[Histochemical and histological studies on the vagina of pigs with in various phases of the estrus cycle (author's transl)].

During estrus (1st day) the vaginal epithelium is highly proliferated; its thickness amounts up to 20 cell layers and even more. During metestrus (3rd day) the epithelium measures 12 to 15 layers due to degeneration and desquamation. During diestrus a further decrease in height is noticed. During late diestrus (16th day) the epithelium reaches its minimal height with 3 to 5 layers. The stratum superficiale consists during this phase of tall columnar cells. Starting from day 18 proliferation begins again. During all phases of the genital cycle the presence of infiltrated leucocytes is highest during middle and late diestrus. Leucocytes are easily recognized by their strong reaction for alkaline phosphatase whereas the epithelium proper remains negative. Mucification in the porcine vaginal epithelium is but moderate. Mucous substances occupy from from proestrus to early diestrus the intercellular gaps in the adluminal half of the epithelium. During middle and late diestrus mucous substances are localized in the supranuclear region of the superficial columnar cells. Histochemical tests for enzymes of oxidative pathways give relatively uniform and weak results during the entire cycle. Fluctuations of epithelial esterase activity may be correlated with phases of proliferation and differentiation.