358 REPRODUCTION 



The hormone responsible seems to be produced either 

 in the epitheUal or in the interstitial cells. There is some 

 positive evidence that it is independent of the corpus 

 luteum. 



Function of the Corpus Luteum 



The corpus luteum is beUeved to furnish a hormone 

 which is responsible for the changes in the uterine wall 

 which occur during the early stages of pregnancy and 

 which are necessary for the proper nutrition and fixation 

 of the embryo. When the ovaries are removed early in 

 pregnancy abortion occurs, but when the operation is 

 performed at a later period there is no interruption of the 

 normal course of events. 



In pseudo-pregnancy the uterus undergoes very pro- 

 nounced hypertrophy, congestion and great glandular 

 development under the influence of the corpus luteum in 

 just the same way as happens during true pregnancy. 

 Moreover, after a mechanical stimulus (introduction of a 

 foreign body or incision of the wall), decidua cells are 

 formed, but only if corpora lutea ate present in the ovary. 



The corpus luteum is also considered responsible for a 

 hormone which initiates the hypertrophy of the mam- 

 mary gland. This is discussed more fully later. 



Correlation of the Ovarian and Uterine Cycles 



There is no certain cUnical evidence to show whether 

 in women the process of ovulation precedes, succeeds or 

 is coincident with menstruation. But the identification 

 of menstruation with the period of pro-oestrum, and the 

 known synchronisation of the subsequent period of oestrus 

 in lower animals with the ripening of the folhcle, are strong 

 arguments in favour of menstruation preceding ovulation. 

 On this view the purpose of menstruation is a kind of 

 freshening up of the uterine mucosa preparatory to the 

 reception of the fertihsed ovum. In some animals rupture 

 of the ripened folhcle occurs only as a reflex effect of 



