TYPES OF (ESTROUS CYCLE 63 



Heape's division in Scninopithccits and Macaciis, distinguished 

 four main stages : 



(a) period of rest. 

 {b) period of growth. 

 (c) period of destruction. 

 {d) period of regeneration. 



Of these stages in woman the first is said by WilHams (638) 

 to last twelve days, the second (the stage of premenstrual 

 congestion) five days, the third (the actual period of menstrua- 

 tion) four days and the last seven days. According to other 

 workers, however, the initial premenstrual changes begin much 

 earlier than this, the period of quiescence being correspondingly 

 shorter. 



Shaw states that the earliest signs of activity in the inter- 

 menstrual endometrium become apparent about fourteen days 

 after the beginning of the previous menstrual period. The 

 surface epithelium becomes more columnar and then hyper- 

 trophied and dilated. Typical translucent areas appear behind 

 the nuclei of the gland cells, which begin to secrete b}' the 

 twentieth day. By this time also, the general hypertrophy 

 has become much greater. After the twentieth day other 

 changes become evident. Three la^^ers can now be distinguished 

 in the stroma : 



{a) A dense layer immediately below the surface epithelium; 

 the cells are tightly packed together round the gland 

 ducts in this area. 



(b) An oedematous layer which surrounds the glands and in 



which the cells are separated, but the capillaries dilated. 



(c) A basal layer in which the characteristic oedema and 



hypertrophy are absent. 



These changes are accentuated until the 28th day when, if 

 pregnancy fails to supervene, degeneration sets in. This 

 consists essentially in the disorganization and disintegra- 

 tion of the glands of the superficial and middle zones of the 

 endometrium. Coincidently, blood is extravasated from the 

 capillaries and, having formied small hasmatomata, finally 

 reaches the lumen through the disintegrated epithelium. The 

 extent to which the endometrium is destroyed and shed varies 



