OVA. 183 



The ova and Graafian follicles occupy the peripheral or cor- 

 tical portion of the ovary (the " oophoron "), leaving in the 

 interior a medullary region continuous with the hilum, where 

 the vessels enter. 



The epithelial covering of the ovary is a single layer of 

 cuboidal or low columnar cells, called " germinal epithelium " 

 from the fact that the ova are developed from it during fetal 

 life. This epithelium is continuous with the peritoneal endo- 

 thelium, the glistening squamous cells of the latter being 

 here replaced by columnar cells of less lustre. 



The stroma of the ovary is a mass of connective tissue, 

 made up in the cortical region largely of fusiform connective- 

 tissue cells with scanty intercellular elements. On the surface, 

 just beneath the epithelial covering, this tissue is condensed 

 into a layer called the tunica albuginea, continuous and inti- 

 mately connected with the stroma. 



The medullary region and hilum contain the larger vessels, 

 imbedded in connective tissue of a more ordinary kind, in 

 which fibrous elements are more abundant. 



Scattered about in the stroma (more abundantly in certain 

 animals than in the human species) are large epithelioid (?) 

 cells, the interstitial cells, similar to those of the testis. The 

 ovary is well supplied with bloodvessels, and also possesses 

 lymphatics and nerves. 



The ova (called ovules before impregnation), which occupy 

 the peripheral zone of the ovary, originate during foetal life 

 from processes of the germinal epithelium which grow down- 

 ward and are then cut off, leaving isolated nodules of epithe- 

 lial cells in the stroma. In each of these nodules one cell, 

 destined to become the ovum, enlarges, while the other ac- 

 companying (indifferent) epithelial cells form a capsule about 

 it and 'develop ultimately into the tunica granulosa of the 

 mature Graafian follicle. The cortex of the ovary contains 

 large numbers (estimated by some observers at about 70,000 

 in both ovaries) of these primitive ovisacs imbedded in the 

 stroma, each consisting of a large ovule surrounded by a 

 more or less definite envelope of small epithelial cells. In 

 the course of ovulation and menstruation these primitive 

 ovisacs develop as Graafian follicles, and successively mature 

 and discharge the ovules from the ovary, leaving the remains 



