REPRODUCTION 



discharge for each period averages some five ounces. It does 

 not usually coagulate, on account of the presence of alkaline 

 mucus. For five or six days preceding the flow, the uter- 

 ine mucous membrane gradually thickens, the glands be- 

 come longer and more tortuous, the connective tissue cells 

 multiply and the blood-vessels are greatly increased in- size. 

 This is apparently a preparation for the reception of the im- 

 pregnated ovum. A short time before the flow begins there 

 is hemorrhage into the subepithelial tissue, possibly by dia- 

 pedesis, possibly by rupture. In a day or so the super jacent 

 mucous membrane becomes disintegrated and is discharged 

 with the included parts of the glands. The underlying ves- 

 sels, being thus exposed, rupture and the sanguineous dis- 

 charge carries away the debris. 



For three or four days subsequent to the cessation of the 

 flow the uterine mucosa is being repaired. The deeper lay- 

 ers, including the deeper portions of the glands, were not 

 cast off, and the whole is reconstructed from the intact parts. 

 Following the reconstructive period there is a stage of qui- 

 escence lasting some two weeks, until six or seven days prior 

 to the next menstruation. 



At the beginning of each menstrual flow there is general 

 congestion of the pelvic viscera and mammary glands, ac- 

 companied usually by headache and a sense of pelvic oppres- 

 sion. The congestion and discomfort begin to disappear 

 when the flow is established. 



Ovulation probably in most cases takes place just before 

 the menstrual flow begins, but neither occurrence is depen- 

 dent upon the other. Ovulation has frequently been shown 

 to take place in the inter-menstrual period, but the conges- 

 tion of the reproductive organs incident to menstruation 

 probably hastens the rupture of any -Graafian follicle which 

 at that time happens to be near the completion of its devel- 

 opment. 



The relations between ovulation, menstruation and im- 

 pregnation are not definitely determined. Pregnancy lasts 



