646 REPRODUCTIVE ORGANS. 



the body of the uterus during menstruation are not agreed upon 

 by authorities. 



Webster says that "the latest evidence points clearly to the 

 view that there is but a slight denudation, irregular in distribution 

 in the superficial layers of the mucosa." 



The complete menstrual cycle is, according to Marshall, as 

 quoted by the American Text-book of Obstetrics, divisible into 

 four stages : (1) The first or constructive stage is one of prepara- 

 tion for the reception of an ovum, and is characterized by the 

 formation of a menstrual decidua, in the preparation of which 

 swelling of the mucous membrane, enlargement of the uterine 

 glands, and increase of the connective tissue, all take place. This 

 stage probably lasts one week, and is followed, when pregnancy 

 has not occurred, by degenerative changes. 



(2) The second or destructive stage is marked by the destruc- 

 tive processes which give rise to the usual phenomena of the 



FIG. 433. 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 internuni (the mucous membrane tapers down 

 to these openings) (Courty). 



menstrual period, including the discharge of mucus, blood, and 

 disintegrated uterine mucous membrane. Five days constitute the 

 average duration of the menstrual flow, although its continuance 

 may be extended or curtailed, owing to individual peculiarities. 



