312 NORMAIv HISTOLOGY AND ORGANOGRAPHY. 



second passive period, unless fertilization takes 

 place, when the ovum rapidly develops into a new 

 being. By far the large majority of the ova remain 

 undeveloped in the ovarian cortex, where they seem 

 to pass merely a passive existence. We have no 

 explanation of these phenomena beyond attributing 

 them to heredity, the nature of which is still highly 

 speculative. 



The Corpora Lutea. A corpus luteum is the modi- 

 fied Graafian follicle after its rupture and discharge 



Surface of ovary. 

 Epithelial cells. 



Connective-tissue 

 cells. 



Fig. 227. Section of corpus luteum. 



of the ovum. This follicle remains permanently 

 in the cortex of the ovary as a scar. When the 

 rupture takes place the follicular cavity fills up with 

 an exudate and an infusion of blood from the rup- 

 tured blood-vessels. This coagulum is quickly in- 

 vaded by white blood-corpuscles, connective-tissue 

 cells from the theca, and epithelial cells from the 

 stratum granulosum. The corpus luteum thus ulti- 

 mately shows a uniform distribution of epithelial 



