CH. LVII.] 



THE OVARY. 



801 



Some of the Graafian follicles never burst ; they attain a 

 certain degree of maturity, then atrophy and disappear. 



An ovum is a large spheroidal cell surrounded by a trans- 



t 3 



Fig. 613. ^Corpora lutea of different periods. B, corpus luteum of about the sixth week 

 after impregnation, showing its plicated form at that period, i, substance of the 

 ovary ; 2, substance of the corpus luteum ; 3, a greyish coagidum in its cavity. 

 (Paterson.) A, corpus luteum two days after delivery ; D, in the twelfth week after 

 delivery. (Montgomery.) 



Nucleus or germinal vesicle. 



Nucleolus or germinal spot, 



---Space left by retraction of 

 protoplasm. 



Protoplasm containing yolk 

 spherules. 



, Vitelline membrane. 



Fig. 614. A human ovum. (Cadiat.) 



Fig. 615. Germinal epithelium of the surface of the ovary of five days' chick, a, small 

 ovoblawtH ; b, larger ovoblonta. (Cadiat.) 



parent striated membrane called the vitelline membrane, or zona 

 pelludda. The protoplasm is filled with large fatty and albu- 

 minous granules (yolk sphet~uleis), except in the part around the 

 nucleus, which is comparatively free from these granules. It 



K.P. 



A F 



