THE FEMALE SEXUAL ORGANS 695 



2. THE FEMALE SEXUAL ORGANS 



A. THE OVARIES AND OVIDUCTS 



The primordial ova, which are destined ultimately to become the mature 

 ova capable of fertilization, are formed at a very early stage of intrauterine 

 life. In the further course of development they become surrounded by a 

 layer of germinal epithelial cells, the whole group being then known as the 

 primary follicle. 



From this primary follicle what is known as a Graafian follicle is devel- 

 oped in the following manner: The epithelium which surrounds the ovum 

 begins to proliferate and becomes many-layered. Then in the space between 

 these layers a fluid gradually collects, partly by transudation from the sur- 

 rounding blood vessels and partly by disintegration of epithelial cells. In the 

 human ovary this liquor follicularis is found only in that part of the follicle 

 presenting toward the surface of the ovary. On the medial side of the follicle 

 the epithelium forms a mass of cells surrounding the ovum and projecting 

 into the follicular cavity as the discus proligerus. The follicle is also sur- 

 rounded by a connective tissue envelope known as the theca folliculi. 



At the same time the ovum, its nucleus (germinal vesicle) and nucleolus 

 (germinal spot) grow in size and the ovum becomes surrounded by a mem- 

 brane, the zona pellucida, secreted by the follicular epithelium. The mem- 

 brane, however, is separated from the ovum by a small space. 



In the further development of the ovum, the protoplasm from the center 

 outward becomes transformed into yolk spherules, until finally there remains 

 of the true protoplasm only a thin layer situated peripherally, and containing 

 the nucleus. 



Development of the primary follicle into the Graafian follicle takes place 

 before sexual maturity, in fact before the birth of the young female. But 

 the ova are not yet capable of being fertilized and will not be before the 

 beginning of sexual maturity i. e., about the fourteenth year. By this time 

 the ova are about twice as large as when the Graafian follicle was formed, 

 measuring now about 0.2 mm. in diameter, and have extruded from them- 

 selves half the chromatin (staining substance) of their nuclei. 



When the follicle has reached a certain size, an internal proliferation in 

 the inner layer of the theca folliculi takes place which finally leads to its 

 rupture and to the consequent liberation of the ovum. The processes con- 

 cerned in this, according to Nagel's description, shape themselves on this 

 wise: 



The vessels of the theca become strongly developed, and the cells about 

 them multiply enormously. At the same time the protoplasm of the cells 

 becomes filled with a material (lutein) which gives the whole inner wall of the 

 follicle a yellow cast. The lutein cells become bulged out in the form of a 

 papilla on the inner layer of the theca and this bulging continues, crowding 

 the follicular contents more and more toward the thinnest part of the follicular 

 wall turned toward the surface of the ovary, until finally the follicle bursts. 

 Hand in hand with this proliferation of the lutein cells there goes a fatty 

 degeneration of the follicular epithelium, by which the ovum with its epi- 



