334 REPRODUCTION 



intervals of about four weeks. It should, and usually does, enter 

 the outer end of the Fallopian tube, to be conveyed toward the 

 uterus. Obviously only a few, and sometimes none, are ever 

 impregnated. Should the ovum fail to reach the uterus and 

 become fecundated, ectopic gestation will be the result. 



The patent nmbriated extremity of the tube may grasp the 

 ovary at the time of rupture of the Graafian follicle, but this is 

 not probable. " One of the tubal fimbriae is attached to the outer 

 extremity of the ovary and has on its surface a small linear de- 

 pression lined by ciliated epithelium and leading to the tube. 

 The ovum very likely in most cases drops into this depression, 

 and the influence of the cilia is to carry it toward the tube. 



Menstruation. Usually between the fourteenth and seven- 

 teenth years of female life menstruation begins. It is a discharge 

 of blood, epithelium and other parts of the mucous membrane of 

 the uterine cavity, together with mucus from the glands of the 

 uterus and vagina. About the beginning of menstrual life there 

 are marked changes in bodily development, Graafian follicles 

 enlarge and begin to approach the surface, ovulation is begun, 

 and the female is capable of being impregnated. 



In most cases menstruation occurs at regular intervals of 

 twenty-eight days. The function is suspended during pregnancy 

 and usually during lactation. When it is first established it is 

 frequently irregular in its occurrence for several months; a like 

 irregularity usually accompanies the cessation of the function 

 between the fortieth and fiftieth years when the menopause, or 

 climacteric, is established. The normal female may be impreg- 

 nated during menstrual life, but not before or after. 



The average length of time for which the menstrual flow con- 

 tinues is four days. There are many exceptions in both direc- 

 tions for different women, but the time for any one woman prob- 

 ably varies little under normal conditions. The discharge for 

 each period averages some five ounces. It does not usually 

 coagulate, on account of the presence of alkaline mucus. For 



