section, being at least six times as large as the original epithelial 

 cells. 



In the same year as the publication of the paper referred to 

 above, on the sheep's corpus luteum, van der Stricht 1 gave an 

 account of the discharged follicle in bats belonging to the genera 

 Vesperitgo, Vexpertilio y and Placbttis. This was also confirmatory of 

 the conclusion that the follicle-cells hypertrophy and give rise to 

 luteal cells, but mitotic division among these cells was also seen 

 to occur. Van der Stricht calls attention to the appearance of fatty 

 particles at a very early stage in the history of the luteal cells. A 

 point of greater importance is that van der Stricht found that, 

 whereas the majority of the luteal cells are derived from the 

 follicular epithelium, a certain relatively small proportion of them 

 are developed out of interstitial cells in the inner theca of the 

 connective tissue sheath. This observation lends additional interest 

 to Miss Lane- Clay pon's statement that the follicle and interstitial 

 cells have an identical origin, since both are derived from the 

 germinal epithelium, and pass through a similar series of changes. 2 



The structure of the ovary, and the cyclical changes which it 

 undergoes in the case of the " marsupial cat " (Dasynrm vi.rerrinns), 

 have been investigated by Sandes, 3 who shows that the mode of 



1 Van der Stricht, " La Eupture du Follicule Ovarique et l'Histog6nese du 

 Corps Jaime," C. It. de I'Assoc. des Anatomistes, 3rd Session, Lyon, 1901. "La 

 Ponte Ovarique, etc.," Bull, de I' A cad. Roy. de Medecine Belgique, 1901. 



2 Marshall, " The Development of the Corpus Luteum : a Keview," tyttar. 

 Jour. Micr. Science, vol. xlix., 1905. Miss Lane-Claypon's discovery that the 

 follicular epithelial and interstitial cells are probably equipotential may 

 perhaps help to elucidate some of the discrepancies between the accounts by 

 various authors of the formation of the corpus luteum. 



3 Sandes, " The Corpus Luteum of Dasyurus I'iverrinus," Proc. Linnean Soc.^ 

 New South Wales, vol. xxviii., 1903. See also O'Donoghue, " Ueber die Corpoi-a 

 Lutea bei einigen Beuteltieren," Arch. f. ^fik^. Anat., vol. Ixxxiv., 1914. 



