PLATE 1 



EXPLANATION OF FIGURES 



The figures in all of the plates are photomicrographs made by Mr. Wm. Dunn 

 of the Photographic Department of Cornell Medical School. 



1 Squamous epithelial cells contained in the vaginal fluid during the first 

 stage ()f oestrus from animal 1089 9 . The vaginal fluid at this time is mucus 

 filled with abundant cells of this type. 



2 Cells from the second stage vaginal fluid. The great majority are squa- 

 mous epithelial cells from the wall of the vagina with a few uterine epithelial 

 cells. From animal 1066 9 . 



3 and 4 Cells of the second stage more highly magnified from 1066 9 . 



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