688 



THE REPRODUCTIVE ORGANS 



vesicles being found ruptured in the intervals of heat; and females do not ad- 

 mit the males, and never become impregnated, except at those periods. Al- 

 though conception is not confined to the periods of menstruation, yet it is 

 more likely to occur about a menstrual epoch than at other times. 



The exact relation between the discharge of ova and menstruation is not 

 very clear. It was formerly believed that menstruation was the result of 

 a congestion of the uterus arising in association with the enlargement and 

 rupture of a Graafian follicle; but though a Graafian follicle is, as a rule, 

 ruptured at each menstrual epoch, yet instances are recorded in which men- 

 struation has occurred where no Graafian follicle can have been ruptured, and 



FIG. 496. 



FIG. 497- 



FIG. 498. 



FIG. 496. Diagram of Uterus just Before Menstruation. The shaded portion represents the 

 thickened mucous membrane. 



FIG. 497. Diagram of Uterus when Menstruation has just Ceased, Showing the Cavity of the 

 Uterus Deprived of Mucous Membrane. 



FIG. 498. Diagram of Uterus a Week After the Menstrual Flux has Ceased. The shaded por- 

 tion represents renewed mucous membrane. (J. Williams.) 



cases where ova have been discharged in amenorrheic women. It must 

 therefore be admitted that menstruation is not dependent on the matura- 

 tion and discharge of ova. 



Observations made after death, and facts obtained by clinical investiga- 

 tion, support the view that rupture of a Graafian follicle does not happen on 

 the same day of the monthly period in all women. In the minority of cases 

 it may occur toward the close or soon after the cessation of a flow. On the 

 other hand, in almost all subjects examined after death, of which there is 

 record, rupture of the follicle appears to have taken place before the com- 

 mencement of the menstrual flow. 



