Puerperal Diseases of the Uterus 561 



fetal placental arteries, capillaries and veins escapes from 

 the ruptured umbilic veins, causing the placental capillaries 

 of the fetus to collapse, become greatly reduced in volume, 

 and drop away from the capillaries of the maternal placental 

 crypts. There was at no time any anatomical bond of union, 

 but only an intimate contiguity maintained by a mutual at- 

 traction existing between the healthy uterus and living fetal 

 envelopes. When the umbilic cord ruptures and the chori- 

 onic end is necrotic, the attraction between it and the uterus 

 ceases. If it is to be retained, the retention is necessarily 

 dependent upon a pathologic condition which can not develop 

 after the expulsion of the fetus, whether alive or dead, but 

 is dependent absolutely upon the persistence of a metritis 

 which existed in the pregnant uterus. The expulsion of the 

 fetus does not cause, nor permit other factors to cause, re- 

 tention of the membranes, but fetal expulsion reveals the 

 uterine disease and opens the way for important modifica- 

 tions and complications in its course. 



The bovine placental structures are the most complex seen 

 in domestic animals. While the placental system of the ewe 



Fig. 180— Retained Placenta showing- incarceration and disintegra- 

 tion of the choriotic tufts ( fot 1 and extensive infiltration with 

 leucocytes in the maternal portion, some of them already- 

 broken down, x 310 (After Pomayer). 



36 



