THE FEMALE GENITAL ORGANS. 



349 



ova of the primitive or primordial follicles attain a size (in fresh tissue 

 teased in normal salt solution) varying from 48 /* to 69^. They 

 possess a nucleus varying in size from 20 fi to 32^, presenting a 

 doubly contoured nuclear membrane, and containing a distinct 

 chromatin network with a nucleolus and several accessory nucleoli. 

 The protoplasm shows a distinct spongioplastic network containing 

 a clear hyaloplasm. The primitive ova, until they undergo further 

 development, retain this size and structure, irrespective of the age 

 of the individual. They are numerous in embryonic life and early 

 childhood, always found during the ovulation period, but not 



Fig. 281. Transverse section through the cortex of a human ovary ; X 5 : ^ 

 Tunica albuginea ; ep, follicular epithelium, zona granulosa ; y^primordial follicles ; ov, 

 ovum in the discus proligerus ; the, thecaexternafolliculi ; thi, theca interim folliculi with 

 blood-vessels (Sobotta, "Atlas and Epitome of Human Histology"). 



observed in the ovaries of the aged. Changes in the size and 

 structure of the ova accompany the proliferation of the follicular 

 cells in the growing follicles. As soon as the follicular cells of a 

 primitive follicle proliferate, as above described, the ovum of the 

 follicle increases in size until it has attained the size of a fully 

 developed ovum. The zona pellucida now makes its appearance, 

 and after this has reached a certain thickness, yolk granules (deuto- 

 plastic granules) develop in the protoplasm of the ovum. In a 

 fully developed Graafian follicle the ovum presents an outer clearer 

 protoplasmic zone and an inner fine granular zone containing yolk 



