The female cat possesses a characteristic and highly stereotyped pattern of sexual behaviour, which is remarkably constant in individual animals (Stricht, 1911; Greulich, 1934;Bard, 1939;Dawson, 1950;Michael, 1958). The pattern of oestrous behaviour depends upon the secretory activity of the ovaries and is never observed in immature, anoestrous or ovariectomized animals (Bard, 1939;Michael, 1961). It can therefore be regarded as a pattern of behaviour that is hormone-dependent. This study deals mainly with the activation of oestrous behaviour in ovariectomized cats stimulated by treatment with oestrogens, with particular reference to the time taken for mating to occur and the relations between the vaginal and behavioural changes.In order to interpret the results of experiments in which oestrogens were introduced directly into the substance of the brain (Harris & Michael, 1964), it was necessary first to know the effects upon both behaviour and genital tract when oestrogens were administered systemically. In the mouse (Brouha & Simonnet, 1927;Marrian & Parkes, 1930;Mirskaia & Crew, 1930; Wiesner & Mirsakia, 1930), the rat (Allen, Francis, Robertson, Colgate, Johnston, Doisy, Kountz & Gibson, 1924), the guinea-pig (Boling, Young & Dempsey, 1938), and the ewe (Cole & Miller, 1935;Robinson, 1955) it has been found that the dosage of oestrogen required to induce cornification of the vagina is less than that required to evoke mating behaviour, and hence it was important to determine whether this relation also holds true in the feline species. Further, observations upon the natural oestrous cycles of normal cats (Michael, 1961) suggested that the total pattern of sexual behaviour was organized from simpler component reflexes upon a hierarchical basis by increasing levels of ovarian hormone. In the present study oestrogens have been administered to ovariectomized cats under conditions which permit this hypothesis to be tested. The preliminary results obtained were briefly reported by Michael & Scott (1957).
