§5 MODIFICATION IN FOLLICLE 103 



Generally, indeed, both strata remain topographically 

 separate from each other (Fig. 72c). 



d. The corpus atreticum with retention of the ovum is 

 similar to the previous modifications, but goes one step 

 further in that, apart from the persisting granulosa tissue, 

 the egg cell, too, remains intact and usually does not pass 

 to the degeneration stage until the regression phase has set 

 in. A prominent feature in this, however, is again the strong 

 augmentation and hypertrophy of the surrounding theca into 

 theca-lutein gland (Fig. 72d). 



£. The corpus atreticum ruptum is distinguished from the 

 preceding corpus atreticum by the occurrence of a rupture of 

 the follicle accompanied by extrusion of the substance of the 

 egg. The theca-lutein cells show a typically secreting gland- 

 ular character (Fig. 72e). 



C. The atretic cyst. By excessive liquor- or lymph-pres- 

 sure the organization of the gland is checked, and a turgid 

 cyst filled with liquid is formed; the corpus luteum cyst 

 (Fig. 72f). 



These are the possibilities of development in an atretic 

 direction. In addition to either (a) incompletely or (b) 

 completely constructed follicular derivatives consisting only 

 of theca, we see the occurrence of other ones, consisting of 

 ?. mixture of theca and granulosa (c, d). In addition to 

 retention of the ovum (d) there is also a premature ruptur- 

 ing of the follicle (e). 



b. The modifications of the pre-ovulation type. 

 With the pre-ovulation corpora lutea we class all those gland- 

 ular descendants of the follicle in which the granulosa is 

 hypertrophied into lutein cells before the follicle is ruptured, 

 in which process the ovum usually succumbs. The atresia 

 leads, owing to granulosa degeneration, to a theca gland, and 

 the pre-ovulation corpus luteum to a granulosa gland. The 

 destruction of the ovum is the only feature common to both. 

 Again, the pre-ovulation type also shows an analogous 

 modification-series (Fig. 73). 



a. The pre-ovulation corpus luteum cavum is character- 



