CHANGES IN THE UTERUS. 



47 



Both the dccidua vera and the decidua reflexa originally contain tubular and somewhat 

 tortuous glands, which were discovered by Sharpey, and were by him supposed to minister, in 

 the first instance, both to the nutrition and to the attachment of the ovum, the latter by 

 affording depressions for the chorionic villi to penetrate into the substance of the decidua. It 

 has, however, since been shown that these villi do not directly pass into the glands, but 

 rather tend to become attached to the interglandular surface, and indeed at the decidua 

 serotina, where subsequently the main attachment of the chorionic villi occurs, the gland- 

 lumina may become almost entirely obliterated before the villi are here formed. But the 

 greatly enlarged glands of the decidua vera very probably furnish a secretion to assist the 

 nourishment of the ovum previously to the full establishment of the placental circulation. 



Fig. 50. DIAGRAMMATIC SECTION OF THE PREGNANT HUMAN UTERUS AT THE SEVENTH OR 

 EIGHTH WEEK. (Allen Thomson. ) 



c, c, openings of Fallopian tubes into the cavity of the uterus ; c', cervix, filled by a plug of mucus : 

 the letters c and c' are placed within the original cavity of the uterus ; dv, decidua vera ; dr, decidua 

 reflexa ; ds, decidua serotina ; ck, choriou with its villi growing into the decidua reflexa and d. 

 serotina ; in the former the villi are becoming atrophied ; u, umbilical cord, the clotted lines indicate 

 bloodvessels within it ; al, allantois ; y, yolk sac (umbilical vesicle) ; y', its stalk, passing in the 

 umbilical cord and connected with the intestine of the embryo, i ; am, am'nion. 



The decidua undergoes remarkable structural changes during the early months of 

 pregnancy, some of these changes being common to all three parts of the membrane, 



