THE OVARIES. 



1037 



and during the whole of the child-bearing period large and mature, or almost 

 mature, Graafian vesicles are also found in the cortical layer in small numbers, 



and also "corpora lutea," the re- 

 mains of vesicles which have burst 

 and are undergoing atrophy and 

 absorption. Beneath this super- 

 ficial stratum other large and more 

 mature Graafian vesicles are found 

 imbedded in the ovarian stroma. 



Ovum. 



Granular zone. 



Peritoneum. 



FIG. 576. Section of the ovary. (After Schron.) 1. 

 Outer covering. 1'. Attached border. 2. Central stroma. 

 3. Peripheral stroma. 4. Blood-vessels. 5. Graaflau fol- 

 licles in their earliest stiiire. 6, 7, 8. More advanced folli- 

 cles. 9. An almost mature follicle. 9'. Follicle from 

 which the ovum has escaped. 10. Corpus luteum. 



Coats of the 

 Stroma of the ovary \ Graafian vesicle, 

 with blood-vessels. Membrana 

 granulosa. 



FIG. 577. Section of the Graaflan ves- 

 icle. (After Von Baer.) 



These increase in size as they recede from the surface toward a highly vascular 

 stroma in the centre of the organ, termed the medullary substance (zona vasculosa, 

 Waldeyer). This stroma forms the tissue of the hiium by which the ovary is 

 attached, and through which the blood-vessels enter ; it does not contain any 

 Graafian vesicles. 



The larger Graafian follicles consist of an external fibro- vascular coat connected 

 with the surrounding stroma of the ovary by a network of blood-vessels ; and an 

 internal coat, named ovicapsule, which is lined by a layer of nucleated cells, called 

 the membrana granulosa. The fluid contained in the interior of the vesicles is 

 transparent and albuminous, and in it is suspended the ovum. In that part of 

 the mature Graafian vesicle which is nearest the surface of the ovary the cells of 

 the membrana granulosa are collected into a mass which projects into the cavity 

 of the vesicle. This is termed the discus proligerus, and in this the ovum is 

 imbedded. 1 



The ova are formed from the germinal epithelium on the surface of the ovary. 

 This becomes thickened, and in it are seen some cells which are larger and more 

 rounded than the rest ; these are termed the primordial ova. The germinal 

 epithelium grows downward in the form of tubes or columns, termed the egg tubes 

 of Pfliiger, into the ovarian stroma, which grows outward between the tubes, and 

 ultimately cuts them off from the germinal epithelium. These tubes are further 

 subdivided into rounded nests or groups, each containing a primordial ovum which 

 undergoes further development and growth while the surrounding cells of the nest 

 form the epithelium of the Graafian follicle. 



The development and maturation of the Graafian vesicles and ova continue 

 uninterruptedly from puberty to the end of the fruitful period of woman's life, 

 while their formation commences before birth. Before puberty the ovaries are 

 small, the Graafian vessels contained in them are disposed in a comparatively thick 

 layer in the cortical substance ; here they present the appearance of a large number 

 of minute closed vesicles, constituting the early condition of the Graafian vesicle ; 

 many, however, never attain full development, but shrink and disappear. At 

 puberty the ovaries enlarge, and become more vascular, the Graafian vesicles are 

 developed in greater abundance, and their ova are capable of fecundation. 



Discharge of the Ovum. The Graafian vesicles, after gradually approaching 

 the surface of the ovary, burst : the ovum and fluid contents of the vesicles are 



1 For a description of the ovum, see section on Embryology. 



