CORPUS LUTEUM OF PREGNANCY. 581 



tinguished from that which simply follows the ordinary menstrual 

 process. It is proper, therefore, to speak of two kinds of corpora 

 lutea ; one belonging to menstruation, the other to pregnancy. 



The difference between these two kinds of corpora lutea is not 

 an essential or fundamental difference ; since they both originate in 

 the same way, and are composed of the same structures. It is, 

 properly speaking, only a difference in the degree and rapidity of 

 their development. For while the corpus luteum of menstruation 

 passes rapidly through its different stages, and is very soon reduced 

 to a condition of atrophy, that of pregnancy continues its develop- 

 ment for a long time, attains a larger size and firmer organization, 

 and disappears finally only at a much later period. 



This variation in the development and history of the corpus 

 luteum depends upon the unusually active condition of the pregnant 

 uterus. This organ exerts a powerful sympathetic action, during 

 pregnancy, upon many other parts of the system. The stomach 

 becomes irritable, the appetite is capricious, and even the mental 

 faculties and the moral disposition are frequently more or less 

 affected. The ovaries, however, feel the disturbing influence of 

 gestation more certainly and decidedly than the other organs, since 

 they are more closely connected with the uterus in the ordinary 

 performance of their function. The moment that pregnancy takes 

 place, the process of menstruation is arrested. No more eggs come 

 to maturity, and no more Graafian follicles are ruptured, during the 

 whole period of gestation. It is not at all singular, therefore, that 

 the growth of the corpus luteum should also be modified, by an 

 influence which affects so profoundly the system at large, as well 

 as the ovaries in particular. 



During the first three weeks of its formation, the growth of the 

 corpus luteum is the same in the impregnated as in the unimpreg- 

 nated condition. After that time, however, a difference becomes 

 manifest. Instead of commencing a retrograde course during the 

 fourth week, the corpus luteum of pregnancy continues its deve- 

 lopment. The external wall grows thicker, and its convolutions 

 more abundant. Its color alters in the same way as previously 

 described, and becomes a bright yellow by the deposit of fatty 

 matter in microscopic globules and granules. 



By the end of the second month, the whole corpus luteum has 

 increased in size to such an extent as to measure seven-eighths of 

 an inch in length by half an inch in depth. (Fig. 191.) The central 

 coagulum has by this time become almost entirely decolorized, so as 



