696 REPRODUCTION AND GROWTH 



thelium is released from the discus proligerus. The contents of the follicle 

 are replaced in part at least by a blood clot: we then have instead of the 

 Graafian follicle a corpus luteum. 



Thus the ovum comes into the abdominal cavity and is ready to enter the 

 Fallopian tube to be passed on into the uterus. The abdominal opening of 

 the tube spreads out in the form of a funnel surrounded by fringelike proc- 

 esses known as fimbrice, one of which, the fimbria ovarica, comes quite close 

 up to the ovary. Along this fimbria, extending from the ovary to the tube, 

 runs a groove, which, like the fimbriae themselves and. the mucous membrane 

 lining the tubes, is clothed by a ciliated epithelium. These cilia beat in the 

 direction of the tube, creating a current in the surrounding capillary spaces 

 between the viscera, which probably plays a predominant part in guiding the 

 ovum. The production of this current is materially aided by the peculiar 

 position of the tube, its relation to the ovary being such as to form about 

 the latter a sort of pocket, closed off from the abdominal cavity. 



Once in the Fallopian tube the ovum is carried along to the uterus by the 

 movements of the cilia. In this journey, which requires about three days, the 

 remains of the follicular epithelium adherent to the ovum when it is set 

 free, become stripped off, leaving the ovum naked. 



It is probable that many of the ova set free from the ovary never reach the 

 Fallopian tubes, but are lost in the abdominal cavity. 



Opinions differ very much as to the time of ovulation (liberation of the 

 ovum from the ovary), and a definite decision between them cannot be given 

 at this time. Some authors suppose that it takes place only in connection with 

 menstruation (before or after), others that it can occur at any time in connec- 

 tion with copulation. 



B. THE UTERUS 



The uterus is a hollow organ which serves the purpose of harboring the 

 ovum during its development into the mature foetus and of supplying the 

 necessary nourishment for this development. The wall of the uterus con- 

 sists externally of numerous smooth muscle fibers interlaced together, and 

 internally of a mucous membrane lined with a ciliated epithelium, imagina- 

 tions of which toward the muscle layer constitute the mucous glands. The 

 cilia of the epithelium beat from above downward i. e., from the fundus 

 toward the mouth of the uterus. 



The uterus differs radically from all other organs of the body in that its 

 tissues undergo profound alterations under perfectly normal circumstances. 

 Some of these alterations are related to menstruation, some of them to 

 pregnancy. 



By menstruation is meant a periodic discharge of blood from the uterus 

 of the sexually mature female, which occurs about every twenty-eight days 

 and continues on the average about four days. It begins at about the four- 

 teenth year of age and constitutes the external sign of sexual maturity. The 

 quantity of blood discharged at each period has been estimated at from 

 100-200 cc., but the amount is subject to great variations. At the age of 

 forty-five to fifty years menstruation gradually ceases, and with it the ability 

 to bear young is permanently lost. This age is designated as the climacteric. 



