THE OVARIES 



217 



its position toward the surface and the folHcle may cause an appre- 

 ciable bulge in the ovarian surface. It should be remenil)ered that 

 outside the stratum granulosum at this point are the theca interna, 

 theca externa, tunica albuginea, and the germinal epithelium. 

 Due to the great increase in follicular Hquid, all these coats are 

 under considerable tension and are relatively thin. There is finally 

 a rupture at this point, and the liquor foUiculi pours out, carrying 

 with it the ovum surrounded by the cells of the germ hill. This 

 ru])ture at time of ovulation may be accomj^anied by a hemorrhage 

 into the follicle, so that a corpus hsemorrhagicum is formed. 



Fig. 136. — Photograph through a t'ollir-le in the region of the germ hill (Cumulus 

 oophorus). Ovary of the dog. 



After ovulation, the oviun with the surrounding zona radiata 

 passes into the oviduct, in the ui)per portion of which the second 

 maturation division occurs and fertilization takes place. There are 

 two sites of continued activity and histological change following 

 normal ovulation, one in the follicular mass and the other in the 

 uterus following the descent of the fertilized egg. 



Corpus Luteum. — FoWowing the rupture of the mature Graafian 

 follicle and discharge of the ovum, the stratum granulosum of the 

 follicular wall collapses and folds in so that the previous spherical 

 cavity is reduced and irregular in shape. The cells of the granulo- 

 sum layer begin to increase in size and number and a yellow lipoid 

 substance forms in their cytoplasm. The yellow color is often 

 prominent and gives the structure the name of corpus luteum at 



