774 EMBRYOLOGY 



ably from the membrana granulosa, with a projection of looped blood- 

 vessels into the interior of the follicle. This is the first formation of the 

 corpus luteum. At the time of rupture of the follicle, the ovum, with a 

 great part of the membrana granulosa, is discharged. Usually, at the 

 time of rupture of the follicle, there is a discharge of blood into its inte- 

 rior; but this is not invariable, although there is always a gelatinous 

 exudation more or less colored with blood. At the same time the fol- 

 licular wall undergoes hypertrophy, and it becomes convoluted or folded, 

 and highly vascular. This convoluted wall, formed by the proper coat of 

 the follicle, is surrounded with the fibrous tunic, and its thickening is 

 most marked at the deepest portion of the follicle. At the end of about 

 three weeks, the body which is now called the corpus luteum, on ac- 

 count of its yellowish or reddish yellow color has arrived at its maxi- 

 mum of development and measures about half an inch (12.7 millimeters) 

 in depth, by about three-quarters of an inch (19.1 millimeters) in length, 

 its form being ovoid. The convoluted wall then contains a layer of large, 

 pale, finely-granular cells, which are internal and are supposed to be the 

 remains of the epithelium of the follicle. The great mass of this wall, 

 however, is composed of large nucleated cells (leutein cells), contain- 

 ing fatty globules and granules of reddish or yellowish pigmentary matter. 

 The thickness of the wall is about one-eighth of an inch (3.2 millimeters) 

 at its deepest portion. 



After about the third week the corpus luteum begins to contract ; its 

 central portion and the convoluted wall become paler ; and at the end of 

 seven or eight weeks, a small cicatrix marks the point of rupture of the 

 follicle. 



The above are the changes which occur in the Graafian follicles after 

 their rupture and the discharge of ova, when the ova have not been 

 fertilized; and the bodies thus produced are called false corpora 

 lutea, as distinguished from corpora lutea formed after conception, 

 which latter are called true corpora lutea. 



Corpus Luteum of Pregnancy. When a discharged ovum has been 

 fertilized, the corpus luteum passes through its various stages of devel- 

 opment and retrogression more slowly than the ordinary corpus luteum 

 of menstruation. The retrogression begins toward the end of the third 

 month. " During the fourth month, the corpus luteum diminishes by 

 nearly a third, and toward the end of the fifth, it ordinarily is reduced 

 one-half. It still forms, however, during the first days after parturition, 

 and in the greatest number of cases, a tubercle which has a diameter of 

 not less than f to \ of an inch (7.3 to 8.5 millimeters). The tubercle 

 afterward diminishes quite rapidly ; but it is nearly a month before it is 

 reduced to the condition of a little, hardened nucleus, which persists 



