A series of experiments has recently been carried out in ewes at the end of pregnancy in which parturition was monitored by the recording of intra-uterine pressure changes (Hindson, Schofield, Turner & Wolff, 1965; Hindson, Schofield & Turner, 1967, 1968). Some further observations have since been made which are relevant to the conclusions drawn; this paper is by way of being a postscript to the previous publications and carries the additional information.
The frequency of the intra-uterine pressure waves associated with parturition in this series was expressed as time per six waves. Since frequency can also be
expressed in waves per unit time, it seemed appropriate to make a second analysis in order to substantiate the conclusion drawn. Therefore, the original tracings were analysed in