THE OVARIES. 



249 



demonstrable in some mammals. The spherical egg-nucleus, the germinal 

 vesicle, lies eccentrically placed within the deutoplasmic zone and measures 

 from 3045 fJL. It is bounded by a sharply defined nuclear membrane and 

 contains the nucleolus, ox germinal spot (4-8 /*), and the nuclear reticulum. 



Corpus Luteum. When the follicle approaches maturity, the inner layer of the 

 theca becomes the seat of great activity, the blood-vessels increasing and the cells 

 undergoing rapid proliferation and extraordinary growth, the enlarged elements 

 becoming filled with a yellowish substance and transformed into lutein cells. Coin- 

 cidently the follicular epithelium suffers fatty change which results in the partial 



Central 

 connective tissue 



Vascular 

 septa 



Lutein cells 



f Proliferating 

 cells of inner 

 layer of theca 



Blood-vessels 



FIG. 299. Section of human corpus luteum. X 70. 



disintegration of the cumulus and freeing of the ovum, enclosed by the cells of the 

 corona radiata, into the cavity of the follicle. When the latter ruptures the expulsion 

 of its contents is followed by hemorrhage into the cavity of the follicle and, soon 

 afterwards, by closure of the opening in the sac. The position of the rupture corre- 

 sponds to the place (stigtna) where the wall of the follicle is most distended and least 

 vascular and, hence, possesses least vitality and resistance. The rapid proliferation 

 and growth of the lutein cells produces an irregularly plicated wall of increasing 

 thickness that encloses the remains of the follicular epithelium and invades the hem- 

 orrhagic mass. The latter is gradually absorbed until the encroaching projections of 

 lutein cells and invading vascular connective tissue meet and the cavity of the follicle 

 is obliterated, its former position being subsequently indicated by a central core of 

 connective tissue. The complex thus formed, composed of lutein cells and septa of 

 vascular connective tissue, is the corpus luteum. 



When the liberated ovum becomes fertilized, the corpus luteum grows to huge 

 dimensions and forms a conspicuous oval mass that may approach 3 cm. in length and 

 occupy a considerable part of the entire cortex. When associated with pregnancy it 



