Dr. Dweira-Bernson (_Revue Pratique d'Obstétrique et de Pédiatrie_, 1903, p. 370), compared four groups of pregnant women (servants with light work, servants with heavy work, farm girls, dressmakers) who rested for three months before confinement with four groups similarly composed who took no rest before confinement. In every group he found that the difference in the average weight of the child was markedly in favor of the women who rested, and it was notable that the greatest difference was found in the case of the farm girls who were probably the most robust and also the hardest worked. The usual time of gestation ranges between 274 and 280 days (or 280 to 290 days from the last menstrual period), and occasionally a few days longer, though there is dispute as to the length of the extreme limit, which some authorities would extend to 300 days, or even to 320 days (Pinard, in Richet's _Dictionnaire de Physiologie_, vol. vii, pp. 150-162; Taylor, _Medical Jurisprudence_, fifth edition, pp. 44, 98 et seq.; L.M. Allen, "Prolonged Gestation," _American Journal Obstetrics_, April, 1907). It is possible, as Müller suggested in 1898 in a Thèse de Nancy, that civilization tends to shorten the period of gestation, and that in earlier ages it was longer than it is now. Such a tendency to premature birth under the exciting nervous influences of civilization would thus correspond, as Bouchacourt has pointed out (_La Grossesse_, p. 113), to the similar effect of domestication in animals. The robust countrywoman becomes transformed into the more graceful, but also more fragile, town woman who needs a degree of care and hygiene which the countrywoman with her more resistant nervous system can to some extent dispense with, although even she, as we see, suffers in the person of her child, and probably in her own person, from the effects of work during pregnancy. The serious nature of this civilized tendency to premature birth--of which lack of rest in pregnancy is, however, only one of several important causes--is shown by the fact that Séropian (_Fréquence Comparée des Causes de l'Accouchement Prémature_, Thèse de Paris, 1907) found that about one-third of French births (32.28 per cent.) are to a greater or less extent premature. Pregnancy is not a morbid condition; on the contrary, a pregnant woman is at the climax of her most normal physiological life, but owing to the tension thus involved she is specially liable to suffer from any slight shock or strain.