182 



EMBRYOLOGY. 



blood may undergo in any part of the body. The serum is absorbed, 

 the cells disintegrate, and the coloring matter is in part taken up 

 by the tissues and in part crystallizes or takes up other constitu- 

 ents, and presents variations of coloring. Hand in hand with these 

 changes in the blood go important changes in the surrounding 

 tissues. The epithelial cells which are left behind proliferate and 

 form a soft yellowish, very vascular tissue, which presently under- 

 goes fatty degeneration. This yellow mass surrounding and en- 

 closing the remains of the extravasated blood constitutes the corpus 

 luteum, and as it disappears its place is occupied by a dense, firm 

 connective-tissue cicatrix, which may be pigmented. 



How does the corpus luteum behave during pregnancy? 



It then does not degenerate and disappear rapidly as after men- 

 struation, but continues fully as large for several months, and at 

 the end of pregnancy still remains as a clearly marked body. This 

 is shown in the following table from Dalton : 



Corpus Luteum of Menstrua- 

 tion. 



Corpus Luteum of Pregnancy 

 (Dalton). 



f in. in diameter; central clot reddish; convoluted wall 



Larger ; convoluted wall 

 bright yellow ; clot still 

 reddish. 



| in. in diameter ; convo- 

 luted wall bright yellow ; 

 clot perfectly decolorized. 



Size about as at two months ; 

 clot pale and fibrinous ; 

 convoluted wall dull yel- 

 low. 



Still as large as at the end 

 of the second month. Clot 

 fibrinous. Convoluted wall 

 paler. 



| in. in diameter ; central 

 clot converted into a radi- 

 ating cicatrix ; external 

 wall tolerably thick and 

 convoluted, but without 

 any bright yellow color. 



At what time is the ovum liable to impregnation? 



Probably most so immediately before the menstrual period, but 



At the end of 

 three weeks. 

 One month. 



Two months. 

 Four months. 



Six months. 

 Nine months. 



Smaller ; convoluted wall 

 bright yellow ; clot still 

 reddish. 



Reduced to the condition of 

 an insignificant cicatrix. 



Absent or unnoticeable. 



Absent. 



Absent. 



