'A number of things happen during the final stages of a cow's pregnancy. About three weeks before she calves her shape alters perceptibly, due to the calf getting lower in the pelvis. In heifers this is very obvious. At the same time bagging-up, or enlargement of the udder, proceeds apace, but the udder does not usually become really tense till about twenty-four hours before delivery. For about a fortnight before delivery the tail region becomes very swollen, but the swelling subsides as the calving day approaches, and the extent of this swelling is, for Dexters anyway, one of the best guides to the timetable. The depth of the groove between the pin bone (see Fig. 12) and the end of the spine is the other sign commonly employed to estimate the imminence of calving, but must be taken with due appreciation of the other indications described. The signs of imminent calving are most useful when a cow or heifer has been running with a bull and her exact service date is unknown.'