REPRODUCTIVE ORGANS IN THE FEMALE. 325 



Enlargement of the thyroid gland usually accom- 

 panies the menstrual flow. 



From five to ten days before the menstrual flow 

 begins there is a marked hyperemic condition of the 



C 



Fig. 234. Uterus during menstruation, cut open to show the swelling 

 of the whole organ, and particularly the mucous membrane: A, Mucous 

 membrane of cervix; B, C, mucous membrane of corpus, much thickened; 

 D, muscular layer; E, uterine opening of tube; F, os internum (the mu- 

 cous membrane tapers down to these openings) (Courty). 



uterine wall. The congestion of blood causes a 

 marked swelling and growth of the uterine mucosa, 

 so that it attains a thickness of 6.0 mm. This mu- 

 cosa is then called the decidua menstrualis. After 

 these changes have occurred the menstrual flow be- 



