MENSTRUATION 335 



lar intervals of about four weeks. It should, and usually 

 does, enter the outer end of the Fallopian tube, to be con- 

 veyed toward the uterus. Obviously only a few, and some- 

 times none, are ever impregnated. Should the ovum fail to 

 reach the uterus and become fecundated, ectopic gestation 

 will be the result. 



The patent fimbriated 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 depression lined by ciliated epithelium and lead- 

 ing 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 sev- 

 enteenth years of female life menstruation begins. It is a 

 discharge of blood, epithelium and other parts of the mu- 

 cous membrane of the uterine cavity, together with mucus 

 from the glands of the uterus and vagina. About the be- 

 ginning 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 preg- 

 nancy and usually during lactation. When it is first estab- 

 lished 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 impregnated during menstrual life, but not 

 before or after. 



The average length of time for which the menstrual flow 

 continues is four days. There are many exceptions in both 

 directions for different women, but the time for any one 

 woman probably varies little under normal conditions. The 



