THE GENITAL GLANDS AND DUCTS — OVARY 217 



granulosum formed by the original follicle cells there is differentiated from the 

 strorna of the ovary the theca Jolliculi. This is composed of an inner vascular 

 tunicd interna and of an outer fibrous tunica externa. 



Fully formed Graafian follicles are found in the ovaries during the second 

 year and they may even be present before birth. Ovulation may occur at this 

 time, but usually these precociously formed follicles degenerate with their con- 

 tained ova. Thus, although thousands of ova are produced in the ovary, only a 

 comparatively few are set free ready for fertilization during the sexually active 

 life of the female, from puberty to the climacteric period or menopause. The 

 relation of ovulation to menstruation has been discussed on p. 87. 



The Corpus Luteum. — After ovulation, a blood clot, the corpus hemorrhagicum, forms 

 within the empty follicle. The follicle cells of the stratum granulosum proliferate, enlarge, and 

 produce a yellow pigment (R. Meyer, Arch. Gynakol., Bd. 91, 1911). The whole structure, 

 composed of lutein cells and connective tissue strands, is termed the carpus luteum or yellow 

 body. The blood clot is resorbed and replaced by fibrous scar tissue white in color and 

 known as the corpus albicans. If pregnancy does not intervene the corpus luteum spurium 

 reaches its greatest development within two weeks and then degenerates. In cases of preg- 

 nancy the corpus luteum verum continues its growth until, at the thirteenth week, it reaches 

 a maximal diameter of 15 to 30 mm. At birth it is still a prominent structure in the ovary 

 and it is believed to produce an internal secretion, for if the corpus luteum is removed the 

 ovum fails to attach itself to the wall of the uterus, or if alteady embedded, development 

 ceases (Fraenkel). An influence in retarding ovulation and stimulating the mammary gland 

 function has also been shown experimentally (L. Loeb; O'Donoghue). 



The Rete Ovarii. — The cells of the rete ovarii remain compact, distinct, and 

 continuous only with the stroma of the medulla, the medullary cords. The anlage 

 is differentiated into a network of solid cords in 60 mm. (C H) fetuses and these 

 connect with the collecting tubules of the mesonephros. Some time before birth 

 lumina appear in the cords, transforming them temporarily into tubules homol- 

 ogous with those of the rete testis. 



Comparison of the Testis and Ovary. — It is clear that the superficial epi- 

 thehum after forming the inner epithelial mass takes no further part in the dif- 

 ferentiation of the testis and only a small part, if any, in that of the ovary. The 

 testis cords, rete testis, and tunica albuginea are formed early from the inner 

 epithelial mass, which determines their form. The inner epithelial mass of the 

 ovary develops slowly and its passive cells are separated and surrounded by 

 actively ingrowing connective tissue. The primordial follicles when developed 

 are not the homologues of the testis cords, and the tunica albuginea appears late. 

 The ,rete ovarii is the homologue of the rete testis, but remains a rudimentary 

 structure. 



