THE RHYTHM OF GONADAL FUNCTION 577 



II. Rhythmic Gonadal Function in the Adult Female 



Introductory 



Ovulation. The Associated Ovarian Histological Events. The 

 assumption of sexual maturity is associated in the ovary with two 1 histo- 

 logical events which are new to that organ ovulation and the formation 

 of corpora lutea. We are still entirely in the dark as to the causes which 

 determine this new behavior on the part of certain of the follicles, for 

 instead of undergoing atresia, as in prepubertal' life, -they continue to 

 grow, turning into the well-known Graafian follicles, in which the egg after 

 undergoing its first maturation division becomes free in a follicular fluid 

 and is expelled from the ovary by follicular rupture. Nor are these 

 processes clearer to us by the statement that the egg dominates the situation 

 (R. Meyer, Schroeder), for we still have to recognize the sudden assump- 

 tion of vitality on the part of the egg or the removal of some toxic influence 

 which makes it no longer necessary for them to die in the earlier stages 

 of their existence and growth. The literature is filled with similarly 

 indecisive explanations for the act of ovulation itself. Hyperemia of the 

 ovary, the increase of hydrostatic pressure within the follicle and the 

 final tearing of the overlying ovarian tissue (the albuginea and a slight 

 amount of cortical substance) would all appear to be facts. The tear 

 probably occurs merely through the sudden accentuation of changes already 

 well advanced, thereby preventing an adaptive response which so often 

 walls off securely, even if thinly, much larger cysts. 



Several anatomical criteria for impending ovulation have been made 

 out characteristics of the structure of follicles the rupture of which is 

 imminent. These are an increased vascularity of the theca interna, an 

 hypertrophy and appearance of minute globules of fat in the cells of the 

 theca interna and a peculiar activity of these cells is tending to invade 

 the follicle by pushing the basement membrane and granulosa ahead of 

 them so as to cause indippings of the follicular wall, even in spite of the 

 pressure which may be present with distention of the follicular antrum. 

 Finally, the first maturation division and the formation of the first polar 

 body takes place "before follicular rupture occurs. When follicular dis- 

 tention is relieved by bursting and the consequent escape of the egg with a 

 small complement of granulosa cells, a collapse and folding of the follicular 

 wall takes place and, more important 'than this, a change in the structure 

 of the wall, for both thecal envelopes (interna and externa) begin to 

 mingle their structural elements with the granulosa, the boundary separat- 

 ing them previously (the Glashaut or basement membrane) being rapidly 

 obliterated at many points. The hypertrophied internal theca cells are 



