292 



GENERATION. 



Discharge of the Ovum. 



A ripe Graafian follicle measures from f to J an inch in 

 diameter, and presents a rounded elevation, containing a 

 plexus of blood-vessels, upon the surface of the ovary. At 

 its most prominent portion, is an ovoid spot, in which the 

 membranes are entirely free from blood-vessels. At this 



FIG. 29. 



Ovum of the rabbit, from a Graafian follicle ^ of an inch in diameter. a. epithelium of the 

 ovum; &, zona pellucida, with radiating striations (vitelline membrane); c, germinal vesi- 

 cle; d. germinal spot; e. vitellus. (WALDEYER, in STEICKEE, Ilandbuch der Lehre von 

 den Geweben, Leipzig, 1871, S. 555.) 



spot, which is called the macula folliculi, the coverings finally 

 give way, and the contents of the follicle are discharged. For 

 a short time anterior to the rupture of the follicle, important 

 changes have been going on in its structure. In the first place, 



