MENSTR UA TION. 649 



Manton, in Jewett's Practice of Obstetrics, says : " Although 

 menstruation and ovulation should not be considered as necessarily 

 coincident processes, it is altogether probable that the conditions 

 which influence the one have also an effect upon the other, and that, 

 as a rule, the two functions occur simultaneously and are, to a 

 greater or less extent, interdependent." 



Williams concludes, from all the available evidence, " that the 

 two processes usually occur about the same time, but that one not 

 infrequently antedates the other by a few days ; while in exceptional 

 cases they may occur quite independently." 



In discussing the relation between menstruation and ovulation, 

 Edgar says that " they occur about the same time, although ovulation 

 often follows menstruation and may occur between the menses ; 

 that the ovarian changes which precede ovulation by producing 

 ovarian tension, reflexly excite the uterus and cause menstruation ; 

 that both processes are under some nervous control, yet either may 

 occur independently." 



It would appear, then, that the relation existing between ovula- 

 tion and menstruation is not definitely determined, but that they 

 are intimately associated cannot be questioned, for the removal of 

 the ovaries, as a rule, is followed by a discontinuance of men- 

 struation. 



As to the relation between a particular menstrual period and 

 the process of ovulation, Marshall says, that the decidua of a 

 particular menstrual period is related not to the ovum discharged 

 at that period, but to the ovum discharged at the preceding period, 

 and which takes, probably, a week in its passage from the ovary 

 to the uterus. 



Formation of Corpus Luteum. After an ovum has been dis- 

 charged from a Graafian follicle certain changes take place 

 in the latter structure which result in the formation of a corpus 

 luteum. The cavity of the follicle is filled with blood from the 

 lacerated blood-vessels of the walls of the follicle, and this under- 

 goes coagulation, the serum being expressed and absorbed, and the 

 clot, at first red, later becomes decolorized. Into this penetrates the 

 tunica interna of the theca folliculi, which undergoes proliferation. 

 In this proliferated tissue are lutein cells containing lutein, which 

 gives the characteristic yellow color from which the corpus luteum 

 derives its name, and fibrous connective tissue with blood-vessels 

 whose capillaries penetrate between the lutein cells. The inner wall 

 of the corpus luteum becomes folded in or convoluted, and the cen- 

 tral portion of this body undergoes degeneration and is absorbed. 

 Afterward the corpus luteum undergoes hyaloid degeneration, 

 and the corpus albicans results, so called because of the white 

 color which replaces the yellow. This is ultimately absorbed, and 

 there remains but a small amount of connective tissue. 



While a corpus luteum which occurs during menstruation exists 



