730 



GENERATION AND DEVELOPMENT. 



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 

 during the first half of pregnancy, till the cavity is reduced 

 to a comparatively small size, or is obliterated; in the 

 latter case, merely a white stelliform cicatrix remains in 

 the centre of the corpus luteum. 



Fig. 204.* 



An effusion of blood generally takes place into the cavity 

 of the G-raafian vesicle at the time of its rupture, especially 

 in the liuman subject ; but it has no share in forming the 

 yellow body ; it gradually loses its colouring matter, and 

 acquires the character of a mass of fibrin. The serum of 

 the blood sometimes remains included within a cavity in 

 the centre of the coagulum, and then the decolorized fibrin 

 forms a membraniform sac, lining the corpus luteum. At 



* Fig. 204. Corpora lutea of different periods. B. Corpus luteum of 

 about the sixth week after impregnation, showing its plicated form at 

 that period. I. Substance of the ovary. 2. Substance of the corpus 

 luteum. 3. A greyish coagulum in its cavity. After Dr. Paterson. 

 A. Corpus luteum, two days after delivery. D. In the twelfth week 

 after delivery. After Dr. Montgomery. 



