PLATE 1 



Fig. 1. Endometrial cups from mare 4 sacrificed on 105111 day of pregnancy. 

 The cups are pendulous at this stage. Note the tremendous enlargement of the 

 lumens of the uterine glands in the cup area. al. c, allantochorion; e.cs., en- 

 dometrial-cup secretion; u.g.c, uterine glands in cup area; u.g., uterine glands 

 outside of cup area, x 7. 



Fig. 2. Endometrial cup from mare 2 sacrificed on 63d day of pregnancy. The 

 uterine epithelium is entirely absent and there is autolysis of all tissues in center 

 of cup. X 14. 



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