THE REPRODUCTIVE ORGANS. 



761 



lobules projecting from the opposite walls of the Graafian follicle appear 

 in a section to be separated by the thinnest possible lamina of semi- 

 transparent tissue. 



When a follicle is about to burst and expel the ovum, it becomes 

 highly vascular and opaque ; and, immediately before the rupture takes 

 place, its walls appear thickened on the interior by a reddish glutinous 

 or fleshy-looking substance. Immediately after the rupture, the inner 

 layer of the wall of the vesicle appears pulpy and flocculent. It is 

 thrown into wrinkles by the contraction of the outer layer, and, soon, 

 red fleshy mammillary processes grow from it, and gradually enlarge till 

 they nearly fill the vesicle, and even protrude from the orifice in the 

 external covering of the ovary. Subsequently this orifice closes, but the 

 fleshy growth within still increases during the earlier period of preg- 

 nancy, the color of the substance gradually changing from red to yellow, 

 and its consistence becoming firmer. 



The human corpus luteum (fig. 457) differs from that of the domestic 

 quadruped in being of a firmer texture, and having more frequently a 



Fig. 457. Corpora lutea of different periods. B, corpus luteum of about the sixth week 

 after impregnation, showing its plicated form at that period. 1, substance of the ovary; 2, sub- 

 stance of the corpus luteum ; 3, a grayish coagulum in its cavity. (Paterson.) A, corpus lu- 

 teum two days after delivery ; D, in the twelfth week after delivery. (Montgomery. ) 



persistent cavity at its centre, and in the stelliform cicatrix, which re- 

 mains in the cases where the cavity is obliterated, being proportionately 

 of much larger bulk. The quantity of yellow substance formed is also 

 much less: and although the deposit increases after the vesicle has 

 burst, yet it does not usually form mammillary growths projecting into 

 the cavity of the vesicle, and never protrudes from the orifice, as is the 

 case in other Mammalia. It -maintains the character of a uniform, or 

 nearly uniform, layer, which is thrown into wrinkles, in consequence of 

 the contraction of the external tunic of the vesicle. After the orifice of 

 the vesicle has closed, the growth of the yellow substance continues dur- 

 ing the first half of pregnancy, till the cavity is reduced to a compara- 

 tively small size, or is obliterated ; in the latter case, merely a white 

 stelliform cicatrix remains in the centre of the corpus luteum. 



An effusion of blood generally takes place into the cavity of the fol- 



