§ 5 



MODIFICATION IN FOLLICLE 



105 



of the egg flows out. In this it resemjbles the corpus atreticum 

 ruptum; it consists, however, chiefly of granulosa-lutein cells 

 (Fig. 73d). 



e. As transition to the post-ovulation corpus luteum we 

 find a second form of the corpus luteum ruptum, in which 

 the ovum is not destroyed, but emerges, at a far advanced 

 stage of the corpus luteum, as a result of the rupture, and 

 becomes fertilised. Since this particular modification has 

 hitherto been observed as normal in only one mammal, i.e., 

 in Elephantulus rnyurus (VAN DEr Horst, 1940) we pro- 

 pose to call this corpus the "Elephantulus type". It forms the 

 bridge to the actual post-ovulation corpus luteum, from 

 which it is distinguished either by very early luteinisation or 

 by very much retarded ovulation. As in many post-ovulation 

 corpora lutea, it is not only the granulosa, but also the theca 

 which luteinises (Fig. 73e). 



;. Owing to an abundant liquor- and/or lymph pressure, 

 during which the formation of glands is checked, a corpus 

 luteum cyst (Fig. 73 f) is formed. 



c. Modifications of the post-ovulation corpus luteum. 

 a. The post -ovulation corpus luteum cavum owes its exist- 

 ence to the incomplete development of its granulosa gland 

 after ovulation, a central cavity remaining free, while the 

 corpus luteum remains small. It is identical with the corpus 

 luteum menstruationis in women (Fig. 74a) . 



post-ovulation corpus luteum 



Fig. 74. Modifications of the post-ovulation corpus luteum. 



