REP ROD UL'TION. 



455 



ovary to be taken up by the Fallopian tube. The empty follicle undergoes 

 changes and becomes the corpus luteum (cl). Usually the corpus luteum de- 

 generates within a few days and ultimately disappears. If, however, pregnancy 

 follows ovulation, it grows very large, perhaps because of the congested state 

 of the reproductive organs, and remains for months before the retrograde 

 metamorphosis sets in. Not all Graafian follicles reach maturity and burst, 

 for many, after developing to a considerable size, undergo degenerative 

 changes, characterized by liquefaction and disappearance of their contents. 



The discharge of the ovum is known technically as ovulation. In most 

 animals ovulation is a periodic phenomenon accompanying certain seasons, and 

 is marked by general sexual activity. In woman and many domesticated ani- 

 mals the relation to the seasons no longer exists, but too little is known of the 

 causes and time-relations of the phenomenon and its general bearings upon 

 other physiological processes, notably upon menstruation in woman. A large 



Fig. 222.— Diagram of the female reproductive organs (modified from Henle and Symington) : o, ovary ; 

 G./, Graafian follicle containing an ovum; cl, corpus luteum; p, parovarium ; /, fimbriated end of F. t, 

 Fallopian tube ; u, body, and c, cervix of uterus ; o.e, os uteri externum ; vg, vagina ; h, hymen ; u, open- 

 ing of urethra; v, vulval cleft; n, labia minora, or nymphiu; /•»(, labia majora. 



but not wholly decisive literature upon the subject in the human being has 

 been written. It is a common belief, originating in the seventeenth century, 

 that ovulation in woman is a periodic phenomenon occurring regularly every 

 month and contemporaneous with the occurrence of the menstrual flow, and 

 numerous post-mortem observations of the presence in the ovary of freshly- 

 discharged Graafian follicles at the menstrual period afford evidence of the 

 frequent coincidence of the two phenomena. But ovulation at the time of 

 menstruation, though probably usual, is not exclusive of ovulation at other 



