GESTATION (Lat. gestatio, from gestare, frequentative of gerere, to carry). The term ap plied in physiology to the period that intervenes in the mammalia between impregnation and the bringing forth of the young. The length of gesta tion and the number of young produced at a. birth vary extremely in different mammals, but usually stand in an inverse ratio to one another. Thus, in the larger Herbivora,as,for example, the elephant, the horse, the ox, and the camel, the female seldom produces more than one at a time, but the period of gestation is long; while in the smaller ones the progeny is numerous, but the period of gestation is only a few weeks. In the elephant the period of gestation extends over 21 or 22 months; in the giraffe it is 14 months; in the dromedary it is 12 months; in the mare upward of 11 months; in the tapir, between 1G and 11; in the cow, 9; and in many of the larger deer, somewhat more than 8 months. In the sheep and goat the period is 5 months. In the sow, which produces a numerous litter, the period is 4 months. In the Rodentia the progeny is nu merous and imperfectly developed, and the period of gestation is comparatively short; in the beaver, one of the largest of the order, it is 4 months; in the rabbit and hare, from 30 to 40 days; in the dormouse, 31 days; in the squirrel and rat, 4 weeks; and in the guinea-pig, 3 weeks or less. The young of the Carnivora, like the young of the Rodentia, are born with their eyes closed, and in a very immature condition; and even in the larger Carnivora the period of gestation is far shorter than in'the larger Rumi nantia or Pachydermata; it is 6 months in the bear; 108 days in the lion (the period in this animal is stated by Van der Hoeven at 3 months) ; 79 days in the puma; 62 to 63 days in the dog, the wolf, and the fox; and 55 or 56 days in the cat. Of the Marsupialia, gestation in the
kangaroo lasts 39 days, in the opossum 26 days. Of the Quadrumana, the period of gestation lasts 7 months in the monkey, which bears one, rarely two, young at term. Of the Cetacea, the whale's normal pregnancy lasts 10 months. Domesticated animals breed oftener than those in a wild condi tion. Wild pigeons breed twice, domesticated pigeons six or more times a year.
In woman, the accepted period of gestation is 275 days from insemination, or 280 days (on an average) from the last day of the previous menstruation. In a young mother, the first preg nancy may be much shorter than succeeding pregnancies. Prolongation of gestation to 300 days is possible, counting from the last menstrual flow. French law admits the legitimacy of a child born 300 days after the separation of the parents; Scotch law allows 10 months; English law allows the lapse of 11 months between the death or departure of the husband and the birth of a legitimate child; in the United States it was decided, in the case of the Commonwealth vs. Porter, that a child born 317 days after the absence of the father began was not a bastard.