REPRODUCTION 



513 



majora, extend downwards and backwards on each side of a median 

 cleft, beyond which they again unite. On separating the labia 

 majora a shallow genito-urinary sinus, into which the urethra and 

 vagina open, is exposed. At the upper portion of this sinus lies the 

 clitoris, a small and very sensitive erectile organ, resembling a 

 miniature penis in structure, except that it has no corpus spon- 

 giosum and is not traversed by the uretha. From the clitoris de- 

 scend two folds of mucous membrane, the nymphce or labia interna, 

 between which is the vestibule, a recess containing above, the open- 

 ing of the short female urethra, and, below, the aperture of the 

 vagina, which is in the virgin more or less closed by a thin dupli- 

 cature of mucous membrane, the hymen. 



FIG. 153. A section of a Mammalian ovary, considerably magnified. 1, outer 

 capsule of ovary; 2, 3, 3', stroma; 4, blood-vessels; 5, rudimentary Graafian fol- 

 licles; 6, 7, 8, follicles beginning to enlarge and mature, and receding from the sur- 

 face; 9, a nearly ripe follicle which is extending towards the surface preparatory to 

 discharging the ovum; a, membrana granulosa; 6, discus proligenis; c, ovum, with 

 d, germinal vesicle, and e, germinal spot. The general cavity of the follicle (in 

 which 9 is printed) is filled with lymph-like transudation liquid during life. 



Microscopic Structure of the Ovary. The main mass of the 

 ovary consists of a dense connective-tissue stroma, containing un- 

 striped muscle, blood-vessels, and nerves: it is covered externally 

 by a peculiar germinal epithelium, and contains embedded in it 

 many minute cavities, the Graafian follicles, in which ova lie. If a 

 thin section of an ovary be examined with the microscope many 

 hundreds of small Graafian follicles, each about 0.25 mm. (y^j- 

 inch) in diameter, will be found embedded in it near the surface. 



