PLATE 2 



Fig. 3. Higher magnification from area near base of cup shown in figure 2. 

 Compare with figure 5 for variations in character of the interglandular tissue. 

 X 170. 



Fig. 4. Higher magnification from area of cup sho^vn in figure 1, to show the 

 sparseness of interglandular tissue at this later stage. Compare with figure 6. 

 Though the glandular epithelium is low, an abundant secretion is pouring out 

 from the wide-necked uterine glands, x 29. 



Fig. 5. Large polyhedral cells in endometrial cup from mare 3 sacrificed on 

 67th day of pregnancy. Decidual cells of this type were present in two of three 

 mares sacrificed at this stage. We have not observed them in the endometrium 

 outside of the cup area, x 156. 



Fig. 6. To show the character of the endometrial cup of mare 3 from the base 

 to the surface. Though autolysis is not evident in this case, the uterine epi- 

 thelium is completely absent and the superficial layers of decidual cells are 

 being sloughed, x 29. 



nii8] 



