The question therefore of the _partus serotinus_; as far as these data are concerned, remains still undecided: of 10 cases which have occurred under our own immediate notice, where the patients determined the commencement of their pregnancy from other data than the last appearance of the catamenia, a similar variation was observed, viz. that nearly one-third went beyond 280 days, six of these individuals reckoned from their marriage, and four from peculiar sensations connected with sexual intercourse, which convinced them that impregnation had taken place: of these, seven did not go beyond the 280th day, two having been delivered upon that day, and three went beyond it, viz. to the 285th, 288th, and 291st days: the two former reckoned from their respective marriages; the latter, who went 291 days, from her peculiar sensations. The calculation from the date of marriage is liable to the same objections as that taken from the last appearance of the catamenia; for if it had been solemnized (as is usually the case where it is possible) shortly after a menstrual period, and if conception did not take place until a fortnight or three weeks afterwards, the patient's pregnancy would thus have appeared to have lasted so much longer than the natural term. The case, however, which is stated to have gone 291 days, does not come under this head, for here the pregnancy really appears to have lasted 10 or 11 days beyond the full period, which cannot be accounted for in the way above mentioned: we should not have ventured to quote this, if a similar instance had not been recorded by Dr. Dewees. "The husband of a lady, who was obliged to absent himself many months, in consequence of the embarrassment of his affairs, returned, however, one night clandestinely, and his visit was only known to his wife, her mother, and ourselves. The consequence of this visit was the impregnation of his wife; and she was delivered of a healthy child in 9 months and 13 days after this nocternal visit. The lady was within a week of her menstrual period, which was not interrupted, and which led her to hope she had suffered nothing from her intercourse; but the interruption of the succeeding period gave rise to the suspicion she was not safe, and which was afterwards realized by the birth of a child."[60] Although it is to be regretted that this case has been calculated in the ordinary vague manner of calendar months, yet it is perfectly evident that the pregnancy was longer than the ordinary duration. We shall, therefore, endeavour to investigate the possibility of over-term pregnancy still more closely by a consideration of the second question, viz. what are the causes which determine the period at which labour usually comes on?