VAGINAL EPITHELIUM OF GUINEA-PIG 443 
7. Stage 4. During this stage leucocytes appear in the lumen 
of the vagina for the first time since the beginning of the cycle. 
Smears contain epithelial cells and leucocytes. 
8. Stage 5 or interval. Vaginal smears contain leucocytes and 
mucus, but very few or no epithelial cells. The epithelium has 
become reduced to its lowest condition, one to two cells. The 
epithelium is rapidly regenerated at the end of the interval 
immediately preceding the next cycle. 
9. Stage 4 of Stockard and Papanicolaou, marked by the ap- 
pearance of blood, is very doubtful. 
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