536 



THE REPRODUCTIVE SYSTEM 



similar cells occur in the decidua menstrualis, this is denied by Minot 

 (1903), who states that in a considerable number of menstrual decidua 

 examined, no such cells were ever found. 



The superficial epithelium is soon desquamated and the tunica propria 

 comes into contact with the fetal chorion. The glandular epithelium is 

 also partially degenerated, often becoming flattened and of irregular shape. 

 It is frequently desquamated into the glandular lumen; this lumen is thus 



FIG. 470. CHORIONIC VILLI FROM THE HUMAN PLACENTA AT FULL TERM. 

 Hematein and eosin. Photo. X 114. 



reduced to a narrow crevice, which is so elongated during the dilatation of 

 the uterine wall that the axis of the glandular remnant becomes nearly 

 parallel to the surface of the decidua. 



The decidual membrane which is thus formed is divisible into three 

 portions, according to its relation to the tissues of the embryo: 1, that 

 portion upon which the developing ovum directly rests, which is known 

 as the decidua serotina or decidua basalis but later forms the placenta 

 uterina or maternal portion of the placenta; 2, at the margins of the 



