Photomicrographs of exfoliated vaginal cells smear taken during various stages of the estrous cycle A) Proestrus phase- showing several polyhedral superficial nucleated cells (An), single or in clusters and containing dark (glycogen) granules. Leucocytes (Leu) are seen but very scanty. B) Oestrus phase- Note the characteristic highly cellular nature of smear which is deeply basophilic stained. Superficial nucleated cells (Sp) are abundant, few parabasal (Pb) and Leucocytes (Leu) are seen. C) Metestrus phase- Note few superficial cells (polygonal in outline) and parabasal (Pb) cells, Leucocytes (Leu) begin to appear in this phase. D) Diestrus phase- Note the abundant leucocytes (Leu) i.e marked leukocytosis which is predominantly seen in the smear, also few superficial nucleated cells (Sp) are seen. Modified Papanicolaou stain.