INTERNAL SECRETION OF OVARY 261 



luteum menstruationis and the corpus luteum graviditatis. 

 The menstrual bleeding is only one of two alternative processes 

 which the uterus undergoes after the premenstrual changes 

 have set in; these premenstrual changes are followed by 

 pregnancy when an egg has been fertilized and has entered 

 into the uterus, or else they end by an expulsion of the hyper- 

 aemic mucosa if fertilization has not taken place. There is not,, 

 however, complete unanimity among the different authors in 

 regard to the dependence on the corpus luteum of the cyclic 

 uterine changes in man. This question we shall return to in the 

 next section. 



The statements of Marshall and Hainan (1917) on the corre- 

 lation existing between ovarian changes and those in the 

 uterus and in the mammary glands of non-pregnant dogs after 

 the period of heat, are of interest here. The authors kept under 

 observation bitches for about 30 to 40 days after the beginning 

 of bleeding from the vaginal opening. Histological examina- 

 tion of the ovaries revealed the persistence of corpora lutea, 

 which were in different stages of development. The uterus 

 and the mammary glands were found to undergo changes of a 

 similar kind to those which take place during pregnancy, but 

 not to reach the same degree of development. Retrogression 

 of these organs set in about 30 days after ovulation, but the 

 mammary gland remained for a longer period in a state of 

 activity. Marshall and Hainan conclude that in the case of 

 the non-pregnant dog after "heat," a series of changes homo- 

 logous with the changes occurring in the pseudo-pregnant 

 rabbit takes place ; in both cases the changes are correlated with 

 luteal development in the ovary. The persistence of corpora 

 lutea in the ovary of the non-pregnant dog, "which is possibly 

 greater in some individuals than in others, elucidates the not 

 uncommon phenomenon of bitches which had not been im- 

 pregnated secreting milk at or near the end of the pseudo- 

 pregnant period." An investigation on the correlation existing 

 between ovarian and uterine changes was made also by 

 Gerlinger (1923 b) in the laboratory of Bouin. There is no 

 doubt that the phenomena of heat are correlated with follicular 

 processes in the ovary. 



It is a question of a different order as to why after fertihzation 

 further changes take place in the uterine wall, and especially 

 in the mammary glands, which are a long distance off from the 



