THE GENERATIVE ORGANS. 203 



of the cells which remain after the rupture of the 

 follicle. These differences cannot be considered 

 here. The process of formation and disappearance 

 of the corpus luteum, under all circumstances, is 

 essentially the following : The blood which is poured 

 out into the cavity passes through the same retro- 

 gressive metamorphosis which extravasated blood 

 in any part of the body may undergo : it coagulates, 

 the serum is absorbed, the red cells disintegrate, and 

 the coloring matter is in part taken up by surround- 

 ing tissues, in part transformed into yellowish or red 

 hematoidin (bilirubin) crystals, which in turn may 

 change into a dark brown or black pigment, and be 

 taken up by surrounding tissues, or remain for a long 

 time unchanged. Hand in hand with these changes 

 in the extravasated blood, go important changes in 

 the follicular epithelium which is left behind, and in 

 the cells of the theca folliculi. These cells prolifer- 

 ate and form a soft, yellowish, very vascular tissue, 

 resembling mucous tissue, which presently under- 

 goes fatty degeneration. This yellow mass, sur- 

 rounding and enclosing the remains of the extrava- 

 sated blood, constitutes the corpus luteum ; and, as 

 it disappears, its place is occupied by firm, dense 

 connective tissue, which usually persists for a long 

 time in the form of an irregular cicatrix, whose cells 

 not infrequently still contain yellow or brown or 

 black pigment. 



In order to understand all the forms which the 



