Puerperal Diseases of the Uterus 563 



is similar in plan, the chorionic tufts are not so large and 

 hence the cotyledonal crypts of the uterus are not so deep 

 and intricate as in the cow. This is well shown by a study 

 of the placental systems of the two animals on pages 59 to 

 66, including Figures 27 to 34. When infection invades the 

 placental structures, it is virtually impossible for the ma- 

 ternal crypts to become inflamed without the intimately con- 

 tiguous chorionic tufts promptly becoming involved. As in 

 inflammations involving other parts, so in the placental 

 tissues, the capillaries become engorged, the blood stream 

 slows and finally stops, the red blood cells heap up and per- 

 ish, and the white blood cells pass out through the capillary 

 walls into the intervening spaces. The result is indicated in 

 Figures 180-182. The accumulation of the red blood cells in 

 the capillaries and the migration of the leucocytes into 

 neighboring tissues, with the extravasation of lymph and of 

 red cells into the parts, increase greatly the volume of the in- 

 dividual structures, such as the chorionic tufts, and through 

 this detailed enlargement the volume of the structure as a 

 whole becomes vastly increased. The inflamed cotyledon is 

 frequently quadrupled in volume because of the disease. The 

 result is incarceration of the enlarged, swollen chorionic 

 tufts within the similarly enlarged placental crypts. The 

 placenta is retained. The pathologic processes involved in 

 retention of the fetal membranes probably occur in all cases 

 of abortion but are not always recognizable. The uterus of 

 the female bovine fetus shows clearly the placental areas. 

 When a heifer becomes pregnant, the placental areas have 

 already been fixed and, as soon as the embryonic sac is es- 

 tablished, the placental-contact points of the chorion throw 

 out placental tufts which enter the cotyledonal crypts and 

 quickly establish a physiologic bond of intimate contiguity. 

 As pregnancy advances the chorionic tufts grow larger, 

 longer, and more intricately branched, and the cotyledonal 

 crypts become constantly deeper and more complex. It is 

 not probable that a fetus ever dies until some or all pla- 

 cental areas have undergone serious pathologic changes of 

 a character essentially identical with retained fetal mem- 



