Stimuli from the cervix and adjacent parts of the reproductive tract have a critical role to play in ovulation, pseudopregnancy and possibly parturition. Appreciable evidence even suggests that stimulation of these regions during coitus may precipitate the release of luteinizing hormone (LH) in those animals which have previously been regarded as spontaneous ovulators. The rat, for example, ovulates to coitus after the spontaneous event has been inhibited by continuous illumination (Dempsey & Searles, 1943) or pharmacological agents such as chlorpromazine (Harrington, Eggert, Wilbur & Linkenheimer, 1966) and pentobarbitone (Everett, 1967). Also, Taleisnik, Caligaris & Astrada (1966) found a dramatic rise in the level of serum LH in the rat within minutes of mating. Very little is known about the central pathway taken by stimuli from the lower parts of the reproductive tract. Presumably, the stimuli pass to various parts of the diencephalon, since the anterior hypothalamus is involved in ovulation