THE DECIDUA SEROTINA 



431 



core of connective tissue of a delicate embryonic type, in which 

 are the fetal blood vessels. Even the smallest villi contain capil- 

 lary loops of broad calibre, which are supplied by fetal arteries, 

 derived from the umbilic,al arteries, which distribute their branches 

 throughout the chorionic connective tissue. The fetal veins accom- 

 pany the arteries. 



THE DECIDUA SEROTINA (Decidua asalis).This portion 

 of the maternal decidua receives the insertion of the chorionic 

 villi; its superficial compact portion belongs rather to the pla- 

 centa than to the uterine mucosa, since it separates from the uter- 

 ine wall along with the chorionic tissues when the placenta is dis- 

 lodged at parturition. The substance of this layer is formed by 



Vi 



me 



348. THE HUMAN DECIDUA SEROTINA AT THE SEVENTH MONTH. 



D', cavernous layer of the decidua ; D", compact layer ; me, margin of the muscular 

 coat of the uterus ; Fi, chorionic villi, the spaces between which were filled with maternal 

 blood. (After Minot.) 



the decidual connective tissue in which the enlarged decidual cells 

 are specially numerous. It transmits the maternal blood vessels, 

 and with its surface the main stems of the chorionic villi, at their 

 occasional points of attachment, are intimately blended. Here 

 and there the decidual connective tissue is continued inward for 

 some distance between the chorionic villi to form incomplete septa 



