THE INTERNAL ORGANS OF REPRODUCTION 427 



follicle occurs on an average nine days in advance of 

 the bleeding. 1 While the ovum is moving along the 

 tube the transformation of the membrana granulosa, 

 of the ruptured Graafian follicle, to the corpus luteum 

 is taking place. The tenth day before menstruation 

 is the surest time for impregnation. 



There are many theories on the above which are not 

 mentioned as they are beyond the scope of this book. 



Menstruation. This is a process characterized by a 

 discharge of blood from the vagina, which takes place 

 periodically, except during pregnancy and lactation, 

 when the mammary glands are secreting milk. It 

 occurs from the time of puberty to the menopause 

 (change of live). Ordinarily it comes on every four 

 weeks and lasts from three to five days. It varies 

 as to frequency and duration in different individuals. 



The age at which the menses (periodic sickness) 

 commences, varies in different countries, being earlier 

 in warm and later in cold climates. The average age 

 in a temperate climate is about the fourteenth to 

 fifteenth year. 



There have been several theories expressed in 

 regard to the changes taking place in the mucous 

 membrane of the uterus at the time of menstruation. 

 Some authorities claim that the entire mucous mem- 

 brane of the uterus is broken down and thrown off in 

 the menstrual flow. Again, others claim that there is 

 no destruction of tissue, and the menses results from 

 a thickening of the mucous membrane of the uterus 

 (womb), engorgement of its superficial bloodvessels, 

 followed by the escape of blood, due in part to the 

 rupturing of these vessels, and the passing of blood 

 through the walls of the arteries (diapedesis) . Follow- 

 ing the period of hemorrhage a certain amount of 

 degeneration of the cells takes place in the mucous 



1 The above facts as per Dr. Miller, Berliner klinische Wochen- 

 schrift, May 5, 1913; N. Y. Med. Journal. 



