Volume of Necromys lasiurus placenta and of three main layers according to the time of gestation. (A) Total volumes of placenta and of main layers during gestation in N. lasiurus and in Mus musculus domesticus at 15.5 days of gestation. A significant difference (p < 0.05) was observed in the total volume of the placenta, and in the labyrinth and junctional zone layers between 10/11 and 15/16 days of gestation. There were no statistically significant differences in relation to the volume of the decidua during the gestation. (B) Relative volumes of placenta and of main layers during gestation in N. lasiurus and M. musculus near the term. (*) indicates a significant difference in the volume of decidua between the days 10/11 and 21 days of gestation (p < 0.05). The total volumes of each layer were determined using the Cavalieri method as described in material and methods.