390 THE CORPUS LUTEUM OF DASyCIli'S, 



in the hitherto passive theca folliculi as to enable it to form a 

 large parenchymatous cellular structure like the corpus luteum. 



But, apart from these general arguments, a solution of the 

 question for Dasyurus will be found on observation of the actual 

 processes of corpus luteum formation in that animal, and perhaps 

 the most important point in time is that, just after the rupture 

 of the follicle takes place, ^vhen the process of corpus luteum 

 formation is carried on with great rapidity, particularly in small 

 animals. On this account, Biihler sa3's that Sobotta has not 

 observed in the rabbit and mouse the first alteration of these 

 folliculi, in which sprouting of the thecal tissue into the cavity of 

 the corpus luteum takes place; and he says also that an observer 

 who is unaware of the existence of these sprouts or cones of thecal 

 tissue might regard them as parts of the epithelial laj^er. This 

 criticism is entirely erroneous, for in both the cases of the rabbit 

 and mouse, under the sections dealing with the freshly ruptured 

 follicle and early corpus luteum, Sobotta has described, though 

 perhaps not fully, these cones of thecal tissue sprouting from the 

 theca interna. Certainl}^ in his figures this point might have 

 been made more clear, but there is no doubt that he has both 

 recognised and described them. To resume, in Dasyurus, 

 owing to the comparatiN e simplicity of the theca folliculi, it is 

 eas}^ to follow its future development. At first it does not trans- 

 gress the membrana propria, but soon ruptures it and wedges its 

 vfcij towards the cavity of the corpus luteum, and e^en at this 

 time before it reaches the cavity it can be seen in many cases 

 that the changes in the cells of the membrana granulosa are well 

 marked, whilst between the sprouts are seen the membrana 

 granulosa cells still sharply separated from the theca by the 

 basal membrane. In some instances, too, the cavit}' of the follicle 

 is almost filled with the hypertrophied cells of the membrana 

 granulosa, even before the vascular connective tissue sprouts 

 from the theca have time to gain the cavit}' of the follicle. The 

 rate of alteration in the membrana granulosa cells and in the 

 theca folliculi is not absolutely constant, but varies within limits, 

 so that at given stages of the segmenting ovum there may in one 



