Allen, "Prolonged Gestation," _American Journal Obstetrics_, April, 1907).

It is possible, as Mueller suggested in 1898 in a These 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 Seropian (_Frequence Comparee des Causes de l'Accouchement Premature_, These de Paris, 1907) found that about one-third of French births (32.28 per cent.) are to a greater or less extent premature.