THE OVUM CORPORA LUTEA. 



567 



Frg. 393. 





formed ovum a well-marked vesicular nucleus, the germinal vesicle. 

 This is g ^ of an inch in diameter with clear contents; and a ho- 

 mogeneous round nucleolus (of ^^Vo f an inch) on its surface 

 the germinal spot. (Figs. 55 and 393.) 



The arteries of the ovary enter from 

 its inferior border, and terminate partly 

 in the stroma, and partly in the walls 

 of the ovisacs, where is an inner finer 

 plexus of capillaries extending to the 

 basement-membrane under the mem- 

 brana granulosa. A few lymphatics 

 come out from the hilus ovarii, and pro- 

 ceed to the lumbar and pelvic glands. 

 The nerves come from the spermatic 

 plexus, and enter the ovary with the 

 arteries. Their ultimate distribution is 

 not yet ascertained. 



The ovisacs are constantly becoming 

 matured, and then burst as above men- 

 tioned, from the commencement of pu- 

 berty till menstruation ceases ; this oc- 

 curring principally, but not exclusively, 

 at the menstrual period. As they ap- 

 proach the time of bursting, they ac- 

 quire a diameter of 4 to 6 lines, and at 



length project beyond the Surface Of 

 ,! T..T ,1 -n 



the ovary. Meantime the tunica albu- 

 ginea and the peritoneal coat become thinner, and at length give way ; 

 when the ovum, being situated at the point of rupture as before ex- 

 plained, escapes, surrounded by the germinal disk, and makes its way 

 into the uterus through the Fallopian tube. The empty ovisac is 

 now termed a corpus luteum. (Fig. 394.) Occurring in the ordinary 

 course of menstruation they are termed fa Ise corpora lutea; and true 

 corpora lutea, if in connection with impregnation of an ovum. 

 Fig. 395 represents three corpora lutea of pregnancy, at two days 

 and at twelve weeks after delivery and in the sixth week after 

 conception; but a particular description of them is out of place 

 here. The yellow plicated appearance in the interior is due to the 

 thickened condition of the fibrous membrane of the ovisac; and 



Mammalian ova. Upper figure an 

 immature, and the lower a mature 

 ovum. a. Zona pellucida. b. Yolk. c. 

 Germinal vesicle, d. Germinal spot, 

 a pellucida, 



b, and the germinal vesicle have escaped 

 through the opening. (Coste.) 



