66 INTERNAL SECRETIONS OF THE OVARY 



refers to enlargement of the nipples concurrent with menstrua- 

 tion. In the human, mammary hypertrophy during the im- 

 mediate premenstrual phase is well known and has been 

 considered in detail by Dieckmann (159). 



The interpretation of the Primate cycle. Much controversy still 

 exists as to the precise significance of the menstrual cycle in 

 Primates. There can be little doubt that it is strictly compar- 

 able with the cycle in lower mammals, though the changes are 

 greatly exaggerated at the uterine haemorrhage stage. Apart 

 from hypotheses which maintain that no correspondence exists 

 between the menstrual cycle and the cycle in lower mammals, 

 three different theories have been maintained at one time or 

 other: 



(a) Most clinicians and embryologists have supposed that the 

 premenstrual growth of the uterine endometrium is 

 designed to facilitate the implantation of the embryo, 

 and is thus a postoestrous phase, corresponding to the 

 luteal or pseudo-pregnant phase of lower mammals. 

 Menstruation on this view is supposed to represent 

 solely the destruction of the prepared endometrium 

 when the fertilized ovum has failed to materialize : in 

 other words, to represent the abortion of an unwanted 

 decidua. There is much evidence in favour of this view. 

 Premenstrual congestion begins after ovulation, and 

 the breakdown of the endometrium coincides with 

 retrogressive changes in the corpora lutea. Degene- 

 ration of pseudo-pregnant congestion, sometimes ac- 

 companied by haemorrhage, has been described in the 

 rabbit by Hammond (264) and Ancel and Bouin (31), 

 in the dog by Gerlinger (241), in the sow by Corner 

 (122), and also occurs in the mouse. 



Further evidence in support of this view is that 

 X-ray sterilization stops the menstrual cycle in the 

 human, whereas in lower mammals such treatment 

 causes the disappearance of the luteal phase, but not of 

 the follicular phase (see p. 177). Seitz and Wintz (557) 

 even state that X-irradiation during the first half of the 

 inter-menstrual period (i.e. early enough to stop the 

 formation of the corpus luteum) leads to immediate 



