THE MAMMALIAN SEXUAL CYCLE 



53 



the preceding period or from the cells of the glands. At this 

 stage the blood vessels become reduced in size and number. The 

 stage of repair is followed by a stage of apparent quiescence, 

 but it seems probable that in many individuals the uterus 

 commences to undergo growth changes which are continued in 

 the succeeding constructive stage. 



The constructive changes probably represent those of an 



Fig. 30. — Section through mucosa of human uterus, showing 

 extravasation of blood. (From Sellheim.) 



abbreviated pseudo-pregnancy, while the destruction which 

 follows may perhaps be 'the equivalent of pseudo-pregnant and 

 procestrous, degeneration telescoped into one period. Corner has 

 shown that in some individual monkeys in which ovulation has 

 not occurred and there is no corpus luteum in the ovaries, the 

 constructive processes do not take place. This is completely 

 in accordance with what is known of the lower mammals in 

 which pseudo-pregnant growth is invariably correlated with 

 the presence of the corpus luteum. The monkeys, however, 

 experience menstrual hyperaemia and destruction in spite of 

 there having been no previous constructive changes in the uterus. 



