344 THE GENITOURINARY ORGANS. 



C THE FEMALE GENITAL ORGANS. 



J. THE OVUM. 



The product of the ovaries is the matured " ovum," or egg, hav- 

 ing a diameter of from 0.22 to 0.32 mm.- It forms a single cell 

 with a thick membrane, from 7 // to 1 1 fi. in thickness, known as 

 the zona pellucida. The ovum consists of a cell-body known as 

 the yolk or vitellus, and a nucleus, from 30^ to 40 ft in diameter, 

 termed the germinal vesicle. The vitellus consists of two sub- 

 stances a protoplasmic network, with a somewhat denser arrange- 

 ment at the periphery of the cell and in the neighborhood of the 

 germinal vesicle, and of small, highly refractive, and mostly oval 

 bodies imbedded between the meshes of the protoplasm :the yolk 

 globules. These latter, as a rule, are merely browned on being 

 treated with osrnic acid, although occasionally a true fatty reaction 

 may be obtained. The germinal vesicle is surrounded by a distinct 

 membrane having a double contour. In its interior we find a 

 scanty lining framework containing very little chromatin, and one or 

 two relatively large false nucleoli, or germinal spots, from /// to io// 

 in diameter, due to a nodal thickening of the chromatin. In the 

 latter a further very distinct differentiation is sometimes seen in the 

 shape of a small body (vacuole ?) of doubtful origin, which has 

 been called Schron's granule. The germinal vesicle and spot were 

 formerly known as " Purkinje's vesicle" and "Wagner's spot/' 

 respectively, from their discoverers. 



2. THE OVARY. 



The ovaries are almost entirely covered by peritoneum. The 

 mesothelial cells of the latter, however, undergo here a differentia- 

 tion, to form the germinal epithelium. At the hilum the peritoneal 

 covering is absent, and it is here that the connective-tissue elements 

 of the ovarian ligament penetrate into the organ to form its con- 

 nective-tissue framework, the so-called stroma of the ovary. At an 

 early period in the development of the ovaries, the germinal epithe- 

 lium begins a process of invagination into the stroma of the ovary, 

 so that at the periphery of the organ a zone is soon formed which 

 consists of both connective tissue and epithelial (mesothelial) ele- 

 ments. This zone is called the cortex, or parenchymatous zone. 

 That portion of the organ in the neighborhood of the hilum (aside 

 from the rudimentary structure known as the epoophoron) consists 

 of connective tissue containing numerous elastic fibers and unstriped 

 muscle-cells, and is known as the medullary substance, or vascular 

 zone. This connective tissue penetrates here and there into the cor- 

 tex, separates the epithelial elements of the latter from each other, 

 and is in direct continuation with a stratum immediately beneath the 

 germinal epithelium, called the tunica albuginea. This latter layer 

 of connective tissue is generally distinct in the adult ovary, although 



