THE HORMONES IN HUMAN REPRODUCTION 



trated in Plate XII, C, a photograph of one of the earliest 

 known human embryos, obtained by Dr. Arthur T. Hertig of 

 Boston, and preserved in Baltimore at the Department of 

 Embryology of the Carnegie Institution of Washington. The 

 uterus in which this 11 -day embryo has attached itself is in 

 the typical progestational phase, as shown by the form of 

 the glands. 



The menstrual breakdown. About the 14th or 15th day 

 after ovulation, the corpus luteum begins to degenerate, as in 

 other animals. The uterus, thus deprived of support by pro- 

 gesterone, undergoes a violent reaction. In its innermost layer 

 the circulation of blood is disturbed, the surface epithelial 

 cells, the glands and the connective tissue are damaged, and 

 the tissues break down. Blood from small ruptured vessels fills 

 the cavity of the uterus and trickles toward the vaginal canal. 

 A section of the endometrium at this time shows a remarkable 

 picture ; the surface layer has sloughed away, and the stumps 

 of the glands jut into the central mass of blood and cellular 

 debris. In the course of a few days a process of repair sets in, 

 the lost surface cells are replaced, the glands restored and the 

 debris cleared up. 



The various stages of the uterine cycle are shown in 

 Plates XXI and XXII, which present a series of specimens 

 from the Rhesus monkey. 



The sequence of these events is summarized in the diagram, 

 Fig. 22. From this it will be seen that ovulation takes place 

 about the middle of the interval between the two menstrual 

 periods. It is customary to count the days of the primate 



Plate XXI. Three stages of the cycle of the uterus of the Rhesus monkey. 



A, 16th day of cycle, just after ovulation; interval stage. B, 23d day of cycle. 

 Effect of corpus luteum hormone appears in the glands; early premenstrual 

 stage. C, 27th day of cycle. Menstruation due one day later. Full progestational 

 (premenstrual) stage. All magnified 10 times. A, Corner collection (no. 2)} 



B, courtesy of C. G. Hartman (H. 326); C, courtesy of G. W. Bartelmea 

 (B. 123). 



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